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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Association between sperm DNA integrity and seminal plasma antioxidant levels in health workers occupationally exposed to ionizing radiation

There is a paucity of data regarding the association between occupational radiation exposure and risk to human fertility. Recently, we provided the first evidence on altered sperm functional characteristics, DNA damage and hypermethylation in radiation health workers. However, there is no report elucidating the association between seminal plasma antioxidants and sperm chromatin integrity in occupationally exposed subjects. Here, we assessed the seminal plasma antioxidants and lipid peroxidation level in 83 men who were occupationally exposed to ionizing radiation and then correlated with the sperm chromatin integrity. Flow cytometry based sperm chromatin integrity assay revealed a significant decline in αt value in the exposed group in comparison to the non-exposed group (P<0.0001). Similarly, both total and reduced glutathione levels and total antioxidant capacity in the seminal plasma were significantly higher in exposed group than the non-exposed group (P<0.01, 0.001 and 0.0001, respectively). However, superoxide dismutase level and malondialdehyde level, which is an indicator of lipid peroxidation in the seminal plasma, did not differ significantly between two groups. The total antioxidant capacity (TAC) and GSH level exhibited a positive correlation with sperm DNA integrity in exposed subjects. To conclude, this study distinctly shows that altered sperm chromatin integrity in radiation health workers is associated with increase in seminal plasma antioxidant level. Further, the increased seminal plasma GSH and TAC could be an adaptive measure to tackle the oxidative stress to protect genetic and functional sperm deformities in radiation health workers. - Highlights: • Seminal plasma antioxidants were measured in men occupationally exposed to radiation. • Sperm chromatin integrity was significantly affected in the exposed group. • Glutathione and total antioxidant capacity was significantly higher in exposed group. • Sperm DNA damage in exposed subjects affected seminal plasma antioxidant level.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Effect of nicotine on melanogenesis and antioxidant status in HEMn-LP melanocytes

Nicotine is a natural ingredient of tobacco plants and is responsible for the addictive properties of tobacco. Nowadays nicotine is also commonly used as a form of smoking cessation therapy. It is suggested that nicotine may be accumulated in human tissues containing melanin. This may in turn affect biochemical processes in human cells producing melanin. The aim of this study was to examine the effect of nicotine on melanogenesis and antioxidant status in cultured normal human melanocytes HEMn-LP. Nicotine induced concentration-dependent loss in melanocytes viability. The value of EC{sub 50} was determined to be 7.43 mM. Nicotine inhibited a melanization process in human light pigmented melanocytes and caused alterations of antioxidant defense system. Significant changes in cellular antioxidant enzymes: superoxide dismutase and catalase activities and in hydrogen peroxide content were stated. The obtained results may explain a potential influence of nicotine on biochemical processes in melanocytes in vivo during long term exposition to nicotine. - Graphical abstract: Nicotine inhibits melanogenesis and induces oxidative stress in HEMn-LP melanocytes. - Highlights: • Nicotine induces concentration-dependent loss in melanocytes viability. • Nicotine in non-cytotoxic concentrations inhibits melanogenesis. • Nicotine in higher concentrations induces oxidative stress.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Physiological and biochemical responses of two keystone polychaete species: Diopatra neapolitana and Hediste diversicolor to Multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) are one of the most important carbon Nanomaterials (NMs). The production and use of these carbon NMs is increasing rapidly and, therefore, the need to assess their presence in the environment and associated risks has become increasingly important. However, limited literature is available regarding the impacts induced in aquatic organisms by this pollutant, namely in invertebrate species. Diopatra neapolitana and Hediste diversicolor are keystone polychaete species inhabiting estuaries and shallow water bodies intertidal mudflats, frequently used to evaluate the impact of environmental disturbances in these systems. To our knowledge, no information is available on physiological and biochemical alterations on these two species due to MWCNTs exposure. Thus, the present study aimed to assess the toxic effects of different MWCNTs concentrations (0.01; 0.10 and 1.00 mg/L) in both species physiological (regenerative capacity and respiration rate) and biochemical (energy reserves, metabolic activities, oxidative stress related biomarkers and neurotoxicity markers) performance, after 28 days of exposure. The results obtained revealed that exposure to MWCNTs induced negative effects on the regenerative capacity of D. neapolitana. Additionally, higher MWCNTs concentrations induced increased respiration rates in D. neapolitana. MWCNTs altered energy-related responses, with higher values of electron transport system activity, glycogen and protein concentrations in both polychaetes exposed to this contaminant. Furthermore, when exposed to MWCNTs both species showed oxidative stress with higher lipid peroxidation, lower ratio between reduced and oxidized glutathione, and higher activity of antioxidant (catalase and superoxide dismutase) and biotransformation (glutathione-S-transferases) enzymes in exposed organisms. - Highlights: • MWCNTs induced negative effects on the regenerative capacity of Diopatra neapolitana. • Diopatra neapolitana and Hediste diversicolor exposed to MWCNTs showed oxidative stress. • Both species under MWCNTs increased their metabolic capacity. • Inhibition of cholinesterases confirmed neurotoxicity of MWCNTs in both species. • D. neapolitana and H. diversicolor are potential bioindicators to monitor carbon NMs pollution.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Irradiation of rainbow trout at early life stages results in a proteomic legacy in adult gills. Part A; proteomic responses in the irradiated fish and in non-irradiated bystander fish

