In this present work, the cobalt tungstate (CoWO4) and La were doped into the CoWO4 structure with various percentages (1, 3, & 5%), then it was made into a nanocomposite when incorporated with a 2D layered rGO matrix. Bare, La doping and its nanocomposite were prepared via a simple chemical reflux method. From the structural analysis, the diffraction peak shifted to a higher 2θ and suppressed its intensity, signifying La interspaced into Co sites, which influences to generate internal stress in the host lattice and oxygen vacancies. Additionally, spherical NPs morphology can lead to even after La is doped into the host material lattice. The spin state of the cobalt element (Co2p) makes differentiated energies by the Co2p3/2–2p1/2 spin–orbit level energy spacing of 16.2 eV for high-spin Co2+ and low-spin Co3+. From the three-electrode configuration, CoWL5-rGO nanocomposite has exhibited specific capacitance (Csp) of 547.0847 Fg−1 at 1 Ag−1; b value of 0.7597, then surface-diffusion capacitance has 53.29% when compared to other counterparts. The high capacitance value achieved, due to the synergetic effect of dopant 5% La and 2D layered rGO sheet with metal oxides, has provided numerous active sites, facilitating ion transfer, improving electrolyte penetration and ionic conductivity when defects occur in the host material lattice. Finally, switch over to a real-time application, its fabricated asymmetric supercapacitor (ASC) CoWL5-rGO||rGO device has delivered 19.51 Fg−1 at 1 Ag−1, retains of 60% after 10,000 cycles, with energy density (ED) and power density (PD) of 6.94 W h kg−1 and 2399 W kg−1, respectively.

Lithium-ion batteries (LIBs) have become the leading energy storage systems for both portable electronic devices and stationary energy storage applications. However, their further advancement is hindered by the lack of fast-charging, durable anode materials. Metal-organic frameworks (MOFs) have emerged as promising candidate anode materials owing to their high porosity and diverse structures. This study developed a novel LIB anode Bi/C@C featuring a distinctive core-shell structure via a metal-organic framework (MOF)-derived approach, exhibiting rapid lithium storage performance (275 mAh g-1 at 5000 mA g-1) and exceptional cycling stability (85% capacity retention over 2000 cycles). This structure contains a 3D Bi-C porous core and a dense yet defect-rich carbon shell, enabling efficient ion/charge transport, functional interfacial isolation, and mechanical buffering against volume changes. DFT calculations further demonstrate that the core-shell structure possesses strong lithium-ion adsorption and a low reaction energy barrier (-0.32 eV), effectively facilitating electrochemical kinetics. Furthermore, the Bi/C@C-500//LiNi0.5Co0.2Mn0.3O2 full cell demonstrates unparalleled rate capacity (183 mAh g-1at 20 C) and remarkable cycling stability (86% capacity retention after 100 cycles). These findings establish the 3D porous core-shell Bi/C@C as a highly promising anode for LIBs, holding great significance for advancing the development of high-performance energy storage technologies.

High-energy-density lithium-sulfur batteries (LSBs) are promising next-generation energy storage systems but face challenges such as the polysulfide shuttle effect and sluggish reaction kinetics, leading to poor sulfur utilization and short cycle life. This study employed theoretical calculations to evaluate group VIII metal disulfides (MS2, M = Fe, Co, Ni) as sulfur host materials. Results indicated FeS2 exhibits stronger adsorption for lithium polysulfides (LiPSs) due to synergistic S-S covalent bonds and Fe-S coordination. Based on these insights, SMS2@KBCNT composites were synthesized as cathodes. Electrochemical tests demonstrated that the SFeS2@KBCNT cathode exhibited outstanding long-cycle performance, maintaining excellent cycling stability with a capacity decay rate of only 0.0564 % per cycle over 1,200 cycles at a current density of 0.5C. Even at 2C, it maintained structural stability and high discharge capacity, outperforming CoS2 and NiS2 counterparts. Adsorption experiments confirmed FeS2's strong affinity for LiPSs. Furthermore, FeS2 mitigates the shuttle effect and enhances redox kinetics by facilitating electron/ion transport. This study provides valuable guidance for designing high-performance sulfur hosts with suppressed shuttle effects in LSBs.

