Gd3+ Encapsulation on 2D-g-C3N4 Nanostructure for Spintronics and Ultrasound Assisted Photocatalytic Applications: First-Principles and Experimental Studies.

Atomically thin two-dimensional (2D) semiconductors have high potential in optoelectronics and magneto-optics appliances due to their tunable band structures and physicochemical stability. The work demonstrates that Gd3+ incorporated 2D-g-C3N4 nanosheet (Gd3+/2D-g-C3N4 NS) is synthesized through chemisorption methodology for defect enrichment. The material characterizations reveal that the ion decoration enhances the surface area and defect concentration of the 2D sheet. The experimental observations have been further corroborated with the help of density functional theory (DFT) simulation. Spin asymmetry polarizations near the Fermi level, obtained through the partial density of states (PDOS) analyses, reveal the magnetic nature of the synthesized material, validating the room temperature ferromagnetism obtained through a vibrating-sample magnetometer (VSM). Gd3+/2D-g-C3N4 NS shows significant enhancement in saturation magnetization (Ms) experimentally and computationally compared to the pristine one. The magnetic catalyst shows 98% remediation efficiency for ultrasound-assisted visible-light-driven photodegradation of methyl orange (MO). The synergistic approach of liquid chromatography-mass spectrometry (LC-MS) analyses and DFT studies elucidates reaction intermediates and unveils the degradation mechanism. Post-characterization studies assure the stability of the magnetic catalyst through optical, chemical, magnetic, and microscopic analyses. So, the synthesized material can be proficiently used as a magnetic nanocatalyst in wastewater treatments and spin-electronics applications.

Enhanced Photocatalytic Performance under Ultraviolet and Visible Light Illumination of ZnO Thin Films Prepared by Modified Sol-Gel Method.

Semiconductor oxides are frequently used as active photocatalysts for the degradation of organic agents in water polluted by domestic industry. In this study, sol-gel ZnO thin films with a grain size in the range of 7.5-15.7 nm were prepared by applying a novel two-step drying procedure involving hot air treatment at 90-95 °C followed by conventional furnace drying at 140 °C. For comparison, layers were made by standard furnace drying. The effect of hot air treatment on the film surface morphology, transparency, and photocatalytic behavior during the degradation of Malachite Green azo dye in water under ultraviolet or visible light illumination is explored. The films treated with hot air demonstrate significantly better photocatalytic activity under ultraviolet irradiation than the furnace-dried films, which is comparable with the activity of unmodified ZnO nanocrystal powders. The achieved percentage of degradation is 78-82% under ultraviolet illumination and 85-90% under visible light illumination. Multiple usages of the hot air-treated films (up to six photocatalytic cycles) are demonstrated, indicating improved photo-corrosion resistance. The observed high photocatalytic activity and good photo-corrosion stability are related to the hot air treatment, which causes a reduction of oxygen vacancies and other defects and the formation of interstitial oxygen and/or zinc vacancies in the films.

Quenching-Induced Defect-Rich Platinum/Metal Oxide Catalysts Promote Catalytic Oxidation.

Enhancing oxygen activation through defect engineering is an effective strategy for boosting catalytic oxidation performance. Herein, we demonstrate that quenching is an effective strategy for preparing defect-rich Pt/metal oxide catalysts with superior catalytic oxidation activity. As a proof of concept, quenching of α-Fe2O3 in aqueous Pt(NO3)2 solution yielded a catalyst containing Pt single atoms and clusters over defect-rich α-Fe2O3 (Pt/Fe2O3-Q), which possessed state-of-the-art activity for toluene oxidation. Structural and spectroscopic analyses established that the quenching process created abundant lattice defects and lattice dislocations in the α-Fe2O3 support, and stronger electronic interactions between Pt species and Fe2O3 promote the generation of higher oxidation Pt species to modulate the adsorption/desorption behavior of reactants. In situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) characterization studies and density functional theory (DFT) calculations determined that molecular oxygen and Fe2O3 lattice oxygen were both activated on the Pt/Fe2O3-Q catalyst. Pt/CoMn2O4, Pt/MnO2, and Pt/LaFeO3 catalysts synthesized by the quenching method also offered superior catalytic activity for toluene oxidation. Results encourage the wider use of quenching for the preparation of highly active oxidation catalysts.

