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Made available in DSpace on 2021-06-25T11:14:28Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Since the optical and electrical properties of organic thin films devices depend on their supramolecular arrangement and the molecular chemical structure, the understanding of such characteristics is essential for the optimization of these devices. In this study, we determine the supramolecular arrangement of thin films produced using the Langmuir-Schaefer (LS) technique and explain how its supramolecular arrangement is affected by the molecular chemical structure using two perylene derivatives: bis-butylimide (BuPTCD) and bis-phenethylimide (PhPTCD). The optical absorption measurements reveal that both films grow homogeneously and indicate that the presence of H aggregates (forbidden emission) is higher for BuPTCD LS film than for PhPTCD LS film. Atomic force microscopic analysis shows that the PhPTCD LS film is rougher than the BuPTCD film. In addition, FTIR analyses indicate that both films have head-on molecular organization. XRD patterns reveal that both the BuPTCD LS film and the PhPTCD LS film are crystalline, but that crystallinity is more prevalent in the BuPTCD LS film. Thus, the results show that the difference presented in the chemical structures leads the films to have different supramolecular arrangements, with consequences for their optical properties. School of Technology and Applied Sciences São Paulo State University (UNESP) School of Technology and Applied Sciences São Paulo State University (UNESP)

Made available in DSpace on 2020-12-12T02:13:44Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Instituto Nacional de Ciência e Tecnologia em Eletrônica Orgânica Universidade Estadual Paulista Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Transitions from the singlet electronic excited states higher than S1 level (S2) to the fundamental state (S0) are unlikely, although such transitions are observed for perylene derivative compounds. This rareness led us to investigate the role of the molecular structure of two perylene derivatives (bis(butylimido) – BuPTCD and bis(phenetylimido) – PhPTCD), as well as their supramolecular arrangements, such as molecular organization, crystallinity, and molecular aggregates (before and after thermal treatment) on the radiative transition S2→S0. The emission spectra of BuPTCD and PhPTCD solutions (monomers) indicated that differences in their molecular structures (lateral groups) do not influence such transitions. Besides, it was verified that the relative intensity (RI) S1→S0 over S2→S0 (RI = IS1→S0/IS2→S0) obtained for BuPTCD and PhPTCD PVD films increases around 15 and 1.5, respectively (in comparison to their respective solutions). However, it was surprising to observe a decrease of RI = IS1→S0/IS2→S0 by a factor of 88 for both BuPTCD and PhPTCD PVD films after their thermal treatment at 200 °C for 2 h. The latter led to an increase of the emission intensity from S2→S0 transition in relation to S1→S0. The decrease of H aggregates, presence of J aggregates and formation of other types of molecular aggregates, induced by thermal treatment, seem to be the cause of the S2→S0 emission increase, which is supported by theoretical calculations. São Paulo State University (UNESP) School of Technology and Applied Sciences São Paulo State University (UNESP) Campus of Itapeva São Paulo State University (UNESP) School of Technology and Applied Sciences São Paulo State University (UNESP) Campus of Itapeva FAPESP: 2013/14262–7 FAPESP: 2016/09633–4 CNPq: 420449/2018–3 CNPq: 448310/2014–7

Eu-doped 1, 3 and 5 % CaZrO3 red-emitting phosphors were synthesized for the first time using the microwave-assisted hydrothermal method followed by heat treatment at 1200 °C. After the crystallization, the orthorhombic CaZrO3 and the non-stoichiometric cubic Ca0.15Zr0.85O 1.85 phases were identified for all samples, and the portion of the non-stoichiometric phase increases as the Eu3+ concentration increases. The excitation spectra of the phosphors display Eu3+ f-f excitation bands (namely at 395 nm and 464 nm) and the Eu3+→O2- charge transfer band at 250 nm, confirming that the CaZrO3 host acts as sensitizer for the Eu3+ luminescence. Likewise, the emission spectra feature the typical Eu3+ emission within the red spectral region, displaying CIE color coordinates of (0.642; 0.332), (0.663; 0.330) and (0.668; 0.327) for the 1, 3 and 5 % doped samples, respectively, indicating high emission color purity. By using Eu3+ as spectroscopic probe, the high-resolution selective emission spectra (14 K) confirm that Eu3+ replaces Ca2+ and Zr4+ local sites in both CaZrO3 and the Ca0.15Zr0.85O1.85 phases. Finally, the high absolute emission quantum yield of the 3 %-doped phosphor found at 393 nm (0.29 ± 0.03) confirms its potential application as red-emitting phosphor, especially in rapid identification of latent fingerprints, security ink or as red-emitting coating of near-UV LEDs for WLED applications.