| dc.description.abstract | ENGLISH ABSTRACT
Surface-enhanced Raman scattering (SERS) is a sensitive analysis tool for molecular
detection across various research fields. Nonetheless, the practical applications of SERS have
been impeded by its limited reproducibility for 30+ years. This work presents a novel SERS
sensor built with indium gallium nitride quantum wells (InGaN QWs), exhibiting greatly
improved reproducibility in space and time. Not only showing improved reproducibility, the
nitride QWs also deliver enhanced SERS intensity.
The roles of QW in SERS were investigated by detecting rhodamine 6G molecules on
the substrates with varied QW structures. It was found that the QWs improve SERS
performances via two routes: i) amplifying the SERS intensities and ii) forming the hot surface
by enlarging and interconnecting SERS-active regions. The two routes result from enhanced
effects of charge transfer resonance and localized surface plasmon resonance. Effective control
over electron distribution by QW number and surface morphology leads to a linear dependence
of SERS enhancement factor on surface electron concentration. In addition, QWs-induced
electrons were shown to coherently oscillate with those on gold nanoparticles, greatly enlarging
the hotspots and thus delivering the prevalent single-molecule signals.
The superior performance of InGaN QWs-based SERS substrates were applied to the
detection of circulating tumor deoxyribonucleic acid (ctDNA) and glucose. Specifically, by
combining aluminum nanostructures and QWs, we successfully achieved a sensitive (i.e.,
concentration of 10-13M), specific (single-base mismatch discrimination), and stable sensing of
ctDNA for pancreatic cancer diagnosis. Moreover, overcoming the challenges of low Raman
cross-section and complex environmental interference, we achieved an unprecedented detection
of glucose (1-87 mM) in culture cell medium, which was realized on gold nanostructures with
the QW-based hot surface. Furthermore, band-gap engineering of InGaN QWs led to enhanced
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SERS specificity, delivering distinct SERS signals of the two single-stranded ctDNA (10-5 M)
related to pancreatic and thyroid cancers.
These promising results can be further improved by optimizing the QW structures,
including surface morphology, well/barrier thickness, and doping concentration, paving the
way for practical applications of SERS biosensors. | en_US |