Responsible of the Brillouin Spectroscopy Lab

UNESCO scientific classification (6 digits): 220101, 220503, 220913, 221119, 221123, 331208

 

I'm physicist. Doctor rerum naturalis (Dr. rer. nat.) of the University of the Saar (UdS, Germany) and Doctor in Sciences (Physics) of the University Autónoma de Madrid (UAM, Spain). 

 After having finished my University studies (UAM, Madrid 1986) I left for Germany (Doctorate and Post-Doc) and stayed for 10 years at the UdS in Saarbrücken. During 2 years I worked in France as University teacher at the Université de Lorraine in Nancy. Nowadays I’m senior scientist at the ICMM in Madrid.

My speciality is Condensed Matter Physics especially in the field of the elastic and optical properties. The experimental technique that I use since 1988 is the Brillouin spectroscopy. I am responsible for the Lab at the ICMM devoted to this technique (BS-Lab).

 

 Soy físico, Doctor rerum naturalis (Dr. rer. nat.) por la  Universidad del Sarre (UdS, Alemania) y Doctor en Ciencias (Físicas) por la Universidad Autónoma de Madrid (UAM, España). 

Mi trayectoria profesional me ha llevado desde España (Licenciatura en 1986) a Alemania (10 años, doctorado y post doctorado en la Universidad del Sarre en Saarbücken, UdS) y a Francia (2 años, profesor en la Université de Lorraine en Nancy). Actualmente detento un puesto de Investigador Científico en el ICMM.

Mi especialidad es la física de la materia condensada especialmente en el terreno de las propiedades elásticas y ópticas. La técnica experimental que utilizo habitualmente desde 1988 es la espectroscopía Brillouin. Soy responsable del laboratorio dedicado a esta técnica en el ICMM (BS-Lab).

 

POSITIONS

• Investigador Científico del CSIC en el Instituto de Ciencia de Materiales de Madrid (Desde Marzo 2010)
• Científico Titular del CSIC en el Instituto de Ciencia de Materiales de Madrid (Agosto 2000- Marzo 2010)
• Científico Titular Interino (por oposición) en el Instituto de Ciencia de Materiales de Madrid (Enero - Agosto 2000)
• Maître de Conférences en la Facultad de Ciencias de la Universidad Henri Poincaré Nancy 1 (Cursos 1998 -1999 y 1999 - 2000)
• Colaborador contratado en el Instituto de Ciencia de Materiales de Madrid (CSIC) (Sept. 1995- Febrero 1999).
• Puesto de Post doctorado en la Universidad del Sarre en Saarbrücken (Enero 1993 - Sept.1995) subvencionado por la Comunidad de Investigación Alemana (DFG). Proyecto: KR653/5-2. (Colaborador contratado).
• Beca de F.P.U. (Ref.: PG89 00802408) del Ministerio de Educación y Ciencia (Saarbrücken, Dic. 1988 - Dic. 1992). (Doctorando).
• Beca de intercambio del DAAD (313/025/006/8) en Saarbrücken (Sept. 1987 - Agosto 1988). (Becario de investigación).
• Científico invitado en el marco del "Área especial de Investigación (SFB) 130 Ferroelektrika" en la Universidad del Sarre en Saarbrücken (Sept. 1986 - Mayo 1987). (Colaborador contratado).

Publications

Dehydroxylation processing and lasing properties of a Nd alumino-phosphate glass

Monica Munoz-Quinonero, Jon. Azkargorta, Ignacio Iparraguirre, Rafael J. Jimenez-Rioboo, Gregory Tricot, Chongyoun Shao, Francisco Munoz, Joaquin Fernandez, Rolindes Balda,

J Alloy Compd 896, 163040 (2022).

