ABSTRACT
Converting a nonwetting surface to a highly wetting one, aided by ultraviolet radiation, is well explored. Here, in this work, we show just the reverse behavior of a copper-copper oxide nanocomposite surface where ultraviolet radiation turned the superhydrophilic surface to a superhydrophobic one. This observation is explained both experimentally and theoretically using first-principles density functional theory-based calculations considering the metal-oxygen (Cu-O) bond breaking and related change in surface chemistry. This observation has further been corroborated with electron irradiation on the same nanocomposite material. To the best of our knowledge, for the first time, we show that the radiation-induced breaking of the copper-oxygen bond makes the nanostructure surface energetically unfavorable for water adsorption.
ABSTRACT
P3HT-coupled CdS heterostructured nanophotocatalysts have been synthesized by an inexpensive and scalable chemical bath deposition approach followed by drop casting. The presence of amorphous regions corresponding to P3HT in addition to the lattice fringes [(002) and (101)] corresponding to hexagonal CdS in the HRTEM image confirm the coupling of P3HT onto CdS. The shift of π* (CâC) and σ* (C-C) peaks toward lower energy losses and prominent presence of σ* (C-H) in the case of P3HT-CdS observed in electron energy loss spectrum implies the formation of heterostructured P3HT-CdS. It was further corroborated by the shifting of S 2p peaks toward higher binding energy (163.8 and 164.8 eV) in the XPS spectrum of P3HT-CdS. The current density recorded under illumination for the 0.2 wt % P3HT-CdS photoelectrode is 3 times higher than that of unmodified CdS and other loading concentration of P3HT coupled CdS photoelectrodes. The solar hydrogen generation studies show drastic enhancement in the hydrogen generation rate i.e. 4108 µmol h(-1)g(-1) in the case of 0.2 wt % P3HT-CdS. The improvement in the photocatalytic activity of 0.2 wt % P3HT-CdS photocatalyst is ascribed to improved charge separation lead by the unison of shorter lifetime (τ1=0.25 ns) of excitons, higher degree of band bending, and increased donor density as revealed by transient photoluminescence studies and Mott-Schottky analysis.
ABSTRACT
The electrokinetic and adsorption characteristics of alumina suspensions in the presence of Darvan C as dispersant have been investigated. The interaction of Darvan C with alumina has been interpreted in terms of electrokinetic and adsorption measurements. The adsorption density of Darvan C increases greatly with decreasing pH. The isoelectric point (iep) of the sample under investigation is found to be located at pH 9.1. For pH values near and below the point of zero charge, there is an added electrostatic attractive potential for adsorption, which results in high-affinity adsorption behavior. Possible mechanisms of interaction between alumina and Darvan C are described and discussed.
ABSTRACT
Additive interactions and their effects on electrokinetic properties of colloidal alumina suspension are presented in this study. Dibasic ammonium citrate (DAC), natural egg albumin, and octanol-2 are chosen as additives. The surface charge behavior of a 5% (w/v) colloidal alumina suspension in the presence of these additives has been studied in detail. The optimum dosage of DAC to have a stable suspension is found to be 3 mg/g of alumina whereas it is 105 and 164 mg/g of alumina for albumin and octanol-2, respectively. Albumin was found to be a better dispersant than DAC and interacts more strongly than DAC with the surface of alumina, while octanol-2 shows physisorbing characteristics. Turbidity measurements indicate that albumin and DAC interact. When the DAC : albumin molar ratio exceeds 10, the turbidity of the solution is higher than the turbidity of pure albumin, indicating the formation of complexes.
