基于光谱分析技术的农林生物质燃料特性的快速检测研究

快速检测生物质燃料特性对农林废弃物能源化利用具有重要意义。本研究利用光谱分析技术建立了松木、杉木和棉杆三类农林废弃物生物质的水分、灰分、挥发分、固定碳和热值预测模型。这些模型交叉校验决定系数均高于0．88。应用潜变量神经网络建模法后,水分平均决定系数达到了0．95。结果表明,应用光谱分析技术结合化学计量学方法,可完全替代传统的工业分析方法,为农林废弃物能源化利用提供一种快速检测生物质燃料特性的技术手段。     

甲基环己烷催化转化反应对改性工业Y沸石酸性的表征

以甲基环己烷（MCH）的催化转化反应为模型反应,并结合吡啶吸附红外光谱和羟基红外光谱技术对三种具有不同硅铝比和介孔孔隙的改性工业脱铝Y沸石的酸性(酸量、酸强和酸性点的可接近性)进行了表征研究。通过MCH催化转化反应的反应结果分析,可以得出,MCH的反应活性（总转化率）依赖于Y沸石催化剂表面的酸量, 而TOF值可反映沸石内质子位酸性点的可接近性。MCH催化转化的产品由裂解、芳香烃和异构三类产品构成,其中裂解产物的产率随着沸石微孔中强质子酸位点的浓度的增加而增加;随着Y沸石脱铝程度的增加,沸石内酸量减少,分子的扩散距离缩短从而导致二次反应的几率降低,从而使芳香烃的产率随之降低;同时,裂解产物中C7产物和烯烃/烷烃比率增加。研究结果还显示出,i-C4产物的选择性随脱铝Y沸石在其羟基红外光谱中3600cm-1处的吸收峰强度的增加而增加,即i-C4产物的选择性可反映沸石内强质子酸位点的数目。     

Dielectric response and polarization mechanism of alkali silicate glasses in gigahertz to terahertz frequency range

Oxide glasses are dielectric materials with potential applications in high-frequency communications; hence, their dielectric properties in the gigahertz to terahertz frequency range should be investigated. In this study, the dielectric properties of silica glass and five single alkali silicate glasses were measured at 0.5–10 THz using terahertz time-domain spectroscopy and far-infrared spectroscopic ellipsometry. At 0.5–10 THz, the silica glass exhibited low dielectric dispersion with a low dielectric constant and loss. By contrast, the alkali silicate glasses exhibited high dielectric dispersion, and the dielectric constant and loss were higher than those of the silica glass. The shape of the dielectric dispersion profile depended on the alkali-metal ions; it was broader for lighter ions such as Li ions and sharper for heavier ions such as Cs ions. The peak dielectric loss shifted toward a lower frequency as the weight of the alkali-metal ions in the alkali-silicate glass increased. To understand the dielectric dispersion, the complex permittivity was calculated using molecular dynamics simulations. The theoretical results qualitatively agreed with the experimental data. Ion dynamics analysis revealed that alkali-metal ions vibrate and migrate under an applied electric field, which affects the dielectric constant and loss of alkali-silicate glasses at gigahertz to terahertz frequencies. To fabricate filter devices at low temperatures, alkali metals should be added to silicate glass; therefore, a minimum amount of light alkali metals should be used to minimize the dielectric loss of the glass materials while maintaining productivity.     

Predicting and optimizing the physical and spectroscopic properties of phosphate laser glasses using a phase diagram approach

Despite the significant technological applications of laser glasses, the quantitative prediction and optimization of their properties, particularly the spectroscopic properties, remain challenging. Here we address this problem by regarding the nearest-neighboring congruently melting compounds as the “component and structural motifs” based on the phase diagram approach. The composition–structure–property (CSP) relationships of Nd³⁺-doped ternary phosphate glasses are investigated. Spectroscopic properties are quantitatively predicted with an error of less than 10% compared to the experimental results. In particular, the fluorescence lifetime (τ_m) can be accurately calculated using the phase diagram approach, which is difficult to be predicted previously. Furthermore, the CSP databases with over 1000 compositions are established for the optimization of commercial laser glasses. This study enriches the CSP database of traditional laser glass and provides guiding significance for future research.     