Impact of nano-morphology, lattice defects and conductivity on the performance of graphene based electrochemical biosensors.

Diverse properties of graphenic materials have been extensively explored to determine properties that make good electrochemical nanomaterial-based biosensors. These are reviewed by critically examining the influence of graphene nano-morphology, lattice defects and conductivity. Stability, reproducibility and fabrication are discussed together with sensitivity and selectivity. We provide an outlook on future directions for building efficient electrochemical biosensors.

High-pressure torsion for new hydrogen storage materials.

High-pressure torsion (HPT) is widely used as a severe plastic deformation technique to create ultrafine-grained structures with promising mechanical and functional properties. Since 2007, the method has been employed to enhance the hydrogenation kinetics in different Mg-based hydrogen storage materials. Recent studies showed that the method is effective not only for increasing the hydrogenation kinetics but also for improving the hydrogenation activity, for enhancing the air resistivity and more importantly for synthesizing new nanostructured hydrogen storage materials with high densities of lattice defects. This manuscript reviews some major findings on the impact of HPT process on the hydrogen storage performance of different titanium-based and magnesium-based materials.

Lattice Defects and Electronic Modulation of Flower-Like Zn3 In2 S6 Promote Photocatalytic Degradation of Multiple Antibiotics.

Photocatalysis is an effective technique to remove antibiotic residues from aquatic environments. Typical metal sulfides like Zn3 In2 S6 have been applied to a wide range of photocatalytic applications. However, there are currently no readily accessible methods to increase its antibiotic-degrading activity. Here, a facile hydrothermal approach is developed for the preparation of flower-like Zn3 In2 S6 with tunable sulfur lattice defects. Photogenerated carriers can be separated and transferred more easily when there is an adequate amount of lattice defects. Moreover, lattice defect-induced electronic modulation enhances light utilization and adsorption properties. The modified Zn3 In2 S6 demonstrates outstanding photocatalytic degradation activity for levofloxacin, ofloxacin, and tetracycline. This work sheds light on exploring metal sulfides with sulfur lattice defects for enhancing photocatalytic activity.

Flame Spray Pyrolysis Synthesis of Vo-Rich Nano-SrTiO3-x.

Engineering of oxygen vacancies (Vo) in nanomaterials allows diligent control of their physicochemical properties. SrTiO3 possesses the typical ABO3 structure and has attracted considerable attention among the titanates due to its chemical stability and its high conduction band energy. This has resulted in its extensive use in photocatalytic energy-related processes, among others. Herein, we introduce the use of Flame Spray Pyrolysis (FSP); an industrial and scalable process to produce Vo-rich SrTiO3 perovskites. We present two types of Anoxic Flame Spray Pyrolysis (A-FSP) technologies using CH4 gas as a reducing source: Radial A-FSP (RA-FSP); and Axial A-FSP (AA-FSP). These are used for the control engineering of oxygen vacancies in the SrTiO3-x nanolattice. Based on X-ray photoelectron spectroscopy, Raman and thermogravimetry-differential thermal analysis, we discuss the role and the amount of the Vos in the so-produced nano-SrTiO3-x, correlating the properties of the nanolattice and energy-band structure of the SrTiO3-x. The present work further corroborates the versatility of FSP as a synthetic process and the potential future application of this process to engineer photocatalysts with oxygen vacancies in quantities that can be measured in kilograms.

Enhancing Biocidal Capability in Cuprite Coatings.

