We thank you for your interest in our research group at Michigan State University. We encourage you to explore this website to learn more about our interdisciplinary research and the students who are engaed in the projects.
Google Scholar: http://scholar.google.com/citations?user=WI4v_OoAAAAJ&hl=en
ResearcherID: B-302302010 http://www.researcherid.com/rid/B-3023-2010
Director, Summer REU Program in Cross-Disciplinary Research in Sustainable Chemistry and Chemical Processes
Department of Chemical Engineering and Materials Science
Center for Coatings and Diamond Technologies (MSU)
Visiting Professor, Domaine Universitaire, Grenoble, France (summer 2001)
Special Visiting Researcher (CAPES), Universidade Federal de São Carlos (Brazil), 2013-2016
ACS Committee on Professional Training, Member, 2015-present
Guest Editor, Special Issue - "Nanocarbon Electrochemistry and Electroanalysis", Electroanalysis (Wiley), print date Jan 2016
Guest Editor, Special Issue - "Electrochemical Properties and Applications of Advanced Carbon Materials", Electrochimica Acta (Elsevier), print data Jan. 2016
Associate Editor, Critical Reviews in Analytical Chemistry, 2014-present
Advisory Board, Advanced Engineering Materials, 2014-present
Editorial Board, Diamond and Related Materials (Elsevier), 2006-present
Editor-in-Chief, Diamond and Related Materials, 2011-2014
Editor, Diamond and Related Materials, 2009-2011
Research in our group is interdisciplinary and spans several fields: physical and analytical electrochemistry, carbon materials, corrosion science and neuroscience. We conduct fundamental research with advanced carbon materials to address key problems and technological needs in energy, health and the environment. Our core science lies in the preparation, processing and application of diamond and diamond-like carbons. We seek to considerably improve the ability to prepare and control the material properties of single and polycrystalline diamond, and nitrogenincorporated tetrahedral amorphous carbon, and to explore frontier applications where the unique material properties are essential for performance.
The following descriptions provide an overview of ongoing and new research projects in the group.
Amperometric Sensors and Biosensors for Health and the Environment
We are making use of nanostructured carbon materials and chemical functionalization strategies to develop a novel array of amperometric sensors and biosensors for use in human health. It is anticipated that the results derived from this research will provide several new and simple sensors that can be applied for important biomedical measurements in complex physiological samples.
The following sensors and biosensors are being developed for different applications:
1. Nitric oxide - This is an important enteric inhibitory neurosignaling molecule in the gastrointestinal tract. We are using this sensor in vitro to study how NO-mediated signaling is altered in obesity.
2. Peroxynitrite (PON) - This is an important marker of inflammation. We are using this sensor in vitro to probe for the presence of inflammation in the gut wall in obesity.
3. ATP - This is an important vasoconstricting neurotransmitter released from sympathetic nerves that innervate blood vessels. It is also an enteric inhibitory transmitter in the gut. We are using this biosensor in vitro to study how purinergic signaling in the vasculature and gut is altered in obesity.
4. Acetylcholine - This is an excitatory transmitter in motor neurons in the gut. We are using this biosensor in vitro to investigate ACh-mediated signaling in GI disorders.
The NO and PON sensors are also part of a noninvasive analyzer being developed for exhaled breath. The goal of this project is to detect trace levels of these biomarkers in exhaled breath. The innovative sensor-based technology could provide on-site and point-of-care detection of these exhaled biomarkers that are relevant in the diagnosis of asthma, cystic fibrosis, cancer and other respiratory diseases. This project is collaborative with faculty in the Departments of Medicine and the Lung Transplant Program.
An array of sensors is being developed using ink-jet printing technology for application in a “smart bandage”. The sensor system will report on the status of wound healing by measuring oxygen levels, pH, uric acid and toxins produced by infectious bacteria. The sensor array will also incorporate an electrode for electrogenerating oxidants to inactivate infectious bacteria, thus lessening the need for antibiotics. This project is collaborative with faculty in the Departments of Physiology, Microbiology and Molecular Genetics, Small Animal Clinical Sciences and EPFL (Switzerland).
Single Cell Analysis - Adipocytes
It has recently been discovered that adipocytes in perivascular adipose tissue contain and potentially release catecholmines (e.g., norepinephrine and dopamine). The mechanisms of synthesis, storage, release and clearance are poorly understood. Secretion of these molecules could have important implications in obesity-associated hypertension. We are working toward using amperometric and voltammetric methods along with pharmacological approaches to investigate the mechanisms of release and clearance from single cells. We are also working toward using CE-EC to quantify catecholamines in single cells. This work is being performed collaboratively with faculty in the Department of Pharmacology and Toxicology.
Neuroelectrochemical Measurements in the Peripheral Vasculature and Gastrointestinal Tract
Neuroeffector transmission mechanisms differ depending on the target tissue. Abnormalities in signaling are associated with various diseases including hypertension and gastrointestinal disorders (e.g., IBS). We use diamond and carbon fiber microelectrodes along with in vitro electrochemical methods to investigate neuroeffector signaling in peripheral tissues. These measurements are useful for probing dynamic changes in concentration of an electroactive analyte in response to a stimulus. They also provide insight on the local neuropharmacology. Specifically, we are using these analytical methods to better understand the dysregulation in obesity-associated (i) hypertension and (ii) gut dysmotility. Nearly 70% of American adults are either overweight or obese. Being obese puts one at a higher risk for diseases such as heart disease, stroke, high blood pressure, diabetes and more. Inexpensive conducting diamond is an enabling electrode material for these measurements because of its superior response sensitivity, reproducibility and stability in the complex tissue environment.
