Abstract. We performed pulsed laser ablation (PLA) of a silicon target in liquid environment to prepare a silicon colloid solution. The nanoparticles were observed by SEM and TEM measurements. The result of Raman scattering indicates that this particle is mainly composed of silicon nanocrystallites. The optical gap energies of the colloid solutions varied by changing the solvents; 2.9 and 3.5 eV for colloids prepared in water and hexane, respectively. These colloid solutions showed efficient PL intensity. Since Si-(CH 3 ) n related bonds were observed for the specimen prepared in hexane, surface effects other than the quantum confinement effect should be taken into account for the origin of the PL. Our results indicate that new kinds of Sibased colloid solutions can be prepared by PLA in solvent. Since the PL peak energies were sensitive to the surface conditions, these colloid solutions are promising for biological applications such as bio-sensors.
Antioxidants are important in preventing oxidative stress by scavenging oxygen free radicals. In this study, a series of 2,2-dimethyl-2,3-dihydrobenzofuran-5-ols with amino, methoxy, chloro and nitro groups at the ortho position relative to the phenolic OH group were newly synthesized, and their galvinoxyl and hydroxyl radical scavenging activities were measured. Substituted 2,3-dihydrobenzofuran-5ols showed higher activity than the corresponding 6-chromanols, especially 6amino-2,2-dimethyl-2,3-dihydrobenzofuran-5-ol, which possessed the highest activity among the tested compounds. The results demonstrated that the planarity and electron-donating capacity of these molecules enhanced their radical scavenging activities, as is known for 6-chromanols.
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