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2020


Effect of Gold Particles Size over Au/C Catalyst Selectivity in HMF Oxidation Reaction


Megias-Sayago, C; Lolli, A; Bonincontro, D; Penkova, A; Albonetti, S; Cavani, F; Odriozola, JA; Ivanova, S
Chemcatchem (2020)

ABSTRACT

A series of gold nanoparticles in the 4-40 nm range were prepared, immobilized on activated carbon and further tested, at low base concentration, in the catalytic oxidation of 5-hydroxymethyl furfural (HMF) to 2,5-furandicarboxylic acid (FDCA). Gold particles size variation has no influence on HMF conversion but significantly affects product selectivity and carbon balance. This behavior is ascribed to the thermodynamically favorable oxygen reduction reaction on Au(100) faces. As the gold particle size decreases the Au(100)/Au(111) exposure ratio, estimated by using the van Hardeveld-Hartog model, increases as well as the FDCA selectivity. The smaller the gold particle size the smaller the 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) to FDCA ratio pointing to the gold size dependent behavior of the oxidation of the alcohol function of the HMF molecule.


Enero, 2020 | DOI: 10.1002/cctc.201901742

Processing and properties of Bi0.98R0.02FeO3 (R = La, Sm, Y) ceramics flash sintered at similar to 650 degrees C in <5 s


Gil-Gonzalez, E; Perejon, A; Sanchez-Jimenez, PE; Raj, R; Perez-Maqueda, LA
Journal of the American Ceramic Society, 103 (2020) 136-144

ABSTRACT

We show that flash sintering produces single‐phase, nanograin‐sized polycrystals of isovalent‐substituted multiferroic ceramics of complex compositions. Single‐phase polycrystals of Bi0.98R0.02FeO3 (R = La, Sm, Y) were produced at a furnace temperature of ~650°C in a few seconds by the application of an electric field of 50 V cm−1, with the current limit set to 40 mA mm−2. The dielectric and insulating properties compared favorably with expected values. Impedance spectroscopy suggests electrically homogenous microstructure, except for the sample Bi0.98La0.02FeO3 that shows a small grain boundary contribution to the impedance. These results reinforce the enabling nature of flash sintering for ceramics which pose difficulties in conventional sintering because they contain low melting constituents or develop secondary phases during the sintering protocol.


Enero, 2020 | DOI: 10.1111/jace.16718

Finite Size Effects on Light Propagation throughout Random Media: Relation between Optical Properties and Scattering Event Statistics


Miranda-Munoz, JM; Esteso, V; Jimenez-Solano, A; Lozano, G; Miguez, H
Advanced Optical Materials, 8 (2020) 1901196

ABSTRACT

This work introduces a thorough analysis of light transport in thin optically disordered media. The diffusive properties of a turbid material are generally dictated by the transport mean free path, lt. For depths larger than this characteristic length, light propagation can be considered fully randomized. There is however a range of thicknesses for which light becomes only partly randomized, as it only undergoes a single or very few scattering events. The effects of such finitude are experimentally and theoretically studied on the optical properties of the material, such as the angular distribution of scattered light. Simulations provide insight into the phenomena that occur within the optically disordered slab, like the number of scattering events that photons undergo during propagation throughout the material, as a function of the built‐in wavelength dependent scattering mean free path, lsc. This approach provides fundamental information about photon transport in finite optically random media, which can be put into practice to design diffusers with specific requirements in terms of the spectral and angular properties of the scattered light.


Enero, 2020 | DOI: 10.1002/adom.201901196

New waste-based clinkers for the preparation of low-energy cements. A step forward toward circular economy


Martinez-Martinez, S; Perez-Villarejo, L; Eliche-Quesada, D; Sanchez-Soto, PJ; Christogerou, A; Kanellopoulou, DG; Angelopoulos, GN
International Journal of Applied Ceramic Technology, 17 (2020) 12-21

ABSTRACT

This paper describes the use of industrial wastes arising from different production processes of the ceramic and marble industries as raw materials for the design and formulation of new cement clinkers with a high content of dicalcium silicate (Belite). The aim was to reintroduce these wastes in the industrial sector and take advantage of them for a greater environmental benefit, as indicated by the principles of the circular economy. Formulations containing 2.5, 5 and 10 wt% of chamotte and marble sludge, respectively, and a waste-free formulation have been designed to obtain clinkers with a content of dicalcium silicate higher than 60 wt%. The different blends have been studied up to a maximum temperature of 1390 degrees C by Thermal Analysis. Other techniques such as XRD, XRF, Modified Bogue Equation, Quality Indexes (LSF, AM, SM) and Optical Microscopy have been used for the study and characterization of industrial wastes, the raw materials and the high belite-type cement dosages. The results indicate that this type of cements can be designed using different types of wastes and in this way reduce the environmental impacts caused by the extraction of raw materials and the deposition of the wastes in landfills, improving the circular economy of the construction industry.


