Pyruvate ester type carbon dot photoinitiator, preparation therefor and use thereof

Abstract

The present invention relates to a pyruvate ester type carbon dot photoinitiator. The surface of each carbon dot has a group containing a pyruvate ester structure moiety, and the average particle size of carbon dots is 1-50 nm. As a photoinitiator, the pyruvate ester type carbon dot photoinitiator can exhibit good initiation performance in a range of 200-750 nm, especially 250-500 nm, and can effectively initiate the photopolymerization of photopolymerizable monomers, especially (meth)acrylate monomers. The present invention further relates to a method for preparing the pyruvate ester type carbon dot photoinitiator and a use thereof. The pyruvate ester type carbon dot photoinitiator is particularly suitable for UV-VIS LED light source curing. The photoinitiator of the present invention features low biotoxicity, low mobility and excellent biocompatibility, can be used in the fields of photopolymerizable materials, biomacromolecules, etc., and has a simple synthesis route, thereby offering extremely high practical value.

Description

Pyruvate-type carbon dot photoinitiator and its preparation and application Technical Field

[0001] The present invention belongs to the field of photocuring technology, and specifically relates to a pyruvate-type carbon dot photoinitiator, which is particularly suitable for UV-VIS LED light source curing. The present invention also relates to the preparation and application of the pyruvate-type carbon dot photoinitiator. Technical Background

[0002] Photoinitiators, also known as photosensitizers or photocuring agents, are substances that absorb energy of a certain wavelength to generate free radicals and cations, thereby initiating polymerization, crosslinking, and curing of monomers. In recent years, photocurable materials have developed rapidly and are widely used in traditional fields such as coatings, inks, microelectronics, and printing, as well as in emerging fields such as the preparation of laser recording and three-dimensional components. Photoinitiators are one of the most important components in photocurable materials. Although their content is low in photocurable systems, they are a key component, determining whether the formulation can rapidly crosslink and cure upon exposure to light, transforming from a liquid to a solid state.

[0003] Pyruvate photoinitiators, due to their outstanding activity and excellent photosensitivity, are becoming increasingly popular. In recent years, several patents related to pyruvate photoinitiators have been published, such as CN 117142994 A, which discloses an amphiphilic polyetherified α-keto(hetero)aryl thioester compound and its preparation, and CN 117142995 A, which discloses a pyruvic acid(hetero)aryl thioester compound and its preparation. While these photoinitiators exhibit excellent photoinitiating activity, they still have some shortcomings in terms of post-photocuring residual properties, which require further improvement. For example, during the photocuring process, residual photoinitiators of this type easily migrate to the product surface, producing a certain odor. This significantly limits the application of pyruvate photoinitiators in food packaging, medical and health care, and other fields.

[0004] In view of this, research and development of pyruvate photoinitiators with higher environmental performance remains the core work in this field, especially the development of new pyruvate photoinitiators with low biological toxicity and low mobility that are suitable for the rapidly developing species, which has gradually become the current research direction of pyruvate photoinitiators. Summary of the Invention

[0005] In view of the problems existing in the prior art, the inventors of the present invention have conducted extensive and in-depth research on pyruvate photoinitiators with higher environmental performance, in order to find a new pyruvate photoinitiator with low biological toxicity and low mobility.

[0006] The inventors surprisingly discovered that by using carbon dots as a basis and regulating the surface groups of the carbon dots, a specific pyruvate structure was introduced on the surface of the carbon dots in a post-modification manner to form a new type of pyruvate-type carbon dot photoinitiator, which can be used for UV-VIS LED light source curing. The pyruvate-type carbon dot photoinitiator of the present invention maintains the morphology of the carbon dots and has a uniform size distribution (1-50nm). It can show good initiation performance in the range of 200-750nm, especially 250-500nm, and can effectively initiate the photopolymerization reaction of photopolymerizable monomers, especially (meth)acrylate monomers. In addition, the photoinitiator of the present invention has low biological toxicity, low mobility, and excellent biocompatibility. It can be used in the fields of photopolymerizable materials and biomacromolecules, and the synthesis route is simple, thus having extremely high practical value.

[0007] The purpose of the present invention is achieved based on the above findings.

[0008] Therefore, an object of the present invention is to provide a pyruvate-type carbon dot photoinitiator, which not only has an absorption wavelength suitable for UV-VIS LED light source radiation curing, but also has low biotoxicity, low mobility, and excellent biocompatibility.

[0009] Another object of the present invention is to provide a method for preparing the pyruvate-type carbon dot photoinitiator of the present invention.

[0010] Another object of the present invention is to provide the use of the pyruvate-type carbon dot photoinitiator of the present invention as a photoinitiator or photosensitizer.

[0011] The technical solutions for achieving the above-mentioned purpose of the present invention can be summarized as follows:

[0012] 1. A pyruvate-type carbon dot photoinitiator, wherein the carbon dot surface has a group containing a pyruvate moiety, and the average particle size of the carbon dot is 1-50 nm.

[0013] 2. The pyruvate-type carbon dot photoinitiator according to item 1, wherein the average particle size of the carbon dots is 1-20 nm, preferably 1-15 nm, more preferably 1-10 nm.

[0014] 3. The pyruvate-type carbon point photoinitiator according to item 1 or 2, wherein the group containing the pyruvate structural portion has a structure as shown in the following formula (1):

[0015] in:

[0016] * indicates the connection position with the carbon dots;

[0017] R1 represents C1-C 20 Alkyl, C3-C20 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 10 Alkyl, C2-C 20 Alkenyl, C3-C 20 Cycloalkenyl, C3-C 10 Cycloalkenyl-C1-C 10 Alkyl, C6-C 20 Aryl or C6-C 10 Aryl-C1-C 10 Alkyl, wherein the aforementioned C1-C 20 Alkyl, C3-C 20 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 10 Alkyl, C2-C 20 Alkenyl, C3-C 20 Cycloalkenyl, C3-C 10 Cycloalkenyl-C1-C 10 Alkyl, C6-C 20 Aryl or C6-C 10 Aryl-C1-C 10 The alkyl group is optionally substituted by one or more groups independently selected from the group consisting of C1-C6 alkyl, C1-C6 alkylthio, C1-C6 alkoxy, halogen, nitro, amino, cyano, mono(C1-C6 alkyl)amino, di(C1-C6 alkyl)amino and mercapto, and the aforementioned C3-C6 20 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 10 Alkyl, C3-C 20 Cycloalkenyl, C3-C 10 Cycloalkenyl-C1-C 10 Alkyl, C6-C 20 Aryl or C6-C 10 Aryl-C1-C 10 The ring carbon atoms of the alkyl group are optionally replaced by one or more heteroatoms selected from N, S and O.

[0018] 4. The aceruvate-type carbon-dot photoinitiator according to item 3, wherein:

[0019] R1 represents C1-C 12 Alkyl, C3-C 12 Cycloalkyl, C3-C8 cycloalkyl-C1-C4 alkyl, C2-C 12 Alkenyl, C3-C 12 Cycloalkenyl, C3-C8 cycloalkenyl-C1-C4 alkyl, C6-C 12 Aryl or C6-C 10 Aryl-C1-C4 alkyl, wherein the aforementioned C1-C 12Alkyl, C3-C 12 Cycloalkyl, C3-C8 cycloalkyl-C1-C4 alkyl, C2-C 12 Alkenyl, C3-C 12 Cycloalkenyl, C3-C8 cycloalkenyl-C1-C4 alkyl, C6-C 12 Aryl or C6-C 10 The aryl-C1-C4 alkyl group is optionally substituted by one or more groups independently selected from the group consisting of C1-C4 alkyl, C1-C4 alkylthio, C1-C4 alkoxy, halogen, nitro, amino, cyano, mono(C1-C4 alkyl)amino, di(C1-C4 alkyl)amino and mercapto, and the aforementioned C3-C 12 Cycloalkyl, C3-C8 cycloalkyl-C1-C4 alkyl, C3-C 12 Cycloalkenyl, C3-C8 cycloalkenyl-C1-C4 alkyl, C6-C 12 Aryl or C6-C 10 The ring carbon atoms of the aryl-C1-C4alkyl group are optionally replaced by one or more heteroatoms selected from N, S and O;

[0020] Preferably, R1 represents C1-C 10 Alkyl, C3-C 10 Cycloalkyl, C3-C6 cycloalkyl-C1-C4 alkyl, C3-C 10 Cycloalkenyl, C3-C6 cycloalkenyl-C1-C4 alkyl, phenyl or naphthyl, wherein the aforementioned C1-C 10 Alkyl, C3-C 10 Cycloalkyl, C3-C6 cycloalkyl-C1-C4 alkyl, C3-C 10 Cycloalkenyl, C3-C6 cycloalkenyl-C1-C4 alkyl, phenyl or naphthyl is optionally substituted by fluorine, chlorine, bromine and C1-C4 alkyl, and the aforementioned C3-C6 10 Cycloalkyl, C3-C6 cycloalkyl-C1-C4 alkyl, C3-C 10 The ring carbon atoms of the cycloalkenyl, C3-C6 cycloalkenyl-C1-C4 alkyl, phenyl or naphthyl are optionally replaced by one or more heteroatoms selected from N, S and O.

