UV Raman spectroscopy--a technique for biological and mineralogical in situ planetary studies

We report on the great advantages of using deep UV Raman system for in situ planetary applications. Among them are to be mentioned: (I) higher scattering efficiency compared to VIS-IR Raman excitation wavelengths, (II) electronic resonance effects which increase the intrinsically weak Raman signal thus improving the S/N ratio of the detected Raman signals and (III) spectral separation of Raman and fluorescence signals. All these advantages are making UV Raman a valuable technique for in situ planetary applications. Mineral as well as biological samples were analyzed using Raman deep UV excitation and the results are presented. For the mineral samples a comparison with excitation in the NIR-VIS spectral regions is made. The impact of fluorescence on Raman data acquisition at different laser excitation wavelengths is assessed. Making use of the resonance effects, spectra of microorganisms were recorded with a high S/N ratio, allowing afterwards a very precise identification and classification (to the strain level) of the measured samples.     

Chlorine detection in cement with laser-induced breakdown spectroscopy in the infrared and ultraviolet spectral range

A significant parameter to monitor the status of concrete buildings like bridges or parking garages is the determination of the depth profile of the chlorine concentration below the exposed concrete surface. This information is required to define the needed volume of restoration for a construction. Conventional methods like wet chemical analysis are time- and cost-intensive so an alternative method is developed using laser-induced breakdown spectroscopy (LIBS). The idea is to deploy LIBS to analyze drill cores by scanning the sample surface with laser pulses. Chlorine spectral lines in the infrared (IR) and ultraviolet (UV)-range were studied for chlorine detection in hydrated cement samples. The excitation energies of these spectral lines are above 9.2 eV. Hence high plasma temperatures and pulse energies in the range of some hundred millijoules are needed to induce sufficient line intensity levels at the required working distance. To further increase the line intensity and to lower the detection limit (LOD) of chlorine a measuring chamber is used where different ambient pressures and gases can be chosen for the measurements. The influences on the line intensity for pressures between 5 mbar and 400 mbar using helium as process gas and the influence of different laser burst modi like single and collinear double pulses are investigated. For the first time a LOD according to DIN 32 645 of 0.1 mass% was achieved for chlorine in hydrated cement using the UV line 134.72 nm.     

Comparison of 1064 nm and 266 nm excitation of laser-induced plasmas for several types of plastics and one explosive

Comparative measurements of Laser-Induced Breakdown Spectroscopy (LIBS) for ultraviolet (UV) and near infrared (NIR) excitation wavelengths on a wide range of plastics and one kind of explosive are presented. The focus of work is on the influence of laser wavelength on the Signal-to-peak to peak noise ratio (SPPNR) for selected emission lines as well as the plasma thresholds for NIR and UV excitation wavelengths. The merits of both excitation wavelengths are discussed with respect to the detection of explosives.     

Combination of the ionic-to-atomic line intensity ratios from two test elements for the diagnostic of plasma temperature and electron number density in Inductively Coupled Plasma Atomic Emission Spectroscopy

In Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES) spectrochemical analysis, the MgII(280.270 nm)/MgI(285.213 nm) ionic to atomic line intensity ratio is commonly used as a monitor of the robustness of operating conditions. This approach is based on the univocal relationship existing between intensity ratio and plasma temperature, for a pure argon atmospheric ICP in thermodynamic equilibrium. In a multi-elemental plasma in the lower temperature range, the measurement of the intensity ratio may not be sufficient to characterize temperature and electron density. In such a range, the correct relationship between intensity ratio and plasma temperature can be calculated only when the complete plasma composition is known. We propose the combination of the line intensity ratios of two test elements (double ratio) as an effective diagnostic tool for a multi-elemental low temperature LTE plasma of unknown composition. In particular, the variation of the double ratio allows us discriminating changes in the plasma temperature from changes in the electron density. Thus, the effects on plasma excitation and ionization possibly caused by introduction of different samples and matrices in non-robust conditions can be more accurately interpreted. The method is illustrated by the measurement of plasma temperature and electron density in a specific analytic case.     