Carbon quantum dots (CQDs) possess excellent ultraviolet absorption, tunable photoluminescence, and environmental friendliness, making them strong candidates as phosphor alternatives for white light-emitting diodes (WLEDs). However, lighting devices based on single-component CQDs that enable continuously tunable correlated color temperature (CCT) remain relatively rare. In this study, we synthesized dual-emissive boron and nitrogen co-doped CQDs (B, N-CQDs) through a facile solvothermal approach, utilizing citric acid, 1,8-diaminonaphthalene, and boric acid as precursor materials. The obtained B, N-CQDs show bright white fluorescence with a high quantum yield (QY) of 35.4 % and dual emission peaks at 475 and 575 nm. Structural and optical characterization revealed that the short-wavelength emission state originates from surface states modified by boron hydroxyl bonds, while the long-wavelength emission is caused by additional electronic states introduced through doping. WLEDs fabricated using B, N-CQDs exhibit a sinusoidal correlation between their CCT and excitation wavelength. Therefore, CCT can be adjusted with near-infinite precision by altering the excitation wavelength of the UV chip; when the excitation wavelength changes from 325 to 380 nm, the CCT can be adjusted from 4218 K to 6072 K. This study provides a novel pathway toward environmentally friendly and highperformance WLEDs for multiple scenarios.

The construction of an anode material with a conversion-alloying dual mechanism is an efficient way to develop high energy density lithium-ion batteries (LIBs). Here, we report a novel conversion-alloying dual mechanism anode material of BiSBr for the first time, which significantly improves the efficient lithium storage. Owing to its unique open ribbon structure, BiSBr possesses a high Li+ diffusion and electrical conductivity of 141 S cm-1 along the c-axis. In-situ X-ray diffraction and ex-situ transmission electron microscopy analyses verify that Li-ion intercalation/deintercalation proceeds via both conversion and alloying/dealloying reactions, enabling a volumetric capacity of 4231 mAh cm-3 and a theoretical specific capacity of 644 mAh g-1 with an average working potential as low as 0.6 V. To tackle the problems of polysulfide dissolution and volumetric expansion, BiSBr nanorods were intimately encapsulated in flexible polypyrrole (PPy) shell to fabricate BiSBr-PPy core-shell composite, which demonstrates three times higher than that of BiSBr with a reversible capacity as high as 634 mAh g-1 at 100 mA g-1, maintaining 98 % theoretical specific capacity after 460 cycles. This work provides a feasible anode material with conversion-alloying dual mechanism that can be enhanced for high-performance lithium storage by polypyrrole coating.

In recent years, heterostructures composed of two-dimensional (2D) materials have demonstrated broad application prospects across various domains, primarily attributed to their exceptional electrical and optical properties. The superior performance of these heterostructures is rooted in the interlayer interactions and the diversity of the constituent materials. Notably, their applications have been greatly advanced in optical fields such as photodetectors, lasers, modulators, optical sensors, and nonlinear optics. etc. This review delineates the advancement of heterostructures based on 2D materials and discusses the electronic structural properties of their interfaces and band alignments while summarizing their carrier dynamics and nonlinear optical characteristics. Furthermore, it explores the synthesis techniques of 2D heterostructures and their applications as saturable absorbers in laser Q-switching and mode-locking, emphasizing the critical role that type-I and type-II heterojunctions have played in advancing laser technology. Lastly, the challenges and future opportunities in the application of 2D heterostructures in laser technologies are reviewed, offering insights on the potential directions for further research in this field.

