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Rational assembly of nanoparticles is of vital importance for exploring fundamental electronic and optical properties and for constructing novel nanoscale devices. Through controlling aggregation kinetics, dimers and trimers of gold nanoparticles were generated and encapsulated with polymer by using a one-pot synthesis that involved simple heating and cooling. Dimers of gold nanoparticles were enriched from the resulting solution by centrifugation. The polymer shells maintain the stability of the nanoparticle organization, preventing aggregation and disintegration during subsequent purification, enrichment, and application. A typical enriched sample showed that the dimer population reached 61% among 989 nanoparticles surveyed. In a proof-of-concept application, the gold nanoparticle dimers were used as catalyst to guide the growth of dimeric zinc oxide nanowires. Nanowire dimers with unprecedented narrow spacing (20 to 60 nm) were achieved using a vapor transport growth method; dimeric nanowire population reached approximately 25%.

The technique to pattern aminosilanes on hydroxyl-terminated substrates will open up extensive applications in many fields. There are some existing methods to pattern aminosilanes, in particular, (3-aminopropyl)triethoxysilane (APTES) on SiO(2) and glass substrates through indirect routes. However, few reports focus on the direct patterning of APTES by microcontact printing (microCP), due to the volatility of "inks" which consist of APTES and organic solvents. This report shows that high-quality APTES patterns on hydroxyl-terminated substrates can be directly obtained by microCP using an APTES aqueous solution as "ink". Gold nanoparticles (Au NPs) have been used to verify the presence and quality of APTES patterns on which they are selectively adsorbed. Thus-obtained Au NP patterns can serve as templates for the growth of ZnO nanostructures. Lectins are also successfully immobilized on the APTES patterns, with glutaraldehyde as linker. We believe that our method will serve as a general approach and find a wide range of applications in the fabrication of patterns and devices.

Designing geometrical structures and making chemical modifications are two effective routes to tailor wettability. ZnO-based hierarchical nanostructures, in particular, vertically aligned nanoneedles and nanonails were employed as a platform to study the effect of surface morphology. The hydrophobicity and the variation of contact angle in the as-grown samples were attributed to the combined effects of surface roughness and partial water-solid contact. Subsequent chemical modifications with stearic acid led to superhydrophobic ZnO surfaces, while annealing in air resulted into superhydrophilicity. Under the alternations of coating and removal of stearic acid, reversible transitions between superhydrophilicity and hydrophobicity were realized.

We have fabricated p-type La0.7Sr0.3MnO3 thin film/n-type ZnO nanowires (nanosheets) heterostructures. A lower-temperature growth with Zn source and a higher-temperature growth with ZnO/graphite source led to the formations of nanowires and nanosheets, respectively. While the nanosheets showed an epitaxial relationship with the manganite film, the high processing temperature resulted in interfacial diffusion and reaction, which were reflected in the x-ray diffraction, magnetic, and electrical transport measurements. The manganite thin film/ZnO nanowires (nanosheets) p-n junctions exhibited good rectification behaviors. Such heterostructures are promising to find potential applications in electronic and spintronic devices.