Article

Energy Transfer from CdSe/CdS Nanorods to Amorphous Carbon

Institute of Physical Chemistry, University of Hamburg, Grindelallee 117, 20146 Hamburg, Germany.
Nano Letters (Impact Factor: 12.94). 12/2011; 11(12):5179-83. DOI: 10.1021/nl202370q
Source: PubMed

ABSTRACT Semiconductor nanocrystals placed nearby a metal film significantly change their optical properties. In this work, we examine the change in fluorescence intensity, lifetime, and blinking behavior of individual CdSe/CdS nanorods close to a 9 nm thick amorphous carbon film. Energy transfer between the donor and acceptor was investigated in detail yielding a R(-4) distance dependence for the nanorod-carbon system. The Förster critical distance was determined to be R0=24.9 nm, which is nearly identical with the theoretical value of 24.8 nm predicted by the classical approach. Additionally, antibunching measurements were performed in order to prove the presence of single isolated emitters.

1 Follower
 · 
133 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: Complementary fluorescence microscopy and ultrafast transient absorption spectroscopy measurements spanning a range of time scales from seconds to femtoseconds probe the interfacial dynamics of charge carriers in CdSe nanorod/polymer blends. Together, these very different techniques provide new information about the origin and dynamics of below-band-edge emission from CdSe nanorods in CdSe/PMMA and CdSe/P3HT/PMMA films [PMMA = poly(methyl methacrylate); P3HT = poly(3-hexylthiophene)]. Emission below the band edge of the CdSe nanorods is associated with surface defects (traps) at the nanoparticle/polymer interface, where conduction band electrons radiatively relax to the intraband defect sites. The fluorescence microscopy experiments simultaneously monitor both the trap emission and the band edge emission from single nanoparticles, and reveal that the two emission channels are distinct. Transitions between the two emissive states occur on time scales longer than 20 ms, and always involve an intermediate dark state in which no emission is observed. The presence of P3HT increases the relative band edge emission intensity and reduces the fluorescence intermittency (blinking) of both emissive states. The ultrafast transient absorption experiments monitor the evolution of a stimulated emission band below the CdSe band edge following excitation of P3HT. The measurements reveal ultrafast electron transfer from photoexcited P3HT to the CdSe nanorods within the instrument response time of approximately 140 fs, and confirm that there is strong coupling between the nanorods and P3HT in these dilute blends. Analysis of separate CdSe nanorod etching experiments suggests that the trap states are formed by the removal of atoms from the ends of the nanorods in the presence of chloroform. Mechanisms for charge trapping at the nanoparticle/polymer interface are discussed.
    The Journal of Physical Chemistry C 09/2013; 117(37):18818–18828. DOI:10.1021/jp404585j · 4.84 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We have prepared epitaxial graphene by a Si sublimation method from 4H-SiC. Single-particle spectroscopy of CdTe quantum dots (QDs) on epitaxial graphene covered with polyvinylpyrrolidone (PVP) or polyethylene glycol (PEG) showed the suppression of luminescence blinking and ∼10 times decreased luminescence intensity as compared with those on a glass. The electronic coupling constant, H01, between CdTe QDs and graphene was calculated to be (3.3 ± 0.4) × 102 cm−1 in PVP and (3.7 ± 0.8) × 102 cm−1 in PEG based on Marcus theory of electron transfer and Tang-Marcus model of blinking with statistical distribution.
    Applied Physics Letters 08/2014; 105(8):083102-083102-4. DOI:10.1063/1.4893667 · 3.52 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The near-field Coulomb interaction between a nano-emitter and a graphene monolayer results in strong F\"orster-type resonant energy transfer and subsequent fluorescence quenching. Here, we investigate the distance dependence of the energy transfer rate from individual, i) zero-dimensional CdSe/CdS nanocrystals and ii) two-dimensional CdSe/CdS/ZnS nanoplatelets to a graphene monolayer. For increasing distances $d$, the energy transfer rate from individual nanocrystals to graphene decays as $1/d^4$. In contrast, the distance dependence of the energy transfer rate from a two-dimensional nanoplatelet to graphene deviates from a simple power law, but is well described by a theoretical model, which considers a thermal distribution of free excitons in a two-dimensional quantum well. Our results show that accurate distance measurements can be performed at the single particle level using graphene-based molecular rulers and that energy transfer allows probing dimensionality effects at the nanoscale.
    Nano Letters 01/2015; 15(2). DOI:10.1021/nl5044192 · 12.94 Impact Factor