CA2046391A1 - Process for the preparation of inorganic microstructures from langmuir-blodgett films - Google Patents
Process for the preparation of inorganic microstructures from langmuir-blodgett filmsInfo
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- CA2046391A1 CA2046391A1 CA002046391A CA2046391A CA2046391A1 CA 2046391 A1 CA2046391 A1 CA 2046391A1 CA 002046391 A CA002046391 A CA 002046391A CA 2046391 A CA2046391 A CA 2046391A CA 2046391 A1 CA2046391 A1 CA 2046391A1
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- Prior art keywords
- inorganic
- support
- metal ion
- langmuir
- organic
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D1/00—Processes for applying liquids or other fluent materials
- B05D1/18—Processes for applying liquids or other fluent materials performed by dipping
- B05D1/20—Processes for applying liquids or other fluent materials performed by dipping substances to be applied floating on a fluid
- B05D1/202—Langmuir Blodgett films (LB films)
- B05D1/208—After-treatment of monomolecular films
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
Abstract
~ HOE 90/F 208 Abstract of the disclosure Process for the preparation of inorganic microstructures from Langmuir-Blodgett films Process fox the preparation of inorganic microstructures from Langmuir-Blodgett films, in which one or more layers of salts of organic acids are transferred to a support while maintaining their order. Adjacent layers on the support are made up of identical or different salts. The organic component is then thermodesorbed by heating, leaving the inorganic component on the support.
Description
2 ~ 9 ~
~OECHST AKT~ENGESELLSC~AFT ~OE 90/F 208 Dr. DS/PL
~escription Process for the preparation of inorqani~ ~ cro~tructure~
from Langmuir-Blodgett films Coated supports are gaining increasing importance in industrial technology. Thus, for example, optical wave-guide systems or filters for optical purposes are coated with thin films, which, owing to their low critical surface tension, are also suitable for improving the friction properties of these materials, for the prepar ation of protective layers and for further relPvant applications. ~he preparation of monomolecular layers and the construction of system~ composed of monomolecular layers of inorganic metals or metal ions i5 important for studying surface reaction~, such a~ catalysis or corro-sion, but in particular also for ~he construction of magnetic information stores and for optical applications.
The most simple method seems to be to start with mono-molecular layer3 as subunits for the construction of complex systems. These layers are obtained by transer of monomolecular films from a liquid surface to a suitable solid support. On a water ~urface, films of this type, for example composed of molecule~ of a fatty acid having 20 carbon atoms (arachidic acid, C~3-(CH2)18-COO~), can be easily formed and tightly packed. To thi~ end, a solution of the organic acid i~ added dropwise to a water ~urface which i~ limited by rigid barriers and a movable float.
The solvent evaporateq, and the remaining molecule~ are compressed and tightly packed by a defined force acting on the float. Since the molecule have a hydrophilic (for example a carboxyl group) and a hydrophobic portion (for example a hydrocarbon chain) and are very ~paringly soluble in water, they are oriented at the water sur~ace.
The hydrophilic groups remain in the water, and the hydrophobic chains point upwards.
..
, 2~4~39~
To transfer ("apply") a tightly packed ~angmuir-Blodgett film from the water surface to a solid support, the latter is immersed and again withdrawn. When it is withdrawn, the hydrophilic group~ of the film adhere to the hydrophilic 6upport surface, and the sheet i8 thus covered with a monomolecular layer. In contrast, a hydrophobic ~ubstrate i8 already coated during the initial immersion. In each further dipping process (immersion and withdrawal), two further monomolecular layers are transferred. The interaction betw~en the hydrophilic groupæ or hydrophobic end groups causes each layer transferred to adhere to the previous one~
For years, Langmuir-Blodgett (LB) films were only con-sidered to be of interest because of their monomolecular layer structures. In 1967 Kuhn (Kuhn, Naturwissenschaften 1967, 54, 429) caused a ~ensation with his new strategy of arranging multilayers in which "clever" molecules were disposed in an inert matrix of fatty acid molecules. This was the starting point for a large num~er of functionally designed LB films. Polymerization, polycondensation, redox reactions and in-situ synthe~es in this ordered state were developed (~uaudel-Teixier, Rosilio, Barraud, Thin Solid Films, 1980, 68, 7). In the organized solid state, reactivity i8 closely related to structure, 80 that it i8 of great interest to prepare films of this type selectively for the desired areas of application.
