Patterning porous matrices and planar substrates with quantum dots

摘要: Silica hydrogels and planar substrates were patterned with CdS nanoparticles using a photolithographic method based on the photo dissociation of thiols cadmium-thiolate complexes. prepared via standard base-catalyzed route. The solvent was exchanged an aqueous solution CdSO4 2-mercaptoethanol, samples then exposed to focused ultraviolet beam. Planar by illuminating precursor spin coated substrates. formed in illuminated spots, had diameter below about 2 nm. spots UV beam could be varied from few hundred μm, both Samples characterized transmission electron microscopy, X-ray photoelectron spectroscopy, diffraction, optical absorption, photoluminescence Raman spectroscopies. All these techniques confirmed chemical identity nanoparticles. To investigate mechanism nanoparticle formation, we took absorption spectra as function irradiation time. In unirradiated solutions, noticed maximum at 250 nm, characteristic Cd-thiolate nm decreased increasing A new band appeared 265 for exposures around 5 min, that shifted 290 10 min. yellow precipitate after 30 XRD showed cubic CdS, mean particle size 1.4 We attribute formation photodissociation Cd-thiolates. precursors yields series species can react Cd2+, such RS·, S2− H2S. Small form initial stages illumination, present bands 265–290 region. These aggregates grow, coalesce longer times.