Gadolinium Nitrate Research Articles

The Synthesis, Structural Characterization, and DFT Calculation of a New Binuclear Gd(III) Complex with 4-Aacetylphenoxyacetic Acid and 1,10-Phenanthroline Ligands and Its Roles in Catalytic Activity.

A new binuclear Gd(III) complex, [Gd2(L)6(Phen)2]·4H2O, was synthesized via the reaction of gadolinium(III) nitrate hexahydrate, 4-acetylphenoxyacetic acid (HL), NaOH, and 1,10-phenanthroline (Phen) in a solution of water-ethanol (v:v = 1:1). The Gd(III) complex was characterized using IR, UV-vis, TG-DSC, fluorescence, and single-crystal X-ray diffraction analyses. The results showed that the Gd(III) complex crystallizes in the triclinic system, space group P-1, and each Gd(III) ion was coordinated with two nitrogen atoms (N1, N2, or N1a, and N2a) from two Phen ligands and seven oxygen atoms (O1, O2, O7a, O9, O8, O8a, O10a, or O1a, O2a, O7, O8, O8a, O9a, and O10) from six L ligands, respectively, forming a nine-coordinated coordination mode. The Gd(III) complex molecules formed a one-dimensional chained and three-dimensional network structure via benzenering π-π stacking. The Hirschfeld surface analysis and the calculations of the electron density distributions of the frontier molecular orbitals of the Gd(III) complex were performed. The catalytic activities of the photocatalytic CO2 reduction and benzyl alcohol oxidation using the Gd(III) complex as a catalyst were performed. The results of the photocatalytic CO2 reduction showed that the yield and the selectivity of CO reached 41.5 μmol/g and more than 99% after four hours, respectively. The results of the benzyl alcohol oxidation showed that the yield of benzaldehyde was 45.7% at 120 °C with THF as the solvent under 0.5 MPa O2 within 2 h.

WITHDRAWN: Organic molecule-mediated synthesis of GdPO4:Eu3+ micro/nano-luminescent materials and MRI tracing performance evaluation

The influence of the introduction of structural modifiers citric acid and acetic acid on the morphology, luminescence properties and magnetic resonance imaging (MRI) tracer properties of GdPO4:Eu3+ micro-nanoparticles synthesized in ethanol system was investigated in the paper. In this system, GdPO4:Eu3+ micro-nanomaterials such as square flake, hexagram, waist drum morphologies can be prepared by adjusting the ratios of structural modifier, phosphoric acid and gadolinium nitrate, respectively. In addition, the synthesized products were analyzed by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), fluorescence spectroscopy (PL), and magnetic resonance imaging (MRI) detection. The products were found to exhibit good crystallinity, particularly in terms of their luminescent properties, which exhibited notable differences. Overall, the luminescent properties of GdPO4:Eu3+ synthesized by citric acid modification were significantly enhanced compared with acetate modification, with at least five times more luminescent intensity than that of acetate modification. And amazingly, the GdPO4:Eu3+ luminescence intensity is strongest when the square flake-hexagram coexisting. The tracer properties of GdPO4:Eu3+ MRI with better luminescent square flake, hexagram, and square flake-hexagram coexisting morphologies were also investigated. It was found that the square flake had better T1-longitudinal relaxation imaging with a relaxation rate r1 value of 0.79 mM−1s−1. This work is a good advancement for organic molecule-mediated modulation, synthesis of gadolinium phosphate-based rare-earth micro-nanomaterials and study of their applications in luminescence and MRI tracing.

A green approach for synthesizing high pure gadolinium zirconate nano-particles using microwave energy

Nano crystalline high purity gadolinium zirconate powder has been prepared by wet chemical synthesis method using microwave energy. Co-precipitation of zirconium oxychloride and gadolinium nitrate under the influence of microwave energy is studied. The powder has been characterized using thermal TG-DTA/DSC, XRD, EDS and FESEM. The average crystallite size (ACS) of the ZrO2 (600 °C) nano-particles is found to be 26 nm. The characterization studies have shown the existence of non agglomerated nano-crystalline particles with regular and uniform spherical morphology. Microwave energy is found to assist in achieving the desired properties of gadolinium zirconate. The microwave assisted synthesis is faster, better and green chemistry approach which not only provides the enhanced reaction rates and high yields but also, it provides short reaction time, higher selectivity and reduction of pollutant solvents. The key features of obtaining the pure non agglomerated nano-structured gadolinium zirconate powder are the notable attractions of the present study.

