Doped semiconductor nanocrystals, preparation methods and applications thereof

Abstract

The present invention relates to a group of nanocrystals comprising a semiconductor, the semiconductor comprising A representing a metal or metalloid in a +III oxidation state and B representing an element in a -III oxidation state, the nanocrystals, on average per nanocrystal, being doped with C atoms selected from transition metals in a +I or +II oxidation state. The present invention also relates to a method for preparing the same and various applications thereof.

Description

Technical Field

[0001] The present invention relates to the technical field of luminescent semiconductor nanocrystals, in particular to doped semiconductor nanocrystals.

[0002] More specifically, the invention proposes nanocrystals based on III-V type semiconductors, weakly doped with transition metals in the +I or +II oxidation state, said nanocrystals optionally coated with a semiconducting shell, the semiconductor of the shell being the same or different from that of the nanocrystal.

[0003] The invention also relates to a method for preparing such nanocrystals and various uses thereof. In fact, the application fields of these nanocrystals include, for example, light emitting diodes, photovoltaic cells, fluorescent labeling of chemical molecules, in particular for anti-counterfeiting purposes, and fluorescent labeling of biomolecules, in particular for biological imaging and detection. Background Art

[0004] In general, nanoparticles have received great attention due to their many possible applications, such as image display devices, information storage, biomarkers, diagnostic imaging, drug delivery, theranostics, photovoltaics, sensors, and catalysts.

[0005] Optical properties required for this purpose are, inter alia, a narrow emission profile (pure color emission), in particular in the red or near infrared range (NIR), a high photoluminescence quantum yield (PLQY) and the absence of overlap between absorption and emission spectra (Stokes shift).

[0006] Furthermore, these optical properties may have additional features depending on the intended application. Thus, for in vivo biological applications, an optical transparency window between 650 nm and 950 nm is required, and for luminescent solar concentrators, the Stokes shift needs to be large.

[0007] Among the nanoparticles that can be used, semiconductor nanocrystals are luminescent materials known for decades and their size is approximately in the range of 1nm to 10nm. These semiconductor nanocrystals are also referred to as "quantum dots". By properly selecting the size and composition of semiconductor nanocrystals, the entire color range of visible light colors, near infrared light colors and ultraviolet light colors can be obtained by semiconductor nanocrystals.

[0008] In general, the optical quality of luminescent materials consisting of semiconductor nanocrystals depends on several parameters, the most important of which are:

[0009] i) the size of the semiconductor nanocrystals, which tunes the emission wavelength;

[0010] ii) the size distribution of semiconductor nanocrystals, which controls the emission linewidth;

[0011] iii) Surface passivation of semiconductor nanocrystals, which is responsible for the fluorescence quantum yield and stability over time. This passivation is achieved by growing a semiconductor shell with a larger band gap around the semiconductor nanocrystal that forms the "core". This system is referred to as "core / shell" in the scientific literature.

[0012] Semiconductor nanocrystals can be binary, such as chalcogenides of cadmium and lead. The latter have some desired optical properties, i.e. narrow emission profiles and high photoluminescence quantum yields in the red or near-infrared range. However, the Stokes shift is not large enough to avoid the loss caused by reabsorption. In addition, the European RoHS Directive (Restriction of Hazardous Substances) is intended to remove the following substances from electrical and electronic equipment (EEE) listed in Europe from July 1, 2006: lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBB), polybrominated diphenyl ethers (PBDE), thereby preventing its application in the preparation of semiconductor nanocrystals.

[0013] There are also nanocrystals of multinary I-III-VI type semiconductors, for example those with CuInS 2. The latter are difficult to use in the envisaged applications because of the very broad emission in the red range and the poorly defined absorption.

[0014] Doped semiconductor nanocrystals have also been described in the prior art.

[0015] Therefore, patent US 9,260,652 [1] generally proposes II-VI type or III-V type semiconductor nanocrystals, which are doped with a dopant that can be a transition metal, and which are optionally coated with a semiconductor shell. In the nanocrystals considered in [1], the content of the dopant is 1 atomic mass % to 50 atomic mass %. In the experimental part of [1], 2 atomic mass % to 20 atomic mass % of copper atoms are introduced into indium phosphide (InP) nanocrystals coated with or not coated with zinc selenide (ZnSe). This introduction causes the emission profile in the red range to be broadened, which is contrary to the desired optical properties.

