Fordham University


 

  


John J. McMahon. Associate Professor of Chemistry .
B.S. University of Massachusetts-Dartmouth
M.S. University of Massachusetts-Boston
Ph.D. Michigan State University.

Department of Chemistry, Fordham College of Rose Hill.



Office:

Fordham University
441 E. Fordham Road
John Mulcahy Hall Room 632
Bronx, New York  10458


Email:


Phone:

(718) 817-4495


Fax:

(718) 817-4432


 

Subjects Taught:

Physical Chemistry

Physical Chemistry Laboratory
Surface Spectroscopy

General Chemistry Recitation

Materials Science and Nanotechnology

 

 

Research Speciality:

Spectroscopic and Electrochemical Studies of Structure and Processes at Electrode Surfaces

 


Topics in Physical Chemistry

(Thermodynamics, Quantum Mechanics, Kinetics)

Thermodynamics (Carnot Cycle)
Pressure-volume expansions and compressions between a hot and a cold temperature permit extraction of work from the cycle (- Wmax is the red area under the curve.) .

 

 

 

Quantum Mechanics

(Fourier series)

A particle defined by P(x) existing between -1 and 1 is fit with a superposition of Fourier component waves, f(x), of different wavelengths. The more waves used, the better the fit, the more confident we are of the particle's position. However, the more waves we use, the larger the range of wavelengths and, according to deBrogile, the larger the range of momenta (mv). Thus, the more certain we are of a particle's position the less certain we become of its momentum. - Heisenberg uncertainty principle.

 

 

 

(molecular vibrations of water)

 

 

 

 

Because each atom of a molecule may move along x, y, or z, a molecule with N atoms has 3(N) degrees of freedom of motion. Water, with three atoms, has 3(3) or 9 degrees of freedom. Translation of the entire molecule along the x, y, and z axes constitutes 3 of the 9 degrees of freedom. Rotation of the entire molecule about the x, y, and z axes constitutes 3 more of the 9 degrees of freedom. The remaining degrees of freedom are internal vibrational motions. For non-linear molecules, like water, we therefore expect 3(N)-6 vibrational motions. The 3 vibrations in water are shown at the left.

 

 

 

Kinetics

(interactive Demo: hard sphere collision theory)

The likelihood of collisions between molecules, a prerequisite to chemical reactions called the "law of mass action", depends upon the size of the collisional cross section, S. Molecules that approach close enough so that the separation of their centers is contained within S will collide. The larger the collisional cross section, the more likely a collision, the faster the rate of reaction between the molecules. The size of S naturally depends upon the diameter (d12) of the approaching molecules, but also will depend on the relative velocity (Vr) of the two molecules and on whether the two molecules have attractive (att) or repulsive (rep) potential energies of interaction (Ur). The above interactive demonstration allows adjustment of each of these parameters, along with an impact parameter, b, defined in the figure above. The impact parameter, b, has a maximum value, bmax, above which the molecules will not collide which is defined by the size of the collisional cross section, S.

 

 



 

Research Specialties

Spectroscopic and Electrochemical Studies of Structure and Processes at Electrode Surfaces
surface and normal Raman spectroscopy(SERS) , fuel cells, mass spectrometry.

 

SERS

Surface-Enhanced Raman Spectrum
of Bis-(4-pyridyl)-acetylene (BPA)
Adsorbed at a Silver Electrode

The surface-enhanced Raman spectrum for BPA adsorbed at a silver electrode is tracked as a function of applied voltage at the silver. Beginning around -0.5 V and accompanying the passage of reduction current (insert) the SERS indicates that BPA reduces to an ethylenic product. The reduction is evidenced by loss of intensity at 2230 cm-1 (the symmetric stretch of the acetylenic bridge) and replacement with a peak at 1635 cm-1 (the symmetric stretch in the ethylenic reduction product), one of the new red peaks that appear at more negative applied voltages.

