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Crisp, Ryan W.,Pach, Gregory F.,Kurley, J. Matthew,France, Ryan M.,Reese, Matthew O.,Nanayakkara, Sanjini U.,MacLeod, Bradley A.,Talapin, Dmitri V.,Beard, Matthew C.,Luther, Joseph M. American Chemical Society 2017 Nano letters Vol.17 No.2
<P>We developed a monolithic CdTe–PbS tandem solar cell architecture in which both the CdTe and PbS absorber layers are solution-processed from nanocrystal inks. Due to their tunable nature, PbS quantum dots (QDs), with a controllable band gap between 0.4 and ∼1.6 eV, are a promising candidate for a bottom absorber layer in tandem photovoltaics. In the detailed balance limit, the ideal configuration of a CdTe (<I>E</I><SUB>g</SUB> = 1.5 eV)–PbS tandem structure assumes infinite thickness of the absorber layers and requires the PbS band gap to be 0.75 eV to theoretically achieve a power conversion efficiency (PCE) of 45%. However, modeling shows that by allowing the thickness of the CdTe layer to vary, a tandem with efficiency over 40% is achievable using bottom cell band gaps ranging from 0.68 and 1.16 eV. In a first step toward developing this technology, we explore CdTe–PbS tandem devices by developing a ZnTe–ZnO tunnel junction, which appropriately combines the two subcells in series. We examine the basic characteristics of the solar cells as a function of layer thickness and bottom-cell band gap and demonstrate open-circuit voltages in excess of 1.1 V with matched short circuit current density of 10 mA/cm<SUP>2</SUP> in prototype devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2017/nalefd.2017.17.issue-2/acs.nanolett.6b04423/production/images/medium/nl-2016-04423k_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl6b04423'>ACS Electronic Supporting Info</A></P>
Isostructural metal-insulator transition in VO<sub>2</sub>
Lee, D.,Chung, B.,Shi, Y.,Kim, G.-Y.,Campbell, N.,Xue, F.,Song, K.,Choi, S.-Y.,Podkaminer, J. P.,Kim, T. H.,Ryan, P. J.,Kim, J.-W.,Paudel, T. R.,Kang, J.-H.,Spinuzzi, J. W.,Tenne, D. A.,Tsymbal, E. Y. American Association for the Advancement of Scienc 2018 Science Vol.362 No.6418
<P><B>Separating structure and electrons in VO<SUB>2</SUB></B></P><P>Above 341 kelvin—not far from room temperature—bulk vanadium dioxide (VO<SUB>2</SUB>) is a metal. But as soon as the material is cooled below 341 kelvin, VO<SUB>2</SUB> turns into an insulator and, at the same time, changes its crystal structure from rutile to monoclinic. Lee <I>et al.</I> studied the peculiar behavior of a heterostructure consisting of a layer of VO<SUB>2</SUB> placed underneath a layer of the same material that has a bit less oxygen. In the VO<SUB>2</SUB> layer, the structural transition occurred at a higher temperature than the metal-insulator transition. In between those two temperatures, VO<SUB>2</SUB> was a metal with a monoclinic structure—a combination that does not occur in the absence of the adjoining oxygen-poor layer.</P><P><I>Science</I>, this issue p. 1037</P><P>The metal-insulator transition in correlated materials is usually coupled to a symmetry-lowering structural phase transition. This coupling not only complicates the understanding of the basic mechanism of this phenomenon but also limits the speed and endurance of prospective electronic devices. We demonstrate an isostructural, purely electronically driven metal-insulator transition in epitaxial heterostructures of an archetypal correlated material, vanadium dioxide. A combination of thin-film synthesis, structural and electrical characterizations, and theoretical modeling reveals that an interface interaction suppresses the electronic correlations without changing the crystal structure in this otherwise correlated insulator. This interaction stabilizes a nonequilibrium metallic phase and leads to an isostructural metal-insulator transition. This discovery will provide insights into phase transitions of correlated materials and may aid the design of device functionalities.</P>
Microneedle-Mediated Transdermal Delivery of Bevacizumab
Courtenay, Aaron J.,McCrudden, Maelí,osa T. C.,McAvoy, Kathryn J.,McCarthy, Helen O.,Donnelly, Ryan F. American Chemical Society 2018 Molecular pharmaceutics Vol.15 No.8
