Search Results (3,007)

A quantum prism, a new structure, consisting of many quantum wires with a diameter that gradually decreases from the base to the top, is the focus of our research. This distribution of quantum wires leads to a dispersive emitted spectrum. The red edge of the spectrum is determined by the band gap width of the bulk semiconductor, and the blue edge is determined by the quantum size of the excitons at the top of the prism. The PL spectrum of the silicon prismatic sample was excited by weak and strong light absorption. At weak absorption (hν_ex = 1.2 eV), the PL spectrum is located in the visible part of the spectrum, from 1.4 eV to 1.9 eV, with an energy higher than the band gap of the Si crystal. Such a “blue shift” of PL spectra by 0.7 eV is characteristic of the quantum confinement effect. It is a rainbow spectrum with an optical upconversion. The quantum prism is a new type of nano light source, as it replaces two elements in a conventional spectrometer: a light source and a dispersive element. These features enable to create a nano-spectrometer for measuring the absorption spectrum of individual molecules or viruses. Full article

This study explores the influence of solution concentration, specifically that of water and ethylene glycol mixtures, on the optical and supercapacitive properties of cobalt tungstate (CoWO₄) nanoparticles. CoWO₄ nanoparticles were synthesized using varying ratios of water to ethylene glycol to ascertain the optimal conditions for enhanced performance. Detailed characterization was conducted using UV–Vis spectroscopy, photoluminescence (PL) spectroscopy, cyclic voltammetry (CV), and galvanostatic charge–discharge (GCD) to evaluate the optical properties and electrochemical behavior, respectively. The results revealed that the solution concentration significantly impacted the bandgap, absorbance, and emission properties of the CoWO₄ nanoparticles. Effective bandgap tuning was achieved by altering the solution concentration. When using only water, the nanoparticles displayed the lowest bandgap of 2.57 eV. In contrast, a solution with equal water and ethylene glycol concentrations resulted in the highest bandgap of 2.65 eV. Additionally, the electrochemical studies demonstrated that the water/ethylene glycol ratio markedly influenced the charge storage capacity and cyclic stability of the nanoparticles. The results indicated that the solvent concentration significantly influenced the crystallinity, particle size, and surface morphology of the CoWO₄ nanoparticle nanoparticles, which affected their optical properties and electrochemical performance. Notably, nanoparticles synthesized with a 1.25:0.75 proportion of water to ethylene glycol exhibited superior supercapacitive performance, with a specific capacitance of 661.82 F g⁻¹ at a current density of 7 mA cm⁻² and 106% capacitance retention after 8000 charge–discharge cycles. These findings underscore the critical role of solvent composition in tailoring the functional properties of CoWO₄ nanoparticles, providing insights for their application in optoelectronic devices and energy storage systems. Full article

Organic–inorganic hybrid perovskite quantum dots (QDs) have garnered significant research interest owing to their unique structure and optoelectronic properties. However, their poor optical performance in ambient air remains a significant limitation, hindering their advancement and practical applications. Herein, three amino acids (valine, threonine and cysteine) were chosen as surface ligands to successfully prepare highly luminescent CH₃NH₃PbBr₃ (MAPbBr₃) QDs. The morphology and XRD results suggest that the inclusion of the amino acid ligands enhances the octahedral structure of the QD solutions. Moreover, the observed blue-shifted phenomenon in the photoluminescence (PL) aligns closely with the blue-shifted phenomenon observed in the ultraviolet–visible (UV-Vis) absorption spectra, attributed to the quantum confinement effect. The time-resolved spectra indicated that the introduction of the amino acid ligands successfully suppressed non-radiative recombination, consequently extending the fluorescence lifetime of the MAPbBr₃ QDs. The photoluminescence quantum yields (PLQYs) of the amino acid-treated MAPbBr₃ QDs are increased by 94.8%. The color rendering index (CRI) of the produced white light-emitting diode (WLED) is 85.3, with a correlated color temperature (CCT) of 5453 K. Our study presents a novel approach to enhancing the performance of perovskite QDs by employing specially designed surface ligands for surface passivation. Full article

