ABSTRACTThermal conductivity of hydrogenated hexagonal boron nitride (h-BN) nanosheets was investigated using molecular dynamics simulation method. A newly parameterized reactive force field (ReaxFF) for hydrogen and h-BN interactions was used. ReaxFF was used due to its higher accuracy compared to other simpler interatomic potentials. Accurate thickness selection of a monolayer h-BN nanosheet has been shown to produce high thermal conductivity values for pristine armchair and zigzag nanosheets. It was further found that hydrogenation diminishes thermal conductivity of hydrogenated h-BN nanosheets. This reduction in thermal conductivity was due to the occurrence of sp2 to sp3 bonding transition when hydrogen atoms were placed on top of B and N atoms. The increase in temperature was also found to diminish thermal conductivity due to the occurrence of phonon–phonon scattering at higher temperatures. N-vacancy defect has then been shown to exhibit lower thermal conductivity compared to B-vacancy defect. Furthermore, the removal of more atoms contributes to higher decline in thermal conductivity. However, vacancy defect constructed along vertical direction provides the highest reduction in thermal conductivity. It is expected that this work provides useful insights for the design of an effective hydrogen storage system using these novel h-BN nanosheets.

ABSTRACTThe incorporation of different functional groups into organic molecules is a common method to construct soft liquid crystalline materials with multiple properties and adjust mesophases from one-dimensional to three-dimensional structures. This article reports the synthesis, characterization, self-assembly, and binding selectivity behaviors of the first isoflavone-based hexacatenar liquid crystalline materials with an isoflavone as central rigid core and two 1,2,3-triazole dendritic wings as terminal functional units. Polarized optical microscopy, differential scanning calorimetry, and small-angle X-ray scattering (SAXS) investigations indicated that all the compounds could self-assemble into rectangular columnar mesophase. The differences in temperature range of mesophase and sequence of mesophase compared with previously reported coumarin-based polycatenars were attributed to the change of position of carbonyl. The optical spectra indicated that these compounds display selectivity for Fe2+ among the different and cations. FT-IR and density functional theory calculations before and after interaction with Fe2+ were employed to demonstrate the recognition sites. The design strategy here provides a simple method to construct supramolecular self-assembly materials with wide properties and potentials.

ABSTRACTIn this study, modified natural polymeric-based pH-responsive hydrogels (GNAHs) were formulated using guar gum-grafted-poly(N-acryloyl phenyl alanine), 2-hydroxy ethyl acrylate, and 2-acrylamido-2-methyl-1-propane sulfonic acid. GNAH hydrogels were synthesized using a single-step radical polymerization reaction using N,N’-methylenebisacrylamide as a crosslinker and potassium persulfate as an initiator. The GNAH was used for the controlled release of Imatinib mesylate (IMS), an anticancer drug. The FTIR spectroscopy confirmed the IMS loading as well as grafting reaction between GG-g-PNPA and PHEA-co-PAMPS. This was further confirmed by XRD and DSC studies. The IMS also reduced the negative surface charge of the GNAH hydrogel. The microscopic images showed that the GNAH hydrogels have porous and canal structures with IMS molecules entrapped within the pores. The mode of drug release mechanism was assessed by applying various kinetic equations (non-Fickian diffusion mechanism, Higuchi square root and Korsmeyer–Peppas kinetic models) that showed pH-dependent drug release of hydrogels exhibiting an excellent controlled-release pattern for IMS for more than 48 h. Based on the drug release behavior of the as-synthesized amino acid-functionalized hydrogel, it can be suggested that GNAH hydrogels could also be used as a potential pH-responsive anticancer drug delivery system for other anticancer drugs.

