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1. Effect of nanoscale dielectric environments on concentration quenching

   https://doi.org/10.1515/nanoph-2021-0132  

   Rout, Sangeeta; Koutsares, Samantha R.; Courtwright, Devon; Mills, Ezekiel; Shorter, Ayanna; Prayakarao, Srujana; Bonner, Carl E.; Noginov, Mikhail A. (August 2021, Nanophotonics)

   Abstract We have studied the dependence of concentration quenching of luminescence (donor–acceptor energy transfer) on the thickness d of dye-doped polymeric films (HITC:PMMA) and found its strong inhibition at small values of d . This phenomenon is tentatively explained by a limited number of acceptors, which donors’ excitation can reach in thin samples, if the film’s thickness is comparable to the diffusion length of the energy transfer. The latter mechanism, along with effective reduction of the dye concentration, is responsible for an inhibition of the concentration quenching of dye molecules impregnating porous alumina membranes. The elongation of emission kinetics in thick (≥3 μm) HITC:PMMA films is cautiously attributed to the samples’ crystallinity. 

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2. Effect of Fabry-Perot Cavities on Concentration Quenching

   https://doi.org/10.1364/CLEO_AT.2019.JTh2A.20  

   Koutsares, S.; Prayakarao, S.; Courtwright, D.; Bonner, C. E.; Noginov, M. A. (January 2019, CLEO: QELS_Fundamental Science 2019)

   We show that concentration quenching of emission of dye molecules – an energy transfer to quenching centers – is inhibited in subwavelength Fabry-Perot cavities (or metal-insulator-metal, MIM, waveguides). 

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3. Effect of Fabry-Perot Cavities on Concentration Quenching

   S. Koutsares, S. Prayakarao (January 2019, Cleo)

   We show that concentration quenching of emission of dye molecules – an energy transfer to quenching centers – is inhibited in subwavelength Fabry-Perot cavities (or metal-insulator-metal, MIM, waveguides). 

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4. Effect of Random Nanostructured Metallic Environments on Spontaneous Emission of HITC Dye

   https://doi.org/10.3390/nano10112135  

   Rout, Sangeeta; Qi, Zhen; Petrosyan, Ludvig S.; Shahbazyan, Tigran V.; Biener, Monika M.; Bonner, Carl E.; Noginov, Mikhail A. (November 2020, Nanomaterials)

   null (Ed.)

   We have studied emission kinetics of HITC laser dye on top of glass, smooth Au films, and randomly structured porous Au nanofoams. The observed concentration quenching of luminescence of highly concentrated dye on top of glass (energy transfer to acceptors) and the inhibition of the concentration quenching in vicinity of smooth Au films were in accord with our recent findings. Intriguingly, the emission kinetics recorded in different local spots of the Au nanofoam samples had a spread of the decay rates, which was large at low dye concentrations and became narrower with increase of the dye concentration. We infer that in different subvolumes of Au nanofoams, HITC molecules are coupled to the nanofoams weaker or stronger. The inhibition of the concentration quenching in Au nanofoams was stronger than on top of smooth Au films. This was true for all weakly and strongly coupled subvolumes contributing to the spread of the emission kinetics. The experimental observations were explained using theoretical model accounting for change in the Förster radius caused by the strong energy transfer to metal. 

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5. Emission kinetics of HITC laser dye on top of arrays of Ag nanowires

   https://doi.org/10.1515/nanoph-2021-0374  

   Rout, Sangeeta; Peters, Vanessa N.; Pradhan, Sangram K.; Bonner, Carl E.; Noginov, Mikhail A. (October 2021, Nanophotonics)

   Abstract We have grown arrays of silver nanowires in pores of anodic alumina membranes (metamaterials with hyperbolic dispersion at λ  ≥ 615 nm), spin coated them with the dye-doped polymer (HITC:PMMA), and studied the rates of radiative and nonradiative relaxation as well as the concentration quenching (Förster energy transfer to acceptors). The results were compared to those obtained on top of planar Ag films and glass (control samples). The strong spatial inhomogeneity of emission kinetics recorded in different spots across the sample and strong inhibition of the concentration quenching in arrays of Ag nanowires are among the most significant findings of this study. 

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