Optical Luminescence Research Articles

Controlled synthesis of SrFCl: Tb nanoscintillators with improved X-ray detection limit

Lanthanide-doped fluoride nanoparticles show promising applications in X-ray imaging. Enhancing the intensity of lanthanide activators in X-ray excited optical luminescence (XEOL) is crucial for reducing the risk of X-ray irradiation. In this work, we report that the SrFCl: Tb nanoparticles can be employed as scintillator for X-ray detection. The sizes of SrFCl: Tb are tuned by changing the chlorination temperature. The XEOL intensity of the SrFCl: Tb nanoscintillators (NSs) is approximately 4.3 times higher than that of SrF2: Tb seeds. Moreover, under the same X-ray irradiation conditions, the XEOL intensity of SrFCl: Tb is stronger than those of common CaF2: Tb, BaF2: Tb, and NaYF4: Tb NSs with similar mean particle sizes. The X-ray detection limit of the SrFCl: 15Tb NSs is as low as 30.71 nGy·s-1. Our results will promote the exploration of lanthanide-doped fluoride NSs with high X-ray detection performances.

High Defect Tolerance Breaking the Design Limitation of Full-Spectrum Multimodal Luminescence Materials.

With the development of optical anti-counterfeiting and the increasing demand for high-level information encryption, multimodal luminescence (MML) materials attract much attention. However, the discovery of these multifunctional materials is very accidental, and the versatile host suitable for developing such materials remains unclear. Here, a grossite-type fast ionic conductor CaGa4O7, characterized by layered and tunnel structure with excellent defect tolerance, is found to meet the needs of various luminescent processes. Almost all luminescent modes, including down/up-conversion luminescence (DCL/UCL), long persistent luminescence (LPL), mechanoluminescence (ML), and X-ray excited optical luminescence (XEOL), are realized in this single host. Full-spectrum (from violet to near-infrared) photoluminescence and ML as well as multicolor XEOL are achieved by simply changing the doped luminescent center. A series of anti-counterfeiting devices, including the quasi-dynamic display of famous paintings, digital information encryption, and multi-color handwritten signatures, are designed to show the encryption of information in temporal and spatial dimensions. This study clarifies the importance of defect tolerance of the host for the development of MML materials, and provides a unique insight into the cross-field applications of special functional materials, which is a new strategy to accelerate the development of novel MML materials.

Electron traps in (Y0.97Zr0.03)2O3 transparent ceramics and its suppression by heavy Eu3+ doping

AbstractIn this paper, Eu3+:(Y0.97Zr0.03)2O3 transparent ceramics with different doping concentrations of Eu3+ were prepared by vacuum sintering. This series of transparent ceramic samples exhibits strong red emission when excited by an electron beam at the keV level. However, color changes observed in the samples after high‐energy electron irradiation. This is due to the capture of electrons by traps related to oxygen vacancies within the Y2O3 lattice. Specifically, under electron beam irradiation, the capture of the electrons by oxygen vacancy‐related defects in the Y2O3 lattice occurs, leading to radiation damage. The color change can be suppressed to some extent by the incorporation of Zr4+ into the Y2O3 lattice, which can effectively suppress the generation of oxygen vacancies. Interestingly, samples with heavy doping of Eu3+ exhibit stronger resistance to electron irradiation damage. Based on the detailed characterizations, including optical transmittance, cathodoluminescence, photoluminescence, thermoluminescence and luminescence decay time, it is found that under heavy doping conditions, Eu3+, which has a stronger cationic character than Y3+ can more effectively suppress the generation of electron traps induced by the oxygen vacancies and the interstitial oxygen in the Y2O3 lattice, thereby enhancing radiation resistance. This research can advance the understanding of defect suppression mechanisms and benefit the application of Y2O3‐based functional transparent ceramics in high‐energy electron and β‐ray irradiation environment.

