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In this study, polymer-supported graphene-based material was designed for electrochemical determination based on the hybridization of DNA. First, dispersions containing graphene oxide (GO) and poly...

We studied the production and electrochemical performance of NiCo2S4 electrodeposited reduced graphene oxide (rGO) paper for use as a freestanding flexible electrode for the simultaneous determination of folic acid (FA) and ascorbic acid (AA). Production of rGO paper was achieved through vacuum filtration of the aqueous dispersion of graphene oxide, followed by chemical reduction in hydrogen iodide solution. NiCo2S4/rGO paper material was fabricated with a simple approach using electrodeposition of hydrothermal synthesized NiCo2S4 nanoparticles directly on rGO paper. The physicochemical properties of as-prepared flexible NiCo2S4/rGO paper were characterized by means of field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray powder diffraction patterns. This freestanding paper electrode demonstrated high sensitivity, a wide linear range, and a low detection limit towards the simultaneous detection of FA and AA. NiCo2S4/rGO paper sensor, possessing easy preparation, low cost, and high flexibility, was tested in real samples with promising recoveries. This study exhibited that the approach of the electrodeposition of bimetallic sulfides on freestanding graphene paper substrates has great potential to develop high-performance flexible electrochemical sensors.

We proposed a new type of freestanding Catalase (EC 1.11.1.6) (Cat) modified paper electrode based on Fe3O4 crystals decorated freestanding reduced graphene oxide (rGO) paper (Cat-Fe3O4/rGO) using a facile electrodeposition method. This enzyme modified paper electrode was used for the specific determination of hydrogen peroxide (H2O2). Structural, chemical, and morphological characterization of the Fe3O4 crystals formed on rGO paper was investigated by (i) using scanning electron microscopy (SEM), (ii) energy-dispersive X-ray spectroscopy (EDS), (iii) X-ray photoelectron spectroscopy (XPS), (iv) X-ray diffraction spectroscopy (XRD), (v) Raman spectroscopy, (vi) electrochemical impedance spectroscopy (EIS) and (vii) cyclic voltammetry (CV) techniques. The Cat enzyme was successfully adsorbed on the Fe3O4 nanocrystals surface which was demonstrated by fluorescence microscopy. The Cat-Fe3O4/rGO paper electrode showed excellent electrocatalytic activity toward H2O2. It is found that Cat-Fe3O4/rGO paper electrode shows a wide linear range, high sensitivity, and a low detection limit for H2O2 detection.