Influence of gadolinium doping on structural, optical, and electronic properties of polymeric graphitic carbon nitride.

Polymeric graphitic carbon nitride (gCN) materials have received great attention in the fields of photo and electrocatalysis due to their distinct properties in metal-free systems with high physicochemical stability. Nevertheless, the activity of undoped gCN is limited due to its relatively low specific surface area, low conductivity, and poor dispersibility. Doping Gd atoms in a gCN matrix is an efficient strategy to fine-tune its catalytic activity and its electronic structure. Herein, the influence of various wt% of gadolinium (Gd) doped in melon-type carbon nitride was systematically investigated. Gadolinium-doped graphitic carbon nitride (GdgCN) was synthesized by adding gadolinium nitrate to dicyandiamide during polymerization. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) results revealed that the crystallinity and the morphological properties are influenced by the % of Gd doping. Furthermore, X-ray photoelectron spectroscopy (XPS) studies revealed that the gadolinium ions bonded with nitrogen atoms. Complementary density functional theory (DFT) calculations illustrate possible bonding configurations of Gd ions both in bulk material and on ultrathin melon layers and provide evidence for the corresponding bandgap modifications induced by gadolinium doping.

Thermal behavior of gadolinium-silica gels prepared via sol–gel route combined to γ-irradiation process

Gadolinium-silica (Gd-silica) gels were prepared via sol–gel route combined to γ-irradiation (0–30 kGy), starting from Tetra-Ethyl-Orthosilicate (Si(OCH2CH3)4, TEOS) and gadolinium nitrate Gd(NO3).6H2O used as raw materials. The phase transformation and morphology of the gels derived from both precursors were characterized by XRD and TEM analysis. Differential scanning calorimetry (DSC) under non-isothermal conditions was used to determine the crystallization activation energy (E c) at different γ-doses (0, 8, 15, 25 and 30 kGy), using the methods suggested by Kissinger, Moynihan and Ozawa. XRD analysis of the samples calcined up to 1100°C for 2 h reveals the formation of gadolinium silicate (Gd4.67 (SiO4)3O) apatite crystalline phase with the presence of small traces of gadolinium pyrosilicate (Gd2Si2O7), the average particle sizes about 50 nm. TEM observations show spherical Gd-silicate nanoparticles homogeneously dispersed in silica matrix, the mean diameter size is about 40 nm. From DSC analysis, it was observed that the onset crystallization temperature (T x) and peak crystallization temperature (T c) both increase with increasing γ-dose. According to Kissinger, Moynihan and Ozawa models, the crystallization activation energies for Gd-silicate phase formation were found to be 465.2, 474.5 and 465.7 kJ mol−1, respectively for unirradiated samples and 429.1, 447 and 438 kJ mol−1 when the γ-irradiation reaches 30 kGy respectively. Results revealed that the values of E c decreased when the γ-dose increases and attains the minimum value at the dose of 15 kGy and then increase at higher doses. The crystallization rate factor (K) was also seen to decrease with increasing of γ-dose. Gamma irradiation increases the crystallization peak temperature (T c). The crystallization activation energy (E c) estimated from the three models is in good agreement and much well with those reported for silicate systems. Gamma irradiation decreases the E c and crystallization rate factor (K). These preliminary results can provide useful technical information for a better understanding and control of the crystallization process of this type of nanomaterial.

Facilitated luminescence via pH regulation of GdF3:5%Eu3+ and NaGdF4:5%Eu3+ morphologies

