Prism-based infrared spectrographs using modern-day detectors.

A comparison of prism-based spectrographs to grating-based spectrographs is made when each of the systems is coupled to a modern-day liquid-nitrogen-cooled photovoltaic array detector. A comparison of the systems is also made using a room-temperature microbolometer array detector. Finally, infrared microspectroscopy of samples whose size is approximately 10 micrometers will be demonstrated using a prism spectrograph outfitted with both types of detectors. The results of the study show that prism-based spectrographs offer an economical alternative to grating-based systems when spectral coverage is more critical than spectral resolution. The results also demonstrate that spectra with good signal-to-noise ratios can be collected on any of the systems with a total integration time of 10 seconds or less.

The influence of core size on electronic coupling in shell-core nanoparticles: gold clusters capped with pyrenoxylalkylthiolate.

The mean size of the metallic core of monolayer-protected gold clusters densely capped with 9-(1-pyrenoxyl)octane-1-thiol or 1-dodecanethiol can be adjusted by controlling the thiol/HAuCl4 ratio during synthesis. Upon reduction of tetrachloroaurate by NaBH4, lower mean metal core diameters were attained in those composites prepared from mixtures with higher thiol/Au ratios. The efficiency of electronic coupling between the core metal cluster and pyrenyl groups appended as an outer shell in this size-graded family was studied by absorption and fluorescence spectroscopy. The observed emission intensity from the bound fluorophores is independent of the gold core size.