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This study involved preparation and modification of Saccharum officinarium as adsorbent used for the removal of chromium (VI) ions in a batch process. The adsorbent was modified with oxalic acid for improved performance of the adsorbent by increasing the surface area of the adsorbent. Surface morphology of the adsorbents was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD), while Fourier transform infrared (FT-IR) analysis was carried out before and after the adsorption of Cr (VI) ions to determine the participating functional group in the processes. The optimum adsorption was attained at pH 2 and contact time of 180 min with efficiency of adsorption of 56.7 and 92.6% onto RSO and MSO, respectively. The adsorption capacity increases with increase in initial metal ion concentration of the sorption mixture. The isotherms studies indicate that the experimental data were best fitted to Freundlich, Langmuir, and Sips models with R2 = 0.999 for adsorption of Cr (VI) ions onto raw S. officinarium (RSO) and modified S. officinarium (MSO). The maximum adsorption capacity obtained were 227.27 and 243.90 mg*g−1 while the adsorption energy obtained from D-R were found to be 3.460 and 6.325 kJ*mol−1 onto RSO and MSO, respectively. This revealed that the physiosorption process was favored in interaction of Cr (VI) ions onto both adsorbents. Separation factors obtained showed that the process is favored with increase in initial concentration of the adsorbate. Thermodynamic parameter values obtained showed that the sorption of Cr (VI) ions onto RSO and MSO is feasible, spontaneous, and endothermic in nature. The positive value of ΔS° indicates increase in disorderliness of the adsorption process. Kinetic data achieved at different initial concentrations of adsorbate have been analyzed, and the mechanism of the reaction was also studied by intra-particle and Bangham kinetic model. Each of the models was tested with R2 ˃ 0.9, where pseudo-second-order is the best-fitted model and Bangham mechanism only fitted with adsorption of Cr (VI) ions onto RSO. The reusability potential of RSO and MSO contributes to the economic values and reliability of the adsorbents for removal of Cr (VI) ions from aqueous solution. [ABSTRACT FROM AUTHOR]

Meeting the requirements and developments of modern society will be unachievable without a sustainable source of energy. However, dye sensitized solar cell (DSSC) has been found worthy to produce reliable energy source. Recently, researchers have inputted great effort toward the modulation of organic dyes to achieve highly efficient dye sensitizers for solar cell purposes. Herein, D-π-A architectural design was employed to generate ten phenoxazine-based dye engineered with five different thiophene π-linkers and two acceptor units. Density functional theory (DFT) and time-dependent DFT were used to optimize the molecules in order to cognize their intramolecular charge transport, optoelectronic properties, light-harvesting efficiency (LHE) and open-circuit voltage (Voc). DFT conceptual was engaged to elucidate the chemical reactivity parameters of the photosensitizers. Among the π-linkers employed, 2,6-diethenylbisthieno[3,2-b:2′,3′-d]thiophene (D3) remarkably improved the intramolecular charge transfer, thus generated an exceptional HOMO/LUMO energy gap (Eg), strong bathochromic shift, suitable LHE and notable Voc. The qualities of the dyes were further enhanced by replacing 2-cyano-2-pyran-4-ylidene-acetic acid with cyanoacrylic acid acceptor moiety. Comparison of these systems with other reported molecules reveals that majority of the simulated poses improved properties that are recommendable for solar cells applications. [ABSTRACT FROM AUTHOR]

In this research, the removal of cadmium(II) ions (Cd) from wastewater using zinc oxide nanoparticles (ZnONp) and carbonized sawdust composite was examined. ZnONp were synthesized by precipitation using sodium hydroxide (NaOH) and zinc nitrate tetrahydrate as precursors, while carbonized sawdust was produced from sawdust obtained from a nearby wood plant. The synthesized ZnONp were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV–visible spectroscopy and X-ray diffractometry (XRD). The adsorption of Cd(II) ions from wastewater was investigated at varying initial concentrations (10–200 mg/L). The preliminary method was coordinated in batches treated with ZnONp, carbonized sawdust and ZnONp/carbonized sawdust composite. The effects of factors such as pH, contact time, initial concentrations of the adsorbate and adsorbent and temperature were inspected. The experiments showed that the best sorption time was 100 min and that the pseudo-second-order model, with a regression coefficient (R2) of 0.999, gave the best description for the sorption kinetics. Isotherm analyses were also conducted to further understand the sorption process. The results indicated that Freundlich isotherms gave the best fit for the sorption reaction with an R2 assessment of 0.9989, which shows the proximity of Cd adsorption in a multiple-layer structure on the adsorbent. Both models and data indicated that ZnONp–carbonized sawdust gave higher sorption fulfilment levels, removing Cd(II) ions with a 90% efficiency rate. The reusability study also showed that the adsorbents can be reused with high efficiency after two cycles of reuse. [ABSTRACT FROM AUTHOR]

Modulation of metal free organic (MFO) molecules become imperative to researchers to obtain low-cost sensitizer for dye sensitized solar cells (DSSCs) purposes. A series of metal free phenothiazine-based (PTZ) organic dyes are designed and optimized as sensitizers for DSSCs application. Their electronic and optical properties were probed using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) approaches. Effects of additional donor unit, π-conjugation bridges, and benzothiadiazole (BTDA) were investigated. Introducing BTDA in the acceptor unit leads to the tailoring of the energy band gap and promotion of charge transfer within donor and anchor groups with increased effective parameters in DSSC efficiency. The addition of diphenylamine, triphenylamine, or hexyloxyphenyl to the PTZ unit increased electron delocalization and enhanced intramolecular charge transfer. Changing π-spacer from phenyl to thiophene has a great effect on the electronic properties and absorption spectra of the dyes. The relationship between light harvesting efficiency (LHE) and chemical hardness (ƞ) shows that structural design that consists of BTDA and thiophene as π-spacer tends most towards excellent performance as dye sensitizers in DSSCs. [ABSTRACT FROM AUTHOR]

A systematic conceptual study of the properties of tin oxide nanoclusters SnnOm (n = 1–6; 2n+1 ≤ m ≤ 4n+2) with ozonide ion or mixed ozonide with molecular O20, oxide (O2−), peroxide (O−) or superoxide (O2−) was investigated using the ab initio density functional theory perspective. Bader charge calculations revealed the oxidation state of Sn and established formation of terminal oxide moiety in the nanoclusters. The stability investigation was carried out by calculations of the binding energy (BE) per atom, the second difference total energy (Δ2E(m)) and the gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) while adsorption energy per O2 and O3 was investigated. Exploring the variation of the reactivity parameters and reaction energy with sizes revealed size dependence on physicochemical properties of the nanoclusters. Magnetism studies show the contribution of O2, O−, O2− and O3− to the magnetic moment of the nanoclusters. Graphical abstract [ABSTRACT FROM AUTHOR]