Abstract

In this work, we have studied the preparation and properties of an alumino-phosphate glass with composition 13Na2O-13K2O-16BaO-4Al2O3-54P2O5 (mol%). The first part of the work deals with the study of the processing conditions of the dehydroxylation of the phosphate glass, which was performed by remelting under N2 flow using graphite crucibles. Glass samples from 5 to 50 g and Nd2O3 doped were submitted to dehydroxylation and the influence of temperature, time, mass of glass and viscosity were correlated with the content of water in the glasses through the coefficient of absorption of OH ions. The network structure of the glasses was also determined by means of 31P and 27Al 1D/2D nuclear magnetic resonance and the local environment of Nd3+ ions was probed by electron paramagnetic resonance. The optimized conditions of processing were then used to obtain a dehydroxylated glass with a 2.5 wt% Nd2O3 whose spectroscopic and laser emission properties were studied. The spectroscopic properties of Nd3+ ions which include, JuddOfelt calculation, stimulated emission cross-section of the laser transition, lifetime, and quantum efficiency are presented. Site-selective laser spectroscopy and stimulated emission obtained under selective wavelength pumping along the 4I9/2 -> 4F5/2 absorption band were performed to determine the distribution of crystal field in which the rare earth is located, together with its influence in the pump wavelength dependence of the spontaneous and laser emissions of Nd3+ in this glass matrix. (c) 2021 The Author(s). Published by Elsevier B.V. CC_BY_4.0

Paper

Transitioning from Ionic Liquids to Deep Eutectic Solvents

Huan Zhang, Jose Manuel Vicent-Luna, Shuxia Tao, Sofia Calero, Rafael J. Jimenez Rioboo, Maria Luisa Ferrer, Francisco del Monte, Maria Concepcion Gutierrez,

Acs Sustainable Chem. Eng. 10, 1231 (2022).

Abstract

Ionic liquids (ILs) and deep eutectic solvents (DESs) have been lately the solvents of choice in a number of processes because they offer a valid alternative to conventional solvents. Despite main interactions in ILs differ from those in DESs (e.g., electrostatic-type in the former and H-bond-type in the latter), these two neoteric solvents are more closely related that appeared and can be seen as the two sides, the face and the cross, of the same coin. Herein, we hypothesized about a way for transitioning from one to the other. In particular, we promoted the transition from 1-ethyl-3-methylimidazolium chloride (EMIMCI) to EMIMCI-nAcOH-based DESs by the simple addition of stoichiometric amounts of acetic acid (AcOH) to EMIMCI. H-1 NMR spectroscopy and DSC studies confirmed the occurrence of such a transition. Molecular dynamics (MD) simulations revealed the capability of the Cl anion to fully accommodate up to 4 AcOH molecules (e.g., EMIMCl center dot 1AcOH, EMIMCl center dot 2AcOH, EMIMCl center dot 3AcOH, and EMIMCl center dot 4AcOH) without signs of H-bond self-interactions between AcOH molecules. These DESs also exhibited quite different solvent properties, with alpha and beta Kamlet-and-Taft parameters that differed from those of EMIMCl and 1-ethyl-3-methylimidazolium acetate (EMIMOAc). Interestingly, excess molar volume and excess viscosity measurements as well as Brillouin spectroscopic experiments indicated that aqueous dilutions of EMIMCl center dot AcOH-based DESs deviated from ideality as a consequence of the formation of HBs between water molecules and the anion, as observed by H-1 NMR spectroscopy.

Paper

Stress-mediated solution deposition method to stabilize ferroelectric BiFe1-xCrxO3 perovskite thin films with narrow bandgaps

Ricardo Jimenez, Jesus Ricote, Inigo Bretos, Rafael J. Jimenez Rioboo, Federico Mompean, Ana. Ruiz, Haibing Xie, Monica Lira-Cantu, M. Lourdes Calzada,

J Eur Ceram Soc 41, 3404 (2021).

