Photoluminescence Properties Research Articles

Thermally Stimulated Luminescence and Photoluminescence Properties of Dy-Doped Al2O3-SiO2 Glasses

Storage-type phosphors absorb and temporarily store the energy of ionizing radiation and emit low-energy photons when an external stimulus such as heat or light is applied. Since the number of emitted photons is proportional to the energy of the absorbed ionizing radiation, it is possible to estimate the irradiated dose. For this reason, they are applied in various fields such as personal radiation dosimetry and medical imaging. Storage-type phosphors are classified according to the type of external stimulus applied: optically stimulated luminescence (OSL) and thermally stimulated luminescence (TSL) materials. The mechanisms of OSL and TSL can be explained below. When a storage-type phosphor is irradiated with ionizing radiation, a large number of carriers are generated, and these carriers are trapped in the trapping centers in the material, which assumes a metastable state. Subsequent stimulation with heat or light causes the carriers to be re-excited, resulting in luminescence. These storage-type phosphors are required to have high emission intensity, wide dynamic range, and low fading. In particular, when applied to personal dosimeters, the materials must have tissue equivalency.Al2O3-SiO2 glasses focused on in this study have good characteristics such as high hardness, high melting point and elastic modulus, and low electric conductivity. Therefore, this glass composition has been considered for optical amplifiers and lasers. These properties are also advantageous in terms of material durability when used for dosimetry. In addition, the effective atomic number (Zeff = 11.8) of Al2O3-SiO2 glasses is close to that of human soft tissues, making it a promising storage-type phosphor for personal dosimeters. Therefore, the purpose of this study was to investigate the TSL properties of this glass system in detail and to evaluate the dose-response characteristics.We prepared the Dy-doped 10Al2O3-90SiO2 glasses with various Dy concentrations (0.1, 0.3, 1.0, and 3.0%) by the melt-quenching method and investigated the photoluminescence (PL) and TSL properties. We measured the TSL glow curves of all samples to research the concentration dependence of Dy. As a result, all samples showed the TSL at around 200℃, and the 0.3% Dy-doped 10Al2O3-90SiO2 glass showed the highest TSL intensity. It was found that the TSL originated from the 4f–4f transition of Dy3+ by measuring the TSL spectrum. In addition, the lower detection limit of the 0.3% Dy-doped sample was at least 0.1 mGy. Other details on optical, TSL, and these characteristics changes due to Dy concentration in the glass will be presented in our presentation.

Comprehensive study on epitaxial growth of GeSn(111) layers with high Sn content on Si(111) featuring Ge buffer layer

Spin MOSFETs are attractive for new functional devices having both switching and memory functionalities. We focused on germanium tin (GeSn), which is a group-IV alloy semiconductor, for channel materials because they can be direct transition semiconductor with a sufficiently high Sn content and strain [1]. Direct transition nature will lead larger spin diffusion length and spin lifetime than those of germanium (Ge) because inter-valley scattering of electron can be suppressed at the conduction band of L points [2]. The objective of this study is to realize (111) orientated direct transition GeSn toward the epitaxial growth of Co-based Heusler alloy thin films, which are promising ferromagnetic electrodes for realizing highly efficient spin injections [3]. Theoretical calculation suggests that GeSn(111) can show the direct transition nature even at a lower Sn content under a biaxial compressive strain [2]. However, the growth and characterization of direct transition GeSn(111) epitaxial layers have not been achieved yet.In this study, we examined the pseudomorphic growth of compressively strained GeSn epitaxial layer on a strain-relaxed Ge buffer prepared on Si(111) substrate. After the chemical and thermal cleaning of Si(111) wafer, a Ge buffer layer was grown by the two-step growth method [4] using molecular beam epitaxy (MBE) system; a 100 nm-thick Ge layer was firstly grown at a low temperature (LT-Ge) of 320 °C and then a 300–900 nm-thick Ge layer was grown at a high temperature of 400 °C (HT-Ge). Subsequently, a 100 nm-thick GeSn layer with a Sn content of 8–9% was grown at 150 °C.The crystalline structure of Ge and GeSn layers was characterized using X-ray diffraction two-dimensional reciprocal lattice space mapping. All samples exhibit the complete strain-relaxation of the Ge buffer layers and the partly strain relaxation of GeSn layers on the Ge layers; the compressive strain to GeSn with a Sn content of 8–9% was estimated to an approximately 0.9–1.0%. Considering the theoretical estimation [3], the prepared compressively strained GeSn layers with a high Sn content are likely to become a direct transition semiconductor.Furthermore, the 𝜔-rocking curve for the GeSn layers revealed that the full-widths of half maximum (FWHM) decreases with increasing the HT-Ge thickness and FWHM was saturated for the samples with a HT-Ge thickness of 500 nm or greater. However, the samples with a HT-Ge thickness of 700 nm or greater showed a slight increase in the intensity at the tail region of the diffraction peak which related to the existence of low-crystalline-quality region. Therefore, the thickness of 500 nm for HT-Ge buffer layer was the optimum condition to achieve with the smallest FWHM and tail intensity in this study. In the presentation, the photoluminescence properties of GeSn layers will be also discussed.

