Saud I. Al-Resayes

Microwave synthesis of graphene sheets supporting metal nanocrystals in aqueous and organic media

We have developed a facile and scalable chemical reduction method assisted by microwave irradiation for the synthesis of chemically converted graphene sheets and metal nanoparticles dispersed on the graphene sheets. The method allows rapid chemical reduction of exfoliated graphite oxide (GO) using a variety of reducing agents in either aqueous or organic media. It also allows the simultaneous reduction of GO and a variety of metal salts thus resulting in the dispersion of metallic and bimetallic nanoparticles supported on the large surface area of the thermally stable 2D graphene sheets.

Evaluation and characterisation of Citrullus colocynthis (L.) Schrad seed oil: Comparison with Helianthus annuus (sunflower) seed oil.

The physicochemical properties, fatty acid, tocopherol, thermal properties, (1)H NMR, FTIR and profiles of non-conventional oil extracted from Citrullus colocynthis (L.) Schrad seeds were evaluated and compared with conventional sunflower seed oil. In addition, the antioxidant properties of C. colocynthis seed oil were also evaluated. The oil content of the C. colocynthis seeds was 23.16%. The main fatty acids in the oil were linoleic acid (66.73%) followed by oleic acid (14.78%), palmitic acid (9.74%), and stearic acid (7.37%). The tocopherol content was 121.85 mg/100g with γ-tocopherol as the major one (95.49%). The thermogravimetric analysis showed that the oil was thermally stable up to 286.57°C, and then began to decompose in four stages namely at 377.4°C, 408.4°C, 434.9°C and 559.2°C. The present study showed that this non-conventional C. colocynthis seed oil can be used for food and non-food applications to supplement or replace some of the conventional oils.

From Biomass to Chemicals: Synthesis of Precursors of Biodegradable Surfactants from 5‐Hydroxymethylfurfural

The selective acetalization of 5-hydroxymethylfurfural (HMF) with long-chain alkyl alcohols has been performed to obtain precursors of molecules with surfactant properties. If direct acetalization of HMF with n-octanol is performed in the presence of strong acids (homogeneous and heterogeneous catalysts), an increase in etherification versus acetalization occurs. Beta zeolite catalyzes both reactions. However, if the acidity of a zeolite (Beta) was controlled by partial exchange of H(+) with Na(+), the dioctyl acetal of HMF can be achieved in 95% yield by transacetalization. It is possible to achieve a high yield in a very short reaction time through a two-step one-pot process, which includes the synthesis of the dimethyl acetal of HMF followed by transacetalization with n-octanol. The one-pot process could be extended to other alcohols that contain 6-12 carbon atoms to afford 87-98% yield of the corresponding dialkyl acetal with a selectivity higher than 96%. The optimized catalyst with an adequate Na content (1.5NaBeta) could be recycled without loss of activity or selectivity.

In vitro DNA binding, molecular docking and antimicrobial studies on a newly synthesized poly(o-toluidine)–titanium dioxide nanocomposite

A poly(o-toluidine)–titanium dioxide (POT–TiO2) nanocomposite has been synthesized for the first time by in situ chemical oxidative polymerization of o-toluidine (OT) in the presence of titanium dioxide (TiO2) nanoparticles. FTIR, SEM, TEM, XRD, TGA and DTA were used to characterize the POT–TiO2 nanocomposite. The characterization results confirmed that there is a strong interaction between POT and TiO2 nanoparticles and the nanocomposite showed higher thermal stability than pristine POT. The in vitro DNA binding studies of POT and POT–TiO2 nanocomposite with ct-DNA in physiological buffer (pH-7.4) were investigated using spectrophotometry and circular dichroism. The absorption spectra of the POT and POT–TiO2 nanocomposite with DNA showed a hypochromic effect. The four types of 3D molecular field descriptors or field points as extrema of electrostatic, steric, and hydrophobic fields are described. These field points are used to define the properties necessary for a molecule to bind in a characteristic way into a specified active site. A molecular docking simulation was used to predict the modes of interactions of the drugs (POT and POT–TiO2) with DNA. The molecular docking results indicated that the modes of interactions between the two (POT and POT–TiO2) and DNA helix can be considered as groove binding. Moreover, the comparative antimicrobial activities of POT and its POT–TiO2 nanocomposite were tested and were found to exhibit antibacterial activity against Gram positive as well as Gram negative bacterial strains at micromolar concentration.

