Associate Professor of Chemistry
Postdoctoral Fellow McGill University (2012)
Columbia University Ph.D. (2009)
Columbia University M.Phil. (2008)
Columbia University M.A. (2005)
Queens College, CUNY B.A. (2003)
Subir Research Group
The aim of our research group is to elucidate chemistry that takes place in the atmosphere, environment and at nanoscale level from the perspective of surface science. Surfaces are everywhere, which split nature into phases. For instance, approximately two-third of the earth’s surface is air-water interface. The chemical processes that occur at the interfacial region are in general different from that of the bulk (i.e. gas or liquid phase) chemistry. Therefore, it is of fundamental interest to understand surface phenomena. Using surface selective nonlinear laser spectroscopy, along with traditional spectroscopic methods of UV-Vis, fluorescence, IR, and Raman, we investigate the influence of surfaces on chemical processes relevant to atmospheric, environmental and nano-science.
(1) Environmental Colloidal Surface Chemistry
Colloids (or suspended particles) are everywhere. Examples of colloids include atmospheric aerosols, emulsions, and metallic nanoparticles in the size range of 10–9 to 10–6 m. At this length scale, particles exhibit large surface area to volume ratio. Thus, chemistry at these surfaces can dominate. Of particular interest is the colloidal natural organic matter (NOM) present in the aquatic environment. The surface of colloidal NOM can play a role in aquatic pollutant distribution and transformation, but exactly how and to what extent remains unclear. Our research focus is to understand: (1) binding interactions of emerging contaminants with model NOM particles and (2) photochemical processes at the colloidal surfaces. Ultimately, the impact of the surface chemistry on the fate and transport of these pollutants and potential remediation techniques are elucidated.
Fig. 1 Generalized illustration of surface and heterogeneous chemistry pertaining to an aerosol particle
Photovoltaic cells (PVCs) based on sensitized and hybrid nanoparticles are cost-effective and can potentially be highly efficient. Nanoparticles (NPs) provide a large surface area to volume ratio. Thus, molecular adsorption and surface chemistry play an important role in nanoparticle based solar cells. As a result, understanding the interfacial properties (Fig. 2) of NPs is of crucial importance. Our research focuses on surveying interfacial properties of an array of sensitized NPs applicable to the development of PVCs in a systematic way.
Fig. 2 Interfacial properties and chemical processes at NP surface
List of Publications
- Tyler Williams, Clare Walsh, Keith Murray, and Mahamud Subir*. Interactions of Emerging Contaminants with Model Colloidal Microplastics, C60 Fullerene, and Natural Organic Matter – Effect of Surface Functional Group and Adsorbate Properties. Environmental Science: Processes & Impacts. 2020, 22, 1190-1200.
- Daniel Headley, Ryan S. Young, Margaret Reece, and M. Subir*. Variation in Average Molecular Orientation of an Organic Anion at the Air-Aqueous Interface. Journal of Physical Chemistry C. 2018, 122 (9), 4945-4954.
- C. B. Nelson, T. Zubkov, J. D. Adair and M. Subir*. A Synergistic Combination of Local Tight Binding Theory and Second Harmonic Generation Elucidating Surface Properties of ZnO Nanoparticles. Physical Chemistry Chemical Physics. 2017, 19, 29991-29997.
- Tyler A. Williams, Jenny Lee, Cory A. Diemler, and M. Subir*. Magnetic vs. non-magnetic Colloids - A Comparative Adsorption Study to Quantify the Effect of Dye-Induced Aggregation on the Binding Affinity of an Organic Dye. Journal of Colloid and Interface Science. 2016, 481, 20-27.
- P. A. Ariya*, M. Amyot, A. Dastoor, D. Deeds, A. Feinberg, G. Kos, A. Poulain, A. Ryjkov, K. Semeniuk, M. Subir and K. Toyota. Mercury Physicochemical and Biogeochemical Transformation in the Atmosphere and at Atmospheric Interfaces: A Review and Future Directions. Chemical Reviews. 2015, 115 (10), 3760-3802. Special Issue: 2015 Chemistry in Climate.
- M. Subir*, N. Eltouny, and P. A. Ariya*. A Surface Second Harmonic Generation Investigation of Volatile Organic Compound Adsorption on a Liquid Mercury Surface. RSC Advances. 2015, 119, 5, pp 2630 – 2636.
- C. B. Nelson, K. E. Shane, A. A. Al-Nossiff§, and M. Subir*. Optical Second Harmonic Generation from ZnO Nanofluids—A Tight Binding Approach in Determining Bulk χ(2). J. Phys. Chem. C. 2015, 119 (5), pp 2630 – 2636.
- M. Subir, P. A. Ariya*, and Dastoor, A. P. A Review of the Sources of Uncertainties in Atmospheric Mercury Modeling II. Mercury Surface and Heterogeneous Chemistry – A Missing Link. Atmospheric Environment, 2011, 46, 1-10.
- M. Subir, P. A. Ariya*, and Dastoor, A. P. A Review of the Sources of Uncertainties in Atmospheric Mercury Modeling I. Uncertainties in existing kinetic parameters – Fundamental Limitations and the Importance of Heterogeneous Chemistry. Atmospheric Environment, 2011, 45, 5664-5676.
- Rao, Y., Subir, M., McArthur E. A., Turro, N. J., and Eisenthal K. B.*, Organic Ions at the Air/Water Interface. Chemical Physics Letter. 2009, 477, 241-244.
- Subir, M., Liu, J., and Eisenthal, K. B.*, Protonation at the Aqueous Interface of Polymer Nanoparticles with Second Harmonic Generation. J. Phys. Chem. C. 2008, 112, 15809-15812.
- Liu, J., Subir, M., Nguyen, K., and Eisenthal, K. B.*, Second Harmonic Studies of Ions Crossing Liposome Membranes in Real Time. J. Phys. Chem. B. 2008, 112, 15263-15266.