This very paper is focusing on the preparation and characterization of silicon nano-structures prepared via hydrothermal growth technology. The morphology and the structure given by the transmission electron microscope indicates that the silicon nanostructures are nano-crystallites, nano-wires and even nano-tubes, all of which are coated with the silica layer. Luminescence performance investigation presents that there is a strong photoluminescence emission at about 400 nm and the weak one at about 700 nm. The controllability over the thickness of the silica coating and the size of silicon nano-core were achieved via the post HF etching procedure or done by prolonging the growth period, respectively. Accordingly, the mechanism of photoluminescence emissions is discussed, which proposes that both the surface radiative recombination center be responsible for 400 nm emission, and so does the confinement effect of the optical phonon for 700 nm. It might, also, come to that the Si-H-x bonds on the surface of the exorbitantly HF etched SiNS samples probably gives rise to the 390 nm emission. (c) 2012 Elsevier B.V. All rights reserved.