Лаборатория физической химии супрамолекулярных систем Функциональные супрамолекулярные системы на межфазных поверхностях Арсланов Владимир Валентинович Тел. 955 44 89, 955 44 08 E-mail: pcss_lab@mail. ru
НАПРАВЛЕНИЯ ИССЛЕДОВАНИЙ: Планарные супрамолекулярные системы на основе самоорганизованных монослоев и пленок Ленгмюра-Блоджетт линейных, макроциклических и сетчатых соединений. Самосборка, структура и свойства. Новые подходы к созданию гибридных материалов и «интеллектуальных» наноустройств: сенсоров, переключателей, машин и шаблонов. 1. Особые свойства межфазных границ. 2. Предорганизация ансамблей. Управление сборкой. 3. Фото- и редокс-управляемые превращения в организованных ансамблях. 4. Стабильность супрамолекулярных устройств. 5. Наносенсоры – новые принципы. 6. Биоминерализация. 7. Мягкая гелевая ЛБ-литография. 8. Фазовый распад на ЛТК – нано(микро)гетерогенные поверхности. 9. Супергидрофобные и суперолеофобные поверхности.
• Химия молекулярных ансамблей и межмолекулярных связей • Химия нековалентных связей • Химия вне молекулы
Молекулярная и супрамолекулярная химия: сравнение диапазонов Молекулярная химия 3 молекулярные предшественники Молекула (ковалентные связи) Супрамолекулярная химия хозяин гость Супрамолекулярный комплекс n Супрамолекулярный ансамбль
КАТИОН-ИНДУЦИРОВАННАЯ АГРЕГАЦИЯ КРАУН-ЗАМЕЩЕННЫХ ТЕТРАПИРРОЛЬНЫХ МАКРОЦИКЛОВ: МОНОМЕР - ДИМЕР - ПОЛИМЕР тетра-15 -краун-5 -фталоцианинат рутения с аксиально координированными молекулами триэтилендиамина тетра-15 -краун-5 фталоцианинат лютеция = K+ тетра-15 -краун-5 -фталоцианинат кобальта
VCH, 1995 “NAUKA”, 1998 Dijon, April 08 April
Dijon, April 08 April
Арига
1987 Nobel Prize to Donald J. Cram Jean-Marie Lehn Charles J. Pedersen For their development of the field of supramolecular chemistry Dijon, April 08 April
Jean-Marie Lehn 1939 Donald Cram 1919 -2001 Charles J. Pedersen 1904 -1989 Dijon, April 08 April
Объекты и термины • Наноразмерные системы: ~ 1 – 1000 нм • Создает свои объекты, подражая, но не всегда копируя принципы сборки, используемые Природой. Биомиметика • Комплементарность, распознавание, самоорганизация (самосборка), предорганизация и даже саморепликация - характерные термины супрамолекулярной химии
SUPRAMOLECULAR CHEMISTRY AT THE INTERFACES
Две проблемы: 1. Иммобилизация молекул на поверхности. 2. Организация молекул в ансамбли.
Interlocking molecules The goal of many modern works is to develop methods to link functional molecules to surfaces In particular, creating surface-attached catenanes and rotaxanes. Such surface-attachment is the natural progression towards building single molecule detectors and/or devices and integrating them with conventional electronics.
