Musen Li

Preparation of reduced graphene oxide–Ni(OH)2 composites by electrophoretic deposition: application for non-enzymatic glucose sensing

A sensitive and stable non-enzymatic sensing platform for D-glucose based on a reduced graphene oxide (rGO) matrix modified with Ni(OH)2 nanostructures was established. The sensing matrix was fabricated in one-step through an electrophoretic deposition approach. It is based on the mixing of negatively charged graphene oxide (GO) with nickel ions resulting in a positively charged composite making cathodic electrophoretic deposition possible. The thickness of the resulting rGO/Ni(OH)2 matrix deposited on Au could be controlled by varying the time of electrophoretic deposition. The rGO/Ni(OH)2 matrix was characterized by X-ray photoelectron spectroscopy, Raman spectroscopy and cyclic voltammetry. The rGO/Ni(OH)2 electrodes exhibited excellent electrocatalytic behaviour towards glucose oxidation in alkaline medium. The response current of the sensor is linear to glucose concentrations from 15 μM to 30 mM with a sensitivity of 11.4 ± 0 mA cm−2 mM−1. The interface was much more stable than drop-cast films. These results pave the way for electrophoretic deposition as a competitive alternative over drop-casting for the fabrication of rGO modified interfaces.

Preparation of reduced graphene oxide/Cu nanoparticle composites through electrophoretic deposition: application for nonenzymatic glucose sensing

The paper reports on the simultaneous reduction/deposition of reduced graphene oxide/copper nanoparticles (rGO/Cu NPs) on a glass/Ti/Au electrode using an electrophoretic deposition (EPD) technique from a colloidal suspension of graphene oxide (GO) and copper sulphate (CuSO4) in ethanol. The method allows controlling the nanoparticle density by adjusting the deposition time. Structural characterization and chemical composition analysis of the modified electrode showed the simultaneous reduction of GO with the concomitant deposition of metallic CuNPs with a Cu(OH)2 shell. The electrocatalytic activity of the modified electrode was evaluated for non-enzymatic glucose sensing in alkaline medium. While the Au electrode modified only with rGO did not show obvious electrocatalytic activity, the electrode coated with rGO/CuNPs exhibited excellent electrocatalytic behavior towards glucose oxidation with a high sensitivity of 447.65 μA mM−1 cm−2. The response current of the sensor is linear to glucose concentrations up to 1.2 mM with a detection limit of 3.4 μM. Furthermore, the interference from various oxidizable molecules such as dopamine, uric acid, ascorbic acid and carbohydrate molecules such as fructose, lactose and galactose was negligible, indicating a good selectivity of detection. The application of this glucose sensor in real samples has also been demonstrated successfully.

Sensitive sugar detection using 4-aminophenylboronic acid modified graphene.

A sensitive electrochemical active interface for sugar sensing based on the specific boronic acid-diol binding was established. The sensing matrix was formed by stirring a suspension of graphene oxide (GO) with 4-aminophenylboronic acid (APBA). The resulting composite consists of a water insoluble precipitate of reduced graphene oxide (rGO) with APBA incorporated into the rGO matrix. Differential pulse voltammetry (DPV) on glassy carbon electrodes modified with rGO/APBA was used for the detection of fructose, mannose and glucose. The fabricated sensor exhibited a wide linear range with detection limits of 100 nM for fructose, and around 800 nM for mannose and glucose.

Green chemistry approach for the synthesis of ZnO-carbon dots nanocomposites with good photocatalytic properties under visible light.

We report on a simple and one-pot synthetic method to produce ZnO/carbon quantum dots (ZnO/CQDs) nanocomposites. The morphological features and chemical composition of the nanocomposites were characterized using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analyses (TGA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The optical properties of the nanocomposites were examined using UV-visible (UV-vis) spectrophotometry. The photocatalytic activity of the ZnO/CQDs was evaluated for the degradation of a model organic pollutant, rhodamine B, under visible light irradiation at room temperature. The highly efficient photodegradation capability of the nanocomposite was demonstrated by comparison with ZnO particles, prepared using identical experimental conditions. Overall, the present approach adheres to green chemistry principles and the nanocomposite holds promise for the development of remarkably efficient catalytic systems.

Cobalt phthalocyanine tetracarboxylic acid modified reduced graphene oxide: a sensitive matrix for the electrocatalytic detection of peroxynitrite and hydrogen peroxide

The quantification of peroxynitrite (ONOO−, PON) and hydrogen peroxide (H2O2) is intrinsically difficult as both species show similar oxidative features located within a narrow potential. The sub-second lifetime of ONOO− at neutral pH further complicates the analysis. In this paper, we examine the electrocatalytic activity of cobalt phthalocyanine tetracarboxylic acid (CoPc–COOH) loaded reduced graphene oxide (rGO) films towards peroxynitrite and hydrogen peroxide detection. The rGO/CoPc–COOH matrix is synthesized by the reaction of graphene oxide (GO) and CoPc–COOH at 90 °C for 5 h under ultrasonication. The integration of CoPc–COOH and the reduction of GO to rGO was confirmed by X-ray photoelectron spectroscopy, FTIR, Raman, UV-vis spectroscopy and electrochemistry. The rGO/CoPc–COOH film showed high electrocatalytic activity and specificity for ONOO− at anodic potential with a sensitivity of ≈11.5 ± 1 nA nM−1 and a peroxynitrite detection limit of ≈1.7 nM. The rGO/CoPc–COOH films further exhibited electrocatalytic reduction of H2O2 with a sensitivity of 14.5 μA mM−1 and a detection limit of ≈60 μM for H2O2.

