Xianliang Zheng

Well-dispersed palladium nanoparticles on graphene oxide as a non-enzymatic glucose sensor

Palladium nanoparticles with excellent uniform size and even distribution were prepared on graphene oxide (Pd NPs/GO) by using a simple and environmentally-friendly ultrasonic method in an ice bath. Ultrasonication time and composition ratios of GO and Pd influenced the morphology of the palladium nanoparticles and their electrocatalytic performance. Transmission electron microscopy (TEM) and electrochemical characterization demonstrated that GO acted as a good supportive substrate for controlling the size and activity of palladium nanoparticles. The optimized nanocomposite exhibited high electrochemical activity for electrocatalytic oxidation of glucose in alkaline medium. The Pd NPs/GO nanocomposite was developed as a non-enzymatic biosensor for the determination of glucose with a linear range of 0.2–10 mM, which is nearly insusceptible to common electroactive interfering species. This simple and effective composite platform could potentially be extended to other metal/graphene nanomaterials, and have broad applications in biosensing, fuel cells, and other fields.

Synthesis of graphene on a polycrystalline Co film by radio-frequency plasma-enhanced chemical vapour deposition

Graphene of 1–5 layers was synthesized on a polycrystalline Co film by radio-frequency plasma-enhanced chemical vapour deposition at a relatively low temperature of 800 ◦ C for only 40 s in a mixture of gases of CH4/H2/Ar (1/5/20, with a total gas flow rate of 78 sccm). The obtained graphene is of high quality as revealed by Raman spectroscopy and x-ray photoelectron spectroscopy. It exhibits a high optical transmittance of more than 70% in the wavelength range 500–1200 nm, and a sheet resistivity of 2661 � /sq. A possible formation mechanism is proposed. The significant influence of octahedral and tetrahedral lattice interstitial sites in the Co crystallites on the formation of graphene is discussed. (Some figures in this article are in colour only in the electronic version)

Engineering graphene/carbon nanotube hybrid for direct electron transfer of glucose oxidase and glucose biosensor

The graphene/carbon nanotube hybrid was designed and implemented by a deoxygenation process for direct electron transfer of glucose oxidase and glucose biosensor. The procedure was analyzed by transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectra, etc. The strategy of structurally engineering one-dimensional carbon nanotube (CNT) and two-dimensional graphene oxide (GO) presented three benefits: (a) a deoxygenation process between GO and acid-CNT was introduced under strongly alkaline condition; (b) GO prevented the irreversible integration of CNT; and (c) CNT hindered the restacking of GO. The RGO interacted with CNT through the van der Waals forces and π–π stacking interaction. The three-dimensional hybrid not only had a high surface area, but also exhibited a good electronic conductivity. A direct electrochemistry of glucose oxidase was obtained on the nanohybrid modified electrode which showed good response for glucose sensing. This study would provide a facile and green method for the preparation of nanohybrid for a wide range of applications including biosensing, super capacitor, and transparent electrode.

One-pot photochemical synthesis of ultrathin Au nanocrystals on co-reduced graphene oxide and its application

In this study, we have developed a simple and green method for one-pot synthesis of ultrathin gold nanocrystals attached to graphene through photo irradiation. High-yield ultrathin Au nanocrystals are distributed on the reduced graphene oxide, immediately followed by the deoxygenation of graphene oxide in the absence of chemical reductants and surfactants. The procedure has been thoroughly completed and the products have been analyzed by transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), etc. The results show that both graphene oxide and photo irradiation play essential roles in the formation of ultrathin Au nanocrystals. The nanohybrids also display excellent electro-catalytical performance to methanol oxidation. This study not only has potential in the applications of bio-sensing and fuel cells, but also provides new procedures for the preparation of metal/graphene nanomaterials.

Kinetic effects in the photomediated synthesis of silver nanodecahedra and nanoprisms: combined effect of wavelength and temperature

Photomediated synthesis is a reliable, high yield method for the production of a variety of morphologies of silver nanoparticles. Here, we report synthesis of silver nanoprisms and nanodecahedra with tunable sizes via control of the reaction temperature and the irradiation wavelength. The results show that shorter excitation wavelengths and lower reaction temperatures result in high yields of nanodecahedra, while longer excitation wavelengths and higher reaction temperatures result in the formation of nanoprisms. The mechanism for the growth condition dependent evolution in the morphology of the silver particles is discussed as a kinetically controlled process. This is based on analysis of the reaction kinetics at various excitation wavelengths and temperatures. The energy barrier for the transformation from seeds to nanodecahedra is relatively high and requires a shorter wavelength. Thus longer wavelength illumination leads to the formation of nanoprisms. Thermodynamically stable five-fold twinning structures are shown to evolve from twin plane structures. The fast reaction rate at higher temperature favors the growth of nanoprisms by preferential Ag deposition on planar structures in a kinetics-controlled mode, while slower rates yield thermodynamically favored nanodecahedra.

Ultrathin Carbon Film Protected Silver Nanostructures for Surface-Enhanced Raman Scattering

In this paper, ultrathin carbon film protected silver substrate (Ag/C) was prepared via a plasma-enhanced chemical vapor deposition (PECVD) method. The morphological evolution of silver nanostructures underneath, as well as the surface-enhanced Raman scattering (SERS) activity of Ag/C hybrid can be tuned by controlling the deposition time. The stability and reproducibility of the as-prepared hybrid were also studied.