Enhanced modulation of magnetic field on surface plasmon coupled emission (SPCE) by magnetic nanoparticles

This article demonstrates the enhancement of magnetic nanoparticles on magnetic field modulation of surface plasmon coupled emission (SPCE), and this method is designed as a biosensor to prove the feasibility of magnetic field modulated SPCE to be employed in the field of biosensing and biodetection.     

α-淀粉酶在阴离子化PET表面的自组装膜及其AFM研究

采用分子沉积技术制备了α-淀粉酶的自组装膜，并用AFM研究了在不同的pH值溶液和不同电荷密度基底上得到的自组装膜。结果表明：pH值从6.0变到4.0，形状变得尖细，膜中陷点多；基底的电荷密度增大时，酶分子的外观形状较细，膜中缺陷点少；α-淀粉酶自组装膜的厚度保持约5～10nm。     

Enhanced modulation of magnetic field on surface plasmon coupled emission (SPCE) by magnetic nanoparticles

The obvious enhancement effect of magnetic nanoparticles (MNPs) introduced in Cr/Co/Cr/Au substrate on the pulsed magnetic field-modulated surface plasmon coupled emission (SPCE) was investigated, and the observed enhancement factor was 4 comparing with the magnetic field modulated SPCE without MNPs. This is the new observation for the magnetic field modulated SPCE, and this method was designed as a biosensor, which to our knowledge, is the first application of magnetic field-modulated SPCE in biosensing and detection field. This strategy is a universal approach to increase the fluorescence signal and helps to build the new SPCE based stimulus-response system.     

Characterization of aliphatic and aromatic polyester hyperbranched dendrimers by AFM imaging

The aggregates of aliphatic (AL-PE) and aromatic polyester (AR-PE) hyperbranched dendrimers were imaged by tapping mode atomic force microscopy (AFM). The second and third generations of AL-PE dendrimers were adsorbed on mica in large aggregates of 150- and 166-nm diameters with little heights (ca. 1–2 nm). The origin of such flattened aggregates is attributed to their favorable adsorption on mica in view of the presence of –OH surface groups. AR-PE did not show such flattened aggregates instead small aggregates of 63 nm were observed in an organized manner beaving a cavity in the center of each aggregate. The organized aggregates of AR-PE with smaller dimension than AL-PE are ascribed to less favorable adsorption of the latter on mica in view of its stronger hydrophobicity.     

AFM探针刮擦诱导金属加速溶解行为及缓蚀剂抑制效果研究

应用原子力显微镜(AFM)探针刮伤技术研究缓蚀剂对探针诱导铜镍合金加速溶解作用的影响.实验表明,在1.5 mol/L NaC l和0.01 mol/L HC l溶液中,使用AFM探针在750 nN的力负载条件下以接触模式对铜镍合金表面持续扫描,会加速样品的溶解,并在探针刮擦区域形成蚀坑.将有机缓蚀剂十二胺及无机缓蚀剂铬酸钠添加到腐蚀介质中后,由于在合金表面形成了吸附膜和钝化膜,从而抑制探针刮擦引起的铜镍合金的加速溶解.     

Elastic properties of chemically modified baker's yeast cells studied by AFM

Chemical pretreatment is widely used to facilitate transformation of living cells when foreign components are introduced into a cell through the cell wall. The influence of appropriate chemicals on the wall properties and mechanism of transformation is still a matter of intensive studies. Saccharomyces cerevisiae cells (also known as baker's yeast) were investigated by atomic force microscopy (AFM). The cell walls were modified by lithium acetate and dithiothreitol. The AFM imaging was performed in liquid water‐based environment. The living cells were fixed by trapping into the holes of a polycarbonate membrane. Mechanical and morphological properties of initial intact cells and treated cells were investigated. The increased stiffness of the chemically treated cells was observed. As deduced from the applied theoretical Hertz‐Sneddon model, the treated cells show completely different response mechanism to applied mechanical pressure in comparison with the intact cells. Also, the increased roughness of the cell wall of the treated yeasts was observed. Copyright © 2011 John Wiley & Sons, Ltd.     

Investigation of influence of constant magnetic fields on the structure and properties of chloroprene latex based films

The influence of constant magnetic fields with induction up to 0.6 T on the supermolecular structure and properties of chloroprene latex based films was investigated. The method used were X-ray analysis, volume resistivity measurement, light microscopy and photocurrent measurement in polarized light, mechanical properties of films and density measurements. It was found that the changes in magnetic field induction have significant effects on the film structure and all properties investigated. The observed dependences may be connected to different ratios between magnetic field induction, which acts as an orientating force, and the material's elastic forces, which act in a disorientating manner.     

