A facile fabrication of platinum nanoparticle-modified graphite pencil electrode for highly sensitive detection of hydrogen peroxide

Accepted Manuscript A facile fabrication of platinum nanoparticle-modified graphite pencil electrode for highly sensitive detection of hydrogen peroxide Abdel-Nasser Kawde, Md Aziz, Nadeem Baig, Yassin Temerk PII: DOI: Reference:

S1572-6657(15)00006-5 http://dx.doi.org/10.1016/j.jelechem.2015.01.005 JEAC 1964

To appear in:

Journal of Electroanalytical Chemistry

Received Date: Revised Date: Accepted Date:

30 August 2014 22 December 2014 7 January 2015

Please cite this article as: A-N. Kawde, M. Aziz, N. Baig, Y. Temerk, A facile fabrication of platinum nanoparticlemodified graphite pencil electrode for highly sensitive detection of hydrogen peroxide, Journal of Electroanalytical Chemistry (2015), doi: http://dx.doi.org/10.1016/j.jelechem.2015.01.005

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A facile fabrication of platinum nanoparticle-modified graphite pencil electrode for highly sensitive detection of hydrogen peroxide Abdel-Nasser Kawdea,b,*, Md Aziza,c, Nadeem Baig a, Yassin Temerkb,* a

Chemistry Department, King Fahd University of Petroleum and Minerals, Dhahran, 31261, Kingdom of Saudi Arabia b

Chemsitry Department, Faculty of Science, Assiut University, Assiut71516, Egypt

c

Center of Research Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia Corresponding E-mail addresses: [email protected] (Y. Temerk); [email protected] (A. Kawde).

ABSTRACT A novel platinum nanoparticle-modified graphite pencil electrode (PtNP-GPE) for a nonenzymatic determination of H2O2 is proposed. The PtNP-GPE is prepared by heating a GPE in an aqueous solution of ammonium tetrachloroplatinate(II) and ascorbic acid at 75 ο

C for 15 min. Both unmodified and PtNP-GPE are characterized using field-emission-

SEM and cyclic voltammetry. The PtNP-GPE showed better electrocatalytic properties toward the electrochemical redox reaction of H2O2than that of the unmodified GPE. The PtNP-GPE amperometric response is tested at four different potentials (+0.7, +0.5, -0.2 and -0.3V vs. Ag/AgCl reference electrode). Taking into consideration both the intensity of the amperometric response and detector stability, the applied potential of +0.5 V is the best among the tested potentials. The PtNP-GPE amperometric response of H2O2 at +0.5V is linear from 10 to 110µM (R2 = 0.999) with a detection limit of 3.6 µM. Keywords:

platinum nanoparticles, graphite pencil electrode, chemical preparation,

hydrogen peroxide, amperometric detection

1

1.Introduction Hydrogen peroxide (H2O2) is commonly used in wide areas such as textile, cleaning products, food industry, organic compounds, and effluent treatments. As a result, H2O2 is haphazardly distributed in the environment especially in water and industrial products. The toxicity of H2O2 to living organisms is notable [1]. On the other hand, it is a signal generating molecule in many biosensors, e.g. enzyme-based glucose and lactate sensors [2-4]. In enzyme-based glucose sensors, glucose oxidase produces H2O2 from glucose and oxygen [2, 3]. The generated H2O2was quantified to determine the glucose concentration indirectly [2, 3]. Therefore, simple, cheap, quick, accurate and reliable methods for the sensitive detection of hydrogen peroxide are of interest to many fields; such as food and food additives, cosmetics, pharmaceutical's products, environmental analysis and biosensor fabrication. Up to date, various methods were developed to detect H2O2 based on titrimetric, spectrophotometric, fluorescence, chemiluminescence and electroanalytical methods [5-9]. Among those; electroanalytical methods have attracted much attention due to its high sensitivity, portability, and short response time and low cost. For the last two decades, nanomaterial-modified electrodes are widely applied as transducers in various fields like sensors due to their better physical, chemical, electrochemical properties and higher surface area compared to their counter bulk materials [10-13]. Particularly, many research groups applied platinum nanoparticlemodified electrodes for the electrochemical detection of H2O2 as the PtNP-modified electrodes have shown impressively electrocatalytic properties toward H2O2 [3, 14-17]. However, using of PtNP-modified electrode for often detection of H2O2 is limited due to 2

