Exhibited Emission Peaks Research Articles

Photoluminescence and thermally stimulated luminescence properties of Sr3Y(PO4)3 single crystals doped with dy

Sr3Y(PO4)3 (SYPO) is recognized as a highly promising material for dosimetry applications, owing to its dosimetric properties. In this work, we synthesized the SYPO single crystals doped with 0.1, 0.5, 1, and 5 % Dy using the floating zone furnace to evaluate the photoluminescence and thermally stimulated luminescence (TSL) characteristics. All the SYPO single crystals doped with Dy exhibited emission peaks at 480, 580, 670, and 760 nm in PL and TSL spectra. These emission peaks were typical for the 4f–4f transitions of Dy3+ ions. The SYPO single crystal doped with 0.1 % Dy displayed a glow peak in the TSL glow curve at 70 °C. The SYPO single crystals doped with 0.5, 1, and 5 % Dy showed two glow peaks at approximately 70 and 110 °C. The SYPO single crystal doped with 0.5 % Dy exhibited the highest TSL intensity with a lower detection limit of 0.1 mGy. The SYPO single crystal doped with 0.5 % Dy showed a spatial resolution of 50.0 μm after X-ray irradiation of 1Gy.

Instrument-free detection of natamycin in beer and wastewater based on Eu-MOF ratiometric fluorescence response

Excessive intake of natamycin (NAT) is harmful to human health, so it is of great significance and necessity to effectively detect the content of NAT in food. In this study, we synthesized a dual-emission fluorescence probe, Eu@UiO-66(OH)2/(COOH)2, which exhibited emission peaks at 439nm and 614nm. This probe was obtained through the europium post-modification of UiO-66 type metal-organic frameworks (Eu-MOFs), which consisted of two types of ligands, 2, 5-dihydroxyterephthalic acid and pyromellitic acid. As expected, this probe Eu@UiO-66(OH)2/(COOH)2 can specifically respond to NAT with distinguishable ratiometric fluorescence changed from purple-red to blue with low limit of detection (0.15μM, approximately 0.10mg/kg), wide linear range (0-100μM), fast response (less than 1min), good selectivity and interference resistance. Based on the ratiometric fluorescence responsiveness, Eu@UiO-66(OH)2/(COOH)2 had been successfully used for the quantitative detection of NAT in wastewater, beer, yoghurt, and juice, demonstrating good recovery through smartphone-based colorimetric analysis. Thus, this work provides a ratiometric fluorescent probe for rapid, instrument-free and on-site detection of NAT in real samples such as beverage and environmental water.

Microstructure and properties of Cu-doped β-Ga2O3 rod prepared with liquid metallic gallium

One-dimensional β-Ga2O3 is expected for potential applications in electronics, sensors, and optoelectronics. Gallium hydroxide (GaO(OH)) with different Cu doping was prepared via the hydrothermal method using liquid metallic gallium and copper chloride dihydrate (CuCl2·2H2O) as the starting materials. The material was then transformed to β-Ga2O3 after calcination at 800 °C. SEM images reveal that the obtained powders are well dispersed and have a uniform rod morphology with a length of 13–14 μm and a width of approximately 500 nm. The addition of Cu ion significantly improves the surface morphology of the rod and effectively inhibits the generation of intrinsic oxygen vacancies. And the relative Fermi energy level of Cu-doped β-Ga2O3 undergoes a notable shift from 2.81 eV to 1.25 eV, suggesting the formation of p-type conductivity. Meanwhile, the PL spectra of the Cu-doped samples exhibit emission peaks in the red wavelength range, which is expected for new applications.

Suppression of efficiency roll-off in solution-processed OLEDs using pyrimidine-based iridium complexes modified with sterically hindered groups

Three bis-cyclometalated iridium complexes Ir1-Ir3 were successfully synthesized through mild reaction conditions. All complexes exhibit emission peaks at 507-509 nm, with excellent photoluminescence quantum efficiencies (PLQY) ranging from 69% to 97%. Self-quenching is significantly reduced because the steric spacers lead to minimum bimolecular interactions. Accordingly, the electroluminescence device based on complex Ir3 exhibits a maximum luminous efficiency of 39.6 cd A−1, a high EQE of 13.1% with an efficiency roll-off of 4.2% at 1000 cd m−2, which is much smaller than that (10.8%) of the Ir1-based device. Moreover, its devices exhibit excellent stability even at elevated doping concentrations, suggesting a notable reduction in intermolecular interactions caused by the steric pinene spacer.

