99 research outputs found
Optical and magneto-optical properties of Au:Conanoparticles and Co:Aunanoparticles doped magnetoplasmonic systems
© 2015 AIP Publishing LLC. We report a study of Au:CoNPs and Co:AuNPs doped magnetoplasmonic systems. In particular, we analyze the effect of adding different concentrations of Co (or Au) nanoparticles (NPs) in a Au (or Co) matrix on both the optical and magneto-optical constants. Through the use of a simple effective medium model, relevant changes in the optical properties of the Au NPs compared to those of bulk material have been identified. Such effects are not observed in the Co NPs system. However, in both systems, there is an increase of the effective diameter of the NPs as compared to the real diameter that can be due to interface effects surrounding the NPs. Moreover, the magneto-optical constants values of both systems are smaller (in absolute values) than expected, which could also be attributed to interface effects such as hybridization between Au and Co.This work was supported by the Spanish MINECO under Project Nos. MAT2011-29194-C02 (MAPS), CSD2007-00041 (NANOSELECT), and CSD2008-00023 (FUNCOAT).
http://dx.doi.org/10.1063/1.4906946Peer Reviewe
Core-Satellite Gold Nanoparticle Complexes Grown by Inert Gas-Phase Condensation
Spontaneous growth of complexes consisted of a number of individual nanoparticles in a controlled manner, particularly in demanding environments of gas-phase synthesis, is a fascinating opportunity for numerous potential applications. Here, we report the formation of such core-satellite gold nanoparticle structures grown by magnetron sputtering inert gas condensation. Combining high-resolution scanning transmission electron microscopy and computational simulations, we reveal the adhesive and screening role of H2O molecules in formation of stable complexes consisted of one nanoparticle surrounded by smaller satellites. A single layer of H2O molecules, condensed between large and small gold nanoparticles, stabilizes positioning of nanoparticles with respect to one another during milliseconds of the synthesis time. The lack of isolated small gold nanoparticles on the substrate is explained by Brownian motion that is significantly broader for small-size particles. It is inferred that H2O as an admixture in the inert gas condensation opens up possibilities of controlling the final configuration of the different noble metal nanoparticles.Peer reviewe
Capping layer effects in the structure and composition of Co nanoparticle ultrathin films
In this work, we present the correlation of the magnetic and structural properties of Co nanoparticles deposited by sputtering on Si3N4 substrates at different temperatures, and covered with different capping layers, two insulators, AlN and MgO, and a metal, Pt. High-resolution transmission electron microscopy shows the formation of CoPt3 and Co2N, for the Pt and AlN capping layers, respectively, giving to a significant change of the magnetic behavior. When using a cap of MgO, energy-filtered transmission electron microscopy shows an oxidized shell covering the Co nanoparticles with thickness decreasing as the deposition temperature increases, explaining the changes in the magnetic response induced by the MgO capping layer.This work has been funded by the Spanish Project No.MAT2002-04484-C03-02. Y.H. acknowledges the Consejo Superior de Investigaciones Científicas CSIC and Ramón y
Cajal Program for financial support.Peer reviewe
Modification of AFM tips by depositing nanoparticles with an Ion Cluster Source. Enhancement of the aspect-ratio and lateral resolution
Póster presentado en la NanoSpain Conference (Nanoiberian Conference), celebrada en Bilbao del 11 al 14 de abril de 2011.One of the factors that limit the spatial resolution in atomic force microscopy (AFM) is the physical
size of the probe. This limitation is particularly severe when the imaged structures are comparable
in size to the tip¿s apex. The resolution in the AFM is usually enhanced by using sharp tips with
high aspect ratios. In the present paper we propose an approach to modify AFM tips that consists of
depositing nanoclusters on standard silicon tips. We show that the use of those tips leads to atomic
force microscopy images of higher aspect ratios and spatial resolution. The present approach has two
major properties. It provides higher aspect-ratio images of nanoscale objects and, at the same time,
enables to functionalize the AFM tips by depositing nanoparticles with well-controlled chemical
composition.Peer Reviewe
Aspect-ratio and lateral-resolution enhancement in force microscopy by attaching nanoclusters generated by an ion cluster source at the end of a silicon tip
One of the factors that limit the spatial resolution in atomic force microscopy (AFM) is the physical size of the probe. This limitation is particularly severe when the imaged structures are comparable in size to the tip’s apex. The resolution in the AFM is usually enhanced by using sharp tips with
high aspect ratios. In the present paper we propose an approach to modify AFM tips that consists of depositing nanoclusters on standard silicon tips. We show that the use of those tips leads to atomic force microscopy images of higher aspect ratios and spatial resolution. The present approach has two major properties. It provides higher aspect-ratio images of nanoscale objects and, at the same time, enables to functionalize the AFM tips by depositing nanoparticles with well-controlled chemical
composition.The authors acknowledge the Spanish Ministerio de Ciencia e Innovación and Comisión Interministerial para
la Ciencia Y la Tecnología—CICYT under Contract Nos. MAT2008-06765-C02-02, MAT2009-08650, and CSD2007 00041 (Nanoselect) and through the FPI and “Juan de La Cierva” programs for financial support.Peer reviewe
Application of diamond-like carbon coatings to elastomers frictional surfaces
