Hydrophilic Media Research Articles

Ultra-fast mechanochemical strategy to obtain stable colloidal dispersions of MWCNT in hydrophilic media: Never has been so easy

In this paper, we present a new protocol that allows the dispersion of multi-wall carbon nanotubes (MWCNT) in the form of stable colloids in a hydrophilic medium up to concentrations of ca. 0.06 % (w/w). The strategy involves using a combination of mechanochemical treatment and surfactants. In this study, we processed MWCNTs with surfactants in a ball mill without using any solvents. The mechanochemical treatment consists of processing mixtures of MWCNTs (0.35 g) with different surfactants (4.5 g of CTAB, 3.6 g of SDS and 4.5 g of F127 as cationic anionic and neutral surfactants, respectively) in a ball mill for only 20 min at 300 rpm. The resulting black powder is then used directly to prepare dispersions in hydro-alcoholic media, which maintain colloidal stability for at least 25 days. Although various strategies for dispersal have been proposed in the literature, many involve time-consuming and multi-step processes with low yields. The MWCNTs modified non-covalently using our protocol are synthesised in a single step with a 100 % yield without any loss of reagents. MWCNT have shown potential in many emerging applications of great interest. Its use necessarily implies the achievement of a good dispersion in different solvents, and this aspect, in the case of hydrophilic media, still does not have a satisfactory answer. The absence of solvent during the mechanochemical treatment is the key aspect of our strategy. This small change represents a significant improvement. We demonstrate the outstanding stability of the obtained suspensions and the preservation of the nano-/microstructure of the MWCNTs, which remains unaltered during their preparation. Furthermore, using environmentally friendly solutions for dispersion makes this protocol a Green Chemistry approach.

Capillary‐Driven Backflow During Salt Precipitation in a Rough Fracture

AbstractSalt precipitation is a crucial process occurring during CO2 injection into saline aquifers. It significantly alters the porous space, leading to reduced permeability and impaired injectivity. While the dynamics of precipitation have been studied within porous media, our understanding of precipitation patterns and permeability evolution within rough fractures remains inadequate. Here, we conduct flow‐visualization experiments on salt precipitation, wherein dry air invades brine‐filled rough fractures under various flow rate conditions. Our observations reveal that the precipitation pattern shifts from ex situ precipitation to homogeneous form as the flow rate (capillary number Ca) increases. Through real‐time imaging of the salt precipitation process, we determine that ex situ precipitation is due to capillary‐driven backflow. This backflow phenomenon occurs when previously precipitated salt, acting as a hydrophilic porous medium, attracts the brine flow backward. As a result, precipitation occurs at a location different from the original site. We further show that the impact of capillary‐driven backflow is significant at low flow rates and is gradually suppressed as the flow rate increases. We provide a theoretical estimation for the critical Ca for the occurrence of capillary‐driven backflow. As Ca is smaller than this critical value, backflow‐precipitation positive feedback causes fracture voids to become completely clogged, thereby leading to a more substantial permeability reduction. In contrast, a homogeneous precipitation pattern tends to only partially clog the fracture voids, causing a relatively smaller permeability reduction. This study enhances our understanding of the role of capillary‐driven backflow in controlling salt precipitation and permeability reduction in fractures.

An integrated simulation approach for demulsification of water-in-oil emulsions by medium coalescence

Medium coalescence, as a low energy consumption demulsification method, has been widely applied in many industries. During the water-in- oil emulsions flowing through medium bed, the dispersed water droplets not only collide and aggregate with each other, but also deposit and wet on the hydrophilic medium surface. Moreover, the formed large droplets may also breakup into small ones by the turbulent flow or the tiny fibers. Thus, an integrated approach is needed to predict the demulsification performance of water-in-oil (W/O) emulsion by medium coalescence. In this work, the population balance model (PBM) with considering Boltzmann motion and differential settlement was used to predict suspension droplets aggregation. The interaction between dispersed droplets and medium bed was calculated by a modified deposition model. Moreover, a published breakage model was selected to simulate the complex droplet breakage process. Then, the demulsification performance of W/O emulsion can be obtained by the variation of droplet size profile. To verify the integrated simulation approach, the existing experimental datasets were compared with the simulation results. After that, a sensitivity analysis was carried out to study parameters that affect the demulsification performance, such as flow velocity, capillary size, and continuous viscosity. The integrated approach proposed in this paper fills in the blank of the demulsification simulation of W/O emulsion by medium coalescence. It provides an in-depth understanding of the relationship between droplets behaviors and medium coalescence performance.

