  In this paper, a charge transfer mechanism in transition metal dichalcogenide
(TMDC) quantum dots (QDs) is studied. A common dye, Rhodamine 6G (R6G), has
been used as fluorescent molecule and QDs of molybdenum disulfide
($\rm{MoS_2}$) and tungsten disulfide ($\rm{WS_2}$) have been used as acceptors
of electrons in the photo-induced charge transfer process. The MoS$_2$ and
WS$_2$ QDs have been synthesized using ultrasonication method. These QDs have
been characterized using transmission electron microscope (TEM), UV-Vis
spectrophotometer, and fluorimeter. The TEM images of these QDs show well
dispersed particles of size $~$2 nm. These QDs show intense fluorescence
emission when excited with light having wavelength, $\lambda < $ 350 nm. In
presence of light, the photons help in creating charges in fluorescent dye
molecule, and TMDCs QDs felicitate the charge transfer in the process. The
charge transfer phenomenon has been studied using time correlated single photon
counting (TCSPC) set-up, which is a time resolved fluorescence spectroscopic
technique. The time resolved fluorescence study shows a drastic change in the
fluorescence (FL) lifetime of R6G molecules in the presence of QDs. This
decrease in FL lifetime of R6G shows that the MoS$_2$, and WS$_2$ QDs provide
additional path to the photo-generated electrons in the excited state of R6G.
This study can be further extended to optoelectronic devices, where charge
transfer plays an important role in the device efficiency and performance.
