Photoluminescence Emission Spectra Research Articles

Graphene Quantum Dots in Bacterial Cellulose Hydrogels for Visible Light-Activated Antibiofilm and Angiogenesis in Infection Management

A novel bacterial cellulose (BC)-based composite hydrogel with graphene quantum dots (BC-GQDs) was developed for photodynamic therapy using blue and green light (BC-GQD_blue and BC-GQD_green) to target pathogenic bacterial biofilms. This approach aims to address complications in treating nosocomial infections and combating multi-drug-resistant organisms. Short-term illumination (30 min) of both BC-GQD samples led to singlet oxygen production and a reduction in pathogenic biofilms. Significant antibiofilm activity (>50% reduction) was achieved against Staphylococcus aureus and Escherichia coli with BC-GQD_green, and against Pseudomonas aeruginosa with BC-GQD_blue. Atomic force microscopy images revealed a substantial decrease in biofilm mass, accompanied by changes in surface roughness and area, further confirming the antibiofilm efficacy of BC-GQDs under blue and green light, without any observed chemical alterations. Additionally, the biocompatibility of BC-GQDs was demonstrated with human gingival fibroblasts (HGFs). For the first time, in vitro studies explored the visible light-induced potential of BC-GQD composites to promote wound healing processes, showing increased migratory potential and the upregulation of eNOS and MMP9 gene expressions in HGFs. Chemical characterization revealed a 70 nm upshift in the photoluminescence emission spectra compared to the excitation wavelength. These novel photoactive BC-GQD hydrogel composites show great promise as effective agents for wound healing regeneration and infection management.

Tunable photoluminescence and energy transfer in Dy3+ and Eu3+ co-doped NaCaGd(WO4)3 phosphors for pc-WLED applications.

Elevated temperatures can lead to reabsorption and color drift, compromising the quality of phosphor-converted white light-emitting diode (pc-WLED) devices. To ensure the performance of WLEDs under these conditions, it is essential to develop luminescent materials that maintain stable color. Consequently, there is a pressing need for single-phase white-emitting phosphors with robust chromatic stability. In this work, we synthesize a series of color-tunable NaCaGd(WO4)3 (NCGW) phosphors using conventional solid-state reaction method, co-doping with Dy3+ and Eu3+ in varying ratios. X-ray diffraction, Rietveld refinement and scanning electron microscopy analyses are carried out to identify the phase purity and morphology. The photoluminescence (PL) properties are investigated under excitations of 352 nm and 393 nm. The PL emission spectra and fluorescence decay curves reveal efficient energy transfer between the Dy3+ and Eu3+ ions within the NCGW host, demonstrating tunable PL emission properties through manipulation of this energy transfer. At elevated temperatures of up to 200 °C, the positions of the characteristic emission peaks of Dy3+ and Eu3+ in NCGW phosphors remain essentially unchanged. Although the emission band intensities decrease due to thermal quenching, they retain a significant portion of their initial intensity compared to room temperature levels. For proof-of-concept studies, a single-phase NCGW:0.05%Dy3+-0.05%Eu3+ phosphor is combined with a commercial 365 nm UV chip to create a WLED device prototype. This prototype achieves a color rendering index of 81.7, a correlated color temperature of 4862 K and Commission International de I'Eclairage chromaticity coordinates of (0.35, 0.37), exhibiting comparable or superior colorimetric values to those reported in previous research. The results indicate that Dy3+ and Eu3+ co-doped NCGW phosphors, with their high chromaticity stability, have significant potential for full-spectrum WLED applications.

In Situ X-Ray Study During Thermal Cycle Treatment Combined with Complementary Ex Situ Investigation of InGaN Quantum Wells.

