Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 91
Filtrar
Mais filtros

Base de dados
País/Região como assunto
Tipo de documento
Intervalo de ano de publicação
1.
J Am Chem Soc ; 2024 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-39051979

RESUMO

A battery is composed of two electrodes that depend on and interact with each other. However, galvanostatic charging-discharging measurement, the most widely used method for battery evaluation, cannot simultaneously reflect performance metrics [capacity, Coulombic efficiency (CE), and cycling stability] of both electrodes because the result is generally governed by the lower-capacity electrode of the cell, namely the limiting reagent of the battery reaction. In studying stoichiometric Li-S cells operating under application-relevant high-mass-loading and lean-electrolyte conditions, we take advantage of the two-stage discharging behavior of sulfur to construct a simple framework that allows us to analyze both electrodes simultaneously. The cell capacity and its decay are anode performance descriptors, whereas the first plateau capacity and cell CE are cathode performance descriptors. Our analysis within this frame identifies Li stripping/plating and polysulfide shuttling to be the limiting factors for the cycling performance of the stoichiometric Li-S cell. Using our newly developed framework, we examine various previously reported strategies to mitigate these bottleneck problems and find modifying the separator with a reduced graphene oxide layer to be an effective means, which improves the capacity retention rate of the cell to 99.7% per cycle.

2.
Small ; 19(26): e2207919, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36938911

RESUMO

Constructing active heterointerfaces is powerful to enhance the electrochemical performances of transition metal dichalcogenides, but the interface density regulation remains a huge challenge. Herein, MoO2 /MoS2 heterogeneous nanorods are encapsulated in nitrogen and sulfur co-doped carbon matrix (MoO2 /MoS2 @NSC) by controllable sulfidation. MoO2 and MoS2 are coupled intimately at atomic level, forming the MoO2 /MoS2 heterointerfaces with different distribution density. Strong electronic interactions are triggered at these MoO2 /MoS2 heterointerfaces for enhancing electron transfer. In alkaline media, the optimal material exhibits outstanding hydrogen evolution reaction (HER) performances that significantly surpass carbon-covered MoS2 nanorods counterpart (η10 : 156 mV vs 232 mV) and most of the MoS2 -based heterostructures reported recently. First-principles calculation deciphers that MoO2 /MoS2 heterointerfaces greatly promote water dissociation and hydrogen atom adsorption via the O-Mo-S electronic bridges during HER process. Moreover, benefited from the high pseudocapacitance contribution, abundant "ion reservoir"-like channels, and low Na+ diffusion barrier appended by high-density MoO2 /MoS2 heterointerfaces, the material delivers high specific capacity of 888 mAh g-1 , remarkable rate capability and cycling stability of 390 cycles at 0.1 A g-1 as the anode of sodium ion battery. This work will undoubtedly light the way of interface density engineering for high-performance electrochemical energy conversion and storage systems.

3.
Phys Chem Chem Phys ; 25(42): 29303-29309, 2023 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-37876211

RESUMO

Near-infrared (NIR) phosphors with high thermal stability are significant for NIR light-emitting diodes (LEDs). For a decade, Debye temperature has been a successful indicator of structural rigidity and thermal stability for phosphors, but some exceptions exist due to its dependence on atomic mass. Inspired by the Debye temperature model that relates the elastic properties of solids, our density functional theory calculations revealed that the Vickers hardness of Cr3+-doped NIR phosphors was negatively correlated with Stokes shifts (Pearson's R = -0.81) and positively correlated with thermal stabilities (Pearson's R = 0.85) within a set of 13 distinct material types. Highlighting the predictive power of Vickers hardness, two new NIR phosphors were investigated: KMg(PO3)3:Cr3+ showed low thermal stability, correlating with its lower Vickers hardness, in contrast to the high thermal stability and correspondingly higher Vickers hardness of La2MgSnO6:Cr3+. Vickers hardness can be used to screen potential hosts for Cr3+-doped NIR phosphors with high thermal stabilities, due to the advantages of the predictable feature by density functional theory calculation and low independence on atomic mass.

