Fluorescence Spectroscopy of Gel-Immobilized Single-Wall Carbon Nanotubes with Microfluidic Control of the Surfactant Environment

Abstract

We describe the design and use of a microfluidic fluorescence cell for nanoparticle spectroscopy. The cell allows for microfluidic control of solvent and surfactant environments to study interfacial processes of nanoscale systems. We present a spectroscopic investigation on the effect of surfactant type and concentrations on the first subband exciton transition of (6,5) single-wall carbon nanotubes (SWNTs). SWNT fluorescence here serves as a surface-sensitive probe of changes at the surfactant−nanotube interface. The experiments show that a displacement of H 2 O or of adsorbed DNA by sodium cholate from solution leads to a pronounced blue-shift of exciton emission features and a roughly 5-fold increase of photoluminescence (PL) intensities. This is due to a combination of physical and chemical interactions. The major contribution to changes in PL quantum yield and exciton peak position can be attributed to changes in dielectric screening and its effect on exciton oscillator strengths.

Ultralarge Modulation of Single Wall Carbon Nanotube Fluorescence Mediated by Neuromodulators Adsorbed on Arrays of Oligonucleotide Rings

“…Recent work has shown that when added to DNA-SWNT suspensions, surfactants such as sodium cholate (SC) adsorb to exposed SWNT surface, displace adsorbed ssDNA, and alter the SWNT's surface dielectric properties, thereby causing a solvatochromic shift in exciton optical transition energies (Figure 2a, 2b). 36,37,38 As expected, addition of SC to (GT)N-SWNT induce solvatochromic shifts in (GT)N-SWNT fluorescence center wavelengths ( Figure 2b). All constructs showed characteristic SC-induced blue-shifting of center wavelengths corresponding to all SWNT chiralities in the sample.…”

DNA–Carbon Nanotube Complexation Affinity and Photoluminescence Modulation Are Independent

“…6b–c). The intensity enhancement, often used as a proxy for nanotube surface coverage, 10, 20 also did not correlate with the time constants (Fig. 6d).…”

A comparison of Raman and photoluminescence spectra for the assessment of single-wall carbon nanotube sample quality

“…In addition, the Raman ratios may be obscured by superposition of resonant scattering from the (6,5) SWNTs with non-resonant scattering contributions from other SWNT types. More specifically, the DGU samples contain >80% (6,5) SWNTs [21,26] and the Raman signal thus originates predominantly from (6,5) SWNTs while the (6,5) SWNT concentration in unprocessed samples represents only a small percentage of the total SWNT distribution (compare Fig. 1) and Raman signals probably contain a stronger contribution from off-resonantly excited SWNTs.…”

“…Catalyst material and larger aggregates were removed by 2 min bench-top centrifugation. Sample type 2 (processed) was prepared from the raw material stock solutions using density gradient ultracentrifugation (DGU) described in more detail elsewhere [21]. The processed samples thus contained mostly isolated SWNTs and were strongly enriched in the (6,5) SWNT species.…”