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Enhancing optical absorption in visible light of ZnO co-doped with europium and promethium by first principles study through modified Becke and Johnson potential scheme
摘要： By using first-principle calculations we studied the electronic, optical and magnetic properties of ZnO co-doped with Eu and Pm. In this calculation, we used Wien2k code based on Full potential linearized augmented plane waves (FP-LAPW) method with the modified Becke-Johnson (mBJ) approximation. This correction gives good band gap compared to experimental band gap. The introduction of Eu and Pm codoping leads to an increase in the band gap. Electrons can transit easily from the valence band to the conduction band, which results in an enhancement of visible light absorption in a wider absorption range. Absorption spectra reach a high value in visible and infrared light regions. With the significance of the obtained results, the studied compounds may potentially find spintronic and optoelectronic applications.
关键词： transmittance,Zinc Oxide,density functional theory,band gap,spintronics,Rare Earth,magnetic properties,absorption,modified Becke-Johnson,photovoltaic
更新于2025-09-10 09:29:36
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Simulation and Experimental Study on Properties of Ag/SnO <sub/>2</sub> Contact Materials Doped with Different Ratios of Ce
摘要： SnO2 in the Ag/SnO2 contact material is a kind of high hardness and almost insulated wide bandgap semiconductor material. In the process of use, the contact resistance is larger and the temperature rise is higher, which reduces the reliability of contacts and shortens the electrical life. In order to improve the properties of Ag/SnO2 contact materials, based on the first principle of density functional theory, this paper presents a method of doping SnO2 with the calculation of different proportions of rare earth Ce electrical and mechanical properties. The results of energy band, density of state, and elastic constant show that when the doping ratio of Ce is 0.125, the electron mobility is the highest, the conductivity is the best; the hardness decreases, and the universal elastic anisotropy index is the smallest. Finally, in the experiment, SnO2 powders with different doping ratios are prepared by the sol-gel method, and Ag/SnO2 contacts with different doping proportions are prepared by powder metallurgy. Arc energy, contact resistance, and hardness are measured; scanning electron microscopy was used to observe and analyze the surface morphology. The final simulation and experimental results are well matched.
关键词： doping,contact materials,rare earth Ce,conductivity,hardness,Ag/SnO2
更新于2025-09-10 09:29:36
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Rare earth-functionalized nanodiamonds for dual-modal imaging and drug delivery
摘要： Nanodiamonds (NDs) have attracted much attention in biomedical research for their high chemical stability, low toxicity and good biocompatibility. However, the insufficient fluorescence of NDs largely inhibit their multi-functional bio-applications ， such as simultaneous diagnosis and chemotherapy. Herein, a multifunctional NDs-based nanoparticles(ND-TTA:RE) with excellent fluorescence and paramagnetic properties has been fabricated by covalently functionalizing NDs with rare-earth (RE=Eu3+, Gd3+) 2-Thenoyltrifluoroacetone (TTA) complexes. The NDs-based nanoparticles exhibit intense red emission and could enhance the T1-weighted MR image due to the coordinated RE ions. The in vitro/in vivo experiments demonstrate its large potential for optical and MR imaging. In addition, the ND-TTA:RE also shows good drug storage capability that reach to 375 ug/mg toward anticancer drug doxorubicin (Dox) and exhibits significant pH-dependent drug-release behavior. The MTT assays shows that the as-synthesized ND-TTA:RE have low toxicity in a concentration range from 0 to 150 mg/mL, while the Dox-loaded ND-TTA:RE (ND-TTA:RE-Dox) shows effective chemotherapy towards gastric cancer cells. The dual-mode imaging and drug delivery abilities make ND-TTA:RE a promising nanomaterial for multifunctional applications. In addition, this work may also provide a new strategy for the design of multi-functional nanoplatform.
关键词： Dual-modal imaging,Nanodiamond,Rare earth,Drug delivery.
