Search

A fast, sensitive, automated Fourier transform (FT) photoluminescence (PL) spectrometer with tunable excitation has been developed for analyzing carbon nanotube suspensions over a wide spectral range. A commercially available spectrometer was modified by the addition of a tunable excitation source, custom collection optics, and computer software to provide control and automated data collection. The apparatus enables excitation from 400 to 1100 nm and detection from 825 to 1700 nm, permitting the analysis of virtually all semiconducting single-walled nanotubes (SWNTs), including those produced by the high pressure carbon monoxide conversion and laser processes. The FT approach provides an excellent combination of high sensitivity and fast measurement. The speed advantage exists because the entire emission spectrum is collected simultaneously, while the sensitivity advantage stems from the high optical throughput. The high sensitivity is demonstrated in the measurement of very dilute SWNT suspensions and the observation of novel spectral features, and the speed is demonstrated by measuring the real-time changes in the SWNT PL during rebundling. This contribution describes the assembly of components, the methods for automating data collection, and the procedures for correcting the wavelength-dependent excitation intensity and the interferometer and detector responses. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) have been the subject of considerable study in theoretical physics, and water soluble QDs now appear to have numerous applications in biological tagging, molecular electronic devices, and nanoscale engineering. The work reported here supports the notion that the aliphatic chains of the trioctylphosphine oxide molecules decorating these (CdSe)ZnS core-shell QDs are stabilized by the hydrophobic cyclodextrin (CD) lumen. Photoluminescence studies show a redshift of over 15 nm in the emission wavelength of the QDs upon complexation with the CD, and first-principles calculations reveal an exothermic exchange of the S in the ZnS shell with the CD hydroxyl oxygen. Unlike simple water-driven surface transformations, the directed bonding of hydroxyl groups to the ZnS shell results in stable structures, verified by photoluminescence and Fourier transform infrared spectroscopy. [ABSTRACT FROM AUTHOR]

Discusses a study in which researchers were able to cool a sample of solid glass using an infrared laser light, reported in the periodical 'Physical Review Letters.' Process known as anti-Stokes luminescence, by which the generation of excess thermal energy which usually occurs with lasers is bypassed; Development of optical refrigerators based on anti-Stokes photoluminescence.

Abstract: We fabricate photovoltaics comprised layers and blends of a hole-transporting derivative of poly(p-phenylene-vinylene) with a variety of electron-transporters: titanium dioxide, a cyano-substituted PPV, and a fullerene derivative (PCBM) to enhance device performance. Photovoltaic device characterization is combined with time-resolved and steady-state photoluminescence to understand the nature of the excited state and its effect upon device performance. We find that morphological differences, such as chain conformation or domain size, often overshadow the effect of charge transfer, so that device performance is not necessarily correlated with rapid decay times. Exciton generation is found to be a similarly important factor in most devices. These results provide insight into non-optimized device morphologies. [Copyright &y& Elsevier]