- Email: [email protected]
Flexible printed paper electrode with silver nano-ink for electrochemical applications
Journal Pre-proof
Flexible printed paper electrode with silver nano-ink for electrochemical applications Tushar Kant , Kamlesh Shrivas , Vellaichamy Ganesan , Yugal Kishor Mahipal , Rama Devi , Manas Kanti Deb , Ravi Shankar PII: DOI: Reference:
S0026-265X(19)33187-X https://doi.org/10.1016/j.microc.2020.104687 MICROC 104687
To appear in:
Microchemical Journal
Received date: Revised date: Accepted date:
8 November 2019 11 January 2020 2 February 2020
Please cite this article as: Tushar Kant , Kamlesh Shrivas , Vellaichamy Ganesan , Yugal Kishor Mahipal , Rama Devi , Manas Kanti Deb , Ravi Shankar , Flexible printed paper electrode with silver nano-ink for electrochemical applications, Microchemical Journal (2020), doi: https://doi.org/10.1016/j.microc.2020.104687
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier B.V.
1
Highlights
Development of low-cost paper based disposable printed electrodes with silver nano-ink using desktop inkjet printer
Fabricated paper electrode exploited as a counter electrode in cyclic voltammetry (CV) analysis
Printed paper electrode is demonstrated to used as a working electrode for analysis of nitrate in CV
2
Flexible printed paper electrode with silver nano-ink for electrochemical applications Tushar Kant1, Kamlesh Shrivas1*, Vellaichamy Ganesan2, Yugal Kishor Mahipal 3, Rama Devi4, Manas Kanti Deb1 and Ravi Shankar5
1
School of Studies in Chemistry, Pt. Ravishanakar Shukla University, Raipur-492010, CG, India 2
Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi221005, UP, India
3
School of Studies in Physics and Astrophysics, Pt. Ravishanakar Shukla University, Raipur-492010, CG, India
4
Department of Chemistry, National Institute of Technology, Raipur-492010, CG, India 5
Nanoscience and Nanoengineering Program, South Dakota School of Mines and Technology, Rapid City, South Dakota-57701, USA
*Corresponding author Email: [email protected]
3
ABSTRACT Development of low-cost paper based disposable electrodes printed with silver nano-ink using desktop inkjet printer is reported in this work. A stable nano-ink was prepared by dissolving 3% silver nanoparticles (AgNPs) capped with polyvinylpyrrolidone (PVP) in ethanol as a dispersing solvent. Highly stable silver nano-ink with surface tension of 21.1 mN/M and viscosity of 2.6 mPa.S was prepared for printing on photo paper that can be used as an electrode for electrochemical analyses. The fabricated paper electrode was exploited as a counter electrode in cyclic voltammetry (CV) analysis of potassium ferricyanide with better stability and reproducibility (relative standard deviation (RSD) 1.6%) for multiple times of analyses (n=60) and compared with the results of conventional electrodes. Further, the printed paper electrode was demonstrated to be used as a working electrode for analysis of nitrate by CV. The use of paper electrode is found to be simple, rapid, user-friendly and can be applied at the sample source for determination of nitrate from different samples.
Keywords: Inkjet Printing, Flexible Paper Electrodes, Nano-Ink, Cyclic Voltammetric Analyses
4
1. Introduction There is always increasing demand for more facile and cost-effective route to prepare the electronic devices that should be flexible, eco-friendly, light weight and disposable. The attention has been drawn in the direction of preparation of flexible printed electronics using metal nanoparticles (NPs) based conductive nano-inks. Recently, different techniques including physical lithography, sputtering, chemical vapor deposition and spin coating have been demonstrated for fabrication of conducting inks on solid surfaces to prepare electronic devices [1-2]. These techniques provide a homogenous and smooth deposition of functional materials on solid surface, but they need controlled temperature and contaminant free environment which are found to be expensive and difficult to maintain. Screen printing is also used for large scale production of electronic devices where mesh is used to fabricate the substrate, which is time consuming and tedious process. To overcome these disadvantages, the improvement of useful and low-cost processing technique is needed to fabricate the conductive materials. There are other alternative simple and low-cost techniques available for fabrication of nanomaterials on solid substrates such as direct writing, roller ball pen, sketching and brush painting [3,4]. The drawbacks of these techniques are formation of non-uniform layer of fabricated materials on solid substrate. Recently, inkjet printing has wide application due to its low cost, rapidity and simplicity in printing the designed digital file. In inkjet printing, the head ejects a very small quantity of ink on to the substrate based on the design of fabrication. Inkjet printing is considered to be an efficient and highly well-designed technique for micro scale patterning of metallic nanomaterial’s [5]. Flexible circuit and printed electronic devices are produced by deposition of single or multiple layers of active materials like conductive inks or dielectric inks onto the solid substrates such as plastic, glass, polymers, ceramics, etc [6,7]. The devices made from theses substrates are expensive as well as after the use it is non-biodegradable into the environment. The research and
5
development should always need to decrease the electronic waste as well as it should be biodegradable, flexible and harmless to human beings. Paper substrate is being a better substitute in place of plastics because it is eco-friendly, inexpensive, flexible and sustainable [8]. Paper based devices have been emerging as a recent trend in developing new analytical devices for wide range of applications in the fields such as clinical, food and environmental monitoring [9]. Paper is also compatible to fabricate the conducting metal NPs because of limited penetration of particles onto the porous substrate [10]. Thus, paper substrate is found to be better material to print the silver nano-ink for preparation of electrode for electrochemical applications. Recently, metal NPs like silver (Ag) and copper (Cu) are commonly used as nano-ink due to their high conductivity, high stability and low cost that make the material for commercialization in the market. The decrease in size of particles to few nanometers results in the fall of their melting point and sintering process helps in the formation of a dense layer of NPs on the solid surface. For such reasons, noble metals have been widely used for the synthesis of conducting ink [11]. CuNPs is frequently used to prepare conducting ink due to its high conductivity and being inexpensive as compared to noble metals. But it has a disadvantage of easy oxidation which causes the loss of its conductivity [12]. However, AgNPs, because of its better conductivity and stability than Cu and low cost compared with Pt or Au can be considered as a best choice. Recently, we demonstrated the fabrication of silver nano-ink on paper substrates using direct writing with ball point pen and used for electrochemical determination and lighting of LED bulb [13]. There are many reports that illustrated the use of silver nano-ink for fabrication of conductive track, electronic devices such as touch pads, solar cells, radio frequency identification tag (RFID), etc. Thus, the use of silver nano-ink will be a better alternative for fabrication on paper substrate which can be exploited in the field of analytical chemistry for electrochemical analyses [14].
6
Electrochemical analysis is powerful analytical technique for qualitative and quantitative determination of inorganic and organic components based on the measurement of current against the applied potential. In the electrochemical determinations, three electrode systems are generally used. These conventional electrodes have many drawbacks like fragile, expensive and toxic to human health as well as non-biodegradable in the environment. Chemically modified electrodes have been frequently used as working electrodes in electrochemical analysis due to their high sensitivity and excellent selectivity. To date, several modified electrodes have been developed for the determination of several analytes includes multi-walled carbon nanotubes electrode [15], modified glassy carbon electrode [16] and metal NPs electrodes [10, 13]. Among these, metal NPs are found to be the greater choice for preparation of electrode material due to its better sensitivity for detection of variety of analytes. Here, the synthesis of AgNPs, nano-ink formulation, optimization of different substrates, sintering process to prepare conductive track and preparation of paper electrode for electrochemical application were demonstrated. UV-Vis, transmission electron microscope (TEM), dynamic light scattering (DLS), and X-ray diffraction (XRD) are used to determine the size, shape, and purity of silver nano-ink; Fourier-transform infra-red (FTIR) spectroscopy and thermogravimetric analysis (TGA) were applied for estimation of surface modification and stability of nano-ink at particular temperature. The printed paper electrode with silver nano-ink is demonstrated to be used as counter and working electrodes for electrochemical applications for analysis of potassium ferricyanide, nitrate.
2. Experimental Section 2.1. Chemicals and reagents All the chemicals used were of analytical reagent (AR) grade. Silver nitrate (99.9%), polyvinyl pyrrolidone (PVP, molecular weight >40,000 Da), sodium borohydride (98.0%), potassium nitrate (99.0%), potassium ferricyanide (98.0%), potassium chloride (99.5%), and ethanol
7
(99.0%) were purchased from Himedia ((Mumbai, India). Triply distilled water was used for the preparation of standard solutions and for the cyclic voltammetry (CV) analysis. 2.2. Synthesis of AgNPs/PVP AgNPs modified with PVP were prepared from silver nitrate in water using NaBH4 as a reducing agent [17]. In brief, 0.5 g of AgNO3 and 0.5 g of PVP were dissolved in 100 mL water under vigorous stirring till the formation of clear solution and then 10 mL of freshly prepared 0.25 M NaBH4 was added to the solution mixture. The color of the solution changed from colorless to dark yellow. The resultant solution was centrifuged at 6,000 rpm to remove excess PVP or any impurities. The precipitate obtained was washed several times with acetone to remove any impurity from the product. Then it was dried at room temperature followed by the preparation of conducting ink in ethanol as shown in scheme 1(a). 2.3. Preparation of silver nano-ink Different types of organic solvents such as ethanol, methanol, propanol, diethylene glycol, toluene, and water were used for formulation of silver nano-ink. Different concentrations of nano-ink from 2% to 10 % were prepared separately by dissolving an appropriate amount of AgNPs/PVP in different organic solvents in different proportions. The prepared nano-ink was used to print on photo paper using desktop printer as shown in scheme 1(b). 2.4. Printing of paper based electrode with silver nano-ink HP Deskjet-1112 printer was used for the printing of silver nano-ink on different types of paper substrates such as JK photo paper, JK Excel Bond Paper, normal printing paper and Whatman filter paper No.1 as shown in scheme 1(c). The paper electrode of 7.0 cm length and 0.4 cm width with a bottom area of 1 cm2 was printed on different paper substrates as shown in scheme 1(d). The printed electrode was sintered in oven at different temperatures and at different time intervals for obtaining the better conductive materials on the paper substrate (scheme 1e). The
8
printed electrodes were tested for electrochemical analysis in CV, schematically shown in Fig. 1(f) and 1(g). 2.5. Apparatus The size of AgNPs/PVP was preliminarily estimated with UV-Vis spectrophotometer (type Carry 60, Agilent Technologies, USA) by measuring the localized surface plasmon resonance (LSPR) band of AgNPs/PVP. Transmission electron microscopy (TEM) images were recorded (Jeol JEM- 2100, Waitham, MA) at a maximum accelerating voltage of 200 kV was used to determine the size and shape of AgNPs at an accelerating voltage of 100 kV. Fourier transforminfrared spectroscopy (FTIR) of type-nicolet-10 (Thermo Scientific, USA) was used to know the presence of stabilizing molecules (PVP) on the surface of NPs. Thermogravimetric analysis (TGA) (Bruker, Germany) was used to estimate the loss of PVP from the surface of AgNPs in nitrogen gas atmosphere (70 mLmin-1) at the temperance range of 25-600 oC. Malvern Panalytical, XPert3 X-ray diffraction s stem was used to determine the phase crystalline structure of NPs. Digital multimeter (Type-DT830D, Unity, India) was used to determine the resistance of printed paper electrodes. Surface tension instrument- Dyne Master-DY-300 (Kyowa Interface Science Co. Ltd.) and NI RUN Bionics digital rotational viscometer (Model nu: BSTARV10/A) were used to determine the surface tension and viscosity of the formulated nano-ink, respectively.
