首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 125 毫秒
1.
基于激光诱导生物荧光技术,分别采用紫外355nm和266nm激光作为激发光源,构建生物气溶胶荧光雷达监测系统模型.综合考虑不同激发波段,臭氧吸收以及太阳背景光等因素对激光雷达荧光探测效果的影响,对系统性能进行数值仿真分析.仿真结果表明,在四倍频266nm紫外波段的激光激发下,系统受地表臭氧的影响,白天的有效探测距离非常有限;在系统信噪比为10(SNR=10),臭氧浓度为50μg/L时,最大探测距离仅为300m;而夜间情况下,太阳背景光影响减弱,探测距离约为450m.三倍频355nm激发时,臭氧对系统的探测性能影响较小,夜间探测距离可达750m;白天太阳背景光对355nm的系统影响较大,在相同0.5mrad接收视场角下,其有效探测距离约为330m.为减少白天背景光的影响,将望远镜接收视场角压缩到0.3mrad,同时选用50nm带宽的滤光片,此时系统的探测距离为480m.由于355nm波段的激发荧光受白天太阳背景光的影响较大,在进行夜间探测时才可获得较好的效果;而266nm的激发波段可以很好的抑制背景光影响,能够实现对生物气溶胶的白天有效探测.  相似文献   

2.
The efficiency of upconversion fluorescence for Er3+ and Yb3+ codoped into NaYF4 powder crystals is investigated. The dependence of Er3+ green (540 nm) and red (660 nm) upconversion fluorescence intensities on laser excitation intensity and the ratio of the green and red fluorescence intensities respectively under 355‐nm and 936‐nm excitations have been measured and analyzed in terms of radiative and nonradiative relaxation mechanisms. It is shown that the intensity of both the green and red upconversion fluorescence bands is affected at high pumping intensities by a low‐lying state acting as a bottleneck, with the red fluorescence less affected than the green. In addition to two‐photon, two‐step excitation and energy transfer processes, nonlinear optical coupling mechanisms of avalanche processes appear responsible for reducing the bottleneck saturation of the red upconversion fluorescence.  相似文献   

3.
The objective of this study is to develop a quantitative measurement of temperature from fluoranthene fluorescence under conditions with elevated temperatures and pressures. Absorption and fluorescence of fluoranthene are studied in a pressure and temperature range of 0.1–4 MPa and 473–873 K for the two excitation wavelengths of 266 and 355 nm. The influence of thermodynamic parameters such as pressure, temperature and gas composition is characterized in a high-pressure and high-temperature facility. When increasing the pressure, the vibrational relaxation mechanisms are favored, which involves an increase of the fluorescence quantum yield. Concerning the temperature effect, the fluorescence decreases with increasing temperature, this is explained by efficient radiative mechanisms of intersystem crossing. The quenching effect is strongly efficient in air, with a fluorescence evolution described by the Stern–Volmer relation. Over the temperature range studied, the fluorescence quantum yield decreases exponentially by two orders of magnitude. From the temperature dependence of fluoranthene fluorescence in different ambient gases for 266 and 355 nm excitation, the potential temperature measurements in homogeneously and inhomogeneously seeded systems are suggested: the single-color detection technique, the single-excitation two-color detection technique and the dual-excitation wavelength technique.  相似文献   

4.
In this work, highly luminescent carbon dots (CDs) were synthesized by the hydrothermal method at 170 °C for 12 h using pasteurized milk as a carbon source. The prepared CDs exhibited bright blue fluorescence under UV light illumination at 365 nm. The CDs show fluorescence life time of ~4.89 ns at excitation wavelength of 370 nm. The effect of different solvents on the fluorescence property of CDs was also investigated. The lisinopril (Lis)-loaded CDs were fabricated by self-assembly of lisinopril on the surfaces of CDs, which were characterized by UV-visible and FT-IR spectroscopic techniques. The controlled release of lisinopril from the Lis-CDs was realized at pH values of 5.2, 6.2 and 7.4, respectively. The results of the cytotoxicity and confocal laser scanning microscopic images indicate that the Lis-CDs were successfully uptaken by HeLa cells without apparent cytotoxicity. The synthesized CDs show great potential as drug vehicles with good biocompatibility, sustained release of lisinopril from CDs, indicating that the CDs can act as a promising drug delivery system for therapeutic delivery and/or bioimaging applications.  相似文献   

