Dual-layer Metallic grating(DMG)structures as surface-enhanced Raman scattering(SERS)substrates are studied using benzenethiol as the probe analyte.The DMG structure consists of a SiO2 grating and 100-nm-thick gold coating layers.An enhancement factor of 105 is achieved by optimizing the SiO 2 grating height within the range from 165 to 550 nm.The enhancement factor dependence on the SiO2 grating height is due to the surface plasmon excitation,which is dependent on the polarization of the incident light,and confirmed by finite difference time domain simulations.This study demonstrates the advantages of high uniformity,reproducibility and sensitivity in the DMG structures for SERS applications.
This paper describes a new method to create nanoscale SiO 2 pits or channels using single-walled carbon nanotubes (SWNTs) in an HF solution at room temperature within a few seconds. Using aligned SWNT arrays, a pattern of nanoscale SiO 2 channels can be prepared. The nanoscale SiO 2 patterns can also be created on the surface of three- dimensional (3D) SiO 2 substrate and even the nanoscale trenches can be constructed with arbitrary shapes. A possible mechanism for this enhanced etching of SiO 2 has been qualitatively analysed using defects in SWNTs, combined with H 3 O + electric double layers around SWNTs in an HF solution.
A novel sonochemical method is described for the preparation of Fe_(3)O_(4)–TiO_(2)photocatalysts in which nanocrystalline titanium dioxide particles are directly coated onto a magnetic core.The Fe_(3)O_(4)nanoparticles were partially embedded in TiO_(2)agglomerates.TiO_(2)nanocrystallites were obtained by hydrolysis and condensation of titanium tetraisopropyl in the presence of ethanol and water under high-intensity ultrasound irradiation.This method is attractive since it eliminated the high-temperature heat treatment required in the conventional sol–gel method,which is important in transforming amorphous titanium dioxide into a photoactive crystalline phase.In comparison to other methods,the developed method is simple,mild,green and efficient.The magnetization hysteresis loop for Fe_(3)O_(4)–TiO_(2)nanocomposites indicates that the hybrid catalyst shows superparamagnetic characteristics at room temperature.Photocatalytic activity studies confirmed that the as-prepared nanocomposites have high photocatalytic ability toward the photodegradation of RhB solution.Furthermore,the photodecomposition rate decreases only slightly after six cycles of the photocatalysis experiment.Thus,these Fe_(3)O_(4)–TiO_(2)nanocomposites can be served as an effective and conveniently recyclable photocatalyst.
