Construction of triphase interface for catalytic ozonation of polluted water.

The utilization efficiency of ozone determines the cost of catalytic ozonation in water treatment. Herein, a triphase catalytic system was constructed by aerating ozone through a CeO2 loaded Al2O3 ceramic membrane (CeO2-CM) for disinfection and antibiotic degradation. Ozone aeration and a packed catalyst system (CeO2-Packing) were set as the controls. Results showed that CeO2-CM reduced the ozone escape by 34.6%-56.2%. The ozone utilization capacity of CeO2-CM for E. coli inactivation was 33.1% and 33.8% higher than those of CeO2-Packing and ozone aeration, respectively. The ozone utilization capacity of CeO2-CM for sulfamethoxazole degradation was 88.5% and 183.1% higher than those of CeO2-Packing and ozone aeration, respectively. CeO2-CM, with the lowest ozone escape and highest ozone utilization efficiency, significantly enhanced the performance of catalytic ozonation in disinfection and antibiotic degradation. This work proposes a feasible strategy for minimizing ozone consumption in water treatment.

Optimization of Co3O4 surface sites for photo-ozone catalytic mineralization of dichloromethane.

Obtaining high removal rate of chlorinated volatile organic compounds (CVOCs) and CO2 selectivity with a low ratio of O3/CVOC and energy consumption is challenging. Dodecylamine was used in this study to create active sites on Co3O4 for photo-ozone catalytic mineralization of dichloromethane (DCM). Amine-Co3O4-450 is a dodecylamine-modified sample with high density of Co3+, Co2+, and hydroxyl due to its nanosheet structure and exposed (112) facets. The optimized surface significantly enhanced the cleavage of the C-Cl bond at low temperatures. Photocatalysis primarily participated in the oxidation of intermediates following DCM dichlorination and significantly improved CO2 selectivity. The respective DCM removal rate and mineralization efficiency of Amine-Co3O4-450 with an O3/DCM molar ratio of 1.27 and one-sun irradiation were 14.9 and 15.0 times higher than the sum of those in the presence of light irradiation or O3 alone. This finding indicated that a strong synergistic effect exists between O3 and light.

Effect of photothermal conversion on ozone uptake over deposited mineral dust.

The deposited dust provides a large surface for heterogeneous ozone uptake reactions in urban regions. Prior studies have barely considered the effect of the photothermal conversion of deposited dust and underlying surface on ozone uptake. In this study, Fe2O3, TiO2, α-Al2O3, and SiO2 were selected as model mineral dusts (MDs) to evaluate the photothermal effect. With an irradiation intensity of 100 mW/cm2, the uptake coefficients of ozone by Fe2O3, TiO2, α-Al2O3, and SiO2 were 2.4, 30, 2.72, and 2.83 times higher than those in a dark condition. For SiO2 and α-Al2O3, the increase in the uptake coefficient was due to the temperature increase induced by photothermal conversion. For Fe2O3 and TiO2, photoelectric and photothermal conversion simultaneously participated in ozone uptake reactions. At 70 °C, the contribution of thermal catalysis to ozone uptake over Fe2O3 and TiO2 was approximately 55.4 % and 55.0 %, respectively. The temperature increase induced by photothermal conversion also promoted MDs' activity for ozone uptake after removing the light source (after sunset). This work proves that the ozone uptake induced by the photothermal effect of deposited MDs and the underlying surface was the primary ozone elimination pathway in urban atmospheres.

Optimization of photothermal conversion and catalytic sites for photo-assisted-catalytic degradation of volatile organic compounds.

Solar energy conversion is a promising strategy to enhance the elimination of volatile organic compounds (VOCs) and minimize power consumption. Herein, non-noble metal WC@WO3 as cocatalyst was composited with CeO2 to optimize photochemical and photothermal conversion for the catalytic ozonation of toluene and acetone. The photothermal conversion efficiencies of visible and infrared lights on 20%WC@WO3-CeO2 were 2.2 and 10.4 times higher than those on CeO2, respectively, which indicates that the equilibrium temperature of the catalyst remarkably increased under full-spectrum light irradiation. Moreover, WC@WO3 transferred electrons to CeO2 in 20%WC@WO3-CeO2 and thus remarkably improved the activity of catalytic sites. The synergy factor of light and O3 on 20%WC@WO3-CeO2 was 5.8, and the reaction rate of toluene and acetone reached 9274.5 and 35779.0 mg/(m3∙min), respectively. This work provides a low-cost and high-efficient catalyst for the utilization of solar energy for VOC control.