This manuscript describes the synthesis of green long afterglow nanophosphors SrAl₂O₄:Eu²⁺, Nd³⁺ using the combustion process. The study encompassed the photoluminescence behavior, elemental composition, chemical valence, morphology, and phase purity of SrAl₂O₄:Eu²⁺, Nd³⁺ nanoparticles. The results demonstrate that after introducing Eu²⁺ into the matrix lattice, it exhibits an emission band centered at 508 nm when excited by 365 nm ultraviolet light, which is induced by the 4f⁶5d¹→4f⁷ transition of Eu²⁺ ions. The optimal doping concentrations of Eu²⁺ and Nd³⁺ were determined to be 2% and 1%, respectively. Based on X-ray diffraction (XRD) analysis, we have found that the physical phase was not altered by the doping of Eu²⁺ and Nd³⁺. Then, we analyzed and compared the quantum yield, fluorescence lifetime, and afterglow decay time of the samples; the co-doped ion Nd³⁺ itself does not emit light, but it can serve as an electron trap center to collect a portion of the electrons produced by the excitation of Eu²⁺, which gradually returns to the ground state after the excitation stops, generating an afterglow luminescence of about 15 s. The quantum yields of SrAl₂O₄:Eu²⁺ and SrAl₂O₄:Eu²⁺, Nd³⁺ phosphors were 41.59% and 10.10% and the fluorescence lifetimes were 404 ns and 76 ns, respectively. In addition, the E_g value of 4.98 eV was determined based on the diffuse reflectance spectra of the material, which closely matches the calculated bandgap value of SrAl₂O₄. The material can be combined with polyacrylic acid to create optical anti-counterfeiting ink, and the butterfly and ladybug patterns were effectively printed through screen printing; this demonstrates the potential use of phosphor in the realm of anti-counterfeiting printing. Full article

New heterometallic antenna terephthalate MOFs, namely, (Eu_xM_1−x)₂bdc₃·4H₂O (M = Y, La, Gd) (x = 0.001–1), were synthesized by a one-step method from aqueous solutions. The resulting compounds are isomorphic to each other; the crystalline phase corresponds to Ln₂bdc₃∙4H₂O. Upon 300 nm excitation to the singlet excited state of terephthalate ions, all compounds exhibit a bright red emission corresponding to the of ⁵D₀–⁷F_J (J = 0–4) f-f transitions of Eu³⁺ ions. The Eu(III) concentration dependence of the photophysical properties was carefully studied. We revealed that Gd-doping results in photoluminescence enhancement due to the heavy atom effect. To quantitatively compare the antenna effect among different compounds, we proposed the new approach, where the quantum yield of the ⁵D₀ formation is used to characterize the efficiency of energy transfer from the ligand antenna to the Eu³⁺ emitter. Full article

Group 14 metalloles have attracted much attention as core structures of conjugated functional materials. In this work, we prepared dithieno[3,2-b:4,5-c’]germole as a new unsymmetrically condensed dithienogermole and benzo[4,5]thieno[2,3-c]germole as the benzene-condensed analog. The electronic states and properties of these unsymmetrically condensed germoles are discussed on the basis of the results of optical and electrochemical measurements with the help of quantum chemistry calculations on the simplified model compounds. The Stille cross-coupling reactions of bromodithieno[3,2-b:4,5-c’]germole with di(stannylthienyl)- and di(stannylthiazolyl)benzothiadiazole provided conjugated donor–acceptor compounds that exhibited clear solvatochromic behavior in the photoluminescence spectra, indicating the potential application of the dithieno[3,2-b:4,5-c’]germole unit as an electron donor in donor–acceptor systems. Full article

