Self assembled surface adjoined mesoscopic spheres of SnO2 quantum dots and their optical properties

A simple one pot acidic solution single precursor synthesis method has lead to highly crystalline SnO2 quantum dots (QD) that self assemble to form mesoscopic spheres. The precursor solvent and pH conditions were changed to optimise the crystalline quality, particle size and luminescence properties of SnO2 QDS. X-ray diffraction and high resolution transmission electron microscopy clearly reveal the crystalline nature of SnO2 particles of size about 2.5 nm with well defined lattice fringes and the surface adjoining to form mesoscopic spheres. Band gap enhancement due to quantum confinement effect has been observed. Blue luminescence and fast decay (1.2 ns) indicate creation of exciton and recombination with an oxygen vacancy centre. The results suggest that the optical properties follow the quantum size effect whereas the mesoscopic spheres of self assembled QDs lower the surface energy and provide large surface area for applications such as photovoltaic and gas sensing.