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Paper chromatography is a low-cost and facile analytical method traditionally used to analyze hydrophilic substances. For the application to substances with lower polarity, we prepared a stationary phase based on filter paper modified with phenyl isocyanate (PI-FP), bearing phenyl carbamate moieties for hydrophobic, π-π, and electrostatic interactions. The preparation and chromatographic methods were established by selecting papers, comparing different chemical structures, optimizing the modification procedure, investigating eluents, and quantitatively parameterizing the separation behavior based on the character of the analytes. PI-FP exhibited better separation performance than esterified FPs and enabled chromatographic analysis of various dyes with both positive and negative clogP (calculated water-octanol partition coefficient). We also demonstrated an application of this system for a preparative separation of dyes using thread-like paper modified with PI. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bilayered V 2 O 5 nH 2 O xerogel constructed 2D nanopapers were synthesized. • The V 2 O 5 nH 2 O Xerogel combines oxygen defect engineering. • Oxygen defect improves Zn2+/Mg2+ insertion/extraction kinetics. Aqueous zinc ion batteries (AZIBs) and aqueous magnesium ion batteries (AMIBs) offer powerful alternatives for large-scale energy storage because of their high safety and low cost. Consequently, the design of high-performance cathode materials is essential. In this paper, we present a simple strategy that combines oxygen defect (O d) engineering with a 2D-on-2D homogeneous nanopape-like bilayer V 2 O 5 nH 2 O xerogel (BL-HVO d NPS). This strategy employs O d to improve Zn2+/Mg2+insertion/extraction kinetics and reduce irreversible processes for high-performance AZIBs/AMIBs. And interlayer water molecules serve as an effective spacer to stabilize the expanded interlayer gap in BL-HVO d NPS, thereby providing extended diffusion channels for Zn2+/Mg2+ during insertion/extraction. The interlayer water molecules help shield the electrostatic interaction between Zn2+/Mg2+ and BL-HVO d NPS lattice, which improves diffusion kinetics during repeated. In addition, electrochemical characterization results indicate that the BL-HVO d NPS can effectively the surface adsorption and internal diffusion of Zn2+/Mg2+. More importantly, the successfully prepared unique 2D-on-2D homogenous nanopaper structure enhances electrolyte/electrode contact and reduces the migration/diffusion path of electrons/Zn2+ and Mg2+, thus greatly improving rate performance. As a result, the BL-HVO d NPS as AZIBs/AMIBs electrodes offer better reversible capacity of 361.8 and 162.8 mA h g−1 (at 0.2 A g−1), while displaying impressively long cycle lifes. This method provides a way to prepare advanced xerogel cathode materials for AZIBs and AMIBs. [ABSTRACT FROM AUTHOR]

The objective of the present work is to evaluate the application of an amphoteric polymer, with acidic and basic groups on the polymer chain, as a paper dry strength additive. The polymer studied here is random terpolymer of high electrostatic charge density, and high molecular weight. The results of our work showed that the balance between the charge densities of the surface and the polymer structures is an important factor to be considered when using this polymer. The highest paper strength value, measured by tensile index, was found at the polyampholyte’s isoelectric point (ca. pH of 7.3) when the charge of the fiber surface was negative and the polymer structure charge was symmetric. This observation agrees with our dynamic light scattering results which, demonstrated that at the isoelectric point there was a maximum in association among polyampholyte molecules, leading to a maximum in size of molecular aggregates. When adsorbed on an electrically charged surface, the maximum amount of adsorbed polymer, measured by the shift in resonance frequency in a quartz crystal microgravimetric balance, was observed for the same isoelectric point. Better results for paper dry strength were found when the fiber surface and the polymer structures were oppositely charged or at the isoelectric point of the polymer. Less effective addition strategies were found in the case when the fiber surfaces and the polymer structures had same sign of charge. DOI: 2446941601022015065

• PNFs are tightly wound around GO nanosheets through strong electrostatic interaction, forming a nacre like microstructure. • Chemical crosslinking and hydrogen bonding synergize with interlayer entanglement effect among different PNFs. • Nacre-inspired PBO papers exhibits excellent tensile strength and toughness as high as 338.3 MPa and 16.04 MJ/m3. • The paper exhibits excellent fatigue resistance, extreme temperature resistance (−196～300 °C), and chemical stability. In extreme environments, it is difficult to balance the strength and toughness of ultra-thin film materials. To address this problem, we propose a promising strategy to build ultra strong, tough and extreme environments resistant Poly(p-phenylene-2,6-benzobisoxazole) (PBO) papers with a nacre-like structure constructed by synergistic electrostatic interaction and interlayer entanglement through the sol–gel-film method and hot press orientation. Highly interconnected PBO nanofibres （PNFs） with positive charges are tightly wound around the anisotropic graphene oxide (GO) nanosheets with negative charges through strong electrostatic interaction, forming a nacre like microstructure. The addition of Fe (Ⅲ) can form a coordination bond with the amino group on PNFs. Chemical crosslinking and hydrogen bonding synergize with interlayer entanglement effect among different PNFs，which can effectively dissipate interlayer energy and alleviate the conflict between strength and toughness. The resultant tensile strength and toughness are as high as 338.3 MPa and 16.04 MJ/m3，which are 197.7 % and 425.4 % of those of the intrinsic PBO paper, respectively. Additionally, after 5000 folding-unfolding cycles, the tensile strength retention and toughness retention of the PBO/GO/Fe (PGFe) paper were still 85.4 % and 71.9 %, respectively. Moreover, the paper exhibits excellent tolerance to extreme temperature environments and showed extremely strong chemical stability. [ABSTRACT FROM AUTHOR]

