Abstract
Nanoscale miniaturization of chalcogenide semiconductors such as lead sulfide (galena) can generate interesting quantum confinement effects in the field of optoelectronic applications. In this work, we developed a process in order to obtain SiO2 nanospheres coated with Galena, as the denominated core–shell system; this process is based on Stöber’s method, where the magnetic stirring was replaced by an ultrasonic bath to achieve well rounded and highly stable silica nanoparticles with diameters average of 70 nm. The PbS shell cover presents a thickness of 10 nm around. The nanostructures’ chemical composition, morphology, and optical properties were determined by transmission electron microscopy and UV–Vis spectroscopy. As a result, the nanoshells correspond to cubic PbS, presenting some interplanar distances of 2.95 Å and 3.41 Å; this nanoshell also shown an optical spectrum shift toward blue and a remarkable increase of 3.75 eV in its band gap, compared with the PbS bulk value. The chemical composition is studied by energy scattering spectroscopy and X-ray photoelectron spectroscopy analysis.
Highlights
Heavy metals sulfides, like PbS are semiconductor materials used in different electronic devices as thermal detectors [1], photoresistors [2] and thin films solar cells [3]
SiO2-PbS structures were synthesized in aqueous phase by using an organic compound of sulfur, at the same time, lead acetate as precursors PbS particles were prepared by placing 2.5 ml of lead acetate (Pb(C2H3O2)2) 0.5M solution in a 100 ml beaker, followed by the addition of 2.5 ml of sodium hydroxide (NaOH) 2 M, 3 ml of thiourea (SC(NH2)2) 1 M, 1 ml of triethanolamine TEA (C6H15NO3) 1 M, 0.5 ml of citric acid (C6H8O7) 1 M, and the total volume of the solution was completed to 50 ml by adding deionized water
± 10 nm). 60 days after the synthesis was accomplished the TEM measures, which demonstrates the stability of the nanoparticles
Summary
Like PbS are semiconductor materials used in different electronic devices as thermal detectors [1], photoresistors [2] and thin films solar cells [3]. Both solutions are mixed and, using the sonochemical method, the silica nanospheres are covered with PbS, and the core-shell nanometric structures are formed.
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