Carbon quantum dots (CQD), with tunable surface properties and environmentally friendly, represent a practical approach for achieving deep blue solid-state fluorescence. However, to address the aggregation-caused quenching (ACQ) of CQD, researchers often modify it with polymer chains or incorporate macromolecular networks, which increases the complexity of the synthesis process and raises safety concerns. This study proposed a one-step, dope-free synthesis method of self-coated deep blue solid-state fluorescence CQD (DBSF-CQD). Citric acid and methanol were used to synthesize DBSF-CQD under solvothermal at 180 degrees C. Unlike conventional approaches that researchers eliminate ACQ by surface passivation or macromolecular networks. Here we provide an oxygen-rich reaction environment to hydroxyl/carboxyl-functionalize the DBSF-CQD surface, modulate the density of states to match with the precursor, and a self-coating precursor layer is formed by hydrogen bond adsorption. This strategy effectively eliminates ACQ and enables the synthesis of DBSF-CQD composed solely of carbon (C), hydrogen (H), and oxygen (O), offering an environmentally friendly and dope-free alternative method. The as-prepared DBSF-CQD exhibits deep blue emission at 417 nm with a quantum yield of 28 %, excellent anti-ACQ, and high stability due to a hydrogen-bond-induced self-coating layer. Furthermore, the applications of the DBSF-CQD in LEDs and fingerprint detection were explored. This work presents a green and sustainable approach to designing high-performance DBSF-CQD, paving the way for the next-generation deep blue materials.

Carbon quantum dots (CQDs) hold great potential as fluorescence probes due to their tunable optical properties, but remain challenges in tailoring surface functionalization for selective metal ion detection, which is essential for environmental monitoring and water quality analysis. This work, synthesized nitrogen and sulfur co-doped carbon quantum dots (N, S-CQDs) were via a one-pot solvothermal method with two different solvents, N, Ndimethylformamide (DMF) and acetone. The influences of solvent selectivity on the surface functionality of CQDs and their fluorescence quenching mechanisms were evaluated in both experimental and computational methods. To represent CQDs surfaces, density functional theory (DFT) calculations of the total density of states (TDOS) and partial density of states (PDOS) were conducted. Our findings revealed that synthesized CQDs in DMF and acetone exhibited fluorescence quenching as static and dynamic. We have achieved the highest quantum yields of 37.85 % and 28.59 %. This shows excellent sensitivities of Fe3+ at 0.82 mu M and 1.19 mu M for Co2+. Furthermore, the study extended to validated in real water sample analysis. This approach enabled the development of a novel strategy for the selective and sensitive detection of Fe3+ and Co2+ ions.

The synthesis and characterisation of two series of cyanoterphenyl-based liquid crystal dimers containing sulfur links between the spacer and mesogenic units, the 34-{ω-[(4'-cyano-[1,1'-biphenyl]-4-yl)thio]alkyl}-[11,21:24,31-terphenyl]-14-carbonitriles (CBSnCT), and the 34-({ω-[(4'-cyano-[1,1'-biphenyl]-4-yl)thio]alkyl}oxy)-[11,21:24,31-terphenyl]-14-carbonitriles (CBSnOCT) are described. The odd members of both series show twist-bend nematic and nematic phases, whereas the even members exhibit only the nematic phase. This is consistent with the widely held view that molecular curvature is a prerequisite for the observation of the twist-bend nematic phase. The nematic-isotropic and twist-bend nematic-nematic transition temperatures are higher for the dimers containing cyanoterphenyl groups than for the corresponding cyanobiphenyl-based dimers. This change is more pronounced for the nematic-isotropic transition temperatures and is attributed to the enhanced interaction strength parameter associated with the cyanoterphenyl fragment whereas the molecular shapes, as governed by the spacer, are rather similar. The behaviour of CBS2CT appears somewhat anomalous and exhibits a higher value of the twist-bend nematic-nematic transition temperature than expected, and this is attributed to the presence of highly bent molecular conformations.

