Resolving Ultraviolet-Visible Spectra for Complex Dissolved Mixtures of Multitudinous Organic Matters in Aerosols.

Light-absorbing organic aerosols, referred to as brown carbon (BrC), play a vital role in the global climate and air quality. Due to the complexity of BrC chromophores, the identified absorbing substances in the ambient atmosphere are very limited. However, without comprehensive knowledge of the complex absorbing compounds in BrC, our understanding of its sources, formation, and evolution mechanisms remains superficial, leading to great uncertainty in climatic and atmospheric models. To address this gap, we developed a constrained non-negative matrix factorization (NMF) model to resolve the individual ultraviolet-visible spectrum for each substance in dissolved organic aerosols, with the power of ultrahigh-performance liquid chromatography-diode array detector-ultrahigh-resolution mass spectrometry (UHPLC-DAD-UHRMS). The resolved spectra were validated by selected standard substances and validation samples. Approximately 40,000 light-absorbing substances were recognized at the MS1 level. It turns out that BrC is composed of a vast number of substances rather than a few prominent chromophores in the urban atmosphere. Previous understanding of the absorbing feature of BrC based on a few identified compounds could be biased. Weak-absorbing substances missed previously play an important role in BrC absorption when they are integrated due to their overwhelming number. This model brings the property exploration of complex dissolved organic mixtures to a molecular level, laying a foundation for identifying potentially significant compositions and obtaining a comprehensive chemical picture.

Non-Interacting Ni and Fe Dual-Atom Pair Sites in N-Doped Carbon Catalysts for Efficient Concentrating Solar-Driven Photothermal CO2 Reduction.

Solar-to-chemical energy conversion under weak solar irradiation is generally difficult to meet the heat demand of CO2 reduction. Herein, a new concentrated solar-driven photothermal system coupling a dual-metal single-atom catalyst (DSAC) with adjacent Ni-N4 and Fe-N4 pair sites is designed for boosting gas-solid CO2 reduction with H2 O under simulated solar irradiation, even under ambient sunlight. As expected, the (Ni, Fe)-N-C DSAC exhibits a superior photothermal catalytic performance for CO2 reduction to CO (86.16 µmol g-1 h-1 ), CH4 (135.35 µmol g-1 h-1 ) and CH3 OH (59.81 µmol g-1 h-1 ), which are equivalent to 1.70-fold, 1.27-fold and 1.23-fold higher than those of the Fe-N-C catalyst, respectively. Based on theoretical simulations, the Fermi level and d-band center of Fe atom is efficiently regulated in non-interacting Ni and Fe dual-atom pair sites with electronic interaction through electron orbital hybridization on (Ni, Fe)-N-C DSAC. Crucially, the distance between adjacent Ni and Fe atoms of the Ni-N-N-Fe configuration means that the additional Ni atom as a new active site contributes to the main *COOH and *HCO3 dissociation to optimize the corresponding energy barriers in the reaction process, leading to specific dual reaction pathways (COOH and HCO3 pathways) for solar-driven photothermal CO2 reduction to initial CO production.

Highly efficient ozone elimination by metal doped ultra-fine Cu2O nanoparticles.

Nowadays, ozone contamination becomes dominant in air and thus challenges the research and development of cost-effective catalyst. In this study, metal doped Cu2O catalysts are synthesized via reduction of Cu2+ by ascorbic acid in base solutions containing doping metal ions. The results show that compared with pure Cu2O, the Mg2+ and Fe2+ dopants enhance the O3 removal efficiency while Ni2+ depresses the activity. In specific, Mg-Cu2O shows high O3 removal efficiency of 88.4% in harsh environment of 600,000 mL/(g·hr) space velocity and 1500 ppmV O3, which is one of the highest in the literature. Photoluminescence and electron paramagnetic spectroscopy characterization shows higher concentration of crystal defects induced by the Mg2+ dopants, favoring the O3 degradation. The in-situ diffuse reflectance Fourier transform infrared spectroscopy shows the intermediate species in the O3 degradation process change from O22- dominant of pure Cu2O to O2- dominant of Mg-Cu2O, which would contribute to the high activity. All these results show the promising prospect of the Mg-Cu2O for highly efficiency O3 removal.

