Synthesis and Structural Characterization of Branched Bimetallic AuPd Nanoparticles with a Highly Tunable Optical Response

Funding Information: This work received financial support from Portugal national funds [Fundação para a Ciência e Tecnologia and Ministério da Ciência, Tecnologia e Ensino Superior (FCT/MCTES)] through the Projects UIDB/50006/2020 and UIDP/50006/2020. Silvia Nuti, Carlos Lodeiro, José-Luis Capelo-Martinez, Adrián Fernández-Lodeiro, and Javier Fernández-Lodeiro thank the financial support from national funds (FCT/MCTES) through Project Met4Cat (EXPL/QUI-COL/0263/2021). The authors thank the financial support by the PROTEOMASS Scientific Society (Portugal) (General Funding Grant 2023). The authors acknowledge funding from the European Union’s Horizon 2020 Research and Innovation Program under Grant 823717-ESTEEM3, and Ana B. Hungría thanks the financial support from Junta de Andalucía Project P20_00968. Silvia Nuti thanks FCT/MCTEC (Portugal) for her doctoral grant associated with the chemistry Ph.D. program (SFRH/BD/144618/2019). Javier Fernández-Lodeiro thanks FCT for the research contract through the Program DL 57/2016-Norma Transitória. The work was carried out partially through the INL User Facilities (Braga, Portugal) and the Electron Microscope Division (DME) of the Servicios Centrales de Investigación Científica y Tecnológica (SC-ICYT) at Cadiz University (Cadiz, Spain). The authors thank Dr. Jamila Djafari for the assistance with the design of the graphical abstract. Funding Information: This work received financial support from Portugal national funds [Fundação para a Ciência e Tecnologia and Ministério da Ciência, Tecnologia e Ensino Superior (FCT/MCTES)] through the Projects UIDB/50006/2020 and UIDP/50006/2020. Silvia Nuti, Carlos Lodeiro, José-Luis Capelo-Martinez, Adrián Fernández-Lodeiro, and Javier Fernández-Lodeiro thank the financial support from national funds (FCT/MCTES) through Project Met4Cat (EXPL/QUI-COL/0263/2021). The authors thank the financial support by the PROTEOMASS Scientific Society (Portugal) (General Funding Grant 2023). The authors acknowledge funding from the European Union’s Horizon 2020 Research and Innovation Program under Grant 823717-ESTEEM3, and Ana B. Hungría thanks the financial support from Junta de Andalucía Project P20_00968. Silvia Nuti thanks FCT/MCTEC (Portugal) for her doctoral grant associated with the chemistry Ph.D. program (SFRH/BD/144618/2019). Javier Fernández-Lodeiro thanks FCT for the research contract through the Program DL 57/2016–Norma Transitória. The work was carried out partially through the INL User Facilities (Braga, Portugal) and the Electron Microscope Division (DME) of the Servicios Centrales de Investigación Científica y Tecnológica (SC-ICYT) at Cadiz University (Cadiz, Spain). The authors thank Dr. Jamila Djafari for the assistance with the design of the graphical abstract. Publisher Copyright: © 2023 The Authors. Published by American Chemical Society.Bimetallic nanostructures composed of gold (Au) and palladium (Pd) have garnered increased interest for their applications in heterogeneous catalysis. This study reports a simple strategy for manufacturing Au@Pd bimetallic branched nanoparticles (NPs), which offer a tunable optical response, using polyallylamine-stabilized branched AuNPs as template cores for Pd overgrowth. The palladium content can be altered by manipulating the concentration of PdCl42- and ascorbic acid (AA) that are injected, which permit an overgrowth of the Pd shell up to ca. 2 nm thick. The homogeneous distribution of Pd at the surfaces of Au NPs can be carried out regardless of their size or branching degree, which allows for an adjustment of the plasmon response in the near-infrared (NIR) spectral range. As a proof of concept, the nanoenzymatic activity of pure gold and gold-palladium NPs was compared, exploring their peroxidase-like activity in the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). The bimetallic AuPd NPs demonstrate an increase in the catalytic properties attributed to the presence of palladium at the surface of gold.publishersversionpublishe

