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Introducing Manganese-Doped Lead Halide Perovskite Quantum Dots: A Simple Synthesis Illustrating Optoelectronic Properties of Semiconductors
摘要： Quantum dots (QDs) are considered useful for demonstrating quantum phenomena in undergraduate laboratories due to their monodisperse size and excellent optical properties. Although doping has an increasingly important role in QD fabrication in the semiconductor field, it has rarely been discussed in the context of the undergraduate laboratory. In this work, a simple synthesis and characterization method for Mn-doped CsPbCl3 QDs for an upper-level undergraduate inorganic chemistry laboratory is reported. The Mn-doped CsPbCl3 system benefits from a simplified synthesis and straightforward characterization. This experiment introduces QD research to students and offers opportunities for instructors to discuss many important concepts in inorganic chemistry, such as energy band theory, particle-in-a-box model, electron paramagnetic resonance, ligand field theory, and nanochemistry.
关键词： Inorganic Chemistry,Crystal Field/Ligand Field Theory,EPR/ESR Spectroscopy,Upper-Division Undergraduate,Hands-On Learning/Manipulatives,Laboratory Instruction,Nanotechnology
更新于2025-11-20 15:33:11
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Optical and luminescence studies on Tm3+-doped KCl single crystals
摘要： Thulium-doped KCl crystals have been successfully grown using Bridgman–Stockbarger technique. The crystals were characterized by optical absorption, photoluminescence (PL), thermoluminescence glow, TL emission, powder X-ray diffraction, scanning electron microscopy (SEM), laser Raman spectroscopy and electron paramagnetic resonance spectroscopy (EPR). PL spectra exhibit broadband blue emission at 468 nm for the application of light-emitting diodes. The trap parameters of the TL glow curve are calculated using Chen’s peak shape method. XRD analysis carried out on the grown crystals and lattice parameters predicted that it crystallized in cubic structure. SEM studies revealed the presence of microcrystalline structure. EPR measurements were made at X-band frequencies with 9–10 GHz ?eld modulation at room temperature, and the g-factor value of 2.4 was calculated by using Lande formula.
关键词： Optical absorption,TL emission,PL,TL glow,EPR
更新于2025-11-14 14:48:53
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Light-induced EPR study of spin-assisted charge transport in PFOT:PC61BM composite
摘要： Magnetic resonance, relaxation and dynamic parameters of polaron spins and methanfullerene radical anions, initiated by the infrared-visible-ultraviolet photons in bulk heterojunctions of the composite formed by narrow-band poly[(9,9-dioctylfluorenyl-2.7-diyl)-co-(bithiophene)] (PFOT, F8T2) copolymer and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) globules were investigated by the direct Light-Induced Electron Paramagnetic Resonance (LEPR) spectroscopy. It was shown that some of the polarons are captured by spin traps formed in the copolymer matrix due to its disordering. The number, spatial distribution and energy depth of such traps depend on the structure and morphology of composite. It is shown that the main parameters of both charge carriers are determined by the exchange interaction of the spin ensembles, as well as the energy of the photons. The formation of spin traps in the copolymer matrix and the exchange interaction between different spin packets cause the extreme sensitivity of the composite's magnetic resonance and electronic parameters to the number and energy of the initiating photons. The predominant photoinitiation of localized polarons in the copolymer matrix was demonstrated. This process is substantially accelerated when the composite is illuminated by photons with the energy lying near 1.8 and 2.7 eV. The recombination of both charge carriers can be described in terms of a bimolecular process of the second order. It was found that the contributions of polarons and methanofullerene radical anions to the effective paramagnetic susceptibility increase substantially near the photon energy of 2.6 and 2.1 eV due to the exchange interaction of these charge carriers. It is shown that the mobility of polarons varies monotonically throughout all the photon energy range, whereas the librational spin dynamics of the methanofullerene globules is substantially accelerated near the photon energy of 2.0 and 2.7 eV.
