Hang Liu

Ionic liquid-assisted exfoliation of graphite oxide for simultaneous reduction and functionalization to graphenes with improved properties

A novel one-step approach for the pH-triggered electrochemically interacted exfoliation of graphene sheets in graphite oxide and simultaneous reduction and functionalization with the aid of the ionic liquid is reported. The developed method shows significant advantages over the conventional functionalized/chemically reduced graphene. Particularly, for the first time, no additional stabilizer or modifier is needed to stabilize the resulting processible graphene dispersion. The prepared graphene oxide and its functionalized graphene are characterized by SEM, TEM, FTIR, UV-vis, XRD, Raman, XPS, and NMR. The results indicate that, with the aid of the IL during the reaction, the resulting functionalized graphene shows improved organophilicity, good wettability and improved interfacial interactions as well as significant resistance to thermal degradation. The methodology paves a new way for use of the IL as a processing aid and reaction medium to promote chemical functionalization of graphene through the electrochemically interacted exfoliation of graphene sheets and can be expected to provide a new approach with great promise for its organophilic wettability and enhanced interfacial adhesion as well as improved thermal stability. Furthermore, the controlled modifications of graphene nanoreinforcements can also be expected to alter the nature of the interactions between components.

Exploration of AgNW/PU nanoweb as ECG textile electrodes and comparison with Ag/AgCl electrodes

This study aims to measure ECG signals by the AgNW/PU nanoweb electrodes, and, to compare with signals measured by the conventional Ag/AgCl electrodes. Finally, to investigate the usage potential of the AgNW/PU nanoweb as ECG textile electrodes. The ECG textile electrodes were fabricated, using the polyurethane (PU) nanoweb (Pardam, s.r.o., Czech Republic) coated with 1 wt% of silver nanowires (AgNW) dispersed in ethanol (KLK Co., Korea). To measure the ECG signals, eight participants (Male:Female=1:1) were collected, and then, the signals were measured at rest-state and stress-state in anechoic chamber using Lead I method. From the measured ECG signals, heart rate (HR) and R-R intervals were acquired by using MP150 (Biopac system Inc., USA) and Acqknowledge (ver. 4.2, Biopac system Inc., USA), and then, analyzed by using Kubios HRV (ver. 2.0., Biosignal Analysis and Medical Imaging Group, Finland). To examine the morphology of the signals, direct visual evaluation was performed. Also, to statistically compare to the signals, Wilcoxon signed-rank test was conducted by using R statistical language and RStudio (1.0.143 ver., RStudio, Inc., USA). As a result, the ECG waveforms measured by the two different types of electrodes looked similar, especially, QRS-complex, P-wave and T-wave as well as R-peaks properly appeared. Also, there was not a significant difference of HR and RR-intervals measured by the two different types of electrodes. It demonstrated that the new AgNW/PU nanoweb electrodes could perform properly as ECG electrodes.

Preparation of a lignin-based vitrimer material and its potential use for recoverable adhesives

A fully biobased vitrimer material with high lignin content is demonstrated. Ozone treated Kraft lignin is cured with sebacic acid epoxy to form bond-exchangeable crosslinked networks. The biobased vitrimer shows excellent shape memory and repairing properties at elevated temperatures. By taking advantage of these features, a promising recoverable adhesive is also demonstrated.

Eco-Friendly Post-Consumer Cotton Waste Recycling for Regenerated Cellulose Fibers

In this study, post-consumer cotton waste was chemically recycled to produce regenerated fibers using eco-friendly alkaline/urea solvent systems. Both white and colored cotton waste was shredded and hydrolyzed using sulfuric acid to reduce the molecular weight of the cotton fibers. Two solvent systems, i.e., sodium hydroxide/urea and lithium hydroxide/urea, were used to dissolve the hydrolyzed cotton to prepare solutions for fiber regeneration by wet spinning. The diameter, morphology, thermal properties, crystallinity, and tensile properties of the regenerated fibers were characterized by SEM, TGA, XRD, and tensile testing. Results showed that, using this recycling method, fibers with tensile properties comparable to current commercial regular rayon fibers made from wood pulp could be produced, and dyes in the original cotton waste could be conserved to produce fibers with intrinsic colors, thus eliminating the need for dyeing processes. This study demonstrated an economical upcycling method for post-consumer cotton waste with environmentally friendly solvents.