4.
Pestic Biochem Physiol ; 195: 105543, 2023 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-37666614

RESUMO

The rapid evolution of pest resistance threatens the sustainable utilization of bioinsecticides such as abamectin, and so deciphering the molecular mechanisms affecting toxicity and resistance is essential for their long-term application. Historical studies of abamectin resistance in arthropods have mainly focused on mechanisms involving the glutamate-gated chloride channel (GluCl) targets, with the role of metabolic processes less clear. The two-spotted spider mite, Tetranychus urticae, is a generalist herbivore notorious for rapidly developing resistance to pesticides worldwide, and abamectin has been widely used for its control in the field. After reanalyzing previous transcriptome and RNA-seq data, we here identified an ABC transporter subfamily C gene in T. urticae named multidrug resistance-associated protein 1 (TuMRP1), whose expression differed between susceptible and resistant populations. Synergism bioassays with the inhibitor MK-571, the existence of a genetic association between TuMRP1 expression and susceptibility to abamectin, and the effect of RNA interference mediated silencing of TuMRP1 were all consistent with a direct role of this transporter protein in the toxicity of abamectin. Although ABC transporters are often involved in removing insecticidal compounds from cells, our data suggest either an alternative role for these proteins in the mechanism of action of abamectin or highlight an indirect association between their expression and abamectin toxicity.


Assuntos
Tetranychidae , Animais , Tetranychidae/genética , Proteínas Associadas à Resistência a Múltiplos Medicamentos , Ivermectina/toxicidade
5.
Angew Chem Int Ed Engl ; 62(35): e202307868, 2023 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-37366547

RESUMO

Orange Eu2+ -doped phosphors are essential for light-emitting diodes for cornering lights to prevent fatal road accidents at night, but such phosphors require features of high thermal, chemical stability and facile synthesis. This study reports a series of yellow-orange-red emitting SrAl2 Si3 ON6 :Eu2+ oxynitride phosphors, derived from the SrAlSi4 N7 nitride iso-structure by replacing Si4+ -N3- with Al3+ -O2- . The introduction of a certain amount of oxygen enabled the facile synthesis under atmospheric pressure using the air-stable raw materials SrCO3 , Eu2 O3 , AlN and Si3 N4 . SrAl2 Si3 ON6 has a smaller band gap and lower structure rigidity than SrAlSi4 N7 (5.19 eV vs 5.50 eV, Debye temperature 719 K vs 760 K), but exhibits higher thermal stability with 100 % of room temperature intensity remaining at 150 °C compared to 85 % for SrAlSi4 N7 . Electron paramagnetic resonance, thermoluminescence and density functional theory revealed that the oxygen vacancy electron traps compensated the thermal loss. Additionally, no decrease in emission intensity was found after either being heated at 500 °C for 2 hours or being immersed in water for 20 days, implying both of the thermal and chemical stability of SrAl2 Si3 ON6 :Eu2+ phosphors. The strategy of oxynitride-introduction from nitride promotes the development of low-cost thermally and chemically stable luminescent materials.