Photobleaching of reduced nicotinamide adenine dinucleotide and the development of highly fluorescent lesions in rat basophilic leukemia cells during multiphoton microscopy

Endogenous reduced nicotinamide adenine dinucleotide (NADH) fluorescence provides an intrinsic indicator of the cellular metabolic state, but prolonged monitoring is limited by photobleaching and/or phototoxicity. Multiphoton excitation of NADH by ultrashort, 740-nm laser pulses provides a significant improvement over UV excitation by eliminating peripheral photobleaching; however, molecules within the subfemtoliter excitation volume remain susceptible. We have investigated the photophysical mechanisms responsible for multiphoton photobleaching of NADH in living cells to permit the imaging technique to be optimized. The loss of fluorescence because of multiphoton photobleaching was measured by repetitively imaging individual planes within rat basophilic leukemia cells. The photobleaching rate was proportional to the fourth power of the laser intensity. Based on these measurements, we propose a double-biphotonic, four-photon photobleaching mechanism and estimate the quantum yield of photobleaching of intracellular NADH to be 0.0073 +/- 0.0002 by this mechanism. In addition to photobleaching, the development of bright, punctate fluorescent lesions can also be observed. The frequency of lesion formation also increased approximately as the fourth power of the laser intensity after an intensity-dependent threshold number of images had been exceeded. The consequences for two-photon metabolic imaging are discussed.     

Sm3+掺杂CaO-SiO2-B2O3发光玻璃的制备、表征及性质

用高温固相法合制备了以CaO-SiO₂-B₂O₃为基质，Sm³⁺为激活离子的发光玻璃。对Sm³⁺的淬灭浓度、基质中的硼硅比例、其他稀土离子的敏化作用以及基质组成等因素对玻璃发光特性的影响进行了探讨，并用红外和X-衍射分析对样品的结构进行了表征。结果表明：当Sm^3＋掺杂的物质的量分数为1.2%,激发波长λ ＝ 404 nm时,玻璃体60CaO-20SiO₂-20B₂O₃∶1.2Sm^3＋的发光强度为4 838 A.U.( λ ＝ 606 nm );这种发光玻璃具有将紫外及近紫外光转换为橙红色光的特点。少量的Eu^3＋的掺入，对玻璃体的发光起敏化作用；玻璃体中的组分CaO可被ZnO替代。     

Electrochemical/chemical synthesis of highly-oriented single-crystal ZnO nanotube arrays on transparent conductive substrates

Arrays of ZnO nanotube (ZNT) were prepared by a two-step electrochemical/chemical process on a transparent, conductive substrate from an aqueous solution at 85 °C. The as-grown ZNTs are single crystals with wurtzite structure and have good crystalline state. The tubular morphology was formed by the proton generated from anodic splitting of water and defect-selective etching of the electrodeposited ZnO nanorod (ZNR) along the c-axis. The photoluminescence and cathodoluminescence spectra of the ZNT arrays show two emission bands located in the ultraviolet (UV) and visible region, respectively. It was found that the PL intensity in the UV band as well as the ratio of I_uv/I_visible increased with increasing of the excitation intensity.     

含铽配合物的合成及其荧光性研究

采用稀土铽金属醇盐与丙烯酸、乙酰丙酮、中性配体(邻菲啰啉或联吡啶）反应，在非水介质下合成具有高聚合活性的含铽配合物单体，通过元素分析、红外光谱、紫外光谱确定了它们的组成和结构，合成的铽配合物单体溶于一般的有机溶剂并能强烈吸收紫外光谌芤杭胺勰┳刺卵芯空庑┑ヌ宓挠庑浴T谧罴鸭し⒉ǔは拢蔷芊⑸滹胱拥奶卣饔猓ド越虾谩Q返淖刺叭芗恋募远耘浜衔锏牡ヌ宓挠庑杂薪洗笥跋欤行耘涮辶诜茊⒘拎さ囊芴岣咚堑挠夥⑸淝慷取     

