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Bal JK, Kundu S, Hazra S. Role of metal ions in growth and stability of Langmuir-Blodgett films on homogeneous and heterogeneous surfaces. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2012; 35:79. [PMID: 22918612 DOI: 10.1140/epje/i2012-12079-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2012] [Revised: 05/27/2012] [Accepted: 07/18/2012] [Indexed: 06/01/2023]
Abstract
Structure and stability of cadmium arachidate (CdA) Langmuir-Blodgett (LB) films on homogeneous (i.e., OH-, H-passivated Si(001) substrates) and heterogeneous (i.e., Br-passivated Si(001) substrates) surfaces were studied using X-ray reflectivity and atomic force microscopy techniques and compared with those of nickel arachidate (NiA) LB films. While on OH-passivated Si, an asymmetric monolayer (AML) structure starts to grow, on H-passivated Si, a symmetric monolayer (SML) of CdA forms, although for both the films, pinhole-type defects are present as usual. However, on heterogeneous Br-passivated Si substrates, a combination of AML, SML, shifted SML and SML on top of AML (i.e., AML/SML), all types of structures are found to grow in such a way that, due to the variation of heights in the out-of-plane direction, ring-shaped in-plane nanopatterns of CdA molecules are generated. Probably due to stronger head-head interactions and higher metal ion-carboxylic ligand bond strength for CdA molecules compared to NiA, easy flipping of SML on top of another preformed SML, i.e. a SML/SML structure formation was not possible and as a result a wave-like modulation is observed for the CdA film on such heterogeneous substrate. The presence of hydrophilic/hydrophobic interfacial stress on the heterogeneous substrate thus modifies the deposited molecular structure so that the top surface morphology for a CdA film is similar to monolayer buckling while that for NiA film is similar to monolayer collapse.
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Affiliation(s)
- J K Bal
- Surface Physics Division, Saha Institute of Nuclear Physics, Kolkata, India.
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2
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Reuter S, Amado E, Busse K, Kraska M, Stühn B, Tschierske C, Kressler J. Formation of 2D spherulites in Langmuir films of amphiphilic T-shaped liquid crystals. J Colloid Interface Sci 2012; 372:192-201. [DOI: 10.1016/j.jcis.2012.01.036] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Revised: 01/19/2012] [Accepted: 01/20/2012] [Indexed: 10/14/2022]
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3
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Giancane G, Manno D, Serra A, Sgobba V, Valli L. Characterization of Composite Phthalocyanine–Fatty Acid Films from the Air/Water Interface to Solid Supports. J Phys Chem B 2011; 115:14956-62. [DOI: 10.1021/jp209108r] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- G. Giancane
- Dipartimento di Ingegneria dell’Innovazione, Università degli Studi del Salento, I-73100 Lecce, Italy
| | - D. Manno
- Dipartimento di Scienze dei Materiali, Università degli Studi del Salento, I-73100 Lecce, Italy
| | - A. Serra
- Dipartimento di Scienze dei Materiali, Università degli Studi del Salento, I-73100 Lecce, Italy
| | - V. Sgobba
- Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials, Friedrich-Alexander-Universität Erlangen-Nürnberg, Egerlandstrasse, 3, D-91058 Erlangen, Germany
| | - L. Valli
- Dipartimento di Ingegneria dell’Innovazione, Università degli Studi del Salento, I-73100 Lecce, Italy
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Reuter S, Hofmann AM, Busse K, Frey H, Kressler J. Langmuir and Langmuir-Blodgett films of multifunctional, amphiphilic polyethers with cholesterol moieties. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:1978-1989. [PMID: 21175221 DOI: 10.1021/la104274d] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Langmuir films of multifunctional, hydrophilic polyethers containing a hydrophobic cholesterol group (Ch) were studied by surface pressure-mean molecular area (π-mmA) measurements and Brewster angle microscopy (BAM). The polyethers were either homopolymers or diblock copolymers of linear poly(glycerol) (lPG), linear poly(glyceryl glycidyl ether) (lPGG), linear poly(ethylene glycol) (lPEG), or hyperbranched poly(glycerol) (hbPG). Surface pressure measurements revealed that the homopolymers lPG and hbPG did not stay at the water surface after spreading and solvent evaporation, in contrast to lPEG. Because of the incorporation of the Ch group in the polymer structure, stable Langmuir films were formed by Ch-lPG(n), Ch-lPGG(n), and Ch-hbPG(n). The Ch-hbPG(n), Ch-lPEG(n), Ch-lPEG(n)-b-lPG(m), Ch-lPEG(n)-b-lPGG(m), and Ch-lPEG(n)-b-hbPG(m) systems showed an extended plateau region assigned to a phase transition involving the Ch groups. Typical hierarchically ordered morphologies of the LB films on hydrophilic substrates were observed for all Ch-initiated polymers. All LB films showed that Ch of the Ch-initiated homopolymers is able to crystallize. This strong tendency of self-aggregation then triggers further dewetting effects of the respective polyether entities. Fingerlike morphologies are observed for Ch-lPEG(69), since the lPEG(69) entity is able to undergo crystallization after transfer onto the silicon substrate.