Gadolinium fluoride micromaterials with eight morphologies of embroidered sphere, copper coin, rotor, irregular rhombus, cocoon pupa, rod, and hollow tubes (small and large) were synthesized in the absence of any surfactant and templating agent using gadolinium nitrate and sodium fluoroborate as raw materials and green water as a solvent. The physical and chemical properties of the products were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), infrared spectroscopy (FT-IR) and fluorescence spectroscopy (PL). The composition and morphology of the products were mainly regulated by pH value, with pH = 1.7, 3.7, 5.7, 7.7 and 8.7 resulting in the formation of embroidered spherical, copper coin, rotor, irregular diamond and cocoon pupae shaped GdF3:5%Eu3+ microparticles, and with pH = 9.7, 10.7 and 11.7 leading to the shaping of rod, small hollow tube and large hollow tube NaGdF4:5%Eu3+ microparticles. Their luminescent properties were also significantly distinguishable. As a whole, the luminescence of GdF3:5%Eu3+ is stronger than that of the NaGdF4:5%Eu3+ microparticles, both emitting orange‒red light. Among them, the embroidered spherical GdF3:5%Eu3+ microparticles prepared at pH = 1.7 showed the strongest luminescence with a fluorescence lifetime of 10.11 ms and CIE color coordinates of 0.6061 and 0.3934. Possible mechanisms for the preparation of gadolinium fluorides with various morphologies at different pH values were analyzed, and the reasons for their effect on fluorescence properties were further investigated. GdF3 micromaterials not only provide the basis for a wide range of applications in upconversion luminescence but also have potential applications in downconversion luminescence, providing good research support for the synthesis and application screening of micronanomaterials containing gadolinium for morphology modulation.

Construction of A sqc6 Topology Ni‐Gd Framework Employing 2,2’‐Phosphinico‐dibenzoate and Oxalate: Structure and Magnetic Properties

AbstractA 3d–4f heterometallic compound, namely [Ni6GdL4(ox)(H2O)12]⋅[NO3]⋅14.5H2O (1) (L=2,2’‐phosphinico‐dibenzoate and ox=oxalate), was obtained by self‐assembly of nickel nitrate, gadolinium nitrate, oxalic acid, and 2,2’‐phosphinico‐dibenzoic acid (H3L). Such compound has been structurally characterized via single‐crystal X‐ray diffraction analysis and infrared spectroscopy. This compound features a basic unit of {Ni4Gd} clusters and 2,2’‐phosphinico‐dibenzoate ligands. Each unit is connected by another Ni2+ through the axial coordination of benzoate oxygen to form a layer. Meanwhile, each oxalate ligand bridges the expanded Ni4Gd‐Ni4 net, constructing a 3‐D framework. From the viewpoint of network topology, this compound can be simplified as a sqc6 topology. Magnetic analysis shows ferromagnetic interactions between the Ni(II) and Gd(III) centers in Ni4Gd nodes and antiferromagnetic coupling with oxalate bridges in this compound.

Structure, morphology and functional characteristics of Gd2Ti2O7 nanocrystals formed under various annealing conditions

This article is devoted to the study of the processes of formation and growth of nanocrystals with the pyrochlore structure in the TiO2-Gd2O3 system. A mixture of an aqueous solution of gadolinium nitrate and a solution of titanium isopropoxide with polyethylene glycol in isopropyl alcohol was evaporated to a gel state, and then it was heat-treated using a one- or two-stage scheme. The study showed that the material being formed has a trabecular structure with a developed system of macropores. The use of the two-stage roasting method allows a uniform distribution of titanium and gadolinium atoms in the sample. Gadolinium titanate with a pyrochlore structure, which is formed using an aggregation mechanism at a temperature T = 700 °C from an X-ray amorphous precursor, is a variable composition compound. It has been shown that in terms of obtaining a monophasic product, the possibility of varying the size of nanocrystals, and defects in the pyrochlore structure, the most promising heat treatment mode is synthesis in the temperature range of 750–900 °C. In this case, the possibility of controlling the above characteristics of Gd2Ti2O7 nanoparticles can be implemented by varying the ratio of titanium- and gadolinium-containing precursors in the initial mixture, the duration of the isothermal exposure process.

Robust synthesis and characteristics of novel one-dimensional gadolinium oxide nanorods decorated multiwalled carbon nanotubes based antibacterial nanocomposites for health care applications

