​Abstract:  Hydrogels have attracted attention due to their interesting mechanical properties which makes them suitable for wide range of applications. Metallo-supramolecular hydrogels are particularly important due to their tenability. In this study, we report a simple method for synthesizing copper-containing polymer hydrogels made from nontoxic poly(methyl vinyl ether-alt-maleic anhydride) (PVM-MA) in the absence or presence of added carboxylate ligands: dicarboxylates, such as adipate and terephthalate, tricarboxylates, such as nitrilotriacetate (NTA) and citrate or tetracarboxylate such as ethylenediaminetetraacetic acid. Our copper hydrogels are wet precursors to a new family of amorphous porous materials, consisting of a metal-polycarboxylate backbone and carboxylate spacer ligands between polymer strands engineered via non-covalent interactions. Rheological measurements revealed that the mechanical stability of the hydrogels was enhanced by the addition of supplementary dicarboxylate ligands. We determined that the optimal ratio of polymer to dicarboxylate to Cu2+ was 10:4:2.5. Our scanning electron microscope (SEM) and cryo-SEM imaging and physical adsorption measurements revealed the formation of pores. 

The Brunauer–Emmett–Teller (BET) surface area of the dried hydrogels was tunable with the addition of supplementary dicarboxylate ligands. The BET surface area increased from 177.96 m2 g−1 in a dried hydrogel without added dicarboxylate to 646.9 and 536.4 m2 g−1 with the addition of adipate and terephthalate, respectively. Moreover, addition of dicarboxylate ligands increased the pore volume and CO2 gas adsorption capacity. Separation of CO2 from post-combustion flue gases is important for environmental and economic sustainability. Our copper-based hydrogel with dicarboxylate spacer ligands offers the possibility of a new material for post-combustion CO2. At commercial conditions (298 K and 1 bar), the hydrogel samples with adipate as a spacer ligand, showed notable promising CO2/N2 selectivity of 78.46 and a high CO2/CH4 selectivity reaching 26.09 at 1 bar. 

Furthermore, we investigated in detail the effect of metal ion on the rigidity and structure of hydrogels. A series of transition metal ions such as iron nitrate (Fe(NO3)3, aluminum nitrate (Al(NO3)3, zinc nitrate Zn(NO3)2, nickel nitrate Ni(NO3)2 and cobalt nitrate Co(NO3)2 were investigated for hydrogel formation. Scaling up of the synthesis of hydrogels was achieved using the filling machine which was used to fill silver hydrogels with antibacterial properties.

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• CONTACTLinda J. Sapolu

Abstract:  This lecture discusses the incipient development of the first artificial water channels systems. We include only systems that integrate synthetic elements in their water selective translocation unit. Therefore, we exclude peptide channels because their sequences derive from the proteins in natural channels. We review many of the natural systems involved in water and related proton transport processes. We describe how these systems can fit within our primary goal of maintaining natural function within bio-assisted artificial systems. In the last part, we present several inspiring breakthroughs from the last decade in the field of biomimetic artificial water channels. All these examples demonstrate how the novel interactive water-channels can parallel biomolecular systems. At the same time these simpler artificial water channels offer a means of understanding water structures useful to understanding many biological scenarios. Moreover they can be used for the preparation of highly selective membranes for desalination.

[1] M. Barboiu and A. Gilles, Acc. Chem. Res. 2013, 46, 2814–2823.
[2] M. Barboiu, Angew. Chem. Int. Ed. 2012, 51, 11674-11676.
[3] Y. Le Duc, et al., Angew. Chem. Int. Ed. 2011, 50(48), 11366-11372.
[4] E. Licsandru, et al., J. Am. Chem. Soc., 2016, 138, 5403-5409.
[5] M. Barboiu, Chem. Commun., 2016, 52, 5657- 5665.
[6] I. Kocsis, et al. Science Adv. 2018, 4, eaao5603.

