Search Results (208)

Cd-based perovskite materials have the advantages of high emission efficiency and tunable emission, as well as broad application prospects in the field of optoelectronics. However, achieving multimode dynamic luminescence under UV light excitation in a single system is a great challenge. Here, we successfully prepared Sb³⁺/Pb²⁺ co-doped Cs₇Cd₃Br₁₃ crystals by a simple hydrothermal method. Tunable emission from orange to white and then to blue, covering the wavelength range between 370 and 800 nm, was achieved by varying the doping concentration of Pb²⁺ ions in Cs₇Cd₃Br₁₃:0.5%Sb³⁺. Temperature-dependent photoluminescence (PL) spectra and density functional theory (DFT) calculations confirm that the wide-band white-light emission of Cs₇Cd₃Br₁₃: Sb³⁺/Pb²⁺ crystal comes from the first self-trapped exciton (STE1) of undoped Cs₇Cd₃Br₁₃ intrinsic capture state and the emission of free excitons (FEs) and STE2 induced by the confining effect and the Jahn–Teller effect by Pb²⁺ incorporation, as well as the Sb triplet self-trapped exciton (STE3). More specifically, the samples with the best co-doped ratio exhibit significant excitation-wavelength-dependent luminescence characteristics and can realize the conversion of the emission color from white and blue to orange. Based on the tunable emission characteristics of three emission colors, the material has good prospects in encryption and anti-counterfeiting applications. This work provides a new strategy for the application of Cd-based halides in the field of anti-counterfeiting. Full article

Renewable fuels produced from animal- and plant-based edible oils have emerged as an alternative to oil and natural gas. Burgeoning interest in renewables can be attributed to the rapid depletion of fossil fuels caused by the global energy demand and the environmental advantages of renewables, specifically reduced emissions of greenhouse gases. An important property of the feedstock that is crucial for the conversion of edible oils to renewable fuels is the total acid number (TAN), as even a small increase in TAN for the feedstock can lead to corrosion of the catalyst in the refining process. Currently, the TAN is determined by potentiometric titration, which is time-consuming, expensive, and requires the preparation of reagents. As part of an effort to promote the use of renewable fuels, a partial least squares regression method with orthogonal signal correction to remove spectral information related to the sample background was developed to determine the TAN from the mid-infrared (IR) spectra of the feedstock. Digitally blended mid-IR spectral data were generated to fill in regions of the PLS calibration where there were very few samples. By combining experimental and digitally blended mid-IR spectral data to ensure adequate sample representation in all regions of the spectra–property calibration and better understand the spectra–property relationship through the identification of sample outliers in the original data that can be difficult to detect because of swamping, a PLS regression model for TAN (R² = 0.992, cross-validated root mean square error = 0.468, and bias = 0.0036) has been developed from 118 experimental and digitally blended mid-IR spectra of commercial feedstock. Thus, feedstock whose TAN value is too high for refining can be flagged using the proposed mid-IR method, which is faster and easier to use than the current titrimetric method. Full article

This study explores the optical properties of a close-packed monolayer composed of core/shell-alloyed CdSeS/ZnS quantum dots (QDs) of two different sizes and compositions. The monolayers were self-assembled in a stacked configuration at the water/air interface using Langmuir–Blodgett (LB) techniques. Under continuous 532 nm laser illumination on the red absorption edge of the blue-emitting smaller QDs (QD450), the red-emitting larger QDs (QD645) exhibited oscillatory temporal dynamics in their photoluminescence (PL), characterized by a pronounced blueshift in the emission peak wavelength and an abrupt decrease in peak intensity. Conversely, excitation by a 405 nm laser on the blue absorption edge induced a drastic redshift in the emission wavelength over time. These significant shifts in emission spectra are attributed to photon- and anisotropic-strain-assisted interlayer atom transfer. The findings provide new insights into strain-driven atomic rearrangements and their impact on the photophysical behavior of QD systems. Full article

