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Sample records for patterning cyclodextrin monolayers

  1. 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.

  2. 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.

  3. Contact electrochemical replication of hydrophilic-hydrophobic monolayer patterns.

    PubMed

    Zeira, Assaf; Chowdhury, Devasish; Maoz, Rivka; Sagiv, Jacob

    2008-12-23

    Contact electrochemical replication (CER) is a novel pattern replication methodology advanced in this laboratory that offers the unprecedented capability of direct one-step reproduction of monolayer surface patterns consisting of hydrophilic domains surrounded by a hydrophobic monolayer background (hydrophilic @ hydrophobic monolayer patterns), regardless of how the initial "master" pattern was created. CER is based on the direct electrochemical transfer of information, through aqueous electrolyte bridges acting as an information transfer medium, between two organosilane monolayers self-assembled on smooth silicon wafer surfaces. Upon the application of an appropriate voltage bias between a patterned monolayer/silicon specimen playing the role of "stamp" and a monolayer/silicon specimen playing the role of "target", the hydrophilic features of the stamp are copied onto the hydrophobic surface of the target. It is shown that this electrochemical printing process may be implemented under a variety of experimental configurations conducive to the formation of nanometric electrolyte bridges between stamp and target; however, using plain liquid water for this purpose is, in general, not satisfactory because of the high surface tension, volatility, and incompressibility of water. High-fidelity replication of monolayer patterns with variable size of hydrophilic features was achieved by replacing water with a sponge-like hydrogel that is nonvolatile, compressible, and binds specifically to the hydrophilic features of such patterns. Since any copy resulting from the CER process can equally perform as stamp in a subsequent CER step, this methodology offers the rather unique option of multiple parallel reproduction of an initially fabricated master pattern. PMID:19206292

  4. Surface patterned pH-sensitive fluorescence using β-cyclodextrin functionalized poly(ethylene glycol).

    PubMed

    Kim, Sung Han; Sharker, Shazid Md; In, Insik; Park, Sung Young

    2016-08-20

    This paper reports the development of a pH-responsive molecular pattern that shows specific and selective affinity for particular host-guest interactions, and its use as a pH fluorescent sensor. The pH-responsive boronate ester is formed via interactions between the diol group of β-cyclodextrin (CD) and phenylboronic acid of poly(ethylene glycol), and is strategically designed to allow reversible formation of a molecular lining pattern. Printing on a versatile substrate provides a method to monitor the positioning of different molecules by using a pH-responsive boronate ester, allowing specific host-guest interactions on any surface. Confocal laser scanning microscopy, fluorescence spectroscopy, and (1)H NMR results indicate that the assembled CD monolayer can be removed by washing with an acidic pH buffer, demonstrating the presence of a boronate ester connective bridge, which is acid labile. Therefore, visualization of the pH-responsive fluorescence sensor using a rhodamine-CD complex allows straightforward discrimination between different molecules on any substrate, thus facilitating application of this sensor in clinical diagnostics and environmental monitoring. PMID:27178950

  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. PMID:26844645

  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. 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.

  9. Antifouling self-assembled monolayers on microelectrodes for patterning biomolecules.

    PubMed

    Noel, John; Teizer, Winfried; Hwang, Wonmuk

    2009-01-01

    We present a procedure for forming a poly(ethylene glycol) (PEG) trimethoxysilane self-assembled monolayer (SAM) on a silicon substrate with gold microelectrodes. The PEG-SAM is formed in a single assembly step and prevents biofouling on silicon and gold surfaces. The SAM is used to coat microelectrodes patterned with standard, positive-tone lithography. Using the microtubule as an example, we apply a DC voltage to induce electrophoretic migration to the SAM-coated electrode in a reversible manner. A flow chamber is used for imaging the electrophoretic migration and microtubule patterning in situ using epifluorescence microscopy. This method is generally applicable to biomolecule patterning, as it employs electrophoresis to immobilize target molecules and thus does not require specific molecular interactions. Further, it avoids problems encountered when attempting to pattern the SAM molecules directly using lithographic techniques. The compatibility with electron beam lithography allows this method to be used to pattern biomolecules at the nanoscale. PMID:19707178

  10. 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.

  11. Control of crystal nucleation by patterned self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Aizenberg, Joanna; Black, Andrew J.; Whitesides, George M.

    1999-04-01

    An important requirement in the fabrication of advanced inorganic materials, such as ceramics and semiconductors, is control over crystallization. In principle, the synthetic growth of crystals can be guided by molecular recognition at interfaces. But it remains a practical challenge to control simultaneously the density and pattern of nucleation events, and the sizes and orientations of the growing crystals. Here we report a route to crystal formation, using micropatterned self-assembled monolayers,, which affords control over all these parameters. We begin with a metal substrate patterned with a self-assembled monolayer having areas of different nucleating activity-in this case, an array of acid-terminated regions separated by methyl-terminated regions. By immersing the patterned substrates in a calcium chloride solution and exposing them to carbon dioxide, we achieve ordered crystallization of calcite in the polar regions, where the rate of nucleation is fastest; crystallization can be completely suppressed elsewhere by a suitable choice of array spacing, which ensures that the solution is undersaturated in the methyl-terminated regions. The nucleation density (the number of crystals formed per active site) may be controlled by varying the area and distribution of the polar regions, and we can manipulate the crystallographic orientation by using different functional groups and substrates.

  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. Mathematical modelling of the transport of hydroxypropyl-β-cyclodextrin inclusion complexes of ranitidine hydrochloride and furosemide loaded chitosan nanoparticles across a Caco-2 cell monolayer.

    PubMed

    Sadighi, Armin; Ostad, S N; Rezayat, S M; Foroutan, M; Faramarzi, M A; Dorkoosh, F A

    2012-01-17

    Chitosan nanoparticles (CS-NPs) have been used to enhance the permeability of furosemide and ranitidine hydrochloride (ranitidine HCl) which were selected as candidates for two different biopharmaceutical drug classes having low permeability across Caco-2 cell monolayers. Drugs loaded CS-NPs were prepared by ionic gelation of CS and pentasodium tripolyphosphate (TPP) which added to the drugs inclusion complexes with hydroxypropyl-β-cyclodextrin (HP-βCD). The stability constants for furosemide/HP-βCD and ranitidine HCl/HP-βCD were calculated as 335 M(-1) and 410 M(-1), whereas the association efficiencies (AE%) of the drugs/HP-βCD inclusion complexes with CS-NPs were determined to be 23.0 and 19.5%, respectively. Zetasizer and scanning electron microscopy (SEM) were used to characterise drugs/HP-βCD-NPs size and morphology. Transport of both nano and non-nano formulations of drugs/HP-βCD complexes across a Caco-2 cell monolayer was assessed and fitted to mathematical models. Furosemide/HP-βCD-NPs demonstrated transport kinetics best suited for the Higuchi model, whereas other drug formulations demonstrated power law transportation behaviour. Permeability experiments revealed that furosemide/HP-βCD and ranitidine HCl/HP-βCD nano formulations greatly induce the opening of tight junctions and enhance drug transition through Caco-2 monolayers. PMID:22101294

  14. [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

  15. 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.

  16. Controlling the adhesion of conducting polymer films with patterned self-assembled monolayers

    SciTech Connect

    Rozsnyai, L.F.; Wrighton, M.S.

    1996-02-01

    A photosensitive self-assembled monolayer (SAM) is selectively irradiated to fabricate a pattern on an Au electrode, and a thin film of aniline or 3-methylthiophene is deposited on it by electopolymerization. Adhesion of the polymer films can be controlled by the monolayer terminal group. Applying tape to the sample and peeling it away selectively removes the conducting polymer film to the tape in a near-micron resolution pattern. 14 refs., 1 fig.

  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. Ionic liquids: nondestructive, nonvolatile imaging fluids for submicrometer-scale monolayer patterns.

    PubMed

    Hozumi, Atsushi; Bien, Pei; McCarthy, Thomas J

    2010-04-28

    A method for visualizing submicrometer-scale patterns of approximately 1.0-nm-thick monolayers terminated with CF(3) and CH(3) groups using an ionic liquid (IL) is described. Bis(hydroxyethyl)dimethylammonium methanesulfonate (BHDAMS) was spin-cast onto the photolithographically patterned samples. The BHDAMS wetted the photodecomposed regions selectively. Pattern widths of the mask ranged from 500 nm to 10 microm, and the IL-replicated patterns were observed using optical and laser microscopy. The nonvolatile BHDAMS had sufficient contrast to image submicrometer-scale patterns of monolayers over large areas. We note that this imaging technique involves no damage and is compatible with readily available laboratory equipment. PMID:20373769

  20. 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).

  1. Mass spectrometry assisted lithography for the patterning of cell adhesion ligands on self-assembled monolayers.

    PubMed

    Kim, Young-Kwan; Ryoo, Soo-Ryoon; Kwack, Sul-Jin; Min, Dal-Hee

    2009-01-01

    Pattern of events: A simple and flexible method has been developed for patterning cell adhesion ligands. Locally erasing self-assembled monolayers with tri(ethyleneglycol) groups on a gold substrate by using a MALDI-TOF MS nitrogen laser and filling the exposed gold surface with an alkanethiol presenting carboxylic acid groups enables subsequent immobilization of maleimide and a cell adhesion peptide, which can then recognize cells (see scheme). PMID:19347909

  2. 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.

  3. 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

  4. Surface plasmon resonance phase imaging measurements of patterned monolayers and DNA adsorption onto microarrays

    PubMed Central

    Halpern, Aaron R.; Chen, Yulin; Corn, Robert M.; Kim, Donghyun

    2011-01-01

    The optical technique of surface plasmon resonance phase imaging (SPR-PI) is implemented in a linear microarray format for real-time measurements of surface bioaffinity adsorption processes. SPR-PI measures the phase shift of p-polarized light incident at the SPR angle reflected from a gold thin film in an ATR Kretschmann geometry by creating an interference fringe image on the interface with a polarizer-quartz wedge depolarizer combination. The position of the fringe pattern in this image changes upon the adsorption of biomolecules to the gold thin film. By using a linear array of 500 μm biosensor element lines that are perpendicular to the interference fringe image, multiple bioaffinity adsorption measurements can be performed in real time. Two experiments were performed to characterize the sensitivity of the SPR-PI measurement technique; first, a ten line pattern of a self-assembled monolayer of 11-mercaptoundecamine (MUAM) was created via photopatterning to verify that multiple phase shifts could be measured simultaneously. A phase shift difference (Δφ) of Δφ = 182.08 ± 0.03° was observed for the 1.8-nm MUAM monolayer; this value agrees with the phase shift difference calculated from a combination of Fresnel equations and Jones matrices for the depolarizer. In a second demonstration experiment, the feasibility of SPR-PI for in situ bioaffinity adsorption measurements was confirmed by detecting the hybridization and adsorption of single stranded DNA (ssDNA) onto a six component DNA line microarray patterned monolayer. Adsorption of a full DNA monolayer produced a phase shift difference of Δφ = 28.80 ± 0.03° at the SPR angle of incidence and the adsorption of the ssDNA was monitored in real time with the SPR-PI. These initial results suggest that SPR-PI should have a detection limit roughly 100 times lower than traditional intensity-based SPR imaging measurements. PMID:21355546

  5. 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. PMID:25606939

  6. Direct electron beam patterning of sub-5nm monolayer graphene interconnects

    NASA Astrophysics Data System (ADS)

    Qi, Zhengqing J.; Rodríguez-Manzo, Julio A.; Hong, Sung Ju; Park, Yung Woo; Stach, Eric A.; Drndić, Marija; Johnson, A. T. Charlie

    2013-03-01

    The industry's march towards higher transistor density has called for an ever-increasing number of interconnect levels in logic devices. The historic transition from aluminum to copper was necessary in reducing timing delays while future technology nodes presents an opportunity for new materials and patterning techniques. One material for consideration is graphene, a single atomic layer of carbon atoms. Graphene is known to have excellent electrical properties [1], driving strong interest in its integration into the wafer fabrication processes for future electronics [2], and its ballistic transport properties give promise for use in on-chip interconnects [3]. This study demonstrates the feasibility of a direct electron beam lithography technique to pattern sub-5nm metallic graphene ribbons, without using a mask or photoresist, to act as next generation interconnects. Sub-5nm monolayer and multilayer graphene ribbons were patterned using a focused electron beam in a transmission electron microscope (TEM) through direct knock-on ejection of carbon atoms. These ribbons were measured during fabrication to quantify their electrical performance. Multilayered graphene nanoribbons were found to sustain current densities in excess of 109 A/cm2, orders of magnitude higher than copper, while monolayer graphene provides comparable performance to copper but at the level of a single atomic layer. High volume manufacturing could utilize wafer-size chemical vapor deposition (CVD) graphene [4] transferred directly onto the substrate paired with a direct write multi-beam tool to knock off carbon atoms for patterning of nanometer sized interconnects. The patterning technique introduced here allows for the fabrication of small foot-print high performance next generation graphene interconnects that bypass the use of a mask and resist process.

  7. Scanning microwave microscope imaging of micro-patterned monolayer graphene grown by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Myers, J.; Mou, S.; Chen, K.-H.; Zhuang, Y.

    2016-02-01

    Characterization of micro-patterned chemical vapor deposited monolayer graphene using a scanning microwave microscope has been presented. Monolayer graphene sheets deposited on a copper substrate were transferred to a variety of substrates and micro-patterned into a periodic array of parallel lines. The measured complex reflection coefficients exhibit a strong dependency on the operating frequency and on the samples' electrical conductivity and permittivity. The experiments show an extremely high sensitivity by detecting image contrast between single and double layer graphene sheets. Correlating the images recorded at the half- and quarter-wavelength resonant frequencies shows that the relative permittivity of the single layer graphene sheet is above 105. The results are in good agreement with the three dimensional numerical electromagnetic simulations. This method may be instrumental for a comprehensive understanding of the scanning microwave microscope image contrast and provide a unique technique to estimate the local electrical properties with nano-meter scale spatial resolution of two dimensional materials at radio frequency.

  8. Preparation and characterization of self-assembled monolayers and mesoscale protein patterning

    NASA Astrophysics Data System (ADS)

    Noomuna, Panae

    Bottom-up approach was used to develop self-assembled monolayers of octadecyltrichlorosilane (OTS) and undecenyltrichlorosilane(UTS) on Si(100) wafer. Undecenyltrichlorosilane monolayer was oxidized at the vinyl terminal to generate a carboxylic acid group. Lysozyme protein was immobilized on the polar carboxylic acid group. The developed protein patterns were investigated using fluorescence microscopy. Lysozyme has an isoelectronic point of 11.35. At a pH below this value the protein is positively charged making it a good candidate for electrostatic adsorption on the negatively charge -COO- group. Fluorescence images confirm formation of lysozyme across the silicon wafer. The patterned Si(100) wafer can be used as a biosensor against lysozyme antibodies. Another approach to develop varied surface properties was used to grow OTS on oxidized UTSox via chemical phase deposition (CVD). In this case we used polystyrene and silicon nanospheres as masking agents on the already developed and oxidized UTS. Fluorescence images revealed that OTS layers were formed on the interstitial spaces of the nanosphere masks. Varied protein can be immobilized on this surface due to different terminal groups on the surface.

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

    PubMed

    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 b-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

  10. 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

  11. Selective atomic layer deposition with electron-beam patterned self-assembled monolayers

    SciTech Connect

    Huang, Jie; Lee, Mingun; Kim, Jiyoung

    2012-01-15

    The authors selectively deposited nanolines of titanium oxide (TiO{sub 2}) through atomic layer deposition (ALD) using an octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) as a nucleation inhibition layer. Electron-beam (e-beam) patterning is used to prepare nanoline patterns in the OTS SAM on SiO{sub 2}/Si substrates suitable for selective ALD. The authors have investigated the effect of an e-beam dose on the pattern width of the selectively deposited TiO{sub 2} lines. A high dose (e.g., 20 nC/cm) causes broadening of the linewidth possibly due to scattering, while a low dose (e.g., 5 nC/cm) results in a low TiO{sub 2} deposition rate because of incomplete exposure of the OTS SAMs. The authors have confirmed that sub-30 nm isolated TiO{sub 2} lines can be achieved by selective ALD combined with OTS patterned by EBL at an accelerating voltage of 2 kV and line dose of 10 nC/cm. This research offers a new approach for patterned gate dielectric layer fabrication, as well as potential applications for nanosensors and solar cells.

  12. Inkjet printing as a tool for the patterned deposition of octadecylsiloxane monolayers on silicon oxide surfaces.

    PubMed

    Belgardt, Christian; Sowade, Enrico; Blaudeck, Thomas; Baumgärtel, Thomas; Graaf, Harald; von Borczyskowski, Christian; Baumann, Reinhard R

    2013-05-28

    We present a case study about inkjet printing as a tool for molecular patterning of silicon oxide surfaces with hydrophobic functionality, mediated by n-octadecyltrichlorosilane (OTS) molecules. In contrast to state-of-the-art techniques such as micro contact printing or chemical immersion with subsequent lithography processes, piezo drop-on-demand inkjet printing does not depend on physical masters, which allows an effective direct-write patterning of rigid or flexible substrates and enables short run-lengths of the individual pattern. In this paper, we used mesithylene-based OTS inks, jetted them in droplets of 10 pL on a silicon oxide surface, evaluated the water contact angle of the patterned areas and fitted the results with Cassie's law. For inks of 2.0 mM OTS concentration, we found that effective area coverages of 38% can be obtained. Our results hence show that contact times of the order of hundred milliseconds are sufficient to form a pattern of regions with OTS molecules adsorbed to the surface, representing at least a fragmented, inhomogeneous self-assembled OTS monolayer (OTS-SAM). PMID:23417102

  13. 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.

  14. 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

  15. Neutron diffraction of alpha, beta and gamma cyclodextrins: Hydrogen bonding patterns

    SciTech Connect

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

    1984-08-01

    Cyclodextrins (CD's) have proved useful as model systems for the study of hydrogen bonding. They are torus-shaped molecules composed of six(alpha), seven(beta) or eight(gamma) (1----4) linked glucoses. Because of their particular geometry, they are able to act as a host to form inclusion complexes with guest molecules very much like enzymes. Cyclodextrins have been shown to exert catalytic activity on suitable included-substrate molecules; they catalyze the hydrolysis of phenylacetates, of organic pyrophosphates and of penicillin derivatives. They also accelerate aromatic chlorinations and diazo coupling by means of their primary and/or secondary hydroxyl groups, so that the rates of hydrolysis are enhanced by up to a factor of 400. In order to understand the hydrogen bonding in these enzyme models, neutron diffraction data were collected to unambiguously determine the hydrogen atom positions, which could not be done from the x-ray diffraction data. 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 alpha-CD complex formation has been proposed. Circular hydrogen bond networks have also been found for 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 in equilibrium O...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. 33 references.

  16. Settlement of Ulva zoospores on patterned fluorinated and PEGylated monolayer surfaces.

    PubMed

    Finlay, John A; Krishnan, Sitaraman; Callow, Maureen E; Callow, James A; Dong, Rong; Asgill, Nicola; Wong, Kaiming; Kramer, Edward J; Ober, Christopher K

    2008-01-15

    Various designs for coatings that resist the attachment of marine organisms are based on the concept of "ambiguous" surfaces that present both hydrophobic and hydrophilic functionalities as surface domains. In order to facilitate the optimal design of such surfaces, information is needed on the scale of the domains that the settling stages of marine organisms are able to distinguish. Previous experiments showed that Ulva zoospores settle (attach) in high numbers onto fluorinated monolayers compared to PEGylated monolayers. The main aim of the present study was to determine, when zoospores of the green alga Ulva are presented with a choice of fluorinated or PEGylated surfaces, what the minimum dimensions of the two types of surface are that zoospores can detect and consequently settle on. Silicon wafers were chemically modified to produce a pattern of squares containing alternating fluorinated and PEGylated stripes of different widths on either a uniform fluorinated or PEGylated background. Each 1 cm x 1 cm square contained stripes with widths of 500, 200, 100, 50, 20, 5, or 2 microm as well as an unpatterned square with a chemistry opposite that of the background. Spores were selective in choosing where to settle, settling at higher densities on fluorinated stripes compared to PEGylated stripes. However, the magnitude of response, and the consequences for settlement on patterned areas overall, was dependent on both the width of the stripes and the chemistry of the background. The data are discussed in relation to the ability of spores to "choose" favorable sites for settlement and the implications for the development of novel antifouling coatings. PMID:18081330

  17. 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

  18. 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

  19. 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.

  20. 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.

  1. 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

  2. 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).

  3. Resistive switching of alkanethiolated nanoparticle monolayers patterned by electron-beam exposure.

    PubMed

    Reissner, Patrick A; Fedoryshyn, Yuriy; Tisserant, Jean-Nicolas; Stemmer, Andreas

    2016-08-17

    Carbon-based electronic devices are promising candidates for complementing silicon-based electronics in memory device applications. For example, sputtered thin films of amorphous carbon exhibit memristive behavior. The reported devices, however, have a minimal active area of about 50 nm diameter, leading to large set currents in the μA range. Although power efficiency would benefit from reduced drive currents, resistive switching of amorphous carbon confined to a few cubic nanometers has remained largely unexplored. Here, we investigate resistive switching in 30 nm long and 25 nm wide monolayer arrays of 10 nm gold nanoparticles patterned by direct electron-beam exposure followed by a purpose-designed emulsion-based development process. Electron-beam irradiation transforms the alkanethiol ligands of the gold nanoparticles into a solvent-resistant amorphous carbonaceous matrix allowing pattern development and imparting electronic function. We measure changes in conductivity of up to five orders of magnitude for set currents in the nA range. PMID:27492444

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. Nonequilibrium pattern formation in Langmuir-phase assisted assembly of alkylsiloxane monolayers

    SciTech Connect

    Wang, R.; Parikh, A.N.; Beers, J.D.; Shreve, A.P.; Swanson, B.

    1999-11-18

    Prepolymerized n-octadecyltrichlorosilane (OTS) monolayers were deposited onto oxidized silicon substrates from precursor Langmuir monolayers (at an air-water interface) in two-dimensional liquid expanded (LE), liquid condensed (LC), or mixed (LE/LC coexistence phase) states at four different pulling rates. Morphologies of the transferred monolayers have been investigated using atomic force microscopy (AFM). The OTS monolayers formed from the LE phase precursor reveal an incipient condensation transition exhibiting a novel ring-in-a-ring morphology, wherein uniformly distributed circular domains consisting of two concentric walls of ordered OTS molecules in a high density phase both sandwich and encapsulate disordered OTS molecules in a reduced density phase. On the other hand, the monolayers formed from the LC/LE phase precursor implicate a complete condensation transition, evidenced in the AFM images showing a uniform tiling of near-circular domains composed of ordered OTS molecules in a dense monolayer phase. The monolayers derived from the 2D solid or LC precursor state reveal near-complete surface coverages and uniform film structures, comparable to those obtained by adsorption from a dilute organic solution of OTS molecules (conventional self-assembly process). These structural reconstructions at the substrate surface, namely lateral redistribution into 2D domains, condensation transitions and film coverages, are discussed in terms of the competition between short range and long range interactions. The most dominant effect of increasing pulling rates is the appearance of coalesced domain structures, presumably due to drainage of the water layer at the substrate surface as well as occasional substrate pinning. These results substantiate the idea that templating surface self-assembly of monolayers by using their Langmuir-phase precursors provides a useful alternative to classical solution-phase self-assembly approaches, and affords a wide range of control over

  9. Hybrid subtractive micro-patterning of a self-assembled SiO2 nano/microsphere monolayer

    NASA Astrophysics Data System (ADS)

    Han, Seungyong; Hong, Sukjoon; Kang, Hyun Wook; Wanit, Manorokul; Kang, Bongchul; Ko, Seung Hwan

    2015-10-01

    Colloidal self-assembly and direct micro-patterning of functional materials have drawn intense interest as an alternative to the conventional photolithography based microelectronics fabrication process. In this paper, we introduce a facile subtractive micro contact printing method to create a patterned colloidal nano/micro sphere monolayer on a wafer scale by combining an additive ‘bottom-up’ self-assembly and subtractive ‘top-down’ printing process. A vacuum-assisted contact printing method enabled precise and uniform pressure control to directly fabricate a large-area micro-patterned hexagonally close packed structure of nano/micro spheres on the target substrate very fast, at low cost, under ambient conditions. In addition, analysis on the hybrid printing pressure and the patterning time has been conducted.

  10. Effective Method for Micro-Patterning Arene-Terminated Monolayers on a Si(111) Electrode.

    PubMed

    Yamanoi, Yoshinori; Kobayashi, Tetsuhiro; Maeda, Hiroaki; Miyachi, Mariko; Ara, Masato; Tada, Hirokazu; Nishihara, Hiroshi

    2016-07-12

    Microstructured electrodes are significant to modern electrochemistry. A representative aromatic group, 4-ferrocenylphenyl one, was covalently bound to a micropatterned silicon electrode via the arylation of a hydrogen-terminated silicon(111) surface formed selectively on a Si wafer. Starting from a silicon(100)-on-insulator (SOI) wafer, the aromatic monolayer was attached sequentially by spin-coating a resist, electron beam lithography, Cr/Au deposition, lift-off, anisotropic etching with aqueous KOH solution, and Pd-catalyzed arylation. Cyclic voltammetry (CV) and X-ray photoelectron spectroscopy (XPS) are used to characterize the coupling reaction between 4-ferrocenyl group and silicon substrate, and to confirm performance of the final modified microsized electrode. These data show that this synthetic protocol gives chemically well-defined and robust functionalized monolayers on a silicon semiconducting surface with a small electrode. PMID:27328628

  11. 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. PMID:27351974

  12. 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

  13. 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

  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. 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.

  16. 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.

  17. Support-Free Transfer of Ultrasmooth Graphene Films Facilitated by Self-Assembled Monolayers for Electronic Devices and Patterns.

    PubMed

    Wang, Bin; Huang, Ming; Tao, Li; Lee, Sun Hwa; Jang, A-Rang; Li, Bao-Wen; Shin, Hyeon Suk; Akinwande, Deji; Ruoff, Rodney S

    2016-01-26

    We explored a support-free method for transferring large area graphene films grown by chemical vapor deposition to various fluoric self-assembled monolayer (F-SAM) modified substrates including SiO2/Si wafers, polyethylene terephthalate films, and glass. This method yields clean, ultrasmooth, and high-quality graphene films for promising applications such as transparent, conductive, and flexible films due to the absence of residues and limited structural defects such as cracks. The F-SAM introduced in the transfer process can also lead to graphene transistors with enhanced field-effect mobility (up to 10,663 cm(2)/Vs) and resistance modulation (up to 12×) on a standard silicon dioxide dielectric. Clean graphene patterns can be realized by transfer of graphene onto only the F-SAM modified surfaces. PMID:26701198

  18. Dynamic pattern formation of liquid crystals using binary self-assembled monolayers on an ITO surface under DC voltage.

    PubMed

    Ishida, Takao; Oyama, Makiko; Terada, Kei-ichi; Haga, Masa-aki

    2014-12-01

    There have been numerous studies of liquid crystal (LC) convection using sandwich-type LC cells under AC voltage. In contrast to previous LC convection studies under AC voltage, we propose the use of a binary self-assembled monolayer (SAM) with a redox-active Ru complex and insulating octadecyl phosphonic acid (C18) molecules on an indium tin oxide (ITO) surface as the electrode of sandwich-type LC cells under DC bias voltage. This is because the functionalized molecules immobilized on the ITO surface are expected to control the LC orientation and electrical conduction of LC cells, under an exact DC bias voltage. We successfully achieved LC pattern formation using ITO electrodes with binary SAMs in LC cells. Moreover, we confirmed that the LC pattern size was increased by increasing the coverage of the Ru complex in binary SAMs. We consider that a combination of three factors, electrical conduction change, controlling of LC orientation in the initial stage and redox-activity of the Ru-complex, is the reason for LC convection although we cannot fully explain the distribution of these three factors. We believe that our LC pattern formation is promising for new type devices e.g., artificial compound eyes using the LC device technology. PMID:25327940

  19. Mixed alkanethiol monolayers on submicrometric gold patterns: a controlled platform for studying cell-ligand interactions.

    PubMed

    Fishler, Rami; Artzy-Schnirman, Arbel; Peer, Elad; Wolchinsky, Ron; Brener, Reuven; Waks, Tova; Eshhar, Zelig; Reiter, Yoram; Sivan, Uri

    2012-09-12

    Nanoscale organization of surface ligands often has a critical effect on cell-surface interactions. We have developed an experimental system that allows a high degree of control over the 2-D spatial distribution of ligands. As a proof of concept, we used the developed system to study how T-cell activation is independently affected by antigen density and antigen amount per cell. Arrays of submicrometer gold islands at varying surface coverage were defined on silicon by electron beam lithography (EBL). The gold islands were functionalized with alkanethiol self-assembled monolayers (SAMs) containing a small antigen, 2,4,6-trinotrophenyl (TNP), at various densities. Genetically engineered T-cell hybridomas expressing TNP-specific chimeric T-cell antigen receptor (CAR) were cultured on the SAMs, and their activation was assessed by IL-2 secretion and CD69 expression. It was found that, at constant antigen density, activation increased monotonically with the amount of antigen, while at constant antigen amount activation was maximal at an intermediate antigen density, whose value was independent of the amount of antigen. PMID:22900991

  20. Patterning a hydrogen-bonded molecular monolayer with a hand-controlled scanning probe microscope.

    PubMed

    Green, Matthew F B; Esat, Taner; Wagner, Christian; Leinen, Philipp; Grötsch, Alexander; Tautz, F Stefan; Temirov, Ruslan

    2014-01-01

    One of the paramount goals in nanotechnology is molecular-scale functional design, which includes arranging molecules into complex structures at will. The first steps towards this goal were made through the invention of the scanning probe microscope (SPM), which put single-atom and single-molecule manipulation into practice for the first time. Extending the controlled manipulation to larger molecules is expected to multiply the potential of engineered nanostructures. Here we report an enhancement of the SPM technique that makes the manipulation of large molecular adsorbates much more effective. By using a commercial motion tracking system, we couple the movements of an operator's hand to the sub-angstrom precise positioning of an SPM tip. Literally moving the tip by hand we write a nanoscale structure in a monolayer of large molecules, thereby showing that our method allows for the successful execution of complex manipulation protocols even when the potential energy surface that governs the interaction behaviour of the manipulated nanoscale object(s) is largely unknown. PMID:25383304

  1. Patterning a hydrogen-bonded molecular monolayer with a hand-controlled scanning probe microscope

    PubMed Central

    Green, Matthew F B; Esat, Taner; Wagner, Christian; Leinen, Philipp; Grötsch, Alexander; Tautz, F Stefan

    2014-01-01

    Summary One of the paramount goals in nanotechnology is molecular-scale functional design, which includes arranging molecules into complex structures at will. The first steps towards this goal were made through the invention of the scanning probe microscope (SPM), which put single-atom and single-molecule manipulation into practice for the first time. Extending the controlled manipulation to larger molecules is expected to multiply the potential of engineered nanostructures. Here we report an enhancement of the SPM technique that makes the manipulation of large molecular adsorbates much more effective. By using a commercial motion tracking system, we couple the movements of an operator's hand to the sub-angstrom precise positioning of an SPM tip. Literally moving the tip by hand we write a nanoscale structure in a monolayer of large molecules, thereby showing that our method allows for the successful execution of complex manipulation protocols even when the potential energy surface that governs the interaction behaviour of the manipulated nanoscale object(s) is largely unknown. PMID:25383304

  2. 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

  3. 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

  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. 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

  6. 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

  7. 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.

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

    PubMed

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

    2013-01-01

    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. PMID:23900310

  9. Significantly improved adhesion of poly(3,4-ethylenedioxythiophene) nanofilms to amino-silane monolayer pre-patterned SiO2 surfaces.

    PubMed

    Pang, Ilsun; Kim, Sungsoo; Lee, Jaegab

    2007-11-01

    This study reports a novel patterning method for highly pure poly(3,4-ethylenedioxythiophene) (PEDOT) nanofilms having a particularly strong adhesion to a SiO2 surface. An oxidized silicon wafer substrate was micro-contact printed with n-octadecyltrichlorosilane (OTS) monolayer, and subsequently its negative pattern was self-assembled with three different amino-functionalized alkylsilanes, (3-aminopropyl)trimethoxysilane (APS), N-(2-aminoethyl)-3-aminopropyltrimethoxy silane (EDAS), and (3-trimethoxysilylpropyl) diethylenetriamine (DETS). Then, PEDOT nanofilms were selectively grown on the aminosilane pre-patterned areas via the vapor phase polymerization method. To evaluate the adhesion and patterning, the PEDOT nanofilms and SAMs were investigated with a Scotch tape test, contact angle analyzer, optical and atomic force microscopes. The evaluation revealed that the newly developed bottom-up process can successfully offer a strongly adhered and selectively patterned PEDOT nanofilm on an oxidized Si wafer surface. PMID:18047060

  10. 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.

  11. 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

  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. Site-selective growth of surface-anchored metal-organic frameworks on self-assembled monolayer patterns prepared by AFM nanografting

    PubMed Central

    Ladnorg, Tatjana; Welle, Alexander; Heißler, Stefan; Wöll, Christof

    2013-01-01

    Summary Surface anchored metal-organic frameworks, SURMOFs, are highly porous materials, which can be grown on modified substrates as highly oriented, crystalline coatings by a quasi-epitaxial layer-by-layer method (liquid-phase epitaxy, or LPE). The chemical termination of the supporting substrate is crucial, because the most convenient method for substrate modification is the formation of a suitable self-assembled monolayer. The choice of a particular SAM also allows for control over the orientation of the SURMOF. Here, we demonstrate for the first time the site-selective growth of the SURMOF HKUST-1 on thiol-based self-assembled monolayers patterned by the nanografting technique, with an atomic force microscope as a structuring tool. Two different approaches were applied: The first one is based on 3-mercaptopropionic acid molecules which are grafted in a 1-decanethiolate SAM, which serves as a matrix for this nanolithography. The second approach uses 16-mercaptohexadecanoic acid, which is grafted in a matrix of an 1-octadecanethiolate SAM. In both cases a site-selective growth of the SURMOF is observed. In the latter case the roughness of the HKUST-1 is found to be significantly higher than for the 1-mercaptopropionic acid. The successful grafting process was verified by time-of-flight secondary ion mass spectrometry and atomic force microscopy. The SURMOF structures grown via LPE were investigated and characterized by atomic force microscopy and Fourier-transform infrared microscopy. PMID:24205458

  14. 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

  15. 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.

  16. 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.

