Browsing by Author "Smith, Kimberly A."

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    DESIGNING EFFICIENT LOCALIZED SURFACE PLASMON RESONANCE-BASED SENSING PLATFORMS: OPTIMIZATION OF SENSOR RESPONSE BY CON-TROLLING THE EDGE LENGTH OF GOLD NANOPRISMS
    (Office of the Vice Chancellor for Research, 2012-04-13) Joshi, Gayatri K.; McClory, Phillip J.; Muhoberac, Barry B.; Kumbhar, Amar; Smith, Kimberly A.; Sardar, Rajesh
    Over the last few years, the unique localized surface plasmon resonance (LSPR) properties of plasmonic nanostructures have been used to design la-bel-free biosensors. In this research, we demonstrate that it is the difference in edge length of gold nanoprisms that significantly influences their bulk re-fractive index sensitivity and local sensing efficiency. Nanoprisms with edge lengths in the range of 28-51 nm were synthesized by the chemical-reduction method and sensing platforms were fabricated by chemisorptions of these nanoprisms onto silanized glass substrates. The plasmonic nanosensors prepared from 28 nm edge length nanoprisms exhibited the largest sensitivity to change in bulk refractive index with a value of 647 nm/RIU. The refractive index sensitivity decreased with increasing edge length, with nanoprisms of 51 nm edge lengths displaying a sensitivity of 384 nm/RIU. In contrast, we found that the biosensing efficiency of sensing platforms modified with biotin increased with increasing edge length, and the sensing platforms fabricated from 51 nm edge length nanoprisms displaying the highest local sensing efficiency. The lowest concentration of streptavidin that could be measured reliably was 1.0 pM and the limit of detection for the sensing platforms fabricated from 51 nm edge length nanoprisms was 0.5 pM, which is much lower than found with gold bipyramids, nanostars, and nanorods.
  • Thumbnail Image
    Item
    Designing of Gold Nanoprism-Based Reversible and Ultra-sensitive Molecular Sensors
    (Office of the Vice Chancellor for Research, 2013-04-05) Joshi, Gayatri K.; Smith, Kimberly A.
    Photoswitchable molecules have attracted a great deal of attention over the past few years in designing molecular machines. Among photoswitchable molecules, azobenzene is widely studied due to its transcis photoisomeration, which produces a simple structure and spectra, and is photo and electrochemically active. The localized surface plasmon resonance (LSPR) properties of the metal nanostructures in conjunction with the photswitching properties of the azobenzene molecules allow the nanoscale environment to be more controlled and to ultimately improve the sensing abilities of the metallic nanostructures. We have developed a method of constructing a self-assembled monolayer (SAM) of azobenzene-containing alkanethiol molecules on the surface of chemically synthesized gold nanoprisms as molecular sensor. The reversible photoswiching properties of azobenzene were studied by monitoring the LSPR peak shift of gold nanoprisms by absorption spectroscopy. It was found that the substratebound gold nanoprisms functionalized with azobenzene alkanethiol molecules resulted in a ~30 nm LSPR peak red shift. The photoswitching behavior of the azobenzene molecules attached to the prisms was monitored after cycling exposure to UV and visible light. A ~12 nm LSPR blue shift was observed as the light exposure was switched from visible to UV light due to the trans to cis isomeration of the azobenze. The LSPR peak shift was found to be reversible as the light source was switched back and forth several times from UV to visible light. The reversible photoswitching of azobenzene-functionalized gold nanoprisms demonstrates their potential as ultra-sensitive molecular sensors for a broad range of applications from nanoelectrochemical systems to medicine.