Chemical modification of biopolymers, before use in thermoplastic applications, can reduce the susceptibility to open environment degradation. We demonstrate carbon dots (CDs) as green photocatalytic triggers that can render the common cellulose derivative, cellulose acetate (CA), degradable under open environment relevant conditions. CD-modified cellulose acetate (CA + CD) films were subjected to UV-A irradiation in air and simulated sea water, and the degradation process was mapped by multiple spectroscopic, chromatographic, and microscopy techniques. The addition of CDs effectively catalyzed the deacetylation reaction, the bottleneck preventing biodegradation of CA. The photocatalytically activated degradation process led to significant weight loss, release of small molecules, and regeneration of cellulose fibers. The weight loss of CA + CD after 30 days of UV-A irradiation in air or simulated sea water was 53 and 43%, respectively, while the corresponding values for plain CA films were 12 and 4%. At the same time the weight average molar mass of CA + CD decreased from 62,000 to 11,000 g/mol and 15,000 g/mol during UV-A irradiation in air and simulated sea water, respectively, and the degree of substitution (DS) decreased from 2.2 to 1.6 both in air and in water. The aging in water alone did not affect the weight average molar mass, but the DS was decreased to 1.9. Control experiments confirmed the generation of hydrogen peroxide when aqueous CD dispersion was subjected to UV-A irradiation, indicating a free radical mechanism. These results are promising for the development of products, such as mulching films, with photocatalytically triggered environmental degradation processes.
Iodine in the atmosphere destroys ozone and can nucleate particles by formation of iodic acid, HIO. Recent field observations suggest iodate recycles from particles sustaining significant gas-phase IO radical concentrations (0.06 pptv) in aged stratospheric air, and in elevated dust plumes.
A woman in her early 20s with progressive keratoconus underwent corneal collagen cross-linking using the sub400 protocol. The central 5.5 mm of the epithelium was removed after the application of 20% alcohol.
Monomers of -hydroxypyridine-2(1)-thione were isolated in low-temperature matrices of solid normal hydrogen (n-H). The matrix-isolated compound was irradiated with UV-B (λ = 305 nm) or UV-A (λ > 360 nm) light. Upon such irradiation, the initial form of -hydroxypyridine-2(1)-thione was completely consumed and converted into photoproducts.
Propylene epoxidation in mild conditions using molecular O is a highly desirable reaction that represents a significant challenge in the field of heterogeneous catalysis for the synthesis of oxygenated organic compounds of industrial interest. In this work, CuO/TiO composites with different mominal CuO loadings (in the range of 0.5-8.