  17. Enzymatic production of cyclodextrins.

    PubMed

    Biwer, A; Antranikian, G; Heinzle, E

    2002-09-01

    Cyclodextrins (CD) are enzymatically modified starches with a wide range of applications in food, pharmaceutical and chemical industries, agriculture and environmental engineering. They are produced from starch via enzymatic conversion using cyclodextrin glycosyl transferases (CGTases) and partly alpha-amylases. Due to its low solubility in water, separation and purification of beta-CD is relatively easy compared to alpha- and gamma-CD. In recent years more economic processes for gamma-CD and especially alpha-CD production have been developed using improved CGTases and downstream processing. New purification steps, e.g. affinity adsorption, may reduce the use of complexing agents. The implementation of thermostable CGTases can simplify the production process and increase the selectivity of the reaction. A tabular overview of alpha-CD production processes is presented. PMID:12226716

  18. 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

  19. 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.

  20. 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. PMID:26343162

  1. 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

  2. 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

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

    PubMed Central

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

    2015-01-01

    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 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) and 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

  4. 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

  5. Cyclodextrin-Templated Porphyrin Nanorings**

    PubMed Central

    Liu, Pengpeng; Neuhaus, Patrik; Kondratuk, Dmitry V; Balaban, T Silviu; Anderson, Harry L

    2014-01-01

    α- and β-Cyclodextrins have been used as scaffolds for the synthesis of six- and seven-legged templates by functionalizing every primary CH2OH with a 4-pyridyl moiety. Although these templates are flexible, they are very effective for directing the synthesis of macrocyclic porphyrin oligomers consisting of six or seven porphyrin units. The transfer of chirality from the cyclodextrin templates to their nanoring hosts is evident from NMR and circular dichroism spectroscopy. Surprisingly, the mean effective molarity for binding the flexible α-cyclodextrin-based template within the six-porphyrin nanoring (74 m) is almost as high as for the previously studied rigid hexadentate template (180 m). The discovery that flexible templates are effective in this system, and the availability of a template with a prime number of binding sites, open up many possibilities for the template-directed synthesis of larger macrocycles. PMID:24916813

  6. Cyclodextrin-templated porphyrin nanorings.

    PubMed

    Liu, Pengpeng; Neuhaus, Patrik; Kondratuk, Dmitry V; Balaban, T Silviu; Anderson, Harry L

    2014-07-21

    α- and β-cyclodextrins have been used as scaffolds for the synthesis of six- and seven-legged templates by functionalizing every primary CH2OH with a 4-pyridyl moiety. Although these templates are flexible, they are very effective for directing the synthesis of macrocyclic porphyrin oligomers consisting of six or seven porphyrin units. The transfer of chirality from the cyclodextrin templates to their nanoring hosts is evident from NMR and circular dichroism spectroscopy. Surprisingly, the mean effective molarity for binding the flexible α-cyclodextrin-based template within the six-porphyrin nanoring (74 M) is almost as high as for the previously studied rigid hexadentate template (180 M). The discovery that flexible templates are effective in this system, and the availability of a template with a prime number of binding sites, open up many possibilities for the template-directed synthesis of larger macrocycles. PMID:24916813

  7. 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.

  8. 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

  9. Titanocene / cyclodextrin supramolecular systems: a theoretical approach

    PubMed Central

    2012-01-01

    Background Recently, various metallocenes were synthesized and analyzed by biological activity point of view (such as antiproliferative properties): ruthenocenes, cobaltoceniums, titanocenes, zirconocenes, vanadocenes, niobocenes, molibdocenes etc. Two main disadvantages of metallocenes are the poor hydrosolubility and the hydrolytic instability. These problems could be resolved in two ways: synthetically modifying the structure or finding new formulations with enhanced properties. The aqueous solubility of metallocenes with cytostatic activities could be enhanced by molecular encapsulation in cyclodextrins, as well as the hydrolytic instability of these compounds could be reduced. Results This study presents a theoretical approach on the nanoencapsulation of a series of titanocenes with cytotoxic activity in α-, β-, and γ-cyclodextrin. The HyperChem 5.11 package was used for building and molecular modelling of titanocene and cyclodextrin structures, as well as for titanocene/cyclodextrin complex optimization. For titanocene/cyclodextrin complex optimization experiments, the titanocene and cyclodextrin structures in minimal energy conformations were set up at various distances and positions between molecules (molecular mechanics functionality, MM+). The best interaction between titanocene structures and cyclodextrins was obtained in the case of β- and γ-cyclodextrin, having the hydrophobic moieties oriented to the secondary face of cyclodextrin. The hydrophobicity of titanocenes (logP) correlate with the titanocene-cyclodextrin interaction parameters, especially with the titanocene-cyclodextrin interaction energy; the compatible geometry and the interaction energy denote that the titanocene/β- and γ-cyclodextrin complex can be achieved. Valuable quantitative structure-activity relationships (QSARs) were also obtained in the titanocene class by using the same logP as the main parameter for the in vitro cytotoxic activity against HeLa, K562, and Fem-x cell

  10. 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

  11. Ofloxacin/beta-cyclodextrin complexation.

    PubMed

    Koester, L S; Guterres, S S; Le Roch, M; Eifler-Lima, V L; Zuanazzi, J A; Bassani, V L

    2001-07-01

    Ofloxacin (OFX) is a fluorquinolone characterized by photochemical instability. With the goal to improve its photostability in aqueous solutions, the complexation of ofloxacin with beta-cyclodextrin was investigated. The complexes showed a water solubility enhancement of approximately 2.6 times; nevertheless, the photodegradation of ofloxacin was not reduced. The complexes obtained were characterized by thermal and 1H nuclear magnetic resonance (NMR) analysis, which revealed an interaction between ofloxacin and beta-cyclodextrin. The last analysis indicated that only partial inclusion of the N-methylpiperazinyl moiety occurred, which can explain the fact that photostabilization was not improved. This partial inclusion phenomenon could be explained also by computer-aided molecular modeling. PMID:11548860

  12. 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

  13. 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.

  14. 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.

  15. Monolayer Tungsten Disulfide Laser

    NASA Astrophysics Data System (ADS)

    Ye, Yu; Wong, Zi Jing; Lu, Xiufang; Ni, Xingjie; Zhu, Hanyu; Chen, Xianhui; Wang, Yuan; Zhang, Xiang

    Two-dimensional van der Waals materials have opened a new paradigm for fundamental physics exploration and device applications because of their emerging physical properties. Unlike gapless graphene, monolayer transition-metal dichalcogenides are two-dimensional semiconductors that undergo an indirect-to-direct band gap transition, creating new optical functionalities for next-generation ultra-compact photonics and optoelectronics. Here, we report the realization of a two-dimensional excitonic laser by embedding monolayer tungsten disulfide in a microdisk resonator.

  16. 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.

  17. 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.

  18. Synergistic radical scavenging potency of curcumin-in-β-cyclodextrin-in-nanomagnetoliposomes.

    PubMed

    Aadinath, W; Bhushani, Anu; Anandharamakrishnan, C

    2016-07-01

    Curcumin is a highly potent nutraceutical associated with various health benefits. However, its hydrophobic nature affects its bioavailability and bioactivity, and limits nutraceutical applications. Drug-in-cyclodextrin-in-liposome has the ability to mask the hydrophobic nature of drug and achieve better encapsulation. Also, encapsulating iron oxide nanoparticles (IONPs) within liposomes endow additional beneficial functionalities of IONPs. In the present study, curcumin-β-cyclodextrin inclusion complex (IC) and IONPs were co-encapsulated within liposomes (curcumin-in-β-cyclodextrin-in-nanomagnetoliposomes) to achieve the synergistic antioxidant potential of curcumin and IONPs. IC of curcumin-β-cyclodextrin was prepared by a simple rapid method and successful inclusion was confirmed by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Mean diameter of IONPs was found to be 180nm and X-ray diffraction pattern confirmed the formation of hematite nanoparticles. Band gap energy calculated using absorption spectra was 2.25eV, which falls in close proximity with the theoretically calculated values of hematite. Mean diameter of curcumin-in-β-cyclodextrin-in-nanomagnetoliposomes was 67nm and encapsulation efficiency of curcumin was found to be 71%. Further, the co-encapsulated particles possessed significantly low IC50 value (64.7791μg/ml, p<0.01) compared to conventional curcumin liposome and IONPs, indicating its synergistically enhanced radical scavenging property. PMID:27127056

  19. 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

  20. 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

  1. 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

  2. Dehydration, dissolution, and melting of cyclodextrin crystals.

    PubMed

    Specogna, Erika; Li, King Wo; Djabourov, Madeleine; Carn, Florent; Bouchemal, Kawthar

    2015-01-29

    Cyclodextrins are a family of oligosaccharides with a toroid shape that exhibit a unique ability of entrapping guest molecules in their internal cavity. Water is the primary guest molecule and is omnipresent in the crystalline phases stabilizing the overall architecture. Despite the presence of water molecules inside the cavity, cyclodextrins provide a hydrophobic environment where poorly soluble molecules can easily fit. In this investigation we put in evidence different types of water in the hydrated α-, β-, and γ-cyclodextrin crystals. Thermogravimetric measurements identify various binding sites of water and highlight the difference between the crystals equilibrated under various humid atmospheres. We establish by microcalorimetry the limit of solubility versus temperature and measure for the first time the melting temperatures of the hydrated crystals. Dissolution and melting enthalpies are derived and the solubility curves are compared to existing literature. The specific features of each cyclodextrin are underlined. PMID:25565266

  3. Monolayer excitonic laser

    NASA Astrophysics Data System (ADS)

    Ye, Yu; Wong, Zi Jing; Lu, Xiufang; Ni, Xingjie; Zhu, Hanyu; Chen, Xianhui; Wang, Yuan; Zhang, Xiang

    2015-11-01

    Two-dimensional van der Waals materials have opened a new paradigm for fundamental physics exploration and device applications because of their emerging physical properties. Unlike gapless graphene, monolayer transition-metal dichalcogenides (TMDCs) are two-dimensional semiconductors that undergo an indirect-to-direct bandgap transition, creating new optical functionalities for next-generation ultra-compact photonics and optoelectronics. Although the enhancement of spontaneous emission has been reported on TMDC monolayers integrated with photonic crystals and distributed Bragg reflector microcavities, coherent light emission from a TMDC monolayer has not been demonstrated. Here, we report the realization of a two-dimensional excitonic laser by embedding monolayer WS2 in a microdisk resonator. Using a whispering gallery mode with a high quality factor and optical confinement, we observe bright excitonic lasing at visible wavelengths. This demonstration of a two-dimensional excitonic laser marks a major step towards two-dimensional on-chip optoelectronics for high-performance optical communication and computing applications.

  4. 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. PMID:25159382

  5. Chemoresponsive Monolayer Transistors

    SciTech Connect

    Guo,X.; Myers, M.; Xiao, S.; Lefenfeld, M.; Steiner, R.; Tulevski, G.; Tang, J.; Baumert, J.; Leibfarth, F.; et al.

    2006-01-01

    This work details a method to make efficacious field-effect transistors from monolayers of polycyclic aromatic hydrocarbons that are able to sense and respond to their chemical environment. The molecules used in this study are functionalized so that they assemble laterally into columns and attach themselves to the silicon oxide surface of a silicon wafer. To measure the electrical properties of these monolayers, we use ultrasmall point contacts that are separated by only a few nanometers as the source and drain electrodes. These contacts are formed through an oxidative cutting of an individual metallic single-walled carbon nanotube that is held between macroscopic metal leads. The molecules assemble in the gap and form transistors with large current modulation and high gate efficiency. Because these devices are formed from an individual stack of molecules, their electrical properties change significantly when exposed to electron-deficient molecules such as tetracyanoquinodimethane (TCNQ), forming the basis for new types of environmental and molecular sensors.

  6. 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.

  7. 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

  8. Cyclodextrin-Based Solid-Gas Clathrates.

    PubMed

    Pereva, Stiliana; Himitliiska, Tsveta; Spassov, Tony; Stoyanov, Simeon D; Arnaudov, Luben N; Dudev, Todor

    2015-07-29

    "Cyclodextrin-gas" clathrates were obtained by crystallization from water solution of α-, β-, and γ-cyclodextrins (CDs) under pressure of the gas to be entrapped into the CD molecules. When the pressure is released, these clathrates are stable at ambient conditions and dissociate at elevated temperature, which makes them interesting for various applications as foam boosters in food and other industries. It was found that under these conditions α-CD forms clathrates with all of the gases used in this study (N2, N2O, CO2, Ar), whereas β- and γ-CDs can form clathrates only with N2. The concentration of the cyclodextrin and the temperature and pressure of the gas were varied for achieving higher clathrate yield and larger amount of embedded gas. Highest values of about 2 wt % were found for α-CD-N2O, as it releases in the temperature range of 40-60 °C. PMID:26132981

  9. 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

  10. Chemoresponsive monolayer transistors

    PubMed Central

    Guo, Xuefeng; Myers, Matthew; Xiao, Shengxiong; Lefenfeld, Michael; Steiner, Rachel; Tulevski, George S.; Tang, Jinyao; Baumert, Julian; Leibfarth, Frank; Yardley, James T.; Steigerwald, Michael L.; Kim, Philip; Nuckolls, Colin

    2006-01-01

    This work details a method to make efficacious field-effect transistors from monolayers of polycyclic aromatic hydrocarbons that are able to sense and respond to their chemical environment. The molecules used in this study are functionalized so that they assemble laterally into columns and attach themselves to the silicon oxide surface of a silicon wafer. To measure the electrical properties of these monolayers, we use ultrasmall point contacts that are separated by only a few nanometers as the source and drain electrodes. These contacts are formed through an oxidative cutting of an individual metallic single-walled carbon nanotube that is held between macroscopic metal leads. The molecules assemble in the gap and form transistors with large current modulation and high gate efficiency. Because these devices are formed from an individual stack of molecules, their electrical properties change significantly when exposed to electron-deficient molecules such as tetracyanoquinodimethane (TCNQ), forming the basis for new types of environmental and molecular sensors. PMID:16855049

  11. 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...

  12. 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 ...

  13. 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 ...

  14. Cyclodextrin-based nanosponges as drug carriers

    PubMed Central

    Zanetti, Marco; Cavalli, Roberta

    2012-01-01

    Summary Cyclodextrin-based nanosponges, which are proposed as a new nanosized delivery system, are innovative cross-linked cyclodextrin polymers nanostructured within a three-dimensional network. This type of cyclodextrin polymer can form porous insoluble nanoparticles with a crystalline or amorphous structure and spherical shape or swelling properties. The polarity and dimension of the polymer mesh can be easily tuned by varying the type of cross-linker and degree of cross-linking. Nanosponge functionalisation for site-specific targeting can be achieved by conjugating various ligands on their surface. They are a safe and biodegradable material with negligible toxicity on cell cultures and are well-tolerated after injection in mice. Cyclodextrin-based nanosponges can form complexes with different types of lipophilic or hydrophilic molecules. The release of the entrapped molecules can be varied by modifying the structure to achieve prolonged release kinetics or a faster release. The nanosponges could be used to improve the aqueous solubility of poorly water-soluble molecules, protect degradable substances, obtain sustained delivery systems or design innovative drug carriers for nanomedicine. PMID:23243470

  15. Cyclodextrins: a versatile tool in separation science.

    PubMed

    Schneiderman, E; Stalcup, A M

    2000-08-01

    Cyclodextrins have been used extensively in separation science because they have been shown to discriminate between positional isomers, functional groups, homologues and enantiomers. This property makes them one of the most useful agents for a wide variety of separations. The main goal of this review is a discussion of somewhat more exotic applications of cyclodextrins to separation methods. Techniques examined in detail include gel electrophoresis, isotachophoresis, isoelectric focusing, preparative scale electrophoretic techniques, thin-layer chromatography, electrochemically modulated liquid chromatography, use of monolithic media in liquid chromatography, microdialysis, separation on hollow fibers, foam flotation enrichment, solid- and liquid-phase extractions, countercurrent chromatography, separation through liquid and composite membranes, and cyclodextrin applications in molecularly imprinted polymers. Since a lot of attention has been paid to use of cyclodextrins in capillary electrophoresis, liquid, gas and supercritical fluid chromatography, these techniques will be only briefly discussed. The second goal of this review is a discussion of a scaling-up the analytical separations to semi-preparative or preparative techniques. It was found that despite a need for large scale separations in the industry, development of these techniques has been somewhat lagging behind development of miniaturized analytical separations. It is hoped that the focus on areas outside more traditional separation applications might stimulate further research. PMID:10997705

  16. Divinyl sulfone cross-linked cyclodextrin-based polymeric materials: synthesis and applications as sorbents and encapsulating agents.

    PubMed

    Morales-Sanfrutos, Julia; Lopez-Jaramillo, Francisco Javier; Elremaily, Mahmoud A A; Hernández-Mateo, Fernando; Santoyo-Gonzalez, Francisco

    2015-01-01

    The aim of this study was to evaluate the crosslinking abilities of divinyl sulfone (DVS) for the preparation of novel water-insoluble cyclodextrin-based polymers (CDPs) capable of forming inclusion complexes with different guest molecules. Reaction of DVS with native α-cyclodextrin (α-CD), β-cyclodextrin (β-CD) and/or starch generates a variety of homo- and hetero-CDPs with different degrees of crosslinking as a function of the reactants' stoichiometric ratio. The novel materials were characterized by powder X-ray diffraction, electron microscopy and for their sorption of phenol and 4-nitrophenol. They were further evaluated as sorbents with phenolic pollutants (bisphenol A and β-naphthol) and bioactive compounds (the hormone progesterone and curcumin). Data obtained from the inclusion experiments show that the degree of cross-linking has a minor influence on the yield of inclusion complex formation and highlight the important role of the CDs, supporting a sorption process based on the formation of inclusion complexes. In general, the inclusion processes are better described by a Freundlich isotherm although an important number of them can also be fitted to the Langmuir isotherm with R2 ≥ 0.9, suggesting a sorption onto a monolayer of homogeneous sites. PMID:25706758

  17. 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

  18. Investigation of the beta-cyclodextrin-hydrocortisone inclusion compound.

    PubMed

    Frank, S G; Kavaliunas, D R

    1983-10-01

    The formation of an inclusion compound by beta-cyclodextrin with hydrocortisone has been studied by proton magnetic resonance (1H-NMR) and phase solubility analysis. The magnitude of the chemical shifts of the interior and exterior beta-cyclodextrin protons in the presence of hydrocortisone indicated that hydrocortisone is included within the beta-cyclodextrin cavity and probably interacts with protons on the edge of the torus. The overall stoichiometry of the inclusion compound was not a single, simple relationship, but was unusual in that it was variable and apparently dependent on the relative amounts of hydrocortisone and beta-cyclodextrin in the system. PMID:6644576

  19. Bioadhesive properties and biodistribution of cyclodextrin-poly(anhydride) nanoparticles.

    PubMed

    Agüeros, Maite; Areses, Paloma; Campanero, Miguel Angel; Salman, Hesham; Quincoces, Gemma; Peñuelas, Ivan; Irache, Juan Manuel

    2009-06-28

    This work describes the preparation, characterization and evaluation of the nanoparticles formed by the copolymer of methyl vinyl ether and maleic anhydride (Gantrez) AN) and cyclodextrins, including beta-cyclodextrin (CD) hydroxypropyl-beta-cyclodextrin (HPCD) and 6-monodeoxy-6-monoamino-beta-cyclodextrin (NHCD). The cyclodextrin-poly(anhydride) nanoparticles were prepared by a solvent displacement method and characterized by measuring the size, zeta potential, morphology and composition. For bioadhesion studies, nanoparticles were fluorescently labelled with rhodamine B isothiocianate (RBITC). For in vivo imaging biodistribution studies, (99m)Tc-labelled nanoparticles were used. Nanoparticles displayed a size of about 150nm and a cyclodextrin content which was found optimal under the following experimental conditions: cyclodextrin/poly(anhydride) ratio of 0.25 by weight, 30min of incubation time between the cyclodextrin and the polymer. Moreover, the oligosaccharide content was higher with CD than with NHCD and HPCD. Overall, cyclodextrin-poly(anhydride) nanoparticles displayed homogeneous bioadhesive interactions within the gut. The intensity of these interactions was higher than for control nanoparticles. The high bioadhesive capacity was observed for HPCD-NP and NHCD-NP which can be related with their rough morphology and, thus, a higher specific surface than for smooth nanoparticles (CD-NP). Finally, from in vivo studies, no evidence of translocation of distribution to other organs was observed when these nanoparticles were orally administered. PMID:19491010

  20. 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. PMID:25933534

  1. 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

  2. Ordered chlorinated monolayer silicene structures

    NASA Astrophysics Data System (ADS)

    Li, Wenbin; Sheng, Shaoxiang; Chen, Jian; Cheng, Peng; Chen, Lan; Wu, Kehui

    2016-04-01

    We report on a systematic experimental study on the chlorination of monatomic silicene layer on Ag(111) by scanning tunneling microscopy. Monolayer silicene on Ag(111) can form 4×4, (√13×√13)R ± 13.9°, and (2√3×2√3)R30° reconstructions due to their different buckling configurations. We found that at low dosage, Cl atoms attach to the upper buckled Si atoms without changing the buckling configuration of the silicene monolayer. However, at high coverage, the global buckling configuration will be significantly changed, resulting in new ordered structures. Interestingly, all monolayer silicene structures, regardless of their initial reconstructions, tend to form a local silicene 1×1 structure at the saturation coverage. The mechanism for chlorination of monolayer silicene is explained.

  3. 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.

  4. 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

  5. [Pharmaceutical applications of sulfobuthylether-beta-cyclodextrin].

    PubMed

    Sebestyén, Zita; Szepesi, Katalin; Szabó, Barnabás

    2013-01-01

    Sulfobuthylether-beta-cyclodextrin (SBECD) is a substituted derivative of a cyclic oligosaccharide containing seven glucopyranose units, which bear pH-independent negative charges because of sulfonate groups. This derivative has better solubility and toxicological characteristics than the unsubstituted beta-cyclodextrin, and the presence of sulfobuthyl groups opens new dimensions in the interactions acting the part of the complex formation. These create opportunities for the pharmaceutical applications of this compound. Currently six pharmaceutical preparations circulate--moiety of these circulates in Hungary also--which have a composition containing SBECD as pharmaceutical excipient. Out of the main effects of the complex-forming agent the solubility enhancement is utilized in these compositions to achieve the solution of a therapeutic dose in the case of intravascular administration. Available experimental evidences and published patents are indicative of broadening the circle of the applications in point of both technological advantages and dosage forms. PMID:23926650

  6. 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

  7. "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

  8. 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

  9. 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.

  10. 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

  11. Thermodynamic analysis of the binding of a hepatoprotectant drug, thioctic acid, by beta-cyclodextrin.

    PubMed

    Junquera, E; Aicart, E

    1999-06-01

    Spectroscopic and thermodynamic studies of the binding of a hepatoprotectant drug, thioctic acid, by beta-cyclodextrin (beta-CD) have been carried out using UV-vis and pH potentiometric measurements. The UV-vis spectra and the pH of the aqueous solutions of the drug were measured (i) as a function of total drug concentration in the absence of cyclodextrin, and (ii) as a function of cyclodextrin concentration at constant drug concentration. The spectroscopic study was done at pH = 7 and 25 degrees C, while the potentiometric study was performed at several temperatures ranging from 15 to 40 degrees C. From the spectroscopic data, the molar absorption coefficient, epsilon, for the pure drug in aqueous media and the stoichiometry of the inclusion complex with beta-CD were determined. The dissociation constant, Ka, of the pure drug (which is a weak acid), and the association constants of the complexes formed by beta-cyclodextrin and both the nonionized (HTIO) and ionized (TIO-) forms of the drug, have been simultaneously determined at several temperatures from the pH data, without the necessity of working with buffered solutions. The nonionic forms are complexed by the beta-CD with higher affinity than their ionic counterparts. From the dependency of the association constants on temperature (van't Hoff analysis), the inclusion complexes formed by HTIO or TIO- and the beta-CD were found to be enthalpy driven, with a favorable enthalpic term dominant over an unfavorable entropic term. Both contributions were found to show a possible dependence with temperature (DeltaCpo not equal 0). This pattern may reveal the contribution of van der Waals interactions, hydrophobic effect, and solvent reorganization as the main driving forces promoting the complexation. PMID:10350499

  12. 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

  13. 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

  14. Preparation and Characterization of Pioglitazone Cyclodextrin Inclusion Complexes

    PubMed Central

    Pandit, V; Gorantla, R; Devi, K; Pai, RS; Sarasija, S

    2011-01-01

    Pioglitazone, a class II Biopharmaceutical Classification System drug having poor water solubility and slow dissolution rate may have a negative impact on its subtherapeutic plasma drug levels leading to therapeutic failure. In order to improve its water solubility and thus dissolution, cyclodextrin complexation technique was followed. The phase solubility studies were carried using three different types of cyclodextrins viz., β, methyl-β and γ-cyclodextrins. The Gibbs free energy was calculated in order to determine ease of the complexation. Binary systems of pioglitazone with cyclodextrins were prepared by kneading method and spray drying method. The phase solubility profiles with all the three cyclodextrins were classified as AL-type, indicating the formation of 1:1 stoichiometric inclusion complexes. The complexation capability of cyclodextrins with pioglitazone increased in the order of methyl-β > β > γ-cyclodextrin. The Gibbs free energy was found to be in the order γ > methyl-β > β cyclodextrin. Characterization of inclusion complexes was done by solubility studies, in vitro dissolution studies, Fourier transformation-infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry and X-ray powder diffractometry studies. Inclusion complexes exhibited higher rates of dissolution than the corresponding physical mixtures and pure drug. Greater solubility was observed with spray-dried methyl-β cyclodextrin complexes (2.29 ± 0.001 mg/ml) in comparison to the kneaded methyl-β cyclodextrin complexes (1.584 ± 0.053 mg/ml) and pure drug (0.0714 ± 0.0018 mg/ml). PMID:22224032

  15. Adhesive Bonding to Dentin Improved by Polymerizable Cyclodextrin Derivatives

    PubMed Central

    Bowen, Rafael L.; Schumacher, Gary E.; Giuseppetti, Anthony A.; Guttman, Charles M.; Carey, Clifton M.

    2009-01-01

    The objective of this work was to determine bonding characteristics of a hydrophilic monomer formulation containing polymerizable cyclodextrin derivatives. The hypothesis was that a formulation containing hydrophilic cross-linking diluent comonomers and cyclodextrins with functional groups attached by hydrolytically stable ether linkages could form strong adhesive bonds to dentin. The previously synthesized polymerizable cyclodextrin derivatives were formulated with sorbitol dimethacrylate, methacrylic acid and phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide photoinitiator. The same formulation without the polymerizable cyclodextrin derivatives isolated the effects of the polymerizable cyclodextrin derivatives. A commercial self-etching bonding system was tested as a comparative control. Ground mid-coronal dentin was etched with 37 % phosphoric acid (H3PO4) for 15 s and rinsed with distilled water for 10 s. Formulations were applied to the moist dentin and light-cured 10 s. A packable composite was then applied through irises and light-cured 60 s. Teeth were stored in water for 24 h before bonds were tested in a shearing orientation. One-way ANOVA was performed on the data. The average values of shear bond strengths were defined as loads at fracture divided by the 4 mm diameter iris areas. The average value of shear bond strength for the formulation containing the polymerizable cyclodextrin derivatives was higher (p < 0.05), where p is a fraction of the probability distribution) than that of the same monomeric formulation except that the polymerizable cyclodextrin derivatives were not included. This was supporting evidence that the polymerizable cyclodextrin derivatives contributed to improved bonding. The average value of shear bond strength for the formulation containing the polymerizable cyclodextrin derivatives was also higher (p < 0.05) than that of the commercial self-etching bonding system. These preliminary results are in accordance with the hypothesis

  16. Monolayer coated aerogels and method of making

    SciTech Connect

    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.

  17. 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.

  18. 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

  19. 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

  20. 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

  1. 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

  2. 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.

  3. Structural studies on the chiral selector capacity of cyclodextrin derivatives.

    PubMed

    Tokés, Béla; Ferencz, László; Buchwald, Peter; Donáth-Nagy, Gabriella; Vancea, Szende; Sánta, Nándor; Kis, Erika Lilla

    2008-04-24

    Chromatographic separation of enantiomers to assure or enhance chiral purity is of considerable importance and can be achieved by the use of selectors of great structural variety. Cyclodextrins are an important and frequently used class, and they are multimodal selectors since multiple chiral interactions are possible by very different mechanisms. Here, the results of a preliminary examination on the possible value of computational molecular modeling approaches for the predictability of cyclodextrin selector effects for compounds that possess both geometrical and optical isomerism are presented. Interactions between various cyclodextrins and pyrethroic acids are modeled, interpreted, and compared to experimental capillary electrophoresis data. PMID:18280575

  4. Synthesis of uniform cyclodextrin thioethers to transport hydrophobic drugs.

    PubMed

    Becker, Lisa F; Schwarz, Dennis H; Wenz, Gerhard

    2014-01-01

    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

  5. 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

  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. Cyclodextrines as functional agents for decontamination of the skin contaminated by nerve agents.

    PubMed

    Cabal, Jirí; Kuca, Kamil; Sevelová-Bartosová, Lucie; Dohnal, Vlastimil

    2004-01-01

    Three decontamination solutions of beta-cyclodextrines were prepared. Their abilities to decontamine rat skin contamined with nerve agent soman were tested. Decontamination efficacy of the tested cyclodextrine solutions was compared with the same decontamination means but without the cyclodextrines. The efficacy of tested decontaminants was evaluated by the assessment of the ID50 values. Two decontamination prescriptions with cyclodextrines (tetraborate buffer and tetraborate buffer with acetone) do not show significantly better decontamination efficacies in comparison with prescriptions without cyclodextrines. Only in case of aqueous solution of 2-aminoethanol the addition of beta-cyclodextrine resulted in significant increase (32%) in decontamination efficacy. PMID:15446361

  8. 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. PMID:26237660

  9. 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.

  10. 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. PMID:26471761

  11. 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.

  12. 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. PMID:25952853

  13. 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

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

    PubMed

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

    2016-01-01

    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

  15. Predictions for partial and monolayer coverages of O2 on graphite

    NASA Technical Reports Server (NTRS)

    Pan, R. P.; Etters, R. D.; Kobashi, K.; Chandrasekharan, V.

    1982-01-01

    Monolayer properties of O2 on graphite are calculated using a pattern recognition, optimization scheme. Equilibrium monolayers are predicted at two different densities with properties in agreement with recent X-ray diffraction, specific heat, and neutron scattering data. Properties of the extremely low density regime are calculated using a model based upon a distribution of two-dimensional O2 clusters. The results are consistent with experimental evidence.

  16. Sodium monolayers on thermionic cathodes

    NASA Astrophysics Data System (ADS)

    Almanstötter, Jürgen; Eberhard, Bernd; Günther, Klaus; Hartmann, Thomas

    2002-07-01

    Under certain conditions alkali vapours form dipole monolayers on metallic electrodes that can lower the work function of the bulk material. In this case, the power balance of the electrode, the electrode fall voltage and the electrode loss power can change considerably. To verify this effect a pyrometric technique was adapted and optimized for the diagnostics of tungsten electrodes in high pressure sodium discharges. Using an already verified model of thermally emitting cathodes the effect was observed in a Na DC discharge and the range of existence was investigated. An interpretation of the results is given using a Langmuir description of forming the Na monolayers and first-principles electronic structure calculations using a pseudopotential plane wave method to solve the Kohn-Sham equations of density-functional theory.

  17. 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...

  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. 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

  20. 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.

  1. 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.

  2. Equilibrating nanoparticle monolayers using wetting films.

    PubMed

    Pontoni, Diego; Alvine, Kyle J; Checco, Antonio; Gang, Oleg; Ocko, Benjamin M; Pershan, Peter S

    2009-01-01

    Monolayers of bimodal gold nanoparticles on silicon are investigated by a combination of microscopy (dry monolayers) and x-ray diffraction (dry and wet monolayers). In the presence of an excess of small particles, the nanoscale packing structure closely resembles the small-particle-rich scenario of the structural crossover transition that has been predicted and also observed with micron-scale hard-sphere colloids. Structural morphology is monitored in situ during monolayer dissolution and reassembly within the thin liquid wetting film. This approach allows investigation of size and solvent effects on nanoparticles in quasi-two-dimensional confinement. PMID:19257214

  3. Hematite nanoparticle monolayers on mica electrokinetic characteristics.

    PubMed

    Morga, Maria; Adamczyk, Zbigniew; Oćwieja, Magdalena

    2012-11-15

    Electrokinetic properties of α-Fe(2)O(3) (hematite) nanoparticle monolayers on mica were thoroughly characterized using the streaming potential method. Hematite suspensions were obtained by acidic hydrolysis of ferric chloride. The average size of particles (hydrodynamic diameter), determined by dynamic light scattering (DLS) and AFM, was 22 nm (pH=5.5, I=10(-2)M). The hematite monolayers on mica were produced under diffusion-controlled transport from the suspensions of various bulk concentration. The monolayer coverage, quantitatively determined by AFM and SEM, was regulated within broad limits by adjusting the nanoparticle deposition time. This allowed one to uniquely express zeta potential of hematite monolayers, determined by the streaming potential measurements, in terms of the particle coverage. Such dependencies, obtained for various pH, were successfully interpreted in terms of the three-dimensional electrokinetic model. A universal calibrating graph was produced enabling one to determine hematite monolayer coverage from the measured value of the streaming potential. The influence of the ionic strength, varied between 10(-4) and 10(-2)M, on the zeta potential of hematite monolayers was also studied. Additionally, the stability of monolayers (desorption kinetics) was determined under in situ conditions using the streaming potential method. Our experimental data prove that it is feasible to produce uniform and stable hematite particle monolayers of well-controlled coverage. Such monolayers may find practical applications as universal substrates for protein immobilization (biosensors) and in electrocatalytic applications. PMID:22921408

  4. 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

  5. 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

  6. 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

  7. Monolayers at air-water interfaces: from origins-of-life to nanotechnology.

    PubMed

    Ariga, Katsuhiko; Hill, Jonathan P

    2011-08-01

    The air-water interface presents several interesting features, namely a) a molecularly flat environment, b) a boundary region between two phases with different dielectric constants, c) permits or promotes dynamic interactions within the interface region, and d) a point of interaction between hydrophobic compounds and aqueous molecules. Accordingly, Langmuir monolayers at the air-water interface have several unique characteristics and properties, which require investigation. In this review-type personal account, typical examples of molecular recognition and molecular patterning at air-water interfaces are first introduced, followed by descriptions of specific and unusual properties of monolayers on water. In addition, two examples of our own results concerning Langmuir monolayers are explained. We have selected examples from two apparently unrelated research areas, these being the origin of life and future nanotechnology, in order to emphasize the diverse scientific contribution of research on monolayers at the air-water interface. PMID:21739568

  8. 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

  9. 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

  10. 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.