A photo-responsive surface based on switchable fluorinated molecular shuttles. Illumination with 240– 400 nm a, Polaro(hydro)phobic surface. Light-switchable rotaxanes with the fluoroalkane region (orange) exposed (E-1) were hysisorbed onto a SAM of 11 -MUA on Au(111) deposited on either glass or mica. b, Polaro(hydro)philic surface. Light isomerization of the E rotoxanes to Z ones causes a nanometre displacement of the macrocycle which encapsulates the fluoroalkane units leaving a more polaro(hydro)philic surface Photoemission spectroscopy data are consistent with the molecular shuttles lying parallel to the Au surface (but they are not directionally aligned or necessarily linear as depicted for clarity in this cartoon). J. Berna et al. , Nature materials, 2005
Lateral photographs of light-driven directional transport of a 1. 25 µl iiodomethane drop across the surface of a E-1/11 -MUA/Au(111) substrate on glass The direction of transportation was controlled by irradiation with a perpendicular beam of 240– 400 nm light focused on one side of the drop and the adjacent surface. The irradiation time required for transport and the distance the droplet travels depends on the precise position of the lamp. a) Before irradiation contact angle (Ө) 35± 2◦. UV-illumination Immediately after this image was taken, the ultraviolet light beam positioned as indicated was switched on. b) After 900 s of irradiation, contact angle 13± 2◦ (illuminated side), 15± 2◦ (non-illuminated side). The diiodomethane drop has spread from the high E/Z-1 ratio area in the direction of the low E/Z-1 ratio region, increasing the total wetted area. c) After 1, 010 s of irradiation (just after transport), contact angle 13± 2◦. d) After 1, 110 s of irradiation (at the photostationary state), contact angle 12± 2◦. Evaporation of the 1. 25 µl drop of diiodomethane becomes significant after about 1 h. J. Berna et al. , Nature materials, 2005
Lateral photographs of light-driven directional transport of a 1. 25 µl diiodomethane drop across the surface of a E-1/11 -MUA/Au(111) substrate on mica. a, Before irradiation (pristine E-1). b, After 215 s of irradiation (20 s before transport). c, After 370 s of irradiation (just after transport). d, After 580 s of irradiation (at the photostationary state). The rear end of the droplet could be transported more than 1. 5 mm (compared with 0. 8 mm using Au(111) on glass J. Berna et al. , Nature materials, 2005
Lateral photographs of light-driven transport of a 1. 25 µl diiodomethane drop on a E-1/11 -MUA/Au(111) substrate on mica up a 12◦ incline For clarity, on photographs b–d a yellow line is used to indicate the surface of the substrate a) Before irradiation (pristine E-1). b) After 160 s of irradiation (just before transport). c) After 245 s of irradiation (just after transport). d) After 640 s of irradiation (at the photostationary state). J. Berna et al. , Nature materials, 2005
Ability of the monolayer of molecular shuttles to do macroscopic work against gravity by driving a droplet up a 12◦ incline using rotaxate modified mica mm 1. 38 a - Drop volume, Vdrop=1. 25 l; - Liquid (CH 2 I 2) density, = 3. 325 gml-1; - Shift of the drop, l = 1. 38 mm; - Incline, a = 12 o; -velosity, c ~ 16 ms-1 mgh = v l Sina g The work done against gravity by the collective action of the monolayer of molecular machines is (1. 25 x 10− 9 m 3 x 3. 325 x 103 kg m− 3)(mass in kg) x (1. 38 x 10− 3 m x 0. 21(sin 12◦))(height in metres) x (9. 8 m s− 2)(gravity)= 1. 2 x 10− 8 J. The molecular shuttles each occupy an area of ~ 3 nm 2, so ~2 x 1012 molecules are under the elongated drop just before transport. If around 40% of the shuttles have been isomerized by the time the droplet is transported uphill, each molecular machine’s contribution to the collective work Against gravity—energy stored as potential energy by their action — is ~ 1. 5 x 10− 20 J, that is ~ 9 k. Jmol− 1. Extra work, lost as heat, also has to be done to overcome the viscous forces that resist transport of the droplet.