5.
Motivated by the photochemical and photophysical properties of curcumin-based composites, the characteristics of a new curcumin-based water-soluble salt were investigated via absorption and fluorescence spectroscopy. Photobleaching was investigated using a set of LEDs in three different wavelengths (405 nm, 450 nm and 470 nm) to illuminate an aqueous solution of curcumin, evaluating its degradation for five different exposure times (0, 5, 15, 45 and 105 minutes). The results were compared with equivalent measurements of dark degradation and illumination in the presence of a singlet-oxygen quencher. Three solution concentrations (50, 100 and 150 μg/ml) were studied. To measure the fluorescence, it was used low power 405 nm excitation laser source. Time dependent photodegradation of curcumin was observed, as compared to the natural degradation of samples maintained on a dark environment. Two main absorption peaks were detected and their relation responded to both concentration and wavelength of the illumination source. A spectral correlation between absorption of curcumin and the emission bands of the sources showed an optimal spectral overlap for the 450 nm LED. For this source, photobleaching showed a less intense degradation on the presence of singlet oxygen quencher. This last result confirmed singlet oxygen production in vitro, indicating a strong potential of this composite to be used as a blue-light-activated photosensitizer.  相似文献   

6.
A concept for temperature determination of fuel–air mixtures using Laser-Induced Fluorescence (LIF) is presented. For this purpose the fluorescence spectra of gasoline were measured after excitation by frequency quadrupled Nd:YAG laser light at 266 nm in a temperature range between 373 K and 448 K. Experiments were performed with colorless near-standard gasoline conforming to the Euro-super specifications. It is shown that the intensities of two fluorescence bands (290–302 nm and 332–344 nm) can be used to determine the temperature.  相似文献   

7.
胡继明  曾云鹗 《发光学报》1990,11(4):300-305
本文以Nd:YAG泵浦的染料激光器为激发光源,门控光学多道分析仪为检测器,自制的触发器和荧光盒组装成一台激光诱导时间分辨光谱装置。采用此装置研究了在表面活性剂Triton X-100存在下铕、钐-二苯甲酰甲烷-三正辛基氧化膦(Eu、Sm-DBM-TOPO)体系的激光诱导发光光谱特性和荧光衰减动力学特性。讨论了荧光发射过程中的能量传递机制。拟定出测定痕有铕和钐的时间分辨光谱方法,用于高纯稀土氧化物等样品中痕量铕和钐的测定,结果满意。  相似文献   

8.
The high-fluorescence background of jade creates a great impact on the Raman spectra measurements that impedes their application in jade analysis and treatment, particularly with ancient jade. The five most important materials of Chinese ancient jade are amphibole, serpentine, turquoise, agate/chalcedony, and anorthite-zoisite (Dushan jade). This study comparatively analyzed the Raman spectra of different wavelengths' excitation light sources (514.5 nm, 632.8 nm, 785 nm) in identifying these Chinese jades, and this article discusses the most applicable ones to the analysis of different jade materials. The results show that although 632.8 nm He-Ne laser is appropriate for turquoise jades, generally speaking, Raman spectra produced by the 785 nm semiconductor laser and the 632.8 nm He-Ne laser are better for most kinds of jades than the spectra produced by the 514.5 nm argon ion laser, and both of them can be effectively used jointly in research by nondestructive phase analysis of Chinese ancient jade.  相似文献   

9.
The spectral luminescent, photophysical, photochemical, lasing, nonlinear optical, and sensor characteristics of a series of new synthesized complexes of zinc and difluoroborate with dipyrrines of different structure have been studied. It is found that many of these compounds exhibit stimulated emission in different solvents when excited by the second (532 nm) and third (355 nm) harmonics of a Nd:YAG laser in the range of 548–692 nm. It is shown that not only efficient fluorophores belonging to dipyrrine difluoroborates (with a quantum fluorescence yield close to 1), but also compounds with a fluorescence yield equal to 0.3, generate laser radiation with a high resource; phosphorescence is also observed along with fluorescence. Transmission of UV radiation (355 nm) is shown to decrease with an increase in the pulsed excitation power density; this is a manifestation of nonlinear optical properties. The change of phosphorescence signal in dependence of the composition of the gas mixture around a solid-state sample colored by dipyrrinate complexes indicates that a number of the compounds under consideration exhibit sensor abilities.  相似文献   

10.
本文介绍了一种激光诱导荧光光谱探测系统。以355nm固体YAG激光作为激光光源,OMA光学多通道分析仪为荧光收集系统,通过在多个人体肺癌和食道癌样品上的应用,成功地测得了多种组织的荧光光谱。本文也初步探讨了一些与此相关的技术问题。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号