Absorbent bioactive aerogels based on germinated wheat starch and grape skin extract

This study aimed to produce water-absorbent bioactive aerogels using biodegradable raw materials, wheat starch and poly ethylene oxide (PEO), and derived from agro-industrial residues (grape skin) obtained in the wine industry. The aerogels were produced using germinated wheat starch (GWS), with and without PEO, and incorporating grape skin extract (GSE) at concentrations of 5 and 10 % (w/w). The GSE was evaluated for total and individual phenolic compounds, anthocyanins, and antioxidant activity. The starch aerogels were characterized for morphology, density, porosity, functional groups by FT-IR, relative crystallinity and diffraction pattern, water absorption capacity, antioxidant activity, and in vitro release profile of phenolic compounds in food simulant medium. The total phenolic compounds in GSE was 226.25 ± 0.01 mg equivalent of gallic acid/g GSE. The aerogels showed low density and high porosity. All aerogels demonstrated high water absorption capacity (581.4 to 997.5 %). The antioxidant activity of the aerogels increased with increasing GSE concentration and the addition of PEO. The aerogels could release GSE gradually for up to 120 days in the hydrophilic simulant medium and 240 h for the hydrophobic medium. Starch-based aerogels with GSE showed potential to be applied as exudate absorbers with antioxidant activity to develop active food packaging.

Influence of vibration on droplet dynamics in a three-dimensional porous medium

In this study, the effects of vibration on droplet dynamics inside a three-dimensional (3D) porous medium are investigated with a focus on frequency, amplitude, and surface wettability. A lattice Boltzmann method based on the Allen–Cahn equation (A-C LBM) is used. The results show that the volume of the drained drop and drainage duration of the droplet are significantly affected by the contact angle. The hydrophilic nature of the pores causes the droplet to spread inside the medium and resist the vibration force, resulting in a lower discharged liquid volume and delayed drainage. In contrast, a hydrophobic surface repels the droplet and leads to quicker drainage. It is also observed that the speed of droplet drained from the porous medium is higher for hydrophobic conditions, causing the separated drop to rebound and jump back toward the medium after impacting the surrounding wall boundaries. A thorough investigation is conducted on the combined implication of the surface adhesion, amplitude, and frequency of vibration on the first separation time of the droplet from the porous medium and full drainage duration. The results show that with increasing the hydrophobicity, the required vibration amplitude for complete drainage has decreased. In this way, the interplay between the adhesive force and the vibration force impedes the liquid phase separation from the hydrophilic porous medium at a low vibration amplitude. However, the results demonstrate that even in these conditions, an increase in the vibration frequency can enhance the separation and improve the drainage of the liquid phase from the pores.

UV Light as an Efficient Tool for Reducing Surface Defects of ZnSe-MSA Quantum Dots.

Defects in ZnSe quantum dots are responsible for increasing the trap states, which can lead to the drastic reduction of their fluorescence output, being one of the major drawbacks of these materials. As surface atoms become more relevant in these nanoscale structures, energy traps due to surface vacancies, play a very definite role in the final emission quantum yield. In the present study, we report the use of photoactivation procedures to decrease surface defects of ZnSe QDs stabilized with mercaptosuccinic acid (MSA), in order to improve the radiative pathways. We applied the colloidal precipitation procedure in a hydrophilic medium and evaluated the role of Zn/Se molar ratios as well as the Zn2+ precursors (nitrate and chloride salts) on their optical properties. Best results (i.e. increment of 400% of the final fluorescence intensity) were obtained for nitrate precursor and a Zn/Se = 1.2 ratio. Thus, we suggest that the chloride ions may compete more efficiently than nitrate ions with MSA molecules decreasing the passivation capability of this molecule. The improvement in ZnSe QDs fluorescence can potentialize their use for biomedical applications.

