Fabrication of graphene‐silver/polyurethane nanofibrous scaffolds for cardiac tissue engineering

The graphene‐based nanocomposites are considered as great candidates for enhancing electrical and mechanical properties of nonconductive scaffolds in cardiac tissue engineering. In this study, reduced graphene oxide‐silver (rGO‐Ag) nanocomposites (1 and 2 wt%) were synthesized and incorporated into polyurethane (PU) nanofibers via electrospinning technique. Next, the human cardiac progenitor cells (hCPCs) were seed on these scaffolds for in vitro studies. The rGO‐Ag nanocomposites were studied by X‐ray diffraction (XRD), Raman spectroscopy, and transmission electron microscope (TEM). After incorporation of rGO‐Ag into PU nanofibers, the related characterizations were carried out including scanning electron microscope (SEM), TEM, water contact angle, and mechanical properties. Furthermore, PU and PU/nanocomposites scaffolds were used for in vitro studies, wherein hCPCs showed good cytocompatibility via 3‐(4, 5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide (MTT) assay and considerable attachment on the scaffold using SEM studies. Real‐time polymerase chain reaction (PCR) and immunostaining studies confirmed the upregulation of cardiac specific genes including GATA‐4, T‐box 18 (TBX 18), cardiac troponin T (cTnT), and alpha‐myosin heavy chain (α‐MHC) in the PU/rGO‐Ag scaffolds in comparison with neat PU ones. Therefore, these nanofibrous rGO‐Ag–reinforced PU scaffolds can be considered as suitable candidates in cardiac tissue engineering.     

Free‐standing and Flexible MoS2/rGO Paper Electrode for Amperometric Detection of Folic Acid

The development of flexible electrodes is of considerable current interest because of the increasing demand for modern electronics, portable medical products, and compact devices. We report a new type of flexible electrochemical sensor fabricated by integrating graphene and MoS₂ nanosheets. A highly flexible and free‐standing conductive MoS₂ nanosheets/reduced graphene oxide (MoS₂/rGO) paper was prepared by a two‐step process: vacuum filtration and chemical reduction treatment. The MoS₂/graphene oxide (MoS₂/GO) paper obtained by a simple filtration method was transformed into MoS₂/rGO paper after a chemical reduction process. The obtained MoS₂/rGO paper was characterized by scanning electron microscopy, X‐ray diffraction spectroscopy, X‐ray photoelectron spectroscopy, Raman spectroscopy, electrochemical impedance spectroscopy. The electrochemical behavior of folic acid (FA) on MoS₂/rGO paper electrode was investigated by cyclic voltammetry and amperometry. Electrochemical experiments indicated that flexible MoS₂/rGO composite paper electrode exhibited excellent electrocatalytic activity toward the FA, which can be attributed to excellent electrical conductivity and high specific surface area of the MoS₂/rGO paper. The resulting biosensor showed highly sensitive amperometric response to FA with a wide linear range.     

Hybrid Fibers Made of Molybdenum Disulfide,Reduced Graphene Oxide,and Multi‐Walled Carbon Nanotubes for Solid‐State,Flexible, Asymmetric Supercapacitors

One of challenges existing in fiber‐based supercapacitors is how to achieve high energy density without compromising their rate stability. Owing to their unique physical, electronic, and electrochemical properties, two‐dimensional (2D) nanomaterials, e.g., molybdenum disulfide (MoS₂) and graphene, have attracted increasing research interest and been utilized as electrode materials in energy‐related applications. Herein, by incorporating MoS₂ and reduced graphene oxide (rGO) nanosheets into a well‐aligned multi‐walled carbon nanotube (MWCNT) sheet followed by twisting, MoS₂‐rGO/MWCNT and rGO/MWCNT fibers are fabricated, which can be used as the anode and cathode, respectively, for solid‐state, flexible, asymmetric supercapacitors. This fiber‐based asymmetric supercapacitor can operate in a wide potential window of 1.4 V with high Coulombic efficiency, good rate and cycling stability, and improved energy density.     

Preparation of MoS2‐graphene Hybrid Nanosheets and Simultaneously Electrochemical Determination of Levodopa and Uric Acid

MoS₂ nanoflakes were prepared by exfoliating commercial MoS₂ powders with the assistance of ultrasound and graphene foam was synthesized by chemical vapor deposition using nickel foam as the template. MoS₂‐graphene hybrid nanosheets were developed through the combination of MoS₂ nanoflakes and graphene nanosheets by ultrasonic dispersion. The hybrid nanosheets were sprayed onto the ITO coated glass, which acts as an electrode for the simultaneously electrochemical determination of levodopa and uric acid. The MoS₂‐graphene hybrid nanosheets were characterized by scanning electron microscopy, X‐ray diffraction and Raman spectroscopy. The results show that the hybrid nanosheets are composed of MoS₂ and graphene with a sheet‐like morphology. The sensitivity of the electrode for levodopa and uric acid is 0.36 μA μM⁻¹ and 0.39 μA μM⁻¹, respectively. The electrode also shows low limit of detection, good selectivity, reproducibility and stability. And it is potential for use in clinical research.     

