有机磷农药残留的表面增强拉曼光谱快速检测

农药残留严重影响人类身体健康与生命安全,故亟需建立一种简单高效的农药残留快速检测方法。本文以金纳米溶胶作为表面增强拉曼光谱(SERS)的增强基底,结合便携式拉曼光谱仪,实现了倍硫磷与对硫磷等常用有机磷农药的多靶标同时检测。结果表明倍硫磷和对硫磷分别在1053 cm~(-1),1216 cm~(-1)和857 cm~(-1),1112 cm~(-1)处具有特征拉曼谱峰,且两者互不干扰。同时进一步研究表明,倍硫磷和对硫磷的浓度与其特征拉曼谱峰强度线性相关,故可实现定量检测,其中倍硫磷检测限可达0.01μg/mL对硫磷检测限可达0.025μg/mL。同时,该SERS方法可直接用于菠菜实际样品中多种农药残留的多靶标快速检测,检测限达到0.05μg/mL。该SERS方法具有方便、快速、灵敏度高、多靶标同时检测等优点,有望实现农药残留的现场快速检测。     

表面增强拉曼光谱准确检测玉米中杀螟硫磷农药残留

杀螟硫磷是一种在农作物上广泛使用的有机磷杀虫剂,常用于玉米上害虫的防治。过量或者不合理施用导致的残留积累关系到食品安全和人体健康。常规检测杀螟硫磷的方法有气相色谱-质谱法、高效液相色谱法,其准确性虽好,但存在需要专业人员介入、样品前处理复杂、检测时间长等缺点。表面增强拉曼光谱(SERS)法具有分析速度快、检测灵敏度高和特异性好等优点,被广泛应用于农产品中痕量残留的快速检测。利用表面增强拉曼光谱结合化学计量学方法实现玉米中杀螟硫磷残留的准确检测。以两步种子生长法合成的纳米金棒作为拉曼增强基底,测量600～1 800 cm-1范围内的拉曼光谱。对比杀螟硫磷乙醇溶液和金棒的光谱,确定杀螟硫磷的特征峰在650,830,1 082,1 241,1 344和1 581 cm-1处。采用简单预处理方法快速提取玉米中的杀螟硫磷残留。将受污染的玉米样品粉碎后,利用乙醇溶剂对残留进行两次提取,每次获取的提取液经离心获得上清液,将上清液合并混匀,在水浴中蒸发浓缩,浓缩后的上清液用于采集SERS光谱。每个浓度制备50个平行样本。各浓度残留提取液中的残留参考值采用色质联用方法测定。对比残留提取液的光谱,1 082,1 241和1 581 cm-1处特征峰强度随残留浓度的降低而迅速变弱甚至消失,650,830和1 344 cm-1处的特征峰直至残留浓度为0.48 μg·mL-1时依然可见。当浓度低至0.37 μg·mL-1时,所测光谱与空白提取液光谱相似。采用主成分分析(PCA)提取不同浓度杀螟硫磷残留光谱的主体信息,其中残留为0.37 μg·mL-1和空白提取液光谱的主成分得分重叠,进而判断SERS方法对玉米中杀螟硫磷残留的检测限可达到0.48 μg·mL-1,低于国家规定的农作物中最大残留限,体现出SERS检测的高灵敏性。选取浓度为14.25 μg·mL-1的50个样本分析其650,830和1344 cm-1处的特征峰强度变化可知,所采集的光谱呈现出较好的重复性,相对标准偏差(RSD)值仅为3.12%。对杀螟硫磷残留的定量分析采用支持向量机回归(SVR)实现,Savitzky-Golay卷积平滑和小波变换(WT)用于本次光谱数据的预处理。校正集和预测集样本的划分采用Kennard-Stone算法实现,模型的性能采用校正均方根误差(RMSEC)、校正集决定系数(R2_c)、预测均方根误差(RMSEP)和预测集决定系数(R2_p)评估。最优模型为SVR结合WT所构建的,具有最小的预测误差,其中校正集的RMSEC=0.103 2 μg·mL-1,R2_ｃ=0.999 74,预测集的RMSEP=0.134 1 μg·mL-1,R2_p=0.999 60。同时,最优模型的预测值与色质联用法所测值基本一致,其预测回收率为95.31%～100.66%。以上表明,SERS结合化学计量学方法检测玉米中杀螟硫磷残留是准确可行的,且有望推广到农作物中多种农药残留的检测,为农产品的安全检测提供一种新思路。     

胶束电泳法测定五味子中的3种有效成分

建立了基于一种快速、高效分离与测定五味子中五味子甲素、五味子乙素和五味子酯甲含量的胶束毛细管电泳-紫外检测分析新方法。以毛细管(70cm×50μm i.d×375μm o.d)为分离通道,在最佳电泳介质(30mmol/L SDS,pH=7.2,20mmol/L磷酸盐缓冲溶液)中,当分离电压为21kV时,3种待测物质在11min内达到基线分离。在254nm波长处,五味子甲素、五味子乙素和五味子酯甲的线性响应范围分别为5.0—150.0μg/mL、1.0—100.0μg/mL和1.5—150.0μg/mL;检出限分别为1.0、0.22μg/mL和0.4μg/mL。该方法具有良好的重现性,以100.0μg/mL的五味子甲素、五味子乙素和五味子酯甲测定其保留时间和峰高相对标准偏差(RSD)(n=7)均小于2.98%。本方法用于中药五味子中五味子甲素、五味子乙素和五味子酯甲的含量测定,结果令人满意。     

