Crystal Powder Research Articles

Developing Aqueous Processed Transition Metal Oxide Cathodes with Sustainable Binders for High Energy Density Lithium-Ion Batteries from Lab Scale to Manufacturing Scale

Transitioning toward more sustainable materials and manufacturing methods is critical to continue supporting the rapidly expanding market for lithium-ion batteries (LIBs). Meanwhile, energy storage applications are requiring higher power and energy densities with demanding performance targets like fast charging and a wide range of operating voltages. Alongside high-performance demands, environmental considerations such as organic solvent use, low abundance of Co and other mining related issues, urgently need to be addressed by the LIBs community [1]. High voltage spinel LiNi0.5Mn1.5O4 (LNMO) is considered a highly promising cathode candidate for the next generation high performance LIBs due to a high energy density (650 W H kg -1), high operating voltage (∼4.7 V vs Li), low environmental impact, and low-cost fabrication [2]. However, severe capacity degradation during cycling has impeded wide application and commercialization.In this study, we investigated LNMO thoroughly as a cathode material using only aqueous processing, covering the processing range from small scale to the research pilot line level. Aqueous electrode processing is highly critical to eliminate organic solvent use in LIBs production. On the anode side, aqueous processing has already been established on the industrial level, whilst cathode aqueous processing still needs to be tuned to reach to the same level of feasibility. The main challenge in aqueous processing of transition metal oxides is the high surface sensitivity towards water, resulting in Li/proton exchange. Consequently, pronounced Li+ loss is observed on the electrode during cycling. In literature, acid treatment is one of the most common approaches to avoid this phenomenon during slurry preparation [3]. In this work, we investigate different crystal structure with combination of two binders. Understanding the impact of the different crystal structure of LNMO particles on lithium leaching during slurry processing is one the targets of the study. On the particle level, single, poly crystalline and mixed of single and poly crystal powders are characterized to select the most promising candidate in terms of processing and cycling performance. Two different binder systems were studied, including carboxymethyl cellulose (CMC) with acrylic based binder as baseline for water-borne cathodes, and Na-Alginate as a more sustainable binder option specifically for LNMO.The formulation development started at the laboratory scale with slurries characterized with pH control and regarding their rheological behavior. Detailed electrochemical analysis with cycling and electrochemical impedance spectroscopy (EIS) was performed along with comprehensive surface characterization and scanning electron microscopy (SEM) before cycling and post-mortem. Subsequently, the most promising candidates were successfully upscaled to the research pilot line. By characterizing three crystal structures of LNMO with two binders, we demonstrate the capabilities of LNMO as an active material using the most sustainable processing conditions. Depending on the crystal structure, single crystal LNMO with Na-Alginate binder was found to be the most promising candidate (capacity retention ∼130 mAh g -1 after 150 cycles), especially for fast charging applications. This study is to serve as guideline for better understanding of LNMO and its aqueous processability.

Two new Mn-LMOF based on an AIEgens ligand for selective detection of Al3+ and other ions in aqueous solution

Two novel multifunctional chemical sensor Mn-LMOF, namely, [Mn2(TPPE)(ndc)2(H2O)]n (LMOF-1) and [Mn2(TPPE)(oba)2]n (LMOF-2) were solvothermally synthesized by introducing an AIE luminogens (AIEgens) ligand, 1,1,2,2-tetra[4-(pyridin-4-yl)phenyl]ethylene(TPPE), and analyzed by single crystal X-ray diffraction, thermogravimetric and powder X-ray diffraction and other methods. LMOF-1 and LMOF-2 have high stability and strong luminescence properties in solutions. The sensing experiments testify that LMOF-1 can be used as a selectively sensor for Al3+, with the limit of detection is 1.83 × 10−5 M. And LMOF-1 and LMOF-2 can identify Fe3+, CrO42− and Cr2O72− ions in aqueous solution, and LMOF-1 has a higher Ksv for all three ions than LMOF-2.