Molecular arrangements of this type have new interesting properties, which in some cases differ con0iderably from those of the starting ~ubstances.
The heat treatment of Langmuir-Blodgett films on the water surface in order to prepare high-quality calcium arachidate layers i8 know~ (Xato, Oh~hi~a, Suzuki, Thin Solid Films, 178, 37-~5). In this procedure, insoluble monolayeræ are compres3ed on the air/water interface, subjected to a heat treatment and then applied to a support. This is ~uppo~ed to lead to virtually defect-free calcium arachidate LB films.
.
2~3~-~
The heat treatment of layers composed of various metals has been described many times in the li erature. In this process, thin films composed of metals or inorganic compounds (for example metals of rare earths, gallium arsenides) are applied to a support, for example by vapor deposition, and then subjected to a heat treatment, resulting in the formation of a variety of intermetallic phases or othex formations. The temperatures appliPd in these processes are between 200 and 700C. (J. Vac. Sci, Technol. A, 7 (5), 3016-3022; Mater. Res. Soc. Symp.
Proc. 144, 526-530, CA 112 (14): 129936 v; J. Les~-Common Met. 151, 263-9; CA ~ 111 (12)s 105999 w).
However, these processes do not en~ure the preparation of layer~ having a defined molecular structure. Therefore, there was still the object of finding a process which enables metal films having a defined film thickness in the order of magnitude of molecules to be prepared selectively, in which the metal, depending on the parti-cular application, can be present in oxide or atomic form on the support. The present process achieves this ob~ect.
It is based on the finding that in multilayers composed of salts of organic acids the organic component can be selectively desorbed from the individual layers by a heat treatment, as a rasult of which the inorganic component remains on the support.
The process according to the i~vention makes it po~sible to produce inorganic microstructure~ composed of Langmuir-Blodgett films by transferring one or more monomolecular layers of salts of organic acid~ to a support while maintaining their order and then de~orbing the organic component by heating, as a result of which the metal ion remains on the support surface. The ad-jacent layers applied to the support can, as desired, be composed of identical or different salts.
The proce~s according to the invention comprises in principle three steps:
' ~'- ~ ' ' ~ ' :
~ 4 ~ 2~ 6 3 ~ 1 a) construction of a layered structure b) heat treatment of the multilayer c) optional aftertreatment of the multilayer.
The construction of a layered structure comprising several monomolecular layers can be effected by the Langmuir-Blodgett method in a very simple manner. Ti~htly packed mono- or multilayers can be prepared by spreading salts of organic acids on a water surface or else by spreading organic acids on a ~ubphase in which metal ions are dissolved (Thin Solid Films, 146 (1987) L15-L17), compression of this layer, followed by tran~fer to a support. ~he organic component of the salt aan be, for example, an arachidic acid, stearic acid, palmitic acid or other fatty acid radical, or another amphiphilic acid, for example a charged phospholipid. Inorganic components which can be used are in general all metals; preferably all transition metals, in particular iron, cobalt, cadmium, chromium, aopper, nickel, manganese, platinum, silver, gold and rhodium, but also sodium, potas~ium, calcium, strontium and barium. Furthermore the starting materials used can also be polymer salts ~he layers suitable for the process accordinq to the invention can be prepared by adsorption processes or by the Langmuir-Blodgett method. The term "~angmuir-Blodgett films" is in general understood in this context to mean thin, ideally monomolecular, layers or multilayers of defined struc-ture.
The layered structures should be such that the di~tribu-tion of metal ions and organic componenta alternates along the surface normal. To this end, a monolayer of an organic acid is spread on a water surface. ~he aqueous subphase has a p~ of more than 5, preferably in the range from 5 to 9, as a result of which a proton di~sociate~
from the organic acid and the metal ions are transferred ~5 to the subphase by addition of an inorganic ~ lt ~for example chloride, bromide, iodide, nitrate, and the like). When a divalent metal i8 incorporated, ltS
.