The SARS-CoV-2 global pandemic has reinvigorated interest in the creation and widespread deployment of durable, cost-effective, and environmentally benign antipathogenic coatings for high-touch public surfaces. While the contact-kill capability and mechanism of metallic copper and its alloys are well established, the biocidal activity of the refractory oxide forms remains poorly understood. In this study, commercial cuprous oxide (Cu2O, cuprite) powder was rapidly nanostructured using high-energy cryomechanical processing. Coatings made from these processed powders demonstrated a passive "contact-kill" response to Escherichia coli (E. coli) bacteria that was 4× (400%) faster than coatings made from unprocessed powder. No viable bacteria (>99.999% (5-log10) reduction) were detected in bioassays performed after two hours of exposure of E. coli to coatings of processed cuprous oxide, while a greater than 99% bacterial reduction was achieved within 30 min of exposure. Further, these coatings were hydrophobic and no external energy input was required to activate their contact-kill capability. The upregulated antibacterial response of the processed powders is positively correlated with extensive induced crystallographic disorder and microstrain in the Cu2O lattice accompanied by color changes that are consistent with an increased semiconducting bandgap energy. It is deduced that cryomilling creates well-crystallized nanoscale regions enmeshed within the highly lattice-defective particle matrix. Increasing the relative proportion of lattice-defective cuprous oxide exposed to the environment at the coating surface is anticipated to further enhance the antipathogenic capability of this abundant, inexpensive, robust, and easily handled material for wider application in contact-kill surfaces.

An empirical potential for simulating hydrogen isotope retention in highly irradiated tungsten.

We describe the parameterization of a tungsten-hydrogen empirical potential designed for use with large-scale molecular dynamics simulations of highly irradiated tungsten containing hydrogen isotope atoms, and report test results. Particular attention has been paid to getting good elastic properties, including the relaxation volumes of small defect clusters, and to the interaction energy between hydrogen isotopes and typical irradiation-induced defects in tungsten. We conclude that the energy ordering of defects changes with the ratio of H atoms to point defects, indicating that this potential is suitable for exploring mechanisms of trap mutation, including vacancy loop to plate-like void transformations.

Effects of Oxygen on Lattice Defects in Single-Crystalline Mg2Si Thermoelectrics.

Lattice defect engineering has attracted attention due to its ability to develop thermoelectric materials with low thermal conductivity. For Mg2Si single crystals (SCs), Si vacancy (VSi) defects can be introduced and consequently result in the formation of dislocation cores. These lattice defects confer Mg2Si SCs with a lower thermal conductivity compared to Mg2Si polycrystals. To reveal a mechanism for the stabilisation of VSi in the Mg2Si SCs, we investigated the effects of oxygen (O) on lattice defects by performing electronic structure calculations, secondary ion mass spectrometry, X-ray photoelectron spectroscopy, and photoelectron holography. On the basis of these calculations, we predicted that O stabilised the formation of VSi when it was located at the Si site or at an interstitial site. All experiments confirmed the presence of O inside the Mg2Si SCs. However, O was suggested to be located not at the specific site in the crystal lattice of Mg2Si but at dislocation cores. The interaction between O and the dislocation cores in the Mg2Si SC is expected to immobilise dislocation cores, leading to the stabilisation of VSi formation.

Effect of Substitutional Oxygen on Properties of Ti3 C2 Tx MXene Produced Using Recycled TiO2 Source.

MXenes are an emerging class of 2D materials with unique properties including metallic conductivity, mechanical flexibility, and surface tunability, which ensure their utility for diverse applications. However, the synthesis of MXenes with high crystallinity and atomic stoichiometry in a low-cost process is still challenging because of the difficulty in controlling the oxygen substitute in the precursors and final products of MXenes, which limits their academic understanding and practical applications. Here, a novel cost-effective method is reported to synthesize a highly crystalline and stoichiometric Ti3 C2 Tx MXene with minimum substitutional oxygen impurities by controlling the amount of excess carbon and time of high-energy milling in carbothermal reduction of recycled TiO2 source. The highest used content (2 wt%) of excess-carbon yields TiC with the highest carbon content and minimal oxygen substitutes, which leads to the Ti3 AlC2 MAX phase with improved crystallinity and atomic stoichiometry, and finally Ti3 C2 Tx MXene with the highest electrical conductivity (11738 S cm-1 ) and superior electromagnetic shielding effectiveness. Additionally, the effects of carbon content and substitutional oxygen on the physical properties of TiC and Ti3 AlC2 are elucidated by density-functional-theory calculations. This inexpensive TiO2 -based method of synthesizing high-quality Ti3 C2 Tx MXene can facilitate large-scale production and thus accelerate global research on MXenes.

