Search Results (117)

The transition to sustainable energy systems demands efficient recycling methods for critical raw materials like lithium. In this study, we present a new class of pH- and light-switchable flotation collectors based on isomeric derivatives of the natural product Punicine, termed inverse Punicines. These amphoteric molecules were synthesized via a straightforward four-step route and structurally tuned for hydrophobization by alkylation. Their performance as collectors was evaluated in microflotation experiments of lithium aluminate (LiAlO₂) and silicate matrix minerals such as melilite and calcium silicate. Characterization techniques including ultraviolet-visible (UV-Vis), nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spectroscopy as well as contact angle, zeta potential (ζ potential) and microflotation experiments revealed strong pH- and structure-dependent interactions with mineral surfaces. Notably, N-alkylated inverse Punicine derivatives showed high flotation yields for LiAlO₂ at pH of 11, with a derivative possessing a dodecyl group attached to the nitrogen as collector achieving up to 86% recovery (collector conc. 0.06 mmol/L). Preliminary separation tests showed Li upgrading from 5.27% to 6.95%. Radical formation and light-response behavior were confirmed by ESR and flotation tests under different illumination conditions. These results demonstrate the potential of inverse Punicines as tunable, sustainable flotation reagents for advanced lithium recycling from complex slag systems. Full article

The ionic soil stabilizer (ISS) can synergistically enhance the mechanical properties and improve the engineering characteristics of iron tailings soil in conjunction with cementitious materials such as cement. In this paper, the influence of ISS on the cement hydration process and the charge repulsion between iron tailings soil particles was studied. By means of Isothermal calorimetry, X-ray diffraction (XRD), Scanning electron microscope (SEM), and Low-field nuclear magnetic resonance microscopic analysis methods such as (LF-NMR), X-ray photoelectron spectroscopy (XPS), Non-evaporable water content and Zeta potential were used to clarify the mechanism of ISS-enhanced cement stabilization of the mechanical properties of iron tailings soil. The results show that in the cement system, ISS weakens the mechanical properties of cement mortar. When ISS content is 1.67%, the 7 d compressive strength of cement mortar decreases by 59.8% compared with the reference group. This retardation arises due to carboxyl in ISS forming complexes with Ca²⁺, creating a barrier on cement particle surfaces, hindering the hydration reaction of the cement. In the cement-stabilized iron tailings soil system, ISS has a positive modification effect. At 0.33% ISS, compared with the reference group, the maximum dry density of the samples increased by 6.5%, the 7 d unconfined compressive strength increased by 35.3%, and the porosity decreased from 13.58% to 11.85%. This is because ISS reduces the double electric layer structure on the surface of iron tailings soil particles, reduces the electrostatic repulsion between particles, and increases the compactness of cement-stabilized iron tailings soil. In addition, the contact area between cement particles increases, the reaction energy barrier height decreases, the formation of Ca(COOH)₂ reduces, and the retarding effect on hydration weakens. Consequently, ISS exerts a beneficial effect on augmenting the mechanical performance of cement-stabilized iron tailings soil. Full article

In this work, mesoporous silicas with two types of mesoporous structures were synthesized and functionalized with sulfonic acid groups: MCM-41-SO₃H (honeycomb-like hexagonal structure) and MSU-2-SO₃H (three-dimensional porous structure with wormhole pores). The synthesized materials were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, nitrogen adsorption–desorption, Fourier-transform infrared spectroscopy, ²⁹Si solid-state nuclear magnetic resonance spectroscopy, and elemental analysis. The obtained functionalized materials were evaluated as sorbents for strong cation-exchange solid-phase extraction (SPE) to determine their efficiency in the adsorption and desorption of tropane alkaloids (atropine and scopolamine). The loading solvents, loading volume, analyte concentration, and elution volume were studied, using 50 mg of both materials. Analyses were carried out by ultra-high performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry. The synthesized MCM-41-SO₃H material presented the highest recovery efficiency and has proven to be a promising sorbent for strong cation-exchange SPE of atropine and scopolamine in aqueous media. The high degree of functionalization of MCM-41-SO₃H and the high accessibility of the sulfonic groups for the target analytes, due to the regularity and uniformity of their pores, maximize the contact between the alkaloids and the sorbent, favoring efficient adsorption. Full article