.:
concentration in the subpha~e is preferably 10-4 to 10-3 M
and in the case of trivalent or higher valent ions the concentration can be many time~ les~, while in the ca~e of monovalent metals it ~hould be more than 10-4, prefer-ably more than 10-2 M. The ~alt can be tran~ferred by the LB method to a support whi~h can be made, for example, of glass or silicon, multilayers in which the layers com pxiqing aliphatic chains are intercalated by a metal layer being produced by repeated immersion and with-drawal. By changing the ~ubphase between the individual dipping processes, it is also possible to con~truct intercalating layers compri~ing different metal ions. In this manner, the process according to the invention makes it possible to produce microstructures composed of different metals or metal ion~.
~he multilayer can be melted or sublimed by subsequent heat treatment. Selection of a suitable temperature allows desorption of the organic component (at 100 to 350C), while the inorganic ~omponent remains on the support surface. The temperatures to be used in each case are dependent on the corresponding ion and counterion.
The ~ollowing two mechanisms of thermodesorption of multilayers have been disclosed to date:
-a) When multilayerq are heated to 100-160C, fir~t droplets are formedO When the temperature is further increased, the surface breakæ up more and more with further formation of droplets, the organic component is desorbed and what remains are cluster~ of the corre~ponding metal or the corresponding metal ions.
(Example 1 ) -b) When the multilayer i3 heated, the layer doe~ not break up and no fo~mation o~ droplet~ takes place.
The organic component is desorbed and the metal or the metal ion remain on the support as a coherent layer. ~Example 1 ~.
- .
- ; . . .
;........ .;
, 2~39~
Thus, depending on the selection of the inorganic and organic components, the process according to the inven-tion makes it possible to produce micro~truc~ures of different design. Using the example of desorption of iron stearate, it has bee~ shown that plate-like olids linked to one another and containing iron(III) which differ from those formed b~ thermodesorption of cadmium arachidate can be formed.
The diameter of the cadmium clusters i~ usu~lly in the range from 0~5 to 2 ~m at a spacing of 3 to 5 ~m (Example 2). The clusters formed are in this case not linked to one another.
The distribution of ~he microstructures can be controlled by adjusting preparation parameters such as desorption kinetics, nucleation or layer thickness.
The thermodesorption temperatures used in each ca-~e depend on the organic and inorganic components used. The bond between metal and acid radical mu~t not be too weak nor too strong in order to en~ure desorption at suffi-ciently low temperatures and thus the microstructureformation of the metal ions. The advantage of the process according to the invention is in particular that rela-tively mild temperatures are used. The microstructures themselves which predominantly contain the metal com-ponent but hardly any carbon are only de~orbed attemperatures above 350C or even higher, depending on the metal ion used.
By treating the layers thus formed with hot hydrogen (T = 500C), it is possible to change the oxidation states of the metal ions. U~ing the exzmple of iron stearate, it could be shown by Mo~bauer spectroscopy that after thermodesorption of the stearate radical first iron(III) ions are present which are reduced by the hydrogen t~eatment, so that afterwards the iron atom~ are also present in the oxidation state "0". By varying the .. : .. .
7 2 ~
treatment time and temperature, it is pos~ible to control the reduction ratio. (Working Example 3).
The process according to the invention makes it possible to construct inorganic microstructures at relatively low temperatures, which have a high degree of order and can additionally be structured laterally by means o~ photo-lithography. Possible aspects of economic interest are in particular in the area of applications in optics, data storage, catalyst technology but al80 in magnetometry.
Working examples Example 1:
XPS (X-ray-induced photoelectron spectroscopy) measure-ments on transferred ~B films before and after thermo-desorption provided information on the composition of the lS chemical elements of the layers.
The measurements were carried out on a cadmium arachidate (Figure la) and an iron(III) stearate (Figure lb) multi-layer. Coating was carried out by the con~entional ~B
method; the support used was hydrophilic silicon having a natural silicon dioxide layer of about 20-50 A.
The cadmium arachidate film comprising 7 monolayers was applied after spreading arachidic acid onto Millipore water to~ether with 10 3 M CdCl2 at a pH of 7 ~6 mg of NaHCO3/l of water) at 20C~ followed by compres3ion at a constant pressure of 30 mN/m. The iron(IIX) stearate multilayer (17 monolayers) was formed from stearic acid on a subphase containing 4x10-5 M FeCl3, pH 5.5, 40C and under a pressure of 30 mN~m. In both cases, the xate of application was 10 mm/min.