Bu çalışmada; esnek, müstakil ve dayanıklı PtCu/indirgenmiş grafen oksit (iGrO) hibrit kağıt sentezlenmiş ve p-nitrofenolün (PNP) elektrokimyasal olarak tespiti için kullanılmıştır. PtCu/iGrO hibrit kağıt, PtCu alaşım nanokompozit yapısının iGrO kağıt elektrot üzerine elektrokimyasal olarak kaplanmasıyla üretilmiştir. Elde edilen PtCu/iGrO hibrit kağıt, taramalı elektron mikroskobu, X-ışını kırınım spektroskopisi, X-ışını fotoelektron spektroskopisi, Raman spektroskopisi, elektrokimyasal empedans spektroskopisi ile karakterize edildi. PtCu/iGrO hibrit kağıdının morfolojik analizi, iGrO elektrot yüzeyinde oluşan çiçek benzeri nanoyapıların çok sayıda keskin kenarlı PtCu nanotabakalarından oluştuğunu göstermiştir. PNP’nin elektrokimyasal belirlenmesinde kullanılan, PtCu/iGrO hibrit kağıt elektrotun, iGrO kağıda kıyasla yüksek elektrokatalitik performans, geniş doğrusal aralık (0.08-760 µM) ve düşük algılama limiti (0.022 µM) sergilediği belirlenmiştir. PtCu/iGrO hibrit kağıt sensör ayrıca musluk suyunda PNP tespiti için yüksek geri kazanım değerleri göstermiştir. Pratik ve uygulanması kolay bir yöntem ile hazırlanan hibrit kağıt sensörü mekanik olarak esnek ve dayanık özellik sergilemiştir. Ayrıca, PtCu/iGrO kağıdın stabilite testleri, bu hibrit elektrotun yüksek performanslı esnek sensör uygulamaları için önemli bir aday olduğunu göstermiştir., In this study; a flexible, self-contained and durable PtCu/reduced graphene oxide (iGrO) hybrid paper was synthesized and used for the electrochemical detection of p-nitrophenol (PNP). PtCu/iGrO hybrid paper was fabricated through electrodeposition of PtCu composite structure on iGrO paper electrode. The obtained PtCu/iGrO hybrid paper was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, electrochemical impedance spectroscopy. The morphological analysis of PtCu/iGrO hybrid paper showed that flower-like nanostructures formed on the iGrO electrode surface consist of numerous sharp-edged nano layer of PtCu. PtCu/iGrO hybrid paper electrode demonstrated high electrocatalytic performance compared to iGrO paper and exhibited a wide linear range (0.08-760 µM) and a low detection limit (0.022 µM) for the determination of PNP. The PtCu/iGrO hybrid paper sensor also showed high recovery values for PNP detection in tap water. The hybrid paper sensor prepared with a practical and easy-to-apply method exhibited mechanically flexible and durable properties. Moreover, stability tests of PtCu/iGrO paper displayed that this hybrid electrode is an important candidate for high-performance flexible sensor applications.

Bu calismada, serbest duran, yuksek esneklik ve dayaniklilik ozelligine sahip, yuzeyi MnO 2 kapli indirgenmis grafen oksit (MnO 2 /rGO) kagit hazirlanmistir. Elde edilen MnO 2 /rGO kagit, taramali elektron mikroskobu-enerji dagilimli X-isini spektroskopisi (SEM-EDS), X-isini kirinim spektroskopisi (XRD), X-isini foto elektron spektroskopisi (XPS) ve Raman spektroskopisi gibi teknikler ile karakterize edilmistir. Dopaminin (DA) elektrokimyasal davranisi, esnek MnO 2 /rGO kagit uzerinde, donusumlu voltametri ve amperometri metotlari ile incelenmistir. Elektrokimyasal sonuclar, esnek MnO 2 /rGO kagit elektrotun yuksek spesifik yuzey alanina sahip olmasindan dolayi, DA'ya karsi mukemmel elektrokatalitik aktivite sergiledigini gostermistir. Ayrica, elde edilen esnek elektrokimyasal sensor, DA'nin amperometrik tayininde; genis bir dogrusal aralik, dusuk tayin siniri ve oldukca hassas tepki gostermistir.

Highly flexible graphene/poly(methylene blue)/AgNPs composite paper was successfully prepared for amperometric biosensing of NADH. For this purpose, a dispersion including graphene oxide (GO), methylene blue (MB) and silver nanoparticles (AgNPs) was prepared and GO/MB/AgNPs paper was acquired by vacuum-filtration of this dispersion through a suitable membrane. After peeling it off from membrane, it was transformed to rGO/MB/AgNPs paper by performing reduction with hydriodic acid. In a three-electrode cell, which is containing 0.1 M phosphate buffer solution (pH: 9.0), rGO/MB/AgNPs paper was used as working electrode and rGO/poly(MB)/AgNPs composite paper was generated by surface-confined electropolymerization of MB using successive cyclic voltammetry approach in a suitable potential window. Characterization of this composite paper was carried out by using scanning electron microscopy, scanning tunneling microscopy, X-ray photoelectron spectroscopy, powder X-ray diffraction spectroscopy, Raman spectroscopy, four-point probe conductivity measurement and cyclic voltammetry techniques. Flexible rGO/poly(MB)/AgNPs composite paper has demonstrated high sensitivity, wide linear range and low detection limit for amperometric quantification of NADH.