the high cost. The cost of the PtNP-modified electrode depends on the used substrate as well as on the PtNP attachment/preparation method. Among substrates, the graphite pencil electrode (GPE) is the cheapest and most available one. Nevertheless, it shows poorly electrocatalytic properties towards many electroactive molecules [18, 19].To improve the electrocatalytic properties of the GPEs, various approaches for either pretreatment [20,21] or modifications[22-27]were reported. Since a high electrocatalytic property is required to fabricate sensitive electrochemical sensors, modification of GPE with PtNP is logic to make a high electrocatalytic electrode for the sensitive detection of hydrogen peroxide. For the modification of GPE with metal or metal oxide NP, chemical vapor deposition from metal precursor and electrochemical deposition from polymerattached NPs were reported [28-31]. Both chemical vapor deposition and electrochemical methods are extremely fast processes, thus generate irreproducible surfaces where a reproducible surface is essential to make an efficient sensor. Moreover, such methods require sophisticated instruments and quite skilled persons that increase the overall sensor fabrication cost. As a result, development of a simple chemical method for the preparation of PtNP-modified GPE is quite meaningful. Recently, Compton et al. developed facile methods for the preparation of Pt, Ag, PdNP-modified glassy carbon (GC) microsphere in a solution phase using correspondence metal precursors and a reductant (ascorbic acid (AA) or hydrazine) in the absence or presence of stabilizers at elevated temperatures [32, 33]. To the best of our knowledge, there are no reports for a single-step chemical preparation of PtNP-modified GPE using a metal precursor, reductant and GPE. The proposed PtNP-GPE is a disposable, sensitive and selective hydrogen peroxide detector

3

combining the advantages of PtNP and GPE. The morphological characterization of the fabricated PtNP-GPE is shown in the following sections along with its electrochemical characterization, to explore its electrocatalytic properties toward redox reaction of H2O2. 2. Experimental 2.1. Instrumentation UV experiments were performed using Ocean Optics USB4000-UV-VIS Spectrophotometer (Dunedin, FL, USA). A Jedo mechanical pencil (Korea) was used as a holder for both bare and PtNP-modified graphite pencil leads. Electrical contact with the lead was achieved by soldering copper wire to the metallic part that holds the lead in place inside the pencil. The pencil was fixed vertically with 15 mm of the pencil lead extruded outside, and 10 mm of the lead immersed in the solution. Such length corresponds to a geometric electrode area of 15.90 mm2. Details of the pencil electrode were described earlier [34]. CHI 660C (CH Instruments Inc., Austin, TX, USA) was used for the entire electrochemical work. The electrochemical cell contained bare- or PtNPsmodified GPE as a working electrode, a Pt wire counter electrode and Ag/AgCl (Sat. KCl) reference electrode. Field emission scanning electron microscopic (FE-SEM) images are recorded using TESCAN LYRA 3 (Brno, Czech Republic) at the Center of Research Excellence in Nanotechnology, King Fahd University of Petroleum and Minerals, Kingdom of Saudi Arabia.

2.2. Chemicals and reagents Ammonium tetrachloroplatinate(II) ((NH4)2PtCl4 ), L-ascorbic acid (AA), uric acid (UA), 4-acetamidophenol (AAP), dopamine (DA),hydrogen peroxide (H2O2) and

4

sodium hydroxide (NaOH) were purchased from Sigma-Aldrich (St. Louis, MO, USA). Disodium hydrogen phosphate and sodium dihydrogen phosphate were supplied by Fisher Scientific Company (Pittsburgh, PA, USA). Hi-polymer graphite pencil HB black leads were obtained from Pentel Co. LTD. (Japan). All leads had a total length of 60 mm and a diameter of 0.5 mm, and were used as received. All solutions were prepared with deionized water of resistivity of 18.6 MΩcm-1 , which was obtained directly from PURELAB® Ultra Laboratory Water Purification System (Siemens, Washington, DC, USA).

