The University of Maryland MRSEC grants ended in September 2013 after 17 years of successful operation. This site remains as a history of the center, but will not be actively maintained.

Undergraduate/Graduate Programs

2004 REU Projects

Thin film growth and characterization of Dilute magnetic semiconductors (DMS)

Dilute magnetic semiconductors (DMS) have attracted a great deal of attention in the recent past due to the exciting features they offer for spintronic studies and possible applications. The underlying Physics is still intriguing, nonetheless, challenging to probe in to. Several wide-bang-gap systems doped with small amounts of magnetic impurities turn in to correlated magnetic systems. ZnO and TiO2 dope with Mn and Co have been studied for interesting magnetic behavior even though the origin of magnetic behavior is not clearly understood. The term, _spintronics_, refers to utilizing the spin-degree of freedom of an electron apart from its charge-degree-of-freedom. It is desirable to produce materials with tunable electrical and magnetic properties to envisage applications in this new field of study. Thin film growth offers a great deal of opportunity to explore new oxide based wide-band-systems amenable to magnetic ion (transition and rare-earth) doping: search for new DMS systems. Pulsed laser deposition (PLD), a versatile technique to realize epitaxial/highly oriented thin films of oxide electronic materials would be used to grow high quality thin films of new doped systems (ex., Co/Mn/Mo/Ho doped CuAlO2. AgGaO2, HfO2 systems). Structural characterization (using X-ray diffraction and Rutherford backscattering (RBS)), electrical resistivity (as a function of temperature (4-300K)) and magnetic field and magnetization (using a magnetometer) would be carried out on thin films grown under different conditions. An important aspect of study would be the microstructure-physical property correlation. Atomic Force Microscopy (AFM) tool will be used for microstructural analysis of the PLD grown films. Work involves: Thin film growth using pulsed laser deposition (PLD), XRD, RBS, AFM, electrical and magnetic property studies.

Nanopatches: Electrical Properties of Single Layers of Dichalcogenide Compounds

Self-assembled zero-dimensional (e.g. quantum dot) and one-dimensional (e.g. nanotube, nanowire) nanomaterials have received much attention, but studies on two-dimensional nanomaterials are lacking. We are using a variety of methods to attempt to prepare single three-atom-thick layers of the layered transition-metal dichalcogenide compounds on insulating substrates so they may be studied by electrical measurements. Transition-metal dichalcogenides are an interesting class of layered materials which comprise semiconductors, metals, superconductors, and charge-density-wave materials. Two-dimensional versions of these materials would allow the study of new two-dimensional electron systems with properties radically different than found in semiconductor heterostructures. The REU student will be involved in materials preparation and characterization, imaging with scanning electron microscopy and scanning probe microscopy, device fabrication (electron-beam lithography), and electrical measurements of devices at cryogenic temperatures.

Directed evolution of semiconductor surfaces through spatial patterning and growth or sublimation.

The continued drive toward devices of ever-smaller dimensions and simultaneously higher densities is expected to exceed the capabilities of existing photolithographic and direct-write technologies within the next several years. Continued progress will require a new paradigm. One of the most promising is that of directed self-assembly, i. e. inducing a spontaneous ordering of atoms or molecules into useful structures using some sort of spatially modulated field or template. The experiments use both epitaxial growth of ultra thin semiconductor films on patterned substrates and sublimation from patterned substrates to control the structures which develop. This project will include both involvement in atomic force microscopy measurements of the structures, and analysis of the results.

Self-Sorting Polymers

Self-Sorting - the ability to efficiently distinguish self- from non-self even within complex mixtures – is commonplace in Natural and Biological Systems, but is still rare in designed supramolecular systems. We have recently begun to explore the ability of complex ensembles of molecules to undergo high fidelity self-sorting inorganic and aqueous solution by non-covalent interactions (e.g. hydrogen bonds, metal-ligand interactions, electrostatic interactions, and the hydrophobic effect). We are currently learning how to control the behavior of these molecular ensembles through the use of suitable stimuli (e.g. light, electrochemistry, or the addition of exogenous components). In this summer project students will use synthetic organic chemistry to prepare oligomeric and polymeric versions of "molecular clips" and study their self-sorting in chloroform solution. Questions to be addressed include: 1) Do different length oligomers selectively recognize oligomers of identical length? 2) Do oligomers of a single handedness recognize oligomers of identical or opposite handedness?

