Hydrogen peroxide sensor: Uniformly decorated silver nanoparticles on polypyrrole for wide detection range
Graphical abstract
Introduction
In the recent decades, the hydrogen peroxide (H2O2) detection has gained huge interest due to its important role in the biochemical, chemical, pharmaceutical and various other fields [1]. Many different methods have been developed for detecting H2O2, such as spectrophotometry [2], titrimetry [3], chemiluminescence [4], chromatography [5], spectrofluorometry [6], and electrochemistry [7], [8], [9], [10]. The electrochemical nonenzymatic sensors have been extremely used in determination of H2O2 due to their high sensitivity and their good selectivity.
The composites containing metal nanoparticles and conducting polymers (CPs) are very interesting materials due to their easy preparation, high conductivity and good environmental stability as well as their catalytic properties [11], [12], [13], [14], [15], [16], [17], [18], [19], [20]. The electrodeposition of conducting polymers and metallic particles can be carried out independently in the same solution containing both components [11], [21] or in two different solutions (one containing the monomer and the other the metal salt) [14], [22], [23]. Through electrochemical techniques, by controlling electrodeposition time, current and potential, the composition and the structure of composites can be modified. The amount, dispersion and method of incorporating particles of metal into the conducting polymer film have a considerable effect on the catalytic properties of these materials [24], [25].
The combination of conducting polymers with metal particles gives a promising way to strengthen the CPs as well as introducing electrical properties based on the electrical synergy between the two components. By reducing the size of the materials to nanoscale, the conducting polymer–metal composite properties further increased [26], [27], [28], [29]. In nanocomposites, the electrocatalytic activities increased with reducing the material sizes [11], [30], [31], [32]. The conducting polymers can prevent the aggregation of metal nanoparticles along with easing the electron transfer which increases the sensitivity and selectivity [33].
Among the CPs, polypyrrole (PPy) is one of the most favorable conducting polymers due to excellent redox properties, ease of synthesis, high conductivity, and superior environmental stability [14], [15]. The conjugated bonds in the polymer backbone, high electron affinities and low oxidation potential are the fundamental properties of polypyrrole for their unique electrical properties. By a doping process, the conductivity of polypyrrole can be increased which results in the incorporation of counter ions or dopants including inorganic anions and cations, organic molecules, etc. [34]. Polypyrrole's particular properties such as flexibility, high electrical conductivity and ease of fabrication make it an interesting matrix for composites. Polypyrrole has been favorably electropolymerized as the conducting matrix of composite materials for incorporating noble metals such as Ag, Au, Pt, Ru and Pd [35], [36], [37], [38], [39]. In recent years, due to their multifunctional abilities, the composites of polypyrrole decorated with metal nanoparticle have thus been drawn a huge attention of several research groups [40], [41]. Among the mentioned nanocomposites, the composite of polypyrrole which was decorated with silver nanoparticles (AgNPs) has been constantly investigated since they are effective for various applications [36], [42], [43]. Excellent catalytic activity for the hydrogen peroxide reduction is one of the important characteristics of the Ag nanoparticles (AgNPs) [44]. Electrochemical data revealed that the presence of silver nanoparticles was responsible for high sensitivity of the modified electrode toward the reduction of H2O2 [45], [46].
Although numerous publications have focused on developing new ways for the preparation of the metal nanoparticles and conducting polymers composites, most of them involved a complicated fabrication method. The preparation for the metal nanoparticles-CP composites with controlled nanostructure in a simple and cost-effective way is still a novel challenge. In the present work, in order to prepare a high sensitive hydrogen peroxide sensor, the electrochemical deposition of polypyrrole–silver nanoparticles (PPy-AgNPs) with increased sensing ability toward hydrogen peroxide (H2O2) is presented. By decorating silver nanoparticles (25 nm) on the surface of polypyrrole, a novel modified electrode based on conducting polymer–metal nanoparticles with intricate structure was formed. The electrochemical properties, morphology, chemical composition and electrocatalytic activity of the prepared polypyrrole decorated with Ag nanoparticles were studied in details.
Section snippets
Chemicals and reagents
Ammonia solution, silver nitrate (99%), potassium permanganate (99%), sulfuric acid (99.99%), sodium hydroxide (98%), hydrochloric acid (38%), hydrogen phosphate potassium (70%), lithium perchlorate (99%), potassium dihydrogen phosphate (99%), pyrrole (99.5%) and hydrogen peroxide (30%) were purchased from Sigma–Aldrich. Before using, pyrrole monomer was distillated. All the chemicals were of analytical grade purity. The solutions were deoxygenated and all the experiments were carried out at
Results and discussion
A field emission scanning electron micrograph (FESEM) and particle size distribution of the AgNPs-1-PPy, AgNPs-2-PPy, AgNPs-3-PPy and AgNPs-4-PPy/GCE are shown in Fig. 1. As depicted in Fig. 1a and b, the AgNPs with an average size of 25 nm and particle size with a narrow distribution have been decorated, uniformly dispersed on the polypyrrole surface and anchored on most parts of the polypyrrole surface. As can be seen in Fig. 1c–f, as the concentration of Ag(NH3)2OH increased, the average size
Conclusion
AgNPs-1-PPy/GCE has been successfully prepared via an in situ electrochemical deposition process. XRD, FT-IR, EDX and EIS results confirmed the presence of AgNPs and PPy. The FESEM images of the modified electrode revealed that PPy and AgNPs were uniformly formed and PPy was decorated with small particle size of AgNPs (25 nm). The electrochemical behavior of GCE coated with the AgNPs-1-PPy/GCE film showed the highest electrocatalytic activity as compared with other modified GCEs. AgNPs-1-PPy/GCE
Acknowledgments
Pooria Moozarm Nia wishes to thank Mahtab Mahdavifar for precious reviews and Dr. Mehrdad Gholami and Dr. Farnaz Lorestani for their help and support.
This research is supported by High Impact Research MoE Grant UM.C/625/1/HIR/MoE/SC/04 from the Ministry of Education Malaysia, UMRG Program RP012A-14SUS, PRGS grant PR002-2014A and University Malaya Centre for Ionic Liquids (UMCiL).
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