Volemitol production from Yarrowia lipolytica via transaldolase gene (TAL) disruption and erythrose-4-phosphate (E4P) flux regulation

Volemitol (D-glycero-D-manno-Heptitol, C7H16O7 with CAS No.488–38–0), a seven-carbon (C7) sugar-derived alcohol, has the potential to be used as a natural sweetener. The natural scarcity of sugar alcohols restricts their practical uses. However, Yarrowia lipolytica has shown significant promise in industrial production due to its capability to efficiently produce sugar alcohols like erythritol, D-threitol, mannitol, and xylitol by generating key biosynthetic intermediates through glycolysis and the phosphopentose (PPP) pathway. In this study, the transaldolase gene (TAL) in the erythritol synthesis pathway was knocked out in the erythritol-producing Y. lipolytica strain CGMCC7326 to inhibit erythritol production. TAL-deleted strain Y. lipolytica CGMCC7326ΔTAL exhibited a notable decline in erythritol production; however, a novel substance, volemitol, was generated from glucose at a titer of 50 g/L. Volemitol with 99 % purity was obtained as a white microneedle powder crystal through the enzymatic activity of mannitol dehydrogenase (MDH2), which reduces sedoheptulose to volemitol. The proposed biosynthetic pathway in Y. lipolytica CGMCC7326ΔTAL is: sedoheptulose-7-phosphate was converted to sedoheptulose, then was reduced to volemitol. In conclusion, this study is the first to report efficient volemitol production from glucose via fermentation by engineered Y. lipolytica.

Ionic Hydrogen-Bonded Organic Frameworks with a Two-Photon Synergistic Color Change and Their Information Encryption Applications.

Photochromic hydrogen-bonded organic frameworks (HOFs) can introduce different luminescent functional groups to achieve synergistic controlled multiple color change properties, which are in great demand for diverse information encryption applications. We report in this paper switchable photochromic and photoluminescent dual luminescent functional group HOFs constructed with synergistic effects by N,N'-bis(2-phenylalanine)-1,4,5,8-naphthalenediimine (H2PheNDI) and benzenecarboximidamide 4,4'-azobis(hydrochloride) (AZBH). The crystal powder of iHOF-41 is orange-red in color, which can be changed to black under the irradiation of a 365 nm ultraviolet (UV) light source for 15 min. The photoisomerization rate of the crystal solution under continuous UV irradiation for 5 h was close to 99%. The composite membranes can achieve the properties of photochromism and photoluminescence when they are discolored under 365 nm UV irradiation and, at the same time, excite red bright fluorescence. This work achieves the construction of HOFs based on switching biluminescent functional groups and explores the synergistic mechanism of the photoisomerization process and photochromism as well as its practical application in information encryption.

Analysis on optical, thermal and third-order nonlinear properties of L-histidine hydrochloride monohydrate single crystal

This research contributes valuable insights into the understanding of third-order nonlinear optical effects in L-histidine hydrochloride monohydrate (LHHC) single crystal, offering a foundation for future work in optimizing its properties for practical applications in the field of nonlinear optics. It presents a systematic analysis into the LHHC crystal properties harvested by slow evaporation solution (SEST) method. Originally, structure of the compound was confirmed through single crystal x-ray diffraction and powder x-ray diffraction analysis. FTIR analysis was performed to get information about molecular composition of the compound. The assessment of the optical quality of LHHC single crystal was done by UV–Visible and photoluminescence spectroscopies. TG-DTA was employed to assess the stability of the single crystal under different temperature conditions. Z-scan technique, with an open aperture (OA) & closed aperture (CA) configuration, was employed to comprehensively explore the third-order nonlinear response of LHHC single crystal. The nonlinear absorption coefficient β is determined to be 5.32 × 10−10 cm W−1. The NLR index (n2) is calculated as −2.72 × 10−15 cm2 W−1.

