Search Results (17)

Ultrafine bubbles (UFBs) have been proposed as interfacial agents that modulate colloidal interactions, yet their role in early-stage flocculation remains insufficiently quantified. Using amidine latex (AL) as a cationic model colloid under controlled end-over-end mixing, we combined flocculation kinetics with electrokinetic and interfacial measurements to elucidate the mechanism by which UFBs promote aggregation. Electrophoretic measurements show adsorption-driven charge regulation by bubbles; increasing the UFB-to-AL ratio progressively neutralizes the surface and at sufficient dose reverses its charge. The neutrality point occurs at a characteristic ratio that is only weakly sensitive to background sodium chloride (NaCl). Interfacial measurements reveal a thicker hydrodynamic layer at higher ionic strength, consistent with closer packing of adsorbed UFBs under double layer compression, and micrographs of particle dimers confirm a larger inter-particle separation that directly visualizes this layer. Aggregation accelerates at 10 mM sodium chloride but remains slow at 0.1 mM, indicating that electrolyte screening is required for efficient adsorption and bridging; pH modulated the process secondarily. Together, the results support a coherent picture in which UFB adsorption creates patchy, charge-compensated surfaces and a soft hydrodynamic layer that enlarges the effective collision cross-section, thereby enhancing early-stage flocculation. Full article

In the process of oilfield development, the surfactant–polymer (SP) composite system has shown significant effects in enhancing oil recovery (EOR) due to its excellent interfacial activity and viscoelastic properties. However, with the continuous increase in the volume of composite flooding injection, a decline in injection–production capacity (I/P capacity) has been observed. Through the observation of frozen core slices, it was found that during the secondary composite flooding (SCF) process, a large amount of residual oil in the form of intergranular adsorption remained in the core pores. This phenomenon suggests that the displacement efficiency of the composite flooding may be affected. Research has shown that polymers undergo flocculation reactions with clay minerals (such as kaolinite, Kln) in the reservoir, leading to the formation of high-viscosity mixtures of migrating particles and crude oil (CO). These high-viscosity mixtures accumulate in local pores, making it difficult to further displace them, which causes oil trapping and negatively affects the overall displacement efficiency of secondary composite flooding (SCF). To explore this mechanism, this study used a microscopic visualization displacement model (MVDM) and microscopy techniques to observe the migration of particles during secondary composite flooding. By using kaolinite water suspension (Kln-WS) to simulate migrating particles in the reservoir, the displacement effects of the composite flooding system on the kaolinite water suspension, crude oil, and their mixtures were observed. Experimental results showed that the polymer, acting as a flocculant, promoted the flocculation of kaolinite during the displacement process, thereby increasing the viscosity of crude oil and affecting the displacement efficiency of secondary composite flooding. Full article

A good integration of the polymer materials that form a mixed-matrix membrane (MMM) for gas separation is essential to reaching interesting permselective properties. In this work, a porous polymer network (PPN), obtained by combining triptycene and trifluoroacetophenone, has been used as a filler, which was blended with two o-hydroxypolyamides (HPAs) that act as polymer matrices. These polymer matrices have been thermally treated to induce a thermal rearrangement (TR) of the HPAs to polybenzoxazoles (β-TR-PBOs) through a solid-state reaction. For its structural study, various techniques have been proposed that allow us to undertake a morphological investigation into the integration of these materials. To access the internal structure of the MMMs, three different methods were used: a polishing process for the material surface, the partial dissolution of the polymer matrix, or argon plasma etching. The argon plasma technique has not only revealed its potential to visualize the internal structure of these materials; it has also been proven to allow for the transformation of their permselective properties. Force modulation and phase contrast in lift-mode techniques, along with the topographic images obtained via the tapping mode using a scanning probe microscope (SPM), have allowed us to study the distribution of the filler particles and the interaction of the polymer and the filler. The morphological information obtained via SPM, along with that of other more commonly used techniques (SEM, TGA, DSC, FTIR, WASX, gas adsorption, and permeability measurements), has allowed us to postulate the most probable structural configuration in this type of system. Full article