TheXPSmeasurementsbeforethermodesorption (Figure la,b) showed with both samples tha~ ~he organic componen~ (high C signal) and the inorganic metal ion (high cadmium : ;
. ~
- 8 - 2~3~
or iron intensity) had been transferred to the substrate.
The measurements after thermodesorption ~Figure la, b, the samples were heated to 250C for 30 minute~) show that the organic component i8 almost completely de~orbed (considerably lower C intensity), the metal ion however remains on the support tdistinct Cd, Fe signals). In the sample containing cadmium, the support signal (Si) i8 clearly visible after de60rption (Figure la). This can only be explained by the fact that large portions of the ~upport are uncovered and the cadmium ions are present on the support in the form of clusters which are not linked toqether. In the iron sample, the support signal is hardly visible, since the silicon support is covered by a coherent iron layer (probably in the form of iron oxide), making it impossible ~o detect any electrons having the binding energy of silicon.
Bxampl~ 2:
The melting of a cadmium arachidate layer (7 monolayers on silicon, preparation conditions as in Example 1) was monitored under a ~omarski microscope. The breakup of the layer and the subsequent droplet formation accompanied by desorption could be observed. At a heating rate of 0.7 K/s, followed by cooling to room temperature, the brig~t cadmium clusters (Figure 2) having a diameter of 0.5 to ~ ~m can be seen.
In the iron stearate samples neither droplet nor cluster formation was observed.
Fxample 3:
In order to determine the oxidation state of the iron ions, the thermode~orbed iron multilayers were investigated by conversion electxon Mo~bauer spectro~
scopy. Figure 3 shows such a measurement. The ~ample (15 monolayer~) was prepared as described in Example 1, :
, .
. .
9 2~4~39~
except that up to 95 % of enriched Fe57(III) chloride was u~ed. Desorption was carried ou~ at 510C under a hydro-gen atmosphere (1 hour). This gave a proportion of 36 %
of Fe3+, 24 % of FeZ~ ion~ and 40 % of Fe ~metallic iron).
Figure l:
XPS spectra (intensity plotted versus bonding energy) of a silicon support, originally coated with a) 7 monolayers of cadmium arachidate, b) 17 monolayers of iron(III) stearate before (25C) and after thermodesorption (heated at 250C
for 30 minutes and then cooled to room temperature).
Figure 2:
Photograph under a Nomarski microscope of a film compris-ing 7 monolayers of cadmium arachidate on silicon, heated at a rate of 0.7 K/s up to 350C and then cooled to xoom temperature.
Figure 3:
Conversion electron Ma~bauer spectrum of a multilayer originally comprising 15 monolayer~ of iron(III) stear-ate, followed by thermodesorption (1 hour) at 510C undera hydrogen atmosphere.
~ ' , ' , , . '~ . :
. . . .
.. .. . . . .
~OECHST AKT~ENGESELLSC~AFT ~OE 90/F 208 Dr. DS/PL
~escription Process for the preparation of inorqani~ ~ cro~tructure~
from Langmuir-Blodgett films Coated supports are gaining increasing importance in industrial technology. Thus, for example, optical wave-guide systems or filters for optical purposes are coated with thin films, which, owing to their low critical surface tension, are also suitable for improving the friction properties of these materials, for the prepar ation of protective layers and for further relPvant applications. ~he preparation of monomolecular layers and the construction of system~ composed of monomolecular layers of inorganic metals or metal ions i5 important for studying surface reaction~, such a~ catalysis or corro-sion, but in particular also for ~he construction of magnetic information stores and for optical applications.
The most simple method seems to be to start with mono-molecular layer3 as subunits for the construction of complex systems. These layers are obtained by transer of monomolecular films from a liquid surface to a suitable solid support. On a water ~urface, films of this type, for example composed of molecule~ of a fatty acid having 20 carbon atoms (arachidic acid, C~3-(CH2)18-COO~), can be easily formed and tightly packed. To thi~ end, a solution of the organic acid i~ added dropwise to a water ~urface which i~ limited by rigid barriers and a movable float.
The solvent evaporateq, and the remaining molecule~ are compressed and tightly packed by a defined force acting on the float. Since the molecule have a hydrophilic (for example a carboxyl group) and a hydrophobic portion (for example a hydrocarbon chain) and are very ~paringly soluble in water, they are oriented at the water sur~ace.
The hydrophilic groups remain in the water, and the hydrophobic chains point upwards.