Colloidal Synthesis and Photoluminescence Properties of Near-IR-Responsive Ag8GeS6 Quantum Dots

Near-infrared (NIR)-responsive quantum dots (QDs) hold immense promise for a range of applications, such as photovoltaics, photocatalysts, and biomedical imaging. Their unique optoelectronic properties, including tunable photoluminescence (PL) peaks and high PL quantum yields (QY), originate from the quantum confinement effect. In biomedical imaging, QDs offer superior photostability and enhanced biocompatibility compared to traditional organic fluorophores. Although binary QDs, such as CdTe, CdSe, PbS, and HgTe, have been extensively explored, their practical use is limited by the content of heavy metals with high toxicity. Here, we report the first synthesis of Ag8GeS6 QDs emitting a NIR PL peak at 920 nm and their potential as luminescent probes for in vivo bioimaging.Ge(gly)2(H2O)2 was prepared by the modified method described in previous study, as a germanium precursor resistant to air and moisture.[1] Precursor powders of Ge(gly)2(H2O)2, silver(I) diethyldithiocarbamate, and thiourea were dispersed in a mixture solvent containing 1-dodecanethiol and oleylamine, followed by the heat treatment at 423 K for 20 min. The obtained Ag8GeS6 QDs were surface-coated with a ZnS shell layer with different shell thicknesses.Spherical Ag8GeS6 QDs were formed with the average size of 4.2–4.6 nm. XRD diffraction patterns showed that the obtained QDs had an orthorhombic Ag8GeS6 crystal structure. The absorption spectra were broad and structureless, with an onset wavelength at around 850 nm. The energy gap was almost constant at 1.48-1.48 eV, regardless of the Ge/(Ag+Ge) ratio in the precursors. The Ag8GeS6 QDs prepared with Ge/(Ag+Ge) = 0.82 exhibited a broad PL peak at 920 nm with a PLQY of 11%. The surface coating with a ZnS shell enhanced the PLQY to 40–42%. The ligand exchange of the QDs with 3-mercaptopropionic acid (MPA) enabled uniform dispersion in an aqueous solution for the application to in vivo bioimaging. The resulting MPA-modified Ag8GeS6@ZnS QDs maintained similar size distribution but the PL QY was slightly decreased to ca. 23%. These QDs were successfully applied for in vivo bioimaging by injecting them into the back of mouse, in which a clear PL image was obtained and the detected PL intensity was proportional to the concentration of injected QDs.In conclusion, the present Ag8GeS6@ZnS QDs seem promising as a probe for bio-imaging, marking a significant advancement in the field and opening avenues for safer and more effective NIR-responsive QDs.[1] A.S.R. Chesman, et al., Chem. Mater, 26, 5726 (2014).