Nanomaterials have been the focus of intense study and growth in the modern era across the globe because of their outstanding qualities, which are brought about by their nanoscale size; for instance, increased adsorption and catalysis capabilities plus significant reactivity. Multiple investigations have verified the fact that nanoparticles may successfully remove a variety of pollutants from water, and, as a result, they have been utilized in the treatment of both water and wastewater. Therefore, the current research intent is to examine the nonlinear heat source/sink influence on the 3D flow of water-based silver nanoparticles incorporated in an Eyring–Powell fluid across a deformable sheet with concentration pollutants. Silver particles have been used intensively to filter water, due to their potent antibacterial properties. The leading equations involving partial differential equations are renewed into the form of ordinary ordinary differential equations through utilizing the appropriate similarity technique. Then, these converted equations are solved by utilizing an efficient solver bvp4c. Visual displays and extensive exploration of the different impacts of the non-dimensional parameters on the concentration, temperature, and velocity profiles are provided. Also, the important engineering variables including skin friction, the rate of heat, and mass transfer are examined. The findings suggest that the mass transfer rate declines due to pollutant parameters. Also, the results suggest that the friction factor is uplifted by about 15% and that the heat transfer rate, as well as the mass transfer rate, declines by about 21%, due to the presence of the nanoparticle volume fraction. We believe that these results may improve the flow rate of nanofluid systems, improve heat transfer, and reduce pollutant dispersal. Full article

The present study aimed to investigate the mineralogical and morphological properties of two South African clays, namely bentonite and kaolin. These clays are mined in specific regions of the country but have not been fully characterized in terms of their properties for potential application in a number of industries. Bentonite was found to have a larger specific surface area, pore size, and more interchangeable cations than kaolin. The bentonite was also identified as Na-bentonite due to the huge Na content present in the clay. The powder X-ray diffraction (PXRD) patterns revealed that both clays are crystalline, together with the Fourier-transform infrared (FTIR) spectrophotometer results; presumably, some impurities of quartz could be present in the clay materials. The most prevalent functional groups present include Al-OH, Si-O-Mg, Si-O, and Si-O-Al groups. The surface charge of bentonite was consistently negative across all pH values, indicating its potential for adsorption applications. On the other hand, kaolin exhibited a negative charge at pH values greater than 2.4. The scanning electron microscopy (SEM) images provided visual evidence of the presence of pores in the clay structures, which supported the Brunauer–Emmett–Teller (BET) results classifying both bentonite and kaolin as mesoporous and macroporous materials. The particle size analysis revealed a broad distribution for bentonite and a bimodal distribution for kaolin. Overall, the clays revealed interesting features that can be useful for application in several industries, for example, in the treatment of wastewater. Further research and development can explore their potential to address environmental challenges, particularly the application of bentonite and kaolin in water treatment processes to remove toxic metal ions. Full article

Jamun (Syzygium cumini L.) is a fruit rich in anthocyanins, an important group of natural pigments, with color ranging from red to blue, soluble in water, highly antioxidant. Despite its great potential for use as a natural dye, its application is a challenge, due to the instability of these compounds in the environmental conditions of processing and storage commonly used by the food industry. Therefore, this study evaluated the microencapsulation of anthocyanin-rich jamun pulp by ionic gelation (IG) and its protein-coating by electrostatic interaction (PC). The effect of the ratio of sodium alginate solids and jamun pulp (1:0.40 to 1:2, w/w) and the concentration of gelatin coating solution (0% to 10%, w/w) on the morphology, water and total protein content and anthocyanins content in the microparticles were evaluated. Visually, the IG particles showed color tones ranging from reddish to purplish, which became less intense and opaque after being submitted to the gelatin coating process. Microscopic images demonstrated that microparticles formed had an irregular and heterogeneous shape with disorganized gel network formation is due to the presence of solid structures of jamun pulp, observed within the microparticles. The greater the concentration of gelatin in the coating solution, the greater the protein adsorption for the formation of the protective layer, ranging from 21.82 ± 0.72% (T1) to 55.87 ± 4.23% (T6). Protein adsorption on the GI resulted in a decrease in moisture content (ranging from 87.04 ± 0.22 to 97.06 ± 0.12%) and anthocyanins contents (ranging from 5.84 ± 0.62 to 0.78 ± 0.14%) in the PC microparticles. Full article

