Diffuse Reflectance Spectra Research Articles

Dual nanoparticles with rich Ni–CeO2 interfaces for efficient photothermal catalytic CO2 reduction by CH4

Reducing CO2 by CH4 (CRM) is of great significance for alleviating greenhouse effects and fuel shortages. However, the high energy consumption and low yield of fuel, as well as the deactivation of Ni based catalysts constrained its development. Herein, a novel Ni–CeO2/Al2O3 catalyst for photothermal catalytic CRM merely upon focused light irradiation was reported. Very high yield of H2 and CO (80.2 and 96.3 mmol min−1 g−1) and excellent catalytic durability were achieved. The results of UV-VIS-IR diffuse reflectance spectra and experimental test indicate that high yield of H2 and CO originates from efficient photothermal conversion and the molecular activation effect of light. More importantly, Ni–CeO2/Al2O3 exhibits better carbon deposition resistance than Ni/Al2O3. The structural characterization and experimental evidences reveal that the active lattice oxygen in CeO2 nanoparticles can be transferred to Ni nanoparticles via Ni–CeO2 interface to accelerate carbon oxidation and form oxygen vacancies. The formed oxygen vacancies can re-adsorb and activate CO2 to form new active lattice oxygen.

Polarized Raman, infrared and dielectric spectra of lead-free K0.5Na0.5NbO3 piezoelectric system: insights from ab-initio theoretical and experimental studies

The K0.5Na0.5NbO3 (KNN) system has emerged as one of the most promising lead-free piezoelectric over the years. In this work, we perform a comprehensive investigation of electronic structure, lattice dynamics and dielectric properties of room temperature phase of KNN by combining ab-initio DFT based theoretical analysis and experimental characterization. We assign the symmetry labels to KNN vibrational modes and obtain ab-initio polarized Raman spectra, Infrared reflectivity, Born-effective charge tensors, oscillator strengths etc. The KNN ceramic samples are prepared using conventional solid-state method and Raman and UV–Vis diffuse reflectance spectra are obtained. The computed Raman spectrum is found to agree well with the experimental spectrum. In particular, the results suggest that the mode in range ∼840–870 cm−1 reported in the experimental studies is longitudinal optical with A1 symmetry. The Raman mode intensities are calculated for different light polarization set-ups that suggests the observation of different symmetry modes in different polarization set-ups. The electronic structure of KNN is investigated and optical absorption spectrum is obtained. Further, the performances of DFT semi-local, meta-GGA and hybrid exchange-correlations functionals, in the estimation of KNN band gaps are investigated. The KNN bandgap computed using GGA-1/2 and HSE06 hybrid functional schemes are found to be in excellent agreement with the experimental value. The COHP, electron localization function and Bader charge analysis is also performed to deduce the nature of chemical bonding in the KNN. Overall, our study provides several bench-mark important results on KNN that have not been reported so far.

Thermally enhanced luminescence and photoluminescence properties of green-emitting Lu2(1-x)Tb2x(WO4)3 phosphors

A series of Lu2(1-x)Tb2x(WO4)3 (x = 0.00–1.00) white powder materials were prepared by a high-temperature solid-phase method. The crystal structure, microscopic morphology, elemental composition, bandgap energy, photoluminescence properties, and thermal stability of luminescence of the prepared materials were analyzed and studied through room and high temperature X-ray diffraction patterns, field emission scanning electron microscopy images, energy energy-dispersive spectra and X-ray photoelectron spectra, diffuse reflectance spectra, room and high temperature photoluminescence spectra. Under 260 nm excitation, the green emitting Lu2(1-x)Tb2x(WO4)3 samples exhibited an optimum Tb3+ doping concentration at x = 0.30. Calculated results illustrate that the concentration quenching was mainly caused by dipole-dipole interaction. Lu1.98Tb0.02(WO4)3 phosphor exhibited thermally enhanced luminescence at 120 °C, with a maximum luminescence intensity of 254 % of the initial room temperature intensity. Lu1.4Tb0.6(WO4)3 phosphor exhibited thermally enhanced luminescence at 150 °C, with a maximum luminescence intensity of 109 % of the initial room temperature intensity. The mechanism of the thermally enhanced luminescence phenomenon is further discussed to be the adsorbed crystal water and the negative thermal expansion of the material. Thermally enhanced luminescence is of great significance in overcoming luminescent thermal quenching phenomenon, improving the luminescence efficiency, optimizing the material design, and so forth. It has potential applications in high-temperature lighting, display technology, temperature sensing, and optical anti-counterfeiting.

