Method for preparing textiles with chemisorbed graphene oxide or reduced graphene oxide

Abstract

The present invention relates to a method for preparing textiles, for example cotton-based, comprising chemisorbed graphene oxide or reduced graphene oxide covalently bonded to the surface of the textile fibres.

Description

[0001] METHOD FOR PREPARING TEXTILES WITH CHEMISORBED GRAPHENE OXIDE OR REDUCED GRAPHENE OXIDE

[0002] The present invention relates to a method for preparing textiles with chemisorbed graphene oxide or reduced graphene oxide. In particular, the present invention relates to a method for preparing textiles, for example cotton-based, comprising chemisorbed graphene oxide or reduced graphene oxide covalently bonded to the surface of textile fibres.

[0003] It is well known that the physicochemical and bacteriostatic properties of graphene can be exploited for the manufacture of latest-generation textiles, where both the electrical conductivity of the composite and its biocompatibility have fundamental importance. However, graphene as such, understood as a single atomic layer of graphite, is usually prepared in low-yield polar solvents and its use is only possible with the aid of specific surfactants.

[0004] One of the carbon materials most similar to graphene known to date is reduced graphene oxide (RGO), which is synthesised following the reduction -chemical or thermal - of graphene oxide (GO), i.e. an atomic layer of oxidised graphite. These oxygenated functional groups render GO hydrophilic and, at the same time, capable of binding weakly by means of hydrogen bonds (physisorption) to the surface of cotton fibres, which are in turn rich in hydroxyl functionalities.

[0005] Various methods for preparing cotton-based textiles with graphene nanomaterials, including RGO, for a variety of applications, such as, for example, the production of e-textiles, are known in the literature.

[0006] In particular, the known methods that regard the production of fabrics with RGO provide for physisorption between GO or RGO and the fabric, which generates interactions of weak entity, or rely on the use of polymers.

[0007] For example, in an article by Zhou et al. (1), cotton is first impregnated with GO by means of the “dyeing” and “dip-drying” manufacturing methods and, subsequently, to reduce GO to RGO, it is treated with hydrazine, which is a toxic species.

[0008] In another study (2), the GO was fixed onto the cotton by means of a polymerisation reaction induced both physically and chemically and involving triallyl-isocyanurate, an irritant species. The cotton with the adsorbed GO (RGO is not mentioned) was subsequently used as a bactericidal species, also after multiplewashes.

[0009] In another study (3) a composite of commercial multilayer graphene (graphene nanoplatelets, Directa Plus) with polyurethane (non-biodegradable polymer) was deposited on cotton in order to improve its thermal dissipation. In a further study (4), RGO obtained from the reduction of GO with ascorbic acid and sodium dithionite was instead dispersed in water in the presence of polymers such as poly(sodium 4-styrenesulfonate) and polyvinyl alcohol and subsequently deposited on cotton yarns through a dyeing process. This textile was used, finally, as a wearable sensor and is one of the first examples of e-textiles. However, in this case, the RGO is physiosorbed onto the surface of the cotton through the formation of hydrogen bonds between the cellulose -OH groups and the residual ones present on the layers of atomic thickness of the nanomaterial.

[0010] There are also known methods in which use is made of polyurethane to produce composites with graphene (5-8). For example, there is a known method for producing e-textiles (5) in which GO, used as the starting material for graphene synthesis, is dispersed in water and some aliquots are deposited on a very fine sheet of polyurethane on paper. Subsequently, a physical reduction of GO is carried out using a laser with the formation of graphene engraved on the surface. Finally, the device is fixed onto a part of the textile by exerting pressure at a high temperature. Also known in the field of e-textiles is a graphene-based ink prepared by means of a microfluidic technique, used for screen-printing production of e-textiles for recording brain activity (9). Moreover, there is also a published study similarly based on the screen-printing technique, but using GO, electrochemically reduced to RGO in situ (10).

[0011] Finally, there is further known literature on the preparation of textiles (cotton, silk, jute) with graphene (11-24), and textiles with graphene already exist on the market.

[0012] However, the main disadvantage to be found in fabrics with graphene obtained with the known methods lies in the non-covalent anchorage of the materials based on graphene, such as GO and RGO, to the fabric. Though physisorption of GO and RGO onto cotton is possible because of Van der Waals interactions and hydrogen bonds, with use, and in particular with washes in water and perspiration, there is a loss of material (1,2,7,11). This can lead to the dispersion of the graphene-based material into the environment and, in the specific case ofwater by immersion of the fibres with GO in an aqueous solution of a chemical reducing agent, preferably a biocompatible, low-cost one, followed by cycles of washing in water (preferably ultrapure) and optional final air drying. Therefore, the immersion of GO-rich fibres in an aqueous solution of a reducing agent gives rise to formation of RGO.

