A novel two-dimensional Janus TiSiGeN4 monolayer with N vacancies for efficient photocatalytic nitrogen reduction.

The photocatalytic nitrogen reduction reaction (pNRR) is a clean technology that converts H2O and N2 into NH3 under environmental conditions using inexhaustible sunlight. Herein, we designed a novel two-dimensional (2D) Janus TiSiGeN4 structure and evaluated the pNRR performance of the structure with the presence of nitrogen vacancies at different positions using density functional theory (DFT) calculations. The intrinsic dipoles in the Janus TiSiGeN4 structure generate a built-in electric field, which promotes the migration of photogenerated electrons and holes towards the (001) and (00-1) surfaces, respectively, to achieve efficient charge separation. For the pNRR, the Si atoms exposed after the formation of top N vacancies can realize the efficient activation of N2 through the "acceptance-donation" mechanism, while the presence of middle N vacancies not only suppresses the hydrogen evolution reaction, a competition reaction, but also lowers the reaction barrier for the protonation of N atoms. The limiting potential of TiSiGeN4 with the coexistence of both top and middle N vacancies (TiSiGeN4-VN-mt) is as low as -0.44 V. In addition, the introduction of N vacancies generates defect levels, narrowing the band gap and improving the light response. This work provides theoretical guidance for the design of efficient pNRR photocatalysts under mild conditions.

Mating behavior and responses to sublethal concentrations of imidacloprid in the predator Cyrtorhinus lividipennis.

BACKGROUND: Mating is an essential factor that governs the size of insect populations that reproduce sexually. The extensive application of insecticides has both lethal and sublethal effects on the physiology and mating behavior of insect natural enemies. The predatory bug Cyrtorhinus lividipennis is a natural enemy of planthopper and leafhopper populations in the rice ecosystem. Unfortunately, the effects of insecticides on the mating behavior of C. lividipennis are not well-understood. RESULTS: The mating behavior of C. livdipennis consisted of mounting, antennal touch and mating attempts, genital insertion, adjustment of posture, and separation of the mating pair. Approximately 82.5% of the C. lividipennis mating pairs displayed their first mating at 12-36 h postemergence. Mating activity occurred throughout a 24-h period, with peak activity at 12:00-14:00 h, and the mean duration of mating was 48.75 min. Sublethal exposure to imidacloprid increased mating latency. Compared with the controls, the duration of courtship, pre-mating and adjusting posture for males treated with imidacloprid were prolonged. The duration of mating for females treated with imidacloprid was prolonged relative to untreated controls. The fecundity and daily spawning capacity of females treated with imidacloprid were higher than the untreated controls. CONCLUSION: Our results provide insight into the mating process of C. lividipennis. Imidacloprid prolonged the duration of mating, which may explain the enhanced reproductive output in C. lividipennis females treated with imidacloprid. These findings will be useful in both rearing C. lividipennis and deploying this natural enemy in rice fields. © 2024 Society of Chemical Industry.

Forked Vein Structure W/WO3- x with Dual Active Sites in W and Oxygen Vacancies to Enhance Methylene Self-Coupling for Efficient Conversion of Methane to Ethylene.

The directional conversion of methane to ethylene is challenging due to the dissociation of the C─H bond and the self-coupling of methyl intermediates. Herein, a novel W/WO3- x catalyst with the fork vein structure consisting of an alternating arrangement of WO3- x and W is developed. Impressively, the catalyst achieves an unprecedented C2 H4 yield of 1822.73 µmol g-1  h-1 , with a selectivity of 82.49%. The enhanced catalytic activity is ascribed to the multifunctional synergistic effect induced by oxygen vacancies and W sites in W/WO3- x . Oxygen vacancies provide abundant coordination of unsaturation sites, which promotes the adsorption and activation of CH4 , thus reducing the dissociation energy barrier of the C─H bond. The CH2 coupling barrier on the metal W surface is significantly lower compared to WO3 , so CH2 can migrate to the W site for coupling. Importantly, the W/WO3- x with high periodicity provides multiple ordered local microelectric fields, and CH2 intermediates with dipole moments undergo orientation polarization and displacement polarization driven by the electric field, thus enabling CH2 migration. This work opens a new avenue for the structural design and modulation of photocatalysts, and provides new perspectives on the migration of methylene between multiple active sites.