关键词： Polymer nanocomposites,Spin recombination,Transport properties,Spin interaction,Polaron,Light-induced EPR
更新于2025-09-23 15:23:52
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Paramagnetic surface defects in LiMgPO<sub>4</sub>
摘要： The EPR spectra obtained at 300 K and 115 K are indicative of the existence of charged defects in LiMgPO4. The main imperfections are identified as a radical CO-3 (g=2) and a singly charged oxygen vacancy (g1=2.45, g2=2.20, g3=2.00). The presence of carbon-containing groups is proved by Raman spectroscopy. The assumption is made that the defects are located mainly on the surface of the grains. Thermoluminescent characteristics of LiMgPO4 annealed in atmospheres with different pO2 demonstrate that the surface defects impair the efficiency of LiMgPO4 as a dosimetric material.
关键词： Thermoluminescence.,Defects,EPR,Raman spectroscopy,LiMgPO4
更新于2025-09-23 15:23:52
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Development of UVB Radiation-Emitting Gd3+-Doped Na3YSi2O7 Host Material
摘要： In this work, we synthesized and characterized a narrow-band, ultraviolet-emitting Na3YSi2O7:Gd3+ material. A series of Na3Y1-xSi2O7:Gdx (x = 0.01 ≤ x ≤ 0.11) samples were synthesized using a sol–gel process. X-ray diffraction patterns of all the samples were found to be similar to the hexagonal Na3YSi2O7 phase. Morphology and functional group analysis were performed using scanning electron microscopy and Fourier transform infrared spectroscopy. The effects of gadolinium concentration on the luminescence intensity of the Na3YSi2O7:Gd3+ samples were investigated. The developed sample exhibited an ultraviolet emission peaking at 313 nm under 273-nm excitation. The dominant band at 313 nm was attributed to 6P7/2 → 8S7/2 transition of Gd3+ ions. The electron paramagnetic resonance (EPR) studies revealed the presence of Gd3+ ions in octahedral Y3+ sites in the host lattice.
关键词： EPR,Na3YSi2O7,photoluminescence,XRD,Gd3+ ions,Sol–gel
更新于2025-09-23 15:22:29
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Composite materials based on active carbon/TiO2 for photocatalytic water purification
摘要： The present work describes the preparations of active carbon (AC) – titania composites with different AC/TiO2 ratio, their characterization using XRD, BET and SEM and evaluation of adsorption capacity and photocatalytic activity in aqueous solution using azo-dye Acid Orange 7 (AO7). Composite materials based on AC/TiO2 were prepared from commercial active carbon (1737 m2/g) and TiO2 (P25, 45 m2/g) materials by the mixing method. The studied parameters were the ratio of AC/TiO2, hydrothermal treatment and milling of as-prepared composites. The composites show increased BET surface area proportional to the content of AC in the material. The disappearance of AO7 is due to the combination two processes, e. g. adsorption and photocatalytic oxidation which takes place in parallel. Thus the overall removal of AO7 has been corrected on adsorption (measured in dark) to obtain the rate of AO7 disappearance due to photocatalytic oxidation (PO). The optimum ratio of AC/TiO2 was found to be 0.23 where PO rate is only slightly lower than that for P25 and overall AO7 removal is twice higher than for P25 itself. The less intensive (low-frequency) milling of the composite results in the decrease of carbon particle size, increase in AO7 adsorption and decline in the PO of AO7. More intensive milling (high-frequency) results in the decrease of the anatase content, appearance of the small amount of brookite and almost negligible PO rate of AO7. Irradiation of low-frequency milled AC/TiO2 composite in aqueous suspensions resulted in the generation of a comparable concentration of hydroxyl radical spin-adduct (?DMPO-OH) as non-milled composite, high-frequency milled composite revealed substantially lower ?DMPO-OH concentration which can be explained by the increased concentration of carbon-centered radicals in AC acting as scavengers of photogenerated electrons.
关键词： adsorption,Active carbon,P25,EPR spectroscopy,AO7,photocatalytic oxidation
更新于2025-09-23 15:22:29
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Preparation, characterization and photocatalytic evaluation of aluminum doped metal ferrites
摘要： Spinel ferrite nano-particles have shown a growing interest in recent years due to their specific magnetic and electrical properties. In this manuscript different types of metal ferrites were prepared and doped with different amounts of Al. Full characterization of the prepared ferrites was performed using X-Ray spectrophotometer (XRD), Electron paramagnetic resonance(EPR), and BET surface area measurements. Photo catalytic activity for degradation of organic dye was examined also for all samples. The results showed that the doping of ferrites with Aluminum make a dramatic change in the photocatalytic behavior. A correlation between the structure and magnetic proprieties with the photocatalytic behavior was evaluated.