Coordination-Controlled Catalytic Activity of Cobalt Oxides for Ozone Decomposition.

Nowadays, it is still elusive and challenging to discover the active sites of cobalt (Co) cations in different coordination structures, though Co-based oxides show their great potency in catalytic ozone elimination for air cleaning. Herein, different Co-based oxides are controllably synthesized including hexagonal wurtzite CoO-W with Co2+ in tetrahedral coordination (CoTd2+) and CoAl spinel with dominant CoTd2+, cubic rock salt CoO-R with Co2+ in octahedral coordination (CoOh2+), MgCo spinel with dominant Co3+ in octahedral coordination (CoOh3+), and Co3O4 with mixed CoTd2+ and CoOh3+. The valences are proved by X-ray photoelectron spectroscopy, and the coordinations are verified by X-ray absorption fine structure analysis. The ozone decomposition performances are CoOh3+ ∼ CoOh2+ ≫ CoTd2+, and CoOh3+ and CoOh2+ show a lower apparent activation energy of ∼42-44 kJ/mol than CoTd2+ (∼55 kJ/mol). In specific, MgCo shows the highest decomposition efficiency of 95% toward 100 ppm ozone at a high space velocity of 1,200,000 mL/gh, which still retains at 80% after a long-term running of 36 h at room temperature. The high activity is explained by the d-orbital splitting in the octahedral coordination, favoring the electron transfer in ozone decomposition reactions, which is also verified by the simulation. These results show the promising prospect of the coordination tuning of Co-based oxides for highly active ozone decomposition catalysts.

Heterojunctioned CuO/Cu2O catalyst for highly efficient ozone removal.

In recent years, near surface ozone pollution, has attracted more and more attention, which necessitates the development of high efficient and low cost catalysts. In this work, CuO/Cu2O heterojunctioned catalyst is fabricated by heating Cu2O at high temperature, and is adopted as ozone decomposition catalyst. The results show that after Cu2O is heated at 180°C conversion of ozone increases from 75.2% to 89.3% at mass space velocity 1,920,000 cm3/(g·hr) in dry air with 1000 ppmV ozone, which indicates that this heterojunction catalyst is one of the most efficient catalysts reported at present. Catalysts are characterized by electron paramagnetic resonance spectroscopy and ultraviolet photoelectron spectroscopy, which confirmed that the heterojunction promotes the electron transfer in the catalytic process and creates more defects and oxygen vacancies in the CuO/Cu2O interfaces. This procedure of manufacturing heterostructures would also be applicable to other metal oxide catalysts, and it is expected to be more widely applied to the synthesis of high-efficiency heterostructured catalysts in the future.

Capacitive Desalination and Disinfection of Water Using UiO-66 Metal-Organic Framework/Bamboo Carbon with Chitosan.

The zirconium-based metal-organic framework (MOF) (UiO-66)/bamboo carbon (BC) composite with chitosan was prepared using hydrothermal and impregnation methods and used for capacitive desalination (CDI) and disinfection of water. The results showed that these composites had fast ion exchange and charge transfer properties. During the CDI process, these composites' electrodes exhibited good cycle stability, electrosorption capacity (4.25 mg/g) and excellent bactericidal effect. These carbon-based composites electrodes' bactericidal rate for Escherichia coli could reach 99.99% within 20 minutes; therefore, they had good performance and were a good choice for high-performance deionization applications.

Abatement of dichloromethane with high selectivity over defect-rich MOF-derived Ru/TiO2 catalysts.

The regulation of oxygen vacancies and Ru species using metal-organic frameworks was synergically adopted in a rational design to upgrade Ru/TiO2 catalysts, which are highly active for the catalytic oxidation of dichloromethane (DCM) with less undesired byproducts. In this work, Ru/M-TiO2 and Ru/N-TiO2 catalysts were synthesized by the pyrolysis of MIL-125 and NH2-MIL-125 incorporated with Ru, the existence of Ru nanoclusters and nanoparticles was detected by XAFS, respectively, and the catalytic performance was analyzed comprehensively. Complete oxidation of DCM was obtained at ∼290 °C over Ru/M-TiO2 and Ru/N-TiO2 catalysts, while Ru/N-TiO2 showed quite less monochloromethane (MCM) and higher CO2 yields, and better dechlorination capacity in oxidation. The distinction comes down to that the easier desorption of chlorine could be achieved over Ru4+ which act as the main activated adsorption sites for DCM in Ru/N-TiO2, compared to oxygen vacancies that serve as the main dissociation sites in Ru/M-TiO2. Additionally, Ru/N-TiO2 exhibited superior stability and excellent resilience in moisture. An in situ DRIFTS experiment further indicated the different DCM catalytic degradation process as well as the reaction mechanism over the as-prepared catalysts.

