Ultrasound assisted pseudo-digestion of street dust samples prior to determination by atomic absorption spectrometry

A sample preparation method based on ultrasound assisted pseudo-digestion of Pb, Cu, Zn and Ni from street dust samples under ultrasonic effect has been described. Parameters influencing pseudo-digestion, such as sonication time, sample mass, particle size and solvent system were fully optimized. Final solutions obtained upon sonication were analyzed by atomic absorption spectrometry. The best conditions for metal pseudo-digestion were as follows: a 25 min sonication time, a 0.3 g sample mass (in 25 ml solvent), a particle size <63 μm and a mixture of concentrated HNO₃-HClO₄-HF (2:1:1, v/v/v). Analytical results for the four metals by ultrasound assisted pseudo-digestion, acid bomb and conventional wet digestion methods showed a good agreement, thus indicating the possibility of using mild conditions for sample preparation instead of intensive treatments inherent with the digestion methods. In addition, this method reduces the time required for all treatments (pseudo-digestion or digestion, heating to dryness, cooling and separation) with acid bomb and conventional wet digestion methods approximately from 9 to 1 h. The accuracy of the method was tested either by comparing obtained results with those of acid bomb and conventional wet digestion methods or by application on two standard reference materials. The average relative standard deviation of ultrasound assisted pseudo-digestion method varied between 0.9 and 1.8% for N = 12, depending on the analyte.     

A new synthesis of vitamin C

l-Arabinose was reduced to l-arabinitol and condensed with formaldehyde to give two bis(di-0-methylene-l-arabityloxymethane and two di-O-methylene-l-arabinitol derivatives. Cis-fused 1,3:2,4-Di-O-methylene-l-arabinitol and trans-fused 2,4:3,5-Di-O-methylene-l-arabinitol were also isolated; only the former was affected by the oxidation to give the corresponding aldehyde, which was converted successively to the hydroxy amide, the ethyl hydroxy ester, the corresponding keto ester and vitamin C.     

Preparation,characterization, and binding profile of imprinted semi-IPN cryogel composite for aluminum

Human body is greatly exposed to aluminum due to its high abundance in the environment. This nonessential metal is a threat to the patients of chronic renal disorders, as it is easily retained in their plasma and quickly accumulates in different tissues. Thus, there is great need to remove it from the aqueous environment. In this study, Al³⁺ imprinted semiinterpenetrating polymer network (semi-IPN)-based cryogel composite was prepared and applied for the purification of environmental and drinking water samples from aluminum. Poly (2-hydroxyethyl methacrylate) (pHEMA) discs were produced via cryogenic treatment and imprinted semi-IPN was introduced to the 3-(trimethoxysilyl) propyl acrylatemodified macroporous cryogel discs. The adsorption properties and selectivity of the aluminum (III) imprinted semi-IPN cryogel composite were studied in detail. The imprinted semi-IPN cryogel composite showed good selectivity towards aluminum (III) ions with the imprinting factor (IF) of 76.4 in the presence of competing copper (II), nickle (II), and iron (III) ions. The maximum adsorption capacity of 271 μmol g^-1 was obtained for aluminum (III) at pH 7.0 within 10 min using imprinted semi-IPN cryogel composite. The good selectivity and reusability of aluminum (III)-imprinted semi-IPN cryogel composite makes this material an eligible candidate for the purification of drinking water from aluminum (III) leaving important minerals remained in the water.     

DFT and TD-DFT calculations on thieno[2,3-b]indole-based compounds for application in organic bulk heterojunction (BHJ) solar cells

Research on Chemical Intermediates - Eight novel organic compounds with donor–π–acceptor (D–π–A) structure were designed for use as donors in organic bulk...     

A branch and bound algorithm for class based storage location assignment

Class-based storage implementation decisions have significant impact on the required storage space and the material handling cost in a warehouse. In this paper, a nonlinear integer programming model is proposed to capture the above. Effects of storage area reduction on order picking and storage space cost are incorporated. A branch and bound algorithm is developed to solve the model. Computational experience with randomly generated data sets and an industrial case shows that branch and bound algorithm is computationally more efficient than a baseline dynamic programming algorithm. It is further observed that the class based policy results in lower total cost of order picking and storage space than the dedicated policy.     

PTFE/EP Reinforced MOF/SiO2 Composite as a Superior Mechanically Robust Superhydrophobic Agent towards Corrosion Protection,Self-Cleaning and Anti-Icing

Organic resin cross-linking ZIF-67/SiO₂ superhydrophobic (SHPB) multilayer coating was successfully fabricated on metal substrate. The perfluoro-octyl-triethoxy silane (POTS) modified ZIF-67 and SiO₂ coating was applied on primary coated polytetrafluoroethylene (PTFE) and epoxy resin (EP) via spray coating method. Here, we present that the robust superhydrophobicity can be realized by structuring surfaces at two different length scales, with a nanostructure design to provide water repellence and a microstructure design to provide durability. The as-fabricated multilayer coating displayed superior water-repellence (CA=167.4°), chemical robustness (pH=1–14) and mechanical durability undergoing 120th linear abrasion or 35th rotatory abrasion cycle. By applying different acidic and basic corrosive media and various weathering conditions, it can still maintain superior-hydrophobicity. To get a better insight of interaction between inhibitor molecules and metal surface, density functional theory (DFT) calculations were performed, showing lower energy gap and increased binding energy of ZPS/SiO₂/PTFE/EP (ZPS=ZIF-67+POTS) multilayer coating compared to the ZIF-67/SiO₂/PTFE/EP, thereby supporting the experimental findings. Additionally, such coatings may be useful for applications such as anti-corrosion, self-cleaning, and anti-icing multi-functionalities.     