  11. Elaboration of antibiofilm surfaces functionalized with antifungal-cyclodextrin inclusion complexes.

    PubMed

    Gharbi, Aïcha; Humblot, Vincent; Turpin, Frédéric; Pradier, Claire-Marie; Imbert, Christine; Berjeaud, Jean-Marc

    2012-07-01

    To tackle the loss of activity of surfaces functionalized by coating and covalently bound molecules to materials, an intermediate system implying the noncovalent immobilization of active molecules in the inner cavity of grafted cyclodextrins (CDs) was investigated. The antifungal and antibiofilm activities of the most stable complexes of Anidulafungin (ANF; echinocandin) and thymol (THY; terpen) in various CDs were demonstrated to be almost the same as the free molecules. The selected CD was covalently bond to self-assembled monolayers on gold surfaces. The immobilized antifungal agents reduced the number of culturable Candida albicans ATCC 3153 attached to the surface by 64 ± 8% for ANF and 75 ± 15% for THY. The inhibitory activity was persistent for THY-loaded samples, whereas it was completely lost for ANF-loaded surfaces after one use. However, reloading of the echinocandin restored the activity. Using fluorescent dying and confocal microscopy, it was proposed that the ANF-loaded surfaces inhibited the adherence of the yeasts, whereas the activity of immobilized THY was found fungicidal. This kind of tailored approach for functionalizing surfaces that could allow a progressive release of ANF or THY gave promising results but still needs to be improved to display a full activity. PMID:22268719

  12. Improvement of water solubility and in vitro dissolution rate of aceclofenac by complexation with beta-cyclodextrin and hydroxypropyl-beta-cyclodextrin.

    PubMed

    Ranpise, Nisharani S; Kulkarni, Nilesh S; Mair, Parth D; Ranade, Arati N

    2010-01-01

    The present study deals with the inclusion complexation of aceclofenac with beta-cyclodextrin by grinding, microwave and spray-drying techniques. A derivative of beta-cyclodextrin, hydroxypropyl-beta-cyclodextrin, was also subjected to the complexation process with aceclofenac by spray-drying technique. The samples were subjected to in-vitro dissolution studies, fourier transform infra-red spectroscopy, differential scanning calorimetry, nuclear magnetic resonance spectroscopy and x-ray diffraction studies. The in-vitro dissolution of aceclofenac-hydroxypropyl-beta-cyclodextrin complex was faster as compared to the aceclofenac- beta-cyclodextrin complex and aceclofenac alone. Spray-dried aceclofenac-beta-cyclodextrin complex were subjected to anti-inflammatory and analgesic activity and showed significant anti-inflammatory and analgesic activity. PMID:19505225

  13. 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.

  14. Study of Benzyl Salicylate/beta-Cyclodextrin Inclusion Complex Formation by Positron Annihilation

    NASA Astrophysics Data System (ADS)

    Bellitto, V. J.; Hsu Hadley, F. H., Jr.; Trinh, T.

    1996-11-01

    Results of positron annihilation lifetime spectra of beta-cyclodextrin and beta-cyclodextrin complexed with benzyl salicylate,benzyl acetate, or ethyl salicylate in air and vacuum were used to determine the fraction of beta-cyclodextrin which remains uncomplexed in the benzyl salicylate/beta-cyclodextrin 1:2 molar ratio inclusion complex. The intensity of the longest-lived component in vacuum was shown to decrease when the beta-cyclodextrin cavity was filled with benzyl salicylate, benzyl acetate, or ethyl salicylate guest molecules. Comparison of the intensity for beta-cyclodextrin, benzyl salicylate/beta-cyclodextrin 1:2 molar ratio, and 1:1 molar ratio indicated that the benzyl and salicylate moieties each formed an inclusion complex with a molecule of beta-cyclodextrin in the benzyl salicylate/beta-cyclodextrin 1:2 complex. It was determined that the benzyl moiety of the benzyl salicylate molecule is preferred by the beta-cyclodextrin "host" and that only 34of the salicylate moieties are complexed in the benzyl salicylate/beta-cyclodextrin 1:2 sample.

  15. (13)C and (15)N solid-state NMR studies on albendazole and cyclodextrin albendazole complexes.

    PubMed

    Ferreira, M João G; García, A; Leonardi, D; Salomon, Claudio J; Lamas, M Celina; Nunes, Teresa G

    2015-06-01

    (13)C and (15)N solid-state nuclear magnetic resonance (NMR) spectra were recorded from albendazole (ABZ) and from ABZ:β-cyclodextrin, ABZ:methyl-β-cyclodextrin, ABZ:hydroxypropyl-β-cyclodextrin and ABZ:citrate-β-cyclodextrin, which were prepared by the spray-drying technique. ABZ signals were typical of a crystalline solid for the pure drug and of an amorphous compound obtained from ABZ:cyclodextrin samples. Relevant spectral differences were correlated with chemical interaction between ABZ and cyclodextrins. The number and type of complexes revealed a strong dependence on the cyclodextrin group substituent. Solid-state NMR data were consistent with the presence of stable inclusion complexes. PMID:25843843

  16. 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

  17. Monolayer Graphene as Ultimate Chemical Passivation Layer for Arbitrarily Shaped Metal Surfaces

    SciTech Connect

    Sutter E.; Albrecht, P.; Camino, F.E.; Sutter, P.

    2010-12-01

    Monolayer graphene was grown on polycrystalline Ru thin films on patterned fused silica. The Ru films grow with columnar structure with strongly aligned grains exposing flat (0 0 0 1) surface facets within the 3D geometric patterns and on the adjacent planar silica surface. The monolayer graphene was found to completely and uniformly cover the Ru films on the complex engineered substrates. In addition, we demonstrate that the single atomic layer graphene protects the underlying metal surface against reaction with ambient gases of particular importance for applications such as concave focusing mirrors, non-planar microelectrode arrays, etc.

  18. 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…

  19. Bacillus thuringiensis: a specific gamma-cyclodextrin producer strain.

    PubMed

    Goo, Bon Geun; Hwang, You Jin; Park, Jae Kweon

    2014-03-11

    An anaerobic microbial isolate Bacillus species, designated B. thuringiensis GU-2, was isolated from soil as a specific γ-cyclodextrin (CD) producer strain in alkaline medium under anaerobic conditions. The optimum pH and temperature for bacterial growth and γ-CD production were estimated to be pH 8.5 and 37°C in the presence of 1.0% starch substrate, respectively. A high purity yield >95% of γ-CD from the total CD yield in the reaction mixture was obtained from starch that was supposed to be converted by gamma-cyclodextrin glycotransferase, tentatively named as γ-CGTase. The maximum γ-CGTase activity was estimated at 2.45U/mL under optimized condition. This is the first report demonstrating the generation of a specific γ-cyclodextrin (CD) producer strain by the action of a γ-CGTase under anaerobic conditions. PMID:24456970

  20. Continuous production of β-cyclodextrin from starch by highly stable cyclodextrin glycosyltransferase immobilized on chitosan.

    PubMed

    Schöffer, Jéssie da Natividade; Klein, Manuela Poletto; Rodrigues, Rafael C; Hertz, Plinho Francisco

    2013-11-01

    Cyclodextrin glycosyltransferase (CGTase) from Thermoanaerobacter sp. was covalently immobilized on glutaraldehyde-activated chitosan spheres and used in a packed bed reactor to investigate the continuous production of β-cyclodextrin (β-CD). The optimum temperatures were 75 °C and 85 °C at pH 6.0, respectively for free and immobilized CGTase, and the optimum pH (5.0) was the same for both at 60 °C. In the reactor, the effects of flow rate and substrate concentration in the β-CD production were evaluated. The optimum substrate concentration was 4% (w/v), maximizing the β-CD production (1.32 g/L) in a flow rate of 3 mL/min. In addition, the biocatalyst had good operational stability at 60 °C, maintaining 61% of its initial activity after 100 cycles of batch and 100% after 100 h of continuous use. These results suggest the possibility of using this immobilized biocatalyst in continuous production of CDs. PMID:24053808

  1. 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

  2. The structure of percolating lipid monolayers.

    PubMed

    Risović, D; Frka, S; Kozarac, Z

    2012-05-01

    The lattice structure and in plane molecular organization of Langmuir monolayer of amphiphilic material is usually determined from grazing incidence X-ray diffraction (GIXD) or neutron reflectivity. Here we present results of a different approach for determination of monolayer lattice structure based on application of fractal analysis and percolation theory in combination with Brewster angle microscopy. The considerations of compressibility modulus and fractal dimension dynamics provide information on percolation threshold and consequently by application of percolation theory on the lattice structure of a monolayer. We have applied this approach to determine the monolayer lattice structures of single chain and double chain lipids. The compressibility moduli were determined from measured π-A isotherms and fractal dimensions from corresponding BAM images. The monolayer lattice structures of stearic acid, 1-hexadecanol, DPPC and DPPA, obtained in this way conform to the corresponding lattice structures determined previously by other authors using GIXD. PMID:22209411

  3. Cyclodextrin assisted nanophase determination of alkaloid salts.

    PubMed

    Csernák, Orsolya; Buvári-Barcza, Agnes; Barcza, Lajos

    2006-04-15

    The poor water solubility of the free base and the high dissociation constant (K(a)) hinder mainly the assay of alkaloid salts. We have elaborated an environment friendly method that can be carried out in aqueous media. The stability difference of the cyclodextrin (CD) complexes of free and protonated bases were used for this purpose. The base is included into the hydrophobic cavity of the CD (which serves as an apolar solvent phase on molecular level) and its solubility in water is increased. Since the base forms more stable inclusion complex than its protonated species, the pK(a) is decreased and the potentiometric titration is promoted by this way, too. Six different hydrohalide alkaloid salts have been investigated and the most appropriate CDs were chosen (depending on the size of the molecules and/or substituents). The results of the assays agree well with those obtained by the direct nonaqueous titrations. The stability constants of the inclusion complexes have been also computed. PMID:18970584

  4. 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

  5. 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

  6. 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

  7. Studies on coumestrol/beta-cyclodextrin association: Inclusion complex characterization.

    PubMed

    Franco, Camila; Schwingel, Liege; Lula, Ivana; Sinisterra, Rubén D; Koester, Letícia Scherer; Bassani, Valquiria Linck

    2009-03-18

    Coumestrol is an estrogenic and antioxidant agent, characterized by its low solubility in aqueous and lipophilic media, once in the aglicone form. In order to improve its solubility in water, coumestrol was associated with beta-cyclodextrin in aqueous media followed by freeze-drying and characterized by SEM, (1)H NMR and molecular modeling. The analysis proved the existence of an inclusion complex, with higher probability of inclusion of the coumestrol B-ring into the wider rim of the beta-cyclodextrin molecule. PMID:19028558

  8. A cyclodextrin-based polymer for sensing diclofenac in water.

    PubMed

    Xiao, Pu; Weibel, Nicolas; Dudal, Yves; Corvini, Philippe F-X; Shahgaldian, Patrick

    2015-12-15

    An assay for the determination of diclofenac concentration, in the micromolar range in water, was developed. It is based on the use of a recently developed cyclodextrin-based polymer that possesses an inherent affinity for the target pharmaceutical. This competitive assay is exploiting the possibility to displace a fluorescent dye, adsorbed in the cyclodextrin-based polymer, by the target drug. This displacement is followed by measuring the increase in fluorescence polarization of the dye released in solution. The assay was successfully tested on a real wastewater sample with a limit of detection of 1 μM. PMID:26164704

  9. Interaction of beta-cyclodextrin with cadmium(II) ions.

    PubMed

    Norkus, Eugenijus; Grinciene, Giedre; Vuorinen, Tapani; Vaitkus, Rimantas; Butkus, Eugenijus

    2003-12-01

    Reduction of Cd(II) on a dropping mercury electrode was used to study interaction of beta-cyclodextrin with Cd(II) ions. It was found that Cd(II) forms Cdbeta-CD(OH)(2)(2-) hydroxy-complex with the anion of beta-cyclodextrin in alkaline solutions (pH>11), the logarithm of stability constant being 10.4+/-0.1 (20 degrees C; I=1.0). The calculated value of the diffusion coefficient equal to 1.0x10(-6)cm(2)/s shows a large size Cd(II) complex species formation in alkaline solutions containing beta-CD. PMID:14607371

  10. Investigating the Response of Microbial Communities to Cyclodextrin

    NASA Astrophysics Data System (ADS)

    Szponar, N.; Slater, G.; Smith, J.

    2009-05-01

    Recent studies have found applications of hydroxypropyl-β-cyclodextrin (HPβCD) to be highly effective in removing DDT from soils in situ. However, the persistence of HPβCD within the soil and its impact on soil microbial communities is still unclear. It has been suggested that cyclodextrin might provide a substrate for microbial communities resulting in changes in the ongoing effectiveness of remediation and/or soil hydraulic properties. The potential exists that stimulation of the soil microbial community may contribute to removal of DDT, along with the solubilization effects normally associated with cyclodextrin treatment. This study investigated the response of soil microbial communities from a site undergoing remediation of DDT with HPβCD through microcosm and bench scale column studies. Phospholipid fatty acid (PLFA) analysis and their natural abundance 13C signatures can be used to identify in situ microbial metabolism of HPβCD. Heterotrophic organisms have PLFA with 13C signatures 3 to 6‰ depleted from their carbon source. Cyclodextrin was found to have a δ13C of -16‰ resulting from its formation via enzymatic degradation of cornstarch. In contrast, soil organic matter, had a predominantly C3 plant derived signature and a δ13C of -25‰. Incorporation of HPβCD by soil microbial communities would therefore cause a shift to a more enriched isotopic value. While microcosm studies demonstrated no noticeable change in biomass and few changes in PLFA distribution, column studies treated with a 10% solution of HPβCD demonstrated an approximate doubling of microbial biomass after 6 weeks of application based on PLFA concentrations. Concurrent changes in PLFA distribution further indicated a response to cyclodextrin. Changes in PLFA concentration and distribution were concurrent with isotopic enrichment of PLFA in treated columns. This isotopic enrichment provided direct evidence for microbial consumption of cyclodextrin. Incorporation of 13C enriched

  11. Surface-immobilized pyridine-functionalized gamma-cyclodextrin: alkanethiol co-adsorption-induced reorientation.

    PubMed

    Mallon, Colm T; Forster, Robert J; McNally, Andrea; Campagnoli, Elena; Pikramenou, Zoe; Keyes, Tia E

    2007-06-19

    Monolayers of di-6A,6B-deoxy-6-(4-pyridylmethyl)amino-gamma-cyclodextrin (gamma-CD-(py)2) have been formed on polycrystalline platinum electrodes and investigated using electrochemical and surface-enhanced Raman spectroscopy (SERS). The behavior of self-assembled monolayers of (gamma-CD-(py)2) alone, (gamma-CD-(py)2) backfilled with 1-nonanethiol, and 1-nonanethiol are reported. The potential dependence of the capacitance indicates that the film capacitance is higher for the backfilled CD layers than for 1-nonanethiol layers, most likely due to ion flux through the CD cavity. SERS spectra of the backfilled layer exhibit features associated with both pyridine-functionalized CD and alkane moieties. Investigations using [Fe(CN)6]4- as a solution-phase probe indicate that the backfilled CD-alkane thiol layer exhibits enhanced blocking properties compared to gamma-CD-(py)2 films alone. Complete blocking was achieved by a combination of backfilling and insertion of a high-affinity guest 1-adamantylamine into the cavity. Significantly, an electroactive guest with high affinity for gamma-CD, [Co(biptpy)2]2+, does not exhibit a redox response at the gamma-CD-(py)2 layer but molecular recognition is turned on by backfilling the CD layer with 1-nonanethiol molecules. This switching on of the electrochemical activity suggests that the CD hosts are initially inaccessible but reorientate upon backfilling, exposing the CD opening to solution and permitting a supramolecular host-guest complex to form. The binding of [Co(biptpy)2]2+ to gamma-CD in the backfilled monolayer depends on the bulk concentration of guest and is modeled by the Langmuir isotherm, yielding an association constant for the Co2+ state of 1.45 +/- 0.46 x 105 M-1 and a limiting surface coverage 1.49 +/- 0.25 x 10-11 mol cm-2. The surface coverage of the divalent state is higher than the trivalent state, reflecting the dynamic nature of the inclusion. PMID:17521206

  12. 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.

  13. Buckling in polymer monolayers: Molecular-weight dependence

    SciTech Connect

    Srivastava, S.; Basu, J.K.

    2010-11-12

    We present systematic investigations of buckling in Langmuir monolayers of polyvinyl acetate formed at the air-water interface. On compression the polymer monolayers are converted to a continuous membrane with a thickness of {approx}2-3 nm of well-defined periodicity, {lambda}{sub b}. Above a certain surface concentration the membrane undergoes a morphological transition buckling, leading to the formation of striped patterns. The periodicity seems to depend on molecular weight as per the predictions of the gravity-bending buckling formalism of Milner et al. for fluidlike films on water. However anomalously low values of bending rigidity and Young's modulus are obtained using this formalism. Hence we have considered an alternative model of buckling-based solidlike films on viscoelastic substrates. The values of bending rigidity and Young's modulus obtained by this method, although lower than expected, are closer to the bulk values. Remarkably, no buckling is found to occur above a certain molecular weight. We have tried to explain the observed molecular-weight dependence in terms of the variation in isothermal compressive modulus of the monolayers with surface concentration as well as provided possible explanations for the obtained low values of mechanical properties similar to that observed for ultrathin polymer films.

  14. Reversible lability by in situ reaction of self-assembled monolayers.

    PubMed

    Saavedra, Héctor M; Thompson, Christopher M; Hohman, J Nathan; Crespi, Vincent H; Weiss, Paul S

    2009-02-18

    We describe a new methodology for the fabrication of controllably displaceable monolayers using a carboxyl-functionalized self-assembled monolayer and in situ Fischer esterification, a simple and reversible chemical reaction. Using an 11-mercaptoundecanoic acid monolayer as a model system, we show that in situ esterification results in the creation of subtle chemical and structural defects. These defects promote molecular exchange reactions with n-dodecanethiol molecules, leading to the complete and rapid displacement of the exposed areas. Displacement results in well-ordered crystalline n-dodecanethiolate monolayer films. We also show that the complementary hydrolysis reaction can be employed to quench the reacted monolayer, significantly hindering further displacement. The generality of reversible lability was tested by applying the in situ esterification reaction to the structurally distinct carboxyl-functionalized molecule 3-mercapto-1-adamantanecarboxylic acid. Beyond its applicability to create mixed-composition monolayers, this methodology could be combined with chemical patterning techniques, such as microdisplacement printing, to fabricate complex functional surfaces. PMID:19170497

  15. 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

  16. Epitaxial growth of a single-domain hexagonal boron nitride monolayer.

    PubMed

    Orlando, Fabrizio; Lacovig, Paolo; Omiciuolo, Luca; Apostol, Nicoleta G; Larciprete, Rosanna; Baraldi, Alessandro; Lizzit, Silvano

    2014-12-23

    We investigate the structure of epitaxially grown hexagonal boron nitride (h-BN) on Ir(111) by chemical vapor deposition of borazine. Using photoelectron diffraction spectroscopy, we unambiguously show that a single-domain h-BN monolayer can be synthesized by a cyclic dose of high-purity borazine onto the metal substrate at room temperature followed by annealing at T=1270 K, this method giving rise to a diffraction pattern with 3-fold symmetry. In contrast, high-temperature borazine deposition (T=1070 K) results in a h-BN monolayer formed by domains with opposite orientation and characterized by a 6-fold symmetric diffraction pattern. We identify the thermal energy and the binding energy difference between fcc and hcp seeds as key parameters in controlling the alignment of the growing h-BN clusters during the first stage of the growth, and we further propose structural models for the h-BN monolayer on the Ir(111) surface. PMID:25389799

  17. Formulation and characterisation of beads prepared from natural cyclodextrins and vegetable, mineral or synthetic oils.

    PubMed

    Trichard, L; Fattal, E; Le Bas, G; Duchêne, D; Grossiord, J-L; Bochot, A

    2008-04-16

    A continuous external shaking for 2.5 days of a mixture composed of alpha-cyclodextrin (6%), soybean oil (19.6%) and water (74.4%) resulted in a calibrated lipid carrier namely bead with a high fabrication yield. The purpose of this work was to explore the possibility to substitute alpha-cyclodextrin by other natural cyclodextrins, i.e. beta- and gamma-cyclodextrin and then soybean oil by mineral (Primol) 352 and Marcol 82) or synthetic (Silicon 200) fluid 10, 50 or 100cSt) oils. Beads can be successfully prepared using Marcol 82 with alpha-cyclodextrin and Silicon 50 or 100cSt with gamma-cyclodextrin. The area inside oil/cyclodextrin/water ternary diagram corresponding to bead occurrence was superior for the Marcol 82/alpha-cyclodextrin couple compared to that observed with soybean oil/alpha-cyclodextrin couple. Only a few ratios of Silicon 50 and 100cSt/gamma-cyclodextrin/water led to beads. The combinations which did not induce bead occurrence gave either emulsions, two non-miscible liquids or a solid mixture. Whatever the materials used, beads exhibited similarities: presence of a crystalline organisation and viscoelastic properties. Manufacturing process of paraffin- and silicon-based beads need further optimisation to increase fabrication yield and later on, to take advantages from the high stability of both oils for the formulation of drugs with beads. PMID:18063325

  18. Influence of hydrophilic polymers on the complexation of carbamazepine with hydroxypropyl-β-cyclodextrin.

    PubMed

    Medarević, Djordje; Kachrimanis, Kyriakos; Djurić, Zorica; Ibrić, Svetlana

    2015-10-12

    In this study binary carbamazepine-hydroxypropyl-β-cyclodextrin, as well as ternary carbamazepine-hydroxypropyl-β-cyclodextrin-hydrophilic polymer systems were used to improve dissolution rate of carbamazepine. It has been shown that addition of hydrophilic polymers (Soluplus® and two types of hydroxypropyl methylcellulose-Metolose® 90SH-100 and Metolose® 65SH-1500) significantly increased solubilization capacity of hydroxypropyl-β-cyclodextrin for carbamazepine. Evaluation of carbamazepine-hydroxypropyl-β-cyclodextrin-hydrophilic polymer interactions using molecular modeling techniques showed interactions between carbamazepine, which dissociates from inclusion complexes and hydroxypropyl methylcellulose that can prevent crystallization of dissolved carbamazepine. These results can contribute to better understanding of drug-cyclodextrin-hydrophilic polymer interactions which are still not well understood. After evaluation of carbamazepine solubilization with hydroxypropyl-β-cyclodextrin and hydrophilic polymers, both binary carbamazepine-hydroxypropyl-β-cyclodextrin and ternary carbamazepine-hydroxypropyl-β-cyclodextrin-hydrophilic polymer systems were prepared by spray drying. The results of solid state characterization methods showed amorphous nature of carbamazepine in all spray dried systems, which together with the results of molecular modeling techniques indicates inclusion complex formation. Carbamazepine dissolution rate was significantly improved from spray dried formulations compared to pure drug. Binary carbamazepine-hydroxypropyl-β-cyclodextrin and ternary carbamazepine-hydroxypropyl-β-cyclodextrin-Soluplus® systems exhibited the fastest carbamazepine release, wherein the entire amount of carbamazepine was released during first 5 min. PMID:26255049

  19. Monolayer coated gold nanoparticles for delivery applications

    PubMed Central

    Rana, Subinoy; Bajaj, Avinash; Mout, Rubul; Rotello, Vincent M.

    2011-01-01

    Gold nanoparticles (AuNPs) provide attractive vehicles for delivery of drugs, genetic materials, proteins, and small molecules. AuNPs feature low core toxicity coupled with the ability to parametrically control particle size and surface properties. In this review, we focus on engineering of the AuNP surface monolayer, highlighting recent advances in tuning monolayer structures for efficient delivery of drugs and biomolecules. This review covers two broad categories of particle functionalization, organic monolayers and biomolecule coatings, and discusses their applications in drug, DNA/RNA, protein and small molecule delivery. PMID:21925556

  20. 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.

  1. Mineralized cyclodextrin nanoparticles for sustained protein delivery.

    PubMed

    Sivasubramanian, Maharajan; Thambi, Thavasyappan; Park, Jae Hyung

    2013-09-12

    The extensive therapeutic potential of protein drugs has been severely limited by their instability and short biological half-lives in vivo. To prolong their therapeutic effects, a sustained delivery system is required. In this study, cyclodextrin-based polymeric nanoparticles (CD-NPs), mineralized by calcium phosphate as the diffusion barrier, were developed as a carrier for sustained protein delivery. Spherical CD-NPs were readily prepared by a conjugate, composed of β-CD as the protein-binding moiety and carboxymethyl dextran as the substrate for mineralization in a physiological solution. Owing to the presence of carboxylic acids in CD-NPs, they were effectively mineralized by sequential addition of calcium nitrate and ammonium phosphate. The physicochemical characteristics of mineralized CD-NPs were characterized using FT-IR, thermogravimetric analysis, transmission electron microscopy and energy dispersive X-ray photoelectron spectroscopy. Mineralization reduced CD-NP particle size from 310 nm to 121 nm in PBS (pH 7.4) indicating the formation of compact nanoparticles. Carbonic anhydrase B (CAB), chosen as the model protein, was loaded into the mineralized CD-NPs with a high loading efficiency (80%) by a simple dialysis method. In vitro release tests showed that CAB was completely released from bare CD-NPs in 3 days. Interestingly, the mineralized CD-NPs released CAB in a sustained manner for 21 days, which was due to the stable calcium phosphate barrier inhibiting CAB release. The enzymatic activity of CAB, which was released from the nanoparticles, did not significantly deteriorate compared to native CAB. Overall, mineralized CD-NPs could be a promising carrier for sustained protein delivery. PMID:23911496

  2. 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

  3. 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...

  4. 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...

  5. Cyclodextrins as Protective Agents of Protein Aggregation: An Overview.

    PubMed

    Oliveri, Valentina; Vecchio, Graziella

    2016-06-01

    Cyclodextrins are extensively used in different fields (e.g., catalysis, chromatography, pharma, supramolecular chemistry, bioorganic chemistry, and bioinorganic chemistry), and their applications have been widely reviewed. Their main application in the field of pharmaceutical is as a drug carrier. This review overviews, for the first time, the use of cyclodextrins and their derivatives as antiaggregant agents in a number of proteins (e.g., amyloid-β, insulin, recombinant human growth hormone, prion protein, transthyretin, and α-synuclein) and some multimeric enzymes. There are many diseases that are correlated to protein misfolding and amyloid formation processes affecting numerous organs and tissues. There are over 30 different amyloid proteins and a number of corresponding diseases. Alzheimer's disease is the most common neurodegenerative disease. Treatment of these diseases is still a goal to reach, and many molecules are studied in this perspective. Cyclodextrins have also been studied, and they show great potential; as such, further studies could be very promising. This review aims to be a stimulus for the design of new cyclodextrin derivatives to obtain multifunctional systems with antiaggregant activity. PMID:27037956

  6. 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…

  7. 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...

  8. 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

  9. 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...

  10. 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. PMID:26563470

  11. 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

  12. 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...

  13. 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

  14. 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...

  15. Preparation and characterization of albendazole beta-cyclodextrin complexes.

    PubMed

    Castillo, J A; Palomo-Canales, J; Garcia, J J; Lastres, J L; Bolas, F; Torrado, J J

    1999-12-01

    Albendazole (ABZ), mebendazole (MBZ), and ricobendazole (RBZ) are low-soluble anthelmintic benzimidazole carbamate drugs. To increase their aqueous solubility, three different types of beta-cyclodextrins (CyDs): beta-cyclodextrin (CD), hydroxypropyl-beta-cyclodextrin (HPCD), and methyl-beta-cyclodextrin (MCD) were used. Solubility depended on the type of CyDs. Increased solubility was obtained when the more substituted CyDs (HPCD or MCD) were used instead of nonsubstituted CD. Stability constants were calculated assuming a 1:1 stoichiometry. Calculated stability constant values depended on initial solubility of drug and pH of the medium. Solid ABZ complexes were prepared by coprecipitation and freeze-drying methods. These products were compared with physical mixtures of ABZ and CyDs. The characterization of these products was made by differential scanning calorimetry (DSC) and drug release studies. True inclusion complexes were obtained only by the freeze-drying method. Drug release studies showed that the freeze-dried inclusion complexes increased the solubility rate of ABZ, although a supersaturation effect was observed when drug release studies were performed in nonsink conditions. A bioavailability study on mice was done with a formulation of ABZ:HPCD complex and was compared to a conventional ABZ suspension. A significantly (p < .05) shorter Tmax of absorption was obtained by using the complex formulation. Greater and significant (p < .05) differences for AUC and Cmax were observed. PMID:10612019

  16. 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.

  17. 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.

  18. Enantiomeric Interactions between Liquid Crystals and Organized Monolayers of Tyrosine-Containing Dipeptides

    PubMed Central

    Bai, Yiqun; Abbott, Nicholas L.

    2011-01-01

    We have examined the orientational ordering of nematic liquid crystals (LCs) supported on organized monolayers of dipeptides with the goal of understanding how peptide-based interfaces encode intermolecular interactions that are amplified into supramolecular ordering. By characterizing the orientations of nematic LCs (4-cyano-4′-pentylbiphenyl (5CB) and TL205 (a mixture of mesogens containing cyclohexane-fluorinated biphenyls and fluorinated terphenyls)) on monolayers of either L-cysteine-L-tyrosine, L-cysteine-L-phenylalanine or L-cysteine-L-phosphotyrosine formed on crystallographically textured films of gold, we conclude that patterns of hydrogen bonds generated by the organized monolayers of dipeptides are transduced via macroscopic orientational ordering of the LCs. This conclusion is supported by the observation that the ordering exhibited by the achiral LCs is specific to the enantiomers used to form the dipeptide-based monolayers. The dominate role of the –OH group of tyrosine in dictating the patterns of hydrogen bonds that orient the LCs was also evidenced by the effects of phosphorylation of the tyrosine on the ordering of the LCs. Overall, these results reveal that crystallographic texturing of gold films can direct the formation of monolayers of dipeptides with long-range order, thus unmasking the influence of hydrogen bonding, chirality and phosphorylation on the macroscopic orientational ordering of LCs supported on these surfaces. These results suggest new approaches based on supramolecular assembly for reporting the chemical functionality and stereochemistry of synthetic and biological peptide-based molecules displayed at surfaces. PMID:22091988

  19. Simulations of zwitterionic and anionic phospholipid monolayers.

    PubMed

    Kaznessis, Yiannis N; Kim, Sangtae; Larson, Ronald G

    2002-04-01

    Results of atomistic molecular dynamics simulations of dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol monolayers at the air/water interface are presented. Dipalmitoylphosphatidylcholine is zwitterionic and dipalmitoylphosphatidylglycerol is anionic at physiological pH. NaCl and CaCl2 water subphases are simulated. The simulations are carried out at different surface densities, and a simulation cell geometry is chosen that greatly facilitates the investigation of phospholipid monolayer properties. Ensemble average monolayer properties calculated from simulation are in agreement with experimental measurements. The dependence of the properties of the monolayers on the surface density, the type of the headgroup, and the ionic environment are explained in terms of atomistically detailed pair distribution functions and electron density profiles, demonstrating the strength of simulations in investigating complex, multicomponent systems of biological importance. PMID:11916834

  20. 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

  1. 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)

  2. 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.

  3. Unusual Cyclodextrin Derivatives as a New Avenue to Modulate Self- and Metal-Induced Aβ Aggregation.

    PubMed

    Oliveri, Valentina; Bellia, Francesco; Pietropaolo, Adriana; Vecchio, Graziella

    2015-09-28

    Mounting evidence suggests an important role of cyclodextrins in providing protection in neurodegenerative disorders. Metal dyshomeostasis is reported to be a pathogenic factor in neurodegeneration because it could be responsible for damage involving oxidative stress and protein aggregation. As such, metal ions represent an effective target. To improve the metal-binding ability of cyclodextrin, we synthesized three new 8-hydroxyquinoline-cyclodextrin conjugates with difunctionalized cyclodextrins. In particular, the 3-difunctionalized regioisomer represents the first example of cyclodextrin with two pendants at the secondary rim, resulting in a promising compound. The derivatives have significant antioxidant capacity and the powerful activity in inhibiting self-induced amyloid-β aggregation seems to be led by synergistic effects of both cyclodextrin and hydroxyquinoline. Moreover, the derivatives are also able to complex metal ions and to inhibit metal-induced protein aggregation. Therefore, these compounds could have potential as therapeutic agents in diseases related to protein aggregation and metal dyshomeostasis. PMID:26298549

  4. Exciton Binding Energy of Monolayer WS2

    PubMed Central

    Zhu, Bairen; Chen, Xi; Cui, Xiaodong

    2015-01-01

    The optical properties of monolayer transition metal dichalcogenides (TMDC) feature prominent excitonic natures. Here we report an experimental approach to measuring the exciton binding energy of monolayer WS2 with linear differential transmission spectroscopy and two-photon photoluminescence excitation spectroscopy (TP-PLE). TP-PLE measurements show the exciton binding energy of 0.71 ± 0.01 eV around K valley in the Brillouin zone. PMID:25783023

  5. STM studies of synthetic peptide monolayers

    SciTech Connect

    Bergeron, David J.; Clauss, Wilfried; Johnson, Alan T.; Pilloud, Denis L.; Leslie Dutton, P.

    1998-08-11

    We have used scanning probe microscopy to investigate self-assembled monolayers of chemically synthesized peptides. We find that the peptides form a dense uniform monolayer, above which is found a sparse additional layer. Using scanning tunneling microscopy, submolecular resolution can be obtained, revealing the alpha helices which constitute the peptide. The nature of the images is not significantly affected by the incorporation of redox cofactors (hemes) in the peptides.

  6. Nitrogenated, phosphorated and arsenicated monolayer holey graphenes.

    PubMed

    Yagmurcukardes, Mehmet; Horzum, Seyda; Torun, Engin; Peeters, Francois M; Senger, R Tugrul

    2016-01-28

    Motivated by a recent experiment that reported the synthesis of a new 2D material nitrogenated holey graphene (C2N) [Mahmood et al., Nat. Commun., 2015, 6, 6486], the electronic, magnetic, and mechanical properties of nitrogenated (C2N), phosphorated (C2P) and arsenicated (C2As) monolayer holey graphene structures are investigated using first-principles calculations. Our total energy calculations indicate that, similar to the C2N monolayer, the formation of the other two holey structures are also energetically feasible. Calculated cohesive energies for each monolayer show a decreasing trend going from the C2N to C2As structure. Remarkably, all the holey monolayers considered are direct band gap semiconductors. Regarding the mechanical properties (in-plane stiffness and Poisson ratio), we find that C2N has the highest in-plane stiffness and the largest Poisson ratio among the three monolayers. In addition, our calculations reveal that for the C2N, C2P and C2As monolayers, creation of N and P defects changes the semiconducting behavior to a metallic ground state while the inclusion of double H impurities in all holey structures results in magnetic ground states. As an alternative to the experimentally synthesized C2N, C2P and C2As are mechanically stable and flexible semiconductors which are important for potential applications in optoelectronics. PMID:26744752

  7. 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.