<P>Bevacizumab is a recombinant humanized monoclonal antibody used clinically as a combination chemotherapeutic. Antibody therapeutics are usually formulated as parenteral injections, owing to their low oral bioavailability. Microneedle technology provides a transdermal alternative for drug-delivery using micron-scale needle structures to penetrate directly through the <I>stratum corneum</I> into the dermal interstitium. This study describes the design, formulation, and <I>in vitro</I> characterization of both dissolving and hydrogel-forming microneedle array platforms for transdermal delivery of bevacizumab. Bevacizumab recovery and transdermal permeation studies were conducted and analyzed using bevacizumab specific ELISA. Prototype microneedle-patches were tested <I>in vivo</I> in Sprague-Dawley rats with serum, exterior lumbar and axial lymph nodes, spleen, and skin tissue concentrations of bevacizumab reported. This work represents the first example of high dose transdermal delivery of an antibody therapeutic <I>in vivo</I> using dissolving and hydrogel-forming microneedle platforms. Basic pharmacokinetic parameters are described including hydrogel-forming microneedles: <I>C</I><SUB>max</SUB> 358.2 ± 100.4 ng/mL, <I>T</I><SUB>max</SUB> 48 h, AUC 44357 ± 4540, and <I>C</I><SUB>ss</SUB> 942 ± 95 ng/mL, highlighting the potential for these devices to provide sustained delivery of antibody therapeutics to the lymph and systemic circulation. Targeted delivery of chemotherapeutic agents to the lymphatic system by MN technology may provide new treatment options for cancer metastases.</P> [FIG OMISSION]</BR>
Lukeman, Ryan J.,Beveridge, Leah F.,Flynn, Andrea D.,Garbary, David J. The Korean Society of Phycology 2012 ALGAE Vol.27 No.1
A mathematical model of the commercial harvest of Palmaria palmata (Dulse) is presented based on a logistic model and field data collected on Digby Neck, Nova Scotia from 14 harvested shores during May to August, 2010. Field observations used to estimate model parameters included cover of Dulse before and after harvest from Dulse dominated boulders for which surface area was estimated, and from which fresh biomass of harvested Dulse was weighed. Over all the surveys the average harvest fraction was about 50%, and the total resource was about $1,600g\;m^{-2}$. With growth rates in excess of 4% per day and a 50% harvest of the standing crop each month, the model suggests that the Dulse resource is sustainable at current harvest levels.
Nolis, Gene M.,Adil, Abdullah,Yoo, Hyun Deog,Hu, Linhua,Bayliss, Ryan D.,Lapidus, Saul H.,Berkland, Lisa,Phillips, Patrick J.,Freeland, John W.,Kim, Chunjoong,Klie, Robert F.,Cabana, Jordi American Chemical Society 2018 The Journal of Physical Chemistry Part C Vol.122 No.8
<P>In this report, the feasibility of reversible Ca<SUP>2+</SUP> or Zn<SUP>2+</SUP> intercalation into a crystalline cubic spinel Mn<SUB>2</SUB>O<SUB>4</SUB> cathode has been investigated using electrochemical methods in an aqueous electrolyte. A combination of synchrotron XRD and XANES studies identified the partial structural transformation from a cubic to a tetragonally distorted spinel Mn<SUB>3</SUB>O<SUB>4</SUB>, accompanied by the reduction of Mn<SUP>4+</SUP> to Mn<SUP>3+</SUP> and Mn<SUP>2+</SUP> during discharge. TEM/EDX measurements confirmed that practically no Ca<SUP>2+</SUP> was inserted upon discharge. However, non-negligible amounts of Zn were detected after Mn<SUB>2</SUB>O<SUB>4</SUB> was reduced in the Zn<SUP>2+</SUP> electrolyte, but through the formation of secondary phases that, in some cases, appeared adjacent to the surface of a cathode particle. This report aims to identify bottlenecks in the application of manganese oxide cathodes paired with Ca or Zn metal anodes and to justify future efforts in designing prototype multivalent batteries.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2018/jpccck.2018.122.issue-8/acs.jpcc.7b12084/production/images/medium/jp-2017-12084c_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp7b12084'>ACS Electronic Supporting Info</A></P>
Wan, Liwen F.,Cho, Eun Seon,Marangoni, Tomas,Shea, Patrick,Kang, ShinYoung,Rogers, Cameron,Zaia, Edmond,Cloke, Ryan R.,Wood, Brandon C.,Fischer, Felix R.,Urban, Jeffrey J.,Prendergast, David American Chemical Society 2019 Chemistry of materials Vol.31 No.8