Photon energy estimation in diagnostic radiology using OSL dosimeters: Experimental validation and Monte Carlo simulations

The EGSnrc Monte Carlo software toolkit was used to evaluate the energy response and estimate the photon energy based on the E3/E4 ratio for the InLight XA Optical Luminescence Dosimeters (OSLDs).The InLight XA OSLDs were irradiated with Cs-137 source and ISO 4037-1 narrow-spectrum series X-ray qualities (N40, N60, N80, and N100). The virtual OSLDs on the surface of the PMMA phantom were constructed in EGSnrc, energy response and ratio E3/E4 of the dosimeters was determined and compared to the physical measurements.Good agreement was found between the simulated and measurement approaches in estimating the photon energy with a percentage difference of less than 6%. The E3/E4 ratio from simulation, physical measurements, and microStar system showed very good agreement results with the maximum difference of 9.3% and 10.94%, respectively. Furthermore, the OSLDs energy response varied significantly at energy below 100 keV due to the photoelectric effect.The results of this study identify and address the over-response of OSLDs to low-energy photons, offering correction factors to minimize errors, especially in diagnostic radiology applications. These findings have the potential to improve dose accuracy for patients and radiation workers by providing more precise photon energy estimations, particularly at lower energy ranges, such as in diagnostic X-rays. The function used to evaluate photon energy using E3/E4 ratio has a great influence on the accuracy of such algorithms. It also ensures that imaging equipment is properly calibrated for the specific energy ranges needed, enhancing diagnostic accuracy. Furthermore, precise dose measurements are essential for maintaining regulatory compliance and long-term patient exposure records, ultimately promoting safer and more effective radiological practices.

Optical performance and luminescence properties of Dy3+-doped LaMgB5O10 phosphors

Despite significant advancements in borate-based phosphors, improving luminescent efficiency and thermal stability, particularly at high temperatures, remains a persistent challenge. In this study, Dy3+-doped LaMgB5O10 (LMBO) phosphors were synthesized and characterized for their photoluminescent properties to address these issues. Under 344 nm excitation, the Dy3+-activated LMBO phosphors exhibited strong luminescence with characteristic peaks at 482 nm (blue), 578 nm (yellow), and 663 nm (red), corresponding to specific Dy3+ transitions. Optimal luminescence was achieved at a doping level of 2 wt% Dy3+, beyond which quenching effects reduced emission intensity. The critical quenching distance (Rc) was estimated at 24.66 Å, indicating predominant non-radiative energy transfer. Moreover, thermal quenching was reduced, with the activation energy for thermal quenching determined to be 0.1975 eV, demonstrating that the material can maintain reasonable luminescence efficiency at elevated temperatures. Time-resolved photoluminescence spectroscopy revealed multi-exponential decay behavior, indicating the presence of multiple decay processes. The average luminescence lifetimes were calculated as 632 µs for the 2 wt% Dy3+ sample and 539 µs for the 3 wt% Dy3+ sample, with a clear concentration quenching effect observed at higher dopant levels. Colorimetric analysis in the CIE 1931 color space revealed a shift toward yellow with increasing Dy3+ concentration, achieving a correlated color temperature (CCT) of 6595 K at 2 wt% Dy3+. This shift supports the material’s potential for photonic and lighting applications. These findings highlight a significant advancement in addressing the thermal stability issue in phosphor materials, making Dy3+-doped LMBO phosphors promising candidates for advanced photonic technologies.

Absence of inhibitory effects of two new glucanases on streptococcus mutans growth