Preparation of highly dispersed Ni single-atom doped ultrathin g-C3N4 nanosheets by metal vapor exfoliation for efficient photocatalytic CO2 reduction.

Single-atom photocatalysts can modulate the utilization of photons and facilitate the migration of photogenerated carriers. However, the preparation of single-atom uniformly doped photocatalysts is still a challenging topic. Herein, we propose the preparation of Ni single-atom doped g-C3N4 photocatalysts by metal vapor exfoliation. The Ni vapor produced by calcining nickel foam at high temperature accumulates in between g-C3N4 layers and poses a certain vapor pressure to destroy the interlayer van der Waals forces of g-C3N4. Individual metal atoms are doped into the structure while exfoliating g-C3N4 into nanosheets by metal vapor. Upon optimization of Ni content, the Ni single atom doped g-C3N4 nanosheets with 2.81 wt% Ni exhibits the highest CO2 reduction performance in the absence of sacrificial agents. The generation rates of CO and CH4 are 19.85 and 1.73 µmol g-1h-1, respectively. The improved photocatalytic performance is attributed to the anchoring Ni of single atoms on g-C3N4 nanosheets, which increases both carrier separation efficiency and reaction sites. This work provides insight into the design of photocatalysts with highly dispersed single-atom.

Covalent Bonding Enhanced Polypropylene Based T-ZIF-8 Masterbatch with Superior Photocatalytic and Antibacterial Performances.

In order to solve the problem of poor compatibility between modified-ZIF-8 nanoparticles and mask matrix polypropylene (PP) and melt-blown materials, in this work, PP based modified-ZIF-8 antibacterial masterbatch was prepared employing surface modification and torque blending method. IR, SEM, XRD, XPS, DSC results confirm that the antibacterial masterbatch maintains the chemical and crystal structure of modified-ZIF-8 and the thermal stability of PP. Photocatalytic performance indicates that the antibacterial masterbatch basically maintains the photoresponse range of modified-ZIF-8, has narrower band gap and the superior photocatalytic performance than that of modified-ZIF-8. The photocatalytic antibacterial mechanism of ·O2- and h+ as antibacterial active species is revealed according to the energy band structure and free radical capture experiment. The photocatalytic antibacterial activity of the antibacterial masterbatch against Staphylococcus aureus and Escherichia coli under different dosage holds that the relationship between antibacterial rate and antibacterial agent concentration conforms to Beta distribution, demonstrating second-order kinetic behavior. The antibacterial properties reach the maximum when the loading of modified-ZIF-8 is 2% of the total weight of PP and melt-blown materials. S. aureus and E. coli could be completely killed when the simulated sunlight is irradiated for 30 min. These results indicate that PP based modified-ZIF-8 antibacterial masterbatch has potential application in photocatalytic antibacterial masks.

A Dual-Wavelength Phosphorescent Anti-Counterfeiting Copolymer Containing Eu(III) and Tb(III).

The anti-counterfeiting technology of banknotes, bills and negotiable securities is constantly copied, and it is urgent to upgrade its anti-counterfeiting technology. In view of the defect of easy replication of single-wavelength anti-counterfeiting technology, the bonded copolymer PMEuTb was synthesized, employing the technique of first coordination and then polymerization. The molecular structure of copolymer PMEuTb was confirmed by infrared spectrum and UV-vis absorption spectrum. The internal mechanism of negative correlation between initiator concentration and number-average molecular weight Mn of the copolymer was revealed, and the positive correlation between Mn and luminescent behavior of the copolymer was analyzed. The luminescent properties of copolymer PMEuTb with initiator amount of 0.1% were investigated, the copolymer PMEuTb exhibits dual-wavelength emission of green light and red light under the excitation of ultraviolet light at 254 nm and 365 nm. The copolymer has the lifetime of 1.083 ms at 5D4-7F5 transition and 0.665 ms at 5D0-7F2 transition, which belongs to phosphorescent emitting materials. The copolymer remains stable at 240 °C, and variable temperature photoluminescent spectra demonstrate the luminescent intensity remains 85% at 333 K, meeting the requirements of room temperature phosphorescent anti-counterfeiting materials. The luminescent patterns made by standard screen printing display the green and cuticolor logo at 254 nm and 365 nm, respectively, indicating that the bonded phosphors PMEuTb has potential application in phosphorescent anti-counterfeiting.