The new method of antibacterial-drug-activity investigation in vitro is proposed as a powerful strategy for understanding how carriers affect drug action during long periods (7 days). In this paper, we observed fluoroquinolone moxifloxacin (MF) antibacterial-efficiency in non-covalent complexes, with the sulfobutyl ether derivative of β-cyclodextrin (SCD) and its polymer (SCDpol). We conducted in vitro studies on two Escherichia coli strains that differed in surface morphology. It was found that MF loses its antibacterial action after 3–4 days in liquid media, whereas the inclusion of the drug in SCD led to the increase of MF antibacterial activity by up to 1.4 times within 1–5 days of the experiment. In the case of MF-SCDpol, we observed a 12-fold increase in the MF action, and a tendency to prolonged antibacterial activity. We visualized this phenomenon (the state of bacteria, cell membrane, and surface morphology) during MF and MF-carrier exposure by TEM. SCD and SCDpol did not change the drug’s mechanism of action. Particle adsorption on cells was the crucial factor for determining the observed effects. The proteinaceous fimbriae on the bacteria surface gave a 2-fold increase of the drug carrier adsorption, hence the strains with fimbriae are more preferable for the proposed treatment. Furthermore, the approach to visualize the CD polymer adsorption on bacteria via TEM is suggested. We hope that the proposed comprehensive method will be useful for the studies of drug-delivery systems to uncover long-term antibacterial action. Full article

The influence of an external constant strong electric field, formed using a pyramidal structure under a high electric potential, on an enzyme located near its apex, is studied. Horseradish peroxidase (HRP) is used as a model. In our experiments, a 27 kV direct current (DC) voltage was applied to two electrodes with a conducting pyramidal structure attached to one of them. The enzyme particles were visualized by atomic force microscopy (AFM) after the adsorption of the enzyme from its 0.1 µM solution onto mica AFM substrates. It is demonstrated that after the 40 min exposure to the electric field, the enzyme forms extended structures on mica, while in control experiments compact HRP particles are observed. After the exposure to the electric field, the majority of mica-adsorbed HRP particles had a height of 1.2 nm (as opposed to 1.0 nm in the case of control experiments), and the contribution of higher (>2.0 nm) particles was also considerable. This indicates the formation of high-order HRP aggregates under the influence of an applied electric field. At that, the enzymatic activity of HRP against its substrate 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) remains unaffected. These results are important for studying macroscopic effects of strong electromagnetic fields on enzymes, as well as for the development of cellular structure models. Full article

In this research, the influence of a dodecahedron-shaped structure on the adsorption behavior of a horseradish peroxidase (HRP) enzyme glycoprotein onto mica substrates was studied. In the experiments, samples of an aqueous HRP solution were incubated at various distances (0.03 m, 2 m, 5 m, and control at 20 m) from the dodecahedron surface. After the incubation, the direct adsorption of HRP onto mica substrates immersed in the solutions was performed, and the mica-adsorbed HRP particles were visualized via atomic force microscopy (AFM). The effect of the increased HRP aggregation was only observed after the incubation of the enzyme solution at the 2 m distance from the dodecahedron. In addition, with respect to the control sample, spectrophotometric measurements revealed no change in the HRP enzymatic activity after the incubation at any of the distances studied. The results reported herein can be of use in the modeling of the possible influences of various spatial structures on biological objects in the development of biosensors and other electronic equipment. Full article

As a future clean energy resource, the exploration and exploitation of natural gas hydrate are favorable for solving the energy crisis and improving environmental pollution. Detecting the spatial distribution of natural gas hydrate in the reservoir is of great importance in natural gas hydrate exploration and exploitation. Fracture-filling hydrate, one of the most common types of gas hydrate, usually appears as a massive or layered accumulation below the seafloor. This paper aims to detect the spatial distribution variation of fracture-filling hydrate in sediments using the electrical property in the laboratory. Massive hydrate and layered hydrate are formed in the electrical resistivity tomography device with a cylindrical array. Based on the electrical resistivity tomography data during the hydrate formation process, the three-dimensional resistivity images of the massive hydrate and layered hydrate are established by using finite element forward, Gauss–Newton inversion, and inverse distance weighted interpolation. Massive hydrate is easier to identify than layered hydrate because of the big difference between the massive hydrate area and surrounding sediments. The diffusion of salt ions in sediments makes the boundary of massive hydrate and layered hydrate change with hydrate formation. The average resistivity values of massive hydrate (50 $\mathsf{\Omega }\cdot \mathrm{m}$) and layered hydrate (1.4 $\mathsf{\Omega }\cdot \mathrm{m}$) differ by an order of magnitude due to the difference in the morphology of the fracture. Compared with the theoretical resistivity, it is found that the resistivity change of layered hydrate is in accordance with the change tendency of the theoretical value. The formation characteristic of massive hydrate is mainly affected by the pore water distribution and pore microstructure of hydrate. The hydrate formation does not necessarily cause the increase in resistivity, but the increase of resistivity must be due to the formation of hydrate. The decrease of resistivity in fine-grains is not obvious due to the cation adsorption of clay particles. These results provide a feasible approach to characterizing the resistivity and growth characteristics of fracture-filling hydrate reservoirs and provide support for the in-situ visual detection of fracture-filling hydrate. Full article

