Fast sensing ammonia at room temperature with proline ionic liquid incorporated cellulose acetate membranes

Journal of Molecular Liquids 305 (2020) 112820

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Journal of Molecular Liquids journal homepage: www.elsevier.com/locate/molliq

Fast sensing ammonia at room temperature with proline ionic liquid incorporated cellulose acetate membranes Priya Mehta a, Seenuvasan Vedachalam b, Gopal Sathyaraj c, Somenath Garai b, Gangasalam Arthanareeswaran d,⁎, Kamatchi Sankaranarayanan a,e,⁎⁎ a

Department of Energy and Environment, National Institute of Technology, Tiruchirappalli - 620015, Tamilnadu, India Department of Chemistry, National Institute of Technology, Tiruchirappalli - 620015, Tamilnadu, India. CLRI-CATERS, CSIR-Central Leather Research Institute, Chennai - 600020, Tamilnadu, India. d Membrane Research Laboratory, Department of Chemical Engineering, National Institute of Technology, Tiruchirappalli - 620015, Tamilnadu, India. e Biophysics - Physical Sciences Division, Institute of Advanced Study in Science and Technology (an Autonomous Institute Under DST, Govt. of India), Vigyan Path, Paschim Boragaon, Garchuk, Guwahati - 781035, Assam, India. b c

a r t i c l e

i n f o

Article history: Received 17 December 2019 Received in revised form 16 February 2020 Accepted 1 March 2020 Available online 03 March 2020 Keywords: Cellulose acetate membrane Ionic liquid Amino acid ionic liquid Gas sensing Ammonia sensor

a b s t r a c t Gas sensors based on polymeric membrane using cellulose acetate and amino acid ionic liquids (AAIL) were prepared using the phase inversion method. Initially, AAIL was prepared by the neutralisation method of amino acids L-Proline and L-Phenylalanine with the IL EMIM OH (base) to form ProIL and PheIL. The prepared membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, atomic force microscopy. Asymmetric nature and finger-like macrovoids was confirmed using SEM and AFM. The synthesized cellulose acetate membrane incorporated with IL and AAILs was tested for the gas sensing by quantifying the change in resistance, in the absence and presence of the test gas inside a chamber. CA membranes with CA-ProIL displayed the best ammonia sensing with lowest value of 1 ppm detection and response and recovery times of 60 s and 78 s respectively. The results suggest that the CA membranes have great potential for gas sensing application and by incorporating IL, AAILs into the matrix it is further increased by a significant amount. Further, NMR analysis suggests the possible mechanism of adduct formation of ammonia with ProIL. © 2020 Elsevier B.V. All rights reserved.

1. Introduction Gas sensors have found significant necessity in industrial locations where toxic gases are generated. Inorganic gases like ammonia (NH3) produced due to rapid industrialization and modernization cause hazardous effects on health and environment with a threshold limit value of 35 ppm [1,2]. Exposure to a high concentration of ammonia vapour may be fatal for humans as well as animals [3–5]. NH3 gas sensors with sensitivity at ppm levels working at room temperature with accurate rapid detection is of immediate need to monitor the quality of air in many industrial processes [6–8]. Metal oxide semiconductors, carbon nanotubes, polymers, are majorly used as gas sensors [9–11]. However, ⁎ Correspondence to: G. Arthanareeswaran, Department of Chemical Engineering, National Institute of Technology, Tiruchirappalli - 620015, Tamilnadu, India. ⁎⁎ Correspondence to: K. Sankaranarayanan, Biophysics - Physical Sciences Division, Institute of Advanced Study in Science and Technology (an Autonomous Institute Under DST, Govt. of India), Vigyan Path, Paschim Boragaon, Garchuk, Guwahati - 781035, Assam, India. E-mail addresses: [email protected] (G. Arthanareeswaran), [email protected], [email protected] (K. Sankaranarayanan).

https://doi.org/10.1016/j.molliq.2020.112820 0167-7322/© 2020 Elsevier B.V. All rights reserved.

