Emergence of photoluminescence on bulk MoS2 by laser thinning and gold particle decoration

We demonstrate a facile and effective approach to significantly improve the photoluminescence of bulk MoS2 via laser thinning followed by gold particle decoration. Upon laser thinning of exfoliated bulk MoSz photoluminescence emerges from the laser-thinned region. After further treatment with an AuCl3 solution, gold particles self-assemble on the laser-thinned region and thick edges, further increasing the fluorescence of bulk MoS2 28 times and the Raman response 3 times. Such fluorescence enhancement can be attributed to both surface plasmon resonance and p-type doping induced by gold particles. The combination of laser thinning and AuCl3 treatment enables the functionalization of bulk MoS2 for optoelectronic applications. It can also provide a viable strategy for mask-free and area-selective p-type doping on single MoS2 flakes.

Synthesis and High Electrocatalytic Performance of Hexagram Shaped Gold Particles Having an Open Surface Structure with Kinks

Hexagram shaped gold particles and their analogues enclosed by high index facets with kinks have been successfully synthesized by reducing HAuCl4 with ascorbic acid （AA） in the presence of poly（diallyldimethylammonium chloride） at room temperature. By using electron microscopy, the surfaces of the hexagram shaped Au particle were found to be {541} planes, which contain high-density steps and kinks. In addition, it was found that hexagonal shield-like and other kind of particles present in the product were analogues of the hexagram shaped Au particles structure, in that they had the same surface structure. In order to confirm the surface structure of all the prepared particles, surface structure sensitive underpotential deposition of Pb was carried out, and the cyclic voltammetric profile was in accordance with the proposed {541} surface. Finally, structure-property relationships of the Au hexagrams were experimentally analyzed by employing the electrocatalytic oxidation of AA as a probe reaction. The electrocatalytic reactions of gold cubes with low-index {100} facets and gold trioctahedra with {221} facets were studied as references. The experimental results showed that the hexagram shaped Au particles and their analogues with exposed {541} facets have the highest catalytic activity among the three kinds of gold particles, owing to the high density of kink atoms. This study should motivate us to further explore methods for the preparation of other well-defined polyhedral metal nanocrystals enclosed by high index surfaces.

A Simple and Rapid Colloidal Gold-based Immunochromatogarpic Strip Test for Detection of FMDV Serotype A

A sandwich format immunochromatographic assay for detecting foot-and-mouth disease virus (FMDV) serotypes was developed. In this rapid test,affinity purified polyclonal antibodies from Guinea pigs which were immunized with sucking-mouse adapted FMD virus (A/AV88(L) strain) were conjugated to colloidal gold beads and used as the capture antibody,and affinity purified polyclonal antibodies from rabbits which were immunized with cell-culture adapted FMD virus (A/CHA/09 strain) were used as detector antibody. On the nitrocellulose membrane of the immunochromatographic strip,the capture antibody was laid on a sample pad,the detector antibody was printed at the test line(T) and goat anti-guinea pigs IgG antibodies were immobilized to the control line(C). The lower detection limit of the test for a FMDV 146S antigen is 11.7ng/ml as determined in serial tests after the strip device was assembled and the assay condition optimization. No cross reactions were found with FMDV serotype C,Swine vesicular disease (SVD),Vesicular stomatiti svirus (VSV) and vesicular exanthema of swine virus (VES) viral antigens with this rapid test. Clinically,the diagnostic sensitivity of this test for FMDV serotypes A was 88.7% which is as same as an indirect-sandwich ELISA. The specificity of this strip test was 98.2% and is comparable to the 98.7% obtained with indirect-sandwich ELISA. This rapid strip test is simple,easy and fast for clinical testing on field sites; no special instruments and skills are required,and the result can be obtained within 15 min. To our knowledge,this is the first rapid immunochromatogarpic assay for serotype A of FMDV.