Glucanohydrolases have shown promise in degrading exopolysaccharides in cariogenic biofilms, making them a potential strategy for biofilm control without disrupting the oral microbiota. However, their direct antimicrobial effects remain unclear. Aim: To determine the antimicrobial activity on S. mutans of two newly discovered glucanases characterized by our group, PmGH87 (mutanase) from Prevotella melaninogenica and CoGH66 (dextranase) from Capnocytophaga ochracea, using a commercial dextranase from Penicillum sp. as a control. Methods: Their effects on growth were assessed using a luciferase reporter system coupled with the promoter of the ldh gene in Streptococcus mutans. Results: Quantification of optical density and luminescence over a 10-hour growth period revealed that the commercial dextranase exhibited inhibitory effects on S. mutans growth. However, these effects were neutralized by heat treatment, suggesting the presence of a heat-sensitive contaminant or an additional antimicrobial property associated with the commercial dextranase from Penicillum sp. On the other hand, the purified mutanase and dextranase enzymes had no inhibitory effect on S. mutans growth. Conclusion: In conclusion, the absence of inhibitory effects on S. mutans growth by the newly discovered enzymes emphasizes their potential for biofilm control while preserving the delicate balance of the oral microbiota and preventing the emergence of resistance.

The effect of laser beam shaping on the structural and XEOL properties of laser-sintered LiBaPO4:Eu ceramics

In this work, we investigated the impact of laser beam shaping during laser sintering on the structural and XEOL properties of Eu-doped LiBaPO4 ceramic phosphors synthesized via the sol-gel method with PVA. Structural and optical properties were characterized using X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Absorption Near Edge Structure (XANES), X-ray fluorescence (XRF), and X-ray Excited Optical Luminescence (XEOL). XRD analysis revealed a primary trigonal phase (LiBaPO4, space group P31c) alongside a minor Ba3(PO4)2 phase. SEM images indicated a uniform grain size distribution, while XEOL spectra showed emission peaks corresponding to Eu3+ and Eu2+ ions, as well as defects from laser ablation. The Eu2+/Eu3ratio varied from the center to the edge of the ceramic body. Additionally, the laser beam shape contributed to a more homogeneous distribution of Eu ions in the center compared to the edge of the ceramic body.

Reversible Structural Phase Transitions in Zero-Dimensional Cu(I)-Based Metal Halides for Dynamically Tunable Emissions.

Exploring structural phase transitions and luminescence mechanisms in zero-dimensional (0D) metal halides poses significant challenges, that are crucial for unlocking the full potential of tunable optical properties and diversifying their functional capabilities. Herein, we have designed two inter-transformable 0D Cu(I)-based metal halides, namely (C19H18P)2CuI3 and (C19H18P)2Cu4I6, through distinct synthesis conditions utilizing identical reactants. Their optical properties and luminescence mechanisms were systematically elucidated by experiments combined with density functional theory calculations. The bright cyan-fluorescent (C19H18P)2CuI3 with high photoluminescence quantum yield (PLQY) of 77 % is attributed to the self-trapped exciton emission. Differently, the broad yellow-orange fluorescence of (C19H18P)2Cu4I6 displays a remarkable PLQY of 83 %. Its luminescence mechanism is mainly attributed to the combined effects of metal/halide-to-ligand charge transfer and cluster-centered charge transfer, which effects stem from the strong Cu-Cu bonding interactions in the (Cu4I6)2- clusters. Moreover, (C19H18P)2CuI3 and (C19H18P)2Cu4I6 exhibit reversible structural phase transitions. The elucidation of the phase transitions mechanism has paved the way for an unforgeable anti-counterfeiting system. This system dynamically shifts between cyan and yellow-orange fluorescence, triggered by the phase transitions, bolstering security and authenticity. This work enriches the luminescence theory of 0D metal halides, offering novel strategies for optical property modulation and fostering optical applications.

Reversible Structural Phase Transitions in Zero‐Dimensional Cu(I)‐Based Metal Halides for Dynamically Tunable Emissions