Highlights: • The effects of early life irradiation on the trout gill proteome was investigated. • The bystander effect proteomic responses in non-irradiated fish were investigated. • Proteomic responses of embryonic irradiation were anti-tumorigenic or anti-oxidant. • Proteomic responses of larval or first feeder irradiation were “dual function”. • Bystander effect proteomic responses were anti-tumorigenic or protective. Exposure to a single 0.5 Gy X-ray dose of eggs at 48 h after fertilisation (48 h egg), eyed eggs, yolk sac larvae (YSL) and first feeders induces a legacy effect in adult rainbow trout. This includes the transmission of a bystander effect to non-irradiated adult trout which had swam with the irradiated fish. The aim of this study was to investigate this legacy by analysing the gill proteome of these irradiated and bystander fish. Irradiation at all of the early life stages resulted in changes to proteins which play a key role in development but are also known to be anti-tumorigenic and anti-oxidant: upregulation of haemoglobin subunit beta (48 h egg), haemoglobin, serum albumin 1 precursor (eyed eggs), clathrin heavy chain 1 isoform X10 (eyed eggs and first feeders), and actin-related protein 2/3 complex subunit 4 (first feeders), downregulation of pyruvate dehydrogenase, histone 1 (48 h egg), triosephosphate isomerase (TPI), collagen alpha-1(1) chain like proteins (YSL), pyruvate kinase PKM-like protein (YSL and first feeders), ubiquitin-40S ribosomal proteins S27 and eukaryotic translation initiation factor 4 A isoform 1B (first feeders). However irradiation of YSL and first feeders (post hatching early life stages) also induced proteomic changes which have a complex relationship with tumorigenesis or cancer progression; downregulation of alpha-1-antiprotease-like protein precursor, vigilin isoform X2 and nucleoside diphosphate kinase (YSL) and upregulation of hyperosmotic glycine rich protein (first feeders). In bystander fish some proteomic changes were similar to those induced by irradiation: upregulation of haemoglobin subunit beta (48 h egg), haemoglobin (eyed eggs), actin-related protein 2/3 complex subunit 4, hyperosmotic glycine rich protein (first feeders), and downregulation of alpha-1-antiprotease-like protein, vigilin isoform X2, nucleoside diphosphate kinase (YSL), pyruvate kinase PKM-like protein and ubiquitin-40S ribosomal protein S27a-like (first feeders). Other proteomic changes were unique to bystander fish; downregulation of TPI, ubiquitin-40S ribosomal protein S2 (eyed egg), cofilin-2, cold-inducible RNA-binding protein B-like isoform X3 (YSL) and superoxide dismutase (first feeder), and upregulation of haemoglobin subunit alpha, collagen 1a1 precursor, apolipoprotein A-1-1 and A-1–2 precursor (first feeders). These bystander effect proteomic changes have been shown to be overwhelmingly anti-tumorigenic or protective of the fish gill.

