Lithium niobate crystal exhibits versatile properties including piezoelectric, nonlinear and birefringence. Its stable physicochemical characteristics, doping amenability, and suitability for high-quality optical waveguide fabrication make it promising for integrated optics. However, the growth of large-size lithium niobate crystals presents significant challenges, with several critical issues remaining unresolved. Firstly, its low thermal conductivity causes a heat accumulation at the crystal-melt interface due to mismatched latent heat transport and release rates. This leads to eccentric growth and interface remelting. Secondly, the large crucible required for large-size crystal growth results in a reduced radial temperature gradient across the melt surface and an oversized cold core, which complicates necking initiation and shouldering control, ultimately compromising crystallinity. Finally, fixed thermal field configurations fail to accommodate divergent thermal requirements across different growth stages as crystal size increases. In this study, the fixed thermal field configuration and methodologies for mitigating eccentric crystal growth were investigated. In addition, the impact of dynamic thermal fields on stage-specific thermal requirements during crystal growth was also analyzed.

This work conducted the Czochralski growth of 6 in CLN (congruent lithium niobate) crystals in a fixed thermal field. A preliminary 6 in thermal field was firstly designed according to the CLN crystal growth requirements, and then by root-cause analysis of eccentric growth and thermal field optimization. The crucible position relative to the induction coil was gradually elevated, while maintaining identical growth parameters. Subsequently, comparative experiments of fixed crucible position and constant process conditions with the diminished upper insulation assessed their impact on the eccentric growth. To resolve conflicting thermal requirements across growth stages, a dynamic thermal field Czochralski technique was developed via integrating an active afterheater. This enabled real-time regulation of the temperature gradient by adjusting power to the main heater and active afterheater. Comparative analysis of the constant-diameter lengths in grown crystals could demonstrate the efficacy of the dynamic thermal field technique.

In a fixed thermal field, the causes of eccentric growth during the late constant-diameter growth stage are analyzed. During the actual crystal growth, the melt level progressively decreases as the constant-diameter length increases, gradually revealing an exposed crucible wall effect. This reduces the radial temperature gradient across the melt surface. Simultaneously, a radiative influence from the crucible wall appears on the crystal intensifies. When crystallization latent heat cannot be efficiently transported from the crystal, a heat accumulation occurs, triggering random protrusions at the solid-liquid interface that radiate heat directly upward, resulting in eccentric growth. Thermal field optimization is achieved via elevating the crucible position relative to the induction coil and reducing upper insulation. Consequently, the constant-diameter length increases from 15 mm to approximately 70 mm, effectively mitigating an eccentric growth.

The development of a dynamic thermal field crystal growth technique, enabled by the introduction of an active afterheater, demonstrates critical advantages over conventional fixed thermal fields, i.e., 1) Fixed thermal fields exhibit temperature gradients solely determined by structural design, precluding manual intervention during growth. Conversely, dynamic thermal fields facilitate different temperature gradient control in different stages through coordinated power modulation of the primary and secondary heaters, thereby altering system heat dissipation, 2) Large-size crystal growth requires substantial melt volumes with a high thermal mass, resulting in prolonged adjustment response time and significant thermal hysteresis. The dynamic approach achieves a superior diameter control via directly manipulating furnace heat dissipation by an active afterheater power. This rapidly modifies temperature gradients within the crystal bulk and near the solid-liquid interface, reducing hysteresis and enabling diameter precision, and 3) Unlike fixed configurations necessitating furnace shutdowns due to thermal design failures, dynamic systems resolve thermal incompatibilities control through power adjustments to the MF (Medium-Frequency) Power Supply and active afterheater. This eliminates costly interruptions, saving both time and cost.

This work designed a fixed thermal field for 6 in CLN crystal growth. The analysis revealed that the primary cause of eccentric growth in 6 in CLN crystal was an insufficient radial temperature gradient across the melt surface during the late constant-diameter growth stage. The thermal field optimization was achieved via elevating the crucible position relative to the induction coil and reducing upper insulation, extending the constant-diameter length from 15 mm to approximately 70 mm.

To address limitations in fixed thermal field optimization, a dynamic thermal field Czochralski technique was developed, which enabled real-time regulation of temperature gradients during crystal growth. This approach could accommodate divergent thermal requirements across different growth stages, significantly mitigating an eccentric growth in 6 in CLN crystal and further increasing the constant-diameter length from 70 mm to 90 mm, thus establishing a novel paradigm for large-sizer crystal growth.

