RESUMO
This review article is focused on element composition of medicinal plants and herbs as well as their decoctions and infusions determined by atomic spectrometry methods. Considering quality and safety of these herbal beverages, widely practiced in herbalism for medicinal and supplementing purposes, element analysis is important, and quality of its results should not raise any doubts about reliability. Hence, original researches devoted to element analysis of decoctions and infusions of medicinal plants and herbs, published after 2000, have been surveyed in details, particularly focusing on sources of elements in medicinal plants, their availability for the intake during preparation of infusions and decoctions as well as different methodological aspects related to element analysis by atomic spectrometry, including sample pretreatment and preparation before measurements, calibration methods used, and verification of reliability of results.
Assuntos
Medicina Herbária/métodos , Extratos Vegetais/análise , Plantas Medicinais , Espectrofotometria Atômica/métodos , Animais , Medicina Herbária/tendências , Humanos , Extratos Vegetais/química , Plantas Medicinais/química , Espectrofotometria Atômica/tendênciasRESUMO
Photoluminescence and photomodulated reflectivity measurements of ZnOSe alloys are used to demonstrate a splitting of the valence band due to the band anticrossing interaction between localized Se states and the extended valence band states of the host ZnO matrix. A strong multiband emission associated with optical transitions from the conduction band to lower E- and upper E+ valence subbands has been observed at room temperature. The composition dependence of the optical transition energies is well explained by the electronic band structure calculated using the kp method combined with the band anticrossing model. The observation of the multiband emission is possible because of relatively long recombination lifetimes. Longer than 1 ns lifetimes for holes photoexcited to the lower valence subband offer a potential of using the alloy as an intermediate band semiconductor for solar power conversion applications.