Explore the vast range of titles available.

As a typical class of single‐atom catalysts (SACs) possessing prominent advantages of high reactivity, high selectivity, high stability, and maximized atomic utilization, emerging metal‐nitrogen‐doped carbon (M‐N‐C) materials, wherein dispersive metal atoms are coordinated to nitrogen atoms doped in carbon nanomaterials, have presented a high promise to replace the conventional metal or metal oxides‐based catalysts. In this work, recent progress in M‐N‐C‐based materials achieved in both theoretical and experimental investigations is summarized and general principles for novel catalysts design from electronic structure modulating are provided. Firstly, the applications and mechanisms on the advantages and challenges of M‐N‐C‐based materials for a variety of sustainable fuel generation and bioinspired reactions, including the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen evolution reaction (HER), carbon dioxide reduction reaction (CO2RR), nitrogen reduction reaction (NRR), and nanozyme reactions are reviewed. Then, strategies toward enhancing the catalytic performance by engineering the nature of metal ion centers, coordinative environment of active centers, carbon support, and their synergistic cooperation, are proposed. Finally, prospects for the rational design of next generation high‐performance M‐N‐C‐based catalysts are outlined. It is expected that this work will provide insights into high‐performance catalysts innovation for sustainable and environmental technologies. The rational design of metal‐nitrogen‐doped carbon (M‐N‐C) materials is at the cutting‐edge of materials research. Herein, the recent progress of M‐N‐C in sustainable fuel generation and biological applications is reviewed. General principles toward designing high‐performance M‐N‐C based nanocatalysts by engineering the nature of metal ion centers, the coordinative environment of active centers, the carbon support, and beyond are outlined.

This review focuses on optical refrigeration with the anti-Stokes fluorescence of rare-earth (RE)-doped low-phonon micro- and nanocrystals. Contrary to bulk samples, where the thermal energy is contained in internal vibrational modes (phonons), the thermal energy of nanoparticles is contained in both the translational motion and internal vibrational (phonons) modes of the sample. Much theoretical and experimental research is currently devoted to the laser cooling of nanoparticles. In the majority of the related work, only the translational energy of the particles has been suppressed. In this review, the latest achievements in hybrid optical refrigeration of RE-doped low-phonon micro- and nanoparticles are presented. Hybrid cooling permits the suppression of not only the translational energy of the RE-doped particles, but also their internal vibrational phonon thermal energy. Laser cooling of nanoparticles is not a simple task. Mie resonances can be used to enhance laser cooling with the anti-Stokes fluorescence of nanoparticles made of low-phonon RE-doped solids. Laser-cooled nanoparticles is a promising tool for fundamental quantum-mechanical studies, nonequilibrium thermodynamics, and precision measurements of forces.

High-precision placement of rare-earth ions in scalable silicon-based nanostructured materials exhibiting high photoluminescence (PL) emission, photostable and polarized emission, and near-radiative-limited excited state lifetimes can serve as critical building blocks toward the practical implementation of devices in the emerging fields of nanophotonics and quantum photonics. Introduced herein are optical nanostructures composed of arrays of ultrathin silicon carbide (SiC) nanowires (NWs) that constitute scalable one-dimensional NW-based photonic crystal (NW-PC) structures. The latter are based on a novel, fab-friendly, nanofabrication process. The NW arrays are grown in a self-aligned manner through chemical vapor deposition. They exhibit a reduction in defect density as determined by low-temperature time-resolved PL measurements. Additionally, the NW-PC structures enable the positioning of erbium (Er ) ions with an accuracy of 10 nm, an improvement on the current state-of-the-art ion implantation processes, and allow strong coupling of Er ions in NW-PC. The NW-PC structure is pivotal in engineering the Er -induced 1540-nm emission, which is the telecommunication wavelength used in optical fibers. An approximately 60-fold increase in the room-temperature Er PL emission is observed in NW-PC compared to its thin-film analog in the linear pumping regime. Furthermore, 22 times increase in the Er PL intensity per number of exited Er ions in NW-PC was observed at saturation while using 20 times lower pumping power. The NW-PC structures demonstrate broadband and efficient excitation characteristics for Er , with an absorption cross-section (~2 × 10 cm ) two-order larger than typical benchmark values for direct absorption in rare-earth-doped quantum materials. Experimental and simulation results show that the Er PL is photostable at high pumping power and polarized in NW-PC and is modulated with NW-PC lattice periodicity. The observed characteristics from these technologically friendly nanophotonic structures provide a promising route to the development of scalable nanophotonics and formation of single-photon emitters in the telecom optical wavelength band.