Tuning Ternary Alloyed Nanoparticle Composition and Morphology by Exsolution in Double Perovskite Electrodes for CO2 Electrolysis

[EN] The intermittent nature of renewable energy resources makes imperative the development of efficient energy storage technologies. Solid oxide electrolysis cells (SOECs) are a promising alternative to energy conversion devices. SOECs can play an important role in the control of greenhouse gases by improving processes such as CO2 electrolysis. In order to enhance SOEC performance, exsolution of metal nanoparticles is emerging for the catalytic surface functionalization of electrodes, preventing sintering issues related to classical impregnation methods and enabling tailoring specific catalytic functions. In this work, a medium-entropy, double perovskite system SrxFeCo0.2Ni0.2Mn0.1Mo0.5O6-delta (x = 2.0, 1.9, and 1.8) was studied. We provide evidence of Fe-Co-Ni ternary alloyed exsolved nanoparticles, revealing that the alloy composition can be tuned by adjusting the reducing conditions. Exsolution temperature is critical for Fe content in nanoparticles, increasing as temperature increases, but Ni and Co are not significantly affected. Temperature adjustments allowed control over nanoparticle size and population, shrinking and growing, respectively, as temperature decreases. In contrast to what is usually described, A-site deficiency resulted in a decrease in nanoparticle exsolution because of NiO phase formation in x = 1.9 and 1.8, so that the x = 2.0 compound outperformed both non-stoichiometric materials, showing significantly larger populations. The three compounds exhibit important conductivity under both oxidizing and reducing atmospheres, which makes them promising electrodes. The Sr2FeCo0.2Ni0.2Mn0.1Mo0.5O6-delta material was integrated as a cathode in an asymmetrical electrolyte-supported cell, and its electrochemical performance under CO2 electrolysis conditions was studied. Our results showed a boost in electrocatalytic activity upon exsolution at 600 degrees C when compared to the fuel electrode without exsolved nanoparticles or exsolved at 800 degrees C, where the appearance of the secondary Ruddlesden-Popper phase was observed. Overall, here, we proved the possibility of obtaining ternary alloy exsolved nanoparticles and tuning their composition to enhance the performance of SOEC devices, paving the path for optimized metal-alloyed exsolved nanoparticle design, which might extend its applicability to other electrocatalytic processes in energy conversion and storage.The project that gave rise to these results received the support of a fellowship from Spanish Government (RTI2018-102161 grant) and "la Caixa" Foundation (ID 100010434 and grant LCF/BQ/PI20/11760015). Authors acknowledge the use of instrumentation and the technical advice provided by the National Facility ELECMI ICTS, node "Division de Microscopia Electronica"at Universidad de Cadiz. We thank the support of the Electronic Microscopy Service of the Universitat Politecnica de Valencia.López-García, A.; Almar-Liante, L.; Escolástico Rozalén, S.; Hungría, AB.; Carrillo-Del Teso, AJ.; Serra Alfaro, JM. (2022). Tuning Ternary Alloyed Nanoparticle Composition and Morphology by Exsolution in Double Perovskite Electrodes for CO2 Electrolysis. ACS Applied Energy Materials. 5(11):13269-13283. https://doi.org/10.1021/acsaem.2c01829132691328351

Understanding the role of Ti-rich domains in the stabilization of gold nanoparticles on mesoporous silica-based catalysts

