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Spectroscopy XRD

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Lesson 3 of 4 in the series of spectroscopic methods in Inorganic Chemistry

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Spectroscopy XRD

  1. 1. Spectroscopy XRD (X-Ray Diffraction on powders) Dr. Chris UP, Feb. 2016
  2. 2. Energy regions of electromagnetic waves
  3. 3. Different principles (1) Energy absorption E1 and E2 are different states of a molecule:  Vibrational states -> IR spectroscopy  Nuclear spin states -> NMR spectroscopy  electronic states -> UV/VIS spectroscopy
  4. 4. (2) Energy emission Raman (infrared) Fluorescence (uv)
  5. 5. (3) XRD “spectroscopy” Different principle: reflection of X-Rays on a sample
  6. 6. Generation of X-Rays The target metal defines the energy of the x-rays
  7. 7. Excitation of INNER electrons, falling back emits X-Rays Typical metals are Mo (λ = 0.07 nm) and Cu (λ = 0.154 nm)
  8. 8. XRD Principle Different planes in a crystal give different signals = positive interference of waves
  9. 9. Why 2 ϴ ? The Bragg diffraction condition contains only one factor of θ: 2dsinθ=nλ It should be noted that θ refers to the incidence angle of the x-ray beam, and the beam is actually deflected by an angle of 2θ, as illustrated in the image below:
  10. 10. Bragg’s Law
  11. 11. PLANES IN CRYSTALS MILLER INDICES
  12. 12. Crystal lattices – 3 cubic structures NaCl type
  13. 13. Movie clip: youtube.com/watch?v=pMTA_wiY784
  14. 14. Indices h k l http://slideplayer.org/slide/792387/#
  15. 15. Identify crystal layers Miller indices h k l http://www.iue.tuwien.ac.at/phd/dhar/node17.html
  16. 16. Practice Miller layers ½  2
  17. 17. Negative indices
  18. 18. Examples
  19. 19. Miller Indices Example http://www.wolframalpha.com/widget/widgetPopup.jsp?p =v&id=cc011df99e5873930ccb659743a221b&title=Calculat e%20Miller%20Indices%20for%20Planes&theme=purple&i 0=1&i1=2&i2=0&podSelect=&showAssumptions=1&show Warnings=1
  20. 20. Cubic structure – interplanar distances
  21. 21. Calculate plane distances
  22. 22. Examples
  23. 23. Examples http://www.slideshare.net/meonly21Icandependonh imallmylifeAA/xrd-lecture-1
  24. 24. What is the unit cell dimension a of NaCl ? Use plane 111 with 2x theta = 27 deg and λ = 1.54 nm (Cu-Kα)
  25. 25. Which plane will give a signal at 2x theta = 46 deg when the cubic constant a = 0.5 nm and λ = 1.54 nm ?
  26. 26. X-rays with wavelength 1.54 Å are “reflected” from the (1 1 0) planes of a cubic crystal with unit cell a = 6 Å. Calculate the Bragg angle, ϴ, for orders of reflection, n = 1-5.
  27. 27. Use Braggs Law to calculate possible values for ϴ : Solution:
  28. 28. Indexing Example
  29. 29. constant Find out which hkl combinations using in this formula will give a constant value.
  30. 30. ESTIMATED PARTICLE SIZES
  31. 31. http://mahendrakoppolu.blogspot.com/2013/07 /online-crystallite-size-calculator.html
  32. 32. AG NANOPARTICLES
