Search Results (174)

We report the development of highly luminescent, bovine serum albumin (BSA)-stabilized gold–silver bimetallic nanoclusters (Au-AgNCs@BSA) as a novel platform for high-sensitivity, ratiometric intracellular temperature sensing. Precise and non-invasive temperature sensing at the nanoscale is crucial for applications ranging from intracellular thermogenesis monitoring to localized hyperthermia therapies. Traditional luminescent thermometric platforms often suffer from limitations such as high cytotoxicity and low photostability. Here, we synthesized Au-AgNCs@BSA via a one-pot aqueous reaction, achieving significantly enhanced photoluminescence quantum yields (PL QYs, up to 18%) and superior thermal responsiveness compared to monometallic counterparts. The dual-emissive Au-AgNCs@BSA exhibit a linear ratiometric fluorescence response to temperature fluctuations within the physiological range (20–50 °C), enabling accurate and concentration-independent thermometry in live cells. Time-resolved PL and Arrhenius analyses reveal two distinct emissive states and a high thermal activation energy (E_a = 199 meV), indicating strong temperature dependence. Silver doping increases radiative decay rates while maintaining low non-radiative losses, thus amplifying fluorescence intensity and thermal sensitivity. Owing to their small size, excellent photostability, and low cytotoxicity, these nanoclusters were applied to non-invasive intracellular temperature mapping, presenting a promising luminescent nanothermometer for real-time cellular thermogenesis monitoring and advanced bioimaging applications. Full article

Perovskite solar cells (PSCs) are emerging as leading candidates for sustainable energy generation due to their high power conversion efficiencies and low fabrication costs. However, their performance remains constrained by non-radiative recombination losses primarily at grain boundaries, interfaces, and within the perovskite bulk that are difficult to characterize under realistic operating conditions. Traditional methods such as photoluminescence offer valuable insights but are complex, time-consuming, and often lack scalability. In this study, we present a novel Long Short-Term Memory (LSTM)-based deep learning framework for dynamically predicting dominant recombination losses in PSCs. Trained on light intensity-dependent current–voltage (J–V) characteristics, the proposed model captures temporal behavior in device performance and accurately distinguishes between grain boundary, interfacial, and band-to-band recombination mechanisms. Unlike static ML approaches, our model leverages sequential data to provide deeper diagnostic capability and improved generalization across varying conditions. This enables faster, more accurate identification of efficiency limiting factors, guiding both material selection and device optimization. While silicon technologies have long dominated the photovoltaic landscape, their high-temperature processing and rigidity pose limitations. In contrast, PSCs—especially when combined with intelligent diagnostic tools like our framework—offer enhanced flexibility, tunability, and scalability. By automating recombination analysis and enhancing predictive accuracy, our framework contributes to the accelerated development of high-efficiency PSCs, supporting the global transition to clean, affordable, and sustainable energy solutions. Full article

This study presents the fabrication and characterization of ZnO–CNT composite-based optoelectronic synaptic devices via a sol–gel process. By incorporating various concentrations of CNTs (0–2.0 wt%) into ZnO thin films, we investigated their effects on synaptic behaviors under ultraviolet (UV) stimulation. The CNT addition enhanced the electrical and optical performance by forming a p–n heterojunction with ZnO, which promoted charge separation and suppressed recombination. As a result, the 1.5 wt% CNT device exhibited the highest excitatory postsynaptic current (EPSC), improved paired-pulse facilitation, and prolonged memory retention. Learning–forgetting cycles revealed that repeated stimulation reduced the number of pulses required for relearning while extending the forgetting time, mimicking biological memory reinforcement. Energy consumption per pulse was estimated at 16.34 nJ, suggesting potential for low-power neuromorphic applications. A 3 × 3 device array was also employed for visual memory simulation, showing spatially controllable and stable memory states depending on CNT content. To support these findings, structural and optical analyses were conducted using scanning electron microscopy (SEM), UV-visible absorption spectroscopy, photoluminescence (PL) spectroscopy, and Raman spectroscopy. These findings demonstrate that the synaptic characteristics of ZnO-based devices can be finely tuned through CNT incorporation, providing a promising pathway for the development of energy-efficient and adaptive optoelectronic neuromorphic systems. Full article