The preparation and stabilization of gold nanoparticles with a precise control of size and dispersion is highly attractive for a variety of applications, and a key aspect is thermal stability of the nanoparticles. This paper focuses on understanding the effect of TiO2-based nanodomains, dispersed on mesoporous silicas, and how they control gold nanoparticle stability. The anatase domains have been incorporated through two different strategies: co-hydrolysis of Si and Ti reagents that directly form the mesoporous material through self-assembling with surfactant micelles, or the post-impregnation of the mesosporous silica with Ti(acac)2. Both strategies lead to different incorporation of the anatase domains: partially embedded inside the silica walls, or occupying the mesopores. We have observed that the inclusion in the pores favors the stability of the final material due to a more favorable gold-support interaction and also due to a stabilizing effect associated with a scaffold effect of the anatase crystals, which hinders the collapse of the mesostructure

3D characterization of CdSe nanoparticles attached to carbon nanotubes

The crystallographic structure of CdSe nanoparticles attached to carbon nanotubes has been elucidated by means of high resolution transmission electron microscopy and high angle annular dark field scanning transmission electron microscopy tomography. CdSe rod-like nanoparticles, grown in solution together with carbon nanotubes, undergo a morphological transformation and become attached to the carbon surface. Electron tomography reveals that the nanoparticles are hexagonal-based with the (001) planes epitaxially matched to the outer graphene layer.Comment: 7 pages, 8 figure

The complete genome sequence of Chromobacterium violaceum reveals remarkable and exploitable bacterial adaptability

Chromobacterium violaceum is one of millions of species of free-living microorganisms that populate the soil and water in the extant areas of tropical biodiversity around the world. Its complete genome sequence reveals (i) extensive alternative pathways for energy generation, (ii) ≈500 ORFs for transport-related proteins, (iii) complex and extensive systems for stress adaptation and motility, and (iv) wide-spread utilization of quorum sensing for control of inducible systems, all of which underpin the versatility and adaptability of the organism. The genome also contains extensive but incomplete arrays of ORFs coding for proteins associated with mammalian pathogenicity, possibly involved in the occasional but often fatal cases of human C. violaceum infection. There is, in addition, a series of previously unknown but important enzymes and secondary metabolites including paraquat-inducible proteins, drug and heavy-metal-resistance proteins, multiple chitinases, and proteins for the detoxification of xenobiotics that may have biotechnological applications

Heterogeneous photocatalysis: Light-matter interaction and chemical effects in quantum efficiency calculations

In this contribution we analyze the calculation of the quantum efficiency observable in the gas-phase heterogeneous photocatalytic oxidation of toluene. To this end, we carried out porosimetry, UV–visible optical, and TEM tomography measurements together with the mathematical modeling of the most significant physico-chemical factors influencing the quantum efficiency observable. Critical factors concern physical properties related to the light-matter interaction as well as the chemical properties defining the outcome of the reaction. Among the firsts, we analyze the effective catalyst surface area illuminated and provide a detailed formulation of the radiation model, including main absorbance, transmittance and reflectance events. For chemical properties not only the activity but also the selectivity was considered. The work was carried out with a dual aim. First, by scanning a basis set containing most common reactor geometries and light sources, we illustrate quantitatively (numerically) and qualitatively (relative among factors) the importance of each one of the above mentioned factors in quantum efficiency calculations. Second, using a series of samples with “continuous” variation of chemical, textural, morphological and optical properties we calibrate the goodness of common simplifications utilized to represent the above mentioned physical/chemical factors and measure their numerical effects in the quantum efficiency observable. Combination of these two approaches provides a general scheme to bundle and interpret all physico-chemical factor effects in quantum efficiency outputs and can serve as a guide to calibrate current quantum efficiency formulations accuracy.A. Kubacka and M.J. Muñoz-Batista thank MINECO − Spain for support through, respectively, the postdoctoral “Ramón y Cajal” and predoctoral FPI programs. Financial support by MINECO is also acknowledged (Project ENE2013-46624-C4-1 partially financed by FEDER).Peer Reviewe

Characterization of Active Sites/Entities and Redox/Catalytic Correlations in Copper-Ceria-Based Catalysts for Preferential Oxidation of CO in H2-Rich Streams

