We report the fabrication and characterization of CdS/TiO(2) nanotube-array coaxial heterogeneous structures. Such structures may potentially be applied in various photocatalytic fields, such as water photocatalytic decomposition and toxic pollutant photocatalytic degradation. Thin films of CdS are conformally deposited onto TiO(2) nanotubes using a modified method of electrochemical atomic layer deposition. We propose that such nanostructured electrodes can overcome the poor absorption and high charge-carrier recombination observed with nanoparticulate films. The practical electrochemical deposition technique promotes the deposition of CdS onto the TiO(2) tube walls while minimizing deposition at the tube entrances, thus preventing pore clogging. The coaxial heterogeneous structure prepared by the new electrochemical process significantly enhances CdS/TiO(2) and CdS/electrolyte contact areas and reduces the distance that holes and electrons must travel to reach the electrolyte or underlying conducting substrate. This results in enhanced photon absorption and photocurrent generation. The detailed synthesis process and the surface morphology, structure, elemental analysis, and photoelectrochemical properties of the resulting films with the CdS/TiO(2) nanotube-array coaxial heterogeneous structure are discussed. In comparison with a pure TiO(2) nanotube array, a 5-fold enhancement in photoactivity was observed using the coaxial heterogeneous structure. This methodology may be useful in designing multijunction semiconductor materials for coating of highly structured substrates.

An effective approach to enhance the thermoelectric performance (ZT) of polycrystalline In4Se3 based samples by crystallographic and microstructural engineering is proposed and demonstrated. Cu intercalation, Br substitution at selenium sites, and incorporation of dispersed hierarchical nanoparticles are discussed. An improved ZT of 1.1 at 723 K is achieved in CuBr2 doped In4Se2.5.

The single-filled skutterudite Yb 0.2 Co 4 Sb 12 has been long known as a promising bulk thermoelectric material. In this work, we adopted a melting-milling-hot pressing procedure to prepare nanocomposites that consist of a micrometer-grained Yb 0.2 Co 4 Sb 12 matrix and well-dispersed AgSbTe 2 nanoinclusions on the matrix grain boundaries. Different weight percentages of AgSbTe 2 inclusions were added to optimize the thermoelectric performance. We found that the addition of AgSbTe 2 nanoinclusions systematically and simultaneously optimized the otherwise adversely inter-dependent electrical conductivity, Seebeck coefficient and thermal conductivity. In particular, the significantly enhanced carrier mobility led to a $3-fold reduction of the electrical resistivity. Meanwhile the absolute value of Seebeck coefficient was enhanced via the energy filtering effect at the matrix-nanoinclusion interfaces. Moreover there is a topological crossover of the AgSbTe 2 inclusions from isolated nanoparticles to a nano-plating or nano-coating between 6 wt% and 8 wt% of nanoinclusions. Above the crossover, further addition of nanoinclusions degraded the Seebeck coefficient and the electrical conductivity. Meanwhile, the addition of nanoinclusions generally reduced the lattice thermal conductivity. As a result, the power factor of the 6 wt% sample was $7 times larger than that of the nanoinclusion-free sample, yielding a room temperature figure of merit ZT $ 0.51.

Indium-filled CoSb3 skutterudites have been shown previously to have promising thermoelectric properties but the thermal conductivity still remains somewhat high. In order to further decrease the thermal conductivity, the double-filling approach has been adopted using ytterbium, in conjunction with indium, due to its heavy mass and small size. The In0.1YbyCo4Sb12 (y=0.00, 0.05, 0.10, and 0.20) samples have been prepared by a melting method and subsequently characterized by means of electron microscopy, electrical resistivity, Seebeck coefficient, thermal conductivity, and Hall coefficient measurements. The results show that the ytterbium filling effectively decreases the thermal conductivity without degrading the power factor, resulting in an enhancement of the dimensionless figure of merit ZT. A state-of-the-art ZT value of 0.97 is attained in In0.1Yb0.1Co4Sb12 at 750 K.