Due to their all-electrical nature, impedance biosensors have significant potential for use as simple and portable sensors for environmental studies and environmental monitoring. Detection of two endocrine-disrupting chemicals (EDC), norfluoxetine and BDE-47, is reported here by impedance biosensing, with a detection limit of 8.5 and 1.3 ng/mL for norfluoxetine and BDE-47, respectively. Although impedance biosensors have been widely studied in the academic literature, commercial applications have been hindered by several technical limitations, including possible limitations to small analytes, the complexity of impedance detection, susceptibility to nonspecific adsorption, and stability of biomolecule immobilization. Recent research into methods to overcome these obstacles is briefly reviewed. New results demonstrating antibody regeneration atop degenerate (highly doped) Si are also reported. Using 0.2 M KSCN and 10 mM HF for antibody regeneration, peanut protein Ara h 1 is detected daily during a 30 day trial.

Electrochemical biosensors have potential applications for agriculture, food safety, environmental monitoring, sports medicine, biomedicine, and other fields. One of the primary challenges in this field is the immobilization of biomolecular probes atop a solid substrate material with adequate stability, storage lifetime, and reproducibility. This review summarizes the current state of the art for covalent bonding of biomolecules onto solid substrate materials. Early research focused on the use of Au electrodes, with immobilization of biomolecules through ω-functionalized Au-thiol self-assembled monolayers (SAMs), but stability is usually inadequate due to the weak Au–S bond strength. Other noble substrates such as C, Pt, and Si have also been studied. While their nobility has the advantage of ensuring biocompatibility, it also has the disadvantage of making them relatively unreactive towards covalent bond formation. With the exception of Sn-doped In₂O₃ (indium tin oxide, ITO), most metal oxides are not electrically conductive enough for use within electrochemical biosensors. Recent research has focused on transition metal dichalcogenides (TMDs) such as MoS₂ and on electrically conductive polymers such as polyaniline, polypyrrole, and polythiophene. In addition, the deposition of functionalized thin films from aryldiazonium cations has attracted significant attention as a substrate-independent method for biofunctionalization.

We report room temperature deposition of compact Si films onto 6061 Al alloy from aqueous solutions containing 10 mM HF and 20 mM Na₂SiF₆ in 80 wt % formic acid (HCO₂H) by a combination of galvanic and electroless deposition. Deposition for 30 h. yields a 7–10 μm thick, dark grey Si thin film that does not change color upon exposure to air. Elemental analysis demonstrates that the as-deposited film contains 2–3 atom % Al, 4–5 atom % Cu, and 92–94 atom % Si. We believe that this is the first report of aqueous, room temperature deposition of thick, compact Si films.

Studies by electrochemical impedance spectroscopy demonstrate that the wild-type glucose-galactose receptor (GGR) protein does not interact significantly with a Au surface, even through nonspecific interactions. Only the GGR A1C mutant, where alanine is replaced by a cysteine residue at the N-terminus, can form a protein film on Au suitable for creating an impedance biosensor. Impedance measurements of glucose binding at equilibrium allow estimation of the dissociation constant as approximately 6.6 , about 32 times higher than that for the native protein in solution. This change likely arises from surface immobilization rather than from cysteine introduction.