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In this work, the mechanisms for creating a combined electronic–radiative local state beneath the conduction band, consisting of intrinsic and activator electron–hole states, are experimentally substantiated. In the first part of this work, the mechanisms of the formation of intrinsic and activator electron–hole trapping centers are experimentally demonstrated in all four matrices with activators. Intrinsic electronic states are localized on activators and anions of the matrix, forming intrinsic and activator electronic states. The hole component of the electron–hole pairs is localized near the activators. Thus, the energy of intrinsic electronic excitations localized in the matrix in the form of combined electronic–radiative states is observed at 3.06–3.1 eV and 2.92–2.95 eV. Radiative states are excited by photon energies of ~4.5 eV and ~4.0 eV, resulting in recombination emissions at 3.06–3.1 eV and 2.92–2.95 eV, as well as activator emissions at 2.06 eV for M n 2 + , 2.5 eV for T b 3 + , and 2.56 eV and 2.16 eV for D y 3 + . Energy transfer from the matrix to emitters or activators occurs during the decay of the combined radiative state. Upon heating, electrons localized on anions and activators delocalize at temperatures of 200–350 K. The energy released during the recombination of an electron with a hole near the activators is transferred to the activators. This process facilitates energy transfer to activators in dosimeters and detectors. [ABSTRACT FROM AUTHOR]

Abstract Hydrochar from waste biomass is a promising material for removing emerging contaminants (e.g., antibiotics) in water/soil environment. Abundant small-sized hydrochar particles (HPs) with a high content of reactive functional groups and high mobility are easily released into ecosystems through hydrochar applications. However, the photodegradation ability and corresponding structures of HPs are largely unknown, which hinder accurate estimation of the remediation effect of hydrochar in ecosystems. Herein, photodegradation performance of HP towards targeted norfloxacin (NOR, a typical antibiotic) under light irradiation (visible and UV light) were investigated after adsorption processes upon release into soil/water, and its reactive species and photoactive structures were clarified and compared with those of residual bulk hydrochar (BH) comprehensively. The results showed that: (1) photodegradation percentages of HPs were 4.02 and 4.48 times higher than those of BHs under UV and visible light, in which reactive species of both HPs and BHs were ·OH and ·O2 −; (2) density functional theory (DFT) results identified that the main photoactive structure of graphitic-N decreased the energy gap (Eg) of HPs, and C=O, COOH groups improved electron donating ability of BHs; (3) well-developed graphitization structure of HP resulted from higher polymerization reaction was an significant photoactive structure involving its superior photodegradation ability relative to that of BH. The distinct heterogeneities of photodegradation ability in HP and BH and underlying photoactive structures provide an in-depth understanding of hydrochar application for removing emerging contaminants in soil/water environment. Identifying photoactive structures is helpful to predict photodegradation ability of hydrochar according to their abundance. Graphical Abstract

Hydrochar from waste biomass is a promising material for removing emerging contaminants (e.g., antibiotics) in water/soil environment. Abundant small-sized hydrochar particles (HPs) with a high content of reactive functional groups and high mobility are easily released into ecosystems through hydrochar applications. However, the photodegradation ability and corresponding structures of HPs are largely unknown, which hinder accurate estimation of the remediation effect of hydrochar in ecosystems. Herein, photodegradation performance of HP towards targeted norfloxacin (NOR, a typical antibiotic) under light irradiation (visible and UV light) were investigated after adsorption processes upon release into soil/water, and its reactive species and photoactive structures were clarified and compared with those of residual bulk hydrochar (BH) comprehensively. The results showed that: (1) photodegradation percentages of HPs were 4.02 and 4.48 times higher than those of BHs under UV and visible light, in which reactive species of both HPs and BHs were ·OH and ·O2−; (2) density functional theory (DFT) results identified that the main photoactive structure of graphitic-N decreased the energy gap (Eg) of HPs, and C=O, COOH groups improved electron donating ability of BHs; (3) well-developed graphitization structure of HP resulted from higher polymerization reaction was an significant photoactive structure involving its superior photodegradation ability relative to that of BH. The distinct heterogeneities of photodegradation ability in HP and BH and underlying photoactive structures provide an in-depth understanding of hydrochar application for removing emerging contaminants in soil/water environment. Identifying photoactive structures is helpful to predict photodegradation ability of hydrochar according to their abundance. Highlights: Photodegradation percentage of HP from hydrochar application was ~4 times superior to that of BH in degradation of NOR. Major reactive species of HPs and BHs (·OH and ·O2−) were generated from graphitic-N and C=O/COOH groups, respectively. Photoactivity of HPs superior to BHs was mainly generated from well-developed graphitization structure of former. [ABSTRACT FROM AUTHOR]

