Search Results (282)

Aerosol-assisted chemical vapor deposition (AACVD) was used to prepare a thin film of the heterojunction MnO₂/WO₃ onto an FTO glass substrate. The WO₃/MnO₂ heterojunction thin film exhibited a monoclinic WO₃ structure characterized by a nanorod-like shape and substantial interfacial bonding. The detected surface area of the WO₃/MnO₂ thin film is 32.58 ± 0.79 μm², while the values of R_a and R_q are 23.20 ± 2.26 nm and 29.60 ± 2.40 nm, respectively, which are higher than pure MnO₂ (R_a =13.40 ± 0.99 nm), while lower than pure WO₃ (R_a = 69.75 ± 1.34 nm) thin films. The UV–Vis spectra demonstrated extensive absorption in the visible to near-infrared range. The absorption spectrum of UV–Vis (200–900 nm) displayed a distinct absorption edge under 400 nm. The band gap of the pure WO₃ thin film equals 2.79 eV, whereas an effective band gap of WO₃/MnO₂ was observed to equal 1.51 eV, which is significantly smaller than that of the individual oxides (MnO₂ = 4.47 eV and WO₃ = 2.79 eV). Photoluminescence (PL) verified the robust interfacial electronic interaction. The investigation of the PEC performance exhibited the best performance and the greatest photocurrent under illumination than either pure component. Additionally, there was a good enhancement and improvement in the charge separation due to combining the catalytic MnO₂ thin film with a photoactive WO₃, owing to its effective charge transfer and decreased recombination. Full article

Photocatalysis is a promising route for the environmentally friendly destruction of organic pollutants and recycling the polluted water in industrial contexts for future environmental challenges. In this novel research work, the coupling of definite proportions of silver phosphate and g-C₃N₄ is carried out sonochemically for engineering S-scheme Ag₃PO₄/g-C₃N₄ heterojunctions. With the data obtained from a N₂-adsorption–desorption isotherm, a diffuse reflectance spectrum, X-ray diffraction, a high-resolution transmission electron microscope and zeta potential measurement, as-synthesized nanocomposites are fully characterized and defined. Successful coupling of Ag₃PO₄/g-C₃N₄ heterojunctions was verified given the existence of diffraction peaks of g-C₃N₄ and Ag₃PO₄; the shift in the peak position of the DRS spectrum of g-C₃N₄ from 440 to 463 nm; and the decrease of 68% in the photoluminescence emission peak. The crystalline size of the nanocomposite decreased from 76 to 25 nm, which was ascribed to coupling of Ag₃PO₄ on g-C₃N₄ under sonochemical conditions. The as-synthesized nanocomposites exhibited different trends in the destruction of rhodamine B dye. The experimental results indicated that the sample containing 15 weight % of Ag₃PO₄ degraded 89% of the RhB dye. Precise analysis of reactive radicals species experiments indicated that superoxide radicals and positive roles directed the charge transportation between g-C₃N₄ and Ag₃PO₄ semiconductors toward the S-scheme mechanism that produces charge radicals of auspicious redox efficiency. Full article

Integrated and tunable light sources are critical for advancing quantum nanophotonic chips in quantum computing, communications, and sensing. However, efficient and tunable emission amplification post-fabrication poses major challenges. Hybrid metasurfaces combining niobium pentoxide (Nb₂O₅), copper indium sulfide (CIS) quantum dots or hexagonal boron nitride (hBN), and antimony trisulfide (Sb₂S₃) as a low-loss phase-change material offer a compelling solution for dynamic control and amplification of photoluminescence and quantum light emission. In this work, an active hybrid metasurface supporting tunable bound states in the continuum (BIC) resonances in the visible regime is demonstrated, achieving experimental Q-factors up to 206 at an amorphous state and strong amplification of CIS QDs photoluminescence, as well as quantum light emission of hBN single-photon emitters. The metasurface enables BIC resonance shifts of 33.5 nm in the visible spectrum via phase transition of Sb₂S₃, and 17 nm through dimensional parametric tuning. The experiment demonstrates a highly directional photoluminescence amplification up to 33-fold, alongside broad tunable amplified PL emission upon Sb₂S₃ phase modulation. Furthermore, amplified, tunable, and on-demand strong coupling of hBN single-photon emitters is proposed with the tunable BIC metasurface for next-generation broadband quantum nanophotonic chips. This work sets a new benchmark in reconfigurable nanophotonic platforms for efficient quantum light sources in integrated photonic systems. Full article