Multicomponent Crystals of Phthalocyanines–A Possibility of Fine-Tuning Properties

Phthalocyanines (Pcs) are 18-electron π-conjugated macrocyclic ring systems with proven activities in diverse fields, including pharmaceuticals and catalysis. These demonstrated activities are often alluded to as their fascinating photophysical and photochemical dispositions, which are usually dependent on their molecular structures. However, many of these molecules suffer from aggregation due to π–π stacking and have limited insolubility in hydrophilic media, which limits their extensive utilisation in pharmaceutical applications. This review will explore the possibility of fine-tuning the physicochemical properties of phthalocyanines when designed as multicomponent crystals. Among the proven and SMART approaches that have been shown to enhance drug solubility without altering the molecular structure is co-crystallisation. This protocol involves the design and formation of non-covalent interactions between two or more molecular entities to create a supramolecular assembly and subsequently afford multicomponent crystals (MCCs). A systematic review of the Cambridge Structural Database repository yielded several single and multicomponent crystals of Pcs; however, most of them were either salts or solvates, with only a few reports on their co-crystals.

From Nanothermometry to Bioimaging: Lanthanide-Activated KY3F10 Nanostructures as Biocompatible Multifunctional Tools for Nanomedicine.

Lanthanide-activated fluoride-based nanostructures are extremely interesting multifunctional tools for many modern applications in nanomedicine, e.g., bioimaging, sensing, drug delivery, and photodynamic therapy. Importantly, environmental-friendly preparations using a green chemistry approach, as hydrothermal synthesis route, are nowadays highly desirable to obtain colloidal nanoparticles, directly dispersible in hydrophilic media, as physiological solution. The nanomaterials under investigation are new KY3F10-based citrate-capped core@shell nanostructures activated with several lanthanide ions, namely, Er3+, Yb3+, Nd3+, and Gd3+, prepared as colloidal water dispersions. A new facile microwave-assisted synthesis has been exploited for their preparation, with significant reduction of the reaction times and a fine control of the nanoparticle size. These core@shell multifunctional architectures have been investigated for use as biocompatible and efficient contrast agents for optical, magnetic resonance imaging (MRI) and computerized tomography (CT) techniques. These multifunctional nanostructures are also efficient noninvasive optical nanothermometers. In fact, the lanthanide emission intensities have shown a relevant relative variation as a function of the temperature, in the visible and near-infrared optical ranges, efficiently exploiting ratiometric intensity methods for optical thermometry. Importantly, in contrast with other fluoride hosts, chemical dissolution of KY3F10 citrate-capped nanocrystals in aqueous environment is very limited, of paramount importance for applications in biological fluids. Furthermore, due to the strong paramagnetic properties of lanthanides (e.g., Gd3+), and X-ray absorption of both yttrium and lanthanides, the nanostructures under investigation are extremely useful for MRI and CT imaging. Biocompatibility studies of the nanomaterials have revealed very low cytotoxicity in dfferent human cell lines. All these features point to a successful use of these fluoride-based core@shell nanoarchitectures for simultaneous diagnostics and temperature sensing, ensuring an excellent biocompatibility.

Efficiency and sensitivity optimization of a protocol to quantify indoor airborne SARS-CoV-2 levels

BackgroundDevelopment of methodologies to quantify airborne microorganisms is needed for the prevention and control of risk infections. It is difficult to conclude which is the most efficient and sensitivity strategy to assess airborne SARS-CoV-2 RNA levels given the disparity of results reported in clinical settings.AimTo improve our previously reported method of measuring SARS-CoV-2 RNA levels, was based on bioaerosol collection with a liquid impinger and RNA quantification with droplet digital PCR (ddPCR).MethodsAir samples were collected in COVID-19 patient rooms to assess efficiency and/or sensitivity of different air samplers, liquid collection media and reverse transcriptases (RT).FindingsMineral oil better retains airborne RNA than hydrophilic media without impairing integrity. SARS-CoV-2 ORF1ab target was detected in 80% of the air samples using BioSampler® with mineral oil. No significant differences in effectiveness were obtained with MD8® sampler provided with gelatine membrane filters, but the SARS-CoV-2 copies/m3 air obtained with the latter were lower (28.4±6.1 vs 9±1.7). SuperScript II RT allows the detection of one single SARS-CoV-2 genome RNA molecule by ddPCR with a high efficiency. This was the only RT that allowed the detection of SARS-CoV-2 N1 target in air samples.ConclusionOptimizing collection efficiency and detection sensitivity for quantification od SARS-CoV-2 RNA in indoor air is important to improve our understanding of the microbiological safety of indoor air.

