Nanopatterning of Recombinant Proteins and Viruses Using Block Copolymer Templates

The study of interfaces is important in understanding biological interactions, including cellular signaling and virus infection. This thesis is an original effort to examine the interaction between a block copolymer and both a protein and a virus. Block copolymers intrinsically form nanometer-scale structures over large areas without expensive processing, making them ideal for the synthesis of the nanopatterned surfaces used in this study. The geometry of these nanostructures can be easily tuned for different applications by altering the block ratio and composition of the block copolymer. Block copolymers can be used for controlled uptake of metal ions, where one block selectively binds metal ions while the other does not. 5-norbornene-2,3-dicarboxylic acid is synthesized through ringopening metathesis polymerization. It formed spherical domains with spheres approximately 30 nm in diameter, and these spheres were then subsequently loaded with nickel ion. This norbornene block copolymer was tested for its ability to bind histidine-tagged green fluorescent protein (hisGFP), and it was found that the nickel-loaded copolymer was able to retain hisGFP through chelation between the histidine tag and the metal-containing portions of the copolymer surface. Poly(styrene-b-4-vinylpyridine) (PS/P4VP) was also loaded with nickel, forming a cylindrical microstructure. The binding of Tobacco mosaic virus and Tobacco necrosis virus was tested through Tween 20 detergent washes. Electron microscopy allowed for observation of both block copolymer nanostructures and virus particles. Results showed that Tween washes could not remove bound Tobacco mosaic virus from the surface of PS/P4VP. It was also seen that The size and tunability of block copolymers and the lack of processing needed to attain different structures makes them attractive for many applications, including microfluidic devices, surfaces to influence cellular signaling and growth, and as a nanopatterning surface for organized adhesion

Confined lithium–sulfur reactions in narrow-diameter carbon nanotubes reveal enhanced electrochemical reactivity

We demonstrate an unusual electrochemical reaction of sulfur with lithium upon encapsulation in narrow-diameter (subnanometer) single-walled carbon nanotubes (SWNTs). Our study provides mechanistic insight on the synergistic effects of sulfur confinement and Li+ ion solvation properties that culminate in a new mechanism of these sub-nanoscale-enabled reactions (which cannot be solely attributed to the lithiation-delithiation of conventional sulfur). Two types of SWNTs with distinct diameters, produced by electric arc (EA-SWNTs, average diameter 1.55 nm) or high-pressure carbon monoxide (HiPco-SWNTs, average diameter 1.0 nm), are investigated with two comparable electrolyte systems based on tetraethylene glycol dimethyl ether (TEGDME) and 1,4,7,10,13-pentaoxacyclopentadecane (15-crown-5). Electrochemical analyses indicate that a conventional solution-phase Li-S reaction occurs in EA-SWNTs, which can be attributed to the smaller solvated [Li(TEGDME)]+ and [Li(15-crown-5)]+ ions within the EA-SWNT diameter. In stark contrast, the Li-S confined in narrower diameter HiPco-SWNTs exhibits unusual electrochemical behavior that can be attributed to a solid-state reaction enabled by the smaller HiPco-SWNT diameter compared to the size of solvated Li+ ions. Our results of the electrochemical analyses are corroborated and supported with various spectroscopic analyses including operando Raman, X-ray photoelectron spectroscopy, and first-principles calculations from density functional theory. Taken together, our findings demonstrate that the controlled solid-state lithiation-delithiation of sulfur and an enhanced electrochemical reactivity can be achieved by sub-nanoscale encapsulation and one-dimensional confinement in narrow-diameter SWNTs.Fil: Fu, Chengyin. University Of California Riverside; Estados UnidosFil: Oviedo, María Belén. University Of California Riverside; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Zhu, Yihan. Zhejiang University Of Technology; ChinaFil: von Wald Cresce, Arthur. U. S. Army Research Laboratory; Estados UnidosFil: Xu, Kang. U. S. Army Research Laboratory; Estados UnidosFil: Li, Guanghui. University Of California Riverside; Estados UnidosFil: Itkis, Mikhail E.. University Of California Riverside; Estados UnidosFil: Haddon, Robert C.. University Of California Riverside; Estados UnidosFil: Chi, Miaofang. Oak Ridge National Laboratory; Estados UnidosFil: Han, Yu. King Abdullah University Of Science And Technology; Arabia SauditaFil: Wong, Bryan M.. University Of California Riverside; Estados UnidosFil: Guo, Juchen. University Of California Riverside; Estados Unido