Two 2-dimensional Mn(II)-based coordination polymers: synthesis, structure and luminescence properties

Luminescent ligand 4-([4,2′:6′,4″-terpyridin]-4′-yl)-N,N-diphenylaniline (tpatpy) was coordinated to MnX2 (X = Cl, Br) to construct two novel coordination polymers (CPs) by two-solvent interdiffusion, delivering compounds 1 (C66H48Br2MnN8) and 2 (C66H48Cl2MnN8). Single-crystal X-ray diffraction revealed that the two CPs both possessed microstructures of 2-dimensional layers which were tuned by six-coordinate Mn2+ ions. Compounds 1 and 2 display broad photoluminescent emission with intense peaks at ca. 468 nm, attributed to π*→n or π*→π transitions mixed with the ligand-to-ligand charge transfer (LLCT) transition. Their crystal structures, powder diffraction (PXRD) and thermogravimetry (TG) are also discussed.

Comprehensive study of photoluminescence and device properties in Cu2Zn(Sn1−xGex)S4 monograins and monograin layer solar cells

Ge-alloying of Cu2ZnSnS4 is a promising strategy for producing wide-bandgap absorber materials suitable for use in tandem structures or indoor solar cell applications. Incorporating Ge can suppress Sn-related defects while maintaining the kesterite structure and p-type conductivity throughout the entire range of composition. In this study, Cu2Zn(Sn1−xGex)S4 monograins were synthesized in molten salt by the synthesis-growth method, where value x was varied from 0 to 1, with a step of 0.2. The inclusion of Ge into the crystals was confirmed by energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction analysis. The bandgaps of Cu2Zn(Sn1−xGex)S4 solid solutions were determined as Eg = 1.50–2.25 eV by external quantum efficiency measurement. A detailed study of temperature and laser power-dependent photoluminescence (PL) for powder crystals with x = 0, x = 0.2 and x = 0.4 revealed that the dominant recombination mechanisms originate from defect clusters involving a shallow acceptor and deep donor defect. Ge-alloying helped to suppress the harmful SnZn donor defects, but at the same time shifted the defects' energy levels deeper into the bandgap. The obtained activation energies indicate that the acceptor defect becomes shallower with the inclusion of Ge. At the mid-temperature range (T = 60–200 K), the presence of two different recombinations was revealed in the system, originating from very closely located PL emission bands.

Selective Synthesis and Crystal Chemistry of Candidate Rare-Earth Kitaev Materials: Honeycomb and Hyperhoneycomb Na2PrO3.

Rare-earth oxides have attracted interest as a platform for studying frustrated magnetism arising from bond-dependent anisotropic interactions. Ordered rock salt compounds Na2PrO3 crystallize in two polymorphs (α and β) comprising honeycomb and hyperhoneycomb lattices of octahedrally coordinated Pr4+ (4f1). Although possible realization of antiferromagnetic Kitaev interactions is anticipated for these phases on the basis of ab initio models, the air sensitivity of the two polymorphs has hampered reliable crystal growth and physical property measurements. Here, we have succeeded in preparing powder and single crystals of both α- and β-Na2PrO3 using modified synthetic procedures. Revised crystal structures for both polymorphs are obtained from refinement of untwinned single-crystal X-ray diffraction data.

Inclusion complexes of α-cyclodextrin with p-aminobenzoic acid and nicotinic acid: Crystal structure, DSC and IR spectroscopy analysis in solid state and 1H NMR and ITC calorimetric studies of complexation in solutions

In this work, inclusion complexes of α-cyclodextrin with p-aminobenzoic acid (PABA) and nicotinic acid (NIK) were studied. Solid-state complexes were obtained and studied with single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry, and FT-IR spectroscopy. Additionally, the formation of complexes was studied in aqueous solutions with isothermal titration calorimetry and 1H NMR spectroscopy in DMSO‑d6 solutions. Single crystal studies, FT-IR spectroscopy and powder diffraction confirmed the inclusion of PABA and NIK inside the cyclodextrin cavity. From the results of the isothermal titration calorimetry, the stoichiometry (n) and standard thermodynamic functions (ΔH, ΔG, ΔS) of complexation, as well as binding constants (K) for the formed complexes were calculated. The obtained results confirmed the thermodynamically spontaneous formation of complexes in exothermic reactions. Furthermore, the results obtained were compared for complexes of PABA/NIK acids with β-cyclodextrin. A database survey of α-cyclodextrin complexes with different benzoic acids available in the CSD database was performed.