[0013] Thus, the method according to the present invention advantageously solves the problem of the weak bonds present between the GO or the RGO and the fabric.

[0014] Furthermore, according to some embodiments, the method of the invention provides for the use of nontoxic reducing agents, unlike the known methods.

[0015] Furthermore, the method of the invention does not provide for the use of RGO as such for impregnating the fibre surfaces by physisorption, but it rather provides for the synthesis thereof in situ from GO previously chemisorbed onto the fabric.

[0016] Through the method of the invention, in fact, both the GO and, following reduction, the RGO, are covalently bonded to the surface of the textile fibres and remain thereupon even after a number of washes in water. Furthermore, the fibres are hydrophilic in the presence of GO and become more hydrophobic after the formation in situ of RGO. Additionally, in the presence of the latter, there is a decrease in the electrical resistivity of the textile composite.

[0017] The process according to the invention, moreover, enables an even distribution of the nanomaterial (GO) prior to the reduction.

[0018] As regards the use of the mordant, this leads to chemisorption and advantageously enables the composite material to be reused even following washes in water and surfactants and, furthermore, it entails a limited release of the graphene-based nanomaterials into the environment and in contact with biological surfaces (skin, burns, surgical wounds).

[0019] As far as the properties of the composites obtained with the method of the invention are concerned, as shown further below the textile with chemisorbed RGO shows the highest electrical conductivity and greatest tenacity of the fibres, compared to cotton with GO and cotton as such, in addition to a marked bacteriostatic activity against the strain E. coli. Furthermore, it was observed that the biocompatibility of the cotton gauze used in the example shown further below does not change following the chemisorption both of GO and the reduced species thereof, RGO.

[0020] The textiles with GO and RGO prepared according to the process of thepresent invention, and in particular cotton textiles (e.g. wadding and gauzes, as well as articles of clothing), can advantageously have the following consequences in terms of application:

[0021] I. medical fabrics, such as, for example, wadding or gauzes with RGO, to be used during surgical interventions and for dressings, exploiting the bacteriostatic properties of RGO; in this case, the release of graphene into biological tissues would be limited thanks to the chemisorption of the graphene onto the textile;

[0022] II. face masks (surgical and non-surqical): the amount of RGO - bacteriostatic species - capable of reaching the airways through breathing would be limited thanks to the chemisorption thereof onto the textile; furthermore, the two-dimensionality of the graphene and the arrangement of layers on the surface of the textile, appropriately woven, could also be exploited for the filtration of PM10 and PM2.5 particulate matter;

[0023] III. textile filtration: production of filters using cotton with RGO (hydrophobic species) for the abatement of organic pollutants such as VOCs (volatile organic compounds) and polycyclic aromatic hydrocarbons (PAHs) with a low molecular weight; cotton with GO (hydrophilic species) could be used for the abatement of metal ions; items II and III can be correlated, since it is possible to manufacture masks with RGO capable of filtering atmospheric particulate matter and the organic molecules specified above;

[0024] IV. e-textiles (for example miniaturised fabrics or wearable garments): by exploiting the high electrical conductivity of RGO, which can be increased according to the type of reducing agent used, it is possible to manufacture cotton-based systems that may be used to monitor vital parameters;

[0025] V. Flame retardants;

[0026] VI. Composites: production of cotton yarn with improved tenacity.

[0027] Therefore, a specific object of the present invention is a method for preparing a textile fibre or fabric comprising graphene oxide (GO) or reduced graphene oxide (RGO) covalently bonded to said fibre, said method comprising or consisting of the following steps:

[0028] a) placing a textile fibre or fabric comprising cellulose in contact with an aqueous dispersion of graphene oxide (GO) in order to obtain a textile fibre into which said aqueous dispersion is absorbed or onto which said aqueous dispersionis adsorbed;

[0029] b) placing the fibre obtained in step a) in contact with a mordant capable of being coordinated by the OH groups of said cellulose and by the OH groups of said GO, so as to obtain dative covalent bonds between said cellulose and said GO; and optionally

[0030] c) placing the textile fibre obtained in step b) in contact with a reducing agent, preferably a reducing agent selective for the GO epoxy groups, to obtain the reduction of the GO, covalently bonded to the fibre, to RGO and, therefore, to obtain RGO covalently bonded to said fibre.

[0031] Preferably, said textile fibre is a cellulose-based natural fibre, such as, for example, cotton, jute or linen, preferably cotton.

[0032] According to the present invention, the textile fibre can consist partially or wholly of cellulose, which is rich in OH groups. For example, said textile fibre can comprise at least 5% or at least 10% cellulose relative to its total composition.

[0033] According to one embodiment of the present invention, said textile fibre or fabric is medical cotton, for example in the form of wadding (e.g. cotton balls) or gauzes (preferably sterile and with 100% purity).

