J-aggregates Of Dyes Research Articles

Polymorphism of 2D monolayer J-aggregates of cyanine dyes

Meso- and nanoscale structural polymorphism of monolayer J-aggregates of four cyanine dyes are investigated. Three mesoscale morphological types are observed: ribbons, rhombic leaves, and tubes. Tubes are formed during cylindrical spinning of ribbons. Lined substructure characterized by the line width of about 7 nm is found in the case of monolayers of monomethine cyanine dyes at the nanoscale.

Resonance energy transfer between a spherical nanoparticle and a J-Aggregate

This paper describes the nonradiation (Forster) energy transfer between a dye J-aggregate and closely located nanoparticles possessing the properties of two-level systems. Nanoparticles can be quantum dots (QDs) or a spherical symmetric package of atoms. The dynamics of the process is described by deriving the equations that characterize the density matrix dynamics in a two-level medium and the evolution of exciton pulses in an extended quasi-one-dimensional dye J-aggregate. It is shown that effective controlled resonant transfer of the energy stored in QDs is implemented in the system and manifested in the amplification of the exciton pulses. In turn, there is a possibility of the reverse process of exciton energy transfer in partial inversion of two-level transitions of QDs. The results of this paper are confirmed by the experimental data from the literature.

Formation of J-Aggregates of an Anionic Oxacarbocyanine Dye Upon Interaction with Proteins and Polyelectrolytes

J-aggregation of the anionic oxacarbocyanine dye 3,3′-di-(γ-sulfopropyl)-5,5′-diphenyl-9-ethyloxacarbocyanine betaine was studied in aqueous solutions in the presence of proteins (collagens, immunoglobulin G, serum albumins) and polyelectrolytes (polyethyleneimine, polyvinylpyrrolidone). It was found that denaturation of human serum albumin by urea stimulated J-aggregation of the dye. The dye formed two types of J-aggregates in the presence of denatured albumin and polyethyleneimine. J-aggregates formed in the presence of polyethyleneimine rearranged over time.

Mode Modification of Plasmonic Gap Resonances Induced by Strong Coupling with Molecular Excitons

Plasmonic cavities can be used to control the atom-photon coupling process at the nanoscale, since they provide an ultrahigh density of optical states in an exceptionally small mode volume. Here we demonstrate strong coupling between molecular excitons and plasmonic resonances (so-called plexcitonic coupling) in a film-coupled nanocube cavity, which can induce profound and significant spectral and spatial modifications to the plasmonic gap modes. Within the spectral span of a single gap mode in the nanocube-film cavity with a 3 nm wide gap, the introduction of narrow-band J-aggregate dye molecules not only enables an anticrossing behavior in the spectral response but also splits the single spatial mode into two distinct modes that are easily identified by their far-field scattering profiles. Simulation results confirm the experimental findings, and the sensitivity of the plexcitonic coupling is explored using digital control of the gap spacing. Our work opens up a new perspective to study the strong coupling process, greatly extending the functionality of nanophotonic systems, with the potential to be applied in cavity quantum electrodynamic systems.

Exploring the coherent interaction in a hybrid system of hollow gold nanoprisms and cyanine dye J-aggregates: role of plasmon-hybridization mediated local electric-field enhancement.

In this work, we probed the possibility of observing strong plasmon-exciton interactions in hollow gold nanoprism-J-aggregate nanocomposites. Several different hollow gold nanoprisms (HGNs) with different aspect ratios were synthesized. This allowed us to systematically tune the LSPR energies through the exciton energy of the PIC-J-aggregate, which in turn allowed us to have direct determination of the coupling strength of HGN-J-aggregate composites. Hybrid nanosystems were prepared by adsorbing and assembling 1,1'-diethyl-2,2'-cyanine (pseudoisocyanine or PIC) iodide onto the surface of hollow gold nanoprisms. Plasmon-exciton interactions were studied using extinction spectroscopy. The experimental results were analysed, and complemented by the results obtained from numerical simulations. Our results reveal that the HGN-PIC-J-aggregate hybrid nanosystem shows coherent coupling between the localized surface plasmons of the HGN and excitons of the PIC-J-aggregate, as obvious from the observation of a clear transparency dip and the formation of two new hybrid plexcitonic modes in the plexcitonic spectra. Anti-crossing behaviour of the plexcitonic modes, together with large Rabi splitting and coupling constant, asserts strong coupling between the plasmon and the exciton, overwhelming the decoherence effects, in our hybrid nanosystem. Analysis of the calculated near-field distribution establishes that the plasmon-hybridization mediated large electric-field enhancement holds the key to the strong coupling.