关键词： BET,Aluminum dopant,EPR,Ferrites,XRD,Photocatalyst
更新于2025-09-23 15:22:29
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BaWO4:Ce Single Crystals Codoped with Na Ions
摘要： Single crystals of BaWO4, BaWO4: 0.5 at. % Ce; BaWO4: 1 at. % Ce; BaWO4: 0.5 at. % Ce, 1 at. % Na; and BaWO4: 1 at. % Ce, 2 at. % Na were grown from an inductively heated iridium crucible by the Czochralski method on a Malvern MSR4 puller. They were investigated using Electron Paramagnetic Resonance (EPR) spectroscopy at helium temperatures. One isolated center of high (D2d or S4) symmetry was found and two or more other centers of lower symmetry were identified, depending on crystal doping. From the fitting using the EPR-NMR program, the following parameters of g-matrix for the high symmetry center were found: gx = 1.505, gy = 1.505, and gz = 2.731. The linewidth vs. temperature revealed an increasing exponential tendency with increasing temperature. It showed one phonon at the lower temperatures and a Raman + Orbach effect at the higher temperatures. Radioluminescence and pulse height spectra showed rather poor scintillation properties, without any contribution from cerium emission.
关键词： scheelite,EPR,local symmetry,roadmap,BaWO4,structural refinement
更新于2025-09-23 15:22:29
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Histology and antitumor activity study of PTX-loaded micelle, a fluorescent drug delivery system prepared by PEG-TPP
摘要： We synthesized PEG-TPP as carrier to encapsulate paclitaxel (PTX) in the form of micelles to overcome its water-solubility problem. PTX-loaded micelles possess a-week stability and appropriate particle size (152.1±1.2 nm) which is beneficial for enhanced permeability and retention (EPR) effect. Strong pH dependence of PTX releasing from micelles is verified by in vitro release study. At cellular level, PTX-loaded micelles can target mitochondria effectively which may results a better cytotoxicity of micelles (especially IC50 = 0.123±0.035 μmol/L of micelles and 0.298±0.067 μmol/L of PTX alone on MCF-7 cells). The fluorescence distributions of both isolated and sliced organs show that the micelles can effectively target tumors. Moreover, we further prove the enhanced therapeutic effects of micelles in tumor-bearing mice comparing with PTX alone. The results show that the biodegradable drug delivery system prepared by PEG-TPP can overcome the poor solubility of paclitaxel and improve its tumor targeting and antitumor activity.
关键词： PEG-TPP,Mitochondria,Paclitaxel,EPR,Micelles,Anticancer
更新于2025-09-23 15:22:29
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Hyaluronic Acid-zinc Protoporphyrin Conjugates for Photodynamic Antitumor Therapy
摘要： Zinc (II) protoporphyrin IX (ZnPP) strongly inhibits antioxidative enzyme heme oxygenase-1 (HO-1), and ZnPP generates reactive oxygen species (ROS) upon light irradiation. ZnPP can induce lethal oxidative stress in the tumor, when ZnPP is selectively delivered to the tumor followed by light irradiation. In this study, ZnPP was conjugated to hyaluronic acid (HA-ZnPP) for improving its solubility in aqueous media and tumor selective delivery of ZnPP by the enhanced permeability and retention (EPR) effect. Though photosensitizing activity of the HA-ZnPP was quenched in phosphate buffered saline, it was partially recovered by addition of lecithin. Similar to other polymer-conjugated ZnPP, cellular uptake of the HA-ZnPP was lower than that of the free ZnPP in HeLa cells. In tumor-bearing mice, plasma half-life of HA-ZnPP became longer than that of free ZnPP, and thus selective accumulation of the HA-ZnPP in the tumor by the EPR effect was observed. Combination of the HA-ZnPP and light irradiation potentially suppressed the tumor growth, approximately 60% tumor volume reduction was observed without apparent adverse effects at day 31 after the drug treatment. These data demonstrate that HA is a preferable carrier for ZnPP, and the HA-conjugated ZnPP is a promising antitumor agent for photodynamic therapy.
关键词： Nanomedicine,EPR,Zinc protoporphyrin,Photodynamic therapy,Hyaluronic acid
更新于2025-09-23 15:22:29