Three Techniques of Ultra Thin Organized Film Formation • Self-Assembled Monolayers (1983, R. Nuzzo, D. Allara) • Layer-by-Layer Self-Assembly (1977, G. Decher) • Langmuir – Blodgett Technique (1917, 1932) Dijon, April 08 April
Types of molecules and substrates to be used by these methods Molecules Substrates • Langmuir – Blodgett Technique – amphiphilic, whatever • Self-Assembled Monolayers - thiols, silanes, reactive • Layer-by-Layer Self-Assembly – charged, charged In relation of Molecules and Substrates used, LB technique is the most universal Dijon, April 08 April
Self-Assembled Monolayers (SAMs) • Self-assembled monolayers are formed by immersing a substrate into a solution of a surface-active material. • Necessary conditions for the formation of 2 D assembly include: 1. Chemical bond formation of molecules with the surface; 2. Intermolecular interactions. Dijon, April 08 April
Self-Assembled Monolayers (SAMs) from Thiols In the preparation of SAMs, the substrate is immersed into a dilute (10 m. M to 1 m. M) solution of the desired thiol. For thiols on gold, initial adsorption is fast (seconds); then an organization phase follows which should be allowed to continue for > 15 h for best results. Self-assembled monolayers grown from vapor Dijon, April 08 April
Striped Phases 100 A STM images for increasing exposures of mercaptohexanol vapor on Au(111) (A) Сlean “herringbone” reconstructed Au(111) surface; inset shows stable islands nucleated between herringbone double rows after first stage of exposition. (B) Striped phase island (pointing finger). (C) Continued striped phase growth displacing herringbone elbows. (D) Continued striped phase growth with Au vacancy islands (pointing finger) becoming visible. (E) Nucleation of standing-up phase within striped phase. (F) Growth of standing-up phase at expense of striped phase until saturation. From G. E. Poirier, Langmuir 1999. Dijon, April 08 April
Soft Lithography The fundamental characteristic of Soft lithography is the formation of a contact on the molecular scale between the elastomeric stamp and the substrate. Soft lithography uses of a patterned elastomer made of polydimethylsiloxane as a stamp. High quality patterns and structures can be created with lateral dimensions from George Whitesides, father of soft lithography based on SAM technique 5 nm to 500 nm Dijon, April 08 April
Procedure for making a PDMS stamp for µCP “top-down” “master” Microcontact printing (µCP) is a method for patterning SAMs on surfaces that is analogous to printing ink with a rubber stamp on paper - The first step is deposition a thin layer of photoresist onto a silicon wafer, followed by exposure to UV light through a shadow mask. - The exposed photoresist is washed away with developer (or alternatively the unexposed photoresist is washed away). - The patterned "master" treated with perfluoroalkyltrichlorosilane to reduce its stickiness. A PDMS prepolymer is then poured onto the “master”, cured and removed to form the PDMS stamp. - The stamp impregnated with thiols is placed in contact with a bare gold surface and thiols diffuse from the stamp into the surface where they assemble.
Soft Lithography - Microcontact Printing Vapor Transport Diffusion from Stamp Surface Diffusion Metallic Grains of Substrate Dense, Well-ordered Structures Disordered, Structures Striped Phases (a) Application of a PDMS stamp containing thiols to a polycrystalline metal film. The grayscale gradient approximates the concentration of thiols adsorbed in the stamp itself. The primary mechanisms of mass transport from the stamp to the surface are shown. (b) Magnified schematic view that illustrates the variety of structural arrangements found in SAMs prepared by μCP when the stamp is wetted with a 1 -10 m. M solution and applied to the substrate for 110 s.
h=50 nm h=20 nm h=50 nm Scanning electron microscopy (SEM) images of test patterns of silver (a–d), gold (e), and copper ( f) that were fabricated using μCP with HDT, followed by wet chemical etching. The patterns in (a) and (b) were printed with rolling stamps; the patterns in (c–f ) were printed with planar stamps. The bright regions are metals; the dark regions are Si/Si. O 2 exposed where the etchant has removed the unprotected metals. (g, h) SEM images of silicon structures fabricated by anisotropic etching of Si(100), with patterned structures of silver or gold as resists. The structure in (h) was generated using a combination of shadow evaporation and anisotropic etching of Si(100).
Strategy for the soft patterning of substrates using electron beam lithography PMMA resist on gold SAM (B) e-Beam Writing Photoresist Lift-Off Gold Developing SAM (A) Patterns as small as 40 nm can be achieved using this technique with an edge resolution of 3. 5 nm.
Dip-Pen Nanolithography f o l ro t n ? N P D o C "One molecule thick letters written using Dip-Pen Nanolithography: Octadecanethiol is the ink and gold is the substrate. Visualized with an atomic force microscope.
