Self-diffusion Coefficient Of Water Research Articles

Water diffusion mechanisms in bitumen studied through molecular dynamics simulations

Water transport is one of the major factors responsible for moisture damage in asphalt pavements. To study the thermodynamics and kinetics of water transport in bitumen and to uncover microscale mechanisms of moisture-induced damage, molecular dynamics simulations were performed for up to 600 ns for water–bitumen systems with realistic water contents that varied from 0 to 1.76 wt%. Hydrogen bonding interactions and clustering of water molecules at various combinations of temperature and water content were investigated, and their effects on the self-diffusion coefficient of water and bitumen properties are computed and discussed. It is shown that the saturated water concentration in bitumen is small, especially at low temperatures, and additional water molecules tend to form large water clusters via hydrogen bonding, indicating micro-phase separation of the water and bitumen phases inside the simulation box. Hydrogen bonding and water clustering play a crucial role on the magnitude of the self-diffusion coefficient of water. Physical properties of bitumen that include viscosity and cohesive energy are affected by water. The presence of large water clusters is indicative of how degradation in cohesion is observed on the microscale.

Molecular Dynamics Study of Peptide in Water at Different Temperature

Molecular dynamics approach has been carried out to study the structural properties of peptide to estimate the self-diffusion coefficients of water at different temperatures 290 K, 300 K, and 310 K respectively. The energy profiles show the stability of system which ensures a well-balanced molecular structure of the system. The radial distribution functions (RDFs) of the solvent-solvent, solute-solute, and solute-solvent show the distribution of system within the required references. The self-diffusion coefficients of water have been determined using respective mean square displacement (MSD) curves through the Einstein’s relation. The self-diffusion coefficients of water at different temperatures are 0.44 ×10-5 cm2s-1, 0.48 ×10-5 cm2s-1, and 0.50 ×10-5 cm2s-1 respectively. Calculations show that the MSD of water throughout the system is increasing on increasing temperature. The results are also valid with the theoretical as well as available experimental data.

Self-diffusion coefficients of heavy water in low n-alkanes

The self-diffusion coefficients of D2O (i.e., heavy water or 2H2O) in eight n-alkanes at 298 K were investigated using 2H NMR diffusometry. D tended to decrease in the n-alkanes with increasing carbon number and be inversely proportional to the n-alkane viscosity to a fractional power. The hydrodynamic radius of D2O in the n-alkanes, calculated from Stokes-Einstein-Sutherland equation with stick boundary conditions, decreased with increasing n-alkane size and was smaller in the n-alkanes than in the bulk phase due to the absence of hydrogen bonds. This study provides fundamental data on the diffusion properties of water molecules dissolved in n-alkanes with applications to, for instance, molecular dynamics simulations or interpretation of Ostwald ripening.

Characteristic length and curvature of the AOT/brine/squalane “sponge” L3 phases

The effect of salinity (NaCl concentration) was determined at 25 ​°C for systems composed of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and equal volumes of squalane and brine. At all the NaCl concentrations the samples are triphasic with an upper phase made of pure squalane while brine is present in two other phases. At NaCl concentration (in brine) below 1.6 %w/v there is the coexistence of lamellar and sponge (L3) phases. Loading with NaCl above 1.6 %w/v one observes the coexistence of L3 and pure brine. The amount of AOT dissolved in the AOT bilayer has been quantified by thermogravimetric analysis. At salinity above 2 %w/v of NaCl in brine, the AOT sponge phase shrinks expelling brine and the squalane whose presence in the bilayer becomes negligible. The L3 phases have been further characterized by SAXS and diffusion-NMR. The measured self-diffusion coefficients of water and AOT are essentially coincident with those measured at the same salinity in the absence of squalane. The SAXS curves of sponge phases have been fitted to a single equation accounting for the contributions of the bilayer structure and of the large-scale interactions allowing the determination of the average interpore separation D∗ and the bilayer correlation length ξ. The correlation length has been interpreted as reflecting static randomness of connected bilayer instead of the dynamic thermal undulations. Considering the correlation length as the displacement along the bilayer surface subtending a critical angular change (θ∗) below which the surface appears as flat, permits to define the curvature (H) as |H| =θ∗ξ. The correlation length scales linearly with the square of the bilayer volume fraction as proposed by a previous theoretical model assuming the sponge phases are thermodynamically constrained to a curvature that equals the spontaneous curvature.

Molecular dynamics simulation studies of 1,3-dimethyl imidazolium nitrate ionic liquid with water.

