Patent Application: US-57104005-A

Abstract:
the present invention relates to functionalized silicon and / or germanium surfaces , methods for the preparation of such tailor - made functionalized silicon and / or germanium surfaces , the use of such tailor - made functionalized silicon and / or germanium surfaces for the preparation of surface - bonded organic materials and the use in industrial devices . the silicon and / or germanium surfaces comprise silicon nitride , silicon carbide , germanium nitride , germanium carbide and silicon germanium surfaces .

Description:
according to the invention , a is a linear , branched or cyclic alkylene or alkenylene group having 2 to 24 carbon atoms , wherein the alkenylene group is a 1 - alkenylene or an internal alkenylene group . examples of suitable alkylene groups are ethylene , propylene , butylene , pentylene , decylene , octadecylene and eicosenylene and the like . examples of suitable alkenylene groups are propenylene , but - 2 - enylene , oct - 4 - enylene and the like . according to a most particular preferred embodiment of the present invention , the alkyl and alkenyl moieties comprise at least one internal ethynylene moiety . that is , that a is in particular a linear group having 6 to 24 carbon atoms according to the formula : wherein p is in the range of 1 to 7 and q is in the range of 1 to 7 , the groups —( ch 2 )— and —( c ≡ c )— optionally occurring in a random sequence , and wherein the right terminus of a is bonded to b . such ethynylene moieties can be polymerized to provide a cross - linked network that will reduce the permeability of the monolayer , and that will provide more stabilization to the monolayer . examples of this linear group are : preferably , the linear group has the formula — ch 2 — ch 2 —( ch 2 ) p —( c ≡ c ) q —( ch 2 ) r —, wherein p is 1 to 9 , preferably 7 , r is 1 to 9 and q is 1 or 2 . according to the invention , b can be selected from the functional groups as defined above . suitable examples of — ch ═ cr 2 r 3 groups are ethenyl , 2 - propenyl , 4 - butenyl and the like . the formula — ch ═ cr 2 r 3 may represent a cyclic structure having a carbon carbon double bond in the ring or having an exo carbon carbon double bond , that is that the formula — ch ═ cr 2 r 3 includes structures such as cyclopent - 3 - enyl and 2 - methylene cyclopentyl . suitable examples of — c ≡ cr 2 groups are ethynyl , 2 - propynyl and the like . suitable examples of the — xr 2 group are — oh , — sh , — ome , — oet and the like , wherein me represents methyl and et represents ethyl . suitable examples of the — n ( r 2 ) 2 group include primary , secondary and tertiary amino groups such as — nh 2 , — nhet and — nme 2 . a suitable example of the urea group — nr 2 — c ( o )— n ( r 2 ) 2 is — nh — c ( o )— nh 2 . the group — o —[( c ( r 4 ) 2 ) p o ] q — r 2 represents oligomers and polymers of alkylene oxides . r 4 is selected from the group consisting of hydrogen and c 1 - c 4 alkyl , e . g . methyl , ethyl , n - propyl and i - propyl . preferably , r 4 is hydrogen or methyl and p is 2 . the group — o —[( c ( r 4 ) 2 ) p o ] q — r 2 encompasses diblock , triblock , multiblock or comb - like oligomers and polymers , e . g . — o —[( ch 2 o ) s —( chmeo ) t ]— r 2 wherein s + t = q . a suitable diblock polymer consists for example of a polyethylene oxide block and a polypropylene oxide block . in addition , these oligomers and polymers may be terminated with a hydroxyl group or an alkoxy group ( e . g . a methoxy group ), the latter being represented by — or 2 as appears from the formula . suitable examples of the — c ( x ) xr 1 group are ester groups and thioester groups , e . g . — c ( o ) ome , — c ( o ) oet , — c ( s ) sme and the like . suitable examples of the amide groups or thioamide groups — c ( x ) nr 2 r 3 are — c ( o ) nme 2 and — c ( s ) nme 2 . suitable examples of the sulfino group — s ( o ) or 1 are — s ( o ) ome and — s ( o ) oet . suitable examples of the sulfonyl group — s ( o ) 2 or 1 are — s ( o ) 2 ome and — s ( o ) 2 oet . likewise , a suitable example of the group — s ( o ) nr 2 r 3 includes — s ( o ) nme 2 . a suitable