Enero, 2020 | DOI: 10.1111/ijac.13390

Obituary: Prof. José Manuel Criado


Perez-Maqueda, LA; Real, C; Gotor, FJ; Alcala, MD; Malek, J; Koga, N
Journal of Thermal Analysis and Calorimetry, (2020)

ABSTRACT

Influence of DSC thermal lag on evaluation of crystallization kinetics


Svoboda, R; Maqueda, LP; Podzemna, V; Perejon, A; Svoboda, O
Journal of Non-Crystalline Solids, 528 (2020) 119738

ABSTRACT

Influence of added thermal resistance on crystallization kinetics, as measured by differential scanning calorimetry (DSC), of the Se70Te30 glass was studied. The increase of thermal resistance was achieved by adding polytetrafluorethylene discs of different thicknesses (up to 0.5 mm) in-between the DSC platform and the pan with sample. Increase of the thermal resistance led to an apparent decrease (by more than 30%) in the crystallization enthalpy. Significant change of model-free kinetics occurred: apparent activation energy E of the crystallization process decreased (by more than 20%) due to the DSC data being progressively shifted to higher temperatures with increasing heating rate. The model-based kinetics was changed only slightly; the DSC peaks retained their asymmetry and the choice of the appropriate model was not influenced by the added thermal resistance. The temperature shift caused by added thermal lag was modeled for the low-to-moderate heating rates.


Enero, 2020 | DOI: 10.1016/j.jnoncrysol.2019.119738

Low gas consumption fabrication of He-3 solid targets for nuclear reactions


Fernandez, A; Hufschmidt, D; Colaux, JL; Valiente-Dobon, JJ; Godinho, V; de Haro, MCJ; Feria, D; Gadea, A; Lucas, S
Materials & Design, 186 (2020) 108337

ABSTRACT

Nanoporous solids that stabilize trapped gas nanobubbles open new possibilities to fabricate solid targets for nuclear reactions. A methodology is described based on the magnetron sputtering (MS) technique operated under quasistatic flux conditions to produce such nanocomposites films with He-3 contents of up to 16 at.% in an amorphous-silicon matrix. In addition to the characteristic low pressure (3-6 Pa) needed for the gas discharge, the method ensures almost complete reduction of the process gas flow during film fabrication. The method could produce similar materials to those obtained under classical dynamic flux conditions for MS. The drastic reduction (>99.5%) of the gas consumption is fundamental for the fabrication of targets with scarce and expensive gases. Si:He-3 and W:He-3 targets are presented together with their microstructural (scanning and transmission electron microscopy, SEM and TEM respectively) and compositional (Ion Beam Analysis, IBA) characterization. The He-3 content achieved was over 1 x 10(18) at/cm(2) for film thicknesses between 1.5 and 3 mu m for both Si and W matrices. First experiments to probe the stability of the targets for nuclear reaction studies in inverse kinematics configurations are presented. 


Enero, 2020 | DOI: 10.1016/j.matdes.2019.108337

Enhanced Stability of Perovskite Solar Cells Incorporating Dopant-Free Crystalline Spiro-OMeTAD Layers by Vacuum Sublimation


Barranco, A; Lopez-Santos, MC; Idigoras, J; Aparicio, FJ; Obrero-Perez, J; Lopez-Flores, V; Contreras-Bernal, L; Rico, V; Ferrer, J; Espinos, JP; Borras, A; Anta, JA; Sanchez-Valencia, JR
Advanced Energy Materials, (2020) 1901524