Visualization study on preferential flow in highly saturated and super hydrophilic porous media by combining dye tracking and infrared imaging

• New method to track finger flow in highly saturated superhydrophilic porous media. • Preferential flow recurrence was observed at high saturation. • The preferential flow was found to impair desalination efficiency. • The temperature distribution was controlled by preferential flow. Air-gap diffusion distillation (AGDD) is a practical desalination technique. The highly saturated super hydrophilic porous medium as its evaporation surface has a decisive influence on the desalination efficiency of AGDD. In experiments, we found preferential flow in porous media. However, the preferential flow in highly saturated super hydrophilic porous media has not been studied, and the effect of preferential paths on evaporation from porous media surfaces remains poorly understood. The method of combining dye tracking and infrared imaging was used to visualize the process of thermal seepage in highly saturated super hydrophilic porous media. Under the condition of uniform and continuous liquid supply on the upper surface, the preferential flow characteristics of hot stream seepage in porous media are tracked; Point source infiltration experiments were carried out at room temperature to compare the difference between preferential flow in super hydrophilic porous media and general soil (sand). The experimental results of thermal seepage showed that the preferential flow greatly influences the uneven temperature distribution of the porous media, which directly impairs the desalination efficiency of AGDD. According to the coefficient of variation (CV), the preferential flow development process can be divided into three stages: stable development, exponential development, and high-speed growth. As the seepage flow is stabilized, the influence of preferential flow on the flow field and temperature field still exists and is affected by these three stages. Preferential flow characteristics were also captured in the saturated capillary rise zone at the bottom of the porous medium (below the phreatic level). The point source infiltration experiment found that the preferential flow in superhydrophilic porous medium will reappear at high saturation, which is completely different from the soil (sand) studied by previous studies. In addition, the effects of inlet temperature, flow rate, thickness, and hydrophilic, hygroscopicity on preferential flow were discussed. Increasing the flow rate and inlet temperature and reducing the thickness of the porous media can weaken the influence of preferential flow on the temperature field. But increasing the temperature only superficially weakens the preferential flow. Increasing hydrophilicity and hygroscopicity can also reduce the preferential flow.

A Kinetic Study of 2-Amino-4-(Methyl-Thio) Butanoic Acid By Quinaldinium Fluorochromate In Selected Hydrophilic Solvent Medium

A Major role in oxidation kinetics is to determine the reaction mechanism that comprise chemical reaction. In the present paper we derived rate law for reaction mechanism and to recognized the order of reaction, give rate equation, calculate the rate constant. Identify the product of this oxidation reaction.The chemical oxidation of 2-Amino-4-methyl thio-butanoic acid by Quinaldinium Fluorochromate was studied in 50-50 (v/v) selected hydrophilic solvent medium at 308 Kelvin. The reaction is acid catalysed and exhibits first order dependence with respect to oxidant, substrate, and fractional order respect to H+ ion concentrations. Chemical oxidation kinetics is the study of the rate of chemical reaction.the factors Manganesh sulphate, Acrylonitrile, Sodium perchlorate that affect these rates (or) not, and draw of ln Kobs/T verses 1/T energy diagram to find the activation energy. Addition of sodium perchlorate slightly decreases the rate of reaction. However, Acrylonitrile is not induced by the polymerization reaction, showing that there is no free radical route. Added Mn2+ increases with slightly increase rate in the reaction medium. 2-Amino-4-(MethylThio)-Butanoic acid by Quinaldinium Fluorochromate has not been reported. Hence, the investigation of oxidation of 2-Amino-4-Methyl Thio-Butanoic acid by QNFC in selected hydrophilic solvent medium and the corresponding mechanistic aspects are discussed in this research paper. A systematic kinetic work carried out to explore the physical characterization of the reactance. The characterstic effects like Substrate, Oxidant, Perchloric acid, Solvent, Sodium perchlorate, Acrylonitrile, Manganes sulphate and Influence Temperature it clearly shows effect on that reaction path. The process was carried out at four different temperatures to determine the activation conditions. The measured kinetic findings ΔH# and ΔS# are derived from the value.