Toward Cavity Quantum Electrodynamics with Hybrid Photon Gap-Plasmon States.

Combining localized surface plasmons (LSPs) and diffractive surface waves (DSWs) in metallic nanoparticle gratings leads to the emergence of collective hybrid plasmonic-photonic modes known as surface lattice resonances (SLRs). These show reduced losses and therefore a higher Q factor with respect to pure LSPs, at the price of larger volumes. Thus, they can constitute a flexible and efficient platform for light-matter interaction. However, it remains an open question if there is, in terms of the Q/V ratio, a sizable gain with respect to the uncoupled LSPs or DSWs. This is a fundamental point to shed light upon if such modes want to be exploited, for instance, for cavity quantum electrodynamic effects. Here, using aluminum nanoparticle square gratings with unit cells consisting of narrow-gap disk dimers-a geometry featuring a very small modal volume-we demonstrate that an enhancement of the Q/V ratio with respect to the pure LSP and DSW is obtained for SLRs with a well-defined degree of plasmon hybridization. Simultaneously, we report a 5× increase of the Q/V ratio for the gap-coupled LSP with respect to that of the single nanoparticle. These outcomes are experimentally probed against the Rabi splitting, resulting from the coupling between the SLR and a J-aggregated molecular dye, showing an increase of 80% with respect to the DSW-like SLR sustained by the disk LSP of the dimer. The results of this work open the way toward more efficient applications for the exploitation of excitonic nonlinearities in hybrid plasmonic platforms.

Hollow Gold Nanoprism as Highly Efficient “Single” Nanotransducer for Surface-Enhanced Raman Scattering Applications

In this Article, we report the optical properties of anisotropic hollow nanostructure, hollow gold nanoprism (HGN, an equilateral triangular gold nanoprism with a circular cavity) and its application as a highly active “nonaggregated” surface-enhanced Raman scattering (SERS) substrate. Small colloidal HGNs are prepared using sacrificial galvanic replacement method. Our study reveals that HGNs are highly stable nanostructure in solution and robust against salt or ligand induced aggregation. We find that the LSPR spectra of the HGNs can be tuned by controlling their aspect ratios. Excellent SERS were detected from the J-aggregates of pseudoisocyanine dye, adsorbed on the HGN surface. Interestingly, strong SERS is obtained without the need of any aggregation of the nanoparticles. Numerical simulations reveal that a single HGN can not only harvest large local electromagnetic fields but also offer large sensing volume due to efficient plasmon hybridization, due to the presence of the cavity. This large sensing...

Stability of J-aggregated species in an indocarbocyanine dye in Langmuir–Blodgett Films

Here, the stability behaviour of J-aggregate of an indocarbocyanine dye 1,1′-Dioctadecyl-3,3,3′,3′-Tetramethylindocarbocynine perchlorate (DiI) in fatty acid mixed (XDiI=0.4) Langmuir–Blodgett (LB) films under different condition was reported. Surface pressure–area per molecule (π–A) isotherm measurement suggest that the molecular interaction between the constituent molecules changes with subphase temperature. UV–vis absorption and fluorescence spectroscopy and Atomic Force Microscopy (AFM) were used to study the stability behaviour. It has been observed that prominent J-aggregate of DiI occurred in the mixed films at subphase temperature 15°C. With the passage of time as well as post heat treatment DiI J-aggregate decayed to excimer in both mono- and multilayer LB films. Total transition from J-aggregate to excimer occurred in monolayer films, whereas, the transition was partial in multilayer films. The stability of DiI J-aggregate in monolayer films was increased by two ways – (i) depositing the DiI-SA mixed LB films at higher surface pressure, (ii) exposing the films at 50°C for 5min. It has been observed that after heat treatment the DiI J-aggregate remained almost stable even after 200 days. AFM investigations gave the compelling visual evidences of the same.

