Fabrication,characterization and photoelectrochemical performance of chromium-sensitized titania nanotubes as efficient photoanodes for solar water splitting

Chromium-sensitized titanium dioxide nanotubes (CTNT) with high photocatalytic activity were prepared by a chemical bath deposition technique. The resulting films were characterized by SEM, EDX, and XRD. Results showed that the fabricated films have the ordered nanotubes with diameter of 90–140 nm, wall thickness of 20–50 nm, and tube lengths in the range of 24 μm. Diffuse reflectance spectra showed an increase in the visible absorption relative to bare titanium dioxide nanotubes (TNT). The photoelectrochemical performance was examined under light irradiation in 1 M NaOH electrolyte. Photoelectrochemical characterization shows that chromium sensitizing efficiently enhances the photocatalytic water splitting performance of CTNT composite. The sample (C3TNT) exhibited better photocatalytic activity than the TNT and CTNT fabricated using other chromium concentrations. This inexpensive photoanodes prepared free of noble metals showed enhanced high photocurrent density with good stability and is a highly promising photoanode for solar hydrogen production.     

Novel composite membranes embedded with molecularly imprinted porous polymeric nanospheres for targeted phenol

In the present research, novel hybrid molecularly imprinted polymer (HMIP) membranes were synthesized for selective adsorption and separation of phenol toxic molecules from aqueous solutions. Molecularly imprinted polymer (MIP) nanospheres for targeted phenol were successfully prepared using precipitation polymerization of methacrylic acid, trimethylolpropane trimethacrylate, and ethylene glycol dimethacrylate, followed by integrating into polysulfone matrix to create the HMIP membranes via a phase inversion method. The fabricated materials were characterized from the viewpoints of spectroscopic analysis, structural and surface morphological properties, porosimetry, and batch rebinding assays. The imprinted polymeric nanospheres with mean diameter value ranging from 210 to 250 nm and average pore diameter of 8 nm were obtained according to the morphological and Brunauer–Emmett–Teller analysis, respectively. Scanning electron microscopy pictures demonstrated that the MIP spheres were uniformly distributed on the surface and in the bulk polymer phase of the hybrid membrane. The surface roughness, porosity, and permeate flux of membrane were significantly augmented by addition of the imprinted polymer particles in the dope solution. HMIP‐2 membrane containing 10 wt% of MIP showed the highest binding capacity and an excellent molecular recognition for phenol with respect to the correlative blank membrane. The selective recognition of phenol on the HMIP‐2 membrane was 3.5 times larger than the analogous compound (i.e. catechol). Moreover, the maximum separation factor of phenol was obtained as 2.19 relative to catechol through selective permeation studies, which was also observed for HMIP‐2 membrane. Copyright © 2015 John Wiley & Sons, Ltd.     

Digital versatile disc bipolar electrode: A fast and low-cost approach for visual sensing of analytes and electrocatalysts screening

This work represents a new, extremely low cost and easy method for fabrication of bipolar electrode (BPE) for rapid and simultaneous screening of potential candidates for electrocatalytic reactions and sensing applications. Our method takes advantage of the silver reflective layer deposited on already available recordable digital versatile disc (DVD-R) polycarbonate substrate which acts as BPE. Oxidation of the reflective layer of the DVD-R in anodic pole of the BPE results in a permanent and visually measurable dissolute length. Therefore, one could correlate the electrocatalytic activity of the catalyst at the cathodic pole of the BPE, as well as the concentration of analyte in the solution, to the dissolution length of the BPE. To illustrate the promising applications of this new substrate as BPE, p-benzoquinone (BQ) and hydrogen peroxide were tested as model targets for the sensing application. Moreover, in order to show the feasibility of using DVD BPEs for screening applications, the electrocatalytic activity of Pt, Pd, Au, and pristine DVD substrate toward hydrogen evolution reaction (HER) were compared using an array of BPEs prepared on DVD substrate.     

A Facile and Efficient One‐Pot Electrochemical Synthesis of Thiazole Derivatives in Aqueous Solution

In the present work, the electrooxidation of hydroquinones 1a and 1b , and catechols 1c and 1d was studied in the presence of rhodanine ( 3 ) as nucleophile in a mixture of EtOH and phosphate buffer solution as ‘green’ media using cyclic voltammetry and controlled‐potential coulometry. The results indicated that the corresponding p‐ and o‐quinones formed from the hydroquinones and catechols, respectively, participate in Michael addition reaction to yield new thiazole derivatives. The electrochemical syntheses of these new thiazole derivatives were performed successfully at three graphite rod electrodes in undivided cells in good‐to‐excellent yields at room temperature without any catalyst.     

