Research in the Penner Group focuses on the development of new synthetic methods for preparing nanomaterials that have unique and useful properties for chemical sensing, and for other applications (thermoelectrics, optoelectronics, 2^o battery electrode materials, etc.). We focus on electronic materials including metals, metal oxides, semiconductors, thermoelectric materials, and electronically conductive polymers. We are, first and foremost, electrochemists and electrodeposition is the starting point for all our synthetic methods. This means that nanostructure "synthesis" begins on a conductive electrode surface (composed of graphite or silicon) from precursors (metal ions, organic monomers, etc.) present in a contacting liquid phase. Additional processing steps that do not involve electrochemistry are also sometimes employed to obtain compounds of interest. We call this "Electrochemical/Chemical" synthesis. The rigorous structural characterization of the nanomaterials we prepare consumes a large fraction of our day-to-day research effort and routinely involves six methods (TEM, SAED, SEM, EDX, XPS, and powder XRD).

Many projects in the group proceed sequentially through three phases: Phase 1: synthesis and structural characterization of a nanomaterial, Phase 2: measurement of one or more "functional" fundamental, properties that may be optical, electronic, thermal, magnetic, etc., and, Phase 3: evaluation of performance in a prototype device that exploits the properties probed in Phase 2. While breakthroughs can happen in Phases 1 and 2, We believe that the most important discoveries in chemical sensing and in other applications will involve proceeding all the way to Phase 3. The reason is that the behavior of a particular nanomaterial in a particular application or device can not be predicted based on its structural attributes and chemical composition. Consequently, we target nanomaterials that are likely to exhibit useful behavior, and we stay alert for surprises! We are interested in how the composition and structure of a nanomaterial produces the properties that make it useful, and we are willing to devote time and effort to the elucidation of this structure-property relationship. Our central premise is that nanomaterials with unique attributes, and over which we have direct synthetic control, will lead to breakthroughs in chemical sensing and other applications.

The six objectives of our research program are the following:

1. Identify and understand the processes that lead to size dispersion in the electrochemical growth of nanostructures such as nanoparticles and nanowires.
2. Devise electrochemical methods for circumventing these processes; methods that enable the electrodeposition of "size monodisperse" nanometer-scale structures.
3. Synthesize nanostructures composed of compounds possessing desirable and technologically useful electronic properties. The family of methods we are developing for this purpose are called "Electrochemical/Chemical Methods". Materials of current interest include semiconductors (e.g., MoS₂, CdS), thermoelectrics (Bi₂Te₃), and electronically conductive polymers (e.g. polythiophene).
4. Discover new strategies for enforcing a two-dimensional organization on the electrodeposition of nanostructures on flat electrode surfaces.
5. Measure and understand the size-dependant physical and chemical properties of nanostructures including the conductivity, electro- and photoluminescence, thermoelectricity, magnetoresistance, and chemical reactivity.
6. Exploit the unique properties of these nanostructures in chemical sensors and other types of devices in new and interesting ways.