Study of electrospun nanofibers loaded with Ru(ii) phenanthroline complexes as a potential material for use in dye-sensitized solar cells (DSSCs).

Dye-sensitized solar cells (DSSCs) are an increasingly attractive alternative energy source because of their low cost. Therefore, researchers have intensified efforts over the past decade to increase their energy conversion efficiency by employing new materials in each DSSC component. The present research focuses on synthesizing electrospun nanofibers as a potential new material as a counter electrode in DSSCs. Two Ru(ii) half sandwich 1,10 phenanthroline (phen) Ru-1 and 5-amino- phen Ru-2 complexes were prepared for its functionalization. As a deposition medium, poly(caprolactone) (PCL) dissolved in chloroform was used. Different Ru(ii) complex concentrations were made at 0.1% wt., 0.5% wt., and 1% wt. Thermal characterization studies using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were conducted to evaluate the behavior and weight loss of the samples with temperature variations. Fourier transform infrared spectroscopy (FTIR) measurements were taken to observe the bond interaction of the ruthenium complexes and the PCL. Finally, scanning electron microscopy (SEM) was used to structurally and morphologically evaluate the fiber distribution and porosity. These fibers have a homogeneous morphology, without bulbs, but with evident solid inlays on the surface, with fibers between ∼0.58 to 2.47 µm and percentages of porosity ∼45%. TGA and DSC thermograms show minor temperature variations that demonstrate the incorporation of the Ru(ii) complexes into the fiber. Furthermore, the melting and degradation temperature of the fibers is suitable for use in a DSSC approach. The incorporation of the ruthenium compounds into PCL fibers, along with the addition of the NH2 group into complex Ru-2, resulted in a higher current density for both anodic and cathodic peaks in Cyclic Voltammetry (CV). It is noteworthy that from I-V curves, PCL-Ru2 1% fibers demonstrated a conductivity of 0.461 µS cm-1, which is comparable to other PCL fibers carrying a higher metal load. Future studies will delve into the mechanical properties of these fibers to highlight their potential for application in this field.

Electrochemical functionalization strategy for chemical vapor deposited graphene on silicon substrates: grafting, electronic properties and biosensing.

Herein, we present an electrochemical functionalization strategy for high quality single-layer and multilayer chemical vapor deposited (CVD) graphene directly on a Si/SiO2 chip facilitating electronic interfacing. This method avoids oxidation and tearing of graphene basal planes. We demonstrate effective functionalization by D-(+)-biotin (Bio), 4-(phenyldiazenyl)-aniline (Dz), and gallic acid (Gall) using cyclic voltammetry. Raman spectroscopy and XPS are used to demonstrate effective functionalization. In order to evaluate the effect of the electrochemical functionalization on graphene properties, DC electrical conductivity, XPS, mobility, and carrier density analysis are presented. We show that this functionalization strategy does not degrade graphene mobility (103 cm2 V-1s-1). After functionalization we observe a rise in Fermi level of ∼0.06 eV. In addition, we prove sensing capabilities with a CVD graphene monolayer on the biotin/avidin system by electrical resistance measurements and electrochemical impedance spectroscopy reaching a detection of 2.5 ng ml-1. This paper demonstrates an effective strategy to functionalize high quality CVD graphene on a chip compatible with an electronic interface readout.

Synthetic hydroxyapatite and its use in bioactive coatings.

An approach to solve the limitations of autologous bone grafting procedures in bone injury treatment is to develop bioactive coatings in the implantation system. The objective of this work is to compare the temperature effect on the stability of hydroxyapatite, graphene, and collagen colloidal suspensions to be used as biocompatible and bioactive coatings on a carbon fiber composite surface. Synthesized hydroxyapatite was assessed by X-ray diffraction. Zeta potential at different temperatures was evaluated. Specimens were characterized using scanning electron microscopy and Raman analysis. The results showed that the best hydroxyapatite/graphene ratio was 85/15, while those of the hydroxyapatite/collagen mixtures were 85/15. A hydroxyapatite/graphene/collagen mixture was synthesized based on these results.

Sequential electrochemical treatment of dairy wastewater using aluminum and DSA-type anodes.

Dairy wastewater is characterized by a high content of hardly biodegradable dissolved, colloidal, and suspended organic matter. This work firstly investigates the performance of two individual electrochemical treatments, namely electrocoagulation (EC) and electro-oxidation (EO), in order to finally assess the mineralization ability of a sequential EC/EO process. EC with an Al anode was employed as a primary pretreatment for the conditioning of 800 mL of wastewater. A complete reduction of turbidity, as well as 90 and 81% of chemical oxygen demand (COD) and total organic carbon (TOC) removal, respectively, were achieved after 120 min of EC at 9.09 mA cm(-2). For EO, two kinds of dimensionally stable anodes (DSA) electrodes (Ti/IrO2-Ta2O5 and Ti/IrO2-SnO2-Sb2O5) were prepared by the Pechini method, obtaining homogeneous coatings with uniform composition and high roughness. The (·)OH formed at the DSA surface from H2O oxidation were not detected by electron spin resonance. However, their indirect determination by means of H2O2 measurements revealed that Ti/IrO2-SnO2-Sb2O5 is able to produce partially physisorbed radicals. Since the characterization of the wastewater revealed the presence of indole derivatives, preliminary bulk electrolyses were done in ultrapure water containing 1 mM indole in sulfate and/or chloride media. The performance of EO with the Ti/IrO2-Ta2O5 anode was evaluated from the TOC removal and the UV/Vis absorbance decay. The mineralization was very poor in 0.05 M Na2SO4, whereas it increased considerably at a greater Cl(-) content, meaning that the oxidation mediated by electrogenerated species such as Cl2, HClO, and/or ClO(-) competes and even predominates over the (·)OH-mediated oxidation. The EO treatment of EC-pretreated dairy wastewater allowed obtaining a global 98 % TOC removal, decreasing from 1,062 to <30 mg L(-1).