Fluorescence rejection in resonance Raman spectroscopy using a picosecond-gated intensified charge-coupled device camera
Fluorescence rejection in resonance Raman spectroscopy using a picosecond-gated intensified charge-coupled device camera
复制标题
DOI：
10.1366/000370207781269873
复制
发表时间：
2007-06-01
影响因子：
3.5
通讯作者：
Ariese, Freek
中科院分区：
文献类型：
--
作者：
Efremov, Evtim V.;Buijs, Joost B.;Ariese, Freek
组装并测试拉曼仪器，其通常拒绝98-99%的背景荧光。为了在脉冲期间记录拉曼信号，同时阻断大部分荧光，使用短（皮秒）激光脉冲和时间选通检测。我们的方法使用超快门控增强电荷耦合器件（ICCD）相机作为ps Kerr门控的简单而直接的替代方案。荧光抑制效率主要取决于荧光寿命和门的关闭速度（在我们的设置中约为80 ps）。提出了一个计算该抑制因子的公式。门控增强器可以在80 MHz下工作，因此可以使用高重复频率和低脉冲能量，从而最大限度地减少光降解。对于激发，我们使用具有3 ps的脉冲宽度的三倍频或倍频Ti：蓝宝石激光器;鉴于所需的光谱分辨率，其不应更短。测试的其他关键方面包括增强器效率作为门宽度的函数，门脉冲在整个光谱的均匀性，以及与非门检测相比的光谱分辨率。仪器的总分辨率在蓝光区为7 cm（-1），在紫外区为15 cm（-1）。该装置允许使用共振拉曼光谱（RRS）获得额外的灵敏度和选择性，即使在强背景荧光的情况下。不再需要避免可见光或UV范围内的激发波长。该设置的有效性证明了一个测试系统：芘在甲苯荧光（λ（exc）= 257 nm）的存在下。此外，良好的时间门控RRS光谱显示为强荧光Havoprotein（λ（exc）= 405 nm）。这种方法的优点和缺点RRS进行了讨论。
A Raman instrument was assembled and tested that rejects typically 98-99% of background fluorescence. Use is made of short (picosecond) laser pulses and time-gated detection in order to record the Raman signals during the pulse while blocking most of the fluorescence. Our approach uses an ultrafast-gated intensified charge-coupled device (ICCD) camera as a simple and straightforward alternative to ps Kerr gating. The fluorescence rejection efficiency depends mainly on the fluorescence lifetime and on the closing speed of the gate (which is about 80 ps in our setup). A formula to calculate this rejection factor is presented. The gated intensifier can be operated at 80 MHz, so high repetition rates and low pulse energies can be used, thus minimizing photodegradation. For excitation we use a frequency-tripled or -doubled Ti: sapphire laser with a pulse width of 3 ps; it should not be shorter in view of the required spectral resolution. Other critical aspects tested include intensifier efficiency as a function of gate width, uniformity of the gate pulse across the spectrum, and spectral resolution in comparison with ungated detection. The total instrumental resolution is 7 cm(-1) in the blue and 15 cm(-1) in the ultraviolet (UV) region. The setup allows one to use resonance Raman spectroscopy (RRS) for extra sensitivity and selectivity, even in the case of strong background fluorescence. Excitation wavelengths in the visible or UV range no longer have to be avoided. The effectiveness of this setup is demonstrated on a test system: pyrene in the presence of toluene fluorescence (lambda(exc) = 257 nm). Furthermore, good time-gated RRS spectra are shown for a strongly fluorescent Havoprotein (lambda(exc) = 405 nm). Advantages and disadvantages of this approach for RRS are discussed.