Si Nanopowder for Photoluminescence and Hydrogen Generation Materials

Si nanopowder fabricated from Si swarf using the beads milling method exhibits two kinds of photoluminescence (PL), green-PL and blue-PL. Green-PL arises from band-to-band transition of Si nanopowder with band-gap enlarged by the quantum confinement effect. Blue-PL, on the other hand, is attributable to adsorbed 9,10-dimethylanthracene (DMA) impurity in hexane because the structure of the observed PL spectra is nearly identical to that of DMA solvent. The peaked PL spectra arise from vibronic interaction of DMA, and nearly the identical separation energies between the neighboring peaks correspond to the vibrational energy of DMA in the electronic ground-state. The PL intensity of DMA is enhanced by 60,000 times due to adsorption of DMA on Si nanopowder. For excitation photon energies higher than 4.0 eV, new peaks appear in the energy region higher than the (0, 0) band, attributable to transition from vibrational excited-states.