Multilayered Molybdate Microflowers Fabricated by One-Pot Reaction for Efficient Water Splitting.

The development of high-performance, low-cost and rapid-production bifunctional electrocatalysts towards overall water splitting still poses huge challenges. Herein, the authors utilize a facile hydrothermal method to synthesize a novel structure of Co-doped ammonium lanthanum molybdate on Ni foams (Co-ALMO@NF) as self-supported electrocatalysts. Owing to large active surfaces, lattice defect and conductive channel for rapid charge transport, Co-ALMO@NF exhibits good electrocatalytic performances which requires only 349/341 mV to achieve a high current density of 600 mA cm-2 for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), respectively. Besides, a low cell voltage of 1.52 V is required to reach the current density of 10 mA cm-2 in alkaline medium along with an excellent long-term stability for two-electrode configurations. Density functional theory calculations are performed to reveal the reaction mechanism on Co-ALMO@NF, which shows that the Mo site is the most favorable ones for HER, while the introduction of Co is beneficial to reduce the adsorption intensity on the surface of Co-ALMO@NF, thus accelerating OER process. This work highlighted the importance of the structural design for self-supporting electrocatalysts.

Lattice Vacancy Induced Energy Renormalization of Photonic Quasiparticles in Two-Dimensional Semiconductors.

Coulomb interactions among dense charges and quasiparticle energy renormalization are at the center of quantum science because they significantly reshape the fundamental electronic and photonic properties of materials. While lattice vacancies are ubiquitous in solid materials, their physical effect on the Coulomb interaction among quasiparticles is normally weak and negligible. Here we show that in atomically thin semiconductors the presence of lattice vacancies emerges as an important but unexplored origin for the nontrivial renormalization of quasiparticle binding energies, due to the subtle modification of overall dielectric functions at low dimensionality. Such a renormalization effect leads to unusual reduction in the energy scales of photonic quasiparticles and red shifts of photoluminescence as the density of lattice vacancies increases. With strict configurative form factors derived, a dielectric screening model is also established for the generalized trilayer systems to capture the fine modification in the energy scales of quasiparticles and to elucidate the dielectric functions versus realistic Bohr lengths. This finding highlights the essential but commonly neglected role of lattice vacancies and deciphers the longstanding enigma of unpredictable photoluminescent line shifts in low-dimensional systems.

Black titania by sonochemistry: A critical evaluation of existing methods.

In the field of photocatalysis, the fabrication of black titania is a booming topic, as it offers a system with improved solar light harvesting properties and increased overall efficiency. The darkening of white TiO2 powders can be ascribed to surface hydroxylation, oxygen vacancies, Ti3+ centres, or a combination thereof. A handful of studies suggests these defects can be conveniently introduced by acoustic cavitation, generated during sonochemical treatment of pristine TiO2 powders. In reproducing these studies, P25 TiO2 samples were ultrasonicated for various hours with a power density of 8000 W/L, resulting in powders that indeed became gradually darker with increasing sonication time. However, HAADF-STEM revealed that extensive erosion of the sonotrode tip took place and contaminated the samples, which appeared to be the primary reason for the observed colour change. This was confirmed by UV-Vis DRS and DRIFTS, that showed no significant alteration of the catalyst surface after sonication. EPR measurements showed that only an insignificant fraction of Ti3+ centres were produced, far less than in a TiO2 sample that was chemically reduced with NaBH4. No evidence of the presence oxygen vacancies could be found. The enhanced photocatalytic activities of ultrasonicated materials reported in literature can therefore not be ascribed to the synthesis of actual black (defected) TiO2, but rather to specific changes in morphology as a result of acoustic cavitation. Also, this study underlines the importance of considering probe erosion in sonochemical catalyst synthesis, which is an unavoidable side effect that can have an important impact on the catalyst appearance, properties and performance.

Construction of Hexagonal Prism-like Defective BiOCL Hierarchitecture for Photocatalytic Degradation of Tetracycline Hydrochloride.