Sub-Nanosecond Resonance Energy Transfer in the Near-Infrared within Self-Assembled Conjugates of PbS Quantum Dots and Cyanine Dye J-Aggregates.

Energy transfer (EnT) of near-infrared (NIR) excitons enables applications in harvesting of solar energy and biological imaging. Fast exciton extraction from NIR-absorbing Pb-chalcogenide quantum dots (QDs) may allow utilization of the photon downconversion (multiple exciton generation) process that occurs in those QDs to amplify signal in QD-based sensors or photocurrent in QD-based photovoltaics. This paper describes subnanosecond extraction of NIR excitons from PbS QDs by adsorbed J-aggregates of cyanine dye in aqueous dispersions. The QD/J-aggregate complexes form through electrostatic self-assembly, and the rate and yield of EnT within the complexes can be optimized by adjusting spectral overlap between QD emission and the J-aggregate absorption, which are controlled by density of charged ligands on the QD surface and the pH. The primary EnT pathways have rate constants ranging from (800 ps)(-1) to (2.2 ns)(-1), which are 1-2 orders of magnitude faster than previously reported examples with PbS QDs as exciton donors. The fastest EnT process occurs in 90 ps and is potentially competitive with Auger recombination of biexcitonic states in PbS QDs.

The plasmon–exciton interaction in layered nanostructures with two-dimensional J-aggregates

The transformation of the electronic excitation energy in a plane-layered nanostructure with two-dimensional J-aggregates of a cyanine dye has been studied theoretically. The dependences of the plasmon–exciton interaction energy on the system parameters have been determined. In the case of small values of the Rabi frequency, the rates of nonradiative energy transfer from surface plasmon–polaritons of the metal substrate to molecular excitons of J-aggregates have been calculated in terms of the perturbation theory. The dispersion laws for hybrid plasmon–exciton states have been determined, and it has been shown that the Rabi splitting can range up to 100 meV.

Highly Oriented J-Aggregates of Nitroazo Dye and Its Surface-Induced Chromism.

Highly oriented J-aggregates of a nitroazo dye were obtained in solid thin films on aligned poly(tetrafluoroethylene) surfaces. During film deposition on a friction-transferred poly(tetrafluoroethylene) layer, a sharp peak grew in the polarized absorption spectra around 613 nm, which was red-shifted 117 nm from the peak in dilute dichloromethane solution. The peak showed remarkable optical anisotropy: dichroic ratios D of up to 22 were observed, and the intrinsic D value should substantially exceed this value. These results indicate that the peak is attributable to highly oriented J-aggregates. On glass, however, H-like aggregates grew, exhibiting an absorption peak at 410 nm. Hence, the substrate surface induced the remarkable chromism observed as a 203 nm red shift.

Multichromic J-aggregates of cyanine dyes for visible and IR range of spectrum

It is shown that on the platform of the metallocomplexis J-aggregates of anionic cyanine dyes, the “self-assembly” of J-aggregates of different cationic cyanine dyes occurs according to the matrix-synthesis method. It is concluded that the matrix synthesis of multichromic J-aggregates is promising technology for the self-assembly of wide-zone nanooptical elements for the visible and IR ranges of spectrum.

Multilayer J-aggregates of cyanine dyes

It is shown that the introduction into the aqueous solution of anionic thiamonomethinecyanine of the Mg2+ cation promotes the formation of the multilayer dye J-aggregates. It is also established that, on the J-aggregates or on the metallocomplex J-aggregates of anionic thiamonomethinecyanine, a multilayer and simultaneously multichrome system of new J-aggregate is formed due to the additional introduction of cationic cyanine dye into the solution, which absorbs light in a different region of the spectrum than anionic dye.

Non-Radiative Energy Transfer Mediated by Hybrid Light-Matter States.

