Electrochemical preparation and characterization of gold-polyaniline core-shell nanocomposites on highly oriented pyrolytic graphite

A simple electrochemical method for the in situ preparation of homogeneously dispersed gold-polyaniline core/shell nanocomposite particles with controlled size on the highly oriented pyrolytic graphite(HOPG)was demonstrated.The HOPG surface was modified preferentially by covalent bonding of a two-dimensional 4-aminophenyl monolayer employing diazonium chemistry.AuCl4 -ions were attached to the Ar-NH2 termination and reduced electrochemically.This results in the formation of Au nuclei that could be further grown into gold nanoparticles.The formation of polyaniline as the shell wrap of Au nanoparticle was established by localized electro-polymerization.These core-shell nanocomposites prepared were characterized by AFM and cyclic voltammetry.The results show that the gold-polyaniline core-shell composites on HOPG have a mean particle size of 100 nm in diameter and the polyaniline shell thickness is about 15 nm.

Electrochemical Determination of Epinephrine with a Pyrolytic Graphite Electrode in the Presence of Ascorbic Acid and Dopamine

A method for determination of epinephrine（EP） in the presence of ascorbic acid （AA） and dopamine （DA） with bare pyrolytic graphite electrodes has been described for the first time. In pH 7.0 phosphate buffer solution, the linear relationship was observed between the reduction peak current of EP and its concentration over the range from 1×10^-4 to 5×10^-7 mol/L, the related coefficient is 0.9992 （N=8）.

Some Unusual Features of Highly Oriented Pyrolytic Graphite Observed by Electrochemical Scanning Tunneling Microscopy

Highly oriented pyrolytic graphite (HOPG) is the substrate often used in scanningtunneling Ancroscopy (STM). It is well known that STM images of the basal plane of HOPG showsome unusual structUral patterns. In this letter, we present in situ STM images of some unusualfeatures on HOPG in solutions, including normal or abnormal chain-like featUres and hexagonal oroblique superPeriodic structures. These features emerge both next to and apart from the step ofHOPG.

Raman spectrum study of graphite irradiated by swift heavy ions

Highly oriented pyrolytic graphites are irradiated with 40.5-Me V and 67.7-Me V ^112Sn-ions in a wide range of fluences： 1×10^11 ions/cm^2–1×10^14ions/cm^2. Raman spectra in the region between 1200 cm^-1 and 3500cm^-1 show that the disorder induced by Sn-ions increases with ion fluence increasing. However, for the same fluence, the amount of disorder is greater for 40.5-Me V Sn-ions than that observed for 67.7-Me V Sn-ions, even though the latter has a slightly higher value for electronic energy loss. This is explained by the ion velocity effect. Importantly, ～ 3-cm^-1frequency shift toward lower wavenumber for the D band and ～ 6-cm^-1 shift toward lower wavenumber for the 2D band are observed at a fluence of 1×10^14 ions/cm^2, which is consistent with the scenario of radiation-induced strain. The strain formation is interpreted in the context of inelastic thermal spike model, and the change of the 2D band shape at high ion fluence is explained by the accumulation of stacking faults of the graphene layers activated by radiation-induced strain around ion tracks. Moreover,the hexagonal structure around the ion tracks is observed by scanning tunneling microscopy, which confirms that the strains near the ion tracks locally cause electronic decoupling of neighboring graphene layers.

Eleciroreduction of Oxygen on Pyrolytk Graphite Electrode with Adsorbed Layer of Cobalt Tetra.sulfonaied Phthalocyaninc In Acetonitrile and Dimethylformamide

The catjpdoc polarization characteristics indicate that the presence of a pre-adsorbed surface layer of CoTSPc innibits the reduction of O2 to O2- on an ordinary pyroiytic graphite electrode (OPG) in AN and DMF solution of 0. 1 mol/L, TEAP, The transfer coefficient a and the heterogeneous rate constant k for this reaction or, OPG with and without pre-adsorbed CoTSPc obtained by rotating disk electrode method were found to be fairly close to thar obtained by cyclic voltammetry. The a remains almost the same, bat the k de creases by a factor of 2-5 with CoTSPc as compared with OPG alone. The possible reason is that the adsorbed CoTSPc as an anion renders the effective potential diffaence less negative, which thus lowers the rase of O2 reduction.

A High-Efficiency X-Ray Crystal Spectrometer for X-Ray Thomson Scattering

Highly oriented pyrolitic graphite （HOPG） has high X-ray diffraction efficiency due to its unique mosaic crystal structure, and thus is very suitable for its application to X-ray Thomson scattering measurement of solid-density plasmas. In this article, by using the K-shell X-ray source from laser-produced Ti plasma, the properties of the HOPG spectrometer are characterized and compared with those of the flat Pentaerythritol （PET） spectrometer. The results show that the diffraction efficiency of the HOPG spectrometer under focusing condition is an order higher than that of the PET spectrometer, while the spectral resolution of the HOPG is about 320, high enough to be used in the measurement of X-ray Thomson scattering spectra.

