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Sample records for patterning cyclodextrin monolayers

  1. Graphoepitaxy for Pattern Multiplication of Nanoparticle Monolayers

    NASA Astrophysics Data System (ADS)

    Ferraro, Mark E.; Bonnecaze, Roger T.; Truskett, Thomas M.

    2014-08-01

    We compute the free energy minimizing structures of particle monolayers in the presence of enthalpic barriers of a finite height βVext using classical density functional theory and Monte Carlo simulations. We show that a periodic square template with dimensions up to at least 10 times the particle diameter disrupts the formation of the entropically favored hexagonally close-packed 2D lattice in favor of a square lattice. The results illustrate how graphoepitaxy can successfully order nanoparticulate films into desired patterns many times smaller than those of the prepatterned template.

  2. Comparison between cucurbiturils and β-cyclodextrin interactions with cholesterol molecules present in Langmuir monolayers used as a biomembrane model.

    PubMed

    Tovani, Camila Bussola; de Souza, João Francisco Ventrici; Cavallini, Thiago de Souza; Demets, Grégoire Jean-François; Ito, Amando; Barioni, Marina Berardi; Pazin, Wallance Moreira; Zaniquelli, Maria Elisabete Darbello

    2013-11-01

    Specific surface techniques can probe the interaction of cholesterol (Chol) with substances that are able to host and/or sequester this biomolecule, provided that the additives are properly assembled at the interface. Reports on inclusion complexes of Chol with β-cyclodextrins exist in the literature. Here we compare the interaction of β-cyclodextrin and cucurbiturils with Chol present in Langmuir phospholipid (dipalmitoylphosphatidylcholine, DPPC) monolayers, used as a biomembrane model. Cucurbiturils, CB[n], comprise macrocyclic host molecules consisting of n glycoluril units. Classic surface pressure curves, dilatational surface viscoelasticity measurements, and fluorescence emission spectra and images obtained by time-resolved fluorescence of the corresponding Langmuir-Blodgett films have shown that homologues with 5 and 6 glycoluril units, CB[5] and CB[6], do not form inclusion complexes. Higher-order homologues, such as CB[7], are likely to complex with Chol with changes in the minimum molecular areas recorded for DPPC/Chol monolayers, the fluorescence decay lifetimes, and the dilatational surface viscosities of the monolayers generated in the presence of these molecules. Moreover, we proof the removal of cholesterol from the biomimetic interface in the presence of CB[7] by means of fluorescence spectra from the subphase support of monolayers containing fluorescent-labeled Chol.

  3. Phase emerging from intramonolayer cycloaddition on micro-patterned monolayer

    SciTech Connect

    Tajuddin, Hairul A.; Manning, Robert J.; Leggett, Graham J.; Williams, Nicholas H.

    2012-11-27

    Cu(I)-catalyzed cycloaddition between azide and acetylene, followed by hydrolysis of ester were performed on micro-patterned self-assembled monolayer to produce smaller features. The reactions were initially performed on mixed monolayers and analysed by water contact angle (CA) and confirmed by X-ray Photoelectron Spectroscopy (XPS). The contact angle measurement has shown a drastic wetting of water on the surface of mixed monolayer indicating that the terminal groups on mixed monolayer has changed into carboxylic acid and hydroxyl terminals. The reactions work in a similar way on micro-patterned SAM and analyzed by using friction force microscope. The emerging of the new lines with high friction force on the border suggested a successful intramonolayer reactions on the border of the patterned SAM.

  4. Phase emerging from intramonolayer cycloaddition on micro-patterned monolayer

    NASA Astrophysics Data System (ADS)

    Tajuddin, Hairul A.; Manning, Robert J.; Leggett, Graham J.; Williams, Nicholas H.

    2012-11-01

    Cu(I)-catalyzed cycloaddition between azide and acetylene, followed by hydrolysis of ester were performed on micro-patterned self-assembled monolayer to produce smaller features. The reactions were initially performed on mixed monolayers and analysed by water contact angle (CA) and confirmed by X-ray Photoelectron Spectroscopy (XPS). The contact angle measurement has shown a drastic wetting of water on the surface of mixed monolayer indicating that the terminal groups on mixed monolayer has changed into carboxylic acid and hydroxyl terminals. The reactions work in a similar way on micro-patterned SAM and analyzed by using friction force microscope. The emerging of the new lines with high friction force on the border suggested a successful intramonolayer reactions on the border of the patterned SAM.

  5. Monolayer-Mediated Patterning of Electroceramic Thin Films

    SciTech Connect

    Clem, P.G.; Payne, D.A.

    1998-10-11

    Integrated electroceramic thin film devices on semiconductor and insulator substrates feature a variety of attractive attributes, including high capacitance density, nonvolatile memory, sensor/actuator ability, and other unique electronic and optical properties. The ability to pattern such ceramic materials atop semiconductor substrates, thus, is a critical technology. Patterned oxide thin film devices are typically formed by uniform film deposition followed by somewhat complicated post-deposition ion-beam or chemical etching in a controlled environment. We review here the development of an ambient atmosphere technique which allows selective deposition of electroceramic thin layers without such post-deposition etching. In this method, substrate surfaces are selectively functionalized with hydrophobic self-assembled monolayer to modify the adhesion of subsequently deposited solution-derived electroceramics. The selective fictionalization is achieved through microcontact printing (v-CP) of self-assembled monolayer of the chemical octadecyltrichlorosilane on substrates of technical interest. Subsequent sol-gel deposition of ceramic oxides on these functionalized substrates, followed by lift-off from the monolayer, yields high quality, patterned oxide thin layers only on the unfunctionalized regions. A variety of micron- scale dielectric oxide devices have been fabricated using this process, with lateral resolution as fine as 0.5Lm. In this paper, we review the monolayer patterning and electrical behavior of several patterned electroceramic thin films, including Pb(Zr,Ti)03 [PZT], LiNb03, and Ta205. An applied device example is also presented in combination with selective MOCVD deposition of metal electrodes: integrated, fully monolayer-patterned Pt//PZT//PSi(Si(100) ferroelectric memory cells.

  6. Assembly of designed protein scaffolds into monolayers for nanoparticle patterning.

    PubMed

    Mejias, Sara H; Couleaud, Pierre; Casado, Santiago; Granados, Daniel; Garcia, Miguel Angel; Abad, Jose M; Cortajarena, Aitziber L

    2016-05-01

    The controlled assembly of building blocks to achieve new nanostructured materials with defined properties at different length scales through rational design is the basis and future of bottom-up nanofabrication. This work describes the assembly of the idealized protein building block, the consensus tetratricopeptide repeat (CTPR), into monolayers by oriented immobilization of the blocks. The selectivity of thiol-gold interaction for an oriented immobilization has been verified by comparing a non-thiolated protein building block. The physical properties of the CTPR protein thin biomolecular films including topography, thickness, and viscoelasticity, are characterized. Finally, the ability of these scaffolds to act as templates for inorganic nanostructures has been demonstrated by the formation of well-packed gold nanoparticles (GNPs) monolayer patterned by the CTPR monolayer.

  7. Patterning of silica microsphere monolayers with focused femtosecond laser pulses

    SciTech Connect

    Cai Wenjian; Piestun, Rafael

    2006-03-13

    We demonstrate the patterning of monolayer silica microsphere lattices with tightly focused femtosecond laser pulses. We selectively removed microspheres from a lattice and characterized the effect on the lattice and the substrate. The proposed physical mechanism for the patterning process is laser-induced breakdown followed by ablation of material. We show that a microsphere focuses radiation in its interior and in the near field. This effect plays an important role in the patterning process by enhancing resolution and accuracy and by reducing the pulse energy threshold for damage. Microsphere patterning could create controlled defects within self-assembled opal photonic crystals.

  8. Cyclodextrins.

    PubMed

    Kurkov, Sergey V; Loftsson, Thorsteinn

    2013-08-30

    Although cyclodextrins (CDs) have been studied for over 100 years and can be found in at least 35 pharmaceutical products, they are still regarded as novel pharmaceutical excipients. CDs are oligosaccharides that possess biological properties that are similar to their linear counterparts, but some of their physicochemical properties differ. CDs are able to form water-soluble inclusion complexes with many poorly soluble lipophilic drugs. Thus, CDs are used to enhance the aqueous solubility of drugs and to improve drug bioavailability after, for example, oral administration. Through CD complexation, poorly soluble drugs can be formulated as aqueous parenteral solutions, nasal sprays and eye drop solutions. These oligosaccharides are being recognized as non-toxic and pharmacologically inactive excipients for both drug and food products. Recently, it has been observed that CDs and CD complexes in particular self-assemble to form nanoparticles and that, under certain conditions, these nanoparticles can self-assemble to form microparticles. These properties have changed the way we perform CD research and have given rise to new CD formulation opportunities. Here, the pharmaceutical applications of CDs are reviewed with an emphasis on their solubilizing properties, their tendency to self-assemble to form aggregates, CD ternary complexes, and their metabolism and pharmacokinetics.

  9. Carbon nanotube monolayer patterns for modulating stem cell behavior

    NASA Astrophysics Data System (ADS)

    Park, Sung Young; Lee, Ki-Bum; Hong, Seunghun

    2010-03-01

    Nanostructures and nanomaterials intrinsically can interact with biological systems at the fundamental molecular levels with high specificity, which has held great potential for developing methods of controlling cell behaviors such as adhesion, proliferation, and differentiation. For instance, carbon nanotubes (CNTs), as extracellular scaffolds, have been used to guide neural cell growth and regulate cell polarity. However, in order to harness the potential of nanomaterials as artificial scaffolds, there is a clear need to develop methods of patterning nanomaterials over large surfaces with high precision and maintaining biocompatibility of patterned nanostructures. Herein, we report a novel method to regulate stem cell behaviors by using of combinatorial CNT patterns with different shapes and sizes in an effective way. Importantly, the SCs exhibited preferential growth on CNT patterns, and the CNT monolayer patterns did not show cytotoxicity during the long-term cell culture. These results clearly show that CNT monolayer patterns have enormous potentials as a platform for basic research and applications in stem cell tissue-engineering.

  10. Electrochemical and surface plasmon resonance characterization of β-cyclodextrin-based self-assembled monolayers and evaluation of their inclusion complexes with glucocorticoids

    NASA Astrophysics Data System (ADS)

    Frasconi, Marco; Mazzei, Franco

    2009-07-01

    This paper describes the characterization of a self-assembled β-cyclodextrin (β-CD)-derivative monolayer (β-CD-SAM) on a gold surface and the study of their inclusion complexes with glucocorticoids. To this aim the arrangement of a self-assembled β-cyclodextrin-derivative monolayer on a gold surface was monitored in situ by means of surface plasmon resonance (SPR) spectroscopy and double-layer capacitance measurements. Film thickness and dielectric constant were evaluated for a monolayer of β-CD using one-color-approach SPR. The selectivity of the β-CD host surface was verified by using electroactive species permeable and impermeable in the β-CD cavity. The redox probe was selected according to its capacity to permeate the β-CD monolayer and its electrochemical behavior. In order to evaluate the feasibility of an inclusion complex between β-CD-SAM with some steroids such as cortisol and cortisone, voltammetric experiments in the presence of the redox probes as molecules competitive with the steroids have been performed. The formation constant of the surface host-guest by β-CD-SAM and the steroids under study was calculated.

  11. Tip-enhanced Raman spectroscopic imaging of patterned thiol monolayers

    PubMed Central

    Stadler, Johannes; Schmid, Thomas; Opilik, Lothar; Kuhn, Phillip; Dittrich, Petra S

    2011-01-01

    Summary Full spectroscopic imaging by means of tip-enhanced Raman spectroscopy (TERS) was used to measure the distribution of two isomeric thiols (2-mercaptopyridine (2-PySH) and 4-mercaptopyridine (4-PySH)) in a self-assembled monolayer (SAM) on a gold surface. From a patterned sample created by microcontact printing, an image with full spectral information in every pixel was acquired. The spectroscopic data is in good agreement with the expected molecular distribution on the sample surface due to the microcontact printing process. Using specific marker bands at 1000 cm−1 for 2-PySH and 1100 cm−1 for 4-PySH, both isomers could be localized on the surface and semi-quantitative information was deduced from the band intensities. Even though nanometer size resolution information was not required, the large signal enhancement of TERS was employed here to detect a monolayer coverage of weakly scattering analytes that were not detectable with normal Raman spectroscopy, emphasizing the usefulness of TERS. PMID:22003457

  12. Electrodeposition of gold templated by patterned thiol monolayers

    NASA Astrophysics Data System (ADS)

    She, Zhe; Di Falco, Andrea; Hähner, Georg; Buck, Manfred

    2016-06-01

    The electrochemical deposition of Au onto Au substrates modified by self-assembled monolayers (SAMs) was studied by linear sweep voltammetry (LSV), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Patterned SAMs exhibiting electrochemical contrast were prepared by two different methods. One used microcontact printing (μCP) to generate a binary SAM of ω-(4‧-methyl-biphenyl-4-yl)-propane thiol (CH3-C6H4-C6H4-(CH2)3-SH, MBP3) and octadecane thiol (CH3(CH2)17SH, ODT). Templated by the SAM, a gold microelectrode structure was electrodeposited featuring a line 15 μm wide and 3 mm long. After transfer to an epoxy substrate the structure proved to be electrically conductive across the full length. The other patterning method applied electron beam lithography (EBL) where electrochemical contrast was achieved by crosslinking molecules in a single component SAM of MBP3. An electron dose above 250 mC/cm2 results in a high deposition contrast. The choice of parameters for the deposition/lift-off process is found to be more critical for Au compared to Cu studied previously. The origin of the differences and implications for nanoscale patterning are discussed.

  13. Ultraviolet nanoimprint lithography using cyclodextrin-based porous template for pattern failure reduction

    NASA Astrophysics Data System (ADS)

    Takei, Satoshi; Hanabata, Makoto

    2015-10-01

    An approach to ultraviolet (UV) nanoimprint lithography using a cyclodextrin-based porous template was investigated for the reduction of air trapping and template damage caused by gases such as nitrogen and oxygen generated from UV cross-linked materials. The accuracy of the printed pattern using UV nanoimprint lithography with the porous transparent template was improved because of enhanced material adsorption and increased permeability to gaseous species. The use of volatile solvents in the UV cross-linked materials for nanoimprint lithography has been limited because of high pattern failure rates. However, using the cyclodextrin-based porous template, the UV cross-linked materials with a 5 wt. % volatile solvent exhibited well-defined nanoscale patterns. Based on this study, acceptable chemistries for the UV cross-linked materials have been expanded, which will be beneficial for future device applications using UV nanoimprint lithography.

  14. Patterning Self-Assembled Monolayers on Gold: Green Materials Chemistry in the Teaching Laboratory

    ERIC Educational Resources Information Center

    McFarland, Adam D.; Huffman, Lauren M.; Parent, Kathryn, E.; Hutchison, James E.; Thompson, John E.

    2004-01-01

    An experiment demonstrating self-assembled monolayer (SAM) chemistry, organic thin-film patterning and the use of molecular functionality to control macroscopic properties is described. Several important green chemistry principles are introduced.

  15. [Effect of β-cyclodextrin inclusion complex on transport of major components of Xiangfu Siwu decoction essential oil in Caco-2 cell monolayer model].

    PubMed

    Xi, Jun-zuan; Qian, Da-wei; Duan, Jin-ao; Liu, Pei; Zhu, Yue; Zhu, Zhen-hua; Zhang, Li

    2015-08-01

    Although the essential oil of Xiangfu Siwu decoction (XFSWD) has strong pharmacological activity, its special physical and chemical properties restrict the clinical application and curative effect. In this paper, Xiangfu Siwu decoction essential oil (XFS-WO) was prepared by forming inclusion complex with β-cyclodextrin (β-CD). The present study is to investigate the effect of β-CD inclusion complex on the transport of major components of XFSWO using Caco-2 cell monolayer model, thus to research the effect of this formation on the absorption of drugs with low solubility and high permeability, which belong to class 2 in biopharmaceutics classification system. A sensitive and rapid UPLC-MS/MS method was developed for simultaneous quantification of senkyunolide A, 3-n-butylphthalide, Z-ligustilide, dehydrocostus lactone and α-cyperone, which are active compounds in XFSWO. The transport parameters were analyzed and compared in free oil and its β-CD inclusion complex. The result revealed that the formation of XFSWO/β-CD inclusion complex has significantly increased the transportation and absorption of major active ingredients than free oil. Accordingly, it can be speculated that cyclodextrin inclusion complex can improve bioavailability of poorly water-soluble drugs. Above all these mentioned researches, it provided foundation and basis for physiological disposition and pharmaceutical study of XFSWD. PMID:26677694

  16. [Effect of β-cyclodextrin inclusion complex on transport of major components of Xiangfu Siwu decoction essential oil in Caco-2 cell monolayer model].

    PubMed

    Xi, Jun-zuan; Qian, Da-wei; Duan, Jin-ao; Liu, Pei; Zhu, Yue; Zhu, Zhen-hua; Zhang, Li

    2015-08-01

    Although the essential oil of Xiangfu Siwu decoction (XFSWD) has strong pharmacological activity, its special physical and chemical properties restrict the clinical application and curative effect. In this paper, Xiangfu Siwu decoction essential oil (XFS-WO) was prepared by forming inclusion complex with β-cyclodextrin (β-CD). The present study is to investigate the effect of β-CD inclusion complex on the transport of major components of XFSWO using Caco-2 cell monolayer model, thus to research the effect of this formation on the absorption of drugs with low solubility and high permeability, which belong to class 2 in biopharmaceutics classification system. A sensitive and rapid UPLC-MS/MS method was developed for simultaneous quantification of senkyunolide A, 3-n-butylphthalide, Z-ligustilide, dehydrocostus lactone and α-cyperone, which are active compounds in XFSWO. The transport parameters were analyzed and compared in free oil and its β-CD inclusion complex. The result revealed that the formation of XFSWO/β-CD inclusion complex has significantly increased the transportation and absorption of major active ingredients than free oil. Accordingly, it can be speculated that cyclodextrin inclusion complex can improve bioavailability of poorly water-soluble drugs. Above all these mentioned researches, it provided foundation and basis for physiological disposition and pharmaceutical study of XFSWD.

  17. Increased monolayer domain size and patterned growth of tungsten disulfide through controlling surface energy of substrates

    NASA Astrophysics Data System (ADS)

    Godin, Kyle; Kang, Kyungnam; Fu, Shichen; Yang, Eui-Hyeok

    2016-08-01

    We report a surface energy-controlled low-pressure chemical vapor deposition growth of WS2 monolayers on SiO2 using pre-growth oxygen plasma treatment of substrates, facilitating increased monolayer surface coverage and patterned growth without lithography. Oxygen plasma treatment of the substrate caused an increase in the average domain size of WS2 monolayers by 78%  ±  2% while having a slight reduction in nucleation density, which translates to increased monolayer surface coverage. This substrate effect on growth was exploited to grow patterned WS2 monolayers by patterned plasma treatment on patterned substrates and by patterned source material with resolutions less than 10 µm. Contact angle-based surface energy measurements revealed a dramatic increase in polar surface energy. A growth model was proposed with lowered activation energies for growth and increased surface diffusion length consistent with the range of results observed. WS2 samples grown with and without oxygen plasma were similar high quality monolayers verified through transmission electron microscopy, selected area electron diffraction, atomic force microscopy, Raman, and photoluminescence measurements. This technique enables the production of large-grain size, patterned WS2 without a post-growth lithography process, thereby providing clean surfaces for device applications.

  18. Patterning monolayer graphene with zigzag edges on hexagonal boron nitride by anisotropic etching

    NASA Astrophysics Data System (ADS)

    Wang, Guole; Wu, Shuang; Zhang, Tingting; Chen, Peng; Lu, Xiaobo; Wang, Shuopei; Wang, Duoming; Watanabe, Kenji; Taniguchi, Takashi; Shi, Dongxia; Yang, Rong; Zhang, Guangyu

    2016-08-01

    Graphene nanostructures are potential building blocks for nanoelectronic and spintronic devices. However, the production of monolayer graphene nanostructures with well-defined zigzag edges remains a challenge. In this paper, we report the patterning of monolayer graphene nanostructures with zigzag edges on hexagonal boron nitride (h-BN) substrates by an anisotropic etching technique. We found that hydrogen plasma etching of monolayer graphene on h-BN is highly anisotropic due to the inert and ultra-flat nature of the h-BN surface, resulting in zigzag edge formation. The as-fabricated zigzag-edged monolayer graphene nanoribbons (Z-GNRs) with widths below 30 nm show high carrier mobility and width-dependent energy gaps at liquid helium temperature. These high quality Z-GNRs are thus ideal structures for exploring their valleytronic or spintronic properties.

  19. Nanopatterns by phase separation of patterned mixed polymer monolayers

    DOEpatents

    Huber, Dale L; Frischknecht, Amalie

    2014-02-18

    Micron-size and sub-micron-size patterns on a substrate can direct the self-assembly of surface-bonded mixed polymer brushes to create nanoscale patterns in the phase-separated mixed polymer brush. The larger scale features, or patterns, can be defined by a variety of lithographic techniques, as well as other physical and chemical processes including but not limited to etching, grinding, and polishing. The polymer brushes preferably comprise vinyl polymers, such as polystyrene and poly(methyl methacrylate).

  20. Low-Temperature, Dry Transfer-Printing of a Patterned Graphene Monolayer

    PubMed Central

    Cha, Sugkyun; Cha, Minjeong; Lee, Seojun; Kang, Jin Hyoun; Kim, Changsoon

    2015-01-01

    Graphene has recently attracted much interest as a material for flexible, transparent electrodes or active layers in electronic and photonic devices. However, realization of such graphene-based devices is limited due to difficulties in obtaining patterned graphene monolayers on top of materials that are degraded when exposed to a high-temperature or wet process. We demonstrate a low-temperature, dry process capable of transfer-printing a patterned graphene monolayer grown on Cu foil onto a target substrate using an elastomeric stamp. A challenge in realizing this is to obtain a high-quality graphene layer on a hydrophobic stamp made of poly(dimethylsiloxane), which is overcome by introducing two crucial modifications to the conventional wet-transfer method – the use of a support layer composed of Au and the decrease in surface tension of the liquid bath. Using this technique, patterns of a graphene monolayer were transfer-printed on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate and MoO3, both of which are easily degraded when exposed to an aqueous or aggressive patterning process. We discuss the range of application of this technique, which is currently limited by oligomer contaminants, and possible means to expand it by eliminating the contamination problem. PMID:26648526

  1. Low-Temperature, Dry Transfer-Printing of a Patterned Graphene Monolayer

    NASA Astrophysics Data System (ADS)

    Cha, Sugkyun; Cha, Minjeong; Lee, Seojun; Kang, Jin Hyoun; Kim, Changsoon

    2015-12-01

    Graphene has recently attracted much interest as a material for flexible, transparent electrodes or active layers in electronic and photonic devices. However, realization of such graphene-based devices is limited due to difficulties in obtaining patterned graphene monolayers on top of materials that are degraded when exposed to a high-temperature or wet process. We demonstrate a low-temperature, dry process capable of transfer-printing a patterned graphene monolayer grown on Cu foil onto a target substrate using an elastomeric stamp. A challenge in realizing this is to obtain a high-quality graphene layer on a hydrophobic stamp made of poly(dimethylsiloxane), which is overcome by introducing two crucial modifications to the conventional wet-transfer method - the use of a support layer composed of Au and the decrease in surface tension of the liquid bath. Using this technique, patterns of a graphene monolayer were transfer-printed on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate and MoO3, both of which are easily degraded when exposed to an aqueous or aggressive patterning process. We discuss the range of application of this technique, which is currently limited by oligomer contaminants, and possible means to expand it by eliminating the contamination problem.

  2. Tunable subwavelength photonic lattices and solitons in periodically patterned graphene monolayer.

    PubMed

    Huang, Changming; Ye, Fangwei; Sun, Zhipei; Chen, Xianfeng

    2014-12-01

    We study linear and nonlinear mode properties in a periodically patterned graphene sheet. We demonstrate that a subwavelength one-dimensional photonic lattice can be defined across the graphene monolayer, with its modulation depth and correspondingly the associated photonic band structures being controlled rapidly, by an external gate voltage. We find the existences of graphene lattice solitons at the deep-subwavelength scales in both dimensions, thanks to the combination of graphene intrinsic self-focusing nonlinearity and the graphene plasmonic confinement effects.

  3. Evaluation of Organic Monolayers Formed on Si(111): Exploring the Possibilities for Application in Electron Beam Nanoscale Patterning

    NASA Astrophysics Data System (ADS)

    Yamada, Taro; Takano, Nao; Yamada, Keiko; Yoshitomi, Shuhei; Inoue, Tomoyuki; Osaka, Tetsuya

    2001-08-01

    The methods of preparing organic monolayers on Si(111), the effects of electron-beam irradiation onto these monolayers, and the deposition of metal atoms over the irradiated areas have been investigated in order to develop a process of mass-scale production of nanometer-scale patterns on Si(111) wafer surfaces. The organic monolayers were fabricated on hydrogen-terminated Si(111) wafer surfaces using previously reported methods for the electrolysis of para-substituted benzenediazonium salts and the Grignard reaction with various alkyl moieties and reaction procedures. Using these electrolysis methods, partially well-defined two-dimensional monolayers were formed, which were, however, obscured by precipitated by-products. The Grignard reaction deposited homogeneous monolayer moieties of alkyl groups which were randomly arranged and are suitable for surface passivation. Electron-beam bombardment of the organic monolayers on Si(111) was performed in an atmosphere of O2 or H2O@. The bombarded area was effectively oxidized in a well-controlled manner. By immersing the bombarded specimen into an aqueous NiSO4+(NH4)2SO4 solution, Ni was selectively impregnated only within the area of electron bombardment. Based on these results, application of organic monolayers for fabricating nanometer-scale monolayer patterns is proposed.

  4. Manipulation of the ultimate pattern of polypyrrole film on self-assembled monolayer patterned substrate by negative or positive electrodeposition

    NASA Astrophysics Data System (ADS)

    Zhou, Feng; Liu, Zhilu; Yu, Bo; Chen, Miao; Hao, Jingcheng; Liu, Weimin; Xue, Qunji

    2004-07-01

    Micro printed self-assembled monolayer may lead to different ultimate patterns of polypyrrole (PPy) by way of positive or negative deposition in guiding the electrodeposition of pyrrole. This article gives a detailed investigation of the effects of experimental conditions on the ultimate patterns of the PPy films on self-assembled monolayer (SAM)-patterned silicon and gold substrates. The effects of the substrate surface electric properties and the nature of the solvent and supporting electrolyte on the selective deposition and the PPy film morphology are also discussed. As the results, negative deposition occurs on the octadecyltrichlorosilane (OTS)-covered area of semiconductor Si surface in non-aqueous acetonitrile solution and results in positive patterns, while positive deposition occurs in aqueous solution and gives birth to negative patterns. This is attributed to the accessibility of the monomer solution to the substrate surface. The electrodeposition preferentially occurs on the exposed area of a gold substrate, though the deposition on the octadecanthiol (ODT)-covered area is unavoidable due to the hydrophobic-hydrophobic interaction. The lypophilic properties of the deposited PPy can be modified by selecting different salts as the supporting electrolytes and doping different anions during the electrodeposition. Subsequently, the morphology of the electro-deposited PPy layer can be tailored making use of the interaction between the PPy oligomer and the surfaces of different chemical functionalities.

  5. Chemical patterns of octadecyltrimethoxysilane monolayers for the selective deposition of nanoparticles on silicon substrate.

    PubMed

    Ressier, L; Viallet, B; Grisolia, J; Peyrade, J P

    2007-10-01

    The use of nano-objects to make the active part of reproducible nanodevices requires their controlled assembling on specific areas of substrates. In this work, we propose to use van der Waals interactions to assemble selectively gold particles covered by alkyl-thiol ligands on hydrophobic OctadecylTriMethoxySilane (OTMS) patterns defined on SiO(2)/Si substrates by a process combining nano-imprint lithography (NIL) or high resolution electron beam lithography (HREBL) and atmospheric chemical vapor deposition (CVD) of silane. A study by atomic force microscopy (AFM) reveals that homogeneous patterns of OTMS self-assembled monolayers, extending on several square millimeters, have been made. These OTMS patterns, with a lateral dimension ranging from 2mum down to 50nm, can be located at a precise place of a nanodevice, for example, between nanoelectrodes. Preliminary results of selective nanoparticle deposition on these chemical patterns are presented.

  6. Patterned arrays of lateral heterojunctions within monolayer two-dimensional semiconductors.

    PubMed

    Mahjouri-Samani, Masoud; Lin, Ming-Wei; Wang, Kai; Lupini, Andrew R; Lee, Jaekwang; Basile, Leonardo; Boulesbaa, Abdelaziz; Rouleau, Christopher M; Puretzky, Alexander A; Ivanov, Ilia N; Xiao, Kai; Yoon, Mina; Geohegan, David B

    2015-07-22

    The formation of semiconductor heterojunctions and their high-density integration are foundations of modern electronics and optoelectronics. To enable two-dimensional crystalline semiconductors as building blocks in next-generation electronics, developing methods to deterministically form lateral heterojunctions is crucial. Here we demonstrate an approach for the formation of lithographically patterned arrays of lateral semiconducting heterojunctions within a single two-dimensional crystal. Electron beam lithography is used to pattern MoSe2 monolayer crystals with SiO2, and the exposed locations are selectively and totally converted to MoS2 using pulsed laser vaporization of sulfur to form MoSe2/MoS2 heterojunctions in predefined patterns. The junctions and conversion process are studied by Raman and photoluminescence spectroscopy, atomically resolved scanning transmission electron microscopy and device characterization. This demonstration of lateral heterojunction arrays within a monolayer crystal is an essential step for the integration of two-dimensional semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin devices.

  7. Monolayer-directed Assembly and Magnetic Properties of FePt Nanoparticles on Patterned Aluminum Oxide

    PubMed Central

    Yildirim, Oktay; Gang, Tian; Kinge, Sachin; Reinhoudt, David N.; Blank, Dave H.A.; van der Wiel, Wilfred G.; Rijnders, Guus; Huskens, Jurriaan

    2010-01-01

    FePt nanoparticles (NPs) were assembled on aluminum oxide substrates, and their ferromagnetic properties were studied before and after thermal annealing. For the first time, phosph(on)ates were used as an adsorbate to form self-assembled monolayers (SAMs) on alumina to direct the assembly of NPs onto the surface. The Al2O3 substrates were functionalized with aminobutylphosphonic acid (ABP) or phosphonoundecanoic acid (PNDA) SAMs or with poly(ethyleneimine) (PEI) as a reference. FePt NPs assembled on all of these monolayers, but much less on unmodified Al2O3, which shows that ligand exchange at the NPs is the most likely mechanism of attachment. Proper modification of the Al2O3 surface and controlling the immersion time of the modified Al2O3 substrates into the FePt NP solution resulted in FePt NPs assembly with controlled NP density. Alumina substrates were patterned by microcontact printing using aminobutylphosphonic acid as the ink, allowing local NP assembly. Thermal annealing under reducing conditions (96%N2/4%H2) led to a phase change of the FePt NPs from the disordered FCC phase to the ordered FCT phase. This resulted in ferromagnetic behavior at room temperature. Such a process can potentially be applied in the fabrication of spintronic devices. PMID:20480007

  8. Inkjet Printing Based Mono-layered Photonic Crystal Patterning for Anti-counterfeiting Structural Colors

    PubMed Central

    Nam, Hyunmoon; Song, Kyungjun; Ha, Dogyeong; Kim, Taesung

    2016-01-01

    Photonic crystal structures can be created to manipulate electromagnetic waves so that many studies have focused on designing photonic band-gaps for various applications including sensors, LEDs, lasers, and optical fibers. Here, we show that mono-layered, self-assembled photonic crystals (SAPCs) fabricated by using an inkjet printer exhibit extremely weak structural colors and multiple colorful holograms so that they can be utilized in anti-counterfeit measures. We demonstrate that SAPC patterns on a white background are covert under daylight, such that pattern detection can be avoided, but they become overt in a simple manner under strong illumination with smartphone flash light and/or on a black background, showing remarkable potential for anti-counterfeit techniques. Besides, we demonstrate that SAPCs yield different RGB histograms that depend on viewing angles and pattern densities, thus enhancing their cryptographic capabilities. Hence, the structural colorations designed by inkjet printers would not only produce optical holograms for the simple authentication of many items and products but also enable a high-secure anti-counterfeit technique. PMID:27487978

  9. Inkjet Printing Based Mono-layered Photonic Crystal Patterning for Anti-counterfeiting Structural Colors

    NASA Astrophysics Data System (ADS)

    Nam, Hyunmoon; Song, Kyungjun; Ha, Dogyeong; Kim, Taesung

    2016-08-01

    Photonic crystal structures can be created to manipulate electromagnetic waves so that many studies have focused on designing photonic band-gaps for various applications including sensors, LEDs, lasers, and optical fibers. Here, we show that mono-layered, self-assembled photonic crystals (SAPCs) fabricated by using an inkjet printer exhibit extremely weak structural colors and multiple colorful holograms so that they can be utilized in anti-counterfeit measures. We demonstrate that SAPC patterns on a white background are covert under daylight, such that pattern detection can be avoided, but they become overt in a simple manner under strong illumination with smartphone flash light and/or on a black background, showing remarkable potential for anti-counterfeit techniques. Besides, we demonstrate that SAPCs yield different RGB histograms that depend on viewing angles and pattern densities, thus enhancing their cryptographic capabilities. Hence, the structural colorations designed by inkjet printers would not only produce optical holograms for the simple authentication of many items and products but also enable a high-secure anti-counterfeit technique.

  10. Patterned arrays of lateral heterojunctions within monolayer two-dimensional semiconductors

    DOE PAGESBeta

    Mahjouri-Samani, Masoud; Lin, Ming-Wei; Wang, Kai; Lupini, Andrew R.; Lee, Jaekwang; Basile, Leonardo; Boulesbaa, Abdelaziz; Rouleau, Christopher M.; Puretzky, Alexander A.; Ivanov, Ilia N.; et al

    2015-07-22

    The formation of semiconductor heterojunctions and their high density integration are foundations of modern electronics and optoelectronics. To enable two-dimensional (2D) crystalline semiconductors as building blocks in next generation electronics, developing methods to deterministically form lateral heterojunctions is crucial. Here we demonstrate a process strategy for the formation of lithographically-patterned lateral semiconducting heterojunctions within a single 2D crystal. E-beam lithography is used to pattern MoSe2 monolayer crystals with SiO2, and the exposed locations are selectively and totally converted to MoS2 using pulsed laser deposition (PLD) of sulfur in order to form MoSe2/MoS2 heterojunctions in predefined patterns. The junctions and conversionmore » process are characterized by atomically resolved scanning transmission electron microscopy, photoluminescence, and Raman spectroscopy. This demonstration of lateral semiconductor heterojunction arrays within a single 2D crystal is an essential step for the lateral integration of 2D semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin circuitry.« less

  11. Inkjet Printing Based Mono-layered Photonic Crystal Patterning for Anti-counterfeiting Structural Colors.

    PubMed

    Nam, Hyunmoon; Song, Kyungjun; Ha, Dogyeong; Kim, Taesung

    2016-01-01

    Photonic crystal structures can be created to manipulate electromagnetic waves so that many studies have focused on designing photonic band-gaps for various applications including sensors, LEDs, lasers, and optical fibers. Here, we show that mono-layered, self-assembled photonic crystals (SAPCs) fabricated by using an inkjet printer exhibit extremely weak structural colors and multiple colorful holograms so that they can be utilized in anti-counterfeit measures. We demonstrate that SAPC patterns on a white background are covert under daylight, such that pattern detection can be avoided, but they become overt in a simple manner under strong illumination with smartphone flash light and/or on a black background, showing remarkable potential for anti-counterfeit techniques. Besides, we demonstrate that SAPCs yield different RGB histograms that depend on viewing angles and pattern densities, thus enhancing their cryptographic capabilities. Hence, the structural colorations designed by inkjet printers would not only produce optical holograms for the simple authentication of many items and products but also enable a high-secure anti-counterfeit technique. PMID:27487978

  12. Patterned arrays of lateral heterojunctions within monolayer two-dimensional semiconductors

    SciTech Connect

    Mahjouri-Samani, Masoud; Lin, Ming-Wei; Wang, Kai; Lupini, Andrew R.; Lee, Jaekwang; Basile, Leonardo; Boulesbaa, Abdelaziz; Rouleau, Christopher M.; Puretzky, Alexander A.; Ivanov, Ilia N.; Xiao, Kai; Yoon, Mina; Geohegan, David B.

    2015-07-22

    The formation of semiconductor heterojunctions and their high density integration are foundations of modern electronics and optoelectronics. To enable two-dimensional (2D) crystalline semiconductors as building blocks in next generation electronics, developing methods to deterministically form lateral heterojunctions is crucial. Here we demonstrate a process strategy for the formation of lithographically-patterned lateral semiconducting heterojunctions within a single 2D crystal. E-beam lithography is used to pattern MoSe2 monolayer crystals with SiO2, and the exposed locations are selectively and totally converted to MoS2 using pulsed laser deposition (PLD) of sulfur in order to form MoSe2/MoS2 heterojunctions in predefined patterns. The junctions and conversion process are characterized by atomically resolved scanning transmission electron microscopy, photoluminescence, and Raman spectroscopy. This demonstration of lateral semiconductor heterojunction arrays within a single 2D crystal is an essential step for the lateral integration of 2D semiconductor building blocks with different electronic and optoelectronic properties for high-density, ultrathin circuitry.

  13. Manipulating the Local Light Emission in Organic Light-Emitting Diodes by using Patterned Self-Assembled Monolayers.

    PubMed

    Mathijssen, Simon G J; van Hal, Paul A; van den Biggelaar, Ton J M; Smits, Edsger C P; de Boer, Bert; Kemerink, Martijn; Janssen, René A J; de Leeuw, Dago M

    2008-07-17

    Patterned organic light-emitting diodes are fabricated by using microcontact- printed self-assembled monolayers on a gold anode (see background figure). Molecules with dipole moments in opposite directions result in an increase or a decrease of the local work function (foreground picture), providing a direct handle on charge injection and enabling local modification of the light emission. PMID:25213893

  14. Selective Surface Acoustic Wave-Based Organophosphorus Sensor Employing a Host-Guest Self-Assembly Monolayer of β-Cyclodextrin Derivative

    PubMed Central

    Pan, Yong; Mu, Ning; Shao, Shengyu; Yang, Liu; Wang, Wen; Xie, Xiao; He, Shitang

    2015-01-01

    Self-assembly and molecular imprinting technologies are very attractive technologies for the development of artificial recognition systems and provide chemical recognition based on need and not happenstance. In this paper, we employed a β-cyclodextrin derivative surface acoustic wave (SAW) chemical sensor for detecting the chemical warfare agents (CWAs) sarin (O-Isoprophyl methylphosphonofluoridate, GB). Using sarin acid (isoprophyl hydrogen methylphosphonate) as an imprinting template, mono[6-deoxy-6-[(mercaptodecamethylene)thio

  15. Spatially Modulating Interfacial Properties of Transparent Conductive Oxides: Patterning Work Function with Phosphonic Acid Self-Assembled Monolayers

    SciTech Connect

    Knesting, Kristina M.; Hotchkiss, Peter J.; MacLeod, Bradley A.; Marder, Seth R.; Ginger, David S.

    2011-09-29

    The interface between an organic semiconductor and a transparent conducting oxide is crucial to the performance of organic optoelectronics. We use microcontact printing to pattern pentafluorobenzyl phosphonic acid self-assembled monolayers (SAMs) on indium tin oxide (ITO). We obtain high-fidelity patterns with sharply defined edges and with large work function contrast (comparable to that obtained from phosphonic acid SAMs deposited from solution).

  16. Self-assembled monolayers and titanium dioxide: From surface patterning to potential applications.

    PubMed

    Paz, Yaron

    2011-01-01

    The ability to control the properties of self-assembled monolayers (SAMs) attached to solid surfaces and the rare photocatalytic properties of titanium dioxide provide a rationale for the study of systems comprising both. Such systems can be realized in the form of SAMs grown on TiO(2) or, in a complementary manner, as TiO(2) grown on SAMs. Accordingly, the current status of knowledge regarding SAMs on TiO(2) is described. Photocatalytic phenomena that are of specific relevance to SAMs, such as remote degradation, and cases where SAMs were used to study photocatalytic phenomena, are discussed as well. Mastering of micro-patterning is a key issue en route to a successful assimilation of a variety of titanium dioxide based devices. Accordingly, particular attention is given to the description of a variety of methods and techniques aimed at utilizing the photocatalytic properties of titanium dioxide for patterning. Reports on a variety of applications are discussed. These examples, representing the areas of photovoltaics, microelectronics, microelectromechanics, photocatalysis, corrosion prevention and even biomedicine should be regarded as appetizers paving the way for further studies to be performed.

  17. Single-layer ionic conduction on carboxyl-terminated silane monolayers patterned by constructive lithography

    NASA Astrophysics Data System (ADS)

    Berson, Jonathan; Burshtain, Doron; Zeira, Assaf; Yoffe, Alexander; Maoz, Rivka; Sagiv, Jacob

    2015-06-01

    Ionic transport plays a central role in key technologies relevant to energy, and information processing and storage, as well as in the implementation of biological functions in living organisms. Here, we introduce a supramolecular strategy based on the non-destructive chemical patterning of a highly ordered self-assembled monolayer that allows the reproducible fabrication of ion-conducting surface patterns (ion-conducting channels) with top -COOH functional groups precisely definable over the full range of length scales from nanometre to centimetre. The transport of a single layer of selected metal ions and the electrochemical processes related to their motion may thus be confined to predefined surface paths. As a generic solid ionic conductor that can accommodate different mobile ions in the absence of any added electrolyte, these ion-conducting channels exhibit bias-induced competitive transport of different ionic species. This approach offers unprecedented opportunities for the realization of designed ion-conducting systems with nanoscale control, beyond the inherent limitations posed by available ionic materials.

  18. Self-assembled monolayers and titanium dioxide: From surface patterning to potential applications

    PubMed Central

    2011-01-01

    Summary The ability to control the properties of self-assembled monolayers (SAMs) attached to solid surfaces and the rare photocatalytic properties of titanium dioxide provide a rationale for the study of systems comprising both. Such systems can be realized in the form of SAMs grown on TiO2 or, in a complementary manner, as TiO2 grown on SAMs. Accordingly, the current status of knowledge regarding SAMs on TiO2 is described. Photocatalytic phenomena that are of specific relevance to SAMs, such as remote degradation, and cases where SAMs were used to study photocatalytic phenomena, are discussed as well. Mastering of micro-patterning is a key issue en route to a successful assimilation of a variety of titanium dioxide based devices. Accordingly, particular attention is given to the description of a variety of methods and techniques aimed at utilizing the photocatalytic properties of titanium dioxide for patterning. Reports on a variety of applications are discussed. These examples, representing the areas of photovoltaics, microelectronics, microelectromechanics, photocatalysis, corrosion prevention and even biomedicine should be regarded as appetizers paving the way for further studies to be performed. PMID:22259769

  19. Direct patterning of coplanar polyethylene glycol alkylsilane monolayers by deep-ultraviolet photolithography as a general method for high fidelity, long-term cell patterning and culture.

    PubMed

    Wilson, Kerry; Stancescu, Maria; Das, Mainak; Rumsey, John; Hickman, James

    2011-03-01

    This manuscript details a general method for patterning coplanar alkylsilane monolayers using deep-ultraviolet photolithography that has broad application for high fidelity patterning of cells of varying phenotype in long-term cultures. A polyethylene glycol monolayer was formed on a silica substrate and then patterned using 193 nm light from an ArF excimer laser. The regions of photoablation were then rederivatized with (3-trimethoxysilyl propyl) diethyltriamine (DETA), yielding high contrast cytophilic islands that promoted cell adhesion and growth. Rat hippocampal neurons, motoneurons, and myoblasts were then cultured in a defined, serum-free medium on the patterned surfaces for periods in excess of 40 days. This approach has been shown to be useful as a general method for the long-term culture of multiple cell types in highly defined spatial patterns and can be used for supporting complex cocultures for creating in vitro models for biological systems.

  20. Neutron diffraction of. cap alpha. ,. beta. and. gamma. cyclodextrins: hydrogen bonding patterns

    SciTech Connect

    Hingerty, B.E.; Klar, B.; Hardgrove, G.; Betzel, C.; Saenger, W.

    1983-01-01

    Cyclodextrins (CD's) are torus-shaped molecules composed of six (..cap alpha..), seven (..beta..) or eight (..gamma..) (1 ..-->.. 4) linked glucoses. ..cap alpha..-CD has been shown to have two different structures with well-defined hydrogen bonds, one tense and the other relaxed. An induced-fit-like mechanism for ..cap alpha..-CD complex formation has been proposed. Circular hydrogen bond networks have also been found for ..cap alpha..-CD due to the energetically favored cooperative effect. ..beta..-CD with a disordered water structure possesses an unusual flip-flop hydrogen bonding system of the type O-H H-O representing an equilibrium between two states; O-H O reversible H-O. ..gamma..-CD with a disordered water structure similar to ..beta..-CD also possesses the flip-flop hydrogen bond. This study demonstrates that hydrogen bonds are operative in disordered systems and display dynamics even in the solid state.

  1. Patterned Growth of Organic Semiconductors: Selective Nucleation of Perylene on Self-Assembled Monolayers.

    PubMed

    Pick, André; Witte, Gregor

    2016-08-16

    Organic semiconductors (OSC) have received a large amount of attention because they afford the fabrication of flexible electronic devices. However, the limited resistance to radiation and etching of such materials does not permit their patterning by photolithography, which has been a driving force for the development of integrated circuits and therefore requires alternative structuring techniques. One approach is based on precoating the substrate with self-assembled monolayers (SAMs) to control the nucleation of subsequently deposited OSC layers, but the underlying mechanism is barely understood. Here, we used alkanethiols with different chemical terminations to prepare SAMs on gold substrates serving as model systems to identify the mechanism of selective nucleation for the case of the OSC perylene. Using atomic force microscopy and fluorescence microscopy, we demonstrate that the chemical functionalization of the SAMs determines the adhesion forces for the OSC that are smallest for CF3-terminated and largest for OH-terminated SAMs, hence yielding distinctly different sticking probabilities upon perylene deposition at room temperature. Microcontact printing and immersion were employed to prepare SAM patterns that enable the selective growth of polycrystalline perylene films. A quite different situation is found upon printing long-chain thiols with low vapor pressure, which leads to the transfer of multilayers and favors the growth of perylene single crystallites. In a more abstract scenario, patterns of silicone oil droplets were printed on a gold substrate, which was previously covered with a repelling fluorinated SAM. Such droplets provide nucleation centers for liquid-mediated growth, often yielding platelet-shaped perylene single crystallites without unwanted perylene nucleation on the remaining surface. PMID:27441921

  2. Pattern formation in fatty acid-nanoparticle and lipid-nanoparticle mixed monolayers at water surface

    NASA Astrophysics Data System (ADS)

    Choudhuri, M.; Datta, A.; Iyengar, A. N. Sekar; Janaki, M. S.

    2015-06-01

    Dodecanethiol-capped gold nanoparticles (AuNPs) are self-organized in two different amphiphilic monolayers one of which is a single-tailed fatty acid Stearic acid (StA) and the other a double-tailed lipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). In the StA-AuNP film the AuNPs self-organize to form an interconnected network of nanoclusters on compression while in the DMPC-AuNP film the AuNPs aggregate to form random, isolated clusters in the film. The long time evolution of the films at constant surface pressure reveals ring structures in the former and diffusion limited aggregates in the latter that with time evolve into an irregular porous maze of AuNPs in the DMPC film. The difference in structure of the AuNP patterns in the two films can be attributed to a difference in the lipophilic interactions between the NPs and the amphiphilic molecules. The mean square intensity fluctuations f(ln) calculated along a typical line for the 2D structures in both the films at initial and final stages of long time evolution reflect the structural changes in the films over time.

  3. Free-Standing, Patternable Nanoparticle/Polymer Monolayer Arrays Formed by Evaporation Induced Self-Assembly at a Fluid Interface

    SciTech Connect

    Pang, Jiebin; Xiong, Shisheng; Jaeckel, Felix; Sun, Zaicheng; Dunphy, Darren; Brinker, C.Jeffrey

    2008-12-03

    We report a general and facile method to prepare free-standing, patternable nanoparticle/polymer monolayer arrays by interfacial NP assembly within a polymeric photoresist. The ultrathin monolayer nanoparticle/polymer arrays are sufficiently robust that they can be transferred to arbitrary substrates and suspended as free-standing membranes over cm-sized holes -- even with free edges. More importantly, the polymethylmethacrylate (PMMA) in the system serves as a photoresist enabling two modes of electron beam (e-beam) patterning. Lower e-beam doses direct differential nanoparticle solubility and result in nanoparticle patterns with somewhat diffuse interfaces. At higher e-beam doses the PMMA serves as a negative resist resulting in submicrometer patterns with edge roughness comparable to that of the nanoparticle diameter. These ultrathin films of monolayer nanoparticle arrays are of fundamental interest as 2D artificial solids for electronic, magnetic, and optical properties and are also of technological interest for a diverse range of applications in micro- and macroscale devices including photovoltaics, sensors, catalysis, and magnetic storage.

  4. Site-selective biofunctionalization of aluminum nitride surfaces using patterned organosilane self-assembled monolayers.

    PubMed

    Chiu, Chi-Shun; Lee, Hong-Mao; Gwo, Shangjr

    2010-02-16

    Surface biochemical functionalization of group-III nitride semiconductors has recently attracted much interest because of their biocompatibility, nontoxicity, and long-term chemical stability under demanding physiochemical conditions for chemical and biological sensing. Among III-nitrides, aluminum nitride (AlN) and aluminum gallium nitride (AlGaN) are particularly important because they are often used as the sensing surfaces for sensors based on field-effect transistor or surface acoustic wave (SAW) sensor structures. To demonstrate the possibility of site-selective biofunctionalization on AlN surfaces, we have fabricated two-dimensional antibody micropatterns on AlN surfaces by using patterned self-assembled monolayer (SAM) templates. Patterned SAM templates are composed of two types of organosilane molecules terminated with different functional groups (amino and methyl), which were fabricated on AlN/sapphire substrates by combining photolithography, lift-off process, and self-assembly technique. Because the patterned SAM templates have different surface properties on the same surface, clear imaging contrast of SAM micropatterns can be observed by field-emission scanning electron microscopy (FE-SEM) operating at a low accelerating voltage in the range of 0.5-1.5 kV. Furthermore, the contrast in surface potential of the binary SAM microstructures was confirmed by selective adsorption of negatively charged colloidal gold nanoparticles (AuNPs). The immobilization of AuNPs was limited on the positively charged amino-terminated regions, while they were scarcely found on the surface regions terminated by methyl groups. In this work, selective immobilization of green fluorescent protein (GFP) antibodies was demonstrated by the specific protein binding of enhanced GFP (EGFP) labeling. The observed strong fluorescent signal from antibody functionalized regions on the SAM-patterned AlN surface indicates the retained biological activity of specific molecular recognition

  5. Spin-Cast and Patterned Organophosphonate Self-Assembled Monolayer Dielectrics on Metal-Oxide-Activated Si

    SciTech Connect

    O Acton; D Hutchins; L Arnadottir; T Weidner; N Cernetic; G Ting; T Kim; D Castner; H Ma; A Jen

    2011-12-31

    An efficient process is developed for modifying Si with self-assembled monolayers (SAMs) through in situ metal oxide surface activation and microcontact printing or spin-coating of phosphonic-acid-based molecules. The utility of this process is demonstrated by fabricating self-organized and solution-processed low-voltage organic thin-film transistors enabled by patterned and spin-cast phosphonate SAM/metal oxide hybrid dielectrics.

  6. Formation of highly stable self-assembled alkyl phosphonic acid monolayers for the functionalization of titanium surfaces and protein patterning.

    PubMed

    Han, Xuemingyue; Sun, Xiangyu; He, Tao; Sun, Shuqing

    2015-01-01

    A protocol for the preparation of improved phosphonate monolayers on a titanium (Ti) substrate is presented. Zirconium ions were used to enhance the bonding between the phosphonate headgroup and the pretreated Ti surface. Contact angle and X-ray photoelectron spectroscopy were used to characterize self-assembled monolayers (SAMs) of alkylphosphonic acid that formed spontaneously on Zr-mediated Ti (Zr/Ti) surfaces. The surfaces that were treated with an aqueous solution of zirconium oxychloride showed significantly enhanced stability in buffer compared with those formed directly on the native oxidized Ti. A bifunctional molecule, 10-mercaptodecanyl phosphonic acid (MDPA), was also used to form SAMs on Zr/Ti surfaces using an identical method, which enabled us to regulate the surface functionality through the terminal functional group. Protein patterning on the surface was carried out using UV irradiation through a mask to selectively degrade regions of the MDPA molecules. The surface was then backfilled with a protein-resistant molecule in the exposed regions followed by selective immobilization of proteins to the unexposed areas using a heterobifunctional linker molecule. The presented strategy significantly improved the stability of the phosphonate SAMs on oxidized Ti surfaces, which provided an ideal approach foundation for biomolecular immobilization and patterning onto the Ti surfaces. Thus, this method provided a versatile platform to activate the surfaces of biomedical Ti implants.

  7. Orthogonally Spin-Coated Bilayer Films for Photochemical Immobilization and Patterning of Sub-10-Nanometer Polymer Monolayers.

    PubMed

    Janes, Dustin W; Kim, Chae Bin; Maher, Michael J; Ellison, Christopher J

    2016-07-12

    Versatile and spatiotemporally controlled methods for decorating surfaces with monolayers of attached polymers are broadly impactful to many technological applications. However, current materials are usually designed for very specific polymer/surface chemistries and, as a consequence, are not very broadly applicable and/or do not rapidly respond to high-resolution stimuli such as light. We describe here the use of a polymeric adhesion layer, poly(styrene sulfonyl azide-alt-maleic anhydride) (PSSMA), which is capable of immobilizing a 1-7 nm thick monolayer of preformed, inert polymers via photochemical grafting reactions. Solubility of PSSMA in very polar solvents enables processing alongside hydrophobic polymers or solutions and by extension orthogonal spin-coating deposition strategies. Therefore, these materials and processes are fully compatible with photolithographic tools and can take advantage of the immense manufacturing scalability they afford. For example, the thicknesses of covalently grafted poly(styrene) obtained after seconds of exposure are quantitatively equivalent to those obtained by physical adsorption after hours of thermal equilibration. Sequential polymer grafting steps using photomasks were used to pattern different regions of surface energy on the same substrate. These patterns spatially controlled the self-assembled domain orientation of a block copolymer possessing 21 nm half-periodicity, demonstrating hierarchical synergy with leading-edge nanopatterning approaches.

  8. Critical role of wettability in assembly of zirconia nanoparticles on a self-assembled monolayer-patterned substrate

    NASA Astrophysics Data System (ADS)

    Yang, Mi-Sun; Lee, Seung-Hoon; Moon, Byung Kee; Yoo, Seung Ryul; Hwang, Seongpil; Jang, Jae-Won

    2016-08-01

    This study investigated which factors decisively influence colloidal nanoparticle (NP) assembly on a self-assembled monolayer (SAM)-patterned substrate. Zirconia (ZrO2) NP assembly on a poly(dimethylsiloxane) (PDMS)-stamped SAM-patterned Au substrate was carried out while the size and surface charge state of the NPs and the substrate wettability were altered. ZrO2 particles with diameters of 350 nm, 560 nm, and 1100 nm were employed to examine the effect of NP size on the assembly. Bare ZrO2 NPs with a negatively charged surface and ZrO2 NPs with a positively charged surface through 3-aminopropyltriethoxysilane encapsulation were prepared for the NP assembly. Moreover, the substrate wettability effect on the NP assembly was evaluated by comparing the assembly on substrates with the PDMS-patterned SAMs of thiols with polar and non-polar functional groups. From the characterization of the number of NPs in a pattern and the effective area of assembled NPs (Aeff), positively charged ZrO2 NP assembly on negatively charged patterns showed the highest number density of particles in a pattern compared with the other combinations in both 350-nm and 560-nm ZrO2 NPs. This observation can be attributed to negatively charged 16-mercaptohexadecanoic acid SAMs having greater polarity (more polar groups) than positively charged 11-amino-1-undecanethiol SAMs within the condition of the colloidal ZrO2 NP assembly.

  9. Site-selective assembly of quantum dots on patterned self-assembled monolayers fabricated by laser direct-writing.

    PubMed

    Wu, Chong; Wang, Yongsheng; Han, Xuemingyue; Hu, Xinming; Cheng, Qianyi; Han, Baohang; Liu, Qian; Ren, Tianling; He, Yonghong; Sun, Shuqing; Ma, Hui

    2012-06-15

    A simple and efficient route for quantum dot (QDs) patterning using self-assembled monolayers (SAMs) as templates is described. By means of a laser direct-writing (LDW) technique, SAMs of octadecylphosphonic acid formed by adsorption on native oxide layer of titanium film were patterned through laser-induced ablation of the SAM molecules. This technique allows the creation of chemical-specific patterns accompanied by slight change in the topography. Using atomic force microscopy and friction force microscopy, the dependence of feature size and characteristics on the irradiation dose was demonstrated. Upon immersion of a substrate with patterned SAMs bearing thiol as the terminal group into a dispersion of QDs resulted in the assembly of QDs on the specific thiol-terminated areas. Patterns of QDs with different photoluminescent wavelength were generated. The LDW technique, which is convenient and flexible due to its path-directed and maskless fabrication process, provided a new powerful approach for patterning materials on surfaces for various applications. PMID:22595703

  10. Site-selective assembly of quantum dots on patterned self-assembled monolayers fabricated by laser direct-writing

    NASA Astrophysics Data System (ADS)

    Wu, Chong; Wang, Yongsheng; Han, Xuemingyue; Hu, Xinming; Cheng, Qianyi; Han, Baohang; Liu, Qian; Ren, Tianling; He, Yonghong; Sun, Shuqing; Ma, Hui

    2012-06-01

    A simple and efficient route for quantum dot (QDs) patterning using self-assembled monolayers (SAMs) as templates is described. By means of a laser direct-writing (LDW) technique, SAMs of octadecylphosphonic acid formed by adsorption on native oxide layer of titanium film were patterned through laser-induced ablation of the SAM molecules. This technique allows the creation of chemical-specific patterns accompanied by slight change in the topography. Using atomic force microscopy and friction force microscopy, the dependence of feature size and characteristics on the irradiation dose was demonstrated. Upon immersion of a substrate with patterned SAMs bearing thiol as the terminal group into a dispersion of QDs resulted in the assembly of QDs on the specific thiol-terminated areas. Patterns of QDs with different photoluminescent wavelength were generated. The LDW technique, which is convenient and flexible due to its path-directed and maskless fabrication process, provided a new powerful approach for patterning materials on surfaces for various applications.

  11. Site-selective assembly of quantum dots on patterned self-assembled monolayers fabricated by laser direct-writing.

    PubMed

    Wu, Chong; Wang, Yongsheng; Han, Xuemingyue; Hu, Xinming; Cheng, Qianyi; Han, Baohang; Liu, Qian; Ren, Tianling; He, Yonghong; Sun, Shuqing; Ma, Hui

    2012-06-15

    A simple and efficient route for quantum dot (QDs) patterning using self-assembled monolayers (SAMs) as templates is described. By means of a laser direct-writing (LDW) technique, SAMs of octadecylphosphonic acid formed by adsorption on native oxide layer of titanium film were patterned through laser-induced ablation of the SAM molecules. This technique allows the creation of chemical-specific patterns accompanied by slight change in the topography. Using atomic force microscopy and friction force microscopy, the dependence of feature size and characteristics on the irradiation dose was demonstrated. Upon immersion of a substrate with patterned SAMs bearing thiol as the terminal group into a dispersion of QDs resulted in the assembly of QDs on the specific thiol-terminated areas. Patterns of QDs with different photoluminescent wavelength were generated. The LDW technique, which is convenient and flexible due to its path-directed and maskless fabrication process, provided a new powerful approach for patterning materials on surfaces for various applications.

  12. Patterned Array of Poly(ethylene glycol) Silane Monolayer for Label-Free Detection of Dengue.

    PubMed

    Rosly, Nor Zida; Ahmad, Shahrul Ainliah Alang; Abdullah, Jaafar; Yusof, Nor Azah

    2016-01-01

    In the present study, the construction of arrays on silicon for naked-eye detection of DNA dengue was demonstrated. The array was created by exposing a polyethylene glycol (PEG) silane monolayer to 254 nm ultraviolet (UV) light through a photomask. Formation of the PEG silane monolayer and photomodifed surface properties was thoroughly characterized by using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. The results of XPS confirmed that irradiation of ultraviolet (UV) light generates an aldehyde functional group that offers conjugation sites of amino DNA probe for detection of a specific dengue virus target DNA. Employing a gold enhancement process after inducing the electrostatic interaction between positively charged gold nanoparticles and the negatively charged target DNA hybridized to the DNA capture probe allowed to visualize the array with naked eye. The developed arrays demonstrated excellent performance in diagnosis of dengue with a detection limit as low as 10 pM. The selectivity of DNA arrays was also examined using a single base mismatch and noncomplementary target DNA. PMID:27571080

  13. Patterned Array of Poly(ethylene glycol) Silane Monolayer for Label-Free Detection of Dengue

    PubMed Central

    Rosly, Nor Zida; Ahmad, Shahrul Ainliah Alang; Abdullah, Jaafar; Yusof, Nor Azah

    2016-01-01

    In the present study, the construction of arrays on silicon for naked-eye detection of DNA dengue was demonstrated. The array was created by exposing a polyethylene glycol (PEG) silane monolayer to 254 nm ultraviolet (UV) light through a photomask. Formation of the PEG silane monolayer and photomodifed surface properties was thoroughly characterized by using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. The results of XPS confirmed that irradiation of ultraviolet (UV) light generates an aldehyde functional group that offers conjugation sites of amino DNA probe for detection of a specific dengue virus target DNA. Employing a gold enhancement process after inducing the electrostatic interaction between positively charged gold nanoparticles and the negatively charged target DNA hybridized to the DNA capture probe allowed to visualize the array with naked eye. The developed arrays demonstrated excellent performance in diagnosis of dengue with a detection limit as low as 10 pM. The selectivity of DNA arrays was also examined using a single base mismatch and noncomplementary target DNA. PMID:27571080

  14. First principles kinetic Monte Carlo study on the growth patterns of WSe2 monolayer

    NASA Astrophysics Data System (ADS)

    Nie, Yifan; Liang, Chaoping; Zhang, Kehao; Zhao, Rui; Eichfeld, Sarah M.; Cha, Pil-Ryung; Colombo, Luigi; Robinson, Joshua A.; Wallace, Robert M.; Cho, Kyeongjae

    2016-06-01

    The control of domain morphology and defect level of synthesized transition metal dichalcogenides (TMDs) is of crucial importance for their device applications. However, current TMDs synthesis by chemical vapor deposition and molecular beam epitaxy is in an early stage of development, where much of the understanding of the process-property relationships is highly empirical. In this work, we use a kinetic Monte Carlo coupled with first principles calculations to study one specific case of the deposition of monolayer WSe2 on graphene, which can be expanded to the entire TMD family. Monolayer WSe2 domains are investigated as a function of incident flux, temperature and precursor ratio. The quality of the grown WSe2 domains is analyzed by the stoichiometry and defect density. A phase diagram of domain morphology is developed in the space of flux and the precursor stoichiometry, in which the triangular compact, fractal and dendritic domains are identified. The phase diagram has inspired a new synthesis strategy for large TMD domains with improved quality.

  15. Patterned Array of Poly(ethylene glycol) Silane Monolayer for Label-Free Detection of Dengue.

    PubMed

    Rosly, Nor Zida; Ahmad, Shahrul Ainliah Alang; Abdullah, Jaafar; Yusof, Nor Azah

    2016-01-01

    In the present study, the construction of arrays on silicon for naked-eye detection of DNA dengue was demonstrated. The array was created by exposing a polyethylene glycol (PEG) silane monolayer to 254 nm ultraviolet (UV) light through a photomask. Formation of the PEG silane monolayer and photomodifed surface properties was thoroughly characterized by using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and contact angle measurements. The results of XPS confirmed that irradiation of ultraviolet (UV) light generates an aldehyde functional group that offers conjugation sites of amino DNA probe for detection of a specific dengue virus target DNA. Employing a gold enhancement process after inducing the electrostatic interaction between positively charged gold nanoparticles and the negatively charged target DNA hybridized to the DNA capture probe allowed to visualize the array with naked eye. The developed arrays demonstrated excellent performance in diagnosis of dengue with a detection limit as low as 10 pM. The selectivity of DNA arrays was also examined using a single base mismatch and noncomplementary target DNA.

  16. Substrate-mediated effects in photothermal patterning of alkanethiol self-assembled monolayers with microfocused continuous-wave lasers.

    PubMed

    Schröter, Anja; Kalus, Mark; Hartmann, Nils

    2012-01-01

    In recent years, self-assembled monolayers (SAMs) have been demonstrated to provide promising new approaches to nonlinear laser processing. Most notably, because of their ultrathin nature, indirect excitation mechanisms can be exploited in order to fabricate subwavelength structures. In photothermal processing, for example, microfocused lasers are used to locally heat the substrate surface and initiate desorption or decomposition of the coating. Because of the strongly temperature-dependent desorption kinetics, the overall process is highly nonlinear in the applied laser power. For this reason, subwavelength patterning is feasible employing ordinary continuous-wave lasers. The lateral resolution, generally, depends on both the type of the organic monolayer and the nature of the substrate. In previous studies we reported on photothermal patterning of distinct types of SAMs on Si supports. In this contribution, a systematic study on the impact of the substrate is presented. Alkanethiol SAMs on Au-coated glass and silicon substrates were patterned by using a microfocused laser beam at a wavelength of 532 nm. Temperature calculations and thermokinetic simulations were carried out in order to clarify the processes that determine the performance of the patterning technique. Because of the strongly temperature-dependent thermal conductivity of Si, surface-temperature profiles on Au/Si substrates are very narrow ensuring a particularly high lateral resolution. At a 1/e spot diameter of 2 µm, fabrication of subwavelength structures with diameters of 300-400 nm is feasible. Rapid heat dissipation, though, requires high laser powers. In contrast, patterning of SAMs on Au/glass substrates is strongly affected by the largely distinct heat conduction within the Au film and in the glass support. This results in broad surface temperature profiles. Hence, minimum structure sizes are larger when compared with respective values on Au/Si substrates. The required laser powers, though

  17. Patterning of self-assembled monolayers by phase-shifting mask and its applications in large-scale assembly of nanowires

    SciTech Connect

    Gao, Fan; Zhang, Dakuan; Wang, Jianyu; Sheng, Yun; Wang, Xinran; Chen, Kunji; Zhou, Minmin; Yan, Shancheng; Shen, Jiancang; Pan, Lijia; Shi, Yi

    2015-01-26

    A nonselective micropatterning method of self-assembled monolayers (SAMs) based on laser and phase-shifting mask (PSM) is demonstrated. Laser beam is spatially modulated by a PSM, and periodic SAM patterns are generated sequentially through thermal desorption. Patterned wettability is achieved with alternating hydrophilic/hydrophobic stripes on octadecyltrichlorosilane monolayers. The substrate is then used to assemble CdS semiconductor nanowires (NWs) from a solution, obtaining well-aligned NWs in one step. Our results show valuably the application potential of this technique in engineering SAMs for integration of functional devices.

  18. Creating periodic local strain in monolayer graphene with nanopillars patterned by self-assembled block copolymer

    SciTech Connect

    Mi, Hongyi; Mikael, Solomon; Seo, Jung-Hun; Gui, Gui; Ma, Alice L.; Ma, Zhenqiang E-mail: mazq@engr.wisc.edu; Liu, Chi-Chun; Nealey, Paul F. E-mail: mazq@engr.wisc.edu

    2015-10-05

    A simple and viable method was developed to produce biaxial strain in monolayer graphene on an array of SiO{sub 2} nanopillars. The array of SiO{sub 2} nanopillars (1 cm{sup 2} in area, 80 nm in height, and 40 nm in pitch) was fabricated by employing self-assembled block copolymer through simple dry etching and deposition processes. According to high resolution micro-Raman spectroscopy and atomic force microscopy analyses, 0.9% of maximum biaxial tensile strain and 0.17% of averaged biaxial tensile strain in graphene were created. This technique provides a simple and viable method to form biaxial tensile strain in graphene and offers a practical platform for future studies in graphene strain engineering.

  19. Single-layer ionic conduction on carboxyl-terminated silane monolayers patterned by constructive lithography.

    PubMed

    Berson, Jonathan; Burshtain, Doron; Zeira, Assaf; Yoffe, Alexander; Maoz, Rivka; Sagiv, Jacob

    2015-06-01

    Ionic transport plays a central role in key technologies relevant to energy, and information processing and storage, as well as in the implementation of biological functions in living organisms. Here, we introduce a supramolecular strategy based on the non-destructive chemical patterning of a highly ordered self-assembled monolayer that allows the reproducible fabrication of ion-conducting surface patterns (ion-conducting channels) with top -COOH functional groups precisely definable over the full range of length scales from nanometre to centimetre. The transport of a single layer of selected metal ions and the electrochemical processes related to their motion may thus be confined to predefined surface paths. As a generic solid ionic conductor that can accommodate different mobile ions in the absence of any added electrolyte, these ion-conducting channels exhibit bias-induced competitive transport of different ionic species. This approach offers unprecedented opportunities for the realization of designed ion-conducting systems with nanoscale control, beyond the inherent limitations posed by available ionic materials.

  20. Single-layer ionic conduction on carboxyl-terminated silane monolayers patterned by constructive lithography.

    PubMed

    Berson, Jonathan; Burshtain, Doron; Zeira, Assaf; Yoffe, Alexander; Maoz, Rivka; Sagiv, Jacob

    2015-06-01

    Ionic transport plays a central role in key technologies relevant to energy, and information processing and storage, as well as in the implementation of biological functions in living organisms. Here, we introduce a supramolecular strategy based on the non-destructive chemical patterning of a highly ordered self-assembled monolayer that allows the reproducible fabrication of ion-conducting surface patterns (ion-conducting channels) with top -COOH functional groups precisely definable over the full range of length scales from nanometre to centimetre. The transport of a single layer of selected metal ions and the electrochemical processes related to their motion may thus be confined to predefined surface paths. As a generic solid ionic conductor that can accommodate different mobile ions in the absence of any added electrolyte, these ion-conducting channels exhibit bias-induced competitive transport of different ionic species. This approach offers unprecedented opportunities for the realization of designed ion-conducting systems with nanoscale control, beyond the inherent limitations posed by available ionic materials. PMID:25849368

  1. Biomaterial Surface patterning of self assembled monolayers for controlling neuronal cell behavior

    PubMed Central

    Murugan, Ramalingam; Molnar, Peter; Rao, Koritala P.; Hickman, James J.