2.3. Preparation of PtNP-modified graphite pencil electrode Equal volumes of 1.5 mL aqueous solution of 1.1 mM AA and 1.0 mM(NH4)2PtCl4 were mixed using a pipette at room temperature (RT) in 3.0 mL test tube. Afterward, a bare GPE was immersed into a 3.0 mL test tube containing the freshly prepared solution of (NH4)2PtCl4 and AA. To fabricate the PtNPs-modified GPE, that test tube was placed into a water bath preheated to 75 oC and kept for 15 min. The PtNPsmodified GPE was removed and washed by gentle dipping two times into deionized water, then dried at 60 oC for 5 min prior to use.

3. Results and Discussion 3.1. Reductive capacity of AA to form PtNP from [PtCl4]2It is reported that AA or salt of AA is a good reductant to form AuNP quickly at room temperature (RT) from gold precursor [35]. Besides, Compton group prepared PtNP on GC microsphere by stirring the mixture of GC microsphere, precursor of Pt and

5

AA at 70 °C for 2 hours with no explanation for the necessity of heat treatment [25]. In the present work, UV experiments are performed initially to understand the necessity of heat treatment to form PtNP using AA as a reductant. Fig. 1 (i) and (ii) shows the UV spectra of 0.5mM (NH4)2PtCl4 (aq.) and 0.5 mM AA (aq.), respectively.

The AA shows almost no absorbance within the tested wavelength range (320 to 700 nm), where (NH4)2PtCl4 shows absorbance between 360 to 545 nm with λmax 387 nm. Fig. 1 (iii) and (iv) are the UV spectra of the aqueous solution of 0.5mM (NH4)2PtCl4 and 0.5mM AA. Fig. 1 (iii) is recorded spectrum right after making the solution, whereas spectrum (iv) is for the same prepared solution after 15 min at RT. There are almost no differences among spectra (i), (iii) and (iv) of Fig. 1, i.e. AA does not reduce PtCl42- at RT within 15 min period. The freshly prepared aqueous solution mixture of 0.5mM (NH4)2PtCl4 and 0.55 mM AA is colorless, and with heating at 75 °C started to turn to light black (grey color). The UV spectrum of the 15 min heated reaction mass (Fig. 1(v)) shows a high absorbance without any peaks. The UV spectrum (Fig. 1(v)) is characteristics for the aqueous solution of PtNP [36, 37] i.e. AA can easily reduce the PtCl42- to form PtNP at elevated temperatures.

3.2. Preparation and characterization of the PtNP-modified GPE In the previous section, we concluded that AA could not reduce PtCl42- at RT within 15 min in the absence of the GPE. However, that possibility is there in the presence of GPE as it composed of graphite and clay. The catalytic growth of PtNP on any of the GPE components at RT from the aqueous solution of PtCl42- and AA is a

6

concern. To check the catalytic growth of PtNP, initially GPE is immersed in the aqueous solution of 0.5mM (NH4)2PtCl4 and 0.55mM AA for 15 min at RT. Afterward, the RT treated electrode was subjected to record FE-SEM images (Fig. 2b) and cyclic voltammogram (CV) in 0.1 M NaOH (Fig. 3b). For comparison, the FE-SEM images (Fig. 2a) and CV in 0.1 M NaOH (Fig. 3a) of bare GPE are recorded. There are no differences in the FE-SEM images of the RT treated and bare GPE i.e. there is no formation of PtNP at RT on GPE from the aqueous solution of 0.5mM (NH4)2PtCl4 and 0.55mM AA. Besides, the CVs of the bare GPE and treated GPE in an aqueous solution of 0.5 mM (NH4)2PtCl4 and 0.55 mM AA at RT are more or less the same i.e. the CV data is further confirming that there is no formation of PtNP on GPE from same solutions at RT. By immersing a bare GPE in an aqueous solution of 0.5mM (NH4)2PtCl4 and 0.55mMAA and heating at 75 °C for 15 min, the PtNP-modified GPE is obtained. Comparing the FESEM images (Fig. 2c) of the 75 °C treated electrode with that of bare GPE (Fig. 2a), and RT treated GPE (Fig. 2b), indicates that the heat treatment is required to prepare PtNP on GPE from the aqueous solutions of 0.5 mM (NH4)2PtCl4 and 0.55 mM AA. The size of the formed PtNP on GPE is in the range between 25 to 50 nm. However, some of them are attached each other. The lower magnification view of the PtNP-modified GPE (Fig. 2c (B)) clearly shows the homogeneous distribution of the PtNP on GPE. This PtNPmodified GPE, prepared at 75 °C, is denoted as PtNP-GPE in the rest part of the manuscript. The CV of PtNP-GPE (Fig. 3c) in 0.1 M NaOH shows higher current in anodic or cathodic scan compared to that of bare one. The reason of higher current might be the presence of PtNP on GPE. 7