3. Results and Discussion 3.1. Characterization of AgNPs/PVP The preliminary investigation was done for the preparation of suitable sized AgNPs by monitoring the LSPR band in the wavelength range of 200-800 nm. AgNPs capped with PVP showed the LSPR band around 420 nm confirming the size of NPs was found in the range of 1050 nm [13,18], shown in Fig. 1(a). The size and shape of AgNPs was verified by TEM and the results are shown in Fig. 1(b) and 1(c) where the average size of NPs was 13+2 nm. Next, the
9
composition of NPs was estimated by EDX analysis. Fig. 1(d) shows the EDX spectrum of AgNPs/PVA with presence of intense peak of silver along with other peaks of carbon, nitrogen, and oxygen from the stabilizing agent of AgNPs. In addition, the DLS measurement was performed to know the size distribution of NPs in ethanol and the average size distribution of particles was found to be 13+3 nm, shown in Fig. 1(e). Thus, the data obtained with UV-Vis, TEM and DLS were comparable to each other which confirm the size of NPs. XRD analysis was done to know the idea about the crystallinity and purity of synthesized metal NPs. Fig. 2(a) represents the XRD patterns of AgNPs/PVP containing characteristic diffraction peaks at 38.4, 44.6, 64.7, and 77.8 (2θo) which is allocated to the presence of (111), (200), (220), and (311) planes of cubic structure of silver, respectively. The sharp peak at 38.4 demonstrates the high purity of cubic structure of silver, the broad peak at lower 2θo shows the capping of PVA molecules which are present on the surface of the AgNPs [19,20]. Next, the presence of stabilizing molecules on the surface of NPs was characterized using FTIR. Fig. 2(b) shows the FTIR spectra of pure PVP and PVP modified AgNPs in the wave number range of 800-4000 cm-1. The peak assigned at 3432 cm-1 is due to the N-H stretching of amine group and peak at 2919 cm-1 corresponded to C-H stretching of alkyl group from the stabilizing agent. The signal at 1647 cm-1 can be attributed to C=O stretching. The peaks at 1223 and 1387 cm-1 are corresponded to the vibrations of N–H–O of PVP molecule. The shift and decrease in signal intensity related to N-H or C=O stretching show the adsorption of PVP molecules on the surface of NPs [21]. Next, TGA study was also performed to estimate the stability of synthesized AgNPs/PVP. Fig. 2(c) shows the TGA curve of AgNPs/PVP where weight loss of PVP stabilizing agent against the temperature from 25 to 600 oC. The weight loss of substance could be observed as the temperature increased from 50 to 155 oC and then remained constant up to 190 oC and after that there was a gradual decrease in weight up to 550 oC. The weight loss with
10
increase of temperature is due to the evaporation or thermal decomposition of stabilizing agents or solvent molecules from the surface of AgNPs [20, 21]. Fig. 3(a) shows the paper electrode with silver nano-ink which exhibited no change in conductivity after multiple folding. This is confirmed by the measurement of resistance of folded paper after the sintering process, as shown in Fig. 3(b). The paper electrode shows the low value of resistance that would be preferable to use as electrodes in electrochemical analysis. 1.0 cm length of paper electrode was used to measure the resistance of printed materials during the optimization of sintering temperature and sintering time process. Further, we demonstrated the lighting of LED bulb using 9 V battery to observe the continuity of prepared electrode for flow of current, shown in Fig. 3(c). The gloving of LED bulb demonstrated that the flexible paper electrode could be used as electrodes in electrochemical analyses. 3.2. Formulation of stable silver nano-ink The basic requirements for preparation of metal NPs based ink are similar to that of preparation of standard ink for inkjet printers. The ink should have properties of better compatibility with substrate materials, better conductivity, and minimum printer maintenance. These are achieved through the optimization of different parameters, such as selection of organic solvents, concentration of NPs, and choice of paper substrates to obtain the better conductivity. In formulation of nano-ink, the selection of solvents, NPs concentrations and addition of stabilizing agents are considered for effective dispersion of particles to get a stable ink that should not be aggregated and precipitated after a long time of storage and should give a reproducible performance [10,11,13]. The stability of nano-ink was obtained by optimizing the physical properties such as surface tension and viscosity. Different types of organic solvents from non-polar, mid polar, and polar solvents such as hexane, toluene, chloroform, ethylene glycol, ethanol, and propanol were chosen to formulate the silver nano-ink. The well dispersion of NPs was found in ethanol and ethylene glycol. Other
11
solvents such as hexane, toluene and chloroform did not show the better dispersion of silver NPs. The reason for forming a stable ink with ethanol and ethylene glycol is due to the presence of polar functional groups on the PVP molecule capped on AgNPs [20,21]. Next, the formulated ink was tested for fabrication on paper substrate using thermal inkjet printer. The better printing pattern was obtained with nano-ink prepared in ethanol. On contrary, the ink with ethylene glycol showed blocking of cartridges after a few numbers of printing. Further, the formulation was done with ethanol as an organic solvent for preparation of silver nano-ink. Polavarapu et al. prepared silver nano-ink (3%) in ethanol and demonstrated for fabrication on glass and plastic substrate for preparation of solar cells and flexible electronics [17]. Thus, ethanol was selected as a solvent for preparation of silver nano-ink for further studies. The concentration of NPs, surface tension and viscosity that decides the formation of appropriate drop size and drop placement from printer nozzle head are investigated. This resulted in the better wetting and adhesion to solid substrates for obtaining the better conductivity [10,11]. For this different concentration of silver ink from 0.5 to 7% was prepared in ethanol and their respective surface tension and viscosity were measured using tensiometer and viscosity meter, respectively. The results are given in Table S1. The resistance of different concentration of NPs that printed on paper substrate was determined with multimeter to identify the best performing ink. The surface tension of the ink was found to decrease with increasing the concentration of NPs to 7.0%. However, the surface tension of 21.1 mN/M was found sufficient to get the better printing pattern on paper substrate. Consequently, there was decrease in the resistance as the concentration of NPs increased to 3.0% and after that no significant change in the value was observed. Similarly, the viscosity for different concentrations of AgNPs in ethanol was also investigated. In this case, there was an increase in the viscosity as the concentration of NPs increased from 0.5 to 7.0% and the better printing on paper substrate was obtained when the viscosity was 2.6 mPa.S. In addition, the optimum conductivity was obtained at this value of
12
viscosity. In the literatures, it is mentioned that the thermal printer head requires viscosity below 3 mPa.S and surface tension should be in the given range (21.1 mN/M) when ethanol is used as a dispersing solvent [22-24]. Thus, the surface tension (21.1 mN/M), concentration of NPs (3%), and viscosity (2.6 mPa.S) of silver nano-ink was kept constant for further fabrication of paper electrodes. Finally, the stability of the silver nano-ink was studied by monitoring the LSPR absorption band of AgNPs/PVA for a period of 2 months (60 days) using UV-Vis. The result is shown in Fig. S1. The repeatability of the results was obtained when the AgNPs capped with PVP for 60 consecutive days showing the high stability of formulated silver nano-ink. 3.3. Optimization of paper substrates for printing silver nano-ink Further, different paper substrates such as photo paper, normal printing paper, bond paper, and butter paper were fabricated with 3% silver nano-ink to find a better substrate that would be used as an electrode. For this, paper electrode of 7 × 0.4 cm with bottom area of 1 cm2 was printed with nano-ink on different paper substrates and the resistance of paper electrode was recorded after sintering at 100 oC for 30 min. Figs. S2(a) to S2(d) show optical images (with smart phone) of fabricated electrode with nano-ink on different paper substrates. Among these, electrode printed on photo paper showed the lowest value of resistance compared to other paper substrates. This is due to the homogenous and thin coating of NPs on photo paper compared to normal paper, bond paper, and butter paper. The coating of NPs on different substrates was also verified by recording the images using optical microscope, shown in Fig. S2(a’) toS2(d’). In the previous works, we also demonstrated the better conductivity of nano-ink on photo paper because of smooth surface, fine pore size and moderate absorption of the NPs within the photo paper [13,18]. Therefore, photo paper was utilized for fabricating nano-ink to prepare a paper electrode for electrochemical investigations. 3.4. Optimization of sintering temperature and sintering time of printed paper substrate
13
The optimization of sintering temperature and sintering time is also necessary in order to get high conductivity of printed electrode with nano-ink for electrochemical and electronic applications [10-13]. As the silver nano-ink was stabilized with organic stabilizing agent (PVP) and formulated in ethanol as an organic solvent, the presence of PVP on NPs surface acts as an insulating agent to prevent the formation of continuous interconnected particles and results in the low electrical conductivity on paper substrate. The problem of low conductivity of NPs was overcome by sintering the printed substrate at particular temperature and time in oven. Sintering is a process where the capping agents and solvent in between the NPs evaporates and particles get close to interconnect together to form a continuous conductive layer. There are several methods of sintering that achieved by exposure of heat (thermal sintering), intense light irradiation (photonic sintering), microwave radiation, plasma, etc [13,25,26]. Here, we used the thermal sintering method in which the printed substrates were heated at different temperatures for various time intervals. The stability and conductivity of paper electrode was tested by changing the sintering temperature from 20 to 160 oC for 30 min of sintering time. The results are shown in Fig. S3(a). The lowest resistance of the printed electrode was obtained when sintering temperature was 100 oC. At this temperature most of the NPs interconnected with each other and showed the lowest value of resistance and the temperature above 100 oC caused the increase in resistance value because of the removal of carbonaceous material from the surface of paper. The similar results were obtained in other literatures [13,18]. Next, different sintering time also affect the conductivity and stability of paper electrode, conductivity was tested by heating the fabricated paper substrate at 100 oC for different time interval of 0, 15, 30, 45, 60, and 75 min to obtain better paper-based electrode. The results are given in Fig. S3(b). The lowest resistance was acquired when the sintering time was 30 min and further increase in sintering time could cause the increase in resistance value. The increase in the resistance value after 30 min of sintering time is due the degradation of paper substrate. Thus,
14
30 min of sintering time and 100 oC of sintering temperature were found satisfactory for preparation of efficient paper-based electrode for electrochemical applications. 3.5. Electrochemical applications of printed paper based electrodes Here, the printed paper electrode was exploited as counter and working electrodes for measurement of electrical current of 0.1 M K3 Fe (CN)6 solution containing 1.0 M KCl as a supporting electrolyte. Firstly, we used the paper electrode as a counter electrode and commercially available Ag/AgCl and copper were used as counter and working electrodes, respectively. The CV measurements were performed by sweeping the potential from 1.0 to -1.0 V at the scan rate of 0.1 V/s. The result is shown in Fig. 4(a). The curve showed an anodic peak when the potential was varied from -1.0 to 1.0 (forward scan) and the maximum current was obtained when the applied potential was +0.2 V. This is due to the oxidation of Fe(CN)64- to Fe(CN)63- when the electrode become strong oxidant. A cathodic peak was observed during the backward scan from 1.0 to -1.0 V which is due the reduction of Fe(CN)63- to Fe(CN)64- and maximum reduction current was obtained when the potential was -0.1 V. Next, the result obtained above was compared by performing CV analysis with commercially available electrodes, i.e. platinum, Ag/AgCl and copper as counter, reference and working electrodes, respectively at constant experimental conditions, shown in Fig. 4(b). We obtained the similar results as obtained when printed electrode was used as a counter electrode. Finally, printed paper electrode was used as a working electrode for analysis of 0.1 M K3 Fe(CN)6 and keeping the platinum and Ag/AgCl as counter and reference electrodes, respectively. However, unusual oxidation and reduction peak as well as shift in potentials were observed during the use of paper electrode as a working electrode. This could be due to the electrocatalytic nature of AgNPs towards the reduction of K3 (Fe(CN)6 . The result is given in Fig S4. Hence, the printed paper electrode with silver nano-ink could be used as counter electrode for electrochemical determination in CV analysis [27].