The fundamental understanding of intermolecular interactions of ionic liquids (ILs) with water is essential in predicting IL-water thermodynamic properties. In this study, intermolecular or noncovalent interactions were studied for 1,3-dimethyl imidazolium [DMIM]+ cation and nitrate [NO3]- anion with water, employing quantum mechanics and molecular dynamics simulations. Molecular dynamics simulations were performed using a revised multipolar polarizable force field. The effect of water on ionic liquids was evaluated in terms of thermodynamic and dynamic properties. Thermodynamic properties included liquid densities ρ, excess molar volumes ΔVE, and liquid structures gr. Dynamic properties included self-diffusion coefficients D of mixture constituents as a function of water concentration. The density of ionic liquid-water mixtures monotonically decrease with increasing concentration of water. A negative excess volume was obtained for low and high water concentrations, demonstrating strong intermolecular interactions of water with ionic liquid components. Liquid structures of ionic liquid-water mixtures revealed a tendency for anions to interact with cations at shorter intermolecular distances when the water concentration is increased. Diffusion rates were found to increase for all mixture components with increase in the fraction of water. A significant change in the diffusion rate was found at ∼0.3 weight fraction of water. However, the water self-diffusion coefficient was dominant at all concentrations. The ratio of water/anion and anion/cation self-diffusion coefficients was found to decrease linearly with increasing concentration of water molecules.

Functionalization of Metal–Organic Framework Nanochannels for Water Transport and Purification

Artificial water nanochannels (AWCs) have drawn great attention due to their potential use in water purification. Herein, we propose an AWC design, which is based on coordinatively functionalizing unsaturated metal sites found in metal–organic frameworks (MOFs) with one-dimensional nanochannels. As a computational demonstration, we consider two MOFs, namely, Ni-CPO-27 and Ni-CPO-54, and graft proline, imidazolecarboxylic acid, imidazolecarboxaldehyde, pyrazolecarboxylic acid, and pyrazole carbaldehyde molecules into the MOF nanochannels. To assess the strength of the molecule-metal binding, binding energies were calculated using density functional theory. The results indicate that the MOFs containing either proline or 2-imidazolecarboxylic acid form water-stable AWCs with binding energies twice that of the binding energy of water. To shed light on the water diffusion mechanism in the proline-Ni-CPO-27/54 and 2-imidazolecarboxylic-Ni-CPO-27/54 AWCs, molecular dynamics simulations were performed to calculate the mean-squared displacement of water molecules and nonbonded interaction energies between select pairs of atoms in water and coordinated molecules were analyzed. It was found that the fastest water diffusion occurs in proline-Ni-CPO-54 with a self-diffusion coefficient of 7.2 ± 0.5 × 10–8 cm2/s. In comparison, the fastest water self-diffusion coefficient reported in a carbon nanotube-based AWC is 9 × 10–6 cm2/s. Nonbonded interactions between specific atom pairs regulate water diffusion in the functionalized MOF nanochannels. In particular, the change in water mean-squared displacement with changing water loading correlates well with the nonbonded energies between the partially positively charged hydrogen atoms in water and the partially negatively charged oxygen and nitrogen atoms in the proline and 2-imidazolecarboxylic acid molecules. The results presented herein indicate that water-stable MOFs could perform well as AWCs, thereby lending support to the further design and synthesis of MOF-based AWCs for water purification.

Structure and self-diffusivity of alkali-halide electrolytes in neutral and charged graphene nanochannels.

Understanding the microscopic behaviour of aqueous electrolyte solutions in graphene-based ultrathin nanochannels is important in nanofluidic applications such as water purification, fuel cells, and molecular sensing. Under extreme confinement (<2 nm), the properties of water and ions differ drastically from those in the bulk phase. We studied the structural and diffusion behaviour of prototypical aqueous solutions of electrolytes (LiCl, NaCl, and KCl) confined in both neutral and positively-, and negatively-charged graphene nanochannels. We performed molecular dynamics simulations of the solutions in the nanochannels with either one, two- or three-layer water structures using the effectively polarisable force field for graphene. We analysed the structure and intermolecular bond network of the confined solutions along with their relation to the self-diffusivity of water and ions. The simulations show that Na and K cations can more easily rearrange their solvation shells under the graphene nanoconfinement and adsorb on the graphene surfaces or dissolve in the confinement-induced layered water than the Li cation. The negative surface charge together with the presence of ions orient water molecules with hydrogens towards the graphene surfaces, which in turn weakens the intermolecular bond network. The one-layer nanochannels have the biggest effect on the water structure and intermolecular bonding as well as on the adsorption of ions with only co-ions entering these nanochannels. The self-diffusivity of confined water is strongly reduced with respect to the bulk water and decreases with diminishing nanochannel heights except for the negatively-charged one-layer nanochannel. The self-diffusivity of ions also decreases with the reducing the nanochannel heights except for the self-diffusivity of cations in the negatively-charged one-layer nanochannel, evidencing cooperative diffusion of confined water and ions. Due to the significant break-up of the intermolecular bond network in the negatively-charged one-layer nanochannel, self-diffusion coefficients of water and cations exceed those for the two- and three-layer nanochannels and become comparable to the bulk values.