Two-dimensional (2D) hybrid organic–inorganic perovskites (HOIPs) have attracted considerable attention in optoelectronic applications, owing to their remarkable characteristics. Nevertheless, the application of 2D HOIPs encounters inherent challenges due to the presence of insulating organic spacers, which create barriers for efficient interlayer charge transport (CT). To tackle this issue, we propose a BA₂MAPb₂I₇/PEA₂MA₂Pb₃I₁₀ bilayer heterostructure, where efficient interlayer energy transfer (ET) facilitates compensation for the restricted charge transport across the organic spacer. Our findings reveal that under 532 nm light illumination, the BA₂MAPb₂I₇/PEA₂MA₂Pb₃I₁₀ heterostructure photodetector exhibits a significant photocurrent enhancement compared with that of the pure PEA₂MA₂Pb₃I₁₀ device, mainly due to the contribution of the ET process. In contrast, under 600 nm light illumination, where ET is absent, the enhancement is rather limited, emphasizing the critical role of ET in boosting device performance. The overlap of the PL emission peak of BA₂MAPb₂I₇ with the absorption spectra of PEA₂MA₂Pb₃I₁₀, alongside the PL quenching of BA₂MAPb₂I₇ and the enhanced emission of PEA₂MA₂Pb₃I₁₀ provide confirmation of the existence of ET in the BA₂MAPb₂I₇/PEA₂MA₂Pb₃I₁₀ heterostructure. Furthermore, the PL enhancement factor followed a 1/d² relationship with the thickness of the hBN layer, indicating that ET originates from 2D-to-2D dipole–dipole coupling. This study not only highlights the potential of leveraging ET mechanisms to overcome the limitations of interlayer CT, but also contributes to the fundamental understanding required for engineering advanced 2D HOIP optoelectronic systems. Full article

This study reports the synthesis, structural characterization, adsorption studies, nanoscale interaction, and photocatalytic application of pure and Fe-doped ZnS quantum dots for the degradation of the antibiotic cefalexin in aqueous solution. Nanoparticles were synthesized via the microwave-assisted method, and Fe doping was introduced at a 1% molar ratio. HRTEM images confirmed quasi-spherical morphology and high crystallinity, with particle sizes averaging 2.4 nm (pure) and 3.5 nm (doped). XRD analysis showed a consistent cubic ZnS structure. UV-vis spectra showed strong absorption at 316 nm for both samples, and PL measurements revealed emission quenching upon Fe doping. Photocatalytic tests under UV light demonstrated significantly higher degradation rates of 10 ppm cefalexin with Fe-doped ZnS, reaching near-complete removal within 90 min. Adsorption experiments revealed higher affinity and adsorption capacity of Fe-doped ZnS toward cefalexin compared to pure ZnS, as demonstrated by the Freundlich isotherm analyses, contributing significantly to enhanced photocatalytic degradation performance. High-resolution QTOF LC-MS analysis confirmed the breakdown of the β-lactam and thiazolidine rings of cefalexin and the formation of low-mass degradation products, including fragments at m/z 122.0371, 116.0937, and 318.2241. These findings provide strong evidence for the structural destruction of the antibiotic and validate the enhanced photocatalytic performance of Fe-doped ZnS. Full article

The synthesis process employed solid-state reaction methods to produce phosphors with varying CaO contents, specifically at x values of 0, 0.2, 0.4, 0.6, 0.8, and 1.0. As the CaO content (represented by the x value) increases, the crystalline structure of Ca_2+xGa₄O_8+x + 0.01 Bi₂O₃ + 0.07 ZnO compositions underwent notable transformations. X-ray diffraction was used to characterize these structural changes, and we found that CaGa₂O₄, CaO, Ga₂O₃, and Ca₃Ga₄O₉ were clearly identified. The diffraction intensities of CaGa₂O₄ and CaO phases increased and those of Ga₂O₃ and Ca₃Ga₄O₉ decreased with the x value. Our findings revealed that the photoluminescence excitation (PLE) spectra consistently peak around 340 nm across all samples, while the photoluminescence emission (PL) spectra exhibited slight variations within the range of 474–477 nm. Most notably, the intensity of both PLE and PL spectra demonstrated a non-linear relationship with CaO content, initially increasing with higher CaO concentration, reaching maximum intensity at x = 0.4, and subsequently decreasing as the x value continued to rise. This research provides valuable insights into the relationship between composition, crystal structure, and luminescent behavior in Ca_2+xGa₄O_8+x phosphor systems, and the theoretical mechanisms underlying these observed trends were thoroughly discussed. Full article