15
3.6. Stability of paper electrode in CV analyses The stability of the printed paper electrode was tested by 60 CV cycles in 0.1 M K3 Fe(CN)6 solution. Fig. 5(a) and 5(b) show the oxidation and reduction peaks when printed paper with AgNPs was used as a counter electrode. The number of analyses (n=60) in CV helped to determine the stability as well as the reproducibility in terms of the relative standard deviation percentage (RSD, %). The RSD for oxidation current was ±1.5% and reduction current was ±1.2% when used as a counter electrode. Thus, the obtained low RSD values when paper electrode was used as a counter electrode demonstrates the better stability and repeatability of the results with high precision. 3.7. Application of paper electrode for analysis of nitrate Nitrate (NO3)- is an essential micro nutrient for animals and plants. It exists in food and water samples and responsible for proper growth through the nitrogen fixation and protein synthesis. Spectrophotometric [28,29] and fluorometric
[30] methods are commonly used for
determination of nitrate in variety of samples. In these methods, chromophoric and fluorophoric reagents are used to form the colored and fluorescence complex with target analyte; and then absorption and fluorescence signal intensity were measured with respective methods. Sometimes, chromophoric and fluorophoric reagents react with other chemical substances present in sample and interfere in the determination of target analyte. On the other hand, CV is a simple and selective technique for analysis of nitrate in different types of samples [31,32]. Here, the use of paper electrode (as a working electrode) is illustrated for measurement of nitrate while keeping the conventional platinum and Ag/AgCl as counter and reference electrodes, respectively with a scan rate of 0.1 V/s. The result is shown in Fig. 6(a). There was no any oxidation/reduction peak in the absence of nitrate; however, a reduction peak was observed when the fabricated electrode was used as a working electrode. This is due to the reduction of nitrate ions on the surface of AgNPs. Based on this result, different concentration of nitrate was spiked in water and the CV
16
curves were recorded keeping another parameters constant (Fig. 6(b)). The proposed analytical method exhibited a good linearity over the range of 60 μM to 1000 μM with a correlation coefficient of 0.993, shown in Fig 6(c). The mechanism for detection of nitrate using silver electrode was illustrated somewhere in the literatures [33-35]. The increase in nitrate ions in sample solution increases the reduction current. Thus, the paper electrode was effectively presented for determination of nitrate present in water samples. The mechanical flexibility of the paper electrode was also evaluated by bending the paper electrode at different angles (15o, 30o and 45o) and the CV measurements were performed for analysis of 0.1 mM KNO3 at scan rate of 0.1 Vs-1. The result is given in Table S5. The obtained results showed that there was no significance change in the CV curves after bending at different angles. This demonstrated the application of flexible paper electrode for determination of nitrate in sample solution. 3.8. Comparison for preparation of stable silver nano-ink and conductive materials for preparation of printed paper electrode Table 1 presents the comparison of capping agent, % of NPs, substrate, fabrication technique, sintering temperature, viscosity, resistivity and viscosity for the preparation of conductive materials [7,13,17,36-42]. The lower % of AgNPs was used in the present work for the fabrication of paper electrode compared to other approaches. Most of the methods use the polymeric material, silicon, and glass substrates for the fabrication of NPs for electronic and electrochemical applications. In addition, the resistivity of the printed paper electrode was found to be less than the most of the fabricated substrates. Thus, the use of low % AgNPs, sintering temperature, and resistivity demonstrated the effectiveness of the printed electrode for electrochemical applications comparison with other reported methods.
17
4. Conclusions In summary, the stable silver nano-ink was prepared in ethanol and used for fabrication on photo paper substrate using desktop inkjet office printer. The paper electrode was successfully exploited as counter electrode for analysis of K3Fe(CN)6 in CV with high reproducibility for multiple analyses. In addition, we also demonstrated the use of printed paper as a working electrode for the determination of nitrate. The advantages of present method are simple, low cost, flexible and user-friendly fabrication procedure compared to commercially available electrodes. In addition, low concentration of silver nano-ink (3%) was used for the electrode fabrication. In near future, the paper based printed electrodes can be used for the determination of nitrate in various real samples. Contribution of work by different authors Tushar Kant: Performed experimental works Kamlesh Shrivas: Writing and Experimental design of the manuscript Vellaichamy Ganesan: Editing of the manuscript Yugal Kishor Mahipal: XRD and FTIR measurements Rama Devi: TEM and UV-Vis measurements Manas Kanti Deb: Interpretation of the data analytical results Ravi Shankar: Interpretation of cyclic voltammetric results
Declaration of interests: None
☐ We declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
18
Acknowledgement We would like to thank the Science and Engineering Research Board (SERB), New Delhi for awarding Kamlesh Shrivas an Extra Mural Research Project (File No : EMR/2016/005813). We also thank Council of Scientific & Industrial Research (CSIR, New Delhi) for providing financial support (09/266(0078)/2017-EMR-I) to Tushar Kant in the form of junior research fellowship (JRF).
References [1]
Q. Guo, X. Teng, S. Rahman, H. Yang, Patterned Langmuir-Blodgett Films of Monodisperse nanoparticles of iron oxide using soft lithography, J. Am. Chem. Soc. 125 (2003) 630−631.
[2]
F. Iacopi, P. M. Vereecken, M. Schaekers, M. Caymax, N. Moelans, B. Blanpain, O. Richard, C. Detavernier, H. Griffiths, Plasma-enhanced chemical vapour deposition growth of si nanowires with low melting point metal catalysts: an effective alternative to au-mediated growth, Nanotechnology 18 (2007) 505307.
[3]
Y. C. Liao, Z. K. Kao, Direct writing patterns for electroless plated copper thin film on plastic substrates, ACS Appl. Mater. Interfaces 4 (2012) 5109−5113.
[4]
H. Jia, J. Wang, X. Zhang, Y. Wang, Pen-writing polypyrrole arrays on paper for versatile cheap sensors, ACS Macro Lett. 3 (2014) 86−90.
[5]
M. D. Dankoco, G.Y. Tesfay, E. Benevent, M. Bendahan, Ttemperature sensor realized by inkjet printing process on flexible substrate, Mater. Sci. Eng. B 205 (2016) 1–5.
[6]
S. Liu, X. Wu, D. Zhang, C. Guo, P. Wang, W. Hu, X. Li, X. Zhou, H. Xu, C. Luo, J. Zhang, J. Chu, Ultrafast dynamic pressure sensors based on graphene hybrid structure, ACS Appl. Mater. Interfaces 9 (2017) 24148−24154.
19
[7]
W. J. Hyun, S. Lim, B. Y. Ahn, J. A. Lewis, C. D. Frisbie, L. F. Francis, Screen printing of highly loaded silver inks on plastic substrates using silicon stencils, ACS Appl. Mater. Interfaces 7 (2015) 12619−12624.
[8]
S. Ge, L. Ge, M. Yan, X. Song, J. Yu, J. Huang, A disposable paper-based electrochemical sensor with an addressable electrode array for cancer screening, Chem. Commun. 48 (2012) 9397–9399.
[9]
A. W. Martinez, S. T. Phillips, M. J. Butte, G. M. Whitesides, Patterned paper as a platform for inexpensive, low-volume, portable bioassays, Angew. Chem. Int. Ed. 46 (2007) 1318 –1320.
[10]
R. Shankar, A. Amert, J. J. Kellar, K. W. Whites, Rheological optimization and stability study of silver nano-ink for inkjet printing of solar electrodes using industrial printhead, NSTI-Nanotech. 3 (2012) 611−614.
[11]
K. Black, J. Singh, D. Mehta, S. Sung, C. J. Sutcliffe, P. R. Chalker, Silver ink formulations for sinter free printing of conductive films, Sci. Rep. 6 (2016) 1-7.
[12]
S. Jeong, H. C. Song, W. W. Lee, S. S. Lee, Y. Choi, W. Son, E. D. Kim, C. H. Paik, S. H. Oh, B. H. Ryu, Stable aqueous based cu nanoparticle ink for printing welldefined highly conductive features on a plastic substrate, Langmuir 27 (2011) 3144– 3149.
[13]
A. Ghosale, R. Shankar, V. Ganesan, K. Shrivas, Direct-writing of paper based conductive track using silver nano-ink for electroanalytical application, Electrochim. Acta 209 (2016) 511–520.
[14]
R. Z. Li, A. Hu, T. Zhang, K. D. Oakes, Direct writing on paper of foldable capacitive touch pads with silver nanowire inks, ACS Appl. Mater. Interfaces 6 (2014) 21721−21729.
