Search Results (39)

The efficient depolymerization of lignin has become a key challenge in the preparation of high-value-added chemicals. Graphitic carbon nitride (g-C₃N₄)-based photocatalytic system shows potential due to its mild and green characteristics over other depolymerization methods. However, its inherent defects, such as a wide band gap and rapid carrier recombination, severely limit its catalytic performance. In this paper, a g-C₃N₄ modification strategy of K⁺ doping and surface alkalinization is proposed, which is firstly applied to the photocatalytic depolymerization of the lignin β-O-4 model compound (2-phenoxy-1-phenylethanol). K⁺ doping is achieved by introducing KCl in the precursor thermal polymerization stage to weaken the edge structure strength of g-C₃N₄, and post-treatment with KOH solution is combined to optimize the surface basic groups. The structural/compositional evolution of the materials was analyzed by XRD, FTIR, and XPS. The morphology/element distribution was visualized by SEM-EDS, and the optoelectronic properties were evaluated by UV–vis DRS, PL, EIS, and transient photocurrent (TPC). K⁺ doping and surface alkalinization synergistically regulate the layered structure of the material, significantly increase the specific surface area, introduce nitrogen vacancies and hydroxyl functional groups, effectively narrow the band gap (optimized to 2.35 eV), and inhibit the recombination of photogenerated carriers by forming electron capture centers. Photocatalytic experiments show that the alkalinized g-C₃N₄ can completely depolymerize 2-phenoxy-1-phenylethanol with tunable product selectivity. By adjusting reaction time and catalyst dosage, the dominant product can be shifted from benzaldehyde (up to 77.28% selectivity) to benzoic acid, demonstrating precise control over oxidation degree. Mechanistic analysis shows that the surface alkaline sites synergistically optimize the C_β-O bond breakage path by enhancing substrate adsorption and promoting the generation of active oxygen species (·OH, ·O₂⁻). This study provides a new idea for the efficient photocatalytic depolymerization of lignin and lays an experimental foundation for the interface engineering and band regulation strategies of g-C₃N₄-based catalysts. Full article

This study presents a novel method for dynamically tuning singular states in one-dimensional (1D) photonic lattices (PLs) using air-slit-based structural modifications. Singular states, arising from symmetry-breaking-induced resonance radiation, generate diverse spectral features through interactions between resonance modes and background radiation. By strategically incorporating air slits to break symmetry in 1D PLs, we demonstrated effective control of resonance positions, enabling dual functionalities including narrowband band pass and notch filtering. These singular states originate from asymmetric guided-mode resonances (aGMRs), which can be interpreted by analytical modeling of the equivalent slab waveguide. Moreover, the introduction of multiple air slits significantly enhances spectral tunability by inducing multiple folding behaviors in the resonance bands. This approach allows for effective manipulation of optical properties through simple adjustments of air-slit displacements. This work provides great potential for designing multifunctional photonic devices with advanced metamaterial technologies. Full article

Wound healing is a complex biological process involving inflammation, proliferation, and remodeling phases. Effective healing is essential for maintaining skin integrity, driving the need for advanced materials like hydrogels, known for their high water retention and tunable mechanical properties. In this study, we synthesized a biocompatible composite hydrogel composed of γ-polyglutamic acid (γ-PGA) and ε-polylysine (ε-PL) through a Schiff base reaction, forming a stable crosslinked network. Its physicochemical properties, including rheological behavior and swelling capacity, were systematically evaluated. Biocompatibility was assessed via in vitro hemolysis and cytotoxicity assays, and in vivo testing was performed using a full-thickness skin defect model in Sprague Dawley (SD) rats to evaluate wound-healing efficacy. The PGA-PL hydrogel demonstrated excellent physicochemical properties, with a maximum swelling ratio of 65.6%, and biocompatibility as evidenced by low hemolysis rates (<5%) and high cell viability (>80%). It promoted wound healing by inhibiting the inflammatory response, reducing levels of the inflammatory cytokine IL-6, enhancing angiogenesis, and accelerating collagen deposition. The hydrogel showed complete biodegradation within 21 days in vivo without inducing a significant inflammatory response and significantly accelerated wound healing, achieving an 86% healing rate within 7 days compared to 67% in the control group. The PGA-PL composite hydrogel exhibits excellent mechanical strength and biocompatibility, and its effective wound-healing capabilities lay the groundwork for future development and optimization in various tissue engineering applications. Full article

