The photocatalytic activity of new nanostructures of CdS (nanofiber) was investigated in the 4-nitrophenol reduction under either visible or UV light irradiation, using Na2SO3 as reducing agent. The nanostructures of CdS were synthesized by precipitation method in an ethylenediamine-water solution at moderate conditions (low temperatures and short aging time) and their structural, optical and morphological properties were characterized by X-ray diffraction, UV-vis spectroscopy and transmission electron microscopy. The new CdS nanofiber with quantum confinement effect presented the highest photo-efficiency for the photoreduction of 4-nitrophenol under visible light irradiation; however when the quantum confinement effect was extremely strong their maximum photoactivity was only observed under UV light irradiation. (C) 2013 Elsevier B.V. All rights reserved.