Technology performance of SiO2 nanoparticles deposition techniques over carbon-based substrates

This work compares the performance of electrospray and drop-casting for depositing nanostructured silicon dioxide (SiO₂) layers onto flexible carbon-based substrates, a key challenge in the fabrication of functional carbon electrodes for energy-harvesting and sensing devices. SiO₂ nano- and microparticles with diameters ranging from 353 nm to 9.98 μm were deposited onto hydrophilic carbon cloth (HCC), super-hydrophilic carbon cloth (SHCC), MnOx on hydrophilic carbon cloth (MnOx/HCC), and carbon paper. Because these substrates are woven, highly porous, and topographically uneven, achieving uniform and reproducible coatings is challenging. To address this, key deposition parameters, including temperature, drying duration, and deposition time, were systematically varied for three types of layer architectures: homolayers, mixed heterolayers, and thermally assisted stepwise heterolayers at 60 °C. The resulting structures were characterized by optical microscopy and scanning electron microscopy (SEM). Surface coverage was quantified by ImageJ-based pixel analysis of SEM micrographs, while particle retention was evaluated by weighing the substrates before and after deposition. The results show that electrospray is particularly effective for producing homogeneous nanolayer structures, whereas thermally assisted stepwise heterolayers yielded the highest coverage and retention for both techniques. Under optimal conditions, SiO₂ coverage above ~85 % and retention efficiencies above ~90 % were achieved, especially on carbon paper. These results clarify how deposition technique, layer architecture, and thermal assistance jointly control the formation and robustness of SiO₂ coatings on flexible carbon-based substrates, and provide practical guidelines for the fabrication of robust carbon/SiO₂ interfaces for future energy-harvesting and sensing devices. • This work presents, for the first time, a novel approach to studying two deposition techniques for nano- and microparticles on flexible substrates. • Determining the specific conditions for applying the deposition techniques: Electrospray and drop casting, considering parameters such as flow rate, deposited volume, drying time, and temperature, with variations in the distance between the emitter and opposing electrodes. • Analysing the resulting structures from the deposition techniques, including homolayer and heterolayer configurations, and comparing the results obtained from each method. • Evaluating the feasibility of combining both techniques to apply nanoparticles in single or multiple layers, and studying the effect of temperature during the deposition and drying process. • Analysing the impact of the deposition techniques on the distribution, coverage, and adhesion of nano- and microparticles on flexible and porous carbon substrates. • Comparing the effectiveness of Electrospray and drop casting techniques in terms of coverage and adhesion of the deposited particles.