AbstractExploring structural phase transitions and luminescence mechanisms in zero‐dimensional (0D) metal halides poses significant challenges, that are crucial for unlocking the full potential of tunable optical properties and diversifying their functional capabilities. Herein, we have designed two inter‐transformable 0D Cu(I)‐based metal halides, namely (C19H18P)2CuI3 and (C19H18P)2Cu4I6, through distinct synthesis conditions utilizing identical reactants. Their optical properties and luminescence mechanisms were systematically elucidated by experiments combined with density functional theory calculations. The bright cyan‐fluorescent (C19H18P)2CuI3 with high photoluminescence quantum yield (PLQY) of 77 % is attributed to the self‐trapped exciton emission. Differently, the broad yellow‐orange fluorescence of (C19H18P)2Cu4I6 displays a remarkable PLQY of 83 %. Its luminescence mechanism is mainly attributed to the combined effects of metal/halide‐to‐ligand charge transfer and cluster‐centered charge transfer, which effects stem from the strong Cu−Cu bonding interactions in the (Cu4I6)2− clusters. Moreover, (C19H18P)2CuI3 and (C19H18P)2Cu4I6 exhibit reversible structural phase transitions. The elucidation of the phase transitions mechanism has paved the way for an unforgeable anti‐counterfeiting system. This system dynamically shifts between cyan and yellow‐orange fluorescence, triggered by the phase transitions, bolstering security and authenticity. This work enriches the luminescence theory of 0D metal halides, offering novel strategies for optical property modulation and fostering optical applications.

Soil Genesis of Alluvial Parent Material in the Qinghai Lake Basin (NE Qinghai–Tibet Plateau) Revealed Using Optically Stimulated Luminescence Dating

Alluvial parent material soil is an important soil type found on the Qinghai–Tibet Plateau (QTP) in China. However, due to the limited age data for alluvial soils, the relationship between alluvial geomorphological processes and soil pedogenic processes remains unclear. In this study, three representative alluvial parent material profiles on the Buha River alluvial plain in the Qinghai Lake Basin, northeast QTP, were analyzed using the optical luminescence (OSL) dating method. Combined with physical and chemical analyses of the soil, we further analyzed the pedogenic process of alluvial soil. The alluvial parent material of the Buha alluvial plain predominately yielded ages between 11.9 and 9.1 ka, indicating that the alluvial soil began to form during the early Holocene. The development of the alluvial soil on the first-order terrace presents characteristics of entisol with multiple burial episodes, mainly between 8.5 and 4.0 ka, responding to the warm and humid middle Holocene and high lake levels.

Hard X-ray nanoprobe to study the emission properties of Ce-doped YAG wafer by using XEOL and TR-XEOL

In this study, the valent state, emission properties, and decay lifetime of Ce-doped yttrium aluminum garnet (Y3Al5O12, YAG) wafer have been probed using X-ray absorption (XAS), X-ray excited optical luminescence (XEOL), and time-resolved XEOL (TR-XEOL). The XAS spectrum demonstrates that Ce ions are in the trivalent state, and the XEOL spectrum exhibits typical 5 d1-4f1(2F5/2) and 5 d1-4f1(2F7/2) transitions of Ce3+ ions, with emission peaks at ∼528 nm and 582 nm, respectively. From the TR-XEOL measurements, the decay lifetimes of 5 d1-4f1(2F5/2) and 5 d1-4f1(2F7/2) transitions are about ∼90 ns and ∼100 ns, respectively. We found that the reabsorption effects will not only make the 5 d1-4f1(2F7/2) transitions have longer decay lifetime, but also the higher emission intensity. By comparison with photoluminescence (PL) and time-resolved PL using a pulsed laser at 375 nm, we found that the emission spectra and decay lifetime of Ce-doped YAG (111) wafer are different when using X-ray irradiation. The longer decay lifetime measured by TR-XEOL compared TR-PL are caused by high X-ray dose irradiation. In addition, high X-ray doses provided by the nano-focus X-ray beam will be influenced the emission behaviors of Ce-doped YAG (111) wafer. Which phenomena have been demonstrated by using time-dependent XEOL with irradiation for 10 h. These peculiar emission behaviors observed with a hard X-ray nanoprobe may be able to provide important information on quantum technologies and scintillators used in hard X-ray detectors.