Study of Progress on Nanocrystalline Cellulose and Natural Fiber Reinforcement Biocomposites

Cellulosic biomass hydrolysis yields a nanoscale substance known as nanocrystalline cellulose (NCC). Gel, liquid, or powder is adaptable to a variety of uses. Nanocrystalline cellulose has unique renewability, biodegradability, and mechanical and physicochemical qualities, and abundance boosts the material’s mechanical strength by many orders of magnitude when introduced into the material matrix (polymer, ceramic, or metal). Nanocrystalline cellulose is not related with any serious environmental issues because it is a natural substance. The progress of this biomaterial as a green and renewable biomaterial for the fabrication of lightweight and biodegradable composite materials gives further impetus. The current aim of nanocrystalline cellulose research is to optimise nanocrystalline cellulose characteristics for dispersion in hydrophilic and hydrophilic media. To assess the nanocrystalline cellulose reinforcing, antibacterial, stability, hydrophilicity, and biodegradability, imaging methods and protocols in complicated matrices will need to be developed. This review includes a discussion on nanocrystalline cellulose biocomposites.

Study of Fingering Dynamics of Two Immiscible Fluids in a Homogeneous Porous Medium with Considering Wettability Effects Using a Pore-Scale Multicomponent Lattice Boltzmann Model

In the present study, a pore-scale multicomponent lattice Boltzmann method (LBM) is employed for the investigation of the immiscible-phase fluid displacement in a homogeneous porous medium. The viscous fingering and the stable displacement regimes of the invading fluid in the medium are quantified which is beneficial for predicting flow patterns in pore-scale structures, where an experimental study is extremely difficult. Herein, the Shan-Chen (S-C) model is incorporated with an appropriate collision model for computing the interparticle interaction between the immiscible fluids and the interfacial dynamics. Firstly, the computational technique is validated by a comparison of the present results obtained for different benchmark flow problems with those reported in the literature. Then, the penetration of an invading fluid into the porous medium is studied at different flow conditions. The effect of the capillary number (Ca), dynamic viscosity ratio (M), and the surface wettability defined by the contact angle (θ) are investigated on the flow regimes and characteristics. The obtained results show that for M<1, the viscous fingering regime appears by driving the invading fluid through the pore structures due to the viscous force and capillary force. However, by increasing the dynamic viscosity ratio and the capillary number, the invading fluid penetrates even in smaller pores and the stable displacement regime occurs. By the increment of the capillary number, the pressure difference between the two sides of the porous medium increases, so that the pressure drop Δp along with the domain at θ=40∘ is more than that of computed for θ=80∘. The present study shows that the value of wetting fluid saturation Sw at θ=40∘ is larger than its value computed with θ=80∘ that is due to the more tendency of the hydrophilic medium to absorb the wetting fluid at θ=40∘. Also, it is found that the magnitude of Sw computed for both the contact angles is decreased by the increment of the viscosity ratio from Log(M)=−1 to 1. The present study demonstrates that the S-C LBM is an efficient and accurate computational method to quantitatively estimate the flow characteristics and interfacial dynamics through the porous medium.

Triplet-triplet annihilation photon-upconversion in hydrophilic media with biorelevant cholesteryl triplet energy acceptors

We report two new biorelevant cholesteryl-based triplet energy acceptors, derivatives of DPA or 9,10-diphenylanthracene (C–DPA and C2–DPA). Using two different triplet sensitizers: QDN (ET ≈ 1.67 eV in PEG200) and PdTPP (ET ≈ 1.78 eV in PEG200), we were able to achieve both endothermic (with QDN) and exothermic (with PdTPP) triplet sensitization of DPA, C–DPA and C2–DPA in hydrophilic PEG200 media. While the maximum rate of triplet energy transfer (TET) was achieved with PdTPP and DPA (kTET = 4.7 × 107 M−1 s−1), for the cholesteryl-based acceptors, we found that the kinetic of the TET process was dependent upon the concentration of the acceptor. For PdTPP/C–DPA pair, the rate of the dynamic triplet energy quenching was kTET = 1.9 × 107 M−1 s−1; however, at higher concentrations of the quencher, the system reached a stationary state due to formation of self-assembled sub-domains of C–DPA that likely slowed the TET process. It was also found that this aggregation of C–DPA in PEG200 led to a 3.5 folds increase in the Ith compared to 133 mW cm2 for DPA. Subsequently, we estimated the ΦUC for these donor/acceptor pairs: QDN/DPA, PdTPP/DPA, and PdTPP/C–DPA. With respect to the estimated threshold intensity (Ith), we found that the quantum yields of TTA-UC were 2 ≤ QYUC≤12%.

