Stephanie L. Brock Title Professor Division Inorganic (Solid State and Nanomaterials) Education B.S., University of Washington, 1990 Ph.D., University of California, Davis, 1995 Postdoctoral Associate, University of Connecticut, 1995-1999 Office Chem 145 Phone (313)577-3102 E-Mail Group http://chem.wayne.edu/brockgroup

Our research efforts are centered on the synthesis and characterization of novel inorganic solid state materials with unique and tunable properties, particularly low dimensional solids and nanomaterials. The research is highly interdisciplinary, with the aim to develop a fundamental understanding of how structure, particle size, and material physical properties are related in order to advance technologies such as information storage, sensing, energy conversion, catalysis, and biomedical applications. Projects presently underway include:

I. Transition Metal Pnictide Nanoparticles: Novel Materials for Magnetic and Catalytic Applications Transition-metal pnictides (pnicogen = Group 15 element) exhibit a wide range of magnetic and electronic properties of fundamental and practical interest including superconductivity, ferromagnetism, and semiconductivity. We have developed a range of strategies for the synthesis of transition metal pnictides as nanoparticles and nanostructures and have applied these successfully to ferromagnetic phosphides and arsenides of Mn and Fe, as well as to Ni₂P catalysts for hydrotreating of petroleum feedstocks. The magnetic properties of Mn and Fe pnictides (conducted in collaboration with Prof. Gavin Lawes in Physics) suggest that magnetic structure is highly dependent on the particle size of the nanoparticles prepared, whereas the work on Ni₂P, is allowing us to evaluate size and shape effects on hydrodesulfurization activity (in collaboration with Prof. Mark Bussell, Western Washington University).

II. Sol-gel Strategies for Assembly of Metal Chalcogenide Nanoparticles into Functional Architectures A major hurdle to the implementation of nanoparticles in solid state devices is a lack of methodologies that permit them to be assembled into functional architectures while retaining the unique, size-defined properties of the nanoparticle building block. We have recently shown that sol-gel strategies, long exploited for oxides, can also be used to assemble metal chalcogenide nanoparticles, including CdS, CdSe, PbS, and ZnS. The resultant gels resemble a cross-linked particulate polymeric network. This network can be dried supercritically to form low-density, highly porous aerogels. These materials combine the unique optical properties of the nanoparticle building blocks with the high surface area and electronically conducting framework of the aerogel. Currently, we are investigating the suitability of these materials for thermoelectric and photovoltaic applications and exploiting this assembly methodology for phosphide nanoparticles.

III. Inorganic-Organic Hybrid Materials for Patterning and Biomedical Applications Hybrid materials permit the co-mingling of dissimilar properties, such as the mechanically hard behavior of inorganic ceramics with the soft behavior of polymers. We are collaborating with several groups on campus to synthesize and characterize novel nanoscale hybrids. Specifically, we are investigating nucleation and growth of organic crystals from inorganic nanoparticles with Prof. Mao in Engineering. We are also working with Prof. Oupick? in Pharmaceutical Sciences on developing nanoparticle-stimuli-responsive-polymer hybrids for drug delivery and with Prof. Chow in Chemistry and Prof. Al-Katib in Cancer Biology on tumor-specific quantum dot-based imaging agents.

Muthuswamy, E.; Savithra, G. H. L.; Brock, S. L. "Synthetic Levers Enabling Independent Control of Phase, Size, and Morphology in Nickel Phosphide Nanoparticles" ACS Nano, 2011, 5, 2402.

Pala, I. R.; Arachchige, I. U.; Georgiev, D. G.; Brock, S. L. "Reversible Gelation of II-VI Nanocrystals: The Nature of Interparticle Bonding and the Origin of Nanocrystal Photochemical Instability" Angew. Chem. Int. Ed., 2010, 49, 3661.

Senevirathne, K.; Tackett, R.; Kharel, P.; Lawes, G.; Somaskandan, K.; Brock, S. L. "Discrete, Dispersible MnAs Nanocrystals from Solution Methods: Phase Control on the Nanoscale and Magnetic Consequences," ACS Nano, 2009, 3, 1129.

Yao, Q.; Arachchige, I. U.; Brock, S. L. "Expanding the Repertoire of Chalcogenide Nanocrystal Networks: Ag2Se Gels and Aerogels by Cation Exchange Reactions," J. Am. Chem. Soc., 2009, 131, 2800.

Aitken, J. A.; Tsoi, G.; Wenger, L. E.; Brock, S. L. "Phase Segregation of MnP in Chalcopyrite Dilute Magnetic Semiconductors: A Cautionary Tale", Chem. Mater., 2007, 19, 5272.

Mohanan, J. L.; Arachchige, I. U.; Brock, S. L. "Porous Semiconductor Chalcogenide Aerogels," Science, 2005, 307, 397.