Nanotechnology • What is nano? • Nanotechnology? Creation of nanostructures Applications of the nanostructures
Nanofabrication techniques Y.-P. Zhao, “Growth and Synthesis of Nanostructured Thin Films,” in “Functional Thin Films and Nanostructures for Sensors” edited by A. Zribi and J. Fortin (Springer, 2008)
Top-down • Photo lithography • Electron beam lithography • Microcontact printing • Nanoimprint • Nanosphere lithography? • And so on… Mask or maskless ?
Han, J.T. et al. J. Am. Chem. Soc.,126 (15), 4796 -4797, 2004 Combination of top-down and bottom-up methods Hah, J. H. et al.J. Vac. Sci. Technol. B (2006). 10.1116/1.2244541 Bottom-up • Supramolecular assembly • nanoparticle formation • monolayer self-assembly • … The dividing line of top-down and bottom-up sometime is vague and it is only a matter of opinion
Thermo-vapor transport method A general setup for thermal-vapor transport method
Catalyst-assisted fabrication Deposition of a catalyst layer, e.g. thermal evaporation of a 10 nm thick metal film or injection of a precursor which decomposes into particles ZnO nanorods on Au and NiO catalysts
Thermal evaporation (resistively, electron beam) • Sputtering (gas ion bombardment) • Pulsed laser deposition (laser beam)
Chemical Vapor Deposition (CVD) Reactant gases Precursors/carrier gas Laser beam or plasma can be introduced to enhanced the reaction Can fabricate: carbon nanotubes, inorganic oxide nanorods, nanowire etc.
Liquid Phase Methods • Sol-gel dip-coating • Electro-spin coating • Block-copolymer • Electro-chemical deposition/etching
Applications Just name a few • Biosensor • Chemical sensor • Drug delivery • Self-cleaning • Energy harvesting …
dye + target target antibody Conventional fluorescence antibody method gold antibody + Si nanorods dye Enhanced fluorescence antibody method The fluorescence signal will be greatly enhanced by a large amount of dye molecules on the nanorods. Biosensor bacterial/virus detection Thank the author for sharing her research results Junxue Fu et al 2008 Nanotechnology19 155502
What are these dark dots and what is the material? SEM image of Si nanorods: top view and side view TEM image of Au coated Si nanorods
gold Si nanorods Bio-functionalization of Au/Si Nanorods antibody dye
NH2 NH2 45˚C, overnight NH2 NH2 + 2% (3-Aminopropyl)triethoxysilane (APTES) in Acetone O C N H C 1 hour at room temperature and overnight at 4°C + O Alexa488-succinimide ester NH Wash by DI water Dye immobilization on Au/Si Nanorods
Observation under fluorescence microscope Do sonication in DI water Fluorescence Scan Si film/Alexa488 IF Si rods/ Alexa488 IR
Salmonella detection Sample: Anti-Sal/Au/Si nanorods/Alexa488/2%BSA + Salmonella Control: Au/Si nanorods/Alexa488/2%BSA + Salmonella The bacteria were fixed on the glass slides by 95% ethanol. The unbound nanorods should be washed away by 0.05% Tween 20/FA buffer after the incubation.
Sample: Anti-Sal/Au/Si nanorods/Alexa488/2%BSA Fluorescence Scan 532nm(ex.)/526nm SP emission filter Fluorescence image Bright field image The Alexa488 labeled nanorods (darker particles) stick on the bacteria due to the antibody-antigen interaction.
Salmonella detection Control: Au/Si nanorods/Alexa488/2%BSA The control shows there is no fluorescence signal since the nanorods cannot attach to the bacteria without the antibody. Fluorescence Scan 532nm(ex.)/526nm SP emission filter Fluorescence image Bright field image
Lotus effect: self cleaning A Barthlot et al. Planta 202, 1 (1997) Feng et al. Adv, Mater. 14, 1857 (2002)
Motivation wings of a Cicada orni Water strider’s leg Gao et al. Nature 36, 432(2004) Lee et al. Langmuir 20, 7665 (2004)
165o Tune the nanorod coverage Si coverage f ~ 32% Si coverage f ~ 48% Deposition angle = 84o Deposition angle = 88o After coating a fluorocarbon monolayer 148o
Water droplets bounce on a sold surface Water droplets impacting a superhydrophobic surface vs. a normal hydrophobic surface
Challenge? Nonspecific binding can lead to false signal
Au nanoparticle for in vivo tumor targeting PEG is a popular polymer in the pharmaceutical industry for reducing nonspecific uptake of drugs and drug-delivery systems Qian et al. Nature Biotechnology