This article reviews work done at authors’ laboratories about catalysts based on combinations between copper and ceria for preferential oxidation of CO in H2-rich streams (CO-PROX). The main focus of this review is the characterization of active sites for the process on the basis of spectroscopic analysis of the systems under reaction conditions (operando techniques). On such a basis, it is exposed the state of the art in this field in connection with results obtained in other laboratories.This work was funded by Ministerio de Ciencia e Innovación and Ministerio de Economía y Competitividad (Plan Nacional Projects CTQ2009-14527 and CTQ2012-32928) and Comunidad de Madrid (Project DIVERCEL, Ref.: S2009/ENE-1475). Support from EU COST CM1104 action is also acknowledged. Antonio López Cámara acknowledges a PhD grant from the CSIC JAE program.We acknowledge support by the CSIC Open Access Publication Initiative through its Unit of Information Resources for Research (URICI)

Microwave-Assisted synthesis and luminescence of mesoporous RE-Doped YPO 4 (RE = Eu, Ce, Tb, and Ce + Tb) nanophosphors with lenticular shape

Mesoporous tetragonal RE:YPO 4 nanophosphors (RE = Eu, Ce, Tb, and Ce + Tb) with a lenticular morphology, narrow size distribution, and high surface area have been prepared by an homogeneous precipitation procedure consisting of aging, at low temperature (80-120 °C) in a microwave oven, ethylene glycol solutions containing only yttrium acetylacetonate and phosphoric acid. This synthesis method involves important advantages such as its simplicity, rapidness (reaction time = 7 min), and high reaction yields. The mechanism of nanoparticle growth has been also addressed finding that the lenticular nanoparticles are formed through an ordered aggregation of smaller entities, which explains their porosity. In all cases, the doping levels were systematically varied in order to optimize the nanophosphors luminescence. All optimum nanophosphors presented a high luminescence quantum yield (QY). In particular, for the Eu and Tb doped systems, the obtained QY values (60% for Eu and 80% for Tb) were the highest so far reported for this kind of nanomaterial. The morphological, microstructural, and luminescent properties of these nanophosphors and their dispersibility in water make them suitable for biomedical applications. © 2011 American Chemical Society.Peer Reviewe

Cerium–terbium mixed oxides as potential materials for anodes in solid oxide fuel cells

Highly homogeneous (Ce,Tb) oxides are prepared by a microemulsion technique, and their structural and electronic state after high temperature calcination is examined with X-ray diffraction, high resolution transmission electron microscopy, X-ray photoelectron and absorption (XANES) spectroscopies and impedance spectroscopy measurements. Addition of Tb stabilizes significantly (in comparison to pure ceria) specific surface area and small particles sizes during high temperature calcination (up to 1100 °C); phase decomposition at these high temperatures, similar to that occurring when stabilization of ceria is carried out with Zr, does not occur, and the mixed oxide remains homogeneous throughout. Tb addition to ceria may thus be beneficial when used as a component of SOFC anodes. TEM data indicate reshaping of oxide particles and provide evidence of crystal superstructures after high temperature treatments, while XPS and XANES reveal an increase in the Tb4+/Tb3+ ratio (for a given pretreatment) with the Tb/Ce ratio; Ce seems to be less reducible to Ce3+ in the presence of Tb. Total electrical conductivity of CT samples under H2 is mediated by electron transport (involving probably only Ce) and is lower than in gadolinia-doped ceria (GCO); in air conductivity is higher than for GCO, particularly at low temperatures, and it is probable that a p-type transport mechanism predominates in this case.Thanks are given to CICYT (Project MAT2003-03925) for financial support of this research, to the Universities of Madrid (Complutense) and Cádiz for the facilities given for the obtention of TEM data, to ICP-Unidad de Apoyo staff for chemical analysis results and XRD recording, to technical staff at Daresbury Laboratory Station 9.3 (Drs. I. Harvey and A.R. Lennie) for the help given during recording of the XAFS spectra, and to Mr. A. Macías for assistance in recording the XPS data.Peer reviewe