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTAN↗
DOE OSTI2018

Diphenyl diselenide regulates Nrf2/Keap-1 signaling pathway and counteracts hepatic oxidative stress induced by bisphenol A in male mice

Highlights: • BPA exposure induced hepatic oxidative stress in a sex-dependent manner in mice. • BPA exposure deregulates Nrf2/keap1 pathway in the mouse liver. • (PhSe){sub 2} reversed hepatic oxidative stress caused by BPA in male mice. • (PhSe){sub 2} modulates NrF2/keap1 pathway in male mice exposed to BPA. Bisphenol A (BPA) is a chemical toxicant that has deleterious effects on human. BPA causes oxidative stress in tissues, including the liver. Diphenyl diselenide (PhSe){sub 2} improves the antioxidant response via activation of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/Kelch-like ECH-associated protein (keap 1) pathway in macrophage cells. In the present study, we investigated whether (PhSe){sub 2} counteracts hepatic oxidative stress induced by BPA in male and female Swiss mice. Three-week-old mice received by the intragastric (i.g.) route BPA (5 mg/kg) from 21st to 60th postnatal day (PND). At PND 61, the mice were treated with (PhSe){sub 2} (1 mg/kg, i.g.) for seven days. Parameters of hepatic damage and oxidative stress were determined in male and female mice. The results show that BPA increased the activity of aspartate aminotransferase in female mice, and in male mice the activity of alanine aminotranseferase was increased. Male and female mice had an increase in fat mass accumulation. Male mice showed an increase in hepatic oxidative damage of proteins and a decrease in non-enzymatic (ascorbic acid and non-protein thiol) and enzymatic (superoxide dismutase) defenses, which are consistent with oxidative stress status. Male mice were more susceptible than female mice to hepatic oxidative stress induced by BPA. BPA decreased Nrf2/Keap1 protein content in male mice. (PhSe){sub 2} reduced hepatic oxidative stress induced by BPA in male mice. Our results demonstrate that male mice were more susceptible to hepatic oxidative stress induced by BPA than female mice. (PhSe){sub 2} regulated Nrf2/Keap-1 signaling pathway and countered hepatic oxidative stress induced by BPA in male mice.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2012

Apolipoprotein E Genotype-Dependent Paradoxical Short-Term Effects of {sup 56}Fe Irradiation on the Brain

Purpose: In humans, apolipoprotein E (apoE) is encoded by three major alleles ({epsilon}2, {epsilon}3, and {epsilon}4) and, compared to apoE3, apoE4 increases the risk of developing Alzheimer disease and cognitive impairments following various environmental challenges. Exposure to irradiation, including that of {sup 56}Fe, during space missions poses a significant risk to the central nervous system, and apoE isoform might modulate this risk. Methods and Materials: We investigated whether apoE isoform modulates hippocampus-dependent cognitive performance starting 2 weeks after {sup 56}Fe irradiation. Changes in reactive oxygen species (ROS) can affect cognition and are induced by irradiation. Therefore, after cognitive testing, we assessed hippocampal ROS levels in ex vivo brain slices, using the ROS-sensitive fluorescent probe, dihydroethidium (DHE). Brain levels of 3-nitrotyrosine (3-NT), CuZn superoxide dismutase (CuZnSOD), extracellular SOD, and apoE were assessed using Western blotting analysis. Results: In the water maze, spatial memory retention was impaired by irradiation in apoE2 and apoE4 mice but enhanced by irradiation in apoE3 mice. Irradiation reduced DHE-oxidation levels in the enclosed blade of the dentate gyrus and levels of 3-NT and CuZnSOD in apoE2 but not apoE3 or apoE4 mice. Finally, irradiation increased apoE levels in apoE3 but not apoE2 or apoE4 mice. Conclusions: The short-term effects of {sup 56}Fe irradiation on hippocampal ROS levels and hippocampus-dependent spatial memory retention are apoE isoform-dependent.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Selenoprotein P Inhibits Radiation-Induced Late Reactive Oxygen Species Accumulation and Normal Cell Injury