In this work, the mechanisms for creating a combined electronic–radiative local state beneath the conduction band, consisting of intrinsic and activator electron–hole states, are experimentally substantiated. In the first part of this work, the mechanisms of the formation of intrinsic and activator electron–hole trapping centers are experimentally demonstrated in all four matrices with activators. Intrinsic electronic states are localized on activators and anions of the matrix, forming intrinsic and activator electronic states. The hole component of the electron–hole pairs is localized near the activators. Thus, the energy of intrinsic electronic excitations localized in the matrix in the form of combined electronic–radiative states is observed at 3.06–3.1 eV and 2.92–2.95 eV. Radiative states are excited by photon energies of ~4.5 eV and ~4.0 eV, resulting in recombination emissions at 3.06–3.1 eV and 2.92–2.95 eV, as well as activator emissions at 2.06 eV for Mn2+, 2.5 eV for Tb3+, and 2.56 eV and 2.16 eV for Dy3+. Energy transfer from the matrix to emitters or activators occurs during the decay of the combined radiative state. Upon heating, electrons localized on anions and activators delocalize at temperatures of 200–350 K. The energy released during the recombination of an electron with a hole near the activators is transferred to the activators. This process facilitates energy transfer to activators in dosimeters and detectors.

Piperazin-1-ium 4-aminobenzoate monohydrate (PPAB) single crystals were grown by slow evaporation method. The grown crystal PPAB has been characterized by single-crystal X-ray diffraction, FTIR, FT-Raman, and UV-visible analysis. The B3LYP method and 6-311G (d, p) basis set were used to optimize the structure. The title compound was investigated theoretically and experimentally by FT-IR, FT-Raman, and UV-Vis spectral analysis. The presence of various functional groups in the structure was elucidated by FTIR and FT-Raman spectral studies. The intermolecular interactions within the crystal structure were investigated using Hirshfeld surface analysis. The crystal packing diagram reveals interesting non-covalent interactions involving C–H···O, N–H···O, and N–H···N hydrogen bonds, leading to the generation of 3D supramolecular architecture. The charge transfer within the molecule was deeply analyzed by using the NBO approach. The molecular electrostatic potential (MEP) and the local reactivity descriptors, such as Fukui function (fk+, fk−) analyses were performed to determine the reactive sites within the molecule. The HOMO and LUMO analysis was used to determine the chemical reactivity and bioactivity of the molecule. Hole-electron analysis was performed to analyze the charge transfer in an excited state. Based on the hole-electron analysis, the inter-fragment charge transfer (IFCT) analysis establishes the amount of charge transfer among different fragments. Topological analyses, such as AIM, RDG, and ELF were carried out to identify the non-covalent interaction within the molecule. The molecular docking studies of the molecule are performed to investigate the binding affinity of the ligand with the protein receptor. Drug-likeness properties, such as Lipinski's rule of five, adsorption, distribution, metabolism, excretion, and toxicity (ADMET) have been investigated by in silico web-based tools like SwissADME and ADMETlab. [ABSTRACT FROM AUTHOR]

The construction of heterojunction is considered to be an effective strategy for achieving efficient photocatalyst. The pure CdS shows low hydrogen production activity, for the low charges separation efficiency and the short electron and hole lifetime, which greatly limit its practical application. Therefore, we constructed heterojunction photocatalysts of NiMoO4/CdS by a simple solvothermal method. The photocatalytic hydrogen production activity of CdS was obviously improved by NiMoO4 loaded. The NiMoO4/CdS‐2 sample shows the highest H2 generation rate, which could reach 5830.49 μmolg−1 h−1, which is 122.3 times higher than that of pure CdS. The construction of heterojunction between CdS and NiMoO4 inhibits the recombination of photogenerated charges, prolongs the lifetime of photogenerated charges and improves photocatalytic hydrogen production performance. This work is important for the construction of an efficient catalytic system for the photocatalytic H2 evolution from water splitting. [ABSTRACT FROM AUTHOR]