[0034] According to the method of the present invention, said mordant can be a polyvalent metal ion.

[0035] In particular, said polyvalent metal ion can be selected from Al3+(trivalent aluminium), Ca2+(bivalent calcium), Co2+(bivalent cobalt), Cr2+(bivalent chromium), Cr3+(trivalent chromium), Fe2+(bivalent iron), Fe3+(trivalent iron), Y3+(trivalent yttrium), La3+(trivalent lanthanum), Mg2+(bivalent magnesium), Mn2+(bivalent manganese), Nd3+(trivalent neodymium), Ni2+(bivalent nickel), Pb2+(bivalent lead), Sn2+(bivalent tin), Ti4+(tetravalent titanium), W6* (hexavalent tungsten), Zn2+(bivalent zinc), and Zr4* (tetravalent zirconium).

[0036] According to the present invention, when said mordant is a polyvalent metal ion, the latter is added in step b) in the form of a compound consisting of the polyvalent metal ion and an anion. For example, said compound can be a salt, a hydroxide, an oxide or an oxychloride. More particularly, said polyvalent metal ion of said compound can be selected from Al3+(trivalent aluminium), Ca2+(bivalent calcium), Co2+(bivalent cobalt), Cr2+(bivalent chromium), Cr3+(trivalent chromium), Fe2+(bivalent iron), Fe3+(trivalent iron), Y3+(trivalent yttrium), La3+(trivalent lanthanum), Mg2+(bivalent magnesium), Mn2+(bivalent manganese), Nd3+(trivalentneodymium), Ni2+(bivalent nickel), Pb2+(bivalent lead), Sn2+(bivalent tin), Ti4+(tetravalent titanium), W6* (hexavalent tungsten), Zn2+(bivalent zinc), and Zr4+(tetravalent zirconium) and said anion of said compound can be selected from chloride, sulphate, nitrate, fluoride, acetate, formate, citrate, lactate, alum, glycinate, hydroxide, carbonate, malate, oxide, oxychloride, fluoroborate, perchlorate, and lysinate.

[0037] Therefore, according to the present invention, the compound from which the mordant is released can be each of the compounds obtained by combining each of the metal ions listed above with each of the anions listed above.

[0038] Said mordant can, for example, be released from a compound selected from aluminium salts, chromium salts, tungsten salts, copper salts, tin salts, iron salts, and calcium salts, preferably aluminium salts.

[0039] In particular, an Al3+ion is bonded by means of dative covalent bonds to both the hydroxyl oxygen atoms of cellulose and those of GO (a species very rich in OH groups). The final result is the colouring, precisely, of the cellulose-based fibre. Chromium, tungsten, copper, tin, iron and calcium cations behave similarly to aluminium ions. According to the invention, the latter is preferable, as it is less toxic (especially compared to chromium, tungsten, and tin) and more efficient than divalent copper and calcium ions. Furthermore, both aluminium chloride and aluminium lactate are white in colour and do not alter the colouring of the fibre.

[0040] According to the present invention, said aluminium salts can be selected from aluminium lactate and aluminium chloride, preferably aluminium lactate.

[0041] Table 1 shows a list exemplifying possible compounds comprising the mordant - some of which can be both hydrated and anhydrous - and which can be used in the method of the present invention:

[0042] Table 1

[0043] Compound Formula

[0044] Potassium alum KAI(SO4)2 12H2O

[0045] Ammonium alum NH4AI(SO4)2 12H2O

[0046] Jurbanite AISO4(OH)-5H2O

[0047] Aluminium chloride AICI3

[0048] Aluminium nitrate AI(NO3)3

[0049]

[0050] Aluminium perchlorate AI(CIO4)3Aluminium sulphate Al2(SO4)3

[0051] Aluminium fluoride AIF3

[0052] Aluminium acetate AI(CH3CO2)3 Aluminium glycinate AIC2H6NO4 Aluminium citrate AICeHsO?

[0053] Aluminium alginate - Aluminium lactate AI(C3H5O3)3

[0054] Calcium chloride CaCI2

[0055] Calcium sulphate CaSO4

[0056] Calcium hydroxide Ca(OH)2

[0057] Calcium acetate Ca(CH3CO2)2

[0058] Calcium formate Ca(HCOO)2

[0059] Calcium citrate [Ca3(H5C6O7)2(H2O)2] 2H2O Calcium lysinate Ca(CeHi3N2O2)2- XH2O Calcium glycinate Ca(C2H4NO2)2xH2O Calcium lactate Ca(C6Hio06)-5H20 Cobalt sulphate CoSO4(H2O) xH2O Cobalt chloride C0CI2