A simple simulation-derived descriptor for the deposition of polymer-wrapped carbon nanotubes on functionalized substrates.

Controlling the deposition of polymer-wrapped single-walled carbon nanotubes (s-CNTs) onto functionalized substrates can enable the fabrication of s-CNT arrays for semiconductor devices. In this work, we utilize classical atomistic molecular dynamics (MD) simulations to show that a simple descriptor of solvent structure near silica substrates functionalized by a wide variety of self-assembled monolayers (SAMs) can predict trends in the deposition of s-CNTs from toluene. Free energy calculations and experiments indicate that those SAMs that lead to maximum disruption of solvent structure promote deposition to the greatest extent. These findings are consistent with deposition being driven by solvent-mediated interactions that arise from SAM-solvent interactions, rather than direct s-CNT-SAM interactions, and will permit the rapid computational exploration of potential substrate designs for controlling s-CNT deposition and alignment.

Membrane Remodeling and Stimulation of Aggregation Following α-Synuclein Adsorption to Phosphotidylserine Vesicles.

α-Synuclein is an intrinsically disordered protein abundant in presynaptic terminals in neurons and in synaptic vesicles. α-Synuclein's interaction with lipid bilayers is important not only for its normal physiological function but also in its pathological aggregation and deposition as Lewy bodies in Parkinson's disease. α-Synuclein binds preferentially to lipids with acidic head groups and to high-curvature vesicles and can modulate membrane curvature. The relationship between the protein's role as a membrane curvature sensor and generator and the role of membranes in facilitating its aggregation remains unknown. We investigated the interaction of α-synuclein with vesicles of 1,2-dioleoyl-sn-glycero-3-phospho-l-serine (DOPS) or 1,2-dilauroyl-sn-glycero-3-phospho-l-serine (DLPS). Using nanoparticle tracking along with electron microscopy, we demonstrate that α-synuclein induces extensive vesicle disruption and membrane remodeling into discoids, tubules, and ribbons with DLPS vesicles but not DOPS. Coarse-grained molecular dynamics simulations revealed that adsorption of α-synuclein to DLPS but not DOPS vesicles induced vesicle elongation and redistribution of protein to regions of higher curvature, a process that could drive protein aggregation. In agreement with this hypothesis, DLPS but not DOPS strongly stimulated α-synuclein aggregation. Our results provide new insights into the critical contribution of bilayer stability in the membrane response to α-synuclein adsorption and in stimulation of aggregation.

Recycling of multilayer plastic packaging materials by solvent-targeted recovery and precipitation.

Many plastic packaging materials manufactured today are composites made of distinct polymer layers (i.e., multilayer films). Billions of pounds of these multilayer films are produced annually, but manufacturing inefficiencies result in large, corresponding postindustrial waste streams. Although relatively clean (as opposed to municipal wastes) and of near-constant composition, no commercially practiced technologies exist to fully deconstruct postindustrial multilayer film wastes into pure, recyclable polymers. Here, we demonstrate a unique strategy we call solvent-targeted recovery and precipitation (STRAP) to deconstruct multilayer films into their constituent resins using a series of solvent washes that are guided by thermodynamic calculations of polymer solubility. We show that the STRAP process is able to separate three representative polymers (polyethylene, ethylene vinyl alcohol, and polyethylene terephthalate) from a commercially available multilayer film with nearly 100% material efficiency, affording recyclable resins that are cost-competitive with the corresponding virgin materials.

Revisiting the Growth Mechanism of Hierarchical Semiconductor Nanostructures: The Role of Secondary Nucleation in Branch Formation.