ТЕРМОХИМИЧЕСКАЯ НАНОЛИТОГРАФИЯ (Thermochemical nanolithography – TCNL) Роль иглы выполняет кремниевый зонд атомно-силового микроскопа (АСМ), который, разогреваясь до необходимой температуры ~1000 o. C, проходит по поверхности тонкой полимерной пленки. Логотип Технического Института Джорджии, нанесенный с помощью TCNL Под влиянием разогретого зонда гидрофобная поверхность становится гидрофильной. Это позволяет осаждать необходимые вещества (ионы металлов). - Скорость нанесения дорожек ~1 мм/с (DPN - 0. 0001 мм/с) - Количество циклов нагревания/остывания до 1000000 раз в секунду - Предельное разрешение термохимической нанолитографии (TCNL) – 12 нм Основная проблема в зондовых методах – необходим переход на матричную многозондовую обработку поверхности. Ведутся работы с матрицей 64 х64 острия на площади около 7 мм 2. Производительность - сотни Мбайт/с как при записи, так и при считывании, а также с матрицей из 55000 зондов.
The Thermal Dip-Pen Nanolithography Diagram illustrating thermal dip pen nanolithography. When the cantilever is cold (left) no ink is deposited. When the cantilever is heated (right), the ink melts and is deposited onto the surface см файл DPN
The Thermal Dip-Pen Nanolithography Topographic image of a surface scanned with a heated AFM cantilever tip for 256 seconds in each of four 500 nanometer squares. The cantilever temperature is shown for each of the four scans. No deposited material is observed from the two low-temperature scans. The scan at 98 o. C resulted in light deposition. Robust deposition occurred during the final scan when the cantilever temperature was 122 o. C.
Nanoplotter - array of cantilevers The array simultaneously scribes 10 different octanethiol nanoscale patterns on a gold surface
СТМ литография (размер скана 256 х256 нм 2) На СТМ изображении трехмонослойной проводящей пленки Ленгмюра-Блоджетт (б) видны кратерообразные дефекты после локального приложения трех импульсов напряжения (а)
Механическая СТМ литография Название фирмы IBM составлено из 35 атомов ксенона (светлые точки), осажденных на поверхность никеля. Игла подводилась к выбранному атому Xe, и на нее подавалось электрическое напряжение, которое заставляло атом прилипнуть к игле. Затем игла перемещалась в заданное место, и подачей отрицательного импульса напряжения атом стряхивался с иглы обратно на подложку. На рисунках а) – г) показаны последовательные стадии поатомной сборки самой маленькой в мире рекламы (размер скана ~ 10× 10 нм 2).
Механическая модификация поверхности «Квантовый загон» - круговая структура(коралл) с радиусом 71. 3 А собрана на поверхности Cu(111) из 48 индивидуальных атомов Fe с использованием иглы низкотемпературного СТМ.
Локальное анодное оксидирование (электрохимическая нанолитография) + Схема процесса локального анодного оксидирования с помощью проводящего АСМ зонда Изображение сверхтонкой пленки титана на поверхности кремния, окисленной в заданных точках (размер скана 200 х200 нм 2)
ВЕКТОРНАЯ И РАСТРОВАЯ ЛИТОГРАФИЯ (размер скана 500 х500 нм 2) ВЕКТОРНАЯ ЛИТОГРАФИЯ перемещение зонда вдоль заданных векторов и формирование линий и более сложных объектов. Векторная литография осуществляется по заранее заданному рисунку, (размер скана 2. 5 х3. 0 мкм 2) РАСТРОВАЯ ЛИТОГРАФИЯ, осуществляется в процессе сканирования поверхности. Зонд проходит по всем точкам выбранной области сканирования, Шаблон - заранее загружаемый графический файл.
Статическая силовая литография (наногравировка) (размер скана 1. 6 х1. 6 мкм 2) Изображение поверхности алюминия с нанесенной на нее царапиной динамическое воздействие - наночеканка
Field Effect Transistor
Nano. FET for p. H sensing via SAM of -APS the mechanism and electrical characteristics of p-doped Nano. FET Nanowire sensor boron-doped silicon nanowires p. H-dependent conductance Mechanism: - the change in surface charge during protonation and deprotonation. - at high p. H, an increase of surface negative charge will attract additional holes into the p-channel of the FET and, therefore, enhance its conductance. - at low p. H, both the amines and silanols are protonated and the increase in surface positive charge will repel holes from the p-channel and decrease the conductance.
