Fluid phase transitions inside single, isolated carbon nanotubes are predicted to deviate substantially from classical thermodynamics. This behaviour enables the study of ice nanotubes and the exploration of their potential applications. Here we report measurements of the phase boundaries of water confined within six isolated carbon nanotubes of different diameters (1.05, 1.06, 1.15, 1.24, 1.44 and 1.52 nm) using Raman spectroscopy. The results reveal an exquisite sensitivity to diameter and substantially larger temperature elevations of the freezing transition (by as much as 100 °C) than have been theoretically predicted. Dynamic water filling and reversible freezing transitions were marked by 2-5 cm shifts in the radial breathing mode frequency, revealing reversible melting bracketed to 105-151 °C and 87-117 °C for 1.05 and 1.06 nm single-walled carbon nanotubes, respectively. Near-ambient phase changes were observed for 1.44 and 1.52 nm nanotubes, bracketed between 15-49 °C and 3-30 °C, respectively, whereas the depression of the freezing point was observed for the 1.15 nm nanotube between -35 and 10 °C. We also find that the interior aqueous phase reversibly decreases the axial thermal conductivity of the nanotube by as much as 500%, allowing digital control of the heat flux.

We demonstrate a polymer-free carbon-based photovoltaic device that relies on exciton dissociation at the SWNT/C(60) interface, as shown in the figure. Through the construction of a carbon-based photovoltaic completely free of polymeric active or transport layers, we show both the feasibility of this novel device as well as inform the mechanisms for inefficiencies in SWNTs and carbon based solar cells.

Nanopores that approach molecular dimensions demonstrate exotic transport behaviour and are theoretically predicted to display discontinuities in the diameter dependence of interior ion transport because of structuring of the internal fluid. No experimental study has been able to probe this diameter dependence in the 0.5-2 nm diameter regime. Here we observe a surprising fivefold enhancement of stochastic ion transport rates for single-walled carbon nanotube centered at a diameter of approximately 1.6 nm. An electrochemical transport model informed from literature simulations is used to understand the phenomenon. We also observe rates that scale with cation type as Li þ 4K þ 4Cs þ 4Na þ and pore blocking extent as K þ 4Cs þ 4Na þ 4Li þ potentially reflecting changes in hydration shell size. Across several ion types, the pore-blocking current and inverse dwell time are shown to scale linearly at low electric field. This work opens up new avenues in the study of transport effects at the nanoscale.

Graphene from two different preparative routes was successfully functionalized with 4-propargyloxybenzenediazonium tetrafluoroborate in order to study a subsequent attachment by click chemistry (1,3-dipolar azideÀalkyne cycloaddition) of a short chain polyethylene glycol with terminal carboxylic end group (PEG-COOH). The reaction steps were studied by FTIR and Raman spectroscopies, as well as zeta-potential and surface tension measurements. In the first route, pristine graphene was surfactant dispersed from a stage controlled expanded graphite before reaction, resulting in colloidally stable dispersions after dialysis removal of the surfactant following the two functionalization steps. The chemistry was shown to increase the zeta-potential from À45.3 to À54.6 mV and increase the surface tension from 48.5 to 63.0 mN/m compared to those of the precursor solution. The magnitudes of the zeta-potential and the resulting solution concentration were shown to increase with grafting density up to 14.2 μg/mL. A colloidal stability model was used to estimate the maximum grafting density of the PEG-COOH groups yielding a value of 1 per 10 nm 2 . Raman mapping before and after the two-step functionalization suggests that edges and defects are preferentially reacted. In the second route, we investigated the same click chemistry functionalization on chemical vapor deposition (CVD) synthesized monolayer graphene films, which showed higher reactivity than solution-dispersed graphene. Because these methods do not originate with the more oxidized forms of graphene, the results point to new ways of more precisely controlling the chemistry of graphene.