  8. 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

  9. 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

  10. 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. PMID:26824520

  11. Photocatalytic nanolithography of self-assembled monolayers and proteins.

    PubMed

    Ul-Haq, Ehtsham; Patole, Samson; Moxey, Mark; Amstad, Esther; Vasilev, Cvetelin; Hunter, C Neil; Leggett, Graham J; Spencer, Nicholas D; Williams, Nicholas H

    2013-09-24

    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 Ni(2+), 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

  12. Self-assembled monolayers on a ferromagnetic permalloy surface.

    PubMed

    Mattera, Michele; Torres-Cavanillas, Ramón; Prieto-Ruiz, Juan P; Prima-García, Helena; Tatay, Sergio; Forment-Aliaga, Alicia; Coronado, Eugenio

    2015-05-19

    Self-assembled monolayers (SAMs) are nowadays broadly used as surface protectors or modifiers and play a key role in many technological applications. This has motivated the study of their formation in all kind of materials; however, and despite the current interest in molecular spintronics, the study of SAMs on ferromagnetic surfaces remains almost unexplored. In this paper, we report for the first time a methodology for the formation of SAMs of n-alkylphosphonic acids on permalloy in ambient conditions. The formed monolayers have been fully characterized by means of contact angle measurements, atomic force microscopy, X-ray photoelectron spectroscopy, matrix assisted laser desorption ionization time-of-flight mass spectrometry, infrared reflection absorption spectroscopy, and X-ray reflectometry. Additionally, the magnetic stability of the modified permalloy after the solution process required for the SAM formation has been confirmed by magneto-optical Kerr effect magnetometry. Moreover, by means of microcontact printing lithography, very accurate SAM patterns have been transferred onto permalloy surfaces and used as resist mask in a chemical etching process giving rise to submicrometric permalloy surface patterns with potential interest in nanomagnetism, spintronics, and storage technologies. PMID:25919007

  13. 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

  14. 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

  15. Dislocations in Monolayers and Semiconductors.

    NASA Astrophysics Data System (ADS)

    Ren, Qiang

    1995-01-01

    Four different aspects of the properties of dislocations in monolayer and semiconductors have been investigated: (i) Using atomic relaxation techniques, dislocation dipoles of various sizes and orientations have been studied for monolayers with the Lennard-Jones potential (LJP) and the nearest-neighbour piecewise linear force (PLF) interactions. In the WP system the lower energy vacancy dipoles have over a wide range of angles an energy which is mainly a function of the vacancy content of the dipole. There is a competition between the elastic forces and the topological constraints which favour a five-fold coordinate vacancy (FCV) at the centre of each core. For the short range PLF system the lattice usually compresses upon the introduction of a dislocation, a consequence of the soft core of the interaction potential, and interstitial dipoles are lower in energy. For the long range LJP system the dislocations are mobile whereas for the PLF system they are pinned. The relevance of these results to existing theories of melting are discussed. (ii) Using generalized stacking-fault (GSF) energies obtained from first-principles density-functional calculations, a zero-temperature model for dislocations in silicon is constructed within the framework of a Peierls-Nabarro (PN) model. Core widths, core energies, PN pinning energies, and stresses are calculated for various possible perfect and imperfect dislocations. Both shuffle and glide sets are considered. 90^circ partials are shown to have a lower Peierls stress (PS) than 30 ^circ partials in accord with experiment. (iii) We have also studied by atomic relaxation techniques the properties of dislocations in silicon, modelled by the empirical potential of Stillinger and Weber. In order to compare with the preceding calculation no reconstruction is allowed. We find no evidence of dissociation in the shuffle dislocations. Within this model shuffle dislocations glide along their slipping planes. On the other hand, glide sets

  16. 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.

  17. 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. PMID:25909996

  18. 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. PMID:26308145

  19. Functionalized self-assembled monolayers on mesoporous silica nanoparticles with high surface coverage

    PubMed Central

    2012-01-01

    Mesoporous silica nanoparticles (MSNs) containing vinyl-, propyl-, isobutyl- and phenyl functionalized monolayers were reported. These functionalized MSNs were prepared via molecular self-assembly of organosilanes on the mesoporous supports. The relative surface coverage of the organic monolayers can reach up to 100% (about 5.06 silanes/nm2). These monolayer functionalize MSNs were analyzed by a number of techniques including transmission electron microscope, fourier transform infrared spectroscopy, X-ray diffraction pattern, cross-polarized Si29 MAS NMR spectroscopy, and nitrogen sorption measurement. The main elements (i.e., the number of absorbed water, the reactivity of organosilanes, and the stereochemistry of organosilane) that greatly affected the surface coverage and the quality of the organic functionalized monolayers on MSNs were fully discussed. The results show that the proper amount of physically absorbed water, the use of high active trichlorosilanes, and the functional groups with less steric hindrance are essential to generate MSNs with high surface coverage of monolayers. PMID:22720819

  20. 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.

  1. 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

  2. Phase-Specific Diffusivity of DPPG Monolayers

    NASA Astrophysics Data System (ADS)

    Dewitt, Joel; Thapa, Prem; Flanders, Bret

    2004-03-01

    The primary role of lung surfactant is to reduce the alveolar surface tension during exhalation in a reversible manner. Failure to do so results in respiratory distress syndrome. Model lung surfactants provide simplified systems for studying the mechanisms that underlie this essential role of alveolar surfactant. Dipalmitoyl-phosphatidylglycerol (DPPG) monolayers exhibit reversible folding when compressed to a critical surface tension. This process may exemplify how the compression-expansion cycle attains reversibility and, thus, requires penetrating study. The buckling theory for reversible collapse provides a promising though untested description of this process, but poor knowledge of domain boundary widths in DPPG monolayers impedes the evaluation of this theory as a model for the observed behavior. In turn, the measurement of the domain boundary widths requires knowledge of the phase-specific viscosities of the monolayer. In this study, multi-particle tracking has been used to determine the phase-specific diffusion coefficients of polystyrene spheres embedded in DPPG monolayers. By invoking a Stokes-Einstein relationship that is appropriate for spheres diffusing in a viscous surfactant, the phase specific viscosities of the monolayers have been estimated. The rationale for this work is that this knowledge will promote the quantitative evaluation of buckling as a model for reversible folding and, thus, promote growth in understanding of the folding mechanism in model lung surfactants.

  3. 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

  4. 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. PMID:25129728

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. Fluorescent H-Aggregates Hosted by a Charged Cyclodextrin Cavity.

    PubMed

    Mudliar, Niyati H; Singh, Prabhat K

    2016-05-23

    Most macrocyclic host molecules, including cyclodextrins, usually prevent self-aggregation of the guest organic molecules, by exploiting inclusion complexation of the guest with the host. In this work, it was found that a negatively charged β-cylcodextrin derivative induces aggregation of a well-known amyloid sensing dye, Thioflavin-T, and leads to an unprecedented formation of the rarely observed emissive H-type aggregates of the dye. PMID:27028039

  10. Formation of supramolecular permethrin/β-cyclodextrin nanorods

    NASA Astrophysics Data System (ADS)

    Yang, Guang-Fu; Wang, Hong-Bo; Yang, Wen-Chao; Gao, Daquan; Zhan, Chang-Guo

    2006-09-01

    Molecular dynamics simulations along with scanning tunneling microscopy (STM) imaging demonstrate the formation of a novel type of nanorods, with a stable [permethrin(β-CD)2]n structure in which the host:guest ratio is 2:1 and n =21-27 giving a length of ˜30.0-38.5nm and an average diameter of ˜1.5nm, self-assembled from an inclusion complex composed of permethrin and biocompatible β-cyclodextrin.

  11. 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. PMID:23265490

  12. Catalytic beta-cyclodextrin enzyme mimics as soman hydrolases

    SciTech Connect

    Seltzman, H.H.; Lonikar, M.S.

    1993-05-13

    The use of chemically accessible artificial enzymes as in vivo scavengers of soman offers an attractive approach for protecting the soldier from the debilitating and often fatal effects of this organophosphate poison. The ability of modified B-cyclodextrins to scavenge soman both in vitro and in vivo has been demonstrated. These enzyme mimics however are stoichiometric in their reaction, consuming and being consumed by one molecule of soman. The ability to inactivate multiple soman molecules, that is to function as a true catalytic enzyme, would further enhance scavenging by a factor that would be proportional to the turnover rate. We now report the synthesis and activity of a series of iodosobenzoic acid-B-cyclodextrin conjugates (IBA-BCD) that catalytically hydrolyzes soman. Two assays for enzyme like activity were conducted. The first for enhanced scavenging ability demonstrated that the IBA-BCD conjugates enhanced the scavenging of soman by nearly three orders of magnitude in a structure dependent manner compared to soman scavenging by BCD. The second assay, for catalytic activity, demonstrated that the tested compounds were able to scavenge a stoichiometric excess of soman (with turnover rates in the range of 5 to 13 mole soman/mole mimic/min). This is in contrast to stoichiometric scavengers, tested as controls, that were able to scavenge only one soman per cyclodextrin molecule.

  13. Development of Orodispersible Tablets of Candesartan Cilexetil- β -cyclodextrin Complex.

    PubMed

    Sravya, Maddukuri; Deveswaran, Rajamanickam; Bharath, Srinivasan; Basavaraj, Basappa Veerbadraiah; Madhavan, Varadharajan

    2013-01-01

    The aim of this study was to investigate the use of inclusion complexation technique employing β-cyclodextrin in improving the dissolution profile of candesartan cilexetil, a BCS class-II drug, and to formulate the inclusion complex into orodispersible tablets. The inclusion complexes were formed by physical mixing, kneading, coevaporation, and lyophilisation methods. Inclusion complexes were characterized by FTIR, DSC, XRD, NMR, and mass spectral studies. Inclusion complexes prepared using kneading, and lyophilisation techniques in the molar ratio 1 : 5 with β-cyclodextrin were used for formulating orodispersible tablets by direct compression with different superdisintegrants like croscarmellose sodium, crospovidone, sodium starch glycolate, and low substituted hydroxypropyl cellulose in varying concentrations. The directly compressible powder was evaluated for precompression parameters, and the prepared orodispersible tablets were evaluated for postcompression parameters. Drug-excipient compatibility studies showed no interaction, and characterization proved the formation of inclusion complex. In vitro disintegration time was found to be within 3 minutes, and all the formulations showed complete drug release of 100% within 20 minutes. The optimized formulation was found to be stable after 6 months and showed no significant change in drug content. This work proved β-cyclodextrins to be effective solubilizing agent in improving the solubility of poorly water soluble drugs. PMID:26555987

  14. 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

  15. 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

  16. 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

  17. 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.

  18. Giant piezoelectricity of monolayer group IV monochalcogenides

    NASA Astrophysics Data System (ADS)

    Fei, Ruixiang; Li, Wenbin; Li, Ju; Yang, Li

    We predict enormous, anisotropic piezoelectric effects in intrinsic monolayer group IV monochalcogenides (MX, M =Sn or Ge, X =Se or S), including SnSe, SnS, GeSe, and GeS. Using first-principle simulations based on the modern theory of polarization, we find that their piezoelectric coefficients are about one to two orders of magnitude larger than those of other 2D materials, such as MoS2 and GaSe, and bulk quartz and AlN which are widely used in industry. This enhancement is a result of the unique ``puckered'' C2v symmetry and electronic structure of monolayer group IV monochalcogenides. Given the achieved experimental advances in the fabrication of monolayers, their flexible character, and ability to withstand enormous strain, these 2D structures with giant piezoelectric effects may be promising for a broad range of applications such as nano-sized sensors, piezotronics, and energy harvesting in portable electronic devices.

  19. 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

  20. 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.

  1. 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

  2. Solubilization of ibuprofen with β-cyclodextrin derivatives: energetic and structural studies.

    PubMed

    di Cagno, Massimiliano; Stein, Paul C; Skalko-Basnet, Nataša; Brandl, Martin; Bauer-Brandl, Annette

    2011-06-01

    The aim of this work was to investigate the complexation of ibuprofen as model drug with various β-cyclodextrins (native β-cyclodextrin, hydroxypropyl-β-cyclodextrin with two different molar degrees of substitution, and methyl-β-cyclodextrin). Solutions of the commercially available β-cyclodextrins were prepared in phosphate buffer (73mM). The pH value was adjusted to 7.4 and the solutions were isotonized with NaCl. A solution of ibuprofen was prepared in the same way. A thermal activity monitor was used for isothermal titration calorimetry (ITC). (1)H NMR analysis was employed to investigate the structures of the complexes. ITC analysis showed that each type of β-cyclodextrin had its characteristic values of both enthalpy and mass equilibrium constant for the complexation processes with the drug molecules. (1)H NMR spectroscopy of the complexes showed through significant differences in chemical shifts that the physical interaction between the cyclodextrins and ibuprofen molecules were also different, probably due to different three-dimensional arrangements of ibuprofen in the cyclodextrin cavity, induced by the different substituents bonded to the glucose rings. These differences were connected to the thermodynamic parameters of the complexes. PMID:21411261

  3. 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-...

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

    PubMed

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

    2016-12-01

    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. PMID:27033850

  5. Response surface methodology to optimize novel fast disintegrating tablets using β cyclodextrin as diluent.

    PubMed

    Late, Sameer G; Banga, Ajay K

    2010-12-01

    The objective of this work was to apply response surface approach to investigate main and interaction effects of formulation parameters in optimizing novel fast disintegrating tablet formulation using β cyclodextrin as a diluent. The variables studied were diluent (β cyclodextrin, X (1)), superdisintegrant (Croscarmellose sodium, X (2)), and direct compression aid (Spray dried lactose, X (3)). Tablets were prepared by direct compression method on B2 rotary tablet press using flat plain-face punches and characterized for weight variation, thickness, disintegration time (Y (1)), and hardness (Y (2)). Disintegration time was strongly affected by quadratic terms of β cyclodextrin, croscarmellose sodium, and spray-dried lactose. The positive value of regression coefficient for β cyclodextrin suggested that hardness increased with increased amount of β cyclodextrin. In general, disintegration of tablets has been reported to slow down with increase in hardness. However in the present study, higher concentration of β cyclodextrin was found to improve tablet hardness without increasing the disintegration time. Thus, β cyclodextrin is proposed as a suitable diluent to achieve fast disintegrating tablets with sufficient hardness. Good correlation between the predicted values and experimental data of the optimized formulation validated prognostic ability of response surface methodology in optimizing fast disintegrating tablets using β cyclodextrin as a diluent. PMID:21086083

  6. 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. PMID:25743620

  7. 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.

  8. Aripiprazole-Cyclodextrin Binary Systems for Dissolution Enhancement: Effect of Preparation Technique, Cyclodextrin Type and Molar Ratio

    PubMed Central

    M. Badr-Eldin, Shaimaa; A. Ahmed, Tarek; R Ismail, Hatem

    2013-01-01

    Objective(s): The aim of this work was to investigate the effect of the natural and the chemically modified form of cyclodextrins namely; β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD) respectively on the solubility and dissolution rate of aripiprazole; an antipsychotic medication showing poor aqueous solubility. Materials and Methods: Phase solubility of aripiprazole with the studied CDs and the complexation efficiency values (CE) which reflect the solubilizing power of the CDs towards the drug was performed. Solid binary systems of aripiprazole with CDs were prepared by kneading, microwave irradiation and freeze-drying techniques at 1:1 and 1:2 (drug to CD) molar ratios. Drug-CD physical mixtures were also prepared in the same molar ratios for comparison. The dissolution of aripiprazole-binary systems was carried out to select the most appropriate CD type, molar ratio and preparation technique. Results: Phase solubility study indicated formation of higher order complexes and the complexation efficiency values was higher for HP-β-CD compared to β-CD. Drug dissolution study revealed that aripiprazole dissolution was increased upon increasing the CD molar ratio and, the freeze-drying technique was superior to the other studied methods especially when combined with the HP-β-CD. The cyclodextrin type, preparation technique and molar ratio exhibited statistically significant effect on the drug dissolution at P≤ 0.05. Conclusion: The freeze-dried system prepared at molar ratio 1:2 (drug: CD) can be considered as efficient tool for enhancing aripiprazole dissolution with the possibility of improving its bioavailability. PMID:24570827

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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).

  16. 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.

  17. Valley Polarization in Size-Tunable Monolayer Semiconductor Quantum Dots

    NASA Astrophysics Data System (ADS)

    Wei, Guohua; Czaplewski, David A.; Jung, Il Woong; Lenferink, Erik J.; Stanev, Teodor K.; Stern, Nathaniel P.

    Controlling the size of semiconductor nanostructures allows manipulation of the optical and electrical properties of band carriers. We show that laterally-confined monolayer MoS2 quantum dots can be created through top-down nanopatterning of an atomically-thin two-dimensional semiconductor. Semiconductor-compatible nanofabrication processing allows for these low-dimensional materials to be integrated into complex systems that harness their controllable optical properties. Size-dependent exciton energy shifts and linewidths are observed, demonstrating the influence of quantum confinement. The patterned dots exhibit the same valley polarization characteristics as in a continuous MoS2 sheet, suggesting that monolayer semiconductor quantum dots could have potential for advancing quantum information applications. This work is supported by ISEN, the DOE-BES (DE-SC0012130), the NSF MRSEC program (DMR-1121262), and the Center for Nanoscale Materials, DOE-BES (DE-AC02-06CH11357). N.P.S. is an Alfred P. Sloan Research Fellow.

  18. Cyclodextrin-promoted Diels Alder reactions of a polycyclic aromatic hydrocarbon under mild reaction conditions

    PubMed Central

    Chaudhuri, Sauradip; Phelan, Tyler; Levine, Mindy

    2015-01-01

    Reported herein is the effect of cyclodextrins on the rates of aqueous Diels Alder reactions of 9-anthracenemethanol with a variety of N-substituted maleimides. These reactions occurred under mild reaction conditions (aqueous solvent, 40 °C), and were most efficient for the reaction of N-cyclohexylmaleimide with a methyl-β-cyclodextrin additive (94% conversion in 24 hours). These results can be explained on the basis of a model wherein the cyclodextrins bind the hydrophobic substituents on the maleimides and activate the dienophile via electronic modulation of the maleimide double bond. The results reported herein represent a new mechanism for cyclodextrin-promoted Diels Alder reactions, and have significant potential applications in the development of other cyclodextrin-promoted organic transformations. Moreover, the ability to deplanarize polycyclic aromatic hydrocarbons (PAHs) under mild conditions, as demonstrated herein, has significant applications for PAH detoxification. PMID:26692588

  19. Investigation of the interactions between the hydrophobic cavities of cyclodextrins and pullulanase.

    PubMed

    Yu, Bo; Wang, Jinpeng; Zhang, Huanxin; Jin, Zhengyu

    2011-01-01

    The effects of cyclodextrins and derivatives on the activity and structure of pullulanase were investigated in this study. Our results showed that cyclodextrins and derivatives decreased the activity of pullulanase. This decrease was attributed to the interaction between the hydrophobic cavities of cyclodextrins and pullulanase. The hydrophobic cavity was confirmed to encapsulate the groups of pullulanase molecules by the addition of competitive guests. The results obtained from fluorescence spectroscopy analysis showed that β-CD showed more efficient interactions with pullulanase molecules and the side chain groups of cyclodextrin significantly prevented the interaction between the hydrophobic cavities of β-CD and pullulanase molecules. These findings suggest that the geometric dimension of hydrophobic cavities was crucial for matching between cyclodextrins and pullulanase and steric hindrance caused by side chains led to the decrease of the interaction. PMID:21475123

  20. 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.

  1. Combining Raman and infrared spectroscopy as a powerful tool for the structural elucidation of cyclodextrin-based polymeric hydrogels.

    PubMed

    Venuti, V; Rossi, B; D'Amico, F; Mele, A; Castiglione, F; Punta, C; Melone, L; Crupi, V; Majolino, D; Trotta, F; Gessini, A; Masciovecchio, C

    2015-04-21

    A detailed experimental and theoretical vibrational analysis of hydrogels of β-cyclodextrin nanosponges (β-CDNS), obtained by polymerization of β-cyclodextrin (β-CD) with the cross-linking agent ethylenediaminetetraacetic acid (EDTA), is reported here. Thorough structural characterization is achieved by exploiting the complementary selection rules of FTIR-ATR and Raman spectroscopies and by supporting the spectral assignments by DFT calculations of the spectral profiles. The combined analysis of the FTIR-ATR spectra of the polymers hydrated with H2O and D2O allowed us to isolate the HOH bending of water molecules not involved in symmetrical, tetrahedral environments. The analysis of the HOH bending mode was carried out as a function of temperature, showing the existence of a supercooled state of the water molecules. The highest level of cooperativity of the hydrogen bond scheme was reached at a value of the β-CD/EDTA molar ratio n = 6. Finally, the connectivity pattern of "uncoupled" water molecules bound to the nanosponge backbone was found to be weakened by increasing T. The temperature above which the population of non-tetracoordinated water molecules becomes predominant turned out to be independent of the parameter n. PMID:25798878

  2. 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

  3. Comparison of charge state distribution in commercially available sulfated cyclodextrins used as chiral resolving agents in capillary electrophoresis.

    PubMed

    Estrada, Roy; Vigh, Gyula

    2012-02-24

    The charge state distributions of randomly sulfated cyclodextrins from Sigma-Aldrich and Beckman-Coulter, as well as single isomer sulfated cyclodextrins from TM Chemicals LP were investigated using hydrophilic interaction liquid chromatography (HILIC). A cross-linked diol phase and an unbonded silica phase were used as HILIC stationary phases. Groups of sulfated cyclodextrins with different charge states were resolved from each other, while regioisomers in a charge group were partially separated. A ladder of sulfated cyclodextrins having a charge state distribution from 1 to 14 was prepared and was used to determine the charge state heterogeneity of the commercially available sulfated cyclodextrin samples. Wide charge state and regioisomer distributions are seen for the randomly sulfated cyclodextrins, while HILIC analysis of every single isomer sulfated cyclodextrin sample indicates the presence of a single species. PMID:21872870

  4. 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

  5. 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.

  6. 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

  7. 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.

  8. Optical spectroscopy of organic semiconductor monolayers

    NASA Astrophysics Data System (ADS)

    He, Rui; Tassi, Nancy G.; Blanchet, Graciela B.; Pinczuk, Aron

    2011-02-01

    Growing interest in organic molecular semiconductors is stimulated by their promising applications in flexible devices. Pentacene is a benchmark organic semiconductor material because of its potential applications in high mobility thin film transistors and optoelectronic devices. Highly uniform monolayers of pentacene grown on polymeric substrate of poly alpha-methylstyrene exhibit sharp and intense free exciton (FE) luminescence at low temperatures. The FE emission displays characteristic intensity that grows quadratically with the number of layers. Large enhancements of Raman scattering intensities at the FE resonance enable the first observations of low-lying lattice vibrational modes in films reaching the single monolayer level. The low-lying modes exhibit characteristic changes when going from a single monolayer to two layers, revealing that a phase akin to a thin film phase of pentacene already emerges in structures of only two monolayers. A simple analysis of mode splittings offers estimates of the strength of inter-layer interactions. The results demonstrate novel venues for ultra-thin film characterization and studies of interface effects in organic molecular semiconductor structures.

  9. Optical spectroscopy of organic semiconductor monolayers

    NASA Astrophysics Data System (ADS)

    He, Rui; Tassi, Nancy G.; Blanchet, Graciela B.; Pinczuk, Aron

    2010-10-01

    Growing interest in organic molecular semiconductors is stimulated by their promising applications in flexible devices. Pentacene is a benchmark organic semiconductor material because of its potential applications in high mobility thin film transistors and optoelectronic devices. Highly uniform monolayers of pentacene grown on polymeric substrate of poly alpha-methylstyrene exhibit sharp and intense free exciton (FE) luminescence at low temperatures. The FE emission displays characteristic intensity that grows quadratically with the number of layers. Large enhancements of Raman scattering intensities at the FE resonance enable the first observations of low-lying lattice vibrational modes in films reaching the single monolayer level. The low-lying modes exhibit characteristic changes when going from a single monolayer to two layers, revealing that a phase akin to a thin film phase of pentacene already emerges in structures of only two monolayers. A simple analysis of mode splittings offers estimates of the strength of inter-layer interactions. The results demonstrate novel venues for ultra-thin film characterization and studies of interface effects in organic molecular semiconductor structures.

  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. Subpicomolar Iron Sensing Platform Based on Functional Lipid Monolayer Microarrays.

    PubMed

    Kenaan, Ahmad; Nguyen, Tuyen D; Dallaporta, Hervé; Raimundo, Jean-Manuel; Charrier, Anne M

    2016-04-01

    We report herein the fabrication of novel microarrays based on air-stable functional lipid monolayers over silicon using a combination of e-beam lithography and lift-off. We demonstrate these microarrays can be use as ultrasensitive platform for Kelvin probe force microscopy in sensing experiments. Specificity of the detection is given by the functional group grafted at the lipid headgroup. The arrays developed for the detection of ferric ions, Fe(3+), using a γ-pyrone derivative chelator, demonstrate subpicomolar limit of detection with high specificity. In addition, the technique takes advantage of the structure of the array with the silicon areas playing the role of reference for the measurement, and we determine critical pattern dimensions below which the probe size/shape impacts the measured results. PMID:26974586

  12. 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.

  13. 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.

  14. Preparation of solid drug/cyclodextrin complexes of acidic and basic drugs.

    PubMed

    Loftsson, T; Sigurdsson, H H; Másson, M; Schipper, N

    2004-01-01

    One of the main obstacles in pharmaceutical applications of cyclodextrins is their increase of the formulation bulk. Even at maximum incorporation 500 mg of a solid drug/cyclodextrin complex will only contain between 50 and 125 mg of the drug, assuming a low molecular weight drug (MW 200 to 400 Dalton) and an average molecular weight cyclodextrin (MW about 1500 Dalton). In general, the complexation efficiency is low and consequently the complex powder contains a significant amount of empty cyclodextrin molecules. In the present study the complexation efficiency is increased by ionization of the drug molecule through addition of volatile acid (i.e. acetic acid) or base (i.e. ammonia) to the aqueous complexation media of basic or acidic drugs, respectively. The volatile acid or base was then removed during lyophilization and heating in a vacuum oven resulting in formation of solid cyclodextrin complexes of the unionized drug. Thus, the complexation efficiency was temporary increased by the ionization but then again decreased leading to formation of the thermodynamically unstable solid drug/cyclodextrin complexes. When dissolved the energy of the system was lowered by expelling the drug molecules from the cyclodextrin cavities resulting in formation of supersaturated drug solutions and ultimately precipitation of the drug. PMID:14964417

  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. Use of cyclodextrins to manipulate plasma membrane cholesterol content: evidence, misconceptions and control strategies

    PubMed Central

    Zidovetzki, Raphael

    2007-01-01

    The physiological importance of cholesterol in the cell plasma membrane has attracted increased attention in recent years. Consequently, the use of methods of controlled manipulation of membrane cholesterol content has also increased sharply, especially as a method of studying putative cholesterol-enriched cell membrane domains (rafts). The most common means of modifying the cholesterol content of cell membranes is the incubation of cells or model membranes with cyclodextrins, a family of compounds, which, due to the presence of relatively hydrophobic cavity, can be used to extract cholesterol from cell membranes. However, the mechanism of this activity of cyclodextrins is not completely established. Moreover, under conditions commonly used for cholesterol extraction, cyclodextrins may remove cholesterol from both raft and non-raft domains of the membrane as well as alter the distribution of cholesterol between plasma and intracellular membranes. In addition, other hydrophobic molecules such as phospholipids may also be extracted from the membranes by cyclodextrins. We review the evidence for the specific and non-specific effects of cyclodextrins and what is known about the mechanisms for cyclodextrin-induced cholesterol and phospholipid extraction. Finally, we discuss useful control strategies that may help to verify that the observed effects are due specifically to cyclodextrin-induced changes in cellular cholesterol. PMID:17493580

  17. Superstructures of fluorescent cyclodextrin via click-reaction.

    PubMed

    Maciollek, Arkadius; Ritter, Helmut; Beckert, Rainer

    2013-01-01

    Mono-(6-azido-6-deoxy)-β-cyclodextrin (CD) was covalently attached to an alkyne-modified 5-methyl-2-(pyridin-2-yl)thiazol-4-ol yielding a fluorophore containing CD in a click-type reaction. Intermolecular complexes were formed by poly(host-guest)-interactions. The supramolecular structures were characterized by (1)H NMR-ROESY spectroscopy, dynamic light scattering, UV-vis spectroscopy, fluorescence spectroscopy, and asymmetric flow field-flow fractionation. By adding potassium adamantane-1-carboxylate, the thiazol dye is displaced from the CD-cavity and the elongated noncovalent polymeric structures collapse. PMID:23766796

  18. Electric-field modulation of liquid crystal structures in contact with structured surfactant monolayers.

    PubMed

    Guillamat, Pau; Sagués, Francesc; Ignés-Mullol, Jordi

    2014-05-01

    We present experiments in which we use an electric field to switch between different configurations in the cellular patterns induced in a confined nematic liquid crystal by the contact with a surfactant monolayer that features lateral order and surface defects. By using different combinations of far-field alignment and mesogen dielectric anisotropy, we unravel the nature and stability of point defects and disclinations resulting from the hybrid boundary conditions. PMID:25353818

  19. Influence of Surface Morphology on the Shear-Induced Wear of Alkylsilane Monolayers: Molecular Dynamics Study.

    PubMed

    Summers, Andrew Z; Iacovella, Christopher R; Billingsley, Matthew R; Arnold, Steven T; Cummings, Peter T; McCabe, Clare

    2016-03-15

    Chemisorbed alkylsilane monolayer coatings have been shown to possess favorable lubrication properties; however, film degradation prevents the widespread use of these materials as lubricants in micro- and nanoelectromechanical systems (MEMS/NEMS). In this work, molecular dynamics (MD) simulations are used to provide insight into the conditions that promote the degradation and wear of these materials. This is achieved through removal of interfacial chain-substrate bonds during shear and the examination of the mobility of the resulting free, unbound chains. Specific focus is given to the effects of surface morphology, which has been shown previously to strongly influence frictional forces in monolayer systems. In-plane order of chain attachments is shown to lead to pressure-induced orientational ordering of monolayers, promoting film stability. This behavior is lost as nonideality is introduced into the substrate and chain patterning on the surface becomes disordered. The presence of surface roughness is found to reduce film stability, with localization of wear observed for chain attachment sites nearest the interface of contact. The influence of substrate nonideality on monolayer degradation is shown to diminish as chain length is increased. PMID:26885941

  20. 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

    2015-01-01

    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. PMID:25630052

  1. 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

  2. [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. PMID:25532345

  3. 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

  4. 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

  5. Multi-terminal Monolayer WSe2 devices

    NASA Astrophysics Data System (ADS)

    Zhao, Wenjin; Palomaki, Tauno; Finney, Joe; Fei, Zaiyao; Nguyen, Paul; McKay, Frank; Cobden, David

    Two-dimensional transition-metal dichalcogenide (TMD) semiconductors are promising materials for next-generation electronic and optoelectronic devices. WSe2 in particular has shown excellent optical properties, but it has proven difficult to make reliable electrical contacts to this material. We use a new chemical vapor deposition technique to grow monolayer single crystal WSe2 reliably on a large scale with edges up to 15 microns long. We then fabricate these crystals into multi-terminal devices encapsulated in boron nitride using dry transfer techniques. We achieve sufficiently good electrical contacts reproducibly to allow comprehensive study of the intrinsic optical and electrical properties of gated WSe2 monolayers as a function of temperature and magnetic field.

  6. Trion dynamics in Transition Metal Dichalcogenide Monolayers

    NASA Astrophysics Data System (ADS)

    Singh, Akshay; Tran, Kha; Wu, Sanweng; Ross, Jason; Moody, Galan; Xu, Xiaodong; Li, Elaine

    2015-03-01

    Transition Metal Dichalcogenides (TMD's) in the monolayer limit, exhibit interesting phenomena including increased photoluminescence, spin-valley coupling and many-body effects. Excitons (bound electron-hole pairs) and trions (charged excitons) in these materials have unusually large binding energy and dominate the optical response near the band gap. In particular, trions can drift under application of an electric field and have higher spin lifetimes increasing applications in quantum spin models. We study the temporal dynamics of excitons and trions including their formation and lifetimes using time resolved two-color pump-probe spectroscopy on a monolayer TMD (MoSe2). Trions are observed to have vastly different temporal dynamics with much slower decay than excitons. We also observe rapid formation of trions when resonantly pumped while a slow rise (in temporal response) is seen for other excitation energies. We suggest that localization of trions needs to be taken into account to explain these observations.

  7. 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

  8. Transport measurement of Li doped monolayer graphene

    NASA Astrophysics Data System (ADS)

    Khademi, Ali; Sajadi, Ebrahim; Dosanjh, Pinder; Folk, Joshua; Stöhr, Alexander; Forti, Stiven; Starke, Ulrich

    Lithium adatoms on monolayer graphene have been predicted to induce superconductivity with a critical temperature near 8 K, and recent experimental evidence by ARPES indicates a critical temperature nearly that high. Encouraged by these results, we investigated the effects of lithium deposited at cryogenic temperatures on the electronic transport properties of epitaxial and CVD monolayer graphene down to 3 K. The change of charge carrier density due to Li deposition was monitored both by the gate voltage shift of the Dirac point and by Hall measurements, in low and high doping regimes. In the high doping regime, a saturation density of 2×1013 cm-2 was observed independent of sample type, initial carrier density and deposition conditions. No signatures of superconductivity were observed down to 3 K.

  9. Molecular recognition in gels, monolayers, and solids

    NASA Astrophysics Data System (ADS)

    Prime, Kevin L.; Chu, Yen-Ho; Schmid, Walther; Seto, Christopher T.; Chen, James K.