Alternate Layer-by-Layer Self-Assembly • Iler in 1966 discovered that certain surfaces modified with cationic surfactants bind monolayers of negatively charged colloidal silica or latex particles • Decher in 1991 extended the concept to layer-by-layer (Lb. L) growth of soluble organic polyelectrolytes
The build up of electrostatic multilayers of soluble polyelectrolytes (A). The generalization of the procedure to charged objects such as clusters, sheets and rods (B) A Charged substrate B
Assembly procedure A positive solid support, is immersed into a solution of an anionic polyelectrolyte for the adsorption of a monolayer, and then it is rinsed. Then the support is immersed into a solution of a cationic polyelectrolyte for the adsorption of a monolayer, then it is rinsed.
Layer constituents • Synthetic polyelectrolytes • Inorganic nanoparticles • Lipids • Ceramics • Biomolecules Schematic representation of the protein-polyion multilayer Protein/polyion multilayers • Complex biofunctional architectures • Enhanced functional stability
Bionanoparticles: shell assembly on micro/nanocores The assembly process for a solid support may be extended to an assembly on porous carriers (e. g. membranes, porous beads and fibers) or on the surface of charged micro- or nanocores. Protein shell assembly on a latex sphere (d = 20 -500 nm) for the creation of complex catalytic colloids.
Hollow nanocapsules Preparation Encapsulated core Removal of the core Hollow Capsule Core: e. g. melamine formaldehyde particles d=100 nm The melamine formaldehyde latex cores was dissolved at p. H 1 and obtained hollow polymer capsules with wall thickness of 40 nm Confocal cross-sectional image of 4 -micron diameter shell with 20 nm thick wall of (PSS/PAA)4 composition (a), and AFM-image of the collapsed shell (b). Concept of loading such capsules with enzymes and monomers for synthesis of nano-confined polymer particles. PAA - poly(allylamine). http: //www. latech. edu/tech/engr/ifm
Controlled encapsulation of molecules Nanocapsules suspended in a solution may be loaded via diffusion with molecules of interest and concentration gradients drive movement of molecules to the interior of capsules. Two methods can be used as possibilities to control permeability of nanocapsule walls after formation. These include changing the p. H and dielectric constant of the solvent. Loading in water closed ethanol/water 1: 1, open in water encapsulated
Encapsulation of drug microcrystals for sustained release purposes In step 1, precursor layers of (PSS/PDDA) are assembled onto positively charged furosemide microcrystals. In step 2, (PSS/ gelatin) layers are added. The assembly is done at p. H of 4 because the low solubility of furosemide at this p. H ensures that the microcrystal shapes and sizes are not altered. In step 3, drug release in aqueous solution at p. H 7. 4 (blood) is monitored poly(styrenesulfonate) poly(dimethyldiallyl ammonium chloride) The release rate of furosemide from the encapsulated particles was reduced by 300 times compared to uncoated furosemide p. H 4. 0 p. H 7. 4
Layer-by-Layer Self-Assembled film formed of polyviologen and poly(styrene sulfonate) layers Redox active multilayer film Schematic of electron hopping between polyviologen layers redox reversible electron hopping between colorless(2+)- deep-blue(l+) viologen units
Optical performance for PEDOT: PSS-PXV multilayers of 40 and 60 bilayers at different potential Electrochromic films on ITO At a negative potential, the colorless dicationic PHV undergoes a reduction to its deep-blue colored radical cation, and the PEDOT: PSS also becomes colored due to an undoping of the conductive state Polyanion: PEDOT: PSS - poly(3, 4 -ethylenedioxythiophene): poly(styrene sulfonate) Polycation: PHV - polyhexylviologen
Langmuir – Blodgett Technique
Langmuir Monolayer or Insoluble Monolayer at the Air - Water Interface – precursor of LB film
Langmuir-Blodgett Film one or multilayer film formed by the transfer of monolayers from the air-water interface onto solid supports
Benjamin Franklin, 1774 Наблюдал распространение на большой площади оливкового масла, нанесенного из чайной ложки на поверхность Клапамского озера (Лондон), а также гашение волн пленкой Benjamin Franklin 1706 -1790 Triolein (main component of olive oil) 1 teaspoon has a volume ~ 5 ml = 5 cm 3 = 5 x 10 -6 m 3 1/2 acre ~ 2 x 103 m 2 Assuming once it spread it retains the same total volume, V= Area * Thickness Then its final thickness = 5 x 10 -6 m 3 / 2 x 103 m 2 = 2. 5 x 10 -9 m = 2. 5 nm