    2009-01-01

    Control of the position, growth and subsequent function of living cells is a fundamental problem in tissue and cellular engineering. The development of a generation of ‘smart’ biomaterial substrates requires strict control over the material’s surface properties, because the initial response of the cultured cells to the biomaterials mainly depends upon the surface characteristics of the engineered material. Since most of the cells in the body are arranged in distinct patterns during development, it would be beneficial if one could create patterned environments in-vitro for regulating cell behavior, for applications in vivo, in particular for CNS neurons. Accordingly, in this article, we provide design strategies and methodologies developed for nano- and micro-scale surface patterning and the subsequent control of cellular responses in-vitro. PMID:20174479

  2. Preparation and photolithography of self-assembled monolayers of 10-mercaptodecanylphosphonic acid on glass mediated by zirconium for protein patterning.

    PubMed

    Han, Xuemingyue; Sun, Shuqing; He, Tao

    2013-08-01

    Self-assembled monolayers (SAMs) formed by adsorption of octadecylphosphonic acid (ODPA) on zirconium mediated glass substrates were prepared. In this sandwich structure, Zr(4+) was used as a bi-linker to bind phosphonic acid head group in ODPA to glass substrates. The contact angle of the as-prepared SAMs was measured to be around 104°. X-ray photoelectron spectroscopy (XPS) characterization indicated the modification of Zr(4+) on glass substrates was critical for the formation of reasonably dense, well-ordered SAMs similar in quality to those typically formed on other metal oxide surfaces. Bifunctional molecule, 10-mercaptodecanylphosphonic acid (MDPA), bearing thiol terminal groups for various chemical reactions, was synthesized and formed SAMs on glass using the same approach, which allowed us to control the surface chemistry and functionality through photooxidation of the thiol terminal group. Photopatterning of proteins was performed first by exposing the SAMs to UV light through a mask, followed by protein immobilization to the masked regions through a heterobifunctional linker, while the exposed areas prohibit nonspecific protein absorption. The present strategy, which combined the SAMs assembly and photolithography, offered a facile approach for the fabrication of biomolecule patterning and could be applied to construction of biochips and other applications.

  3. Preparation and photolithography of self-assembled monolayers of 10-mercaptodecanylphosphonic acid on glass mediated by zirconium for protein patterning.

    PubMed

    Han, Xuemingyue; Sun, Shuqing; He, Tao

    2013-08-01

    Self-assembled monolayers (SAMs) formed by adsorption of octadecylphosphonic acid (ODPA) on zirconium mediated glass substrates were prepared. In this sandwich structure, Zr(4+) was used as a bi-linker to bind phosphonic acid head group in ODPA to glass substrates. The contact angle of the as-prepared SAMs was measured to be around 104°. X-ray photoelectron spectroscopy (XPS) characterization indicated the modification of Zr(4+) on glass substrates was critical for the formation of reasonably dense, well-ordered SAMs similar in quality to those typically formed on other metal oxide surfaces. Bifunctional molecule, 10-mercaptodecanylphosphonic acid (MDPA), bearing thiol terminal groups for various chemical reactions, was synthesized and formed SAMs on glass using the same approach, which allowed us to control the surface chemistry and functionality through photooxidation of the thiol terminal group. Photopatterning of proteins was performed first by exposing the SAMs to UV light through a mask, followed by protein immobilization to the masked regions through a heterobifunctional linker, while the exposed areas prohibit nonspecific protein absorption. The present strategy, which combined the SAMs assembly and photolithography, offered a facile approach for the fabrication of biomolecule patterning and could be applied to construction of biochips and other applications. PMID:23524079

  4. Design and fabrication of antireflective GaN subwavelength grating structures using periodic silica sphere monolayer array patterning

    NASA Astrophysics Data System (ADS)

    Ko, Yeong Hwan; Yu, Jae Su

    2013-12-01

    We designed and fabricated gallium nitride (GaN) subwavelength grating (SWG) structures on GaN/sapphire via patterning using the periodic silica sphere monolayer array as an etch mask and a subsequent dry etching for efficient antireflection coatings. Theoretical optimization of GaN SWG structures was performed in terms of their geometrical parameters by the rigorous coupled-wave analysis simulation using a theoretical structural model. The bullet-like parabola-shaped SWGs with a large height-to-diameter ratio ( R H/D) yielded good broadband and wide-angle antireflective surface properties. Considering the R H/D, the GaN SWG structure using 320-nm silica spheres theoretically and experimentally exhibited the most efficient antireflection property because it provided a linearly graded effective refractive index profile with relatively long relaxation length. For various geometries of the fabricated GaN SWGs on GaN/sapphire, the calculated reflectance results showed a similar tendency with the experimental results.

  5. Transparency and damage tolerance of patternable omniphobic lubricated surfaces based on inverse colloidal monolayers

    NASA Astrophysics Data System (ADS)

    Vogel, Nicolas; Belisle, Rebecca A.; Hatton, Benjamin; Wong, Tak-Sing; Aizenberg, Joanna

    2013-07-01

    A transparent coating that repels a wide variety of liquids, prevents staining, is capable of self-repair and is robust towards mechanical damage can have a broad technological impact, from solar cell coatings to self-cleaning optical devices. Here we employ colloidal templating to design transparent, nanoporous surface structures. A lubricant can be firmly locked into the structures and, owing to its fluidic nature, forms a defect-free, self-healing interface that eliminates the pinning of a second liquid applied to its surface, leading to efficient liquid repellency, prevention of adsorption of liquid-borne contaminants, and reduction of ice adhesion strength. We further show how this method can be applied to locally pattern the repellent character of the substrate, thus opening opportunities to spatially confine any simple or complex fluids. The coating is highly defect-tolerant due to its interconnected, honeycomb wall structure, and repellency prevails after the application of strong shear forces and mechanical damage. The regularity of the coating allows us to understand and predict the stability or failure of repellency as a function of lubricant layer thickness and defect distribution based on a simple geometric model.

  6. Transparency and damage tolerance of patternable omniphobic lubricated surfaces based on inverse colloidal monolayers

    SciTech Connect

    Vogel, Nicolas; Belisle, Rebecca A.; Hatton, Benjamin; Wong, Tak-Sing; Aizenberg, Joanna

    2013-07-31

    A transparent coating that repels a wide variety of liquids, prevents staining, is capable of self-repair and is robust towards mechanical damage can have a broad technological impact, from solar cell coatings to self-cleaning optical devices. Here we employ colloidal templating to design transparent, nanoporous surface structures. A lubricant can be firmly locked into the structures and, owing to its fluidic nature, forms a defect-free, self-healing interface that eliminates the pinning of a second liquid applied to its surface, leading to efficient liquid repellency, prevention of adsorption of liquid-borne contaminants, and reduction of ice adhesion strength. We further show how this method can be applied to locally pattern the repellent character of the substrate, thus opening opportunities to spatially confine any simple or complex fluids. The coating is highly defect-tolerant due to its interconnected, honeycomb wall structure, and repellency prevails after the application of strong shear forces and mechanical damage. The regularity of the coating allows us to understand and predict the stability or failure of repellency as a function of lubricant layer thickness and defect distribution based on a simple geometric model.

  7. Transparency and damage tolerance of patternable omniphobic lubricated surfaces based on inverse colloidal monolayers

    DOE PAGESBeta

    Vogel, Nicolas; Belisle, Rebecca A.; Hatton, Benjamin; Wong, Tak-Sing; Aizenberg, Joanna

    2013-07-31

    A transparent coating that repels a wide variety of liquids, prevents staining, is capable of self-repair and is robust towards mechanical damage can have a broad technological impact, from solar cell coatings to self-cleaning optical devices. Here we employ colloidal templating to design transparent, nanoporous surface structures. A lubricant can be firmly locked into the structures and, owing to its fluidic nature, forms a defect-free, self-healing interface that eliminates the pinning of a second liquid applied to its surface, leading to efficient liquid repellency, prevention of adsorption of liquid-borne contaminants, and reduction of ice adhesion strength. We further show howmore » this method can be applied to locally pattern the repellent character of the substrate, thus opening opportunities to spatially confine any simple or complex fluids. The coating is highly defect-tolerant due to its interconnected, honeycomb wall structure, and repellency prevails after the application of strong shear forces and mechanical damage. The regularity of the coating allows us to understand and predict the stability or failure of repellency as a function of lubricant layer thickness and defect distribution based on a simple geometric model.« less

  8. Inside Front Cover: Manipulating the Local Light Emission in Organic Light-Emitting Diodes by using Patterned Self-Assembled Monolayers (Adv. Mater. 14/2008).

    PubMed

    Mathijssen, Simon G J; van Hal, Paul A; van den Biggelaar, Ton J M; Smits, Edsger C P; de Boer, Bert; Kemerink, Martijn; Janssen, René A J; de Leeuw, Dago M

    2008-07-17

    The inside cover shows an optical micrograph picture of an organic light-emitting diode with patterned, micro-contact-printed self-assembled monolayers (SAMs) that modify the work function of the anode, reported by Simon Mathijssen, Dago de Leeuw, and co-workers on p. 2703. In this particular light-emitting diode a fluorinated alkanethiol has been used that increases the work function and therefore improves the injection of holes. This results in a higher light emission on the positions where the SAM has been printed, which can be observed as the red pattern. PMID:25213911

  9. "Click" Patterning of Self-Assembled Monolayers on Hydrogen-Terminated Silicon Surfaces and Their Characterization Using Light-Addressable Potentiometric Sensors.

    PubMed

    Wang, Jian; Wu, Fan; Watkinson, Michael; Zhu, Jingyuan; Krause, Steffi

    2015-09-01

    Two potential strategies for chemically patterning alkyne-terminated self-assembled monolayers (SAMs) on oxide-free silicon or silicon-on-sapphire (SOS) substrates were investigated and compared. The patterned surfaces were validated using a light-addressable potentiometric sensor (LAPS) for the first time. The first strategy involved an integration of photolithography with "click" chemistry. Detailed surface characterization (i.e. water contact angle, ellipsometry, AFM, and XPS) and LAPS measurements showed that photoresist processing not only decreases the coverage of organic monolayers but also introduces chemically bonded contaminants on the surfaces, thus significantly reducing the quality of the SAMs and the utility of "click" surface modification. The formation of chemical contaminants in photolithography was also observed on carboxylic acid- and alkyl-terminated monolayers using LAPS. In contrast, a second approach combined microcontact printing (μCP) with "click" chemistry; that is azide (azido-oligo(ethylene glycol) (OEG)-NH2) inks were printed on alkyne-terminated SAMs on silicon or SOS through PDMS stamps. The surface characterization results for the sample printed with a flat featureless PDMS stamp demonstrated a nondestructive and efficient method of μCP to perform "click" reactions on alkyne-terminated, oxide-free silicon surfaces for the first time. For the sample printed with a featured PDMS stamp, LAPS imaging showed a good agreement with the pattern of the PDMS stamp, indicating the successful chemical patterning on non-oxidized silicon and SOS substrates and the capability of LAPS to image the molecular patterns with high sensitivity.

  10. Endocytosis of fluorescent cyclodextrins by intestinal Caco-2 cells and its role in paclitaxel drug delivery.

    PubMed

    Réti-Nagy, Katalin; Malanga, Milo; Fenyvesi, Éva; Szente, Lajos; Vámosi, György; Váradi, Judit; Bácskay, Ildikó; Fehér, Pálma; Ujhelyi, Zoltán; Róka, Eszter; Vecsernyés, Miklós; Balogh, György; Vasvári, Gábor; Fenyvesi, Ferenc

    2015-12-30

    Cyclodextrins are widely used excipients in pharmaceutical formulations. They are mainly utilized as solubilizers and absorption enhancers, but recent results revealed their effects on cell membranes and pharmacological barriers. In addition to the growing knowledge on their interaction with plasma membranes, it was confirmed that cyclodextrins are able to enter cells by endocytosis. The number of the tested cyclodextrins was limited, and the role of this mechanism in drug absorption and delivery is not known. Our aim was to examine the endocytosis of fluorescently labeled hydroxypropyl-β-cyclodextrin, random methyl-β-cyclodextrin and soluble β-cyclodextrin polymer, and the cellular uptake of the fluorescent paclitaxel derivative-random methyl-β-cyclodextrin complex. The studied cyclodextrin derivatives were able to enter Caco-2 intestinal cells and localized in vesicles in the cytoplasm, while their permeability was very limited through Caco-2 monolayers. We demonstrated for the first time that the fluorescent paclitaxel derivative and rhodamine-labeled random methyl-β-cyclodextrin were detected in the same intracellular vesicles after treating cells with their inclusion complex. These results indicate that the endocytosis of cyclodextrin complexes can contribute to drug absorption processes.

  11. Multiple equilibria interaction pattern between the ionic liquids C(n)mimPF6 and β-cyclodextrin in aqueous solutions.

    PubMed

    Zhang, Jingjing; Shen, Xinghai

    2011-10-20

    The interactions of ionic liquids (ILs) 1-alkyl-3-methylimidazolium hexafluorophosphate (C(n)mimPF(6), n = 2, 4, 6, 8) with β-cyclodextrin (β-CD) in aqueous solutions are investigated in this article. The stoichiometry and apparent association constants were obtained by the competitive fluorescence method, NMR measurements, and isothermal titration calorimetry (ITC). The results showed that C(2)mimPF(6), C(4)mimPF(6), and C(6)mimPF(6) form 1:1 (guest:host) inclusion complexes with β-CD whereas the 1:2 inclusion complex can be formed between C(8)mimPF(6) and β-CD. We studied the existence state of the ILs and found that they exist mainly as separated ions with a minor percentage existing as associated ion pairs within the concentration studied. By ESI/HRMS, the coexistence of different complexes including C(n)mim(+)·PF(6)(-)-β-CD, C(n)mim(+)-β-CD (or C(n)mim(+)-β-CD(2)), and PF(6)(-)-β-CD was observed. It is also deduced that the intermediate complex, (β-CD-cation)·(anion-β-CD), may dissociate into cation-β-CD and anion-β-CD complexes. Thermodynamic parameters determined by ITC indicate that, while the inclusion process for C(6)mimPF(6)/β-CD complex is entropy and enthalpy driven, the interactions of other C(n)mimPF(6) (n = 2, 4, 8) with β-CD are enthalpy controlled. Based on these results, a more comprehensive pattern involving multiple equilibria on the interaction between C(n)mimPF(6) and β-CD in aqueous solutions is presented herein.

  12. Theoretical and computational analysis of second- and third-harmonic generation in periodically patterned graphene and transition-metal dichalcogenide monolayers

    NASA Astrophysics Data System (ADS)

    Weismann, Martin; Panoiu, Nicolae C.

    2016-07-01

    Remarkable optical and electrical properties of two-dimensional (2D) materials, such as graphene and transition-metal dichalcogenide (TMDC) monolayers, offer vast technological potential for novel and improved optoelectronic nanodevices, many of which rely on nonlinear optical effects in these 2D materials. This paper introduces a highly effective numerical method for efficient and accurate description of linear and nonlinear optical effects in nanostructured 2D materials embedded in periodic photonic structures containing regular three-dimensional (3D) optical materials, such as diffraction gratings and periodic metamaterials. The proposed method builds upon the rigorous coupled-wave analysis and incorporates the nonlinear optical response of 2D materials by means of modified electromagnetic boundary conditions. This allows one to reduce the mathematical framework of the numerical method to an inhomogeneous scattering matrix formalism, which makes it more accurate and efficient than previously used approaches. An overview of linear and nonlinear optical properties of graphene and TMDC monolayers is given and the various features of the corresponding optical spectra are explored numerically and discussed. To illustrate the versatility of our numerical method, we use it to investigate the linear and nonlinear multiresonant optical response of 2D-3D heteromaterials for enhanced and tunable second- and third-harmonic generation. In particular, by employing a structured 2D material optically coupled to a patterned slab waveguide, we study the interplay between geometric resonances associated to guiding modes of periodically patterned slab waveguides and plasmon or exciton resonances of 2D materials.

  13. Controlling self assembled monolayers

    NASA Astrophysics Data System (ADS)

    Wei, Yanhu

    2007-12-01

    In this thesis, we demonstrate novel methods of controlling the morphology of self-assembled monolayers at the solution-graphite interface. Scanning tunneling microscopy is used to evaluate the capacity of chain length and weak dipolar interactions to direct packing and neighboring chain selection within monolayers. We designed and synthesized a series of 1,5-substituted anthracene derivatives and investigated the relationship between side chain structure and monolayer morphology. We report that the morphology of monolayers formed on HOPG from symmetrically substituted anthracene derivatives switches from a 2D racemate to a 2D conglomerate by the addition of a single methylene unit to each side chain, i.e., by changing the side chain lengths from even to odd. We introduced ether groups into the side chains of anthracene derivatives in an attempt to use dipolar interactions to alter monolayer morphology. We report that the insertion of electronegative oxygen atoms into the side chains of anthracene derivatives can disturb the odd - even effect of chain length and influence monolayer morphology. By introducing a proper number of ether groups at specific side chain locations, we designed two self-repelling and complementary chains: COC12OC and C2OC10OC 2. COC12OC (or C2OC10OC2) chains repel themselves but select the other C2OC10OC 2 (or COC12OC) chains as their neighbors in self-assembled monolayers. Taking into account chain length matching and dipolar complementary as mechanisms for adjacent side chain selection, we designed and synthesized two symmetrical anthracenes 12 (COC12OC-An-COC 12OC), 13 (C2OC10OC2-An-C 2OC10OC2) and two unsymmetrical anthracenes 15 (C11OC-An-COC12OC) and 16 (C 18OC2-An-C2OC10OC2). Using a mixture solution of these molecules, we prepared a highly ordered AABB monolayer pattern in which paired rows of 15 alternate with paired rows of 16, and a highly ordered AAB monolayer pattern in which rows consisting of 12 are sandwiched between paired

  14. Comparison of host-guest Langmuir-Blodgett multilayer formation by two different amphiphilic cyclodextrins

    SciTech Connect

    Parazak, D.P.; Khan, A.R.; D`Souza, V.T.; Stine, K.J.

    1996-08-07

    We report here our results for Langmuir monolayers of the derivatives of cyclodextrin shown: hexakis(6-deoxy-6-dodecylamino)-{alpha}-cyclodextrin (1a), heptakis(6-deoxy-6-dodecylamino)-{beta}-cyclodextrin (1b), and heptakis(6-deoxy-6-dodecylthio)-{beta}-cyclodextrin (2b ), which was found to be partially substituted. Langmuir films of these derivatives were examined using {Pi}-A isotherm measurements and Brewster angle microscopy. Langmuir-Blodgett (LB) multilayer films of these derivatives were deposited from subphases containing p-nitrophenol to determine the extent of incorporation of the guest molecule in the LB film. The transfer ratios of the film exhibited a noteworthy evolution with the transfer pressure. The variation in the extent of guest molecule incorporation is discussed and compared with the binding behavior in solution of unmodified cyclodextrins. 29 refs., 4 figs.

  15. Effect of β-cyclodextrin on the internalization of nanoparticles into intestine epithelial cells.

    PubMed

    García-González, Lorena; Yépez-Mulía, Lilián; Ganem, Adriana

    2016-01-01

    The influence of β-cyclodextrin on the interaction and internalization of PLGA nanoparticles into intestine epithelial cells was assessed. For this purpose β-cyclodextrin was adsorbed on PLGA nanoparticles. Interaction of nanoparticles with Caco-2 cells, determined by fluorescence, was expressed as the number of particles per cell. Confocal microscopy confirmed the localization of the particles in the cell monolayer. The results showed that adsorption of β-cyclodextrin on the surface of PLGA nanoparticles reduces interaction with mucin, enhancing in this way the internalization into the Caco-2 cells.

  16. Comparative enantiomer affinity pattern of β-blockers in aqueous and nonaqueous CE using single-component anionic cyclodextrins.

    PubMed

    Feng, Ying; Wang, Tingting; Jiang, Zhengjin; Chankvetadze, Bezhan; Crommen, Jacques

    2015-06-01

    A series of eight chiral β-blocker drugs, acebutolol, atenolol, carazolol, carteolol, carvedilol, propranolol, sotalol, and talinolol, have been enantioseparated using two single-component anionic β-CD derivatives, namely heptakis (2,3-di-O-methyl-6-sulfo)-β-CD (HDMS-β-CD) and heptakis (2,3-di-O-acetyl-6-sulfo)-β-CD (HDAS-β-CD), in aqueous CE and NACE. The influence of the nature of substituents (methyl or acetyl) in positions 2 and 3 on the CD derivatives and of the electrophoretic medium (water or methanol) on the enantioselectivity and enantiomer affinity pattern (EAP) of these structurally related compounds was systematically studied. All eight β-blockers could be enantioseparated at least partially in the four CE systems, except sotalol with HDMS-β-CD in NACE. In general, lower affinity and enantioselectivity were obtained in the presence of HDMS-β-CD compared to HDAS-β-CD. Reversals of EAPs were observed for all compounds. EAPs toward these two CDs were found to be opposite to each other in NACE for all compounds except carvedilol and in aqueous CE for atenolol, carteolol, talinolol, and sotalol. It is particularly noteworthy that opposite EAPs were also observed using the same CD derivative when the aqueous BGE was replaced with the methanolic one: for carazolol, carvedilol, and propranolol in the presence of HDMS-β-CD and for acebutolol and carvedilol with HDAS-β-CD.

  17. Perforated monolayers

    SciTech Connect

    Regen, S.L.

    1989-12-01

    The goals of this DOE-sponsored program are to create novel organic thin films that possess well-defined and adjustable molecular pores; i.e. perforated monolayers,'' and to use such film for fabricating composite membranes that have unique permeation characteristics. The specific strategy that has been adopted involves (1) the synthesis of surfactant molecules bearing internal pores, i.e., porous surfactants,'' (2) the assembly of such molecules at an air--water interface, and (3) the stabilization of the resulting assembly via polymerization, before or after transfer to a macroporous support. Research that has been carried out to date has demonstrated the feasibility of using suitably designed calix(n)arene molecules as a basis for constructing perforated monolayers. Specifically, a broad range of calix(n)arenes have been mercurated with mercury trifluoracetate, and used to form polymerized and porous monolayers at the air--water interface. In related studies, p-tert- butylcalix(6)arene has been shown to produce stable monolayers at the air--water interface; removal of the p-tert-butyl groups afford a unique vesicle-forming surfactant, calix(6)arene.

  18. Mechanical Model of Geometric Cell and Topological Algorithm for Cell Dynamics from Single-Cell to Formation of Monolayered Tissues with Pattern

    PubMed Central

    Kachalo, Sëma; Naveed, Hammad; Cao, Youfang; Zhao, Jieling; Liang, Jie

    2015-01-01

    Geometric and mechanical properties of individual cells and interactions among neighboring cells are the basis of formation of tissue patterns. Understanding the complex interplay of cells is essential for gaining insight into embryogenesis, tissue development, and other emerging behavior. Here we describe a cell model and an efficient geometric algorithm for studying the dynamic process of tissue formation in 2D (e.g. epithelial tissues). Our approach improves upon previous methods by incorporating properties of individual cells as well as detailed description of the dynamic growth process, with all topological changes accounted for. Cell size, shape, and division plane orientation are modeled realistically. In addition, cell birth, cell growth, cell shrinkage, cell death, cell division, cell collision, and cell rearrangements are now fully accounted for. Different models of cell-cell interactions, such as lateral inhibition during the process of growth, can be studied in detail. Cellular pattern formation for monolayered tissues from arbitrary initial conditions, including that of a single cell, can also be studied in detail. Computational efficiency is achieved through the employment of a special data structure that ensures access to neighboring cells in constant time, without additional space requirement. We have successfully generated tissues consisting of more than 20,000 cells starting from 2 cells within 1 hour. We show that our model can be used to study embryogenesis, tissue fusion, and cell apoptosis. We give detailed study of the classical developmental process of bristle formation on the epidermis of D. melanogaster and the fundamental problem of homeostatic size control in epithelial tissues. Simulation results reveal significant roles of solubility of secreted factors in both the bristle formation and the homeostatic control of tissue size. Our method can be used to study broad problems in monolayered tissue formation. Our software is publicly

  19. Cyclodextrins and antioxidants.

    PubMed

    López-Nicolás, José Manuel; Rodríguez-Bonilla, Pilar; García-Carmona, Francisco

    2014-01-01

    In recent years, the growth of the functional foods industry has increased research into new compounds with high added value for use in the fortification of traditional products. One of the most promising functional food groups is those enriched in antioxidant compounds of a lipophilic nature. In spite of the numerous advantages reported for such antioxidant molecules, they may also have disadvantages that impede their use in functional foods, although these problems may well avoided by the use of encapsulant agents such as cyclodextrins. This explains the recent increase in the number of research papers dealing with the complexation of different guest molecules possesing important antioxidant properties using natural and modified cyclodextrins. This paper presents a review of the most recent studies on the complexes formed between several important types of antioxidant compounds and cyclodextrins, focusing on the contradictory data reported in the literature concerning to the antioxidant activity of the host/guest molecule complexes, the different complexation constants reported for identical complexes, the bioavailability of the antioxidant compound in the presence of cyclodextrins and recommendation concerning the use of natural or modified cyclodextrins. Moreover, the use of cyclodextrins as antibrowning agents to prevent enzymatic browning in different foods is revised. Finally, we look at studies which suggest that cyclodextrins act as ''secondary antioxidants," enhancing the ability of traditional antioxidants to prevent enzymatic browning.

  20. Cyclodextrins and antioxidants.

    PubMed

    López-Nicolás, José Manuel; Rodríguez-Bonilla, Pilar; García-Carmona, Francisco

    2014-01-01

    In recent years, the growth of the functional foods industry has increased research into new compounds with high added value for use in the fortification of traditional products. One of the most promising functional food groups is those enriched in antioxidant compounds of a lipophilic nature. In spite of the numerous advantages reported for such antioxidant molecules, they may also have disadvantages that impede their use in functional foods, although these problems may well avoided by the use of encapsulant agents such as cyclodextrins. This explains the recent increase in the number of research papers dealing with the complexation of different guest molecules possesing important antioxidant properties using natural and modified cyclodextrins. This paper presents a review of the most recent studies on the complexes formed between several important types of antioxidant compounds and cyclodextrins, focusing on the contradictory data reported in the literature concerning to the antioxidant activity of the host/guest molecule complexes, the different complexation constants reported for identical complexes, the bioavailability of the antioxidant compound in the presence of cyclodextrins and recommendation concerning the use of natural or modified cyclodextrins. Moreover, the use of cyclodextrins as antibrowning agents to prevent enzymatic browning in different foods is revised. Finally, we look at studies which suggest that cyclodextrins act as ''secondary antioxidants," enhancing the ability of traditional antioxidants to prevent enzymatic browning. PMID:24188271

  1. Perforated monolayers

    SciTech Connect

    Regen, S.L.

    1992-01-01

    Our research over this past grant period has focused on (1) developing methods for making in situ permeation measurements at the air-water interface, (2) defining the structural and conformational behavior of selected calix(4)arenes, (3) defining the metal complexation properties of certain upper-rim functionalized calix(4)arenes, and (4) synthesizing a broad series of polymerizable calixarenes, to be used for constructing perforated monolayers and multilayers.

  2. Direct Patterning of Organic Self-Assembled Monolayer (SAM) on GaAs Surfaces via Dip-Pen Nanolithography (DPN)

    NASA Astrophysics Data System (ADS)

    Xiong, Peng; Keiper, Timothy; Wang, Xiaolei; Zhao, Jianhua

    2015-03-01

    Hybrid structures of functional molecules and solid-state (SS) materials have attracted extensive interest in surface nanoscience and molecular electronics. The formation and micro/nano patterning of organic SAMs on SS surfaces are a key step in fabricating such devices. Here we report realization of high quality MHA SAMs on GaAs and direct formation of micro/nanoscale patterns of MHA SAM on the surface by micro-contact printing (μ CP) and DPN. The process begins with the preparation of an oxide-free surface of GaAs, for which we employed treatment by an ammonium polysulfide ((NH4)2 Sx) solution. The treatment strips native oxides from GaAs creating an atomic layer of sulfur covalently bonded to the fresh surface. Formation of high-quality SAMs of thiol molecules on GaAs then proceeds through exchange of the sulfur and the thiol terminal of the molecules. The effects of the sulfur-passivation and formation of MHA SAM on the treated surface were confirmed by XPS, HRTEM, and DPN. To the best of our knowledge, this is a first realization of direct DPN of nanoscale organic SAM on a semiconductor free of surface oxide. We further evidence the utility of the hybrid platform by demonstrating directed self-assembly of Au nanoparticles onto MHA/ODT SAM templates on GaAs.

  3. Moiré pattern induced by the electronic coupling between 1-octanol self-assembled monolayers and graphite surface.

    PubMed

    Silly, Fabien

    2012-06-01

    Two-dimensional self-assembly of 1-octanol molecules on a graphite surface is investigated using scanning tunneling microscopy (STM) at the solid/liquid interface. STM images reveal that this molecule self-assembles into a compact hydrogen-bonded herringbone nanoarchitecture. Molecules are preferentially arranged in a head-to-head and tail-to-tail fashion. A Moiré pattern appears in the STM images when the 1-octanol layer is covering the graphite surface. The large Moiré stripes are perpendicular to the 1-octanol lamellae. Interpretation of the STM images suggests that the Moiré periodicity is governed by the electronic properties of the graphite surface and the 1-octanol layer periodicity. PMID:22572595

  4. Appearance and disappearance of dendritic and chiral patterns in domains of Langmuir monolayers observed with Brewster angle microscopy.

    PubMed

    Hoffmann, Frank; Stine, Keith J; Hühnerfuss, Heinrich

    2005-01-13

    Investigations on the aggregation behavior and morphology of Langmuir films of enantiomeric (L) and racemic (DL) N-acyl amino acids on pure aqueous as well as metal cation containing subphases were carried out at the mesoscale level with the help of Brewster angle microscopy (BAM). In the case of N-hexadecanoyl alanine on a pure aqueous subphase at 298 K the L-enantiomer forms crystal platelets, while the irregular fractal-like shape of the domains of the racemic mixture can be explained by a diffusion limited aggregation (DLA) growth mechanism. At 303 K the L-enantiomer shows a dendritic growth pattern, which leads to explicitly chiral domain shapes that correspond with the chirality of the film-forming molecules and for which hydrogen bridges as directed attractive forces are assumed to be responsible. The compression of the L-enantiomer on a zinc ion containing subphase is accompanied by a remarkable metamorphosis of the condensed structure. Starting from torus-like domains they were at first converted into strongly wound S-shaped domains, finally turning into a seahorse-like appearance. The origin of these chiral shapes can be explained on the basis of an electrostatic growth model. The enantiomer of N-hexadecanoyl alanine methyl ester shows three different asymmetric dendritic growth patterns. The domains of the racemic mixture are dendritic too, but in contrast they are symmetric and have a notably low branching density. On a pure aqueous subphase the L-enantiomer of N-octadecanoyl valine exhibits dendritic growth as well, but the overall outer shape of the domains is not explicitly chiral. PMID:16851010

  5. Cholesterol Depletion from a Ceramide/Cholesterol Mixed Monolayer: A Brewster Angle Microscope Study

    NASA Astrophysics Data System (ADS)

    Mandal, Pritam; Noutsi, Pakiza; Chaieb, Sahraoui

    2016-06-01

    Cholesterol is crucial to the mechanical properties of cell membranes that are important to cells’ behavior. Its depletion from the cell membranes could be dramatic. Among cyclodextrins (CDs), methyl beta cyclodextrin (MβCD) is the most efficient to deplete cholesterol (Chol) from biomembranes. Here, we focus on the depletion of cholesterol from a C16 ceramide/cholesterol (C16-Cer/Chol) mixed monolayer using MβCD. While the removal of cholesterol by MβCD depends on the cholesterol concentration in most mixed lipid monolayers, it does not depend very much on the concentration of cholesterol in C16-Cer/Chol monolayers. The surface pressure decay during depletion were described by a stretched exponential that suggested that the cholesterol molecules are unable to diffuse laterally and behave like static traps for the MβCD molecules. Cholesterol depletion causes morphology changes of domains but these disrupted monolayers domains seem to reform even when cholesterol level was low.

  6. Perforated monolayers

    SciTech Connect

    Regen, S.L.

    1992-12-01

    Goal of this research program is to create ultrathin organic membranes that possess uniform and adjustable pores ( < 7[angstrom] diameter). Such membranes are expected to possess high permeation selectivity (permselectivity) and high permeability, and to provide the basis for energy-efficient methods of molecular separation. Work carried out has demonstrated feasibility of using perforated monolayer''-based composites as molecular sieve membranes. Specifically, composite membranes derived from Langmuir-Blodgett multilayers of the calix[6]arene-based surfactant shown below plus poly[l-(trimethylsilyl)-l-propyne] (PTMSP) were found to exhibit sieving behavior towards He, N[sub 2] and SF[sub 6]. Results of derivative studies that have also been completed are also described in this report.

  7. Charge and aggregation pattern govern the interaction of plasticins with LPS monolayers mimicking the external leaflet of the outer membrane of Gram-negative bacteria.

    PubMed

    Michel, J P; Wang, Y X; Dé, E; Fontaine, P; Goldmann, M; Rosilio, V

    2015-11-01

    Bacterial resistance to antibiotics has become today a major public health issue. In the development of new anti-infectious therapies, antimicrobial peptides appear as promising candidates. However, their mechanisms of action against bacterial membranes are still poorly understood. We describe for the first time the interaction and penetration of plasticins into lipid monolayers and bilayers modeling the two leaflets of the asymmetrical outer membrane of Gram-negative bacteria. The lipid composition of these monolayers mimics that of each leaflet: mixtures of LPS Re 595 mutant and wild type S-form from Salmonella enterica for the external leaflet, and SOPE/SOPG/cardiolipin (80/15/5) for the inner one. The analysis of the interfacial behavior of native (PTCDA1) and modified (PTCDA1-KF) antimicrobial plasticins showed that PTCDA1-KF exhibited better surface properties than its unmodified counterpart. Both peptides could penetrate into the model monolayers at concentrations higher than 0.1 μM. The penetration was particularly enhanced for PTCDA1-KF into the mixed LPS monolayer, due to attractive electrostatic interactions. Grazing X-ray diffraction and atomic force microscopy studies revealed the changes in LPS monolayers organization upon peptide insertion. The interaction of plasticins with liposomes was also monitored by light scattering and circular dichroism techniques. Only the cationic plasticin achieved full disaggregation and structuration in α helices, whereas the native one remained aggregated and unstructured. The main steps of the penetration mechanism of the two plasticins into lipid models of the external leaflet of the outer membrane of Gram-negative bacteria have been established.

  8. Asymmetric printing of molecules and zeolites on self assembled monolayers.

    PubMed

    Kehr, Nermin Seda; Schäfer, Andreas; Ravoo, Bart Jan; De Cola, Luisa

    2010-04-01

    Microcontact printing (mCP) is used to immobilize dyes and peptides asymmetrically, by a "peptide coupling" reaction, on monolayers of zeolite L crystals in the contact area between the stamp and the surface of the monolayer. Chemically patterned surfaces of monolayers of zeolite L crystals are obtained by using patterned stamps with different ink solutions. Additional printing of functionalized nano-objects on SAMs of zeolite L crystals is demonstrated.

  9. Submicron patterns obtained by thermal-induced reconstruction of self-assembled monolayer of Ag nanoparticles and their application in SERS

    NASA Astrophysics Data System (ADS)

    Ruan, Weidong; Zhou, Tieli; Cui, Yinqiu; Dong, Yujie; Liu, Zhuo; Dong, Fengxia; Wang, Haiyang; Luan, Xintong; Wang, Xu; Song, Wei; Zhao, Bing

    2014-08-01

    The layer-by-layer (LbL) self-assembly technique was employed for the deposition of poly(diallyldimethylammonium chloride) (PDDA) and triangular Ag nanoplates on glass substrates. A thermal-induced reconstruction of these polyelectrolyte-linked nanoparticle (NP) films was presented. Before the reconstruction, triangular Ag nanoplates were distributed uniformly on the surface with an average interval of 50 ± 15 nm. After the reconstruction, the triangular Ag nanoplates accumulated into discrete stacks with an average interval of 90 ± 25 nm. The temperature-dependent experiments were done and the optimal temperature for the formation of the reconstructed patterns was 120 °C. The possible mechanism of the NP movement and stacking was analyzed. Under the experimental conditions, a hydrophobic environment was formed because of the vacuum and heating. As a result the polyelectrolyte-linked Ag NPs preferred to congregate due to the lowered surface energy. Finally the submicron patterns were formed. The ultraviolet-visible (UV-vis) absorption and surface-enhanced Raman scattering (SERS) properties of the films before and after the reconstruction was investigated. The reconstructed films with submicron patterns had better SERS enhancement ability, which was 1300 times to the original films. The reconstruction method of the monolayer films showed great potential in the surface design and related applications. AFM images were obtained to clarify the three dimensional structures of the reconstructed films obtained at 120 °C. As shown in Fig. 2, the Ag NP stacks had an average diameter of 1.0 ± 0.2 μm and an average height of 170 ± 30 nm. The diameter and height of the stacks were shaped by the aggregates of tens of triangular Ag nanoplates. The AFM cross-sectional contour showed the clear intervals of the stacks, which was corresponding to the SEM characterization.XRD patterns of the polyelectrolyte-linked NP films before and after thermal post-treatment are showed in

  10. Selective surface activation of a functional monolayer for the fabrication of nanometer scale thiol patterns and directed self-assembly of gold nanoparticles.

    PubMed

    Fresco, Zachary M; Fréchet, Jean M J

    2005-06-15

    Application of a voltage bias between the tip of an atomic force microscope (AFM) and a silicon substrate causes the localized modification of a specially designed self-assembled monolayer (SAM), transforming a surface-bound thiocarbonate into a surface-bound thiol. The resulting surface-bound thiols are used to direct the patternwise self-assembly of gold nanoparticles (AuNPs). This methodology is applied to deposit individual AuNPs onto a surface with nanometer precision and to produce 10 nm lines of closely spaced AuNPs that are a single nanoparticle in width.

  11. Cyclodextrin-based molecular machines.

    PubMed

    Hashidzume, Akihito; Yamaguchi, Hiroyasu; Harada, Akira

    2014-01-01

    This chapter overviews molecular machines based on cyclodextrins (CDs). The categories of CD-based molecular machines, external stimuli for CD-based molecular machines, and typical examples of CD-based molecular machines are briefly described.

  12. Solid microparticles based on chitosan or methyl-β-cyclodextrin: a first formulative approach to increase the nose-to-brain transport of deferoxamine mesylate.

    PubMed

    Rassu, Giovanna; Soddu, Elena; Cossu, Massimo; Brundu, Antonio; Cerri, Guido; Marchetti, Nicola; Ferraro, Luca; Regan, Raymond F; Giunchedi, Paolo; Gavini, Elisabetta; Dalpiaz, Alessandro

    2015-03-10

    We propose the formulation and characterization of solid microparticles as nasal drug delivery systems able to increase the nose-to-brain transport of deferoxamine mesylate (DFO), a neuroprotector unable to cross the blood brain barrier and inducing negative peripheral impacts. Spherical chitosan chloride and methyl-β-cyclodextrin microparticles loaded with DFO (DCH and MCD, respectively) were obtained by spray drying. Their volume-surface diameters ranged from 1.77 ± 0.06 μm (DCH) to 3.47 ± 0.05 μm (MCD); the aerodynamic diameters were about 1.1 μm and their drug content was about 30%. In comparison with DCH, MCD enhanced the in vitro DFO permeation across lipophilic membranes, similarly as shown by ex vivo permeation studies across porcine nasal mucosa. Moreover, MCD were able to promote the DFO permeation across monolayers of PC 12 cells (neuron-like), but like DCH, it did not modify the DFO permeation pattern across Caco-2 monolayers (epithelial-like). Nasal administration to rats of 200 μg DFO encapsulated in the microparticles resulted in its uptake into the cerebrospinal fluid (CSF) with peak values ranging from 3.83 ± 0.68 μg/mL (DCH) to 14.37 ± 1.69 μg/mL (MCD) 30 min after insufflation of microparticles. No drug CSF uptake was detected after nasal administration of a DFO water solution. The DFO systemic absolute bioavailabilities obtained by DCH and MCD nasal administration were 6% and 15%, respectively. Chitosan chloride and methyl-β-cyclodextrins appear therefore suitable to formulate solid microparticles able to promote the nose to brain uptake of DFO and to limit its systemic exposure. PMID:25620068

  13. Multicellular density fluctuations in epithelial monolayers

    NASA Astrophysics Data System (ADS)

    Zehnder, Steven M.; Wiatt, Marina K.; Uruena, Juan M.; Dunn, Alison C.; Sawyer, W. Gregory; Angelini, Thomas E.

    2015-09-01

    Changes in cell size often accompany multicellular motion in tissue, and cell number density is known to strongly influence collective migration in monolayers. Density fluctuations in other forms of active matter have been explored extensively, but not the potential role of density fluctuations in collective cell migration. Here we investigate collective motion in cell monolayers, focusing on the divergent component of the migration velocity field to probe density fluctuations. We find spatial patterns of diverging and converging cell groups throughout the monolayers, which oscillate in time with a period of approximately 3-4 h. Simultaneous fluorescence measurements of a cytosol dye within the cells show that fluid passes between groups of cells, facilitating these oscillations in cell density. Our findings reveal that cell-cell interactions in monolayers may be mediated by intercellular fluid flow.

  14. Morphological transitions in polymer monolayers under compression.

    PubMed

    Srivastava, S; Basu, J K; Sprung, M; Wang, J

    2009-05-01

    We present a systematic investigation of morphological transitions in poly vinylacetate Langmuir monolayers. On compression, the polymer monolayer is converted to a continuous membrane with a thickness of approximately 2-3 nm. Above a certain surface concentration the monolayer, on water, undergoes a morphological transition-buckling, leading to formation of striped patterns of period of lambda(b) approximately 160 nm, as determined from in situ grazing incidence small angle x-ray scattering measurements. The obtained value is much smaller than what has been typically observed for Langmuir monolayers on water or thin films on soft substrates. Using existing theories for buckling of fluidlike films on fluid substrates, we obtain very low values of bending rigidity and Young's modulus of the polymer monolayer compared to that observed earlier for lipid or polymeric monolayers. Since buckling in these monolayers occurs only above a certain surface concentration, we have looked at the possibility that the buckling in these films occurs due to changes in their mechanical properties under compression. Using the model of Huang and Suo of buckling of solidlike films on viscoelastic substrates, we find values of the mechanical properties, which are much closer to the bulk values but still significantly lower. Although the reduction could be along the lines of what has been observed earlier for ultrathin polymer film or surface layers of polymers, the possibility of micromechanical effects also determining the buckling in such polymer monolayers cannot be ruled out. We have provided possible explanation of the buckling of the poly vinylacetate monolayers in terms of the change in isothermal compression modulus with surface concentration. PMID:19425809

  15. Processing polymers with cyclodextrins

    NASA Astrophysics Data System (ADS)

    Williamson, Brandon Robert

    Cyclodextrins (CDs) are cyclic starch molecules that have the unique ability to include a variety of small molecules and polymers inside their cavities, forming "Inclusion Complexes" (ICs). While much work has been done to understand the formation and behavior of these ICs, far less is known about the fundamental property changes that can occur when CD is used to alter polymer chain morphology. The goal of my graduate research has been to discover different ways to improve upon existing polymer properties through CD processing, as well as explore the possibility of creating a novel type of IC using non-traditional forms of cyclodextrin. Poly(ε-caprolactone) (PCL) was processed with alpha-CD to form an IC. The cyclodextrin was then stripped away to yield a PCL with elongated, unentangled, and constrained polymer chains, a process referred to as coalescence. The physical and rheological property changes resulting from this coalescence were then examined. It was found that reorganizing PCL in this manner resulted in an increase in the melt crystallization temperature of up to 25°C. Coalescence also decreased the tan delta of the material and increased the average hardness and Young's modulus by 33 and 53%, respectively. Non-stoichiometric ICs (NS-ICs), or ICs with at least parts of some polymer chains uncovered, were formed between poly (methyl methacrylate) (PMMA) and gamma-CD as well as a synthesized poly(ε-caprolactone)-poly(propylene glycol)-poly(ε-caprolactone) (PCL-PPG-PCL) triblock copolymer and beta-CD. The property changes of the non-complexed polymer chains were then studied. The PMMA/gamma-CD NS-IC samples were determined to be extremely heterogeneous, however glass transition temperature increases of up to 27°C above that of as-received PMMA were observed. Diffraction data for the PMMA NS-ICs suggests slight crystallinity at partial coverage, with a similar crystal structure to that of the fully covered IC. XRD, DSC and FTIR data revealed an almost

  16. Direct patterning of negative nanostructures on self-assembled monolayers of 16-mercaptohexadecanoic acid on Au(111) substrate via dip-pen nanolithography

    NASA Astrophysics Data System (ADS)

    Zheng, Zhikun; Yang, Menglong; Liu, Yaqing; Zhang, Bailin

    2006-11-01

    Both bare and self-assembled monolayer (SAM) protected gold substrate could be etched by allyl bromide according to atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometric (ICPMS) analysis results. With this allyl bromide ink material, negative nanopatterns could be fabricated directly by dip-pen nanolithography (DPN) on SAMs of 16-mercaptohexadecanoic acid (MHA) on Au(111) substrate. A tip-promoted etching mechanism was proposed where the gold-reactive ink could penetrate the MHA resist film through tip-induced defects resulting in local corrosive removal of the gold substrate. The fabrication mechanism was also confirmed by electrochemical characterization, energy dispersive spectroscopy (EDS) analysis and fabrication of positive nanopatterns via a used DPN tip.

  17. Methods of making monolayers

    DOEpatents

    Alford, Kentin L.; Simmons, Kevin L.; Samuels, William D.; Zemanian, Thomas S.; Liu, Jun; Shin, Yongsoon; Fryxell, Glen E.

    2009-09-15

    The invention pertains to methods of forming monolayers on various surfaces. The surfaces can be selected from a wide array of materials, including, for example, aluminum dioxide, silicon dioxide, carbon and SiC. The substrates can be planar or porous. The monolayer is formed under enhanced pressure conditions. The monolayer contains functionalized molecules, and accordingly functionalizes a surface of the substrate. The properties of the functionalized substrate can enhance the substrate's applicability for numerous purposes including, for example, utilization in extracting contaminants, or incorporation into a polymeric matrix.

  18. Methods of making monolayers

    DOEpatents

    Alford, Kentin L.; Simmons, Kevin L.; Samuels, William D.; Zemanian, Thomas S.; Liu, Jun; Shin, Yongsoon; Fryxell, Glen E.

    2009-12-08

    The invention pertains to methods of forming monolayers on various surfaces. The surfaces can be selected from a wide array of materials, including, for example, aluminum dioxide, silicon dioxide, carbon and SiC. The substrates can be planar or porous. The monolayer is formed under enhanced pressure conditions. The monolayer contains functionalized molecules, and accordingly functionalizes a surface of the substrate. The properties of the functionalized substrate can enhance the substrate's applicability for numerous purposes including, for example, utilization in extracting contaminants, or incorporation into a polymeric matrix.

  19. In vitro assessment of acyclovir permeation across cell monolayers in the presence of absorption enhancers.

    PubMed

    Shah, Pranav; Jogani, Viral; Mishra, Pushpa; Mishra, Anil Kumar; Bagchi, Tamishraha; Misra, Ambikanandan

    2008-03-01

    The aim of the investigation was to establish transepithelial permeation of acyclovir across Caco-2 and Madin-Darby canine kidney (MDCK) cell monolayers and attempt to improve its permeation by employing absorption enhancers (dimethyl beta cyclodextrin, chitosan hydrochloride and sodium lauryl sulfate) and combinations thereof. Caco-2 and MDCK cell monolayers have been widely employed in studying drug transport, mechanisms of drug transport, and screening of absorption enhancers and excipients. Transepithelial electrical resistance and permeation of 99mTc-mannitol were employed as control parameters to assess the tight junction and paracellular integrity. Permeation of acyclovir in the presence of absorption enhancers was found to be significantly higher compared with drug permeation in their absence when assessed as apparent permeability coefficients (Papp). Synergistic improvements in Papp values of acyclovir were obtained in case-selected combinations of absorption enhancers; dimethyl beta cyclodextrin-chitosan hydrochloride, chitosan hydrochloride-sodium lauryl sulfate, and dimethyl beta cyclodextrin-sodium lauryl sulfate, were used. Recovery and viability assessment studies of both cell monolayers suggested reestablishment of paracellular integrity and no damage to cell membranes. Significantly improved permeation of acyclovir in the presence of selected combinations of absorption enhancers may be used as a viable approach in overcoming the problem of limited oral bioavailability of acyclovir.

  20. Cyclodextrin Inclusion Polymers Forming Hydrogels

    NASA Astrophysics Data System (ADS)

    Li, Jun

    This chapter reviews the advances in the developments of supramolecular hydrogels based on the polypseudorotaxanes and polyrotaxanes formed by inclusion complexes of cyclodextrins threading onto polymer chains. Both physical and chemical supramolecular hydrogels of many different types are discussed with respect to their preparation, structure, property, and gelation mechanism. A large number of physical supramolecular hydrogels were formed induced by self-assembly of densely packed cyclodextrin rings threaded on polymer or copolymer chains acting as physical crosslinking points. The thermo-reversible and thixotropic properties of these physical supramolecular hydrogels have inspired their applications as injectable drug delivery systems. Chemical supramolecular hydrogels synthesized from polypseudorotaxanes and polyrotaxanes were based on the chemical crosslinking of either the cyclodextrin molecules or the included polymer chains. The chemical supramolecular hydrogels were often made biodegradable through incorporation of hydrolyzable threading polymers, end caps, or crosslinkers, for their potential applications as biomaterials.

  1. Sensitive detection of trypsin using liquid-crystal droplet patterns modulated by interactions between poly-L-lysine and a phospholipid monolayer.

    PubMed

    Zhang, Minmin; Jang, Chang-Hyun

    2014-08-25

    Liquid-crystal (LC) droplet patterns are formed on a glass slide by evaporating a solution of nematic LC dissolved in heptane. In the presence of an anionic phospholipid, 1,2-dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DOPG), the LCs display a dark cross pattern, indicating a homeotropic orientation. When LC patterns are incubated with an aqueous mixture of DOPG and poly-L-lysine (PLL), there is a transition in the LC pattern from a dark cross to a bright fan shape due to the electrostatic interaction between DOPG and PLL. Known to catalyze the hydrolysis of PLL into oligopeptide fragments, trypsin is preincubated with PLL, significantly decreasing the interactions between PLL and DOPG. LCs adopt a perpendicular orientation at the water-LC droplet interface, which gives rise to a dark cross pattern. This optical response of LC droplets is the basis for a quick and sensitive biosensor for trypsin. PMID:24850496

  2. Diamondoid monolayers as electron emitters

    DOEpatents

    Yang, Wanli; Fabbri, Jason D.; Melosh, Nicholas A.; Hussain, Zahid; Shen, Zhi-Xun

    2013-10-29

    Provided are electron emitters based upon diamondoid monolayers, preferably self-assembled higher diamondoid monolayers. High intensity electron emission has been demonstrated employing such diamondoid monolayers, particularly when the monolayers are comprised of higher diamondoids. The application of such diamondoid monolayers can alter the band structure of substrates, as well as emit monochromatic electrons, and the high intensity electron emissions can also greatly improve the efficiency of field-effect electron emitters as applied to industrial and commercial applications.

  3. Diamondoid monolayers as electron emitters

    DOEpatents

    Yang, Wanli; Fabbri, Jason D.; Melosh, Nicholas A.; Hussain, Zahid; Shen, Zhi-Xun

    2012-04-10

    Provided are electron emitters based upon diamondoid monolayers, preferably self-assembled higher diamondoid monolayers. High intensity electron emission has been demonstrated employing such diamondoid monolayers, particularly when the monolayers are comprised of higher diamondoids. The application of such diamondoid monolayers can alter the band structure of substrates, as well as emit monochromatic electrons, and the high intensity electron emissions can also greatly improve the efficiency of field-effect electron emitters as applied to industrial and commercial applications.

  4. Cyclodextrin stabilised emulsions and cyclodextrinosomes.

    PubMed

    Mathapa, Baghali G; Paunov, Vesselin N

    2013-11-01

    We report the preparation of o/w emulsions stabilised by microcrystals of cyclodextrin-oil inclusion complexes. The inclusion complexes are formed by threading cyclodextrins from the aqueous phase on n-tetradecane or silicone oil molecules from the emulsion drop surface which grow further into microrods and microplatelets depending on the type of cyclodextrin (CD) used. These microcrystals remain attached on the surface of the emulsion drops and form densely packed layers which resemble Pickering emulsions. The novelty of this emulsion stabilisation mechanism is that molecularly dissolved cyclodextrin from the continuous aqueous phase is assembled into colloid particles directly onto the emulsion drop surface, i.e. molecular adsorption leads to effective Pickering stabilisation. The β-CD stabilised tetradecane-in-water emulsions were so stable that we used this system as a template for preparation of cyclodextrinosomes. These structures were produced solely through formation of cyclodextrin-oil inclusion complexes and their assembly into a crystalline phase on the drop surface retained its stability after the removal of the core oil. The structures of CD-stabilised tetradecane-in-water emulsions were characterised using optical microscopy, fluorescence microscopy, cross-polarised light microscopy and WETSEM while the cyclodextrinosomes were characterised by SEM. We also report the preparation of CD-stabilised emulsions with a range of other oils, including tricaprylin, silicone oil, isopropyl myristate and sunflower oil. We studied the effect of the salt concentration in the aqueous phase, the type of CD and the oil volume fraction on the type of emulsion formed. The CD-stabilised emulsions can be applied in a range of surfactant-free formulations with possible applications in cosmetics, home and personal care. Cyclodextrinosomes could find applications in pharmaceutical formulations as microencapsulation and drug delivery vehicles. PMID:24043288

  5. Cholesterol Depletion from a Ceramide/Cholesterol Mixed Monolayer: A Brewster Angle Microscope Study

    PubMed Central

    Mandal, Pritam; Noutsi, Pakiza; Chaieb, Sahraoui

    2016-01-01

    Cholesterol is crucial to the mechanical properties of cell membranes that are important to cells’ behavior. Its depletion from the cell membranes could be dramatic. Among cyclodextrins (CDs), methyl beta cyclodextrin (MβCD) is the most efficient to deplete cholesterol (Chol) from biomembranes. Here, we focus on the depletion of cholesterol from a C16 ceramide/cholesterol (C16-Cer/Chol) mixed monolayer using MβCD. While the removal of cholesterol by MβCD depends on the cholesterol concentration in most mixed lipid monolayers, it does not depend very much on the concentration of cholesterol in C16-Cer/Chol monolayers. The surface pressure decay during depletion were described by a stretched exponential that suggested that the cholesterol molecules are unable to diffuse laterally and behave like static traps for the MβCD molecules. Cholesterol depletion causes morphology changes of domains but these disrupted monolayers domains seem to reform even when cholesterol level was low. PMID:27245215

  6. Towards allosteric receptors – synthesis of β-cyclodextrin-functionalised 2,2’-bipyridines and their metal complexes

    PubMed Central

    Kremer, Christopher; Schnakenburg, Gregor

    2014-01-01

    Summary Herein, we present three new 2,2’-bipyridines that carry two β-cyclodextrin moieties in different substitution patterns. When coordinated by zinc(II) or copper(I) ions (or their complexes), these compounds undergo conformational changes and switch between “open” and “closed” forms and thereby bringing together or separating the cyclodextrin moieties from each other. PMID:24778736

  7. A nano-patterned self assembled monolayer (SAM) rutile titania cancer chip for rapid, low cost, highly sensitive, direct cancer analysis in MALDI-MS.

    PubMed

    Manikandan, M; Gopal, Judy; Hasan, Nazim; Wu, Hui-Fen

    2014-12-01

    We developed a cancer chip by nano-patterning a highly sensitive SAM titanium surface capable of capturing and sensing concentrations as low as 10 cancer cells/mL from the environment by Matrix Assisted Laser Desorption and Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS). The current approach evades any form of pretreatment and sample preparation processes; it is time saving and does not require the (expensive) conventional MALDI target plate. The home made aluminium (Al) target holder cost, on which we loaded the cancer chips for MALDI-TOF MS analysis, is about 60 USD. While the conventional stainless steel MALDI target plate is more than 700 USD. The SAM surface was an effective platform leading to on-chip direct MALDI-MS detection of cancer cells. We compared the functionality of this chip with the unmodified titanium surfaces and thermally oxidized (TO) titanium surfaces. The lowest detectable concentration of the TO chip was 10(3) cells/mL, while the lowest detectable concentration of the control or unmodified titanium chips was 10(6) cells/mL. Compared to the control surface, the SAM cancer chip showed 100,000 times of enhanced sensitivity and compared with the TO chip, 1000 times of increased sensitivity. The high sensitivity of the SAM surfaces is attributed to the presence of the rutile SAM, surface roughness and surface wettability as confirmed by AFM, XRD, contact angle microscope and FE-SEM. This study opens a new avenue for the potent application of the SAM cancer chip for direct cancer diagnosis by MALDI-TOF MS in the near future.

  8. Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations.

    PubMed

    Raffaini, Giuseppina; Mazzaglia, Antonino; Ganazzoli, Fabio

    2015-01-01

    Amphiphilically modified cyclodextrins may form various supramolecular aggregates. Here we report a theoretical study of the aggregation of a few amphiphilic cyclodextrins carrying hydrophobic thioalkyl groups and hydrophilic ethylene glycol moieties at opposite rims, focusing on the initial nucleation stage in an apolar solvent and in water. The study is based on atomistic molecular dynamics methods with a "bottom up" approach that can provide important information about the initial aggregates of few molecules. The focus is on the interaction pattern of amphiphilic cyclodextrin (aCD), which may interact by mutual inclusion of the substituent groups in the hydrophobic cavity of neighbouring molecules or by dispersion interactions at their lateral surface. We suggest that these aggregates can also form the nucleation stage of larger systems as well as the building blocks of micelles, vesicle, membranes, or generally nanoparticles thus opening new perspectives in the design of aggregates correlating their structures with the pharmaceutical properties. PMID:26734094

  9. Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations.

    PubMed

    Raffaini, Giuseppina; Mazzaglia, Antonino; Ganazzoli, Fabio

    2015-01-01

    Amphiphilically modified cyclodextrins may form various supramolecular aggregates. Here we report a theoretical study of the aggregation of a few amphiphilic cyclodextrins carrying hydrophobic thioalkyl groups and hydrophilic ethylene glycol moieties at opposite rims, focusing on the initial nucleation stage in an apolar solvent and in water. The study is based on atomistic molecular dynamics methods with a "bottom up" approach that can provide important information about the initial aggregates of few molecules. The focus is on the interaction pattern of amphiphilic cyclodextrin (aCD), which may interact by mutual inclusion of the substituent groups in the hydrophobic cavity of neighbouring molecules or by dispersion interactions at their lateral surface. We suggest that these aggregates can also form the nucleation stage of larger systems as well as the building blocks of micelles, vesicle, membranes, or generally nanoparticles thus opening new perspectives in the design of aggregates correlating their structures with the pharmaceutical properties.

  10. Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations

    PubMed Central

    Mazzaglia, Antonino; Ganazzoli, Fabio

    2015-01-01

    Summary Amphiphilically modified cyclodextrins may form various supramolecular aggregates. Here we report a theoretical study of the aggregation of a few amphiphilic cyclodextrins carrying hydrophobic thioalkyl groups and hydrophilic ethylene glycol moieties at opposite rims, focusing on the initial nucleation stage in an apolar solvent and in water. The study is based on atomistic molecular dynamics methods with a “bottom up” approach that can provide important information about the initial aggregates of few molecules. The focus is on the interaction pattern of amphiphilic cyclodextrin (aCD), which may interact by mutual inclusion of the substituent groups in the hydrophobic cavity of neighbouring molecules or by dispersion interactions at their lateral surface. We suggest that these aggregates can also form the nucleation stage of larger systems as well as the building blocks of micelles, vesicle, membranes, or generally nanoparticles thus opening new perspectives in the design of aggregates correlating their structures with the pharmaceutical properties. PMID:26734094

  11. Spectrofluorometric analytical applications of cyclodextrins.

    PubMed

    Elbashir, Abdalla A; Dsugi, Nuha Fathi Ali; Mohmed, Tamador Omer Mohamoud; Aboul-Enein, Hassan Y

    2014-02-01

    Cyclodextrins (CDs) are a family of cyclic oligosaccharides composed of α-(1,4)-linked glucopyranose subunits. The most important feature of CDs is their ability to form inclusion complexes (host-guest complexes) with a very wide range of solid, liquid and gaseous compounds by a molecular complexation. During the last decade, a considerable number of research papers has been focused on the use of CDs to enhance fluorescence intensity of different analytes and to develop CD-induced spectrofluorimetric method. In this review, the various spectrofluorimetric methods based on host-inclusion complex are presented.

  12. Enhanced Chiral Recognition by Cyclodextrin Dimers

    PubMed Central

    Voskuhl, Jens; Schaepe, Kira; Ravoo, Bart Jan

    2011-01-01

    In this article we investigate the effect of multivalency in chiral recognition. To this end, we measured the host-guest interaction of a β-cyclodextrin dimer with divalent chiral guests. We report the synthesis of carbohydrate-based water soluble chiral guests functionalized with two borneol, menthol, or isopinocampheol units in either (+) or (−) configuration. We determined the interaction of these divalent guests with a β-cyclodextrin dimer using isothermal titration calorimetry. It was found that—in spite of a highly unfavorable conformation—the cyclodextrin dimer binds to guest dimers with an increased enantioselectivity, which clearly reflects the effect of multivalency. PMID:21845101

  13. Fosinopril-cyclodextrin inclusion complexes: phase solubility and physicochemical analysis.

    PubMed

    Sbârcea, L; Udrescu, L; Drăgan, L; Trandafirescu, C; Szabadai, Z; Bojiţă, M

    2011-08-01

    Fosinopril is one of the most hydrophobic substances among the angiotensin-converting enzyme inhibitors, exhibiting low water solubility and poor bioavailability following oral administration. Inclusion complexes between the drug substance and cyclodextrins (CDs) were obtained in order to improve its solubility. The purpose of this study was to investigate the guest-host interaction of fosinopril sodium (FOS) with beta-cyclodextrin (beta-CD) and its derivative, randomly methylated beta-cyclodextrin (RAMEB) in solution by phase solubility diagrams (PSD) and in solid state by using thermal analysis, powder X-ray diffractometry (PXRD) and Fourier transform infrared spectroscopy (FTIR). The phase solubility analysis indicated that the solubility of FOS in simulated gastric fluid was increased in the presence of CDs and revealed for RAMEB an A(L)-type diagram, suggesting the formation of a 1:1 inclusion complex, and for beta-CD a B(s)-type phase diagram. The estimated apparent stability constant (K1:1), according to the Higuchi and Connors method, is 3209.99 M(-1) and 1770.34 M(-1) for RAMEB and beta-CD complexes respectively. The binary systems FOS/CDs were prepared using the kneading method in the molar ratio 1:1. The PXRD patterns and the thermograms indicated a drug amorphization process, higher for FOS/RAMEB binary system and the FTIR analysis suggested that the ester group of FOS is probably enclosed in the CD's cavity. The results of this study confirm the formation of inclusion complexes both in solution and in solid state and suggest that the complexes formation between FOS and CDs could improve the bioavailability of the drug due to the enhancing absorption expected from increased drug solubility.

  14. Bandgap engineering of rippled MoS2 monolayer under external electric field

    NASA Astrophysics Data System (ADS)

    Qi, Jingshan; Li, Xiao; Qian, Xiaofeng; Feng, Ji

    2013-04-01

    In this letter we propose a universal strategy combining external electric field with the ripple of membrane to tune the bandgap of semiconducting atomic monolayer. By first-principles calculations we show that the bandgap of rippled MoS2 monolayer can be tuned in a large range by vertical external electric field, which is expected to have little effect on MoS2 monolayer. This phenomenon can be explained from charge redistribution under external electric field by a simple model. This may open an avenue of optimizing monolayer MoS2 for electronic and optoelectronic applications by surface patterning.

  15. Switching light with light - advanced functional colloidal monolayers

    NASA Astrophysics Data System (ADS)

    Bley, K.; Sinatra, N.; Vogel, N.; Landfester, K.; Weiss, C. K.

    2013-12-01

    Colloidal monolayers comprising of highly ordered two dimensional crystals are of high interest to generate surface patterns for a variety of different applications. Mostly, unfunctionalized polymer or silica colloids are assembled into monolayers. However, the incorporation of functional molecules into such colloids offers a convenient possibility of implementing additional properties to the two-dimensional crystal. Here, we present the formation of novel functional colloidal monolayers with photoswitchable fluorescence. The miniemulsion polymerization technique was used to incorporate an appropriate dye system of a perylene-based fluorophore and a bis-arylethene as a photochrome in polymeric colloids in defined ratios. Upon irradiation with UV or visible light the photochrome reversibly isomerizes from the ring-closed form, which is able to absorb light of the emission wavelength of the fluorescent dye and the ring-open form, which is not. The fluorescence emission of the dye can thus be reversibly switched on and off with light even when embedded in colloids. The colloids were self-assembled at the air-water interface to produce hexagonally ordered functional monolayers and more complex binary crystals. We investigate in detail the influence of the polymeric matrix on the switching properties of the fluorophore/photochrome system and find that the rate constants for the photoswitching, which all lie in the same range, are less influenced by the polymeric environment than expected. We demonstrate the reversible switching of the fluorescence emission in self-assembled colloidal monolayers. The arrangement of broadly distributed functional colloids into ordered monolayers with high addressability was obtained by the formation of binary colloidal monolayers.Colloidal monolayers comprising of highly ordered two dimensional crystals are of high interest to generate surface patterns for a variety of different applications. Mostly, unfunctionalized polymer or silica

  16. Cyclodextrin-based drug stabilizing system

    NASA Astrophysics Data System (ADS)

    Roik, N. V.; Belyakova, L. A.

    2011-02-01

    UV spectroscopy study of para-aminosalicylic acid behaviour in the presence of β-cyclodextrin and without it in buffer solutions was realized. Influence of duration of contact, acidity of solution, temperature, and content of reagents in the binary solutions on the complex formation between β-cyclodextrin and para-aminosalicylic acid was examined. The stability constants of the supramolecular complexes formed at pH = 1.00 and pH = 6.86 were calculated by the Ketelar equation at various temperatures. It was found that the inclusion interaction of β-cyclodextrin with protonated type of para-aminosalicylic acid is superior to that for its anionic one. From the temperature dependence of stability constants the thermodynamic parameters involved in the complex formation (ΔG, ΔH, ΔS) were calculated. It was proved that complex formation between β-cyclodextrin and para-aminosalicylic acid is spontaneous process accompanied by the release of heat and decrease of entropy. To characterize the solid product of para-aminosalicylic acid inclusion into the cavity of β-cyclodextrin supramolecular complex with a 1:1 mole ratio of components have been prepared by kneading method and studied by IR spectroscopy and X-ray diffraction.

  17. Separation of sulfoalkylated cyclodextrins with hydrophilic interaction liquid chromatography.

    PubMed

    Jaramillo, Michael; Kirschner, Daniel L; Dai, Zhipeng; Green, Thomas K

    2013-11-01

    Determination of the charged state distributions of partially- and fully-substituted sulfoalkylated cyclodextrins was achieved using hydrophilic interaction liquid chromatography (HILIC). HILIC analysis of a spiked sample of the partially sulfopropylated cyclodextrins was achieved using a gradient to baseline resolve the charged states from -1 to -14. The fully-substituted CDs yielded a major peak with some trace impurities and the partially-substituted sulfopropylated cyclodextrins showed a wide range of charge states present in the mixture. Small changes in the structure of the cyclodextrins have a significant impact on the retention times of the various types of cyclodextrins investigated.

  18. Temperature Dependence of Positron Annihilation in beta-Cyclodextrin and beta-Cyclodextrin Complexes

    NASA Astrophysics Data System (ADS)

    Hu, Y.; Hsu Hadley, F. H., Jr.; Trinh, T.

    1996-11-01

    The effects of temperature on positron annihilation in beta-cyclodextrin and beta-cyclodextrin complexed with benzyl salicylate, benzyl acetate, ethyl salicylate, geraniol, linalool and nerol were studied. Samples were prepared by slurry, air-dried and freeze-dried methods. Lifetime spectra were measured as a function of temperature for each sample. Comparison of the annihilation rate and intensity of the longer-lived component showed that positronium formation was affected by guest molecules, preparation methods and temperature variations. Results can be used to explain beta-cyclodextrin complex formation with different guest molecules.

  19. Phenomenological Modeling for Langmuir Monolayers

    NASA Astrophysics Data System (ADS)

    Baptiste, Dimitri; Kelly, David; Safford, Twymun; Prayaga, Chandra; Varney, Christopher N.; Wade, Aaron

    Experimentally, Langmuir monolayers have applications in molecular optical, electronic, and sensor devices. Traditionally, Langmuir monolayers are described by a rigid rod model where the rods interact via a Leonard-Jones potential. Here, we propose effective phenomenological models and utilize Monte Carlo simulations to analyze the phase behavior and compare with experimental isotherms. Research reported in this abstract was supported by UWF NIH MARC U-STAR 1T34GM110517-01.

  20. Phase Transitions in Dipalmitoylphosphatidylcholine Monolayers.

    PubMed

    Zuo, Yi Y; Chen, Rimei; Wang, Xianju; Yang, Jinlong; Policova, Zdenka; Neumann, A Wilhelm

    2016-08-23

    A self-assembled phospholipid monolayer at an air-water interface is a well-defined model system for studying surface thermodynamics, membrane biophysics, thin-film materials, and colloidal soft matter. Here we report a study of two-dimensional phase transitions in the dipalmitoylphosphatidylcholine (DPPC) monolayer at the air-water interface using a newly developed methodology called constrained drop surfactometry (CDS). CDS is superior to the classical Langmuir balance in its capacity for rigorous temperature control and leak-proof environments, thus making it an ideal alternative to the Langmuir balance for studying lipid polymorphism. In addition, we have developed a novel Langmuir-Blodgett (LB) transfer technique that allows the direct transfer of lipid monolayers from the droplet surface under well-controlled conditions. This LB transfer technique permits the direct visualization of phase coexistence in the DPPC monolayer. With these technological advances, we found that the two-dimensional phase behavior of the DPPC monolayer is analogous to the three-dimensional phase transition of a pure substance. This study has implications in the fundamental understanding of surface thermodynamics as well as applications such as self-assembled monolayers and pulmonary surfactant biophysics. PMID:27479299

  1. Micro- and nanopatterning of functional organic monolayers on oxide-free silicon by laser-induced photothermal desorption.

