The Performance Evaluation of Meso-Tetraphenyl Porphyrin and Azo Dyes as Photosensitizers in Dye-sensitized Solar Cells.

The photovoltaic properties of five different mono-azo function and meso-tetraphenyl porphyrin dyes have been investigated by computational DFT/TDDFT calculations and measurement of the J-V properties of their cells. The photovoltaic efficiency of the cells based on these dyes were determined by both experimental and theoretical methods. The efficiency-to-cost ratios of the azo-dye cells showed that they could be cheaper substitutes to porphyrin-based cells. Eriochrome blue black (EBB) and eriochrome black T (EBT) cells were shown to possess the best photovoltaic properties by the two methods employed (theory and experiment). The presence of two naphthol moieties at both ends of their -N = N- group has been adduced as possible reason for their relatively outstanding performance. The extremely low efficiency-to-cost ratio obtained for cell-POR suggests that the use of porphyrin as sensitizer may not be as economically viable as some azo dyes. MTO, EBB and EBT were found to be the most cost-effective among the investigated dyes. The porphyrin's low performance may have been amplified by the absence of an effective anchor group in its molecular structure.

Adsorption study of Methylene blue dye: an effluents from local textile industry using Pennisteum pupureum (elephant grass).

This study evaluates the adsorptive capacity of elephant grass (EG) in the removal of Methylene blue (MB) dye from wastewater sourced from two major local dyeing industries in Ogun State, Nigeria. Batch adsorption method was used to determine the optimum conditions, characterization of the adsorbent, equilibrium Isotherm models, kinetics and thermodynamics studies were conducted to evaluate the nature of the adsorption process. The optimum adsorption conditions obtained for the standard solution of MB dye were; pH 7, Temp 40 °C, contact time 180 min and adsorbent dosage 2.0 g. The presence of oxygen containing functional groups and shift or disappearance of bands in the FTIR suggested the suitability of EG for the process. The SEM of EG revealed presence and disappearance of pores before and after the adsorption process. The mechanism of this adsorption is complex, the adsorption data is best fitted to Langmuir isotherm, the mean adsorption energy E (≤6.455 kJ/mol), and activation energy (10.84 kJ/mol) represents physical process but, the thermodynamic studies revealed spontaneity (ΔG° -15.93 to -14.26 kJ mol-1), randomness, and endothermic (ΔH° 40.1 kJ/mol) nature, representing chemisorption. Therefore, local dyers around the study sites can make use of the freely available EG for the remediation of their wastewater.

Elephant grass (EG) abundantly thrives on the study sites where dye wastewater is released by local dyers. This serves as the impetus for this research as no other plants thrive on the dye-polluted environment. A favorable adsorption was obtained with EG as adsorbent for the Methylene blue (MB) dye that is a major constituent of the wastewater from the two major local dyeing industries investigated. Therefore, this study provides scientific support for the local dyers around the study sites to make use of the freely available EG for the remediation of their wastewater.

Poly[beta-(1-->4)-2-amino-2-deoxy-D-glucopyranose] based zero valent nickel nanocomposite for efficient reduction of nitrate in water.

Chemical reduction of nitrate using metal nanoparticles has received increasing interest due to over-dependence on groundwater and consequence health hazard of the nitrate ion. One major drawback of this technique is the agglomeration of nanoparticles leading to the formation of large flocs. A low cost biopolymeric material, poly [beta-(1-->4)-2-amino-2-deoxy-D-glucopyranose] (beta-PADG) obtained from deacetylated chitin was used as stabilizer to synthesize zero valent nickel (ZVNi) nanoparticles. The beta-PADG-ZVNi nanocomposite was characterized using infra red (IR), UV-Vis spectrophotometric techniques and Scanning Electron Microscope (SEM). The morphology of the composite showed that beta-PADG stabilized-ZVNi nanoparticles were present as discrete particles. The mean particle size was estimated to be (7.76 +/- 2.98) nm and surface area of 87.10 m2/g. The stabilized-ZVNi nanoparticles exhibited markedly greater reactivity for reduction of nitrate in water with 100% conversion within-2 hr contact owing to less agglomeration. Varying the beta-PADG-to-ZVNi ratio and the ZVNi-to-nitrate molar ratio generally led to a faster nitrate reduction. About 3.4-fold difference in the specific reaction rate constant suggests that the application of the beta-PADG-stabilizer not only increased the specific surface area of the resultant nanoparticles, but also greatly enhanced the surface reactivity of the nanoparticles per unit area.