等离子体增强MOCVD法生长ZnO薄膜

利用等离子体增强MOCVD法生长出 ZnO薄膜，用X射线衍射谱观察到位于 2θ34．56°处（0002）的衍射峰，表明ZnO沿c方向呈柱状生长．通过荧光光谱，观察到来自于激子的高强度的近带边紫外光发射（375um）．紫外发射光强度与深能级复合发射光强度比高达 193，显示出材料的高质量，并通过原子力显微镜加以验证．为了实现高阻ZnO薄膜，利用高温富氧分段退火和用N2 气进行掺氮两种方法生长高阻ZnO薄膜．结果表明，电阻率由0．65 Ω·cm分别升高到1100 Ω·cm（分段退火）和5×104Ω·cm（掺氮）．进一步比较发现，掺氮的样品不仅电阻率高，而且光荧光特性好，显示出更高的薄膜质量．     

Sensitivity limit of rapidly swept continuous wave cavity ring-down spectroscopy

The averaged transmitted intensity of a cavity excited by a linearly frequency swept laser with finite line width is derived and presented as a sum over passes, analytical integrals (where the sum of passes is converted to a continuous time variable), and an approximate but computationally more stable stationary phase approximation expression. The transmitted waveform is used to derive the bias in extraction of the cavity decay rate from such a cavity transient for three different fitting models. Numerical simulation of cavity excitation gives statistical fluctuations in the transmitted intensity that leads to noise in the cavity decay rate. For a range of parameters spanning those likely to be encountered in real experiments, numerical results are presented. These demonstrate that the theoretical signal-to-noise ratio and thus sensitivity of swept cavity (or equivalently, frequency) CRDS is substantially below that for CRDS where one attenuates the laser either with current modulation or with an external modulator.     

pH Resistant Ratiometric Measurement of Nicotinamide Adenine Dinucleotide Levels by Time-resolved Fluorescence Spectroscopy

Circular permutation fluorescent protein is a novel method to construct biosensors. The ratio of two excitation channels is employed to quantitatively calibrate the level of analysts. SoNar is one of them, which can be used to monitor cellular NADH/NAD⁺ levels. However, the 490 nm excitation channel of these biosensors is sensitive to pH environments, which is negative in real applications. In this work, we demonstrated that the fractional intensity ratio extracted from time-resolved fluorescence spectroscopy could be used to quantify NADH levels with one excitation (420 nm) and one emission channels. The 420-nm excitation channel was pH resistant. Comparing to average lifetime, the fractional intensity ratio had a 3.2-fold dynamic range, which was much wider than average lifetimes.     

Development and characterization of a DNA solar dosimeter

In this paper, we report the development and characterization of a solar ultraviolet (UV) dosimetry system that can be used as a film badge for radiation monitoring. DNA molecules are coated on a thin nylon membrane as a UV dosimeter. The membrane is sealed in a polyethylene filter envelope with silica gel to keep the humidity low. After exposure to UV or solar light, induced DNA damage is measured by an immunochemical reaction. The intensity of color developed during the immunological reaction can be correlated linearly with the irradiated UV dose delivered by an Oriel solar simulator within a limited dose range. We observe no effects of temperature on the level of damage induction. The membrane is proficient for measuring DNA damage for more than 21 days when stored at either 37 or 4°C. The induced damage remains stable on the membrane for at least 22 days at both 37 and 4°C. In addition to these indoor experiments, we report measurements of solar UV dose in outdoor experiments.     