[15]
J.-S. Ye, Y. Wen, W. D. Zhang, L. M. Gan, G. Q. Xu, F. –S. Sheu, Nonenzymatic
20
glucose detection using multi-walled carbon nanotube electrodes, Electrochem. 6 (2004) 66−70. [16]
S. Rahim, A. Rauf, S. Rauf, M. R. Shah, M. I. Malik, Enhanced electrochemical response of a modified glassy carbon electrode by poly(2-vinlypyridine-b-methyl methacrylate) conjugated gold nanoparticles for detection of nicotine, RSC Adv. 8 (2018) 35776−35786 .
[17]
L. Polavarapu, K. K. Manga, H. D. Cao. K. P. Loh, Q.-H. Xu, Preparation of conductive silver films at mild temperatures for printable organic electronics, Chem. Mater. 23 (2011) 3273−3276.
[18]
A. Ghosale, K. Shrivas, R. Shankar, And V. Ganesan, Low cost paper electrode fabricated by direct writing with silver nanoparticles based ink for detection of hydrogen peroxide in waste water, Anal. Chem. 89 (2017) 776−782.
[19]
A. Ghosale, K. Shrivas, M. K. Deb, V. Ganesan, I. Karbhal, P. K. Bajpai, R. Shankar, a low-cost screen-printed glass electrode with silver nano-ink for electrochemical detection of H2O2, Anal. Methods 10 (2018) 3248−3255.
[20]
A. Mirzaei, K. Janghorban, B. Hashemi, M. Bonyani, S. G. Leonardi, G. Neri, Characterization and optical studies of pvp-capped silver nanoparticles, J. Nanostruct. Chem. 7 (2017) 37–46.
[21]
M. Kumar, P. Devi, A. Kumar, Structural analysis of pvp capped silver nanoparticles synthesized at room temperature for optical, electrical and gas sensing properties, J. Mater Sci: Mater Electron. 28 (2017) 5014–5020.
[22]
A. Kamyshny, J. Steinke, S. Magdassi, Metal-based inkjet inks for printed electronics, Open J. Appl. Phys. 4 (2011) 19−36.
[23]
M. M. Nir, D. Zamir, I. Haymov, Electrically conductive inks for inkjet printing. in: magdassi s, ed. the chemistry of inkjet inks. New Jersey-London-Singapore: World
21
Scientific 2010, PpP. 225−54. [24]
P. Calvert, Inkjet printing for materials and devices, Chem. Mater. 13 (2001) 3299−3305.
[55]
D.Q. Vo, E.W. Shin, J.S. Kim, S. Kim, Low-temperature preparation of highly conductive thin films from acrylic acid-stabilized silver nanoparticles prepared through ligand exchange, Langmuir 26 (2010) 17435–17443.
[26]
I. Jung, K. Shin, N.R. Kim, H.M. Lee, Synthesis of low-temperature-processable and highly conductive ag ink by a simple ligand modification: the role of adsorption energy, J. Mater. Chem. C 1 (2013) 1855–1862.
[27]
A. C. Sun, C. Yao, A. G. Venkatesh, D. A. Hall, An efficient power harvesting mobile phone-based electrochemical biosensor for point-of-care health monitoring, Sens. Actuators B 235 (2016) 126–135.
[28]
R. C. Jagessar, L. Sooknundun, Determination of nitrate ion in waste water from nine selected areas of coastal guyana via a spectrophotometric methods, Int. J. Res. Appl. Stud. 7 (2011) 203−212.
[29]
N. Lohumia, S. Gosain, A. Jain, V. K. Gupta, K. K. Verma, Determination of nitrate in environmental water samples by conversion into nitrophenols and solid phase extraction−spectrophotometry, liquid chromatography or gas chromatography–mass spectrometry, Anal. Chim. Acta 505 (2004) 231–237.
[30]
J.-S. Li, H. Wang, X. Zhang, H.-S. Zhang, Spectrofluorimetric determination of total amount of nitrite and nitrate in biological sample with a new fluorescent probe 1,3,5,7Tetramethyl-8-(3,4-Diaminophenyl)-Difluoroboradiazas-Indacence, Talanta 61 (2003) 797−802.
[31]
S. M. Shariar, T. Hinoue, Simultaneous voltammetric determination of nitrate and nitrite ions using a copper electrode pretreated by dissolution/redeposition, Anal. Sci.
22
26 (2010) 1173−1179. [32]
M. Shivakumar, K. L. Nagashree, S. Manjappa, M. S. Dharmaprakash, Electrochemical detection of nitrite using glassy carbon electrode modified with silver nanospheres (agns) obtained by green synthesis using pre-hydrolysed Liquor, Electroanalysis 29 (2017) 1–10
[33]
S. Dhanya, V. Saumya, T. P. Rao, Synthesis of silver nanoclusters, characterization and application to trace level sensing of nitrate in aqueous media, Electrochim. Acta 102 (2013) 299–305.
[34]
J. Krista, M. Kopanica, L. Novotony, Voltammetric determination of nitratesusing silver electrodes, Electroanalysis 12 (2000) 199–204.
[35]
D. Kim, I.B. Goldberg, J.W. Judy, Chronocoulometric determination of nitrate on silver electrode and sodium hydroxide electrolyte, Analyst 132 (2007) 350–357.
[36]
M. Vaseem, K. M. Lee, A. Hong, Y.-B. Hahn, Inkjet printed fractal-connected electrodes with silver nanoparticle ink, ACS Appl. Mater. Interfaces 4 (2012) 3300−3307.
[37]
R. Shankar, L. Groven, A. Amert, K. W. Whites, J. J. Kellar, Non-aqueous synthesis of silver nanoparticles using tin acetate as a reducing agent for the conductive ink formulation in printed electronics, J. Mater. Chem. 21 (2011) 10871−10877
[38]
I.-K. Shim, Y. Lee, K. J. Lee, J. Joung, An organometallic route to highly monodispersed silver nanoparticles and their application to ink-jet printing, Chem. Phys. 110 (2008) 316–321
[39]
K. Balantrapu, D. V. Goia, Silver nanoparticles for printable electronics and biological applications. J. Mater. Res. 24 (2009) 2828−2836
[40]
Q. Huang, Y. Zhu, Gravure Printing of water-based silver nanowire ink on plastic substrate for flexible electronics, Sci. Rep. 8 (2018) 15167.
23
[41]
H. H. Lee, K. S. Chou, K. C. Huang, Inkjet printing of nanosized silver colloids, Nanotechnology 16 (2005) 2436–2441
[42]
S. B. Walker, J. A. Lewis, Reactive silver inks for patterning high-conductivity features at mild temperatures, J. Am. Chem. Soc. 134 (2012) 419−1421
24
Scheme 1. Schematic presentations: (a) synthesis of silver nano-ink, (b) formulation of silver nano-ink, (c) fabrication of nano-ink on paper substrate using inkjet printer, (d) printed electrodes, (e) sintering of electrode, (f) application of prepared electrode in CV measurements, and (g) CV responses
25
(a)
(b)
(c)
20 nm
5 nm
(d)
(e)
Fig. 1. (a) UV-Vis spectra of AgNPs/PVA, (b) TEM image of AgNPs/PVA, (c) Enlarged view of AgNPs/PVA, (d) EDX of AgNPs/PVA, and (e) DLS measurement showing the size distribution of AgNPs/PVA
26
(a)
(b)
(c)
Fig. 2. (a) XRD patterns of AgNPs/PVP, (b) FTIR spectra of pure PVP and AgNPs/PVP, and (c) TGA curve of AgNPs/PVP.
27
(a)
(b)
(c)
Fig. 3. (a) Flexible printed electrodes on photo paper with silver nano-ink, (b) measurement of resistance on paper electrode using multimeter, and (c) lighting of LED bulb showing the conductivity of printed material on paper substrate.
28
(a)
(b)
Fig. 4. (a) CV measurements of 0.1 M K3 (Fe(CN)6 + 1.0 M KCl when printed paper electrode was used as a counter electrode while conventional Ag/AgCl and copper were used as reference and working and electrodes, respectively with 0.1 V/s scan rate (b) CV measurements of 0.1 M K3 (Fe(CN)6 + 1.0 M KCl when conventional platinum, Ag/AgCl and copper as counter, reference and working electrodes, respectively with 0.1 V/s of scan rate.
29
(a)
(b)
Fig. 5. (a) 60 continuous CV cycles of 0.1 M K3 Fe(CN)6 when paper electrode was used as a counter electrode and Ag/AgCl and copper electrodes were used as reference and working electrodes, respectively in the presence of KCl with a scan rate of 0.1 V/s and (b) 60 continuous CV cycles of 0.1 M K3 Fe(CN)6 when conventional Ag/AgCl, platinum and copper were used as reference, counter and working electrodes, respectively in the presence of KCl with a scan rate of 0.1 V/s.
30
(a)
(b)
(c)
Fig. 6. CV analyses of 0.1 mM KNO3 when printed paper electrode was used as a working electrode in the presence of 1.0 M NaH2PO4 at scan rate of 0.1 Vs-1 while platinum and Ag/AgCl electrodes were used as counter and reference electrodes, respectively; (b) CV measurements of different concentration KNO3 from 60 μM to 1000 μM when printed paper electrode was used as a
31
working electrode while platinum and Ag/AgCl were used as counter and reference electrodes, respectively with 0.1 V/s scan rate and (c) Calibration curve for determination of nitrate in water.
32
Table 1. Comparison of capping agent, % of NPs, substrate, fabrication technique, sintering temperature, viscosity, resistivity and viscosity of conductive materials Capping Agent
Reducin
NPs, %
Substrate
g agent
Fabrication Sintering technique
Resistivity Surface O
(Temp in C)
−5
(10 Ωcm) tension
Viscosity
Ref.
(mPa.s)
(mN/M) PVP
NaBH4
3
PET
Inkjet
50
∼0.5
-
-
17
printing PVP
Ethylen
10
Si/SiO2
Printing
200
∼1
∼40.7
5.47
36
12
Paper
Ball Pen
150
∼8.8
-
-
13
300
-
-
1–2
37
400
-
∼12
∼12
38
200
∼0.5
-
∼10
7
125
∼7.42
-
-
39
150
-
∼28.8
-
40
260
∼0.3
∼33.5
7.4
41
90
-
-
2
42
100
0.4
21.1
2.6
Present
e glycol Oleyl
Ascorbi
amine
c acid
Dodecyl
Tin
amine
acetate
PVP
PVP
20
Polymer
printing Inkjet
wafer
printing
Polyimid
Screen
e film
printing
Polymeri
Inkjet
ne
c
printing
hydrate
substrate
Diethan
(acrylic
ol
acid)
amine
Gum
hydrazi
Ethylen
20
77
20
5
PET
e glycol
Formald
Aerosol-jet
Silicon
Poly
PVP
writing
PVP
Inkjet printing
25
Glass
ehyde
Inkjet printing
Formic
Fluoro
Acid
polymer
PVP
NaBH4
22
Silicon
Inkjet printing
3
Paper
Inkjet printing
work
Flexible printed paper electrode with silver nano-ink for electrochemical applications Tushar Kant , Kamlesh Shrivas , Vellaichamy Ganesan , Yugal Kishor Mahipal , Rama Devi , Manas Kanti Deb , Ravi Shankar PII: DOI: Reference:
S0026-265X(19)33187-X https://doi.org/10.1016/j.microc.2020.104687 MICROC 104687
To appear in:
Microchemical Journal
Received date: Revised date: Accepted date:
8 November 2019 11 January 2020 2 February 2020
Please cite this article as: Tushar Kant , Kamlesh Shrivas , Vellaichamy Ganesan , Yugal Kishor Mahipal , Rama Devi , Manas Kanti Deb , Ravi Shankar , Flexible printed paper electrode with silver nano-ink for electrochemical applications, Microchemical Journal (2020), doi: https://doi.org/10.1016/j.microc.2020.104687
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier B.V.
