Method for functionalizing carbon nano-objects, composition comprising functionalized carbon nano-objects suspended in an organic solvent and uses thereof

Abstract

The invention relates to a method allowing functionalization of carbon nano-objects and in particular carbon nanotubes and graphene nanosheets, a composition comprising nano-objects functionalized by this method, suspended in an organic solvent, as well as to the uses of this composition. Suitable applications include elaboration of composite materials and, in particular, of nano-composite materials, materials intended for photovoltaics, detection devices of the detector/sensor or biodetector/biosensor type, photocatalysis systems, targeted vectorization systems for compounds of therapeutic or diagnostic interest or further contrast agents for medical imaging.

Claims

1. A method for functionalizing carbon nano-objects by forming at least one layer of a crosslinked polymer around the nano-objects, comprising: a) dispersing the nano-objects in an aqueous solution of a surfactant to form a suspension in which each nano-object is surrounded with surfactant molecules, each surfactant molecule having a hydrophobic portion oriented towards the nano-object and a hydrophilic portion in contact with the water of the suspension; b) mixing the suspension formed in a) with a solution comprising at least one organic or organo-inorganic monomer in an organic solvent non-miscible with water, the monomer having a dichloromethane/deionized water partition coefficient at least equal to 5 at a temperature of 25 C. and comprising at least three polymerizable chemical groups, the mixing comprising stirring to bring the solution of the monomer to an interface between the nano-objects and the surfactant molecules surrounding the nano-objects; c) removing the organic solvent from the mixture obtained in b); d) polymerizing and crosslinking the monomer at the interface between the nano-objects and the surfactant molecules surrounding the nano-objects, to form a crosslinked polymer layer around the nano-objects, the crosslinked polymer layer being surrounded by surfactant molecules; e) removing the surfactant molecules which surround the crosslinked polymer layer; and f) recovering the thereby functionalized nano-objects.

2. The method of claim 1, wherein the nano-objects are carbon nanotubes or graphene nanosheets.

3. The method of claim 1, wherein the crosslinked polymer is a homopolymer or a copolymer.

4. The method of claim 1, wherein the monomer is selected from: compounds comprising a chromophore; complexes of a transition metal, wherein the metal is coordinated to a plurality of molecules of one or more organic ligands; complexes of a rare earth, wherein the rare earth is coordinated to a plurality of molecules of one or more organic ligands; and inorganic nanoparticles stabilized by an organic ligand.

5. The method of claim 4, wherein the monomer is selected from compounds comprising an azobenzene, anthraquinone, indigotin, triarylmethane, acridine, xanthene, -carotene, quinoline, chlorin, porphyrin, phthalocyanin, naphthalocyanin, fluorescein, rhodamine, bore-dipyromethene, coumarin or cyanin group.

6. The method of claim 4, wherein the polymerizable chemical groups are thiol, selenol, real alkyne, cyclooctyne, azide, maleimide, diene, dienophilic and/or haloacetyl groups.

7. The method of claim 1, wherein the polymerizable chemical groups are thiol or selenol groups.

8. The method of claim 1, wherein the monomer includes at least four polymerisable chemical groups.

9. The method of claim 1, wherein the monomer comprises at least three spacer groups and the polymerizable chemical groups are located at an end of the spacer groups.

10. The method of claim 1, wherein the stirring in b) comprises a sonication.

11. The method of claim 1, wherein the sonication in c) further comprises a heating of the mixture.

12. The method of claim 11, wherein the mixture is brought to a temperature ranging from 40 C. to 50 C.

13. The method of claim 7, wherein the monomer includes thiol or selenol groups protected with an acetyl group, and d) comprises a deprotection of the thiol or selenol groups, the deprotection comprising a treatment of the nano-objects obtained in c): with a deacetylation agent used in excess relatively to the thiol or selenol groups, and then with a base used in excess relatively to the thiol or selenol groups, under an oxidizing atmosphere.

14. The method of claim 13, wherein the nano-objects are treated at room temperature.

15. The method to claim 1, wherein e) comprises a plurality of rinses of the nano-objects obtained in d) with water and then organic solvents.

16. The method of claim 1, which further comprises a dispersion of the nano-objects obtained in e) in an organic solvent.

