Oil Powders and Gels from Particle-Stabilized Emulsions

Horst Adelmann, Bernard P. Binks, and Raffaele Mezzenga

pp 1694–1697

Publication Date (Web): January 6, 2012 (Letter)

DOI: 10.1021/la204811c

Forced Desorption of Nanoparticles from an Oil–Water Interface

Valeria Garbin, John C. Crocker, and Kathleen J. Stebe*

Department of Chemical and Biomolecular Engineering,University of Pennsylvania, 220 South 33rd Street, Philadelphia, Pennsylvania 19104-6393, United States

Langmuir, 2012, 28 (3), pp 1663–1667

DOI: 10.1021/la202954c

Publication Date (Web): September 20, 2011

Copyright © 2011 American Chemical Society

While nanoparticle adsorption to fluid interfaces has been studied from a fundamental standpoint and exploited in application, the reverse process, that is, desorption and disassembly, remains relatively unexplored. Here we demonstrate the forced desorption of gold nanoparticles capped with amphiphilic ligands from an oil–water interface. A monolayer of nanoparticles is allowed to spontaneously form by adsorption from an aqueous suspension onto a drop of oil and is subsequently compressed by decreasing the drop volume. The surface pressure is monitored by pendant drop tensiometry throughout the process. Upon compression, the nanoparticles are mechanically forced out of the interface into the aqueous phase. An optical method is developed to measure the nanoparticle area density in situ. We show that desorption occurs at a coverage that corresponds to close packing of the ligand-capped particles, suggesting that ligand-induced repulsion plays a crucial role in this process.

Snake modulates constriction in response to prey's heartbeat

1. Scott M. Boback1,*, 
2. Allison E. Hall1, 
3. Katelyn J. McCann1,
4. Amanda W. Hayes1, 
5. Jeffrey S. Forrester2 and 
6. Charles F. Zwemer1

Abstract

Many species of snakes use constriction—the act of applying pressure via loops of their trunk—to subdue and kill their prey. Constriction is costly and snakes must therefore constrict their prey just long enough to ensure death. However, it remains unknown how snakes determine when their prey is dead. Here, we demonstrate that boas (Boa constrictor) have the remarkable ability to detect a heartbeat in their prey and, based on this signal, modify the pressure and duration of constriction accordingly. We monitored pressure generated by snakes as they struck and constricted warm cadaveric rats instrumented with a simulated heart. Snakes responded to the beating heart by constricting longer and with greater total pressure than when constricting rats with no heartbeat. When the heart was stopped midway through the constriction, snakes abandoned constriction shortly after the heartbeat ceased. Furthermore, snakes naive to live prey also responded to the simulated heart, suggesting that this behaviour is at least partly innate. These results are an example of how snakes integrate physiological cues from their prey to modulate a complex and ancient behavioural pattern.

Autonomic Restoration of Electrical Conductivity

1. Benjamin J. Blaiszik¹, 
2. Sharlotte L. B. Kramer¹, 
3. Martha E. Grady², 
4. David A. McIlroy¹, 
5. Jeffrey S. Moore³, 
6. Nancy R. Sottos^1,*, 
7. Scott R. White^4,*

1. Advanced Materials

   Volume 24, Issue 3, pages 398–401, January 17, 2012

Self-healing of an electrical circuit is demonstrated with nearly full recovery of conductance less than one millisecond after damage. Crack damage breaks a conductive pathway in a multilayer device, interrupting electron transport and simultaneously rupturing adjacent microcapsules containing gallium–indium liquid metal (top). The released liquid metal flows to the area of damage, restoring the conductive pathway (bottom).

America's Science Decline by Neil deGrasse Tyson

A Surprise from 1954: Siloxane Equilibration Is a Simple, Robust, and Obvious Polymer Self-Healing Mechanism

Peiwen Zheng and Thomas J. McCarthy*

Polymer Science and Engineering Department,University of Massachusetts, 120 Governors Drive, Amherst, Massachusetts 01003, United States

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/ja2113257

Publication Date (Web): January 18, 2012

Copyright © 2012 American Chemical Society

Lead Transformation to Pyromorphite by Fungi

• Young Joon Rhee¹, 
• Stephen Hillier², 
• Geoffrey Michael Gadd^1, , 

• ¹ Division of Molecular Microbiology, College of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
• ² The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, Scotland, UK

• Received 3 November 2011. Revised 7 December 2011. Accepted 7 December 2011. Available online 12 January 2012. Published online: January 12, 2012.