Charge Transfer Luminescence of LiCa3MgV3O12 and LiCa3ZnV3O12 Under Ionizing Radiation Excitation

A scintillator is a material that generates a large number of excited electrons and holes under ionizing radiation excitation and immediately emits light with recombination of electrons and holes. When a scintillator combined with a photodetector, it is used as a radiation detector. Radiation detectors equipped with scintillators are applied in various fields such as medical care, security, and radiation protection. Researches are still being conducted to find novel materials with higher performance. In particular, we are attracted to compounds containing lithium (Li). This is because the Li isotope 6Li causes a nuclear reaction with neutrons, so Li-containing materials could be used as neutron scintillators. The Ce-doped lithium silicate glass (lithium glass) and the Eu-doped LiI single crystal are known as conventional Li-containing scintillators; however, the segregation of dopants in these materials can be a problem. For example, the lithium glass can be divided into areas with high and low emission intensity by the dopant segregation. It causes a double-peak in the pulse height spectra under neutron irradiation, and measurement accuracy will deteriorate. In this study, we focused on LiCa3MgV3O12 and LiCa3ZnV3O12 as candidates for scintillators that contain Li and do not require dopants. The photoluminescence properties of powder samples of LiCa3MgV3O12 and LiCa3ZnV3O12 have already been reported; however, scintillation properties have not yet been investigated. We prepared the sintered ceramics of LiCa3MgV3O12 and LiCa3ZnV3O12 and evaluated their scintillation properties. High-purity powders of Li2CO3, CaO, MgO, ZnO, and V2O5 were used as raw materials. They were weighed in stoichiometric proportions and ground using aluminum mortar and pestle, and then calcined at 750℃ for 6 hours in aluminum crucibles. The obtained powders were ground again, pressed into pellets, and then sintered at 850℃ for 6 hours. The X-ray diffraction (XRD) patterns of the samples were measured and compared with those in the previous literature, and we confirmed that each of them had a single phase. In the X-ray induced scintillation spectra, broad luminescence peaking at around 500 nm was observed in each sample. Both emissions can be explained by the charge transfer transition between V5+–O2-.

Synthesis and Near-IR Photoluminescence Property of Ag-Au-S Quantum Dots

Quantum dots (QDs), semiconductor nanoparticles, exhibit size-dependent tunable optical properties, a phenomenon known as the quantum size effect [1]. They have attracted much attention for the application to biomedical imaging, solar cells, photocatalysts, and light-emitting diodes (LEDs) [2]. Over the past few decades, extensive research has been conducted on binary QDs composed of group II–VI and IV–VI elements, such as CdTe, HgTe, and PbS. However, the toxicity associated with the content of heavy metal elements, such as Cd, Hg, and Pb, has severely restricted their practical use [3]. Recently, there has been intensive investigation into QDs with narrower energy bandgaps (Egs) for developing novel materials that exhibit near-IR photoluminescence (PL), with potential applications as in vivo biomarkers and near-IR sensors. In our previous papers, we successfully prepared I-III-VI-based QDs of less toxicity, such as Ag(In,Ga)(S,Se)2, which exhibited a sharp bandedge PL, the peak wavelength being controllable with their size and composition [4]-[6]. In this study, we report the solution-phase synthesis of Ag-Au-S QDs and investigate their near-IR photoluminescence property.Colloidal Ag-Au-S QDs were synthesized by reacting corresponding metal complexes and sulfur compounds as precursors in a hot organic solution. The resulting Ag-Au-S QDs were isolated by the addition of methanol or ethanol as a non-solvent followed by dispersing in chloroform. Ag-Au-S QDs of several nanometers were formed and their Eg controlled between 2.3 and 1.3 eV by tuning the Ag fraction in the precursors. Since the estimated Eg values were larger than that of the bulk Au2S (1.8 eV) and Ag2S (1.1 eV) [7], it was found that the obtained Ag-Au-S QDs showed a quantum size effect. The electronic energy structure of these QDs was assessed by measuring their ionization potential using photoelectron yield spectroscopy in air (PYSA). The valence band maximum level remained relatively constant, regardless of the Ag fraction, while the conduction band minimum shifted to lower energy as the Ag fraction in the QDs increased. The PL peak originating from defect sites was controlled within the range of 735 nm to 835 nm in the near-IR region, by adjusting the particle composition. Furthermore, the PL quantum yield of Ag-Au-S QD shows remarkable enhancement with InSx shell coating, owing to the removal of non-radiative recombination sites on the surface of Ag-Au-S QD. In conclusion, the prepared Ag-Au-S QDs are composed of low-toxicity elements and exhibit near-IR PL suitable for the application to in vivo imaging.

