液相色谱-高分辨质谱法测定壮阳类保健品中非法添加物

采用液相色谱-高分辨质谱法检测壮阳类保健品中的5种非法添加物。样品经甲醇超声提取后,以C18色谱柱为分离柱,以0.1%(体积分数)乙酸溶液与乙腈组成的混合溶液为流动相进行梯度洗脱,采用电喷雾正离子源及全扫描/二级质谱目标离子扫描模式进行测定。5种非法添加物的线性范围为1.0~50μg·L-1,方法测定下限(10S/N)在0.3~0.4μg·L-1之间。对样品进行加标回收试验,回收率在78.0%~102%之间,测定值的相对标准偏差(n=6)在0.62%~2.3%之间。     

TiO2上原子分散的Fe位点促进光催化CO2还原:增强的催化活性、DFT计算和机制洞察(英文)

光催化CO₂高效、环保地转化为高附加值化工产品(CH₄, CO, CH₃OH等),能够有效降低环境污染并且促进资源利用.商用P25(TiO₂)因其具有无毒、化学稳定性和强氧化还原电位而被广泛研究.然而, TiO₂的带隙高达3.0 e V,只有在紫外光激发下才能产生光生载流子,这极大地限制了其在光催化领域的应用.单原子催化剂(SACs)具有金属原子利用率高、选择性高和活性高等优点,可用于精细化工合成、氧还原和污染物降解等催化领域.由于单个原子具有极高的表面自由能,因此如何稳定地保持原子分散,避免原子团聚成为SACs制备和反应过程中的一大挑战.本文通过简单的负压封装后热解方法实现了Fe在TiO₂表面的原子级分散负载,所制备的Fe SA/TiO₂催化剂展现出高效的光催化CO₂还原性能,并且利用多种表征手段及理论计算研究了TiO₂表面Fe位点促进CO₂高效转化的反应机制.扫描透...     

自由空间光学Comega多级互连网络特性研究

光学Ｃｏｍｅｇａ网络是一种新颖的易于光学实现的多级光互连网络。本文对该网络结构及特性进行了详细分析，和到了网络的互连函数，并给出了它与Ｓｔａｒａｎ，Ｃｒｏｓｓｏｖｅｒ，Ｏｍｅｇａ，Ｂａｎｙａｎ及基准等常见网络的拓扑等价证明。     

N,N-二乙基丙烯酰胺与丙烯酸在聚丙烯薄膜表面光接枝制备二元接枝膜及其温度、pH值敏感特性研究

以二苯甲酮为引发剂,聚丙烯薄膜(CPP)为基材,通过紫外光接枝的方法制备了具有温度和pH值双重敏感特性的聚N,N-二乙基丙烯酰胺(PNDEA)与聚丙烯酸(PAA)二元接枝膜.在PNDEA一次接枝膜的制备过程中,引发剂与单体配比相同时,本体接枝方法的接枝速率在反应初期明显高于溶液接枝方法;采用溶液法时,增大引发剂与单体配比等可提高接枝率.用本体法所制得的PNDEA一次膜光活化接枝PAA时接枝速率较溶液法高,并且能够实现较高的PAA接枝率.用红外光谱(FTIR)、X射线光电子能谱化学分析(ESCA)对接枝层组成的表征结果证实了二元接枝层的存在.在不同温度下,PNDEA一次接枝膜的FTIR谱图中酰胺Ⅰ带特征吸收峰发生位移表明它具有温度敏感特性.用扫描电子显微镜(SEM)对PNDEA接枝层表征结果表明,用不同接枝手段所制备的接枝膜具有不同的表面形貌.通过吸水率测定研究了二元接枝膜的温度及pH值敏感特性.     

Na，NBA－Ga－Si－ZSM－5杂原子沸石分子筛的表征

Ｎａ，ＮＢＡ┐Ｇａ┐Ｓｉ┐ＺＳＭ┐５杂原子沸石分子筛的表征高志贤程昌瑞谭长瑜李源（中国科学院山西煤炭化学研究所，太原０３０００１）关键词Ｇａ－Ｓｉ－ＺＳＭ－５沸石分子筛，正丁胺，表征，模板作用近年来的研究结果表明，使用不同类型的有机胺或醇作引导剂，甚...     

Fabrication and measurement of traceable pitch standard with a big area at trans-scale

Atom lithography with chromium can be utilized to fabricate a pitch standard,which is directly traceable to the wavelength of the laser standing waves. The result of a calibrated commercial AFM measurement demonstrates that the pitch standard is(212.8±0.1) nm with a peak-to-valley-height(PTVH) better than 20 nm. The measurement results show the high period accuracy of traceability with the standing laser wavelength(λ /2 = 212.78 nm). The Cr nano-grating covers a 1000 μm×500 μm area, with a PTVH better than 10 nm. The feature width broadening of the Cr nanostructure has been experimentally observed along the direction of the standing waves. The PTVH along the Gaussian laser direction is similar to a Gaussian distribution. Highly uniform periodic nanostructures with a big area at the millimeter scale, and the surface growth uniformity of the Cr nano-grating, show its great potential in the application of a traceable pitch standard at trans-scales.     

