Hydrogen Nuclear Magnetic Resonance Research Articles

Preparation and performance evaluation of a low-damage thickener suitable for fracturing medium and deep coalbed methane

The middle to deep coalbed methane reservoirs have the characteristics of higher burial depth, developed natural fractures and cleats, and are susceptible to damage from gel residue. To solve those problems, a CBM thickener was synthesized by using 2-acrylamido-2-methylpropanesulfonic acid (AMPS), acrylic acid (AA), methacryl propyl trimethyl ammonium chloride (DMC), and hydroxyethyl methacrylate (HEMA) monomers as raw materials through aqueous solution polymerization. The molecular structure and aqueous solution morphology were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance hydrogen spectroscopy (1H NMR), and scanning electron microscopy (SEM), respectively. The drag reduction rate and viscosity of different thickener dosages were tested. When the thickener dosage were 0.1 wt%∼1.0 wt%, the drag reduction rate were 81.3%∼61.5%, and the viscosity was 6 mPa·s∼117 mPa·s, and further exploration was conducted by using a rheometer to investigate the temperature and shear resistance at 25–120 °C and the viscoelasticity at 25 °C and 120 °C of 0.6 wt% thickener aqueous solution, indicating its good performance as a fracturing fluid. Finally, the gas permeability changes of the gel breaker with a thickener dosages of 0.4 wt%∼1.0 wt% were investigated to calculate its matrix damage rate, which corresponds to 9.2%∼11.1%, and SEM have been used to characterize the morphological changes of the rock core before and after the gel breaker solution displacement, and verify its damage mechanism. Ultimately, it was proven that the synthesized CBM thickener can be suitable for fracturing operations in middle to deep coalbed methane, with high efficiency in drag reduction and low matrix damage rate.

Development of a new method using dispersive liquid-liquid microextraction with hydrophobic natural deep eutectic solvent for the analysis of multiclass emerging contaminants in surface water by liquid chromatography-mass spectrometry.

A new analytical method was developed for the determination of 14 multiclass emerging organic contaminants in surface waters using LC-MS, and Dispersive Liquid-Liquid Microextraction (DLLME) for extraction. Different Natural Deep Eutectic Solvents (NADESs) composed of terpenes and organic acids were tested as extraction solvents and characterized by Fourier Transform Infrared Spectroscopy (FTIR), Hydrogen Nuclear Magnetic Resonance Spectroscopy (1H-NMR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), density, and viscosity, eliminating the need to use traditional chlorinated solvents. NADES produced with butyric acid and thymol showed the best results and was selected for application for the first time in the extraction of emerging organic contaminants of different classes in water samples. Vortex was used as the dispersion mode, eliminating the use of the dispersion solvent. Chromatographic conditions and sample preparation were optimized using multivariate experimental designs. The optimized chromatographic conditions included the column oven temperature, mobile phase modifiers, and stationary phase type. The optimized conditions for sample preparation included the extraction temperature and pH, salting out effect, and extraction solvent volume. The analytical performance was evaluated through repeatability and intermediate precision tests, with RSD values below 20%, and recoveries between 70 and 120%. The coefficient of determination was greater than 0.98 for all analytes. LOQs varied between 1.5 and 35 μg L-1. DLLME is a simple technique, it does not require expensive and specific equipment. Furthermore, replacing traditional chlorinated solvents with NADES makes the procedure more environmentally friendly. The method presented here can be applied to a wide range of analytes for the analysis of fresh, brackish, and salt waters. Up to the present moment, this is the first study using NADES based thymol and butyric acid for the determination of multiclass emerging contaminants in surface waters samples.

PLL-g-HPA Hydrogel Loaded Human Umbilical Cord Mesenchymal Stem Cells Promote Burn Wound Healing in Rat Model by Regulating Inflammation Response.

