Amorphous High-Entropy Hydroxides of Tunable Wide Solar Absorption for Solar Water Evaporation

The high-entropy materials have raised much attention in recent years due to their extraordinary performances in mechanical, catalysis, energy storage fields. Herein, a new type of high-entropy hydroxides (e.g., NiFeCoMnAl(OH)_x) that are amorphous and capable of broad solar absorption is reported. A facile one-pot co-precipitation method is employed to synthesize these amorphous high-entropy hydroxides (a-HEHOs) under ambient conditions. The a-HEHOs thus obtained display widely tunable bandgap (e.g., from 2.6 to 1.1 eV) due to their high-entropy and amorphous characteristics, enabling efficient light absorbance and photothermal conversion in the solar regime. Further solar water evaporation measurements show that the a-HEHOs delivered a considerable energy conversion efficiency of 55%, comparable to black titanium oxides that are synthesized using more complex and expensive methods.     

The pentacene films on the glass/ITO surface: structure and optical properties

Abstract

The structure, morphology and optical transmittance spectra of pentacene films on the (glass/ITO) surface were studied. The films were grown by two methods - the thermal vacuum deposition (TVD) and pulsed laser deposition (PLD). The electron diffraction pattern from thermally deposited pentacene films confirms their polycrystalline structure while the diffraction pattern of PLD-coated layers has a diffusion character. The results obtained showed that layers deposited by the TVD method has an optical spectrum that is characteristic for the pentacene film in contrary to the layers deposited by the PLD method. It is found a sensitivity of the optical transmittance of pentacene films to the ammonia action, which may be used for development the optical gas sensor.     

Molecular structure,vibrational spectroscopic and chemical reactivity of nematogenic p-n-alkylbenzoic acids: A comparative computational analysis

Molecular structure and vibrational spectroscopic studies of higher homologous series nematogenic p-n-alkylbenzoic acids (nBAC) that have 6 (6BAC) and 7 (7BAC) carbon atoms in the alkyl chain have been investigated using the Density Functional Becke3-Lee-Yang-Parr (B3LYP) level with the basis set 6-31++G (d.p) and Hartree Fock (HF) with the same basis set. The observed vibrational spectra has been resolved and assigned in detail for comparision with both the molecules. These results indicate that DFT and HF values are slightly different at both the levels. A comparision of chemical reactivity such as HOMO (E_H), LUMO (E_L) energies, energy gap (E_g), ionization energy (I), electron affinity (A), electro negativity (χ), chemical hardness (η), electronic chemical potential (μ), electrophilicity index (ω), and softness (S) has been made. It has been observed that the decrement has occurred in the energy band gap value of isolated molecule with increment in alkyl chain length. This provides valuable information regarding enhancing the stability of liquid crystal materials by maintaining the conductivity.     

XANES/EPR Evidence of the Oxidation of Nickel(II) Quinolinylpropioamide and Its Application in Csp3−H Functionalization

An in situ generated oxidation species of nickel quinolinylpropioamide intermediate was produced. Characterization by X-ray absorption near edge structure (XANES) and EPR provides complementary insights into this oxidized nickel species. With aliphatic amides and isocyanides as substrates, a nickel-catalyzed facile synthesis of structurally diverse five-membered lactams could be achieved.     

