Presence Of Polyethyleneimine Research Articles

Improvement of CO2 capture by graphite oxide in presence of polyethylenimine

In this study, we developed a new CO2 adsorbents based on graphite oxide (GO) modified with amine groups from polyethylenimine. GO was prepared by a modified Hummers' method. An investigation of CO2 adsorption by the polyethylenimine-impregnated GO showed that the CO2 adsorption capacity increased with increasing polyethylenimine content. Polyethyleneimine increases the amount of adsorption of CO2 resulting from a chemical bond. The polyethylenimine-impregnated GO exhibited higher CO2 adsorption capacity than pristine GO. From the results, the maximum CO2 adsorption capacity and CO2/N2 selectivity were 32.89 mg g−1 and 37.13, respectively, at a polyethylenimine content of 60 wt%.

Organic Amine-Mediated Synthesis of Polymer and Carbon Microspheres: Mechanism Insight and Energy-Related Applications.

A general organic amine-mediated synthesis of polymer microspheres is developed based on the copolymerization of resorcinol, formaldehyde, and various organic amines at room temperature. Structure formation and evolution of colloidal microspheres in the presence of polyethylenimine are monitored by dynamic light scattering measurements. It is found that the colloidal clusters are formed instantaneously and then experience an anomalous shrinkage-growth process. This should be caused by two different reaction pathways: cross-linking inside the microspheres and step-growth polymerization of substituted resorcinol on the microsphere surface, leading to the formation of core-shell heterogeneous structures as confirmed by TEM observation and XPS analysis. A formation mechanism of polymer microspheres is provided based on the aggregation of polyethylenimine/resorcinol-formaldehyde (PEI-RF) self-assembled nuclei, which is apparently different from the conventional Stöber process. Furthermore, nitrogen-doped carbon microspheres are prepared by the direct carbonization of these polymer microspheres, which exhibit microporous BET surface areas of 400-500 m(2) g(-1), high nitrogen contents of 5-6 wt %, and a good CO2 adsorption capacity up to 3.6 mmol g(-1) at 0 °C. KOH activation is further employed to develop the porous texture of carbon microspheres without sacrificing the spherical morphology. The resultant activated carbon microspheres exhibit small particle size (<80 nm), high BET surface areas of 1500-2000 m(2) g(-1), and considerable nitrogen content of 2.2-2.0 wt %. When used as the electrode materials for supercapacitors, these activated carbon microspheres demonstrate a high capacitance up to 240 F g(-1), an unprecedented rate performance and good cycling performance.

A facile synthesis of Ag/AgCl hybrid nanostructures with tunable morphologies and compositions as advanced visible light plasmonic photocatalysts.

This paper describes a simple and fast aqueous-phase route to the synthesis of Ag/AgCl hybrid nanostructures. These hybrid nanostructures were synthesized by reduction of AgCl nanoparticles with controlled shapes prepared by reacting Ag(+) with Cl(-) in the presence of polyethyleneimine (PEI) in an aqueous-phase. We could easily control the morphology and composition of the nanostructures by varying the experimental conditions, including the reaction temperature and the amount of the reducing agent. The as-synthesized Ag/AgCl hybrid nanostructures exhibited enhanced photocatalytic activity and stability during the degradation of methyl orange under visible light irradiation because of their strong surface plasmon resonance (SPR) effect.

Deciphering the aggregation mechanism of bacteria (Shewanella oneidensis MR1) in the presence of polyethyleneimine: Effects of the exopolymeric superstructure and polymer molecular weight

Aggregation tests between bacteria and Polyethyleneimine (PEI) of low (600g/mol) and high (750,000g/mol) molecular weight were performed in order to address the physico-chemical mechanisms underlying the interactions between cationic polymer and bacterial membranes. The selected strain, Schewanella oneidensis MR-1, produces a lipopolysaccharide (LPS) of various lengths depending on the growth conditions. Optical density, bioaggregate size, electrophoretic mobility measurements, TEM and AFM observations, and cell lysis tests (crystal violet release), were collected to describe the PEI-mediated aggregation of LPS-O-antigen-free and LPS-O-antigen-decorated bacteria. The results show that PEI of low molecular weight (600g/mol) fails to aggregate bacteria, whereas PEIs of higher molecular weight (60,000 and 750,000g/mol) lead to flocculation at low polymer concentrations. In addition, the LPS-O antigen bacterial superstructure is shown to act as a protective barrier, thus delaying the harmful effects of the cationic polymer. Despite this protection, the interaction of bacterial membranes with increasing concentrations of PEI leads to a series of deleterious processes including biosurface modification (peeling, membrane permeabilization and/or lysis), aggregation of bacterial cells, and complexation of PEI with both released biosurface fragments and cytoplasmic residues issued from lysis.