Two-dimensional (2D) materials can uniquely span the physical dimensions of a surrounding composite matrix in the limit of maximum reinforcement. However, the alignment and assembly of continuous 2D components at high volume fraction remain challenging. We use a stacking and folding method to generate aligned graphene/polycarbonate composites with as many as 320 parallel layers spanning 0.032 to 0.11 millimeters in thickness that significantly increases the effective elastic modulus and strength at exceptionally low volume fractions of only 0.082%. An analogous transverse shear scrolling method generates Archimedean spiral fibers that demonstrate exotic, telescoping elongation at break of 110%, or 30 times greater than Kevlar. Both composites retain anisotropic electrical conduction along the graphene planar axis and transparency. These composites promise substantial mechanical reinforcement, electrical, and optical properties at highly reduced volume fraction.

The ability to actively manipulate and transport single molecules in solution has the potential to revolutionize chemical synthesis and catalysis. In previous work, we developed a nanopore platform using the interior of a single-walled carbon nanotube (diameter = 1.5 nm) for the Coulter detection of single cations of Li(+), K(+), and Na(+). We demonstrate that as a result of their fabrication, such systems have electrostatic barriers present at their ends that are generally asymmetric, allowing for the trapping of ions. We show that above this threshold bias, traversing the nanopore end is not rate-limiting and that the pore-blocking behavior of two parallel nanotubes follows an idealized Markov process with the electrical potential. Such nanopores may allow for high-throughput linear processing of molecules as new catalysts and separation devices.

Patients with chest pain account for 10% of US emergency room visits according to data from the Center for Disease Control and Prevention (2013). For triage of these patients, cardiac biomarkers troponin I and T are endorsed as standard indicators for acute myocardial infarction (AMI, or heart attack). Thus, there is significant interest in developing a rapid, point-of-care (POC) device for troponin detection. In this work, a rapid, quantitative, and label-free assay, which is specific for cardiac troponin T (cTnT) detection, using fluorescent single-walled carbon nanotubes (SWCNTs), is demonstrated. Chitosan-wrapped carbon nanotubes are cross-linked to form a thin gel that is further functionalized with nitrilotriacetic acid (NTA) moieties. Upon chelation of Ni(2+) , the Ni(2+) -NTA group binds to a hexa-histidine-modified troponin antibody, which specifically recognizes the target protein, troponin T. As the troponin T binds to the antibody, the local environment of the sensor changes, allowing direct troponin detection through intensity changes in SWCNT bandgap fluorescence. This platform represents the first near-infrared SWCNT sensor array for cTnT detection. Detection can be completed within 5 min, demonstrating a linear response to cTnT concentration and an experimental detection limit of 100 ng mL(-1) (2.5 nm). This platform provides a promising new tool for POC AMI detection in the future. Moreover, the work presents two new methods of quantifying the number of amines and carboxylic groups, respectively, in a carbon hydrogel matrices.

Low dimensional materials are those that possess at least one physical boundary small enough to confine the electrons or phonons. This quantum confinement reduces the dimensionality of the material and imparts unique and novel properties that are not seen in their bulk forms. Examples include quantum dots (0-D), carbon nanotubes (1-D), and graphene (2-D). Accordingly, these materials exhibit new concepts in mass and energy transport that can be exploited for technological applications. In this Perspective, we review several topics related to mass and energy transport in and around carbon-based low dimensional materials. Recent developments in the study of matter being transported through carbon nanotube and graphene nanopores are reviewed, as well as applications of excitonic, thermal, and electronic energy transport in carbon nanotubes. The nanometer-scale interior of a single-walled carbon nanotube (SWCNT) has been studied as a unique nanopore, exhibiting periodic ionic conduction currents and dimensionally confined material phases. The mechanism of gas transport through atomic-scale holes in graphene, which is otherwise a perfect barrier material, has been analytically studied. These insights on nanoscale mass transport will have important implications in systems ranging from biological nanopores to advanced water filtration devices. The electronic structure of semiconducting SWCNTs allows photogenerated excitons to be harnessed for single-molecule biosensing and as elements of a new class of all-nanocarbon near-infrared photovoltaics. The extremely high thermal and electrical conductivities of carbon nanotubes allows the generation of electrical energy from chemical reactions. The understanding of how low dimensional physics and chemistry influences mass and energy transport will facilitate the application of these materials to a variety of scientific challenges.