Peptide Assisted Growth of Silver Nanoparticles on a Semiconductor Substrate for use in Plasmonic Nanosensing

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2 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

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

Eric 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

1
mM

AgNO
3
,

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
-
6
m)

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 AgNO
3

for 5 min under room light

Image: bowtie shape optical field
enhancement caused by SPR
1


1

By Arizona Center for Mathematical Sciences. University of Arizona.