To reveal the varieties and color genesis of emerald-green tourmaline crystals from Tanzania, a systematic study was conducted using conventional gemological tests, X-ray diffraction, Fourier-transform infrared spectroscopy, polarized ultraviolet–visible spectroscopy (UV–vis), X-ray photoelectron spectroscopy (XPS), low-temperature photoluminescence (PL) spectroscopy, and electron probe microanalysis (EPMA). The results indicate that the tourmaline is dravite. Its UV–vis absorption spectrum shows strong broad absorption bands at approximately 436 and 600 nm, with a pronounced transmission at 520 nm, which directly accounts for its emerald green color. Obvious polarized absorption was observed along and perpendicular to the c-axis. XPS and PL results confirm that chromium is present in the samples in the form of Cr³⁺. EPMA compositional analysis indicated a low Cr₂O₃ content of 0.804 wt.%; combined with crystal structural properties and spectral responses, these results suggest that Cr³⁺ preferentially occupies the Y site in the crystal structure and that d–d electronic transitions represent the underlying mechanism of its color formation. This study comprehensively illustrated the mineralogical and spectral properties of Cr-bearing dravite, providing fundamental data for further research on its genesis and gemological application. Full article

This study demonstrates a single phosphor material system capable of continuously tuning color across the entire visible spectrum while integrating multiple luminescent functionalities. A series of these phosphors was conveniently synthesized with varying Al/Sr ratios in the reactants, enabling the emission color to progress through red, orange, yellow, green and blue. We systematically investigated the photoluminescence mechanisms by correlating crystal phase evolution with europium ion site occupancy and exploiting the resulting multicolor-emitting phosphors in optical display and anti-counterfeiting demonstrations. The relationships between composition, structure, and luminescence were revealed commendably, alongside more functional evaluations of europium-doped strontium aluminate phosphors. Notably, at an equimolar Al/Sr ratio of 1 (with 2 at% Eu doping), the phosphor achieves a high absolute quantum yield of 66.2% and functions as a luminescent optical thermometer with a relative sensitivity of 0.27% K⁻¹ and temperature resolution of ~0.005 K. At a non-equimolar Al/Sr ratio of 2, the Eu-doped phosphor exhibits efficient photothermal conversion, reaching ~72.8 °C under 980 nm laser irradiation (1 W·cm⁻²) within 10 s. This work introduces a facile composition-regulation strategy for designing multicolor-tunable, multifunctional phosphors, highlighting promising applications in optical displays, anti-counterfeiting, luminescence thermometry and photothermal conversion. Full article

Zinc–antimony–boro–germanate glasses highly doped with Sm₂O₃ were synthesized by the conventional melt-quenching method. Their structural, optical, and luminescent properties were systematically investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance UV–Vis (DR-UV–Vis), and photoluminescence (PL) spectroscopy. XRD analysis confirmed the amorphous nature of all prepared samples. XPS measurements were used to examine the surface chemical composition of the Sm₂O₃-doped glasses, with particular focus on verifying samarium incorporation and identifying its oxidation state after synthesis, since Sm ions act as the luminescent centers in these materials. For the sample containing the highest Sm₂O₃ concentration, the DR-UV–Vis spectrum exhibited ten absorption bands assigned to intra 4f electronic transitions. Based on these data, the nephelauxetic and bonding parameters were determined, indicating that increasing Sm₂O₃ content enhances the ionic character of the bonds within the glass network. PL spectra revealed three characteristic emission bands associated with Sm³⁺ luminescent centers. The emission intensity reached a maximum at 3 mol% Sm₂O₃, while further increases in samarium content led to luminescence quenching. The most intense emission band was in the yellow–orange region of the visible spectrum, highlighting the potential of these materials for yellow–orange-emitting solid-state laser applications. The excitation spectra show that the optical response is strongly dependent on concentration, with a sample doped with 3 mol% Sm₂O₃ exhibiting the highest excitation efficiency. The dominant excitation band centered near 402 nm, together with weaker bands in the blue region, indicating that these glasses are promising candidates for near-UV-pumped orange-emitting photonic devices. Full article