polymeric membrane-based gas sensors are the emerging area of research and can be one of the future technologies and have several advantages such as high sensitivities, short response times and usually highly efficient at room temperatures compared to the commercially available sensors using metal oxide semiconductors [12,13]. Recently, polyvinylidene fluoride polymer-based membrane together with metal organic framework has been used for gaseous HCl sensing [14]. Commercial Matrimid polymer - MOF composite membrane has been used for the detection of alcohols and other gas analytes [15]. Our earlier work on polysulfone based polymer membranes incorporated with ionic liquid tuned TiO2 nanoparticles showed good gas sensing properties [15]. However, the quest to develop a low cost membrane for gas sensor is essential which can be useful in the commercial scale. Cellulose is an abundant material available in the earth, which can be used for developing polymer membranes for gas sensing applications. Cellulose acetate (CA) is one of the commonly used low-cost membrane materials for various applications like reverse osmosis, ultrafiltration, gas permeation [16,17] due to its long life time, high hydrophilicity and biodegradability [16]. It is reported that the performance of CA may be enhanced by mixing it with suitable additives like ionic liquids to

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accomplish new requirements and improvised membrane properties [18]. Room-temperature ionic liquids (RTILs) have gained widespread applications in many areas [19], for their unique properties such as low vapour pressure [20] and has been used as green solvents. Reports show that ionic liquids can alter the structural organization at the nanoscale, which drives spontaneous ordering in nanomaterials [21–23] and hence can be used in tuning the surface properties. We have earlier reported the structural organization and tuning from anatase to rutile phase in TiO2 nanoparticles using different ionic liquids [24]. Amino acid ionic liquids (AAILs) are another class of ionic liquids derived using amino acids. AAILs are broadly used in dissolving biomass like DNA, cellulose or carbohydrates, as a gas absorbing medium especially CO2 capture [25]. In this work, we have worked on room temperature gas sensing using CA based polymer membranes incorporated with AAIL. 1-ethyl3-methylimidazolium bromide was used as IL together with the amino acids Proline and Phenylalanine for the synthesis of AAIL. It has been reported that L-Proline has a high pKa (pKa = 10.64) and when blended with monoethanolamine (MEA) shows high loading capacity for CO2 [26]. Proline with tetrabutylphosphonium and trihexyl(tetradecyl) phosphonium has been tested for gas separation, features the highest CO2 permeability and could absorb large amount of CO2 under wide pressure range [27,28]. Phenylalanine based IL application research work is scarce in literature. Incorporation of AAILs in the polymer membranes is a novel work and has not been reported so far. We report the sensitivity, selectivity, response and recovery time which are the key components of thin-film gas sensors. Selectivity studies have been carried out on the cellulose acetate membrane sensor for various gases such as ammonia, ethanol, acetone, and toluene [29–32] in different ppm concentrations of the target gas and measured their sensitivity.

stirred under cooling for 12 h. followed by evaporating the water at 40–50 °C. To this reaction mixture 90 mL of aceonitrile and 10 mL of methanol was added, and it was stirred vigorously and after filtering the excess amino acid was removed. The product was dried in vacuo for 2 days at 80 °C. Structure of the resulting amino acid ionic liquid was confirmed by 1H NMR spectroscopy (Bruker-300 MHz). 2.3. Preparation of CA-IL and CA-AAIL membranes For fabrication of CA-IL and CA-AAILs membranes phase inversion method was used. The neat CA membrane was prepared by adding 17.5 wt% of CA in 21.7 mL of DMF solvent followed by magnetic stirring. For IL incorporated membranes, 5 wt% of IL and AAILs were added in 21.7 mL of DMF under constant stirring and dispersed well by ultrasonication. CA was added to the solution and complete dispersion was further ensured by ultrasonication for 30 min. The thickness of the membrane was fixed as 400 μm using a film applicator (elcometer). After about half a minute of evaporation time, the membrane was dipped in distilled water maintained at 15 °C. The casted membrane was then immersed in the gelation bath with water as non-solvent and DMF as solvent in addition to sodium lauryl sulphate (SLS) for 30 min, to leaching out the solvent from the membrane [33] using the phase inversion technique. This technique will ensure morphologies with suitable pore size due to the significance of immersion precipitation [34]. Fig. S1 (Supporting document) shows the step by step process for fabrication of membrane using phase inversion method and shows prepared dope solution and fabricated membrane immersed in water bath. Porosity of the membranes were calculated using the equation [35] Porosity ¼

