Xiang-Dong Tian

A bioorthogonal Raman reporter strategy for SERS detection of glycans on live cells.

National Instrumentation Program [2011YQ030124]; National Basic Research Program of China (973 Program) [2012CB917303]; National Natural Science Foundation of China [21172013]

Quantitative SHINERS analysis of temporal changes in the passive layer at a gold electrode surface in a thiosulfate solution.

Shell-isolated gold nanoparticles (SHINs) were employed to record shell-isolated nanoparticle-enhanced Raman spectra (SHINERS) of a passive layer formed at a gold surface during gold leaching from thiosulfate solutions. The (3-aminopropyl)triethoxysilane (APTES) and a sodium silicate solution were used to coat gold nanoparticles with a protective silica layer. This protective silica layer prevented interactions between the thiosulfate electrolyte and the gold core of the SHINs when the SHINs-modified gold electrode was immersed into the thiosulfate lixiviant. The SHINERS spectra of the passive layer, formed from thiosulfate decomposition, contained bands indicative of hydrolyzed APTES. We have demonstrated how to exploit the presence of these APTES bands as an internal standard to compensate for fluctuations of the surface enhancement of the electric field of the photon. We have also developed a procedure that allows for removal of the interfering APTES bands from the SHINERS spectra. These methodological advancements have enabled us to identify the species forming the passive layer and to determine that the formation of elemental sulfur, cyclo-S8, and polymeric sulfur chains is responsible for inhibition of gold dissolution in oxygen rich thiosulfate solutions.

Quantitative Surface-Enhanced Raman Spectroscopy through the Interface-Assisted Self-Assembly of Three-Dimensional Silver Nanorod Substrates

The realization of surface-enhanced Raman spectroscopy (SERS) to be a reliable quantitative analytical technique requires sensitive and reproducible enhancing substrates. Here, uniform three-dimensional (3D) Ag nanorod (AgNR) substrates with well-defined interlayer spacings are prepared through the air-liquid interface-assisted self-assembly of AgNR in a layer-by-layer manner. The correlation of the SERS performance with the 3D AgNR structures is performed by SERS mapping the substrates. SERS mapping reveals the excellent enhancement uniformity of the 3D substrates with the relative standard deviation (RSD) less than 10%. It finds that both of the number of layers (NL) and the length of the AgNR have effects on the SERS performance of the 3D AgNR substrates. It is demonstrated that the intergaps between layers contribute much to the SERS intensity of the 3D AgNR by creating the interlayer (out-of-plane) plasmonic coupling. The impact of the excitation wavelengths (532, 633, and 785 nm) on SERS performance is also determined. The optimal 3D AgNR structures achieved by the correlation study is further used to detect a set of related molecules (l-tryptophan (Trp), l-phenylalanine (Phe), urea, and melamine). The 3D AgNR SERS of the analytes exhibits linear responses over wide concentration ranges. The sensitivity of the 3D AgNR SERS is proved by comparing to that of the current methods. Moreover, the 3D AgNR substrates maintain the performance stability during 4 weeks of storage.