Silicon nanowires (NWs) are attracting the interest of the scientific community as building blocks for a wide range of future nanoscaled devices. We demonstrate the realization of a 2D random fractal array of vertically aligned Si NWs by using metal-assisted chemical etching without any lithographic process and by a cheap, fast and maskless approach compatible with Si technology. We were able to control and tune the optical properties of the system, by realizing different fractal geometry through the optimization of NW spatial arrangement [1-2]. NW achieved by this technique exhibited a very bright room temperature PL and EL, tunable with NW size in agreement with the occurrence of quantum confinement effects. An innovative Si NW-based optical biosensor is realized, which exploits the PL properties for the detection of proteins in a wide range of concentrations, down to the femtomolar limit in serum. Moreover, we demonstrate the aptitude of these Si nanowires for revealing few copies of pathogen DNA by the quenching of the PL signal with very strong selectivity.Si NW optical biosensors present a fast time of analysis, a broad flexibility of detection over a wide concentration range, an extreme selectivity opening the route towards a new generation of portable sensing devices at low cost for the primary health care diagnostic.
1. Light: Science & Applications 5 (4), e16062, 2016
2. Nano Letters, 16 (7), pp 4181–4188, 2016