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 demons...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.展开更多
This paper establishes a new Laplacian comparison theorem which is specially useful tothe mathelds of nonpositive curvature. It leads naturally to the corresponding heat kernelcomparison and eigenvalue comparison theo...This paper establishes a new Laplacian comparison theorem which is specially useful tothe mathelds of nonpositive curvature. It leads naturally to the corresponding heat kernelcomparison and eigenvalue comparison theorems. Furthermore, a lower estimate of L2-spectrumof an n-dimensional non-compact complete Cartan-Hadamard manifold is given by (n-1)k/4,provided its mRicci curvature -(n -1)k (k= const. 0).展开更多
基金Project(50721003)supported by the Creative Research Group of National Natural Science Foundation of ChinaProject(50825102)supported by the National Science Fund for Distinguished Young Scholars,China
文摘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.
文摘This paper establishes a new Laplacian comparison theorem which is specially useful tothe mathelds of nonpositive curvature. It leads naturally to the corresponding heat kernelcomparison and eigenvalue comparison theorems. Furthermore, a lower estimate of L2-spectrumof an n-dimensional non-compact complete Cartan-Hadamard manifold is given by (n-1)k/4,provided its mRicci curvature -(n -1)k (k= const. 0).
