Efficient Inner-to-Outer Wall Energy Transfer in Highly Pure Double-Wall Carbon Nanotubes Revealed by Detailed Spectroscopy

Abstract

The coaxial stacking of two single-wall carbon nanotubes (SWCNTs) into a double-wall carbon nanotube (DWCNT), forming a so-called one-dimensional van der Waals structure, leads to synergetic effects that dramatically affect the optical and electronic properties of both layers. In this work, we explore these effects in purified DWCNT samples by combining absorption, wavelength-dependent infrared fluorescence−excitation (PLE), and wavelength-dependent resonant Raman scattering (RRS) spectroscopy. Purified DWCNTs are obtained by careful solubilization that strictly avoids ultrasonication or by electronic-type sorting, both followed by a density gradient ultracentrifugation to remove unwanted SWCNTs that could obscure the DWCNT characterization. Chirality-dependent shifts of the radial breathing mode vibrational frequencies and transition energies of the inner and outer DWCNT walls with respect to their SWCNT analogues are determined by advanced two-dimensional fitting of RRS and PLE data of DWCNT and their reference SWCNT samples. This exhaustive data set verifies that fluorescence from the inner DWCNT walls of wellpurified samples is severely quenched through efficient energy transfer from the inner to the outer DWCNT walls. Combined analysis of the PLE and RRS results further reveals that this transfer is dependent on the inner and outer wall chirality, and we identify the specific combinations dominant in our DWCNT samples. These obtained results demonstrate the necessity and value of a combined structural characterization approach including PLE and RRS spectroscopy for bulk DWCNT samples.

p-Type Functionalized Carbon Nanohorns and Nanotubes in Perovskite Solar Cells

“…In general, the UV–vis–NIR spectra of CNHs and DWCNTs are featureless in H 2 O-SBDS dispersions, which is attributed to their nonuniform size and shape and the presence of different diameters and lengths. − Additionally, no PLE features of these materials are normally detected, except that luminescent impurities are attributed to the presence of SWCNTs in the samples. This behavior is in line with the expected PLE quenching induced by the presence of different walls. , Then, Raman spectra of all of the functionalized CNMs (Figures b,c and S13–S16) were recorded to determine the changes in the spectral features after the functionalization process and evaluate their electronic properties. In general, covalent bond formation in CNMs is accompanied by sp 3 distortion of the sp 2 hybridized carbon network.…”

Carbon Nanomaterial Fluorescent Probes and Their Biological Applications

“…301,302 Tretiak and co-workers have theorized that emission is dependent on the breaking of orbital symmetry in the excited state when the CNH backbone is partially planar due to the strain of the ring system. 575 The strain present in [5]CPP and [6]CPP, unlike larger ring systems, inhibits the planarization and thus prevents breaking the symmetry. 575 Smaller CPPs [n = 5−9] have low to moderate charge mobilities, while larger CPPs [n = 10−12] have mobilities of more than 1.…”

“…4,5 Other members of the CNT family, including DWCNTs and MWCNTs, are nonfluorescent because the coaxial geometry of nested nanotubes facilitates efficient nonradiative relaxation from otherwise fluorescent single tubes. 6,7 Therefore, DWCNTs and MWCNTs are not a focus of this review. Carbon nanocones (CNCs, also known as carbon nanohorns) encompass another class of sp 2 hybridized rolled graphene sheets with conical, as opposed to cylindrical, geometry.…”

Photophysics of metal-organic frameworks: A brief overview

“…Specifically, absorption spectroscopy measures the fraction of incident radiation absorbed by MOFs over a range of frequencies, which typically characterize the electronic band structure and the strength of two-state transition; [24] emission spectroscopy examines the wavelengths of photons emitted by MOFs, which can reflect the interband or intraband radiation relaxation process of excited electrons; [25,26] PLE spectroscopy checks the emission intensity at a fixed wavelength as a function of excitation light wavelength, which can shed light on the electronic level structure of MOFs; [27] Raman spectroscopy focuses on the frequency shifts in the scattered light of MOFs, which can provide detailed information about chemical structure, phase and polymorphy, crystallinity and molecular interactions of MOFs. [28] There is no doubt that steady-state spectroscopy can provide a wealth of optoelectronic information in MOFs, however, this time-averaged information makes it hard to reflect the ongoing photophysics in MOFs which typically occurs on extremely short time scales. Therefore, ultrafast or transient spectroscopies, a class of techniques capable of measuring the ongoing photophysics in MOFs on timescales ranging from femtoseconds to microseconds, have received widespread attention from researchers.…”