Identification of reactive dyes in spent dyebaths and wastewater by capillary electrophoresis-mass spectrometry

Capillary electrophoresis with diode array detection and mass spectrometry combined with solid-phase extraction were employed for the identification of reactive vinylsulfone and chlorotriazine dyes and their hydrolysis products in spent dyebaths and raw and treated wastewater. Recoveries of dyes from treated wastewater as their tetrabutylammonium ion-pairs using C18 reversed-phase cartridges ranged from 81 to 121%. Detection limits in sewage effluent of the different dyes and hydrolysis products ranged from 23 to 42 microg/l. The method was successfully applied to the detection of the hydrolysis products of five reactive dyes in influents and effluents of a municipal wastewater treatment plant receiving dyehouse effluents.     

Two organophosphorus pesticides: methyl parathion and dicapthon

Structural studies performed in this laboratory of organophosphorus pesticides continue with these related compounds. The –NO₂ groups of methyl parathion (systematic name: dimethyl 4‐nitrophenyl phosphorothioate, C₈H₁₀NO₅PS) and dicapthon (systematic name: 2‐chloro‐4‐nitrophenyl dimethyl phosphorothioate, C₈H₉ClNO₅PS) make dihedral angles of 10.67 (8) and 5.8 (1)°, respectively, with the planes of their attached rings, which accompanies angular distortion at the ring C atoms to which the –NO₂ groups are attached. Similar distortions are observed at the C atom to which the thiophosphate groups are attached. Significant differences in distances and angles around the phenolic O, versus the –OMe groups, explain why it is the site of hydrolysis for these compounds. A comparison of a torsion angle involving the thiophosphate group and phenolic O atom with similar pesticide structures is given and indicates steric influences on that angle.     

On the potentiality of a cluster-beam source to produce free-standing one-dimensional and two-dimensional FeAg nanostructures: mechanisms underlying their shape genesis

Controlling the morphology and composition of one-dimensional (1D) and two-dimensional (2D) assemblies of matter is essential to design and create nanostructures with exceptional material properties, for applications ranging from nanoelectronics to nanomedicine. Within this latter, a great interest is placed on assembling magnetoplasmonic nanostructures to enable multimodal biosensing and bioimaging for early diagnosis and prognosis of diseases. To date, the synthesis of such complex nanostructures is mostly relying on wet chemistry and templates. Herein, we employed a templateless physical method to generate FeAg-based anisotropic nanostructures, using a modified cluster source. Under tuned experimental conditions, we demonstrated the successful magnetic-assisted assembly of Fe nanoclusters (Fe NCs), to form stable and permanent branched Fe nanorods (Fe NRs), core@shell Fe@Ag-NRs, Fe nanosheets (Fe NSs), and Fe/Ag-NSs. This assembly is driven by the need to reduce their magnetic interaction energy on one hand and their overall surface energy on the other hand. When NCs and NRs are magnetically brought into intimate contact, they undergo a coalescence process, through the interfacial diffusion of the surface atoms, resulting in the formation of 1D and 2D nanostructures. For Fe@Ag NRs, the advantage conferred by the Ag shell is to protect Fe NRs from oxidation and prevent them from aggregation at the same time. The observed contrast reversal in Scanning Electron Microscopy (SEM) images of Fe NRs and Fe NSs is discussed.     

Conducting polymers in redox devices and intelligent materials systems

Applications opportunities are described for conducting polymer devices, including (1) batteries and redox capacitors, (2) electromechanical actuators, (3) electrochromic windows and displays, (4) chemical separation and chemical delivery systems, and (5) indicators and sensors. Each of these potential application areas depends upon the dramatic property changes which occur during chemical or electrochemical doping. Since the properties profiles of conducting polymers can be reversibly changed either chemically or electrochemically, these polymers also provide exciting candidates for intelligent materials systems - where sensor, logic element, and actuator functions can be either partially or fully integrated. Results of device and properties investigations are used to evaluate future possibilities for conducting polymers in intelligent material systems.     

High sensitivity and high selectivity terahertz biomedical imaging

We demonstrate two distinct emerging terahertz (THz) biomedical imaging techniques.One is based on the use of a new single frequency THz quantum cascade laser and the other is based on broadband THz time domain spectrocopy.The first method is employed to derive a metastasis lung tissue imaging at 3.7 THz with clear contrast between cancerous and healthy areas.The second approach is used to study an osseous tissue under several imaging modalities and achieve full THz spectroscopic imaging based on the freque...     

New chiral benzothiazine ligand and its use in the synthesis of a chiral receptor

The development of chiral ligands to direct the course and stereoselectivity of many catalytic asymmetric reactions is an important area of interest for many research groups. As part of a program examining the chemistry of 2,1-benzothiazines, we have prepared a new chiral benzothiazine ligand. This ligand can be made in as few as three steps from commercially available starting materials. Presented herein is the synthesis of the ligand along with the synthesis of a chiral molecular receptor that potentially presages a new class of chiral molecular tweezers.     

Relevance of cage recombination in the plastic deformation of polymers

For a polymer in which permanent rupture of individual molecules is the rate-limiting process for plastic deformation, the kinetics of chain-end diffusion and secondary radical reactions should be compared with the kinetics of caged radical recombination in the calculation of activation parameters for plastic deformation. If mechanisms of cage escape are slower than those for cage recombination, the activation parameters for plastic deformation will differ from those for the initial bond-breaking process. For the case of polyethylene deformed in the vicinity of 250°K, the critical thermally activated event appears to involve scission of the polymer molecule near the site of an abstracted hydrogen atom. For this system the dominant cage-escape mechanism is diffusion, which is faster than either hydrogen abstraction or unzipping to the monomer. However, at low stresses the rate of cage recombination is expected to be higher than the rate of cage escape, so that the activation parameters for deformation should be the sum of those for chain scission and diffusion. The contribution of diffusion (ca. 15 kcal/mole) to the activation energy for deformation (E^*, extrapolated to zero stress conditions) is relatively modest. However, the calculated molar activation volume for deformation V^* increases by almost an order of magnitude, i.e., from ca. 10 to ca. 76 cm³/mole when diffusion is required. Consideration of experimental values of E^* and V^* for high molecular weight polyethylene indicates that, in the regime examined, chain scission plus chain-end diffusion is required to effect plastic deformation.     

Theoretical investigation of electromechanical effects for graphyne carbon nanotubes

We present a theoretical study of the electronic and mechanical properties of graphyne-based nanotubes (GNTs). These semiconducting nanotubes result from the elongation of one-third of the covalent interconnections of graphite-based nanotubes by the introduction of yne groups. The effect of charge injection on the dimensions of GNTs was investigated using tight-binding calculations. Low amounts of electron injection are predicted to cause qualitatively different responses for armchair and zigzag graphyne nanotubes. Although the behavior is qualitatively similar to the usual carbon nanotubes, the charge-induced strains are predicted to be smaller for the GNTs than for ordinary single walled carbon nanotubes.