Molecular nature of PbS nanoclusters attached on the silica spheres

Abstract

The mixture of phenyltrimethoxysilane (PTMS) and mercaptopropyltrimethoxysilane (MPTMS) has been covalently bonded to the surface of the monodisperse silica spheres to attach the PbS nanoclusters. The Fourier transform infrared (FTIR) spectra of the modified silica spheres (MSSPh) with PTMS and MPTMS clearly indicates the phenyl ring and carbohydrate absorption band. The FTIR spectra of MSSPh after attaching the Pb²⁺ and converting Pb²⁺ to PbS show the characteristic absorption peaks. The stopband of unmodified silica spheres located at 830 nm. However, the stopband disappears after surface modification and PbS formation due to the hydrophobic nature of the silica spheres. The field emission scanning electron microscope images of the MSSPh and MSSPh-PbS show similar surface texture. The compositions of the MSSPh-PbS obtained by energy dispersive spectroscopy include silicon, oxygen, carbon, sulfur and lead with the atomic ratio (weight ratio) of 33.34 (46.31), 32.60 (25.80), 32.90 (19.55), 0.40 (0.64) and 0.75 % (7.70 %), respectively. The photoluminescence (PL) spectrum shows several luminescence peaks between 600 to 840 nm. The PL results indicate that the PbS nanoclusters (NCs) may have molecular characteristics with this growth process. A precisely controlled growth can be achieved by extensive washing and centrifuge processes.