Temperature dependent excited state dynamics in dual emissive CdSe nano-tetrapods

Time resolved spectroscopic investigation has been performed on nano-tetrapods, which are exotic nanocrystals with zinc blende type core structure and four arms with wurtzite structure. Dual emission is observed in these nanostructures. A band-edge emission occurs at 500-600 nm and a broad surface state emission occurs in the 600-900 nm region. The band-edge emission decays almost completely in a few ps, indicating the operation of an efficient trapping process. Incomplete recovery kinetics of ground state bleach from transient absorption experiments signifies the existence of a long-lived excited state. The lifetime of the surface state emission is in tens of nanoseconds. At liquid nitrogen temperature, surface state emission is enhanced to a greater degree than band edge emission, indicating suppression of various deactivation pathways at this temperature. Thus, an idea of excited state dynamics of these systems is developed, with a view of future tuning of photoluminescence properties by playing with the different radiative and nonradiative pathways involved.