Chemical looping with oxygen uncoupling (CLOU) materials is actively sought for combustion of carbonaceous materials to achieve complete conversion and capture of carbon dioxide. These materials may play a vital role in reducing atmospheric carbon via negative carbon output. However, there is no one‐size‐fits‐all approach as different operating conditions and feedstocks may require different CLOU materials. As a result, the exploration and discovery of high‐performance CLOU materials can be a slow process. To address this challenge, a high‐throughput inverse machine learning workflow that identifies optimum materials from perovskite oxides for a given set of targets is developed—temperature and Gibbs free energy of oxygen formation. The model is trained on high‐throughput density functional theory calculations of CLOU materials and inverts the materials design process using a genetic algorithm to produce realistic substituted SrFeO3‐δ compositions as output. Using the inverse model, it is able to identify several interesting new families of CLOU materials: Sr1‐xAxFe1‐yByO3‐δ (e.g., A = Ca or K; B = Mg, Bi, Mn, Ni, Co, Cu, or Zn). These materials have shown promising properties, and some of them even outperform the benchmark material in terms of oxygen release kinetics under relevant CLOU operating conditions. Taking the calculated Gibbs free energy of oxygen vacancy formation as inputs, an inverse high‐throughput machine learning workflow is developed to predict chemical formula of perovskite for chemical looping applications. Using this generic algorithm model, several new families of perovskites are identified as useful oxygen carrier materials. Particularly, a predicted new high‐performance oxygen carrier material, Sr0.89K0.11Fe0.80Zn0.20O3‐δ, is experimentally verified.

Single‐atom catalysts (SACs) have garnered interest in designing their ligand environments, facilitating the modification of single catalytic sites toward high activity and selectivity. Despite various synthetic approaches, it remains challenging to achieve a catalytically favorable coordination structure simultaneously with the feasible formation of SACs at low temperatures. Here, a new type of coordination structure for Pt SACs is introduced to offer a highly efficient hydrogen evolution reaction (HER) catalyst, where Pt SACs are readily fabricated by atomically confining PtCl2 on chemically driven NO2 sites in two‐dimensional nitrogen‐doped carbon nanosheets at room temperature. The resultant Pt SACs form the NO2–Pt–Cl2 coordination structure with an atomic dispersion, as revealed by X‐ray spectroscopy and transmission electron microscopy investigations. Moreover, our first‐principles density functional theory (DFT) calculations show strong interactions in the coordination by computing the binding energy and charge density difference between PtCl2 and NO2. Pt SACs, established on the NO2‐functionalized carbon support, demonstrate the onset potential of 25 mV, Tafel slope of 40 mV dec−1, and high specific activity of 1.35 A mgPt−1. Importantly, the Pt SACs also exhibit long‐term stability up to 110 h, which is a significant advance in the field of single‐atom Pt catalysts. The newly developed coordination structure of Pt SACs features a single Pt active center, providing hydrogen binding ability comparable to that of Pt(111), enhanced long‐term durability due to strong metal‐support interactions, and the advantage of room‐temperature fabrication. This study presents the fabrication of Pt SACs with a new type of coordination environment at room temperature by introducing the chemically driven NO2 sites for atomically immobilizing PtCl2 on two‐dimensional nitrogen‐doped carbon nanosheets. The result is that Pt SACs demonstrate long‐term durability in hydrogen evolution reactions due to their stable coordination environment, which comprises the NO2–Pt–Cl2 structure.

Many interesting materials phenomena such as the emergence of high- T c superconductivity in the cuprates and colossal magnetoresistance in the manganites arise out of a doping-driven competition between energetically similar ground states. Doped multiferroics present a tantalizing evolution of this generic concept of phase competition. Here, we present the observation of an electronic conductor–insulator transition by control of band-filling in the model antiferromagnetic ferroelectric BiFeO 3 through Ca doping. Application of electric field enables us to control and manipulate this electronic transition to the extent that a p–n junction can be created, erased and inverted in this material. A ‘dome-like’ feature in the doping dependence of the ferroelectric transition is observed around a Ca concentration of ∼1/8, where a new pseudo-tetragonal phase appears and the electric modulation of conduction is optimized. Possible mechanisms for the observed effects are discussed on the basis of the interplay of ionic and electronic conduction. This observation opens the door to merging magnetoelectrics and magnetoelectronics at room temperature by combining electronic conduction with electric and magnetic degrees of freedom already present in the multiferroic BiFeO 3 . Multiferroics offer intriguing opportunities for sensing and information storage applications, although their integration into electronic devices has been difficult owing to a lack of suitable electronic control. Electric modulation of conduction is now achieved for a doped multiferroic, resulting in complete control over the ferroelectric state itself.