[0021] 5. The pyruvate-type carbon point photoinitiator according to item 3 or 4, wherein R1 represents a C1-C8 alkyl group, a C3-C8 cycloalkyl group, a C3-C6 cycloalkyl-C1-C2 alkyl group, a C3-C8 cycloalkenyl group, a C3-C6 cycloalkenyl-C1-C2 alkyl group, a phenyl group or a naphthyl group, wherein the aforementioned C1-C8 alkyl group, a C3-C8 cycloalkyl group, a C3-C6 cycloalkyl-C1-C2 alkyl group, a C3-C8 cycloalkenyl group, a C3-C6 cycloalkenyl-C1-C2 alkyl group, a phenyl group or a naphthyl group is optionally substituted with a C1-C4 alkyl group, and the ring carbon atoms of the aforementioned C3-C8 cycloalkyl group, a C3-C6 cycloalkyl-C1-C2 alkyl group, a C3-C8 cycloalkenyl group, a C3-C6 cycloalkenyl-C1-C2 alkyl group, a phenyl group or a naphthyl group are optionally replaced with one or more heteroatoms selected from N, S and O.

[0022] 6. The pyruvate-type carbon dot photoinitiator according to any one of items 3 to 5, wherein R1 represents methyl, ethyl, n-propyl, 1-methylethyl, cyclopropyl, phenyl, naphthyl, 2-furyl, 3-furyl, 2-thienyl or 3-thienyl, preferably methyl or ethyl.

[0023] 7. A method for preparing the pyruvate-type carbon dot photoinitiator according to any one of items 1 to 6, comprising the following steps:

[0024] S1: subjecting a compound having at least one aldehyde group and / or hydroxyl group to a carbonization reaction under hydrothermal or solvothermal conditions to obtain carbon dots having aldehyde groups on their surfaces;

[0025] S2: allowing the carbon dots having aldehyde groups on their surfaces from step S1 to undergo an acetal reaction with pyruvic acid to obtain carbon dot pyruvic acid; and

[0026] S3: subjecting the carbon-dot pyruvic acid obtained in step S2 to an esterification reaction to obtain a corresponding pyruvate-type carbon-dot photoinitiator.

[0027] 8. The method according to item 7, wherein the compound having at least one aldehyde group and / or hydroxyl group is selected from compounds having a cyclic structure and having at least one aldehyde group and / or hydroxyl group, and linear compounds having at least 5 carbon atoms and having at least one aldehyde group and / or hydroxyl group, wherein the cyclic structure is optionally substituted with one or more groups independently selected from the group consisting of C1-C6 alkyl, C1-C6 alkylthio, C1-C6 alkoxy and halogen;

[0028] Preferably, the cyclic structure has 5-10 ring members, more preferably 5-8 ring members, for example 5 or 6 ring members, wherein the ring members are C atoms and optionally 1-3 heteroatoms selected from N, O or S, and the cyclic structure is optionally substituted by one or more groups independently selected from the group consisting of C1-C4 alkyl, C1-C4 alkylthio, C1-C4 alkoxy and chlorine.

[0029] 9. The method according to item 7 or 8, wherein the compound having at least one aldehyde group and / or hydroxyl group has 1 to 4, such as 1 or 2, aldehyde groups and / or hydroxyl groups;

[0030] Preferably, the compound having at least one aldehyde group and / or hydroxyl group is of biomass origin, such as furfural, hydroxymethylfurfural, vanillin or cinnamaldehyde.

[0031] 10. The method according to item 8 or 9, wherein the solvent in step S1 is selected from C1-C6 alkyl alcohol, preferably ethanol, N,N-dimethylformamide or dimethyl sulfoxide.

[0032] 11. The method according to any one of items 7 to 10, wherein the mass ratio of the compound having at least one aldehyde group and / or hydroxyl group to water or solvent is 1:1-1:15, preferably 1:2-1:10.

[0033] 12. The method according to any one of items 7 to 11, wherein the carbonization temperature in step S1 is 100-250° C., preferably 120-200° C.; and / or the pressure is 0.1-7 MPa, preferably 0.2-3 MPa; and / or the reaction time is 4-15 h, preferably 6-12 h.

[0034] 13. The method according to any one of items 7 to 12, wherein the acetalization reaction of step S2 is carried out in the presence of one or more catalysts, preferably the catalyst is selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium hydride, sodium carbonate, sodium bicarbonate, sodium acetate, sodium tert-butoxide or sodium ethoxide, preferably sodium hydroxide or potassium hydroxide.

[0035] 14. The method according to any one of items 7 to 13, wherein in the acetalization reaction in step S2, the mass ratio of the carbon dots having aldehyde groups on the surface to pyruvic acid is 1:1-1:12, preferably 1:1-1:10.

[0036] 15. The method according to any one of items 7 to 14, wherein the esterification reaction in step S3 is carried out using an esterification reagent selected from the compounds of the following formula (Va) or (Vb):

[0037] R1-OH(Va) or R1-SH(Vb)

[0038] wherein R1 is as defined in any one of items 3-6.

[0039] 16. The method according to any one of items 7 to 15, wherein the esterification reaction of step S3 is carried out in the presence of one or more catalysts, preferably the catalyst is selected from dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 4-dimethylaminopyridine (DMAP), 3-methylpiperidine and triethylamine, preferably dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP).

[0040] 17. The method according to item 15 or 16, wherein in the esterification reaction of step S3, the mass ratio of the carbon-dot pyruvic acid to the esterification reagent is 1:1-1:12, preferably 1:1-1:10.

[0041] 18. Use of the pyruvate-type carbon dot photoinitiator obtained according to any one of items 1 to 6 or according to any one of items 7 to 17 as a photoinitiator, especially use as a photoinitiator in a UV-VIS LED light source curing system, especially use as a photoinitiator in a light source curing system with a radiation wavelength of 200-750 nm, especially 250-500 nm.

[0042] 19. A photocurable composition comprising at least one pyruvate-type carbon-dot photoinitiator obtained according to any one of items 1 to 6 or according to the method of any one of items 7 to 17.

[0043] 20. A cured material obtainable from the photocurable composition of item 19.

[0044] 21. A method for preparing a photocurable material, comprising the steps of irradiating the photocurable composition of item 19 with a light source having a radiation wavelength of 200-750 nm, especially 250-500 nm, such as a UV-VIS LED light source. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG1 is a transmission electron micrograph of carbon dots, carbon dot pyruvic acid, and carbon dot pyruvic ester obtained in steps S1 / S2 / S3 of Example 1 of the present invention;

[0046] FIG2 is a UV-visible absorption spectrum of carbon dots, carbon dot pyruvic acid, and carbon dot pyruvic ester obtained in steps S1 / S2 / S3 of Example 1 of the present invention;

[0047] FIG3 is an infrared absorption spectrum of carbon dots, carbon dot pyruvic acid, and carbon dot pyruvic ester obtained in steps S1 / S2 / S3 of Example 1 of the present invention;

[0048] FIG4 is an XRD spectrum of carbon dots, carbon dot pyruvic acid, and carbon dot pyruvic ester obtained in steps S1 / S2 / S3 of Example 1 of the present invention;

[0049] FIG5 is a photopolymerized film obtained by polymerizing diurethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA) by initiating polymerization of the carbon-dot pyruvate obtained in Example 1 of the present invention under a 365 nm LED light source;

[0050] FIG6 is a comparative mobility test graph of the carbon dot pyruvate obtained in Example 1 of the present invention and commercial methyl benzoylformate (MBF);

[0051] FIG7 is a graph showing the cell viability of carbon-dot pyruvate obtained in Example 1 of the present invention compared with commercial MBF. DETAILED DESCRIPTION

[0052] According to a first aspect of the present invention, a pyruvate-type carbon dot photoinitiator is provided, wherein the carbon dots have groups containing pyruvate structural moieties on their surfaces, and the average particle size of the carbon dots is 1-50 nm.