Abstract

Ferroelectric oxides with low bandgaps are mainly based on the BiFeO3 perovskite upon the partial substitution of iron with different cations. However, the structural stability of many of these perovskites is only possible by their processing at high pressures (HP, >1GPa) and high temperatures (HT, >700?C). Preparation methods under these severe conditions are accessible to powders and bulk ceramics. However, transferring these conditions to the fabrication of thin films is a challenge, thus limiting their use in applications. Here, a chemical solution deposition method is devised, which overcomes many of these restrictions. It is based on the application of an external compressive-stress to the film sample during the thermal treatment required for the film crystallization, promoting the formation and stabilization of these HP perovskites. We demonstrate the concept on BiFe1-xCrxO3 (BFCO) thin films deposited on SrTiO3 (STO) substrates and with large chromium contents. The resulting BFCO perovskite films show narrow bandgaps (Eg-2.57 eV) and an excellent ferroelectric response (remnant polarization, PR- 40 ?C cm-2). The polarized thin films under illumination present a large out-put power of -6.4 ?W cm-2, demonstrating their potential for using in self-powered multifunctional devices. This stress-mediated solution deposition method can be extended to other perovskite films which are unviable under conventional deposition methods.

Paper

Tools for extending the dilution range of the "solvent-in-DES" regime

Huan Zhang, M. Luisa Ferrer, Rafael J. Jimenez-Rioboo, Francisco del Monte, Maria C. Gutierrez,

J Mol Liq 329, 115573 (2021).

Abstract

Deep eutectic solvents (DESs) and dilutions thereof are currently gaining increased interest in sustainable processes. DES dilutions are particularly interesting in the so-called "solvent-in-DES" regime where the intriguing features of DESs remain (coming from hydrogen bonding among the components) and some typical drawbacks (e.g., high viscosity, low electrical conductivity, etc.) are mitigated. Actually, DES dilutions may exhibit excellent performances (more so than the original neat DESs) in certain applications. Knowing about the tools that allow predicting (and eventually extending) the dilution range of the "solvent-in-DES" regime is obviously of interest. With this aim, we herein studied two sets of DES dilutions. In the first set, we used the DES composed of choline chloride (ChCl) and urea (U) and its dilutions in H2O, methanol (MeOH) and ethanol (EtOH). In the second set, we studied two DESs composed of ethylene glycol (EG) and either tetraethylammonium bromide (TEABr) or tetrabutylammonium bromide (TBABr), and their dilutions in H2O. Data coming from DSC, H-1 NMR spectroscopy, and Brillouin spectroscopy revealed how the dilution range of the "solvent-in-DES" regime in ChClU dilutions in H2O, MeOH and EtOH increased in the order H2O < MeOH < EtOH while in aqueous dilutions of TEABrEG and TBABrEG increased in the order TEABrEG < TBABrEG. Our results suggest that the extension of the dilution range of the "water-in-DES" regime could be tuned by both the DES components solubility in the different solvents, and the strength and/or number of the hydrogen bonds established between DES components and solvent molecules. (C) 2021 Elsevier B.V. All rights reserved.

Paper

Further Extending the Dilution Range of the "Solvent-in-DES" Regime upon the Replacement of Water by an Organic Solvent with Hydrogen Bond Capabilities

N. Lopez-Salas, J. M. Vicent-Luna, E. Posada, S. Imberti, R. M. Madero-Castro, S. Calero, C. O. Ania, R. J. Jimenez-Rioboo, M. C. Gutierrez, M. L. Ferrer, F. del Monte,

Acs Sustainable Chem. Eng. 8, 12120 (2020).

