Highly sensitive hydrazine chemical sensor based on mono-dispersed rapidly synthesized PEG-coated ZnS nanoparticles

Monodispersed PEG-coated ZnS (P-ZnS) nanoparticles (NPs) were synthesized by facile microwave process and utilized as efficient electron mediators for the fabrication of highly sensitive hydrazine chemical sensor. The detailed morphological and structural properties revealed the monodispersity and good crystallinity for synthesized P-ZnS NPs. A high-sensitivity of ∼89.3 μA cm⁻² μM and low limit of detection of 1.07 μM, based on S/N ratio, were obtained for the fabrication of hydrazine chemical sensor based on P-ZnS NPs. To the best of our knowledge, this is the first report which demonstrates the utilization of P-ZnS NPs for the fabrication of efficient hydrazine chemical sensor. By this work, it could be concluded that simply synthesized ZnS NPs can be used as efficient electron mediators for the fabrication of effective hydrazine chemical sensors.     

Magnetic properties of isostructural M(H2O)4[Au(CN)4]2-based coordination polymers (M = Mn, Co, Ni, Cu, Zn) by SQUID and μSR studies

A series of isomorphous M(H(2)O)(4)[Au(CN)(4)](2)·4H(2)O (M = Mn, Co, Ni, Zn; Cu is similar) coordination polymers was synthesized from the reaction of M(II) with KAu(CN)(4); they consist of octahedrally coordinated metal centres with four equatorial water molecules and trans-axial N-cyano ligands from [Au(CN)(4)](-) moieties, generating a linear 1-D chain of M(H(2)O)(4)[Au(CN)(4)]-units. An additional interstitial [Au(CN)(4)](-) unit forms AuN and hydrogen bonds with adjacent chains. The Cu(II) system readily loses water to yield Cu[Au(CN)(4)](2)(H(2)O)(4), which was not structurally characterized. The magnetic properties of these polymers were investigated by a combination of SQUID magnetometry and zero-field muon spin relaxation (ZF-μSR). Only weak antiferromagnetic interactions along the chains are mediated by the [Au(CN)(4)]-units, but the ZF-μSR data indicates that interchain interactions yield a phase transition to a magnetically ordered state for Cu[Au(CN)(4)](2)(H(2)O)(4) below 0.6 K, while for M(H(2)O)(4)[Au(CN)(4)](2)·4H(2)O (M = Co), depopulation of zero-field split Kramer's doublets to an effective "S = 1/2" ground state yields a transition to a spin-frozen magnetic state below 0.26 K. On the other hand, only a simple slowing-down of spins above 0.02 K is observed for the more weakly zero-field split M(H(2)O)(4)[Au(CN)(4)](2)·4H(2)O (M = Mn, Ni) complexes.     

Detailed investigations of ZnO photoelectrodes preparation for dye sensitized solar cells

Wurtzite ZnO hexagonal nanopyramids were successfully synthesized in the liquid phase from homogeneous methanolic solutions of zinc acetate and tetramethylammonium hydroxide at an excess of zinc ions. The formation and properties of the nanocrystals were examined as a function of synthesis conditions. No significant influence of the [Zn(2+)]/[OH(-)] ratio was noticed on the final particle size, in spite of increased amounts of OH(-) ions, which tend to accelerate the particle nucleation and growth. Nevertheless, the reactant concentration ratio influences the surface properties of the ZnO nanocrystals. Mesoporous ZnO films were prepared by doctor blading ethanolic pastes containing ZnO nanoparticles and ethyl cellulose onto FTO conductive glass substrate followed by calcination. Additionally, the influence of a plasticizer (triacetin)-used during the paste preparation-on the film quality was investigated. A higher content of ZnO nanoparticles and plasticizer in the pastes improved the film quality. Four different temperatures (i.e., 400, 425, 450, and 475 °C) were used for the film calcination and their influence on the structural properties of the films was characterized. In principle, increasing the calcination temperature goes hand in hand with an increase of particle size, as well as the pore diameter and reduction of the surface area. Suitable mesoporous films were employed as photoanodes in dye sensitized solar cells (DSSCs). In order to assess the effect of the varied parameters on complete DSSC devices-using cis-diisothiocyanato-bis(2,2'-bipyridyl-4,4'-dicarboxylato) ruthenium(II)bis(tetrabutylammonium (N719) as a sensitizer-incident photon to current efficiency (IPCE) and current voltage measurements were carried out. The IPCE measurements confirmed photoinduced electron injection from the dye, reaching IPCE values up to 76%. Furthermore, current-voltage characteristics of complete cells emphasized the importance of the proper preparation methods and temperatures. These features are important assets for the preparation of nanocrystalline ZnO based photoelectrodes and for improving the DSSC performance.     

