REU Site:  Nanoscale Science Undergraduate Research Experiences (NanoSURE)
at UNC Charlotte

NanoSURE Faculty Research Project Descriptions

 

Characterization of the Potential Toxicity of Metal Nanoparticles in Marine Ecosystems.  Faculty Advisor:  Amy Ringwood, Assistant Professor, Department of Biology.
The Ringwood Laboratory is currently investigating the toxicity and accumulation of nanoparticles in aquatic organisms.  While primarily oysters (Crassostrea virginica) are being used as valuable models for responses in filter-feeding organisms, there is interest in expanding these studies to other invertebrates.  Currently, this work involves laboratory exposures with adult and embryonic oysters as well as with isolated hepatopancreas cells.  Students use a variety of toxicity assays, including a lysosomal destabilization assay, to determine the potential for hepatotoxicity, and lipid peroxidation and protein oxidation assays are being used to assess oxidative damage.  The effects on antioxidant status are being evaluated by measuring the levels of glutathione, superoxide dismutase, etc., and gene and protein responses (e.g. heat shock proteins, metallothioneins) are also being evaluated.  Students use a variety of techniques to evaluate the accumulation of nanoparticles in the tissues and cells, including atomic absorption spectroscopy for metal nanoparticles, and fluorescent confocal microscopy for fullerenes and quantum dots.  These kinds of basic studies are essential for addressing the potential impacts of nanoengineered particles on fundamental cellular processes as well as aquatic organisms.

Creation of Nanoparticles Loaded with Antibiotics to Treat and Prevent Bacterial Infections.  Faculty Advisor:  Michael Hudson, Professor, Department of Biology.
The Hudson laboratory has three specific aims:  1)  To develop two distinct nanoparticle (FDA Approved) antibiotic-delivery systems. One system will release drugs rapidly, while the other will release drugs slowly. REU students will work with three different antibiotics in the study, targeting gram-positive, gram-negative, and specific anaerobes, respectively.  2)  To test the nanoparticle antibiotic-delivery system in vitro against purely extracellular and purely intracellular Staphylococcus aureus. Students will work with this organism as a model bacterium since it lives extracellularly and intracellularly, is resistant to most antibiotics, and community-acquired methicillin-resistant strains will kill more Americans this year than will die of AIDS.  And 3) To test the nanoparticle antibiotic-delivery system in vivo using models of soft tissue and bone injury.

Stress Adaptation and Tolerance in Marine Ecotherms.  Faculty Advisor:  Inna Sokolova, Associate Professor, Department of Biology.Students in Sokolova’s research group participate in research related to the physiological and molecular mechanisms of stress adaptation and tolerance in marine ectotherms, in particular in understanding interactive effects of multiple stressors on metabolic physiology and disease resistance in eastern oysters, Crassostrea virginica. Currently, there are two major projects running in Dr. Sokolova’s laboratory.  One project uses the eastern oyster as a model organism in order to obtain a comprehensive physiological model of the temperature-dependent action of cadmium and to identify key mitochondrial targets for cadmium in poikilothermic (“cold-blooded”) animals, which are currently unknown. The students involved in this research would gain experience in modern physiological and molecular methods such as determination of mitochondrial respiration and membrane potential, measurements of activities of key metabolic enzymes, determination of mRNA and protein expression for key metabolic enzymes, stress proteins and metallothioneins, determinations of whole-organism aerobic and anaerobic capacity, measurements of the tissue oxidative stress and redox status and others that could be applied to nanotechnology applications of biological systems. The second project lies in the understanding of the mechanisms of P.marinus infection and in testing the role of environmental stressors, such as heavy metals, which are known to stimulate apoptosis or programmed cell death on host-parasite interactions. Students involved in this project would learn methods of maintenance of P.marinus culture and primary cultures of oyster immune cells (hemocytes), determination of the proportions of apoptotic, necrotic and viable cells using FACS cell sorter, measurements of activities of apoptotic enzymes (such as caspases) as well as methods of in vivo and in vitro infections of oysters with P.marinus.  In both projects, students gain experience using research techniques that may be applied to nanoscale science research focused on problems in biology and medicine.

