A New, Simple, Inexpensive Method for Non- Invasive Particle Size Measurements of Suspensions and Droplets D.Fairhurst Colloid Consultants Ltd., Congers, NY H.S.Dhadwal, B.Mukherjee SUNY Stony Brook, NY S.W.Race XiGo Nanotools Inc., Morganville, NJ NSTI Nanotech Anaheim, CA May,2005 ™ ™

Time-dependent Light Scattering by Any Other Name IFS - Intensity Fluctuation Spectroscopy DLS - Dynamic Light Scattering PCS - Photon Correlation Spectroscopy QELS - Quasi-elastic Light Scattering

Light Scattering History Rayleigh Scattering Theory Einstein Fluctuation Theory Debye Theory for Polymer solutions Pecora Theory for DLS Cummins verifies experimentally Pike suggests digital autocorrelator (PCS) 1990’s - Single-mode fiber optics introduced

Nanomaterials will require tools for QC & for raw material specification in manufacturing  Tools that can be used with minimal training  single key-stroke operation  Tools that are portable  to go where you go, lab-to-plant  Tools with customer replaceable parts  easily serviced, no down-time  Tools priced to fit QC applications New materials demand new solutions to old problems  Take the instrument to the application

Fiber Optics Classic DLS instrumentation use metal plate of large mass on which to configure the optics.  expensive and requires precise alignment Fiber optics arrangements are:  More compact  More robust  Less expensive Many application advantages  Remote sensing  inaccessible, hostile environments  Higher concentration systems  dilution, wash cycles and particle concentration effects eliminated

Fiber Optics Problems and difficulties with previous fiber optic designs Multimode fibers  Reduced intercept/baseline ratio  Polarization not preserved Single fiber system  Coupling Signal/concentration effects  Low  (<0.001) – local oscillator (homodyne)  High  (>0.2) – self beating

Back Scatter Light Scattering Fiber optic probe design patented  Eliminates need for directional coupler  Self beating detection of scattered light  Independent control of scattering volume and angle

Back Scatter Light Scattering Elliptical Spot shape in the center of the scattering volume: 0.48mm x 0.35mm

Brownian Motion of Particles and Fluctuation in Light Intensity Rate of intensity fluctuations varies with size of particles

Instantaneous Photon Counts

Photon Count Correlation Possible to measure the spectrum of frequencies contained in the intensity fluctuations arising from Brownian motion  very inefficient Advent of digital auto correlator makes it easy  construct correlation function  analyze correlogram  various algorithms  Cumulants, NNLS, Contin…..

Photon Count Correlation The coherence factor,  : The correlation function, g ( 2 ) (  :  s is the spatial coherence factor  t is the temporal coherence factor

Correlators are extremely complex electronic devices and add a significant cost in the manufacture of a particle sizing instrument It is possible to obtain size information directly from the photon stream, without the need for correlation  Photon counting fluctuations represented by a doubly stochastic procedure  Poisson process of the random arrival of photons  Gaussian process of the Brownian motion Photon Counting Fluctuations

Scattered intensity from particles undergoing Brownian motion has a Lorentzian power spectrum The variance of the random process associated with scattered intensity is: Brownian Motion I s is the time average intensity T s is the sample time  is the Linewidth parameter (D t q 2 )

Linewidth,  = D t  q 2 Scattering Wave Vector, q = 4  n sin(  /2) o Stokes-Einstein Equation, D t = k b T 3  d h d h is the hydrodynamic particle diameter Basic Equations

Consequence of hydrodynamic size Sample diluted in 0.01M KCl Avg. Size = 106nm Dist. Width = 24nm Sample diluted in DI water Avg. Size = 113nm Dist. Width = 27nm Polystyrene Latex Sample Nominal size 105nm Dist. Width = 24nm

Coherence Factor Measurement of coherence at several integration times leads to particle size

Computation of Particle Size The computational process can be simplified:  Measurement of coherence at only two integration times  Use of approximations in calculation of the coherence factor, 

Real Time Measurement of Particle Size Diameters from 3nm to 3000nm can be detected

1 Brookhaven BI90 37 kg + PC! VGA PCPC Malvern Mastersizer 2000 VGA PCPC 31 kg + PC! Malvern Zetasizer Nano PCPC VGA 18 kg + PC! Xigo Nanotools Acorn <1 kg, no PC required! Size Comparison and Everyone else!

The Particle Sizer Unit Size: 200 x 100 x 60 mm (LxWxH) Unit Weight: 0.5 Kg Probe dimension: 120mm long 3 mm diameter Viscosity Temperature Compensation Cable length: 0.5 meter (std) up to 100 meter Size Measurement Range: 3 to 3000 nm Specifications

The Particle Sizer Battery operated GUI for easy use USB2.0 data interface CFR21 GMP compliant UL and CE certified Flash Memory Data Storage & Transfer Features

Experimental results using the Nominal Conventional Acorn Particle Size DLS (90 0 ) (nm) (nm) (nm)

Applications using the

Particle Size as a function of Concentration for Ludox Silica

Applications using the

Microemulsion Technology  Stratification and hydrodynamic instabilities Emulsion Polymerization  Particle size growth Biochemical Manufacturing  Real-time monitoring Radioactive waste Monitoring  Remote sensing

Advantages of the in Particle Sizing Portable Fits in your hand Simple to use Can be used in minutes Wide dynamic size range Spans the range Rugged Withstands QC demands Remote measurements Versatile Absolute No calibration Precise Reproducible

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