Characterization of Thin Polymer Films on the Nanometer Scale with Confocal Raman AFM

The combination of an atomic force microscope (AFM) with a Confocal Raman Microscope (CRM) has been used to study the composition of various thin films of polymer blends. The high spatial resolution of the AFM enables the morphological characterization of the polymer blends on the nanometer scale. Furthermore, when operating the AFM in Digital Pulsed Force Mode (DPFM), topographic information and local stiffness can be simultaneously recorded. This allows the material-sensitive characterization of heterogeneous materials. Thin films where PMMA (at room temperature a glassy polymer) is blended with two different styrene-butadiene rubbers are investigated. The presence of PMMA in both phase-separated thin films allows the comparison of the mechanical properties of the two different rubber phases using DPFM-AFM. When PMMA is blended with PET due to their similar mechanical properties (both are in the glassy state at room temperature) the assignment of the two phases to the corresponding polymers by AFM is rather difficult. Here, Raman spectroscopy provides additional information on the chemical composition of materials. In combination with a confocal microscope, the spatial distribution of the various phases can be determined with a resolution down to 200 nm. Therefore, the topographically different structures observed in AFM images can be associated to the chemical composition by using the Confocal Raman Microscope (CRM).     

A Surface Masking Technique for the Determination of Plasma Polymer Film Thickness by AFM

A method for the determination of coating film thicknesses at nanometer resolution based on surface masking and atomic force microscopy (AFM) is described. A polymeric mask is used to cover part of a substrate during the deposition of thin polymeric coatings by plasma polymerization, allowing the production of well defined polymer steps of heights of a few tens of nanometers. Tapping mode AFM has been employed to analyze the topography of these steps at high resolution. This method has also allowed accurate measurement of the kinetics of the deposition of plasma polymer films over a range of exposure times. XPS analysis of different substrate surfaces following mask removal found barely detectable residues, suggesting that the underlying surface chemistry remains unchanged, and accessible for further modification. In combination with quartz crystal microgravimetry, the method has been applied to the measurement of the density of plasma polymer coatings in the thickness range 4–50 nm.     

Construction of a portable sample preparation device with a magnetic poly(methacrylic acid‐co‐ethylene dimethacrylate) monolith as the extraction medium and its application in the enrichment of UV filters in water samples

A portable sample preparation device with a magnetic polymer monolith as the extraction medium was constructed. The monolith was synthesized by polymerizing methacrylic acid and ethylene dimethacrylate around a cylindrical magnet. In this way, the monolith with a magnetic core could be readily attached to the extraction device by magnetism. The constructed device was evaluated for the enrichment of UV filters in water samples, followed by high‐performance liquid chromatographic analysis. The extraction efficiency for the targets was satisfactory with no matrix interference. Good linearities were obtained for the UV filters with the correlation coefficients >0.9986. The limits of detection and quantification for the UV filters were 0.3–0.8 and 1.0–2.4 ng/mL, respectively. The recoveries of the UV filters from the spiked water samples at the concentration of 100 ng/mL were 95.3–101.7%, with relative standard deviations <10%. Accordingly, the proposed portable device was demonstrated to be suitable for on‐site simultaneous sampling, purification, and preconcentration within a single step.     

Preparation and characterization of 3D collagen materials with magnetic properties

In this study 3D collagen materials with magnetic properties were prepared by lyophilization technique. Magnetic particles were synthesized by precipitation of iron (II) sulfate heptahydrate and iron (III) chloride hexahydrate in an aqueous solution of chitosan and then added to a collagen solution. Starch dialdehyde (DAS) was used as a cross-linking agent for the materials. The properties of the obtained materials were studied using infrared spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Additionally, mechanical properties, porosity, density, swelling and moisture content were measured.It was found that 3D composites made from collagen with magnetic particles are hydrophilic with a high swelling ability. Cross-linking of such collagen materials with dialdehyde starch (DAS) alters the swelling degree, porosity and density of materials. The addition of magnetic particles to collagen materials decreases its porosity, and increases the density of the studied materials. Collagen 3D materials with magnetic particles are rigid and inflexible. Magnetic properties of the 3D collagen materials containing magnetic particles were confirmed by the interaction of this material with a magnet.     