example of the sulfamoyl group — s ( o ) 2 nr 2 r 3 is — s ( o ) 2 nme 2 . a suitable example of the group — p ( o )( r 1 )( or 1 ) is — p ( o )( me )( ome ) and a suitable example of the group — p ( o )( or 1 ) 2 is — p ( o )( ome ) 2 . suitable examples of the groups according to formula ( 2 ) are shown below as belonging to preferred embodiments of b . according to a preferred embodiment of the present invention , b is a functional group selected from — ch ═ cr 2 r 3 ; — c ≡ cr 2 ; — or 2 ; — n ( r 2 ) 2 ; — nr 2 — c ( o )— n ( r 2 ) 2 ; — o —[( c ( r 4 ) 2 ) p o ] q — r 2 ; — c ( o ) or 1 ; — c ( o ) sr 1 ; — c ( o ) nr 2 r 3 ; — s ( o ) or 1 ; — s ( o ) 2 or 1 ; — s ( o ) nr 2 r 3 ; — s ( o ) 2 nr 2 r 3 ; — p ( o )( r 1 )( or 1 ); — p ( o )( or 1 ) 2 ; — cn ; — cl ; — nco ; — ocn ; and according to a more preferred embodiment of the present invention , b is a functional group selected from — ch ═ cr 2 r 3 ; — c ≡ cr 2 ; — or 2 ; — n ( r 2 ) 2 ; — o —[( c ( r 4 ) 2 ) p o ] q — r 2 wherein r 4 is hydrogen or methyl , p is 2 and q is an integer within the range of 1 - 250 ; — c ( o ) or 1 ; — c ( o ) nr 2 r 3 ; — s ( o ) or 1 ; — s ( o ) 2 or 1 ; — s ( o ) nr 2 r 3 ; or — s ( o ) 2 nr 2 r 3 ; and wherein n is 1 . it is furthermore preferred that a is a linear alkylene or alkenylene group having 2 to 24 carbon atoms . more preferably , a is a linear alkylene or alkenylene group having 6 to 20 carbon atoms . even more preferably , a is a linear alkylene or alkenylene group having 8 to 18 carbon atoms . the present invention also provides a process for the preparation of a functionalized si / ge surface , wherein a si / ge surface is subjected to the following steps : ( a ) etching the si / ge surface with an etching agent to form an etched si / ge surface ; and ( b ) reacting the etched si / ge surface with an co - functionalized alkene represented by the general formula ( 4 ) or with an ω - functionalized alkyne represented by the general formula ( 5 ) or with a mixture thereof : wherein p is a linear , branched or cyclic alkenyl group having 2 to 24 carbon atoms , the alkenyl group being a 1 - alkenyl group or an internal alkenyl group ; q is a linear , branched or cyclic alkynyl group having 2 to 24 carbon atoms , the alkynyl group being a 1 - alkynyl group or an internal alkynyl group ; c is a functional group selected from : — ch ═ cr 2 r 3 ; — c ≡ cr 2 ; — nr 2 — c ( o )— n ( r 2 ) 2 ; — o —[( c ( r 4 ) 2 ) p o ] q — r 1 ; — c ( x ) xr 1 ; — c ( x ) nr 2 r 3 ; — s ( o ) or 1 ; — s ( o ) 2 or 1 ; — s ( o ) nr 2 r 3 ; — s ( o ) 2 n 2 r 3 ; — p ( o )( r 1 )( or 1 ); — p ( o )( or 1 ) 2 ; — cn ; — cl , — br ; — i ; or — ncx ; — xcn ; or — xc ( x ) r 1 ; — nr 2 c ( x ) r 1 ; — xr 5 ; — xsi ( r 1 ) 3 ; — os ( o )( or 1 ); — os ( o ) 2 or 1 ; — p ( o )( r 1 )( or 1 ); — op ( o )( or 1 ) 2 ; a group of the general formula ( 6 ) and tautomers thereof : wherein r 1 , r 2 , r 3 , r 4 , p and q are as defined above ; r 5 is a monofunctional hydroxy or thiohydroxy protecting group ; r 6 represents a protected — oh or — nh 2 group , wherein the protected — oh group is selected from the groups defined for — xr 5 wherein x is o and wherein the protected — nh 2 group is selected from the groups defined for — nr 2 c ( x ) r 1 ; and wherein n is an integer in the range of 1 to 3 . according to the present invention , r 5 is a monofunctional hydroxy or thiohydroxy protecting group . such protecting groups are well known in the art as well as methods for adding such groups to — xh groups and methods for removing such protecting groups under conditions that do not affect the molecular structure of the functionalized si / ge surface obtained . 