Biography: Mihail Barboiu graduated from University Politehnica of Bucharest and received his PhD in 1998 from the University of Montpellier before spending 2 years as post-doctoral researcher at the University Louis Pasteur in Strasbourg. He is CNRS Research Leader at the Institut Europeen des Membranes in Montpellier and Fellow of Royal Society of Chemistry. Since 2014 he is also Extraordinary Professor in Sun-Yat-sen University in Guangzhou, China. A major focus of his research is Dynamic Constitutional Chemistry toward Dynamic Interactive Systems: adaptive biomimetic membranes, delivery devices etc. Author of more than 215 scientific publications, 3 books and 20 chapters and 310 conferences and lectures, Dr Barboiu has received in 2004 the EURYI Award in Chemistry and in 2015 the RSC Surfaces and Interfaces Award for the development of Artificial Water Channels.

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• CONTACTLinda J. Sapolu

​ABSTRACT: Artificially structured nanoscale materials have attracted immense attention in scientific and technical communities during past decades due to the potential for controlling their optical, electronic and chemical properties. Cs-based perovskite nanocrystals (PNCs) possess alluring optical and electronic properties via compositional and structural versatility, tunable bandgap, high photoluminescence (PL) quantum yield (QY) and facile chemical synthesis. Despite the recent progress, origins of PL emission in various types of PNCs are still unclear. 

Unlike conventional chalcogenide NCs that are primarily composed of binary compounds, perovskite materials have predominantly "soft" ionic lattice structure and typically crystalize into the quasi-cubic A_nPbX_m-type structures (A⁺- methylammonium, formamidinium or cesium (Cs⁺), while X^- is a halide anion such as Cl^-, Br^- or I^-).² Such structures can be conveniently depicted as comprised of lead halide octahedra [PbX₆] surrounded with A⁺ cations, residing in the voids between them and arranged with varying degrees of interconnections. Here, we study the photon emission from individual 3D (CsPbBr₃) and 0D (Cs₄PbBr₆) perovskite NCs. Using time-correlated, time-stamped single photon counting (TCSPC), we obtain PL intensity trajectories and extract PL lifetimes and second–order correlation functions, g²(t) at different excitation levels. Blinking traces show "burst-like" intensity behavior, with large bin-to-bin fluctuations, akin to molecular fluorophores. PL lifetimes extracted from the sub-100 ms burst intervals are between 8-11 ns for all studied PNCs regardless of excitation levels. Recorded single photon emission statistics indicate that some of the measured PNCs are single photon emitters, others contain several emissive centers with very similar lifetimes. Few of the PNCs exhibited effects of photobrightening – superlinear increase of PL emission intensity due to the activation of an additional number of emissive centers within the PNC. Aided by DFT modeling, we provide a compelling evidence that green PL emission in Cs₄PbBr₆ PNCs stems from exciton recombination at Br vacancy centers within [PbX₆]^4- octahedra, unrelated to external confinement. Thus, we demonstrate that emission statistics of both type of PNCs are akin to individual molecular fluorophores, rather than traditional semiconductor quantum dots. These findings provide key information about the nature of defect formation and the origin of emission in cesium lead halide perovskite materials, which foster their utilization in the emerging optoelectronic applications. 


BIOGRAPHY: Prof. Malko is the head of the optics and ultrafast spectroscopy laboratory in the Department of Physics at the University of Texas at Dallas. He obtained a BS degree in physics and applied math from Moscow Institute of Physics and Technology, Russia in 1998, and a PhD in Physics/EE from New Mexico State University/Los Alamos National Laboratory, USA in 2002 studying ultrafast dynamics of semiconductor nanocrystals with Dr. Victor Klimov. He later was a postdoctoral scholar at Swiss Federal Institute of Technology in Lausanne (EPFL) in 2002-2005 and then at LANL from 2005-2007 working on various aspects of spectroscopy and development of low dimensional semiconductor nanostructures. He joined the University of Texas at Dallas in 2007 where he is currently an Associate Professor of Physics and Materials Science. Dr. Malko spent Spring 2017 on a sabbatical leave to Solar Center at KAUST.

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• CONTACTMazen E. Mero

​ABSTRACT: Organic photovoltaics has emerged as a promising technology for electricity generation. The essential component in an organic solar cell is the bulk heterojunction absorber layer, typically a blend of an electron donor and an electron acceptor. Efforts have been made to design new materials such as donor polymers and novel acceptors to improve the power conversion efficiencies. Recently, non-fullerene acceptors have edged out the traditional fullerene acceptors. In general, these new acceptors provide low cost synthesis routes and provide tenability of their optoelectronic and electrochemical properties. Despite the huge efforts, still not much is known about the photopysical processes in these blends that limit the performance. In this respect, time-resolved spectroscopy such as transient absorption and time-resolved photoluminescence, can provide in-depth insight into the various (photo)physical processes in bulk heterojunction solar cell. 

