What does it take to accurately measure concentration of nanoparticles in colloids

Transcription

1 What does it take to accurately measure concentration of nanoparticles in colloids Jan Kuba Tatarkiewicz, PhD VP Engineering MANTA Instruments, Inc.

2 Counts Volume

3 Beginnings NASA sponsored ICESCAPE Project two cruises on USCGC Healy BEAUFORT SEA SIBERIA CHUKCHI SEA ALASKA -50

4 Results Density of PSD [ cm -3 µm -1 ] NanoSight Coulter 2 m, station #15 27 m, station # m, station #15 Calibration function 3 power function-like PSD of mixture nearly flat PSD of mixture fitted calibration function Particle diameter d [ µm ] J. J. Tatarkiewicz, R. A. Reynolds, and D. Stramski Counting and sizing of colloidal particles in the Arctic Ocean 2012 Ocean Sci Meeting A Particle diameter d d [ µm [ µm ] ] This is a very strange function...

5 2 nd generation NTA Multispectral Advanced Nanoparticle Tracking Analysis NSF grant for MRI # , MANTA Instruments, Inc. founded in 2014 US patents granted up to now: , , ,

6 Visualization investigated volume light sheet thickness light sheet scattered light light source microscope + camera

7 MANTA 1.0E E+03 Scattering cross-section [nm²] 1.0E E E E E E E E ,000 Diameter [nm] Mie calculations for 445 nm, 520 nm and 635 nm polarized laser beams scattering on PSL in water (n=1.337), objective NA=0.28, integration

8 Sizes Mean Squared Distance MSD (2D, N frames track, n frameslag*): MSD(n) = 1 N n N n (x i+n x i ) 2 + (y i+n y i ) 2 i=1 Diffusion coefficient D (least-squares fit of MSD as a function of n): MSD( n) = ( 4 Δt D) n Hence hydrodynamic diameter:! " = $ %& 3()* * ergodicity: assembly average time average

9 Statistics Cramér-Rao statistics decides length of each track used for optimal MSD fitting X. Michalet and A.J. Berglund Optimal diffusion coefficient estimation in SPT, Phys Rev E85, (2012) Binning diameters with different schemes (like equal or logarithmic widths) into density of particle-size distribution (PSD) with variable investigated volume (explained later) Statistical parameters of PSD (average size, standard deviation)

10 Mode? Report ABT-308_after_30min+ Measurement date: 2/16/2018 Measurement time: 10:10:12 Measurement type: NTA Operator: QT Report ABT-308_after_30min+ Measurement date: 2/16/2018 Measurement time: 10:10:12 Measurement type: NTA Operator: QT Report ABT-308_after_30min+ Measurement date: 2/16/2018 Measurement time: 10:10:12 Measurement type: NTA Operator: QT Instrument information Serial number: 024 Software version: , WeekBuild 2617 Calibration constant: [nm/pixel] Instrument information Serial number: 024 Software version: , WeekBuild 2617 Calibration constant: [nm/pixel] Instrument information Serial number: 024 Software version: , WeekBuild 2617 Calibration constant: [nm/pixel] narrow equal bins wide equal bins logarithmic bins variable bins

11 Counts 25 (or more) short videos (300 frames each) recorded* Track and count particles detected on 1 st frame of each video Mixing sample between videos to get different aliquots (magnetic stirrer) external fluidics for magnetic materials and low concentration samples do not use sample flow during recording Proper PSD binning (bin widths) for polydispersity * typically between 100 and 150 particles tracked per video

12 Thickness! = # $ %&'()* +, $ (, light sheet

13 Volume How to calibrate volume: Measure concentrations for standards of different sizes and made out of different materials (various RIs) Determine effective volumes Create look-up surface of volumes Extrapolate by using intensity of individual tracks and applying Mie scattering cross-section formula! = # $%&'()%* # %+,%-.%*! / I Intensity Volume V Lookup surface d Diameter

14 Histogram Density of PSD! " = $ 1 & " ( ), ) * +, = $! " & " = $ $ 1 ( ) "-+, "-+ ) Concentration from 50 nm to 700 nm = area of density of PSD histogram

15 Concentration Integrate density of PSD (counts/ml/nm) across sizes of interest, for example from 50 to 700 nm, to get concentration (counts/ml) Instruments are calibrated for optics scaling (nm/pix) and for laser(s) power (mw) (manufacturing variability of active elements) For unknown materials, extrapolate investigated volumes by using Mie scattering cross-sections of known test materials Use measured data with statistically significant number of counts, do not use fitted distributions (PSD is not an invariant)

16 NIST exploratory mix Density of PSD [counts/ml/nm] 1.0e+7 1.0e+6 1.0e+5 1.0e+4!~ 1 $ % Concentration [counts/ml] 1.0E E E E+07 N = 1.02E+13*d e Diameter [nm] 1.0E Diameter [nm]

17 TEM, DLS & NTA vs. MANTA TEM, DLS & cnta vs. MANTA α-lactalbumin nanoparticles made as per Arroyo-Maya et al. J Dairy Sci 95, 6204 (2012) 10 Testowanie cd. 10 α-lactalbumin nanoparticles made as per Arroyo-Maya et al. J. Dairy Sci. (2012) 95, Particle concentration N [ cm -3 nm -1 ] Density of PSD [counts/ml/nm] α-lactalbumin 10 9 nanoparticles α-lactalbumin nanoparticles TEM Zdjęcie dr. Nia Bell, UCSD Particle 0diameter 100 d [ nm 200 ] TEM MANTA NanoSight DLS TEM Particle diameter [nm] MANTA NTA 3x DLS

18 Thank you Jan Kuba Tatarkiewicz, PhD VP Engineering MANTA Instruments, Inc.