    1991-12-01

    This paper describes work in four areas: affinity electrophoresis of carbonic anhydrase in cross-linked polyacrylamide derived gels containing immobilized derivatives of aryl sulfonamides; inhibition of the hemagglutination of erythrocytes induced by influenza virus using water-soluble polyacrylamides bearing sialic acid groups; the application of self-assembled monolayers (SAMs) of alkyl thiolates on gold to the study of protein adsorption on organic surfaces; and the use of networks of hydrogen bonds to generate new classes of non-covalently assembled organic materials, both in solution and in crystals. This paper summarizes research in two areas of molecular recognition: affinity polymers and molecular self assembly. We illustrate these areas by examples drawn from affinity gel electrophoresis, soluble synthetic macromolecular inhibitors of binding of influenza virus to erythrocytes protein adsorption on self assembled monolayers and self assembling hydrogen bonded molecular aggregates.

  10. 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

  11. Single photon ionisation of self assembled monolayers

    NASA Astrophysics Data System (ADS)

    King, B. V.; Savina, M. R.; Tripa, C. E.; Calaway, W. F.; Veryovkin, I. V.; Moore, J. F.; Pellin, M. J.

    2002-05-01

    Self assembled monolayers formed from benzenethiol, diphenylsulphide and diphenyldisulphide have been analysed using secondary ion mass spectrometry (SIMS), sputter neutral mass spectrometry (SNMS) and laser desorption photoionisation mass spectrometry (LDPI). The peak corresponding to the parent ion was much stronger in LDPI than with SIMS or SNMS analysis and fragmentation was lower. A useful yield of order 0.5% was obtained for LDPI from diphenyldisulphide.

  12. 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

  13. 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

  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. 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.

  16. Exploring atomic defects in molybdenum disulphide monolayers.

    PubMed

    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 × 10(13) 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

  17. Biocompatible Ferromagnetic Cr-Trihalide Monolayers

    NASA Astrophysics Data System (ADS)

    Sun, Qiang

    Cr with an electronic configuration of 3d54s1 possesses the largest atomic magnetic moment (6µB) of all elements in the 3d transition metal series. Furthermore, the trivalent chromium (Cr3+) is biocompatible and is widely found in food and supplements. Here using first principles calculations combined with Monte Carlo simulations based on Ising model, we systematically study a class of 2D ferromagnetic monolayers CrX3 (X = Cl, Br, I). The feasibility of exfoliation from their layered bulk phase is confirmed by the small cleavage energy and high in-plane stiffness. Spin-polarized calculations, combined with self consistently determined Hubbard U that accounts for strong correlation energy, demonstrate that CrX3 (X =Cl, Br, I) monolayers are ferromagnetic and Cr is trivalent and carries a magnetic moment of 3µB, the resulting Cr3+ ions are biocompatible. The corresponding Curie temperatures for CrCl3 CrBr3 CrI3 are are found to 66, 86, and 107 K, respectively, which can be increased to 323, 314, 293 K by hole doping. The biocompatibility and ferromagnetism render these Cr-containing trichalcogenide monolayers unique for applications.

  18. Robust ferromagnetism in monolayer chromium nitride

    PubMed Central

    Zhang, Shunhong; Li, Yawei; Zhao, Tianshan; Wang, Qian

    2014-01-01

    Design and synthesis of two-dimensional (2D) materials with robust ferromagnetism and biocompatibility is highly desirable due to their potential applications in spintronics and biodevices. However, the hotly pursued 2D sheets including pristine graphene, monolayer BN, and layered transition metal dichalcogenides are nonmagnetic or weakly magnetic. Using biomimetic particle swarm optimization (PSO) technique combined with ab initio calculations we predict the existence of a 2D structure, a monolayer of rocksalt-structured CrN (100) surface, which is both ferromagnetic and biocompatible. Its dynamic, thermal and magnetic stabilities are confirmed by carrying out a variety of state-of-the-art theoretical calculations. Analyses of its band structure and density of states reveal that this material is half-metallic, and the origin of the ferromagnetism is due to p-d exchange interaction between the Cr and N atoms. We demonstrate that the displayed ferromagnetism is robust against thermal and mechanical perturbations. The corresponding Curie temperature is about 675 K which is higher than that of most previously studied 2D monolayers. PMID:24912562

  19. 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

  20. Computational study on the molecular inclusion of andrographolide by cyclodextrin.

    PubMed

    Zhou, Hongwei; Lai, Wai-Ping; Zhang, Zhiqiang; Li, Wai-Kee; Cheung, Hon-Yeung

    2009-03-01

    Due to the poor water solubility of andrographolide (andro), an inclusion technique has been developed to modify its physical and chemical properties so as to improve its bioavailability. In contrast with the immense experimental studies on the inclusion complexes of andro:cyclodextrin, no computational study has so far been carried out on this system. In this work, preliminary docking experiments with AutoDock were performed. Density Functional Theory (DFT) and Austin Model 1 (AM1) calculations upon the docking instances were applied to investigate the two possible modes of molecular inclusions between andro and x-cyclodextrin (xCD, where x is alpha, beta or gamma). Atoms-in-Molecules (AIM) analysis based on the B3LYP/cc-pVDZ wavefunction was applied to verify the existence of the intermolecular hydrogen bonds. It was found that the most stable complex among the six possible inclusion complexes was the one formed between andro and betaCD with andro's decalin ring moiety wrapped by CD at a ratio of 1:1. The hydrogen bonds between andro and CD were responsible for the stability of the inclusion complexes. The calculated data were found to be consistent with the experimental results. Thus, the results of this study can aid new drug design processes. PMID:18841328

  1. 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. PMID:23954237

  2. 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

  3. 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.

  4. 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.

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

    PubMed

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

    2016-04-28

    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. PMID:27074402

  6. 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.

  7. 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

  8. Piroxicam-β-cyclodextrin: a GI safer piroxicam.

    PubMed

    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 to a

  9. 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'.

  10. Effect of β-cyclodextrin on Rheological Properties of some Viscosity Modifiers.

    PubMed

    Rao, G Chandra Sekhara; Ramadevi, K; Sirisha, K

    2014-01-01

    Cyclodextrins are a group of novel excipients, extensively used in the present pharmaceutical industry. Sometimes they show significant interactions with other conventional additives used in the formulation of dosage forms. The effect of β-cyclodextrin on the rheological properties of aqueous solutions of some selected viscosity modifiers was studied in the present work. β-cyclodextrin showed two different types of effects on the rheology of the selected polymers. In case of natural polymers like xanthan gum and guar gum, enhanced apparent viscosity was found and in case of semi-synthetic polymers like sodium carboxymethyl cellulose and methyl cellulose, reduction in apparent viscosity was found. β-cyclodextrin was included at 0.5, 1 and 2% w/v concentrations into the polymeric solutions. These findings are useful in the adjustment of concentrations of viscosity modifiers during the formulation of physically stable disperse systems. PMID:25593389

  11. 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

  12. 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...

  13. 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

  14. 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...

  15. Anion recognition in water by a rotaxane containing a secondary rim functionalised cyclodextrin stoppered axle.

    PubMed

    Řezanka, Michal; Langton, Matthew J; Beer, Paul D

    2015-03-14

    The synthesis of a water soluble [2]rotaxane is reported using hydrophilic secondary rim functionalised permethylated β-cyclodextrin derivatives as the axle stopper groups. The rotaxane recognises halide anions in pure water with impressive selectivity over sulfate. PMID:25682747

  16. 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

  17. 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

  18. 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...

  19. In Vitro and In Vivo Evaluation of Oxatomide β-Cyclodextrin Inclusion Complex

    PubMed Central

    Hashem, Fahima M.; Mostafa, Mohamed; Shaker, Mahmoud; Nasr, Mohamed

    2013-01-01

    The objective of this study was to evaluate the influence of oxatomide β-cyclodextrin inclusion complex on the physicochemical properties and bioavailability of the drug. Oxatomide β-cyclodextrin solid complex was prepared with equimolar ratio of both oxatomide and β-cyclodextrin in presence or absence of water soluble polymers using different techniques. The coevaporated complex prepared in presence of PVP-K15 showed a prompt drug release and significantly increased % dissolution efficiency (P < 0.05) compared to the pure oxatomide. Moreover, the results of bioavailability evaluation of this complex in rabbits compared to commercial drug product indicated a 73.15% increase in the oral bioavailability of oxatomide. In conclusion, inclusion complex of oxatomide with β-cyclodextrin prepared by coevaporation in presence of PVP-K15 not only results in an enhancement of the oxatomide dissolution rate but also improves the bioavailability of oxatomide. PMID:26555988

  20. Two novel ternary albendazole-cyclodextrin-polymer systems: dissolution, bioavailability and efficacy against Taenia crassiceps cysts.

    PubMed

    Palomares-Alonso, Francisca; González, Cesar Rivas; Bernad-Bernad, Ma Josefa; Montiel, María Dolores Castillo; Hernández, Guadalupe Palencia; González-Hernández, Iliana; Castro-Torres, Nelly; Estrada, Enrique Pinzón; Jung-Cook, Helgi

    2010-01-01

    The effect of two water-soluble polymers: pectin and polyvinylpyrrolidone in combination with beta-cyclodextrin, on the dissolution, bioavailability and cysticidal efficacy of albendazole was evaluated using a commercial suspension as reference product. The dissolution of the albendazole-beta-cyclodextrin-pectin formulation was slow and incomplete (44.7%). No statistical differences in C(max) and AUC were found between this formulation and the reference. Also its cysticidal efficacy (33%) was similar to the reference (38%). The albendazole-beta-cyclodextrin-polyvinylpyrrolidone formulation exhibited the highest dissolution rate (78.5%) and its bioavailability was also significantly increased (2.3-fold). In addition, the cysticidal activity of this formulation (83%) was greater than a commercial suspension. Our results suggest that the ternary system of albendazole-beta-cyclodextrin-polyvinylpyrrolidone could be a potential alternative for the treatment of systemic helmintic diseases and it is worth to continue its preclinical evaluation. PMID:19769931

  1. 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.

  2. 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.

  3. 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

  4. 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

  5. IK1 heterogeneity affects genesis and stability of spiral waves in cardiac myocyte monolayers

    PubMed Central

    Sekar, Rajesh B.; Kizana, Eddy; Cho, Hee C.; Molitoris, Jared M.; Hesketh, Geoffrey G.; Eaton, Brett P.; Marbán, Eduardo; Tung, Leslie

    2009-01-01

    Previous studies have postulated an important role for the inwardly rectifying potassium current (IK1) in controlling the dynamics of electrophysiological spiral waves responsible for ventricular tachycardia and fibrillation. In this study, we developed a novel tissue model of cultured neonatal rat ventricular myocytes (NRVMs) with uniform or heterogeneous Kir2.1 expression achieved by lentiviral transfer to elucidate the role of IK1 in cardiac arrhythmogenesis. Kir2.1-overexpressed NRVMs showed increased IK1 density, hyperpolarized resting membrane potential and increased action potential upstroke velocity compared with GFP-transduced NRVMs. Opposite results were observed in Kir2.1-suppressed NRVMs. Optical mapping of uniformly Kir2.1 gene-modified monolayers showed altered conduction velocity (CV) and action potential duration (APD) compared with non-transduced and empty vector-transduced monolayers, but functional reentrant waves could not be induced. In monolayers with an island of altered Kir2.1 expression, CV and APD of the locally transduced and non-transduced regions were similar to those of the uniformly transduced and non-transduced monolayers, respectively, and functional reentrant waves could be induced. The waves were anchored to islands of Kir2.1 overexpression and remained stable, but dropped in frequency and meandered away from islands of Kir2.1 suppression. In monolayers with an inverse pattern of IK1 heterogeneity, stable high frequency spiral waves were present with IK1 overexpression, whereas lower frequency, meandering spiral waves were observed with IK1 suppression. Our study provides direct evidence for the contribution of IK1 heterogeneity and level to the genesis and stability of spiral waves and highlights the potential importance of IK1 as an anti-arrhythmia target. PMID:19122180

  6. Spectroscopic investigation of the interaction between β-cyclodextrin and ascorbic acid

    NASA Astrophysics Data System (ADS)

    Bratu, Ioan; Muresan-Pop, Marieta; Kacso, Irina; Fărcaş, Sorin I.

    2009-08-01

    Inclusion compound of vitamin C (ascorbic acid) with β-cyclodextrin (β-CD), prepared by different methods (kneading, co-precipitation and freeze-drying) has been caracterized by several spectroscopic techniques (FTIR, 1H NMR, UV-Vis), powder X-ray diffraction and DSC technique. Based on the chemical shifts observed in the 1H-NMR and on FTIR spectra the tentative conclusion is that vitamin C probably enters the cyclodextrin torus forming the inclusion complex.

  7. Structure of CO2 monolayer on KCl(1 0 0)

    NASA Astrophysics Data System (ADS)

    Wu, Taiquan; Cao, Dan; Wang, Xinyan; Jiao, Zhiwei; Jiang, Zhouting; Chen, Miaogen; Luo, Honglei; Zhu, Ping

    2015-06-01

    The first-principle technique has been employed to determine the structure of carbon dioxide (CO2) dimers, molecular chains, monolayers and the CO2/KCl(1 0 0) system. Their potential structures have been proposed. CASTEP calculation shows that CO2 molecular chains and monolayers based on two stable dimers by the electric interaction are all self-assembly system. At the coverage of 1.00 ML, two stable structures have been proposed when CO2 monolayer on the KCl(1 0 0) surface. The best one is the monolayer adsorbed on the surface with the C atom in the bridge site, the angle α between the molecular bond and the surface is 24°. The better one is the monolayer horizontally adsorbed on the surface with the C atom in the top-Cl site. The structural parameters in the adsorption system are similar to those in the monolayer.

  8. Infrared imaging of a solid phase surfactant monolayer.

    PubMed

    Conover, T A; Saylor, J R

    2006-08-01

    A new method for visualizing solid phase surfactant monolayers is presented. This method utilizes infrared (IR) imaging of the surface of a warm subphase covered by the monolayer. When the subphase is deep, natural convection occurs, resulting in a complex surface temperature field that is easily visualized using an IR camera. The presence of a surfactant monolayer changes the hydrodynamic boundary condition at the interface, dramatically altering the surface temperature field, and permitting the differentiation of surfactant-covered and surfactant-free regions. In this work, solid phase monolayers are imaged using this IR method. Fractures in the monolayer are dramatically visualized because of the sudden elimination of surfactant in the region opened up by the crack. The method is demonstrated in a wind/water tunnel, where a stearic acid monolayer is deposited and a crack is created through shear on the surfactant surface, created by suddenly increasing the velocity of the air over the water. PMID:16863234

  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. 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

  11. Cyclodextrin KnowledgeBase a web-based service managing CD-ligand complexation data.

    PubMed

    Hazai, Eszter; Hazai, Istvan; Demko, Laszlo; Kovacs, Sandor; Malik, David; Akli, Peter; Hari, Peter; Szeman, Julianna; Fenyvesi, Eva; Benes, Edina; Szente, Lajos; Bikadi, Zsolt

    2010-08-01

    Cyclodextrins are cyclic oligosaccharides that are able to form water-soluble inclusion complexes with small molecules. Because of their complexing ability, they are widely applied in food, pharmaceutical and chemical industries. In this paper we describe the development of a free web-service, Cyclodextrin KnowledgeBase: ( http://www.cyclodextrin.net ). The database contains four modules: the Publication, Interaction, Chirality and Analysis Modules. In the Publication Module, almost 50,000 publication details are collected that can be retrieved by text search. In the Interaction and Chirality Modules relevant literature data on cyclodextrin complexation and chiral recognition are collected that can be retrieved by both text and structural searches. Moreover, in the Analysis Module, the geometries of small molecule-cyclodextrin complexes can be predicted using molecular docking tools in order to explore the structures and interaction energies of the inclusion complexes. Complex geometry prediction is made possible by the built-in database of 95 cyclodextrin derivatives, where the 3D structures as well as the partial charges are calculated and stored for further utilization. The use of the database is demonstrated by several examples. PMID:20521083

  12. 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

  13. Synthesis and characterization of poly(2-hydroxyethylacrylate)/β-cyclodextrin hydrogels obtained by frontal polymerization.

    PubMed

    Nuvoli, Daniele; Alzari, Valeria; Nuvoli, Luca; Rassu, Mariella; Sanna, Davide; Mariani, Alberto

    2016-10-01

    For the first time, the synthesis of polymeric hydrogels containing cyclodextrins (CDs) obtained by frontal polymerization (FP) is reported. In particular, the effects of CDs on poly(2-hydroxyethylacrylate) hydrogel properties are investigated. In a first series of materials, β-cyclodextrin is dispersed into the polymer matrix, while in the second one acryloyl-β-cyclodextrin is grafted to poly(2-hydroxyethylacrylate) chains. FP parameters (front velocity and maximum temperature), swelling properties, glass transition temperatures and mechanical properties of the hydrogels are studied. Results show that both types of cyclodextrin influence the above properties, and the major effects are found for concentration higher than 1mol% of acryloyl-β-cyclodextrin. Namely, a significant increase of glass transition temperature and of compression moduli are found. Finally, this study demonstrates that FP is a convenient technique to obtain CD-containing hydrogels, in which the type and amount of cyclodextrin can be suitably modulated to tune polymer properties, in function of the desired hydrogel applications. PMID:27312626

  14. 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

  15. Separation of Folinic Acid Diastereomers in Capillary Electrophoresis Using a New Cationic β-Cyclodextrin Derivative

    PubMed Central

    Yu, Jia; Liang, Xinlei; Wang, Zhaokun; Guo, Xin; Sun, Tiemin; Guo, Xingjie

    2015-01-01

    A method for the separation of folinic acid diastereomers by capillary electrophoresis in chiral separation media was developed. Aiming to achieve a good separation of the anionic analytes, a newly synthesized cationic β-cyclodextrin derivative, mono-6-deoxy-6-piperdine-β-cyclodextrin, was applied as the chiral selector. The effect of background electrolyte pH, the concentration of the cyclodextrin additive, and organic modifier on the separation was investigated. A good separation of folinic acid diastereomers was obtained with 30 mmol/L phosphate buffer at pH 6.50 containing 6.0 mmol/L of mono-6-deoxy-6-piperdine-β-cyclodextrin in 10% acetonitrile. Based on the capillary electrophoresis data, the binding constants of each diastereomer with mono-6-deoxy-6-piperdine-β-cyclodextrin were determined. Moreover, a computational modeling study, using the semi-empirical PM3 method, was used to discuss the possible mechanism of separation of folinic acid with mono-6-deoxy-6-piperdine-β-cyclodextrin. PMID:25781478

  16. 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

  17. 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

  18. Ordered and disordered colloidal particle monolayers at liquid crystal interfaces

    NASA Astrophysics Data System (ADS)

    Wei, Wei-Shao; Lohr, Matthew; Gharbi, Mohamed Amine; Stebe, Kathleen; Yodh, A. G.

    2014-03-01

    In this work, we investigate ordered colloidal particle monolayers at the air/liquid-crystal (LC) interface. Specifically, silica microparticles are treated with DMOAP to create homeotropic anchoring of LC mesogens at their surfaces. These particles are then spread on an air-exposed interface of the LC 5CB. Macroscopic ordered patterns of these microparticles form due to long-range interactions between particles that are mediated by elastic deformations of the underlying LC. Different confinement conditions lead to various self-assembled patterns ranging from hexagonal lattices to chain-like dipole formations. Using dark-field video microscopy, we track and analyze the dynamics of the colloidal particles in the hexagonal crystal packing, deriving mean squared displacements, phonon modes and density of states, etc., under several conditions. Further, heating of the nematic LC into its isotropic phase enables us to observe melting dynamics of this unusual quasi-2D crystal. The investigations provide insight into crystalline packings controlled by liquid-crystal mediated colloidal interactions. This work is funded by NSF Grant DMR12-05463, PENN MRSEC Grant DMR11-20901, and NASA Grant NNX08AO0G.

  19. Production of β -cyclodextrin from pH and thermo stable Cyclodextrin Glycosyl Transferase, obtained from Arthrobacter mysorens and its evaluation as a drug carrier for Irbesartan.

    PubMed

    Rajesh, Y; Narayanan, K; Reddy, M Sreenivasa; Bhaskar, Vijaya K; Shenoy, G Gautham; Subrahmanyam, V M; Rao, J Venkata

    2015-01-01

    Cyclodextrins (CDs) are carrier molecules produced by cyclization of α-1,4-glucans by Cyclodextrin Glycosyl Transferase (CGTase). These torus shaped molecules have hydrophobic cavity and hydrophilic shell making them useful in pharmaceutical, food, textile, pesticide and cosmetic industries. In this study, culture conditions for the production of CGTase by organism belonging to Arthrobacter genus obtained from a paddy field soil were optimized by single parameter mode. Soluble starch, yeast extract and magnesium sulphate played an important role in CGTase production. Percentage increase in CGTase yield under optimized conditions was 396.77%. The enzyme precipitated by 60% ammonium sulphate was purified using DEAE-sepharose. The molecular weight of the purified protein as determined by SDS-PAGE was 75 kDa. Purified CGTase was thermostable and stable over a wide pH range. Dissolution studies on β -cyclodextrin-Irbesartan complex revealed that β -CDs formed were useful in preparing immediate release oral dosage forms. PMID:25901452

  20. 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.

  1. Low-lying lattice modes of highly uniform pentacene monolayers

    NASA Astrophysics Data System (ADS)

    He, Rui; Tassi, Nancy G.; Blanchet, Graciela B.; Pinczuk, Aron

    2009-06-01

    The authors report that monolayers of pentacene grown on a functionalized polymeric substrate display high uniformity that enable observations of Raman spectra of low-lying optical vibrations. The evolution of the frequencies and widths of the modes has been studied in films reaching the single monolayer level. Raman spectra of low-lying lattice modes display major changes when the film thickness changes from 1 to 2 monolayers, revealing that a phase akin to a thin film phase of pentacene already emerges in films of only 2 monolayers.

  2. 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

  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. Ionically self-assembled monolayers (ISAMs)

    NASA Astrophysics Data System (ADS)

    Janik, John

    2001-04-01

    Ionically self-assembled monolayers (ISAMs), fabricated by alternate adsorption of cationic and anionic components, yield exceptionally homogeneous thin films with sub-nanometer control of the thickness and relative special location of the component materials. Using organic electrochromic materials such as polyaniline, we report studies of electrochromic responses in ISAM films. Reversible changes in the absorption spectrum are observed with the application of voltages on the order of 1.0 V. Measurements are made using both liquid electrolytes and in all-solid state devices incorporating solid polyelectrolytes such as poly(2-acylamido 2-methyl propane sulfonic acid) (PAMPS).

  5. 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.

  6. 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

  7. 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.

  8. 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. PMID:24947884

  9. 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

  10. Cyclodextrin complexes for treatment improvement in infectious diseases.

    PubMed

    Imperiale, Julieta C; Sosnik, Alejandro D

    2015-05-01

    Infectious diseases are a heterogeneous group of maladies that represent a serious burden to healthcare systems worldwide. Most of the available antimicrobial drugs display poor biopharmaceutical properties that compromise their effectiveness. Cyclodextrins (CDs) are cyclic oligosaccharides of glucopyranose formed by a variable number of repeating units that combine a hydrophilic surface with a hydrophobic cavity. The production of drug/CD complexes has become one of the most extensively investigated technology approaches to improve the stability, solubility, dissolution rate and bioavailability of drugs. The present work overviews the applications of CDs for the formulation of anti-infective agents along with the most relevant administration routes. Finally, an update on the complexes with CDs available on the market to treat infectious diseases is presented. PMID:26008196

  11. Self-assembly vesicles made from a cyclodextrin supramolecular complex.

    PubMed

    Jing, Bo; Chen, Xiao; Wang, Xudong; Yang, Chunjie; Xie, Yizhou; Qiu, Huayu

    2007-01-01

    Self-assembly vesicles have been made from a cyclodextrin (CD) supramolecular complex, which is cooperatively formed with natural beta-CD, 1-naphthylammonium chloride (NA), and sodium bis(2-ethyl-1-hexyl)sulfosuccinate (AOT) by weak noncovalent interactions. In the complex structure, a NA molecule is included inside a beta-CD molecule while it is coupled with an AOT molecule on one side. The supramolecular structure and morphology of the vesicles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS), respectively. The mechanism of vesicle formation and transition is discussed along with the data obtained from induced circular dichroism (ICD) and UV/visible spectroscopy, polarized optical microscopy (POM), and (1)H NMR spectroscopy. Both the fabrication and the transition of vesicles are controlled by the inclusion equilibria and the cooperative binding of noncovalent interactions, which include the "key-lock" principle, electrostatic interactions, pi-pi stacking, and amphiphilic hydrophobic association. PMID:17663495

  12. Encapsulation of biocides by cyclodextrins: toward synergistic effects against pathogens.

    PubMed

    Nardello-Rataj, Véronique; Leclercq, Loïc

    2014-01-01

    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. Cyclodextrin inclusion complex of racecadotril: effect of drug-β- cyclodextrin ratio and the method of complexation.

    PubMed

    Semalty, Mona; Panchpuri, Mitali; Singh, Devendra; Semalty, Ajay

    2014-06-01

    Racecadotril is an antisecretory and antidiarrheal agent against watery diarrhoea in children. Racecadotril is a class II drug (as per Biopharmaceutical Classification System) with poor aqueous solubility and dissolution rate limited absorption. β-cyclodextrin complexation of solubility or dissolution rate limited drugs provides an amphiphilic complex with improved solubility and dissolution profile. Thus Racecadotril - β-cyclodextrin complex were prepared to improve its solubility and dissolution by imparting an environment of improved hydrophilicity. Racecadotril was complexed with β-cyclodextrin (in 1:1 and 1:2 molar ratios) by two different methods (solvent evaporation and kneading method). These inclusion complexes were evaluated for solubility, drug content, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X ray powder diffraction (XRPD) and in vitro dissolution study. The highest drug content (30.83%) was found in complex made by kneading method (RK1:1) in 1:1 molar ratio. Complex prepared by solvent evaporation method (RSE1:1, RSE1:2) were found to be showing irregular disc shaped non-porous surface, while the complexes prepared by kneading method (RK1:1, RK1:2) showed rough, fluffy, non-porous and irregular surface in SEM. Solubility of the drug improved up to 2 to 3 folds in the complexes. The complex RK1:1 showed the greatest improvement in solubility (from 28.98 to76.56 µg/ml). The dissolution of the complexes was also found to be improved. Complex prepared by solvent evaporation method in 1:1 molar ratio (RSE1:1) showed a marked improvement in percent drug release (100.33%) than that of pure drug (52.58%) at the end of 1 hour in dissolution study. FTIR, DSC and XRPD data confirmed the formation of inclusion complex. It was concluded that water solubility of all the complexes were increased when the drug was complexed with β-CD in 1:1 molar ratio. The complex made in 1:1 molar ratio (irrespective of the method) showed

  15. β-cyclodextrin assistant flavonoid glycosides enzymatic hydrolysis

    PubMed Central

    Jin, Xin; Zhang, Zhen-hai; Sun, E.; Jia, Xiao-Bin

    2013-01-01

    Background: The content of icaritin and genistein in herba is very low, preparation with relatively large quantities is an important issue for extensive pharmacological studies. Objective: This study focuses on preparing and enzymic hydrolysis of flavonoid glycosides /β-cyclodextrin inclusion complex to increase the hydrolysis rate. Materials and Methods: The physical property of newly prepared inclusion complex was tested by differential scanning calorimetry (DSC). The conditions of enzymatic hydrolysis were optimized for the bioconversion of flavonoid glycosides /β-cyclodextrin inclusion complex by mono-factor experimental design. The experiments are using the icariin and genistein as the model drugs. Results: The solubility of icariin and genistein were increased almost 17 times from 29.2 μg/ml to 513.5 μg/ml at 60°C and 28 times from 7.78 μg/ml to 221.46 μg/ml at 50°C, respectively, demonstrating that the inclusion complex could significantly increase the solubility of flavonoid glycosides. Under the optimal conditions, the reaction time of icariin and genistin decreased by 68% and 145%, when compared with that without β-CD inclusion. By using this enzymatic condition, 473 mg icaritin (with the purity of 99.34%) and 567 mg genistein(with the purity of 99.46%), which was finally determined by melt point, ESI-MS, UV, IR, 1H NMR and 13C NMR, was obtained eventually by transforming the inclusion complex(contains 1.0 g substrates). Conclusion: This study can clearly indicate a new attempt to improve the speed of enzyme-hydrolysis of poorly water-soluble flavonoid glycosides and find a more superior condition which is used to prepare icaritin and genistein. PMID:24143039

  16. Thermodynamics of hydrogen bond and hydrophobic interactions in cyclodextrin complexes.

    PubMed Central

    Ross, P D; Rekharsky, M V

    1996-01-01

    Values of K, delta G(o), delta H(o), delta S(o) and delta C(po) for the binding reaction of small organic ligands forming 1:1 complexes with either alpha- or beta-cyclodextrin were obtained by titration calorimetry from 15 degrees C to 45 degrees C. A hydrogen bond or hydrophobic interaction was introduced by adding a single functional group to the ligand. The thermodynamics of binding with and without the added group are compared to estimate the contribution of the hydrogen bond or hydrophobic interaction. A change in the environment of a functional group is required to influence the binding thermodynamics, but molecular size-dependent solute-solvent interactions have no effect. For phenolic O-H-O hydrogen bond formation, delta H(o) varies from -2 to -1.4 kcal mol(-1) from 15 degrees C to 45 degrees C, and delta C(p) is increased by 18 cal K(-1) mol(-1). The hydrophobic interaction has an opposite effect: in alpha-cyclodextrin, delta C(po) = -13.3 cal K(-1) mol(-1) per ligand -CH(2)-, identical to values found for the transfer of a -CH(2)-group from water to a nonpolar environment. At room temperature, the hydrogen bond and the -CH(2)-interaction each contribute about -600 cal mol(-1) to the stability (delta G(o)) of the complex. With increased temperature, the hydrogen bond stability decreases (i.e., hydrogen bonds "melt"), but the stability of the hydrophobic interaction remains essentially constant. PMID:8889190

  17. 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

  18. Exciton formation in monolayer transition metal dichalcogenides.

    PubMed

    Ceballos, Frank; Cui, Qiannan; Bellus, Matthew Z; Zhao, Hui

    2016-06-01

    Two-dimensional transition metal dichalcogenides provide a unique platform to study excitons in confined structures. Recently, several important aspects of excitons in these materials have been investigated in detail. However, the formation process of excitons from free carriers has yet to be understood. Here we report time-resolved measurements on the exciton formation process in monolayer samples of MoS2, MoSe2, WS2, and WSe2. The free electron-hole pairs, injected by an ultrashort laser pulse, immediately induce a transient absorption signal of a probe pulse tuned to the exciton resonance. The signal quickly drops by about a factor of two within 1 ps and is followed by a slower decay process. In contrast, when excitons are resonantly injected, the fast decay component is absent. Based both on its excitation excess energy and intensity dependence, this fast decay process is attributed to the formation of excitons from the electron-hole pairs. This interpretation is also consistent with a model that shows how free electron-hole pairs can be about twice more effective than excitons in altering the exciton absorption strength. From our measurements and analysis of our results, we determined that the exciton formation times in these monolayers to be shorter than 1 ps. PMID:27219022

  19. 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

  20. Electronic correlations in monolayer VS2

    NASA Astrophysics Data System (ADS)

    Isaacs, Eric B.; Marianetti, Chris A.

    The layered transition metal dichalcogenide vanadium disulfide (VS2), which nominally has 1 electron in the 3 d shell, is potent for strong correlation physics and is possibly another realization of the one-band Hubbard model beyond the cuprates. Here we investigate the octahedral (OCT) and trigonal prismatic (TP) phases of monolayer VS2 using density functional theory plus Hubbard U calculations. Unlike the OCT phase, the TP phase has an isolated low-energy band due to the crystal field splitting and the nearest-neighbor V-V hopping. Within DFT, ferromagnetism spin splits this band leading to a low-band-gap S = 1 / 2 ferromagnetic insulating TP phase, which is lower in energy than the OCT phase. The on-site interaction U, which we find to be approximately 4 eV via linear response, increases the band gap, leads to Mott insulating behavior, and for sufficiently high values stabilizes the ferromagnetic OCT phase. We explore the impact of charge density waves in monolayer VS2 and discuss the possibility to experimentally realize the TP phase.

  1. Electrosorbed carbon monoxide monolayers on Pt(111).

    SciTech Connect

    Chang, K.-C.; Menzel, A.; Komanicky, V.; You, H.; Materials Science Division; Paul Scherrer Inst.; Slovakia Sci. Acad. Sci.

    2007-05-10

    We review structures of high-density CO monolayers on Pt(1 1 1) surfaces in CO-saturated electrolytes or in gaseous CO at near atmospheric pressure, using surface X-ray scattering (SXS) and scanning tunneling microscopy (STM). In electrolytes, we confirmed the well-known (2 x 2)-3CO and ({radical}19 x {radical}19)-13CO structures and were able to study the transition between them. For gas-phase studies, we were able to stabilize extremely well-ordered CO monolayers by emersion transfer from an electrochemical cell. We found that the hexagonal close-packed (2 x 2)-3CO structure is the equilibrium phase at room temperature in {approx}1 atm CO gas pressure. This commensurate (C) phase transforms continuously to an incommensurate (IC) phase at elevated temperature (a second-order phase transition). We also confirm that the ({radical}19 x {radical}19)-13CO structure is stable at lower CO partial pressure. This C phase transforms discontinuously to an IC phase (a first-order phase transition). A tentative phase diagram and a brief review of structure details of the (2 x 2)-3CO and ({radical}19 x {radical}19)-13CO phases will be presented.

  2. 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

  3. 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

  4. Exciton formation in monolayer transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Ceballos, Frank; Cui, Qiannan; Bellus, Matthew Z.; Zhao, Hui

    2016-06-01

    Two-dimensional transition metal dichalcogenides provide a unique platform to study excitons in confined structures. Recently, several important aspects of excitons in these materials have been investigated in detail. However, the formation process of excitons from free carriers has yet to be understood. Here we report time-resolved measurements on the exciton formation process in monolayer samples of MoS2, MoSe2, WS2, and WSe2. The free electron-hole pairs, injected by an ultrashort laser pulse, immediately induce a transient absorption signal of a probe pulse tuned to the exciton resonance. The signal quickly drops by about a factor of two within 1 ps and is followed by a slower decay process. In contrast, when excitons are resonantly injected, the fast decay component is absent. Based both on its excitation excess energy and intensity dependence, this fast decay process is attributed to the formation of excitons from the electron-hole pairs. This interpretation is also consistent with a model that shows how free electron-hole pairs can be about twice more effective than excitons in altering the exciton absorption strength. From our measurements and analysis of our results, we determined that the exciton formation times in these monolayers to be shorter than 1 ps.

  5. Rapid removal of organic micropollutants from water by a porous β-cyclodextrin polymer

    NASA Astrophysics Data System (ADS)

    Alsbaiee, Alaaeddin; Smith, Brian J.; Xiao, Leilei; Ling, Yuhan; Helbling, Damian E.; Dichtel, William R.