Purpose: Radiation is a common mode of cancer therapy whose outcome is often limited because of normal tissue toxicity. We have shown previously that the accumulation of radiation-induced late reactive oxygen species (ROS) precedes cell death, suggesting that metabolic oxidative stress could regulate cellular radiation response. The purpose of this study was to investigate whether selenoprotein P (SEPP1), a major supplier of selenium to tissues and an antioxidant, regulates late ROS accumulation and toxicity in irradiated normal human fibroblasts (NHFs). Methods and Materials: Flow cytometry analysis of cell viability, cell cycle phase distribution, and dihydroethidium oxidation, along with clonogenic assays, were used to measure oxidative stress and toxicity. Human antioxidant mechanisms array and quantitative real-time polymerase chain reaction assays were used to measure gene expression during late ROS accumulation in irradiated NHFs. Sodium selenite addition and SEPP1 overexpression were used to determine the causality of SEPP1 regulating late ROS accumulation and toxicity in irradiated NHFs. Results: Irradiated NHFs showed late ROS accumulation (4.5-fold increase from control; P<.05) that occurs after activation of the cell cycle checkpoint pathways and precedes cell death. The mRNA levels of CuZn- and Mn-superoxide dismutase, catalase, peroxiredoxin 3, and thioredoxin reductase 1 increased approximately 2- to 3-fold, whereas mRNA levels of cold shock domain containing E1 and SEPP1 increased more than 6-fold (P<.05). The addition of sodium selenite before the radiation treatment suppressed toxicity (45%; P<.05). SEPP1 overexpression suppressed radiation-induced late ROS accumulation (35%; P<.05) and protected NHFs from radiation-induced toxicity (58%; P<.05). Conclusion: SEPP1 mitigates radiation-induced late ROS accumulation and normal cell injury.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2011

Reaction Mechanisms for the Limited Reversibility of Li-O2 Chemistry in Organic Carbonate Electrolytes

The Li-O2 chemistry in nonaqueous carbonate electrolytes and the underneath reason of its limited reversibility was exhaustively investigated. The discharge products collected from the air cathode in a Li-O2 battery at different depth of discharge (DOD) were systematically analyzed with X-ray diffraction. It is revealed that, independent of the discharge depth, lithium alkylcarbonate (either lithium propylenedicarbonate - LPDC, or lithium ethylenedicarbonate - LEDC, with other related derivatives) and lithium carbonate (Li2CO3) are always the main products, obviously originated from the electrolyte solvents propylene carbonate (PC) and ethylene carbonate (EC). These lithium alkylcarbonates are obviously generated from the single-electron reductive decomposition of the corresponding carbonate solvents initiated by the attack of superoxide radical anions. On the other hand, neither lithium peroxide (Li2O2) nor lithium oxide (Li2O) is detected. More significantly, from in situ gas chromatography/mass spectroscopy it is found that Li2CO3 and Li2O cannot be oxidized even when charged up to 4.6 V vs. Li/Li+, while LPDC, LEDC and Li2O2 are readily able to, with CO2 and CO released with the re-oxidation of LPDC and LEDC. It is therefore concluded that the quasi-reversibility of Li-O2 chemistry observed hitherto in an organic carbonate-based electrolyte is actually reliant on the formation of lithium alkylcarbonates through the reductive decomposition of carbonate solvents during discharge process and the subsequent oxidation of these same alkylcarbonates during charge process. It is the poor oxidizability of these alkylcarbonate species that constitutes the obstruction to an ideal rechargeable Li-O2 battery.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Fabrication and characterization of flower-like BiOI/Pt heterostructure with enhanced photocatalytic activity under visible light irradiation