Abstract

Aqueous dilutions of deep eutectic solvents (DESs) have lately allowed exploring new and more demanding applications where neat DESs are not able to perform well. However, the use of DES dilutions with nonaqueous hydrogen-bond-forming solvents remains basically unexplored. It is worth noting the obvious interest of using organic solvents in those cases where any reagent or byproduct is nonsoluble, nonmiscible, or unstable in water, the presence of water might alter the reaction kinetics (for instance, when water is a byproduct), or a cosolvent with low vapor pressure allows exploring reaction processes (high temperatures or solvothermal conditions, among others) not suitable for water. Herein, we investigated benzyl alcohol (BA) dilutions of RUChCl, a DES composed of resorcinol (R), urea (U), and choline chloride (ChCl). In particular, neutron scattering, nuclear magnetic resonance, and Brillouin experiments revealed how BA was accommodated within the hydrogen-bond (HB) complex structure of RUChCl for BA contents of up to 67 wt % whereas this HB complex structure basically disappeared for higher BA contents. This behavior somehow resembled that found in aqueous solutions, with two well-differentiated regimes-e.g., the "solvent-in-DES" and the "DES-in-solvent"-depending on the DES content. However, the "solvent-in-DES" regime was preserved for much higher solvent contents of BA than H2O-e.g., 60-65 versus 18-20 wt %, respectively. Interestingly, the specific BA dilution where transition from one regime to the other occurs was particularly well suited to develop a spinodal decomposition process when used as the precursor for the preparation of polymer resins (by polycondensation between R and p-phthalaldehyde).

Paper

Raman amplification in the ultra-small limit of Ag nanoparticles on SiO2 and graphene: Size and inter-particle distance effects

Sandra Cortijo-Campos, Rafael Ramirez-Jimenez, Esteban Climent-Pascual, Montserrat Aguilar-Pujol, Felix Jimenez-Villacorta, Lidia Martinez, Rafael Jimenez-Rioboo, Carlos Prieto, Alicia de Andres,

Mater Design 192, 108702 (2020).

Abstract

Size, shape and hot spots are crucial to optimize Raman amplification from metallic nanoparticle (NPs). The am-plification from radius = 1.8 +/- 0.4 nm ultra-small silver NPs was explored. Increasing NP density redshifts and widens their plasmon that, according to simulations for NPs arrays, is originated by the reduction of the interpar-ticle distance, d, becoming remarkable for d <= R. Inter-particle interaction red-shifts (>130 nm) and widens (>90 nm) the standard plasmon of non-interacting spherical particles. Graphene partly delocalizes the carriers enhancing the NIR spectral weight. Raman amplification of graphene phonons is moderate and depends smoothly on d while that of Rhodamine 6G (R6G) varies almost exponentially due to their location at hot-spots that depend strongly on d. The experimental correlation between amplification and plasmon position is well reproduced by simulations. The amplification originated by the ultra-small NPs is compared to that of larger particles, granular silver films with 7 < R < 15 nm grains, with similar extinction values. The amplification is found to be larger for the 1.8 nm NPs due to the higher surface/volume ration that allows higher density of hot spots. It is demonstrated that Raman amplification can be efficiently increased by depositing low density layers of ultra -small NPs on top of granular films. (c) 2020 The Authors. Published by Elsevier Ltd.

Paper

Aqueous-Eutectic-in-Salt Electrolytes for High-Energy-Density Supercapacitors with an Operational Temperature Window of 100 degrees C, from-35 to+65 degrees C

Xuejun Lu, Rafael J. Jimenez-Rioboo, Donal Leech, Maria C. Gutierrez, M. Luisa Ferrer, Francisco del Monte,

Acs Appl. Mater. Interfaces 12, 29181 (2020).

Abstract

Water-in-salt (WIS) electrolytes are gaining increased interest as an alternative to conventional aqueous or organic ones. WIS electrolytes offer an interesting combination of safety, thanks to their aqueous character, and extended electrochemical stability window, thanks to the strong coordination between water molecules and ion salt. Nonetheless, cost, the tendency of salt precipitation, and sluggish ionic transfer leading to poor rate performance of devices are some intrinsic drawbacks of WIS electrolytes that yet need to be addressed for their technological implementation. It is worth noting that the absence of "free'' water molecules could also be achieved via the addition of a certain cosolvent capable of coordinating with water. This is the case of the eutectic mixture formed between DMSO and H2O with a molar ratio of 1:2 and a melting point as low as -140 degrees C. Interestingly, addition of salts at near-saturation conditions also resulted in an increase of the boiling point of the resulting solution. Herein, we used a eutectic mixture of DMSO and H2O for dissolution of LiTFSI in the 1.1-8.8 molality range. The resulting electrolyte (e.g., the so-called aqueous-eutectic-in-salt) exhibited excellent energy and power densities when operating in a supercapacitor cell over a wide range of extreme ambient temperatures, from as low as -35 degrees C to as high as +65 degrees C.