Treatment of severe burn wound injury remains a significant clinical challenge as serious infections/complex repair process and irregulating inflammation response. Human umbilical cord mesenchymal stem cells (hUC-MSCs) have a multidirectional differentiation potential and could repair multiple injuries under appropriate conditions. Poly(L-lysine)-graft-4-hydroxyphenylacetic acid (PLL-g-HPA) hydrogel is an enzyme-promoted biodegradable in hydrogel with good water absorption, biocompatibility and anti-bacterial properties. Therefore, the aim of this study was to evaluate the therapeutic effect of hUC-MSCs combined with PLL-g-HPA hydrogel on full thickness burn injury in rat model. The PLL-g-HPA hydrogel was developed and characterized by Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), Hydrogen-1 nuclear magnetic resonance (H-NMR). The cytotoxicity to human foreskin fibroblasts (HFF) were assessed by CCK-8 assay and live/dead quantification and antibacterial activity against Escherichia coli and Staphylococcus aureus was also detected by colony forming unit. A full-thickness burn wound injury model in 12 SD rats was established, and the therapeutic effect of PLL-g-HPA hydrogel combined with hUC-MSCs was detected by healing time/Histology/inflammation factor expression level. The findings from SEM, FTIR, and HFF analyses demonstrated the successful synthesis of PLL-g-HPA hydrogels. These hydrogels exhibited low cytotoxicity at minimal concentrations while maintaining excellent moisture retention and antibacterial properties. Compared to the control group, treatment with PLL-g-HPA hydrogel in conjunction with hUC-MSCs significantly enhanced wound healing, modulated inflammatory responses, and promoted angiogenesis as well as re-epithelialization in rat models. The PLL-g-HPA hydrogel in conjunction with hUC-MSCs represents a promising therapeutic approach for the management of burn wounds.

Curcumin encapsulation in self-assembled nanoparticles based on amphiphilic stearic acid-grafted inulin: Preparation, characterization, and functional evaluation.

The clinical application of curcumin (CUR) is restricted by its low solubility, instability, and poor bioavailability. To overcome these limitations, we developed a novel stearic acid-grafted inulin-based nano-delivery system for CUR encapsulation. The structure of stearoyl inulin (SA-IN) was characterized using Fourier-transform infrared spectroscopy, hydrogen nuclear magnetic resonance, thermogravimetric analysis, and contact angle measurements. CUR-loaded SA-IN nanoparticles (CUR@SA-IN NPs) demonstrated a high encapsulation efficiency of 91.59 % ± 3.26 %, nanoscale dispersion, and an average particle size of 190.6 ± 11.2 nm. The CUR@SA-IN NPs exhibited excellent stability and sustained-release properties. Compared with free CUR, the minimum inhibitory concentration of CUR@SA-IN NPs against Escherichia coli and Staphylococcus aureus decreased by 1.5- and 1.6-fold, respectively. The antioxidant activity increased by 2.34-fold with CUR@SA-IN NPs compared with free CUR. Also, the NPs showed superior efficacy in suppressing the expression of inflammatory cytokines and inhibiting cancer cell proliferation. The cellular uptake studies confirmed enhanced CUR absorption from the NPs compared with free CUR. The CUR@SA-IN NPs exhibited good biocompatibility. These findings highlighted the potential of amphiphilic SA-IN as an effective delivery vector for hydrophobic bioactive compounds, thereby offering a promising approach for developing efficient nanoparticle-based delivery systems.

Supramolecular encapsulation of eugenol with acyclic cucurbit[n]urils: Enhancing water solubility and in vitro antioxidant activity.

In recent years, consumer demand for healthy foods containing natural food additives has increased. Eugenol (EUG) is an essential oil popular as a natural antiseptic. However, its limited water solubility, high volatility, strong odor, and fragile stability hinder its application and storage in the field of food preservation. To address these limitations and unleash the potential of EUG in food preservation, this study utilized acyclic cucurbit[n]urils (ACBs) M1 and M2 as molecular containers to encapsulate EUG to overcome the challenges associated with EUG in food preservation and improve its freshness preservation effect. The nature and behavior of the inclusion complex were confirmed by techniques such as Nuclear magnetic resonance of hydrogen (1H NMR),2D Rotating frame Overhauser effect spectroscopy (2D-ROESY), Field emission scanning electron microscopy (SEM-FEG), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Thermogravimetric analysis (TGA), and Differential scanning calorimetry (DSC). In addition, the in vitro antioxidant capacity and antibacterial activity of the host-guest inclusion complexes were also studied. The results demonstrate that a stable complex is formed between ACBs and EUG, and the water solubility of the M1/EUG and M2/EUG complexes is significantly improved after encapsulation. These two complexes maintained the better antioxidant and antibacterial activity of EUG. This study provides a promising strategy for the application of EUG as a food additive in food preservation.

