Photonic biosensor based on photocorrosion of GaAs/AlGaAs quantum heterostructures for detection of Legionella pneumophila.

Photocorrosion of semiconductors is strongly sensitive to the presence of surface states, and it could be influenced by electrically charged molecules immobilized near the semiconductor/electrolyte interface. The underlying mechanism is related to band bending of the semiconductor structure near the surface and the associated distribution of excited electrons and holes. The authors have employed photoluminescence of GaAs/AlGaAs quantum heterostructures for monitoring in situ the photocorrosion effect, and demonstrating detection of nongrowing Legionella pneumophila suspended in phosphate buffered saline solution. Antibody functionalized samples allowed direct detection of these bacteria at 10(4) bacteria/ml. The authors discuss the sensitivity of the process related to the ability of creating conditions suitable for photocorrosion proceeding at extremely slow rates and the interaction of an electric charge of bacteria with the surface of a biofunctionalized semiconductor.