[0053] In one embodiment of the present invention, the average particle size of the carbon dots is 1-20 nm, preferably 1-15 nm, and more preferably 1-10 nm.

[0054] In a particularly preferred embodiment of the present invention, the average particle size of the carbon dots is 1-5 nm.

[0055] In one embodiment of the present invention, the group containing the pyruvate moiety has the structure shown in the following formula (1):

[0056] in:

[0057] * indicates the connection position with the carbon dots;

[0058] R1 represents C1-C 20 Alkyl, C3-C 20 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 10 Alkyl, C2-C 20 Alkenyl, C3-C 20 Cycloalkenyl, C3-C 10 Cycloalkenyl-C1-C 10 Alkyl, C6-C 20 Aryl or C6-C 10 Aryl-C1-C 10 Alkyl, wherein the aforementioned C1-C 20 Alkyl, C3-C 20 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 10 Alkyl, C2-C 20 Alkenyl, C3-C 20 Cycloalkenyl, C3-C 10Cycloalkenyl-C1-C 10 Alkyl, C6-C 20 Aryl or C6-C 10 Aryl-C1-C 10 The alkyl group is optionally substituted by one or more groups independently selected from the group consisting of C1-C6 alkyl, C1-C6 alkylthio, C1-C6 alkoxy, halogen, nitro, amino, cyano, mono(C1-C6 alkyl)amino, di(C1-C6 alkyl)amino and mercapto, and the aforementioned C3-C6 20 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 10 Alkyl, C3-C 20 Cycloalkenyl, C3-C 10 Cycloalkenyl-C1-C 10 Alkyl, C6-C 20 Aryl or C6-C 10 Aryl-C1-C 10 The ring carbon atoms of the alkyl group are optionally replaced by one or more heteroatoms selected from N, S and O.

[0059] In the present invention, the prefix "C n -C m " in each case means that the number of carbon atoms contained in the group is nm.

[0060] "Halogen" refers to fluorine, chlorine, bromine and iodine. In the present invention, preferably halogen is fluorine, chlorine, bromine or a combination thereof.

[0061] The term "C n -C m "Alkyl" means a branched or unbranched saturated hydrocarbon radical having nm, for example 1 to 20, carbon atoms, for example methyl, ethyl, n-propyl, 1-methylethyl, n-butyl, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, tert-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 2,2-dimethylpropyl, 1-ethylpropyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylbutyl, 2,2-dimethylpropyl -methylpentyl, 4-methylpentyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, 3,3-dimethylbutyl, 1-ethylbutyl, 2-ethylbutyl, 1,1,2-trimethylpropyl, 1,2,2-trimethylpropyl, 1-ethyl-1-methylpropyl, 1-ethyl-2-methylpropyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl and its isomers, etc.

[0062] The term "C6-C mThe term "aryl" refers to a monocyclic or bicyclic aromatic hydrocarbon group containing 6 to m carbon atoms, such as 6 to 20 carbon atoms, for example, phenyl, tolyl, ethylphenyl, propylphenyl, butylphenyl, xylyl, methylethylphenyl, diethylphenyl, methylpropylphenyl, naphthyl and isomers thereof.

[0063] The term "C2-C m "Alkenyl" refers to a branched or unbranched unsaturated hydrocarbon group having 2 to 20 carbon atoms, for example, 2 to 20 carbon atoms, and having one double bond located at any position, for example, ethenyl, 1-propenyl, 2-propenyl, 1-methylethenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-methyl-1-propenyl, 2-methyl-1-propenyl, 1-methyl-2-propenyl, 2-methyl-2-propenyl and isomers thereof.

[0064] The term "C3-C m The term "cycloalkyl" refers to a saturated alicyclic monocyclic group having 3 to 20 ring carbon atoms, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl and isomers thereof.

[0065] The term "C3-C m The term "cycloalkenyl" refers to an unsaturated alicyclic monocyclic group having 3 to 20 ring carbon atoms, for example, cyclopropenyl, cyclobutenyl, cyclopentenyl, cyclohexenyl, cycloheptenyl, cyclooctenyl, cyclodecenyl and isomers thereof.

[0066] The term "C3-C m Cycloalkyl-C n -C m "Alkyl" means C3-C m Cycloalkyl substituted C n -C m Alkyl, in which case the two m's may be the same or different, wherein C n -C m Alkyl and C3-C m The definition of cycloalkyl herein applies. For example, C3-C m Cycloalkyl-C n -C m The alkyl group can be a C3-C6 cycloalkyl-C1-C4 alkyl group, such as cyclopropylmethyl, cyclopropylethyl, cyclopropylpropyl, cyclopropylbutyl, cyclobutylmethyl, cyclobutylethyl, cyclobutylpropyl, cyclobutylbutyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylpropyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylpropyl, cyclohexylbutyl and isomers thereof.

[0067] The term "C3-C m Cycloalkenyl-C n -C m"Alkyl" means C3-C m Cycloalkenyl-substituted C n -C m Alkyl, in which case the two m's may be the same or different, wherein C n -C m Alkyl and C3-C m The definition of cycloalkenyl herein applies. For example, C3-C m Cycloalkenyl-C n -C m The alkyl group can be a C3-C6 cycloalkenyl-C1-C4 alkyl group, such as cyclopropenylmethyl, cyclopropenylethyl, cyclopropenylpropyl, cyclopropenylbutyl, cyclobutenylmethyl, cyclobutenylethyl, cyclobutenylpropyl, cyclobutenylbutyl, cyclopentenylmethyl, cyclopentenylethyl, cyclopentenylpropyl, cyclopentenylbutyl, cyclohexenylmethyl, cyclohexenylethyl, cyclohexenylpropyl, cyclohexenylbutyl and isomers thereof.

[0068] The term "C6-C m Aryl-C n -C m "Alkyl" means C6-C m Aryl-substituted C n -C m Alkyl, in which case the two m's may be the same or different, wherein C n -C m Alkyl and C6-C m The definition of aryl herein applies. m Aryl-C n -C m The alkyl group can be C6-C 10 Aryl-C1-C4 alkyl, such as benzyl, phenethyl, naphthylmethyl, naphthylethyl, etc.

[0069] The term "C n -C m "Alkoxy (thio) group" includes "C n -C m Alkoxy" and "C n -C m "Alkylthio" refers to a C n -C m Alkyl corresponding open chain C n -C m Any carbon atom of an alkane is bonded with an oxygen atom or a sulfur atom as a linking group. n -C mAlkyl groups such as C1-C6 alkoxy(thio) groups, for example, C1-C6 alkoxy groups such as methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, 2-butoxy, tert-butoxy, pentyloxy, isopentyloxy, hexyloxy and isomers thereof, and C1-C6 alkylthio groups such as methylthio, ethylthio, propylthio, isopropylthio, n-butylthio, 2-butylthio, tert-butylthio, pentylthio, isopentylthio, hexylthio and isomers thereof, etc.

[0070] In one embodiment of the present invention, R1 represents C1-C 12 Alkyl, C3-C 12 Cycloalkyl, C3-C8 cycloalkyl-C1-C4 alkyl, C2-C 12 Alkenyl, C3-C 12 Cycloalkenyl, C3-C8 cycloalkenyl-C1-C4 alkyl, C6-C 12 Aryl or C6-C 10 Aryl-C1-C4 alkyl, wherein the aforementioned C1-C 12 Alkyl, C3-C 12 Cycloalkyl, C3-C8 cycloalkyl-C1-C4 alkyl, C2-C 12 Alkenyl, C3-C 12 Cycloalkenyl, C3-C8 cycloalkenyl-C1-C4 alkyl, C6-C 12 Aryl or C6-C 10 The aryl-C1-C4 alkyl group is optionally substituted by one or more groups independently selected from the group consisting of C1-C4 alkyl, C1-C4 alkylthio, C1-C4 alkoxy, halogen, nitro, amino, cyano, mono(C1-C4 alkyl)amino, di(C1-C4 alkyl)amino and mercapto, and the aforementioned C3-C 12 Cycloalkyl, C3-C8 cycloalkyl-C1-C4 alkyl, C3-C 12 Cycloalkenyl, C3-C8 cycloalkenyl-C1-C4 alkyl, C6-C 12 Aryl or C6-C 10 The ring carbon atoms of the aryl-C1-C4alkyl group are optionally replaced by one or more heteroatoms selected from N, S and O.