Folic acid-mediated enhancement of the diagnostic potential of luminescent europium-doped hydroxyapatite nanocrystals for cancer biomaging

Early and accurate cancer diagnosis is crucial for improving patient survival rates. Luminescent nanoparticles have emerged as a promising tool in fluorescence bioimaging for cancer diagnosis. To enhance diagnostic accuracy, ligands promoting endocytosis into cancer cells are commonly incorporated onto nanoparticle surfaces. Folic acid (FA) is one such ligand, known to specifically bind to folate receptors (FR) overexpressed in various cancer cells such as cervical and ovarian carcinoma. Therefore, surface modification of luminescent nanoparticles with FA can enhance both luminescence efficiency and diagnostic accuracy. In this study, luminescent europium-doped hydroxyapatite (EuHAp) nanocrystals were prepared via hydrothermal method and subsequently modified with (3-Aminopropyl)triethoxysilane (APTES) followed by FA to target FR-positive human cervical adenocarcinoma cell line (HeLa) cells. The sequential grafting of APTES and then FA formed a robust covalent linkage between the nanocrystals and FA. Rod-shaped FA-modified EuHAp nanocrystals, approximately 100 nm in size, exhibited emission peaks at 589, 615, and 650 nm upon excitation at 397 nm. Despite a reduction in photoluminescence intensity following FA modification, fluorescence microscopy revealed a remarkable 120-fold increase in intensity compared to unmodified EuHAp, attributed to the enhanced uptake of FA-modified EuHAp. Additionally, confocal microscope observations confirmed the specificity and the internalization of FA-modified EuHAp nanocrystals in HeLa cells. In conclusion, the modification of EuHAp nanocrystals with FA presents a promising strategy to enhance the diagnostic potential of cancer bioimaging probes.

Antioxidant, antibacterial, enzyme inhibition and fluorescence characteristics of unsymmetrical thiourea derivatives

A series of six unsymmetrical thiourea derivatives, namely 1-cyclohexyl-3-(pyridin-2-yl) thiourea (1), 1-cyclohexyl-3-(3-methylpyridin-2-yl)thiourea (2), 1-cyclohexyl-3-(2,4-dimethylphenyl) thiourea (3), 1-(4-chlorophenyl)-3-cyclohexylthiourea (4), 1-(3-methylpyridin-2-yl)-3-phenylthiourea (5), and 1-(3-chlorophenyl)-3-phenylthiourea (6), were successfully synthesized via reaction between different amines with isothiocyanates under a non-catalytic environment. Structural elucidation of compounds (1–6) was performed using FT-IR and NMR (1H and 13C) spectroscopy. The infrared spectra displayed characteristic stretching vibrations, while the 13C NMR chemical shifts of the thiourea moiety (CS) were observed in the range of 179.1–181.4 ppm. The antioxidative and antimicrobial properties of the compounds were assessed, as well as their inhibitory effects on acetylcholinesterase and butyrylcholinesterase were evaluated. In order to analyze the fluorescence characteristics of each compound (1–6), the excitation (λex) and emission (λem) wavelengths were scanned within the range of 250–750 nm, with the solvent blank serving as a standard. It was observed that when dissolved in acetone, toluene, tetrahydrofuran, and ethyl acetate, these compounds exhibited emission peaks ranging from 367 to 581 nm and absorption peaks ranging from 275 to 432 nm.

Enhancing OLED emitter efficiency through increased rigidity.