Development of TiF4-Dendrimer Complex Gel as an Anti-Demineralization Agent for Dentin: An In Vitro Study

ObjectiveThe anti-caries effects of titanium tetrafluoride (TiF4) are well-documented, but its low pH challenges clinical application. This study evaluated PEG citrate dendrimer as a carrier to enhance TiF4 stability and efficacy. MethodsPEG-citrate dendrimer and TiF4-dendrimer gel were synthesized, and their structures confirmed using Fourier Transform Infrared Spectroscopy (FTIR), Hydrogen Nuclear Magnetic Resonance (¹H NMR), and Liquid Chromatography–Mass Spectrometry (LC-MS). Thirty-six intact human teeth were prepared, randomly divided into three groups (n=12) and subjected to pH cycling with the following treatments: titanium tetrafluoride (T), dendrimer (D), and dendrimer with TiF4 (TD). Vickers microhardness and Raman spectroscopy evaluated dentin demineralization. EDS analysis measured titanium and fluoride penetration into dentin in T and TD groups and mineral content (calcium and phosphorus) in all groups compared to controls. ResultsThe T group showed the highest microhardness loss (p<0.001), followed by D and TD groups. EDS analysis revealed no significant difference in titanium and fluorine content between the surface and subsurface in TD (p=0.344), while T had more titanium on the surface (p<0.001). TD had higher subsurface calcium content than T (p=0.008). Raman spectroscopy revealed significant changes in phosphate-to-amide and carbonate-to-amide ratios before and after pH cycling in all groups (p<0.001), with no statistical differences among groups. ConclusionUsing dendrimer as a carrier for TiF4 increased pH and enhanced TiF44 ability to limit dentin demineralization and microhardness loss. Clinical RelevanceThe application of the newly-developed TiF4-dendrimer gel might be an effective approach to prevent/ limit dentin demineralization and dentin caries.

Effect of Modification by β-Amylase and α-Glucosidase on the Structural and Physicochemical Properties of Maize Starch.

Single enzymatic modifications are limited to starch. Complex modification with synergistic amylases will improve starch properties more significantly. In this study, maize starch was compound modified by β-amylase and α-glucosidase. The structure and physicochemical properties of the corn starch were determined by scanning electron microscopy (SEM), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance hydrogen spectroscopy (1HNMR), high-performance anion-exchange chromatography (HPAEC-PAD), differential scanning calorimetry (DSC) and Rapid Visco analyzer (RVA) to determine the changes in the structure and physicochemical properties of maize starch before and after the dual enzyme modification. The branching degree (4.95-7.10%) of maize starch was increased after bi-enzymatic modification, the amylose content (28.77-18.60%) was decreased, and the amylopectin content (70.79-81.71%) was elevated. The relative crystallinity (20.41-30.20%) and short-range ordered structure of the starch increased, and the dual enzyme modification led to a more compact structure. Dual enzyme-modified maize starch showed a decrease in long chains, an increase in short chains, and its degree of branching was elevated. Dual enzyme modification also affected the thermal stability, pasting, light transmittance (1.40-2.16%), solubility (20.15-13.76%), and swelling (33.97-45.79%) of maize starch. It can be concluded that the complex modification of maize starch by β-amylase and α-glucosidase significantly changed the amylose/amylopectin ratio of the starch and made its structure denser. These results can provide a theoretical basis for the enzymatic preparation of maize starch with different amylose/amylopectin ratios and the development and utilization of functional starches.

Investigation of early hydration of cement by hydrogen nuclear magnetic resonance (1H NMR): New insights into paramagnetic effect

The paramagnetic substances can affect the result accuracy of hydrogen nuclear magnetic resonance (1H NMR), which restricts the application of this technology in cement-based materials. In this study, the effect of paramagnetic substances (Fe2O3) with different content of 0–5 % on 1H NMR signals of cement paste within 72 h of hydration was quantitatively analyzed, and the influencing mechanisms were discussed. The degree of cement hydration was quantified by hydration heat using calorimetry simultaneously. The results showed that the influence of Fe2O3 is time-varying and reduced with hydration time. Based on this, a rational Taylor model fitting was applied to the reductions in 1H NMR signal intensities of various samples at different hydration times, and a correction coefficient ω for 1H NMR signal intensity was put forward to effectively eliminate the signal attenuation caused by paramagnetic iron. This result can provide some new insights into the application of 1H NMR in cement-based materials.

