Nonpolar Liquids Research Articles

Fluorinated Metal-Organic Coatings with Selective Wettability.

Surface chemistry is a major factor that determines the wettability of materials, and devising broadly applicable coating strategies that afford tunable and selective surface properties required for next-generation materials remains a challenge. Herein, we report fluorinated metal-organic coatings that display water-wetting and oil-repelling characteristics, a wetting phenomenon different from responsive wetting induced by external stimuli. We demonstrate this selective wettability with a library of metal-organic coatings using catechol-based coordination and silanization (both fluorinated and fluorine-free), enabling sensing through interfacial reconfigurations in both gaseous and liquid environments, and establish a correlation between the coating wettability and polarity of the liquids. This selective wetting performance is substrate-independent, spontaneous, durable, and reversible and occurs over a range of polar and nonpolar liquids (60 studied). These results provide insight into advanced liquid-solid interactions and a pathway toward tuning interfacial affinities and realizing robust, selective superwettability according to the surrounding conditions.

Nonpolar Liquid Lubricant Submerged Triboelectric Nanogenerator for Current Amplification via Direct Electron Flow

AbstractTriboelectric nanogenerators (TENGs) can convert a mechanical energy input to an electric energy output through Maxwell's displacement current. By increasing the electrical output and overcoming the mechanical limitations of TENGs, such devices can be used as an auxiliary power source for portable electronics. Nevertheless, the generation mechanism and structure must be optimized to compensate for the electrical and mechanical limitations of TENGs. This paper reports on a nonpolar liquid lubricant submerged TENG (LLS‐TENG), which can overcome the existing electrical and mechanical limitations of the TENG. When a nonpolar liquid lubricant is filled in the LLS‐TENG, the air breakdown can be effectively blocked owing to the large Debye length of such lubricants. In addition, the rolling friction and lubrication present in the LLS‐TENG can significantly reduce the friction wear of the device. Consequently, the LLS‐TENG can charge a commercial capacitor and battery by generating a high voltage and current output of up to 200 V and 170 mA, respectively.

Fabrication of a Novel Protein Sponge with Dual-Scale Porosity and Mixed Wettability Using a Clean and Versatile Microwave-Based Process.

An open-porous protein sponge with mixed wettability is presented made entirely from whey proteins and with promising applications in biomedicine, pharmaceutical, and food industry. The fabrication relies on an additive-free, clean and scalable process consisting of foaming followed by controlled microwave-convection drying. Volumetric heating throughout the matrix induced by microwaves causes fast expansion and elongation of the foam bubbles, retards crust formation and promotes early protein denaturation. These effects counteract collapse and shrinkage typically encountered in convection drying of foams. The interplay of high protein content, tailored gas incorporation and controlled drying result in a dried structure with dual-scale porosity composed of open macroscopic elongated foam bubbles and microscopic pores in the surrounding solid lamellae induced by water evaporation. Due to the insolubility and mixed wettability of the denatured protein network, polar and non-polar liquids are rapidly absorbed into the interconnected capillary system of the sponge without disintegrating. While non-watery liquids penetrate the pores by capillary suction, water diffuses also into the stiff protein matrix, inducing swelling and softening. Consequently, the water-filled soft sponge can be emptied by compression and re-absorbs any wetting liquid into the free capillary space.

ZIF-L(Co) coated stainless steel meshes with superwettability for efficient multiphase liquid separation

In this work, a leaf-like zeolitic imidazolate framework ZIF-L(Co) coated stainless steel mesh (ZIF-L(Co)@SSM) is fabricated through a simple and facile one-pot method. The obtained ZIF-L(Co)@SSM shows superlyophobicity to nonpolar liquids under polar liquids. Taking advantage of the strong coordination interaction between the Co2+ and -SH group, the ZIF-L(Co)@SSM is easily modified by octadecanethiol, the resultant ZIF-L(Co)/Thiol@SSM displays a superlyophobic state for polar liquids under nonpolar liquids. Benefiting from their special superwettability, on-demand and highly effective multiphase organic liquids separation can achieve by the ZIF-L(Co)@SSM and ZIF-L(Co)/Thiol@SSM, with the separation efficiency above 96%. The simple preparation route and excellent performance make the MOFs coated meshes suitable in various organic liquid separation practices.

