Cetyltrimethylammonium Chloride Research Articles

Cetyltrimethylammonium-chloride assisted in situ metabolic incorporation of nano-sized ROS-generating cascade-reaction containers in Gram-positive and Gram-negative peptidoglycan layers for the control of bacterially-induced sepsis

Cascade-reaction containers generating reactive oxygen species (ROS) as an alternative for antibiotic-based strategies for bacterial infection control, require endogenous oxygen-sources and ROS-generation close to or preferably inside target bacteria. Here, this is achieved by cetyltrimethylammonium-chloride (CTAC) assisted in situ metabolic labeling and incorporation of mesoporous SiO2-nanoparticles, dual-loaded with glucose-oxidase and Fe3O4-nanoparticles as cascade-reaction containers, inside bacterial cell walls. First, azide-functionalized d-alanine (D-Ala-N3) was inserted in cell wall peptidoglycan layers of growing Gram-positive pathogens. In Gram-negatives, this could only be achieved after outer lipid-membrane permeabilization, using a low concentration of CTAC. Low concentrations of CTAC had no adverse effect on in vitro blood clotting or hemolysis nor on the health of mice when blood-injected. Next, dibenzocyclooctyne-polyethylene-glycol modified, SiO2-nanoparticles were in situ click-reacted with d-Ala-N3 in bacterial cell wall peptidoglycan layers. Herewith, a two-step cascade-reaction is facilitated inside bacteria, in which glucose-oxidase generates H2O2 at endogenously-available glucose concentrations, while subsequently Fe3O4-nanoparticles catalyze generation of •OH from the H2O2 generated. Generation of •OH inside bacterial cell walls by dual-loaded mesoporous SiO2-nanoparticles yielded more effective in vitro killing of both planktonic Gram-positive and Gram-negative bacteria suspended in 10 % plasma than SiO2-nanoparticles solely loaded with glucose-oxidase. Gram-positive or Gram-negative bacterially induced sepsis in mice could be effectively treated by in situ pre-treatment with tail-vein injected CTAC and d-Ala-N3, followed by injection of dual-loaded cascade-reaction containers without using antibiotics. This makes in situ metabolic incorporation of cascade-reaction containers as described attractive for further investigation with respect to the control of other types of infections comprising planktonic bacteria. Statement of SignificanceIn situ metabolic-incorporation of cascade-reaction-containers loaded with glucose-oxidase and Fe3O4 nanoparticles into bacterial cell-wall peptidoglycan is described, yielding ROS-generation from endogenous glucose, non-antibiotically killing bacteria before ROS inactivates. Hitherto, only Gram-positives could be metabolically-labeled, because Gram-negatives possess two lipid-membranes. The outer membrane impedes direct access to the peptidoglycan. This problem was solved by outer-membrane permeabilization using a quaternary-ammonium compound. Several studies on metabolic-labeling perform crucial labeling steps during bacterial-culturing that in real-life should be part of a treatment. In situ metabolic-incorporation as described, can be applied in well-plates during in vitro experiments or in the body as during in vivo animal experiments. Surprisingly, metabolic-incorporation proceeded unhampered in blood and a murine, bacterially-induced sepsis could be well treated.

Analysis of the Drag Reduction Performance and Rheological Properties of Drag-Reducing Additives.

In the practical application of hydraulic rotating machinery, it is essential to thoroughly explore drag reduction and rheological characteristics of drag-reducing additives to optimize machinery efficiency and reduce equipment consumption. This paper combines simulation and experimental approaches to investigate the drag-reduction performance and rheological properties of drag-reducing additives. Numerical simulations are initially conducted to investigate the shear-thinning properties of drag-reducing fluid and explore variations in drag-reduction rate. Turbulent phenomena characteristics are described by analyzing turbulent statistical quantities. Subsequently, the rheological behaviors of polyethylene oxide (PEO), cetyltrimethyl ammonium chloride (CTAC), and their mixed solutions under different conditions are scrutinized using a rotational rheometer. The findings indicate that the drag reduction effect amplifies as the rheological index n and characteristic time λ decrease. The numerical simulations show a maximum drag reduction rate of 20.18%. In rheological experiments, a three-stage viscosity variation is observed in single drag-reducing additives: shear thickening, shear thinning, and eventual stabilization. Composite drag-reducing additives significantly reduce the apparent viscosity at low shear rates, thereby strengthening the shear resistance of the system.