Structure-performance relationship in tailored poly(amide-sulfone) membranes for desalination

Poly(amide-sulfone)s were considered the missing link for water desalination membranes, owing to their exceptional properties resulting from the synergism effects of two amide and sulfone structures. To achieve this, a sulfone-based diamine was first synthesized by reacting 4,4′-dichlorodiphenyl sulfone with 3-aminophenol. Subsequently, alternative copolymers of poly(amide-sulfone) were prepared via polycondensation reactions of the synthesized diamine monomer and various diacid chlorides including adipoyl dichloride, isophthaloyl dichloride, and terephthaloyl dichloride. The chemical structures were approved using Fourier transform infrared spectroscopy and hydrogen nuclear magnetic resonance spectroscopy. Porous membranes of the polymers as substrates were prepared by solution casting and phase-inversion method. To form thin film composite membranes, a thin polyamide layer was created through interfacial polymerization on the top surface of prepared substrates using m-phenylenediamine and trimesoyl chloride. After characterization, the performance of all membranes was assessed by evaluating pure water flux, NaCl rejection, and flux recovery ratio using a cross-flow filtration system. The impact of the amide group within the poly(amide-sulfone) substrate structure on thin-film efficiency was explored. Results, revealed that the structure significantly influenced membrane performance. Specifically, the highest pure water flux was 549.50 L.m−2.h−1. Also, NaCl rejection of 98.27 % and flux recovery ratio of 94.21 % were observed among them at pressure of 10 bar. This study provided valuable insights for developing novel poly(amide-sulfone) membranes tailored for desalination applications.

Synthesized Crosslinking Suspension Stabilizer for Spacer Fluid in High-Temperature Conditions: Synthesis, Behavior, and Mechanism Research

Summary High-temperature stability of spacer fluid is a vital prerequisite to ensure the safety of cementing operations in deep or ultradeep wells. Faced with this problem, the thermal stability of the suspension agent in the spacer fluid at high temperatures is improved from the aspects of polymerization monomer and molecular chain. A terpolymer SAD was synthesized by free radical polymerization of sodium styrene sulfonate (SSS), acrylamide (AM), and N, N’-diethylacrylamide (DEAA) in aqueous solution. The name of the terpolymer, SAD, is the initial letter composition of the three polymerization monomers. Polyethyleneimine (PEI) can improve the molecular chain structure of SAD by transamidation reaction with the amide group in SAD, so a high temperature suspension agent PSAD (polyethyleneimine + SAD) was obtained by compounding PEI with SAD. The structure and properties of PSAD were characterized by Fourier infrared spectroscopy, hydrogen nuclear magnetic resonance (NMR) spectroscopy, gel permeation chromatography, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis, scanning electron microscopy (SEM), and viscosity test. In addition, the comprehensive properties of the spacer fluid under the action of PSAD are evaluated. The results showed that the crosslinking degree of PSAD gradually increased with the increase in temperature. After aging at 200°C, the decomposition temperature of PSAD was 305°C, which show terrific thermal stability. At the same time, the spacer fluid prepared by PSAD not only has excellent rheological properties in the range of 90 ~ 200°C but also keeps the density difference between the upper and lower parts of the slurry less than 0.02 g/cm3 and the filtration loss of the slurry less than 50 mL.

Two-step synthesis of ionic liquid demulsifiers for demulsification of water-in-oil emulsion

Stabilized water-in-oil emulsions present significant challenges for oil production. However, current demulsifiers often face limitations such as high demulsification temperatures, low efficiencies, and complex synthesis processes, making the resolution of this challenge a demanding task. In this study, we successfully synthesized two ionic liquid demulsifiers, PEDA-Br and GEDA-Br, employing a straightforward two-step procedure. The objective was to enable effective treatment of water-in-oil emulsions at low temperatures with high efficiency. The structure of the demulsifiers was characterized utilizing Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectra (1H NMR). Bottle tests were then conducted to evaluate their demulsification efficiency (DE) in water-in-oil (W/O) emulsions. The results demonstrated that GEDA-Br achieved a DE of 98.92 % at a concentration of 500 mg/L and a temperature of 50 °C after 2 h. Additionally, both PEDA-Br and GEDA-Br exhibited DE values exceeding 95 % at a salinity level of 10,000 mg/L, and both proved effective across a broad pH range of 4 to 12. These findings highlight their robust resistance to high salinity and both acidic and alkaline conditions. The study also examined the demulsification mechanism in terms of interfacial tension (IFT), elastic modulus of the interfacial film, three-phase contact angle (TCA), and microscopic observations. The excellent interfacial activity, ability to reduce interfacial tension, and electrostatic neutralization capability are responsible for its outstanding demulsification performance.