Zero-dimensional tin-based halide perovskites have garnered considerable interest owing to their remarkable optical properties, including broad-band emission, high photoluminescence (PL) efficiency, and low self-absorption. Nevertheless, enhancing the PL efficiency and stability of these materials remains a pressing challenge. In this study, the enhancement of PL and stability in Cs₄SnBr₆ zero-dimensional perovskite was investigated through Ce³⁺ doping. Our experimental results demonstrate that the incorporation of Ce³⁺ can significantly boost the light emission intensity from self-trapped excitons (STEs) in Cs₄SnBr₆, achieving over a 150% increase compared to the undoped sample, with a PL quantum yield of approximately 64.7%. Moreover, the thermal stability of the corresponding doped sample is markedly enhanced. Through comprehensive analyses, including X-ray diffraction, energy-dispersive spectroscopy, time-resolved PL, and temperature-dependent PL measurements, we elucidate that the enhanced light emission is attributed to the distortion of the [SnBr₆]⁴⁻ octahedral structure induced by Ce³⁺ doping, which strengthens electron–phonon coupling and elevates the binding energy of STEs. Full article

CaWO₄ nanoparticles were obtained by facile mechanochemical synthesis at room temperature, applying two different milling speeds. Additionally, a solid-state reaction was employed to assess the phase composition, structural, and optical characteristics of CaWO₄. The samples were analyzed by X-ray diffraction (XRD), transition electron microscopy (TEM), and Raman, infrared (IR), ultraviolet–visible (UV–Vis) reflectance, and photoluminescence (PL) spectroscopies. The phase formation of CaWO₄ was achieved after 1 and 5 h of applied milling speeds of 850 and 500 rpm, respectively. CaWO₄ was also obtained after heat treatment at 900 °C for 12 h. TEM and X-ray analyses were used to calculate the average crystallite and grain size. The Raman and infrared spectroscopies revealed the main vibrations of the WO₄ groups and indicated that more distorted structural units were formed when the compound was synthesized by the solid-state method. The calculated value of the optical band gap of CaWO₄ significantly increased from 2.67 eV to 4.53 eV at lower and higher milling speeds, respectively. The determined optical band gap of CaWO₄, prepared by a solid-state reaction, was 5.36 eV. Blue emission at 425 (422) nm was observed for all samples under an excitation wavelength of 230 nm. CaWO₄ synthesized by the solid-state method had the highest emission intensity. It was established that the intensity of the PL peak depended on two factors: the morphology of the particles and the crystallite sizes. The calculated color coordinates of the CaWO₄ samples were located in the blue region of the CIE diagram. This work demonstrates that materials with optical properties can be obtained simply and affordably using the mechanochemical method. Full article

In this study, we synthesized pure and cobalt-doped NiTiO₃ perovskite nanostructures using a sol–gel method and characterized them to investigate the impact of cobalt incorporation on their photocatalytic hydrogen production under UV light. XRD analysis confirmed the formation of the hexagonal ilmenite structure, with lattice parameters increasing with cobalt doping, indicating the substitution of larger Co²⁺ ions onto smaller Ni²⁺ sites. Raman spectroscopy revealed a decrease in the intensity of active modes, suggesting crystal structure distortion and oxygen vacancy generation. UV-vis spectroscopy showed a decrease in bandgap energy from 2.24 to 2.16 eV with cobalt doping up to 5%, enhancing UV light absorption. SEM and TEM images revealed nanoparticle agglomeration, while cobalt doping did not significantly alter particle size up to 5% doping. Photoluminescence spectroscopy revealed an initial increase in PL intensity for NiTiO₃-1%Co, followed by a systematic decrease with higher cobalt concentrations, with NiTiO₃-10%Co exhibiting the lowest intensity. Photocatalytic experiments demonstrated a remarkable improvement in hydrogen evolution rate with increasing cobalt doping, with NiTiO₃-10%Co exhibiting the highest rate of 940 μmol∙g⁻¹·h⁻¹, a 60.4% increase compared to pure NiTiO₃. This enhanced performance is attributed to the substitution of Co²⁺ on Ni²⁺ sites, the modification of electronic structure, the suppression of electron–hole recombination, and the creation of surface catalytic sites induced by cobalt incorporation. The proposed mechanism involves the introduction of Co²⁺/Co³⁺ energy levels within the NiTiO₃ bandgap, facilitating charge separation and transfer, with the Co⁺/Co²⁺ redox couple aiding in suppressing electron–hole recombination. These findings highlight the potential of cobalt doping to tune the properties of NiTiO₃ perovskite for efficient hydrogen production under UV light. Full article

