nanoparticle optics part 1 gold and silver nanoparticles group 1 – luke, matt, and jeff
TRANSCRIPT
Nanoparticle Nanoparticle Optics Part 1Optics Part 1
Gold and Silver Gold and Silver NanoparticlesNanoparticles
Group 1 – Luke, Matt, and Group 1 – Luke, Matt, and JeffJeff
TheoryTheory The color of the sol arises from a combination of absorption and The color of the sol arises from a combination of absorption and
scattering of light and depends on particle size. More scattering of light and depends on particle size. More specifically it is due to a resonance of the free electrons in the specifically it is due to a resonance of the free electrons in the metal particle. The light’s electromagnetic field causes them to metal particle. The light’s electromagnetic field causes them to slosh back and forth (plasmon oscillations).slosh back and forth (plasmon oscillations).
At a characteristic frequency which depends of the size and the At a characteristic frequency which depends of the size and the metal, the sloshing is the most intense. This is the frequency metal, the sloshing is the most intense. This is the frequency where plasmon oscillations are excited. The plasmon resonance where plasmon oscillations are excited. The plasmon resonance is easily seen in the extinction spectrum of the sol.is easily seen in the extinction spectrum of the sol.
The particles experience the constant buffeting of Brownian The particles experience the constant buffeting of Brownian motion which also helps to keep them in suspension.motion which also helps to keep them in suspension.
ObjectiveObjective
Learn about scattering and absorption Learn about scattering and absorption in gold and silver nanoparticles.in gold and silver nanoparticles.
Visually observe how particle size Visually observe how particle size effects scattering.effects scattering.
Learn to use a Tyndall beam.Learn to use a Tyndall beam. Observe sub-diffraction limit Observe sub-diffraction limit
nanoparticles in the optical microscope.nanoparticles in the optical microscope. Become familiar with optical and Become familiar with optical and
electron microscopy.electron microscopy.
Procedure: Gold Procedure: Gold NanoparticlesNanoparticles
Bring to a boil 50 mL of 2.5Bring to a boil 50 mL of 2.5×10×10-4-4 M M chloroauric acid solutionchloroauric acid solution Add 0.16 mL of 34 mM sodium citrate solution to the boiling Add 0.16 mL of 34 mM sodium citrate solution to the boiling
solution while stirringsolution while stirring After a minute will be faint blue and then darkening over 5 min to After a minute will be faint blue and then darkening over 5 min to
a brilliant red a brilliant red Repeat procedure with 0.30 mL and 1.0 mL of sodium citrate to Repeat procedure with 0.30 mL and 1.0 mL of sodium citrate to
produce three samples of different sized gold nanoparticles.produce three samples of different sized gold nanoparticles. Fill cuvette with sample and place in spectrophotometer. Record Fill cuvette with sample and place in spectrophotometer. Record
absorbance of each sample from 200 nm to 800 nm.absorbance of each sample from 200 nm to 800 nm.
Procedure: Optical Procedure: Optical MicroscopyMicroscopy
Use micropipette to place 20 Use micropipette to place 20 L of sample on a L of sample on a microscope slide.microscope slide.
Place cover slip over sample.Place cover slip over sample. Place slide under 20X objective lens for total Place slide under 20X objective lens for total
magnification of about 200X.magnification of about 200X. Use coarse and fine focus knobs to find nanoparticles. Use coarse and fine focus knobs to find nanoparticles.
Use the plane of cover slip and slide as a reference.Use the plane of cover slip and slide as a reference. Observe stationary nanoparticles on cover slip and Observe stationary nanoparticles on cover slip and
slide. Nanoparticles in solution are randomly moving slide. Nanoparticles in solution are randomly moving because of Brownian motion.because of Brownian motion.
Procedure: Electron Procedure: Electron MicroscopyMicroscopy
Using a micropipette, Using a micropipette, put a few drops of put a few drops of sample on light side sample on light side of carbon grid.of carbon grid.
Wick away excess Wick away excess with filter paper.with filter paper.
Let sample dry for Let sample dry for several hours.several hours.
View sample in TEM View sample in TEM and take photos for and take photos for later analysis.later analysis.
Results: Visual InspectionResults: Visual Inspection Solution changed from blue to red within five minutes as Solution changed from blue to red within five minutes as
expected.expected. Sample with 0.16 mL sodium citrate turned a duller red Sample with 0.16 mL sodium citrate turned a duller red
than the other two samples.than the other two samples.
Results: Absorption Results: Absorption SpectraSpectra
Fit of Mie Plot data to Fit of Mie Plot data to Spectrophotometer data resulted Spectrophotometer data resulted in gold nanoparticle radii of 14.8 in gold nanoparticle radii of 14.8 nm, 15.6 nm, and 35 nm (diameter nm, 15.6 nm, and 35 nm (diameter of 29.6 nm, 31.2 nm, and 70 nm).of 29.6 nm, 31.2 nm, and 70 nm).