A novel and sustainable approach to efficiently modify cotton material via a physical flash-explosion with sub- or SCF-CO2 as medium

A novel and eco-friendly approach to modify natural cotton fiber by flash-explosion with a sub- or supercritical fluid of carbon dioxide (sub- or SCF-CO2) for improving its structure and properties was constructed for the first time. The achieved results demonstrate that remarkable improvements in the coloration performance of cotton fiber by 71.1 % and the water retention by 1001.2 % against the control could be readily available by employing the flashily-explosion method at a recommended condition with 4-cycle explosion in sub- or SCF-CO2, and system temperature, fluid treatment duration and explosion number exhibited much more pronounced positive influences among all parameters. Additionally, minimal influences from the supercritical explosion on cotton fiber micronaire value, thermal property and tensile breaking strength were also observed. The scanning electron microscopy (SEM) and porosity investigations clearly show that plenty of micropores and/or strip fissures were formed on the fiber surfaces and their inner phases, and notably improved fiber surface area, pore volume and size were also obtained after a subsupercritical flash-explosion. Nuclear magnetic resonance hydrogen spectroscopy (1H NMR) and Fourier transform infrared spectroscopy (FT-IR) analysis disclose that numbers of hydrogen bonds between the fiber macrochains and/or from their intramolecular chains were broken by generating numerous free hydroxyl groups, which reasonably supported the improvements of the dye uptake behaviors and water retention properties, etc. The Energy-dispersive X-ray spectroscopy (EDS) analysis on the fiber cross-sections further confirms that a loosening of the inner aggregation structure of the cotton fiber was achieved after a flash explosion by significantly enhancing its coloration performance, etc. This innovative approach provides a promising idea and possibility as an alternative to chemical methods via mechanically and physically modifying fiber or other materials with sub- or SCF-CO2 fluid in an eco-friendly and sustainable manner.

A novel biobased prepreg from flax and thermosetting poly(lactic acid): Synthesis, curing and processing

Flax fiber-reinforced thermosetting poly (lactic acid) (PLA) composites, a fully degradable plant fiber-reinforced composites, were prepared by hot-melt pre-impregnation, which consists of two processes, the preparation and curing of the prepreg. Firstly, thermosetting PLA with intrinsic flame-retardancy was synthesized and its molecular structure was verified by Fourier transform infrared spectroscopy and nuclear magnetic resonance hydrogen spectroscopy. The non-isothermal viscosity of the thermosetting PLA resin system was investigated to determine the film-formation temperature (55°C) and the impregnation temperature (65°C) during the preparation of the prepreg. On this basis, novel flax fiber-reinforced thermosetting PLA prepreg was prepared and its curing kinetics was investigated using differential scanning calorimetry (DSC). A curing simulation model of the prepreg was developed using the finite difference method, which was used to design and optimize the curing cycle of the flax fiber-reinforced thermosetting PLA prepreg. Finally, the flax fiber-reinforced thermosetting PLA composites with different lay-ups were prepared using the optimal curing cycles and their mechanical and flame retardant properties were investigated, with tensile and flexural strengths up to 128 MPa and 98.8 MPa, and flame retardant ratings up to UL-94 V-1. Overall, the results of this study can provide an important basis for expanding the application of flax fiber reinforced thermosetting PLA composites.

Dual cross-linked network of the active starch film by incorporating palmitic acid and geraniol: A comprehensive evaluation of the hydrophobic mechanism and antimicrobial activity

In this study, (3-Aminopropyl) triethoxysilane (APTES) was employed as a bridging agent to enhance the compatibility between the hydrophilic starch/pectin film and the hydrophobic palmitic acid (PA) coating through hydrogen bonding and chemical reactions. To address the insufficient antibacterial activity of starch films, geraniol was also incorporated. The intermolecular interactions among APTES, PA, and starch were confirmed using x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and hydrogen nuclear magnetic resonance spectroscopy (1H NMR). Notably, the inclusion of APTES and PA significantly increased the film's hydrophobicity, resulting in a water contact angle (WCA) of 95.12°, a water vapor permeability (WVP) of 2.08 × 10−10 g/(mm·s·Pa), and an oxygen permeability (OP) of 2.61 × 10−9 g·mm·mm−2·s−1. Molecular dynamics (MD) simulations revealed strong non-covalent interactions and exceptional compatibility between starch and PA. Furthermore, the integration of pectin and geraniol improved the mechanical strength and antimicrobial properties of the modified films compared to unmodified starch films. These environmentally friendly and biodegradable starch-based films present a promising option for sustainable packaging materials in food preservation.