Voltammetric detection of l-dopa and carbidopa on graphene modified glassy carbon interfaces

The present work reports on the use of graphene nanosheets, deposited on glassy carbon, as electrode materials, and their electrochemical characterization. The graphene nanosheets were obtained by chemical reduction of graphene oxide using hydrazine. The possibility of analyzing L-dopa and carbidopa, two important catecholamines found in pharmaceutical products, separately and simultaneously by differential pulse voltammetry utilizing graphene modified GC interfaces is investigated. Voltammetric peak currents showed a linear response for both catecholamines in the range of 1-16 μM. The detection limit was about two times lower for L-dopa than carbidopa being 0.8 μM and 1.8 μM, respectively with a current sensitivity of (2.15 ± 0.5) and (0.48 ± 0.3) μA μM(-1). Simultaneous detection of both catecholamines can be achieved on these electrodes. Equivalent amounts of L-dopa and carbidopa have no effect on the detection limit of L-dopa. In addition, the presence of L-dopa with concentrations 4 times higher than carbidopa has no influence on the voltammetric profile.

Thiol–Yne Click Reactions on Alkynyl–Dopamine‐Modified Reduced Graphene Oxide

The large-scale preparation of graphene is of great importance due to its potential applications in various fields. We report herein a simple method for the simultaneous exfoliation and reduction of graphene oxide (GO) to reduced GO (rGO) by using alkynyl-terminated dopamine as the reducing agent. The reaction was performed under mild conditions to yield rGO functionalized with the dopamine derivative. The chemical reactivity of the alkynyl function was demonstrated by post-functionalization with two thiolated precursors, namely 6-(ferrocenyl)hexanethiol and 1H,1H,2H,2H-perfluorodecanethiol. X-ray photoelectron spectroscopy, UV/Vis spectrophotometry, Raman spectroscopy, conductivity measurements, and cyclic voltammetry were used to characterize the resulting surfaces.

Detection of folic acid protein in human serum using reduced graphene oxide electrodes modified by folic-acid

The detection of disease markers is considered an important step for early diagnosis of cancer. We design in this work a novel electrochemical sensing platform for the sensitive and selective detection of folic acid protein (FP). The platform is fabricated by electrophoretic deposition (EPD) of reduced graphene oxide (rGO) onto a gold electrode and post-functionalization of rGO with folic acid. Upon FP binding, a significant current decrease can be measured using differential pulse voltammetry (DPV). Using this scheme, a detection limit of 1pM is achieved. Importantly, the method also allows the detection of FP in serum being thus an appealing approach for the sensitive detection of biomarkers in clinical samples.

Surface Plasmon Resonance based sensing of lysozyme in serum on Micrococcus lysodeikticus-modified graphene oxide surfaces

Lysozyme is an enzyme found in biological fluids, which is upregulated in leukemia, renal diseases as well as in a number of inflammatory gastrointestinal diseases. We present here the development of a novel lysozyme sensing concept based on the use of Micrococcus lysodeikticus whole cells adsorbed on graphene oxide (GO)-coated Surface Plasmon Resonance (SPR) interfaces. M. lysodeikticus is a typical enzymatic substrate for lysozyme. Unlike previously reported sensors which are based on the detection of lysozyme through bioaffinity interactions, the bioactivity of lysozyme will be used here for sensing purposes. Upon exposure to lysozyme containing serum, the integrity of the bacterial cell wall is affected and the cells detach from the GO based interfaces, causing a characteristic decrease in the SPR signal. This allows sensing the presence of clinically relevant concentrations of lysozyme in undiluted serum samples.

One-step synthesis of Au nanoparticle–graphene composites using tyrosine: electrocatalytic and catalytic properties

An easy and environmentally friendly method is described for the in situ synthesis of a reduced graphene oxide/gold nanoparticle (rGO/Au NPs) nanocomposite through the simultaneous reduction of GO and HAuCl4 using tyrosine in water. The rGO/Au NPs/Tyr nanocomposite has been characterized using different techniques such as UV-vis spectrometry, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electrochemical measurements. The electrocatalytic and catalytic activities of the resulting hybrid nanomaterial have been investigated for the nonenzymatic electrochemical detection of hydrogen peroxide (H2O2) and nitrophenol reduction, respectively. The sensor displayed a detection limit of 20 μM over a wide linear range from 0.02 to 25 mM with a sensitivity of 46.46 μM mM−1 cm−2. In addition, the sensor also showed good selectivity for H2O2 detection, long-term stability and reproducibility. Furthermore, the rGO/Au NPs/Tyr nanocomposite exhibited good catalytic activity toward 4-nitrophenol reduction.