利用AFM和SNOM对淋巴细胞膜表面超微结构及其光学性质的初步研究

利用原子力显微镜(Atomic Force Microscopy，AFM)对淋巴细胞表面形貌进行了形态学的初步研究，观察到了其膜表面其他显微技术所不能发现的超微结构．同时也运用扫描近场光学显微镜(Scanning Near field Optical Microscopy，SNOM)对淋巴细胞进行成像，观察了其对光的透射、吸收等光学性质，并对两种成像方法进行了比较．研究发现：淋巴细胞膜表面凹凸不平，分布着大量直径几十到几百纳米不等的小颗粒；淋巴细胞中央部位有自发荧光现象．结果表明，AFM和SNOM可作为进一步探讨淋巴细胞的结构与功能关系的有力工具．     

AFM study on the wettability of mica and graphite modified with surfactant DTAB

In this work atomic force microscopy (AFM) was applied to study the wettability of mica and graphite modified with surfactant dodecyltrimethylammonium bromide (DTAB) at varying DTAB concentrations (below the cmc) and adsorption time. The coverage states of DTAB on surfaces were analyzed from the AFM images, while the contact angle measurement was made for the wettability of DTAB-modified surfaces. The experimental results have shown that the adsorption aggregates formed as needle-like dots covering on the mica surface with the surfactant concentration of 10^?6–10^?4?mol/L. The coverage of DTAB aggregates increased with the increasing concentration, leading to a strong hydrophobicity on the surfaces. However, the large aggregates which might be caused by bilayer adsorption of surfactant occurred on mica surface at surfactant concentration of 10^?3?mol/L, resulting in the reverse of the wettability as the adsorption time extended. In the case of hydrophobic graphite, DTAB aggregates mainly formed as stripe covering on the surfaces, leading to the reduction of hydrophobicity. This reduction became stronger as more DTAB aggregates covered on graphite surfaces.     

Hybridization of commercial polymeric microparticles and magnetic nanoparticles for the dispersive micro-solid phase extraction of nitroaromatic hydrocarbons from water

In this article, the combination of commercial polymeric microparticles (OASIS MCX) and cobalt ferrite nanoparticles is evaluated in dispersive micro-solid phase extraction (D-μSPE) for the determination of six nitroaromatic hydrocarbons in water. The high affinity of the polymeric material toward the target analytes as well as the magnetic behavior of cobalt ferrite nanoparticles are combined in a synergic way to developed an efficient and simple D-μSPE approach. The sorptive performance of the hybrid material is compared with that most usual sorbents and the effect of its synthesis steps on the extraction capability is also evaluated in depth. After the optimization of selected variables, D-μSPE method was assessed in terms of linearity, sensitivity, precision and accuracy. The new extraction method allows the determination of the target compounds with limits of detection in the range from 0.12 to 1.26 μg/L and relative standard deviations lower than 9.6%. The recovery study was performed in two different water samples obtaining percentages from 71 to 103%, which demonstrated the applicability of the hybrid sorbent for the selected analytical problem.     

Synthesis and magnetic properties of a porphine-based photosynthesizer with magnetic nano-carriers

The coupling of benzyl protected dopamine with meso-tetra(4-carboxyphenyl)porphine (m-TCPP) and a simple deprotection by hydrogenation under catalyst (Pd/C) to remove the benzyl groups afforded the meso-tetra(4-carboxyphenyl)porphine-dopamine conjugate, m-TCPPD (1). Previously prepared superparamagnetic iron oxide nanoparticles (SPIONs) were coated with m-TCPPD by sonication in methanol, and then the m-TCPPD coated SPIONs (2) were separated with a permanent magnet. The microstructure and magnetic properties of the m-TCPPD coated SPIONs were characterized by UV, ¹H NMR, MALDI MS, XRD, TEM, FT-IR, TGA and VSM. The crystallite size obtained from X-ray line profile fitting is comparable with the particle size obtained from TEM. Magnetization measurements reveal that m-TCPPD coated SPIONs do not reach saturation even at high fields. The absence of remanance and weak magnetization, which are characteristic features of superparamagnetics, has been observed. The average particle size has been determined, by fitting the Langevin function to the experimental M−H hysteresis curves, as approximately 8 nm.     

Solid solution of transition metal-dicarboxylates with tunable magnetic properties

Single crystals of inorganic–organic hybrid compounds, M₅(OH)₂[CO₂(CH₂)₂CO₂]₄ [M = Mn(Mn-s), Fe(Fe-s), Co(Co-s), Mn/Fe(Mn---Fe-n) and Mn/Co(Mn---Co-n)] were prepared under hydrothermal condition at 180 °C from a mixture of transition metal(II) chlorides, succinic acid, potassium hydroxide, and water. Crystal structure of all compounds present the same structural type in the single-crystal X-ray diffraction refinements and X-ray powder diffraction analysis. The single crystal structural analyses for three homo-metallic compounds were performed and the prepared compounds have divalent metal ions on the basis of bond valence sum calculations. The unit cell constants for the hetero-metallic compounds, e.g., Mn/Fe, Mn/Co solid solutions were determined. Magnetic measurements show that the Mn-s may have antiferromagnetic interaction at low temperature. The Fe-s and the Co-s compounds have ferrimagnetic coupling below 10 K. The Mn---Co-n compounds show the ferromagnetic magnetic behavior while the Mn---Fe-n compounds present antiferromagnetic ordering.     