[0016] Thuy et al. (2013) [2] described a system doped with large amounts (several atomic mass %) of europium ions (Eu 3+ ) is a chemical synthesis of In(Zn)P alloy nanocrystals that are then coated with a zinc sulfide (ZnS) shell. These nanocrystals have a weak dopant emission signal that is only visible when there is a delay between the excitation and detection of photoluminescence.

[0017] In addition, US Pat. No. 9,543,385 [3] describes doping of type I-VII, type II-VI, type III-V, type IV-VI, type III-VI or type IV semiconductor nanocrystals by at least two atoms of a dopant / nanocrystal. In [3], the doping of indium arsenide (InAs) nanocrystals with silver (Ag) is illustrated. From the experimental results obtained, the initial emission signal of the undoped InAs nanocrystals broadens and decreases sharply with the addition of silver. In addition, neither the undoped InAs nanocrystals nor the doped nanocrystals show a large Stokes shift.

[0018] Finally, Sahu et al. (2012) [4] presented an example in which a low-doping regime with a dopant (Ag) close to each II-VI nanocrystal (cadmium selenide (CdSe)) was explored. Under these conditions, the use of a small amount of dopant per nanocrystal (typically 2 or 3 dopants per nanocrystal) resulted in a significant improvement in the phosphorescence efficiency in the band-edge emission, while neither a red shift nor an increase in the Stokes shift (typically 15 nm to 25 nm) was observed.

[0019] In view of the growing interest in semiconductor nanocrystals, the inventors have set themselves the goal of proposing semiconductor nanocrystals that exhibit all the desired optical properties, namely a narrow emission distribution (especially in the red or near-infrared range), a high photoluminescence quantum yield and a large Stokes shift. Summary of the invention

[0020] The present invention makes it possible to achieve the objectives defined by the inventors and therefore relates to semiconductor nanocrystals having all or some of the optical properties sought and listed above.

[0021] In fact, the inventors have demonstrated in a surprising manner that by weakly doping nanocrystals comprising III-V type semiconductors with an average of one transition metal atom in the +I or +II oxidation state per nanocrystal, nanocrystals having interesting optical properties can be obtained, since these nanocrystals have a narrow emission profile (in particular a narrower profile than the same nanocrystals doped with, on average, more than one atom of the same transition metal), and a Stokes shift greater than 50 nm, in particular greater than 75 nm, in particular greater than 100 nm.

[0022] For example, when the weakly doped nanocrystals according to the present invention are silver-doped InP nanocrystals and coated with a ZnS shell, the latter have an adsorption of about 530 nm, an emission in the red / near infrared range of about 700 nm, a line width at a midline height of 70 nm to 80 nm, and a fluorescence quantum yield greater than 20%. It should be noted that the presence of the shell contributes to the efficiency of the photoluminescence without affecting the position or line width of the emission peak.

[0023] These results are surprising and unexpected, especially the results given in reference [4] are surprising and unexpected, and are obtained for II-VI type nanocrystals weakly doped with transition metals in the +I oxidation state. In this prior art, the weak doping did not result in a shift of the emission peak or an increase in the Stokes shift (usually between 15nm and 25nm). In contrast, in the present invention, the emission at the band edge is completely eliminated and a new emission peak appears, which has a Stokes shift of at least 150nm and is far red-shifted, indicating that the emission mechanisms in the two systems are completely different.

[0024] The present invention relates to a set of nanocrystals comprising a semiconductor comprising A representing a metal or metalloid in the +III oxidation state and B representing an element in the -III oxidation state, the nanocrystals being doped, on average per nanocrystal, with C atoms selected from transition metals in the +I or +II oxidation state.

[0025] Advantageously, the nanocrystals according to the invention are in colloidal form.

[0026] The nanocrystals according to the invention comprise a semiconductor comprising A representing a metal or metalloid in the +III oxidation state and B representing an element in the -III oxidation state, this type of semiconductor being known as III-V.

[0027] A, a metal or metalloid in the +III oxidation state, together with B forms the semiconductor included in the nanocrystal according to the present invention, selected from gallium (Ga), indium (In), aluminum (Al) and mixtures thereof.