Carboxymethyl cellulose- and fluorapatite-coated silver[orthophosphate-bromide] nanostructures for photodegradation of an azo dye from the textile industry

Visible light photoactive silver[orthophosphate-bromide] loaded on fluorapatite (FA) and carboxymethyl cellulose (CMC) supports were prepared by an ionic liquid-assisted precipitation method and used as effective light driven heterogeneous systems for removal of Acid Blue 92 (AB92) azo dye and E. coli gram-negative bacteria from the wastewaters. The prepared samples were characterized by X-ray diffraction (XRD) powder, diffuse reflectance spectroscopy (DRS), Furrier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and nitrogen adsorption-desorption isotherms (BET). The XRD patterns well proved the formation of Ag₃PO₄ and AgBr photocatalytic crystalline phases of the nanostructures. Besides, the SEM images demonstrated that the photoactive particles were homogenously dispersed on the surface and the average size of the particles is below 90 nm. The antibacterial experiments showed that the products particularly the FA-based photocatalyst can also be utilized as efficient antimicrobial agents. According to the results, the CMC-based photocatalyst was more active during the first time of using while the other one was determined to be promising enough during the recycling tests.     

Impact of modified electrodes on boosting power density of microbial fuel cell for effective domestic wastewater treatment:A case study of Tehran

Utilizing microbial fuel cells (MFCs) is a promising technology for energy-efficient domestic wastewater treatment, but it still faces practical barriers such as low power generation. In this study, the LaMnO₃ perovskite-type oxide nanoparticles and nickel oxide/carbon nanotube/polyaniline (NCP) nanocomposite (the cathode and anode catalysts, respectively) have been prepared and used to enhance power density of MFC. The prepared La-based perovskite oxide catalysts were characterized by X-ray diffraction (XRD) and scanning electron microscopies (SEM). The electrocatalytic properties of the prepared catalysts were investigated through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) and Tafel plot at ambient temperature. Results show the exchange current densities of LaMnO₃/carbon cloth cathode and NCP nanocomposite/carbon cloth anode were 1.68 and 7 times more compared to carbon cloth cathode, respectively. In comparison to the bare carbon cloth anode, the MFC with the modified electrodes shows 11 times more enhancement in power density output which according to electrochemical results, it can be due to the enhancement of the electron transfer capability. These cathodic and anodic catalysts were examined in batch and semi-continuous modes to provide conditions close to industrial conditions. This study suggests that utilizing these low cost catalysts has promising potential for wastewater treatment in MFC with high power generation and good COD removal efficiency.     

Photophysical Properties and Kinetic Studies of 2-Vinylpyridine-Based Cycloplatinated(II) Complexes Containing Various Phosphine Ligands

A series of cycloplatinated(II) complexes with general formula of [PtMe(Vpy)(PR₃)], Vpy = 2-vinylpyridine and PR₃ = PPh₃ (1a); PPh₂Me (1b); PPhMe₂ (1c), were synthesized and characterized by means of spectroscopic methods. These cycloplatinated(II) complexes were luminescent at room temperature in the yellow–orange region’s structured bands. The PPhMe₂ derivative was the strongest emissive among the complexes, and the complex with PPh₃ was the weakest one. Similar to many luminescent cycloplatinated(II) complexes, the emission was mainly localized on the Vpy cyclometalated ligand as the main chromophoric moiety. The present cycloplatinated(II) complexes were oxidatively reacted with MeI to yield the corresponding cycloplatinated(IV) complexes. The kinetic studies of the reaction point out to an S_N2 mechanism. The complex with PPhMe₂ ligand exhibited the fastest oxidative addition reaction due to the most electron-rich Pt(II) center in its structure, whereas the PPh₃ derivative showed the slowest one. Interestingly, for the PPhMe₂ analog, the trans isomer was stable and could be isolated as both kinetic and thermodynamic product, while the other two underwent trans to cis isomerization.     

A new method to detect periodically correlated structure

In this paper, we introduce a new method to test whether a discrete-time periodically correlated model explains an observed time series. The proposed method is based on the estimation of the support of spectral measure. Comparisons between our procedure and the methods which were proposed by Broszkiewicz-Suwaj et al. (Phys A 336:196–205, 2004) show that our testing procedure is more powerful. We investigate the performance of the proposed method by using real and simulated datasets.     

On the Calderón problem in periodic cylindrical domain with partial Dirichlet and Neumann data

We consider the Calderón problem in an infinite cylindrical domain, whose cross section is a bounded domain of the plane. We prove log–log stability in the determination of the isotropic periodic conductivity coefficient from partial Dirichlet data and partial Neumann boundary observations of the solution. Copyright © 2017 John Wiley & Sons, Ltd.     

Electrochemical behavior of polypyrrole-coated AZ31 alloy modified by fluoride anions

The electrochemical polymerization of polypyrrole (Ppy) films on AZ31Mg alloys was carried out using cyclic voltammetery in 0.5 M sodium salicylate solution containing 0.25 M pyrrole and different concentration of sodium fluoride (NaF). Corrosion performance of the Ppy film was assessed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests in 3.5 % NaCl solution. It was observed that Ppy coatings doped in the presence of 100 ppm NaF provide the best corrosion protection for magnesium and the corrosion potential shifted about 290 mV toward nobler potentials and decrease the corrosion current density about one order of magnitude. The surface analysis of the coatings showed that the addition of F^? dopant anions led to an improvement in the smoothness, thickness, and adhesion quality of the synthesized Ppy coating on the Mg surface. The scanning electron microscopy (SEM) studies of the fluoride-doped Ppy films revealed that the synthesized coating has a closely packed globular structure which was composed of nanoparticles of Ppy.