John William Strutt (Lord Rayleigh), 1890 1842 -1919 Rayleigh – repeated Franklin’s experiment and concluded that the films were only a single molecule thick. Lord Rayleigh was the first to measure the lowering of the water surface tension quantitatively due to spreading of olive oil. A. Pockels (1891) made a valuable contribution to monolayer investigations. She developed a rudimentary surface balance in her kitchen sink, which she used to determine (water) surface contamination as a function of area of the surface for different oils. Surface Film Balance – introduced by Pockels Agnes Pockels 1862 -1935 Barrier A rectangular tin trough, 70 cm. long, 5 cm. wide, 2 cm. high, is filled with water to the brim, and a strip of tin about 1. 5 cm.
Langmuir 1881 -1957 • Irwing Langmuir was the first to perform systematic studies on floating monolayers on water in the late 1910's and early 1920's. These studies led to him being awarded the Nobel Prize (1932). • As early as 1920 he reported the transfer of fatty acid molecules from water surfaces onto solid supports. • However, the first detailed description of sequential monolayer transfer was given several years later by Katherine Blodgett. • These built-up monolayer assemblies are therefore referred to as Langmuir. Blodgett (LB-) films. • The term "Langmuir film" is normally reserved for a floating monolayer Langmuir demonstrated that long chain fatty acid molecules displayed the same area per molecules irrespective of the number of carbon atoms (~ 20 A 2) – from such observations he deduced that the films were monolayer thick, and were oriented at the water surface with their polar head groups in the water and the hydrocarbon chains nearly normal to the surface.
Irving Langmuir (1881 – 1957)
Katharine Burr Blodgett (1898 – 1979)
Langmuir Film (Monolayer) Amphiphilic molecules – contain both hydrophobic (water hating) and hydrophilic (water loving) portions Hydrophobic portion (e. g. hydrocarbon, -(CH 2)n-CH 3 Hydrophilic head group (e. g. carboxylic acid, -COOH ) H 2 O Aqueous subphase. Pure water, with controlled p. H, ion concentration etc. The hydrophobic part must be large enough to make the molecule insoluble in the subphase whilst the hydrophilic head-group must have sufficient attraction to the water to keep the molecules anchored at the interface – and prevent thick film build- up.
Non-Polar nonfunctional specie Polar functional molecule Non-Polar functional molecule Classic amphiphilic molecule hydrocarbon chain connector functional group spacer Polar group Polar nonfunctional specie
To spread a film at the air-water interface • The molecules are usually dissolved in a small amount of volatile solvent (e. g. hexane, chloroform, . . ) with a positive spreading coefficient. • A few drops are placed at the air-water interface – this expands rapidly spreading the amphiphiles across the surface. • The solvent evaporates – leaving the monolayer Compression of the monolayer The monolayer is gradually compressed using the movable barrier - to reduce the area available per molecule. Movable barrier Wilhelmy plate Monolayer Langmuir film balance (NIMA, Engl. )
PREPARATION OF MONOLAYER Spreading from Bulk and Solution Typical value of Equilibrium Surface Pressure – 10 m. N/m. Stearic acid – 7. 3 m. N/m. A B A AB Spreading coefficient: Spontaneous spreading : SB/A (oleic acid/water) = 24. 6 m. N/m SB/A (benzene/water) = 8. 8 m. N/m WAB = A + B - AB - work of adhesion WBB = 2 B - work of cohesion
Surface Tension & Surface Pressure Surface tension of water is 72. 8 m. Nm-1 Surfactants act to decrease surface tension. The surface pressure, π, is defined as the difference between the surface tension of the bare subphase, ο, and the surface tension of the subphase covered by amphiphiles, . π = ο -
Wilhelmy Plate Method At equilibrium A thin plate (perimeter about 40 mm) is lowered to the surface of a liquid and the downward force directed to the plate is measured. A couple of very important points air water 1. The plate must be completely wetted before the measurement to ensure that the contact angle between the plate and the liquid is zero. 2. The position of the plate must be correct, meaning that the lower end of the plate is exactly on the same level than the surface of the liquid. Otherwise the buoyancy effect must be calculated separately.
