Synthesis and characterization of NaX nanozeolite using stem sweep and application of Ag-modified nanozeolite in electrocatalytic reduction of H2O2

Hydrogen peroxide (H2O2) has a significant role in diverse fields such as synthesis of various organic compounds, food and agricultural, pharmaceutical, biological, clinical, environmentaland chemical industry and fuel cells. Therefore, it is worthwhile to make efforts to develop a rapid, simple, accurate and reliable method for determination of H2O2 [1]. Electrochemical methods have been used for determination of H2O2 due to their inexpensive, effective, simpleand high sensitivity nature. However, the direct oxidation or reduction of H2O2 at bare electrode has drawbacks like slow electron transfer kinetics and high overpotential for redox reactions. Metal particles, such as Ag as a typical noble metal particles show excellent catalytic activity forH2O2 reduction because they not only have common characteristics of noble metal particles but also have unique properties of biocompatibility, availability, catalysis and low toxicity [2]. Zeolite is one of the nanoporous materials that have a high potential application in the variousfields such as catalysis, sensing, ion exchange and absorption for separation of various chemical species. Recently, exceptional attention has been paid to synthesis of nanocrystalline zeolites. Nanocrystalline zeolites are materials with dimensions of less than 100 nm with specialproperties. In the electrochemical fields, zeolites have been applied in construction of electrochemical sensors and Electrocatalysis. Zeolite-modified electrodes (ZMEs) are asubcategory of the so-called chemically modified electrode, which are electrodes based on theion exchange ability of zeolite between electroactive and nonelectroactive cations in the surface located zeolite particles [3]. In the present work we synthesized template-free NaX nano-zeolitefrom SSA as silica source by the hydrothermal method. NaX was modified through the replacement of Na+ with Ag (I). In order to prepare the modified carbon paste electrode (Ag/XCPE), zeolite and graphite powder (30:70 w/w) were hand-mixed in diethyl ether. Afterward, 2to 3 drops of paraffin was added and this mixture was thoroughly mixed. The resulting carbon paste was packed in the bottom of glassy tube (internal radius of 1.5 mm) and copper wire was inserted through another end of the tube to create electrical contact. Prior to each experiment,constructed electrode (NaX-CPE) was immersed in 0.1 M AgNO3 solution for 10 min. Finally, the silver ions were electrochemically reduced at -1 V vs. Ag| AgCl for 5 min. The Ag/X-CPE electrode was used for electrochemical determination of H2O2. The synthesized nanoparticleswere characterized using X-ray diffraction, scanning electronic microscopy, Brunauer–Emmett– Teller (BET) and FT-IR techniques. The synthesized nanozeolite is used incorporating Ag (I) ions for preparing modified carbon paste electrode (Ag/X-CPE) as an electrochemical sensor forthe reduction of H2O2. Electrochemical results demonstrate that nanozeolite provides a promising platform for the development of electrochemical sensors in biosensing and Ag/X-CPE electrode possesses the remarkable catalytic activity toward the H2O2 reduction. Amprometric results showthat this sensor could detect H2O2 in linear ranges of 20 mM to 1.76 mM and 1.76–11.76 mM with a detection limit of 9.1 mM at a signal-to-noise ratio of 3 and a response time of 2 s. Furthermore, this sensor exhibited good anti-interference and selectivity. The prepared nonenzymatic H2O2 sensor indicated a remarkable analytical performance, including wide linear range, low detection limit, rapid response and high sensitivity toward the detection of H2O2because of the existence of silver active sites in the pores of zeolites at the surface of modified carbon paste electrode.

کلیدواژه ها:

Stem sweep ، Ag particles ، NaX nanozeolite ، modified electrode ، Hydrogen peroxide