Development of Instrumentation for Photochemical Studies

荧光、磷光、闪光光解和电子自旋共振等光谱技术对于阐明环境化学物质的光物理和光化学是必要的。由于许多所需的设备要么无法从商业上获得，要么不能提供所需的功能，因此我们自己建造或现代化/升级大部分设备。这包括与计算机的接口，以便于数据采集和处理。两个旧的光谱荧光仪(稳态和相位调制)已合并为一个T形单元，现已进行升级，以测量磷光光谱和光漂白。激光闪光光解装置有一种新的更强大的激光器(Surelite II)用于激发。通过使用可调谐的OPO系统，激发波长的选择从400 nm扩展到红外，该系统由Surelite激光器的355 nm谐波泵浦。添加了在强激光激发后刷新厌氧样品的流动系统，以防止照射区域的漂白。这种新的激光闪光光解装置通过加入一个电磁铁和一个新的分析灯来观察在电动势存在下的瞬时光谱，从而适用于电动势的研究。Surelite激光器还与EPR光谱仪对准，在从激光脉冲中吸收多光子后，直接在EPR光谱仪的腔体中产生自由基。我们的单线态氧光谱仪目前正用于测量单线态分子氧与我们所研究的生物和环境底物的相互作用。此外，稳态单线态氧分光光度计正在升级，以测量非光化学反应中单线态氧的产生。该系统还经过改进，允许直接观察生长在单层中的角质形成细胞。在这个仪器的帮助下，我们第一次能够直接检测细胞中的单线态氧。为了正确解释单态氧磷光数据，我们必须确定不同环境对单态氧性质的影响。我们已经测量了极性、正电性和极化率在一些溶剂和溶剂混合物中的影响。目前，这些研究正在扩展到与生物环境更密切相关的非均相(胶束)体系。随着新技术的出现，上述所有系统都在不断地进行修改。这些变化还经常需要建立新的接口和开发新的控制软件。我们目前正在建造一个原型光电导池，以测量介电液体中的电光电导，并结合ESR检测。该电池将连接到时间分辨激光闪光光解光谱仪(见上文)，以允许研究无法用光学观察到的系统。激光闪光光解系统已经升级，配备了模拟染料激光的可调谐激光系统。通过加入电磁铁，这一新系统已被用于电动势研究。我们正在改进我们的红外光谱仪以研究细胞和组织。为了了解环境化学物质的光化学和光物理，有必要使用现代化学分析技术，包括多种光谱技术。该项目的目标是建造、测试和接口光物理研究所需的光谱仪。

Spectral techniques such as fluorescence, phosphorescence, flash photolysis, and ESR are necessary to elucidate the photophysics and photochemistry of environmental chemicals. Because much of the needed equipment is either not available commercially or does not offer the desired features, we build or modernize/upgrade most of it ourselves. This includes the interfacing to computers for ease of data acquisition and manipulation. Two old spectrophotofluorometers (steady state and phase modulation) that have been combined into one T-configured unit have being upgraded to measure phosphorescence spectra and photobleaching. The laser flash photolysis set-up has a new more powerful laser (Surelite II) for excitation. The choice of excitation wavelengths has been extended from 400nm to the infrared by using a tunable OPO system that is pumped by the 355nm harmonic from the Surelite laser. A flow system that refreshes anaerobic samples after strong laser excitation has been added to prevent the bleaching of the irradiated area. This new laser flash photolysis set-up has been adapted for EMF studies by incorporating an electromagnet and a new analytical lamp to observe the transient spectra in the presence of EMF. The Surelite laser has also been aligned with the EPR spectrometer to generate radicals directly in the cavity of the EPR spectrometer after multi-photon absorption from laser pulses. Our singlet oxygen spectrometers are being presently used to measure the interaction of singlet molecular oxygen with biological and environmental substrates we investigate. In addition, the steady-state singlet oxygen spectrophotometer is being upgraded to measure singlet oxygen production in non-photochemical reactions. This system has also been modified to permit the direct observation of keratinocytes grown in a monolayer. With the aid of this instrumentation we have been able for the first time to detect singlet oxygen directly in cells. To interpret the singlet oxygen phosphorescence data correctly, we have to establish how singlet oxygen properties may be affected by different environment. We have already measured the influence of polarity, proticity and polarizability in a number of solvents and solvent mixtures. Presently, these investigations are being extended over the heterogeneous (micellar) systems, which more closely relates to biological environments. As new technology becomes available, all of the above systems are continually being modified. These changes frequently also require the building of new interfaces and the development of new software for control. We are presently building a prototype photoconductivity cell to measure electrical photoconductivity in dielectric liquids in conjunction with ESR detection. This cell will be interfaced to the time-resolved laser flash photolysis spectrometer (vide supra) to permit studies of systems that cannot be observed optically. The laser flash photolysis system has been upgraded with a tunable laser system which emulates dye lasers. This new system has been adapted for EMF studies by incorporating an electromagnet. We are modifying our infrared spectrometer to study cells and tissues. In order to understand the photochemistry and photophysics of environmental chemicals it is necessary to use the techniques of modern chemical analysis including spectroscopic techniques of many kinds. The object of this project is to build, test and interface spectrometers that are needed for photophysical studies.