  33. 33. From jcpds database http://comptech.compres.us/tools/jcpds/ In Angstrom = 10 x nm VERSION: 4 COMMENT: Silver (04-0783, shock wave) K0: 120.800 K0P: 4.84000 SYMMETRY: CUBIC A: 4.08620 ALPHAT: 0.000000 DIHKL: 2.3590 100. 1.00 1.00 1.00 DIHKL: 2.0440 52. 2.00 0.00 0.00 DIHKL: 1.4450 32. 2.00 2.00 0.00 DIHKL: 1.2310 36. 3.00 1.00 1.00 DIHKL: 1.1760 12. 2.00 2.00 2.00 DIHKL: 1.0215 6. 4.00 0.00 0.00 DIHKL: 0.9375 23. 3.00 3.00 1.00 DIHKL: 0.9137 22. 4.00 2.00 0.00 DIHKL: 0.8341 23. 4.00 2.00 2.00
  34. 34. Ag Nanoparticles XRD http://www.azonano.com/article.aspx?ArticleID=2318#5
  35. 35. Particle size estimation Debye-Scherrer Formula: λ = 0.154 nm , W = width at half maximum = 0.011 rad, Theta = 45 deg
  36. 36. Plane distance http://pubs.rsc.org/en/content/articlehtml/2013/ce/c3ce40497h
  37. 37. a = b = c = 0.4081 nm  Distance between 111 planes  between 100 planes
  38. 38. GRAPHITE AND GRAPHENE OXIDE (GO)
  39. 39. JCPDS DatabaseVERSION: 4 COMMENT: Graphite K0: 100.000 K0P: 4.00000 SYMMETRY: HEXAGONAL A: 2.456 C: 6.696 VOLUME: 34.9786 ALPHAT: 00.00E0 DIHKL: 3.3480 100. 0 0 2 DIHKL: 2.1270 3. 1 0 0 DIHKL: 2.0271 17. 1 0 1 DIHKL: 1.7953 3. 1 0 2 DIHKL: 1.6740 7. 0 0 4 DIHKL: 1.5398 5. 1 0 3 DIHKL: 1.2280 2. 1 1 0 DIHKL: 1.1529 3. 1 1 2 DIHKL: 1.1333 2. 1 0 5 DIHKL: 1.1160 2. 0 0 6 It needs 4 indices to describe the planes in hexagonal structure
  40. 40. Indices for HCP structures http://www.materials.ac.uk/elearning/matter /crystallography/indexingdirectionsandplanes /indexing-of-hexagonal-systems.html
  41. 41. https://www.youtube.com/watch?v=vK913oWl_XI
  42. 42. Graphite and Graphene Oxide http://www.rsc.org/suppdata/cc/c 0/c0cc01259a/c0cc01259a.pdf
  43. 43. Graphite structure
  44. 44. http://bgcryst.com/symp14/papers/291_Shalaby_ BCC_47-1_2015.pdf
  45. 45. Reduced GO: 2θ = 26.29 degree With λ = 0.154 nm the distance between the planes: The close d-spacing of RGO to pristine graphite and disappearance of peak at 2θ = 12.43 degree indicate that the oxygen containing group of graphite oxide have been efficiently removed
  46. 46. From: Nanomaterials 2015, 5, 826-834 Graphene Oxide Synthesis from Agro Waste The peak at 2θ = 11.6° indicates an interlayer distance of 0.79 nm  fully oxidized graphite sheets
  47. 47. FT-IR spectrum of GO
  48. 48. In the IR spectrum typical peaks of functional groups can be identified: Around 3500 cm-1: O-H stretching 1700 cm-1: typical for C=O stretching 1600 cm-1: C-C vibrations of graphite 1210 cm-1: C-OH stretching
  49. 49. From: Chem. Commun., 2011,47, 12370-12372 One-pot reduction of graphene oxide at subzero temperatures
  50. 50. From: J. Chil. Chem. Soc. vol.58 no.4 Concepción dic. 2013 http://dx.doi.org/10.4067/S0717-97072013000400067 GREEN SYNTHESIS AND CHARACTERIZATION OF GRAPHITE OXIDE BY ORTHOGONAL EXPERIMENT Different oxidation parameters for graphite
  51. 51. From: SENSORS AND ACTUATORS B CHEMICAL 199:190–200 · AUGUST 2014
  52. 52. ZINC OXIDE NANOPARTICLES
  53. 53. Hexagonal Closest Packing
  54. 54. Zinc oxide XRD – Wurzite Structure http://www.hindawi.com/journals/isrn/2012/372505/
  55. 55. Estimate particle sizes
  56. 56. Nanoscience and Nanotechnology 2015, 5(1): 1-6 Synthesis of Zinc Oxide Nanoparticles via Sol – Gel Route and Their Characterization
  57. 57. Hope this was helpful ! Please follow Ajarn Chris on Facebook

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