Kinetics analysis of oxygen vacancies in TiO2 solar water reduction: Revealing effects and eliminating disadvantages.

A consensus is yet to be reached on the effects of oxygen vacancy (VO) on the performance of TiO2 for photocatalytic water splitting as contrasting viewpoints have been presented in the latest researches. Herein, a comprehensive set of spectroelectrochemical methods are deployed to clearly reveal the advantages and disadvantages of VO on the performance of TiO2. The results indicate that surface VO improves the photocatalytic activity while bulk VO has a negative effect on the water reduction performance of TiO2. Intensity-modulated photocurrent spectroscopy (IMPS) and UV-vis spectroscopy provide compelling evidence that the improvement of H2 evolution can be attributed to the presence of defect level, while the low interface charge transfer efficiency caused by surface VO limits the further improvement of photocatalytical H2 evolution, which can be alleviated by an organic hole transport coating. The density functional theory (DFT) and surface photovoltaic (SPV) analyses confirm that the built-in field between TiO2 and hole molecules is the reason for the interface charge transfer efficiency improvement. Our findings provide a comprehensive understanding of VO in TiO2 by carrier behavior analysis and a scheme to further promote the photocatalytic performance.

A 3D C@TiO2 multishell nanoframe for simultaneous photothermal catalytic hydrogen generation and organic pollutant degradation.

Rapid heat loss and fast charge carrier recombination constitute two crucial issues that hinder the development of efficient solar energy utilization and conversion over the semiconductor in a photothermal catalytic system. Inspired by energy production from waste water, we designed an advanced 3D C@TiO2 multishell nanoframe (MNF) photocatalyst. Its unique structural features of heat confinement and vibrant photocarrier kinetics lead to excellent photo-thermal conversion for synchronous superior photocatalytic H2 evolution (503 µmol g-1h-1) and 98.2% RhB removal without the use of any co-catalyst and sacrificial reagent under simulated sunlight irradiation (AM 1.5G). Mechanism exploration reveals that the difference between the inner and outer gas pressure formed inside C@TiO2 precursor facilitates the selective cleavage of outer TiO2 layers at selected temperatures during calcination. Synergistic effects between residual carbon core and multi-shelled TiO2 framework endow C@TiO2 MNF with excellent heat confinement and vibrant photocarrier kinetics. Such MNF photo-thermocatalyst concept provides a novel strategy for effective utilization of solar energy, and this work may open a novel avenue towards advanced nanostructures for efficient waste-to-energy conversion.

Self-Doping Surface Oxygen Vacancy-Induced Lattice Strains for Enhancing Visible Light-Driven Photocatalytic H2 Evolution over Black TiO2.

The synergistic effect of surface oxygen vacancy with induced lattice strains on visible light-driven photocatalytic H2 evolution over black TiO2 was investigated. Experimental measurements and theoretical calculations on the lattice parameters of black TiO2 show that surface oxygen vacancies induce internal lattice strain during two-step aluminothermic reduction, which regulates the band structure and optimizes the photoinduced charge behavior of black TiO2. The hydrogen evolution rate of black TiO2 with strain modification shows a 12-fold increase to 1.882 mmol/g· h (equal to 4.705 µmol/cm2·h) under visible light illumination. The metastable state caused by the surface oxygen vacancies leads to the formation of a high-energy surface, which enhances visible light absorption and improves the photoinduced charge separation efficiency. Furthermore, the internal lattice strain provides the driving force and channel for the directional movement of photoinduced electrons from the bulk to the high-energy surface for photocatalytic H2 evolution. This strategy provides a new method for designing a high-performance photocatalyst for H2 production.

