Edreese Alsharaeh

Synthesis and characterization of the in situ bulk polymerization of PMMA containing graphene sheets using microwave irradiation.

Polymethylmethacrylate–graphene (PMMA/RGO) nanocomposites were prepared via in situ bulk polymerization using two different preparation techniques. In the first approach, a mixture of graphite oxide (GO) and methylmethacrylate monomers (MMA) were polymerized using a bulk polymerization method with a free radical initiator. After the addition of the reducing agent hydrazine hydrate (HH), the product was reduced via microwave irradiation (MWI) to obtain R-(GO-PMMA) composites. In the second approach, a mixture of graphite sheets (RGO) and MMA monomers were polymerized using a bulk polymerization method with a free radical initiator to obtain RGO-(PMMA) composites. The composites were characterized by FTIR, 1H-NMR and Raman spectroscopy and XRD, SEM, TEM, TGA and DSC. The results indicate that the composite obtained using the first approach, which involved MWI, had a better morphology and dispersion with enhanced thermal stability compared with the composites prepared without MWI.

Enhanced electrocatalytic activity of gold nanoparticles on hydroxyapatite nanorods for sensitive hydrazine sensors

Well-designed noble metals and ceramic nanoarchitectures are significantly important for the development of high performance, selective, sensitive and cost effective electrochemical sensors. Here, we report gold (Au) nanoparticles (NPs) uniformly dispersed on hydroxyapatite (HAp) nanorods forming particles on rod nanoarchitectures for sensitive hydrazine sensors. The Au/HAp nanocomposites were prepared by a versatile hydrothermal precipitation method. The precipitated citrate-stabilized Au NPs were 6–8 nm in size and strongly anchored onto rod-shaped HAp with a diameter of 10 nm and length of 65 nm. The structural, chemical, and electrochemical properties and growth mechanism of the Au nanoparticles on the HAp nanorods (NRs) are presented. Progress toward the application of hybrid nanocomposites in electrochemical oxidation of hydrazine is reviewed. Compared to Au NPs, the incorporation of Au NPs into HAp NRs favored the adsorption of hydrazine, thus bringing hydrazine much closer to the catalytic sites of Au NPs and then increasing the efficiency of hydrazine oxidation in neutral solution. The amperometric (i–t) hydrazine sensor, using the as-prepared Au/HAp as the electrochemical catalyst, shows a wide linear response range of 0.5–1429 μM, a lower detection limit (0.017 μM) and very high sensitivity of 0.5 μA μM−1 cm−2. Furthermore, the Au/HAp nanocomposites showed an excellent anti-interference property towards the various organic and inorganic electroactive compounds, and good inter-electrode and intra-electrode reproducibility. Our present technique shows both qualitative and quantitative measurement of hydrazine in various water samples with high sensitivity, cost effectiveness and rapid analysis time.

Ion Mobility of Ground and Excited States of Laser-Generated Transition Metal Cations

The application of ion mobility to separate the electronic states of first-, second-, and third-row transition metal cations generated by the laser vaporization/ionization (LVI) technique is presented. The mobility measurements for most of the laser-generated transition metal cations reveal the presence of two or three mobility peaks that correspond to ground and excited states of different electronic configurations. The similarity of the measured reduced mobilities for the metal cations generated by LVI, electron impact, and glow discharge ion sources indicates that the same electronic configurations are produced regardless of the ion source. However, in comparison with electron impact of volatile organometallic compounds, the LVI populates fewer excited states due to the thermal nature of the process. Significant contributions to the production and populations of excited states of Ni+, Nb+, and Pt+ cations have been observed in the presence of argon during the LVI process and attributed to the Penning ionization mechanism. The origin of the mobility difference between the ground and the excited states is mainly due to the different interaction with helium. The ratio of the reduced mobilities of the excited and ground states decreases as one goes from the first- to the second- to the third-row transition metal cations. This trend is attributed to the ion size, which increases in the order 6sd(n-1) > 5sd(n-1) > 4sd(n-1). This work helps to understand the mechanisms by which transition metal cations react in the gas phase by identifying the ground and excited states that can be responsible for their reactivity.

Microwave Irradiation Effect on the Dispersion and Thermal Stability of RGO Nanosheets within a Polystyrene Matrix

Polystyrene-reduced graphene oxide (PSTY/RGO) composites were prepared via the in situ bulk polymerization method using two different preparation techniques. The general approach is to use microwave irradiation (MWI) to enhance the exfoliation and the dispersion of RGO nanosheets within the PSTY matrix. In the first approach, a mixture of GO and styrene monomers (STY) were polymerized using a bulk polymerization method facilitated by microwave irradiation (MWI) to obtain R-(GO-PSTY) composites. In the second approach, a mixture of RGO and STY monomers were polymerized using a bulk polymerization method to obtain RGO-(PSTY) composites. The two composites were characterized by FTIR, 1 H-NMR, XRD, SEM, HRTEM, TGA and DSC. The results indicate that the composite obtained using the first approach, which involved MWI, had a better morphology and dispersion with enhanced thermal stability, compared with the composites prepared without MWI. Moreover, DSC results showed that the Tg value of the composites after loading the RGO significantly increased by 24.6 °C compared to the neat polystyrene.