15 suitable examples of monofunctional hydroxy and thiohydroxy protecting groups include methoxymethyl , methylthiomethyl , 2 - methoxyethoxymethyl , bis ( 2 - chloroethoxy ) methyl , tetrahydropyranyl , tetrahydrothiopyranyl , 4 - methoxytetrahydropyranyl , 4 - methoxytetrahydrothiopyranyl , tetrahydrofuranyl , tetrahydrothiofuranyl , 1 - ethoxyethyl , 1 - methoxy1 - methoxyethyl , 2 -( phenylselenyl ) ethyl , t - butyl , allyl , benzyl , optionally substituted triphenylmethyl ( trityl ). however , it is preferred that the monofunctional hydroxyl or thiohydroxy protecting group is selected from the group of allyl , benzyl , optionally substituted trityl , and tetrahydropyranyl . it is even more preferred that the monofunctional hydroxyl or thiohydroxy protecting group is selected from benzyl and tetrahydropyranyl . suitable examples of the — si ( r 1 ) 3 group are trimethylsilyl , triethylsilyl , triisopropylsilyl , isopropyldimethylsilyl , t - butyldimethylsilyl , t - butyldiphenylsilyl and tribenzylsilyl . methods of the introduction and removal of such groups are well known in the art . 16 preferably , c is a functional group selected from — ch ═ cr 2 r 3 ; — c ≡ cr 2 ; — nr 2 — c ( o )— n ( r 2 ) 2 ; — o —[( c ( r 4 ) 2 ) p o ] q — r 1 ; — c ( o ) or 1 ; — c ( o ) nr 2 r 3 ; — s ( o ) or 1 ; — s ( o ) 2 or 1 ; — s ( o ) nr 2 r 3 ; — s ( o ) 2 nr 2 r 3 ; — p ( o )( r 1 )( or 1 ); — p ( o )( or 1 ) 2 ; — cn ; — cl ; and — nco ; — ocn ; or c is a protected functional group selected from — oc ( o ) r 1 ; — nr 2 c ( o ) r 1 ; — or 5 ; — osi ( r 1 ) 3 ; — os ( o )( or 1 ); — os ( o ) 2 or 1 ; — p ( o )( r 1 )( or 1 ); — op ( o )( or 1 ) 2 ; and a group of the general formula ( 6 ) and tautomers thereof which is shown above , wherein r 6 represents a protected — oh or — nh 2 group , wherein the protected — oh group is selected from the groups defined for — xr 5 wherein x is o and wherein the protected — nh 2 group is selected from the groups defined for — nr 2 c ( x ) r 1 ; wherein r 5 is a monofunctional hydroxy or thiohydroxy protecting group ; and wherein n is 1 . even more preferably , c is a functional group selected from — ch ═ cr 2 r 3 ; — c ≡ cr 2 ; — o —[( c 4 ) 2 ) p o ] q — r 1 wherein r 4 is hydrogen or methyl , p is 2 and q is an integer within the range of 1 - 10 ; — c ( o ) or 1 ; — c ( o ) nr 2 r 3 ; — s ( o ) or 1 ; — s ( o ) 2 or 1 ; — s ( o ) nr 2 r 3 ; — s ( o ) 2 nr 2 r 3 ; or c is a protected functional group selected from — oc ( o ) r 1 ; — nr 2 c ( o ) r 1 ; — or 5 ; — osi ( r 1 ) 3 ; and a group of the general formula ( 6 ) and tautomers thereof which is shown above , wherein r 6 represents a protected — oh or nh 2 group , wherein the protected — oh group is selected from the groups defined for — xr 5 wherein x is o and wherein the protected — nh 2 group is selected from the groups defined for — nr 2 c ( x ) r 1 ; wherein r 5 is a monofunctional hydroxy or thiohydroxy protecting group ; and wherein n is 1 . according to the present invention , it is preferred that c is in the ω - position of the alkenyl and alkynyl groups . consequently , it is therefore preferred that the functionalized alkene is a ω - c - 1 - alkene and that the functionalized alkyne is a ω - c - 1 - alkyne , the ω - position being dependent on the number of carbon atoms of the alkene or alkyne , respectively . according to a most particular preferred embodiment of the present invention , the alkenyl groups p and the alkynyl groups q comprise at least one internal ethynylene moiety . that is , that p and q are in particular a linear group having 6 to 24 carbon atoms according to the formula : wherein p is in the range of 1 to 7 and q is in the range of 1 to 7 , the groups —( ch 2 )— and —( c ≡ c )— optionally occurring in a random sequence , and wherein the right terminus of p and q are bonded to c . preferably , the linear groups p and q have the formula wherein p is 1 to 9 , preferably 7 , r is 1 to 9 and q is 1 or 2 . the etching agent is preferably selected from hf , nh 4 f / hf or h 3 po 4 . when nh 4 / hf is used , the ratio of nh 4 f to hf is preferably 1 : 1 to 20 : 1 , most preferably 5 : 1 to 15 : 1 . most preferably , however , the etching agent is hf . according to the invention , the etching step is performed for at least about 0 . 01 h . to about 100 h . the etching agent is usually used as a solution in water , said solution comprising about 0 . 1 to about 10 . 0 wt . %, preferably about 1 . 0 to 3 . 