Mg-doped ZnO (Zn_1−xMg_xO, x = 0.00–0.05) thin films were successfully grown on glass substrates with a c-axis orientation at 600 °C using the sol–gel dip-coating technique. The structural features, defect-related photoluminescence, and optical constants of the films were systematically investigated as a function of Mg concentration. X-ray diffraction (XRD) patterns confirmed a single-phase hexagonal wurtzite structure with a preferential (₀₀₂) orientation for all compositions, indicating the successful substitution of Mg²⁺ ions into the ZnO lattice. The crystallite size (D₀₀₂) was found to vary between 28.49 and 41.18 nm, while microstrain and stress exhibited non-monotonic behavior depending on Mg content. This behavior reveals a transition from compressive to tensile stress due to lattice distortion and defect formation. Photoluminescence (PL) spectra showed a dominant near-band-edge (NBE) ultraviolet emission, along with broad visible emissions extending from violet to red. Optical constants were accurately extracted using a double-facet-coated substrate (DFCS) model, combined with nonlinear curve fitting using the Nelder–Mead optimization algorithm. The films showed a strong absorption edge at about 370 nm and exceptional optical transparency (≈60–80%) in the visible spectrum. The systematic blue shift in the extinction coefficient with increasing Mg content confirms bandgap engineering in Zn_1−xMg_xO thin films. The refractive index dispersion was successfully modeled using the Cauchy relation, demonstrating composition-dependent tunable optical properties. Depending on the Mg content, the optical bandgap values ranged from approximately 3.265 to 3.315 eV. The band-edge states and optical constants are strongly affected by the combined effects of defect development, Mg-induced lattice distortion, and changes in optical dispersion. These results indicate that sol–gel-derived Mg-doped ZnO thin films with composition-dependent stress states, defect states, and tunable optical properties are promising candidates for UV photodetectors, optical coatings, and transparent optoelectronic devices. Full article

Hydrophobic carbon quantum dots (hbCQDs) with tunable photoluminescence were synthesized via a solvothermal approach and further hybridized with Rhodamine B (RhB) to extend emission into the visible range. The hbCQDs exhibit quasi-spherical morphology with an average particle size of 8 nm and predominantly disordered graphitic structure, as confirmed by TEM and XRD analyses. FTIR and XPS characterizations reveal surface functional groups including C–N, C=O/C–O, and S–H, which govern the photoluminescence properties. Pure hbCQDs display blue emission at 453 nm under excitation, with a quantum yield (QY) of 6.2%. Incorporation of RhB leads to dual-emission behavior: the surface-state emission remains in the blue region, while molecular-state emission from RhB appears in the orange-red region. The 0.2 mL RhB–CQD composite exhibits optimal properties, including a QY of 13% and a production yield of 82%, emitting white light under 365 nm UV excitation. Increasing RhB loading to 0.4 mL results in a shift in emission peaks and a reduced QY (<9%), with weaker orange fluorescence. These findings demonstrate that controlled RhB hybridization effectively tunes the emission spectrum of hbCQDs, offering a simple and reproducible strategy to achieve dual-color and white-light emission. The optimized hbCQDs/RhB composites hold significant potential for applications in hydrophobic media-compatible organic optoelectronics, light-emitting devices, and bioimaging. Full article

Dual-emission photoluminescence (PL) nanoprobes provide improved analytical performance to develop a reliable and sensitive sensing platform for quantifying chloramphenicol in pharmaceutical samples, thereby ensuring therapeutic efficacy and patient safety. In this work, a dual-emission PL sensing platform combining carbon dots (CDs) and AgInS₂ quantum dots (QDs) capped with mercaptopropionic acid (MPA) was developed for the quantitative determination of chloramphenicol, resorting to chemometric methods for data analysis. CDs, CdTe QDs, and AgInS₂ QDs were synthesized and individually evaluated considering their photostability, PL response and kinetics of their interaction with the antibiotic. After this, two dual-emission probes, CDs/MPA-CdTe and CDs/MPA-AgInS₂, were prepared and assessed based on the complementarity of their individual emission features. The obtained kinetic PL dataset was processed using unfolded partial least squares (U-PLS) in order to explore the multidimensional information of the dual-emission systems and to evaluate the performance of both sensing platforms. CDs/MPA-AgInS₂ probe was demonstrated to be the most efficient sensing platform due to its better compromise between sensitivity and photostability, as well as its cadmium-free composition, allowing the implementation of a more environmentally friendly analytical methodology. The optimization of the U-PLS models involved the assessment of the kinetic acquisition time and different spectral regions. The results showed that reliable, sensitive and efficient quantification could be achieved within the first 5 min of interaction and using the full emission spectrum of the sensing probe. Additionally, different interaction mechanisms were observed for each nanomaterial in the combined probe, being static for the CDs/chloramphenicol interaction and dynamic for MPA-AgInS₂/chloramphenicol interaction, which supports the synergetic behavior of the combined probe. The proposed methodology was effectively applied to commercial pharmaceutical formulations, yielding accurate results with good figures of merit. Therefore, this approach can be used as a relevant alternative to existing methodologies for a rapid, robust, and environmentally friendly method for chloramphenicol quantification. Full article

