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Preparation of Free-standing and Flexible Graphene/ Ag Nanoparticles/Poly(pyronin Y) Hybrid Paper Electrode for Amperometric Determination of Nitrite Kader Dagci, and Murat Alanyalioglu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.5b10973 • Publication Date (Web): 12 Jan 2016 Downloaded from http://pubs.acs.org on January 19, 2016
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ACS Applied Materials & Interfaces
Preparation of Free-standing and Flexible Graphene/Ag Nanoparticles/Poly(pyronin Y) Hybrid Paper Electrode for Amperometric Determination of Nitrite
Kader Dağcı, Murat Alanyalıoğlu*
Atatürk University, Sciences Faculty, Department of Chemistry, 25240, Erzurum, Turkey
* Corresponding author; E-mail:
[email protected]; Phone: +90 442 231 4283; Fax: +90 442 231 4109
Abstract: A flexible and free-standing graphene-based hybrid paper was successfully fabricated by successive applications of vacuum filtration and electropolymerization. First, a suspension including graphene oxide (GO) and silver nanoparticles (AgNPs) was prepared and GO/AgNPs paper was obtained by vacuum-filtration of this suspension through a membrane. This GO/AgNPs paper was transformed to rGO/AgNPs paper by using both chemical reduction with HI and thermal annealing procedures. rGO/AgNPs/poly(PyY) hybrid paper electrode was formed by electropolymerization of Pyronin Y (PyY) on rGO/AgNPs paper electrode from a PyY monomer-containing (pH: 1.0) solution. Structural, chemical, and morphological characterization of this hybrid paper was carried out by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, infrared spectroscopy, UV-Vis. absorption spectroscopy, four-point probe conductivity measurement
and
cyclic
voltammetry
techniques.
Electrooxidation
of
nitrite
on
rGO/AgNPs/poly(PyY) hybrid paper electrode has been achieved at 860 mV with the linear range of 0.1-1000 µM, sensitivity of 13.5 µAµM-1cm-2 and the detection limit of 0.012 µM. Amperometry studies have shown that the hybrid paper electrode is suitable for amperometric
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determination of nitrite in both standard laboratory samples and real samples. Moreover, this paper electrode selectively detects nitrite even in the presence of 100-fold common ions and also exhibits an excellent operational stability and good flexibility.
Keywords: graphene paper electrode, electropolymerization, pyronin Y, amperometric detection, nitrite
1. Introduction Nitrite (NO2-) has an important role in food technology for curing meat because it prevents bacterial growth. On the other hand, high toxicity of nitrite requires its control as food additive because nitrite in meat reacts with degradation products of amino acids and forms nitrosamines, which are known as carcinogen compounds. The role of nitrite in blocking botulism, which is a fatal illness caused by a toxin produced by the “Clostridium Botulinum” bacteria, prevents the complete removal of nitrite from cured meat. Meat generally cannot be labeled as "cured" without nitrite addition. World Health Organization and the European Commission's Scientific Committee on Food have set daily maximum intake of nitrite as 0.07 mg nitrite ion/kg body weight. Therefore, the quantitative analysis of nitrite in food samples is of great importance, especially for the supervision of the quality of food. Determination of nitrite has started with Griess assay1 and many methods have been developed up to date for quantitative analysis of nitrite such as, colorimetry,2 spectrophotometry,3 fluorometry,4 chromatography,5 and electrochemistry.6-21 Owing to high sensitivity, relatively good selectivity, fast response, simple use, easy application under ambient conditions, environmentally-friendly instrumentation and low cost, electrochemical techniques are favorable for nitrite determination. In recent years, flexible graphene papers (GPs) have been prepared due to their high
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ACS Applied Materials & Interfaces
mechanical flexibility, electrochemical performance and chemical stability in various potential
applications
such
as
fuell
cells,22
membranes,23
Li-ion
batteries,24
supercapacitors,25,26 and electrochemical sensors.27,28 The electrical conductivity of GPs is as low as 100 S/cm because of defects and residual oxygen-containing groups. In general two protocols are applied to increase the electrical conductivity and electrochemical activity of GPs; doping GPs with the nanomaterials and thermal or chemical reduction. Doping GPs with different amounts of nanomaterials e.g. metal nanoparticles,22,24,27,28,31,32,33 conductive polymers,25,29,30 carbon nanotubes,26,31,32 and dyes33 can also supply tuning opportunity of physical properties of GPs as desired. GPs can be made of either graphene oxide (GO) or reduced graphene oxide (rGO) by relatively simple, rapid, and low-cost procedures, which involve
vacuum
filtration,22-25,29,30,32-34
centrifugation,27
mold-casting,28,31
ink-jet
printing,26,30,35 and pressing36 of graphene-containing suspension. Pyronin Y (PyY) is a water-soluble xanthene-type dye molecule, which contains two tertiary amine groups in a position of xanthene ring.13 PyY has high absorption coefficient and electron actuator property. Therefore, it may be supposed that presence of PyY in GPs structure decreases the electrooxidation potential of nitrite and increases electroactive electrode surface area, which may cause the electrocatalytical effect. When compared to graphene-supported electrodes, amperometric determination on free-standing GBPs is more suitable for modular applications due to their high flexibility, moldability, foldability, and cuttability as desired. GBPs supply also larger electroactive surface area and more current density than graphene-supported electrodes with their double-sided surface and this case increases the sensitivity of the sensor. To the best of our knowledge, amperometric determination of nitrite has not been performed by using GPs until now. In this paper, we have firstly prepared a flexible and free-standing rGO/AgNPs/poly(PyY) hybrid paper by using the following steps: vacuum-filtration of GO/AgNPs suspension
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through a membrane, followed by peeling it off, reduction of GO/AgNPs free-standing paper, and then electropolymerization of PyY on rGO/AgNPs paper. This hybrid paper electrode has shown an excellent electrocatalytical activity, which is confirmed by the sensitive and selective determination of nitrite. More importantly, this flexible hybrid paper electrode also exhibits fast response time, long-term stability, flexibility, reproducibility and tolerance to physical deformation, which offer possibilities of the quantitative determination of nitrite in real samples.
2. Experimental Section
2.1. Materials All the chemicals used in this study were of analytical reagent grade and used as received. Milli-Q ultra-pure water (conductivity: 5.5 µS.m-1) was used all through this study. Phosphate buffer solutions (PBS, 0.1 M) of different pH values were prepared by mixing stock solutions of 0.1 M H3PO4 and KH2PO4, and the pH of the buffer solution was adjusted to desired value by using a Hanna pH-meter. 0.1 M H2SO4 (Sigma Aldrich, ACS reagent) solution was used as pH 1.0 solution. Solution of 1.0x10-3 M NaNO2 was prepared by directly dissolving sodium nitrite (Sigma Aldrich, ACS reagent) in PBSs. The solutions were deaerated by passing dry nitrogen through the electrochemical cell for 15 min prior to each experiment.
2.2. Synthesis of GO GO was synthesized from graphite powder (Sigma Aldrich, 99.99% purity, particle size
