Solvent-Mediated Affinity of Polymer-Wrapped Single-Walled Carbon Nanotubes for Chemically Modified Surfaces

Abstract

Semiconducting single-walled carbon nanotube (s-CNT) arrays are being explored for next-generation semiconductor electronics. Even with the multitude of alignment and spatially localized s-CNT deposition methods designed to control s-CNT deposition, fundamental understanding of the driving forces for s-CNT deposition is still lacking. The individual roles of the dispersant, solvent, target substrate composition, and the s-CNT itself are not completely understood because it is difficult to decouple deposition parameters. Here, we study poly­[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(6,6′-[2,2′-{bipyridine}])] (PFO-BPy)-wrapped s-CNT deposition from solution onto a chemically modified substrate. We fabricate various self-assembled monolayers (SAMs) to gain a greater understanding of substrate effects on PFO-BPy-wrapped s-CNT deposition. We observe that s-CNT deposition is dependent on both the target substrate and s-CNT dispersion solvent. To complement the experiments, molecular dynamics simulations of PFO-BPy-wrapped s-CNT deposition on two different SAMs are performed to obtain mechanistic insights into the effect of the substrate and solvent on s-CNT deposition. We find that the global free-energy minimum associated with favorable s-CNT adsorption occurs for a configuration in which the minimum of the solvent density around the s-CNT coincides with the minimum of the solvent density above a SAM-grafted surface, indicating that solvent structure near a SAM-grafted surface determines the adsorption free-energy landscape driving s-CNT deposition. Our results will help guide informative substrate design for s-CNT array fabrication in semiconductor devices.

Binding Affinity and Conformational Preferences Influence Kinetic Stability of Short Oligonucleotides on Carbon Nanotubes

“…An alternative and a powerful way to characterize the corona phase includes computational modeling approaches, such as classical molecular dynamics (MD) simulations, which enable atomic resolution on the timescale of hundreds of nanoseconds 1,2,[29][30][31][32] . Yet, as reorganization of long polymers on SWNT surfaces occurs on a timescale of several nanoseconds, determining most probable equilibrium distributions of polymers in the corona phase necessitates enhanced sampling approaches, such as temperature replica exchange (T-REMD) MD simulations 33 .…”

Chemical and topographical patterns combined with solution shear for selective-area deposition of highly-aligned semiconducting carbon nanotubes

“…The polymer-wrapped s-CNTs prefer to adsorb on SiO 2 compared to octadecylsilane (OTS)-grafted silicon oxide due to solvent structure effects. 42 To take advantage of s-CNT adsorption preferences to drive selective-area deposition, alternating stripes of SiO 2 and OTS were patterned using an electron-beam lithography (EBL) process illustrated in Fig. 1a .…”

“…Recently through a systematic study, we reported that varying the substrate chemistry by using self-assembled monolayers (SAMs) impacts the number density of deposited s-CNTs from solution. 42 While substrate water contact angle alone was insufficient to explain the observed s-CNT adsorption trends on these chemically modified substrates, molecular dynamics (MD) simulations provided useful mechanistic insights. In particular, the solvent-mediated affinity of polymer-wrapped s-CNTs played a key role in s-CNT deposition onto a surface.…”

Carbon Nanomaterials for Wastewater Treatment

“…So far, various type of adsorbents are in use for the treatment of wastewater such as carbon nanotubes [8][9][10], graphenes and its derivatives [11], natural zeolites, and modified organic wastes [12]. Currently, the interest in using chemically modified organic wastes as adsorbents for the treatment of wastewater has increased due to their cost effectiveness and biodegradability.…”