Upscaling perovskite solar cells and modules requires precise laser patterning for series interconnection and spatial characterization of cell parameters to understand laser–material interactions and their impact on performance. This study investigates the use of nanosecond (ns) and picosecond (ps) laser pulses at varying fluences for the P3 patterning step of perovskite solar cells. Hyperspectral photoluminescence (PL) imaging was employed to map key parameters such as optical bandgap energy, Urbach energy, and shunt resistance. The mappings were correlated with electrical measurements, revealing that both ns and ps lasers can be utilized for effective series interconnections with minimal performance losses at optimized fluences. Our findings provide a deeper understanding of fluence-dependent effects in P3 patterning. Moreover, the results demonstrate that the process window is robust, allowing for reasonable cell performance even with deviations from optimal parameters. This robustness, coupled with the scalability of the laser patterning process, emphasize its suitability for industrial module production. Full article

Recent advances in electrochemiluminescence (ECL) leveraging thermally activated delayed fluorescence (TADF) have highlighted its potential for near-unity exciton harvesting. However, there are still very limited examples of TADF-ECL emitters. We present a rigid diboron-embedded multiple-resonance TADF emitter, which exhibits blue–green emission at 493 nm with a remarkably narrow bandwidth (FWHM = 22 nm) and minimized singlet-triplet energy gap (ΔE_ST = 0.2 eV), achieving a 67% photoluminescence quantum yield. DFT calculations confirm the short-range charge transfer, enabling narrowband emission. Co-reactant-dependent ECL shows that tripropylamine (TPrA) improves the ECL efficiency from 11% (annihilation) to 51%, while benzoyl peroxide (BPO) yields 1% due to poor radical stabilization. ECL spectra align with photoluminescence, confirming the singlet-state dominance without exciplex interference. TPrA enhances stable radical formation and energy transfer, whereas BPO induces non-radiative losses. These findings establish molecular rigidity and co-reactant selection as pivotal factors in developing high-performance TADF-ECL systems, providing fundamental guidelines for designing organic electrochemiluminescent materials with optimized exciton harvesting efficiency. Full article

In order to break through the limitations of the application of traditional temperature measurement technology, non-contact optical temperature sensing material with good sensitivity is one of the current research hotspots. Herein, a series of Dy³⁺ and Mn⁴⁺ co-doping Mg₃Ga₂SnO₈ fluorescent materials were prepared successfully, and the crystal structure, phase purity, and morphology of the synthesized phosphors were comprehensively investigated, as well as their photoluminescence properties, energy transfer, and high-temperature thermal stability. The two pairs of independent thermally coupled energy levels of Dy³⁺ ions and Mn⁴⁺ ions in Mg₃Ga₂SnO₈ are utilized to realize the dual-mode optical temperature detection with excellent performance. On the one hand, based on the different ionic energy level transitions of ⁴F_9/2→⁶H_13/2 and ²E_g→⁴A_2g responding differently to temperature, two emission bands of 577 nm and 668 nm were chosen to construct the fluorescence intensity ratio thermometry, and the maximum sensitivity of 1.82 %K⁻¹ was achieved at 473 K. On the other hand, based on the strong temperature dependence of the lifetime of Mn⁴⁺ in Mg₃Ga₂SnO₈:0.06Dy³⁺,0.009Mn⁴⁺, fluorescence lifetime thermometry was constructed and a maximum sensitivity of 2.75 %K⁻¹ was achieved at 473 K. Finally, the Mg₃Ga₂SnO₈: 0.06Dy³⁺,0.009Mn⁴⁺ sample realizes dual-mode optical temperature measurement with high sensitivity and a wide temperature detection range, indicating that the sample has promising applications in optical temperature measurement. Full article