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Affiliation(s)
- Sascha Reuter
- Department of Chemistry, Martin Luther University Halle-Wittenberg, D-06099 Halle (Saale), Germany
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Kundu S, Raychaudhuri AK. Effect of water and air-water interface on the structural modification of Ni-arachidate Langmuir-Blodgett films. J Colloid Interface Sci 2011; 353:316-21. [PMID: 20950821 DOI: 10.1016/j.jcis.2010.09.048] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 09/16/2010] [Accepted: 09/17/2010] [Indexed: 11/25/2022]
Abstract
Nickel arachidate (NiA) Langmuir-Blodgett (LB) films have been deposited on hydrophilic Si(0 0 1) substrates by three (up-down-up) and five (up-down-up-down-up) strokes. During deposition, substrates were kept inside the water subphase for different times after each down stroke. Structural information of all the LB films have been obtained from X-ray reflectivity (XRR) studies. One and two symmetric monolayer (SML) was deposited on top of the asymmetric monolayer (AML) in three and five stokes respectively. All the preformed LB films were then used to go through the air-water interface with the same speed that was used at the time of film deposition. Structural information obtained from the XRR studies show that mainly the top layer density decreases after passing through the air-water interface but the layered structure remains the same. Information obtained from both the XRR and atomic force microscopy (AFM) studies suggest that molecules peeled from the top SML layer do not reincorporate with the LB film through tail-tail hydrophobic interaction. Our study shows that NiA LB film has better stability compared with cadmium arachidate LB film inside the water subphase without forming any out-of-plane molecular reorganization.
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Affiliation(s)
- Sarathi Kundu
- Department of Materials Science, S.N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake City, Kolkata 700 098, India.
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Schwartz DK, Garnaes J, Viswanathan R, Zasadzinski JA. Surface order and stability of langmuir-blodgett films. Science 2010; 257:508-11. [PMID: 17778681 DOI: 10.1126/science.257.5069.508] [Citation(s) in RCA: 187] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Angstrom-resolution atomic force microscope images of Langmuir-Blodgett monolayers and multilayers of cadmium arachidate in air and under water show a dramatic change from a disordered arrangement to a crystalline lattice by the addition or removal of a single layer of molecules. The disordered surface is less stable than the ordered one to mechanical stresses such as atomic force microscopy tip forces or at the air-water contact line during contact angle measurements. The difference in the degree of order in the alkyl chains is attributed to the strong attractive interaction between headgroups in the presence of the divalent cation.