Sputter-Deposited Ag Nanoparticles on Electrospun PCL Scaffolds: Morphology, Wettability and Antibacterial Activity

Porous scaffolds made of biocompatible and environmental-friendly polymer fibers with diameters in the nano/micro range can find applications in a wide variety of sectors, spanning from the biomedical field to textiles and so on. Their development has received a boost in the last decades thanks to advances in the production methods, such as the electrospinning technique. Conferring antimicrobial properties to these fibrous structures is a primary requirement for many of their applications, but the addition of antimicrobial agents by wet methods can present a series of drawbacks. In this work, strong antibacterial action is successfully provided to electrospun polycaprolactone (PCL) scaffolds by silver (Ag) addition through a simple and flexible way, namely the sputtering deposition of silver onto the PCL fibers. SEM-EDS analyses demonstrate that the polymer fibers get coated by Ag nanoparticles without undergoing any alteration of their morphological integrity upon the deposition process. The influence on wettability is evaluated with polar (water) and non-polar (diiodomethane) liquids, evidencing that this coating method allows preserving the hydrophobic character of the PCL polymer. Excellent antibacterial action (reduction > 99.995% in 4 h) is demonstrated against Escherichia coli. The easy fabrication of these PCL-Ag mats can be applicable to the production of biomedical devices, bioremediation and antifouling systems in filtration, personal protective equipment (PPE), food packaging materials, etc.

AF2400/polyketone composite organic solvent reverse osmosis membrane for organic liquid separation

Organic liquid separation is frequently encountered in chemically relevant industries. Herein, an organic solvent reverse osmosis (OSRO) membrane fabricated by spin coating a Teflon polymer, AF2400, onto a solvent-resistant polyketone support is proposed for organic liquid separation. Nonpolar AF2400 promotes the permeation of nonpolar liquids while inhibiting the transportation of polar liquids, resulting in the efficient separation of polar and nonpolar liquids. A mixture of ethanol and 1-hexane was used as a model, and the effects of feed composition, applied pressure, and filtration time on separation performance were investigated. The optimized membrane demonstrated an impressively high separation factor of 9.5 for 1-hexane over ethanol and an acceptable flux of 1.6 kg m−2 h−1 under 4 MPa (a permeance of 0.04 kg m−2 h−1 bar−1), outperforming the reported membranes in selectivity. The separation performances in alcohol/1-hexane, ethanol/alkane, and ethanol/toluene mixtures were also investigated and the results demonstrated that the molecular size and polarity of the liquids affected the selectivity. The developed membrane contributes to the development of energy-efficient approaches for separating organic liquids.

Collective dynamics of liquid acetone investigated by inelastic X-ray scattering

The dynamic structure factors S(Q,ω) of liquid acetone were measured in a wide Q range 1.9–41.2 nm−1 with a high-resolution inelastic X-ray scattering (IXS) spectrometer installed at BL35XU of the SPring-8. Highly damped collective excitations of the longitudinal acoustic (LA) phonons are observed. The IXS spectra were analyzed by using a generalized Langevin formalism with the help of a sparse modeling to deduce reasonable Q dependences of the fitting parameters. The dispersion relation of the LA phonon excitations shows a highly positive deviation by about 65% from the adiabatic velocity of sound, which is larger than that in non-polar liquids such as CCl4 and benzene with van der Waals interactions, due probably that the acetone is a polar liquid. Microscopic dynamic parameters, such as viscoelastic relaxation rates and viscosity, are discussed by comparing with existing macroscopic dynamic properties. The fast and slow viscoelastic relaxations correspond to the vibration dynamics and reorientation correlations, respectively.

Video-based fractional order identification of diffusion dynamics for the analysis of migration rates of polar and nonpolar liquids: Water and oil studies.

Diffusion dynamics of water and oil are observed in real-time using video images. Savitzky-Golay derivative filtering ensures accurate localization of the liquid front. System identification demonstrates that a fractional-order model with only two parameters may be used to describe the dynamics of the diffusion process. The method paves the way for video-based cellulose filter paper microfluidics and lateral flow assays, which are low cost and have broad diagnostic applications.

