Fluorescence imaging of onion epidermal cell utilizing highly luminescent water-soluble CdTe colloidal quantum dots

Water-soluble CdTe colloidal QDs were synthesized using 3-Mercaptopropionic acid (3-MPA) as a stabilizing agent at different growth times to obtain green, yellow and red emissions. The absorption and emission spectra were red-shifted with relation to refluxing time due to an increase in particle size with quantum confinement. The cubic zinc-blende crystal structure was confirmed by XRD studies with reflections in the (111), (220), and (31 1) planes and the crystallite size increased from 2.24 nm to 2.53 nm. FTIR analysis shows the capping effect of the thiol group of 3-MPA on the QD surface. Further, the structural and elemental composition were confirmed by the Raman spectra, which revealed the longitudinal optical phonon peak of CdTe. The morphologies of CdTe QDs were studied by HRTEM with an average particle size of 3 nm, 4.4 nm, and 5.8 nm for different reflexing times (1 h, 3 h, and 7 h) and EDX analysis revealed the elements present in green CdTe QDs. The fluorescence images of onion epidermal cells were recorded using the green, yellow and red emission (lambda maxat-538 nm,-585 nm, and-650 nm) of aqueous CdTe QDs. The different staining patterns of the onion epidermal cells showed their clear morphology. The cells treated with green emitting CdTe QDs show excellent luminance compared to yellow and red emitting CdTe QDs, and they do not bind with any of the interior of the cellular parts of the onion cells. The green CdTe colloidal QDs in aqueous medium are efficient fluorescent probes for fluo-rescence imaging of onion epidermal cells.