A porous silicon optical microcavity for sensitive bacteria detection.

A porous silicon microcavity (PSM) is highly sensitive to subtle interface changes due to its high surface area, capillary condensation ability and a narrow resonance peak (∼10 nm). Based on the well-defined optical properties of a PSM, we successfully fabricated a bacteria detection chip for molecular or subcellular analysis by surface modification using undecylenic acid (UA), and the specific recognition binding of vancomycin to the D-alanyl-D-alanine of bacteria. The red shift of the PSM resonance peak showed a good linear relationship with bacteria concentration ranging from 100 to 1000 bacteria ml( - 1) at the level of relative standard deviation of 0.994 and detection limit of 20 bacteria ml( - 1). The resulting PSM sensors demonstrated high sensitivity, good reproducibility, fast response and low cost for biosensing.