Surface-Confined Light Harvesting, Energy Transfer, and Amplification of Fluorescence Emission in Chromophore-Labeled Self-Assembled Monolayers

Abstract

Light harvesting and energy transfer have received considerable attention in the literature because of their important role in natural photosynthesis. These processes involve the use of a light-absorbing antenna (donor) moiety that is capable of transferring the absorbed energy to a nearby secondary energy acceptor species. The energy-transfer process is influenced by the spatial relationship of the donor and acceptor chromophores, and recently researchers have sought to mimic the efficient arrangements found in nature. These include chromophore-functionalized polymers, [1] dendrimers, [2] supported Langmuir ± Blodgett films, [3] thin films, [4] and microspheres. [5] Here, we report the use of self-assembled monolayers (SAMs) to align the donor and acceptor chromophores and facilitate intermolecular energy transfer. Intermolecular interactions between adjacent adsorbates have previously been applied to improve the chemical stability of monolayers [6] and to facilitate surface-directed polymerization [7] or surface-confined photodimerization. [8] We extend the exploration of these interactions to include long-range photo-induced Förster energy transfer [9] between donor and acceptor chromophores on SAMs. This process involves a through-space dipole ± dipole interaction that does not occur by ªhoppingº through bonds. Energy transfer can thus be facilitated by assembly of donor and acceptor chromophores as mixed monolayers.We have recently reported efficient light harvesting by chromophore-labeled dendrimers in which light is funneled through space by Förster energy transfer from multiple coumarin-2 (1) donor dyes at the dendrimer periphery to a single coumarin-343 (2) acceptor chromophore. [10] These dyes were also chosen for our chromophore-labeled monolayers 2.

In Situ Generation of Wavelength‐Shifting Donor–Acceptor Mixed‐Monolayer‐Modified Surfaces

“…Considerable success has been achieved with synthetic covalently tethered donor–acceptor systems, for example, dendritic structures,4 in which energy absorbed by peripheral donor units is transferred to a central acceptor unit,5 such as dendrimers containing pyrene or coumarin donor units and a perylene acceptor unit,6 multiporphyrin systems,7 cyclic porphyrin hexamer arrays,8 and donor–acceptor polymers based on a 4‐aminonaphthalimide donor and bidentate Ru acceptor complex 9. 10 Self‐assembly approaches offer advantages over covalent systems in terms of synthesis, as demonstrated in functionalized polymers,9, 11 Langmuir–Blodgett films,12 thin films,13 microfibers,14 and in monolayers composed of mixtures of energy‐donor–acceptor molecules on quartz, indium tin oxide (ITO), and silicon surfaces 10a. 15 In the latter approach, a recurring challenge is to avoid phase separation of donor and acceptor units and to control and optimize the ratio of components immobilized on the surfaces.…”

Microcontainers with Fluorescent Anisotropic Zeolite L Cores and Isotropic Silica Shells

“…The organization of photophysically active units in nanostructures gives rise to collective effects that can be used for the design of new functional materials 1. Various strategies have been followed to achieve organized multichromophoric systems, ultimately leading to the development of photoactive polymers,2 dendrimers,3 self‐assembled monolayers,4 and mesoporous silica structures 5. Among them, zeolite L crystals have emerged as potential new components for artificial antenna devices,6 for self‐assembly in functional supramolecular systems,7 and even as connecting units between living organisms 8.…”

Heck reactions of stilbenoid chromophores with alkoxysilyl-substituted styrenes: Synthesis of monomers for luminescent polymers

“…A device-oriented approach immobilizes the functional units on the substrate, often on surfaces pretreated with reactive silanes [26], chromophores linked to siloxane anchor groups are valuable components [27,28]. A general strategy for the conjunction between π -system and curable unit uses flexible spacers with different chain lengths [29,30], often based on readily available and reactive aminoor chloropropyl-alkoxysilanes [31][32][33][34]. The direct connection of donor-substituted benzenes with triethoxysilane moieties is possible via Pd-catalysed coupling of the arylhalides with the hydrosilane [35,36].…”