基于光谱法的晶体厚度测量

首次提出利用光谱特性来确定晶体厚度。从理论上推导出其实现的可行性 ,然后结合实验分析了测量系统的具体实现过程及计算厚度的算法 ,并分析了影响测量精度的主要因素。     

Single-Atom Bi Alloyed Pd Metallene for Nitrate Electroreduction to Ammonia

Electrochemical reduction of nitrate to ammonia (NO₃RR) holds a great promise for attaining both NH₃ electrosynthesis and wastewater purification. Herein, single-atom Bi alloyed Pd metallene (Bi₁Pd) is reported as a highly effective NO₃RR catalyst, showing a near 100% NH₃-Faradaic efficiency with the corresponding NH₃ yield of 33.8 mg h⁻¹ cm⁻² at −0.6 V versus RHE, surpassing those of almost all ever reported NO₃RR catalysts. In-depth theoretical and operando spectroscopic investigations unveil that single-atom Bi electronically couples with its neighboring Pd atoms to synergistically activate NO₃⁻ and destabilize *NO on Bi₁Pd, leading to the reduced energy barrier of the potential-determining step (*NO→*NOH) and enhanced protonation energetics of NO₃⁻-to-NH₃ pathway.     

Lewis Acid Fe-V Pairs Promote Nitrate Electroreduction to Ammonia

Electrochemical reduction of nitrate to ammonia (NO₃RR) has been recognized as an appealing approach to realize both sustainable NH₃ production and waste nitrate removal. Herein, from the perspective of Lewis acid-base interaction, a single-atom Fe-doped V₂O₅ (Fe-V₂O₅) catalyst enriched is designed with Lewis acid sites, which present the maximum NH₃-Faradaic efficiency of 97.1% with the corresponding NH₃ yield of 12.5 mg h⁻¹ cm⁻² at –0.7 V versus RHE. Mechanistic studies based on theoretical calculations and operando spectroscopic characterizations identify the creation of Lewis acid Fe-V pairs on Fe-V₂O₅, which can synergetically activate the NO₃⁻, promote the hydrogenation energetics, and restrain the hydrogen evolution, leading to the enhanced NO₃RR activity and selectivity.     

阿魏酸对黄嘌呤氧化酶的抑制机理

为系统地探讨阿魏酸抑制黄嘌呤氧化酶(xanthine oxidase,XO)活性的分子机制,采用酶学和光谱学方法测定了阿魏酸对XO抑制可逆性、抑制动力学、结合性质及结构的影响,采用分子模拟技术预测了阿魏酸与XO的结合构象。结果表明:在混合竞争的方式下,阿魏酸能可逆地抑制XO活性,抑制常数为4.5μmol/L,与咖啡酸、对香豆酸、绿原酸和没食子酸相比,阿魏酸对XO的抑制能力最强,其半抑制浓度为116.2μmol/L。荧光滴定实验结果表明:阿魏酸通过动态静态混合猝灭方式使XO荧光减少,其中静态猝灭占主导,且与XO存在一个结合位点,结合常数为3.38×10⁴L/mol(298K)；ΔG<0、ΔH<0和ΔS>0,表明该结合过程主要是以氢键和疏水作用力驱动且自发进行。分子对接结果揭示了阿魏酸进入了XO中黄素腺嘌呤二核苷酸活性区域,影响XO正常催化过程。同步荧光光谱和圆二色光谱实验表明:阿魏酸能改变XO的二级和三级结构,使XO中酪氨酸和色氨酸残基周围极性增加及疏水性降低,并且α-螺旋含量升高,β-折叠含量降低,使XO二级结构趋于紧密,这是影响XO活性的另一原因。研究以期为阿魏酸作为XO抑制剂改善高尿酸血症提供一定的理论依据。     

蓝宝石衬底损伤层厚度和折射率的椭偏测量

为了定量测量蓝宝石衬底在化学机械抛光过程中产生的损伤层厚度d和折射率n，提出了一种光谱椭偏测量法。首先，测量蓝宝石衬底反射光谱（波长范围：250~1650 mm）偏振态的改变量（即振幅比和相位差）：然后，通过光学建模和测量数据反演，获得损伤层d和n。实验研究了Al，0。和SiO，两种磨料加工蓝宝石衬底损伤层d和n的变化趋势，前者d呈现波动趋势且最小值（约1.4mm）出现在40min左右，后者d持续下降，在20min接近1mm；二者损伤层n均小于蓝宝石晶体n。另外，实验和仿真分析结果表明相位差与厚度变化趋势一致，因无需建模反演，可作为快速表征损伤层 d变化趋势的参量。总之，所提方法作为光学无损测量模式，适用于加工过程监测。