Visible Light-Induced Photocatalyst with Au/TiO2 Nanocomposites Fabricated through Pulsed Laser-Induced Photolysis

Porous silicon decorated with Au/TiO2 nanocomposites for efficient photoinduced enhanced Raman spectroscopy

In this study, we investigated the potential of porous silicon (PSi) modified with Au/TiO₂ nanocomposites (NCPs) as a substrate for photoinduced enhanced Raman spectroscopy (PIERS). One-step pulsed laser-induced photolysis (PLIP) was used to embed Au/TiO₂ NCPs in the surface of PSi. Scanning electron microscopy revealed that adding TiO₂ nanoparticles (NPs) during PLIP led to the formation of predominantly spherical Au NPs with a diameter of approximately 20 nm. Furthermore, modifying the PSi substrate with Au/TiO₂ NCPs considerably enhanced the Raman signal of rhodamine 6G (R6G) after 4 h of ultraviolet (UV) irradiation. Real-time monitoring of the Raman signals of R6G at different concentrations under UV irradiation revealed that the amplitude of the signals increased with the irradiation time for R6G concentrations ranging from 10^-3 M to 10^-5 M. PSi substrates decorated with Au/TiO₂ NCPs may be used to develop materials for PIERS applications.

Pulsed-Laser Induced Photolysis of Synthesizing Magnetic Fe3O4 Nanoparticles for Visible-Light Photocatalysis

Our report is the first example describing the successful synthesis of magnetic Fe3O4 nanoparticles (NPs), for which we used pulsed-laser induced photolysis (PLIP). Compared with the previous method of using pulsed-laser ablation of a target, or strong energy of pulsed-laser light to decompose precursors in generating a solvated-ion reaction, the PLIP method used here is dependent on hydrogen peroxide (H2O2) to generate a hydrolysis reaction. Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were used to demonstrate the Fe3O4 crystalline structure of the synthesized NPs. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed that the average size of the NPs was about 20–50 nm. Regarding their magnetic characteristics, the synthesized NPs exhibited a saturation magnetization of 5.62 emu/g, remanence of 3.82 emu/g, and coercive force of 49.8 Oe. The photocatalytic experiments confirmed that the synthesized magnetic Fe3O4 NPs have visible light-degradation effects based on their ability to photocatalytically degrade methylene blue (MB). The MB degradation efficiency was 60–80% under white-light exposure for 180 min. This study presents a new route for synthesizing magnetic Fe3O4 NPs for their potential use in photocatalysis.

A Modified Sol-Gel Synthesis of Anatase {001}-TiO2/Au Hybrid Nanocomposites for Enhanced Photodegradation of Organic Contaminants

A sol-gel synthesis technique was employed for the preparation of anatase phase {001}-TiO2/Au hybrid nanocomposites (NCs). The scalable, schematic, and cost-efficient method was successfully modified using HF and NH4OH capping agents. The photocatalytic activity of the as-synthesized {001}-TiO2/Au NCs were tested over 2-cycle degradation of methylene blue (MB) dye and pharmaceutical active compounds (PhACs) of ibuprofen and naproxen under direct sunlight illumination at 35 °C and 44,000 lx. Transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), fast Fourier transform (FFT), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) were employed for the characterization of the as-prepared sample. The characterization results from the TEM, XPS, and XRD studies established both the distribution of Au colloids on the surface of TiO2 material, and the presence of the highly crystalline structure of anatase {001}-TiO2/Au NCs. Photodegradation results from the visible light irradiation of MB indicate an enhanced photocatalytic performance of Au/TiO2 NCs over TiO2. The results from the photocatalytic activity test performed under direct sunlight exposure exhibited promising photodegradation efficiencies. In the first cycle, the sol-gel synthesized material exhibited relatively better efficiencies (91%) with the MB dye and ibuprofen, while the highest degradation efficiency for the second cycle was 79% for the MB dye. Pseudo first-order photodegradation rates from the first cycle were determined to be comparatively slower than those from the second degradation cycle.