Aerobic degradation of chlorophenols

Chlorinated phenols are toxic compounds and often released into natural environments from improper disposal or non-point sources. One important factor in assessing the environmental fate and transport is the rates of microbial degradation in soils and natural waters. In this study, eight chlorophenols (4-chlorophenol (4-CP), 2,4-dichlorophenol (2,4-DCP), 3,4-dichlorophenol (3,4-DCP), 3,5-dichlorophenol (3,5- DCP), 2,3,5-trichlorophenol (2,3,5-TCP), 2,4,5-trichlorophenol (2,4,5-TCP), 3,4,5- trichlorophenol (3,4,5-TCP), and 2,4,6-trichlorophenol (2,4,6-TCP)) were chosen as the model compounds because they represent the major degradation products for the anaerobic metabolic products of pentachlorophenol (PCP). Aerobic degradation rates of all eight compounds were determined under controlled laboratory conditions. A mixed bacterial culture was seeded from a municipal wastewater treatment plant and were grown with acetate as a primary substrate and the eight chlorophenols as secondary substrates. Rates of degradation were measured in a batch reactor with an initial concentration of acetate of 1000 mg/l and of the individual chlorophenol of 0.1 mg/l. Rate of acetate and chlorophenols were modelled using a Monod model. The maximum rate of acetate utilization was zero-order in relation to acetate concentration and first-order with respect to organism concentration. The rate of chlorophenol degradation were zero-order in relation to the chlorophenol concentration. The relative rates of degradation were in general as follows: monochlorophenol > dichlorophenols > trichlorophenols

Gate-induced insulator to band-like transport transition in organolead halide perovskite

Understanding the intrinsic charge transport in organolead halide perovskites is essential for the development of high-efficiency photovoltaics and other optoelectronic devices. Despite the rapid advancement of the organolead halide perovskite in photovoltaic and optoelectronic applications, the intrinsic charge carrier transport in these materials remains elusive partly due to the difficulty of fabricating electrical devices and obtaining good electrical contact. Here, we report the fabrication of organolead halide perovskite microplates with monolayer graphene as low barrier electrical contact. A systematic charge transport studies reveal an insulator to band-like transport transition. Our studies indicate that the insulator to band-like transport transition depends on the orthorhombic-to-tetragonal phase transition temperature and defect densities of the organolead halide perovskite microplates. Our findings are not only important for the fundamental understanding of charge transport behavior but also offer valuable practical implications for photovoltaics and optoelectronic applications based on the organolead halide perovskite.Comment: 18 pages, 5 figure

Acid Treatment Enables Suppression of Electron-Hole Recombination in Hematite for Photoelectrochemical Water Splitting

We report a new strategy for efficient suppression of electron-hole recombination in hematite photoanodes. Acid-treated hematite show substantially enhanced photocurrent density compared to untreated samples. Electrochemical impedance spectroscopy studies reveal that the enhanced photocurrent is partly due to improved efficiency of charge separation. Transient absorption spectroscopic studies coupled to electrochemical measurements indicate that in addition to improved bulk electrochemical properties, acid treated hematite has significantly decreased surface electron-hole recombination losses due to a greater yield of the trapped photoelectrons being extracted to the external circuit

Construction and Synergistic Effect of Recombinant Yeast Co-expressing Pig IL-2/4/6 on Immunity of Piglets to PRRS Vaccination

AbstractIn order to develop cost-effective immunomodulator, the recombinant Pichia pastoris were firstly constructed to co-express porcine IL-2/4/6 genes, and then fermented to feed 45-days Tibetan piglets at different doses to evaluate its effects on immunity of piglets to PRRS vaccination, which simultaneously received intramuscular injection of inactivated PRRS vaccine. The results were found that the leukocytes, IgG and specific antibody to PRRSV, Th and Tc cells increased significantly in the blood of treated piglets in comparison with those of the control (P<0.05); the mRNA expression of TLRs (TLR-2, 3, 4, 7, 9), IFN-γ, IL-2, IL-4, IL-6, IL-7, IL-12 and IL-15 genes were elevated significantly in the immune cells from the blood of treated piglets (P<0.05). Moreover, the growth of the treated piglets also markedly improved whose average net weight gain was significantly higher than the control on 58 days post inoculation (P<0.05). These results suggest that the recombinant yeast can effectively enhance the systematic innate and adaptive immunity of piglets as well as promote the growth of piglet, which could be further developed as cost-effective promising immunomodulator to improve the control of pig PRRS disease

Wafer-scale growth of large arrays of perovskite microplate crystals for functional electronics and optoelectronics