BeO ceramics in the wurtzite (w -BeO) form either pure or doped with lanthanide ions present high Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) sensitivity. However, the mechanism of defect formation governing the charge carrier dynamics associated with the TL and OSL signals is not well understood yet. Thus, this work aims to develop a study on the structural, mechanical, dielectric, and defect properties of Europium ion–doped w -BeO ceramics. We develop a new set of potential parameters to describe the Be–O bond. By using these potential parameters, we describe the physical and chemical properties with good agreement. Defect calculations employing the Mott and Littleton two-region strategy show that the distorted structure of pure w -BeO ceramics favours the Frenkel–type defect formation in the basal plane of the crystal lattice. When doped with Eu3+, we observed a change in the defect arrangement. It replaces preferentially two Be sites, eliminating beryllium interstices and keeping the beryllium vacancy from the initial configuration. We also observed that it is unlikely the Eu3+/Eu2+ coexist due to the solution energy values. Lastly, we have observed a most significant electron–hole interaction which may be associated with the intrinsic luminescence band of the w -BeO ceramics. In addition, TL and OSL measurements are presented to corroborate the defect calculations. The results presented here bring new insight to elucidate the charge carrier dynamic associated with the luminescent properties. [ABSTRACT FROM AUTHOR]

A theoretical evaluation of radical scavenging activity and UV absorbing ability of chalcone named 2ʹ, 5ʹ, 3, 4-Tetrahydroxychalcone has been performed in the gas phase and aqueous media. The DFT-B3LYP/6–311+G (d, p) level of theory was utilized for geometry optimization and the calculation of reaction enthalpies, while the CAM-B3LYP/6–311+G (d, p) level of theory was employed for TDDFT analysis. Three potential working mechanisms of radical scavenging activity, hydrogen atom transfer mechanisms (HAT), stepwise electron transfer proton transfer (SET-PT), and sequential proton loss electron transfer mechanisms (SPLET) were investigated within the gas phase and aqueous phase. The results obtained demonstrate that the HAT will be the probable mechanism in the gas phase whereas SPLET will be in the water medium. Using the same level of theory, explicit surface analysis of the title compound was performed. The compound wave function analysis and molecular docking investigations were also performed in the optimized structure. The theoretical UV spectra were recorded in both the solvents and the compound's electronic absorption spectrum was analyzed using the TD-DFT method. The distribution of hole and electrons in the peaks of maximal oscillator strength corresponds to local excitation within the molecule. The Quantum Theory of Atoms in Molecule (QTAIM) was used to compute the strength of intramolecular hydrogen bonds and non-covalent interactions. The global reactivity parameters and electrostatic potential (ESP) were also included to define the reactivity of the whole molecule. The spin density distribution analysis was come upon to be complementary to the radical scavenging activity. Besides the radical scavenging activity of the compound, it can also be used as a potential UVA filter.

Superfluidity has been predicted and now observed in a number of different electron-hole double-layer semiconductor heterostructures. In some of the heterostructures, such as GaAs and Ge-Si electron-hole double quantum wells, there is a strong mismatch between the electron and hole effective masses. We systematically investigate the sensitivity to unequal masses of the superfluid properties and the self-consistent screening of the electron-hole pairing interaction. We find that the superfluid properties are insensitive to mass imbalance in the low density BEC regime of strongly-coupled boson-like electron-hole pairs. At higher densities, in the BEC-BCS crossover regime of fermionic pairs, we find that mass imbalance between electrons and holes weakens the superfluidity and expands the density range for the BEC-BCS crossover regime. This permits screening to kill the superfluid at a lower density than for equal masses. [ABSTRACT FROM AUTHOR]

Superfluidity has been predicted and now observed in a number of different electron-hole double-layer semiconductor heterostructures. In some of the heterostructures, such as GaAs and Ge-Si electron-hole double quantum wells, there is a strong mismatch between the electron and hole effective masses. We systematically investigate the sensitivity to unequal masses of the superfluid properties and the self-consistent screening of the electron-hole pairing interaction. We find that the superfluid properties are insensitive to mass imbalance in the low density BEC regime of strongly-coupled boson-like electron-hole pairs. At higher densities, in the BEC-BCS crossover regime of fermionic pairs, we find that mass imbalance between electrons and holes weakens the superfluidity and expands the density range for the BEC-BCS crossover regime. This permits screening to kill the superfluid at a lower density than for equal masses.