As shown in Fig. 4, the EDX spectrum analysis was also performed in order to investigate the composition of the PtNP-GPE. Two main peaks corresponding to the C and Pt elements existed in the EDX spectrum. The measured atomic ratios of C and Pt were 95.49% and 4.51%, respectively. These results indicate that the Pt nanoparticles were successfully immobilized on the surface of GPE.

3.3. Electrocatalytic properties of bare and PtNP-GPE Fig.5A (a) and Fig.5B (a) are the CVs of bare GPE in 0.1MPB (pH 7.0) in the absence and presence of 1.0 mM H2O2, respectively. Bare GPE shows poor electrocatalytic properties toward the oxidation of H2O2 as shown in Fig.5B(a). Similarly, the CVs of PtNP-GPE are recorded in 0.1M PB (pH 7.0) without (Fig.5A (b)) and with (Fig.5B (b)) 1.0 mM H2O2.

The presence of PtNP causes a small increase in the background current of PtNPGPE (Fig.5A(b)), compared to that of bare GPE (Fig.5A(a)). Among the recorded CVs, only Fig.5B(b) shows peaks at +0.668 V and -0.195 V on the anodic and cathodic scans, respectively. Hence, PtNP-GPE oxidizes and reduces the H2O2 at low potential. Moreover, the Fig.5B(b) shows higher currents at both anodic and cathodic scans among the recorded CVs. The above discussion proofs that PtNP-GPE has much higher electrocatalytic properties towards the oxidation as well as the reduction of H2O2 compared to that of the bare GPE. The electroactive surface area of the PtNP- and bareGPE was estimated from the slope of Randles-Sevcik plot (Figure 5C)described by equation 1. ip = 2.69 x 105 n3/2 ν1/2 D1/2 A C

8

(1)

Where i is the current (A), n is the number of electrons, ν is the scan rate (V s-1), D is the diffusion coefficient (cm2 s-1), A is the area of the electrode (cm2) and C is the concentration (M) [38]. The electroactive surface area obtained using5.0 mM H2O2 for both bare- and PtNP-GP electrodes. A linear trend is observed in the whole range of scan rates investigated as shown in Figure 5C, and the calculated electroactive surface areas for PtNP-GPE and bare GPE were 1.92 x 10-5 cm2 and 0.51 x 10-5 cm2, respectively. The larger electroactive surface area justifies the higher current for H2O2 atthe PtNP-GPE as compared to that obtained at the bare GPE. Moreover, such increases in the electroactive surface area for the PtNP-GPE (vs. the bare GPE) did not accompany with any dramatic background/noise increases. Table S1 (Supporting Information) shows a comparison between the corresponding S/N ratio of CV data reported in Fig. 5A and B for 1.0 mM H2O2responses at bare- and PtNP-modified GPEs. The S/N ratio (at +0.6 V) for bare- and PtNP-GPE were 1.62 and 27.36, respectively. 3.4. Reproducibility of the PtNP-GPE To test the reproducibility of the PtNP-GPE, CVs are recorded in 0.1M PB containing 1.0 mM H2O2 at five different PtNP-GPEs (data not shown). The CVs showed quite reproducible behavior with a relative standard deviation of the anodic peak current for 1.0 mM H2O2 is 3%, and hence the prepared PtNP-GPEs are good candidates for electroanalysis of H2O2.

