Ultrasensitive Detection of a Variety of Analytical Targets Based on a Functionalized Low‐Resistance AuNPs/β‐Ni(OH)₂ Nanosheets/Ni Foam Sensing Platform

Abstract Simple, low‐cost and yet accurate, sensitive, and quantitative detection of a broad range of analytical targets by means of small footprint sensing devices has the potential to revolutionize medical diagnostics, food safety, and environmental monitoring. This work demonstrates a functional nucleic acids (FNAs) tethered AuNPs/β‐Ni(OH)₂ nanosheets (NS)/Ni foam nanocomposite as a miniaturized electrode. Through the rational design of a low‐barrier ohmic contact of AuNPs to β‐Ni(OH)₂ NS and a target mediated nanochannel electron transfer effect, a variety of analytical targets, ranging from a disease marker (thrombin, 16.3 × 10⁻¹² m detection limit) to an important biological cofactor (adenosine, 3.2 × 10⁻¹² m detection limit), and to a toxic metal ion (Hg²⁺, 3.1 × 10⁻¹² m detection limit), are detected with ultrasensitivity. The presence of target triggers the conformational change of FNAs, introducing strong steric hindrance and electrostatic repulsion to the diffusion of electron indicators toward the electrode surface, ultimately leading to the changes in impedance. A novel equivalent circuit considering the capacitive reactance is proposed to describe the 2D NS‐based impedance DNA bioelectrode. This sensing platform is easily applicable to the detection of many other targets in diverse sample matrices through the use of other suitable FNAs materials.