ABSTRACTPickering emulsion plays an important role in various industrial fields including food, catalysis, and bioscience. Soy protein isolate (SPI) has been proved feasible for stabilizing Pickering emulsion after modification, though such methods were either difficult to proceed or application restrictive. Herein, we report a simple fabrication of oil-in-water Pickering emulsion using a complex of SPI and carbon nanotubes (CNTs)/carboxymethyl cellulose sodium (CMC-Na). The stability of our emulsion could be kept at a wide range of CNTs diameter, oil fraction, and pH, while the emulsion droplet size might be controlled through the tuning of pH and dispersed phase solvent as well. A strong interaction between SPI and CNTs/CMC-Na is a key factor for the homogeneous distribution of CNTs at the aqueous–organic interface, which benefits the Pickering emulsion formation. Our work will offer some useful thoughts for improving the stability of protein-integrated emulsion.

ABSTRACTWe present a theoretical study of the orientational and electrical behaviors of a cholesteric liquid crystal dispersed with ferroelectric nanoparticles. We assume a soft planar coupling between the liquid crystal molecules and the nanoparticles. We consider two spiral structures in the ferroelectric nano-dispersed system under an external electric field. This assumption is due to the fact that the director and the polarization vector would have different pitches of spiral structure. We study the behavior of the average polarization and the pitch of the helical structure as a function of the field strength. The impact of ferroelectric nanoparticles on cholesteric-nematic phase transition is investigated by calculating the critical electric field. The influence of field strength and material parameters on the phase transition is also discussed. The calculations are based on a developed continuum theory and a modified form of free energy for the helical supramolecular structure. The influence of nanoparticle volume fraction on the helix unwinding of both spiral structures is studied. It is found that an electric field with a sufficiently high strength causes an increase in the pitch of the helical structure of polarization. We obtain a critical volume fraction of nanoparticles, after which the pitch of the polarization helical structure differs from the director pitch.

ABSTRACTSpontaneous symmetry breaking has been shown to be the genesis of self-assembly in a mixture of spherically symmetric chemically active and passive colloids, forming dense clusters. Here, we study the kinetics of such self-assembly, driven by the phoretic motion of passive colloids following the chemical gradient generated by the active seeds. A non-monotonic effect of activity on aggregation is the key observation in this work. We rationalize such non-monotonicity in the clustering by the hybrid coarse-grained simulations. The average cluster population and the variation of their size as a function of time, the stability of clusters, and their dynamics are the key quantifications that help us comprehend the aggregation.

ABSTRACTGelatin hydrogels containing the Chromolaena odorata (Siam Weed) crude extract were fabricated to study the morphology, the percentage of swelling, the total flavonoids released under a system without and with the external voltage stimulation, and the antibacterial properties. The percentage of pore area per cross-sectional area of the hydrogel was 23.56%. The hydrogels showed the extraordinarily high swelling percentage of 1,087.32 ± 16.16%. The total released flavonoids increased over time for both the systems without and with the external voltage stimulation. The total released flavonoid content from the systems with the external voltage stimulation was in larger quantities and more rapidly release comparing to the system in the absence of external voltage stimulation. The equivalent amount of the total released flavonoid tended to increase with the stimulating voltage of 0–0.3 V, but decreased when the excitation voltage was more than 0.3 V. Preferred amount of the total flavonoids released from hydrogels could be partly controlled by specific voltage stimulation. The fabricated hydrogel exhibits novel and great initial properties for wound healing materials and wound care application not only due to its extremely water absorption characteristic, but also perfectly in Gram-positive bacteria growth inhibition, which is ideal for the treatment of certain wounds with infection.

ABSTRACTInteraction with components of the extracellular matrix, particularly various forms of collagen, is essential for the design of successful scaffolds for tissue engineering applications. Both Type II and Type III collagen are found in various connective tissues in the body, providing stability, wound healing, and in some cases assisting in fibrillogenesis. In this study, we designed short peptide conjugates with phenyl pyrazole moieties and examined their interactions with Type II and III triple helical collagen models. The number of hydrophobic groups was varied by varying the phenyl pyrazole moieties that were conjugated with three separate peptides (SYED; SLKD and SLYD). Molecular dynamics (MD) and docking studies revealed that in most cases conjugating with phenyl pyrazole improved binding affinity and stability compared to neat peptides. Computational studies were also carried out to examine the formation of stable scaffold assemblies using MD simulations by integrating the peptide conjugates with either Type II or III collagen and chondroitin sulfate, in order to mimic the formation of a scaffold. As a proof of concept, we examined the binding interactions of the short peptides with Type II and III collagen using SPR and CD spectroscopy, and then synthesized two of the peptide conjugates and integrated them with either Type II or Type III collagen and chondroitin sulfate by layer-by-layer assembly to develop scaffolds to validate computational results. AFM imaging showed the formation of fibrillary structures. The cytocompatibility of the scaffolds was then examined in the presence of mesenchymal stem cells, that showed the formation of cell-scaffold matrices particularly with SLYD conjugates. Our results indicate that such peptide-pyrazole conjugates, may be developed for designing scaffolds for tissue engineering applications.