Colloid Mill-Assisted Ultrasonic-Fractional Centrifugal Purification of Low-Grade Attapulgite and Its Modification for Adsorption of Congo Red.

Attapulgite (APT) is widely used in wastewater treatment due to its exceptional adsorption and colloidal properties, as well as its cost-effectiveness and eco-friendliness. However, low-grade APT generally limits its performance. Here, a colloid mill-assisted ultrasonic-fractional centrifugal purification method was developed to refine low-grade APT. This process successfully separated and removed impurity minerals such as quartz and dolomite from the raw ore, resulting in a refined APT purity increase from 16.9% to 60% with a specific surface area of 135.5 m2∙g-1. Further modifying of the refined APT was carried out through the hydrothermal method using varying dosages of cetyltrimethylammonium chloride (CTAC), resulting in the production of four different APT adsorbents denoted as QAPT-n (n = CTAC mole number) ranging from 0.5 to 5 mmol. Using Congo red (CR) as the target pollutant, the QAPT-5 sample exhibited the best adsorption capacity with the maximum quantity of 1652.2 mg∙g-1 in a neutral solution at 30 °C due to the highest surface charge (zeta potential = 8.25 mV). Moreover, the QAPT-5 pellets (~2.0 g adsorbent) shaped by the alginate-assisted molding method removed more than 96% of 200 mL aqueous solution containing 200 mg∙L-1 CR and maintained this efficiency in 10 adsorption-elution cycles, which exhibited the promising practical application.

One‐pot preparation of nanoparticles via self‐assembly of sodium lignosulfonate and quaternary ammonium for controlled release of emamectin benzoate

AbstractNanoformulation was an important strategy to reduce the use of pesticides and the impacts on the environment. However, complex process and high cost hurdled the application in agriculture. In this work, sodium lignosulfonate (SL) and cetyltrimethyl ammonium chloride (CTAC) were combined into nanoparticles and utilized as carriers for emamectin benzoate (EB), using a one‐pot method at mild conditions. The structure of nanoparticle was investigated by dynamic light scattering, ζ‐potential measurement, Fourier transform infrared spectroscopy, and transmission electron microscopy, and related to the loading and release properties. The mass ratio of SL and CTAC had great impacts on the structure of nanoparticle. The release of EB from SL‐CTAC nanoparticles was pH‐triggered. The retarding efficacy was enhanced in the medium of higher pH, due to the increased interaction between the EB and carrier. The incorporation into the nanoparticles greatly increased the insecticidal toxicity of EB. The median lethal concentration, against Spodoptera litura Fabricius larvae, of typical nanoformulation was 55% and 63% of that of conventional formulation emulsifiable concentrates after feeding for 24 and 48 h, respectively. The results indicated SL‐CTAC nanoparticles were good candidates of nanovehicles with high efficiency and low‐cost, which was of great significance to prompt the nanopesticides from laboratory investigation to agricultural application.

Single Crystal and Pentatwinned Gold Nanorods Result in Chiral Nanocrystals with Reverse Handedness.

