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      Ultrasensitive detection of toxic cations through changes in the tunnelling current across films of striped nanoparticles

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          Abstract

          Although multiple methods have been developed to detect metal cations, only a few offer sensitivities below 1 pM, and many require complicated procedures and sophisticated equipment. Here, we describe a class of simple solid-state sensors for the ultrasensitive detection of heavy-metal cations (notably, an unprecedented attomolar limit for the detection of CH(3)Hg(+) in both standardized solutions and environmental samples) through changes in the tunnelling current across films of nanoparticles (NPs) protected with striped monolayers of organic ligands. The sensors are also highly selective because of the ligand-shell organization of the NPs. On binding of metal cations, the electronic structure of the molecular bridges between proximal NPs changes, the tunnelling current increases and highly conductive paths ultimately percolate the entire film. The nanoscale heterogeneity of the structure of the film broadens the range of the cation-binding constants, which leads to wide sensitivity ranges (remarkably, over 18 orders of magnitude in CH(3)Hg(+) concentration).

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          The Electrical Resistance of Binary Metallic Mixtures

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            Surface-structure-regulated cell-membrane penetration by monolayer-protected nanoparticles.

            Nanoscale objects are typically internalized by cells into membrane-bounded endosomes and fail to access the cytosolic cell machinery. Whereas some biomacromolecules may penetrate or fuse with cell membranes without overt membrane disruption, no synthetic material of comparable size has shown this property yet. Cationic nano-objects pass through cell membranes by generating transient holes, a process associated with cytotoxicity. Studies aimed at generating cell-penetrating nanomaterials have focused on the effect of size, shape and composition. Here, we compare membrane penetration by two nanoparticle 'isomers' with similar composition (same hydrophobic content), one coated with subnanometre striations of alternating anionic and hydrophobic groups, and the other coated with the same moieties but in a random distribution. We show that the former particles penetrate the plasma membrane without bilayer disruption, whereas the latter are mostly trapped in endosomes. Our results offer a paradigm for analysing the fundamental problem of cell-membrane-penetrating bio- and macro-molecules.
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              Ecological effects, transport, and fate of mercury: a general review

              Chemosphere, 40(12), 1335-1351
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                Author and article information

                Journal
                Nature Materials
                Nature Mater
                Springer Science and Business Media LLC
                1476-1122
                1476-4660
                November 2012
                September 9 2012
                November 2012
                : 11
                : 11
                : 978-985
                Article
                10.1038/nmat3406
                22961202
                139a5eed-8d70-4363-87b6-94eb1c68c770
                © 2012

                http://www.springer.com/tdm

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