Raman spectra were measured using a Horiba LabRAM HR Evolution Raman microscope (Horiba Scientific) using 633 nm excitation from a Helium-Neon laser. The laser light was focused on the sample using an infinity-corrected achromatic 100× objective (0.9 NA, MPLN100X, Olympus) with the average power ranging from to 2.5 mW to 17.9 mW. Acquisition times ranged between 30 -360 s per spectrum. Spectral acquisition parameters were carefully chosen to balance maximizing signal-to-noise and mitigating photodegradation of samples. Under the illumination conditions used, we observed no visual signs or spectral signatures of sample degradation (Figure ). The scattered light was collected by the focusing objective in a 180°backscattering geometry. The scattered light was focused into a spectrometer and dispersed using a 600 gr/mm grating. Spectra were imaged using a Synapse EM CCD camera (1600X200-FV, Horiba Scientific).