AuPt bimetallic loaded defect state g-C3N4 enhances photocatalytic H2 evolution: Exploring synergistic effects and charge transfer mechanisms

AuPt alloy nanoparticles (NPs) were prepared using a simple photodeposition method to modify defective state g-C3N4 nanosheets (HCN) which contained N vacancies, B doping, and CN groups. The visible diffuse reflectance spectra (DRS) indicate that AuPt/HCN exhibits high light absorption capability. The photoluminescence spectrum (PL) and steady-state surface photovoltage (SPV) indicate that AuPt/HCN possesses a high rate of photogenerated charge separation and a high efficiency of photogenerated electron transfer. The electrochemical tests indicate that AuPt/HCN exhibits lower electrochemical impedance. AuPt/HCN (1.0 wt%) exhibits outstanding photocatalytic hydrogen evolution efficiency, producing hydrogen at a rate of 2095 μmol·g−1·h−1 under visible light, which is 2.10 times and 1.55 times higher than that of monometallic Au/HCN (1.0 wt%) (997 μmol·g−1·h−1) and Pt/HCN (1.0 wt%) (1349 μmol·g−1·h−1), respectively. The bimetallic synergistic effect of AuPt alloy NPs co-catalysts enhances the photocatalytic hydrogen evolution activity of AuPt/HCN composite photocatalysts.

Evaluation of photocatalytic properties of TiO2/g-C3N4 core-shell hybrid catalyst supported on Sr4Al14O25:eu,dy phosphor

TiO2/g-C3N4 hybrid compounds were supported as core-shell catalyst on Sr4Al14O25:Eu,Dy phosphor powder by a 2-step hydrothermal and solvothermal self-assembly method. Surface and chemical characterizations confirmed that the phosphor substrate and the hybrid catalysts co-existed as a multi-composite material. Where nano spherical TiO2 particles were dominant as core/shell catalyst. Diffuse reflectance spectra were shifted toward the visible light region (400 nm to 600 nm) in composites with g-C3N4 as shell-catalyst. X-ray photon spectroscopy (XPS) confirmed the chemical integrity and binding of g-C3N4 on phosphor/TiO2 material. When g-C3N4 was coated as shell-catalyst on phosphor/TiO2, superior photocatalytic performances of above 90% efficiency were obtained in comparison to where TiO2 was coated as shell-catalyst under both ultraviolet and visible light illumination. Thus, g-C3N4 is more active as shell-catalyst owing to its lower band gap of 2.7 eV than core TiO2 (3.2 eV).

Enhancing and broadening the photoresponse of CdS nanowire by constructing core–shell heterostructure

Limited by the severe surface recombination and large bandgap, it is still a challenge to achieve a high-performance broad-spectrum photodetector based on CdS nanowires (NWs). In this work, the CdS/GeS core–shell heterostructure is constructed to enhance and broaden the photoresponse of CdS NWs. The CdS/GeS core–shell heterostructure NWs are prepared by the chemical vapor deposition method, exhibiting smooth surfaces, controlled shell thicknesses, and compositions. From the UV-Vis-near-infrared (NIR) diffuse reflectance spectrum, PL, and time-resolved photoluminescence studies, it is found that the surface recombination is weakened and the light absorption range is widened after the constructing core–shell heterostructure. When configured into photodetectors, the responsivity of the CdS/GeS core–shell heterostructure NWs is up to 76.8 A W−1, which is 10 folds higher than that of pristine CdS NWs. Furthermore, the photoresponse wavelength of the CdS/GeS core–shell heterostructure NWs is extended from 405 to 850 nm. The improved photodetection performance is attributed to the effective separation of photogenerated carriers at the heterostructure interface, weakened surface recombination, and excellent light absorption of the GeS shell. All results imply that constructing core–shell heterostructures is an effective strategy for constructing high-performance photodetectors.