Triplet–triplet transfer photochemical reactions are essential in many biological, chemical, and photonic applications. Here, the Pd-octaethylporphyrin sensitizer along with triplet–triplet annihilator (TTA) active 9,10-diphenylantracenes (DPA) and the related substituted variants in low concentrations were examined. A full experimental approach is presented for finding the necessary rate parameters with statistical standard deviation parameters. This was achieved by solving the pertinent non-analytical kinetic differential equation and fitting it to the experimental time-resolved photoluminescence of both slow fluorescence and sensitizer phosphorescence. The efficiency of the triplet–triplet energy transfer rate was found to be around 90% in THF but only around 75% in toluene. This appears to follow from the shorter lifetime of the sensitizer triplet in toluene. Moreover, the TTA transfer rate was on average more than 40% in THF toluene whereas a considerably lower value around 20–30% was found for toluene. This originated in an order of magnitude higher solvent quenching rate using toluene, based on the analysis of the delayed fluorescence decay traces. These are also higher than the statistically expected 1/9 TTA efficiency but in accordance with recent results in the literature, that attributed these high values to an inverse intersystem crossing process. In addition, quantum chemical calculations were carried out to reveal the pertinent excited triplet molecular orbitals of the lowest triplet excited state for a series of substituted DPAs, in comparison with the singlet ground state. Conclusively, these states distribute mainly in an anthracene ring in all compounds being in the range 1.64–1.65 eV above the ground state. The TTA efficiency was found to vary depending on the DPA annihilator substitution scheme and found to be smaller in THF. This is likely because the molecular framework over which the T1 excited molecular orbitals distribute is less sensitive for a longer lifetime of the annihilator triplet state. Full article

This research studied the recycling of borosilicate glass wastes from damaged laboratory glassware. The luminescent glasses were prepared by doping glass waste powder with rare earth ions, namely, dysprosium ions (Dy³⁺) and samarium ions (Sm³⁺), as well as co-doping with Dy³⁺ and Sm³⁺ at a concentration of 2% by weight. The sintering process was conducted in a microwave oven for a duration of 15 min. The photoluminescence spectra of the doped glasses were obtained under excitation at 401 nm and 388 nm. The results showed that the emission characteristics depended on the doping concentrations of Dy³⁺ and Sm³⁺ and the excitation wavelengths. Upon excitation at 401 nm, the co-doped glasses exhibited the maximum emission peak of Sm³⁺ at 601 nm (yellowish and orange region in the CIE chromaticity diagram) due to the energy transition from ⁴G_5/2 to ⁶H_7/2. When excited at 388 nm, however, the emission spectra of the co-doped glasses were similar to the characteristic emission peaks of Dy³⁺ (white region in the CIE chromaticity diagram), but the peak position exhibits a red shift. This could be attributed to an increase in the amount of non-bridging oxygens (NBOs) by co-doping. Full article

A series of AlGaN/GaN high-electron-mobility transistor (HEMT) structures, with an AlN thin buffer, GaN thick layer and Al_0.25Ga_0.75N layer (13–104 nm thick), is prepared by metal–organic chemical vapor deposition and investigated via multiple techniques. Spectroscopic ellipsometry (SE) and temperature-dependent measurements and penetrative analyses have achieved significant understanding of these HEMT structures. Bandgaps of AlGaN and GaN are acquired via SE-deduced relationships of refraction index n and extinguish coefficient k vs. wavelength λ in a simple but straightforward way. The optical constants of n and k, and the energy gap E_g of AlGaN layers, are found slightly altered with the variation in AlGaN layer thickness. The Urbach energy E_U at the AlGaN and GaN layers are deduced. High-resolution X-ray diffraction and calculations determined the extremely low screw dislocation density of 1.6 × 10⁸ cm⁻². The top AlGaN layer exhibits a tensile stress influenced by the under beneath GaN and its crystalline quality is improved with the increase in thickness. Comparative photoluminescence (PL) experiments using 266 nm and 325 nm two excitations reveal and confirm the 2DEG within the AlGaN-GaN HEMT structures. DUV (266 nm) excitation Raman scattering and calculations acquired carrier concentrations in compatible AlGaN and GaN layers. Full article

