# Scalable, Microwave‐Enabled Synthesis of Ternary WxTi1‐xO2 and Heterostructured TiO2‐WO3‐x Colloidal Nanocrystals: Carrier Dynamics and Photocatalytic Properties

## TL;DR

This paper presents a scalable microwave method to create nanocrystals with enhanced photocatalytic properties for solar-driven chemical reactions.

## Contribution

A fast, scalable microwave synthesis method for ternary and heterostructured nanocrystals with improved photocatalytic performance.

## Key findings

- MW synthesis enables size-controlled production of WxTi1-xO2 and TiO2-WO3-x nanocrystals.
- Heterostructures show enhanced photocatalytic activity under solar-simulated light.
- Ultrafast cooling of hot electrons in plasmonic domains contributes to improved performance.

## Abstract

In solar‐light‐driven chemical processes, designing ever‐new strategies for synthesizing functional, doped, or defective semiconducting oxide nanostructures remains key. Techniques like bandgap engineering and interface heterostructuring, among others, have driven the development of brand‐new synthetic schemes that enable efficient charge carrier extraction. In this context, microwave (MW) chemistry has effectively established bottom‐up synthetic strategies. This study details a fast MW hydroalcohothermal synthesis for the scalable production of ternary WxTi1‐xO2 and heterostructured TiO2‐WO3‐x colloidal nanocrystals. MWs allow for size control at the nanoscale, and, in the case of heterostructures, support the anisotropic nucleation of oxygen‐deficient plasmonic WO3‐x nanobelts directly onto the surfaces of pre‐existing TiO2 seeds, establishing unique reaction pathways. Femtosecond transient absorption spectroscopy reveals the formation and ultrafast cooling of hot electrons within the plasmonic domains at near‐infrared (NIR) wavelengths. Both nanostructures exhibit significant photo‐oxidant activity toward 4‐methoxybenzyl alcohol in a liquid aerobic environment, concurrently demonstrating enhanced selectivity toward aldehyde products. While the ternary material shows activity and notable selectivity exclusively under UV excitation, the heterostructures provide compelling functionality, especially under solar‐simulated light irradiation. This superior performance is ascribed to the synergistic coupling of the NIR‐assisted photocatalytic effect driven by hot carriers, along with the photothermal effect arising from plasmon excitation.

Two microwave‐assisted synthetic methods, specifically a one‐pot and a seeded‐growth approach, have been developed within a hydroalcoholic solution for the growth of single‐phase ternary WxTi1‐xO2 and heterostructured TiO2‐WO3‐x colloidal nanocrystals. Both types of nanocrystals show significant photocatalytic activity for 4‐methoxybenzyl alcohol oxidation and exhibit selectivity toward aldehyde products in a liquid aerobic environment, under UV and solar‐simulated light irradiation, respectively.