Students will be exposed to the techniques of needed for their synthesis and characterization including 1H NMR spectroscopy, gel permeation chromatography, and UV/Vis spectroscopy.

Self assembled monolayers of bifunctional Silane molecules : An x-ray photoelectron spectroscopic (XPS) investigation

Research in organized molecular assemblies has always been multidisciplinary encompassing physics, chemistry and biology. In applications such as sensing or molecular electronics, metal–organic interfaces and metal-organic-metal sandwich structures obviously have an important role. So the formations of monolayers with functional groups, which can attach other metals or molecules, are particularly important for these applications.

In the proposed project, a systematic study of the monolayer formation of bifunctional silane molecules on various surfaces is proposed. The idea of this study is to investigate how the end groups determine the self assembly process and how well do they order on various surfaces. The availability and the chemical nature of free terminal functionality will be studied by attaching nanoparticles to these well ordered surfaces. In this project the REU student will get training for the use of x-ray photoelectron spectrometer and other surface characterization techniques.

Interactions between magnetic nanoparticles and biological (or their equivalent) molecules

The cells in most biological molecules react to a magnetic field, but they are not magnetic (they are diamagnetic). This means that a large magnetic field is needed to have them interact. In our group, we are looking at the possibility of mixing magnetic nanoparticles with the biological cells in order to reduce the magnitude of the field needed for interaction. We have shown that we can reduce it by at least an order of magnitude. We have found preliminarily that this also depends on what organic molecule covers the magnetic particle. The organic molecule is needed to make the nanoparticles mix with the biological molecules. In this project, we will experiment with different organic molecules to see how they influence the effect of the magnetic nanoparticles.

Vesicles in Jell-OTM: Trapping Self-Assembled Nanocontainers within Biopolymer Gels

In our lab, we “play” with nanoscale structures that mimic those existing in nature. One such structure of interest to us is that of vesicles, which are formed by the self-assembly of soap-like molecules in water. Vesicles are hollow nanoscale structures covered by a bilayer membrane and can thus be viewed as primitive models for biological cells. The hollow structure of vesicles allows them to be used as nanocontainers for the transport and delivery of drugs. However, vesicles are fragile structures that are disrupted easily by changes in pH or by the addition of salt. There is thus a need for a method to transport vesicles in a stable and robust form to their application site. In this context, we are exploring the possibility of trapping vesicles within biopolymer gels. For example, we have recently shown that vesicles can be trapped in a gelatin gel (Jell-OTM) and can be subsequently released by heating the gel. The present REU project will further explore the use of biopolymer gels to trap vesicles. Furthermore, we will examine the controlled release of molecules present inside the vesicles. We are also interested in ways to tune the release rate using external fields such as light or by the addition of enzymes.

Dynamics of biopolymer networks

We will investigate the dynamics of biopolymer networks using hologrpahic laser tweezers and confocal microscopy techniques. The aim is to understand how biopolymers, which form the scaffolding of cells (such as actin), generate forces and assist in cell motion e.g. during wound healing. The student will learn to work with laser tweezers, confocal microscopy, and assist in the development of image processing techniques. The work will involve biological samples ranging from pure proteins to bacterial model systems, with a focus to be determined depending on qualifications.

Dynamics of granular flows

The flow properties of a vertically vibrated mixture of particles of different size will be studied experimentally. We find that even in a mixture, different size particles flow at different speeds. In addition, the shape of convective flows is very sensitive to boundary conditions. Using high speed imaging and particle tracking techniques we will systematically investigate flow speeds and flow patterns in a vertically vibrated mixture of granular matter.

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