In vitro and in vivo low-dose exposure of simulated cooking oil fumes to assess adverse biological effects.

Cooking oil fumes (COFs) represent a major indoor environmental pollutant and exhibit potent mutagenic or carcinogenic health effects caused by containing various heterocyclic aromatic amines (HAAs) and long-chain aldehydes. Despite some evaluation of the cumulative exposure of COFs to cancer cells under high concentration were evaluated, their biological adverse effects with low-dose exposure to healthy cells had been inadequately investigated. Herein, we firstly scrutinized the three selected typically toxic compounds of heterocyclic amine 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 3,8-dimethylammidazo[4,5-f]quinoxalin-2-amine (MeIQx) and trans, trans-2,4-decadienal (TDA)) emitted from COFs. In vitro studies revealed that the PhIP, MeIQx and TDA aerosol particles were negligible toxicity to cancer cells (A549 and HepG-2) but strong cytotoxicity to normal healthy cells (HelF and L02) under 0.5-4 µg/mL low dose exposure based on the reactive oxygen species (ROS) mechanism. In vivo studies demonstrated that PhIP caused significant lung and liver damage after exposure to PhIP for 30 days with mice. These results indicated the direct proof of healthy cell damage even at low-dose exposure to HAAs and aldehydes.

Aqueous Strippable Polymer Coating for Highly Efficient Primary Radioactive Uranium Decontamination with Versatility on Diversified Surface.

The decontamination of radioactive materials on the surfaces of nuclear facilities has generated large quantities of waste from the rapid development of the nuclear industry, posing a potential threat globally. Strippable coating has been employed for some time to remove radioactive contamination due to its high performance and removability, flexibility, and compatibility with various substrates. Herein, an aqueous strippable coating based on an adsorbent/polyvinyl alcohol (PVA) polymer was developed to remove radioactive uranium from stainless-steel surfaces that showed greater decontamination than that of DeconGel, with an efficiency of 87.2% for 5 g/L uranium and 95.5% for 22.5 g/L uranium, along with a high repeatability and better mechanical properties. Furthermore, the prepared coating was versatile and could be applied to a range of substrate surfaces (lacquered, aluminum, glass, plastic, and ceramic), with outstanding performance ranging from 79.2 to 95.4% for 1 g/L uranium. The prepared coating could also be applied through brushing or spraying to horizontal or vertical substrates. The exceptional performance could be due to the synergistic effect of the introduction of ethylene diamine tetra-acetic acid disodium salt (EDTA-2Na) as a chelating agent and the nano-adsorbent CaCO3/TiO2.

Magnet-assisted electrochemical immunosensor based on surface-clean Pd-Au nanosheets for sensitive detection of SARS-CoV-2 spike protein.

Tracking and monitoring of low concentrations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can effectively control asymptomatic transmission of current coronavirus disease 2019 (COVID-19) in the early stages of infection. Here, we highlight an electrochemical immunosensor for sensitive detection of SARS-CoV-2 antigen marker spike protein. The surface-clean Pd-Au nanosheets as a substrate for efficient sensing and signal output have been synthesized. The morphology, chemical states and excellent stable electrochemical properties of this surface-clean heterostructures have been studied. Functionalized superparamagnetic nanoparticles (MNPs) were introduced as sample separators and signal amplifiers. This biosensor was tested in phosphate buffered saline (PBS) and nasopharyngeal samples. The results showed that the sensor has a wide linear dynamic range (0.01 ng mL-1 to 1000 ng mL-1) with a low detection limit (0.0072 ng mL-1), which achieved stable and sensitive detection of the spike protein. Therefore, this immunosensing method provides a promising electrochemical measurement tool, which can furnish ideas for early screening and the reasonable optimization of detection methods of SARS-CoV-2.