[0071] In a preferred embodiment of the present invention, R1 represents C1-C 10 Alkyl, C3-C 10 Cycloalkyl, C3-C6 cycloalkyl-C1-C4 alkyl, C3-C 10 Cycloalkenyl, C3-C6 cycloalkenyl-C1-C4 alkyl, phenyl or naphthyl, wherein the aforementioned C1-C 10 Alkyl, C3-C 10 Cycloalkyl, C3-C6 cycloalkyl-C1-C4 alkyl, C3-C 10Cycloalkenyl, C3-C6 cycloalkenyl-C1-C4 alkyl, phenyl or naphthyl is optionally substituted by fluorine, chlorine, bromine and C1-C4 alkyl, and the aforementioned C3-C6 10 Cycloalkyl, C3-C6 cycloalkyl-C1-C4 alkyl, C3-C 10 The ring carbon atoms of the cycloalkenyl, C3-C6 cycloalkenyl-C1-C4 alkyl, phenyl or naphthyl are optionally replaced by one or more heteroatoms selected from N, S and O.

[0072] In a more preferred embodiment of the present invention, R1 represents C1-C8 alkyl, C3-C8 cycloalkyl, C3-C6 cycloalkyl-C1-C2 alkyl, C3-C8 cycloalkenyl, C3-C6 cycloalkenyl-C1-C2 alkyl, phenyl or naphthyl, wherein the aforementioned C1-C8 alkyl, C3-C8 cycloalkyl, C3-C6 cycloalkyl-C1-C2 alkyl, C3-C8 cycloalkenyl, C3-C6 cycloalkenyl-C1-C2 alkyl, phenyl or naphthyl is optionally substituted with C1-C4 alkyl, and the ring carbon atoms of the aforementioned C3-C8 cycloalkyl, C3-C6 cycloalkyl-C1-C2 alkyl, C3-C8 cycloalkenyl, C3-C6 cycloalkenyl-C1-C2 alkyl, phenyl or naphthyl are optionally replaced with one or more heteroatoms selected from N, S and O.

[0073] In a particularly preferred embodiment of the present invention, R1 represents methyl, ethyl, n-propyl, 1-methylethyl, cyclopropyl, phenyl, naphthyl, 2-furyl, 3-furyl, 2-thienyl or 3-thienyl, preferably methyl or ethyl.

[0074] In some particularly preferred embodiments of the present invention, the pyruvate-type carbon point photoinitiator of the present invention has the structure shown in the following formula (I)-(II):

[0075] According to a second aspect of the present invention, there is provided a method for preparing the pyruvate-type carbon dot photoinitiator of the present invention, comprising the following steps:

[0076] S1: subjecting a compound having at least one aldehyde group and / or hydroxyl group to a carbonization reaction under hydrothermal or solvothermal conditions to obtain carbon dots having aldehyde groups on their surfaces;

[0077] S2: allowing the carbon dots having aldehyde groups on their surfaces from step S1 to undergo an acetal reaction with pyruvic acid to obtain carbon dot pyruvic acid; and

[0078] S3: subjecting the carbon-dot pyruvic acid obtained in step S2 to an esterification reaction to obtain a corresponding pyruvate-type carbon-dot photoinitiator.

[0079] In order to prepare the pyruvate-type carbon dot photoinitiator of the present invention, it is necessary to start from a specific compound having at least one aldehyde group and / or hydroxyl group, first perform a carbonization reaction to obtain carbon dots with aldehyde groups on the surface, then perform an acetal reaction to introduce pyruvate groups, and then convert the carboxyl groups in the pyruvate groups into corresponding ester groups through an esterification reaction, thereby obtaining the pyruvate-type carbon dot photoinitiator of the present invention.

[0080] carbonization reaction

[0081] In the carbonization reaction of step S1 , a specific compound having at least one aldehyde group and / or hydroxyl group is subjected to a carbonization reaction under hydrothermal or solvothermal conditions to obtain carbon dots having aldehyde groups on their surfaces.

[0082] In the carbonization reaction, the compound having at least one aldehyde group and / or hydroxyl group that can be used is selected from a compound having a cyclic structure and having at least one aldehyde group and / or hydroxyl group and a linear compound having at least 5 carbon atoms and having at least one aldehyde group and / or hydroxyl group, wherein the cyclic structure is optionally substituted by one or more groups independently selected from the group consisting of C1-C6 alkyl, C1-C6 alkylthio, C1-C6 alkoxy and halogen.

[0083] In one embodiment of the present invention, the cyclic structure of the compound having at least one aldehyde group and / or hydroxyl group has 5-10 ring members, more preferably 5-8 ring members, for example 5 or 6 ring members, wherein the ring members are C atoms and optionally 1-3 heteroatoms selected from N, O or S, and the cyclic structure is optionally substituted by one or more groups independently selected from the following groups: C1-C4 alkyl, C1-C4 alkylthio, C1-C4 alkoxy and chlorine.

[0084] In a preferred embodiment of the present invention, the compound having at least one aldehyde group and / or hydroxyl group has 1 to 4, such as 1 or 2, aldehyde groups and / or hydroxyl groups.

[0085] In a more preferred embodiment of the present invention, the compound having at least one aldehyde group and / or hydroxyl group is of biomass origin, such as furfural, hydroxymethylfurfural, vanillin or cinnamaldehyde.

[0086] In order to accelerate the carbonization reaction, the above reaction is usually carried out under hydrothermal or solvent thermal conditions. As the solvent, C1-C6 alkyl alcohol, preferably ethanol, N,N-dimethylformamide or dimethyl sulfoxide can be used.

[0087] In the carbonization reaction of step S1, the mass ratio of the compound having at least one aldehyde group and / or hydroxyl group to water or solvent is 1:1-1:15, preferably 1:2-1:10.

[0088] The temperature range of the carbonization reaction is 100-250° C., preferably 120-200° C.; the pressure is 0.1-7 MPa, preferably 0.2-3 MPa; and the reaction time can be 4-15 hours, preferably 6-12 hours.

[0089] After the carbonization reaction in step S1 is completed, the reaction system can be naturally cooled to room temperature before removing the precipitate. There is no particular limitation on the means for removing the precipitate, and it can usually be removed by centrifugation. After removing the precipitate, a supernatant is obtained. The supernatant is dialyzed through a dialysis bag of specific specifications, such as a dialysis bag with a molecular weight cutoff of 300 Da for 1-3 days, preferably 2 days, to obtain a carbon dot solution containing aldehyde groups on the surface. The aldehyde content in the obtained carbon dot solution is measured by potentiometric titration, and the measurement result is about 7.5 mmol / g-200 mmol / g, preferably 10 mmol / g-100 mmol / g.

[0090] Acetal reaction

[0091] In the acetalization reaction of step S2, the carbon dots having aldehyde groups on their surfaces obtained in step S1 undergo an acetalization reaction with pyruvic acid to obtain carbon dot pyruvic acid.

[0092] The acetalization reaction is usually carried out in an organic solvent, preferably in a polar organic solvent. The solvent that can be used includes, for example, anhydrous ethanol or hydrous ethanol. The amount of solvent used is conventional and can be determined by common sense in the art or by several routine preliminary experiments.

[0093] To promote the complete acetalization reaction, a catalyst such as sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium hydride, sodium carbonate, sodium bicarbonate, sodium acetate, sodium tert-butoxide, sodium ethoxide, or a mixture thereof is generally added, preferably sodium hydroxide or potassium hydroxide. The amount of catalyst used is conventional and can be determined by common knowledge in the art or by a few routine preliminary experiments.

[0094] In the acetalization reaction in step S2, the mass ratio of the carbon dots having aldehyde groups on the surface to the pyruvic acid is 1:1-1:12, preferably 1:1-1:10.

[0095] The temperature range of the acetalization reaction is usually room temperature to 100° C., preferably 30-80° C. The acetalization reaction time is also not particularly limited, and is usually 0.4-15 hours, preferably 0.5-10 hours.

[0096] After the acetalization reaction in step S2 is completed, aftertreatment can be carried out according to the operation routine in this area. For example, naturally cool to room temperature first, then rotary evaporation removes the solvent in the system, then dissolves the product with deionized water, and then washes with an organic solvent such as ethyl acetate. Washing operation can be carried out repeatedly. When carrying out repeatedly, a single solvent can be used, or different solvents can be used in sequence. Afterwards, dilute acid such as dilute hydrochloric acid can be used to regulate the pH value of the aqueous phase to acidic conditions, and then an organic solvent such as ethyl acetate can be used to extract. Extraction operation can be carried out repeatedly. When carrying out repeatedly, a single solvent can be used, or different solvents can be used in sequence. Collect organic phase and rotary evaporation removes the solvent in the organic phase to obtain carbon-point pyruvic acid.