17. The method of claim 1, wherein a) to f) are repeated at least one time.

18. The method of claim 1, wherein the polymerizable chemical groups are protected with a protective group and d) comprises a deprotection of the polymerization chemical groups.

19. A method for functionalizing carbon nano-objects by forming at least one layer of a crosslinked polymer around the nano-objects, comprising: a) dispersing the nano-objects in an aqueous solution of a surfactant to form a suspension in which each nano-object is surrounded with surfactant molecules, each surfactant molecule having a hydrophobic portion oriented towards the nano-object and a hydrophilic portion in contact with the water of the suspension; b) mixing the suspension formed in a) with a solution comprising at least one organic or organo-inorganic monomer in an organic solvent non-miscible with water, the monomer having a dichloromethane/deionized water partition coefficient at least equal to 5 at a temperature of 25 C. and comprising at least three polymerizable chemical groups, the chemical groups comprising thiol or selenol groups, and the mixing comprising stirring to bring the solution of the monomer to an interface between the nano-objects and the surfactant molecules surrounding the nano-objects; c) removing the organic solvent from the mixture obtained in b); d) polymerizing and crosslinking the monomer at the interface between the nanoobjects and the surfactant molecules surrounding the nano-objects to form a crosslinked polymer layer around the nano-objects, the crosslinked polymer layer being surrounded by surfactant molecules; e) removing the surfactant molecules which surround the crosslinked polymer layer; and f) recovering the thereby functionalized nano-objects.

Description

SHORT DESCRIPTION OF THE DRAWINGS

(1) FIG. 1, already commented on, schematically illustrates, in a transverse sectional view, a carbon nano-object with a circular cross-section, for example a carbon nanotube, after: inclusion of this nano-object into molecules of a surfactant (part A of FIG. 1); penetration of a solution comprising one or several monomer(s) into an organic solvent as far as the interface between the nano-object and the surfactant molecules (part B of FIG. 1); and after removal of the organic solvent, deprotection of the polymerizable chemical groups of the monomer(s) if these groups are protected, and polymerization/crosslinking of the monomer(s) (part C of FIG. 1).

(2) FIG. 2 illustrates a first example of a monomer which may be used in the method of the invention, which corresponds to a derivative of the free base, 5,10,15,20-tetra(4-carboxyphenyl)porphyrin, which includes four thiol groups as polymerizable chemical groups and in which each thiol group is connected to one of the carboxylic acid groups of the porphyrin via a spacer group NH(CH.sub.2).sub.2.

(3) FIG. 3 illustrates a second example of monomers which may be used in the method of the invention, which correspond to derivatives of metallated 5,10,15,20-tetra(4-carboxyphenyl)porphyrins (M representing a metal atom, for example of Zn, Cu, Co, Ni, Au, Fe, Pt, etc.), which include four thiol groups as polymerizable chemical groups and in which each thiol group is bound to one of the carboxylic acid groups of porphyrin via a spacer group NH(CH.sub.2).sub.2.

(4) FIG. 4 illustrates a reaction scheme with which it is possible to synthesize the monomer of FIG. 2, in a form in which each of its thiol groups is protected by an acetyl group, from the free base 5,10,15,20-tetra(4-carboxyphenyl)-porphyrin.

(5) FIG. 5 schematically illustrates a single-walled carbon nanotube as obtained: after penetration, as far as the interface between this nanotube and the surfactant molecules which surround it, of an organic solution comprising the monomer of FIG. 2, for which each of the thiol groups is protected with an acetyl group (part A of FIG. 5); and after deprotection of the thiol groups of this monomer, polymerization/crosslinking of said monomer and removal of the layer of surfactant molecules (part B of FIG. 5).

(6) It should be noted that on part A of FIG. 5, the surfactant molecules, although present, have voluntarily not been illustrated for reasons of legibility.

(7) FIG. 6 illustrates the UV-Visible-NIR absorption spectrum (300-1,400 nm) of single-walled carbon nanotubes of the CoMoCAT SG 65 type as illustrated in FIG. 5B, suspended in N-methyl-2-pyrrolidone.

(8) FIG. 7 corresponds to images taken with a scanning electron microscope (SEM), of single-walled carbon nanotubes, part A of this figure corresponding to carbon nanotubes as illustrated in part B of FIG. 5, and part B of FIG. 7 corresponding to carbon nanotubes not having been functionalized by the method of the invention.