Rubber-Composite-Nanoparticle-Modified Epoxy Powder Coatings with Low Curing Temperature and High Toughness.

In this study, a rubber-composite-nanoparticle-modified epoxy powder composite coating with low curing temperature and high toughness was successfully fabricated. The effects of N,N-dimethylhexadecylamine (DMA) carboxy-terminated nitrile rubber (CNBR) composite nanoparticles on the microstructure, curing behavior, and mechanical properties of epoxy-powder coating were systematically investigated. SEM and TEM analysis revealed a uniform dispersion of DMA-CNBR in the epoxy-powder coating, with average diameter of 100 nm. The curing temperature of the epoxy-composite coatings had reduced almost 19.1% with the addition of 1phr DMA-4CNBR into the coating. Impact strength tests confirmed that DMA-CNBR-modified epoxy-composite coatings showed significant improvements compared with the neat EP coating, which was potentially attributed to the nanoscale dispersion of DMA-CNBR particles in epoxy coatings and their role in triggering microcracks. Other mechanical properties, including adhesion and cupping values, were improved in the same manner. In addition, thermal and surface properties were also studied. The prepared epoxy composite powder coating with the combination of low curing temperature and high toughness broadened the application range of the epoxy coatings.

Roles of Oxygen Vacancies of CeO2 and Mn-Doped CeO2 with the Same Morphology in Benzene Catalytic Oxidation.

Mn-doped CeO2 and CeO2 with the same morphology (nanofiber and nanocube) have been synthesized through hydrothermal method. When applied to benzene oxidation, the catalytic performance of Mn-doped CeO2 is better than that of CeO2, due to the difference of the concentration of O vacancy. Compared to CeO2 with the same morphology, more oxygen vacancies were generated on the surface of Mn-doped CeO2, due to the replacement of Ce ion with Mn ion. The lattice replacement has been analyzed through XRD, Raman, electron energy loss spectroscopy and electron paramagnetic resonance technology. The formation energies of oxygen vacancy on the different exposed crystal planes such as (110) and (100) for Mn-doped CeO2 were calculated by the density functional theory (DFT). The results show that the oxygen vacancy is easier to be formed on the (110) plane. Other factors influencing catalytic behavior have also been investigated, indicating that the surface oxygen vacancy plays a crucial role in catalytic reaction.

Porous Au@Pt nanoparticles with superior peroxidase-like activity for colorimetric detection of spike protein of SARS-CoV-2.

The development of colorimetric assays for rapid and accurate diagnosis of coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is of practical importance for point-of-care (POC) testing. Here we report the colorimetric detection of spike (S1) protein of SARS-CoV-2 based on excellent peroxidase-like activity of Au@Pt nanoparticles, with merits of rapidness, easy operation, and high sensitivity. The Au@Pt NPs were fabricated by a facile seed-mediated growth approach, in which spherical Au NPs were premade as seeds, followed by the Pt growth on Au seeds, producing uniform, monodispersed and porous Au@Pt core-shell NPs. The as-obtained Au@Pt NPs showed a remarkable enhancement in the peroxidase-mimic catalysis, which well abided by the typical Michaelis-Menten theory. The enhanced catalysis of Au@Pt NPs was ascribed to the porous nanostructure and formed electron-rich Pt shells, which enabled the catalytic pathway to switch from hydroxyl radical generation to electron transfer process. On a basis of these findings, a colorimetric assay of spike (S1) protein of SARS-CoV-2 was established, with a linear detection range of 10-100 ng mL-1 of protein concentration and a low limit of detection (LOD) of 11 ng mL-1. The work presents a novel strategy for diagnosis of COVID-19 based on metallic nanozyme-catalysis.

Nonpolar GaAs Nanowires Catalyzed by Cu5As2: Insights into As Layer Epitaxy.

