Influence of of the separation procedure on the properties of magnetic nanoparticles: Gaining in vitro stability and T-1-T-2 magnetic resonance imaging performance

Ultrasmall superparamagnetic iron oxide nanoparticles (USPIOs) coated with polyacrylic acid (PAA) were synthesized by a hydrothermal method in gram-scale quantity and extensively characterized. Only the nanoparticles subjected to an additional centrifugation step showed narrow size distribution, high polymeric coverage, and ideal superparamagnetism. In addition to improved physico-chemical properties, these nanoparticles feature high stability in vitro as well as dual T1-T2 performance as contrast agents (CAs) for magnetic resonance imaging (MRI), highlighting the importance of the additional separation step in obtaining material with the desired properties.status: publishe

Multiresponsive Hybrid Colloids Based on Gold Nanorods and Poly(NIPAM-co-allylacetic acid) Microgels: Temperature- and pH-Tunable Plasmon Resonance

Karg M, Lu Y, Carbo-Argibay E, et al. Multiresponsive Hybrid Colloids Based on Gold Nanorods and Poly(NIPAM-co-allylacetic acid) Microgels: Temperature- and pH-Tunable Plasmon Resonance. Langmuir. 2009;25(5):3163-3167.This work describes the control and manipulation of the optical properties of multiresponsive organic/inorganic hybrid colloids, which consist of thermo-responsive poly-(NIPAM-co-allylacctic acid) microgel cores and gold nanorods assembled on their surface. These composites are multifunctional, in the sense that they combine the interesting optical properties of the rod-shaped gold particles-exhibiting two well-differentiated plasmon modes-with the sensitivity of the copolymer microgel toward external stimuli, such is temperature or solution pH. It is shown that the collapse of the microgel core, induced by changes in either temperature or pH, enhances the electronic interactions between the gold nanorods on the gel surface, as a result of the subsequent increase of the packing density arising from the surface decrease of the collapsed microgel. Above a certain nanorod density, such interactions lead to remarkable red-shifts of the longitudinal plasmon resonance

Magnetite Nanoparticles for Stem Cell Labeling with High Efficiency and Long-Term in Vivo Tracking

Superparamagnetic iron oxide nanoparticles (SPIO-PAA), ultrasmall iron oxide nanoparticles (USPIO-PAA), and glucosamine-modified iron oxide nanoparticles (USPIO-PAA-GlcN) were studied as mesenchymal stem cell (MSCs) labels for cell tracking applications by magnetic resonance imaging (MRI). Pronounced differences were found in the labeling performance of the three samples in terms of cellular dose and labeling efficiency. In combination with polylysine, SPIO-PAA showed nonhomogeneous cell internalization, while for USPIO-PAA no uptake was found. On the contrary, USPIO-PAA-GlcN featured high cellular uptake and biocompatibility, and sensitive detection in both in vitro and in vivo experiments was found by MRI, showing that glucosamine functionalization can be an efficient strategy to increase cell uptake of ultrasmall iron oxide nanoparticles by MSCs.status: publishe

Design and Synthesis of Highly Active Al-Ni-P Foam Electrode for Hydrogen Evolution Reaction

© 2015 American Chemical Society. An effective method to boost the electrocatalytic activity of nickel phosphides in H2 evolution reaction is reported. The method took advantage of density functional theory calculations that allowed the design of a highly active material based on the combination of d-metal with p-metal within a phosphide structure. Furthermore, the principle is proven experimentally through successful synthesis of self-supported ternary Al-Ni-P foam electrocatalyst by alloying of Ni and Al followed by the gas transport phosphorization reaction. As a cathode for H2 evolution reaction in acidic electrolyte, Al-Ni-P significantly outperforms pure Ni-P, and it has an exchange current density of 0.6 mA/cm2 and a Tafel slope of 65 mV/decade.status: publishe

Multimodal Plasmonic Hybrids: Efficient and Selective Photocatalysts

Important efforts are currently under way in order to implement plasmonic phenomena in the growing field of photocatalysis, striving for improved efficiency and reaction selectivity. A significant fraction of such efforts has been focused on distinguishing, understanding and enhancing specific energy transfer mechanisms from plasmonic nanostructures to their environment. Herein we report a synthetic strategy that brings together two of the main physical mechanisms driving plasmonic photocatalysis into an engineered system by rationally combining the photochemical features of energetic charge carriers and the electromagnetic field enhancement inherent to the plasmonic excitation. We do so by creating hybrid photocatalysts that integrate multiple plasmonic resonators in a single entity, controlling their joint contribution through spectral separation and differential surface functionalization. This strategy allows us to study the combination of different photosensitization mechanisms when activated simultaneously. Our results show that hot electron injection can be combined with an energy transfer process mediated by near-field interaction, leading to a significant increase of the final photocatalytic response of the material. In this manner, we overcome the limitations that hinder photocatalysis driven only by a single energy transfer mechanism, and move the field of plasmonic photocatalysis closer to energy-efficient applications. Furthermore, our multimodal hybrids offer a test system to probe the properties of the two targeted mechanisms in energy-related applications such as the photocatalytic generation of hydrogen and open the door to wavelength-selective photocatalysis and novel tandem reactions

Tuning coherent-phonon heat transport in LaCoO3/SrTiO3 Superlattices

Accessing the regime of coherent phonon propagation in nanostructures opens enormous possibilities to control the thermal conductivity in energy harvesting devices, phononic circuits, etc. In this paper we show that coherent phonons contribute substantially to the thermal conductivity of LaCoO3/SrTiO3 oxide superlattices, up to room temperature. We show that their contribution can be tuned through small variations of the superlattice periodicity, without changing the total superlattice thickness. Using this strategy, we tuned the thermal conductivity by 20% at room temperature. We also discuss the role of interface mixing and epitaxial relaxation as an extrinsic, material dependent key parameter for understanding the thermal conductivity of oxide superlatticesThis work has received financial support from Ministerio de Economía y Competitividad (Spain) under project Nos. MAT2016-80762-R and PID2019-104150RB-I00, Xunta de Galicia (Centro singular de investigación de Galicia accreditation 2019-2022, ED431G 2019/03), the European Union (European Regional Development Fund-ERDF), and the European Commission through the Horizon H2020 funding by H2020-MSCA-RISE-2016- Project No. 734187-SPICOLOST. E.L. is a Serra Húnter Fellow (Generalitat de Catalunya). D.B. acknowledges financial support from MINECO (Spain) through an FPI fellowship (BES-2017-079688). V.P. and A.O.F. were supported by the MINECO of Spain through the project PGC2018-101334-B-C21. A.O.F. thanks MECD for the financial support received through the FPU grant FPU16/02572. This work was carried out in part through the use of the INL User FacilitiesS