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Mattu JS, Leach GW. Large Scale Crystallinity in Kinetically Stable Polythiophene-Based Langmuir−Blodgett Films. J Am Chem Soc 2010; 132:3204-10. [DOI: 10.1021/ja910390g] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jusroop S. Mattu
- Department of Chemistry, 4D LABS, and Laboratory for Advanced Spectroscopy and Imaging Research, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6 Canada
| | - Gary W. Leach
- Department of Chemistry, 4D LABS, and Laboratory for Advanced Spectroscopy and Imaging Research, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6 Canada
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Li R, Chen Q, Zhang D, Liu H, Hu Y. Mixed monolayers of Gemini surfactants and stearic acid at the air/water interface. J Colloid Interface Sci 2008; 327:162-8. [DOI: 10.1016/j.jcis.2008.07.038] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 07/19/2008] [Accepted: 07/21/2008] [Indexed: 10/21/2022]
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Thordarson P, Atkin R, Kalle WHJ, Warr GG, Braet F. Developments in Using Scanning Probe Microscopy To Study Molecules on Surfaces — From Thin Films and Single-Molecule Conductivity to Drug–Living Cell Interactions. Aust J Chem 2006. [DOI: 10.1071/ch06043] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Scanning probe microscopy (SPM) techniques, including atomic force microscopy (AFM) and scanning tunnelling microscopy (STM), have revolutionized our understanding of molecule–surface interactions. The high resolution and versatility of SPM techniques have helped elucidate the morphology of adsorbed surfactant layers, facilitated the study of electronically conductive single molecules and biomolecules connected to metal substrates, and allowed direct observation of real-time processes such as in situ DNA hybridization and drug–cell interactions. These examples illustrate the power that SPM possesses to study (bio)molecules on surfaces and will be discussed in depth in this review.
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Deng J, Viers BD, Esker AR, Anseth JW, Fuller GG. Phase behavior and viscoelastic properties of trisilanolcyclohexyl-POSS at the air/water interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2005; 21:2375-2385. [PMID: 15752028 DOI: 10.1021/la047568w] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A trisilanol polyhedral oligomeric silsesquioxane (POSS), trisilanolcyclohexyl-POSS (TCyP), has recently been reported to undergo a series of phase transitions from traditional Langmuir monolayers to unique rodlike hydrophobic aggregates in multilayer films that are different from "collapsed" morphologies seen in other systems at the air/water interface. This paper focuses on the phase transitions and morphology of films varying in average thickness from monolayers to trilayers and the corresponding viscoelastic properties of trisilanolcyclohexyl-POSS molecules at the air/water interface by means of surface pressure-area per molecule (Pi-A) isotherms, Brewster angle microscopy (BAM), and interfacial stress rheometry (ISR) measurements. The morphology studies by BAM reveal that the TCyP monolayer can collapse into different 3D structures by homogeneous or heterogeneous nucleation mechanisms. For homogeneous nucleation, analysis by Vollhardt et al.'s nucleation and growth model reveals that TCyP collapse is consistent with instantaneous nucleation with hemispherical edge growth at Pi = 3.7 mN.m(-1). Both surface storage (Gs') and loss (Gs") moduli obtained by ISR reveal three different non-Newtonian flow regimes that correlate with phase transitions in the Pi-A isotherms: (A) A viscous liquidlike "monolayer"; (B) a "biphasic regime"between a liquidlike viscous monolayer and a more rigid trilayer; and (C) an elastic solidlike "trilayer". These observations provide interesting insights into collapse mechanisms and structures in Langmuir films.
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Affiliation(s)
- Jianjun Deng
- Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA
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11
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Structure and thermal stability of Langmuir–Blodgett films of barium arachidate. Colloids Surf A Physicochem Eng Asp 2005. [DOI: 10.1016/j.colsurfa.2004.10.103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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12
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Bantchev GB, Schwartz DK. Structure of beta-casein layers at the air/solution interface: atomic force microscopy studies of transferred layers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:11692-11697. [PMID: 15595799 DOI: 10.1021/la048380f] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We report the nanoscale structural changes associated with the interfacial gelation of adsorbed beta-casein layers as a function of aging time. Adsorbed layers were transferred to solid supports and imaged by atomic force microscopy. The aging of the layer was accompanied by the formation of distinct disk-shaped protein nanoparticles ( approximately 20 nm in diameter). Under conditions where a gelled layer was expected (from previous interfacial rheology experiments), we observed ordering of the particles and the formation of elongated aggregates or linear rows. Brewster angle microscopy images were also obtained during the adsorption and gelation processes and during the degradation of the protein layer following addition of the surfactant sodium dodecyl sulfate (SDS). If SDS was added prior to interfacial protein gelation, the layer developed a foamlike morphology consistent with a fluid interfacial protein layer. However, if SDS was added after gelation, the protein layer was observed to fracture, consistent with the behavior of a solid phase.