6.
Arch Gynecol Obstet ; 305(1): 139-147, 2022 01.
Artigo em Inglês | MEDLINE | ID: mdl-34528140

RESUMO

PURPOSE: The aim of this study was to investigate differentially expressed proteins (DEPs) and their functions in the uteruses of primary dysmenorrhea (PD) rats using label-free quantitative proteomics analysis. METHODS: The PD rat model was induced by injecting both estradiol benzoate and oxytocin. Twenty rats were equally divided into two groups: a control group (normal rats), a PD model group (PD rats). Writhing scores and serum levels of Prostaglandin E2 (PGE2) and Prostaglandin F2α (PGF2α) were used to evaluate the success of the rat PD model. The DEPs were identified and analyzed by label-free quantitative proteomics and bioinformatics analyses. RESULTS: A total of 276 DEPs were identified, including 119 up-regulated DEPs and 157 down-regulated DEPs. Bioinformatics revealed that the DEPs were mainly associated with 'protein binding', 'metabolism', 'signal conduction' and 'focal adhesion'. The proteomic findings were verified by western blot analysis, which confirmed that myosin light-chain kinase (MLCK), heat shock protein 90 AB1 (HSP90AB1), apolipoprotein A1 (Apoa1), p38 MAP kinase, c-Jun N-terminal kinase (JNK), and extracellular signal-related kinase 1/2 (ERK1/2) were significantly differentially expressed in the control and PD samples. CONCLUSIONS: These results provide a deeper understanding of the molecular pathogenesis of PD. The DEPs found in the present study may provide new ideas for further study of the mechanism of PD and aid the search for biomarkers for early diagnosis and treatment.


Assuntos
Dismenorreia , Proteômica , Animais , Biologia Computacional , Dinoprostona , Dismenorreia/terapia , Feminino , Humanos , Ratos , Útero
7.
Angew Chem Int Ed Engl ; 61(28): e202204411, 2022 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-35481661

RESUMO

The minimization of thermal quenching, which leads to luminescence loss at high temperatures, is one of the most important issues for near-infrared phosphors. In the present work, we investigated the properties of near-infrared Ca(Sc,Mg)(Al, Si)O6 : Cr3+ phosphors with a pyroxene-type structure under blue light excitation. The CaScAlSiO6 : Cr3+ end member of Ca(Sc,Mg)(Al,Si)O6 : Cr3+ phosphor led to broadband emission at a full-width half maximum of 215 nm, whereas the CaMgSi2 O6 : Cr3+ end member exhibited high thermal stability at 150 °C, with an intensity of 88.4 % of that at room temperature. The structural analysis and density functional theory calculations revealed the absence of soft conformations and local space confinement contributed to the high structural rigidity and weakened the thermal quenching effect.

8.
Angew Chem Int Ed Engl ; 60(8): 3940-3945, 2021 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-33200499

RESUMO

A solvent-vapor transport route produces centimeter-sized single-crystal red phosphors. The epitaxial growth route to yield its core-shell structure at ambient temperature was adopted. These red phosphors could be applied in all-inorganic WLED devices. Cs2 TiF6 :Mn4+ (CTFM) single crystal provides enhancement of quantum efficiency, moisture resistance, and thermal stability compared to polycrystalline powders. The internal quantum efficiency can reach as high as 98.7 %. To further improve waterproof stability, the Cs2 TiF6 (CTF) shell with tunable thickness has been epitaxially grown on the CTFM single crystal surface and a unique three-step photoluminescence intensity evolution mechanism has been proposed. By combining as-prepared CTFM@CTF core-shell structured single crystal, YAG:Ce single crystal and blue-chip, warm WLEDs with excellent color rendition (Ra =90, R9 =94), low correlated color temperature (CCT=3155 K), and high luminous efficacy were fabricated without any organic resins.

9.
Small ; 16(28): e2000040, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32519511

RESUMO

Structures comprising high capacity active material are highly desirable in the development of advanced electrodes for energy storage devices. However, the structure degradation of such material still remains a challenge. The construction of amorphous and crystalline heterostructure appears to be a novel and effectual strategy to figure out the problem, owing to the distinct properties of the amorphous protective layer. Herein, crystalline-Co3 O4 @amorphous-TiO2 core-shell nanoarrays directly grown on the carbon cloth substrate are rationally designed to construct the free-standing electrode. In the unique structure, the 3D porous nanoarrays provide increased availability of electrochemical active sites, and the array with a unique heterostructure of crystalline Co3 O4 core and amorphous TiO2 shell exhibits intriguing synergistic properties. Besides, the amorphous TiO2 protective layer shows elastic behavior to mitigate the volume effect of Co3 O4 . Benefiting from these structural advantages, the as-prepared free-standing electrode exhibits superior lithium storage properties, including high coulombic efficiency, outstanding cyclic stability, and rate capability. Pouch cells with high flexibility are also fabricated and show remarkable electrochemical performances, holding great potential for flexible electronic devices in the future.

