China
Africa
Explore chapters and articles related to this topic
The Endangered Global Atmosphere
Published in Stanley E. Manahan, Environmental Chemistry, 2022
A common measure taken against the effects of another atmospheric hazard, ultraviolet radiation, provides an example of adaptation. This measure is the use of sunscreens placed on the skin as lotions to filter out UV-B and in some formulations UV-A radiation, thus reducing the likelihood of skin cancer. The active ingredient of sunscreen must absorb or reflect ultraviolet light effectively. Suspensions of small particles of zinc oxide or titanium oxide are used in sunscreen formulations as physical blockers of ultraviolet radiation. Water-insoluble suspensions of organic octinoxate (octyl methoxycinnamate) absorb UV-B radiation, and oxybenzone is effective against UV-A radiation (see the structural formulas that follow). These and related compounds act as chemical absorbers, which are generally aromatic compounds conjugated with a carbonyl group. Chemical absorbers normally act by absorbing ultraviolet radiation to reach an excited state and then dissipate the absorbed energy by reverting to the ground state to regenerate the absorbing species.
The Endangered Global Atmosphere
Published in Stanley Manahan, Environmental Chemistry, 2017
A common measure taken against the effects of another atmospheric hazard, ultraviolet radiation, provides an example of adaptation. This measure is the use of sunscreens placed on the skin as lotions to filter out UV-B and in some formulations UV-A radiation, thus reducing the likelihood of skin cancer. The active ingredient of sunscreen must absorb or reflect ultraviolet light effectively. Suspensions of small particles of zinc oxide or titanium oxide are used in sunscreen formulations as physical blockers of ultraviolet radiation. Water-insoluble suspensions of organic octinoxate (octyl methoxycinnamate) absorb UV-B radiation, and oxybenzone is effective against UV-A radiation (see structural formulas below). These and related compounds act as chemical absorbers, which are generally aromatic compounds conjugated with a carbonyl group. Chemical absorbers normally act by absorbing ultraviolet radiation to reach an excited state and then dissipate the absorbed energy by reverting to the ground state to regenerate the absorbing species.
Straightforward sustainable synthesis of novel non-endocrine disruptive bio-based organic UV-B filters with antimicrobial activity
Published in Green Chemistry Letters and Reviews, 2023
Matthieu M. Mention, Cédric Peyrot, Blandine Godon, Jimmy Alarcan, Fanny Brunissen, Marina Grimaldi, Patrick Balaguer, Albert Braeuning, Florent Allais
In order to evaluate the UV properties of the synthesized furfural and HMF derivatives, their UV-Vis spectra were recorded and compared to that of octinoxate in regard of their maximum absorbance and wavelength coverage. Several phenolic-based alternatives for UV-B filters have already been studied (15,16,17,21) and, while they provide interesting results, their coverage does not entirely fit that of octinoxate. As modification on the ester moiety proved to be of minor impact on the wavelength coverage (15), we first focused on the conjugation system, switching from phenols to furfural and HMF. Looking at the resulting UV-Vis spectra (Figure 1), modification of the conjugation system provided the desired hypsochromic shift. Both sinapic acid and sinapic diacid exhibited maximum absorption wavelength out of sync from the one of octinoxate (309 nm), at 325 and 330 nm, respectively, while the HMF based diacid (11) did not show a significant shift with a maximum absorption wavelength at 317 nm. The furfural derivative (1) offered a perfect fit to the octinoxate spectrum in the UV-B region, with similar level of absorbance and a maximum absorption wavelength at 308 nm. Once the modification of the conjugation system proved to be efficient to better fit the spectrum of octinoxate, emphasis was placed on the substitution on the ester moiety in an attempt to modulate the absorbance level.