Carbon quantum dots as a dual platform for the inhibition and light-based destruction of collagen fibers: implications for the treatment of eye floaters.

Common in myopia and aging, vitreous opacities arise from clumped collagen fibers within the vitreous body that cast shadows on the retina, appearing as 'floaters' to the patient. Vitreous opacities degrade contrast sensitivity function and can cause significant impairment in vision-related quality-of-life, representing an unmet and underestimated medical need. One therapeutic approach could be the use of versatile light-responsive nanostructures which (i) interfere with the formation of collagen fibers and/or (ii) destroy aggregates of vitreous collagen upon pulsed-laser irradiation at low fluences. In this work, the potential of positively and negatively charged carbon quantum dots (CQDs) to interfere with the aggregation of type I collagen is investigated. We demonstrate that fibrillation of collagen I is prevented most strongly by positively charged CQDs (CQDs-2) and that pulsed-laser illumination allowed to destroy type I collagen aggregates and vitreous opacities (as obtained from patients after vitrectomy) treated with CQDs-2.

On the local order of amorphous La2Mo2O6.7.

The amorphous reduction product of the oxide ion conductor La2Mo2O9 was previously shown to be a good, sulphur-tolerant, anode material for solid oxide fuel cell devices (X. C. Lu, J. H. Zhu, J. Electrochem. Soc., 2008, 155(10), B1053). In this paper, we study the local order of amorphous La2Mo2O6.7 using X-ray absorption spectroscopy analyses and electronic paramagnetic resonance. The extended X-ray absorption fine structure analysis of local arrangements around Mo in La2Mo2O6.7 is first carried out on the basis of strong distortions from three crystalline models of La2Mo2O9, La7Mo7O30 and La2Mo2O7. The extended X-ray absorption fits obtained from both La2Mo2O9 and La7Mo7O30 yield similar atomic arrangements in the amorphous phase, upon large atomic displacements. However it is also possible to fit the spectrum using the paths of La2Mo2O7, in better agreement with EPR results suggesting the presence of Mo-Mo pairs. Simpler arrangements, built from theoretical single scattering paths, are considered. All models are discussed and compared. A most probable short range structure around Mo in this amorphous phase is proposed. It both fulfills EPR results and appears coherent with the presence of ionic conductivity.

Reduction Kinetics of La2Mo2O9 and Phase Evolution during Reduction and Reoxidation.

An amorphous reduced form of oxide ion conductor La2Mo2O9 had been proposed as sulfur-tolerant anode material for solid oxide fuel cell, but its oxygen content was not known. In this paper, we investigate the reduction kinetics by diluted hydrogen of La2Mo2O9 to amorphous, and the oxygen range of the amorphous form. The reduction kinetics is studied as a function of the powder specific surface area and of the temperature, on powders synthesized by solid state reaction and by polyol process using two different solvents. The reduction process was carried out by TGA under 10% H2 diluted in argon, and its kinetics is analyzed and modeled. As expected, small particles and high temperature lead to higher reduction rates. Several reduction steps were identified by XRD during the process. At 700 °C La2Mo2O9 is directly reduced into the amorphous phase La2Mo2O7-y, whereas at 760 °C reduction occurs through an intermediate crystallized La7Mo7O30 (≅ La2Mo2O8.57) phase before amorphization. In both cases, further reduction of La2Mo2O6.2 amorphous phase leads to an exsolution of metallic molybdenum and a molybdenum deficiency in the amorphous phase. Reoxidation of amorphous La2Mo2O7-y was studied by TGA, DTA and XRD. At low temperature in air, the reduced compounds are reoxidized while remaining amorphous. The annealing for 60 h at 350 °C in air of reduced La2Mo2O6.66, obtained beforehand by solid state reaction, gives an amorphous phase with composition La2Mo2O8.85. The existence domain of the reduced amorphous phase in terms of oxygen content therefore ranges at least from O6.2 to O8.85, thus including the composition La2Mo2O8.50 of the amorphous surface layer at the origin of a huge increase of ionic conductivity recently reported in nanowires of La2Mo2O9.