Flower-like Pt/BiOI composite nanosheets were successfully constructed by a photo-reduction method. The nanosized Pt/BiOI composites exhibited considerably enhanced photocatalytic performance for rhodamine B (RhB) and phenol degradation under visible-light irradiation (λ > 420 nm) when compared with that of pure BiOI. Various characterization methods were used to evaluate the mechanism of enhanced photocatalytic activity. The highest photocatalytic activity was achieved when the composites had a Pt content of 3 wt%, which is 17.8 times and 9 times higher than that of pure BiOI, respectively. The enhanced catalytic efficiency was attributed to the low rate of recombination of electron-hole pairs. Superoxide radicals and holes were found to be crucial species during the photocatalytic degradation. A possible mechanism of photocatalysis was also proposed based on the results of experiments. - Highlights: • Flower-like BiOI/Pt heterostructure are synthesized by a two step method. • The photocatalytic performance of as prepared samples are carried out under visible light irradiation. • The mechanism for the catalyst activity is discussed in detail.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Fabrication of a magnetic nanocomposite photocatalysts Fe{sub 3}O{sub 4}@ZIF-67 for degradation of dyes in water under visible light irradiation

As organic dyes are a major group of water pollutants, the development of materials for the removal of dyes is of great significance for the environment. Here, a novel flower-like Fe{sub 3}O{sub 4}@ZIF-67 photocatalyst was synthesized using a simple method at room temperature. It was found that the Fe{sub 3}O{sub 4}@ZIF-67 exhibited the ability of degrading Congo red (CR) quickly under visible light irradiation in a short time after adsorption equilibrium. Free radical trapping experiments revealed that the photo-induced active species superoxide radical (• O{sup 2−}) and holes (h{sup +}) were the predominant active species in the photocatalytic system. In addition, results demonstrated that the Fe{sub 3}O{sub 4}@ZIF-67 can be magnetically recycled, and maintain high photocatalytic activity after reuse over five cycles with no obvious decrease in the removal efficiency. It suggested that the synthesized material had a potentially promising application for CR removal from waste water. - Graphical abstract: A flower-like structure of ZIF-67 loaded with Fe{sub 3}O{sub 4} was synthesized by a facile method. It showed high photocatalysis activity that can degradate congo red (CR) completely in a short time. Display Omitted - Highlights: • A flower-like structure of ZIF-67 was synthesized. • It presents high photocatalytic activity to CR. • The product could be collected conveniently by magnets.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Enhanced photodegradation activity of methyl orange over Ag{sub 2}CrO{sub 4}/SnS{sub 2} composites under visible light irradiation

Highlights: • Novel visible-light-driven Ag{sub 2}CrO{sub 4}/SnS{sub 2} composites are synthesized. • Ag{sub 2}CrO{sub 4}/SnS{sub 2} exhibits higher photocatalytic activity than pure Ag{sub 2}CrO{sub 4} and SnS{sub 2}. • Ag{sub 2}CrO{sub 4}/SnS{sub 2} exhibits excellent stability for the photodegradation of MO. • The possible photocatalytic mechanism was discussed in detail. - Abstract: Novel Ag{sub 2}CrO{sub 4}/SnS{sub 2} composites were prepared by a simple chemical precipitation method and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. The visible light photocatalytic tests showed that the Ag{sub 2}CrO{sub 4}/SnS{sub 2} composites enhanced photocatalytic activities for the photodegradation of methyl orange (MO) under visible light irradiation (λ > 420 nm), and the optimum rate constant of Ag{sub 2}CrO{sub 4}/SnS{sub 2} at a weight content of 1.0% Ag{sub 2}CrO{sub 4} for the degradation of MO was 2.2 and 1.5 times larger than that of pure Ag{sub 2}CrO{sub 4} and SnS{sub 2}, respectively. The improved activity could be attributed to high separation efficiency of photogenerated electrons-hole pairs on the interface of Ag{sub 2}CrO{sub 4} and SnS{sub 2}, which arised from the synergistic effect between Ag{sub 2}CrO{sub 4} and SnS{sub 2}. Moreover, the possible photocatalytic mechanism with superoxide radical anions and holes species as the main reactive species in photocatalysis process was proposed on the basis of experimental results.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Facile fabrication of micro-floriated AgBr/Bi{sub 2}O{sub 3} as highly efficient visible-light photocatalyst