This study investigates the synthesis and photoluminescent properties of carbon quantum dots (CQDs) derived from Actinidia deliciosa using the hydrothermal method. The effect of concentration and pH on the composition, structure, and optical properties of CQDs was analyzed using characterization techniques such as TEM, EDS, FTIR, UV-Vis, and photoluminescence (PL) spectroscopy. The CQDs exhibited particle sizes ranging from 1 to 10 nm, with a graphitic structure and oxygen-containing functional groups, as identified by FTIR bands corresponding to OH, C=O, and C=C. The stability analysis revealed particle agglomeration over 30 days, increasing the size up to <40 nm. Regarding the optical properties, the CQDs displayed absorption peaks at 225 and 280 nm and a bandgap of ~3.78–3.82 eV. The PL characterization demonstrated tunable emission from violet to green, depending on the excitation wavelength. CQDs synthesized at an acidic pH of 2 exhibited enhanced luminescence due to protonation effects, whereas an alkaline pH led to a reduction in emission intensity. The hydrothermal method enabled a simple and eco-friendly synthesis, using water as the sole solvent, yielding stable CQDs with a luminescence lifespan exceeding 30 days. Their optical and electronic properties make them promising candidates for photocatalysis, heavy metal detection, and bioimaging applications. Full article

Metal halide perovskite quantum dots (MHP QDs), as a kind of fluorescent material, have attracted much attention due to their excellent photoluminescence (PL) quantum yield (QY), narrow full width at half maximum (FWHM), broad absorption, and tunable emission wavelength. However, the instability and biological incompatibility of MHP QDs greatly hinder their application in the field of biomedicine. Hydrogels are three-dimensional polymer networks that are widely used in biomedicine because of their high transparency and excellent biocompatibility. This review not only introduces the latest research progress in improving the mechanical and optical properties of hydrogels/MHP QDs but also combines it with the existing methods for enhancing the stability of MHP QDs in hydrogels, aiming to provide new ideas for researchers in material selection and methods for constructing MHP QD-embedded hydrogels. Finally, their application prospects and future challenges are introduced. Full article

Background/Objectives: Chronic skin wounds (CSWs) are a worldwide healthcare problem with relevant impacts on both patients and healthcare systems. In this context, innovative treatments are needed to improve tissue repair and patient recovery and quality of life. Cord blood platelet lysate (CB-PL) holds great promise in CSW treatment thanks to its high growth factors and signal molecule content. In this work, thermo-sensitive hydrogels based on an amphiphilic poly(ether urethane) (PEU) were developed as CB-PL carriers for CSW treatment. Methods: A Poloxamer 407^®-based PEU was solubilized in aqueous medium (10 and 15% w/v) and added with CB-PL at a final concentration of 20% v/v. Hydrogels were characterized for their gelation potential, rheological properties, and swelling/dissolution behavior in a watery environment. CB-PL release was also tested, and the bioactivity of released CB-PL was evaluated through cell viability, proliferation, and migration assays. Results: PEU aqueous solutions with concentrations in the range 10–15% w/v exhibited quick (within a few minutes) sol-to-gel transition at around 30–37 °C and rheological properties modulated by the PEU concentration. Moreover, CB-PL loading within the gels did not affect the overall gel properties. Stability in aqueous media was dependent on the PEU concentration, and payload release was completed between 7 and 14 days depending on the polymer content. The CB-PL-loaded hydrogels also showed biocompatibility and released CB-PL induced keratinocyte migration and proliferation, with scratch wound recovery similar to the positive control (i.e., CB-PL alone). Conclusions: The developed hydrogels represent promising tools for CSW treatment, with tunable gelation properties and residence time and the ability to encapsulate and deliver active biomolecules with sustained and controlled kinetics. Full article

