APPLICATION AND CHARACTERIZATION OF CHARGE-COUPLED DEVICE ARRAY DETECTORS FOR ANALYTICAL SPECTROSCOPY.

摘要

The research described in this dissertation is the first evaluation of two-dimensional charge coupled devices (CCDs) for low light level analytical spectroscopy. The electro-optical properties of several unique two-dimensional CCDs are evaluated, including quantum efficiency, detector read noise, linearity, dynamic range, dark current, and blooming. Theoretical models describing the sensitivity and dynamic range of CCDs on a single detector element basis are developed. Based on this model and the characteristics of a CCD detector system built for this research, it is shown that a single detector element of a CCD has comparable or superior sensitivity than the most sensitive single channel detectors. The results of the CCD detector system applied to fluorescence, emission, absorption, and time and spatially resolved spectroscopies are presented. The charge binning readout mode, which combines charge packets from several detector elements into a single charge packet, is critically evaluated for increasing the sensitivity and dynamic range of spectroscopic measurements. Equations describing the sensitivity and dynamic range enhancement achieved through charge binning are derived and experimentally verified in atomic emission and molecular fluorescence spectroscopies. The results of operating the CCD in two specialized readout modes developed in this research termed high-speed framing and spectral framing are presented. High speed framing allows the CCD to rapidly acquire two-dimensional images with high sensitivity. The spectral framing readout mode enables the CCD to record time-resolved spectra at a rate of approximately one spectra every two microseconds with great sensitivity. The design and evaluation of a CCD based molecular fluorescence spectrograph using a mercury pen lamp excitation source is described. The limit of detection for anthracene is 1 x 10 ⁻¹²M and is superior to the results obtained by fluorometers employing laser sources and photomultiplier detection. The design and evaluation of a spatially resolving spectrograph for absorbance spectroscopy of optically dense films is presented. The measurement of the absorption spectra of spatially heterogeneous metal-phthalocyanine thin-film electrodes with peak absorbances greater than five absorbance units is described.