Strain-Modulated and Nanorod-Waveguided Fluorescence in Single Zinc Oxide Nanorod-Based Immunodetection

Area of Science:

• Nanomaterials Science
• Biophotonics
• Biosensing

Background:

• Mechanical strain offers tunable control over nanomaterial properties.
• Controlling fluorescence signals from bioanalytes on nanomaterials is crucial for sensitive detection.

Purpose of the Study:

• To investigate the effect of mechanical strain on fluorescence signals from bioanalytes coupled to individual zinc oxide nanorods (ZnO NRs).
• To determine how nanorod length and protein concentration influence strain-induced changes in waveguided fluorescence intensity.

Main Methods:

• Utilized a model immunoassay with tumor necrosis factor-α (TNF-α) and a fluorophore-labeled antibody.
• Formed Alexa488-TNF-α immunocomplexes on individual ZnO NRs.
• Applied tensile and compressive strain to ZnO NRs and measured changes in fluorescence intensity, fluorescence intensification on nanorod ends (FINE), and degree of FINE (DoF).

Main Results:

• Tensile strain increased, while compressive strain decreased waveguided fluorescence signals.
• Both FINE and DoF showed a linear dependence on strain type and magnitude, independent of protein concentration.
• Longer ZnO NRs exhibited greater strain-dependent fluorescence changes and a higher linear correlation between protein concentration and fluorescence intensity.

Conclusions:

• Mechanical strain is an effective method to enhance and tune optical signals from bioanalytes on ZnO NRs.
• Nanorod length is a critical factor for maximizing strain-induced signal modulation and achieving sensitive bioanalyte quantification.
• This work supports the development of miniaturized, highly sensitive biosensors optimized by strain application for ultra-trace level detection.