W w −W d Am Lm dw

ð1Þ

2. Experimental methods 2.1. Chemicals and reagents All chemicals and reagents used were of analytical grade and used without any further purification. 1-ethyl-3-methylimidazolium bromide, Proline, Phenylalanine, Dowex 1 × 8 chloride and Cellulose acetate (CA) were obtained from Sigma Aldrich, India limited. N, N′dimethyl formamide (DMF) were purchased from Qualigens fine chemicals, Glaxo India limited. Millipore water was obtained from the laboratory for the experiments. 2.2. Procedure for amino acid ionic liquids (AAILS) synthesis Fig. 1 shows a schematic diagram of the synthesis of Proline and Phenylalanine ionic liquids. Initially, 1-Ethyl-3-methylimidazoliumhydroxide ([emim][OH]) aqueous solution was prepared from 1-ethyl-3methylimidazolium bromide using anion exchange resin (Dowex 1 × 8 chloride). [emim][OH] aqueous solution was then added drop wise to a slightly excess equimolar amino acid aqueous solution. The mixture was

where Ww is the wet weight of the membrane in g, Wd is the dry weight of the membrane in g, dw is the density of water in g/cm3, Am is the area of the membrane is cm2, and Lm is the thickness of the membrane is cm. 2.4. Characterization Synthesized Structure of the resulting amino acid ionic liquid was confirmed by 1H NMR spectroscopy (Bruker-300 MHz). Contact angle measurement was performed using a contact angle measurement setup (Model no. HO-IAD-CAM-01A, Holmarc, India), and the analysis was done to check the wettability of the prepared membranes. FTIR spectroscopy study is done for the analysis of molecular structures and the conformations of macromolecules. It was done using Spectrum Two FT-IR Spectrometer, Perkin Elmer. The thermal stability and the degradation of the materials was studied using thermogravimetric analysis (TGA) using TGA 4000, Pyris-6 TGA (Perkin Elmer, USA). Differential scanning calorimetry (DSC) was done to analyse the glass transition temperature of membranes using DSC 6000, Pyris-6 DSC (Perkin Elmer, USA). Cross-sectional morphology of

Fig. 1. Anion exchange method for preparation of AAILs using 1-ethyl-3-methylimidazolium bromide as IL and Proline and Phenylalanine as amino acid to produce [emim][Pro] and [emim][Phe].

P. Mehta et al. / Journal of Molecular Liquids 305 (2020) 112820

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2.5. Gas sensing The gas sensing measurements were carried out using the procedure as given [24]. In this study, initially the chemicals were vaporized using a high temperature flash vaporizer. The membrane (20 mm × 10 mm size) was mounted on the sample stage and using silver paste ohmic contact between the samples and probes was created. The working temperature of the sensor was controlled with a PID temperature controller (Selec PID-500-2-0-04, India). This study was performed at room temperature (TW = 25 °C). The resistance of the sensor was measured using a Keithley 2450 interactive digital source measure unit by sourcing the voltage and computing the current. The entire sensing setup was controlled GUI using LabVIEW. The resistance of the ambient air was taken as the base resistance and after stabilization, the target gas was injected through the gas inlet valve. The change in the resistance, also known as the sensitivity (S) of the thin-film gas sensor was calculated using Eq. (2) [36]. Fig. 2. FTIR analysis of the fabricated membranes.

S ¼ Ra =Rg

ð2Þ

where Ra and Rg are the resistance in air and in gas, respectively. membranes was visualised using SIGMA Scanning Electron Microscopes from Carl Zeiss. Atomic force microscope in the noncontact mode was used for analysing the surface morphology (Park systems (modelNX10)).