Observation of oscillations in the transport for atomic layer MoS_2

In our experiment, an atomic layer MoS_2 structure grown on SiO_2/Si substrates is used in transport test. The voltage U14,23 oscillates and the corresponding period varies with applied current. The largest period appears at 45 μA. The oscillation periods are different when samples are under laser radiation or in darkness. We discover that under the laser irradiation, the oscillation period occurs at lower current than in the darkness case. Meanwhile, the drift velocity is estimated at ~10~7 cm/s. Besides, by studying the envelope of U14,23 versus applied current, we see a beating phenomenon at a certain current value. The beating period in darkness is larger than under laser irradiation. The difference between beating periods reveals the energy difference of electrons. Similar results are obtained by using different laser power densities and different light sources. The possible mechanism behind the oscillation period is discussed.     

Improvement of laser damage thresholds of fused silica by ultrasonic-assisted hydrofluoric acid etching

Polished fused silica samples were etched for different durations by using hydrofluoric(HF) acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular structure parameters before and after the etching process were characterized by using a fluorescence microscope and infrared(IR) spectrometer, respectively. The laser induced damage thresholds(LIDTs) of the samples were measured by using pulsed nanosecond laser with wavelength of 355 nm. The results showed that surface and subsurface polishing residues can be effectively reduced by the acid etching process, and the LIDTs of fused silica are significantly improved. The etching effects increased with the increase of the HF concentration from 5 wt.% to 40 wt.%. The amount of polishing residues decreased with the increase of the etching duration and then kept stable. Simultaneously, with the increase of the etching time, the mechanical strength and molecular structure were improved.     

氢化物发生-原子荧光光谱法测定三种鸡蛋中硒含量的研究

探讨氢化物发生-原子荧光光谱法测定鸡蛋中硒含量的最佳仪器工作条件,建立电热板混酸消解-氢化物发生-原子荧光光谱法检测硒含量的分析方法,并通过检测市售乌鸡蛋、土鸡蛋和普通鸡蛋中的硒含量,以期为人们进行鸡蛋消费选择提供理论实践参考。为提高原子荧光光谱法检测鸡蛋中硒含量方法的精确度和准确度,试验分别对消解液的比例、预还原剂的浓度选择、硼氢化钾的浓度等反应条件进行比较分析,并通过计算精密度、回收率、最低检出限等指标对该方法检测结果的可行性进行检验。试验结果显示：鸡蛋样品用体积比为1∶1的浓硝酸与高氯酸的混合液消解过夜后,放于200 ℃微控数显电热板上加热消解至透明清亮,同时将电热板温度调至160 ℃,当锥形瓶温度冷却至室温后,再加入5 mL的6 mol·L-1的盐酸进行预还原反应,再次将锥形瓶放在电热板上加热,至溶液变透明清亮后取下,冷却至室温后,将锥形瓶内溶液转移置100 mL容量瓶中,加入1.00 mL 10%铁氰化钾溶液,用10%盐酸定容,摇匀,待测,同时做样品空白对照。将处理后的鸡蛋样品放在高性能空心阴极硒灯下,以1.5%的硼氢化钾溶液为还原剂和2%盐酸溶液为载流液对鸡蛋样品进行连续测定。在最佳消解条件和仪器工作状态下,硒在0～8 μg·L-1的浓度范围内呈现良好的线性关系,硒标准曲线方程式为I_F=114.19C＋1.30,标准曲线相关系数为0.999 9,最低检出限为0.01 μg·L-1,相对标准偏差为0.07%～0.72%,加标回收率为96.12%～99.1%。建立了电热板混酸消解-氢化物发生-原子荧光光谱法准确测定鸡蛋中硒含量的方法,该法具有简单易操作、精密度高、灵敏性高等优点,并利用该法对普通鸡蛋、土鸡蛋和乌鸡蛋中的硒含量进行了检测分析,结果显示乌鸡蛋、土鸡蛋和普通鸡蛋的硒含量分别为0.191,0.195和0.141 mg·kg-1,乌鸡蛋和土鸡蛋中的硒含量差异不显著（p＞0.05）,但二者的硒含量均显著高于普通鸡蛋（p＜0.05）。该研究为禽蛋中硒含量的科学检测及人们进行鸡蛋消费选择提供了理论实践依据。     

Characterization of atomic-layer MoS_2 synthesized using a hot filament chemical vapor deposition method

Atomic-layer MoS_2 ultrathin films are synthesized using a hot filament chemical vapor deposition method. A combination of atomic force microscopy(AFM), x-ray diffraction(XRD), high-resolution transition electron microscopy(HRTEM), photoluminescence(PL), and x-ray photoelectron spectroscopy(XPS) characterization methods is applied to investigate the crystal structures, valence states, and compositions of the ultrathin film areas. The nucleation particles show irregular morphology, while for a larger size somewhere, the films are granular and the grains have a triangle shape. The films grow in a preferred orientation(002). The HRTEM images present the graphene-like structure of stacked layers with low density of stacking fault, and the interlayer distance of plane is measured to be about 0.63 nm. It shows a clear quasihoneycomb-like structure and 6-fold coordination symmetry. Room-temperature PL spectra for the atomic layer MoS_2 under the condition of right and left circular light show that for both cases, the A1 and B1 direct excitonic transitions can be observed. In the meantime, valley polarization resolved PL spectra are obtained. XPS measurements provide high-purity samples aside from some contaminations from the air, and confirm the presence of pure MoS_2. The stoichiometric mole ratio of S/Mo is about 2.0–2.1, suggesting that sulfur is abundant rather than deficient in the atomic layer MoS_2 under our experimental conditions.