Novel bio-based propylene-derived phthalonitrile compounds: Synthesis, curing behavior and thermal properties

Bio-based bisphenol compounds were prepared using eugenol from biomass as the initial raw material. A reaction of nucleophilic substitution takes place with 4-nitrophthalonitrile in an environmentally friendly solvent to produce bio-based propenyl-derived phthalonitrile monomers. The effective preparation of compounds was proven using hydrogen and carbon nuclear magnetic resonance and fourier transform infrared spectroscopy (FT-IR). By employing the process of free radical catalysis, it is possible to directly cure the novel phthalonitrile monomers without the need for a specific small molecule curing agent. The cured resin was reported to have high glass transition temperature, good thermal stability, and processing properties by FT-IR, differential scanning calorimetry, thermogravimetric analyzer, dynamic mechanical analyzer, and rheometer techniques. The flexural test and scanning electron microscopy results show that both resins have a consistent, flawless structure and improved mechanical properties. Eugenol is derived from sustainable biomass, offering an environmentally friendly approach to utilizing biological monophenols effectively. It provides the benefits of carbon reduction and renewability, making it a valuable and eco-conscious resource.

Fundamental physicochemical properties, intermolecular interactions and CO2 absorption properties of binary mixed solutions of monoethanolamine + diethylenetriamine

This work presents experimental data on the density (ρ), viscosity (η), and surface tension (γ) of monoethanolamine (MEA), diethylenetriamine (DETA), and their binary mixed solutions across 298.15–318.15 K. Using these physicochemical data, the work also explored properties like excess molar volume (VmE) and viscosity deviation (Δη) of the solutions. The experimental results were modeled using the Jouyban-Acree model, McAllister four-body model, and Redlich-Kister (R-K) equation. The application of these parametric models confirmed strong intermolecular interactions (The length (1.911 Å) and energy (HF value: −2237.54 kJ/mol and Des: −21.61 kJ/mol) of hydrogen bond) within the MEA + DETA binary mixed solutions. Spectroscopic analyses, including Raman and nuclear magnetic resonance hydrogen spectroscopy, revealed the presence of intermolecular hydrogen bonding (OH⋯N(H2)) in the MEA + DETA binary mixed solutions. Lastly, the CO2 absorption capacity of the solutions was experimentally studied, providing a theoretical foundation and reference data for future experiments and process design of CO2 capture.

Chitosan grafted with gallic acid and cerium dioxide hybrid nanocomposites as environmentally friendly corrosion inhibitors for mild steel: An experimental and computational study

Chitosan grafted with gallic acid (CS-GA), along with CS-GA doped with CeO2 nanoparticles (CS-GA-CeO2) were synthesized as novel environmentally friendly mild steel corrosion inhibitors. The formation of these derivatives was confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), hydrogen nuclear magnetic resonance spectroscopy (1H NMR), and thermal analysis (TGA). Based on potentiodynamic polarization curves (PDP) measurements, the inhibitors acted primarily as hybrid inhibitors, while following the Langmuir adsorption theory model. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy(XPS) and 3D surface profiles, confirmed that CS-GA-CeO2 adsorbed on the mild steel forming a protective layer thus preventing the invasion of corrosive media. The corrosion protection mechanism of chitosan derivatives was investigated by molecular dynamics simulations. Electrochemical measurements were used to investigate the corrosion inhibition by CS-GA and CS-GA-CeO2 on mild steel in a 3.5 % NaCl solution. At room temperature, the highest inhibition efficiency (93.58 %) was achieved at 200 ppm CS-GA-CeO2. Modified chitosan nanocomposites were confirmed as promising corrosion inhibitors.

Synthesis and Kinetics of CO2-Responsive Gemini Surfactants.

