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SiO2-engineered nanoparticles (SiO2-ENPs) are one of the most commonly employed nanomaterials. There was a lack of research on the comprehensive effects of environmental factors on the stability of SiO2-ENPs. In the present work, the aggregation size, surface charge, and percentage of nanoparticles have been studied under the presence of monovalent/divalent cations combined with natural organic matter (NOM), in an effort to provide a comprehensive investigation of the stability of SiO2-ENPs in complex environmental conditions. Results show that NOM adsorbed to the particles and made their zeta potential more negative, hence stabilizing them by electrostatic repulsion, and the stability of nano-SiO2 in NOM solutions follows the order of pH 9 > pH 7 > pH 5. In addition, SiO2-ENPs size in solutions with humic acid (HA) was larger than that with fulvic acid (FA). The aggregation of SiO2-ENPs enhanced with the increase of cation concentrations, and divalent cations (Ca2+) show stronger influence on SiO2-ENPs aggregate than monovalent cations. Divalent cations partially neutralized the adsorbed organic matter, and aggregation was enhanced with Ca2+, suggesting the presence of specific Ca2+-NOM bridges. The aggregation of SiO2-ENPs in electrolyte (CaCl2 or NaCl) and CaCl2 + NOM solutions follows in the order of pH 5~pH 9 > pH 7, showing that weakly acidic or alkaline conditions are not favorable for the stability of SiO2-ENPs in complex environmental systems. [ABSTRACT FROM AUTHOR]

In this study, we showcase the use of silicon dioxide (SiO2) nanoparticles and hexamethyldisilazane (HMDS) treatment to regulate the thin film morphology and manipulate charge transport of solution-processed, small-molecular, organic semiconductors. 6,13-Bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) was blended with SiO2 nanoparticles as an exemplary organic semiconductor. A higher concentration of SiO2 nanoparticles were observed near the edge of TIPS pentacene crystals and enlarged the width of crystal edges. This greatly reduced the dendritic crystal growth pattern of TIPS pentacene and contributed to its enhanced orientation uniformity. In addition, the HMDS treatment effectively passivated the silanol groups on the hydrophilic gate dielectrics. As a result, bottom-gate, top-contact TIPS pentacene/SiO2 nanoparticle-based organic thin-film transistors boosted a performance consistency enhancement (defined by the ratio of average mobility to the standard deviation of mobility). The combinational approach to employ SiO2 nanoparticles and HMDS treatment as demonstrated in this work sheds light on important applications in high-performance organic electronics devices on flexible substrate. [ABSTRACT FROM AUTHOR]

Previous studies on the fate of engineered nanoparticles (ENPs) incorporated in paints mainly focused on the release of the particles as affected by a limited number of factors or monitoring their release from natural sources. In this study, the effects of four factors (i.e., weathering duration, water pH, rainfall duration and intensity) were investigated on the release of SiO-ENPs, Ag-ENPs, and TiO-ENPs from paints applied on panels. The static water immersion test showed that the concentrations of studied particles all increased with weathering duration. At low and high pH, SiO-ENPs and Ag-ENPs showed a higher release, while the release of TiO-ENPs was relatively high at low pH. With increased simulated rainfall duration, the concentration released decreased for Si, and the opposite was observed for Ag, while no obvious correlation was noted for Ti. With greater rainfall intensity, there was increasing release of all particles. In total, the releases of Ag-ENPs and TiO-ENPs were extremely low and within the level of 21.32-42.16 μg Land 0.6-2.3 μg L, respectively, while the values for SiO-ENPs were in the range of 7.5-12 mg L. Additionally, microscopic results highlighted that SiO-ENPs were mainly released in the form of agglomerates, and only a small fraction was below 0.1 μm. Considering these influence factors together, conclusions may be made that weathering time and rainfall duration are more important in controlling release than water pH. [ABSTRACT FROM AUTHOR]