Comparative study of the structure and durability of commercial silicate glasses for food consumption and cosmetic packaging

Four commercial glass compositions were investigated to understand their mechanisms of alteration in light of the current and future regulations on food contact materials. Lead crystal (fine glassware), soda-lime (food and cosmetic containers), borosilicate (cookware) and barium glass (tableware) powders and slabs were altered for 3 years, in acetic acid (4% vol) at pH = 2.4 and 70 °C. The leaching solution was analyzed by ICP-AES while glass slabs were investigated by ToF-SIMS and Spectroscopic Ellipsometry. As a result, in acidic medium, the polymerization of the silicate network as well as the glass composition impacted the alteration rates and depleted depths of alkalis and earth-alkalis elements. Yet the rate of hydrolysis measured from the release of Si, remained similar under identical alteration conditions, whatever the glass structure and composition. For lead crystal glass, repolymerization of the silicate network was observed in the course of alteration.

Three new complexes of Zn(II) with a quinoline based Schiff base ligand: Syntheses, crystal architectures, Hirshfeld surface analyses, DFT study, photoluminescence and thermal properties

This report deals with one dinuclear and two mononuclear zinc(II) complexes of compositions [Zn2L2(μ1,1-N3)(N3)] (1), [ZnL(NCO)(H2O)] (2) and [ZnL(NCS)(H2O)] (3), where HL ((E)-2-ethoxy-6-((quinolin-8-ylimino)methyl)phenol)) is the 1:1 condensation product of 3-ethoxysalicylaldehyde and 8-aminoquinoline. All the three metal complexes have been characterized by C, H, N elemental analyses, FT-IR spectra, single crystal X-ray structures and powder XRD. The structures of 2 and 3 are isomorphous. The metal centres in 1–3 are five coordinated and adopt vacant octahedral or distorted square pyramidal geometry for 1 and distorted trigonal bipyramidal geometry for 2 and 3. Supramolecular interactions and topologies in all the three crystal structures have been analyzed, revealing 3–D assemblies in 1–3 due to a number of non-covalent interactions (C–H···O, C–H···N and π···π in 1; C–H···O, O–H···O, O–H···N, π···π and C–H···π in 2; C–H···S, O–H···O, O–H···N, π···π and C–H···π in 3). To gain additional insight into the intermolecular contacts and their relative contributions towards the packing, Hirshfeld surface analyses have been undertaken for 1–3 and demonstrated in detail with respect to structural parameters, depressions in surfaces, fingerprint plots and enrichment ratios. The thermo-gravimetric and differential thermal analyses (TG/DTA) have been performed and the decomposition patterns are well explained. Steady state and time resolved fluorescence properties have been investigated. Optical band gaps have been determined from the data of the UV–Vis spectra. DFT calculations have been undertaken. The DFT computed HOMO-LUMO gaps corroborate the optical gaps and the DFT computed electrostatic potential (ESP) surfaces rationalize the supramolecular interactions nicely.

