Characteristics and catalytic activity in hydrogen production from formic acid of Au catalysts supported on porous N-free (Au/C) and N-doped carbon (Au/N-C) have been compared with those of Au/SiO2 and Au/Al2O3 catalysts. Among the catalysts examined, the Au/N-C catalyst showed the highest Au mass-based catalytic activity. The following trend was found at 448 K: Au/N-C > Au/SiO2 > Au/Al2O3, Au/C. The trend for the selectivity in hydrogen production was different: Au/C (99.5%) > Au/Al2O3 (98.0%) > Au/N-C (96.3%) > Au/SiO2 (83.0%). According to XPS data the Au was present in metallic state in all catalysts after the reaction. TEM analysis revealed that the use of the N-C support allowed obtaining highly dispersed Au nanoparticles with a mean size of about 2 nm, which was close to those for the Au catalysts on the oxide supports. However, it was by a factor of 5 smaller than that for the Au/C catalyst. The difference in dispersion could explain the difference in the catalytic activity for the carbon-based catalysts. Additionally, the high activity of the Au/N-C catalyst could be related to the presence of pyridinic type nitrogen on the N-doped carbon surface, which activates the formic acid molecule forming pyridinium formate species further interacting with Au. This was confirmed by density functional theory (DFT) calculations. The results of this study may assist the development of novel Au catalysts for different catalytic reactions.
Because of the unpredictable hypotensive effect and serious complications during continuous-wave cyclophotocoagulation (CW-CPC), the use of this method in the treatment of glaucoma is limited. Therefore, a new technique was developed, known as micropulse trans-scleral cyclophotocoagulation (MP-CPC). During MP-CPC, a series of short bursts of laser pulses deliver energy to the ciliary body at the near-infrared wavelength of 810 nm, which is strongly absorbed by melanin. As shown by experimental studies, there are several acting mechanisms which reduce IOP decrease during MP-CPC. In clinical studies, patients with different forms and stages of glaucoma received laser energy of similar parameters during MP-CPC. It may be concluded that MP-CPC is a safe and effective alternative to traditional CW-CPC. However if laser irradiation directed to the ciliary body during MP-CPC gets longer, the incidence of complications increases. The variation of glaucoma forms in patients who underwent MP-CPC and a relatively small number of cases involved in the studies prevent us from making an unambiguous recommendation of this technique at the moment. An extensive research of the technique is required.
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