The application of spread-spectrum signals (arbitrary pulse width and position (APWP) sequences) in air-coupled resonant ultrasound spectroscopy is studied. It was hypothesized that spread-spectrum signal optimization should be based on te signal to noise ratio (SNR). Six APWP signal optimization criteria were proposed for this purpose. Experimental measurements were conducted using a thin polycarbonate sample using two standard spread-spectrum signals, linear and nonlinear frequency modulation, together with six optimized APWP signals. It was found that the performance of APWP signals derived from linear frequency modulation was better. The two best performing optimization criteria are SNR improvement on a linear scale with the SNR as an additional weight and energy improvement on a dB scale. The influence of spectral coverage on measurement errors was evaluated. It was found that it is sufficient to cover the sample resonance peak and the valley. The lowest error rates for density, 3%, and for thickness, 3.5%, were achieved when the upper valley was covered. For velocity, the best result, 5%, was achieved when the lower valley was covered. The lowest error rate for attenuation, 3.8%, was achieved in the case when both valleys were covered. Yet no significant performance degradation was noted when a whole −30 dB passband was covered. Full article

This study introduces a novel water-insoluble dispersant for coal water slurry (CWS), namely, a poly(sodium styrene sulfonate)-grafted SiO₂ nanoparticle (SiO₂-g-PSSNa). SiO₂-g-PSSNa was synthesized by combining the surface acylation reaction with surface-initiated atom transfer radical polymerization (SI-ATRP). Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS), energy dispersive spectrometer (EDS), nuclear magnetic resonance spectroscopy (NMR) and thermogravimetric analysis (TGA) verified that SiO₂-g-PSSNa with the desired structure was successfully obtained. Afterwards, the performance of SiO₂-g-PSSNa as a dispersant in CWS preparation was evaluated. The results indicated that the optimal dosage of SiO₂-g-PSSNa was 0.3%. Compared to the famous commercial products, PSSNa and lignosulfonate (LS), SiO₂-g-PSSNa exhibits improved viscosity reduction performance. When SiO₂-g-PSSNa was used as the dispersant, the maximum coal loading of CWS was 64.2%, which was higher than LS (63.4%) and PSSNa (63.9%). All CWSs obtained in this study were pseudoplastic fluids and more consistent with the Herschel–Bulkley rheological model. The turbiscan stability index (TSI) of CWS prepared with SiO₂-g-PSSNa was 0.05, which was significantly lower than CWSs obtained from PSSNa (0.30) and LS (0.36). Therefore, SiO₂-g-PSSNa also exhibits excellent stability performance. This result was confirmed by rod penetration tests. The underlying mechanism was also clarified by various measurements, such as contact angle, zeta potential, EDS and low-field nuclear magnetic resonance spectra (low-field NMR). The results reveal that SiO₂-g-PSSNa can adsorbed onto the coal surface. SiO₂-g-PSSNa possesses a special branched structure, which bears a higher charge density as compared to linear ones with approximate chemical composition. As a result, coal particles adsorbed with SiO₂-g-PSSNa exhibit more electronegativity. With the enhancement of the electrostatic repulsive between coal particles, the apparent viscosity was lowered and the static stability was improved. This study demonstrated that solubility in water is not an essential factor in engineering the dispersant. Densely charged groups are probably more important. Full article

Apurinic/apyrimidinic endonuclease 1 (APE1) is responsible for the hydrolysis of the phosphodiester bond on the 5′ side of an apurinic/apyrimidinic site during base excision repair. Moreover, in DNA, this enzyme can recognize nucleotides containing such damaged bases as 5,6-dihydro-2′-deoxyuridine (DHU), 2′-deoxyuridine (dU), alpha-2′-deoxyadenosine (αA), and 1,N6-ethenoadenosine (εA). Previously, by pulsed electron–electron double resonance spectroscopy and pre-steady-state kinetic analysis, we have revealed multistep DNA rearrangements during the formation of the catalytic complex. In the present study, the modeling of the eversion trajectory of nucleotides with various damaged bases was performed by directed molecular dynamics simulations. It was found that each damaged base at the beginning of the eversion interacts with protein loop Val196-Arg201, which should be moved to enable further nucleotide eversion. This movement involves a shift in loop Val196-Arg201 away from loop Asn253-Thr257 and requires the disruption of contacts between these loops. The Glu260Ala substitution facilitates the separation of the two loops. Moreover, conformational changes in the Asn253-Thr257 loop should occur in the second half of the lesion eversion trajectory. All these perturbations within the protein globule tend to reduce steric interactions of each damaged base with the protein during the eversion of the nucleotide from DNA and movement to the active site. These perturbations are important determinants of substrate specificity of endonuclease APE1. Full article

The family of BiS₂-based superconductors has attracted considerable attention since their discovery in 2012 due to the unique structural and electronic properties of these materials. Several experimental and theoretical studies have been performed to explore the basic properties and the underlying mechanism for superconductivity. In this review, we discuss the current understanding of pairing symmetry in BiS₂-based superconductors and particularly the role of point-contact spectroscopy in unravelling the mechanism underlying the superconducting state. We also review experimental results obtained with different techniques including angle-resolved photoemission spectroscopy, scanning tunnelling spectroscopy, specific heat measurements, and nuclear magnetic resonance spectroscopy. The integration of experimental results and theoretical predictions sheds light on the complex interplay between electronic correlations, spin fluctuations, and Fermi surface topology in determining the coupling mechanism. Finally, we highlight recent advances and future directions in the field of BiS₂-based superconductors, underlining the potential technological applications. Full article

