Adhesive hydrogels for bioelectronics

Benefiting from the unique advantages of superior biocompatibility,strong stability,good biodegradability,and adjustable mechanical properties,hydrogels have attracted extensive research interests in bioelectronics.However,due to the existence of an interface between hydrogels and human tissues,the transmission of electrical signals from the human tissues to the hydrogel electronic devices will be hindered.The adhesive hydrogels with adhesive properties can tightly combine with the human tissue,which can enhance the contact between the electronic devices and human tissues and reduce the contact resistance,thereby improving the performance of hydrogel electronic devices.In this review,we will discuss in detail the adhesion mechanism of adhesive hydrogels and elaborate on the design principles of adhesive hydrogels.After that,we will introduce some methods of performance evaluation for adhesive hydrogels.Finally,we will provide a perspective on the development of adhesive hydrogel bioelectronics.

Anti-corrosion mechanism of epoxy-resin and different content Fe2O3 coatings on magnesium alloy

In this study, anti-corrosion coatings were prepared and coated success- fully on magnesium alloy substrates by mixing nanopowders, solvent, curing agent with epoxy resin. The effect of the amount of iron trioxide （Fe2O3） on the adhesion strength and corrosion resistance on magnesium alloy was investigated with standard protocols, and electrochemical measurements were also made in 3.5 wt.% NaCl solutions. The surface morphology and corrosion mechanism after corrosion tests was characterized using FESEM analysis. Nanoparticies in matrix acted as filler, and interstitial cross-linked spaces and other coating artifacts regions （micro cracks and voids） would all affect the anti-corrosion properties of coating. The results showed the proper powder content not only provided adhesion strength to these coatings but also improved obviously their anticorrosion. Hydrogen bound to the amine nitrogen （1N） could take part in the curing process rather than hydrogen of the amide site due to the smaller AG and the more stable configuration.

Hollow carbon spheres and their noble metal-free hybrids in catalysis

Hollow carbon spheres have garnered great interest owing to their high surface area,large surface-tovolume ratio and reduced transmission lengths.Herein,we overview hollow carbon sphere-based materials and their noble metal-free hybrids in catalysis.Firstly,we summarize the key fabrication techniques for various kinds of hollow carbon spheres,with a particular emphasis on controlling pore structure and surface morphology,and then heterogeneous doping as well as their metal-free/containing hybrids are presented;next,possible applications for non-noble metal/hollow carbon sphere hybrids in the area of energy-related catalysis,including oxygen reduction reaction,hydrogen evolution reaction,oxygen evolution reaction,water splitting,rechargeable Zn-air batteries and pollutant degradation are discussed;finally,we introduce the various challenges and opportunities offered by hollow carbon spheres from the perspective of synthesis and catalysis.

Miscibility and Isothermal Crystallization of Poly(L-lactide) and Poly(trimethylene carbonate) Blends

Miscibility, isothermal crystallization kinetics, and morphology of poly（L-lactide）/poly（trimethylene carbonate） （PLLA/PTMC） crystalline/amorphous blends were studied by differential scanning calorimetry （DSC） and optical microscopy （OM）. The heterogeneity of OM images and an unchanged glass transition temperature showed that PLLA was immiscible with PTMC. During isothermal crystallization, the crystallization rate of PLLA improved when the PTMC content was low （≤ 20%）. However, when the PTMC content was high （≥ 30%）, the crystallization rate decreased significantly. The reason of these nonlinear changes in crystal kinetics was analyzed according to the nucleation and growth process by virtue of a microscope heating stage. The isothermal crystallization morphologies of the blends were also studied by polarized optical microscopy and the results confirmed the conclusions obtained from crystallization kinetics.

Effects of Functionalized Graphenes on the Isothermal Crystallization of Poly(L-lactide) Nanocomposites

The effects of graphene oxide（GO） with polar groups and functionalized GO（f GO） with nonpolar groups on the isothermal crystallization of poly（L-lactide）（PLLA） were compared. Functionalized GO was obtained by grafting octadecylamine and characterized by FTIR, WAXD and TGA. Isothermal crystallization kinetics of PLLA/GO and PLLA/f GO nanocomposites were investigated by combining DSC data and Avrami equation. The results showed that f GO could improve PLLA crystallization rate more obviously than GO. By analyzing the morphology obtained from POM, SEM and TEM, it was found f GO with large layer space dispersed better in PLLA and supplied more nucleation sites than GO. Therefore, for the multilayer graphene, increasing the layer spaces is important to improve its dispersion in polymers, which will cause the crystal kinetics changing of polymers.

Size-controllable synthesis of monodispersed nitrogen-doped carbon nanospheres from polydopamine for high-rate supercapacitors

Monodispersed nitrogen-doped carbon nanospheres with tunable particle size(100-230 nm)were synthesized via self-polymerization of biochemical dopamine in the presence of hexamethylenetetramine as a buffer and F127 as a size controlling agent.Hexamethylenetetramine can mildly release NH3,which in turn initiates the polymerization reaction of dopamine.The carbon nanospheres obtained exhibited a significant energy storage capability of 265 F·g^(-1)at 0.5 A·g^(-1)and high-rate performance of 82%in 6 mol·L^(-1)KOH(20 A·g^(-1)),which could be attributed to the presence of abundant micromesoporous structure,doped nitrogen functional groups and the small particle size.Moreover,the fabricated symmetric supercapacitor device displayed a high stability of 94%after 5000 cycles,revealing the considerable potential of carbon nanospheres as electrode materials for energy storage.