Crystallography of ordered colloids using optical microscopy. 2. Divergent-beam technique

• Published in: Applied optics (2004) 2008-04, Vol.47 (11), p.1867-1879
• Main Authors: Rogers, Richard B, Lagerlöf, K Peter D
• Format: Article
• Language: English
• Subjects: Algorithms; Colloids - chemistry; Crystallography - methods; Image Interpretation, Computer-Assisted - methods; Microscopy - methods; Molecular Conformation; Optics and Photonics; Refractometry - methods
• ISSN: 1559-128X
• DOI: 10.1364/AO.47.001867

A technique has been developed to extract quantitative crystallographic data from randomly oriented colloidal crystals using a divergent-beam approach. This technique was tested on a series of diverse experimental images of colloidal crystals formed from monodisperse suspensions of sterically stabilized poly-(methyl methacrylate) spheres suspended in organic index-matching solvents. Complete sets of reciprocal lattice basis vectors were extracted in all but one case. When data extraction was successful, results appeared to be accurate to about 1% for lattice parameters and to within approximately 2 degrees for orientation. This approach is easier to implement than a previously developed parallel-beam approach with the drawback that the divergent-beam approach is not as robust in certain situations with random hexagonal close-packed crystals. The two techniques are therefore complimentary to each other, and between them it should be possible to extract quantitative crystallographic data with a conventional optical microscope from any closely index-matched colloidal crystal whose lattice parameters are compatible with visible wavelengths.