0 wt . % of the etching agent , based on the total weight of the solution . the etching step can be performed as is well known in the art . in step ( b ) mixtures of ω - functionalized alkenes or mixtures of o - functionalized alkynes may be used . step ( b ) may furthermore be performed in an inert organic solvent and elevated temperature , e . g . at reflux , or using microwave irradiation . the inert organic solvent is preferably a hydrocarbon such as mesitylene . however , according to the invention step ( b ) may be performed without solvent , i . e . that the etched si / ge surface is reacted with neat functionalized alkene according to the general formula ( 4 ) or neat functionalized alkyne according to the general formula ( 5 ). an important advantage of the functionalized si / ge surfaces is their versatility , i . e . that they can provided with hydrophobic or hydrophilic properties depending on the nature of the functional groups b , which in addition can be converted into other groups as will be apparent to those skilled in the art . for example , the functional groups b may me made ionic , e . g . by converting amino groups into cationic ammonium groups or by converting carboxyl groups into anionic carboxylate groups . the present invention further relates to the use of the functionalized si / ge surfaces in the preparation of si / ge surfaces bearing pendant groups , wherein the pendant groups are derived from biologically active groups or host molecules . as discussed in u . s . pat . no . 6 , 569 , 979 , incorporated by reference herein , the biologically active groups may be proteins , dna or rna molecules or fragments or derivatives thereof , e . g . single stranded oligonucleotides that have for example been used in gene sequencing , drug research , medical diagnostics and binding studies of ligands to oligonucleotides . additionally , the host molecules may be selected from calixarenes , dendrimers or fragments and derivatives thereof and mono - oligo - and polysaccharides . the present invention also relates to si / ge surfaces bearing pendant groups , wherein alkyl or alkenyl moieties as defined above are covalently bonded to the si / ge surface , wherein the alkyl or alkenyl moieties bear a pendant group , preferably in their co - position , that are derived from biologically active groups or host molecules . as will be apparent to those skilled in the art , such si / ge surfaces bearing pendant groups can be prepared from the functionalized si / ge surfaces as disclosed herein , wherein the functional groups b provide a linking means for bonding the biologically active groups or host molecules . for example , b may be an — oh group that by way of an esterification can be bonded to a host molecule bearing a carboxylic group . obviously , if b is a protected functional group such as a — osime 3 group , b must first be deprotected prior to the addition of the host molecule bearing a carboxylic group . it will be apparent to the person skilled in synthetic organic chemistry how to conduct the syntheses of such si / ge surfaces bearing pendant groups . the present invention therefore also relates to a process for the preparation of si / ge surfaces bearing pendant groups , wherein a functionalized si / ge surface is attached to a pendant group , wherein the pendant groups are derived from biologically active groups or host molecules . low - stress silicon - enriched silicon nitride surfaces ( 1 cm 2 , 200 nm thickness ) were deposited on polished silicon wafers using low - pressure chemical vapor deposition . the higher than stoichiometric si / n ratio may direct the chemistry of silicon nitrides towards the chemistry of silicon , e . g . h - termination by treatment with hf solutions and monolayer attachment . xps measurements show the presence of si , c , n and o in solvent - cleaned but un - etched silicon nitrides ( see examples ); the presence of c in the unmodified sample is attributed to environmental contamination . prolonged exposure to hf leaves the nitride layer largely intact : almost complete removal of oxygen is observed , while there are no significant changes in the n signal ( xps data ; see fig1 : n1s and o1s xps spectra of si 3 n x before ( a ) and after ( b ) etching in 2 . 