Physicochemical Characterization
Nanoparticle Tracking Analysis (NTA)
Particle-by-particle size distribution and concentration in liquid suspension.
Purpose
To visualise and quantify nanoparticle size distribution and concentration in liquid suspension on a particle-by-particle basis. Especially useful for polydisperse or low-concentration samples.
Principle
NTA uses laser illumination and a microscope with a high-sensitivity camera to track the Brownian motion of individual nanoparticles in real time. Software calculates size (via the Stokes-Einstein equation) and counts particles per mL.
Standard protocol
- 1
Instrument setup
- Turn on the laser and camera.
- Allow a 10–15 min warm-up.
- Clean the flow cell or chamber with filtered water.
- 2
Sample dilution
- Dilute the sample to achieve 10⁷–10⁹ particles/mL (ideal for tracking).
- Over-concentration causes overlapping tracks; under-concentration yields poor statistics.
- 3
Loading sample
- Fill the chamber via syringe or pipette (~1 mL).
- Avoid bubbles.
- 4
Acquisition settings
- Camera level: 13–16 (optimise for good particle visibility without saturation).
- Laser: 405 nm or 532 nm (depending on sample scattering).
- Capture time: 60 seconds (3 videos of 20–30 s recommended).
- Temperature: 25 °C.
- 5
Run measurement
- Start recording.
- Software tracks individual particles and generates the size distribution (nm), particle concentration (particles/mL) and a video of particle movement.
- 6
Data analysis
- Review videos to ensure proper focus and tracking.
- Adjust blur, detection threshold and minimum track length if needed.
- Report mean size, mode and particle concentration.
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