Multifunctional virus scaffolds fore energy applications : nanomaterials synthesis and two dimensional assembly

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.Includes bibliographical references.Biological systems inherently posses the ability to synthesize and assemble nanomaterials with remarkable precision, as evident in biomineralization. These unique abilities of nature continue to inspire us to develop new approaches of nanobiotechnology to integrate advanced materials into medicine and electronics. Particularly, peptides are believed to play an important role in biotemplating and biological self-assembly. In order to understand the interface between inorganic materials and peptides and realize biological self-assembly, this work adopted M13 virus as a model system. The genetic engineering of M13 viruses enables us to grow various nanomaterials and achieve virus monolayer assembly on charged polyelectrolyte multilayers. The fundamental understanding and new discoveries obtained by this work can mature into an engineering discipline demonstrating that biological approaches may represent a new paradigm to provide novel technological advantages. The use of a biological template for a nanostructured battery electrode ramps up the device's performance and scales down its overall size. This work presents a new way of exploiting biological entities for the bottom-up assembly of battery devices by utilizing biological self-assembly and biotemplating. Viruses are genetically engineered such that they function as a toolkit for constructing the battery.by Ki Tae Nam.Ph.D

Metasurface zone plate for light manipulation in vectorial regime

Fresnel zone plates consisting of multiple concentric rings have been realized by tailoring amplitude, phase and polarization of light, but conventional Fresnel zone plates require totally different materials to control each property reducing light controllability. Here, a metasurface zone plate in which rings are composed of subwavelength antenna arrays is proposed to individually control amplitude, phase and polarization by the consistent material platform of metasurfaces. Hence, versatile degrees of freedom can be achieved to focus electromagnetic waves. We verify that dielectric metasurfaces can generate arbitrary poloarization states to cover the whole Poincare sphere in the visible regime, allowing light manipulation in the vectorial regime, which is not feasible by a conventional single liquid crystal film. Experimental demonstration of a polarization-modulated metasurface zone plate confirms the functional capability of dielectric metasurfaces exhibiting higher focusing efficiency than amplitude-modulated zone plates.11Ysciescopu

Waveguide-Type Head-Mounted Display System for AR Application

Currently, a lot of institutes and industries are working on the development of the virtual reality and augmented reality techniques, and these techniques have been recognized as the determination for the direction of the three-dimensional display development in the near future. In this chapter, we mainly discussed the design and application of several wearable head-mounted display (HMD) systems with the waveguide structure using the in- and out-couplers which are fabricated by the diffractive optical elements or holographic volume gratings. Although the structure is simple, the waveguide-type HMDs are very efficient, especially in the practical applications, especially in the augmented reality applications, which make the device light-weighted. In addition, we reviewed the existing major head-mounted display and augmented reality systems

Effects of paramagnetic fluctuations on the thermochemistry of MnO (100) surfaces in the oxygen evolution reaction

We investigated the effects of paramagnetic (PM) fluctuations on the thermochemistry of the MnO(100) surface in the oxygen evolution reaction (OER) using the "noncollinear magnetic sampling method \textit{plus} $U$" (NCMSM$+U$). Various physical properties, such as the electronic structure, free energy, and charge occupation, of the MnO (100) surface in the PM state with several OER intermediates, were reckoned and compared to those in the antiferromagnetic (AFM) state. We found that PM fluctuation enhances charge transfer from a surface Mn ion to each of the intermediates and strengthens the chemical bond between them, while not altering the overall features, such as the rate determining step and resting state, in reaction pathways. The enhanced charge transfer can be attributed to the delocalized nature of valence bands observed in the PM surface. In addition, it was observed that chemical-bond enhancement depends on the intermediates, resulting in significant deviations in reaction energy barriers. Our study suggests that PM fluctuations play a significant role in the thermochemistry of chemical reactions occurring on correlated oxide surfaces.Comment: Maintext: 15 pages, 3 figures 2 tables; SI: 3 pages, 2 figure

Coordination tuning of cobalt phosphates towards efficient water oxidation catalyst