    PubMed

    Scheres, Luc; Klingebiel, Benjamin; ter Maat, Jurjen; Giesbers, Marcel; de Jong, Hans; Hartmann, Nils; Zuilhof, Han

    2010-09-01

    The photothermal laser patterning of functional organic monolayers, prepared on oxide-free hydrogen-terminated silicon, and subsequent backfilling of the laser-written lines with a second organic monolayer that differs in its terminal functionality, is described. Since the thermal monolayer decomposition process is highly nonlinear in the applied laser power density, subwavelength patterning of the organic monolayers is feasible. After photothermal laser patterning of hexadecenyl monolayers, the lines freed up by the laser are backfilled with functional acid fluoride monolayers. Coupling of cysteamine to the acid fluoride groups and subsequent attachment of Au nanoparticles allows easy characterization of the functional lines by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Depending on the laser power and writing speed, functional lines with widths between 1.1 μm and 250 nm can be created. In addition, trifluoroethyl-terminated (TFE) monolayers are also patterned. Subsequently, the decomposed lines are backfilled with a nonfunctional hexadecenyl monolayer, the TFE stripes are converted into thiol stripes, and then finally covered with Au nanoparticles. By reducing the lateral distance between the laser lines, Au-nanoparticle stripes with widths close to 100 nm are obtained. Finally, in view of the great potential of this type of monolayer in the field of biosensing, the ease of fabricating biofunctional patterns is demonstrated by covalent binding of fluorescently labeled oligo-DNA to acid-fluoride-backfilled laser lines, which--as shown by fluorescence microscopy--is accessible for hybridization.

  2. Fluorescence Concentric Triangles: A Case of Chemical Heterogeneity in WS2 Atomic Monolayer.

    PubMed

    Liu, Hongwei; Lu, Junpeng; Ho, Kenneth; Hu, Zhenliang; Dang, Zhiya; Carvalho, Alexandra; Tan, Hui Ru; Tok, Eng Soon; Sow, Chorng Haur

    2016-09-14

    We report a novel optical property in WS2 monolayer. The monolayer naturally exhibits beautiful in-plane periodical and lateral homojunctions by way of alternate dark and bright band in the fluorescence images of these monolayers. The interface between different fluorescence species within the sample is distinct and sharp. This gives rise to intriguing concentric triangular fluorescence patterns in the monolayer. The novel optical property of this special WS2 monolayer is facilitated by chemical heterogeneity. The photoluminescence of the bright band is dominated by emissions from trion and biexciton while the emission from defect-bound exciton dominates the photoluminescence at the dark band. The discovery of such concentric fluorescence patterns represents a potentially new form of optoelectronic or photonic functionality. PMID:27479127

  3. Applications of cyclodextrins in medical textiles - review.

    PubMed

    Radu, Cezar-Doru; Parteni, Oana; Ochiuz, Lacramioara

    2016-02-28

    This paper presents data on the general properties and complexing ability of cyclodextrins and assessment methods (phase solubility, DSC tests and X-ray diffraction, FTIR spectra, analytical method). It focuses on the formation of drug deposits on the surface of a textile underlayer, using a cyclodextrin compound favoring the inclusion of a drug/active principle and its release onto the dermis of patients suffering from skin disorders, or for protection against insects. Moreover, it presents the kinetics, duration, diffusion flow and release media of the cyclodextrin drug for in vitro studies, as well as the release modeling of the active principle. The information focuses on therapies: antibacterial, anti-allergic, antifungal, chronic venous insufficiency, psoriasis and protection against insects. The pharmacodynamic agents/active ingredients used on cotton, woolen and synthetic textile fabrics are presented. PMID:26796039

  4. Switching light with light - advanced functional colloidal monolayers

    NASA Astrophysics Data System (ADS)

    Bley, K.; Sinatra, N.; Vogel, N.; Landfester, K.; Weiss, C. K.

    2013-12-01

    Colloidal monolayers comprising of highly ordered two dimensional crystals are of high interest to generate surface patterns for a variety of different applications. Mostly, unfunctionalized polymer or silica colloids are assembled into monolayers. However, the incorporation of functional molecules into such colloids offers a convenient possibility of implementing additional properties to the two-dimensional crystal. Here, we present the formation of novel functional colloidal monolayers with photoswitchable fluorescence. The miniemulsion polymerization technique was used to incorporate an appropriate dye system of a perylene-based fluorophore and a bis-arylethene as a photochrome in polymeric colloids in defined ratios. Upon irradiation with UV or visible light the photochrome reversibly isomerizes from the ring-closed form, which is able to absorb light of the emission wavelength of the fluorescent dye and the ring-open form, which is not. The fluorescence emission of the dye can thus be reversibly switched on and off with light even when embedded in colloids. The colloids were self-assembled at the air-water interface to produce hexagonally ordered functional monolayers and more complex binary crystals. We investigate in detail the influence of the polymeric matrix on the switching properties of the fluorophore/photochrome system and find that the rate constants for the photoswitching, which all lie in the same range, are less influenced by the polymeric environment than expected. We demonstrate the reversible switching of the fluorescence emission in self-assembled colloidal monolayers. The arrangement of broadly distributed functional colloids into ordered monolayers with high addressability was obtained by the formation of binary colloidal monolayers.Colloidal monolayers comprising of highly ordered two dimensional crystals are of high interest to generate surface patterns for a variety of different applications. Mostly, unfunctionalized polymer or silica

  5. Cyclodextrins in delivery systems: Applications

    PubMed Central

    Tiwari, Gaurav; Tiwari, Ruchi; Rai, Awani K.

    2010-01-01

    Cyclodextrins (CDs) are a family of cyclic oligosaccharides with a hydrophilic outer surface and a lipophilic central cavity. CD molecules are relatively large with a number of hydrogen donors and acceptors and, thus in general, they do not permeate lipophilic membranes. In the pharmaceutical industry, CDs have mainly been used as complexing agents to increase aqueous solubility of poorly soluble drugs and to increase their bioavailability and stability. CDs are used in pharmaceutical applications for numerous purposes, including improving the bioavailability of drugs. Current CD-based therapeutics is described and possible future applications are discussed. CD-containing polymers are reviewed and their use in drug delivery is presented. Of specific interest is the use of CD-containing polymers to provide unique capabilities for the delivery of nucleic acids. Studies in both humans and animals have shown that CDs can be used to improve drug delivery from almost any type of drug formulation. Currently, there are approximately 30 different pharmaceutical products worldwide containing drug/CD complexes in the market. PMID:21814436

  6. Switching light with light--advanced functional colloidal monolayers.

    PubMed

    Bley, K; Sinatra, N; Vogel, N; Landfester, K; Weiss, C K

    2014-01-01

    Colloidal monolayers comprising of highly ordered two dimensional crystals are of high interest to generate surface patterns for a variety of different applications. Mostly, unfunctionalized polymer or silica colloids are assembled into monolayers. However, the incorporation of functional molecules into such colloids offers a convenient possibility of implementing additional properties to the two-dimensional crystal. Here, we present the formation of novel functional colloidal monolayers with photoswitchable fluorescence. The miniemulsion polymerization technique was used to incorporate an appropriate dye system of a perylene-based fluorophore and a bis-arylethene as a photochrome in polymeric colloids in defined ratios. Upon irradiation with UV or visible light the photochrome reversibly isomerizes from the ring-closed form, which is able to absorb light of the emission wavelength of the fluorescent dye and the ring-open form, which is not. The fluorescence emission of the dye can thus be reversibly switched on and off with light even when embedded in colloids. The colloids were self-assembled at the air-water interface to produce hexagonally ordered functional monolayers and more complex binary crystals. We investigate in detail the influence of the polymeric matrix on the switching properties of the fluorophore/photochrome system and find that the rate constants for the photoswitching, which all lie in the same range, are less influenced by the polymeric environment than expected. We demonstrate the reversible switching of the fluorescence emission in self-assembled colloidal monolayers. The arrangement of broadly distributed functional colloids into ordered monolayers with high addressability was obtained by the formation of binary colloidal monolayers. PMID:24227011

  7. Band structures in silicene on monolayer gallium phosphide substrate

    NASA Astrophysics Data System (ADS)

    Ren, Miaojuan; Li, Mingming; Zhang, Changwen; Yuan, Min; Li, Ping; Li, Feng; Ji, Weixiao; Chen, Xinlian

    2016-07-01

    Opening a sizable band gap in the zero-gap silicene is a key issue for its application in nanoelectronics. We design new 2D silicene and GaP heterobilayer (Si/GaP HBL) composed of silicene and monolayer (ML) GaP. Based on first-principles calculations, we find that the interaction energies are in the range of -295.5 to -297.5 meV per unit cell, indicating a weak interaction between silicene and gallium phosphide (GaP) monolayer. The band gap changes ranging from 0.06 to 0.44 eV in hybrid HBLs. An unexpected indirect-direct band gap crossover is also observed in HBLs, dependent on the stacking pattern. These provide a possible way to design effective FETs out of silicene on GaP monolayer.

  8. Observation of intervalley quantum interference in epitaxial monolayer tungsten diselenide

    PubMed Central

    Liu, Hongjun; Chen, Jinglei; Yu, Hongyi; Yang, Fang; Jiao, Lu; Liu, Gui-Bin; Ho, Wingking; Gao, Chunlei; Jia, Jinfeng; Yao, Wang; Xie, Maohai

    2015-01-01

    The extraordinary electronic structures of monolayer transition metal dichalcogenides, such as the spin–valley-coupled band edges, have sparked great interest for potential spintronic and valleytronic applications based on these two-dimensional materials. In this work, we report the experimental observation of quasi-particle interference patterns in monolayer WSe2 using low-temperature scanning tunnelling spectroscopy. We observe intervalley quantum interference involving the Q valleys in the conduction band due to spin-conserving scattering processes, while spin-flipping intervalley scattering is absent. Our results establish unequivocally the presence of spin–valley coupling and affirm the large spin splitting at the Q valleys. Importantly, the inefficient spin-flipping scattering implies long valley and spin lifetime in monolayer WSe2, which is a key figure of merit for valley-spintronic applications. PMID:26324205

  9. EDTA-Cross-Linked β-Cyclodextrin: An Environmentally Friendly Bifunctional Adsorbent for Simultaneous Adsorption of Metals and Cationic Dyes.

    PubMed

    Zhao, Feiping; Repo, Eveliina; Yin, Dulin; Meng, Yong; Jafari, Shila; Sillanpää, Mika

    2015-09-01

    The discharge of metals and dyes poses a serious threat to public health and the environment. What is worse, these two hazardous pollutants are often found to coexist in industrial wastewaters, making the treatment more challenging. Herein, we report an EDTA-cross-linked β-cyclodextrin (EDTA-β-CD) bifunctional adsorbent, which was fabricated by an easy and green approach through the polycondensation reaction of β-cyclodextrin with EDTA as a cross-linker, for simultaneous adsorption of metals and dyes. In this setting, cyclodextrin cavities are expected to capture dye molecules through the formation of inclusion complexes and EDTA units as the adsorption sites for metals. The adsorbent was characterized by FT-IR, elemental analysis, SEM, EDX, ζ-potential, and TGA. In a monocomponent system, the adsorption behaviors showed a monolayer adsorption capacity of 1.241 and 1.106 mmol g(-1) for Cu(II) and Cd(II), respectively, and a heterogeneous adsorption capacity of 0.262, 0.169, and 0.280 mmol g(-1) for Methylene Blue, Safranin O, and Crystal Violet, respectively. Interestingly, the Cu(II)-dye binary experiments showed adsorption enhancement of Cu(II), but no significant effect on dyes. The simultaneous adsorption mechanism was further confirmed by FT-IR, thermodynamic study, and elemental mapping. Overall, its facile and green fabrication, efficient sorption performance, and excellent reusability indicate that EDTA-β-CD has potential for practical applications in integrative and efficient treatment of coexistenting toxic pollutants.

  10. β-cyclodextrin-poly(β-amino ester) nanoparticles for sustained drug delivery across the blood-brain barrier.

    PubMed

    Gil, Eun Seok; Wu, Linfeng; Xu, Lichong; Lowe, Tao Lu

    2012-11-12

    Novel biodegradable polymeric nanoparticles composed of β-cyclodextrin and poly(β-amino ester) segments have been developed for sustained drug delivery across the blood-brain barrier (BBB). The nanoparticles have been synthesized by cross-linking β-cyclodextrin with poly(β-amino ester) via the Michael addition method. The chemical, physical, and degradation properties of the nanoparticles have been characterized by matrix-assisted laser desoption/ionization time-of-flight, attenuated total reflectance Fourier transform infrared spectroscopy, nuclear magnetic resonance, dynamic light scattering, and atomic force microscopy techniques. Bovine and human brain microvascular endothelial cell monolayers have been constructed as in vitro BBB models. Preliminary results show that the nanoparticles do not affect the integrity of the in vitro BBB models, and the nanoparticles have much higher permeability than dextran control across the in vitro BBB models. Doxorubicin has been loaded into the nanoparticles with a loading efficiency of 86%, and can be released from the nanoparticles for at least one month. The developed β-cyclodextrin-poly(β-amino ester) nanoparticles might be useful as drug carriers for transporting drugs across the BBB to treat chronic diseases in the brain.

  11. Supramolecular interactions between beta-cyclodextrin and hydrophobically end-capped poly(ethylene glycol)s: a quartz crystal microbalance study.

    PubMed

    Kham, Khémara; Guerrouache, Mohamed; Carbonnier, Benjamin; Lazerges, Mathieu; Perrot, Hubert; Millot, Marie-Claude

    2007-11-15

    In this study, the supramolecular interactions occurring between beta-cyclodextrin-based surfaces and macromolecular chains modified at one end with naphthyl, adamantyl, or phenyladamantyl hydrophobic groups were investigated by means of a quartz crystal microbalance. beta-Cyclodextrin-functionalized gold electrodes were obtained through the amide-coupling reaction between mono-6-deoxy-6-amino-beta-cyclodextrin and 11-mercaptoundecanoic acid self-assembled monolayer allowing the reproducible preparation of densely grafted surfaces with host properties. The interaction data obtained for the three different modified poly(ethylene glycol)s are in good agreement with our previous studies performed by high performance liquid chromatography and surface plasmon resonance. This evidences that the driving force for the supramolecular interaction is based on the inclusion of the hydrophobic terminal group of the chains within the cyclodextrin cavities. The reversibility of the inclusion process was proven through the regeneration of the original host properties of the sensing surfaces using sodium dodecylsulfate as a competitor for the desorption of the poly(ethylene glycol) chains.

  12. Monolayer coated aerogels and method of making

    DOEpatents

    Zemanian, Thomas Samuel; Fryxell, Glen; Ustyugov, Oleksiy A.

    2006-03-28

    Aerogels having a monolayer coating are described. The aerogel and a monolayer forming precursor are provided in a supercritical fluid, whereupon the aerogel and the monolayer forming precursor are reacted in said supercritical fluid to form a covalent bond between the aerogel and the monolayer forming precursor. Suitable aerogels are ceramic oxides such as silica, alumina, aluminosilicate, and combinations thereof. Suitable monolayer forming precursors include alkyl silanes, chlorosilanes, boranes, chloroboranes, germanes, and combinations thereof. The method may also include providing a surface preparation agent such as water, or hydroetching an aerogel to enhance the coating of the monolayer.

  13. Characterization of aspartame-cyclodextrin complexation.

    PubMed

    Sohajda, Tamás; Béni, Szabolcs; Varga, Erzsébet; Iványi, Róbert; Rácz, Akos; Szente, Lajos; Noszál, Béla

    2009-12-01

    The inclusion complex formation of aspartame (guest) and various cyclodextrins (host) were examined using 1H NMR titration and capillary electrophoresis. Initially the protonation constants of aspartame were determined by NMR-pH titration with in situ pH measurement to yield log K1=7.83 and log K2=2.96. Based on these values the stability of the complexes formed by aspartame and 21 different cyclodextrins (CDs) were studied at pH 2.5, pH 5.2 and pH 9.0 values where aspartame exists predominantly in monocationic, zwitterionic and monoanionic form, respectively. The host cyclodextrin derivatives differed in various sidechains, degree of substitution, charge and purity so that the effect of these properties could be examined systematically. Concerning size, the seven-membered beta-cyclodextrin and its derivatives have been found to be the most suitable host molecules for complexation. Highest stability was observed for the acetylated derivative with a degree of substitution of 7. The purity of the CD enhanced the complexation while the degree of substitution did not provide obvious consequences. Finally, geometric aspects of the inclusion complex were assessed by 2D ROESY NMR and molecular modelling which proved that the guest's aromatic ring enters the wider end of the host cavity. PMID:19586735

  14. CYCLODEXTRINS AS MODIFIERS OF MYCOTOXIN FLUORESCENCE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cyclodextrins, cyclic oligosaccharides composed of amylose subunits, are known to interact with mycotoxins, although the exact stoichiometry and mechanism of the interaction have not been reported. The interactions may be useful to analytical chemists by altering the properties of the mycotoxin of ...

  15. Linkage and pryanosyl ring twisting in cyclodextrins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crystalline acylated cyclodextrins (CDs) in the literature were studied to gain perspective on maltose octapropanoate in the preceding paper. That led to studies of other CDs and to increased understanding of distortion in CDs and, ultimately, non-crystalline regions in starch. Classic CDs have six ...

  16. Characterization of aspartame-cyclodextrin complexation.

    PubMed

    Sohajda, Tamás; Béni, Szabolcs; Varga, Erzsébet; Iványi, Róbert; Rácz, Akos; Szente, Lajos; Noszál, Béla

    2009-12-01

    The inclusion complex formation of aspartame (guest) and various cyclodextrins (host) were examined using 1H NMR titration and capillary electrophoresis. Initially the protonation constants of aspartame were determined by NMR-pH titration with in situ pH measurement to yield log K1=7.83 and log K2=2.96. Based on these values the stability of the complexes formed by aspartame and 21 different cyclodextrins (CDs) were studied at pH 2.5, pH 5.2 and pH 9.0 values where aspartame exists predominantly in monocationic, zwitterionic and monoanionic form, respectively. The host cyclodextrin derivatives differed in various sidechains, degree of substitution, charge and purity so that the effect of these properties could be examined systematically. Concerning size, the seven-membered beta-cyclodextrin and its derivatives have been found to be the most suitable host molecules for complexation. Highest stability was observed for the acetylated derivative with a degree of substitution of 7. The purity of the CD enhanced the complexation while the degree of substitution did not provide obvious consequences. Finally, geometric aspects of the inclusion complex were assessed by 2D ROESY NMR and molecular modelling which proved that the guest's aromatic ring enters the wider end of the host cavity.

  17. Microwave-assisted synthesis of cyclodextrin polyurethanes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cyclodextrin (CD) has often been incorporated into polyurethanes in order to facilitate its use in encapsulation or removal of organic species for various applications. In this work a microwave-assisted method has been developed to produce polyurethanes consisting of alpha-, ß-, and gamma-CD and thr...

  18. Electromelting of Confined Monolayer Ice

    NASA Astrophysics Data System (ADS)

    Qiu, Hu; Guo, Wanlin

    2013-05-01

    In sharp contrast to the prevailing view that electric fields promote water freezing, here we show by molecular dynamics simulations that monolayer ice confined between two parallel plates can melt into liquid water under a perpendicularly applied electric field. The melting temperature of the monolayer ice decreases with the increasing strength of the external field due to the field-induced disruption of the water-wall interaction induced well-ordered network of the hydrogen bond. This electromelting process should add an important new ingredient to the physics of water.

  19. Electromelting of confined monolayer ice.

    PubMed

    Qiu, Hu; Guo, Wanlin

    2013-05-10

    In sharp contrast to the prevailing view that electric fields promote water freezing, here we show by molecular dynamics simulations that monolayer ice confined between two parallel plates can melt into liquid water under a perpendicularly applied electric field. The melting temperature of the monolayer ice decreases with the increasing strength of the external field due to the field-induced disruption of the water-wall interaction induced well-ordered network of the hydrogen bond. This electromelting process should add an important new ingredient to the physics of water. PMID:23705718

  20. Complex formation between benzene carboxylic acids and β-cyclodextrin

    NASA Astrophysics Data System (ADS)

    Belyakova, L. A.; Lyashenko, D. Yu.

    2008-05-01

    Complex formation between benzene carboxylic acids and β-cyclodextrin in aqueous solutions at 290 300 K was studied using UV spectroscopy. The formation of 1:1 supramolecular inclusion compounds β-cyclodextrin-benzene and β-cyclodextrin-salicylic acid was found. Stability constants (Ks) of the complexes and thermodynamic parameters for formation of the inclusion compounds (ΔG, ΔH, and ΔS) were calculated.

  1. Glycemic Response to Corn Starch Modified with Cyclodextrin Glycosyltransferase and its Relationship to Physical Properties.

    PubMed

    Dura, A; Yokoyama, W; Rosell, C M

    2016-09-01

    Corn starch was modified with cyclodextrin glycosyltransferase (CGTase) below the gelatinization temperature. The porous granules with or without CGTase hydrolysis products may be used as an alternative to modified corn starches in foods applications. The amount and type of hydrolysis products were determined, containing mainly β-cyclodextrin (CD), which will influence pasting behavior and glycemic response in mice. Irregular surface and small holes were observed by microscopic analysis and differences in pasting properties were observed in the presence of hydrolysis products. Postprandial blood glucose in mice fed gelatinized enzymatically modified starch peaked earlier than their ungelatinized counterparts. However, in ungelatinized enzymatically modified starches, the presence of β- CD may inhibit the orientation of amylases slowing hydrolysis, which may help to maintain lower blood glucose levels. Significant correlations were found between glycemic curves and viscosity pattern of starches. PMID:27277075

  2. Random Walk Model for the Growth of Monolayer in Dip Pen Nanolithography

    NASA Astrophysics Data System (ADS)

    Kim, H.; Ha, S.; Jang, J.

    2013-02-01

    By using a simple random-walk model, we simulate the growth of a self-assembled monolayer (SAM) pattern generated in dip pen nanolithography (DPN). In this model, the SAM pattern grows mainly via the serial pushing of molecules deposited from the tip. We examine various SAM patterns, such as lines, crosses, and letters by changing the tip scan speed.

  3. Enantiomers resolution in capillary zone electrophoresis by using cyclodextrins.

    PubMed

    Schutzner, W; Fanali, S

    1992-01-01

    Cyclodextrins added to the background electrolyte are shown to be useful for the resolution of racemic compounds in their enantiomers. Several parameters have to be controlled in order to achieve resolution, e.g., cyclodextrin type, concentration, analyte shape, as well as column temperature. The resolution of nor-epinephrine, epinephrine and isoproterenol in their enantiomers decreased by increasing the column temperature. Octopamine and ketamine have been resolved by supporting the background electrolyte with 2, 6-di-O-methyl-beta-cyclodextrin. In spite of the stronger inclusion-complex of ketamine than octopamine with the modified cyclodextrin its resolution was not satisfactory.

  4. Cationic β-cyclodextrin polymer applied to a dual cyclodextrin polyelectrolyte multilayer system.

    PubMed

    Junthip, Jatupol; Tabary, Nicolas; Leclercq, Laurent; Martel, Bernard

    2015-08-01

    A polyelectrolyte multilayer film (PEM) based on cationic and anionic β-cyclodextrin polyelectrolytes was coated onto a textile substrate for future drug delivery purposes. We firstly synthesized a novel cationic β-cyclodextrin polymer (polyEPG-CD) by crosslinking β-cyclodextrin (βCD) with epichlorohydrin (EP) under basic conditions, in the presence of glycidyltrimetrylammonium chloride (GTMAC) as cationizing group. The influence of preparation conditions has been investigated in order to preferably obtain a water soluble fraction whose charge density and molecular weights were optimal for the layer-by-layer (LbL) deposition process. The different cationic cyclodextrin polymers obtained were characterized by FTIR, NMR, colloidal titration, conductimetry, thermogravimetric analysis and size exclusion chromatography. Besides, the counterpart polyelectrolyte was a β-cyclodextrin polymer crosslinked with citric acid, polyCTR-CD, whose synthesis and characterization have been previously reported. Finally we realized the Layer by Layer (LbL) build-up of the PEM coating onto the textile support, using the dip coating method, by alternatively soaking it in cationic polyEPG-CD and anionic polyCTR-CD solutions. This multilayer self-assembly was monitored by SEM, gravimetry and OWLS in function of both polyelectrolytes concentrations and ratios. Solutions parameters such as pH, ionic strenght were also discussed.

  5. "Back to the Future": A New Look at Hydroxypropyl Beta-Cyclodextrins.

    PubMed

    Malanga, Milo; Szemán, Julianna; Fenyvesi, Éva; Puskás, István; Csabai, Katalin; Gyémánt, Gyöngyi; Fenyvesi, Ferenc; Szente, Lajos

    2016-09-01

    Since the discovery about 30 years ago (2-hydroxypropyl) beta-cyclodextrin, a highly soluble derivative of beta-cyclodextrin, has become an approved excipient of drug formulations included both in the United States and European Pharmacopoeias. It is recommended to use as solubilizer and stabilizer for oral and parenteral formulations. Recently, its pharmacological activity has been recognized in various diseases. The increasing applications require a closer look to the structure-activity relationship. As (2-hydroxypropyl) beta-cyclodextrin (HPBCD) is always a mixture of isomers with various degrees and pattern of hydroxypropylation, no wonder that the products of different manufacturers are often different. Several HPBCDs were compared applying a battery of analytical tools including thin layer chromatography, high performance liquid chromatography (HPLC), HPLC-mass spectrometry (MS), and matrix-assisted laser desorption MS. We studied how the average degree of substitution affects the aggregation behavior, the toxicity, and the solubilizing effect on poorly soluble drugs. We found that the products with low average degree of substitution are more prone to aggregation. The samples studied are nontoxic to Caco-2 cells and have low hemolytic activity. The solubility enhancement of poorly soluble drugs decreases or increases with increasing degree of substitution or shows a maximum curve depending on the properties of the guest. PMID:27317368

  6. Alkanephosphonates on hafnium-modified gold: a new class of self-assembled organic monolayers.

    PubMed

    Jespersen, Michael L; Inman, Christina E; Kearns, Gregory J; Foster, Evan W; Hutchison, James E

    2007-03-14

    A new method for assembling organic monolayers on gold is reported that employs hafnium ions as linkers between a phosphonate headgroup and the gold surface. Monolayers of octadecylphosphonic acid (ODPA) formed on gold substrates that had been pretreated with hafnium oxychloride are representative of this new class of organic thin films. The monolayers are dense enough to completely block assembly of alkanethiols and resist displacement by alkanethiols. The composition and structure of the monolayers were investigated by contact angle goniometry, XPS, PM-IRRAS, and TOF-SIMS. From these studies, it was determined that this assembly strategy leads to the formation of ODPA monolayers similar in quality to those typically formed on metal oxide substrates. The assembly method allows for the ready generation of patterned surfaces that can be easily prepared by first patterning hafnium on the gold surface followed by alkanephosphonate assembly. Using the bifunctional (thiol-phosphonate) 2-mercaptoethylphosphonic acid (2-MEPA), we show that this new assembly chemistry is compatible with gold-thiol chemistry and use TOF-SIMS to show that the molecule attaches through the phosphonate functionality in the patterned region and through the thiol in the bare gold regions. These results demonstrate the possibility of functionalizing metal substrates with monolayers typically formed on metal oxide surfaces and show that hafnium-gold chemistry is complementary and orthogonal to well-established gold-thiol assembly strategies.

  7. New synthetic strategies for xanthene-dye-appended cyclodextrins.

    PubMed

    Malanga, Milo; Darcsi, Andras; Balint, Mihaly; Benkovics, Gabor; Sohajda, Tamas; Beni, Szabolcs

    2016-01-01

    Xanthene dyes can be appended to cyclodextrins via an ester or amide bridge in order to switch the fluorescence on or off. This is made possible through the formation of nonfluorescent lactones or lactams as the fluorophore can reversibly cyclize. In this context we report a green approach for the synthesis of switchable xanthene-dye-appended cyclodextrins based on the coupling agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). By using 6-monoamino-β-cyclodextrin and commercially available inexpensive dyes, we prepared rhodamine- and fluorescein-appended cyclodextrins. The compounds were characterized by NMR and IR spectroscopy and MS spectrometry, their UV-vis spectra were recorded at various pH, and their purity was determined by capillary electrophoresis. Two potential models for the supramolecular assembly of the xanthene-dye-appended cyclodextrins were developed based on the set of data collected by the extensive NMR characterization. PMID:27340446

  8. Cyclodextrin-mediated enantioseparation in microemulsion electrokinetic chromatography.

    PubMed

    Borst, Claudia; Holzgrabe, Ulrike

    2013-01-01

    Chiral separation by means of cyclodextrins has a long-standing tradition in capillary electrophoresis techniques. Here we present a chiral method utilizing the recently introduced microemulsion electrokinetic chromatography. The microemulsion consisting of 1.0% SDS, 4.0% 1-butanol, 3.0% 2-propanol, 0.5% ethylacetate, and 91.5% 20 mM phosphate buffer pH 2.5 serves as a pseudostationary phase which is complemented by sulfated cyclodextrin as a second phase. The analytes partition between the aqueous running buffer and both pseudostationary phases, the oil droplets and the cyclodextrins. Enantiomers are separated due to the formation of transient diastereomeric complexes with the cyclodextrins. For the racemates of ephedrine derivatives studied here sulfated β-cyclodextrin was successfully applied. The method is appropriate to resolve an entire series of chiral phenethylamines and can be used for separation of the racemates and impurity profiling, e.g., the determination of the enantiomeric excess.

  9. Functionalized β-cyclodextrin based potentiometric sensor for naproxen determination.

    PubMed

    Lenik, Joanna; Łyszczek, Renata

    2016-04-01

    Potentiometric sensors based on neutral β-cyclodextrins: (2-hydroxypropyl)-β-cyclodextrin, heptakis(2,3,6-tri-O-methyl)-β-cyclodextrin, heptakis(2,3,6-tri-O-benzoyl)-β-cyclodextrin and anionic β-cyclodextrin: (2-hydroxy-3-N,N,N-trimethylamino)propyl-β-cyclodextrin chloride for naproxen are described. Inclusion complexes of naproxen with the above-mentioned cyclodextrins were studied using IR spectroscopy. The electrode surface was made from PVC membranes doped with the appropriate β-cyclodextrin as ionophores and quaternary ammonium chlorides as positive charge additives that were dispersed in plasticizers. The optimum membrane contains heptakis(2,3,6-tri-O-benzoyl)-β-cyclodextrin, o-nitrophenyloctyl ether and tetraoctyl ammonium chloride as a lipophilic salt. The electrode is characterized by a Nernstian response slope of -59.0 ± 0.5 mV decade(-1) over the linear range of 5.0 × 10(-5)-1.0 × 10(-2) mol L(-1) and the detection limit 1.0 × 10(-5) mol L(-1), as well as the response time 10s. It can be used in the pH range 6.2-8.5 for 10 months without any considerable deterioration. Incorporation of β-cyclodextrins improved the electrode selectivity towards naproxen ions from several inorganic and organic interferents and some common drug excipients due to concovalent interactions (host molecule-guest molecule). The notable advantages of the naproxen-selective electrode include its high sensitivity, high selectivity, cost-effectiveness as well as accurate and comfortable application in drug analysis and milk samples. PMID:26838835

  10. Effect of cholesterol-loaded-cyclodextrin on sperm viability and acrosome reaction in boar semen cryopreservation.

    PubMed

    Lee, Yong-Seung; Lee, Seunghyung; Lee, Sang-Hee; Yang, Boo-Keun; Park, Choon-Keun

    2015-08-01

    This study was undertaken to examine the effect of cholesterol-loaded-cyclodextrin (CLC) on boar sperm viability and spermatozoa cryosurvival during boar semen cryopreservation, and methyl-β-cyclodextrin (MBCD) was treated for comparing with CLC. Boar semen treated with CLC and MBCD before freezing process to monitor the effect on survival and capacitation status by flow cytometry with appropriate fluorescent probes. Sperm viability was higher in 1.5mg CLC-treated sperm (76.9±1.01%, P<0.05) than un-treated and MBCD-treated sperm before cryopreservation (58.7±1.31% and 60.3±0.31%, respectively). For CTC patterns, F-pattern was higher in CLC treated sperm than MBCD-treated sperm, for B-pattern was higher in CLC-treated sperm than fresh sperm (P<0.05). For AR pattern (an acrosome-reacted sperm) was lower in CLC-treated sperm than MBCD-treated sperm (P<0.05). Moreover, we examined in vitro development of porcine oocytes after in vitro fertilization using CLC-treated frozen-thawed semen, in which CLC treatment prior to freezing and thawing increased the development of oocytes to blastocyst stage in vitro. In conclusion, CLC could protect the viability of spermatozoa from cryodamage prior to cryopreservation in boar semen. PMID:26091957

  11. Structure and shear response of lipid monolayers

    SciTech Connect

    Dutta, P.; Ketterson, J.B.

    1990-02-01

    Organic monolayers and multilayers are both scientifically fascinating and technologically promising; they are, however, both complex systems and relatively inaccessible to experimental probes. In this Progress Report, we describe our X-ray diffraction studies, which have given us substantial new information about the structures and phase transitions in monolayers on the surface of water; our use of these monolayers as a unique probe of the dynamics of wetting and spreading; and our studies of monolayer mechanical properties using a simple but effective technique available to anyone using the Wilhelmy method to measure surface tension.

  12. Regioselective self-acylating cyclodextrins in organic solvent

    PubMed Central

    Cho, Eunae; Yun, Deokgyu; Jeong, Daham; Im, Jieun; Kim, Hyunki; Dindulkar, Someshwar D.; Choi, Youngjin; Jung, Seunho

    2016-01-01

    Amphiphilic cyclodextrins have been synthesized with self-acylating reaction using vinyl esters in dimethylformamide. In the present study no base, catalyst, or enzyme was used, and the structural analyses using thin layer chromatography, nuclear magnetic resonance spectroscopy and mass spectrometry show that the cyclodextrin is substituted preferentially by one acyl moiety at the C2 position of the glucose unit, suggesting that cyclodextrin functions as a regioselective catalytic carbohydrate in organic solvent. In the self-acylation, the most acidic OH group at the 2-position and the inclusion complexing ability of cyclodextrin were considered to be significant. The substrate preference was also observed in favor of the long-chain acyl group, which could be attributed to the inclusion ability of cyclodextrin cavity. Furthermore, using the model amphiphilic building block, 2-O-mono-lauryl β-cyclodextrin, the self-organized supramolecular architecture with nano-vesicular morphology in water was investigated by fluorescence spectroscopy, dynamic light scattering and transmission electron microscopy. The cavity-type nano-assembled vesicle and the novel synthetic methods for the preparation of mono-acylated cyclodextrin should be of great interest with regard to drug/gene delivery systems, functional surfactants, and carbohydrate derivatization methods. PMID:27020946

  13. Regioselective self-acylating cyclodextrins in organic solvent

    NASA Astrophysics Data System (ADS)

    Cho, Eunae; Yun, Deokgyu; Jeong, Daham; Im, Jieun; Kim, Hyunki; Dindulkar, Someshwar D.; Choi, Youngjin; Jung, Seunho

    2016-03-01

    Amphiphilic cyclodextrins have been synthesized with self-acylating reaction using vinyl esters in dimethylformamide. In the present study no base, catalyst, or enzyme was used, and the structural analyses using thin layer chromatography, nuclear magnetic resonance spectroscopy and mass spectrometry show that the cyclodextrin is substituted preferentially by one acyl moiety at the C2 position of the glucose unit, suggesting that cyclodextrin functions as a regioselective catalytic carbohydrate in organic solvent. In the self-acylation, the most acidic OH group at the 2-position and the inclusion complexing ability of cyclodextrin were considered to be significant. The substrate preference was also observed in favor of the long-chain acyl group, which could be attributed to the inclusion ability of cyclodextrin cavity. Furthermore, using the model amphiphilic building block, 2-O-mono-lauryl β-cyclodextrin, the self-organized supramolecular architecture with nano-vesicular morphology in water was investigated by fluorescence spectroscopy, dynamic light scattering and transmission electron microscopy. The cavity-type nano-assembled vesicle and the novel synthetic methods for the preparation of mono-acylated cyclodextrin should be of great interest with regard to drug/gene delivery systems, functional surfactants, and carbohydrate derivatization methods.

  14. Regioselective self-acylating cyclodextrins in organic solvent.

    PubMed

    Cho, Eunae; Yun, Deokgyu; Jeong, Daham; Im, Jieun; Kim, Hyunki; Dindulkar, Someshwar D; Choi, Youngjin; Jung, Seunho

    2016-01-01

    Amphiphilic cyclodextrins have been synthesized with self-acylating reaction using vinyl esters in dimethylformamide. In the present study no base, catalyst, or enzyme was used, and the structural analyses using thin layer chromatography, nuclear magnetic resonance spectroscopy and mass spectrometry show that the cyclodextrin is substituted preferentially by one acyl moiety at the C2 position of the glucose unit, suggesting that cyclodextrin functions as a regioselective catalytic carbohydrate in organic solvent. In the self-acylation, the most acidic OH group at the 2-position and the inclusion complexing ability of cyclodextrin were considered to be significant. The substrate preference was also observed in favor of the long-chain acyl group, which could be attributed to the inclusion ability of cyclodextrin cavity. Furthermore, using the model amphiphilic building block, 2-O-mono-lauryl β-cyclodextrin, the self-organized supramolecular architecture with nano-vesicular morphology in water was investigated by fluorescence spectroscopy, dynamic light scattering and transmission electron microscopy. The cavity-type nano-assembled vesicle and the novel synthetic methods for the preparation of mono-acylated cyclodextrin should be of great interest with regard to drug/gene delivery systems, functional surfactants, and carbohydrate derivatization methods. PMID:27020946

  15. Cyclodextrins, blood-brain barrier, and treatment of neurological diseases.

    PubMed

    Vecsernyés, Miklós; Fenyvesi, Ferenc; Bácskay, Ildikó; Deli, Mária A; Szente, Lajos; Fenyvesi, Éva

    2014-11-01

    Biological barriers are the main defense systems of the homeostasis of the organism and protected organs. The blood-brain barrier (BBB), formed by the endothelial cells of brain capillaries, not only provides nutrients and protection to the central nervous system but also restricts the entry of drugs, emphasizing its importance in the treatment of neurological diseases. Cyclodextrins are increasingly used in human pharmacotherapy. Due to their favorable profile to form hydrophilic inclusion complexes with poorly soluble active pharmaceutical ingredients, they are present as excipients in many marketed drugs. Application of cyclodextrins is widespread in formulations for oral, parenteral, nasal, pulmonary, and skin delivery of drugs. Experimental and clinical data suggest that cyclodextrins can be used not only as excipients for centrally acting marketed drugs like antiepileptics, but also as active pharmaceutical ingredients to treat neurological diseases. Hydroxypropyl-β-cyclodextrin received orphan drug designation for the treatment of Niemann-Pick type C disease. In addition to this rare lysosomal storage disease with neurological symptoms, experimental research revealed the potential therapeutic use of cyclodextrins and cyclodextrin nanoparticles in neurodegenerative diseases, stroke, neuroinfections and brain tumors. In this context, the biological effects of cyclodextrins, their interaction with plasma membranes and extraction of different lipids are highly relevant at the level of the BBB.

  16. Exciton band structure of monolayer MoS2

    NASA Astrophysics Data System (ADS)

    Wu, Fengcheng; Qu, Fanyao; MacDonald, Allan

    2015-03-01

    We describe a theory of the momentum-dependent exciton spectrum of monolayer molybdenum disulfide. Low-energy excitons occur both at the Brillouin zone center and at the Brillouin-zone corners. We find that binding energies at the Brillouin-zone center deviate qualitatively from the (n - 1 / 2) - 2 pattern of the two-dimensional hydrogenic model. Moreover, the four 2 p states of A series are lower in energy than the corresponding 2 s states and not degenerate. The two-fold ground-state valley degeneracy is lifted linearly at small momenta by electron-hole exchange processes that establish inter valley coherence. We conclude that atlhough monolayer MoS2 is a direct-gap semiconductor when classified by its quasiparticle band structure it may well be an indirect gap material when classified by its excitation spectra, and speculate on the role of this property in luminescence characteristics.

  17. Continuity of Monolayer-Bilayer Junctions for Localization of Lipid Raft Microdomains in Model Membranes

    PubMed Central

    Ryu, Yong-Sang; Wittenberg, Nathan J.; Suh, Jeng-Hun; Lee, Sang-Wook; Sohn, Youngjoo; Oh, Sang-Hyun; Parikh, Atul N.; Lee, Sin-Doo

    2016-01-01

    We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed between the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates. PMID:27230411

  18. Continuity of monolayer-bilayer junctions for localization of lipid raft microdomains in model membranes

    DOE PAGESBeta

    Ryu, Yong -Sang; Wittenberg, Nathan J.; Suh, Jeng -Hun; Lee, Sang -Wook; Sohn, Youngjoo; Oh, Sang -Hyun; Parikh, Atul N.; Lee, Sin -Doo

    2016-05-27

    We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed betweenmore » the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Furthermore, our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates.« less

  19. Continuity of Monolayer-Bilayer Junctions for Localization of Lipid Raft Microdomains in Model Membranes.

    PubMed

    Ryu, Yong-Sang; Wittenberg, Nathan J; Suh, Jeng-Hun; Lee, Sang-Wook; Sohn, Youngjoo; Oh, Sang-Hyun; Parikh, Atul N; Lee, Sin-Doo

    2016-01-01

    We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed between the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates. PMID:27230411

  20. Continuity of Monolayer-Bilayer Junctions for Localization of Lipid Raft Microdomains in Model Membranes.

    PubMed

    Ryu, Yong-Sang; Wittenberg, Nathan J; Suh, Jeng-Hun; Lee, Sang-Wook; Sohn, Youngjoo; Oh, Sang-Hyun; Parikh, Atul N; Lee, Sin-Doo

    2016-05-27

    We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed between the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates.

  1. Cyclodextrins as encapsulation agents for plant bioactive compounds.

    PubMed

    Pinho, Eva; Grootveld, Martin; Soares, Graça; Henriques, Mariana

    2014-01-30

    Plants possess a wide range of molecules capable of improve healing: fibre, vitamins, phytosterols, and further sulphur-containing compounds, carotenoids, organic acid anions and polyphenolics. However, they require an adequate level of protection from the environmental conditions to prevent losing their structural integrity and bioactivity. Cyclodextrins are cyclic oligosaccharides arising from the degradation of starch, which can be a viable option as encapsulation technique. Cyclodextrins are inexpensive, friendly to humans, and also capable of improving the biological, chemical and physical properties of bioactive molecules. Therefore, the aim of this review is to highlight the use of cyclodextrins as encapsulating agents for bioactive plant molecules in the pharmaceutical field.

  2. Complex formation of fenchone with α-cyclodextrin: NMR titrations.

    PubMed

    Nowakowski, Michał; Ejchart, Andrzej

    2014-01-01

    (13)C NMR titration studies of inclusion complexes of bicyclic terpenoid, fenchone enantiomers with α-cyclodextrin revealed their 1:2 guest-host stoichiometry. Sequential binding constants were determined indicating a strong binding cooperativity of two α-cyclodextrin to fenchone. The overall association constants were used to calculate the Gibbs free energies of diastereomeric complex formation, which might be used as a measure of chiral recognition of fenchone by α-cyclodextrin. These results were compared with corresponding data derived for camphor, which is an isomeric bicyclic terpenoid.

  3. Cyclodextrins: a new group of industrial basic materials.

    PubMed

    Szejtli, J

    1985-01-01

    Adequate toxicological studies, discovery of numerous potential fields of utilization and last but not least, the production of cyclodextrins on industrial scale with high homogeneity and low price led to their recognition as a new group of industrial basic materials. Until now cyclodextrins were considered merely as agents for molecular encapsulation, however intensive research of the past few years revealed quite new and unexpected aspects: cyclodextrins, their derivatives and polymers can be applied--not exclusively due to their complexing ability--in foods, cosmetics, pharmaceuticals, chromatography, pesticide formulations, in photochemistry, etc.

  4. Cyclodextrin nanoassemblies: a promising tool for drug delivery.

    PubMed

    Bonnet, Véronique; Gervaise, Cédric; Djedaïni-Pilard, Florence; Furlan, Aurélien; Sarazin, Catherine

    2015-09-01

    Among the biodegradable and nontoxic compounds that can form nanoparticles for drug delivery, amphiphilic cyclodextrins are very promising. Apart from ionic cyclodextrins, which have been extensively studied and reviewed because of their application in gene delivery, our purpose is to provide a clear description of the supramolecular assemblies of nonionic amphiphilic cyclodextrins, which can form nanoassemblies for controlled drug release. Moreover, we focus on the relationship between their structure and physicochemical characteristics, which is crucial for self assembly and drug delivery. We also highlight the importance of the nanoparticle technology preparation for the stability and application of this nanodevice. PMID:26037681

  5. Enantioselective determination by capillary electrophoresis with cyclodextrins as chiral selectors.

    PubMed

    Fanali, S

    2000-04-14

    This review surveys the separation of enantiomers by capillary electrophoresis using cyclodextrins as chiral selector. Cyclodextrins or their derivatives have been widely employed for the direct chiral resolution of a wide number of enantiomers, mainly of pharmaceutical interest, selected examples are reported in the tables. For method optimisation, several parameters influencing the enantioresolution, e.g., cyclodextrin type and concentration, buffer pH and composition, presence of organic solvents or complexing additives in the buffer were considered and discussed. Finally, selected applications to real samples such as pharmaceutical formulations, biological and medical samples are also discussed.

  6. Synthesis of uniform cyclodextrin thioethers to transport hydrophobic drugs

    PubMed Central

    Becker, Lisa F; Schwarz, Dennis H

    2014-01-01

    Summary Methyl and ethyl thioether groups were introduced at all primary positions of α-, β-, and γ-cyclodextrin by nucleophilic displacement reactions starting from the corresponding per-(6-deoxy-6-bromo)cyclodextrins. Further modification of all 2-OH positions by etherification with iodo terminated triethylene glycol monomethyl ether (and tetraethylene glycol monomethyl ether, respectively) furnished water-soluble hosts. Especially the β-cyclodextrin derivatives exhibit very high binding potentials towards the anaesthetic drugs sevoflurane and halothane. Since the resulting inclusion compounds are highly soluble in water at temperatures ≤37 °C they are good candidates for new aqueous dosage forms which would avoid inhalation anaesthesia. PMID:25550759

  7. Multifunctional self-assembled monolayers

    SciTech Connect

    Zawodzinski, T.; Bar, G.; Rubin, S.; Uribe, F.; Ferrais, J.

    1996-06-01

    This is the final report of at three year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The specific goals of this research project were threefold: to develop multifunctional self-assembled monolayers, to understand the role of monolayer structure on the functioning of such systems, and to apply this knowledge to the development of electrochemical enzyme sensors. An array of molecules that can be used to attach electrochemically active biomolecules to gold surfaces has been synthesized. Several members of a class of electroactive compounds have been characterized and the factors controlling surface modification are beginning to be characterized. Enzymes have been attached to self-assembled molecules arranged on the gold surface, a critical step toward the ultimate goal of this project. Several alternative enzyme attachment strategies to achieve robust enzyme- modified surfaces have been explored. Several means of juxtaposing enzymes and mediators, electroactive compounds through which the enzyme can exchange electrons with the electrode surface, have also been investigated. Finally, the development of sensitive biosensors based on films loaded with nanoscale-supported gold particles that have surface modified with the self-assembled enzyme and mediator have been explored.

  8. β-Cyclodextrin Production by Cyclodextrin Glucanotransferase from an Alkaliphile Microbacterium terrae KNR 9 Using Different Starch Substrates.

    PubMed

    Rajput, Kiransinh N; Patel, Kamlesh C; Trivedi, Ujjval B

    2016-01-01

    Cyclodextrin glucanotransferase (CGTase, EC 2.4.1.19) is an important member of α-amylase family which can degrade the starch and produce cyclodextrins (CDs) as a result of intramolecular transglycosylation (cyclization). β-Cyclodextrin production was carried out using the purified CGTase enzyme from an alkaliphile Microbacterium terrae KNR 9 with different starches in raw as well as gelatinized form. Cyclodextrin production was confirmed using thin layer chromatography. Six different starch substrates, namely, soluble starch, potato starch, sago starch, corn starch, corn flour, and rice flour, were tested for CD production. Raw potato starch granules were found to be the best substrate giving 13.46 gm/L of cyclodextrins after 1 h of incubation at 60°C. Raw sago starch gave 12.96 gm/L of cyclodextrins as the second best substrate. To achieve the maximum cyclodextrin production, statistical optimization using Central Composite Design (CCD) was carried out with three parameters, namely, potato starch concentration, CGTase enzyme concentration, and incubation temperature. Cyclodextrin production of 28.22 (gm/L) was achieved with the optimized parameters suggested by the model which are CGTase 4.8 U/L, starch 150 gm/L, and temperature 55.6°C. The suggested optimized conditions showed about 15% increase in β-cyclodextrin production (28.22 gm/L) at 55.6°C as compared to 24.48 gm/L at 60°C. The degradation of raw potato starch granules by purified CGTase was also confirmed by microscopic observations. PMID:27648307

  9. β-Cyclodextrin Production by Cyclodextrin Glucanotransferase from an Alkaliphile Microbacterium terrae KNR 9 Using Different Starch Substrates

    PubMed Central

    Trivedi, Ujjval B.

    2016-01-01

    Cyclodextrin glucanotransferase (CGTase, EC 2.4.1.19) is an important member of α-amylase family which can degrade the starch and produce cyclodextrins (CDs) as a result of intramolecular transglycosylation (cyclization). β-Cyclodextrin production was carried out using the purified CGTase enzyme from an alkaliphile Microbacterium terrae KNR 9 with different starches in raw as well as gelatinized form. Cyclodextrin production was confirmed using thin layer chromatography. Six different starch substrates, namely, soluble starch, potato starch, sago starch, corn starch, corn flour, and rice flour, were tested for CD production. Raw potato starch granules were found to be the best substrate giving 13.46 gm/L of cyclodextrins after 1 h of incubation at 60°C. Raw sago starch gave 12.96 gm/L of cyclodextrins as the second best substrate. To achieve the maximum cyclodextrin production, statistical optimization using Central Composite Design (CCD) was carried out with three parameters, namely, potato starch concentration, CGTase enzyme concentration, and incubation temperature. Cyclodextrin production of 28.22 (gm/L) was achieved with the optimized parameters suggested by the model which are CGTase 4.8 U/L, starch 150 gm/L, and temperature 55.6°C. The suggested optimized conditions showed about 15% increase in β-cyclodextrin production (28.22 gm/L) at 55.6°C as compared to 24.48 gm/L at 60°C. The degradation of raw potato starch granules by purified CGTase was also confirmed by microscopic observations.

  10. β-Cyclodextrin Production by Cyclodextrin Glucanotransferase from an Alkaliphile Microbacterium terrae KNR 9 Using Different Starch Substrates

    PubMed Central

    Trivedi, Ujjval B.

    2016-01-01

    Cyclodextrin glucanotransferase (CGTase, EC 2.4.1.19) is an important member of α-amylase family which can degrade the starch and produce cyclodextrins (CDs) as a result of intramolecular transglycosylation (cyclization). β-Cyclodextrin production was carried out using the purified CGTase enzyme from an alkaliphile Microbacterium terrae KNR 9 with different starches in raw as well as gelatinized form. Cyclodextrin production was confirmed using thin layer chromatography. Six different starch substrates, namely, soluble starch, potato starch, sago starch, corn starch, corn flour, and rice flour, were tested for CD production. Raw potato starch granules were found to be the best substrate giving 13.46 gm/L of cyclodextrins after 1 h of incubation at 60°C. Raw sago starch gave 12.96 gm/L of cyclodextrins as the second best substrate. To achieve the maximum cyclodextrin production, statistical optimization using Central Composite Design (CCD) was carried out with three parameters, namely, potato starch concentration, CGTase enzyme concentration, and incubation temperature. Cyclodextrin production of 28.22 (gm/L) was achieved with the optimized parameters suggested by the model which are CGTase 4.8 U/L, starch 150 gm/L, and temperature 55.6°C. The suggested optimized conditions showed about 15% increase in β-cyclodextrin production (28.22 gm/L) at 55.6°C as compared to 24.48 gm/L at 60°C. The degradation of raw potato starch granules by purified CGTase was also confirmed by microscopic observations. PMID:27648307

  11. Stilling Waves with Ordered Molecular Monolayers

    ERIC Educational Resources Information Center

    Vitz, Ed

    2008-01-01

    A demonstration of the damping effect of an oil monolayer on water waves is described. The history of this remarkable demonstration--with a 2000 (or more) year span--and a brief explanation in terms of the properties of water and the monolayer are presented. If a layer of olive oil, one molecule thick (about one-ten millionth of a centimeter), is…

  12. Studying on inclusion complexes of Wogonin with β-cyclodextrin and hydroxypropyl-cyclodextrin.

    PubMed

    Li, Jinxia; Chao, Jianbin; Zhang, Min

    2012-02-15

    The formation of the complexes of Wogonin with β-cyclodextrin (β-CD) and hydroxypropyl-cyclodextrin (HP-β-CD) was studied by fluorescence spectra and nuclear magnetic resonance spectroscopy (NMR). The formation constants (Ks) of complexes were determined by fluorescence method. The results suggested that HP-β-CD was easier to form inclusion with Wogonin than β-CD in solution. In different pH solutions, CDs have different inclusive capacity to Wo. β-CD was most suitable for inclusion of neutral form and HP-β-CD was suitable for acidic form. In addition, the experimental resulted confirmed the existence of 1:1 inclusion complex of Wogonin with CDs. Besides, kinetic studies of DPPH with Wogonin and CDs complexes were done. The results obtained indicated that the complex was the most reactive form. Special configuration of complex has been proposed on NMR technique.

  13. Studying on inclusion complexes of Wogonin with β-cyclodextrin and hydroxypropyl-cyclodextrin

    NASA Astrophysics Data System (ADS)

    Li, Jinxia; Chao, Jianbin; Zhang, Min

    2012-02-01

    The formation of the complexes of Wogonin with β-cyclodextrin (β-CD) and hydroxypropyl-cyclodextrin (HP-β-CD) was studied by fluorescence spectra and nuclear magnetic resonance spectroscopy (NMR). The formation constants (Ks) of complexes were determined by fluorescence method. The results suggested that HP-β-CD was easier to form inclusion with Wogonin than β-CD in solution. In different pH solutions, CDs have different inclusive capacity to Wo. β-CD was most suitable for inclusion of neutral form and HP-β-CD was suitable for acidic form. In addition, the experimental resulted confirmed the existence of 1:1 inclusion complex of Wogonin with CDs. Besides, kinetic studies of DPPH rad with Wogonin and CDs complexes were done. The results obtained indicated that the complex was the most reactive form. Special configuration of complex has been proposed on NMR technique.

  14. Directing Translational and Orientational Order of Rectangular Particle Monolayers

    NASA Astrophysics Data System (ADS)

    Ferraro, Mark; Truskett, Thomas; Bonnecaze, Roger

    2015-03-01

    Recent advances have shown that the tunability of nanoparticle interactions can lead to a large number of thermodynamically accessible structures. The role of an external field in the assembly of particulate systems, however, is still incompletely understood. The use of larger scale patterned substrates to drive smaller scale assembly of particle monolayers can potentially expand the set of achievable lattices, and could be used in nanopatterning processes or in the manufacture of functional materials. In this presentation, grand canonical Monte Carlo (GCMC) simulations are used to assess the suitability of graphoepitaxial assembly for particle monolayers. Our prior work has shown that topographically or chemically patterned substrates can sufficiently organize hard-spheres, but many motivating applications can utilize anisotropic particle shapes (e.g. rectangular particles for bit-patterned media). Here, we describe our recent GCMC results for structures formed by rectangular particles in the presence of sparse enthalpic barriers. We examine systems of varying chemical potential, template geometry, and particle aspect ratio. Templates are evaluated by their ability to induce orientational and translational order, while maximizing pattern multiplication effects.

  15. Cyclodextrin nanoaggregates and their assembly with protein: a spectroscopic investigation

    NASA Astrophysics Data System (ADS)

    Micali, N.; Villari, V.; Mazzaglia, A.; Monsú Scolaro, L.; Valerio, A.; Rencurosi, A.; Lay, L.

    2006-07-01

    Light scattering and time-resolved fluorescence spectroscopy results showed that specially designed amphiphilic cyclodextrins are able to bind a specific protein, PA-I lectin. When containing a galactosyl group, the self-assembled cyclodextrins interact with the protein affecting the dynamical properties of the system and the fluorescence lifetimes (as well as the fluorescence anisotropy) of the protein itself. The self-assembled cyclodextrins containing a glucosyl group, on the other hand, do not induce any change in these measured quantities, suggesting no interaction with protein. This binding capability of galactosyl-modified cyclodextrins offers perspectives on exploiting self-assembled supramolecular structures as nano-carriers to deliver drugs to target tissues.

  16. Biomimetic Nanotubes Based on Cyclodextrins for Ion-Channel Applications.

    PubMed

    Mamad-Hemouch, Hajar; Ramoul, Hassen; Abou Taha, Mohammad; Bacri, Laurent; Huin, Cécile; Przybylski, Cédric; Oukhaled, Abdelghani; Thiébot, Bénédicte; Patriarche, Gilles; Jarroux, Nathalie; Pelta, Juan

    2015-11-11

    Biomimetic membrane channels offer a great potential for fundamental studies and applications. Here, we report the fabrication and characterization of short cyclodextrin nanotubes, their insertion into membranes, and cytotoxicity assay. Mass spectrometry and high-resolution transmission electron microscopy were used to confirm the synthesis pathway leading to the formation of short nanotubes and to describe their structural parameters in terms of length, diameter, and number of cyclodextrins. Our results show the control of the number of cyclodextrins threaded on the polyrotaxane leading to nanotube synthesis. Structural parameters obtained by electron microscopy are consistent with the distribution of the number of cyclodextrins evaluated by mass spectrometry from the initial polymer distribution. An electrophysiological study at single molecule level demonstrates the ion channel formation into lipid bilayers, and the energy penalty for the entry of ions into the confined nanotube. In the presence of nanotubes, the cell physiology is not altered.

  17. Compactible powders of omega-3 and β-cyclodextrin.

    PubMed

    Vestland, Tina Lien; Jacobsen, Øyvind; Sande, Sverre Arne; Myrset, Astrid Hilde; Klaveness, Jo

    2015-10-15

    Omega-3 fatty acids are used in both nutraceuticals and pharmaceuticals in the form of triglycerides and ethyl esters. Administration forms available for omega-3 include bulk oil, soft gel capsules, emulsions and some powder compositions. Cyclodextrins are substances well known for their ability to encapsulate lipophilic molecules. In the present work, powders loaded with omega-3 oil, ranging from 10 to 40% (w/w), have been prepared by vacuum drying, freeze drying or spray granulation of aqueous mixtures of omega-3 oil and β-cyclodextrin. The powders were found to be partially crystalline by powder X-ray diffraction and to contain crystalline phases not present in pure β-cyclodextrin, indicating true complexation. The compactibility of the powders has been explored, revealing that a dry and compactible powder can be prepared from various omega-3 oils and β-cyclodextrin. Spray granulation was found to be the superior drying method for the preparation of compactible powders.

  18. Space filling of β-cyclodextrin and β-cyclodextrin derivatives by volatile hydrophobic guests

    PubMed Central

    Fourmentin, Sophie; Ciobanu, Anca; Landy, David

    2013-01-01

    Summary The inclusion of volatile derivatives of benzene and cyclohexane in β-cyclodextrin (β-CD), hydroxypropyl-β-CD, and hydrophilic β-CD-thioethers was investigated by static headspace gas chromatography (HS-GC) and molecular modelling. The obtained binding constants strongly increase with the amount of space filling of the CD cavity and the salt concentration. β-CD thioethers show a 3–10 times higher binding potential than native β-CD. PMID:23843912

  19. Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

    PubMed Central

    Letort, Sophie; Balieu, Sébastien; Erb, William; Gouhier, Géraldine

    2016-01-01

    Summary The aim of this review is to provide an update on the current use of cyclodextrins against organophosphorus compound intoxications. Organophosphorus pesticides and nerve agents play a determinant role in the inhibition of cholinesterases. The cyclic structure of cyclodextrins and their toroidal shape are perfectly suitable to design new chemical scavengers able to trap and hydrolyze the organophosphorus compounds before they reach their biological target. PMID:26977180

  20. Complexation thermodynamics of modified cyclodextrins: extended cavities and distorted structures.

    PubMed

    Schönbeck, Christian; Westh, Peter; Holm, René

    2014-08-28

    Inclusion complexes between two bile salts and a range of differently methylated β-cyclodextrins were studied in an attempt to rationalize the complexation thermodynamics of modified cyclodextrins. Calorimetric titrations at a range of temperatures provided precise values of the enthalpies (ΔH°), entropies (ΔS°), and heat capacities (ΔCp) of complexation, while molecular dynamics simulations assisted the interpretation of the obtained thermodynamic parameters. As previously observed for several types of modified cyclodextrins, the substituents at the rims of the cyclodextrin induced large changes in ΔH° and ΔS°, but due to enthalpy-entropy compensation the changes in Gibbs free energy, and the binding constant, were much smaller. For the methylated β-cyclodextrins, the substituent-induced increments in ΔH° and ΔS° were nonmonotonic with an initial strong increase in both ΔH° and ΔS° and then a strong decrease when the degree of substitution exceeded some threshold. Exactly the same trend was observed for ΔCp. The dehydration of nonpolar surface, as quantified by the simulations, can to a large extent explain the variation in the thermodynamic parameters. The methyl substituents form additional hydrophobic contacts with the bile salt, but at high degrees of methylation they also cause significant distortion of the otherwise circular cyclodextrin structure. These two opposing contributions to the dehydration are the major causes for the observed variations in the thermodynamic functions. The structural effects are not expected to be specific for methylated cyclodextrins but should be observed for most modified cyclodextrins. An even more general conclusion is that variations in the extent of hydration are an important underlying reason for the commonly observed phenomenon termed enthalpy-entropy compensation and also for the less frequent reports of entropy convergence around 110 °C.

  1. Self assembly of highly-ordered nanoparticle monolayers.

    SciTech Connect

    Bigioni, T. P.; Lin, X.-M.; Nguyen, T. T.; Corwin, E. I.; Witten, T. A.; Jaeger, H. M.; Univ. of Chicago

    2006-01-01

    When a drop of a colloidal solution of nanoparticles dries on a surface, it leaves behind coffee-stain-like rings of material with lace-like patterns or clumps of particles in the interior. These non-uniform mass distributions are manifestations of far-from-equilibrium effects, such as fluid flows and solvent fluctuations during late-stage drying. However, recently a strikingly different drying regime promising highly uniform, long-range-ordered nanocrystal monolayers has been found. Here we make direct, real-time and real-space observations of nanocrystal self-assembly to reveal the mechanism. We show how the morphology of drop-deposited nanoparticle films is controlled by evaporation kinetics and particle interactions with the liquid-air interface. In the presence of an attractive particle-interface interaction, rapid early-stage evaporation dynamically produces a two-dimensional solution of nanoparticles at the liquid-air interface, from which nanoparticle islands nucleate and grow. This self-assembly mechanism produces monolayers with exceptional long-range ordering that are compact over macroscopic areas, despite the far-from-equilibrium evaporation process. This new drop-drying regime is simple, robust and scalable, is insensitive to the substrate material and topography, and has a strong preference for forming monolayer films. As such, it stands out as an excellent candidate for the fabrication of technologically important ultra thin film materials for sensors, optical devices and magnetic storage media.

  2. Oriented cell division affects the global stress and cell packing geometry of a monolayer under stretch.

    PubMed

    Xu, Guang-Kui; Liu, Yang; Zheng, Zhaoliang

    2016-02-01

    Cell division plays a vital role in tissue morphogenesis and homeostasis, and the division plane is crucial for cell fate. For isolated cells, extensive studies show that the orientation of divisions is sensitive to cell shape and the direction of extrinsic mechanical forces. However, it is poorly understood that how the cell divides within a cell monolayer and how the local stress change, due to the division, affects the global stress of epithelial monolayers. Here, we use the vertex dynamics models to investigate the effects of division orientation on the configurations and mechanics of a cell monolayer under stretch. We examine three scenarios of the divisions: dividing along the stretch axis, dividing along the geometric long axis of cells, and dividing at a random angle. It is found that the division along the long cell axis can induce the minimal energy difference, and the global stress of the monolayer after stretch releases more rapidly in this case. Moreover, the long-axis division can result in more random cell orientations and more isotropic cell shapes within the monolayer, comparing with other two cases. This study helps understand the division orientation of cells within a monolayer under mechanical stimuli, and may shed light on linking individual cell's behaviors to the global mechanics and patterns of tissues. PMID:26774292

  3. Oriented cell division affects the global stress and cell packing geometry of a monolayer under stretch.

    PubMed

    Xu, Guang-Kui; Liu, Yang; Zheng, Zhaoliang

    2016-02-01

    Cell division plays a vital role in tissue morphogenesis and homeostasis, and the division plane is crucial for cell fate. For isolated cells, extensive studies show that the orientation of divisions is sensitive to cell shape and the direction of extrinsic mechanical forces. However, it is poorly understood that how the cell divides within a cell monolayer and how the local stress change, due to the division, affects the global stress of epithelial monolayers. Here, we use the vertex dynamics models to investigate the effects of division orientation on the configurations and mechanics of a cell monolayer under stretch. We examine three scenarios of the divisions: dividing along the stretch axis, dividing along the geometric long axis of cells, and dividing at a random angle. It is found that the division along the long cell axis can induce the minimal energy difference, and the global stress of the monolayer after stretch releases more rapidly in this case. Moreover, the long-axis division can result in more random cell orientations and more isotropic cell shapes within the monolayer, comparing with other two cases. This study helps understand the division orientation of cells within a monolayer under mechanical stimuli, and may shed light on linking individual cell's behaviors to the global mechanics and patterns of tissues.

  4. Safety assessment of gamma-cyclodextrin.

    PubMed

    Munro, I C; Newberne, P M; Young, V R; Bär, A

    2004-06-01

    Gamma-cyclodextrin (gamma-CD) is a cyclic alpha-(1,4)-linked oligosaccharide consisting of eight glucose molecules. Like other cyclodextrins, gamma-CD can form inclusion complexes with a variety of organic molecules because the inner side of the torus-like molecule is less polar than the outer side. In foods, gamma-CD may be used as a carrier for flavors, vitamins, polyunsaturated fatty acids, and other ingredients. It also has useful properties as a stabilizer in different food systems. The daily intake from all its intended uses in food at highest feasible concentrations has been estimated at 4.1g/person/day for consumers of gamma-CD containing foods. The present review summarizes the safety data of gamma-CD. The toxicity studies consist of standard genotoxicity tests, subchronic rat studies with oral and intravenous administration of gamma-CD for up to 3 months, a subchronic (3-month) toxicity study in dogs, a (1-year) oral toxicity study in rats, and embryotoxicity/teratogenicity studies in rats and rabbits. In the studies with oral administration, gamma-CD was given at dietary concentrations of up to 20%. All these studies demonstrated that gamma-CD is well tolerated and elicits no toxicological effects. Metabolic studies in rats showed that gamma-CD is rapidly and essentially completely digested by salivary and pancreatic amylase. Therefore, the metabolism of gamma-CD closely resembles that of starch and linear dextrins. A human study with ingestion of single doses of 8 g gamma-CD or 8 g maltodextrin did not reveal a difference in gastrointestinal tolerance of these two products. An interaction of ingested gamma-CD with the absorption of fat-soluble vitamins or other lipophilic nutrients is not to be expected because the formation of inclusion complexes is a reversible process, gamma-CD is readily digested in the small intestine, and studies with beta-CD, a non-digestible cyclodextrin, have shown that the bioavailability of vitamins (A, D, and E) is not

  5. Self-assembled monolayer facilitates epithelial-mesenchymal interactions mimicking odontogenesis.

    PubMed

    Muni, Tanvi; Mrksich, Milan; George, Anne

    2014-01-01

    Cell-cell interactions are vital for embryonic organ development and normal function of differentiated cells and tissues. In this study we have developed a self-assembled monolayer-based co-culture system to study tooth morphogenesis. Specifically, we designed a 2-D microenvironment present in the dental tissue by creating a well-structured, laterally organized epithelial and mesenchymal cell co-culture system by patterning the cell-attachment substrate. Chemical modifications were used to develop tunable surface patterns to facilitate epithelial-mesenchymal interactions mimicking the developing tooth. Such a design promoted interactions between monolayer's of the 2 cell types and provided signaling cues that resulted in cellular differentiation and mineralized matrix formation. Gene expression analysis showed that these co-cultures mimicked in-vivo conditions than monolayer cultures of a single cell type.

  6. Study of the effects of cyclodextrins on the fluorescence detection of zearalenone

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Successful applications of inclusion complexes to improve isolation and detection of small molecules have made cyclodextrins increasingly popular components in methods of detection. Studies of the effects of cyclodextrins on aflatoxins have advanced mycotoxin detection research. Recently, a capill...

  7. Analytical applications of retinoid-cyclodextrin inclusion complexes. 1. Characterization of a retinal-beta-cyclodextrin complex.

    PubMed

    Muñoz Botella, S; Martìn, M A; del Castillo, B; Menéndez, J C; Vázquez, L; Lerner, D A

    1996-06-01

    In studies in these laboratories on the supramolecular chemistry of the retinoids, it has been recently confirmed that inclusion of these substances within the cavity of cyclodextrins protects their excited states, thus improving their photochemical stability. In the present paper, the isolation is described of a crystalline stable complex between retinal and beta-cyclodextrin, which has been characterized by means of several techniques including atomic force microscopy (AFM). The complex shows distinct spectroscopic differences from both retinal and beta-cyclodextrin. Thus, it absorbs at lambda(max) = 380 nm in water whereas retinal is insoluble; it shows room-temperature luminescence, which retinal does not; finally, it give 1H-NMR and 13C-NMR spectra in d6-DMSO with clear differences in chemical shifts with respect to those of beta-cyclodextrin. Besides these studies in solution, the behaviour of the complex in the solid state has been compared with that of physical mixtures of retinal and beta-cyclodextrin. IR spectroscopy shows clear differences, particularly a shift in the retinal carbonyl absorption (1644-1672 cm-1). AFM studies reveal the existence of aggregates; X-ray diffractometry also supports the formation of a cyclodextrin-retinal complex.

  8. Electrochemical Deposition Of Thiolate Monolayers On Metals

    NASA Technical Reports Server (NTRS)

    Porter, Marc D.; Weissharr, Duane E.

    1995-01-01

    Electrochemical method devised for coating metal (usually, gold) surfaces with adherent thiolate monolayers. Affords greater control over location and amount of material deposited and makes it easier to control chemical composition of deposits. One important potential use for this method lies in fabrication of chemically selective thin-film resonators for microwave oscillators used to detect pollutants: monolayer formulated to bind selectively pollutant chemical species of interest, causing increase in mass of monolayer and corresponding decrease in frequency of resonance. Another important potential use lies in selective chemical derivatization for purposes of improving adhesion, lubrication, protection against corrosion, electrocatalysis, and electroanalysis.

  9. Structural prediction for scandium carbide monolayer sheet

    NASA Astrophysics Data System (ADS)

    Ma, Hong-Man; Wang, Jing; Zhao, Hui-Yan; Zhang, Dong-Bo; Liu, Ying

    2016-09-01

    A two-dimensional tetragonal scandium carbide monolayer sheet has been constructed and studied using density functional theory. The results show that the scandium carbide sheet is stable and exhibits a novel tetracoordinated quasiplanar structure, as favored by the hybridization between Sc-3d orbitals and C-2p orbitals. Calculations of the phonon dispersion as well as molecular dynamics simulations also demonstrate the structural stability of this scandium carbide monolayer sheet. Electronic properties show that the scandium carbide monolayer sheet is metallic and non-magnetic.

