Pd2 and CoPd dimers/N-doped graphene sensors with enhanced sensitivity for CO detection: A first-principles study.

CONTEXT: The detection and monitoring of CO gas are essential to avoid human health problems. Therefore, the CO adsorption on Pd2 and PdCo dimers deposited on pyridinic Nx-doped graphene (PNxG; x = 1 - 3) was investigated employing the auxiliary density functional theory. In the most stable arrangements for the Pd2 dimer supported on PNxG, a Pd atom is in the PNxG vacancy, and the other Pd atom is placed on C atoms. For the PdCo dimer deposited on PNxG, the most stable interaction is like Pd2 dimer supported on PNxG, but with the Co atom centered over the vacancy site. Concerning the stability of the Pd2 and PdCo dimers supported on PNxG, the interaction energies (Eint) of the PdCo dimer deposited on PNxG are higher than those obtained with the Pd2 dimer. Also, the Eint of Pd2 and PdCo dimers deposited on PNxG are higher than those supported on pristine graphene. The CO adsorption energies on Pd2/PNxG and PdCo/PNxG composites are higher than those reported in the literature for pristine graphene, showing that the Pd2/PNxG and PdCo/PNxG composites have a good sensitivity toward the CO molecule. METHODS: All electronic structure calculations were performed using the auxiliary density functional theory implemented in the deMon2k program. For exchange and correlation functional, the revised PBE was used. The Pd atoms were treated with an 18-electron QECP|SD basis set, while the remaining atoms were subjected to a DZVP-GGA basis set. The GEN-A2* auxiliary-function-set was used for all computations.

(Chitosan-g-glycidyl methacrylate)-xanthan hydrogel implant in Wistar rats for spinal cord regeneration.

This work reports the results of in vivo assays of an implant composed of the hydrogel Chitosan-g-Glycidyl Methacrylate-Xanthan [(CTS-g-GMA)-X] in Wistar rats. Degradation kinetics of hydrogels was assessed by lysozyme assays. Wistar rats were subjected to laminectomy by cutting the spinal cord with a scalpel. After the surgical procedure, hydrogels were implanted in the injured zone (level T8). Somatosensory evoked potentials (SEPs) obtained by electric stimulation onto periphery nerves were registered in the corresponding central nervous system (CNS) areas. Rats implanted with the biomaterials showed a successful recovery compared with the non-implanted rats after 30days. Lysozyme, derived from egg whites, was used for in vitro assays. This study serves as the basis for testing the biodegradability of the hydrogels (CTS-g-GMA)-X that is promoted by enzymatic hydrolysis. Hydrogels' hydrolysis was studied via lysozyme kinetics at two pH values, 5 and 7, under mechanical agitation at 37°C. Results show that our materials' hydrolysis is slower than pure CTS possibly due to the steric hindrance imposed by the GMA grafting of functionalization. This hydrolysis helps degrade the biomaterial and at the same time it provides support for spinal cord recovery. Combination of these results may prove useful in the use of these hydrogels as scaffolds for cells proliferation and their application as implants in living organisms.