Removal of methanol from water by capacitive deionization system combined with functional nanoporous graphene membrane

In this article, molecular dynamics simulations were used to examine the feasibility of capacitive deionization (CDI) system combined with a functionalized nanoporous graphene (NPG) membrane for removing methanol from water. The radial distribution function of electrode-methanol and methanol-water, the self-diffusion coefficient of methanol and water, the water density near the membrane, the interaction energy between methanol and membrane, the hydrogen bond structure between methanol and water, and the 2D density map of methanol molecules near the membrane under different electric field (EF) (to simulate the effect of capacitance) were examined to evaluate the separation performance of NPG membranes with hydrogen-passivated pores for methanol. The findings show that an EF with appropriate strength can decrease the amount of water molecules near methanol, increase the self-diffusion coefficient of methanol and water, increase hydrophobicity of hydrogenated pores, decrease the interaction between the NPG membrane and methanol, and weaken hydrogen bond interaction between water and methanol molecules. All these findings suggest that an appropriate EF can improve the NPG membrane's permeability to methanol, and verify the feasibility of CDI system combined with hydrogenated NPG membrane to remove methanol from water. This study is expected to propose a potential CDI application technology, and also give a novel idea for the removal of small organic molecules in water by functionalized NPG membrane.

Mobility of Dissolved Gases in Smectites under Saturated Conditions: Effects of Pore Size, Gas Types, Temperature, and Surface Interaction

In a nuclear waste repository, the corrosion of metals and the degradation of the organic material in the waste matrix can generate significant amounts of gases. These gases should be able to migrate through the multibarrier system to prevent a potential pressure build-up that could lead to a loss of barrier integrity. Smectite mineral particles form a tortuous pore network consisting of larger interparticle pores and narrow interlayer pores between the platelets of the smectite minerals. These pores are normally saturated with water, so one of the most important mechanisms for the transport of gases is diffusion. The diffusion of gases through the interparticle porosity depends on the distribution of gas molecules in the water-rich phase, their self-diffusion coefficients, and the tortuosity of the pore space. Classical molecular dynamics simulations were applied to study the mobility of gases (CO2, H2, CH4, He, and Ar) in Na-montmorillonite (Na-MMT) under saturated conditions. The simulations were used to estimate the gas diffusion coefficient (D) in saturated Na-MMT as a function of nanopore size and temperature. The temperature dependence of the diffusion coefficient was expressed by the Arrhenius equation for the activation energy (Ea). The predicted D values of gases were found to be sensitive to the pore size as the D values gradually increase with increasing pore size and asymptotically converge to the gas diffusion coefficient in bulk water. This behavior is also observed in the self-diffusion coefficients of water in Na-MMT. In general, H2 and He exhibit higher D values than Ar, CO2, and CH4. The predicted Ea values indicate that the confinement affects the activation energy. This effect is due to the structuring of the water molecules near the clay surface, which is more pronounced in the first two layers of water near the surface and decreases thereafter. Atomic density profiles and radial distribution functions obtained from the simulations show that the interaction of the gas with the liquid and the clay surface influences mobility. The obtained diffusion coefficient for different gases and slit pore size were parameterized with a single empirical relationship, which can be applied to macroscopic simulations of gas transport.

