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One of the most significant drawbacks of metal oxide (MOS) based chemiresistive gas sensors is the requirement of high operating temperature (250–450 °C), which results in significant power consumption and shorter lifetime. To develop room temperature (21±2 °C) MOS chemiresistive gas sensors, the sensing performance of different MOS nanostructures (i.e., tin (IV) oxide (SnO2) nanoparticles (NPs), indium (III) oxide (In2O3) NPs, zinc oxide (ZnO) NPs, tungsten trioxide (WO3) NPs, copper oxide (CuO) nanotubes (NTs), and indium tin oxide (In90Sn10O3 (ITO)) NPs) were systematically investigated toward different toxic industrial chemicals (TICs) (i.e., nitrogen dioxide (NO2), ammonia (NH3), hydrogen sulfide (H2S), carbon monoxide (CO), sulfur dioxide (SO2) and volatile organic compounds (VOCs) (i.e., acetone (C3H6O), toluene (C6H5CH3), ethylbenzene (C6H5CH2CH3), and p-xylene (C6H4(CH3)2)) in the presence and absence of 400 nm UV light illumination. Sensing performance enhancement through photoexcitation is strongly dependent on the target analytes. Under 400 nm UV photoexcitation at 76.0 mW/cm2 intensity, room temperature (21±2 °C) NO2 sensing was readily achieved where SnO2 NPs exhibited the highest sensor response (S = 474.4 toward 10 ppmm (parts per million by mass)) with good recovery followed by ZnO NPs > In2O3 NPs > ITO NPs. Meanwhile, indirect bandgap n-type WO3 NPs showed limited NO2 sensing performance under illumination, whereas p-type CuO NTs showed relatively good sensing response. The most significant improvements in SnO2 compared to other MOS nanoparticles might be attributed to the highest number of photogeneration electrons, which rapidly reacted with adsorbed species to enhance the reaction kinetics. WO3 NPs showed a unique sensing response toward aromatic compounds (e.g., ethylbenzene and p-xylene) under UV illumination, where maximum sensitivity was achieved under 36 mW/cm2 irradiation. Changing light intensity from 0.0 to 36.4 mW/cm2, WO3 showed 15.4-fold and 6.3-fold enhancement in sensing response toward 25 ppmm ethylbenzene and 100 ppmm p-xylene, respectively. 400 nm optical excitation has a limited effect on the sensing performance toward CO, SO2, toluene, and acetone. 

The recalcitrance of some emerging organic contaminants through conventional water treatment systems may necessitate advanced technologies that use highly reactive, non-specific hydroxyl radicals. Here, polyacrylonitrile (PAN) nanofibers with embedded titanium dioxide (TiO 2 ) nanoparticles were synthesized via electrospinning and subsequently carbonized to produce mechanically stable carbon/TiO 2 (C/TiO 2 ) nanofiber composite filters. Nanofiber composites were optimized for reactivity in flow through treatment systems by varying their mass loading of TiO 2 , adding phthalic acid (PTA) as a dispersing agent for nanoparticles in electrospinning sol gels, comparing different types of commercially available TiO 2 nanoparticles (Aeroxide® P25 and 5 nm anatase nanoparticles) and through functionalization with gold (Au/TiO 2 ) as a co-catalyst. High bulk and surface TiO 2 concentrations correspond with enhanced nanofiber reactivity, while PTA as a dispersant makes it possible to fabricate materials at very high P25 loadings (∼80% wt%). The optimal composite formulation (50 wt% P25 with 2.5 wt% PTA) combining high reactivity and material stability was then tested across a range of variables relevant to filtration applications including filter thickness (300–1800 μm), permeate flux (from 540–2700 L m −2 h), incident light energy (UV-254 and simulated sunlight), flow configuration (dead-end and cross-flow filtration), presence of potentially interfering co-solutes (dissolved organic matter and carbonate alkalinity), and across a suite of eight organic micropollutants (atrazine, benzotriazole, caffeine, carbamazepine, DEET, metoprolol, naproxen, and sulfamethoxazole). During cross-flow recirculation under UV-irradiation, 300 μm thick filters (30 mg total mass) produced micropollutant half-lives ∼45 min, with 40–90% removal (from an initial 0.5 μM concentration) in a single pass through the filter. The initial reaction rate coefficients of micropollutant transformation did not clearly correlate with reported second order rate coefficients for reaction with hydroxyl radical ( k OH ), implying that processes other than reaction with photogenerated hydroxyl radical ( e.g. , surface sorption) may control the overall rate of transformation. The materials developed herein represent a promising next-generation filtration technology that integrates photocatalytic activity in a robust platform for nanomaterial-enabled water treatment. 

Abstract Electrospinning is a versatile method for synthesizing nanofibrous structures from nearly all polymers, offering a solution for the industrial‐scale mass production of nanomaterials in a wide range of applications. However, the continuous non‐woven structure intrinsic to electrospun fibers limits their applications, where a smaller length scale is desired. Here, we present a novel method to synthesize polymeric nanofiber‐fragments based on colloid electrospinning of polymer and sacrificial silica nanoparticles, followed by mechanical fracturing with ultrasonication. The size and hydrophobicity of silica nanoparticles are optimized for their improved integration within the polymer matrix, and the controllability of nanofiber‐fragment length by the amount of silica nanoparticle loading, down to 2 µm in length for poly(vinylidene fluoride‐trifluoroethylene) nanofibers with an average fiber diameter of approximately 100 nm, is shown. The resultant nanofiber‐fragments are shown to maintain their material properties including piezoelectric coefficients and their enhanced injectability for drug delivery application is demonstrated with an animal model.