Hybrid Fibers Made of Molybdenum Disulfide,Reduced Graphene Oxide,and Multi‐Walled Carbon Nanotubes for Solid‐State,Flexible, Asymmetric Supercapacitors

One of challenges existing in fiber‐based supercapacitors is how to achieve high energy density without compromising their rate stability. Owing to their unique physical, electronic, and electrochemical properties, two‐dimensional (2D) nanomaterials, e.g., molybdenum disulfide (MoS₂) and graphene, have attracted increasing research interest and been utilized as electrode materials in energy‐related applications. Herein, by incorporating MoS₂ and reduced graphene oxide (rGO) nanosheets into a well‐aligned multi‐walled carbon nanotube (MWCNT) sheet followed by twisting, MoS₂‐rGO/MWCNT and rGO/MWCNT fibers are fabricated, which can be used as the anode and cathode, respectively, for solid‐state, flexible, asymmetric supercapacitors. This fiber‐based asymmetric supercapacitor can operate in a wide potential window of 1.4 V with high Coulombic efficiency, good rate and cycling stability, and improved energy density.     

Mussel‐inspired decoration of Ni(OH)2 nanosheets on 2D MoS2 towards enhancing thermal and flame retardancy properties of poly(lactic acid)

In the present work, a facile and environmental method was developed to fabricate the novel functionalized MoS₂ hybrid. Firstly, MoS₂ nanosheets were coated with polydopamine (PDA) through the self‐polymerization of dopamine (MoS₂‐PDA) in a buffer solution. Then the decoration of Ni(OH)₂ on the MoS₂‐PDA was synthesized because of the strong affinity of Ni²⁺ with hydroxyl groups in PDA. Finally, the as‐synthesized MoS₂‐PDA@Ni(OH)₂ was introduced into poly(lactic acid) (PLA) matrix to explore flame retardancy, thermal stability, and crystalline property of the composites. As confirmed by X‐ray diffraction (XRD), Fourier‐transform infrared spectrometer (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA), the MoS₂ nanosheets were dually modified with PDA and Ni(OH)₂ without destroying the original structures. The thermal degradation of PLA with MoS₂‐PDA@Ni(OH)₂ generated a notably higher yield of char. Moreover, the crystallization rate of composites is higher than neat PLA. The cone calorimeter test revealed that the introduction of 3% MoS₂‐PDA@Ni(OH)₂ resulted in lower Peak Heat Release Rate (PHRR) (decreased by 21.7%). Thus, the research provided an innovative functionalization method for manufacturing PLA composites with high performances.     

Covalent Assembly of MoS2 Nanosheets with SnS Nanodots as Linkages for Lithium/Sodium‐Ion Batteries

Weak van der Waals interactions between interlayers of two‐dimensional layered materials result in disabled across‐interlayer electron transfer and poor layered structural stability, seriously deteriorating their performance in energy applications. Herein, we propose a novel covalent assembly strategy for MoS₂ nanosheets to realize unique MoS₂/SnS hollow superassemblies (HSs) by using SnS nanodots as covalent linkages. The covalent assembly based on all‐inorganic and carbon‐free concept enables effective across‐interlayer electron transfer, facilitated ion diffusion kinetics, and outstanding mechanical stability, which are evidenced by experimental characterization, DFT calculations, and mechanical simulations. Consequently, the MoS₂/SnS HSs exhibit superb rate performance and long cycling stability in lithium‐ion batteries, representing the best comprehensive performance in carbon‐free MoS₂‐based anodes to date. Moreover, the MoS₂/SnS HSs also show excellent sodium storage performance in sodium‐ion batteries.     

Hydrothermal exfoliated molybdenum disulfide nanosheets as anode material for lithium ion batteries

Ultrathin MoS2nanosheets were prepared in high yield using a facile and effective hydrothermal intercalation and exfoliation route. The products were characterized in detail using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. The results show that the high yield of MoS2nanosheets with good quality was successfully achieved and the dimensions of the immense nanosheets reached 1 μm–2 μm. As anode material for Li-ion batteries, the as-prepared MoS2nanosheets electrodes exhibited a good initial capacity of 1190 mAh g-1and excellent cyclic stability at constant current density of 50 mA g-1. After 50 cycles, it still delivered reversibly sustained high capacities of 750 mAh g-1.     