Experimental and molecular dynamics approach to evaluate the thermo-rheological properties of CuO nanofluids for heat transfer application

The experimental and Molecular Dynamics (MD) simulation studies of nanofluids have substantially gained traction among many researchers in recent years as both studies complement each other. The main aim of this work is to investigate the stability, thermal conductivity (TC) and rheological behavior of copper oxide (CuO) based nanofluids at different particle concentrations (0.1–2.0%) and temperatures (20–60 °C) with the use of experimental and atomistic study. Nanofluid appears as a non-Newtonian fluid with a shear rate between 12 and 232 s−1 and they exhibit shear thickening behavior. MD study has confirmed the presence of nanolayer and enhanced self-diffusion coefficient of water which have been attributed to the viscosity and TC enhancement of the nanofluid. The maximum enhancement of TC is found to be 7% for CuO-SDS nanofluid over the base fluid at the highest concentration and temperature. The percentage of TC enhancement increases with temperature and concentration. MD study has also confirmed the same with a maximum error of 11% at the lowest temperature. Viscosity ratio of nanofluid increases with temperature and concentration. The same has been investigated using Green-Kubo formalism via MD and observed a maximum error of 8% at the lowest temperature.

Machine learning-generated TIP4P-BGWT model for liquid and supercooled water

Accurately calculating the crucial physical properties of liquid and supercooled water is quite challenging by molecular simulations owing to limited model parameters. Machine learning (ML) techniques and temperature-dependent parameters provide a path to efficiently reparametrize TIP4P model. Here, 7000 molecular dynamics (MD) samples for liquid and supercooled water from 253 K to 373 K are generated to train the back-propagation neural network with better generalization ability. This network could rapidly and accurately provide adequate data for genetic algorithm to reparametrize the molecular model without extra time-consuming molecular simulations. Based on the proposed optimized approach, a water model TIP4P-BGWT with temperature-dependent model parameters is established. It exhibits excellent predictive performance with comprehensive balance for the four crucial physical properties (density, vaporization enthalpy, self-diffusion coefficient and viscosity) of water. The corresponding mean absolute percentage error is 3.26 %, which is lower than the existing water models. Furthermore, the calculated results of the temperature of maximum density, thermal expansion coefficient, isothermal compressibility, surface tension, radial distribution function and the average number of hydrogen bonds per molecule are also in good consistent with experiments. It is notable that the established water model exhibits excellent performance for the supercooled water. The present study offers an accurate numerical model of liquid and supercooled water for the molecular simulation-based researches on the nanoflow, nanodroplet, interfacial fluids and bio-molecular systems, etc.

Shear viscosity and Stokes-Einstein violation in supercooled light and heavy water.

We report shear viscosity of heavy water supercooled 33K below its melting point, revealing a 15-fold increase compared to room temperature. We also confirm our previous data for the viscosity of supercooled light water and reach a better accuracy. Our measurements, based on the spontaneous Brownian motion of 350nm spheres, disagree at the lowest temperature with the only other available data, based on Poiseuille flow in a narrow capillary, which may have been biased by electro-osmotic effects. Here we provide a detailed description of the experiment and its analysis. We review the literature data about dynamic properties of water (viscosity, self-diffusion coefficient, and rotational correlation time), discuss their temperature dependence, and compare their decoupling in the two isotopes.

Thermodynamic and transport properties of amoxicillin

We have carried out MD simulations of amoxicillin, a drug molecule used as antibacterial agent, in water and ethanol to study thermodynamic properties like solvation free energy and transport phenomena like diffusion, viscosity. The free energy of solvation of amoxicillin in water and ethanol have been estimated at 310 K using thermodynamic integration (TI) and free energy perturbation (FEP) based methods. It has been obtained that the free energy of solvation of amoxicillin in water is higher by ≈ 105 kJ/mol in TIP3P model than in ethanol. We have also reported the solvent accessible surface area (SASA) of solute as well as the hydrogen bonds between solute and solvent for different solvents. The analysis of SASA and hydrogen bond provides more insight on effect of solvent environment in solvation process of amoxicillin. We have also estimated the diffusion coefficient and our results show that diffusion coefficients of amoxicillin depends on solvent environment, as expected, and it is higher in water than that of ethanol. Also, applying the idea of system size dependence of diffusion coefficient, the viscosity coefficient of water and solution of amoxicillin in water have also been estimated. Furthermore, the effects of temperature on diffusion has been studied. The estimated values of self-diffusion coefficients of water are in good agreement with previously reported experimental data within ≈13.5%.