[0097] Esterification reaction

[0098] In the esterification reaction of step S3, the carboxyl group in the pyruvic acid group is converted into an ester group, thereby obtaining carbon-dot pyruvic acid ester.

[0099] According to the present invention, the esterification reaction in step S3 is carried out by reacting the carbon-dot pyruvic acid obtained in step S2 with an esterification reagent. The above-mentioned esterification reaction is conventional for those skilled in the art, and there is no particular limitation on the esterification reagent, as long as the carboxyl group in the carbon-dot pyruvic acid obtained in step S2 can be converted into an ester group. For example, corresponding (thiol) compounds can be used, and these (thiol) compounds can be represented by formula (Va) or (Vb):

[0100] R1-OH(Va) or R1-SH(Vb)

[0101] wherein R1 is as defined in formula (1).

[0102] In order to accelerate the esterification reaction, the esterification reaction is usually carried out in the presence of one or more catalysts suitable for the esterification reaction, preferably the catalyst is selected from dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 4-dimethylaminopyridine (DMAP), 3-methylpiperidine and triethylamine, preferably dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). The amount of catalyst used is conventional and can be determined by common sense in the art or by a few routine preliminary experiments.

[0103] The esterification reaction is typically carried out in a solvent, preferably an organic solvent. Examples of solvents commonly used include methanol, ethanol, dichloromethane, ethyl acetate, tetrahydrofuran, and N,N-dimethylformamide. When the solvent is an alcohol such as methanol or ethanol, it can also serve as the esterification agent described above. Preferably, the reaction is carried out in methanol or ethanol. The amount of solvent used is conventional and can be determined by common knowledge in the art or by a few routine preliminary experiments.

[0104] In the esterification reaction of step S3, the mass ratio of the carbon-dot pyruvic acid to the esterification reagent of formula (Va) or (Vb) is 1:1-1:12, preferably 1:1-1:10.

[0105] The esterification reaction is usually carried out at a temperature ranging from -20°C to 40°C, preferably from -10°C to 30°C, preferably in an ice bath. The esterification reaction time is also not particularly limited, and is usually carried out for 0.5-10 hours, preferably 1-8 hours.

[0106] After the esterification reaction is completed, the reaction system can be post-treated to obtain the purified pyruvate-type carbon dot photoinitiator of the present invention. According to the present invention, it is advantageous that after the reaction is completed, the solvent in the system is removed by rotary evaporation. The spin-dried sample is added with water and a solvent such as ethanol and the pH is adjusted to an acidic condition with a dilute acid such as dilute hydrochloric acid. The sample is stirred under acidic conditions, and then filtered to remove insoluble matter. An organic solvent such as ethyl acetate is used for extraction. The extraction operation can be performed multiple times; when it is performed multiple times, a single solvent can be used, or different solvents can be used in sequence. The organic phase is collected and the solvent in the organic phase is removed by rotary evaporation. Thereafter, the residual water is removed by drying. To this end, anhydrous sodium sulfate can usually be used for drying to obtain a crude product of the pyruvate-type carbon dot photoinitiator of the present invention.

[0107] If the purity of the pyruvate-type carbon dot photoinitiator of the present invention is desired to be further improved, the crude product may be further purified, for example, by dialysis. The choice of dialysis solvent is conventional and not particularly limited. According to the present invention, the crude product of the pyruvate-type carbon dot photoinitiator of the present invention is advantageously dialyzed using deionized water, dichloromethane, ethyl acetate, methanol, ethanol, or a mixture thereof.

[0108] The pyruvate-based carbon dot photoinitiator of the present invention can be used for UV-VIS LED light source curing. It exhibits excellent initiation performance in the wavelength range of 200-750 nm, particularly 250-500 nm, and can effectively initiate the photopolymerization of photopolymerizable monomers, especially (meth)acrylate monomers. Furthermore, the photoinitiator of the present invention has low biotoxicity, low mobility, and excellent biocompatibility, making it suitable for applications in photopolymerizable materials and biomacromolecules. Furthermore, its simple synthesis route makes it highly practical.

[0109] Therefore, according to the third aspect of the present invention, there is provided the use of the pyruvate-type carbon dot photoinitiator of the present invention. The pyruvate-type carbon dot photoinitiator of the present invention can be applied to UV-VIS LED photocuring technology and can effectively initiate a curing reaction. It is particularly preferred that the pyruvate-type carbon dot photoinitiator of the present invention is used as a photoinitiator in a photocuring system with a radiation wavelength of 200-750nm, especially 250-500nm. The pyruvate-type carbon dot photoinitiator of the present invention can also be used as a photoinitiator or photosensitizer in the fields of coatings, inks, microelectronics, printing, etc. When the pyruvate-type carbon dot photoinitiator of the present invention is used as a photoinitiator, its dosage is conventional, or can be determined by routine preliminary tests.

[0110] According to a fourth aspect of the present invention, there is provided a photocurable composition comprising the pyruvate-type carbon-dot photoinitiator of the present invention.

[0111] In the photocurable composition, the amount of the photoinitiator of the present invention is generally 0.01 to 10% by weight, preferably 0.1 to 6% by weight, such as 0.2 to 5% by weight, based on the amount of active ingredients of the photocurable composition.

[0112] In the context of this disclosure, active ingredients refer to the ingredients in the photocurable composition other than the solvent.

[0113] In addition to the photoinitiator of the present invention, the photocurable composition further comprises a photocurable resin.

[0114] In the present invention, a photocurable resin refers to an oligomer or prepolymer containing unsaturated carbon-carbon double bonds. Upon exposure to light, this oligomer or prepolymer undergoes a polymerization reaction initiated by a photoinitiator, leading to crosslinking and curing. Photocurable resins are the main component of photocurable products (e.g., UV coatings, UV inks, and UV adhesives).

[0115] As the photocurable resin, there may be mentioned epoxy (meth)acrylate resins, polyester (meth)acrylates, polyurethane (meth)acrylates, ethylenically unsaturated polyesters, amino (meth)acrylate resins, photoimageable alkali-soluble resins, etc. According to the present invention, it is advantageous to use epoxy (meth)acrylate resins, polyester (meth)acrylates, polyurethane (meth)acrylates, or combinations thereof.

[0116] The epoxy (meth)acrylate resin is preferably bisphenol A epoxy (meth)acrylate, bisphenol A epoxy acrylate diluted with tripropylene glycol di(meth)acrylate, or a combination thereof, such as bisphenol A epoxy acrylate WSR-U125 from Wuxi Resin Factory, modified bisphenol A epoxy acrylate 623-100 from Taiwan Changxing Chemical Company, modified bisphenol A epoxy acrylate 6231A-80 diluted with 20% tripropylene glycol diacrylate from Taiwan Changxing Chemical Company, etc.

[0117] The polyester (meth)acrylate is preferably a high-functionality hyperbranched polyester acrylate resin, particularly a hyperbranched polyester acrylate resin with a functionality of 5-30, such as a hyperbranched polyester acrylate prepolymer with a functionality of 6-20. Examples of such prepolymers include hyperbranched polyester acrylate prepolymer 932-100 (6 functionality) from Wuxi Knox Co., Ltd., and hyperbranched polyester acrylate prepolymers CN2300 (8 functionality), CN2301 (9 functionality), and CN2302 (16 functionality) from Sartomer Co., Ltd., USA.

[0118] The polyurethane (meth)acrylate is preferably an aliphatic polyurethane acrylate resin. Examples of the polyurethane (meth)acrylate include aliphatic polyurethane acrylate CN9013 (9-functionality) from Sartomer, Inc., USA; aliphatic polyurethane acrylate CN966B85 (2-functionality) diluted with 15% 1,6-hexanediol diacrylate (HDDA) from Sartomer, Inc., USA; and aliphatic polyurethane acrylate CN962 (2-functionality).

[0119] The photocurable resin is generally used in the photocurable composition in an amount of 10 to 90% by weight, preferably 55 to 80% by weight, based on the amount of active ingredients in the photocurable composition.

[0120] The photocurable composition may further include a multifunctional reactive diluent.