3.5. Influence of the applied potential on the amperometric response and stability Fig. 6 is the amperograms of 10mM H2O2 in PB (pH 7.0) at PtNP-GPE under different positive applied electrode potential for a long period. The amperometric 9

response of H2O2 increases with the increase of the electrode applied potential up to +0.5 V (Fig.6 and its inset A). However, as the applied potential is further increases towards the positive direction, the amperometric response decreases (Fig.6 and its inset A). Where Fig. S1 (Supporting Information) shows the signal-to-noise ratio (S/N) vs. various applied potentials, inset B of Fig.6 shows the plot of the amperometric current decrease % for H2O2 vs. these applied potentials. The current (I) decrease % is defined as [(Iinitial–Ifinal)/ Iinitial]*100. There are no significant signal changes at applied potentials +0.3 and +0.4 V for the same tested period. Besides, only ~20% of I is decreased at +0.5 V applied potential, whereas 50, and 42% are obtained at +0.7, and +0.9 V, respectively. By considering the intensity of amperometric response and stability, +0.5 V is selected among the tested potential for further experiments to detect H2O2. 3.6. Amperometric detection of H2O2 at PtNP-GPE It is well known that amperometry under stirred condition is more sensitive than cyclic voltammetry [39].As a result, the amperometry technique is used to get lower detection limit of hydrogen peroxide. Fig.7A shows typical amperograms of PtNP-GPE at +0.5 and +0.7 V for successive additions of 10µL of 10mMH2O2 into continuously stirred 10mL of 0.1 M PB (pH 7.0). The Oxidation current at +0.5V increase linearly with increasing the concentration from 10 to 110µMH2O2 (R2 = 0.9992) with a detection limit of 3.6 µMat 3σ (Fig.7A and its inset). Whereas, the oxidation response at +0.7 V shows linearity from 10to 50 µM concentration of H2O2 (R2 = 0.9976) range with a detection limit of 7.8 µM

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at 3σ (Fig.7A and its inset). However, further increase on the concentration of H2O2 deviates the linearity (Fig.7A and its inset). The obtained lower linearity and higher detection limit at +0.7 V compared to that at +0.5 V are expected. As shown in Fig.6, PtNP-GPE shows lower response and less stability at +0.7 V than that at +0.5 V upon the spiking of same H2O2 concentration. Although good detection limit with stable signal of H2O2 at PtNP-GPE is achieved at +0.5 V applied potential, numerous relevant substances are expected to be oxidized at such a potential and hence interfere. This interference will be a serious obstacle during the detection of H2 O2 in the presence of relatively high concentration of interferents. Using a lower applied potential, however, reduces or eliminates these interferences. As a result, -0.2 and -0.3 V are also applied on the PtNPmodified GPE in separate experiments for the detection of H2O2 for minimizing the interferences from the potential interferents (Fig.7B). The reduction current response at -0.2 V increased linearly with increase the concentration of H2O2 from 50to 250µM (R2 = 0.9967) (Fig.7B and its inset). The detection limit at applied potential of -0.2 V is 48 µMat 3σ. Further increase of the H2O2 concentration deviates the linearity. The obtained linear range of H2O2 determination is 50to 550µM (R2 = 0.9996), at a -0.3 V applied potential. The achieved detection limit at 0.3 V applied potential is 45 µMof H2O2. The performances of the developed PtNP-GPE are compared with other PtNP-modified electrodes for the detection of H2O2 in Table 1.Moreover, Tables S2-S5 (Supporting Information) show the corresponding mean, standard deviation and relative standard deviation of each H2O2concentration inthe calibration curves of Fig. 7. Thus, the developed PtNP-GPEs are quite reproducible as well.