Lasers operating within a spectral range of 1.5-1.7 μm are essential for eye-safe applications like laser ranging, lidar, and optical communications, etc.. Nevertheless, conventional laser crystals such as Er:YAG and Er:LuYO₃ have limitations in emission cross-sections or attainable crystal dimensions, thereby constraining their utilization in high-power, large-scale laser systems. To address these challenges, the development of novel laser crystals with substantial crystal sizes and high emission cross-sections is thus imperative. Yttria-stabilized zirconia (YSZ) doped with rare-earth ions emerges as a promising candidate due to its disordered crystalline structure that enables a broader wavelength tunability and a reduced thermal loading under resonant pumping conditions. Specifically, erbium (Er³⁺) doped YSZ crystals have a significant potential due to its intense emission at 1.5 μm (⁴I_13/2→⁴F_15/2 transition) for eye-safe laser. This study was to investigate the growth of large-scale Er³⁺-doped YSZ crystals by a skull melting technique, and the optical and spectral properties were systematically investigated to explore a novel laser gain medium in the infra-red region.

Pure YSZ and Er³⁺-doped YSZ crystals (i.e., 0.36%, 1.60% and 2.54% in mole) were grown by a skull melting method (or a cold crucible technique), and a radio frequency (RF) generator was used to heat up the charges. A large-scale furnace with a diameter of approximately 150 cm was employed to accommodate the spontaneous nucleation. Graphite electrodes were used for initial arcing due to the poor conductivity of ZrO₂ at < 1200 ℃. At >1200 ℃, raw materials became an electric conductor to form the melting pool. The lowering mechanism started to work at a lowering rate of 2 mm/h, and the melt crystallized from the bottom to the top. After the growth, annealing process was performed to release the internal stresses. The phase and crystal structures of as-grown crystals were characterized by X-ray diffraction (XRD). The transmittance and absorption properties were analyzed by UV-Vis-NIR spectroscopy. The luminescence and decay curve were also systematically evaluated.

The results show that Large-sized YSZ and Er-doped YSZ crystals with the diameters and lengths of exceeding 150 mm (6 inches) are grown, representing the largest YSZ single crystals reported. The XRD patterns indicate the cubic structure with a preferred <111> preferred orientation. The lattice parameters increase slightly with Er³⁺ concentration, indicating the effective incorporation of Er³⁺ into the YSZ lattice. The transmission of exceeding 74% in the range of 400-1650 nm occurs for pure YSZ crystals, confirming relatively high crystalline qualities. The absorption spectra for Er-doped crystals show some characteristic peaks at 378, 408, 451, 489, 518, 546, 654, 971, 1460 nm and 1530 nm, corresponding to Er³⁺ transitions from the ground state ⁴F_15/2 to excited states such as ⁴G_11/2 and ⁴F_11/2. The most intense absorption band occurs at 971 nm, which is attributed to the ⁴F_15/2→⁴F_11/2 transition. Under 971 nm excitation, the emission spectra exhibit a dominant peak at 1530 nm for the ⁴I_13/2→⁴F_15/2 transition, which is ideal for eye-safe lasers. The great emission intensity appears at an Er³⁺ mole concentration of 1.60%, with an emission cross-section of 4.811×10^-20 cm², which is significantly higher than that of Er:YAG (i.e., 0.6×10^-20 cm²) and Er:LuYO₃ (i.e., 0.261×10^-20 cm²). Correspondingly, the decay time of YSZ: 0.36, YSZ: 1.60and YSZ: 2.54 crystals is 1.836 ms, 1.149 ms and 0.797 ms, respectively.

This study demonstrated the effective growth of large-scale (6-inch) YSZ and Er-doped YSZ crystals by a skull melting method. YSZ: Er crystals exhibited an intense emission at 1530 nm under 971 nm excitation. In particular, a high emission cross-section of 4.811×10^-20 cm² and suitable fluorescence lifetime of 1.149 ms appeared for Er³⁺ of 1.60% in mole. YSZ:Er crystals could be used as a highly promising gain medium for high-power, eye-safe lasers at 1.5 μm due to the ultra-large crystal size and relatively large emission cross-section.

This review analyzes critical oxygen control strategies in CZ silicon growth, essential for achieving substrate specifications across diverse applications. The primary approaches focus on reducing oxygen dissolution through thermal field design and crucible modification, optimizing melt convection and oxygen transport via rotation and magnetic fields, and enhancing free surface volatilization by controlling argon atmosphere.

Some challenges persist, requiring a further research to clarify fundamental mechanisms. Key uncertainties include the temperature dependence of oxygen solubility and the precise mechanism relating crucible temperature reduction to lower crystal oxygen levels (primarily due to reduced dissolution or altered flow patterns). Understanding the complex coupling among detailed magnetic field distributions, resulting melt flow patterns and oxygen transport also requires a further investigation. Quantifying the influence of argon shear stress interacting with Marangoni forces on the melt surface is equally essential for refining volatilization models.

Furthermore, complicating these challenges is the multi-variable, strongly coupled nature of the CZ system, which makes conventional trial-and-error optimization approaches time-consuming and costly. A future research should therefore prioritize the developing intelligent control systems that leverage artificial intelligence (AI) and machine learning for data-driven modeling, prediction, and efficient multi-parameter optimization.

