改性纳米二氧化钛的探讨

用溶胶-凝胶法制备了掺有钼元素的二氧化钛溶胶,将它和没有掺杂的二氧化钛溶胶一起用紫外分光光度计扫描发现:掺杂的二氧化钛溶胶的吸收波段红移了。用均匀沉淀法制备的分别掺有硒、镧、铈的纳米二氧化钛,它们对甲基橙的降解能力依次降低,但与没掺杂的产品比较,其光催化降解能力都增强了。在掺杂量小于1%时,掺入硒效果最好。     

桑椹天然植物染料的稳定性能

研究了桑椹天然植物染料在不同条件下的稳定性能.通过测试染液可见吸收光谱来探讨酸碱、温度、光照以及金属离子对桑椹天然植物染液的影响.结果显示:桑椹天然植物染液可见吸收光谱在紫外区域出现新的吸收峰且峰形尖锐,随pH提高而出现吸收峰红移现象(逐渐减弱并消失),染料适合在酸性浴(pH≤4)或碱性浴(pH≥8)中染色;在80℃以下稳定性良好,但耐光性较差,长时间的光照使染液色泽灰暗,鲜艳度下降:Al<'3+>使染液表现出明显的增色效应和轻微的吸收峰红移现象,Mg<'2+>对染液颜色影响很小、Cu<'2+>有轻微增色效应,加入Fe<'3+>染液吸收峰红移(逐渐减弱消失并在紫外光区域出现末端吸收效应).     

Multi-Mode Optical Manometry Based on Li4SrCa(SiO4)2:Eu2+ Phosphors

Optical manometry is a highly promising method for measuring pressure. However, its wider application is limited by the lower sensitivity and influenced by environmental factors. Herein, multi-mode optical pressure sensors based on Eu²⁺-doped Li₄SrCa(SiO₄)₂ phosphors suitable for a variety of complex pressure-measuring environments are designed. The phosphors contain two separate luminescence centers at 443 nm (Eu_Sr) and 584 nm (Eu_Ca), respectively. In the lower pressure range, the emission peak undergoes a massive redshift of 5.19 nm GPa⁻¹ of Eu_Ca, which is 14× better than commercially available ruby sensors. In order to improve the pressure response range and the accuracy of pressure measurement, for the first time, a new approach in the pressure readout method in which single Eu²⁺ ions doping based on fluorescence intensity ratio (FIR) pressure measurement is realized in designed materials. Meanwhile, the measured full width at half maximum (FWHM) as an indicator of pressure sensor performance also reveals that the sensing performance is d FWHM/d P ≈ 1.23 nm GPa⁻¹ and d FWHM/d P ≈ 0.84 nm GPa⁻¹ for Eu_Sr and Eu_Ca positions, respectively. Additionally, the structural stability of the phosphor is confirmed by in situ Raman spectrum. The above results indicate that the Li₄SrCa(SiO₄)₂:0.04Eu²⁺ phosphor is a good candidate for multi-mode optical pressure sensors.     

Experimental and theoretical analysis on the charge transfer band of Y_2O_3:Eu nanocrystals

Nanocrystalline cubic Y2O3:Eu were prepared by combustion reaction.The crystal structure and morphology were analyzed by means of X-ray diffraction(XRD) and transmission electron microscopy(TEM).The luminescent properties of the powder were investigated.The charge transfer band position showed redshift from 241 to 251 nm,which was related to the change of the local surroundings of Eu3+ ions in nanocrystalline Y2O3:Eu.The ground-state electronic structure and charge transfer transition of both the bulk and nanocrystalline cubic Y2O3:Eu crystals were calculated by the ab initio self-consistent relativistic DV-Xα(discrete variational Xα) method.A complete 35-ion cluster was selected to simulate the local coordination surroundings of Eu doped in Y2O3 bulk crystals while five additional incomplete clusters were also selected to simulate the local surroundings of Eu ions in nanocrystals.It could be found that the charge transfer energies of the nanocrystalline Y2O3:Eu were less than that of the bulk counterpart,which was consistent with the redshift phenomenon of the CT band in the excitation spectrum of the nanocrystalline Y2O3:Eu.     

