Uniform silicon single nanodots were synthesized by laser ablation with a differential mobility analyzer (DMA) technique. The Si nanoparticles
generated by laser irradiation of a silicon target were actively classified by a DMA and were impacted on the solid surface by a “nanoparticle
beam”. By measuring the current of the beam, we determined the size distribution of generated particles in situ. From transmission electron
microscope (TEM) observation of deposited dots, it was found that they were well-isolated and uniform in size. High-resolution TEM images
indicated that they were single crystals with a diameter of 10, 7, and 5 nm. However, the particles less than 4 nm seemed to have no crystallinity
(amorphous).
We report an efficient solid-phase synthesis of diverse 1,3N-disubstituted quinazoline-2,4-diones. Since substitutions at the 1N-position of quinazolidine-2,4-diones were introduced by reaction between primary amines and 2-fluoro-5-nitrobenzoyl amides (S N Ar reaction), substitutions that cannot be prepared by alkylation or arylation can be easily introduced. In addition, the nitro group of quinazoline-2,4-diones can be repeatedly reduced to provide 3N-amines for quinazoline-2,4-dione syntheses, allowing the synthesis of quinazoline-2,4-dione oligomers and polymers. An oligomer with four quinazoline-2,4-dione units was successfully synthesized.
Silicon (Si) nanocrystallites have been synthesized using pulsed-laser ablation in inert background gases, for studying the structures and optical properties as one of the quantum confinement effects. We extracted a process condition where well-dispersed Si nanocrystallites devoid of droplets and debris are prepared, by varying excitation laser conditions. Furthermore, we investigate the influence of the inert background gas pressures on transition from amorphous-like thin films to nanocrystallites. It was clarified that there is a processing window of the inert background gas pressure in which the quantum confinement effects for carriers and phonons become apparent.
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