In situ X-ray reciprocal space mapping was performed during the interval heating and cooling of InGaN/GaN quantum wells (QWs) grown via metal-organic vapor phase epitaxy (MOVPE). Our detailed in situ X-ray analysis enabled us to track changes in the peak intensities and radial and angular broadenings of the reflection. By simulating the radial diffraction profiles recorded during the thermal cycle treatment, we demonstrate the presence of indium concentration distributions (ICDs) in the different QWs of the heterostructure (1. QW, bottom, 2. QW, middle, and 3. QW, upper). During the heating process, we found that the homogenization of the QWs occurred in the temperature range of 850 °C to 920 °C, manifesting in a reduction in ICDs in the QWs. Furthermore, there is a critical temperature (T = 940 °C) at which the mean value of the indium concentration starts to decrease below 15% in 1. QW, indicating the initiation of decomposition in 1. QW. Moreover, further heating up to 1000 °C results in extended diffuse scattering along the angular direction of the diffraction spot, confirming the propagation of the decomposition and the formation of trapezoidal objects, which contain voids and amorphous materials (In-Ga). Heating InGaN QWs up to T = 1000 °C led to a simultaneous decrease in the indium content and ICDs. During the cooling phase, there was no significant variation in the indium concentrations in the different QWs but rather an increase in the defect area, which contributes to the amplification of diffuse scattering. A comparison of ex situ complementary high-resolution transmission microscopy (Ex-HRTEM) measurements performed at room temperature before and after the thermal cycle treatment provides proof of the formation of four different types of defects in the QWs, which result from the decomposition of 1. QW during the heating phase. This, in turn, has strongly influenced the intensity of the photoluminescence emission spectra without any detectable shift in the emission wavelength λMQWs.

Structural and luminescent properties of a Cr3+/Sm3+ doped GdAlO3 orthorhombic perovskite for solid-state lighting applications.

The Cr3+ and Sm3+ doped GdAlO3 perovskite with formula Gd0.995Sm0.005Al0.995Cr0.005O3, was synthesized via a solid-state reaction method, and its structure, morphology, and photoluminescence properties were thoroughly investigated. The compound crystallizes in the orthorhombic Pbnm space group, with Cr3+ transition-metal ions substituting Al3+ in the octahedral symmetry site, and Sm3+ lanthanide (rare-earth) ions occupying the tetrahedral site. The material's morphology and chemical composition homogeneity were evaluated through Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray analysis. Photoluminescence excitation (PLE) and emission spectra (PL) were used to shed light on the electronic structure of the Cr3+ cations, through crystal field analysis in the O h symmetry site. Theoretical studies enabled the precise assignment of the Cr3+ 3d-3d transitions. The intra-configurational 4f-4f transitions of Sm3+ resulted in a variety of excitation bands appearing in the high-wavelength range of the PLE spectrum. The photoluminescence studies supported the occurrence of energy transfer in the doped GdAlO3 perovskite between Gd3+, Sm3+ and Cr3+ ions. The obtained results suggest the high potential of the synthesized material for solid state lighting applications.

Sulfur isotope engineering in heterostructures of transition metal dichalcogenides.

Heterostructuring of two-dimensional materials offers a robust platform to precisely tune optoelectronic properties through interlayer interactions. Here we achieved a strong interlayer coupling in a double-layered heterostructure of sulfur isotope-modified adjacent MoS2 monolayers via two-step chemical vapor deposition growth. The strong interlayer coupling in the MoS2(34S)/MoS2(32S) was affirmed by low-frequency shear and breathing modes in the Raman spectra. The photoluminescence emission spectra showed that isotope-induced changes in the electronic structure and strong interlayer coupling led to the suppression of intralayer excitons, resulting in dominant emission from the MoS2(32S) layer. Time-resolved photoluminescence experiments indicated faster lifetimes in the MoS2(34S)/MoS2(32S) heterostructure compared to the conventional bilayers with the natural isotopic abundance, highlighting nuanced interlayer exciton dynamics due to the isotopic modification. This study underscores the great potential of isotope engineering in van der Waals heterostructures, as it enables tailoring the band structure and exciton dynamics at the nuclear level without the need of chemical modification.

Investigation of Spectroscopic Parameters and Trap Parameters of Eu3+-Activated Y2SiO5 Phosphors for Display and Dosimetry Applications.

