Analog and digital detection of plasmon-enhanced upconverting nanoparticles

Area of Science:

• Nanotechnology
• Biomedical Engineering
• Optical Physics

Background:

• Upconverting nanoparticles (UCNPs) enable sensitive, background-free biosensing.
• Low intrinsic upconversion efficiency and non-linear excitation intensity dependence pose challenges for quantitative applications.
• Plasmon-enhanced upconversion can boost sensitivity but introduces optical field inhomogeneities.

Purpose of the Study:

• To compare digital and analog readout methods for quantitative biosensing using plasmon-enhanced UCNPs.
• To evaluate the repeatability and reliability of each detection method under plasmonic enhancement.

Main Methods:

• UCNPs were imaged using diverging surface plasmon polaritons.
• Digital detection involved counting individual UCNPs.
• Analog detection involved integrating pixel intensity for luminescence quantification.

Main Results:

• Analog detection showed significantly greater signal variability compared to digital detection.
• Digital detection demonstrated superior repeatability in quantifying UCNP signals.
• Plasmon-enhanced UCNP signals exhibited non-uniformity, impacting analog readout accuracy.

Conclusions:

• Digital detection is more suitable for quantitative biosensing with plasmon-enhanced UCNPs due to its higher repeatability.
• Overcoming signal variability is crucial for reliable quantitative analysis in plasmon-enhanced UCNP biosensing.
• This study highlights the importance of readout strategy in optimizing UCNP-based biosensor performance.