Controlled synthesis of GaAs nanowires (NWs) with specific phases and orientations is important and challenging, which determines their electronic performances. Herein, single-crystalline GaAs NWs are successfully synthesized by using complementary metal-oxide semiconductor compatible Cu2O catalysts via chemical vapor deposition at an optimized temperature of 560 °C. In contrast to typically Au catalyzed GaAs NWs, the Cu2O catalyzed ones are found to grow along nonpolar orientations of zincblende <110> and <211> and wurtzite <1̅100> and <2̅110>. The Cu2O catalysts are found to change into orthorhombic Cu5As2 after the NW growth, which is also significantly distinguished from the Au-Ga catalyst alloy in the literature. The Cu5As2 alloy plays the epitaxy role in the nonpolar GaAs NW growth due to the lattice matching with the nonpolar planes of GaAs, which is verified by the atomic stack model. These nonpolar oriented GaAs NWs have minimized stacking faults, promising for the other semiconductor synthesis as well as electronic applications.

Ordered Mesoporous Carbon with Chitosan for Disinfection of Water via Capacitive Deionization.

Capacitive deionization (CDI) with water disinfection materials is a potential method to produce fresh water from aqueous solutions. Therefore, an ordered mesoporous carbon with chitosan (OMC-CS) was coated on the active carbon (AC) electrode as a capacitive deionization disinfection (CDI) electrode. Comparing with OMC-CS-4,6,8 as CDI electrodes, it was found that OMC-CS-6 as a CDI electrode had an excellent disinfection efficiency, killing about 99.99% Escherichia coli (E. coli) in the CDI process at an applied 1.2 V. The OMC-CS material was did not pollute the water and will not contaminate to the environment in comparison with other chemical antibacterial agents. This CDI electrode could play a huge role in biocontaminated water in the future.

Three-dimensional cubic ordered mesoporous carbon with chitosan for capacitive deionization disinfection of water.

Three-dimensional cubic ordered mesoporous carbon with chitosan (Ia3d-CS), which was synthesized via exothermic reaction between liquid potassium and carbon monoxide gas, was coated on the active carbon (AC) electrode as a capacitive deionization (CDI) disinfection electrode. The results showed that Ia3d-CS-2 as CDI electrode exhibited the quick ion diffusion and strong charge transfer performance, due to the three-dimensional pore structure and specific surface area. The electrode of Ia3d-CS-2 displayed a specific capacity of 191.22 F/g at a scan rate of 100 mV·s-1 in 0.5 M NaCl aqueous solution. In a CDI recycling system, Ia3d-CS-x electrode showed good cyclic stability, and the electrosorption capacity of Ia3d-CS-2 electrode can achieve 1.31 mg/g at 1.2 V in 100 mg/l NaCl aqueous solutions. Subsequently, Ia3d-CS-2 electrode had an excellent disinfection efficiency of killing about 99.99% Escherichia coli within 30 min during the CDI process at applied 1.2 V. Considering those excellent properties of the fabricated Ia3d-CS-x electrode, which should be a better candidate for high-performance deionization application.

Sensitive Cross-Linked SnO2:NiO Networks for MEMS Compatible Ethanol Gas Sensors.

Nowadays, it is still technologically challenging to prepare highly sensitive sensing films using microelectrical mechanical system (MEMS) compatible methods for miniaturized sensors with low power consumption and high yield. Here, sensitive cross-linked SnO2:NiO networks were successfully fabricated by sputtering SnO2:NiO target onto the etched self-assembled triangle polystyrene (PS) microsphere arrays and then ultrasonically removing the PS microsphere templates in acetone. The optimum line width (~ 600 nm) and film thickness (~ 50 nm) of SnO2:NiO networks were obtained by varying the plasma etching time and the sputtering time. Then, thermal annealing at 500 °C in H2 was implemented to activate and reorganize the as-deposited amorphous SnO2:NiO thin films. Compared with continuous SnO2:NiO thin film counterparts, these cross-linked films show the highest response of ~ 9 to 50 ppm ethanol, low detection limits (< 5 ppm) at 300 °C, and also high selectivity against NO2, SO2, NH3, C7H8, and acetone. The gas-sensing enhancement could be mainly attributed to the creating of more active adsorption sites by increased stepped surface in cross-linked SnO2:NiO network. Furthermore, this method is MEMS compatible and of generality to effectively fabricate other cross-linked sensing films, showing the promising potency in the production of low energy consumption and wafer-scale MEMS gas sensors.