Multiphoton-Excited Visible Emission by Serotonin Solutions

Nonlinear excitation of the neurotransmitter serotonin (5HT) in aqueous solution is shown to generate a blue-green-emitting photoproduct in addition to UV fluorescence characteristic of native 5HT. The visible emission rate in diffusional steady-state measurements scales as the sixth power of excitation intensity, demonstrating that absorption of six near-IR photons is required to generate emission of one visible photon. Transient measurements reveal that this process is composed of two sequential nonlinear steps, the first excited by four photons and the second by two photons. These results, in combination with measurements of multiphoton-excited serotonin UV fluorescence, support a model in which 5HT is photochemically transformed as a consequence of four-photon absorption (E_tot?6 eV) to a photoproduct that then emits in the visible region via two-photon excitation. A minimum bound of ?10^-51 cm⁴ s photon^-1 is observed for the two-photon emission action cross section at 830 nm. Photoionization, rather than reaction with a dissolved oxygen species, appears to be the primary mechanism for generation of the blue-green-emitting photoproduct. The peak intensities required to generate significant blue-green emission (?5 times 10¹¹ W cm^-2 from 80 MHz 150 fs titanium: sapphire laser pulses) are approximately five-fold higher than are typically used in two-photon laser scanning microscopy but are still substantially lower than the estimated intensity needed to induce dielectric breakdown of water.     

CALCIUM-DEPENDENT FLUORESCENCE LIFETIMES OF INDO-1 FOR ONE- AND TWO-PHOTON EXCITATION OF FLUORESCENCE

Abstract— We characterized the fluorescence intensity decays of Indo-1, which is commonly used as an emission wavelength-ratiometric calcium probe. The apparent lifetime of the long-wavelength side of the emission of Indo-1 is dependent on Ca²⁺. This long-wavelength emission displays the characteristics of an excited-state reaction, that is, a negative preexponential component in thc multiexponential analysis. The emission spectra and lifetime of Indo-1 appear to be identical for one-photon and two-photon excitation at 351 and 702 mn, respectively, suggesting that the relative one- and two-photon cross sections are similar for the calcium-free and calcium-bound forms of Indo-1. Also, the two-photon cross section of Indo-1 is relatively high, about 4 × 10⁻⁴⁹ cm⁴ s/photon molecule at 690 nm for both the calcium-free and calcium-bound forms. Hence, Indo-1 can be used for calcium imaging based on one- or two-photon excitation, using either emission wavelength ratios or lifetime imaging methods.     

分子离子双激发解离通道的竞争

建立了三原子分子离予XYZ＋（XY2^＋）解离产生多种离子产物时Eα和Eβ两个解离通道之间竞争的理论模型．实验测量出碎片产物分支比和对两束解离光光强比的依赖关系后,由理论公式对数据进行拟合获得拟合参数,可以计算出两个激发解离通道α和β的激发截面分支比．     

新Schiff碱SAAQ的合成及其分析应用研究(Ⅰ)——荧光光度法测定镓

常用于测定镓的荧光试剂有8-羟基喹啉类、Schiff碱类、偶氮类及黄酮类等^[1～8]。而水杨醛缩-8-氨基喹啉(简称SAAQ)的合成及分析应用研究尚未见报道.本文研究了该试剂的合成方法及其分析应用.     

ZnO nanobelt arrays grown directly from and on zinc substrates: synthesis, characterization, and applications

In situ growth of ZnO nanobelt arrays from and on zinc substrates (foils and microparticles) has been accomplished by controlled thermal oxidation in the presence of oxygen. The nanobelts grow approximately perpendicular to the Zn substrate surface along the 110 direction of ZnO, which has a thickness of approximately 3-4 nm, a width tapering from about 50 to 300 nm, and a length of approximately 10-20 mum. On the basis of the structural analysis and kinetic studies, a tip-growth mechanism is proposed, which underlines the transport of Zn from the substrate to the growing tip. The ratio of UV to green photoluminescent emissions of the as-synthesized ZnO nanobelt arrays could be controlled by varying the reaction conditions. Sharp UV stimulated emission peak is also observed at moderate threshold excitation intensity ( approximately 0.7 mJ/cm(2)) showing the high quality of the ZnO nanobelts. The ZnO nanobelts array has also been tested for sensing NH(3) gas, and high sensitivity, reversibility, and rapid response have been demonstrated.     