ABSTRACTA new rapid microwave-assisted approach has been employed to prepare the γ-Fe3O4 magnetic nanoparticles (γ-Fe3O4 MNPs). The formation of spherical γ-Fe3O4 MNPs with an average size of 45 nm and bandgap of 2.3 eV is confirmed by FESEM and UV–Visible spectroscopy. γ-Fe3O4 is doped (0.01 wt% and 0.02 wt%) in the lyotropic liquid crystalline (LLC) lamellar phases of Pluronic F127/N,N dimethylformamide (DMF) to prepare the LLC nanocolloids. Polarizing optical microscopy measurement reveals that γ-Fe3O4 doping does not affect the lamellar LLC structures except 0.02 wt% at 10:90 wt%:wt% system where lamellar to nematic LLC phase transition is observed. Pure LLC phases and nanocolloids are studied for steady and dynamic rheological behavior. LLC phases and LLC nanocolloids possess shear thinning and solid viscoelastic behavior. A complex moduli study of LLCs and LLC nanocolloids is done which indicates the highly elastic strength-based lamellar and nematic phases. Shear-thinning and highly viscoelastic nature of LLCs and LLC nanocolloids have future applications in lubrication, cleaning, cosmetics, and pharmaceutical.

ABSTRACTThe smectic-A to chiral smectic-C* (SmA–SmC*) phase transition in the mixture of graphene nanoparticles and ferroelectric liquid crystal is studied. Combination of Flory–Huggins free energy of isotropic mixing and Landau theory is applied to explain the effects of graphene nanoparticles on the SmA–SmC* phase transition. The temperature and concentration of graphene nanoparticles dependence of tilt angle, spontaneous polarization and dielectric susceptibility in the smectic-C* phase of the SmA–SmC* phase transition are discussed. A qualitative agreement between theoretical results and experimental results is found.

ABSTRACTWith the booming growth of flexible human-computer interactions and telecommunications, it is desirable to fabricate a high-sensitivity strain sensor to monitor human movement and develop an electromagnetic interference (EMI) shielding materials to protect modern microelectronics and humans from electromagnetic damage. Herein, the biocompatible, stretchable, and compressible cellulose/MXene hydrogel has been prepared to first realize the dual-functional applications in strain sensor and EMI shielding. Two-dimensional MXene nanosheets serve as conductive sensing materials and fillers to construct conductive networks. The hydrogen bond interaction between them enhances the mechanical property of hydrogel. Benefiting from the excellent electrical conductivity and good mechanical property of the cellulose/MXene hydrogel, the resultant strain sensor displays excellent tensile strain (~144.4%), high sensitivity (gauge factor ~ -6.97), adjustable detection range (0-68.7%), fast response time (~100 ms), and great stability (~1000 cycles). It can monitor human motion, including pulse beating, speech recognition, writing sensing and pressure distribution induction of 4 × 4 sensor array platform. Moreover, the cellulose/MXene hydrogel presents an absorption-predominant EMI shielding performance in the frequency of X-band. This work provides a new inspiration for the development of multifunctional hydrogel in artificial intelligence, human-computer interaction, and EMI shielding technique.