Gold Inks for Inkjet Printing on Photo Paper: Complementary Characterisation.

Nowadays, cost-effective, available, and flexible paper-based electronics play an essential role in the electronics industry. Herein, we present gold nanoparticles (AuNPs) as a potential raw material for gold inks in the future for such purposes. AuNPs in this research were synthesised using the ultrasonic spray pyrolysis (USP) technique from two precursors: gold (III) chloride tetrahydrate and gold (III) acetate. Synthesised AuNPs were collected in a suspension composed of deionised (D.I.) water and the stabiliser polyvinylpyrrolidone (PVP). AuNPs’ suspensions were subjected to the rotavapor process to obtain gold inks with higher Au concentration (>300 ppm). ICP-MS measurements, the size and shape of AuNPs, ζ-potential, Ultraviolet-visible (UV-Vis) spectrophotometry measurements, and scanning electron microscop y (SEM) of gold inks were carried out in order to find the optimal printing parameters. In the final stage, the optical contact angle measurements were performed using a set of polar to non-polar liquids, allowing for the determination of the surface free energy of gold inks. Inkjet printing of gold inks as defined stripes on photo paper were tested, based on the characterisation results.

Determination of the zeta potential of planar solids in nonpolar liquids

ZetaSpin determines zeta potential by measuring the streaming potential generated by rotating a disk-shaped sample about its axis while submerged in the liquid. The apparatus and procedure developed for ZetaSpin in aqueous solutions was adapted for use in highly nonpolar fluids like surfactant-doped alkanes. Perhaps most unexpected is the need for up to 10 min (instead of a fraction of one second for aqueous solutions) for the electrometer to display changes in streaming potential in response to changes in rotation speed. Four tests (suggested by theory) confirm that the potential finally reported by the electrometer was indeed the streaming potential. Compared to electrophoresis, ZetaSpin does not require a value for the Debye length, avoids the complication caused by the electric-field-dependence of electrophoretic mobility and can be used with planar samples as well as colloidal particles.

Surface Modification of Polypropylene by Atmospheric Pressure Plasma

In this investigation, we studied the influence of atmospheric pressure plasma treatment on the surface properties of polypropylene (PP). The PP samples were treated for various durations using a gliding arc plasma source with air as a working gas. The formation of polar groups (–OH and C = O) on the PP surface after plasma treatment was evaluated and analyzed using Raman spectroscopy and attenuated total reflection–Fourier transform infrared spectroscopy. The contact angle was measured using polar and non-polar liquids to obtain the polar and dispersive components as well as the surface free energy of the PP before and after treatment. A sevenfold increase after treatment was observed for the polar component, while hydrophobicity decreased 73% after treatment. Finally, changes in topography were observed using atomic force microscopy (AFM) analysis before and after plasma treatment. AFM images showed that under atmospheric treatment, the PP surface underwent etching, reducing the surface roughness. Microhardness measurements of the films also revealed significant changes in mechanical properties after plasma treatment.

Comparative study of the dynamics of laser breakdown in water and hexane using interference microscopy

The changes in the optical properties of water and hexane under femtosecond irradiation (Ti : Al2O3 laser, wavelength 800 nm, intensity ∼1013 W cm−2) are investigated in the cavitation (bubble-formation) regime using interference microscopy in a time interval of ∼1.5 ns since the impact onset. A comparison of the dynamics of radiation-induced processes (solvation of excess electrons, pair recombination, and development of precavitation processes) is performed. The excited-carrier concentration is estimated, and these estimates are found to be inconsistent with the amount of energy that must be transferred to the liquid during a pulse to implement its heating and subsequent cavitation. This inconsistency is especially pronounced for hexane, where ionisation processes can barely be detected by interferometry. The experimental results put new questions about the mechanisms of energy transfer in both polar and nonpolar liquids subjected to intense laser irradiation.