Shoulder on 0.3 mL sample is Shoulder on 0.3 mL sample is because of larger particles also in because of larger particles also in the solution.the solution.
0.16 mL sodium citrate solution
Wavelength (nm)
400 500 600 700 800
Abs
orb
an
ce
0
1
2
3
4
5
Spectrophotometer dataMie Plot data, 35 nm
0.3 mL sodium citrate solution
Wavelength (nm)
400 500 600 700 800
Abs
orba
nce
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Spectrophotometer dataMie Plot data, 15.6 nm
1 mL sodium citrate solution
Wavelength (nm)
400 500 600 700 800
Ab
sorb
ance
0.0
0.2
0.4
0.6
0.8
1.0
1.2
Spectrophotometer dataMie Plot data, 14.8 nm
Results: TEMResults: TEM
0.16 mL, 100 nm scale 0.16 mL, 100 nm scale
0.3 mL, 20 nm scale
Results: TEMResults: TEM
0.3 mL, 100 nm scale 0.3 mL, 20 nm scale 1 mL, diffraction
Analysis: TEMAnalysis: TEM Particles in each picture were measured with a ruler to get Particles in each picture were measured with a ruler to get
a size distribution.a size distribution. Data agrees well with estimations from absorption spectraData agrees well with estimations from absorption spectra
.16mL Sodium Citrate Gold Nanoparticlesmean = 54.63 nm, stdev = 24.80 nm
0
5
10
15
20
25
30
7.1 20.3 33.5 46.6 60 73 86.2 99.3 More
Nanoparticle Diameter (nm)
Fre
qu
ency
0.3 mL Sodium Citrate Gold Nanoparticlesmean = 30.1 nm, stdev = 4.3 nm
0
5
10
15
20
25
30
35
40
45
50
21.4 23.1 24.7 26.3 27.9 29.5 31.2 32.8 34.4 36.0 37.7 More
Nanoparticle Diameter (nm)
Fre
qu
en
cy
Analysis: TEM DiffractionAnalysis: TEM Diffraction Measured radii of diffraction rings to Measured radii of diffraction rings to
determine lattice constant of gold.determine lattice constant of gold.Measured Measured
Radius (cm)Radius (cm)Miller IndexMiller Index Plane Spacing Plane Spacing
(nm)(nm)Lattice Lattice
Constant (nm)Constant (nm)
QuestionsQuestions Approximate Size: r = 14.8 nm, 15.6 nm, and 35 nmApproximate Size: r = 14.8 nm, 15.6 nm, and 35 nm Atoms per nanoparticleAtoms per nanoparticle
For r = 14.8 nm:For r = 14.8 nm:
lenanopartic
Auatoms
mol
Auatoms
g
mol
cm
g
lenanopartic
cm
cmgandcmrV Au
6233
317
33173
100.810022.697.196
13.191036.1
/3.191036.13
4
For r = 15.6 nm: 9.4 * 10^6 atoms/nanoparticleFor r = 15.6 nm: 9.4 * 10^6 atoms/nanoparticle For r = 35 nm: 106 * 10^6 atoms/nanoparticleFor r = 35 nm: 106 * 10^6 atoms/nanoparticle
QuestionsQuestions Fraction of atoms on surfaceFraction of atoms on surface
For r = 14.8 nm:For r = 14.8 nm:
0035.0100.8
27500
27500101075.2
1075.24
6
215211
2112
lenanoparticinatoms
surfaceonatoms
surfaceonatomsAucm
atomscm
cmrSA
For r = 15.6 nm: 0.0033For r = 15.6 nm: 0.0033 For r = 35 nm: 0.0015For r = 35 nm: 0.0015
QuestionsQuestions
Number of nanoparticles per mLNumber of nanoparticles per mL For r = 14.8 nm:For r = 14.8 nm:
mLlesnanoparticmL
lesnanopartic
lesnanoparticAuatoms
lesnanoparticAuatoms
Auatomsmol
atomsAumol
AumolsolutionmLacidchlorauricM
/1088.150
1041.9
1041.9100.8
11053.7
1053.710022.625.1
25.150105.2
910
106
17
1717
5
For r = 15.6 nm: 1.6 * 10^9 nanoparticles/mLFor r = 15.6 nm: 1.6 * 10^9 nanoparticles/mL For r = 35 nm: 0.14 * 10^9 nanoparticles/mLFor r = 35 nm: 0.14 * 10^9 nanoparticles/mL
QuestionsQuestions
Nanoparticle surface area per mLNanoparticle surface area per mL For r = 14.8 nm:For r = 14.8 nm:
mL
cm
lenanopartic
cm
mL
lesnanopartic 22119 052.01075.21088.1
For r = 15.6 nm: 0.049 cm^2/mLFor r = 15.6 nm: 0.049 cm^2/mL For r = 35 nm: 0.022 cm^2/mLFor r = 35 nm: 0.022 cm^2/mL