Large emission enhancement and emergence of strong coupling with plasmons in nanoassemblies: Role of quantum interactions and finite emitter size

Abstract

1 Experimental Methods: a) Materials: Cadmium oxide (CdO) powder, Zinc oxide (ZnO), Trioctylphosphine (T OP ), Selenium powder, Sulphur, Oleic acid (OA), ODE, Chloroform and Toluene, were obtained from Sigma-Aldrich (Germany) for the synthesis of QDs. Dodecanethiol (DDT ), HAuCl 4 , N aBH 4 granules, N aOH, Hexene also procured from Sigma-Aldrich and Acetone,hexane, HCL from HDFCL for AuNP synthesis. Deionized water (18.2 Megaohms-cm, Milipore) was used for all Langmuir-Blodgett (LB) film transfer. b) Synthesis and characterization of Quantum Dot: The CdSe-ZnS core-shell quantum dots are prepared traditional hot-injection synthesis of CdSe cores followed by slow growth of a ZnS shell from solution. CdO and ZnO are mixed and dissolved in OA and ODE and the mixture is heated up to 310 deg C to get clear solution and then inject required amount of TOP-S and TOP-Se stock solution in the three neck flux containing hot Cadmium based growth solution. After injection, we maintain a constant temperature of 300 deg C for desired amount of time to get proper size of QD. This quantum dot has Cadmium selenide (CdSe) spherical core and it is covered by Zinc-Selenide (ZnS) shell. By keeping the temperature constant at 300 degree for 10 min, the formed QD has diameter around 6.7 nm and Photoluminescence emission at wavelength 570 nm. c)Synthesis and characterization of Gold Nano Praticle: Gold nanoparticles (AuNP) are made in water by borohydride reduction and phase-transferred to hexane. This dodecanethiolate-protected gold nanoparticles synthesis is a fast process and does not require a cleaning step. The stock solution of 50 mM gold chloride was made by dissolving HAuCl 4 − 3H 2 O with the same molar concentration of HCl in a glass vial and the aqueous stock solution of 50 mM borohydride was made by dissolving N aBH 4 granules with the same molar amount of N aOH. Now 100 µL of the AuCl 4 solution added with water and later injected 300 µL of the borohydride solution to that while stirring the mixture on a mechanical shaker for uniform * murugesh@iisc.ac.in † basu@iisc.ac.in

Electrical Tuning of Optical Properties of Quantum Dot–Graphene Hybrid Devices: Interplay of Charge and Energy Transfer

“…Now we have another similar geometry where the QDs are placed closely with lesser surface separation emerging due to shorter dielectric ligand of sulfur (Sul). In the first case of TOPO QD on SLG, the surface−surface separation between QDs, 2 × δ, is ∼2.2 nm, 32,57,58 while for Sul QD this value is reduced to ∼0.6 nm (Figure 1c). 59 The corresponding separations, δ, between the QDs and graphene are 1.1 and 0.3 nm, respectively, for TOPO and Sul QD on SLG.…”

“…In the case of compact quasi-ordered QD films, the TRPL data are often found to be best described by a multiexponential function indicative of nearest and next nearest neighbor energy transfer between QDs. 27,28,30,32 The decay profiles were thus fitted with triple exponential decay functions of the form (3) and…”

“…We have recently shown that doping such materials with tiny plasmonic MNPs can lead to the emergence of quantum correlations and a novel strong coupling regime induced by many-body emitter-metal nanoparticle coupling at very small separations. 32 At a fundamental level, the optoelectronic properties of QD−graphene based hybrid materials depend on the band alignment of the QD used with respect to graphene. 35 While the QD band structure is fixed by it size and chemical properties, 36−38 graphene band structure is highly tunable through electrostatic gating or chemical doping, especially in a field-effect transistor device.…”

Strongly Coupled Exciton–Surface Lattice Resonances Engineer Long-Range Energy Propagation

“…We use a square lattice of silver NPs which can support SLRs and CdSe/ZnS graded core–shell SQDs as emitters, as shown in Figure . We disperse the SQDs on the lattice through Langmuir–Schaefer (LS) deposition, , which creates multiple layers of compact, close-packed SQDs. We call SQD layered systems prepared in this manner “ C -configurations” for their compact nature.…”

Radiative decay of an emitter due to non-Markovian interactions with dissipating matter

“…This divergence of SERS from first-principle theoretical predictions has been widening for decades, as the reported SERS enhancements grew from 10 4 to 10 14 [19][20][21]. Meanwhile, anomalous enhancements of spontaneous emission near fully absorbing metal nanoparticles less than 10 nm in dimensions, have also been reported [22][23][24][25][26].…”