Glutathione and its structural modifications recognized by Raman Optical Activity and Circularly Polarized Luminescence

Raman Optical Activity combined with Circularly Polarized Luminescence (ROA-CPL) was used in the spectral recognition of glutathione peptide (GSH) and its model post-translational modifications (PTMs). We demonstrate the potential of ROA spectroscopy and CPL probes (EuCl3, Na3[Eu(DPA)3], NaEuEDTA) in the study of unmodified peptide, i.e. GSH, and its derivatives, i.e. glutathione oxidized (GSSG), S-acetylglutathione (GSAc) and S-nitrosoglutathione (GSNO). ROA spectral features of GSH, GSSG, and GSAc were determined along with thier changes upon the different pH conditions. Apart from the ROA, induced CPL signals of Eu(III) probes also proved to be sensitive to the structural modifications of GSH-based model PTMs, enabling their spectral recognition, especially by the NaEuEDTA probe.

Collagens of placenta composition in obese puerperant women who gave birth to сhildren at St. Petersburg State Pediatric Medical University in 2018–2021

BACKGROUND: The relevance of the problem of obesity is associated with the high frequency and steady growth of this pathology in the population. The epigenetic influence of maternal obesity on the course of pregnancy and childbirth, as well as on the condition of the fetus and newborn, is currently being studied. This article analyzes changes in the composition of the connective tissue of the placenta against the background of obesity in pregnant and puerperas. AIM: The aim of this study is to identify the pathomorphological features of the placenta and the composition of placental collagens in women who were obese before pregnancy and at the time of delivery at the Perinatal Center of St. Petersburg State Medical University from 2018 to 2021 to assess potential fetal risks and to predict possible complications during pregnancy and in the postnatal period for the mother. MATERIALS AND METHODS: A histological examination of the placentas of obese women (18 patients) and the ones with a normal body mass index (18 patients) who gave birth to mature newborns at the Perinatal Center of St. Petersburg State Medical University from 2018 to 2021 was performed followed by immunohistochemical examination. Staining of placenta specimens was carried out in accordance with the standard immunohistochemical protocol, using primary antibodies to type I–IV collagen. RESULTS: Microscopic examination of chorionic villi revealed no significant differences in the presence of chronic inflammation and angiogenesis disorders between the groups. When studying collagen expression levels, the following differences have been found: in the group of pregnant obese patients, the optical luminescence density and distribution area for type I–III collagen in the placenta were significantly higher, while for type IV collagen they were significantly lower compared with the control group. CONCLUSIONS: The following features of the formation of connective tissue in the placenta in obese mothers have been revealed: an increase in type I–III collagen production and a decrease in type IV collagen production. The obtained findings indicate an earlier functional and morphological change in the placenta than those detected by standard histological methods.

Preliminary investigations into the use of the ancient pigments Han blue and Han purple as luminescent dusting powders for the detection of latent fingermarks

Here we present our preliminary studies into the inorganic pigments Han blue (BaCuSi4O10) and Han purple (BaCuSi2O6) as near-infrared luminescent fingerprint dusting powders. These pigments were developed in ancient China around 800 BCE and both show luminescence in the NIR region. There remains, however, ambiguity in the literature concerning their photophysical properties. Samples of Han blue and Han purple artist’s pigments were characterized by optical microscopy, infrared, ultraviolet-visible absorbance and luminescence spectroscopy. Their performance as fingerprint dusting powders, without any further treatment, on non-porous surfaces were compared to exfoliated lipophilic coated Egyptian blue and commercial fluorescent powders in a pilot study. These results demonstrate for the first time that both ancient pigments show promise as alternative dusting powders for latent fingermarks.

Synthesis, structure, spectral and luminescence studies of novel guanidinium aryl(oxy)(sulfanyl)(sulfonyl)acetates