A facile and scalable chemical method for synthesizing one-dimensional (1D) gadolinium oxide nanorods decorated multiwalled carbon nanotubes (MWCNTs) based nanocomposites (GNR) as antibacterial agents for biomedical applications is introduced in this paper. The hybrid nanocomposite was obtained by using gadolinium nitrate hexahydrate as gadolinium precursor and MWCNTs as resource material with hydrogen peroxide as a reducing agent and citric acid and cytosine as a reducing agent and stabilizers. The advanced nanocomposite was further studied using sophisticated techniques like XRD, FTIR, XPS, UV–Visible spectroscopy, Thermal Studies /TG-DTA analysis, SEM, TEM and EDS analysis. SEM and TEM studies reveal the simultaneous existence of nanorods and nanotubes in the prepared hybrid nanocomposite material. This kind of morphological orientation has significantly improved the nanocomposite’s antibacterial properties. The XPS studies depicts the binding energy of gadolinium oxide and MWCNTs. Different concentrations of nanocomposite and MWCNTs were tested against Gram −ve and gram +ve bacterial strains: Escherichia Coli, Staphylococcus Aureus, Klebsiella pneumonia, and Micrococcus luteus, respectively by disc diffusion method. Nanocomposite showed better performance against both types of bacteria, especially against gram +ve bacteria, in which MWCNTs did not establish any bacterial zone of inhibition. We believe that the developed advanced nanocomposite has enormous potential for healthcare applications based on these antibacterial properties.

Novel GdTaO4 phase for efficient photocatalytic degradation of organic dye under visible light irradiation: An X-ray spectroscopic investigation

The novel GdTaO4 phase exhibits good photocatalytic activity under visible light irradiation and holds great promise for the removal of organic dyes from industrial wastes. The GdTaO4 samples were synthesized using the hydrothermal and calcination process with different weight ratios of gadolinium nitrate hydrate (G) and tantalum pentachloride (T), and their structural studies confirmed the formation of the GdTaO4 (GT) phase. Among the samples, GT-4 (with a weight ratio of 4:1) exhibited the highest photocatalytic activity for the degradation of Methyl Orange (MO) dye under visible light irradiation. To enhance the photocatalytic performance, H2O2 was used as a green additive, and the photocatalytic abilities were examined by varying dye types and concentrations. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) revealed the local atomic and electronic structures around Ta and Gd and highlighted the contribution of Gd3+ to the GT system, which is a crucial factor in supporting the enhanced photocatalytic performance. Moreover, in-situ XAS at Gd M5-edge and O K-edge were examined under illumination/dark conditions to explore the electronic structures of photo-excited electron transition in the photocatalytic process. The analytical results provided strong evidence correlating the electronic structure and photocatalytic property of the GT. This study demonstrates that GdTaO4 exhibits good photocatalytic activity under visible light irradiation, making it a promising new Ta-based photocatalyst for the effective removal of organic dyes from industrial wastes.

Feasibility study of on-line monitoring gadolinium based on neutron induced gamma activation

Gadolinium is a soluble neutron poison for ensuring criticality safety of nuclear facility. A neutron induced gamma activation device was developed for the on-line measurement of gadolinium. The experimental device consisted of an 241Am–Be neutron source, six 3He detectors and a liquid scintillation detector. The size of sample container was optimized by using Monte Carlo simulations. Aqueous sample containing gadolinium nitrate were conducted with the device to obtain the calibration curve, and neutron self-shielding effect was also studied to correct the non-linear response. The results showed the minimum detectable concentration (MDC) of gadolinium was 0.426 mg/L. Two test samples were conducted to evaluate the performance of the device. The results demonstrated that the discrepancies were within 10%, which indicate the developed system can be successfully used for on-line monitoring of gadolinium.

Scalable novel lanthanide-ligand complex for robust flexible micro-supercapacitors

Herein we report on the excellent, supercapacitor performance and flexible device application of a robust, new polymeric metal-ligand complex, which is readily synthesized at room temperature via a straightforward, one-step protocol using the N4 donor, namely 3,3′-diaminobenzidine (DAB) and gadolinium(III) nitrate. Thus, the coordination polymer (Gd-DAB) complex synthesized in a facile and economically feasible synthesis route paves the way for realizing a new class of affordable, durable energy devices for storage applications. The results of complementary characterization techniques not only corroborated the proposed structure but also revealed a potential two-dimensional (2D)/sheet-like organization similar to the coordination polymer (COP). The electrochemical tests performed on the as-prepared sample, in the form of an electrode active component, showed brilliant supercapacitive characteristics with the capacitive retention exceeding over 100% even after 5000 cycles. The complex has been used as an active media for the fabrication of an interdigitated flexible and symmetric supercapacitor. The electrochemical storage device evaluation, under different bending angles (up to 180o) and twisting conditions at the current density of 10 μA/cm2 for 5000 cycles, revealed the capacitive retention of ∼50% after 5000 cycles.