The n-TiO₂ nanoballs–sticks (TiO₂ NBSs) were successfully deposited on p-lightly boron-doped diamond (LBDD) substrates by the hydrothermal method. The temperature-dependent optoelectronic properties and carrier transport behavior of the n-TiO₂ NBS/p-LBDD heterojunction were investigated. The photoluminescence (PL) of the heterojunction detected four distinct emission peaks at 402 nm, 410 nm, 429 nm, and 456 nm that have the potential to be applied in white-green light-emitting devices. The results of the I-V characteristic of the heterojunction exhibited excellent rectification characteristics and good thermal stability at all temperatures (RT-200 °C). The forward bias current increases gradually with the increase in external temperature. The temperature of 150 °C is ideal for the heterojunction to exhibit the best electrical performance with minimum turn-on voltage (0.4 V), the highest forward bias current (0.295 A ± 0.103 mA), and the largest rectification ratio (16.39 ± 0.005). It is transformed into a backward diode at 200 °C, which is attributed to a large number of carriers tunneling from the valence band (VB) of TiO₂ to the conduction band (CB) of LBDD, forming an obvious reverse rectification effect. The carrier tunneling mechanism at different temperatures and voltages is analyzed in detail based on the schematic energy band structure and semiconductor theoretical model. Full article

In recent years, the morphology control of semiconductor nanomaterials has been attracting increasing attention toward maximizing their functional properties and reaching their end use in real-world devices. However, the development of easy and cost-effective methods for preparing large-scale patterned semiconductor structures on flexible temperature-sensitive substrates remains ever in demand. In this study, vapor post-treatment (VPT) is investigated as a potential, simple and low-cost post-preparative method to morphologically modify gravure-printed zinc oxide (ZnO) nanoparticulate thin films at low temperatures. Exposing nanoparticles (NPs) to acidic vapor solution, spontaneous restructuring pathways are observed as a consequence of NPs tending to reduce their high interfacial energy. Depending on the imposed environmental conditions during the treatment (e.g., temperature, vapor composition), various ZnO thin-film morphologies are produced, from dense to porous ones, as a result of the activation and interplay of different spontaneous interface elimination mechanisms, including dissolution–precipitation, grain boundary migration and grain rotation–coalescence. The influence of VPT on structural/optical properties has been examined via XRD, UV–visible and photoluminescence measurements. Controlling NP junctions and network nanoporosity, VPT appears as promising cost-effective, low-temperature and pressureless post-preparative platform for preparing supported ZnO NP-based films with improved connectivity and mechanical stability, favoring their practical use and integration in flexible devices. Full article

Accurate and selective monitoring of thiamine levels in multivitamin supplements is essential for preventing deficiencies and ensuring product quality. To achieve this, a Förster resonance energy transfer (FRET) system using carbon dots (CDs) as energy donors and citrate-stabilized silver nanoparticles (AgNPs) as energy acceptors was developed. The aqueous synthesis of AgNPs using microwave irradiation was optimized to obtain efficient plasmonic nanoparticles for FRET applications, targeting maximal absorbance intensity, stability, and wavelength alignment. Using a central composite orthogonal design (CCOD), the optimal conditions were identified as a 12.5 min microwave reaction time, a Ag molar ratio of 0.72, and a pH of 8.28. The FRET sensing scheme was applied for thiamine determination, where the vitamin’s presence impaired the FRET process, restoring CDs’ photoluminescence (PL) emission in a concentration-dependent manner. To mitigate interference from other vitamins, PL kinetic data and excitation–emission matrix (EEM) data were analyzed using unfolded partial least-squares (U-PLS) with the subsequent application of the residual bilinearization technique (RBL), achieving high sensitivity and specificity for thiamine detection. This method demonstrated its accuracy and robustness by attaining a determination coefficient (R²) of 0.952 and a relative error of prediction (REP%) of 11%. This novel method offers highly sensitive and interference-free thiamine detection, with significant potential for a wide range of analytical applications. Full article