(9) FIG. 8 illustrates the UV-Visible-NIR absorption spectrum (300-1,400 nm) of single-walled carbon nanotubes synthesized by laser ablation which were functionalized with a layer of an organometallic polymer from polymerization/crosslinking of a monomer as illustrated in FIG. 3, in which M represents a zinc atom, the carbon nanotubes being suspended in N-methyl-2-pyrrolidone.

(10) FIG. 9 corresponds to images, taken in a high resolution transmission electron microscope (TEM), of carbon nanotubes synthesized by laser ablation which were functionalized with a layer of a polymer from the polymerization/crosslinking of a monomer as illustrated in FIG. 3, in which M represents a platinum atom, part A and C of this figure corresponding to an observation of these nanotubes in a bright field mode or BF mode, and parts B and D corresponding to an observation of the same nanotubes in a high angle annular dark field (or HAADF mode).

(11) FIG. 10 illustrates a further example of monomer(s) which may be used in the method of the invention, which correspond to particles of a metal, of a semi-conductor, of an alloy with semi-conducting properties or of a metal oxide, stabilized with molecules of a ligand derived from hexadecanedioic acid, which includes a thiol group as a polymerizable chemical group and in which this thiol group is bound to one of the terminal carboxylic acid groups of the ligand via a spacer group NH(CH.sub.2).sub.2; part A of FIG. 10 shows the formula which the ligand fits when its thiol group is protected with an acetyl group, while part B of this figure shows the formula which the same ligand fits when its thiol group is not protected.

(12) FIG. 11 illustrates the UV-Visible-NIR absorption spectrum (300-1,400 nm) of single-walled carbon nanotubes of the CoMoCAT SG 65 type which were functionalized with two layers of different polymers, one of which is a layer of an organic polymer from the polymerization/crosslinking of the monomer of FIG. 2, while the other one is a layer of an organometallic polymer from the polymerization/crosslinking of a monomer as illustrated in FIG. 3, in which M represents a platinum atom, the carbon nanotubes being suspended in N-methyl-2-pyrrolidone.

(13) FIG. 12 illustrates a fourth example of monomers which may be used in the method of the invention, which correspond to tetracarboxylated derivatives of cyanin 3 (n=1) and of cyanin 5 (n=3), which include four thiol groups as polymerizable groups and in which each thiol group is bound to a carboxylic acid group via a spacer group NH(CH.sub.2).sub.2.

(14) FIG. 13 illustrates a reaction scheme with which the monomer as illustrated in FIG. 12 may be synthesized, in which n=1, in a form in which each of its thiol groups is protected with an acetyl group, from 5-carboxyl-2,3,3-trimethyl-3H-indolenine.

(15) FIG. 14 illustrates the UV-Visible-NIR absorption spectrum (300-1,400 nm) of single-walled carbon nanotubes which were functionalized with a layer of an organometallic polymer from the polymerization/crosslinking of two different monomers, one of which is a monomer as illustrated in FIG. 3, in which M represents a zinc atom, while the other one is a monomer derived from cyanin 3 as illustrated in FIG. 12, the carbon nanotubes being suspended in N-methyl-2-pyrrolidone with 0.1% trifluoroacitic acid.

(16) FIG. 15 illustrates the UV-Visible-NIR absorption spectrum (300-1,400 nm) of graphene nanosheets which were functionalized with a layer of an organometallic polymer from the polymerization/crosslinking of a monomer as illustrated in FIG. 3, in which M represents a zinc atom, the graphene nanosheets being suspended in N-methyl-2-pyrrolidone.

DETAILED DISCUSSION OF PARTICULAR EMBODIMENTS

(17) Introductory Remark:

(18) In the examples which follow, all the sonications were carried out by using an electronic ultrasound bath Elma, model T 490DH, with a frequency of 40 kHz and delivering at full power 130 watts with peaks ranging up to 260 watts. The sonication power may be modified with an arbitrary scale ranging from 20 to 140%. Also, in the following, mild sonication corresponds to the use of a power level ranging from 20 to 40% moderate sonication corresponds to the use of a power level ranging from 60 to 80% whilst strong sonication corresponds to the use of a power level ranging from 100 to 140%.