ABSTRACTThe chemical precipitation was used to obtain carbon fibers (CF) with surface modified by magnetite particles (Fe3O4). Processing was carried out by employing up to three subsequent coating stages of ultrasonic treatments. After each sonication stage, the coating was 17, 33, and 47 wt. % of the total weight of the modified fibers. Raman spectroscopy indicates the presence in the coating of a mixture of iron II and III states. As-decorated fibers were used to fabricate composites with an epoxy resin (ED-20) matrix cured with PEPA. The quantity of the carbon fiber filler was of 1, 3, and 6 wt %. At room temperature, the saturation magnetization of the soft magnetic samples was 0.37, 0.83, and 1.72 emu/g for the indicated compositions. Carbon fiber reinforced polymer materials with extra functions such as magnetic in this case, are expected to be useful in applications from the power and energy industries.

ABSTRACTMicroenvironment of majority chronic wounds exhibits pH in the range of 7.5 to 8.5, leading to poor healing prognosis. The elevated pH adds to dysregulation of healing cascade by creating hypoxia, elevating matrix metalloproteinase (MMP) activity and chances of infection. The current work focuses on fabrication of pH regulating agar-citric acid bi-layer dressing for effective management of chronic wounds. The desired pH in the range of 6 to 7 was achieved by unidirectional release of citric acid through bi-layer arrangement of agar-citric acid films in contact with wound simulating fluid of pH ~ 8.5. At lower pH (6.5), both MMP 9 and MMP 2 degraded lesser gelatin (0.11 µg/mg ± 0.003 µg/mg) as compared to higher pH (8.5) value (0.18 µg/mg ± 0.004 µg/mg). The dressing also exhibited bacteriostatic effect on Staphylococcus aureus and Pseudomonas aeruginosa bacteria cultured in-vitro. The bilayer dressing exhibited an average tensile strength of 27 MPa ± 2.5 MPa along with 52 ± 5% elongation at break. The percentage swelling and water vapor transmission rate of dressing was 112% ± 20% and 2156 g/m2/day ± 128 g/m2/day respectively.

ABSTRACTThermoresponsive polymers, with special emphasis on poly(N-isopropylacrylamide) (PNIPAAM) have been the focus of several investigations due to its potential applications in many fields of physical and polymer chemistry. PNIPAAM has a “lower critical solution temperature” at 32°C. The LCST can be finely tuned by copolymerization with hydrophobic or hydrophilic comonomers, and with a change of physical chemical parameters, such as ionic strength of the solution. We investigated the effect of polymer concentration on the LCST in two different solution environment, in pure water and in 50 mM NaCl solution with small-angle X-ray scattering (SAXS) of relatively low molecular mass polymers. We showed that the radius of gyration of the pNIPAAM chains increases with the addition of NaCl to the system due to the low level of specific adsorption of chloride ions on the polymer, whilst increasing the temperature causes a shrinkage of the polymer chains. Furthermore, by increasing the temperature the attractive interaction between the individual polymer chains is enhanced which turns into aggregation at the LCST.

ABSTRACTNine new C3-symmetric 2,7,12-tris(decanoxy)-3,8,13-tris(alkoxy)truxene discogens were synthesized, and all exhibited only one three-dimensionally ordered hexagonal columnar mesophase with a wide mesogenic temperature range, as characterized by polarizing optical microscopy, differential scanning calorimetry, and X-ray diffractometry. Crucially, as the length of the alkoxy chain increased, the melting points first increased and then decreased, and, at the same time, the temperatures of the clearing point decreased gradually. In addition, these compounds were found to be highly thermally stable, having decomposition temperatures occurring well above 350°C, as determined by thermogravimetric analysis. The self-assembly behaviors in solution were studied using variable-concentration 1H-NMR, revealing that the truxenes self-aggregated in solution via the π–π facial interactions of the polycyclic aromatic units, and scanning tunneling microscopy results revealed that one of the discotic liquid crystal compounds periodically assembled in a hexagonal geometry at the liquid–solid interface of highly oriented pyrolytic graphite.