Optical fibers are the basis for applications that have grown considerably in recent years (telecommunications, sensors, fiber lasers, etc). Despite undeniable successes, it is necessary to develop new generations of amplifying optical fibers that will overcome some limitations typical of silica glass. In this sense, the amplifying Transparent Glass Ceramics (TGC), and particularly the fibers based on this technology, open new perspectives that combine the mechanical and chemical properties of a glass host with the augmented spectroscopic properties of embedded nanoparticles. This paper is an opportunity to make a state of the art on silica-based optical fibers containing nanoparticles of various types, particularly rare-earth-doped oxide nanoparticles, and on the methods for making such fibers. In the first section of this article, we will review basics on standard optical fibers and on nanoparticle-doped fibers. In the second section we will recall some fabrication methods used for standard optical fibers, and in the third section we will describe how TGC fibers can be obtained. This new generation of fibers, initiated a decade ago, already show very positive outlook and results departing from those obtained previously in homogeneous silica fibers. The next few years should see the emergence of new components based on these optical fibers.

Iron-doped Zinc oxide nanoparticles were produced by the sol-gel combustion method. This study aims to see how iron doping affects the structural, optical, and photocatalytic characteristics of ZnO composites. XRD examined all samples to detect the structural properties and proved that all active materials are a single hexagonal phase. The morphology and particle size were investigated by TEM. Computational Density functional theory (DFT) calculation of the band structure, density of state, and charge distributions for ZnO were investigated in comparison with ZnO dope iron. We reported the application results of ZnO doped Fe for Methylene blue dye removal under photocatalytic degradation effect. The iron concentrations affect the active material’s band gap, producing higher photocatalytic performance. The acquired results could be employed to enhance the photocatalytic properties of ZnO.

Heterometallic zeolite imidazole framework materials (ZIF) exhibit highly attractive properties and have drawn increased attention. In this study, a petal-like zinc based ZIF-8 crystal and materials doped with cobalt and nickel ions were efficiently prepared in an aqueous solution at room temperature. It was observed that doped cobalt and nickel had obviously different effects on the morphology of ZIF-8. Cobalt ions were beneficial for the formation of ZIF-8, while addition of nickel ions tended to destroy the original configuration. Then we compared the absorption ability for metal ions between petal-like ZIF-8 and its doped derivatives with anion dichromate ions (Cr2O72−) and cation copper ions (Cu2+) as the absorbates. Results indicated that saturated adsorption capacities of Co@ZIF-8 and Ni@ZIF-8 for Cr2O72− reach 43.00 and 51.60 mg/g, while they are 1191.67 and 1066.67 mg/g for Cu2+, respectively, which are much higher than the original ZIF-8 materials. Furthermore, both the heterometallic ZIF-8 materials show fast adsorption kinetics to reach adsorption equilibrium. Therefore, petal-like ZIF-8 with doped ions can be produced through a facile method and can be an excellent candidate for further applications in heavy-metal treatment.

Nanocomposites based on chitin (CT) and cashew gum (CG) with different concentrations of silver doped zinc oxide nanoparticles (Ag–ZnO) were prepared and characterized by FTIR, UV, XRD, TEM, SEM, DSC, TGA, electrical conductivity measurements. FTIR spectra showed that the characteristic absorption band of the blend was shifted to a higher frequency in nanocomposites, indicating the intermolecular interaction between the blend and nanoparticles. The change in the UV absorption of nanocomposites relative to that of pure blend indicated the successful encapsulation of crystalline metal oxide nanoparticles in the blend matrix. XRD patterns showed that the diffraction peak of the composites were shifted near to the metal oxide peak which indicated that the surface of Ag–ZnO was perpendicular to CT/CG and changed from a semi-crystalline nature to a crystalline structure. The morphological analysis using SEM and TEM showed a uniform attachment of nanoparticles within the CT/CG blend. DSC analysis showed the increased glass transition temperature by the addition of nanoparticles. Thermal stability of nanocomposites was higher than the blend and thermal stability increased with an increase in the content of nanoparticles. The different electrical properties such as AC conductivity and dielectric behaviour of the composites were increased with an increased loading of nanoparticles.