Metal halides with efficient, stable, and tunable white light emission are ideal for lighting applications, because their emission properties can be effectively optimized through rational doping and precise compositional engineering. However, the synthesis of such materials often requires strict conditions and complex procedures. In this work, we report a phase transition from Sb-doped Cs₂InCl₅·H₂O to Cs₂NaInCl₆, along with tunable white light emission. Partial substitution of Na⁺ enables the formation of high-energy multiple emission centers, resulting in efficient white light with an adjustable correlated color temperature ranging from 2500 K to 5000 K under 365 nm excitation. The photoluminescence quantum yield reaches up to 45.24%. Efficient energy transfer among emission centers and the doping concentration of Na⁺ are critical for achieving high-performance tunable white light. The synthesized Cs₂Na_xInCl_5+x:Sb composite exhibits excellent stability under ultraviolet irradiation and environmental conditions such as oxygen and humidity, even after 200 h of ultraviolet irradiation, the emission spectrum remains stable, with more than 80% of its initial efficiency being preserved. Our results show its potential for advanced lighting applications and provide valuable insight for a desirable emission-tunable metal halide design. Full article

Perovskite quantum dots (PQDs) based on CsPbX₃ (X = Cl, Br, I) have attracted extensive attention due to their outstanding optoelectronic properties; however, their practical applications are hindered by poor environmental stability. In this work, a sequential surface-modification strategy is developed to address these limitations. First, CsPbBr₃ PQDs are passivated with (3-aminopropyl) triethoxysilane (APTES), which reduces surface defects and enhances the photoluminescence quantum yield (PLQY) from 38.5% to 74.4%. Subsequently, a dense silica shell is constructed via in situ hydrolysis of tetramethyl orthosilicate (TMOS), further improving the PLQY to 95.6% and significantly boosting environmental stability. Structural and optical characterizations confirm effective defect passivation and suppress non-radiative recombination, with carrier lifetimes extended from 2.5 ns to 36.9 ns. Remarkably, the silica-coated PQDs retain over 50% of their initial emission intensity after 100 min of water immersion, far exceeding the stability of uncoated counterparts. Furthermore, when integrated with a commercial K₂SiF₆: Mn⁴⁺ red phosphor and a blue light-emitting diode (LED) chip, the resulting white LED (WLED) exhibits a wide color gamut covering 104% of the National Television System Committee (NTSC) standard and Commission Internationale de l’Éclairage (CIE) coordinates of (0.323, 0.331), closely matching standard white light. Importantly, only the silica-coated PQDs maintain a stable electrically driven device emission spectrum after water exposure. Full article

Flavonoids, natural organic compounds from the polyphenolic group with broad bioactive and pharmaceutical properties, are strong ligands for many metal ions. This work describes the formation of the complex between Zn(II) and morin. The synthesized compound is characterized using three analytical techniques, i.e., ¹H NMR, IR, and thermal gravimetric analysis. Importantly, the complex was successfully obtained in the form of a solid, which enables its further physicochemical and structural characterization. Physicochemical characterization of the Morin-Zn complex was performed by steady-state and time-resolved spectroscopy. The absorption spectrum of the complex contains two main bands at ca. 407–415 nm and ca. 265 nm, and the complex emits yellow-green light with higher intensity than the free ligand. In the next step, morin and zinc complex were dispersed in a PMMA (poly (methyl methacrylate)) polymer matrix, and respective thin layers were produced. The studied thin films were deposited on silicon substrates by using the spin-coating method and characterized by X-ray photoelectron spectroscopy (XPS), Atomic Force Microscopy (AFM), Spectroscopic Ellipsometry (SE), UV-VIS spectroscopy, and photoluminescence (PL). The absorption of thin layers showed, similarly to solutions, the presence of two transitions: π→π* and n→π*, and a bathochromic shift for the morin-zinc complex compared to morin. The photoluminescence of the complex thin film showed two bands, the first in the range of 380–440 nm corresponding to PMMA, and the second with a maximum at 490 nm, derived from the synthesized compound. Full article