Photochemically Produced Superhydrophobic Silane@polystyrene‐Coated Polypropylene Fibrous Network for Oil/Water Separation

Cost-effective separation of oil and immiscible organic contaminants from water has become an urgent challenge to protect aquatic and human life from devastating effects. Therefore, it has become imperative to develop super-selective materials for efficiently separating oil from water. In this work, a superhydrophobic surface has been formed that consists of a silane@polystyrene-coated polypropylene fibrous network (silane@PS-PPF) for efficient separation of accidentally spilled oil from water. The superhydrophobic PPFs were designed by a simple, cost-effective two-step process that includes photochemically controlled polymerization of styrene and subsequent dip coating in octadecyltrichlorosilane solution. The hydrophobic surface (CA=129°±4°) of the PS coated PPF after treating with silane was turned into a superhydrophobic body (CA=161°±2°). The achieved silane@PS-PPF fibrous network selectively allowed the fast permeation of the oils and non-polar organic liquids by altogether rejecting water during operation. The separation efficiency for various oils from the contaminated water was 96 to 99%, with a high flux in the range of 7606±312 L m-2 h-1 to 9870±151 L m-2 h-1 . Apart from being used as a filter, the silane@PS-PPF was also used as an oil absorber and has shown an absorption capacity in the range of 1185 to 1535% for various oils. We anticipate that the developed silane@PS-PPF, due to its facile synthetic route, cost-effectiveness, and high performance, can be effectively used in oily wastewater treatment and clean-up of large oil spills from water.

What Can You Learn about Apparent Surface Free Energy from the Hysteresis Approach?

The apparent surface free energy is one of the most important quantities in determining the surface properties of solids. So far, no method of measuring this energy has been found. The essence of contact angle measurements is problematic. Contact angles should be measured as proposed by Young, i.e., in equilibrium with the liquid vapors. This type of measurement is not possible because within a short time, the droplet in the closed chamber reaches equilibrium not only with vapors but also with the liquid film adsorbed on the tested surface. In this study, the surface free energy was determined for the plasma-activated polyoxymethylene (POM) polymer. Activation of the polymer with plasma leads to an increase in the value of the total apparent surface free energy. When using the energy calculations from the hysteresis based approach (CAH), it should be noted that the energy changes significantly when it is calculated from the contact angles of a polar liquid, whereas being calculated from the angles of a non-polar liquid, the surface activation with plasma changes its value slightly.

Universal and tunable liquid\u2013liquid separation by nanoparticle-embedded gating membranes based on a self-defined interfacial parameter

Superwetting porous membranes with tunable liquid repellency are highly desirable in broad domains including scientific research, chemical industry, and environmental protection. Such membranes should allow for controllable droplet bouncing or spreading, which is difficult to achieve for low surface energy organic liquids (OLs). Here we develop an interfacial physical parameter to regulate the OL wettability of nanoparticle-embedded membranes by structuring synergistic layers with reconfigurable surface energy components. Under the tunable solid-liquid interaction in the aggregation-induced process, the membranes demonstrate positive/negative liquid gating regularity for polar protic liquids, polar aprotic liquids, and nonpolar liquids. Such a membrane can be employed as self-adaptive gating for various immiscible liquid mixtures with superior separation efficiency and permeation flux, even afford successive achievement of high-performance in situ extraction-back extraction coupling. This study should provide distinctive insights into intrinsic wetting behaviors and have pioneered a rational strategy to design high-performance separation materials for diverse applications.

Correction: Space charge limited release of charged inverse micelles in non-polar liquids.

Correction for 'Space charge limited release of charged inverse micelles in non-polar liquids' by Manoj Prasad et al., Phys. Chem. Chem. Phys., 2016, 18, 19289-19298, DOI: .