[Display omitted] • Experimental FT-IR, FT-Raman spectral characterizations of CPE are in good agreement with the theoretical vibrational assignments. • Electronic properties were evaluated for the different solvents. • Reactivity analysis-MEP map, and localized molecular orbital (NHO, NLMO, NBO) analyses were estimated. • Topology analyses viz., ELF, LOL, and RDG were estimated. • TD-DFT /MO62X in solvent phases (acetone, water, and DMSO) were discussed with the experimental value. • Molecular Docking was performed for the HNMT inhibitor protein targets for the fungal and bacterial ailments accomplished lesser binding energy interactions. The phenyl-substituted piperazine derivative molecule was taken into consideration in the current investigation of the organic drug molecule (±)-2-(2-{4-[(4-chlorophenyl)-phenylmethyl] piperazin-1-yl} ethoxy) ethanol (CPE), evaluating the spectral characterization using both simulated and recorded FT-IR, FT-Raman, and UV spectral studies. The theoretical computations have been conducted using DFT/B3LYP/6–311++G(d,p)as a basis set. The stable optimized structure was attained by selecting suitable dihedral angles using PES analysis and molecular geometrical parameters were obtained and matched with the available literature data. The vibrational assignments along with the PED contributions were obtained and matched with the recorded values. The electronic properties were analyzed for the various solvents and found that acetone possesses a lesser band energy gap of 5.3637 eV implies the stability of the header composite. Further, the UV–Vis spectra for the various solvents and corresponding parameters were obtained along with excitation analysis with electron-hole isosurface contributions. The maximum absorption wavelength of the CPE obtained in the liquid phase and the recorded wavelength compared with the simulated data. Intermolecular reliability of the molecule emanating from hyperconjugative interactions of charge delocalization by NBO analysis. The accomplishment of nucleophilic and electrophilic regions of the solvents such as acetone, water, and DMSO was implemented using Molecular Electrostatic Potential (MEP) for the molecule. Electron localization function (ELF) Localized orbital locator (LOL) and Reduced density Gradient (RDG) were attained using the above-mentioned basis set for the topological behavior of the title molecule. According to molecular docking studies, the amino acid residues present at the active site region of the ligand (CPE) are particularly suited to Histamine N-methyltransferase (HNMT) with suitable targets (PDB: 2AOT,1JQD, and 2AOU) and the minimum binding energy for the receptor target is 2AOU is −6.90 kcal/mol respectively. [ABSTRACT FROM AUTHOR]

Condensation of spatially indirect excitons, with the electrons and holes confined in two separate layers, has recently been observed in two different double layer heterostructures. High transition temperatures were reported in a double Transition Metal Dichalcogenide (TMD) monolayer system. We briefly review electron-hole double layer systems that have been proposed as candidates for this interesting phenomenon. We investigate the double TMD system WSe 2 /hBN/MoSe 2 , using a mean-field approach that includes multiband effects due to the spin-orbit coupling and self-consistent screening of the electron-hole Coulomb interaction. We demonstrate that the transition temperature observed in the double TMD monolayers, which is remarkably high relative to the other systems, is the result of (i) the large electron and hole effective masses in TMDs, (ii) the large TMD band gaps, and (iii) the presence of multiple superfluid condensates in the TMD system. The net effect is that the superfluidity is strong across a wide range of densities, which leads to high transition temperatures that extend as high as T B K T = 150 K.