Handedness is an essential attribute of chiral nanocrystals, having a major influence on their properties. During chemical growth, the handedness of nanocrystals is usually tuned by selecting the corresponding enantiomer of chiral molecules involved in asymmetric growth, often known as chiral inducers. We report that, even using the same chiral inducer enantiomer, the handedness of chiral gold nanocrystals can be reversed by using Au nanorod seeds with either single crystalline or pentatwinned structure. This effect holds for chiral growth induced both by amino acids (e.g. cystine) and by chiral micelles (comprising cetyltrimethylammonium chloride and1,1'-binaphthyl-2,2-diamine). Although it was challenging to discern the morphological handedness forL-cystine-directed particles, even using electron tomography, both cases showed circular dichroism bands of opposite sign, with nearly mirrored chiroptical signatures for chiral micelle-directed growth, along with quasi-helical wrinkles of inverted handedness. These results expand the chiral growth toolbox with an effectthat might be exploited to yield a host of interesting morphologies with tunable optical properties.

Single Crystal and Pentatwinned Gold Nanorods Result in Chiral Nanocrystals with Reverse Handedness

Handedness is an essential attribute of chiral nanocrystals, having a major influence on their properties. During chemical growth, the handedness of nanocrystals is usually tuned by selecting the corresponding enantiomer of chiral molecules involved in asymmetric growth, often known as chiral inducers. We report that, even using the same chiral inducer enantiomer, the handedness of chiral gold nanocrystals can be reversed by using Au nanorod seeds with either single crystalline or pentatwinned structure. This effect holds for chiral growth induced both by amino acids (e.g. cystine) and by chiral micelles (comprising cetyltrimethylammonium chloride and 1,1’‐binaphthyl‐2,2‐diamine). Although it was challenging to discern the morphological handedness for L‐cystine‐directed particles, even using electron tomography, both cases showed circular dichroism bands of opposite sign, with nearly mirrored chiroptical signatures for chiral micelle‐directed growth, along with quasi‐helical wrinkles of inverted handedness. These results expand the chiral growth toolbox with an effect that might be exploited to yield a host of interesting morphologies with tunable optical properties.

Seedless synthesis of Au nanoplates with tunable plasmonic peaks

Au nanoplates with tunable in-plane dipolar localized surface plasmon resonance peaks in a broad range from the visible to near-infrared region were obtained in high yield using a seedless wet chemical growth method after purification. Cetyltrimethylammonium chloride was used as a surfactant, while hydrogen peroxide and sodium borohydride were used as the weak and strong reducing agents, respectively. The edge length and in-plane dipolar localized surface plasmon resonance peak of the Au nanoplates could be adjusted by varying the amounts of hydrogen peroxide and sodium borohydride. The Au nanoplates were further used as the saturable absorber to generate pulsed laser output in a passively Q-switched solid-state laser at approximately 2 µm. Our study offers a new method for obtaining Au nanoplates with tunable plasmonic peaks over a broad range.

Mediated Electrosynthesis of Nanocomposites of Gold Nanoparticles with Cyclobis (paraquat-p-phenylene)

The result of cyclobis(paraquat-p-phenylene) (CBPQT4+) –mediated reduction of gold ions generated by anodic oxidation of metallic gold in MeCN (50% vol.)—H2O/0.05 M Bu4NCl medium in the absence and presence of such stabilizers as cetyltrimethylammonium chloride and polyvinylpyrrolidone is polydisperse aggregated composite nanoparticles with sizes ranging from several nm to 100 nm or more. The resulting AuNP@(CBPQT4+)n nanocomposite is a gold nanoparticle encapsulated in a shell of macrocycle molecules. CBPQT4+ is bound to the surface of the gold nanoparticle by donor-acceptor interactions between the electron-withdrawing viologen units and the electron-donating metal particle. Theoretical calculations suggest that the cavity of the bound macrocycle is not empty, but filled with 10–12 gold atoms. CBPQT4+ presumably forms a monomolecular layer on the metal surface, and its excess amount is involved in the aggregation and sedimentation of the nanocomposites. The encapsulation of AuNPs in the macrocyclic shell is the main reason for the suppression of the metal catalytic activity in the test reaction of p-nitrophenol reduction with sodium borohydride.