Photoluminescence Properties of Lead Halide Perovskite Nanocrystals Revealed By Single-Dot Spectroscopy

Lead halide perovskites have attracted much attention as a new class of optoelectronic device materials because of their outstanding optical, electronic, and transport properties [1,2]. In addition, halide perovskite nanocrystals (NCs), which can be synthesized by simple chemical methods, show near unity photoluminescence (PL) quantum yields, with keeping the superior optoelectronic properties of their bulk counterparts [3,4]. Because of the small orbital degeneracy of the band edge, PL properties of halide perovskite NCs are governed by the formation and recombination dynamics of excitons, trions, and biexcitons [5,6]. Since individual NCs show narrow PL linewidths at low temperatures, multipeak PL structures appear and their origins are an exciton, a trion, and a biexciton. Single dot spectroscopy is a powerful tool to investigate the exciton–exciton, exciton–electron, and exciton–phonon interactions in perovskite NCs.Here, we prepared three types of perovskite NC samples, CsPbBr3, CsPbI3 and FAPbBr3, and studied their PL spectra of single NCs at room temperature and low temperatures. At room temperature, all NCs show PL blinking, and nonradiative Auger recombination of trions and biexcitons determines the PL dynamics [7–10]. At low temperatures, all NC samples show strong PL, and several PL peaks originating a trion, a biexciton, and longitudinal-optical-phonon side bands of an exciton were clearly observed in the low energy side of the strong exciton peak [11–13]. The PL spectra of all samples were very similar to each other. We clarified the NC size dependence of the trion and biexciton binding energies and the Huang–Rhys (HR) factors, i.e., the strength of the exciton–phonon coupling, in three different perovskites. The positive binding energies of trions and biexcitons show the attractive exciton–exciton Coulomb interactions in the perovskite NCs, and these binding energies increase with decreasing NC size [11,13]. In addition, these size dependences follow a universal scaling curve regardless of composition when the binding energy and the NC size are normalized by the bulk exciton binding energy and the exciton Bohr radius, respectively [13]. The PL linewidths of all inorganic CsPbBr3 and CsPbI3 NCs were narrower than those of organic-inorganic hybrid FAPbBr3 NCs, suggesting the strong exciton–phonon coupling with large organic cation. In FAPbBr3 NCs, the size dependence of the HR factors is similar to that of the Urbach energy [10,11]. In all samples, the LO-phonon energies are independent of the NC size, while the HR factors increase as the NC size decreases [11,12]. Our findings provide new insights into understanding of the optical responses of halide perovskite NCs and the design of the single photon sources.Part of this work was supported by JST-CREST (JPMJCR21B4) and JSPS KAKENHI (JP19H05465).

Design, synthesise, and evaluate photoluminescent properties of novel 3,6-diphenylpyrazine-2-carbonitrile derivatives

Design, synthesise, and evaluate photoluminescent properties of novel 3,6-diphenylpyrazine-2-carbonitrile derivatives

Crystal structure, bandgap, photoluminescence and resistivity properties of double perovskite Cs2AgBiCl6 single crystal and its thin film.