Self-assembled titanium-based hybrids with cyclopentadienyl-titanium network bonding

Unprecedented stable hybrid materials with cyclopentadienyl-titanium bonds have been obtained from the hydrolysis of suitable precursors. Their inorganic network is not fully condensed and they show variable short-range self-organizations, the type of which depends on the shape of the ligands.     

Synthesis of functionalized arylpyridines and -pyrimidines by domino [4+2]/retro [4+2] cycloadditions of electron-rich dienes with alkynylpyridines and -pyrimidines

Aryl-substituted pyridines and pyrimidines were prepared by [4+2] cycloadditions of alkynyl-substituted pyridines and -pyrimidines with electron-rich dienes. The reactions proceed by formation of a bridged cycloadduct and subsequent thermal extrusion of ethylene. The pyridine moiety plays a crucial role for the success of the reaction.     

Theoretical investigation of half‐metallicity in Co/Ni substituted AlN

Results of Co and Ni substituted AlN in the zinc blende phase are presented. For spin up states, the hybridized N‐2p and Co/Ni‐3d states form the valance bands with a bandgap around the Fermi level for both materials, while in the case of the spin down states, the hybridized states cross the Fermi level and hence show metallic nature. It is found that, Al_0.75Co_0.25N and Al_0.75Ni_0.25N are ferromagnetic materials with magnetic moments of 4 μ_B and 3 μ_B, respectively. The integer magnetic moments and the full spin polarization at the Fermi level make these compounds half‐metallic semiconductors. Furthermore it is also found that the interaction with the N‐2p state splits the 5‐fold degenerate Co/Ni‐3d states into t_2g and e_g states. The t_2g states are located at higher energies than the e_g states caused by the tetrahedral symmetry of these compounds. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Modeling a clinical incineration process using fuzzy autocatalytic set

In this paper we have investigated and explored the realm of fuzzy graph in its relation to autocatalytic sets. A new concept namely fuzzy autocatalytic set have been defined. This relation has produced some results in the forms of theorems which have been proven. A clinical waste incineration process has been modeled using this new concept indicates to be more accurate than using crisp graph.     

Characteristic absolute efficiency response curves of a high purity germanium detector in the energy range 50–1500 keV

The characteristic absolute efficiency response curves of a high purity germanium detector (HPGe) for different counting geometries have been established in the energy range 50–1500 keV by measuring the absolute efficiencies using both mono-energetic and multi-gamma emitting radionuclide point calibrated sources supplied by IAEA. Several fitting functions proposed in the literature were assessed for interpolation within the intermediate energy range of interest. The values of the function parameters have been determined by using the linear least square methods. The problems associated with the measurements of experimental efficiency data at small source–detector distances and the importance of the correlation matrix in the estimation of precise uncertainties have been shown. It was found that the inclusion of correlation matrices in the propagation of error formulae plays a significant role up to 450 keV gamma-ray energy and results in a drastic reduction of errors associated with the predicted efficiencies. The discrepancy at closer counting geometries in the absence of true gamma-gamma coincidence corrections is found to reach to about 30%.