In this thesis, PCE10 was used as donor polymer and paired with different non fullerene acceptors. More specifically, in the first part of this thesis the impact of the core structure (cyclopenta-[2,1-b:3,4-b']dithiophene (CDT) versus indacenodithiophene (IDTT)) of malononitrile (BM)-terminated acceptors, abbreviated as CDTBM and IDTTBM, on the photophysical characteristics of BHJ solar cells is reported. Using PCE10 as donor polymer, the IDTT-based acceptor achieves power conversion efficiencies of 8.4%, higher than those of the CDT-based acceptor (5.6%), because of a concurrent increase in short-circuit current and open-circuit voltage. Using (ultra)fast transient spectroscopy we demonstrate that reduced geminate recombination in PCE10:IDTTBM blends is the reason for the difference in short-circuit currents. External quantum efficiency measurements indicate that the higher energy of interfacial charge-transfer states observed for the IDTT-based acceptor blends is the origin of the higher open-circuit voltage. 

In the second part of this thesis, I report the impact of acceptor side chains on the photo-physical processes of BHJ solar cells using three different IDT-based acceptors, namely O-IDTBR, EH-IDTBR and O-IDTBCN blended with PCE10 as donor polymer. Power conversion efficiencies as high as 10 % were achieved. The transient absorption spectroscopy experiments provide insight into sub-picosecond exciton dissociation and charge generation which is followed by nanosecond triplet state formation in PCE10:O-DTBR and PCE10:EH-IDTBR blends, while in O-IDTBCN triplets are not observed. In addition, sensitive external quantum efficiency (EQE) measurements and photothermal deflection spectroscopy (PDS) were performed to extract the energy of interfacial charge transfer states. Time delayed collection field experiments (TDCF) were performed to address the charge carrier generation and examine its dependence on electric field. Finally, time-resolved photoluminescence spectroscopy has been conducted to study energy transfer processes in these polymer:non-fullerene acceptor blends.

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• CONTACTMazen E. Mero

​Abstract:  Global problems including energy conversion and storage, clean water and human health require increasingly complex, multi-component and functional materials with unprecedented control over composition, structure, and order down to the nanoscale. This talk will give examples for the rational design of novel functional hybrid nanomaterials inspired by biological examples. Discussion will include formation of self-assembled hybrid nanoparticles referred to as Cornell dots (C dots) as well as polymer-nanoparticle self-assembly derived synthetic porous materials with amorphous, polycrystalline, and epitaxially grown single-crystal structures. Experiments will be compared to theoretical predictions to provide physical insights into formation principles. The aim of the described work is to understand the underlying fundamental chemical, thermodynamic and kinetic formation principles enabling generalization of results over a wide class of materials systems. Examples will cover the formation of hierarchical structures at equilibrium as well as via processes far away from equilibrium. Targeted applications of the prepared systems will include the development of fluorescent hybrid probes for nanomedicine, nanostructured hybrids for energy conversion and storage devices, as well as membranes for ultrafiltration applications.