Microplastics (MPLs) and nanoplastics (NPLs) are smaller particles derived from larger plastic material, polymerization, or refuse. In context to environmental health, they are separated into the industrially-created “primary” category or the degradation derivative “secondary” category where the particles exhibit different physiochemical characteristics that attenuate their toxicities. However, some particle types are more well documented in terms of their fate in the environment and potential toxicological effects (secondary) versus their industrial fabrication and chemical characterization (primary). Fourier Transform Infrared Spectroscopy (FTIR/µ-FTIR), Raman/µ-Raman, Proton Nuclear Magnetic Resonance (H-NMR), Curie Point-Gas Chromatography-Mass Spectrometry (CP-gc-MS), Induced Coupled Plasma-Mass Spectrometry (ICP-MS), Nanoparticle Tracking Analysis (NTA), Field Flow Fractionation-Multiple Angle Light Scattering (FFF-MALS), Differential Scanning Calorimetry (DSC), Thermogravimetry (TGA), Differential Mobility Particle [Sizing] (DMPS), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Scanning Transmission X-ray Microspectroscopy (STXM) are reviewed as part of a suite of characterization methods for physiochemical ascertainment and distinguishment. In addition, Optical-Photothermal Infrared Microspectroscopy (O-PTIR), Z-Stack Confocal Microscopy, Mueller Matrix Polarimetry, and Digital Holography (DH) are touched upon as a suite of cutting-edge modes of characterization. Organizations, like the water treatment or waste management industry, and those in groups that bring awareness to this issue, which are in direct contact with the hydrosphere, can utilize these techniques in order to sense and remediate this plastic polymer pollution. The primary goal of this review paper is to highlight the extent of plastic pollution in the environment as well as introduce its effect on the biodiversity of the planet while underscoring current characterization techniques in this field of research. The secondary goal involves illustrating current and theoretical avenues in which future research needs to address and optimize MPL/NPL remediation, utilizing nanotechnology, before this sleeping giant of a problem awakens. Full article

Optical instruments require extremely high precision, and even minor surface contamination can severely impact their performance. Peelable coatings offer an effective and non-damaging method for removing contaminants from optical surfaces. In this study, an amphiphilic polyacrylate copolymer (PMLEA) was synthesized via solution radical copolymerization using the lipophilic monomer lauryl acrylate (LA) and hydrophilic monomers ER-10, methyl methacrylate (MMA), and butyl acrylate (BA). The structure and molecular weight of the copolymer were characterized using Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC). The hydrophilic–lipophilic balance, surface tension, and wettability of the copolymer were analyzed through water titration, the platinum plate method, and liquid contact angle tests. The cleaning performance of the copolymer coating on quartz glass surface contaminants was evaluated using optical microscopy and Ultraviolet-Visible Near-Infrared (UV-Vis-NIR) spectroscopy. The study examined the effect of varying the ratio of LA to ER-10 on the hydrophilicity, lipophilicity, cleaning efficiency, and mechanical properties of the copolymer coating. The results showed that when the mass ratio of LA to ER-10 was 1:2, the synthesized copolymer exhibited optimal performance in removing dust, grease, and fingerprints from quartz glass surfaces. The coating had a tensile strength of 2.57 MPa, an elongation at break of 183%, and a peeling force of 2.07 N m⁻¹. Full article

Wettability is a key parameter that determines the distribution and behavior of fluids in the porous media of oil reservoirs. Understanding and controlling wettability significantly impacts the effectiveness of various enhanced oil recovery (EOR) methods and CO2 sequestration. This review article provides a comprehensive analysis of various methods for measuring and altering wettability, classifying them by mechanisms and discussing their applications and limitations. The main methods for measuring wettability include spontaneous imbibition methods such as Amott–Harvey tests and USBM, contact angle measurement methods, and methods based on the characteristics of imbibed fluids such as infrared spectroscopy (IR) and nuclear magnetic resonance (NMR). These methods offer varying degrees of accuracy and applicability depending on the properties of rocks and fluids. Altering the wettability of rocks is crucial for enhancing oil recovery efficiency. The article discusses methods such as low-salinity water flooding (LSWF), the use of surfactants (SAAs), and carbonated water injection (CWI). LSWF has shown effectiveness in increasing water wettability and improving oil displacement. Surfactants alter interfacial tension and wettability, aiding in better oil displacement. CWI also contributes to altering the wettability of the rock surface to a more water-wet state. An important aspect is also the alteration of wettability through the dissolution and precipitation of minerals in rocks. The process of dissolution and precipitation affects pore structure, capillary pressure, and relative permeabilities, which in turn alters wettability and oil displacement efficiency. Full article