[0060] Cobalt nitrate Co(NO3)2xH2O Cobalt fluoride C0F2

[0061] Cobalt acetate Co(CH3CO2)2’4H2O Cobalt formate Co(HCO2)2

[0062] Cobalt citrate CO3(C6H5O7)2' XH2O Cobalt lactate Co(C3HsO3)2

[0063] Cobalt glycinate CO(H2NCH2CO2)3 Cobalt carbonate CoCCh-nH2O Chromium alum KCr(SO4)212H2O Chromium chloride CrCI3

[0064] Chromium nitrate Cr(NO)3

[0065] Chromium acetate Cr(CH3CO2)4(H2O)2 Chromium formate Cr(HCOO)3Chromium citrate Cr(H5C6O7) Chromium lactate Cr(C3H5O3)3-3H2O Potassium dichromate K2Cr2O7

[0066] Ferrous sulphate FeSO4

[0067] Ferric chloride FeCh

[0068] Ammonium ferric citrate [NH4]{y}[Fe{x}(C6H4O7)] Ammonium ferric alum NH4Fe(SO4)2-12H2O Ferrous chloride FeCI2

[0069] Ferric sulphate Fe2(SO4)3

[0070] Ferrous fluoride FeF24H2O

[0071] Ferric fluoride

[0072]

[0073] FeFs 3H2OFerric nitrate Fe(NO3)3 (H2O)n Ferrous nitrate Fe(NOs)2-6H2O

[0074] Ferrous acetate Fe(CH3CO2)2(H2O)n Ferric formate Fe(CHO2)3

[0075] Ferric glycinate Fe(H2NCH2COO)3xH2O Ferrous glycinate Fe(H2NCH2COO)22H2O Ferrous lactate Fe(CH3CH(OH)CO2)2(H2O)2Ferrous perchlorate Fe(CIO4)2 xH2O

[0076] Ferric perchlorate Fe(CIO4)3-xH2O Ferrous carbonate FeCOs

[0077] Yttrium chloride YCI3

[0078] Yttrium sulphate Y2(SO4)3

[0079] Yttrium nitrate Y(NO3)3

[0080] Lanthanum chloride LaCb

[0081] Lanthanum sulphate La2(SO4)3 xH2O Lanthanum nitrate La(NO3)3XH2O Lanthanum acetate La(CH3CO2)3 Magnesium sulphate MgSO47H2O Magnesium chloride MgCl2 xH2O Magnesium nitrate Mg(NO3)2(H2O)x Magnesium acetate Mg(C2H3O2)2 Magnesium formate Mg(C2H2O4) Magnesium citrate Mg(H2C6H5O7)2Magnesium lactate Mg(CH3CH(OH)CO2)2Magnesium lysinate Mg(CeHi3N2O2)2xH2O Magnesium glycinate Mg(C2H4NO2)2XH2O Manganese sulphate MnS04

[0082] Nickel sulphate NiSO46H2O

[0083] Nickel chloride NiCI2

[0084] Nickel nitrate Ni(NO3)2

[0085] Nickel fluoride NiF2

[0086] Nickel acetate Ni(CH3CO2)2 xH2O Nickel formate Ni(HCOO)2

[0087] Nickel citrate Ni3(C6H5O7)2XH2O Lead acetate Pb(C2H3O2)2-3H2O Lead acetate, basic Pb(CH3COO)2Pb(OH)2Lead fluoride PbF2

[0088] Lead nitrate Pb(NO3)2

[0089] Lead chloride PbCI2

[0090] Lead lactate Pb(C3H4O6)2

[0091] Lead formate Pb(CHO2)2

[0092] Lead tetraacetate

[0093]

[0094] Pb(C2H3O2)4Copper sulphate CuSO4

[0095] Copper chloride CuCI2

[0096] Copper nitrate CU(NO3)2XH2O

[0097] Copper glycinate CU(C2H4NO2)2 XH2O

[0098] Copper acetate CU(CH3CO2)2 XH2O

[0099] Copper lysinate Cu(CeHi3N2O2)2 XH2O

[0100] Stannous chloride SnCI2

[0101] Tin sulphate SnSO4

[0102] Stannic chloride SnCk

[0103] Titanyl sulphate TiOSO4

[0104] Zinc tetrafluoroborate Zn(BF4)2 xH2O

[0105] Zinc glycinate Zn(C2H4O2N)2 H2O

[0106] Zinc perchlorate Zn(CIO4)2

[0107] Zinc chloride ZnCI2

[0108] Zirconium oxychloride ZrOCI2-8H2O

[0109] Zirconium sulphate

[0110]

[0111] Zr(SO4)2(H2O)n

[0112] Preferably, the compound comprising the mordant, e.g. a salt, a hydroxide, an oxide or an oxychloride, is a water-soluble or fairly water-soluble compound. More preferably, the compound comprising the mordant is a compound having a solubility greater than or equal to 1 g / L.

