1. Characterization of Nanomaterials 1- Scanning Electron Microscopy (SEM) It is one of the most widely used techniques in the characterization of the morphology, shape and size of the nanomaterial. The instruments can operate at magnifications from ~10 to over 300,000 times. Dr. Ammar Elsanousi

2. Layout of SEM instrumentation Dr. Ammar Elsanousi

5. SEM image of : TiO 2 nanoparticles Dr. Ammar Elsanousi

6. 2- Transmission Electron Microscopy (TEM) It is a key tool for imaging the internal structure of ultra thin specimens and hollow structured nanomaterials such as hollow nano-spheres and nanotubes. The greatest advantages that TEM offers are the high magnification ranging (from 50 to l0 6 ) and its ability to provide both image and diffraction information from a single sample. Dr. Ammar Elsanousi

7. Layout of TEM instrumentation Dr. Ammar Elsanousi

10. In TEM one can switch between imaging the sample and viewing its diffraction pattern (EDX) by changing the strength of the intermediate lens. TEM image of TiO 2 nanotubes Energy Dispersive X-ray Spectrum (EDX) Dr. Ammar Elsanousi

11. 3- X-Ray Diffraction (XRD) X-ray diffraction (XRD) is a very important experimental technique that has long been used to address all issues related to the crystal structure of solids, including lattice constants and geometry, identification of unknown materials, orientation of single crystals, preferred orientation of polycrystals, defects, stresses, etc. Dr. Ammar Elsanousi

12. In XRD, a collimated beam of X-rays is incident on a specimen and is diffracted by the crystalline phases in the specimen according to Bragg's law:  n = 2d sin  Dr. Ammar Elsanousi

15. Particle size calculation from XRD If there is no inhomogeneous strain, the crystallite size, D, can be estimated from the peak width with the Scherrer's formula: where is the X-ray wavelength,  is the full width of height maximum (FWHM) of a diffraction peak,  is the diffraction angle, and K is the Scherrer’s constant of the order of unity for usual crystal. Dr. Ammar Elsanousi

16. Example: In the X-ray diffraction pattern of ZnO nanoparticles sample the full width of height maximum of the strongest peak was found to be 0.005 at 2θ angle of 28. If the wavelength of the X-ray is 1.54178 Å, calculate the mean particle size of the sample. (Scherrer’s constant K= 0.94) Dr. Ammar Elsanousi

17. -UV-Vis Spectroscopy. The UV-vis region of energy for the electromagnetic spectrum covers 1.5 - 6.2 eV which relates to a wavelength range of 800 - 200 nm. 4- Optical Spectroscopy Optical spectroscopy uses the interaction of light with matter as a function of wavelength or energy in order to obtain information about the material. For example, absorption or emission (photoluminescence or PL). Dr. Ammar Elsanousi

18. The Beer-Lambert Law is the principle behind absorbance spectroscopy. Where: A is absorbance, a = the molar absorptivity of the compound or molecule in solution, b = path length, and c = concentration of the solution. Dr. Ammar Elsanousi

19. Photoluminescence spectroscopy is a contactless method of probing the electronic structure of materials. Light is directed onto a sample, where it is absorbed and thereby raises an electron from the valence band up to the conduction band across the energy gap. The electron generally has excess energy which it loses before coming to rest at the lowest energy in the conduction band. At this point the electron eventually falls back down to the valence band. As it falls down, the energy it loses is converted back into a luminescent photon which is emitted from the material. -Photoluminescence Spectroscopy (PL) Dr. Ammar Elsanousi