Biogenic synthesis of Zinc oxide nanostructures from Nigella sativa seed: Prospective role as food packaging material inhibiting broad-spectrum quorum sensing and biofilm

Bacterial spoilage of food products is regulated by density dependent communication system called quorum sensing (QS). QS control biofilm formation in numerous food pathogens and Biofilms formed on food surfaces act as carriers of bacterial contamination leading to spoilage of food and health hazards. Agents inhibiting or interfering with bacterial QS and biofilm are gaining importance as a novel class of next-generation food preservatives/packaging material. In the present study, Zinc nanostructures were synthesised using Nigella sativa seed extract (NS-ZnNPs). Synthesized nanostructures were characterized hexagonal wurtzite structure of size ~24 nm by UV-visible, XRD, FTIR and TEM. NS-ZnNPs demonstrated broad-spectrum QS inhibition in C. violaceum and P. aeruginosa biosensor strains. Synthesized nanostructures inhibited QS regulated functions of C. violaceum CVO26 (violacein) and elastase, protease, pyocyanin and alginate production in PAO1 significantly. NS-ZnNPs at sub-inhibitory concentrations inhibited the biofilm formation of four-food pathogens viz. C. violaceum 12472, PAO1, L. monocytogenes, E. coli. Moreover, NS-ZnNPs was found effective in inhibiting pre-formed mature biofilms of the four pathogens. Therefore, the broad-spectrum inhibition of QS and biofilm by biogenic Zinc oxide nanoparticles and it is envisaged that these nontoxic bioactive nanostructures can be used as food packaging material and/or as food preservative.

Reactions between Aromatic Hydrocarbons and Heterocycles: Covalent and Proton-Bound Dimer Cations of Benzene/Pyridine

Despite the fact that benzene (Bz) and pyridine (Py) are probably the most common and extensively studied organic molecules, the observation of a covalent adduct in the ionized benzene/pyridine system has never been reported. This Article reports the first experimental and theoretical evidence of a covalent (Bz x Py)(*+) adduct that results from the reaction of Bz(*+) with pyridine or Py(*+) with benzene. These reactions are studied using mass-selected ion mobility, chemical reactivity, collisional dissociation, and ab initio calculations. The (Bz x Py)(*+) adduct does not exchange ligands with Bz to form Bz(2)(*+) or with Py to form (Py)(2)H(+) despite the strong bonds in these homodimers. The thermochemistry then suggests that the (Bz x Py)(*+) heterodimer is bonded covalently with a bonding energy of >33 kcal/mol. Correspondingly, ab initio calculations identify covalently bonded propeller-shaped isomers of (Bz x Py)(*+) with bonding energies of 31-38 kcal/mol, containing a C-N bond. The mobility of the (Bz x Py)(*+) adduct in helium is consistent with these covalent dimers. As to noncovalent adducts, the computations identify novel distonic hydrogen-bonded complexes (C(5)H(5)NH(+) x C(6)H(5)(*)) where the charge resides on one component (PyH(+)), while the radical site resides on the other component (C(6)H(5)(*)). Collisional dissociation suggests that the covalent and distonic dimers may interconvert at high energies. The most stable distonic (C(5)H(5)NH(+) x C(6)H(5)(*)) complex contains a hydrogen bond to the phenyl radical carbon site with a calculated dissociation energy of 16.6 kcal/mol. This bond is somewhat stronger than the NH(+) x pi hydrogen bonds of PyH(+) to the pi system of the phenyl radical and of the benzene molecule. For this NH(+) x pi bond in the PyH(+) x Bz dimer, the measured binding energy is 13.4 kcal/mol, and ab initio calculations identify two T-shaped isomers with the NH(+) pointing to the center of the benzene ring or to the negatively charged C atoms of the ring. In contrast, the more stable proton-bound PyH(+) x Py dimer contains a linear NH(+)...N hydrogen bond. The formation of the (benzene/pyridine)(*+) adduct may represent a general class of addition reactions that can form complex heterocyclic species in ionizing environments.