[0113] According to the method of the present invention, said reducing agent can be selected from ascorbic acid or salts thereof, such as, for example, sodium ascorbate; hydrazine; sodium dithionite; hydroiodic acid or a salt thereof; and sodium borohydride; preferably ascorbic acid or salts thereof, more preferably sodium ascorbate.

[0114] According to the present invention, when the GO needs to be reduced to RGO, use is preferably made of ascorbic acid or salts thereof, e.g. sodium ascorbate, since ascorbic acid, despite being known as a weak reducing agent, is capable of efficiently reducing GO to RGO and, compared to other reducing agents, does not have toxic, corrosive or polluting effects, is not flammable and does not spoil the fibre.

[0115] According to one embodiment of the method of the invention, said step a) is carried out by immersing said textile fibre in said dispersion. In particular, said step a) is preferably carried out by immersing the textile fibre in said dispersion and, subsequently, said step b) is carried out by adding said mordant to the dispersion comprising the textile fibre.According to the present invention, in said step a), the textile fibre can be left in contact with said aqueous dispersion of GO for a time ranging from 30 minutes to 96 hours, preferably from 12 hours to 36 hours, more preferably for about 24 hours. In particular, preferably said textile fibre is immersed in said dispersion, and the mixture is left under stirring for the times specified above.

[0116] Moreover, according to the present invention, said method can further comprise a step d), following said step b) and / or said step c), of washing said textile fibre with water and drying it.

[0117] According to the present invention, in said step b), the textile fibre obtained in step a) can be left in contact with said mordant for a time ranging from 30 minutes to 96 hours, preferably from 12 hours to 36 hours, more preferably for about 24 hours and preferably under stirring.

[0118] Furthermore, according to the present invention, in said step c) the textile fibre can be left in contact with said reducing agent for a time ranging from 30 minutes to 144 hours, preferably from 24 hours to 96 hours, more preferably for about 72 hours, preferably under stirring.

[0119] According to the invention, the aqueous dispersion of GO used in said step a) can be prepared by dispersing the GO in water and applying sonication.

[0120] In particular, according to the present invention, the concentration of GO present in the dispersion may range from 0.1 g / L to 3.0 g / L, preferably from 0.3 g / L to 1 g / L, for example from 0.33 to 1 g / L, for example 0.64 g / L, more preferably 0.7 g / L.

[0121] According to the present invention, the concentration of mordant may range from 3 mM to 100 mM, preferably from 10 mM to 31 mM, e.g. from 10.2 to 30.6 mM, for example 20.4 mM, more preferably 21 mM.

[0122] Furthermore, according to the invention, the concentration of reducing agent may range from 4 mM to 119 mM, e.g. from 3.9 to 119 mM, preferably from 12 mM to 35 mM, e.g. from 11.6 to 34.8 mM, for example 23.2 mM, more preferably 24 mM.

[0123] The method according to the present invention can be carried out a temperature ranging from 10 °C to 100 °C for each of the steps, preferably from 20 °C to 40 °C, more preferably at room temperature.

[0124] The present invention also relates to a textile fibre obtainable with the abovedescribed process.

[0125] A further object of the present invention is a textile fibre, or fabric, comprisingcellulose, said fibre being characterised in that it comprises graphene oxide (GO) or reduced graphene oxide (RGO) chemisorbed onto said fibre or fabric, wherein said GO or said RGO is covalently bonded to said fibre or fabric by means of dative covalent bonds between the OH groups of said cellulose and the OH groups of said GO or RGO.

[0126] According to the present invention, said textile fibre can be characterised by an electrical resistivity ranging from 108to 1014Q cm. In particular, said textile fibre can have an electrical resistivity ranging from 1014to 1013Q cm, for example 1.4x10130-cm, when said fibre comprises chemisorbed GO, or it can have an electrical resistivity ranging from 109to 108Q cm, for example 4.0x108Q-cm, when said fibre comprises chemisorbed RGO.

[0127] Furthermore, when said fibre comprises chemisorbed RGO, said fibre can be characterised by a tenacity ranging from 2.4 to 4.7 N mm, for example said fibre can be characterised by an average tenacity of 3.3 N mm.

[0128] Preferably, the fibre of the invention is biocompatible. Furthermore, the fibre of the invention is preferably characterised by a bacteriostatic action, in particular against the strain E. coli. Therefore, the fibre of the present invention can be advantageously used in the medical field.

[0129] The present invention also concerns the use of a textile fibre or fabric as defined above for the preparation of clothing fabrics, medical fabrics, face masks or flame retardants.

[0130] Furthermore, the fibre according to the present invention can be used for textile filtration.