曲线距离法的二维光纤光谱弯曲校正

多目标光纤光谱望远镜可以在一次观测中获得大量的不同天体的光谱数据。从天体探测到的光在通过光纤之后，再通过光谱仪狭缝，然后在CCD传感器中成像为二维光谱图；之后经过光纤光谱数据处理系统的一系列软件处理，最终输出可供天文界使用的一维光谱并存储起来。一维光谱是天文学家研究目标天体的主要手段，它是通过处理二维光谱图得到的。以LAMOST为例，望远镜系统在一次观测后首先会得到32幅由250条光纤光谱组成的二维光谱，然后经过一系列的处理得到一维光谱。在这个过程中，会有很多因素影响到最终一维光谱的精确度。比如由于望远镜使用时间的增加，某些元件会产生磨损、老化或变形，使得二维光谱中光纤形状会产生一定程度的弯曲，这种弯曲在二维光谱的两侧表现得尤为明显。在一幅常见的二维光谱中，纵坐标方向代表了抽取的一维光谱的波长方向，横坐标方向代表了抽取的一维光谱的流量方向，这种弯曲形变的产生会影响到之后的波长定标和流量定标，使得抽取的一维谱信息不准确。目前初步的解决办法是通过与定标灯谱的比对来尽量减少其影响。但这样不仅造成了时间和人力的浪费，而且准确率和效率不高。就这一现状，提出了一种基于曲线距离法的思想，将弯曲的二维谱线校直：首先采用灰度重心法将一幅二维光谱中的250条光纤中心轨迹进行定位，将异常点采用稳健的局部回归方法剔除；然后将中心轨迹进行曲线拟合，得到光纤中心轨迹的方程；通过模仿曲线变弯的逆过程，即保持轨迹上两点间的曲线距离不变，再将弯曲的光谱映射到竖直的法线上，完成校直过程。在整个过程中保持各个对应点的灰度值不变，通过边缘处理和插值运算解决产生的像素点稀疏问题。最后采用累加法进行一维谱抽取，并将校直后抽取的一维光谱与未校直抽取的一维光谱进行比对，比对后可发现校直前后在一维光谱的两端差别较大，其差值谱线也说明了这一点。该方法实现了二维光谱的自动校直，大大提高了抽取一维谱的效率和准确性。二维光谱的预处理和校直方法首先在LAMOST数据上进行验证，鉴于多目标光纤光谱望远镜系统原理的相似性，该处理方法也适用于其他的多目标光纤光谱望远镜系统，具有较好的参考和应用价值。     

温度对AZO薄膜红外辐射性能的影响

随着全球资源的减少和环境的恶化，节能减排已成为人们关注的焦点，具有保温隔热功能的低辐射玻璃成为研究的热点。提高玻璃保温隔热性能最有效的方法就是在其表面涂覆低辐射率层。原材料丰富、导电性能好、可见光透过率高等优势使得Al掺杂ZnO (AZO)薄膜成为最具潜力的低辐射率层。系统研究了温度对AZO薄膜红外辐射性能的影响，分析了变化机理。首先研究了在一定的温度下持续一段时间后，AZO薄膜的红外比辐射率的变化情况。然后研究了在变温环境中红外比辐射率的变化情况。采用直流磁控溅射法在室温下玻璃基片上沉积500 nm厚的AZO薄膜，将薄膜放到马弗炉中进行热处理，在100～400 ℃空气气氛下保温1 h，随炉冷却。采用X射线衍射仪对AZO薄膜进行物相分析，采用扫描电子显微镜观察薄膜表面形貌变化。利用四探针测试法测量AZO薄膜的电阻率，采用红外比辐射率测试仪测试薄膜红外比辐射率, 可见分光光度计测量可见光谱。测试的结果表明，薄膜热处理前后均为六角纤锌矿结构，(002)择优取向。300 ℃及以下热处理1 h后，(002)衍射峰增强，半高宽变窄，晶粒尺寸长大。随着热处理温度的升高，薄膜的电阻率先减小后增大，200 ℃热处理后的薄膜具有最小的电阻率(0.9×10-3 Ω·cm)。热处理温度升高，晶粒长大使得薄膜电阻率降低。热处理温度过高，薄膜会从空气中吸收氧，电阻率下降。薄膜的红外比辐射率变化趋势和电阻率的一致，在200 ℃热处理后获得最小值(0.48)。自由电子对红外光子有较强的反射作用，当电阻率低，自由电子浓度高的时候，更多的红外光子被反射，红外辐射作用弱，红外比辐射率小。薄膜的可见光透过率随着热处理温度的升高先减小后增大，200 ℃热处理后的薄膜的可见光透过率最小，但仍高达82%。这种变化是由于自由电子浓度变化引起的，自由电子对可见光有很强的反射作用。选取未热处理和200 ℃热处理后的样品进行变温红外比辐射率的测量，将样品放在可加热的样品台上，位置固定，在室温到350 ℃的升温和降温过程中每隔25 ℃测量一次红外比辐射率，结果表明，在室温到350 ℃的温度范围内，AZO薄膜的红外比辐射率在升温过程中随着温度的上升而增大，在降温过程中减小，经过整个升、降温过程后，薄膜的红外比辐射率增大。     