    2016-01-01

    The global occurrence in water resources of organic micropollutants, such as pesticides and pharmaceuticals, has raised concerns about potential negative effects on aquatic ecosystems and human health. Activated carbons are the most widespread adsorbent materials used to remove organic pollutants from water but they have several deficiencies, including slow pollutant uptake (of the order of hours) and poor removal of many relatively hydrophilic micropollutants. Furthermore, regenerating spent activated carbon is energy intensive (requiring heating to 500-900 degrees Celsius) and does not fully restore performance. Insoluble polymers of β-cyclodextrin, an inexpensive, sustainably produced macrocycle of glucose, are likewise of interest for removing micropollutants from water by means of adsorption. β-cyclodextrin is known to encapsulate pollutants to form well-defined host-guest complexes, but until now cross-linked β-cyclodextrin polymers have had low surface areas and poor removal performance compared to conventional activated carbons. Here we crosslink β-cyclodextrin with rigid aromatic groups, providing a high-surface-area, mesoporous polymer of β-cyclodextrin. It rapidly sequesters a variety of organic micropollutants with adsorption rate constants 15 to 200 times greater than those of activated carbons and non-porous β-cyclodextrin adsorbent materials. In addition, the polymer can be regenerated several times using a mild washing procedure with no loss in performance. Finally, the polymer outperformed a leading activated carbon for the rapid removal of a complex mixture of organic micropollutants at environmentally relevant concentrations. These findings demonstrate the promise of porous cyclodextrin-based polymers for rapid, flow-through water treatment.

  6. Hydroxymethylnitrofurazone:dimethyl-beta-cyclodextrin inclusion complex: a physical-chemistry characterization.

    PubMed

    Grillo, Renato; Melo, Nathalie Ferreira Silva; Moraes, Carolina Morales; Rosa, André Henrique; Roveda, José Arnaldo Frutuoso; Menezes, Carla M S; Ferreira, Elizabeth Igne; Fraceto, Leonardo Fernandes

    2007-12-01

    Hydroxymethylnitrofurazone (NFOH) is active against Trypanosoma cruzi; however, its low solubility and high toxicity precludes its current use in treatment of parasitosis. Cyclodextrin can be used as a drug carrier system, as it is able to form inclusion (host-guest) complexes with a wide variety of organic (guest) molecules. Several reports have shown the interesting use of modified beta-cyclodextrins in pharmaceutical formulation, to improve the bioavailability of drugs and to decrease their toxicity. The aim of this work was to characterize inclusion complexes formed between NFOH and dimethyl-beta-cyclodextrin (DM-beta-CD) by complexation/release kinetics and solubility isotherm experiments using ultraviolet (UV)-visible spectrophotometry and by the measurement of the dynamics information obtained from T(1) relaxation times and diffusion (DOSY) experiments using nuclear magnetic resonance (NMR) spectroscopy. The complex was prepared at different NFOH and DM-beta-CD molar ratios. The UV-visible measurements were recorded in a spectrophotometer, and NMR experiments were recorded at 20 degrees C on a NMR spectrometer (Varian Inova) operating at 500 MHz. Longitudinal relaxation times were obtained by the conventional inversion-recovery method and the DOSY experiments were carried out using the BPPSTE sequence. The kinetics of complexation revealed that 30 h is enough for stabilization of the NFOH absorbance in presence of cyclodextrin. Solubility isotherm studies show a favorable complexation and increase in solubility when NFOH interacts with cyclodextrin. The analysis of the NMR-derived diffusion coefficients and T(1) relaxation times shows that in the presence of DM-beta-CD, NFOH decreases its mobility in solution, indicating that this antichagasic compound interacts with the cyclodextrin cavity. The release kinetics assays showed that NFOH changes its release profile when in the presence of cyclodextrin due to complexation. This study was focused on the

  7. Rapid removal of organic micropollutants from water by a porous β-cyclodextrin polymer.

    PubMed

    Alsbaiee, Alaaeddin; Smith, Brian J; Xiao, Leilei; Ling, Yuhan; Helbling, Damian E; Dichtel, William R

    2016-01-14

    The global occurrence in water resources of organic micropollutants, such as pesticides and pharmaceuticals, has raised concerns about potential negative effects on aquatic ecosystems and human health. Activated carbons are the most widespread adsorbent materials used to remove organic pollutants from water but they have several deficiencies, including slow pollutant uptake (of the order of hours) and poor removal of many relatively hydrophilic micropollutants. Furthermore, regenerating spent activated carbon is energy intensive (requiring heating to 500-900 degrees Celsius) and does not fully restore performance. Insoluble polymers of β-cyclodextrin, an inexpensive, sustainably produced macrocycle of glucose, are likewise of interest for removing micropollutants from water by means of adsorption. β-cyclodextrin is known to encapsulate pollutants to form well-defined host-guest complexes, but until now cross-linked β-cyclodextrin polymers have had low surface areas and poor removal performance compared to conventional activated carbons. Here we crosslink β-cyclodextrin with rigid aromatic groups, providing a high-surface-area, mesoporous polymer of β-cyclodextrin. It rapidly sequesters a variety of organic micropollutants with adsorption rate constants 15 to 200 times greater than those of activated carbons and non-porous β-cyclodextrin adsorbent materials. In addition, the polymer can be regenerated several times using a mild washing procedure with no loss in performance. Finally, the polymer outperformed a leading activated carbon for the rapid removal of a complex mixture of organic micropollutants at environmentally relevant concentrations. These findings demonstrate the promise of porous cyclodextrin-based polymers for rapid, flow-through water treatment. PMID:26689365

  8. Electrical release of dopamine and levodopa mediated by amphiphilic β-cyclodextrins immobilized on polycrystalline gold

    NASA Astrophysics Data System (ADS)

    Foschi, Giulia; Leonardi, Francesca; Scala, Angela; Biscarini, Fabio; Kovtun, Alessandro; Liscio, Andrea; Mazzaglia, Antonino; Casalini, Stefano

    2015-11-01

    Vesicles of cationic amphiphilic β-cyclodextrins have been immobilized on polycrystalline gold by exploiting the chemical affinity between their amino groups and Au atoms. The presence of cyclodextrins has been widely investigated by means of AFM, XPS, kelvin probe and electrochemical measurements. This multi-functional coating confers distinct electrochemical features such as pH-dependent behavior and partial/total blocking properties towards electro-active species. The host-guest properties of β-cyclodextrins have been successfully exploited in order to trap drugs, like dopamine and levodopa. The further release of these drugs was successfully achieved by providing specific electrical stimuli. This proof-of-concept led us to fabricate an electronic device (i.e. an organic transistor) capable of dispensing both dopamine and levodopa in aqueous solution.Vesicles of cationic amphiphilic β-cyclodextrins have been immobilized on polycrystalline gold by exploiting the chemical affinity between their amino groups and Au atoms. The presence of cyclodextrins has been widely investigated by means of AFM, XPS, kelvin probe and electrochemical measurements. This multi-functional coating confers distinct electrochemical features such as pH-dependent behavior and partial/total blocking properties towards electro-active species. The host-guest properties of β-cyclodextrins have been successfully exploited in order to trap drugs, like dopamine and levodopa. The further release of these drugs was successfully achieved by providing specific electrical stimuli. This proof-of-concept led us to fabricate an electronic device (i.e. an organic transistor) capable of dispensing both dopamine and levodopa in aqueous solution. Electronic supplementary information (ESI) available: Kelvin probe, AFM and electrochemical data are reported. Furthermore, the chemical backbone of both types of cyclodextrins are shown. See DOI: 10.1039/c5nr05405b

  9. 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. PMID:26134943

  10. Egg yolk and glycerol requirements for freezing boar spermatozoa treated with methyl β-cyclodextrin or cholesterol-loaded cyclodextrin.

    PubMed

    Blanch, Eva; Tomás, Cristina; Hernández, Marta; Roca, Jordi; Martínez, Emilio A; Vázquez, Juan M; Mocé, Eva

    2014-04-24

    Egg yolk (EY) and glycerol are common constituents of extenders used for sperm cryopreservation. It has been demonstrated that using cholesterol-loaded cyclodextrins (CLC) improves sperm cryosurvival in several species. However, standard freezing extenders might not be the most appropriate for CLC-treated sperm. This study evaluated the EY and glycerol requirements for freezing CLC-treated boar spermatozoa. Semen samples from 34 ejaculates coming from 4 boars were used. Each ejaculate was split into three aliquots: one was used untreated (control), and the other two were treated with 1 mg of CLC or methyl-β-cyclodextrin/120 × 10(6) sperm for 15 min at 22 C prior to cryopreservation. Our results indicated that reducing the concentration of EY was detrimental for sperm viability after thawing (31.57 ± 2 vs. 19.89% ± 2 for 20 and 10% EY, respectively; P <0.05), even in semen treated with CLC. On the other hand, it was observed that the traditional concentration of glycerol (3%) was not the appropriate for freezing CLC-treated sperm (61.10 ± 3 vs. 47.87% ± 3 viable sperm for control and CLC-treated sperm, respectively; P <0.05). Thus, CLC-treated sperm showed a higher tolerance to high glycerol concentrations (5%) in terms of sperm viability (59.19% ± 3) than non-treated sperm (45.58% ± 3; P<0.05). Therefore, it could be necessary to modify the freezing extenders for CLC-treated sperm. Nevertheless, additional studies will be needed to evaluate alternative cryoprotectants and to determine the effect of high glycerol concentrations on sperm functionality. PMID:24492655

  11. Egg Yolk and Glycerol Requirements for Freezing Boar Spermatozoa Treated with Methyl β-Cyclodextrin or Cholesterol-loaded Cyclodextrin

    PubMed Central

    BLANCH, Eva; TOMÁS, Cristina; HERNÁNDEZ, Marta; ROCA, Jordi; MARTÍNEZ, Emilio A.; VÁZQUEZ, Juan M.; MOCÉ, Eva

    2014-01-01

    Egg yolk (EY) and glycerol are common constituents of extenders used for sperm cryopreservation. It has been demonstrated that using cholesterol-loaded cyclodextrins (CLC) improves sperm cryosurvival in several species. However, standard freezing extenders might not be the most appropriate for CLC-treated sperm. This study evaluated the EY and glycerol requirements for freezing CLC-treated boar spermatozoa. Semen samples from 34 ejaculates coming from 4 boars were used. Each ejaculate was split into three aliquots: one was used untreated (control), and the other two were treated with 1 mg of CLC or methyl-β-cyclodextrin/120 × 106 sperm for 15 min at 22 C prior to cryopreservation. Our results indicated that reducing the concentration of EY was detrimental for sperm viability after thawing (31.57 ± 2 vs. 19.89% ± 2 for 20 and 10% EY, respectively; P <0.05), even in semen treated with CLC. On the other hand, it was observed that the traditional concentration of glycerol (3%) was not the appropriate for freezing CLC-treated sperm (61.10 ± 3 vs. 47.87% ± 3 viable sperm for control and CLC-treated sperm, respectively; P <0.05). Thus, CLC-treated sperm showed a higher tolerance to high glycerol concentrations (5%) in terms of sperm viability (59.19% ± 3) than non-treated sperm (45.58% ± 3; P<0.05). Therefore, it could be necessary to modify the freezing extenders for CLC-treated sperm. Nevertheless, additional studies will be needed to evaluate alternative cryoprotectants and to determine the effect of high glycerol concentrations on sperm functionality. PMID:24492655

  12. 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

  13. 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

  14. A pentacene monolayer trapped between graphene and a substrate.

    PubMed

    Zhang, Qicheng; Peng, Boyu; Chan, Paddy Kwok Leung; Luo, Zhengtang

    2015-09-21

    A self-assembled pentacene monolayer can be fabricated between the solid-solid interface of few-layered graphene (FLG) and the mica substrate, through a diffusion-spreading method. By utilizing a transfer method that allows us to sandwich pentacene between graphene and mica, followed by controlled annealing, we enabled the diffused pentacene to be trapped in the interfaces and led to the formation of a stable monolayer. We found that the formation of a monolayer is kinetically favored by using a 2D Ising lattice gas model for pentacene trapped between the graphene-substrate interfaces. This kinetic Monte Carlo simulation results indicate that, due to the graphene substrate enclosure, the spreading of the first layer proceeds faster than the second layer, as the kinetics favors the filling of voids by molecules from the second layer. This graphene assisted monolayer assembly method provides a new avenue for the fabrication of two-dimensional monolayer structures. PMID:26272514

  15. The influence of plant hormones on phospholipid monolayer stability.

    PubMed

    Gzyl-Malchera, Barbara; Filek, Maria; Brezesinski, Gerald; Fischer, Antje

    2007-01-01

    The influence of hormones in water subphase on the stability of monolayers built of phospholipid mixtures extracted from embryogenic (PLE) and nonembryogenic (PLNE) wheat calli was examined. Additionally, experiments on individual lipids, dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidic acid (DPPA), were performed. DPPC was chosen because it was the main phospholipid present in both calli. Negatively charged DPPA could mimic a negatively charged natural mixture of lipids. As hormones, auxins (IAA and 2,4-D), cytokinins (zeatin and kinetin) and zearalenone were chosen. The time of monolayer stability for PLNE calli was much longer than for PLE calli. Kinetics of monolayer stability of PLNE was similar to DPPA, whereas that of PLE was similar to DPPC. Generally, hormones increased the time after which the monolayer stability was reached and decreased the surface pressure. The greatest effect was observed for auxins (especially IAA), whereas cytokinins affected the monolayer stability to a lesser degree. PMID:17425106

  16. 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. PMID:26439853

  17. Monolayer-by-monolayer stacked pyramid-like MoS2 nanodots on monolayered MoS2 flakes with enhanced photoluminescence

    NASA Astrophysics Data System (ADS)

    Yuan, Cailei; Cao, Yingjie; Luo, Xingfang; Yu, Ting; Huang, Zhenping; Xu, Bo; Yang, Yong; Li, Qinliang; Gu, Gang; Lei, Wen

    2015-10-01

    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.

  18. A pentacene monolayer trapped between graphene and a substrate

    NASA Astrophysics Data System (ADS)

    Zhang, Qicheng; Peng, Boyu; Chan, Paddy Kwok Leung; Luo, Zhengtang

    2015-08-01

    A self-assembled pentacene monolayer can be fabricated between the solid-solid interface of few-layered graphene (FLG) and the mica substrate, through a diffusion-spreading method. By utilizing a transfer method that allows us to sandwich pentacene between graphene and mica, followed by controlled annealing, we enabled the diffused pentacene to be trapped in the interfaces and led to the formation of a stable monolayer. We found that the formation of a monolayer is kinetically favored by using a 2D Ising lattice gas model for pentacene trapped between the graphene-substrate interfaces. This kinetic Monte Carlo simulation results indicate that, due to the graphene substrate enclosure, the spreading of the first layer proceeds faster than the second layer, as the kinetics favors the filling of voids by molecules from the second layer. This graphene assisted monolayer assembly method provides a new avenue for the fabrication of two-dimensional monolayer structures.A self-assembled pentacene monolayer can be fabricated between the solid-solid interface of few-layered graphene (FLG) and the mica substrate, through a diffusion-spreading method. By utilizing a transfer method that allows us to sandwich pentacene between graphene and mica, followed by controlled annealing, we enabled the diffused pentacene to be trapped in the interfaces and led to the formation of a stable monolayer. We found that the formation of a monolayer is kinetically favored by using a 2D Ising lattice gas model for pentacene trapped between the graphene-substrate interfaces. This kinetic Monte Carlo simulation results indicate that, due to the graphene substrate enclosure, the spreading of the first layer proceeds faster than the second layer, as the kinetics favors the filling of voids by molecules from the second layer. This graphene assisted monolayer assembly method provides a new avenue for the fabrication of two-dimensional monolayer structures. Electronic supplementary information (ESI

  19. The growth scale and kinetics of WS2 monolayers under varying H2 concentration.

    PubMed

    Kang, Kyung Nam; Godin, Kyle; Yang, Eui-Hyeok

    2015-01-01

    The optical and electronic properties of tungsten disulfide monolayers (WS2) have been extensively studied in the last few years, yet growth techniques for WS2 remain behind other transition metal dichalcogenides (TMDCs) such as MoS2. Here we demonstrate chemical vapor deposition (CVD) growth of continuous monolayer WS2 films on mm(2) scales and elucidate effects related to hydrogen (H2) gas concentration during growth. WS2 crystals were grown by reduction and sulfurization of WO3 using H2 gas and sulfur evaporated from solid sulfur powder. Several different growth formations (in-plane shapes) were observed depending on the concentration of H2. Characterization using atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed etching of the SiO2 substrate at low concentrations of H2 and in the presence of an Ar carrier gas. We attribute this to insufficient reduction of WO3 during growth. High H2 concentrations resulted in etching of the grown WS2 crystals after growth. The two dimensional X-ray diffraction (2D XRD) pattern demonstrates that the monolayer WS2 was grown with the (004) plane normal to the substrate, showing that the WS2 conforms to the growth substrate. PMID:26279085

  20. The growth scale and kinetics of WS2 monolayers under varying H2 concentration

    NASA Astrophysics Data System (ADS)

    Kang, Kyung Nam; Godin, Kyle; Yang, Eui-Hyeok

    2015-08-01

    The optical and electronic properties of tungsten disulfide monolayers (WS2) have been extensively studied in the last few years, yet growth techniques for WS2 remain behind other transition metal dichalcogenides (TMDCs) such as MoS2. Here we demonstrate chemical vapor deposition (CVD) growth of continuous monolayer WS2 films on mm2 scales and elucidate effects related to hydrogen (H2) gas concentration during growth. WS2 crystals were grown by reduction and sulfurization of WO3 using H2 gas and sulfur evaporated from solid sulfur powder. Several different growth formations (in-plane shapes) were observed depending on the concentration of H2. Characterization using atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed etching of the SiO2 substrate at low concentrations of H2 and in the presence of an Ar carrier gas. We attribute this to insufficient reduction of WO3 during growth. High H2 concentrations resulted in etching of the grown WS2 crystals after growth. The two dimensional X-ray diffraction (2D XRD) pattern demonstrates that the monolayer WS2 was grown with the (004) plane normal to the substrate, showing that the WS2 conforms to the growth substrate.

  1. 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.

  2. Spin-correlations and magnetic structure in an Fe monolayer on 5d transition metal surfaces.

    PubMed

    Simon, E; Palotás, K; Ujfalussy, B; Deák, A; Stocks, G M; Szunyogh, L

    2014-05-01

    We present a detailed first principles study on the magnetic structure of an Fe monolayer on different surfaces of 5d transition metals. We use the spin-cluster expansion technique to obtain parameters of a spin model, and predict the possible magnetic ground state of the studied systems by employing the mean field approach and, in certain cases, by spin dynamics calculations. We point out that the number of shells considered for the isotropic exchange interactions plays a crucial role in the determination of the magnetic ground state. In the case of Ta substrate we demonstrate that the out-of-plane relaxation of the Fe monolayer causes a transition from ferromagnetic to antiferromagnetic ground state. We examine the relative magnitude of nearest neighbour Dzyaloshinskii-Moriya (D) and isotropic (J) exchange interactions in order to get insight into the nature of magnetic pattern formations. For the Fe/Os(0 0 0 1) system we calculate a very large D/J ratio, correspondingly, a spin spiral ground state. We find that, mainly through the leading isotropic exchange and Dzyaloshinskii-Moriya interactions, the inward layer relaxation substantially influences the magnetic ordering of the Fe monolayer. For the Fe/Re(0 0 0 1) system characterized by large antiferromagnetic interactions we also determine the chirality of the 120° Néel-type ground state. PMID:24759288

  3. Quantum magnetotransport properties of a MoS2 monolayer

    NASA Astrophysics Data System (ADS)

    Tahir, M.; Vasilopoulos, P.; Peeters, F. M.

    2016-01-01

    We study transport properties of a MoS2 monolayer in the presence of a perpendicular magnetic field B . We derive and discuss its band structure and take into account spin and valley Zeeman effects. Compared to a conventional two-dimensional electron gas, these effects lead to new quantum Hall plateaus and new peaks in the longitudinal resistivity as functions of the magnetic field. The field B leads to a significant enhancement of the spin splitting in the conduction band, to a beating of the Shubnikov-de Haas (SdH) oscillations in the low-field regime, and to their splitting in the high-field regime. The Zeeman fields suppress significantly the beating of the SdH oscillations in the low-field regime and strongly enhance their splitting at high fields. The spin and valley polarizations show a similar beating pattern at low fields and are clearly separated at high fields in which they attain a value higher than 90 % .

  4. Selective isolation of gold facilitated by second-sphere coordination with α-cyclodextrin

    PubMed Central

    Liu, Zhichang; Frasconi, Marco; Lei, Juying; Brown, Zachary J.; Zhu, Zhixue; Cao, Dennis; Iehl, Julien; Liu, Guoliang; Fahrenbach, Albert C.; Botros, Youssry Y.; Farha, Omar K.; Hupp, Joseph T.; Mirkin, Chad A.; Fraser Stoddart, J.

    2013-01-01

    Gold recovery using environmentally benign chemistry is imperative from an environmental perspective. Here we report the spontaneous assembly of a one-dimensional supramolecular complex with an extended {[K(OH2)6][AuBr4](α-cyclodextrin)2}n chain superstructure formed during the rapid co-precipitation of α-cyclodextrin and KAuBr4 in water. This phase change is selective for this gold salt, even in the presence of other square-planar palladium and platinum complexes. From single-crystal X-ray analyses of six inclusion complexes between α-, β- and γ-cyclodextrins with KAuBr4 and KAuCl4, we hypothesize that a perfect match in molecular recognition between α-cyclodextrin and [AuBr4]− leads to a near-axial orientation of the ion with respect to the α-cyclodextrin channel, which facilitates a highly specific second-sphere coordination involving [AuBr4]− and [K(OH2)6]+ and drives the co-precipitation of the 1:2 adduct. This discovery heralds a green host–guest procedure for gold recovery from gold-bearing raw materials making use of α-cyclodextrin—an inexpensive and environmentally benign carbohydrate. PMID:23673640

  5. Modulating Pluronics micellar rupture with cyclodextrins and drugs: effect of pH and temperature

    NASA Astrophysics Data System (ADS)

    Valero, M.; Dreiss, C. A.

    2014-11-01

    Micelles of the triblock copolymer Pluronic F127 can encapsulate drugs with various chemical structures and their architecture has been studied by small-angle neutron scattering (SANS). Interaction with a derivative of β-cyclodextrin, namely, heptakis(2,6-di-O- methyl)-β-cyclodextrin (DIMEB), induces a complete break-up of the micelles, providing a mechanism for drug release. In the presence of drugs partitioned within the micelles, competitive interactions between polymer, drug and cyclodextrin lead to a modulation of the micellar rupture, depending on the nature of the drug and the exact composition of the ternary system. These interactions can be further adjusted by temperature and pH. While the most widely accepted mechanism for the interaction between Pluronics and cyclodextrins is through polypseudorotaxane (PR) formation, involving the threading of β-CD on the polymer backbone, time-resolved SANS experiments show that de-micellisation takes place in less than 100 ms, thus unambiguously ruling out an inclusion complex between the cyclodextrin and the polymer chains.

  6. Thermodynamic origin of selective binding of β-cyclodextrin derivatives with chiral chromophoric substituents toward steroids.

    PubMed

    Chen, Yong; Li, Fang; Liu, Bo-Wen; Jiang, Bang-Ping; Zhang, Heng-Yi; Wang, Li-Hua; Liu, Yu

    2010-12-16

    Two β-cyclodextrin derivatives with chiral chromophoric substituents, that is, L- (1) and D-tyrosine-modified β-cyclodextrin (2), were synthesized and fully characterized. Their inclusion modes, binding abilities, and molecular selectivities with four steroid guests, that is, cholic acid sodium salt (CA), deoxycholic acid sodium salt (DCA), glycochoic acid sodium salt (GCA), and taurocholic acid sodium salt (TCA), were investigated by the circular dichroism, 2D NMR, and isothermal titration microcalorimetry (ITC). The results obtained from the circular dichroism and 2D NMR showed that two hosts adopted the different binding geometry, and these differences subsequently resulted in the significant differences of molecular binding abilities and selectivities. As compared with native β-cyclodextrin and tryptophan-modified β-cyclodextrin, host 2 showed the enhanced binding abilities for CA and DCA but the decreased binding abilities for GCA and TCA; however, host 1 showed the decreased binding abilities for all four bile salts. The best guest selectivity and the best host selectivity were K(S)(2-DCA)/K(S)(2-TCA) = 12.6 and K(S)(2-CA)/K(S)(1-CA) = 10, respectively, both exhibiting great enhancement as compared with the corresponding values of the previously reported L- and D-tryptophan-modified β-cyclodextrins. Thermodynamically, it was the favorable enthalpic gain that led to the high guest selectivity and host selectivity. PMID:20695496

  7. Spray-dried voriconazole-cyclodextrin complexes: solubility, dissolution rate and chemical stability.

    PubMed

    Miletic, Tijana; Kyriakos, Kachrimanis; Graovac, Adrijana; Ibric, Svetlana

    2013-10-15

    The present work investigates the effect of complexation with hydroxypropyl-beta-cyclodextrin (HPBCD) and 2-O-methyl-beta-cyclodextrin (2-O-MBCD), on voriconazole solubility, dissolution rate and chemical stability. Drug-cyclodextrin complexes were prepared as aqueous solutions, which were spray-dried, and their properties were compared to wet ground samples and physical mixtures. DSC analysis revealed absence of crystalline voriconazole from spray-dried complexes. FTIR spectroscopy indicated changes in the H-bonding network of the hydroxyl groups of cyclodextrin following drug inclusion. Dissolution rate of voriconazole was significantly higher from spray-dried complexes with either cyclodextrin in comparison with free drug, physical mixtures, or wet ground mixtures. However, two degradation impurities were found in aged samples, with slightly higher impurity level with HPBCD. Performed solubility studies suggested that 2-O-MBCD is more efficient solubilizer. Molecular docking simulations showed a difference in the 1:1 binding affinities and sites, with HPBCD surprisingly forming complexes of much lower energy, thus suggesting a multiple rather than a 1:1 complexation. PMID:23987325

  8. Cyclodextrins in pharmaceutical formulations I: structure and physicochemical properties, formation of complexes, and types of complex.

    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 the noncomplexed form of a drug. Cyclodextrins 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 discuss the physical chemical properties of various cyclodextrins, including the effects of substitutions on these properties. Additionally, we report on the regulatory status of their use, commercial products containing cyclodextrins, toxicological considerations, and the forces involved in complex formation. We also highlight the types of complex formed and discuss the methods used to determine the types of complex present. PMID:26686054

  9. Selective isolation of components from natural volatile oil by countercurrent chromatography with cyclodextrins as selective reagent.

    PubMed

    Tong, Shengqiang; Lu, Mengxia; Chu, Chu; Yan, Jizhong; Huang, Juan; Ying, Yongfei

    2016-04-29

    Selective separation of chemical components from seven kinds of volatile oil by countercurrent chromatography with three types of cyclodextrins as selective reagent was investigated in this work. Preparative separation of chemical components from volatile oil is generally quite challenging due to their extremely complexity of the composition. A biphasic solvent system n-hexane-0.10molL(-1) cyclodextrin (1:1, v/v) was selected for separation of components from volatile oil and three types of cyclodextrins were investigated, including β-cyclodexrin, methyl-β-cyclodexrin and hydroxypropyl-β-cyclodexrin. All kinds of volatile oils are from seven kinds of traditional Chinese herb. Results showed that some chemical components could be well separated with high purity from each kind of volatile oil using different type of cyclodextrin as selective reagent. For example, germacrone and curcumenone could be selectively separated from volatile oil of Curcumae Rhizoma with methyl-β-cyclodexrin and hydroxypropyl-β-cyclodexrin as selector respectively, and other five components were selectively separated from volatile oil of Chuanxiong Rhizoma, Myristicae Semen, Aucklandiae Radix and Angelicae Sinensis Radix by countercurrent chromatography with different cyclodexrin as selective reagent. Separation mechanism for separation of components from volatile oil by countercurrent chromatography with cyclodextrin as selective reagent was proposed. Peak resolution of the present separation method could be greatly influenced by the chemical compositions of volatile oil. PMID:27036211

  10. β-Cyclodextrins enhance artemisinin production in Artemisia annua suspension cell cultures.

    PubMed

    Durante, Miriana; Caretto, Sofia; Quarta, Angela; De Paolis, Angelo; Nisi, Rossella; Mita, Giovanni

    2011-06-01

    Artemisinin is a sesquiterpene antimalarial compound produced, though at low levels (0.1-1% dry weight), in Artemisia annua in which it accumulates in the glandular trichomes of the plant. Due to its antimalarial properties and short supply, efforts are being made to improve our understanding of artemisinin biosynthesis and its production. Native β-cyclodextrins, as well as the chemically modified heptakis(2,6-di-O-methyl)-β-cyclodextrin (DIMEB) and 2-hydroxypropyl-β-cyclodextrins, were added to the culture medium of A. annua suspension cultures, and their effects on artemisinin production were analysed. The effects of a joint cyclodextrin and methyl jasmonate treatment were also investigated. Fifty millimolar DIMEB, as well as a combination of 50 mM DIMEB and 100 μM methyl jasmonate, was highly effective in increasing the artemisinin levels in the culture medium. The observed artemisinin level (27 μmol g(-1) dry weight) was about 300-fold higher than that observed in untreated suspensions. The influence of β-cyclodextrins and methyl jasmonate on the expression of artemisinin biosynthetic genes was also investigated. PMID:21468706

  11. Influence of β-cyclodextrin on the Properties of Norfloxacin Form A.

    PubMed

    Chierentin, Lucas; Garnero, Claudia; Chattah, Ana Karina; Delvadia, Poonam; Karnes, Thomas; Longhi, Marcela Raquel; Salgado, Hérida Regina Nunes

    2015-06-01

    Cyclodextrins are able to form host-guest complexes with hydrophobic molecules to result in the formation of inclusion complexes. The complex formation between norfloxacin form A and β-cyclodextrin was studied by exploring its structure affinity relationship in an aqueous solution and in the solid state. Kneading, freeze-drying, and physical mixture methods were employed to prepare solid complexes of norfloxacin and β-cyclodextrin. The solubility of norfloxacin significantly increased upon complexation with β-cyclodextrin as demonstrated by a solubility isotherm of the AL type along with the results of an intrinsic dissolution study. The complexes were also characterized in the solid stated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffractometry, scanning electron microscopy (SEM), and solid-state nuclear magnetic resonance (ssNMR) spectrometry. The thermal analysis showed that the thermal stability of the drug is enhanced in the presence of β-cyclodextrin. Finally, the microbiological studies showed that the complexes have better potency when compared with pure drug. PMID:25511811

  12. Mucoadhesive, thermosensitive, prolonged-release vaginal gel for clotrimazole:beta-cyclodextrin complex.

    PubMed

    Bilensoy, Erem; Rouf, M Abdur; Vural, Imran; Sen, Murat; Hincal, A Atilla

    2006-01-01

    The purpose of this study was to achieve a better therapeutic efficacy and patient compliance in the treatment for vaginitis. Clotrimazole (1%) has been formulated in a vaginal gel using the thermosensitive polymer Pluronic F127 (20%) together with mucoadhesive polymers such as Carbopol 934 and hydroxypropylmethylcellulose (0.2% for both). To increase its aqueous solubility, clotrimazole was incorporated as its inclusion complex with 1:1 molar ratio with beta-cyclodextrin. The inclusion complex was thoroughly characterized using various techniques, including 1H NMR spectroscopy, FT IR spectrophotometry, differential scanning calorimetry, scanning electron microscopy, phase solubility studies, and determination of stability constant (k(1:1)). The gelation temperature and rheological behavior of different formulations at varying temperatures were measured. In vitro release profiles of the gels were determined in pH 5.5 citrate buffer. It was observed that complexation with cyclodextrin slowed down the release of clotrimazole considerably. Carbopol 934, on the other hand, was found to interact with beta-cyclodextrin, inducing precipitation. As far as rheological properties are concerned, thermosensitive in situ gelling was obtained with formulations containing drug:cyclodextrin complex rather than with free drug. Thus, the optimum formulation for a controlled-release thermosensitive and mucoadhesive vaginal gel was determined to be clotrimazole:beta-cyclodextrin 1% with 0.2% hydroxypropylmethylcellulose in Pluronic F127 gel (20%) providing continuous and prolonged release of active material above MIC values. PMID:16796356

  13. [Preparation of phenylcarbamoylated β-cyclodextrin chiral stationary phases and the enantioseparation of flavonoids].