Nanoscale Porosity of High Surface Area Gadolinium Oxide Nanofoam Obtained With Combustion Synthesis

AbstractNanoscale gadolinium oxide (Gd2O3) is a promising nanomaterial with unique physicochemical properties that finds various applications ranging from biomedicine to catalysis. The preparation of highly porous Gd2O3 nanofoam greatly increases its surface area thereby boosting its potential for functional use in applications such as water purification processes and in catalytic applications. By using the combustion synthesis method, a strong exothermic redox reaction between gadolinium nitrate hexahydrate and glycine causes the formation of crystalline nanoporous Gd2O3. In this study, the synthesis of Gd2O3 nanofoam is achieved with combustion synthesis at large scale (grams). Its nanoscale porosity is investigated by nitrogen physisorption and its nanoscale 3D structure by electron tomography, and the formation process is investigated as well by means of in situ heating inside the transmission electron microscope. The bulk nanofoam product is highly crystalline and porous with a surface area of 67 m2 g−1 as measured by physisorption, in good agreement with the electron tomographic 3D reconstructions showing an intricate interconnected pore network with pore sizes varying from 2 to 3 nm to tens of nanometers. In situ heating experiments point to many possibilities for tuning the porosity of the Gd2O3 nanofoam by varying the experimental synthesis conditions.

Dimethyl ether from methanol on mesoporous γ-alumina catalyst prepared from surfactant free highly porous pseudo-boehmite

Different samples of mesoporous nano-sized γ-alumina were prepared through surfactant-free sol-gel process, using aluminum nitrate as precursor. The influence of variables such as addition of alcohol, metal salts and also effect of changing the aluminum source were investigated on the synthesis method. The products, which were obtained on different conditions, were then characterized by XRD, FT-IR, SEM, TEM. Moreover, textural properties were also measured by BET. To study thermal stability of prepared alumina; Cerium nitrate, magnesium nitrate, lanthanum nitrate and gadolinium nitrate were added as dopants. The catalytic performance of the synthesized mesoporous alumina (with a surface area of ​​272 m2/g, pore volume of 0.94 cm3/g and pore size of 13.8 nm) was studied for the methanol conversion to dimethyl ether, and the result was compared by commercial γ-alumina. Synthesized mesostructured catalyst has comparable activity and DME selectivity at 300°C to that of commercial alumina at 400 °C.

Phase Equilibria and Thermodynamic Properties of Phases in the H2O–Gd(NO3)3 System

Solid–liquid equilibria in the system H2O–Gd(NO3)3 were measured from –20 to 70°C using the isothermal saturation method. The Pitzer–Simonson–Clegg thermodynamic model was implemented to obtain the temperature dependence of Gd(NO3)3⋅6H2O solubility constant, to calculate salt solubility and to construct a phase diagram of the system from eutectic point to hydrate melting. Thermochemical properties of gadolinium nitrate aqueous solutions, such as dilution enthalpies and heat capacities, were assessed also. The model has shown to be reliable for phase equilibria calculation from –35 to 90°C and from 0 up to ~15 mol % of salt as well as the thermodynamic properties of Gd(NO3)3 aqueous solutions at room temperature and around it.

Fiber Ring Laser Sensor Based on Micro-Nano Fiber Interferometer and Highly Sensitive Detection of Gadolinium Nitrate

Fiber Ring Laser Sensor Based on Micro-Nano Fiber Interferometer and Highly Sensitive Detection of Gadolinium Nitrate

Mechanistic aspects of in - situ combustion synthesis: Low Temperature gadolinium oxide formation during the high temperature interactions between gadolinium nitrate hexahydrate and glycine through solid state route

Current studies describe the application of simultaneous TG–DTA–EGA(FTIR) techniques in the in-situ synthesis of nano - sized gadolinium oxide through solid state route, using the high temperature interactions between Gadolinium nitrate hexahydrate and Glycine through in-situ combustion. Individual decomposition behavior of gadolinium nitrate hexahydrate, glycine and their interaction, in three different mole ratios, has been studied in inert and oxidative environments and respective reaction mechanisms have been proposed. It has been confirmed through thermal studies that gadolinium nitrate hexahydrate and glycine decompose independently in fuel deficient mixture. Results obtained from TG – DTA – EGA (FTIR), EDS and PXRD match well and suggests the formation of Gd2O3 at 400 0C. These studies confirm the formation of Gd2O3 at low temperature in inert environment using stoichiometric and fuel excess ratio mixtures.