Three new blue materials, TPI-InCz, PAI-InCz, and CN-PAI-InCz, have been developed. In the film state, TPI-InCz and PAI-InCz exhibited emission peaks at 411 and 431 nm indicating deep blue emission. CN-PAI-InCz showed a peak emission at 452 nm, within the real blue region. When these three materials were used as the emissive layer to fabricate non-doped devices, CN-PAI-InCz showed the highest current efficiency of 2.91 cd A-1, power efficiency of 1.93 lm W-1, and external quantum efficiency of 3.31%. Among the synthesized materials, CN-PAI-InCz exhibited superior charge balance due to the introduction of CN groups, as confirmed by hole-only devices and electron-only devices. PAI-InCz demonstrated fast hole mobility with a value of 1.50 × 10-3 cm2 V-1 s-1, attributed to its planar and highly rigid structure. In the resulting devices, the Commission Internationale de l'Eclairage coordinates for TPI-InCz, PAI-InCz, and CN-PAI-InCz were (0.162, 0.048), (0.0161, 0.067), and (0.155, 0.099), all indicating emission in the blue region.

Effect of Sm(DBM)3Phen incorporation methodology on spectroscopic properties of PVA nanofibres

Electrospun nanofibres are an advancing area of research because of their flexible characteristics and numerous applications in sensors, optoelectronic devices, etc. Herein, we first prepared lanthanide complex Sm(DBM)3Phen. The synthesized complex was then incorporated into and onto the surface. The detailed study of spectroscopic properties of electrospun nanofibres into and onto the surface is presented. The fabricated nanofibres of Sm(DBM)3Phen into the nanofibres surface had a diameter of around 295 nm and length > 200 µm and the surface morphology of the complex incorporated nanofibres presented that the nanofibres were smooth and straight and were highly interlaced. The nanofibres with Sm complex on the surface presented a rough surface morphology. The spectroscopic analysis shows energy transfer from the ligand Dibenzoylmethane (DBM) to Sm3+ ion, enhancing its photoluminescence intensity. Under UV excitation, the Sm(DBM)3Phen incorporated nanofibres exhibited emission peaks between 550 nm and 710 nm and with sharp peaks at 564, 598 nm, and 646 nm, which are assigned to the transition from 4G5/2 to 6HJ (J = 5/2, 7/2, and 9/2) attributed to DBM. The photoluminescence intensity of the two nanofibres varied with the incorporation method. A detailed spectroscopic analysis of the synthesized samples with the incorporation methodology is carried out.

Concentration dependence on optical stimulated luminescence properties of Ce: Y2SiO5 single crystals

Y2SiO5 (YSO) single crystals with various Ce concentrations were fabricated and their photoluminescence (PL) and optically stimulated luminescence (OSL) properties analyzed. From the evaluation of PL properties, there was an emission band centered at 420 nm in Ce:YSO samples. The observed emission originated from the 5d-4f transitions of Ce3+ ions. In OSL properties, OSL spectra under stimulation at 520 nm exhibited emission peaks at 420 nm, and the emission origin was also the 5d-4f transitions of Ce3+ ions. The OSL dose response functions had a lower detection limit of 1 mGy for the 0.5 and 1.0% Ce:YSO samples, and 10 mGy for the 0.1 and 2.0% Ce: YSO samples. The OSL intensity of the 1.0% Ce:YSO sample was approximately 69.3% after 24 h from X-ray irradiation compared to immediately after X-ray irradiation.

Green Synthesis of Silver Nanoparticles: Their Optical and Rheological Properties

The goal of this work was to investigate the green synthesis of silver nanoparticles (Ag NPs) from aqueous Propolis (P) extract, and their optical and rheological properties. Using scanning electron microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-ray diffraction (XRD) studies nanostructure of the prepared Ag NPs were characterized. Further, the aforementioned study suggests that Ag NPs with an average size of around 23 nm have a well-developed polycrystalline cubic structure. In the UV-Vis absorption spectra, the surface plasmon resonance (SPR) peak showed maximum absorption at 418 nm. For an excitation energy corresponding to the wavelength 410 nm, photoluminescence (PL) spectra of Ag NPs exhibited emission peak at 495 nm. To explore temperature (T) dependent flow behaviour of biosynthesized colloidal Ag NPs dispersion in deionized (DI) water, flow curve studies under shear for T= 20, 30 and 40 °C were done using rheometer. The above study illustrated that the colloidal Ag NPs follows shear thickening non-Newtonian behaviour. Moreover, viscosity decreased as temperature increased, indicating that the silver nanofluids can exhibit more rational thermal performance under high temperature conditions.