A library of 2D electronic material inks synthesized by liquid-metal-assisted intercalation of crystal powders

Solution-processable 2D semiconductor inks based on electrochemical molecular intercalation and exfoliation of bulk layered crystals using organic cations has offered an alternative pathway to low-cost fabrication of large-area flexible and wearable electronic devices. However, the growth of large-piece bulk crystals as starting material relies on costly and prolonged high-temperature process, representing a critical roadblock towards practical and large-scale applications. Here we report a general liquid-metal-assisted approach that enables the electrochemical molecular intercalation of low-cost and readily available crystal powders. The resulted solution-processable MoS2 nanosheets are of comparable quality to those exfoliated from bulk crystals. Furthermore, this method can create a rich library of functional 2D electronic inks ( >50 types), including 2D wide-bandgap semiconductors of low electrical conductivity. Lastly, we demonstrated the all-solution-processable integration of 2D semiconductors with 2D conductors and 2D dielectrics for the fabrication of large-area thin-film transistors and memristors at a greatly reduced cost.

Investigating the dielectric characteristics, electrical conduction mechanisms, morphology, and structural features of mullite via sol-gel synthesis at low temperatures

This research explores the fabrication of mullite precursor powder utilizing the sol-gel process at low temperatures. Silicon tetraethoxide (Si(C2H5O)4) and aluminum nitrate nonahydrate (Al(NO3)3.9H2O) were employed as the sources of SiO2 and Al2O3 oxides, respectively. Various analytical techniques, such as Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG), dilatometry, differential thermal analysis (DTA), and X-ray powder diffractometer (XRD), were utilized to investigate the formation and crystallization of the amorphous powder. The microstructure of specimens sintered at 1600 °C for 1 h was examined utilizing scanning electron microscopy (SEM). Measurements of hardness (HV) and coefficient of thermal expansion (CTE) were conducted on mullite samples heated to 1600 °C and then cooled, revealing an increase in HV from 888 to 1000 HV as the sintering temperature rose from 1500 to 1600 °C. The CTE of mullite within the temperature range of 50–1300 °C was determined as 5.23 × 10−6/°C. Additionally, the dielectric and electrical characterization of mullite was analyzed utilizing complex impedance spectroscopy at a frequency of 0.1–106 Hz and conductivity measurements over a temperature range of 40–400 °C. The real and imaginary parts of the dielectric permittivity exhibited frequency-dependent and temperature-dependent behaviors. Significantly, the observed variations in the imaginary component of the modulus and impedance maximum frequency point to a relaxation process that is not Debye-type, with calculated activation energies (Ea) consistent across different methods.

Low-temperature solvent-free synthesis route of blue and green luminescent phases of tris(8-hydroxyquinoline)aluminum (AlQ3)

Recent research studies have shifted towards simple, efficient, and more eco-friendly synthesis methods. The current study focuses on using a free-solvent reaction to synthesize trichelate 8-hydroxyquinoline (8HQ) octahedral Al(III) coordination complex (AlQ3), which still represents the most widely used electroluminescent material in organic light-emitting devices (OLEDs). We have developed a new safe and easy route for synthesizing AlQ3 via a pure solid-state reaction between 8HQ and AlCl3 with sodium carbonate as an inorganic base. The formation of the free-solvent prepared AlQ3 was confirmed using FT-IR, UV–Vis spectroscopy, SEM/EDS analysis, powder, and single crystal. Our investigation overturns the belief that fac-AlQ3 is only formed at high temperature; the developed synthesis method enabled the production of blue-fluorescent AlQ3 at room temperature. Furthermore, this study presents a low-temperature synthesis pathway for obtaining pure AlQ3 phases for the first time. We controlled the washing step of the isolated AlQ3 to produce large amounts of blue and green luminescent AlQ3. The optical properties of the samples were determined using photoluminescence (PL) spectroscopy.

Enhanced Electrochemical Performance in Supercapacitors through KCu-Cy Based Metal-Organic Framework Electrodes.

