Polyelectrolyte‐Assisted Noncovalent Functionalization of Carbon Nanotubes with Ordered Self‐Assemblies of a Water‐Soluble Porphyrin

Abstract

The self-assembly and induced supramolecular chirality of meso-tetrakis(4-sulfonatophenyl)porphyrin (TSPP) on both single-wall (SWCNT) and multiwall carbon nanotubes (MWCNT) are investigated. Under mild pH conditions (pH 3), TSPP forms aggregates when CNTs are dispersed in an aqueous solution containing positively charged polyelectrolytes such as poly-L-lysine (PLL) or poly(allylamine hydrochloride) (PAH). Evidence for the geometry of the porphyrin aggregates is obtained from absorption spectra, whereby the fingerprints of J- and H-aggregates are clearly seen only in the presence of smaller-diameter nanotubes. J-aggregates are better stabilized with PLL, whereas in the presence of PAH mainly H-aggregates prevail. Excited-state interactions within these nanohybrids are studied by steady-state and time-resolved fluorescence. The porphyrin emission intensity in the nanohybrid solution is significantly quenched compared to that of TSPP alone, and this implies strong electronic interaction between CNTs and porphyrin molecules. Fluorescence lifetime imaging microscopy (FLIM) further supports that porphyrin arrays are associated with the MWCNT sidewalls wrapped in PLL. In the case of the SWCNT hybrid, spherical structures associated with longer fluorescence lifetime appeared after one week, indicative of H-aggregates of TSPP. The latter are the result of π-π stacking of porphyrin units on neighboring nanotubes facilitated by the strong tendency of these nanotubes to interact with each other. These results highlight the importance of optimum dimensions and surface-area architectures of CNTs in the control/stability of the porphyrin aggregates with promising properties for light harvesting.

Porphyrin-Polyelectrolyte Nanoassemblies: The Role of Charge and Building Block Architecture in Self-Assembly

“…Other groups also dealt with the structure formation of TPPS with different polyelectrolytes or molecules: Bedard et al made hollow capsules consisting of TPPS and poly(allylamine hydrochloride) and poly(styrene sulfonate), which are able to produce active oxygen species by irradiation with laser light . Andrade et al investigated the interactions of TPPS with suspensions of different carbon nanotubes in presence of either poly‐ l ‐lysine or poly(allylamine hydrochloride) and revealed that the interaction depends on the diameter of the carbon nanotubes, the preparation time, the pH conditions, and on the polyelectrolyte architecture . Costa and co‐workers investigated the interactions of TPPS with polyamidoamine (PAMAM) dendrimers of generations 2 and 4 with steady‐state spectroscopy and time‐resolved fluorescence measurements.…”

Flexible ZnO-mAb nanoplatforms for selective peripheral blood mononuclear cell immobilization

“…Photoluminescence (PL) spectra were recorded at room temperature on a SPEX Fluorolog (Horiba Jobin Yvon) spectrofluorometer, using a 450 W Xe lamp as the excitation source and a solid sample holder to collect light at 22.5°, minimizing stray and reflected light from the sample surface. Fluorescence lifetime imaging microscopy (FLIM) measurements were performed on a time-resolved confocal microscope (MicroTime 200, PicoQuant GmbH) 48 . FLIM measurements of ZnO nanorods were made by taking random images (80 × 80 µm 2 ) throughout the coverslip; in each of these, another set of random (10 × 10 µm 2 ) images was also recorded.…”

Improved Potentiometric and Optic Sensitivity of Polyaniline Film to Dissolved Oxygen by Incorporating Iron‐Porphyrin

“…3 B it can be seen that, the presence of FeTSPP has a drastic effect on the morphology of the film, exhibiting cylindrical shaped filaments covered by polymer growing outwards. The explanation for this behaviour is the well‐known formation of porphyrin J aggregates in acidic aqueous solutions 34, which originates such tri‐dimensional arrangement. A six‐fold increase in the root mean square roughness ( R q ) from 2 nm with the PAn films to 12 nm, in the presence of the porphyrin moiety is observed.…”