Luminescence properties of thiol-stabilized CdTe nanocrystals

Thiol-capped CdTe nanocrystals with cubic zinc blende structure are synthes ized in aqueous solution. Their steady-state and time-resolved luminescence characteristics are studied at room and liquid nitrogen temperatures. A st rong exciton luminescence peak at 2.3 eV dominates the emission spectrum of CdTe nanocrystals at room temperature, whereas the trap band centered at 2 .0 eV undergoes substantial temperature quenching. Luminescence excitation spectra reveal different channels leading to radiative recombination via ei ther excitons or traps. The mean luminescence decay time of CdTe nanocrysta ls at room temperature decreases from 120 ns at 1.94 eV to 20 ns at 2.43 eV . Luminescence:decay kinetics of CdTe nanocrystals are strongly nonexponent ial and are described by extremely bread lifetime distributions lying withi n the range from a few hundred picoseconds to a few hundred nanoseconds.