A p–n heterojunction film consisting of p-type CuFe₂O₄ and n-type ZnFe₂O₄ was fabricated in this study. The n-type ZnFe₂O₄ film was deposited on a stainless steel substrate using the spray pyrolysis method, after which a top layer of p-type CuFe₂O₄ thin film was deposited and annealed. Characterization techniques, such as X-ray diffraction, scanning electron microscopy, UV–Vis diffuse reflectance spectroscopy, and photoluminescence, confirmed the formation of a superlattice p–n heterojunction between CuFe₂O₄ and ZnFe₂O₄. Photoelectrochemical measurements were conducted to investigate the photoelectrochemical properties of the samples, resulting in a photocurrent of 1.2 mA/cm² at 1.5 V (vs. Ag/AgCl) under illumination from a 100-watt LED light source. Utilizing the p–n junction of CuFe₂O₄/ZnFe₂O₄ as a photoanode increased the hydrogen production rate by 30% compared to that of the dark measurement. This enhancement in performance was attributed to the potential barrier at the p–n heterojunction interface, which improved the separation of photoinduced electron–hole pairs and facilitated a more efficient charge transfer. Additionally, coating the stainless steel electrode with this ferrite sample improved both the corrosion resistance and the stability of hydrogen production over extended operation times. Full article

Mono- and binuclear Cu(I) complexes were isolated employing 2,1,3-benzoselenadiazole (BSeD) as the N-donor ligand, and triphenylphosphine or bis[(2-diphenylphosphino)phenyl] ether (DPEphos) as P-donors. Then, ⁷⁷Se NMR was measured for the free ligand and the corresponding Cu(I) derivatives, and the related signal was downshifted by 12.86 ppm in the case of [Cu(BSeD)(PPh₃)₂(ClO₄)], and around 15 ppm for the binuclear species. The structure of [Cu(BSeD)(PPh₃)₂(ClO₄)] and [Cu₂(μ₂-BSeD)(DPEphos)₂(ClO₄)₂] was confirmed by single-crystal X-ray diffraction. The geometry of the Cu(I) complexes was optimized through DFT calculations, and the nature of the Cu···O interaction was investigated through AIM analysis. The three Cu(I) complexes were characterized by intense absorption under 400 nm and, after being excited with blue irradiation, [Cu(BSeD)(PPh₃)₂(ClO₄)] and [Cu₂(μ₂-BSeD)(PPh₃)₄(ClO₄)₂] exhibited weak red emissions centered at 700 nm. The lifetimes comprised between 121 and 159 μs support the involvement of triplet excited states in the emission process. The photoluminescent properties of [Cu(BSeD)(PPh₃)₂(ClO₄)] were supported by TDDFT computations, and the emission was predicted at 710 nm and ascribed to a metal-to-ligand charge transfer (³MLCT) process, in agreement with the experimental data. Full article

In this study, fully aromatic polyether sulfones were developed, bearing blue, yellow, and orange–red π-conjugated semiconducting units. Carbazole-, anthracene-, and benzothiadiazole-based fluorophores are copolymerized with a diphenylsulfone moiety. A diphenylpyridine comonomer was additionally utilized, acting as both a solubilizing unit and a weak blue fluorescent group. Using this rationale, fluorescent polyarylethers with high molecular weights, up to 70 kDa, were developed, showing film formation ability and high thermal stability, while preserving excellent solubility in common organic, nonvolatile, and nonchlorinated solvents. Fine-tuning of the emission color was achieved through subtle changes of the comonomers’ type and ratio. Single-chromophore-bearing copolymers emitted in the blue or the yellow region of the visible spectrum, while the dual-chromophore-bearing terpolymers emitted throughout the visible spectrum, resulting in white light emission. Solutions of 20 wt% in polar aprotic solvents at ambient conditions allowed the deposition of fluorescent copolyethers and printing from non-chlorinated solvents. All polyethers were evaluated for their structural and optoelectronic properties, and selected copolymers were successfully used in the emitting layer (EML) of organic light-emitting diode (OLED) devices, using either rigid or flexible substrates. Remarkable color stability was displayed in all cases for up to 15 V of bias voltage. The Commission Internationale de L’Eclairage (CIE) of the fabricated devices is located in the blue (0.16, 0.16), yellow (0.44, 0.50), or white region of the visible spectrum (0.33, 0.38) with minimal changes according to the ratio of the comonomers. The versatile methodology toward semiconducting polyethersulfones for polymer light-emitting diodes (PLEDs) developed herein led to the scaled-up production of luminescent polymers of up to 25 g of high-molecular-weight single batches, demonstrating the effectiveness of this approach as a straightforward tool to facilitate the synthesis of flexible and printable EMLs for large-area PLED coverage. Full article

