A facile and versatile preparation method of sodium alginate-copper sulfide photothermal coating for efficient solar evaporation.

Utilizing inexhaustible solar energy for water purification represents a green and sustainable solution to water scarcity. However, the developments of efficient, inexpensive, convenient and reliable photothermal materials remain a major challenge. Herein, a facile and versatile preparation strategy of sodium alginate (SA)-CuS composite coating with superior adhesion and stability has been proposed toward high-efficiency solar-driven interfacial evaporation. The fabrication process can be quickly completed in aqueous solution with cheap reagents. The SA-CuS coating can be firmly adhered on different substrates, which can withstand rinsing treatment, iterative freeze-thaw cycles as well as high and low pH environments. The SA-CuS coating can convert various substrates into photothermal materials with broad light absorption for desirable solar evaporation because of high CuS loading and rough surface. As a proof of concept, a wood evaporator covered with the SA-CuS coating can achieve a water evaporation rate of ∼2.2 kg m-2 h- 1 under one sun illumination, which is superior to most reported wood-based solar evaporators.

Optimization of the pre-tension and separation distance for measurement of the dynamic elastic modulus and macromolecular orientation of a polypropylene monofilament via the sonic velocity method.

Using a fiber orientation degree measurement instrument (i.e., a dynamic modulus tester), 28 groups of averaged sonic pulse travel times in a polypropylene monofilament were measured and recorded under five pre-tensions across eight separation distances. The zero-time (or delay time) T0, sonic velocity C, sonic modulus E, Hermans orientation factor F, and orientation angle θ were calculated via two- and multi-point methods. The good agreement observed between the scatter plots of calculated data and the regression lines shows that the multi-point method provides reliable, accurate determination of the sonic modulus (or the dynamic elastic modulus) and the orientation parameters. Surprisingly, the zero-time for sonic pulse propagation depends significantly on the separation distance in practice, although it does not in theory. For easy and rapid measurement or relative comparisons using the two-point method, the optimal range of pre-tension is 0.1 gf/den-0.2 gf/den, and the optimal separation distances are 200 mm and 400 mm. The two-point method is appropriate for industrial applications, while because of its greater accuracy, the multi-point method is preferred for scientific research.

Rheological and ion-conductive properties of injectable and self-healing hydrogels based on xanthan gum and silk fibroin.

The hydrogels with injectable and self-healing properties were prepared from xanthan gum (XG) and silk fibroin (SF) by using sodium trimetaphosphate (STMP) as crosslinker. A three-stage model of oscillation-shear-oscillation experiment was designed to mimic injection process and to observe destruction and regeneration of the hydrogels after shear. The XG3-SF-STMP hydrogels immediately recovered to original storage modulus of 80.6%-93.8% on removing shear. The hydrogels were 3D printed into the self-supporting constructions of hydrogel fibers with connected porous structures, and the XG3-SF-STMP hydrogel fibers exhibited smaller width than XG3-STMP. Oscillation rheological behavior indicated that XG3-SF-STMP hydrogels formed rapidly and exhibited more solid-like gel behavior than XG3-STMP. The hydrogel structures were destroyed under a strain (100%) larger than critical strain, but were rebuilt under a small strain (1%) with recovery ratio of 91.36-93.96% within 120 s, suggesting a self-healing property. Introduction of SF particles into XG3-STMP crosslinked networks improved stiffness and retained recoverability. Carboxyl and phosphate groups in the hydrogel networks are beneficial for XG3-SF-STMP hydrogels to absorb enough liquid electrolytes, leading to effective ionic conductivity. The ion-conductive hydrogel with injectable, self-healing, controlled release and non-cytotoxic properties possesses a promising prospect for tissue engineering and drug release application.

Vancomycin-impregnated electrospun polycaprolactone (PCL) membrane for the treatment of infected bone defects: An animal study.

There is no consensus for the management of critical infected bone defects. The purpose of this study was to produce a vancomycin-impregnated electrospun polycaprolactone (PCL) membrane for the treatment of infected critical bone defects, and test it in a rabbit model. Electrospinning produced a resorbable PCL fiber membrane containing vancomycin approximately 1 mm in thickness, with a pore diameter of <10 µm. Femur defects were made in the limbs of 18 rabbits and infected with Staphylococcus aureus. The rabbits were divided into three groups according to treatment: (1) Experimental group: rabbit freeze-dried allogeneic bone graft and the vancomycin-PCL membrane. (2) Control group 1: bone graft. (3) Control group 2: vancomycin-PCL membrane only. Culture showed no difference in osteoclast activity between the three groups. Transwell testing showed that almost no fibroblasts passed through the membrane during the first 24 h, but some fibroblasts were able to pass it after 72 h. At 12 weeks after surgery, there was significantly less inflammatory cell infiltration in the experimental compared to the control groups. New bone formation and fracture bone callus were greater in the experimental group than control groups. We thus conclude the resorbable electrospun vancomycin-impregnated PCL membrane was effective at controlling bone infection, and in the regeneration of bone in a critical bone defect animal model.

Photopolymerized maleilated chitosan/thiol-terminated poly (vinyl alcohol) hydrogels as potential tissue engineering scaffolds.