The effect of particles size of Gd2O3 on the radiation protection mechanisms of ZnO

There are two mechanisms established for increasing the radiation resistance of optical properties of micron-sized zinc oxide (mZnO) powder modified by gadolinium oxide (nGd2O3) nanoparticles by means of relaxation of the primary radiation defects (electrons and holes): — in atoms of rare-earth element gadolinium; — on Gd2O3 nanoparticles. During modification with gadolinium oxide micron-sized particles, only one (first) mechanism for radiation resistance increasing is enabled. These results are obtained by recording diffuse reflectance spectra in high vacuum in the range of 0.2–2.5 μm under radiation exposure by accelerated electrons (in situ). The established mechanisms for increasing radiation resistance refer not only to the types of powders under the study, but also to other types of oxide semiconductor powders and rare-earth elements. These mechanisms can also be extended to the photo résistance of oxide powders modified by nanoparticles and solid solutions based on them.

Construction of loading g-C3N4/TiO2 on waste cotton-based activated carbon S-scheme heterojunction for enhanced photocatalytic degradation of microplastics: Performance, DFT calculation and mechanism study

In order to achieve the degradation of polyethylene microplastics (PE) in wastewater. The g-C3N4/TiO2/WCT-AC composite photocatalytic materials were prepared by mixed high-temperature thermal polymerization method with the g-C3N4 and the waste cotton based activated carbon (WCT-AC) loaded TiO2 as precursors. The phase morphology, elemental composition, morphology and photochemical properties of the g-C3N4/TiO2/WCT-AC were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM), ultraviolet–visible diffuse reflectance spectrum (UV–vis DRS) and photo luminescence (PL). The results of UV–vis DRS and PL showed that the combination of the g-C3N4 and the TiO2/WCT-AC improved the absorption in the visible region, broadened the spectral response range, and the formation of heterojunctions enabled efficient photoelectron-hole separation and improved the photocatalytic activity. Under visible light irradiation for 200 h, catalyst dosage 50 mg, and system pH = 7.0, the highest removal rate of the g-C3N4/TiO2/WCT-AC for PE microplastics reached 67.58 %, and it still showed excellent stability after 5 cycles. The active groups such as ·O2−, ·OH and h+ produced in the g-C3N4/TiO2/WCT-AC system under visible light excitation realized the degradation of PE microplastics. The whole process is a complex oxidation bond breaking process, and the degradation of PE microplastics by g-C3N4/TiO2/WCT-AC follows the S-type charge transfer mechanism.

In2O3[sbnd]Co3O4 p-n heterojunction sensors: Comparison of efficient interfaces and gas sensing enhancement mechanism through two strategies

The fabrication of heterostructure has been considered as a great potential to improve the gas sensing performances due to its flexible features at the interface. The p-n heterojunction composites with Co3O4 modified In2O3 were synthesized through physical mixing calcination process and hydrothermal method for the effectiveness comparison as gas sensors for detecting of ethanol. The morphology, microstructure, and surface element state of the heterojunction materials were investigated. Furthermore, the forbidden band width and the active oxygen species were analyzed on account of the efficient interface for the heterojunction materials. The gas response of heterojunction sensor by the physical mixing calcination method exhibits an outstanding response of 5585 towards 100 ppm of ethanol gas, which was about 10 times higher than that by two-step hydrothermal method. Moreover, it shows improved adsorption and desorption kinetics with response time of 8 s and 15 s, respectively at the operating temperature of 280 °C. It also reveals a distinct selectivity to ethanol with better reproducibility, the humidity-dependent stability and ambient retention over a period of 30 days with rendering 94 %. Combined with the in-situ infrared diffuse reflection spectrum analysis and Hall effect test from the perspective of catalytic and electrical properties, we inferred the gas sensing enhancement mechanism involved in In2O3Co3O4 p-n heterojunction with the design of proof-of-concept demonstration by surface modification, which could provide an approach to explore the effect of heterojunction interface through the variable method.