浊度干扰下硝酸盐浓度紫外导数光谱检测方法研究

硝酸盐是水中“三氮”（硝酸盐氮、氨氮、总氮）之一，是反映水体受污染程度的一项重要指标。传统 “现场采样-离线分析” 的硝酸盐化学检测方法操作繁琐、耗时长，难以满足现代水环境实时在线检测需求。由于硝酸根在紫外区具有很强的紫外吸收特性，并且紫外吸收光谱法具有简便快速、可实现实时在线监测等特点，近年来被广泛用于硝酸盐浓度的测量。但使用紫外吸收光谱法检测水体硝酸盐含量时，容易受到水体浊度影响，造成谱线非线性抬升，导致测量误差。目前对浊度补偿算法的研究大都用于水中COD含量的检测，对硝酸盐检测中浊度干扰去除研究较少。为此提出一种基于一阶导数紫外吸收光谱的硝酸盐浓度测量方法，该方法可以减小浊度干扰，从而提高紫外光谱快速检测硝酸盐含量的准确度。通过测量福尔马肼与硝酸钠标准溶液和它们混合溶液在190~300 nm波段的紫外吸收光谱并做一阶导数光谱处理，处理后的光谱采用Savitzky-Golay滤波进行去噪平滑处理，比较浊度与硝酸盐紫外吸收一阶导数光谱特征，分波段研究浊度对硝酸盐紫外一阶导数光谱影响，结果表明硝酸盐导数光谱在220~230 nm波段受浊度影响小；选取220~230 nm波段作为光谱分析区间，以30种不同浓度混合的福尔马肼与硝酸钠溶液作为训练样本，利用偏最小二乘算法建立硝酸盐定量分析模型，使用该建模模型预测剩下的6种不同浓度福尔马肼与硝酸钠混合溶液中硝酸盐的浓度，结果表明福尔马肼干扰下硝酸盐测量结果的预测决定系数（correlation coefficient，R2）为0.994 3，预测均方根误差（root mean square error of prediction，RMSEP）为0.346 9 mg·L-1。为进一步验证该方法的准确性与稳定性，使用该建模模型预测高岭土与硝酸钾配制的混合水样中硝酸盐的浓度，结果表明该方法对高岭土干扰下硝酸盐测量结果的预测决定系数r2为0.991 5，预测均方根误差RMSEP为0.362 8 mg·L-1。综上所述，提出的硝酸盐浓度紫外导数光谱检测方法，采用220~230 nm波段的紫外导数光谱数据，结合PLS建模，可以快速准确测量在浊度干扰下水体硝酸盐的浓度，为发展实际水体硝酸盐在线监测技术与设备提供方法基础。     

X-ray absorption spectroscopy study of the electronic structure and local coordination of 1st row transition metal-promoted Chevrel-phase sulfides