[0131] In particular, the present invention relates to the use of a textile fibre comprising chemisorbed RGO as defined above for the abatement of particulate matter and / or organic pollutants, such as VOCs (volatile organic compounds) and / or polycyclic aromatic hydrocarbons (PAHs) with a low molecular weight.

[0132] Furthermore, the invention also regards the use of a textile fibre comprising chemisorbed GO as defined above for the filtration, and thus abatement, of metal ions.

[0133] In addition, the present invention also relates to the use of a textile fibre or fabric as defined above for the preparation of an e-textile (or electronic textile).

[0134] The present invention will now be described by way of non-limiting illustrationaccording to a preferred embodiment thereof, with particular reference to the examples and the figures of the appended drawings, wherein:

[0135] - Figure 1 shows a) a medical cotton gauze as such, b) with GO and c) with RGO. Both graphene nanomaterials are chemisorbed;

[0136] - Figure 2 shows the Raman spectra of the cotton gauze with RGO and GO. The D and G bands are indicative of the graphene-based materials, whilst c denotes the typical signals of cellulose. The spectra were recorded with a 20x objective, 10% laser power (A=514 nm), 10 s of acquisition time and 20 scans;

[0137] - Figure 3 shows a representation of the four-terminal apparatus for measuring the electrical resistivity of the cotton gauze with GO and RGO. For the measurements the gauzes were pressed in order to obtain pads of known area and thickness;

[0138] - Figure 4 shows the measurements of force-elongation carried out on fibres of cotton gauze as such and with the graphene;

[0139] - Figure 5 shows the incubation with cells of Escherichia coli and calculation of viability on the surfaces after different times;

[0140] - Figure 6 shows the study of the biocompatibility of the gauze as such and gauzes covered on the surface with GO and RGO.

[0141] EXAMPLE 1. Example of preparation of a cotton fibre fabric comprising chemisorbed RGO according to the present invention and characterisation thereof.

[0142] Graphene oxide (GO) was synthesised from synthetic graphite following an already well-established protocol reported in the literature (25). The experiments were conducted using 100% pure cotton in the form both of medical cotton balls and sterile gauzes, each 10 cm x 10 cm in size and weighing about 1 g. In particular, the preliminary experiments were conducted using medical cotton balls, then focusing exclusively on gauzes given the difficulty of carrying out mechanical tests on the former. The reagents, of high purity, were purchased from Merck, and the experiments were conducted in Milli-Q water with a resistivity of 18.2 MQ-cm at 25 °C. The cotton textiles with chemisorbed GO and RGO were prepared according to this protocol:

[0143] . two sterile cotton gauzes (Figure 1a) were placed inside a 100 mL roundbottom flask (class A);

[0144] . 32 mg of GO were dispersed in 50 mL of water, and a sonication cycle wascarried out for 20 minutes so as to disperse the nanomaterial completely; . the dispersion of GO was transferred into the flask containing the gauzes;

[0145] the mixture was stirred for 24 hours at room temperature;

[0146] . after this time had elapsed, 300 mg (1.02 mmol) of aluminium lactate were added to the mixture of cotton and GO and the mixture was stirred for another 24 hours at room temperature; after a few hours a colouring of the cotton fibres and the formation of milky clumps (dye lake) were observed; . after this time had elapsed, the gauzes were removed from the bath, washed abundantly with water and, finally, left to air dry in a clean environment to avoid contaminations;

[0147] . one yellow-orange gauze, called gauze@GO (figure 1b), was stored in a sterile 50 mL Falcon tube, whereas the other was put into a 100 mL beaker into which 50 mL of water and 230 mg (1.16 mmol) of sodium ascorbate were added; the mixture was left under stirring for 72 hours at room temperature. After this time had elapsed, the grey-black gauze (figure 1c) called gauze@RGO was removed from the beaker in order to be washed abundantly with water and left to air dry and, finally, stored in a sterile 50 mL Falcon tube.

[0148] Control experiments:

[0149] I. in the absence of mordant, the colouring of the gauzes is almost nil, and it disappears altogether after they are washed or left in water for a few hours;

[0150] II. the pre-mordanting (on-chrome) procedure was investigated: the cotton gauzes were first treated with the mordant and then, after abundant washing with water, immersed in a GO bath under the same experimental conditions as described above; in this case, the cotton fibres were not homogeneously coloured;

[0151] III. the chemisorption of GO and RGO was also observed in the presence of other soluble aluminium salts (in particular aluminium chloride) commonly used in the field of textile dyeing.