We present direct evidence of enhanced non-radiative energy transfer between two J-aggregated cyanine dyes strongly coupled to the vacuum field of a cavity. Excitation spectroscopy and femtosecond pump-probe measurements show that the energy transfer is highly efficient when both the donor and acceptor form light-matter hybrid states with the vacuum field. The rate of energy transfer is increased by a factor of seven under those conditions as compared to the normal situation outside the cavity, with a corresponding effect on the energy transfer efficiency. The delocalized hybrid states connect the donor and acceptor molecules and clearly play the role of a bridge to enhance the rate of energy transfer. This finding has fundamental implications for coherent energy transport and light-energy harvesting.

Raman Imaging of Cells Using Antibody-Derived Carbon Nanotubes Nanoprobes

Microscopy of biological samples with fluorescent dyes exhibits strong signals, but also limitations such as photobleaching, poor long-term stability and low multicolour capabilities. In contrast, Raman imaging of molecules is better adapted for multiplexing, but its intrinsic signal is too weak to be useful for high resolution imaging. To compensate for the low sensitivity of Raman, contrast agents (probes) have been developed over the years to boost the Raman signal to levels near that of fluorescence. By encapsulating dyes inside single-walled carbon nanotubes (dyes@SWCNTs), our group has highlighted interesting optical properties that make them suitable as Raman nanoprobes [1]. Not only these probes show giant Raman signal from the dyes, but they are resistant also to photobleaching and offer multiplexing capabilities as well as versatile chemistry at their surfaces. Recently we show that PEGylated dyes@SWCNTs can indeed be used as nanoprobes having good Raman multiplexing properties for biological imaging [2]. Here, we will present recent results on their covalent functionalization with bifunctional polyethylene-glycols (NH2-PEG-R). A full physicochemical characterization of the probes carried out using TGA, Raman spectroscopy, AFM and 1H NMR will be presented. The covalent functionalization of these Dyes@PEGylated-SWCNTs nanoprobes with antibodies was developed to produce active targeting agents for cells. Using Raman hyperspectral imaging, we have demonstrated that these antibody-functionalized nanoprobes can effectively target living or fixed human and mouse cancer cells and that they can selectively attach, depending on the antibody, to specific targets immobilized on surfaces. [1] E. Gaufrès, N.Y.-W. Tang, F. Lapointe, J. Cabana, M.-A. Nadon, N. Cottenye, et al., Giant Raman scattering from J-aggregated dyes inside carbon nanotubes for multispectral imaging, Nat. Photonics. 8 (2013) 72–78. doi:10.1038/nphoton.2013.309. [2] N. Cottenye, N.Y.-W. Tang, E. Gaufrès, A. Leduc, J. Barbeau, R. Martel, Raman tags derived from dyes encapsulated inside carbon nanotubes for Raman imaging of biological samples, Phys. Status Solidi. 211 (2014) 2790–2794. doi:10.1002/pssa.201431401. [3] This work was made possible because of financial support from NSERC (Canada) and Photon Etc.

Luminescence properties of hybrid associates of colloidal CdS quantum dots with J-aggregates of thiatrimethine cyanine dye

Luminescence properties of water-soluble hybrid associates of semiconductor colloidal CdS quantum dots (QDs) with average size of 2.5nm, 3.2nm, 4.2nm and J-aggregates of 3,3′-di-(γ-sulfopropyl)-4,4′,5,5′-dibenzo-9-ethylthiacarbocyanine betaine pyridinium salt (Dye) in gelatin were investigated using the methods of absorption, steady-state and time-resolved luminescence spectroscopy. The decrease in luminescence intensity of CdS QDs and increase in luminescence intensity of Dye J-aggregates were detected with increasing of Dye concentration. It was shown that curves of luminescence decay of CdS QDs are non-exponential. The decreasing of luminescence lifetime of CdS QDs with increasing of Dye J-aggregates concentration was observed. It was concluded that dynamic quenching due to non-radiative resonance energy transfer takes place. It was shown that overlap integral between luminescence spectra of CdS QDs and absorption spectra of Dye J-aggregates increases with the increase of average diameter of CdS QDs and luminescence decay of CdS QDs is accelerated. Energy transfer efficiency for all three sizes of QDs was more than 31%.

