New Route to Fluorescent Single-Walled Carbon Nanotube/Silica Nanocomposites: Balancing Fluorescence Intensity and Environmental Sensitivity

Abstract

We investigate the relationship between photoluminescence (PL) intensity and environmental sensitivity of surfactant-wrapped single walled carbon nanotubes (SWNTs). SWNTs were studied under a variety of conditions in suspension as well as encapsulated in silica nanocomposites, which were prepared by an efficient chemical vapor into liquids (CViL) sol-gel process. The dramatically improved silica encapsulation process described here has several advantages, including fast preparation and high SWNT loading concentration, over other encapsulation methods used to prepare fluorescent SWNT/silica nanocomposites. Further, addition of glycerol to SWNT suspensions prior to performing the CViL sol-gel process allows for the preparation of freestanding fluorescent silica xerogels, which to the best of our knowledge is the first report of such nanocomposites. Our spectroscopic data on SWNTs suspended in aqueous surfactants or encapsulated in silica show that achieving maximum PL intensity results in decreased sensitivity of SWNT emission response to changes imparted by the local environment. In addition, silica encapsulation can be used to "lock-in" a surfactant micelle structure surrounding SWNTs to minimize interactions between SWNTs and ions/small molecules. Ultimately, our work demonstrates that one should consider a balance between maximum PL intensity and the ability to sense environmental changes when designing new SWNT systems for future sensing applications.

Two-color spectroscopy of UV excited ssDNA complex with a single-wall nanotube photoluminescence probe: Fast relaxation by nucleobase autoionization mechanism

“…Thus the DNA unwrapping, if it happened, should be easily detectable in our experiments. We note that we did not observe the effect in tubes suspended with DOC or SDBS, where the concentration of the free surfactant in solution is always high and surfactant molecules may indeed exchange between solvated phase and the phase agglomerated on the tube surface [89,90].…”

Photoluminescence imaging of solitary dopant sites in covalently doped single-wall carbon nanotubes

“…100 μL of the final doped SWCNT solution in 1% (w/v) DOC were thoroughly mixed with 10 μL TMOS (Sigma Aldrich, Lot#: 14628TD). 25,26 10 μL of this mixed solution were transferred onto quartz cover slips (ESCO optics, R525025) and a second cover slip was placed on top to sandwich the solution. After an average of 2-3 h the gelation progressed enough to stop diffusion of individual SWCNTs and constant imaging conditions could be achieved.…”

Stable and Fluid Multilayer Phospholipid–Silica Thin Films: Mimicking Active Multi-lamellar Biological Assemblies

“…Sol–gel techniques have been used to synthesize functional biomaterials − and structured mesoporous silica materials using a variety of sacrificial templates (including biomolecular assemblies). − Despite the success of these techniques, the acids and alcohols used in typical sol–gel processes precludes their use in encapsulation of fragile bioassemblies. , Recently, we described a sol–gel synthesis methodology based on chemical vapor deposition into liquids, which generates minimal alcohol and can be performed at neutral pH. This technique stabilizes various nano- and microscale bioassemblies, including liposomes, enzymes, microorganisms, , and surfactant-wrapped carbon nanotubes. , …”