The pressure response of bulk and two−dimensional (2D) MoS₂ crystals (monolayer, bilayer, and many–layered), directly transferred to the diamond surface of the diamond anvil cell (DAC) used for high−pressure application, is examined by means of Raman and photoluminescence (PL) spectroscopy. For the high–pressure experiments of 2D MoS₂, the Daphne 7474 oil and the 4:1 methanol–ethanol mixture are alternatively used as pressure-transmitting media (PTM), while the former is also used as PTM in the case of bulk MoS₂. Characteristic differences are observed in the pressure evolution of the Raman spectral profile and the pressure coefficients of the peak frequencies between the bulk and the 2D MoS₂ crystals of various thicknesses, which also depend on the PTM used. These observations, along with the pressure evolution of the PL spectrum of 2D MoS₂, are ascribed to the different stress conditions in each case (hydrostatic vs. uniaxial compression perpendicular to the MoS₂ layers), the adhesion of the 2D MoS₂ crystals on the diamond anvil, as well as the nature of the particular PTM used and its interaction with the studied system. Full article

The present work systematically investigates the impact of multilayer architecture—specifically 5, 10, and 15 layers—on the structural, morphological, optical, and dielectric properties of zinc oxide (ZnO) thin films, aiming to tailor their characteristics for optoelectronic applications. The films were characterized using a comprehensive suite of techniques. X-ray diffraction (XRD) analysis of the 15-layer sample confirmed the formation of polycrystalline ZnO with a hexagonal wurtzite crystal structure, showing prominent (100), (002), and (101) diffraction peaks. Measurements indicated that the film thickness progressively increased from 43.81 nm for 5 layers to 80.68 nm for 15 layers. Concurrently, the surface roughness significantly decreased from 5.54 nm (5 layers) to 2.00 nm (15 layers) with increasing layer count, suggesting enhanced film quality and densification. Optical studies using ultraviolet–visible (UV-Vis) spectroscopy revealed an increase in absorbance and a corresponding decrease in transmittance in the UV-Vis spectrum as the film thickness increased. The calculated optical band gap showed a slight redshift, decreasing from 3.26 eV for the 5-layer film to 3.23 eV for the 15-layer film. Photoluminescence (PL) spectra exhibited characteristic near-band-edge UV emission, with the 5-layer film demonstrating the highest PL intensity. Furthermore, analysis of optical constants revealed that the refractive index, extinction coefficient, optical conductivity, and both the real and imaginary parts of the dielectric constant generally increased with an increasing number of layers, particularly in the visible region, while more nuanced and non-monotonic trends were observed in the UV range. These results underscore the significant influence of layer number on the physical properties of ZnO thin films, providing valuable insights for optimizing their performance in various optoelectronic devices. Full article

The organic/inorganic hybrid compound bis(2-amino-6-bromopyridinium) tetrachloridocuprate(II) (HABPy)₂[CuCl₄] was synthesized in crystalline form in a 77% yield from aqueous HCl solutions containing Cu(OAc)₂ and 2-amino-6-bromopyridine (ABPy). Single-crystal X-ray diffraction analysis revealed that the compound crystallizes in the monoclinic, centrosymmetric space group C2/c. The Cu atom shows a distorted tetrahedral coordination geometry with a τ₄ value of 0.69 (τ₄ = 1 for a perfect tetrahedron). The structure consists of organic (HABPy)⁺ cation layers at z = 0 and z = ½, alternating with inorganic [CuCl₄]²⁻ dianion layers at z = ¼ and z = ¾. These layers, parallel to the (001) plane, are interconnected by a plethora of supramolecular forces such as N–H···Cl hydrogen bonds, forming a three-dimensional network. Powder X-ray diffraction confirmed the purity of the synthesized bulk material. Fourier-transform infrared (FT-IR) spectroscopy and Raman spectroscopy support the protonation of the pyridine N atom. Hirshfeld surface analysis allowed us to further study the supramolecular forces in the crystal structure. The material shows purely paramagnetic behavior according to S = ½ with an effective magnetic moment µ_eff of 1.85 µB and a g factor of 2.14, in keeping with magnetically isolated [CuCl₄]²⁻ dianions. UV-vis diffuse reflectance spectroscopy of the orange-red material showed a tiny band at 314 nm and an intense band peaking at 622 nm. The optical gap was found to be 2.25 eV. The photoluminescence spectrum shows a partially structured band with maxima at 416 and 436 nm when irradiating at 370 nm, the wavelength of the maximum band found in the excitation spectrum. Full article