Here, cadmium sulphide quantum dots (CdS QDs) have been synthetized and functionalized with Bovine Serum Albumin (BSA) in a colloidal aqueous solution with a stability of over 3 months. Specific synthesis conditions, in homogeneous phase and at low temperature, have allowed limitation of S2− concentration, hence, as a consequence, there is restricted growth of the nanoparticles (NPs). This fact allows binding with BSA in the most favorable manner for the biomolecule. The presence of Cd2+ ions on the surface of the CdS nanoparticle is counteracted by the negatively charged domains of the BSA, resulting in the formation of small NPs, with little tendency for aggregation. Temperature and pH have great influence on the fluorescence characteristics of the synthetized nanoparticles. Working at low temperatures (4 °C) and pH 10–11 have proven the best result as shown by hydrolysis kinetic control of the thioacetamide precursor of S2− ion. Biological activity of the coupled BSA is maintained allowing subsequent bioconjugation with other biomolecules such as antibodies. The chemical conjugation with anti-Glutathione S-transferase (α-GST) antibody, a common tag employed in human recombinant fusion proteins, produces a strong quenching of fluorescence that proves the possibilities of its use in biological labelling. Finally, p53, onco-human recombinant protein (GST tagged in COOH terminus), has been in situ IVTT (in vitro transcription-translation) expressed and efficiently captured by the α-GST-CdS QD conjugate as a proof of the biocompatibility on IVTT systems and the functionality of conjugated antibody.

This paper report a straightforward approach for the synthesis of CdSe quantum dots (CdSe QDs) in aqueous solution. This method, performed in homogeneous phase, affords optimal sizes and high quantum yields for each application desired. It is ana la carteprocedure for the synthesis of nanoparticles aimed at their later application. By controlling the experimental conditions, CdSe QDs of sizes ranging between 2 and 6 nm can be obtained. The best results were achieved in an ice-bath thermostated at 4°C, using mercaptoacetic acid as dispersant. Under these conditions, a slow growth of quantum nanocrystals was generated and this was controlled kinetically by the hydrolysis ofSeSO32-to generateSe2-  in situ, one of the forming species of the nanocrystal. The organic dispersant mercaptoacetate covalently binds to the Cd2+ion, modifying the diffusion rate of the cation, and plays a key role in the stabilization of CdSe QDs. In optimum conditions, when kept in their own solution CdSe QDs remain dispersed over 4 months. The NPs obtained under optimal conditions show high fluorescence, which is a great advantage as regards their applications. The quantum efficiency is also high, owing to the formation under certain conditions of ananoshellof Cd(OH)2, values of 60% being reached.

We report an easy approach for the synthesis of CdS Quantum Dots (CdS QDs) with high luminescence and temporal stability through the reaction of Cd(2+) and S(2-) in the presence of mercaptoacetic acid (MAA) as a capping reagent in aqueous medium, under normal pressure and room temperature. The influence of several experimental variables, including temperature, pH, the Cd/S ratio and the Cd/MAA ratio, on the optical properties of the QDs obtained was studied systematically. The experimental results indicate that these variables play an important role in determining the size and state of the surface of the nanoparticles, and hence their luminescent properties and temporal stability. The general aspects of nanocrystal nucleation and growth in the synthesis of nanocrystals were studied. The best conditions for the synthesis of nanoparticles of high quality are also reported. The CdS nanocrystals obtained exhibited a narrow PL band, with reproducible room-temperature quantum yields.