Irradiation induced grain growth and surface emission enhancement of chemically tailored ZnS : Mn/PVOH nanoparticles by Cl<Superscript>+9</Superscript> ion impact

Manganese doped zinc sulfide nanoparticles are fabricated on polyvinyl alcohol dielectric matrix. They are bombarded with energetic chlorine ions (100 MeV). The size of the crystallites is found to increase with ion fluence due to melting led grain growth under ion irradiation. The increased size as a result of grain growth has been observed both in the optical absorption spectra in terms of redshift and in electron microscopic images. The photoluminescence (PL) study was carried out by band to band excitation (λ_ex = 220 nm) upon ZnS : Mn, which results into two emission peaks corresponding to surface states and Mn⁺² emission, respectively. The ion fluence for irradiation experiment so chosen were 1 × 10¹¹, 5 × 10¹¹, 5 × 10¹² and 10¹³ Cl/cm².     

Effects of Samarium Doping on Optical Properties of Zn0.9(Co1-xSmx)0.1O Diluted Magnetic Semiconductor

Transparent ZnO and Zn0.9(Co1-xSmx)0.1O (x=0.0, 0.10, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.0) films were prepared by sol-gel method. For the prepared Zn0.9(Co1-xSmx)0.1O systems, the influences of dopant concentration of Sm on the structural and optical properties were investigated. Three additional absorption peaks around 570, 620, and 660 nm wavelengths were observed in low Sm content films, which is attributed to the d-d transitions of Co2 ions in tetrahedral crystalline. The redshift of band gap in doped samples was discussed in detail.     

基于小波分析和密度估计的红移测速导航研究

基于光谱红移天文自主导航思路以及天文学领域求解红移值的方法,提出一种用小波分析和密度估计相结合的方法测飞行器红移值,进而求解速度的测速导航方法。首先采用小波变换滤除噪声并进行光谱归一化,然后采用整体阈值和局部阈值相结合的方法,提取特征谱线,用密度估计法求出红移值,最后结合天文测角信息,计算出飞行器相对于惯性坐标系的速度。采用实测的太阳光谱数据,进行了红移模拟与解算。实验证明该方法在高信噪比的情况下,计算速度快,求解结果精度高达96％,为基于光谱红移的天文导航提供一种新的速度计算方法。     

Deep-red-emitting SrLaLiTeO6: Mn4+ double perovskites: Correlation between Mn4+-O2− bonding and photoluminescence

Mn⁴⁺-activated deep red-emitting SrLaLiTeO₆ phosphors are investigated for indoor plant growth LED applications for the first time. The phosphors crystallize in monoclinic (P2₁/n) symmetry is isostructural with SrLaLiTeO₆ host. B-site substitution of Mn⁴⁺ ions is confirmed from the redshift of high energy phonon modes in both Raman and IR spectra. The phosphor exhibited a far-red emission centered at 696 nm corresponding to the ²E_g → ⁴A_2g spin-forbidden transition of the Mn⁴⁺ ions. Approximate crystal field parameters depict the weak influence of neighboring ligand fields on Mn⁴⁺ ions and the least covalence of Mn⁴⁺-ligand bonding compared to other double perovskite phosphors. Moreover, the phosphors exhibit excellent thermal stability with an activation energy of 0.23 eV. Phosphor parameters including CCT, color purity, and quantum yield are evaluated and their values meet the requirements of a red-emitting phosphor for LED applications. Furthermore, the PL emission spectrum of SrLaLiTeO₆: Mn⁴⁺ matches with the absorption spectrum of plant phytochromes denoting the prospects of this phosphor for indoor plant growth LED applications.     

碳热还原氮化法合成稀土掺杂氮系荧光粉

采用碳热还原氮化法(CRN)制备了Eu2+掺杂SiN4-基氮化物、氮氧化物以及氧化物LED用荧光粉,通过X射线衍射仪和扫描电子显微镜对其结构和形貌进行分析,并通过激发-发射光谱研究了相关荧光粉的光谱特性。结果表明,随着氮化时间的延长以及氮化温度的升高,Eu2+掺杂的SrSiO3∶Eu2+、SrSi2O2N2∶Eu2+、Sr2Si5N8∶Eu2+荧光粉的主要成分比例发生变化,从而导致激发峰位发生变化,主要发射波长出现红移。这类荧光粉能够被近紫外-蓝光之间的光谱激发,呈现出橘红色、黄色、黄绿色、蓝绿色光发射。