Surface modification of zinc oxide nanoparticles (ZnO NPs) with covalently attachable organosilane species is a promising route for the preparation of hybrid nanomaterials in which optical and physicochemical properties can be easily tuned. As a continuation of our ongoing studies regarding the surface modification of ZnO NPs with adjustable optical properties, we here report a novel series of hybrid zinc oxide quantum dots (ZnO QDs) modified with vinyltrimethoxysilane (VTMS). The modified ZnO QDs, with sizes spanning the range 3-4 nm, were obtained through a simple and low-cost precipitation method. They were morpho-structurally characterized by means of X-ray diffraction, high-resolution transmission electron microscopy and Fourier transform infrared spectroscopy, while their optical properties were studied by UV-vis spectroscopy. When applied as thin films on glass substrate, the obtained ZnO QDs showed excellent optical transmittance between 85 and 90%, and low reflectance in the visible domain. The photoluminescence spectra showed a significant blue-shift of the emission bands, from 578 nm for unmodified ZnO to 540nm for ZnO modified with 10% VTMS. A new opposite trend of band gap variation from 3.494 eV for unmodified ZnO to 3.32 eV for ZnO modified with 10% VTMS was detected, while an organosilane loading higher than 10% was found to reincrease both nanoparticles size and band gap energy. These results highlighted the better ability of VTMS to attain a higher degree of nanoparticles size reduction, along with the tuning of the optical properties, with respect to the previously reported ZnO-MPS series. (C) 2015 Elsevier B.V. All rights reserved.