10.
Angew Chem Int Ed Engl ; 59(47): 20909-20913, 2020 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-32761724

RESUMO

The practical applications of non-aqueous lithium-oxygen batteries are impeded by large overpotentials and unsatisfactory cycling durability. Reported here is that commonly encountered fatal problems can be efficiently solved by using a carbon- and binder-free electrode of titanium coated with TiO2 nanotube arrays (TNAs) and gold nanoparticles (AuNPs). Ultraviolet irradiation of the TNAs generates positively charged holes, which efficiently decompose Li2 O2 and Li2 CO3 during recharging, thereby reducing the overpotential to one that is near the equilibrium potential for Li2 O2 formation. The AuNPs promote Li2 O2 formation, resulting in a large discharge capacity. The electrode exhibits excellent stability with about 100 % coulombic efficiency during continuous cycling of up to 200 cycles, which is due to the carbon- and binder-free composition. This work reveals a new strategy towards the development of highly efficient oxygen electrode materials for lithium-oxygen batteries.

11.
Angew Chem Int Ed Engl ; 56(35): 10357-10361, 2017 08 21.
Artigo em Inglês | MEDLINE | ID: mdl-28649746

RESUMO

Samples of the Ca3 Sc2 Si3 O12 (CSS) host singly doped with Eu2+ or Yb3+ , doubly doped with Eu2+ and Yb3+ , and triply doped with Ce3+ , Eu2+ and Yb3+ were synthesized by a sol-gel combustion process under reducing conditions. Unlike previous reports of Eu2+ →Yb3+ energy transfer in other systems, the energy transfer is resonant in the CSS host and the transfer efficiency reaches 100 % for lightly doped samples. The transfer mechanism is multipolar rather than electron transfer for the sample compositions employed herein. The emission intensity of Yb3+ is further enhanced by co-doping with Ce3+ in addition to Eu2+ . The quantum efficiencies of the doped materials range between 9 % and 93 %.

12.
Inorg Chem ; 53(21): 11589-97, 2014 Nov 03.
Artigo em Inglês | MEDLINE | ID: mdl-25303629

RESUMO

The solubility of Ce in the La(1-x)Ce(x)SrGa3O(7+δ) and La(1.54-x)Ce(x)Sr0.46Ga3O(7.27+δ) melilites was investigated, along with the thermal redox stability in air of these melilites and the conductivity variation associated with oxidization of Ce(3+) into Ce(4+). Under CO reducing atmosphere, the La in LaSrGa3O7 may be completely substituted by Ce to form the La(1-x)Ce(x)SrGa3O(7+δ) solid solution, which is stable in air to ∼600 °C when x ≥ 0.6. On the other side, the La(1.54-x)Ce(x)Sr0.46Ga3O(7.27+δ) compositions displayed much lower Ce solubility (x ≤ 0.1), irrespective of the synthesis atmosphere. In the as-made La(1-x)CexSrGa3O(7+δ), the conductivity increased with the cerium content, due to the enhanced electronic conduction arising from the 4f electrons in Ce(3+) cations. At 600 °C, CeSrGa3O(7+δ) showed a conductivity of ∼10(-4) S/cm in air, nearly 4 orders of magnitude higher than that of LaSrGa3O7. The oxidation of Ce(3+) into Ce(4+) in CeSrGa3O(7+δ) slightly reduced the conductivity, and the oxygen excess did not result in apparent increase of oxide ion conduction in CeSrGa3O(7+δ). The Ce doping in air also reduced the interstitial oxide ion conductivity of La1.54Sr0.46Ga3O7.27. Neutron powder diffraction study on CeSrGa3O7.39 composition revealed that the extra oxygen is incorporated in the four-linked GaO4 polyhedral environment, leading to distorted GaO5 trigonal bipyramid. The stabilization and low mobility of interstitial oxygen atoms in CeSrGa3O(7+δ), in contrast with those in La(1+x)Sr(1-x)Ga3O(7+0.5x), may be correlated with the cationic size contraction from the oxidation of Ce(3+) to Ce(4+). These results provide a new comprehensive understanding of the accommodation and conduction mechanism of the oxygen interstitials in the melilite structure.

