Hydrophobic Chromophores in Aqueous Micellar Solution Showing Large Two‐Photon Absorption Cross Sections

Abstract

A series of new hydrophobic two‐photon absorbing (2PA) chromophores with varied electron‐donating groups in quasi‐linear and multibranched structures are synthesized to correlate their structure/photophysical property relationships. The feasibility of using these large two‐photon absorption cross‐sectional (δ, expressed in GM = 1 × 10–50 cm4 s photon–1 molecule–1) materials in aqueous solution is also explored. All four hydrophobic 2PA materials can be encapsulated into micelles generated by dispersing an amphiphilic block copolymer, poly(methacrylic acid)‐block‐polystyrene (PMAA‐b‐PS), into water. The micellar nanostructures are characterized using dynamic light scattering, atomic force microscopy, and transmission electron microscopy. After these dyes are incorporated into micelles, they exhibit strong fluorescence in water. It is found that the quantum yield and δ values of these chromophores are strongly dependent on the diameters of the micelles, concentrations of the PMAA‐b‐PS, and molecular structures of the 2PA chromophores. One of the compounds that has a strong triarylamino donor and a multibranched structure exhibits a large δ value of 2790 GM and high quantum yield (0.56) in micelle‐containing water. Although this value is smaller than the original value of 5300 GM in toluene, it is still substantially larger than the values of most water‐soluble 2PA materials, which have δ values of less than 100 GM.

Gigantic Two-Photon Absorption Cross Sections and Strong Two-Photon Excited Fluorescence in Pyrene Core Dendrimers with Fluorene/Carbazole as Dendrons and Acetylene as Linkages

“…In this case, the comparison of TPA activity between nanoparticles and organic solutions was performed with femtosecond pulses at 76 MHz repetition rate at the wavelength of 740 nm. Similar reduction in TPA due to aggregation effects was reported for hydrophobic chromophores loaded into the core of micelles . Although the reduction in TPA can be attributed to the geometrical distortions of T-compounds that takes place in aggregation, the exact mechanism for that TPA reduction in organic nanoparticles is unknown, and the effect deserves further investigation.…”

Enhancement of Aggregation‐Induced Emission in Dye‐Encapsulating Polymeric Micelles for Bioimaging

“…The excess amount of HPS donor provides efficient absorption of the photon energy to transfer to the acceptor. Although the exact distance between donor and acceptor in the micellar core could not be determined experimentally, it has been demonstrated that the nanoconfinement of micelles facilitates the spatial distribution between donor and acceptor in close proximity for efficient FRET to occur 16b. The increase in sizes of dye‐encapsulating polymeric micelles (determined by DLS) are consistent with the increase of loading ratio between HPS and NPAFN from 0:1 to 16:1 (Supporting Information, Table S2).…”

Direct Three-Dimensional Microfabrication of Hydrogels via Two-Photon Lithography in Aqueous Solution

“…When the solvent is water with added PF127, an increase and greater consistency in the δΦ F values is seen. A similar effect was seen when Tian et al solubilized different hydrophobic chromophores in water using the block copolymer poly(methacrylic acid)- block -polystyrene . This effect is believed to be due to micelle formation which leads to a dilution effect and reduced aggregation of the chromophores.…”