更新于2025-09-10 09:29:36
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Plasmon-enhanced upconversion photoluminescence: mechanism and application
摘要： The enhanced local electromagnetic field (EM) excited on the noble metallic nanostructure exhibits potential application in various areas, particularly in surface-enhanced spectroscopy (SES). Resonant coupling of SPs to luminous centers can strongly moderate the emission spectra properties, including the angular distribution, the intensity, the speed of radiative decay, and even the spectrum radiation polarization, or so-called plasmon-enhanced fluorescence (PEF). Due to the low efficiency of emission and small absorption section of rare earth ions, plasmon-enhanced upconversion photoluminescence(PUCPL) has attracted increasing attention recently. In this review, we focus on recent advanced reports on PUCPL. First, the mechanism of the conventional upconversion process and related reports will be introduced. We will then demonstrate that the introduction of plasmonic nanostructure, including nonperiodic and periodic metallic nanostructures, has a critical effect on upconversion nanoparticles(UCNPs). The recent advances in plasmon-enhanced fluorescence with metallic tip configuration are also noted. Finally, the recent applications of PUCPL are introduced. As a result, the combination of a rare-earth luminescent center with plasmonic nanostructure can largely expand the application of upconversion materials.
关键词： surface-enhanced spectroscopy,mechanism,plasmonic nanostructure,Plasmon-enhanced upconversion photoluminescence,application,rare earth ions
更新于2025-09-10 09:29:36
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Influence of the Tb3+ concentration on the luminescent properties of high silica glass
摘要： Tb3+- doped high silica glass was prepared by sintering porous glass. The density, valence state and amount of Tb, transmittance, photoexcitation spectra, photoluminescence spectra, and cathodoluminescence spectra (CL) were recorded and the luminescence decay kinetics analyzed in details. These results show that the doping concentration in high silica glass is in direct proportion to the concentration in solution, and the density increases with the increasing concentration of rare earth ions as well as the intensity of emission spectrum. The largest emission intensity of 0.2 mol/L is more than 2 times higher than the intensity of the 0.05 mol/L. Besides, the “red” shift phenomenon could be distinguished clearly in the transmittance spectra. There is a broad band at the “red” region in the CL spectra. The decay time which is in the millisecond range in di?erent spectral range were measured and analyzed revealing that the decay time of 5D3 is shorter than that of 5D4.
关键词： Luminescent properties,Rare earth ions,High silica porous glass
更新于2025-09-10 09:29:36
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Leaching of Rare Earth Metals from Phosphor Coating of Waste Fluorescent Lamps
摘要： Phosphors made from compounds of rare earth metals (REMs) are very efficient. This material needs to be recycled for recovery of REMs after the fluorescent lamps (FLs) reach end of life. This work focuses on the leaching studies of REMs from phosphor. The phosphor was recovered from the spent linear FLs by end cut-push method. After detailed characterization of phosphor, effects of parameters viz. leachant, concentration, temperature, and pulp density were studied to determine the optimum leaching conditions. By using 9% (v/v) H2SO4, 98.6% (w/w) yttrium and 96.2% (w/w) europium could be leached out from phosphor at temperature, 70 °C, time, 4 h, and pulp density, 10% (w/v). The residue generated was treated with 54% (v/v) HCl to leach out 98.9% (w/w) lanthanum, 98.2% (w/w) cerium and 96.5% (w/w) terbium at temperature, 90 °C, time, 2 h, and pulp density, 10% (w/v). Kinetic studies of leaching reactions were also carried out.
关键词： Phosphor,Leaching,Waste recycling,Rare earth metals,Fluorescent lamps
更新于2025-09-09 09:28:46
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Color tunable emission from CaS:Cu+, Mn2+ rare-earth-free phosphors prepared by a simple carbon-thermal reduction method
摘要： Photoluminescence properties of CaS:Cu+, CaS:Mn2+ and CaS:Cu+, Mn2+ rare-earth-free phosphors prepared by a carbon-thermal reduction method were investigated. The emission spectrum of Cu+-doped CaS consists of two overlapped bands peaking at 415 nm (attributed to isolated Cu+ activator) and 475 nm (attributed to aggregated Cu+ center). The influence of Cu+ doping concentration on the emission spectrum is discussed. The emission spectrum of Mn2+-doped CaS exhibits a band emission peaking at 568 nm under 250 nm excitation. The emission spectra of the doubly activated CaS:Cu+, Mn2+ phosphors consist of Cu+ and Mn2+ emissions simultaneously, and their shapes depend strongly on the Mn2+ concentration. Based on the emission and excitation spectra of the CaS:0.15 mol%Cu+, xMn2+ phosphors, the energy transfer from Cu+ to Mn2+ takes place. The emitting colors of the doubly activated phosphors can also be tuned. In particular, the emitting color of CaS:0.15 mol% Cu+, 0.6 mol % Mn2+ sample is close to white light.