The increasing risk of heavy metals causes many concerns as one of the nonnegligible problems in modern environmental conservation. As one of the most common heavy metals, copper (II) has a dominant effect in such a pollution. The accumulation of copper (II) in water can eventually give rise to the overexpression of copper in humans, showing to be directly associated with Alzheimer's, Parkinson's, Menkes, and Wilson's disease. As a result, the residue of copper (II) in wastewater becomes a ubiquitous environmental challenge. The development of smart materials that are capable of detecting and removing copper (II) simultaneously can pave an effective approach to solving this puzzling issue. Halloysite nanotubes (HNTs) are natural hollow aluminosilicate clays with a chemical composition similar to kaolin (i.e., Al₂Si₂O₅(OH)₄·nH₂O). HNTs display a superior water dispersibility due to the large cavity volume and surface charge repulsion. The attractive properties including low-cost, environmental friendliness, biocompatibility, good stability, and ease of surface modification also make HNTs promising composite materials in the fields of environmental protection, catalysts, bio-medical materials, and sensors.. In this study, tetraphenylethene (TPE) moiety was immobilized on aminated HNTs with oxalyl chloride for the preparation of TPE-functionalized HNTs (HNTs-TPE-NH₂).

TPE-2NH₂ (184 mg, 0.5 mmol), HNTs-COCl, mL and and 10 N,N-Dimethylformamide (DMF) were mixed in a flask. The system was stirred at room temperature to make nanoparticles well-dispersed and then reacted at 60 ℃ for 8 h. After cooling to ambient temperature, the suspension was centrifugated and the obtained residue was washed by DMF, tetrahydrofuran (THF), and ethanol.

The coumarin unit was bonded to the HNTs-TPE-NH₂ via a condensation reaction by treating 7-hydroxy-2-oxo-2H-chromene-5-carbaldehyde with HNTs-TPE-NH₂ to afford the Schiff base-containing product (HNTs-TPE-Cou). HNTs-TPE-NH₂ (1.0 g) and compound M1 (50 mg, 0.25 mmol) were added to a flask containing absolute ethanol (15 mL), and vacuum-filled with argon gas was repeated for three times. The mixture was refluxed and stirred at 70 ℃ for 12 h. After cooling to ambient temperature, the suspension was centrifugated and the obtained residue was washed sequentially by THF and ethanol. After vacuum-drying, the product HNTs-TPE-Cou was obtained as a faint yellow solid. The obtained HNTs-TPE-Cou was then deposited on the surface of polyurethane foam (PUF) to afford the composite PUF@HNTs-TPE-Cou based on the surface charge of the nanotubes. The obtained product HNTs-TPE-Cou was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, solid-state nuclear magnetic resonance spectroscopy, thermogravimetric analysis, transmission electron microscopy, respectively.

HNTs-TPE-Cou aqueous solution has a fluorescence emission peak at a wavelength of 560 nm. The chelation between Cu²⁺ and HNTs-TPE-Cou can destroy the aggregation state of TPE units and give rise to a "turn off" effect on the fluorescence intensity of HNTs-TPE-Cou aqueous solution. he maximum fluorescence intensity of HNTs-TPE-Cou appears as the Cu²⁺ ion concentration is 0 μmol/L. The fluorescence intensity of HNTs-TPE-Cou decreases gradually with the increase of Cu²⁺ ion concentration, showing a typical concentration-dependent manner. F₀ and F represent the fluorescent intensities at 560 nm without and with different concentrations of Cu²⁺ ion, respectively. The F₀/F of HNTs-TPE-Cou at 560 nm has a good linear correlation to the concentration of Cu²⁺ ion when the Cu²⁺ ion concentration in the solution to be measured is between 0.2 μmol/L and 0.6 μmol/L. Other metal ions, including Ni²⁺, Mg²⁺, Ca²⁺, Co²⁺, Mn²⁺, Al³⁺, Ba²⁺, Na⁺, K⁺, Zn²⁺, and Cd²⁺, do not exhibit the quenching phenomenon with the addition to HNTs-TPE-Cou aqueous solution.

The yielded PUF@HNTs-TPE-Cou composites are cut into special shapes to fill the glass columns. A Gel-like separation column is prepared, which can be used to retain Cu²⁺ ions selectively. Moreover, the fluorescence intensity can serve as a nake-eyes identified indicator, which is useful to display the degree of usage. When the fluorescence intensity changes to non-emission, it means the end of useful life, and new columns are needed. The column (20 cm × 2 cm) is used to purify the Cu²⁺-containing water ([Cu²⁺] = 1×10^-4 mol/L). The concentration of Cu²⁺ effluent water is detected. The results indicate the concentration of Cu²⁺ is lower than LOD calculated in the first 100 mL eluting water, having a high purification efficiency.

