The characteristic properties of graphene make it useful in an assortment of applications. One particular application--the use of graphene in biosensors--requires a thorough understanding of graphene-peptide interactions. In this study, the binding of glycine (G) capped amino acid residues (termed GXG tripeptides) to trilayer graphene surfaces in aqueous solution was examined and compared to results previously obtained for peptide binding to single-layer free-standing graphene [A. N. Camden, S. A. Barr, and R. J. Berry, J. Phys. Chem. B 117, 10691-10697 (2013)]. In order to understand the interactions between the peptides and the surface, binding enthalpy and free energy values were calculated for each GXG system, where X cycled through the typical 20 amino acids. When the GXG tripeptides were bound to the surface, distinct conformations were observed, each with a different binding enthalpy. Analysis of the binding energy showed the binding of peptides to trilayer graphene was dominated by van der Waals interactions, unlike the free-standing graphene systems, where the binding was predominantly electrostatic in nature. These results demonstrate the utility of computational materials science in the mechanistic explanation of surface-biomolecule interactions which could be applied to a wide range of systems.

Molecular dynamics simulations of a coarse-grained bead–spring model have been used to study the effects of molecular crowding on the accumulation of tension in the backbone of bottle-brush polymers tethered to a flat substrate. The number of bottle-brushes per unit surface area, Σ, as well as the lengths of the bottle-brush backbones Nbb (50 ≤ Nbb ≤ 200) and side chains Nsc (50 ≤ Nsc ≤ 200) were varied to determine how the dimensions and degree of crowding of bottle-brushes give rise to bond tension amplification along the backbone, especially near the substrate. From these simulations, we have identified three separate regimes of tension. For low Σ, the tension is due solely to intramolecular interactions and is dominated by the side chain repulsion that governs the lateral brush dimensions. With increasing Σ, the interactions between bottle-brush polymers induce compression of the side chains, transmitting increasing tension to the backbone. For large Σ, intermolecular side chain repulsion increases, forcing side chain extension and reorientation in the direction normal to the surface and transmitting considerable tension to the backbone.

Molecular dynamics (MD) simulations were used to study the structural and dynamic properties of multilayer adsorption of each of three halomethanes, CF(4), CF(3)Cl, and CF(3)Br, adsorbed onto the (001) surface of either of two atomically flat but chemically and structurally different substrates (graphite and hydroxylated α-quartz) at temperatures ranging from 60 to 300 K. Analysis of the data shows a strong influence on the adsorption characteristics of these halomethane films due to the surface characteristics of the chosen substrate. In particular, the nature of the hydroxylation of α-quartz shows a striking ability to alter the affinity with which species adsorb onto its surface. This effect appears to be at least partly responsible for the differences in the orientation and packing of molecules in the first film layer as well as differences in the effect of temperature variation on phase behavior and dynamics.

An approach for printing micron-scale electronic devices built from two-dimensional materials is presented. Experimental phage display techniques and computational atomistic simulation approaches were used to identify a peptide molecule that effectively anchors to the basal plane surface of two-dimensional (2D) MoS2 to SiO2 surfaces. This peptide was suspended in water to develop an ink suitable for aerosol jet printing. The printed substrates were then dip coated with a suspension of liquid phase exfoliated 2D MoS2 particles. Strong adhesion of physically continuous lines of these particles was observed only on regions of the substrate patterned with the peptide-based ink, thereby enabling aerosol jet printing as a template for devices based on 2D materials. Graphene was also bound to SiO2 via a similar approach, but with a different peptide known from prior work to selectively adhere to the basal plane of graphene. Fundamental peptide-surface interactions for MoS2, graphene, and SiO2 were explored via simulation and experiment. This printing method is proposed as a route towards large-scale, low temperature patterning of 2D materials and devices. The electrical properties of continuous lines of MoS2 particles printed in a single pass of peptide ink printing were measured via transmission line measurements. The results indicate that this molecular attachment approach to printing possesses several advantages such as overcoming nozzle clogging due to nanomaterial aggregation, decoupling of particle size from any dimensions associated with the printer, and single-pass printing of electrically continuous films.