Hierarchical Polyimide Microparticles with Controllable Morphology.

Hierarchical polyimides (PIs) not only show outstanding thermal stability and high mechanical strength but also have great advantages in terms of microstructure and surface area, which makes them highly valuable in various fields such as aerospace, microelectronics, adsorption, catalysis, and energy storage. However, great challenges still remain in the synthesis of hierarchical PIs with well-defined microstructure. Herein, polyamide acid salts (PAAS) with tunable ionization degree are synthesized first via the polymerization of dianhydride and diamine monomers in deionized water with 1,2-dimethylimidazole (DMIZ). Then cationic cetyltrimethylammonium chloride (CTAC) is added to the PAAS aqueous solution to induce the formation of polyelectrolyte-surfactant complexes based on electrostatic interaction. After a typical hydrothermal reaction (HTR) procedure, hierarchical PIs with different microstructures such as urchin-like PI microparticles, flower-like PI microparticles, and lamellar PI petals can be fabricated simply by changing the additive amount of DMIZ and CTAC. The nanostructure self-assemblies of PAAS are dominated by the charges on macromolecular chains and the formation of hierarchical structures of polymers is ascribed to a geometrical selection process during crystal growth. This work provides valuable insights into the self-assembly behaviors of polyelectrolyte systems for synthesizing well-defined hierarchical polymers.

Synthesis and application feasibility study of cetyltrimethylammonium p-toluenesulfonate

Abstract To improve the insufficient performance of anion on cationic surfactants and to further study the influence of anion on the surface properties, a cationic surfactant (cetyltrimethylammonium p-toluenesulfonate, CTATS) was prepared, and the relevant surface properties, including surface tension, critical micelle concentration, foaming ability and stability, corrosion inhibition and oil displacement efficiency were studied. Compared to cetyltrimethylammonium chloride (CTAC), CTATS exhibited higher surface activity, lower foaming volume, higher foam stability, higher corrosion inhibition performance and oil displacement efficiency. The results indicate that the CTATS has better performances as a surfactant type in oil and gas fields.

Ir-Doped CuPd Single-Crystalline Mesoporous Nanotetrahedrons for Ethylene Glycol Oxidation Electrocatalysis: Enhanced Selective Cleavage of C-C Bond.

The development of highly efficient electrocatalysts for complete oxidation of ethylene glycol (EG) in direct EG fuel cells is of decisive importance to hold higher energy efficiency. Despite some achievements, their progress, especially electrocatalytic selectivity to complete oxidated C1 products, is remarkably slower than expected. In this work, we developed a facile aqueous synthesis of Ir-doped CuPd single-crystalline mesoporous nanotetrahedrons (Ir-CuPd SMTs) as high-performance electrocatalyst for promoting oxidation cleavage of C-C bond in alkaline EG oxidation reaction (EGOR) electrocatalysis. The synthesis relied on precise reduction/co-nucleation and epitaxial growth of Ir, Cu and Pd precursors with cetyltrimethylammonium chloride as the mesopore-forming surfactant and extra Br- as the facet-selective agent under ambient conditions. The products featured concave nanotetrahedron morphology enclosed by well-defined (111) facets, single-crystalline and mesoporous structure radiated from the center, and uniform elemental composition without any phase separation. Ir-CuPd SMTs disclosed remarkably enhanced electrocatalytic activity and excellent stability as well as superior selectivity of C1 products for alkaline EGOR electrocatalysis. Detailed mechanism studies demonstrated that performance improvement came from structural and compositional synergies, which kinetically accelerated transports of electrons/reactants within active sites of penetrated mesopores and facilitated oxidation cleavage of high-energy-barrier C-C bond of EG for desired C1 products. More interestingly, Ir-CuPd SMTs performed well in coupled electrocatalysis of anode EGOR and cathode nitrate reduction, highlighting its high potential as bifunctional electrocatalyst in various applications.