13.
Inorg Chem ; 53(13): 6962-8, 2014 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-24903712

RESUMO

K/Na-doped SrSiO3-based oxide ion conductors were recently reported as promising candidates for low-temperature solid-oxide fuel cells. Sr0.7K0.3SiO2.85, close to the solid-solution limit of Sr1-xKxSiO3-0.5x, was characterized by solid-state (29)Si NMR spectroscopy and neutron powder diffraction (NPD). Differing with the average structure containing the vacancies stabilized within the isolated Si3O9 tetrahedral rings derived from the NPD study, the (29)Si NMR data provides new insight into the local defect structure in Sr0.7K0.3SiO2.85. The Q(1)-linked tetrahedral Si signal in the (29)Si NMR data suggests that the Si3O9 tetrahedral rings in the K-doped SrSiO3 materials were broken, forming Si3O8 chains. The Si3O8 chains can be stabilized by either bonding with the oxygen atoms of the absorbed lattice water molecules, leading to the Q(1)-linked tetrahedral Si, or sharing oxygen atoms with neighboring Si3O9 units, which is consistent with the Q(3)-linked tetrahedral Si signal detected in the (29)Si NMR spectra.

14.
Int J Mol Sci ; 15(8): 13550-63, 2014 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-25100168

RESUMO

Neuroprotection of lithium for axotomized retinal ganglion cells (RGCs) is attributed to upregulated intraretinal Bcl-2. As lithium also upregulates brain-derived neurotrophic factor (BDNF) which can rescue axotomized RGCs, it is hypothesized that lithium could protect RGCs through BDNF. This study investigated this hypothesis and a possible relationship between the dose and protection of lithium. All adult experimental rats received daily intraperitoneal injections of lithium chloride (LiCl) at 30, 60 or 85 mg/kg·bw until they were euthanized 2, 7 or 14 days after left intraorbital optic nerve (ON) transection. Our results revealed that RGC densities promoted and declined with increased dose of LiCl and the highest RGC densities were always in the 60 mg/kg·bw LiCl group at both 7 and 14 day points. Similar promotion and decline in the mRNA and protein levels of intraretinal BDNF were also found at the 14 day point, while such BDNF levels increased in the 30 mg/kg·bw LiCl group but peaked in the 60 and 85 mg/kg·bw LiCl groups at the 7 day point. These findings suggested that lithium can delay the death of axotomized RGCs in a dose-dependent manner within a certain period after ON injury and such beneficial effect is interrelated with an upregulated level of intraretinal BDNF.


Assuntos
Fator Neurotrófico Derivado do Encéfalo/metabolismo , Cloreto de Lítio/farmacologia , Substâncias Protetoras/farmacologia , Células Ganglionares da Retina/efeitos dos fármacos , Regulação para Cima/efeitos dos fármacos , Animais , Fator Neurotrófico Derivado do Encéfalo/genética , Relação Dose-Resposta a Droga , Feminino , Imuno-Histoquímica , Traumatismos do Nervo Óptico/metabolismo , Traumatismos do Nervo Óptico/patologia , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Retina/metabolismo , Retina/patologia , Células Ganglionares da Retina/metabolismo , Fatores de Tempo
15.
Nat Commun ; 15(1): 3209, 2024 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-38615033