Lead-free Cs2AgBiCl6 double perovskite (Cs2AgBiCl6-DP) material, as a substitute for lead halide perovskite materials, has the advantages of environmental friendliness and high stability and has attracted much attention. However, the photoluminescence and conductive properties of Cs2AgBiCl6-DP have not been well studied. In this study, we prepared Cs2AgBiCl6-DP single crystals (SCs) by coordination-dissolution and coordination-precipitation method. Single- and powder-XRD, SEM, EDS, XPS, and EPR characterization were performed to confirm the structural characteristics of Cs2AgBiCl6-DP SCs. The Tauc diagram based on UV-visible (UV-vis) absorption spectroscopy reveals that the optical bandgap of Cs2AgBiCl6-DP SCs is extrapolated to 2.51 eV. Steady-state fluorescence spectra and time-resolved fluorescence spectra show that Cs2AgBiCl6-DP SCs has four fluorescence peaks entered at 443, 615, 650 and 723 nm and a fluorescence lifetime of about 4.16 ns. Cs2AgBiCl6/PMMA thin films were prepared by spin coating suspension (Cs2AgBiCl6 DP and PMMA in acetone solvent). The intensity of emission peak increases with the increase of light intensity at 369 nm. The intensity of emission peak located at 576 nm decreases with increasing incidence wavelength (from 369 to 454 nm) at 10 W m-2. The emission intensity remains basically unchanged under continuous illumination for 9 hours at 369 nm at 5 W m-2, which indicates that the Cs2AgBiCl6-DP thin film has good stability. In addition, the resistivity and block resistance show a negative exponential change with increasing temperature. These results provide some interesting ideas for the fields of photoluminescence and thermistors.

High-pressure exciton engineering in two-dimensional metal halide perovskite toward intense deep-blue emission and regulated photocurrent property

Exciton engineering in two-dimensional (2D) hybrid metal halide perovskites (HMHPs) is crucial for optimizing photoluminescent (PL) and photocurrent (PC) properties, yet it remains a great challenge. In this work, high pressure is applied to accurately control the conversion equilibrium among free carriers (FCs), free excitons (FEs), and trapped excitons in 2D HMHPs of 10% Pb2+-doped BDACdBr4 (BDA = 1, 4-butanediamine). Initial compression induces noticeable interlayer approach and limited intralayer distortion. Reduced self-trapping energy facilitates reverse intersystem crossing of self-trapped excitons (STEs), leading to visible PL transformation from STE to FE emission. Under sufficient compression, phase transition occurs, and significant structural distortions are accompanied by further exciton release. The FE emission is enhanced with more symmetric line shape, achieving intense deep-blue emission that meets the international specification of deep-blue display. Sufficiently decreased binding energy also promotes the dissociation of FEs to simultaneously enhance PC property.

Impact of molecular configuration on the photoluminescence and electrical characteristics of poly-pyrrol-thiazol-imine polymers films

The optical, photoluminescence, and electrical properties of Poly(Z)-PTI and Poly(E)-PTI, two Poly-Pyrrol-Thiazol-Imine polymers with comparable chemical structures but distinct configurations, were examined. Using the dip-casting method, polymer films were deposited on ITO substrates. UV-VIS spectroscopy revealed that both polymers diverged between 500 and 800 nm, showing the impact of molecular arrangement, but showed similar absorption behavior for wavelengths shorter than 500 nm. For Poly(Z)-PTI, the direct optical energy gaps were 2.06 eV, while for Poly(E)-PTI, they were 1.78 eV. Poly(Z)-PTI displayed an emission peak at 610 nm (red) according to laser photoluminescence spectra, while Poly(E)-PTI peaked at 563 nm (green-yellow). The capacitance behavior was revealed by electrochemical impedance spectroscopy. Nyquist plots suggested an equivalent circuit model of Rs (CRct)(QR)(CR) for both polymers, and the relaxation times were 15.9 ns for Poly(Z)-PTI and 89.5 ns for Poly(E)-PTI. The Mott-Schottky analysis verified the n-type conductivity, revealing 2.18 × 1016 cm− 3 carrier densities for Poly(Z)-PTI and 1.78 × 1016 cm− 3 for Poly(E)-PTI. At lower frequencies, both polymers exhibited limited conductivity and large dielectric constants. Insights into the possible uses of Poly-Pyrrol-Thiazol-Imine polymers in electrical and optoelectronic devices are provided by this study, which emphasizes the influence of molecular configuration on these polymers’ characteristics.