..
, 2~4~39~
To transfer ("apply") a tightly packed ~angmuir-Blodgett film from the water surface to a solid support, the latter is immersed and again withdrawn. When it is withdrawn, the hydrophilic group~ of the film adhere to the hydrophilic 6upport surface, and the sheet i8 thus covered with a monomolecular layer. In contrast, a hydrophobic ~ubstrate i8 already coated during the initial immersion. In each further dipping process (immersion and withdrawal), two further monomolecular layers are transferred. The interaction betw~en the hydrophilic groupæ or hydrophobic end groups causes each layer transferred to adhere to the previous one~
For years, Langmuir-Blodgett (LB) films were only con-sidered to be of interest because of their monomolecular layer structures. In 1967 Kuhn (Kuhn, Naturwissenschaften 1967, 54, 429) caused a ~ensation with his new strategy of arranging multilayers in which "clever" molecules were disposed in an inert matrix of fatty acid molecules. This was the starting point for a large num~er of functionally designed LB films. Polymerization, polycondensation, redox reactions and in-situ synthe~es in this ordered state were developed (~uaudel-Teixier, Rosilio, Barraud, Thin Solid Films, 1980, 68, 7). In the organized solid state, reactivity i8 closely related to structure, 80 that it i8 of great interest to prepare films of this type selectively for the desired areas of application.
Molecular arrangements of this type have new interesting properties, which in some cases differ con0iderably from those of the starting ~ubstances.
The heat treatment of Langmuir-Blodgett films on the water surface in order to prepare high-quality calcium arachidate layers i8 know~ (Xato, Oh~hi~a, Suzuki, Thin Solid Films, 178, 37-~5). In this procedure, insoluble monolayeræ are compres3ed on the air/water interface, subjected to a heat treatment and then applied to a support. This is ~uppo~ed to lead to virtually defect-free calcium arachidate LB films.
.
2~3~-~
The heat treatment of layers composed of various metals has been described many times in the li erature. In this process, thin films composed of metals or inorganic compounds (for example metals of rare earths, gallium arsenides) are applied to a support, for example by vapor deposition, and then subjected to a heat treatment, resulting in the formation of a variety of intermetallic phases or othex formations. The temperatures appliPd in these processes are between 200 and 700C. (J. Vac. Sci, Technol. A, 7 (5), 3016-3022; Mater. Res. Soc. Symp.
Proc. 144, 526-530, CA 112 (14): 129936 v; J. Les~-Common Met. 151, 263-9; CA ~ 111 (12)s 105999 w).
However, these processes do not en~ure the preparation of layer~ having a defined molecular structure. Therefore, there was still the object of finding a process which enables metal films having a defined film thickness in the order of magnitude of molecules to be prepared selectively, in which the metal, depending on the parti-cular application, can be present in oxide or atomic form on the support. The present process achieves this ob~ect.
It is based on the finding that in multilayers composed of salts of organic acids the organic component can be selectively desorbed from the individual layers by a heat treatment, as a rasult of which the inorganic component remains on the support.
The process according to the i~vention makes it po~sible to produce inorganic microstructure~ composed of Langmuir-Blodgett films by transferring one or more monomolecular layers of salts of organic acid~ to a support while maintaining their order and then de~orbing the organic component by heating, as a result of which the metal ion remains on the support surface. The ad-jacent layers applied to the support can, as desired, be composed of identical or different salts.
The proce~s according to the invention comprises in principle three steps:
' ~'- ~ ' ' ~ ' :
~ 4 ~ 2~ 6 3 ~ 1 a) construction of a layered structure b) heat treatment of the multilayer c) optional aftertreatment of the multilayer.
The construction of a layered structure comprising several monomolecular layers can be effected by the Langmuir-Blodgett method in a very simple manner. Ti~htly packed mono- or multilayers can be prepared by spreading salts of organic acids on a water surface or else by spreading organic acids on a ~ubphase in which metal ions are dissolved (Thin Solid Films, 146 (1987) L15-L17), compression of this layer, followed by tran~fer to a support. ~he organic component of the salt aan be, for example, an arachidic acid, stearic acid, palmitic acid or other fatty acid radical, or another amphiphilic acid, for example a charged phospholipid. Inorganic components which can be used are in general all metals; preferably all transition metals, in particular iron, cobalt, cadmium, chromium, aopper, nickel, manganese, platinum, silver, gold and rhodium, but also sodium, potas~ium, calcium, strontium and barium. Furthermore the starting materials used can also be polymer salts ~he layers suitable for the process accordinq to the invention can be prepared by adsorption processes or by the Langmuir-Blodgett method. The term "~angmuir-Blodgett films" is in general understood in this context to mean thin, ideally monomolecular, layers or multilayers of defined struc-ture.