Diffusion of glucose in water: A molecular dynamics study

A glucose molecule, simple structure of carbohydrate, has many functions in our body. It is transported to every cell and served as of energy source. The investigation of transport properties of glucose in aqueous medium would be useful to understand the body metabolism. In this research work, molecular dynamics (MD) simulations have been utilized to study the transport and structural properties of glucose in water at different temperature (298.15 K, 303.15 K, 308.15 K, and 312.15 K). The self diffusion coefficients of glucose and water have been estimated from mean square displacement plot (MSD) by using Einstein’s relation. Further, Darken’s relation has been used to find the binary diffusion coefficients of the mixture. The structural analysis of the system has been estimated with the help of radial distribution function (RDF) of its constituent atom/molecule pairs. The outcomes from the MD simualtions depicts that the temperature dependence of self diffusion coefficients of solute and solvent follow Arrhenius behavior, which further assist to calculate the activation energy of the system. The results from the present work agree well with the previously reported experimental values.

Effect of the carbon mesoporous structure on the transport properties of confined lithium chloride aqueous solutions

Accurate determination of fluid dynamics in confined carbons with pore size distribution (PSD) ranging from micro to mesopores is a fundamental aspect for many relevant applications, such as lithium battery electrodes, supercapacitors, or fuel cells. Here we present a synthesis route that enables the preparation of carbons with tailored PSD, which are characterized by nitrogen adsorption methods and nuclear magnetic resonance (NMR). The combination of micro and mesopores is determined straightforwardly by the determination of confined water self-diffusion coefficients and longitudinal relaxation times. Employing 2D-NMR experiments pore interconnectivity was characterized, determining exchange rates for water between micropores, mesopores, and bulk solution. Furthermore, their functionality was tested in simple ion release experiments of a solution of LiCl carried out both by conductivity and NMR experiments. We found that the lithium release rate can be set by tailoring the connectivity between micro and mesopores. For samples with mesopores larger than 5 nm and a small content of micropores, ion mobility is mainly restricted by the material's porosity. On the other hand, tortuosity analysis reveals that carbon wall-ion interaction is the main factor of the sluggish diffusion in materials with a large fraction of micropores well connected to the mesopore network.

Effect of Water Models on Transmembrane Self-Assembled Cyclic Peptide Nanotubes.

Self-assembling cyclic peptide nanotubes can form nanopores when they are inserted in lipid bilayers, acting as ion and/or water permeable channels. In order to improve the versatility of these systems, it is possible to specifically design cyclic peptides with a combination of natural and non-natural amino acids, enabling the control of the nature of the inner cavity of the channels. Here, the behavior of two types of self-assembling peptide motifs, alternating α-amino acids with γ- or δ-aminocycloalkanecarboxylic acids, is studied via molecular dynamics (MD) simulations. The behavior of water molecules in nanopores is expected to affect the properties of these channels and therefore merits detailed examination. A number of water models commonly used in MD simulations have been validated by how well they reproduce bulk water properties. However, it is less clear how these water models behave in the nanoconfined condition inside a channel. The behavior of four different water models—TIP3P, TIP4P, TIP4P/2005, and OPC—are evaluated in MD simulations of self-assembled cyclic peptide nanotubes of distinct composition and diameter. The dynamic behavior of the water molecules and ions in these designed artificial channels depends subtly on the water model used. TIP3P water molecules move faster than those of TIP4P, TIP4P/2005, and OPC. This demeanor is clearly observed in the filling of the nanotube, in water diffusion within the pore, and in the number and stability of hydrogen bonds of the peptides with water. It was also shown that the water model influences the simulated ion flux through the nanotubes, with TIP3P producing the greatest ion flux. Additionally, the two more recent models, TIP4P/2005 and OPC, which are known to reproduce the experimental self-diffusion coefficient of bulk water quite well, exhibit very similar results under the nanoconfined conditions studied here. Because none of these models have been parametrized specifically for waters confined in peptide nanotubes, this study provides a point of reference for further validation.

Effect of alkyl chain length of protic ionic liquids on dynamic and static properties of alkylammonium nitrate/water mixtures

Mixtures of alkylammonium nitrate (AAN) as a protic ionic liquid (IL) with water were investigated with regard to their dynamic (self-diffusion coefficient, viscosity) and static (chemical shift, density, radial distribution function) properties. As a result, the chemical shift of the cation and the solution volume did not change significantly at 0–60 mol% water, which suggests that the liquid structure of AAN was maintained and water had entered the liquid structure of AAN. In the same concentration range, the chemical shift of the water in AAN showed a downfield shift that was clearly larger than that in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) as an aprotic IL. The microscopic mobility (self-diffusion coefficient) of water also changed more sensitively to the macroscopic mobility (viscosity) in the AAN/water mixture than in the [BMIM][BF4]/water mixture. The mobility of the water in the AAN/water mixture is thus more restricted to a liquid structure than the water in the [BMIM][BF4]/water mixture. These results are considered to be due to the difference in the strength of the hydrogen bonds between AAN and [BMIM][BF4]. On the other hand, the chemical shift of cation and water, the sensitivity of the microscopic mobility of water to the macroscopic mobility of AAN/water mixture, the coordination number of water to cation and water to anion did not change significantly with the alkyl chain length. Therefore, it is expected that water is present near the polar domain composed of ammonium groups and nitrate, which is not easily affected by the alkyl chains.

