Aggregation Control of α-Sexithiophene via Isothermal Encapsulation Inside Single-Walled Carbon Nanotubes

Abstract

Liquid-phase encapsulation of α-sexithiophene (6T) molecules inside individualized single-walled carbon nanotubes (SWCNTs) is investigated using Raman imaging and spectroscopy. By taking advantage of the strong Raman response of this system, we probe the encapsulation isotherms at 30 and 115 °C using a statistical ensemble of SWCNTs deposited on a oxidized silicon substrate. Two distinct and sequential stages of encapsulation are observed: Stage 1 is a one-dimensional (1D) aggregation of 6T aligned head-to-tail inside the nanotube, and stage 2 proceeds with the assembly of a second row, giving pairs of aligned 6Ts stacked together side-by-side. The experimental data are fitted using both Langmuir (type VI) and Ising models, in which the single-aggregate (stage 1) forms spontaneously, whereas the pair-aggregate (stage 2) is endothermic in toluene with formation enthalpy of ΔH = (260 ± 20) meV. Tunable Raman spectroscopy for each stage reveals a bathochromic shift of the molecular resonance of the pair-aggregate, which is consistent with strong intermolecular coupling and suggestive of J-type aggregation. This quantitative Raman approach is sensitive to roughly 10 molecules per nanotube and provides direct evidence of molecular entry from the nanotube ends. These insights into the encapsulation process guide the preparation of well-defined 1D molecular crystals having tailored optical properties.

Dyes@BNNT Nanohybrids for Photostable Fluorescence Imaging

“…The Consistent to other reports on similar oligothiophene encapsulation inside SWCNTs 19,20,31,32 , the results confirm the encapsulation of the 6Ts inside BNNTs. The assembly of dyes inside BNNTs into aligned and structured aggregates is consistent with the assembly behavior observed on elongated dyes encapsulated inside SWCNTs [19][20][21][22]31,33 . The similarities between these systems are striking, as both provide higher stability against photodegradation and exposure to ROSs.…”

Confinement of Dyes inside Boron Nitride Nanotubes: Photostable and Shifted Fluorescence down to the Near Infrared

“…Because of efficient energy transfer processes between dyes and SWCNT hosts ( E g < 1 eV), it became apparent that the dye fluorescence is readily quenched in most, if not all, of the nanohybrids with carbon nanotubes. [ 22,23 ] Hence, we turn our attention to the boron nitride nanotube (BNNT), which has a large bandgap ( E g ≈ 5.5 eV) [ 24,25 ] and hence high optical transparency over a wide range of wavelengths. In the context of life science, large diameter BNNTs ( d ≈ 50 nm) have been studied as cargo for drug delivery [ 26 ] and the toxicity in vivo and in vitro of different BNNTs is currently investigated in the field.…”

Reversible Charge Transfer with Single‐Walled Carbon Nanotubes Upon Harvesting the Low Energy Part of the Solar Spectrum

“…Hybrid nanostructures consisted of a carbon nanotube (CNT) core and an organic dye shell or, vice versa, an organic dye encapsulated in a CNT shell became a subject of growing research interest in recent years . CNTs are known as perspective semiconductor elements and nanoelectrodes in carbon electronics, photovoltaic, and photocatalytic systems, due to their high charge carrier mobility and exciton diffusion, enhanced photochemical and thermal stability, etc.…”