Defective TiO2 Nanotube Arrays for Efficient Photoelectrochemical Degradation of Organic Pollutants

Oxygen vacancies (OVs) are one of the most critical factors that enhance the electrical and catalytic characteristics of metal oxide-based photoelectrodes. In this work, a simple procedure was applied to prepare reduced TiO₂ nanotube arrays (NTAs) (TiO_2-x) via a one-step reduction method using NaBH₄. A series of characterization techniques were used to study the structural, optical, and electronic properties of TiO_2-x NTAs. X-ray photoelectron spectroscopy confirmed the presence of defects in TiO_2-x NTAs. Photoacoustic measurements were used to estimate the electron-trap density in the NTAs. Photoelectrochemical studies show that the photocurrent density of TiO_2-x NTAs was nearly 3 times higher than that of pristine TiO₂. It was found that increasing OVs in TiO₂ affects the surface recombination centers, enhances electrical conductivity, and improves charge transport. For the first time, a TiO_2-x photoanode was used in the photoelectrochemical (PEC) degradation of a textile dye (basic blue 41, B41) and ibuprofen (IBF) pharmaceutical using in situ generated reactive chlorine species (RCS). Liquid chromatography coupled with mass spectrometry was used to study the mechanisms for the degradation of B41 and IBF. Phytotoxicity tests of B41 and IBF solutions were performed using Lepidium sativum L. to evaluate the potential acute toxicity before and after the PEC treatment. The present work provides efficient PEC degradation of the B41 dye and IBF in the presence of RCS without generating harmful products.

X-ray micromodulated luminescence tomography in dual-cone geometry

We propose a scanning method utilizing dual-cone beams of x-rays to induce luminescence from nanophosphors and reconstruct the three-dimensional distribution of these particles in a biological sample or a small animal. For this purpose, x-rays are focused through a polycapillary lens onto a spot of a few micrometers in size. Such x-ray scanning can be point-wise performed to acquire photon emission data on an object surface. The x-ray-induced luminescence data allow for reliable image reconstruction with high spatial resolution and large imaging depth. We describe several numerical simulation studies to demonstrate the feasibility and merits of the proposed approach.