Nanosurfaces & Characterisation Flashcards
Name 4 key factors that make nano surfaces and internal interfaces important
1) Surface/Internal Energy
2) SA:V Ratios
3) Self-Assembly (Static Structure)
4) Self-Organisation (Dynamic Structure)
Explain the relevance of surface area to volume ratios
SA:V varies with r, therefore highly impacted by the nanoscale
More contact with surfaces and interfaces when size decreases
Explain the concept of surface energy
Surface energy is the energy required to break up the original crystal structure when forming new surfaces
What is internal interfacial energy a function of?
NP curvature
What is the SA:V ratio a function of?
Radius (SA:V varies with 1/r)
What techniques could be used to quantify size and morphology of nanoparticles?
Microscopy (Mainly electron)
SEM/TEM
Explain the concept of SEM Imagery
Sample irradiated with e-
Results in the reflection of electrons back to a detector
1) SE from surface 2) BSE from deeper down
What causes SEM contrast in BSE mode?
Atomic Number (Ar)
What causes TEM contrast and why?
Density
TEM involves the transmission of electrons through a sample
How is structure characterised in NPs?
Diffraction
X-Ray (XRD) or Electron
How can XRD be used to quantify the structure of NPs?
An XRD graph is produced with peaks corresponding as such:
IDENTITY = Peak Location
CRYSTAL SIZE Peak Width
Name 3 factors that can influence the peak broadening in XRD
1) Instrumental Broadening
2) Crystallite Size Broadening
3) Lattice Strain Broadening
Name 3 spectroscopic techniques for characterising chemical composition
1) XPS
2) UV-Vis
3) Photon Correlation Spectroscopy
Explain how XPS is used to quantify chemical composition
Irradiation of sample with x-rays releases photoelectrons
Production of peak-wise graph (Counts vs Energy)
IDENTITY = Peak Location
HEIGHT = No. of surface atoms
Ion bombardment allows for deeper analysis