The layered structures should be such that the di~tribu-tion of metal ions and organic componenta alternates along the surface normal. To this end, a monolayer of an organic acid is spread on a water surface. ~he aqueous subphase has a p~ of more than 5, preferably in the range from 5 to 9, as a result of which a proton di~sociate~
from the organic acid and the metal ions are transferred ~5 to the subphase by addition of an inorganic ~ lt ~for example chloride, bromide, iodide, nitrate, and the like). When a divalent metal i8 incorporated, ltS
.
.:
concentration in the subpha~e is preferably 10-4 to 10-3 M
and in the case of trivalent or higher valent ions the concentration can be many time~ les~, while in the ca~e of monovalent metals it ~hould be more than 10-4, prefer-ably more than 10-2 M. The ~alt can be tran~ferred by the LB method to a support whi~h can be made, for example, of glass or silicon, multilayers in which the layers com pxiqing aliphatic chains are intercalated by a metal layer being produced by repeated immersion and with-drawal. By changing the ~ubphase between the individual dipping processes, it is also possible to con~truct intercalating layers compri~ing different metal ions. In this manner, the process according to the invention makes it possible to produce microstructures composed of different metals or metal ion~.
~he multilayer can be melted or sublimed by subsequent heat treatment. Selection of a suitable temperature allows desorption of the organic component (at 100 to 350C), while the inorganic ~omponent remains on the support surface. The temperatures to be used in each case are dependent on the corresponding ion and counterion.
The ~ollowing two mechanisms of thermodesorption of multilayers have been disclosed to date:
-a) When multilayerq are heated to 100-160C, fir~t droplets are formedO When the temperature is further increased, the surface breakæ up more and more with further formation of droplets, the organic component is desorbed and what remains are cluster~ of the corre~ponding metal or the corresponding metal ions.
(Example 1 ) -b) When the multilayer i3 heated, the layer doe~ not break up and no fo~mation o~ droplet~ takes place.
The organic component is desorbed and the metal or the metal ion remain on the support as a coherent layer. ~Example 1 ~.
- .
- ; . . .
;........ .;
, 2~39~
Thus, depending on the selection of the inorganic and organic components, the process according to the inven-tion makes it possible to produce micro~truc~ures of different design. Using the example of desorption of iron stearate, it has bee~ shown that plate-like olids linked to one another and containing iron(III) which differ from those formed b~ thermodesorption of cadmium arachidate can be formed.
The diameter of the cadmium clusters i~ usu~lly in the range from 0~5 to 2 ~m at a spacing of 3 to 5 ~m (Example 2). The clusters formed are in this case not linked to one another.
The distribution of ~he microstructures can be controlled by adjusting preparation parameters such as desorption kinetics, nucleation or layer thickness.
The thermodesorption temperatures used in each ca-~e depend on the organic and inorganic components used. The bond between metal and acid radical mu~t not be too weak nor too strong in order to en~ure desorption at suffi-ciently low temperatures and thus the microstructureformation of the metal ions. The advantage of the process according to the invention is in particular that rela-tively mild temperatures are used. The microstructures themselves which predominantly contain the metal com-ponent but hardly any carbon are only de~orbed attemperatures above 350C or even higher, depending on the metal ion used.
By treating the layers thus formed with hot hydrogen (T = 500C), it is possible to change the oxidation states of the metal ions. U~ing the exzmple of iron stearate, it could be shown by Mo~bauer spectroscopy that after thermodesorption of the stearate radical first iron(III) ions are present which are reduced by the hydrogen t~eatment, so that afterwards the iron atom~ are also present in the oxidation state "0". By varying the .. : .. .
7 2 ~
treatment time and temperature, it is pos~ible to control the reduction ratio. (Working Example 3).