Gram-scale synthesis of ultra-fine Cu2O for highly efficient ozone decomposition.

Nowadays, it is necessary and challenging to prepare Cu2O in a large scale for various applications such as catalysis due to its excellent properties. Here, gram-scale Cu2O with nm size is successfully prepared using a simple liquid-phase reduction method at 25 °C. The amount of NaOH is found to be the key factor to determine the particle size of Cu2O by modifying the complexation and reduction reactions. The obtained ultra-fine Cu2O exhibits high performance of >95% efficiency for removing high-concentration (3000 ppm) ozone at 25 °C and even at a high relative humidity (RH) of 90% for more than 8 h. Furthermore, the Cu2O nanoparticles are coated onto an aluminium honeycomb substrate to form a monolithic catalyst, which shows high ozone removal efficiency of >99% in dry air and >97% in 90% RH for >10 h at a space velocity of 8000 h-1. The high performance could be attributed to the enhanced release of the ozone decomposition intermediate by the small size of Cu2O, as verified by O2 temperature-programmed desorption and X-ray photoelectron spectroscopy. All these results show the industrial promise of the large scale synthesis of ultrafine Cu2O applicable for high-performance ozone removal.

A one-pot synthesis of a monolithic Cu2O/Cu catalyst for efficient ozone decomposition.

Nowadays, it is necessary and challenging to prepare monolithic catalysts, which are ready for use, preventing the tedious and complicated integration procedure of the powder materials onto a porous substrate. Herein, Cu2O nanoparticles are successfully synthesized onto a porous Cu foam in one pot via the surface oxidation, coordination and precipitation reactions in a NH4OH and HCl solution, and the optimum synthesis conditions are a NH3 : HCl ratio of 1 : 0.9, oxidation temperature of 80 °C and time of 18 h. The obtained Cu2O/Cu catalyst (mostly <100 nm) shows a highly active O3 decomposition performance with >98% and >80% conversion efficiency in dry and 90% relative humidity air for >10 h at an O3 concentration of 20 ppm and a gas hourly space velocity of 12 500 h-1. The high efficiency can be attributed to the porous Cu foam providing a large contact area, abundant crystal defects in the nanometer-sized Cu2O materials serving as the active sites, and also to the Schottky barrier formed in the Cu2O/Cu interface facilitating the electron transfer for O3 degradation. All these results show the potency of the easily fabricated monolithic Cu2O/Cu catalyst for the highly efficient O3 contaminant removal.

Sr-Doped Cubic In2O3/Rhombohedral In2O3 Homojunction Nanowires for Highly Sensitive and Selective Breath Ethanol Sensing: Experiment and DFT Simulation Studies.

In recent years, it is urgent and challenging to fabricate highly sensitive and selective gas sensors for breath analyses. In this work, Sr-doped cubic In2O3/rhombohedral In2O3 homojunction nanowires (NWs) are synthesized by one-step electrospun technology. The Sr doping alters the cubic phase of pure In2O3 into the rhombohedral phase, which is verified by the high-resolution transmittance electron microscopy, X-ray diffraction, and Raman spectroscopy, and is attributable to the low cohesive energy as calculated by the density functional theory (DFT). As a proof-of-concept of fatty liver biomarker sensing, ethanol sensors are fabricated using the electrospun In2O3 NWs. The results show that 8 wt % Sr-doped In2O3 shows the highest ethanol sensing performance with a high response of 21-1 ppm, a high selectivity over other interfering gases such as methanol, acetone, formaldehyde, toluene, xylene, and benzene, a high stability measured in 6 weeks, and also a high resistance to high humidity of 80%. The outstanding ethanol sensing performance is attributable to the enhanced ethanol adsorption by Sr doping as calculated by DFT, the stable rhombohedral phase and the preferred (104) facet exposure, and the formed homojunctions favoring the electron transfer. All these results show the effective structural modification of In2O3 by Sr doping, and also the great potency of the homojunction Sr-doped In2O3 NWs for highly sensitive, selective, and stable breath ethanol sensing.