Thermally stable luminescence and dosimetric features of Ho(III) activated tungstate double perovskite

Luminescent efficient tungstate double perovskites Ca3WO6 doped with Ho3+ were synthesized via the solid-state reaction at 1200 C°. The resulting phosphors were analyzed using Rietveld refinement of X-ray diffraction (XRD) data, confirming a monoclinic crystal structure with crystallite sizes ranging between 50 and 55 nm. Optical bandgap determination was facilitated by diffusion reflectance spectra (DRS). Fourier transform infrared (FTIR) studies were conducted to identify functional group vibrations. The optical excitation of the Ca3WO6:Ho3+ phosphors under different excitation conditions resulted in intense green photoluminescence (PL) emission at 545 nm, indicative of the 5F4–5I8 transition of Ho3+ ions. Thermal stability assessment of Ca3WO6:1 % Ho3+ phosphor under blue excitation (454 nm) revealed good thermally stable luminescence about 85.32 % at LED working temperature (150 °C). PL decay studies were conducted to analyze fluorescent behaviour, wherein by means of PL decay lifetime, the PL quantum efficiency of Ca3WO6:1 % Ho3+ phosphor is computed to be 91.1 %. The CIE color coordinates of the phosphors being investigated reside within the green spectral region, with a calculated color purity of 93.25 % observed for Ca3WO6:1%Ho3+. Furthermore, the phosphors under study exhibited high-quality thermoluminescence (TL) after beta irradiation. The detailed TL characterization conducted to assess dosimetric properties. The impact of Ho3+ concentrations and beta dose on TL intensity are two major aspects that have been investigated in detail. TL fading experiments were performed to determine dose storage capacity over a month after beta irradiation. Additionally, the various heating rate (VHR) experiments are conducted to determine the TL kinetic parameters. Besides, the glow curve deconvolution (GCD) for trap parameter determination is also applied, where the results obtained are comparable with the VHR results.

Synthesis, structure and characterization of two new silver-iron based phosphates AgFe2(PO4)2F(H2O)2 and Ag3Fe2(PO4)(HPO4)3

Two new silver-iron based phosphates AgFe2(PO4)2F(H2O)2 (1) with monoclinic P21/n and Ag3Fe2(PO4)(HPO4)3 (2) with triclinic P-1 were synthesized by a conventional hydrothermal method, featuring a dimer structure and a twisted honeycomb-like lattice, respectively. XPS and BVS (Bond Valence Sum) calculations indicated only Fe3+ ions in both compounds, while FT-IR spectra proved the presence of [H2O] in 1 and [OH] groups in 2. Solid-state UV–vis–NIR diffuse reflectance spectra suggested their wide optical band gaps of 2.31 eV and 1.94 eV, respectively. Magnetic measurements indicated that both compounds display a long-range antiferromagnetic ordering at low temperature, showing the change of magnetic entropy of 9.59 J mol−1 K−1 in 1 and that of 14.87 J mol−1 K−1 in 2, respectively.

Sonochemical synthesis of S-scheme CuO/CeO2 heterojunction for enhanced photocatalytic degradation of rhodamine B dye under solar radiations