3. Results and discussion Firstly, the prepared amino acid ionic liquids were verified using 1H NMR spectroscopy (Bruker-300 MHz) (Fig. S2 - Supporting

Fig. 3. DSC curves of CA membranes with IL and AAILs.

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Fig. 4. TGA curves of CA membranes with IL and AAILs.

information). The spectrum of the prepared AAIL matches with the literature and hence confirms the formation of the [emim][Pro] or Pro-IL and [emim][Phe] or Phe-IL [37]. These AAILs were then used to prepare the CA based membranes and were analysed using FTIR, DSC and TGA. FTIR spectra in the region 4000-500 cm−1 for all the fabricated membranes is shown in Fig. 2. All the samples exhibit a broad absorption band at 3300–3500 cm−1 corresponding to stretching of OH group. The spectrum 2925 cm−1 and 2937 cm−1 for CA-IL and CAProIL respectively dominated by the CH2 bands. The band at 1732–1764 cm−1 is associated with the overlapped ester carbonyls (C=O) in CA. This peak is a characteristic peak for CA as other bands may also occur in other cellulosic polymers [38]. In the 1690–1630 cm−1C = O absorption region, this corresponds to the amide. The 1440 cm−1 absorption peak was attributed to CH2 vibration [39], in addition, the sharp absorption peak at 1230 cm−1 was ascribed to C\\O stretching [40]. A band in the region 1200–1270 cm−1 corresponds to the stretching vibration of C\\N groups. Finally, the band in 903 cm−1 can be assigned to the out-of-plane bending of hydroxyl group. DSC thermogram of the prepared membranes is presented in the Fig. 3. It is reported that the pure CA membrane shows a glass transition temperature of 55 °C [41]. As the membranes were fabricated using wet process increase in glass transition temperature might be due to presence of moisture in the samples. It is observed that with the addition of IL and AAILs there is a shift in the glass transition temperature as

(a)

(c)

compared to the neat membrane. It is seen from the Table S1 (Supporting information) that the onset temperature of the membranes is increasing with the addition of IL and AAILs. TGA thermogram (Fig. 4) of all the membranes were found to have similar initial weight loss behaviour may be attributed due to the loss of moisture present in the membrane samples. Thermal degradation of CA membrane starts nearly around 260 °C [42]. Neat membrane and membrane with IL shows a two-step degradation. The first step of degradation between 25 °C and 300 °C may be due to the evaporation of the solvent, whereas the second step above 300 °C, may be attributed to the degradation of the CA chain due to the dehydration, depolymerization and decomposition of glucose units in the membrane [43]. It is interesting to observe that the membrane with AAILs shows degradation above 300 °C. This proves that the addition of AAILs in the solvent during the preparation of dope solution of the membrane has enhanced the thermally stability as seen from the one step degradation compared to CA and CA-IL. Hydrophilicity of each prepared membranes were measured using contact angle. In general, contact angle values for hydrophilicity should be 0°, and above 90° the surface is hydrophobic [44]. Fig. 5 shows contact angle measurements of all prepared membranes. The work of adhesion (W) has been calculated from the contact angle ɵ using the Young– Dupre equation (Eq. (3)), and the values are tabulated in Table 1. W ¼ σ ð1 þ Cos ɵÞ

ð3Þ

where σ denotes surface tension of water. It can be seen from Table 1 that addition of IL and AAILs effectively varies the contact angle and work of adhesion of the prepared membranes. As all the membranes were fabricated through wet process so it shows the hydrophilic behaviour. Presence of hydrophobic bromide based IL increased the contact angle for CA-IL compared to neat membrane. As AA (Proline and Phenylalanine) are hydrophobic in nature, addition of these AAILs shows a slight increase in the angle as compared to neat membrane. This hydrophobic nature of the membranes is expected to help counteract the interference caused due to humidity [45,46]. Scanning Electron Microscopy was used to verify the membrane morphology. Fig. 6 shows the cross-sectional view of the prepared membranes. We observe an asymmetric structure comprising of the archetypal finger-like macrovoids enclosed in a continuous polymer matrix. Fig. 6 shows that with the addition of IL and AAIL the finger-like macrovoids are visibly prominent as compare to the neat membrane. It can be also seen that there are changes in the density of macrovoids with the addition of IL and AAIL. Proline based IL membrane seems to be denser than the PheIL. These kinds of macrovoid structures are formed due to the surface tension gradient and diffusion of solvent