Luminescent Cd(II)–organic frameworks with chelating NH2 sites for selective detection of Fe(III) and antibiotics

Excess and deficiency of iron(III) and antibiotics from normal permissible limits will induce serious disorders, so their detection is important but challenging. In this work, by introducing a new amino triazole ligand N1-(4-(1H-1,2,4-triazole-1-yl)benzyl)-N1-(2-aminoethyl)ethane-1,2-diamine (L), a series of Cd(II)-based metal–organic frameworks (MOFs) [Cd3(BDC)3(DMF)2] (1), [Cd(L)(BDC)]2·2DMF·H2O (2), [NaCd2(L)(BDC)2.5]·9H2O (3), [Cd2(L)(2,6-NDC)2]·DMF·5H2O (4) and [Cd2(L)(BPDC)2]·DMF·9H2O (5) were synthesized. MOFs 1, 2 and 3 obtained under the same conditions with the same auxiliary ligand (H2BDC) but different amounts of alkali (NaOH) show distinct 3D, 1D and 3D framework structures, respectively, in which L and BDC2− exhibit varied coordination modes. 4 and 5 with 3D structures were isolated by using longer auxiliary ligands of 2,6-H2NDC and H2BPDC. The porosity and excellent fluorescence performance of 3, 4 and 5 make them potential luminescent sensors for Fe(III) and antibiotics. The results show that 3, 4 and 5 represent high sensitivity for the detection of Fe(III) ions with detection limits of 155 ppb for 3, 209 ppb for 4 and 297 ppb for 5 due to the existence of open channels and chelating NH2 sites. In addition, the strong emissions of 3, 4 and 5 can be quenched efficiently by trace amounts of NFs (nitrofurazone, NZF; nitrofurantoin, NFT; furazolidone, FZD) antibiotics even in the presence of other competing antibiotics such as β-lactams (penicillin, PCL). They are responsive to NZF with detection limits of 162 ppb for 3, 75 ppb for 4 and 60 ppb for 5.

Excited states dipole moments and polarizabilities of uracil and cytosine 5-halo derivatives

Abstract Dipole moments and polarizabilities of different excited states of uracil and cytosine 5-halo derivatives have been calculated using solvent shift methods and CNDO/S calculations. The results are discussed in relation to different solute–solvent interactions and the nature of the electronic transition.

Synthesis, spectroscopic characterization and biological activities of N4O2 Schiff base ligand and its metal complexes of Co(II), Ni(II), Cu(II) and Zn(II)

The Schiff base ligand, bis(indoline-2-one)triethylenetetramine (L) obtained from condensation of triethylenetetramine and isatin was used to synthesize the complexes of type, [ML]Cl(2) [M=Co(II), Ni(II), Cu(II) and Zn(II)]. L was characterized on the basis of the results of elemental analysis, FT-IR, (1)H and (13)C NMR, mass spectroscopic studies. The stoichiometry, bonding and stereochemistries of complexes were ascertained on the basis of results of elemental analysis, magnetic susceptibility values, molar conductance and various spectroscopic studies. EPR, UV-vis and magnetic moments revealed an octahedral geometry for complexes. L and its Cu(II) and Zn(II) complexes were screened for their antibacterial activity. Analgesic activity of Cu(II) and Zn(II) complexes was also tested in rats by tail flick method. Both complexes were found to possess good antibacterial and moderate analgesic activity.

Effects of homogenization process parameters on physicochemical properties of astaxanthin nanodispersions prepared using a solvent-diffusion technique.

Nanodispersion systems allow incorporation of lipophilic bioactives, such as astaxanthin (a fat soluble carotenoid) into aqueous systems, which can improve their solubility, bioavailability, and stability, and widen their uses in water-based pharmaceutical and food products. In this study, response surface methodology was used to investigate the influences of homogenization time (0.5–20 minutes) and speed (1,000–9,000 rpm) in the formation of astaxanthin nanodispersions via the solvent-diffusion process. The product was characterized for particle size and astaxanthin concentration using laser diffraction particle size analysis and high performance liquid chromatography, respectively. Relatively high determination coefficients (ranging from 0.896 to 0.969) were obtained for all suggested polynomial regression models. The overall optimal homogenization conditions were determined by multiple response optimization analysis to be 6,000 rpm for 7 minutes. In vitro cellular uptake of astaxanthin from the suggested individual and multiple optimized astaxanthin nanodispersions was also evaluated. The cellular uptake of astaxanthin was found to be considerably increased (by more than five times) as it became incorporated into optimum nanodispersion systems. The lack of a significant difference between predicted and experimental values confirms the suitability of the regression equations connecting the response variables studied to the independent parameters.

Formation and stability of 3–5 atom gold clusters from gold complexes during the catalytic reaction: dependence on ligands and counteranions

Gold complexes and salts decompose to catalytically active 3-5 atom gold clusters during the one-pot acylation-hydration of propargyl alcohols. Kinetic and spectroscopic studies show that released ligands and counteranions exert a direct effect on the formation and stability of the clusters.

Garden cress (Lepidium sativum Linn.) seed oil as a potential feedstock for biodiesel production

Lepidium sativum L. (garden cress) is a fast growing annual herb, native to Egypt and west Asia but widely cultivated in temperate climates throughout the world. L. sativum seed oil (LSO) extracted from plants grown in Tunisia was analyzed to determine whether it has potential as a raw material for biodiesel production. The oil content of the seeds was 26.77%, mainly composed of polyunsaturated (42.23%) and monounsaturated (39.62%) fatty acids. Methyl esters (LSOMEs) were prepared by base-catalyzed transesterification with a conversion rate of 96.8%. The kinematic viscosity (1.92 mm(2)/s), cetane number (49.23), gross heat value (40.45), and other fuel properties were within the limits for biodiesel specified by the ASTM (American Standard for Testing and Materials). This study showed that LSOMEs have the potential to supplement petroleum-based diesel.