1
Highlights
Development of low-cost paper based disposable printed electrodes with silver nano-ink using desktop inkjet printer
Fabricated paper electrode exploited as a counter electrode in cyclic voltammetry (CV) analysis
Printed paper electrode is demonstrated to used as a working electrode for analysis of nitrate in CV
2
Flexible printed paper electrode with silver nano-ink for electrochemical applications Tushar Kant1, Kamlesh Shrivas1*, Vellaichamy Ganesan2, Yugal Kishor Mahipal 3, Rama Devi4, Manas Kanti Deb1 and Ravi Shankar5
1
School of Studies in Chemistry, Pt. Ravishanakar Shukla University, Raipur-492010, CG, India 2
Department of Chemistry, Institute of Science, Banaras Hindu University, Varanasi221005, UP, India
3
School of Studies in Physics and Astrophysics, Pt. Ravishanakar Shukla University, Raipur-492010, CG, India
4
Department of Chemistry, National Institute of Technology, Raipur-492010, CG, India 5
Nanoscience and Nanoengineering Program, South Dakota School of Mines and Technology, Rapid City, South Dakota-57701, USA
*Corresponding author Email: [email protected]
3
ABSTRACT Development of low-cost paper based disposable electrodes printed with silver nano-ink using desktop inkjet printer is reported in this work. A stable nano-ink was prepared by dissolving 3% silver nanoparticles (AgNPs) capped with polyvinylpyrrolidone (PVP) in ethanol as a dispersing solvent. Highly stable silver nano-ink with surface tension of 21.1 mN/M and viscosity of 2.6 mPa.S was prepared for printing on photo paper that can be used as an electrode for electrochemical analyses. The fabricated paper electrode was exploited as a counter electrode in cyclic voltammetry (CV) analysis of potassium ferricyanide with better stability and reproducibility (relative standard deviation (RSD) 1.6%) for multiple times of analyses (n=60) and compared with the results of conventional electrodes. Further, the printed paper electrode was demonstrated to be used as a working electrode for analysis of nitrate by CV. The use of paper electrode is found to be simple, rapid, user-friendly and can be applied at the sample source for determination of nitrate from different samples.
Keywords: Inkjet Printing, Flexible Paper Electrodes, Nano-Ink, Cyclic Voltammetric Analyses
4
1. Introduction There is always increasing demand for more facile and cost-effective route to prepare the electronic devices that should be flexible, eco-friendly, light weight and disposable. The attention has been drawn in the direction of preparation of flexible printed electronics using metal nanoparticles (NPs) based conductive nano-inks. Recently, different techniques including physical lithography, sputtering, chemical vapor deposition and spin coating have been demonstrated for fabrication of conducting inks on solid surfaces to prepare electronic devices [1-2]. These techniques provide a homogenous and smooth deposition of functional materials on solid surface, but they need controlled temperature and contaminant free environment which are found to be expensive and difficult to maintain. Screen printing is also used for large scale production of electronic devices where mesh is used to fabricate the substrate, which is time consuming and tedious process. To overcome these disadvantages, the improvement of useful and low-cost processing technique is needed to fabricate the conductive materials. There are other alternative simple and low-cost techniques available for fabrication of nanomaterials on solid substrates such as direct writing, roller ball pen, sketching and brush painting [3,4]. The drawbacks of these techniques are formation of non-uniform layer of fabricated materials on solid substrate. Recently, inkjet printing has wide application due to its low cost, rapidity and simplicity in printing the designed digital file. In inkjet printing, the head ejects a very small quantity of ink on to the substrate based on the design of fabrication. Inkjet printing is considered to be an efficient and highly well-designed technique for micro scale patterning of metallic nanomaterial’s [5]. Flexible circuit and printed electronic devices are produced by deposition of single or multiple layers of active materials like conductive inks or dielectric inks onto the solid substrates such as plastic, glass, polymers, ceramics, etc [6,7]. The devices made from theses substrates are expensive as well as after the use it is non-biodegradable into the environment. The research and
5
development should always need to decrease the electronic waste as well as it should be biodegradable, flexible and harmless to human beings. Paper substrate is being a better substitute in place of plastics because it is eco-friendly, inexpensive, flexible and sustainable [8]. Paper based devices have been emerging as a recent trend in developing new analytical devices for wide range of applications in the fields such as clinical, food and environmental monitoring [9]. Paper is also compatible to fabricate the conducting metal NPs because of limited penetration of particles onto the porous substrate [10]. Thus, paper substrate is found to be better material to print the silver nano-ink for preparation of electrode for electrochemical applications. Recently, metal NPs like silver (Ag) and copper (Cu) are commonly used as nano-ink due to their high conductivity, high stability and low cost that make the material for commercialization in the market. The decrease in size of particles to few nanometers results in the fall of their melting point and sintering process helps in the formation of a dense layer of NPs on the solid surface. For such reasons, noble metals have been widely used for the synthesis of conducting ink [11]. CuNPs is frequently used to prepare conducting ink due to its high conductivity and being inexpensive as compared to noble metals. But it has a disadvantage of easy oxidation which causes the loss of its conductivity [12]. However, AgNPs, because of its better conductivity and stability than Cu and low cost compared with Pt or Au can be considered as a best choice. Recently, we demonstrated the fabrication of silver nano-ink on paper substrates using direct writing with ball point pen and used for electrochemical determination and lighting of LED bulb [13]. There are many reports that illustrated the use of silver nano-ink for fabrication of conductive track, electronic devices such as touch pads, solar cells, radio frequency identification tag (RFID), etc. Thus, the use of silver nano-ink will be a better alternative for fabrication on paper substrate which can be exploited in the field of analytical chemistry for electrochemical analyses [14].
6
Electrochemical analysis is powerful analytical technique for qualitative and quantitative determination of inorganic and organic components based on the measurement of current against the applied potential. In the electrochemical determinations, three electrode systems are generally used. These conventional electrodes have many drawbacks like fragile, expensive and toxic to human health as well as non-biodegradable in the environment. Chemically modified electrodes have been frequently used as working electrodes in electrochemical analysis due to their high sensitivity and excellent selectivity. To date, several modified electrodes have been developed for the determination of several analytes includes multi-walled carbon nanotubes electrode [15], modified glassy carbon electrode [16] and metal NPs electrodes [10, 13]. Among these, metal NPs are found to be the greater choice for preparation of electrode material due to its better sensitivity for detection of variety of analytes. Here, the synthesis of AgNPs, nano-ink formulation, optimization of different substrates, sintering process to prepare conductive track and preparation of paper electrode for electrochemical application were demonstrated. UV-Vis, transmission electron microscope (TEM), dynamic light scattering (DLS), and X-ray diffraction (XRD) are used to determine the size, shape, and purity of silver nano-ink; Fourier-transform infra-red (FTIR) spectroscopy and thermogravimetric analysis (TGA) were applied for estimation of surface modification and stability of nano-ink at particular temperature. The printed paper electrode with silver nano-ink is demonstrated to be used as counter and working electrodes for electrochemical applications for analysis of potassium ferricyanide, nitrate.
2. Experimental Section 2.1. Chemicals and reagents All the chemicals used were of analytical reagent (AR) grade. Silver nitrate (99.9%), polyvinyl pyrrolidone (PVP, molecular weight >40,000 Da), sodium borohydride (98.0%), potassium nitrate (99.0%), potassium ferricyanide (98.0%), potassium chloride (99.5%), and ethanol
7
(99.0%) were purchased from Himedia ((Mumbai, India). Triply distilled water was used for the preparation of standard solutions and for the cyclic voltammetry (CV) analysis. 2.2. Synthesis of AgNPs/PVP AgNPs modified with PVP were prepared from silver nitrate in water using NaBH4 as a reducing agent [17]. In brief, 0.5 g of AgNO3 and 0.5 g of PVP were dissolved in 100 mL water under vigorous stirring till the formation of clear solution and then 10 mL of freshly prepared 0.25 M NaBH4 was added to the solution mixture. The color of the solution changed from colorless to dark yellow. The resultant solution was centrifuged at 6,000 rpm to remove excess PVP or any impurities. The precipitate obtained was washed several times with acetone to remove any impurity from the product. Then it was dried at room temperature followed by the preparation of conducting ink in ethanol as shown in scheme 1(a). 2.3. Preparation of silver nano-ink Different types of organic solvents such as ethanol, methanol, propanol, diethylene glycol, toluene, and water were used for formulation of silver nano-ink. Different concentrations of nano-ink from 2% to 10 % were prepared separately by dissolving an appropriate amount of AgNPs/PVP in different organic solvents in different proportions. The prepared nano-ink was used to print on photo paper using desktop printer as shown in scheme 1(b). 2.4. Printing of paper based electrode with silver nano-ink HP Deskjet-1112 printer was used for the printing of silver nano-ink on different types of paper substrates such as JK photo paper, JK Excel Bond Paper, normal printing paper and Whatman filter paper No.1 as shown in scheme 1(c). The paper electrode of 7.0 cm length and 0.4 cm width with a bottom area of 1 cm2 was printed on different paper substrates as shown in scheme 1(d). The printed electrode was sintered in oven at different temperatures and at different time intervals for obtaining the better conductive materials on the paper substrate (scheme 1e). The
8
printed electrodes were tested for electrochemical analysis in CV, schematically shown in Fig. 1(f) and 1(g). 2.5. Apparatus The size of AgNPs/PVP was preliminarily estimated with UV-Vis spectrophotometer (type Carry 60, Agilent Technologies, USA) by measuring the localized surface plasmon resonance (LSPR) band of AgNPs/PVP. Transmission electron microscopy (TEM) images were recorded (Jeol JEM- 2100, Waitham, MA) at a maximum accelerating voltage of 200 kV was used to determine the size and shape of AgNPs at an accelerating voltage of 100 kV. Fourier transforminfrared spectroscopy (FTIR) of type-nicolet-10 (Thermo Scientific, USA) was used to know the presence of stabilizing molecules (PVP) on the surface of NPs. Thermogravimetric analysis (TGA) (Bruker, Germany) was used to estimate the loss of PVP from the surface of AgNPs in nitrogen gas atmosphere (70 mLmin-1) at the temperance range of 25-600 oC. Malvern Panalytical, XPert3 X-ray diffraction s stem was used to determine the phase crystalline structure of NPs. Digital multimeter (Type-DT830D, Unity, India) was used to determine the resistance of printed paper electrodes. Surface tension instrument- Dyne Master-DY-300 (Kyowa Interface Science Co. Ltd.) and NI RUN Bionics digital rotational viscometer (Model nu: BSTARV10/A) were used to determine the surface tension and viscosity of the formulated nano-ink, respectively.
