MALDI-TOF Mass Spectrometry, Crystal Morphology, Dendritic Crystal Growth

My students and I use MALDI-TOF mass spectrometry to investigate a variety of problems. These include the identification of dyes and pigments from very small samples, the degradation of materials of potential utility for organic electronics, and the identification of steroids.

MALDI-TOF mass spectrometry offers several special advantages, including high sensitivity for the analyte, tolerance of foreign substances, ease of sample preparation, and rapid spectrum acquisition.


"Metal Contamination in MALDI Samples Prepared with the Vortex Solvent-free Method”
Rapid Communications in Mass Spectrometry (2009) 23, 462-464.

"MALDI-TOF Mass Spectrometric Identification of Dyes and Pigments"
Journal of the American Society for Mass Spectrometry
(2007) 18, 2001-2006.

“Identification of a Quenching Species in Ruthenium Tris-Bipyridine Electroluminescent Devices”
Journal of the American Chemical Society (2006) 128, 7761-7764.

“Interpretation of MALDI-TOF Spectra of Transition Metal Complexes in the Presence of Matrix Adducts”
Rapid Communications in Mass Spectrometry (2005) 19, 2473-2479.

“Dye Analysis Using 9-aminoacridine for Negative Ion MALDI-TOF Mass Spectrometry”
Sanibel Conference on Mass Spectrometry in Forensic Science and Counterterrorism, January 2005.

“Small Molecule MALDI-TOF Mass Spectrometry Using a Polymer Matrix”
Rapid Communications in Mass Spectrometry (2004) 18, 1455-1458.

We have also studied the relationship between crystal structure and crystal morphology. When crystals are grown rapidly (i.e., far from equilibrium), they often take on the tree-like shape called "dendritic." The dendritic shape is quite different from the normal, simple polyhedral shapes assumed by crystals grown near equilibrium. This is spatial self-organization. The ammonium chloride dendrite shown on my top page is an example of this type of crystal growth. We have been accumulating evidence that suggests that increasing the rate of crystal growth produces specific distortions in the polyhedral morphology that interact with the concentration gradient around the crystal to produce a positive feedback leading to the extreme dendritic morphology. Positive feedback is often, if not always, involved in the instabilities leading to self-organization. We are able to visualize these concentration gradients using interference microscopy.

Acta Crystallographica, (1999), B55, 882-885.
Acta Crystallographica, (1998), B54, 384-390.
Acta Crystallographica, (1994), B50, 518-524.
Acta Crystallographica, (1992), A48, 457-461.