Thermally activated delayed fluorescence (TADF) materials with high photoluminescence quantum yields and a fast reverse intersystem crossing (RISC) are of the highest interest for organic light-emitting diodes (OLEDs). In the past decade, triaryl boranes with multiple resonance effect (MR) have captured significant attention. The efficiency of MR-TADF emitters strongly depends on small singlet–triplet energy gaps (ΔE_ST), but also on large reverse intersystem crossing (RISC) rate constants (k_RISC). The latter effect has strongly been focused on very recently and has drawn attention to heavier elements, including sulfur and selenium, the large spin–orbit coupling (SOC) of which accelerates RISC effects. Within the context of MR-TADF emitters, the 5,9-X₂-13b-boranaphtho [3,2,1-de]anthracene scaffold (X-B-X, X = donor heteroatom, e.g., N, O, S, Se) has been recognized as a promising narrowband-emissive TADF material. However, the incorporation of sulfur and selenium as highly SOC-inducing elements has proven to be difficult. Most synthetic strategies apply protocols initially suggested by Hatakeyama to obtain nitrogen- and oxygen-doped materials. We present an alternative route over the established methodology, which affords highly sought-after sulfur- and selenium-doped materials with a high yield and purity. Full article

Photoluminescent carbon dots (CDs) have received increasing attention because of their admirable photophysical performances. The current strategies for synthesizing CDs typically require high energy consumption levels, and the ability to synthesize CDs at ambient temperature would be highly desirable. Herein, we design an energy-efficient approach to synthesize CDs through a Schiff base crosslinking between 2,5-dihydroxy-1,4-benzoquinone and tetraethylenepentamine at room temperature. The obtained CDs possess maximum photoluminescence (PL) emissions of 492 nm. Moreover, the proposed CDs possess good stability and a concentration-dependent PL and their maximum emissions can redshift from 492 to 621 nm as the CDs concentration increases. Because of their good luminescent properties, the CDs can be employed as optical probes for doxorubicin detection using the inner filter effect. This study develops a powerful approach for the large-scale synthesis of CDs with a superior performance. Full article

AlGaN is attractive for fabricating deep ultraviolet (DUV) optoelectronic and electronic devices of light-emitting diodes (LEDs), photodetectors, high-electron-mobility field-effect transistors (HEMTs), etc. We investigated the quality and optical properties of Al_xGa_1−xN films with high Al fractions (60–87%) grown on sapphire substrates, including AlN nucleation and buffer layers, by metal–organic chemical vapor deposition (MOCVD). They were initially investigated by high-resolution X-ray diffraction (HR-XRD) and Raman scattering (RS). A set of formulas was deduced to precisely determine x(Al) from HR-XRD data. Screw dislocation densities in AlGaN and AlN layers were deduced. DUV (266 nm) excitation RS clearly exhibits AlGaN Raman features far superior to visible RS. The simulation on the AlGaN longitudinal optical (LO) phonon modes determined the carrier concentrations in the AlGaN layers. The spatial correlation model (SCM) analyses on E₂(high) modes examined the AlGaN and AlN layer properties. These high-x(Al) Al_xGa_1−xN films possess large energy gaps E_g in the range of 5.0–5.6 eV and are excited by a DUV 213 nm (5.8 eV) laser for room temperature (RT) photoluminescence (PL) and temperature-dependent photoluminescence (TDPL) studies. The obtained RTPL bands were deconvoluted with two Gaussian bands, indicating cross-bandgap emission, phonon replicas, and variation with x(Al). TDPL spectra at 20–300 K of Al_0.87Ga_0.13N exhibit the T-dependences of the band-edge luminescence near 5.6 eV and the phonon replicas. According to the Arrhenius fitting diagram of the TDPL spectra, the activation energy (19.6 meV) associated with the luminescence process is acquired. In addition, the combined PL and time-resolved photoluminescence (TRPL) spectroscopic system with DUV 213 nm pulse excitation was applied to measure a typical AlGaN multiple-quantum well (MQW). The RT TRPL decay spectra were obtained at four wavelengths and fitted by two exponentials with fast and slow decay times of ~0.2 ns and 1–2 ns, respectively. Comprehensive studies on these Al-rich AlGaN epi-films and a typical AlGaN MQW are achieved with unique and significant results, which are useful to researchers in the field. Full article