Determination of size and concentration of gold and silica nanoparticles from absorption and turbidity spectra. Nikolai Khlebtsov

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1 Determination of size and concentration of gold and silica nanoparticles from absorption and turbidity spectra Nikolai Khlebtsov Institute of Biochemistry and Physiology of Plants and Microorganisms (IBPPM), Russian Academy of Sciences Saratov State University, Saratov, Russia

2 IBPPM gallery of plasmonic nanoparticles, hybrid multifunctional nanostructures and atomic clusters

3 Paracelsius ( ) M. Faraday ( ) R. Zsigmondy ( NP 1925) Lord Rayleigh ( NP 1904) T. Svedberg ( NP 1926) G. Mie ( )

4 Gold nanospheres: Founding Fathers and basic properties Abs Wavelength M. Faraday G. Mie R. Zsigmondy 20 nm 50 nm

5 The average Au particle size is determined by the spectral position of plasmonic peak. The particle concentration can be determined from the absorption in the short wavelength part of spectrum (e.g., at nm) independently on the particle size.

6 Anal. Chem These plots represent schematic fits of experimental data

7 In Situ Determination of Colloidal Gold Concentrations with UV Vis Spectroscopy: Limitations and Perspectives Thomas Hendel, et al. Anal. Chem. 2014

8 max [nm] 580 Sp Sp Sp2-1 Sp1-0 Sp Equivolume diameter [nm] Mie theory vs experiment

9 The calculated Mie data are affected by: The input optical constants, that can be size-dependent! The particle-size distribution The particle shape is not regular or spherical 2.0 Re(n) a 8 Im(n) b Schulz 2 Irani 3 Hageman 4 Canifeld 5 Otter 6 John.-Chr. 7 Weaver nm Wavelength [nm] Wavelength [nm]

10 X, X 23 d= [ X 17 1]/ 0.06, X 23 X 500 max Eq.(15) fit:

11 Deviations of the extinction peak positions of Au nanorods from Mie theory as a function of the particle aspect ratio. The inset shows the initial part of the curves together with the experimental points 120 Mie max max max [nm] max e 20 b d ev =60 50 (b) a Aspect ratio e=a/b

12 Calculated ratios of the extinction ratio of Au nanorods depending on their equivolume diameter and aspect ratio 1, 1.2, and 1.4. The inset shows linear fits for the logarithmic abscissa. A max /A e=a/b b a Equivolume diameter [nm]

13 Effects of polydispersity on the extinction position and peak value. Experimental points for citrate Au spherical particles were taken from Khlebtsov(1996), Haiss (2007), and Njoki (2007). max [nm] (a) A max (b) 580 W i 1 =0.5 =0 1.6 = d/d av A max /A 450 = = =0.5 d av Equivolume diameter [nm] Equivolume diameter [nm]

14 Main conclusions : 1. Extinction spectra can be used for a simple and cheap in situ estimation of Au particle size and concentration. 2. Expected errors can be about 15-20%, except for very fine particles with diameters less than 3-5 nm where the bulk optical constants of Au become quite questionable. 3. Most critical factors affecting the method accuracy are the particle nonspherical shape, the size polydispersity, and uncertain optical constants of ligand-stabilized particles. TOC graph created by Thomas Hendel et al, 2014.

15 l A/ l NCsca ( x, m) N ( d / 2) Qsca ( x, m) Three unknown parameters: N, d, m x= d/ is the diffraction parameter

16 Large-scale high-quality 2D silica crystals: Formation and decoration with gold nanorods and nanospheres for SERS analysis V. Khanadeev, B. Khlebtsov, S. Klimova et al., Nanotechnology, Enhancement Factor = 5000=10*Enh. Factor of Au Nanorods

17 Solution STER 1 Determination of the particle refractive index by using ethanol/dmso immersion media <n> = (a) 1 (b) Extinction ratio, A(n m )/A(n m0 ) n= d=90nm =100 n m0 =1.364 =400, 500nm Extinction ratio, A(n m )/A(n m0 ) n= d=215nm =100 n m0 =1.364 =400, 500nm Refractive index n m Refractive index n m

18 Solution STER 1 Determination of the particle refractive index by using ethanol/dmso immersion media <n> =

19 Solution STER 2 Measuring the absorption spectra at several wavelength to redefine the solution w log / log Wavelength exponent is a function of the particle size

20 Example1: Mie calibration plots for a polydisperse silica spheres Average diameter d av [ m] E <C sca > Q sca 1E+006 Q sca, w 2 0 w 1E+004 1E+002 1E+000 <C sca > [nm 2 ] Size parameter, x= d av n m / 1E-002

21 Final STER 3 Determination of the particle size and concentration directly from extinction spectrum

22 Example 2: Determination the silica particle size and concentration by different methods (TEM, DLS, AFM, STT)

23 Example 3: Test of the method for 5 polystyrene latexes ( nm)

24 Main conclusions : 1. Extinction spectra can be used for a simple and cheap in situ estimation of Silica particle size ( nm) and concentration. 2. We propose an optical method and provide experimental data on a direct determination of the refractive index of silica particles n=1.475± Finally, we exemplify our method by determining the particle size and concentration for 10 samples to show good agreement with TEM, AFM, and dynamic light scattering data. 4. Most critical factor affecting the method accuracy is the accuracy in determination of the wavelength exponent. Typically, variations in w are about 0.01 thus leading to 10-15% errors in the average particle size (compared to TEM).

25 Thank you for your attention and patience!

26 2016

27 HRTEM images of 15CIT-NMs with hollow nm gaps

28 Distribution of the internal and external field intensities in equatorial plane (θ=0) calculated for an NM with radii 7.5, 8.5, and 25 nm at 785 nm

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30 2014

31 Photos, TEM-images, and spectra of samples d ACS NANO 2011

32 Representative photos of tumors for five different rat groups three days after different treatments

33 Dark-Field Microscopy Movie Starring: Peritoneal Rat Cells and Gold Nanorods