Phase and Structural Thermal Evolution of Bi–Si–O Catalysts Obtained via Laser Ablation

Abstract

Laser methods are successfully used to prepare complex functional nanomaterials, especially for biomedicine, optoelectronics, and heterogeneous catalysis. In this paper, we present complex oxide and composite nanomaterials based on Bi and Si produced using laser ablation in liquid followed by subsequent powder annealing. Two synthesis approaches were used, with and without laser post-treatment of mixed (in an atomic ratio of 2:1) laser-generated Bi and Si colloids. A range of methods were used to characterize the samples: UV-Vis diffusion reflection, IR and Raman spectroscopy, synchronous thermal analysis, X-ray diffraction, transmission electron microscopy, as well as specific surface-area evaluation. We also followed the dynamics of phase transformations, as well as composition, structure and morphology of annealed powders up to 800 °C. When heated, the non-irradiated series of samples proceeded from metallic bismuth, through β-Bi2O3, and resulted in bismuth silicates of various stoichiometries. At the same time, in their laser-irradiated counterparts, the formation of silicates proceeded immediately from the amorphous Bi2SiO5 phase formed after laser treatment of mixed Bi and Si colloids. Finally, we show their ability to decompose persistent organic molecules of Rhodamine B and phenol under irradiation with a soft UV (375 nm) source.

Влияние условий синтеза на структурные, оптические и электрофизические свойства нанокомпозитов TiO-=SUB=-2-=/SUB=-/Cu-=SUB=-x-=/SUB=-O

“…Для определения коэффициента поглощения α(λ) в широком диапазоне длин волн необходимо получить зависимость S(λ). Однако на практике при определении ширины запрещенной зоны всегда считают, что диапазон длин волн, в котором производится линейная аппроксимация зависимости α(λ), достаточно узок (в нашем случае -20 nm), чтобы можно было считать S константой в этом диапазоне [19,20].…”

“…3, a. Спектры диффузного рассеяния света позволяют определить по так называемому краю собственного поглощения величину оптической ширины запрещенной зоны E g полупроводниковых наноматериалов. Несмотря на то, что точной теории множественных рассеяний не существует, достаточно широко применяется теория диффузного отражения и пропускания оптически непрозрачных образцов -так называемая двухкомпонентная теория Кубелки и Мунка (см., например,[19,20]). В этой теории предполагается, что отраженное излучение является изотропным, т. е. не зависящим от направления, а облучающий свет -монохроматическим.…”

Gas Sensing of Laser-Produced Hybrid TiO2-ZnO Nanomaterials under Room-Temperature Conditions

“…Pulsed laser ablation in liquid (PLAL) is a simple, easy-to-use, and convenient method to generate diverse nanomaterials at a laboratory scale [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. It is an environmentally friendly approach that has become increasingly popular over the last 2–3 decades for its ability to produce metallic, metal oxide, sulfide, and carbide nanoparticles (NPs), among others, with “clean” surface and controlled sizes, chemical composition, and morphology [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 ]. Typically, a laser beam is focused on a solid target that is immersed in a liquid medium, resulting in plasma, vapor, or molten metal drops ejected into the liquid phase.…”

“…Typically, a laser beam is focused on a solid target that is immersed in a liquid medium, resulting in plasma, vapor, or molten metal drops ejected into the liquid phase. After further quenching and/or reaction with the liquid, such species form nuclei and clusters that then grow as NPs whose morphology, size, and chemical composition depend on the laser pulses, target, and liquid used [ 1 , 3 , 4 , 5 , 6 , 7 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. When noble metals are ablated, pure metal NPs are generated [ 4 , 6 ], while the ablation of more reactive metals in water or organic solvents leads to the production of metal oxide NPs [ 4 , 6 , 7 , 10 , 11 , 12 , 13 , 14 , 15 ].…”

“…When noble metals are ablated, pure metal NPs are generated [ 4 , 6 ], while the ablation of more reactive metals in water or organic solvents leads to the production of metal oxide NPs [ 4 , 6 , 7 , 10 , 11 , 12 , 13 , 14 , 15 ]. Because of extremely high-temperature gradient and quenching rates created in the ablation zone during PLAL, nanomaterials rich in defects, with metastable phases or unique morphologies are often formed [ 3 , 4 , 5 , 6 , 7 ]. This explains why such nanomaterials are potentially attractive for catalysis, photocatalysis, optics, and optoelectronics, as well as for gas sensing applications [ 3 , 4 , 5 , 6 , 7 , 8 , 9 ].…”