[0028] B, an element in -III oxidation state, which together with A forms the semiconductor included in the nanocrystal according to the present invention, is selected from antimony (Sb), arsenic (As), phosphorus (P), nitrogen (N) and mixtures thereof.

[0029] The example of the semiconductor of formula AB included in the nanocrystal according to the present invention is GaAs, GaSb, GaN, GaP, InAs, InSb, InN, InP, AlAs, AlSb, AlN, AlP, GaNP, GaNAs, GaPAs, AlNP, AlNAs, AlPAs, InGaAs, InGaSb, InGaN, InGaP, InAlAs, InAlSb, InAlN, InAlP, InNP, InNAs, InPAs, GaAlAs, GaAlSb, GaAlN, GaAlP, GaAlNP, GaAlNAs, GaAlPAs, GaInNP, GaInNAs, GaInPAs, InAlNP, InAlNAs, InAlPAs and mixtures thereof. Particularly, the nanocrystal according to the present invention comprises a semiconductor of formula AB selected from InP, InAs, InGaP and mixtures thereof, and more particularly, the semiconductor is InP.

[0030] Advantageously, the nanocrystals according to the invention consist only of semiconductor of formula AB as defined above, and one C atom per nanocrystal. In a particular embodiment, the doped nanocrystals used in the invention consist only of C:InP.

[0031] Alternatively, nanocrystal according to the present invention, except the semiconductor of formula AB as defined above and one C atom of each nanocrystal, also comprises at least one other element.In this alternative, can refer to the alloy that comprises semiconductor AB as defined above and additional element D.This alloy has formula A (D) B, wherein A and B are as defined above, and D represents the additional element in the metal or metalloid form that is in+II or+III oxidation state.

[0032] Examples of additional elements of formula D included in the nanocrystals according to the invention are in particular barium (Ba), zinc (Zn), calcium (Ca), magnesium (Mg), manganese (Mn), copper (Cu), iron (Fe(II)), lead (Pb(II)), mercury (Hg(II)), cobalt (Co), nickel (Ni), gallium (Ga(III)), aluminum (Al(III)) and mixtures thereof. In particular, the nanocrystals according to the invention include an alloy of formula A(D)B selected from In(Zn)P, In(Ga)P and mixtures thereof, and more particularly, the alloy is In(Zn)P.

[0033] Advantageously, the nanocrystals according to the invention consist only of semiconductors of formula A(D)B as defined above and one C atom per nanocrystal. In a particular embodiment, the nanocrystals according to the invention consist only of C:In(Zn)P.

[0034] The invention is characterized by a very weak doping of nanocrystals comprising a semiconductor comprising A representing a metal or metalloid in the +III oxidation state and B representing an element in the -III oxidation state. In fact, the set of nanocrystals that are the subject of the invention has, on average per nanocrystal, one atom of a dopant C chosen from a transition metal in the +I or +II oxidation state. It should be noted that the dopant C can be in the crystal lattice forming the nanocrystal according to the invention, or on the surface of the latter.

[0035] By techniques known to those skilled in the art, such as mass spectrometry and / or optical emission spectra with high frequency induced plasma, it is easy to verify the weak doping of the nanocrystals as the subject of the present invention. In addition, the weakly doped nanocrystals as the subject of the present invention have specific optical and physicochemical properties. In fact, as given in the following experimental section, the weakly doped nanocrystals as the subject of the present invention have the same X-ray diffraction pattern as the same undoped nanocrystals, and for the nanocrystals, on average, each nanocrystal is doped with more than one C atom as defined above, and the diffraction peak shifts. Regarding the optical properties of the weakly doped nanocrystals as the subject of the present invention, relative to the same undoped nanocrystals, the latter have an emission peak that migrates to the red, a Stokes shift of at least 50nm, particularly at least 75nm, particularly at least 100nm, and a half-height line width of less than 100nm, particularly less than 90nm, particularly less than 80nm, and for the nanocrystals doped with more than one C atom as defined above per nanocrystal on average, a broad emission with a line width generally greater than 100-150nm is obtained.