Highlights: • We successfully fabricate micro-floriated AgBr/Bi{sub 2}O{sub 3} composites by one simple hydrothermal react with precusor BiOBr. This micro-floriated Bi{sub 2}O{sub 3} heterojunction composite is rarely reported by others. • Heterojunction AgBr/Bi{sub 2}O{sub 3} composite exhibits highly efficient photocatalytic activity to decompose pollutant. • The enhanced photocatalytic activity was attributed to the improved visible light harvesting ability and higher separation efficiency of photogenerated electron–hole pairs by the introduction of AgBr. • This composite is beneficial to industrial applications to eliminate the organic pollutants from waste water. - Abstract: Semiconductor with photocatalytic property is the potential solution to solve the problem about water pollution. Novel floriated AgBr/Bi{sub 2}O{sub 3} fabricated through a facile simple two-step hydrothermal method is an efficient photocatalyst. The eminent performance for degradation of methyl orange (MO) was evaluated under visible light irradiation. Many characterization methods, including XPS, XRD, FT-IR, SEM, TEM and UV–vis diffuse reflection spectroscopy, were used to investigate the structure, elemental composition, morphology and catalytic activity. Broad contact between AgBr and Bi{sub 2}O{sub 3} interface enabled hybrid materials possess superior efficiency for the decomposition of MO under visible light irradiation. The optimum photocatalytic activity of samples was approximately 11.7 times higher than pure Bi{sub 2}O{sub 3}. In addition, the photo-generated reactive species were identified based on free radicals trapping experiments, which revealed that superoxide radical is the key factor to the photocatalytic process.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Visible-light-driven ZnFe{sub 2}O{sub 4}/Ag/Ag{sub 3}VO{sub 4} photocatalysts with enhanced photocatalytic activity under visible light irradiation

Highlights: • The ZnFe2O4/Ag/Ag3VO4 composites were successfully synthesized by a hydrothermal method. • ZnFe2O4/Ag/Ag3VO4 composites showed better photocatalytic activity for MO and TC degradation under visible light. • The ZnFe2O4/Ag/Ag3VO4 photocatalyst is promising for designing an environmental purification material. - Abstract: A novel visible-light driven ZnFe{sub 2}O{sub 4}/Ag/Ag{sub 3}VO{sub 4} photocatalyst was successfully fabricated through a two-step hydrothermal method. The structure, morphology and composition of the samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photo-electron spectroscopy (XPS). The as-prepared ZnFe{sub 2}O{sub 4}/Ag/Ag{sub 3}VO{sub 4} composites possessed an excellent performance in the photocatalytic degradation of methyl orange and tetracycline under visible-light irradiation. The results of electrochemical impedance spectroscopy (EIS) indicated that the ZnFe{sub 2}O{sub 4}/Ag/Ag{sub 3}VO{sub 4} composite could facilitate the separation of photo-generated carriers, as well as accelerated charge transfer. The 5% ZnFe{sub 2}O{sub 4}/Ag/Ag{sub 3}VO{sub 4} composite exhibited the upmost photocatalytic activity, the degradation constant of 5% ZnFe{sub 2}O{sub 4}/Ag/Ag{sub 3}VO{sub 4} is as high as 1.49 times to that of Ag/Ag{sub 3}VO{sub 4}. Also, according to the trapping experiments, it’s found that the superoxide radicals (·O{sub 2}{sup −}) and hole (h{sup +}) were the predominant reactive species in this system. The ZnFe{sub 2}O{sub 4}/Ag/Ag{sub 3}VO{sub 4} photocatalyst is promising for designing as an environmental purification material in treatment of antibiotic pollutant.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Enhanced photocatalytic degradation of phenol over Ag3PO4-BiOCl1−xBrx composites