Carbon dots (CDs) have emerged as a promising class of carbon-based nanomaterials due to their unique properties and versatile applications. Carbon dots (CDs), also known as carbon quantum dots (CQDs) or graphene quantum dots (GQDs), are nanoscale carbon-based materials with dimensions typically less than 10 nanometers. They exhibit intriguing optical, electronic, and chemical properties, making them attractive for a wide range of applications, including sensing, imaging, catalysis, and energy conversion, among many others. Both bottom-up and top-down synthesis approaches are utilized for the synthesis of carbon dots, with each method impacting their physicochemical characteristics. Carbon dots can exhibit diverse structures, including amorphous, crystalline, or hybrid structures, depending on the synthesis method and precursor materials used. CDs have diverse chemical structures with modified oxygen, polymer-based, or amino groups on their surface. These structures influence their optical and electronic properties, such as their photoluminescence, bandgap, and charge carrier mobility, making them tunable for specific applications. Various characterization methods such as HRTEM, XPS, and optical analysis (PL, UV) are used to determine the structure of CDs. CDs are cutting-edge fluorescent nanomaterials with remarkable qualities such as biocompatibility, low toxicity, environmental friendliness, high water solubility, and photostability. They are easily adjustable in terms of their optical properties, making them highly versatile in various fields. CDs find applications in bio-imaging, nanomedicine, drug delivery, solar cells, photocatalysis, electrocatalysis, and other related areas. Carbon dots hold great promise in the field of solar cell technology due to their unique properties, including high photoluminescence, high carbon quantum yield (CQY), and excellent charge separation. Full article

Semiconducting conjugated polymers (CPs) are pivotal in advancing organic electronics, offering tunable properties for solar cells and field-effect transistors. Here, we carry out first-principle calculations to study individual cis-polyacetylene (cis-PA) oligomers and their ensembles. The ground electronic structures are obtained using density functional theory (DFT), and excited state dynamics are explored by computing nonadiabatic couplings (NACs) between electronic and nuclear degrees of freedom. We compute the nonradiative relaxation of charge carriers and photoluminescence (PL) using the Redfield theory. Our findings show that electrons relax faster than holes. The ensemble of oligomers shows faster relaxation compared to the single oligomer. The calculated PL spectra show features from both interband and intraband transitions. The ensemble shows broader line widths, redshift of transition energies, and lower intensities compared to the single oligomer. This comparative study suggests that the dispersion forces and orbital hybridizations between chains are the leading contributors to the variation in PL. It provides insights into the fundamental behaviors of CPs and the molecular-level understanding for the design of more efficient optoelectronic devices. Full article

Organic/inorganic hybrid perovskite materials, such as CH₃NH₃PbX₃ (X = I, Br), have attracted the attention of the scientific community due to their excellent properties such as a widely tunable bandgap, high optical absorption coefficient, excellent power conversion efficiency, etc. The exposure of perovskite solar cells and photovoltaic devices to heat can significantly degrade their performance. Therefore, elucidating their temperature-dependent optical properties is essential for performance optimization of perovskite solar cells. We synthesized CH₃NH₃PbBr₃ (MAPbBr₃) single crystals through the polymer-controlled nucleation route and investigated the optical properties and molecular structure evolution of them with temperature. Through temperature evolution photoluminescence (PL) spectroscopy, we found that the fluorescence intensity was greatly affected by increasing the temperature, with an asymmetric PL profile suggesting that more captured excitons undergo radiative complexation. The optical photographs showed that the color of MAPbBr₃ single crystals faded. Raman spectroscopy revealed that during the heating process, the structure of MAPbBr₃ was still preserved at 90 °C since all of the Raman bands were very clear. When the temperature increased to 120 °C, the Raman bands of the internal modes became very weak. On further heating, the inorganic framework on sample’s surface started to disintegrate above 210 °C. During the heating process, the PL spectra exhibited significant changes in spectral intensity, peak position and Full Width Half Maximum (FWHM). The PL spectral intensity decreased abruptly with increasing temperature. The peak position was blue shifted with increasing temperature, and the peak shape showed an obvious asymmetry. The FMWH of the PL spectra was gradually broadened with the increase in the temperature, and there was a sharp increase from 270 °C to 300 °C. These variations in the PL spectra with temperature indicate that the optical properties of MAPbBr₃ are greatly affected by temperature, which in turn affects the application of MAPbBr₃ in fields such as optical devices. These results may be instructive for the application of MAPbBr₃. Full article

