As simple and ubiquitous redox-active
organic molecules, quinones
participate in diverse electron transfer processes in chemistry and
biological systems for energy transformation and signal transduction.
We introduce here a practical exercise to study the redox potentials
of benzoquinone and its two derivatives by combining the electrochemistry
method with quantum chemistry computation. The practical reduction
potentials of three quinones were measured by cyclic voltammetry experiment.
Quantum chemistry computation, on the other hand, provided theoretical
Gibbs free energy change and reduction potentials of the three quinones,
which were found to be in line with the experimental results. Detailed
thermodynamic energy analysis based on the computation results revealed
that the reduction Gibbs free energy changes of the three quinones
were mainly contributed from the electronic energies change of the
molecules, while thermal energy and entropy played a relatively minor
role. The energy levels of the lowest unoccupied molecular orbital
(LUMO) of the three quinones, which were modulated by substituent
groups and conjugation structures, were further identified as the
main origin of the reduction potential. This experiment provides practical
and theoretical training on the fundamental ideas involved in major
courses like thermodynamics, quantum chemistry, electrochemistry,
and organic chemistry, and promotes students to find the tie between
macroscopic redox properties of chemicals and their microscopic molecular
structures, a key topic in chemistry education.
Ordered high surface area microporous carbon molecular sieves containing well-dispersed platinum nanoparticles have been prepared by chemical vapor deposition method. Acetonitrile was employed as carbon and nitrogen precursors to yield N-doped carbon molecular sieves. N-doped carbons have an average nitrogen content of ~ 4.1 wt%. Electrochemical tests showed that the rectangular-shaped CVs of N-doped carbons could be well retained over a wide range of scan rates (5~100 mV/s), and the CV curves presented a steep current change at the switching potentials. N-doped carbons exhibited excellent performance as an electrochemical supercapacitor with a calculated specific capacitance of 168 F/g. Meanwhile, it was noticed that a reasonable Pt loading would help to improve the capacitance. It was proposed that the polarizability or surface state modification by nitrogen doping and regular interconnected porous structure might contribute to the improvement of N-doped carbons’ electrochemical properties.
The glycerides of castor oil (GCO) were copolymerized with isophorone diisocyanate (IPDI) to generate glyceride-based polyurethane (GCPU), meanwile blending with hydroxyapatite (HA) powder to fabricate porous composite scaffolds. The effect of HA content on mechanical properties of the resulting polymer scaffolds and the in vitro cell response of HA/GCPU scaffolds were investigated, by use of mechanical testing, FTIR, SEM and MTT assay. The results showed that the compressive strength increased with HA content, and the HA/GCPU scaffold with 40 wt% HA reached about 4.6 MPa, much higher than the scaffold without HA (only 605 kPa). The SEM observation, live-dead staining assay and MTT assay demonstrated the excellent biological properties of HA/GCPU scaffolds, which support cell adhesion and proliferation. This novel class of HA/GCPU porous scaffolds have prospect and advantage for bone repair and regeneration.
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