<p>Noble metal nanostructures display collective
oscillation of the surface conduction electrons upon light irradiation as a
form of localized surface plasmon resonance (LSPR) properties. Size, shape and
the refractive index of surrounding environment are the key features that
controls the LSPR properties. Surface passivating ligands have the ability to
modify the charge density of nanostructures to allow resonant wavelength to
match that of the incident light, a phenomenon called “plasmoelectric effect,”.
According to the drude model Red and blue shifts of LSPR peak of nanostructures
are observed in the event of reducing and increasing charge density,
respectively. However, herein we report unusual LSPR properties of gold triangular
nanoprisms (Au TNPs) upon functionalization with para-substituted thiophenols
(X-Ph-SH, X = -NH<sub>2</sub>, -OCH<sub>3</sub>, -CH<sub>3</sub>, -H, -Cl, -CF<sub>3</sub>,
and -NO<sub>2</sub>). Accordingly, we hypothesized that an appropriate energy
level alignment between the Au Fermi energy and the HOMO or LUMO of ligands
allows delocalization of surface plasmon excitation at the hybrid
inorganic-organic interface, and thus provides a thermodynamically driven
plasmoelectric effect. We further validated our hypothesis by calculating the
HOMO and LUMO levels and also work function changes of Au TNPs upon
functionalization with para substituted thiol. We further utilized our unique
finding to design ultrasensitive plasmonic substrate for biosensing of cancer
microRNA in bladder cancer and owe to unpresidential sensitivity of the
developed Au TNPs based LSPR sensor, for the first time we have been utilized
to analysis the tumor suppressor microRNA for more accurate diagnosis of BC.
Additionally, we have been advancing our sensing platform to mitigate the false
positive and negative responses of the sensing platform using surface enhanced
fluorescence technique. This noninvasive, highly sensitive,
highly specific, also does not have false positives technique provide strong
key to detect cancer at very early stage, hence increase the cancer survival
rate. Moreover, the electromagnetic
field enhancement of Surface-Enhanced Raman Scattering (SERS) and other related
surface-enhanced spectroscopic processes resulted from the LSPR property. This
dissertation describes the design and development of entirely
new SERS nanosensors using flexible SERS substrate based on unique LSPR
property of Au TNPs and developed sensors shows excellent SERS activity
(enhancement factor = ~6.0 x 106) and limit of detection (as low as 56
parts-per-quadrillions) with high selectivity by chemometric analyses among
three commonly used explosives (TNT, RDX, and PETN). Further we achieved the
programable self-assembly of Au TNPs using molecular tailoring to form a 3D
supper lattice array based on the substrate effect. Here we achieved the
highest reported sensitivity for potent drug analysis, including opioids and
synthetic cannabinoids from human plasma obtained from the emergency room. This
exquisite sensitivity is mainly due to the two reasons, including molecular
resonance of the adsorbate molecules and the plasmonic coupling among the
nanoparticles. Altogether we are highly optimistic that our research will not
only increase the patient survival rate through early detection of cancer but
also help to battle the “war against drugs” that together is expected to
enhance the quality of human life. </p>
<p> </p>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/11347520 |
| Date | 11 December 2019 |
| Creators | Thakshila Liyanage (8098115) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/NANOPLASMONIC_EFFICACY_OF_GOLD_TRIANGULAR_NANOPRISMS_IN_MEASUREMENT_SCIENCE_APPLICATIONS_RANGING_FROM_BIOMEDICAL_TO_FORENSIC_SCIENCES/11347520 |
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