[0036] Typically, the transition metal C in the +I or +II oxidation state doped with the nanocrystals according to the invention is selected from copper (Cu), silver (Ag), mercury (Hg), gold (Au) and mixtures thereof. Advantageously, the transition metal C in the +I or +II oxidation state doped with the nanocrystals according to the invention is selected from copper (Cu(I) or Cu(II)), silver (Ag(I)), gold (Au(I)) and mixtures thereof.

[0037] In particular, the nanocrystals according to the invention correspond to one of the following formulae: Ag:InP, Au:InP, Cu:InP, Ag:In(Zn)P, Au:In(Zn)P and Cu:In(Zn)P.

[0038] In order to further improve the emission efficiency of nanocrystal according to the present invention, the latter can have the shell that is arranged on its whole or part surface or coats its whole or part surface, and nanocrystal forms the core of this core / shell structure.The outside of this shell comprises such as SiO2 or Al2O3 oxide or semiconductor material or by such as SiO2 or Al2O3 oxide or semiconductor material composition.The latter's composition is identical or different with the composition of the undoped nanocrystal that uses among the present invention.

[0039] The shell of the nanocrystal according to the invention may consist of a single layer or multiple layers (ie a multilayered shell). In the case where the shell consists of only one layer, the outer portion of the shell corresponds to said layer.

[0040] In the case where the shell is composed of multiple layers, the exterior of the shell corresponds to the outer layer of the shell. Within the meaning of the present invention, "outer layer" refers to the shell that is farthest from the core of the nanocrystal and in direct contact with the medium or environment in which the nanocrystal is located. The multilayered shell can include 2 to 10 layers, particularly 2 to 5 layers of different semiconductors.

[0041] In addition, one or more layers of the shell of nanocrystal according to the present invention can have uniform chemical composition, or have different chemical compositions, particularly the chemical composition of gradient form in the same layer.In this case, the outside of the shell will be composed of the outer region of the single layer shell and the outer region of the outer layer of the multilayered shell.

[0042] The outer layer of the shell, and one or more layers between the core and the outer layer of the nanocrystal (if the shell is multilayered) can include or be composed of an oxide or semiconductor material, such as SiO or AlO, the composition of the semiconductor material being the same or different from the composition of the undoped nanocrystal used in the present invention. The semiconductor material can contain a IV group element, a II-VI group compound, a II-V group compound, a III-VI group compound, a III-V group compound, a IV-VI group compound, an I-III-VI group compound, a II-IV-VI group compound, a II-IV-V group compound, an alloy comprising any of the foregoing elements or compounds, and / or a mixture comprising any of the foregoing elements or compounds, the alloy or mixture being able to be a ternary or quaternary alloy or mixture.

[0043] As illustrative and non-limiting examples, the outer layer of the shell and one or more layers between the core and the outer layer of the nanocrystal (when the shell is multilayer) can include or consist of an oxide or semiconductor material selected from the group consisting of SiO2, Al2O3, ZnO, ZnS, ZnSe, ZnTe, CaO, CaS, CaSe, CaTe, SrO, SrS, SrSe, SrTe, BaO, BaS, BaSe, BaTe, CdO, CdS, CdSe, C dTe, MgS, MgSe, MgTe, GaAs, GaN, GaP, GaSe, GaSb, HgO, HgS, HgSe, HgTe, InAs, InN, InP, InGaP, InSb, AlAs, AIN, AlP, AlSb, SnS, SnSe, SnTe, TiN, TiP, TiAs, TiSb, TiO2, PbO, PbS, PbSe, PbTe, Ge, Si, alloys of any of the foregoing, and / or mixtures of any of the foregoing.

[0044] In a specific embodiment, the nanocrystals according to the present invention have a shell, the outer portion of which comprises the formula ZnS 1-x E x A semiconductor of , wherein E represents an element in -II oxidation state and x is a decimal number such that 0≤x<1. E is an element in -II oxidation state, which is in particular selected from oxygen (O), selenium (Se), tellurium (Te) and mixtures thereof.

[0045] More particularly, the nanocrystal according to the present invention has a core and a shell, the core comprising or consisting of a semiconductor material corresponding to any of the following formulae: Ag:InP, Au:InP, Cu:InP, Ag:In(Zn)P, Au:In(Zn)P and Cu:In(Zn)P, the shell comprising a semiconductor material of the formula ZnS 1-x E x Semiconductor materials or ZnS 1-x E x A semiconductor material composition of , wherein E and x are as defined above.