3. Results and Discussion 3.1. Characterization of AgNPs/PVP The preliminary investigation was done for the preparation of suitable sized AgNPs by monitoring the LSPR band in the wavelength range of 200-800 nm. AgNPs capped with PVP showed the LSPR band around 420 nm confirming the size of NPs was found in the range of 1050 nm [13,18], shown in Fig. 1(a). The size and shape of AgNPs was verified by TEM and the results are shown in Fig. 1(b) and 1(c) where the average size of NPs was 13+2 nm. Next, the
9
composition of NPs was estimated by EDX analysis. Fig. 1(d) shows the EDX spectrum of AgNPs/PVA with presence of intense peak of silver along with other peaks of carbon, nitrogen, and oxygen from the stabilizing agent of AgNPs. In addition, the DLS measurement was performed to know the size distribution of NPs in ethanol and the average size distribution of particles was found to be 13+3 nm, shown in Fig. 1(e). Thus, the data obtained with UV-Vis, TEM and DLS were comparable to each other which confirm the size of NPs. XRD analysis was done to know the idea about the crystallinity and purity of synthesized metal NPs. Fig. 2(a) represents the XRD patterns of AgNPs/PVP containing characteristic diffraction peaks at 38.4, 44.6, 64.7, and 77.8 (2θo) which is allocated to the presence of (111), (200), (220), and (311) planes of cubic structure of silver, respectively. The sharp peak at 38.4 demonstrates the high purity of cubic structure of silver, the broad peak at lower 2θo shows the capping of PVA molecules which are present on the surface of the AgNPs [19,20]. Next, the presence of stabilizing molecules on the surface of NPs was characterized using FTIR. Fig. 2(b) shows the FTIR spectra of pure PVP and PVP modified AgNPs in the wave number range of 800-4000 cm-1. The peak assigned at 3432 cm-1 is due to the N-H stretching of amine group and peak at 2919 cm-1 corresponded to C-H stretching of alkyl group from the stabilizing agent. The signal at 1647 cm-1 can be attributed to C=O stretching. The peaks at 1223 and 1387 cm-1 are corresponded to the vibrations of N–H–O of PVP molecule. The shift and decrease in signal intensity related to N-H or C=O stretching show the adsorption of PVP molecules on the surface of NPs [21]. Next, TGA study was also performed to estimate the stability of synthesized AgNPs/PVP. Fig. 2(c) shows the TGA curve of AgNPs/PVP where weight loss of PVP stabilizing agent against the temperature from 25 to 600 oC. The weight loss of substance could be observed as the temperature increased from 50 to 155 oC and then remained constant up to 190 oC and after that there was a gradual decrease in weight up to 550 oC. The weight loss with
10
increase of temperature is due to the evaporation or thermal decomposition of stabilizing agents or solvent molecules from the surface of AgNPs [20, 21]. Fig. 3(a) shows the paper electrode with silver nano-ink which exhibited no change in conductivity after multiple folding. This is confirmed by the measurement of resistance of folded paper after the sintering process, as shown in Fig. 3(b). The paper electrode shows the low value of resistance that would be preferable to use as electrodes in electrochemical analysis. 1.0 cm length of paper electrode was used to measure the resistance of printed materials during the optimization of sintering temperature and sintering time process. Further, we demonstrated the lighting of LED bulb using 9 V battery to observe the continuity of prepared electrode for flow of current, shown in Fig. 3(c). The gloving of LED bulb demonstrated that the flexible paper electrode could be used as electrodes in electrochemical analyses. 3.2. Formulation of stable silver nano-ink The basic requirements for preparation of metal NPs based ink are similar to that of preparation of standard ink for inkjet printers. The ink should have properties of better compatibility with substrate materials, better conductivity, and minimum printer maintenance. These are achieved through the optimization of different parameters, such as selection of organic solvents, concentration of NPs, and choice of paper substrates to obtain the better conductivity. In formulation of nano-ink, the selection of solvents, NPs concentrations and addition of stabilizing agents are considered for effective dispersion of particles to get a stable ink that should not be aggregated and precipitated after a long time of storage and should give a reproducible performance [10,11,13]. The stability of nano-ink was obtained by optimizing the physical properties such as surface tension and viscosity. Different types of organic solvents from non-polar, mid polar, and polar solvents such as hexane, toluene, chloroform, ethylene glycol, ethanol, and propanol were chosen to formulate the silver nano-ink. The well dispersion of NPs was found in ethanol and ethylene glycol. Other
11
solvents such as hexane, toluene and chloroform did not show the better dispersion of silver NPs. The reason for forming a stable ink with ethanol and ethylene glycol is due to the presence of polar functional groups on the PVP molecule capped on AgNPs [20,21]. Next, the formulated ink was tested for fabrication on paper substrate using thermal inkjet printer. The better printing pattern was obtained with nano-ink prepared in ethanol. On contrary, the ink with ethylene glycol showed blocking of cartridges after a few numbers of printing. Further, the formulation was done with ethanol as an organic solvent for preparation of silver nano-ink. Polavarapu et al. prepared silver nano-ink (3%) in ethanol and demonstrated for fabrication on glass and plastic substrate for preparation of solar cells and flexible electronics [17]. Thus, ethanol was selected as a solvent for preparation of silver nano-ink for further studies. The concentration of NPs, surface tension and viscosity that decides the formation of appropriate drop size and drop placement from printer nozzle head are investigated. This resulted in the better wetting and adhesion to solid substrates for obtaining the better conductivity [10,11]. For this different concentration of silver ink from 0.5 to 7% was prepared in ethanol and their respective surface tension and viscosity were measured using tensiometer and viscosity meter, respectively. The results are given in Table S1. The resistance of different concentration of NPs that printed on paper substrate was determined with multimeter to identify the best performing ink. The surface tension of the ink was found to decrease with increasing the concentration of NPs to 7.0%. However, the surface tension of 21.1 mN/M was found sufficient to get the better printing pattern on paper substrate. Consequently, there was decrease in the resistance as the concentration of NPs increased to 3.0% and after that no significant change in the value was observed. Similarly, the viscosity for different concentrations of AgNPs in ethanol was also investigated. In this case, there was an increase in the viscosity as the concentration of NPs increased from 0.5 to 7.0% and the better printing on paper substrate was obtained when the viscosity was 2.6 mPa.S. In addition, the optimum conductivity was obtained at this value of
12
viscosity. In the literatures, it is mentioned that the thermal printer head requires viscosity below 3 mPa.S and surface tension should be in the given range (21.1 mN/M) when ethanol is used as a dispersing solvent [22-24]. Thus, the surface tension (21.1 mN/M), concentration of NPs (3%), and viscosity (2.6 mPa.S) of silver nano-ink was kept constant for further fabrication of paper electrodes. Finally, the stability of the silver nano-ink was studied by monitoring the LSPR absorption band of AgNPs/PVA for a period of 2 months (60 days) using UV-Vis. The result is shown in Fig. S1. The repeatability of the results was obtained when the AgNPs capped with PVP for 60 consecutive days showing the high stability of formulated silver nano-ink. 3.3. Optimization of paper substrates for printing silver nano-ink Further, different paper substrates such as photo paper, normal printing paper, bond paper, and butter paper were fabricated with 3% silver nano-ink to find a better substrate that would be used as an electrode. For this, paper electrode of 7 × 0.4 cm with bottom area of 1 cm2 was printed with nano-ink on different paper substrates and the resistance of paper electrode was recorded after sintering at 100 oC for 30 min. Figs. S2(a) to S2(d) show optical images (with smart phone) of fabricated electrode with nano-ink on different paper substrates. Among these, electrode printed on photo paper showed the lowest value of resistance compared to other paper substrates. This is due to the homogenous and thin coating of NPs on photo paper compared to normal paper, bond paper, and butter paper. The coating of NPs on different substrates was also verified by recording the images using optical microscope, shown in Fig. S2(a’) toS2(d’). In the previous works, we also demonstrated the better conductivity of nano-ink on photo paper because of smooth surface, fine pore size and moderate absorption of the NPs within the photo paper [13,18]. Therefore, photo paper was utilized for fabricating nano-ink to prepare a paper electrode for electrochemical investigations. 3.4. Optimization of sintering temperature and sintering time of printed paper substrate
13
The optimization of sintering temperature and sintering time is also necessary in order to get high conductivity of printed electrode with nano-ink for electrochemical and electronic applications [10-13]. As the silver nano-ink was stabilized with organic stabilizing agent (PVP) and formulated in ethanol as an organic solvent, the presence of PVP on NPs surface acts as an insulating agent to prevent the formation of continuous interconnected particles and results in the low electrical conductivity on paper substrate. The problem of low conductivity of NPs was overcome by sintering the printed substrate at particular temperature and time in oven. Sintering is a process where the capping agents and solvent in between the NPs evaporates and particles get close to interconnect together to form a continuous conductive layer. There are several methods of sintering that achieved by exposure of heat (thermal sintering), intense light irradiation (photonic sintering), microwave radiation, plasma, etc [13,25,26]. Here, we used the thermal sintering method in which the printed substrates were heated at different temperatures for various time intervals. The stability and conductivity of paper electrode was tested by changing the sintering temperature from 20 to 160 oC for 30 min of sintering time. The results are shown in Fig. S3(a). The lowest resistance of the printed electrode was obtained when sintering temperature was 100 oC. At this temperature most of the NPs interconnected with each other and showed the lowest value of resistance and the temperature above 100 oC caused the increase in resistance value because of the removal of carbonaceous material from the surface of paper. The similar results were obtained in other literatures [13,18]. Next, different sintering time also affect the conductivity and stability of paper electrode, conductivity was tested by heating the fabricated paper substrate at 100 oC for different time interval of 0, 15, 30, 45, 60, and 75 min to obtain better paper-based electrode. The results are given in Fig. S3(b). The lowest resistance was acquired when the sintering time was 30 min and further increase in sintering time could cause the increase in resistance value. The increase in the resistance value after 30 min of sintering time is due the degradation of paper substrate. Thus,
14
30 min of sintering time and 100 oC of sintering temperature were found satisfactory for preparation of efficient paper-based electrode for electrochemical applications. 3.5. Electrochemical applications of printed paper based electrodes Here, the printed paper electrode was exploited as counter and working electrodes for measurement of electrical current of 0.1 M K3 Fe (CN)6 solution containing 1.0 M KCl as a supporting electrolyte. Firstly, we used the paper electrode as a counter electrode and commercially available Ag/AgCl and copper were used as counter and working electrodes, respectively. The CV measurements were performed by sweeping the potential from 1.0 to -1.0 V at the scan rate of 0.1 V/s. The result is shown in Fig. 4(a). The curve showed an anodic peak when the potential was varied from -1.0 to 1.0 (forward scan) and the maximum current was obtained when the applied potential was +0.2 V. This is due to the oxidation of Fe(CN)64- to Fe(CN)63- when the electrode become strong oxidant. A cathodic peak was observed during the backward scan from 1.0 to -1.0 V which is due the reduction of Fe(CN)63- to Fe(CN)64- and maximum reduction current was obtained when the potential was -0.1 V. Next, the result obtained above was compared by performing CV analysis with commercially available electrodes, i.e. platinum, Ag/AgCl and copper as counter, reference and working electrodes, respectively at constant experimental conditions, shown in Fig. 4(b). We obtained the similar results as obtained when printed electrode was used as a counter electrode. Finally, printed paper electrode was used as a working electrode for analysis of 0.1 M K3 Fe(CN)6 and keeping the platinum and Ag/AgCl as counter and reference electrodes, respectively. However, unusual oxidation and reduction peak as well as shift in potentials were observed during the use of paper electrode as a working electrode. This could be due to the electrocatalytic nature of AgNPs towards the reduction of K3 (Fe(CN)6 . The result is given in Fig S4. Hence, the printed paper electrode with silver nano-ink could be used as counter electrode for electrochemical determination in CV analysis [27].
