Research Interests: The Zeng lab is interested in the study of fundamental and applied interfacial phenomena, particularly the design and control of molecular characters and characterizations of the dynamic reactions at electrode interfaces. Current projects in Zeng lab are: (1) Understanding the interfacial composition, structure and properties of ionic liquids and conductive polymers for sensor and energy storage applications; (2) Applying principles from chemistry and biology for directed assembly or synthesis of thin films of conductive polymers, biological molecules (peptides, proteins and carbohydrates), cells and inorganics on electrode surfaces; (3) Developing miniaturized analysis platforms that combines high performance, chip-scale instrumentation electronics with multi-transduction-mode sensor array devices by collaboration with engineers especially Dr. Mason’s lab in ECE at MSU. This research direction is motivated by the increasing needs of new sensor technology for a broad range of applications relating to national security, health care, the environment, energy, food safety, and manufacturing. Although new and improved sensor technology will continue to be developed, the most crucial needs in any sensors are the recognition elements at the interface and the fundamental understanding of the molecular recognition events at the interfaces. By collaboration with various scientists and engineers, we have identified new sensor recognition elements (i.e. recombinant antibody, carbohydrate, ionic liquid, biopolymers and cells) and demonstrated their use as chemical and biosensing materials for fabricating new sensor structures with strong potential capabilities including limited size, weight and power consumption by using label free transducers. Furthermore, the fundamental understanding of the interface properties of various chemical and biointerfaces allow us to explore new directions in Lithium ion battery electrolytes, electrocatalysis for fuel cells and solid state fuel cells and new research directions in biomedical research including cancer and infectious diseases.
All current and completed projects are interdisciplinary in nature (electrochemistry, spectroscopy, material science, bioengineering, biology and medicine) involve using of multiple electrochemical, spectroscopic and microscopic techniques in order to determine the composition, structure and dynamic interfacial properties at electrode interfaces. By combining the results of diverse in situ techniques (electrochemical quartz crystal microbalance (EQCM), rotating ring disk electrodes (RRDE), cyclic voltammetry (CV), electrochemical impedance spectroscopy, surface plasmon resonance (SPR), ellipsometry, ATR and RA FT-IR, scanning probe techniques (i.e. atomic force microscope (AFM) and scanning tunneling microscope (STM)), fundamental understanding of the electrode interface properties can be obtained. This in turn enables the development of new electrode surfaces in which interesting properties can be tailored by incorporating appropriate inorganic, organic and biological constituents for a broad range of applications from electrochemical energy conversion (fuel cell, batteries and electrocatalysis) to chemical sensors and biosensors for clinical diagnosis, environmental monitoring and biomedical research.
Examples of Prior Funded Projects in Zeng Lab
· Autonomous Electrochemical Gas Detection Microsystem for Mine Safety, multiple PIs: Xiangqun Zeng (Oakland) and Andrew Mason (Michigan State Univ.), NIOSH R01, 2010-2014.
In this project, key ionic liquid based sensor, instrumentation and data analysis technologies are being investigated so that they can be integrated to form a miniaturized intelligent electrochemical gas analysis system (iEGAS) tailored to the needs and challenges of mine safety applications. We have characterized diverse gaseous molecules’ redox properties in ionic liquids, including CH4, SO2, NO, NO2, H2, CO, CO2, and O2. The fundamental understandings were used to develop strategies for highly selective multiple gas detection sensors, especially in harsh environment. Many detection strategies are the first of the kind. We are in the process of developing an operational model of the iEGAS system and we are also in the process of characterizing it in a laboratory where gas concentrations and environmental parameters can be accurately controlled to mimic the range of conditions within underground mines. Four peer reviewed papers and four conference papers have been published and four manuscripts are in preparation for this project.
· Wearable Microsystem Array for Acute Pollutant Exposure Assessment, multiple PIs: Xiangqun Zeng (Oakland) and Andrew Mason (Michigan State Univ.), 2014- 2018, NIH-NIEHS
This project was just funded with a starting date of 12/1/2013. The goals of this project are (1) to provide researchers with a new tool to better assess the impacts of pollutant exposure to respiratory and cardiovascular disease, and (2) to provide individuals with an inexpensive wearable device for real-time reporting of exposure data for personalized alerts and managed care services. In the long term, a significantly improved medical understanding of air toxics would allow more relevant regulation of toxic air pollutants and more effective personal prevention plans.
· Engineered Self-Assembling Peptide or scFv for Label Free Immunosensors
NIH R21/R33 2002-2009: Engineered Self-Assembling Fvs for Piezoimmunosensor; NIH R21, 2010-2013: ScFv Piezoimmunosensor Detection of Therapeutic Antibodies in Human Serum.
We have demonstrated the single chain fragment viarable (scFv) recombinant antibody’s capability and potential as a superior new type of immuno-recognition elements by protein engineering of the binding aminoacids (i.e. cysteine, histidine and arginine) into the peptide linker which links the heavy (VH) and the light (VL) chain variable domains. This allows the direct immobilization of scFv in their native state on the gold surface or to pre-formed functionalized self-assembled monolayers template so that the antigen-binding site is oriented toward the solution phase. Our results show that use of engineered scFvs solves most of the problems in immobilizing antibodies to the sensor, i.e., the low density and poor orientation of antibody binding sites immobilized on transducer surfaces. Furthermore, we have demonstrated that phage display selections of the peptides (i.e. antigen mimotopes) bearing a particular functional sequence could be applied for developing a new generation of affinity-based immunosensors to detect a broad range of clinical biomarkers. Short synthetic peptides (15-20 amino acids) are generally more stable and easier to chemically synthesize in comparison to antibodies or recombinant proteins. Synthetic peptides can also be more readily synthesized on a large scale under controlled conditions to ensure peptide quality and batch-to-batch reproducibility. As such, the cost to produce a peptide-based immunosensor can be significantly reduced. These projects resulted in an issued patent, two patent discloure, 18 high quality peer reviewed publications, one book chapter and one invited review article.
· Ionic Liquids: New Materials for Chemical Sensing
ONR, 2010- 2013: Electrochemical and Piezoelectric Sensors for Standoff Explosive Detection;
NIOSH R21, 2009-2012: Ionic Liquid Gas Sensors for Detection of Flammable Gases in Workplace.
As liquid salts containing organic ions, ionic liquids (ILs) can behave as the reactant and the reaction media simultaneously, enabling a foundation to engineer sensor devices with efficient recognition and optimized immobilization protocols. The excellent redox activity and/or sorption properties of target compounds in ILs will allow orthogonal sensing of these compounds with piezoelectric, amperometric and impedance readouts, rendering them ideal for selective detection strategies. We have systematically investigated IL as sensing elements via the rational design and selection of ILs and their composites in various sensing platforms in order to provide multidimensional solutions for detections of a broad range of volatile and gaseous analytes. We have elucidated the design factors responsible for the discriminative power of the ILs towards different gas explosives and proves that generation of sensing signals are pre-dominantly non-bonding ones (e.g., polarizibility, cavity formation effects) whereas hydrogen bonding and π-electronic cloud effects have a far less significant role to play. ILs equal usefulness in both piezoelectric and electrochemical formats with orthogonality to provide chemo- and regio-selectivity through functionalized ionics were validated for orthogonal Electrochemical and Quartz Crystal Microbalance (EQCM) sensing. Our fundamental study helps understanding the molecular-level interactions within IL/EQCM gas sensors and opens up new possibilities for the rational design of ion structures leading to enhanced-performance sensors. These projects resulted in four issued patents, 11 high quality peer reviewed publications, one book chapter and one invited review article by Accounts of Chemical Research.