Solution combustion synthesis and physico-chemical properties of ultrafine CeO2 nanoparticles and their photocatalytic activity

Ultrafine cerium oxide (CeO2) nanoparticles have been confirmed to be capable photocatalysts for environmental remediation because of their strong redox ability, long-term stability, nontoxicity, and cost effectiveness. CeO2 nanoparticles were successfully synthesized by a solution combustion method using cerium nitrate and urea. The physical, chemical, thermal and optical properties of the as-prepared samples were characterized using various analytical techniques. X-ray diffraction data confirm that the synthesized nanocrystalline CeO2 samples have cubic structure with an average grain size of 10, 8 and 19 nm corresponding to as-prepared, 300 and 600 °C annealed samples, respectively. The HRTEM results confirmed that the synthesized nanoparticles exhibit good polycrystalline nature with spherical ultrafine nanoparticles having size in the range of ∼9 nm. The UV/vis spectrum shows a maximum absorption at 294 nm and the band gap of CeO2 was tuned by adjusting the annealing temperature. In the PL spectra, a strong and broad emission band was observed at 425 nm due to the presence of a blue shift in the visible region. The photocatalytic activities of annealed CeO2 nanoparticles were investigated by photodegradation of methylene blue (MB) under UV light irradiation. It was found that the ultra-fine CeO2 nanoparticles exhibited better photocatalytic activity than that of already available commercial photocatalysts. Based on the investigation, these ultra-fine CeO2 nanoparticles possess adaptable potential applications for wastewater purification.

Intracluster Ion Molecule Reactions Following the Generation of Mg+ Within Polar Clusters

In this work we investigated the intracluster ion molecule reactions following the generation of Mg+ within the polar clusters (water, methanol, ether and acetonitrile), using time of flight mass spectrometry. In the case of Mg+/water and Mg+/methanol, dehydrogenation reactions are observed after the addition of five molecules. However, no dehydrogenation reactions are observed in the case of Mg+/ether or Mg+/acetonitrile clusters. This confirms the role of the H atom in (O–H) in the dehydrogenation reaction, and rules out any contribution from the H atom in the CH3 group. In addition, the magic numbers in the time of flight (TOF) mass spectra of the Mg+Xn clusters (X = H2O, CH3OH, CH3OCH3 and CH3CN) have been investigated. Finally, the role of ground electronic magnesium ion Mg+(2S1/2), and excited electronic magnesium ion Mg+(2P1/2) in the dehydrogenation reaction were investigated using Ion Mobility Mass spectrometry. The results offer direct evidence confirming the absence of the electronically excited, Mg+(2P1/2).

Enhanced hydroxyapatite nanorods formation on graphene oxide nanocomposite as a potential candidate for protein adsorption, pH controlled release and an effective drug delivery platform for cancer therapy

Herein, we report an eco-friendly hydrothermal synthesis of one dimensional (1D) hydroxyapatite (HAp) nanorods which were grown on two dimensional (2D) graphene oxide (GO) sheets (1D-on-2D) using creatine phosphate as a biomolecular source for phosphorus. Comprehensive analyses were performed to study the structural, morphological and bio-physical properties of the as-prepared nanocomposites using several analytical techniques. Enthrallingly, the as-prepared nanocomposite was explored to study the adsorption–desorption property of bovine serum albumin (BSA) on the HAp/GO nanocomposite. Notably, the observed data of adsorption–desorption process confirm the faster adsorption of BSA on HAp/GO nanocomposite. A maximum protein adsorption (Qo) of 350 mg g−1 in a neutral pH was attained for this nanocomposite and maximum release was obtained at a lower pH of 4. In addition, andrographolide, a model anticancer drug, was effectively loaded onto the HAp/GO nanocomposite through electrostatic and hydrophobic interactions. Experimental results showed that the HAp/GO nanocomposite not only exhibited good biocompatibility but also acted as good carrier for anticancer drugs, thereby greatly reducing the side effects of free anticancer drugs administered at high doses. Also, we include the results of the MTT assay of andrographolide loaded nanocomposite in a normal cell line (HaCaT) for selective anti-cancer activity. Therefore, the as-synthesized HAp/GO nanocomposite may act as a promising drug delivery platform due to its good biocompatibility, pH sensitivity, high drug loading efficiency, selectivity, and excellent biodegradability.

Polystyrene-Poly(methyl methacrylate) Silver Nanocomposites: Significant Modification of the Thermal and Electrical Properties by Microwave Irradiation

This work compares the preparation of nanocomposites of polystyrene (PS), poly(methyl methacrylate) (PMMA), and PSMMA co-polymer containing silver nanoparticles (AgNPs) using in situ bulk polymerization with and without microwave irradiation (MWI). The AgNPs prepared were embedded within the polymer matrix. A modification in the thermal stability of the PS/Ag, PMMA/Ag, and PSMMA/Ag nanocomposites using MWI and in situ was observed compared with that of neat PSMMA, PS, and PMMA. In particular, PS/Ag, and PSMMA/Ag nanocomposites used in situ showed better thermal stability than MWI, while PMMA/Ag nanocomposites showed improved thermal stability. The electrical conductivity of the PS/Ag, PMMA/Ag, and PSMMA/Ag composites prepared by MWI revealed a percolation behavior when 20% AgNPs were used as a filler, and the conductivity of the nanocomposites increased to 103 S/cm, 33 S/cm, and 40 mS/cm, respectively. This enhancement might be due to the good dispersion of the AgNPs within the polymer matrix, which increased the interfacial interaction between the polymer and AgNPs. The polymer/Ag nanocomposites developed with tunable thermal and electrical properties could be used as conductive materials for electronic device applications.