Irregular expression of MicroRNA-21 (miRNA-21) is considered as a promising biomarker for early cancer diagnosis. In this paper, a new genosensor based on paper and nanozyme activity of cysteamine-capped gold nanoparticles (Cys/AuNPs) was developed to detect picomolar concentrations of miRNA-21. Such nanozyme catalyzes the colorimetric reaction of hydrogen peroxide (H2O2) and 3,3′,5,5′ tetramethylbenzidine (TMB), to produce a blue color measurable by a smartphone. Due to their positive charge, Cys/AuNPs were attached to the negative phosphate groups of the DNA strand backbone via electrostatic interactions, leading to the quantitative determination of miRNA-21 concentration by the peroxidase-like activity of Cys/AuNPs. Furthermore, a paper-based assay was carried out on nylon disk devices to allow fast immobilization of DNAprobe. After performing the paper-based assay, a good linear range was observed between 1 pM and 1 nM (Y = 0.080 [MiRNA-21]/pM + 13.846, R2 = 0.993) with a detection limit of 0.5 pM. The developed method was effective, selective, and sensitive for the miRNA-21 detection. The application of the proposed method for miRNA-21 detection was examined in a human serum sample, and a recovery rate of 90.0–97.6% was obtained showing the acceptable accuracy of the developed approach. [ABSTRACT FROM AUTHOR]

Polydiacetylenes (PDAs) are a family of highly conjugated polymers that generate optical response sensitively if exposed to stimuli, the color would change from blue to red. PDAs with reusability and color reversibility are at the central of current research efforts generously. They enhance the electrostatic interaction between cations and the negatively charged carboxylate head groups to increase the rigidity and decrease the energy barrier by introducing Ni2+ into the side chains of PDAs. The amphiphilic 10,12‐pentacosadiynoic acid (PCDA) molecules with the hydrophilic and hydrophobic group are dispersed into Ni2+ aqueous solution and self‐assembled in situ into nanoparticles. Transferring the solution onto a paper base to yield a precisely controlled thickness of PDAs thermal paper. The thermal paper undergoes UV‐induced topological chemical polymerization and further cross‐linking to form stably blue. Because of the reduced energy barrier, red thermal paper after thermal stimulation can undergo color reduction under UV light irradiation. Increasing the photopolymerization time from 5 s to 600 s leads to the rising of the color change temperature from approximately 76.4 °C to 105.4 °C. The polydiacetylene/Ni2+ (PDA/Ni2+) thermal paper can be available for green printing, thermal history recording, and temperature visualization. [ABSTRACT FROM AUTHOR]

Flameproof modification of paper can improve safety and application performance. However, traditional paper is prone to moisture absorption, resulting in significant reduction in flame retardant performance, even complete failure, greatly limiting the application environment. In order to achieve long-term flame retardant properties of paper, while avoiding the loss of physical properties caused by the introduction of flame retardants, in this work, a plant acid/phosphate and melamine formaldehyde coating (PyA/PA-MF) is prepared through electrostatic self-assembly for durable flame retardant performance of cellulose paper. Due to the electrostatic interaction, the paper surface become greatly rough with introduction of PyA/PA-MF, a uniform microsphere structure is formed on the surface of the paper cellulose, which effectively fix the phosphorus-containing groups. The oxygen index reaches 33 % and the carbon length was only 6.3 ± 0.2 cm, the pHRR and THR are decreased by 80 % and 73 %, respectively. After being immersed for 72 h, the oxygen index is still 31.4 % and carbon length is no more than 12 cm. mechanical property of modified paper is significant increased in the tensile strength (2.4 MPa) compared to the blank paper (1 MPa), as well as that the whiteness of the surface of the modified paper will not change. In summary, PyA/PA-MF endows paper long-term flame retardant performance while maintaining its basic performance. [Display omitted] [ABSTRACT FROM AUTHOR]

This work describes the synthesis of red-emitting copper nanoclusters (CuNCs) by using DNA as the template. DNA-templated CuNCs combined with blue-emitting carbon dots (CDs) form the self-assembled complex DNA-CuNC/CDs through electrostatic interactions. In the presence of arginine (Arg), the blue fluorescence of CDs (with excitation/emission maxima at 350/440 nm) is quenched. Addition of acetaminophen (AP) induces the competitive combination of Arg and AP for the CDs. This results in the release of Arg from CDs and the recovery of blue fluorescence. On addition of both Arg and AP, the red fluorescence of CuNCs (with excitation/emission maxima at 350/670 nm) undergoes only slight changes. Hence, the DNA-CuNC/CD complex can serve as a dually emitting ratiometric probe to determine both Arg and AP, with detection limits of 0.35 μM and 0.26 μM, respectively. The probe also enables on-site, visual determination of Arg and AP in aqueous samples, best by placing the system in cuvettes or dropping it onto filter paper strips. An "INHIBIT" logic gate was designed based on this ratiometric and visual fluorometric assay, with Arg and AP as the inputs. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) are hazardous to the environment and human health. Thus, tremendous effort has gone into developing effective/efficient techniques for separation of VOCs from their aqueous mixtures. In this work, a simple and versatile strategy was proposed to fabricate a new material for hydrophobic VOC separations, in which a self-assembling hydrogel consisting of TEMPO-oxidized cellulose nanofibers (TOCNs) and cationic guar gum (CGG) was used. Specifically, TOCNs and CGG were deposited onto a filter paper via a layer-by-layer procedure, resulting in a TOCN/CGG hydrogel-coated filtering material, in which no crosslinking agent was used. The hydrogel is spontaneously formed by electrostatic interactions and hydrogen bonding. The as-prepared filtering material exhibits oil-repellence and underwater oleophobicity resulting from the formation of hydration layer on hydrogel, thus demonstrating good VOC separation performance. One-layer of TOCN/CGG hydrogel coating (dried mass of 0.032 g·m− 2) was proved to realize the VOC separation (separation efficiency of around 99 % and water flux of as high as 905.14 L·m− 2·h− 1). Further increase of the hydrogel layers has negligible influence on the separation efficiency although it decreases the water flux. This filtering material also exhibits good stability during recycling. Consequently, this TOCN/CGG self-assembling hydrogel-coated filtering material has great potential in VOCs-contaminated wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • New biocathode including BOD, 4-APA, and BP electrode (BP/4-APA/BOD is suggested. • The biocathode is prepared by electrografting method. • Membraneless paper type EBFCs using this biocathode are fabricated. • This paper type EBFC is well operated even in a condition of living body fluid. • OCV/MPD of this paper type EBFC are 0.612 ± 0.002 V/92.025 ± 0.892 μW cm−2. A new biocathode consisting of bilirubin oxidase (BOD), 4-aminophthalic acid (4-APA) and buckypaper (BP) electrode is suggested for enzymatic biofuel cells (EBFCs). Here, to enhance the electron transfer rate of BOD, electrografting method is imported. When this method and 4-APA are utilized, BP surface has negative charges by the polarity arrangement of 4-APA, forming BP/4-APA structure. With the modification of surface charge, T1 active site within BODs having positive charges are strongly bonded with the negative charges of BP/4-APA in neutral pH condition, while the orientation of T1 site is well aligned by electrostatic interaction. This treatment increases both reactivities of cathodic reaction and EBFC performance. To prove that, the performance of membraneless paper-type EBFCs using the new flexible BP/4-APA/BOD biocathode is investigated. According to the evaluations, their maximum power density and open circuit voltage are 92.025 ± 0.892 μW cm−2 and 0.612 ± 0.002 V with injection of 10 mM glucose which is a condition of living body fluid. Such performances are far better than those of other membraneless EBFCs and are large enough to be utilized as a power source of implantable devices for the human body. [ABSTRACT FROM AUTHOR]