Nitrile-butyl rubber-like materials were coated with amorphous hydrogenated diamond-like carbon (DLC) coatings in order to modify their surface and tribological properties. Measurements of water contact angle were performed by the sessile drop method and showed that the coated samples are more hydrophobic with water contact angles up to 116°. The surface free energy of the elastomers was calculated by the acid-base regression method considering polar and dispersive contributions and the results were correlated with changes in the surface chemistry measured by X-ray photoelectron spectroscopy. It has been found that the lower presence of oxygen functional groups on the elastomer surfaces led to lower surface free energies, even though the polar contribution was not predominant. We also found that the DLC coatings led to a significant decrease of the surface free energy (up to 16%) and that there is a good correlation between the surface free energy values and the corresponding water contact angle values. The coefficient of friction was also measured and presented a significant decrease after coating with DLC. © 2008 Elsevier Ltd. All rights reserved.The authors acknowledge the financial support of the EU from the Sixth framework programme in the KRISTAL Project no. 515837-2. L. Martínez and Y. Huttel acknowledge the Spanish “Ministerio de Educación y Ciencia” for the “Juan de la Cierva” and “Ramón y Cajal” programmes, respectively. R. Nevshupa acknowledges the “Marie Curie” programme (MIF1-CT-2006-22067)
Versatile Graphene-Based Platform for Robust Nanobiohybrid Interfaces
Technologically useful and robust graphene-based interfaces for devices
require the introduction of highly selective, stable, and covalently bonded
functionalities on the graphene surface, whilst essentially retaining the
electronic properties of the pristine layer. This work demonstrates that highly
controlled, ultrahigh vacuum covalent chemical functionalization of graphene
sheets with a thiol-terminated molecule provides a robust and tunable platform
for the development of hybrid nanostructures in different environments. We
employ this facile strategy to covalently couple two representative systems of
broad interest: metal nanoparticles, via S-metal bonds, and thiol-modified DNA
aptamers, via disulfide bridges. Both systems, which have been characterized by
a multi-technique approach, remain firmly anchored to the graphene surface even
after several washing cycles. Atomic force microscopy images demonstrate that
the conjugated aptamer retains the functionality required to recognize a target
protein. This methodology opens a new route to the integration of high-quality
graphene layers into diverse technological platforms, including plasmonics,
optoelectronics, or biosensing. With respect to the latter, the viability of a
thiol-functionalized chemical vapor deposition graphene-based solution-gated
field-effect transistor array was assessed
Experimental Station for Generation, Processing and Diagnostics of Nanoparticles of Astrophysical Interest
Europhysics Sectional Conference on the Atomic and Molecular Physics of Ionized Gases. ESCAMPIG XXIV.Glasgow July 17-21 (2018). .--file:///C:/Users/BIBLIO~1/AppData/Local/Temp/CONGRESOS_Y_CONFERENCIAS752874-1.pd
Growth and magnetic characterization of Co nanoparticles obtained by femtosecond pulsed laser deposition
We present a detailed study on the morphology and magnetic properties of Co nanostructures deposited onto oxidized Si substrates by femtosecond pulsed laser deposition. Generally, Co disks of nanometric dimensions are obtained just above the ablation threshold, with a size distribution characterized by an increasingly larger number of disks as their size diminishes, and with a maximum disk size that depends on the laser power
density. In Au/Co/Au structures, in-plane magnetic anisotropy is observed in all cases, with no indication of superparamagnetism regardless of the amount of material or the laser power density. Magnetic force microscopy observations show coexistence of single-domain and vortex states for the magnetic domain structure of
the disks. Superconducting quantum interference device magnetometry and x-ray magnetic circular dichroism measurements point to saturation magnetization values lower than the bulk, probably due to partial oxidation of the Co resulting from incomplete coverage by the Au capping layer.Work was supported in part by the U.S. Department of Energy, Basic Energy Sciences (Grant No. DE-FG02-06ER46273), NSF FOCUS Center, the Spanish Ministerio de
Educación y Ciencia (References No. PR2005-0017 and No.MAT2005-05524-C02), Comunidad de Madrid (Reference No. S-0505/MAT/0194 NANOMAGNET), and CSIC (Reference No. 200650I130). Support from the SRS staff during the XMCD experiments is greatly acknowledged. Y.H. and L.M. also acknowledge financial support from the “Ramón y
Cajal” and “Juan de la Cierva” programs, respectively, from the Spanish Ministerio de Investigación y Ciencia and Consejo
Superior de Investigaciones Científicas (CSIC).Peer reviewe
Nanomaterials to aid wound healing and infection control
The management and treatment of infectious bacterial diseases in wound healing have both become significant research areas in the biomedical field. While current treatments show limitations related to toxicity and exposure time, nanotechnology has become a potential alternative to overcome such challenges. The application of different nanomaterials, with a wide range of elemental compositions, morphologies, and features, has become an essential tool in managing wound healing infections. This book chapter shows an updated view of the newest trends in the control and treatment of bacterial proliferation in the wound bed by utilizing various metal- and nonmetal-based nanostructures
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