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3.7. Interferences Fig.8 represents the amperometric responses of successive additions of hydrogen peroxide (H2O2), ascorbic acid (AA), uric acid (UA), 4-acetamidophenol (AAP) and dopamine (DA) at +0.5 V and -0.2 V for PtNP-GPE. At applied potential +0.5 V, a welldefined response is observed upon spiking of 0.1 mM H2O2. However, further spiking of each 1.0µM concentration of AA, UA, AAP and DA did not show any observable interference. Also, a well-defined response is observed at -0.2 V applied potential upon spiking of 0.25mM H2O2, whereas no signal is observed for further subsequent spiking of each 0.5 mM level concentration of AA, UA, AAP and DA. These experimental results reflect the good selectivity besides the sensitivity of the prepared PtNP-GPE towards H2O2 sensing.

Fig.8. Amperometric responses of PtNP-GPE at +0.5 and -0.2 V for successive spikes ofH2O2, uric acid (UA), ascorbic acid (AA), 4-acetamidophenol (AAP), and dopamine (DA). Other preparation and working conditions, as in Fig. 2c and Fig.7, respectively. 4. Conclusions In summary, PtNP-GPE is fabricated via a facile one-step simple chemical method for H2O2 sensing. The fabricated PtNP-GPE effectively catalyzes, with high reproducibility,

greater

analytical

selectivity,

sensitivity,

and

stability,

the

electrochemical redox reaction of H2O2.Simplicity and good analytical performance are promising features of the developed non-enzymatic H2O2 detector. Besides its remarkable

12

specs, the fabricated PtNP-GPE is considered as an excellent candidate for various analyses.

Conflict of Interest The authors declare that there is no conflict of interest.

Acknowledgements The authors acknowledge the support provided by King Fahd University of Petroleum & Minerals (KFUPM) for funding this work through project No. IN101033.

Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, athttp://XXXXX

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[39] S. A. Kitte, B. D. Assresahegn, T. R. Soreta, Electrochemical determination of hydrogen peroxide at glassy carbon electrode modified with palladium nanoparticles, J. Serb. Chem. Soc. 78 (2013) 701-711. [40] F. Zhang, Z. Wang, Y. Zhang, Z. Zheng, C. Wang, Y. Du, W. Ye, Microwaveassisted synthesis of Pt/graphene nanocomposites for nonenzymatic hydrogen peroxide sensor, Int. J. Electrochem. Sci. 7 (2012) 1968-1977. [41] H. Zhong, R. Yuan, Y. Chai, Y. Zhang, C. Wang, F. Jia, Non-enzymatic hydrogen peroxide amperometric sensor based on a glassy carbon electrode modified with an MWCNT/polyaniline composite film and platinum nanoparticles, Microchim. Acta 176 (2012) 389-395. [42] C. Guzman, G. Orozco, Y. Verde, S. Jiménez, L. A. Godinez, E. Juaristi, E. Bustos, Hydrogen peroxide sensor based on modified vitreous carbon with multiwall carbon nanotubes and composites of Pt nanoparticles-dopamine, Electrochim. Acta 54 (2009) 1728-1732. [43] J. Wan, W. Wang, G. Yin, X. Ma, Nonenzymatic H2O2 sensor based on Pt nanoflower electrode, J Clust Sci 23 (2012) 1061-1068. [44] R. Yu, L. Wang, Q. Xie, S. Yao, High-performance amperometric sensors using catalytic platinum nanoparticles-thionine-multiwalled carbon nanotubes nanocomposite, Electroanalysis 22 (2010) 2856-2861.

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Figure Captions Fig. 1. UV-visible spectra of an aqueous solution of (i) 0.5mM(NH4)2PtCl4, (ii) 0.55 mM AA, (iii) 0.5mM (NH4)2PtCl4 and 0.55mM AA (just after preparation), (iv) 0.5mM (NH4)2PtCl4 and 0.55mM AA after 15 min at room temperature for (v) 0.5mM (NH4)2PtCl4 and 0.55mM AA after heating at 75 οC for 15 min.