Diffusion‐to‐Imbibition Transition in Water Sorption in Nanoporous Media: Theoretical Studies

AbstractThe ability to predict multiphase fluid transport in nanoporous rocks such as shales is critical for many geoscience applications, for example unconventional hydrocarbon production, geologic carbon sequestration, and nuclear waste disposal. When the pore sizes approach nanoscales, the impact of the molecular interaction forces between fluids and solids becomes increasingly important. These forces can alter macroscopic fluid phase behavior and control transport. Recent experimental studies have shown that capillary condensation and subsequent imbibition of liquid water can occur in hydrophilic nanoporous media even if the vapor phase is at a critical relative humidity (rhcrit) well below vapor saturation. This study presents a theoretical investigation of the processes controlling adsorption, capillary condensation and imbibition in nanoporous media, using the square‐gradient classical density functional theory. The proposed theoretical model explicitly includes the relevant interaction forces among fluids and solids in macroscopic porous media. Application of the model to a relative‐humidity‐controlled water adsorption experiment is presented to demonstrate the impact of water‐pore wall attractive forces on multiphase water behavior in a hydrophilic silicon nanoporous medium. The model represents well the measured time‐dependent evolution of the water imbibition front inside the nanoporous medium and also explains the diffusion‐like water transport regimes observed at rh < rhcrit and the imbibition‐like flow regimes observed at rh > rhcrit. The study furthermore gives an insight on hysteresis phenomenon in adsorption and desorption isotherms.

Preparation of O/W nanoemulsion containing saffron aqueous solution and sesame oil and evaluation of its properties

Objective(s): The oil-in-water (O/W) nanoemulsion is employed in a diverse range of biomedical applications due to the unique properties. Saffron is the valuable medicinal food product with many health benefits. Sesame oil is an edible vegetable oil with medicinal properties and potential applications. The aim of this study was to prepare and evaluate O/W nanoemulsion containing aqueous solution of saffron as hydrophilic medium and sesame oil as lipophilic medium. Methods: In the presence study, the O/W nanoemulsion was prepared by sesame oil in the presence of saffron aqueous solution and poly ethylene glycol (PEG) using span 80 surfactants and homogenizer at room temperature. The sample size was characterized by dynamic light scattering (DLS) and atomic force microscopy (AFM). The rheological properties of nanoemulsion were determined by measurement of viscosity at room temperature. The antibacterial activity of samples was measured against an important pathogen bacterium, Escherichia coli (E. coli) using inhibition zone diameter. The cytotoxicity of samples was investigated by MTT assay for HEK239 human cell line at three different concentrations for 1 and 5 days of time.Results: Based on the results, the nanoemulsions showed the antibacterial activity with low toxicity. The presence of saffron and PEG increased the size, viscosity and antibacterial activity.Conclusions: The study showed that nanoemulsions based on aqueous solution of saffron and sesame oil can be a good candidate for medicinal applications.

Luminescent Quantum Dots Stabilized by N-Heterocyclic Carbene Polymer Ligands

We have tested the ability of N-heterocyclic carbene (NHC)-modified ligands to coordinate and stabilize luminescent CdSe-ZnS core-shell quantum dot (QD) dispersions in hydrophilic media. In particular, we probed the effects of ligand structure and coordination number on the coating affinity to the nanocrystals. We find that such NHC-based ligands rapidly coordinate onto the QDs (requiring ∼5-10 min of reaction time), which reflects the soft Lewis base nature of the NHC groups, with its two electrons sharing capacity. Removal of the hydrophobic cap and promotion of carbene-driven coordination on the nanocrystals have been verified by 1H NMR spectroscopy, while 13C NMR was used to identify the formation of carbene-Zn complexes. The newly coated QD dispersions exhibit great long-term colloidal stability over a wide range of conditions. Additionally, we find that coordination onto the QD surfaces affects the optical and spectroscopic properties of the nanocrystals. These include a size-dependent red-shift of the absorption and fluorescence spectra and a pronounced increase in the measured fluorescence intensity when the samples are stored under white light exposure compared to those stored in the dark.