Paper

Brillouin Spectroscopy as a Suitable Technique for the Determination of the Eutectic Composition in Mixtures of Choline Chloride and Water

Huan Zhang, M. Luisa Ferrer, Maria J. Roldan-Ruiz, Rafael J. Jimenez-Rioboo, Maria C. Gutierrez, Francisco del Monte,

J Phys Chem B 124, 4002 (2020).

Abstract

Deep eutectic solvents (DESs) resulting from the right combination between a hydrogen-bond donor (HBD) and a hydrogen-bond acceptor (HBA) are becoming quite popular in number of applications. More recently, natural DESs (NADESs) containing sugars, natural organic acids, and amino acids as HBDs and ChCl as HBA have received great attention because of their further environmental sustainability as compared to regular DESs. Within this context, mixing water in controlled amounts has been widely accepted as a simple and practical way of altering DES chemical and thermodynamic properties, with viscosity and conductivity experiencing the most significant changes. However, the number of papers describing eutectic mixtures with water as the only HBD is scarce and basically none has been done in fundamental terms. Herein, we investigated mixtures composed of water as the only HBD and ChCl as the HBA using differential scanning calorimetry (DSC) as well as H-1 nuclear magnetic resonance (NMR) and Brillouin spectroscopies. We found the aqueous dilution of ChCl/2H2O with a ChCl/2H2O content of ca. 80 wt % was an eutectic. Interestingly, this mixture could be considered a NADES according to its eutectic distance (Delta T-me), in range to eutectics obtained in aqueous dilutions of salt hydrates.

Paper

Carbon and carbon composites obtained using deep eutectic solvents and aqueous dilutions thereof

Gaspar Carrasco-Huertas, Rafael J. Jimenez-Rioboo, Maria Concepcion Gutierrez, Maria Luisa Ferrer, Francisco del Monte,

Chem Commun 56, 3592 (2020).

Abstract

The aim of this featured article is to illustrate some of the most recent applications of deep eutectic solvents (DESs) in the synthesis of carbon and carbon composites. DESs can be obtained by the complexation of quaternary ammonium salts with hydrogen-bond donors. DESs have typically been referred to as a related class of ionic liquids because they share many properties. However, DESs present the advantage of easier and low-cost preparation. Moreover, their compositional flexibility can eventually be translated into materials that provide advanced functionalities and/or tailored hierarchical structures. Interestingly, the use of the liquid binary mixtures of DESs and H2O for the preparation of carbon materials plays a critical role with regard to the achievement of some particular porous morphologies. Herein, we will also summarize some recent studies performed on DES/H2O liquid binary mixtures, revealing the possibility of obtaining new eutectic mixtures upon the simple addition of water to DESs while keeping the DES contents at a certain pseudo-concentrated range. This finding will pave the way to novel applications, especially in those fields in which the preparation of high-tech products via low-cost processes is critical. We hope that this featured article will encourage scientists to explore the promising perspectives offered by DESs and aqueous dilutions thereof.

Paper

Chemical and structural heterogeneities in Nd-doped oxynitride phosphate laser glasses

Francisco Munoz, Rafael J. Jimenez-Rioboo, Rolindes Balda,

J Alloy Compd 816, 152657 (2020).