In this study, HNTs were used as scaffolds and surface modified with tetraphenylethylene and coumarin moieties. The obtained product HNTs-TPE-Cou could be used to detect and separate of Cu²⁺ ions in water solution. HNTs-TPE-Cou displayed an intense fluorescence emission peak at a wavelength of 560 nm in water under the excitation of 365 nm light, while a repaid "turn off" effect on fluorescence appeared, showing a chelation behavior after the addition of Cu²⁺ ions. The as-prepared HNTs-TPE-Cou had high specificity and precision in detecting and removing Cu²⁺ without the recourse to energy consumption. Furthermore, HNTs-TPE-Cou was developed as composite materials by a facile deposition method, which could be further used as gel-like separation columns. The established method could pave a path on the simultaneously detecting and removing metal ions in aqueous solution.

The key formation mechanisms and electrical properties of oxygen-related defects remain some challenges. The crystal growth for 300 mm wafers involves complex multi-physics (i.e., thermal, flow, electromagnetic fields) in large systems (i.e., 34-37 in crucibles, 300-450 kg charge). Maintaining radial uniformity is difficult due to the V/G criterion (where V is pull rate, and G is axial temperature gradient). Deviations lead to vacancy-rich (V) or interstitial-rich (I) regions, with a transition zone prone to forming a ring of "P-band" native oxygen-related defects. This causes a radial non-uniformity in oxygen clustering during device processing, concerning the radial defect non-uniformity and nucleation anomalies in 300 mm crystals. We should also focus on the interaction between oxygen-related defects and metallic impurities in Cz-Si used for solar cells.

We can benefit from effective control of oxygen-related defect in Large-diameter Cz-Si. The effective control requires a multi-pronged approach, i.e., sophisticated crystal growth optimization (thermal/flow fields, magnetic fields, doping), strategic impurity engineering (nitrogen, isovalent dopants), and tailored thermal processing. A further research into defect interactions, advanced characterization, and multi-scale modeling is essential for pushing the performance limits of next-generation silicon devices.

This paper was to prepare amino-modified porous geopolymer (NH₂-3HGeo) based on geopolymer via acid treatment and post-grafting, and investigate its adsorption performance and mechanism for lead in water. Acid treatment increased the specific surface area of the geopolymer and optimized its pore structure. The maximum adsorption capacity of NH₂-3HGeo for Pb²⁺ reached 521.6 mg·g^-1. The adsorption process followed the pseudo-second-order kinetics and the Langmuir model, indicating a monolayer chemical adsorption. Geopolymer could mainly adsorb Pb²⁺ through ion exchange, while NH₂-3HGeo primarily complexe with Pb²⁺ through functional groups. After five cycles, the Pb²⁺ removal rate of NH₂-3HGeo still reached 90.6%, demonstrating a good recyclability. The results indicated that the material could have a great potential in the field of heavy metal pollution control in water bodies.

In the preparation process of amino-modified porous geopolymer, 400 g of metakaolin and 100 g of white carbon black were uniformly mixed, and then put in a sodium hydroxide solution prepared via dissolving 200 g of NaOH in 400 mL of deionized water as an alkaline activator and 10 mL of hydrogen peroxide solution under stirring. The resulting slurry was cast into polypropylene cubic molds and finally cured in an oven at 80 ℃ for 24 h to obtain the geopolymer (Geo). Subsequently, Geo was crushed and sieved to a fine powder with the sizes of 20-40 mesh. 80 g of Geo was added into 400 mL of nitric acid solutions at different concentrations (i.e., 1, 2, 3, and 4 mol·L^-1). The mixtures were placed in a constant temperature oscillator and agitated in 200 r·min^-1 at 80 ℃ for 5 h. After the reaction, the mixtures were filtered through a 0.45 μm membrane, and the products were collected, washed until neutral, and dried in an oven at 105 ℃ for 12 h, resulting in acid-treated porous geopolymers (i.e., 1HGeo, 2HGeo, 3HGeo, and 4HGeo). Finally, 20 g of acid-treated porous geopolymer was placed in a round-bottom flask containing 100 mL of xylene and stirred for 30 min. Afterwars, 20 mL of aminopropyltriethoxysilane (APTES) dissolved in 100 mL of xylene was added to a flask and stirred with 200 r·min^-1 at 80 ℃ for 12 h. The solid product was collected, cleaned with xylene, and dried at 80 ℃ for 12 h to obtain the amino-modified porous geopolymers (i.e., NH₂-1HGeo, NH₂-2HGeo, and NH₂-3HGeo). In addition, the control sample NH₂-Geo was also prepared by the same procedure.