High‐Resolution Electrochemical Mapping of the Hydrogen Evolution Reaction on Transition‐Metal Dichalcogenide Nanosheets

High‐resolution scanning electrochemical cell microscopy (SECCM) is used to image and quantitatively analyze the hydrogen evolution reaction (HER) catalytically active sites of 1H‐MoS₂ nanosheets, MoS₂, and WS₂ heteronanosheets. Using a 20 nm radius nanopipette and hopping mode scanning, the resolution of SECCM was beyond the optical microscopy limit and visualized a small triangular MoS₂ nanosheet with a side length of ca. 130 nm. The electrochemical cell provides local cyclic voltammograms with a nanoscale spatial resolution for visualizing HER active sites as electrochemical images. The HER activity difference of edge, terrace, and heterojunction of MoS₂ and WS₂ were revealed. The SECCM imaging directly visualized the relationship of HER activity and number of MoS₂ nanosheet layers and unveiled the heterogeneous aging state of MoS₂ nanosheets. SECCM can be used for improving local HER activities by producing sulfur vacancies using electrochemical reaction at the selected region.     

Self‐Optimization of the Active Site of Molybdenum Disulfide by an Irreversible Phase Transition during Photocatalytic Hydrogen Evolution

The metallic 1T‐MoS₂ has attracted considerable attention as an effective catalyst for hydrogen evolution reactions (HERs). However, the fundamental mechanism about the catalytic activity of 1T‐MoS₂ and the associated phase evolution remain elusive and controversial. Herein, we prepared the most stable 1T‐MoS₂ by hydrothermal exfoliation of MoS₂ nanosheets vertically rooted into rigid one‐dimensional TiO₂ nanofibers. The 1T‐MoS₂ can keep highly stable over one year, presenting an ideal model system for investigating the HER catalytic activities as a function of the phase evolution. Both experimental studies and theoretical calculations suggest that 1T phase can be irreversibly transformed into a more active 1T′ phase as true active sites in photocatalytic HERs, resulting in a “catalytic site self‐optimization”. Hydrogen atom adsorption is the major driving force for this phase transition.     

二硫化钼纳米片/碳纳米纤维杂化材料的制备及其析氢性能

以碳纳米纤维(CNFs)作为负载基体和反应器采用静电纺丝技术和碳化工艺生长和调控二硫化钼(MoS_2)纳米片。通过改变前驱体溶液浓度来调控纳米片的形貌和结构,利用MoS_2纳米片的高催化活性和CNFs高比表面积、良好的稳定性以及高电导率的协同作用,研究不同形貌和结构的杂化纳米材料在电催化析氢方面的应用,探索杂化材料形貌与性能之间的潜在规律。运用多种分析测试技术对制备得到的纳米杂化材料进行表征,并对所制备的MoS_2/CNFs杂化材料的电催化析氢性能(HER)进行研究,研究表明近似皮芯结构的MoS_2/CNFs-10杂化材料的电催化析氢性能最好,初始析氢过电位在220 mV,Tafel斜率为110m V·dec~(-1)。     

二硫化钼纳米片/碳纳米纤维杂化材料的制备及其析氢性能

以碳纳米纤维（CNFs）作为负载基体和反应器采用静电纺丝技术和碳化工艺生长和调控二硫化钼（MoS₂）纳米片。通过改变前驱体溶液浓度来调控纳米片的形貌和结构,利用MoS₂纳米片的高催化活性和CNFs高比表面积、良好的稳定性以及高电导率的协同作用,研究不同形貌和结构的杂化纳米材料在电催化析氢方面的应用,探索杂化材料形貌与性能之间的潜在规律。运用多种分析测试技术对制备得到的纳米杂化材料进行表征,并对所制备的MoS₂/CNFs杂化材料的电催化析氢性能（HER）进行研究,研究表明近似皮芯结构的MoS₂/CNFs-10杂化材料的电催化析氢性能最好,初始析氢过电位在220 mV,Tafel斜率为110 mV·dec^-1。     