15
3.6. Stability of paper electrode in CV analyses The stability of the printed paper electrode was tested by 60 CV cycles in 0.1 M K3 Fe(CN)6 solution. Fig. 5(a) and 5(b) show the oxidation and reduction peaks when printed paper with AgNPs was used as a counter electrode. The number of analyses (n=60) in CV helped to determine the stability as well as the reproducibility in terms of the relative standard deviation percentage (RSD, %). The RSD for oxidation current was ±1.5% and reduction current was ±1.2% when used as a counter electrode. Thus, the obtained low RSD values when paper electrode was used as a counter electrode demonstrates the better stability and repeatability of the results with high precision. 3.7. Application of paper electrode for analysis of nitrate Nitrate (NO3)- is an essential micro nutrient for animals and plants. It exists in food and water samples and responsible for proper growth through the nitrogen fixation and protein synthesis. Spectrophotometric [28,29] and fluorometric
[30] methods are commonly used for
determination of nitrate in variety of samples. In these methods, chromophoric and fluorophoric reagents are used to form the colored and fluorescence complex with target analyte; and then absorption and fluorescence signal intensity were measured with respective methods. Sometimes, chromophoric and fluorophoric reagents react with other chemical substances present in sample and interfere in the determination of target analyte. On the other hand, CV is a simple and selective technique for analysis of nitrate in different types of samples [31,32]. Here, the use of paper electrode (as a working electrode) is illustrated for measurement of nitrate while keeping the conventional platinum and Ag/AgCl as counter and reference electrodes, respectively with a scan rate of 0.1 V/s. The result is shown in Fig. 6(a). There was no any oxidation/reduction peak in the absence of nitrate; however, a reduction peak was observed when the fabricated electrode was used as a working electrode. This is due to the reduction of nitrate ions on the surface of AgNPs. Based on this result, different concentration of nitrate was spiked in water and the CV
16
curves were recorded keeping another parameters constant (Fig. 6(b)). The proposed analytical method exhibited a good linearity over the range of 60 μM to 1000 μM with a correlation coefficient of 0.993, shown in Fig 6(c). The mechanism for detection of nitrate using silver electrode was illustrated somewhere in the literatures [33-35]. The increase in nitrate ions in sample solution increases the reduction current. Thus, the paper electrode was effectively presented for determination of nitrate present in water samples. The mechanical flexibility of the paper electrode was also evaluated by bending the paper electrode at different angles (15o, 30o and 45o) and the CV measurements were performed for analysis of 0.1 mM KNO3 at scan rate of 0.1 Vs-1. The result is given in Table S5. The obtained results showed that there was no significance change in the CV curves after bending at different angles. This demonstrated the application of flexible paper electrode for determination of nitrate in sample solution. 3.8. Comparison for preparation of stable silver nano-ink and conductive materials for preparation of printed paper electrode Table 1 presents the comparison of capping agent, % of NPs, substrate, fabrication technique, sintering temperature, viscosity, resistivity and viscosity for the preparation of conductive materials [7,13,17,36-42]. The lower % of AgNPs was used in the present work for the fabrication of paper electrode compared to other approaches. Most of the methods use the polymeric material, silicon, and glass substrates for the fabrication of NPs for electronic and electrochemical applications. In addition, the resistivity of the printed paper electrode was found to be less than the most of the fabricated substrates. Thus, the use of low % AgNPs, sintering temperature, and resistivity demonstrated the effectiveness of the printed electrode for electrochemical applications comparison with other reported methods.
17
4. Conclusions In summary, the stable silver nano-ink was prepared in ethanol and used for fabrication on photo paper substrate using desktop inkjet office printer. The paper electrode was successfully exploited as counter electrode for analysis of K3Fe(CN)6 in CV with high reproducibility for multiple analyses. In addition, we also demonstrated the use of printed paper as a working electrode for the determination of nitrate. The advantages of present method are simple, low cost, flexible and user-friendly fabrication procedure compared to commercially available electrodes. In addition, low concentration of silver nano-ink (3%) was used for the electrode fabrication. In near future, the paper based printed electrodes can be used for the determination of nitrate in various real samples. Contribution of work by different authors Tushar Kant: Performed experimental works Kamlesh Shrivas: Writing and Experimental design of the manuscript Vellaichamy Ganesan: Editing of the manuscript Yugal Kishor Mahipal: XRD and FTIR measurements Rama Devi: TEM and UV-Vis measurements Manas Kanti Deb: Interpretation of the data analytical results Ravi Shankar: Interpretation of cyclic voltammetric results
Declaration of interests: None
☐ We declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
18
Acknowledgement We would like to thank the Science and Engineering Research Board (SERB), New Delhi for awarding Kamlesh Shrivas an Extra Mural Research Project (File No : EMR/2016/005813). We also thank Council of Scientific & Industrial Research (CSIR, New Delhi) for providing financial support (09/266(0078)/2017-EMR-I) to Tushar Kant in the form of junior research fellowship (JRF).
References [1]
Q. Guo, X. Teng, S. Rahman, H. Yang, Patterned Langmuir-Blodgett Films of Monodisperse nanoparticles of iron oxide using soft lithography, J. Am. Chem. Soc. 125 (2003) 630−631.
[2]
F. Iacopi, P. M. Vereecken, M. Schaekers, M. Caymax, N. Moelans, B. Blanpain, O. Richard, C. Detavernier, H. Griffiths, Plasma-enhanced chemical vapour deposition growth of si nanowires with low melting point metal catalysts: an effective alternative to au-mediated growth, Nanotechnology 18 (2007) 505307.
[3]
Y. C. Liao, Z. K. Kao, Direct writing patterns for electroless plated copper thin film on plastic substrates, ACS Appl. Mater. Interfaces 4 (2012) 5109−5113.
[4]
H. Jia, J. Wang, X. Zhang, Y. Wang, Pen-writing polypyrrole arrays on paper for versatile cheap sensors, ACS Macro Lett. 3 (2014) 86−90.
[5]
M. D. Dankoco, G.Y. Tesfay, E. Benevent, M. Bendahan, Ttemperature sensor realized by inkjet printing process on flexible substrate, Mater. Sci. Eng. B 205 (2016) 1–5.
[6]
S. Liu, X. Wu, D. Zhang, C. Guo, P. Wang, W. Hu, X. Li, X. Zhou, H. Xu, C. Luo, J. Zhang, J. Chu, Ultrafast dynamic pressure sensors based on graphene hybrid structure, ACS Appl. Mater. Interfaces 9 (2017) 24148−24154.
19
[7]
W. J. Hyun, S. Lim, B. Y. Ahn, J. A. Lewis, C. D. Frisbie, L. F. Francis, Screen printing of highly loaded silver inks on plastic substrates using silicon stencils, ACS Appl. Mater. Interfaces 7 (2015) 12619−12624.
[8]
S. Ge, L. Ge, M. Yan, X. Song, J. Yu, J. Huang, A disposable paper-based electrochemical sensor with an addressable electrode array for cancer screening, Chem. Commun. 48 (2012) 9397–9399.
[9]
A. W. Martinez, S. T. Phillips, M. J. Butte, G. M. Whitesides, Patterned paper as a platform for inexpensive, low-volume, portable bioassays, Angew. Chem. Int. Ed. 46 (2007) 1318 –1320.
[10]
R. Shankar, A. Amert, J. J. Kellar, K. W. Whites, Rheological optimization and stability study of silver nano-ink for inkjet printing of solar electrodes using industrial printhead, NSTI-Nanotech. 3 (2012) 611−614.
[11]
K. Black, J. Singh, D. Mehta, S. Sung, C. J. Sutcliffe, P. R. Chalker, Silver ink formulations for sinter free printing of conductive films, Sci. Rep. 6 (2016) 1-7.
[12]
S. Jeong, H. C. Song, W. W. Lee, S. S. Lee, Y. Choi, W. Son, E. D. Kim, C. H. Paik, S. H. Oh, B. H. Ryu, Stable aqueous based cu nanoparticle ink for printing welldefined highly conductive features on a plastic substrate, Langmuir 27 (2011) 3144– 3149.
[13]
A. Ghosale, R. Shankar, V. Ganesan, K. Shrivas, Direct-writing of paper based conductive track using silver nano-ink for electroanalytical application, Electrochim. Acta 209 (2016) 511–520.
[14]
R. Z. Li, A. Hu, T. Zhang, K. D. Oakes, Direct writing on paper of foldable capacitive touch pads with silver nanowire inks, ACS Appl. Mater. Interfaces 6 (2014) 21721−21729.
