Solution-processed near-infrared
organic light-emitting diodes
(NIR-OLEDs) with structure glass/indium–tin oxide/poly(3,4-ethylenedioxythiophene)-poly(styrene
sulfonate)/Er-complex/Ca/Al based on a novel Er(III) complex, [Er(tfnb)3(bipy)] (Htfnb = 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione
and bipy = 2,2′-bipyridine) have been manufactured and their
properties have been studied. A complete quenching of the organic
ligand visible emission is shown, and only the sensitized 1.5 μm
electroluminesce from Er(III) results. From the electrical characteristic
we present the mobility dependence on applied voltage using a numerical
model, comparing it to poly(9,9-dioctylfluorene), a commercial semiconducting
polymer with optical properties close to those of the molecular ligands.
The synthesis of the novel complex together with a detailed analysis
of its structure elucidated by XRD, 1H NMR, Raman, and
Fourier-transform infrared spectroscopies is presented. A wide-ranging
characterization of its photophysical properties in terms of absorption
and steady and transient photoluminescence is used to investigate
the energy-transfer process from the organic ligand to the central
Er(III) ion.
By-products from the wax production process from carnauba palm (leaves), from the extraction of oil from macauba seeds (endocarp) and from pine nut production (shell) have been assessed for activated carbon production, using H3PO4 or CaCl2 for their chemical activation. The resulting activated charcoals have been thoroughly characterized by elemental and thermal analysis, X-ray diffraction, infrared spectroscopy, electron scanning microscopy and N2 adsorption behavior. Subsequently, their adsorption capacity for the removal of rhodamine B (RhB) from aqueous solutions has been evaluated by studying different parameters: contact time, pH, adsorbent dose, initial dye concentration and solution temperature. The adsorption of RhB followed Freundlich's model in all cases. Kinetic studies indicate that the pseudo-second order model can be used for describing the dynamics of the adsorption process. Thermodynamic parameters have also been evaluated, indicating its endothermic and spontaneous nature. Finally, a preliminary analysis of the impact of cellulose content in the carbon precursor materials has been conducted, by using a mixture of native cellulose with one of the lignocellulosic materials.
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Three novel ternary Er 3+ complexes emitting in the C band transmission window for fiber optic communications have been synthesised and their structures have been elucidated by single crystal X-ray diffraction. The fluorinated b-diketonate ligand, 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, combines a good absorption cross-section in the ultraviolet region with reduction of non-radiative quenching of the Er 3+ emission, while the rigidity and bulkiness of the three different N,N-donors (2,2 0 -bipyridine, bathophenanthroline and 5-nitro-1,10-phenanthroline) have a pronounced impact on the emission intensity of luminescence. Furthermore, the choice of the ancillary ligand also determines the efficiency of the antenna effect, leading to complete quenching of the ligand-associated visible emission for the optimized complex with 5-nitro-1,10-phenanthroline. Solution processed 1.54 mm organic light-emitting diodes have been manufactured and characterized for this complex, confirming the aforementioned complete resonant energy transfer from the ligands to the Er 3+ ion. The features of the reported device fabrication show a simple way to obtain large area NIR-OLEDs.
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