5 % hf for 2 min .). in addition , x - ray reflectivity measurements indicate no observable change in the silicon nitride layer thickness upon etching . the static water contact angle θ was found to increase from ˜ 20 ° to ˜ 60 ° after 2 min etching with 2 . 5 % hf solution , indicating the formation of the less polar si — h bonds . the presence of n ( partially as nh and nh 2 sites at the surface ) makes θ for the h - terminated silicon nitride surface lower than that obtained for h - terminated si surfaces . 8 the residual amount of oxygen that is observed after etching is at least partially due to deeply embedded atoms that cannot be removed upon etching , but which are therefore not expected to be reactive at the surface ( a small fraction of surface re - oxidation can probably also not be fully excluded at this stage ). 3 the effect of the reaction time on the quality of 1 - hexadecene monolayers on silicon nitride surfaces , as studied by measuring θ , is shown in fig2 ( variation of the static water contact angle θ of a 1 - hexadecene - derived monolayer on silicon nitride as a function of reaction time ). stable and almost densely packed monolayers are obtained after ˜ 24 h reaction time ( θ ˜ 107 °). this is much better than obtained without hf etching ( θ ˜ 83 °), 11 which is attributed to the formation of reactive si — h bonds at the surface upon hf etching . support for monolayer formation also comes from xps c1s spectra that show a clear increase in the amount of carbon upon modification after different time intervals ( fig3 : xps c1s spectra of si 3 n , before ( reference spectrum ), and after monolayer attachment of 1 - hexadecene , for 2 and 8 h , respectively ). the c1s signals due to the alkyl chain are not resolved from si — c bond formation ( 284 . 9 and 283 . 1 ev , respectively ). 14 the shoulder at 286 . 9 ev that appears only for modified si 3 n x is likely due to n — c bond formation . 14 no precise indication of the ratio of n — c and si — c bond formation can be given at this stage , but without wishing to be bound by any theory , the inventors believe that both these data strongly support covalent monolayer attachment . increase of the 1 - alkene concentration to neat reaction mixtures yields a rise of θ by 1 - 2 ° to ˜ 106 - 108 ° ( example 3 ), which points to the formation of an almost densely packed hydrophobic monolayer . this packing is no indication for high ordering in this case , as shown by infrared reflection absorption spectroscopy ( irras , 1 cm − 1 resolution ). irras yields peaks corresponding to anti - symmetric and symmetric ch 2 vibrations at 2923 and 2855 cm − 1 , respectively ( see fig4 ). these irras spectra strongly support the presence of a well - defined monolayer . in addition , they also point to a significant degree of disorder in these monolayers , as the peak at 2923 cm − 1 is intermediate between that obtained for ch 2 in isotropic media ( 2928 cm − 1 ) and that obtained in crystalline media ( 2919 cm − 1 ). 1 the inventors attribute this disorder partially to the surface roughness of hf - etched silicon nitride surfaces , and likely also to a slightly diminished packing density of the monolayer . finally , functionalization of these monolayers has been shown via the attachment of a trifluoroethanol - ester derived alkene ( ch 2 ═ ch —( ch 2 ) 9 cooch 2 cf 3 ; example 4 and fig4 : irras data of modified silicon nitride ( left ) ch 2 vibrations after reaction of silicon nitride with different 1 - alkenes . ( right ) c ═ o vibrations after reaction of silicon nitride with ch 2 ═ ch ( ch 2 ) 9 co 2 ch 2 cf 3 , before ( d ) and after ( e ) hydrolysis ). attachment shows in irras the appearance of a c ═ o stretching vibration at 1740 cm − 1 , characteristic for the ester functionality . hydrolysis of this moiety under basic conditions ( 0 . 25 m potassium tert - butoxide in dmso ) reduced θ from 88 ° to 44 °. this was also visible in the irras spectrum , which yields a shift of the c ═ o stretch frequency from 1740 to 1640 cm − 1 . hydrolysis of this moiety under acidic conditions ( 2 n hcl ) reduced θ from 88 ° to 32 °. this was also visible in the irras spectrum , which yields a shift of the c ═ o stretch frequency from 1740 to 1640 cm − 1 . stability of the alkyl monolayer under these circumstances was shown by a near - constant intensity of the ch 2 stretching vibrations . organic monolayers on this h - terminated si 3 n x surface were prepared by placing the wafer in refluxing solutions of 1 - alkene or 1 - alkyne ( 0 . 