Magnetic paper manufactures are nowadays widely used in information storage, electromagnetic shielding and security industry for its outstanding performances. In this article, Tb-doped germanium borosilicate glass was prepared by melt quenching technique and they were used as magnetic sources of magnetic paper to loading into the bamboo fibers. Magnetic paper has been successfully produced by adding inorganic magnetic particles modified by different concentrations of graphene oxide (GO) solution. The samples were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Raman Spectroscopy, Superconducting Quantum Interferometer Device (SQUID) and Scanning Electron Microscope (SEM). The results shown that the structure of magnetic particle are made from [BO 3 ], [BO 4 ], [A1O 6 ], [SiO 4 ] and [GeO 4 ]. GO sheets had been successfully immobilized on magnetic particles (MPs) surface via electrostatic interaction. SQUID indicated that the magnetic particles and papers were paramagnetic materials. SEM images clearly shown that the MPs loaded into the lumen of bamboo fibers and the interstitial of fibers. Bridge-fibers that connecting other cellulose fibers and MPs by hydrogen bonds were formed in the network of paper due to the functional groups on surface of magnetic particles. The mechanical properties of papers increased with the increment of GO concentration, which is correlated with the hydrogen-bonding that forming by bridge-fibers and other cellulose fibers in network of paper. [ABSTRACT FROM AUTHOR]

Due to the rapid industrialization, heavy metals contamination in the aquatic environment has become more serious. Thus, it is urgent to develop enhanced removal technology for heavy metals. Graphene oxide (GO) based composite paper-like materials have been widely applied for adsorption of heavy metals from wastewater. Herein, we fabricated for the first time an advanced, highly-ordered and homogenous PVC/PPD/GO paper-like material using a resin-infiltration technique. This process is complimentary to layer-by-layer assembly, where the assembling components are required to interact strongly (e.g., via hydrogen bonding or electrostatic attraction). The results showed that the composite papers could achieve high removal efficiency of the heavy metals from water. The amount of Pb(II) adsorbed at equilibrium as achieved by GO, PVC/GO-0.05, PVC/GO-0.08, PVC/PPD/GO-0.05 and PVC/PPD/GO-0.08 buckypapers were 17.61, 22.17, 25.41, 33.57 and 44.80 mg g−1, respectively. In addition, the effects of experimental factors (e.g. GO content, ionic strength of heavy metal ions, temperature and solution pH) on heavy metal adsorption were discussed. Furthermore, the as-prepared PVC/PPD/GO-0.08 composite papers exhibited superior stability and could be recycled more than 900 h based on their 15 regeneration cycles. The improved heavy metal removal efficiency was attributed to the enhanced morphology and the formation of micro- and nano-channels created by the entangled PPD/GO. The findings indicated that the PVC/PPD/GO composite buckypapers could be used as promising materials for the adsorption of heavy metals from wastewater. [Display omitted] • Novel PVC/PPD/GO and PVC/GO composite papers were prepared and characterized. • The p-Phenylenediamine acts as a functional agent and nitrogen dopant. • The PVC/PPD/GO composite papers could remove Pb(II), Cu(II), Ni(II), Co(II), Zn(II) and Cd(II). • The adsorption of heavy metal ions occurs via electrostatic interactions. • The PVC/PPD/GO composite papers exhibited superior reusability after repeated cycles. [ABSTRACT FROM AUTHOR]

Abstract: A dual‐emission ratiometric fluorescent sensing film for metal ion detection is designed. This dual‐emission film is successfully prepared from chitosan, graphitic carbon nitride (g‐C3N4), and gold nanoclusters (Au NCs). Here, it is shown that the g‐C3N4 not only serves as the fluorescence emission source, but also enhances the mechanical and thermal stability of the film. Meanwhile, the Au NCs are adsorbed on the surface of chitosan film by the electrostatic interaction. The as‐prepared dual‐emission film can selectively detect Cu2+, leading to the quench of red fluorescence of Au NCs, whereas the blue fluorescence from g‐C3N4 persists. The ratio of the two fluorescence intensities depends on the Cu2+ concentration and the fluorescence color changes from orange red to yellow, cyan, and finally to blue with increasing Cu2+ concentration. Thus, the as‐prepared dual‐emission film can be worked as ratiometric sensing paper for Cu2+ detection. Furthermore, the film shows high sensitivity and selectivity, with low limit of detection (LOD) (10 ppb). It is observed that this novel gold‐cluster‐based dual‐emission ratiometric fluorescent sensing paper is an easy and convenient way for detecting metal ions. It is believed that this research work have created another avenue for the detection of metal ions in the environment. [ABSTRACT FROM AUTHOR]

