B. Lian, H. Li, J. Guo, D. Fan
The University of Texas at Austin,
United States
Keywords: optoelectric, molecule preconcentration, biosensing, surface-enhanced Raman scattering, SERS, simulation, muti-scale simulation, silicon, nanorods, microfluidics
Summary:
Detecting low-concentration biomolecules quickly and with ultra-sensitivity is critical for early disease diagnosis, but this remains a challenge due to the nature of nanosensors. While their small size enhances sensitivity, it also increases the time needed to detect dilute molecules. In this work, we present a novel optoelectric sensing scheme, along with an innovative device design and fabrication approach, to overcome this challenge. Our method leverages the strong optoelectric effect of silicon nanowires to concentrate trace biomolecules at a laser focus point, while simultaneously detecting their Raman signals. The device features large arrays of silicon nanorods integrated with electrodes and silver nanoparticles for surface-enhanced Raman spectroscopy (SERS) detection. Operating at just -0.8V, these nanosensors achieve a remarkable 150-fold signal enhancement, pushing the detection limit for adenine down to 0.6 femtomolar (fM)—an improvement of five orders of magnitude. This enhancement is robust across 1 micromolar (μM) concentrations to 1 fM. The sensing mechanism is effective not only for small molecules like adenine but also for larger charged molecules such as vertebrate DNA. Multiscale simulations have revealed the underlying mechanism, providing a deep understanding of this breakthrough. This research addresses a key bottleneck in nanobiosensing and is expected to lead to the development of a new class of biochemical sensors, crucial for the detection of trace biomolecules in clinical diagnostics.