Abstract

The electronic structures of S and Mo as well as the local coordination of Mo are investigated as a function of metal promotion Chevrel-phase (CP) sulfides. We observe the effect of metal promoter-induced electron donation into the stoichiometric range M_xMo₆S₈ (M?=?Fe, Ni, Cu; x?=?0–2) through analysis of X-ray absorption near-edge structure regions. We further observe the effect of this promotion on the bonding environment of Mo₆ metal centers through extended X-ray absorption fine structure analysis. We monitor expansion and contraction of Mo₆ octahedra with and without metal promotion, as has been predicted by Hückel molecular orbital theory. We further observe a marked tunability in the electronic structure of sulfur upon charge transfer between promoting species and Mo₆S₈ units. Average Mo₆ octahedron Mo–Mo bond contraction from 2.76 Å to as short as 2.69 Å was observed upon incorporation of metal promoters, while intercluster separation displays a pronounced increase for promoter-host lattices compared to un-promoted Mo₆S₈. To corroborate spectroscopically observed phenomena, we performed computational analyses of spin-polarized densities of state for the CP materials investigated herein, where a detectable increase in sulfur-based frontier orbital population is observed in accordance with experimentally validated orbital filling.     

Performance of Pleurotus ostreatus Mushrooms and Spent Substrate for the Biosorption of Cd(II) From Aqueous Solution

The capacities of Pleurotus ostreatus mushroom and spent substrate were evaluated for the biosorption of cadmium (II) from aqueous solution in order to select the most efficient material for bioremediation. The optimum sorption conditions were optimized, including the pH of the aqueous solution, contact time, biomass dosage, initial metal concentration, and temperature. The sorption of cadmium on both biosorbents was also evaluated by several kinetic, equilibrium, and thermodynamic models. The possible heavy metal biosorption mechanisms were evaluated through point of zero charge (pH_pzc), Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy coupled with energy dispersive X-ray microanalysis (SEM-EDX). Based on the results of column studies, the effectiveness of the P. ostreatus spent substrate was confirmed as a biosorbent for Cd(II) removal from aqueous solutions.     

利用带无标签数据的双支持向量机对恒星光谱分类

恒星光谱分类是天文技术与方法领域一直关注的热点问题之一。随着观测设备持续运行和不断改进，人类获得的光谱数量与日俱增。这些海量光谱为人工处理带来了极大挑战。鉴于此，研究人员开始关注数据挖掘算法，并尝试对这些光谱进行数据挖掘。近年来，神经网络、自组织映射、关联规则等数据挖掘方法广泛应用于恒星光谱分类。在这些方法中，支持向量机(SVM)以其强大的学习能力和高效的分类性能而备受推崇。SVM的基本思想是试图在两类样本之间找到一个最优分类面将两类分开。SVM在求解时，通过将其最优化问题转化为具有(QP)形式的凸问题，进而得到全局最优解。尽管该方法在实际应用中表现优良，但为了进一步提高其分类能力，有的学者提出双支持向量机(TSVM)。该方法通过构造两个非平行的分类面将两类分开，每一类靠近某个分类面，而远离另一个分类面。TSVM的计算效率较之传统SVM提高近4倍，因此，自TSVM提出后便受到研究人员的持续关注，并出现若干改进算法。在恒星光谱分类中，一般分类算法都是根据历史观测光谱来建立分类模型，其中最关键的是对光谱进行人工标注，这项工作极为繁琐，且容易犯错。如何利用已标记的光谱以及部分无标签的光谱来建立分类模型显得尤为重要。因此，提出带无标签数据的双支持向量机(TSVMUD)用以实现对恒星光谱智能分类的目的。该方法首先将光谱分为训练数据集和测试数据集两部分；然后，在训练集上进行学习，得到分类依据；最后利用分类依据对测试集上的光谱进行验证。继承了双支持向量机的优势，更重要的是，在训练集上学习分类模型过程中，不仅考虑有标记的训练样本，也考虑部分未标记的样本。一方面提高了学习效率，另一方面得到更优的分类模型。在SDSS DR8恒星光谱数据集上的比较实验表明，与支持向量机SVM、双支持向量机TSVM以及K近邻(KNN)等传统分类方法相比，带无标签数据的双支持向量机TSVMUD具有更优的分类能力。然而，该方法亦存在一定的局限性，其中一大难题是其无法处理海量光谱数据。该工作将借鉴海量数据随机采样思想，利用大数据处理技术，来对所提方法在大数据环境下的适应性展开进一步研究。