Search Results (223)

Highly integrable silicon carbide (SiC) has emerged as a promising platform for photonic integrated circuits (PICs), offering a comprehensive set of material and optical properties that are ideal for the integration of nonlinear devices and solid-state quantum defects. However, despite significant progress in nanofabrication technology, the development of SiC on an insulator (SiCOI)-based photonics faces challenges due to fabrication-induced material optical losses and complex processing steps. An alternative approach to mitigate these fabrication challenges is the direct deposition of amorphous SiC on an insulator (a-SiCOI). However, there is a lack of systematic studies aimed at producing high optical quality a-SiC thin films, and correspondingly, on evaluating and determining their optical properties in the telecom range. To this end, we have studied a single-source precursor, 1,3,5-trisilacyclohexane (TSCH, C₃H₁₂Si₃), and chemical vapor deposition (CVD) processes for the deposition of SiC thin films in a low-temperature range (650–800 °C) on a multitude of different substrates. We have successfully demonstrated the fabrication of smooth, uniform, and stoichiometric a-SiCOI thin films of 20 nm to 600 nm with a highly controlled growth rate of ~0.5 Å/s and minimal surface roughness of ~5 Å. Spectroscopic ellipsometry and resonant micro-photoluminescence excitation spectroscopy and mapping reveal a high index of refraction (~2.7) and a minimal absorption coefficient (<200 cm⁻¹) in the telecom C-band, demonstrating the high optical quality of the films. These findings establish a strong foundation for scalable production of high-quality a-SiCOI thin films, enabling their application in advanced chip-scale telecom PIC technologies. Full article

The synthesis of 2-phenylbenzoxazole fluorosulfate derivatives was carried out using the SuFEx reaction. To study the anticancer properties of the obtained compounds, the cell lines PC-3 (obtained from prostate adenocarcinoma), BT-474, and MCF-7 (both obtained from breast carcinoma) were used. The cytotoxicity on murine 3T3L1 embryonic was also investigated. Among the tested compounds, the ortho-substituted fluorosulfate derivative (BOSo) exhibited significant cytotoxicity against MCF-7 cells. The biological findings are consistent with molecular docking results, which revealed a structural similarity between BOSo and known inhibitors of hER and HER2 receptors—tamoxifen and SYR127063. Therefore, BOSo shows promise as a potential therapeutic agent with antiproliferative properties. The photoluminescent characteristics of the fluorosulfate derivatives were examined in the solid state, in acetonitrile solution and in PBS, with the highest quantum yields reaching up to 64% for the para-fluorosulfate derivative in acetonitrile. Overall, these compounds demonstrate considerable potential for the development of new multifunctional molecular tools that combine biological activity with fluorescent properties. Full article

The natural sunlight driven photocatalytic degradation of organic pollutants is a sustainable solution for water purification. The use of heterojunction nanocomposites in this process shows promise for improved photodegradation efficiency. In this work, nanocrystalline Zn₂SnO₄/SnO₂ obtained by the solid-state synthesis method was tested as a heterojunction photocatalyst material for the degradation of methylene blue (MB) and Rhodamine B (RhB) dyes as single and multicomponent systems in natural sunlight. Characterization of the structure and morphology of the synthesized nanocomposite using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDS), and photoluminescence (PL) spectroscopy confirmed the formation of Zn₂SnO₄/SnO₂ and heterojunctions between Zn₂SnO₄ and the SnO₂ nanoparticles. A photodegradation efficiency of 99.1% was achieved in 120 min with 50 mg of the photocatalyst for the degradation of MB and 70.6% for the degradation of RhB under the same conditions. In the multicomponent system, the degradation efficiency of 97.9% for MB and 53.2% for RhB was obtained with only 15 mg of the photocatalyst. The degradation of MB occurred through N-demethylation and the formation of azure intermediates and degradation of RhB occurred through sequential deethylation and fragmentation of the xanthene ring, both in single and multicomponent systems. Full article