In this study, Lu_2.5Y_0.5(Al_2.5Ga_2.5)O₁₂ (LuYAGG) single-crystal scintillators doped with terbium ions (Tb³⁺) at concentrations of 0.5, 1, 5, and 10 mol% were successfully synthesized using the floating zone method. The structural, optical, photoluminescence (PL), and scintillation properties of the Tb³⁺-doped crystals were systematically investigated with a focus on their potential for high-performance scintillator applications. X-ray diffraction (XRD) confirmed the formation of a pure garnet phase without any secondary phases, indicating the successful incorporation of Tb³⁺ into the LuYAGG lattice. Optical transmittance spectra revealed high transparency in the visible range. Photoluminescence measurements showed characteristic Tb³⁺ emission peaks, with the strongest green emission observed from the ⁵D₄ → ⁷F₅ transition, particularly for the 5 mol% sample. The PL decay curves further confirmed that this concentration offers a favorable balance between radiative efficiency and minimal non-radiative losses. Under γ-ray excitation, the 5 mol% Tb³⁺-doped crystal exhibited the highest light yield, surpassing the performance of other concentrations and even outperforming Bi₄Ge₃O₁₂ (BGO) in relative comparison, with an estimated yield of approximately 60,000 photons/MeV. Scintillation decay time analysis revealed that the 5 mol% sample also possessed the fastest decay component, indicating its superior capability for radiation detection. Although 10 mol% Tb³⁺ still showed good performance, slight quenching effects were observed, while lower concentrations (0.5 and 1 mol%) suffered from longer decay and lower emission efficiency due to limited activator density. These findings clearly identify with 5 mol% Tb³⁺ as the optimal dopant level in LuYAGG single crystals, offering a synergistic combination of high light yield and excellent optical transparency. This work highlights the strong potential of LuYAGG:Tb³⁺ as a promising candidate for the next-generation scintillator materials used in medical imaging, security scanning, and high-energy physics applications. Full article

In this study, Mn²⁺ and Eu²⁺-codoped Sr_3−xBa_xMgSi₂O₈ (x = 0–1.5) phosphors were synthesized at 1400 °C under a reducing atmosphere composed of 5% H₂ and 95% N₂ to produce materials with blue light emission. The resulting powders were characterized using several analytical techniques: X-ray diffraction (XRD) was employed to identify the crystalline phases, scanning electron microscopy (SEM) was used to observe the microstructure, and photoluminescence excitation (PLE) and emission (PL) spectra were measured using a fluorescence spectrophotometer. The results revealed several key findings. XRD analysis showed that the Sr₃MgSi₂O₈ (Sr_3−xBa_xMgSi₂O₈) phase coexisted with secondary phases of Sr₂SiO₄ and Sr₂MgSi₂O₇. SEM observations indicated that the synthesized powders exhibited a distinctive needle-like structure anchored on the surfaces of the particles. The PL and PLE intensities increased sharply as the BaO content increased from x = 0 to x = 0.6, followed by a more gradual increase, reaching a peak at x = 1.2. Additionally, as the value of x increased, the wavelengths corresponding to maximum PL and PLE intensities exhibited a blue shift, moving to shorter wavelengths. Further investigation focused on the excitation behavior by replotting the PLE spectra using energy (eV) as the x-axis. A Gaussian fitting function was applied to deconvolute the excitation bands, enabling an in-depth analysis of how compositional variations influenced the Stokes shift. Full article

