A novel two-step controlled basic water phase method for synthesizing size-tunable CdTe/Cd(OH)2 core/shell quantum dots with high quantum yield and excellent stability

A novel two-step controlled basic water phase method has been developed for synthesizing size-tunable and water-soluble CdTe/Cd(OH) 2 core/shell quantum dots with high quantum yield and good stability. The size of the prepared CdTe/Cd(OH) 2 core/shell quantum dots can be easily manipulated by varying the concentrations of NaOH solution step by step. The maximal emission wavelengths of the series CdTe/Cd(OH) 2 core/shell QDs were from 513   nm to 610   nm (emission colors tuned from green to red). The CdTe/Cd(OH) 2 core/shell quantum dots not only possess high quantum yield (up to 83%) but also exhibit excellent photostability (being stable after being stored for more than 2 months). The CdTe/Cd(OH) 2 core/shell quantum dots were characterized by transmission electron microscopy , high-resolution transmission electron microscopy, X-ray powder diffraction spectrometry , ultraviolet–visible spectrometry and fluorescence spectrometry. The water-soluble nature of the CdTe/Cd(OH) 2 core/shell quantum dots offers great potentiality for their chemical and biological applications. This method is easily controlled, low-cost and reproducible. So it is possible to extend this approach to the preparation of other size-tunable inorganic metal hydroxide capped core/shell quantum dots.