Tunable white light emission of an anti-ultraviolet rare-earth polysiloxane phosphors based on near UV chips.

A novel white-light copolymer matched with 365 nm chips is prepared by bonding the vinyl-functionalized complexes Eu(TTA)2(Phen)(MAA), Tb(p-BBA)3(UA) and Zn(BTZ)(UA) to polysiloxaneprepolymer(synthesized by polycondensation of vinyltrimethoxysilane and diphenylsilanediol) through a technical route of polymerization after coordination. Its structure was characterized by infrared and ultraviolet. Under the excitation of 365 nm, when the ratio of the tricolor complexes is controlled to be 0.5: 3: 1.5, white light copolymer with CIE color coordinates of (0.327, 0.321) was obtained and packaged to get white light LED devices. After aging, the CIE color coordinates of the device change from (0.325, 0.329) to (0.341, 0.348), the color rendering index changes from 91 to 88, and the correlated color temperature changes from 5967 K to 5612 K. The loss of brightness is only 10.4%, which shows good resistance to UV aging. Moreover, the initial decomposition temperature of the copolymer is 235°C. The above results show that the bonding-type anti-ultraviolet copolymer phosphor has potential application in near ultraviolet LEDs.

Length-dependent corrosion behavior, Ni2+ release, cytocompatibility, and antibacterial ability of Ni-Ti-O nanopores anodically grown on biomedical NiTi alloy.

In the present work, nickel-titanium-oxygen nanopores with different length (0.55-114 µm) were anodically grown on nearly equiatomic nickel-titanium (NiTi) alloy. Length-dependent corrosion behavior, nickel ion (Ni2+) release, cytocompatibility, and antibacterial ability were investigated by electrochemical, analytical chemistry, and biological methods. The results show constructing nanoporous structure on the NiTi alloy improve its corrosion resistance. However, the anodized samples release more Ni2+ than that of the bare NiTi alloy, suggesting chemical dissolution of the nanopores rather than electrochemical corrosion governs the Ni2+ release. In addition, the Ni2+ release amount increases with nanopore length. The anodized samples show good cytocompatibility when the nanopore length is <11 µm. Encouragingly, the length scale covers the one (1-11 µm) that the nanopores showing favorable antibacterial ability. Consequently, the nanopores with length in the range of 1-11 µm are promising as coatings of biomedical NiTi alloy for anti-infection, drug delivery, and other desirable applications.

Type 1 Metallothionein (ZjMT) Is Responsible for Heavy Metal Tolerance in Ziziphus jujuba.

Metallothioneins (MTs) are a family of low molecular weight, cysteine-rich, metal-binding proteins that are able to make cells to uptake heavy metals from the environment. Molecular and functional characterization of this gene family improves understanding of the mechanisms underlying heavy metal tolerance in higher organisms. In this study, a cDNA clone, encoding 74-a.a. metallothionein type 1 protein (ZjMT), was isolated from the cDNA library of Ziziphus jujuba. At the N- and C-terminals of the deduced amino acid sequence of ZjMT, six cysteine residues were arranged in a CXCXXXCXCXXXCXC and CXCXXXCXCXXCXC structure, respectively, indicating that ZjMT is a type 1 MT. Quantitative PCR analysis of plants subjected to cadmium stress showed enhanced expression of ZjMT gene in Z. jujuba within 24 h upon Cd exposure. Escherichia coli cells expressing ZjMT exhibited enhanced metal tolerance and higher accumulation of metal ions compared with control cells. The results indicate that ZjMT contributes to the detoxification of metal ions and provides marked tolerance against metal stresses. Therefore, ZjMT may be a potential candidate for tolerance enhancement in vulnerable plants to heavy metal stress and E. coli cells containing the ZjMT gene may be applied to adsorb heavy metals in polluted wastewater.

