Electrostatic-induced synthesis of tungsten bronze nanostructures with excellent photo-to-thermal conversion behavior

Abstract

A simple one-step hydrothermal route is developed to synthesize one-dimensional (1D) hexagonal tungsten bronze (HTB) nanostructures. The key to this route is utilizing the electrostatic attraction between negatively charged tungstate and protonated ethylenediamine (EDA) to create a special local reductive environment in a non-reductive aqueous solution, which contributes to the in situ reduction of some of the hexavalent tungsten atoms during the 1D growth process and the mixed-valent nature of the final HTB structure. The as-prepared HTB nanomaterials are characterized to be highly crystalline and of uniform 1D morphology. Influences of synthetic conditions, such as the pH value, reaction time, temperature and amount of EDA, are systematically investigated. Meanwhile, this strategy is successfully introduced to prepare a series of metal-doped 1D HTB nanomaterials by simply changing the type of starting alkali tungstate. Experimental evidence reveals that the formation of the products follows an electrostatic-induced reductive nucleation–dissolution–recrystallization process, and the electrostatic interaction between the two oppositely charged species plays an indispensable role in the growth of mixed-valent HTB nanostructures. More importantly, these nanomaterials show efficient transformation of near-infrared light into local heat, indicating their potential applications as a new genre of functional materials in photothermal energy conversion as well as other relevant criteria.