Ultraviolet sunlight Solar System

However, unlike photosynthesis in green plants, the titanium oxide photocatalyst does not absorb visible light and, therefore, it can make use of only 3-4% of solar photons that reach the Earth. Therefore, to address such enormous tasks, photocatalytic systems which are able to operate effectively and efficiently not only under ultraviolet (UV) but also under sunlight must be established. To this end, it is vital to design and develop unique titanium oxide photocatalysts which can absorb and operate with high efficiency under solar and/or visible-light irradiation [9-16]. 

Sunlight in the near infrared, visible, and near ultraviolet regions possesses considerable energy utilization of this through photochemical reactions could make a considerable contribution to energy resources. Sinoe biosynthesis itself is relatively inefficient 111 conversion of solar energy, emphasis has been placed upon the fabrication of artificial photochemical systems. One of the more promising approaches has involved application of photoelectric chemical cells or catalysts of semiconductor materials. 

The major measurement of sunscreen photoprotection is the sun protection factor (SPF), which defines a ratio of the minimal dose of incident sunlight that will produce erythema or redness (sunburn) on skin with the sunscreen in place (protected) and the dose that evokes the same reaction on skin without the sunscreen (unprotected). The SPF provides valuable information regarding UVB protection but is useless in documenting UVA efficacy because no standard systems have been developed to measure UVA protection. Such protocols are needed because more than 85% of solar ultraviolet radiation reaching earth s surface is UVA, which penetrates more deeply into human skin than does UVB and appears to play an important role in photoaging and photocarcinogenesis. 

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