[0046] Even more particularly, the nanocrystals according to the present invention have a core and a shell, wherein the core comprises or consists of a semiconductor material corresponding to any of the following formulae: Ag:InP, Au:InP, Cu:InP, Ag:In(Zn)P, Au:In(Zn)P and Cu:In(Zn)P, and the shell comprises or consists of a semiconductor material of the formula ZnS, ZnO, ZnSe or ZnTe and mixtures thereof.

[0047] The core of the weakly doped nanocrystal according to the invention which is not coated with a shell, ie the weakly doped nanocrystal according to the invention, has an average diameter of between 1 nm and 10 nm, in particular between 1.5 nm and 8 nm, in particular between 2 nm and 6 nm.

[0048] When there is a shell, the shell of the weakly doped nanocrystal according to the present invention has an average thickness between 0.3nm and 6nm, particularly between 0.5nm and 4nm, particularly between 1nm and 2nm. Therefore, the core / shell type weakly doped nanocrystal according to the present invention has an average diameter less than 15nm, particularly less than 12nm, particularly less than 10nm.

[0049] The invention also relates to a method for preparing a set of weakly doped nanocrystals as defined above, said nanocrystals optionally being partially or completely coated with a shell as previously defined.

[0050] Advantageously, the method for preparing the set of weakly doped nanocrystals as defined above, which is the subject of the present invention, comprises the following steps:

[0051] a) preparing nanocrystals comprising a semiconductor comprising A representing a metal or metalloid in a +III oxidation state and B representing an element in a -III oxidation state, and optionally D representing a metal or metalloid in a +II or +III oxidation state;

[0052] b) mixing the nanocrystals prepared in step (a) with a precursor of C at a temperature T b Next contact period D b , so that nanocrystals comprising a semiconductor can be obtained, wherein C is selected from a transition metal in a +I or +II oxidation state, the semiconductor comprises A representing a metal or metalloid in a +III oxidation state and B representing an element in a -III oxidation state and optionally D representing a metal or metalloid in a +II oxidation state, the above nanocrystals, on average per nanocrystal, being doped with C atoms selected from a transition metal in a +I or +II oxidation state;

[0053] c) optionally coating all or part of the surface of the nanocrystals comprising a semiconductor obtained in step (b) with a shell, the semiconductor comprising A representing a metal or metalloid in a +III oxidation state and B representing an element in a -III oxidation state, the nanocrystals, on average per nanocrystal, being doped with C atoms selected from transition metals in a +I or +II oxidation state, the outer part of the shell comprising or consisting of an oxide or semiconductor material.

[0054] In step (a) of the method according to the invention, any technique known to a person skilled in the art may be used to prepare nanocrystals comprising a semiconductor comprising A representing a metal or metalloid in a +III oxidation state and B representing an element in a -III oxidation state, and optionally D representing a metal or metalloid in a +II or +III oxidation state.

[0055] Advantageously, step (a) of the method according to the invention comprises the following sub-steps:

[0056] a1) At temperature T a1 preparing a solution comprising at least one precursor of A and optionally at least one precursor of D;

[0057] a2) heating the mixture obtained in sub-step (a1) from a temperature T a1 Increase to a temperature greater than T a1 Temperature T a2 ;

[0058] a3) obtaining and maintaining the temperature T in sub-step (a2) a2 introducing at least one precursor of B into the mixture; and

[0059] a4) optionally purifying nanocrystals comprising a semiconductor comprising A representing a metal or metalloid in a +III oxidation state and B representing an element in a -III oxidation state, and optionally D representing a metal or metalloid in a +II or +III oxidation state.

[0060] Within the meaning of the present invention, the precursor of A used in sub-step (a1) of the above-mentioned method is selected from the group consisting of: precursors of indium, precursors of gallium, precursors of aluminum and mixtures thereof. All precursors of indium, aluminum and gallium known to those skilled in the art (in particular precursors in liquid or solid form) can be used in the present invention.

