On-site fuel electroanalysis: Determination of lead,copper and mercury in fuel bioethanol by anodic stripping voltammetry using screen-printed gold electrodes

The potential application of commercial screen-printed gold electrodes (SPGEs) for the trace determination of lead, copper, and mercury in fuel bioethanol is demonstrated. Samples were simply diluted in 0.067 mol L⁻¹ HCl solution prior to square-wave anodic stripping voltammetry (SWASV) measurements recorded with a portable potentiostat. The proposed method presented a low detection limit (<2 μg L⁻¹) for a 240 s deposition time, linear range between 5 and 300 μg L⁻¹, and adequate recovery values (96–104%) for spiked samples. This analytical method shows great promise for on-site trace metal determination in fuel bioethanol once there is no requirement for sample treatment or electrode modification.     

Controllable synthesis and property of graphene-based magnetic metal nanostructures

A facile and effective solution phase reduction method was developed to synthesize graphene-based magnetic metal nanocomposites. Metals (Co, and Ni) or alloys (Fe₅₁Co₄₉, Fe₄₈Ni₅₂, Ni₄₉Co₅₁, Co₅₁Cu₄₉, and Ni₅₂Cu₄₈)/reduced graphene oxide (RGO) nanocomposites were successfully prepared by reduction of the corresponding aqueous metal ions and ethylenediamine (EDA)–graphene oxide (GO) with hydrazine hydrate at 353 K for 1 h under N₂ atmosphere. The effects of synthetic parameters such as metal ions concentration, adding sequence of NaOH and N₂H₄·H₂O, linkage agent and reaction time on the formation of nanocomposites were investigated. The experimental results showed that using ethylenediamine and adding sequence played critical roles in the formation of metals or alloys/RGO nanocomposites. Magnetic hysteresis measurements revealed that the as-synthesized metals or alloys in nanocomposites showed excellent soft magnetic behavior with enhanced saturation magnetization, and could have promising applications in biotechnology, catalysis, and magnetic storage devices.     

Molecular Architecture with Nucleobases,Metal Ions and Water Molecules: Mixed Adenine,Hypoxanthine Quartet Containing trans -(NH 3 ) 2 Pt II and Ag + and Harboring a Water Hexamer in Its Chair Conformation

The formation and X-ray crystal structure of a molecular rectangle of 14.25(2) Å ‐ 10.36(2) Å, comprised of two neutral 9-methyladenine (9-MeA) and two anionic 9-methylhypoxanthinate (9-MeHx) model nucleobases as well as two trans -(NH 3 ) 2 Pt II and two Ag + entities, and further cross-linked intermolecularly by Ag + ions, is described: trans -[{(NH 3 ) 2 Pt(9-MeA)(9-MeHx)Ag(NO 3 ) (H 2 O)} 2 Ag](NO 3 ) 3 6H 2 O ( 4 ). The water molecules are located between adjacent purine quartets and adopt a cyclic water hexamer structure in a chair conformation. In addition, the X-ray crystal structure of the precursor of 4 , trans -[(NH 3 ) 2 Pt(9-MeA)(9-MeHxH)](NO 3 ) 2 H 2 O ( 2 ), is reported. 4 is discussed in terms of its relationship to proposals in the literature concerning possible structures of metalated forms of purine quartets.     

Multi-Element Analysis of Landfill Gas by ICP Emission and Mass Spectrometry

Methodology for the determination of trace elements in landfill gas by inductively coupled plasma emission and mass spectrometry is described. The approach is based on direct injection of landfill gas into the ICP using a simple gas sampling manifold. Chlorine and sulphur were quantified in landfill gas by ICP-OES while Sn, Mg, Cu and Zn were measured by ICP-MS. Due to the complex chemical composition of landfill gas, measurements in both emission and mass spectrometry were compromised by spectral interferences. The possibility for multi-element analysis of landfill gas samples based on the use of aqueous standard solutions was demonstrated.     

Analysis of the role of various biochar in the remediation of heavy metals in contaminated water and its kinetics study

Biochar prepared from agricultural wastes has gained great attention as a cost-effective treatment for metal-contaminated water. In this study, the effectiveness of corn cob and sugarcane bagasse-derived biochar for metals (Pb, Ni, and Cu) removal from an aqueous medium was examined following their physical, chemical, and structural characterization. Batch sorption experiments were carried out by employing the Langmuir and Freundlich equations. The results indicated that separation factor (R_L) values lay in the range of 0 and 1 representing the productive adsorption. The optimum dosage for metal adsorption can be recommended as 30 g L^?1. The optimum adsorption conditions were found at 6.5 and 5.5 pH, 1.5 g adsorbent dose, and at 180 min equilibrium time, for both corn cob and sugarcane bagasse biochars. At pH 6.5, adsorption capacities of Pb, Ni, and Cu were found maximum i.e., 11.34, 15.71, and 11.96 mg kg^?1 for corn cob and 8.96, 15.46, and 12 mg kg^?1, for sugarcane bagasse biochars, respectively. The metal adsorption kinetics was analyzed via four different types of the pseudo-second-order kinetic model. Moreover, the corn cob biochar showed a more pronounced activity in the removal of metals compared to sugarcane bagasse biochar. Hence, it was concluded that corncob and sugarcane bagasse-derived biochars could be utilized as economical bio-adsorbents for the heavy metals removal from wastewater.     

Perpendicular-current studies of electron transport across metal/metal interfaces

We review what we have learned about the scattering of electrons by the interfaces between two different metals (M1/M2) in the current-perpendicular-to-plane (CPP) geometry. In this geometry, the intrinsic quantity is the specific resistance, AR, the product of the area through which the CPP current flows times the CPP resistance. We describe results for both non-magnetic/non-magnetic (N1/N2) and ferromagnetic/non-magnetic (F/N) pairs. We focus especially upon cases where M1/M2 are lattice matched (i.e., have the same crystal structure and the same lattice parameters to within ∼1%), because in these cases no-free-parameter calculations of 2AR agree surprisingly well with measured values. But we also list and briefly discuss cases where M1/M2 are not lattice matched, either having different crystal structures, or lattice parameters that differ by several percent. The published calculations of 2AR in these latter cases do not agree so well with measured values.     

The Vertex Coloring Problem and its generalizations

This is a summary of the author’s PhD thesis supervised by Paolo Toth and defended on 29 May 2007 at the Università di Bologna. The thesis is written in English and is available from the author upon request. The first part of this work deals with the Vertex Coloring Problem and its generalizations, for which models, bounds and algorithms are proposed. The Second Part is dedicated to a different problem on graphs, namely a Routing Problem in telecommunication networks where not only the efficiency, but also the fairness of the solution is considered.