Example 1

Functionalization of Single-Walled Carbon Nanotubes With a Layer of an Organic Polymer

(19) In this example, single-walled CNTs are functionalized with a layer of an organic polymer which is derived from the polymerization/crosslinking of a monomer of FIG. 2, designated as monomer 1 hereafter.

(20) To do this, an aqueous suspension of CNTs is prepared on the one hand by dispersing 0.060 mg of CoMoCAT SG 65 CNTs (Sigma-Aldrich) into 4 ml of an aqueous solution of 2% by mass of sodium cholate and, a solution comprising 1 mg of the monomer 1 on the other hand, in a form in which each of its thiol groups is protected by an acetyl group (COCH.sub.3), in 600 L of dichloromethane (DCM).

(21) The monomer 1, with its protected thiol groups, was obtained beforehand from the free base 5,10,15,20-tetra(4-carboxyphenyl)porphyrin, by reacting, as shown in FIG. 4, this porphyrin with S-acetylcysteamine hydrochloride in the presence of benzotriazol-1-yl-oxy-tripyrrolidinophosphonium hexafluorophosphate (PyBOP) and of N-ethyl-N,N-diisopropylamine (DIEA) in N-methyl-2-pyrrolidone (NMP), under standard conditions. The S-acetylcysteamine hydrochloride was itself obtained beforehand by reaction between cysteamine and acetyl chloride.

(22) In order to functionalize the CNTs, the organic solution of monomer 1 is added in a reactor to the aqueous suspension of CNTs.

(23) Both phases present in the reactor are then subject to strong sonication, with a duration of 30 minutes, in order to obtain mixing of these phases and penetration of the organic solution of monomer 1 as far as the interface between the CNTs and the sodium cholate molecules which surround them.

(24) And then, mild sonication is carried out, with a duration of one hour, with heating to 40 C., in order to obtain evaporation of the DCM without disorganizing the sodium cholate molecules which surround the CNTs.

(25) An aqueous suspension of CNTs is then obtained, in which the CNTs are surrounded by a layer of monomer 1 moleculesas schematically illustrated on part A of FIG. 5, this layer of molecules being itself surrounded by sodium cholate molecules.

(26) An aqueous 17 M hydroxylamine solution (400 equivalents relatively to the monomer 1) is then added in to the reactor and the contents of the reactor are stirred for one hour, at room temperature, in order to deprotect the thiol groups of the monomer 1.

(27) And then, triethylamine (400 equivalents relatively to the monomer 1) is added to the reactor and the contents of the reactor are stirred for 14 hours, under an oxygen atmosphere, in order to allow polymerization and crosslinking of the monomer 1.

(28) After which, the contents of the reactor are filtered on a polytetrafluoroethylene (Teflon) membrane, having pores with a diameter of 0.2 m and the residue retained on this membrane is successively rinsed with large volumes of water, of methanol, of acetone, of NMP, of tetrahydrofuran (THF) and of DCM, in order to remove the unreacted molecules of the monomer 1, the excess reagents as well as the sodium cholate molecules surrounding the CNTs.

(29) And then, the residue is dispersed in the 4 mL of anhydrous NMP, with moderate sonication, for 10 minutes.

(30) A suspension of CNTs in NMP is thereby obtained, in which the CNTs are functionalized with a layer of a polymer resulting from the reaction of molecules of monomer 1 with each other and forming a shell around the CNTs, as schematically illustrated in part B of FIG. 5.

(31) The UV-Visible-NIR absorption spectrum (300-1,400 nm) of the thereby obtained functionalized CNTs suspended in NMP (after dilution of the suspension in order to avoid a saturation of the signal emitted by the recurrent units from the monomer 1), is illustrated in FIG. 6. This spectrum has a peak at 420 nm which confirms the presence of said polymer layer around the CNTs.

(32) Moreover, the pictures taken with the SEM of FIG. 7 show a difference between the aspect which the thereby functionalized CNTs (part A of FIG. 7) have and the one which they had before functionalization (part B of FIG. 7).

Example 2

Functionalization of Single-Walled Carbon Nanotubes With a Layer of an Organometallic Polymer

(33) In this example, single-walled CNTs are functionalized with a layer of an organometallic polymer, stemming from the polymerization/crosslinking of a monomer as illustrated in FIG. 3, in which M represents a platinum atom, designated as monomer 2 hereafter.