RESUMO

The manipulation of excitation modes and resultant emission colors in luminescent materials holds pivotal importance for encrypting information in anti-counterfeiting applications. Despite considerable achievements in multimodal and multicolor luminescent materials, existing options generally suffer from static monocolor emission under fixed external stimulation, rendering them vulnerability to replication. Achieving dynamic multimodal luminescence within a single material presents a promising yet challenging solution. Here, we report the development of a phosphor exhibiting dynamic multicolor photoluminescence (PL) and photo-thermo-mechanically responsive multimodal emissions through the incorporation of trace Mn2+ ions into a self-activated CaGa4O7 host. The resulting phosphor offers adjustable emission-color changing rates, controllable via re-excitation intervals and photoexcitation powers. Additionally, it demonstrates temperature-induced color reversal and anti-thermal-quenched emission, alongside reproducible elastic mechanoluminescence (ML) characterized by high mechanical durability. Theoretical calculations elucidate electron transfer pathways dominated by intrinsic interstitial defects and vacancies for dynamic multicolor emission. Mn2+ dopants serve a dual role in stabilizing nearby defects and introducing additional defect levels, enabling flexible multi-responsive luminescence. This developed phosphor facilitates evolutionary color/pattern displays in both temporal and spatial dimensions using readily available tools, offering significant promise for dynamic anticounterfeiting displays and multimode sensing applications.

16.
Adv Mater ; : e2406164, 2024 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-38924614

RESUMO

The quest for artificial light sources mimicking sunlight has been a long-standing endeavor, particularly for applications in anticounterfeiting, agriculture, and color hue detection. Conventional sunlight simulators are often cost-prohibitive and bulky. Therefore, the development of a series of single-phase phosphors Ca9LiMg1-xAl2x/3(PO4)7:0.1Eu2+ (x = 0-0.75) with sunlight-like emission represents a welcome step towards compact and economical light source alternatives. The phosphors are obtained by an original heterovalent substitution method and emit a broad spectrum   spanning from violet to deep red. Notably, the phosphor with x = 0.5 exhibits an impressive full width at half-maximum of 330 nm. A synergistic interplay of experimental investigations and theory unveils the mechanism behind sunlight-like emission due to the local structural perturbations introduced by the heterovalent substitution of Al3+ for Mg2+, leading to a varied distribution of Eu2+ within the lattice. Subsequent characterization of a series of organic dyes combining absorption spectroscopy with convolutional neural network analysis convincingly demonstrates the potential of this phosphor in portable photodetection devices. Broad-spectrum light source testing empowers the model to precisely differentiate dye patterns. This points to the phosphor being ideal for mimicking sunlight. Beyond this demonstrated application, the phosphor's utility is envisioned in other relevant domains, including visible light communication and smart agriculture.

17.
Opt Express ; 21(3): 3161-9, 2013 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-23481775

RESUMO

An efficient near-infrared (NIR) phosphor LiSrPO(4):Eu(2+), Pr(3+) is synthesized by solid-state reaction and systematically investigated using x-ray diffraction, diffuse reflection spectrum, photoluminescence spectra at room temperature and 3 K, and the decay curves. The UV-Vis-NIR energy transfer mechanism is proposed based on these results. The results demonstrate Eu(2+) can be an efficient sensitizer for harvesting UV photon and greatly enhancing the NIR emission of Pr(3+) between 960 and 1060 nm through efficient energy feeding by allowed 4f-5d absorption of Eu(2+) with high oscillator strength. Eu(2+)/Pr(3+) may be an efficient donor-acceptor pair as solar spectral converter for Si solar cells.


