Deposition Of Ag(Au) Nanoparticles On The Hierarchical Oxide Semiconductor And SERS Study

A lack of notable metal Surface-enhanced Raman scattering (SERS) substrate limitsthe breadth of practical applications. In this work, we had a study aboutsemiconductor-based SERS substrate, which has an important and significance. Thestudy enrichs the kinds of the SERS substrates, but also widen the application of SERStechnique. The main contents and results are listed as following:First, the fabrication of assemblies of gold nanoparticles organized on the mouthsurface and the inner walls of TiO₂nanotube array was conducted via a facile in situcontrolled seed growth method. The size of Au nanoparticles can be effectivelycontrolled by changing the time of in situ growth. Gold nanoparticles organized onthe mouth surface and the inner walls of TiO₂nanotube array were clearly testifiedby FE-SEM and TEM. A potential application of thus-obtained Au decorated TiO₂nanotube arrays composite substates for SERS has been shown by using theRhodamine6G (Rh6G) molecule as a probe. Nanostructures comprised of Aunanoparticles with a close-packed arrangement result in large Raman enhancementfactors due to long range coupling between nanoparticles, high 'hot spot' surfacedensity, and TiO₂-assisted enhanced charge-transfer from Au to Rh6G. The preparedsubstrate can offer a higher degree of homogeneity and accuracy. In addition, it alsohas good recyclability. Through SERS analysis, the substrate can be purified andreused for other SERS measurement.Second, single-layer polycrystalline anatase TiO₂nanosheet with porous structurewas prepared via a simple solvothermal method by employing rod-like titanylsulfateas the starting material in the presence of glycerol followed by the calcination.The possible formation mechanism was proposed based on the experimental results.The obtained TiO₂nanosheets possess polycrystalline and highly porous net-likestructure made of interconnected nanoparticles. Polycrystalline sheets are assemblies of nanoparticles, which is very different from the previously reported singlecrystalline TiO₂nanosheets formed on the basis of the normal concept for crystalgrowth. Then it was modified with well-dispersed Ag nanoparticles as SERSsubstrate to study the SERS activity using4-Aminothiophenol (4-ATP) andRhodamine6G (Rh6G) as molecular probes, it was found that the as-synthesizedpolycrystalline anatase Ag/TiO₂nanosheet composites substrate exhibited highSERS activity, overall good uniformity and reliability.Third, TiO₂nanoflower arrays were prepared through a solvothermal method, andthen ZnO nanorods were growthed on the TiO₂nanoflower arrays, so theheterojunction structure was obtained. In this process, the content of ZnO can becontrolled. After this step, Ag nanoparticles were deposited on the surface of theZnO/TiO₂composites film via a facile in situ deposition. The obtained substrateexhibited high SERS activity, overall good uniformity and reliability compared withthe pure ZnO and TiO₂substrates.Fourth, chain-like Ag nanoparticles aggregates were prepared via a simple solutionreaction process in the presence of PEI and sodium citrate. In the synthesis process, PEIwas used to protect and connect the Ag nanoparticles. In the experiment, different Agaggregated degree can be obtained by controlling the experimental conditions,such asreaction time, reaction temperature and time. Colloids prepared with PEI formedchainlike aggregated Ag nanoparticles, the number of aggregated particles increasedupon increasing the reaction time and temperature. Due to high SERS activity andstability of the chain-like Ag nanoparticles aggregates, it is expected to be as SERSsubstrate in the trace detection and identification of the use of biotechnology.