Nancy S. Ferris

Tunable near-infrared Raman spectroscopy

Abstract Approaches to generating fluorescence-free Raman spectra using excitation in the near-infrared (near-IR) region of the spectrum are not limited to the use of Fourier transform (FT) Raman spectroscopy. Although FT-Raman does introduce the well-established advantages of Fourier transform methods to the field of Raman spectroscopy, it is clearly not the only alternative to obtaining a Raman spectrum with near-IR excitation. The coupling of laser excitation at wavelengths longer than 700 nm with low noise multichannel detection can also produce fluorescence-free Raman spectra. In this paper we describe the capabilities and use of a slow scan camera system employing a silicon charge-coupled device (CCD) specifically fabricated with enhanced performance in the near-IR region of the spectrum as a detector for near-IR Raman spectroscopy. This highly sensitive detection method provides a convenient means to rapidly generate high-quality and nearly fluorescence-free spectra using a variety of excitation sources including diode lasers tuned beyond 800 nm. Examples of spectra generated with CCD detection and the FT-Raman technique are compared. A discussion of the appropriate conditions for application of the two approaches is also included.

Synthesis and study of imidazole-bearing copper(I) complexes and their reversible reaction with dioxygen

Magnetochemical and resonance-Raman spectroscopic measurements have been made on oxygenated solutions of {2,6-bis[1-(2-imidazol-4-ylethylimino)ethyl]pyridine}copper(I) cation and related complexes to characterize more fully the nature of the copper–dioxygen interaction. The role, if any, of the imidazole–nitrogen proton in the reversible oxygenation process has been examined. A possible correlation between the redox potential of the CuII⇌ CuI couple and the reaction of the copper(I) centre towards O2 has been studied, and for completeness, copper(II) and zinc(II) analogues of all the copper(I) species have also been prepared and fully characterized. Although inconclusive in an absolute sense, the present studies are consistent with the oxygenation products of these copper(I) species being relatively stable Cu–O2 or Cu–O2–Cu adducts, at least in the initial stages of oxygenation.

Capabilities of a charge-coupled device with enhanced red responsivity for use in Raman spectroscopy

The performance of a slow-scan camera system using a silicon CCD fabricated specifically to have good performance in th near-rn a detector for Raman spectroscopy is described. The capabilities of the red-enhanced CCD for producing high-quality spectra with red excitation wavelengths at moderate laser powers and relatively short integration times are demonstrated using benzoic acid. The SNR performance is compared to a conventional CCD and an intensified photodiode array. Utility of the red-enhanced CCD system for a variety of applications is demonstrated with near-JR examples of resonance Raman, SERS, and conventional Raman with a low-power source. Problems associated with the sensitivity of CCDs in general, and the red-enhanced CCD in particular, to highenergy particles are described. Methods for minimizing the problem by adding shielding, using only the illuminated part of the detector, using multiple exposures, and using the minimum amount of binning necessary are presented.

Analytical Raman and atomic spectroscopies using charge-coupled-device detection

Scientific grade CCDs operated in cooled, slow-scan cameras offer numerous advantages over single-channel and other multichannel detectors in analytical spectroscopy. Although these advantages have long been recognized and exploited, the applicability of CCDs to analytical spectroscopy has recently been expanded by the development of devices with unique capabilities. Specifically, analytical plasma emission spectroscopy requires a multichannel detector with a very large number of pixels and which has very high resistance to blooming. Analytical Raman spectroscopy is currently undergoing a push to use longer laser excitation wavelengths, and at these longer wavelengths high sensitivity becomes an even greater concern. Two new CCDs and their application in these two fields of analytical spectroscopy are described. Preliminary results obtained with a large format antiblooming CCD used with a custom-built echelle spectrometer are presented, and the capabilities of a red-response- enhanced CCD for tunable near-IR Raman spectroscopy are compared with Fourier transform Raman spectroscopy.

A vibrational spectroscopic study of metal chalcogenide spin-on-glasses

Abstract Thin films of germanium diselenide have been prepared by a spin-on-glass technique from ethylenediamine solutions. The solutions and the films at various stages of processing have been characterized using infrared and Raman spectroscopies. The results indicate that amorphous GeSe 2 films are formed after complete processing. At stages prior to the formation of the final film several chemically distinct species are observed. The identification of some of these species offers insight into the formation of solid GeSe 2 networks.