  10. Drug induced `softening' in phospholipid monolayers

    NASA Astrophysics Data System (ADS)

    Basak, Uttam Kumar; Datta, Alokmay; Bhattacharya, Dhananjay

    2015-06-01

    Compressibility measurements on Langmuir monolayers of the phospholipid Dimystoryl Phospatidylcholine (DMPC) in pristine form and in the presence of the Non-steroidal Anti-inflammatory Drug (NSAID) Piroxicam at 0.025 drug/lipid (D/L) molecular ratio at different temperatures, show that the monolayer exhibits large increase (and subsequent decrease) in compressibility due to the drug in the vicinity of the Liquid Expanded - Liquid Condensed (LE-LC) phase transition. Molecular dynamics simulations of the lipid monolayer in presence of drug molecules show a disordering of the tail tilt, which is consistent with the above result.

  11. Dynamic behaviors of fractal-like domains in monolayers

    NASA Astrophysics Data System (ADS)

    Wang, Mu; Sun, Cheng; Peng, Ru-Wen; Ming, Nai-Ben; Esch, Jan Van; Ringsdorf, Helmut; Bennema, Piet

    1996-06-01

    In this paper we report our recent investigations on the morphological evolution of fractal-like domains of the liquid-condensed (LC) phase in lipid monolayers. It is demonstrated that the dimension of the LC domains increases upon continuous illumination of microscope light. The experimental data indicate that the increasing rate of fractal dimension of the LC domains depends on the concentration of fluorescence probes. By analyzing the domain growth process we find that the self-similarity of the pattern disappears gradually during its growth. The possible mechanism behind the observed phenomena is discussed.

  12. Effect of cyclodextrin complexation on the in vivo disposition of the brain imaging radiopharmaceutical 99mTechnetium ethyl cysteinate dimer (99mTc-ECD).

    PubMed

    Oliver, D W; Dormehl, I C; Louw, W; Kilian, E; de Beco, V; Morretti, J L

    2000-08-01

    The brain imaging radiopharmaceutical, 99mTechnetium ethyl cysteinate dimer (99mTc-ECD, 99mTc-bicisate) is the most recent addition to the available set of radiopharmaceuticals for measuring cerebral blood flow. Ideally radiotracers should be trapped in the brain long enough so that their distribution can be quantitated and should demonstrate good spatial resolution. Furthermore, the stability (chemical and metabolic) and bioavailability of radiopharmaceuticals have in general proved to be a challenge during development and clinical administration. In view of these challenges and background, this study with 99mTc-ECD is presented. The aims of this research program were to develop novel approaches to improve the chemical and metabolic stability and the bioavailability of 99mTc-ECD across the blood brain barrier for cerebral blood flow determinations, using the well known non-human primate in vivo baboon model. These aims were addressed by investigating the influence of cyclodextrin--99mTc-ECD complexation on normal cerebral blood flow patterns, using two different cyclodextrins, i.e., gamma-cyclodextrin (CAS 17465-86-0) and beta-trimethylcyclodextrin (CAS 55216-11-0). The effect of incubation of 99mTc-ECD (with or without cyclodextrin complexation) in plasma, on metabolic esterase action, was also investigated. Possible protection against plasma esterase by acetylcholine (CAS 51-84-3) of 99mTc-ECD was further determined. The current study has shown that cyclodextrin complexation of 99mTc-ECD indeed offers a useful approach to improve the stability of the radiopharmaceutical against peripheral metabolism. The acetylcholine shows also potential to protect 99mTc-ECD. However, it is clear from the current data that the choice of cyclodextrin is of utmost importance, as has been observed from significantly reduced the bioavailability of 99mTc-ECD when complexed with beta-trimethylcyclodextrin. The plasma incubation procedures showed that gamma-cyclodextrin offers

  13. Novel band structures in silicene on monolayer zinc sulfide substrate.

    PubMed

    Li, Sheng-shi; Zhang, Chang-wen; Yan, Shi-shen; Hu, Shu-jun; Ji, Wei-xiao; Wang, Pei-ji; Li, Ping

    2014-10-01

    Opening a sizable band gap in the zero-gap silicene without lowering the carrier mobility is a key issue for its application in nanoelectronics. Based on first-principles calculations, we find that the interaction energies are in the range of -0.09‒0.3 eV per Si atom, indicating a weak interaction between silicene and ZnS monolayer and the ABZn stacking is the most stable pattern. The band gap of silicene can be effectively tuned ranging from 0.025 to 1.05 eV in silicene and ZnS heterobilayer (Si/ZnS HBL). An unexpected indirect-direct band gap crossover is also observed in HBLs, dependent on the stacking pattern, interlayer spacing and external strain effects on silicene. Interestingly, the characteristics of Dirac cone with a nearly linear band dispersion relation of silicene can be preserved in the ABS pattern which is a metastable state, accompanied by a small electron effective mass and thus the carrier mobility is expected not to degrade much. These provide a possible way to design effective FETs out of silicene on a ZnS monolayer.

  14. Inhibition of cyclodextrins on α-galactosidase.

    PubMed

    Yao, Di; Zhu, Zhenzhou; Cai, Hongyan; Chen, Xuan; Sun, Wei; Barba, Francisco J; Li, Fang; Shen, Wangyang; Ding, Wenping

    2017-02-15

    This work successfully investigated the effects of different influential factors and hydrophobic cavities of cyclodextrins (CDs) on α-galactosidase (α-Gal) by detecting α-Gal activity. The highest inhibitory concentration of three kinds of CDs (α-, β-, and γ-CD) on α-Gal was 10mM. Moreover, the highest inhibition of α-Gal was obtained under the following conditions: reaction time of 90min, temperature of 30°C, and pH 6.0. Compared with other CDs, β-CD showed more ability to interact with α-Gal due to its appropriate cavity geometric dimensions. From circular dichroism and nuclear magnetic resonance it was observed that β-CD changed the secondary structure of α-Gal and formed a hydrogen bond with this enzyme. PMID:27664608

  15. Cucurbituril and Cyclodextrin Complexes of Dendrimers

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Kaifer, Angel E.

    This chapter reviews the growing body of data on the binding interactions between dendrimers and two types of well-established molecular hosts: cyclodextrins and cucurbit[n]urils. Dendrimers are highly branched macromolecules to which functional groups can be attached in spatially defined locations. The attachment of guest functional groups to dendrimers allows the investigation of their binding interactions with freely diffusing hosts/receptors. The effect of dendrimer size on the thermodynamics of these host-guest reactions varies widely depending on factors described here. In optimum cases, it is possible to use these binding interactions to exert redox control on dendrimer self-assembly and even control the size of the resulting assemblies.

  16. Recognition of Monomers and Polymers by Cyclodextrins

    NASA Astrophysics Data System (ADS)

    Wenz, Gerhard

    Cyclodextrins (CDs), cyclic oligomers consisting of 6, 7, 8, or more α(1 → 4)-linked glucose units, are readily available, water-soluble organic host compounds that are able to complex organic guest molecules if the latter contain a suitable hydrophobic binding site. The main driving forces are nonpolar interactions such as hydrophobic and van der Waals interactions. CDs are able to recognize the thickness, polarity, and chirality of monomeric and polymeric guest molecules. In addition, functional groups can be covalently attached to CDs to modify or improve the molecular recognition capability of CDs. In this review, the binding potentials of the most important CDs and CD derivatives are summarized, and general rules for the recognition of monomeric and polymeric guests are derived. A supramolecular tool box of water-soluble hosts and guests is provided, which allows the assembly of many sophisticated supramolecular structures, as well as rotaxanes and polyrotaxanes.

  17. Functional Cyclodextrin Polyrotaxanes for Drug Delivery

    NASA Astrophysics Data System (ADS)

    Yui, Nobuhiko; Katoono, Ryo; Yamashita, Atsushi

    The mobility of cyclodextrins (CDs) threaded onto a linear polymeric chain and the dethreading of the CDs from the chain are the most fascinating features seen in polyrotaxanes. These structural characteristics are very promising for their possible applications in drug delivery. Enhanced multivalent interaction between ligand-receptor systems by using ligand-conjugated polyrotaxanes would be just one of the excellent properties related to the CD mobility. Gene delivery using cytocleavable polyrotaxanes is a more practical but highly crucial issue in drug delivery. Complexation of the polyrotaxanes with DNA and its intracellular DNA release ingeniously utilizes both CD mobility and polyrotaxane dissociation to achieve effective gene delivery. Such a supramolecular approach using CD-containing polyrotaxanes is expected to exploit a new paradigm of biomaterials.

  18. Cyclodextrins in non-viral gene delivery.

    PubMed

    Lai, Wing-Fu

    2014-01-01

    Cyclodextrins (CDs) are naturally occurring cyclic oligosaccharides. They consist of (α-1,4)-linked glucose units, and possess a basket-shaped topology with an "inner-outer" amphiphilic character. Over the years, substantial efforts have been undertaken to investigate the possible use of CDs in drug delivery and controlled drug release, yet the potential of CDs in gene delivery has received comparatively less discussion in the literature. In this article, we will first discuss the properties of CDs for gene delivery, followed by a synopsis of the use of CDs in development and modification of non-viral gene carriers. Finally, areas that are noteworthy in CD-based gene delivery will be highlighted for future research. Due to the application prospects of CDs, it is anticipated that CDs will continue to emerge as an important tool for vector development, and will play significant roles in facilitating non-viral gene delivery in the forthcoming decades. PMID:24103652

  19. Cyclodextrin-based gene delivery systems.

    PubMed

    Ortiz Mellet, Carmen; García Fernández, José M; Benito, Juan M

    2011-03-01

    Cyclodextrin (CD) history has been largely dominated by their unique ability to form inclusion complexes with guests fitting in their hydrophobic cavity. Chemical funcionalization was soon recognized as a powerful mean for improving CD applications in a wide range of fields, including drug delivery, sensing or enzyme mimicking. However, 100 years after their discovery, CDs are still perceived as novel nanoobjects of undeveloped potential. This critical review provides an overview of different strategies to promote interactions between CD conjugates and genetic material by fully exploiting the inside-outside/upper-lower face anisotropy of the CD nanometric platform. Covalent modification, self-assembling and supramolecular ligation can be put forward with the ultimate goal to build artificial viruses for programmed and efficient gene therapy (222 references).

  20. Microwave-assisted synthesis of cyclodextrin polyurethanes.

    PubMed

    Biswas, Atanu; Appell, Michael; Liu, Zengshe; Cheng, H N

    2015-11-20

    Cyclodextrin (CD) has often been incorporated into polyurethanes in order to facilitate its use in encapsulation or removal of organic species for various applications. In this work a microwave-assisted method has been developed to produce polyurethanes consisting of α-, β-, and γ-CD and three common diisocyanates. As compared to conventional heating, this new synthetic method saves energy, significantly reduces reaction time, and gets similar or improved yield. The reaction products have been fully characterized with (13)C, (1)H, and two-dimensional NMR spectroscopy. With suitable stoichiometry of starting CD and diisocyanate, the resulting CD polyurethane is organic-soluble and water-insoluble and is shown to remove Nile red dye and phenol from water. Possible applications include the removal of undesirable materials from process streams, toxic compounds from the environment, and encapsulation of color or fragrance molecules.

  1. Microwave-assisted synthesis of cyclodextrin polyurethanes.

    PubMed

    Biswas, Atanu; Appell, Michael; Liu, Zengshe; Cheng, H N

    2015-11-20

    Cyclodextrin (CD) has often been incorporated into polyurethanes in order to facilitate its use in encapsulation or removal of organic species for various applications. In this work a microwave-assisted method has been developed to produce polyurethanes consisting of α-, β-, and γ-CD and three common diisocyanates. As compared to conventional heating, this new synthetic method saves energy, significantly reduces reaction time, and gets similar or improved yield. The reaction products have been fully characterized with (13)C, (1)H, and two-dimensional NMR spectroscopy. With suitable stoichiometry of starting CD and diisocyanate, the resulting CD polyurethane is organic-soluble and water-insoluble and is shown to remove Nile red dye and phenol from water. Possible applications include the removal of undesirable materials from process streams, toxic compounds from the environment, and encapsulation of color or fragrance molecules. PMID:26344257

  2. A spectrofluorimetric method for determining the association constants of pyrene with cyclodextrins based on polarity variation

    NASA Astrophysics Data System (ADS)

    Kusumoto, Yoshihumi

    1987-05-01

    The association constants of pyrene inclusion complexes with β-cyclodextrin and methylated β-cyclodextrins were determined using equations which provide an accurate description of the variation in the vibronic-band-intensity ratio of pyrene monomer fluorescence in the presence of cyclodextrins.

  3. Multicellular automaticity of cardiac cell monolayers: effects of density and spatial distribution of pacemaker cells

    NASA Astrophysics Data System (ADS)

    Elber Duverger, James; Boudreau-Béland, Jonathan; Le, Minh Duc; Comtois, Philippe

    2014-11-01

    Self-organization of pacemaker (PM) activity of interconnected elements is important to the general theory of reaction-diffusion systems as well as for applications such as PM activity in cardiac tissue to initiate beating of the heart. Monolayer cultures of neonatal rat ventricular myocytes (NRVMs) are often used as experimental models in studies on cardiac electrophysiology. These monolayers exhibit automaticity (spontaneous activation) of their electrical activity. At low plated density, cells usually show a heterogeneous population consisting of PM and quiescent excitable cells (QECs). It is therefore highly probable that monolayers of NRVMs consist of a heterogeneous network of the two cell types. However, the effects of density and spatial distribution of the PM cells on spontaneous activity of monolayers remain unknown. Thus, a simple stochastic pattern formation algorithm was implemented to distribute PM and QECs in a binary-like 2D network. A FitzHugh-Nagumo excitable medium was used to simulate electrical spontaneous and propagating activity. Simulations showed a clear nonlinear dependency of spontaneous activity (occurrence and amplitude of spontaneous period) on the spatial patterns of PM cells. In most simulations, the first initiation sites were found to be located near the substrate boundaries. Comparison with experimental data obtained from cardiomyocyte monolayers shows important similarities in the position of initiation site activity. However, limitations in the model that do not reflect the complex beat-to-beat variation found in experiments indicate the need for a more realistic cardiomyocyte representation.

  4. Microcontact printing of self-assembled monolayers: applications in microfabrication

    NASA Astrophysics Data System (ADS)

    Wilbur, James L.; Kumar, Amit; Biebuyck, Hans A.; Kim, Enoch; Whitesides, George M.

    1996-12-01

    This paper describes applications in microfabrication using patterned self-assembled monolayers (SAMs) formed by microcontact printing. Microcontact printing 0957-4484/7/4/028/img1 is a flexible new technique that forms patterned SAMs with regions terminated by different chemical functionalities (and thus different physical and chemical properties), in patterns with 0957-4484/7/4/028/img2 dimensions. Patterns of SAM are formed using an alkanethiol as an `ink', and printing the alkanethiol on a metal support with elastomeric `stamp'. We fabricate the stamp by moulding a silicone elastomer using a master prepared by optical or x-ray microlithography or by other techniques. SAMs of long-chain alkanethiolates on gold and other metals can act as nanometer resists by protecting the supporting metal from corrosion by appropriately formulated etchants: the fabrication of microstructures of gold and silicon demonstrates the utility of patterned SAMs (formed by 0957-4484/7/4/028/img3) as nm resists. Patterned SAMs formed by 0957-4484/7/4/028/img3 can also control the wettability of a surface on the 0957-4484/7/4/028/img2 scale. The organization of liquids in patterned arrays with 0957-4484/7/4/028/img2 dimensions, and the patterned deposition of microcrystals and microcrystal arrays illustrate the use of controlled wettability for microfabrication.

  5. Laser-Induced Spallation of Microsphere Monolayers.

    PubMed

    Hiraiwa, Morgan; Stossel, Melicent; Khanolkar, Amey; Wang, Junlan; Boechler, Nicholas

    2016-08-01

    The detachment of a semiordered monolayer of polystyrene microspheres adhered to an aluminum-coated glass substrate is studied using a laser-induced spallation technique. The microsphere-substrate adhesion force is estimated from substrate surface displacement measurements obtained using optical interferometry, and a rigid-body model that accounts for the inertia of the microspheres. The estimated adhesion force is compared with estimates obtained using an adhesive contact model together with interferometric measurements of the out-of-plane microsphere contact resonance, and with estimated work of adhesion values for the polystyrene-aluminum interface. Scanning electron microscope images of detached monolayer regions reveal a unique morphology, namely, partially detached monolayer flakes composed of single hexagonal close packed crystalline domains. This work contributes to the fields of microsphere adhesion and contact dynamics, and demonstrates a unique monolayer delamination morphology. PMID:27409715

  6. Monolayer graphene from a green solid precursor

    NASA Astrophysics Data System (ADS)

    Kalita, Golap; Wakita, Koichi; Umeno, Masayoshi

    2011-06-01

    Monolayer and bilayer graphene sheets are synthesized by simple control pyrolysis of solid botanical derivative camphor (C 10H 16O), a green and renewable carbon source. Raman studies show much intense 2D peak than that of G peak, signifying presence of monolayer graphene. Transmission electron microscopic study shows predominately monolayer or bilayer graphene sheets, while trilayer graphene sheet were also observed. Synthesized graphene film on copper foil is transferred to poly(ethylene terephthalate) substrate to fabricate transparent electrode. Electrical and optical measurement shows a sheet resistance of 860 Ω/sq with a transmittance of 91% at 550 nm wavelength of the graphene film. The technique to fabricate monolayer or bilayer graphene based film from camphor is both viable and scalable for potential large area electronic applications.

  7. Accurate Molecular Dimensions from Stearic Acid Monolayers.

    ERIC Educational Resources Information Center

    Lane, Charles A.; And Others

    1984-01-01

    Discusses modifications in the fatty acid monolayer experiment to reduce the inaccurate moleculary data students usually obtain. Copies of the experimental procedure used and a Pascal computer program to work up the data are available from the authors. (JN)

  8. Large Friction Anisotropy of a Polydiacetylene Monolayer

    SciTech Connect

    Burns, A.R.; Carpick, R.W.; Sasaki, D.Y.

    1999-05-11

    Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties.

  9. Nonequilibrium bubbles in a flowing langmuir monolayer.

    PubMed

    Muruganathan, Rm; Khattari, Z; Fischer, Th M

    2005-11-24

    We investigate the nonequilibrium behavior of two-dimensional gas bubbles in Langmuir monolayers. A cavitation bubble is induced in liquid expanded phase by locally heating a Langmuir monolayer with an IR-laser. At low IR-laser power the cavitation bubble is immersed in quiescent liquid expanded monolayer. At higher IR-laser power thermo capillary flow around the laser-induced cavitation bubble sets in. The thermo capillary flow is caused by a temperature dependence of the gas/liquid line tension. The slope of the line tension with temperature is determined by measuring the thermo capillary flow velocity. Thermodynamically stable satellite bubbles are generated by increasing the surface area of the monolayer. Those satellite bubbles collide with the cavitation bubble. Upon collision the satellite bubbles either coalesce with the cavitation bubble or slide past the cavitation bubble. Moreover we show that the satellite bubbles can also be produced by the emission from the laser-induced cavitation bubbles.

  10. Synthesis of polyrotaxanes from acetyl-β-cyclodextrin

    NASA Astrophysics Data System (ADS)

    Ristić, I. S.; Nikolić, L.; Nikolić, V.; Ilić, D.; Budinski-Simendić, J.

    2011-12-01

    Polyrotaxanes are intermediary products in the synthesis of topological gels. They are created by inclusion complex formation of hydrophobic linear macromolecules with cyclodextrins or their derivatives. Then, pairs of cyclodextrin molecules with covalently linkage were practically forming the nodes of the semi-flexible polymer network. Such gels are called topological gels and they can absorb huge quantities of water due to the net flexibility allowing the poly(ethylene oxide) chains to slide through the cyclodextrin cavities, without being pulled out altogether. For polyrotaxane formation poly(ethylene oxide) was used like linear macromolecules. There are hydroxyl groups at poly(ethylene oxide) chains, whereby the linking of the voluminous molecules should be made. To avoid the reaction of cyclodextrin OH groups with stoppers, they should be protected by, e.g., acetylation. In this work, the acetylation of the OH groups of β-cyclodextrin was performed by acetic acid anhydride with iodine as the catalyst. The acetylation reaction was assessed by the FTIR and HPLC method. By the HPLC analysis was found that the acetylation was completed in 20 minutes. Inserting of poly(ethylene oxide) with 4000 g/mol molecule mass into acetyl-β-cyclodextrin with 2:1 poly(ethylene oxide) monomer unit to acetyl-β-cyclodextrin ratio was also monitored by FTIR, and it was found that the process was completed in 12 h at the temperature of 10°C. If the process is performed at temperatures above 10°C, or for periods longer than 12 hours, the process of uncontrolled hydrolysis of acetate groups was initiated.

  11. Functionalized self-assembled monolayers as templates for mineral oxide thin film deposition

    NASA Astrophysics Data System (ADS)

    Collins, Rochael Jeannine

    Alkyl-trichlorosilanes functionalized with thioacetate and nitrate groups were synthesized and deposited to form Self-Assembled Monolayers (SAMs). In situ transformation of the thioacetate and nitrate moieties yielded monolayers functionalized with sulfonate and alcohol groups, respectively. Percent conversion was determined to be 98% by X-ray photoelectron spectroscopy (XPS) for the thioacetate to sulfonate transformation, and 100% by XPS and IR for the nitrate to alcohol transformation. The as-deposited and transformed monolayers were characterized by wettability, XPS and ellipsometry. The alcohol terminated films were investigated as templates for the deposition of subsequent self-assembled monolayers. Multilayers, up to three layers, were demonstrated for nitrate films, with each layer adding an average of 2.25 nm to the overall film thickness. A fourth layer of octadecyltrichlorosilane was deposited and was found to add an additional 1.31 nm to the structure. Analysis of the multilayer constructions revealed increasing disorder as the number of layers increases. Other in situ functionalizations of alcohol terminated monolayers were demonstrated. Transformation to electrophilic, haloacetyl films was accomplished, and their reactivity with thiol nucleophiles was examined. In addition, the alcohol terminated SAMs were functionalized, in situ, with sulfate and phosphate groups. These films were characterized by wettability, XPS and ellipsometry. Furthermore, photopatterning of terminal functional groups was accomplished by irradiation through a mask. Patterned monolayers consisting of regions of thioacetate (masked)/sulfonate (irradiated) and nitrate (masked)/alcohol (irradiated) were demonstrated. Characterization of the patterned monolayers was carried out by XPS and SEM. A variety of terminal functional groups on the SAM were investigated as templates for bioinspired deposition of mineral oxide films. Thin films of FeOOH, SiOsb2,\\ TiOsb2,\\ Ysb2Osb3,\\ ZrOsb2

  12. Molecular organization in phospholipid monolayer domains by correlative fluorescence microscopy and electron diffraction.

    PubMed

    Hui, S W; Yu, H

    1994-04-01

    Lipid monolayer is a half leaflet model for lipid bilayer, which forms the basis of biological membranes. Within a certain range of surface area per molecular of phospholipid monolayers at the air-water interface, where the compressibility was nearly infinite, two phases with different molecular packings were observable by fluorescence microscopy. Mixed-phase monolayers of L-1,2-dipalmitoyl-N-monomethyl-3-phosphatidylethanolamine [DP(Me)PE] or L-1,2-dipalmitoyl-N-dimethyl-3-phosphatidyl-ethanolamine [DP(Me)2PE] were deposited on marker grids coated with Formvar films. The molecular organization in the dark and bright fluorescent areas on the grids was investigated by low dose, selected area electron diffraction. Sharp reflection arcs, at a spacing of 4.2A and arranged in a hexagon pattern, were detected from dark domains of both lipids. A diffuse reflection ring at a spacing of 4.6A was derived from the bright background areas. Diffraction patterns were obtained from neighboring areas along selected dark domains of both lipids. The orientations of diffraction patterns from areas along smooth and curving boundaries of DP(Me)2PE domains were found to turn with the boundaries. In the branching domains of DP(Me)PE, the orientations of diffraction patterns indicated that the branches were formed by twinning. Electron diffraction thus provides an unique way to sample the local molecular packing order and orientation within individual domains in phospholipid monolayers.

  13. A versatile approach towards the compaction, decompaction, and immobilization of DNA at interfaces by using cyclodextrins.

    PubMed

    González-Pérez, Alfredo; Ruso, Juan M

    2013-08-01

    We investigate the temperature dependence of interactions of β-cyclodextrin (CD)/hexadecyltrimethylammonium bromide (CTAB) self-assemblies with DNA during the decompaction of DNA/CTAB complexes. By combining direct imaging techniques with density and sound-velocity measurements, we can explain the decompaction process and suggest a suitable model. The DNA-decompaction process by using CDs is accompanied by interactions with surfaces, such as glass or mica. The mechanism of β-CD/CTAB self-assembly is elucidated and the immobilization of DNA onto negatively charged surfaces is explained. Differences between the fractal dimensions of DNA that is adsorbed onto the surfaces are related to strong and weak binding, which permit the partial relaxation of DNA on the surfaces. The β-CD/CTAB self-assembled monolayers are demonstrated to be a facile and efficient route for surface functionalization, which allows for the immobilization of biomacromolecules in close proximity without any intermediate binding or deprotection steps. Moreover, this route is expected to show several advantages that might contribute to improving the performance of future biosensors as gentle immobilization-limiting alteration of the protein structure, oriented immobilization, thereby allowing homogeneous accessibility, reversible immobilization, thereby allowing reutilizations, and high compatibility with various types of biomacromolecules.

  14. Cyclodextrin-modified zeolites: host-guest surface chemistry for the construction of multifunctional nanocontainers.

    PubMed

    Szarpak-Jankowska, Anna; Burgess, Christine; De Cola, Luisa; Huskens, Jurriaan

    2013-10-25

    The functionalization of nanoporous zeolite L crystals with β-cyclodextrin (CD) has been demonstrated. The zeolite surface was first modified with amino groups by using two different aminoalkoxysilanes. Then, 1,4-phenylene diisothiocyanate was reacted with the amino monolayer and used to bind CD heptamine by using its remaining isothiocyanate groups. The use of the different aminoalkoxysilanes, 3-aminopropyl dimethylethoxysilane (APDMES) and 3-aminopropyl triethoxysilane (APTES), led to drastic differences in uptake and release properties. Thionine was found to be absorbed and released from amino- and CD-functionalized zeolites when APDMES was used, whereas functionalization by APTES led to complete blockage of the zeolite channels. Fluorescence microscopy showed that the CD groups covalently attached to the zeolite crystals could bind adamantyl-modified dyes in a specific and reversible manner. This strategy allowed the specific immobilization of His-tagged proteins by using combined host-guest and His-tag-Ni-nitrilotriacetic acid (NTA) coordination chemistry. Such multifunctional systems have the potential for encapsulation of drug molecules inside the zeolite pores and non-covalent attachment of other (for example, targeting) ligand molecules on its surface.

  15. Mass spectrometric analysis of monolayer protected nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhu, Zhengjiang

    Monolayer protected nanoparticles (NPs) include an inorganic core and a monolayer of organic ligands. The wide variety of core materials and the tunable surface monolayers make NPs promising materials for numerous applications. Concerns related to unforeseen human health and environmental impacts of NPs have also been raised. In this thesis, new analytical methods based on mass spectrometry are developed to understand the fate, transport, and biodistributions of NPs in the complex biological systems. A laser desorption/ionization mass spectrometry (LDI-MS) method has been developed to characterize the monolayers on NP surface. LDI-MS allows multiple NPs taken up by cells to be measured and quantified in a multiplexed fashion. The correlations between surface properties of NPs and cellular uptake have also been explored. LDI-MS is further coupled with inductively coupled plasma mass spectrometry (ICP-MS) to quantitatively measure monolayer stability of gold NPs (AuNPs) and quantum dots (QDs), respectively, in live cells. This label-free approach allows correlating monolayer structure and particle size with NP stability in various cellular environments. Finally, uptake, distribution, accumulation, and excretion of NPs in higher order organisms, such as fish and plants, have been investigated to understand the environmental impact of nanomaterials. The results indicate that surface chemistry is a primary determinant. NPs with hydrophilic surfaces are substantially less toxic and present a lower degree of bioaccumulation, making these nanomaterials attractive for sustainable nanotechnology.

  16. Cyclodextrin-surfactant coassembly depends on the cyclodextrin ability to crystallize.

    PubMed

    Carlstedt, Jonas; Bilalov, Azat; Krivtsova, Elena; Olsson, Ulf; Lindman, Björn

    2012-02-01

    Full equilibrium phase diagrams are presented for two ternary systems composed of the cationic surfactant dodecyltrimethylammonium bromide (DTAB), water (D(2)O), and a cyclodextrin, either β-cyclodextrin (β-CD) or (2-hydroypropyl)-β-cyclodextrin (2HPβCD). (2)H NMR, SAXS, WAXS, and visual examination were used to determine the phase boundaries and characterize the nature of the phases formed. Additionally, diffusion (1)H NMR was used to investigate parts of the diagrams. The water solubility of 2HPβCD is 80% (w/w), whereas it is only 1.85% (w/w) for β-CD. Solubility increases for both species upon complexation with DTAB; while the increase is minute for 2HPβCD, it is dramatic for β-CD. Both systems displayed an isotropic liquid solution (L(1)) one-phase region, the extension of which differs extensively between the two systems. Additionally, the DTAB:2HPβCD:water system also comprised a normal hexagonal (H(1)) area, which was not found for the DTAB:β-CD:water system. In the DTAB:β-CD:water system, on the other hand, we found cocrystallization of DTAB and β-CD. From this work we conclude that DTAB and CD molecules form 1:1 inclusion complexes with high affinities. Moreover, we observed indications of an association of 2HPβCD to DTAB micelles in the isotropic solution phase, which was not the case for β-CD and DTAB micelles. This is, to our knowledge, the first complete phase diagrams of surfactant-CD mixtures; as a novel feature it includes the observation of cocrystallization at high concentrations.

  17. New synthetic strategies for xanthene-dye-appended cyclodextrins

    PubMed Central

    Darcsi, Andras; Balint, Mihaly; Benkovics, Gabor; Sohajda, Tamas; Beni, Szabolcs

    2016-01-01

    Summary Xanthene dyes can be appended to cyclodextrins via an ester or amide bridge in order to switch the fluorescence on or off. This is made possible through the formation of nonfluorescent lactones or lactams as the fluorophore can reversibly cyclize. In this context we report a green approach for the synthesis of switchable xanthene-dye-appended cyclodextrins based on the coupling agent 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM). By using 6-monoamino-β-cyclodextrin and commercially available inexpensive dyes, we prepared rhodamine- and fluorescein-appended cyclodextrins. The compounds were characterized by NMR and IR spectroscopy and MS spectrometry, their UV–vis spectra were recorded at various pH, and their purity was determined by capillary electrophoresis. Two potential models for the supramolecular assembly of the xanthene-dye-appended cyclodextrins were developed based on the set of data collected by the extensive NMR characterization. PMID:27340446

  18. Cyclodextrin-based hydrogels toward improved wound dressings.

    PubMed

    Pinho, Eva; Grootveld, Martin; Soares, Graça; Henriques, Mariana

    2014-12-01

    Optimal wound dressings should be capable of mechanical wound protection and also facilitate the healing process via maintenance of suitable environmental conditions and the controlled delivery of bioactive molecules. Hydrogels present suitable properties for wound-dressing applications such as good biocompatibility, together with a high water content, the latter of which is important for the maintenance of a moist environment and ready removal from the wound with a minimal level of associated pain. However, their properties as drug delivery systems can be improved by the use of cyclodextrins as cross-linking agents. Cyclodextrins have been extensively used as "carriers" on food, textile, cosmetic and, most especially, in the pharmaceutical industry in view of their powerful complexation abilities and biocompatibilities, together with further desirable characteristics. The conjugation of cyclodextrins with hydrogels may allow the achievement of an optimal wound-dressing material, because the hydrogel component will maintain the moist environment required for the healing process, and the cyclodextrin moiety has the ability to protect and modulate the release of bioactive molecules. Therefore, this review aims to gather information regarding cyclodextrin-based hydrogels for possible wound-dressing applications.

  19. Cyclodextrins in Food Technology and Human Nutrition: Benefits and Limitations.

    PubMed

    Fenyvesi, É; Vikmon, M; Szente, L

    2016-09-01

    Cyclodextrins are tasteless, odorless, nondigestible, noncaloric, noncariogenic saccharides, which reduce the digestion of carbohydrates and lipids. They have low glycemic index and decrease the glycemic index of the food. They are either non- or only partly digestible by the enzymes of the human gastrointestinal (GI) tract and fermented by the gut microflora. Based on these properties, cyclodextrins are dietary fibers useful for controlling the body weight and blood lipid profile. They are prebiotics, improve the intestinal microflora by selective proliferation of bifidobacteria. These antiobesity and anti-diabetic effects make them bioactive food supplements and nutraceuticals. In this review, these features are evaluated for α-, β- and γ-cyclodextrins, which are the cyclodextrin variants approved by authorities for food applications. The mechanisms behind these effects are reviewed together with the applications as solubilizers, stabilizers of dietary lipids, such as unsaturated fatty acids, phytosterols, vitamins, flavonoids, carotenoids and other nutraceuticals. The recent applications of cyclodextrins for reducing unwanted components, such as trans-fats, allergens, mycotoxins, acrylamides, bitter compounds, as well as in smart active packaging of foods are also overviewed. PMID:25764389

  20. Characterization of folic acid/native cyclodextrins host-guest complexes in solution

    NASA Astrophysics Data System (ADS)

    Ceborska, Magdalena; Zimnicka, Magdalena; Wszelaka-Rylik, Małgorzata; Troć, Anna

    2016-04-01

    The complexation of folic acid (FA) with native cyclodextrins was studied and this process was used for the comparison of 1H NMR, ITC and ESIMS for the evaluation of association constants. The stability increases in the series: α-cyclodextrin/FA < γ-cyclodextrin/FA < β-cyclodextrin/FA. 1H NMR and ITC gave comparable results in regard to association constant values, while results obtained for MS were considerably higher due to different interactions (electrostatic instead of hydrophobic) responsible for the stabilization of the complexes. The dimerization of FA in water was also studied, as well as its impact on the process of complexation with native cyclodextrins.

  1. Mysterious Lattice Rotations in Adsorbed Monolayers

    NASA Astrophysics Data System (ADS)

    Diehl, Renee D.

    1997-03-01

    Lattice rotations due to a mismatch in structure have been observed in film growth for many years, probably beginning in the 1930's with the Nishiyama-Wasserman and Kurdjumov-Sachs orientations observed when fcc(111) films grow on bcc(110) surfaces, or vice versa. Early analysis of this problem was carried out with the aid of Moiré patterns and the observation that the preferred lattice orientations are those which maximize the Moiré fringe spacing. Later energy calculations indicated that the structures which were predicted by the the Moiré technique actually do correspond to energy minima. Epitaxial rotation in adsorbed monolayers is a conceptually simpler problem since in principle it involves only two planes of atoms, and it was first observed in 1977 for Ar on a graphite surface(C. G. Shaw, M. D. Chinn, S. C. Fain, Jr. Phys. Rev. Lett. 41 (1978) 955.). This observation came only a few months after a new theory, based on the expected elastic behavior of an overlayer, was developed by A. D. Novaco and J. P. McTague(A. D. Novaco and J. P. McTague, Phys. Rev. Lett. 38 (1977) 1286.), and the agreement with the experimental results was remarkable. It was later shown that a few symmetry principles similar to those used for the film growth studies sometimes can also predict the observed structures. However, the situation for incommensurate layers physisorbed on metal surfaces currently looks bleak. None of the existing theories or models appears to describe the experimental results. New data for physisorbed gases on metal surfaces will be presented, along with some half-baked (and probably wrong) ideas for what might be happening. This work was supported by NSF.

  2. Protein-Induced Surface Structuring in Myelin Membrane Monolayers

    PubMed Central

    Rosetti, Carla M.; Maggio, Bruno

    2007-01-01

    Monolayers prepared from myelin conserve all the compositional complexity of the natural membrane when spread at the air-water interface. They show a complex pressure-dependent surface pattern that, on compression, changes from the coexistence of two liquid phases to a viscous fractal phase embedded in a liquid phase. We dissected the role of major myelin protein components, myelin basic protein (MBP), and Folch-Lees proteolipid protein (PLP) as crucial factors determining the structural dynamics of the interface. By analyzing mixtures of a single protein with the myelin lipids we found that MBP and PLP have different surface pressure-dependent behaviors. MBP stabilizes the segregation of two liquid phases at low pressures and becomes excluded from the film under compression, remaining adjacent to the interface. PLP, on the contrary, organizes a fractal-like pattern at all surface pressures when included in a monolayer of the protein-free myelin lipids but it remains mixed in the MBP-induced liquid phase. The resultant surface topography and dynamics is regulated by combined near to equilibrium and out-of-equilibrium effects. PLP appears to act as a surface skeleton for the whole components whereas MBP couples the structuring to surface pressure-dependent extrusion and adsorption processes. PMID:17905850

  3. Photocatalytic Nanolithography of Self-Assembled Monolayers and Proteins

    PubMed Central

    2013-01-01

    Self-assembled monolayers of alkylthiolates on gold and alkylsilanes on silicon dioxide have been patterned photocatalytically on sub-100 nm length-scales using both apertured near-field and apertureless methods. Apertured lithography was carried out by means of an argon ion laser (364 nm) coupled to cantilever-type near-field probes with a thin film of titania deposited over the aperture. Apertureless lithography was carried out with a helium–cadmium laser (325 nm) to excite titanium-coated, contact-mode atomic force microscope (AFM) probes. This latter approach is readily implementable on any commercial AFM system. Photodegradation occurred in both cases through the localized photocatalytic degradation of the monolayer. For alkanethiols, degradation of one thiol exposed the bare substrate, enabling refunctionalization of the bare gold by a second, contrasting thiol. For alkylsilanes, degradation of the adsorbate molecule provided a facile means for protein patterning. Lines were written in a protein-resistant film formed by the adsorption of oligo(ethylene glycol)-functionalized trichlorosilanes on glass, leading to the formation of sub-100 nm adhesive, aldehyde-functionalized regions. These were derivatized with aminobutylnitrilotriacetic acid, and complexed with Ni2+, enabling the binding of histidine-labeled green fluorescent protein, which yielded bright fluorescence from 70-nm-wide lines that could be imaged clearly in a confocal microscope. PMID:23971891

  4. Ultraclean and large-area monolayer hexagonal boron nitride on Cu foil using chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wen, Yao; Shang, Xunzhong; Dong, Ji; Xu, Kai; He, Jun; Jiang, Chao

    2015-07-01

    Atomically thin hexagonal boron nitride (h-BN) has been demonstrated to be an excellent dielectric layer as well as an ideal van der Waals epitaxial substrate for fabrication of two-dimensional (2D) atomic layers and their vertical heterostructures. Although many groups have obtained large-scale monolayer h-BN through low pressure chemical vapor deposition (LPCVD), it is still a challenge to grow clean monolayers without the reduction of domain size. Here we report the synthesis of large-area (4 × 2 cm2) high quality monolayer h-BN with an ultraclean and unbroken surface on copper foil by using LPCVD. A detailed investigation of the key factors affecting growth and transfer of the monolayer was carried out in order to eliminate the adverse effects of impurity particles. Furthermore, an optimized transfer approach allowed the nondestructive and clean transfer of the monolayer from copper foil onto an arbitrary substrate, including a flexible substrate, under mild conditions. Atomic force microscopy indicated that the root-mean-square (RMS) roughness of the monolayer h-BN on SiO2 was less than 0.269 nm for areas with fewer wrinkles. Selective area electron diffraction analysis of the h-BN revealed a pattern of hexagonal diffraction spots, which unambiguously demonstrated its highly crystalline character. Our work paves the way toward the use of ultraclean and large-area monolayer h-BN as the dielectric layer in the fabrication of high performance electronic and optoelectronic devices for novel 2D atomic layer materials.

  5. A novel approach for grafting of β-cyclodextrin onto wool via laccase/TEMPO oxidation.

    PubMed

    Yu, Yuanyuan; Wang, Qiang; Yuan, Jiugang; Fan, Xuerong; Wang, Ping

    2016-11-20

    This study demonstrated a new enzymatic methodology to graft β-cyclodextrin onto wool. The primary hydroxyl groups in β-cyclodextrin were oxidized to aldehyde groups using laccase/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), which reacted with the amino groups of wool to form Schiff bases. The effects of treatment conditions (treatment temperature, laccase dosage, TEMPO dosage, treatment time) on the aldehyde and carboxyl contents in β-cyclodextrin were studied. FTIR spectrum of oxidized β-cyclodextrin showed the presence of aldehyde and carboxyl groups. Results of MALDI-TOF mass spectroscopy confirmed the coupling of β-cyclodextrin to tyrosine, which was used as a model compound for wool. ATR-FTIR spectroscopy of the grafted wool confirmed the presence of β-cyclodextrin in grafted wool and the formation of a Schiff base between β-cyclodextrin and wool.

  6. A novel approach for grafting of β-cyclodextrin onto wool via laccase/TEMPO oxidation.

    PubMed

    Yu, Yuanyuan; Wang, Qiang; Yuan, Jiugang; Fan, Xuerong; Wang, Ping

    2016-11-20

    This study demonstrated a new enzymatic methodology to graft β-cyclodextrin onto wool. The primary hydroxyl groups in β-cyclodextrin were oxidized to aldehyde groups using laccase/2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), which reacted with the amino groups of wool to form Schiff bases. The effects of treatment conditions (treatment temperature, laccase dosage, TEMPO dosage, treatment time) on the aldehyde and carboxyl contents in β-cyclodextrin were studied. FTIR spectrum of oxidized β-cyclodextrin showed the presence of aldehyde and carboxyl groups. Results of MALDI-TOF mass spectroscopy confirmed the coupling of β-cyclodextrin to tyrosine, which was used as a model compound for wool. ATR-FTIR spectroscopy of the grafted wool confirmed the presence of β-cyclodextrin in grafted wool and the formation of a Schiff base between β-cyclodextrin and wool. PMID:27561518

  7. Cetirizine release from cyclodextrin formulated compressed chewing gum.

    PubMed

    Stojanov, Mladen; Larsen, Kim L

    2012-09-01

    Beside the efficient effect on masking cetirizine bitter taste, the cyclodextrins (CDs) as well could have influence on the release from the formulation. In vitro release profiles of cetirizine from compressed chewing gums containing α-, β- and γ-CD were investigated using a three cell chewing apparatus. Different cetirizine/CD formulations were produced and analysed with respect to type of CD (α-, β- and γ-CD), the molar ratio between cetirizine and CD and the formulation of cetirizine (complex or physical mixture). Release experiments from all compressed chewing gum formulations gave similar release patterns, but with variations in the total amount released. Chewing gum formulated with cetirizine alone, demonstrated a release of 75% after 8 min of chewing. The presence of CDs resulted in increased cetirizine release. The analysis of variance (ANOVA) demonstrated that parameters with the most important influence on the release were the molar ratio of cetirizine/CD (P < 0.05) and the formulation of cetirizine/CD (complex or physical mixture) (P < 0.05). The compressed chewing gum formulations with 1:5 molar ratio of cetirizine/CD in complexed form demonstrated the highest release. Even though the statistical analysis (ANOVA) demonstrated significance in the release (P < 0.05) for the complex/physical mixture factor, this difference was negligible compared to the release from chewing gums containing cetirizine without CD. This makes physical mixtures suitable for use in cetirizine/CD formulations instead the complexes with respect to release yield. Thus unnecessary expenses for the complex preformulation may be avoided.

  8. Investigation of inclusion complex of epothilone A with cyclodextrins.

    PubMed

    Xiao, Chuan-Fan; Li, Ke; Huang, Rong; He, Guo-Jin; Zhang, Jian-Qiang; Zhu, Li; Yang, Qing-Yi; Jiang, Kun-Ming; Jin, Yi; Lin, Jun

    2014-02-15

    The inclusion complexation of Epothilone A with native cyclodextrin (β- or γ-CD) and its derivative hydroxypropyl-β-cyclodextrin (HPβCD) were prepared. Their behavior, characterization, and binding ability were investigated in both solution and the solid state by means of UV-vis, NMR, XRD, DSC and SEM. The results show that the water solubility and solution stability obviously increased in the inclusion complex with cyclodextrins. Meanwhile, the inclusion complexes still retained anticancer activity against A549 and MCF-7 cells, similar to free Epothilone A. This satisfactory water solubility, high solution stability, and high anticancer activity of the Epothilone A/CD complexes will be potentially useful as an anticancer therapy.

  9. β-Cyclodextrin- para-aminosalicylic acid inclusion complexes

    NASA Astrophysics Data System (ADS)

    Roik, N. V.; Belyakova, L. A.; Oranskaya, E. I.

    2010-11-01

    Complex formation of β-cyclodextrin with para-aminosalicylic acid in buffer solutions is studied by UV spectroscopy. It is found that the stoichiometric proportion of the components in the β-cyclodextrin-para-aminosalicylic acid inclusion complex is 1:1. The Ketelar equation is used to calculate the stability constants of the inclusion complexes at different temperatures. The thermodynamic parameters of the complex formation process (ΔG, ΔH, ΔS) are calculated using the van't Hoff equation. The 1:1 β-cyclodextrin-para-aminosalicylic acid inclusion complex is prepared in solid form and its characteristics are determined by IR spectroscopic and x-ray diffraction techniques.

  10. Stability of two-dimensional PN monolayer sheets and their electronic properties.

    PubMed

    Ma, ShuangYing; He, Chaoyu; Sun, L Z; Lin, Haiping; Li, Youyong; Zhang, K W

    2015-12-21

    Three two-dimensional phosphorus nitride (PN) monolayer sheets (named as α-, β-, and γ-PN, respectively) with fantastic structures and properties are predicted based on first-principles calculations. The α-PN and γ-PN have a buckled structure, whereas β-PN shows puckered characteristics. Their unique structures endow these atomic PN sheets with high dynamic stabilities and anisotropic mechanical properties. They are all indirect semiconductors and their band gap sensitively depends on the in-plane strain. Moreover, the nanoribbons patterned from these three PN monolayers demonstrate a remarkable quantum size effect. In particular, the zigzag α-PN nanoribbon shows size-dependent ferromagnetism. Their significant properties show potential in nano-electronics. The synthesis of the three phases of the PN monolayer sheet is proposed theoretically, which is deserving of further study in experiments.

  11. Toward Ferroelectric Control of Monolayer MoS2.

    PubMed

    Nguyen, Ariana; Sharma, Pankaj; Scott, Thomas; Preciado, Edwin; Klee, Velveth; Sun, Dezheng; Lu, I-Hsi Daniel; Barroso, David; Kim, SukHyun; Shur, Vladimir Ya; Akhmatkhanov, Andrey R; Gruverman, Alexei; Bartels, Ludwig; Dowben, Peter A

    2015-05-13

    The chemical vapor deposition (CVD) of molybdenum disulfide (MoS2) single-layer films onto periodically poled lithium niobate is possible while maintaining the substrate polarization pattern. The MoS2 growth exhibits a preference for the ferroelectric domains polarized "up" with respect to the surface so that the MoS2 film may be templated by the substrate ferroelectric polarization pattern without the need for further lithography. MoS2 monolayers preserve the surface polarization of the "up" domains, while slightly quenching the surface polarization on the "down" domains as revealed by piezoresponse force microscopy. Electrical transport measurements suggest changes in the dominant carrier for CVD MoS2 under application of an external voltage, depending on the domain orientation of the ferroelectric substrate. Such sensitivity to ferroelectric substrate polarization opens the possibility for ferroelectric nonvolatile gating of transition metal dichalcogenides in scalable devices fabricated free of exfoliation and transfer.

  12. Efficient Biocatalytic Production of Cyclodextrins by Combined Action of Amylosucrase and Cyclodextrin Glucanotransferase.

    PubMed

    Koh, Dong-Wan; Park, Min-Oh; Choi, Seong-Won; Lee, Byung-Hoo; Yoo, Sang-Ho

    2016-06-01

    A novel enzymatic process for cyclodextrin (CD) production was developed by utilizing sucrose as raw material instead of corn starch. Cyclodextrin glucanotransferase (CGTase) from Bacillus macerans was applied to produce the CDs from linear α-(1,4)-glucans, which were obtained by Neisseria polysaccharea amylosucrase (NpAS) treatment on sucrose. The greatest CD yield (21.1%, w/w) was achieved from a one-pot dual enzyme reaction at 40 °C for 24 h. The maximum level of CD production (15.1 mg/mL) was achieved with 0.5 M sucrose in a simultaneous mode of dual enzyme reaction, whereas the reaction with 0.1 M sucrose was the most efficient with regard to conversion yield. Consequently, dual enzyme synthesis of CDs was successfully carried out with no need of starch material. This result can be applied as a novel efficient bioconversion process that does not require the high temperature necessary for starch liquefaction by thermostable α-amylase in conventional industrial processing. PMID:27169988

  13. Electrochemical and scanning probe microscopic characterization of spontaneously adsorbed organothiolate monolayers at gold

    SciTech Connect

    Wong, Sze-Shun Season

    1999-12-10

    This dissertation presented several results which add to the general knowledge base regarding organothiolates monolayer spontaneously adsorbed at gold films. Common to the body of this work is the use of voltammetric reductive resorption and variants of scanning probe microscopy to gain insight into the nature of the monolayer formation process as well as the resulting interface. The most significant result from this work is the success of using friction force microscopy to discriminate the end group orientation of monolayer chemisorbed at smooth gold surfaces with micrometer resolution (Chapter 4). The ability to detect the differences in the orientational disposition is demonstrated by the use PDMS polymer stamp to microcontact print an adlayer of n-alkanethiolate of length n in a predefine pattern onto a gold surface, followed by the solution deposition of a n-alkanethiol of n {+-} 1 to fill in the areas on the gold surface intentionally not coated by the stamping process. These two-component monolayers can be discriminated by using friction force microscopy which detects differences in friction contributed by the differences in the orientation of the terminal groups at surfaces. This success has recently led to the detection of the orientation differences at nanometer scale. Although the substrates examined in this work consisted entirely of smooth gold films, the same test can be performed on other smooth substrates and monolayer materials.

  14. Aging of Transition Metal Dichalcogenide Monolayers.

    PubMed

    Gao, Jian; Li, Baichang; Tan, Jiawei; Chow, Phil; Lu, Toh-Ming; Koratkar, Nikhil

    2016-02-23

    Two-dimensional sheets of transition metal dichalcogenides are an emerging class of atomically thin semiconductors that are considered to be "air-stable", similar to graphene. Here we report that, contrary to current understanding, chemical vapor deposited transition metal dichalcogenide monolayers exhibit poor long-term stability in air. After room-temperature exposure to the environment for several months, monolayers of molybdenum disulfide and tungsten disulfide undergo dramatic aging effects including extensive cracking, changes in morphology, and severe quenching of the direct gap photoluminescence. X-ray photoelectron and Auger electron spectroscopy reveal that this effect is related to gradual oxidation along the grain boundaries and the adsorption of organic contaminants. These results highlight important challenges associated with the utilization of transition metal dichalcogenide monolayers in electronic and optoelectronic devices. We also demonstrate a potential solution to this problem, featuring encapsulation of the monolayer sheet by a 10-20 nm thick optically transparent polymer (parylene C). This strategy is shown to successfully prevent the degradation of the monolayer material under accelerated aging (i.e., high-temperature, oxygen-rich) conditions.

  15. Aging of Transition Metal Dichalcogenide Monolayers.

    PubMed

    Gao, Jian; Li, Baichang; Tan, Jiawei; Chow, Phil; Lu, Toh-Ming; Koratkar, Nikhil

    2016-02-23

    Two-dimensional sheets of transition metal dichalcogenides are an emerging class of atomically thin semiconductors that are considered to be "air-stable", similar to graphene. Here we report that, contrary to current understanding, chemical vapor deposited transition metal dichalcogenide monolayers exhibit poor long-term stability in air. After room-temperature exposure to the environment for several months, monolayers of molybdenum disulfide and tungsten disulfide undergo dramatic aging effects including extensive cracking, changes in morphology, and severe quenching of the direct gap photoluminescence. X-ray photoelectron and Auger electron spectroscopy reveal that this effect is related to gradual oxidation along the grain boundaries and the adsorption of organic contaminants. These results highlight important challenges associated with the utilization of transition metal dichalcogenide monolayers in electronic and optoelectronic devices. We also demonstrate a potential solution to this problem, featuring encapsulation of the monolayer sheet by a 10-20 nm thick optically transparent polymer (parylene C). This strategy is shown to successfully prevent the degradation of the monolayer material under accelerated aging (i.e., high-temperature, oxygen-rich) conditions. PMID:26808328

  16. Vibrational spectrum of water confined in and around cyclodextrins

    NASA Astrophysics Data System (ADS)

    Jana, Madhurima; Bandyopadhyay, Sanjoy

    2011-06-01

    The effects of α-, β-, and γ-cyclodextrins (ACD, BCD, and GCD) on the low-frequency vibrational spectrum of water present around them and those confined inside their cavities have been investigated from molecular dynamics simulations. Attempts have been made to understand the effects of variation of the number of glucose rings and the ability of these macromolecules to form hydrogen bonds with water on the distribution of the vibrational density of states of water. It is observed that these bands for water in and around the cyclodextrins suffer blue shifts, the extent of the shifts are sensitive to the degree of confinement within the cavities and their hydrogen bonding status.

  17. Supramolecular cyclodextrin-based drug nanocarriers.

    PubMed

    Simões, Susana M N; Rey-Rico, Ana; Concheiro, Angel; Alvarez-Lorenzo, Carmen

    2015-04-14

    Supramolecular systems formed by the binding of several cyclodextrins (CDs) to polymers or lipids, either via non-covalent or covalent links, open a wide range of possibilities for the delivery of active substances. CDs can perform as multifunctionalizable cores to which very diverse (macro)molecules and drugs can be conjugated. Grafting with amphiphilic molecules can lead to nanoassemblies exhibiting a variety of architectures. CDs can also polymerize with other CDs or can be used to functionalize preexisting polymers to form polymers/networks with enhanced capability to form inclusion complexes. Alternatively, CDs can be exploited as transient cross-linkers to form poly(pseudo)rotaxane-based networks or zipper-like assemblies. Combination of mutifunctionality and complexation ability of CDs has been shown to be useful to develop depot-like formulations and colloidal nanocarriers with improved performances regarding easiness of administration, protection of the encapsulated substances, control of the delivery rate, and cell interactions. The aim of this review is to provide an overall view of the diversity of designs of CD-based supramolecular nanosystems with a special focus on the advances materialized in the last five years, including clinical trials. PMID:25679097

  18. Cyclodextrin promotes atherosclerosis regression via macrophage reprogramming

    PubMed Central

    Zimmer, Sebastian; Grebe, Alena; Bakke, Siril S.; Bode, Niklas; Halvorsen, Bente; Ulas, Thomas; Skjelland, Mona; De Nardo, Dominic; Labzin, Larisa I.; Kerksiek, Anja; Hempel, Chris; Heneka, Michael T.; Hawxhurst, Victoria; Fitzgerald, Michael L; Trebicka, Jonel; Gustafsson, Jan-Åke; Westerterp, Marit; Tall, Alan R.; Wright, Samuel D.; Espevik, Terje; Schultze, Joachim L.; Nickenig, Georg; Lütjohann, Dieter; Latz, Eicke

    2016-01-01

    Atherosclerosis is an inflammatory disease linked to elevated blood cholesterol levels. Despite ongoing advances in the prevention and treatment of atherosclerosis, cardiovascular disease remains the leading cause of death worldwide. Continuous retention of apolipoprotein B-containing lipoproteins in the subendothelial space causes a local overabundance of free cholesterol. Since cholesterol accumulation and deposition of cholesterol crystals (CCs) triggers a complex inflammatory response, we tested the efficacy of the cyclic oligosaccharide 2-hydroxypropyl-β-cyclodextrin (CD), a compound that increases cholesterol solubility, in preventing and reversing atherosclerosis. Here we show that CD treatment of murine atherosclerosis reduced atherosclerotic plaque size and CC load, and promoted plaque regression even with a continued cholesterol-rich diet. Mechanistically, CD increased oxysterol production in both macrophages and human atherosclerotic plaques, and promoted liver X receptor (LXR)-mediated transcriptional reprogramming to improve cholesterol efflux and exert anti-inflammatory effects. In vivo, this CD-mediated LXR agonism was required for the anti-atherosclerotic and anti-inflammatory effects of CD as well as for augmented reverse cholesterol transport. Since CD treatment in humans is safe and CD beneficially affects key mechanisms of atherogenesis, it may therefore be used clinically to prevent or treat human atherosclerosis. PMID:27053774

  19. Cyclodextrin promotes atherosclerosis regression via macrophage reprogramming.

    PubMed

    Zimmer, Sebastian; Grebe, Alena; Bakke, Siril S; Bode, Niklas; Halvorsen, Bente; Ulas, Thomas; Skjelland, Mona; De Nardo, Dominic; Labzin, Larisa I; Kerksiek, Anja; Hempel, Chris; Heneka, Michael T; Hawxhurst, Victoria; Fitzgerald, Michael L; Trebicka, Jonel; Björkhem, Ingemar; Gustafsson, Jan-Åke; Westerterp, Marit; Tall, Alan R; Wright, Samuel D; Espevik, Terje; Schultze, Joachim L; Nickenig, Georg; Lütjohann, Dieter; Latz, Eicke

    2016-04-01

    Atherosclerosis is an inflammatory disease linked to elevated blood cholesterol concentrations. Despite ongoing advances in the prevention and treatment of atherosclerosis, cardiovascular disease remains the leading cause of death worldwide. Continuous retention of apolipoprotein B-containing lipoproteins in the subendothelial space causes a local overabundance of free cholesterol. Because cholesterol accumulation and deposition of cholesterol crystals (CCs) trigger a complex inflammatory response, we tested the efficacy of the cyclic oligosaccharide 2-hydroxypropyl-β-cyclodextrin (CD), a compound that increases cholesterol solubility in preventing and reversing atherosclerosis. We showed that CD treatment of murine atherosclerosis reduced atherosclerotic plaque size and CC load and promoted plaque regression even with a continued cholesterol-rich diet. Mechanistically, CD increased oxysterol production in both macrophages and human atherosclerotic plaques and promoted liver X receptor (LXR)-mediated transcriptional reprogramming to improve cholesterol efflux and exert anti-inflammatory effects. In vivo, this CD-mediated LXR agonism was required for the antiatherosclerotic and anti-inflammatory effects of CD as well as for augmented reverse cholesterol transport. Because CD treatment in humans is safe and CD beneficially affects key mechanisms of atherogenesis, it may therefore be used clinically to prevent or treat human atherosclerosis. PMID:27053774

  20. Glucosylation of steroidal saponins by cyclodextrin glucanotransferase.

    PubMed

    Wang, Yong-ze; Feng, Bing; Huang, Hong-zhi; Kang, Li-ping; Cong, Yue; Zhou, Wen-bin; Zou, Peng; Cong, Yu-wen; Song, Xin-Bo; Ma, Bai-ping

    2010-10-01

    It is known that the sugar chains of steroidal saponins play an important role in the biological and pharmacological activities. In order to synthesize steroidal saponins with novel sugar chains in one step for further studies on pharmacological activity, we here describe the glucosylation of steroidal saponins, and 5 compounds, timosaponin AIII (1), saponin Ta (2), saponin Tb (3), trillin (4) and cantalasaponin I (5), were converted into their glucosylated products by Toruzyme 3.0 L, a cyclodextrin glucanotransferase (CGTase). 12 glucosylated products were isolated and their structures elucidated on the basis of spectral data; they were all characterized as new compounds. The results showed that Toruzyme 3.0 L had the specific ability to add the α-D-glucopyranosyl group to the glucosyl group linked at the sugar chains of steroidal saponins, and the glucosyl group was the only acceptor. This is the first report of steroidal saponins with different degrees of glucosylation. The substrates and their glucosylated derivatives were evaluated for their cytotoxicity against HL-60 human promyelocytic leukemia cell by MTT assay. The substrates all exhibited high cytotoxicity (IC(50) < 10 µmol/L), excluding compound 5 (IC(50) > 150 µmol/L), and the cytotoxicity of most of the products showed no obvious changes compared with those of their substrates.

  1. Nonlinear optical techniques for surface studies. [Monolayers

    SciTech Connect

    Shen, Y.R.

    1981-09-01

    Recent effort in developing nonlinear optical techniques for surface studies is reviewed. Emphasis is on monolayer detection of adsorbed molecules on surfaces. It is shown that surface coherent antiStokes Raman scattering (CARS) with picosecond pulses has the sensitivity of detecting submonolayer of molecules. On the other hand, second harmonic or sum-frequency generation is also sensitive enough to detect molecular monolayers. Surface-enhanced nonlinear optical effects on some rough metal surfaces have been observed. This facilitates the detection of molecular monolayers on such surfaces, and makes the study of molecular adsorption at a liquid-metal interface feasible. Advantages and disadvantages of the nonlinear optical techniques for surface studies are discussed.

  2. Electromagnetic interference shielding effectiveness of monolayer graphene.

    PubMed

    Hong, Seul Ki; Kim, Ki Yeong; Kim, Taek Yong; Kim, Jong Hoon; Park, Seong Wook; Kim, Joung Ho; Cho, Byung Jin

    2012-11-16

    We report the first experimental results on the electromagnetic interference (EMI) shielding effectiveness (SE) of monolayer graphene. The monolayer CVD graphene has an average SE value of 2.27 dB, corresponding to ~40% shielding of incident waves. CVD graphene shows more than seven times (in terms of dB) greater SE than gold film. The dominant mechanism is absorption rather than reflection, and the portion of absorption decreases with an increase in the number of graphene layers. Our modeling work shows that plane-wave theory for metal shielding is also applicable to graphene. The model predicts that ideal monolayer graphene can shield as much as 97.8% of EMI. This suggests the feasibility of manufacturing an ultrathin, transparent, and flexible EMI shield by single or few-layer graphene. PMID:23085718

  3. Efficient extraction and detection of aromatic toxicants from crude oil and tar balls using multiple cyclodextrin derivatives.

    PubMed

    Serio, Nicole; Levine, Mindy

    2015-06-15

    Herein we report the efficient extraction of aromatic analytes from crude oil and tar balls using multiple cyclodextrin derivatives. The known propensity of the cyclodextrins to bind hydrophobic guests in their hydrophobic interiors enhanced the extraction of aromatic analytes from the oil layer to the aqueous layer, with methyl-β-cyclodextrin and β-cyclodextrin providing the most significant enhancement in extraction efficiencies of aromatic toxicants (69% aromatic toxicants in aqueous layer in the presence of methyl-β-cyclodextrin compared to 47% in cyclodextrin-free solution for tar ball oil extraction), and provide optimal tunability for developing efficient extraction systems. The cyclodextrin derivatives also promoted efficient energy transfer in the aqueous solutions, with up to 86% efficient energy transfer observed in the presence of γ-cyclodextrin compared to 50% in the absence of cyclodextrin for oil spill oil extraction. Together, this dual function extraction followed by detection system has potential in the development of environmental remediation systems.

  4. Adherence of Mycoplasma hyopneumoniae to cell monolayers.

    PubMed

    Zielinski, G C; Young, T; Ross, R F; Rosenbusch, R F

    1990-03-01

    This work was an attempt to develop an in vitro adherence model for Mycoplasma hyopneumoniae, using monolayers of human and porcine lung fibroblasts and porcine kidney cells. Mycoplasma hyopneumoniae grown in Friis mycoplasma broth was radiolabeled with 35[S]-methionine, washed, concentrated, and inoculated on the monolayers. After 15 minutes of centrifugation to facilitate adherence, monolayers were washed 3 times, dissolved with 0.1N NaOH, and suspended in scintillation liquid, and the radioactivity was determined in a liquid scintillation counter. Adherence, measured as a percentage of counts added, varied according to the mycoplasma strain and the cell line used. Comparison of strains J, 144L, and 232 of M hyopneumoniae revealed 7.5 +/- 5.9, 31.9 +/- 13, and 9.6 +/- 5% adherence to porcine kidney cells, respectively. Slightly different, but proportionally the same relationships were obtained with swine or human fibroblasts. Adherence was decreased slightly by repeated washings of the mycoplasma-treated cell monolayers; however, a plateau was reached, indicating irreversibility of the adherence process. Pretreatment of cell monolayers with nonlabeled organisms substantially blocked adherence by labeled organisms. Dilution of labeled organisms resulted in an increased proportion adhering. Therefore, it appears that the adherence was a receptor-dependent event. Treatment of the mycoplasmas with trypsin prior to the inoculation of monolayers resulted in a marked reduction in adherence. Treatment of the mycoplasmas with hyperimmune swine serum against M hyopneumoniae or normal swine serum resulted in 80 to 90% reduction of adherence; however, no inhibition occurred when mycoplasmas were treated with purified IgG from the hyperimmune serum.

  5. Multichannel surface imaging and analysis of self-assembled monolayers and proteins

    NASA Astrophysics Data System (ADS)

    Pyo, Hyeon-Bong; Shin, Yong-Beom; Kim, Min-Gon; Yoon, Hyun C.

    2004-03-01

    Multichannel images of 11-Mercaptoundecanoic acid and 11-Mercapto-1-undecanol self-assembled monolayers (SAMs) together with a biospecific interferon-gamma (IFN-gamma)/anti-IFN-gamma antibody immunoreaction were observed by two-dimensional surface plasmon resonance (2D-SPR) imaging system. Patterning process for SAM was simplified by exploiting direct photooxidation of thiol bonding (photolysis) instead of conventional photolithography. Sharper images were resolved by using a white light source in combination with a narrow bandpass filter, minimizing the diffraction patterns on the images. The line profile calibration of the image contrast caused by different resonance conditions at each points on the sensor surface enabled us to discriminate the monolayer thickness in a sub-nanometer scale. For protein patterning, a precipitation scheme induced by biocatalytic reaction was implied for the signal amplification. Specific binding of IFN-gamma antigen with surface-immobilized antibody was found detectable down to the concentration of 1 ng/mL.

  6. Monolayer Topological Insulators: Silicene, Germanene, and Stanene

    NASA Astrophysics Data System (ADS)

    Ezawa, Motohiko

    2015-12-01

    We report the recent progress on the theoretical aspects of monolayer topological insulators including silicene, germanene and stanene, which are monolayer honeycomb structures of silicon, germanium and tin, respectively. They show quantum spin Hall effects in nature due to the spin-orbit interaction. The band gap can be tuned by applying perpendicular electric field, which induces a topological phase transition. We also analyze the topological properties of generic honeycomb systems together with the classification of topological insulators. Phase diagrams of topological insulators and superconductors in honeycomb systems are explicitly determined. We also investigate topological electronics including a topological field-effect transistor, the topological Kirchhoff's law and the topological spin-valleytronics.

  7. Low temperature photoresponse of monolayer tungsten disulphide

    SciTech Connect

    Cao, Bingchen; Shen, Xiaonan; Shang, Jingzhi; Cong, Chunxiao; Yang, Weihuang; Eginligil, Mustafa E-mail: meginligil@ntu.edu.sg; Yu, Ting E-mail: meginligil@ntu.edu.sg

    2014-11-01

    High photoresponse can be achieved in monolayers of transition metal dichalcogenides. However, the response times are inconveniently limited by defects. Here, we report low temperature photoresponse of monolayer tungsten disulphide prepared by exfoliation and chemical vapour deposition (CVD) method. The exfoliated device exhibits n-type behaviour; while the CVD device exhibits intrinsic behaviour. In off state, the CVD device has four times larger ratio of photoresponse for laser on/off and photoresponse decay–rise times are 0.1 s (limited by our setup), while the exfoliated device has few seconds. These findings are discussed in terms of charge trapping and localization.

  8. Nonlinear optical studies of organic monolayers

    SciTech Connect

    Shen, Y.R.

    1988-02-01

    Second-order nonlinear optical effects are forbidden in a medium with inversion symmetry, but are necessarily allowed at a surface where the inversion summary is broken. They are often sufficiently strong so that a submonolayer perturbation of the surface can be readily detected. They can therefore be used as effective tools to study monolayers adsorbed at various interfaces. We discuss here a number of recent experiments in which optical second harmonic generation (SHG) and sum-frequency generation (SFG) are employed to probe and characterize organic monolayers. 15 refs., 5 figs.

  9. Monochromatic electron photoemission from diamondoid monolayers

    SciTech Connect

    Yang, Wanli; Yang, Wanli L.; Fabbri, J.D.; Willey, T.M.; Lee, J.R.I.; Dahl, J.E.; Carlson, R.M.K.; Schreiner, P.R.; Fokin, A.A.; Tkachenko, B.A.; Fokina, N.A.; Meevasana, W.; Mannella, N.; Tanaka, K.; Zhou, X.J.; van Buuren, T.; Kelly, M.A.; Hussain, Z.; Melosh, N.A.; Shen, Z.-X.

    2007-02-27

    We found monochromatic electron photoemission from large-area self-assembled monolayers of a functionalized diamondoid, [121]tetramantane-6-thiol. Photoelectron spectra of the diamondoid monolayers exhibited a peak at the low-kinetic energy threshold; up to 68percent of all emitted electrons were emitted within this single energy peak. The intensity of the emission peak is indicative of diamondoids being negative electron affinity materials. With an energy distribution width of less than 0.5 electron volts, this source of monochromatic electrons may find application in technologies such as electron microscopy, electron beam lithography, and field-emission flatpanel displays.

  10. Active Tensile Modulus of an Epithelial Monolayer

    NASA Astrophysics Data System (ADS)

    Vincent, Romaric; Bazellières, Elsa; Pérez-González, Carlos; Uroz, Marina; Serra-Picamal, Xavier; Trepat, Xavier

    2015-12-01

    A general trait of cell monolayers is their ability to exert contractile stresses on their surroundings. The scaling laws that link such contractile stresses with the size and geometry of constituent cells remain largely unknown. In this Letter, we show that the active tension of an epithelial monolayer scales linearly with the size of the constituent cells, a surprisingly simple relationship. The slope of this relationship defines an active tensile modulus, which depends on the concentration of myosin and spans more than 2 orders of magnitude across cell types and molecular perturbations.

  11. Bupivacaine hydrochloride complexation with some alpha- and beta-cyclodextrins studied by potentiometry with membrane electrodes.

    PubMed

    Kopecký, Frantisek; Vojteková, Mária; Kaclík, Pavol; Demko, Marek; Bieliková, Zuzana

    2004-05-01

    Membrane electrodes selective to bupivacaine cations were developed and those with PVC-dibutylphthalate membrane containing sparingly soluble bupivacaine phosphotungstate appeared to be the most suitable. Inclusion complexation of bupivacaine cations with cyclodextrins was studied by potentiometric measurements of the free bupivacaine cation concentration in aqueous solutions of bupivacaine hydrochloride with cyclodextrin using the prepared electrodes. Native alpha-cyclodextrin (alpha-CD) and beta-cyclodextrin (beta-CD), as well as their random-substituted derivatives hydroxypropyl-alpha-cyclodextrin (HP-alpha-CD), hydroxypropyl-beta-cyclodextrin (HP-beta-CD) and methyl-beta-cyclodextrin (M-beta-CD), were chosen for the study. The measured potentiometric data processed both by a linear and nonlinear regression corroborated the formation of weak 1:1 bupivacaine cation-cyclodextrin complexes and the corresponding complexation constants K(11) approximately 50-155 M(-1) were evaluated by the non-linear least-squares method. The mutual order of K(11) values, especially alpha-CD > beta-CD, suggested that the bupivacaine butyl group was mainly responsible for the inclusion complexation; the highest K(11) was exhibited by M-beta-CD followed by alpha-CD. The observed complexation may substantially modify properties of bupivacaine hydrochloride dosage forms with sufficient concentration of cyclodextrin but bupivacaine cations are readily released from the weak cyclodextrin complexes by dilution.

