Novel Bi2MoO6 Nanosheets/Vertical TiO2 Nanorods Arrays Heterojunction with Enhanced Photoelectrochemical Performance under Visible Light Irradiation

Novel Bi₂MoO₆/TiO₂ heterojunction was fabricated by growing Bi₂MoO₆ nanosheets arrays on the vertically aligned TiO₂ nanorods arrays via a two-step solvothermal method. The obtained Bi₂MoO₆/TiO₂ hierarchical heterojunction showed excellent visible light photoelectrochemical performance. Compared with the pure TiO₂ and Bi₂MoO₆, the photocurrent density of the heterojunction was increased 57 and 29 times, respectively. Furthermore, the hydrogen generation rate of the Bi₂MoO₆/TiO₂ for photoelectrocatalytic water-splitting was about 6 times higher than that of the pure Bi₂MoO₆. The improved performance can be attributed to the synergistic effects of enhanced absorption of visible light, increase of migration rate and separation efficiency of photo-induced carriers.     

Tuning the properties of a black TiO2-Ag visible light photocatalyst produced by a rapid one-pot chemical reduction

A highly efficient black TiO₂-Ag photocatalytic nanocomposite, active under both UV and visible light illumination, was synthesized by decorating the surface of 25 nm TiO₂ particles with Ag nanoparticles. The material was obtained via a rapid, one-pot, simple (surfactant and complexing agent free) chemical reduction method using silver nitrate and formaldehyde as a metal salt and reducing agent, respectively. The nanocomposite shows an increase of over 800% in the rate of photocatalytic methylene blue dye degradation, compared to commercial unmodified TiO_2, under UV-VIS illumination. Unlike pure TiO₂, the nanocomposite exhibits visible light activation, with a corresponding drop in optical reflectance from 100% to less than 10%. The photocatalytic properties were shown to be strongly enhanced by post-reduction annealing heat treatments in air, which were observed to decrease, rather than coarsen, silver particle size, and increase particle distribution. This, accompanied by a variation in the silver surface oxidation states, appear to dramatically affect the photocatalytic efficiency under both UV and visible light. This highly active photocatalyst could have wide ranging applications in water and air pollution remediation and solar fuel production.     

Quantitative colorimetric-imaging analysis of nickel in iron meteorites

A quantitative analytical imaging approach for determining the nickel content of metallic meteorites is proposed. The approach uses a digital image of a series of standard solutions of the nickel-dimethylglyoxime coloured chelate and a meteorite sample solution subjected to the same treatment as the nickel standards for quantitation. The image is processed with suitable software to assign a colour-dependent numerical value (analytical signal) to each standard. Such a value is directly proportional to the analyte concentration, which facilitates construction of a calibration graph where the value for the unknown sample can be interpolated to calculate the nickel content of the meteorite. The results thus obtained were validated by comparison with the official, ISO-endorsed spectrophotometric method for nickel.The proposed method is fairly simple and inexpensive; in fact, it uses a commercially available digital camera as measuring instrument and the images it provides are processed with highly user-friendly public domain software (specifically, ImageJ, developed by the National Institutes of Health and freely available for download on the Internet).In a scenario dominated by increasingly sophisticated and expensive equipment, the proposed method provides a cost-effective alternative based on simple, robust hardware that is affordable and can be readily accessed worldwide. This can be especially advantageous for countries were available resources for analytical equipment investments are scant. The proposed method is essentially an adaptation of classical chemical analysis to current, straightforward, robust, cost-effective instrumentation.     

CdS/石墨烯复合材料的制备及其可见光催化分解水产氢性能

以氧化石墨烯和CdS为原料, 在乙醇水溶液中采用CdS光催化还原法制备了CdS/石墨烯复合光催化材料, 并用透射电子显微镜(TEM)、X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、X射线光电子能谱(XPS)和瞬态光电流等技术对复合材料的结构和光电性能进行了表征. 可见光照射下(λ≥420 nm), 研究了该复合材料光催化分解水产氢的性能. 结果表明, 可见光照射下CdS的光生电子可有效地还原氧化石墨烯, 得到CdS与石墨烯之间具有强相互作用力的CdS/石墨烯复合材料. 与CdS相比, 复合材料中石墨烯作为良好的电子受体和传递介质, 可明显加快CdS光生电子的迁移速率, 提高光生载流子的分离效率, 从而增强复合材料的光电性能和光催化分解水产氢的活性.     