Designing a high capacity and long cycle life MnO-based composite material for lithium ion batteries (LIBs) is still a great challenge because of the intrinsically low electrical conductivity and dramatic volume variations during lithiation/delithiation. In this paper, the MnO nanoparticles (MnO NPs) are recombined with multi-walled carbon nanotubes (MWCNTs) and reduced graphene oxide (r-GO) to rationally construct a novel MnO NPs@MWCNTs/r-GO multilayer sandwich structure via electrostatic interaction self-assembly and vacuum filtration processes. As a result, the MnO NPs are closely attracted in the conductive MWCNTs network, and the MWCNTs adsorbed on the surface of MnO NPs can be served as a soft and flexible carbon coating layer to self-adapt the huge volume expansion. For another, the r-GO between two MnO NPs@MWCNTs layers is the cause to form a free-standing paper, enhancing the transverse conductivity of the whole electrode simultaneously. These features will contribute to achieve excellent cycling stability and improved rate capability. [ABSTRACT FROM AUTHOR]

In this study, preparation of a nylon film–TiO 2 composite sheet with both physical durability under UV irradiation and TiO 2 photocatalysis functionality was investigated. First, a nylon film was directly prepared on paper by interfacial polymerization using ethylenediamine and terephthaloyl chloride in a cyclohexane–chloroform mixture (3:1, v/v). Next, the nylon-coated paper was treated with tetraethyl orthosilicate and 3-aminopropyltrimethoxysilane to prepare polysiloxane on its surface. This was followed by fixation of TiO 2 powder via electrostatic interactions with the polysiloxane. Although nylon films on paper usually decompose under TiO 2 photocatalysis, the nylon film–TiO 2 composite sheets prepared using 0.5%–1.0% (w/v) TiO 2 did not decompose under photocatalysis. The residual rate of strength of the sheet remained at almost 100% after 240 h, which could be attributed to protection of the sheet by the polysiloxane layer. The nylon film was fibrous and could effectively adsorb acetaldehyde gas. All of the nylon film–TiO 2 composite sheets prepared using 0.5%–5.0% TiO 2 photocatalytically removed acetaldehyde under UV irradiation and no acetaldehyde gas was detected after 240–300 min. These results show the nylon film–TiO 2 composite sheet can effectively remove acetaldehyde gas by photocatalysis and adsorption and could be applied to removal of volatile organic compounds in indoor air. Image 1 • A nylon film is directly prepared on paper using interfacial polymerization. • The nylon can adsorb acetaldehyde gas. • Polysiloxane is coated on the nylon by electrostatic interactions and fixes TiO 2. • The nylon film–TiO 2 composite sheet is durable under TiO 2 photocatalysis. • The nylon film–TiO 2 composite sheet is photocatalytic. [ABSTRACT FROM AUTHOR]

Electrochromic devices have many important commercial applications ranging from electronic paper like displays, antiglare rear-view mirrors in cars, to energy-saving smart windows in buildings. Monovalent ions such as H+, Li+, and Na+ are widely used as insertion ions in electrochromic devices, but they have limitations such as instability, high cost, and hard handling. The utilization of multivalent ions as insertion ions has been overlooked probably because of the strong electrostatic interactions between ions and intercalation framework as well as the resulted difficulties of intercalation.The bivalent cation, Mg2+, has been proved to be efficient electrochromic insertion ions for the electrochromic processes of the nonstoichiometric W18O49 nanowires. Using Mg2+ based aqueous electrolyte, the electrochromic W18O49 nanowires shows a short coloration/bleaching time of 2.7/3.6 s, and a high tinting productiveness of 116 cm2/c, together with excellent cyclic constancy. The utilization of bivalent Mg2+ as insertion ions will benefit electrochromic devices with low cost, high stability and simple operation. [ABSTRACT FROM AUTHOR]

Peter Politzer (1937–2022) grew up with no doubt in his mind that he would pursue a career in chemistry. His research interests ranged from theoretical concepts such as electronegativity and chemical hardness to applications of electrostatic potentials and average local ionization energies to molecular interactive behavior and bonding, as well as to the study of chemical reactions and the reaction force in a variety of disciplines, including energetic materials. He will be remembered as a world-renowned leader in halogen bonding and other σ-hole bonding interactions and other areas of theoretical and computational chemistry, with over 520 research publications in scientific journals and books, leaving quite a legacy, with a marked tendency toward simplicity. [ABSTRACT FROM AUTHOR]

The detection and quantification of antioxidant molecules is an important task in food science, the fine chemical industry and healthcare. Antioxidants help in preventing the deterioration of nutrition and healthcare products, while eliminating over-the-limit exogenic reactive species, which may lead to illnesses. In our contribution, an inexpensive and rapid method to determine the concentration of various molecular antioxidants was developed. The principle of the analysis relies on the cupric ion reducing antioxidant capacity (CuPRAC) method, which is based on the color-changing reduction of chelated Cu2+ ions. This complex was successfully immobilized on an alginate-functionalized layered double hydroxide (dLDH) nanosheet via electrostatic interactions. The synthesis conditions of alginate (NaAlg) and the cupric complex were optimized, and the optimized composite was fabricated on cellulose paper to obtain a sensing platform. The paper-based sensor was superior to the ones prepared without the dLDH support, as the limit of detection (LOD) values decreased, and the linearity ranges broadened. The results offer a single-point measurement to evaluate the antioxidant efficiency in a cuvette-based method. The superior ability of the sensor was assigned to the presence of solid dLDH particles, as they offer adsorption sites for the dissolved antioxidant molecules, which contributes significantly to the decrease of the diffusion limitation during the detection process. [ABSTRACT FROM AUTHOR]

