We aim to utilize the high surface area of a porous silicon (PSi) matrix
coupled with semiconductor quantum dot (QD) amplifiers for ultrasensitive
optical detection of small biomolecules using a dual-mode detection scheme.
In our system, QDs attached to the target biomolecule serve as signal
amplifiers by providing an additional refractive index increase beyond that
of the smaller target molecules. The strong photoluminescence (PL) from the
QDs serves as a secondary indication of target molecule attachment in the
pores. A resulting increase in optical thickness of ∼190 nm and detection
sensitivity of ∼700 nm/RIU have been demonstrated for attachment of
glutathione capped CdTe QDs in the porous silicon matrix. Reflectance and PL
measurements, combined with simulations, have been used to characterize the
surface area coverage of the QDs within the porous framework, which is
estimated at 10% for glutathione capped CdTe QDs.