Gram-scale, cost-effective and eco-friendly synthesis, structural and optical properties of Fe:CdS colloidal nanocrystals

The synthesis of luminescent nanocrystals via easily handled methods has received tremendous attention in recent years, especially toward scaling-up fabrication. In this work, we present a gram-scale, cost-effective and eco-friendly strategy for synthesis of water-soluble and emissive Fe:CdS nanocrystals with highly tunable properties. The structural and optical properties of the as-synthesized nanocrystals were systematically explored. The obtained Fe:CdS nanocrystals possess cubic zinc blende structure, and the Fe:CdS nanocrystals are nearly spherical and show narrow size distribution. Utilizing thioglycollic acid as the capping agent finally facilitates the water solubility of Fe:CdS nanocrystals, which makes them very useful for biomedical applications. The influence of reaction temperature on the optical properties of the as-prepared nanocrystals was investigated in detail. The particle size and optical properties of the resulting Fe:CdS nanocrystals are found to be easily tailored by simply adjusting the reaction temperature, in which the emission peaks of the Fe:CdS nanocrystals red-shift with an increase in the particle sizes of the nanocrystals. Compared to bulk CdS, the remarkable blue shift of absorption peaks induced by reaction temperature indicates strong quantum confinement effect. More interestingly, the band gap of the as-formed nanocrystals can be tailored in a broad range of 3.40 to 3.10 eV by altering the reaction temperature. The synthetic strategy displayed here is preponderant in that the precursors are nontoxic and easily available, and the particle size and optical properties of the resulting nanocrystals are readily tailored. This work offers a reliable and green synthetic route toward water-soluble and highly luminescent nanocrystals with tunable optical properties.