Alumina Coating of Ultrafine nanoporous Gold At Room Temperature and Their Optical Properties

Amorphous alumina is deposited on chemically etched nanoporous gold films using atomic layer deposition at room temperature. Nanoporous gold with ultrafine pores of 7 nm in diameter is uniformly coated with alumina film as thin as 1.4 nm. Localized surface plasmon resonance of gold skeleton exhibits a detectable red-shift in the optical transmittance spectra, the magnitude of which depends on the thickness of the alumina layer. The tunable optical properties of nanoporous gold–alumina composites provide one possibility for implementing miniaturized optical devices with high performances

One-step Fabrication of Sub-10-nm Plasmonic nanogaps for Reliable SERS Sensing of Microorganisms

Nanoscale gaps in noble metal films can produce intense electromagnetic enhancement. When Raman-active molecules are positioned in these regions, their surface-enhanced Raman scattering (SERS) signals can be dramatically enhanced. However, the lack of convenient and reliable fabrication methods with ultrasmall nanogaps (\u3c10 nm) severely block the application of SERS. Here, we propose a cost-effective and reproducible technique to fabricate the large-area Ag SERS-active substrates which are full of the high-density, sub-10-nm nanogaps by high pressure sputtering, and the enhancement factor (EF) is testified to improve by 10(3) times compared to the continuous Ag film with a smooth surface (the roughness is 0.5 nm) and without nanogaps. Since there are no chemicals used during fabrication, this substrate has a clean surface, which is crucial for acquiring reliable SERS spectra. This SERS-active substrate has then been applied to identify a series of microorganisms, and excellent, reproducible SERS spectra were obtained. Finally, a set of piecewise-linear equations is provided according to the correlation between SERS intensity and rhodamine 6G (R6G) concentration, and the detection limit is calculated to be 0.2×10(-8)M. These results suggest that the high pressure sputtering is an excellent, reliable technique for fabricating sub-10-nm plasmonic nanogaps, and the SERS-based methodology is very promising for being used in biological sensing field

Surface modification of permalloy (Ni80Fe20) nanoparticles for biomedical applications

We report a simple and novel method for surface biofunctionalization onto recently reported NiFe permalloy nanoparticles (~71 nm) and the immobilization of a model protein, IgG from human serum. The strategy of protein immobilization involved attachment of histidine-tagged streptavidin to the NiFe nanoparticles via a non-covalent ligand binding followed by biotinylated human IgG binding on the nanoparticle surface using the specific high affinity avidin-biotin interaction. The biofunctionalization of NiFe permalloy nanoparticles was confirmed by Fourier Transform InfraRed (FTIR) spectroscopy and protein denaturing gel electrophoresis (lithium dodecyl sulfate- polyacrylamide gel electrophoresis, LDS-PAGE). This protocol for surface functionalization of the novel nanometer-sized NiFe permalloy particles with biological molecules could open diverse applications in disease diagnostics and drug delivery