 

 

Fuel Cells

Photocatalysis of the Oxygen Reduction Reaction in Fuel Cells

The BPA-covered silver working electrode was irradiated with light from an argon ion (Ar+) laser at 514 nm (green) in a timed experiment...
4 sec off / 4 sec on / 4 sec off.

The resultant current observed during the irradiation period accompanies the reduction of dissolved oxygen.
CONCLUSION...
The efficiency of fuel cells, limited by the slow kinetics of oxygen reduction, can be improved by irradiating the cathode.

 

Secondary Ion Mass Spectrometry (SIMS)

SIMS of Stilbazole (MW 181) Adsorbed at a Silver Electrode

SIMS at m/z = 181
video capture of the surface
mass spectrum of stilbazole
SIMS image was gathered by rastering a beam of cesium ions (Cs+) across the electrode surface and collecting secondary ions of mass m/z = 181, the molecular weight of stilbazole.
Photograph of the same surface.
Secondary Ion mass spectrum of stilbazole adsorbed at a silver electrode surface.

 

 


Recent Publications

Book authored: Textbook: Physical Chemistry, Reason and Experiment, John J. McMahon, published iBook on iTunes July 25, 2014, CC&J Publishing, New York, ISBN: 9780692261859.

"MS Analysis of Surface Photoproducts - Stilbazole at Silver" Proceedings of the 47th ASMS Conference on Mass Spectrometry and Allied Topics, June 13 - 17, 1999, Dallas, Texas, published on searchable CD-ROM.(full text in pdf format)

"Photochemical Charge Transfer Excitation of Trans-4-Stilbazole at a Silver Electrode", J. J. McMahon, T. J. Gergel, D. M. Otterson, C. R. McMahon, R. M. Kabbani, Surface Science 440(3), 357-374 (1999). (full text in pdf format)

"Secondary Ion Mapping of Ca in Bone", P. J. Todd, C. A. McCandlish, J. J. McMahon, J. M. McMahon, Proceedings of the 48th ASMS Conference on Mass Spectrometry and Related Topics, published on searchable CD-ROM, (2000). (full text document in pdf format)

"Synthesis of 2-Acetamido-5,6-dihalo-phenyl Acetates", D. D. Clarke, H. Gershon, J. J. McMahon, Monatshefte fur Chemie Chemical Monthly, 131(7) 795 - 798 (2000). (full text in pdf format).

"SIMS Imaging of trans-4-Stilbazole Adsorbed at a Silver Electrode"J. J. McMahon, J. M. McMahon , T. G. Schaff , Peter J. Todd, Proceedings of the 49th ASMS Conference on Mass Spectrometry and Related Topics, published on searchable CD-ROM, (2001). (full text document in pdf format)

"Preparation and fungitoxicity of some dibromo-8-quinolinols?h Gershon, Herman; Clarke, Donald D.; McMahon, John J.; Gershon, Muriel. Monatshefte fuer Chemie  132(7),  833-838 (2001). (full text in pdf format)

Imaging Charge Transfer Induced Surface Photochemistry with Ion Trap SIMS , J. J. McMahon*; T. G. Schaaff; J. M. McMahon; P. J. Todd, Proceedings of the 50th ASMS Conference on Mass Spectrometry and Related Topics, published on searchable CD-ROM, (2002). (full text document in pdf format)

"Preparation and Antifungal Activity of 3-Iodo- and 6-Iodo-8-quinolinols", H. Hershon, D. D. Clarke, J. J. McMahon, Monatshefte fur Chemie Chemical Monthly, 133(10) 1325-1330 (2002). (full text in pdf format)

"Effect of Dimethyl Sulfoxide and Dimethylformamide on the Stability of 4-Halo-8-quinolinols?h Gershon, Herman; Clarke, Donald D.; McMahon, John J..  Monatshefte fuer Chemie   134(8),  1099-1104 (2003). (full text in pdf format)

"SERS and Photocatalysis of Oxygen Reduction at Bis-(4-Pyridyl)Acetylene-Covered Silver", J.J. McMahon, K. Breen, M.S. Barry, Proceedings of the 20th International Conference on Raman Spectroscopy, Yokohama, Japan, 2006 (view abstract) , (view poster)

“Photocatalytic Electrode and Fuel Cell”, J. J. McMahon, U.S. Patent Application Serial No. 11/393630, filed March 30, 2006, published October 4, 2007.