The development of efficient and stable water oxidation catalysts is necessary for the realization of practically viable water-splitting systems. Although extensive studies have focused on the metal-oxide catalysts, the effect of metal coordination on the catalytic ability remains still elusive. Here we select four cobalt-based phosphate catalysts with various cobalt-and phosphate-group coordination as a platform to better understand the catalytic activity of cobalt-based materials. Although they exhibit various catalytic activities and stabilities during water oxidation, Na2CoP2O7 with distorted cobalt tetrahedral geometry shows high activity comparable to that of amorphous cobalt phosphate under neutral conditions, along with high structural stability. First-principles calculations suggest that the surface reorganization by the pyrophosphate ligand induces a highly distorted tetrahedral geometry, where water molecules can favourably bind, resulting in a low overpotential (similar to 0.42 eV). Our findings emphasize the importance of local cobalt coordination in the catalysis and suggest the possible effect of polyanions on the water oxidation chemistry.

Estimating remineralized phosphate and its remineralization rate in the northern East China Sea during Summer 1997 : a snapshot study before Three-Gorges Dam construction

© The Author(s), 2016. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Terrestrial, Atmospheric and Oceanic Sciences 27 (2016): 955-963, doi:10.3319/TAO.2016.01.24.01(Oc).The northern East China Sea (a.k.a., “The South Sea”) is a dynamic zone that exerts a variety of effects on the marine ecosystem due to Three-Gorges Dam construction. As the northern East China Sea region is vulnerable to climate forcing and anthropogenic impacts, it is important to investigate how the remineralization rate in the northern East China Sea has changed in response to such external forcing. We used an historical hydrographic dataset from August 1997 to obtain a baseline for future comparison. We estimate the amount of remineralized phosphate by decomposing the physical mixing and biogeochemical process effect using water column measurements (temperature, salinity, and phosphate). The estimated remineralized phosphate column inventory ranged from 0.8 to 42.4 mmol P m-2 (mean value of 15.2 ± 12.0 mmol P m-2). Our results suggest that the Tsushima Warm Current was a strong contributor to primary production during the summer of 1997 in the study area. The estimated summer (June - August) remineralization rate in the region before Three-Gorges Dam construction was 18 ± 14 mmol C m-2 d-1.T. Lee was supported by 2-Year Research Grant of Pusan National University. H.-C. Kim was partly supported by KOPRI project (PG15010). I.-N. Kim was partly supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2015R1C1A1A01052051). K.-T. Park was partly supported by KOPRI project (PE17010). J.-H. Kim was partly supported by the program of “Management of Marine Organisms Causing Ecological Disturbance and Harmful Effects” funded by KIMST/MOF. A.M. Macdonald’s contribution was supported by NOAA grant: #NA110AR4310063 and NSF grant: #OCE-1059881

Tidal Effects on Intermediate Waters: A Case Study in the East/Japan Sea

Although tides are believed to be the most important source for diapycnal mixing in the ocean, few studies have directly simulated open-ocean circulation including tides. Because the East/Japan Sea (EJS) has been considered to be a “miniature ocean,” tidal effects on the intermediate water of the EJS are investigated by using an eddy-resolving ocean general circulation model that can take account of M2 and K1 tides as well as oceanic flows. The simulated temperature and salinity in the intermediate layer are significantly improved by including tides. The improvement results from the combined effect of two internal tides. The M2 internal tide, propagating into the interior of the EJS, enhances vertical mixing and brings watermass characteristics closer to those observed. The K1 internal tide, trapped along the coast, induces southwestward flow along the Russian coast in the upper layer and thereby enhances the so-called Liman Current, which transports fresh waters with density conducive to the ventilation of intermediate waters in the EJS

Chirality control of inorganic materials and metals by peptides or amino acids

Chirality exists everywhere in nature and may be one of the most important features in biological systems. The chirality of amino acid molecules is transferred to the peptide sequences, determining the secondary and further three-dimensional structures. As a result, even the macroscopic chirality observed in many living features can be controlled by the peptide sequence. Interestingly, recent studies have shown that achiral inorganic materials and metals, according to the crystallographic point group, can develop chiral morphologies that are precisely controlled by the amino acids and peptides. As a result, strong chiral optical responses can be generated even at visible wavelengths. In this review, we have highlighted recent pioneering examples to show the enantioselective interactions between inorganic materials/metals and amino acids/peptides and discussed the underlying mechanisms.Y