Surfactants are hailed as "industrial monosodium glutamate", and are widely used as emulsifiers, demulsifiers, water treatment agents, etc., in the petroleum industry. However, due to the unidirectivity of conventional surfactants, the difficulty in demulsifying petroleum emulsions generated after emulsification with such surfactants increases sharply. Therefore, it is of great significance and application value to design and develop a novel switchable surfactant for oil exploitation. In this study, a CO2-switchable Gemini surfactant of N,N'-dimethyl-N,N'-didodecyl butylene diamine (DMDBA) was synthesized from 1, 4-dibromobutane, dodecylamine, formic acid, and formaldehyde. Then, the synthesized surfactant was structurally characterized by infrared (IR) spectroscopy, hydrogen nuclear magnetic resonance (1H NMR) spectroscopy, and electrospray ionization mass spectrometry (ESI-MS); the changes in conductivity and Zeta potential of DMDBA before and after CO2/N2 injection were also studied. The results show that DMDBA had a good CO2 response and cycle reversibility. The critical micelle concentration (CMC) of cationic surfactant obtained from DMDBA by injecting CO2 was 1.45 × 10-4 mol/L, the surface tension at CMC was 33.4 mN·m-1, and the contact angle with paraffin was less than 90°, indicating that it had a good surface activity and wettability. In addition, the kinetic law of the process of producing surfactant by injecting CO2 was studied, and it was found that the process was a second-order reaction. The influence of temperature and gas velocity on the reaction dynamics was explored. The calculated values from the equation were in good agreement with the measured values, with a correlation coefficient greater than 0.9950. The activation energy measured during the formation of surfactant was Ea = 91.16 kJ/mol.

Assessing Popper Purity—Implications for the Regulation and Recreational Use of Alkyl Nitrites

Alkyl nitrites (“poppers”) are a diverse class of volatile chemical compounds with a varied legal and medical history. Though once commonly prescribed to treat angina, popper use is now almost exclusively recreational. Currently, poppers are widely available and sold legally under labels like “solvent cleaner”, despite marketing suggesting they are meant to be consumed. As a result, there is little incentive for producers to implement robust quality controls to protect users. In this study, nine common popper brands were analyzed using hydrogen-1 and carbon-13 nuclear magnetic resonance spectroscopy to assess the presence of impurities. Physical labels on all nine samples indicated the contents were “pure” isobutyl nitrite, despite contradictory online marketing in several cases. Spectral results showed isobutyl nitrite was present in all popper samples. However, there was evidence that various unlabeled compounds were also present in all samples. The identity and concentration of these contaminants were not clear, but the seemingly ubiquitous presence of impurities and lack of consistency in the tested samples are concerning and may represent a threat to users’ health. We hope the results of this study draw attention to the potential dangers of recreational popper use and the need to reassess how these compounds are regulated.

Engineering fully quaternized (Dimethylamino)ethyl methacrylate-based photoresins for 3D printing of biodegradable antimicrobial polymers

Nowadays, medical devices or implants are widely used in the medical field to treat different diseases. However, bacterial infections are one of the significant problems associated with medical devices and are recognized as a concern in healthcare worldwide. Addressing this problem has driven the exploration of new materials with potent antibacterial properties. In this regard, quaternary ammonium compounds (QACs), which are organic salts with an alkane chain and a charged part of quaternary ammonium groups, came up with a potent antibacterial activity. Herein, we report for the first-time dimethylamino ethyl methacrylate (DMAEM) derived quaternary ammonium monomer and crosslinker to prepare photoresins for DLP (Digital light processing) 3D printing. The structure of the synthesized monomer and crosslinker was confirmed via FTIR (Fourrier Transform Infrared) and 1H NMR (Hydrogen Nuclear Magnetic Resonance) while the physicochemical properties of the 3D printed polymer were investigated using TGA (Thermogravimetric Analysis), DSC (Differential Scanning Calorimeter) and UTM (Universal testing machine). By optimizing the printing conditions and monomer to crosslinker ratio, we can print high-resolution 3D-printed objects. Additionally, in vitro biodegradation, cytocompatibility, and hemocompatibility tests revealed that the printed polymers are biodegradable, cytocompatible, and hemocompatible in nature. More importantly, the printed polymers exhibited strong antibacterial activity against both gram-negative and gram-positive bacteria, suggesting their potential utility in personalized antibacterial medical devices.