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Affiliation(s)
- Grigor B Bantchev
- Department of Chemical Engineering, University of Colorado at Boulder, Boulder, Colorado 80309-0424, USA
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Ye S, Noda H, Nishida T, Morita S, Osawa M. Cd2+-induced interfacial structural changes of Langmuir-Blodgett films of stearic acid on solid substrates: a sum frequency generation study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:357-365. [PMID: 15743078 DOI: 10.1021/la036008e] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The molecular structures and their stabilities at the outmost-layer of the Langmuir-Blodgett (LB) films of stearic acid on solid substrates have been investigated by a highly surface-sensitive spectroscopic technique, sum frequency generation (SFG), in air and in aqueous solution, using the combination of both normal and deuterated stearic acid. Peaks observed in the SFG spectra are mainly attributed to the terminal methyl group at the outmost layer of the LB films. The SFG spectra in air are virtually identical and are independent of the odd-even property and thickness (1-12) of the LB films, indicating that the even-numbered LB film changes its surface structure after passing through the interface between the water subphase and air, especially when the Cd2+ cation was included in the water subphase. Furthermore, we have demonstrated for the first time using in situ SFG measurement that the interfacial molecular structure at the LB bilayer of stearic acid on the hydrophilic substrates significantly change with immersion in the water subphase containing Cd2+ cation while such a structural change has not been observed in the water subphase without Cd2+. These results clearly indicate that a reorganization process takes place on the surface of the stearic acid bilayer induced by the Cd2+ cation. The electrostatic interaction between the carboxylate headgroup of stearic acid via the Cd2+ cation seems to play an important role in the surface reorganization process both in air and in solution.
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Affiliation(s)
- Shen Ye
- Catalysis Research Center, Hokkaido University, Sapporo 001-0021, Japan.
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Holman J, Davies PB, Neivandt DJ. Sum Frequency Spectroscopy of Langmuir−Blodgett Fatty Acid Films on Hydrophobic Gold. J Phys Chem B 2004. [DOI: 10.1021/jp036654m] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jasper Holman
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, U.K
| | - Paul B. Davies
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, U.K
| | - David J. Neivandt
- Department of Chemical and Biological Engineering, University of Maine, Orono, Maine, 04469
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Takamoto DY, Aydil E, Zasadzinski JA, Ivanova AT, Schwartz DK, Yang T, Cremer PS. Stable ordering in Langmuir-Blodgett films. Science 2001; 293:1292-5. [PMID: 11509723 DOI: 10.1126/science.1060018] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Defects in the layering of Langmuir-Blodgett (LB) films can be eliminated by depositing from the appropriate monolayer phase at the air-water interface. LB films deposited from the hexagonal phase of cadmium arachidate (CdA2) at pH 7 spontaneously transform into the bulk soap structure, a centrosymmetric bilayer with an orthorhombic herringbone packing. A large wavelength folding mechanism accelerates the conversion between the two structures, leading to a disruption of the desired layering. At pH > 8.5, though it is more difficult to draw LB films, almost perfect layering is obtained due to the inability to convert from the as-deposited structure to the equilibrium one.
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Affiliation(s)
- D Y Takamoto
- Department of Chemical Engineering and Materials, University of California, Santa Barbara, CA 93106, USA
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Peng JB, Barnes GT, Gentle IR. The structures of Langmuir-Blodgett films of fatty acids and their salts. Adv Colloid Interface Sci 2001; 91:163-219. [PMID: 11392356 DOI: 10.1016/s0001-8686(99)00031-7] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Recent advances in several experimental techniques have enabled detailed structural information to be obtained for floating (Langmuir) monolayers and Langmuir-Blodgett films. These techniques are described briefly and their application to the study of films of fatty acids and their salts is discussed. Floating monolayers on aqueous subphases have been shown to possess a complex polymorphism with phases whose structures may be compared to those of smectic mesophases. However, only those phases that exist at high surface pressures are normally used in Langmuir-Blodgett (LB) deposition. In single LB monolayers of fatty acids and fatty acid salts the acyl chains are in the all-trans conformation with their long axes normal to the substrate. The in-plane molecular packing is hexagonal with long-range bond orientational order and short-range positional order: known as the hexatic-B structure. This structure is found irrespective of the phase of the parent floating monolayer. The structures of multilayer LB films are similar to the structures of their bulk crystals, consisting of stacked bilayer lamellae. Each lamella is formed from two monolayers of fatty acid molecules or ions arranged head to head and held together by hydrogen bonding between pairs of acids or ionic bonding through the divalent cations. With acids the acyl chains are tilted with respect to the substrate normal and have a monoclinic structure, whereas the salts with divalent cations may have the chains normal to the substrate or tilted. The in-plane structures are usually centred rectangular with the chains in the trans conformation and packed in a herringbone pattern. Multilayer films of the acids show only a single-step order-disorder transition at the melting point. This temperature tends to rise as the number of layers increases. Complex changes occur when multilayer films of the salts are heated. Disorder of the chains begins at low temperatures but the arrangement of the head groups does not alter until the melting temperature is reached. Slow heating to a temperature just below the melting temperature gives, with some salts, a radical change in phase. The lamellar structure disappears and a new phase consisting of cylindrical rods lying parallel to the substrate surface and stacked in a hexagonal pattern is formed. In each rod the cations are aligned along the central axis surrounded by the disordered acyl chains.
