silver – Inorganic Nanoparticles Group

Probing the surface reactivity of nanocrystals by the catalytic degradation of organic dyes: the effect of size, surface chemistry and composition. Published in Journal of Materials Chemistry A

Editor — Fri, 28 Sep 2018 10:00:57 +0000

We herein present a comprehensive study on how the catalytic performance and reusability of Au nanocrystals (NCs) are affected by systematic variations of crystal size, surface coating and composition. The reductions of different organic dyes (4-nitrophenol, rhodamine B and methylene blue) by borohydride ions were used as model catalytic reactions. The catalytic performance of the Au NCs ranged between 3.6 to 110 nm was found to be dependent on crystal size, indicating that Au surface atoms have a distinct size-dependent reactivity in this reaction. Similarly, the catalytic performance was found to be strongly dependent on the nature of the coating molecule, obtaining lower catalytic activities for molecules strongly bound to the Au surface. Finally, the catalytic performance was found to be dependent on the chemical composition of the NC (Au, Ag, Pt) and the model dye used as a testing system, with the highest degradation rate found for methylene blue, followed by 4-nitrophenol and rhodamine B. We believe that this study provides a better understanding of the catalytic performance of Au NCs upon controlled modifications of the structural and morphological parameters, and a working environment that can be used to facilitate the selection of the optimum NC size, coating molecule and evaluation system for a particular study of interest.

Probing the surface reactivity of nanocrystals by the catalytic degradation of organic dyes: the effect of size, surface chemistry and composition

New Paper on the Study of the Localized Multipolar Surface Plasmon Resonances of Silver Nanoparticles Published in Langmuir.

Editor — Fri, 10 Mar 2017 19:33:43 +0000

Silver nanoparticles absorb and scatter light with extraordinary efficiency due to the collective oscillations of the conduction electrons of the metal surface when they are excited by light of an specific wavelengths. These oscillations, known as a localized surface plasmon resonances (LSPRs) are determined by the size, shape and local environment in which the nanoparticle is embedded. In this work, we have spectroscopically investigated the effect of the size and surface coating on the sensitivity of localized multipolar surface plasmon resonances in high-quality silver colloidal solutions with precisely controlled sizes from 10 to 220 nm and well-defined surface chemistry, identifying the size-dependence of dipolar, quadrupolar and octapolar modes. Besides, we studied how these multipolar resonances are affected by modifications of the NP’ surface coating, in particular the dependences on the length and the anchor group of the molecule attached at its surface, revealing the higher sensitivity of larger sizes, dipolar than higher-order modes, thiol than amine groups, and long than short molecules. We also extend this study to gold nanoparticles, aiming to compare the sensitivity of both materials, quantifying the higher sensitivity of silver. The work has now been published in Langmuir under the title “Quantifying the Sensitivity of Multipolar (Dipolar, Quadrupolar and Octapolar) Surface Plasmon Resonances in Silver Nanoparticles: The Effect of Size, Composition and Surface Coating.”

New Paper on High-Index Surface Platinum Hollow Nanocrystals Published in Journal of Materials Chemistry A.

Editor — Fri, 10 Mar 2017 17:58:03 +0000

One of the main focus of the group is the development of synthetic strategies for the production of advanced hollow NCs allowing the precise morphological control of its surface. This aspect, of critical importance for the understanding of the unique properties of the materials at the nanoscale, is also useful in a wide range of applications, such as catalysis, where the development of highly active and low-cost materials represents a landmark for the development of industrial technologies. This time we show how combining solid state chemistry techniques and colloidal synthesis allows us to prepare exotic materials, such as PtAg@Pt single-crystal hollow NCs with high-index planes, at room temperature (green temperature) by controlled corrosion of silver templates, which minimize Pt consumption and maximize surface reactivity. We are further working on the applicability use of these NC-based catalysts. The work, carried out with the collaboration of Prof. Jordi Arbiol from the Catalan Institute of Nanoscience and Nanotechnology (ICN2), has now been published in Journal of Materials Chemistry A under the title ” Enhanced reactivity of high-index surface platinum hollow nanocrystals“

Our work on hollow complex nanostructures has been published in Science!

Editor — Tue, 20 Dec 2011 19:57:13 +0000

One of the main works from Dr. Edgar Gonzalez’s doctorate in our group was the synthesis of highly complex metallic hollow nanostructures. He obtained gold and silver nanocages and nanoboxes (multi-walled and/or multi-chambered polyhedra and wires). The degree of structural complexity was not the only achievement here, but also the fact that the synthetic procedure can be performed at room temperature (green chemistry), unlike previous attempts where high temperatures were required.

This work, carried out with the collaboration of Prof. Jordi Arbiol from the Institute of Materials Science of Barcelona (ICMAB), has now been published in Science, “Carving at the Nanoscale: Sequential Galvanic Exchange and Kirkendall Growth at Room Temperature”. Its value also resides in the fact that the concept relies in “carving” the hollow structure out of a solid one (controlled corrosion). And this is fundamentally different from the general trend of thinking that complex precious nanostructures should be built assembling objects atom-by-atom or molecule-by-molecule. This conceptual move is also well framed in the Perspective article by W. Parak that introduces our paper in the Science issue: “Complex Colloidal Assembly”. It is also well explained in simpler terms in the BBC Technology news item “Nanoparticle hollowing method promises medical advances”.

Gonzalez, E., Arbiol, J., & Puntes, V. F. (2011). Carving at the Nanoscale: Sequential Galvanic Exchange and Kirkendall Growth at Room Temperature. Science, 334(6061), 1377–1380.

http://www.sciencemag.org/content/334/6061/1377

Selected media coverage and related:

Wolfgang J. Parak (2011). Complex Colloidal Assembly. Science 334(6061), 1359-1360.

http://www.sciencemag.org/content/334/6061/1359

BBC Online: Nanoparticle hollowing method promises medical advances, by Leo Kelion. December 8, 2011.

http://www.bbc.co.uk/news/technology-16101495

PhysicsWorld.com: Corrosion carves out 3D nanostructures, by Belle Dumé. December 12, 2012.

http://physicsworld.com/cws/article/news/2011/dec/12/corrosion-carves-out-3d-nanostructures

RSC Chemistry World: Molecular suitcases created by corrosion, by Simon Hadlington. December 8, 2012.

http://www.rsc.org/chemistryworld/News/2011/December/08121105.asp

El Mundo Newspaper: ‘Matriuskas’ en las estructuras internas de las nanopartículas. December 8, 2011.

http://www.elmundo.es/elmundo/2011/12/07/nanotecnologia/1323285656.html

ScienceDaily: Carving at the Nanoscale. December 10, 2011

http://www.sciencedaily.com/releases/2011/12/111208142013.htm

MaterialsToday.com: Carving goes nanoscale. December 12, 2011.

http://www.materialstoday.com/view/22582/carving-goes-nanoscale/

Phys.org: Carving at the nanoscale. December 8, 2011.

http://phys.org/news/2011-12-nanoscale.html

Nanowiki.info: Why hollow?… No, why solid!, by Victor Puntes. December 19, 2011.

http://www.nanowiki.info/#[[Why%20hollow%3F…%20No%2C%20why%20solid!]]