Si/Pyrex glass and poly(dimethylsiloxane)-based microfluidic devices with integrated heating elements for TiO2 nanoparticle synthesis

Abstract

This paper presents two microreactors used to synthesize titanium(IV) oxide (TiO₂) nanoparticles. The microreactors under investigation incorporate integrated heaters and possess distinct microchannel dimensions. The first microreactor comprises silicon and Pyrex glass, with its integrated heater produced through p-type diffusion. Conversely, the second microreactor is constructed from polydimethylsiloxane (PDMS) and features a wire-based integrated heater. Recognizing the significance of temperature control in the synthesis process, both experimental and simulation results pertaining to the behavior of the microreactor heaters are provided. The synthesis of TiO₂ nanoparticles serves as a means to validate the efficacy of the microreactors. Comparative analysis reveals that the PDMS microreactor exhibits superior functionality when compared to the silicon/Pyrex glass counterpart. It has been demonstrated that upon a reaction time of 2 min within the microreactors, amorphous nanoparticles are formed, accompanied by partially developed crystallites corresponding to the anatase and rutile phases. Subsequent heating facilitates the complete conversion of the amorphous phase into the anatase phase. The utilization of a PDMS microreactor exhibits a heightened suitability for the synthesis of TiO₂ nanoparticles with good photocatalytic efficiency, achieving 93.59 % methylene blue (MB) degradation after 90 min. This suitability arises from several key factors: enhanced production speed, the cost-effectiveness inherent in the material, and the prevention of channel blockage attributed to calcification during the reaction process.