The Role of Spacers as a Probe in Variation of Photoluminescence Properties of Mono- and Bi-Nuclear Boron Compounds.

A series of N,O donor-based mono- and binuclear four-coordinated boron complexes were synthesized. Depending on the substitution and spacer, these complexes exhibit intense blue, green and yellow emission in solution states. Notably, the fluorescence quantum yields (ΦF) and fluorescence decay (lifetime, τ) of mononuclear boron complexes (2 a-2 e) were higher than the binuclear boron complexes (2 f-2 k). The lowest lifetime and quantum yield in binuclear boron complexes were due to intramolecular rotation induced non radiative processes. The disulphide spacer-based boron complexes 2 i-2 k showed aggregation-caused quenching in the THF/H2O mixture whereas no other complexes were ACQ responsive. These complexes show large Stokes shift, one of them i. e. 2 e has the highest Stokes shift of 130 nm. Further, the electrochemical study suggests the presence of two redox incidences. Theoretical studies show close corroboration between the TD-DFT computed and experimentally measured absorption maxima as well as DFT (GIAO) calculated and experimentally measured 11B NMR values. This complements the appropriate selection of the theoretical methods to shed light on the electronic transitions in the mono- and binuclear BF2 complexes.

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.

Ferromagnetic and photoluminescence properties of transparent conductive Cd1-xSnxO thin films for light emitting diode applications

Ferromagnetic and photoluminescence properties of transparent conductive Cd1-xSnxO thin films for light emitting diode applications

Rapid and precise large area mapping of rare-earth doping homogeneity in luminescent materials

Doping of luminescent materials by rare-earth ions is common practice to achieve desired emission properties for a large variety of applications. As several rare-earths ions are frequently combined, it is subsequently difficult to effectively detect and control their homogeneous distribution within the host material. Here, we present a simple, rapid, large scale and precise method of rare-earth mapping using a commercial UV-Vis scanner. We discuss the influence of rare-earth distribution on the physical, optical and luminescent properties with no observable qualitative effect on photoluminescent properties and optical anisotropy. On the contrary, rare-earth-rich areas exhibit significantly higher values of refractive index and optical absorption, which allowed for their identification by the commercial scanner device. The presented method thus provides fast and accurate information about the rare-earth distribution in the material volume with high resolution (≈2.7 µm) and low limit of concentration difference detection (≈0.014 at.%) compared to other techniques, which makes it a promising candidate for high throughput measurements.

High‐Efficiency Deep‐Blue Solution‐Processed Organic Light‐Emitting Diodes Using Carbazole Dendrons Modified Hybridized Local and Charge‐Transfer Emitters

AbstractIn the pursuit of efficient and cost‐effective organic light‐emitting diodes (OLEDs), the development of solution‐processed hybridized local and charge transfer (HLCT) emitters presents a promising approach. HLCT materials uniquely integrate the advantages of both singlet and triplet excitons, surpassing the traditional spin statistical limit of 25 % while offering high photoluminescence efficiency and balanced charge transport properties. Herein, we report the synthesis and characterization of two new deep blue, solution‐processable HLCT fluorophores, G1FTPI and G2FTPI. These compounds incorporate fluorenyl carbazole dendron units into the HLCT luminogenic triphenylamine‐phenanthroimidazole (TPI) molecule. Their HLCT and photoluminescence (PL) properties were experimentally and theoretically investigated using solvation effects and density functional theory (DFT) calculations. The molecules exhibit deep blue emission with a high solid‐state fluorescence quantum yield, good solution‐processed film‐forming quality, and high hole mobility values of 2.18–2.61×10−6 cm2 V−1 s−1. Both compounds were successfully employed as non‐doped emissive layers in solution‐processed OLEDs, demonstrating excellent electroluminescent (EL) performance. Notably, the G2FTPI‐based device emitted a deep blue light at 432 nm with CIE coordinates of (0.158, 0.098) and achieved a maximum current efficiency (CEmax) of 3.13 cd A−1 and a maximum external quantum efficiency (EQEmax) of 5.30 %.

