Ultrafast Charge Transfer and Trapping Dynamics in a Colloidal Mixture of Similarly Charged CdTe Quantum Dots and Silver Nanoparticles

Abstract

The interaction between colloidal CdTe quantum dots (QDs) and silver nanoparticles (Ag NPs), both in their negatively charged state, is studied to determine the importance of surface charge and epitaxial coupling of the two components to achieve the potential activity of the metal–semiconductor nanocomposites. An unexpected strong interaction between the two similarly charged species is evident from dramatic quenching of the excitonic emission of the QDs by the Ag NPs. Direct evidence of electron transfer from the photoexcited QDs to Ag NPs is obtained from an accelerated bleach recovery of the first exciton band of the QDs and a faster carrier cooling in the presence of Ag NPs in transient absorption measurements. The evidence of charge carrier trapping is demonstrated by the observation of a new broad positive transient absorption in the visible–near-infrared region, which was absent in their isolated counterparts. The electron transfer and charge carrier trapping processes are further substantiated by the results of similar measurements on core/shell (CdTe/ZnS) QDs. As ultrafast charge carrier (especially the hole) trapping slows the charge recombination process, the present findings open up new possibilities of harnessing solar energy and improving the photocatalytic activity by employing these colloidal mixtures.

Release of Warfarin from Human Serum Albumin by Water‐soluble CdSe Nanotetrapods

“…Two picosecond components of bleach recovery can be attributed to electron trapping for shallow and deep trap states. [27,67] Competition between electron trapping and electron-hole recombination processes can contribute to the long component in nanosecond time scale for incomplete bleach recovery.…”

“…Exciton dynamics in these nanotetrapods has been studied and a potential application has been proposed. Very few studies on ultrafast dynamics in water soluble quantum dots (QDs) exist in literature, [24][25][26][27] where influence of different ligands are discussed with ultrafast dynamics. The present study is a foray into this less explored territory.…”

Silver nanoparticles-sensitized cobalt complex for highly-efficient photocatalytic activity

“…The bare Co-2TPABTz exhibited an MLCT band at 440 nm with an intense transition in the visible-light region [5,70]. While the strong and broad absorption band of those samples 1-5 further approach the visible-light region, ascribing to the photosensitizing and SPR effect of Ag NPs [18,54]. It is well-known that pure Ag NPs exhibit SPR absorption at about 400 nm [71], while this peak cannot be observed in this system due to the optical cutoff from the Co-2TPABTz substrate [72,73].…”

“…It also suggests that the Ag NPs provide extra nonradiative pathways for charge transfer. Moreover, the charge trapping ability can be promoted by increasing the Ag NPs concentration [54].…”

Ultrafast Electron Transfer from CdSe Quantum Dots to an [FeFe]-Hydrogenase Mimic

“…originating from hot electron transfer. [65][66][67] The photon energy of the excitation pulse is sufficient to initially excite higher excitonic levels. A fast transfer of conduction band electrons competing with intraband relaxation to the band edge reduces the population of the band edge states and, hence, reduces the bleach signal intensity after the initial cooling process.…”