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Platinum-based nanocages with subnanometer-thick walls and well-defined, controllable facets
Zhang, Lei,Roling, Luke T.,Wang, Xue,Vara, Madeline,Chi, Miaofang,Liu, Jingyue,Choi, Sang-Il,Park, Jinho,Herron, Jeffrey A.,Xie, Zhaoxiong,Mavrikakis, Manos,Xia, Younan American Association for the Advancement of Scienc 2015 Science Vol.349 No.6246
<P><B>Etching platinum nanocage catalysts</B></P><P>Although platinum is an excellent catalyst for the oxygen reduction reaction that occurs in fuel cells, its scarcity continues to drive efforts to improve its utilization. Zhang <I>et al.</I> made nanocages of platinum by coating palladium nanocrystals with only a few layers of platinum and then etching away the palladium core (see the Perspective by Strasser). Platinum nanocages made using nanoscale octahedra and cubes of palladium displayed different catalytic activity for the oxygen reduction reaction.</P><P><I>Science</I>, this issue p. 412; see also p. 379</P><P>A cost-effective catalyst should have a high dispersion of the active atoms, together with a controllable surface structure for the optimization of activity, selectivity, or both. We fabricated nanocages by depositing a few atomic layers of platinum (Pt) as conformal shells on palladium (Pd) nanocrystals with well-defined facets and then etching away the Pd templates. Density functional theory calculations suggest that the etching is initiated via a mechanism that involves the formation of vacancies through the removal of Pd atoms incorporated into the outermost layer during the deposition of Pt. With the use of Pd nanoscale cubes and octahedra as templates, we obtained Pt cubic and octahedral nanocages enclosed by {100} and {111} facets, respectively, which exhibited distinctive catalytic activities toward oxygen reduction.</P>
Zhang, Xiaobo,Pint, Cary L.,Lee, Min Hyung,Schubert, Bryan Edward,Jamshidi, Arash,Takei, Kuniharu,Ko, Hyunhyub,Gillies, Andrew,Bardhan, Rizia,Urban, Jeffrey J.,Wu, Ming,Fearing, Ronald,Javey, Ali American Chemical Society 2011 NANO LETTERS Vol.11 No.8
<P>A simple approach is described to fabricate reversible, thermally- and optically responsive actuators utilizing composites of poly(<I>N</I>-isopropylacrylamide) (pNIPAM) loaded with single-walled carbon nanotubes. With nanotube loading at concentrations of 0.75 mg/mL, we demonstrate up to 5 times enhancement to the thermal response time of the nanotube-pNIPAM hydrogel actuators caused by the enhanced mass transport of water molecules. Additionally, we demonstrate the ability to obtain ultrafast near-infrared optical response in nanotube-pNIPAM hydrogels under laser excitation enabled by the strong absorption properties of nanotubes. The work opens the framework to design complex and programmable self-folding materials, such as cubes and flowers, with advanced built-in features, including tunable response time as determined by the nanotube loading.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2011/nalefd.2011.11.issue-8/nl201503e/production/images/medium/nl-2011-01503e_0002.gif'></P>
Zhang, Zhengcheng,Lu, Jun,Assary, Rajeev S.,Du, Peng,Wang, Hsien-Hau,Sun, Yang-Kook,Qin, Yan,Lau, Kah Chun,Greeley, Jeffrey,Redfern, Paul C.,Iddir, Hakim,Curtiss, Larry A.,Amine, Khalil American Chemical Society 2011 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.115 No.51
<P>The successful development of Li-air batteries would significantly increase the possibility of extending the range of electric vehicles. There is much evidence that typical organic carbonate based electrolytes used in lithium ion batteries form lithium carbonates from reaction with oxygen reduction products during discharge in lithium-air cells so more stable electrolytes need to be found. This combined experimental and computational study of an electrolyte based on a tri(ethylene glycol)-substituted trimethylsilane (<ext-link xlink:type='simple'>1NM3</ext-link>) provides evidence that the ethers are more stable toward oxygen reduction discharge species. X-ray photoelectron spectroscopy (XPS) and FTIR experiments show that only lithium oxides and no carbonates are formed when <ext-link xlink:type='simple'>1NM3</ext-link> electrolyte is used. In contrast XPS shows that propylene carbonate (PC) in the same cell configuration decomposes to form lithium carbonates during discharge. Density functional calculations of probable decomposition reaction pathways involving solvated oxygen reduction species confirm that oligoether substituted silanes, as well as other ethers, are more stable to the oxygen reduction products than propylene carbonate. These results indicate that the choice of electrolyte plays a key role in the performance of Li-air batteries.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-51/jp2087412/production/images/medium/jp-2011-087412_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp2087412'>ACS Electronic Supporting Info</A></P>
Health and Economic Burden of HPV-related Diseases in Singapore
Low, Jeffrey Jen Hui,Ko, Yu,Ilancheran, Arunachalam,Zhang, Xu Hao,Singhal, Puneet K.,Tay, Sun Kuie Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.1
Objective: To assess the health and economic burden of human papillomavirus (HPV)-related diseases (cervical cancer, cervical intraepithelial neoplasia (CIN) 1/2/3, and genital warts) in Singapore over a period of 25 years beginning in 2008. Methods: Incidence-based modeling was used to estimate the incidence cases and associated economic burden, with the assumption that age-stratified incidence rates will remain the same throughout the period of 25 years. The incidence rates in 2008 were projected based on data obtained from the National Cancer Registry for cervical cancer, and from a combination of published data and hospital registry review for CIN1/2/3 and genital warts. The population growth rate was factored into the projection of incidence cases over time. Direct cost data per cervical cancer and per CIN1/2/3 case were obtained from the financial database of large local hospitals while cost data for genital warts were obtained from the National Skin Center; these costs were multiplied by the number of incidence cases to produce an aggregate estimate of the economic burden over the 25-year period (in 2008 Singapore dollars) using a 3% discount rate. Results: The total number of incidence cases of HPV-disease over 25 years beginning in 2008 was estimated to be 60,183, including 8,078 for cervical cancer, 11,685 for CIN 2/3, 8,849 for CIN1, and 31,572 for genital warts. The estimated total direct cost was 83.2 million Singapore Dollars over 25 years: 57.6 million attributable to cervical cancer, 13.0 million to CIN2/3, 6.83 million to CIN1, and 5.70 million to genital warts. Conclusion: HPV-related diseases are expected to impose significant health and economic burden on the Singapore healthcare resources in the next 25 years.