[0152] The presence of the carbonaceous nanomaterials on the surface of the cotton fibres was tested through micro-Raman spectroscopy measurements. In particular, the fibre samples collected were subjected to laser irradiation (Xiaser= 514 nm) and the recorded spectra (Figure 2) showed the presence of the diagnostic D and G bands of the GO, whose intensity ratio increases in the presence of RGO, in agreement with the literature (26).As previously alluded to, electrical resistivity measurements were performed on the cotton gauzes with GO and RGO using the four-terminal method represented in figure 3; in particular, the gauze with GO has an electrical resistivity of 1.4X1013O-cm, which decreases to 4.0xl08Q-cm in the presence of the more conductive RGO.

[0153] The mechanical properties of the individual cotton yams taken from the gauzes as such and treated gauzes, characterised by a comparable linear density (12±1 mg-rrr1), were determined by means of force-elongation measurements (figure 4). The measurements are all directly comparable as the initial length of the yams is equal (50 mm). Furthermore, a deformation velocity of 2 mm-mim1was used and the elastic constant was determined from the initial slope of the F (N) vs. elongation (mm) plot. Tenacity was calculated from the integral of the force (N) vs. elongation (mm) curve and the gauze@RGO yams showed to be more tenacious than the cotton as such, especially due to a significantly higher strain at break (Table 2).

[0154] The values obtained with respect to the mechanical properties analysed are shown in Table 2.

[0155] Table 2

[0156] Sample Elastic Elongation at Strain at Breakin Tenacity constant break (mm) break (%) g force (Nxmm) (N / mm) (N)

[0157] Gauze

[0158] 1.1 ±0.2 1.9±0.2 3.8±0.4 1.7±0.3 1.6 (n=6±SD)

[0159] Gauze@GO

[0160] 0.8±0.2 2.3±0.5 5±1 1.8±0.2 1.8 (n=5±SD)

[0161] Gauze@RG

[0162] 0.6±0.1 3.5±0.5 7±1 1.9±0.2 3.3 0 (n=6±SD)

[0163]

[0164] Furthermore, the bacteriostatic properties of the cotton gauzes as such and with GO and RGO were investigated. The results, shown in figure 5, demonstrate a very high bacteriostatic activity in the first 6 hours for the gauzes with RGO.

[0165] In order to assess the toxicity of the fabrics, use was made of Vero cells (SIAL, CCL-81) seeded onto a 24-well plate (Coming) with a density of 5x104cellsper well. After seeding, the cells were incubated at 37 °C and 5% CO2 for 24 hours. In the meantime, the fabrics were completely immersed in culture media inside centrifuge tubes (Falcon) at 37 °C and 5% CO2. After 24 hours, the cell culture medium was replaced with the one in which the fabrics had been immersed, and the cells were further incubated at 37 °C and 5% CC for another 24 hours. Cell viability was determined using the CellTiter-Glo® kit (Promega). For this test, a volume of CellTiter-Glo® reagent equivalent to that of the culture medium was added to each well. The plate was then shaken for 2 minutes at room temperature to assure complete cell lysis; this was followed by a further 10-minute incubation in darkness at room temperature. The luminescence was measured with the Cytation 3 Cell Imaging Multi-Mode Reader (Biotek). The results were expressed as a percentage compared to the (untreated) control cells. The data were analysed using one-way ANOVA and no significant inhibition of cell growth was detected. The conclusion that there is no significant reduction of cell viability indicates that the tested fabrics do not release toxic compounds in quantities which are harmful for Vero cells, thus confirming the biocompatibility of the materials evaluated (Figure 6).