Wilhelmy plate method l h p and w - density of the plate and water. ho and h 1 – portions of the plate submerged in water. and t – width and thickness of the plate. - contact angle. P – perimeter of the plate. water The forces acting on the plate Net forces = gravity + surface tension + buoyancy. Pure water: Fo = pl tg + o. Cos 2(t+ ) - who tg Monolayer: F 1 = pl tg + 1 Cos 2(t+ ) - wh 1 tg = ( o- 1) = (Fo- F 1) + w tg(ho – h 1) Cos 2(t+ ) = 0 (Fo- F 1) = ( o- 1) = 2(t+ ) = F/P Surface pressure is directly the force divided by the perimeter of the plate.
AREA PER MOLECULE (A) – PARAMETER OF COMPRESSION ISOTHERM (insoluble surfactant) M∙S A = m∙N a [Å2] M – molecular weight of surfactant S – area of monolayer m – weighted portion Na – Avogadro number
Surface Pressure vs. Area Isotherms Solid π (m. Nm-1) Surface Pressure Displays 2 -D analogues of gaseous, liquid and solid phases Liquid Vapor (Gaseous) Molecular area Area per molecule (A 2)
Automated Langmuir film balance with a Wilhelmy plate electrobalance measuring the surface pressure, and barrier for reducing the available surface area (KSV 5000)
Monolayer Phases of Amphiphilic Molecules Surface pressure (m. N/m) A simple terminology used to classify different monolayer phases of fatty acids has been proposed by W. D. Harkins in 1952. At large area the monolayers exist in the gaseous state (G) and can on compression undergo a phase transition to the liquid-expanded state (L 1). Upon further compression, the L 1 phase undergoes a transition to the liquid-condensed state (L 2), and at even higher densities the monolayer finally reaches the solid state (S). If the monolayer is further compressed after reaching the S state the monolayer will collapse into three-dimensional structures. The collapse is generally seen as a rapid decrease in the surface pressure or as a horizontal break in the isotherm if the monolayer is in a liquid state. collapse S L 2 I L 1 -G Area per molecule (nm 2) G
Typical isotherms of a fatty acid and a phospholipid Surface pressure (m. N/m) Fatty acid Phospholipid Area per molecule (A 2) L 1 – L 2 equivalent to LE - LC Typical isotherms of a fatty acid with a single hydrocarbon chain and a phospholipid with two hydrocarbon chains are illustrated in the Figure. Fatty acid has three distinct regions gas (G), liquid (L 1) and solid (S), while the phospholipid has an additional almost horizontal transition phase (L 2 -L 1) between the two different liquid phases. This is very common for phospholipids and the position of this horizontal transition phase is very temperature dependent. As the temperature is increased the surface pressure value at which the horizontal transition phase occurs will increase and vice versa.