ABSTRACTVia molecular dynamics simulation with Langevin thermostat we study the structure and dynamics of a flexible bead-spring active polymer model after a quench from good to poor solvent conditions. The self propulsion is introduced via a Vicsek-like alignment activity rule which works on each individual monomer in addition to the standard attractive and repulsive interactions among the monomeric beads. We observe that the final conformations are in the globular phase for the passive as well as for all the active cases. By calculating the bond length distribution, radial distribution function, etc., we show that the kinetics and also the microscopic details of these pseudo equilibrium globular conformations are not the same in all the cases. Moreover, the center-of-mass of the polymer shows a more directed trajectory during its motion and the behavior of the mean-squared-displacement gradually changes from super-diffusive to ballistic under the influence of the active force in contrast to the diffusive behavior in the passive case.

ABSTRACTCurrent research on coronavirus 2 disease (SARS-CoV-2) has been focused on developing reliable gold nanomaterials and methods for the detection of viral spike protein (S-proteins). Here, we describe the fluorescence quenching of spike proteins in the presence of robust gold-aryl nanoparticles. The obtained results demonstrated a strong binding affinity between S-proteins and tryptophan immobilized on gold-carbon nanoparticles (Trp-AuNPs) based on the binding constant value of 11.098 M−1. Förster non-radiative energy transfer (FRET) calculations showed an average binding distance of r = 3.06 nm and a critical energy transfer distance of R0 = 2.5 nm. Time-resolved fluorescence studies of conjugated S-proteins onto Trp-AuNPs revealed a short fluorescence lifetime and dynamic quenching.

ABSTRACTBesides being known by food and perfume industries, vanillin has also important pharmacological properties such as anti-inflammatory and antibacterial activities. The use of magnetic nanoparticles as carriers for a vanillin delivery system is a way to explore its benefits in human beings. In this paper, poly(lactic-co-glycolic acid) (PLGA) nanoparticles stabilized by poly(vinyl alcohol) (PVA) and containing magnetic CoFe2O4 and vanillin have been prepared using a double emulsion-solvent evaporation method. The morphology, particle size, structure, and surface properties of the nanoparticles were investigated by transmission electron microscopy, zeta-potential measurements, X-ray diffractometry, Fourier transform infrared spectroscopy, magnetic hysteresis loops, and thermogravimetric analysis. The spherical nanoparticles presented negative charge, with zeta-potential values ranging from −9.15 to −5.64 mV, high thermal stability, superparamagnetic properties, and excellent encapsulation of the vanillin (around 80%). Accordingly, such PLGA/PVA nanoparticles encapsulating vanillin and CoFe2O4 exhibited the desired features to suggest their potential use as drug delivery systems.

ABSTRACTA series of amphiphilic rodlike α-cyanostilbene mesogens bearing an α-cyanostilbene core, with one/three lipophilic and flexible alkyl chains at one end and a polar oligooxyethylene (EO) at the opposite end, have been synthesized and investigated by polarized optical microscopy (POM), differential scanning calorimetry (DSC), X-ray scattering, scanning electron microscope (SEM), UV-vis spectroscopy and photoluminescence as well as CV measurements. These compounds can self-assemble into photoresponsive liquid crystalline phases and possess AIEE characteristics, mechanofluorochromic properties and Fe3+ recognition properties. The conductivity of the lithium cation complex was also measured to be 2.6 × 10−7 S m−1. Such compounds can be considered as a kind of multifunctional materials.

ABSTRACTMost xanthan gum-based hydrogels are crosslinked by physical methods, but they typically have inadequate mechanical strength and low thermal, pH, and salt stability. To improve the physicochemical properties of XG-based hydrogels, this study applied periodate oxidation of XG to produce ring-opened products with dialdehyde groups for forming chemically crosslinked hydrogels. The research investigated the effects of oxidized xanthan gum (OXG) at different degrees on the properties of its hydrogels with N,O-carboxymethyl chitosan (NOCC), a water-soluble chitosan derivative. Results show that the rigidity and brittleness of NOCC/OXG hydrogels were enhanced with the increased oxidation of XG. Additionally, the swelling ratio of NOCC/OXG hydrogels was increased by 3.5 times and the degradation rate was reduced by 1.5 times. These hydrogels are promising biomaterials for drug delivery, cell therapy, or tissue regeneration applications.