Anomalous photoluminescence Stokes shift in CdSe nanoparticle and carbon nanotube hybrids

Abstract

A very large decrease in the Stokes shift in CdSe nanoparticle photoluminescence is seen from hybrid materials in which the nanoparticles are attached to single-walled carbon nanotubes after pyridine treatment relative to unbound nanoparticles capped by pyridine. This is observed particularly for very small nanoparticles, for hybrids composed of core-only and core-shell nanoparticles, and for hybrids made with bundles of mixtures of semiconducting and metallic nanotubes or with semiconducting nanotubes only, and is likely due to fast Förster resonance energy transfer (FRET) from the nanoparticles to the nanotubes. A simple model demonstrates the plausibility of the hot luminescence explanation of this decreased Stokes shift.2

Passivation of CdSe Quantum Dots by Graphene and MoS2 Monolayer Encapsulation

“…They also show the diameter of the core, d, as determined from the peak wavelength, by using the calibration between the core diameter and first exciton peak in absorption 26 and the ~70 meV Stokes shift between this absorption peak and the PL peak. 27 Aside from the points at 185 h (see below), the diameter of the CdSe core decreases monotonically with time due to oxidation, and this decrease is slower in both covered chip regions than in their uncovered counterparts due to slower oxidation. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 PL was also measured on several ch...…”

Probing differential optical and coverage behavior in nanotube–nanocrystal heterostructures synthesized by covalent versus non-covalent approaches

“…5C is consistent with previous observations of hot carrier emission which had been prominently featured in time-integrated emission spectra under conditions of efficient energy transfer in QD-NT heterostructures. 32 The loss of the deep trap emission at 730 nm and the corresponding absence of band edge recombination are characteristic of ultrafast electronic interactions. In effect, in the absence of covalent interactions which lead to efficient carrier trapping, it is reasonable to assume that energy transfer will dominate.…”

“…For CdSe QDs with charge trapping ligands on the surface and little to no trap emission, this extremely shortened PL lifetime is expected. [32][33][34][35] The Raman spectra for (i) DWNTs, (ii) as-prepared CdSe QDs, as well as (iii) DWNT-CdSe QD heterostructures synthesized by both covalent and non-covalent (π-π stacking) means are shown in Fig. 6 and in Fig.…”

Enhancing the cooling potential of photoluminescent materials through evaluation of thermal and transmission loss mechanisms

“…PL effect occurs at wavelengths equal or shorter than absorption edge wavelength ( λ AE ) of the photoluminescent material 7 , 8 . The remaining part of the absorbed energy with wavelengths equal or shorter than λ AE is released through thermal radiation mechanisms including thermalization, quenching, and Stokes shift 9 – 11 . The incident radiation with wavelengths longer than λ AE is also transmitted through the photoluminescent layer, as it does not have the required energy to induce electronic excitation to the next energy level 9 , 12 .…”