Nucleation, growth, and dissolution of silver nanostructures formed in nanotubular J-aggregates of amphiphilic cyanine dyes

Solution fabricated high aspect ratio silver nanowires are of interest because of their usability in plasmonic devices or transparent electrodes. Recently, silver nanowires with diameters of 6.5nm and lengths exceeding tens or hundreds of microns were grown by reduction of silver ions within the inner volume of nanotubular J-aggregates of an amphiphilic cyanine dye. Unlike in other soft template systems, the anisotropic growth of the silver wires is not caused by different screening of the diverse facets of silver crystals. Instead, the shape of the wires replicates the inner space of the tubes without destroying the template. This effect is demonstrated by ex-situ observation of the growth of the silver wires via transmission electron microscopy. The wire growth is initiated by exposure to blue light and starts with small, isolated crystallites within the tubular aggregates. The crystallites grow into pieces of wires that finally coalesce into continuous wires. The growth is mediated by material transport through the membrane-like wall of the dye aggregates. This wall permeability is further demonstrated by dissolution of the silver wires via oxidative etching by addition of sodium chloride. It is concluded that the cyanine double layer wall is permeable for ions such as silver, sodium, chlorine, and water molecules. This permeability permits control of the wire length through the concentration of chlorine when oxygen is removed from the solvent.

The formation and luminescent properties of hybrid associates of colloidal Ag2S quantum dots with J-aggregates of trimethinecyanine dye

Spectral patterns of hybrid association in the mixture of colloidal Ag2S quantum dots (QDs) with an average size of 2.5 to 0.3 nm with J-aggregates of a pyridinium salt of 3,3’-di(γ-sulphopropyl)-9-ethyl-4,5,4’,5-dibenzothiacarbocyanine betaine (Dye), prepared by the sol-gel method in gelatin, are investigated. A conclusion about the preferential formation of cis-J-aggregates in the hybrid associates of Dye with Ag2S QDs is made. The effect of photosensitization of IR luminescence (1000–1300 nm) of colloidal Ag2S QDs by J-aggregates of Dye is revealed. On the basis of the results, a photosensitization scheme implying the resonance nonradiative transfer of the electronic excitation energy from cis-J-aggregates to the recombination luminescence centers of Ag2S QDs is suggested.

Optical bistability in a system of molecular J-aggregates and gold nanoparticles

This paper considers a thin plane nanosystem consisting of molecular chains of dye J-aggregates forming bundles elongated in one direction and spherical gold nanoparticles located near them. Expressions are derived for the polarization of the exciton transition in the external field under the mutual influence of the dipole fields of the monomers constituting the dye J-aggregates and for the induced dipole of the nanoparticle. It is shown that in this system, mirrorless optical bistability of the fluorescence spectral density of the dye J-aggregates is possible, depending on the pump field intensity. The parameters of this dependence are critically determined by the distance between the molecular bundles and nanoparticles and by the angle between the field polarization direction and the axis of the bundle of J-aggregates. The use of the nanosystem as a sensor is discussed.

Excitonic photovoltaic effect in a cyanine dye molecular assembly electronically coupled to n- and p-type semiconductors

Abstract A solar cell of configuration N-[DDD----D]-P with a molecularly organized dye J-aggregate [DDD---D] electronically coupled to n- and p-type semiconductors is illustrated by fabricating a model device with TiO 2 and CuSCN as the n- and p-type substrates and the thiocyanate of a cationic pentamethine cyanine dye as D. Functional moieties in D anchors to TiO 2 establishing electronic coupling and serving as a template for assembly of a J-aggregated film. Bonding of sulfur in thiocyanate anions at the other end of the aggregate create the electronic coupling needed to facilitates transfer of holes to CuSCN. The cell exhibits photo-response originating from excitons generated in the bulk of the thick dye film as well as direct sensitized injection at the first interface. The dye molecular assembly is found to admit exciton transport over relatively long distances and significant hole mobility.