ABSTRACT

The main handicap still hindering the eventual exploitation of organometal halide perovskite-based solar cells is their poor stability under prolonged illumination, ambient conditions, and increased temperatures. This article shows for the first time the vacuum processing of the most widely used solid-state hole conductor (SSHC), i.e., the Spiro-OMeTAD [2,2 ',7,7 '-tetrakis (N,N-di-p-methoxyphenyl-amine) 9,9 '-spirobifluorene], and how its dopant-free crystalline formation unprecedently improves perovskite solar cell (PSC) stability under continuous illumination by about two orders of magnitude with respect to the solution-processed reference and after annealing in air up to 200 degrees C. It is demonstrated that the control over the temperature of the samples during the vacuum deposition enhances the crystallinity of the SSHC, obtaining a preferential orientation along the pi-pi stacking direction. These results may represent a milestone toward the full vacuum processing of hybrid organic halide PSCs as well as light-emitting diodes, with promising impacts on the development of durable devices. The microstructure, purity, and crystallinity of the vacuum sublimated Spiro-OMeTAD layers are fully elucidated by applying an unparalleled set of complementary characterization techniques, including scanning electron microscopy, X-ray diffraction, grazing-incidence small-angle X-ray scattering and grazing-incidence wide-angle X-ray scattering, X-ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy.


Enero, 2020 | DOI: 10.1002/aenm.201901524

Bimodal Nd-Doped LuVO4 Nanoprobes Functionalized with Polyacrilic Acid for X-Ray Computed Tomography and NIR Luminescent Imaging


Nuñez, NO; Cusso, F; Cantelar, E; Martin-Gracia, B; de la Fuente, JM; Corral, A; Balcerzyk, M; Ocaña, M
Nanomaterials, 10 (2020) 149

ABSTRACT

Uniform Nd3+-doped LuVO4 nanophosphors have been synthesized for the first time in literature by using a poliol-based method at 120 degrees C from Nd3+ and vanadate precursors. After optimizing the Nd doping level, these phosphors present intense luminescence in the near-infrared biological windows. The X-ray attenuation capacity of the optimum nanophosphor has been found to be higher than that of a commercial X-ray computed tomography contrast agent. After surface coating with polyacrylic acid, such nanoparticles present high colloidal stability in physiological pH medium and high cell viability. Because of these properties, the developed Nd3+-doped LuVO4 nanoparticles have potential applications as a bimodal probe for NIR luminescent bioimaging and X-ray computed tomography.


Enero, 2020 | DOI: 10.3390/nano10010149

Tribomechanical properties of hard Cr-doped DLC coatings deposited by low-frequency HiPIMS


Santiago, JA; Fernandez-Martinez, I; Sanchez-Lopez, JC; Rojas, TC; Wennberg, A; Bellido-Gonzalez, V; Molina-Aldareguia, JM; Monclus, MA; Gonzalez-Arrabal, R
Surface & Coatings Technology, 382 (2020) 124899

ABSTRACT

Cr-doped diamond-like carbon (Cr-DLC) films with Cr contents ranging from 3 up to 20 at. % were synthesised in a codeposition process with HiPIMS (Cr deposition) and DC-pulsed technology (C deposition). The application of HiPIMS at low frequencies was observed to significantly enhance the energy density during the Cr plasma discharge due to the interaction of Cr-C species. The higher energy bombardment at low HiPIMS frequencies allowed doping with Cr the DLC structure avoiding the graphitization of the carbon structure. EELS spectroscopy was used to evaluate sp(3) content and Raman was used for sp(2) structural characterization of the films. Enhanced mechanical properties (hardness up to 30 GPa) were observed with nanoindentation for Cr-doped DLC at low frequencies. High temperature nanoindentation tests were also performed from room temperature to 425 degrees C in order to evaluate the evolution of hardness and Young Modulus with temperature. The results showed that the mechanical properties at high temperature mainly depend on the initial sp(3)-sp(2) structure. Tribological tests were carried out in air from room temperature to 250 degrees C. Cr-doped DLC coatings deposited by low-frequency HiPIMS showed lower friction and wear compared to undoped DLC.


Enero, 2020 | DOI: 10.1016/j.surfcoat.2019.124899



2019


Graphene Formation Mechanism by the Electrochemical Promotion of a Ni Catalyst


Espinos, JP; Rico, VJ; Gonzalez-Cobos, J; Sanchez-Valencia, JR; Perez-Dieste, V; Escudero, C; de Lucas-Consuegra, A; Gonzalez-Elipe, AR
ACS Catalysis, 9 (2019) 11447-11454

