Xu Dong Gao

Necklace-like NiO-CuO Heterogeneous Composite Hollow Nanostructure: Preparation, Formation Mechanism and Structure Control

Composite hollow nanostructure composed by transition metal oxides are promising materials in electrochemistry, catalyst chemistry and material science. In this contribution, necklace-like NiO-CuO heterogeneous composite hollow nanostructures were synthesized by annealing Ni/Cu superlattice nanowires in air. Two kinds of morphologies including CuO nanotube linked core-shell structures and CuO nanotube linked hollow structures were obtained. The structure can be tuned easily by adjusting the relative length of Cu segments in Ni/Cu superlattice nanowires and the annealing temperature. The relative diffusion amount of Cu to Ni segments was proved to be the key factor to influence the annealed sample morphology. The formation mechanism was discussed in detail based on Kirkendal effect and high temperature oxidation of alloy. We demonstrated that hollow structure or core-shell structure is related to whether the oxidation exists only in external sites or co-exists in external and internal sites during annealing.

Solvothermal synthesis, stirring-assisted assembly and photoelectric performance of Te nanowires

Tellurium nanowires (NWs) are attractive one-dimensional materials for many applications, yet most synthesis processes require hazardous chemical reducing agents and extreme operating conditions. Here we described a solvothermal synthesis of Te NWs using a non-toxic reducing agent, ascorbic acid. Then the Te NWs were assembled into a well-aligned film through a stirring-assisted oil-water-air interface assembly method and a Te NWs photodetector was fabricated which is sensitive to infrared radiation. The photodetector based on the well-aligned Te NWs film had a series of more excellent photoelectric properties than that based on those being randomly oriented. For example, the photoresponsivity of the former is 103 times larger, and the response time is 1.15 × 103 times shorter, than those of the latter.

Tunable broadband wavelength-selective enhancement of responsivity in ordered Au-nanorod array-modified PbS photodetectors

Herein, we report an enhanced tunable broadband wavelength-selective lead sulfide (PbS) film detector integrated with Au-nanorod arrays that were obtained by using an ultrathin open-ended porous titanium dioxide membrane (UOP-TM) as a mask. The responsivity of the PbS films with periodic Au-nanorods exhibits a drastic enhancement by up to 125%–175% due to the enhancement of the localized electromagnetic fields around the gold nanorods. Notably, the location of the strongest enhancement peak of photocurrent shifted from 450 to 980 nm as the height of the Au-nanorods increased from 30 to 120 nm. In addition, the responsivity and detectivity of the hybrid PbS film modified with 90 nm Au-nanorod arrays under laser illumination of 980 nm are as high as 944 mA W−1 and 1.72 × 1010 cm Hz1/2 W−1, respectively. These excellent figures-of-merit of the tunable broadband plasma-enhanced PbS films could be a promising candidate in future wavelength-selective photodetector applications.

Controlled solvothermal synthesis of single-crystal tellurium nanowires, nanotubes and trifold structures and their photoelectrical properties

Uniform tellurium nanowires (NWs), nanotubes (NTs) and trifold nanorods (NRs) were synthesized using a facile, environmentally benign solvothermal method with ethylene glycol as solvent, polyvinylpyrrolidone as surfactant and non-hazardous ascorbic acid as a reducing agent. By adjusting the amounts of the surfactant and the reducing agent, Te NWs, NTs and trifold NRs were prepared. The diameter of the Te NWs and NTs are 30–40 nm and 120–150 nm, respectively. A morphology evolution diagram based on different amounts of polyvinylpyrrolidone and ascorbic acid aqueous solution are presented. The effects of temperature are also investigated meticulously. The growth mechanism of the Te NTs and trifold Te NRs are discussed based on the crystallization law. The photoelectrical properties of the Te NWs and trifold Te NRs were measured. The photocurrent and responsivity of the photodetector based on Te NWs are 0.17 mA and 25.8 A W−1, respectively.

Noble-metal Ag nanoparticle chains: annealing Ag/Bi superlattice nanowires in vacuum.

One-dimensional noble-metal Ag nanoparticle chains have been prepared by electrodepositing Ag/Bi superlattice nanowires in a porous anodic alumina oxide (AAO) template and following an annealing process in vacuum. It is found that Bi, as a sacrificial metal, can be removed completely after annealing at 450 °C with a vacuum degree of 10(-5) Torr. The regulation of particle size, shape and interparticle spacing of Ag NP chains has been realized by adjusting the segment length of the Ag/Bi superlattice nanowires and the annealing condition. With an extension of the annealing time, it is observed that Ag particles display the transform trend from ellipsoid to sphere. Our findings could inspire further investigation on the design and fabrication of metal nanoparticle chains.