Charge Transfer Tuned by the Surrounding Dielectrics in TiO2-Ag Composite Arrays

Abstract

TiO2/Ag bilayer films sputtered onto a 2D polystyrene (PS) bead array in a magnetron sputtering system were found to form a nanocap-shaped nanostructure composed of a TiO2-Ag composite on each PS bead, in which the Ag nanoparticles were trapped partially or fully in the TiO2 matrix, depending on the TiO2 thickness. X-ray Photoelectron Spectroscopy (XPS) results showed the opposite shifts of binding energy for Ti 2p and Ag 3d, indicating the transfer of electrons from metallic Ag to TiO2 owing to the Ag-O-TiO2 composite formation. UV-Vis absorption spectra showed the blue shifts of the surface plasma resonance peaks, and the maximum absorption peak intensity was obtained for TiO2 at 30 nm. The surface-enhanced Raman scattering (SERS) peak intensity first increased and then decreased when the TiO2 thickness changed. The observations of SERS, XPS, and UV-Vis absorption spectra were explained by the dependency of the charge-transfer process on TiO2 thickness, which was ascribed to the changing dielectric properties in the metal/semiconductor system.

Application of Silver Nanoparticles in Parasite Treatment

“…The composite of AgNPs with other materials increases the compatibility for specific applications extending the unique properties of AgNPs to a broader space. For example, AgNP-TiO 2 composites have good biocompatibility and high antibacterial activity [ 70 ], and Ag/ZnO nanocomposites with silver nanoparticles loaded on ZnO surface showed an inhibitory effect on Streptococcus mutans with better antibacterial activity than ZnO nanorods [ 71 ].…”

Enhanced Surface Plasmon by Clusters in TiO2-Ag Composite

“…Our investigations show the surface plasma resonance peaks have a blue shift when the TiO 2 thickness changed for bilayer film TiO 2 /Ag on two-dimensional (2D) polystyrene (PS) bead array, which is because the intermediate electrical properties of metal and semiconductor composite systems have changed. Compared with Ag and TiO 2 bilayer films, Ag and TiO 2 co-sputtering can reduce the aggregation of silver nanoparticles [ 27 , 28 ]. In addition, the enhanced roughness is observed for the same time.…”

Unique gap-related SERS behaviors of p-aminothiophenol molecules absorbed on TiO2 surface in periodic TiO2/Ni nanopillar arrays

“…Despite many reports about the sensitive detection with metal/semiconductor composite substrates, the research on regulation and controlling of semiconductors in SERS substrates is still far behind that of metals. Fortunately, in recent years, researchers have found that semiconductors also can be modulated in some parameters (size [23][24][25][26][27], thickness [28][29][30][31][32] and morphology [27,33]), and hence to promote their CT resonance enhancement and further optimize their SERS activities [26,34], just like the regulation of noble metals [35,36]. For example, Lombardi et al [23] optimized the size of ZnSe nanoparticles and obtained an enhancement factor of 2 × 10 6 .…”