Emeritus Professor of Chemistry
Ph.D. Cornell University, 1968
Current research in the Macklin laboratory involves spectrometric studies to obtain structural information about intermolecularly associated molecules and ions in solution and adsorbed, self-assembled interfacial aggregates. Such structural indications lead to improved understanding of structure-function relationships for numerous important chemical processes. Micro-Raman spectrometry is the primary tool used for structural characterization of dissolved and adsorbed substances. The micro-Raman measurements are generally complemented or corroborated by ultra-violet visible (uv-vis), Fourier transform infrared (FTIR) and/or nuclear magnetic resonance (NMR) spectrometric measurements.
In one such effort, uv-vis and Raman spectrometry are used to study aggregation of various dyes in solution. The dyes of interest are the photo-active cyanine dyes and others that are useful in photographic, photovoltaic and other photochemical and electrical applications. The measurements are carried out as a function of dye concentration, the concentration of an added electrolyte and temperature in order to gain information about thermodynamics and structure of the associated species. The resulting interpretations will be further established by FTIR and NMR measurements.
Another example of ongoing research activity involves the development of ultra-sensitive chemical sensing capabilities based on micro-Raman spectroelectrochemical indications. The approach chosen in this case is to begin with chromophores that adsorb strongly from solution onto a silver surface and by resonance and surface enhancement show extremely high Raman intensities. We have obtained Raman measurements of attogram quantities of some chromophoric substances adsorbed onto a silver surface with a diameter of about 50 microns by this method. These molecules are then chemically altered so as to interact in an expected manner with specific target molecules. Changes in the enhanced Raman spectrum of the surface adsorbed substance due to the presence of a target molecule can be taken as indicative of the expected chemical interaction. The goal is to discover changes that are capable of indicating chosen biochemical interactions and/or the presence of small concentrations of environmental contaminants.
Reevaluation of Raman Spectra for KH2PO4 High-Temperature Phases, J. Anand Subramony, Brian J. Marquerdt, John W. Macklin and Bart Kahr, Chemistry of Materials, (1999), 11, 1312.
A New Method for Obtaining Raman Spectra of Extremely Small Quantities of Light Absorbing Substances Adsorbed onto Silver from very Dilute Solutions, J. W. Macklin, J. Raman Spec., (1995), 1077, 26.
Detection of Fullerene in an LDEF Impact Crater, T. Bunch, F. Radicati and J.W. Macklin, Nature, (1994), 369, 37.
Visible Raman and Near IR-FT-Raman Characterization of Adsorbed 4,4'-cyanine, D.L. Akins, J.W. Macklin, and H.-R. Zhu, J. Phys. Chem., (1992), 96, 4515.
pH and Excitation Wavelength Dependence of the Raman Spectrum of 2,2'-Cyanine Adsorbed on a Silver Electrode. D.L. Akins and J.W. Macklin. J. Phys. Chem., (1989), 93, 5999.
Micro-Raman Spectroscopic Measurement of Carbon in Meteorites and Interplanetary Dust Particles, J.W. Macklin, D. Brownlee, S. Chang, and T. Bunch, Microbeam Analysis (Roy Geiss, Ed.) 211 (1987).
FTIR Studies of the Association of Pyroglutamic Acid with Mineral Substances at Elevated Temperatures, J.W. Macklin and D. H. White, Spectrochemica Acta, (1985), 41A, 851.
Stanford and NASA-ASEE Summer Research Fellowship