This study prepares amino-modified porous geopolymers via acid treatment and post-grafting with porous geopolymers as a base material. The results of the BET specific surface area measurement indicate that acid treatment significantly increases the BET specific surface area of the geopolymer material. The specific surface area of sample 3HGeo (i.e., 343.87 m²·g^-1) and pore volume (i.e., 0.1679 cm³·g^-1) are 12.94 times and 3.29 times greater than the specific surface area (i.e., 26.57 m²·g^-1) and pore volume (i.e., 0.0511 cm³·g^-1) of sample Geo, respectively. The XRD patterns, FTIR spectra, and thermogravimetric analysis show that acid treatment increases the porosity and silanol content of the porous geopolymers, thereby increasing the grafting amount of amino groups. The amino groups are grafted onto the geopolymers. The results of adsorption test show that the adsorption amount is positively correlated to the BET specific surface area and amino content. The adsorption rate of NH₂-3HGeo for Pb²⁺ rapidly increases and stabilize as the adsorbent dosage increases. of adsorption time, the removal rates of NH₂-1HGeo, NH₂-2HGeo, and NH₂-3HGeo for Pb²⁺ are 48.1%, 70.1%, and 99.9% at 360 min, 300 min, and 240 min, respectively, with the increase of adsorption time. The adsorption amount of Pb²⁺ increases as the temperature increases. The adsorption capacities of NH₂-1HGeo, NH₂-2HGeo, and NH₂-3HGeo increase as the initial Pb²⁺ concentration increases from 100 mg·L^-1 to 700 mg·L^-1. The adsorption amount continuously increases as the solution pH vale increases. Different coexisting ions (i.e., K⁺, Na⁺, Ca²⁺, and Mg²⁺) affect the adsorption performance of NH₂-3HGeo for Pb²⁺, with divalent cations having a greater impact than monovalent cations. The adsorption kinetics follows the pseudo-second-order model, indicating the chemical adsorption. The results of adsorption isotherm indicate that the adsorption process involves monolayer adsorption. The adsorption thermodynamic results show that moderately increasing the temperature is beneficial to adsorption. The results of recycling experiment show that after five cycles of adsorption-desorption, the adsorption rate of NH₂-3HGeo remains 90.2%, having a good recyclability. The contribution of different adsorption mechanisms indicates that Geo mainly adsorbs Pb²⁺ through ion exchange, while NH₂-3HGeo primarily relies on a functional group chelation.

Amino-modified porous geopolymers with a high specific surface area and a multi-pore structure were prepared by acid treatment and amino modification with porous geopolymers as a base material. The results of nitrogen adsorption showed that acid treatment significantly increased the specific surface area of the geopolymer and effectively improved the pore structure. The thermogravimetric analysis indicated that acid treatment created more active sites on the surface of the geopolymer (such as silanol groups Si—OH), which could act as active centers for subsequent grafting reactions. The prepared NH₂-3HGeo sample had a high adsorption capacity for Pb²⁺ and a good recyclability, with a maximum adsorption capacity for Pb²⁺ of 521.6 mg·g^-1. After five adsorption-desorption cycles, the adsorption rate was still 90.2%, providing an effective approach for the application of geopolymer materials in the treatment of heavy metal-containing wastewater. The results of XPS analysis showed that the complexation between—NH₂ and Pb²⁺ essentially involved the protonation of —NH₂ to form —NH₃⁺. The adsorption mechanisms indicated that Geo mainly adsorbed Pb²⁺ through ion exchange, while NH₂-3HGeo primarily did that through functional group chelation. This work could lay a certain theoretical foundation for understanding the microstructure of geopolymers and modified geopolymers, as well as the mechanism of their adsorption of heavy metal ions.

UiO-66-NH₂ is used as a photocatalyst for CO₂ reduction, but it still faces some problems such as a narrow light absorption range, easy agglomeration, and a high recombination rate of electron-hole pairs. Various modification strategies (i.e., metal doping, introducing cocatalysts, and constructing heterojunctions with semiconductors) are proposed to enhance their photocatalytic efficiency. Although these methods can effectively improve the performance of the catalysts, the high synthesis cost of MOFs still restricts their practical application. Using widely available and low-cost natural non-metallic minerals as supports to develop high-performance composite catalysts can significantly reduce the production and application costs of catalysts and effectively enhance their application performance. Compared to conventional three-dimensional porous materials, diatomite has abundant active hydroxyl groups on its surface, which are the main reaction sites for surface grafting and coordination, having a good affinity for organic ligands. In addition, the alkaline centers on the surface of diatomite also have a certain catalytic assistance effect. In this paper, a purified diatomite was used as a support, and UiO-66-NH₂ was anchored on the surface and in the pores of diatomite by an one-step hydrothermal method to prepare UiO-66-NH₂/diatomite composite, thereby providing an idea for the development of low-cost and high-performance photocatalytic CO₂ reduction materials.

