Assistant 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) Aerosol Chemistry
While Earth’s atmosphere is primarily composed of gas molecules, atmospheric aerosols (mixtures of solid or liquid particles suspended in air) play a significant role in transporting and chemically transforming atmospheric gases. Aerosols have both direct and indirect effect on global climate and locally, they can affect pulmonary function and other aspects of human health. As a result, understanding aerosol chemistry is of major scientific interest. Because aerosols are heterogeneous (composed of multiple phases) and range from nano- to micro-meters in size, they can provide sufficient surfaces for interfacial chemistry to take place (Fig. 1). To better understand the impact of aerosols on overall atmospheric processes, knowledge of aerosol surface chemistry is essential. Our current focus is to understand: (1) uptake of atmospheric pollutants to heterogeneous aerosol mixtures (2) adsorption and co-adsorption of volatile organic compounds (3) chemical reactivity at gas/aerosol interfaces and (4) spectral identification of heterogeneous aerosol composition.
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
1. Mercury Physicochemical and Biogeochemical Transformation in the Atmosphere and at Atmospheric Interfaces: A Review and Future Directions. Parisa A. Ariya, Marc Amyot, Ashu Dastoor, Daniel Deeds, Aryeh Feinberg, Gregor Kos, Alexandre Poulain, Andrei Ryjkov, Kirill Semeniuk, M. Subir, and Kenjiro Toyota. Chem. Rev., 2015, 115 (10), pp 3760–3802.
2. A surface second harmonic generation investigation of volatile organic compound adsorption on a liquid mercury surface. Mahamud Subir, Nermin Eltouny and Parisa A. Ariya. RSC Adv., 2015, 5, 23464-23470.
3. Optical Second Harmonic Generation from ZnO Nanofluids—A Tight Binding Approach in Determining Bulk χ(2). Christopher B. Nelson, Kevin E. Shane, Amani A. Al-Nossiff , and Mahamud Subir. J. Phys. Chem. C. 2015, 119 (5), pp 2630-2636.
4. Subir, M., 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
5. Subir, M., 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
6. Rao, Y., Subir, M., McArthur E. A., Turro, N. J., and Eisenthal K. B., Organic Ions at the Air/Water Interface. Chemical Physics Letter (Editor’s choice). 2009, 477, 241-244
7. 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
8. 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