Nitrogen doping is a widely used method for enhancing the performance of carbon quantum dots (CQD). However, the precise relationship between nitrogen content and emission spectra remains unclear when preparing high-performance nitrogen-doped CQD (N-CQD). This study systematically investigates the effects of nitrogen content on the crystalline structure, optical properties, and electronic band structure of N-CQD. Citric acid was used as the carbon source, and ethylenediamine monohydrate was used as the nitrogen source, with their ratio controlled to hydrothermal synthesized N-CQD with N/C ratios ranging from 0 to 0.4. Notably, when the N/C ratio increases from 0 to 0.2, the N-CQD exhibits redshifted emission with excitation dependence. However, when the N/C ratio rises from 0.2 to 0.4, the N-CQD shows blueshifted emission with excitation-independence. We define it as the dual-phase emission behavior of N-CQD attributed to the transition of doping sites from graphitic nitrogen to pyridine nitrogen with increased nitrogen content. DFT calculations indicate that different doping sites influence electron transfer in N-CQD, resulting in distinct optical behaviors. Importantly, this work comprehensively explains the relationship between nitrogen content and the emission behavior of N-CQD for the first time, providing crucial insights for refining the theoretical framework of N-CQD.

In this work, we show that a metasurface can be used to improve the performance of the two-dimensional (2D) material saturable absorber in a Nd:YVO 4 solid-state laser. To our knowledge, the hybrid saturable absorber was fabricated by spraying the NiPS 3 nanoflakes onto a silica metasurface for the first time. It is shown that the optical absorption, modulation depth, saturation intensity, and ultrafast recovery time of the metasurface-NiPS 3 saturable absorber exhibit better performance than the 2D material control device. In a proof-of-concept experiment, the Q-switched pulses with a pulse duration of 20.5 ns, repetition rate of 4.35 MHz, output power of 2.3 W, peak power of 30.61 W, and pulse energy of 0.63 μJ were experimentally demonstrated. These findings suggest that a hybrid saturable absorber is a promising candidate for developing pulsed laser and optical modulators.

This study investigated the polarization characteristics of nitrogen-doped carbon quantum dots (CQDs) and their correlation with nitrogen doping levels through experimental and theoretical approaches. We compared carbon quantum dots with different nitrogen doping contents and discovered that with increasing nitrogen content, the lattice dimensions of the nitrogen-doped CQDs decrease while their anisotropy becomes more distinct. These changes resulted in significant variations in polarization and phase. Furthermore, the introduction of nitrogen elements was found to influence the fluorescence emission properties of the CQDs as well as the hybridization state of the carbon atoms. The findings underscored the potential to tailor the polarization properties of carbon quantum dots through controlled nitrogen doping, opening up new avenues for their application in advanced display technologies.

Nitrogen-doped carbon quantum dots (N-doped CQDs) were prepared using a one-step sintering technique, with ammonium citrate as the precursor. These were compared to carbon quantum dots (CQDs) synthesized from citric acid. A range of characterization techniques, including x-ray diffraction analysis (XRD), raman spectroscopy, transmission electron microscopes (TEM), x-ray photoelectron spectroscopy (XPS), ultraviolet–visible absorption spectroscopy (UV–Vis absorption spectra), and fourier transform infrared spectroscopy (FT-IR spectra), were utilized to analyze the structures of two types of CQDs. The results revealed that nitrogen doping profoundly alters the carbon structure, promoting a shift from diamond-like carbon (sp3 C) to graphite carbon (sp2 C). This alteration greatly hastens the graphitization process of the CQDs, thereby broadening fluorescence emission specturm. Moreover, the fluorescenet properties of N-doped CQDs showed a pronounced sensitivity to pH variations. Specifically, the fluorescent properties of N-doped CQDs demonstrated notable sensitivity to pH variations. It was quantitatively represented by two distinct linear relationships: in acidic conditions, it follows y=0.28+1.08*x , and in alkaline conditions, y=15.06-x . (where y is the normalized fluorescence intensity and x is the pH value). For original CQDs, the change is less pronounced, with a linear relationship of y=6.62-0.022*x . Therefore, the N-doped CQDs exhibit a strong correlation between the fluorescence intensity and pH value in both acidic and alkaline environments, while also demonstrating the ability to change fluorescence color, indicating its potential applications in rapid response and convenient pH detection.