Four cyclometalated iridium(III) complex-based chemosensors for turn-on response to thiourea in fruit juice and their application in test strips

Excessive thiourea(TU) was demonstrated to be harmful to both environmental system and human body, so it is essential to create selective and sensitive sensors to detect TU. Herein, Four iridium(III) complexes, [(fppy)2Ir(PD)]PF6 (Ir-fppy, fppy = 2-(4-fluorophenyl)pyridine), [(fpiq)2Ir(PD)]PF6 (Ir-fpiq, fpiq = 1-(4-fluorophenyl)isoquinoline), [(dfppy)2Ir(PD)]PF6 (Ir-dfppy, dfppy = 2-(3,5-difluorophenyl)pyridine) and [(dfpiq)2Ir(PD)]PF6 (Ir-dfpiq, dfpiq = 1-(3,5-difluorophenyl)isoquinoline) bearing 1,10-phenanthroline-5,6-dione (PD) as ancillary ligands, were designed and synthesized, and employed as efficient chemosensors to identify thiourea. These iridium(III) complexes exhibited emission peaks between 541 nm and 583 nm with PLQY ranging from 0.12 to 0.26 and lifetime in the range of 2.65–2.74 μs. All the four iridium(III) complexes showed significant turn-on response to TU with low limit of detect on the order of 10−8 M. Furthermore, these iridium(III) complexes-based chemosensors exhibited excellent recoveries toward TU in various juice samples including orange, kiwi fruit and lemon juice. Four complexes-composite test strips showed marker color change after adding TU.

Fluorescent material based on Al-MOF and phenazine groups for detection of water content in organic solvents

[Formula: see text]-MIL-101(Al) material containing phenazine groups, i.e. 1-metal-organic framework (MOF) has been prepared and characterized via FT-IR, PXRD, TGA, SEM and [Formula: see text] adsorption and desorption isotherm in this work. 1-MOF can exhibit emission peaks at 447 nm (in pure aqueous solvent) and 595 nm (in pure organic solvents) under 327 nm ultraviolet excitation, respectively. Based on this interesting feature, 1-MOF has been effectively used as a ratiometric fluorescent probe to detect water content in organic solvents. The luminescence color of 1-MOF changed obviously from red to blue with the increasing of water content in organic solvents, which can be observed by the naked eyes. The route to detect water content in organic solvents is fast, accurate and possessing great application potential.

Deep-Level Emission Tailoring in ZnO Nanostructures Grown via Hydrothermal Synthesis

Zinc oxide (ZnO) nanostructures are widely used in various fields of science and technology due to their properties and ease of fabrication. To achieve the desired characteristics for subsequent device application, it is necessary to develop growth methods allowing for control over the nanostructures' morphology and crystallinity governing their optical and electronic properties. In this work, we grow ZnO nanostructures via hydrothermal synthesis using surfactants that significantly affect the growth kinetics. Nanostructures with geometry from nanowires to hexapods are obtained and studied with photoluminescence (PL) spectroscopy. Analysis of the photoluminescence spectra demonstrates pronounced exciton on a neutral donor UV emission in all of the samples. Changing the growth medium chemical composition affects the emission characteristics sufficiently. Apart the UV emission, nanostructures synthesized without the surfactants demonstrate deep-level emission in the visible range with a peak near 620 nm. Structures synthesized with the use of sodium citrate exhibit emission peak near 520 nm, and those with polyethylenimine do not exhibit the deep-level emission. Thus, we demonstrate the correlation between the hydrothermal growth conditions and the obtained ZnO nanostructures' optical properties, opening up new possibilities for their precise control and application in nanophotonics, UV-Vis and white light sources.