  12. Continuous tank reactor synthesis of highly substituted sulphobutylether β-cyclodextrins.

    PubMed

    Savage, Tammy; Mitchell, John; Trivedi, Vivek; Wicks, Stephen; Waters, Laura J

    2015-11-30

    Batch synthesis of sulphobutyl ether β-cyclodextrin (also known as SBE-β-CD or SBECD) is a process effectively divided into three main stages, i.e. initial reagent dissolution, a sulphoalkylation reaction and final reaction quenching. This reaction is followed by downstream processing and purification, and ultimate isolation of the solid SBECD material. However, a feature associated with using this synthetic method is that a high proportion of lower substituted SBECD is observed. There is therefore a need to provide an improved synthetic method for producing higher substituted cyclodextrins. The authors here present a Continuous Tank Reactor (CTR) method for preparing sulphobutyl ether-cyclodextrins. The method comprises first contacting cyclodextrin with a base to form activated cyclodextrin. The method then involves separately contacting the activated cyclodextrin with an 1,4-butane sultone to form sulphoalkyl ether-cyclodextrin. The activation reaction is carried out in batch synthesis mode and the sulphoalkylation reaction is carried out under continuous flow conditions resulting in a novel method for the synthesis of highly derivatised cyclodextrins. The work is particularly concerned with producing controlled substitution in sulphobutyl ether β-cyclodextrins and novel compositions of highly substituted sulphoalkyl ether β-cyclodextrins are described.

  13. Aqueous electrodeposition of Ge monolayers.

    PubMed

    Liang, Xuehai; Kim, Youn-Geun; Gebergziabiher, Daniel K; Stickney, John L

    2010-02-16

    The electrodeposition of germanium on Au(111) in aqueous solutions has been investigated by means of cyclic voltammetry, Auger electron spectroscopy, and in situ scanning tunneling microscopy (STM). The data yield a picture of germanium deposition, which starts with the formation of two well-ordered hydroxide phases, with 1/3 ML and 4/9 ML coverages upon initial reduction of the Ge(IV) species (probably H(2)GeO(3) at pH 4.7). Those structures appear to result from a three-electron reduction to form surface-limited structures with (square root(3) x square root(3))R30 degrees or (3 x 3) unit cells, respectively. Further reduction, probably in a two-electron process from the hydroxide structures, resulted in a germanium hydride structure, again surface-limited, with a coverage of close to 0.8 ML. The hydride structure is very flat, though with the periodic modulation characteristic of a Moiré pattern. Longer deposition times and lower potentials resulted in increased coverage of Ge in some cases, but with apparently limited coverage as a function of pH. The maximum Ge coverage, about 4 ML, was observed using a pH 9.32 deposition solution. At potentials negative of the Moiré pattern, about -850 mV versus Ag/AgCl, a "corruption" of the smooth Moiré pattern occurred. This roughening appears to mark the initial formation of a Au-Ge alloy, accounting for the observation of coverage in excess of that needed to form the Moiré pattern at some pH values.

  14. Measurement of Resonant Frequencies and Modes of Freestanding Nanoparticle Monolayers

    NASA Astrophysics Data System (ADS)

    Kanjanaboos, Pongsakorn; Lin, Xiao-Min; Jaeger, Heinrich; Guest, Jeffrey

    2012-02-01

    We recently showed that freestanding membranes of ligated nanoparticles can be assembled in a one-step drying-mediated process [1]. These 10nm thin membranes can stretch over holes up to 100 microns in diameter and are supported by a substrate only along their outer edge, thereby freely suspending of the order of 100 million close-packed particles [2]. Previous work has focused on quasi-static mechanical properties [1-3]. Here we present the first investigation of the full dynamic response of freely suspended nanoparticle membranes, utilizing a high frequency laser interferometer with picometer sensitivity. This instrument allows us to rapidly measure the dynamical properties of freestanding nanoparticle monolayers for the first time including resonant frequencies, quality factors, and images of different modes.[4pt] [1] Klara E. Mueggenburg et al., ``Elastic membranes of close-packed nanoparticle arrays,'' Nature Materials 6, 656-660 (2007). [0pt] [2] Jinbo He et al., ``Fabrication and Mechanical properties of large-scale freestanding nanoparticle membranes,'' Small 6, 1449-1456 (2010).[0pt] [3] Pongsakorn Kanjanaboos et al., ``Strain Patterning and Direct Measurement of Poisson's Ratio in Nanoparticle Monolayer Sheets,'' Nano Letters 11, 2567-2571 (2011).

  15. Lipid dip-pen nanolithography on self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Gavutis, Martynas; Navikas, Vytautas; Rakickas, Tomas; Vaitekonis, Šarūnas; Valiokas, Ramūnas

    2016-02-01

    Dip-pen nanolithography (DPN) with lipids as an ink enables functional micro/nanopatterning on different substrates at high process speeds. However, only a few studies have addressed the influence of the physicochemical properties of the surface on the structure and phase behavior of DPN-printed lipid assemblies. Therefore, by combining the scanning probe and optical imaging techniques in this work we have analyzed lipid microdomain formation on the self-assembled monolayers (SAMs) on gold as well-defined model surfaces that displayed hydrophilic (protein-repellent) or hydrophobic (protein-adhesive) characteristics. We have found that on the tri(ethylene glycol)-terminated SAM the lipid ink transfer was fast (~10-1 μm3 s-1), quasi-linear and it yielded unstable, sparsely packed lipid microspots. Contrary to this, on the methyl-terminated SAM the lipid transfer was ~20 times slower, nonlinear, and the obtained stable dots of ~1 μm in diameter consisted of lipid multilayers. Our comparative analysis indicated that the measured lipid transfer was consistent with the previously reported so-called polymer transfer model (Felts et al 2012, Nanotechnology 23 215301). Further on, by employing the observed distinct contrast in the DPN ink behavior we constructed confined lipid microdomains on pre-patterned SAMs, in which the lipids assembled either into monolayer or multilamellar phases. Such microdomains can be further utilized for lipid membrane mimetics in microarray and lab-on-a-chip device formats.

  16. Catalytic etching of monolayer graphene at low temperature via carbon oxidation.

    PubMed

    Jin, Jun Eon; Lee, Jae-Hyun; Choi, Jun Hee; Jang, Ho-Kyun; Na, Junhong; Whang, Dongmok; Kim, Do-Hyun; Kim, Gyu Tae

    2016-01-01

    In this work, an easy method to etch monolayer graphene is shown by catalytic oxidation in the presence of ZnO nanoparticles (NPs). The catalytic etching of monolayer graphene, which was transferred to the channel of field-effect transistors (FETs), was performed at low temperature by heating the FETs several times under an inert gas atmosphere (ZnO + C → Zn + CO or CO2). As the etching process proceeded, diverse etched structures in the shape of nano-channels and pits were observed under microscopic observation. To confirm the evolution of etching, current-voltage characteristics of monolayer graphene were measured after every step of etching by catalytic oxidation. As a result, the conductance of monolayer graphene decreased with the development of etched structures. This decrease in conductance was analyzed by percolation theory in a honeycomb structure. Finally, well-patterned graphene was obtained by oxidizing graphene under air in the presence of NPs, where Al was deposited on graphene as a mask for designed patterns. This method can substitute graphene etching via carbon hydrogenation using H2 at high temperature. PMID:26225821

  17. Synthesis of Phenyl-Adducted Cyclodextrin through the Click Reaction

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A new derivative of ß-cyclodextrin (CD) has been made incorporating the phenyl group through the use of click reaction. The resulting product exhibits a self-association phenomenon through the formation of inclusion compound between the phenyl group and CD. The product has been characterized by 1H...

  18. Cyclodextrin-based nanosponges: effective nanocarrier for tamoxifen delivery.

    PubMed

    Torne, Satyen; Darandale, Sharad; Vavia, Pradeep; Trotta, Francesco; Cavalli, Roberta

    2013-01-01

    The purpose of the present study was to develop Tamoxifen loaded β-cyclodextrin nanosponges for oral drug delivery. The three types of Tamoxifen loaded β-cyclodextrin nanosponges were synthesized by varying the molar ratios of β-cyclodextrin to carbonyldiimidazole as a crosslinker viz. 1:2, 1:4 and 1:8. The Tamoxifen nanosponge complex (TNC) with particle size of 400-600 nm was obtained by freeze drying method. Differential scanning calorimetry, Fourier transformed infra-red spectroscopy and X-ray powder diffraction studies confirmed the complexation of Tamoxifen with cyclodextrin nanosponge. AUC and Cmax of TNC formulation (1236.4 ± 16.12 µg · mL(-1) h, 421.156 ± 0.91 µg/mL) after gastric intubation were 1.44 fold and 1.38 fold higher than plain drug (856.079 ± 15.18 µg · mL(-1) h, 298.532 ± 1.15 µg/mL). Cytotoxic studies on MCF-7 cells showed that TNC formulation was more cytotoxic than plain Tamoxifen after 24 and 48 h of incubation. PMID:22235935

  19. INTERACTIONS BETWEEN ORGANIC COMPOUNDS AND CYCLODEXTRIN-CLAY SYSTEMS

    EPA Science Inventory

    Computational and experimental techniques are combined in order to better understand interactions involving organic compounds and cyclodextrin (CD)-clay systems. CD-clay systems may have great potential in the containment of organic contaminants in the environment. This study w...

  20. A closer look at cyclodextrins in mycotoxin analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cyclodextrins have seen increased use as components in analytical methods to detect and quantitate a broad range of low molecular weight molecules. Improved detection is frequently associated with inclusion complex formation, and, in some cases, modulation of spectroscopic properties. These cyclic...

  1. Enhancement of mycotoxin fluorescence with cyclodextrins, and analytical applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Certain of the mycotoxins are known to form host-guest complexes with cyclodextrins (CDs), cyclic oligosaccharides containing a relatively hydrophobic pore. The interactions between mycotoxins and CDs can alter the properties of the mycotoxin, namely the fluorescence, absorption, or chromatographic...

  2. A Closer Look at Cyclodextrins in Mycotoxin Analysis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cyclodextrins are a class of cyclic oligosaccharides with a variety of applications, including use as recognition components for low molecular weight molecules in methods of detection. These cyclomaltoses are of special interest in mycotoxin analysis for enhancing spectroscopic properties of severa...

  3. Cyclodextrin-Functionalized Monolithic Capillary Columns: Preparation and Chiral Applications.

    PubMed

    Adly, Frady G; Antwi, Nana Yaa; Ghanem, Ashraf

    2016-02-01

    In this review, the recently reported approaches for the preparation of cyclodextrin-functionalized capillary monolithic columns are highlighted, with few applications in chiral separations using capillary liquid chromatography (CLC) and capillary electrochromatography (CEC). Chirality 28:97-109, 2016. © 2015 Wiley Periodicals, Inc.

  4. THE BINDING OF COCAINE TO CYCLODEXTRINS. (R826653)

    EPA Science Inventory

    Abstract

    Cocaine binds into small beta, Greek-cyclodextrin, but not detectably into small alpha, Greek

  5. Amphiphilic phthalocyanine-cyclodextrin conjugates for cancer photodynamic therapy.

    PubMed

    Lourenço, Leandro M O; Pereira, Patrícia M R; Maciel, Elisabete; Válega, Mónica; Domingues, Fernando M J; Domingues, Maria R M; Neves, Maria G P M S; Cavaleiro, José A S; Fernandes, Rosa; Tomé, João P C

    2014-08-01

    Three phthalocyanines (Pcs) conjugated with α-, β- and γ-cyclodextrins (CDs) were prepared and their application as photosensitizer (PS) agents was assessed by photophysical, photochemical and in vitro photobiological studies. The photoactivity of Pc-α-CD and Pc-γ-CD ensures their potential as PDT drugs against UM-UC-3 human bladder cancer cells. PMID:24943806

  6. A thermostable cyclodextrin glycosyltransferase from Thermoanaerobacter sp. 5K

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cyclodextrin glycosyltransferase (CGTase) from the thermophilic anaerobe Thermoanaerobacter sp. 5K was purified and characterized. The enzyme was purified with ammonium sulfate precipitation followed by a-CD-bound, epoxy-activated Sepharose 6B affinity chromatography. Molecular weight of the purifie...

  7. Supramolecular Inclusion in Cyclodextrins: A Pictorial Spectroscopic Demonstration

    ERIC Educational Resources Information Center

    Haldar, Basudeb; Mallick, Arabinda; Chattopadhyay, Nitin

    2008-01-01

    A spectroscopic experiment is presented that reveals that the hydrophobically end-modified water-soluble polymeric fluorophore, pyrene end-capped poly(ethylene oxide) (PYPY), interacts differently with [alpha], [beta], and [gamma]-cyclodextrins (CD) to form supramolecular inclusion complexes. The emission spectrum of PYPY in aqueous solution shows…

  8. Cyclodextrin-based microcapsules as bioreactors for ATP biosynthesis.

    PubMed

    Li, Jian-Hu; Wang, Yi-Fu; Ha, Wei; Liu, Yan; Ding, Li-Sheng; Li, Bang-Jing; Zhang, Sheng

    2013-09-01

    A biomimetic energy converter was fabricated via the assembly of CF0F1-ATPase on lipid-coated hollow nanocapsules composed of α-cyclodextrins/chitosan-graft-poly(ethylene glycol) methacrylate. Upon entrapped GOD into these capsules, the addition of glucose could trigger proton-motive force and then drive the rotation of ATPase to synthesize ATP. PMID:23962233

  9. [Development of Cyclodextrin-based Cancer Treatment].

    PubMed

    Motoyama, Keiichi

    2015-01-01

    Drug delivery techniques to tumor cells have attracted considerable attention. For instance, folic acid (FA) as a tumor-targeting ligand is widely used because of overexpression of folate receptor-α (FR-α) in various kinds of epithelial tumor cells. On the other hand, methyl-β-cyclodextrin (M-β-CyD) is acknowledged to induce cell death through the extraction of cholesterol from lipid rafts. It was recently reported that intraperitoneal administration of M-β-CyD exerted antitumor activity in human tumor xenografted athymic nude mice. However, the cytotoxic activity of M-β-CyD is known to lack tumor cell selectivity. Therefore in the present study, in an attempt to confer tumor cell selectivity to M-β-CyD, we newly synthesized folate-appended M-β-CyD (FA-M-β-CyD) and evaluated its potential as a novel antitumor agent. FA-M-β-CyD showed potent antitumor activity in various FR-α-positive cells such as KB cells, Ihara cells, and M213 cells but not in FR-α-negative cells, A549 cells. FA-M-β-CyD induced the formation of autophagic vacuoles in KB cells. In addition, the antitumor activity of FA-M-β-CyD, but not M-β-CyD, was inhibited by addition of the autophagy inhibitors chloroquine and bafilomycin A1 in KB cells. A single intravenous injection of FA-M-β-CyD drastically inhibited tumor growth and significantly improved survival rate in Colon-26 cells-allografted or M213 cells-xenografted mice. In conclusion, FA-M-β-CyD has potential as a novel tumor-selective anticancer agent due to FR-α-mediated cellular uptake. The present results provide useful information for the design and development of novel antitumor drug carriers and antitumor drugs based on CyDs. PMID:26521878

  10. Molecular Processing of Polymers with Cyclodextrins

    NASA Astrophysics Data System (ADS)

    Tonelli, Alan E.

    We summarize our recent studies employing the cyclic starch derivatives called cyclodextrins (CDs) to both nanostructure and functionalize polymers. Two important structural characteristics of CDs are taken advantage of to achieve these goals. First the ability of CDs to form noncovalent inclusion complexes (ICs) with a variety of guest molecules, including many polymers, by threading and inclusion into their relatively hydrophobic interior cavities, which are roughly cylindrical with diameters of ˜ 0.5 - 1.0 nm. α-, β-, and γ-CD contain six, seven, and eight α-1,4-linked glucose units, respectively. Warm water washing of polymer-CD-ICs containing polymer guests insoluble in water or treatment with amylase enzymes serves to remove the host CDs and results in the coalescence of the guest polymers into solid samples. When guest polymers are coalesced from the CD-ICs by removing their host CDs, they are observed to solidify with structures, morphologies, and even conformations that are distinct from bulk samples made from their solutions and melts. Molecularly mixed, intimate blends of two or more polymers that are normally immiscible can be obtained from their common CD-ICs, and the phase segregation of incompatible blocks can be controlled (suppressed or increased) in CD-IC coalesced block copolymers. In addition, additives may be more effectively delivered to polymers in the form of their crystalline CD-ICs or soluble CD-rotaxanes. Secondly, the many hydroxyl groups attached to the exterior rims of CDs, in addition to conferring water solubility, provide an opportunity to covalently bond them to polymers either during their syntheses or via postpolymerization reactions. Polymers containing CDs in their backbones or attached to their side chains are observed to more readily accept and retain additives, such as dyes and fragrances. Processing with CDs can serve to both nanostructure and functionalize polymers, leading to greater understanding of their behaviors

  11. Effects of cogrinding with β-cyclodextrin on the solid state fentanyl.

    PubMed

    Ogawa, Noriko; Higashi, Kenjirou; Nagase, Hiromasa; Endo, Tomohiro; Moribe, Kunikazu; Loftsson, Thorsteinn; Yamamoto, Keiji; Ueda, Haruhisa

    2010-12-01

    Fentanyl base and β-cyclodextrin (β-CD) were coground at 1:1 and 1:2 molar ratios (fentanyl: β-CD) and the physicochemical characteristics of the mixtures were studied using differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), solid state (13)C nuclear magnetic resonance (NMR) spectroscopy and powder X-ray diffraction (PXRD) measurement. Additionally, portions of the coground samples were exposed to high relative humidity to investigate fentanyl and β-CD interactions. The results of DSC and PXRD analyses indicate that the ground mixtures are in an amorphous state, and the FTIR measurements show hydrogen bonding interactions between fentanyl and β-CD. Solid state (13)C NMR indicates that a fentanyl/β-CD inclusion compound is formed in the humidified mixture. Furthermore, PXRD data from the humidified mixtures are similar to the PXRD patterns from the inclusion complex.

  12. Binding of a double-chain surfactant-cobalt(III) complex to CT DNA: effect of β-cyclodextrin in the medium.

    PubMed

    Nagaraj, Karuppiah; Arunachalam, Sankaralingam

    2013-11-01

    The interaction of cis-[Co(phen)2(HA)2](ClO4)3, a cationic surfactant complex (phen=1,10-phenanthroline, HA=hexadecylamine), with calf thymus DNA has been studied by UV-vis absorption, fluorescence spectroscopy, cyclic voltammetry, circular dichroism, and viscosity measurements. The spectroscopic studies together with cyclic voltammetry and viscosity experiments support that the surfactant-cobalt(III) complex binds to calf thymus DNA (CT DNA) by intercalation through the aliphatic chain present in the complex into the base pairs of DNA. The presence of phenanthroline ligand with larger π-frame work may also enhance intercalation. Besides the effect of binding of surfactant cobalt(III) complex to DNA in presence of β-cyclodextrin has also studied. In presence of β-cyclodextrin the binding occurs through surface and (or) groove binding. The complex was investigated as one of the potential selective anticancer prodrugs. The complex was tested also in vitro on human monolayer tumor cell lines: HepG2 (human hepatocellular liver carcinoma). PMID:24041997

  13. Design and compressibility of Langmuir monolayers from organometallic nanocyclic complexes

    NASA Astrophysics Data System (ADS)

    Grushevskaya, H. V.; Krylova, N. G.; Lipnevich, I. V.

    2016-08-01

    We propose to control design of organometallic conducting Langmuir monolayer by utilizing geometrodynamic approach. By means of this approach the compressibility of the monolayer, which consists of molecules of thiophene-pyrrole series oligomer with covalently bound hydrophobic alkyl chain, has been analyzed for different subphase with iron salts. It has been discovered that the monolayers are polymerized and turn into monolayers of nanocyclic organometallic coordination compounds at a two-dimensional phase transition of the first order.

  14. Glitter in a 2D monolayer.

    PubMed

    Yang, Li-Ming; Dornfeld, Matthew; Frauenheim, Thomas; Ganz, Eric

    2015-10-21

    We predict a highly stable and robust atomically thin gold monolayer with a hexagonal close packed lattice stabilized by metallic bonding with contributions from strong relativistic effects and aurophilic interactions. We have shown that the framework of the Au monolayer can survive 10 ps MD annealing simulations up to 1400 K. The framework is also able to survive large motions out of the plane. Due to the smaller number of bonds per atom in the 2D layer compared to the 3D bulk we observe significantly enhanced energy per bond (0.94 vs. 0.52 eV per bond). This is similar to the increase in bond strength going from 3D diamond to 2D graphene. It is a non-magnetic metal, and was found to be the global minima in the 2D space. Phonon dispersion calculations demonstrate high kinetic stability with no negative modes. This 2D gold monolayer corresponds to the top monolayer of the bulk Au(111) face-centered cubic lattice. The close-packed lattice maximizes the aurophilic interactions. We find that the electrons are completely delocalized in the plane and behave as 2D nearly free electron gas. We hope that the present work can inspire the experimental fabrication of novel free standing 2D metal systems.

  15. Monolayer phase coarsening using oscillatory flow

    NASA Astrophysics Data System (ADS)

    Leung, J.; Lopez, J. M.; Vogel, M. J.

    2005-11-01

    The co-existing phase domains of monolayers commonly observed via microscope are examined on flowing systems. Recent evidence shows that co-existing phase domains have profound effects on monolayer response to bulk flow. The present flow geometry consists of an open-top rectangular cavity in which the flow is driven by the periodic oscillation of the floor in its own plane. The oscillation of the floor dilates and compresses any film at the gas/liquid interface while still maintaining an essentially flat interface. A range of flow conditions (oscillation frequency and amplitude) is chosen so that the flow remains essentially two-dimensional. Measurements at the interface, initially covered by an insoluble monolayer (vitamin K1 or stearic acid), are made using a Brewster angle microscope system with a pulsed laser. Various phenomena such as fragmentation (breaking up of co-existing domains into finer ones) had previously been observed in sheared monolayer flows. In this new flow regime, we have seen dramatic coarsening of the domains. Interesting relaxation behavior at short and long time scales will also be discussed.

  16. Adsorption of Ions at Uncharged Insoluble Monolayers.

    PubMed

    Peshkova, Tatyana V; Minkov, Ivan L; Tsekov, Roumen; Slavchov, Radomir I

    2016-09-01

    A method is proposed for the experimental determination of the adsorption of inorganic electrolytes at a surface covered with insoluble surfactant monolayer. This task is complicated by the fact that the change of the salt concentration alters both chemical potentials of the electrolyte and the surfactant. Our method resolves the question by combining data for the surface pressure versus area of the monolayer at several salt concentrations with data for the equilibrium spreading pressure of crystals of the surfactant (used to fix a standard state). We applied the method to alcohols spread at the surface of concentrated halide solutions. The measured salt adsorption is positive and has nonmonotonic dependence on the area per surfactant molecule. For the liquid expanded film, depending on the concentration, there is one couple of ions adsorbed per each 3-30 surfactant molecules. We analyzed which ion, the positive or the negative, stands closer to the surface, by measuring the effect of NaCl on the Volta potential of the monolayer. The potentiometric data suggest that Na(+) is specifically adsorbed, while Cl(-) remains in the diffuse layer, i.e., the surface is positively charged. The observed reverse Hofmeister series of the adsorptions of NaF, NaCl, and NaBr suggests the same conclusion holds for all these salts. The force that causes the adsorption of Na(+) seems to be the interaction of the ion with the dipole moment of the monolayer. PMID:27529571

  17. Hydrolytic kinetics of biodegradable polyester monolayers

    SciTech Connect

    Lee, W.K.; Gardella, J.A. Jr.

    2000-04-04

    The rate of hydrolysis of Langmuir monolayer films of a series of biodegradable polyesters was investigated at the air/water interface. The present study investigated parameters such as degradation medium, pH, and time. The hydrolysis of polyester monolayers strongly depended on both the degradation medium used to control subphase pH and the concentration of active ions. Under the conditions studied here, polymer monolayers showed faster hydrolysis when they were exposed to a basic subphase rather than that of acidic or neutral subphase. The basic (pH = 10) hydrolysis of [poly(l-lactide)/polycaprolactone](l-PLA/PCL 1/1 by mole) blend was faster than that of each homopolymer at the initial stage. This result is explained by increasing numbers of base attack sites per unit area owing to the very slow hydrolysis of PCL, a dilution effect on the concentration of l-PLA monolayers. Conversely the hydrolytic behavior of l-lactide-co-caprolactone (1/1 by mole) was similar to that of PCL even though the chemical compositions of the blend and the copolymer are very similar to each other. The resistance of the copolymer to hydrolysis might be attributed to the hydrophobicity and the steric hindrance of caprolactone unit in the copolymer.

  18. Nanotubes based on monolayer blue phosphorus

    NASA Astrophysics Data System (ADS)

    Montes, E.; Schwingenschlögl, U.

    2016-07-01

    We demonstrate structural stability of monolayer zigzag and armchair blue phosphorus nanotubes by means of molecular dynamics simulations. The vibrational spectrum and electronic band structure are determined and analyzed as functions of the tube diameter and axial strain. The nanotubes are found to be semiconductors with a sensitive indirect band gap that allows flexible tuning.

  19. Adsorption of Ions at Uncharged Insoluble Monolayers

    NASA Astrophysics Data System (ADS)

    Peshkova, T. V.; Minkov, I. L.; Tsekov, R.; Slavchov, R. I.

    2016-08-01

    A method is proposed for the experimental determination of the adsorption of inorganic electrolytes at a surface covered with insoluble surfactant monolayer. This task is complicated by the fact that the change of the salt concentration alters both chemical potentials of the electrolyte and the surfactant. Our method resolves the question by combining data for the surface pressure versus area of the monolayer at several salt concentrations with data for the equilibrium spreading pressure of crystals of the surfactant (used to fix a standard state). We applied the method to alcohols spread at the surface of concentrated halide solutions. The measured salt adsorption is positive and has nonmonotonic dependence on the area per surfactant molecule. For the liquid expanded film, depending on the concentration, there is one couple of ions adsorbed per each 3–30 surfactant molecules. We analyzed which ion, the positive or the negative, stands closer to the surface, by measuring the effect of NaCl on the Volta potential of the monolayer. The potentiometric data suggest that Na+ is specifically adsorbed, while Cl– remains in the diffuse layer, i.e., the surface is positively charged. The observed reverse Hofmeister series of the adsorptions of NaF, NaCl, and NaBr suggests the same conclusion holds for all these salts. The force that causes the adsorption of Na+ seems to be the interaction of the ion with the dipole moment of the monolayer.

  20. Convective Assembly of a Particle Monolayer.

    PubMed

    Fleck, N A; McMeeking, R M; Kraus, T

    2015-12-29

    Recently, the steady-state process of convective assembly has emerged as a viable production route for colloidal monolayers. The present study models the regions of particle assembly: Region I comprises convective concentration of a particle suspension in a liquid below a meniscus, Region II comprises permeation of fluid through the dense particle monolayer, and Region III comprises capillary densification. For each region, the dominant physics and nondimensional groups are identified, and quantitative models are derived to describe the evolution of microstructure in terms of the main process parameters. The concentration profile within the assembly zone of Region I is predicted, including the role of a concentration-dependent diffusion constant and the shape of the meniscus. The fluid flow through the assembled monolayer is treated in Region II, along with a stability calculation to reveal that isolated particle clusters do not survive on top of the monolayer. The physics of capillary crystallization is addressed in Region III, with an emphasis on the density of cracks that emerge. The Peclet number and Capillary number both play important roles but in different regions of the assembly process.

  1. Supramolecular inclusion complexes between a coumarin dye and β-cyclodextrin, and attachment kinetics of thiolated β-cyclodextrin to gold surface

    NASA Astrophysics Data System (ADS)

    Velic, Dusan; Knapp, Martin; Köhler, Gottfried

    2001-10-01

    Supramolecular host-guest complexes formed between dye molecules, which are absorbing and fluorescing in the visible range, and cyclodextrin molecules are studied with the aim to generate a self-assembled nanostructured layer on a surface. Studies in solution show that an aminocoumarin dye, i.e. coumarin-6, binds strongly to β-cyclodextrin and yields fluorescent structures. The complex formation is substantiated by 17 nm blue shift of the fluorescence spectrum. The binding of thiolated cyclodextrin, 6-monodeoxy-6-monothio-β-cyclodextrin, to gold surface is then studied by induced change in the second-harmonic signal intensity generated from the surface. The saturation times of surface adsorption, as a measure of binding kinetics, are estimated for thiolated cyclodextrin as well as hexadecanethiol. The results support formation of self-assembled layers of the host molecules, which can serve as basis for the formation of supramolecular host-guest surface layers.

  2. Study on the interaction between the inclusion complex of hematoxylin with β-cyclodextrin and DNA.

    PubMed

    Xu, Dongling; Wang, Xingming; Fei, Dan; Ding, Lisheng

    2010-11-01

    Ultraviolet-visible (UV-vis) spectra, fluorescence spectra, electrochemistry, and the thermodynamic method were used to discuss the interaction mode between the inclusion complex of hematoxylin with β-cyclodextrin and herring sperm DNA. On the condition of physiological pH, the result showed that hematoxylin and β-cyclodextrin formed an inclusion complex with binding ratio n(hematoxylin):n(β-cyclodextrin) = 1:1. The interaction mode between β-cyclodextrin-hematoxylin and DNA was a mixed binding, which contained intercalation and electrostatic mode. The binding ratio between β-cyclodextrin-hematoxylin and DNA was n(β-cyclodextrin -hematoxylin):n(DNA) = 2:1, binding constant was K(⊖)(298.15K) = 5.29 × 10⁴ L·mol⁻¹, and entropy worked as driven force in this action.

  3. Impact of Mixed β-Cyclodextrin Ratios on Pluronic Rotaxanation Efficiency and Product Solubility.

    PubMed

    Mondjinou, Yawo A; Hyun, Seok-Hee; Xiong, Manxi; Collins, Christopher J; Thong, Pooi Ling; Thompson, David H

    2015-11-01

    Water-soluble polyrotaxanes have been prepared under heterogeneous conditions from mixtures of β-cyclodextrin (β-CD), 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), methyl-β-cyclodextrin, or 6-monoazido-β-cyclodextrin with 4-sulfobutyl ether-β-cyclodextrin (SBE-β-CD) and Pluronic L81 copolymer modified with cholesterol end caps. Threading reactions gave polyrotaxane products in modest chemical yield that were reflective of the β-CD feed ratios in the reaction. Polyrotaxanes containing mixtures of HP-β-CD and SBE-β-CD were screened and found to be biologically active in an in vitro model of Niemann-Pick Type C disease where they mobilize aberrantly stored cholesterol similarly to monomeric cyclodextrin controls.

  4. Inclusion and functionalization of polymers with cyclodextrins: current applications and future prospects.

    PubMed

    Folch-Cano, Christian; Yazdani-Pedram, Mehrdad; Olea-Azar, Claudio

    2014-01-01

    The numerous hydroxyl groups available in cyclodextrins are active sites that can form different types of linkages. They can be crosslinked with one another, or they can be derivatized to produce monomers that can form linear or branched networks. Moreover, they can form inclusion complexes with polymers and different substrates, modifying their physicochemical properties. This review shows the different applications using polymers with cyclodextrins, either by forming inclusion complexes, ternary complexes, networks, or molecularly imprinted polymers (MIPs). On one hand, the use of cyclodextrins enhances the properties of each polymer, and on the other the use of polymers decreases the amount of cyclodextrins required in different formulations. Both cyclodextrins and polymers contribute synergistically in several applications such as pharmacological, nutritional, environmental, and other industrial fields. The use of polymers based on cyclodextrins is a low cost easy to use potential tool with great future prospects.

  5. Cyclodextrins found in enzyme- and heat-processed starch-containing foods.

    PubMed

    Szente, Lajos; Harangi, Janos; Greiner, Manfred; Mandel, Friedrich

    2006-09-01

    Native and branched-type (glucosylated and maltosylated) cyclodextrins have been isolated and identified in different enzyme- and heat-processed starch-containing food products. Amylolytic enzyme-processed foods such as different beer samples, corn syrup of different dextrose equivalents, and thermally-processed food such as bread, contained minute amounts of different types of cyclodextrins. HPLC/MS Analyses of appropriately preconcentrated and purified food samples indicated the presence of parent beta- and gamma-cyclodextrins and all the three, alpha-, beta-, and gamma-branched cyclodextrins with different degrees of glycosylation. The data presented in this account are thought to be of practical importance in terms of both the analysis methods used for the cyclodextrins and the approval status of different cyclodextrin-containing food, cosmetic, and pharmaceutical products.

  6. A computer model of engineered cardiac monolayers.

    PubMed

    Kim, Jong M; Bursac, Nenad; Henriquez, Craig S

    2010-05-19

    Engineered monolayers created using microabrasion and micropatterning methods have provided a simplified in vitro system to study the effects of anisotropy and fiber direction on electrical propagation. Interpreting the behavior in these culture systems has often been performed using classical computer models with continuous properties. However, such models do not account for the effects of random cell shapes, cell orientations, and cleft spaces inherent in these monolayers on the resulting wavefront conduction. This work presents a novel methodology for modeling a monolayer of cardiac tissue in which the factors governing cell shape, cell-to-cell coupling, and degree of cleft space are not constant but rather are treated as spatially random with assigned distributions. This modeling approach makes it possible to simulate wavefront propagation in a manner analogous to performing experiments on engineered monolayer tissues. Simulated results are compared to previously published measured data from monolayers used to investigate the role of cellular architecture on conduction velocities and anisotropy ratios. We also present an estimate for obtaining the electrical properties from these networks and demonstrate how variations in the discrete cellular architecture affect the macroscopic conductivities. The simulations support the common assumption that under normal ranges of coupling strength, tissues with relatively uniform distributions of cell shapes and connectivity can be represented using continuous models with conductivities derived from random discrete cellular architecture using either global or local estimates. The results also reveal that in the presence of abrupt changes in cell orientation, local estimates of tissue properties predict smoother changes in conductivity that may not adequately predict the discrete nature of propagation at the transition sites. PMID:20441739

  7. Cyclodextrin-based Polymeric Nanoparticles as Efficient Carriers for Anticancer Drugs.

    PubMed

    Duchene, Dominique; Cavalli, Roberta; Gref, Ruxandra

    2016-01-01

    Among the difficulties encountered in the treatment of cancer are the physico-chemical properties of the chemotherapeutic agents; in particular low water solubility and low stability, resulting in poor efficacy. Due to their capability to form molecular inclusions with apolar molecules (or part of them) cyclodextrins constitute a powerful tool to prepare more efficient chemotherapeutic delivery systems such as nanoparticles. This review focuses on polymeric nanoparticles for cancer therapy prepared from either cyclodextrin molecules, or polymer and cyclodextrins. PMID:26517333

  8. Phosphorus-containing cyclodextrins. Characteristics of the synthesis and chemical behaviour

    NASA Astrophysics Data System (ADS)

    Grachev, M. K.

    2013-11-01

    Published data on the preparation of phosphorus-containing cyclodextrins are summarized. It is demonstrated that some significant features of their synthesis and chemical behaviour are caused by specific supramolecular interactions involving the inner chiral cavity of cyclodextrins capable of incorporating various guests, which often leads to alteration of customary routes of chemical transformations. The possibilities of practical applications of phosphorus-containing cyclodextrins are briefly analyzed. The bibliography includes 89 references.

  9. Collective cell streams in epithelial monolayers depend on cell adhesion

    NASA Astrophysics Data System (ADS)

    Czirók, András; Varga, Katalin; Méhes, Előd; Szabó, András

    2013-07-01

    We report spontaneously emerging, randomly oriented, collective streaming behavior within a monolayer culture of a human keratinocyte cell line, and explore the effect of modulating cell adhesions by perturbing the function of calcium-dependent cell adhesion molecules. We demonstrate that decreasing cell adhesion induces narrower and more anisotropic cell streams, reminiscent of decreasing the Taylor scale of turbulent liquids. To explain our empirical findings, we propose a cell-based model that represents the dual nature of cell-cell adhesions. Spring-like connections provide mechanical stability, while a cellular Potts model formalism represents surface-tension driven attachment. By changing the relevance and persistence of mechanical links between cells, we are able to explain the experimentally observed changes in emergent flow patterns.

  10. A self assembled monolayer based microfluidic sensor for urea detection

    NASA Astrophysics Data System (ADS)

    Srivastava, Saurabh; Solanki, Pratima R.; Kaushik, Ajeet; Ali, Md. Azahar; Srivastava, Anchal; Malhotra, B. D.

    2011-07-01

    Urease (Urs) and glutamate dehydrogenase (GLDH) have been covalently co-immobilized onto a self-assembled monolayer (SAM) comprising of 10-carboxy-1-decanthiol (CDT) via EDC-NHS chemistry deposited onto one of the two patterned gold (Au) electrodes for estimation of urea using poly(dimethylsiloxane) based microfluidic channels (2 cm × 200 μm × 200 μm). The CDT/Au and Urs-GLDH/CDT/Au electrodes have been characterized using Fourier transform infrared (FTIR) spectroscopy, contact angle (CA), atomic force microscopy (AFM) and electrochemical cyclic voltammetry (CV) techniques. The electrochemical response measurement of a Urs-GLDH/CDT/Au bioelectrode obtained as a function of urea concentration using CV yield linearity as 10 to 100 mg dl-1, detection limit as 9 mg dl-1 and high sensitivity as 7.5 μA mM-1 cm-2.

  11. Collective cell streams in epithelial monolayers depend on cell adhesion

    PubMed Central

    Czirók, András; Varga, Katalin; Méhes, Előd; Szabó, András

    2013-01-01

    We report a spontaneously emerging, randomly oriented, collective streaming behavior within a monolayer culture of a human keratinocyte cell line, and explore the effect of modulating cell adhesions by perturbing the function of calcium-dependent cell adhesion molecules. We demonstrate that decreasing cell adhesion induces narrower and more anisotropic cell streams, reminiscent of decreasing the Taylor scale of turbulent liquids. To explain our empirical findings, we propose a cell-based model that represents the dual nature of cell-cell adhesions. Spring-like connections provide mechanical stability, while a cellular Potts model formalism represents surface-tension driven attachment. By changing the relevance and persistence of mechanical links between cells, we are able to explain the experimentally observed changes in emergent flow patterns. PMID:24363603

  12. Propulsion and navigation within the advancing monolayer sheet

    NASA Astrophysics Data System (ADS)

    Kim, Jae Hun; Serra-Picamal, Xavier; Tambe, Dhananjay T.; Zhou, Enhua H.; Park, Chan Young; Sadati, Monirosadat; Park, Jin-Ah; Krishnan, Ramaswamy; Gweon, Bomi; Millet, Emil; Butler, James P.; Trepat, Xavier; Fredberg, Jeffrey J.

    2013-09-01

    As a wound heals, or a body plan forms, or a tumour invades, observed cellular motions within the advancing cell swarm are thought to stem from yet to be observed physical stresses that act in some direct and causal mechanical fashion. Here we show that such a relationship between motion and stress is far from direct. Using monolayer stress microscopy, we probed migration velocities, cellular tractions and intercellular stresses in an epithelial cell sheet advancing towards an island on which cells cannot adhere. We found that cells located near the island exert tractions that pull systematically towards this island regardless of whether the cells approach the island, migrate tangentially along its edge, or paradoxically, recede from it. This unanticipated cell-patterning motif, which we call kenotaxis, represents the robust and systematic mechanical drive of the cellular collective to fill unfilled space.

  13. Effects of cyclodextrins on the structure of LDL and its susceptibility to copper-induced oxidation.

    PubMed

    Ao, Meiying; Gan, Chaoye; Shao, Wenxiang; Zhou, Xing; Chen, Yong

    2016-08-25

    Cyclodextrins (CDs) have long been widely used as drug/food carriers and were recently developed as drugs for the treatment of diseases (e.g. Niemann-Pick C1 and cancers). It is unknown whether cyclodextrins may influence the structure of low-density lipoprotein (LDL), its susceptibility to oxidation, and atherogenesis. In this study, four widely used cyclodextrins including α-CD, γ-CD, and two derivatives of β-CD (HPβCD and MβCD) were recruited. Interestingly, agarose gel electrophoresis (staining lipid and protein components of LDL with Sudan Black B and Coomassie brilliant blue, respectively but simultaneously) shows that cyclodextrins at relatively high concentrations caused disappearance of the LDL band and/or appearance of an additional protein-free lipid band, implying that cyclodextrins at relatively high concentrations can induce significant electrophoresis-detectable lipid depletion of LDL. Atomic force microscopy (AFM) detected that MβCD (as a representative of cyclodextrins) induced size decrease of LDL particles in a dose-dependent manner, further confirming the lipid depletion effects of cyclodextrins. Moreover, the data from agarose gel electrophoresis, conjugated diene formation, MDA production, and amino group blockage of copper-oxidized LDL show that cyclodextrins can impair LDL susceptibility to oxidation. It implies that cyclodextrins probably help to inhibit atherogenesis by lowering LDL oxidation. PMID:27140842

  14. Effects of cyclodextrins on the structure of LDL and its susceptibility to copper-induced oxidation.

    PubMed

    Ao, Meiying; Gan, Chaoye; Shao, Wenxiang; Zhou, Xing; Chen, Yong

    2016-08-25

    Cyclodextrins (CDs) have long been widely used as drug/food carriers and were recently developed as drugs for the treatment of diseases (e.g. Niemann-Pick C1 and cancers). It is unknown whether cyclodextrins may influence the structure of low-density lipoprotein (LDL), its susceptibility to oxidation, and atherogenesis. In this study, four widely used cyclodextrins including α-CD, γ-CD, and two derivatives of β-CD (HPβCD and MβCD) were recruited. Interestingly, agarose gel electrophoresis (staining lipid and protein components of LDL with Sudan Black B and Coomassie brilliant blue, respectively but simultaneously) shows that cyclodextrins at relatively high concentrations caused disappearance of the LDL band and/or appearance of an additional protein-free lipid band, implying that cyclodextrins at relatively high concentrations can induce significant electrophoresis-detectable lipid depletion of LDL. Atomic force microscopy (AFM) detected that MβCD (as a representative of cyclodextrins) induced size decrease of LDL particles in a dose-dependent manner, further confirming the lipid depletion effects of cyclodextrins. Moreover, the data from agarose gel electrophoresis, conjugated diene formation, MDA production, and amino group blockage of copper-oxidized LDL show that cyclodextrins can impair LDL susceptibility to oxidation. It implies that cyclodextrins probably help to inhibit atherogenesis by lowering LDL oxidation.

  15. γ-Cyclodextrin capped silver nanoparticles for molecular recognition and enhancement of antibacterial activity of chloramphenicol.

    PubMed

    Gannimani, Ramesh; Ramesh, Muthusamy; Mtambo, Sphamandla; Pillay, Karen; Soliman, Mahmoud E; Govender, Patrick

    2016-04-01

    Computational studies were conducted to identify the favourable formation of the inclusion complex of chloramphenicol with cyclodextrins. The results of molecular docking and molecular dynamics predicted the strongest interaction of chloramphenicol with γ-cyclodextrin. Further, the inclusion complex of chloramphenicol with γ-cyclodextrin was experimentally prepared and a phenomenon of inclusion was verified by using different characterization techniques such as thermogravimetric analysis, differential scanning calorimetry, (1)H nuclear magnetic resonance (NMR) and two dimensional nuclear overhauser effect spectroscopy (NOESY) experiments. From these results it was concluded that γ-cyclodextrins could be an appropriate cyclodextrin polymer which can be used to functionalize chloramphenicol on the surface of silver nanoparticles. In addition, γ-cyclodextrin capped silver nanoparticles were synthesized and characterized using UV-visible spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), Fourier transform infrared spectroscopy (FTIR) and zeta potential analysis. Molecular recognition of chloramphenicol by these cyclodextrin capped silver nanoparticles was confirmed by surface enhanced raman spectroscopy (SERS) experiments. Synergistic antibacterial effect of chloramphenicol with γ-cyclodextrin capped silver nanoparticles was evaluated against Pseudomonas aeruginosa (ATCC 27853), Enterococcus faecalis (ATCC 5129), Klebsiella pneumoniae (ATCC 700603) and Staphylococcus aureus (ATCC 43300). The results from the antibacterial experiment were favourable thus allowing us to conclude that the approach of modifying organic drug molecules with cyclodextrin capped inorganic silver nanoparticles could help to enhance the antibacterial activity of them.

  16. Adsorption of environmental pollutants using magnetic hybrid nanoparticles modified with β-cyclodextrin

    NASA Astrophysics Data System (ADS)

    Wang, Niejun; Zhou, Lilin; Guo, Jun; Ye, Qiquan; Lin, Jin-Ming; Yuan, Jinying

    2014-06-01

    Graft through strategy was utilized to coat magnetic Fe3O4 nanoparticles with poly(glycidyl methacrylate) using ordinary radical polymerization and then β-cyclodextrin was linked onto the surface of nanoparticles. With these nanoparticles modified with cyclodextrin groups, adsorption of two model environmental pollutants, bisphenol A and copper ions, was studied. Host-guest interactions between cyclodextrin and aromatic molecules had a great contribution to the adsorption of bisphenol A, while multiple hydroxyls of cyclodextrin also helped the adsorption of copper ions. These magnetic nanoparticles could be applied in the elimination, enrichment and detection of some environmental pollutants.

  17. β-Cyclodextrin as the suitable molecular container for isopulegol enantiomers.

    PubMed

    Ceborska, Magdalena; Szwed, Kamila; Suwinska, Kinga

    2013-09-12

    Isopulegol, an insoluble in water and highly volatile compound, due to its neuroactive properties is a potentially important agent for medical applications. Formation of "host-guest" molecular complexes with cyclodextrins would lead to the increase of its water solubility and bioavailability. Interactions between native cyclodextrins (α, β and γ) and isopulegol enantiomers were studied in solution proving the formation of inclusion complexes for β- and γ-cyclodextrins. For the more stable complexes with β-cyclodextrin crystal structures were obtained showing the formation of molecular capsules forming molecular container able to accommodate two guest molecules. PMID:23911483

  18. Cyclodextrin nanosponge-sensitized enantiodifferentiating photoisomerization of cyclooctene and 1,3-cyclooctadiene.

    PubMed

    Liang, Wenting; Yang, Cheng; Nishijima, Masaki; Fukuhara, Gaku; Mori, Tadashi; Mele, Andrea; Castiglione, Franca; Caldera, Fabrizio; Trotta, Francesco; Inoue, Yoshihisa

    2012-01-01

    Enantiodifferentiating geometrical photoisomerizations of (Z)-cyclooctene and (Z,Z)-1,3-cyclooctadiene were performed by using the pyromellitate-linked cyclodextrin network polymer, termed "cyclodextrin nanosponge (CDNS)", as a supramolecular sensitizing host. The photochirogenic behavior of the nanosponges incorporating β- or γ-cyclodextrin was significantly different from that reported for the conventional sensitizer-appended monomeric cyclodextrins, affording chiral (E)-cyclooctene and (E,Z)-cyclooctadiene in enantiomeric excesses critically dependent on the solution pH and solvent composition employed, revealing the active roles of chiral void spaces of CDNS in the photochirogenic reaction.

  19. Enhanced Fenton degradation of hydrophobic organics by simultaneous iron and pollutant complexation with cyclodextrins.

    PubMed

    Lindsey, Michele E; Xu, Guoxiang; Lu, Jia; Tarr, Matthew A

    2003-05-20

    The effectiveness and selectivity of Fenton degradation of hydrophobic organic compounds (HOCs) can be improved by simultaneous complexation of Fe(2+) and the organic compound with a cyclodextrin or derivatized cyclodextrin. Such selective complexation of a target substrate and a catalytic metal is a crude mimic of enzyme systems. Both beta-cyclodextrin and carboxymethyl-beta-cyclodextrin (CMCD) were able to simultaneously complex Fe(2+) and an aromatic hydrocarbon, such as phenol, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls (PCBs). Degradation of compounds included in cyclodextrins was unaffected by hydroxyl radical scavengers, indicating that the radical was formed at the ternary complex (HOC-cyclodextrin-iron) and in close proximity to the included molecule. Without cyclodextrins, humic acid (HA) decreased degradation efficiency. However, in the presence of CMCD, HA did not inhibit degradation of the target compound. CMCD is capable of removing HOCs from HA binding sites while at the same time complexing Fe(2+). PCBs sorbed to glass were resistant to Fenton degradation, but were significantly degraded using a cyclodextrin modified Fenton system. In all of these systems, the ternary HOC-cyclodextrin-iron complexes effectively direct hydroxyl radical reaction toward the HOC, increasing the efficiency of Fenton degradation. One potential application of such targeted degradation systems is the in situ remediation of hydrophobic organic pollutants in contaminated soil and groundwater or in industrial waste streams.

  20. Redox-controlled interaction of biferrocenyl-terminated dendrimers with beta-cyclodextrin molecular printboards.

    PubMed

    Nijhuis, Christian A; Dolatowska, Karolina A; Ravoo, Bart Jan; Huskens, Jurriaan; Reinhoudt, David N

    2007-01-01

    This paper describes the synthesis and electrochemistry of biferrocenyl-terminated dendrimers and their beta-cyclodextrin (beta-CD) inclusion complexes in aqueous solution and at surfaces. Three generations of poly(propylene imine) (PPI) dendrimers, decorated with 4, 8, and 16 biferrocenyl (BFc) units, respectively, were synthesized. A water-soluble BFc derivative forms stable inclusion complexes with beta-CD. The intrinsic binding constant is K(i)=2.5 x 10(4) M(-1). The BFc dendrimers were solubilized in water by complexation of the end groups with beta-CD, resulting in large water-soluble supramolecular assemblies. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) showed that all the end groups are complexed to beta-CD. Adsorption of the dendrimers at self-assembled monolayers (SAMs) of heptathioether-functionalized beta-CD on gold ("molecular printboards") resulted in stable monolayers of the dendrimers due to the formation of multivalent host-guest interactions between the BFc end groups of the dendrimers and the immobilized beta-CD molecules. The number of interacting end groups is 3, 4, and 4 for dendrimer generations 1, 2, and 3, respectively. The complexation of BFc to beta-CD is sensitive to the oxidation state of the BFc unit. Oxidation of neutral BFc-Fe(2) ((II,II)) to the cationic, mixed-valence biferrocenium BFc-Fe(2) ((II,III)+) resulted in dissociation of the host-guest complexes. Scan-rate-dependent CV and DPV analyses of the dendrimer-beta-CD assemblies immobilized at the beta-CD host surface and in solution revealed that the dendrimers are oxidized in three steps. First, the surface-beta-CD-bound BFc moieties are oxidized to the mixed-valence state, Fe(2) ((II,III)+), followed by the oxidation of the non-surface-interacting BFc groups to the Fe(2) ((II,III)+) state. The third step involves the oxidation of all the BFc moieties to the Fe(2) ((III,III)2+) state.

  1. Monolayer-Mediated Growth of Organic Semiconductor Films with Improved Device Performance.

    PubMed

    Huang, Lizhen; Hu, Xiaorong; Chi, Lifeng

    2015-09-15

    Increased interest in wearable and smart electronics is driving numerous research works on organic electronics. The control of film growth and patterning is of great importance when targeting high-performance organic semiconductor devices. In this Feature Article, we summarize our recent work focusing on the growth, crystallization, and device operation of organic semiconductors intermediated by ultrathin organic films (in most cases, only a monolayer). The site-selective growth, modified crystallization and morphology, and improved device performance of organic semiconductor films are demonstrated with the help of the inducing layers, including patterned and uniform Langmuir-Blodgett monolayers, crystalline ultrathin organic films, and self-assembled polymer brush films. The introduction of the inducing layers could dramatically change the diffusion of the organic semiconductors on the surface and the interactions between the active layer with the inducing layer, leading to improved aggregation/crystallization behavior and device performance. PMID:25992464

  2. Extended Moment Formation in Monolayer WS2 Doped with 3d Transition-Metals.

    PubMed

    Singh, Nirpendra; Schwingenschlögl, Udo

    2016-09-14

    First-principles calculations with onsite Coulomb interaction and spin-orbit coupling are used to investigate the electronic structure of monolayer WS2 doped substitutionally with 3d transition-metals. While neither W vacancies nor strain induce spin polarization, we demonstrate an unprecedented tendency to extended moment formation under doping. The extended magnetic moments are characterized by dopant-specific spin density patterns with rich structural features involving the nearest neighbor W and S atoms. PMID:27571717

  3. Seeded Growth of Highly Crystalline Molybdenum Disulphide Monolayers at Controlled Locations

    NASA Astrophysics Data System (ADS)

    Naylor, Carl; Han, Ganghee; Kybert, Nicholas; Ping, Jinglei; Johnson, A. T. Charlie

    2015-03-01

    Various approaches have been demonstrated for growth on insulating substrates of molybdenum disulphide (MoS2) , but to date growth of isolated crystalline flakes has been only at random locations. We have developed a method to obtain MoS2 flakes in precisely defined locations. By patterning molybdenum source material that acted both as material feedstock and growth seed at predetermined areas across a wafer, we were able to grow isolated flakes of MoS2 at these locations with micrometre-scale resolution. These MoS2 flakes are predominantly of monolayer thickness and high material quality, as confirmed by atomic force microscopy, transmission electron microscopy, Raman and photoluminescence spectroscopy. Since the monolayer flakes are isolated and in predetermined locations, fabrication of transistor structures requires only a single lithographic step. Thus we are able to obtain multiple arrays of MoS2 transistors, that are highly crystalline and monolayer, making this method ideal for large scale production. Device measurements showed a carrier mobility and on/off ratio that exceeded 10 cm2V-1s-1 and 106, respectively. This growth technique provides a path for in-depth physical analysis of monolayer MoS2 as well as fabrication of MoS2-based integrated circuits.

  4. Seeded growth of highly crystalline molybdenum disulphide monolayers at controlled locations.

    PubMed

    Han, Gang Hee; Kybert, Nicholas J; Naylor, Carl H; Lee, Bum Su; Ping, Jinglei; Park, Joo Hee; Kang, Jisoo; Lee, Si Young; Lee, Young Hee; Agarwal, Ritesh; Johnson, A T Charlie

    2015-01-28

    Monolayer transition metal dichalcogenides are materials with an atomic structure complementary to graphene but diverse properties, including direct energy bandgaps, which makes them intriguing candidates for optoelectronic devices. Various approaches have been demonstrated for the growth of molybdenum disulphide (MoS2) on insulating substrates, but to date, growth of isolated crystalline flakes has been demonstrated at random locations only. Here we use patterned seeds of molybdenum source material to grow flakes of MoS2 at predetermined locations with micrometre-scale resolution. MoS2 flakes are predominantly monolayers with high material quality, as confirmed by atomic force microscopy, transmission electron microscopy and Raman and photoluminescence spectroscopy. As the monolayer flakes are isolated at predetermined locations, transistor fabrication requires only a single lithographic step. Device measurements exhibit carrier mobility and on/off ratio that exceed 10 cm(2) V(-1) s(-1) and 10(6), respectively. The technique provides a path for in-depth physical analysis of monolayer MoS2 and fabrication of MoS2-based integrated circuits.

  5. Interplay between intercalated oxygen superstructures and monolayer h -BN on Cu(100)

    DOE PAGESBeta

    Ma, Chuanxu; Park, Jewook; Liu, Lei; Kim, Yong-Sung; Yoon, Mina; Baddorf, Arthur P.; Gu, Gong; Li, An-Ping

    2016-08-18

    The confinement effect of intercalated atoms in van der Waals heterostructures can lead to interesting interactions between the confined atoms or molecules and the overlaying two-dimensional (2D) materials. In this paper, we report the formation of ordered Cu(100) p(2×2) oxygen superstructures by oxygen intercalation under the monolayer hexagonal boron nitride (h-BN) on Cu after annealing. By using scanning tunneling microscopy and x-ray photoelectron spectroscopy, we identify the superstructure and reveal its roles in passivating the exposed Cu surfaces, decoupling h-BN and Cu, and disintegrating h-BN monolayers. The oxygen superstructure appears as a 2D pattern on the exposed Cu surface ormore » quasi-1D stripes of paired oxygen intercalated in the interface of h-BN and Cu predominantly oriented along the moiré modulations. The oxygen superstructure is shown to etch the overlaying h-BN monolayer in a thermal annealing process. After extended annealing, the h-BN monolayer disintegrates into nanoislands with zigzag edges. Finally, we discuss the implications of these findings on the stability and oxidation resistance of h-BN and relate them to challenges in process integration and 2D heterostructures.« less

  6. Interplay between intercalated oxygen superstructures and monolayer h -BN on Cu(100)

    NASA Astrophysics Data System (ADS)

    Ma, Chuanxu; Park, Jewook; Liu, Lei; Kim, Yong-Sung; Yoon, Mina; Baddorf, Arthur P.; Gu, Gong; Li, An-Ping

    2016-08-01

    The confinement effect of intercalated atoms in van der Waals heterostructures can lead to interesting interactions between the confined atoms or molecules and the overlaying two-dimensional (2D) materials. Here we report the formation of ordered Cu(100) p (2 ×2 ) oxygen superstructures by oxygen intercalation under the monolayer hexagonal boron nitride (h -BN) on Cu after annealing. By using scanning tunneling microscopy and x-ray photoelectron spectroscopy, we identify the superstructure and reveal its roles in passivating the exposed Cu surfaces, decoupling h -BN and Cu, and disintegrating h -BN monolayers. The oxygen superstructure appears as a 2D pattern on the exposed Cu surface or quasi-1D stripes of paired oxygen intercalated in the interface of h -BN and Cu predominantly oriented along the moiré modulations. The oxygen superstructure is shown to etch the overlaying h -BN monolayer in a thermal annealing process. After extended annealing, the h -BN monolayer disintegrates into nanoislands with zigzag edges. We discuss the implications of these findings on the stability and oxidation resistance of h -BN and relate them to challenges in process integration and 2D heterostructures.

  7. Molecular Dynamics in Self-Assembled Monolayers

    NASA Astrophysics Data System (ADS)

    Bochinski, Jason; Stevens, Derrick; Scott, Mary; Guy, Laura; Dedeugd, Casey; Clarke, Laura

    2007-03-01

    Silane self-assembled monolayers (SAMs) are an important tool for both scientific research and technological applications. Despite their widespread use, few experimental investigations have addressed molecular motion within these films, which offer a unique and useful physical system for fundamental scientific studies, such as observing dipolar and other glass transitions in two-dimensions. In addition, relaxations such as ``rotator'' phases where molecular groups rotate in a plane parallel to the surface have been correlated with film conductivity, adhesive, and wetting properties. We utilize surface-sensitive, dielectric relaxation spectroscopy to probe molecular motion as a function of temperature within silane chemistry-based monolayers formed upon interdigitated electrodes. Our latest results exploring a previously published motion as well as comparisons to linear polymer films will be discussed.

  8. Fracture Characteristics of Monolayer CVD-Graphene

    PubMed Central

    Hwangbo, Yun; Lee, Choong-Kwang; Kim, Sang-Min; Kim, Jae-Hyun; Kim, Kwang-Seop; Jang, Bongkyun; Lee, Hak-Joo; Lee, Seoung-Ki; Kim, Seong-Su; Ahn, Jong-Hyun; Lee, Seung-Mo

    2014-01-01

    We have observed and analyzed the fracture characteristics of the monolayer CVD-graphene using pressure bulge testing setup. The monolayer CVD-graphene has appeared to undergo environmentally assisted subcritical crack growth in room condition, i.e. stress corrosion cracking arising from the adsorption of water vapor on the graphene and the subsequent chemical reactions. The crack propagation in graphene has appeared to be able to be reasonably tamed by adjusting applied humidity and stress. The fracture toughness, describing the ability of a material containing inherent flaws to resist catastrophic failure, of the CVD-graphene has turned out to be exceptionally high, as compared to other carbon based 3D materials. These results imply that the CVD-graphene could be an ideal candidate as a structural material notwithstanding environmental susceptibility. In addition, the measurements reported here suggest that specific non-continuum fracture behaviors occurring in 2D monoatomic structures can be macroscopically well visualized and characterized. PMID:24657996

  9. Piezoelectric monolayers as nonlinear energy harvesters.

    PubMed

    López-Suárez, Miquel; Pruneda, Miguel; Abadal, Gabriel; Rurali, Riccardo

    2014-05-01

    We study the dynamics of h-BN monolayers by first performing ab-initio calculations of the deformation potential energy and then solving numerically a Langevine-type equation to explore their use in nonlinear vibration energy harvesting devices. An applied compressive strain is used to drive the system into a nonlinear bistable regime, where quasi-harmonic vibrations are combined with low-frequency swings between the minima of a double-well potential. Due to its intrinsic piezoelectric response, the nonlinear mechanical harvester naturally provides an electrical power that is readily available or can be stored by simply contacting the monolayer at its ends. Engineering the induced nonlinearity, a 20 nm2 device is predicted to harvest an electrical power of up to 0.18 pW for a noisy vibration of 5 pN. PMID:24722065

  10. Inclusion complexation between baicalein and β-cyclodextrin and the influence of β-cyclodextrin on the binding of baicalein with DNA: a spectroscopic approach.

    PubMed

    Sameena, Yousuf; Chandrasekaran, Sowrirajan; Israel V M V, Enoch

    2016-07-01

    This work deals with the commonly studied cyclic oligosaccharide and gains importance as it is entered on a drug delivering carbohydrate and provides insight into the oligosaccharide complex-biomolecular interaction. The binding of a flavone, baicalein, to β-cyclodextrin and calf thymus DNA is studied. The binding of baicalein to calf thymus DNA in the presence of β-cyclodextrin is analysed using the UV-vis absorption and fluorescence spectroscopy. The mode of binding and structure of the baicalein-β-cyclodextrin complex are reported. The role of the structure and the stoichiometry of the inclusion complex of baicalein-β-cyclodextrin in its influence on DNA binding are analysed. Highlights • This paper deals with the binding of a flavone, baicalein to β-cyclodextrin and/or DNA. • The inclusion complexation between baicalein and β-cyclodextrin is analysed. • The stoichiometry and the binding strength of the inclusion complex is reported. • The role of β-cyclodextrin in tuning the binding of baicalein to DNA is emphasized. • Spectroscopic and docking analysis are used to articulate the results.

  11. Growth of a collapsing Langmuir monolayer

    SciTech Connect

    Kundu, S.; Datta, A.; Hazra, S.

    2006-05-15

    Langmuir monolayers of stearic acid on Co ions in the aqueous subphase have been deposited at different stages of constant pressure collapse, on hydrophilic Si(001) using a modified version of the inverse Langmuir-Schaefer method of horizontal deposition. The electron density profiles (EDPs) along the depth of the deposited films, extracted from the x-ray reflectivity data, show that a monolayer to bi-molecular layer transformation takes place after collapse. The molecules in the lower monolayer have asymmetric configurations with head groups touching water and tails in air, whereas molecules in the upper layer are in symmetric configurations with tails on both sides of the heads. Atomic force microscopy images of the deposited films after collapse, however, show nearly circular islands of height more than that of the bimolecular layer observed in the EDP. As pressure increases, ridges are seen to coexist with these islands. Although the coverage of such islands and ridges is low, they play an important role in determining the growth mode. The growth of the wetting and island layers, taken together, has a striking similarity with the Stranski-Krastanow mode, observed usually for heteroepitaxial growth.

  12. Atomistic simulations of langmuir monolayer collapse.

    PubMed

    Lorenz, Christian D; Travesset, Alex

    2006-11-21

    Monolayers at the vapor/water interface collapse by exploring the third dimension at sufficient lateral compression, either by forming three-dimensional structures or by solubilization into the aqueous solution. In this paper, we provide an atomistic description of collapse from molecular dynamics (MD) simulations. More specifically, we investigate monolayers of arachidic acids spread on pure water and in an aqueous solution with Ca2+ ions in the subphase. In both cases, it is found that the collapsed systems generally lead to the formation of multilayer structures, which in the system with Ca2+ ions, proceeds by an intermediate regime where the monolayer exhibits significant roughness (of the order of 4 A). If no roughness is present, the system forms collapsed structures into the aqueous solution. The computational cost of atomic MD limits our simulations to relatively small system sizes, fast compression rates, and temporal scales on the order of a nanosecond. We discuss the issues caused by these limitations and present a detailed discussion of how the collapse regime proceeds at long time scales. We conclude with a summary of the implications of our results for further theoretical and experimental studies. PMID:17106994

  13. Investigation on gallium ions impacting monolayer graphene

    SciTech Connect

    Wu, Xin; Zhao, Haiyan Yan, Dong; Pei, Jiayun

    2015-06-15

    In this paper, the physical phenomena of gallium (Ga{sup +}) ion impacting monolayer graphene in the nanosculpting process are investigated experimentally, and the mechanisms are explained by using Monte Carlo (MC) and molecular dynamics (MD) simulations. Firstly, the MC method is employed to clarify the phenomena happened to the monolayer graphene target under Ga{sup +} ion irradiation. It is found that substrate has strong influence on the damage mode of graphene. The mean sputtering yield of graphene under 30 keV Ga{sup +} ion irradiation is 1.77 and the least ion dose to completely remove carbon atoms in graphene is 21.6 ion/nm{sup 2}. Afterwards, the focused ion beam over 21.6 ion/nm{sup 2} is used for the irradiation on a monolayer graphene supported by SiO2 experimentally, resulting in the nanostructures, i.e., nanodot and nanowire array on the graphene. The performances of the nanostructures are characterized by atomic force microscopy and Raman spectrum. A plasma plume shielding model is put forward to explain the nanosculpting results of graphene under different irradiation parameters. In addition, two damage mechanisms are found existing in the fabrication process of the nanostructures by using empirical MD simulations. The results can help us open the possibilities for better control of nanocarbon devices.

  14. Intrinsic structural defects in monolayer molybdenum disulfide

    SciTech Connect

    Zhou, Wu; Idrobo Tapia, Juan C

    2013-01-01

    Monolayer molybdenum disulfide (MoS2) is a two-dimensional direct band gap semiconductor with distinctive mechanical, electronic, optical and chemical properties that can be utilized for novel nanoelectronics and optoelectronics devices. The performance of these electronic devices strongly depends on the quality and defect morphology of the MoS2 layers. Yet, little is known about the atomic structure of defects present in monolayer MoS2 and their influences on the material properties. Here we provide a systematic study of various intrinsic structural defects, including point defects, grain boundaries, and edges, in chemical vapor phase grown monolayer MoS2 via direct atomic resolution imaging, and explore their energy landscape and electronic properties using first-principles calculations. We discover that one-dimensional metallic wires can be created via two different types of 60 grain boundaries consisting of distinct 4-fold ring chains. A new type of edge reconstruction, representing a transition state during growth, was also identified, providing insights into the material growth mechanism. The atomic scale study of structural defects presented here brings new opportunities to tailor the properties of MoS2 via controlled synthesis and defect engineering.

  15. Exploring atomic defects in molybdenum disulphide monolayers

    PubMed Central

    Hong, Jinhua; Hu, Zhixin; Probert, Matt; Li, Kun; Lv, Danhui; Yang, Xinan; Gu, Lin; Mao, Nannan; Feng, Qingliang; Xie, Liming; Zhang, Jin; Wu, Dianzhong; Zhang, Zhiyong; Jin, Chuanhong; Ji, Wei; Zhang, Xixiang; Yuan, Jun; Zhang, Ze

    2015-01-01

    Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment–theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 1013 cm−2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices. PMID:25695374

  16. Inclusion of terpenes in cyclodextrins: Preparation, characterization and pharmacological approaches.

    PubMed

    Lima, Pollyana S S; Lucchese, Angélica M; Araújo-Filho, Heitor G; Menezes, Paula P; Araújo, Adriano A S; Quintans-Júnior, Lucindo J; Quintans, Jullyana S S

    2016-10-20

    Terpenes constitute the largest class of natural products and are important resources for the pharmaceutical, food and cosmetics industries. However, due to their low water solubility and poor bioavailability there has been a search for compounds that could improve their physicochemical properties. Cyclodextrins (natural and derived) have been proposed for this role and have been complexed with different types of terpenes. This complexation has been demonstrated by using analytical techniques for characterizing complexes such as DSC, NMR, XRD, FTIR, and TGA. The formation of inclusion complexes has been able to improve drug characteristics such as bioavailability, solubility and stability; and to enhance biological activity and efficacy. This review shows strong experimental evidence that cyclodextrins improve the pharmacological properties of terpenes, and therefore need to be recognized as being possible targets for clinical use. PMID:27474645

  17. Complexation of cyclodextrins with flavines in aqueous solutions

    NASA Astrophysics Data System (ADS)

    Terekhova, I. V.

    2014-01-01

    Data on the binding mode and thermodynamics of complex formation for various cyclodextrins (CDs) with flavines are summarized. It is shown that the governing factors of complexation are the size, degree of hydration, and hydrophobicity of the guest molecule. It is found that the presence of small hydrophobic substituents in a flavine's structure increases their affinity toward cyclodextrin cavities, raising the stability of a complex. In contrast, the presence of bulky and polar side groups in a flavine's structure prevents its inclusion in a macrocyclic cavity and weakens complexation. The size of a CD cavity plays a minor role in the interaction between CDs and flavines, since the inclusion of a guest molecule is only partial.

  18. Colloidal particles containing labeling agents and cyclodextrins for theranostic applications.

    PubMed

    Zafar, Nadiah; Fessi, Hatem; Elaissari, Abdelhamid

    2014-09-10

    This review aims to give to the reader some new light on cyclodextrin (CD)-based theranostic agents in order to complete our recently published review dedicated to CD-particles conjugates in drug delivery systems (Zafar et al., 2014). CDs are biocompatible sugar-based macrocycles used in a wide range of biomedical applications. Here, we mainly focus on fundamental theranostic approaches combining the use of cyclodextrin molecules and colloidal particles as theranostic agents. The system's key features are discussed and a few recent pertinent applications are presented. CDs are used in order to enhance theranostic properties by providing apolar cavities for the encapsulation of hydrophobic moieties. Thus, CD molecules are used to enhance the loading capacity of particles by hosting active molecules. The relevance of CDs in enhancing the labeling properties of particles and the preparation of controlled drug release particles is also highlighted.