A series of promising luminescent materials, nonlinear optical crystals, and physiologically active compounds – aryl(oxy)(sulfanyl)(sulfonyl)acetates of guanidine (A) of unknown type was synthesized. Various functional groups present in (A) were identified using FTIR spectroscopy. 1H and 13C NMR spectral studies further confirm the molecular structure (A). Crystals of guanidinium 4-chlorophenyl(sulfanyl)acetate (1) and guanidinium 4-chlorophenyl(sulfonyl)acetate (2) were successfully grown. They belong to the same lowest symmetry category, but to different crystal systems: monoclinic (1) and orthorhombic (2).It has been established that intrinsic optical absorption begins at a wavelength of ∼ 290 nm for crystalline compound (1) and ∼ 335 nm for crystal (2). The intrinsic luminescence spectrum of crystal (1) includes two bands with maxima at 300 and 515 nm. In the intrinsic luminescence spectrum of crystal (2), only one band is observed with a maximum at 350 nm. Such luminescence in both crystals is excited in the intrinsic absorption bands, as well as by X-ray radiation. In addition, in the near ultraviolet and throughout the visible region, where optical absorption is not detected (it is very weak), low-inertia (less than 10 ns) rather intense luminescence of uncontrolled impurity-defect centers is excited.The spectral bands of optical absorption, photo- and X-ray luminescence discovered in experiments were systematized using a diagram of energy levels and quantum transitions in crystals and defect centers of the compounds under study.

Sub‐10 nm Lanthanide‐Doped Lu6O5F8 Nanoscintillators for Real‐Time High‐Resolution Dynamic 3D X‐Ray Imaging

AbstractLanthanide‐doped fluoride nanoscintillators (NSs) have emerged as promising candidates for X‐ray imaging. However, strong afterglow, long lifetime, and poor irradiation stability pose key challenges for real‐time dynamic X‐ray imaging. In this study, the sub‐10 nm Lu6O5F8:Tb NSs with tunable morphologies are prepared via incorporating Li+/Na+ ions. The X‐ray excited optical luminescence (XEOL) intensity of the Lu6O5F8:15Tb/10Li NSs is stronger than that of NaLuF4:15 Tb NSs with a similar particle size while its afterglow is only ≈2.7% compared to that of NaLuF4:15 Tb NSs. Utilizing the Lu6O5F8:15 Tb/10Li NSs‐integrated film as a scintillator screen, a high resolution of ≈21.6 lp/mm is achieved. Even at a low dose of 0.23 µGy, the fringe detail in the electron device is clearly observed in the X‐ray image. The afterglow intensity of the Lu6O5F8:10Eu/10Li NSs decays to 0.7% at 40 µs, which is better than that of CsI:Tl (3.6%@40 µs). Moreover, the Lu6O5F8:10Eu/10Li NSs with a lifetime of 1.65 µs are verified for use in dynamic 3D X‐ray imaging. These findings represent a significant advancement in the development of new NSs for high‐performance dynamic X‐ray imaging.

Electroluminescent white quantum dot light-emitting diodes based on high pressure synthesis of graphitic C3N4 semiconductor

Graphitic carbon nitride (g-C3N4) has shown promising potentials for quantum dot light-emitting diodes (QLEDs), which might be an effective alternative of the mostly used Cd(Se,S)/Zn(S,Se) emitting layers and can achieve both low toxicity and high stability, meeting the goal of sustainable development. Herein, we for the first report a white electroluminescent QLED device with blue and orange dual-color emissions, which were attributed to the σ*-LP, π*- π, and π*-LP transitions, respectively, from a single-compound g-C3N4 quantum dots (QDs) by synthesizing the precursor at 0.8 Mpa high-pressure N2. By selectively exciting the δ and π bonds with X-ray, the luminescence mechanism was approved with the synchrotron radiation techniques of X-ray absorption near edge structure (XANES) and the X-ray excited optical luminescence (XEOL).The chromaticity coordinate changes from cayan color space with CIE (0.2034, 0.1939) to white color space with CIE (0.3009, 0.2697) as pressure increases from 0.06 to 0.8 Mpa, with the increased overlap of the δ* and π* orbital upon the contraction of crystal lattice. The breakthrough achieved in this work will promisingly promote the development of future white light sources as thin as paper for human home and office lighting by using direct current-driven electroluminescence of QDs, instead of photoluminescence of phosphors.

