Laboratory for Surface Modification (LSM)

Seminars Archives

August 2017 | September 2017 | October 2017

Friday, September 01, 2017
Earth-Abundant Thin Film Photovoltaics: Improving Performance for Industrial Applications (Followed by a Discussion of Careers in Industry)
Richard Haight
IBM TJ Watson Research Center
1:30 PM WL 231

The multi-elemental material, CZTS,Se- Cu2ZnSn(SxSe1-x)4 holds considerable promise as an Earth-abundant, non-toxic thin film light absorber in solar cells. But significant challenges to increasing output voltage and overall efficiency have hampered its utilization for large scale power generation. In this talk I will give a brief overview of photovoltaics (PV) in general, including thin film technologies. I will describe our efforts to understand the bulk, grain boundary and interface properties that impact CZTS,Se PV device performance and discuss a unique solution, based on a modification of the back contact that has produced a nearly 200 mV increase in open circuit voltage (Voc) while maintaining near-record efficiency. This work has culminated in our development of a monolithic, 1.85cm2 serially connected device that generates 5.7V under 1 sun and >2V under office light and is capable of powering autonomous devices for use in, for example, the “Internet-of-Things”. For the second part of my talk I will discuss careers in industry and open the floor to undergraduate, graduate students and post-docs for all questions and lively conversation.
Thursday, September 07, 2017
Advanced Microscopy for Probing the Structure and Properties of Complex Materials
Nan Yao
Science and Technology of Materials
Princeton University
12:00 Noon CHEM 260

With the latest development in nanotechnology, advanced microscopy continues to increase its importance as the most powerful engine for discovery and fundamental understanding of nanoscale phenomena and structures in complex materials. This talk describes our recent development at Princeton in probing structure and properties of various materials using an array of microscopy techniques, including double Cs corrected high-resolution electron imaging, ion beam fabrication, 3D X-ray microscope, CryoEM, and in-situ techniques. A few diverse examples will be presented including topological insulator heterostructures, natural quasicrystal, functional materials, dental zirconia crowns, and single proteins particles, etc.
Thursday, September 14, 2017
Tetrahedral Transition Metal Chalcogenides as Functional Inorganic Materials
Efrain Rodriguez
Chemistry and Biochemistry
University of Maryland
12:00 Noon CHEM 260

Transition metal dichalcogenides (TMDs) have resurfaced as functional inorganic materials for their diverse applications including transistor-type devices, sensors, and hydrogen evolution catalysis. We present a more recent category of layered materials we term tetrahedral transition metal chalcogenides (TTMCs) that display different functional behavior from TMDs. These layered TTMCs are built of square metal lattices with electron rich transition metals such as Fe(II) and Co(II) in tetrahedral coordination. Due to the weak van der Waals interactions that hold the chalcogenide layers together, intercalation chemistry in aqueous solutions can be utilized to prepare new phases with interesting magnetic and electronic properties including ferromagnetism and superconductivity. Our group’s strategy has been to incorporate guest species into the TTMC hosts to tune the physical properties. We construct a simple bonding model to interpret the electronic structure of the square metal lattice in TTMCs, and use it to predict the properties of future phases. Furthermore, we demonstrate that these layered metal chalcogenides could be made into novel two-dimensional (2D) materials either as single layers or as heterostructures with other 2D motifs.
Thursday, September 21, 2017
Wetting In Color Kit (WICK)
Joanna Aizenberg
Chemistry and Chemical Biology
Harvard University
12:00 Noon CHEM 260

“Colorimetric litmus tests such as pH paper have enjoyed wide commercial success due to their inexpensive production and exceptional ease of use. Many such techniques operate based on a chemical tag whose optical absorption or fluorescence spectrum changes in response to a specific analyte. Specificity is an advantage in this case, but limits the variety of substances for which such a sensor can be used. On the other hand, the use of structural color has no inherent specific chemical requirements. Thus, tunable structural color carries the potential for broad applicability in colorimetric sensing.

We developed a technique for patterning multiple chemical functionalities throughout the inner surfaces of a highly ordered iridescent 3D photonic crystal, generating complex wettability patterns. When immersed in a liquid, the pores are selectively infiltrated in a unique spatial pattern, creating an optical fingerprint of that liquid through the color contrast between wetted and non-wetted regions. Using this platform, we have illustrated multilevel encryption, with selective decoding by specific liquids. A remarkable selectivity of wetting, combined with the easily detectable optical response, allow us to also exploit this system as a colorimetric indicator for liquids. Moreover, by functionalizing the surfaces with an environment-sensitive groups and observing the changes in the wetting behavior, we can follow the history of the exposure of the material to a certain stimulus. WICK may find applications in a broad range of technologies, including a convenient and direct method for liquid detection and encryption, or as a tag for low-cost monitoring of tampering or material aging.”
Thursday, September 28, 2017
Tailoring Metallic Nanostructures for Electrocatalytic Applications
Chao Wang
Chemical and Biomolecular Engineering
John Hopkins University
12:00 Noon CHEM 260

Electrocatalysts play a vital role in the development of renewable energy technologies based on electrical-chemical energy conversions, such as fuel cells, electrolyzers, photoelectrochemical solar cells and metal-air batteries. Nanomaterials have emerged as promising candidates for many of such electrocatalytic applications, but the performance still needs to be substantially improved to meet the technical and cost-effectiveness standards for practical implementations. This usually requires comprehensive understanding of the structure-property relationships of the electrocatalysts, which traditionally relies on the model catalyst studies of well-defined extended surfaces. Albeit the progress that has been made, knowledge gaps are also realized to be present between the extended surfaces and nanomaterials, probably not only due to the intrinsically different crystalline and surface structures at these two extreme size dimensions, but also caused by the challenges in probing the active sites and reaction pathways on nanostructured materials.

This presentation aims to discuss two examples of our efforts on tailoring metallic nanostructures for electrocatalytic applications: i) highly dense Cu nanowires for the electroreduction of CO2 and CO, and ii) Co/Pt core/shell nanoparticles as sustainable electrocatalysts for the oxygen reduction reaction (ORR). These nanostructures are characterized by combining electron-based microscopic imaging, diffraction and elemental mapping, while the surface structures are probed by using surface-specific adsorption/desorption of small molecules (e.g., COad and OHad). The gained structural information is correlated to the measured catalytic activity, durability and/or selectivity, based on which computational simulations are further performed to understand the established structure-property relationships, depict the active sites and reveal the catalytic enhancement mechanisms. Our work highlights the great potential of tailoring nanostructured materials toward the advancement of renewable energy technologies.

You may also view a summary of past and upcoming seminars.