The Primary Demonstration of Exciton Coupling Effects on Optical Limiting Properties of Blue Double-Decker Lanthanide Phthalocyanine Salts
- Authors: Sekhosana, Kutloano E , Nkhahle, Reitumetse , Nyokong, Tebello
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234614 , vital:50213 , xlink:href="https://doi.org/10.1002/slct.201800597"
- Description: In this manuscript, novel green and blue sandwich-type rare-earth phthalocyanines (LnPc2) are presented. This parent green LnPc2 complex is named bis-{2(3),9(10),16(17),23(24)-tetra(4-tert-buylphenoxy) phthalocyaninato} neodymium (III) (2) and modified into blue LnPc2 complexes (3), (4) and (5) based on hexadecyltrimethylammonium ion, mononeodymium(III) diacetate and monodysprosium(III) diacetate as counter ions, respectively. These stable blue lanthanide Pc salts are highly soluble in many organic and inorganic solvents. All complexes 2, 3, 4 and 5 were studied for optical limiting for the first time using Z-scan at nanosecond regime in the visible absorption spectral wavelength (532 nm). Our studies reveal the advantage of exciton coupling in blue sandwich-type rare-earth phthalocyanines over the π-radicals (characterized by blue valence at 485 nm) in the green counterpart which are in resonance with the 532 nm wavelength for optical limiting application. Large singlet ground state to excited state absorption cross section ratios were found, particularly for complex 5 in comparison to that of complex 2.
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- Date Issued: 2018
Wood preservation with gold hydroxyapatite system
- Authors: Ion, Rodica-Mariana , Nyokong, Tebello , Nwahara, Nnamdi , Suica-Bunghez, Ioana-Raluca , Iancu, Lorena , Teodorescu, Sofia , Dulama, Ioana D , Stirbescu, Raluca M , Gheboianu, Anca , Grigorescu, Ramona M
- Date: 2018
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187840 , vital:44702 , xlink:href="https://doi.org/10.1186/s40494-018-0202-5"
- Description: Over centuries, the external factors such as fire, low temperature, light or microbiological agents, act on the wood and induce some degradation processes, sometimes irreversible, identified by discoloration, fragility and unsightly appearance. Although there are numerous literature reports about different nanomaterials used for preservation and restoration of wood surfaces (calcium hydroxides, magnesium hydroxides, hydroxyapatite, or even organic resins as Paraloid B72), in this paper it is proposed a new system—gold hydroxyapatite (AuHAp), tested on the hazelnut wood samples (young and aged specimens), as a new solution for preservation of some wooden artifacts. This paper addresses a broad range of analytical methods: X-ray diffraction, UV–Vis spectrophotometry, Fourier transformed infrared spectroscopy, Raman spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, chromatic parameters and hardness test. Also, humidity sorption/desorption measurements are used for humidity sorption and desorption evaluation. The adsorption and desorption tests determined the hydroscopic sorption properties of the wood specimens by measuring the mass of the specimens in equilibrium with air at a specific temperature and RH. All the results concluded that after the application of the new system on the hazelnut wood surface, a well distributed and uniform layer consisting from AuHAp systems with a network aspect are observed, which covers the wood vessels and fibers, filling the voids and stopping the wood weathering process, more accentuated at aged wood than at the young species.
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- Date Issued: 2018