MAPLE-deposited polymer films for improved organic device performance

Matrix-assisted pulsed-laser evaporation (MAPLE) provides a mechanism for layer-by-layer growth to control the polymer–dielectric interface in organic metal–insulator–semiconductor (MIS) diodes and field-effect transistors (FETs). MAPLE-deposited copolymers of polyfluorene (PF) and polythiophene maintain their structural and optical properties, as determined by Raman spectroscopy, absorption, and photoluminescence. These films are further utilized in MIS and FET structures with SiO₂ and other polymer dielectrics. Since common polymer dielectrics prevent spin coating of solution processable polymers due to solubility effects, MAPLE is one of the only deposition techniques for investigating all polymer semiconductor-insulator interfaces. In this paper we present optical and electrical studies of MAPLE-deposited PF and polythiophene films in FETs and MIS structures. The FET carrier mobilities of these devices compare well with spin-coated devices. Capacitance–voltage and conductance–voltage from MIS structures with MAPLE-deposited PF copolymer films yield interface trap densities in the low 10¹² eV⁻¹ cm⁻² range.     

A novel series of M(II) complexes of 6‐methylpyridine‐2‐carboxylic acid with 4(5)methylimidazole: Synthesis,crystal structures, α‐glucosidase activity,density functional theory calculations and molecular docking

Novel complexes of 6‐methylpyridine‐2‐carboxylic acid and 4(5)methylimidazole, namely [Mn(6‐mpa)₂(4(5)MeI)₂] ( 1 ), [Zn(6‐mpa)₂(4(5)MeI)₂] ( 2 ), [Cd(6‐mpa)₂(4(5)MeI)₂] ( 3 ), [Co(6‐mpa)₂(4(5)MeI)₂] ( 4 ), [Ni(6‐mpa)₂(4(5)MeI)(OAc)] ( 5 ) and [Cu(6‐mpa)₂(4(5)MeI)] ( 6 ), were synthesized for the first time. The structures of complexes 1 – 4 and complexes 5 and 6 were determined using X‐ray diffraction and mass spectrometric techniques, respectively. The experimental spectral analyses for these complexes were performed using Fourier transform infrared and UV–visible techniques. The α‐glucosidase inhibition activity values (IC₅₀) of complexes 1 – 6 were identified in view of genistein reference compound. Moreover, the DFT/HSEh1PBE/6‐311G(d,p)/LanL2DZ level was used to obtain optimal molecular geometry and vibrational wavenumbers for complexes 1 – 6 . Electronic spectral behaviours and major contributions to the electronic transitions were investigated using TD‐DFT/HSEh1PBE/6‐311G(d,p)/LanL2DZ level with conductor‐like polarizable continuum model and SWizard program. Finally, in order to investigate interactions between the synthesized complexes ( 1 – 6 ) and target protein (template structure S. cerevisiae isomaltase), a molecular docking study was carried out.     

A new dinuclear copper (II) complex of 2,5–Furandicarboxyclic acid with 4(5)‐Methylimidazole as a high potential α‐glucosidase inhibitor: Synthesis,Crystal structure,Cytotoxicity study,and TD/DFT calculations

A new dinuclear copper (II) complex of 2,5–furandicarboxyclic acid with 4(5)‐methylimidazole, [Cu (FDCA)((4(5)MeI)₂]₂·2H₂O, was synthesized, and its structure characterized by XRD, FT–IR and UV–Vis spectroscopic techniques. The α‐glucosidase inhibition and cytotoxicity study of the synthesized Cu (II) complex were determined by IC₅₀ values. The optimized geometry and vibrational harmonic frequencies for the Cu (II) complex were obtained by using Density Functional Theory (DFT) of HSEh1PBE/6–311++G(d,p)/LanL2DZ level. TD‐DFT/HSEh1PBE/6–311++G(d,p)/LanL2DZ level with CPCM model was applied to examine the electronic spectral properties and major contributions were determined via Swizard program. To investigate linear and nonlinear optical behavior of the synthesized Cu (II) complex, the α, Δα and χ⁽¹⁾/β, γ and χ⁽³⁾ parameters called linear/nonlinear optical parameters in gas phase and ethanol solvent were computed at the same level and basis set. Furthermore, molecular electrostatic potential (MEP) surface was determined by using the same level. The docking study of the Cu (II) complex to the binding site of the target protein (the template structure S. cerevisiae isomaltase) is fulfilled. Natural bond orbital (NBO) analysis was used to investigate the hyperconjugative interactions, inter‐ and intra‐molecular bonding and to determine coordination around Cu (II) ion. Finally, present work is the first remarkable scientific report of mixed‐ligand (H₂FDCA and 4(5)MeI) Cu (II) complex as novel drug candidate for DM II. It is also determined that microscopic third?NLO parameters for the Cu (II) complex is remarkable.