CeO2 is renowned photocatalyst with 2.8 eV band gap energy and exceptional optical features. However, the slow charge transportation and the fast recombination of the electron-hole pair hindered the photocatalytic efficiency. In this pioneering research, S-scheme CuO/CeO2 heterojunctions were engineered sonochemically with rational compositions of CeO2 and CuO nanoparticles for enhanced the photocatalytic efficiency of CeO2 in destructing rhodamine B dye under full solar radiations. Diffuse reflectance spectrum [DRS], photoluminescence [PL], high resolution transmission electron microscope [HRTEM], selected area electron diffraction [SAED], N2-adsorption-desorption isotherm, X-ray photoelectron spectroscopy [XPS] and X-ray diffraction [XRD] investigated the physicochemical properties of CuO/CeO2 heterojunction. Monoclinic CuO nanoparticles of 8 nm size are facilely incorporated in cubic CeO2 crystallites of 27.3 nm through substitution of Ce4+ by Cu2+ ions which ascribed to smaller ionic radii of Cu2+ compared with Ce4+ and Ce3+ ions. Homogeneous distribution of CuO nanoparticles on CeO2 surface was further investigated by SEM and TEM analysis. HRTEM, XRD, SAED and XPS analysis recorded the co-existence of crystalline peaks of CeO2 and CuO implying the successful construction of CuO/CeO2 heterojunction. The depression in the surface area of CeO2 from 91.4 to 83.6 m2/g with incorporating 5 wt % of CuO revealed the deposition of CuO on CeO2 surface. XPS analysis implied the existence of Ce3+ and oxygen vacancies that provide more adsorption sites for oxygen, which are beneficial for enhancing the catalytic performance of catalysts. CuO nanoparticles with 1.3 eV band energy enhanced the visible light absorbability of the heterojunctions in deep visible region for broading the photocatalytic response. Significant reduction in photoluminescence signals intensity by 60 % with incorporation 5 wt % of CuO revealed the favorable reduction in the rate of electron-hole recombination. In particular, CeCu5 containing 5 wt % CuO expelled 96 % of RhB dye within 6-h under solar simulator compared with 13 % removal on pristine CeO2 and CuO surface. Hot radicals and positive holes degraded RhB dye molecules on the heterojunction surface as elucidated from scavenger experiments and PL analysis of terephthalic acid. The exceptional removal of RhB dye under solar radiation was ascribed to the alignment in the band structure of CeO2 and CuO nanoparticles and the successful production of an efficient S-scheme heterojunction with strong redox potential and better electron transportation and separation.

Synthesis, structure and luminescence properties of PbLaTb(WO4)4 phosphor ceramics for LEDs applications: Role of Tb rare earth

The development and applications of phosphor ceramics have been driven by their ability to convert various forms of energy into visible light with high efficiency, durability, and specific color outputs. This study reports on synthesis of a novel series of solid solutions, PbLa2-2xTb2x(WO4)4 (0 ≤ x ≤ 0.5), using the solid-phase reaction method. The crystal structure, photoluminescence, excitation spectrum, decay kinetics, diffused reflectance spectra, and morphology of the compounds are characterized. The results reveal that the energy band gap has become even lower due to an increase in the concentration of the activator, and an absorption band of the Tb3+ ion is also observed at 380, 370, 354 and 342 nm, respectively; they correspond to the following quantum transitions 7F6 → 5D3, 7F6 → 5G6, 7F6 → 5L10 and 7F6 → 5L9, respectively. Our prepared PbLaTb(WO4) phosphor ceramics have a wide range of applications, from everyday lighting to advanced display technologies and medical devices, highlights their importance in modern technology.

Photoluminescence emission enhancement in the LiSrVO4:Eu3+ vanadate phosphor by partial substitution of M+ ions (M+=Li+/Na+/K+); optical thermometry; and optical transition probabilities using Judd-Ofelt analysis