Water-dispersible boronate nanoparticles as support materials for noble metals in the hydrogenation of levulinic acid to γ-valerolactone

The sequential dehydration reaction of benzene-1,4-diboronic acid with pentaerythritol in the presence of polyethyleneimine (PEI) led to polymeric 3-benzo-2,4,8,10-tetraoxa- 3,9-diboraspiro[5.5]undecane, resulting in the formation of a PEI-coated boronate nanoparticle (BNP) with a mean diameter of 121 ± 43 nm through the spontaneous self-assembly. Subsequently, noble metal deposition on the boronate particle (M/BNP, M = Ru, Pd and Pt) was successfully achieved by NaBH4 reduction of RuCl3, and in the presence of BNP. Exploration of boronate-based catalytic systems applicable to the conversion of biomass to chemicals revealed that Ru/BNP has excellent catalytic activity for the hydrogenation of levulinic acid to γ-valerolactone (GVL) in H2O under 0.8 MPa of H2 at 100 °C; after 4 h, the reaction afforded GVL in 94.6% yield. The catalytic performance and recyclability of Ru/BNP in the reaction were investigated.

A Simple and Fast Aqueous-Phase Synthesis of Ultra-Highly Concentrated Silver Nanoparticles and Their Catalytic Properties.

A simple and fast synthetic route to ultra-highly concentrated silver nanoparticles with long-term stability by reducing AgNO3 with ascorbic acid in the presence of polyethyleneimine (PEI) as a stabilizer in an aqueous phase is reported. The concentration of silver precursor was as high as 2000 mm (200 g of Ag nanoparticle per liter of water) and the reaction time was less than 10 min. The resulting silver nanoparticles show long-term stability after two months of storage at room temperature without any signs of particle aggregation or precipitation in an aqueous phase. The successful ligand exchange of PEI-stabilized silver nanoparticles to polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) without particle aggregation is also demonstrated. In addition, the catalytic activities of silver nanoparticles stabilized by various stabilizers prepared by the ligand exchange method was investigated. The PEI-stabilized silver nanoparticles exhibited a higher stability than those of PEG- and PVP-stabilized silver nanoparticles in the diffusion-controlled catalytic reduction of 4-nitrophenol to 4-aminophenol by NaBH4 .

A simple hydrothermal synthesis and fabrication of zinc oxide–copper oxide heterostructure for the sensitive determination of nonenzymatic glucose biosensor

Zinc oxide nanorods and copper oxide nanospheres (ZnO–CuO), were prepared through a simple hydrothermal method. The nanorods and nanospheres readily occurred in the presence of polyethyleneimine which acts as a stabilizing or reducing agent for the growth of nanocomposite and makes them more stable. The obtained nanocomposite was confirmed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and cyclic voltammetric studies. The nanocomposite ZnO–CuO is further coated on the glassy carbon electrode (ZnO–CuO/GCE). The ZnO–CuO/GCE showed an excellent electrocatalytic performance toward the determination of glucose. The as-modified electrode achieved wider linear range from 0.1 to 4167μM with a very low detection limit (LOD) of 0.038μM. The developed sensor displayed high sensitivity of 1457.5μAmM−1cm−2. In addition, the ZnO–CuO/GCE is able to detect the glucose even in the presence of biologically interfering molecules. The sensor achieved appreciable repeatability, reproducibility and long term stability (up to 38 days). The practicality of the sensor was demonstrated in the human serum samples.

Computational Chemistry and Electrochemical Studies of Adsorption Behavior of Organic Additives during Gold Deposition in Cyanide-free Electrolytes

In this work, a combined approach using density functional theory (DFT), molecular dynamic simulations, and electrochemical experiments was developed to study organic additives used for a cyanide-free gold electrodeposition process. When 5,5-dimethylhydantoin (DMH) is used as the complexing agent, organic additives with either imino groups or nitrogenous heterocyclic rings including polyethyleneimine (PEI), 2,2′-bipyridine, and nicotinic acid (NA) were systematically investigated. Electronic properties and orbital information of these studied additives were determined by quantum chemical calculations based on DFT. Compared to the other additives, PEI was predicted as the most promising one for the introduced DMH based gold electrodeposition. The theoretical prediction was further verified by using experimental results. In particular, the cathodic polarization of the gold electrodeposition was significantly improved in the presence of PEI. Also, the resulting gold electrodeposit shows obviously finer crystalline particles largely. In addition, molecular dynamic simulations determined that PEI molecules possess optimized adsorption behavior on the gold surface, suggesting its effectiveness to be additive in the studied cyanide-free Au-electrodeposition electrolytes.