(34) In order to do this, an aqueous suspension of CNTs is prepared by dispersing 0.12 mg of single-walled CNTs synthesized by laser ablation (Doctor Oliver JostDresden UniversityGermany), with an average diameter of 1.3 nm, in 6 ml of a 9.84 ml/l sodium dodecylsulfate aqueous solution on the one hand and, a solution comprising 8 mg of the monomer 2, in a form in which each of its thiol groups is protected with an acetyl group, in 600 L of DCM on the other hand.

(35) The monomer 2, with its protected thiol groups, was synthesized beforehand from platinum 5,10,15,20-tetra(4-carboxyphenyl)porphyrin according to a reaction scheme similar to the one illustrated in FIG. 4.

(36) In order to functionalize the CNTs, the organic solution of monomer 2 is added in a reactor to the aqueous suspension of CNTs.

(37) And then, the same operating procedure is followed as the one described in Example 1 hereinbefore, with the exception that the filtration residue, once it is washed, is dissolved in 6 ml (instead of 4 ml) of anhydrous NMP.

(38) The UV-Visible-NIR absorption spectrum (300-1,400 nm) of the thereby obtained functionalized CNTs, suspended in NMP (after dilution of the suspension in order to avoid saturation of the signal emitted by the recurrent units from the monomer 2), is illustrated in FIG. 8.

(39) This spectrum has a peak at 400 nm which confirms the presence around the CNTs of a polymer resulting from the reaction of monomer 2 molecules with each other.

(40) Moreover, the pictures taken with an SEM at a high resolution of FIG. 9 show the presence at the surface of the CNTs (illustrated by the white arrow) of chains formed by recurrent units from this monomer (illustrated by black arrows).

Example 3

Functionalization of Single-Walled Carbon Nanotubes With a Layer of an Organometallic Polymer

(41) In this example, single-wall CNTs are functionalized with a layer of an organometallic polymer which is derived from the polymerization/crosslinking of a monomer as illustrated in FIG. 10, in which the particle is a particle of ferric oxide Fe.sub.3O.sub.4, designated as monomer 3 hereafter.

(42) To do this, an aqueous suspension of CNTs is prepared on the one hand by dispersing 0.08 mg of CNTs synthesized by laser ablation (Doctor Oliver JostUniversity of DresdenGermany), in 4 ml of a 9.84 mmol/l sodium dodecylsulfate (SDS) solution and a solution comprising 3.5 mg of the monomer 3 is prepared on the other hand in a form in which the thiol group of each of its ligand molecules is protected with an acetyl group, in 400 L of toluene.

(43) The monomer 3, with its protected thiol groups, was obtained beforehand from particles of ferric oxide stabilized by oleic acid molecules (Sigma-Aldrich, reference 700312) by replacing these oleic acid molecules with molecules of the ligand shown in part A of FIG. 10, by the ligand exchange method described by Lattuada and Hatton (Langmuir 2007, 23, 2158-2168, reference [3]).

(44) In order to functionalize the CNTs, the organic solution of monomer 3 is added in a reactor to the aqueous suspension of CNTs.

(45) Both phases present in the reactor are then subject to strong sonication, with a duration of 30 minutes, in order to obtain the mixing of these phases and the penetration of the organic solution of monomer 3 as far as the interface between the CNTs and the SDS molecules which surround them.

(46) Next, mild sonication is carried out with a duration of one hour with heating to 40 C., but by placing the reactor in vacuo in order to obtain evaporation of the toluene.

(47) The same operating procedure is then followed as the one described in Example 1 hereinbefore, except that the filtration residue, once it is washed, is dispersed in 4 ml of an anhydrous NMP/toluene mixture (instead of only anhydrous NMP).

Example 4

Functionalization of Single-Walled Carbon Nanotubes With Two Layers of Polymers of Different Nature

(48) In this example, single-walled CNTs, already functionalized with a first layer of a polymer from the polymerization/crosslinking of monomer 1, are functionalized with a second layer of an organometallic polymer which itself stems from the polymerization/crosslinking of a monomer 2.

(49) To do this, 1 ml of a suspension comprising 0.06 mg of functionalized CNTs are added in to a reactor, as obtained in Example 1 hereinbefore, in NMP, to 10 ml of a 2% sodium cholate aqueous solution.