All-inorganic perovskite semiconductors have received significant interest for their potential stability over heat and humidity. However, the typical CsPbI₃ displays phase instability despite its desirable bandgap of ~1.73 eV. Herein, we studied the mixed halide perovskite CsPbI₂Br by varying the silver doping concentration. For this purpose, we examined its bandgap tunability as a function of the silver doping by using density functional theory. Then, we studied the effect of silver on the structural and optical properties of CsPbI₂Br. Resultantly, we found that ‘silver doping’ allowed for partial bandgap tunability from 1.91 eV to 2.05 eV, increasing the photoluminescence (PL) lifetime from 0.990 ns to 1.187 ns, and, finally, contributing to the structural stability when examining the aging effect via X-ray diffraction. Then, through the analysis of the intermolecular interactions based on the solubility parameter, we explain the solvent engineering process in relation to the solvent trapping phenomena in CsPbI₂Br thin films. However, silver doping may induce a defect morphology (e.g., a pinhole) during the formation of the thin films. Full article

Silver-based chalcogenide semiconductors exhibit low toxicity and near-infrared optical properties and are therefore extensively employed in the field of solar cells, photodetectors, and biological probes. Here, we report a facile mixture precursor hot-injection colloidal route to prepare Ag₂Te_xS_1−x ternary quantum dots (QDs) with tunable photoluminescence (PL) emissions from 950 nm to 1600 nm via alloying band gap engineering. As a proof-of-concept application, the Ag₂Te_xS_1−x QDs-based near-infrared photodetector (PD) was fabricated via solution-processes to explore their photoelectric properties. The ICP-OES results reveal the relationship between the compositions of the precursor and the samples, which is consistent with Vegard’s equation. Alloying broadened the absorption spectrum and narrowed the band gap of the Ag₂S QDs. The UPS results demonstrate the energy band alignment of the Ag₂Te_0.53S_0.47 QDs. The solution-processed Ag₂Te_xS_1−x QD-based PD exhibited a photoresponse to 1350 nm illumination. With an applied voltage of 0.5 V, the specific detectivity is 0.91 × 10¹⁰ Jones and the responsivity is 0.48 mA/W. The PD maintained a stable response under multiple optical switching cycles, with a rise time of 2.11 s and a fall time of 1.04 s, which indicate excellent optoelectronic performance. Full article

Quantum-well intermixing (QWI) technology is commonly considered as an effective methodology to tune the post-growth bandgap energy of semiconductor composites for electronic applications in diode lasers and photonic integrated devices. However, the specific influencing mechanism of the interfacial strain introduced by the dielectric-layer-modulated multiple quantum well (MQW) structures on the photoluminescence (PL) property and interfacial quality still remains unclear. Therefore, in the present study, different thicknesses of SiO₂-layer samples were coated and then annealed under high temperature to introduce interfacial strain and enhance atomic interdiffusion at the barrier–well interfaces. Based on the optical and microstructural experimental test results, it was found that the SiO₂ capping thickness played a positive role in driving the blueshift of the PL peak, leading to a widely tunable PL emission for post-growth MQWs. After annealing, the blueshift in the InGaAs/AlGaAs MQW structures was found to increase with increased thickness of the SiO₂ layer, and the largest blueshift of 30 eV was obtained in the sample covered with a 600 nm thick SiO₂ layer that was annealed at 850 °C for 180 s. Additionally, significant well-width fluctuations were observed at the MQW interface after intermixing, due to the interfacial strain introduced by the thermal mismatch between SiO₂ and GaAs, which enhanced the inhomogeneous diffusion rate of interfacial atoms. Thus, it can be demonstrated that the introduction of appropriate interfacial strain in the QWI process is of great significance for the regulation of MQW band structure as well as the control of interfacial quality. Full article