Graphical abstract The Sr 2 FeTaO 6 /NaTaO 3 heterojunctions with the controllable molar ratio and transitional zone space exhibit higher photocatalytic performances, due to introducing narrow-bandgap Sr 2 FeTaO 6 component, which could obviously enhance its absorbability in visible light region and separation efficiency of photo-generated electron-hole pairs. Highlights • Nano-sized Sr 2 FeTaO 6 /NaTaO 3 heterojunctions were fabricated under a mild condition. • Molar ratio and transitional zone space could be controlled by temperature and time. • It exhibited higher photocatalytic performances in NO removal and H 2 evolution. • It enhanced visible light absorbability and electron-hole separating efficiency. • Transitional zone space is an important factor in photocatalytic performances. Abstract The Sr 2 FeTaO 6 /NaTaO 3 heterojunctions with the controllable molar ratio and space of heterojunction transitional zone were fabricated using in situ hydrothermal method by adjusting hydrothermal temperature and time. Comparing with the pure NaTaO 3 nanosheets and Sr 2 FeTaO 6 nanoparticles, the Sr 2 FeTaO 6 / NaTaO 3 heterojunctions exhibit higher photocatalytic performances, due to introducing narrow-bandgap Sr 2 FeTaO 6 component, which could obviously enhance its absorbability in visible light region and separation efficiency of photo-generated electron-hole pairs. Under visible light irradiation, the optimal Sr 2 FeTaO 6 /NaTaO 3 heterojunction, with the molar ratio of 0.53 and space of heterojunction transitional zone of 0.35 nm, shows the best photocatalytic activity with the NO removal ratio of 72% in 40 min, hydrogen evolution rate of 1334 μmol h−1 g−1 in 5 h, and apparent quantum efficiency (AQE) for hydrogen evolution of 38.8% at 420 nm. More interestingly, the space of heterojunction transitional zone, related to the interface bonding degree of heterojunction material, may not be the only factor which influences transferring and separating efficiency of photo-generated charge carriers, but it is certainly an important one, which provides a new cognitive perspective for constructing and understanding efficient heterostructure photocatalyst. [ABSTRACT FROM AUTHOR]

Biases in mutation rate can influence molecular evolution, yielding rates of evolution that vary widely in different parts of the genome and even among neighboring nucleotides. Here, we explore one possible mechanism of influence on sequence-specific mutation rates, the electron-hole, which can localize and potentially trigger a replication mismatch. A hole is a mobile site of positive charge created during one-electron oxidation by, for example, radiation, contact with a mutagenic agent, or oxidative stress. Its quantum wavelike properties cause it to localize at various sites with probabilities that vary widely, by orders of magnitude, and depend strongly on the local sequence. We find significant correlations between hole probabilities and mutation rates within base triplets, observed in published mutation accumulation experiments on four species of bacteria. We have also computed hole probability spectra for hypervariable segment I of the human mtDNA control region, which contains several mutational hotspots, and for heptanucleotides in noncoding regions of the human genome, whose polymorphism levels have recently been reported. We observe significant correlations between hole probabilities, and context-specific mutation and substitution rates. The correlation with hole probability cannot be explained entirely by CpG methylation in the heptanucleotide data. Peaks in hole probability tend to coincide with mutational hotspots, even in mtDNA where CpG methylation is rare. Our results suggest that hole-enhanced mutational mechanisms, such as oxidation-stabilized tautomerization and base deamination, contribute to molecular evolution. [ABSTRACT FROM AUTHOR]

• Synthesized, experimental and theoretical characterizations of 4CNB were performed. • FMO's, electronic properties, MEP map for different solvents elucidated. • NBO, Fukui function, Topology analyses (ELF, LOL) were estimated. • In silico analysis with different protein targets were examined. Being of the benzohyrazide derivatives, the molecule in consideration is quite significant in the pharmaceutical industry. In the present article, a novel compound has been synthesized and compared between the theoretical and experimental characterization such as FT-IR, UV–Vis and NMR techniques were employed. The quantum simulation studies (DFT) have been discussed for a higher basis set as B3LYP/6–311++G(d,p). Molecular vibrational assignments, chemical and electronic characteristics of 4-chloro-N -(2,6-dichlorobenzylidene) benzohydrazide (4CNB) were performed. The potential energy surface, geometrical optimization, wave numbers, and electronic structure stability were calculated by density function theory (DFT) through a higher basis set. The spectral characterizations of the molecule have been correlated with the observed spectrum. The chemical property of frontier orbital theory (FMO's) and electron-hole excitation analysis (D-index, Δr index,t index and excited states) for the different solvents such as DMSO, Chloroform, water and methanol were analysed. The DOS and orbital overlap functions were investigated. The stability of the structure, electrophilic and nucleophilic attacks for the different solvents, intra molecular analysis through NBO, molecular electrostatic potential (MEP) and local descriptors such as Fukui function (f+, f-, f0), topological analyses were performed and discussed. Molecular docking studies were performed by Auto-dock software to establish the information about the interactions between the antifungal and antibacterial inhibitor and lest binding energy is observed for Candida glabrata (−7.50 kcal/mol) protein. [ABSTRACT FROM AUTHOR]