In the realm of electronics and electric energy storage, the convergence of organic and metallic materials has yielded promising outcomes. In this study, we introduce a novel metal-organic polymer synthesized from Cyamelurate and copper (KCu-Cy) and explore its application as an electrode for a supercapacitor. This material was pressed onto a stainless-steel grid as a thin film and synthesized on nickel foam. Comprehensive characterization was carried out to confirm the synthesis, ensure phase purity, and investigate atomic interactions. Single Crystal X-ray Diffraction (SCXRD) and Powder X-ray Diffraction (PXRD) analyses verified the synthesis and phase purity, shedding light on atomic arrangements. Fourier Transform Infrared Spectroscopy (FTIR) analyses provided insights into characteristic peaks within the material. Thermal Gravimetric Analysis (TGA) gauged stability and durability. Electrochemical performance was assessed through cyclic voltammetry. Notably, the nickel-supported electrodes, devoid of binders, exhibited exceptional specific capacity, reaching 1210.89 F/g at a scan rate of 5 mV/s, in contrast to 363.73 F/g for the pressed thin film on the stainless-steel grid, which incorporated a conductive agent and binder. Cu-Cy displayed impressive cyclization resistance, with a capacity retention of 90 % even after 11000 cycles. These findings underline the promise of Cu-Cy as a high-performance electrode material for supercapacitors, particularly in binder-free configurations, and suggest its potential in advanced energy storage applications.

Penternary Wurtzitic Nitrides Li1-xZnxGe2-xGaxN3: Powder Synthesis, Crystal Structure, and Potentiality as a Solar-Active Photocatalyst.

We developed a new penternary wurtzitic nitride system Li1-xZnxGe2-xGaxN3 (0 ≤ x ≤ 1) by hybridizing LiGe2N3 and ZnGeGaN3. Fairly stoichiometric fine powder samples were synthesized by the reduction-nitridation process at 900 °C. While the end member LiGe2N3 possessed a relatively large band gap of 4.16 eV, the band gap of the developed penternary system varied in a broad range of 3.81 to 3.10 eV, showing promising responsivity to the solar spectrum. The crystal structure of LiGe2N3 was precisely determined by time-of-flight neutron powder diffraction for the first time, revealing the complete ordering of Li and Ge in the Cmc21 structure. The structural evolution from completely ordered LiGe2N3 to fully disordered ZnGeGaN3 was quantitatively analyzed by Rietveld refinement based on a partially disordered Cmc21 model, and the obtained results were also supported by 71Ga solid-state NMR spectroscopy. The synthesized Li1-xZnxGe2-xGaxN3 powder samples exhibited photocatalytic activities for the water reduction and oxidation reactions under solar light irradiation, with the H2 evolution rate of 0.3-59.0 μmol/h and the O2 evolution rate of 3.1-296.2 μmol/h, depending on the composition. Stable solar hydrogen generation of up to 48 h was demonstrated by the x = 0.80 sample, with the total amount of H2 evolved over 1.6 mmol and an external quantum efficiency of 2.1%.

1D heteronuclear coordination polymers of hexacyanocobaltate(III) with 2-hydroxymethylpyridine

Three new hexacyanocobaltate(III) complexes, {[M2(hmpy)4Co(µ-CN)4(CN)2]∙2H2O}n (M = Cu(II) (1), Zn(II) (2) and Cd(II) (3)) were synthesized with 2-hydroxymethylpyridine (hmpy) ligand, and characterized by vibration (FT-IR and Raman) spectral, single crystal X-ray diffraction (SC-XRD) and powder X-ray diffraction (PXRD), thermal and elemental analyses techniques. The crystallographic analyses revealed that cyanide complexes 1–3 are infinite one-dimensional coordination polymers. Each M ion is coordinated by two nitrogen and two oxygen atoms from the hmpy ligands and two nitrogen atoms from the cyanide ligands, displaying a distorted octahedral coordination geometry. Similarly, each Co(III) ion is coordinated by six carbon atoms from cyanide ligands to form a distorted octahedral coordination geometry. These complexes form 3D supramolecular networks through OH···O hydrogen bonds and CH···N interactions. Additionally, structural analyses such as metal salts, pH values of the compounds obtained under different conditions were evaluated. A synthesis-structural analyses relation was made from these data.