In recent years, scientists are paying increased attention to the development of intelligent nanocontainers in applications such as biomedical, catalysis, and anticorrosion [¹]. Preparation of anticorrosion coatings containing smart nanocontainers loaded with corrosion inhibitors, which can be initiated when the barrier coatings are damaged, favor the long-term function, as uncontrolled loss by leaching is inhibited [²]. The aim of the present study is to optimize the amount of an organic inhibitor (1-H benzotriazole (BTA)) that can be in situ encapsulated in a mesoporous silica nanocontainer, prepared by an original sol-gel formulation. Materials and methods: For the synthesis of silica mesoporous, nanoparticles loaded with BTA were used with three silica co-precursors: tetraethylorthosilicate (TEOS), phenyltriethoxysilane (PTES), and octyltriethoxysilane (OTES), at a 5/1/1 gravimetric ratio. The synthesis was carried out in the presence of a solvent (ethanol) and of a surfactant (Igepal CA-630). The pH of the sol–gel system was adjusted to ~9 by dripping an aqueous solution of NH₄OH (25%). Prior to the addition to the sol–gel reaction system, BTA was completely dissolved in ethanol. Various amounts of BTA were loaded to the sol–gel systems: 0.25; 0.5; 0.75; 1; 1.25; 1.5; and 2 g (corresponding to 0.09; 0.18; 0.27; 0.35; 0.44; 0.53; and 0.70% grav. of the total amount of sol–gel mixture, respectively). Furthermore, a similar set of samples was prepared in the presence of a constant amount of rhodamine B, dissolved in ethanol. This second set was obtained in order to perform a visual evaluation of the encapsulation efficiency. Particles dimensions, size distributions, and particles charging in the final dispersions were evaluated by the dynamic light scattering (DLS) technique and Zeta potential measurements. Surface morphology was observed by SEM. The structural characteristics of the silica mesoporous particles were investigated by N₂ adsorption–desorption analysis on the calcined samples. Results: During the in situ synthesis of silica nanoparticles, the aromatic molecules of the corrosion inhibitor BTA were linked via a hydrophobic interaction with the phenyl groups from the silica pores formed by the hydrophobic functions of silica co-precursors, i.e., PTES and OTES. In addition, the corrosion inhibitor was trapped inside the surfactant micelles of Igepal and encapsulated together inside the silica pores formed by the surfactant. Moreover, it was observed that only a small amount of BTA can be encapsulated in the absence of the surfactant. Conclusions: An optimized method was developed to obtain mesoporous silica nanoparticles loaded with 1-H Benzotriazole (BTA) as a corrosion inhibitor. The optimal range of the BTA concentration was found to be between 0.18 and 0.35%. Full article

Fresh Ag nanoparticles (NPs) dispersed on a transparent SiO₂ exhibit an intense optical extinction band originating in localized surface plasmon resonance (LSPR) in the visible range. The intensity of the LSPR band weakened when the Ag NPs was stored in ambient air for two weeks. The rate of the weakening and the LSPR wavelength shift, corresponding to visual chromatic changes, strongly depended on the environment in which Ag NPs were set. The origin of a chromatic change was discussed along with both compositional and morphological changes. In one case, bluish coloring followed by a prompt discoloring was observed for Ag NPs placed near the ventilation fan in our laboratory, resulted from adsorption of large amounts of S and Cl on Ag NP surfaces as well as particle coarsening. Such color changes deduce the presence of significant amounts of S and Cl in the environment. In another case, a remarkable blue-shift of the LSPR band was observed for the Ag NPs stored in the desiccator made of stainless steel, originated in the formation of CN and/or HCN compounds and surface roughening. Their color changed from maroon to reddish, suggesting that such molecules were present inside the desiccator. Full article