(b)

(d)

Fig. 5. Contact angle measurement performed on prepared membranes (a) CA-Neat Membrane, (b) CA-IL (EMIM Br) (c) CA-ProIL (d) CA-PheIL.

P. Mehta et al. / Journal of Molecular Liquids 305 (2020) 112820 Table 1 Measured value of contact angle and work of adhesion of the prepared membranes. Membrane samples

Contact angle (θ) (±1 ͦ)

Work of adhesion (J m−2)

% Porosity (±1%)

CA CA-IL CA-ProIL CA-PheIL

58.57 64.80 60.06 65.00

110.76 103.79 108.53 103.56

51.11 57.03 49.86 58.29

expelled from the surrounding polymer solution causes macrovoid growth in the membrane and is suitable for ultrafiltration processes and can be employed as support layers for composite membranes [47]. In phase inversion at room temperature, the solvent evaporates fastly, resulting in high porosity structures as are effectively observed in the membranes, and hence the solvent evaporation rate plays a major role in the morphology of the membranes [47]. The addition of ILs reduced the aggregation tendency to some extent because of the intermolecular interaction between the polymers. The SEM images show that the addition of ProIL greatly affected the membrane formation and the membrane structure. This result is also verified using the porosity measurements and are presented in Table 1, and agrees quite well with the contact angle and SEM analysis. To further study the morphology of the membranes, atomic force microscopy was carried out. Fig. 7 shows the topographical image of the fabricated membranes and it can be clearly seen that the incorporation of ProIL (Fig. 7c) has better pores and corroborates with the SEM analysis.

5

The gas sensitivity of a membrane, measured using the change in resistance when exposed to a particular gas is primarily due to chemisorption that occurs on the surface of the membrane. In the present study, gas sensing measurements were carried out at room temperature (25 °C) for the target gases such as ammonia, acetone, ethanol and toluene. Table S2 (Supporting information) shows the sensitivity (Ra/Rg) of prepared membranes for 100 ppm of different target gases. A comparative histogram for the selectivity of all fabricated membranes at 100 ppm of each gas is shown in Fig. 8. It is inferred from the results that all the fabricated membranes are showing good sensitivity towards ammonia gas compared to other three gases. Fig. 9 shows ammonia gas sensing of CA membrane with IL and AAILs. Furthermore, the membrane with ionic liquid showed higher sensitivity to ammonia at higher ppm compared to neat membrane. This shows that the presence of IL and AAILs in the membranes plays a key role in gas sensing. The presence of macrovoids in the membrane as seen in SEM and AFM, due to the incorporation of IL and AAILs could be the reason for the higher sensitivity. CA membranes incorporated with AAILs shows highest selectivity towards the sensing of ammonia compared to neat membrane. As per our knowledge, this is the first report to use IL incorporated polymer membranes using cellulose acetate, for gas sensing application. CA membrane with IL and AAILs proves to be good candidate for a sensor element in gas sensors for ammonia sensing. In general, a best gas sensor is expected to have a minimum response and recovery time. For the sake of clarity, we have presented the response and recovery time of CA-ProIL in Fig. 10 for 100 ppm of ammonia. The response time which is the time taken to detect the gas and recovery time is the time taken to return to the base resistance when

(a)

(b)

(c)

(d)

Fig. 6. SEM of the cross-sectional view of prepared membranes (a) CA-Neat Membrane, (b) CA-IL (EMIM Br) (c) CA-ProIL (d) CA-PheIL.

