633 nm Laser for Raman Instrument

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Commercially produced carbon nanotubes are mixtures of multiple nanotube types, which range in conductivity properties from semiconducting to metallic. This mixture of nanotube types is detrimental to commercial applications, as devices require pure samples of either metallic or semiconducting nanotubes, depending on the application. Our research efforts are focused on separating and purifying carbon nanotubes according to type, which will allow many applications to come to fruition. However, all efforts to purify nanotubes require access to techniques that can identify the nanotube types in processed samples. Such identification can only be achieved using spectroscopic measurements that can differentiate between different nanotube types. One extremely powerful technique for nanotube identification is Raman Spectroscopy, which measures scattered light from a laser and allows determination of vibrational modes present within a sample. Different nanotubes types are sensitive to different laser excitation wavelengths, and to get a complete picture of sample composition, one must use multiple laser excitation wavelengths. One of the most useful wavelengths for nanotube characterization is 633 nm, which allows for simultaneous excitation of both semiconducting and metallic carbon nanotubes. It is only by using this specific excitation wavelength that one can determine the relative semiconducting vs. metallic nanotube composition within a sample, allowing the evaluation of methods for separating these different nanotube species. Currently, there is no Raman instrument at McMaster University that is equipped with a 633 nm laser source. This application therefore requests an upgrade to an existing, fully functional Raman instrument at McMaster that will provide the capability to excite samples at 633 nm. This instrument is in dire need by a number of research groups, and will enable numerous studies that are currently impossible at McMaster.