Ag3PO4/MoS2纳米片复合催化剂制备及可见光催化性能

采用机械球磨法成功制备Ag₃PO₄/MoS₂纳米片复合催化剂。运用X射线衍射仪（XRD）、透射电子显微镜（TEM）、扫描电子显微镜（SEM）、紫外可见漫反射光谱（UV-Vis）和荧光发射光谱（PL）对复合催化剂的结构和形貌进行了表征。结果表明,Ag₃PO₄纳米粒子均匀地附着在MoS₂纳米片层结构上,两者形成紧密结合。以亚甲基蓝为模拟污染物,研究复合催化剂在可见光照射下的光催化特性;通过循环实验考察复合催化剂的稳定性。结果显示,含有1%的MoS₂纳米片与Ag₃PO₄形成的复合催化剂在30 min内对亚甲基蓝的降解率为95%,其降解动力学常数是纯相Ag₃PO₄的2倍。经过5次循环实验后复合催化剂对于亚甲基蓝的降解率为84%,而纯Ag₃PO₄对于亚甲基蓝的降解率仅为35%。Ag₃PO₄/MoS₂纳米片复合催化剂具有优良的光催化活性和高稳定性,主要归因于二硫化钼纳米片与磷酸银形成异质结,磷酸银激发的电子和二硫化钼纳米片产生的空穴直接复合,从而促使光生电子从磷酸银晶体表面快速分离,减轻了磷酸银的光电子腐蚀,同时也提高了复合物的光催化活性。     

Ag_3PO_4/MoS_2纳米片复合催化剂制备及可见光催化性能

采用机械球磨法成功制备Ag_3PO_4/MoS_2纳米片复合催化剂。运用X射线衍射仪(XRD)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、紫外可见漫反射光谱(UV-Vis)和荧光发射光谱(PL)对复合催化剂的结构和形貌进行了表征。结果表明,Ag_3PO_4纳米粒子均匀地附着在MoS_2纳米片层结构上,两者形成紧密结合。以亚甲基蓝为模拟污染物,研究复合催化剂在可见光照射下的光催化特性;通过循环实验考察复合催化剂的稳定性。结果显示,含有1%的MoS_2纳米片与Ag_3PO_4形成的复合催化剂在30 min内对亚甲基蓝的降解率为95%,其降解动力学常数是纯相Ag_3PO_4的2倍。经过5次循环实验后复合催化剂对于亚甲基蓝的降解率为84%,而纯Ag_3PO_4对于亚甲基蓝的降解率仅为35%。Ag_3PO_4/MoS_2纳米片复合催化剂具有优良的光催化活性和高稳定性,主要归因于二硫化钼纳米片与磷酸银形成异质结,磷酸银激发的电子和二硫化钼纳米片产生的空穴直接复合,从而促使光生电子从磷酸银晶体表面快速分离,减轻了磷酸银的光电子腐蚀,同时也提高了复合物的光催化活性。     

Electrospun nanofibers of ZnO‐TiO2 hybrid: characterization and potential as an extracellular scaffold for supporting myoblasts

One‐dimensional nanofibers have attracted tremendous attention because of their potential applications. Electrospinning technology enables industrial production of these nanofibers. This study aims to fabricate one‐dimensional ZnO doped TiO₂ by electrospinning and to characterize these hybrid nanofibers. The nanocomposite was prepared using colloidal gel composed of zinc nitrate, titanium isopropoxide and polyvinyl acetate. X‐ray diffraction, energy dispersive x‐ray analysis and transmission electron microscopy analysis confirmed the purity and crystalline nature of this material, whereas the diameter of these nanofibres estimated from scanning electron microscope (SEM), field emission SEM and transmission electron microscopy are between 200 and 300 nm. Cell counting with Kit‐8 assay at regular time intervals and phase‐contrast microscopy data revealed that C2C12 cells proliferated well on ZnO/TiO₂ nanofibers between 1 and 10 µg/ml, and cellular attachments are visible by SEM. The nanostructured ZnO/TiO₂ hybrid nanofibers show higher cell adhesion, proliferation and spreading behavior compared with the titanium substrate and control. Our study suggests that ZnO/TiO₂ nanofibers could potentially be used in tissue engineering applications. The scalability, low cost, reproducibility and high‐throughput capability of this technology is potentially beneficial to examine and optimizing a wide array of cell‐nanofiber systems prior to in vivo experiments. Copyright © 2013 John Wiley & Sons, Ltd.     