Identifying the components of the solid–electrolyte interphase in Li-ion batteries

The importance of the solid–electrolyte interphase (SEI) for reversible operation of Li-ion batteries has been well established, but the understanding of its chemistry remains incomplete. The current consensus on the identity of the major organic SEI component is that it consists of lithium ethylene di-carbonate (LEDC), which is thought to have high Li-ion conductivity, but low electronic conductivity (to protect the Li/C electrode). Here, we report on the synthesis and structural and spectroscopic characterizations of authentic LEDC and lithium ethylene mono-carbonate (LEMC). Direct comparisons of the SEI grown on graphite anodes suggest that LEMC, instead of LEDC, is likely to be the major SEI component. Single-crystal X-ray diffraction studies on LEMC and lithium methyl carbonate (LMC) reveal unusual layered structures and Li+ coordination environments. LEMC has Li+ conductivities of >1 × 10−6 S cm−1, while LEDC is almost an ionic insulator. The complex interconversions and equilibria of LMC, LEMC and LEDC in dimethyl sulfoxide solutions are also investigated

Correlating Li⁺ Solvation Sheath Structure with Interphasial Chemistry on Graphite

In electrolytes with unique electrochemical signature, the structure of Li⁺ solvation sheath was quantitatively analyzed in correlation with its electrochemical behavior on graphitic anodes. For the first time, a direct link between Li⁺ solvation sheath structure and formation chemistry of the solid electrolyte interphase (SEI) is established. Quantum chemistry calculations and molecular dynamics simulations were performed to explain the observed reversed preference of propylene carbonate (PC) over ethylene carbonate (EC) by Li⁺

Modeling Insight into Battery Electrolyte Electrochemical Stability and Interfacial Structure

ConspectusElectroactive interfaces distinguish electrochemistry from chemistry and enable electrochemical energy devices like batteries, fuel cells, and electric double layer capacitors. In batteries, electrolytes should be either thermodynamically stable at the electrode interfaces or kinetically stable by forming an electronically insulating but ionically conducting interphase. In addition to a traditional optimization of electrolytes by adding cosolvents and sacrificial additives to preferentially reduce or oxidize at the electrode surfaces, knowledge of the local electrolyte composition and structure within the double layer as a function of voltage constitutes the basis of manipulating an interphase and expanding the operating windows of electrochemical devices. In this work, we focus on how the molecular-scale insight into the solvent and ion partitioning in the electrolyte double layer as a function of applied potential could predict changes in electrolyte stability and its initial oxidation and reduction reactions. In molecular dynamics (MD) simulations, highly concentrated lithium aqueous and nonaqueous electrolytes were found to exclude the solvent molecules from directly interacting with the positive electrode surface, which provides an additional mechanism for extending the electrolyte oxidation stability in addition to the well-established simple elimination of “free” solvent at high salt concentrations. We demonstrate that depending on their chemical structures, the anions could be designed to preferentially adsorb or desorb from the positive electrode with increasing electrode potential. This provides additional leverage to dictate the order of anion oxidation and to effectively select a sacrificial anion for decomposition. The opposite electrosorption behaviors of bis­(trifluoromethane)­sulfonimide (TFSI) and trifluoromethanesulfonate (OTF) as predicted by MD simulation in highly concentrated aqueous electrolytes were confirmed by surface enhanced infrared spectroscopy.The proton transfer (H-transfer) reactions between solvent molecules on the cathode surface coupled with solvent oxidation were found to be ubiquitous for common Li-ion electrolyte components and dependent on the local molecular environment. Quantum chemistry (QC) calculations on the representative clusters showed that the majority of solvents such as carbonates, phosphates, sulfones, and ethers have significantly lower oxidation potential when oxidation is coupled with H-transfer, while without H-transfer their oxidation potentials reside well beyond battery operating potentials. Thus, screening of the solvent oxidation limits without considering H-transfer reactions is unlikely to be relevant, except for solvents containing unsaturated functionalities (such as CC) that oxidize without H-transfer. On the anode, the F-transfer reaction and LiF formation during anion and fluorinated solvent reduction could be enhanced or diminished depending on salt and solvent partitioning in the double layer, again giving an additional tool to manipulate the order of reductive decompositions and interphase chemistry. Combined with experimental efforts, modeling results highlight the promise of interphasial compositional control by either bringing the desired components closer to the electrode surface to facilitate redox reaction or expelling them so that they are kinetically shielded from the potential of the electrode