关键词： Carbon-thermal reduction method,Photoluminescence,CaS:Cu+, Mn2+,Rare-earth-free phosphor
更新于2025-09-09 09:28:46
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Surface potential and thin film quality of low work function metals on epitaxial graphene
摘要： Metal films deposited on graphene are known to influence its electronic properties, but little is known about graphene’s interactions with very low work function rare earth metals. Here we report on the work functions of a wide range of metals deposited on n-type epitaxial graphene (EG) as measured by Kelvin Probe Force Microscopy (KPFM). We compare the behaviors of rare earth metals (Pr, Eu, Er, Yb, and Y) with commonly used noble metals (Cr, Cu, Rh, Ni, Au, and Pt). The rare earth films oxidize rapidly, and exhibit unique behaviors when on graphene. We find that the measured work function of the low work function group is consistently higher than predicted, unlike the noble metals, which is likely due to rapid oxidation during measurement. Some of the low work function metals interact with graphene; for example, Eu exhibits bonding anomalies along the metal-graphene perimeter. We observe no correlation between metal work function and photovoltage, implying the metal-graphene interface properties are a more determinant factor. Yb emerges as the best choice for future applications requiring a low-work function electrical contact on graphene. Yb films have the strongest photovoltage response and maintains a relatively low surface roughness, ~5 nm, despite sensitivity to oxidation.
关键词： work function,Kelvin Probe Force Microscopy,photovoltage,rare earth metals,graphene
更新于2025-09-09 09:28:46
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Efficient improvement of 2.7μm luminescence of Er3+:oxyfluorideglass containing gallium by Yb3+ions codoping
摘要： Mid-infrared laser materials with low phonon energy have significant applications. However, the development of available glass systems for high-power laser gain medium have posed a great challenge. Therefore, we investigated the 2.7 μm spectroscopic properties of Er3+/Yb3+-codopedoxyfluoride glass containing gallium, which were prepared by typically melting and quenching methods. The 2.7 μm luminescence properties of the Er3+/Yb3+-codopedoxyfluoride glass containing gallium were recorded by a 980 nm laser diode. The Judd–Ofelt parameters, decay curves, emission cross section, energy transfer efficiency, and quantum efficiency were calculated. The maximum emission cross section of YbFGa-0.5 is 1.63×10?20 cm2 by 980 nm excitation. The energy transfer efficiency is calculated to be 77.8% for the YbFGa-0.5 glass around 2700 nm. The quantum efficiency at 1530 nm is 65.6%. The resulting reveals that the best doping concentration ratio of Er3+:Yb3+ ions is 1:0.5, and suggests an effective energy transfer from Yb3+ to Er3+ ions.
关键词： optical materials,rare-earth ions doped,optical spectroscopy,mid-infrared,energy transfer
更新于2025-09-09 09:28:46
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Future prospects of fluoride based upconversion nanoparticles for emerging applications in biomedical and energy harvesting
摘要： Rare earth doped/codoped phosphors have been extensively studied for different types of applications based on their intense luminescence features. For this, researchers have tried to choose the inorganic host matrices having both a low phonon cut-off frequency and a high refractive index. Many articles have been published on oxide based phosphor materials, but due to their high cut-off phonon frequency, use of these materials is restricted for optical based applications. This is why additional research has been carried out on fluoride based host materials because of their low phonon frequencies, low composition degradation, and high quantum efficiency. In this paper, the authors review the rare earth fluoride based host nano- and micromaterials for different applications and discuss possible mechanisms.
关键词： biomedical applications,fluoride based upconversion nanoparticles,energy harvesting,luminescence,rare earth doped phosphors
更新于2025-09-09 09:28:46