Lead (Pb) is a serious environmental pollutant in all its chemical forms [1]. Attempts have been made to immobilize lead in soil as the mineral pyromorphite using phosphate amendments (e.g., rock phosphate, phosphoric acid, and apatite [ [2], [3], [4] and [5]]), although our work has demonstrated that soil fungi are able to transform pyromorphite into lead oxalate [ [6] and [7]]. Lead metal, an important structural and industrial material, is subject to weathering, and soil contamination also occurs through hunting and shooting [ [8] and [9]]. Although fungi are increasingly appreciated as geologic agents [ [10], [11] and [12]], there is a distinct lack of knowledge about their involvement in lead geochemistry. We examined the influence of fungal activity on lead metal and discovered that metallic lead can be transformed into chloropyromorphite, the most stable lead mineral that exists. This is of geochemical significance, not only regarding lead fate and cycling in the environment but also in relation to the phosphate cycle and linked with microbial transformations of inorganic and organic phosphorus. This paper provides the first report of mycogenic chloropyromorphite formation from metallic lead and highlights the significance of this phenomenon as a biotic component of lead biogeochemistry, with additional consequences for microbial survival in lead-contaminated environments and bioremedial treatments for Pb-contaminated land.

Visualizing Gas Molecules Interacting with Supported Nanoparticulate Catalysts at Reaction Conditions

Hideto Yoshida,* Yasufumi Kuwauchi, Joerg R. Jinschek,Keju Sun,Shingo Tanaka,Masanori Kohyama,
Satoshi Shimada,Masatake Haruta,Seiji Takeda†
Science 20 January 2012: 
Vol. 335 no. 6066 pp. 317-319 
DOI: 10.1126/science.121319



Understanding how molecules can restructure the surfaces of heterogeneous catalysts under reaction
conditions requires methods that can visualize atoms in real space and time. We applied a newly
developed aberration-corrected environmental transmission electron microscopy to show that adsorbed
carbon monoxide (CO) molecules caused the {100} facets of a gold nanoparticle to reconstruct
during CO oxidation at room temperature. The CO molecules adsorbed at the on-top sites of gold
atoms in the reconstructed surface, and the energetic favorability of this reconstructed structure was
confirmed by ab initio calculations and image simulations. This atomic-scale visualizing method
can be applied to help elucidate reaction mechanisms in heterogeneous catalysis

Syntheses of nanostructured Cu- and Ni-based micro-assemblies with selectable 3-D hierarchical biogenic morphologies

Yunnan Fang a, John D. Berrigan a, Ye Cai a, Seth R. Marder ba and Kenneth H. Sandhage *ab

^aSchool of Materials Science and Engineering, Georgia Institute of Technology, 771 Ferst Drive, Atlanta, GA 30332, USA. E-mail: ken.sandhage@mse.gatech.edu

^bSchool of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, GA 30332, USA 
J. Mater. Chem., 2012, 22, 1305-1312





A combined layer-by-layer (LbL) surface amine amplification and electroless deposition process has been developed to convert biologically replicable three-dimensional (3-D) nanostructured micro-assemblies (such as siliceous diatom frustules) into freestanding Cu-bearing or Ni-bearing structures that retain the starting biogenic microscale 3-D shapes and nanoscale patterns. After reacting the hydroxyl-bearing surfaces of these biotemplates with an aminosilane, a LbL polyacrylate/polyamine deposition process was used to dendritically amplify the surface amine concentration. Subsequent binding of metal chloride catalysts to these amine-enriched surfaces enabled the rapid electroless deposition of thin, conformal, continuous, and nanocrystalline or amorphous metallic coatings on the 3-D biotemplates. Selective removal of the underlying templates then yielded freestanding Cu-bearing or Ni-bearing structures. The conformality and continuity of the thin coatings, and the fidelity with which the biogenic shape and fine features were preserved in the freestanding structures, were significantly enhanced by the amplification of surface amines (and the associated enrichment of catalytic sites) resulting from the LbL polyacrylate/polyamine treatment. Monolithic and multicomponent structures (e.g., Cu, multilayer Au/Cu, CuO, and Ni–P alloy) with bio-derived morphologies have been synthesized utilizing this approach. This readily-scalable process may be used to convert self-assembled rigid templates (of biological or synthetic origin) into nanostructured transition metal-based micro-assemblies with a wide variety of selectable 3-D hierarchical morphologies for use in numerous functional and structural applications.

