The enormous amount of basic research into carbon nanotubes has sparked interest in the potential applications of these novel materials. One promising use of carbon nanotubes is as fillers in a composite material to improve mechanical behaviour, electrical transport and thermal transport. For composite materials with high thermal conductivity, the thermal conductance across the nanotube-matrix interface is of particular interest. Here we use picosecond transient absorption to measure the interface thermal conductance (G) of carbon nanotubes suspended in surfactant micelles in water. Classical molecular dynamics simulations of heat transfer from a carbon nanotube to a model hydrocarbon liquid are in agreement with experiment. Our findings indicate that heat transport in a nanotube composite material will be limited by the exceptionally small interface thermal conductance (G approximately 12 MW m(-2) K(-1)) and that the thermal conductivity of the composite will be much lower than the value estimated from the intrinsic thermal conductivity of the nanotubes and their volume fraction.

We use classical molecular dynamics simulations to study the interfacial resistance for heat flow between a carbon nanotube and octane liquid. We find a large value of the interfacial resistance associated with weak coupling between the rigid tube structure and the soft organic liquid. Our simulation demonstrates the key role played by the soft vibration modes in the mechanism of the heat flow. These results imply that the thermal conductivity of carbon-nanotube polymer composites and organic suspensions will be limited by the interface thermal resistance and are consistent with recent experiments.

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We use molecular dynamics simulations to analyze the role of chemical bonding between the matrix and the fiber on thermal transport in carbon nanotube organic matrix composites. We find that chemical bonding significantly reduces tube-matrix thermal boundary resistance, but at the same time decreases intrinsic tube conductivity. Estimates based on the effective medium theory predict increase, by about a factor of two, of the composite conductivity due to functionalization of single-walled nanotubes with aspect ratios within 100–1000 range. Interestingly, at high degree of chemical functionalization, intrinsic tube conductivity becomes independent of the bond density.

Using nonequilibrium molecular dynamics simulations in which a temperature gradient is imposed, we determine the thermal resistance of a model liquid–solid interface. Our simulations reveal that the strength of the bonding between liquid and solid atoms plays a key role in determining interfacial thermal resistance. Moreover, we find that the functional dependence of the thermal resistance on the strength of the liquid–solid interactions exhibits two distinct regimes: (i) exponential dependence for weak bonding (nonwetting liquid) and (ii) power law dependence for strong bonding (wetting liquid). The identification of the two regimes of the Kapitza resistance has profound implications for understanding and designing the thermal properties of nanocomposite materials.

Recent experiments demonstrated very low percolation thresholds for carbon nanotube composites signified by steep increases in electrical conductivity at very low nanotube loadings. By contrast, thermal transport measurements, even on the same samples, showed no signature of the percolation threshold. These contrasting behaviors are particularly intriguing considering that both transport processes are described by the same continuum equation. In this letter we present a theoretical analysis based on finite element calculations that expose the underlying reasons for markedly different behaviors of electrical and thermal transport in high aspect ratio fiber composites.

Donor−linker−acceptor (D-L-A)-based photoinduced electron transfer (PET) has been frequently used for the construction of versatile fluorescent chemo/biosensors. However, sophisticated and tedious processes are generally required for the synthesis of these probes, which leads to poor design flexibility. In this work, by exploiting a Schiff base as a linker unit, a covalently bound D-L-A system was established and subsequently utilized for the development of a PET sensor. Cysteamine (Cys) and N-acetyl-L-cysteine (NAC) costabilized gold nanoclusters (Cys/ NAC-AuNCs) were synthesized and adopted as an electron acceptor, and pyridoxal phosphate (PLP) was selected as an electron donor. PLP can form a Schiff base (an aldimine) with the primary amino group of Cys/NAC-AuNC through its aldehyde group and thereby suppresses the fluorescence of Cys/NAC-AuNC. The Rehm−Weller formula results and a HOMO−LUMO orbital study revealed that a reductive PET mechanism is responsible for the observed fluorescence quenching. Since the pyridoxal (PL) produced by the acid phosphatase (ACP)-catalyzed cleavage of PLP has a weak interaction with Cys/NAC-AuNC, a novel turn-on fluorescent method for selective detection of ACP was successfully realized. To the best of our knowledge, this is the first example of the development of a covalently bound D-L-A system for fluorescent PET sensing of enzyme activity based on AuNC nanoprobes using a Schiff base.

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