Papers by Keyword: Sun Protection Factor

Abstract: Modern sun protective means (SPM) represent complex compositions of substances which provide effective protection of a person’s skin against sunlight. Organic and inorganic sun protective filters (sunscreens) or combinations of them are used as the active components of SPM. Organic sunscreens absorb ultraviolet radiation due to the presence of chromophores in their structure; while action of inorganic sunscreens is based on physical mechanism of protection, such as dispersion, absorption and reflection of ultraviolet (UV) radiation by inorganic particles. Silicon nanocrystals have attracted increasing attention as a new promising sun protective agent. They possess extremely high extinction coefficient in UV region of the spectrum and at the same time are transparent for visible light. The combination of physical properties related to the quantum size effect of silicon nanoparticles and their biological compatibility allows the development of highly effective sun protective skincare compositions. Efficiency and quality of SPM depend on many factors. The variety of known sunscreens allows finding optimum structures for creation of the most effective sun protective means. The review of the literature presented is devoted to consideration of existing SPM, their characteristics and effective properties. Then a comparative analysis of a totally new sun protective material based on silicon nanocrystals with known, widely used UV protectors is performed.

Abstract: Based on (3-methacryloxypropyl)-Polyhedral oligomeric silsesquioxane (MP-POSS) (MP), vinyl-POSS (VP), (3-glycidoxypropyl)-POSS (GP) and modified with 5, 10, 15, 20 and 25 wt-% titanium tetrabutoxide (TTB), three hybrid nanofilms (f-MPT, f-VPT and f-GPT) were prepared using hydrolytic condensation and crosslinking. The transparency of the films was measured at the ranges of ultraviolet A (UV-A) (320-400 nm) spectrum which can cause a much greater risk of skin changes. The average transparency (AT) values of three films were about 65-78% (320-350 nm) and 85-89% (350-400 nm), which implies that these films indeed can provide a physical barrier for blocking the UV-A absorbed into the skin, indicating functionality of the POSS/TiO2 materials as the sun protection factor (SPF) ingredients in a sunscreen. The AT values of three films were in the order of f-MPT>f-GPT>f-VPT due to complete-cage structures of building blocks (POSS) and the size of organic branches covalently bonded to the silica network in the molecular structures. This indicates that VPT powder might be significantly better to selected for the SPF. The TTB addition results in the hybrid structure containing TiO2 which causes a decrease in the AA radiation from sunlight. Lower transparency of the films containing 25 wt-% TTB fractions is ascribed to more amounts of TTB in the modified films.

Abstract: Using polyhedral oligomeric silsesquioxanes (POSS) derived from the hydrolytic condensation of (3–methacryloxypropyl)trimethoxysilane (MPMS), vinyltrimethoxysilane (VMS), and (3-glycidoxypropyl)trimethoxysilane (GPMS), three hybrid nanofilms, f-MP (film-MPMS-POSS), f-GP and f-VP, were prepared using sol-gel and crosslinking processes. The average transparency (AT) and absorption coefficents (AC) of the films were measured in the ranges of 280-2500 nm. Two film transparency applications are described in this work: 1) The AT values of the POSS films in the range of the ultraviolet B (UV-B) spectrum (280–320 nm) (a skin cancer-causing agent) and 2) the AT values in the visible light (VIS) region (400-750 nm) and the near infrared (NIR) region (750-2500 nm) (providing crops growth energy and the improvement of the photosynthetic process efficiency). The AT values of the POSS films in the UV-B range are only about 13%, indicating these films can provide a physical barrier to block UV-B absorption by the skin, and therefore are possible POSS materials for sunscreen ingredients. The AT values in the VIS region are 95.13%, 89.16% and 91.60%, respectively, and the AT values in the near infrared (NIR) region (750-2500 nm) are 95.39%, 93.11% and 90.50%, respectively. These high AT films are good candidates for greenhouse covers. The AT values among the three films in the 280-2500nm region are different and exhibit varied selectivity for absorbed spectra due to the dissimilar sizes of organic branches covalently bonded to the silica network in the film structure.