[0121] In the present invention, a multifunctional reactive diluent refers to a monomer containing two or more photopolymerizable groups. Multifunctional reactive diluents have low viscosity and strong dissolving power. Upon exposure to a light source, multifunctional reactive diluents can be polymerized by reactive free radicals to form a crosslinked network.

[0122] According to the present invention, the preferred multifunctional reactive diluent is a multifunctional (meth)acrylate reactive diluent. This refers to a monomer containing two or more (meth)acrylate polymerizable groups. Examples of multifunctional (meth)acrylate reactive diluents include trimethylolpropane triacrylate (TMPTA), propoxylated trimethylolpropane triacrylate (PO-TMPTA), ethoxylated trimethylolpropane triacrylate (EO-TMPTA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPEPA), dipentaerythritol hexaacrylate (DPHA), tripropylene glycol diacrylate (TPGDA), 1,6-hexanediol diacrylate (HDDA), triethylene glycol dimethacrylate (TEGDMA), diethylene glycol dimethacrylate (DEGDMA), glycerol diacrylate, and diurethane dimethacrylate (UDMA).

[0123] The amount of the multifunctional reactive diluent used in the photocurable composition is generally 8 to 60% by weight, preferably 15 to 45% by weight, based on the amount of the active ingredients in the photocurable composition.

[0124] According to the present invention, the photocurable composition may further comprise a monofunctional reactive diluent.

[0125] In the present invention, a monofunctional reactive diluent refers to a monomer containing a photopolymerizable group. It has a low viscosity and a strong dissolving power, and can act as a partial organic solvent. After being irradiated by a light source, the monofunctional reactive diluent can be initiated to undergo polymerization by active free radicals. Monofunctional reactive diluents mainly include (meth)acrylate compounds and vinyl compounds. As (meth)acrylate monofunctional reactive diluents, methyl methacrylate (MMA), n-butyl acrylate (BA), isooctyl acrylate (2-EHA), isodecyl acrylate (IDA), lauryl acrylate (LA), hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and some (meth)acrylates with cyclic structures can be mentioned. In addition, as vinyl monofunctional reactive diluents, styrene (St), vinyl acetate (VA), N-vinyl pyrrolidone (NVP), etc. can be mentioned.

[0126] The monofunctional reactive diluent is generally used in the photocurable composition in an amount of 5 to 50% by weight, preferably 8 to 40% by weight, based on the amount of the active ingredients in the photocurable composition.

[0127] The photocurable composition of the present invention may also optionally contain an organic solvent. The selection of the organic solvent is conventional. As the organic solvent, aromatic hydrocarbons such as benzene and toluene, halogenated alkanes such as chloroform, dichloromethane, and ethyl chloride, ketones such as acetone, butanone, and pentanone, and alcohols such as methanol, ethanol, propanol, isopropanol, and ethylene glycol, and glycol ethers, glycol ether acetates, propylene glycol ethers, and propylene glycol ether acetates can be mentioned. The amount of the organic solvent used is conventional and can be determined by common sense in the art or by several routine preliminary experiments.

[0128] The photocurable composition of the present invention may also optionally contain other additives, such as leveling agents, antioxidants, anti-settling agents, colorants, microbicides, such as antibacterial agents and thermal insulation additives. In a preferred embodiment of the present invention, the leveling agent is selected from the group consisting of FLOW series leveling agents, particularly preferably 360S, 372S, 384S, 392S, 400U, 415U, etc. The amount of the additive is conventional and can be determined by common sense in the art or by a few routine preliminary experiments.

[0129] The preparation of the photocurable composition of the present invention is conventional, for example, the various components of the photocurable composition of the present invention are uniformly mixed together.

[0130] According to a fifth aspect of the present invention, a cured material obtainable from the photocurable composition of the present invention is provided. The resulting cured material can be a photocurable coating, including coatings containing functional materials, UV and / or visible light filter coatings; sealants; photolithographic materials; holographic recording materials; 3D printing materials; lithographic materials; materials for preparing optical devices; and materials for improving mechanical properties, such as carbon fiber composites and / or inorganic and / or organic nanoparticles.

[0131] According to a sixth aspect of the present invention, a method for preparing a photocurable material is provided, comprising the steps of irradiating the photocurable composition of the present invention with a light source having a radiation wavelength of 200-750 nm, in particular 250-500 nm, such as a UV-VIS LED light source.

[0132] The pyruvate-based carbon dot photoinitiator disclosed in this invention has a simple synthetic route and is highly suitable for industrial production. This photoinitiator exhibits excellent compatibility with UV-VIS LED light sources with a radiation wavelength of 200-750 nm, particularly 250-500 nm. It can be widely used in applications related to UV-VIS LED photocuring, including traditional applications such as coatings, inks, microelectronics, and printing, as well as emerging applications such as the preparation of laser recording and three-dimensional components. Therefore, the pyruvate-based carbon dot photoinitiator of this invention has promising market prospects.

[0133] In particular, given the shortcomings of pyruvate photoinitiators currently available for UV-VIS LED light source curing in terms of biotoxicity caused by photocuring residues, the pyruvate-based carbon dot photoinitiator of the present invention has low biotoxicity and low mobility, as well as excellent biocompatibility and a simple synthesis route, and can make substantial contributions to promoting the application of green and environmentally friendly UV curing industry.

[0134] Example

[0135] The scheme of the present invention will be explained below with reference to the examples. Those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in this area or the product specifications are followed.

[0136] Example 1:

[0137] Preparation of pyruvate-type carbon dot photoinitiator

[0138] Step S1: Synthesis of biomass-based aldehyde-containing carbon dots

[0139] To a 100-mL polytetrafluoroethylene-lined reactor, 2.5 mL of the biomass raw material furfural was added, followed by 25 mL of anhydrous ethanol, which was thoroughly mixed and dissolved. The reactor was then covered and placed in an oven at 180°C for 8 hours, at autogenous pressure. After the reaction was completed and allowed to cool to room temperature, the lid was opened to yield a black reaction solution. After centrifugation to remove the precipitate, the supernatant was dialyzed for two days using a 300 Da molecular weight cutoff dialysis bag to yield 27 mL of a 10 mg / mL solution of black carbon dots (CDs) containing aldehyde groups on their surfaces. The aldehyde content of the resulting CD solution was determined to be approximately 100 mmol / g by potentiometric titration. The solution was then analyzed using TEM, XRD, UV-visible, and IR spectra (see below for details).

[0140] Step S2: Synthesis of carbon-dot pyruvic acid

[0141] To a 100 mL reaction flask, add 9 mL of the above-mentioned carbon dot solution with aldehyde groups on the surface and 0.84 g of KOH, stir for 20 minutes under ice bath conditions to fully dissolve it. Then, take 0.88 g of pyruvic acid and add it to 20 mL of anhydrous ethanol, add it dropwise to the reaction, and react at 40°C for 7 hours. After the reaction is completed, the ethanol in the system is removed by rotary evaporation to obtain a black solid product. Dissolve the product with 20 mL of deionized water and wash it three times with ethyl acetate. Then adjust the pH of the aqueous phase to 3-4 with dilute hydrochloric acid, extract it with ethyl acetate three times, collect the organic phase and rotary evaporate to remove the solvent in the organic phase. After drying, 0.444 g of black carbon dot pyruvic acid solid is obtained. See below for structure and performance characterization.

[0142] Step S3: Synthesis of carbon-dot pyruvate

[0143] To a 100 mL reaction flask, add 540 mg of DCC and 60 mg of DMAP, followed by 20 mL of anhydrous ethanol, and stir for 25 minutes in an ice bath to fully dissolve. Then, dissolve 0.1 g of the carbon dot pyruvate in 10 mL of anhydrous ethanol, then add dropwise to the reaction system and react for 2 hours in an ice bath. After the reaction, remove the ethanol from the system by rotary evaporation. Add water and ethanol to the spin-dried sample, adjust the pH to 3-4 with dilute hydrochloric acid, and stir for 10 minutes. After filtering to remove insoluble matter, remove the ethanol from the filtrate by rotary evaporation, and extract with ethyl acetate. The organic phase is collected and the solvent is removed by rotary evaporation. Drying yields 0.074 g of a black pyruvate carbon dot solid. See below for structural and performance characterization.

[0144] Example 2

[0145] The method of Example 1 was repeated, except that the biomass raw material in step S1 was hydroxymethylfurfural.

[0146] Example 3

[0147] The method of Example 1 was repeated, except that the biomass raw material in step S1 was cinnamaldehyde.

