Competitive Impedance Spectroscopy in a Schottky-Contacted ZnO Nanorod Structure for Ultrasensitive and Specific Biosensing in a Physiological Analyte

Abstract

To enable detection and discovery of biomarkers, development of label-free, ultrasensitive, and specific sensors is the need of the hour. For addressing this requirement, here, a Schottky-contacted ZnO nanorod biosensor has been demonstrated, which explores the interplay between Schottky junction capacitance and solution resistance, resulting in an interesting sensing principle of competitive impedance spectroscopy. When the transition of dominating impedance occurs from solution resistance to junction capacitance, a notch or a peak appears in the impedance response at a particular frequency (referred to as the corner frequency) depending on the charge of the target molecule. The appearance of the peak or notch acts like an electronic label for selectivity since it is visible only for target molecules even at ultralow concentrations in the physiological analyte, where the magnitude of impedance change overlaps with that for nonspecific molecules. This phenomenon has been successfully applied for the positively charged vascular endothelial growth factor (VEGF) and the negatively charged hepatitis B surface antigen (HBsAg), where the shifts in the higher corner frequencies for 1 aM concentration of the target molecules have been observed to be more than 3 times the changes in the impedance magnitude. Further, the area of the ZnO nanorods was segmented into two zones corresponding to the lower and higher concentration regimes, thereby expanding the dynamic range. To summarize, an ultralow detection limit of 1 aM with a dynamic range up to 1 pM was achieved for VEGF and HBsAg, which is 4 orders of magnitude and 20 times lower than their most sensitive label-free reports, respectively.

Molecularly Imprinted Polymer Interface on Screen-Printed ZnO Nanorod Field Effect Transistors for Serotonin Detection in Clinical Samples

“…Hence, a sensor array on the glass substrate can be realized to operate in the fM as well as the nM range, which will have better potential for clinical applications due to its capability for real-time and reliable detection in comparison to a previous report . A similar approach has been reported elsewhere for sensors operating by a competitive impedance spectroscopy technique over a wide range …”

“…14 A similar approach has been reported elsewhere for sensors operating by a competitive impedance spectroscopy technique over a wide range. 33 3.4. Reproducibility and Stability Studies of the Optimized Sensor.…”

Deformed graphene FET biosensor on textured glass coupled with dielectrophoretic trapping for ultrasensitive detection of GFAP

“…These results in excellent biological stability, good electrical conductivity and a low 1/f noise level, thus making it a suitable candidate to be used for biosensing and detection of biological changes in electrolytes. There are few reports that show sub-femtomolar detection of biomolecules but they either suffer from significant background noise or lack robust control [2,3]. Further reduction in detection limits will be highly desirable for identifying the presence of trace amount of molecules like biomarkers related to traumatic brain injury (TBI).…”

Interaction Study of Anti‐E. coli Immobilization on 1DZnO at Nanoscale for Optical Biosensing Application

“…For instance, ZnO's non-center symmetric structure allows obtaining an extensive collection of nano-morphologies from this compound, such as nanowires, nanorods, and nanotubes, reported for producing sensitive and selective biosensors. [7][8][9][10][11][12][13] These morphologies offer increased surface areas compared to the Developing low-cost biosensing platforms for robust detection response and sensitivity at low concentrations is of great interest. This work reports synthesizing 1D ZnO nanostructured materials (1DZnO) with controllable properties utilizing a metal catalyst-assisted vapor phase growth technique (VLS).…”

“…For instance, ZnO's non‐center symmetric structure allows obtaining an extensive collection of nano‐morphologies from this compound, such as nanowires, nanorods, and nanotubes, reported for producing sensitive and selective biosensors. [ 7–13 ] These morphologies offer increased surface areas compared to the bulk counterpart, improving their biosensing performance. In addition, its high isoelectric point provides good selectivity for the attachment of biomolecules to the surface.…”