Ir‐Doped CuPd Single‐Crystalline Mesoporous Nanotetrahedrons for Ethylene Glycol Oxidation Electrocatalysis: Enhanced Selective Cleavage of C−C Bond

AbstractThe development of highly efficient electrocatalysts for complete oxidation of ethylene glycol (EG) in direct EG fuel cells is of decisive importance to hold higher energy efficiency. Despite some achievements, their progress, especially electrocatalytic selectivity to complete oxidated C1 products, is remarkably slower than expected. In this work, we developed a facile aqueous synthesis of Ir‐doped CuPd single‐crystalline mesoporous nanotetrahedrons (Ir‐CuPd SMTs) as high‐performance electrocatalyst for promoting oxidation cleavage of C−C bond in alkaline EG oxidation reaction (EGOR) electrocatalysis. The synthesis relied on precise reduction/co‐nucleation and epitaxial growth of Ir, Cu and Pd precursors with cetyltrimethylammonium chloride as the mesopore‐forming surfactant and extra Br− as the facet‐selective agent under ambient conditions. The products featured concave nanotetrahedron morphology enclosed by well‐defined (111) facets, single‐crystalline and mesoporous structure radiated from the center, and uniform elemental composition without any phase separation. Ir‐CuPd SMTs disclosed remarkably enhanced electrocatalytic activity and excellent stability as well as superior selectivity of C1 products for alkaline EGOR electrocatalysis. Detailed mechanism studies demonstrated that performance improvement came from structural and compositional synergies, which kinetically accelerated transports of electrons/reactants within active sites of penetrated mesopores and facilitated oxidation cleavage of high‐energy‐barrier C−C bond of EG for desired C1 products. More interestingly, Ir‐CuPd SMTs performed well in coupled electrocatalysis of anode EGOR and cathode nitrate reduction, highlighting its high potential as bifunctional electrocatalyst in various applications.

Plasmonic Dielectric Antennas for Hybrid Optical Nanotweezing And Optothermoelectric Manipulation of Single Nanosized Extracellular Vesicles

AbstractThis study showcases an experimental demonstration of near‐field optical trapping and dynamic manipulation of an individual extracellular vesicle. This is accomplished through the utilization of a plasmonic dielectric nanoantenna designed to support an optical anapole state—a non‐radiating optical state resulting from the destructive interference between electric and toroidal dipoles in the far‐field, leading to robust near‐field enhancement. To further enhance the field intensity associated with the optical anapole state, a plasmonic mirror is incorporated, thereby boosting trapping capabilities. In addition to demonstrating near‐field optical trapping, the study achieves dynamic manipulation of extracellular vesicles by harnessing the thermoelectric effect. This effect is induced in the presence of an ionic surfactant, cetyltrimethylammonium chloride, combined with plasmonic heating. Furthermore, the thermoelectric effect improves trapping stability by a deep trapping potential. In summary, the hybrid plasmonic‐dielectric trapping platform offers a versatile approach for actively transporting, stably trapping, and dynamically manipulating individual extracellular vesicles.

Rheological effects of montmorillonite and ethyl cellulose for Xanthoceras sorbifolium Bunge oil-based lubricants

Xanthoceras sorbifolium Bunge oil exhibits favorable characteristics such as excellent low temperature fluidity, high flash point, and degradability. However, it also suffers from drawbacks including low kinematic viscosity at low temperatures and significant loss of kinematic viscosity at high temperatures. In view of these characteristics of X. sorbifolium oil, it was modified in this work with a combination of ethyl cellulose (EC), montmorillonite (MMT), and cetyltrimethylammonium chloride (CTAB). The effects of temperature, time, and additive content on the rheological properties of lubricating oil were studied. The kinematic viscosity of the prepared lubricating oil reached up to 433 mm2/s at 40 °C and 51.1 mm2/s at 100 °C. The coagulation point could be reduced to -25 °C, the friction coefficient was 0.026, and the average wear spot diameter was 0.81 mm, The anti-friction performance was enhanced, and the anti-wear performance decreased somewhat. The prepared lubricating oil had the characteristics of high kinematic viscosity at high temperature and excellent rheological properties at low temperature. It also met the energy and environmental application requirements of a green, environmentally friendly, and biodegradable sustainable development strategy. This study greatly broadens the application range of lubricating oil.

