2015/03/12 08:56
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NanoBrook产品应用-12-ZetaPALS
文献名: Structural, morphological and optical properties of Bi NPs obtained by laser ablation and their selective detection of L-cysteine 作者: Ramon Gabriel Teixeira Rosaa, Celso de Araujo Duartea , Wido Herwig Schreinera, Ney Pereira Mattoso Filhoa, Arandi Ginane Bezerra Jr.b, Andersson Barisonc, Fernanda Maria Marins Ocamposc a Departamento de Física, Universidade Federal do Paraná Centro Politécnico, CP 19044, 81531-990 Curitiba (PR), Brazil b Departamento Acadêmico de Física, Universidade Tecnológica Federal do Paraná, 80230-901 Curitiba (PR), Brazil c Departamento de Química, Universidade Federal do Paraná Centro Politécnico, CP 19081, 81531-990 Curitiba (PR), Brazil 摘要:In the present work we show the results of the investigation of the properties of bismuth nanoparticles (NPs) obtained by the laser ablation in water. The samples were characterized by various techniques: UV/vis spectroscopy, dynamic light scattering, transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, nuclear magnetic resonance and zeta potential. The NPs were metallic and surface oxidated, exhibiting absorption peak at 257 nm due to the surface plasmon resonance. The interaction between the NPs and various amino acids was studied and revealed a selective sensibility to cysteine on a range of concentration from 80 to 720 μM, which we attribute to a dimerization of cysteine to cystine probably complexed to the nanoparticle surface by electrostatic interactions, leading to the modification of the NP absorption spectrum. 关键词:Bismuth; Nanoparticles; Laser ablation; Cysteine
2015/04/16
NanoBrook产品应用-16-ZetaPALS
文献名: Preparation and application of magnetic graphene oxide coated with a modified chitosan pH-sensitive hydrogel: an efficient biocompatible adsorbent for catechin 作者: Hassan Sereshti, Soheila Samadi, Shohreh Asgaria and Maryam Karimia Department of Chemistry, Faculty of Science, University of Tehran, P.O. Box 14155-64555, Tehran, Iran 摘要:In the present study, graft copolymerization of acrylic acid sodium salt (AAS) onto O-carboxymethyl chitosan (O-CMCs) produced a highly hydrophilic and pH-sensitive hydrogel polymer of O-CMCs-g-AAS with a porous surface morphology. The grafted chitosan copolymer was coated on magnetic graphene oxide (MGO) and characterized with TEM, SEM, and FT-IR techniques. The prepared nanocomposite, [O-CMCs-g-AAS]/MGO, was successfully used as an efficient and biocompatible adsorbent in magnetic solid phase extraction (MSPE) coupled with gas chromatography-mass spectrometry (GC-MS) for preconcentration and determination of catechin in tea beverages. The influence of the main parameters affecting the quality of the coating process was investigated and optimized using a response surface methodology. Under the optimum conditions, the adsorbent demonstrated a satisfactory adsorption capacity (27 mg g?1) for catechin and good linearity in the range of 0.005–5 μg mL?1 with a determination coefficient (R2) of 0.9987. The limit of detection (LOD) and limit of quantification (LOQ) were 0.001 and 0.003 μg mL?1, respectively. The relative standard deviation (RSD) was 4.1% (n = 5, C = 0.5 μg mL?1).
2015/04/10
Study of Protein Hydrodynamics with Light Scatter-ing: Size and Charge of Lysozyme
Proteins are not only important nutrient source for human society, but also play a crucial role in devising various protein-based therapies for many terminal diseases [1]. Therapeutic proteins are usually administrated by the parenteral route. Their dosage form needs to be formulated either as a solution, a suspension or a reconstituted solid dosage form. Therefore, for protein therapeutic products development, protein hydrodynamic behavior in solutions or suspensions is proven to be much more relevant than its isolated and denatured characteristics revealed via advanced microscopy tech-niques. This can be manifested as either protein size monitoring for QC purposes of its purification processes or their charge property control for optimized formulation stability. The critical requirements for these applications often include, but not limited to, non-invasive (in-situ) nature of measurement techniques, easy-of-use and rapidness of tests. Laser light scattering techniques satisfy these require-ments and provide vital access to the hydrodynamic characteris-tics of biological macromolecules in their native application envi-ronments [2]. Their diffusive displacement (“Brownian” motion) can be quantified as diffusion coefficient with a dynamic light scattering measurement. In turn, their hydrodynamic radius can be calculated. When placed under an electric filed, the charged proteins undergo a uniform translational movement, the so-called electrophoretic motion or electrophoresis. It results in a Doppler phase/frequency shift of the light signal scattered from the moving proteins, which can be quantitatively evaluated with a carefully designed electrophoretic light scattering experiment. From the measured phase/frequency shift, the charge status of proteins can be extracted.
2015/03/12
Interfacial silica nanoparticles stabilize cocontinuous polymer blends
We investigated the formation of cocontinuous structures in polymer blends. These polymeric bijels (bicontinuous interfacially jammed emulsion gels) were composed of polystyrene oligomer, polybutene and fluorescent hydrophobic silica nanoparticles. A micron-sized cocontinuous morphology was stabilized by a monolayer of silica nanoparticles at the interface. Real-time observation of coalescence dynamics in co-continuous polymer blends stabilized by interfacial particles was for the first time achieved via laser scanning confocal microscopy. We demonstrated that suppression of coalescence arises from coverage of interfaces by nanoparticles. Furthermore, by combining confocal microscopy with rheology, we correlated the rheological response of a cocontinuous structure with its morphology change. We found that the rheological behavior can be attributed to competition between interface shrinkage and particle network formation. In addition, we showed that a particle scaffold is maintained even after the remixing of two polymer phases above the spinodal point. Finally, we also discussed differences between the shear response of the particle-stabilized cocontinuous structure and normal colloidal gels: the former one is more fragile than the latter under shear.
2015/03/12