Fig. 2. FE-SEM images at two different magnifications, 500 nm (A) and 5 µm (B) of bare(a) and PtNPs-modified GPE prepared by immersing the bare GPE in the aqueous solution of 0.5mM (NH4)2PtCl4 and 0.55mM AA at RT (b) or 75 οC (c) for 15 min.

Fig.3. CVs in 0.1M NaOH aqueous solution at GPE before (a), and after immersing in aqueous solution of 0.5mM (NH4)2PtCl4 and 0.55mM AA at room temperature (b) and at 75 οC (c) for 15 min. Scan rate, 100 mVs-1. CVs were recorded after 20 min argon purging. Fig. 4. EDX spectrum of fabricated PtNP/GPE. Inset is the FE-SEM image at 200 nm magnification. Fig.5. CVs in PB (0.1M, pH 7) in the absence (A) and presence (B) of 1.0 mM H2O2 at bare (a) and PtNP-GPE (b). Scan rate, 100 mVs-1. CVs were recorded after 20 min argon purging. (C) The corresponding linear plot of peak current vs. square root of various CV scan rates of 5.0 mM H2O2 in PB (0.1 M, pH 7) at bare (a) and PtNP-GPE (b).Preparation conditions of PtNP-GPE, as in Fig. 2c. Fig.6. Amperometric responses of PtNP-modified GPE in PB (0.1M, pH 7) upon an addition of 10mM H2O2 at different applied potentials. (A) The corresponding plot of the amperometric current vs. the applied potential. (B) The corresponding plot of the signal decrease percentage vs. the applied potential. Amperograms are recorded after 20 min argon purging. Preparation conditions of PtNP-GPE, as in Fig. 2c. Fig.7. Amperograms of PtNP-GPE in 10 mL PB (0.1 M, pH 7) at different potentials for successive additions of 10µM (A) and 50µM (B) of H2O2. Amperograms (A) and (B) are recorded without and with 20 min Argon purging, respectively. Insets are for the corresponding calibration plots (error bars are for n = 3).Preparation conditions of PtNPGPE, as in Fig. 2c. Fig.8. Amperometric responses of PtNP-GPE at +0.5 and -0.2 V for successive spikes of H2O2, uric acid (UA), ascorbic acid (AA), 4-acetamidophenol (AAP), and dopamine (DA). Other preparation and working conditions, as in Fig. 2c and Fig.7, respectively.

18

Fig. 1.

19

Fig. 2.

20

Fig. 3.

21

Fig.4.

22

Fig.5.

23

Fig.6.

24

Fig.7.

25

Fig.8.

26

Table 1 A comparison of PtNP-modified electrodes for amperometric detection of H2O2

LOD / Electrode

LOQ/

Technique

Sensitivity / -1

-2

µM

µM

(A mM cm )

Ref.

PtNP-GPE

Amperometry

3.6

10

3.70x 10-1

This work

PtNP-Macroporous Au electrode

Amperometry

50

100

2.64 x 10-4

14

PtNP-Nanotubular TiO2

Amperometry

4.0

4.0

0.85 x 10-6

15

PtNP-Poly(3,4ethylenedioxythiophene)-SPCE PtNP-polypyrrole nanowire-GCE

Amperometry

1.6

600

1.99 x 10-5

16

Amperometry

1.2

3.5

Not mentioned

17

PtNP-graphene-GCE

Amperometry

0.8

2.5

2.04 x 10-1

40

PtNP-MWCNT/polyaniline-GCE

Amperometry

2.0

7.0

7.48 x 10-4

41

Dopamine-PtNP-MWCNT-GCE

Amperometry

340

1200

4.07 x 10-6

42

Pt Nanoflower-Au electrode

Amperometry

60

100

2.20x 10-5

43

PtNP-Thionine-MWCNT-Au

Chronoampero-

2.0

5.0

1.95 x 10-3

44

electrode

metry

27

28

Highlights - We developed a simple chemical method for the fabrication of PtNP-GPE. - We tested the fabricated PtNP-GPE for the detection of hydrogen peroxide. - We obtained all figures ofmerit for the developed PtNP-GPE. - We tested theeffect of potential interferences on the PtNP-GPE response.

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