In the synthesis of pure UiO-66-NH₂, ZrCl₄ (0.170 g) and 2-aminoterephthalic acid (0.132 g) were dissolved in a mixed solvent of 24 mL of DMF (N,N-Dimethylformamide) and 6 mL of CH₃COOH. After magnetic stirring for 2 h, the solution was transferred to a 100 mL autoclave and reacted at 120 ℃ for 24 h. After reaction completion, the sample was cooled naturally to room temperature. Subsequently, the product was centrifugally washed for three times with DMF and for three times with C₂H₅OH. Finally, the washed sample was dried in a vacuum oven at 60 ℃ for 8 h to obtain the UiO-66-NH₂ catalyst, designated as UN (UiO-66-NH₂). In the purification via acid leaching, the refined diatomite was employed as a catalyst support. The synthesis method of UND (UiO-66-NH₂/diatomite) composite was as folllows, i.e., a similar method to UN synthesis was employed, with the sole difference at varying masses of diatomite during synthesis. The composites were named as UND-X (where X denotes the theoretical loading of UN).

A 5 mg sample of the photocatalyst was dispersed in 10 mL deionized water. The mixture was vacuum-filtered, and the resulting catalyst-loaded mixed cellulose filter membrane was dried at 40 ℃ for overnight . The membrane was then positioned in a 115 mL photoreactor with 1 mL deionized water added as a sacrificial agent. High-purity CO₂ (99.999%) served as a feedstock gas. In dark adsorption equilibrium, irradiation was performed using a 300 W xenon lamp (i.e., at 320 ≤ λ ≤ 780 nm). Gaseous products were quantified by gas chromatography (GC). The product identification was established through retention time matching, with quantification calibrated against standard curves generated with certified gas mixtures. The photocatalytic CO₂ reduction performance was evaluated via calculating the yield of reduction products per unit mass of catalyst per unit time.

UiO-66-NH₂/diatomite composite catalysts with different theoretical loadings are prepared by a hydrothermal method. The results indicate that UND-60% composite demonstrates the maximum CO production rate of 6.69 μmol·g^-1·h^-1, which is 46% higher than that of UN (i.e., 4.57 μmol·g^-1·h^-1). In addition, the results of cyclic experiments also demonstrate that UND-60% composite has a superior stability. After five cycles, the production rate of CO remains >6.30 μmol·g^-1·h^-1. From the images of scanning electron microscopy (SEM) and high resolution transmission electron microscope (HRTEM), octahedral UiO-66-NH₂ particles are uniformly dispersed on the surface and pores of diatomite. Based on the energy dispersive spectrometer (EDS) elemental mapping images, the presence of Si, O, and Zr elements in the composite indicates the effective preparation of UND-60% composite. According to the X-Ray photoelectron spectroscopy (XPS) analysis, the increased surface hydroxyl groups in the UND-60% composite, stemming from the abundant hydroxyl groups on diatomite, enhance its photocatalytic CO₂ reduction performance. The results of ultraviolet-visible spectroscopy (UV-Vis) spectra, fluorescence spectra, electrochemical impedance spectra, transient photocurrent response spectra and Mott-Schottky curves indicate that UND-60% composite broadens the absorption range of the solar spectrum, and diatomite introduces an promoted separation efficiency of photogenerated carriers, thus improving the photocatalytic performance.

The results of In-situ DRIFTs reveal the photocatalytic CO₂ reduction mechanism in the UND-60% composite, i.e., CO₂ and H₂O adsorb onto the photocatalyst surface, where photo-generated electrons activate CO₂ to form bent anionic radicals (*CO₂^-). Subsequently, *CO₂^- undergoes proton-coupled electron transfer to generate a carboxylate intermediate (*COOH), follows by further protonation and reduction to yield *CO and H₂O. This *CO formation step is rate-limiting. Finally, *CO desorbs from the catalyst surface as gaseous CO, completing the reduction pathway.

The UiO-66-NH₂/diatomite composite was synthesized by a one-step hydrothermal method. UND-60% composite demonstrated a superior photocatalytic CO₂ reduction performance, achieving a CO generation rate of 6.69 umol·g^-1·h^-1. This represented a 1.46-fold enhancement over pristine UiO-66-NH₂ (4.57 umol·g^-1·h^-1). The results of cyclic testing indicated a superior photostability of the composite. Compared to pure UiO-66-NH₂, diatomite incorporation imparted an optimized specific surface area and pore structure, while enhancing catalyst dispersion. This synergistic effect exposed additional active sites and facilitated an improved CO₂ photoreduction performance. Furthermore, the composite had an expanded light absorption range and enhanced photoinduced charge carrier separation efficiency. The results of In-situ DRIFTs analysis on the UND-60% composite revealed the dynamic evolution of surface functional groups during CO₂ photoreduction, establishing the reaction pathway: CO₂ → *CO₂ → CO₂^- → COOH → *CO → CO. These findings could provide valuable insights for designing cost-effective photocatalytic systems for CO₂ reduction.

This review represents a comprehensive and in-depth summary of the La₃Ga_5.5Nb_0.5O₁₄ (LGN) crystal, covering important achievements in various key aspects, such as crystal structure and basic properties, large-size growth technology, nonlinear optical properties, mid-infrared nonlinear optical properties, and applications. In terms of large-size crystal growth, some technical problems of thermal stress cracking and component segregation during the growth of LGN are solved, and the preparation of large-size single crystals with the diameters of 60-80 mm is stablized. Meanwhile, the LGN crystal has nonlinear optical properties and applications, which provides a support for the development of high-power mid-infrared laser systems.