  19. From algal polysaccharides to cyclodextrins to stabilize a urease inhibitor.

    PubMed

    Pro, Danièle; Huguet, Samuel; Arkoun, Mustapha; Nugier-Chauvin, Caroline; Garcia-Mina, José Maria; Ourry, Alain; Wolbert, Dominique; Yvin, Jean-Claude; Ferrières, Vincent

    2014-11-01

    N-Butyl-phosphorotriamide (NBPT) is a fertilizer widely used for its urease inhibiting properties. Nevertheless, formulations currently commercialized are complex and do not avoid severe decrease of activity due to the low stability of the bioactive compound under acidic conditions. According to its structure, NPBT was thought to be able to interact with both polar additives, by its phosphoramide function, and hydrophobic ones, through its alkyl chain. In this context, and in order to simplify formulations of this bioactive compound, a panel of natural polysaccharides was studied, including starch, β-(1,3)-glucans, carraghenans and alginates. We also used cyclodextrins, characterized the most stable inclusion complex with α-cyclodextrin and evaluated the stability of NBPT thus protected against hydrolysis under acidic conditions.

  20. Characterization of cyclodextrin containing nanofilters for removal of pharmaceutical residues.

    PubMed

    Jurecska, Laura; Dobosy, Péter; Barkács, Katalin; Fenyvesi, Éva; Záray, Gyula

    2014-09-01

    Due to the increasing amount of persistent organic pollutants (POPs) in general and pharmaceutical residues in particular in municipal wastewater, the efficiency of water treatment technologies should be improved. Following the biological treatment of wastewater nanofiltration offers a possible way for the removal of POPs. In this study β-cyclodextrin containing nanofilters having different chemical composition and thickness (1.5-3.5mm) were investigated. For their characterization, their adsorption capacity was determined applying ibuprofen containing model solution and total organic carbon (TOC) analyzer. It could be established that the regeneration of nanofilters with ethanol and the application of inorganic additives (NaCl, NaHCO3, NH4HCO3) increased the adsorption capacity of nanofilters. The best results were achieved with chemical composition of 30m/m% β-cyclodextrin polymer beads and 70m/m% ultra-high molecular weight polyethylene in the presence of 12mmol ammonium hydrogen carbonate/nanofilter.

  1. Characterization of organosulfur monolayer formation at gold electrodes

    SciTech Connect

    Tani Woods, N.

    1996-08-01

    Among the many types of organic films, covalently-attached organosulfur monolayers have attracted a great deal of attention. The authors have focused their interest on the fundamental characterization of spontaneously adsorbed organosulfur monolayers. An introductory chapter presents general aspects of monolayer preparation and characterization, followed by a few examples that illustrate the range of applications of these films. This thesis contains two papers. In the first paper, three analogous monolayer precursors are studied to determine their similarities and differences in the monolayer structure. A GC-MS analysis of products form the chemisorption process and open circuit potential measurements are used to derive possible mechanisms behind monolayer formation. The second paper focuses on monolayers formed from thioctic acid, including its characterization and application to cytochrome c electrochemistry. Although thiols and disulfides have been extensively studied as monolayer precursors, thioctic acid is particularly interesting because the disulfide functionality of this asymmetric molecule is contained in a strained five-membered ring. Given the ring strain, steric bulk and asymmetry of the molecule, the study of these monolayers lend insight into the factors important for the formation of organosulfur monolayers. This thesis concludes with a general summary and directions for future studies. 40 refs.

  2. Monolayer MXenes: promising half-metals and spin gapless semiconductors

    NASA Astrophysics Data System (ADS)

    Gao, Guoying; Ding, Guangqian; Li, Jie; Yao, Kailun; Wu, Menghao; Qian, Meichun

    2016-04-01

    Half-metals and spin gapless semiconductors are promising candidates for spintronic applications due to the complete (100%) spin polarization of electrons around the Fermi level. Based on recent experimental and theoretical findings of graphene-like monolayer transition metal carbides and nitrides (also known as MXenes), we demonstrate using first-principles calculations that monolayers Ti2C and Ti2N exhibit nearly half-metallic ferromagnetism with the magnetic moments of 1.91 and 1.00μB per formula unit, respectively, while monolayer V2C is a metal with unstable antiferromagnetism, and monolayer V2N is a nonmagnetic metal. Interestingly, under a biaxial strain, there is a phase transition from a nearly half-metal to truly half-metal, spin gapless semiconductor, and metal for monolayer Ti2C. Monolayer Ti2N is still a nearly half-metal under a suitable biaxial strain. Large magnetic moments can be induced by the biaxial tensile and compressive strains for monolayer V2C and V2N, respectively. We also show that the structures of these four monolayer MXenes are stable according to the calculated formation energy and phonon spectrum. Our investigations suggest that, unlike monolayer graphene, monolayer MXenes Ti2C and Ti2N without vacancy, doping or external electric field exhibit intrinsic magnetism, especially the half-metallic ferromagnetism and spin gapless semiconductivity, which will stimulate further studies on possible spintronic applications for new two-dimensional materials of MXenes.

  3. Macromolecular recognition: Recognition of polymer side chains by cyclodextrin

    NASA Astrophysics Data System (ADS)

    Hashidzume, Akihito; Harada, Akira

    2015-12-01

    The interaction of cyclodextrins (CD) with water soluble polymers possessing guest residues has been investigated as model systems in biological molecular recognition. The selectivity of interaction of CD with polymer-carrying guest residues is controlled by polymer chains, i.e., the steric effect of polymer main chain, the conformational effect of polymer main chain, and multi-site interaction. Macroscopic assemblies have been also realized based on molecular recognition using polyacrylamide-based gels possessing CD and guest residues.

  4. Removal of emerging micropollutants from water using cyclodextrin.

    PubMed

    Nagy, Zsuzsanna Magdolna; Molnár, Mónika; Fekete-Kertész, Ildikó; Molnár-Perl, Ibolya; Fenyvesi, Éva; Gruiz, Katalin

    2014-07-01

    Small scale laboratory experiment series were performed to study the suitability of a cyclodextrin-based sorbent (ß-cyclodextrin bead polymer, BCDP) for modelling the removal of micropollutants from drinking water and purified waste water using simulated inflow test solutions containing target analytes (ibuprofen, naproxen, ketoprofen, bisphenol-A, diclofenac, β-estradiol, ethinylestradiol, estriol, cholesterol at 2-6 μg/L level). This work was focused on the preliminary evaluation of BCDP as a sorbent in two different model systems (filtration and fluidization) applied for risk reduction of emerging micropollutants. For comparison different filter systems combined with various sorbents (commercial filter and activated carbon) were applied and evaluated in the filtration experiment series. The spiked test solution (inflow) and the treated outflows were characterized by an integrated methodology including chemical analytical methods gas chromatography-tandem mass spectrometry (GC-MS/MS) and various environmental toxicity tests to determine the efficiency and selectivity of the applied sorbents. Under experimental conditions the cyclodextrin-based filters used for purification of drinking water in most cases were able to absorb more than 90% of the bisphenol-A and of the estrogenic compounds. Both the analytical chemistry and toxicity results showed efficient elimination of these pollutants. Especially the toxicity of the filtrate decreased considerably. Laboratory experiment modelling post-purification of waste water was also performed applying fluidization technology by ß-cyclodextrin bead polymer. The BCDP removed efficiently from the spiked test solution most of the micropollutants, especially the bisphenol-A (94%) and the hormones (87-99%) The results confirmed that the BCDP-containing sorbents provide a good solution to water quality problems and they are able to decrease the load and risk posed by micropollutants to the water systems. PMID:24775808

  5. Cyclodextrin solubilization of benzodiazepines: formulation of midazolam nasal spray.

    PubMed

    Loftsson, T; Gudmundsdóttir, H; Sigurjónsdóttir, J F; Sigurdsson, H H; Sigfússon, S D; Másson, M; Stefánsson, E

    2001-01-01

    The cyclodextrin solubilization of three benzodiazepines, i.e. alprazolam, midazolam and triazolam, was investigated. The cyclodextrin solubilization was enhanced through ring-opening of the benzodiazepine rings and ionization of the ring-open forms. Additional enhancement was obtained through interaction of a water-soluble polymer with the cyclodextrin complexes. The ring-opening was pH-dependent and completely reversible, the ring-open forms dominating at low pH but the ring-closed forms at physiologic pH. The ring-closed forms were rapidly regenerated upon elevation of pH. In freshly collected human serum in vitro at 37 degrees C, the half-life for the first-order rate constant for the ring-closing reaction was estimated to be less than 2 min for both alprazolam and midazolam. Midazolam (17 mg/ml) was solubilized in aqueous pH 4.3 nasal formulation containing 14% (w/v) sulfobutylether beta-cyclodextrin, 0.1% (w/v) hydroxypropyl methylcellulose, preservatives and buffer salts. Six healthy volunteers received 0.06 mg/kg midazolam intranasally and 2 mg intravenously, and blood samples were collected up to 360 min after the administration. Midazolam was absorbed rapidly reaching maximum serum concentrations of 54.3+/-5.0 ng/ml at 15+/-2 min. The elimination half-life of midazolam was 2.2+/-0.3 h and the absolute availability was 73+/-7%. All mean values+/-SEM. PMID:11165818

  6. Removal of emerging micropollutants from water using cyclodextrin.

    PubMed

    Nagy, Zsuzsanna Magdolna; Molnár, Mónika; Fekete-Kertész, Ildikó; Molnár-Perl, Ibolya; Fenyvesi, Éva; Gruiz, Katalin

    2014-07-01

    Small scale laboratory experiment series were performed to study the suitability of a cyclodextrin-based sorbent (ß-cyclodextrin bead polymer, BCDP) for modelling the removal of micropollutants from drinking water and purified waste water using simulated inflow test solutions containing target analytes (ibuprofen, naproxen, ketoprofen, bisphenol-A, diclofenac, β-estradiol, ethinylestradiol, estriol, cholesterol at 2-6 μg/L level). This work was focused on the preliminary evaluation of BCDP as a sorbent in two different model systems (filtration and fluidization) applied for risk reduction of emerging micropollutants. For comparison different filter systems combined with various sorbents (commercial filter and activated carbon) were applied and evaluated in the filtration experiment series. The spiked test solution (inflow) and the treated outflows were characterized by an integrated methodology including chemical analytical methods gas chromatography-tandem mass spectrometry (GC-MS/MS) and various environmental toxicity tests to determine the efficiency and selectivity of the applied sorbents. Under experimental conditions the cyclodextrin-based filters used for purification of drinking water in most cases were able to absorb more than 90% of the bisphenol-A and of the estrogenic compounds. Both the analytical chemistry and toxicity results showed efficient elimination of these pollutants. Especially the toxicity of the filtrate decreased considerably. Laboratory experiment modelling post-purification of waste water was also performed applying fluidization technology by ß-cyclodextrin bead polymer. The BCDP removed efficiently from the spiked test solution most of the micropollutants, especially the bisphenol-A (94%) and the hormones (87-99%) The results confirmed that the BCDP-containing sorbents provide a good solution to water quality problems and they are able to decrease the load and risk posed by micropollutants to the water systems.

  7. Retention of aroma compounds from Mentha piperita essential oil by cyclodextrins and crosslinked cyclodextrin polymers.

    PubMed

    Ciobanu, A; Mallard, I; Landy, D; Brabie, G; Nistor, D; Fourmentin, S

    2013-05-01

    In this paper, the controlled release of aroma compounds from cyclodextrins (CDs) and CD polymers was studied by multiple headspace extraction (MHE) experiments. Mentha piperita essential oil was obtained by Soxhlet extraction and identification of the major compounds was performed by GC-MS analysis. Menthol, menthone, pulegone and eucalyptol were identified as the major components. Retention of standard compounds in the presence of different CDs and CD polymers has been realised by static headspace gas chromatography (SH-GC) at 25 °C in the aqueous or gaseous phase. Stability constants for standard compounds and for compounds in essential oil have been also determined with monomeric CD derivatives. The obtained results indicated the formation of a 1:1 inclusion complex for all the studied compounds. Molecular modelling was used to investigate the complementarities between host and guest. This study showed that β-CDs were the most versatile CDs and that β-CD polymers could perform the controlled release of aroma compounds.

  8. Formation of β-cyclodextrin complexes in an anhydrous environment.

    PubMed

    Sifaoui, Hocine; Modarressi, Ali; Magri, Pierre; Stachowicz-Kuśnierz, Anna; Korchowiec, Jacek; Rogalski, Marek

    2016-09-01

    The formation of inclusion complexes of β-cyclodextrin was studied at the melting temperature of guest compounds by differential scanning calorimetry. The complexes of long-chain n-alkanes, polyaromatics, and organic acids were investigated by calorimetry and IR spectroscopy. The complexation ratio of β-cyclodextrin was compared with results obtained in an aqueous environment. The stability and structure of inclusion complexes with various stoichiometries were estimated by quantum chemistry and molecular dynamics calculations. Comparison of experimental and theoretical results confirmed the possible formation of multiple inclusion complexes with guest molecules capable of forming hydrogen bonds. This finding gives new insight into the mechanism of formation of host-guest complexes and shows that hydrophobic interactions play a secondary role in this case. Graphical abstract The formation of complexes of β-cyclodextrin with selected n-alkanes, polyaromatics, and organic acids in an anhydrous environment is studied by differential scanning calorimetry, IR spectroscopy, and molecular modeling. The results obtained confirm the possible formation of multiple inclusion complexes with guest molecules capable of forming hydrogen bonds and give a new perspective on the mechanism of formation of host-guest complexes. PMID:27518085

  9. Determination of the glass transition temperature of cyclodextrin polymers.

    PubMed

    Tabary, Nicolas; Garcia-Fernandez, Maria Jose; Danède, Florence; Descamps, Marc; Martel, Bernard; Willart, Jean-François

    2016-09-01

    The aim of this work was to determine the main physical characteristics of β-cyclodextrin polymers, well known for improving complexation capacities and providing enhanced and sustained release of a large panel of drugs. Two polymers were investigated: a polymer of β-cyclodextrin (polyβ-CD) and a polymer of partially methylated (DS=0.57) β-cyclodextrin (polyMe-β-CD). The physical characterizations were performed by powder X-ray diffraction and differential scanning calorimetry. The results indicate that these polymers are amorphous and that their glass transition is located above the thermal degradation point of the materials preventing their direct observation and thus their full characterization. We could however estimate the virtual glass transition temperatures by mixing the polymers with different plasticizers (trehalose and mannitol) which decreases Tg sufficiently to make the glass transition observable. Extrapolation to zero plasticizer concentration then yield the following Tg values: Tg (polyMe-β-CD)=317°C±5°C and Tg (polyβ-CD)=418°C±6°C. PMID:27185128

  10. Catalytic and thermodynamic properties of glycosylated Bacillus cereus cyclodextrin glycosyltransferase.

    PubMed

    Abdel-Naby, Mohamed A; Fouad, Ahmed A; El-Refai, H A

    2015-05-01

    Cyclodextrin glycosyltransferase (CGTase) was covalently coupled to five oxidized polysaccharides differing in structure and chemical nature. The conjugates were evaluated for the retained activity, kinetic and thermodynamic stability. The conjugated CGTase with oxidized dextran (MW 47000) had the highest retained specific activity (70.05%) and the highest half-life (T1/2) at 80°C. Compared to the native enzyme, the conjugated preparation exhibited higher optimum temperature, lower activation energy (Ea), lower deactivation constant rate (kd), higher T1/2, and higher D values (decimal reduction time) within the temperature range of 60-80°C. The values of thermodynamic parameters for irreversible inactivation of native and conjugated CGTase indicated that conjugation significantly decreased entropy (ΔS*) and enthalpy of deactivation (ΔH*). The results of thermodynamic analysis for cyclodextrin production from starch indicated that The enthalpy of activation (ΔH*) and free energy of activation (ΔG*), (free energy of transition state) ΔG*E-T and (free energy of substrate binding) ΔG*E-S values were lower for the conjugated CGTase. Similarly, there was significant impact on improvement of kcat, kcat/Km values. Both native and conjugated enzyme produce α-cyclodextrin from starch.

  11. Interaction of ochratoxin A with quaternary ammonium beta-cyclodextrin.

    PubMed

    Poór, Miklós; Kunsági-Máté, Sándor; Szente, Lajos; Matisz, Gergely; Secenji, Györgyi; Czibulya, Zsuzsanna; Kőszegi, Tamás

    2015-04-01

    Ochratoxin A (OTA) is a widely spread nephrotoxic food contaminant mycotoxin. Unfortunately, attenuation or prevention of the toxic effects of OTA is still an unresolved problem. Molecular inclusion of OTA by cyclodextrins (CDs) results in complexes with low stability. In the human organism, OTA exists mostly in the dianionic state (OTA(2-)). Therefore, our major goal was to develop a chemically modified cyclodextrin which gives a more stable complex with OTA than the previously published derivatives and which shows stronger preference towards OTA(2-). In our fluorescence spectroscopic study we demonstrate that quaternary ammonium beta-cyclodextrin (QABCD) fulfils both of these requirements. The calculated stability constant of the QABCD-OTA(2-) complex was 28,840 M(-1) (about 200-fold higher than that of the β-CD-OTA(2-) complex). We hypothesize, that QABCD may be a suitable tool for the decontamination of different OTA-contaminated drinks; furthermore, for alleviation of the toxic effects of OTA, such complex formation may reduce its absorption from the intestine. PMID:25442535

  12. Interaction of ochratoxin A with quaternary ammonium beta-cyclodextrin.

    PubMed

    Poór, Miklós; Kunsági-Máté, Sándor; Szente, Lajos; Matisz, Gergely; Secenji, Györgyi; Czibulya, Zsuzsanna; Kőszegi, Tamás

    2015-04-01

    Ochratoxin A (OTA) is a widely spread nephrotoxic food contaminant mycotoxin. Unfortunately, attenuation or prevention of the toxic effects of OTA is still an unresolved problem. Molecular inclusion of OTA by cyclodextrins (CDs) results in complexes with low stability. In the human organism, OTA exists mostly in the dianionic state (OTA(2-)). Therefore, our major goal was to develop a chemically modified cyclodextrin which gives a more stable complex with OTA than the previously published derivatives and which shows stronger preference towards OTA(2-). In our fluorescence spectroscopic study we demonstrate that quaternary ammonium beta-cyclodextrin (QABCD) fulfils both of these requirements. The calculated stability constant of the QABCD-OTA(2-) complex was 28,840 M(-1) (about 200-fold higher than that of the β-CD-OTA(2-) complex). We hypothesize, that QABCD may be a suitable tool for the decontamination of different OTA-contaminated drinks; furthermore, for alleviation of the toxic effects of OTA, such complex formation may reduce its absorption from the intestine.

  13. Diagnostic Implementation of Fast and Selective Integrin-Mediated Adhesion of Cancer Cells on Functionalized Zeolite L Monolayers.

    PubMed

    Greco, Arianna; Maggini, Laura; De Cola, Luisa; De Marco, Rossella; Gentilucci, Luca

    2015-09-16

    The rapid and exact identification and quantification of specific biomarkers is a key technology for always achieving more efficient diagnostic methodologies. We present the first application of a nanostructured device constituted of patterned self-assembled monolayers of disk-shaped zeolite L coated with the cyclic integrin ligand c[RGDfK] via isocyanate linker, to the rapid detection of cancer cells. With its high specificity toward HeLa and Glioma cells and fast adhesion ability, this biocompatible monolayer is a promising platform for implementation in diagnostics and personalized therapy formulation devices.

  14. Assessment of ternary iron-cyclodextrin-2-naphthol complexes using NMR and fluorescence spectroscopies

    NASA Astrophysics Data System (ADS)

    Zheng, Weixi; Tarr, Matthew A.

    2006-12-01

    Recent research has indicated that ternary complexes can be formed among carboxymethyl-β-cyclodextrin, certain polycyclic aromatic hydrocarbons (PAHs) (e.g. anthracene and 2-naphthol), and Fe 2+ in aqueous solution. The formation of these ternary complexes has been suggested as the reason for improved reaction efficiency in iron catalyzed Fenton degradation (H 2O 2 + Fe 2+ → rad OH + OH - + Fe 3+) of PAHs and other pollutants. In the present work, several other cyclodextrins were examined to determine their ability to form similar ternary complexes with 2-naphthol and Fe 2+. Fluorescence and NMR techniques were employed in this study. Results showed that hydroxypropyl-β-cyclodextrin, β-cyclodextrin, and α-cyclodextrin were able to encapsulate 2-naphthol molecules, but their binding with Fe 2+ was weak. On the contrary, sulfated-β-cyclodextrin has significant binding with Fe 2+, but it showed little inclusion of 2-naphthol molecules. Consequently, none of these four cyclodextrins formed significant amounts of ternary complexes in aqueous solution. The techniques used in this study provide useful methods for assessing the ability of cyclodextrins to form ternary complexes with guest compounds and metal ions.

  15. Assessment of ternary iron-cyclodextrin-2-naphthol complexes using NMR and fluorescence spectroscopies.

    PubMed

    Zheng, Weixi; Tarr, Matthew A

    2006-12-01

    Recent research has indicated that ternary complexes can be formed among carboxymethyl-beta-cyclodextrin, certain polycyclic aromatic hydrocarbons (PAHs) (e.g. anthracene and 2-naphthol), and Fe(2+) in aqueous solution. The formation of these ternary complexes has been suggested as the reason for improved reaction efficiency in iron catalyzed Fenton degradation (H(2)O(2)+Fe(2+)-->*OH+OH(-)+Fe(3+)) of PAHs and other pollutants. In the present work, several other cyclodextrins were examined to determine their ability to form similar ternary complexes with 2-naphthol and Fe(2+). Fluorescence and NMR techniques were employed in this study. Results showed that hydroxypropyl-beta-cyclodextrin, beta-cyclodextrin, and alpha-cyclodextrin were able to encapsulate 2-naphthol molecules, but their binding with Fe(2+) was weak. On the contrary, sulfated-beta-cyclodextrin has significant binding with Fe(2+), but it showed little inclusion of 2-naphthol molecules. Consequently, none of these four cyclodextrins formed significant amounts of ternary complexes in aqueous solution. The techniques used in this study provide useful methods for assessing the ability of cyclodextrins to form ternary complexes with guest compounds and metal ions.

  16. Sol-Gel Synthesis of Ordered β-Cyclodextrin-Containing Silicas

    NASA Astrophysics Data System (ADS)

    Trofymchuk, Iryna Mykolaivna; Roik, Nadiia; Belyakova, Lyudmila

    2016-03-01

    New approaches for β-cyclodextrin-containing silicas synthesis were demonstrated. Materials with hexagonally ordered mesoporous structure were prepared by postsynthesis grafting and by co-condensation methods. β-Cyclodextrin activated by a N, N'-carbonyldiimidazole was employed for postsynthesis treatment of 3-aminopropyl-modified MCM-41 support as well as for sol-gel synthesis with β-cyclodextrin-containing organosilane and tetraethyl orthosilicate participation in the presence of cetyltrimethylammonium bromide. The successful incorporation of cyclic oligosaccharide moieties in silica surface layer was verified by means of FT-IR spectroscopy and chemical analysis. Obtained β-cyclodextrin-containing materials were characterized by X-ray diffraction, transmission electron microscopy, and low-temperature adsorption-desorption of nitrogen. In spite of commensurable loading of β-cyclodextrin groups attained by both proposed approaches (up to 0.028 μmol · m-2), it was found that co-condensation procedure provides uniform distribution of β-cyclodextrin functionalities in silica framework, whereas postsynthesis grafting results in modification of external surface of silica surface. Adsorption of benzene from aqueous solutions onto the surface of β-cyclodextrin-containing materials prepared by co-condensation method was studied as the function of time and equilibrium concentration. Langmuir and Freundlich models were used to evaluate adsorption processes and parameters. Adsorption experiments showed that β-cyclodextrin-containing silicas could be promising for the trace amount removal of aromatics from water.

  17. Preparation and characterization of amorphous solid dispersions of nimesulide in cyclodextrin copolymers.

    PubMed

    Skiba, M; Skiba, M; Milon, N; Bounoure, F; Fessi, H

    2014-04-01

    A study to enhance the dissolution rate of nimesulide (NIM), a poorly water-soluble, non-steroidal anti-inflammatory drug, was carried out through developing new amorphous solid dispersions (ASD) based on soluble or insoluble water cyclodextrin copolymers (alpha-cyclodextrin, beta-cyclodextrin and y-cyclodextrin polymers) synthesized by direct melt polycondensation. Amorphous solid dispersions of NIM in cyclodextrin copolymers, obtained by solvent evaporation, were characterized by thermogravimetric analyzer (TGA), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD) and fourier transform-infrared spectroscopy (FT-IR). These analyses provided the existence of interactions between amorphous drug and its carrier. A burst release of more than 80% NIM within approximately 70 minutes was seen with soluble alpha-cyclodextrin polymers (poly-alpha-sol) and insoluble gamma-cyclodextrin polymers (poly-gamma-insol) where no significant differences were observed with the other copolymers. Mathematical kinetic models such as zero order, Higuchi and Korsmeyer-Peppas were used to evaluate the kinetic and mechanism of release of NIM from the different ASD compared to lactose reference matrix. The kinetic of release of NIM from different ASD followed a Higuchi model and the mechanism of release was explained by Korsmeyer-Peppas model in which a fickian diffusion for lactose and soluble beta-cyclodextrin polymers (poly-beta-sol) was observed. However, an anomalous non-Fickian transport was found for the other copolymers. PMID:24734689

  18. [Preparation and enantioseparation performance of β-cyclodextrin-silica hybrid chiral stationary phases].

    PubMed

    Wang, Litao; Dong, Shuqing; Zhang Zhixin; Wang, Yangjun; Zhang, Xiaoli; Zhang, Xia; Zhang, Pengyun; Zhao, Liang

    2016-01-01

    A simple preparation method for β-cyclodextrin-silica hybrid chiral stationary phases was developed. Firstly, the β-cyclodextrin-silica derivative was synthesized by the reaction of 3-aminopropyltriethoxysilane and monochlorotriazinyl β-cyclodextrin under weak base condition. Spherical β-cyclodextrin-silica hybrid materials with β-cyclodextrin in the surface of pores by covalent bonding were prepared using 1,2-bis(triethoxysilyl) ethane and the β-cyclodextrin-silica derivative under the alkaline condition by one-step polymerization reaction. The β-Cyclodextrin-silica hybrid chiral stationary phases could be directly used as high performance liquid chromatographic packings after the template removal. The hybrid materials prepared in this paper possessed regular spherical morphology, good monodispersion, high specific surface area, good mechanical property, high chemical stability and simple preparation process. It combined the chiral recognition performance of β-cyclodextrin and the outstanding performance of organic-inorganic hybrid material. The effect of the composition, ratio and pH of mobile phase on chiral separation was investigated, and the best chiral separation conditions had been optimized. The baseline chiral separations for five chiral compounds were obtained under the optimal conditions. The results of enantioseparation showed that the hybrid chiral stationary phases had favorable chiral recognition ability. Compared with the traditional preparation process of chiral stationary phases, a new thought for new type of chiral stationary phase is provided by the present method in this paper. PMID:27319171

  19. Capillary electrophoresis of the mycotoxin zearalenone using cyclodextrin-enhanced fluorescence

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Certain of the cyclodextrins are capable of significantly enhancing the native fluorescence of the estrogenic mycotoxin zearalenone (ZEN). Twenty-two cyclodextrins (CDs) were screened for their ability to enhance the fluorescence of ZEN in a capillary electrophoresis-laser induced fluorescence (CE-...

  20. Structure selective complexation of cyclodextrins with five polyphenols investigated by capillary electrokinetic chromatography.

    PubMed

    Zhang, Qing-Feng; Cheung, Hon-Yeung; Shangguan, Xinchen; Zheng, Guodong

    2012-12-01

    The complexation of five polyphenols, namely trans-resveratrol, astilbin, taxifolin, ferulic acid, and syringic acid (guest molecules) with α-, β-, and γ-cyclodextrin (host molecules), was investigated by capillary electrokinetic chromatography. The binding constants were calculated based on the effective electrophoretic mobility change of guests with the addition of cyclodextrins into the background electrolyte. Because of cavity size, cyclodextrins showed structure-selective complexation property to different guest. The stability of the trans-resveratrol complexes was in the order of β- > α- > γ-cyclodextrin. The cavity size of α-cyclodextrin was too small for astilbin and taxifolin molecules, and thus they could not form complexes. The molecular size of syringic acid was too big for all cyclodextrins cavity, and no cyclodextrin could form complexes with it. Temperature studies showed that the binding constants decreased with the rise of temperature. Enthalpy and entropy values were calculated and the negative values of these parameters indicated that the complexation process was enthalpy-controlled. Van der Waals force and release of high-enthalpy water molecules from the cyclodextrins cavity played important roles in the process. PMID:23184372

  1. Analytical techniques for characterization of cyclodextrin complexes in the solid state: A review.

    PubMed

    Mura, Paola

    2015-09-10

    Cyclodextrins are cyclic oligosaccharides able to form inclusion complexes with a variety of hydrophobic guest molecules, positively modifying their physicochemical properties. A thorough analytical characterization of cyclodextrin complexes is of fundamental importance to provide an adequate support in selection of the most suitable cyclodextrin for each guest molecule, and also in view of possible future patenting and marketing of drug-cyclodextrin formulations. The demonstration of the actual formation of a drug-cyclodextrin inclusion complex in solution does not guarantee its existence also in the solid state. Moreover, the technique used to prepare the solid complex can strongly influence the properties of the final product. Therefore, an appropriate characterization of the drug-cyclodextrin solid systems obtained has also a key role in driving in the choice of the most effective preparation method, able to maximize host-guest interactions. The analytical characterization of drug-cyclodextrin solid systems and the assessment of the actual inclusion complex formation is not a simple task and involves the combined use of several analytical techniques, whose results have to be evaluated together. The objective of the present review is to present a general prospect of the principal analytical techniques which can be employed for a suitable characterization of drug-cyclodextrin systems in the solid state, evidencing their respective potential advantages and limits. The applications of each examined technique are described and discussed by pertinent examples from literature.

  2. Novel exciton systems in 2D TMD monolayers and heterobilayers

    NASA Astrophysics Data System (ADS)

    Yu, Hongyi

    In this talk, two exciton systems in transition metal dichalcogenides (TMDs) monolayer and heterobilayer will be discussed. In TMD monolayers, the strong e-h Coulomb exchange interaction splits the exciton and trion dispersions into two branches with zero and finite gap, respectively. Each branch is a center-of-mass wave vector dependent coherent superposition of the two valleys, which leads to a valley-orbit coupling and possibly a trion valley Hall effect. The exchange interaction also eliminates the linear polarization of the negative trion PL emission. In TMD heterobilayers with a type-II band alignment, the low energy exciton has an interlayer configuration with the e and h localized in opposite layers. Because of the inevitable twist or/and lattice mismatch between the two layers, the bright interlayer excitons are located at finite center-of-mass velocities with a six-fold degeneracy. The corresponding photon emission is elliptically polarized, with the major axis locked to the direction of exciton velocity, and helicity determined by the valley indices of the e and h. Some experimental results on the interlayer excitons in the WSe2-MoSe2 heterobilayers will also be presented. The interlayer exciton exhibits a long lifetime as well as a long depolarization time, which facilitate the observation of a PL polarization ring pattern due to the valley dependent exciton-exciton interaction induced expansion. The works were supported by the Research Grant Council of Hong Kong (HKU17305914P, HKU705513P), the Croucher Foundation, and the HKU OYRA and ROP.

  3. Study of structural order in porphyrin-fullerene dyad ZnDHD6ee monolayers by electron diffraction and atomic force microscopy

    SciTech Connect

    D'yakova, Yu. A.; Suvorova, E. I.; Orekhov, Andrei S.; Orekhov, Anton S.; Alekseev, A. S.; Gainutdinov, R. V.; Klechkovskaya, V. V. Tereschenko, E. Yu.; Tkachenko, N. V.; Lemmetyinen, H.; Feigin, L. A.; Kovalchuk, M. V.

    2013-11-15

    The structure of porphyrin-fullerene dyad ZnDHD6ee monolayers formed on the surface of aqueous subphase in a Langmuir trough and transferred onto solid substrates has been studied. The data obtained are interpreted using simulation of the structure of isolated molecules and their packing in monolayer and modeling of diffraction patterns from molecular aggregates having different sizes and degrees of order. Experiments on the formation of condensed ZnDHD6ee monolayers are described. The structure of these monolayers on a water surface is analyzed using {pi}-A isotherms. The structure of the monolayers transferred onto solid substrates is investigated by electron diffraction and atomic force microscopy. The unit-cell parameters of two-dimensional domains, which are characteristic of molecular packing in monolayers and deposited films, are determined. Domains are found to be organized into a texture (the molecular axes are oriented by the [001] direction perpendicular to the substrate). The monolayers contain a limited number of small 3D domains.

  4. Supported lipid monolayer with improved nanomechanical stability: effect of polymerization.

    PubMed

    El Zein, Racha; Dallaporta, Hervé; Charrier, Anne M

    2012-06-21

    We study the effect of polymerization on the nanomechanical stability of supported lipid monolayers consisting of 1,2-di-(10Z,12Z-tricosadiynoyl)-sn-glycero-3-phosphocholine by means of force mapping using an atomic force microscope. For both nonpolymerized and polymerized lipid monolayers, we investigate the break-through forces required to rupture the monolayers for a whole range of loading velocities. We show that the average break-through force exerted by the tip and required to penetrate the monolayer has a logarithmic dependence on the loading rate. Both Young moduli and intrinsic Gibbs energies have been determined for the nonpolymerized and polymerized lipid monolayers, and we show a drastic effect of polymerization on the nanomechanical stability of the monolayer with an increase by a factor of ∼100 for the young modulus and ∼3 for the intrinsic Gibbs activation energy.

  5. Host-guest inclusion system of mangiferin with β-cyclodextrin and its derivatives.

    PubMed

    Yang, Xuemin; Zhao, Yulin; Chen, Yunjian; Liao, Xiali; Gao, Chuanzhu; Xiao, Dan; Qin, Qixue; Yi, Dong; Yang, Bo

    2013-05-01

    The characterization, inclusion complexation behavior and binding ability of the inclusion complexes of mangiferin (MGF) with β-cyclodextrin and its derivatives (hydroxypropyl-β-cyclodextrin (HPβCD), sulfobutyl ether β-cyclodextrin (SBEβCD) and mono (6-ethylene-diamino-6-deoxy)-β-cyclodextrin (ENβCD)) were investigated in both solution and solid state by means of PL spectroscopy, (1)H and 2D NMR, XRD, TG and DSC. The results showed that the water solubility and thermal stability of MGF were significantly increased in the inclusion complex with cyclodextrins. The MGF/CDs complexes will be potentially useful for the design of a novel formulation of mangiferin for herbal medicine.

  6. Remarkably stable inclusion complexes with heptakis-[6-deoxy-6-(2-aminoethylsulfanyl)]-beta-cyclodextrin.

    PubMed

    Gómez-Biagi, Rodolfo F; Jagt, Richard B C; Nitz, Mark

    2008-12-21

    Complexes of heptakis-[6-deoxy-6-(2-aminoethylsulfanyl)]-beta-cyclodextrin (1) and a series of common cyclodextrin guests were studied by NMR, fluorescence spectroscopy, and ITC experiments. NMR conformational analysis shows that the thioethers of 1 are positioned over the hydrophobic cavity of the cyclodextrin, increasing potential hydrophobic interactions with guest molecules. The combination of the increased hydrophobic character, the electrostatic complementarity and a hypothesized conformational change in 1 lead to a complex with the dye 2,6-ANS (5) that is over 2000 times more stable than with the native beta-cyclodextrin. One of the most stable host-guest complexes between a cyclodextrin and a small molecule measured to date was revealed between 1 and lithocholic acid (4) with an association constant of 5.5 x 10(7) M(-1).

  7. Lanthanide-cyclodextrin complexes as probes for elucidating optical purity by NMR spectroscopy

    SciTech Connect

    Wenzel, T.J.; Bogyo, M.S.; Lebeau, E.L. )

    1994-06-01

    A multidentate ligand is bonded to cyclodextrins by the reaction of diethylenetriaminepentaacetic dianhydride with 6-mono- and 2-mono(ethylenediamine) derivatives of cyclodextrin. Adding Dy(III) to the cyclodextrin derivatives enhances the enantiomeric resolution in the [sup 1]H NMR spectra of carbionoxamine maleate, doxylamine succinate, pheniramine maleate, propranolol hydrochloride, and tryptophan. The enhancement is more pronounced with the secondary derivative. The Dy(III)-induced shifts can be used to elucidate the geometry of cyclodextrin-substrate inclusion complexes. Lanthanide-induced shifts are reported for complexes of aspartame, tryptophan, propranolol, and 1-anilino-8-naphthalenesulfonate with cyclodextrins, and the relative magnitudes of the shifts agree with previously reported structures of the complexes. 37 refs., 9 figs., 5 tabs.

  8. Theoretical study on β-cyclodextrin inclusion complexes with propiconazole and protonated propiconazole.

    PubMed

    Fifere, Adrian; Marangoci, Narcisa; Maier, Stelian; Coroaba, Adina; Maftei, Dan; Pinteala, Mariana

    2012-01-01

    The synthesis of the β-cyclodextrin/propiconazole nitrate inclusion complex and the advantages of the encapsulation of this drug were recently reported, but the experimental data only partially revealed the structure of the supramolecular complex due to the limitations in understanding the intermolecular association mechanism. The present work describes the equilibrium molecular geometries of β-cyclodextrin/propiconazole and β-cyclodextrin/protonated propiconazole, established by the AM1 and PM3 semi-empirical methods. The affinity between different parts of the guest molecule and the cyclodextrin cavity was studied considering that propiconazole possesses three residues able to be included into the host cavity through primary or secondary hydroxyl rims. The results have revealed that the most stable complex is formed when the azole residue of the propiconazole enters the cavity of the cyclodextrin through the narrow hydroxyl's rim.

  9. Formation of nanoparticles by cooperative inclusion between (S)-camptothecin-modified dextrans and β-cyclodextrin polymers.

    PubMed

    Nielsen, Thorbjørn Terndrup; Amiel, Catherine; Duroux, Laurent; Larsen, Kim Lambertsen; Städe, Lars Wagner; Wimmer, Reinhard; Wintgens, Véronique

    2015-01-01

    Novel (S)-camptothecin-dextran polymers were obtained by "click" grafting of azide-modified (S)-camptothecin and alkyne-modified dextrans. Two series based on 10 kDa and 70 kDa dextrans were prepared with a degree of substitution of (S)-camptothecin between 3.1 and 10.2%. The binding properties with β-cyclodextrin and β-cyclodextrin polymers were measured by isothermal titration calorimetry and fluorescence spectroscopy, showing no binding with β-cyclodextrin but high binding with β-cyclodextrin polymers. In aqueous solution nanoparticles were formed from association between the (S)-camptothecin-dextran polymers and the β-cyclodextrin polymers.

  10. Epitaxial Templating of C60 with a Molecular Monolayer.

    PubMed

    Rochford, L A; Jones, T S; Nielsen, C B

    2016-09-01

    Commensurate epitaxial monolayers of truxenone on Cu (111) were employed to template the growth of monolayer and bilayer C60. Through the combination of STM imaging and LEED analysis we have demonstrated that C60 forms a commensurate 8 × 8 overlayer on truxenone/Cu (111). Bilayers of C60 retain the 8 × 8 periodicity of templated monolayers and although Kagome lattice arrangements are observed these are explained with combinations of 8 × 8 symmetry. PMID:27540868

  11. A family of single-isomer, dicationic cyclodextrin chiral selectors for capillary electrophoresis: mono-6(A)-ammonium-6(C)-butylimidazolium-β-cyclodextrin chlorides.

    PubMed

    Dai, Yun; Wang, Shuye; Zhou, Jie; Tang, Jian; Tang, Weihua

    2013-03-01

    The first member of the single-isomer, dicationic cyclodextrin (CD) family, 6(A)-ammonium-6(C)-butylimidazolium-β-cyclodextrin chlorides (AMBIMCD), has been synthesized, analytically characterized, and used to separate a variety of acidic enantiomers and amino acids by CE. Starting from mono-6(A)-azido-β-cyclodextrin, the cationic imidazolium and ammonium moieties were subsequently introduced onto primary ring of β-cyclodextrin via nucleophilic addition and Staudinger reaction. The analytically pure AC regio-isomer CD was further obtained via column chromatography. This dicationic CD exhibited excellent enantioselectivities for selected analytes at concentration as low as 0.5 mM, which were even better than those of its mono-imidazolium or ammonium-substitued counterpart CDs at 10 equivalent concentrations. The effective mobilities of all studied analytes were found to decrease with the concentration of AMBIMCD. Inclusion complexation in combination with eletrostatic interactions seemed to account for the enhanced chiral discrimination process.

  12. Stability of paclitaxel-loaded solid lipid nanoparticles in the presence of 2-hydoxypropyl-β-cyclodextrin.

    PubMed

    Baek, Jong-Suep; Kim, Bo-Sik; Puri, Anu; Kumar, K; Cho, Cheong-Weon

    2016-06-01

    Paclitaxel (PTX)-loaded solid lipid nanoparticles without hydroxyl-β-cyclodextrin (PS) or with hydroxypropyl-β-cyclodextrin (PSC) were prepared by hot-melted sonication. Biocompatible and biodegradable stearic acid was used to produce the solid matrix. The stability of PS and PSC was assessed at different temperatures. Drug stability, as assessed by encapsulation efficiency (EE; %), particle size, and the polydispersity index (PDI), was examined and in vitro release of PTX from PS or PSC for up to 180 days was assessed. After 180 days of storage at 25 °C, no significant change in particle size, PDI, or EE of PS or PSC was observed. PS and PSC displayed similar sustained PTX release patterns. The particle size, PDI, EE, PTX release profile, and cytotoxicity of PS changed significantly with increasing incubation time, whereas those of PSC showed no significant change, when samples were stored at 40 ± 2 °C. PSC was more stable than PS in plasma with regard to particle size and PDI. These results demonstrate that PSC could be a promising formulation to increase drug stability. PMID:27146520

  13. Analysis of the enhanced stability of r(+)-alpha lipoic Acid by the complex formation with cyclodextrins.

    PubMed

    Ikuta, Naoko; Sugiyama, Hironori; Shimosegawa, Hiroshi; Nakane, Rie; Ishida, Yoshiyuki; Uekaji, Yukiko; Nakata, Daisuke; Pallauf, Kathrin; Rimbach, Gerald; Terao, Keiji; Matsugo, Seiichi

    2013-02-07

    R(+)-alpha lipoic acid (RALA) is one of the cofactors for mitochondrial enzymes and, therefore, plays a central role in energy metabolism. RALA is unstable when exposed to low pH or heat, and therefore, it is difficult to use enantiopure RALA as a pharma- and nutra-ceutical. In this study, we have aimed to stabilize RALA through complex formation with cyclodextrins (CDs). α-CD, β-CD and γ-CD were used for the formation of these RALA-CD complexes. We confirmed the complex formation using differential scanning calorimetry and showed by using HPLC analysis that complexed RALA is more stable than free RALA when subjected to humidity and high temperature or acidic pH conditions. Scanning electron microscopy studies showed that the particle size and shape differed depending on the cyclodextrin used for complexation. Further, the complexes of CD and RALA showed a different particle size distribution pattern compared with that of CD itself or that of the physical mixture of RALA and CD.

  14. Does the Digestibility of Cyclodextrins Influence the In Vivo Absorption of Benzo[a]pyrene in Rats?

    PubMed

    Olesen, Niels E; Vana, Vasiliki; Holm, René

    2016-09-01

    An important excipient used to overcome poor solubility is cyclodextrin. However, data in the literature suggest that excessive overdosing of cyclodextrins can decrease the absorption of compounds administered with cyclodextrins, due to their lack of release from the complex. γ-Cyclodextrin is digestible in contrast to β-cyclodextrins. This could potentially limit the sensitivity toward overdose, which was evaluated using benzo[a]pyrene in this study, in which rats were administered benzo[a]pyrene and different doses of the 2 cyclodextrins. Both cyclodextrins lowered the area under the curve and therefore the absorption of benzo[a]pyrene by up to a factor of 2 when dosed in high concentrations, thus indicating that overdosing of cyclodextrins may limit the oral absorption of a compound. This limitation may be artificial because the molar ratio of benzo[a]pyrene:cyclodextrin was >1:50,000 at the concentration where a significant decrease in the absorption was observed. No difference was observed between the 2 cyclodextrins, so digestibility seemed less important. More interesting was that the decrease in absorption was relatively small when compared with literature values, suggesting that the effect of overdosing a compound with cyclodextrins was lower than anticipated.

  15. Carbon phosphide monolayers with superior carrier mobility

    NASA Astrophysics Data System (ADS)

    Wang, Gaoxue; Pandey, Ravindra; Karna, Shashi P.

    2016-04-01

    Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great promise for applications in high-performance electronics and optoelectronics.Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great

  16. Linear magnetotransport in monolayer MoS2

    NASA Astrophysics Data System (ADS)

    Wang, C. M.; Lei, X. L.

    2015-09-01

    A momentum balance equation is developed to investigate the magnetotransport properties in monolayer molybdenum disulphide when a strong perpendicular magnetic field and a weak in-plane electric field are applied simultaneously. At low temperature, in the presence of intravalley impurity scattering, Shubnikov-de Haas oscillation shows up accompanied by a beating pattern arising from large spin splitting and its period may halve due to the high-order oscillating term at large magnetic field for samples with ultrahigh mobility. In the case of intervalley disorders, there exists a magnetic-field range where the magnetoresistivity almost vanishes. For a low-mobility layer, a phase inversion of oscillating peaks is acquired in accordance with recent experiment. At high temperature when Shubnikov-de Haas oscillation is suppressed, the magnetophonon resonances induced by both optical phonons (mainly due to homopolar and Fröhlich modes) and acoustic phonons (mainly due to intravalley transverse and longitudinal acoustic modes) emerge for a suspended system with high mobility. For the single layer on a substrate, another resonance due to surface optical phonons may occur, resulting in a complex behavior of the total magnetoresistance. The beating pattern of magnetophonon resonance due to optical phonons can also be observed. However, for a nonsuspended layer with low mobility, the magnetoresistance oscillation almost disappears and the resistivity increases with field monotonically.

  17. Manganese Atom Ordered Monolayer on Wurtzite Gallium Nitride

    NASA Astrophysics Data System (ADS)

    Chinchore, Abhijit; Wang, Kangkang; Lin, Wenzhi; Pak, Jeongihm; Liu, Yinghao; Smith, Arthur

    2009-03-01

    While transition-metal-doped gallium nitride (GaN) thin films have been explored as potential dilute magnetic semiconductor bulk layers, the structural and magnetic effects of various transition metal adatoms on GaN surfaces are not even well understood. In this work, we investigate the sub-monolayer deposition of manganese (Mn) onto the N-polar wurtzite GaN (000-1) 1x1 surface. The growth is monitored in-situ using reflection high energy electron diffraction (RHEED). A fresh GaN(000-1) 1x1 surface is prepared by rf nitrogen plasma-assisted MBE followed by annealing to remove excess gallium adatoms. The atomically flat GaN surface, held at 200^o C, is then exposed to submonolayer doses of Mn. The deposition rate is maintained at 0.007 ML per second, and a 3x pattern develops along [10-10]; whereas, only 1x is seen along [11-20]. Analysis of the RHEED pattern and subsequent modeling indicates a 3 x3 R 30^o structure consisting of 2/3 ML Mn atoms in a row-like arrangement having spacing 3a/2 along rows and 3a/2 between rows. Scanning tunneling microscopy/spectroscopy studies are currently underway to explore this surface further. This work is supported by DOE (Grant No.DE-FG02-06ER46317) and NSF (Grant No. 0730257).

  18. Synthesis of a thiol-β-cyclodextrin, a potential agent for controlling enzymatic browning in fruits and vegetables.

    PubMed

    Manta, Carmen; Peralta-Altier, Gabriela; Gioia, Larissa; Méndez, María F; Seoane, Gustavo; Ovsejevi, Karen

    2013-11-27

    A thiol-β-cyclodextrin was synthesized by a simple and environmentally friendly three-step method comprising epoxy activation of β-cyclodextrin, thiosulfate-mediated oxirane opening, and further reduction of the S-alkyl thiosulfate to a thiol group. The final step was optimized by using thiopropyl-agarose, a solid phase reducing agent with many advantages over soluble ones. β-Cyclodextrin thiolation was confirmed by titration with a thiol-reactive reagent, NMR studies, and MALDI-TOF/TOF. Thiolated cyclodextrin had an average value of one thiol group per molecule. Thiol-β-cyclodextrin proved to be an excellent agent for controlling polyphenol oxidase activity. This copper-containing enzyme is responsible for browning in fruits and vegetables. Under the same conditions, thiol-β-cyclodextrin generated a reductive microenvironment that increased the antibrowning effect on Red Delicious apples compared to unmodified β-cyclodextrin.

  19. Synthesis of a thiol-β-cyclodextrin, a potential agent for controlling enzymatic browning in fruits and vegetables.

    PubMed

    Manta, Carmen; Peralta-Altier, Gabriela; Gioia, Larissa; Méndez, María F; Seoane, Gustavo; Ovsejevi, Karen

    2013-11-27

    A thiol-β-cyclodextrin was synthesized by a simple and environmentally friendly three-step method comprising epoxy activation of β-cyclodextrin, thiosulfate-mediated oxirane opening, and further reduction of the S-alkyl thiosulfate to a thiol group. The final step was optimized by using thiopropyl-agarose, a solid phase reducing agent with many advantages over soluble ones. β-Cyclodextrin thiolation was confirmed by titration with a thiol-reactive reagent, NMR studies, and MALDI-TOF/TOF. Thiolated cyclodextrin had an average value of one thiol group per molecule. Thiol-β-cyclodextrin proved to be an excellent agent for controlling polyphenol oxidase activity. This copper-containing enzyme is responsible for browning in fruits and vegetables. Under the same conditions, thiol-β-cyclodextrin generated a reductive microenvironment that increased the antibrowning effect on Red Delicious apples compared to unmodified β-cyclodextrin. PMID:24215568

  20. Diacetylene mixed Langmuir monolayers for interfacial polymerization.

    PubMed

    Ariza-Carmona, Luisa; Rubia-Payá, Carlos; García-Espejo, G; Martín-Romero, María T; Giner-Casares, Juan J; Camacho, Luis

    2015-05-19

    Polydiacetylene (PDA) and its derivatives are promising materials for applications in a vast number of fields, from organic electronics to biosensing. PDA is obtained through polymerization of diacetylene (DA) monomers, typically using UV irradiation. DA polymerization is a 1-4 addition reaction with both initiation and growth steps with topochemical control, leading to the "blue" polymer form as primary reaction product in bulk and at interfaces. Herein, the diacetylene monomer 10,12-pentacosadiynoic acid (DA) and the amphiphilic cationic N,N'-dioctadecylthiapentacarbocyanine (OTCC) have been used to build a mixed Langmuir monolayer. The presence of OTCC imposes a monolayer supramolecular structure instead of the typical trilayer of pure DA. Surface pressure, Brewster angle microscopy, and UV-vis reflection spectroscopy measurements, as well as computer simulations, have been used to assess in detail the supramolecular structure of the DA:OTCC Langmuir monolayer. Our experimental results indicate that the DA and OTCC molecules are sequentially arranged, with the two OTCC alkyl chains acting as spacing diacetylene units. Despite this configuration is expected to prevent photopolymerization of DA, the polymerization takes place without phase segregation, thus exclusively leading to the red polydiacetylene form. We propose a simple model for the initial formation of the "blue" or "red" PDA forms as a function of the relative orientation of the DA units. The structural insights and the proposed model concerning the supramolecular structure of the "blue" and "red" forms of the PDA are aimed at the understanding of the relation between the molecular and macroscopical features of PDAs.

  1. Isostructural solid-solid phase transition in monolayers of soft core-shell particles at fluid interfaces: structure and mechanics.

    PubMed

    Rey, Marcel; Fernández-Rodríguez, Miguel Ángel; Steinacher, Mathias; Scheidegger, Laura; Geisel, Karen; Richtering, Walter; Squires, Todd M; Isa, Lucio

    2016-04-21

    We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always showed a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization.

  2. Processing of monolayer materials via interfacial reactions

    DOEpatents

    Sutter, Peter Werner; Sutter, Eli Anguelova

    2014-05-20

    A method of forming and processing of graphene is disclosed based on exposure and selective intercalation of the partially graphene-covered metal substrate with atomic or molecular intercalation species such as oxygen (O.sub.2) and nitrogen oxide (NO.sub.2). The process of intercalation lifts the strong metal-carbon coupling and restores the characteristic Dirac behavior of isolated monolayer graphene. The interface of graphene with metals or metal-decorated substrates also provides for controlled chemical reactions based on novel functionality of the confined space between a metal surface and a graphene sheet.

  3. Cell Volume Fluctuations in MDCK Monolayers

    PubMed Central

    Zehnder, Steven M.; Suaris, Melanie; Bellaire, Madisonclaire M.; Angelini, Thomas E.

    2015-01-01

    Cells moving collectively in tissues constitute a form of active matter, in which collective motion depends strongly on driven fluctuations at the single-cell scale. Fluctuations in cell area and number density are often seen in monolayers, yet their role in collective migration is not known. Here we study density fluctuations at the single- and multicell level, finding that single-cell volumes oscillate with a timescale of 4 h and an amplitude of 20%; the timescale and amplitude are found to depend on cytoskeletal activity. At the multicellular scale, density fluctuations violate the central limit theorem, highlighting the role of nonequilibrium driving forces in multicellular density fluctuations. PMID:25606673

  4. Fibrinogen monolayer characterization by colloid deposition.

    PubMed

    Nattich-Rak, Małgorzata; Adamczyk, Zbigniew; Wasilewska, Monika; Sadowska, Marta

    2013-09-24

    Colloid particle deposition was applied to characterize bovine and human fibrinogen (Fb) monolayers on mica produced by controlled adsorption under diffusion transport at pH 3.5. The surface concentration of Fb was determined by AFM enumeration of single molecules adsorbed over the substrate surface. The electrokinetic properties of Fb monolayers for various ionic strength were studied using the in situ streaming potential measurements. It was shown that Fb adsorbs irreversibly on mica for a broad range of ionic strength of 4 × 10(-4) to 0.15 M, NaCl. The overcharging of initially negative mica surface occurred for fibrinogen surface concentrations higher than 1400 μm(-2). The orientation of fibrinogen molecules in the monolayers was evaluated by the colloid deposition method involving negatively charged polystyrene latex microspheres, 820 nm in diameter. An anomalous deposition of negative latex particles on substrates exhibiting a negative zeta potential was observed, which contradicts the mean-field DLVO predictions. Measurable deposition was observed even at low ionic strength where the minimum approach distance of latex particles to the interface exceeds 70 nm (for 6 × 10(-4) M NaCl). This confirms that, at this pH, fibrinogen molecules adsorb end-on on mica assuming extended conformations with the positive charge located mostly in the end part of the αA chains. This agrees with previous experimental and theoretical results discussed in the literature (Santore, M. M.; Wertz Ch. F. Protein spreading kinetics at liquid-solid interfaces via an adsorption probe method. Langmuir 2005, 21, 10172-10178 (experimental); Adamczyk, Z.; Barbasz, J.; Cieśla, M.; Mechanisms of fibrinogen adsorption at solid substrates. Langmuir, 2011, 25, 6868-6878 (theoretical)). This unusual latex deposition on Fb monolayers was quantitatively interpreted in terms of the model developed in ref 55 (Jin, X.; Wang, N. H. L.; Tarjus, G.; Talbot, J. Irreversible adsorption on nonuniform

  5. Characterization of anti-adhesive self-assembled monolayer for nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Zhou, Weimin; Zhang, Jing; Liu, Yanbo; Li, Xiaoli; Niu, Xiaomin; Song, Zhitang; Min, Guoquan; Wan, YongZhong; Shi, Liyi; Feng, Songlin

    2008-12-01

    In nanoimprint lithography process, resist adhesion to the mold was usually self-assembled and a release agent on the mold surface to detach easily from the imprinted resist. In the paper, the commercially available silane, 1 H,1 H,2 H,2 H-perfluorodecyltrichlorosilane (CF 3-(CF 2) 7-(CH 2) 2-SiCl 3 or FDTS) was used to investigate the anti-adhesion for UV-nanoimprint lithography. A water contact angle as high as 113.11 was achieved by self-assembled monolayer (SAM) deposited on the quarter mold by vapor evaporation, which is desirable for a good anti-adhesion agent between the fused silica and the curing resist. The homogeneous monolayer was also evaluated by AFM and XPS. UV-NIL using FDTS-coated fused silica process good pattern transfer fidelity. It is shown that the FDTS is an excellent and promising release agent material for UV-nanoimprint lithography.

  6. Interaction of native alpha-cyclodextrin, beta-cyclodextrin and gamma-cyclodextrin and their hydroxypropyl derivatives with selected organic low molecular mass compounds at elevated and subambient temperature under RP-HPLC conditions.

    PubMed

    Zarzycki, P K; Ohta, H; Saito, Y; Jinno, K

    2008-08-01

    The main focus of this study was to explore the capability of native alpha-cyclodextrin, beta-cyclodextrin and gamma-cyclodextrin and their hydroxypropyl derivatives for host-guest interaction with 7,8-dimethoxyflavone, selected steroids (estetrol, estriol, estradiol, estrone, testosterone, cortisone, hydrocortisone, progesterone and 17alpha-hydroxyprogesterone) and polycyclic aromatic hydrocarbons (toluene, naphthalene, 1,8-dimethylnaphthalene, 1-acenaphthenol, acenaphthylene and acenaphthene) under reversed-phase liquid-chromatography conditions. The study revealed that native cyclodextrins interact more efficiently with the analytes investigated than do their hydroxypropyl counterparts. In the low-temperature region, enormously high ratios were observed for polycyclic aromatic hydrocarbons, particularly 1,8-dimethylnaphthalene, acenaphthene and acenaphthylene chromatographed on a beta-cyclodextrin-modified mobile phase. In such a case, the retention times of the polycyclic aromatic hydrocarbons were strongly reduced (e.g. from 127 to 1.2 min for 1,8-dimethylnaphthalene) and were close to the hold-up time of the high-performance liquid chromatography (HPLC) system (0.7 min). Moreover, chiral separation of 1-acenaphthenol optical isomers was observed and the elution order of the enantiomers was determined. Within the steroids group, strong interaction was observed for estradiol and testosterone. The results of cluster analysis indicate that beta-cyclodextrin as well as gamma-cyclodextrin and its hydroxypropyl derivative can be most effective mobile-phase additives under reversed-phase HPLC conditions for 3D-shape-recognition-driven separation, performed at subambient and elevated temperatures, respectively. PMID:18563397

  7. Carbon phosphide monolayers with superior carrier mobility.

    PubMed

    Wang, Gaoxue; Pandey, Ravindra; Karna, Shashi P

    2016-04-28

    Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great promise for applications in high-performance electronics and optoelectronics. PMID:27067002

  8. Predicting Two-Dimensional Silicon Carbide Monolayers.

    PubMed

    Shi, Zhiming; Zhang, Zhuhua; Kutana, Alex; Yakobson, Boris I

    2015-10-27

    Intrinsic semimetallicity of graphene and silicene largely limits their applications in functional devices. Mixing carbon and silicon atoms to form two-dimensional (2D) silicon carbide (SixC1-x) sheets is promising to overcome this issue. Using first-principles calculations combined with the cluster expansion method, we perform a comprehensive study on the thermodynamic stability and electronic properties of 2D SixC1-x monolayers with 0 ≤ x ≤ 1. Upon varying the silicon concentration, the 2D SixC1-x presents two distinct structural phases, a homogeneous phase with well dispersed Si (or C) atoms and an in-plane hybrid phase rich in SiC domains. While the in-plane hybrid structure shows uniform semiconducting properties with widely tunable band gap from 0 to 2.87 eV due to quantum confinement effect imposed by the SiC domains, the homogeneous structures can be semiconducting or remain semimetallic depending on a superlattice vector which dictates whether the sublattice symmetry is topologically broken. Moreover, we reveal a universal rule for describing the electronic properties of the homogeneous SixC1-x structures. These findings suggest that the 2D SixC1-x monolayers may present a new "family" of 2D materials, with a rich variety of properties for applications in electronics and optoelectronics. PMID:26394207

  9. Predicting Two-Dimensional Silicon Carbide Monolayers.

    PubMed

    Shi, Zhiming; Zhang, Zhuhua; Kutana, Alex; Yakobson, Boris I

    2015-10-27

    Intrinsic semimetallicity of graphene and silicene largely limits their applications in functional devices. Mixing carbon and silicon atoms to form two-dimensional (2D) silicon carbide (SixC1-x) sheets is promising to overcome this issue. Using first-principles calculations combined with the cluster expansion method, we perform a comprehensive study on the thermodynamic stability and electronic properties of 2D SixC1-x monolayers with 0 ≤ x ≤ 1. Upon varying the silicon concentration, the 2D SixC1-x presents two distinct structural phases, a homogeneous phase with well dispersed Si (or C) atoms and an in-plane hybrid phase rich in SiC domains. While the in-plane hybrid structure shows uniform semiconducting properties with widely tunable band gap from 0 to 2.87 eV due to quantum confinement effect imposed by the SiC domains, the homogeneous structures can be semiconducting or remain semimetallic depending on a superlattice vector which dictates whether the sublattice symmetry is topologically broken. Moreover, we reveal a universal rule for describing the electronic properties of the homogeneous SixC1-x structures. These findings suggest that the 2D SixC1-x monolayers may present a new "family" of 2D materials, with a rich variety of properties for applications in electronics and optoelectronics.

  10. Phase transformations in binary colloidal monolayers.

    PubMed

    Yang, Ye; Fu, Lin; Marcoux, Catherine; Socolar, Joshua E S; Charbonneau, Patrick; Yellen, Benjamin B

    2015-03-28

    Phase transformations can be difficult to characterize at the microscopic level due to the inability to directly observe individual atomic motions. Model colloidal systems, by contrast, permit the direct observation of individual particle dynamics and of collective rearrangements, which allows for real-space characterization of phase transitions. Here, we study a quasi-two-dimensional, binary colloidal alloy that exhibits liquid-solid and solid-solid phase transitions, focusing on the kinetics of a diffusionless transformation between two crystal phases. Experiments are conducted on a monolayer of magnetic and nonmagnetic spheres suspended in a thin layer of ferrofluid and exposed to a tunable magnetic field. A theoretical model of hard spheres with point dipoles at their centers is used to guide the choice of experimental parameters and characterize the underlying materials physics. When the applied field is normal to the fluid layer, a checkerboard crystal forms; when the angle between the field and the normal is sufficiently large, a striped crystal assembles. As the field is slowly tilted away from the normal, we find that the transformation pathway between the two phases depends strongly on crystal orientation, field strength, and degree of confinement of the monolayer. In some cases, the pathway occurs by smooth magnetostrictive shear, while in others it involves the sudden formation of martensitic plates. PMID:25677504

  11. Recombinant albumin monolayers on latex particles.

    PubMed

    Sofińska, Kamila; Adamczyk, Zbigniew; Kujda, Marta; Nattich-Rak, Małgorzata

    2014-01-14

    The adsorption of recombinant human serum albumin (rHSA) on negatively charged polystyrene latex micro-particles was studied at pH 3.5 and the NaCl concentration range of 10(-3) to 0.15 M. The electrophoretic mobility of latex monotonically increased with the albumin concentration in the suspension. The coverage of adsorbed albumin was quantitatively determined using the depletion method, where the residual protein concentration was determined by electrokinetic measurements and AFM imaging. It was shown that albumin adsorption was irreversible. Its maximum coverage on latex varied between 0.7 mg m(-2) for 10(-3) M NaCl to 1.3 mg m(-2) for 0.15 M NaCl. The latter value matches the maximum coverage previously determined for human serum albumin on mica using the streaming potential method. The increase in the maximum coverage was interpreted in terms of reduced electrostatic repulsion among adsorbed molecules. These facts confirm that albumin adsorption at pH 3.5 is governed by electrostatic interactions and proceeds analogously to colloid particle deposition. The stability of albumin monolayers was measured in additional experiments where changes in the latex electrophoretic mobility and the concentration of free albumin in solutions were monitored over prolonged time periods. Based on these experimental data, a robust procedure of preparing albumin monolayers on latex particles of well-controlled coverage and molecule distribution was proposed. PMID:24354916

  12. Study on the interaction of methylene blue with cyclodextrin derivatives by absorption and fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Guomei; Shuang, Shaomin; Dong, Chuan; Pan, Jinghao

    2003-11-01

    The ability of β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD), and carboxymethyl-β-cyclodextrin (CM-β-CD) to break the aggregate of the methylene blue (MB) and to form 1:1 inclusion complexes has been studied by absorption and fluorescence spectroscopy. Experimental conditions including concentrations of various cyclodextrins (β-CD, HP-β-CD and CM-β-CD) and media acidity were investigated for the inclusion formation in detail. The formation constants are calculated by using steady-state fluorimetry, from which the inclusion capacity of different cyclodextrins (CDs) is compared. The results suggest that the charged β-cyclodextrin (CM-β-CD) is more suitable for inclusion of the cationic dye MB than the neutral β-cyclodextrins (β-CD, HP-β-CD) at pH>5. A mechanism is proposed which is consistent with the stronger binding of MB with CM-β-CD compared with the other CDs at pH>5.

  13. Cationic-modified cyclodextrin nanosphere/anionic polymer as flocculation/sorption systems.

    PubMed

    Xiao, Huining; Cezar, Norlito

    2005-03-15

    Simultaneous removal of dissolved and colloidal substances has been a challenging task. The cationic-modified beta-cyclodextrin nanospheres synthesized in this work, in conjunction with a water-soluble polyacrylamide-based anionic polymer, potentially provide a novel approach to address the problem. The cyclodextrin was rendered cationic using (2,3-epoxypropyl)trimethylammonium chloride as a reagent. The cationicity of the modified cyclodextrin and the reaction between cyclodextrin and the reagent were characterized by electrophoresis measurement, polyelectrolyte titration, and NMR. As a dual-component flocculation system, the cationic cyclodextrin/anionic polymer significantly induced clay flocculation, lowering the relative turbidity of the clay suspension over a wide pH range. Meanwhile, as a nanospherical absorbent, the modified cyclodextrins exhibited strong affinity toward aromatic compounds via inclusion complex formation in the hydrophobic cavities, which was monitored by UV spectroscopy. These systems facilitated the simultaneous removal of dissolved and colloidal substances, which was unachievable previously. In addition, the interaction between anionic polymers and the clay particles pretreated with cationic cyclodextrin was investigated in order to reveal the flocculation mechanism.

  14. Investigation of the complexation of albendazole with cyclodextrins for the design of new antiparasitic formulations.

    PubMed

    Pradines, Bénédicte; Gallard, Jean-François; Iorga, Bogdan I; Gueutin, Claire; Loiseau, Philippe M; Ponchel, Gilles; Bouchemal, Kawthar

    2014-10-29

    Albendazole (ABZ) exhibits a potent antiparasitic activity against a broad spectrum of parasites. Unfortunately, the very low water solubility of ABZ (0.2 μg mL(-1), 0.7 μM) impairs considerably its formulation. Phase solubility diagrams showed that α-cyclodextrin (10% w/w), hydroxypropyl-β-cyclodextrin (40% w/w) and sulfobutylether-β-cyclodextrin (40% w/w) allowed an increase of apparent solubility with enhancement factors of 570, 3970, and 5880, respectively. The apparent aqueous solubility of ABZ was markedly increased from 0.2 μg mL(-1) (0.7 μM) without cyclodextrins to 1.52 mg mL(-1) (5.69 mM) with random methyl-β-cyclodextrin (Me-β-CD) (40% w/w). This corresponds to an apparent solubility enhancement factor of 7600 which is the maximal enhancement factor of ABZ apparent aqueous solubility ever reported in the literature using conventional cyclodextrins. The complexation mechanism between ABZ and cyclodextrins has been investigated using phase solubility diagrams, nuclear magnetic resonance ((1)H NMR) coupled with two-dimensional nuclear Overhauser effect (NOESY) experiments and molecular docking calculations. The results showed that the central bicyclic fragment from ABZ interacts with Me-β-CD according to 1:1 stoichiometry.

  15. Cationic-modified cyclodextrin nanosphere/anionic polymer as flocculation/sorption systems.

    PubMed

    Xiao, Huining; Cezar, Norlito

    2005-03-15

    Simultaneous removal of dissolved and colloidal substances has been a challenging task. The cationic-modified beta-cyclodextrin nanospheres synthesized in this work, in conjunction with a water-soluble polyacrylamide-based anionic polymer, potentially provide a novel approach to address the problem. The cyclodextrin was rendered cationic using (2,3-epoxypropyl)trimethylammonium chloride as a reagent. The cationicity of the modified cyclodextrin and the reaction between cyclodextrin and the reagent were characterized by electrophoresis measurement, polyelectrolyte titration, and NMR. As a dual-component flocculation system, the cationic cyclodextrin/anionic polymer significantly induced clay flocculation, lowering the relative turbidity of the clay suspension over a wide pH range. Meanwhile, as a nanospherical absorbent, the modified cyclodextrins exhibited strong affinity toward aromatic compounds via inclusion complex formation in the hydrophobic cavities, which was monitored by UV spectroscopy. These systems facilitated the simultaneous removal of dissolved and colloidal substances, which was unachievable previously. In addition, the interaction between anionic polymers and the clay particles pretreated with cationic cyclodextrin was investigated in order to reveal the flocculation mechanism. PMID:15721912

  16. SYNCHROTRON X - RAY OBSERVATIONS OF A MONOLAYER TEMPLATE FOR MINERALIZATION.

    SciTech Connect

    DIMASI,E.; GOWER,L.B.

    2000-11-27

    Mineral nucleation at a Langmuir film interface has been studied by synchrotron x-ray scattering. Diluted calcium bicarbonate solutions were used as subphases for arachidic and stearic acid monolayers, compressed in a Langmuir trough. Self-assembly of the monolayer template is observed directly, and subsequent crystal growth monitored in-situ.

  17. Hydrogen exchange mass spectrometry of proteins at Langmuir monolayers

    PubMed Central

    Pirrone, Gregory F.; Vernon, Briana C.; Kent, Michael S.; Engen, John R.