Fluorinated Molecular Tweezers with Extended Arene Tethers.  Faculty Advisor:  Markus Etzkorn, Assistant Professor, Department of Chemistry. Since Whitlock’s seminal work on synthetic molecular tweezers, a broad variety of these functional devices has been obtained.  Almost all known molecular tweezers rely to a large degree on p-p stacking and p-cation interaction to bind electron-deficient arenes and cations, respectively. Fluorine substituents in the pincer subunit invert the molecular electrostatic potential in the tweezer’s binding cavity as demonstrated experimentally by Korenaga thus furnishing hosts for electron-rich species, in particular anions. Etzkorn’s laboratory targets fluorinated molecular tweezers of type I - III in a convergent synthetic approach from a tether and fluoroarene library to yield novel efficient and selective molecular receptors for sensing, even sequestering biologically relevant or environmentally hazardous anions. Furthermore, tether-modified fluorinated molecular tweezers will be studied for self-assembly into nanostructure materials, e.g., nanowires.  Undergraduate students will be engaged in an interdisciplinary research project that thoroughly exposes them to organic and supramolecular chemistry.  They will acquire preparative skills in the laboratory as they synthesize novel compounds and gain hands-on experience in modern analytical techniques.  The self-assembly of all new target compounds will be studied by concentration- and temperature-dependent NMR and UV spectroscopy, respectively.

Single Crystal X-Ray Analyses of Various Molecular Building Blocks for Nanomaterials.  Faculty Advisor:  Daniel Jones, Associate Professor, Department of Chemistry.  The Jones laboratory uses the technique of single-crystal X-ray diffraction to determine the detailed molecular structure of chemical compounds. Because this is a completely general method, it can be applied to almost any compound of chemical interest, including nanomaterials.  Thus single crystal X-ray analysis is an important tool in many different areas of research. Dr. Jones has directed many undergraduate students in determining a substance's structure by X-ray methods.  Students have been involved in all phases of the technique including: 1) the preparation of suitable crystals for study, 2) preliminary X-ray investigation for the determination of crystal quality and lattice type, 3) collection of high accuracy intensity data on an automated X-ray diffractometer, and 4) reduction and analysis of the data utilizing high-speed computers.

Rational Organization of Nanoscale Catalysts for Multi-Electron Transfer.  Faculty Advisor:  Sherine Obare, Assistant Professor, Department of Chemistry. Research in the Obare group focuses on designing and establishing new fabrication procedures toward uniform size- and shape-controlled metallic and semiconductor nanomaterials in the 1-2 nm size range. Metallic, bimetallic and semiconductor nanomaterials have unique and tunable electrochemical, optical, magnetic and catalytic properties in the 1-2 nm size range that remain unexplored due to the difficulty in making uniform materials in this size range. Obare’s ability to design and fabricate materials in this size range will enable an understanding of the structure property relationships.  A major thrust is to find ways by which the nanomaterials are used in multi-electron transfer processes. An advantage of systems that transfer multiple electrons is that they avoid high-energy radicals, allow reactions to proceed under mild conditions, and in some cases, are capable of reactions inaccessible to systems that only transfer single electrons. Multi-electron processes are essential for several fields including biological processes. The Obare group has recently demonstrated that their fabricated materials transfer multiple electrons and are capable of splitting H2O to H2, small molecule activation, and environmental remediation.  Unlike molecular multi-electron transfer systems, nanostructures offer three essential features (a) high surface area to volume ratios to achieve high reactivities, (b) design flexibility to allow modifications of reactivities, and (c) the flexibility of surface modification ensures resistance to surface restructuring and enables promotion of specific transformations while retaining all the key advantages of heterogeneity.

Syntheses and Complexation Studies of New Bis(thione) Ligands. Faculty Advisor:  Daniel Rabinovich, Professor, Department of Chemistry.The Rabinovich laboratory has recently prepared the first member of a new family of strongly electron-donating bis(thione) ligands, 1,2-bis(mercaptoimidazolyl)xylene (o‑BmxMe). Our initial survey of its reactivity has lead to the isolation of several coordination complexes, including homoleptic Group 11 metal derivatives, [M(o‑BmxMe)2]X (M = Cu, Ag), neutral cadmium(II) and mercury(II) compounds of general formula (o‑BmxMe)MX2 (M = Cd, Hg) and a fascinating series of homoleptic lead(II) derivatives [Pb(o‑BmxMe)2]X2 that feature unexpected metal-arene interactions.  We intend to expand these initial studies in multiple ways.  NanoSURE participants will be involved in the preparation of additional new ligands displaying different substitution patterns (e.g., the meta- and para- isomers), different ring substituents (e.g., But), or different donor groups (e.g., Se).  They will then use these new ligands to synthesize complexes aimed at better understanding the coordination preferences of toxic heavy metals such as cadmium, mercury and lead in sulfur-rich environments and the potential development of new antibacterial agents containing copper or silver.