Enhanced Photocatalytic Hydrogen Evolution over Hierarchical Composites of ZnIn2S4 Nanosheets Grown on MoS2 Slices

A highly active hierarchical MoS₂/ZnIn₂S₄ composite catalyst was synthesized in situ by using a facile controlled‐growth approach through a solvothermal process. During the solvothermal reaction, 2D ultrathin curled ZnIn₂S₄ nanosheets grew on the surface of MoS₂ slices, which could help to form a more‐homogeneous mixture, effective interfacial contact, and strong interactions between the ZnIn₂S₄ nanosheets and the MoS₂ slices. The intimate contact between ZnIn₂S₄ and MoS₂ favored the formation of junctions between the two components, thereby improving the charge separation and prolonging the mean lifetime of the electron–hole pairs. Moreover, growing ZnIn₂S₄ nanosheets by visible‐light catalysis on MoS₂ slices afforded a higher number of available catalytically active sites. So, the photocatalytic hydrogen‐evolution performance of the hierarchical MoS₂/ZnIn₂S₄ composite was significantly enhanced, owing to a synergistic effect of these factors. This work could provide new insights into the fabrication of a highly efficient and low‐cost non‐noble‐metal co‐catalyst for visible‐light H₂ generation.     

A millimeter-sized negatively charged polymer embedded with molybdenum disulfide nanosheets for efficient removal of Pb(II) from aqueous solution

Molybdenum disulfide (MoS₂) has excellent trapping ability for lead ions whereas its micro-/nanoscale size has greatly impeded its practical applications in the flow-through systems. Herein, a millimeter-sized nanocomposite MoS2?001 was synthesized for Pb²⁺ removal by loading MoS₂ nanosheets into a polystyrene cation exchanger D-001 by a facile hydrothermal method. The proposed structure and adsorption mechanism of MoS₂?001 was confirmed by the scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. The nanocomposite showed outstanding adsorption capacity and rapid adsorption kinetic for Pb²⁺ removal, and the adsorption behavior followed the Langmuir adsorption model and pseudo-first-model kinetic model. Pb²⁺ uptake by MoS₂?001 still maintains a high level even in the presence of extremely highly competitive ions (Ca(II) and Mg(II)), suggesting its high selectivity for Pb²⁺ adsorption. Besides, the fixed-bed column experiments further certified that MoS₂?001 is of great potential for Pb²⁺ removal from the wastewater in practical engineering applications. Even more gratifying is that the exhausted MoS₂?001 can be regenerated by NaCl-EDTANa₂ solution without any significant adsorption capacity loss. Consequently, all the results indicated that MoS₂?001 is a promising candidate adsorbent for lead-containing wastewater treatment.     

Silk Fibroin Combined with Electrospinning as a Promising Strategy for Tissue Regeneration

The development of tissue engineering scaffolds is of great significance for the repair and regeneration of damaged tissues and organs. Silk fibroin (SF) is a natural protein polymer with good biocompatibility, biodegradability, excellent physical and mechanical properties and processability, making it an ideal universal tissue engineering scaffold material. Nanofibers prepared by electrospinning have attracted extensive attention in the field of tissue engineering due to their excellent mechanical properties, high specific surface area, and similar morphology as to extracellular matrix (ECM). The combination of silk fibroin and electrospinning is a promising strategy for the preparation of tissue engineering scaffolds. In this review, the research progress of electrospun silk fibroin nanofibers in the regeneration of skin, vascular, bone, neural, tendons, cardiac, periodontal, ocular and other tissues is discussed in detail.     

Side‐Chain‐Directed Dispersion of MoS2 Nanosheets by V‐Shaped Polyaromatic Compounds

Bulk molybdenum disulfide (MoS₂) itself is virtually insoluble in common organic solvents because of the tight stacks of multiple MoS₂ nanosheets. Here we report that V‐shaped polyaromatic compounds with non‐ionic side chains can efficiently exfoliate and disperse the inorganic nanosheets. Simple grinding and sonication (less than total 1 h) of MoS₂ powder with the V‐shaped compounds gave rise to large MoS₂ nanosheets highly dispersed in NMP through efficient host‐guest S–π interactions. DLS and AFM analyses revealed that the lateral sizes (ca. 150–270 nm) and thicknesses (ca. 2–8 nm) of the products depend on the identity of the non‐ionic side chains on the V‐shaped dispersant.     

A Direct Hybridization between Isocharged Nanosheets of Layered Metal Oxide and Graphene through a Surface‐Modification Assembly Process

An efficient and universal method to directly hybridize isocharged nanosheets of layered metal oxide and reduced graphene oxide (rGO) is developed on the basis of the surface modification and an electrostatically driven assembly process. On the basis of this synthetic method, the CoO₂–rGO nanocomposite can be synthesized with exfoliated CoO₂ and rGO nanosheets, and transformed into CoO–CoO₂–rGO nanocomposites with excellent electrode performance for lithium‐ion batteries. Also, this surface‐modification assembly route is successfully applied for the synthesis of another mesoporous TiO₂–rGO nanocomposite. This result provides clear evidence for the usefulness of the present method as a universal way of hybridizing isocharged anionic nanosheets of inorganic solids and graphene.