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Efeitos da interação de plasma na absorção ótica em super-rede randômica de pontos quânticos.
(Universidade Federal de São Carlos, 2004-09-13) Abreu, Eduardo de Paula; Emmel, Paulo Daniel; https://lattes.cnpq.br/3243982487562261
In this work the ground and first excited states of the electron are calculated in interacting one-dimensional, two-dimensional lattices and multilayers of cylindrical quantum dots containing at the most an electron and considering both infinite and finite potential barriers. The dimensions and the occupation of the quantum dots are chosen randomly using Monte Carlo s method. In the case of finite barrier we calculated the levels of energy through the Density Functional Theory (DFT ). We calculated the envelope function considering the eﬀective mass approximation and using the numeric method developed by Samita Gangopadhyay and B.R. Nag. Once obtained the levels of energy, we calculated the absorption coeﬃcient considering the electron-electron interaction. The calculations show the influence of the plasma interaction in the absorption. The results demonstrate a change of the absorption coeﬃcient as a function of the density of quantum dots. When the electric field is applied the absorption peak moves to the right indicating a collective response of interacting localized electrons.
Estudo das etapas sintéticas de complexos mistos de ftalocianinas de zinco e cobalto com tetrafenilporfirina de zinco
(Universidade Federal de São Carlos, 2004-09-13) Cordeiro, Márcia Regina; Moreira, Wania da Conceição; https://lattes.cnpq.br/3016270106775634
A systematic study of synthetic steps in the formation of phthalocyanine and porphyrin mixed complexes, having pyrazine as bridged ligand is described in this work. Two mixed complexes series were obtained, keeping constant the porphyrin metallic center and changing the metallic phthalocyanine, in order to investigate the effect of the metal ion in the final properties of these series. In all the stages the products were characterized by infrared and UV-vis. spectroscopies, thermal and elemental analysis. Thermogravimetric analysis have shown that pyrazine ligand does not influence zinc phthalocyanine(ZnPc), cobalt phthalocyanine(CoPc) or zinc tetraphenilporphrin(ZnTPP) thermal stability. However, the mass loss temperature of pyrazine ligand was dependent of metallic center in the phthalocyanine complex. The two mixed complexes series produced two different macrocycles sequence, ZnPc(pyz)ZnTPP(pyz)ZnPc; ZnTPP(pyz)ZnPc(pyz)ZnTPP; CoPc(pyz)ZnTPP(pyz)CoPc and ZnTPP(pyz)CoPc(pyz)ZnTPP. The infrared and electronic spectra showed characteristic absorption bands of the two macrocycles. However, the main features observed in the electronic spectra was a blue shift of 16 nm in the position of the Q band related to CoPc. This result indicates that the change of the metal ion at phthalocyanine complex can promote a more intense communication between the porphyrin and phthalocyanine ring. The change of metallic center has also change the thermal properties of the mixed complexes.