Peptide Assisted Growth of Silver Nanoparticles on a Semiconductor Substrate for use in Plasmonic N anosensing Eric Maz

1. Peptide Assisted Growth of Silver Nanoparticles on a Semiconductor Substrate for use in Plasmonic NanosensingEric Mazur, Harvard University, DMR 1005022 Shining light on a metal surface causes the valence, or outermost, electrons to move with a certain frequency. In nanoscale metal structures, the resonance frequency can be tuned by altering their shape and size. This phenomenon is called surface plasmon resonance (SPR) and is also a means for manipulating light on the nanoscale. Research of SPR has led to an interest in the shape controlled growth of metallic nanostructures. Our approach is to work at the interface of biology and materials science to mimic the recognition and patterning capabilities of nature by using selectively binding peptides to grow silver nanoplates directly onto a semiconductor substrate. We pretreat samples of n-type GaAs substrate in solutions of a trigylcine (GGG) peptide or a GaAs binding peptide dissolved in either water or tris-buffered saline (a salt buffer, pH=7.6). The samples are then grown in 1mM AgNO3, for varying amounts of time, under a variety of conditions: various temperatures, under room/fluorescent light or laser light or in the dark or in various combinations of these factors. We hope to grow smooth single crystalline silver nanoplates, at least one micron (10-6m) in size, that can then be post processed into silver bowtie structures. Due to SPR, the bowtie shape causes the concentration of light into the gap between the two ties which greatly enhances the optical field at that location making the the bowtie an ideal nanosensor. These plasmonic nanosensors could then be used to increase the sensitivity of immunoassays, or a biochemical test for a specific substance like a protein in a complex solution such as blood, offering us the ability to do diagnostic tests in a fraction of the time with a sample as small as one drop of blood. Silver nanoplate formation. Sample pretreated with GaAs Pep dissolved in TBS. Grown in 1mM AgNO3 for 5 min under room light Image: bowtie shape optical field enhancement caused by SPR1 1By Arizona Center for Mathematical Sciences. University of Arizona.