Two-Dimensional Phases of Aliphatic Chain Derivatives A generic phase diagram showing all monolayer phases for which either experimental or theoretical evidence exist Top view of the lamellar packing and categorizing the observed phases in terms of the tilt and distortion azimuth NN – tilt or distortion toward the nearest neighbor; NNN - tilt or distortion toward the next nearest neighbor; U – undefined (upright or undistorted); I – intermediate. I. R. Peterson and R. M. Kenn, Langmuir, 1994, 10, 4645
Монослой Ленгмюра – пленка Ленгмюра-Блоджетт Испарение растворителя и образование монослоя монослой барьер вода Сжатие монослоя приводит к образованию упорядоченной структуры вода
ПЕРЕНОС МОНОСЛОЕВ НА ТВЕРДЫЕ ПОДЛОЖКИ Техника Ленгмюра-Блоджетт Датчик Вильгельми Подложка Вода Барьер Ванна Пленка Ленгмюра-Блоджетт
Deposition process of monomolecular films on solid substrate X-type on a hydrophobic surface (head-to-tail) Y-type on a hydrophilic surface (head-to-head) The quantity and the quality of the deposited monolayer on a solid support is measured by a transfer ratio, TR. For ideal transfer the TR is equal to 1. X – up and Z – down, through the surface of pure water Z-type on a hydrophilic surface (tail-to-head) decrease in Langmuir monolayer surface area TR = total surface area of substrate
Example of polar LB assembly (Y-type) AA BB AA CC
Example of polar LB assembly (Y-type) AB AB
Пленки Ленгмюра-Шефера Получение пленок Z-типа Подложка Получение пленок X-типа Подложка Вода
THE REASONS FOR USING THE MONOLAYER AND LB FILM TECHNIQUE FOR STUDIES OF PLANAR SUPRAMOLECULAR SYSTEMS AND IN PARTICULAR INTERACTIONS BETWEEN RECEPTOR AND SUBSTRATE 1. Possibility to combine water-soluble (as subphase) and water- insoluble (as monolayer) substances. 2. Surface pressure control of molecular orientation, conformation, packing density, dipole orientation, viscosity and so on. 3. For many compartment Langmuir trough possibility to transfer monolayer from one liquid subphase to another. It’s important for different types of reactions in monolayer. 4. Because of sensitivity of monolayer technique it requires very small amounts of substances: lipids, proteins, enzymes and so on. 5. Possibility to transfer monolayer onto solid substrate by LB technique and to obtain multilayer (including hybrid one) with given structure and composition.
Advantages and Disadvantages SAMs drawbacks: This technique is limited to few substrates (silicon or gold) and surface active compounds. The monolayer properties are affected by the substrate quality. Moreover SA monolayers are unstable over time because of oxidation processes. Lb. L SA drawbacks: Method is limited to charged substrates and compounds (molecule, particles). Multilayer films exhibit a low level of the order. Langmuir-Blodgett technique drawbacks: ? ? ?
NON-AMPHIPHILIC MOLECULES studied in Laboratory of Physical Chemistry of Supramolecular Systems, IPCE PAS • Epoxy oligomers • Phthalocyanines • Thiophenes • Ionophores
Organization of discotic molecules in monolayers and LB films
Use of LB Technique for Orientation and Assembly of Discotic Molecules in Supramolecular Devices Edge-on (usual) orientation of columns (macrocycles) Organic Field Effect Transistor (OFET) Molecular Orientation in Monolayers on Water Phthalocyanine Porphyrine «Edge-on» C N N Drain Source Si. O 2 Gate (n-Si) Photovoltaic device (OLED) Gas sensor Au N N N Face-on orientation of columns (macrocycles) h NH N HN NH N C N N N HN C N «Face-on» H 2 O Orientation of discotic molecules determines the efficiency of: e-(charge) transfer, complexation, diffusion, reactivity, sensing properties
Aggregation and overturning of discotic molecules in monolayer Aggregation number N = ncalc. /nexper. Kink-point aggregation number, N 2 nd stage 1 st stage (S-S 0) = nexper RT Concentration of monolayer forming solution, [10 -5 mol/l]
Redox controlled multistability of double-decker cerium tetra-(15 -crown-5)-phthalocyaninate ultrathin films
Tuning the properties of double-decker cerium tetra-(15 crown-5)-phthalocyaninate Langmuir-Blodgett films by redox modulating impulses Electrochemical-controlled change in charge of central metal (Ce) leads to oscillations of cation dimension and as consequence to change in the length of stacking Се 3+ Се 4+ Се 3+ Се Се Се Element of supramolecular machine Се It can be used for: Се Се 1. The efficient conversion of chemical energy into mechanical work. Се Се 2. Logic operations. 3. Closure of molecular contacts.
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