[0148] Example 4

[0149] The method of Example 1 was repeated, except that the biomass raw material in step S1 was vanillin.

[0150] Example 5

[0151] The method of Example 1 was repeated, except that the esterification reagent in step S3 was methanol. Analysis and results of carbon dots, carbon dot pyruvic acid, and carbon dot pyruvic ester prepared in steps S1, S2, and S3 of Example 1

[0152] Transmission electron microscopy (TEM) analysis of the carbon dots, carbon dot pyruvic acid, and carbon dot pyruvic ester prepared in steps S1, S2, and S3 of Example 1 was performed, as shown in Figure 1. The results showed that the carbon dots, carbon dot pyruvic acid, and carbon dot pyruvic ester prepared in steps S1, S2, and S3 all had carbon dot particle structures, with a particle size of 1-10 nm.

[0153] XRD analysis was performed on the carbon dots, carbon dot pyruvic acid, and carbon dot pyruvic ester prepared in steps S1, S2, and S3 of Example 1. The XRD results are shown in Figure 4. The results show that the carbon dots exhibit a peak at approximately 20°, indicating an amorphous structure. The particle structure remains unchanged after surface modification, indicating that surface modification does not disrupt the carbon dot structure.

[0154] The carbon dots, carbon dot pyruvic acid, and carbon dot pyruvate prepared in steps S1, S2, and S3 of Example 1 were measured for UV-visible absorption within the wavelength range of 200-700 nm using a UV-visible spectrophotometer. The UV-visible absorption spectra are shown in Figure 2. The results show that, compared to the absorption spectra of carbon dots, the absorption spectra of carbon dot pyruvic acid and pyruvate changed significantly after surface modification, with the primary absorption band being 250-500 nm.

[0155] Furthermore, the changes in the functional groups of the carbon dots, carbon dot pyruvic acid, and carbon dot pyruvic ester prepared in steps S1, S2, and S3 of Example 1 were analyzed by Fourier transform infrared spectroscopy, and their infrared spectra are shown in Figure 3. The results show that: by comparing the infrared spectra of carbon dots and carbon dot pyruvic acid, after surface modification, the carbon dots have a lower 1730 cm -1 The left and right carbonyl peaks are blue-shifted to 1710 cm -1 Around 3400cm -1The -OH characteristic peak on the carboxyl group appears, which indicates that the pyruvic acid functional group has been successfully grafted onto the carbon dot surface. Comparing the infrared spectra of carbon dot pyruvic acid and carbon dot pyruvic ester, at 3400 cm -1 The characteristic peaks of -OH on the left and right sides disappear, and at the same time, the peaks of 2850-2950cm -1 A methylene characteristic peak appeared in the range, which indicated that the carboxyl group on the pyruvic acid was esterified and the preparation of the pyruvic acid ester carbon dot photoinitiator was successful.

[0156] Example 6

[0157] The purpose of Example 6 is to illustrate that the pyruvate-type carbon dot photoinitiator of Example 1 can effectively initiate the photopolymerization reaction of (meth)acrylate monomers under the irradiation of LED light source.

[0158] Taking the carbon dot pyruvate in Example 1 as an example, 10 mg of the carbon dot pyruvate was mixed with 400 mg of triethylene glycol dimethacrylate (TEGDMA) and ultrasonically shaken for 1 minute to fully dissolve it. 600 mg of diurethane dimethacrylate (UDMA) was added to the mixture and ultrasonically shaken for another 1 minute to fully mix it. The mixture was placed under 200 mW / cm 2 Under the irradiation of 365nm LED, photopolymerization reaction was carried out, and the obtained photopolymerized film was shown in Figure 5.

[0159] Example 7

[0160] The purpose of Example 7 is to illustrate that the pyruvate-type carbon dot photoinitiator of Example 1 has a lower mobility.

[0161] Mobility test: Using the carbon dot pyruvate in Example 1 as an example and commercial MBF (provided by Shanghai Aladdin Biochemical Technology Co., Ltd.) as a comparison, a test sample was prepared. Specifically, a photoinitiator (1 wt%) was added to a mixture of UDMA and TEGDMA (6:4) and mixed evenly. A 200 mW / cm 2 The film was then irradiated with 365nm UV light for 15 minutes for photocuring, and the unreacted monomers and initiators on the film surface were rinsed with ethanol. An appropriate amount of film was soaked in ethanol, and the changes in the absorbance of the solution were monitored. The monitoring wavelength for MBF was 241nm, and the monitoring wavelength for the carbon-dot initiator was 279nm. The results are shown in Figure 6. The results show that after 30 minutes, the mobility of the carbon-dot pyruvate photoinitiator was 0.02%, while the mobility of MBF was 0.87%. After 48 hours, the mobility of the carbon-dot pyruvate photoinitiator was 3.19%, while the mobility of MBF was 6.55%. This shows that the mobility of the carbon-dot pyruvate photoinitiator in Example 1 is much lower than that of the commercial MBF initiator.

[0162] Example 8

[0163] The purpose of Example 8 is to illustrate that the pyruvate-type carbon dot photoinitiator of Example 1 has lower cytotoxicity.

[0164] Cytotoxicity test: The cytotoxicity of the photoinitiator was tested using the MTT method, and commercial MBF was used as a comparison. L929 cells (mouse fibroblasts, provided by Shanghai Biotechnology Co., Ltd.) were seeded in a 96-well plate and cultured with different concentrations (25, 50, 100 μg / mL) of photoinitiator for 24 hours. The absorbance of each well was measured using a microplate reader (Bio Tek Instruments, Inc., USA) at a wavelength of 490 nm. The cell survival rate was calculated according to the following formula 1, and the results are shown in Figure 7. The results show that the cytotoxicity of carbon-dot pyruvate is lower than that of commercial pyruvate photoinitiator. When its concentration is 100 μg / mL, the MBF cell survival rate is 81%; while the carbon-dot pyruvate prepared in Example 1 has less cytotoxicity. When its concentration is 100 μg / mL, the cell survival rate is 91%. Cell survival rate = (A 实验组 / A 对照组 )×100%(Formula 1),

[0165] Among them: A 实验组 is the absorbance of the experimental group (with sample) measured by enzyme marker, A 对照组 The absorbance of the control group (without sample) was measured by enzyme-labeled instrument.

Claims

1. A pyruvate-type carbon dot photoinitiator, wherein the carbon dot surface has a group containing a pyruvate structural portion, and the average particle size of the carbon dot is 1-50 nm. 2 . The pyruvate-type carbon dot photoinitiator according to claim 1 , wherein the average particle size of the carbon dots is 1-20 nm, preferably 1-15 nm, more preferably 1-10 nm.

3. The pyruvate-type carbon point photoinitiator according to claim 1 or 2, wherein the group containing the pyruvate structural portion has a structure as shown in the following formula (1): in: * indicates the connection position with the carbon dots; R1 represents C1-C 20 Alkyl, C3-C 20 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 10 Alkyl, C2-C 20 Alkenyl, C3-C 20 Cycloalkenyl, C3-C 10 Cycloalkenyl-C1-C 10 Alkyl, C6-C 20 Aryl or C6-C 10 Aryl-C1-C 10 Alkyl, wherein the aforementioned C1-C 20 Alkyl, C3-C 20 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 10 Alkyl, C2-C 20 Alkenyl, C3-C 20 Cycloalkenyl, C3-C 10 Cycloalkenyl-C1-C 10 Alkyl, C6-C 20 Aryl or C6-C 10 Aryl-C1-C 10 The alkyl group is optionally substituted by one or more groups independently selected from the group consisting of C1-C6 alkyl, C1-C6 alkylthio, C1-C6 alkoxy, halogen, nitro, amino, cyano, mono(C1-C6 alkyl)amino, di(C1-C6 alkyl)amino and mercapto, and the aforementioned C3-C6 20 Cycloalkyl, C3-C 10 Cycloalkyl-C1-C 10 Alkyl, C3-C 20 Cycloalkenyl, C3-C 10 Cycloalkenyl-C1-C 10 Alkyl, C6-C 20 Aryl or C6-C 10 Aryl-C1-C 10 The ring carbon atoms of the alkyl group are optionally replaced by one or more heteroatoms selected from N, S and O.

