Four novel reactive azo-dyes were experimentally synthesized from p-aminobenzaldehyde, 4-amino-3-nitrobenzaldehyde, and aniline through series of condensation and coupling reactions, and their properties were assessed for possible application in dye-sensitized solar cells.
In this study, (E)-5-((4,6-dichloro-1,3,5-triazin-2-yl)amino)-4-hydroxy-3-(phenyldiazenyl)naphthalene-2,7-diylbis(hydrogen sulfite), a cyanurated H-acid (CHA) azo dye, was synthesized and characterized using FT-IR spectrophotometer and GC-MS spectroscopy. A density functional theory (DFT) based B3LYP and CAM-B3LYP method with 6–311 + G (d,p) basis set analysis was computed for HOMO-LUMO, natural bonding orbitals (NBO), UV-Vis absorptions and excitation interactions, in order to understand its molecular orbital excitation properties. A low Energy gap (Eg) of 2.947 eV was obtained from the molecular orbital analysis, which showed that HOMO to LUMO transition is highly feasible; hence CHA is adequate for diverse electronic and optic applications. Studies of the first five excitations (S0 → S1/S2/S3/S4/S5) of CHA revealed that S0 → S1 and S0 → S3 are π → π* type local excitations distributed around the –N=N– group; S0 → S2, a Rydberg type local excitation; S0 → S4, a highly localized π → π* excitation; while S0 → S5 is an n → π* charge transfer from a benzene ring to –N=N– group. From NBO analysis, we obtained the various donor–acceptor orbital interactions contributing to the stabilization of the studied compound. Most significantly, some strong hyper-conjugations (n → n*) within fragments, and non-bondingand anti-bonding intermolecular (n → n*/π* and π → n*/π*) interactions were observed to contribute appreciable energies. This study is valuable for understanding the molecular properties of the azo dyes compounds and for synthesizing new ones in the future.
This research is focused on the sensor properties of pure and X-decorated ([Formula: see text], N, P and S) magnesium oxide (Mg[Formula: see text]O[Formula: see text]) nanocages for melamine (C3H6N6) molecule detection using density functional theory (DFT) electronic structure approach. Comparative adsorption study was carried out on four distinct computational models of hybrid functionals: [Formula: see text]B97XD, PBE0-D3BJ, M062X-D3BJ and DSDPBEP86 with the double-hybrid (DSDPBEP86), being the superior model at the fifth rung of the Jacobi’s ladder, was used as the reference. The atoms-in-molecule (AIM), alongside with the non-covalent interactions (NCIs) as visual extension had been utilized in the study of weak interactions and to affirm the degree of interactions between the clusters and the toxin. In all cases, this study suggests that the adsorption phenomena are best described as chemisorption due to the negative adsorption enthalpy observed. The mean absolute deviation (MAD) and root mean square deviation (RMSD) statistical approaches suggest the behavior of the possible adsorptions to be ranked as follows: PBE0-D3BJ (first rank), [Formula: see text]B97XD (second rank) and finally, M062X-D3BJ (third rank) with ([Formula: see text], 0.7870 and 0.8402) and ([Formula: see text], 0.8946 and 0.9560), respectively. These results are consistent with those of the topological and the sensing parameters, hence, arriving at a conclusive scientific report that Mg[Formula: see text]O[Formula: see text] and Mg[Formula: see text]PO[Formula: see text] surfaces exhibit relatively better sensing performances for the trapping of melamine (MB).
Rechargeable lighting devices are used in Nigeria as alternative source of lighting due to epileptic power supply. They contain printed wiring board, battery and plastic casings containing heavy metals. This waste category is often neglected and disposed of with household garbage with concomitant deleterious consequences on environment. We estimated quantities, disposal methods and concentrations of selected metals in some components of 34 waste rechargeable lighting devices in Nigeria. Estimated quantities and disposal methods were carried out through online survey. Leached metals were prepared and analyzed using standard methods. Approximately 6000 tons/year of waste rechargeable lighting devices were estimated. An average life span of 9 months and 4 rechargeable lighting devices were estimated to be used per household in Nigeria. The commonest disposal method was with household garbage. Lead and copper contents on the boards and Pb in battery electrodes were far higher than permissible limits. All metals determined in plastic casings were within permissible limits. High lead and copper contents in some components makes waste rechargeable lighting devices to be regarded as hazardous materials and should be handled with care at disposal.
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