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991.
Ajeet Kumar Sharma Parul Bansal Gaurav Kumar Nim Prasenjit Kar 《Particle & Particle Systems Characterization》2019,36(12)
This work reports the first synthesis of MAPbBr3 perovskite nanocrystals (PNCs) using amino acids as the ligand with excellent optical properties. A variety of amino acids are used to optimize the luminescence properties. A mechanochemical approach has taken lead over conventional colloidal chemistry during synthesis. All morphological and optical studies are performed to characterize the synthesized perovskite nanoparticles. Later, stability studies are investigated through thermogravimetric analysis, temperature‐dependent photoluminescence, time‐dependent X‐ray diffraction, as well as X‐ray photoelectron spectroscopy. In an application, interestingly, these perovskites show high luminescence upon scratching on flexible conducting plates and on plain paper surface. These results suggest that the amino acid–ligated perovskite nanocrystals can be potential materials for optoelectronic application including light‐emitting diodes and imaging. 相似文献
992.
Photoelectrochemical (PEC) water oxidation for sustainable clean energy and fuel production is a potential solution to the demands of organic pollutant removal and growing energy consumption. Development of high performance photoanodes, which is a key component in the system, is one of the central topics in the area. The crystal defect is an old concept but fruiting new understanding with promotive impact to the development of high performance photoanodes. In this review, we elucidated the typical defects involved in the photoanode with the position where they play the roles in the structure and how the properties of photoanode are influenced. In addition, we summarized the feasible protocols to maximize the pros but reduce the cons brought by having defects to the photoanode performance based on recent most prominent research advancements in the field. Finally, we briefly sketched the future perspective with the challenges of this topic when in the scenario of possible developments into practical applications. 相似文献
993.
《Current Applied Physics》2019,19(9):1052-1061
High brightness and precise adjustment of luminescence colour of phosphors are two main targets in the research of phosphor-converted white LEDs. However, few feasible strategy can be employed to achieve the multicolor-tunable luminescence under the premise of maintaining high quantum efficiency. Here, we demonstrate a high-efficiency energy-transfer process from Tb3+ to Eu3+ ions with a higher luminescent quantum efficiency (64.5% and 53.4%, respectively), and green-red multicolor emission in Lu2GeO5 host via varying the doping content of Tb3+ and Eu3+ ions. Besides, Lu2GeO5:Tb3+, Lu2GeO5: Eu3+ and Lu2GeO5: Tb3+, Eu3+ all exhibit weak thermal quenching which ensures the stable use of white LED device in the high temperature environment. This paper provides a novel multicolor-tunable phosphor with high brightness, efficient energy transfer and weak thermal quenching, which presents a potential application for UV-converted white LEDs. 相似文献
994.
钙钛矿纳米材料的研究取得了飞速发展:一方面,合成方法不断涌现,已经可以实现从零维纳米晶、一维纳米线到二维纳米片的形貌精确控制,对其尺寸和维度依赖的光学性质认识也不断深入;另一方面,钙钛矿纳米材料的光学和光电子应用也得到了快速发展,其中,基于钙钛矿量子点的光致发光和电致发光技术最受关注。 由于钙钛矿的天然层状结构,通过配体调控很容易制备出二维纳米材料,其发光性能可以通过层数和组分进行调节,最高量子产率超过85%,且具有偏振发光特性,有望成为一类新型发光材料。 本文从制备方法、光致发光和电致发光应用等方面综述了基于钙钛矿二维纳米材料的进展,并对其未来的发展方向进行讨论。 相似文献
995.