Bi2S3 holds immense potential to be promoted as an anode material for lithium-ion batteries (LIBs), owing to the high theoretical gravimetric and volumetric capacities. However, the poor electrical conductivity and volume expansion during cycling hinder the practical applications of Bi2S3. Therefore, through subsequent heat treatment, the nitrogen-doped carbon film was successfully loaded on the nanosphere Bi2S3, which we call nitrogen-rich carbon layer-coated Bi2S3 (NC@Bi2S3). Hence, the nanosphere Bi2S3 uniformly covered by a nitrogen-rich carbon layer was successfully coated on the Bi2S3 surface (NC@Bi2S3) through post-treatment. Due to the effective interaction between glutathione and inorganic materials, dopamine hydrochloride molecules are introduced and polymerized on the surface of the spherical Bi2S3 structure and then converted into a nitrogen-rich carbon layer with an average thickness of 10.0 nm. The electrochemical tests reveal that the discharge specific capacities of Bi2S3 and NC@Bi2S3 reach 340.99 and 645.13 mAh/g after 300 cycles at 100 mA/g, respectively. Kinetic analysis shows that the contribution of pseudocapacitance behavior increases by about 10% after the nitrogen-rich carbon layer is coated. These results suggest the potential of NC@Bi2S3 as a high-performance anode material for LIBs; the stability can be enhanced by core-shell structures.

Anode materials combining conversion and alloying mechanisms are increasingly valued in advanced rechargeable batteries for their exceptional theoretical capacities and advantageous working voltages. This study showcases BiSCl as a promising conversion/alloying anode material, demonstrating a high specific capacity and enhanced durability through polypyrrole encapsulation. Employing in-situ X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ex-situ transmission electron microscopy (TEM), and field emission scanning electron microscopy (FESEM), we offer a detailed analysis of the lithiation mechanism in BiSCl. The anode exhibits a low average working potential of approximately 0.6 V, supporting a theoretical specific capacity of 784 mAh g−1 and a volumetric capacity of 4664 mAh cm−3. The innovative BiSCl-PPy core-shell composite effectively addresses the challenges of volumetric expansion and polysulfide dissolution. This composite delivers a remarkable reversible capacity of 753 mAh g–1 at a current rate of 100 mA g−1, maintaining 96% of its specific capacity over 400 cycles, and sustains 419 mAh g–1 at 500 mA g−1 after 800 cycles, demonstrating more superior performance than that of BiSCl. These findings establish BiSCl as a highly promising conversion/alloying anode material for lithium storage, significantly enhanced in durability by the BiSCl-PPy core-shell composite.

Ni-rich layered transition metaloxides are promisingcathodesfor Li-ion batteries due to their low cost and high theoretical capacity.However, their practical applications are hindered by the capacityfading caused by intrinsic lattice structure variations, such as changesin the atom arrangement and valence. In situ neutron powder diffractionis a powerful technique for studying the structure of battery materialsand is expected to provide more information than other techniquesdue to its nondestructive, high-resolution, and light-element probingcapability. Herein, we employed neutron powder diffraction to probethe structural evolution during the synthesis of LiNi0.5Co0.2Mn0.3O2 in real time, includingthe transition metal-oxygen/lithium-oxygen (TM-O/Li-O)bond, phase formation, and lattice parameters as a function of temperatureand isothermal dwelling time. The results revealed that the latticestructure of cathode materials is a function of temperature and isothermaldwelling time. Variations of the TM-O/Li-O bond andlattice parameters with the dwelling time at an annealing temperatureof 850 degrees C indicated that the instability of the structure ofthe layered transition metal oxides may be a possible mechanism forthe changes in the discharging capacity and cycle stability of thebattery performance. Our findings provide insights into the correlationbetween the annealing time of NCM cathodes and the electrochemicalperformance and can be very helpful for synthesizing high-performancetransition metal layered oxide materials.