    2015-01-01

    Hydrogen exchange (HX) mass spectrometry (MS) is valuable for providing conformational information for proteins/peptides that are very difficult to analyze with other methods such as peripheral membrane proteins and peptides that interact with membranes. We developed a new type of HX MS measurement that integrates Langmuir monolayers. A lipid monolayer was generated, a peptide or protein associated with it, and then the monolayer-associated peptide or protein was exposed to deuterium. The deuterated species was recovered from the monolayer, digested, and deuterium incorporation monitored by MS. Test peptides showed that deuterium recovery in an optimized protocol was equivalent to deuterium recovery in conventional solution HX MS. The reproducibility of the measurements was high despite the requirement of generating a new monolayer for each deuterium labeling time. We validated that known conformational changes in the presence of a monolayer/membrane could be observed with the peptide melittin and the myristoylated protein Arf-1. Results in an accompanying paper show that the method can reveal details of conformational changes in a protein (HIV-1 Nef) which adopts a different conformation depending on if it can insert into the lipid layer. Overall, the HX MS Langmuir monolayer method provided new and meaningful conformational information for proteins that associate with lipid layers. The combination of HX MS results with neutron or X-ray reflection of the same proteins in Langmuir monolayers can be more informative than isolated use of either method. PMID:26134943

  18. Hydrogen Exchange Mass Spectrometry of Proteins at Langmuir Monolayers.

    PubMed

    Pirrone, Gregory F; Vernon, Briana C; Kent, Michael S; Engen, John R

    2015-07-21

    Hydrogen exchange (HX) mass spectrometry (MS) is valuable for providing conformational information for proteins/peptides that are very difficult to analyze with other methods such as peripheral membrane proteins and peptides that interact with membranes. We developed a new type of HX MS measurement that integrates Langmuir monolayers. A lipid monolayer was generated, a peptide or protein associated with it, and then the monolayer-associated peptide or protein was exposed to deuterium. The deuterated species was recovered from the monolayer, digested, and deuterium incorporation monitored by MS. Test peptides showed that deuterium recovery in an optimized protocol was equivalent to deuterium recovery in conventional solution HX MS. The reproducibility of the measurements was high, despite the requirement of generating a new monolayer for each deuterium labeling time. We validated that known conformational changes in the presence of a monolayer/membrane could be observed with the peptide melittin and the myristoylated protein Arf-1. Results in an accompanying paper show that the method can reveal details of conformational changes in a protein (HIV-1 Nef), which adopts a different conformation, depending on whether or not it is able to insert into the lipid layer. Overall, the HX MS Langmuir monolayer method provided new and meaningful conformational information for proteins that associate with lipid layers. The combination of HX MS results with neutron or X-ray reflection of the same proteins in Langmuir monolayers can be more informative than the isolated use of either method.

  19. Antibacterial electrospun nanofibers from triclosan/cyclodextrin inclusion complexes.

    PubMed

    Celebioglu, Asli; Umu, Ozgun C O; Tekinay, Turgay; Uyar, Tamer

    2014-04-01

    The electrospinning of nanofibers (NF) from cyclodextrin inclusion complexes (CD-IC) with an antibacterial agent (triclosan) was achieved without using any carrier polymeric matrix. Polymer-free triclosan/CD-IC NF were electrospun from highly concentrated (160% CD, w/w) aqueous triclosan/CD-IC suspension by using two types of chemically modified CD; hydroxypropyl-beta-cyclodextrin (HPβCD) and hydroxypropyl-gamma-cyclodextrin (HPγCD). The morphological characterization of the electrospun triclosan/CD-IC NF by SEM elucidated that the triclosan/HPβCD-IC NF and triclosan/HPγCD-IC NF were bead-free having average fiber diameter of 520 ± 250 nm and 1,100 ± 660 nm, respectively. The presence of triclosan and the formation of triclosan/CD-IC within the fiber structure were confirmed by (1)H-NMR, FTIR, XRD, DSC, and TGA studies. The initial 1:1 molar ratio of the triclosan:CD was kept for triclosan/HPβCD-IC NF after the electrospinning and whereas 0.7:1 molar ratio was observed for triclosan/HPγCD-IC NF and some uncomplexed triclosan was detected suggesting that the complexation efficiency of triclosan with HPγCD was lower than that of HPβCD. The antibacterial properties of triclosan/CD-IC NF were tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. It was observed that triclosan/HPβCD-IC NF and triclosan/HPγCD-IC NF showed better antibacterial activity against both bacteria compared to uncomplexed pure triclosan.

  20. Calorimetric quantification of linked equilibria in cyclodextrin/lipid/detergent mixtures for membrane-protein reconstitution.

    PubMed

    Textor, Martin; Vargas, Carolyn; Keller, Sandro

    2015-04-01

    Reconstitution from detergent micelles into lipid bilayer membranes is a prerequisite for many in vitro studies on purified membrane proteins. Complexation by cyclodextrins offers an efficient and tightly controllable way of removing detergents for membrane-protein reconstitution, since cyclodextrins sequester detergents at defined stoichiometries and with tuneable affinities. To fully exploit the potential advantages of cyclodextrin for membrane-protein reconstitution, we establish a quantitative model for predicting the supramolecular transition from mixed micelles to vesicles during cyclodextrin-mediated detergent extraction. The model is based on a set of linked equilibria among all pseudophases present in the course of the reconstitution process. Various isothermal titration-calorimetric protocols are used for quantifying a detergent's self-association as well as its colloidal and stoichiometric interactions with lipid and cyclodextrin, respectively. The detergent's critical micellar concentration, the phase boundaries in the lipid/detergent phase diagram, and the dissociation constant of the cyclodextrin/detergent complex thus obtained provide all thermodynamic parameters necessary for a quantitative prediction of the transition from micelles to bilayer membranes during cyclodextrin-driven reconstitution. This is exemplified and validated by stepwise complexation of the detergent lauryldimethylamine N-oxide in mixtures with the phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine upon titration with 2-hydroxypropyl-β-cyclodextrin, both in the presence and in the absence of the membrane protein Mistic. The calorimetric approach presented herein quantitatively predicts the onset and completion of the reconstitution process, thus obviating cumbersome trial-and-error efforts and facilitating the rational optimisation of reconstitution protocols, and can be adapted to different cyclodextrin/lipid/detergent combinations.

  1. High-Throughput Phase-Distribution Method to Determine Drug-Cyclodextrin Binding Constants

    PubMed Central

    CHEN, ZHI; LU, DUJUAN; WEBER, STEPHEN G.

    2009-01-01

    A high-throughput method has been developed to measure drug-cyclodextrin binding constants. It measures the distribution ratio of a drug between a polymer film [polyvinyl chloride (PVC) with 67% (w/w) dioctyl sebacate (DOS)] and a cyclodextrin-containing buffer in a 96-well format. Measurements of distribution ratios at several cyclodextrin concentrations lead to binding constants. Binding constants for econazole with six CDs have been determined in one 96-well microplate with four replications of each condition in 10 h. The K1:1/103 M−1 values are 3.98±0.13, 3.90±0.22, 29.3±2.2, 0.66±0.04 1.78±0.30, 4.08±0.50, with (2-hydroxyethyl)-β-cyclodextrin, (2-hydroxypropyl)-β-cyclodextrin, 2,6-di-O-methyl-β-cyclodextrin, hepta-kis(2,3,6-tri-O-methyl)-β-cyclodextrin, α-cyclodextrin, β-cyclodextrin, respectively. It is likely that 1:2 complexes are also formed in some cases. This method has also been applied to study the binding behavior as a function of the drug concentration and pH. Binding weakens at higher drug concentration which may be due to the self-association of the drug. An acidic environment decreases the binding constant of CD with the basic econazole. The formation of the 1:2 complexes is completely suppressed in acid as well. This protocol is faster than the phase-solubility method. Moreover, the material requirement is up to four orders of magnitude lower. PMID:18428984

  2. Cyclodextrins sequester neuroactive steroids and differentiate mechanisms that rate limit steroid actions

    PubMed Central

    Shu, H-J; Zeng, C-M; Wang, C; Covey, D F; Zorumski, C F; Mennerick, S

    2006-01-01

    Background and purpose: Neuroactive steroids are potent modulators of GABAA receptors and are thus of interest for their sedative, anxiolytic, anticonvulsant and anaesthetic properties. Cyclodextrins may be useful tools to manipulate neuroactive effects of steroids on GABAA receptors because cyclodextrins form inclusion complexes with at least some steroids that are active at the GABAA receptor, such as (3α,5α)-3-hydroxypregnan-20-one (3α5αP, allopregnanolone). Experimental approach: To assess the versatility of cyclodextrins as steroid modulators, we investigated interactions between γ-cyclodextrin and neuroactive steroids of different structural classes. Key results: Both a bioassay based on electrophysiological assessment of GABAA receptor function and optical measurements of cellular accumulation of a fluorescent steroid analogue suggest that γ-cyclodextrin sequesters steroids rather than directly influencing GABAA receptor function. Neither a 5β-reduced A/B ring fusion nor a sulphate group at carbon 3 affected the presumed inclusion complex formation between steroid and γ-cyclodextrin. Apparent dissociation constants for interactions between natural steroids and γ-cyclodexrin ranged from 10-60 μM. Although γ-cyclodextrin accommodates a range of natural and synthetic steroids, C11 substitutions reduced inclusion complex formation. Using γ-cyclodextrin to remove steroid not directly bound to GABAA receptors, we found that cellular retention of receptor-unbound steroid rate limits potentiation by 3α- hydroxysteroids but not inhibition by sulphated steroids. Conclusions and implications: We conclude that γ-cyclodextrins can be useful, albeit non-specific, tools for terminating the actions of multiple classes of naturally occurring neuroactive steroids. PMID:17160009

  3. Methylene blue adsorption on a DMPA lipid langmuir monolayer.

    PubMed

    Giner Casares, Juan José; Camacho, Luis; Martín-Romero, Maria Teresa; López Cascales, José Javier

    2010-07-12

    Adsorption of methylene blue (MB) onto a dimyristoylphosphatidic acid (DMPA) Langmuir air/water monolayer is studied by molecular dynamics (MD) simulations, UV reflection spectroscopy and surface potential measurements. The free-energy profile associated with MB transfer from water to the lipid monolayer shows two minima of -66 and -60 kJ mol(-1) for its solid and gas phase, respectively, corresponding to a spontaneous thermodynamic process. From the position of the free-energy minima, it is possible to predict the precise location of MB in the interior of the DMPA monolayer. Thus, MB is accommodated in the phosphoryl or carbonyl region of the DMPA Langmuir air/water interface, depending on the isomorphic state (solid or gas phase, respectively). Reorientation of MB, measured from the bulk solution to the interior of the lipid monolayer, passes from a random orientation in bulk solution to an orientation parallel to the surface of the lipid monolayer when MB is absorbed. PMID:20544777

  4. Methylene blue adsorption on a DMPA lipid langmuir monolayer.

    PubMed

    Giner Casares, Juan José; Camacho, Luis; Martín-Romero, Maria Teresa; López Cascales, José Javier

    2010-07-12

    Adsorption of methylene blue (MB) onto a dimyristoylphosphatidic acid (DMPA) Langmuir air/water monolayer is studied by molecular dynamics (MD) simulations, UV reflection spectroscopy and surface potential measurements. The free-energy profile associated with MB transfer from water to the lipid monolayer shows two minima of -66 and -60 kJ mol(-1) for its solid and gas phase, respectively, corresponding to a spontaneous thermodynamic process. From the position of the free-energy minima, it is possible to predict the precise location of MB in the interior of the DMPA monolayer. Thus, MB is accommodated in the phosphoryl or carbonyl region of the DMPA Langmuir air/water interface, depending on the isomorphic state (solid or gas phase, respectively). Reorientation of MB, measured from the bulk solution to the interior of the lipid monolayer, passes from a random orientation in bulk solution to an orientation parallel to the surface of the lipid monolayer when MB is absorbed.

  5. Monolayer-by-monolayer stacked pyramid-like MoS2 nanodots on monolayered MoS2 flakes with enhanced photoluminescence.

    PubMed

    Yuan, Cailei; Cao, Yingjie; Luo, Xingfang; Yu, Ting; Huang, Zhenping; Xu, Bo; Yang, Yong; Li, Qinliang; Gu, Gang; Lei, Wen

    2015-11-01

    The precise control of the morphology and crystal shape of MoS2 nanostructures is of particular importance for their application in nanoelectronic and optoelectronic devices. Here, we describe a single step route for the synthesis of monolayer-by-monolayer stacked pyramid-like MoS2 nanodots on monolayered MoS2 flakes using a chemical vapor deposition method. First-principles calculations demonstrated that the bandgap of the pyramid-like MoS2 nanodot is a direct bandgap. Enhanced local photoluminescence emission was observed in the pyramid-like MoS2 nanodot, in comparison with monolayered MoS2 flakes. The findings presented here provide new opportunities to tailor the physical properties of MoS2via morphology-controlled synthesis.

  6. [Study on quantitative mechanism and the interference of the UV spectrum of HABS reduced by β-Cyclodextrin].

    PubMed

    Shi, Dong-Po; Yin, Xian-Qing; Zheng, Yan-Cheng; Chen, Wu; Fu, Jia-Xin; Ren, Zhao-Hua

    2014-09-01

    A novel ultraviolet absorption spectrometry method was developed for the quantitative determination of HABS by adding β-cyclodextrin with the molar ratio of 1:1 in strong interference aqueous solution. The results indicated that the effect of several common interfering flooding agents (SAS, OP-10, HPAM) on the determination of HABS could be greatly reduced in β- cyclodextrin aqueous solution. Thus, the determination errors of the determined HABS were less than 2.0% under strong inter- ference, and the detection limit (S/N==3) of the method could be also as high was 8.3-9.1 x 10(-4) mg · L(-1). Various characterization results including 1H-NMR, TG-DSC and FTIR showed the interaction between β-cyclodextrin and HABS. The results of H-NMR analysis showed that HABS molecule could enter into the interior of the cavity of β-cyclodextrin molecule. TG-DSC analysis exhibited that the stable inclusion of β-cyclodextrin and HABS could be automatically formed. The interactions between the functional groups of β-cyclodextrin and HABS were showed by FTIR analysis, which also exhibited that the stable inclusion could be formed by HABS entering from the narrow or the broad mouth of the β-cyclodextrin. The interference of the UV spectrum of HABS could be reduced by β-cyclodextrin since the interaction between β-cyclodextrin due to the interaction between β-cyclodextrin and HABS in the inclusion complex.

  7. Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host–guest complexation

    PubMed Central

    Wang, Jie; Qiu, Zhiqiang; Wang, Yiming; Li, Li; Pham, Duc-Truc; Prud’homme, Robert K

    2016-01-01

    Summary The employment of cyclodextrin host–guest complexation to construct supramolecular assemblies with an emphasis on polymer networks is reviewed. The main driving force for this supramolecular assembly is host–guest complexation between cyclodextrin hosts and guest groups either of which may be discrete molecular species or substituents on a polymer backbone. The effects of such complexation on properties at the molecular and macroscopic levels are discussed. It is shown that cyclodextrin complexation may be used to design functional polymer materials with tailorable properties, especially for photo-, pH-, thermo- and redox-responsiveness and self-healing. PMID:26877808

  8. Host-guest interaction between pinocembrin and cyclodextrins: Characterization, solubilization and stability

    NASA Astrophysics Data System (ADS)

    Zhou, Shu-Ya; Ma, Shui-Xian; Cheng, Hui-Lin; Yang, Li-Juan; Chen, Wen; Yin, Yan-Qing; Shi, Yi-Min; Yang, Xiao-Dong

    2014-01-01

    The inclusion complexation behavior, characterization and binding ability of pinocembrin with β-cyclodextrin (β-CD) and its derivative 2-hydroxypropyl-β-cyclodextrin (HPβCD) were investigated in both solution and the solid state by means of XRD, DSC, 1H and 2D NMR and UV-vis spectroscopy. The results showed that the water solubility and thermal stability of pinocembrin were obviously increased in the inclusion complex with cyclodextrins. This satisfactory water solubility and high stability of the pinocembrin/CD complexes will be potentially useful for their application as herbal medicines or healthcare products.

  9. Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host-guest complexation.

    PubMed

    Wang, Jie; Qiu, Zhiqiang; Wang, Yiming; Li, Li; Guo, Xuhong; Pham, Duc-Truc; Lincoln, Stephen F; Prud'homme, Robert K

    2016-01-01

    The employment of cyclodextrin host-guest complexation to construct supramolecular assemblies with an emphasis on polymer networks is reviewed. The main driving force for this supramolecular assembly is host-guest complexation between cyclodextrin hosts and guest groups either of which may be discrete molecular species or substituents on a polymer backbone. The effects of such complexation on properties at the molecular and macroscopic levels are discussed. It is shown that cyclodextrin complexation may be used to design functional polymer materials with tailorable properties, especially for photo-, pH-, thermo- and redox-responsiveness and self-healing. PMID:26877808

  10. Localized dealloying corrosion mediated by self-assembled monolayers used as an inhibitor system.

    PubMed

    Shrestha, B R; Bashir, A; Ankah, G N; Valtiner, M; Renner, F U

    2015-01-01

    The structure and chemistry of thiol or selenol self-assembled organic monolayers have been frequently addressed due to the unique opportunities in functionalization of materials. Such organic films can also act as effective inhibition layers to mitigate oxidation or corrosion. Cu-Au alloy substrates covered by self-assembled monolayers show a different dealloying mechanism compared to bare surfaces. The organic surface layer inhibits dealloying of noble metal alloys by a suppression of surface diffusion at lower potentials but at higher applied potentials dealloying proceeds in localized regions due to passivity breakdown. We present an in situ atomic force microscopy study of a patterned thiol layer applied on Cu-Au alloy surfaces and further explore approaches to change the local composition of the surface layers by exchange of molecules. The pattern for the in situ experiment has been applied by micro-contact printing. This allows the study of corrosion protection with its dependence on different molecule densities at different sites. Low-density thiol areas surrounding the high-density patterns are completely protected and initiation of dealloying proceeds only along the areas with the lowest inhibitor concentration. Dealloying patterns are highly influenced and controlled by molecular thiol to selenol exchange and are also affected by introducing structural defects such as scratches or polishing defects. PMID:25920488

  11. Metastability of a Supercompressed Fluid Monolayer

    PubMed Central

    Smith, Ethan C.; Crane, Jonathan M.; Laderas, Ted G.; Hall, Stephen B.

    2003-01-01

    Previous studies showed that monomolecular films of extracted calf surfactant collapse at the equilibrium spreading pressure during quasi-static compressions but become metastable at much higher surface pressures when compressed faster than a threshold rate. To determine the mechanism by which the films become metastable, we studied single-component films of 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC). Initial experiments confirmed similar metastability of POPC if compressed above a threshold rate. Measurements at different surface pressures then showed that rates of collapse, although initially increasing above the equilibrium spreading pressure, reached a sharply defined maximum and then slowed considerably. When heated, rapidly compressed films recovered their ability to collapse with no discontinuous change in area, arguing that the metastability does not reflect transition of the POPC film to a new phase. These observations indicate that in several respects, the supercompression of POPC monolayers resembles the supercooling of three-dimensional liquids toward a glass transition. PMID:14581205

  12. New Monolayered Materials Exhibiting Unusual Electronic Properties

    NASA Astrophysics Data System (ADS)

    Lopez-Bezanilla, Alejandro; Martin, Ivar; Littlewood, Peter B.

    Computationally based approaches are allowing to progress in the discovery and design of nano-scaled materials. Here we propose a series of new mono-layered compounds with exotic properties. By means of density functional theory calculations we demonstrate that the pentagonal arrangement of SiC2 yields an inverted distribution of the p-bands which leads to an unusual electronic behaviour of the material under strain [J. Phys. Chem. C, 2015, 119 (33), pp 19469]. A different pentagonal arrangement of C atoms enables the formation of Dirac cones which, unlike graphene, exhibit a strain-mediated tunable band gap. This work is supported by DOE-BES under Contract No. DE-AC02-06CH11357.

  13. Covalently networked monolayer-protected nanoparticle films.

    PubMed

    Tognarelli, D J; Miller, Robert B; Pompano, Rebecca R; Loftus, Andrew F; Sheibley, Daniel J; Leopold, Michael C

    2005-11-22

    Covalently networked films of nanoparticles can be assembled on various substrates from functionalized monolayer-protected clusters (MPCs) via ester coupling reactions. Exposure of a specifically modified substrate to alternating solutions of 11-mercaptoundecanoic acid exchanged and 11-mercaptoundecanol exchanged MPCs, in the presence of ester coupling reagents, 1,3-dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine, results in the formation of a multilayer film with ester bridges between individual nanoparticles. These films can be grown in a controlled manner to various thicknesses and exhibit certain properties that are consistent with films having other types of interparticle connectivity, including chemical vapor response behavior and quantized double layer charging. Ester coupling of MPCs into assembled films is a straightforward and highly versatile approach that results in robust films that can endure harsher chemical environments than other types of films. The stability of these covalent films is assessed and compared to other more traditional MPC film assemblies.

  14. Valley depolarization in monolayer WSe2.

    PubMed

    Yan, Tengfei; Qiao, Xiaofen; Tan, Pingheng; Zhang, Xinhui

    2015-01-01

    We have systematically examined the circular polarization of monolayer WSe2 at different temperature, excitation energy and exciton density. The valley depolarization in WSe2 is experimentally confirmed to be governed by the intervalley electron-hole exchange interaction. More importantly, a non-monotonic dependence of valley circular polarization on the excitation power density has been observed, providing the experimental evidence for the non-monotonic dependence of exciton intervalley scattering rate on the excited exciton density. The physical origination of our experimental observations has been proposed to be in analogy to the D'yakonov-Perel' mechanism that is operative in conventional GaAs quantum well systems. Our experimental results are fundamentally important for well understanding the valley pseudospin relaxation in atomically thin transition metal dichalcogenides. PMID:26490157

  15. Organic Monolayer Protected Topological Surface State.

    PubMed

    Yang, Hung-Hsiang; Chu, Yu-Hsun; Lu, Chun-I; Butler, Christopher John; Sankar, Raman; Chou, Fang-Cheng; Lin, Minn-Tsong

    2015-10-14

    Perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA)/Bi2Se3 and Fe/PTCDA/Bi2Se3 heterointerfaces are investigated using scanning tunneling microscopy and spectroscopy. The close-packed self-assembled PTCDA monolayer possesses big molecular band gap and weak molecule-substrate interactions, which leaves the Bi2Se3 topological surface state intact under PTCDA. Formation of Fe-PTCDA hybrids removes interactions between the Fe dopant and the Bi2Se3 surface, such as doping effects and Coulomb scattering. Our findings reveal the functionality of PTCDA to prevent dopant disturbances in the TSS and provide an effective alternative for interface designs of realistic TI devices.

  16. Modification of the photocatalytic activity of TiO2 by β-Cyclodextrin in decoloration of ethyl violet dye

    PubMed Central

    Velusamy, Ponnusamy; Pitchaimuthu, Sakthivel; Rajalakshmi, Subramanian; Kannan, Nagarathinam

    2012-01-01

    The photocatalytic decoloration of an organic dye, ethyl violet (EV), has been studied in the presence of TiO2 and the addition of β-Cyclodextrin (β-CD) with TiO2 (TiO2-β-CD) under UV-A light irradiation. The different operating parameters like initial concentration of dye, illumination time, pH and amount of catalyst used have also been investigated. The photocatalytic decoloration efficiency is more in the TiO2-β-CD/UV-A light system than TiO2/UV-A light system. The mineralization of EV has been confirmed by Chemical Oxygen Demand (COD) measurements. The complexation patterns have been confirmed with UV–Visible and FT-IR spectral data and the interaction between TiO2 and β-CD have been characterized by powder XRD analysis and UV–Visible diffuse reflectance spectroscopy. PMID:25685468

  17. Advancing atomic nanolithography: cold atomic Cs beam exposure of alkanethiol self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    O'Dwyer, C.; Gay, G.; Viaris de Lesegno, B.; Weiner, J.; Mützel, M.; Haubrich, D.; Meschede, D.; Ludolph, K.; Georgiev, G.; Oesterschulze, E.

    2005-01-01

    We report the results of a study into the quality of functionalized surfaces for nanolithographic imaging. Self-assembled monolayer (SAM) coverage, subsequent post-etch pattern definition and minimum feature size all depend on the quality of the Au substrate used in atomic nanolithographic experiments. We find sputtered Au substrates yield much smoother surfaces and a higher density of {111} oriented grains than evaporated Au surfaces. A detailed study of the self-assembly mechanism using molecular resolution AFM and STM has shown that the monolayer is composed of domains with sizes typically of 5-25 nm, and multiple molecular domains can exist within one Au grain. Exposure of the SAM to an optically-cooled atomic Cs beam traversing a two-dimensional array of submicron material masks ans also standing wave optical masks allowed determination of the minimum average Cs dose (2 Cs atoms per SAM molecule) and the realization of < 50 nm structures. The SAM monolayer contains many non-uniformities such as pin-holes, domain boundaries and monoatomic depressions which are present in the Au surface prior to SAM adsorption. These imperfections limit the use of alkanethiols as a resist in atomic nanolithography experiments. These studies have allowed us to realize an Atom Pencil suitable for deposition of precision quantities of material at the microand nanoscale to an active surface.

  18. Monolayer semiconductor nanocavity lasers with ultralow thresholds

    DOE PAGESBeta

    Wu, Sanfeng; Buckley, Sonia; Schaibley, John R.; Feng, Liefeng; Yan, Jiaqiang; Mandrus, David G.; Hatami, Fariba; Yao, Wang; Vučković, Jelena; Majumdar, Arka; et al

    2015-03-16

    Engineering the electromagnetic environment of a nanoscale light emitter by a photonic cavity can significantly enhance its spontaneous emission rate through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter1–5, providing the ultimate low-threshold laser system with small footprint, low power consumption and ultrafast modulation. A state-of-the-art ultra-low threshold nanolaser has been successfully developed though embedding quantum dots into photonic crystal cavity (PhCC)6–8. However, several core challenges impede the practical applications of this architecture, including the random positions and compositional fluctuations of the dots7, extreme difficulty in current injection8, and lackmore » of compatibility with electronic circuits7,8. Here, we report a new strategy to lase, where atomically thin crystalline semiconductor, i.e., a tungsten-diselenide (WSe2) monolayer, is nondestructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PhCC. A new type of continuous-wave nanolaser operating in the visible regime is achieved with an optical pumping threshold as low as 27 nW at 130 K, similar to the value achieved in quantum dot PhCC lasers7. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within 1 nm of the PhCC surface. The surface-gain geometry allows unprecedented accessibilities to multi-functionalize the gain, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies.« less

  19. Monolayer semiconductor nanocavity lasers with ultralow thresholds

    NASA Astrophysics Data System (ADS)

    Wu, Sanfeng; Buckley, Sonia; Schaibley, John R.; Feng, Liefeng; Yan, Jiaqiang; Mandrus, David G.; Hatami, Fariba; Yao, Wang; Vučković, Jelena; Majumdar, Arka; Xu, Xiaodong

    2015-04-01

    Engineering the electromagnetic environment of a nanometre-scale light emitter by use of a photonic cavity can significantly enhance its spontaneous emission rate, through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter, providing a low-threshold laser system with small footprint, low power consumption and ultrafast modulation. An ultralow-threshold nanoscale laser has been successfully developed by embedding quantum dots into a photonic crystal cavity (PCC). However, several challenges impede the practical application of this architecture, including the random positions and compositional fluctuations of the dots, extreme difficulty in current injection, and lack of compatibility with electronic circuits. Here we report a new lasing strategy: an atomically thin crystalline semiconductor--that is, a tungsten diselenide monolayer--is non-destructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PCC. A continuous-wave nanolaser operating in the visible regime is thereby achieved with an optical pumping threshold as low as 27 nanowatts at 130 kelvin, similar to the value achieved in quantum-dot PCC lasers. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within one nanometre of the PCC surface. The surface-gain geometry gives unprecedented accessibility and hence the ability to tailor gain properties via external controls such as electrostatic gating and current injection, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies.

  20. Electronic correlations in monolayer VS2

    NASA Astrophysics Data System (ADS)

    Isaacs, Eric B.; Marianetti, Chris A.

    2016-07-01

    The layered transition metal dichalcogenide vanadium disulfide (VS2), which nominally has one electron in the 3 d shell, is potent for strong-correlation physics and is possibly another realization of an effective one-band model beyond the cuprates. Here monolayer VS2 in both the trigonal prismatic and the octahedral phases is investigated using density functional theory plus Hubbard U (DFT +U ) calculations. Trigonal prismatic VS2 has an isolated low-energy band that emerges from a confluence of crystal-field splitting and direct V-V hopping. Within spin density functional theory, ferromagnetism splits the isolated band of the trigonal prismatic structure, leading to a low-band-gap, S =1/2 , ferromagnetic Stoner insulator; the octahedral phase is higher in energy. Including the on-site interaction U increases the band gap, leads to Mott insulating behavior, and, for sufficiently high values, stabilizes the ferromagnetic octahedral phase. The validity of DFT and DFT +U for these two-dimensional materials with potential for strong electronic correlations is discussed. A clear benchmark is given by examining the experimentally observed charge density wave in octahedral VS2, for which DFT grossly overestimates the bond length differences compared to known experiments; the presence of charge density waves is also probed for the trigonal prismatic phase. Finally, we investigate why only the octahedral phase has been observed in experiments and discuss the possibility of realizing the trigonal prismatic phase. Our work suggests that trigonal prismatic VS2 is a promising candidate for strongly correlated electron physics that, if realized, could be experimentally probed in an unprecedented fashion due to its monolayer nature.

  1. Monolayer semiconductor nanocavity lasers with ultralow thresholds.

    PubMed

    Wu, Sanfeng; Buckley, Sonia; Schaibley, John R; Feng, Liefeng; Yan, Jiaqiang; Mandrus, David G; Hatami, Fariba; Yao, Wang; Vučković, Jelena; Majumdar, Arka; Xu, Xiaodong

    2015-04-01

    Engineering the electromagnetic environment of a nanometre-scale light emitter by use of a photonic cavity can significantly enhance its spontaneous emission rate, through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter, providing a low-threshold laser system with small footprint, low power consumption and ultrafast modulation. An ultralow-threshold nanoscale laser has been successfully developed by embedding quantum dots into a photonic crystal cavity (PCC). However, several challenges impede the practical application of this architecture, including the random positions and compositional fluctuations of the dots, extreme difficulty in current injection, and lack of compatibility with electronic circuits. Here we report a new lasing strategy: an atomically thin crystalline semiconductor--that is, a tungsten diselenide monolayer--is non-destructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PCC. A continuous-wave nanolaser operating in the visible regime is thereby achieved with an optical pumping threshold as low as 27 nanowatts at 130 kelvin, similar to the value achieved in quantum-dot PCC lasers. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within one nanometre of the PCC surface. The surface-gain geometry gives unprecedented accessibility and hence the ability to tailor gain properties via external controls such as electrostatic gating and current injection, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies. PMID:25778703

  2. Monolayer semiconductor nanocavity lasers with ultralow thresholds

    SciTech Connect

    Wu, Sanfeng; Buckley, Sonia; Schaibley, John R.; Feng, Liefeng; Yan, Jiaqiang; Mandrus, David G.; Hatami, Fariba; Yao, Wang; Vučković, Jelena; Majumdar, Arka; Xu, Xiaodong

    2015-03-16

    Engineering the electromagnetic environment of a nanoscale light emitter by a photonic cavity can significantly enhance its spontaneous emission rate through cavity quantum electrodynamics in the Purcell regime. This effect can greatly reduce the lasing threshold of the emitter1–5, providing the ultimate low-threshold laser system with small footprint, low power consumption and ultrafast modulation. A state-of-the-art ultra-low threshold nanolaser has been successfully developed though embedding quantum dots into photonic crystal cavity (PhCC)6–8. However, several core challenges impede the practical applications of this architecture, including the random positions and compositional fluctuations of the dots7, extreme difficulty in current injection8, and lack of compatibility with electronic circuits7,8. Here, we report a new strategy to lase, where atomically thin crystalline semiconductor, i.e., a tungsten-diselenide (WSe2) monolayer, is nondestructively and deterministically introduced as a gain medium at the surface of a pre-fabricated PhCC. A new type of continuous-wave nanolaser operating in the visible regime is achieved with an optical pumping threshold as low as 27 nW at 130 K, similar to the value achieved in quantum dot PhCC lasers7. The key to the lasing action lies in the monolayer nature of the gain medium, which confines direct-gap excitons to within 1 nm of the PhCC surface. The surface-gain geometry allows unprecedented accessibilities to multi-functionalize the gain, enabling electrically pumped operation. Our scheme is scalable and compatible with integrated photonics for on-chip optical communication technologies.

  3. Acid monolayer functionalized iron oxide nanoparticle catalysts

    NASA Astrophysics Data System (ADS)

    Ikenberry, Myles

    Superparamagnetic iron oxide nanoparticle functionalization is an area of intensely active research, with applications across disciplines such as biomedical science and heterogeneous catalysis. This work demonstrates the functionalization of iron oxide nanoparticles with a quasi-monolayer of 11-sulfoundecanoic acid, 10-phosphono-1-decanesulfonic acid, and 11-aminoundecanoic acid. The carboxylic and phosphonic moieties form bonds to the iron oxide particle core, while the sulfonic acid groups face outward where they are available for catalysis. The particles were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectrometry (XPS), and dynamic light scattering (DLS). The sulfonic acid functionalized particles were used to catalyze the hydrolysis of sucrose at 80° and starch at 130°, showing a higher activity per acid site than the traditional solid acid catalyst Amberlyst-15, and comparing well against results reported in the literature for sulfonic acid functionalized mesoporous silicas. In sucrose catalysis reactions, the phosphonic-sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic-sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. Between the two sulfonic ligands, the phosphonates produced a more tightly packed monolayer, which corresponded to a higher sulfonic acid loading, lower agglomeration, lower recoverability through application of an external magnetic field, and higher activity per acid site for the hydrolysis of starch. Functionalizations with 11-aminoundecanoic acid resulted in some amine groups binding to the surfaces of iron oxide nanoparticles. This amine binding is commonly ignored in iron oxide

  4. Inclusion complex of sulfadimethoxine with cyclodextrins: preparation and characterization.

    PubMed

    Rajendiran, N; Siva, S

    2014-01-30

    The inclusion complexation behavior, characterization and binding ability of sulfadimethoxine (SDMO) with α-cyclodextrin (α-CD) and β-cyclodextrin (β-CD) have been investigated both in solution and solid state by means of absorption, fluorescence, time-resolved fluorescence, (1)H NMR, FT-IR, DSC, SEM, TEM, XRD and molecular modeling methods. The spectral shifts revealed that the part of pyrimidine and aniline rings of SDMO are entrapped in the CD cavity. The stoichiometric ratio and association constant were determined by Benesi-Hildebrand plots and spectroscopic studies respectively. FT-IR spectroscopy was used to compare inclusion systems with physical mixtures, and demonstrated the complex formation in the solid state. The morphology and size of the nanoparticles of SDMO/CD complexes in aqueous solution were observed by TEM. The DSC analysis showed that the thermal stability of SDMO was enhanced in the presence of CD. Investigations of energetic and thermodynamic properties by PM3 method confirmed the stability of the inclusion complexes.

  5. Improvement of tetracaine antinociceptive effect by inclusion in cyclodextrins.

    PubMed

    Franco de Lima, Roberta Aline; de Jesus, Marcelo Bispo; Saia Cereda, Cíntia Maria; Tofoli, Giovana Radomille; Cabeça, Luis Fernando; Mazzaro, Irineu; Fraceto, Leonardo Fernandes; de Paula, Eneida

    2012-01-01

    Local anesthetics (LA) are among the most important pharmacological compounds used to attenuate or eliminate pain. However, systemic toxicity is still a limitation for LA application, especially for ester-type drugs, such as tetracaine (TTC) that presents poor chemical stability (due to hydrolysis by plasma esterases). Several approaches have been used to improve LA pharmaceutical properties, including the employment of drug-delivery systems. Here we used beta-cyclodextrin (β-CD) or hydroxypropyl-beta-cyclodextrin (HP-β-CD) to develop two new TTC formulations (TTC:β-CD and TTC:HP-β-CD). The inclusion complexes formation, in a 1:1 stoichiometry, was confirmed by differential scanning calorimetry, X-ray diffraction, UV-VIS absorption and fluorescence. Nuclear magnetic resonance (DOSY experiments) revealed that TTC association with HP-β-CD is stronger (Ka=1200 mol/L(-1)) than with β-CD (Ka=845 mol/L(-1)). Moreover, nuclear Overhauser effect (NOE) experiments provided information on the topology of the complexes, where TTC aromatic ring is buried inside the CD hydrophobic cavity. In vitro tests with 3T3 fibroblast cells culture revealed that complexation decreased TTC cytotoxicity. In addition, the total analgesic effect of TTC, tested in rats through the infraorbital nerve test, was improved in 36% with TTC:β-CD and TTC:HP-β-CD. In conclusion, these formulations presented potential for future clinical use, by reducing the toxicity and increasing the antinociceptive effect of tetracaine.

  6. Novel drug nanocarriers combining hydrophilic cyclodextrins and chitosan

    NASA Astrophysics Data System (ADS)

    Trapani, A.; Garcia-Fuentes, M.; Alonso, M. J.

    2008-05-01

    The aim of this study was to explore the possibility of obtaining nanoparticles (NPs) containing high amounts of cyclodextrin (CD) derivatives such as carboxymethyl-β-CD and sulphobutyl ether-β-CD. The rationale used was to combine the drug solubilizing and stabilizing properties of cyclodextrins (CDs) with the mucoadhesive properties of chitosan (CS) in a unique nanoparticulate drug delivery system. The size of the resulting NPs was affected by the nature of the CDs, ranging between 275 and 550 nm, whereas the zeta potential of the NPs was always positive and close to +35 mV. The positive zeta values, together with the results from NMR studies, suggest that CS is the major compound on the surface of the NPs, while CD molecules are strongly associated with the NP matrix. The empirical composition of the NPs was quantified by elemental analysis and the results indicated that the amount of CD associated with the NPs was strictly dependent on its electrostatic charge. Finally, in vitro stability studies indicated that the presence of CDs in the NP structure can prevent the aggregation of this nanometric carrier system in simulated intestinal fluid. Overall, this new type of NP represents an attractive drug delivery platform of particular interest for the oral administration of drugs with low bioavailability.

  7. Green extraction of polyphenols from whole pomegranate fruit using cyclodextrins.

    PubMed

    Diamanti, Amalia C; Igoumenidis, Panagiotis E; Mourtzinos, Ioannis; Yannakopoulou, Konstantina; Karathanos, Vaios T

    2017-01-01

    Pomegranate is a source of bioactive phytochemicals. The objective of this study was the derivation of a sustainable method to exploit the whole fruit, both edible and non-edible parts, as a source of polyphenols. Pomegranate peel contains a 10-fold higher phenolic content than the pulp. The fruit was freeze-dried and the resulting dry matter was extracted with solid-liquid percolation equipment using non-toxic and eco-friendly extraction solvents: either deionized water or aqueous solutions of cyclodextrins. Cyclodextrins (CDs) are known molecular encapsulators and our results prove enhancement of the extraction of pomegranate polyphenols by 20%. In order to examine the formation of inclusion complexes between CD's and polyphenols of the extract, polyphenols were isolated using solid-phase extraction. NMR studies with the purified extracts and the individual CDs confirmed inclusion complex formation in water. Pomegranate liquid extracts may be used as raw materials for several end-users in the food, cosmetic and pharmaceutical industries. PMID:27507448

  8. Novel cyclodextrin nanosponges for delivery of calcium in hyperphosphatemia.

    PubMed

    Shende, Pravin; Deshmukh, Kiran; Trotta, Fransesco; Caldera, Fabrizio

    2013-11-01

    Cyclodextrin nanosponges are solid, porous nanoparticulate three dimensional structures, have been used as delivery system of different drugs. In this work, new cyclodextrin-based nanosponges of calcium carbonate were prepared by polymer condensation method to release the calcium in controlled manner in the treatment of hyperphosphatemia as novel carriers. SEM measurements revealed their roughly spherical shape, porous nature and mean particle size of about 400 nm. Zeta potentials of the nanosponges were sufficiently high to obtain stable formulations. The encapsulation efficiencies of calcium in nanosponge formulations were found to be 81-95%. The moisture contents of the nanosponges were in the range of 0.1-0.7%. The optimized formulation produces enteric and controlled release kinetics of calcium in the management and treatment of hyperphosphatemia. It was also observed that calcium ions bound efficiently to free phosphate in a pH-dependent fashion especially at pH 7. In accelerated stability study no significant changes occurred in physical appearance, size and nature of drug in formulation for 3 months. The results of FTIR and DSC confirmed that calcium carbonate was encapsulated in nanosponges structure.

  9. Cyclodextrin Derivatives as Chiral Supramolecular Receptors for Enantioselective Sensing

    PubMed Central

    Shahgaldian, Patrick; Pieles, Uwe

    2006-01-01

    In view of the chiral nature of many bio-molecules (and all bio-macromolecules), most of therapeutically active compounds which target these molecules need to be chiral and “good handed” to be effective. In addition to asymmetric synthetic and separation methodologies, enantioselective chemical sensors, able to distinguish between two enantiomers of the same molecule, are of relevance. In order to design these sensing tools, two major classes of enantioselective layers have been developed. The first is based on molecularly imprinted polymers which are produced (polymerized) in the presence of their target, thus the polymeric material keep in “memory” the size and the shape of this molecule and the system could be used for sensing (not reviewed here). The second approach makes use of sensitive layers containing chiral macrocyclic receptors able of stereoselective molecular recognition; these receptors are mainly based on cyclodextrins. In this contribution, are reviewed achievements in the use of native or chemically modified cyclodextrins for chiral sensing purposes (at interfaces). Potentialities of other chiral macrocycles based on calixarenes, calix-resorcinarenes or crown-ethers as supramolecular receptors for enantioselective sensing are discussed.

  10. Use of cyclodextrins in capillary electrophoresis: resolution of tramadol enantiomers.

    PubMed

    Rudaz, S; Veuthey, J L; Desiderio, C; Fanali, S

    1998-11-01

    Capillary zone electrophoresis was successfully applied to the enantiomeric resolution of racemic tramadol. Both uncoated and polyacrylamide-coated capillaries were tested for method optimization using either negatively charged or native cyclodextrins (CD) added to the background electrolyte (BGE). The resolution was strongly influenced by the CD type and concentration as well as by the pH and the concentration of the BGE. Among the CDs tested, carboxymethylated-beta-cyclodextrin allowed the baseline separation of tramadol enantiomers. After the method was optimized, it was validated in a coated capillary for enantiomeric analysis of tramadol enantiomers in pharmaceutical formulation, including specificity and elution order, linearity, accuracy and precision, determination of limit of detection (LOD) and quantification (LOQ), enantiomeric purity linearity, freedom from interference, and stability of sample solutions. Precision at the target concentration was less than 2%, with an accuracy higher than 99%. Furthermore, the method was able to detect 0.3% and to quantify 1% of the minor enantiomer in the presence of the major one at the target value.

  11. Removal of aromatic hydrocarbon compounds by hydroxypropyl-cyclodextrin

    SciTech Connect

    1999-09-15

    Activated carbon has been used for the recovery and removal of benzene, toluene, and xylenes in air and water for a long time. However, removal of benzene, toluene, and xylenes from soil is very difficult. They can be removed by an increase in the apparent solubility of organic compounds in soil. The apparent solubilities of benzene, toluene, and xylene were investigated to estimate their inclusion behavior into natural cyclodextrins (CDs) and hydroxypropyl-cyclodextrins (HP-CDs) in the liquid phase. The apparent solubilities of benzene, toluene, and xylenes did not increase by adding natural CDs but did increase when HP-CDs were added. Benzene, toluene, and xylenes in a HP-CD solution depended on the relationship between the molecular diameter of benzene, toluene, and xylenes, the CD cavity size, and the 1-octanol-water partition coefficient. That of p-xylene was larger than that of o-xylene and m-xylene because of the smallest steric hindrance of p-xylene.

  12. Multichromophoric cyclodextrins. 4. Light conversion by antenna effect

    SciTech Connect

    Jullien, L. |; Canceill, J.; Lehn, J.M.; Marchi-Artzner, V.; Bardez, E.; Lefevre, J.P. |; Lefevre, J.P. |

    1996-06-12

    A water soluble {beta}-cyclodextrin (CD-NA) bearing seven naphthoyl chromophores forms very stable 1:1 complexes with a merocyanine laser dye DCM-OH (4-dicyanomethylene)-2-methyl-6-(p-(bis(hydroxyethyl)amino)-styryl)-4H-pyran. The antenna effect, i.e. energy transfer from the naphthoyl antenna chromophores to the encased dye, is shown to occur with 100% efficiency. The stability of the complexes is very high (K{sub s} = 10{sup 5}) owing to the contribution of the naphthoate residues. The structural features of the complexes have been examined in detail: circular dichroism experiments confirm the expected axial orientation of DCM-OH in the cavity of CD-NA, and fluorescence anisotropy measurements together with {sup 13}C-NMR longitudinal relaxation time measurements show that the complex formed between CD-NA and DCM-OH is tight. The mechanisms of homotransfer (i.e., between naphthoate chromophores) and heterotransfer (i.e., from naphthoate chromophores to DCM-OH included in the cavity) are discussed in light of existing theories. In both cases, the major contribution arises more likely from Coulombic interaction than from short-range interactions. Such multichromophoric cyclodextrins are good models for mimicry of the antenna function in photosynthesis and show great promise as photochemical microreactors. 38 refs., 11 figs., 3 tabs.

  13. Piroxicam-β-Cyclodextrin: A GI Safer Piroxicam

    PubMed Central

    Scarpignato, C

    2013-01-01

    Although NSAIDs are very effective drugs, their use is associated with a broad spectrum of adverse reactions in the liver, kidney, cardiovascular (CV) system, skin and gut. Gastrointestinal (GI) side effects are the most common and constitute a wide clinical spectrum ranging from dyspepsia, heartburn and abdominal discomfort to more serious events such as peptic ulcer with life-threatening complications of bleeding and perforation. The appreciation that CV risk is also increased further complicates the choices of physicians prescribing anti-inflammatory therapy. Despite prevention strategies should be implemented in patients at risk, gastroprotection is often underused and adherence to treatment is generally poor. A more appealing approach would be therefore to develop drugs that are devoid of or have reduced GI toxicity. Gastro-duodenal mucosa possesses many defensive mechanisms and NSAIDs have a deleterious effect on most of them. This results in a mucosa less able to cope with even a reduced acid load. NSAIDs cause gastro-duodenal damage, by two main mechanisms: a physiochemical disruption of the gastric mucosal barrier and systemic inhibition of gastric mucosal protection, through inhibition of cyclooxygenase (COX, PG endoperoxide G/H synthase) activity of the GI mucosa. However, against a background of COX inhibition by anti-inflammatory doses of NSAIDs, their physicochemical properties, in particular their acidity, underlie the topical effect leading to short-term damage. It has been shown that esterification of acidic NSAIDs suppresses their gastrotoxicity without adversely affecting anti-inflammatory activity. Another way to develop NSAIDs with better GI tolerability is to complex these molecules with cyclodextrins (CDs), giving rise to so-called “inclusion complexes” that can have physical, chemical and biological properties very different from either those of the drug or the cyclodextrin. Complexation of NSAIDs with β-cyclodextrin potentially leads

  14. The Modeling of Pulmonary Particulate Matter Transport Using Langmuir Monolayers

    NASA Astrophysics Data System (ADS)

    Eaton, Jeremy M.

    The effects of a barrier in proximity to the air-water interface on the dynamics of a Langmuir monolayer system are observed. A monolayer of Survanta, bovine lung surfactant, is deposited onto the interface of an aqueous buffer solution. Polystyrene particles one micron in diameter and tagged with fluorescent carboxylate groups are distributed evenly throughout the monolayer surface. The bead-monolayer system is compressed and expanded to induce folding. A polydimethylsiloxane (PDMS) substrate is placed below the monolayer in the buffer solution to study interactions between the folding monolayer and a barrier. The presence of the substrate is shown to shift surface pressure-area isotherms toward regions of lower area by an average of 8.9 mN/m. The surface of the PDMS substrate can be imaged using fluorescence microscopy to detect the presence of particles or surfactant that may have been transported there from the air-water interface during folding. Images show the transferral of particles and monolayer together suggesting the pinch-off of a fold or the direct interaction of a fold with the barrier.

  15. Adhesive and conformational behaviour of mycolic acid monolayers.

    PubMed

    Zhang, Zhenyu; Pen, Yu; Edyvean, Robert G; Banwart, Steven A; Dalgliesh, Robert M; Geoghegan, Mark

    2010-09-01

    We have studied the pH-dependent interaction between mycolic acid (MA) monolayers and hydrophobic and hydrophilic surfaces using molecular (colloidal probe) force spectroscopy. In both cases, hydrophobic and hydrophilic monolayers (prepared by Langmuir-Blodgett and Langmuir-Schaefer deposition on silicon or hydrophobized silicon substrates, respectively) were studied. The force spectroscopy data, fitted with classical DLVO (Derjaguin, Landau, Verwey, and Overbeek) theory to examine the contribution of electrostatic and van der Waals forces, revealed that electrostatic forces are the dominant contribution to the repulsive force between the approaching colloidal probe and MA monolayers. The good agreement between data and the DLVO model suggest that beyond a few nm away from the surface, hydrophobic, hydration, and specific chemical bonding are unlikely to contribute to any significant extent to the interaction energy between the probe and the surface. The pH-dependent conformation of MA molecules in the monolayer at the solid-liquid interface was studied by ellipsometry, neutron reflectometry, and with a quartz crystal microbalance. Monolayers prepared by the Langmuir-Blodgett method demonstrated a distinct pH-responsive behaviour, while monolayers prepared by the Langmuir-Schaefer method were less sensitive to pH variation. It was found that the attachment of water molecules plays a vital role in determining the conformation of the MA monolayers.

  16. Study on inclusion interaction of piroxicam with beta-cyclodextrin derivatives.

    PubMed

    Xiliang, Guo; Yu, Yang; Guoyan, Zhao; Guomei, Zhang; Jianbin, Chao; Shaomin, Shuang

    2003-12-01

    The inclusion behavior of piroxicam (PX) with beta-cyclodextrin (beta-CD), hydroxypropyl-beta-cyclodextrin (HP-beta-CD), and carboxymethyl-beta-cyclodextrin (CM-beta-CD) was investigated by using steady-state fluorescence and nuclear magnetic resonance (NMR) technique. The various factors affecting the inclusion process were examined in detail. The remarkable fluorescence emission enhancement upon addition of CDs suggested that cyclodextrins (CDs) were most suitable for inclusion of the uncharged species of PX. The stoichiometry of the PX-CDs inclusion complexes was 1:1, except for beta-CD where a 1:2 inclusion complex was formed. The formation constants showed the strongest inclusion capacity of beta-CD. NMR showed the inclusion mode of PX with CDs.

  17. Study on inclusion interaction of piroxicam with β-cyclodextrin derivatives

    NASA Astrophysics Data System (ADS)

    Xiliang, Guo; Yu, Yang; Guoyan, Zhao; Guomei, Zhang; Jianbin, Chao; Shaomin, Shuang

    2003-12-01

    The inclusion behavior of piroxicam (PX) with β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD), and carboxymethyl-β-cyclodextrin (CM-β-CD) was investigated by using steady-state fluorescence and nuclear magnetic resonance (NMR) technique. The various factors affecting the inclusion process were examined in detail. The remarkable fluorescence emission enhancement upon addition of CDs suggested that cyclodextrins (CDs) were most suitable for inclusion of the uncharged species of PX. The stoichiometry of the PX-CDs inclusion complexes was 1:1, except for β-CD where a 1:2 inclusion complex was formed. The formation constants showed the strongest inclusion capacity of β-CD. NMR showed the inclusion mode of PX with CDs.

  18. Probing inclusion complexes of cyclodextrins with amino acids by physicochemical approach.

    PubMed

    Roy, Mahendra Nath; Roy, Aditi; Saha, Subhadeep

    2016-10-20

    Formations of host-guest inclusion complexes of two natural amino acids, viz., l-Leucine and l-Isoleucine as guests with α and β-cyclodextrins have been investigated which include diverse applications in modern science such as controlled delivery in the field of pharmaceuticals, food processing etc. Surface tension and conductivity studies establish the formation of inclusion complexes with 1:1 stoichiometry. The interactions of cyclodextrins with amino acids have been supported by density, viscosity, refractive index, hydration and solvation number measurements indicating higher degree of inclusion in case of α-cyclodextrin. l-Leucine interacts more with the hydrophobic cavity of cyclodextrin than its isomer. With the help of stability constant by NMR titration, hydrophobic effect, H-bonds and structural effects the formations of inclusion complexes have been explained. PMID:27474589

  19. Interaction of polyphenol oxidase of Solanum tuberosum with β-cyclodextrin: Process details and applications.

    PubMed

    Singh, Virendra; Jadhav, Swati B; Singhal, Rekha S

    2015-09-01

    Polysaccharides differing in structure and chemical nature were screened for their ability to bind non-covalently with polyphenol oxidase (PPO) from potato (as a model) and their effect on enzyme activity. All the polysaccharides selected inhibited the PPO but β-cyclodextrin showed maximum inhibition under optimum conditions. Process details for the inhibition of PPO were studied with respect to concentration of β-cyclodextrin, temperature, pH, and time. Higher inhibition constant and lower half life was obtained at 40 °C than at 30 °C in the presence of inhibitor. β-Cyclodextrin showed mixed type of inhibition of PPO. β-Cyclodextrin was further exploited as anti-browning agent in selected fruit juices. It not only showed a significant anti-browning effect on freshly prepared potato juice but was also effective in other fruit juices. Better effect was seen in pineapple, apple and pear as compared to banana, sugarcane and guava fruit juices.

  20. The use of cyclodextrins as modifiers of fluorescence in the detection of mycotoxins

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cyclodextrins (CDs), cyclic oligosaccharides composed of amylose subunits, are known to interact with mycotoxins. The interactions may be useful to analytical chemists by altering the properties of the mycotoxin of interest, namely the chromatographic properties, electrophoretic properties, fluores...

  1. Natural & synthetically-modified cyclodextrins and polymers in drug delivery systems.

    PubMed

    Otero-Espinar, Francisco J; Blanco-Méndez, José

    2014-01-01

    Cyclodextrins are natural cyclic oligosaccharides that play a relevant role in different fields as pharmacy, medicine, chemistry, material, food or agricultural science. From the point of view of pharmaceutical and medical applications cyclodextrins have interest for their ability to form inclusion complexes with different host molecules as drugs. In the pharmaceutical industry, cyclodextrins has been used classically as solubilizes of hydrophobic drugs or as stabilizers of some labile molecules but can also offer interesting possibilities for drug control release of both hydrophobic and hydrophilic drugs. New and interesting perspectives for their use is being developed in recent years by the development of novel cyclodextrin derivatives including the polymeric one. The proposed topic for this special number of CTMC aims to provide new successes, challenges and recent advances on the design and applications of new CDs derivatives into the biomedical and pharmaceutical field .

  2. pH dependent in-out isomerism of an amino-beta-cyclodextrin derivative.

    PubMed

    Alcalde, Mercedes Alvarez; Gancedo, Cristina; Jover, Aida; Carrazana, Jorge; Soto, Victor H; Meijide, Francisco; Tato, José Vazquez

    2006-07-13

    An amino derivative of beta-cyclodextrin [6-(6-aminehexanamide)-6-deoxy)-beta-cyclodextrin (6-betaCD)] was synthesized, and the formation of an intramolecular inclusion complex was studied by NMR techniques. The deprotonation/protonation of the amino group stimulates an in/out movement of the pendant group toward/from the cyclodextrin cavity, the protonated species lying outside the hydrophobic cyclodextrin cavity but the unprotonated one residing inside and outside the cavity. The protonation of the amino group is a fast exchange rate NMR time-scale process, but the chain movement is a slow one. The equilibrium constants of both processes were determined from 1H NMR experiments and the kinetic constants for the slow process were determined from exchange spectroscopy (EXSY) experiments. PMID:16821861

  3. Cyclodextrin-based supramolecular systems for drug delivery: Recent progress and future perspective

    PubMed Central

    Zhang, Jianxiang; Ma, Peter X

    2013-01-01

    The excellent biocompatibility and unique inclusion capability as well as powerful functionalization capacity of cyclodextrins and their derivatives make them especially attractive for engineering novel functional materials for biomedical applications. There has been increasing interest recently to fabricate supramolecular systems for drug and gene delivery based on cyclodextrin materials. This review focuses on state of the art and recent advances in the construction of cyclodextrin-based assemblies and their applications for controlled drug delivery. First, we introduce cyclodextrin materials utilized for self-assembly. The fabrication technologies of supramolecular systems including nanoplatforms and hydrogels as well as their applications in nanomedicine and pharmaceutical sciences are then highlighted. At the end, the future directions of this field are discussed. PMID:23673149

  4. INTERACTIONS OF METHYL ORANGE WITH CYCLODEXTRIN/SODIUM-MONTMORILLONITE SYSTEMS PROBED BY UV-VISIBLE SPECTROSCOPY

    EPA Science Inventory

    Clay mineral colloids play important roles in the adsorption of polar organic contaminants in the environment. Similarly, cyclodextrins (CD) can entrap poorly water-soluble organic compounds. A combination of CDs and clay minerals affords great opportunities to investigate simult...

  5. Solubility Enhancement of Steviol Glycosides and Characterization of Their Inclusion Complexes with Gamma-Cyclodextrin

    PubMed Central

    Upreti, Mani; Strassburger, Ken; Chen, You L.; Wu, Shaoxiong; Prakash, Indra

    2011-01-01

    Steviol glycosidesrebaudioside (reb) A, C and D have low aqueous solubilities. To improve their aqueous solubilities, inclusion complex of steviol glycosides, reb A, C and D and gamma cyclodextrin were prepared by freeze drying method and further characterized by means of differential scanning calorimetry, Fourier transform infrared spectroscopy and Raman spectroscopy. The effect of gamma cyclodextrin on chemical shifts of the steviol glycosides was also studied in proton NMR experiments as well as in solid state 13C CP/MAS NMR experiments. These results indicated that the steviol glycosides were clearly in inclusion complex formation with the gamma cyclodextrin which also results in solubility enhancement of these steviol glycosides. Phase solubility studies showed that amounts of soluble reb A, C and D increased with increasing amounts of gamma cyclodextrin indicating formation of 1:1 stoichiometric and higher order inclusion complexes. PMID:22174615

  6. The molecular necklace: a rotaxane containing many threaded α-cyclodextrins

    NASA Astrophysics Data System (ADS)

    Harada, Akira; Li, Jun; Kamachi, Mikiharu

    1992-03-01

    THE importance of non-covalent interactions in biological systems motivates much of the current interest in supramolecular assemblies1. A classic example of a supermolecule is provided by the rotaxanes2-5, in which a molecular 'rotor' is threaded by a linear 'axle'. Previous examples have included cyclic crown ethers threaded by polymers6, paraquat-hydroquinone complexes7 and cyclodextrin complexes8,9. We found recently that α-cyclodextrin will form high yields of a crystalline complex with polyethylene glycol (PEG), and suggested that the PEG penetrates the 'beaker-like' tunnel of the cyclodextrin10,11. We report here the preparation of a compound in which several cyclodextrins are threaded on a single PEG chain and are trapped by capping the chain with bulky end groups. This brings a step closer the 'molecular abacus' proposed by Stoddart and coworkers7. We call this supramolecular assembly a 'molecular necklace'.

  7. Synthesis and Evaluation of Cyclodextrin-based Polymers for Patulin Extraction from Aqueous Solutions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Patulin is a mycotoxin produced by fungi that contaminate fruits, juices, and other agricultural commodities. Sorption properties of polyurethane-beta-cyclodextrin polymers were evaluated for the ability to remove patulin from solutions, including apple juice. Freundlich isotherm analysis determin...

  8. [UV-vis spectroscopic characterization of inclusion compounds of beta-cyclodextrin with lycopene].

    PubMed

    Wang, Luo-xin; Lü, Jun; Du, Zong-liang; Li, Rui-xia; Wu, Da-cheng

    2004-02-01

    Water-soluble inclusion compounds of beta-cyclodextrin with lycopene were prepared by two methods: (1) complexation in solution and (2) complexation by kneading. It was found that UV-Vis spectra of the inclusion complexes in water are different from those of lycopene in water-miscible organic solvents (tetrahydrofuran) and beta-cyclodextrin in water, which confirms the formation of the inclusion complexes. Specific interactions of lycopene and beta-cyclodextrin cause great changes in absorbance maximum (lambdamax) of lycopene. It is considered that the inclusion complexes in water are formed as supermolecular aggregates with nanometer size, after card-pack type lycopene is included by beta-cyclodextrin in molecular level. PMID:15769012

  9. Cyclodextrin multicomponent complexation and controlled release delivery strategies to optimize the oral bioavailability of vinpocetine.

    PubMed

    Ribeiro, Laura S S; Falcão, Amílcar C; Patrício, João A B; Ferreira, Domingos C; Veiga, Francisco J B

    2007-08-01

    In the present work, to maintain a suitable blood level of vinpocetine (VP) for a long period of time, VP-cyclodextrin-tartaric acid multicomponent complexes were prepared and formulated in hydroxypropylmethylcellulose matrix tablets. In vitro and in vivo performances of these formulations were investigated over a VP immediate release dosage form. Solubility studies were performed to evaluate the drug pH solubilization profile and to assess the effect of multicomponent complexation on VP solubility. The drug release process was investigated using United States Pharmacopeia apparatus 3 and a comparative oral pharmacokinetic study was subsequently undertaken in rabbits. Solubility studies denoted the pH-solubility dependence of VP and solubility improvement attained by complexation. Dissolution results showed controlled and almost complete release behavior of VP over a 12-h period from complex hydroxypropylmethylcellulose-based formulations. A clear difference between the pharmacokinetic patterns of VP immediate release and VP complex-based formulations was revealed. The area under the plasma concentration-time curve after oral administration of complex-based formulations was 2.1-2.9 times higher than that for VP immediate release formulation. Furthermore, significant differences found for mean residence time, elimination half-life, and elimination rate constant values corroborated prolonged release of VP from complex-based formulations. These results suggest that the oral bioavailability of VP was significantly improved by both multicomponent complexation and controlled release delivery strategies. PMID:17530626

  10. Supramolecular photochemistry in beta-cyclodextrin hosts: a TREPR, NMR, and CIDNP investigation.

    PubMed

    Krumkacheva, Olesya A; Gorelik, Vitaly R; Bagryanskaya, Elena G; Lebedeva, Natalia V; Forbes, Malcolm D E

    2010-06-01

    A systematic investigation of the photochemistry and ensuing radical chemistry of three guest ketones encapsulated in randomly methylated beta-cyclodextrin (beta-CD) hosts is reported. Dibenzyl ketone (DBK), deoxybenzoin (DOB), and benzophenone (BP) triplet states are rapidly formed after photolysis at 308 nm. Time-resolved electron paramagnetic resonance (TREPR) spectroscopy, steady-state NMR spectroscopy, and time-resolved chemically induced nuclear polarization (TR-CIDNP) experiments were performed on the ketone/CD complexes and on the ketones in free solution for comparison. The major reactivity pathways available from these excited states are either Norrish I alpha-cleavage or H-atom abstraction from the interior of the CD capsule or the solvent. The DOB triplet state undergoes both reactions, whereas the DBK triplet shows exclusively alpha-cleavage and the BP triplet shows exclusively H-atom abstraction. Radical pairs are observed in beta-CDs by TREPR, consisting of either DOB or BP ketyl radicals with sugar radicals from the CD interior. The TREPR spectra acquired in CDs are substantially broadened due to strong spin exchange. The electron spin polarization mechanism is mostly due to S-T(0) radical pair mechanism (RPM) in solution but changes to S-T(-) RPM in the CDs due to the large exchange interaction. The TR-CIDNP results confirm the reactivity patterns of all three ketones, and DOB shows strong nuclear spin polarization from a novel rearrangement product resulting from the alpha-cleavage reaction.

  11. Study of Gallium Oxide Nanoparticles Conjugated with β-Cyclodextrin: An Application To Combat Cancer.

    PubMed

    Ganguly, Bichitra Nandi; Verma, Vivek; Chatterjee, Debanuj; Satpati, Biswarup; Debnath, Sushanta; Saha, Partha

    2016-07-13

    Bioactive nanomaterials, namely, gallium oxyhydroxide GaO(OH), also surface-conjugated GaO(OH) with a giant sugar molecule β-cyclodextrin (CD), have been prepared through a simple wet chemical route such that the same could be suitably used in biomedical diagnostics as well as therapeutic applications. Several physical methods were used for their characterization: powder X-ray diffraction pattern of GaO(OH) NPs for their grain size determination, optical spectroscopic absorption (UV-vis and FT-IR), and fluorescence properties of these NPs to ascertain surface conjugation and also their wide band-gap properties. Besides these, morphological properties of these NPs were studied by transmission electron microscopic (TEM) investigation, justifying the elemental constitution through energy dispersive X-ray analysis (EDX). Further, biological cellular uptake of these nanoparticles have been demonstrated on cancerous HeLa cells and reported with total fetal effect after 72 h, with CD templated GaO(OH) nanoparticles, a fact that has not been reported so far.

  12. Electronic structure and normal vibrations in (+)-catechin and (-)-epicatechin encapsulated beta-cyclodextrin.

    PubMed

    Khedkar, Jayshree K; Gobre, Vivekanand V; Pinjari, Rahul V; Gejji, Shridhar P

    2010-07-29

    Host-guest interactions between beta-cyclodextrin (beta-CD) and flavan-3-Ol enantiomers (guest) namely, (+)-catechin (CA) or (-)-epicatechin (EC), have been analyzed within the framework of density functional theory. Both CA and EC consist of two phenol rings, I and II, and a pyran ring, III, which facilitate a variety of binding patterns with the host, beta-CD. The minimum energy beta-CD-CA complex reveals that ring II of CA interacts with primary hydroxyls of the upper rim and the phenol ring I engenders hydrogen-bonded interactions with secondary hydroxyl from the lower rim of CD. On the other hand, the O-H...O interactions between ring I and primary hydroxyls of beta-CD along with those between one of hydroxyl of ring II and secondary hydroxyl of the host render large stability to the beta-CD-EC complex. Structures of both beta-CD-CA and beta-CD-EC complexes thus obtained are in consonant with those inferred from the experimental NMR data and exhibit distinct features in infrared spectra. The frequency shifts of characteristic vibrations in infrared spectra of these complexes compared to the unbound individual host or guest in its free state have been analyzed with the use of natural bond orbital analyses and combining difference electron density maps with bond critical points in molecular electron density topography.

  13. Study of Gallium Oxide Nanoparticles Conjugated with β-Cyclodextrin: An Application To Combat Cancer.

    PubMed

    Ganguly, Bichitra Nandi; Verma, Vivek; Chatterjee, Debanuj; Satpati, Biswarup; Debnath, Sushanta; Saha, Partha

    2016-07-13

    Bioactive nanomaterials, namely, gallium oxyhydroxide GaO(OH), also surface-conjugated GaO(OH) with a giant sugar molecule β-cyclodextrin (CD), have been prepared through a simple wet chemical route such that the same could be suitably used in biomedical diagnostics as well as therapeutic applications. Several physical methods were used for their characterization: powder X-ray diffraction pattern of GaO(OH) NPs for their grain size determination, optical spectroscopic absorption (UV-vis and FT-IR), and fluorescence properties of these NPs to ascertain surface conjugation and also their wide band-gap properties. Besides these, morphological properties of these NPs were studied by transmission electron microscopic (TEM) investigation, justifying the elemental constitution through energy dispersive X-ray analysis (EDX). Further, biological cellular uptake of these nanoparticles have been demonstrated on cancerous HeLa cells and reported with total fetal effect after 72 h, with CD templated GaO(OH) nanoparticles, a fact that has not been reported so far. PMID:27331869

  14. Nanocavity absorption enhancement for two-dimensional material monolayer systems.

    PubMed

    Song, Haomin; Jiang, Suhua; Ji, Dengxin; Zeng, Xie; Zhang, Nan; Liu, Kai; Wang, Chu; Xu, Yun; Gan, Qiaoqiang

    2015-03-23

    Here we propose a strategy to enhance the light-matter interaction of two-dimensional (2D) material monolayers based on strong interference effect in planar nanocavities, and overcome the limitation between optical absorption and the atomically-thin thickness of 2D materials. By exploring the role of spacer layers with different thicknesses and refractive indices, we demonstrate that a nanocavity with an air spacer layer placed between a graphene monolayer and an aluminum reflector layer will enhance the exclusive absorption in the graphene monolayer effectively, which is particularly useful for the development of atomically-thin energy harvesting/conversion devices.

  15. Molecular beam epitaxy growth of monolayer niobium diselenide flakes

    NASA Astrophysics Data System (ADS)

    Hotta, Takato; Tokuda, Takuto; Zhao, Sihan; Watanabe, Kenji; Taniguchi, Takashi; Shinohara, Hisanori; Kitaura, Ryo

    2016-09-01

    Monolayer niobium diselenide (NbSe2) is prepared through molecular beam epitaxy with hexagonal boron nitride (hBN) as substrates. Atomic force microscopy and the Raman spectroscopy have shown that the monolayer NbSe2 grown on the hBN possesses triangular or truncated triangular shape whose lateral size amounts up to several hundreds of nanometers. We have found that the precisely controlled supply rate and ultraflat surface of hBN plays an important role in the growth of the monolayer NbSe2.

  16. Simulations of calcite crystallization on self-assembled monolayers.

    PubMed

    Freeman, Colin L; Harding, John H; Duffy, Dorothy M

    2008-09-01

    This paper presents simulations of calcium carbonate ordering in contact with self-assembled monolayers. The calculations use potential-based molecular dynamics to model the crystallization of calcium carbonate to calcite expressing both the (00.1) and (01.2) surfaces. The effect of monolayer properties: ionization; epitaxial matching; charge density; and headgroup orientation on the crystallization process are examined in detail. The results demonstrate that highly charged surfaces are vital to stimulate ordering and crystallization. Template directed crystallization requires charge epitaxy between both the crystal surface and the monolayer. The orientation of the headgroup appears to make no contribution to the selection of the crystal surface.

  17. Continuous production of cyclodextrins in an ultrafiltration membrane reactor, catalyzed by cyclodextrin glycosyltransferase from Bacillus circulans DF 9R.

    PubMed

    Rodríguez Gastón, Jorgelina A; Costa, Hernán; Ferrarotti, Susana A

    2015-01-01

    Cyclodextrins (CDs) are cyclic oligosaccharides of wide industrial application, whose synthesis is catalyzed by Cyclodextrin glycosyltransferase (CGTase) from starch. Here, CDs were produced using CGTase from Bacillus circulans DF 9R in continuous process and an ultrafiltration membrane reactor. The batch process was conducted as a control. This method allowed increasing the yield from 40 to 55.6% and the productivity from 26.1 to 99.5 mg of CD per unit of enzyme. The method also allowed obtaining a high-purity product. The flow rate remained at 50% of its initial value after 24 h of process, improving the results described in the literature for starch hydrolysis processes. CGTase remained active throughout the process, which could be explained by the protective effect of the substrate and reaction products on CGTase stability. In addition, batch processes were developed using starches from different sources. We concluded that any of the starches studied could be used as substrate for CD production with similar yields and product specificity.

  18. Development of curcumin-cyclodextrin/cellulose nanocrystals complexes: New anticancer drug delivery systems.

    PubMed

    Ndong Ntoutoume, Gautier M A; Granet, Robert; Mbakidi, Jean Pierre; Brégier, Frédérique; Léger, David Y; Fidanzi-Dugas, Chloë; Lequart, Vincent; Joly, Nicolas; Liagre, Bertrand; Chaleix, Vincent; Sol, Vincent

    2016-02-01

    The synthesis of curcumin-cyclodextrin/cellulose nanocrystals (CNCx) nano complexes was performed. CNCx were functionalized by ionic association with cationic β-cyclodextrin (CD) and CD/CNCx complexes were used to encapsulate curcumin. Preliminary in vitro results showed that the resulting curcumin-CD/CNCx complexes exerted antiproliferative effect on colorectal and prostatic cancer cell lines, with IC50s lower than that of curcumin alone.