(50) Next, 500 L of a solution comprising 50 g of the monomer 2 are added in a form in which each of its thiol groups is protected with an acetyl group, in DCM, so as to obtain 2 equivalents of monomer 2 relatively to the polymer already present at the surface of the CNTs.

(51) The same operating procedure is then followed as the one described in Example 1 herein before, except that the filtration residue, once it is washed, is dissolved in 2 ml (instead of 4 ml) of anhydrous NMP.

(52) The UV-Visible-NIR absorption spectrum (300-1,400 nm) of the thereby obtained doubly functionalized CNTs, suspended in NMP (after dilution of the suspension in order to avoid saturation of the signals emitted by the recurrent units from the monomers 1 and 2), is illustrated in FIG. 11.

(53) This spectrum shows the presence of two peaks: a first peak at 420 nm, noted as A, which confirms the presence around the CNTs of a first layer of a polymer resulting from polymerization/crosslinking of the monomer 1, and the second peak at 400 nm, noted as B, which confirms the presence, around the CNTs, of a second layer of a polymer resulting from the reaction of monomer 2 molecules with each other.

Example 5

Functionalization of Single-Walled Carbon Nanotubes With a Layer of an Organometallic Copolymer

(54) In this example, single-walled CNTs are functionalized with an organometallic copolymer which stems from copolymerization/crosslinking of a monomer as illustrated in FIG. 3, in which M represents a zinc atom, monomer 4 hereafter, and of a monomer derived from cyanin 3 as illustrated in FIG. 12, monomer 5 hereafter.

(55) To do this, an aqueous suspension comprising 0.20 mg of CNTs synthesized by laser ablation (Doctor Oliver JostUniversity of DresdenGermany) in 10 ml of a 9.84 mmol/l SDS aqueous solution on the one hand, and a solution comprising 5 mg of monomer 4 firstly in a form in which each of its thiol groups is protected with an acetyl group, and secondly 5.7 mg of the monomer 5, also in a form in which each of its thiol groups is protected with an acetyl group, in 600 L of DCM, on the other hand.

(56) The monomer 4, with protected thiol groups, was obtained beforehand from the monomer as illustrated in FIG. 4, by reacting this monomer with zinc diacetate (Zn(OAc).sub.2) in a medium consisting of DCM and of methanol, according to a similar procedure to the one described by Wagner et al. (J. Org. Chem. 1995, 60(16), 5266-5273, reference [4]) except that DCM was used instead of chloroform as a solvent.

(57) The monomer 5, with protective thiol groups, was obtained beforehand from 5-carboxyl-2,3,3-trimethyl-3H-indolenine, by following the reaction scheme shown in FIG. 13, 5-carboxyl-2,3,3-trimethyl-3H-indolenine, noted as A in this figure, having been itself obtained beforehand by following the procedure described by Terpetschnig et al. (Analytical Biochemistry 1994, 217, 197-204, reference [5]).

(58) In order to obtain the monomer 5, the compound A (200 mg, 1 nmol) and 3-iodopropanoic acid (1 g, 5 mmol) were introduced into a sealed tube heated to 140 C. for 4 hours. The reaction mixture contained in the compound, noted as B in FIG. 13, was cooled to 100 C. and then anhydrous pyridine (8 ml) was added. The suspension was transferred into a flask, ethyl orthoformate (40 L, 242 mol) was added and the suspension was heated with reflux. Two successive additions of ethyl orthoformate (40 L, 242 mol) separated by 2 hours are then achieved. The progression of the reaction is controlled by UV-Visible absorption with the appearance of a band at 550 nm corresponding to the compound which is noted as C in FIG. 13. The reaction is stopped when the 550 nm band stops changing.

(59) The solvent is evaporated and the crude reaction product is dissolved in ethyl acetate (125 ml) and it is washed with a 10% by mass citric acid aqueous solution (125 ml) and then with a saturated NaCl solution (125 ml). The compound C is extracted from the organic phase with a saturated NaHCO.sub.3 solution (125 ml). The phases are separated and the aqueous solution is washed with dichloromethane (125 ml) and then acidified with 1 M HCl until a pH of 2 is obtained. The suspension is extracted with ethyl acetate (200 ml), dried on anhydrous Na.sub.2SO.sub.4, filtered and evaporated. The compound C is obtained as a red solid.

