Ultrafast dynamics and single particle spectroscopy of Au–CdSe nanorods

Abstract

Time-resolved photoluminescence (PL) and transient absorption (TA) spectroscopy are conducted in order to get knowledge on the excited state of CdSe nanorods (NR), and to assess the impact of Au nanoparticles (NP) on the carrier dynamics of hybrid Au-CdSe NRs. The decay dynamics measured in solution show an increase of non-radiative decay channels in the presence of Au NPs, whose characteristic lifetimes vary from a few ps to tens of ps. The ultrafast electron transfer from CdSe NRs to Au NPs efficiently competes with intraband relaxation dynamics, allowing observation of the hot-electron transfer process. Furthermore, the time-averaged PL decay of CdSe NRs shows a strongly multiexponential feature that was analyzed by single-particle spectroscopy. The PL decay of individual NRs fluctuates in time and is correlated with the PL intensity. We show that the time-averaged decay of bare CdSe NRs is composed of (i) a long lifetime component corresponding to bright CdSe NRs (ON state) and (ii) a short lifetime component corresponding to charged NRs that open additional fast non-radiative channels (OFF state). When Au NPs are attached to CdSe NRs, the ON state PL decays still show a long lifetime component, suggesting that the length of the NRs may hinder electron transfer if the exciton is formed far from the Au NPs. Finally, quantitative analysis of the OFF state decays shows that electron transfer occurs even in the presence of fast non-radiative pathways in charged systems.

Ultrafast Carrier Transfer and Hot Carrier Dynamics in PbS–Au Hybrid Nanostructures

“…A faster rise time than that of CdSe NRs was also observed for Au NP-tipped CdSe NRs. 23,32 In our experiments, the decrease in QD diameter that was observed for larger Au NPs leads to a change in intraband relaxation time. Therefore, the rise time of 1S bleach dynamics in PbS−Au HNs should be compared with that of the PbS QD reference samples with a comparable diameter.…”

Photocatalytic Au–Bi2S3 Heteronanostructures

“…[18][19][20][21] The plasmon-induced electric field enhances the absorption cross-section of the semiconductor domain and can strongly affect the exciton dynamics. [3,16,22,23] Mixing of electronic states at the metal-semiconductor interface also facilitates intraparticle charge transfer. [3,10,11,13,24] Both effects make these materials suitable for the harvesting of solar light and its transformation into chemical/electrical energy, and hence for implementation in photocatalysis, photovoltaics, optoelectronics, biological labeling, and other areas.…”

Photocatalytic Au–Bi2S3 Heteronanostructures

“…The plasmon‐induced electric field enhances the absorption cross‐section of the semiconductor domain and can strongly affect the exciton dynamics 3. 16, 22, 23 Mixing of electronic states at the metal–semiconductor interface also facilitates intraparticle charge transfer 3. 10, 11, 13, 24 Both effects make these materials suitable for the harvesting of solar light and its transformation into chemical/electrical energy, and hence for implementation in photocatalysis, photovoltaics, optoelectronics, biological labeling, and other areas 13.…”