“Photocatalytic Electrode and Fuel Cell”, J. J. McMahon, U. S. Provisional Patent Application Serial No. 60/921,107 filed March 30, 2007, published December 20, 2007. (view patent application)

"Photocatalytic Electrode and Fuel Cell", J. J. McMahon,U. S. Patent Application Serial No. 11/823,760  filed June 28, 2007, published December 20, 2007. (view patent application)

“Photocatalysis of the Oxygen Reduction Reaction at Adsorbate-Covered Silver”, John J. McMahon, Michael Barry, Kristin J. Breen, Anna K. Radziwon, Leanne D. Brooks, Michael R. Blair,  J. Phys. Chem. C 112(4), 1158 -1166 (2008). (full text in pdf format)

“Photocatalytic Electrode and Fuel Cell”, J. J. McMahon, U.S. Patent Application Serial No. 12/719,122, filed March 8, 2010, published July 29, 2010, status: approved February 10, 2011, issued March 15, 2011.

“Photocatalytic Electrode and Fuel Cell”, J. J. McMahon, Russian Application No. 2008143017 filed May 29, 2007, status: issued July 20, 2011.

"Photocatalytic Electrode and Fuel Cell Thereof" U.S. Patent Application No.:  61/676,018 filed and published on July 26, 2012, status: pending.

“Role of the I2/I- Equilibrium in the Photocatalysis of Oxygen Reduction at Ag/AgI”, Lukasz Sztaberek, Jenny Kang, William Chen, Franesco F. Caruana, Kateryna Huz, Jacob Robinson, John Amato, Christina N. Daniels, John J. McMahon, ACS Energy Lett. 2016, 1, 409-413. (full text in pdf format)

Other Publications

"Polycrystalline and Solution Raman Spectra of t-1,2-bis(4-pyridyl)ethylene, its dihydrochloride and its dideuterochloride", J. J. McMahon, G. T. Babcock, Spectrochimica Acta, 38A(11), 1115 - 1122, (1982).

"Raman Investigations of Biselenates. The Raman Spectra of RbHSeO4 in the Range 20 - 300K", R. L. Carter, R. B. Edmonds, J. J. McMahon, Spectroscopy Letters, 15(5), 341-354, (1982).

"Resonance Raman Studies of Copper Pheophytinate", J. S. Keller, J. J. McMahon, R. Chang, R. L. Carter, Spectroscopy Letters, 17(2), 145-149, (1984).

"Surface Enhanced Raman Scattering and Photodimerization of Pyridyl-Substituted Ethylenes at a Silver Electrode Surface", J. J. McMahon, T. P. Dougherty, D. J. Riley, G. T. Babcock, R. L. C, Surface Science 158, 381-392, (1985).

"High-Temperature In-Situ Surface Raman Spectroelectrochemistry in Aqueous Solutions", C. A. Melendres, J. J. McMahon, W. Ruther, J. Electroanal. Chem. 208, 175-178, (1986).

"Surface Raman Scattering and Electrochemistry of Iron Protoporphyrin IX at a Polycrystalline Silver Electrode", J. J. McMahon, S. Baer, and C. A. Melendres, J. Phys. Chem. 90(8), 1572 - 1577, (1986) (full text in pdf format).

"In Situ Laser Raman Spectroelectrochemical Study of the Corrosion of Lead in Dilute Na2SO4 Solution at High Temperature", J. J. McMahon, W. Ruther, C. A. Melendres, J. Electrochem. Soc. 135(3), 557 - 562. (1988). (full text in pdf format).

"An Inexpensive Parallel Interface to a Digital pH Meter", J. J. McMahon, P. R. Braca, J. Chem. Ed. 69(5), A156-A158, (1992) (full text in pdf format).

 


 

 

 

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