Both tungsten trioxide (WO₃) nanosheet arrays and tungsten trioxide/zinc oxide (WO₃/ZnO) nanocomposites were grown on fluorine-doped tin oxide (FTO) coated glass slides using a hydrothermal method to develop a visible-light-driven photocatalyst with easy reusability. Field emission scanning electron microscopy (FE-SEM) observations confirmed the formation of irregular oxide nanosheet arrays on the FTO surfaces. X-ray diffraction (XRD) analysis revealed the presence of hexagonal WO₃ and wurtzite ZnO crystal phases. UV-Vis diffuse reflectance spectroscopy showed that integrating ZnO nanostructures with WO₃ nanosheets resulted in a blue shift of the absorption edge and a reduced absorption capacity in the visible-light region. Photoluminescence (PL) spectra indicated that the WO 0.5/ZnO 2.0 sample exhibited the lowest electron-hole recombination rate among the WO₃/ZnO nanocomposite sample. Photocatalytic degradation tests demonstrated that all WO₃/ZnO nanocomposite samples had higher photodegradation rates for a 10 ppm methylene blue (MB) aqueous solution under visible-light irradiation compared to pristine WO₃ nanosheet arrays. Among them, the WO 0.5/ZnO 2.0 sample showed the highest photocatalytic efficiency. Furthermore, it exhibited excellent recyclability and high photodegradation stability over three cycles. Full article

Dy³⁺ single-doped and Dy³⁺/Eu³⁺ co-doped ZnO:B₂O₃:WO₃:Nb₂O₅ glass was successfully synthesized using the melt quenching method. The amorphous character of the prepared samples was confirmed by X-ray diffraction (XRD). The glass transition and crystallization temperatures were examined by differential scanning calorimetry (DSC). Raman spectroscopy was applied to investigate the glass microstructure. Physical properties like the density, molar volume, oxygen molar volume and oxygen packing density of the glass were also determined. The photoluminescence excitation (PLE) and emission (PL) spectra of the resultant glass types were measured. The obtained Dy³⁺ single-doped glass was characterized by strong luminescence at 482 and 574 nm, corresponding to the ⁴F_9/2 → ⁶H_15/2 (blue) and ⁴F_9/2 → ⁶H_13/2 (yellow) transitions, respectively, and weak luminescence at 663 nm and 753 nm due to the ⁴F_9/2 → ⁶H_11/2 (red) and ⁴F_9/2 → ⁶H_9/2 + ⁶F_11/2 (red) transitions. The luminescence results indicate that energy transfer from the Dy³⁺ to Eu³⁺ ions occurs in the proposed glass system. The emitted light from the Dy³⁺ single-doped glass was found to be yellow-orange. The Dy³⁺/Eu³⁺ co-doped samples emitted darker orange light. The obtained results show that the investigated types of glass have the potential to be used as orange light-emitting materials. Full article

In this study, CdWO₄/CdMoO₄ powders’ heterostructures were synthesized using the microwave-assisted hydrothermal method, characterized, and evaluated for their photocatalytic properties. The samples were analyzed using X-ray diffraction (XRD), Raman and ultraviolet-visible (UV-Vis) spectroscopy, field-emission scanning electron microscopy (FESEM), and photoluminescence (PL). The photocatalytic performance was assessed using methylene blue as a model pollutant. XRD patterns and Raman spectra confirmed the formation of heterostructures containing the Wolframite phase of CdWO₄ and the Scheelite phase of CdMoO₄. FESEM micrographs revealed that the CdWO₄ phase exhibits a plate-like morphology, while the CdMoO₄ phase consists of irregular nanoparticles. Photocatalytic tests demonstrated that the 20Mo sample exhibited the best performance, degrading 96% of the dye after 2 h of reaction. The findings of this study indicate that CdWO₄/CdMoO₄ heterostructures hold significant potential for photocatalytic applications in the degradation of cationic dyes. Full article