Andrews, Jeffrey G.,Buzzi, Stefano,Choi, Wan,Hanly, Stephen V.,Lozano, Angel,Soong, Anthony C. K.,Zhang, Jianzhong Charlie IEEE 2014 IEEE journal on selected areas in communications Vol.32 No.6
<P>What will 5G be? What it will <I>not</I> be is an incremental advance on 4G. The previous four generations of cellular technology have each been a major paradigm shift that has broken backward compatibility. Indeed, 5G will need to be a paradigm shift that includes very high carrier frequencies with massive bandwidths, extreme base station and device densities, and unprecedented numbers of antennas. However, unlike the previous four generations, it will also be highly integrative: tying any new 5G air interface and spectrum together with LTE and WiFi to provide universal high-rate coverage and a seamless user experience. To support this, the core network will also have to reach unprecedented levels of flexibility and intelligence, spectrum regulation will need to be rethought and improved, and energy and cost efficiencies will become even more critical considerations. This paper discusses all of these topics, identifying key challenges for future research and preliminary 5G standardization activities, while providing a comprehensive overview of the current literature, and in particular of the papers appearing in this special issue.</P>
Park, Jinho,Zhang, Lei,Choi, Sang-Il,Roling, Luke T.,Lu, Ning,Herron, Jeffrey A.,Xie, Shuifen,Wang, Jinguo,Kim, Moon J.,Mavrikakis, Manos,Xia, Younan American Chemical Society 2015 ACS NANO Vol.9 No.3
<P>We systematically evaluated two different approaches to the syntheses of Pd@Pt<SUB><I>n</I>L</SUB> (<I>n</I> = 2–5) core–shell octahedra. We initially prepared the core–shell octahedra using a polyol-based route by titrating a Pt(IV) precursor into the growth solution containing Pd octahedral seeds at 200 °C through the use of a syringe pump. The number of Pt atomic layers could be precisely controlled from two to five by increasing the volume of the precursor solution while fixing the amount of seeds. We then demonstrated the synthesis of Pd@Pt<SUB><I>n</I>L</SUB> octahedra using a water-based route at 95 °C through the one-shot injection of a Pt(II) precursor. Due to the large difference in reaction temperature, the Pd@Pt<SUB><I>n</I>L</SUB> octahedra obtained <I>via</I> the water-based route showed sharper corners than their counterparts obtained through the polyol-based route. When compared to a commercial Pt/C catalyst based upon 3.2 nm Pt particles, the Pd@Pt<SUB><I>n</I>L</SUB> octahedra prepared using both methods showed similar remarkable enhancement in terms of activity (both specific and mass) and durability toward the oxygen reduction reaction. Calculations based upon periodic, self-consistent density functional theory suggested that the enhancement in specific activity for the Pd@Pt<SUB><I>n</I>L</SUB> octahedra could be attributed to the destabilization of OH on their Pt<SUB><I>n</I>L</SUB>*/Pd(111) surface relative to the {111} and {100} facets exposed on the surface of Pt/C. The destabilization of OH facilitates its hydrogenation, which was found to be the rate-limiting step of the oxygen reduction reaction on all these surfaces.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2015/ancac3.2015.9.issue-3/nn506387w/production/images/medium/nn-2014-06387w_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn506387w'>ACS Electronic Supporting Info</A></P>
Han, Jongwoo,Zhang, Li Li,Lee, Seungjun,Oh, Junghoon,Lee, Kyoung-Seok,Potts, Jeffrey R.,Ji, Junyi,Zhao, Xin,Ruoff, Rodney S.,Park, Sungjin American Chemical Society 2013 ACS NANO Vol.7 No.1
<P>Chemically modified graphene (CMG) nanoplatelets have shown great promise in various applications due to their electrical properties and high surface area. Chemical doping is one of the most effective methods to tune the electronic properties of graphene materials. In this work, novel B-doped nanoplatelets (borane-reduced graphene oxide, B-rG-O) were produced on a large scale <I>via</I> the reduction of graphene oxide by a borane-tetrahydrofuran adduct under reflux, and their use for supercapacitor electrodes was studied. This is the first report on the production of B-doped graphene nanoplatelets from a solution process and on the use of B-doped graphene materials in supercapacitors. The B-rG-O had a high specific surface area of 466 m<SUP>2</SUP>/g and showed excellent supercapacitor performance including a high specific capacitance of 200 F/g in aqueous electrolyte as well as superior surface area-normalized capacitance to typical carbon-based supercapacitor materials and good stability after 4500 cycles. Two- and three-electrode cell measurements showed that energy storage in the B-rG-O supercapacitors was contributed by ion adsorption on the surface of the nanoplatelets in addition to electrochemical redox reactions.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-1/nn3034309/production/images/medium/nn-2012-034309_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn3034309'>ACS Electronic Supporting Info</A></P>