The flexible, free-standing, durable SnS2-gC3N4/rGO paper material was prepared by vacuum filtration of the composite dispersion containing GO and the SnS2-gC3N4 composite structure which is synthesized by a simple hydrothermal method. The as-prepared SnS2-gC3N4/GO composite paper was converted to SnS2-gC3N4/rGO paper material by applying a chemical reduction process. SnS2-gC3N4/rGO paper material was characterized by using FESEM, XRD, Raman, XPS, and EIS spectroscopy techniques. The SnS2-gC3N4 composite, a porous flower-like structure, uniformly intercalated between the graphene nanosheets exhibited excellent mechanical stability, greatly improved active surface areas, and enhanced surface porosity, in comparison with the pristine rGO paper. SnS2-gC3N4/rGO composite paper material show a highest specific capacitance of 532 F g-1 at 1 A g-1 and good cycling stability with capacitance retention of 60 % at 4 A g-1 after 5000 cycles. Moreover, SnS2-gC3N4/rGO composite paper demonstrate an excellent supercapacitor performance compared to the gC3N4/rGO paper and pristine rGO paper. The flexible symmetric supercapacitor based on SnS2-gC3N4/rGO composite electrode exhibits remarkable mechanical flexibility, high capacitive performance (403 F g-1 at 1 A g-1) and high cycle stability (63.8% at 4 A g-1 after 1500 cycles). As a result, SnS2-gC3N4/rGO composite paper material is expected to be a promising material for high-performance energy storage applications.

The present work demonstrates the fabrication and sensing performance of a free-standing paper electrode composed of boron oxide (B2O3) and graphene for the application of the simultaneous detection of melatonin (MEL) and ascorbic acid (AA). The flexible paper electrode (B-RGO) was fabricated through vacuum filtration of homogeneous composite dispersion (B-GO) consisting of B2O3 in GO, followed by chemical reduction with HI. The structural, chemical and morphological characterization of B-RGO composite paper was performed by using various techniques. This flexible paper electrode exhibited high sensitivity, wide linear range and low detection limit for the simultaneous determination of MEL and AA. The outstanding performance of B-RGO paper electrode could be attributed to the round-edged rod-like B2O3 structures between graphene layers, which provide an increment of the surface area and the electrochemical activity of the composite paper. Furthermore, this paper electrode showed high sensitivity and selectivity for the determination of MEL and AA in real sample analysis.

Poly(methylene blue)/graphene nanocomposite thin films were prepared by electropolymerization of methylene blue in the presence of graphene which have been synthesized by two different methods of a chemical oxidation process and an electrochemical approach. Synthesized nanocomposite thin films were characterized by using cyclic voltammetry, UV–vis. absorption spectroscopy, powder X-ray diffraction, and scanning tunneling microscopy techniques. Electrocatalytical properties of prepared poly(methylene blue)/graphene nanocomposite films were compared toward electrochemical oxidation of nitrite. Under optimized conditions, electrocatalytical effect of nanocomposite films of chemically prepared graphene through electrochemical oxidation of nitrite was better than that of electrochemically prepared graphene.

The electropolymerization of thionine in an aqueous solution has been carried out by using both cycling voltammetry and chronoamperometry experiments. Electropolymerization has been applied at various pHs by using different working electrodes. The characterization of poly(thionine) thin films is performed by using cyclic voltammetry, current–time transients, atomic force microscopy, scanning tunnelling microscopy, ATR-FTIR, and UV–vis absorption spectroscopy techniques. It is deduced from current–time transients and morphological data that poly(thionine) film forms with random adsorption process and exhibits an irregular polymeric film. Poly(thionine) film formation was compared with that of previously published results of phenothiazine derivatives of poly(azure A) and poly(methylene blue). It has been concluded that type of amine functional group of phenothiazine dyes is very effective on the formation of polymeric film structure. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39686.