Biofilm Demolition by [AuIII(N N)Cl(NHC)][PF6]2 Complexes Fastened with Bipyridine and Phenanthroline Ligands; Potent Antibacterial Agents Targeting Membrane Lipid.

The development of new antibacterial drugs is essential for staying ahead of evolving antibiotic resistant bacterial (ARB) threats, ensuring effective treatment options for bacterial infections, and protecting public health. Herein, we successfully designed and synthesized two novel gold(III)- NHC complexes, [Au(1)(bpy)Cl][PF6]2 (2) and [Au(1)(phen)Cl][PF6]2 (3) based on the proligand pyridyl[1,2-a]{2-pyridylimidazol}-3-ylidene hexafluorophosphate (1⋅HPF6) [bpy=2,2'-bipyridine; phen=1,10-phenanthroline]. The synthesized complexes were characterized spectroscopically; their geometries and structural arrangements were confirmed by single crystal XRD analysis. Complexes 2 and 3 showed photoluminescence properties at room temperature and the time-resolved fluorescence decay confirmed the fluorescence lifetimes of 0.54 and 0.62 ns respectively; which were used to demonstrate their direct interaction with bacterial cells. Among the two complexes, complex 3 was found to be more potent against the bacterial strains (Staphylococcus aureus, Gram-positive and Pseudomonas aeruginosa, Gram-negative bacteria) with the MIC values of 8.91 μM and 17.82 μM respectively. Studies revealed the binding of the complexes with the fundamental phospholipids present in the cell membrane of bacteria, which was found to be the leading cause of bacterial cell death. Cytotoxicity was evaluated using an MTT assay on 293 T cell lines; emphasizing the potential therapeutic uses of the Au(III)-NHC complexes to control bacterial infections.

Lignite-derived carbonized polymer dots for oilfield tracers

Oilfield tracers are essential chemical additives in the petroleum extraction process, aiding in understanding reservoir flow characteristics, optimizing production strategies, and ultimately increasing oil recovery rates. Carbon dots (CDs), known for their tunable photoluminescent properties, ease of detection, and low toxicity, are considered promising candidates for the next generation of oilfield tracers. However, aqueous-phase oilfield tracers require CDs to possess good water solubility, high-temperature and high-salinity tolerance, low rock adsorption and detection limit, which renders many CDs unqualified for use. Currently, reports on CDs oilfield tracers are limited, with most being restricted to blue fluorescence, which has weak resistance to background fluorescence interference. In this work, by utilizing the rich organic content (17.5 wt%) of low-value lignite as a precursor, lignite-derived carbonized polymer dots (L-CPDs) exhibit green fluorescence with an absolute quantum yield (QY) of 19.78%. Comprehensive evaluations show L-CPDs offer good salt tolerance, thermal stability, and pH stability, with a detection limit reaching 1 ppb and no significant cytotoxicity. Additionally, the tracing behavior of L-CPDs is demonstrated using a microfluidic chip, highlighting their potential as alternatives to existing tracer products.

