MEASURING THE NUMBER CONCENTRATION OF NANOPARTICLES IN LIQUID MEDIA USING THE ULTRAMICROSCOPY METHOD ON THE RUSSIAN NP COUNTER DEVICE
Vladimir Nikolaevich Kuryakov, NP VISION LLC
Project website: www.npcounter.ru
Relevance of measuring nanoparticle concentration
Nanoparticles and various submicron and nano-objects are increasingly used in the production of various products each year to improve the product’s commercial properties or to impart new useful commercial properties to the product.
Concentration is an important parameter when working with liquid media containing nanoparticles: control of nanoparticle synthesis, the issue of water contamination by mechanical impurities
Examples of objects containing nanoparticles: colloidal silver (dietary supplements, antiseptic treatment), gold nanoparticles, catalysts, magnetic nanoparticles (DNA and RNA isolation), polishing mixtures, paraffin emulsions (material hydrophobization), drug delivery, carbon nanotubes, nanodiamonds.
Existing methods for measuring nanoparticle concentration
Direct methods: Nanoparticle Tracking Analysis (NTA), condensation particle counters (for aerosols), electron and atomic force microscopy, “Coulter Principle”
Indirect methods: absorption spectrophotometry, turbidimetry and nephelometry, gravimetric methods.
Technical foundations of the ultramicroscopy method
Richard Adolf Zsigmondy, Nobel Prize laureate in Chemistry in 1925 “for his demonstration of the heterogeneous nature of colloid solutions and for the methods he used, which have since become fundamental in modern colloid chemistry.”
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1 – light source (electric arc); 2 – lenses; 3 – slit diaphragm; 4 – cuvette with the solution under study
Brownian motion of SiO2 nanoparticles (R=55 nm) in water
In the ultramicroscope, not the nanoparticles themselves are observed, but the diffraction patterns of light on them, which allows tracking the movement (Brownian motion) of nanoparticles in the field of view. There is no limitation associated with the diffraction limit in this method.
NP Counter Device
Calibration
Microphotographs of an object micrometer obtained at various resolutions of the digital camera. Scale division 0.01 mm.
Example of observing various nanoparticles SiO2 nanoparticles 100 nm Latex nanoparticles 160 nm Magnetic nanoparticles Fe2O3 300-600 nm
QD
Example of observing various nanoparticles
Gold nanoparticles (top) R=25 nm and silver (bottom) R=30 nm.
Water purification systems
On the left is an example of observing a sample of medical water for injections (Solopharm LLC, Russia), on the right is water after purification with the Aqualab system. A similar picture for a sample after the Adrona purification system. The water has a resistance of 18.2 MΩ.
Estimated concentration of mechanical impurities 3*107 pcs/ml.
Example of software operation
From the video analysis, the NPVision software allows determining the number concentration of nanoparticles
Method evaluation
[Graph description: X-axis: Set dilution factor, Y-axis: Measured dilution factor. The graph shows a linear relationship between set and measured dilution factors.]
Measured dilution factor and dilution factor of prepared samples
Latex nanoparticles 270 nm, controlled dilution with water by 2, 10, 20, 30, 40, 50, 80, 100, and 150 times.
Technical characteristics
Minimum particle size that this method can work with: • Metallic ~10 nm • Polystyrene particles ~40 nm • Biological objects ~70 nm
Working concentrations: 106 – 109 pcs/ml (higher concentrations with controlled dilution)
Field of view size about 160×130 μm Laser 654 nm, 40 mW
Camera 5 Mpx