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. Full article

We report the investigation of silicon nanoparticle composite anodes for Li-ion batteries, using a combination of two nm-scale atomic force microscopy-based techniques: scanning spreading resistance microscopy for electrical conduction mapping and contact resonance and force volume for elastic modulus mapping, along with scanning electron microscopy-based energy dispersion spectroscopy, nanoindentation, and electrochemical analysis. Thermally curing the composite anode—made of polyethylene oxide-treated Si nanoparticles, carbon black, and polyimide binder—reportedly improves the anode electrochemical performance significantly. This work demonstrates phase segregation resulting from thermal curing, where alternating bands of carbon and silicon active material are observed. This electrode morphology is retained after extensive cycling, where the electrical conduction of the carbon-rich bands remains relatively unchanged, but the mechanical modulus of the bands decreases distinctly. These electrical and mechanical factors may contribute to performance improvement, with carbon bands serving as a mechanical buffer for Si deformation and providing electrical conduction pathways. This work motivates future efforts to engineer similar morphologies for mitigating capacity loss in silicon electrodes. Full article

Ag₃PO₄/g-C₃N₄ photocatalytic composites were synthesized via calcination and hydrothermal synthesis for the degradation of rhodamine B (RhB) in wastewater, and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and diffuse reflectance spectroscopy (DRS). The degradation of RhB by Ag₃PO₄/g-C₃N₄ composites was investigated to evaluate their photocatalytic performance and cyclic degradation stability. The experimental results showed that the composites demonstrated notable photocatalytic activity and stability during degradation. Their high degradation efficiency is attributed to the Z-scheme transfer mechanism, in which the electrons in the Ag₃PO₄ conduction band and the holes in the g-C₃N₄ valence band are annihilated by heterojunction recombination, which greatly limits the recombination of photogenerated electrons and holes in the catalyst and enhances the activity of the composite photocatalyst. In addition, measurements of photocurrent (PC) and electrochemical impedance spectroscopy (EIS) confirmed that the efficient charge separation of photo-generated charges stemmed from strong interactions at the close contact interface. Finally, the mechanism for catalytic enhancement in the composite photocatalysts was proposed based on hole and radical trapping experiments, electron paramagnetic resonance (EPR) analysis, and work function evaluation. Full article

Two series of lactone-terminated alkanethiol adsorbates with five- and six-membered lactone groups, γ-COCnSH and δ-COCnSH (n = 11, 12), were synthesized and employed to create nanoscale self-assembled monolayers (SAMs) on gold substrates to mimic the properties of commercially available poly(lactic-co-glycolic acid) (PLGA) and poly(glycolic acid) (PGA) surfaces. ¹H and ¹³C nuclear magnetic resonance (NMR) were employed to characterize the adsorbate molecules. The thicknesses of the corresponding self-assembled monolayers (SAMs) were evaluated by ellipsometry. The conformational characteristics of the SAMs were analyzed using polarization modulation infrared reflection adsorption spectroscopy (PM-IRRAS), with a focus on the C-H antisymmetric stretching vibrations of the alkyl spacers. To evaluate the packing densities of the monolayers, X-ray photoelectron spectroscopy (XPS) measurements were performed. Separately, contact angle measurements provided insights into the wettability of the surfaces. Remarkably, the contact angle data across a broad range of probe liquids for the γ-COC11SH and γ-COC12SH SAMs were consistently similar to each other and to the contact angle values of the PLGA surface, rather than to PGA. This finding suggests that the lactone-terminated SAMs investigated in this study effectively mimic nanoscale polyester surfaces, enabling the exploration of interfacial properties of polyesters in the absence of swelling and/or surface reconstruction phenomena. Full article

The inherent large number of hydroxyl groups of silica poses strong hydrophilicity, resulting in poor dispersibility in the natural rubber matrix. Here, the silica’s surface was hydrophobically modified with [3-(triethoxysiliconyl) propyl] tetrasulfide (Si69) to improve the dispersibility and reinforce the mechanical properties of silica/natural rubber composites. The structure and morphology of modified silica were characterized by Fourier infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray electron spectroscopy (XPS), nuclear magnetic resonance spectroscopy and the contact angle. Further, the mechanical properties, dynamic mechanical properties and morphology of silica/natural rubber composites were studied with a universal electronic tension machine, dynamic thermal mechanical properties analyzer (DMA) and scanning electron microscope (SEM). The experimental results show that the Si69 was successfully grafted onto the surface of silica, thereby significantly improving the water contact angle (a 158.6% increase) and enhancing the mechanical properties of modified silica/natural rubber composites. Full article