Electron Diffraction Pattern Identification
diffraction patterns as long as
standards are
available.
To ensure accuracy of these comparisons, it is essential that
the same conditions be
used to obtain the diffraction patterns to be compared (that is, kV, camera length, and specimen height). Tis ensures accurate comparisons. Methods 1 and 2 will work
Figure 2: (A) A µD ring pattern from an evaporated gold standard. (B) A µD pattern of several gold particles prepared using toroidal DNA to control the size. (C) Superimposition of gold standard A and identified unknown B. The TEM image (insert) shows the toroidal DNA/gold formation. Note that the inner, more intense rings, when superimposed, become yellow whereas the outer, less intense rings maintain their original color.
even when only milligrams or micrograms of material is available, for example when analyzing NPs
formed in
microfluidic reactors [15]. Te methods described herein (that is, µD where the beam is used to select the area) can be used on any TEM and is especially useful on those TEMs not equipped with a SAD aperture.
Acknowledgments We thank Alexander
Figure 3: (A, red) A µD pattern from an evaporated nickel standard. (B, green) A µD pattern from an aggregate of Ni NPs. (C) Superimposition of nickel standard A and identified unknown B. The TEM image (insert) shows the Nickel NP formation upon DNA mold degradation. When there are numerous particles, the discrete diffracted beams combine to form a continuous ring as compared to Figure 4 where fewer NPs are producing the µD patterns.
Yampolsky for his help in sample preparation and Dr. H. Amalia Pasolli at Rockefeller University for allowing us to use her Tecnai TEM for this work aſter Patrick C. Nahirney leſt Rockefeller University for Victoria, BC, Canada. Tis work was supported by
NSF grants to CMD (CHE-0847997). Hunter College science infrastructure is supported by the National Science Foundation, the National Institutes of Health including the RCMI program (G12-RR-03037), and the City University of New York.
References [1] AP Alivisatos, Science 271 (1996) 933–37. [2] F Stellacci, Nature Materials 4 (2005) 113–14. [3] P Sharma et al., Chem Mater 20 (2008) 6087–94. [4] A Wieckowski et al., Catalysis and Electrocatalysis at Nanoparticle Surfaces, Marcel Dekker, New York, 2003.
Figure 4: µD pattern images displayed on a monitor corresponding to unknown NP aggregates that were identified as ZnO by Method 2 (overhead transparency method).
allowed us to check the results and make a rapid assessment and adjustment to our synthesis within the time frame of a couple of hours. Tis method is the easier of the two methods for comparison of standard selected area diffraction (SAD) patterns or large area µD patterns where ring patterns are formed.
Conclusion A full match of the superimposed standard and
experimental unknown µD patterns by both digital image overlay and overhead transparency methods allow us to obtain a swiſt and accurate determination of the nature of the material investigated without tedious indexing of individual
2011 September •
www.microscopy-today.com
[5] M Grzelczak et al., ACS Nano 4 (2010) 3591–3605. [6] Q Song, J Am Chem Soc 126 (2004) 6164–68. [7] SE Cross et al., Skin Pharmacol Physiol 20 (2007) 148–54. [8] W Beek et al., J Mater Chem 15 (2005) 2985–88. [9] J Samson et al., ACS Nano 3 (2009) 339–44.
[10] O Masala et al., Ann Rev Mater Research 34 (2004) 41–81. [11] JJ Bozzola and LD Russell, Electron Microscopy, Jones and Bartlett Publishers, Boston, 1992, 347–55.
[12] BEP Beeston, RW Horne, and R Markham, Electron Diffraction and Optical Diffraction Techniques, Elsevier Science Ltd., Amsterdam and New York, 1994.
[13] A Eades, Microscopy Today, 19(1) (2011) 72. [14] JW Steeds, in Introduction to Analytical Electron Microscopy, Plenum Press, New York, 1979, ch. 15, 390. [15] Y Song et al., Chem of Mater 18 (2006) 2817–27.
41
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84