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Affiliation(s)
- J B Peng
- Department of Chemistry, The University of Queensland, Brisbane, Australia
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Peng JB, Barnes GT, Gentle IR, Foran GJ. Superstructures and Correlated Metal Ion Layers in Langmuir−Blodgett Films of Cadmium Soaps Observed with Grazing Incidence X-ray Diffraction. J Phys Chem B 2000. [DOI: 10.1021/jp000075p] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- J. B. Peng
- Department of Chemistry, The University of Queensland, Brisbane, QLD 4072, Australia
| | - G. T. Barnes
- Department of Chemistry, The University of Queensland, Brisbane, QLD 4072, Australia
| | - I. R. Gentle
- Department of Chemistry, The University of Queensland, Brisbane, QLD 4072, Australia
| | - G. J. Foran
- Australian Nuclear Science and Technology Organisation, PMB 1, Menai, NSW 2234, Australia
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Methods of deposition and characterization of thin films of amphiphiles. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 1999. [DOI: 10.1016/s0928-4931(99)00082-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Hui-Litwin H, Servant L, Dignam MJ, Moskovits M. Effective Electric Surface Susceptibility Tensor as a Probe of the Thermal Behavior of Langmuir−Blodgett Films. J Phys Chem B 1998. [DOI: 10.1021/jp972084c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- H. Hui-Litwin
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 1A1, Canada
| | - L. Servant
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 1A1, Canada
| | - M. J. Dignam
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 1A1, Canada
| | - M. Moskovits
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario M5S 1A1, Canada
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Sikes HD, Schwartz DK. Two-dimensional melting of an anisotropic crystal observed at the molecular level. Science 1997; 278:1604-7. [PMID: 9374455 DOI: 10.1126/science.278.5343.1604] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A distinctive two-dimensional (2D) melting transition occurring at nearly 100 degrees Celsius ( degrees C) has been observed in Langmuir-Blodgett films by in situ atomic force microscopy (AFM). A 2D orthorhombic crystal phase melted to a 2D smectic phase at about 91 degrees C. The smectic phase was characterized by 1D molecular periodicity with short-range correlations (about 40 angstroms). At 95 degrees C, the smectic order melted to form a hexatic phase. Infrared spectroscopy measurements were consistent with the AFM observations. These observations support the dislocation-mediated melting scenario for an anisotropic 2D crystal predicted by Ostlund and Halperin. A longer wavelength height modulation was also observed in the smectic and hexatic phases.
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Affiliation(s)
- HD Sikes
- Department of Chemistry, Tulane University, New Orleans, LA 70118, USA
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Cao X, Bansil R, Gantz D, Moore EW, Niu N, Afdhal NH. Diffusion behavior of lipid vesicles in entangled polymer solutions. Biophys J 1997; 73:1932-9. [PMID: 9336189 PMCID: PMC1181094 DOI: 10.1016/s0006-3495(97)78224-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Dynamic light scattering was used to follow the tracer diffusion of phospholipid/cholesterol vesicles in aqueous polyacrylamide solutions and compared with the diffusive behavior of polystyrene (PS) latex spheres of comparable diameters. Over the range of the matrix concentration examined (Cp = 0.1-10 mg/ml), the diffusivities of the PS spheres and the large multilamellar vesicles exhibited the Stokes-Einstein (SE) relation, while the diffusivity of the unilamellar vesicles did not follow the increase of the solution's viscosity caused by the presence of the matrix molecules. The difference between the diffusion behaviors of unilamellar vesicles and hard PS spheres of similar size is possibly due to the flexibility of the lipid bilayer of the vesicles. The unilamellar vesicles are capable of changing their shape to move through the entangled polymer solution so that the hindrance to their diffusion due to the presence of the polymer chains is reduced, while the rigid PS spheres have little flexibility and they encounter greater resistance. The multilamellar vesicles are less flexible, thus their diffusion is similar to the hard PS spheres of similar diameter.
