[en] Synthesis of CdTe at the rate CdS core at the rate shell quantum dots using gamma irradiation method is reported through this paper. Quantum dots (QDs), synthesized using hydrothermal techniques, were exposed to gamma radiation from 300 Gy to 20 kGy. These QDs were characterized to confirm the growth of CdTe at the rate CdS core at the rate shell structure of QD using Photo luminescence (PL) spectroscopy and X-ray diffraction (XRD) techniques. Peaks of PL emission curves were shifted to higher wavelength side with boosted in their intensity confirms that the core QDs were epitaxially passivized by inorganic CdS shell. Shift of peaks towards higher 2θ angles in the XRD pattern before and after CdS shell growth confirms that the QD surface is altered by CdS shell. A detailed aspects of all these studies are presented in this paper. (author)

[en] Gamma radiation assisted changes in stability and optical properties of CdTe colloidal quantum dots (QD) capped with 3-mercaptopropionic acid (MPA) molecules have been reported in this article. Synthesized QDs in water, using hydrothermal method, have been exposed to different gamma doses to see the changes in their light absorption and emission properties of QDs. Colour of light absorption and emissions are blue shifted for lower pH conditions followed by precipitation (after few days) of the whole dissolved materials as a response to irradiation due to photo-oxidation. Surprisingly, redshift has been observed for the same gamma doses when pH of QDs solution raised to higher number which also results in improved stability of QDs to with stand against irradiation (compared to acidic pH environment). Therefore, the solution of QDs with higher pH value is stable for future useful modifications of QD structures using radiation. These modifications may include the growth of single or multishells over core QDs by using this irradiation method to enhance their stability and optical properties. (author)

[en] This study investigates pH dependent gamma radiation effects on Mercaptopropionic Acid (MPA) capped CdTe quantum dots (QDs). Gamma radiation, as fast and chemical free catalyser, causes CdS Shell formation on MPA capped CdTe QDs at very high alkaline environment. UV–vis absorption spectroscopic results showed that, with increase in gamma radiation doses, the absorption peak of CdTe QDs decreased to lower wavelength (decrease in particle size) in both acidic & neutral medium (as synthesised), and it increased towards longer wavelength in basic medium indicating the possibility of growth of CdS shell over CdTe core QDs. X-ray diffractogram studies have revealed that the peaks of CdTe QDs shift towards higher angles after irradiation, supporting the notion of the core@shell particle structure of CdTe@CdS. TEM images confirmed the extra stretch around core particles from CdS material resulted in increase of average size of QDs. EDX study revealed the chemical composition of material system. X-ray photoelectron spectroscopic results revealed the shift in the binding energy of both Cd and S thereby indicating the change in the coordination condition after irradiation promoted the particles’ formation of core@shell in nature. The systematic photoluminescence spectroscopic investigation at all possible pH values against ascended gamma radiation doses revealed the formation of CdS shell over CdTe core at optimum pH value (i.e. only at basic pH 12). Contrarily, photo-oxidation of QDs’ was observed at neutral (and below) pH values towards gamma irradiation. The quantum yield is increased only after introducing external shell source material at highest alkaline media confirming the formation of CdS shell on CdTe core.