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A simple hydrogenation treatment is used to synthesize unique oxygen-deficient TiO

In this paper, for the first time, polyaniline nanofibers/TiO

A simple hydrogenation treatment is used to synthesize unique oxygen-deficient TiO2 with a core/shell structure (TiO2@TiO2−xHx), superior to the high H2-pressure process (under 20 bar for five days). It is demonstrated that oxygen-deficient TiO2 nanoparticle film/Si heterojunction possesses improved photoresponse performance compared to the untreated TiO2 nanoparticle film/Si heterojunction. Particularly, under 900 nm of 0.5 μW cm−2, the oxygen-deficient TiO2 nanoparticle film (TiO2@TiO2−xHx core–shell nanoparticle film)/Si heterojunction shows high responsivity (R) of 336 A W−1, prominent sensitivity (S) of 1.3 × 107 cm2 W−1, accompanied with a fast rise and decay time of 6 and 5 ms, respectively. Significantly, the detectivity (D*) of the photodetector is up to 1.17 × 1014 cm Hz1/2 W−1, which is better than that reported in metal oxide nanomaterials/Si heterojunction photodetectors, and is 4–5 orders of magnitude higher than some 2D nanosheets/Si heterojunctions of 109–1010 cm Hz1/2 W−1, indicating the excellent ability to detect weak signals. The oxygen vacancies generated in amorphous shell TiO2−xHx make the Fermi level of TiO2−x shift near the conduction band minimum and can lead to reduced dark current. The high absorption and reduced dark current of the heterojunction ensure excellent photoresponse properties of oxygen-deficient TiO2 nanoparticle film/Si heterojunction. The H-reduced oxygen-deficient amorphous shell may be an excellent candidate to enhance the photoresponse performance of metal oxide/Si heterojunction.

We present a novel model of the effective thermal conductivity for carbon nanotube composites by incorporating the interface thermal resistance with an average polarization theory. The dependence of the effective thermal conductivity on nanotube length, diameter, concentration, and interface thermal resistance has been taken care of simultaneously in our treatment. The model predicts that the large length of the carbon nanotubes embedded plays a key role in the thermal conductivity enhancement, while the large interface thermal resistance across the nanotube-matrix interface causes a significant degradation. Interestingly, the model predicts that the nanotube diameter has a very small effect on the thermal conductivity enhancement of the nanotube composites. In addition, the model predicts that the thermal conductivity enhancement of nanotube composites increases rapidly with decreasing the thermal conductivity of the matrix and increases with increasing the thermal conductivity of the carbon nanotube. Predictions from the novel model are in excellent agreement with the experimentally observed values of the effective thermal conductivity of carbon nanotube nanofluids which the classical models have not been able to explain.

Development of low energy cost membranes for separating helium from natural gas is highly desired. Using van der Waals-corrected first-principles density functional theory (DFT) calculations, we theoretically investigate the helium separation performance of divacancy-defective germanene. The 555 777 divacancy-defective germanene presents a 0.53 eV energy barrier for helium, which is slightly larger than the energy threshold value of gas molecule penetration of a membrane (0.5 eV). Thus, the 555 777 divacancy-defective germanene is difficult for helium to permeate, except under high temperature or pressure. However, the 585 divacancy-defective germanene presents a surmountable energy barrier (0.27 eV) for helium, and it shows extremely high helium selectivities relative to other studied gas molecules. Especially, the He/Ne selectivity can be as high as 1 × 104 at room temperature. Together with the acceptable permeance for helium, the 585 divacancy-defective germanene can be used for helium separation with remarkably good performance.

A model of the effective electrical conductivity for carbon nanotube (CNT) composites is presented by incorporating the interface effect with an average field theory. The dependence of the effective electrical conductivity on CNT length, diameter, concentration, and interface properties has been taken care of simultaneously in our treatment so that the model can describe well the interface effect of CNT composites. Predictions from the model are in good agreement with the experimental values of the effective electrical conductivity of CNT composites which the classical models have not been able to explain.