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Affiliation(s)
- X Cao
- Department of Chemistry, Boston University, Massachusetts 02215, USA
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Relini A, Cavalleri O, Rolandi R. Molecular order in solvent-cast stearic acid films. MATERIALS SCIENCE & ENGINEERING. C, MATERIALS FOR BIOLOGICAL APPLICATIONS 1996. [DOI: 10.1016/s0928-4931(96)00149-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Evenson SA, Badyal JPS, Pearson C, Petty MC. Variation in Intermolecular Spacing with Dipping Pressure for Arachidic Acid LB Films. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp960009g] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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25
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Kurnaz ML, Schwartz DK. Morphology of Microphase Separation in Arachidic Acid/Cadmium Arachidate Langmuir-Blodgett Multilayers. ACTA ACUST UNITED AC 1996. [DOI: 10.1021/jp960665g] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- M. L. Kurnaz
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118
| | - D. K. Schwartz
- Department of Chemistry, Tulane University, New Orleans, Louisiana 70118
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Lindén M, Györvary E, Peltonen J, Rosenholm JB. UV-induced reactivity of linoleic acid monolayers. The influence of subphase conditions. Colloids Surf A Physicochem Eng Asp 1995. [DOI: 10.1016/0927-7757(95)03278-l] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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Viswanathan R, Madsen LL, Zasadzinski JA, Schwartz DK. Liquid to hexatic to crystalline order in Langmuir-Blodgett films. Science 1995; 269:51-4. [PMID: 7604278 DOI: 10.1126/science.7604278] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Atomic force microscope images of zinc arachidate (ZnA2) Langmuir-Blodgett films show that three- and five-layer films are "hexatic," with long-range bond-orientational order and short-range positional correlations of three to five lattice repeats. The monolayer in contact with the substrate is disordered. Films of seven or more layers of ZnA2 are crystalline. A population of dislocations, most likely originating at the substrate, disrupts the positional but not the orientational order of the lattice, leading to hexatic layers intermediate between crystal and liquid. The influence of the substrate propagates farther into ZnA2 films than into cadmium arachidate films because the molecular cohesion is much weaker in ZnA2 than in cadmium arachidate, as evidenced by a less dense molecular packing.
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Affiliation(s)
- R Viswanathan
- Department of Chemical Engineering, University of California, Santa Barbara 93106, USA
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Kajiyama T, Oishi Y, Suehiro K, Hirose F, Kuri T. Direct Observation of Edge Dislocation in Lignoceric Acid Monolayer Based on Atomic Force Microscopy. CHEM LETT 1995. [DOI: 10.1246/cl.1995.241] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Hui SW, Viswanathan R, Zasadzinski JA, Israelachvili JN. The structure and stability of phospholipid bilayers by atomic force microscopy. Biophys J 1995; 68:171-8. [PMID: 7711239 PMCID: PMC1281674 DOI: 10.1016/s0006-3495(95)80172-4] [Citation(s) in RCA: 121] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Atomic force microscopy (AFM) was used to investigate the structure, stability, and defects of the hydrophilic surfaces of Langmuir-Blodgett bilayer films of distearoylphosphatidylcholine (DSPC) and dipalmitoylphosphatidylethanolamine (DPPE) in the solid phase, and dilinoleoylphosphatidylethanolamine (DLPE) in the fluid phase. Their relative resilience to external mechanical stress by the scanning tip and by fluid exchange were also investigated. DPPE monolayers showed parallel ridges at the surface with a period of 0.49 nm, corresponding to the rows of aligned headgroups consistent with the known crystallographic structure. DSPC and DLPE monolayers did not show any periodic order. The solid DSPC and DPPE monolayers were stable to continued rastering by the AFM tip; however, the stability of DLPE monolayers depended on the pH of the aqueous environment. Structural defects in the form of monolayer gaps and holes were observed after fluid exchange, but the defects in DLPE monolayer at pH 11 were stable during consecutive scanning. At pH 9 and below, the defects induced by fluid exchange over DLPE monolayers were more extensive and were deformed easily by consecutive scanning of the AFM tip at a force of 10 nN. The pH dependence of resilience was explained by the increasing bending energy or frustration due to the high spontaneous curvature of DLPE monolayers at low pH. The tangential stress exerted by the AFM tip on the deformable monolayers eventually produced a ripple pattern, which could be described as a periodic buckling known as Shallamach waves.
