Integrating Colloidal Quantum Dots with Porous Silicon for High Sensitivity Biosensing

Abstract

ABSTRACTWe 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.