Flexible nanohybrid substrates utilizing gold nanocubes/nano mica platelets with 3D lightning-rod effect for highly efficient bacterial biosensors based on surface-enhanced Raman scattering.

In this study, gold nanocubes (AuNCs) were quickly synthesized using the seed-mediated growth method and reduced onto the surface of two-dimensional (2D) delaminated nano mica platelets (NMPs), enabling the development of AuNCs/NMPs nanohybrids with a 3D lightning-rod effect. First, the growth-solution amount can be changed to easily adjust the AuNCs average-particle size within a range of 30-70 nm. The use of the cationic surfactant cetyltrimethylammonium chloride as a protective agent allowed the surface of AuNCs and nanohybrids to be positively charged. Positively charged nanohybrid surfaces presented a good adsorption effect for detecting molecules with negative charges on the surface. Additionally, the NMP surfaces were rich in ionic charges and provided a large specific surface area for stabilizing the growth of AuNCs. Delaminated AuNCs/NMPs nanohybrids can generate a 3D hotspot effect through self-assembly to enhance the Raman signal. Surface-enhanced Raman scattering (SERS) is highly sensitive in detecting adenine biomolecules. Its limit of detection (LOD) and Raman enhancement factor reached 10-9 M and 3.6 × 108, respectively. Excellent reproducibility was obtained owing to the relatively regular arrangement of AuNC particles, and the relative standard deviation (RSD) was 10.7%. Finally, the surface of NMPs was modified by adding the hydrophilic poly(oxyethylene)-diamine (POE2000) and amphiphilic PIB-POE-PIB copolymer at different weight ratios. The adjustment of the surface hydrophilicity and hydrophobicity of AuNCs/NMPs nanohybrids led to better adsorption and selectivity for bacteria. AuNCs/POE/NMPs and AuNCs/PIB-POE-PIB/NMPs were further applied to the SERS detection of hydrophilic Staphylococcus aureus and hydrophobic Escherichia coli, respectively. The SERS-detection results suggest that the LOD of hydrophilic Staphylococcus aureus and hydrophobic Escherichia coli reached 92 CFU mL-1 and 1.6 × 102 CFU mL-1, respectively. The AuNCs/POE/NMPs and AuNCs/PIB-POE-PIB/NMPs nanohybrids had different hydrophilic-hydrophobic affinities, which greatly improved the selectivity and sensitivity for detecting bacteria with different hydrophilicity and hydrophobicity. Therefore, fast, highly selective, and highly sensitive SERS biological-detection results were obtained.

Understanding the impact of kaolinite/muscovite ratio in natural clays on oxide contents, physisorbed water, and structural water fractions

The objective of the present work, is to comprehend the impact of two naturals non-swelling phyllosilicates, namely kaolinite/muscovite ratio, denoted as f(K/M), on the physicochemical properties of the sample. This includes oxide content as well as the fractions of physisorbed and the structural water. To achieve this, the adsorbed amount on the clay sample was assessed using the cationic surfactant (cetyltrimethyl ammonium chloride CTACl) by measuring the Streaming Induced Potential (SIP) at the Point of Zero Charge (PZC). Further, the physisorbed water and structural water losses present in the clay sample, were determined through DTA/TGA thermal analysis. In addition, the kaolinite/muscovite ratios, denoted as f(K/M), characterizing the samples, were calculated using the elemental compositions of various metal oxides as obtained via X-ray fluorescence (XRF) analysis.