Abstract

The application of oxynitride glasses in optics has been limited due the issues inherent in their preparation that result in bubbles, metallic inclusions or opacity. Although the synthesis of oxynitride phosphates is easier than in silicates, due to their lower melt viscosity, the remaining water in the form of OH causes, for instance, the neodymium luminescence to be negatively affected. We report on the preparation of oxynitride Nd phosphate glasses that are submitted first to a dehydroxylation, so that their structure and properties can be studied as a function of the nitrogen content taking a completely homogeneous OH-free glass as the starting point of each synthesis. Raman and Brillouin Spectroscopy confirmed the segregation in oxide and N-enriched regions, and NMR of the glasses has been used to calculate the O/P ratio from the distribution of P(O,N)(4) groups. The difference between this and the experimental one obtained from the elemental analyses confirms the segregation in oxide and oxynitride regions that is produced during the ammonolysis of the phosphate glass. The oxynitride glass network could thus be considered a non-homogeneous mixture of the oxide and the nitrided phases that are segregated due to the non-randomness of the nitridation reaction. (C) 2019 Elsevier B.V. All rights reserved.

Paper

Looking at the "Water-in-Deep-Eutectic-Solvent" System: A Dilution Range for High Performance Eutectics

Nieves Lopez-Salas, Jose Manuel Vicent-Luna, Silvia Imberti, Elena Posada, Maria Jesus Roldan, Juan A. Anta, Salvador R. G. Balestra, Rafael M. Madero Castro, Sofia Calero, Rafael J. Jimenez-Rioboo, Maria Concepcion Gutierrez, Maria Luisa Ferrer, Francisco del Monte,

Acs Sustainable Chem. Eng. 7, 17565 (2019).

Abstract

Deep eutectic solvents (DESs) are lately expanding their use to more demanding applications upon aqueous dilution thanks to the preservation of the most appealing properties of the original DESs while overcoming some of their most important drawbacks limiting their performance, like viscosity. Both experimental and theoretical works have studied this dilution regime, the so-called "water-in-DES" system, at near-to stoichiometric amounts to the original DES. Herein, we rather studied the high-dilution range of the "water-in-DES" system looking for enhanced performance because of the interesting properties (a further drop of viscosity) and cost (water is cheap) that it offers. In particular, we found that, in the "water-in-DES" system of a ternary DES composed of resorcinol, urea and choline chloride (e.g., RUChClnW, where n represents mol of water per mole of ternary DES), the tetrahedral structure of water was distorted as a consequence of its incorporation, as an additional hydrogen bond donor or hydrogen bond acceptor, into the hydrogen bond complexes formed among the original DES components. DSC confirmed the formation of a new eutectic, with a melting point below that of its respective components, the original ternary DES and water. This depression in the melting point was also observed in the same regime of reline and malicine aqueous dilutions, thus suggesting the universality of this simple procedure (i.e., water addition to reach the high-dilution range of the "water-in-DES" system) to obtain deeper eutectics eventually providing enhanced performances and lower cost.

Paper

Resilience improvement of an isotactic polypropylene-g-maleic anhydride by crosslinking using polyether triamine agents

Adrien Letoffe, Sandrine Hoppe, Richard Laine, Nadia Canilho, Andreea Pasc, Didier Rouxel, Rafael J. Jimenez Rioboo, Sebastien Hupont, Isabelle Royaud, Marc Poncot,

Polymer 179, 121655 (2019).

Abstract

The elaboration of new hybrid polymer/metal composite materials depends on the development of innovative polymer matrices with improved mechanical properties and high effective adhesion behaviour with metal surfaces. This way, a new type of polyolefin was developed based on a peculiar crosslinking reaction. For this elaboration, an iPP-g-MAH with 1 wt% of MAH was crosslinked with polyether triamine molecules by twin screw reactive extrusion. The evolution of the crosslinking reaction, the microstructure and the mechanical behaviour of the different materials were studied as a function of the NH2 :MAH molar ratio in the range of 0:1 and 1.5:1. Gel content determination and FTIR analysis were performed to characterise the material at the molecular scale, when differential scanning calorimetry, wide angle X-rays scattering and self-successive auto-nucleation techniques were used for a deep microstructure analysis. Brillouin spectroscopy showed an interesting evolution of the elastic constants at the microscopic scale and results were in good agreement with those obtained at the macroscopic scale by a video-controlled uniaxial tensile test. Moreover, it was demonstrated that the true mechanical behaviours switch from brittle to ductile illustrating an important improvement of the resilience ability of the synthesized materials as a function of the NH2:MAH molar ratio even for molar ratio other than an equimolar ratio, with remaining MAH or NH2 chemical groups for further chemical reaction.