[15]
J.-S. Ye, Y. Wen, W. D. Zhang, L. M. Gan, G. Q. Xu, F. –S. Sheu, Nonenzymatic
20
glucose detection using multi-walled carbon nanotube electrodes, Electrochem. 6 (2004) 66−70. [16]
S. Rahim, A. Rauf, S. Rauf, M. R. Shah, M. I. Malik, Enhanced electrochemical response of a modified glassy carbon electrode by poly(2-vinlypyridine-b-methyl methacrylate) conjugated gold nanoparticles for detection of nicotine, RSC Adv. 8 (2018) 35776−35786 .
[17]
L. Polavarapu, K. K. Manga, H. D. Cao. K. P. Loh, Q.-H. Xu, Preparation of conductive silver films at mild temperatures for printable organic electronics, Chem. Mater. 23 (2011) 3273−3276.
[18]
A. Ghosale, K. Shrivas, R. Shankar, And V. Ganesan, Low cost paper electrode fabricated by direct writing with silver nanoparticles based ink for detection of hydrogen peroxide in waste water, Anal. Chem. 89 (2017) 776−782.
[19]
A. Ghosale, K. Shrivas, M. K. Deb, V. Ganesan, I. Karbhal, P. K. Bajpai, R. Shankar, a low-cost screen-printed glass electrode with silver nano-ink for electrochemical detection of H2O2, Anal. Methods 10 (2018) 3248−3255.
[20]
A. Mirzaei, K. Janghorban, B. Hashemi, M. Bonyani, S. G. Leonardi, G. Neri, Characterization and optical studies of pvp-capped silver nanoparticles, J. Nanostruct. Chem. 7 (2017) 37–46.
[21]
M. Kumar, P. Devi, A. Kumar, Structural analysis of pvp capped silver nanoparticles synthesized at room temperature for optical, electrical and gas sensing properties, J. Mater Sci: Mater Electron. 28 (2017) 5014–5020.
[22]
A. Kamyshny, J. Steinke, S. Magdassi, Metal-based inkjet inks for printed electronics, Open J. Appl. Phys. 4 (2011) 19−36.
[23]
M. M. Nir, D. Zamir, I. Haymov, Electrically conductive inks for inkjet printing. in: magdassi s, ed. the chemistry of inkjet inks. New Jersey-London-Singapore: World
21
Scientific 2010, PpP. 225−54. [24]
P. Calvert, Inkjet printing for materials and devices, Chem. Mater. 13 (2001) 3299−3305.
[55]
D.Q. Vo, E.W. Shin, J.S. Kim, S. Kim, Low-temperature preparation of highly conductive thin films from acrylic acid-stabilized silver nanoparticles prepared through ligand exchange, Langmuir 26 (2010) 17435–17443.
[26]
I. Jung, K. Shin, N.R. Kim, H.M. Lee, Synthesis of low-temperature-processable and highly conductive ag ink by a simple ligand modification: the role of adsorption energy, J. Mater. Chem. C 1 (2013) 1855–1862.
[27]
A. C. Sun, C. Yao, A. G. Venkatesh, D. A. Hall, An efficient power harvesting mobile phone-based electrochemical biosensor for point-of-care health monitoring, Sens. Actuators B 235 (2016) 126–135.
[28]
R. C. Jagessar, L. Sooknundun, Determination of nitrate ion in waste water from nine selected areas of coastal guyana via a spectrophotometric methods, Int. J. Res. Appl. Stud. 7 (2011) 203−212.
[29]
N. Lohumia, S. Gosain, A. Jain, V. K. Gupta, K. K. Verma, Determination of nitrate in environmental water samples by conversion into nitrophenols and solid phase extraction−spectrophotometry, liquid chromatography or gas chromatography–mass spectrometry, Anal. Chim. Acta 505 (2004) 231–237.
[30]
J.-S. Li, H. Wang, X. Zhang, H.-S. Zhang, Spectrofluorimetric determination of total amount of nitrite and nitrate in biological sample with a new fluorescent probe 1,3,5,7Tetramethyl-8-(3,4-Diaminophenyl)-Difluoroboradiazas-Indacence, Talanta 61 (2003) 797−802.
[31]
S. M. Shariar, T. Hinoue, Simultaneous voltammetric determination of nitrate and nitrite ions using a copper electrode pretreated by dissolution/redeposition, Anal. Sci.
22
26 (2010) 1173−1179. [32]
M. Shivakumar, K. L. Nagashree, S. Manjappa, M. S. Dharmaprakash, Electrochemical detection of nitrite using glassy carbon electrode modified with silver nanospheres (agns) obtained by green synthesis using pre-hydrolysed Liquor, Electroanalysis 29 (2017) 1–10
[33]
S. Dhanya, V. Saumya, T. P. Rao, Synthesis of silver nanoclusters, characterization and application to trace level sensing of nitrate in aqueous media, Electrochim. Acta 102 (2013) 299–305.
[34]
J. Krista, M. Kopanica, L. Novotony, Voltammetric determination of nitratesusing silver electrodes, Electroanalysis 12 (2000) 199–204.
[35]
D. Kim, I.B. Goldberg, J.W. Judy, Chronocoulometric determination of nitrate on silver electrode and sodium hydroxide electrolyte, Analyst 132 (2007) 350–357.
[36]
M. Vaseem, K. M. Lee, A. Hong, Y.-B. Hahn, Inkjet printed fractal-connected electrodes with silver nanoparticle ink, ACS Appl. Mater. Interfaces 4 (2012) 3300−3307.
[37]
R. Shankar, L. Groven, A. Amert, K. W. Whites, J. J. Kellar, Non-aqueous synthesis of silver nanoparticles using tin acetate as a reducing agent for the conductive ink formulation in printed electronics, J. Mater. Chem. 21 (2011) 10871−10877
[38]
I.-K. Shim, Y. Lee, K. J. Lee, J. Joung, An organometallic route to highly monodispersed silver nanoparticles and their application to ink-jet printing, Chem. Phys. 110 (2008) 316–321
[39]
K. Balantrapu, D. V. Goia, Silver nanoparticles for printable electronics and biological applications. J. Mater. Res. 24 (2009) 2828−2836
[40]
Q. Huang, Y. Zhu, Gravure Printing of water-based silver nanowire ink on plastic substrate for flexible electronics, Sci. Rep. 8 (2018) 15167.
23
[41]
H. H. Lee, K. S. Chou, K. C. Huang, Inkjet printing of nanosized silver colloids, Nanotechnology 16 (2005) 2436–2441
[42]
S. B. Walker, J. A. Lewis, Reactive silver inks for patterning high-conductivity features at mild temperatures, J. Am. Chem. Soc. 134 (2012) 419−1421
24
Scheme 1. Schematic presentations: (a) synthesis of silver nano-ink, (b) formulation of silver nano-ink, (c) fabrication of nano-ink on paper substrate using inkjet printer, (d) printed electrodes, (e) sintering of electrode, (f) application of prepared electrode in CV measurements, and (g) CV responses
25
(a)
(b)
(c)
20 nm
5 nm
(d)
(e)
Fig. 1. (a) UV-Vis spectra of AgNPs/PVA, (b) TEM image of AgNPs/PVA, (c) Enlarged view of AgNPs/PVA, (d) EDX of AgNPs/PVA, and (e) DLS measurement showing the size distribution of AgNPs/PVA
26
(a)
(b)
(c)
Fig. 2. (a) XRD patterns of AgNPs/PVP, (b) FTIR spectra of pure PVP and AgNPs/PVP, and (c) TGA curve of AgNPs/PVP.
27
(a)
(b)
(c)
Fig. 3. (a) Flexible printed electrodes on photo paper with silver nano-ink, (b) measurement of resistance on paper electrode using multimeter, and (c) lighting of LED bulb showing the conductivity of printed material on paper substrate.
28
(a)
(b)
Fig. 4. (a) CV measurements of 0.1 M K3 (Fe(CN)6 + 1.0 M KCl when printed paper electrode was used as a counter electrode while conventional Ag/AgCl and copper were used as reference and working and electrodes, respectively with 0.1 V/s scan rate (b) CV measurements of 0.1 M K3 (Fe(CN)6 + 1.0 M KCl when conventional platinum, Ag/AgCl and copper as counter, reference and working electrodes, respectively with 0.1 V/s of scan rate.
29
(a)
(b)
Fig. 5. (a) 60 continuous CV cycles of 0.1 M K3 Fe(CN)6 when paper electrode was used as a counter electrode and Ag/AgCl and copper electrodes were used as reference and working electrodes, respectively in the presence of KCl with a scan rate of 0.1 V/s and (b) 60 continuous CV cycles of 0.1 M K3 Fe(CN)6 when conventional Ag/AgCl, platinum and copper were used as reference, counter and working electrodes, respectively in the presence of KCl with a scan rate of 0.1 V/s.
30
(a)
(b)
(c)
Fig. 6. CV analyses of 0.1 mM KNO3 when printed paper electrode was used as a working electrode in the presence of 1.0 M NaH2PO4 at scan rate of 0.1 Vs-1 while platinum and Ag/AgCl electrodes were used as counter and reference electrodes, respectively; (b) CV measurements of different concentration KNO3 from 60 μM to 1000 μM when printed paper electrode was used as a
31
working electrode while platinum and Ag/AgCl were used as counter and reference electrodes, respectively with 0.1 V/s scan rate and (c) Calibration curve for determination of nitrate in water.
32
Table 1. Comparison of capping agent, % of NPs, substrate, fabrication technique, sintering temperature, viscosity, resistivity and viscosity of conductive materials Capping Agent
Reducin
NPs, %
Substrate
g agent
Fabrication Sintering technique
Resistivity Surface O
(Temp in C)
−5
(10 Ωcm) tension
Viscosity
Ref.
(mPa.s)
(mN/M) PVP
NaBH4
3
PET
Inkjet
50
∼0.5
-
-
17
printing PVP
Ethylen
10
Si/SiO2
Printing
200
∼1
∼40.7
5.47
36
12
Paper
Ball Pen
150
∼8.8
-
-
13
300
-
-
1–2
37
400
-
∼12
∼12
38
200
∼0.5
-
∼10
7
125
∼7.42
-
-
39
150
-
∼28.8
-
40
260
∼0.3
∼33.5
7.4
41
90
-
-
2
42
100
0.4
21.1
2.6
Present
e glycol Oleyl
Ascorbi
amine
c acid
Dodecyl
Tin
amine
acetate
PVP
PVP
20
Polymer
printing Inkjet
wafer
printing
Polyimid
Screen
e film
printing
Polymeri
Inkjet
ne
c
printing
hydrate
substrate
Diethan
(acrylic
ol
acid)
amine
Gum
hydrazi
Ethylen
20
77
20
5
PET
e glycol
Formald
Aerosol-jet
Silicon
Poly
PVP
writing
PVP
Inkjet printing
25
Glass
ehyde
Inkjet printing
Formic
Fluoro
Acid
polymer
PVP
NaBH4
22
Silicon
Inkjet printing
3
Paper
Inkjet printing
work