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Program Highlights for year 2015

Seeded Growth of Highly Crystalline Molybdenum Disulfide Monolayers at Controlled Locations

Monolayer molybdenum disulfide (MoS2) is a 3-atom thick material with a direct band gap, making it of interest for fundamental science as well as applications in optoelectronics and chemical sensing. Our innovation is a scalable method for “seeded growth” of high quality monolayer MoS2 at controlled locations, which is an important advance towards useful applications of the material.

Fractal Mechanical Structures

How can we wrap a 3d object with a sheet of paper without folds? Wrapping implies the ability to stretch as much as bend.  Using concepts from fractal geometry, we have designed and realized a new class of materials with unprecedented control of stretchability and bendability to conformally wrap any shape or expand to nearly any predetermined shapes.


Research Experience for Undergraduates (REU): Celebration of the 600th REU Student at the Penn-MRSEC

In 2015 we will celebrate the arrival of our 600th REU student in our NSF-supported REU program. This program started in 1989 with a small grant that supported 5 minority students.

IRG-4 Plasmonic Enhancement of Upconversion in Nanorod/Nanophosphor Heterodimers

A central goal of IRG-4 is to use collective interactions between dissimilar nanocrystals to enhance the performance of their assemblies.

Here we demonstrate plasmonic enhancement of optical upconversion luminescence within nanorod-nanophosphor heterodimers (Fig 1a-c).

Using experiment and theory we are able to develop design rules for optimizing heterodimer geometry.

Understanding Plastic Deformation in Glasses from Single-Soft-Spot Dynamics

In crystalline materials, topologial defects such as dislocations mark flow defects, or “soft spots,” corresponding to local regions that are likely to rearrange due to thermal fluctuations or an applied load.  In disordered packings, it is extremely difficult to identify the corresponding soft spots.

Synthesis, self-assembly and response of glycodendrimers

Dendrimers are branched molecules of precise chemistry, and Janus-dendrimers are dendrimers that have two distinct faces, with unique chemistry corresponding to each face. Here, we made a library of carbohydrate containing glycodendrimers (GD) that self assemble into vesicles – a structure that mimics biological materials such as viruses.

Surface Alignment and Handedness of Chromonic Liquid Crystals

Chromonic liquid crystals (CLCs) are different from typical LCs used in displays, in part because they “live” in water and thus hold untapped potential for coupling LC phenomenology with biological media. Furthermore, CLCs twist very easily compared to bend and splay deformation, and the consequences of this giant elastic anisotropy are not well understood.

Graphene-Enhanced Ferroelectric Tunnel Junctions

Ferroelectric tunnel junctions exploit an ultrathin ferroelectric layer, 100,000 times thinner than a sheet of paper, so that electrons can "tunnel" through it. This layer resides between two metal electrodes that can reverse the direction of its polarization by applying electric voltage to it.