Unique High-Resolution Temperature Mapping of Stage 1 Turbine Vane in a Long-Term Engine Test

Abstract In this study, surface temperature maps resulting from a long-term engine test were evaluated on a stage 1 turbine vane using thermal history coatings (THCs). THCs are ceramic-type sensor coatings doped with a lanthanide ion, giving the coating photoluminescent properties. The THC's structure permanently changes when exposed to high temperatures, which in turn alters its photoluminescent properties. Therefore, historic maximum temperature maps are evaluated by optically probing the THC point-by-point across the vane's surface. The vane was exposed to a non-dedicated (multi-cycle, multi temperature-level) engine test lasting over 8 months. Two passes of THC measurements were taken, termed low resolution (LR) and high resolution (HR), each, respectively, with point pitches of 5 mm and 1 mm. The latter provided a unique insight into the historic maximum temperature profile of the vane, particularly around high-temperature gradient regions, such as those close to effusion cooling holes. The THC temperatures were compared to the engine manufacturer's (Doosan Enerbility) heat transfer code (Doosan Integrated Thermal Analysis for Cooling System (DiTACS)) for validation. The THC temperature mapping was successful with good coverage across the vane. The leading edge and pressure side trailing edge regions were typically the hottest. The HR measurements clearly show sharp thermal gradients around the effusion cooling holes on the vane's airfoil and platforms. Critically, the THC measurements were compared very well to the DiTACS measurements, validating THCs as a credible temperature measurement technique for long-term, non-dedicated engine tests for components operating in some of the most extreme environments of an engine.

Patterned Lead-Free Double Perovskite/Polymer Fluorescent Piezoelectric Composite Films for Advanced Anti-Counterfeiting.

The limitations of single fluorescent anti-counterfeiting technologies necessitate the development of more sophisticated encryption methods to protect information and data. Traditional optical anti-counterfeiting encryption techniques, which rely on light sources with varying wavelengths to identify information, are now insufficient to meet contemporary security demands due to their restricted response to a narrow range of wavelengths. In this study, the fabrication of patterned, lead-free double perovskite (DP)/poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) fluorescent piezoelectric composite films (CFs) is reported. These CFs integrate the up-conversion and down-conversion photoluminescent properties of Cs2Na0.8Ag0.2BiCl6:Yb3+/Er3+ DP crystals with the piezoelectric properties of P(VDF-TrFE) film, facilitating multi-modal information protection. The fluorescent signals of different concealed information in CFs are observable under the excitation of 365nm UV light and 980nm infrared (IR) light. Additionally, external pressure applied at various locations on the CFs generates corresponding electrical signals, thereby providing triple-layer encryption for protected information. A multifunctional anti-counterfeiting device has been further developed by integrating patterned optical and electrical responses onto flexible CFs, achieving synergistic protection of information security in cross fields and bringing a significant advancement to the high-level anti-counterfeiting market.

Violet light excitable BaLiZn3(PO4)3: Eu orange-red-emitting phosphor towards white LED application

White light-emitting diode (WLED) has been widely used as solid-state lighting in recent years, with the advantages of energy saving, high luminous efficiency, and safety. Red phosphors are crucial to the color rendering index of WLED, and Eu3+-activated red phosphors can significantly improve the chromaticity performance of WLED. In this work, a series of new orange-red emitting BaLiZn3(PO4)3: Eu3+ phosphors were synthesized through high-temperature solid-state reaction method. The phase composition, crystal structure, morphology and photoluminescence properties of BaLiZn3(PO4)3: Eu3+ samples were investigated. The phosphors can be effectively excited by the violet light at 394 nm and emit orange-red lights corresponding to the electric dipole transition (5D0→7F1) at 594 nm. The optimal doping concentration of Eu3+ ions was about 5 mol%. The concentration quenching was caused by the electric dipole-dipole interaction between Eu3+ ions. Temperature-dependent PL spectra indicate that BaLiZn3(PO4)3: Eu3+ has excellent emission and color stability at high temperatures. The color coordinates were calculated and fall in the orange-red luminescent area. The color purity is about 98.3 %, and the correlated color temperature is 1710K. These results indicate that the new orange-red phosphor BaLiZn3(PO4)3: Eu3+ has potential application prospects in WLED.