The target signaling molecules are (i) norepinephrine and ATP released from sympathetic nerves supplying arteries and or veins, (ii) serotonin released from enterochromaffin cells in the intestinal mucosa and (iii) nitric oxide and ATP released from inhibitory motor neurons in the gut. Tissues from animal models as well as humans are being used in the research. Immunohistochemical and pharmacological approaches, analytical separation methods and in vitro electrochemical methods are being employed to better understand these obesity-linked disorders. The projects are collaborative with faculty in the Departments of Pharmacology and Toxicology. [Current funding = NIH].
Electrochemical Studies of Diamond and Tetrahedral Amorphous Carbon Thin-Film Electrodes - Comparisons in Aqueous Electrolytes and Room Temperature Ionic Liquids
We are investigating the interfacial structure, capacitance-potential profiles and the electron-transfer kinetics of soluble mediators in room temperature ionic liquids (RTILs). RTILs are emerging as a new class of “conducting” liquid with many important uses in electrochemistry. RTILs are composed of purely ions in the liquid state with no solvent. They generally have low volatility, high solubilizing power, good electrical and ionic conductivity, and are electrochemically stable (i.e., wide potential window).
It is well established that the surface cleanliness, microstructure and chemistry affect electron-transfer kinetics at carbon electrodes. The heterogeneous electron-transfer rate constants for some redox systems are more strongly influenced by these variables in aqueous electrolyte solutions than are others. It is unclear if these variables affect electron-transfer kinetics in RTILs in the same manner. We are using conventional voltammetric measurements, digital simulations, electrochemical impedance spectroscopy and scanning electrochemical microscopy to study various redox systems at boron-doped diamond, tetrahedral amorphous carbon, glassy carbon and graphene electrodes. Bulk electrodes and thin films are being studied as are powderous (nanostructured) forms of the carbons. Various material characterization tools are being used to characterize the morphology, microstructure and surface chemistry of the electrodes including SEM/TEM, electrical measurements, contact angle measurements, XPS, XRD and Raman microprobe imaging. The goal of this work is to learn more about electron-transfer reactions in RTILs at different carbon electrodes and to correlate the physical, chemical and electronic properties of the electrodes with the heterogeneous electron-transfer reaction kinetics. [Current funding = Army Research Office].
Inorganic Coatings for Corrosion Prevention
A wide variety of materials are used in aerospace applications including light weight aluminum alloys, carbon fiber-epoxy composites, titanium alloys and steels. These materials, particularly the metals, are deployed with a multilayer coating system that provides corrosion protection. A typical coating system consists of a conversion coating, a primer and top coat. Understanding how to integrate these coatings in ways that minimize galvanic corrosion, pitting corrosion, and the resulting corrosion fatigue, is of paramount importance.
There are three primary goals driving the research: (i) replacement of the toxic Cr(VI)-containing coatings currently in use with more environmentally-friendly, non-chromate inorganic coatings (conversion coatings and primers), (ii) development of tetrahedral amorphous carbon (ta-C) coatings for contacting metal parts that offer both wear and corrosion resistance and (iii) understanding the degradation mechanisms of carbon fiber-epoxy composites when galvanically coupled. Students are studying and optimizing key processing parameters including (i) the method of application, (ii) substrate preparation (roughness, microstructure and chemistry), (iii) coating composition and structure, and (iv) post processing of the coating (aging and heat treatment).
Greater scientific insight regarding the fundamentals of corrosion and coating degradation during different accelerated degradation testing scenarios will lead to new materials, advanced coating systems, improved corrosion-prevention strategies, and thus better overall aerospace material performance. Current funding = Office of Naval Research.
Nanostructured Diamond Powders for Advanced Separations
High surface area, electrically-conducting and corrosion-resistant nanodiamond and nanodiamond/graphene composite powders are being prepared by chemical vapor deposition using a core-shell approach. Depending on the substrate used, the resulting powders can have surface areas in the 100-200 m2/g range and electrical condictivities greater than 0.5 S/cm.
In terms of separations, new research involves the use of these conducting powders as a stationary phase material in electrochemically-modulated liquid chromatography (EMLC). In this method, the stationary phase is made into a working electrode on the column and solute retention is studied as a function of the potential applied to the stationary phase and the temperature. EMLC is being used to better understand (i) the double layer structure formed at these diamond powders in aqueous media and (ii) the thermodynamics of molecular (electrostatic) interactions with the carbon material surface. Powders with various chemical modification are being studied (e.g., H, O, NH2).
Diamond is an excellent material for use in chromatography because it is the hardest material on earth and it is stable under a wide range of temperatures and pH levels. In theory, diamond and functionalized diamond should offer superior performance to silica and functionalized silica. The inertness of diamond may allow it to be used with biologically-sensitive samples that are often pH sensitive and can easily foul a column. In addition, diamond-based stationary phases should allow for the exploration of novel chemistries. To this end, new research is exploring the use of micrometer diamond and functionalized diamond powders as a stationary phase for reversed- and normal-phase liquid chromatography. Potential exists to use diamond as a novel stationary phase for solid phase extractions (SPE).