Mn²⁺-doped phosphors emitting green light have garnered significant interest due to their potential applications in display technologies and solid-state lighting. To facilitate the rapid synthesis of high-performance Mn²⁺-activated green phosphors, this research optimizes a microwave-assisted solid-state (MASS) method for the preparation of Na₂ZnGeO₄:Mn²⁺. Leveraging the unique attributes of the MASS technique, a systematic investigation into the applicability of various Mn-source precursors was conducted. Additionally, the integration of the MASS approach with traditional solid-state reaction (SSR) methods was assessed. The findings indicate that the MASS technique effectively incorporates Mn ions from diverse precursors (including higher oxidation states of manganese) into the crystal lattice, resulting in efficient green emission from Mn²⁺. Notably, the photoluminescence quantum yield (PLQY) of the sample utilizing MnCO₃ as the manganese precursor was recorded at 2.67%, whereas the sample synthesized from MnO₂ exhibited a remarkable PLQY of 17.69%. Moreover, the post-treatment of SSR-derived samples through the MASS process significantly enhanced the PLQY from 0.67% to 8.66%. These results underscore the promise of the MASS method as a novel and efficient synthesis strategy for the rapid and scalable production of Mn²⁺-doped green luminescent materials. Full article

Boronic acids are an important class of molecules diversely used in organic synthesis, catalysis, medicinal chemistry, and for the design of functional materials. Particularly, aryl boronic acids in the solid state are known to exhibit pharmaceutical and photoluminescent properties for antimicrobial, sensing, and drug delivery applications. Furthermore, the phenazine molecule is known for its diverse pharmacological properties, including antibiotic activity. In the case of molecular crystalline solids, it is well established that understanding noncovalent interactions remains key to designing or engineering their functional properties. While both aryl boronic acids and phenazine molecules individually represent an important class of compounds, their co-assembly in the crystalline state is of interest within the context of supramolecular chemistry and crystal engineering. Herein, we report the supramolecular features of two newly synthesized cocrystals, which are composed of para-F/CF₃-substituted phenylboronic acids, respectively, and phenazine, as demonstrated by structure analysis by single-crystal X-ray diffraction. Full article

Tetraphenylethylene (TPE)–thiophene compounds are promising candidates for stimuli-responsive luminescent materials, yet systematic investigations into the influence of substitution patterns on their photophysical properties remain limited. Herein, four regioisomeric TPE–thiophene derivatives have been synthesized by systematically varying the number and positions of TPE substituents on the thiophene core. A comprehensive spectroscopic characterization reveals that substitution patterns critically modulate the photoluminescence quantum yields (PLQYs). The ortho-monosubstituted isomer exhibits the highest PLQY (52.86% in solid state) compared with the meta-monosubstituted isomer (13.87% in solid state). Interestingly, thiophenes with two or three TPEs substituted at positions 2,5 or 2,3,5 have lower PLQYs, which is rare due to the common understanding that increasing the number of AIE parts should increase the PLQY. Further single-crystal structure analyses show that the key factor impacting the PLQY is the dihedral angles of the TPE subunit, which determines the degree of intramolecular twisting. This work establishes regiochemistry as a powerful design lever for tuning TPE–thiophene photophysics, offering underlying principles for the design of TPE-based thiophene molecules with high photoluminescent performance in the future. Full article

Due to their rare properties of solid-state luminescence enhancement (SLE), tricarbonylrhenium complexes are promising candidates for applications as photoluminescent materials. However, the effect of isomerism on optical properties is still not well known. The aim of this in-depth study is to explore the behavior of a 2-(1,2,3-triazol-1-yl)pyridine (tapy) complex and compare it with that of the isomers studied previously. Two derivatives that incorporate a mesoionic carbene ligand and represent an emerging class of molecules were also synthesized and compared with the corresponding isomers. The crystallographic data revealed that compounds in the solid state have little or no π–π interactions. The spectroscopic study was supported by DFT calculations. All the compounds were weakly phosphorescent in solution but exhibited a marked SLE effect. The Re-Tapy complex is an excellent solid-state emitter (PLQY = 0.62), well suited for applications related to aggregation-induced phosphorescence emission (AIPE). Its sensitivity to mechanical stimuli was unprecedented among the isomers considered to date. On the other hand, triazolylidene complexes are less emissive than their pyta_(1,2,3) counterparts. This study shows how the ligand isomerism influences the optical properties of tricarbonylrhenium(I) complexes. It indicates that selecting the right pattern is a key factor for the design of efficient photoluminescent materials. 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

