Muhammad Ashraf Shaheen

An economically viable method for the removal of selected divalent metal ions from aqueous solutions using activated rice husk

Biosorption of divalent metal ions, i.e. Pb(II), Cd(II), Zn(II) and Cu(II) onto rice husk activated (RHA) is investigated over pH range (1-10) via batch adsorption technique. The chemical and thermal activation of rice husk with 0.1M HNO(3) and 1M K(2)CO(3) at 473 K enhanced the removal efficiency of RHA (35+/-2.1-99+/-0.5%, 33+/-1.2-97+/-0.6%, 32+/-1.3-96+/-0.8% and 28+/-1.8-95+/-0.9% before and after treatment, respectively). The surface area analysis of RHA by BET (Brunauer, Emmett and Teller) nitrogen adsorption method provided pore area and average pore diameter to be 542+/-2.3m(2)g(-1) and 1076+/-5.6 nm respectively. SEM and FTIR analyses of RHA were carried out to determine the surface morphology and functional groups involved in metal binding mechanism, respectively. The adsorption equilibrium was well described by Freundlich, Langmuir and Dubinin-Radushkevish (D-R) isotherm models by employing (4.8-48, 8.9-89, 15.3-153 and 15.7-157)x10(-5)M solution concentrations of sorbates, respectively, at equilibrium time of 20 min at pH 6 and onto 0.2g of sorbent. The kinetics of mass transfer and intra-particle diffusion for metal ions sorption onto RHA were studied with Lagergren and Morris-Weber kinetic models. The numerical values of thermodynamic parameters indicated the exothermic nature, spontaneity and feasibility of the sorption process. The desorption study of metal components from RHA surface was carried out with 0.1M HCl. The sorption mechanism developed illustrates the strong interactions of sorbates with the active sites of the sorbent coupled with efficient and environmentally clean exploitation of rice waste product.

Mercury(II) complexes of pyrrolidinedithiocarbamate, crystal structure of bis{[μ2-(pyrrolidinedithiocarbamato-S,S ′)(pyrrolidinedithiocarbamato-S,S ′)mercury(II)]}

Mercury(II) complexes of pyrrolidinedithiocarbamate (PDTC) having the general formula [Hg(PDTC)X] (X = Cl−, SCN−, and CN−) and [Hg(PDTC)2] have been prepared and characterized by elemental analysis, IR, and NMR. The crystal structure of [Hg(PDTC)2] has also been determined by X-ray crystallography, showing that the complex is a centrosymmetric dimer, [Hg2(PDTC)4] (bis[µ2-(pyrrolidinedithiocarbamato-S,S′)(pyrrolidinedithiocarbamato-S,S′)mercury(II)]) (1). The solid-state structure of 1 contains two crystallographically equivalent Hg(II) centers in a distorted tetrahedron.

Structural characterization of a cadmium(II)-sulfato complex, [Cd(N,N′-diethyl thiourea)4(SO4)]

A cadmium(II) complex, tetrakis(N,N′-diethylthiourea)sulfatocadmium(II), [Cd(Detu)4SO4] (1) is prepared and its crystal structure is determined by X-ray crystallography. The crystal structure of the complex consists of an independent molecule with the central cadmium atom coordinated to four thione sulfur atoms of Detu and two oxygen atoms of the sulfate ligand. The Cd atom has a pseudo-octahedral coordination environment with the cis angles varying from 57.68° to 126.57°, while the trans angles fall in the range of 142° to 169°. The new complex was also characterized by IR and NMR spectroscopy and the spectroscopic data are discussed in terms of the nature of bonding.

Synthesis and Crystal Structure of a Cyanido-Bridged Bimetallic Copper(II)–Silver(I) Complex of Imidazole and [Ag(CN)2]−: [Cu(Imidazole)4{Ag(CN)2}2]

A cyanido-bridged Cu(II)–Ag(I) bimetallic complex, [Cu(Imidazole)4{Ag(CN)2}2] has been prepared and structurally characterized. The compound crystallizes in the orthorhombic space group Pmna. The crystal structure of the complex consists of trinuclear molecules made up of one [Cu(Imidazole)4]+2 and two [Ag(CN)2]− units. The trinuclear molecules are interlinked to each other through N–H–N and C–H–N hydrogen bonds. The Cu(II) ions are located on mirrors and assume distorted octahedral geometry with the basal plane consisting of four imidazole N-atoms.Graphical Abstract

Growth and antioxidant response of Brassica rapa var. rapa L. (turnip) irrigated with different compositions of paper and board mill (PBM) effluent

Current study presents the effect of irrigation with different compositions (0%, 20%, 40%, 60%, 80% and 100%) of PBM effluent on growth and antioxidant potential of Brassica rapa var. rapa L. plants. Seeds were exposed to different PBM effluent compositions, which resulted in significant decrease in their germination potential with elevated delay index. Significant changes in growth parameters (plant height, number of leaves and leaf area) were recorded for turnip plants at regular intervals (25, 50 and 75 d) as function of PBM effluent proportion. Response of biochemical and antioxidant constituents in different parts of turnip, against stress induced by PBM effluent, was assessed by estimating the contents of chlorophyll (a+b), carotenoids, protein, phenolics, flavonoids, ascorbic acid and malondialdehyde. Antioxidant activity was evaluated by measuring DPPH radical scavenging potential. The results of this study suggest that the impact of PBM effluent irrigation is dependent on concentration of effluent in irrigation mixture and is very clear on plant growth and antioxidant attributes. Maximum benefits were secured at 40% PBM effluent to irrigate turnip plants till maturity while higher concentrations were found useful for shorter period (25-50 d).