EFFECTS OF WETTABILITY ON DISPLACEMENT EFFICIENCY OF TWO-PHASE FLOW IN POROUS MEDIA

Displacement efficiency and displacement pattern of multiphase flow in porous media have a profound influence on many geo-energy applications such as geologic CO$_{2}$ sequestration and enhanced oil recovery. Wettability is one of the most important factors affecting the displacement pattern and displacement efficiency of multiphase flow in porous media. Here, we combined the glass microfluidics, inverted microscope and high speed CMOS camera to set up a visualization experimental system and modified the surface wettability of the glass microfluidics using the silanization treatment and piranha solution. Pore-scale visualization displacement experiments were conducted on five flow rates and two wetting conditions (hydrophilic and hydrophobic conditions) in glass microfluidics which are fabricated from the pore structure of natural sandstone. Experimental results show that the displacement pattern shifts from capillary fingering to compact displacement pattern both in the hydrophilic and hydrophobic media as the flow rate increases. Under lower flow rates, the capillary force plays the dominant role in the fluid invasion processes. The invasion finger width and the number of air clusters in hydrophilic media are both smaller than those in the hydrophobic media, but the maximum air cluster radius, the average cluster radius and the standard deviation of cluster radius are all greater under hydrophilic conditions. The results also demonstrate that the displacement efficiency under hydrophilic condition is significantly lower than that of hydrophobic conditions due to single-channel flow and by pass flow phenomena which both only occur in hydrophilic media. Finally, a modified capillary number was introduced in order to consider the role of wettability (contact angle) under favourable displacement. Then, a relationship between the displacement efficiency and the modified capillary number was proposed, which provides a potential and useful method for the prediction of displacement efficiency under different wetting conditions during favourable displacement.

Catalytic Enhancement of Inductively Heated Fe3 O4 Nanoparticles by Removal of Surface Ligands.

Heat management in catalysis is limited by each material's heat transfer efficiencies, resulting in energy losses despite current thermal engineering strategies. In contrast, induction heating of magnetic nanoparticles (NPs) generates heat at the surface of the catalyst where the reaction occurs, reducing waste heat via dissipation. However, the synthesis of magnetic NPs with optimal heat generation requires interfacial ligands, such as oleic acid, which act as heat sinks. Surface treatments using tetramethylammonium hydroxide (TMAOH) or pyridine are used to remove these ligands before applications in hydrophilic media. In this study, Fe3 O4 NPs are surface treated to study the effect of induction heating on the catalytic oxidation of 1-octanol. Whereas TMAOH was unsuccessful in removing oleic acid, pyridine treatment resulted in a roughly 2.5-fold increase in heat generation and product yield. Therefore, efficient surfactant removal has profound implications in induction heating catalysis by increasing the heat transfer and available surface sites.

Dual-Mode Fluorescence and Magnetic Resonance Imaging by Perylene Diimide-Based Gd-Containing Magnetic Ionic Liquids.

Bioimaging plays a key role in the diagnosis/treatment of diseases and in scientific research studies. Compared with single imaging techniques, dual-mode and multimode imaging techniques facilitate high accuracy. In this work, a perylene diimide (PDI)-based Gd-containing magnetic ionic liquid, Per-6-Diimi[Gd(NO3)4], is reported for dual-modal imaging, in which a Gd(III) complex was used for magnetic resonance imaging (MRI), while PDI was used for fluorescence imaging. Because of the difference in the biological microenvironment, there is a switch between dispersed and aggregated states of Per-6-Diimi[Gd(NO3)4] molecules in hydrophobic and hydrophilic media. When it was in the aqueous solution, the intensive π-π interaction of PDI cores made Per-6-Diimi[Gd(NO3)4] aggregates to form particles. The paramagnetic nanoparticles ensure prolonging the rotational correlation time, which results in a strong enhancement of MRI with a longitude relaxation coefficient of 14.94 mM-1 s-1. In an in vivo MRI experiment, the tumor site is imaged by MRI through the enhanced permeability and retention effect. However, when the molecule is present on the hydrophobic membrane of the cells, the dispersed Per-6-Diimi[Gd(NO3)4] showed good fluorescence imaging capabilities due to the high fluorescence quantum yield of PDI. Thus, the fluorescence imaging of cells can be carried out. Moreover, ex vivo fluorescence imaging of organs is performed after MRI. Per-6-Diimi[Gd(NO3)4] is enriched in the liver, kidneys, and tumors.