Two coordination polymers assembled with resorcin[4]arenes ligand: Luminescent sensing Fe3+ ion and Cr2O72− anion

Two coordination polymers, [Cd2L(btbp)0.5(DMF)(H2O)]·3DMF (1) and [Zn2L(btbp)0.5(H2O)2]·DMF·3H2O (2) have been synthesized base on resorcin[4]arene, btbp and metal ions in solvothermal conditions (H4L = 2,8,14,20-tetra-ethyl-4,10,16,22-tetrakis(4-carboxybenzyl)oxy)-6,12,18,24-tetra-methoxy-resorcin[4]arene, btbp = 4,4′-bis(1,2,4-triazole-1-ylmethyl)biphenyl)). The structures of CPs 1 and 2 were determined by single-crystal X-ray diffractometer. Structural analysis shows that 1 and 2 exhibit layer structures. CPs 1 and 2 were characterized by Fourier transform infrared spectroscopy (FTIR), Powder X-ray diffraction (PXRD), elemental analysis and UV–vis Spectra. The solid-state emission spectra of 1 and 2 have been carried out and exhibit emission peaks at 452 nm (λex = 364 nm) and 455 nm (λex = 371 nm), respectively. Remarkably, CPs 1 and 2 exhibit excellent luminescent emissions in solid-state. Furthermore, CP 1 was used to detect Fe3+ and Cr2O72− in aqueous solution, and its sensitivity and anti-interference were also studied. The Stern-Volmer constant Ksv were 4.381 × 103 M−1and 1.1109 × 104 M−1, respectively. Further analysis showed that the quenching of CP 1 might be related to the energy competition of Fe3+ and Cr2O72−.

Microwave synthesis of blue emissive carbon dots from 5-sulpho anthranilic acid and 1,5-diphenyl carbazide for sensing of levocetirizine and niflumic acid

In this work, water soluble carbon dots (CDs) were synthesized by using 5- sulpho anthranilic acid (SAA) and 1,5-diphenylycarbazide (DPC) as precursors via microwave-assisted method and named as “SD-CDs”. We studied the effect of SAA and DPC molar ratio (1:3, 2:2 and 3:1) for the preparation of blue fluorescent CDs, showing the best emission properties at molar 3:1 ratio of SAA and DPC. The as-prepared SD-CDs emit bright blue color under UV light at 365 nm, and exhibit emission peak at 392 nm when excited at 319 nm. The as-synthesized SD-CDs act as a fluorescent sensor for detection of levocetirizine and niflumic acid through the fluorescence “turn-on–off” mechanism. The developed probe exhibited good linearity in the concentrations (levocetirizine − 1.0–100 µM and niflumic acid − 0.5–100 µM) with detection limits of 3.92 nM and 0.19 µM for levocetirizine and niflumic acid, respectively. Importantly, the developed analytical method was successfully used for the detection of levocetirizine in tablets and niflumic acid in biofluids of human (serum, plasma and urine), showing good recoveries from 97 to 99 %. Thus, this SD-CDs-based fluorescence method has the potential for levocetirizine and niflumic acid assays in biological and pharmaceutical samples.

Multiobjective Machine Learning-Assisted Discovery of a Novel Cyan-Green Garnet: Ce Phosphors with Excellent Thermal Stability.

Ce-doped garnet phosphors play an important role in the white light-emitting diode (LED) family. In the past years, a lot of trial-and-error experiments guided by experience to discover phosphors suitable for white LEDs have been presented. The working temperature of phosphors may reach 200 °C in white LEDs, and so, the exploration of phosphors with excellent thermal stability at the desired wavelength continues to be a challenge. In the present study, to discover novel cyan-green garnet:Ce phosphors, wavelength and thermal stability machine learning models were built by constructing reasonable features. Among the 171,636 compounds with garnet structures predicted by our models, 25 samples were selected for preparation and characterization by multiobjective optimization based on active learning. Lu1.5Sr1.5Al3.5Si1.5O12:Ce performed the best with excellent thermal stability (≥60% emission intensity was retained at 640 K) and exhibited emission peaks of about 505 nm, and it is a very promising phosphor for future applications, especially in high-temperature operating environments.

