CdSe quantum dots capped with naturally occurring biobased oils

We report a green synthesis of CdSe quantum dots (QDs) using bio-based materials (castor oil and ricinoleic acid) as capping agents. The absorption spectra of the as-synthesized CdSe QDs showed typical features of quantum confinement. The particle sizes of QDs were determined using the absorption band edges and found to be 3.81 to 6.80 nm and 5.91 to 8.31 nm for the entire range of reaction temperatures for QD-capped with castor oil (CSTO) and ricinoleic acid (RA), respectively. The photoluminescence spectra showed narrow emission peaks. The transmission electron microscopy (TEM) images showed spherical particles with sizes comparable to those determined from the absorption spectra. Comparatively, large particles were observed for RA capped CdSe QDs than those stabilized by CSTO. X-ray diffraction patterns revealed that the synthesized CdSe quantum dots have cubic structure. The particle sizes of CdSe deduced from X-ray diffraction measurements were in excellent agreement with those deduced from absorption spectra and TEM images. The d-spacings from the HRTEM images were consistent with those reported in literature. The surface area and the agglomeration number for as-synthesized CdSe QDs of different sizes are also reported.