This work investigates the optical properties of Yb³⁺ ions doped GeO₂-PbO glasses containing Ag nanoclusters (NCs), produced by the melt-quenching technique. The lack in the literature regarding the energy transfer (ET) between these species in these glasses motivated the present work. Tunable visible emission occurs from blue to orange depending on the Yb³⁺ concentration which affects the size of the Ag NCs, as observed by transmission electron microscopy. The ET mechanism from Ag NCs to Yb³⁺ ions (²F_7/2 → ²F_5/2) was attributed to the S₁→T₁ decay (spin-forbidden electronic transition between singlet–triplet states) and was corroborated by fast and slow lifetime decrease (at 550 nm) of Ag NCs and photoluminescence (PL) growth at 980 nm, for excitations at 355 and 405 nm. The sample with the highest Yb³⁺ concentration exhibits the highest PL growth under 355 nm excitation, whereas at 410 nm it is the sample with the lowest concentration. The restriction of Yb³⁺ ions to the growth of NCs is responsible for these effects. Thus, higher Yb³⁺ concentration forms smaller Ag NCs, whose excitation at 355 nm leads to more efficient ET to Yb³⁺ ions compared to 410 nm. These findings have potential applications in the visible to near-infrared regions, such as tunable CW laser sources and photovoltaic devices. Full article

An accurate knowledge of the optical properties of β-Ga₂O₃ is key to developing the full potential of this oxide for photonics applications. In particular, the dependence of these properties on temperature is still being studied. Optical micro- and nanocavities are promising for a wide range of applications. They can be created within microwires and nanowires via distributed Bragg reflectors (DBR), i.e., periodic patterns of the refractive index in dielectric materials, acting as tunable mirrors. In this work, the effect of temperature on the anisotropic refractive index of β-Ga₂O₃ n(λ,T) was analyzed with ellipsometry in a bulk crystal, and temperature-dependent dispersion relations were obtained, with them being fitted to Sellmeier formalism in the visible range. Micro-photoluminescence (μ-PL) spectroscopy of microcavities that developed within Cr-doped β-Ga₂O₃ nanowires shows the characteristic thermal shift of red–infrared Fabry–Perot optical resonances when excited with different laser powers. The origin of this shift is mainly related to the variation in the temperature of the refractive index. A comparison of these two experimental results was performed by finite-difference time-domain (FDTD) simulations, considering the exact morphology of the wires and the temperature-dependent, anisotropic refractive index. The shifts caused by temperature variations observed by μ-PL are similar, though slightly larger than those obtained with FDTD when implementing the n(λ,T) obtained with ellipsometry. The thermo-optic coefficient was calculated. Full article

Because of their bandgap tunability and strong light–matter interactions, two-dimensional (2D) semiconductors are considered promising candidates for next-generation optoelectronic devices. However, their photophysical properties are greatly affected by their surrounding environment because of their 2D nature. In this work, we report that the photoluminescence (PL) of single-layer WS₂ is substantially affected by interfacial water that is inevitably present between it and the supporting mica substrates. Using PL spectroscopy and wide-field imaging, we show that the emission signals from A excitons and their negative trions decreased at distinctively different rates with increasing excitation power, which could be attributed to the more efficient annihilation between excitons than between trions. By gas-controlled PL imaging, we also prove that the interfacial water converted the trions into excitons by depleting native negative charges through an oxygen reduction reaction, which rendered the excited WS₂ more susceptible to nonradiative decay via exciton–exciton annihilation. Understanding the role of nanoscopic water in complex low-dimensional materials will eventually contribute to devising their novel functions and related devices. Full article