ABSTRACT

In this work, we show that multilayer graphene forms by methanol decomposition at 280 degrees C on an electrochemically promoted nickel catalyst film supported on a K-beta Al2O3 solid electrolyte. In operando near ambient pressure photoemission spectroscopy and electrochemical measurements have shown that polarizing negatively the Ni electrode induces the electrochemical reduction and migration of potassium to the nickel surface. This elemental potassium promotes the catalytic decomposition of methanol into graphene and also stabilizes the graphene formed via diffusion and direct K-C interaction. Experiments reveal that adsorbed methoxy radicals are intermediate species in this process and that, once formed, multilayer graphene remains stable after electrochemical oxidation and back migration of potassium to the solid electrolyte upon positive polarization. The reversible diffusion of ca. 100 equivalent monolayers of potassium through the carbon layers and the unprecedented low-temperature formation of graphene and other carbon forms are mechanistic pathways of high potential impact for applications where mild synthesis and operation conditions are required.


Diciembre, 2019 | DOI: 10.1021/acscatal.9b03820

Hydrophobic and Icephobic Behaviour of Polyurethane-Based Nanocomposite Coatings


Przybyszewski, B; Boczkowska, A; Kozera, R; Mora, J; Garcia, P; Aguero, A; Borras, A
Coatings, 9 (2019) 811

ABSTRACT

In this paper, hydrophobic nanocomposite coatings based on polyurethane (PUR) modified by nano-silica and silane-based compounds were manufactured by spraying. The main challenge was to assess and improve the hydrophobic as well as anti-icing properties of initially hydrophilic polymer coatings. The prepared nanocomposite coatings were characterized by means of scanning electron microscopy (SEM), optical profilometry and X-ray photoelectron spectroscopy (XPS). The results obtained showed that in order to achieve hydrophobicity, appropriate amounts of nano-silica must be incorporated in the coating, and complete coverage by nano-silica particles is necessary for achieving hydrophobicity. Coating adhesion and the durability of the hydrophobic behaviour were also studied by scratch test and frosting/defrosting cycles, respectively. The results show that use of both nano-silica and silane-based compounds improve the hydrophobic and anti-icing properties of the coating as compared to a non-modified PUR topcoat. A synergistic effect of both additives was observed. It was also found that the anti-icing behaviour does not necessarily correlate with surface roughness and the materials' wetting properties.


Diciembre, 2019 | DOI: 10.3390/coatings9120811

Porous Graphene-like Carbon from Fast Catalytic Decomposition of Biomass for Energy Storage Applications


Gomez-Martin, A; Martinez-Fernandez, J; Ruttert, M; Winter, M; Placke, T; Ramirez-Rico, J
ACS Omega, 4 (2019) 21446-21458

ABSTRACT

A novel carbon material made of porous graphene-like nanosheets was synthesized from biomass resources by a simple catalytic graphitization process using nickel as a catalyst for applications in electrodes for energy storage devices. A recycled fiberboard precursor was impregnated with saturated nickel nitrate followed by high-temperature pyrolysis. The highly exothermic combustion of in situ formed nitrocellulose produces the expansion of the cellulose fibers and the reorganization of the carbon structure into a three-dimensional (3D) porous assembly of thin carbon nanosheets. After acid washing, nickel particles are fully removed, leaving nanosized holes in the wrinkled graphene-like sheets. These nanoholes confer the resulting carbon material with approximate to 75% capacitance retention, when applied as a supercapacitor electrode in aqueous media at a specific current of 100 A.g(-1) compared to the capacitance reached at 20 mA.g(-1), and approximate to 35% capacity retention, when applied as a negative electrode for lithium-ion battery cells at a specific current of 3720 mA.g(-1) compared to the specific capacity at 37.2 mA.g(-1). These findings suggest a novel way for synthesizing 3D nanocarbon networks from a cellulosic precursor requiring low temperatures and being amenable to large-scale production while using a sustainable starting precursor such as recycled fiberwood.


Diciembre, 2019 | DOI: 10.1021/acsomega.9b03142

Dry Reforming of Ethanol and Glycerol: Mini-Review


Yu, J; Odriozola, JA; Reina, TR
Catalysts, 9 (2019) art. 1015

ABSTRACT

Dry reforming of ethanol and glycerol using CO2 are promising technologies for H-2 production while mitigating CO2 emission. Current studies mainly focused on steam reforming technology, while dry reforming has been typically less studied. Nevertheless, the urgent problem of CO2 emissions directly linked to global warming has sparked a renewed interest on the catalysis community to pursue dry reforming routes. Indeed, dry reforming represents a straightforward route to utilize CO2 while producing added value products such as syngas or hydrogen. In the absence of catalysts, the direct decomposition for H-2 production is less efficient. In this mini-review, ethanol and glycerol dry reforming processes have been discussed including their mechanistic aspects and strategies for catalysts successful design. The effect of support and promoters is addressed for better elucidating the catalytic mechanism of dry reforming of ethanol and glycerol. Activity and stability of state-of-the-art catalysts are comprehensively discussed in this review along with challenges and future opportunities to further develop the dry reforming routes as viable CO2 utilization alternatives.