Using the solid-state reaction technique, varied Y2SiO5 phosphors activated by europium (Eu3+) ions at varied concentrations were made at calcination temperatures of 1000 °C and 1250 °C during sintering in an air environment. The XRD technique identified the monoclinic structure, and the FTIR technique was used to analyze the generated phosphors. Photoluminescence emission and excitation patterns were measured using varying concentrations of Eu3+ ions. The optimal strength was observed at a 2.0 mol% concentration. Emission peaks were detected at 582 nm and 589 nm for the 5D0→7F1 transition and at 601 nm, 613 nm, and 632 nm for the 5D0→7F2 transition under 263 nm excitation. Because Eu3+ is naturally bright, these emission peaks show how ions change from one excited state to another. This makes them useful for making phosphors that emit red light for use in optoelectronics and flexible displays. Based on the computed (1931 CIE) chromaticity coordinates for the photoluminescence emission spectra, it was determined that the produced phosphor may be used in light-emitting diodes. The TL glow curve was examined for various doping ion concentrations and durations of UV exposure levels, revealing a broad peak at 183 °C. Using computerized glow curve deconvolution (CGCD), we calculated the kinetic parameters.

Visualization and Estimation of 0D to 1D Nanostructure Size by Photoluminescence.

We elaborate a method for determining the 0D-1D nanostructure size by photoluminescence (PL) emission spectrum dependence on the nanostructure dimensions. As observed, the high number of diamond-like carbon nanocones shows a strongly blue-shifted PL spectrum compared to the bulk material, allowing for the calculation of their top dimensions of 2.0 nm. For the second structure model, we used a sharp atomic force microscope (AFM) tip, which showed green emission localized on its top, as determined by confocal microscopy. Using the PL spectrum, the calculation allowed us to determine the tip size of 1.5 nm, which correlated well with the SEM measurements. The time-resolved PL measurements shed light on the recombination process, providing stretched-exponent decay with a τ0 = 1 ns lifetime, indicating a gradual decrease in exciton lifetime along the height of the cone from the base to the top due to surface and radiative recombination. Therefore, the proposed method provides a simple optical procedure for determining an AFM tip or other nanocone structure sharpness without the need for sample preparation and special expensive equipment.

Dy doped calcium silicates synthesized using agro-food wastes and conventional chemicals as resources: a comparative study

Based on an earlier study, a mimic composition 38SiO2-60CaO-0.5Dy2O3-0.2Na2O-1MgO-0.1Al2O3-0.1TiO2-0.1Fe2O3 (wt.%) are synthesized by solid-state reaction method. The structural, morphological, and optical properties of the synthesized sample presented in this study are compared with the corresponding properties of a similar sample derived from rice husk ash and eggshell powder as resources. The conventional chemicals derived sample are multi-phasic, containing β−Ca2SiO4, γ−Ca2SiO4, Ca3Si2O7, and CaFeO3 phases, and the CaO/SiO2 ratio was believed to be affecting the room temperature stabilization of the β phase. Field emission scanning electron microscopy images showed that twinned particles, cracks, and edge dislocations were present in the synthesized sample. The presence of precipitates in the micrographs indicated that Dy ions were segregated on the surface of the sample. The optical bandgap of the samples was 3.7 eV, as calculated by diffuse reflectance spectroscopy. The photoluminescence emission spectrum contained characteristic emission peaks of the Dy3+ ions. Apart from these, additional peaks were observed due to the titanium ions present in the sample. Understanding the properties of calcium silicates containing multiple dopant ions is important to develop a white light-emitting diode. The properties of the mineral-derived sample are compared to those of the agro-food waste-derived similar sample.

Multiple stimuli-responsive double perovskite structured Ca2MgWO6: x % Eu3+ (x = 1–11 mol) red-emitting luminescent systems to combat counterfeiting

The rapid escalation of counterfeiting activities in recent years has posed significant challenges across diverse fields, such as pharmaceuticals, currency, luxury goods, and electronics. In response, inorganic phosphors have emerged as promising tools to combat counterfeiting due to their inherent durability and stability. The present work focuses on the synthesis of Ca2MgWO6:x % Eu3+ (x = 1–11 mol) luminescent systems via a gel-combustion route. The structural analysis of the synthesized luminescent systems confirmed a monoclinic crystal phase with a P21/n space group. The morphological study of the luminescent system revealed a network-like structure comprising interconnected particles. Photoluminescence emission spectra show a prominent red emission peak at 616 nm, corresponding to the 5D0→7F2 4f–4f electronic transition of Eu3+ ions in the host matrix. The emitted red light demonstrates a color purity and quantum efficiency of 93.1 % and 77.41 %, respectively. The anti-counterfeiting security patterns were developed using the Ca2MgWO6:x % Eu3+ (x = 9 mol) luminescent system showcase virtually invisible under normal light. However, developed patterns exhibit vivid red luminescence when exposed to multiple stimuli UV light at 365 and 395 nm, which envisages the versatility of the systems for enhancing product authentication and protecting against fraudulent activities across multiple industries. The aforementioned results demonstrated the efficacy of Ca2MgWO6: Eu3+ luminescent systems for integration into advanced security measures.