Morphology control of eprosartan crystals via polymer-directed crystallization

Improving the stability, processability and bioavailability of drug crystals is important during the development of most drugs. In traditional crystal engineering, different crystallization conditions are used to tailor the properties of crystals, often improving one property at the cost of another, or simply optimizing both properties. The influence of soluble polymers on the particle morphology of crystals during the crystallization of eprosartan was investigated to explore the possibility of improving the properties of the drug crystals. The presence of polyethylenimine (PEI) during the crystallization of eprosartan induced the self-assembly of small primary crystals into larger aggregates without changing the crystal polymorph. In particular, spherical aggregates of an ordered structure were obtained when eprosartan was crystallized by changing the pH from 12 to 4.2 in the presence of PEI. This technique of polymer-directed crystallization is promising for the property engineering of drug crystals, which has been limited by a few crystallization variables to date.

Introducing polyethyleneimine (PEI) into the electrospun fibrous membranes containing diiron mimics of [FeFe]-hydrogenase: Membrane electrodes and their electrocatalysis on proton reduction in aqueous media

A number of fibrous membranes with cellulose acetate as a matrix and functionalised with diiron mimics of the diiron subunit of [FeFe]-hydrogenase were prepared by electrospinning technique. Four mimics, [Fe2(μ-edt) (CO)6] (1), [Fe2{μ-SCH2CH(CH2OH)S}(CO)6] (2), [Fe2{(μ-S)2(C6O2H4)}(CO)6] (3) and [Fe2{μ-SCH2CH(OH)CH2(OH)}2(CO)6] (4), bearing 0, 1, 2 and 4 hydroxyl group(s) were incorporated into the electrospun fibrous membranes (EFMs). To improve the conductivity of the EFMs, graphene oxide was chemically gratified onto cellulose acetate. The resultant EFMs membranes were characterized using infrared spectroscopic, thermogravimetric and scanning electron microscopic techniques. The electrochemical behaviours and electrocatalytic performance on proton reduction of the membrane electrodes assembled from the EFMs showed in aqueous media that the membrane (M2) containing complex 2 is most durable and exhibited the best catalytic performance. To the electrospinning system containing complex 2 was further doped with basic polymer PEI to enhance tentatively proton transfer during the electrocatalysis of proton reduction. Our results showed that the presence of PEI in the EFMs did improve the electrocatalytic performance of proton reduction, presumably due to the enhancement in proton transfer in the catalysis.

Enhanced thermal stability and pH behavior of glucose oxidase on electrostatic interaction with polyethylenimine

Electrostatic interactions, mediated by ionic-exchange, between polyethylenimine (PEI) and glucose oxidase (GOx) were used to form GOx–PEI macro-complex, which were evaluated for pH and thermal stability of GOx. Under the experimental conditions, the complex had a dominant GOx presence on its surface and a hydrodynamic diameter of 205±16nm. Activity was evaluated from 40 to 75°C, and at pH from 2 to 12. GOx activity in complex was maintained up to 70°C and it was lost at 75°C. In contrast, free GOx showed a maximum activity at 50°C, which was completely lost at 70°C. This difference, observed by fluorescence analysis, was associated with the compact unfolded structure of GOx in the complex. This GOx stability was not observed under pH variations, and complex formation was only possible at pH≥5 where enzymatic activity was diminished by the presence of PEI.

Fluorescent nanoparticles from starch: facile preparation, tunable luminescence and bioimaging.

Fluorescent organic nanoparticles (FONs) based on carbohydrate polymers were prepared through one-pot hydrothermal treatment of starch in the presence of polyethyleneimine. These FONs (named as PEI-Starch FONs) were characterized by a series of techniques including UV-Vis absorption spectroscopy, fluorescent spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Results showed that the size of PEI-Starch FONs is 10-30 nm. The PEI-Starch FONs exhibited high water dispersibility because of the existence of hydrophilic functional groups on their surface. After excited with different wavelength, PEI-Starch FONs emitted strong and excitation-dependent fluorescence. To evaluate their potential for biomedical applications, biocompatibility and cell uptake behavior of PEI-Starch FONs were further investigated. We demonstrated that PEI-Starch FONs are biocompatible with cells and can be easily internalized by cells within 3h. Taken together, novel FONs have been prepared via a simple and scalable hydrothermal method using starch and polyethyleneimine as precursors. These PEI-Starch FONs showed excellent fluorescence properties, high water dispersibility and good biocompatibility, making them highly potential for various biomedical applications.

