Ming-Liang Zhang

Ordered silicon nanowire arrays via nanosphere lithography and metal-induced etching

Two-dimensional silica colloidal crystal template is used to create metal nanohole arrays on a silicon surface, which enables the controlled fabrication of aligned silicon nanowire (SiNW) arrays via metal catalytic etching. By varying the size of silica colloidal crystals, aligned arrays of SiNWs with desirable diameter and density could be obtained. The formation of ordered SiNW arrays is due to selective and anisotropic etching of silicon induced by the silver pattern. The orientation of SiNW arrays is influenced by silver movement in silicon, and the wire axes are primarily along the ⟨100⟩ direction.

Ag-modified silicon nanowires substrate for ultrasensitive surface-enhanced raman spectroscopy

We report a unique substrate for surface-enhanced raman spectroscopy (SERS) based on silver nanoparticles-embedded silicon nanowires (SiNWs). The SiNWs were prepared by thermal evaporation of SiO powder via oxide-assisted growth, oxide removed with HF, and then used to reduce silver ions to form a highly decorated Ag-embedded surface. Such modified SiNWs substrates yielded ultrahigh SERS sensitivity, which could detect 25μl of 1×10−16M Rhodamine 6G, 1×10−16M crystal violet, and 1×10−14M nicotine in methanol solutions. An Ag-modified SiNW strand could also enable SERS detection of 25μl of 1×10−8mg∕ml calf thymus DNA. The possible mechanisms for the ultrahigh SERS sensitivity were discussed.

A surface-enhanced Raman spectroscopy substrate for highly sensitive label-free immunoassay

Large-scale uniform silicon nanowires (SiNWs) array was fabricated by chemical etching on n-Si(111) wafer. Silver nanoparticles (AgNPs) were loaded on their surfaces. The AgNPs on SiNWs (AgNPs@SiNWs) array exhibit strong surface-enhanced Raman effect. On the substrate surfaces, characteristic Raman signals are generated with trace amount of mouse immunoglobulin G (mIgG), goat-anti-mouse immunoglobulin G (gamIgG), and immune complexes formed from 4ng each of mIgG and gamIgG. The shifted positions and changed intensities in Raman bands indicate the occurrence of immunoreactions. This AgNPs@SiNWs array is a unique substrate for surface-enhanced Raman spectroscopy to show the immune reagents and immunoreactions at higher sensitivity.

High-sensitivity pesticide detection via silicon nanowires-supported acetylcholinesterase-based electrochemical sensors

We report the use of a silicon-based nanocomplex, i.e., gold nanoparticles-coated silicon nanowires, for the improvement of acetylcholinesterase (AChE)-based electrochemical sensors for pesticide detection. Owing to the high electrical conductivity of the nanocomplex and its compatibility with the enzyme, the sensor exhibited significantly enhanced performance. The AChE enzyme bound to the surface possessed Michaelis-Menton constant of 81 mu M, resembling that in its free form. The sensor showed rapid response toward substrate acetylcholine in the concentration range of 1.0 mu M-1.0 mM. This AChE nanosensor could detect as low as 8 ng/L dichlorvos, an organophosphate pesticide

The mutual promotional effect of Au–Pd bimetallic nanoparticles on silicon nanowires: A study of preparation and catalytic activity

Au–Pd nanoparticles were synthesized on the surface of silicon nanowires and used in the degradation of the p-nitroaniline, which exhibited the mutual promotional effect compared with Au/Si and Pd/Si catalysts. This synergistic effect factor was calculated as 2.35. The Au–Pd/Si catalysts might be recycled and used again. The catalytic rate of the catalysts only decreased by 20% after recycling for five times.

Nitrogen-doped silicon nanowires: Synthesis and their blue cathodoluminescence and photoluminescence

Nitrogen-doped silicon nanowires were obtained via a high temperature oxide assisted method. Both their cathodoluminescence and photoluminescence exhibited blue emissions, which might attributed to the nitrogen doping. Both the elemental mapping analysis and smooth cathodoluminescence image suggested uniform nitrogen doping in the silicon nanowires.

Single mullite nanoribbon as a glucose sensor

Mullite (2SiO(2).3Al(2)O(3)) nanoribbons, millimetres in length and with a high width-to-thickness ratio, were synthesized at temperatures as low as 1150 degrees C. This high ratio made it easy to fabricate a single nanoribbon sensor. The I-V relation of the sensor versus concentration of glucose was recorded with a pico-ammeter. The sensor shows good reproducibility and long-term stability. This single nanoribbon sensor may be used as an in situ monitor. The nanoribbons were also characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy and x-ray photoemission spectroscopy.