Highlights: • Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} composites were successfully synthesized and characterized. • The band energy of composites can be tunable by solid-solution strategy. • Appropriate band-gap structure facilitates charge separation property and light absorption. - Abstract: In this paper, a series of Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} composites with adjustable band gap has been fabricated by using a facile two-step synthetic method. The photocatalytic activity of Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} was evaluated by photocatalytic decomposition of phenol aqueous solution under simulated solar light irradiation. The result shows that Ag{sub 3}PO{sub 4}-BiOCl{sub 0.75}Br{sub 0.25} (1:5) composite possesses the best photocatalytic activity among all the as-prepared samples. The photocatalytic activity of Ag{sub 3}PO{sub 4}-BiOCl can be enhanced mainly owing to the strong light absorption ability by loading Ag{sub 3}PO{sub 4} on the surface of BiOCl, while the photocatalytic activities of Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} (x = 0.25, 0.5, 0.75 and 1) composites could be enhanced by restraining the recombination of photo-generated electron-hole pairs. The enhanced solar-light photocatalytic activities of Ag{sub 3}PO{sub 4}-BiOCl{sub 1−x}Br{sub x} composites could be ascribed to the adjustable energy band structure, which facilitates the separation of photoinduced carriers. In addition, superoxide radicals (O{sub 2}{sup −}), holes (h{sup +}) and OH are considered to dominate the photocatalytic degration process. Moreover, a possible mechanism of deep understanding on the base of experimental results was proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Boosting visible light photocatalytic performance of g-C3N4 nanosheets by combining with LaFeO3 nanoparticles

Highlights: • A Z-scheme LaFeO{sub 3}/g-C{sub 3}N{sub 4} hybrid was constructed by in-situ growth strategy. • LaFeO{sub 3}/g-C{sub 3}N{sub 4} exhibited greatly boosted visible light photocatalytic activity. • Holes and superoxide radicals were responsible for methyl orange degradation. • A reasonable Z-scheme was responsible for the augmented photocatalytic activity. - Abstract: A binary direct Z-scheme LaFeO{sub 3}/g-C{sub 3}N{sub 4} nanohybrid photocatalyst composed of LaFeO{sub 3} nanoparticles and g-C{sub 3}N{sub 4} nanosheets was facilely obtained by in-situ growth strategy and employed for the photocatalytic degradation of methyl orange (MO) in aqueous solution under visible light irradiation (λ > 420 nm). As expected, in comparison with pure g-C{sub 3}N{sub 4}, all of the LaFeO{sub 3}/g-C{sub 3}N{sub 4} hybrids exhibited the enhanced photocatalytic performance. Noticeably, the LaFeO{sub 3}(2.0 wt%)/g-C{sub 3}N{sub 4} composite illustrated the highest apparent photodegradation rate constant, which was nearly 17.4 and 4.1 times larger than those of pure LaFeO{sub 3} and g-C{sub 3}N{sub 4}, respectively. Such a greatly augmented catalytic activity was mainly ascribed to the efficient separation of the photogenerated charge carriers through a Z-scheme system composed of g-C{sub 3}N{sub 4} and LaFeO{sub 3}, leading to suppressing the photogenerated electrons and holes recombination in both g-C{sub 3}N{sub 4} and LaFeO{sub 3} and boosting the photocatalytic efficiency. Furthermore, a probable degradation mechanism was also proposed based on active species trapping experiments, photoluminescence spectroscopy and energy band structures.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

One-step reduction synthesis of Ag/Ag3PO4/AgBr sub-micron composites for enhanced visible photocatalytic degradation of methyl orange

Highlights: • Ag/Ag{sub 3}PO{sub 4}/AgBr photocatalysts were synthesized by a one-step reduction method. • The conditions affecting performances of the photocatalysts were optimized. • The main radicals responsible for degrading MO were investigated. • The Ag/Ag{sub 3}PO{sub 4}/AgBr photocatalyst presented excellent stability and recyclability. - Abstract: An efficient semiconductor composite, silver/silver orthophosphate/silver bromide, was successfully synthesized by a facile one-step reduction and ion exchange process. Its crystal structure, morphology, optical property, surface element composition were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible diffuse reflectance spectrometer and X-ray photoelectron spectrometer. The effects of composite proportion and synthesis duration on performances of as-prepared photocatalysts were investigated, and the results showed that Br/P molar ratio of 3 and the synthesis duration of 4 h were the optimum conditions. The radical scavenging experiments indicated that the hole and superoxide radical were the main active species in this reaction system. The Ag/Ag{sub 3}PO{sub 4}/AgBr-3 presented excellent stability and recyclability, maintaining 92% of degradation efficiency after 5 cycles. The good photocatalysis performance could be attributed to the formation of the heterojunction between Ag and Ag{sub 3}PO{sub 4}/AgBr.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Microwave-assistant hydrothermal synthesis of SnO2@ZnO hierarchical nanostructures enhanced photocatalytic performance under visible light irradiation