(60) This compound (200 mg, 291 mol) is dissolved in anhydrous NMP, and S-acetylcysteamine hydrochloride (270 mg, 1.74 mmol), PyBOP (904 mg, 1.74 mmol) and DIEA (912 L, 5.2 mmol) are added. The reaction medium is stirred at room temperature for 3 hours and then diluted with ethyl acetate (80 ml). The solution is washed with a 10% by mass citric acid aqueous solution (80 ml) and then with a saturated NaHCO.sub.3 solution (80 ml) and then with a saturated NaCl solution (80 ml). The organic phase is dried on anhydrous Na.sub.2SO.sub.4, filtered and evaporated. The monomer 5 is thereby obtained.

(61) In order to functionalize the CNTs, the organic solution of monomers 4 and 5 is added in a reactor to the aqueous suspension of CNTs.

(62) Both phases present in the reactor are then subject to strong sonication, with a duration of 30 minutes, in order to obtain the mixing of these phases and penetration of the organic solution of monomers 4 and 5 as far as the interface between the CNTs and the SDS molecules which surround them.

(63) And then, mild sonication is carried out, with a duration of one hour, with heating to 40 C., in order to obtain the evaporation of the DCM without destabilizing the SDS molecules which surround the CNTs.

(64) A 28% ammonia aqueous solution (400 equivalents relatively to the monomers 4 and 5) is then added into the reactor and the contents of the reactor are stirred, for one hour at room temperature, for deprotecting the thiol groups of the monomers 4 and 5. The contents of the reactor are then stirred for 14 hours, under an oxygen atmosphere, in order to allow copolymerization and crosslinking of the monomers.

(65) After which, the contents of the reactor are filtered on a polytetrafluoroethylene (Teflon), membrane, having pores with a diameter of 0.2 m and the residue retained on this membrane is successfully rinsed with large amounts of water, of methanol, of acetone, of NMP, of THF and of DCM.

(66) And the residue is then dispersed in 6 ml of anhydrous NMP, with moderate sonication, for 10 minutes.

(67) The UV-Visible-NIR absorption spectrum (300-1,400 nm) of the thereby obtained functionalized CNTs suspended NMP with 0.1% of TFA (after dilution of the suspension in order to avoid saturation of the signal emitted by the recurrent units from monomers 4 and 5), is illustrated in FIG. 13.

(68) This spectrum shows the presence of two peaks, noted as A and B, respectively located at 430 nm and 570 nm, which confirms the presence around the CNTs of a copolymer resulting from a reaction of molecules of monomers 4 and 5 with each other.

Example 6

Functionalization of Graphene Nanosheets With a Layer of an Organometallic Polymer

(69) In this example, graphene nanosheets are functionalized with an organometallic polymer which stems from polymerization/crosslinking of the monomer 4.

(70) To do this, 600 L of a solution comprising 3 mg of the monomer 4, in a form in which each of its thiol groups is protected with an acetyl group in DCM, are added to 6 ml of an aqueous suspension which comprises 0.30 mg of a mixture of single-layer (27%), bilayer (48%), trilayer (20%), tetralayer and more (5%) graphene nanosheets, in a surfactant, and which is marketed by Nanointegris under the name of PureSheets Mono.

(71) The same operation procedure is then followed as the one described in Example 1 hereinbefore.

(72) The UV-Visible-NIR absorption spectrum (300-1,400 nm) of the thereby obtained functionalized graphene nanosheets, suspended in NMP, is illustrated in FIG. 14.

(73) This spectrum shows the presence of a peak at 420 nm which confirms the presence, around the graphene nanosheets, of a polymer resulting from a reaction of molecules of the monomer 4 with each other.

CITED REFERENCES

(74) [1] Patent application US 2011/0076497 [2] Sriya Das et al., ACS Applied Materials & Interfaces 2011, 3, 1844-1851 [3] Lattuada et Hatton, Langmuir 2007, 23, 2158-2168 [4] Wagner et al., J. Org. Chem. 1995, 60(16), 5266-5273 [5] Terpetschnig et al., Analytical Biochemistry 1994, 217, 197-204