A novel, lightweight (8 mg/cm³), conjugate sponge of karaya gum (Kg) and chitosan (Ch) has been synthesized with very high porosity (~98%) and chemical stability, as a pH-responsive adsorbent material for the removal of anionic and cationic dyes from aqueous solutions. Experimental results showed that Kg-Ch conjugate sponge has good adsorption capacity for anionic dye methyl orange (MO: 32.81 mg/g) and cationic dye methylene blue (MB: 32.62 mg/g). The optimized Kg:Ch composition grants access to the free and pH-dependent ionizable functional groups on the surface of the sponge for the adsorption of dyes. The studies on the adsorption process as a function of pH, adsorbate concentration, adsorbent dose, and contact time indicated that the adsorption capacity of MB was decreased with increasing pH from 5 to 10 and external mass transfer together with intra-particle diffusion. The adsorption isotherm of the anionic dye MO was found to correlate with the Langmuir model (R² = 0.99) while the adsorption of the cationic MB onto the sponge was better described by the Freundlich model (R² = 0.99). Kinetic regression results specified that the adsorption kinetics were well represented by the pseudo-second-order model. The H-bonding, as well as electrostatic interaction between the polymers and the adsorption interactions of dyes onto Kg-Ch sponge from aqueous solutions, were investigated using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, and the highly wrinkled porous morphology was visualized in depth by field-emission scanning electron microscopy (FE-SEM) analysis. Moreover, the samples could be reused without loss of contaminant removal capacity over six successive adsorption-desorption cycles. The hierarchical three-dimensional sponge-like structure of Kg has not been reported yet and this novel Kg-Ch sponge functions as a promising candidate for the uninterrupted application of organic pollutant removal from water. Full article

An aerosol shock tube has been developed for measuring the ignition delay times (t_ig) of aerosol mixtures of low-vapor-pressure fuels and for visualization of the auto-ignition flow-field. The aerosol mixture was formed in a premixing tank through an atomizing nozzle. Condensation and adsorption of suspended droplets were not observed significantly in the premixing tank and test section. A particle size analyzer was used to measure the Sauter mean diameter (SMD) of the aerosol droplets. Three pressure sensors and a photomultiplier were used to detect local pressure and OH emission respectively. Intensified charge-coupled device cameras were used to capture sequential images of the auto-ignition flow-field. The results indicated that stable and uniform aerosol could be obtained by this kind of atomizing method and gas distribution system. The averaged SMD for droplets of toluene ranged from 2 to 5 $\mathsf{\mu }$ m at pressures of 0.14–0.19 MPa of dilute gases. In the case of a stoichiometric mixture of toluene/O₂/N₂, ignition delay times ranged from 77 to 1330 μs at pressures of 0.1–0.3 MPa, temperatures of 1432–1716 K and equivalence ratios of 0.5–1.5. The logarithm of ignition delay times was approximately linearly correlated to 1000/T. In contrast to the reference data, ignition delay times of aerosol toluene/O₂/N₂ were generally larger. Sequential images of auto-ignition flow-field showed the features of flame from generation to propagation. Full article

Biodegradable polymers have been developed for the targeted delivery of therapeutics to tumors. However, tumor targeting and imaging are usually limited by systemic clearance and non-specific adsorption. In this study, we used poly(amino acid) derivatives, such as poly(succinimide), to synthesize a nanomicelle-forming poly(hydroxyethylaspartamide) (PHEA, P) modified sequentially with octadecylamine, polyethylene glycol (PEG, P), and glycine (G) to design PHEA-PEG-glycine (PPG) nanoparticles (NPs). These PPG NPs were further tethered to cyclic Arg-Gly-Asp (cRGD) sequences for formulating tumor-targeting PPG-cRGD NPs, and then loaded with IR-780 dye (PPG-cRGD-IR-780) for visualizing tumor homing. cRGD cloaked in PPG NPs could bind specifically to both tumor endothelium and cancer cells overexpressing α_vβ₃ integrins. PPG-cRGD NPs exhibited enhanced physiological stability, cellular viability, and targeted intracellular uptake in cancer cells. In addition, PPG-cRGD NPs offered enhanced systemic circulation, leading to preferential tumor targeting and prolonged fluorescence tumor imaging for nearly 30 days. Nevertheless, non-targeted formulations demonstrated premature systemic clearance with short-term tumor imaging. Histochemical analysis showed no damage to normal organs, reaffirming the biocompatibility of PHEA polymers. Overall, our results indicated that PPG-cRGD NPs, which were manipulated to obtain optimal particle size and surface charge, and were complemented with tumor targeting, could improve the targeted and theranostic potential of therapeutic delivery. Full article