Crystallographic Profiling, Core-Shell Electronic Configurations, and Investigations of Frequency-Dependent Dielectric Characteristics of Sb2O3-V2O5 Micro Ceramics

A series of V2-xSb2xO5-δ (Sb-V-O) ceramic powder samples with molar concentrations ranging from 0.05 to 0.08 were synthesized using a solid-state reaction method. Crystallographic analysis conducted through Rietveld refinement indicates that at a molar fraction of x=0.05, the orthorhombic V₂O₅ phase is observed. Conversely, at molar concentrations of x=0.06, 0.07, and 0.08, the orthorhombic phase of V2O5 and the tetragonal phase of SbVO4 are present simultaneously. X-ray photoelectron spectroscopy (XPS) was employed to ascertain the elemental oxidation states, revealing the presence of V5+, V4+, Sb3+ ions, and Sb0 metal atoms, along with O1s photoelectron peaks. The photoluminescence (PL) emission spectrum suggests transitions from a shallow donor level to the valance band. The room temperature AC conductivity and dielectric property results reveal a systematic decrease in the dielectric constant. The AC conductivity experimental data was accurately modeled using the Almond-West formalism, yielding high R2 values (0.9968–0.9986) and low chi-square errors (1.157×10⁻11–9.42×10⁻12) obtaining hopping frequency values for each composition (x = 0.05–0.08). AC conductivity (σac) decreased from 5.08×10⁻⁴ S/m to 2.40×10⁻⁴ S/m at 10 MHz, while DC conductivity (σdc) dropped from 7.22×10⁻⁵ S/m to 1.55×10⁻⁵ S/m. This reduction in conductivity is attributed to structural changes from Sb³⁺ substitution, which disrupts polaronic conduction by reducing the number of available O2⁻ ions and promoting SbVO₄ phase formation, hindering charge transport. The Sb₂O₃-V₂O₅ ceramics exhibit promising potential for energy storage applications, particularly in capacitors requiring high dielectric constants at low frequencies. At lower frequencies, grain boundaries inhibit conduction, enhancing dielectric constant values; at elevated frequencies, grain conduction predominates, lowering dielectric constant in accordance with Koop’s phenomenological theory, favoring applications in multi-layer ceramic capacitors. A notably higher dielectric loss factor (εr'') at low frequencies (10 Hz–1 kHz) indicates lossy behavior, beneficial for microwave absorption, while its stabilization above 10 kHz suggests minimal energy dissipation, ideal for high-frequency electronic and dielectric devices.

(Invited) Photoluminescence and Scintillation Properties of Heavy Single Crystal Scintillators for X- and Gamma-Ray Detection

Scintillators are one of the luminescent materials, and have a function to convert a quantum of ionizing radiation to thousands of low energy photons immediately via interactions between the material and ionizing radiation [1,2]. Generally, scintillators are combined with photodetectors, and when the scintillation photons are emitted from the scintillator, photodetectors convert them to electrical signals. When the target ionizing radiation is high energy photons such as X- and gamma-rays, heavy materials are preferable for scintillators since the detection efficiency against high energy photons depends on density and effective atomic number. Up to now, many types of materials have been examined for scintillators, such as single crystals, glasses, and opaque and transparent ceramics [2]. Among them, bulk single crystalline scintillators have been applied for scintillation detectors owing to a superior optical quality including high transmittance and luminescence efficiency.In the conference, some recent results of development of heavy scintillators mainly containing Lu, Hf, Ta and Tl are introduced. These materials were synthesized by some single crystal growth techniques such as the floating zone and bridgman method. After the synthesis, they were examined on optical (photoluminescence excitation and emission spectra and decay curve) and scintillation (scintillation emission spectrum, decay curve, afterglow and pulse height) properties. In Lu-based crystals, rare earth doped Lu2O3 crystals are introduced, and especially, Tb- and Eu-doped ones show a high scintillation light yield. In Hf-based ones, some results of rare earth doped AEHfO3 (AE = alkali earth) crystals are presented, and Ce-doped (Mg,Ca)HfO3 shows a high scintillation light yield [3]. Among Ta-based crystals, Mg4(Nb,Ta)2O9 crystals have a high light yield due to charge transfer luminescence of Ta/Nb and O [4]. In Tl-based crystalline compounds, TlMgCl3 shows a high light yield and energy resolution [5]. In the conference, these results will be introduced.