Water pollution due to organic dyes and radionuclides is a challenging issue to the modern world. Cheap and efficient adsorbents are needed for their removal from wastewaters. Carbon-doped magnesium oxide (C-MgO) and calcium carbonate (C-CaCO3) were synthesized by the in situ hydrothermal treatment of Mg(OH)2 and Ca(OH)2 with carbon, and applied for the removal of eriochrome black T (EBT) at pH = 2.0 and uranium (U(VI)) at pH = 6.0. The Langmuir monolayer adsorption capacities of C-MgO (3.62 × 10−4 mol/g for EBT and 8.10 × 10−4 mol/g for U(VI)) were higher than those of C-CaCO3 (2.53 × 10−4 mol/g for EBT and 5.92 × 10−4 mol/g for U(VI)). The high adsorption capacity of C-MgO was also evidenced with DFT calculations which showed that the sorption energies (ΔE) of C-MgO for EBT (20.62 kcal/mol) and U(VI) (63.41 kcal/mol) were higher than those of C-CaCO3 for EBT (10.21 kcal/mol) and U(VI) (34.29 kcal/mol). In all cases, the electrostatic interactions were involved in the adsorption process. The sorption kinetic data followed pseudo-second-order kinetics. The results demonstrate that both C-MgO and C-CaCO3 are reusable and can be effectively applied for the elimination of EBT and U(VI) from wastewater. [ABSTRACT FROM AUTHOR]

Heparin and protamine are two therapeutically significant biomolecules utilized in surgeries and extracorporeal therapy. Hence, real time monitoring of their concentration levels in body fluids is quite requisite. Herein, we developed, Bovine Serum Albumin stabilized carbon dots by a microwave‐assisted synthesis for the detection of heparin and protamine. Heparin has sulfate and carboxy groups that can interact with the positively charged surface amino groups of protamine through electrostatic interactions and hydrogen bonds. The blue fluorescence exhibited by BSA‐Carbon dots shows decrease in fluorescence emission on addition of negatively charged heparin. When cationic protein protamine is introduced to this system, the fluorescence is recovered due to electrostatic interaction with heparin. The system shows a Limit of detection (LOD) of 0.014 mM and 0.053 mM on addition of heparin and protamine respectively. The probe exhibited positive results with good selectivity and sensitivity towards other coexisting biomolecules and ions that appear in body fluids. The study was extended in biological matrix such as human serum and urine and found good recovery percentage in between 90–120%. The practical applicability was analyzed using a paper strip assay. Hence, a sensitive "turn‐off‐on" probe was effectively developed for the detection of heparin and protamine on a clinical basis. [ABSTRACT FROM AUTHOR]

The paper industry is constantly seeking innovative ways to improve paper quality, increase process efficiency and reduce environmental impact. The unique properties of cationic modification of hemicellulose provide an opportunity to achieve these goals. Herein, eucalyptus hemicellulose was modified with quaternary ammonium groups to yield cationic hemicellulose (CH), which was used to elaborate structural and functional interactions between CH and cellulose nanofibrils (CNFs). These interactions were quantitatively monitored by a quartz crystal microbalance with dissipation (QCM-D). We empirically studied bonding motifs between CNFs and hemicellulose by forming films. The degree of substitution (DS) of CH was made between 0.095 and 0.254 by varying the molar ratio of the reaction, leading to a gamut of positive charges in hemicellulose. The adsorption of CH to a CNF surface was related to electrostatic interactions. The high DS of CH had higher adsorption rate and larger adsorption capacity within the CNF-surface, while CH as a reinforcing agent significantly increased the tensile strength of the film by hydrogen bonding, which was 71% higher than that of unmodified hemicellulose. The strong binding between CH and nanocellulose may highlight a platform to develop paper additives and nanocellulose composites for high-value applications. [ABSTRACT FROM AUTHOR]

Periodic structures are a type of metamaterial in which the physical properties depend not only on the details of the unit cell but also on how unit cells are arranged and interact with each other. In conventional engineering structures, each unit cell interacts with adjacent cells. Methods developed for vibrational and wave propagation analysis in periodic engineering structures consider only nearest-neighbor interactions. The dispersion curves of such systems, in which only adjacent cells interact, have been extensively studied. Metamaterial properties depend on the interactions of a unit cell with other cells. Further interactions, and specifically, interactions beyond the closest neighbors, imply a more complex band structure and wave behavior. In this paper, an example class of such structures, in which electrostatic forces are the driving force, has been investigated. In this paper, properties affecting these periodic structures, such as elastic forces, have been investigated. An attractive property of such structures is that the band structures of such metamaterials can be tuned by changing electric voltages. [ABSTRACT FROM AUTHOR]

The flexible SERS substrate were prepared base on regenerated cellulose fibers, in which the Au nanoparticles were controllably assembled on fiber through electrostatic interaction. The cellulose fiber was regenerated from waste paper through the dry-jet wet spinning method, an eco-friendly and convenient approach by using ionic liquid. The Au NPs could be controllably distributed on the surface of fiber by adjusting the conditions during the process of assembling. Finite-difference time-domain theoretical simulations verified the intense local electromagnetic fields of plasmonic composites. The flexible SERS fibers show excellent SERS sensitivity and adsorption capability. A typical Raman probe molecule, 4-Mercaptobenzoicacid (4-MBA), was used to verify the SERS cellulose fibers, the sensitivity could achieve to 10−9 M. The flexible SERS fibers were successfully used for identifying dimetridazole (DMZ) from aqueous solution. Furthermore, the flexible SERS fibers were used for detecting DMZ from the surface of fish by simply swabbing process. It is clear that the fabricated plasmonic composite can be applied for the identifying toxins and chemicals. [ABSTRACT FROM AUTHOR]