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(b)

(a)

(c)

(d)

Fig. 7. AFM of prepared membranes (a) CA-Neat Membrane, (b) CA-IL (EMIM Br) (c) CA-ProIL (d) CA-PheIL.

the gas is removed from the chamber. From Table 2 we can clearly observe that CA incorporated with AAIL membranes shows faster response and recovery time for ammonia. Even though IL and ProIL incorporation in CA membranes shows good sensing for 100 ppm ammonia, for wide range sensing ProIL incorporated membranes are better as they can sense even 1 ppm ammonia. In order to understand the mechanism of adsorption of ammonia to the AAILs, in a separate experiment, NMR studies were carried out (Fig. S3, S4, supporting information) for all the samples in solution

after exposing to 100 ppm ammonia for the same time as per the sensing experiments. From NMR data it is seen that imidazolium cation and amino acid anion gets charge separated due to the exposure to ammonia, confirming from the change in the integration values of the proton NMR signal. We propose here that the anionic amino acid forms adduct with ammonia and the reaction is predominant in ProIL compared to PheIL and IL, in concurrence with our results using these ionic liquids. Such interactions have been observed in cobalt ionic liquids when exposed to ammonia [48]. Rigorous DFT analysis need to be carried out to verify our observation and the work is under progress. 4. Conclusion

Fig. 8. Selectivity graph of prepared membranes for 100 ppm of different target gases.

In conclusion, out of the many multi-tasking abilities of ILs, this work has shown that the IL in particular, AAILs can be incorporated to polymeric membranes for room temperature gas sensing measurements. The CA membranes were fabricated using phase inversion method and characterized using various techniques. FTIR confirms the formation of well blended membranes. DSC and TGA measurements showed that the presence of IL in the CA membranes improves the thermal stability and degradation. The hydrophilicity of the fabricated membranes was studied by measuring contact angle. The gas sensing behaviour of the polymeric membranes was tested at room temperature. All the fabricated membranes showed the good response and selectivity towards ammonia. CA membranes have great potential for gas sensing application when integrated with AAILs into their matrix. CA-ProIL

P. Mehta et al. / Journal of Molecular Liquids 305 (2020) 112820

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Fig. 9. Sensing response plots for ammonia gas sensing prepared membranes (a) CA-Neat Membrane (b) CA-IL (EMIM Br) (c) CA-ProIL (d) CA-PheIL. The numbers indicated on the plot are the concentrations of gas injected (in ppm).

demonstrated fast sensing of ammonia, as low as 1 ppm concentration at room temperature with the minimal response and recovery time. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements

Fig. 10. Response and recovery curve of CA-ProIL membrane for 100 ppm of ammonia.

Author K.S. thanks Department of Science and Technology, Govt of India, for the Inspire Faculty Award (IFA13-PH-82, Dy.No. 108 Dt. 8.1.2014). Author S.V. thanks DST-INSPIRE faculty award (DST/INSPIRE/04/2015/000328). Author S.G. thanks SERB ECR award (ECR/ 2018/000254). K.S. thanks Dr. K. Jeyadheepan, SASTRA University for gas sensing studies through the Science and Engineering Research Board(SERB), Govt. of India funded project “SB/FTP/PS-038/2013”. The authors acknowledge the MHRD, Government of India for the AFM facility under the plan fund sanctioned to the Department of Physics, NIT Tiruchirappalli. Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi. org/10.1016/j.molliq.2020.112820.

Table 2 Comparison of response and recovery time. Samples

PPM

Response time (s)

Recovery time (s)

Neat membrane CA CA-IL CA-ProIL CA-PheIL

50 75 100 100

236 241 60 67

107 77 78 147

References [1] M.A. Sutton, U. Dragosits, Y.S. Tang, D. Fowler, Atmos. Environ. 34 (2000) 855. [2] L.J. Wilson, P.J. Bacon, J. Bull, U. Dragosits, T.D. Blackall, T.E. Dunn, K.C. Hamer, M.A. Sutton, S. Wanless, Environ. Pollut. 131 (2004) 173.