Phase composition and local environment of iron ions in gadolinium-doped iron oxide nanoparticles

FeO ⋅ Fe2O3 ⋅ nH2O, Fe2.95Gd0.05O4 and Fe2.9Gd0.1O4 powders were obtained by chemical precipitation from aqueous solutions. The phase composition and local environment of iron ions in gadolinium-doped iron oxide nanoparticles were studied by X-ray diffraction analysis and nuclear gamma resonance (NGR) spectroscopy. Interpretation of radiographs and NGR spectra of synthesised samples indicates the presence of a superposition of maghemite γ-Fe2O3 and iron hydroxide α-FeOOH in the samples. It was found that under the deposition of powders in the presence of gadolinium nitrate, an increase in the content of iron hydroxide α-FeOOH is observed, which disappears after annealing at 200 °C.

Bio-inspired gadolinium coated titania nanotubes for orthopaedics

The distinguished corrosion behaviour along with the high strength-to-density ratio makes titanium (Ti) and its alloys an unavoidable material for long-term orthopaedic implant application. Though titanium was used as an implant material for many years in the clinical trial, the osseointegration of titanium implants with the bone around them is minimal leading to implant failure. For this study, combinational treatment of Cp-Ti by anodization using phosphate and fluoride electrolyte to form titania nanotubes (TNT) followed by dip coating with gadolinium nitrate solution. The corrosion behaviour of gadolinium-coated TNT (Gd-TNT) showed better corrosion resistance than TNT. The surface reactivity of the samples were analysed using a scanning electrochemical microscope (SECM). SECM is one of the powerful techniques to determine the surface chemical reactivity of metallic biomaterials in simulated body fluids. X-ray diffraction (XRD) analysis showed the anatase phase of titania nanotube formation. Attenuated Total Reflection Fourier Transform Infrared spectroscopy (ATR-FT-IR) was used to analyse the functional groups of the sample surface. The walls of the TNT were covered with gadolinium oxide which was confirmed by X-ray photoelectron spectroscopy (XPS) studies. Also, the mineralization of Gd-TNT was initiated after 24 h of immersion in simulated body fluid (SBF). The cytocompatibility studies indicated that the cell viability percentage of Gd-TNT was 69 % higher than the bare. In short, Gd-TNT can be used for treating the bone-related disorder.

Effect of temperature and composition on density and dynamic viscosity of (lanthanide metal salts + urea) deep eutectic solvents

• Lanthanide metal-based type IV deep eutectic solvents (DESs) are prepared. • Density of type IV metal DESs are higher compared to the other urea-based DESs. • Dynamic viscosities of these DESs are lower compared to other urea-based DESs. • Viscosity of the DESs exhibits Vogel − Fulcher − Tammann (VFT) temperature dependence. • Density and viscosity both decrease with increase in mole ratio of urea. Deep eutectic solvents (DESs) are rapidly becoming solvent media of prominence due not only to their unique properties but also to their promising environmentally-benign nature. For effective utilization of these neoteric media, assessment of their physical properties is essential. Density and dynamic viscosity of a class of DESs constituted of a hydrated lanthanide salt and urea at varying composition in the temperature range 293.15 to 363.15 K are presented. Specifically, different possible eutectic mixtures of lanthanum nitrate hexahydrate: urea (named La : Urea), cerium nitrate hexahydrate: urea (named Ce : Urea) and gadolinium nitrate hexahydrate: urea (named Gd : Urea) are investigated. DES (Gd : Urea) at 1: 2 mole ratio exhibits the highest density (1.98783 g.cm −3 at 293.15 K) of all the DESs investigated; density is found to decrease with increasing urea. Density of these DESs decreases linearly with increasing temperature. Dynamic viscosity of these DESs also decrease with increasing urea content. The temperature dependence of the dynamic viscosity follows Vogel − Fulcher − Tammann (VFT) expression. While the activation energy of viscous flow ( E a,η ) for these (lanthanide salt : Urea) DESs is closer to those of (choline chloride + H-bond donor) DESs, their viscosity-temperature dependence is similar to that of common imidazolium ionic liquids.