Fe(Ⅲ)-磺基水杨酸褪色光度法测定物样品中的硫普罗宁

建立了Fe(Ⅲ)-磺基水杨酸褪色光度法测定硫普罗宁的新方法.结果表明,在酸性介质中,硫普罗宁分子中的巯基(—SH)可将Fe3+还原为Fe2+,采用磺基水杨酸作为Fe3+的显色剂,借褪色分光光度法间接测定了硫普罗宁含量.显色体系最大吸收波长为480nm,硫普罗宁在0.50-4.0μg/mL浓度范围内与AA呈良好的线性关系,线性回归方程为△A=0.0065+ 13C(μg/mL),线性相关系数r=0.9997,检出限为0.00016μg/mL.方法成功用于实际药品中硫普罗宁的含量测定.     

咪唑功能化聚苯乙烯包覆硅胶微球分离富集——火焰原子吸收光谱法测定痕量银

制备了咪唑功能化聚苯乙烯包覆硅胶微球并用其填充微柱,建立了微柱分离富集--火焰原子吸收光谱法测定痕量银的方法.研究了填充微柱对Ag(I)的吸附性能及影响吸附的因素,用酸性硫脲作洗脱剂,以峰面积检测,测定Ag(I)的线性范围为0.010-0.50μg/mL,相对标准偏差为2.5%(n=3),检出限为0.002μg/mL,灵敏度提高20倍,填充微柱可重复利用.     

分光光度法测定铝合金中的微量铜

介绍了有机试剂5-甲基-3-对乙氧苯基-2-硫代乙内酰脲与Cu2 的络合反应.研究发现,在pH5.91的KH2PO4-Na2HPO4的缓冲溶液中,Cu2 与该试剂形成1:3的络合物,其最大吸收峰位于292.0nm处,摩尔吸光系数ε292.0nm=2.5×104L·mol-1·cm-1,Cu2 浓度在0-30μg/25mL范围内呈线性关系,相关系数r=0.9987.该法操作简单,选择性高,已满意地用于铝合金中微量铜的测定,回收率为97.8%-98.0%.     

碱熔-离子色谱法同时测定植株中氯和硫的含量

样品采用氧化镁-碳酸钠混合熔剂,在恒温马弗炉中800℃加热1h,冷却,用水超声浸提.用碱融-离子色谱法同时测定植株中氯和硫的含量.分析柱:AS14A 4-mm(4×250mm),淋洗液:8.0mmol/L Na2CO3-1.0mmol/L NaHCO3,再生液:50mmol/L H2SO4,流速:1.0mL/min,进样体积:20μL,外标峰面积定量.Cl在0.2-30μg/mL,S在3-100μg/mL浓度范围内具有良好的线性关系.平均回收率Cl为96.95%;S为93.56%.相对标准偏差Cl为1.16%;S为1.42%.实验证明该方法操作简便、快速灵敏、准确.     

三唑磷-鲁米诺-H2O2发光体系的研究与应用

研究了碱性介质中三唑磷-鲁米诺-H2O2体系的化学发光特征,建立了三唑磷流动注射化学发光分析方法,并对反应机理进行了探讨.研究了三唑磷-鲁米诺-H2O2体系的化学发光反应动力学,考察了pH、流速、鲁米诺-H2O2配比等因素对化学发光的影响.在最佳条件下,过氧化氢HOO-负离子可能与三唑磷的磷原子反应生成磷的过氧化合自由基,与鲁米诺作用使得体系化学发光得到增强,3s内达到了最大值;应用于三唑磷的测定,在1.0×10-8-1.0×10-5g/mL范围内呈良好的线性关系,检出限(S/N=3)为6.7×10-9g/mL;测定蔬菜样品,三唑磷浓度分别为1.0-5.0μg/mL时,测定回收率为82.3%-108.6%,测定偏差为1.6%-4.7%.     

微波高压消解-火焰原子吸收光谱法测定精神病患者头发中微量元素

本文提出微波高压消解-火焰原子吸收光谱法（FAAS）测定痕量铜、锌、铁和锰的方法。该方法检检出限CU^2 、Zn^2 、Mn^2 为0.001μg/mL和Fe^3 为0.005μg/ml。Mn^2 、Fe^3 、Cu^2 和Zn^2 的含量分别在0.1-1.0、0.1-5.0、0.1-2.5和0.1-2.5μg/mL范围内测定。线性关系良好，相关系数为0.9997-0.9999，此法巳成功用于人发样中铜、锌、铁和锰含量的测定。     

抑制铁阻抑甲基橙褪色动力学分光光度法测定痕量维生素C

在H2SO4介质中,痕量维生素C的存在对铁(Ⅲ)阻抑KBrO3氧化甲基橙褪色反应有很强的抑制作用,据此建立了阻抑动力学分光光度法测定痕量维生素C的新方法.在选定条件下,方法的线性范围是0.06-0.65μg/mL,检出限为0.0086μg/mL.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.