Search

An experiment was conducted to extract dimeric fullerene oxides in the fullerene soot by using hydrothermally initiated dynamic extraction process. This process requires treating the soot hydrothermally before the extraction by organic solvent. Compared to Soxhlet extraction with organic solvents, this process was 40 times more efficient. Moreover, the analyses showed that the extract includes higher fullerene oxides in addition to dimeric fullerene oxides. Purification procedures for individual fullerene oxide are discussed.

Analyses of excitation spectra at 1200 nm and 1320 nm photoluminescence lines in Si-doped GaAs sample reveal a sharp peak at 1200 nm with a broad background component. The 1320 nm line exhibits two peaks and a broad background component. Excitation of Si(sub Ga) (donor) and Si(sub As) (acceptor) pairs is responsible for these sharp peaks.

The dependence of changes in the photoluminescence (PL) spectrum of gallium arsenide (GaAs) due to heat treatments on the concentration of silicon (Si) impurities is discussed. Various concentrations of GaAs crystals were doped with silicon for the preparation of n-type specimens. The PL spectra of the specimens and the detection and excitation of PL were monitored and photodetected, respectively.

This in vitro study assessed the efficacy of functionalized graphene oxide (f-GO) nanocomposites on the decalcification of dentin, because dental caries of the root surface is becoming one of the new problems in aged society. Hydroxyapatite plates (HAP) and dentin slices were coated with f-GO nanocomposites by comparing them to silver diamine fluoride as a positive control, then treated with decalcification solutions such as ethylenediaminetetraacetic acid and citrate at 37°C for 24 h. Scanning electron microscopy (SEM) revealed significant protection of the surface morphology of HAP and dentin. On the other hand, a cariogenic Streptococcus mutans growth was inhibited by f-GO nanocomposites. In addition, cytotoxicity of them to epithelial cells was much less than that of povidone-iodine, which is commonly used for oral disinfectant. We synthesized 5 different f-GO nanocomposites such as GO-silver (Ag), GO-Ag-calcium fluoride (CaF2), GO-CaF2, GO-zinc, and GO-tricalcium phosphate (Ca3(PO4)2). They were standardized by evaluating under SEM, transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermogravimetry analysis (TGA), and Raman spectra after being synthesized in an aseptic technique. The abilities of GO-Ag, GO-Ag-CaF2, and GO-CaF2 nanocomposites were most preventive for decalcification. In addition, GO-Ag and GO-Ag-CaF2 almost completely inhibited S. mutans growth. However, they did not exhibit cytotoxicity to epithelial cells except at the highest concentration (0.1 w/v%) of GO-Ag and GO-Ag-CaF2. Furthermore, these f-GO nanocomposites exhibited less or no discoloration of dentin, although commonly used silver diamine fluoride causes discoloration of dentin to black. Thus, these f-GO nanocomposites are useful to protect dental caries on the tooth root that becomes a social problem in aged society. [ABSTRACT FROM AUTHOR]