Metal-organic framework derived magnetic nanoporous carbon as an adsorbent for the magnetic solid-phase extraction of chlorophenols from mushroom sample

In this work, a metal-organic framework derived nanoporous carbon(MOF-5-C) was fabricated and modified with Fe_3O_4 magnetic nanoparticles. The resulting magnetic MOF-5-derived porous carbon(Fe_3O_4@MOF-5-C) was then used for the magnetic solid-phase extraction of chlorophenols(CPs) from mushroom samples prior to high performance liquid chromatography–ultraviolet detection. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and N_2 adsorption were used to characterize the adsorbent. After experimental optimization, the amount of the adsorbent was chosen as 8.0 mg, extraction time as 10 min, sample volume as 50 m L, desorption solvent as 0.4 m L(0.2 mL×2)of alkaline methanol, and sample p H as 6. Under the above optimized conditions, good linearity for the analytes was obtained in the range of 0.8–100.0 ng g~(-1)with the correlation coefficients between0.9923 and 0.9963. The limits of detection(S/N = 3) were in the range of 0.25–0.30 ng g~(-1), and the relative standard deviations were below 6.8%. The result showed that the Fe3O4@MOF-5-C has an excellent adsorption capacity for the analytes.     

An automated food protein isolation approach on preparative scale by two‐dimensional liquid chromatography with active modulation interface

In this work, an automated 2D‐LC approach for protein isolation from egg samples on preparative scale is proposed. The method is based on the use of a C18 guard column installed in a switching valve to focus the proteins coming from the first dimension column, before their elution in the second column. For the first dimension separation, a size‐exclusion column, packed with 3 μm ultrapure silica particles was used. An RP column based on core‐shell technology was used for the second dimension separation. A standard mixture of BSA, β‐lactoglobulin, and glucose oxidase, chosen as a protein model system, was used to optimize the chromatographic separation conditions. The fully automated workflow allowed to isolate, in a single‐chromatographic analysis, a protein amount of 50 μg for each peak fraction, with a total time of 15 min for the first separation and additional 30 min of the second separation for each trapped protein. The final aim was the development of proper analytical tools for protein isolation from foodstuffs to be used for the molecular identification by MS, as well as for biotherapeutic uses, allergy testing, and large‐scale investigations in biological systems.     

Theoretical study of the magnetic properties of an SF6 molecule in non-uniform magnetic field

Perturbation theory has been applied to evaluate the induced electronic moments and magnetic field at the nuclei of an SF₆ molecule interacting with an external magnetic field with a spatially uniform gradient. Contributions to magnetic susceptibility and magnetic shielding of the nuclei have been evaluated using the random phase approximation within the framework of accurate Hartree-Fock zero order wavefuctions. The quality of the calculations has been judged by the fulfillment of sum rules for the origin dependence of the response properties.     

Quantitative mapping of elastic moduli at the nanoscale in phase separated polyurethanes by AFM

The micro phase separated nanoscale morphology of phase separated polyurethanes (PUs) was visualized by atomic force microscopy (AFM) height and phase imaging of smooth surfaces obtained by ultramicrotonomy. PUs were obtained from 4,4′-methylenbis (phenyl isocyanate) (MDI), 1,4-butanediol (BD) and poly(tetrahydrofurane) polyether polyol (PTHF). The segmented polyether PUs with varying stoichiometric ratio of the isocyanate and hydroxyl groups were prepared to investigate the effect of molar mass, as well as the type and number of end-groups on their morphology and mechanical performance.The PU samples studied show characteristic “fingerprint” AFM phase images. Novel dynamic imaging modes of AFM, including HarmoniX material mapping and Peak Force Tapping were used to assess the mechanical performance of phase separated polyurethanes quantitatively as a function of their molecular structure. The values of surface elastic moduli were determined with nanoscale resolution and were in excellent agreement for both AFM modes. While tensile testing provides a bulk average value for the elastic modulus of the elastomers, the novel AFM based elastic moduli mappings introduced enable the study of surface stiffness with nanoscale resolution in a quantitative way.