Co-doping at Ba and Ti sites with double rare-earth elements has proven an effective strategy for enhancing the dielectric properties of BaTiO₃ ceramics. Among intermediate-sized rare-earth ions, Tb and Ho exhibit amphoteric behavior, occupying both Ba and Ti sites. Investigating the site occupation, defect chemistry, and dielectric effects of Tb and Ho in BaTiO₃ is therefore valuable. In this work, Tb/Ho-co-doped BaTiO₃ ceramics with the composition (Ba_1−xTb_x)(Ti_1−xHo_x)O₃ (x = 0.01~0.10) were fabricated at 1400 °C via solid-state reaction, and their solid solubility and crystal structures are confirmed. Microstructure, dielectric properties, photoluminescence, and valence states of samples with a single phase were systematically studied. Both the lattice parameter a and unit cell volume increase with doping level. The ceramic with x = 0.02 meets the X5S dielectric specification. Ho and Tb ions both demonstrate amphoteric site occupancy: Ho exists solely as Ho³⁺ at both Ba and Ti sites, while Tb exhibits mixed valence states as Ba-site Tb³⁺ and Ti-site Tb⁴⁺. As the doping content increases, the concentration of Tb⁴⁺ at Ti sites decreases, and the quantity of Ba-site Ho³⁺ ions initially increases to a maximum before decreasing. Defect compensation mechanisms within the samples are also discussed. Full article

Tomato waste (TW) was employed as a sustainable source for the synthesis of fluorescent carbon dots (CDs) via a microwave-assisted hydrothermal carbonization (Mw-HTC) method, aiming at its valorization. Several amines were used as nitrogen additives to enhance the fluorescence quantum yield (QY) of CDs, and a set of reaction conditions, including additive/TW mass ratio (0.04–0.32), dwell time (15–60 min), and temperature (200–230 °C) of the HTC process, were scrutinized. The structural analysis of the tomato waste carbon dots (TWCDs) was undertaken by FTIR and ¹H NMR techniques, revealing their most relevant features. In solid state, transmission electron microscopy (TEM) analysis showed the presence of nearly spherical nanoparticles with an average lateral size of 8.1 nm. Likewise, the topographical assessment by atomic force microscopy (AFM) also indicated particles’ heights between 3 and 10 nm. Their photophysical properties, revealed by UV–Vis, steady-state, and time-resolved fluorescence spectroscopies, are fully discussed. Higher photoluminescent quantum yields (up to 0.08) were attained when the biomass residues were mixed with organic aliphatic amines during the Mw-HTC process. Emission tunability is a characteristic feature of these CDs, which display an intensity average fluorescence lifetime of 8 ns. The new TWCDs demonstrated good antioxidant properties by the ABTS radical cation method (75% inhibition at TWCDs’ concentration of 5 mg/mL), which proved to be related to the dwell time used in the CDs synthesis. Moreover, the synthesized TWCDs suppressed the growth of Escherichia coli and Staphylococcus aureus at concentrations higher than 2000 μg/mL, encouraging future antibacterial applications. Full article

Transition metal (II) complexes stabilized by 2,6-di(pyrazol-3-yl)pyridine as a novel coplanar tridentate nitrogen-donor ligand have been reported for their unusual structures and photoluminescent properties. In this work, the ligand 2,6-bis(5-isopropyl-1H-pyrazole-3-yl)pyridine (denoted as L) and its transition metal (II) halogenido complexes viz [ZnCl₂(L)] (1), [ZnBr₂(L)] (2), [CuCl₂(L)] (3), and [CuCl(L)(thf)](PF₆) (4) were synthesized and characterized by single crystal X-ray crystal analysis. Its structures contained N–H groups in its pyrazole rings and hydrogen bonds between these N–H donors and the coordinated halogenide ions and lattice solvent molecules. Tautomers between 3-pyridyl and 5-pyridyl substitutes were also observed. In L, the N–H group at the pyrazole nitrogen was located adjacent to the pyridine ring to form hydrogen bonds with adjacent pyrazoles. However, on complexation, the H atoms at the pyrazole nitrogens are shifted remotely to the pyridine. The zinc (II) complexes [ZnCl₂(L)] (1) and [ZnBr₂(L)] (2) possessed distorted trigonal pyramidal structures in the solid state. By comparison, the copper (II) complexes [CuCl₂(L)] (3) and [CuCl(L)(thf)](PF₆) (4) adopted square pyramidal geometry with a Jahn–Teller distortion resulting from their d⁹ electron configurations. Full article

