Study of the Chemical Mechanism Involved in the Formation of Tungstite in Benzyl Alcohol by the Advanced QEXAFS Technique

Abstract

Insight into the complex chemical mechanism for the formation of tungstite nanoparticles obtained by the reaction of tungsten hexachloride with benzyl alcohol is presented herein. The organic and inorganic species involved in the formation of the nanoparticles were studied by time-dependent gas chromatography and X-ray diffraction as well as by time-resolved in situ X-ray absorption near-edge structure and extended X-ray absorption fine structure spectroscopy. Principal component analysis revealed two intermediates, which were identified as WCl(4) and WOCl(4) by using linear combination analysis. Quick-scanning extended X-ray absorption fine structure spectroscopy enabled the time-dependent evolution of the starting compound, the intermediates and the product to be monitored over the full reaction period. The reaction starts with fast chlorine substitution and partial reduction during the dissolution of the tungsten hexachloride in benzyl alcohol followed by the generation of intermediates with W=O double bonds and finally the construction of the W-O-W network of the tungstite structure.

Microwave dielectric heating of non-aqueous droplets in a microfluidic device for nanoparticle synthesis

“…Typically tungsten oxide synthesis leads to a WO 3 ·nH 2 O product in the form of platelets independent of the heating method. 27,28 Tungsten oxides nanoparticles have been widely used materials for application in gas sensing, water splitting, electrochromic windows. In addition, unconventional 35 applications of tungsten oxide nanoparticles are for high Tc superconductors, field emission displays and optical recording devices.…”

“…33 The electronics to generate the microwave power at 700-900 MHz are assembled similar to the electronics for 3 GHz frequency. 19 The microwaves are generated with a voltage-controlled oscillator (ZX95-1200W+, 50 Mini-Circuits) and are amplified with a power amplifier (ZHL-211-8 Mini-Circuits). The quasi-static simulation of the electrical field between the electrodes is performed with Ansoft, Maxwell software.…”

“…The error in the 45 temperature measurements comes from the variation of the vertical position of droplets smaller than the channel height, which has an impact on focal point and thus on the fluorescence intensity. 50 There is an ongoing debate whether the enhancement of chemical reactions driven by microwave irradiation is due to rapid heating or whether it is due to selective interaction of electromagnetic field with polar molecules. Our microfluidic -microwave droplet heater, due to its ability to separate conventional heat transfer 55 mechanisms from dielectric heating 44 , can help shine light onto these questions.…”

“…8 was presented. 50 Using a microfluidic device to produce monodisperse templating droplets of tunable size, the materials with up to three levels of hierarchy were prepared. Adding the microwave-reactor to the microfluidic chip could additionally give a control on the chemical composition of porous structures.…”

“…13,14 An alternate means of efficiently increasing the temperature is to heat the sample alone. This can be done through the use of microwaves, which selectively and directly heats the 50 sample itself. [15][16][17] Microwave heating can significantly increase the rate of synthesis of metal oxide nanoparticles in bulk, reducing the reaction time from hours to minutes.…”