Colloidal silica nanophosphors.  Faculty Advisor: Thomas Schmedake, Assistant Professor, Department of Chemistry.  The Schmedake group has developed a simple method to generate nearly monodisperse, luminescent, sub-micron silica spheres via a simple process without the subsequent addition of inorganic or organic dyes (Fig. 1).  The luminescent colloidal silica spheres are grown via co-condensation of aminopropytriethoxysilane (APTES) and tetraethoxysilane in basic ethanolic solution, followed by calcination at high temperature in air.  The technique provides bright luminescent materials similar to the class of “metal-free white phosphors” described by Mike Sailor, and coworkers.  The significant finding of our work is that this material can now be grown in a self-assembled, monodisperse, sub-micron spherical structure.  The probable low bio-toxicity, bright tunable emission, and high monodispersity of these spheres, coupled with cheap and scalable processing may place these spheres at the forefront of basic and applied luminescent colloidal silica research.  Fluorescent labeling of monodisperse spheres is a very active area of research, driven by applications in optics/photonics, solid-state lighting, biotechnology, and sensing.  We anticipate that the inherently luminescent spheres produced via this process could be used in many of these applications.  Recently we have succeeded in modifying this procedure to make luminescent mesoporous colloidal silica spheres.  The resulting spheres have a surface area exceeding 1000 m2/g.  Depending on calcination conditions, luminescence lifetimes ranging from nanoseconds to seconds are observed.  The resulting spheres have potential for photochemical applications due to their uniform pore size, high surface area, low cost, and long lifetime photo-physics.  Preliminary results suggest that photo-induced reductive electron transfer from the luminescent colloidal silica spheres is possible.  An undergraduate researcher will fabricate monodisperse mesoporous silica spheres and then derivatize them with APTES.  Then the spheres will be calcined and the quantum yields will be obtained.  The student will vary this procedure several times to determine the fluorescence properties as a function of APTES concentration and calcination conditions.  Quantum yields are determined using an indexed match solution of the spheres and using the Jobin-Yvon Fluorolog 3 fluorescence spectrometer with TCSPC lifetime capability.

Micro/Nano Robot Research.  Stuart Smith, Professor, Department of Mechanical Engineering and Engineering Science. The Smith laboratory is trying to manufacture miniature robots for assembly of micro and nano –meter sized devices.  Development of such a machine requires research across a broad range of disciplines incorporating micro-mechatronic design, micro-sized component manufacture and the design and testing of micro-grippers. It is envisaged that micro gripper design and manufacture will form the basis of a summer REU study. Currently, gripper ‘fingers’ utilize quartz cantilever oscillators with thin rods (less than 1/10 of a human hair in diameter) attached at the free end.  A major goal will be to attempt scaling the current designs to be a factor of 10 smaller. Additionally, we will be seeking alternative manufacturing processes.  This REU project will provide an opportunity for the student to assess and utilize modern micro manufacturing processes. Additionally, the foundation of design will require background knowledge of mechanical engineering as a function of scaling.

Development of a Combined AFM and Fluorescence Microscope.The combination of atomic force microscopy and fluorescence microscopy capabilities to generate spatially registered mechanical and functional information on single cells and molecules is garnering much attention.  Studies reveal that external mechanical forces have considerable influence on molecular and cellular processes and that measurement of cellular mechanical properties can provide diagnostic information about the state of the cell.  Smith has developed a combined single molecule fluorescence and force spectroscopy measurement system that overcomes current limitations in commercial systems by incorporating precision positioning technology to enable traceable force measurements.  Mechanical and viscoelastic properties of live cells have been measured with a variety of methods, including scanned probe microscopy (SPM) and far-field optical confocal microscopy.  What is lacking in these studies are (1) a precise quantifiable measure of the mechanical properties without one or more extrapolations, and (2) a method that can find utility across a broad range of cells.To meet these project aims, Smith works with an interdisciplinary team of investigators.  Within the scope of this project, multidisciplinary expertise from both physics and mechanical sciences will be incorporated to derive techniques for extraction of quantitative properties, covering the fields of optical and mechanical interactions of physical probes across molecular and cellular scales.

Mechanical Properties and Microstructure Engineering of Advanced Materials.  Faculty Advisor: Qiuming Wei, Assistant Professor, Department of Mechanical Engineering and Engineering Science. Metals and alloys with ultrafine grained (UFG) and nanocrystalline (NC) microstructures exhibit a number of novel properties. The most famous is the Hall-Petch relation which predicts that the strength of a metal is proportional to the inverse square root of its grain size. Recently, investigators have uncovered many new behaviors of UFG and NC metals. For example, strategies to improve the ductility of UFG/NC metals have been proposed and exploited. It has also been observed that the strain rate effect on the mechanical strength of UFG/NC metals has some unique trend depending on the lattice structure of the metals. Such observations are bringing out new ways to produce UFG/NC metals and alloys with desired properties. In Dr. Wei's research group, UFG/NC metals and alloys are processed by various technical routes, including powder metallurgy (high-energy ball milling followed by consolidation), severe plastic deformation (SPD), etc. Microstructure engineering for the processing of multi-phase UFG/NC alloys is of particular interest to his group.