Green Light Emission in Terbium Doped Lanthanum Zirconate Powders

The present article reports the synthesis of Tb-doped La2Zr2O7 phosphors with varying concentrations using the solid-state reaction method at very high temperatures. The photoluminescence (PL), thermoluminescence (TL) properties of prepared Tb-doped La2Zr2O7 material were also elaborated. In PL studies, phosphors at 273 nm excitation emit green light due to 5D4→7F5 transitions of the Tb3+ ion and exhibit emission peaks at 538, 545, 574, and 586 nm. In addition, the concentration of Tb3+ -doping strongly influenced the PL properties, and the quenching concentration is 2 mol% of Tb. The XRD analysis results reveal a cubic crystal structure with an average crystalline size (∼ 52 nm), for La2Zr2O7:Tb3+ phosphors. The chromaticity coordinates (0.37, 0.56) of the La2Zr2O7:Tb3+ phosphor are located in the green region and exhibit green luminescence, this can be used in display devices such as CFLs. Scanning electron microscopy (SEM) is used to find the morphology of the prepared material while elemental detection is done with energy dispersive X-ray analysis (EDX). Here the intensity of TL was also discussed with the result of different concentrations, where it was observed that the intensity increased with an increase in Tb3+ ion concentration, up to 2 mol%, and further reduced with an increase in concentration.

Crystal Interface Control at Low Thermal Gradient and Investigation of the Effect of Cr on the Crystal Structure and Optical Properties of Bismuth Silicate

Single crystals of bismuth silicate (Bi12SiO20) doped with chromium (0.05, 0.25, 0.5, and 1.0 at%) have been grown along ⟨110⟩ by Czochralski technique. The effect of growth parameters like low axial thermal gradient and crystal rotation rate on the crystal−melt interface is investigated by varying these parameters. Further, the effect of Cr incorporation on the lattice parameter, optical bandgap, emission characteristics, and refractive index is studied. It is observed that as the concentration of Cr increases, the lattice parameter increases, because the size of Cr ion is higher than that of Si ion which it replaces. The bandgap is found to decrease with the increase in the concentration of Cr in the lattice of Bi12SiO20. The estimated bandgap energy of all the samples lies between 2.16 and 3.12 eV. The estimated Urbach energy is ≈115 meV for undoped BSO and it is slightly higher (≈200 meV) for Cr‐doped crystals. Further, 0.05 and 0.25 at% Cr‐doped samples exhibit emission peak at around 470 nm on excitation at 420 nm. The refractive index is found to decrease with the increase in Cr concentration in the lattice.

Trypsin encapsulated gold-silver bimetallic nanoclusters for recognition of quinalphos via fluorescence quenching and of Zn2+ and Cd2+ ions via fluorescence enhancement

In this work, gold‑silver bimetallic nanoclusters (AuAg NCs) were produced via a simple synthetic approach by using trypsin as a ligand. The synthesized bimetallic nanoclusters have high intensity and shown red fluorescence. The trypsin-encapsulated AuAg bimetallic NCs exhibit emission peak at 418 nm and 665 nm at excitation of 350 nm. The trypsin-decorated AuAg NCs were successfully applied as probes for fluorescence “turn-off” for quinalphos and “turn-on” for Cd2+ and Zn2+ ions. Under optimal conditions, multiple analytes i.e., quinalphos, Cd2+ and Zn2+ ions were detected and exhibited linear range from 1.0 to 100 μM, achieved detection limits at nanomolar concentration. Attractively, the present study provides a new analytical strategy for multiple pollutants assay of quinalphos via fluorescence “turn-off” and of Cd2+ and Zn2+ ions via fluorescence “turn-on” mechanisms. The practicability of the method is validated by quantifying quinalphos, Cu2+ and Zn2+ ions from food and environmental samples.

Novel Fe-doped ZnO-CdS nanocomposite with enhanced visible light-driven photocatalytic performance

ABSTRACT Chemical precipitation method was employed to synthesize the Fe-doped ZnO-CdS nanocomposites. The influence of incorporated Fe ions on the properties of nanocomposites was examined by various spectroscopic characterisations. XRD patterns of as-prepared sample exhibited a hexagonal crystal phase for both ZnO and CdS. Non-uniformly distributed spherical-shaped morphologies were observed from the SEM and TEM analyses. EPR spectrum displayed a sharp signal at g = 2.02. Photoluminescence spectrum of the prepared sample exhibited emission peaks in ultraviolet and visible regions. In the magnetic study, a significant enhancement was observed in the ferromagnetism by adding Fe impurities to the ZnO-CdS nanocomposite at room temperature. The synthesised Fe-doped ZnO-CdS nanocomposites exhibited a superior catalytic performance than pure ZnO and ZnO-CdS nanocomposites.