• Geometrical parameters, spectroscopic properties (FT-IR, FT-Raman and UV-visible), and electronic properties of novel Metachlorphenprop-p-anisidine (MCPA) was discussed. • Intermolecular interaction in a molecular crystal package and the percentage of close contact within the molecule were studied using Hrishfeld analysis. • The molecular docking study has been carried out in order to give an insight about the bioactive region and active binding site of the compound. • In silico Physicochemical and drug likeness have been carried out to assess qualitatively the chance for a molecule to become an oral drug with respect to bioavailability. The structural and packing feature of novel Metachlorphenprop-p-anisidine (MCPA) single crystal was grown by refluxing stoichiometric amount of Metachlorphenprop (MCP) and p-anisidine (PAS) in ethanol, was investigated by single crystal X-ray diffraction. The title compound was investigated theoretically and experimentally by FT-IR, FT-Raman, TG-DTA and UV–Vis spectra. The theoretical optimized geometrical parameters and vibrational analysis were performed by density functional theory (DFT) with the B3LYP method at 6–311 G (d,p) basis set. The optimized geometrical parameters obtained by DFT calculations were in good agreement with the experimental data. Various intermolecular interactions involved in MCPA were analysed using different topological analysis atoms-in-molecule (AIM), reduced density gradient (RDG), electron localization function (ELF) and natural bond orbital (NBO) analysis. The stability of the molecule arising from intermolecular interaction and charge delocalization have been analysed using NBO analysis. Molecular electrostatic potentials (MEP) was performed to analyse the reactive area of the title molecule, local chemical reactivity was studied by population analysis and Fukui function analysis. The thermal behaviour of the MCPA crystal was analysed by TG-DTA analysis. Hole-electron interaction study divulge that S1-S4 undergo charge transfer excitation. The mechanical strength of the grown material proves that it is a soft material. Molecular docking was performed to confirm the stability of the protein-ligand complex. The results shows that the title compound has antibacterial properties as well as antifungal activities against Escherichia coli and Aspergillus niger organisms. The pharmacokinetics and drug likeness were also performed on titled molecule for the confirmation of drug-like character of title molecule. [ABSTRACT FROM AUTHOR]

In this paper we present the results of investigation of the nature of intrinsic luminescence caused by photon excitation in a wide spectral range from 10.3 eV to 4 eV at a temperature of 15–300 K. It is shown that in alkali metal sulfates the main emission band formed after excitation by X-rays and photons with an energy of 9–11 eV and 4–7.5 eV at 15–300 K is located in the spectral range of 3.65–3.9 eV. When the sulfates are excited by 4–7.75 eV photons, in addition to the emission band at 3.65–3.9 eV the other effective long-wave band at 3.1–2.5 eV appears. It is assumed that the 3.65–3.9 eV radiation results from the recombination of electrons with unevenly located holes of SO 4 − type. The long-wave emission bands in the alkali metal sulfates may be connected with the formation of electron-hole trapping centers after irradiation by photons with energies above 4.4 eV. [ABSTRACT FROM AUTHOR]

Spectroscopic methods were used to investigate the mechanisms of formation of electron–hole capture centers in KNaSO 4 and LiNaSO 4 crystals by irradiation with ultraviolet (UV) light and photons with energies of 4–6.2 eV at 80 K and 300 K. We were the first who showed experimentally that the direct irradiation by photons with an energy of 4–6.2 eV at 80 K forms in KNaSO 4 and LiNaSO 4 crystals electron–hole capture centers registered in the measurements of TSL (thermo stimulated luminescence) and recombination radiation. During irradiation by photons, the electrons in 1t 1 , 3t 2 , 1e, 2t 2 orbitals of S O 4 2 − anion in the sulfate valence band are excited. From this state, the electrons recombine with the self-trapped hole ( S O 4 2 − ) radiatively or with formation of defects. Quantum chemical calculations modeling the decay of the anionic complex confirm energy possibility of such processes. [ABSTRACT FROM AUTHOR]