Quasi-two-dimensional (quasi-2D) perovskites have emerged as a transformative platform for high-efficiency perovskite light-emitting diodes (PeLEDs), benefiting from their tunable quantum confinement, high photoluminescence quantum yields (PLQYs), and self-assembled energy funneling mechanisms. This review systematically explores interfacial energy transfer engineering strategies that underpin advancements in device performance. By tailoring phase composition distributions, passivating defects via additive engineering, and optimizing charge transport layers, researchers have achieved external quantum efficiencies (EQEs) exceeding 20% in green and red PeLEDs. However, challenges persist in blue emission stability, efficiency roll-off at high currents, and long-term operational durability driven by spectral redshift, Auger recombination, and interfacial ion migration. Emerging solutions include dual-cation/halogen alloying for bandgap control, microcavity photon management, and insulator–perovskite–insulator (IPI) architectures to suppress leakage currents. Future progress hinges on interdisciplinary efforts in multifunctional material design, scalable fabrication, and mechanistic studies of carrier–photon interactions. Through these innovations, quasi-2D PeLEDs hold promise for next-generation displays and solid-state lighting, offering a cost-effective and efficient alternative to conventional technologies. Full article

The complexation behavior of lanthanide(III) ions with terephthalic acid (1,4-benzene-dicarboxylic acid) in 0.01 M KNO₃ aqueous solutions was studied across a broad pH range and at two metal-to-ligand ratios using potentiometric titration combined with photoluminescence spectroscopy. Chemometric analysis of titration curves enabled the determination of relative molar fractions, stability constants, and probable stoichiometry of the formed complexes. In solutions with a 1:2 metal-to-ligand ratio, bis-complexes (two terephthalate ligands per lanthanide ion) predominated, while ligand-rich conditions favored the formation of tetra-complexes (four ligands per metal ion). In alkaline media, bis-complexes transform into mixed hydroxy-terephthalate species. Meanwhile, for the tetra-complexes, the addition of NaOH results in the formation of lanthanide ion hydroxo complexes without organic ligands. The structural diversity of these complexes, driven by the terephthalate ligand’s tendency to maximize denticity, suggested dimeric or oligomeric configurations. The stability constants and structural features of complexes in solution were found to align with those of known solid-state lanthanide–terephthalate polymers, highlighting their potential as models for polymeric structures. Full article

Recently, Cu(I)-based metal halides have attracted tremendous attention owing to their remarkable photophysical properties. However, most of them can only be excited by near ultraviolet (UV) light at a wavelength (generally less than 350 nm) with a wide bandgap, which undoubtedly limits their application in solid-state lighting due to the low excitation efficiency at about 400 nm in devices. Here, we report a new zero-dimensional organic cuprous bromide of (C₁₃H₃₀N)₂Cu₅Br₇ single crystals, which can be excited by visible light (390–400 nm) and give a bright yellow and broad self-trapped exciton emission band with the photoluminescence quantum yield (PLQY) of 92.3% at room temperature. The experimental and theoretical results show that the existence of Cu-Br-Cu metal bonds in a Cu₅Br₇ cluster package produces three components of self-trapped excitons (STE) that emit at room temperature but merge into one at 80 K. This occurs because of the anomalously enhanced electron–phonon coupling and electron–electron coupling in the coupled clusters in this system. These effects cause the excitation near visible light and emission broader at higher temperature. Additionally, their remarkable anti-water emission stability was demonstrated even after soaking in water for 6 h. Finally, a highly efficient white-light-emitting diode (WLED) based on (C₁₃H₃₀N)₂Cu₅Br₇ was fabricated. Full article

The commercial flame-retardant 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) was almost quantitatively converted in sodium [2-(2-hydroxyphenyl)phenyl]phosphinate Na[OH-Ph-Ph-PHO₂] and disodium 2-(2-phosphinatophenyl)benzen-1-olate Na₂[O-Ph-Ph-PHO₂] under mild reaction conditions and without the use of toxic reactants. The structure of Na[OH-Ph-Ph-PHO₂] was determined by means of single-crystal X-ray diffraction. The inter- and intramolecular Na-O interactions generate a stair-like framework where the sodium cations are five-coordinated and exhibit a highly distorted coordination sphere. The two compounds are characterized by appreciable blue luminescence at the solid state upon excitation with UV light, attributed to S₁→S₀ decays on the basis of time-resolved measurements and computational calculations. The photoluminescence quantum yield is higher for Na₂[O-Ph-Ph-PHO₂], and the emission and excitation bands are shifted at longer wavelengths. The disodium salt showed affinity towards cellulose, and doped Na₂[O-Ph-Ph-PHO₂]@cellulose samples maintained emission features comparable to those of the pure compound. The nature of the interaction between cellulose and the emitting species was studied by means of periodic density functional theory calculations, that highlighted the role of the sodium cations. Full article