In the future, we need to optimize the crystal growth to obtain more accurate temperature regulation, further shorten the growth cycle, improve the growth efficiency, reduce the internal defects, and improve the annealing process, to obtain larger size (≥4 inches) high-quality LGN crystal, providing a better material base for high-performance mid-infrared laser. In addition, it is also necessary to investigate the performance regulation mechanism of LGN hybrid crystals in depth, and further optimize their nonlinear optical properties via utilizing elemental doping and structural fine-tuning, such as improving the nonlinear coefficient and broadening the gain bandwidth, to provide nonlinear optics crystals with excellent performances for the realization of high-power OPCPA applications. Developing mid-infrared laser sources and optoelectronic devices can meet a demand for mid-infrared wavelength lasers in biomedicine, environmental monitoring, national defense, security, and etc..

The large-scale mining and processing of coal resources inevitably result in the continuous generation and accumulation of solid wastes such as fly ash and coal gasification slag. However, their utilization rate remains low, with primary dependence on open-air stockpiling, leading to substantial resource depletion and ecological hazards. The existing resource utilization of fly ash and coal gasification slag is still confined to low-value-added fields like construction materials and agriculture. It is critically necessary to explore their inherent resource properties and develop high-value utilization pathways, thereby addressing environmental challenges, while enhancing economic benefits. Some researches reveal that fly ash and coal gasification slag both contain abundant silicon components in their phase compositions. This characteristic endows them with significant potential as precursors for synthesizing silicon anode materials. This study was to fabricate silicon/carbon composites with fly ash and coal gasification slag as precursors, provide novel insights into the high-value application of coal-based solid waste resources and expand the methodology for low-cost preparation of silicon-based materials for lithium-ion batteries.

In the fabrication of distinct silicon-carbon composites, a fly ash-derived silicon material was prepared via uniformly grinding a mixture with 1 g of fly ash, 1 g of magnesium powder and 2 g of sodium chloride. Afterwards, the ground mixture was heated in argon atmosphere by magnesiothermic reduction at 750 ℃ for 8 h. A purified silicon material was obtained after sequential washing with hydrochloric acid and hydrofluoric acid. For the fly ash-derived silicon-carbon composite, this silicon material was dispersed with phenolic resin at an equal mass ratio, modified via cetyltrimethylammonium bromide assistance, and carbonized at 800 ℃ for 2 h to form a carbon-coated structure. In contrast, the coal gasification slag-derived composite was synthesized in a single step via subjecting 1 g of coal gasification slag, 0.6 g of magnesium powder, and 2 g of sodium chloride to identical magnesiothermic reduction conditions, thereby retaining inherent carbon to generate an interconnected silicon-carbon architecture.

The morphologies and microcrystalline structures of all the obtained samples were analyzed by X-ray diffraction, Raman spectroscopy, X-ray energy dispersive spectroscopy, scanning electron microscopy, and transmission electron microscopy. The thermal behavior was evaluated by thermogravimetric analysis, and the microstructures were characterized via BET specific surface area and pore size distribution measurements. The two composite materials were assembled into lithium-ion half-cells for charge-discharge cycling, cyclic voltammetry, and impedance testing to evaluate their lithium storage performance.

Silicon materials obtained via the magnesiothermic reduction process with fly ash as a precursor exhibit a high crystallinity, primarily composed of densely packed crystalline particles. The corresponding fly ash-based silicon-carbon composite fabricated via a carbon-coating strategy exhibits a "core-shell structure" with a carbon content of 28.1%. This carbon layer predominantly consists of amorphous carbon enriched with abundant sp³-hybridized structural defects and edge disorders, significantly affecting the interfacial charge transfer dynamics. In contrast, the coal gasification slag-derived composite synthesized via one-step magnesiothermic reduction demonstrates a distinctive mosaic architecture incorporating 36.9% carbon with substantially enhanced sp²-hybridized carbon domains, thus facilitating a superior electrical conductivity.

Fly ash-based silicon-carbon composite and coal gasification slag-derived composite both have high specific surface areas (i.e., 215.7 and 274.8 m²·g^-1) and rich hierarchical pore structures (i.e., synergistic distribution of microporous and mesoporous pores). As lithium-ion battery anodes, fly ash-derived silicon-carbon composite and coal gasification slag-derived silicon-carbon composite exhibit reversible capacities of 800 and 420 mA·h·g^-1 at 50 mA·g^-1, respectively. These composites maintain reversible capacities of 348 and 334 mA·h·g^-1 after 300 cycles at 500 mA·g^-1, respectively, showing superior rate capability and cycling stability. This study demonstrates that silicon-carbon composites with high-performance lithium storage characteristics can be prepared by using low-cost coal-based solid waste-fly ash and coal gasification slag as precursors, which is helpful for promoting the development and application of low-cost, high-performance energy storage materials.

