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In the present work, the enhancement in the efficiency of commercial solar cells through the use of Al2O3/ SiNPs multilayer antireflecting coating, is reported. The Al2O3 coatings were deposited by the atomic layer deposition technique, while the silicon nanoparticles were synthesized using a water-dispersible methodology. Based on photoluminescence and absorbance studies of the SiNPs, the underlying mechanism for this improvement can be attributed to the luminescent down-shifting effect. Thermoluminescence studies were achieved to confirm the formation of the Al2O3 layer. The thickness of the Al2O3 thin films were determined by spectroscopic ellipsometry in a range of 25 to 30 nm, while a SiNPs size of approximately 3 nm was obtained using dynamic light scattering method. The coatings of Al2O3 with SiNPs nanoparticles were deposited over solar cells to study their efficiency enhancement. Under a simulated one-sun illumination, coated solar cells achieved an enhancement of 6.74 mA/cm2, in short-circuit current density; while a 54.9% in power conversion efficiency increase was achieved, relative to those obtained for a pristine cell. The results show that the efficiency of solar cells can be significantly increased by combining the downshifting effect of the Si nanoparticles and the antireflective properties of the Al2O3 films. [ABSTRACT FROM AUTHOR]

This work reports the tribological assessment of ceria (CeO2) nanoparticles supported on multiwalled carbon nanotubes as water-based lubricant additives. Crystalline multiwalled carbon nanotubes (MWCNTs) were obtained by a spray pyrolysis method using alpha-pinene, a renewable feedstock, as carbon source and ferrocene as catalyst. CeO2 nanoparticles with an average diameter of ~ 1.7 nm homogenously distributed on the MWCNTs were synthetized using a microwave-assisted method. MWCNTs at 0.10 wt% and CeO2/MWCNTs composite at 0.10, 0.05 and 0.01 wt% concentrations were completely dispersed in water. Tribological tests were carried out in a commercial pin-on-disk tribometer at an operating load of 10 N for 1 h in steel–steel contacts. The results indicate that CeO2/MWCNTs composite can reduce friction and wear at the proper concentration. The lowest coefficient of friction (~ 0.11) was observed at 0.10 wt%, which represents a 74.4% reduction with respect to pure water. A 39.8% wear reduction was obtained at a 0.05 wt% concentration. The synergistic effect of CeO2 nanoparticles and MWCNTs promotes the formation of a tribofilm consisting of highly aligned graphene layer inside the wear tracks. [ABSTRACT FROM AUTHOR]

Control of the recombination process and improvement of transport charge carriers could be achieved in photocatalysts by modifying the catalytic support. In the present study, our goal was to study the effect of nitrogen doping on graphene oxide sheets using doping sources such as urea, thiourea, or ethylenediamine to produce GO-N catalytic supports which were used to form ZnO/GO-N systems. The synthesis of ZnO and GO-N was carried out through a hydrothermal process under microwave heating. The ZnO/GO-N compounds were tested to study the degradation of the lignin molecule under UV irradiation. A set of characterization techniques were used to study the ZnO/GO-N compounds, including XPS analyses which confirmed the N-doping in the samples. The ZnO compound reached 40% of lignin degradation in 70 min, while the ZnO/GO-N compound produced 79% of lignin degradation, also in 70 min evidencing the positive effect of the GO-N support. The best results of degradation were obtained when thiourea was used as the N-doping media. [ABSTRACT FROM AUTHOR]