We measure the spectrum and efficiency of the infrared light emission from ambipolar carbon nanotube field-effect transistors. The width of the emission peak is strongly device-structure dependent. Long devices (∼50 µm) show narrow spectral peaks that we attribute to relaxed carrier recombination, while short devices (∼500 nm) show broad peaks due to hot carrier recombination. The hot carrier distribution is limited to energies below the energies of the optical/zone boundary phonons near 180 meV. The efficiency of the radiative recombination is between 10 -6 and 10 -7 photons/electron−hole pair, and the possible quenching mechanisms are discussed.

Photoinitiated dispersion polymerization of methyl methacrylate was carried out in a mixture of ethanol and water as dispersion medium in the presence of poly(N‐vinylpyrrolidone) (PVP) as the steric stabilizer and Darocur 1173 as photoinitiator. 93.7% of conversion was achieved within 30 min of UV irradiation at room temperature, and microspheres with 0.94 μm number–average diameter and 1.04 polydispersity index (PDI) were obtained. X‐ray photoelectron spectroscope (XPS) analysis revealed that only parts of surface of the microspheres were covered by PVP. The particle size decreased from 2.34 to 0.98 μm as the concentration of PVP stabilizer increased from 2 to 15%. Extra stabilizer (higher than 15%) has no effect on the particle size and distribution. Increasing medium polarity or decreasing monomer and photoinitiator concentration resulted in a decrease in the particle size. Solvency of reaction medium toward stabilizer, which affects the adsorption of stabilizer on the particle surface, was shown to be crucial for controlling particle size and uniformity because of the high reaction rate in photoinitiated dispersion polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1329–1338, 2008

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