Gas-Phase Synthesis for Label-Free Biosensors: Zinc-Oxide Nanowires Functionalized with Gold Nanoparticles

Area of Science:

• Materials Science
• Nanotechnology
• Biotechnology

Background:

• Metal oxide semiconductor nanowires offer potential for label-free biosensing.
• Conventional biosensors require chemical functionalization for specific analyte detection.
• Gold nanoparticles (Au NPs) can enhance semiconductor-based biosensor performance.

Purpose of the Study:

• To develop a novel method for functionalizing zinc oxide nanowire (ZnO NW) biosensors using gas-phase synthesized gold nanoparticles (Au NPs).
• To demonstrate label-free detection of biomolecules at sub-nanomolar concentrations using Au NP-decorated ZnO NWs.
• To investigate the application of this technique for detecting DNA and streptavidin.

Main Methods:

• Fabrication of uniform ZnO NW devices using a vapor-solid-liquid method in a chemical vapor deposition (CVD) furnace.
• Deposition of size-selected Au NPs onto ZnO NWs via magnetron sputtering and quadrupole mass filtering.
• Electrical detection of DNA binding and atomic force microscopy (AFM) visualization of individual DNA strands.
• Functionalization with DNA aptamers for streptavidin detection.

Main Results:

• Successful decoration of ZnO NWs with Au NPs without additional surface functionalization.
• Label-free electrical detection of DNA binding at sub-nanomolar concentrations.
• Detection of streptavidin and its complementary DNA strand at sub-nanomolar concentrations using aptamer-functionalized sensors.
• Enabled sub-nanomolar DNA detection in passivated ZnO NWs, enhancing stability in aqueous solutions.

Conclusions:

• Gas-phase synthesis of Au NPs provides an effective, label-free functionalization strategy for ZnO NW biosensors.
• This approach achieves high sensitivity for detecting DNA and other biomolecules.
• The method is versatile and applicable to various semiconductor materials for advanced biosensing applications.