Nanotechnology

Growth of Straight Silicon Nanowires on Amorphous Substrates with Uniform Diameter, Length, Orientation, and Location Using Nanopatterned Host-Mediated Catalyst

Abstract

We report a new approach, termed “growth by nanopatterned host-medicated catalyst” (NHC growth), to solve nonuniformities of Si nanowires (NWs) grown on amorphous substrates. Rather than pure metal catalyst, the NHC uses a mixture of metal catalyst with the material to be grown (i.e., Si), nanopatterns them into desired locations and anneals them. The Si host ensures one catalyst-dot per-growth-site, prevents catalyst-dot break-up, and crystallizes catalyst-dot (hence orientating NWs). The growth results straight silicon NWs on SiO2 with uniform length and diameter (4% deviation), predetermined locations, preferred orientation, one-wire per-growth-site, and high density; all are 10–100 times better than conventional growth.

Link

Growth of Straight Silicon Nanowires on Amorphous Substrates with Uniform Diameter, Length, Orientation, and Location Using Nanopatterned Host-Mediated Catalyst

Direct enzyme patterning with microcontact printing and the growth of ZnO nanoparticles on the catalytic templates at room temperature

Abstract

Here we developed a microcontact printing (μCP) process to directly pattern enzymes in a single step without the loss of enzyme activity after printing. By modifying the substrate to display aldehyde groups, the direct stamping of urease enables the simultaneous patterning and covalent cross-linking of urease under the reducing agent NaCNBH4, which does not degrade the enzyme activity. Because the enzyme was not treated by the cross-linker prior to the sampling but rather pre-assembled on the surface of the substrate, only the contact areas of the PDMS stamp reacted with the cross-linker on the substrate, minimizing the poisoning of the enzymatic sites. The exposed urease particles on the substrate, free from the cross-linker, were still catalytically active and utilized to grow crystalline ZnO nanoparticles on the enzyme patterns in ambient conditions and in aqueous solution.

Link

Direct enzyme patterning with microcontact printing and the growth of ZnO nanoparticles on the catalytic templates at room temperature

Fibre laser machining for glassy carbon master mould and soft lithography based two-step printing for Ag nanoparticle structures

Abstract

Traditional manufacturing techniques widely used in semiconductor industries involve many processing steps that consume both time and material and lead to high cost. Soft Lithography (SL) offers a new way to print micro/nano structures, which is a fast and low cost alternative to the conventional route, although the high processing temperature of metals, semiconductors and ceramics limits the application SL techniques. In this paper we report the use of Ag nanoparticles as building blocks to make structures by combing the merits of SL, nanotechnology and laser engineering, which provide a simple additive route with low capital investment. Glassy carbon (GC) was chosen as the material for the rigid master mould, as no release coating is needed for replicating the polydimethylsiloxane (PDMS) mould. GC moulds were machined by a nanosecond-pulsed Yb fibre laser. The machined GC moulds were further cleaned by PDMS and the same fibre laser system to remove the process debris. The master mould was further replicated by PDMS. PDMS replicas with either positive or negative features from the master mould were attainable. A two-step strategy was used to print patterns using PDMS mould and Ag nanoparticle paste. Metal patterns were formed on various substrates, and the PDMS mould was left clean and ready for reuse. The resultant printed patterns were found to be uniform over millimetre range, with negligible residual layer, and the thickness of up to several micrometres. The thermal responses of Ag nanoparticles at various sintering temperatures were investigated. The factors affecting the resolution of printed structures were discussed.

Link

Fibre laser machining for glassy carbon master mould and soft lithography based two-step printing for Ag nanoparticle structures

Page 5 of 18