Many state-of-the art machine learning (ML) interatomic potentials are based on a local or semi-local (message-passing) representation of chemical environments. They, therefore, lack a description of long-range electrostatic interactions and non-local charge transfer. In this context, there has been much interest in developing ML-based charge equilibration models, which allow the rigorous calculation of long-range electrostatic interactions and the energetic response of molecules and materials to external fields. The recently reported kQEq method achieves this by predicting local atomic electronegativities using Kernel ML. This paper describes the q-pac Python package, which implements several algorithmic and methodological advances to kQEq and provides an extendable framework for the development of ML charge equilibration models. [ABSTRACT FROM AUTHOR]

We report on the first development of a simple distance-based β-amyloid (Aβ) protein quantification using a paper-based device (dPAD) to screen for Alzheimer's disease (AD) and to subsequently follow up on its influence, i.e., clinical dementia. This sensor method is based on the transformation of a free acid form and its binding with a basic form of bromocresol purple (BCP) through its electrostatic interaction with an Aβ protein. This sensor can measure the length of color change from yellow to blue-green on a paper strip, with this change proportional to the amount of Aβ protein level. We found that the linearity for Aβ protein monitoring was in the range from 0.50 to 10.0 ng mL−1, and the subsequent naked-eye detection limit for Aβ was 0.20 ng mL−1. This system also provided high reproducibility and with no apparent interference effect for Aβ protein analysis in human urine samples. Furthermore, our developed dPAD constituted an accurate and effective device to precisely determine an Aβ protein concentration in real samples, with percentage recoveries in the range of 97–103%, and with the highest relative standard deviation of 5.41%. Subsequently, the validation of our assay was assessed by comparison with a commercial ELISA approach, with favorable results. Finally, the proposed dPAD was successfully applied to the determination of an Aβ protein in human urine samples and showed more benefits for the unskilled user, such as cost-efficiency, simplicity, low reagent usage, and low time consumption. It is also suitable for point-of-care monitoring. [ABSTRACT FROM AUTHOR]

The excitation energy transfer (EET) process for photosynthetic antenna complexes consisting of subunits, each comprised of multiple chromophores, remains challenging to describe. The multichromophoric Förster resonance energy transfer theory is a popular method to describe the EET process in such systems. This paper presents a new time-domain method for calculating energy transfer based on the combination of multichromophoric Förster resonance energy transfer theory and the Numerical Integration of the Schrödinger Equation method. After validating the method on simple model systems, we apply it to the Light-Harvesting antenna 2 (LH2) complex, a light harvesting antenna found in purple bacteria. We use a simple model combining the overdamped Brownian oscillators to describe the dynamic disorder originating from the environmental fluctuations and the transition charge from the electrostatic potential coupling model to determine the interactions between chromophores. We demonstrate that with this model, both the calculated spectra and the EET rates between the two rings within the LH2 complex agree well with experimental results. We further find that the transfer between the strongly coupled rings of neighboring LH2 complexes can also be well described with our method. We conclude that our new method accurately describes the EET rate for biologically relevant multichromophoric systems, which are similar to the LH2 complex. Computationally, the new method is very tractable, especially for slow processes. We foresee that the method can be applied to efficiently calculate transfer in artificial systems as well and may pave the way for calculating multidimensional spectra of extensive multichromophoric systems in the future. [ABSTRACT FROM AUTHOR]

Global changes and drug abuse are forcing humanity to face various disease problems, and alternative therapies with safe natural substances have important research value. This paper combines various techniques in quantum chemical calculations and molecular simulations to provide molecular-level insight into the dynamics of the self-assembly of N-isopropylacrylamide (NIPAM) for loading curcumin (CUR). The results indicate that increasing the chain length of NIPAM molecules reduces their efficiency in encapsulating and locking CUR, and electrostatic interactions and van der Waals interactions are the main driving forces behind the evolution of system configurations in these processes. The isopropyl groups of NIPAM and the two phenolic ring planes of CUR are the main contact areas for the interaction between the two types of molecules. The thermosensitive effect of NIPAM can alter the distribution of isopropyl groups in NIPAM molecules around CUR. As a result, when the temperature rises from ambient temperature (300 K) to human characteristic temperature (310 K), the NIPAM-CUR interactions and radial distribution functions suggest that body temperature is more suitable for drug release. Our findings offer a vital theoretical foundation and practical guidance for researchers to develop temperature-sensitive drug delivery systems tailored for CUR, addressing its clinical application bottleneck. Curcumin is a natural substance with beneficial pharmacological properties, but its poor solubility, instability and poor absorption hinder its use as a therapeutic agent in the body. Here, the authors use quantum chemical calculations and molecular simulations to explore the self-assembly of N-isopropylacrylamide for its use in the loading and release of curcumin. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrids represent a good solution to improve the solubility and dissolution rates of poorly soluble drugs whose number has been increasing in the last few years. One of the most diffused inorganic matrices is hydroxyapatite (HAP), which is a biocompatible and osteoconductive material. However, the understanding of the hybrids' functioning mechanisms is in many cases limited; thus, thorough physicochemical characterizations are needed. In the present paper, we prepared hybrids of pure and Mg-doped hydroxyapatite with meloxicam, a drug pertaining to the Biopharmaceutical Classification System (BCS) class II, i.e., drugs with low solubility and high permeability. The hybrids' formation was demonstrated by FT-IR, which suggested electrostatic interactions between HAP and drug. The substitution of Mg in the HAP structure mainly produced a structural disorder and a reduction in crystallite sizes. The surface area of HAP increased after Mg doping from 82 to 103 m2g−1 as well as the pore volume, justifying the slightly high drug amount adsorbed by the Mg hybrid. Notwithstanding the low drug loading on the hybrids, the solubility, dissolution profiles and wettability markedly improved with respect to the drug alone, particularly for the Mg doped one, which was probably due to the main distribution of the drug on the HAP surface. [ABSTRACT FROM AUTHOR]

