Highly sensitive capacitive immunosensor based on porous silicon–polyaniline structure: Bias dependence on specificity

Porous silicon/polyaniline (PS/PANI) heterostructure has been prepared electrochemically which provides label free, real-time electrical detection with high sensitivity for the specific model biomolecules (mouse IgG/goat antimouse IgG). The sensor structures based on PS/PANI were prepared easily by directly immobilizing the biomolecule through gluteraldehyde coupler. These structures were used to detect specific biomolecule down to at least a picomolar concentration range and were found to be reusable. High sensitivity and easy processability of PS/PANI structures could be understood by the change in surface charge of the silicon channels in the PS structure that occurs by PANI deposition whilst providing covalent binding with biomolecules with its naturally occurring NH groups. The space charge layer in the PS/PANI channels get further modified by the surface charge change created by the specific analyte–antibody binding giving rise to high sensitivity. It was found that a substrate bias in the accumulation region of porous silicon gives the optimum sensitivity and specificity.