Nitrogen-doped graphene quantum dots (NGQDs) are made by heating a mixture of GQDs and ammonia using a thermochemical method. The optical properties of the samples were studied. Here, the role of the temperature used in the annealing process is investigated. It is found that with the increase in heating temperature, the sp² fraction content continuously increases, and the photoluminescence (PL) blue shift continuously increases. The 550 nm peak of GQDs shifts from 550 nm to 513 nm NGQDs synthesized at 300 °C. The normalized PL intensity shows a significant blue shift in the emission peak of the NGQD samples compared to the GQDs. The peak position of the GQDs is 555 nm, while the peak positions of the NGQDs are 511 nm for NGQDs-250, 488 nm for NGQDs-300, and 480 nm for NGQDs-350. Using a simple thermochemical method, we can effectively dope N into GQDs, and it is evident from the electron energy loss spectra that N doping induces the emergence of a new energy level in the electronic structure, which alters the optical properties of NGQDs. Full article

Two innovative dimeric derivatives of indolo[3,2,1-jk]carbazole (ICz), named 7,7′-biindolo[3,2,1-jk]carbazole (ICzDO) and 4,4′-biindolo[3,2,1-jk]carbazole (ICzDM), have been developed. Both dimers consist of two ICz units coupled through distinct ortho and meta positions. In the solution state, ICzDO and ICzDM exhibited photoluminescence (PL) maxima at 379 nm and 391 nm, demonstrating emission in the deep-blue region. These compounds show exceptionally narrow emission spectra, characterized by full width at half maximum (FWHM) of 28 nm for ICzDO and 26 nm for ICzDM. In the film state, ICzDM exhibited a photoluminescence (PL) maximum at 428 nm, whereas ICzDO showed a red-shifted emission at 507 nm with a broad full width at half maximum (FWHM) of 87 nm, indicating significant red-shifted excimer emission characteristics. This is attributed to its aggregation-enhanced excimer emission (AEEE) characteristics. When used as host materials for red phosphorescent OLEDs, both compounds enabled efficient energy transfer. Devices using ICzDM as the host attained highly efficient external quantum efficiency (EQE) values of 13.5%, coupled with remarkable color purity represented by Commission Internationale de l’Éclairage (CIE) coordinates of (0.685, 0.314). These findings emphasize how strategic variations in linking positions of identical chromophores can markedly enhance OLED device performance, paving the way for innovative material designs in next-generation organic semiconductor technologies. Full article

The study explores the optical and transport properties of polycrystalline ZnO thin films prepared using reactive pulsed mid-frequency sputtering with RF electron cyclotron wave resonance (ECWR) plasma. This deposition method increases the ionization degree of sputtered particles, the dissociation of reactive gas and the plasma density of pulsed reactive magnetron plasma. Optical absorption spectra reveal a sharp Urbach edge, indicating low valence band disorder. Lattice disorder and deep defect concentration are more likely to occur in samples with higher roughness. PL analysis at low temperature reveals in all samples a relatively slow (μs) red emission band related to deep bulk defects. The fast (sub-ns), surface-related blue PL band was observed in some samples. Blue PL disappeared after annealing in air at 500 °C. Room temperature Hall effect measurements confirm n-type conductivity, though with relatively low mobility, suggesting defect-related scattering. Persistent photoconductivity was observed under UV illumination, indicating deep trap states affecting charge transport. These results highlight the impact of deposition and post-treatment on polycrystalline ZnO thin films, offering insights into optimizing their performance for optoelectronic applications, such as UV detectors and transparent conductive oxides. Full article

Two modifications of ZnMoO₄ were successfully obtained by mechanochemical treatment with two milling speeds applied at 500 and 850 rpm. The phase formation was monitored by XRD analysis. The metastable monoclinic ß-ZnMoO₄ was directly synthesized at room temperature using the higher milling speed of 850 rpm. The thermodynamically stable triclinic α-ZnMoO₄ was obtained by combining heat treatment t 600 °C and ball milling at the lower milling speed of 500 rpm. The IR spectra contain typical vibration bands and confirm the formation of both ZnMoO₄ polymorphs. UV-Vis absorption and photoluminescence (PL) spectroscopy are used to study the optical properties of the as-prepared samples. The calculated optical band gaps for α- and ß-ZnMoO₄ are 4.09 and 3.02 eV. The photoluminescence emission spectrum of both samples shows peaks with different maximum intensity at 615 and 403 nm for α and ß phase, respectively. CIE co-ordinates are located in the orange and blue range of the color diagram. Full article