Assuntos
Fontes de Energia Elétrica , Lítio/química , Medições Luminescentes/instrumentação , Energia Solar , Transferência de Energia , Desenho de Equipamento , Análise de Falha de Equipamento , Raios Infravermelhos , Raios Ultravioleta
18.
Phys Chem Chem Phys ; 15(24): 9768-74, 2013 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-23673457

RESUMO

In this work, we selectively prepared two samples with quite different nanocrystal shapes, i.e. nanoplates and nanograins but with almost identical surface areas to make a clear comparison of nanocrystal shapes on electrochemical performance. The electrochemical results indicate that the thinner hexagonal α-Fe2O3 nanoplates considerably enclosed by two larger (0001) basal surfaces exhibit higher capacity and stability than thicker α-Fe2O3 nanograins enclosed by a variety of crystal facets. During the conversion reaction, an orientated growth of porous nanostructure with orientated nanowalls as a stable framework is observed for the nanoplate, readily supplying a pathway for long and easy lithiation-delithiation cycling. The improved electrochemical performance of α-Fe2O3 nanoplates is surely related to the nanostructure with significantly stacked (0001) lattice planes along [0001] direction for orientated growth of γ-Fe2O3 nanodomains along one [111] direction.

19.
Nanomaterials (Basel) ; 13(13)2023 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-37446426

RESUMO

To develop novel luminescent materials for optical temperature measurement, a series of Yb3+- and Er3+-doped Ca3Sc2Si3O12 (CSS) upconversion (UC) phosphors were synthesized by the sol-gel combustion method. The crystal structure, phase purity, and element distribution of the samples were characterized by powder X-ray diffraction and a transmission electron microscope (TEM). The detailed study of the photoluminescence emission spectra of the samples shows that the addition of Yb3+ can greatly enhance the emission of Er3+ by effective energy transfer. The prepared Yb3+ and Er3+ co-doped CSS phosphors exhibit green emission bands near 522 and 555 nm and red emission bands near 658 nm, which correspond to the 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 transitions of Er3+, respectively. The temperature-dependent behavior of the CSS:0.2Yb3+,0.02Er3+ sample was carefully studied by the fluorescence intensity ratio (FIR) technique. The results indicate the excellent sensitivity of the sample, with a maximum absolute sensitivity of 0.67% K-1 at 500 K and a relative sensitivity of 1.34% K-1 at 300 K. We demonstrate here that the temperature measurement performance of FIR technology using the CSS:Yb3+,Er3+ phosphor is not inferior to that of infrared thermal imaging thermometers. Therefore, CSS:Yb3+,Er3+ phosphors have great potential applications in the field of optical thermometry.

20.
Dalton Trans ; 52(15): 4808-4818, 2023 Apr 11.
Artigo em Inglês | MEDLINE | ID: mdl-36939174

RESUMO

A Sm3+-doped YGa1.5Al1.5(BO3)4 (abbreviated as YGAB) phosphor was synthesized via a solid-state reaction with mechanical activation assistance in a high-energy density stirred bead mill. The samples were characterized by laser particle size analysis, specific surface area analysis, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and fluorescence spectroscopy. In addition, the photoluminescence characteristics, luminescence decay, thermal stability, and LED application of the phosphors were also investigated. The results show that the mechanical activation of mixed raw materials before calcination can reduce the particle size and the activation energy of crystallization, resulting in the formation of the YGAB crystal phase at a lower calcination temperature. The mechanical activation in grinding can accelerate the subsequent solid-phase reaction, make Sm3+ ions more easily diffuse into the YGAB lattice, and improve the crystal structure of the synthesized phosphor, thus enhancing the optical properties of the phosphor. According to the photoluminescence emission (PL) and excitation (PLE) spectra, Sm3+ doped in the YGAB lattice can provide an efficient emission under 405 nm excitation. The optimum doping concentration of Sm3+ ions is 0.03 mol%. The optimum photoluminescence intensity, quantum yield, and fluorescence lifetime of the phosphor synthesized from mixed raw materials ground for 45 min can be obtained. The temperature-dependent PL spectra show that the emission intensity of the YGAB:0.03Sm3+ phosphor at 425 K is 84.7% of its initial intensity at room temperature. It is indicated that the YGAB:0.03Sm3+ phosphor synthesized could be used as one of the promising LED lighting materials.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA