Abstract
This paper investigates the factors which can influence the quenching effect from the perspective of energy transfer. The quenched fluorescence of the CdSe semiconductor quantum dots (SQDs) by using plasmonic Au nanocrystals (p-AuNCs) and molecule-like Au nanocrystals (m-AuNCs) in aqueous suspensions and spin-coated films is comparatively investigated. In the aqueous suspensions, the p-AuNCs have larger quenching effect than the m-AuNCs. In the spin-coated films, the p-AuNCs and m-AuNCs have comparable quenching factor. Furthermore, the experiments show that the p-AuNCs simultaneously enhance the radiative and nonradiative rates. But the m-AuNCs only enhance the nonradiative rate of the SQDs, which reveals the difference of quenching process between the p-AuNCs and m-AuNCs. This result of the research has guiding significance for the detection technique based on the fluorescence quenching.
Highlights
In recent years, noble metal nanocrystals have attracted greatly-increasing interests from researchers because of their unique properties
We investigate fluorescence of CdSe SQDs quenched by plasmonic Au nanocrystals (p-AuNCs) and molecule-like Au nanocrystals (m-AuNCs) in aqueous suspensions and solid films
We find that both p-AuNCs and m-AuNCs exhibits strong quenching effect, but there are essential differences in quenching modes between p-AuNCs and m-AuNCs
Summary
Noble metal nanocrystals have attracted greatly-increasing interests from researchers because of their unique properties. The researchers are committed to research the noble metal nanocrystals which have tunable optical response by adjusting their surface factors such as size, shape, and component[4-10], which leads to diverse applications ranging from surface enhanced Raman scattering, bio-imaging, photothermal cancer treatment, photocatalysis, to ultrafast optical information processing[11-14]. The unique optical responses of the Au and Ag nanocrystals (AuNCs and AgNCs) in the quantum size regime have been made many practical achievements[15-18]. The plasmon resonance wavelength of the individual ligand-free AgNCs blue-shifts 500 meV as the nanocrystals’ diameter decreases from 20 nm to less than 2 nm, which is revealed to be caused by the prominently increased quantum confinement effect in the quantumsized nanocrystals[19-22]. Noble metal nanocrystals with strong plasmon resonance are widely used to tune optical emission behaviors of the nearby nanoemitters. For the metal surface plasma has significant extinction and field enhancement effects, the fluorescence could be largely enhanced or significantly quenched by the metal
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