Sketching Electronics

An Implantable Biofuel Cell for a Live Insect

Michelle Rasmussen†, Roy E. Ritzmann‡, Irene Lee†, Alan J. Pollack‡, and Daniel Scherson*†

Departments of ^†Chemistry and ^‡Biology, Case Western Reserve University, Cleveland, Ohio 44106, United States

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/ja210794c

Publication Date (Web): January 3, 2012

Copyright © 2012 American Chemical Society

A biofuel cell incorporating a bienzymatic trehalase|glucose oxidase trehalose anode and a bilirubin oxidase dioxygen cathode using Os complexes grafted to a polymeric backbone as electron relays was designed and constructed. The specific power densities of the biofuel cell implanted in a female Blaberus discoidalis through incisions into its abdomen yielded maximum values of ca. 55 μW/cm² at 0.2 V that decreased by only ca. 5% after ca. 2.5 h of operation.

Quantitative Analysis of the Role Played by Poly(vinylpyrrolidone) in Seed-Mediated Growth of Ag Nanocrystals

Xiaohu Xia, Jie Zeng, L. Kyle Oetjen, Qingge Li, and Younan Xia

Publication Date (Web): December 28, 2011 (Article)

DOI: 10.1021/ja210047e

Regiospecific Plasmonic Assemblies for in Situ Raman Spectroscopy in Live Cells

Liguang Xu†, Hua Kuang†, Chuanlai Xu†, Wei Ma†‡, Libing Wang*†, and Nicholas A. Kotov*‡

^† School of Food Science and Technology, State Key Lab of Food Science and Technology, Jiangnan University, Wuxi, JiangSu, 214122, People's Republic of China

^‡ Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan 48109, United States

 Hunan Entry–Exit Inspection and Quarantine Bureau, Changsha, 410001, People's Republic China

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/ja2088713

Publication Date (Web): December 18, 2011

Copyright © 2011 American Chemical Society

wanglb@hnciq.gov.cn; kotov@umich.edu

Multiple properties of plasmonic assemblies are determined by their geometrical organization. While high degree of complexity was achieved for plasmonic superstructures based on nanoparticles (NPs), little is known about the stable and structurally reproducible plasmonic assemblies made up from geometrically diverse plasmonic building blocks. Among other possibilities, they open the door for the preparation of regiospecific isomers of nanoscale assemblies significant both from a fundamental point of view and optical applications. Here, we present a synthetic method for complex assemblies from NPs and nanorods (NRs) based on selective modification of NRs with DNA oligomers. Three types of assemblies denoted as End, Side, and Satellite isomers that display distinct elements of regiospecificity were prepared with the yield exceeding 85%. Multiple experimental methods independently verify various structural features, uniformity, and stability of the prepared assemblies. The presence of interparticle gaps with finely controlled geometrical parameters and inherently small size comparable with those of cellular organelles fomented their study as intracellular probes. Against initial expectations, SERS intensity for End, Side, and Satelliteisomers was found to be dependent primarily on the number of the NPs in the superstructures rationalized with the help of electrical field simulations. Incubation of the label-free NP–NR assemblies with HeLa cells indicated sufficient field enhancement to detect structural lipids of mitochondria and potentially small metabolites. This provided the first proof-of-concept data for the possibility of real-time probing of the local organelle environment in live cells. Further studies should include structural optimization of the assemblies for multitarget monitoring of metabolic activity and further increase in complexity for applications in transformative optics.