Highly Bright and Photostable Li(Gd,Y)F4:Yb,Er/LiGdF4 Core/Shell Upconversion Nanophosphors for Bioimaging Applications 下载免费PDF全文
Jeehae Shin Youngsun Kim Jiyeon Lee Sehoon Kim Ho Seong Jang 《Particle & Particle Systems Characterization》2017,34(1)
Intense green‐emitting Li(Gd,Y)F4:Yb,Er/LiGdF4 core/shell (C/S) upconversion nanophosphors (UCNPs) with a tetragonal bipyramidal morphology are synthesized. The morphology and UC luminescence of the Li(Gd,Y)F4:Yb,Er UCNPs are significantly affected by the Li precursors, and bright UC green‐emitting Li(Gd,Y)F4:Yb,Er UCNPs with a tetragonal bipyramidal shape, i.e., UC tetragonal bipyramids (UCTBs), are synthesized using LiOH·H2O as a Li precursor. A LiGdF4 shell is grown on the Li(Gd,Y)F4:Yb,Er UCTBs, and the C/S UCNPs exhibit 4.7 times higher luminescence intensity than core UCTBs. The C/S UCNPs show a high absolute UC quantum yield of 4.6% under excitation with 980 nm near infrared (NIR) light, and the UC luminescence from the C/S UCNPs is stable under continuous irradiation with the 980 nm NIR laser for 1 h. The hydrophobic surfaces of the as‐synthesized C/S UCNPs are modified to hydrophilic surfaces by using poly(acrylic acid) (PAA) for bioimaging applications. They are applied to human cervical adenocarcinoma (HeLa) cell imaging and SK‐MEL‐2 melanoma cell imaging and in vivo imaging, including subcutaneous and intramuscular imaging, and UC luminescence images with high signal‐to‐noise ratio are obtained. Furthermore, sentinel‐lymph‐node imaging is successfully conducted with the PAA‐capped Li(Gd,Y)F4:Yb,Er/LiGdF4 C/S UCNPs under illumination with NIR light. 相似文献
996.
《Wave Motion》2017
We introduce an analytic-numerical method to simulate the interaction between ultrasonic guided waves and defective adhesive bonds in multilayer structures. We replace the thin adhesive layer by equivalent continuous distribution of normal and transversal springs and locally reduce the corresponding spring constants to model localized defects. We then formulate the resulting scattering problem as a linear least squares problem and solve it accordingly. The developed formulation is easy to implement and equally well suited to treating anisotropic as well as isotropic constituent layers. We illustrate the application of the proposed method through the simulation of ultrasound inspection of a three-layer isotropic plate and a sixteen-layer anisotropic plate used in the aeronautical industry, indicating in the simulations the guided modes that will most strongly interact with interfacial defects and computing the scattering resulting from the interaction of these modes with localized defects. We believe that the proposed method will serve both to aid in the design of interface inspections and as a basis for solving inverse scattering problems. 相似文献
997.
998.
According to stationary X-ray-excited luminescence spectra and thermally stimulated luminescence spectra of CaF2:Eu nanophosphors, it was found that Eu3+?→?Eu2+ conversion can occur during thermal annealing of fine-grained (d?=?25?nm) nanoparticles in the 200–800°C range, which is accompanied by an increase in their size within 40–189?nm. An important role of the exciton mechanism of Eu2+ luminescence excitation was revealed according to the temperature dependence of X-ray-excited luminescence spectra of CaF2:Eu nanoparticles of 114?nm size. The maximum of the X-ray-excited luminescence light output of CaF2:Eu nanophosphors in the Eu2+ ions’ emission band was traced out at 400–500°C annealing temperature and at the size of nanoparticles of 114–180?nm. The subsequent growth of the annealing temperatures, particularly in the 800–1000°C range, causes the reduction of X-ray-excited luminescence light output because of the increment of lattice defects’ concentration due to a sharp increase in the size of nanoparticles and their agglomeration. 相似文献
999.
K.D. Mynbaev A.V. Shilyaev A.A. Semakova E.V. Bykhanova N.L. Bazhenov 《Opto-Electronics Review》2017,25(3):209-214
Photoluminescence of HgCdTe epitaxial films and nanostructures and electroluminescence of InAs(Sb,P) light-emitting diode (LED) nanoheterostructures were studied. For HgCdTe-based structures, the presence of compositional fluctuations, which localized charge carriers, was established. A model, which described the effect of the fluctuations on the rate of the radiative recombination, the shape of luminescence spectra and the position of their peaks, was shown to describe experimental photoluminescence data quite reasonably. For InAs(Sb,P) LED nanoheterostructures, at low temperatures (4.2–100 K) stimulated emission was observed. This effect disappeared with the temperature increasing due to the resonant ‘switch-on’ of the Auger process involving transition of a hole to the spin-orbit-splitted band. Influence of other Auger processes on the emissive properties of the nanoheterostructures was also observed. Prospects of employing II–VI and III–V nanostructures in light-emitting devices operating in the mid-infrared part of the spectrum are discussed. 相似文献
1000.
利用波的相干叠加原理推导出一维掺杂声子晶体中SH波缺陷模的透射率公式和频率公式,即建立了缺陷模的相干叠加法。将相干叠加法与转移矩阵法和共振理论进行了比较研究,结果表明缺陷模的相干叠加法具备转移矩阵法和共振理论各自的优点,又克服了转移矩阵法和共振理论各自的不足。相干叠加法是研究一维掺杂声子晶体中SH波缺陷模的一种更有效的方法。 相似文献