    PubMed

    Lin, Yuzhou; Zhou, Jie; Tang, Jian; Tang, Weihua

    2016-01-01

    Cyclodextrin (CD) based chiral stationary phases (CSPs) have simulated great attention due to their unique chiral recognition ability. Functionalized cyclodextrins bonded silica gel as chiral stationary phases have been dramatically developed due to their chemical stability and solvent tolerability. To explore the functionalization of phenylcarbamoylated β-cyclodextrin CSPs on their enantioselectivities, 4-chloro-3-methylaniline and 5-chloro-2-methyl phenyl isocyanate were employed. Two CSPs have been thus developed by clicking the CD derivatives onto alkynylated silica support. They include per-4-chloro-3-methylphenylcarbamoylated β-cyclodextrin clicked CSP (CSP1) and per-5-chloro-2-methylphenylcarbamoylated β-cyclodextrin clicked CSP (CSP2), which have both electron-donating (methyl) and withdrawing (chlorine) groups in the phenylcarbamate moieties, but different locations. The CSPs were successfully characterized in terms of structure using nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR) and elementary analysis. Their enantioselectivities were evaluated in reversed-phase high performance liquid chromatography (HPLC). The comparison study on the enantioseparation of nine flavonoids with the two CSPs demonstrates the higher enantioselectivities of CSP1 over CSP2, because of the different locations of electron-donating (methyl) and withdrawing (chlorine) groups in the phenylcarbamate moieties of CD derivatives. The baseline enantioseparations achieved in water/methanol as mobile phase offered great potential for the CSPs to be used in practical application. PMID:27319172

  14. Analytical techniques for characterization of cyclodextrin complexes in aqueous solution: a review.

    PubMed

    Mura, Paola

    2014-12-01

    Cyclodextrins are cyclic oligosaccharides endowed with a hydrophilic outer surface and a hydrophobic inner cavity, able to form inclusion complexes with a wide variety of guest molecules, positively affecting their physicochemical properties. In particular, in the pharmaceutical field, cyclodextrin complexation is mainly used to increase the aqueous solubility and dissolution rate of poorly soluble drugs, and to enhance their bioavailability and stability. Analytical characterization of host-guest interactions is of fundamental importance for fully exploiting the potential benefits of complexation, helping in selection of the most appropriate cyclodextrin. The assessment of the actual formation of a drug-cyclodextrin inclusion complex and its full characterization is not a simple task and often requires the use of different analytical methods, whose results have to be combined and examined together. The purpose of the present review is to give, as much as possible, a general overview of the main analytical tools which can be employed for the characterization of drug-cyclodextrin inclusion complexes in solution, with emphasis on their respective potential merits, disadvantages and limits. Further, the applicability of each examined technique is illustrated and discussed by specific examples from literature. PMID:24680374

  15. Phospholipid monolayers between fluid and solid states.

    PubMed Central

    Helm, C A; Möhwald, H; Kjaer, K; Als-Nielsen, J

    1987-01-01

    Monolayers of the phospholipid dimyristoyl phosphatidic acid on the surface of water have been studied by a combination of the new techniques of synchrotron x-ray diffraction and fluorescence microscopy with classical surface pressure data. The pressure vs. area isotherm changes slope at the surface pressures pi c and pi s. The optical technique demonstrates that between pi c and pi s the fluid phase coexists with a denser "gel" phase. Electron diffraction data have shown that the gel phase has bond orientational order over tens of micrometers. However, the x-ray data demonstrate that positional correlations extend only over tens of angstroms. Thus, the gel phase is not crystalline. Above pi s a solid phase is formed with a positional correlation range that is eight times longer for the chemically purest films. Images FIGURE 1 FIGURE 2 PMID:3651557

  16. Valley depolarization in monolayer WSe2

    PubMed Central

    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

  17. 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

  18. Nonequilibrium spin injection in monolayer black phosphorus.

    PubMed

    Chen, Mingyan; Yu, Zhizhou; Wang, Yin; Xie, Yiqun; Wang, Jian; Guo, Hong

    2016-01-21

    Monolayer black phosphorus (MBP) is an interesting emerging electronic material with a direct band gap and relatively high carrier mobility. In this work we report a theoretical investigation of nonequilibrium spin injection and spin-polarized quantum transport in MBP from ferromagnetic Ni contacts, in two-dimensional magnetic tunneling structures. We investigate physical properties such as the spin injection efficiency, the tunnel magnetoresistance ratio, spin-polarized currents, charge currents and transmission coefficients as a function of external bias voltage, for two different device contact structures where MBP is contacted by Ni(111) and by Ni(100). While both structures are predicted to give respectable spin-polarized quantum transport, the Ni(100)/MBP/Ni(100) trilayer has the superior properties where the spin injection and magnetoresistance ratio maintains almost a constant value against the bias voltage. The nonequilibrium quantum transport phenomenon is understood by analyzing the transmission spectrum at nonequilibrium. PMID:26675820

  19. Nonequilibrium spin injection in monolayer black phosphorus

    NASA Astrophysics Data System (ADS)

    Chen, Mingyan; Yu, Zhizhou; Wang, Yin; Xie, Yiqun; Wang, Jian; Guo, Hong

    Monolayer black phosphorus (MBP) is an interesting emerging electronic material with a direct band gap and relatively high carrier mobility. In this work we report a theoretical investigation of nonequilibrium spin injection and spin-polarized quantum transport in MBP from ferromagnetic Ni contacts, in two-dimensional magnetic tunneling structures. We investigate physical properties such as the spin injection efficiency, the tunnel magnetoresistance ratio, spin-polarized currents, charge currents and transmission coefficients as a function of external bias voltage, for two different device contact structures where MBP is contacted by Ni(111) and by Ni(100). While both structures are predicted to give respectable spin-polarized quantum transport, the Ni(100)/MBP/Ni(100) trilayer has the superior properties where the spin injection and magnetoresistance ratio maintains almost a constant value against the bias voltage. The nonequilibrium quantum transport phenomenon is understood by analyzing the transmission spectrum at nonequilibrium.

  20. 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

  1. 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. PMID:26393876

  2. Ultrafast response of monolayer molybdenum disulfide photodetectors

    PubMed Central

    Wang, Haining; Zhang, Changjian; Chan, Weimin; Tiwari, Sandip; Rana, Farhan

    2015-01-01

    The strong light emission and absorption exhibited by single atomic layer transitional metal dichalcogenides in the visible to near-infrared wavelength range make them attractive for optoelectronic applications. In this work, using two-pulse photovoltage correlation technique, we show that monolayer molybdenum disulfide photodetector can have intrinsic response times as short as 3 ps implying photodetection bandwidths as wide as 300 GHz. The fast photodetector response is a result of the short electron–hole and exciton lifetimes in this material. Recombination of photoexcited carriers in most two-dimensional metal dichalcogenides is dominated by nonradiative processes, most notable among which is Auger scattering. The fast response time, and the ease of fabrication of these devices, make them interesting for low-cost ultrafast optical communication links. PMID:26572726

  3. 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.

  4. Host-guest inclusion system of artesunate with β-cyclodextrin and its derivatives: Characterization and antitumor activity

    NASA Astrophysics Data System (ADS)

    Xie, Hudie; Yang, Bo; Wang, Fen; Zhao, Yulin

    2015-04-01

    Inclusion complexes between artesunate (ATS) and three cyclodextrins, namely β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD) and sulfobutyl ether-β-cyclodextrin (SBE-β-CD), were prepared by a suspension method. The complexes in both liquid and solid were characterized by phase-solubility diagram, nuclear magnetic resonance (NMR), powder X-ray diffraction (XRD) and thermoanalysis. The results suggested that artesunate was partly encapsulated within the cyclodextrin cavity to form a 1:1 stoichiometry host-guest compound. Especially in the SBE-β-CD complex, displayed the greatest stability constant. Significant enhancement of water solubility and thermal stability of ATS in present of β-CDs was shown. The calculated IC50 values indicated that the antitumor activities of inclusion complexes were better than that of ATS. Satisfactory aqueous solubility, along with high thermal stability of inclusion complexes will be potentially useful for their application on the formulation design of natural medicine.

  5. Formation of nanoparticles by cooperative inclusion between (S)-camptothecin-modified dextrans and β-cyclodextrin polymers

    PubMed Central

    Amiel, Catherine; Duroux, Laurent; Larsen, Kim Lambertsen; Städe, Lars Wagner; Wimmer, Reinhard; Wintgens, Véronique

    2015-01-01

    Summary 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. PMID:25670998

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. Anomalous thermal conductivity of monolayer boron nitride

    NASA Astrophysics Data System (ADS)

    Tabarraei, Alireza; Wang, Xiaonan

    2016-05-01

    In this paper, we use nonequilibrium molecular dynamics modeling to investigate the thermal properties of monolayer hexagonal boron nitride nanoribbons under uniaxial strain along their longitudinal axis. Our simulations predict that hexagonal boron nitride shows an anomalous thermal response to the applied uniaxial strain. Contrary to three dimensional materials, under uniaxial stretching, the thermal conductivity of boron nitride nanoribbons first increases rather than decreasing until it reaches its peak value and then starts decreasing. Under compressive strain, the thermal conductivity of monolayer boron nitride ribbons monolithically reduces rather than increasing. We use phonon spectrum and dispersion curves to investigate the mechanism responsible for the unexpected behavior. Our molecular dynamics modeling and density functional theory results show that application of longitudinal tensile strain leads to the reduction of the group velocities of longitudinal and transverse acoustic modes. Such a phonon softening mechanism acts to reduce the thermal conductivity of the nanoribbons. On the other hand, a significant increase in the group velocity (stiffening) of the flexural acoustic modes is observed, which counteracts the phonon softening effects of the longitudinal and transverse modes. The total thermal conductivity of the ribbons is a result of competition between these two mechanisms. At low tensile strain, the stiffening mechanism overcomes the softening mechanism which leads to an increase in the thermal conductivity. At higher tensile strain, the softening mechanism supersedes the stiffening and the thermal conductivity slightly reduces. Our simulations show that the decrease in the thermal conductivity under compressive strain is attributed to the formation of buckling defects which reduces the phonon mean free path.

  11. 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

  12. Electronic states of SnTe and PbTe (001) monolayers with supports

    NASA Astrophysics Data System (ADS)

    Kobayashi, Katsuyoshi

    2015-09-01

    Electronic states of SnTe and PbTe (001) monolayers are theoretically studied by density-functional calculations. The systems investigated are freestanding monolayers, monolayers on NaBr substrates, and monolayers sandwiched between two NaBr surfaces. Though isolated PbTe monolayers assumed in a planar structure have the edge states that suggest topological crystalline insulating states, the planar structure of freestanding monolayers is unstable and the mirror symmetry is lost by buckling. Calculations of monolayers on NaBr substrates show that though the attractive interaction between monolayers and substrates reduces buckling amplitude in monolayers, substrates produce a new asymmetry of electrostatic potential in monolayers. Theoretical calculations show that the SnTe monolayers sandwiched between two NaBr surfaces have the edge states suggesting that they are two-dimensional topological crystalline insulators.

  13. Phonon bandgap engineering of strained monolayer MoS2

    NASA Astrophysics Data System (ADS)

    Jiang, Jin-Wu

    2014-06-01

    The phonon band structure of monolayer MoS2 is characteristic of a large energy gap between acoustic and optical branches, which protects the vibration of acoustic modes from being scattered by optical phonon modes. Therefore, the phonon bandgap engineering is of practical significance for the manipulation of phonon-related mechanical or thermal properties in monolayer MoS2. We perform both phonon analysis and molecular dynamics simulations to investigate the tension effect on the phonon bandgap and the compression induced instability of the monolayer MoS2. Our key finding is that the phonon bandgap can be narrowed by the uniaxial tension, and is completely closed at ε = 0.145; while the biaxial tension only has a limited effect on the phonon bandgap. We also demonstrate the compression induced buckling for the monolayer MoS2. The critical strain for buckling is extracted from the band structure analysis of the flexure mode in the monolayer MoS2 and is further verified by molecular dynamics simulations and the Euler buckling theory. Our study illustrates the uniaxial tension as an efficient method for manipulating the phonon bandgap of the monolayer MoS2, while the biaxial compression as a powerful tool to intrigue buckling in the monolayer MoS2.

  14. Phonon bandgap engineering of strained monolayer MoS₂.

    PubMed

    Jiang, Jin-Wu

    2014-07-21

    The phonon band structure of monolayer MoS₂ is characteristic of a large energy gap between acoustic and optical branches, which protects the vibration of acoustic modes from being scattered by optical phonon modes. Therefore, the phonon bandgap engineering is of practical significance for the manipulation of phonon-related mechanical or thermal properties in monolayer MoS₂. We perform both phonon analysis and molecular dynamics simulations to investigate the tension effect on the phonon bandgap and the compression induced instability of the monolayer MoS₂. Our key finding is that the phonon bandgap can be narrowed by the uniaxial tension, and is completely closed at ε = 0.145; while the biaxial tension only has a limited effect on the phonon bandgap. We also demonstrate the compression induced buckling for the monolayer MoS₂. The critical strain for buckling is extracted from the band structure analysis of the flexure mode in the monolayer MoS₂ and is further verified by molecular dynamics simulations and the Euler buckling theory. Our study illustrates the uniaxial tension as an efficient method for manipulating the phonon bandgap of the monolayer MoS₂, while the biaxial compression as a powerful tool to intrigue buckling in the monolayer MoS₂. PMID:24932612

  15. A comparative study of the effect of α-, β-, and γ-cyclodextrins as stabilizing agents in the synthesis of silver nanoparticles using a green chemistry method.

    PubMed

    Suárez-Cerda, Javier; Nuñez, Gabriel Alonso; Espinoza-Gómez, Heriberto; Flores-López, Lucía Z

    2014-10-01

    This paper describes the effect of different types of cyclodextrins (CDs) in the synthesis of silver nanoparticles (Ag-NPs), using an easy green chemistry method. The Ag-NPs were obtained using an aqueous silver nitrate solution (AgNO3) with α-, β-, or γ-CDs (aqueous solutions) as stabilizing agents, employing the chemical reduction method with citric acid as a reducing agent. A comparative study was done to determine which cyclodextrin (CD) was the best stabilizing agent, and we found out that β-CD was the best due to the number of glucopyranose units in its structure. The formation of the Ag-NPs was demonstrated by analysis of UV-vis spectroscopy, atomic force microscopy (AFM), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and transmission electron microscopy (TEM). SEM-EDS showed the formation of a cluster with a significant amount of silver, for β-CD-Ag-NPs, spherical agglomerates can be observed. However, for α-, γ-CD, the agglomerates do not have a specific form, but their appearance is porous. TEM analysis shows spherical nanoparticles in shape and size between ~0.5 to 7 nm. The clear lattice fringes in TEM images and the typical selected area electron diffraction (SAED) pattern, showed that the Ag-NPs obtained were highly crystalline with a face cubic center structure (FCC). PMID:25175183

  16. Sustained-release matrix tablets of metformin hydrochloride in combination with triacetyl-beta-cyclodextrin.

    PubMed

    Corti, Giovanna; Cirri, Marzia; Maestrelli, Francesca; Mennini, Natascia; Mura, Paola

    2008-02-01

    The low bioavailability and short half-life of metformin hydrochloride (MH) make the development of sustained-release forms desirable. However, drug absorption is limited to the upper gastrointestinal (GI) tract, thus requiring suitable delivery systems providing complete release during stomach-to-jejunum transit. This study was undertaken to develop a MH sustained-release formulation in compliance with these requirements. The strategy proposed is based on direct-compressed matrix tablets consisting of a combination of MH with the hydrophobic triacetyl-beta-cyclodextrin (TAbetaCD), dispersed in a polymeric material. Different polymers were tested as excipients, i.e. hydroxypropylmethylcellulose, xanthan gum, chitosan, ethylcellulose, Eudragit L100-55, and Precirol. Compatibility among the formulation components was assessed by DSC analysis. All the tablets were examined for drug release pattern in simulated gastric and jejunal fluids used in sequence to mimic the GI transit. Release studies demonstrated that blends of a hydrophobic swelling polymer (hydroxypropylmethylcellulose or chitosan) with a pH-dependent one (Eudragit L100-55) were more useful than single polymers in controlling drug release. Moreover, the main role played by the MH-TAbetaCD system preparation method (i.e. grinding or spray-drying) in determining the behaviour of the final formulation was evidenced. In fact, for a given matrix-tablet composition, different sustained-release effects were obtained by varying the relative amounts of MH-TAbetaCD as ground or spray-dried product. In particular, the 1:1 (w/w) blend of such systems, dispersed in a Eudragit-chitosan polymeric matrix, fully achieved the prefixed goal, giving about 30% released drug after 2h at gastric pH, and overcoming 90% released drug within the subsequent 3h in jejunal fluid. PMID:17616379

  17. Ultrafast electron diffraction optimized for studying structural dynamics in thin films and monolayers.

    PubMed

    Badali, D S; Gengler, R Y N; Miller, R J D

    2016-05-01

    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

  18. 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

  19. Implicit-Solvent Coarse-Grained Simulation with a Fluctuating Interface Reveals a Molecular Mechanism for Peptoid Monolayer Buckling.

    PubMed

    Haxton, Thomas K; Zuckermann, Ronald N; Whitelam, Stephen

    2016-01-12

    Peptoid polymers form extended two-dimensional nanostructures via an interface-mediated assembly process: the amphiphilic peptoids first adsorb to an air-water interface as a monolayer, then buckle and collapse into free-floating bilayer nanosheets when the interface is compressed. Here, we investigate the molecular mechanism of monolayer buckling by developing a method for incorporating interface fluctuations into an implicit-solvent coarse-grained model. Representing the interface with a triangular mesh controlled by surface tension and surfactant adsorption, we predict the direction of buckling for peptoids with a segregated arrangement of charged side chains and predict that peptoids with with an alternating charge pattern should buckle less easily than peptoids with a segregated charge pattern. PMID:26647143

  20. The Drug Excipient Cyclodextrin Interacts With d-Luciferin and Interferes With Bioluminescence Imaging.

    PubMed

    Kumar, Jeyan S; Miller Jenkins, Lisa M; Gottesman, Michael M; Hall, Matthew D

    2016-01-01

    Cyclodextrins are well-characterized, barrel-shaped molecules that can solubilize organic small molecules in aqueous solution via host-guest interactions. As such, cyclodextrins are used as excipients for experimental therapeutics in vivo. We observed unanticipated modifications to bioluminescence imaging (BLI) signal intensity when 2-hydroxy-propyl-β-cyclodextrin (HPCD) was coinjected as an excipient. We hypothesized that HPCD bindsd-luciferin and interferes with the BLI signal. Using luciferase-expressing cell lines, we showed that HPCD lowers the BLI signal in a concentration-dependent manner. Flow cytometry revealed that HPCD resulted in reduced cellular accumulation ofd-luciferin, and mass spectrometry revealedd-luciferin HPCD species, confirming a direct interaction. In vivo imaging using a luciferase mouse model demonstrated that HPCD reduced luciferin-mediated BLI compared to luciferin alone. The implications of using HPCD as an excipient in BLI studies are discussed. PMID:27030398

  1. Removal of volatile organic compounds using amphiphilic cyclodextrin-coated polypropylene.

    PubMed

    Lumholdt, Ludmilla; Fourmentin, Sophie; Nielsen, Thorbjørn T; Larsen, Kim L

    2014-01-01

    Polypropylene nonwovens were functionalised using a self-assembled, amphiphilic cyclodextrin coating and the potential for water purification by removal of pollutants was studied. As benzene is one of the problematic compounds in the Water Framework Directive, six volatile organic compounds (benzene and five benzene-based substances) were chosen as model compounds. The compounds were tested as a mixture in order to provide a more realistic situation since the wastewater will be a complex mixture containing multiple pollutants. The volatile organic compounds are known to form stable inclusion complexes with cyclodextrins. Six different amphiphilic cyclodextrin derivatives were synthesised in order to elucidate whether or not the uptake abilities of the coating depend on the structure of the derivative. Headspace gas chromatography was used for quantification of the uptake exploiting the volatile nature of benzene and its derivatives. The capacity was shown to increase beyond the expected stoichiometries of guest-host complexes with ratios of up to 16:1. PMID:25550739

  2. New cyclodextrin derivative containing poly(L-lysine) dendrons for gene and drug co-delivery.

    PubMed

    Ma, Dong; Zhang, Hong-Bin; Chen, Yu-Yun; Lin, Jian-Tao; Zhang, Li-Ming

    2013-09-01

    To develop a multifunctional polymeric carrier for gene and drug co-delivery, a new cyclodextrin derivative containing poly(L-lysine) dendrons was prepared by the click conjugation of per-6-azido-β-cyclodextrin with propargyl focal point poly(L-lysine) dendron of third generation and then characterized by FTIR, (1)H NMR, and GPC analyses. It was found that such a conjugate could form colloidally stable nanocomplexes with plasmid DNA in aqueous system and exhibited high gene transfection efficiency. Moreover, it could load efficiently methotrexate drug with anticancer activity and showed a sustained release behavior. Different from commonly used amphiphilic copolymers with cationic character, the as obtained cyclodextrin derivative may be used directly for the combinatorial delivery of nucleic acid and lipophilic anticancer drugs without a complicated micellization process. PMID:23769303

  3. Electrical release of dopamine and levodopa mediated by amphiphilic β-cyclodextrins immobilized on polycrystalline gold.

    PubMed

    Foschi, Giulia; Leonardi, Francesca; Scala, Angela; Biscarini, Fabio; Kovtun, Alessandro; Liscio, Andrea; Mazzaglia, Antonino; Casalini, Stefano

    2015-12-21

    Vesicles of cationic amphiphilic β-cyclodextrins have been immobilized on polycrystalline gold by exploiting the chemical affinity between their amino groups and Au atoms. The presence of cyclodextrins has been widely investigated by means of AFM, XPS, kelvin probe and electrochemical measurements. This multi-functional coating confers distinct electrochemical features such as pH-dependent behavior and partial/total blocking properties towards electro-active species. The host-guest properties of β-cyclodextrins have been successfully exploited in order to trap drugs, like dopamine and levodopa. The further release of these drugs was successfully achieved by providing specific electrical stimuli. This proof-of-concept led us to fabricate an electronic device (i.e. an organic transistor) capable of dispensing both dopamine and levodopa in aqueous solution. PMID:26565988

  4. Ternary cyclodextrin polyurethanes containing phosphate groups: Synthesis and complexation of ciprofloxacin.

    PubMed

    Moreira, Mirna Pereira; Andrade, George Ricardo Santana; de Araujo, Marcia Valeria Gaspar; Kubota, Tatiana; Gimenez, Iara F

    2016-10-20

    Synthesis of ternary polyurethanes (PUs) from hexamethylenediisocyanate, β-cyclodextrin and β-glycerophosphate (acid and calcium salt) was studies varying synthesis parameters such as monomer proportion, heating method (reflux and microwave), and catalyst amount. Favorable conditions were provided by microwave irradiation and use of β-glycerophosphoric acid although the results suggest that it is possible to obtain ternary PUs with the calcium salt. FTIR data indicated the existence of secondary urea linkages. After characterization of ternary PUs by FTIR spectroscopy, XRD and thermal analysis, as well as evidences that the cyclodextrin cavities remained active toward inclusion of guest molecules, the possibility of inclusion of the antibiotic ciprofloxacin was evaluated. Absence of ciprofloxacin melting peak in DSC curves indicated that it is molecularly dispersed within the polymer, possibly included in the cyclodextrin. In vitro release experiments suggested additional non-inclusion interactions, showing also that the use of dialysis membranes may mask the actual release profile. PMID:27474600

  5. Study on vitamin K 3-cyclodextrin inclusion complex and analytical application

    NASA Astrophysics Data System (ADS)

    Zhenming, Dong; Xiuping, Liu; Guomei, Zhang; Shaomin, Shuang; Jinghao, Pan

    2003-07-01

    The inclusion interaction of the complexes between Vitamin K 3 (VK 3) and β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HP-β-CD) and sulfobutylether-β-cyclodextrin (SBE-β-CD) were studied by using steady-state fluorescence measurements. The various factors affecting the inclusion process were examined in detail. The formation constants and inclusion stoichiometry for VK 3-CDs were determined. The results showed that the inclusion ability of β-CD and its derivatives was the order: SBE-β-CD>HP-β-CD>β-CD. The related inclusion mechanism is proposed to explain the inclusion process. A method of determining VK 3 was established with the linear range was 2.5×10 -6-5.0×10 -4 M, and was used to determine the VK 3 tablets. The recoveries were in the range of 97.52-103.5%. The results were satisfactory.

  6. Inclusion complexes of chlorzoxazone with β- and hydroxypropyl-β-cyclodextrin: Characterization, dissolution, and cytotoxicity.

    PubMed

    Tang, Peixiao; Li, Shanshan; Wang, Lili; Yang, Hongqin; Yan, Jin; Li, Hui

    2015-10-20

    This study aimed to improve the water solubility and reduce the toxicity of chlorzoxazone via complexation with β-cyclodextrin (β-CD) and hydroxypropyl-β-cyclodextrin (HP-β-CD). Inclusion complexes between chlorzoxazone and the two cyclodextrins (CDs) were prepared by freeze-drying method. Formation of the complexes was confirmed by FT-IR, PXRD, (1)H NMR, DSC, and SEM. The water solubility and dissolution rates of chlorzoxazone were significantly increased by complexation with the two CDs. Preliminary in vitro cytotoxicity tests showed that the complexes are less toxic to normal liver cells than free chlorzoxazone. In general, the HP-β-CD complex exhibited better dissolution properties than the β-CD complex in various dissolution media. Therefore, the HP-β-CD complex can be used to design novel formulations of chlorzoxazone. PMID:26256188

  7. Supramolecular biosensors based on electropolymerised pyrrole-cyclodextrin modified surfaces for antibody detection.

    PubMed

    Wajs, Ewelina; Fernández, Núria; Fragoso, Alex

    2016-06-01

    The self-assembly of an adamantane-appended polymer bearing an antigen fragment on a polypyrrole-cyclodextrin modified surface provides a highly sensitive immunosensor with low limits of detection for celiac disease related targets. The pyrrole-carboxylic acid films were formed on the surface of gold electrodes by electropolymerisation and followed by covalent attachment of cyclodextrin units. Surface plasmon resonance measurements confirmed the role of the host/guest interactions between adamantane moieties and β-cyclodextrin hosts in the formation of the supramolecular sensor interface. Furthermore, this novel electrochemical supramolecular platform was effective in the amperometric detection of anti-gliadin antibodies in spiked serum samples with very good signal recovery. PMID:27097527

  8. A γ-cyclodextrin duplex connected with two disulfide bonds: synthesis, structure and inclusion complexes.

    PubMed

    Volkov, Sergey; Kumprecht, Lukáš; Buděšínský, Miloš; Lepšík, Martin; Dušek, Michal; Kraus, Tomáš

    2015-03-14

    Per(2,3,6-tri-O-benzyl)-γ-cyclodextrin was debenzylated by DIBAL-H to produce a mixture of C6(I),C6(IV) and C6(I),C6(V) isomeric diols, which were separated and isolated. The C2-symmetrical C6(I),C6(V) diol was transformed into dithiol and dimerized to produce a γ-cyclodextrin duplex structure. A crystal structure revealed tubular cavity whose peripheries are slightly elliptically distorted. The solvent accessible volume of the cavity of the γ-CD duplex is about 740 Å(3). Due to this large inner space the duplex forms very stable inclusion complexes with steroids; bile acids examined in this study show binding affinities to the γ-cyclodextrin duplex in the range of 5.3 × 10(7) M(-1)-1.9 × 10(8) M(-1). PMID:25616110

  9. Stretching a polymer brush by making in situ cyclodextrin inclusion complexes.

    PubMed

    Joseph, Julie; Dreiss, Cécile A; Cosgrove, Terence

    2008-09-16

    The interaction between poly(ethylene oxide) (PEO) chains grafted onto polystyrene latex particles and alpha-, beta-, and gamma-cyclodextrins (CD) was studied by small-angle neutron scattering. The particles were contrast-matched to the solvent in order that only the scattering from the polymer layers was detected. The signal from the layers was fitted to a double-exponential volume fraction profile. The effects of adding cyclodextrin on the polymer profile are shown as a function of cyclodextrin concentration. The polymer layers are seen to extend on addition of CD, which is consistent with a complexation between the grafted PEO and the CD molecules. The effect is the strongest with alpha-CD. PMID:18712892

  10. Beta-cyclodextrin-appended giant amphiphile: aggregation to vesicle polymersomes and immobilisation of enzymes.

    PubMed

    Felici, Marco; Marzá-Pérez, María; Hatzakis, Nikos S; Nolte, Roeland J M; Feiters, Martin C

    2008-01-01

    A giant amphiphile consisting of polystyrene end-capped with permethylated beta-cyclodextrin was synthesised and found to form vesicular structures when injected as a solution in THF into water. The ability of the cyclodextrins on the surface of the polymersomes to form inclusion complexes with hydrophobic compounds was tested by carrying out a competition experiment with a fluorescent probe sensitive to the polarity of the surrounding medium. It was found that 1-adamantol can displace the fluorescent probe from the cavities of the cyclodextrin moieties of the polymersomes. The recognition of molecules by cell membranes in nature is often based on interactions with specific membrane receptors. To mimic this behaviour, the enzyme horseradish peroxidase was modified with adamantane groups through a poly(ethylene glycol) spacer and its interaction with the polymersomes was investigated. It was established that the presence of adamantane moieties on each enzyme allowed a host-guest interaction with the multifunctional surface of the polymersomes. PMID:18810732

  11. Structure-Dependent Viscoelastic Properties of C(9)-Alkanethiol Monolayers

    SciTech Connect

    Mayer, Thomas M.; Michalske, Terry A.; Shinn, Neal D.

    1999-08-10

    Quartz crystal microbalance techniques and in situ spectroscopic ellipsometry are used to probe the structure-dependent intrinsic viscoelastic properties of self-assembled CH{sub 3}(CH{sub 2}){sub 8}SH alkanethiol monolayer adsorbed from the gas phase onto Au(111)-textured substrates. Physisorbed molecules, mixed chemisorbed-fluid/solid phases and solid-phase domain boundaries make sequentially dominant contributions to the measured energy dissipation in the growing monolayer. Deviations from Langmuir adsorption kinetics reveal a precursor-mediated adsorption channel. These studies reveal the impact of structural heterogeneity in tribological studies of monolayer lubricants.

  12. Interactions between 4-thiothymidine and water-soluble cyclodextrins: Evidence for supramolecular structures in aqueous solutions.

    PubMed

    Rizzi, Vito; Matera, Sergio; Semeraro, Paola; Fini, Paola; Cosma, Pinalysa

    2016-01-01

    Since several years the inclusion of organic compounds (guests) within the hydrophobic cavity (host) of cyclodextrins (CDs) has been the subject of many investigations. Interestingly, the formation of inclusion complexes could affect the properties of the guest molecules and, for example, the influence of the delivery system can be a method to improve/change the photochemical behavior of the guest. In particular, very recent studies have shown the protective role of CDs preventing the degradation of the encapsulated guest. Starting from this consideration, in this work, only the structure and complexation mode of the inclusion complexes involving 4-thiothymidine (S(4)TdR, a known photosensitizer) and five CDs, namely 2-hydroxypropyl-α-cyclodextrin (2-HP-α-CD), 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD), 2-hydroxypropyl-γ-cyclodextrin (2-HP-γ-CD), heptakis-(2,6-di-O-methyl)-β-cyclodextrin (DIMEB CD) and heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB CD) were investigated by different spectroscopic techniques (UV-vis, FTIR-ATR, (1)H NMR) and cyclic voltammetry analysis (CV). This work is necessary for a prospective research on the photoreactivity of S(4)TdR in aqueous environment and in the presence of CDs to prevent its degradation under irradiation. UV-vis, FTIR-ATR and CV measurements suggested the formation of supramolecular structures involving the employed CDs and mainly the pyrimidine ring of S(4)TdR. (1)H NMR analyses confirmed such indication, unveiling the presence of inclusion complexes. The strongest and deepest interactions were suggested when TRIMEB and DIMEB CDs were studied. The S(4)TdR affinity towards CDs was also evaluated by using the Benesi-Hildebrand (B-H) equation at 25 °C employing CV and (1)H NMR methods. The stoichiometry of the interaction was also inferred and it appears to be 1:1 for all examined CDs. PMID:27340447

  13. Interactions between 4-thiothymidine and water-soluble cyclodextrins: Evidence for supramolecular structures in aqueous solutions

    PubMed Central

    Rizzi, Vito; Matera, Sergio; Semeraro, Paola; Fini, Paola

    2016-01-01

    Summary Since several years the inclusion of organic compounds (guests) within the hydrophobic cavity (host) of cyclodextrins (CDs) has been the subject of many investigations. Interestingly, the formation of inclusion complexes could affect the properties of the guest molecules and, for example, the influence of the delivery system can be a method to improve/change the photochemical behavior of the guest. In particular, very recent studies have shown the protective role of CDs preventing the degradation of the encapsulated guest. Starting from this consideration, in this work, only the structure and complexation mode of the inclusion complexes involving 4-thiothymidine (S4TdR, a known photosensitizer) and five CDs, namely 2-hydroxypropyl-α-cyclodextrin (2-HP-α-CD), 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD), 2-hydroxypropyl-γ-cyclodextrin (2-HP-γ-CD), heptakis-(2,6-di-O-methyl)-β-cyclodextrin (DIMEB CD) and heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB CD) were investigated by different spectroscopic techniques (UV–vis, FTIR–ATR, 1H NMR) and cyclic voltammetry analysis (CV). This work is necessary for a prospective research on the photoreactivity of S4TdR in aqueous environment and in the presence of CDs to prevent its degradation under irradiation. UV–vis, FTIR–ATR and CV measurements suggested the formation of supramolecular structures involving the employed CDs and mainly the pyrimidine ring of S4TdR. 1H NMR analyses confirmed such indication, unveiling the presence of inclusion complexes. The strongest and deepest interactions were suggested when TRIMEB and DIMEB CDs were studied. The S4TdR affinity towards CDs was also evaluated by using the Benesi–Hildebrand (B–H) equation at 25 °C employing CV and 1H NMR methods. The stoichiometry of the interaction was also inferred and it appears to be 1:1 for all examined CDs. PMID:27340447

  14. Characterization of pioglitazone cyclodextrin complexes: Molecular modeling to in vivo evaluation

    PubMed Central

    Bramhane, Dinesh M.; Kulkarni, Preethi A.; Martis, Elvis A. F.; Pissurlenkar, Raghuvir R. S.; Coutinho, Evans C.; Nagarsenker, Mangal S.

    2016-01-01

    Aims: The objective of present study was to study the influence of different β-cyclodextrin derivatives and different methods of complexation on aqueous solubility and consequent translation in in vivo performance of Pioglitazone (PE). Material and Methods: Three cyclodextrins: β-cyclodextrin (BCD), hydroxypropyl-β-cyclodextrin (HPBCD) and Sulfobutylether-7-β-cyclodextrin (SBEBCD) were employed in preparation of 1:1 Pioglitazone complexes by three methods viz. co-grinding, kneading and co-evaporation. Complexation was confirmed by phase solubility, proton NMR, Fourier Transform Infrared spectroscopy, Differential Scanning Calorimetry (DSC) and X-Ray diffraction (XRD). Mode of complexation was investigated by molecular dynamic studies. Pharmacodynamic study of blood glucose lowering activity of PE complexes was performed in Alloxan induced diabetic rat model. Results: Aqueous solubility of PE was significantly improved in presence of cyclodextrin. Apparent solubility constants were observed to be 254.33 M–1 for BCD-PE, 737.48 M–1 for HPBCD-PE and 5959.06 M–1 for SBEBCD-PE. The in silico predictions of mode of inclusion were in close agreement with the experimental proton NMR observation. DSC and XRD demonstrated complete amorphization of crystalline PE upon inclusion. All complexes exhibited >95% dissolution within 10 min compared to drug powder that showed <40% at the same time. Marked lowering of blood glucose was recorded for all complexes. Conclusion: Complexation of PE with different BCD significantly influenced its aqueous solubility, improved in vitro dissolution and consequently translated into enhanced pharmacodynamic activity in rats PMID:27134470

  15. 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

    2016-03-23

    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. PMID:26661072

  16. Liquid chromatography of hydrocarbonaeous quaternary amines on cyclodextrin bonded silica

    USGS Publications Warehouse

    Abidi, S.L.