Improving the wettability of structural steels by employing ionic liquids

Surface wetting behavior is tied to different surface phenomena such as lubrication and corrosion resistance of steel surfaces. In this study, the surface wetting behavior of room-temperature ionic liquids (RTILs) treated steel surfaces is investigated. To this end, polished steel surfaces are individually surface-treated using seven imidazolium-based RTILs with varying alkyl chain lengths ([CnMIM], n = 2, 4, 6) and anion groups ([PF6], [NTf2], [Br], [BF4], [AlCl4]) for two different exposure durations (0.5 h and 4 h). The wetting behavior of RTIL-treated steel surfaces is quantified in terms of contact angles and surface energies corresponding to polar (water) and non-polar (diiodomethane) probing liquids. The RTIL surface treatment is observed to improve the surface wetting behavior of steel surfaces for both polar and non-polar probing liquids. The average initial water contact angle of steel surfaces decreased by 24−87% after RTIL surface treatment. Similarly, the average initial non-polar liquid contact angles of RTIL-treated steel surfaces decreased by 25−66% when compared to the untreated steel surface. The water contact angle decreased with an increase in the time elapsed after droplet impingement on the surface, whereas, for the non-polar liquid, the contact angle remained relatively unchanged during the elapsed duration adopted herein. The average surface free energy of RTIL-treated steel specimens increased by 49%−100%, which rendered the RTIL-treated steel surfaces more wettable. The increase in the RTIL treatment time only nominally improved the wetting of steel surfaces for both polar and non-polar probing liquids. The results reported herein can be used to prepare the surfaces of inaccessible structural steel components and bridge bearings for efficient water cleaning and lubrication.

Effects of the charge carrier elimination process on oil conductivity decrease under high electric field intensity

The DC conductivity of insulating oil is key to converter transformers, in which AC and DC electrical fields simultaneously exist. Research on the influence of the electric field on oil conductivity can optimise the insulation design of converter transformers. Although numerous studies have been conducted on the conductance mechanism of non-polar liquids, the explicit mechanism and properties of oil conductivity under a high electrical field remain unclear. This study developed an optimised conductance model considering charge carrier elimination, dissociation, and charge injection process. Thereafter, the authors chose three types of oils for converter transformers and measured the variations in oil conductivity and ion mobility under different electric fields with 0–10 kV/mm range. The result indicates that ion mobility will increase under a high electric field owing to the EHD effects. The conductivity of the insulating oil follows a U-shaped pattern with an increasing electric field, thereby generally matching the optimised theoretical model. Therefore, the decrease in conductivity is mainly the result of the elimination process of free ions, whereas the increase is the result of the injection process that occurs on the electrodes.

Charging Organic Liquids by Static Charge.

Aqueous liquids can be charged effectively by a number of methods for many important applications. Organic liquids, however, cannot be charged effectively by existing methods due to their low conductivities, especially the insulating nonpolar organic liquids; hence, there has not been any significant application developed based on charged organic liquids. This study describes an effective fundamental strategy for charging organic liquids, including nonpolar organic liquids: static charge is simply mixed into the liquid. Analyses suggested that the charged species are molecular ions that reside in the bulk of the liquid after charging. This method is simple and general, and the amount and polarity of charge can be flexibly tunable. The effectiveness of this method gives rise to opportunities for the development of novel applications. Charged organic droplets are manipulated for the first time by an electric field for controlling organic reactions. Particles with charge embedded in their bulk matrices are fabricated for the first time (i.e., via polymerizing the liquid monomers mixed with static charge). The charge in this novel class of bulk-charged particles is stable and permanent, especially when compared to the typical surface-charged particles. Simultaneous bulk-charged and bulk-magnetic particles are fabricated for the first time via simply mixing both the static charge and magnetic nanoparticles into the liquid monomers. These highly versatile particles are responsive to both electric and magnetic fields for practical applications.

Sensory Perception of Non-Deuterated and Deuterated Organic Compounds.

The chemical background of olfactory perception has been subject of intensive research, but no available model can fully explain the sense of smell. There are also inconsistent results on the role of the isotopology of molecules. In experiments with human subjects it was found that the isotope effect is weak with acetone and D6‐acetone. In contrast, clear differences were observed in the perception of octanoic acid and D15‐octanoic acid. Furthermore, a trained sniffer dog was initially able to distinguish between these isotopologues of octanoic acid. In chromatographic measurements, the respective deuterated molecule showed weaker interaction with a non‐polar liquid phase. Quantum chemical calculations give evidence that deuterated octanoic acid binds more strongly to a model receptor than non‐deuterated. In contrast, the binding of the non‐deuterated molecule is stronger with acetone. The isotope effect is calculated in the framework of statistical mechanics. It results from a complicated interplay between various thermostatistical contributions to the non‐covalent free binding energies and it turns out to be very molecule‐specific. The vibrational terms including non‐classical zero‐point energies play about the same role as rotational/translational contributions and are larger than bond length effects for the differential isotope perception of odor for which general rules cannot be derived.