<P>Hydrogen is a long-term clean energy carrier that enables completely carbon-free energy production. However, practical implementation of hydrogen fuel technologies is restricted because of lack of safe and high-performing storage materials. Here, we report Mg nanocrystals encapsulated by narrow, bottom-up synthesized graphene nanoribbons (GNRs) as environmentally stable and high-capacity hydrogen storage materials. As an encapsulation medium, GNRs offer similar functionalities as reduced graphene oxide to protect the encapsulated Mg nanocrystals from extensive oxidation, while allowing penetrations of hydrogen. In addition, the GNRs can be edge functionalized to tune the (de-)hydrogenation kinetics, in particular for the processes occurred at the GNR-Mg interfaces. In this work, four different types of edge-functional groups were introduced into GNRs with the goal of comparing their cycling performances because of edge functionalization. On the basis of detailed kinetic analysis coupled with first-principles calculations, we propose that edge-functional groups can contribute to the reduction of kinetic barriers for surface hydrogen reactions at the interface with the GNR by stabilizing surface defects. Furthermore, the GNR-Mg composite exhibited higher hydrogen storage capacity (7.1 wt % of hydrogen based on the total composite) compared with the current literature while demonstrating long-term air stability. This work suggests that the rational design of edge-functional groups in graphene derivatives can provide a general and novel paradigm for simultaneous encapsulation and hydrogen storage catalysis in simple metal or complex metal nanocrystals.</P> [FIG OMISSION]</BR>
Enhanced Multiple Exciton Generation in PbS|CdS Janus-like Heterostructured Nanocrystals
Kroupa, Daniel M.,Pach, Gregory F.,Vö,rö,s, Má,rton,Giberti, Federico,Chernomordik, Boris D.,Crisp, Ryan W.,Nozik, Arthur J.,Johnson, Justin C.,Singh, Rohan,Klimov, Victor I.,Galli, American Chemical Society 2018 ACS NANO Vol.12 No.10
<P>Generating multiple excitons by a single high-energy photon is a promising third-generation solar energy conversion strategy. We demonstrate that multiple exciton generation (MEG) in PbS|CdS Janus-like heteronanostructures is enhanced over that of single-component and core/shell nanocrystal architectures, with an onset close to two times the PbS band gap. We attribute the enhanced MEG to the asymmetric nature of the heteronanostructure that results in an increase in the effective Coulomb interaction that drives MEG and a reduction of the competing hot exciton cooling rate. Slowed cooling occurs through effective trapping of hot-holes by a manifold of valence band interfacial states having both PbS and CdS character, as evidenced by photoluminescence studies and <I>ab initio</I> calculations. Using transient photocurrent spectroscopy, we find that the MEG characteristics of the individual nanostructures are maintained in conductive arrays and demonstrate that these quasi-spherical PbS|CdS nanocrystals can be incorporated as the main absorber layer in functional solid-state solar cell architectures. Finally, based upon our analysis, we provide design rules for the next generation of engineered nanocrystals to further improve the MEG characteristics.</P> [FIG OMISSION]</BR>
Ryan J. Lukeman,Leah F. Beveridge,Andrea D. Flynn,David J. Garbary 한국조류학회I 2012 ALGAE Vol.27 No.1
A mathematical model of the commercial harvest of Palmaria palmata (Dulse) is presented based on a logistic model and field data collected on Digby Neck, Nova Scotia from 14 harvested shores during May to August, 2010. Field observations used to estimate model parameters included cover of Dulse before and after harvest from Dulse dominated boulders for which surface area was estimated, and from which fresh biomass of harvested Dulse was weighed. Over all the surveys the average harvest fraction was about 50%, and the total resource was about 1,600 g m-2. With growth rates in excess of 4% per day and a 50% harvest of the standing crop each month, the model suggests that the Dulse resource is sustainable at current harvest levels.