In solid state lighting (SSL), pcWLEDs gain more attention for various illumination applications. The Eu3+ activated LiSrVO4:xEu3+ (0–15 mol% in steps of 3) phosphors are prepared by the conventional solid state method and their phase formation is confirmed by PXRD. It suggest that the samples are in a monoclinic structure with P2/m space group. SEM results confirmed that the size of the prepared phosphor is in a micrometer range with an irregular spherical shape. The optical diffuse reflectance spectrum (DRS) consisted broad band absorption in the ultraviolet (UV) region (270–350 nm) and also, they are found to absorb strongly the NUV light (396 nm) and the blue light (466 nm). They exhibit the strongest emission at 617 nm for the samples under 326 nm excitation. The PL intensity of the phosphors are improved by co-doping. The optical transition probabilities of the LiSrVO4:9 mol% Eu3+ phosphor are also analyzed using the Judd-Ofelt theory. The optimized phosphor showed a good thermal stability and the lifetime values are in the millisecond range. The absolute and the relative sensitivities are obtained from the temperature dependent lifetime measurements. The LiSrVO4:9 mol%Eu3+ phosphor yielded CIE coordinates (x, y) of (0.5987, 0.4005), a low CCT of 1468K, and a color purity of 96.4 %. These results indicate the potential application of the LiSrVO4 based phosphors in WLEDs.

Fabrication of high photocatalytic activity photocatalysts with TiO2 supported on lamellar BiOCl

A lamellar nanostructure consisting of anatase TiO2/BiOCl was effectively developed while employing the approach of solvothermal. The samples underwent comprehensive analysis of their phase structures, morphologies, surface areas, optical properties, and electronic states using various techniques including x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) method, UV–vis diffuse reflectance spectra (UV–vis DRS), Fourier transform infrared spectroscopy (FTIR), and photoluminescence spectroscopy(PL). The photoelectrochemical data demonstrated that the incorporation of anatase TiO2 nanoparticles into the BiOCl lamellar structure significantly improved its photocatalytic efficiency to degrade Malachite Green (MG) in UV light, surpassing the performance of both pure BiOCl and anatase TiO2. Additionally, the study delved into the photocatalytic mechanism responsible for this enhanced performance. The superior photocatalytic efficiency of the anatase TiO2/BiOCl composites can be ascribed to higher surface area, smaller crystallite size, stronger light absorption and improved charge separation efficiency.

Cs-Doped WO3 with Enhanced Conduction Band for Efficient Photocatalytic Oxygen Evolution Reaction Driven by Long-Wavelength Visible Light.

Cesium doped WO3 (Cs-WO3) photocatalyst with high and stable oxidation activity was successfully synthesized by a one-step hydrothermal method using Cs2CO3 as the doped metal ion source and tungstic acid (H2WO4) as the tungsten source. A series of analytical characterization tools and oxygen precipitation activity tests were used to compare the effects of different additions of Cs2CO3 on the crystal structure and microscopic morphologies. The UV-visible diffuse reflectance spectra (DRS) of Cs-doped material exhibited a significant red shift in the absorption edge with new shoulders appearing at 440-520 nm. The formation of an oxygen vacancy was confirmed in Cs-WO3 by the EPR signal, which can effectively regulate the electronic structure of the catalyst surface and contribute to improving the activity of the oxygen evolution reaction (OER). The photocatalytic OER results showed that the Cs-WO3-0.1 exhibited the optimal oxygen precipitation activity, reaching 58.28 µmol at 6 h, which was greater than six times higher than that of WO3-0 (9.76 μmol). It can be attributed to the synergistic effect of the increase in the conduction band position of Cs-WO3-0.1 (0.11 V) and oxygen vacancies compared to WO3-0, which accelerate the electron conduction rate and slow down the rapid compounding of photogenerated electrons-holes, improving the water-catalytic oxygen precipitation activity of WO3.