Photocatalysts, TiO 2 /glass fiber (TiO 2 /GF), Cu-doped TiO 2 /glass fiber (Cu–TiO 2 /GF) and Ag-doped TiO 2 /glass fiber (Ag–TiO 2 /GF), were synthesized by a sol–gel method. They were then used to disinfect Escherichia coli ( E. coli ) and Staphylococcus aureus ( S. aureus ) in bioaerosols under visible light irradiation. TiO 2 /GF did not show any significant disinfection effect. Both Cu and Ag acted as intermediate agents to enhance separation efficiency of electron–hole pairs of TiO 2 , leading to improved photocatalytic activity of Cu–TiO 2 /GF and Ag–TiO 2 /GF under visible light. Cu in Cu–TiO 2 /GF acted as a defective agent, increasing the internal quantum efficiency of TiO 2 , while Ag in Ag–TiO 2 /GF acted as a sensitive agent, enhancing the transfer efficiency of the electrons generated. The highest disinfection efficiencies of E. coli and S. aureus by Cu–TiO 2 /GF were 84.85% and 65.21%, respectively. The highest disinfection efficiencies of E. coli and S. aureus by Ag–TiO 2 /GF were 94.46% and 73.12%, respectively. Among three humidity conditions – 40±5% (dry), 60±5% (moderate), and 80±5% (humid) – the moderate humidity condition showed the highest disinfection efficiency for both E. coli and S. aureus . This study also showed that a Gram-negative bacterium ( E. coli ) were more readily disinfected by the photocatalysts than a Gram-positive bacterium ( S. aureus ). [ABSTRACT FROM AUTHOR]

The kinetic modeling of organic pollutant photocatalytic degradation on synthesized ZnO nanoparticles was carried out. The photodegradation kinetic characteristics were investigated under different operational parameters including light intensity, initial organic concentration, ZnO content and pH. Based on the elementary photocatalytic reactions, the new kinetic model was established for prediction of photocatalytic degradation efficiency by taking into account the apparent first order rate constant, light intensity, initial organic concentration and ZnO content. The results demonstrated that the kinetic model could predict adequately photodegradation efficiency when high concentration of photo-induced hole-electron was considered. To compare the accuracy of obtained kinetic model, an empirical kinetic model as function of operational parameters and a 3-layer perceptron neural network were developed. The performance of three models was compared with experimental data by error functions and analysis of variance (ANOVA) calculation. The obtained results showed that three developed models are in good agreement with experimental data. It was also found that there is no significant difference among the developed kinetic, empirical kinetic and artificial neural network models. It was concluded that the kinetic model is developed based on the appropriate understanding from determining elementary reactions occurred in photocatalytic degradation of dye. [ABSTRACT FROM AUTHOR]

Abstract: We describe a technique of fabricating closely spaced electron–hole bilayers in GaAs–AlGaAs heterostructures. Our device incorporates a novel method of making shallow ohmic contacts, to a low density () 2-DEG, using MBE grown doped InAs. These contacts do not require annealing and are completely free from “spiking”. Independent four terminal measurements on both layers (25nm apart) are possible. Hole mobilities and electron mobilities are simultaneously attained at 1.5K. Preliminary Coulomb drag measurements made down to are consistent with the Onsager reciprocity relation for four terminal conductance and indicate an enhancement of Coulomb interaction over the values obtained from a “Thomas–Fermi” calculation. The technique lends itself fully to conventional uniform MBE growth and does not require shadow masking or ion implantation. In the simplest mode of operation a single external voltage, slightly higher than the bandgap of GaAs, is required for simultaneous accumulation of electrons and holes separated by the 25nm barrier. Both carrier densities increase with the applied interlayer bias and the measured densities are reproducible over several cooldowns. A backgate can be added to the structure to get independent control of the carrier densities. Our process is independent of the precise depth of the 2DEG/2DHG or the width of the barrier and will be useful in studying novel phases resulting from a possible excitonic pairing between electrons and holes. [Copyright &y& Elsevier]

Exact solution for two spatially separated particles in two coaxial one-dimensional nanorings has been obtained by using trigonometric sweep method. The structure of the energy spectrum of two electrons and electron-hole pair in nanoring with different sizes has been calculated. The comparative analysis of the quantum size effect on the energy levels in the case of the electron-hole attraction and the electron-electron repulsion is presented. As the radii of coaxial rings merge our results coincide with those obtained previously for one-dimensional nanoring. [ABSTRACT FROM AUTHOR]

A photocatalytic-electrolysis reactor using an anode coated with a TiO2 thin film of an anatase structure, a low surface resistivity, and a large surface area has shown an enhancement of TiO2 photocatalytic reaction efficiency by a reduction of the recombination of photogenerated electron–hole pairs. At the photocatalytic anode under UV irradiation and with a potential to generate oxygen evolution being applied, the photocatalytic enhancement was about 90% because of suppression of the recombination of holes and electrons by taking out forcedly the generated electrons through an external bias into a cathode and by the oxygen generated by the electrolytic reaction acting as an acceptor to the electrons. The photocatalytic enhancement effect occurred only when the cell voltage applied to the photocatalytic-electrolysis reactor was over a certain value. The photocatalytic reaction observed on the catalytic oxide electrodes of RuO2 and IrO2 was because of the existence of TiO2 on the electrode surface, which resulted from the oxidation of Ti substrate itself during sintering for the fabrication of the electrodes. [Copyright &y& Elsevier]