[0166] References

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Claims

CLAIMS1) A method for preparing a textile fibre comprising graphene oxide (GO) or reduced graphene oxide (RGO) covalently bonded to said fibre, said method comprising the following steps:a) placing a textile fibre comprising cellulose in contact with an aqueous dispersion of graphene oxide (GO) in order to obtain a textile fibre into which said aqueous dispersion is absorbed or onto which said aqueous dispersion is adsorbed;b) placing the fibre obtained in step a) in contact with a mordant capable of being coordinated by the OH groups of said cellulose and by the OH groups of said GO, so as to obtain dative covalent bonds between said cellulose and said GO; and optionallyc) placing the textile fibre obtained in step b) in contact with a reducing agent, preferably a reducing agent selective for the GO epoxy groups, to obtain the reduction of the GO, covalently bonded to the fibre, to RGO.2) The method according to claim 1, wherein said textile fibre is a cellulose-based natural fibre, such as, for example, cotton, jute or linen, preferably cotton.3) The method according to any one of the preceding claims, wherein said textile fibre is medical cotton, for example in the form of wadding or gauzes.4) The method according to any one of the preceding claims, wherein said mordant is a polyvalent metal ion.5) The method according to the preceding claim, wherein said polyvalent metal ion is selected from Al3+, Ca2+, Co2+, Cr2+, Cr3+, Fe2+, Fe3+, Y3+, La3+, Mg2+, Mn2+, Nd3+, Ni2+, Pb2+, Sn2+, Ti4+, W6*, Zn2+and Zr4*6) The method according to any one of claims 4-5, wherein said polyvalent metal ion is added in step b) in the form of a compound consisting of said polyvalent metal ion and an anion, such as, for example, a salt, a hydroxide, an oxide or an oxychloride.7) The method according to the preceding claim, wherein said polyvalent metal ion is selected from Al3+, Ca2+, Co2+, Cr2+, Cr3+, Fe2+, Fe3+, Y3+, La3+, Mg2+, Mn2+, Nd3+, Ni2+, Pb2+, Sn2+, Ti4+, W6*, Zn2+and Zr4+and said anion is selected from chloride, sulphate, nitrate, fluoride, acetate, formate, citrate, lactate, alum, glycinate, hydroxide, carbonate, malate, oxide, oxychloride, fluoroborate, perchlorate, and lysinate.8) The method according to claim 6, wherein said compound is a salt selectedfrom aluminium salts, chromium salts, tungsten salts, copper salts, tin salts, iron salts, and calcium salts, preferably aluminium salts.9) The method according to the preceding claim, wherein said aluminium salts are selected from aluminium lactate and aluminium chloride, preferably aluminium lactate.10) The method according to any one of the preceding claims, wherein said reducing agent is selected from ascorbic acid or salts thereof, such as, for example, sodium ascorbate; hydrazine; sodium dithionite; hydroiodic acid or a salt thereof; and sodium borohydride; preferably ascorbic acid or salts thereof, more preferably sodium ascorbate.11) The method according to any one of the preceding claims, wherein said step a) is carried out by immersing said textile fibre in said dispersion.12) The method according to any one of the preceding claims, wherein in said step a) the textile fibre is left in contact with said aqueous dispersion of GO for a time ranging from 30 minutes to 96 hours, preferably from 12 hours to 36 hours, more preferably for about 24 hours.13) The method according to any one of the preceding claims, said method further comprising a step d), following said step b) and / or said step c), of washing said textile fibre with water and drying it.14) The method according to any one of the preceding claims, wherein in said step b) the textile fibre obtained in step a) is left in contact with said mordant fora time ranging from 30 minutes to 96 hours, preferably from 12 hours to 36 hours, more preferably for about 24 hours.15) The method according to any one of the preceding claims, wherein in said step c) the textile fibre is left in contact with said reducing agent for a time ranging from 30 minutes to 144 hours, preferably from 24 hours to 96 hours, more preferably for about 72 hours.16) The method according to any one of the preceding claims, wherein the aqueous dispersion of GO used in said step a) is prepared by dispersing the GO in water and applying sonication.17) The method according to any one of the preceding claims, wherein the concentration of GO present in the dispersion ranges from 0.1 g / L to 3.0 g / L, preferably from 0.3 g / L to 1 g / L, more preferably 0.7 g / L.18) The method according to any one of the preceding claims, wherein theconcentration of mordant ranges from 3 mM to 100 mM, preferably from 10 mM to 31 mM, more preferably 21 mM.19) The method according to any one of the preceding claims, wherein the concentration of the reducing agent ranges from 4 mM to 119 mM, preferably from 12 mM to 35 mM, more preferably 24 mM.20) The method according to any one of the preceding claims, said method being carried out at a temperature ranging from 10 °C to 100 °C for each of the steps, preferably from 20 °C to 40 °C, more preferably at room temperature.21) A textile fibre comprising cellulose, said fibre being characterised in that it comprises graphene oxide (GO) or reduced graphene oxide (RGO) chemisorbed onto said fibre, wherein said GO or said RGO is bonded covalently to said fibre by means of dative covalent bonds between said cellulose and said GO or RGO.22) The textile fibre according to the preceding claim, said textile fibre having an electrical resistivity ranging from 1014to 10130-cm when said fibre comprises chemisorbed GO, or having an electrical resistivity ranging from 109to 108Q cm when said fibre comprises chemisorbed RGO.23) The textile fibre according to any one of claims 21-22, wherein, when said fibre comprises chemisorbed RGO, said fibre is characterised by a tenacity ranging from 2.4 a 4.7 N mm, for example 3.3 N mm.24) Use of a textile fibre as defined in any one of claims 21-23 for the preparation of clothing fabrics, medical fabrics, face masks or flame retardants.25) Uso of a textile fibre comprising chemisorbed RGO as defined in any one of claims 21-23 for the abatement of particulate matter and / or organic pollutants, such as VOCs (volatile organic compounds) and / or polycyclic aromatic hydrocarbons with a low molecular weight.26) Use of a textile fibre comprising chemisorbed GO as defined in any one of claims 21-22 for the filtration of metal ions.27) Use of a textile fibre as defined in any one of claims 21-23 for the preparation of an e-textile.

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