Nano-switch structures are important control elements in nanoelectromechanical systems and have potential applications in future nanodevices. This paper analyzes the effects of surface effects, geometric nonlinearity, electrostatic forces, and intermolecular forces on the nonlinear bending behavior and adhesion stability of nano-switches. Based on the Von Karman geometric nonlinearity theory, four types of boundary conditions for the nano-switch structure were specifically calculated. The results show that surface effects have a significant impact on the nonlinear bending and adhesion stability of nano-switches. Surface effects increase the adhesion voltage of the nano-switch and decrease its adhesion displacement, and as the size of the nano-switch structure increases, the impact of surface effects decreases. A comparative analysis of the linear theory and the nonlinear theory results shows that the adhesion voltage predicted by the linear theory is smaller than that predicted by the nonlinear theory. The effect of geometric nonlinearity increases as the size of the nano-switch structure increases, as the distance between the electrodes increases, and as the aspect ratio of the nano-switch structure increases. These findings provide theoretical support and reference for the design and use of future nanodevices and nanoelectromechanical systems. [ABSTRACT FROM AUTHOR]

Van der Waals heterostructures with incommensurate contact interfaces show excellent tribological performance, which provides solutions for the development of new solid lubricants. In this paper, a facile electrostatic layer-by-layer self-assembly (LBL) technique was proposed to prepare multi-layer van der Waals heterostructures tungsten disulfide/hexagonal boron nitride (vdWH WS2/h-BN). The h-BN and WS2 were modified with poly (diallyldimethylammonium chloride) (PDDA) and sodium dodecyl benzene sulfonate (SDBS) to obtain the positively charged PDDA@h-BN and the negatively charged SDBS@WS2, respectively. When the mass ratio of PDDA to h-BN and SDBS to WS2 were both 1:1 and the pH was 3, the zeta potential of PDDA@h-BN and SDBS@WS2 were 60.0 mV and −50.1 mV, respectively. Under the electrostatic interaction, the PDDA@h-BN and SDBS@WS2 attracted each other and stacked alternately along the (002) crystal plane forming the multi-layer (four-layer) vdWH WS2/h-BN. The addition of the multi-layer vdWH WS2/h-BN (1.0 wt%) to the base oil resulted in a significant reduction of 33.8% in the friction coefficient (0.104) and 16.8% in the wear rate (4.43 × 10−5 mm3/(N·m)). The excellent tribological property of the multi-layer vdWH WS2/h-BN arose from the lattice mismatch (26.0%), a 15-fold higher interlayer slip possibility, and the formation of transfer film at the contact interface. This study provided an easily accessible method for the multi-layer vdWH with excellent tribological properties. [ABSTRACT FROM AUTHOR]

In this paper, the responses of assembled behaviors of block polyelectrolytes (PEs) to the strength of electrostatic interactions are studied through molecular dynamic simulations. The results show that the assembled structures closely depend on the electrostatic strength. It should be noted that PE coacervation can outweigh the nucleation of hydrophobic blocks and invert the micelle structures at strong electrostatic strengths, leading to the formation of inverted micelles of PE cores and hydrophobic coronas. In the poor solvent condition for neutral block, diverse anisotropic micelles are presented; candy-like conventional micelles of hydrophobic cores and PE patches coexist with inverted candy-like micelles of PE cores and hydrophobic patches and with Janus micelles of semi-neutral aggregate and semi-PE cluster in the presence of divalent and trivalent counterions. The formation of conventional or inverted micelle is largely determined by the type of micellar fusion, which results from the nucleation competition between electrostatic correlation and hydrophobic interaction. The merge of micelles mediated by hydrophobic attraction leads to conventional hydrophobic cores, and the fusion induced by electrostatic correlations results in PE cores micelles. At strong electrostatic strengths, the PE chains exhibit rich conformations at trivalent counterions, ranging from a fully collapsed state to a rod-like state, and parallel alignment of PE chains is found. [ABSTRACT FROM AUTHOR]

An electrostatic lattice is composed of many micro-scale traps. It is a powerful tool for manipulating cold polar molecules on a chip with the help of the interaction between the dipole moment and the inhomogeneous electric field. To the best of our knowledge, the existing electrostatic lattice still suffers the nonadiabatic transition that will lead to the escape of molecules from the electrostatic trap. In the paper, we skillfully design the electrode structure to avoid the zero-field zone at the center of every single microtrap, and the nonadiabatic transitions can be prevented. First, we numerically calculate the distribution of the spatial electrostatic field. Then, the influences of voltages on the electric field intensity and the height of the trap center are investigated. We simulate of the trajectory of molecules using the Monte Carlo method and figure out the factors impacting the loading efficiency of our electrostatic lattice. At last, we discuss how the voltages and the loading positions affect the positional distribution of trapped molecules. [ABSTRACT FROM AUTHOR]

Bio-orthogonal chemistry provides a powerful tool for drug delivery systems due to its ability to generate therapeutic agents in situ, minimizing off-target effects. Bio-orthogonal transition metal catalysts (TMCs) with stimuli-responsive properties offer possibilities for controllable catalysis due to their spatial-, temporal-, and dosage-controllable properties. In this paper, we fabricated a stimuli-responsive bio-orthogonal catalysis system based on an enhanced green fluorescent protein (EGFP)–nanozyme (NZ) complex (EGFP-NZ). Regulation of the catalytic properties of the EGFP-NZ complex was directly achieved by modulating the ionic strength of the solution. The dielectric screening introduced by salt ions allows the dissociation of the EGFP-NZ complex, increasing the access of substrate to the active site of the NZs and concomitantly increasing nanozyme activity. The change in catalytic rate of the NZ/EGFP = 1:1 complex was positively correlated with salt concentration from 0 mM to 150 mM. [ABSTRACT FROM AUTHOR]