The process according to the invention makes it possible to construct inorganic microstructures at relatively low temperatures, which have a high degree of order and can additionally be structured laterally by means o~ photo-lithography. Possible aspects of economic interest are in particular in the area of applications in optics, data storage, catalyst technology but al80 in magnetometry.
Working examples Example 1:
XPS (X-ray-induced photoelectron spectroscopy) measure-ments on transferred ~B films before and after thermo-desorption provided information on the composition of the lS chemical elements of the layers.
The measurements were carried out on a cadmium arachidate (Figure la) and an iron(III) stearate (Figure lb) multi-layer. Coating was carried out by the con~entional ~B
method; the support used was hydrophilic silicon having a natural silicon dioxide layer of about 20-50 A.
The cadmium arachidate film comprising 7 monolayers was applied after spreading arachidic acid onto Millipore water to~ether with 10 3 M CdCl2 at a pH of 7 ~6 mg of NaHCO3/l of water) at 20C~ followed by compres3ion at a constant pressure of 30 mN/m. The iron(IIX) stearate multilayer (17 monolayers) was formed from stearic acid on a subphase containing 4x10-5 M FeCl3, pH 5.5, 40C and under a pressure of 30 mN~m. In both cases, the xate of application was 10 mm/min.
TheXPSmeasurementsbeforethermodesorption (Figure la,b) showed with both samples tha~ ~he organic componen~ (high C signal) and the inorganic metal ion (high cadmium : ;
. ~
- 8 - 2~3~
or iron intensity) had been transferred to the substrate.
The measurements after thermodesorption ~Figure la, b, the samples were heated to 250C for 30 minute~) show that the organic component i8 almost completely de~orbed (considerably lower C intensity), the metal ion however remains on the support tdistinct Cd, Fe signals). In the sample containing cadmium, the support signal (Si) i8 clearly visible after de60rption (Figure la). This can only be explained by the fact that large portions of the ~upport are uncovered and the cadmium ions are present on the support in the form of clusters which are not linked toqether. In the iron sample, the support signal is hardly visible, since the silicon support is covered by a coherent iron layer (probably in the form of iron oxide), making it impossible ~o detect any electrons having the binding energy of silicon.
Bxampl~ 2:
The melting of a cadmium arachidate layer (7 monolayers on silicon, preparation conditions as in Example 1) was monitored under a ~omarski microscope. The breakup of the layer and the subsequent droplet formation accompanied by desorption could be observed. At a heating rate of 0.7 K/s, followed by cooling to room temperature, the brig~t cadmium clusters (Figure 2) having a diameter of 0.5 to ~ ~m can be seen.
In the iron stearate samples neither droplet nor cluster formation was observed.
Fxample 3:
In order to determine the oxidation state of the iron ions, the thermode~orbed iron multilayers were investigated by conversion electxon Mo~bauer spectro~
scopy. Figure 3 shows such a measurement. The ~ample (15 monolayer~) was prepared as described in Example 1, :
, .
. .
9 2~4~39~
except that up to 95 % of enriched Fe57(III) chloride was u~ed. Desorption was carried ou~ at 510C under a hydro-gen atmosphere (1 hour). This gave a proportion of 36 %
of Fe3+, 24 % of FeZ~ ion~ and 40 % of Fe ~metallic iron).
Figure l:
XPS spectra (intensity plotted versus bonding energy) of a silicon support, originally coated with a) 7 monolayers of cadmium arachidate, b) 17 monolayers of iron(III) stearate before (25C) and after thermodesorption (heated at 250C
for 30 minutes and then cooled to room temperature).
Figure 2:
Photograph under a Nomarski microscope of a film compris-ing 7 monolayers of cadmium arachidate on silicon, heated at a rate of 0.7 K/s up to 350C and then cooled to xoom temperature.
Figure 3:
Conversion electron Ma~bauer spectrum of a multilayer originally comprising 15 monolayer~ of iron(III) stear-ate, followed by thermodesorption (1 hour) at 510C undera hydrogen atmosphere.
~ ' , ' , , . '~ . :
. . . .
.. .. . . . .
Claims (8)
1. A process for the preparation of inorganic micro-structures, from Langmuir-Blodgett films, which comprises transferring one or more monomolecular layers of salts of organic acids to a support, while maintaining their order, adjacent layers being made up of identical or different salts, then thermo-desorbing the organic component by heating, the inorganic component remaining on the support.