Photocrosslinkable hydrogels composed of natural materials exhibit great application potential in tissue engineering scaffolds. However, weak formation and poor mechanical property can usually be a limitation. Herein, the photo-clickable thiol-ene hydrogels based chitosan were synthesized using photopolymerization of maleic chitosan (MCS) and thiol-terminated poly (vinyl alcohol) (TPVA) in the presence of a biocompatible photoinitiator. Rheological property and absorbing behavior of the MCS/TPVA hydrogels could be tailored by varying the amount of TPVA in the feed. There was strong intermolecular hydrogen bonding between the molecules of MCS and TPVA. Notably, the MCS/TPVA hydrogel (MT-3) exhibited rapid gelation behavior (<120 s), improved stiff (G' = ∼5500 Pa) and compressive strength (0.285 ±â€¯0.014 MPa), which were important for hydrogel scaffolds, especially for injectable hydrogel scaffolds. Photocrosslinked MCS/TPVA hydrogels was cytocompatible and could promote the L929 cells attachment and proliferation, showing their potential as tissue engineering scaffolds.

Paper Electrodes Coated with Partially-Exfoliated Graphite and Polypyrrole for High-Performance Flexible Supercapacitors.

Flexible paper electrodes for supercapacitors were prepared with partially-exfoliated graphite and polypyrrole as the active materials. Graphite was coated on paper with pencil drawing and then electrochemically exfoliated using the cyclic voltammetry (CV) technique to obtain the exfoliated graphite (EG)-coated paper (EG-paper). Polypyrrole (PPy) doped with ß-naphthalene sulfonate anions was deposited on EG-paper through in-situ polymerization, leading to the formation of PPy-EG-paper. The as-prepared PPy-EG-paper showed a high electrical conductivity of 10.0 S·cm-1 and could be directly used as supercapacitor electrodes. The PPy-EG-paper electrodes gave a remarkably larger specific capacitance of 2148 F∙g-1 at a current density of 0.8 mA∙cm-2, compared to PPy-graphite-paper (848 F∙g-1). The capacitance value of PPy-EG-paper could be preserved by 80.4% after 1000 charge/discharge cycles. In addition, the PPy-EG-paper electrodes demonstrated a good rate capability and a high energy density of 110.3 Wh∙kg-1 at a power density of 121.9 W∙kg-1. This work will pave the way for the discovery of efficient paper-based electrode materials.

An all-solid-state yarn supercapacitor using cotton yarn electrodes coated with polypyrrole nanotubes.

A novel all-solid-state yarn supercapacitor (YSC) has been fabricated by using the cotton yarns coated with polypyrrole (PPy) nanotubes. The interconnected network structure of PPy can increase the surface area as well as the electrode/electrolyte interface area, thus resulting in improved electrochemical performance. For the proposed YSC, a high areal-specific capacitance of 74.0mFcm-2 and a desirable energy density of 7.5µWhcm-2 are achieved. The flexibility of the YSC demonstrates that it is suitable for the integration as flexible power sources in wearable electronic textiles.

Photocrosslinked maleilated chitosan/methacrylated poly (vinyl alcohol) bicomponent nanofibrous scaffolds for use as potential wound dressings.

To improve water stability of hydrophilic nanofibers, photocrosslinked maleilated chitosan/methacrylated poly (vinyl alcohol) (MCS/MPVA) bicomponent nanofibrous scaffolds were successfully obtained by electrospinning of aqueous MCS/MPVA solution and consequent photopolymerization. The parameters of MCS/MPVA solutions such as viscosity and conductivity were measured to evaluate electrospinnability of the blend solutions. The bicomponent nanofibrous scaffolds were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis and differential scanning calorimetry (DSC), respectively. SEM results indicated that MCS/MPVA weight ratios significantly influenced the morphology and diameter distribution of the nanofibers. XRD and DSC investigated that there was strong interaction caused by hydrogen bonding between molecular chain of MCS and MPVA. Water stability test confirmed that the photocrosslinked matrix with a MCS/MPVA ratio of 10/90 retained excellent integrity of the fibrous structure in water. The in vitro cytotoxicity evaluation revealed that photocrosslinked nanofibrous scaffolds entailed good cellular compatibility, and could be used as potential wound dressing.

The effect of anchoring group number on molecular structures and absorption spectra of triphenylamine sensitizers: a computational study.

The molecular structures and absorption spectra of triphenylamine dyes containing different numbers of anchoring groups (S1-S3) were investigated by density functional theory (DFT) and time-dependent DFT. The calculated geometries indicate that strong conjugation is formed in the dyes. The interfacial charge transfer between the TiO(2) electrode and S1-S3 are electron injection processes from the excited dyes to the semiconductor conduction band. The simulated absorption bands are assigned to π → π* transitions according to the qualitative agreement between the experimental and calculated results. The effect of anchoring group number on the molecular structures, absorption spectra and photovoltaic performance were comparatively discussed.

Conjugate spacer effect on molecular structures and absorption spectra of triphenylamine dyes for sensitized solar cells: density functional theory calculations.

The molecular structures and absorption spectra of triphenylamine dyes containing variable thiophene units as the spacers (TPA1-TPA3) were investigated by density functional theory (DFT) and time-dependent DFT. The calculated results indicate that the strong conjugation is formed in the dyes and the length of conjugate bridge increases gradually with the increased thiophene spacers. The interfacial charge transfer between the TiO2 electrode and TPA1-TPA3 are electron injection processes from the excited dyes to the semiconductor conduction band. The simulated absorption bands are assigned to π→π* transitions, which exhibit appreciable red-shift with respect to the experimental bands due to the lack of direct solute-solvent interaction and the inherent approximations in TD-DFT. The effect of thiophene spacers on the molecular structures, absorption spectra and photovoltaic performance were comparatively discussed and points out that the choice of appropriate conjugate bridge is very important for the design of new dyes with improved performance.