Paper

Brillouin and NMR spectroscopic studies of aqueous dilutions of malicine: Determining the dilution range for transition from a "water-in-DES" system to a "DES-in-water" one

M. J. Roldan-Ruiz, R. J. Jimenez-Rioboo, M. C. Gutierrez, M. L. Ferrer, F. del Monte,

J Mol Liq 284, 175 (2019).

Abstract

Brillouin and NMR spectroscopy were used to explore transitions in the structuring of liquid binary mixtures composed of water and a deep eutectic solvent (DES) known as malicine and composed of malic acid (MA) and choline chloride (ChCl). Malicine/H2O binary mixtures were studied for DES contents ranging from 100 to 40 wt%. Data representation of sound propagation velocities - obtained from Brillouin spectroscopy - versus DES content exhibited two well-differentiated linear regimes above and below ca. 70 DES wt% while transitioning from a "water-in-DES" system to a "DES-in-water" one along with dilution. Two linear regimes intersecting at ca. 70 DES wt% were also observed when representing the self-diffusion coefficients versus malicine contents, with MA and ChCl - and even water - exhibiting nearly identical self-diffusion coefficients for contents above 70 wt%, that diverged for contents below 70 wt%. Interestingly, further insights about this behaviour were provided by spin-lattice relaxation time of MA, also revealing the occurrence of hydrophobic hydration around non-polar moieties as in other aqueous binary mixtures of non-ionic H-bond co-solvents - e.g., DMSO:H2O or dioxane: water. (C) 2019 Elsevier B.V. All rights reserved.

Paper

Nanophase separation in aqueous dilutions of a ternary DES as revealed by Brillouin and NMR spectroscopy

E. Posada, M. J. Roldan-Ruiz, R. J. Jimenez Rioboo, M. C. Gutierrez, M. L. Ferrer, F. del Monte,

J Mol Liq 276, 196 (2019).

Abstract

Liquid binary mixtures of deep eutectic solvents (DESs) with H2O are lately attracting the interest of many research works because of the improved performance that these dilutions demonstrated in number of application - e.g., catalysis, separations, or biochemistry, among others - as compared to their respective neat DES counterparts. Interestingly, molecular simulations have revealed that, despite the macroscopically homogeneous appearance of the DES/H2O binary mixtures, phase segregation may occur at the nanoscale. Spectroscopic studies corroborating this event in this sort of mixtures are basically limited to NMR-based ones determining diffusion coefficients and some recent Brillouin spectroscopic studies performed for a quite short list of binary DESs -i.e., those composed of one single hydrogen bond donor (HBD) and one single hydrogen bond acceptor (HBA), being urea-choline-chloride-based DES the most widely studied. Interestingly, NMR data such as chemical shifts and relaxation times have also proved quite useful for the study of liquid binary mixtures different than DES-based ones - e.g., ionic-liquid-based ones. Herein, we have obtained a full set of NMR data - chemical shifts, diffusion coefficients and relaxation times - from liquid binary mixtures of H2O and a ternary DESs, in this particular case one composed of two HBD - e.g., resorcinol and hexylresorcinol - and one HBA - tetraethyl ammonium bromide. Good correlation among different NMR data as well as between NMR and Brillouin data was found in the determination of the DES content at which phase segregation occurs. (C) 2018 Published by Elsevier B.V.

Paper