A silicon-carbon composite with a "core-shell structure" was synthesized by using fly ash as a precursor through a magnesia-based reduction process combined with a carbon coating strategy. Also, a silicon-carbon intergrown composite exhibiting an "mosaic architecture" was prepared by using coal gasification slag as a precursor by a one-step magnesia-based reduction process. The abundant sp³ structural defects and edge defects in fly ash-based silicon-carbon composite could enhance its lithium storage capacity, while the significant sp² carbon in the coal gasification slag-based composite could improve its structural stability. Consequently, the composites both exhibited excellent rate performance and cycling stability when used as anodes in lithium-ion batteries. This study could provide some insights for the high-value utilization of coal-based solid waste resources and expand avenues for low-cost preparation of silicon-based materials for lithium-ion batteries.

Cobalt aluminate (CoAl₂O₄) is one of the most common transition metal catalysts and is widely used in the persulfate advanced oxidation process. To improve the dispersion of the cobalt aluminate (CoAl₂O₄) catalyst and enhance its catalytic activity, exfoliated montmorillonite nanosheets (EMMT) as a support were prepared by a freeze-thaw-ultrasonic method. The CoAl₂O₄/EMMT composite material was synthesized by a sol-gel method, and then CoAl₂O₄/EMMT was reduced to the Co-CoAl₂O₄/EMMT composite material. The degradation performance and cycle stability of Co-CoAl₂O₄/EMMT for methyl orange were investigated, and the mechanism of catalytic degradation of methyl orange was discussed.

An appropriate quantity of montmorillonite (MMT) was uniformly dispersed in 50 mL of deionized water. After continuous stirring for 12 h, a well-dispersed MMT suspension was obtained. Subsequently, the MMT suspension was transferred into a refrigerator at -20 ℃ for 12 h. In the freezing process, the frozen MMT suspension was placed at an ambient temperature for 8 h to ensure complete thawing. After thawing, the suspension was thoroughly stirred to achieve a homogeneous state, and then ultrasonic treatment was carried out for 8 min to yield an exfoliated montmorillonite nanosheet (EMMT) suspension. Afterwards, 750 mg of aluminum nitrate nonahydrate (Al(NO₃)₃·9H₂O) and 353 mg of cobalt nitrate hexahydrate (Co(NO₃)₃·6H₂O) in a molar ratio of 2∶1 were added to the EMMT suspension. The mixture was vigorously stirred for 40 min to guarantee the well-dispersion. 384 mg of citric acid and 4.5 mg of sodium dodecyl benzene sulfonate (SDBS) as organic additives were introduced into the above-mentioned solution. The solution was then heated in a water-bath at 70 ℃ for 4 h to form a sol, and the heating process was continued for 2 h to transform the sol into a wet gel. The wet gel was subsequently freeze-dried for 24 h to obtain a dry gel, which was then finely ground. An appropriate amount of the dry-gel powder was weighed and placed in a muffle furnace. The temperature increased at a heating rate of 5 ℃/min, and followed by calcination for 3 h to synthesize CoAl₂O₄/EMMT composite material. The microstructure of the CoAl₂O₄/EMMT composite material was optimized via precisely regulating the calcination temperature. Finally, the Co-CoAl₂O₄/EMMT composite material was synthesized through reduction roasting.

At a ultrasonic power of 600 W, the lamellar thickness of the exfoliated EMMT decreases from 303 nm to 7.6 nm. The Co-CoAl₂O₄/EMMT composite material synthesized at a calcination temperature of 650 ℃ and a reduction temperature of 670 ℃ exhibits the optimal catalytic performance. Its degradation rate of methyl orange reaches 87.5% within 70 min, which is greater than the catalytic performance of Co-CoAl₂O₄ (79.3%) or CoAl₂O₄/EMMT (76.8%) composite materials. Co-CoAl₂O₄/EMMT composite material has a good stability, and the degradation rate of methyl orange still remains at 77.8% after four cycles.

Exfoliated montmorillonite nanosheets (EMMT) as a carrier were prepared by a freezing-thawing-ultrasonication method, and then Co-CoAl₂O₄/EMMT composite was synthesized by a sol-gel reduction approach. Co-CoAl₂O₄/EMMT material prepared at a calcination temperature of 650 ℃ and a reduction temperature of 670 ℃ exhibited the optimal catalytic performance. After activating peroxydisulfate (PDS), the degradation rate of Co-CoAl₂O₄/EMMT for 50 mg/L methyl orange could reach 87.5% within 70 min, accompanied by a superior cycle stability. The results of radical quenching experiments confirmed that SO₄^•- and •OH radicals were the dominant reactive species contributing to methyl orange degradation.