Synthesis, Characterization and Potential Antimicrobial Activity of Selenium Nanoparticles Stabilized with Cetyltrimethylammonium Chloride.

Selenium nanoparticles (Se NPs) have a number of unique properties that determine the use of the resulting nanomaterials in various fields. The focus of this paper is the stabilization of Se NPs with cetyltrimethylammonium chloride (CTAC). Se NPs were obtained by chemical reduction in an aqueous medium. The influence of the concentration of precursors and synthesis conditions on the size of Se NPs and the process of micelle formation was established. Transmission electron microscopy was used to study the morphology of Se NPs. The influence of the pH of the medium and the concentration of ions in the sol on the stability of Se micelles was studied. According to the results of this study, the concentration of positively charged ions has a greater effect on the particle size in the positive Se NPs sol than in the negative Se NPs sol. The potential antibacterial and fungicidal properties of the samples were studied on Escherichia coli, Micrococcus luteus and Mucor. Concentrations of Se NPs stabilized with CTAC with potential bactericidal and fungicidal effects were discovered. Considering the revealed potential antimicrobial activity, the synthesized Se NPs-CTAC molecular complex can be further studied and applied in the development of veterinary drugs, pharmaceuticals, and cosmetics.

Characterization of hair lipid and protein dynamics using EPR spectroscopy and treatment effects

Electron paramagnetic resonance (EPR) spectroscopy of a lipid spin label indicated that hair membrane fluidity is low in the cuticle region and high in the inner region comprising the cortex and medulla. This study evaluated the effect of hair treatments and dehydration on membrane fluidity and protein dynamics. In the cuticle region, treatment of hydrated hair with the ionic surfactants, sodium dodecyl sulfate (SDS, anionic), cetyltrimethylammonium chloride (cationic), and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (zwitterionic), as well as the non-ionic Tween 80, caused notable increases in fluidity, with the anionic surfactant SDS having a lesser effect. Furthermore, oleic acid and the monoterpene linalool increased fluidity, while propylene glycol (at 50 %) reduced fluidity and showed the ability to extract the lipid spin label from hair membranes. In the cortex and medulla region, where lipid fluidity is high, the treatments did not cause any changes. For dry hair, membrane fluidity was significantly reduced both in the cuticle and in the inner region. For lipid-depleted hair (containing only covalently bound lipids), the spin label found membranes of high rigidity both in the cuticle and inner regions. In addition, protein dynamics in the peripheral and inner regions of the hair was evaluated using a protein spin label covalently attached to sulfhydryl groups. Dehydration was found to decrease protein dynamics while treatments with oleic acid, linalool, and ethanol caused small increases in the dynamics. Lower molecular dynamics of hair lipids and proteins could be associated with dehydration, lipid depletion, and stiffness through EPR spectroscopy analysis, while the physical presence of softeners and hair cleansers, such as surfactants, leads to an increase in lipid dynamics. EPR spectroscopy has potential application in determining how the molecular dynamics of lipids and proteins are related to the external appearance of hair.

Molecular dynamics models to investigate the diffusion behavior of emulsified asphalt

The utilization of emulsified asphalt is widespread in the recycling of asphalt pavement due to its eco-friendliness and energy efficiency. While numerous research studies have been conducted on the mixture design and strength assessment of emulsified asphalt, the mechanism by which it diffuses and adheres to the aggregate surface remains inadequately comprehended. This study developed molecular dynamics models to investigate the diffusion behavior of emulsified asphalt on the aggregate surface to clarify the role of emulsifier, water, and asphalt in the adsorption process from a molecular perspective. Interface models are established according to the diffusion state for interfacial adhesion evaluation. The results show that the movement of water molecules is the driving force for the entire emulsified asphalt to adsorb to the aggregate surface, whether the aggregate is silica or reclaimed asphalt pavement (RAP). Compared with anionic surfactant Sodium Dodecylbenzene Sulfonate (SDBS), cationic emulsifier Cetyltrimethylammonium Chloride (CTAC) has a better affinity, stronger adsorption, and higher interfacial adhesion energy with silica. Compared with RAP, emulsified asphalt is more readily adsorbed to the surface of silica. It is concluded that emulsifiers have two distribution conformations during the adsorption process, delamination, and aggregation, with delamination exhibiting stronger interface strength with silica than aggregation. When the emulsified asphalt spreads on the RAP surface, the penetration of water molecules into the aged asphalt layer in the RAP structure reduces the structure's water resistance. These results can provide a molecular perspective for understanding the internal structure of emulsified cold recycle mixture (ECRM) and link the adsorption behavior of emulsified asphalt on aggregate surfaces with the internal interface strength of ECRM.