Facile biosynthesis of Ag-NPs using Otostegia limbata plant extract: Physical characterization and auspicious biological activities

Silver nanoparticles (Ag-NPs) synthesized through reduction by Otostegia limbata green extract are, hereby, reported for the first time. It is very interesting to observe that in this case, O. limbata plant extract acts as a strong chelating agent in Ag-NPs formation through AgNO3. Scanning electron microscope (SEM) studies expose that Ag-NPs formation is highly homogenous and spherical with mean particle size of 32±0.8 nm. A typical Ag absorption peak has been observed at 419 nm by ultra violet (UV)-visible spectroscopy which have endorsed the successful formation of single phase Ag-NPs. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) examination further validates the crystalline pure phase structure of Ag-NPs. Promising results have been recorded against protein kinase inhibition assay and antibacterial assay having prominent pathogenic strains. Our present study explores that biosynthesized eco-friendly Ag-NPs have great potential, in the future, for anticancer drug developme...

A monoclinic polymorph of cysteamine hydro­chloride

The title compound (systematic name: 2-mercaptoethanaminium chloride), C2H8NS+·Cl−, the hydrochloride salt of cysteamine, in contrast to the previously reported triclinic polymorph [Kim et al. (2002 ▶). Polyhedron, 21, 225–228], crystallized in the monoclinic crystal system. In the crystal, the cysteaminium cations are linked to the chloride anions via one S—H⋯Cl and three N—H⋯Cl hydrogen bonds. Two-dimensional slab-like networks are formed, which are stacked in [100]. This arrangement is similar to that observed in the triclinic polymorph.

A Brief Review on Fluorescent Copper Sensor Based on Conjugated Organic Dyes

The design and development of the fluorescence reporting molecules for the trace recognition of the metallic ions in the aqueous, mixed organic aqueous media, environmental specimen, living things e.g., body fluids, serum, urine etc is the evergreen research area. Among several methodologies utilized for these purposes, the fluorescent techniques have wonderful impact in the era of metal sensor development due to their acclamatory features of non-invasive detection process and appreciable sensitivity. The utilization of small organic molecules for the sensation of metallic ions through the fluorescent techniques harvested the wonderful results having some interesting features of chromogenic response on metal binding, robustness in the preparation and applicability to establish the metallic accumulation level inside the live cells via bioimaging studies. The detailed knowledge and background about the several reported chemosening strategies have the utmost importance in order to understand or to design the novel molecules for metal sensing purposes. The objective of the presents review was to compile the best ever used copper sensing strategies via fluorescent means in the running decade. We have summarized the values of optical positions of the spectral lines, spectral shifting upon metal binding, binding/association/dissociation constants, chromogenic changes in the reaction mixture, proposed complexation mechanism of the ligand with the copper, ligand sensitivities toward the copper recognition, binding stoichiometries and the detailed bioimaging results where applicable.

Synthesis, Crystal Structure, DFT Modeling and Biological Activity of a Trinuclear Copper(II) Azide Polymer Containing Imidazole and Bridging Imidazolate Ligands, [Cu3(Imz-H)4(Imz)2(N3)4]n

The title compound, [Cu3(Imz-H)4(Imz)2(N3)4]n (1) (Imz-H = imidazole) was prepared by the reaction of CuCl2·2H2O with imidazole and sodium azide, and its structure was determined by X-ray crystallography. The crystal structure shows that the complex exists in the form of a two dimensional polymer consisting of dimeric [Cu(Imz-H)(Imz)0.5(N3)1.5]2 and monomeric [Cu(Imz-H)2(Imz)(N3)] units. In the dimeric part each Cu(II) ion is bound to two nitrogen atoms of Imz-H or Imz− and three nitrogen atoms of azide adopting a distorted square pyramidal geometry. In the monomeric part, the copper atom is disordered over two positions and is coordinated to two imidazole molecules (Imz-H), two bridging imidazolate (Imz-) groups, and two weakly bound azide ions. In order to validate the obtained structure, the structures of two complexes; [Cu3(Imz-H)5(Imz)(HN3)4(N3)2]3+ containing one monomer and one dimeric unit as a model of 1 and a hypothetical complex, [Cu4(Imz-H)6(Imz)(HN3)4(N3)4]3+ containing only dimeric units were fully optimized at the B3LYP-D3 level of theory. The interaction energy between the dimeric and monomeric units in the former complex was found to be almost twice larger that calculated between the dimeric units in the later complex. Therefore, the theoretical results support that the experimentally determined structure (1) is energetically more preferred than that containing only the dimeric units. The natural bond orbital (NBO) analysis of the model complexes of (1) was performed and the distribution of spin density at the atoms of [Cu3(Imz-H)5(Imz)(HN3)4(N3)2]3+ and [Cu5(Imz-H)8(Imz)2(HN3)6(N3)4]4+ was discussed. The NBO charge on copper cation in the dimeric unit is 0.90 e and is smaller than that on the Cu(II) ion in the monomeric unit by 0.09 e. Antimicrobial properties of the complex were evaluated by minimum inhibitory concentration and the results showed that the complex exhibited no significant activities against the selected microorganisms.

Synthesis and crystal structure of a 3D copper(II)–silver(I) coordination polymer assembled through hydrogen bonding, π–π stacking and metal–π interactions, {[Cu(phen)2(CN)][Ag(CN)2] · 3H2O}n (phen = 1,10-phenanthroline)

Abstract A copper(II) polymeric complex {[Cu(phen)2(CN)][Ag(CN)2] · 3H2O}n, 1 (phen = 1,10-phenanthroline), has been prepared and structurally characterized. The compound crystallizes in the monoclinic space group P21/c with [Cu(phen)2(CN)]+ and [Ag(CN)2]− units and three water molecules. The cationic and anionic units are linked to each other through M-π and π–π interactions. The array is extended further by hydrogen bonding and π–π interactions to form a 3D network.