Diciembre, 2019 | DOI: 10.3390/catal9121015

Silver effect on the tribological and antibacterial properties of a-C:Ag coatings


Dominguez-Meister, S; Rojas, TC; Frias, JE; Sanchez-Lopez, JC
Tribology International, 140 (2019) UNSP 105837

ABSTRACT

a-C:Ag coatings (1.2-23.4 at.% of Ag) were deposited using magnetron sputtering. Ag nanoparticles appear embedded in the carbon matrix or segregated to the column boundaries or surface. The silver doping has not promoted significant changes of the sp(2)/sp(3) ratio although a decrease of the hardness is observed (from 17 to 7 GPa). The tribological behavior did not show a clear dependence on the silver concentration in unlubricated or lubricated conditions (fetal bovinum serum) against alumina or UHMWPE balls. Ag nanoparticle dispersion enhanced the bactericide behavior as determined by the released Ag+ ion in the fluid media. There is no clear effect of friction rubbing on the released silver indicating that diffusion and top segregation are prevalent mechanisms for its dissolution.


Diciembre, 2019 | DOI: 10.1016/j.triboint.2019.06.030

3D Organic Nanofabrics: Plasma-Assisted Synthesis and Antifreezing Behavior of Superhydrophobic and Lubricant-Infused Slippery Surfaces


Alcaire, M; Lopez-Santos, C; Aparicio, FJ; Sanchez-Valencia, JR; Obrero, JM; Saghi, Z; Rico, VJ; de la Fuente, G; Gonzalez-Elipe, AR; Barranco, A; Borras, A
Langmuir, 35 (2019) 16876-16885

ABSTRACT

Herein, we present the development of supported organic nanofabrics formed by a conformal polymer-like interconnection of small-molecule organic nanowires and nanotrees. These organic nanostructures are fabricated by a combination of vacuum and plasma-assisted deposition techniques to generate step by step, single-crystalline organic nanowires forming one-dimensional building blocks, organic nanotrees applied as three-dimensional templates, and the polymer-like shell that produces the final fabric. The complete procedure is carried out at low temperatures and is compatible with an ample variety of substrates (polymers, metal, ceramics; either planar or in the form of meshes) yielding flexible and low solid-fraction three-dimensional nanostructures. The systematic investigation of this progressively complex organic nanomaterial delivers key clues relating their wetting, nonwetting, and anti-icing properties with their specific morphology and outer surface composition. Water contact angles higher than 150° are attainable as a function of the nanofabric shell thickness with outstanding freezing-delay times (FDT) longer than 2 h at −5 °C. The role of the extremely low roughness of the shell surface is settled as a critical feature for such an achievement. In addition, the characteristic interconnected microstructure of the nanofabrics is demonstrated as ideal for the fabrication of slippery liquid-infused porous surfaces (SLIPS). We present the straightforward deposition of the nanofabric on laser patterns and the knowledge of how this approach provides SLIPS with FDTs longer than 5 h at −5 °C and 1 h at −15 °C.


Diciembre, 2019 | DOI: 10.1021/acs.langmuir.9b03116

Design swelling micas: Insights on heavy metals cation exchange reaction


Osuna, FJ; Pavon, E; Alba, MD
Applied Clay Science, 182 (2019) 105298

ABSTRACT

Heavy metal pollution has become one of the most serious environmental problems, demanding specialized remediation mechanisms. Among the studied treatments, ion-exchange processes have been widely used due to their high remediation capacity, efficiency and fast kinetic. Here, the potential use of a new family of design micas as cation exchanger has been analysed. Micas with a layer charge in the range of brittle micas have been synthesized and their heavy metals cation exchange capacity analysed as a function of the nature of the heavy metal cations (Pb2+, Cd2+ or Hg2+), the nature of the counterions (Cl− or NO3−), concentration of the solutions and the micas layer charge. A cation exchange ratio between 35% and 154% of their cation exchange capacity (CEC) was achieved, being more efficient when mica layer charge diminished. In general, the maximum adsorption capacity followed the trend: Hg2+ > Pb2+ > Cd2+. The efficiency of the cation exchange and adsorption mechanism of the synthetic micas depended on the experimental conditions and they were more efficient than raw and modified natural clay minerals.