Enhancement and maximum in the isobaric specific-heat capacity measurements of deeply supercooled water using ultrafast calorimetry

Knowledge of the temperature dependence of the isobaric specific heat (Cp) upon deep supercooling can give insights regarding the anomalous properties of water. If a maximum in Cp exists at a specific temperature, as in the isothermal compressibility, it would further validate the liquid-liquid critical point model that can explain the anomalous increase in thermodynamic response functions. The challenge is that the relevant temperature range falls in the region where ice crystallization becomes rapid, which has previously excluded experiments. Here, we have utilized a methodology of ultrafast calorimetry by determining the temperature jump from femtosecond X-ray pulses after heating with an infrared laser pulse and with a sufficiently long time delay between the pulses to allow measurements at constant pressure. Evaporative cooling of ∼15-µm diameter droplets in vacuum enabled us to reach a temperature down to ∼228 K with a small fraction of the droplets remaining unfrozen. We observed a sharp increase in Cp, from 88 J/mol/K at 244 K to about 218 J/mol/K at 229 K where a maximum is seen. The Cp maximum is at a similar temperature as the maxima of the isothermal compressibility and correlation length. From the Cp measurement, we estimated the excess entropy and self-diffusion coefficient of water and these properties decrease rapidly below 235 K.

Structural and dynamic properties of some aqueous salt solutions.

Aqueous salt solutions are utilized and encountered in wide-ranging technological applications and natural settings. Towards improved understanding of the effect of salts on the dynamic properties of such systems, dilute aqueous salt solutions (up to 1 molar concentration) are investigated here, via experiments and molecular simulations. Four salts are considered: sodium chloride, for which published results are readily available for comparison, ammonium acetate, barium acetate and barium nitrate, for which published data are scarce. In the present work, molecular dynamics (MD) simulations are conducted to quantify viscosity and water self-diffusion coefficients, together with rheometry and Pulsed Field Gradient Spin Echo (PFGSE)-NMR experiments for validation. Simulation predictions are consistent with experimental observations in terms of trend and magnitude of salt-specific effects. Combining insights from the approaches considered, an interpretation of the results is proposed whereby the capacity of salts to influence bulk dynamics arises from their molecular interfacial area and strength of interaction with first hydration-shell water molecules. For the concentration range investigated, the interpretation could be useful in formulating aqueous systems for applications including the manufacturing of advanced catalysts.

Temperature and field dependences of transverse relaxivity of Co–Zn ferrite nanoparticles coated with silica: The role of magnetic properties and different regimes

The transverse relaxivity r2, characterizing the performance of negative contrast agents like magnetic nanoparticles in T2-weighted MRI, depends on multiple factors, most importantly on magnetic properties and the size of the particles, including both the size of magnetic cores and the effective size of whole particles present as individual entities in the suspension. The current study probes the transverse relaxivity of ferrimagnetic CoxZnyFe3-x-yO4 nanoparticles whose behavior varies from the blocked state, across the superparamagnetic regime to the vicinity of the paramagnetic state, while other parameters, namely the size of the magnetic cores (≈10 nm), the size of whole colloidally stable particles, and their geometry (≈30 nm-sized clusters of crystallites uniformly coated with ≈12 nm thick silica shell) are kept the same. Among the samples studied, the silica-coated clusters of Co0·66Zn0·47Fe1·87O4 crystallites show high values of r2 = 534 s−1 mmol(Me3O4)−1 L at room temperature in the magnetic field of 1.5 T. Importantly, the field and temperature dependences of transverse relaxivity are discussed in relation to relevant theoretical models, i.e., motional averaging and static dephasing regimes. The increase in r2 in higher magnetic fields is related to the notable paraprocess in the employed cores, whereas the gradual decrease of r2 with increasing temperature is dominated by the significant increase of the self-diffusion coefficient of water.