In this study, single-crystalline BiSBr is synthesized using a solution-based approach and conducted a systematic characterization of its photoelectric properties and photovoltaic performances. UV photoelectron spectroscopy and density functional theory (DFT) calculations reveal that BiSBr is an indirect p-type semiconductor, characterized by distinct positions and compositions of the valence band maximum and conduction band minimum. The BiSBr single crystal microrod features a significant electrical conductivity of 14 800 S m-1 along the c-axis, denoting minimal carrier resistance in this direction. For photovoltaic performance assessment, the authors successfully fabricated two homogeneous BiSBr films on TiO2 porous substrates: A microsheet array film via physical vapor deposition (PVD) and solvothermal treatment, and a BiSBr microsheet film via PVD and thermal treatment. The solar cell, comprising a BiSBr microsheet array film with an architecture of fluorine-doped tin oxide FTO/TiO2/BiSBr/(I3-/I-)/Pt, demonstrated a power conversation efficiency of 1.40%, approximate to 11 times that of BiSBr microsheet film counterpart. These preliminary results underscore the potential of BiSBr microsheet arrays, producible through low-cost solution processes, as adept light absorbers, enhancing photovoltaic efficiency through effective light scattering and promoting efficient electron-hole separation and transport. A single-crystalline BiSBr microsheet array film is successfully fabricated on a porous TiO2 film through physical vapor deposition (PVD) followed by a solvothermal treatment. Utilizing this film, solar cells with an FTO/TiO2/BiSBr/(I3-/I-)/Pt structure are constructed, exhibiting enhanced light absorption due to scattering, which results in a power conversion efficiency of 1.40%.image

To overcome the application limitations of the individual 2D materials, the Bi2Te3/Sb2Te3-Graphene (BTST-G) bidirectional heterostructures (BHSs) with high crystallinity and significantly enhance optical properties are constructed by a simple self-assembly solvothermal method for the first time. The BHSs not only combine the narrower band gap, larger modulation depth of BTST but also integrate the higher carrier mobility of graphene, enabling them to be excellent absorbers (SAs) for ultra-short-pulse laser technology. This paper further demonstrates that the stable passively Q-switched laser operation can be self-started immediately at a relatively low threshold power of 50 mW using the BTST-G BHSs. The shortest pulse width of 160 ns with a repetition rate of 1026 kHz is obtained, corresponding to the pulse energy of 2.0 & mu;J and the output power of 2.043 W. Compared with the ST-G, BT-G, the peak power increases 2 times and the pulse width is compressed by 66%. This work paves the way for future fabrication of unprecedented 2D heterostructures for application in pulse laser and other research which will bring more opportunities and challenges for the development of science technology and industry.

An optical design study of a beamline proposed for the 3 GeV synchrotron radiation facility, the Shenzhen Light Source, is described. The beamline was designed to cover an energy range from 2.0 to 20 keV with two experimental station, one for X-ray absorption spectroscopy (XAS) experiments and the other for X-ray photon correlation spectroscopy (XPCS) experiments. A 4 m planar undulator with a relatively short magnetic period (20 mm) was used as the radiation source. Horizontally and vertically focusing mirrors separately focus the source along the horizontal and vertical directions, respectively, thus enhancing the flexibility of the beamline. The focus point was employed as the secondary source, and a pair of KB mirrors were used to achieve a near-circular focus spot of about 4.5 mu m x 4.5 mu m. A Si(111) DCM was selected to produce the monochromatic light that covers the 2.0-20 keV energy range. When the photon energy is lower than 10 keV, the energy resolution can be better than 1.47 x 10-4 and the total flux is larger than 1 x 1014 photons/s. The longitudinal coherence length is in a few mu m range. With aperture size adjustment, the transverse coherence length at the sample position is approximately 3 mu m and the coherent flux is up to 1012 phs/s for the photon energy around 2.5 keV. This excellent coherence performance can be applied for the purpose of X-ray photon correlation spectroscopy related experiments.