Inactivation of SARS-CoV-2 variants by nitrogen-doped titanium dioxide loaded with metals as visible-light photocatalysts.

PURPOSE: We examined the inactivation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) by a nitrogen-doped titanium dioxide (N-TiO2) visible-light photocatalyst that was activated via light irradiation in the natural environment and was safe for human use as a coating material. METHODS: The photocatalytic activity of glass slides coated with three types of N-TiO2 without metal or loaded with copper or silver and copper was investigated by measuring acetaldehyde degradation. The titer levels of infectious SARS-CoV-2 were measured using cell culture after exposing photocatalytically active coated glass slides to visible light for up to 60 min. RESULTS: N-TiO2 photoirradiation inactivated the SARS-CoV-2 Wuhan strain and this effect was enhanced by copper loading and further by the addition of silver. Hence, visible-light irradiation using silver and copper-loaded N-TiO2 inactivated the Delta, Omicron, and Wuhan strains. CONCLUSION: N-TiO2 could be used to inactivate SARS-CoV-2 variants, including emerging variants, in the environment.

Study of Excited States and Electron Transfer of Semiconductor-Metal-Complex Hybrid Photocatalysts for CO2 Reduction by Using Picosecond Time-Resolved Spectroscopies.

A semiconductor-metal-complex hybrid photocatalyst was previously reported for CO2 reduction; this photocatalyst is composed of nitrogen-doped Ta2 O5 as a semiconductor photosensitizer and a Ru complex as a CO2 reduction catalyst, operating under visible light (>400 nm), with high selectivity for HCOOH formation of more than 75 %. The electron transfer from a photoactive semiconductor to the metal-complex catalyst is a key process for photocatalytic CO2 reduction with hybrid photocatalysts. Herein, the excited-state dynamics of several hybrid photocatalysts are described by using time-resolved emission and infrared absorption spectroscopies to understand the mechanism of electron transfer from a semiconductor to the metal-complex catalyst. The results show that electron transfer from the semiconductor to the metal-complex catalyst does not occur directly upon photoexcitation, but that the photoexcited electron transfers to a new excited state. On the basis of the present results and previous reports, it is suggested that the excited state is a charge-transfer state located between shallow defects of the semiconductor and the metal-complex catalyst.

Direct assembly synthesis of metal complex-semiconductor hybrid photocatalysts anchored by phosphonate for highly efficient CO2 reduction.

Hybrid photocatalysts consisting of a ruthenium complex and p-type photoactive N-doped Ta(2)O(5) anchored with an organic group were successfully synthesized by a direct assembly method. The photocatalyst anchored by phosphonate exhibited excellent photoconversion activity of CO(2) to formic acid under visible-light irradiation with respect to the reaction rate and stability.

A soft-solution process for recovering rare metals from metal/alloy-wastes by grinding and washing with water.

We have developed a novel process for recovering metals from alloy-wastes by using a mechanochemical (MC) reaction. The process consists of co-grinding both alloy and polyvinyl chloride (PVC) samples, followed by washing with water and filtration. The co-grinding of the wastes causes a solid-state MC reaction to form metal chlorides and hydrocarbon in the product. The former products are soluble in water, so they can be recovered from the wastes by washing with water, followed by filtration. The PVC waste plays a significant role as a chlorine source in the MC reaction. After filtration, the solid residue can be used as a fuel, due to the absence of chlorine in the product, and the filtrate is subjected to hydrometallurgical process to extract metals from the solution.

Estimation of mechanochemical dechlorination rate of poly(vinyl chlorde).

Poly(vinyl chloride) (PVC) was ground in air with CaO in the presence of quartz powder as a grinding aid by a small-scale planetary ball mill to investigate the relation of the dechlorination rate of PVC with the impact energy of the balls calculated from a computer simulation based on the Discrete Element Method under various conditions. Mechanochemical dechlorination proceeds as the grinding progresses and is improved with an increase in both the mill speed and the amount of balls introduced into the mill. The same trend can be seen in the relation between the specific normal impact energy of the balls and the rotational speed. The relationship between the observed dechlorination rate and the computed normal impact energy of the balls is linear, with a correlation coefficient of 0.965. This relationship can be used to estimate the dechlorination rate of PVC in a large-scale planetary ball mill.