Crystallization of KDP in the presence of 4-nitro benzoic acid, L-ornithine hydrochloride and terephthalic acid

The present study is to investigate the optical, thermal and SHG properties of grown potassium dihydrogen phosphate (KDP) crystals using slow evaporation method in the presence of 4-nitro benzoic acid, l-Ornithine Hydrochloride and Terephthalic acid. Powder crystal XRD studies confirm their structure as that of KDP. The presence of functional groups has been tested and confirmed by FTIR. UV–visible spectral analysis - Differential Reflectance Studies (DRS) is used to examine the optical properties of pure and doped KDP crystals within the wavelength range of 200–800 nm and also evaluate the band gap, refractive index, extinction coefficient and optical conductivity of the grown crystals. Thermal properties of grown crystal are analysed by Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Second harmonic generation test is carried out for the grown crystals to analyse nonlinear optical (NLO) properties.

Experimental Optimization, Design Synthesis, and Up-Conversion Luminescence Properties of Y4GeO8: Er3+/Yb3+ Red Phosphors

The Er3+/Yb3+ co-doped Y4GeO8 crystal powders were successfully synthesized us-ing a high-temperature solid-phase method. The crystal structure of the obtained phosphors was confirmed to be pure Y4GeO8 through X-ray diffraction (XRD) analysis. A regression equation correlating Er3+/Yb3+ doping concentrations with luminescent intensity was estab-lished based on the optimized theoretical model derived from experimental design. The op-timal concentrations of Er3+ and Yb3+ under 980 nm laser excitation were determined as 7.41% and 21.34%, respectively, while under 1550 nm laser excitation, the concentrations were 2.66% and 17.42%, respectively. The fluorescence emission spectra of the up-conver-sion samples were measured, revealing intense green and red emissions with peaks at 542, 546, and 654 nm under 980 nm excitation, and peaks at 546, 557, and 663 nm under 1550 nm excitation. These peaks correspond to transitions from 2H11/2 to 4I15/2, 4S3/2 to 4I15/2, and 4F9/2 to 4I15/2 energy levels. The relationship between up-conversion luminescence and laser op-erating current for the optimal samples under 980 nm and 1550 nm was investigated, uncov-ering that up-conversion luminescence occurs through both two-photon and three-photon processes. A detailed analysis and discussion of the up-conversion luminescence mecha-nisms were conducted. Furthermore, the relationship between up-conversion fluorescence and temperature for the optimal samples was studied, revealing excellent temperature-sens-ing characteristics under 980 nm and 1550 nm laser excitations. The calculated illumination region coordinates for the optimal samples under 980 nm and 1550 nm wavelength excitations were (0.5558, 0.4362) and (0.5256, 0.4687), respectively. The research highlights the potential of rare-earth ion-doped up-conversion luminescent materials for diverse anti-coun-terfeiting applications. In particular, the Y4GeO8: Yb3+/Er3+ phosphors, incorporating a dual-excitation mechanism, enhance the security of anticounterfeiting strategies in multifaceted scenarios. The study underscores the promising developments in this field.

Effect of process conditions on the performance of LiNi0.815Co0.15Al0.035O2 positive electrode material powder synthesized by hydrothermal approach

LiNi0.815Co0.15Al0.035O2 (NCA) lithium-ion battery cathode material was prepared using a hydrothermal approach. XRD and SEM analyzed the crystal parameters and powder morphology of the cathode material. The results show that the nickel cobalt precursor exhibits a petal-like morphology, and the nanoneedle primary particles are randomly distributed. Accompanied by the increase in calcination temperature and time, the peak intensity ratio of I003/I104 tends to decrease and then increase. The peak intensity ratio reached a maximum when the NCA sample calcined at 750°C for 8 h, indicating the lowest extent of Li/Ni mixing and the best electrochemical performance of the positive electrode material.