Ag-graphene composite nanosheets (AGCN) with adjustable size and well-controlled densities of Ag nanoparticles (Ag NPs) using Poly(N-vinyl-2-pyrrolidone) (PVP) as a reductant and stabilizer are reported. The obtained AGCN substrate is extremely suitable for surface-enhanced Raman spectroscopy (SERS).

A facile method is proposed for the synthesis of reduced graphene oxide nanosheets (RGONS) and Au nanoparticle-reduced graphene oxide nanosheet (Au-RGONS) hybrid materials, using graphene oxide (GO) as precursor and sodium citrate as reductant and stabilizer. The resulting RGONS and Au-RGONS hybrid materials were characterized by UV-vis spectroscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, atomic force microscopy, transmission electron microscopy, and X-ray diffraction. It was found that the RGONS and Au-RGONS hybrid materials formed stable colloidal dispersions through hydrogen bonds between the residual oxygen-containing functionalities on the surface of RGONS and the hydroxyl/carboxyl groups of sodium citrate. The electrochemical responses of RGONS and Au-RGONS hybrid material-modified glassy carbon electrodes (GCE) to three kinds of biomolecules were investigated, and all of them showed a remarkable increase in electrochemical performance relative to a bare GCE.

A simple and industrially scalable approach to prepare porous carbon (PC) with high surface areas as well as abundant nitrogen element as anode supporting materials for lithium-ion batteries (LIBs) was developed. Herein, the N-doped PC was prepared by carbonizing crawfish shell, which is a kind of food waste with abundant marine chitin as well as a naturally porous structure. The porous structure can be kept to form the N-doped PC in the pyrolysis process. The N-doped PC-Co3O4 nanocomposites were synthesized by loading Co3O4 on the N-doped PC as anode materials for LIBs. The resulting N-doped PC-Co3O4 nanocomposites release an initial discharge of 1223 mA h g(-1) at a current density of 100 mA g(-1) and still maintain a high reversible capacity of 1060 mA h g(-1) after 100 cycles, which is higher than that of individual N-doped PC or Co3O4. Particularly, the N-doped PC-Co3O4 nanocomposites can be prepared in a large yield with a low cost because the N-doped PC is derived from abundant natural waste resources, which makes it a promising anode material for LIBs.

A three-dimensional (3D) macroporous carbon (3D-KSCs) derived from kenaf stem (KS) is proposed as a novel supporting material for electrochemical sensing and a biosensing platform. A series of 3D-KSCs/inorganic nanocomposites such as Prussian blue (PB) nanoparticles (NPs)-carboxylic group-functionalized 3D-KSCs (PBNPs-3D-FKSCs), CuNiNPs-3D-KSCs, and CoNPs-3D-KSCs were prepared by a facile two-step route consisting of carbonization and subsequent chemical synthesis or one-step carbonization of KS-metal ion complex. The obtained 3D-KSCs/inorganic nanocomposites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, and Fourier transform-infrared spectroscopy. A whole piece of 3D-KSCs/nanocomposites was used to prepare an integrated 3D-KSCs/nanocomposite electrode. Compared to the electrode modified by graphene, carbon nanotubes and their derivatives, which can form close-packed structure after assembled on electrode surface, the integrated 3D-KSCs/nanocomposite electrode shows a 3D honeycomb porous structure. Such structure provides a large specific surface area, effectively supports a large number of electro-active species, and greatly enhances the mass and electron transfer. The electrochemical behaviors and electrocatalytic performances of the integrated 3D-KSCs/inorganic nanocomposite electrode were evaluated by cyclic voltammetry and the amperometric method. The resulted PBNPs-3D-FKSCs, CuNiNPs-3D-KSCs, and CoNPs-3D-KSCs electrode show good electrocatalytic performances toward the reduction of H2O2, the oxidation of glucose and amino acid, respectively. Therefore, the low-cost, renewable, and environmentally friendly 3D-KSCs should be promising supporting materials for an electrochemical sensor and biosensor.

Graphene-based SERS substrates are classified and introduced, and their applications in biosensing-related fields are reviewed.

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Metal-organic frameworks (MOFs) have emerged as very fascinating functional materials due to their diversity nature. A nanocomposite consisting of copper nanoparticles dispersed within a carbon matrix (Cu NPs@C) is prepared through a one-pot thermolysis of copper-based metal-organic framework precursors. Cu NPs@C can catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) to form a colored product in the presence of H2 O2 . As a peroxidase mimic, Cu NPs@C not only has the advantages of low cost, high stability, and easy preparation, but also follows Michaelis-Menten behaviors and shows strong affinity to H2 O2 . As the Cu NPs' surfaces are free from stabilizing agent, Cu NPs@C exhibited a higher affinity to H2 O2 than horseradish peroxidase. On the basis of the inhibitory effect of ascorbic acid (AA) on oxidation of TMB, this system serves as a colorimetric method for the detection of AA, suggesting that the present work would expand the potential applications of MOF-derived nanocomposites in biomedical fields.

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