4 m ) in mesitylene , 8 or in neat 1 - alkene at 165 ° c . 15 1 - hexadecene ( aldrich , purity & gt ; 99 %) was purified by double vacuum distillation to achieve a purity of almost 1000 % ( gc ). all the solvents ( acros ) were first distilled at atmospheric pressure before use . silicon nitride coated silicon [ 10 × 10 × 0 . 5 mm 3 single side - polished ] wafers were supplied by aquamarijn , the netherlands , or by lionix , the netherlands . nitride thicknesses between 100 and 200 nm were used in this work . silicon nitride samples were first cleaned by rinsing several times with chemically pure acetone and wiped with a tissue . subsequently , the wafer is sonicated for 5 minutes in acetone . surfaces were further cleaned in air plasma cleaner / sterilizer ( harrick pdc - 32g ) for 3 min followed by 2 × 3 minutes in oxygen plasma . hydrogen termination is carried out by dipping the samples in 2 . 5 % hf for 2 minutes , while the flask with the hf solution and sample is placed within an ultrasonic bath . neat 1 - hexadecene or its solution in mesitylene ( 10 ml , 0 . 4 m ) is placed in a small , three - necked flask fitted with a nitrogen inlet , a condenser with a cacl 2 tube , and a stopper . the solution is then deoxygenated for at least 45 min , by refluxing it at 200 ° c ., while slowly bubbling dry nitrogen through the solution . subsequently a freshly hydrogen - terminated silicon nitride wafer is dropped into the refluxing solution by removing and replacing the stopper quickly . the reaction time varied from 2 - 24 h . finally , the solution was allowed to cool and the sample was removed and rinsed extensively with distilled pe 40 / 60 , etoh , and ch 2 cl 2 . for xps and water contact angle measurements samples of 10 × 10 mm 2 were used , for irras samples of 30 × 15 mm 2 . silicon nitride surfaces were characterized by static water contact angle measurements using an erma contact angle meter g - 1 ( volume of the drop of demineralized h 2 o = 3 . 5 μl ), and by x - ray photoelectron spectroscopy ( xps ) on a phi quantera sxm machine , with as x - ray source the al k - α 1486 . 6 ev line at 24 . 8 w , with a beam diameter of 100 . 0 μm , a 1 . 4 v 15 . 0 μa neutralizer , and the fat analyzer mode . the binding energies were calibrated with respect to si 2p corresponding to si 3 n 4 ( 101 . 80 ev ). the total surface xps spectrum of the original , un - etched but solvent - cleaned silicon nitride is shown in fig5 . irras spectra were measured on a bruker tensor 27 ft - ir spectrometer , using a commercial variable - angle reflection unit ( auto seagull , harrick scientific ). a harrick grid polarizer was installed in front of the detector , and was used for measuring spectra with either p - polarized ( parallel ) or s - polarized ( perpendicular ) radiation with respect to the plane of incidence at the sample surface . single channel transmittance spectra were collected using a spectral resolution of 1 or 4 cm − 1 , using 4096 scans in each measurement . the spectra shown in this paper are the result of spectral subtraction of a solvent - cleaned silicon nitride sample that was used as a background and the spectrum of the modified samples , without any further data manipulation ( no line smoothening or so ). samples were first cleaned by rinsing and sonication in acetone ( p . a .). the wafers were further cleaned for 2 × 3 min in an oxygen plasma using a plasma cleaner / sterilizer ( harrick pdc - 32g ), and used directly afterwards for the attachment of the monolayer . the wafer is placed in hot , nearly refluxing mesitylene (˜ 9 ml ), and should be fully covered by the solution . as soon as the wafer is placed into the mesitylene solution , the solution is brought to reflux within ˜ 30 s . after monolayer preparation the modified wafers are cleaned with petroleum ether ( 40 - 60 ), ethanol , and dichloromethane ( 10 × times each ). all solvents were distilled before use ; all 1 - alkenes and 1 - alkynes were doubly distilled under vacuum before use . the resulting wafers are stable under ambient conditions , i . e . no change in static water contact angle was measured for a 1 - hexadecene - derived monolayer over storage for 1 month . silicon nitride samples with 1 - hexadecyl monolayers prepared according to example 1 were examined by x - ray reflectivity measurements . fit of the x - ray reflectivity data of the modified surface indicates a monolayer thickness of 18 angstrom . silicon nitride samples with 1 - hexadecyl monolayers prepared according to example 1 were dipped in hydrochloric acid solutions , ph = 1 , for different time intervals . the static water contact angle is not affected ( for more than 1 °, the experimental error ) up to 4 hours in both cold and hot acid solutions . slight decreases in the measured contact angles are observed thereafter : the decrease in the water contact angle after 20 hours was only 5 ° ( 103 °, rather than 108 °) silicon nitride samples with 1 - hexadecyl monolayers prepared according to example 1 were immersed in 0 . 1 m aqueous sodium hydroxide solutions for different time intervals . the monolayer stability was monitored by measuring the static water contact angle and recording irras spectra of the monolayer . no significant change in the water contact angle or the quality of the irras spectra was observed up to three hours of treatment . thereafter , contact angle decreased to 90 ° after treating the monolayer for four hours . 1 - octadecyl and 1 - hexadecenyl - modified silicon nitride surfaces prepared according to the method described in example 2 were dipped in alkaline solution , ph = 11 , at 60 ° c . for different time intervals . monolayer stability was monitored by measuring static water contact angle , and further examination on the stability of the monolayer was performed by recording the irras spectra of the treated samples . the values of water contact angles of 1 - octadecyl monolayer attached to silicon nitride decreased from 108 to 104 ° after 6 hours under these conditions . however , 1 - hexadecenyl monolayers showed a much higher stability , as the water contact angle only decreased from 108 to 102 ° after 22 hours under the same conditions . silicon carbide powder ( 1 g ; 400 mesh from aldrich ) was first cleaned by rinsing several times with chemically pure acetone . subsequently , the powder is sonicated for 5 minutes in acetone . the dry powder is then cleaned in an oxygen plasma for 10 minutes to achieve complete removal of any organic impurities . hydrogen termination is obtained by dipping the samples in 2 . 5 % hf for 5 minutes . the powder is then filtered through a millipore filter , and dried by flushing with n 2 . subsequently , the powder is transferred to a deoxygenated refluxing ( 200 ° c .) solution of 1 - hexadecene in mesitylene in the previously described flask , while slowly bubbling dry nitrogen through the solution . the reaction time was set to 15 h . afterwards , the solution was allowed to cool and the sample was removed by filtration on a filter paper and rinsed extensively with distilled pe 40 / 60 , etoh , and ch 2 cl 2 . first , an irras spectrum was recorded for the cleaned sic powder as a background followed by measuring the spectrum of the modified powder . the subtraction of these spectra provides a spectrum displayer material deposited on top of the sic . the antisymmetric and symmetric ch 2 - stretching bands of the subtracted spectra are shown in fig6 . they indicate the presence of a substantial amount of ch 2 moieties , corresponding to covalent monolayer formation . monolayers of trifluoroethanol ester were prepared using 0 . 4 m ester solutions applying the same procedure described previously . silicon nitride modified with trifluoroethanol ester is hydrolyzed by treatment with either 0 . 25 m potassium tert - butoxide in dmso for 3 minutes at room temperature or aqueous 2 . 5 m hcl at 70 ° c . for 2 h . 1 . 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