Fluorescence excitation enhancement by waveguiding nanowires

Area of Science:

• Optoelectronics
• Nanotechnology
• Biophotonics

Background:

• Vertical semiconductor nanowires offer enhanced fluorescence for surface-bound fluorophores, crucial for biosensing applications.
• Increased local excitation light intensity near nanowire surfaces is a hypothesized factor in fluorescence enhancement.
• Detailed experimental studies on this excitation enhancement effect have been limited.

Purpose of the Study:

• To experimentally quantify the excitation light enhancement for fluorophores on semiconductor nanowire surfaces.
• To investigate the dependence of excitation enhancement on nanowire diameter and excitation wavelength.
• To understand the spatial distribution of excitation enhancement around the nanowire.

Main Methods:

• Utilized epitaxially grown Gallium Phosphide (GaP) nanowires.
• Combined theoretical modeling with experimental measurements of fluorescence photobleaching rates.
• Measured photobleaching rates to infer local excitation light intensity.

Main Results:

• Quantified excitation enhancement for nanowires with diameters ranging from 50 to 250 nm.
• Observed that excitation enhancement peaks at specific nanowire diameters, varying with excitation wavelength.
• Demonstrated a rapid decay of excitation enhancement within tens of nanometers from the nanowire sidewall.

Conclusions:

• The study provides experimental validation of excitation enhancement in semiconductor nanowire systems.
• Results offer insights for optimizing nanowire dimensions and excitation conditions for enhanced biosensing.
• Findings facilitate the design of highly sensitive nanowire-based optical systems for bioanalytical applications.