Formation of hybrid nanostructures based on Zn0.5Cd0.5S quantum dots and silver nanoparticles for nonlinear optical applications in the near ultraviolet

The goal of this study was to establish optimal conditions for the formation of hybrid nanostructures based on quantum dots and metal nanoparticles with a nonlinear optical response in the near ultraviolet. The relevance of this study is confirmed by the need to create passive devices for controlling the parameters of laser radiation in the presence of semiconductor colloidal quantum dots (QDs) and plasmonic nanoparticles (NPs). Manifestations of interaction in the nonlinear optical response of Zn0.5Cd0.5S QDs and spherical Ag NPs (10 nm) in the field of laser pulses of 10 ns duration at a probing radiation wavelength of 355 nm have been established using the Z-scan method. Manifestations of the formation of hybrid nanostructures have been established using transmission electron microscopy and optical absorption and luminescence spectroscopy. The interaction of colloidal QDs and NPs was manifested as the recombination luminescencequenching of the former with a peak at a wavelength of 450-480 nm. For ensembles of colloidal Zn0.5Cd0.5S QDs with an average size (2.0, 2.2, 2.4 nm), nonlinear refraction (defocusing) of 10 ns laser pulses in the near ultraviolet (355 nm) was established, the coefficient of which increased with increase in QDs. It has been established that during the interaction of Zn0.5Cd0.5S QDs with Ag NPs, the suppression of nonlinear refraction was observed against the background of a twelvefold increase in the nonlinear absorption coefficient. It was concluded that the most probable reason for the observed changes in the nonlinear optical response is the polarizing effect of plasmonic Ag NPs

Novel Detection Scheme for Temporal and Spectral X-Ray Optical Analysis: Study of Triple-Cation Perovskites

Multimodal x-ray microscopy is key to assessing the property-functionality relationships of semiconductor devices with the utmost sensitivity and spatial resolution. Here, we report on a novel setup—the “Analyzer of X-ray excited Optical Luminescence Offering Temporal and spectraL resolution” (AXOLOTL)—and demonstrate its use by investigating a series of triple-cation mixed-halide perovskite solar cells (PSCs) with varying Cs content. These PSCs exhibit spatially varying performance and are thus ideally probed by multimodal x-ray microscopy to elucidate the origin of the performance variations. Specifically, our nanoscale characterization of the wrinkled perovskite photoabsorber unveils a segregation of I and Br, which is accompanied by a narrowed band gap and an increased charge-carrier lifetime in thick absorber areas. Overall, we demonstrate with this technique the spatial correlation of compositional inhomogeneities, topography, electrical performance, and optical performance, which is of highest interest for identifying loss mechanisms at the nanoscale in high-performance electronic device development, including solar cells. Published by the American Physical Society 2024

Green synthesis of biomass-derived carbon quantum dots for photocatalytic degradation of methylene blue.

Water pollution, significantly influenced by the discharge of synthetic dyes from industries, such as textiles, poses a persistent global threat to human health. Among these dyes, methylene blue, particularly prevalent in the textile sector, exacerbates this issue. This study introduces an innovative approach to mitigate water pollution through the synthesis of nanomaterials using biomass-derived carbon quantum dots (CQDs) from grape pomace and watermelon peel. Utilizing the hydrothermal method at temperatures between 80 and 160 °C over periods ranging from 1 to 24 h, CQDs were successfully synthesized. A comprehensive characterization of the CQDs was performed using UV-visible spectroscopy, Fourier-transform infrared spectroscopy, dynamic light scattering, Raman spectroscopy, and luminescence spectroscopy, confirming their high quality. The photocatalytic activity of the CQDs in degrading methylene blue was evaluated under both sunlight and incandescent light irradiation, with measurements taken at 20 min intervals over a 2 h period. The CQDs, with sizes ranging from 1-10 nm, demonstrated notable optical properties, including upconversion and down-conversion luminescence. The results revealed effective photocatalytic degradation of methylene blue under sunlight, highlighting the potential for scalable production of these cost-effective catalytic nanomaterials for synthetic dye degradation.