    1986-01-01

    Mixtures of n-alkylbenzyldimethylammonium chloride (ABDAC) were resolved into homologous components by high-performance liquid chromatography (HPLC) with a cyclodextrin-bonded silica stationary phase. With a few exceptions, results from this study are similar to those obtained from traditional reversed-phase HPLC. It was found that the presence of electrolytes in aqueous mobile phases is not a critical factor in determining the success of HPLC separation. Under normal HPLC conditions, a mobile phase consisting of either methanol–water (50:50) or acetonitrile–water (30:70) was employed for obtaining adequate resolution of the quaternary ammonium mixtures. Although the percent organic modifier–water profiles were similar to those in previous studies with these compounds, resolution (R) and selectivity (α) parameters were found to be quite susceptible to changes in the mobile phase solvent composition. The retention behavior of the cationic analytes in the homologous series is consistent with the hydrophobic-interaction concept proposed for the retention mechanism via dominant inclusion complex formation. Several electrolytes were chosen for a study of the counter ion effect on the chromatographic characteristics of ABDAC components. Among the electrolytes examined, the perchlorate ion was found most likely to act as an ion-pairing counter ion for ammonium cations in the HPLC system studied. A correlation study established linear relationships between the chain length of ABDAC and the logarithmic capacity factor (k2). The analytical utility of the HPLC method was demonstrated by the analysis of various unknown mixtures.

  17. Transdermal permeation modulation by cyclodextrins: a mechanistic study.

    PubMed

    Williams, A C; Shatri, S R; Barry, B W

    1998-08-01

    The purpose of this study was to investigate permeation modulation by beta- and 2-hydroxypropyl-beta-cyclodextrins (beta-CD and HP-beta-CD, respectively) alone and complexed with penetration enhancers for the test drugs 5-fluorouracil and estradiol through human skin, and to probe the value of the CDs in a barrier cream against toluene exposure. Methods include phase solubility studies, permeation experiments, and thermal analysis of stratum corneum; inclusion complexes were characterized by Karl Fischer titrimetry, infrared spectroscopy, and thermal analysis. Results show that complexes of terpenes or toluene with beta-CD were insoluble, whereas those with HP-beta-CD were soluble. The CDs did not enhance flux of either the polar or lipophilic drugs through skin; estradiol permeation was reduced following membrane pretreatment with either CD. Complexation of the lipophilic terpenes with the CDs reduced enhancer efficacy. When formulated into a barrier ointment both CDs, but particularly beta-CD, retarded toluene permeation through the skin and delayed the onset of maximum flux. It is concluded that the CDs themselves are not penetration enhancers for 5-fluorouracil or estradiol in human skin, and that they may be usefully incorporated into a barrier formulation to reduce percutaneous absorption of toxic materials on occupational exposure. PMID:9742549

  18. Cyclodextrin-grafted chitosan hydrogels for controlled drug delivery.

    PubMed

    Kono, Hiroyuki; Teshirogi, Taku

    2015-01-01

    A series of β-cyclodextrin-grafted carboxymethyl chitosan hydrogels (CD-g-CMCs) were prepared from carboxymethyl chitosan (CMC) and carboxymethyl β-chitosan (CMCD) using a water-soluble carbodiimide as a crosslinker in the presence of N-hydroxysuccinimide. Details of the hydrogel structures were determined via FTIR and solid-state NMR spectroscopic analyses. Increasing the feed ratio of CMCD to CMC in the reaction mixture led to an increase in CD grafting within the gel networks comprising CMC; this was confirmed by SEM observations and rheological analysis of the swollen hydrogels. The prepared CD-g-CMC hydrogels exhibited absorption properties toward acetylsalicylic acid (ASA, or Aspirin) due to the presence of CD in the structure; the amount of ASA absorbed into the hydrogels was enhanced with an increase in the amount of CD incorporated within the hydrogels. In addition, CD-g-CMC hydrogels provided a slower release of the entrapped ASA in comparison to the ASA release profile of a solely CMC-containing hydrogel. From these results, CD-g-CMC hydrogels have the potential to function as a biodegradable active material with controlled drug release ability. PMID:25192852

  19. Hydrothermal Syntheses of Colloidal Carbon Spheres from Cyclodextrins

    SciTech Connect

    Shin, Yongsoon; Wang, Li Q.; Bae, In-Tae; Arey, Bruce W.; Exarhos, Gregory J.

    2008-09-18

    Colloidal carbon spheres have been prepared from aqueous alpha-, beta-, and gamma-cyclodextrin (CD) solutions in closed systems under hydrothermal conditions at 160 oC. Both liquid and solid-state 13C NMR spectra taken for samples at different reaction times have been used to monitor the dehydration and carbonization pathways. CD slowly hydrolyzes to glucose and forms 5-hydroxymethyl furfural (HMF) followed by carbonization into colloidal carbon spheres. The isolated carbon spheres are 70-150 nm in diameter, exhibit a core-shell structure, and are comprised of a condensed core (C=C) peppered with resident chemical functionalities including carboxylate and hydroxyl groups. Evidence from 13C solid-state NMR and FT-IR spectra reveal that the evolving carbon spheres show a gradual increase in the amount of aromatic carbon as a function of reaction time and that the carbon spheres generated from gamma-CD contain significantly higher aromatic carbon than those derived from alpha- and beta-CD.

  20. Effect of cyclodextrins on the degradation rate of benzylpenicillin.

    PubMed

    Popielec, A; Fenyvesi, É; Yannakopoulou, K; Loftsson, T

    2016-02-01

    The effect of cyclodextrin (CD) inclusion complexes on the degradation of benzylpenicillin in aqueous solutions was investigated at several different pH values and 37°C. The effects of neutral as well as both positively and negatively charged CDs were evaluated; all together 13 different CDs. Kinetic studies with HPβCD and RMβCD at pH ranging from 1.2 to 9.6 showed that CDs have stabilizing effect on the β-lactam ring in aqueous acidic media but generally accelerated the hydrolytic cleavage of the β-lactam ring in neutral and basic media. At physiologic pH (pH 7.4) quaternary ammonium CD derivatives (i.e., positively charged CD derivatives) have the highest catalytic effect, resulting in 6- to 18-fold enhancement of hydrolysis rate, while both the neutral methylated CDs had much less effect, resulting in 2- to 3-fold enhancement, and the negatively charged CD derivatives, resulting in only about 1.1- to 1.2-fold enhancement in the hydrolytic cleavage of the β-lactam ring. Addition of water-soluble polymers to the aqueous reaction media containing CDs was shown to decrease the catalyzing effects of CDs on the β-lactam hydrolysis. PMID:27004370

  1. Dissolution enhancement of cefdinir with hydroxypropyl-β-cyclodextrin.

    PubMed

    Guo, Bohong; Zhong, Shufen; Li, Niying; Li, Xiaofang; Yi, Jun; Jin, Miaozhen

    2013-11-01

    The solid state properties and dissolution behavior of binary systems of cefdinir (CEF) with hydroxypropyl-β-cyclodextrin (HP-β-CD) were investigated. CEF-HP-β-CD interaction in the solution state was studied by phase-solubility analysis and demonstrates the ability of HP-β-CD to complex with CEF giving A(L) type profile with 65.28 ± 1.3 M⁻¹ stability constant. The freeze drying technique was adopted to prepare binary systems of CEF with HP-β-CD in 1:1 molar ratio. The solid inclusion was characterized by fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray powder diffractometry (XRD), and scanning electron microscopy (SEM). Aqueous solubility of CEF-HP-β-CD inclusion complex was 2.36-fold of pure CEF. The dissolution profiles of inclusion complexes were determined and compared with those of CEF alone and their physical mixtures. The dissolution rate of inclusion complex was superior than the CEF alone. These approaches indicated that CEF was able to form an inclusion complex with HP-β-CD, and the inclusion compounds exhibited different spectroscopic features and properties. PMID:24087855

  2. Cyclodextrin-polyhydrazine degradable gels for hydrophobic drug delivery.

    PubMed

    Jalalvandi, Esmat; Cabral, Jaydee; Hanton, Lyall R; Moratti, Stephen C

    2016-12-01

    An injectable and biocompatible hydrogel system was designed for hydrophobic drug delivery. This hydrogel consisted of degradable polymers with cyclodextrin (CD) moieties. CD groups were used to increase the solubility of a hydrophobic molecule (nicardipine) in an aqueous solution through the formation of the inclusion complex. Two sets of gels were prepared by mixing oxidized dextran (DA) and CD functionalized polyhydrazine (PH) at physiological conditions and different level of crosslinking via hydrazone bonds. Cytotoxicity studies on the gels and their components confirmed the biocompatibility of these materials. Gel-30 with higher crosslinking density showed a two week degradation period whereas this period was 10days for gel-10, with lower crosslinking density, to complete degradation. The results from swelling tests and rheological measurements were also found to be dependent on crosslinking density of the hydrogels. Release profile of the hydrogel displayed a sustained release of nicardipin up to 6days for gel-30 and a 4day release with initial burst release for gel-10. PMID:27612699

  3. Biodegradable star polymers functionalized with beta-cyclodextrin inclusion complexes.

    PubMed

    Setijadi, Eki; Tao, Lei; Liu, Jingquan; Jia, Zhongfan; Boyer, Cyrille; Davis, Thomas P

    2009-09-14

    Three-armed biodegradable star polymers made from polystyrene (polySt) and poly (polyethylene glycol) acrylate (polyPEG-A) were synthesized via a "core first" methodology using a trifunctional RAFT agent, created by attaching RAFT agents to a core via their R-groups. The resultant three-armed polymeric structures were well-defined, with polydispersity indices less than 1.2. Upon aminolysis and further reaction with dithiodipyridine (DTDP), these three-armed polymers could be tailored with sulfhydryl and pyridyldisulfide (PDS) end functionalities, available for further reaction with any free-sulfhydryl group containing precursors to form disulfide linkages. Nuclear magnetic resonance (NMR) confirmed that more than 98% of the polymer arms retained integral trithiocarbonate active sites after polymerization. Intradisulfide linkages between the core and the arms conferred biodegradability on the star architectures. Subsequently, the arm-termini were attached to cholesterol also via disulfide linkages. The cholesterol terminated arms were then used to form supramolecular structures via inclusion complex formation with beta-cyclodextrin (beta-CD). The star architectures were found to degrade rapidly on treatment with DL-dithiothereitol (DTT). The star polymers and supramolecular structures were characterized using gel permation chromatography (GPC), static light scattering (SLS), 2D NMR, and fluorescence spectroscopy. PMID:19663421

  4. Preliminary In Vitro Evaluation of Genistein Chemopreventive Capacity as a Result of Esterification and Cyclodextrin Encapsulation

    PubMed Central

    Danciu, Corina; Soica, Codruta; Dehelean, Cristina; Zupko, Istvan; Csanyi, Erzsebet; Pinzaru, Iulia

    2015-01-01

    The present study focuses on the synthesis and analysis of a genistein ester derivative with myristic acid followed by beta cyclodextrin encapsulation; physicochemical analysis using consecrated techniques such as FTIR, MS, DSC, and SEM revealed both a successful esterification and inclusion inside the cyclodextrin cavity. Cytotoxic effects were measured in vitro on three human cell lines: HeLa (cervix adenocarcinoma), A2780 (ovary carcinoma), and A431 (skin epidermoid carcinoma). The in vitro biological analysis exhibited rather poor antiproliferative results on all three tested cancer cell lines, behavior that may be due to the high stability of the complex within the in vitro environment. PMID:26161301

  5. Formation of extended probe-cyclodextrin nanotubular supra structures: Endogenous surfactants triggered on-demand release

    NASA Astrophysics Data System (ADS)

    Mallick, Arabinda; Haldar, Basudeb; Roy, Ujjal Kanti

    2013-08-01

    Steady state absorption, emission, and picosecond time resolved fluorescence and transmission electron microscopic (TEM) techniques have been exploited to substantiate and characterize the formation of a substrate—anchored β-cyclodextrin nanotubular suprastructure in aqueous medium. Experimental results reveal that suprastructure is originated from a purely ground state interaction between a newly developed bisindole based drug molecule namely 3,3'-bis(indolyl)-4-chlorophenylmethane (BICPM) with β-cyclodextrin. The bound drug molecule is susceptible to be released out from the supramolecular complex in a controlled manner by the use of endogenous surfactants and is poised to serve a significant purpose in targeted drug delivery preferably at the intestinal region.

  6. Determination of enantiomeric purity of mandelonitrile with derivatized cyclodextrins in water

    NASA Astrophysics Data System (ADS)

    Hickel, Andrea; Gradnig, Günther; Schall, Michael; Zangger, Klaus; Griengl, Herfried

    1997-03-01

    A variety of derivatized cyclodextrins was used for the determination of the optical purity of mandelonitrile by 1H-NMR (nuclear magnetic resonance) spectroscopy in aqueous solution. Mandelonitrile was formed by the enzymatic reaction of benzaldehyde and HCN (or acetone cyanohydrine) with the hydroxynitrile lyase (Hnl) from Hevea brasiliensis (rubber tree). It turned out that the best separation was achieved with acetyl-β-cyclodextrin ( Kd = 12 dm 3 mol -1). A straightforward integration was possible if there was more than 5% of one of the enantiomers in the solution. Below this value, the results were not reproducible enough for quantitative analysis.

  7. Vibrational properties of inclusion complexes: the case of indomethacin-cyclodextrin.

    PubMed

    Rossi, Barbara; Verrocchio, Paolo; Viliani, Gabriele; Scarduelli, Giorgina; Guella, Graziano; Mancini, Ines

    2006-07-28

    Vibrational properties of inclusion complexes with cyclodextrins are studied by means of Raman spectroscopy and numerical simulation. In particular, Raman spectra of the nonsteroidal, anti-inflammatory drug indomethacin undergo notable changes in the energy range between 1600 and 1700 cm(-1) when inclusion complexes with cyclodextrins are formed. By using both ab initio quantum chemical calculations and molecular dynamics, we studied how to relate such changes to the geometry of the inclusion process, disentangling single-molecule effects, from changes in the solid state structure or dimerization processes. PMID:16942160

  8. Optimized methods for preparation of 6I-(ω-sulfanyl-alkylene-sulfanyl)-β-cyclodextrin derivatives

    PubMed Central

    Bednářová, Eva; Hybelbauerová, Simona

    2016-01-01

    Summary A general high-yielding method for the preparation of monosubstituted β-cyclodextrin derivatives which have attached a thiol group in position 6 is described. The thiol group is attached through linkers of different lengths and repeating units (ethylene glycol or methylene). The target compounds were characterized by IR, MS and NMR spectra. A simple method for their complete conversion to the corresponding disulfides as well as a method for the reduction of the disulfides back to the thiols is presented. Both, thiols and disulfides are derivatives usable for well-defined covalent attachment of cyclodextrin to gold or polydopamine-coated solid surfaces. PMID:26977195

  9. Optimized methods for preparation of 6(I)-(ω-sulfanyl-alkylene-sulfanyl)-β-cyclodextrin derivatives.

    PubMed

    Bednářová, Eva; Hybelbauerová, Simona; Jindřich, Jindřich

    2016-01-01

    A general high-yielding method for the preparation of monosubstituted β-cyclodextrin derivatives which have attached a thiol group in position 6 is described. The thiol group is attached through linkers of different lengths and repeating units (ethylene glycol or methylene). The target compounds were characterized by IR, MS and NMR spectra. A simple method for their complete conversion to the corresponding disulfides as well as a method for the reduction of the disulfides back to the thiols is presented. Both, thiols and disulfides are derivatives usable for well-defined covalent attachment of cyclodextrin to gold or polydopamine-coated solid surfaces. PMID:26977195

  10. 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

  11. 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

    2016-01-01

    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

  12. 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

  13. Low-energy electron transmission through organic monolayers: An estimation of the effective monolayer potential by an excess electron interference

    NASA Astrophysics Data System (ADS)

    Yamane, Hiroyuki; Ito, Kazuyuki; Kera, Satoshi; Okudaira, Koji K.; Ueno, Nobuo

    2002-11-01

    In low-energy-electron transmission spectra of monolayer films of various organic-semiconductor molecules deposited on MoS2 and graphite surfaces, we found that the energy positions of spectral minima are proportional to (n+1/2)2, where n is positive integer and 0, independent of molecules and substrates. Despite the complex structure of each molecule, the (n+1/2)2 rule can be simply explained by the interference of an excess electron passing through the potential of the monolayer on the substrate. Using these results, we estimated the effective potential, the potential width and depth, of the monolayer felt by the injected excess electron.

  14. Recognition of Salmonella Typhimurium by Immobilized Phage P22 Monolayers

    PubMed Central

    Handa, Hitesh; Gurczynski, Stephen; Jackson, Matthew P.; Auner, Gregory; Mao, Guangzhao

    2009-01-01

    Phages are promising alternatives to antibodies as the biorecognition element in a variety of biosensing applications. In this study, a monolayer of bacteriophage P22 whose tailspike proteins specifically recognize Salmonella serotypes was covalently bound to glass substrates through a bifunctional cross linker 3-aminopropyltrimethoxysilane. The specific binding of Salmonella typhimurium to the phage monolayer was studied by enzyme-linked immunosorbent assay and atomic force microscopy. Escherichia coli and a Gram-positive bacterium Listeria monocytogenes were also studied as control bacteria. The P22 particles show strong binding affinity to Salmonella typhimurium. In addition, the dried P22 monolayer maintained 50% binding capacity to Salmonella typhimurium after a one-week storage time. This is a promising method to prepare phage monolayer coatings on surface plasmon resonance and acoustic biosensor substrates in order to utilize the nascent phage display technology. PMID:19461940

  15. 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

  16. Recognition of Salmonella typhimurium by immobilized phage P22 monolayers

    NASA Astrophysics Data System (ADS)

    Handa, Hitesh; Gurczynski, Stephen; Jackson, Matthew P.; Auner, Gregory; Walker, Jeremy; Mao, Guangzhao

    2008-04-01

    Phages are promising alternatives to antibodies as the biorecognition element in a variety of biosensing applications. In this study, a monolayer of bacteriophage P22 whose tailspike proteins specifically recognize Salmonella serotypes was covalently bound to glass substrates through a bifunctional cross linker 3-aminopropyltrimethoxysilane. The specific binding of Salmonella typhimurium to the phage monolayer was studied by enzyme-linked immunosorbent assay and atomic force microscopy. Escherichia coli and a Gram-positive bacterium Listeria monocytogenes were also studied as control bacteria. The P22 particles show strong binding affinity to S. typhimurium. In addition, the dried P22 monolayer maintained 50% binding capacity to S. typhimurium after a one-week storage time. This is a promising method to prepare phage monolayer coatings on surface plasmon resonance and acoustic biosensor substrates in order to utilize the nascent phage display technology.

  17. Optical emission and vibrational modes of uniform pentacene monolayers (*)

    NASA Astrophysics Data System (ADS)

    He, Rui; Tassi, Nancy; Blanchet, Graciela; Pinczuk, Aron

    2006-03-01

    Pentacene monolayers are probed by photoluminescence and resonant Raman spectroscopies below 10K. Monolayers grown on polymeric substrate of poly-alpha-methyl-styrene (PAMS) exhibit high uniformity within micron size clusters. These films show sharp exciton luminescence bands, and the energy of the exciton optical emission displays a red-shift as the average film thickness increases. The large resonance enhancements of Raman scattering intensities enable the measurements of low-lying (40- 200cm-1) optical lattice vibrations from these monolayers. These experiments demonstrate that luminescence and resonant Raman scattering from single pentacene monolayers are venues for probing 2D properties, studies of interface effects, and thin film characterization. (*) Supported primarily by the Nanoscale Science and Engineering Initiative of the National Science Foundation under NSF Award No. CHE-0117752 and by the New York State Office of Science, Technology, and Academic Research (NYSTAR), and by a research grant of the W. M. Keck Foundation.

  18. Young's modulus of a solid two-dimensional Langmuir monolayer

    NASA Astrophysics Data System (ADS)

    Bercegol, H.; Meunier, J.

    1992-03-01

    LANGMUIR monolayers-films of amphiphilic molecules at the surface of water-exhibit many phases1,2. Some of these behave like two-dimensional solids on experimental timescales, but previous measurements of the shear modulus of these 'solid' monolayers3-5 have yielded a value too small to be compatible with a two-dimensional crystal. The interpretation of these is complicated, however, by the likelihood of inhomogeneities in the films, which are probably assemblies of microscopic crystalline domains. Here we describe measurements of the Young's modulus of an isolated "solid' domain of NBD-stearic acid monolayers. We obtain a value large enough to be compatible with the modulus of a two-dimensional crystal6-8. This suggests that Langmuir monolayers should provide model systems for studies of melting in two dimensions6-8.

  19. DETECTION OF MOLECULAR MONOLAYERS BY OPTICAL. SECOND HARMONIC GENERATION

    SciTech Connect

    Chen, C. K.; Heinz, T. F.; Ricard, D.; Shen, Y. R.

    1980-12-01

    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,

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. Modeling the effects of cyclodextrin on intracellular membrane vesicles from Cos-7 cells prepared by sonication and carbonate treatment

    PubMed Central

    Kilbride, Peter; Woodward, Holly J.; Tan, Kuan Boone; Thanh, Nguyễn T.K.; Chu, K.M. Emily; Minogue, Shane

    2015-01-01

    Cholesterol has important functions in the organization of membrane structure and this may be mediated via the formation of cholesterol-rich, liquid-ordered membrane microdomains often referred to as lipid rafts. Methyl-beta-cyclodextrin (cyclodextrin) is commonly used in cell biology studies to extract cholesterol and therefore disrupt lipid rafts. However, in this study we reassessed this experimental strategy and investigated the effects of cyclodextrin on the physical properties of sonicated and carbonate-treated intracellular membrane vesicles isolated from Cos-7 fibroblasts. We treated these membranes, which mainly originate from the trans-Golgi network and endosomes, with cyclodextrin and measured the effects on their equilibrium buoyant density, protein content, represented by the palmitoylated protein phosphatidylinositol 4-kinase type IIα, and cholesterol. Despite the reduction in mass stemming from cholesterol removal, the vesicles became denser, indicating a possible large volumetric decrease, and this was confirmed by measurements of hydrodynamic vesicle size. Subsequent mathematical analyses demonstrated that only half of this change in membrane size was attributable to cholesterol loss. Hence, the non-selective desorption properties of cyclodextrin are also involved in membrane size and density changes. These findings may have implications for preceding studies that interpreted cyclodextrin-induced changes to membrane biochemistry in the context of lipid raft disruption without taking into account our finding that cyclodextrin treatment also reduces membrane size. PMID:26528413

  5. Synthesis and Utilization of Trialkylammonium-Substituted Cyclodextrins as Water-Soluble Chiral NMR Solvating Agents for Anionic Compounds.

    PubMed

    Dowey, Alison E; Puentes, Cira Mollings; Carey-Hatch, Mira; Sandridge, Keyana L; Krishna, Nikhil B; Wenzel, Thomas J

    2016-04-01

    Cationic trialkylammonium-substituted α-, β-, and γ-cyclodextrins containing trimethyl-, triethyl-, and tri-n-propylammonium substituent groups were synthesized and analyzed for utility as water-soluble chiral nuclear magnetic resonance (NMR) solvating agents. Racemic and enantiomerically pure (3-chloro-2-hydroxypropyl)trimethyl-, triethyl-, and tri-n-propyl ammonium chloride were synthesized from the corresponding trialkyl amine hydrochloride and either racemic or enantiomerically pure epichlorohydrin. The ammonium salts were then reacted with α-, β-, and γ-cyclodextrins at basic pH to provide the corresponding randomly substituted cationic cyclodextrins. The (1) H NMR spectra of a range of anionic, aromatic compounds was recorded with the cationic cyclodextrins. Cyclodextrins with a single stereochemistry at the hydroxy group on the (2-hydroxypropyl)trialkylammonium chloride substituent were often but not always more effective than the corresponding cyclodextrin in which the C-2 position was racemic. In several cases, the larger triethyl or tri-n-propyl derivatives were more effective than the corresponding trimethyl derivative at causing enantiomeric differentiation. None of the cyclodextrin derivatives were consistently the most effective for all of the anionic compounds studied. PMID:26881414

  6. Gold-Mediated Exfoliation of Ultralarge Optoelectronically-Perfect Monolayers.

    PubMed

    Desai, Sujay B; Madhvapathy, Surabhi R; Amani, Matin; Kiriya, Daisuke; Hettick, Mark; Tosun, Mahmut; Zhou, Yuzhi; Dubey, Madan; Ager, Joel W; Chrzan, Daryl; Javey, Ali

    2016-06-01

    Gold-mediated exfoliation of ultralarge optoelectronically perfect monolayers with lateral dimensions up to ≈500 μm is reported. Electrical, optical, and X-ray photo-electron spectroscopy characterization show that the quality of the gold-exfoliated flakes is similar to that of tape-exfoliated flakes. Large-area flakes allow manufacturing of large-area mono-layer transition metal dichalcogenide electronics. PMID:27007751

  7. 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.

  8. 3D nitrogen-doped graphene/β-cyclodextrin: host-guest interactions for electrochemical sensing

    NASA Astrophysics Data System (ADS)

    Liu, Jilun; Leng, Xuanye; Xiao, Yao; Hu, Chengguo; Fu, Lei

    2015-07-01

    Host-guest interactions, especially those between cyclodextrins (CDs, including α-, β- and γ-CD) and various guest molecules, exhibit a very high supramolecular recognition ability. Thus, they have received considerable attention in different fields. These specific interactions between host and guest molecules are promising for biosensing and clinical detection. However, there is a lack of an ideal electrode substrate for CDs to increase their performance in electrochemical sensing. Herein, we propose a new 3D nitrogen-doped graphene (3D-NG) based electrochemical sensor, taking advantage of the superior sensitivity of host-guest interactions. Our 3D-NG was fabricated by a template-directed chemical vapour deposition (CVD) method, and it showed a large specific surface area, a high capacity for biomolecules and a high electron transfer efficiency. Thus, for the first time, we took 3D-NG as an electrode substrate for β-CD to establish a new type of biosensor. Using dopamine (DA) and acetaminophen (APAP) as representative guest molecules, our 3D-NG/β-CD biosensor shows extremely high sensitivities (5468.6 μA mM-1 cm-2 and 2419.2 μA mM-1 cm-2, respectively), which are significantly higher than those reported in most previous studies. The stable adsorption of β-CD on 3D-NG indicates potential applications in clinical detection and medical testing.Host-guest interactions, especially those between cyclodextrins (CDs, including α-, β- and γ-CD) and various guest molecules, exhibit a very high supramolecular recognition ability. Thus, they have received considerable attention in different fields. These specific interactions between host and guest molecules are promising for biosensing and clinical detection. However, there is a lack of an ideal electrode substrate for CDs to increase their performance in electrochemical sensing. Herein, we propose a new 3D nitrogen-doped graphene (3D-NG) based electrochemical sensor, taking advantage of the superior sensitivity

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. Defect-Tolerant Monolayer Transition Metal Dichalcogenides.

    PubMed

    Pandey, Mohnish; Rasmussen, Filip A; Kuhar, Korina; Olsen, Thomas; Jacobsen, Karsten W; Thygesen, Kristian S

    2016-04-13

    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 a 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 a very similar orbital composition. This indicates a bonding/antibonding 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 nonpolar nanoribbons of the TMDs where we find that only the defect sensitive materials form edge states within the band gap. PMID:27027786

  14. 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.

  15. Mechanical properties of monolayer graphene oxide.

    PubMed

    Suk, Ji Won; Piner, Richard D; An, Jinho; Ruoff, Rodney S

    2010-11-23

    Mechanical properties of ultrathin membranes consisting of one layer, two overlapped layers, and three overlapped layers of graphene oxide platelets were investigated by atomic force microscopy (AFM) imaging in contact mode. In order to evaluate both the elastic modulus and prestress of thin membranes, the AFM measurement was combined with the finite element method (FEM) in a new approach for evaluating the mechanics of ultrathin membranes. Monolayer graphene oxide was found to have a lower effective Young's modulus (207.6 ± 23.4 GPa when a thickness of 0.7 nm is used) as compared to the value reported for "pristine" graphene. The prestress (39.7-76.8 MPa) of the graphene oxide membranes obtained by solution-based deposition was found to be 1 order of magnitude lower than that obtained by others for mechanically cleaved graphene. The novel AFM imaging and FEM-based mapping methods presented here are of general utility for obtaining the elastic modulus and prestress of thin membranes. PMID:20942443

  16. Advancing Edge Speeds of Epithelial Monolayers Depend on Their Initial Confining Geometry.

    PubMed

    Kollimada, Somanna A; Kulkarni, Ankur H; Ravan, Aniket; Gundiah, Namrata

    2016-01-01

    Collective cell migrations are essential in several physiological processes and are driven by both chemical and mechanical cues. The roles of substrate stiffness and confinement on collective migrations have been investigated in recent years, however few studies have addressed how geometric shapes influence collective cell migrations. Here, we address the hypothesis that the relative position of a cell within the confinement influences its motility. Monolayers of two types of epithelial cells--MCF7, a breast epithelial cancer cell line, and MDCK, a control epithelial cell line--were confined within circular, square, and cross-shaped stencils and their migration velocities were quantified upon release of the constraint using particle image velocimetry. The choice of stencil geometry allowed us to investigate individual cell motility within convex, straight and concave boundaries. Cells located in sharp, convex boundaries migrated at slower rates than those in concave or straight edges in both cell types. The overall cluster migration occurred in three phases: an initial linear increase with time, followed by a plateau region and a subsequent decrease in cluster speeds. An acto-myosin contractile ring, present in the MDCK but absent in MCF7 monolayer, was a prominent feature in the emergence of leader cells from the MDCK clusters which occurred every ~125 μm from the vertex of the cross. Further, coordinated cell movements displayed vorticity patterns in MDCK which were absent in MCF7 clusters. We also used cytoskeletal inhibitors to show the importance of acto-myosin bounding cables in collective migrations through translation of local movements to create long range coordinated movements and the creation of leader cells within ensembles. To our knowledge, this is the first demonstration of how bounding shapes influence long-term migratory behaviours of epithelial cell monolayers. These results are important for tissue engineering and may also enhance our

  17. Advancing Edge Speeds of Epithelial Monolayers Depend on Their Initial Confining Geometry

    PubMed Central

    Kollimada, Somanna A.; Kulkarni, Ankur H.; Ravan, Aniket; Gundiah, Namrata

    2016-01-01

    Collective cell migrations are essential in several physiological processes and are driven by both chemical and mechanical cues. The roles of substrate stiffness and confinement on collective migrations have been investigated in recent years, however few studies have addressed how geometric shapes influence collective cell migrations. Here, we address the hypothesis that the relative position of a cell within the confinement influences its motility. Monolayers of two types of epithelial cells—MCF7, a breast epithelial cancer cell line, and MDCK, a control epithelial cell line—were confined within circular, square, and cross-shaped stencils and their migration velocities were quantified upon release of the constraint using particle image velocimetry. The choice of stencil geometry allowed us to investigate individual cell motility within convex, straight and concave boundaries. Cells located in sharp, convex boundaries migrated at slower rates than those in concave or straight edges in both cell types. The overall cluster migration occurred in three phases: an initial linear increase with time, followed by a plateau region and a subsequent decrease in cluster speeds. An acto-myosin contractile ring, present in the MDCK but absent in MCF7 monolayer, was a prominent feature in the emergence of leader cells from the MDCK clusters which occurred every ~125 μm from the vertex of the cross. Further, coordinated cell movements displayed vorticity patterns in MDCK which were absent in MCF7 clusters. We also used cytoskeletal inhibitors to show the importance of acto-myosin bounding cables in collective migrations through translation of local movements to create long range coordinated movements and the creation of leader cells within ensembles. To our knowledge, this is the first demonstration of how bounding shapes influence long-term migratory behaviours of epithelial cell monolayers. These results are important for tissue engineering and may also enhance our

  18. A heuristic model to quantify the impact of excess cyclodextrin on oral drug absorption from aqueous solution.

    PubMed

    Olesen, Niels Erik; Westh, Peter; Holm, René

    2016-05-01

    The intestinal drug solubilising capacity (Dtot(SC)) of a drug formulated as an aqueous cyclodextrin solution is a recently proposed quantity to predict the cyclodextrin concentration needed to fully solubilise the drug in the intestinal lumen. According to this concept, the cyclodextrin concentration in the drug product must be higher than the amount needed to solubilise the compound, due to the displacement of the drug from the cyclodextrin cavity by bile salts in the intestinal lumen. On the other hand, dosing cyclodextrin at >Dtot(SC) is expected to result in decreased free intestinal drug concentrations and thus potentially a lower fraction absorbed. In this study, data from three previous in vivo studies in rats with fixed concentrations of three compounds (danazol, cinnarizine and benzo[A]pyrene) and various cyclodextrin concentrations >Dtot(SC) were analysed. The model was developed for danazol and applied to the two other compounds. Absorption, as quantified from the area under the plasma concentration-time profile, was predicted by the model to decrease at elevated concentrations of co-administered cyclodextrin in accordance with the in vivo data. In addition, at high cyclodextrin concentrations a delay in Tmax and a decrease in Cmax were predicted, again in accordance with the experimental observations. These observations were rationalised in terms of the free intestinal drug concentration by a chemical equilibrium model for Dtot(SC). This model depends on the quantity termed the dimensionless dose concentration, Dtot(∗)=Do/Pn, given as the fraction of the permeation number (Pn) and dose number (Do). The model provides the formulation scientist with a critical quality attribute for assessing the implication of having excess cyclodextrin in an oral solution. PMID:26969263

  19. Comparative adherence of granulocytes to endothelial monolayers and nylon fiber.

    PubMed

    MacGregor, R R; Macarak, E J; Kefalides, N A

    1978-03-01

    Adherence of granulocytes to tissue culture monolayers of endothelium averaged 26.2 +/- 1.3% SEM, which was similar to their adherence on 50-mg nylon fiber columns (27.7 +/- 3.6%). In contrast, adherence to epithelial cells, fibroblasts, kidney cells, and plastic Petri dishes without monolayers was only 12.4, 9.9, 11.1, and 4.3%, respectively. Cyclic nucleotides and adherence-modifying plasma factors induced changes of adherence to endothelium similar to those in nylon fiber columns. Adherence of granulocytes in whole blood was the same as for purified granulocytes in Hank's balanced salt solution. Exposure of endothelial monolayers to 0.18% trypsin for 10 min reduced subsequent granulocyte adherence to 25.2% of control values. Incubation of trypsin-treated monolayers with nutrient medium for 4 h did not improve adherence, but values returned to normal or above by 24 h, with or without serum proteins present in the nutrient medium. The similarity of granulocyte adherence to nylon fiber and to endothelial monolayers in vitro suggests that results with the nylon fiber assay reflect in vivo granulocyte-endothelium interaction. Furthermore, the endothelial monolayer offers a new model for studying this cell-cell relationship in vitro. PMID:641148

  20. 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