Nanocrystalline Cellulose Supported MnO2 Composite Materials for High-Performance Lithium-Ion Batteries.

The rate capability and poor cycling stability of lithium-ion batteries (LIBs) are predominantly caused by the large volume expansion upon cycling and poor electrical conductivity of manganese dioxide (MnO2), which also exhibits the highest theoretical capacity among manganese oxides. In this study, a nanocomposite of nanosized MnO2 and pyrolyzed nanocrystalline cellulose (CNC) was prepared with high electrical conductivity to enhance the electrochemical performance of LIBs. The nanocomposite electrode showed an initial discharge capacity of 1302 mAh g-1 at 100 mA g-1 and exhibited a high discharge capacity of 305 mAh g-1 after 1000 cycles. Moreover, the MnO2-CNC nanocomposite delivered a good rate capability of up to 10 A g-1 and accommodated the large volume change upon repeated cycling tests.

Ni-Co-B nanoparticle decorated carbon felt by electroless plating as a bi-functional catalyst for urea electrolysis.

A free-standing catalyst electrode for urea electrolysis was synthesized by electroless plating of NiCoB alloy onto a flexible carbon felt. The synthesized NiCoB@C catalyst exhibited porous and partially amorphous metallic structure depending on its composition, as analysed by XRD, XPS, and TEM; thus, NiCoB@C catalyst showed a high catalytic activity for urea oxidation reaction as well as hydrogen evolution reaction. The required cell voltage in the electrolysis cell with NiCoB@C as anode and cathode was as low as 1.34 V for the current densities 10 mA cm-2. Similar performance of the urea electrolysis for H2 production using 0.33 M urea and a fresh urine in 1 M KOH was observed. The result indicated that NiCoB could be incorporated on to carbon felt by electroless plating, and it could be used as free-standing bifunctional electrodes for urea electrolysis using urea as well as urine.

Polypyrrole/Graphene Quantum Dot Composites as a Sensor Media for Epinephrine.

In this paper, we discuss a new biosensor for simple and rapid detection of epinephrine (EP) based on polypyrrole/graphene quantum dot (PPy/GQD) composites. Presence of amine groups on the PPy backbone leads to surface passivation of GQDs. As a result, the composites exhibit strong fluorescence emission, which can be up to three times that of pristine GQDs. In neutral to alkaline solution, the EP on the surface of PPy/GQD composites is converted to a quinone, which triggers the fluorescence quenching of PPy/GQD composites via a photoinduced electron transfer process. Hence, the concentration of EP can be effectively monitored by measuring the variation in the fluorescence signal of PPy/GQD composites. The quenched fluorescence intensity of PPy/GQDs was proportional to the concentration of EP (0.7-400 µM). We used our method to determine the concentration of EP in human serum samples and obtained satisfactory results.