[0061] Advantageously, the precursor of A is selected from salts of A, halides of A, oxides of A and organometallic compounds of A. More particularly, "organometallic compounds of A" are defined as trisubstituted compounds of A, carboxylates of A or phosphonates of A.

[0062] "Trisubstituted compounds of A" are defined within the meaning of the present invention as compounds of formula (R1)3A, wherein each R1, identical or different, represents a hydrocarbon group having 1 to 20 carbon atoms, such as an alkyl, alkenyl, alkoxy, aryl or aryloxy group.

[0063] "Carboxylate of A" is defined in the meaning of the present invention as a compound of formula (R2COO)3A, wherein each R2, identical or different, represents a hydrocarbon group having 1 to 20 carbon atoms, such as an alkyl, alkenyl, alkoxy, aryl or aryloxy group.

[0064] "Phosphonates of A" are defined within the meaning of the present invention as compounds of the formula [R3-P(OR4)(OR5)O]3A, wherein

[0065] each R3, identical or different, represents a hydrocarbon group having 1 to 20 carbon atoms, such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group;

[0066] each R4, the same or different, represents a hydrogen atom or a hydrocarbon group of 1 to 20 carbon atoms (such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group), and

[0067] Each R5, which is the same or different, represents a hydrogen atom or a hydrocarbon group of 1 to 20 carbon atoms (such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group).

[0068] Within the meaning of the present invention and unless otherwise stated, an "alkyl group" is defined as an optionally substituted straight-chain, branched or cyclic alkyl group having 1 to 20 carbon atoms, especially 1-15 carbon atoms, in particular 1 to 10 carbon atoms.

[0069] Within the meaning of the present invention, "alkenyl" is defined as an optionally substituted straight-chain, branched or cyclic alkenyl group having 2 to 30 carbon atoms, particularly 2 to 25 carbon atoms, in particular 2 to 20 carbon atoms.

[0070] An "alkoxy group" within the meaning of the present invention is defined as an oxygen atom substituted by an alkyl group as defined above.

[0071] In the meaning of the present invention, an "aryl group" is defined as an optionally substituted monocyclic or polycyclic aromatic group having 6 to 20 carbon atoms, especially 6 to 14 carbon atoms, in particular 6 to 8 carbon atoms.

[0072] An "aryloxy group" within the meaning of the present invention is defined as an oxygen atom substituted by an aryl group as defined above.

[0073] In the meaning of the present invention, "optionally substituted" is defined as a group which is substituted by one or more groups selected from alkyl groups, alkoxy groups, halogen, hydroxy, cyano, trifluoromethyl or nitro.

[0074] "Halogen" within the meaning of the present invention is defined as fluorine, chlorine, bromine or iodine.

[0075] When A is indium, examples of precursors of A that can be used within the meaning of the present invention may include indium trichloride, triethylindium, indium triacetate, indium tri(acetyl-acetonate), indium trioctanoate, indium tristearate, indium trilaurate, indium tripalmitate, indium trimyristate, indium trioleate, and mixtures thereof.

[0076] Within the meaning of the present invention, the precursor of D optionally used in substep (a1) of the process is selected from the group consisting of salts of D, halides of D, oxides of D and organometallic compounds of D. More particularly, "organometallic compounds of D" are defined as disubstituted compounds of D, carboxylates of D or phosphonates of D.

[0077] "Disubstituted compounds of D" in the meaning of the present invention are defined as compounds of the formula (R6)2D, wherein each R6, identical or different, represents a hydrocarbon group having 1 to 20 carbon atoms, such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group.

[0078] "Carboxylate of D" is defined within the meaning of the present invention as a compound of formula (R7COO)2D, in which each R7, identical or different, represents a hydrocarbon group having 1 to 20 carbon atoms, such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group.

[0079] "Phosphonates of D" are defined within the meaning of the present invention as being of the formula [R8-P(OR9)(OR 10 )O]2D compound, wherein

[0080] each R8, the same or different, represents a hydrocarbon group having 1 to 20 carbon atoms, such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group;

[0081] each R9, which is the same or different, represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms (such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group), and

[0082] Each R 10 , which are the same or different, represent a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms (such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group).