Oxygen vacancy manipulation and hierarchical morphology construction in oxygen-containing semiconductors have been demonstrated to be effective strategies for developing high efficiency photocatalysts. In most studies of bismuth-based photocatalysts, hierarchical morphology and crystal defects are achieved separately, so the catalysts are not able to benefit from both features. Herein, using boiling ethylene glycol as the treatment solution, we developed an etching-recrystallization method for the fabrication of 3D hierarchical defective BiOCl at ambient pressure. The target hierarchical 3D-BiOCl is composed of self-assembled BiOCl nanosheets, which exhibit a hexagonal prism-like morphology on a micron scale, while simultaneously containing numerous oxygen vacancies within the crystal structure. Consequently, the target catalyst was endowed with a higher specific surface area, greater light harvesting capability, as well as more efficient separation and transfer of photo-excited charges than pristine BiOCl. As a result, 3D-BiOCl presented an impressive photocatalytic activity for the degradation of tetracycline hydrochloride in both visible light and natural white light emitting diode (LED) irradiation. Moreover, an extraordinary recycling property was demonstrated for the target photocatalyst thanks to its hierarchical structure. This study outlines a simple and energy-efficient approach for producing high-performance hierarchically defective BiOCl, which may also open up new possibilities for the morphological and crystal structural defect regulation of other Bi-based photocatalysts.

Suppressing the Cation Exchange at the Core/Shell Interface of InP Quantum Dots by a Selenium Shielding Layer Enables Efficient Green Light-Emitting Diodes.

Indium phosphide (InP) quantum dots (QDs) have demonstrated great potential for light-emitting diode (LED) application because of their excellent optical properties and nontoxicity. However, the over performance of InP QDs still lags behind that of CdSe QDs, and one of main reasons is that the Zn traps in InP lattices can be formed through the cation exchange in the ZnSe shell growth process. Herein, we realized highly luminescent InP/ZnSe/ZnS QDs by constructing Se-rich shielding layers on the surfaces of InP cores, which simultaneously protect the InP cores from the invasion of Zn2+ into InP lattices and facilitate the ZnSe shell growth via the reaction between Zn2+ precursors and Se2- shielding layers. The as-synthesized green InP/ZnSe/ZnS QDs had a high photoluminescence quantum yield (PLQY) of up to 87%. The fabricated QLEDs present a peak external quantum efficiency of 6.2% with an improved efficiency roll-off at high luminance, which is 2 times higher than that of control devices.

In Situ Construction of Black Titanium Oxide with a Multilevel Structure on a Titanium Alloy for Photothermal Antibacterial Therapy.

Postsurgical infection of orthopedic fixation materials is considered to be the main cause of fixation failure. To address the problem, clinical treatment often relies on long-term antibiotics, secondary surgery, and so forth, which cause pain and suffering to patients. Constructing a light-responsive surface structure on the implant has attracted widespread attention for the management of postsurgical infections because of its noninvasiveness and controllability. Nevertheless, the application of light-responsive structures on implants is still limited by their unsafety and instability. In this work, a black titanium oxide layer with a multilevel structure and lattice defects was in situ constructed on a titanium alloy through pulsed laser ablation treatment. Under the synergistic effect of the multilevel structure and crystal defects, the surface of the titanium alloy exhibited good near-infrared light-responsive photothermal ability. The black titanium oxide multilevel structure reached high antibacterial efficiencies of about 99.37 and 99.29% against Staphylococcus aureus and Escherichia coli under 10 min near-infrared light irradiation. Furthermore, the black titanium oxide layer possessed similar biocompatibility compared with the titanium alloy. This near-infrared light-responsive photothermal therapy based on the construction of a multilevel structure and introduction of lattice defects provides an effective strategy for clinical postsurgical infections of orthopedic fixation.

Supersonic Motion of Atoms in an Octahedral Channel of fcc Copper.