  19. Development of curcumin-cyclodextrin/cellulose nanocrystals complexes: New anticancer drug delivery systems.

    PubMed

    Ndong Ntoutoume, Gautier M A; Granet, Robert; Mbakidi, Jean Pierre; Brégier, Frédérique; Léger, David Y; Fidanzi-Dugas, Chloë; Lequart, Vincent; Joly, Nicolas; Liagre, Bertrand; Chaleix, Vincent; Sol, Vincent

    2016-02-01

    The synthesis of curcumin-cyclodextrin/cellulose nanocrystals (CNCx) nano complexes was performed. CNCx were functionalized by ionic association with cationic β-cyclodextrin (CD) and CD/CNCx complexes were used to encapsulate curcumin. Preliminary in vitro results showed that the resulting curcumin-CD/CNCx complexes exerted antiproliferative effect on colorectal and prostatic cancer cell lines, with IC50s lower than that of curcumin alone. PMID:26739777

  20. Controlled fragrant molecule release from surface-tethered cyclodextrin host-guest inclusion complexes.

    PubMed

    Schofield, W C E; Badyal, J P S

    2011-06-01

    β-cyclodextrin barrels can be tethered to solid surfaces using the Williamson ether synthesis reaction via an intermediate pulsed plasma deposited poly(4-vinylbenzyl chloride) linker layer. The loading and release of perfume molecules through host-guest inclusion complex formation with surface tethered β-cyclodextrin has been followed by infrared spectroscopy and quartz crystal microbalance measurements. Fragrance release lasts for several months and can be easily recharged.

  1. Synthesis, cytotoxicity, and phase-solubility study of cyclodextrin click clusters.

    PubMed

    Le, Hoa Thi; Jeon, Hyun Mi; Lim, Choon Woo; Kim, Tae Woo

    2014-10-01

    To explore the possibility of cyclodextrin click clusters (CCCs) as a new cyclodextrin-based excipient, we prepared three different CCCs; heptakis{6-(4-hydroxymethyl-1H-[1,2,3]triazol-1-yl)-6-deoxy}-β-cyclodextrin (HT-β-CD), heptakis{6-(4-hydroxymethyl-1H-[1,2,3]triazol-1-yl)-6-deoxy}{2,3-di-O-methyl}-β-cyclodextrin (HT-β-CD(OMe)2 ), and heptakis{6-(4-sulfonylmethyl-1H-[1,2,3]triazol-1-yl)-6-deoxy}-β-cyclodextrin (ST-β-CD). The CCCs were prepared using copper(I)-catalyzed azide-alkyne cycloaddition from 6-azido-6-deoxy-β-CD and their water solubility, cytotoxicity, and drug-solubilizing effect were investigated. Water turbidity testing of the CCCs showed that the minimum water solubility of the CCCs is at least 20 times higher than that of β-CD. An MTT cell viability assay performed on HeLa cells demonstrated a low cytotoxicity of the CCCs compared with 2,6-dimethyl-β-cyclodextrin. HT-β-CD(OMe)2 and ST-β-CD did not demonstrate any cytotoxicity within the experimental concentration (∼5 mM) like 2-hydroxypropyl-β-CD. A phase-solubility study of prednisolone with the CCCs suggested that CCCs showed increased solubility of prednisolone in the presence of increasing concentrations of the CCCs. The comparison between the conventional CD derivatives and CCCs on solubility, cytotoxicity, and binding property implies that CCCs are alternative cyclodextrin derivatives useful for overcoming the restrictions of conventional cyclodextrin chemistry.

  2. Instabilities of Monolayered Epithelia: Shape and Structure of Villi and Crypts

    NASA Astrophysics Data System (ADS)

    Hannezo, E.; Prost, J.; Joanny, J.-F.

    2011-08-01

    We study theoretically the shapes of a dividing epithelial monolayer of cells lying on top of an elastic stroma. The negative tension created by cell division provokes a buckling instability at a finite wave vector leading to the formation of periodic arrays of villi and crypts. The instability is similar to the buckling of a metallic plate under compression. We use the results to rationalize the various structures of the intestinal lining observed in vivo. Taking into account the coupling between cell division and local curvature, we obtain different patterns of villi and crypts, which could explain the different morphologies of the small intestine and the colon.

  3. Ultrafast electron diffraction optimized for studying structural dynamics in thin films and monolayers

    PubMed Central

    Badali, D. S.; Gengler, R. Y. N.; Miller, R. J. D.

    2016-01-01

    A compact electron source specifically designed for time-resolved diffraction studies of free-standing thin films and monolayers is presented here. The sensitivity to thin samples is achieved by extending the established technique of ultrafast electron diffraction to the “medium” energy regime (1–10 kV). An extremely compact design, in combination with low bunch charges, allows for high quality diffraction in a lensless geometry. The measured and simulated characteristics of the experimental system reveal sub-picosecond temporal resolution, while demonstrating the ability to produce high quality diffraction patterns from atomically thin samples. PMID:27226978

  4. A sum-frequency generation spectroscopic study of the Gibbs analysis paradox: monolayer or sub-monolayer adsorption?

    PubMed

    Shahir, Afshin Asadzadeh; Nguyen, Khoi Tan; Nguyen, Anh V

    2016-04-01

    The Gibbs adsorption isotherm (GAI) has been considered as the foundation of surfactant adsorption studies for over a century; however, its application in determining the limiting surface excess has recently been intensively discussed, with contradictory experimental evidence either supporting or refuting the theory. The available arguments are based on monolayer adsorption models. In this paper, we experimentally and intellectually propose and validate the contribution of sub-monolayer adsorption to the GAI paradox. We utilize a powerful intrinsically surface-sensitive technique, vibrational sum-frequency generation spectroscopy (SFG), complementing with conventional tensiometric measurements to address these controversies both quantitatively and qualitatively. Our SFG results revealed that the precipitous decrease in surface tension directly corresponds to surface occupancy by adsorbates. In addition, the Gibbs analysis was successfully applied to the soluble monolayer of a surface-active alcohol to full saturation. However, the full saturation of the topmost monolayer does not necessarily mean that the surface adsorption was completed because the adsorption was observed to continuously occur in the sub-monolayer region soon after the topmost monolayer became saturated. Nonetheless, the Gibbs isotherm failed to account for the excess of alcohol adsorbed in this sub-monolayer region. This new concept of surface excess must therefore be treated thermodynamically.

  5. Solubility, spectroscopic properties and photostability of Rhein/cyclodextrin inclusion complex

    NASA Astrophysics Data System (ADS)

    Petralito, Stefania; Zanardi, Iacopo; Memoli, Adriana; Annesini, Maria Cristina; Travagli, Valter

    2009-12-01

    The host-guest interaction between Rhein (Rh) - an anthraquinonic drug characterized by low water solubility and recently considered for its potential antidiabetic and antitumoral activities other than for the well-established anti-inflammatory properties - with cyclodextrins (CDs) was investigated using phase-solubility diagrams. The typical A L phase-solubility profiles suggest the formation of the 1:1 inclusion complexes between Rh and the two CDs investigated, namely β-cyclodextrin and 2-hydroxypropyl-β-cyclodextrin and the resulting constant values of complex formation, Kc, were estimated. Due to the higher Kc value, complex of Rhein with 2-hydroxypropyl-β-cyclodextrin was chosen for further investigation. Characterization in solution of 2-hydroxypropyl-β-cyclodextrin/Rhein complex was achieved both by fluorescence and visible spectroscopic techniques. These results confirm the formation of inclusion complexes in solution and the 1:1 stoichiometry of the binary system. With respect to Rhein aqueous solution behavior, the inclusion complex appears to be able: (i) to enhance Rhein solubility; (ii) to control its neutral/anionic equilibrium; (iii) to affect both its electronic absorption and fluorescence spectra. Finally, the photostability of Rhein in the presence of cyclodextrins was evaluated.

  6. A Comprehensive Review on Cyclodextrin-Based Carriers for Delivery of Chemotherapeutic Cytotoxic Anticancer Drugs.

    PubMed

    Gidwani, Bina; Vyas, Amber

    2015-01-01

    Most of the cytotoxic chemotherapeutic agents have poor aqueous solubility. These molecules are associated with poor physicochemical and biopharmaceutical properties, which makes the formulation difficult. An important approach in this regard is the use of combination of cyclodextrin and nanotechnology in delivery system. This paper provides an overview of limitations associated with anticancer drugs, their complexation with cyclodextrins, loading/encapsulating the complexed drugs into carriers, and various approaches used for the delivery. The present review article aims to assess the utility of cyclodextrin-based carriers like liposomes, niosomes, nanoparticles, micelles, millirods, and siRNA for delivery of antineoplastic agents. These systems based on cyclodextrin complexation and nanotechnology will camouflage the undesirable properties of drug and lead to synergistic or additive effect. Cyclodextrin-based nanotechnology seems to provide better therapeutic effect and sustain long life of healthy and recovered cells. Still, considerable study on delivery system and administration routes of cyclodextrin-based carriers is necessary with respect to their pharmacokinetics and toxicology to substantiate their safety and efficiency. In future, it would be possible to resolve the conventional and current issues associated with the development and commercialization of antineoplastic agents. PMID:26582104

  7. Cyclodextrins in pharmaceutical formulations II: solubilization, binding constant, and complexation efficiency.

    PubMed

    Jambhekar, Sunil S; Breen, Philip

    2016-02-01

    Cyclodextrins are cyclic oligosaccharides that have been recognized as pharmaceutical adjuvants for the past 20 years. The molecular structure of these glucose derivatives, which approximates a truncated cone, bucket, or torus, generates a hydrophilic exterior surface and a nonpolar interior cavity. Cyclodextrins can interact with appropriately sized drug molecules to yield an inclusion complex. These noncovalent inclusion complexes offer a variety of advantages over noncomplexed forms of a drug. Cyclodextrins are carbohydrates that are primarily used to enhance the aqueous solubility, physical chemical stability, and bioavailability of drugs. Their other applications include preventing drug-drug interactions, converting liquid drugs into microcrystalline powders, minimizing gastrointestinal and ocular irritation, and reducing or eliminating unpleasant taste and smell. Here, we focus on the solubilization of drugs by complexation, and discuss the determination and significance of binding constants for cyclodextrin complexes, and the determination of complexation efficiency and factors that influence it. We also make some general observations on cyclodextrin complexation and the use of cyclodextrins in solid, as well as parenteral, dosage forms. PMID:26687191

  8. Diclofenac-β-cyclodextrin for colonic drug targeting: In vivo performance in rats.

    PubMed

    Vieira, Amélia C F; Serra, Arménio C; Veiga, Francisco J; Gonsalves, António M d'A Rocha; Basit, Abdul W; Murdan, Sudaxshina

    2016-03-16

    The aim of this in vivo study was to assess the ability of the prodrug conjugate diclofenac-β-cyclodextrin to release diclofenac in the colon following oral administration, using sulfapyridine (a metabolite of sulfasalazine) as a marker of colonic absorption. Two groups of rats were used; the test rats received a suspension containing the two prodrugs, diclofenac-β-cyclodextrin and sulfasalazine, while the control rats received a suspension containing the corresponding free drugs, sodium diclofenac and sulfapyridine. The rats were fasted overnight with free access to water before and throughout the first 12h of the study. Blood was collected from the tail vein at pre-determined time points and the plasma analyzed for the concentrations of diclofenac and sulfapyridine. Following the oral administration of the two prodrugs, a more extended absorption profile was observed and Cmax was achieved 10h post-dose, in contrast to rapid absorption of the free drugs (tmax of diclofenac being 1.3h, and that of sulfapyridine being 2.1h). In addition to a later tmax, conjugation of diclofenac to β-cyclodextrin also resulted in a reduced Cmax and a reduced AUC. The same tmax for diclofenac-β-cyclodextrin as for sulfasalazine confirms the colonic metabolism of diclofenac-β-cyclodextrin. This study shows the potential of this new cyclodextrin-based prodrug to target and release diclofenac specifically in the colon following oral administration. PMID:26784980

  9. Antipyrine-gamma cyclodextrin inclusion complex: Molecular modeling, preparation, characterization and cytotoxicity studies

    NASA Astrophysics Data System (ADS)

    Gannimani, Ramesh; Perumal, Amanda; Ramesh, Muthusamy; Pillay, Karen; Soliman, Mahmoud E.; Govender, Patrick

    2015-06-01

    Molecular docking, semi-empirical and molecular dynamics studies were conducted for α, β and γ-cyclodextrin-associated inclusion complexes of antipyrine. The results of molecular modeling were systematically analyzed to determine the stability of inclusion complexes. In preliminary computational screening, β and γ-cyclodextrin inclusion complexes of antipyrine were found to be more stable as compared to α-cyclodextrin based on docking score and binding free energies. Further, inclusion complex of antipyrine with γ-cyclodextrin was prepared by freeze drying method. Formation of the inclusion complex was investigated by solid state characterization techniques such as thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy. The changes observed in decomposition temperature, diffractogram, vibrational frequencies and morphological appearance confirmed the formation of inclusion complex. In addition, results from 1H NMR and 2D NOESY studies supported the inclusion phenomenon. The results obtained from computational studies were found to be in consistent with experimental data to ascertain the encapsulation of antipyrine into γ-cyclodextrin. The inclusion complex was found to be non-toxic toward MDCK-1 cell lines. Thus, this approach may be helpful in the formulation of drug molecules using cyclodextrins.

  10. Inclusion Complexes of Ionic Liquids and Cyclodextrins: Are They Formed in the Gas Phase?

    NASA Astrophysics Data System (ADS)

    Fernandes, Ana M.; Schröder, Bernd; Barata, Tânia; Freire, Mara G.; Coutinho, João A. P.

    2014-05-01

    The interaction of imidazolium-based ionic liquids with α- and β-cyclodextrins was investigated by electrospray ionization mass spectrometry with variable collision induced dissociation energy and quantum chemical gas-phase calculations. The center-of-mass energy at which 50 % of a precursor ion decomposes (Ecm,1/2) was determined for the isolated [cyclodextrin + cation]+ or [cyclodextrin + anion]- adduct ions of imidazolium-based ionic liquids with different alkyl chain lengths combined with a large set of anions, such as chloride, bromide, bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, trifluoromethanesulfonate, methanesulfonate, dicyanamide, and hydrogensulfate. Moreover, both symmetric and asymmetric imidazolium cationic cores were evaluated. The relative interaction energies in the adduct ions were interpreted in terms of the influence of cation/anion structures and their inherent properties, such as hydrophobicity and hydrogen bond accepting ability, in the complexation process with the cyclodextrins. The trends observed in the mass spectral data together with quantum-chemical calculations suggest that in the gas phase, cations and anions will preferentially interact with the lower or upper rim of the cyclodextrin, respectively, as opposed to what has been reported in condensed phase where the formation of an inclusion complex between ionic liquid and cyclodextrin is assumed.

  11. A Comprehensive Review on Cyclodextrin-Based Carriers for Delivery of Chemotherapeutic Cytotoxic Anticancer Drugs

    PubMed Central

    Gidwani, Bina; Vyas, Amber

    2015-01-01

    Most of the cytotoxic chemotherapeutic agents have poor aqueous solubility. These molecules are associated with poor physicochemical and biopharmaceutical properties, which makes the formulation difficult. An important approach in this regard is the use of combination of cyclodextrin and nanotechnology in delivery system. This paper provides an overview of limitations associated with anticancer drugs, their complexation with cyclodextrins, loading/encapsulating the complexed drugs into carriers, and various approaches used for the delivery. The present review article aims to assess the utility of cyclodextrin-based carriers like liposomes, niosomes, nanoparticles, micelles, millirods, and siRNA for delivery of antineoplastic agents. These systems based on cyclodextrin complexation and nanotechnology will camouflage the undesirable properties of drug and lead to synergistic or additive effect. Cyclodextrin-based nanotechnology seems to provide better therapeutic effect and sustain long life of healthy and recovered cells. Still, considerable study on delivery system and administration routes of cyclodextrin-based carriers is necessary with respect to their pharmacokinetics and toxicology to substantiate their safety and efficiency. In future, it would be possible to resolve the conventional and current issues associated with the development and commercialization of antineoplastic agents. PMID:26582104

  12. Determination of the kinetic rate constant of cyclodextrin supramolecular systems by high-performance affinity chromatography.

    PubMed

    Zhang, Jiwen; Li, Haiyan; Sun, Lixin; Wang, Caifen

    2015-01-01

    The kinetics of the association and dissociation are fundamental kinetic processes for the host-guest interactions (such as the drug-target and drug-excipient interactions) and the in vivo performance of supramolecules. With advantages of rapid speed, high precision and ease of automation, the high-performance affinity chromatography (HPAC) is one of the best techniques to measure the interaction kinetics of weak to moderate affinities, such as the typical host-guest interactions of drug and cyclodextrins by using a cyclodextrin-immobilized column. The measurement involves the equilibration of the cyclodextrin column, the upload and elution of the samples (non-retained substances and retained solutes) at different flow rates on the cyclodextrin and control column, and data analysis. It has been indicated that cyclodextrin-immobilized chromatography is a cost-efficient high-throughput tool for the measurement of (small molecule) drug-cyclodextrin interactions as well as the dissociation of other supramolecules with relatively weak, fast, and extensive interactions. PMID:25749964

  13. Spectroscopic studies of inclusion complexes of 1-naphthol-4-sulfonate with beta-cyclodextrin in aqueous solution.

    PubMed

    Al-Shihry, Shar S

    2005-09-01

    The photophysical properties of 1-naphthol-4-sulfonate (1N4S) in some solvents and in aqueous beta-cyclodextrin solution have been investigated. The effect of beta-cyclodextrin on the fluorescence quantum yield and on the proton transfer is examined. Fluorescence measurements show 1:1 inclusion of 1N4S in the beta-cyclodextrin cavity with an association constant of 108M(-1). NMR studies are used to study the inclusion phenomena and to provide information on the geometry of 1N4S inside the cavity of beta-cyclodextrin.

  14. Spectroscopic studies of inclusion complexes of 1-naphthol-4-sulfonate with β-cyclodextrin in aqueous solution

    NASA Astrophysics Data System (ADS)

    Al-Shihry, Shar S.

    2005-09-01

    The photophysical properties of 1-naphthol-4-sulfonate (1N4S) in some solvents and in aqueous β-cyclodextrin solution have been investigated. The effect of β-cyclodextrin on the fluorescence quantum yield and on the proton transfer is examined. Fluorescence measurements show 1:1 inclusion of 1N4S in the β-cyclodextrin cavity with an association constant of 108 M -1. NMR studies are used to study the inclusion phenomena and to provide information on the geometry of 1N4S inside the cavity of β-cyclodextrin.

  15. Rare 'head-to-tail' arrangement of guest molecules in the inclusion complexes of (+)- and (-)-menthol with β-cyclodextrin

    NASA Astrophysics Data System (ADS)

    Ceborska, Magdalena; Asztemborska, Monika; Lipkowski, Janusz

    2012-11-01

    The inclusion of (+)- and (-)-menthols in β-cyclodextrin has been studied by X-ray crystallography. The obtained [2:2] complexes show typical for β-cyclodextrin form of head-to-head dimer. In both (+)- and (-)-cases, the menthol molecule in one of cyclodextrins forming dimer exhibits disorder and occupies two major sites. Also both of the diastereoisomeric complexes show unusual 'head to tail' arrangement of guest molecules - two guest molecules are differently oriented inside β-cyclodextrin cavity. Stability constants for both complexes in solution were measured.

  16. Phase solubility, 1H NMR and molecular modelling studies of bupivacaine hydrochloride complexation with different cyclodextrin derivates

    NASA Astrophysics Data System (ADS)

    Jug, Mario; Mennini, Natascia; Melani, Fabrizio; Maestrelli, Francesca; Mura, Paola

    2010-11-01

    A novel method, which simultaneously exploits experimental (NMR) and theoretically calculated data obtained by a molecular modelling technique, was proposed, to obtain deeper insight into inclusion geometry and possible stereoselective binding of bupivacaine hydrochloride with selected cyclodextrin derivatives. Sulphobuthylether-β-cyclodextrin and water soluble polymeric β-cyclodextrin demonstrated to be the best complexing agents for the drug, resulting in formation of the most stable inclusion complexes with the highest increase in aqueous drug solubility. The drug-carrier binding modes with these cyclodextrins and phenomena which may be directly related to the higher stability and better aqueous solubility of complexes formed were discussed in details.

  17. Spectrofluorimetric determination of stoichiometry and association constants of the complexes of harmane and harmine with beta-cyclodextrin and chemically modified beta-cyclodextrins.

    PubMed

    Martín, L; León, A; Olives, A I; Del Castillo, B; Martín, M A

    2003-06-13

    The association characteristics of the inclusion complexes of the beta-carboline alkaloids harmane and harmine with beta-cyclodextrin (beta-CD) and chemically modified beta-cyclodextrins such as hydroxypropyl-beta-cyclodextrin (HPbeta-CD), 2,3-di-O-methyl-beta-cyclodextrin (DMbeta-CD) and 2,3,6-tri-O-methyl-beta-cyclodextrin (TMbeta-CD) are described. The association constants vary from 112 for harmine/DMbeta-CD to 418 for harmane/HPbeta-CD. The magnitude of the interactions between the host and the guest molecules depends on the chemical and geometrical characteristics of the guest molecules and therefore the association constants vary for the different cyclodextrin complexes. The steric hindrance is higher in the case of harmine due to the presence of methoxy group on the beta-carboline ring. The association obtained for the harmane complexes is stronger than the one observed for harmine complexes except in the case of harmine/TMbeta-CD. Important differences in the association constants were observed depending on the experimental variable used in the calculations (absolute value of fluorescence intensity or the ratio between the fluorescence intensities corresponding to the neutral and cationic forms). When fluorescence intensity values were considered, the association constants were higher than when the ratio of the emission intensity for the cationic and neutral species was used. These differences are a consequence of the co-existence of acid-base equilibria in the ground and in excited states together with the complexation equilibria. The existence of a proton transfer reaction in the excited states of harmane or harmine implies the need for the experimental dialysis procedure for separation of the complexes from free harmane or harmine. Such methodology allows quantitative results for stoichiometry determinations to be obtained, which show the existence of both 1:1 and 1:2 beta-carboline alkaloid:CD complexes with different solubility properties.

  18. Protecting the properties of monolayer MoS2 on silicon based substrates with an atomically thin buffer

    DOE PAGESBeta

    Man, Michael K. L.; Deckoff-Jones, Skylar; Winchester, Andrew; Shi, Guangsha; Gupta, Gautam; Mohite, Aditya D.; Kar, Swastik; Kioupakis, Emmanouil; Talapatra, Saikat; Dani, Keshav M.

    2016-02-12

    Semiconducting 2D materials, like transition metal dichalcogenides (TMDs), have gained much attention for their potential in opto-electronic devices, valleytronic schemes, and semi-conducting to metallic phase engineering. However, like graphene and other atomically thin materials, they lose key properties when placed on a substrate like silicon, including quenching of photoluminescence, distorted crystalline structure, and rough surface morphology. The ability to protect these properties of monolayer TMDs, such as molybdenum disulfide (MoS2), on standard Si-based substrates, will enable their use in opto-electronic devices and scientific investigations. Here we show that an atomically thin buffer layer of hexagonal-boron nitride (hBN) protects the rangemore » of key opto-electronic, structural, and morphological properties of monolayer MoS2 on Si-based substrates. The hBN buffer restores sharp diffraction patterns, improves monolayer flatness by nearly two-orders of magnitude, and causes over an order of magnitude enhancement in photoluminescence, compared to bare Si and SiO2 substrates. Lastly, our demonstration provides a way of integrating MoS2 and other 2D monolayers onto standard Si-substrates, thus furthering their technological applications and scientific investigations.« less

  19. Protecting the properties of monolayer MoS₂ on silicon based substrates with an atomically thin buffer.

    PubMed

    Man, Michael K L; Deckoff-Jones, Skylar; Winchester, Andrew; Shi, Guangsha; Gupta, Gautam; Mohite, Aditya D; Kar, Swastik; Kioupakis, Emmanouil; Talapatra, Saikat; Dani, Keshav M

    2016-02-12

    Semiconducting 2D materials, like transition metal dichalcogenides (TMDs), have gained much attention for their potential in opto-electronic devices, valleytronic schemes, and semi-conducting to metallic phase engineering. However, like graphene and other atomically thin materials, they lose key properties when placed on a substrate like silicon, including quenching of photoluminescence, distorted crystalline structure, and rough surface morphology. The ability to protect these properties of monolayer TMDs, such as molybdenum disulfide (MoS2), on standard Si-based substrates, will enable their use in opto-electronic devices and scientific investigations. Here we show that an atomically thin buffer layer of hexagonal-boron nitride (hBN) protects the range of key opto-electronic, structural, and morphological properties of monolayer MoS2 on Si-based substrates. The hBN buffer restores sharp diffraction patterns, improves monolayer flatness by nearly two-orders of magnitude, and causes over an order of magnitude enhancement in photoluminescence, compared to bare Si and SiO2 substrates. Our demonstration provides a way of integrating MoS2 and other 2D monolayers onto standard Si-substrates, thus furthering their technological applications and scientific investigations.

  20. Protecting the properties of monolayer MoS2 on silicon based substrates with an atomically thin buffer

    NASA Astrophysics Data System (ADS)

    Man, Michael K. L.; Deckoff-Jones, Skylar; Winchester, Andrew; Shi, Guangsha; Gupta, Gautam; Mohite, Aditya D.; Kar, Swastik; Kioupakis, Emmanouil; Talapatra, Saikat; Dani, Keshav M.

    2016-02-01

    Semiconducting 2D materials, like transition metal dichalcogenides (TMDs), have gained much attention for their potential in opto-electronic devices, valleytronic schemes, and semi-conducting to metallic phase engineering. However, like graphene and other atomically thin materials, they lose key properties when placed on a substrate like silicon, including quenching of photoluminescence, distorted crystalline structure, and rough surface morphology. The ability to protect these properties of monolayer TMDs, such as molybdenum disulfide (MoS2), on standard Si-based substrates, will enable their use in opto-electronic devices and scientific investigations. Here we show that an atomically thin buffer layer of hexagonal-boron nitride (hBN) protects the range of key opto-electronic, structural, and morphological properties of monolayer MoS2 on Si-based substrates. The hBN buffer restores sharp diffraction patterns, improves monolayer flatness by nearly two-orders of magnitude, and causes over an order of magnitude enhancement in photoluminescence, compared to bare Si and SiO2 substrates. Our demonstration provides a way of integrating MoS2 and other 2D monolayers onto standard Si-substrates, thus furthering their technological applications and scientific investigations.

  1. Tuning electronic properties of novel metal oxide nanocrystals using interface interactions: MoO3 monolayers on Au(111)

    SciTech Connect

    Quek, S; Biener, M M; Biener, J; Friend, C M; Kaxiras, E

    2004-04-20

    Metal oxide nanocrystals deposited on metal surfaces have novel electronic properties due to interface and nanoscale effects. Crystals and nanoscale ribbons of MoO{sub 3} are highly effective catalysts and field emitters. This renders MoO{sub 3} an interesting prototype. Whilst MoO{sub 3} exists as bilayers in the bulk crystal5, in this work, monolayer MoO{sub 3} nanocrystals were grown epitaxially on Au(111). Ab initio calculations reveal that Au stabilizes the MoO{sub 3} monolayer through electronic charge redistribution at the interface. The Mo-O bonds are able to rotate about one another, allowing the MoO{sub 3} monolayer to adjust to the Au lattice. As a result, the monolayer is semimetallic, unlike bulk MoO{sub 3} which is semiconducting. This remarkable flexibility of the oxide lattice suggests the possibility of tuning electronic properties of transition metal oxides via interface interactions. The overall surface pattern obtained is affected by an interplay between the Au(111) surface reconstruction and the edges of the deposited MoO{sub 3} islands.

  2. Protecting the properties of monolayer MoS2 on silicon based substrates with an atomically thin buffer

    PubMed Central

    Man, Michael K. L.; Deckoff-Jones, Skylar; Winchester, Andrew; Shi, Guangsha; Gupta, Gautam; Mohite, Aditya D.; Kar, Swastik; Kioupakis, Emmanouil; Talapatra, Saikat; Dani, Keshav M.

    2016-01-01

    Semiconducting 2D materials, like transition metal dichalcogenides (TMDs), have gained much attention for their potential in opto-electronic devices, valleytronic schemes, and semi-conducting to metallic phase engineering. However, like graphene and other atomically thin materials, they lose key properties when placed on a substrate like silicon, including quenching of photoluminescence, distorted crystalline structure, and rough surface morphology. The ability to protect these properties of monolayer TMDs, such as molybdenum disulfide (MoS2), on standard Si-based substrates, will enable their use in opto-electronic devices and scientific investigations. Here we show that an atomically thin buffer layer of hexagonal-boron nitride (hBN) protects the range of key opto-electronic, structural, and morphological properties of monolayer MoS2 on Si-based substrates. The hBN buffer restores sharp diffraction patterns, improves monolayer flatness by nearly two-orders of magnitude, and causes over an order of magnitude enhancement in photoluminescence, compared to bare Si and SiO2 substrates. Our demonstration provides a way of integrating MoS2 and other 2D monolayers onto standard Si-substrates, thus furthering their technological applications and scientific investigations. PMID:26869269

  3. Monolayers of hard rods on planar substrates. I. Equilibrium.

    PubMed

    Oettel, M; Klopotek, M; Dixit, M; Empting, E; Schilling, T; Hansen-Goos, H

    2016-08-21

    The equilibrium properties of hard rod monolayers are investigated in a lattice model (where position and orientation of a rod are restricted to discrete values) as well as in an off-lattice model featuring spherocylinders with continuous positional and orientational degrees of freedom. Both models are treated using density functional theory and Monte Carlo simulations. Upon increasing the density of rods in the monolayer, there is a continuous ordering of the rods along the monolayer normal ("standing up" transition). The continuous transition also persists in the case of an external potential which favors flat-lying rods in the monolayer. This behavior is found in both the lattice and the continuum models. For the lattice model, we find very good agreement between the results from the specific DFT used (lattice fundamental measure theory) and simulations. The properties of lattice fundamental measure theory are further illustrated by the phase diagrams of bulk hard rods in two and three dimensions. PMID:27544121

  4. Molecular motion in alkylsilane self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Stevens, Derrick; Scott, Mary; Guy, Laura; Bochinski, Jason; Clarke, Laura

    2008-03-01

    We have investigated intra-molecular rotation within polar-substituted alkylsilane self-assembled monolayers (SAMs) on fused silica, utilizing surface-sensitive dielectric spectroscopy. Both trichlorosilanes (which allow crosslinking within the SAM) and monochlorosilanes (attached only to the surface) are utilized to grow monolayer and submonolayer films. Dielectric loss spectra as a function of temperature have been obtained for SAMs with varying carbon chain length, surface coverage, and alkyl terminal group. As shown by ellipsometry, contact angle measurements, and AFM, monochlorosilanes form a more disordered monolayer than trichlorosilanes. This more disordered film may result in additional degrees of freedom within the monolayer, or in the language of phase transitions, a rotator phase. Issues such as uncontrolled vertical polymerization and film growth by island formation and their effect on rotational dynamics will be discussed.

  5. Extraordinary room-temperature photoluminescence in triangular WS2 monolayers.

    PubMed

    Gutiérrez, Humberto R; Perea-López, Nestor; Elías, Ana Laura; Berkdemir, Ayse; Wang, Bei; Lv, Ruitao; López-Urías, Florentino; Crespi, Vincent H; Terrones, Humberto; Terrones, Mauricio

    2013-08-14

    Individual monolayers of metal dichalcogenides are atomically thin two-dimensional crystals with attractive physical properties different from those of their bulk counterparts. Here we describe the direct synthesis of WS2 monolayers with triangular morphologies and strong room-temperature photoluminescence (PL). The Raman response as well as the luminescence as a function of the number of S-W-S layers is also reported. The PL weakens with increasing number of layers due to a transition from direct band gap in a monolayer to indirect gap in multilayers. The edges of WS2 monolayers exhibit PL signals with extraordinary intensity, around 25 times stronger than that at the platelet's center. The structure and chemical composition of the platelet edges appear to be critical for PL enhancement.

  6. Growth of rare-earth monolayers on synthetic fluorine mica

    NASA Astrophysics Data System (ADS)

    Tsui, F.; Han, P. D.; Flynn, C. P.

    1993-05-01

    We have grown single-crystal rare-earth films on cleaved faces of synthetic fluorine mica fluorophlogopite by molecular-beam-epitaxy techniques. This has made it possible to measure material properties such as magnetism in monolayer structures.

  7. Detection of Molecular Monolayers by Optical Second-Harmonic Generation

    SciTech Connect

    Chen, C. K.; Heinz, T. F.; Ricard, D.; Shen, Y. R.

    1980-12-22

    Second harmonic generation is shown to be sensitive enough to detect molecular monolayers adsorbed on a silver surface. Adsorption of AgCl and pyridine on silver during and after an electrolytic cycle can be easily observed,

  8. The Intrinsic Ferromagnetism in a MnO2 Monolayer.

    PubMed

    Kan, M; Zhou, J; Sun, Q; Kawazoe, Y; Jena, P

    2013-10-17

    The Mn atom, because of its special electronic configuration of 3d(5)4s(2), has been widely used as a dopant in various two-dimensional (2D) monolayers such as graphene, BN, silicene and transition metal dichalcogenides (TMDs). The distributions of doped Mn atoms in these systems are highly sensitive to the synthesis process and conditions, thus suffering from problems of low solubility and surface clustering. Here we show for the first time that the MnO2 monolayer, synthetized 10 years ago, where Mn ions are individually held at specific sites, exhibits intrinsic ferromagnetism with a Curie temperature of 140 K, comparable to the highest TC value achieved experimentally for Mn-doped GaAs. The well-defined atomic configuration and the intrinsic ferromagnetism of the MnO2 monolayer suggest that it is superior to other magnetic monolayer materials.

  9. Oxidized Monolayers of Epitaxial Silicene on Ag(111)

    NASA Astrophysics Data System (ADS)

    Johnson, Neil W.; Muir, David I.; Moewes, Alexander

    2016-03-01

    The properties of epitaxial silicene monolayers on Ag(111) at various levels of oxidation are determined through complementary density functional theory calculations and soft X-ray spectroscopy experiments. Our calculations indicate that moderate levels of oxidation do not cause a significant bandgap opening in the epitaxial silicene monolayer, suggesting that oxygen functionalization is not a viable mechanism for bandgap tuning while the silicene monolayer remains on its metallic substrate. In addition, moderate oxidation is calculated to strongly distort the hexagonal Si lattice, causing it to cluster in regions of highest oxygen adatom concentration but retain its 2D sheet structure. However, our experiments reveal that beam-induced oxidation is consistent with the formation of islands of bulk-like SiO2. Complete exposure of the monolayer to ambient conditions results in a fully oxidized sample that closely resembles bulk SiO2, of which a significant portion is completely detached from the substrate.

  10. Monolayered mesenchymal stem cells repair scarred myocardium after myocardial infarction.

    PubMed

    Miyahara, Yoshinori; Nagaya, Noritoshi; Kataoka, Masaharu; Yanagawa, Bobby; Tanaka, Koichi; Hao, Hiroyuki; Ishino, Kozo; Ishida, Hideyuki; Shimizu, Tatsuya; Kangawa, Kenji; Sano, Shunji; Okano, Teruo; Kitamura, Soichiro; Mori, Hidezo

    2006-04-01

    Mesenchymal stem cells are multipotent cells that can differentiate into cardiomyocytes and vascular endothelial cells. Here we show, using cell sheet technology, that monolayered mesenchymal stem cells have multipotent and self-propagating properties after transplantation into infarcted rat hearts. We cultured adipose tissue-derived mesenchymal stem cells characterized by flow cytometry using temperature-responsive culture dishes. Four weeks after coronary ligation, we transplanted the monolayered mesenchymal stem cells onto the scarred myocardium. After transplantation, the engrafted sheet gradually grew to form a thick stratum that included newly formed vessels, undifferentiated cells and few cardiomyocytes. The mesenchymal stem cell sheet also acted through paracrine pathways to trigger angiogenesis. Unlike a fibroblast cell sheet, the monolayered mesenchymal stem cells reversed wall thinning in the scar area and improved cardiac function in rats with myocardial infarction. Thus, transplantation of monolayered mesenchymal stem cells may be a new therapeutic strategy for cardiac tissue regeneration. PMID:16582917

  11. Synthesis and characterizations of heterojunction of monolayer semiconductors

    NASA Astrophysics Data System (ADS)

    Lee, Yi-Hsien; Zhang, Xin-Quan; Tseng, Yu-Wen; Huang, Kuan-Hua; Chen, Chun-An; Chen, Bo-Han

    Monolayers of van der Waals materials, including graphene, and MoS2, offered a burgeoning field in fundamental physics, and optoelectronics.[1-5] Recently, atomically thin heterostructures of monolayer TMDc with various geometrical and energy band alignments are expected to be the key materials for next generation flexible optoelectronics. The individual TMDc monolayers can be adjoined vertically or laterally to construct diverse heterostructures which are difficult to reach with the laborious pick up-and-transfer method of the exfoliated flakes. The ability to produce copious amounts of high quality layered heterostructures on diverse surfaces is highly desirable but it has remained a challenging issue. Here, we have achieved a direct synthesis of various heterostructures of monolayer TMDc. The synthesis was performed using CVD with aromatic molecules as seeding promoters. We will discuss possible growth behaviors, and we examine the symmetry and the interface of these heterostructures using optical analysis and scanning TEM.

  12. Oxidized Monolayers of Epitaxial Silicene on Ag(111)

    PubMed Central

    Johnson, Neil W.; Muir, David I.; Moewes, Alexander

    2016-01-01

    The properties of epitaxial silicene monolayers on Ag(111) at various levels of oxidation are determined through complementary density functional theory calculations and soft X-ray spectroscopy experiments. Our calculations indicate that moderate levels of oxidation do not cause a significant bandgap opening in the epitaxial silicene monolayer, suggesting that oxygen functionalization is not a viable mechanism for bandgap tuning while the silicene monolayer remains on its metallic substrate. In addition, moderate oxidation is calculated to strongly distort the hexagonal Si lattice, causing it to cluster in regions of highest oxygen adatom concentration but retain its 2D sheet structure. However, our experiments reveal that beam-induced oxidation is consistent with the formation of islands of bulk-like SiO2. Complete exposure of the monolayer to ambient conditions results in a fully oxidized sample that closely resembles bulk SiO2, of which a significant portion is completely detached from the substrate. PMID:26936144

  13. Oxidized Monolayers of Epitaxial Silicene on Ag(111).

    PubMed

    Johnson, Neil W; Muir, David I; Moewes, Alexander

    2016-03-03

    The properties of epitaxial silicene monolayers on Ag(111) at various levels of oxidation are determined through complementary density functional theory calculations and soft X-ray spectroscopy experiments. Our calculations indicate that moderate levels of oxidation do not cause a significant bandgap opening in the epitaxial silicene monolayer, suggesting that oxygen functionalization is not a viable mechanism for bandgap tuning while the silicene monolayer remains on its metallic substrate. In addition, moderate oxidation is calculated to strongly distort the hexagonal Si lattice, causing it to cluster in regions of highest oxygen adatom concentration but retain its 2D sheet structure. However, our experiments reveal that beam-induced oxidation is consistent with the formation of islands of bulk-like SiO2. Complete exposure of the monolayer to ambient conditions results in a fully oxidized sample that closely resembles bulk SiO2, of which a significant portion is completely detached from the substrate.

  14. Electrochemical Properties of Organosilane Self Assembled Monolayers on Aluminum 2024

    NASA Technical Reports Server (NTRS)

    Hintze, Paul E.; Calle, Luz Marina

    2004-01-01

    Self assembled monolayers are commonly used to modify surfaces. Within the last 15 years, self assembled monolayers have been investigated as a way to protect from corrosion[1,2] or biofouling.[3] In this study, self assembled monolayers of decitriethoxysilane (C10H21Si(OC2H5)3) and octadecyltriethoxysilane (C18H37Si(OC2H5)3) were formed on aluminum 2024-T3. The modified surfaces and bare Al 2024 were characterized by dynamic water contact angle measurements, x-ray photoelectron spectroscopy (XIPS) and infrared spectroscopy. Electrochemical impedance spectroscopy (EIS) in 0.5 M NaCl was used to characterize the monolayers and evaluate their corrosion protection properties. The advancing water contact angle and infrared measurements show that the mono layers form a surface where the hydrocarbon chains are packed and oriented away from the surface, consistent with what is found in similar systems. The contact angle hysteresis measured in these systems is relatively large, perhaps indicating that the hydrocarbon chains are not as well packed as monolayers formed on other substrates. The results of the EIS measurements were modeled using a Randle's circuit modified by changing the capacitor to a constant phase element. The constant phase element values were found to characterize the monolayer. The capacitance of the monolayer modified surface starts lower than the bare Al 2024, but approaches values similar to the bare Al 2024 within 24 hours as the monolayer is degraded. The n values found for bare Al 2024 quickly approach the value of a true capacitor and are greater than 0.9 within hours after the start of exposure. For the monolayer modified structure, n can stay lower than 0.9 for a longer period of time. In fact, n for the monolayer modified surfaces is different from the bare surface even after the capacitance values have converged. This indicates that the deviation from ideal capacitance is the most sensitive indicator of the presence of the monolayer.

  15. Nonequilibrium 2-Hydroxyoctadecanoic Acid Monolayers: Effect of Electrolytes

    SciTech Connect

    Lendrum, Conrad D.; Ingham, Bridget; Lin, Binhua; Meron, Mati; Toney, Michael F.; McGrath, Kathryn M.

    2012-02-06

    2-Hydroxyacids display complex monolayer phase behavior due to the additional hydrogen bonding afforded by the presence of the second hydroxy group. The placement of this group at the position {alpha} to the carboxylic acid functionality also introduces the possibility of chelation, a utility important in crystallization including biomineralization. Biomineralization, like many biological processes, is inherently a nonequilibrium process. The nonequilibrium monolayer phase behavior of 2-hydroxyoctadecanoic acid was investigated on each of pure water, calcium chloride, sodium bicarbonate and calcium carbonate crystallizing subphases as a precursor study to a model calcium carbonate biomineralizing system, each at a pH of {approx}6. The role of the bicarbonate co-ion in manipulating the monolayer structure was determined by comparison with monolayer phase behavior on a sodium chloride subphase. Monolayer phase behavior was probed using surface pressure/area isotherms, surface potential, Brewster angle microscopy, and synchrotron-based grazing incidence X-ray diffraction and X-ray reflectivity. Complex phase behavior was observed for all but the sodium chloride subphase with hydrogen bonding, electrostatic and steric effects defining the symmetry of the monolayer. On a pure water subphase hydrogen bonding dominates with three phases coexisting at low pressures. Introduction of calcium ions into the aqueous subphase ensures strong cation binding to the surfactant head groups through chelation. The monolayer becomes very unstable in the presence of bicarbonate ions within the subphase due to short-range hydrogen bonding interactions between the monolayer and bicarbonate ions facilitated by the sodium cation enhancing surfactant solubility. The combined effects of electrostatics and hydrogen bonding are observed on the calcium carbonate crystallizing subphase.

  16. Phase diagram, design of monolayer binary colloidal crystals, and their fabrication based on ethanol-assisted self-assembly at the air/water interface.

    PubMed

    Dai, Zhengfei; Li, Yue; Duan, Guotao; Jia, Lichao; Cai, Weiping

    2012-08-28

    Flexible structural design and accurate controlled fabrication with structural tunability according to need for binary or multicomponent colloidal crystals have been expected. However, it is still a challenge. In this work, the phase diagram of monolayer binary colloidal crystals (bCCs) is established on the assumption that both large and small polystyrene (PS) colloidal spheres can stay at the air/water interface, and the range diagram for the size ratio and number ratio of small to large colloidal spheres is presented. From this phase diagram, combining the range diagram, we can design and relatively accurately control fabrication of the bCCs with specific structures (or patterns) according to need, including single or mixed patterns with the given relative content. Further, a simple and facile approach is presented to fabricate large-area (more than 10 cm(2)) monolayer bCCs without any surfactants, using differently sized PS spheres, based on ethanol-assisted self-assembly at the air/water interface. bCCs with different patterns and stoichiometries are thus designed from the established phase diagram and then successfully fabricated based on the volume ratios (V(S/L)) of the small to large PS suspensions using the presented colloidal self-assembling method. Interestingly, these monolayer bCCs can be transferred to any desired substrates using water as the medium. This study allows us to design desired patterns of monolayer bCCs and to more accurately control their structures with the used V(S/L).

  17. Trion formation in monolayer transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Kezerashvili, Roman Ya.; Tsiklauri, Shalva M.

    We present three-body calculations for trions binding energy in monolayer transition metal dichalcogenides using the method of hyperspherical harmonics (HH). In numerical calculations for a proper treatment of Coulomb screening in two dimensions we assume that electrons and holes are interacted via Keldysh potential. The convergences of binding energy calculations for the ground state of the trion as a function of the grand angular momentum are studied. For the trion binding energy in MoS2 we obtain 19.2 mev. This value is remarkably close to the experimental one of 18 meV. A comparison with results of other calculations are presented. We also study solutions of a hyperradial equation in a minimal approximation for the ground angular momentum to examine two regimes: a long range and a short range cases when the inter particle distance is much greater and much less than the screening length. For these cases, we find analytical expressions for the energy and wave function for trion states

  18. Endohedral metallofullerenes in self-assembled monolayers.

    PubMed

    Gimenez-Lopez, Maria Del Carmen; Gardener, Jules A; Shaw, Adam Q; Iwasiewicz-Wabnig, Agnieszka; Porfyrakis, Kyriakos; Balmer, Claire; Dantelle, Geraldine; Hadjipanayi, Maria; Crossley, Alison; Champness, Neil R; Castell, Martin R; Briggs, G Andrew D; Khlobystov, Andrei N

    2010-01-01

    A method has been developed for the attachment of a dithiolane group to endohedral metallofullerenes via a 1,3-dipolar cycloaddition reaction. This sulfur-containing functional group serves as an anchor, enabling efficient immobilisation of endohedral fullerenes on Au(111) surfaces at room temperature, directly from the solution phase. The functionalised fullerenes form disordered monolayers that exhibit no long-range ordering, which is attributed to both the strong bonding of the dithiolane anchor to the surface and to the conformational flexibility of the functional group. Endohedral fullerenes Er(3)N@C(80) and Sc(3)N@C(80) have been used as models for functionalisation and subsequent surface deposition. Their chemical reactivity towards dithiolane functionalisation and their surface behaviour have been compared to that of C(60). The endohedral fullerenes appear to be significantly less reactive towards the functionalisation than C(60), however they bind in a similar manner to a gold surface as their dithiolane terminated C(60) counterparts. The optical activity of Er(3)N@C(80) molecules is preserved after attachment of the functional group. We report a splitting of the endohedral Er(3+) emission lines due to the reduction in symmetry of the functionalised fullerene cage, as compared to the highly symmetrical icosahedral C(80) cage of pristine Er(3)N@C(80).

  19. Surface dilatational viscosity of Langmuir monolayers

    NASA Astrophysics Data System (ADS)

    Lopez, Juan; Vogel, Michael; Hirsa, Amir

    2003-11-01

    With increased interest in microfluidic systems, interfacial phenomena is receiving more attention. As the length scales of fluid problems decrease, the surface to volume ratio increases and the coupling between interfacial flow and bulk flow becomes increasingly dominated by effects due to intrinsic surface viscosities (shear and dilatational), in comparison to elastic effects (due to surface tension gradients). The surface shear viscosity is well-characterized, as cm-scale laboratory experiments are able to isolate its effects from other interfacial processes (e.g., in the deep-channel viscometer). The same is not true for the dilatational viscosity, because it acts in the direction of surface tension gradients. Their relative strength scale with the capillary number, and for cm-scale laboratory flows, surface tension effects tend to dominate. In microfluidic scale flows, the scaling favors viscosity. We have devised an experimental apparatus which is capable of isolating and enhancing the effects of dilatational viscosity at the cm scales by driving the interface harmonically in time, while keeping the interface flat. In this talk, we shall present both the theory for how this works as well as experimental measurements of surface velocity from which we deduce the dilatational viscosity of several monolayers on the air-water interface over a substantial range of surface concentrations. Anomalous behavior over some range of concentration, which superficially indicates negative viscosity, maybe explained in terms of compositional effects due to large spatial and temporal variations in concentration and corresponding viscosity.

  20. Technique for etching monolayer and multilayer materials

    DOEpatents

    Bouet, Nathalie C. D.; Conley, Raymond P.; Divan, Ralu; Macrander, Albert

    2015-10-06

    A process is disclosed for sectioning by etching of monolayers and multilayers using an RIE technique with fluorine-based chemistry. In one embodiment, the process uses Reactive Ion Etching (RIE) alone or in combination with Inductively Coupled Plasma (ICP) using fluorine-based chemistry alone and using sufficient power to provide high ion energy to increase the etching rate and to obtain deeper anisotropic etching. In a second embodiment, a process is provided for sectioning of WSi.sub.2/Si multilayers using RIE in combination with ICP using a combination of fluorine-based and chlorine-based chemistries and using RF power and ICP power. According to the second embodiment, a high level of vertical anisotropy is achieved by a ratio of three gases; namely, CHF.sub.3, Cl.sub.2, and O.sub.2 with RF and ICP. Additionally, in conjunction with the second embodiment, a passivation layer can be formed on the surface of the multilayer which aids in anisotropic profile generation.

  1. Magnetoluminescence study of WS2 monolayers

    NASA Astrophysics Data System (ADS)

    Scrace, T.; Tsai, Y.; Barman, B.; Schweidenback, L.; Petrou, A.; Kioseoglou, G.; Hawrylak, P.

    2014-03-01

    We have studied the photoluminescence (PL) spectra[2] from WS2 monolayers in the 5-150 K temperature range in magnetic fields up to 7 tesla applied along the normal to the sample plane. The luminescence was excited by a 488nm linearly polarized laser beam. The PL spectra have two features identified as the neutral (X) and negatively charged (X-) exciton. At zero magnetic field the X- feature has a large (as high as 30%), laser power-dependent circular polarization, in contrast to the small polarization of Xthat does not depend on laser power. The application of an external magnetic field has a profound effect on the circular polarization of the charged exciton. Its polarization increases by 10% at 7 tesla for any laser-power while its energy exhibits a small magnetic splitting (2meV at 7 tesla). On the other hand, the emitted circular polarization of the free exciton is not affected by the external magnetic field. This work has been supported by ONR.

  2. Defect-Tolerant Monolayer Transition Metal Dichalcogenides

    NASA Astrophysics Data System (ADS)

    Pandey, Mohnish; Rasmussen, Filip A.; Kuhar, Korina; Olsen, Thomas; Jacobsen, Karsten W.; Thygesen, Kristian S.

    2016-04-01

    Localized electronic states formed inside the band gap of a semiconductor due to crystal defects can be detrimental to the material's optoelectronic properties. Semiconductors with lower tendency to form defect induced deep gap states are termed defect tolerant. Here we provide a systematic first principles investigation of defect tolerance in 29 monolayer transition metal dichalcogenides (TMDs) of interest for nanoscale optoelectronics. We find that the TMDs based on group VI and X metals form deep gap states upon creation of a chalcogen (S, Se, Te) vacancy while the TMDs based on group IV metals form only shallow defect levels and are thus predicted to be defect tolerant. Interestingly, all the defect sensitive TMDs have valence and conduction bands with very similar orbital composition. This indicates a bonding/anti-bonding nature of the gap which in turn suggests that dangling bonds will fall inside the gap. These ideas are made quantitative by introducing a descriptor that measures the degree of similarity of the conduction and valence band manifolds. Finally, the study is generalized to non-polar nanoribbons of the TMDs where we find that only the defect sensitive materials form edge states within the band gap.

  3. Structural phase transitions in monolayer molybdenum dichalcogenides

    NASA Astrophysics Data System (ADS)

    Choe, Duk-Hyun; Sung, Ha June; Chang, Kee Joo

    2015-03-01

    The recent discovery of two-dimensional materials such as graphene and transition metal dichalcogenides (TMDs) has provided opportunities to develop ultimate thin channel devices. In contrast to graphene, the existence of moderate band gap and strong spin-orbit coupling gives rise to exotic electronic properties which vary with layer thickness, lattice structure, and symmetry. TMDs commonly appear in two structures with distinct symmetries, trigonal prismatic 2H and octahedral 1T phases which are semiconducting and metallic, respectively. In this work, we investigate the structural and electronic properties of monolayer molybdenum dichalcogenides (MoX2, where X = S, Se, Te) through first-principles density functional calculations. We find a tendency that the semiconducting 2H phase is more stable than the metallic 1T phase. We show that a spontaneous symmetry breaking of 1T phase leads to various distorted octahedral (1T') phases, thus inducing a metal-to-semiconductor transition. We discuss the effects of carrier doping on the structural stability and the modification of the electronic structure. This work was supported by the National Research Foundation of Korea (NRF) under Grant No. NRF-2005-0093845 and Samsung Science and Technology Foundation under Grant No. SSTFBA1401-08.

  4. Surface Charge Transfer Doping of Monolayer Phosphorene via Molecular Adsorption.

    PubMed

    He, Yuanyuan; Xia, Feifei; Shao, Zhibin; Zhao, Jianwei; Jie, Jiansheng

    2015-12-01

    Monolayer phosphorene has attracted much attention owing to its extraordinary electronic, optical, and structural properties. Rationally tuning the electrical transport characteristics of monolayer phosphorene is essential to its applications in electronic and optoelectronic devices. Herein, we study the electronic transport behaviors of monolayer phosphorene with surface charge transfer doping of electrophilic molecules, including 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), NO2, and MoO3, using density functional theory combined with the nonequilibrium Green's function formalism. F4TCNQ shows optimal performance in enhancing the p-type conductance of monolayer phosphorene. Static electronic properties indicate that the enhancement is originated from the charge transfer between adsorbed molecule and phosphorene layer. Dynamic transport behaviors demonstrate that additional channels for hole transport in host monolayer phosphorene were generated upon the adsorption of molecule. Our work unveils the great potential of surface charge transfer doping in tuning the electronic properties of monolayer phosphorene and is of significance to its application in high-performance devices.

  5. C₆₀ fullerene promotes lung monolayer collapse.

    PubMed

    Barnoud, Jonathan; Urbini, Laura; Monticelli, Luca

    2015-03-01

    Airborne nanometre-sized pollutants are responsible for various respiratory diseases. Such pollutants can reach the gas-exchange surface in the alveoli, which is lined with a monolayer of lung surfactant. The relationship between physiological effects of pollutants and molecular-level interactions is largely unknown. Here, we determine the effects of carbon nanoparticles on the properties of a model of lung monolayer using molecular simulations. We simulate phase-separated lipid monolayers in the presence of a model pollutant nanoparticle, C₆₀ fullerene. In the absence of nanoparticles, the monolayers collapse only at very low surface tensions (around 0 mN m(-1)). In the presence of nanoparticles, instead, monolayer collapse is observed at significantly higher surface tensions (up to ca 10 mN m(-1)). Collapse at higher tensions is related to lower mechanical rigidity of the monolayer. It is possible that similar mechanisms operate on lung surfactant in vivo, which suggests that health effects of airborne carbon nanoparticles may be mediated by alterations of the mechanical properties of lung surfactant.

  6. Manipulation of electronic structure in WSe2 monolayer by strain

    NASA Astrophysics Data System (ADS)

    Yang, Cong-xia; Zhao, Xu; Wei, Shu-yi

    2016-11-01

    In this paper, we study the electronic properties of WSe2 monolayer with biaxial tensile strain and compressive strain by using first principles based on the density function theory. Under the biaxial tensile strain, WSe2 monolayer retains direct band gap with increasing strain and the band gap of WSe2 continuously decreases with increasing strain, eventually turn to metal when strain is equal to or more than 13%. Under the biaxial compressive strain, WSe2 monolayer turns to indirect gap and the band gap continuously decreases with increasing strain, finally turn to metal when strain is up to -7%. The strain can reduce the band gap of the WSe2 monolayer regardless of the strain direction. By comparison, we can see that the tensile strain appears to be more effective in reducing the band gap of pristine WSe2 monolayer than the compressive strain from -5% to 5%. But the band gap turns to zero quickly from -6% to -7% under compressive strain, however for tensile strain from 5% to 13%, the band gap decreases slowly. Based on the further analysis of the projected charge density for WSe2 monolayer, the fundamental reason of the change of band structure under biaxial tensile strain is revealed.

  7. Treponema pallidum Invades Intercellular Junctions of Endothelial Cell Monolayers

    NASA Astrophysics Data System (ADS)

    Thomas, D. Denee; Navab, Mahamad; Haake, David A.; Fogelman, Alan M.; Miller, James N.; Lovett, Michael A.

    1988-05-01

    The pathogenesis of syphilis reflects invasive properties of Treponema pallidum, but the actual mode of tissue invasion is unknown. We have found two in vitro parallels of treponemal invasiveness. We tested whether motile T. pallidum could invade host cells by determining the fate of radiolabeled motile organisms added to a HeLa cell monolayer; 26% of treponemes associated with the monolayer in a trypsin-resistant niche, presumably between the monolayer and the surface to which it adhered, but did not attain intracellularity. Attachment of T. pallidum to cultured human and rabbit aortic and human umbilical vein endothelial cells was 2-fold greater than to HeLa cells. We added T. pallidum to aortic endothelial cells grown on membrane filters under conditions in which tight intercellular junctions had formed. T. pallidum was able to pass through the endothelial cell monolayers without altering tight junctions, as measured by electrical resistance. In contrast, heat-killed T. pallidum and the nonpathogen Treponema phagedenis biotype Reiter failed to penetrate the monolayer. Transmission electron micrographs of sections of the monolayer showed T. pallidum in intercellular junctions. Our in vitro observations suggest that these highly motile spirochetes may leave the circulation by invading the junctions between endothelial cells.

  8. High Quality Factor Mechanical Resonators Based on WSe2 Monolayers.

    PubMed

    Morell, Nicolas; Reserbat-Plantey, Antoine; Tsioutsios, Ioannis; Schädler, Kevin G; Dubin, François; Koppens, Frank H L; Bachtold, Adrian

    2016-08-10

    Suspended monolayer transition metal dichalcogenides (TMD) are membranes that combine ultralow mass and exceptional optical properties, making them intriguing materials for opto-mechanical applications. However, the low measured quality factor of TMD resonators has been a roadblock so far. Here, we report an ultrasensitive optical readout of monolayer TMD resonators that allows us to reveal their mechanical properties at cryogenic temperatures. We find that the quality factor of monolayer WSe2 resonators greatly increases below room temperature, reaching values as high as 1.6 × 10(4) at liquid nitrogen temperature and 4.7 × 10(4) at liquid helium temperature. This surpasses the quality factor of monolayer graphene resonators with similar surface areas. Upon cooling the resonator, the resonant frequency increases significantly due to the thermal contraction of the WSe2 lattice. These measurements allow us to experimentally study the thermal expansion coefficient of WSe2 monolayers for the first time. High Q-factors are also found in resonators based on MoS2 and MoSe2 monolayers. The high quality-factor found in this work opens new possibilities for coupling mechanical vibrational states to two-dimensional excitons, valley pseudospins, and single quantum emitters and for quantum opto-mechanical experiments based on the Casimir interaction. PMID:27459399

  9. High Quality Factor Mechanical Resonators Based on WSe2 Monolayers

    PubMed Central

    2016-01-01

    Suspended monolayer transition metal dichalcogenides (TMD) are membranes that combine ultralow mass and exceptional optical properties, making them intriguing materials for opto-mechanical applications. However, the low measured quality factor of TMD resonators has been a roadblock so far. Here, we report an ultrasensitive optical readout of monolayer TMD resonators that allows us to reveal their mechanical properties at cryogenic temperatures. We find that the quality factor of monolayer WSe2 resonators greatly increases below room temperature, reaching values as high as 1.6 × 104 at liquid nitrogen temperature and 4.7 × 104 at liquid helium temperature. This surpasses the quality factor of monolayer graphene resonators with similar surface areas. Upon cooling the resonator, the resonant frequency increases significantly due to the thermal contraction of the WSe2 lattice. These measurements allow us to experimentally study the thermal expansion coefficient of WSe2 monolayers for the first time. High Q-factors are also found in resonators based on MoS2 and MoSe2 monolayers. The high quality-factor found in this work opens new possibilities for coupling mechanical vibrational states to two-dimensional excitons, valley pseudospins, and single quantum emitters and for quantum opto-mechanical experiments based on the Casimir interaction. PMID:27459399

  10. Enabling technologies and green processes in cyclodextrin chemistry.

    PubMed

    Cravotto, Giancarlo; Caporaso, Marina; Jicsinszky, Laszlo; Martina, Katia

    2016-01-01

    The design of efficient synthetic green strategies for the selective modification of cyclodextrins (CDs) is still a challenging task. Outstanding results have been achieved in recent years by means of so-called enabling technologies, such as microwaves, ultrasound and ball mills, that have become irreplaceable tools in the synthesis of CD derivatives. Several examples of sonochemical selective modification of native α-, β- and γ-CDs have been reported including heterogeneous phase Pd- and Cu-catalysed hydrogenations and couplings. Microwave irradiation has emerged as the technique of choice for the production of highly substituted CD derivatives, CD grafted materials and polymers. Mechanochemical methods have successfully furnished greener, solvent-free syntheses and efficient complexation, while flow microreactors may well improve the repeatability and optimization of critical synthetic protocols. PMID:26977187

  11. Effect of cyclodextrin complexation on phenylpropanoids’ solubility and antioxidant activity

    PubMed Central

    Kfoury, Miriana; Landy, David; Auezova, Lizette; Greige-Gerges, Hélène

    2014-01-01

    Summary The complexation abilities of five cyclodextrins (CDs) with seven phenylpropanoids (PPs) were evaluated by UV–visible spectroscopy, phase solubility studies and molecular modeling. Formation constants (K f), complexation efficiency (CE), PP:CD molar ratio, increase in formulation bulk and complexation energy were assessed. All complexes exhibited a 1:1 stoichiometry but their stability was influenced by the nature and the position of the phenyl ring substituents. A relationship between the intrinsic solubility of guests (S 0) and the solubilizing potential of CD was proposed. Molecular modeling was used to investigate the complementarities between host and guest. Finally, the antioxidant activity of encapsulated PPs was evaluated by scavenging of the stable DPPH radical. PMID:25298799

  12. Encapsulation of biocides by cyclodextrins: toward synergistic effects against pathogens

    PubMed Central

    Nardello-Rataj, Véronique

    2014-01-01

    Summary Host–guest chemistry is useful for the construction of nanosized objects. Some of the widely used hosts are probably the cyclodextrins (CDs). CDs can form water-soluble complexes with numerous hydrophobic compounds. They have been widespread used in medicine, drug delivery and are of interest for the biocides encapsulation. Indeed, this enables the development of more or less complex systems that release antimicrobial agents with time. In this paper, the general features of CDs and their applications in the field of biocides have been reviewed. As the key point is the formation of biocide–CD inclusion complexes, this review deals with this in depth and the advantages of biocide encapsulation are highlighted throughout several examples from the literature. Finally, some future directions of investigation have been proposed. We hope that scientists studying biocide applications receive inspiration from this review to exploit the opportunities offered by CDs in their respective research areas. PMID:25550722

  13. Enabling technologies and green processes in cyclodextrin chemistry

    PubMed Central

    Caporaso, Marina; Jicsinszky, Laszlo; Martina, Katia

    2016-01-01

    Summary The design of efficient synthetic green strategies for the selective modification of cyclodextrins (CDs) is still a challenging task. Outstanding results have been achieved in recent years by means of so-called enabling technologies, such as microwaves, ultrasound and ball mills, that have become irreplaceable tools in the synthesis of CD derivatives. Several examples of sonochemical selective modification of native α-, β- and γ-CDs have been reported including heterogeneous phase Pd- and Cu-catalysed hydrogenations and couplings. Microwave irradiation has emerged as the technique of choice for the production of highly substituted CD derivatives, CD grafted materials and polymers. Mechanochemical methods have successfully furnished greener, solvent-free syntheses and efficient complexation, while flow microreactors may well improve the repeatability and optimization of critical synthetic protocols. PMID:26977187

  14. Easy access to modified cyclodextrins by an intramolecular radical approach.

    PubMed

    Alvarez-Dorta, Dimitri; León, Elisa I; Kennedy, Alan R; Martín, Angeles; Pérez-Martín, Inés; Suárez, Ernesto

    2015-03-16

    A simple method to modify the primary face of cyclodextrins (CDs) is described. The 6(I)-O-yl radical of α-, β-, and γ-CDs regioselectively abstracts the H5(II), located in the adjacent D-glucose unit, by an intramolecular 1,8-hydrogen-atom-transfer reaction through a geometrically restricted nine-membered transition state to give a stable 1,3,5-trioxocane ring. The reaction has been extended to the 1,4-diols of α- and β-CD to give the corresponding bis(trioxocane)s. The C2-symmetric bis(trioxocane) corresponding to the α-CD is a stable crystalline solid whose structure was confirmed by X-ray diffraction analysis. The calculated geometric parameters confirm that the primary face is severely distorted toward a narrower elliptical shape for this rim.

  15. Cyclodextrins in capillary electrophoresis: recent developments and new trends.

    PubMed

    Escuder-Gilabert, L; Martín-Biosca, Y; Medina-Hernández, M J; Sagrado, S

    2014-08-29

    Despite the fact that extensive research in the field of separations by capillary electrophoresis (CE) has been carried out and many reviews have been published in the last years, a specific review on the use and future potential of cyclodextrins (CDs) in CE is not available. This review focuses the attention in the CD-CE topic over the January 2013-February 2014 period (not covered by previous more general CE-reviews). Recent contributions (reviews and research articles) including practical uses (e.g. solute-CD binding constant estimation and further potentials; 19% of publications), developments and applications (mainly chiral and achiral analysis; 38 and 24% of publications, respectively) are summarized in nine comprehensive tables and are commented. Statistics and predictions related to the CD-CE publications are highlighted in order to infer the current and expected research interests. Finally, trends and initiatives on CD-CE attending to real needs or practical criteria are outlined.

  16. Efficient regioselective O3-monodesilylation by hydrochloric acid in cyclodextrins.

    PubMed

    Gu, Jiamin; Chen, Tong; Wang, Qifang; Chen, Tieyu; Ling, Chang-Chun

    2015-06-17

    An efficient O3-monodesilylation method has been developed for the derivatization of per-3-O-silylated cyclodextrin (CD) derivatives. Using hydrochloric acid as a reagent, the O3-monodesilylation was found to be regioselective, mild, practical and general as it can be applied to all α-, β- and γ-CDs. The advantage of the methodology is that the acid-catalyzed O3-desilylation can be carried out in a stepwise manner so that different types of functional groups can be introduced to a CD molecule at different stage of the O3-desilylations. This makes the current methodology flexible and versatile. This current methodology constitutes one of the few methodologies available for the regioselective modification of CDs at the secondary face.

  17. Solubility, photostability and antifungal activity of phenylpropanoids encapsulated in cyclodextrins.

    PubMed

    Kfoury, Miriana; Lounès-Hadj Sahraoui, Anissa; Bourdon, Natacha; Laruelle, Frédéric; Fontaine, Joël; Auezova, Lizette; Greige-Gerges, Hélène; Fourmentin, Sophie

    2016-04-01

    Effects of the encapsulation in cyclodextrins (CDs) on the solubility, photostability and antifungal activities of some phenylpropanoids (PPs) were investigated. Solubility experiments were carried out to evaluate the effect of CDs on PPs aqueous solubility. Loading capacities and encapsulation efficiencies of freeze-dried inclusion complexes were determined. Moreover, photostability assays for both inclusion complexes in solution and solid state were performed. Finally, two of the most widespread phytopathogenic fungi, Fusarium oxysporum and Botrytis cinerea, were chosen to examine the antifungal activity of free and encapsulated PPs. Results showed that encapsulation in CDs significantly increased the solubility and photostability of studied PPs (by 2 to 17-fold and 2 to 44-fold, respectively). Free PPs revealed remarkable antifungal properties with isoeugenol showing the lowest half-maximal inhibitory concentration (IC50) values of mycelium growth and spore germination inhibition. Encapsulated PPs, despite their reduced antifungal activity, could be helpful to solve drawbacks such as solubility and stability.

  18. Inhibition of insulin amyloid fibril formation by cyclodextrins.

    PubMed

    Kitagawa, Keisuke; Misumi, Yohei; Ueda, Mitsuharu; Hayashi, Yuya; Tasaki, Masayoshi; Obayashi, Konen; Yamashita, Taro; Jono, Hirofumi; Arima, Hidetoshi; Ando, Yukio

    2015-01-01

    Localized insulin-derived amyloid masses occasionally form at the site of repeated insulin injections in patients with insulin-dependent diabetes and cause subcutaneous insulin resistance. Various kinds of insulin including porcine insulin, human insulin, and insulin analogues reportedly formed amyloid fibrils in vitro and in vivo, but the impact of the amino acid replacement in insulin molecules on amyloidogenicity is largely unknown. In the present study, we demonstrated the difference in amyloid fibril formation kinetics of human insulin and insulin analogues, which suggests an important role of the C-terminal domain of the insulin B chain in nuclear formation of amyloid fibrils. Furthermore, we determined that cyclodextrins, which are widely used as drug carriers in the pharmaceutical field, had an inhibitory effect on the nuclear formation of insulin amyloid fibrils. These findings have significant implications for the mechanism underlying insulin amyloid fibril formation and for developing optimal additives to prevent this subcutaneous adverse effect.

  19. Synthesis of amorphous calcium phosphate using various types of cyclodextrins

    SciTech Connect

    Li Yanbao; Wiliana, Tjandra; Tam, Kam C. . E-mail: mkctam@ntu.edu.sg

    2007-05-03

    Amorphous calcium phosphate (ACP) was synthesised in aqueous solution at room temperature using cyclodextrins. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and thermal analysis (DTA/TGA) were performed on the calcium phosphate precipitates obtained from solutions. We observed that only {beta}-CD could stabilise the amorphous phase in the mother solution because of the lower solubility of {beta}-CD in water and the ACP remained stable in aqueous solution for more than 24 h at room temperature. The ACP particle has an initial particle size of less than 40 nm, Ca/P molar ratio of 1.67 and {beta}-CD absorbed on its surface. The mechanism for the stabilisation of ACP is proposed.

  20. Enabling technologies and green processes in cyclodextrin chemistry.

    PubMed

    Cravotto, Giancarlo; Caporaso, Marina; Jicsinszky, Laszlo; Martina, Katia

    2016-01-01

    The design of efficient synthetic green strategies for the selective modification of cyclodextrins (CDs) is still a challenging task. Outstanding results have been achieved in recent years by means of so-called enabling technologies, such as microwaves, ultrasound and ball mills, that have become irreplaceable tools in the synthesis of CD derivatives. Several examples of sonochemical selective modification of native α-, β- and γ-CDs have been reported including heterogeneous phase Pd- and Cu-catalysed hydrogenations and couplings. Microwave irradiation has emerged as the technique of choice for the production of highly substituted CD derivatives, CD grafted materials and polymers. Mechanochemical methods have successfully furnished greener, solvent-free syntheses and efficient complexation, while flow microreactors may well improve the repeatability and optimization of critical synthetic protocols.