4. The pyruvate-type carbon dot photoinitiator according to claim 3, wherein: R1 represents C1-C 12 Alkyl, C3-C 12 Cycloalkyl, C3-C8 cycloalkyl-C1-C4 alkyl, C2-C 12 Alkenyl, C3-C 12 Cycloalkenyl, C3-C8 cycloalkenyl-C1-C4 alkyl, C6-C 12 Aryl or C6-C 10 Aryl-C1-C4 alkyl, wherein the aforementioned C1-C 12 Alkyl, C3-C 12 Cycloalkyl, C3-C8 cycloalkyl-C1-C4 alkyl, C2-C 12 Alkenyl, C3-C 12 Cycloalkenyl, C3-C8 cycloalkenyl-C1-C4 alkyl, C6-C 12 Aryl or C6-C 10 The aryl-C1-C4 alkyl group is optionally substituted by one or more groups independently selected from the group consisting of C1-C4 alkyl, C1-C4 alkylthio, C1-C4 alkoxy, halogen, nitro, amino, cyano, mono(C1-C4 alkyl)amino, di(C1-C4 alkyl)amino and mercapto, and the aforementioned C3-C 12 Cycloalkyl, C3-C8 cycloalkyl-C1-C4 alkyl, C3-C 12 Cycloalkenyl, C3-C8 cycloalkenyl-C1-C4 alkyl, C6-C 12 Aryl or C6-C 10 The ring carbon atoms of the aryl-C1-C4alkyl group are optionally replaced by one or more heteroatoms selected from N, S and O; Preferably, R1 represents C1-C 10 Alkyl, C3-C 10 Cycloalkyl, C3-C6 cycloalkyl-C1-C4 alkyl, C3-C 10 Cycloalkenyl, C3-C6 cycloalkenyl-C1-C4 alkyl, phenyl or naphthyl, wherein the aforementioned C1-C 10 Alkyl, C3-C 10 Cycloalkyl, C3-C6 cycloalkyl-C1-C4 alkyl, C3-C 10 Cycloalkenyl, C3-C6 cycloalkenyl-C1-C4 alkyl, phenyl or naphthyl is optionally substituted by fluorine, chlorine, bromine and C1-C4 alkyl, and the aforementioned C3-C6 10 Cycloalkyl, C3-C6 cycloalkyl-C1-C4 alkyl, C3-C 10 The ring carbon atoms of the cycloalkenyl, C3-C6 cycloalkenyl-C1-C4 alkyl, phenyl or naphthyl are optionally replaced by one or more heteroatoms selected from N, S and O.

5. The pyruvate-type carbon dot photoinitiator according to claim 3 or 4, wherein R1 represents a C1-C8 alkyl group, a C3-C8 cycloalkyl group, a C3-C6 cycloalkyl-C1-C2 alkyl group, a C3-C8 cycloalkenyl group, a C3-C6 cycloalkenyl-C1-C2 alkyl group, a phenyl group or a naphthyl group, wherein the aforementioned C1-C8 alkyl group, a C3-C8 cycloalkyl group, a C3-C6 cycloalkyl-C1-C2 alkyl group, a C3-C8 cycloalkenyl group, a C3-C6 cycloalkenyl-C1-C2 alkyl group, a phenyl group or a naphthyl group is optionally substituted with a C1-C4 alkyl group, and the ring carbon atoms of the aforementioned C3-C8 cycloalkyl group, a C3-C6 cycloalkyl-C1-C2 alkyl group, a C3-C8 cycloalkenyl group, a C3-C6 cycloalkenyl-C1-C2 alkyl group, a phenyl group or a naphthyl group are optionally replaced with one or more heteroatoms selected from N, S and O.

6. The pyruvate-type carbon dot photoinitiator according to any one of claims 3 to 5, wherein R1 represents methyl, ethyl, n-propyl, 1-methylethyl, cyclopropyl, phenyl, naphthyl, 2-furyl, 3-furyl, 2-thienyl or 3-thienyl, preferably methyl or ethyl.

7. A method for preparing the pyruvate-type carbon dot photoinitiator according to any one of claims 1 to 6, comprising the following steps: S1: subjecting a compound having at least one aldehyde group and / or hydroxyl group to a carbonization reaction under hydrothermal or solvothermal conditions to obtain carbon dots having aldehyde groups on their surfaces; S2: allowing the carbon dots having aldehyde groups on their surfaces from step S1 to undergo an acetal reaction with pyruvic acid to obtain carbon dot pyruvic acid; and S3: subjecting the carbon-dot pyruvic acid obtained in step S2 to an esterification reaction to obtain a corresponding pyruvate-type carbon-dot photoinitiator.

8. The method according to claim 7, wherein the compound having at least one aldehyde group and / or hydroxyl group is selected from compounds having a cyclic structure and having at least one aldehyde group and / or hydroxyl group, and linear compounds having at least 5 carbon atoms and having at least one aldehyde group and / or hydroxyl group, wherein the cyclic structure is optionally substituted with one or more groups independently selected from the group consisting of C1-C6 alkyl, C1-C6 alkylthio, C1-C6 alkoxy and halogen; Preferably, the cyclic structure has 5-10 ring members, more preferably 5-8 ring members, for example 5 or 6 ring members, wherein the ring members are C atoms and optionally 1-3 heteroatoms selected from N, O or S, and the cyclic structure is optionally substituted by one or more groups independently selected from the group consisting of C1-C4 alkyl, C1-C4 alkylthio, C1-C4 alkoxy and chlorine.

9. The method according to claim 7 or 8, wherein the compound having at least one aldehyde group and / or hydroxyl group has 1 to 4, such as 1 or 2, aldehyde groups and / or hydroxyl groups; Preferably, the compound having at least one aldehyde group and / or hydroxyl group is of biomass origin, such as furfural, hydroxymethylfurfural, vanillin or cinnamaldehyde.

10. The method according to claim 8 or 9, wherein the solvent in step S1 is selected from C1-C6 alkyl alcohol, preferably ethanol, N,N-dimethylformamide or dimethyl sulfoxide.

11. The method according to any one of claims 7 to 10, wherein the mass ratio of the compound having at least one aldehyde group and / or hydroxyl group to water or solvent is 1:1 to 1:15, preferably 1:2 to 1:

10.

12. The method according to any one of claims 7 to 11, wherein the carbonization temperature in step S1 is 100-250°C, preferably 120-200°C; and / or the pressure is 0.1-7 MPa, preferably 0.2-3 MPa; and / or the reaction time is 4-15 h, preferably 6-12 h.

13. according to any one of the methods among the claim 7-12, wherein the acetalization reaction of step S2 is carried out in the presence of one or more catalysts, preferably the catalyst is selected from sodium hydroxide, potassium hydroxide, calcium hydroxide, sodium hydride, sodium carbonate, sodium bicarbonate, sodium acetate, sodium tert-butoxide or sodium ethoxide, preferably sodium hydroxide or potassium hydroxide.

14. The method according to any one of claims 7 to 13, wherein in the acetalization reaction in step S2, the mass ratio of the carbon dots having aldehyde groups on the surface to pyruvic acid is 1:1-1:12, preferably 1:1-1:

10.

15. The method according to any one of claims 7 to 14, wherein the esterification reaction in step S3 is carried out using an esterification reagent selected from the group consisting of compounds of the following formula (Va) or (Vb): R1-OH (Va) or R1-SH (Vb) wherein R1 is as defined in any one of claims 3 to 6.

16. The method according to any one of claims 7 to 15, wherein the esterification reaction in step S3 is carried out in the presence of one or more catalysts, preferably the catalyst is selected from dicyclohexylcarbodiimide (DCC), diisopropylcarbodiimide, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide, 4-dimethylaminopyridine (DMAP), 3-methylpiperidine and triethylamine, preferably dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine (DMAP). 17 . The method according to claim 15 , wherein in the esterification reaction in step S3 , the mass ratio of the carbon-dot pyruvic acid to the esterification reagent is 1:1-1:12, preferably 1:1-1:

10.

18. Use of the pyruvate-type carbon dot photoinitiator obtained according to any one of claims 1 to 6 or according to any one of claims 7 to 17 as a photoinitiator, especially use as a photoinitiator in a UV-VIS LED light source curing system, especially use as a photoinitiator in a light source curing system with a radiation wavelength of 200-750 nm, especially 250-500 nm.

19. A photocurable composition comprising at least one pyruvate-type carbon-dot photoinitiator obtained according to any one of claims 1 to 6 or according to the method of any one of claims 7 to 17.

20. A cured material obtainable from the photocurable composition of claim 19.

21. A method for preparing a photocurable material, comprising the steps of irradiating the photocurable composition according to claim 19 with a light source having a radiation wavelength of 200-750 nm, in particular 250-500 nm, such as a UV-VIS LED light source.

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