Raymond E. Schaak

Research interests:  The intersection of solid-state chemistry, materials chemistry, molecular inorganic chemistry, and nanoscience; new low-temperature routes to bulk and nanoscale solid-state materials, particularly non-equilibrium solids made by direct solution methods, reactive structural intermediates, and biological templating; mechanistic studies of nanocrystal reactivity and formation; synthesis and self-assembly of shape-controlled nanocrystals, including nanocomposites and hybrid systems with catalytic, magnetic, optical, and superconducting properties.

Synthesis and Applications of Nanoscale Inorganic Solids

Our research is driven by synthesis – developing new synthetic methodologies that fill critical gaps in the current toolbox of techniques available in the solid-state chemistry and nanoscience communities, and applying these new synthetic tools to important problems in both fundamental and applied science.  In all of our endeavors, we integrate ideas and techniques from solid-state chemistry, solution (molecular) chemistry, and nanoscience, and this allows us to tackle important and often longstanding scientific problems that lie at the interface between chemistry, physics, materials science, and various engineering disciplines.  Our current focus areas, which are integrated by the central theme of low-temperature chemical routes to solid-state materials, are described below.

Low-temperature chemical routes to non-equilibrium solids

The rate-limiting step in traditional solid-state reactions is solid-solid diffusion, which generally necessitates high reaction temperatures and usually leads to products that are the most thermodynamically stable in a particular system.  We have been actively developing alternative low-temperature strategies that side-step the diffusion problem, with an emphasis on elucidating the reaction pathways involved in the formation of solid-state materials using these routes.  Our focus is on using solution-based nanoparticle synthesis methods as an alternative low-temperature platform for the synthesis and discovery of new materials, particularly transition metal intermetallic compounds and chalcogenides.  Some of our targets are found via focused exploratory investigations, but many are chosen because of potential technological interest or long-standing fundamental questions.

“Total synthesis” of complex multi-functional inorganic nanostructures

As inorganic nanostructures become more advanced and their synthesis becomes more mature, the challenges shift toward more complex materials and architectures than are currently straightforward to prepare.  For example, how do we design and synthesize multi-component nanostructures with controlled and pre-determined compositions, structures, morphologies, and spatial organization of components, while simultaneously maintaining robust interfaces (without the use of large organic or biological molecules to mediate coupling)?  Inspired by organic chemistry, we have been developing “total synthesis” strategies for the synthesis of complex inorganic nanostructures.  The application of ideas such as orthogonal reactivity, protection/deprotection, and site-specific reactivity (within the context of all-inorganic solid-state nanostructures) is allowing us to create exceptionally complex multi-functional nanowires, patterned films, and nanoparticle heterostructures.  Our target materials will advance applications in sequential multi-step catalysis and emerging lab-on-a-particle technologies.

Catalytic nanostructures for chemical synthesis and energy applications

Chemical catalysis is an integral component of pharmaceutical and fine chemical synthesis, as well as facilitating reactions that will help to meet current and future energy demands.  New and improved catalysts can often be realized by modifying the sizes, morphologies, compositions, structures, and supports.  Simulataneously addressing all of these issues, which is necessary for achieving optimal performance, represents a synergistic set of important synthetic challenges.  We have been exploring nanostructure design strategies for improving catalytic performance for the oxygen reduction reaction (ORR), CO oxidation, direct H₂O₂ synthesis, and various hydrogenation and oxidation reactions.  Our efforts focus on catalytic metal nanoparticles and carbon-based support materials, with a focus on shape-controlled multi-metal nanoparticle catalysts of non-equilibrium phases that are inspired by model surface studies and computational investigations.

Colloidal synthesis of size- and shape-controlled nanocrystals

Colloidal routes to many types of size- and shape-controlled metal and semiconductor nanocrystals have become ubiquitous in recent years.  However, important synthetic challenges remain.  For example, how do we extend the capabilities developed for benchmark nanomaterials like Au, Ag, ZnO, CdSe, etc. to early transition metal systems, p-block elements, non-equilibrium phases, and more complex binary, ternary, and quaternary alloy phases?  How do we achieve similar results for systems that are chemically challenging to prepare or stabilize, such as metal phosphides, hydrides, borides, and carbides?  Our efforts have centered around the use of strong reducing agents facilitated by rigorously air-free techniques, as well as mild low-temperature benchtop strategies.

Biological routes to inorganic solids

Nature facilitates the synthesis of intricate inorganic nanostructures under ambient conditions, and one of the most significant current challenges in nanostructure design is to mimic these capabilities synthetically in “artificial” systems.  To do so requires a detailed understanding of the factors that underpin the biological templating of inorganic materials, as well as empirical guidelines for how to achieve the desired results.  We have been using M13 bacteriophage as a biological support for both non-specific and materials-specific templating of inorganic nanostructures, with a focus on multi-component and spatially-controllable composite materials with multiple functionalities.  Current efforts include expanding the materials-templating capabilities of M13 bacteriophage, applying the materials-specific characteristics of polypeptides for applications in nanoparticle synthesis and assembly, and using proteins and other biomolecules to direct the synthesis of nanoparticle heterostructures.