Facile synthesis of folic acid-functionalized iron oxide nanoparticles with ultrahigh relaxivity for targeted tumor MR imaging.

We present the polyethyleneimine (PEI)-assisted synthesis of folic acid (FA)-functionalized iron oxide (Fe3O4) nanoparticles (NPs) with ultrahigh relaxivity for in vivo targeted tumor magnetic resonance (MR) imaging. In this work, water-dispersible and stable Fe3O4 NPs were synthesized in the presence of PEI via a facile mild reduction approach. The surface PEI coating afforded the formed Fe3O4 NPs with the ability to be functionalized with polyethylene glycol (PEG)-linked FA and fluorescein isothiocyanate (FI). A further acetylation step to neutralize the remaining PEI surface amines gave rise to the formation of multifunctional FA-functionalized Fe3O4 NPs, which were subsequently characterized via different methods. We show that the developed FA-functionalized Fe3O4 NPs have a good water-dispersibility, good colloidal stability, ultrahigh r2 relaxivity (475.92 mM-1 s-1), and good hemocompatibility and cytocompatibility in the studied concentration range. The targeting specificity of the FA-modified Fe3O4 NPs to FA receptor (FAR)-overexpressing HeLa cells (a human cervical carcinoma cell line) was subsequently validated by flow cytometry and confocal microscopy. Significantly, the developed FA-modified Fe3O4 NPs can be used as a nanoprobe for targeted MR imaging of HeLa cells in vitro and the xenografted tumor model in vivo via an active FA-mediated targeting strategy. The developed multifunctional FA-modified Fe3O4 NPs with an ultrahigh r2 relaxivity may be used as an efficient nanoprobe for the targeted MR imaging of various kinds of FAR-overexpressing tumors.

Deposition of Manganese Oxdies on Graphene Nanoplatelet (GnP) Surface for Energy Applications: Synthesis, Characterization and the Evaluation of Effect of Surfactant on the Synthesis Process

Effective synthesis methods are required to produce metal nanoparticles of controlled size and narrow size distribution as small particles tend to sinter together easily. This problem can be overcome by applying small particles on a support surface. Metal particles supported on carbon/graphitic substrate can find variety of applications in chemical industries; automobiles; energy and power generating devices; hydrogen economy and sensors. Graphene Nanoplatelet (GnP), a material with excellent mechanical properties; thermal and electrical conductivity; excellent corrosion and oxidation resistance; and low impurity levels has the potential to be an excellent substrate for nanoparticle deposition. Manganese Oxides (MnOx) are interesting metal oxide structures with many crystal phases. Different crystal phases and structural arrangements can be obtained through various synthetic methods. In this work MnOx has been deposited on the GnP surface through a redox reaction between KMnO4 and MnSO4.H2O salts in the presence of GnP substrate in aqueous medium. Molar ratio and molar concentration of salts have been used as variable parameters keeping substrate amount; synthesis time and synthesis temperature as constant parameters. The MnOx deposits are characterized in terms of several parameters such as particle morphology; particle size; distribution of particles; crystal phases and surface area. Polyethyleneimine (PEI) is a hydrophilic polymer with an overall positive charge in neutral aqueous solution that gets adsorbed on highly hydrophobic GnP surface and stabilizes the particles in water. It has been observed that MnOx particle morphology and crystal phase changes drastically in the presence of PEI as surfactant. Highly uniform particle distribution can be obtained by controlling the molar concentration of reagent salts. Crystal structure analysis of MnOx particles thus synthesized in this work indicates that the GnP-MnOx composites may find application as Li-ion battery anode, Pseudocapacitor electrode and as catalyst for Li-air battery cathode. Crystal structure and morphological analysis of the MnOx has been performed with X-Ray Diffraction (XRD); Scanning Electron Microscopy (SEM); Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM). Content of MnOx and the net surface area of the composites have been measured with Thermo Gravimetric Analysis (TGA) and Brunauer Emmett Teller (BET) method respectively.