First principle study of cysteine molecule on intrinsic and Au-doped graphene surface as a chemosensor device.

To search for a high sensitivity sensor for cysteine, we investigated the adsorption of cysteine on intrinsic and Au-doped graphene sheets using density functional theory calculations. Binding energy is primarily determined by the type of atom which is closer to the adsorbed sheet. Compared with intrinsic graphene, Au-doped graphene system has higher binding energy value and shorter connecting distance, in which strong Au-S, Au-N and Au-O chemical bond interaction play the key role for stability. Furthermore, the density of states results show orbital hybridization between cysteine and Au-doped graphene sheet, but slight hybridization between the cysteine molecule and intrinsic graphene sheet. Large charge transfers exist in Au-doped graphene-cysteine system. The results of DOS and charge transfer calculations suppose that the electronic properties of graphene can be tuned by the adsorption site of cysteine. Therefore, graphene and Au-doped graphene system both possess sensing ability, except that Au-doped graphene is a better sensor for cysteine than intrinsic graphene.

[Characterization and photoluminescence properties of an azomethin-zinc complex].

A Schiff base organic metal complex, Bis(salicylidene)-1,2-phenylenediam-ine Zinc(II) with high purity, was synthesized and purified by vacuum sublimation. Its structure, thermal stability and energy band structure were investigated by element analysis, FTIR spectra, TG-DTA curve, UV-Vis absorption spectra, fluorescece emission spectra and PL spectra. Experimental results showed that the complex is a thermally stable, polycrystalline material, with glass temperature and decomposition temperature being 183 and 449 degrees C, respectively. In its infrared spectrum, a high intensity band was at about 1 385 cm(-1). This band was typical of the conjugated C=N stretching vibration, which shifted to higher frequency in relation to the free ligand of salicylaldehyde with 1,2-phenylenediamine. The new bnd at 529 cm(-1) was assigned to Zn-O stretching vibration. Its UV absorption bands were at about 297 and 406 nm, and its tetrahydrofuran solution emitted intensive blue-green fluorescence at the peak wavelength of 508 nm. The absorption band at about 406 nm can be assigned to the intrinsic absorption of C=N. Its optical gap was about 2.62 eV, which was determined by the intrinsic absorption band edge of the complex in tetrahydrofuran solution. Under UV excitation at 365 nm, the complex in film emitted yellow-green fluorescence with the maximum emission peak at 562 nm and a full-width at half-maximum of 48.5 nm in PL spectra. Finally, yellow organic light-emitting devices using this complex as the emissive layer were fabricated and investigated.

The structures and antibacterial properties of nano-SiO2 supported silver/zinc-silver materials.

OBJECTIVES: The aims of this study were to investigate the structures and antibacterial properties of two kinds of sterilizing nano-SiO(2) specimens. METHODS: The specimens were synthesized by adsorption methodology. One of them was synthesized by adsorbing silver cation onto nano-SiO(2) carrier (silver-loading nano-SiO(2) specimen (SLS)), and the other one by co-adsorbing zinc and silver cations onto the same kind of carrier (zinc-silver-loading nano-SiO(2) specimen (SLZS)). Chemical compositions of these specimens were estimated. The structure and morphology of the specimens were determined by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Also, the antibacterial properties of the specimens were examined. RESULTS: The amount of silver loaded in SLZS was approximate to that of SLS. Consequently, it can be proved that the amount of nano-SiO(2) adsorbed silver cation did not change with the addition of zinc cation. The obvious differences were not observed among the XRD patterns for each specimen. So it was possible to confirm no formation of new phase(s) after Ag(+)/Zn(2+) absorption. The loaded silver and zinc existed as nano-particles, as observed by HRTEM. Antibacterial properties of SLS and SLZS were excellent against Escherichia coli and S. faecalis. The antibacterial effect of the same antibacterial agent against E. coli or S. faecalis was different. In addition, the antibacterial effect of SLZS was better than that of SLS. SIGNIFICANCE: These results suggested SLS and SLZS can be effectively incorporated in dental resin-based materials to provide antibacterial activity against bacteria.