Porous silicon Bloch surface and sub-surface wave structure for simultaneous detection of small and large molecules
1 Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN 37235, USA
2 Department of Physics, Northwest Nazarene University, Nampa, ID 83686, USA
3 Department of Biochemistry, Vanderbilt University, Nashville, TN 37232, USA
Nanoscale Research Letters 2014, 9:383 doi:10.1186/1556-276X-9-383Published: 7 August 2014
A porous silicon (PSi) Bloch surface wave (BSW) and Bloch sub-surface wave (BSSW) composite biosensor is designed and used for the size-selective detection of both small and large molecules. The BSW/BSSW structure consists of a periodic stack of high and low refractive index PSi layers and a reduced optical thickness surface layer that gives rise to a BSW with an evanescent tail that extends above the surface to enable the detection of large surface-bound molecules. Small molecules were detected in the sensor by the BSSW, which is a large electric field intensity spatially localized to a desired region of the Bragg mirror and is generated by the implementation of a step or gradient refractive index profile within the Bragg mirror. The step and gradient BSW/BSSW sensors are designed to maximize both resonance reflectance intensity and sensitivity to large molecules. Size-selective detection of large molecules including latex nanospheres and the M13KO7 bacteriophage as well as small chemical linker molecules is reported.