8

P. Mehta et al. / Journal of Molecular Liquids 305 (2020) 112820

[3] S. Sinawat, W.-C. Hsaio, J.H. Flockhart, M.H. Kaufman, J. Keith, J.D. West, Hum. Reprod. 18 (2003) 2157. [4] R.A. Coon, R.A. Jones, L.J. Jenkins, J. Siegel Jr., Toxicol. Appl. Pharmacol. 16 (1970) 646. [5] N. Brautbar N, M.P. Wu, E.D. Richter, Arch. Environ. Health 58 (2003) 592. [6] J.W. Erisman, R. Otjes, A. Hensen, P. Jongejan, P. van den Bulk, A. Khlystov, H. M̈ols, S. Slanina, Atmos. Environ. 35 (2001) 1913. [7] W. Ament, J.R. Huizenga, E. Kort, R.G. Mark, G.J. Verkerke, Int. J. Sports Med. 20 (1999) 71. [8] S.Y. Wang, J.Y. Ma, Z.J. Li, H.Q. Su, N.R. Alkurd, W.L. Zhou, L. Wang, B. Du, Y.L. Tang, D.Y. Ao, S.C. Zhang, Q.K. Yu, X.-T. Zu, J. Hazard. Mater. 285 (2015) 368. [9] J. He, X. Yan, A. Liu, R. You, F. Liu, S. Li, J. Wang, C. Wang, P. Sun, X. Yan, B. Kang, J. He, Y. Wang, G. Lu, J. Mater. Chem. A 7 (2019) 4744. [10] Y. Tang, Z. Li, X. Zu, J. Ma, L. Wang, J. Yang, B. Du, Q. Yu, J. Hazard. Mater. 298 (2015) 154. [11] A. Falco, A. Rivadeneyra, F.C. Loghin, J.F. Salmeron, P. Lugli, A. Abdelhalim, J. Mater. Chem. 6 (2018) 7107. [12] H. Bai, G. Shi, Sensors (Basel) 7 (2007) 267. [13] G. Korotcenkov, Handbook of Gas Sensor Materials, Properties, Advantages and Shortcomings for Applications, Conventional Approaches, 1, , Springer-Verlag, New York, 2013. [14] C.W. Zhao, J.P. Ma, Q.K. Liu, X.R. Wang, Y. Liu, J. Yang, J.S. Yang, Y.B. Dong, Chem. Commun. 52 (2016) 38. [15] (a) S. Sachdeva, D. Soccol, D.J. Gravesteijn, F. Kapteijn, E.J.R. Sudhölter, J. Gascon, L.C.P.M. de Smet, ACS Sensors 1 (88) (2016); (b) B. Sasikumar, G. Arthanareeswaran, K. Sankaranarayanan, K. Jeyadheepan, ACS Sustain. Chem. Eng. 7 (2019) 15884. [16] L.A.N. El-Din, A. El-Gendi, N. Ismail, K.A. Abed, A.I. Ahmed, J. Ind. Eng. Chem. 26 (2015) 259. [17] G. Arthanareeswaran, T.K.S. Devi, M. Raajenthiren, Sep. Purif. Technol. 64 (2008) 38. [18] G. Arthanareeswaran, P. Thanikaivelan, K. Srinivasn, D. Mohan, M. Rajendran, Eur. Polym. J. 40 (2004) 2153. [19] K. Sankaranarayanan, M. Kalaiyarasi, B. Sreedhar, B.U. Nair, A. Dhathathreyan, Int. J. Nanosci. 13 (2014), 1450006. [20] T. Welton, Chem. Rev. 99 (1999) 2071. [21] C.M. Correa, M.A. Bizeto, F.F. Camilo, J. Nanopart. Res. 18 (2016) 132. [22] J. Dupont, J. Braz. Chem. Soc. 15 (2004) 341. [23] J. Dupont, J.D. Scholten, Chem. Soc. Rev. 39 (2010) 1780. [24] S.M. Sali, S. Joy, N. Meenakshisundaram, R.K. Karn, C. Gopalakrishnan, P. Karthick, K. Jeyadheepan, K. Sankaranarayanan, RSC Adv. 7 (2017), 37720.