Diciembre, 2019 | DOI: 10.1016/j.clay.2019.105298

Understanding segregation processes in SAMs formed by mixtures of hydroxylated and non-hydroxylated fatty acids


Bueno, OVM; Benitez, JJ; San-Miguel, MA
RSC Advances, 9 (2019) 39252-39263

ABSTRACT

In this paper, we focus on the segregation processes emerging when preparing mixtures with different compositions of aleuritic (9,10,16 trihydroxyhexadecanoic) (ALE) and palmitic (hexadecanoic) (PAL) acids. The combination of atomic force microscopy (AFM) and molecular dynamics (MD) simulations enabled us to prove the role of the functional groups in the formation of self-assembled monolayers (SAMs) on muscovite mica surfaces. MD simulations indicate that segregation processes are favored in high ALE composition mixtures in agreement with the experimental evidence, whereas low ALE compositions promote the co-existence between segregated and dispersed systems. The secondary hydroxyl groups play a central role in the self-assembling mechanism because they control the formation of hydrogen bonding networks guarantying system stability.


Diciembre, 2019 | DOI: 10.1039/c9ra06799j

Low temperature synthesis of an equiatomic (TiZrHfVNb)C5 high entropy carbide by a mechanically-induced carbon diffusion route


Chicardi, E; Garcia-Garrido, C; Gotor, FJ
Ceramics International, 45 (2019) 21858-21863

ABSTRACT

A novel, homogeneous, nanostructured and equiatomic (TiZrHfVNb)C-5 High Entropy Carbide (HEC) was successfully synthesised in a powder form by a mechanosynthesis process from the elemental mixture. This synthesis method for HECs, not previously reported, is simple, reproducible and carried out at room temperature. During milling, the transition metals (Ti, Zr, Hf, V and Nb) alloying and the diffusion of carbon (introduced as graphite) into the alloy structure are simultaneously induced, obtaining the expected (TiZrHfVNb)C-5 HEC. The room temperature method employed contrasts with those reported in the bibliography from binary carbides that are carried out at a very high temperature (1800-2200 degrees C), with the consequent energy savings.


Diciembre, 2019 | DOI: 10.1016/j.ceramint.2019.07.195

Monodisperse Gold Cuboctahedral Nanocrystals Directly Synthesized in Reverse Micelles: Preparation, Colloidal Dispersion in Organic Solvents and Water, Reversible Self-Assembly and Plasmonic Properties


Luna, C; Castaneda-Rodriguez, D; Barriga-Castro, ED; Nunez, NO; Mendoza-Resendez, R
Langmuir, 34 (2019) 14291-14299

ABSTRACT

The synthesis of organic-solvent-dispersible gold nanoparticles in reverse micelles of didodecyldimethylammonium bromide (DDAB) is revisited in the present investigation. Some parameters of synthesis, specifically the reaction volume and the concentration of the reducing agent, were slightly modified obtaining directly monodisperse gold nanocrystals (AuNCs) without the need to use additional active surfactants or additional treatments such as digestive ripening. Interestingly, most of the obtained AuNCs display the same exposed crystalline faces composed of six bounding facets (four {111} faces and two {002} faces), corresponding to single-crystalline face-centered cubic nanoparticles with a cuboctahedron shape. When these AuNCs are subsequently functionalized with 1-decanethiol (C10H21SH) or 1-dodecanethiol (C12H25SH), they don’t experience significant changes in their size or crystalline texture, however, they self-aggregate directly in the suspension at room temperature into faceted supramolecular structures and exhibit collective plasmonic excitations. Such self-organization is reversible under heating treatments allowing the observation of the influence of the AuNCs aggregation state on their plasmonic properties. Fourier transform infrared spectroscopy reveals that thiols only replace partially the DDAB molecules, and thus, DDAB molecules remain present in the thiol-capped AuNCs. To turn the thiol-capped nanocrystals into water-dispersible nanocrystals and extend their technological potential, they are stabilized with poloxamer 407 obtaining highly stable purple colloids in water.


Noviembre, 2019 | DOI: 10.1021/acs.langmuir.9b02374

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