Synthesis of white light emanating mixed lanthanide complexes with organic ligand for laser and optoelectronic applications

A series of mixing of complexes [EuxTb1-x.L3] was synthesized using the solvent-assisted grinding method. The chemical composition of complexes is determined by elemental analysis. Energy dispersive X-ray analysis (EDAX) was applied to ascertain the purity of complexes. The morphology and nature of the synthesized complex were investigated using scanning electron microscopy (SEM) and X-ray powder diffraction (XRD). The photoluminescent excitation (PL) and photoluminescent emission (PLE) spectra were examined as a function of the concentration of Eu3+ and Tb3+ ions to predict the tuning of color in both state solution and solid. Thermogravimetric data analysis reveals that these complexes have good thermal stability, supporting their application in producing organic light-emitting diodes. The radiative rate (Arad), quantum efficiency (φ), and JO intensity parameters (Ωλ) were calculated. Studying these complexes' Urbach energy, optical band gap, and refractive index suggests their potential application in semiconductor and solar cell devices. The Commission International de I'Eclairage 1931 (CIE) coordinates (x,y) can be obtained from the emission spectra of complexes, indicating that color can be adjusted to nearly white light (x = 0.3201,y = 0.3319) by changing the Tb3+ and Eu3+ ion concentrations.

Effect of annealing temperatures on the properties of CdZrS nanoparticles prepared by sol-gel synthesis method

Cadmium zirconium sulphide (CdZrS) nanoparticles (NPs) were prepared using a sol-gel method. The effect of different annealing temperatures on the structural, morphological, optical, and compositional properties of CdZrS NPs was investigated. The structural investigation revealed that the CdZrS samples exhibit hexagonal and cubic structures in both the as-prepared and annealed samples. The crystallite sizes of CdZrS nanoparticles decreased with increasing annealing temperature. The scanning electron microscopy (SEM) images showed a highly agglomerated particle at 500oC. Energy dispersive X-ray spectroscopy (EDS) confirmed the presence of Cd, Zr and S in all samples. UV–Vis analysis confirmed a red shift from 2.61 to 1.62 eV when the annealing temperature was increased. Photoluminescence (PL) emission spectra showed a peak at 462 nm attributed to excitonic recombination of CdZrS and a peak at 557 nm corresponding to interstitial sulfur sites. These materials have potential applications for biosensors or solar cells technology.

Synthesis of pure ZnO and carbon nanoparticle/ZnO nanostructures for highly efficient glucose sensors

ABSTRACT This work presents a promising method to prepare pure zinc oxide (ZnO) films and carbon nanoparticles (CNPs) decorated ZnO (CNP/ZnO) nanostructured films as glucose sensors. ZnO nanostructure film was grown on Zn foil via the anodisation method, whereas the carbon nanoparticles were synthesised by the hydrothermal method, the decoration process of carbon nanoparticles on ZnO film nanocomposites was conducted using the ultrasonication method. Numerous experiments were conducted, such as microstructure observation, crystallinity analysis, and electrochemical property research. The nanostructures were ascertained by energy-dispersive X-ray spectroscopy (EDX), field-emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM), UV-vis spectroscopy, photoluminescence (PL) measurements, and X-ray diffraction (XRD). ZnO NPs displayed a structure with an average crystallite size of 5.12–13.47 nm, and the PL emission spectra were found to be in the 387 nm range, ZnO films were created by annealing ZnO samples at 200°C for 2 h, and FE-SEM presented nanoparticle-like shapes with a particle size range of (20–50 nm) for voltage anodisation (6 v). This led to an elevation of the energy gap to 3.20 eV. The electrochemical characterisation of the CNPs/ZnO nanostructures refines remarkably the sensitivity to glucose via pure zinc oxide nanostructures. The CNP/ZnO nanostructures demonstrated improved glucose-sensing ability with a sensitivity value of 2827 µA. m M − 1 . The low detection limit is 0.8 mm with a linear range from (0.3 mm to 1 mm). The sensitivity and repeatability of the biosensors were assessed by measuring and analysing their I–V characteristics at different glucose concentrations. Based on a straightforward, affordable, and innovative sensor design, this result validates the sensor’s significant potential as a high-performance nonenzymatic glucose sensor. It was observed that when zinc oxide films were decorated with carbon nanoparticles, there was an increase in the sensitivity of glucose detection. This is due to an increase in charge transfer and conductivity, as well as an increase in the oxidation and reduction process.