Stability study of aqueous foams under high-temperature and high-pressure conditions relevant to Enhanced Geothermal Systems (EGS)

In Enhanced Geothermal System (EGS) hydraulic fracturing is carried out by injecting cold water into deep Hot Dry Rocks (HDR) under carefully controlled conditions to create new or reopen existing fractures. Water-based fracturing fluids demonstrate some challenges including immense quantity of water usage, water sensitivity of the formations, water blocking, and lack of proppant carrying capacity and transportation. Thus, an alternative is to use foam-based fracturing fluid which offers potential advantage over conventional water-based fracturing fluid such as minimum water usage, reduced wellbore damage, high proppant carrying capacity, and less environmental damage. However, foams are complex mixture of gaseous phase and liquid phase which are thermodynamically unstable at downhole conditions, and their stability can decrease over time due to liquid drainage, bubble coarsening, and coalescence. This paper shows laboratory experiments executed to study foam stability at high temperature (200 °C) and high pressure (6.9 MPa) conditions which simulates the geothermal environment. Foam stability was characterized by half-life of foam, which is defined as the time taken by the foam to decreases by 50% of its original height due to drainage. In this paper, two types of gaseous phases, nitrogen (N2) and carbon dioxide (CO2) were investigated. Also, based on successful practice of foam-based fracturing fluid in oil and gas industries, four surfactants, including Alpha olefin sulfonate (AOS), Sodium dodecyl sulfonate (SDS), Tergitol™ (NP – 40), and Cetyltrimethylammonium chloride (CTAC) at optimum concentration of 1 wt.% were tested for best stability performance. In addition, different stabilizing agents including guar gum, bentonite clay, crosslinker, silicon dioxide nanoparticles (SiO2), graphene oxide (GO) were also studied. Experimental results showed that N2 foams were more stable than CO2 foams. It was observed that foam half-life decreased with the increase in temperature. Among all the surfactants, AOS foams showed the most promising thermal stability at high temperatures. Moreover, with the addition of stabilizing agents, foam's half-life was enhanced. Stabilizing agents such as crosslinker and GO dispersion showed the most stable foams with half-life recorded at 20 min and 17 min, respectively, at 200 °C and 6.9 MPa. Finally, pressure also showed a positive effect on foam stability; with increased pressure, foam half-life was increased. Based on the experimental data, analytical models for the effect of temperature and pressure were developed, considering foam degradation is a first-order kinetic reaction that linearly depends on the foam drainage mechanism. The effect of temperature on foam half-life was studied as an exponential decay model. In this model, foam half-life is a function of drainage rate constant (DA) and activation energy (Ea) of the foam system. The effect of pressure on foam half-life was found to obey a power-law model where an increase in pressure showed an increase in foam half-life. Furthermore, a linear relation was studied for the effect of pressure on foam activation energy and drainage rate. Then the combined effects of temperature and pressure were studied, which yielded an analytical model to predict the foam stabilities in terms of half-life for different foam compositions. This research indicates that with an appropriate selection of surfactants and stabilizing agents, it is possible to obtain stable foams, which could replace conventional water fracturing fluid under EGS conditions.