Enhanced Photodegradation of Acetaminophen Using Efficient ZnO-NiO Nanofibers

The increasing presence of pharmaceutical pollutants, such as acetaminophen, in water bodies poses a significant environmental challenge due to their persistence and potential toxicity. This study investigated the enhanced photodegradation of acetaminophen using ZnO-NiO nanofibers as superior photocatalysts. The nanofibers synthesized with varying NiO contents (designated as ZN0.5, ZN1, ZN1.5, and ZN2), were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman, FTIR, Brunauer–Emmett–Teller (BET) analysis, and diffuse reflectance spectroscopy (DRS) to elucidate their structural, morphological, and optical properties. Thermogravimetric analysis (TGA) indicated that the nanofibers exhibit high thermal stability, with major weight loss attributed to the decomposition of the polymer matrix and residual organics. The BET analysis revealed that the specific surface area remains stable after increasing the NiO content up to a certain ratio. This stability correlates with the enhanced photocatalytic performance due to increased light absorption and improved charge separation. The diffuse reflectance spectra and Kubelka–Munk plots demonstrated a reduction in bandgap energy with higher NiO content, facilitating greater visible light absorption. Photocatalytic experiments under visible light irradiation, in the presence of peroxymonosulfate (PMS), showed that the ZN1.5 nanofibers achieved the highest acetaminophen degradation rate, i.e., 92%, within 3 h. Mechanistic studies, supported by radical trapping experiments, revealed that the improved photocatalytic efficiency is due to the synergistic effects of ZnO and NiO heterojunctions, which enhance charge separation and reactive oxygen species (ROS) generation. This research highlights the potential of ZnO-NiO nanofibers as effective photocatalysts for the degradation of pharmaceutical pollutants. The findings demonstrate that optimizing the composition and structure of nanofibers can significantly improve their environmental remediation capabilities, providing a promising solution for sustainable water treatment.

Color tuning by Si/Ge substitution in Cr4+ doped melilite inorganic pigments

Rockery constitutes one of the significant elements of Chinese royal garden design, and it becomes an emerging interdisciplinary topic covering both science and art. In this work, we report an attempt to restore the color of the ancient rockeries by finding the appropriate inorganic pigments. Chromium is doped as activators into strontium melilites with varying Si/Ge ratio, and the synthesized powders give a series of color changing from ice blue to dark-sea green. With the structure and spectroscopic characterizations, we discuss the substitutions of Cr in Mg/Si/Ge sites of the melilite host. The Tanabe-Sugano diagram of 3d2 configuration is employed to explain the change of diffuse reflectance spectra caused by Si/Ge substitution. With the work, we hope to inspire the interdisciplinary research and promote the rockery heritage restoration and protection.

Additive patterns in near-infrared diffuse reflectance spectra: Implications for product formulation and analysis

In this study, we investigated the additive patterns observed in near-infrared (NIR) diffuse reflectance spectra within the context of food and pharmaceutical product formulation. Employing the Kubelka–Munk theory, we examined the linear correlation between spectra and concentration in polymer materials and tobacco powder samples. Our findings confirm the principle of spectral additivity in diffuse reflectance spectra, demonstrating a linear relationship when the sample scattering coefficient remains constant. Moreover, our results validate the feasibility of substituting actual mixed spectra with NIR additive spectra in tobacco leaf systems. This approach can potentially enhance formulation design, thereby improving efficiency and accuracy while expanding the scope and combination of formulation materials. Furthermore, this study offers a rapid, information-rich, and environmentally friendly alternative to traditional methods, with significant implications for the future of product formulation.

Host sensitized down conversion emission in KSrVO4:Yb3+− A potential thermally stable phosphor for solar cell applications

This work reports the successful synthesis of an efficient near infra-red (NIR) emitting KSrVO4:Yb3+ phosphor using the combustion method. The X-ray diffraction technique (XRD) confirmed the orthorhombic phase of a material whereas X-ray photoelectron spectroscopy (XPS) analyzed the elemental makeup and chemical states of the phosphor components. Photoluminescence (PL) analysis revealed that the phosphor exhibit superior thermal stability and emit in the NIR region when activated by near-UV light. An upsurge in emission intensity occurs upon the incorporation of Bi3+ as a co-dopant. Using diffuse reflectance spectra (DRS), optical band gap, metallization constant, and refractive index were computed for all ion concentrations in KSr(1-x)VO4:xYb3+ (0 ≤x ≤ 0.06). For the optimized concentration of Yb3+ into the host, numerical values of these parameters were also estimated. The studies reveal that the produced material may be applied as a solar spectrum converter to improve the efficiency of crystalline silicon (c-Si) solar cells.