Stratigraphic analysis of intercalated graphite electrodes in aqueous inorganic acid solutions

A detailed stratigraphic investigation of the intercalation mechanism when graphite electrodes are immersed inside diluted perchloric(HClO_(4))and sulfuric(H_(2)SO_(4))electrolytes is obtained by comparing results when graphite crystals are simply immersed in the same acid solutions.By combining time-of-flight secondary ion mass spectrometry(ToF-SIMS)and in-situ atomic force microscopy(AFM),we provide a picture of the chemical species involved in the intercalation reaction.The depth intensity profile of the ion signals along the electrode crystal clearly shows a more complex mechanism for the intercalation process,where the local morphology of the basal plane plays a crucial role.Solvated anions are mostly located within the first tens of nanometers of graphite,but electrolytes also diffuse inside the buried layers for hundreds of nanometers,the latter process is also aided by the presence of mesoscopic crystal defects.Residual material from the electrolyte solution was found localized in well-defined circular spots,which represent preferential interaction areas.Interestingly,blister-like micro-structures similar to those observed on the highly oriented pyrolytic graphite(HOPG)surface were found in the buried layers,confirming the equivalence of the chemical condition on the graphite surface and in the underneath layers.

The potentially crucial role of quasi-particle interferences for the growth of silicene on graphite

A comprehensive picture of the initial stages of silicene growth on graphite is drawn.Evidence is shown that quasiparticle interferences play a crucial role in the formation of the observed silicene configurations.We propose,on one hand,that the charge modulations caused by those quantum interferences serve as templates and guide the incoming Si atoms to self-assemble to the unique(√3 x√3)R30°honeycomb atomic arrangement.On the other hand,their limited extension limits the growth to about 150 Si atoms under our present deposition conditions.The here proposed electrostatic interaction finally explains the unexpected stability of the observed silicene islands over time and with temperature.Despite the robust guiding nature of those quantum interferences during the early growth phase,we demonstrate that the window of experimental conditions for silicene growth is quite narrow,making it an extremely challenging experimental task.Finally,it is shown that the experimentally observed threedimensional silicon clusters might very well be the simple result of the end of the silicene growth resulting from the limited extent of the quasi-particle interferences.

可回收型各向同性热解石墨导电基底促进光电化学水分解

导电基底发挥着收集和传输光生电荷的关键作用,是光电化学(PEC)水分解用光电极不可或缺的重要组成部分,但构建高效光电极鲜受关注.本工作中,基于各向同性热解石墨(IPG)高电导率和高功函的特性,我们开发了各向同性热解石墨(IPG)作为一种导电基底来构建高性能光电极.相比于氟掺杂的二氧化锡(FTO)和金属箔片等广泛使用的导电基底,该光电极能与Cu_(2)O形成欧姆接触,因此所得IPG/Cu_(2)O光电阴极呈现出比FTO/Cu_(2)O光阴极高60%的光电流密度.IPG基底上经过高温氮化所得的Ta_(3)N5薄膜(IPG/Ta_(3)N_(5))可以获得与Ta箔负载的Ta_(3)N_(5)光阳极相媲美的PEC性能.此外,Ta箔由于在氮化过程中会出现严重氢脆问题而不能循环使用,而IPG基底则可以循环用于光电极的制备,且能生长出具有相同PEC性能的半导体薄膜.这项工作为通过碳基导电基底构建用于PEC水分解的高效光电极提供了一种有吸引力的可替代选择.

Carbon nanodots:a new precursor to achieve reactive nanoporous HOPG surfaces

In the present work we develop an electrochemical assisted method to form nanopores on the surface of highly oriented pyrolytic graphite(HOPG),which was accomplished by a simple electrochemical route and a scalable nanomaterial,carbon nanodots,without applying high voltages,high temperatures or toxic reagents.HOPG electrodes are in a solution of N-enrich carbon nanodots in acidic media and the potential scans applied on HOPG lead to the formation of a spatially inhomogeneous porous surface.The diameter of the resulting nanopores can be tuned by controlling the number of electrochemical reduction cycles.The resulting nanoporous surfaces are characterized by atomic force microscopy,Raman spectroscopy,scanning electrochemical microscopy,electrochemical impedance spectroscopy and electrochemistry.These nanoporous HOPG showed high capacitance.Hence the potential of these surfaces to the development of energy storage devices is demonstrated.