Highlights: • A photocatalyst of SnO{sub 2}@ZnO HNSs is prepared via a microwave-assistant hydrothermal method. • Enhanced photodegradation of methylene blue under the visible light irradiation has been observed. • The defect in photocatalyst is the main photocatalytic mechanism under the visible light irradiation. • The superoxide radical is the main photoactive species. - Abstract: In this paper, for the first time, SnO{sub 2}@ZnO hierarchical nanostructures (HNSs) were synthesized by a simple two-step microwave-assistant hydrothermal method. Systematical characterization of the SnO{sub 2}@ZnO HNSs revealed that the rutile SnO{sub 2} nanowires (NWs) were uniformly and tightly grown on the entire surface of each ZnO nanoflowers (NFs). The photocatalytic performance of the SnO{sub 2}@ZnO HNSs showed a remarkably enhanced photocatalytic performance under visible light irradiation (400 nm≤λ ≤ 800 nm). The photoluminescence (PL) spectrum results indicated that the defect related energy level is the main mechanism of the photocatalytic performance under the visible light irradiation. The unique morphology and heterojunction structures in SnO{sub 2}@ZnO HNSs were the core enhanced mechanism in photodegradation process. The advantage endowed with the microwave-assistant hydrothermal method can result in the efficient spatial charge separation between ZnO nanorods (NRs) and SnO{sub 2} NWs and reduce the charge recombination along the heterojunction, which makes SnO{sub 2}@ZnO HNSs a highly promising for photocatalytic applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Synthesis of Z-scheme g-C3N4/Ag/Ag3PO4 composite for enhanced photocatalytic degradation of phenol and selective oxidation of gaseous isopropanol

Highlights: • g-C3N4/Ag/Ag3PO4 composite was synthesized by a simple in situ deposition method. • Ag3PO4 nanoparticles exhibited regular rhombic dodecahedral morphology. • Photocatalyst of g-C3N4/Ag/Ag3PO4 worked under Z-scheme mechanism. • The composite showed enhanced photocatalytic activity for organics degradation. - Abstract: In this study, g-C{sub 3}N{sub 4}/Ag/Ag{sub 3}PO{sub 4} composites were constructed by a simple in situ deposition method at room temperature, in which Ag{sub 3}PO{sub 4} particles with regular rhombic dodecahedrons morphology were finely coated on the surface of the g-C{sub 3}N{sub 4} sheet. The g-C{sub 3}N{sub 4}/Ag/Ag{sub 3}PO{sub 4} exhibited much improved activity comparing with other classic catalysts such as g-C{sub 3}N{sub 4} and Ag{sub 3}PO{sub 4}. The optimal photocatalyst (AC{sub 1.0}) with Ag{sub 3}PO{sub 4}/g-C{sub 3}N{sub 4} ratio of 1 could dramatically decompose phenol under visible-light irradiation, which showed a degradation rate of 1.13 min{sup −1} and almost 60 and 2.5 times higher than that of pure g-C{sub 3}N{sub 4} and Ag/Ag{sub 3}PO{sub 4}, respectively. After 3 cycling run tests, the AC{sub 1.0} photocatalyst still maintained high photocatalytic activity. Electron paramagnetic resonance spectroscopy and radical quenching tests were employed to investigate hydroxyl and superoxide radicals for organic degradation processes. Furthermore, the photocatalytic activity of AC{sub 1.0} was also tested for gaseous isopropanol (IPA). After 4 h irradiation, 63% of IPA was oxidized with acetone as main outcome product. The highly efficient separation of photogenerated electron-hole pairs was attributed to the construction of Z-scheme mechanism.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