1. 0-D, 1-D, 2-D Structures (not a chapter in our book!)
NANO 101
Introduction to Nanotechnology

2. Overview Bottom Up Top Down Chemistry! Milling Lithography
Large size distribution
No control of shape
Impurities
Crystal Growth
0-D particles
1-D particles
2-D films
Lithography

3. Top-Down Approaches Milling Lithography
Broad size distribution (tens to hundreds of nm)
Varied shape and geometry
Impurities and defects from milling
Lithography
Also includes bottom up method

4. Particle Requirements
Uniform size
Uniform morphology
Uniform chemical composition and crystal structure
Monodispersed

5. Homogeneous Nucleation/
Supersaturated solution
G = Gibbs free energy
K = Boltzmann constant
Co = equilibrium concentration
T = temperature
Ω = atomic volume
Two competing forces
Surface energy
Volume energy
N&N Fig. 3.2

6. Nucleation and Growth Rates
N&N Fig. 3.4

7. Hot Injection A way to separate nucleation and growth:
One ionic precursor is heated to ~ 300 C
Other precursor is a room temp and injected
Rapid nucleation occurs followed by temperature drop and growth phase

8. Hot Injection

9. Growth of Nanoparticles
Chem. Rev., 2014, 114 (15), pp 7610–7630

10. Making Nanoparticles Nucleation Diffusion from bulk to surface
Adsorption to surface
Irreversible incorporation onto surface
Growth
If the slowest step is diffusion  uniform particles
If the slowest step is layer by layer growth  non-uniform particles

11. Favoring Diffusion-limited Growth
Low concentrations
Large diffusion distance
High solution viscosity
Introduce diffusion barrier
Change rate of chemical reactions
Reactants used
Catalysts

12. Other Strategies:
Heat up method – in situ formation of reactive precursors
Slow addition of precursors – for RT growth

13. 0-D Nanostructures: Surface Area and Energy
Surface energy increases
with surface area
Large surface energy = instability
Driven to grow to reduce surface energy
C. Nutzenadel et al., Eur. Phys. J. D. 8, 245 (2000).

14. Electrostatic Stabilization
Establish Surface Charge Density
Adsorption of ions/charged species - +

15. Steric Stabilization “Capping” Anchored Adsorbed Irreversible binding
Random, weak

16. What is on the surface? Current area of research:
Probing the surface of platinum nanoparticles with 13CO by solid-state NMR and IR spectroscopies
Nanoscale, 2014,6,

17. Example: Colloidal Gold
Comprehensive study on synthesis and properties of colloidal gold published by Faraday (1857)
Classic method
Precursor: dilute chlorauric acid (HAuCl4)
Reducing agent: sodium citrate (NaC6H5O7)
Reaction temperature: 100 °C
Product: stable, uniform, ~20 nm particles

18. Colloidal Gold Particle Size
N&N Fig. 3.9

19. Colloidal Gold Particle Size
N&N Fig. 3.9

20. Synthesis of Metallic Nanoparticles
Reduction of metal complexes in dilute solutions
Precursors
Elemental metals, inorganic salts, metal complexes
Reduction agents
Stabilizers
PVA
Sodium polyacrylate

21. Other Methods
Brust Synthesis
Reverse Micelle

22. Influence of “Capping”
Addition of polymer stabilizer
Used on surface to prevent agglomeration
Affects growth by limiting growth site
May interact with solute, catalyst, solvent
Can affect morphology
N&N Fig. 3.13

23. Growth of Pt Nanoparticles
Found that ligands can terminate growth instead of change growth rate.

24. Influence of Temperature
N&N Fig. 3.14

25. Influence of Concentration
J. Phys. Chem. B, Vol. 108, No. 40, 2004

26. Influence of Time Rhodium nanocrystals
J. Phys. Chem. C, Vol. 111, No. 16, 2007

27. Influence of pH Initial pH of reaction can affect size
SnO2 J. Phys. Chem. B, Vol. 108, No. 40, 2004

28. Formation of Nanoparticles in Solution
Advantages:
Stabilization from agglomeration
Extraction of nanoparticles from solvent
Surface modification and application
Mass production

29. MBE Quantum Dots Self-assemble due to lattice mismatch
Self-assemble due to lattice mismatch

30. How are these 0D?
GaAs
GaAs
In As E

31. Formation of Nanoparticles on Substrates
Advantages:
No ligands needed
Very stable
Ready for electronic application
Access different materials easily