We examine the quantum Hall effect in an electron–hole system and its current-driven breakdown. We find that samples with closely matched electron and hole concentrations have vastly reduced critical currents while those with many more electrons than holes show much larger critical currents, though still smaller than those reported for single-carrier type systems. The channel width dependence shows two regimes of behaviour. States with larger critical currents (>5 μA) have linear width dependence, while for narrower channel widths where the critical current is smaller, the critical current has a superlinear relationship with the channel width. [Copyright &y& Elsevier]

Thermal generation in wide bandgap semiconductors can be observed by monitoring the capacitance recovery transients of npn (or pnp) storage capacitors in which the middle layer is floating. In this article, we report a study of thermal generation in 4H and 6H silicon carbide (SiC). Three generation mechanisms are identified: bulk generation in the depletion regions of the pn junctions, surface generation at the periphery of the capacitors, and defect generation associated with imperfections in the material. All three generation mechanisms are thermally activated. Bulk generation and surface generation have activation energies of approximately half bandgap, while defect generation exhibits field-induced barrier lowering resulting in an apparent activation energy less than half bandgap. Because the generation rate is extremely low, most measurements are conducted at elevated temperatures (250-350°C). However, we also describe a long-term measurement at room temperature in which the 1/e recovery time appears to be in excess of 100 years. [ABSTRACT FROM AUTHOR]

CuO and Er-doped CuO nanostructures were synthesized by thermal decomposition of Cu-salophen complexes containing chloro, bromo and nitro substituents as precursors (CuL1, CuL2 and CuL3, respectively). The structure of products was characterized by FT-IR spectroscopy and XRD patterns. XRD patterns indicated that the formation of single-phase monoclinic structures without impurity and also confirmed that erbium ions are successfully doped into CuO crystal lattice. The photocatalytic activity of all samples was measured against the Reactive Black 5 dye under UV radiation. The photocatalytic mineralization of RB-5 was monitored by total organic concentration (TOC) decrease and changes in the UV–Vis spectra. The results revealed that the photocatalytic efficiency of Er-doped CuO samples is much higher than their un-doped counterparts. The highest percentage of dye decomposition was achieved using Er-doped CuO (1). The optical band gaps calculated from UV–Vis spectra were found to be 3.60 eV for both CuO (1) and Er-doped CuO (1). The PL spectrum of Er-doped CuO (1) showed a significant decrease in emission intensity, which was related to the electron-hole separation due to electron transfer from CuO conductive band to Er3+ ions. The BET analysis revealed after Er3+ doping, the surface porosity and specific surface area increased because of the appearance of some surface defects in CuO structure. FE-SEM images of both pure and doped CuO samples displayed that the powders consist of highly agglomerated nano-flakes resulting from overlapping of small particles. Further analysis of Er-doped CuO (1) with TEM indicated the prepared sample is composed of nanoparticles. Image 107562 • CuO and Er-doped CuO nanostructures were prepared by thermal decomposition method. • The photocatalytic activity of samples was evaluated in the degradation of RB5 dye. • Considerable enhancing in photocatalytic activity was obtained by Er-doping. [ABSTRACT FROM AUTHOR]

The energy crisis is one of the most serious issue that we confront today. Among different strategies to gain access to reliable fuel, the production of hydrogen fuel through the water-splitting reaction has emerged as the most viable alternative. Specifically, the studies on defect-rich TiO2 materials have been proved that it can perform as an efficient catalyst for electrocatalytic and photocatalytic water-splitting reactions. In this invited review, we have included a general and critical discussion on the background of titanium sub-oxides structure, defect chemistries and the consequent disorder arising in defect-rich Titania and their applications towards water-splitting reactions. We have particularly emphasized the origin of the catalytic activity in Titania-based material and its effects on the structural, optical and electronic behavior. This review article also summarizes studies on challenging issues on defect-rich Titania and new possible directions for the development of an efficient catalyst with improved catalytic performance. [ABSTRACT FROM AUTHOR]