1,721,003 research outputs found
Electrocatalytic hydrogen redox chemistry on gold nanoparticles
Get PDFElectrocatalytic proton reduction leading to the formation of adsorbed molecular hydrogen on gold nanoparticles of 1-3 and 14-16 nm diameter stabilized by 1-mercapto-undecane-11-tetra(ethyleneglycol) has been demonstrated by cyclic voltammetry using a hanging mercury drop electrode. The nanoparticles were adsorbed to the electrode from aqueous dispersion and formed robust surface layers transferrable to fresh base electrolyte solutions. Unique electrocatalytic proton redox chemistry was observed that has no comparable counterpart in the electrochemistry of bulk gold electrodes. Depending on size, the nanoparticles have a discrete number of electrocatalytically active sites for the two-electron/two-proton reduction process. The adsorbed hydrogen formed is oxidized with the reverse potential sweep. These findings represent a new example of qualitative different behavior of nanoparticles in comparison with the corresponding bulk material.Fil: Brust, Mathias. University of Liverpool; Reino UnidoFil: Gordillo, Gabriel Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; Argentin
Enzymatic disassembly of DNA-gold nanostructures
No full textThe efficient digestion of nanoparticle assemblies connected by DNA linkers is demonstrated using a number of complementary methods (enzymatic cleavage with EcoRI is shown in the scheme). The efficiency of digestion is dependent on the design of the DNA linker. The ability to manipulate DNA enzymatically is important in the development of hierarchical chemical methods of nanoscale assembly
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Interactions of gold nanoparticles with a phospholipid monolayer membrane on mercury
Get PDFIt is demonstrated that a compact monolayer of 1,2-dioleoyl-sn-glycero-3-phosphocholineadsorbed to a hanging mercury drop electrode can serve as a simple electrochemicalmodel system to study biomembrane penetration by gold nanoparticles. The hydrogen redoxchemistry characteristic of ligand-stabilized gold nanoparticles in molecularly close contact with a mercury electrode is used as an indicator of membrane penetration. Results for water-dispersible gold nanoparticles of two different sizes are reported, and comparisons are made with the cellular uptake of the same preparations of nanoparticles by a common human fibroblast cell line. The experimental system described here can be used to study physicochemical aspects of membrane penetration in the absence of complex biological mechanisms, and it could also be a starting point for the development of a test bed for the toxicity of nanomaterials.Fil: Gordillo, Gabriel Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Krpetic, Zeljka. University of Liverpool; Reino UnidoFil: Brust, Mathias. University of Liverpool; Reino Unid
Photogeneration of singlet oxygen by gold nanoparticles
Get PDFPhotodynamic medicine has been known for more than 5000 years when Egyptians, Chinese and Indians used sunlight in combination with some “magic” plants to treat various disorders. Contemporary photodynamic therapy began in the 1900s, received its revival in 1970 due to hematoporphyrin derivative (HpD), and it is now an FDA approved therapeutic option for skin, early lung, and advanced oesophagal cancer in several countries. Although a few photosensitisers have been approved for clinical use, they suffer from several drawbacks such as biological and light instability and lack specificity toward specific types of cells.
In this thesis work, we propose plasmonic gold nanoparticles as photosensitisers to overcome the drawbacks of first- and second-generation photosensitiser and investigate their 1O2 photogeneration efficiency upon CW-laser irradiation at their surface plasmon resonance. First, the singlet oxygen sensitivity of two molecular probes (ABDA and DPBF) in different solvent systems was determined, using Rose Bengal as a photosensitiser. Second, we showed conclusively, for the first time, that gold nanoparticles photogenerate 1O2, and that the quantum yield is extremely small. Lastly, gold nanoparticles were functionalized with bovine serum albumin, and their singlet oxygen quantum yield re-evaluated. Our irradiation results showed that the protein corona, i.e. bovine serum albumin, did not affect the 1O2 production
High Resolution Characterisation of Gold Nanoparticle Coronae by Differential Centrifugal Sedimentation
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