3 years ago

Metal–Ligand Complex-Induced Ultrafast Charge-Carrier Relaxation and Charge-Transfer Dynamics in CdX (X=S, Se, Te) Quantum Dots Sensitized with Nitrocatechol

Metal–Ligand Complex-Induced Ultrafast Charge-Carrier Relaxation and Charge-Transfer Dynamics in CdX (X=S, Se, Te) Quantum Dots Sensitized with Nitrocatechol
Hirendra N. Ghosh, Partha Maity, Sanjay K. Jha, Pallavi Singhal
The present work describes the effect of interfacial complex formation on charge carrier dynamics in CdX (X=S, Se, Te) quantum dots (QDs) sensitized nitro catechol (NCAT). To compare experiments were also carried out with catechol (CAT) where no such complexation was observed. Time-resolved emission studies suggest faster charge separation in CdS(Se)/NCAT system as compared to CdS(Se)/CAT although change in Gibbs free energy for hole transfer is less in former as compared to later. This suggests that complex formation favours charge separation. Similar studies were also carried out in CdTe/NCAT system where hole transfer process was not viable thermodynamically but due to complex formation charge separation was observed. Femtosecond transient absorption studies have been carried out to monitor charge carrier dynamics in early time scale. Transient studies show faster electron cooling in QDs/NCAT system as compared to pure QDs and has been assigned to the complex formation on QDs surface. Interestingly charge recombination dynamics is much faster in QDs/NCAT system as compared to pure QDs which can be attributed to the stronger coupling between QDs and NCAT. Our results suggest a strong metal–ligand complex formation on QDs surface that controls charge carrier dynamics in QDs/molecular adsorbate system and to the best of our knowledge it has never been reported. Going dotty: Steady-state absorption studies shows an interfacial complex formation between QDs and NCAT and because of this, charge-transfer processes were found to be facilitated even though sometimes charge-transfer reactions were not thermodynamically favourable. Transient absorption measurements also suggest both faster charge carrier cooling and charge recombination in QDs/NCAT composite system as compared to pure QDs.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/chem.201701271

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