In this paper, the crystallization behavior of 50ZnO:47B₂O₃:3Nb₂O₃:0.5Eu₂O₃ (G-0 h) glass has been investigated in detail by DSC, XRD and TEM analysis. The luminescent properties of the resulting glass-ceramics were also investigated. By XRD and TEM analysis, crystallization of several crystalline phases has been proved (α-Zn₃B₂O₆, β-Zn₃B₂O₆ and ZnNb₂O₆). By calculating crystal parameters, it was found that europium ions are successfully incorporated in the β-Zn₃B₂O₆. Photo-luminescent spectra showed increased emission in the resulting glass-ceramic samples compared to the parent glass sample due to higher asymmetry of Eu³⁺ ions in the obtained crystalline phases. It was established that the optimum emission intensity is registered for glass-ceramic samples obtained after 25 h heat treatment of the parent glass. Full article

Colloidal semiconductor nanoparticles (NPs) represent an emergent state of matter with unique properties, bridging bulk materials and molecular structures. Their distinct physical attributes, such as bandgap and photoluminescence, are intricately tied to their size and morphology. Ligand passivation plays a crucial role in shaping NPs and determining their physical properties. Ligand exchange (LE) offers a versatile approach to tailoring NP properties, often guided by Pearson’s Hard–Soft Acid–Base theory. Lead sulfide (PbS), a semiconductor of considerable interest, exhibits size-dependent tunable bandgaps from the infrared to the visible range. Here, we present two methods for synthesizing water-soluble, polyvinylpyrrolidone (PVP)-coated PbS NPs. The first involves direct synthesis in an aqueous solution while utilizing PVP as the surfactant for the formation of nano-cubes with a crystal coherence length of ~30 nm, while the second involves LE from octadecylamine-coated PbS truncated nano-cubes to PVP-coated PbS NPs with a crystal coherence length of ~15 nm. Multiple characterization techniques, including X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy, and thermal gravimetric analysis, confirmed the results of the synthesis and allowed us to monitor the ligand exchange process. Our findings demonstrate efficient and environmentally friendly approaches for synthesizing PVP-coated PbS NPs. Full article

Aggregation-induced emitters or AIEgens are generally signified by their stronger photoluminescence in aggregation than in the solution state. Due to high emission efficiency in aggregate and solid states and good processability, organic AIEgens drew attention to the development of advanced luminescent materials. However, as mesogenic materials self-assemble to a different molecular arrangement in different phases, achieving liquid crystallinity and AIE properties in the same molecule would provide a valuable tool to develop solvent-independent AIEgenic materials. With this goal, the present work reports the synthesis of new organic thermotropic liquid crystalline compounds exhibiting aggregation-induced emission (AIE). The synthesized compounds exhibit strong green luminescence in a solid state which sharply quenches upon entering smectic mesophase by heating. This is in addition to the exhibition of dispersion medium (solvent)-dependent emission, thus providing a dual mode of AIE. The mesogenic property of the synthesized compounds was studied by XRD, POM, and DSC. The AIE was studied by fluorescence spectroscopy and variable temperature fluorescence microscopy. A DFT study was carried out to gain an insight into the AIEgenic behavior of the material. Full article