Deciphering the Ethylene Carbonate–Propylene Carbonate Mystery in Li-Ion Batteries

ConspectusAs one of the landmark technologies, Li-ion batteries (LIBs) have reshaped our life in the 21stcentury, but molecular-level understanding about the mechanism underneath this young chemistry is still insufficient. Despite their deceptively simple appearances with just three active components (cathode and anode separated by electrolyte), the actual processes in LIBs involve complexities at all length-scales, from Li⁺ migration within electrode lattices or across crystalline boundaries and interfaces to the Li⁺ accommodation and dislocation at potentials far away from the thermodynamic equilibria of electrolytes. Among all, the interphases situated between electrodes and electrolytes remain the most elusive component in LIBs.Interphases form because no electrolyte component (salt anion, solvent molecules) could remain thermodynamically stable at the extreme potentials where electrodes in modern LIBs operate, and their chemical ingredients come from the sacrificial decompositions of electrolyte components. The presence of an interphase on electrodes ensures reversibility of Li⁺ intercalation chemistry in anode and cathode at extreme potentials and defines the cycle life, power and energy densities, and even safety of the eventual LIBs device. Despite such importance and numerous investigations dedicated in the past two decades, we still cannot explain why, nor predict whether, certain electrolyte solvents can form a protective interphase to support the reversible Li⁺ intercalation chemistries while others destroy the electrode structure. The most representative example is the long-standing “EC–PC Disparity” and the two interphasial extremities induced therefrom: differing by only one methyl substituent, ethylene carbonate (EC) forms almost ideal interphases on the graphitic anode, thus becoming the indispensable solvent in all LIBs manufactured today, while propylene carbonate (PC) does not form any protective interphase, leading to catastrophic exfoliation of the graphitic structure. With one after another hypotheses proposed but none satisfactorily rationalizing this disparity on the molecular level, this mystery has been puzzling the battery and electrochemistry community for decades.In this Account, we attempted to decipher this mystery by reviewing the key factors that govern the interaction between the graphitic structure and the solvated Li⁺ right before interphase formation. Combining DFT calculation and experiments, we identified the partial desolvation of the solvated Li⁺ at graphite edge sites as a critical step, in which the competitive solvation of Li⁺ by anion and solvent molecules dictates whether an electrolyte is destined to form a protective interphase. Applying this model to the knowledge of relative Li⁺ solvation energy and frontier molecular orbital energy gap, it becomes theoretically possible now to predict whether a new solvent or anion would form a complex with Li⁺ leading to desirable interphases. Such molecular-level understanding of interphasial processes provides guiding principles to the effort of tailor-designing new electrolyte systems for more aggressive battery chemistries beyond Li-ion

Free-Standing Na2/3Fe1/2Mn1/2O2@Graphene Film for a Sodium-Ion Battery Cathode

The development of high-performance cathodes for sodium-ion batteries remains a great challenge, while low-cost, high-capacity Na2/3Fe 1/2Mn1/2O2 is an attractive electrode material candidate comprised of earth-abundant elements. In this work, we designed and fabricated a free-standing, binder-free Na2/3Fe1/2Mn 1/2O2@graphene composite via a filtration process. The porous composite led to excellent electrochemical performance due to the facile transport for electrons and ions that was characterized by electrochemical impedance spectroscopy at different temperatures. The electrode delivered a reversible capacity of 156 mAh/g with high Coulombic efficiency. The importance of a fluorinated electrolyte additive with respect to the performance of this high-voltage cathode in Na-ion batteries was also investigated. © 2014 American Chemical Society.