不同形态铈改性的TiO2纳米管阵列的制备及其可见光光电响应性质

采用电化学阴极还原和阳极氧化法,制备了还原态铈和氧化态铈改性的TiO2纳米管阵列,通过扫描电子显微镜(SEM)和X射线衍射(XRD)表征样品形貌和晶相,得出还原态铈以单质铈纳米纤维形式存在于TiO2纳米管内及表面,单质铈改性的TiO2纳米管经阳极氧化后,以CeO2和单质Ce形式共存.测定样品的光电流响应并计算样品的能带宽度.结果表明:单质铈改性的TiO2纳米管阵列在可见光区光电流响应较TiO2纳米管增强,单质铈添加存在最佳值,在10 mmol·L-1溶液中制备的单质铈改性的TiO2纳米管阵列光电流响应最强,能带宽度E9减少到2.88 eV,并且随着单质铈含量的增加,载流子浓度增大,且平带电位向负向移动.单质铈改性的样品经阳极氧化后,样品在紫外光区和可见光区光电流响应都增强,但其在可见光区的响应强度要小于单质铈改性的TiO2纳米管在可见光区的响应强度.     

Characterization of aquatic dissolved organic matter by asymmetrical flow field-flow fractionation coupled to UV-Visible diode array and excitation emission matrix fluorescence

Flow field-flow fractionation (FlFFF) with on-line UV/Visible diode array detector (DAD) and excitation emission matrix (EEM) fluorescence detector has been developed for the characterization of optical properties of aquatic dissolved organic matter (DOM) collected in the Otonabee River (Ontario, Canada) and Athabasca River (Alberta, Canada). The molecular weight (MW) distribution of DOM was estimated using a series of organic macromolecules ranging from 479 to 66,000 Da. Both the number-average (M_n) and weight-average (M_w) molecular weights of Suwannee River fulvic acid (SRFA) and Suwannee River humic acid (SRHA) determined using these macromolecular standards were comparable to those obtained using polystyrenesulfonate (PSS) standards, suggesting that organic macromolecules can be used to estimate MW of natural organic colloids. The MW of eight river DOM samples determined by this method was found to have an M_n range of 0.8–1.1 kDa, which agrees with available literature estimates. The FlFFF-DAD-EEM system provided insight into the MW components of river DOM including the optical properties by on-line absorbance and fluorescence measurement. A red-shift in emission and excitation wavelength maxima associated with lower spectral slope ratios (S_R = S_275–295:S_350–400) was related to higher MW DOM. However, DOM of different origins at similar MW also showed significant difference in optical properties. A difference of 47 and 40 nm in excitation and emission peak C maxima was found. This supports the hypothesis that river DOM is not uniform in size and optical composition.     

Enhancement of ethanol electrooxidation on plasmonic Au/TiO2 nanotube arrays

Novel electrocatalysts Au/TiO₂ nanotube arrays (Au/TiO₂NTs) were prepared by loading low-content(1.9 at.%) of Au nanoparticles (AuNPs) onto highly ordered TiO₂ nanotube arrays (TiO₂NTs). Ethanol electrooxidation indicates that visible-light (λ > 400 nm) irradiation can significantly enhance the activity as well as resistpoisoning of Au/TiO₂NTs electrocatalysts that are activated by plasmon resonance. Au/TiO₂NTs catalysts calcinated at 300 °C display the highest performance due to the strong synergistic interactions between TiO₂ and Au NPs. The combination of visible-light irradiation with a controllable potential offers a new strategyfor enhancing the performance of anodes in direct ethanol fuel cell (DEFC).     

