Development of Nd (III)-Based Terahertz Absorbers Revealing Temperature Dependent Near-Infrared Luminescence

Molecular vibrations in the solid-state, detectable in the terahertz (THz) region, are the subject of research to further develop THz technologies. To observe such vibrations in terahertz time-domain spectroscopy (THz-TDS) and low-frequency (LF) Raman spectroscopy, two supramolecular assemblies with the formula [Nd^III (phen)₃ (NCX)₃] 0.3EtOH (X = S, 1-S; Se, 1-Se) were designed and prepared. Both compounds show several THz-TDS and LF-Raman peaks in the sub-THz range, with the lowest frequencies of 0.65 and 0.59 THz for 1-S and 1-Se, and 0.75 and 0.61 THz for 1-S and 1-Se, respectively. The peak redshift was observed due to the substitution of SCN⁻ by SeCN⁻. Additionally, temperature-dependent TDS-THz studies showed a thermal blueshift phenomenon, as the peak position shifted to 0.68 THz for 1-S and 0.62 THz for 1-Se at 10 K. Based on ab initio calculations, sub-THz vibrations were ascribed to the swaying of the three thiocyanate/selenocyanate. Moreover, both samples exhibited near-infrared (NIR) emission from Nd (III), and very good thermometric properties in the 300–150 K range, comparable to neodymium (III) oxide-based thermometers and higher than previously reported complexes. Moreover, the temperature dependence of fluorescence and THz spectroscopy analysis showed that the reduction in anharmonic thermal vibrations leads to a significant increase in the intensity and a reduction in the width of the emission and LF absorption peaks. These studies provide the basis for developing new routes to adjust the LF vibrational absorption.     

频率上转换掺稀土氧氟纳米微晶玻璃的研究进展

综述了近年来用于上转换发光的掺稀土离子氧氟微品玻璃的研究概况,阐述了氧氟微品玻璃作为上转换发光材料的发展和研究中问题,提出了值得进一步研究的工作并对掺稀土离子氧氯微晶玻璃未来的前景作了展望。     

Blue Luminescence of ZnO Nanoparticles Based on Non‐Equilibrium Processes: Defect Origins and Emission Controls

High concentrations of defects are introduced into nanoscale ZnO through non‐equilibrium processes and resultant blue emissions are comprehensively analyzed, focusing on defect origins and broad controls. Some ZnO nanoparticles exhibit very strong blue emissions, the intensity of which first increase and then decrease with annealing. These visible emissions exhibit strong and interesting excitation dependences: 1) the optimal excitation energy for blue emissions is near the bandgap energy, but the effective excitation can obviously be lower, even 420 nm (2.95 eV < E_g = 3.26 eV); in contrast, green emissions can be excited only by energies larger than the bandgap energy; and, 2) there are several fixed emitting wavelengths at 415, 440, 455 and 488 nm in the blue wave band, which exhibit considerable stability in different excitation and annealing conditions. Mechanisms for blue emissions from ZnO are proposed with interstitial‐zinc‐related defect levels as initial states. EPR spectra reveal the predominance of interstitial zinc in as‐prepared samples, and the evolutions of coexisting interstitial zinc and oxygen vacancies with annealing. Furthermore, good controllability of visible emissions is achieved, including the co‐emission of blue and green emissions and peak adjustment from blue to yellow.     

Multistimuli‐Responsive Display Materials to Encrypt Differentiated Information in Bright and Dark Fields

Visually readable codes play a crucial role in anticounterfeiting measures. However, current coding approaches do not enable time‐dependent codes to be visually read, adjusted, and differentiated in bright and dark fields. Here, using a combined strategy of piezoelectric lattice selection, oxygen vacancy engineering, and activator doping, a lanthanide ion‐doped titanate is developed that integrates mechano‐, thermo‐, and photo‐responsive color change (>18 h for bright field), persistent luminescence (>6 h for dark field), and stimulus‐triggered multimodal luminescence. The feasibility of optical encoding, visual displaying, and stimulus‐responsive encrypting of time‐dependent, dual‐field information by using the developed material is demonstrated. In particular, the differentiated display of dual‐field modes is achieved by combining mechanostimulated abolition of only the persistent luminescence and thermo‐ and photostimulated reversal of both the color change and persistent luminescence. The results provide new insights for designing advanced materials and encryption technologies for photonic displays, information security, and intelligent anticounterfeiting.     

Strong dependence of upconversion luminescence on doping concentration in holmium and ytterbium co-doped Y2O3 phosphor

Under the excitation of 980 nm diode laser, intense green emission (5F4+5S2-5I8) of Ho3+ was observed in Ho3+ and Yb3+ co-doped cubic Y2O3. The doping concentration and laser power dependence of the upconverted emission were studied. The decay curves of 5F4+5S2 emission of Ho3+ under the excitation of 355 nm pulse laser were measured to investigate the energy transfer process between Ho3+ and Yb3+. The results indicated that two-photon process was responsible for the upconversion (UC) emission. The Ho3+ con...     

低色温高显色性大功率白光LED的制备及其发光特性研究

用GaN基大功率蓝光LED芯片作为激发光源，分别用荧光粉转换法和红光LED补偿法制备了不同相关色温及显色指数的白光LED。对器件的发光特性研究表明，采用监光LED芯片激发单一黄色荧光粉，虽可以获得光通量和发光效率较高的白光LED，但其色温较高，显色性较差；在黄色荧光粉中添加红色荧光粉，由于光谱中红色成分的增加，可降低器件的色温，并提高器件的显色性，但由于目前红色荧光粉的转换效率较低，致使器件的整体发光效率不高；采用蓝光LED芯片激发黄色荧光粉，同时用红光LED进行补偿，通过调整蓝光和红光LED芯片的工作电流以及荧光粉的用量，可获得低色温和高显色性白光LED，而且整体发光效率较高。     

脉冲激光沉积法制备无机发光薄膜的研究现状

阐述了脉冲激光沉积法的基本原理、特点及其应用。分别介绍了超快脉冲激光沉积法、双光束脉冲激光沉积法、脉冲激光气相沉积法、脉冲激光液相沉积法、脉冲激光诱导晶化法、直流放电辅助脉冲激光沉积法、脉冲激光分子束外延法的原理及最新研究成果。展望了脉冲激光沉积法制备无机发光薄膜的发展趋势。     

量子限制效应对限制在多量子阱中受主束缚能的影响

从实验和理论上,研究了量子限制效应对限制在GaAs/AIAs多量子阱中受主对重窄穴束缚能的影响.实验中所用的样品是通过分子束外延技术生长的一系列GaAs/AIAs多量子阱,量子阱宽度从3nm到20nm,并且在量子阱中央进行了浅受主铍(Be)原子的δ掺杂.在4,20,40,80和120K不同温度下,分别对上述系列样品进行了光致发光谱(PL)的测量,清楚地观察到了受主束缚激子从ls3/2(Г6)基态到同种宇称2s3/2(Г6)激发态的两空穴跃迁,并且从实验上测得了在不同量子阱宽度下受主的束缚能.理论上应用量子力学中的变分原理,数值计算了受主对重空穴束缚能随量子阱宽度的变化关系,比较发现理论计算和实验结果符合较好.     

Sm~(3+)掺杂ZBLAN玻璃中一种上转换发光现象的分析

对ZBLAN氟化物玻璃中Sm~(3+)离子在脉冲1.06μm激光激发下产生的上转换发光现象(单光子吸收随后发生激发态双光子吸收)进行了详细的计算和分析。