[25] P. Ossowicz, E. Janus, A. Szady-Chełmieniecka, Z. Rozwadowski, J. Mol. Liq. 224 (2016) 211. [26] A.F. Ciftja, A. Hartono, H.F. Svendsen, Energy Procedia 37 (2013) 1597. [27] B.F. Goodrich, J.C. de la Fuente, B.E. Gurkan, Z.K. Lopez, E.A. Price, Y. Huang, J.F. Brennecke, J. Phys. Chem. B 115 (2011) 9140. [28] F. Moghadam, E. Kamio, H. Matsuyama, J. Membr. Sci. 525 (2017) 290. [29] B. Karunagaran, P. Uthirakumar, S.J. Chung, S. Velumani, E.K. Suh, Mater. Charact. 58 (2007) 680. [30] R. Pandeeswari, R.K. Karn, B.G. Jeyaprakash, Sensors Actuators B Chem. 194 (2014) 470. [31] N. Chen, Y. Li, D. Deng, X. Liu, X. Xing, X. Xiao, Y. Wang, Sensors Actuators B Chem. 238 (2017) 491. [32] Y. Liu, L. Wang, H. Wang, M. Xiong, T. Yang, G.S. Zakharova, Sensors Actuators B Chem. 236 (2016) 529. [33] B. Ladewig, M.N.Z. Al-Shaeli, Fundamentals of Membrane Bioreactors: Materials, Systems and Membrane Fouling, Springer Transactions in Civil and Environmental Engineering, , Springer, Singapore, Singapore, 2017. [34] G.R. Guillen, Y. Pan, M. Li, E.M.V. Hoek, Ind. Eng. Chem. Res. 50 (2011) 3798. [35] L.P. Zhang, G.W. Chen, H.W. Tang, Q.Z. Cheng, S.Q. Wang, J. Appl. Polym. Sci. 112 (2009) 550. [36] G. Sakai, N. Matsunaga, K. Shimanoe, N. Yamazoe, Sensors Actuators B Chem. 80 (2001) 125. [37] K. Fukumoto, M. Yoshizawa, H. Ohno, J. Am. Chem. Soc. 127 (2005) 2398. [38] B. Ghorani, S.J. Russell, P. Goswami, International Journal of Polymer Science 2013 (2013), 256161(12 pages). [39] S. Soares, N.M.P.S. Ricardo, S. Jones, F. Heatley, Eur. Polym. J. 37 (2001) 737. [40] D. Murphy, M.N.D. Pinho, J. Membr. Sci. 106 (1995) 245. [41] J.J. Shieh, T.S. Chung, J. Membr. Sci. 140 (1998) 67. [42] P.K. Chatterji, J. Polym. Sci. 6 (1968) 3217. [43] S. Saska, H.S. Barud, A.M.M. Gaspar, R. Marchetto, S.J.L. Ribeiro, Y. Messaddeq, International Journal of Biomaterials 2011 (2011), 175362(8 pages). [44] L. Gao, T.J. McCarthy, Langmuir 22 (2006) 6234. [45] J.G. Huddleston, A.E. Visser, W.M. Reichert, H.D. Willauer, G.A. Broker, R.D. Rogers, Green Chem. 3 (2001) 156. [46] J.Q. Xue, N.N. Liu, G.P. Li, L.T. Dang, Water Sci. Technol. 76 (2017) 3142. [47] C.A. Smolders, A.J. Reuvers, R.M. Boom, I.M. Wienk, J. Membr. Sci. 73 (1992) 259. [48] S. Zeng, L. Liu, D. Shang, J. Feng, H. Dong, Q. Xu, X. Zhang, S. Zhang, Green Chem. 20 (2018) 2075.