Although there have been advances in synthesizing hierarchical semiconductor materials,  few studies have investigated the fundamental nucleation mechanisms to explain the origins of such complex structures. Resolving these nucleation and growth pathways is technically challenging but  critical for developing predictive synthetic capabilities for the synthesis and application of new materials. In this Letter, we use state-of-the-art in situ liquid phase scanning electron microscopy (SEM) and high-resolution transmission electron microscopy in a combination with classical density functional theory (cDFT) to study the nucleation of highly branched wurtzite ZnO nanostructures via a facile, room-temperature aqueous synthesis route. Using a range of precursor concentrations, we systematically vary the hierarchical organization of these nanostructures. In situ liquid phase SEM demonstrates that all branches form through secondary nucleation and grow by classical processes. Neither random aggregation nor oriented attachment is observed. cDFT results imply that the morphological evolution with increasing [Zn2+] arises from an interplay between a rising thermodynamic driving force, which promotes branch number and variability of orientation, and increasing barriers to interfacial transport due to ion correlation forces that alter the anisotropic kinetics of growth. These findings provide a quantitative picture of branching that sets to rest past controversies and advances efforts to decipher growth mechanisms of hierarchical structures in real solution environments.

Solvent-Mediated Affinity of Polymer-Wrapped Single-Walled Carbon Nanotubes for Chemically Modified Surfaces.

Semiconducting single-walled carbon nanotube (s-CNT) arrays are being explored for next-generation semiconductor electronics. Even with the multitude of alignment and spatially localized s-CNT deposition methods designed to control s-CNT deposition, fundamental understanding of the driving forces for s-CNT deposition is still lacking. The individual roles of the dispersant, solvent, target substrate composition, and the s-CNT itself are not completely understood because it is difficult to decouple deposition parameters. Here, we study poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(6,6'-[2,2'-{bipyridine}])] (PFO-BPy)-wrapped s-CNT deposition from solution onto a chemically modified substrate. We fabricate various self-assembled monolayers (SAMs) to gain a greater understanding of substrate effects on PFO-BPy-wrapped s-CNT deposition. We observe that s-CNT deposition is dependent on both the target substrate and s-CNT dispersion solvent. To complement the experiments, molecular dynamics simulations of PFO-BPy-wrapped s-CNT deposition on two different SAMs are performed to obtain mechanistic insights into the effect of the substrate and solvent on s-CNT deposition. We find that the global free-energy minimum associated with favorable s-CNT adsorption occurs for a configuration in which the minimum of the solvent density around the s-CNT coincides with the minimum of the solvent density above a SAM-grafted surface, indicating that solvent structure near a SAM-grafted surface determines the adsorption free-energy landscape driving s-CNT deposition. Our results will help guide informative substrate design for s-CNT array fabrication in semiconductor devices.

Free-Energy Landscape of the Dissolution of Gibbsite at High pH.

The individual elementary reactions involved in the dissolution of a solid into solution remain mostly speculative due to a lack of direct experimental probes. In this regard, we have applied atomistic simulations to map the free-energy landscape of the dissolution of gibbsite from a step edge as a model of metal hydroxide dissolution. The overall reaction combines kink formation and kink propagation. Two individual reactions were found to be rate-limiting for kink formation, that is, the displacement of Al from a step site to a ledge adatom site and its detachment from ledge/terrace adatom sites into the solution. As a result, a pool of mobile and labile adsorbed species, or adatoms, exists before the release of Al into solution. Because of the quasi-hexagonal symmetry of gibbsite, kink site propagation can occur in multiple directions. Overall, our results will enable the development of microscopic mechanistic models of metal oxide dissolution.

Investigation of the Role of Polysaccharide in the Dolomite Growth at Low Temperature by Using Atomistic Simulations.

Dehydration of water from surface Mg(2+) is most likely the rate-limiting step in the dolomite growth at low temperature. Here, we investigate the role of polysaccharide in this step using classical molecular dynamics (MD) calculations. Free energy (potential of mean force, PMF) calculations have been performed for water molecules leaving the first two hydration layers above the dolomite (104) surface under the following three conditions: without catalyst, with monosaccharide (mannose), and with oligosaccharide (three units of mannose). MD simulations reveal that there is no obvious effect of monosaccharide in lowering the dehydration barrier for surface Mg(2+). However, we found that there are metastable configurations of oligosaccharide, which can decrease the dehydration barrier of surface Mg(2+) by about 0.7-1.1 kcal/mol. In these configurations, the molecule lies relatively flat on the surface and forms a bridge shape. The hydrophobic space near the surface created by the nonpolar -CH groups of the oligosaccharide in the bridge conformation is the reason for the observed reduction of dehydration barrier.