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Affiliation(s)
- S W Hui
- Department of Biophysics, Roswell Park Cancer Institute, Buffalo, NY 14263
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Vithana H, Johnson D, Shih R, Adin Mann J. Characterization of 12-8-diacetylene Langmuir-Blodgett films by scanning-force microscopy. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1995; 51:454-461. [PMID: 9962663 DOI: 10.1103/physreve.51.454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Applications of atomic force microscopy to structural characterization of organic thin films. Colloids Surf A Physicochem Eng Asp 1994. [DOI: 10.1016/0927-7757(94)80002-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Schwartz DK, Viswanathan R, Zasadzinski JA. Head–tail competition and modulated structures in planar surfactant (Langmuir–Blodgett) films. J Chem Phys 1994. [DOI: 10.1063/1.468300] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Cavalleri O, Ricci D, Rolandi R. Scanning force imaging of organic multimolecular films. SURF INTERFACE ANAL 1994. [DOI: 10.1002/sia.740210622] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Garnaes J, Larsen NB, Bjørnholm T, Jørgensen M, Kjaer K, Als-Nielsen J, Jørgensen JF, Zasadzinski JA. Langmuir-Blodgett Films of a Functionalized Molecule with Cross-Sectional Mismatch Between Head and Tail. Science 1994; 264:1301-4. [PMID: 17780847 DOI: 10.1126/science.264.5163.1301] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
A functionalized surfactant has been investigated as floating monolayers by synchrotron x-ray diffraction and as bilayers transferred to solid supports by the Langmuir-Blodgett technique through atomic force microscopy. The transfer process is accompanied by an increase of the unit cell area (about 17 percent) and by an increase of the average domain diameter of nanometer-scale domains (about three times). The unit cell area of the floating monolayer corresponds to close packing of the head groups and a noncharacteristic packing of the tifted alkyl chains. The larger unit cell area of the bilayer film is consistent with a particular ordered packing of the alkyl chains, leaving free space for the head groups.
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Abstract
The controlled transfer of organized monolayers of amphiphilic molecules from the airwater interface to a solid substrate was the first molecular-scale technology for the creation of new materials. However, the potential benefits of the technology envisioned by Langmuir and Blodgett in the 1930s have yet to be fully realized. Problems of reproducibility and defects and the lack of basic understanding of the packing of complex molecules in thin films have continued to thwart practical applications of Langmuir-Blodgett films and devices made from such films. However, modern high-resolution x-ray diffraction and scanning probe microscopy have proven to be ideal tools to resolve many of the basic questions involving thin organic films. Here, studies are presented of molecular order and organization in thin films of fatty acid salts, the prototypical system of Katharine Blodgett. Even these relatively simple systems present liquid, hexatic, and crystalline order; van der Waals and strained layer epitaxy on various substrates; wide variations in crystal symmetry and interfacial area with counterions; modulated superstructures; and coexisting lattice structures. The wide variety of possible structures presents both a challenge and an opportunity for future molecular design of organic thin-film devices.
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Affiliation(s)
- J A Zasadzinski
- Department of Chemical and Nuclear Engineering, University of California, Santa Barbara 93106
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Schwartz DK, Viswanathan R, Zasadzinski JA. Commensurate defect superstructures in a Langmuir-Blodgett film. PHYSICAL REVIEW LETTERS 1993; 70:1267-1270. [PMID: 10054333 DOI: 10.1103/physrevlett.70.1267] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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