In a second project, many materials applications pose the need for knowledge about the materials mechanical behavior under high rate (dynamic loading). Quasi-static loading means the strain rate is within the range of 10-4 s-1-100 s-1; dynamic loading means the strain rate is larger than this range. A well defined technique for the measurement of dynamic behavior of materials is the Kolsky Bar (or Split-Hopkinson Pressure Bar--SHPB) systems. Dr. Wei's lab has a conventional SHPB system under construction. Students will also be involved in building a miniature SHPB in his lab.

Finally, the quest for scaling towards smaller devices requires knowledge of the materials behavior at micrometer and nanometer scales. Assumptions that small scale materials behavior being comparable to large scale properties have been proven dubious, inaccurate or even completely erroneous. In light of this, direct probing of mechanical properties of materials at micro/nanometer scale is necessary. Dr. Wei's group is working on using a modified nano-instrumentation to probe the stress-strain behavior of materials at the micro/nano scale.

Chemical Vapor Deposition and Mechanical Testing of 1D Nanostructures.  Faculty Advisor:  Terry Xu, Assistant Professor, Department of Mechanical Engineering and Engineering Science.Dr. Xu’s research group is interested in synthesis and characterization of one-dimensional (1D) functional nanomaterials, understanding their mechanical and physical properties, and exploration of their applications in thermoelectric and solar energy conversion. There are two on-going projects: (1) Boron-based 1D nanostructures for high temperature thermoelectric energy conversion. The research efforts include the synthesis of new boron-based 1D nanostructures using chemical vapor deposition (CVD); the study of thermal stability of as-synthesized 1D nanostructures at various environmental conditions; and the investigation of thermoelectric properties through a collaborative work with experts in the fields of transport property measurement and condensed matter physics. The fundamental understanding of thermal stability behavior and thermoelectric mechanism will provide invaluable information to guide the design and synthesis of novel boron-based thermoelectric 1D nanostructures. (2) Study of mechanical properties of 1D nanostructures using Atomic Force Acoustic Microscopy (AFAM). The research efforts include experimental measurement of elastic properties of 1D nanostructures by AFAM; analytical and numerical investigation of tip-sample interaction and sample-substrate contact mechanics; and comparison of the results with those obtained by nanoindentation. The goal of this project is to develop an AFM-based technique that is capable of quantitatively measuring mechanical properties of nanoscale materials. Currently, students with different academic background such as materials science, solid mechanics and mechanical engineering are involved in these two projects.  REU students from engineering sub-disciplines or engineering and physics may participate in this project.

Nanostructures and Nanomaterials for Electronic and Photonic Applications.  Faculty Advisor:  Haitao Zhang, Assistant Research Professor, Department of Mechanical Engineering and Engineering Science.The Zhang laboratory is interested in nanomaterials and nanostructures for electronic and photonic applications. With at least one-dimension in nanometer range, nanoscale materials and structures have significantly different properties compared to their corresponding bulk forms, and have a variety of potential applications. This research work covers synthesizing metal and metal oxide nanomaterials and nanostructures using both chemical vapor deposition (CVD) and physical vapor deposition, characterizing material structures, and exploring their optical and electronic properties. REU students will be involved in these aspects of his laboratory and may work collaboratively with another REU student from the Xu laboratory.  Current research projects include laser induced CVD growth of self-assembled metal nanogratings and pulsed laser deposition of metal oxide thin films and nanostructures for applications in energy (e.g. solar cell) and bio/chemical sensing.

Chemistry Inside Nano-Droplets One Molecule at a Time.  Faculty Advisor:  Ana Jofre, Assistant Professor, Department of Physics.The Jofre laboratory studies the kinetics of single molecules encapsulated within optically trapped femtoliter volume chemical containers.  The containers, which we call “hydrosomes”, are stable aqueous nanodroplets (» 700 nm diameter) suspended in a low index-of-refraction fluorocarbon medium.  The fluorocarbon medium is immiscible with water and has an index of refraction lower than that of water; therefore droplets (“hydrosomes”) suspended in this medium are stable and optically trappable.  A tightly focused infra-red laser (“optical tweezers”) holds a single hydrosome within a confocal observation volume created by a second laser, a visible probe beam, which fluorescently excites the molecule contained within the hydrosome.  The fluorescence emission of the encapsulated molecule is collected by avalanche photo-diodes and recorded until the molecule photobleaches.  Figure 2 shows a conceptual schematic of an optically trapped hydrosome, probed with a second laser.   The most exciting advantage of using hydrosomes over other femtoliter containers such as liposomes is that hydrosomes spontaneously fuse when they are brought into contact, thereby facilitating mixing of the encapsulated components.  This feature enables the study of chemical reactions on a single molecule level, as two hydrosomes containing distinct species can be optically manipulated and fused.  This will allow direct observation of transient states and reaction pathways.  Figure 3 shows a time-sequence of controlled fusion between two hydrosomes by optical manipulation.