高光谱的刺五加黑斑病的早期检测研究

对感染黑斑病的刺五加叶片进行光谱特性研究,能为药用植物病害的早期筛选与精准治疗提供重要研究资料。实验目的,运用高光谱成像技术实现植物病害的自动监督分类与识别。实验过程,首先使用高光谱成像系统在可见光波段（380～960 nm）内采集刺五加黑斑病的叶片样本,光谱数据经过去除亮暗噪声和平滑预处理后,再经过主成分分析实现数据降维,继而运用基于不同核函数的支持向量机法建立分类模型,最后利用总体分类精度、Kappa系数等因子评价不同核函数对分类器性能的影响。根据叶片表面的特征将其分为四类样本：健康亮部、健康暗部、轻度病害和重度病害等。对比各类样本的光谱可知,刺五加的健康样本在540 nm波长存在一个明显峰值,在620～680 nm光谱曲线急剧上升;而病害样本的光谱反射率呈现缓慢且平稳的上升趋势,上述特征能够将图像空间上反射强度接近的健康亮部和严重病害完全区分开。经对比发现前四个主成分（PC1,PC2,PC3,PC4）在分类表达上存在差异,主要表现为PC1含有的信息多,能够较好地区分各类样本;PC2则出现健康亮部和严重病害的交叉混淆;PC3是对于PC2的补充,能基本完整地表达轻微病害;PC4的贡献率仅有0.19%,依然能够准确地识别严重病害。不同主成分分量在表达各类样本特征中存在的差异能够作为复杂样本分类的参考依据。对比四种核函数对支持向量机分类器性能的影响,结果显示线性核函数的识别过程受光强反射的影响较大,Sigmoid核函数的训练精度易受数据集大小的影响,在识别健康亮或暗,以及轻微病害上均存在一定的误差,多项式核函数与径向基核函数的效果较好,其中,多项式核函数的精度更高,为92.77%。研究表明,利用高光谱成像技术能够准确地识别刺五加的健康叶片和患病叶片,为实现自动诊断药用植物叶片病害提供新方法。     

多位置可见/近红外光谱检测与种鸡蛋受精信息的关系研究

种鸡蛋孵化过程耗时、耗能,但种蛋由于未受精导致胚胎发育率不足100%,种鸡蛋孵化早期快速判别,可有效提高种蛋孵化效率和降低经济损失。近红外光谱分析技术可实现快速、无损检测,用于判别研究孵化早期种鸡蛋受精信息,但现有光谱检测方法未能满足孵化早期受精判别位置要求,亟需构建采集数据时的检测位置与内部信息之间的关系。该研究利用可见/近红外光谱检测系统采集种蛋壳漫反射光谱强度,试验选用壳色相近、表面无裂纹的181个新鲜种鸡蛋,从中随机选择61个样本完成交叉验证。为消除暗电流的影响,进行光谱校正,得出种蛋壳漫反射率,发现受精蛋与未受精蛋的光谱曲线趋势相同,受精蛋和无精蛋赤道处的光谱曲线均高于两端。剔除光谱曲线两端噪声大、信噪比低的波段,选择440.27～874.6 nm作为有效光谱波段,并采用Savitzkg-Golay（S-G）平滑法、二阶导数法Second Derivative、标准正态变量校正SNV、变量标准化Normalization和多元散射校正MSC预处理法分别构建PCA-SVM判别模型。通过对入孵后24,48,72,96和120 h不同位置所采光谱数据,与受精信息综合分析,结果发现二阶导数法Second Derivative和多元散射校正MSC两种预处理方式在同一时间、不同位置的训练集和验证集的判别准确率均相同,说明这两种预处理方法对数据来源位置不敏感;变量标准化Normalization预处理和S-G平滑法预处理验证集的判别准确率则随着时间的推移在一定范围内波动,在种鸡蛋胚胎发育120h时的判别准确率可达91.71%;SNV预处理赤道处验证集判别准确率随着时间的推移呈现上升趋势,对数据来源时间及位置敏感,种鸡蛋胚胎发育越长判别效果越佳,120 h赤道侧的判别准确率为91.16%。且平滑处理、标准正态变量校正和变量标准化三种预处理方式均存在赤道侧判别准确率高于种蛋端部的现象,这主要是由于赤道侧较种鸡蛋两端表面平缓,采集到的信息更多,该研究为早期判别受精蛋与无精蛋的数据采集位置提供新思路和新方法。     

Optical microstrip patch antennas design and analysis

This paper has presented transparent conductor oxide materials (TCOMs) based microstrip patch antennas with glass substrate and copper ground plane, which have been deeply analyzed in the visible spectrum region in comparison with the practical patch antenna model of indium tin oxide patch with glass substrate and different TCOMs based ground plane. As well as the study have investigated the effect of transparent oxide materials on patch antenna design instead of perfect conductor materials such as copper that has low cost and weight. The tradeoff between optical transparency and electrical conductivity will be evaluated for a range of visible regions. Microstrip transmission line feed method is used to predict the skin effects on a patch antenna and their impact on antenna efficiency, resonance frequency and optical transmission are also described. This study have discussed assessment of these tradeoffs and effect of TCOMs parameters on antenna design.