Methylammonium lead iodide perovskite has attracted intensive interest for its diverse optoelectronic applications. However, most studies to date have been limited to bulk thin films that are difficult to implement for integrated device arrays because of their incompatibility with typical lithography processes. We report the first patterned growth of regular arrays of perovskite microplate crystals for functional electronics and optoelectronics. We show that large arrays of lead iodide microplates can be grown from an aqueous solution through a seeded growth process and can be further intercalated with methylammonium iodide to produce perovskite crystals. Structural and optical characterizations demonstrate that the resulting materials display excellent crystalline quality and optical properties. We further show that perovskite crystals can be selectively grown on prepatterned electrode arrays to create independently addressable photodetector arrays and functional field effect transistors. The ability to grow perovskite microplates and to precisely place them at specific locations offers a new material platform for the fundamental investigation of the electronic and optical properties of perovskite materials and opens a pathway for integrated electronic and optoelectronic systems.Comment: 8 pages, 4 figure

Layer-by-Layer Degradation of Methylammonium Lead Tri-iodide Perovskite Microplates

The methylammonium lead iodide (MAPbI3) perovskite has attracted considerable interest for its high-efficiency, low-cost solar cells, but is currently plagued by its poor environmental and thermal stability. To aid the development of robust devices, we investigate here the microscopic degradation pathways of MAPbI3 microplates. Using in situ transmission electron microscopy to follow the thermal degradation process, we find that under moderate heating at 85°C the crystalline structure shows a gradual evolution from tetragonal MAPbI3 to trigonal lead iodide layered crystals with a fixed crystallographic direction. Our solid-state nudged elastic band calculations confirm that the surface-initiated layer-by-layer degradation path exhibits the lowest energy barrier for crystal transition. We further show experimentally and theoretically that encapsulation of the perovskites with boron nitride flakes suppresses the surface degradation, greatly improving its thermal stability. These studies provide mechanistic insight into the thermal stability of perovskites that suggests new designs for improved stability

Layer-by-Layer Degradation of Methylammonium Lead Tri-iodide Perovskite Microplates

The methylammonium lead iodide (MAPbI3) perovskite has attracted considerable interest for its high-efficiency, low-cost solar cells, but is currently plagued by its poor environmental and thermal stability. To aid the development of robust devices, we investigate here the microscopic degradation pathways of MAPbI3 microplates. Using in situ transmission electron microscopy to follow the thermal degradation process, we find that under moderate heating at 85°C the crystalline structure shows a gradual evolution from tetragonal MAPbI3 to trigonal lead iodide layered crystals with a fixed crystallographic direction. Our solid-state nudged elastic band calculations confirm that the surface-initiated layer-by-layer degradation path exhibits the lowest energy barrier for crystal transition. We further show experimentally and theoretically that encapsulation of the perovskites with boron nitride flakes suppresses the surface degradation, greatly improving its thermal stability. These studies provide mechanistic insight into the thermal stability of perovskites that suggests new designs for improved stability

Chemically Modified Metal Oxide Nanostructure for Photoelectrochemical Water Splitting

Hydrogen gas is chemical fuel with high energy density, and represents a clean, renewable and carbon-free burning fuel, which has the potential to solve the more and more urgent energy crisis in today's society. Inspired by natural photosynthesis, artificial photosynthesis to generate hydrogen energy has attracted a lot of attentions in the field of chemistry, physics and material. Photoelectrochemical water splitting based on semiconductors represents a green and low cost method to generate hydrogen fuel. However, the current overall efficiency of solar to hydrogen is quite low, due to some intrinsic limitations such as bandgap, diffusion distance, carrier lifetime and photostability of semiconductors. Although nanostructured semiconductors can improve their photoelectrochemical water splitting performance to some extent, by increasing electrolyte accessible area and shortening minority carrier diffusion distance, nanostructure engineering cannot change their intrinsic electronic properties. Recent development in chemically modified nanostructures such as surface catalyst decoration, element doping, plasmonic modification and interfacial hetero-junction design have led to significant advancement in the photoelectrochemical water splitting, by improving surface reaction kinetics and charge separation, transportation and collection efficiency. In this thesis, I will give a detailed discussion on the chemically modified metal oxide nanostructures for photoelectrocemical hydrogen generation, with a focus on the element doping, hydrogen treatment and catalyst modification. I have demonstrated nitrogen doping on ZnO and Ti doping on hematite can improve their photoelectrochemical performance. In addition, we found hydrogen treatment is a general and effective method to improve the photocatalytic performance, by increasing their carrier desities. Hydrogen treatment has been demonstrated on TiO2, WO3 and BiVO4. In the end, we also used electrochemical catalyt to modify these metal oxide photoelectrode for waste water treatment and chemical fuel generation