Luminescent Tb3+/Sm3+ co-doped hydroxyapatite nanoparticles as an imaging probe in N2a cells

This work reports the synthesis of hydroxyapatite (HAp) nanoparticles co-doped with trivalent terbium (Tb3+) and samarium (Sm3+) ions by a surfactant free chemical precipitation method. Co-doping enables to combine the optical properties of Tb3+ and Sm3+ ions. Characterization techniques like X-Ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, inductively coupled plasma-optical emission spectroscopy (ICP-OES), energy dispersive X-ray spectroscopy (EDX) were used to determine the crystalline and structural properties. These studies confirmed that the lanthanide ions Tb3+ and Sm3+ were successfully doped onto the HAp lattice. The photoluminescence emission spectra exhibited intense emissions from both the lanthanide ions. The Sm3+ photoluminescence spectra showed enhanced emission,indicating that energy is being transferred from the Tb3+ to Sm3+ ions. To examine the cell viability, N2a cellswere subjected to the MTT cytotoxicity assay. As demonstrated by the cell imaging on N2a cells, the synthesised nanoparticles are ideal candidates for fluorescent labelling using lanthanide ions. Furthermore, thestrong cytocompatibility of Tb3+/Sm3+ co-doped hydroxyapatitesuggests that it is a promising nanoscale biomaterial.

A Cr3+-triggered near-infrared tungstate phosphor for organic compound non-destructive detection

Cr3+-doped near-infrared (NIR) luminescent materials have become a research hotspot in luminescence functional materials. However, developing NIR phosphors with emission wavelengths exceeding 1000 nm, suitable for organic compound non-destructive analysis, remains a significant challenge. In this study, LiSc(WO4)2:Cr3+ NIR phosphors were synthesized using a simple solid-state reaction method. Low temperature photoluminescence emission spectrum, electron paramagnetic resonance spectrum, and fluorescence decay curve confirmed that Cr3+ ions occupied both LiO6 and ScO6 octahedron sites, forming two luminescence centers. The sample exhibited an emission wavelength of 1082 nm under 523 nm excitation, with a full width at half maximum (FWHM) of 290 nm. As the Cr3+ concentration increased, the emission peak showed a blue shift. The sample LiSc(WO4)2:0.3Cr3+ with optimal optical performance exhibited an emission wavelength of 1023 nm and an FWHM of 228 nm. Its luminescence intensity retained 38.4% of room temperature value at 380 K, and the internal and external quantum efficiency were 33.2% and 18.9%, respectively. When packaged with a 525 nm green LED, the device as a NIR light source is capable of accurately identifying water, ethanol, ammonia, and silicone oil. This work demonstrates that tungstate materials have great potential in the field of optical materials and offers a new perspective for selecting matrix materials in the development of Cr3+-doped long-wavelength broadband NIR phosphors.

A novel red emitting Eu3+ doped CaSiO3 nanophosphor derived from agro-wastes for advanced forensic applications