Selected References
1.)    K. Ma, Y. Gong, T. Aubert, M. Z. Turker, T. Kao, P. C. Doerschuk, U. Wiesner, Self-assembly of highly symmetrical, ultrasmall inorganic cages directed by surfactant micelles, Nature 558 (2018), 577-580.
2.)    J. G. Werner, G. G. Rodríguez-Calero, H. D. Abruña, U. Wiesner, Block Copolymer Derived 3-D Interpenetrating Multifunctional Gyroidal Nanohybrid for Electrical Energy Storage, Energy Environ. Sci. 11 (2018), 1261-1270.
3.)    S. W. Robbins, P. A. Beaucage, H. Sai, K. W. Tan, J. P. Sethna, F. J. DiSalvo, S. M. Gruner, R. B. van Dover, U. Wiesner, Block copolymer self-assembly directed synthesis of mesoporous gyroidal superconductors, Sci. Adv. 2 (2016), e1501119.
4.)    S. Eun Kim, L. Zhang, K. Ma, M. Riegman, F. Chen, I. Ingold, M. Conrad, M. Z. Turker, M. Gao, X. Jiang, S. Monette, M. Pauliah, M. Gonen, P. Zanzonico, T. Quinn, U. Wiesner, M. S. Bradbury, M. Overholtzer, Ultrasmall Nanoparticles Induce Ferroptosis in Nutrient-Deprived Cancer Cells and Suppress Tumor Growth, Nat. Nanotech. 11 (2016), 977–985.
5.)    K. W. Tan, B. Jung, J. G. Werner, E. R. Rhoades, M. O. Thompson, U. Wiesner, Transient Laser Heating Induced Hierarchical Porous Structures from Block Copolymer Directed Self-Assembly, Science 349 (2015), 54-58.
6.)    E. Phillips, O. Penate-Medina, P. B. Zanzonico, R. D. Carvajal, P. Mohan, Y. Ye, J. Humm, M. Gönen, H. Kaliagian, H. Schöder, H. W. Strauss, S. M. Larson, U. Wiesner, M. S. Bradbury, Clinical translation of an ultrasmall inorganic optical-PET imaging nanoparticle probe, Sci. Transl. Med. 6 (2014), 260ra149.

Biography:  Ulrich (Uli) Wiesner studied Chemistry at the University of Mainz, Germany, and UC Irvine, CA. He gained his Ph.D. in 1991 in Physical Chemistry with work at the Max-Planck-Institute for Polymer Research (MPI-P), Mainz, on holographic information storage in polymer liquid crystals. After a two-year postdoc at E.S.P.C.I. in Paris, France, on local dynamics-mechanical property correlations in polyesters, he returned to the MPI-P in 1993 were he finished his Habilitation in 1998 with work on block copolymers under oscillatory shear and block copolymer ionomers. He joined the Cornell University, NY, MS&E faculty in 1999 as a tenured Associate Professor, became a Full Professor in 2005, and since 2008 is the Spencer T. Olin Professor of Engineering. Since his arrival at Cornell he has worked at the interface between polymer science and inorganic/solid-state chemistry with the goal to generate multifunctional nanomaterials for applications including energy conversion and storage, clean water, and nanomedicine. Since 2015 he is the co-director of the MSKCC-Cornell Center for Translation of Cancer Nanomedicine (MC2TCN), one of six Centers for Cancer Nanotechnology Excellence (CCNE) funded by the NCI (https://www.cancer.gov/sites/ocnr/research/alliance/ccne).
Selected Honors and Awards
2016: Arthur K. Doolittle Award of the American Chemical Society PMSE Division
2015: Elected PMSE Fellow of the American Chemical Society
2008: National Science Foundation Creativity Award.
2005: Mr. & Mrs. Richard F. Tucker’50 Excellence in Teaching Award, Cornell University.
2001: IBM Faculty Partnership Award.
1999: Carl Duisberg Memorial Award of the German Chemical Society (GDCh).
Technology Commercialization
2016-present:    Cofounder Eludica Oncology, Inc.; effort to commercialize C dots for applications in oncology (http://www.elucidaoncology.com)
2013-present:    Cofounder TeraPore Technologies, Inc.; effort to commercialize block copolymer UF membranes (https://teraporetech.com)

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• CONTACTLinda J. Sapolu

​Abstract:  Personal mobility provides strong economic and well-being benefits to our society. However, it relies on the ability to safely & densely store energy, and to later efficiently convert this stored energy into motive power. The current dominant energy conversion technology in this field is the internal combustion engine, with liquid fuels used to store chemical energy. This talk will provide background on challenges facing personal transportation in the 21st century, as well as research performed at Sandia National Laboratories to understand and mitigate these challenges. Some of the topics discussed will include: efficiency of energy conversion and storage systems, gasoline fuel formulation and its influences on efficiency and emissions formation, research challenges faced in high-pressure reacting systems, and the implementation of advanced technologies in the marketplace.

Biography:  David Vuilleumier is a Postdoctoral Appointee at the Combustion Research Facility in Sandia National Laboratories. His research focuses on the interactions between fuel formulation and internal-combustion engine operation. This includes the study of autoignition of gasoline-type fuels, the enabling of advanced operating modes through fuel formulation, and the interactions between fuel characteristics and mixture formation. 

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• CONTACTLinda J. Sapolu