Absolute Counting Method with Multiplexing Capability for Estimating the Number Concentration of Nanoparticles Using...

Area of Science:

• Nanotechnology
• Analytical Chemistry
• Materials Science

Background:

• Accurate nanoparticle number concentration is crucial for characterizing dispersions.
• Estimating concentration for small nanoparticles (around 30 nm) presents significant challenges.
• Existing methods may lack the precision or applicability for diverse nanoparticle types.

Purpose of the Study:

• To develop an absolute and broadly applicable method for quantifying nanoparticle number concentration in aqueous dispersions.
• To enable precise analysis of small nanoparticles and complex nanomaterials.
• To establish a reliable technique for nanoparticle characterization.

Main Methods:

• Innovative immobilization of nanomaterials within anisotropically collapsed agarose gel.
• Utilizing optical microscopy (photon-upconversion, fluorescence, bright-field, dark-field) for nanoparticle counting.
• Coupling counted nanoparticles with a precisely defined sampled volume (517 pL) to determine number concentration.

Main Results:

• Demonstrated applicability across various nanoparticles: photon-upconversion, fluorescent, quantum dots, and silica particles.
• Achieved a limit of detection of 2.0 × 10^6 mL^-1 and a working range of 4.4 × 10^7 to 2.2 × 10^10 mL^-1.
• Successfully quantified nanoparticle clusters and performed multiplexed detection of two nanoparticle types.

Conclusions:

• The developed method provides accurate and sensitive quantification of nanoparticle number concentration.
• The technique is versatile, applicable to diverse nanomaterials and microscopy techniques.
• This approach overcomes limitations in analyzing small nanoparticles and offers potential for advanced nanomaterial characterization.