2. The process as claimed in claim 1, wherein the organic component of the salt is a fatty acid radical or a phospholipid acid radical.
3. The process as claimed in claim 1, wherein the inorganic component of the salt is a transition metal ion, preferably iron, cobalt, cadmium, chro-mium, copper, nickel, manganese, platinum, silver, gold or rhodium.
4. The process as claimed in claim 1, wherein the inorganic component of the salt is an alkali metal ion or an alkaline earth metal ion.
5. The process as claimed in claim 1, wherein the aqueous subphase has a pH of greater than 5, in particular in the range from 5 to 9.
6. The process as claimed in claim 1, wherein the metal ion concentration of the subphase is more than 10-4 M, preferably more than 10-3 M, in the case of divalent metals, and more than 10-4 M, preferably more than 10-2 M, in the case of monovalent metals.
7. The process as claimed in claim 1, wherein the organic component is desorbed at temperatures from 100 to 350°C.
8. The process as claimed in claim 1, wherein the inorganic layer is partially or completely reduced after thermodesorption of the organic component.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19904021733 DE4021733A1 (en) | 1990-07-07 | 1990-07-07 | METHOD FOR PRODUCING INORGANIC MICROSTRUCTURES FROM LANGMUIR BLODGETT LAYERS |
| DEP4021733.7 | 1990-07-07 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2046391A1 true CA2046391A1 (en) | 1992-01-08 |
Family
ID=6409896
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002046391A Abandoned CA2046391A1 (en) | 1990-07-07 | 1991-07-05 | Process for the preparation of inorganic microstructures from langmuir-blodgett films |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0466044A1 (en) |
| JP (1) | JPH0592167A (en) |
| CA (1) | CA2046391A1 (en) |
| DE (1) | DE4021733A1 (en) |
| FI (1) | FI913249A (en) |
| IE (1) | IE912355A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120156389A1 (en) * | 2009-08-31 | 2012-06-21 | The Regents Of The University Of Michigan | Preparation of layer-by-layer materials and coatings from ionic liquids |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3404769B2 (en) * | 1992-10-02 | 2003-05-12 | 松下電器産業株式会社 | Organic film manufacturing method |
| FR2747945B1 (en) * | 1996-04-26 | 1998-08-21 | Lorraine Laminage | METAL SHEET SURFACE TREATMENT |
| DE19928658C2 (en) * | 1999-06-23 | 2002-12-19 | Michael Gleiche | Process for the generation of ordered channel structures by wetting instabilities |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4317043A (en) * | 1979-10-26 | 1982-02-23 | The University Of Rochester | Normal incidence x-ray reflectors and resonant cavities for supporting laser action using the same |
| US5166307A (en) * | 1988-09-07 | 1992-11-24 | Hoechst Aktiengesellschaft | Polyamide and film made from at least one monomolecular layer of a polyamide |
| JPH02123768A (en) * | 1988-11-02 | 1990-05-11 | Mitsubishi Electric Corp | Manufacture of organic semiconductor thin-film and semiconductor device including such thin-film |
-
1990
- 1990-07-07 DE DE19904021733 patent/DE4021733A1/en not_active Withdrawn
-
1991
- 1991-07-04 FI FI913249A patent/FI913249A/en unknown
- 1991-07-05 IE IE235591A patent/IE912355A1/en unknown
- 1991-07-05 CA CA002046391A patent/CA2046391A1/en not_active Abandoned
- 1991-07-05 JP JP20869791A patent/JPH0592167A/en active Pending
- 1991-07-05 EP EP91111208A patent/EP0466044A1/en not_active Withdrawn
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20120156389A1 (en) * | 2009-08-31 | 2012-06-21 | The Regents Of The University Of Michigan | Preparation of layer-by-layer materials and coatings from ionic liquids |
| US8795783B2 (en) * | 2009-08-31 | 2014-08-05 | The Regents Of The University Of Michigan | Preparation of layer-by-layer materials and coatings from ionic liquids |
Also Published As
| Publication number | Publication date |
|---|---|
| FI913249A0 (en) | 1991-07-04 |
| DE4021733A1 (en) | 1992-01-09 |
| EP0466044A1 (en) | 1992-01-15 |
| JPH0592167A (en) | 1993-04-16 |
| FI913249A (en) | 1992-01-08 |
| IE912355A1 (en) | 1992-01-15 |
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