Semiconductor quantum dots reveal dipolar coupling from exciton to ligand vibration

Abstract

Within semiconductor quantum dots (QDs), exciton recombination processes are noteworthy for depending on the nature of surface coordination and nanocrystal/ligand bonding. The influence of the molecular surroundings on QDs optoelectronic properties is therefore intensively studied. Here, from the converse point of view, we analyse and model the influence of QDs optoelectronic properties on their ligands. As revealed by sum-frequency generation spectroscopy, the vibrational structure of ligands is critically correlated to QDs electronic structure when these are pumped into their excitonic states. Given the different hypotheses commonly put forward, such a correlation is expected to derive from either a direct overlap between the electronic wavefunctions, a charge transfer, or an energy transfer. Assuming that the polarizability of ligands is subordinate to the local electric field induced by excitons through dipolar interaction, our classical model based on nonlinear optics unambiguously supports the latter hypothesis.

P band intermediate state (PBIS) tailors photoluminescence emission at confined nanoscale interface

“…Considering the diversity of the ligand binding motif and packing mode on the varied crystallographic planes of metal NCs 6,7,50-52 , the previously reported abnormal luminescence phenomena for metal NCs now can be readily understood due to the formation of diversity of PBIS at the nanoscale interface, such as solvent-induced dual-luminescence emissions, large Stokes shift (near-infrared emission), high quantum yield, long lifetime emission, broad emission peak, and ligand selectivity. We believe that this significant conceptual advance is not only useful for explaining the peculiar optoelectronic properties of semi-conductor quantum dots, carbon (or graphene) quantum dots and MOFs [1][2][3][4]49,[53][54][55][56] , but also provides completely new insights for the understanding of multiexcitonic relaxation of singlet fission and photoluminescent organometallic complexes 43,47,[57][58][59] .…”

How Quantum Dots Aggregation Enhances Förster Resonant Energy Transfer

“…Thanks to the expansion of nanoscience over the years, semiconductor nanocrystals, also called quantum dots (QDs), gathered momentum and proved unavoidable in FRET based biosensors . These nanoparticles exhibit unique electronic and optical properties arising from their nanoscale dimensions which entail quantum confinement effects. QDs band gap energy is therefore size‐dependent, driving to tunable emission spectra .…”

The Prevailing Role of Hotspots in Plasmon-Enhanced Sum-Frequency Generation Spectroscopy

“…where θ SFG is the emission angle of the SFG reflected beam and I(ω) stands for the beam intensity at frequency ω (refractive index of air is unity). The SFG signal experimentally measured is proportional to its total radiated intensity and, after taking into account the wavelength-dependent efficiency of the detection setup, 43 provides the dispersion of |χ (2) eff | 2 , χ (2) eff being the effective, Fresnel-corrected, second order non-linear susceptibility. 41 The complex third rank order tensor χ (2) eff sums up one Lorentzian term per molecular vibration (χ (2) eff,mol ) and one contribution (χ (2) eff,NR ) from the inorganic components, essentially the silicon substrate, labelled non-resonant (NR) with respect to the IR wavelength but varying in amplitude and phase with the visible wavelength.…”