Submicrometer@nano Bimodal TiO2 Particles as Easily Sintered, Crack-Free, and Current-Contributed Scattering Layers for Dye-Sensitized Solar Cells

Submicrometer@nano bimodal TiO2 particles consisting of a submicrometer core and a mesoporous structured shell were synthesized by a chemical deposited method. The submicrometer TiO2 particles were first dispersed in the titanium(IV) bis(ammonium lactato) dihydroxide solution in the presence of polyethyleneimine and urea; after reflowing hydrolysis, the suspension was transferred to a Teflon autoclave and subjected to hydrothermal treatment at 150 °C for 24 h. The as-prepared nanocrystal-coated submicrometer TiO2 (NCS-TiO2) showed a core/shell structure where the outer TiO2 nanocrystals with the size of 5 to 7 nm and in anatase phase uniformly coated on the submicrometer TiO2. When the NCS-TiO2 was fabricated as the scattering layer in dye-sensitized solar cells (DSSCs), it adsorbed more dye molecules while still keeping a high light-harvesting efficiency. Moreover, the presence of TiO2 nanocrystals in NCS-TiO2 reduced the sintering stress between the transparent porous layer and the scattering layer, leading to a crack-free and high-quality photoanode film, which also reduced the serial resistance, as verified by electrochemical impedance spectroscopy. Finally, DSSCs with the NCS-TiO2 scattering layer reached an efficiency of 8.36%, which showed a 20% improvement compared with the one without it.

ChemInform Abstract: Effect of the pH on the Formation of NaYF4:Yb:Er Nanopowders by Co‐Crystallization in Presence of Polyethyleneimine.

AbstractCubic single‐phase samples of the title nanopowders are obtained by addition of rare earth nitrate solutions to aqueous NaF/polyethyleneimine mixtures at pH 10, whereas single‐phase hexagonal precipitates are prepared by addition of aqueous NaF solutions to aqueous rare earth nitrate/polyethyleneimine mixtures at pH 12.

Low-temperature synthesis of polyethyleneimine-entrapped CdS quantum dots

This Letter is focused on the one-pot formation of CdS nanoparticles in aqueous medium in presence of polyethyleneimine (PEI). Quantum dots can be obtained by adding a pre-cooled aqueous Na2S solution to a pre-cooled aqueous CdCl2 solution dropwise in presence of PEI.Field flow fractionation in combination with TEM experiments show a time dependent agglomeration of individual quantum dots from 1.6nm up to 3.2nm in size. The hyperbranched PEI of moderate molar mass (>20000g/mol) is an excellent polymer to prevent a further increase of the particle size. Therefore, stable fluorescent PEI-capped CdS quantum dots are available.

Effect of the pH on the formation of NaYF4:Yb:Er nanopowders by co-crystallization in presence of polyethyleneimine

Study of nanopowder precipitation from aqueous sodium fluoride and yttrium and/or other rare earth nitrate solutions in the presence of polyethyleneimine (PEI) has revealed the strong dependence of the solid phase composition upon the solutions’ pH values and the order of reagent addition. The conditions for single phase formation have been determined for both cubic and hexagonal NaYF4-type phases. Cubic single-phase samples were obtained by adding rare earth element nitrate solutions to aqueous NaF–PEI mixtures at pH=10; while hexagonal single-phase precipitates were synthesized by the addition of aqueous NaF to aqueous rare earth element nitrate solutions+PEI mixtures at pH=12.

Co-Dispersion Behavior of ZrB₂-SiC-B₄C-C Powders with Polyethyleneimine.

The aqueous dispersion behavior of ZrB2, SiC powders with B4C and C as sintering aids was investigated. Well co-dispersed suspension can be obtained in acidic solutions in presence of polyethyleneimine (PEI). The adsorption of PEI on the powder surface was measured by thermal gravimetric (TG) analysis. Rheological measurements displayed the effect of dispersant on the flow behavior of as-prepared slurries. An optimum condition was obtained with 1 wt % PEI. The viscosity of 40 vol % ZrB2–SiC–B4C–C (ZSBC) suspension at 100 s−1 was as low as 0.74 Pa·s, which was suitable for aqueous processing.

Kinetic Study on Polyethylenimine‐Assisted Reactive Crystallization of Monodisperse Strontium Sulfate Microcrystals

AbstractDouble‐jet reactive crystallization of SrSO4 was carried out in the presence of polyethylenimine (PEI). A simple kinetic model of primary nucleation as well as crystal growth was investigated under the condition of producing monodisperse microcrystals. Furthermore, surface free energy in the solution of PEI was estimated. PEI addition causes growth inhibition leading to smaller sizes and modifies the Gibbs free energy gap required for occurring nucleation.