Pre-processing of ultraviolet resonance Raman spectra

The application of UV excitation sources coupled with resonance Raman have the potential to offer information unavailable with the current inventory of commonly used structural techniques including X-ray, NMR and IR analysis. However, for ultraviolet resonance Raman (UVRR) spectroscopy to become a mainstream method for the determination of protein secondary structure content and monitoring protein dynamics, the application of multivariate data analysis methodologies must be made routine. Typically, the application of higher order data analysis methods requires robust pre-processing methods in order to standardize the data arrays. The application of such methods can be problematic in UVRR datasets due to spectral shifts arising from day-to-day fluctuations in the instrument response. Additionally, the non-linear increases in spectral resolution in wavenumbers (increasing spectral data points for the same spectral region) that results from increasing excitation wavelengths can make the alignment of multi-excitation datasets problematic. Last, a uniform and standardized methodology for the subtraction of the water band has also been a systematic issue for multivariate data analysis as the water band overlaps the amide I mode. Here we present a two-pronged preprocessing approach using correlation optimized warping (COW) to alleviate spectra-to-spectra and day-to-day alignment errors coupled with a method whereby the relative intensity of the water band is determined through a least-squares determination of the signal intensity between 1750 and 1900 cm(-1) to make complex multi-excitation datasets more homogeneous and usable with multivariate analysis methods.     

TXRF, PIXE, SYXRF; Principles, critical comparison and applications

Summary At first glance X-Ray fluorescence analysis seems to be a very sensitive and effectful method to detect element traces in the multielement mode. But in praxi the application range is restricted, if X-Ray tubes are used as excitation sources. To overcome this situation, it is necessary to improve the conditions of excitation and to reduce the background, produced by different scattering effects. TXRF, PIXE and SYXRF, which allow multielement analysis in the trace- and ultratrace region are using this strategy. In the case of TXRF a remarkable background reduction is achieved if the sample is prepared as a thin amorphous film on a planar sample holder and the excitation beam of a X-Ray tube is totally reflected on its surface. In the case of PIXE a particle beam of high intensity is used as excitation source, improving the conditions of excitation and giving the opportunity of spatial resolved analyses. In the case of SYXRF the X-Ray fraction of synchrotron radiation is used as excitation source, giving the opportunity, to improve the conditions of excitation as well as to reduce the background by using the high polarisation of the beam. In this case, too, spatial resolved analysis are possible. The principles of the three methods are described, their advantages and disadvantages are critically compared and advanced applications from different analytical fields are presented.     

A glycerol assisted light-emitting diode-induced fluorescence detector for capillary flow systems

A glycerol assisted light-emitting diode (LED)-induced fluorescence detector (IF) for capillary flow systems was constructed and evaluated. A blue LED was used as the excitation source, and optical fibers (OF) were used to transmit the excitation light and collect the fluorescence. A commercial available 5-port manifold was used as detection cell, where the capillary tube and the OF were fixed into the manifold. The precision of the holes on the manifold ensured a self-alignment of optical path. A refractive index matching fluid (RIMF)-glycerol was used to eliminate the interfaces between the OF and the LED, as well as between the fused silica capillary and the transmitting/collecting fiber. The enhancement of excitation light led to 2.8-folds improvement on the signal-to-noise ratio. The use of RIMF also eliminates focusing effect of the capillary wall and reduces both the excitation light directed to the detection cell and background signal, resulting in reduction in the fluorescence intensity and noise level. The intensity was reduced to 47-63% for laser and 60-77% for LED, respectively, for capillaries with i.d. from 50 to 250 microm; while the noise level was reduced to 1/3 when RIMF was used for both laser and LED on the tested capillaries. About 5.6-fold enhancement in signal-to-noise ratio was obtained in total. The detection limit of the LED-IF for fluorescein isothiocyanate (FITC) was 4 nM. Application of the LED-IF for the analysis of FITC-labeled amino acids by electrophoresis was demonstrated.