The plasma weak turbulence theory is a perturbative nonlinear theory, which has been proven to be quite valid in a number of applications. However, the standard weak turbulence theory found in the literature is fully developed for highly idealized unmagnetized plasmas. As many plasmas found in nature and laboratory are immersed in a background static magnetic field, it is necessary to extend the existing discussions to include the effects of ambient magnetic field. Such a task is quite formidable, however, which has prevented fundamental and significant progresses in the subject matter. The central difficulty lies in the formulation of the complete nonlinear response functions for magnetized plasmas. The present paper derives the nonlinear susceptibilities for weakly turbulent magnetized plasmas up to the third order nonlinearity, but in doing so, a substantial reduction in mathematical complexity is achieved by the use of Bessel function addition theorem (or sum rule). The present paper also constructs the weak turbulence wave kinetic equation in a formal sense. For the sake of simplicity, however, the present paper assumes the electrostatic interaction among plasma particles. Fully electromagnetic generalization is a subject of a subsequent paper. [ABSTRACT FROM AUTHOR]

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The combination of electrogenerated chemiluminescence (ECL) and aptamer‐gated indicator delivering (gAID) magnetic mesoporous silica nanoparticles embedded into glass fibre paper functionalised with poly(ethyleneglycol) and N‐(3‐triethoxysilylpropyl)diethanolamine allowed the development of a rapid test that detects penicillin directly in diluted milk down to 50±9 ppt in <5 min. Covalent attachment of the aptamer "cap" to the silica scaffold enabled pore closure through non‐covalent electrostatic interactions with surface amino groups, while binding of penicillin led to a folding‐up of the aptamer thus releasing the ECL reporter Ru(bpy)32+ previously loaded into the material and letting it be detected after lateral flow by a smartphone camera upon electrochemical excitation with a screen printed electrode inserted into a 3D‐printed holder. The approach is simple, generic and presents advantages with respect to sensitivity, measurement uncertainty and robustness compared with conventional fluorescence or electrochemical detection, especially for point‐of‐need analyses of challenging matrices and analytes at ultra‐trace levels. [ABSTRACT FROM AUTHOR]

Paper fiber functionalization by modification with DNA molecules expands the applicability and specificity of paper-substrate analytical devices such as microfluidic paper-based analytical devices (µPADs). In this study, a simple amide condensation reaction was performed on 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized pulp fibers to covalently immobilize oligo DNA chains. The fluorescently labeled DNA with confocal laser scanning microscopy, revealed DNA immobilization on the pulp fiber surface and inside the pulp fiber wall. This immobilized DNA sequence-selectively recognized the complementary strand at concentrations of 10−8 M and above. This DNA duplex formation was also explored in terms of the negative charges on the pulp surface. With greater concentrations of carboxyl groups on the pulp material, DNA duplex formation efficiency was lowered. This is proposed to be due to the negatively charged surface imposing a repulsive electrostatic interaction with the negatively charged DNA. In addition, duplex formation and melting on the pulp surface was shown to be temperature-dependent and reversible. [ABSTRACT FROM AUTHOR]

Considering the increased dye contamination in water bodies, an attempt has been made to utilize waste biomaterials as an eco-friendly dye treatment option. In this paper, we show how to employ a waste material called Tricosanthes cucumerina, popularly known as snake gourd (SG), to remove methylene blue (MB) from water. FTIR, proximate analysis, powder XRD, and SEM images were used to characterize SG. FTIR suggests the presence of poly-phenolic –OH moieties. Powder XRD shows a broad cellulosic hump at 22–24°. pH-Dependent adsorption was seen and maximum adsorption capacity was found to be 48 mg/g at pH 7. Adsorption follows Freundlich model (R2 = 0.997, n = 1.208) and pseudo-second-order kinetics (R2 = 0.999) which suggests a multi-layer, heterogeneous adsorption with partial chemisorption. Heavy metals such as lead and mercury moderately interfere with the adsorption efficiency. About 88% regeneration was achieved with a dilute hydrochloric acid and can be reused. The mechanism was proposed to be a combination of electrostatic interaction, hydrogen bonding, and π-π stacking. Abundant availability, water stability, high removal efficiency, and re-usability recommend SG as a potential choice for MB removal from water. [ABSTRACT FROM AUTHOR]

This paper investigated the antibacterial mechanism of spermidine-capped carbon dots (S-PCDs) against Staphylococcus aureus. The results showed that there were a large number of amino groups on the surface of S-PCDs and they had a high positive charge (+47.06 mV), which could be adsorbed on the negatively charged bacterial surface through electrostatic interaction and changed the permeability of the bacterial cell membrane. The extracellular protein and nucleic acid contents of S. aureus treated with S-PCDs were 5.4 and 1.2 times higher than those of the control group, respectively. The surface folds and defects of the bacterial cell membrane, and the leakage of cell contents were observed using SEM and TEM. The expression of metabolic oxidation regulatory genes dmpI, narJ and narK was upregulated and the intracellular ROS generation was induced, causing bacterial oxidative stress and eventually bacterial death. S-PCDs can effectively inhibit biofilm formation and had low cytotoxicity. The S-PCD treatment successfully inhibited microbial reproduction when pasteurized milk was stored at 25 °C and 4 °C. These results provide important insights into the antimicrobial mechanism of S-PCDs and lay the foundation for their application in the food field as a potentially novel bacteriostatic nanomaterial. [ABSTRACT FROM AUTHOR]