The modified sol–gel approach was utilised to synthesise Eu3+ (1–5 mol%) doped CaSiO3 nanophosphors (NPs) using eggshell (ES) and rice husk ash (RHA) as precursors for SiO2 and CaO, respectively. Powder X-ray diffraction (PXRD) peaks confirm the monoclinic structure of the powdered samples. The photoluminescence (PL) emission spectra display distinct emission peaks corresponding to Eu3+ ions. After optimizing the Eu3+ ion concentration, the highest intensity (CaSiO3:3Eu3+) was achieved at 3 mol%. As the concentration increased beyond this point, the emission intensity decreased due to concentration quenching (CQ). Temperature-dependent photoluminescence (TDPL) was investigated in the range of 303 to 443 K. The results demonstrated that emissions at elevated temperatures are significantly stronger than those at ambient temperature. TDPL studies revealed excellent thermal stability, with emission intensity remaining at 87.5 % even at 423 K. Additionally, the phosphor’s absolute sensitivity of 0.003 K−1 and relative sensitivity of 1.44 % K−1 highlight its strong potential for temperature sensing applications. The suitability of the phosphor for the powder dusting method in fingerprint (FP) detection on various surfaces was also assessed. Under 365 nm UV light, the CaSiO3:3Eu3+ phosphor clearly reveals the level 1–3 structure of LFPs.

Self‐assembled small molecule spherulites under mild conditions: High solid‐state quantum yield and unique interconnected structural and fluorescent colors

AbstractSpherulites are generally fabricated from cooling polymer melts, while their fabrication under mild conditions or from small molecule materials has been barely reported. Besides, organic luminescent molecules typically suffer from low quantum yields in a solid state. Moreover, preparing material with interconnected and simultaneous changes in structural and fluorescent colors is challenging. Here, we present the first solution‐derived spherulites with unique interconnected structural and fluorescent colors, self‐assembled from stearoylated monosaccharides at room temperature. D‐galactose stearoyl ester self‐assembled into banded spherulites, containing twisted nanoplates and interconnected simultaneously changing structural and fluorescent colors. In comparison, D‐mannose stearoyl ester can only form non‐banded spherulites, which contain oriented nanoplates and uniform structural and fluorescent colors. Such materials revealed a novel negative correlation between fluorescence and birefringence, termed alignment‐promoted quenching propensity. Remarkably, the solid‐state fluorescence quantum yields of galactose and mannose‐derived spherulites are as high as 49 ± 2% and 51 ± 2% respectively, approximately ten times higher than those of unmodified monosaccharides. These quantum yield values are among the highest of reported organic nonconventional fluorophores and even comparable to those of conventional aromatic chromophores. Moreover, these spherulites manifested an unexpected excitation‐dependent multicolor photoluminescence with a broad‐spectrum emission (410−620 nm). They show multiple peaks in the photoluminescent emission spectra and broad fluorescence lifetime distributions, which should be attributed to the clustering of a variety of oxygen‐containing functional groups as emissive moieties.

The impact of charge carrier dynamics on the outdoor performance of cesium-lead-halide perovskite photovoltaics

We investigated the optoelectronic characteristics of cesium-based perovskite using various techniques. The steady-state photoluminescence (PL) spectroscopy of this perovskite solar cell composition shows the presence of strong peaks at a wavelength of 759 nm, which that corresponds to a band gap energy 1.63 eV. This band gap energy was estimated using two complementary methods, the PL emission spectra and the UV–vis absorption spectra. The study describes the dependence of photon energy on wavelength using a Gaussian mathematical model. Real-outdoor performance testing was conducted in Ethiopia’s climate during the hottest seasons to study the device performance under outdoor conditions at varying irradiances. Moreover, we investigated power generation from the devices using current–time measurements and analyzed charge carrier dynamics through transient photocurrent measurements.

Preparation and Characterization of Au Quantum Dots Using Laser in Benzene and Study of the Pulse Energy effect on Quantum Size

Here, findings from a study on pulsed laser ablating of noble Au targets submerged in benzene solvent and a study on the effect of pulse energy on quantum size are presented. Three samples of gold quantum dots (AuQDs) are synthesized at pulse fluence of 4, 8, and 12 J/cm2, which is referred to as F1, F2, and F3, respectively. The prepared AuQDs were characterized by UV-Vis, HR-TEM, XRD, XPS, EDX, FTIR, Raman spectroscopy and Photoluminescence measurement. AuQDs that were synthesized have monocrystalline and cubic (FCC) structure, according to XRD patterns. It was found that the direct optical energy gap of AuQDs is enhanced to 2.6 eV. The emission peak of AuQDs photoluminescence emission spectra is at roughly 481, 445, and 437 nm, for F1, F2, F3 samples, respectively. The quantum size was reduced to 2 nm for sample F3. This strategy has the ability to prepare pure AuQDs in one step, with promising biosensor and bioimaging applications.