In this work, the mass transfer along an octahedral channel in an fcc copper single crystal is studied for the first time using the method of molecular dynamics. It is found that the initial position of the bombarding atom, outside or inside the crystal, does not noticeably affect the dynamics of its motion. The higher the initial velocity of the bombarding atom, the deeper its penetration into the material. It is found out how the place of entry of the bombarding atom into the channel affects its further dynamics. The greatest penetration depth and the smallest dissipation of kinetic energy occurs when the atom moves exactly in the center of the octahedral channel. The deviation of the bombarding atom from the center of the channel leads to the appearance of other velocity components perpendicular to the initial velocity vector and to an increase in its energy dissipation. Nevertheless, the motion of an atom along the channel is observed even when the entry point deviates from the center of the channel by up to 0.5 Å. The dissipated kinetic energy spent on the excitation of the atoms forming the octahedral channel is nearly proportional to the deviation from the center of the channel. At sufficiently high initial velocities of the bombarding atom, supersonic crowdions are formed, moving along the close-packed direction ⟨1¯10⟩, which is perpendicular to the direction of the channel. The results obtained are useful for understanding the mechanism of mass transfer during ion implantation and similar experimental techniques.

S-Doping Promotes Pyridine Nitrogen Conversion and Lattice Defects of Carbon Nitride to Enhance the Performance of Zn-Air Batteries.

The efficient operation of Zn-air batteries (ZABs) requires highly active and stable reversible air catalysts. Studies have shown that heteroatom-doped carbonaceous nanomaterials are effective metal-free electrocatalysts for the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR). Herein, we design a facile and scalable catalyst doping scheme to manufacture S-doped carbon nitride (S-C3N4). Surprisingly, this metal-free catalyst exhibits excellent OER and ORR electrocatalytic activities in alkaline electrolytes, being comparable to those of commercial Pt/C. For the first time, it is proved by experiments that S doping can not only effectively increase the lattice defects of C3N4 but also promote the conversion of pyrrolic nitrogen to pyridine nitrogen, thereby enhancing the bifunctional catalytic activity (OER and ORR). When the catalyst is used as an air electrode for rechargeable ZABs, its performance is obviously better than that provided by commercial Pt/C. Our findings and material design strategies are expected to provide new ideas for the synthesis of various high-performance carbon-based electrocatalysts.

Monolayer Graphene Radiation Sensor with Backend RF Ring Oscillator Transducer.

This paper proposes a new graphene gamma- and beta-radiation sensor with a backend RF ring oscillator transducer employed to convert the change in the graphene resistivity due to ionizing irradiation into a frequency output. The sensor consists of a CVD monolayer of graphene grown on a copper substrate, with an RF ring oscillator readout circuit in which the percentage change in frequency is captured versus the change in radiation dose. The novel integration of the RF oscillator transducer with the graphene monolayer results in high average sensitivity to gamma irradiation up to 3.82 kΩ/kGy, which corresponds to a percentage change in frequency of 7.86% kGy-1 in response to cumulative gamma irradiation ranging from 0 to 1 kGy. The new approach helps to minimize background environmental effects (e.g., due to light and temperature), leading to an insignificant error in the output change in frequency of the order of 0.46% when operated in light versus dark conditions. The uncertainty in readings due to background light was analyzed, and the error in the resistance was found to be of the order of 1.34 Ω, which confirms the high stability and selectivity of the proposed sensor under different background effects. Furthermore, the evolution of the graphene's lattice defect density due to radiation was observed using Raman spectroscopy and SEM, indicating a lattice defect density of up to 1.780 × 1011/cm2 at 1 kGy gamma radiation, confirming the increase in the graphene resistance and proving the graphene's sensitivity. In contrast, the graphene's defect density in response to beta radiation was 0.683 × 1011/cm2 at 3 kGy beta radiation, which is significantly lower than the gamma effects. This can be attributed to the lower p-doping effect caused by beta irradiation in ambient conditions, compared with that caused by gamma irradiation. Morphological analysis was used to verify the evolution of the microstructural defects caused by ionizing irradiation. The proposed sensor monitors the low-to-medium cumulative range of ionizing radiations ranging from 0 to 1 kGy for gamma radiation and 0 to 9 kGy for beta radiation, with high resolution and selectivity, filling the research gap in the study of graphene-based radiation sensors at low-to-medium ionizing radiation doses. This range is essential for the pharmaceutical and food industries, as it spans the minimum range for affecting human health, causing cancer and DNA damage.