[0083] The alkyl group, alkoxy group, aryl group and aryloxy group are as defined for the precursor of A. However, for the precursor of D, the alkenyl group is an optionally substituted linear, branched or cyclic alkenyl group having 2 to 20 carbon atoms.

[0084] The solution comprising at least one precursor of A and optionally at least one precursor of D, ie the solution prepared in substep (a1) of the process according to the invention, comprises an organic solvent.

[0085] Advantageously, the organic solvent is an alkane, a secondary or tertiary amine, or an alkene having a T a2 of a boiling point, i.e. having a boiling point higher than the temperature selected for steps (a2) and (a3) ​​of the process according to the invention.

[0086] "Alkanes" are defined within the meaning of the present invention as optionally substituted linear, branched or cyclic alkanes having 1 to 40 carbon atoms, in particular 10 to 35 carbon atoms, in particular 14 to 30 carbon atoms. For example, alkanes that may be used within the meaning of the present invention are hexadecane and squalane (C 30 H 62 ).

[0087] "Secondary or tertiary amines" are defined within the meaning of the present invention as especially dialkylamines and trialkylamines, the alkyl groups of which comprise 4 to 24 carbon atoms, especially 8 to 20 carbon atoms. For example, a secondary (tertiary) amine that may be used within the meaning of the present invention is dioctylamine (trioctylamine), each alkyl chain of which comprises 8 carbon atoms.

[0088] "Olefins" within the meaning of the present invention are defined as optionally substituted linear, branched or cyclic olefins having 2 to 40 carbon atoms, especially 10 to 35 carbon atoms, in particular 14 to 30 carbon atoms. For example, an olefin that may be used within the meaning of the present invention is 1-octadecene (C 18 H 36 ) or squalene (C 30 H 50 ).

[0089] The solvent used more particularly for preparing the precursor solution in sub-step (a1) of the process according to the invention is 1-octadecene (C 18 H 36 ).

[0090] Furthermore, the solution prepared in sub-step (a1) of the method of the present invention may include, in addition to the organic solvent, a component selected from the group consisting of a stabilizer for the surface of the nanocrystals, a primary amine, and one of mixtures thereof.

[0091] In fact, the solution prepared in sub-step (a1) may also contain a stabilizer for the surface of the nanocrystals. "Stabilizer for the surface of the nanocrystals" (also called "stabilizing ligand") is defined within the meaning of the present invention as an organic molecule that binds to the surface of the nanocrystals and thus prevents the nanocrystals from aggregating. Within the meaning of the present invention, any stabilizer known to a person skilled in the art may be used. Advantageously, the stabilizer is selected from thiols, especially aliphatic thiols; alkyl phosphines, especially tri(alkyl) phosphines, wherein the alkyl group comprises 4 to 12 carbon atoms; alkyl phosphine oxides and phosphonic acids, wherein the alkyl group comprises 4 to 12 carbon atoms; carboxylic acids, especially aliphatic or olefinic carboxylic acids, such as lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid or mixtures thereof.

[0092] Within the meaning of the present invention, an aliphatic thiol has the formula C n H 2n+1 -SH, wherein n represents an integer having a value between 1 and 25, in particular between 5 and 20, in particular between 8 and 18. Aliphatic mercaptans that can be used within the meaning of the present invention may include octyl mercaptan (n=8), octadecanethiol (n=18), dodecanethiol (n=12) and mixtures thereof.

[0093] The stabilizer used more particularly for the preparation of the precursor solution during substep (a1) of the process according to the invention is dodecanethiol (n=12).

[0094] Finally, the solution prepared in substep (a1) may also contain a primary amine. Advantageously, the primary amine is an alkylamine or an alkenylamine, wherein the alkyl group or alkenyl group comprises 4 to 24 carbon atoms, in particular 8 to 20 carbon atoms. For example, primary amines that can be used within the meaning of the present invention are octylamine, dodecylamine, hexadecylamine (HDA) and oleylamine.

[0095] The primary amine used more particularly for preparing the precursor solution during substep (a1) of the process according to the invention is oleylamine.

[0096] In a particular embodiment, the solution prepared in substep (a1) of the method according to the invention comprises at least one precursor of A as defined above and optionally one precursor of D as defined above, as well as 1-octadecene (organic solvent), dodecanethiol (n=12) (stabilizer) and oleylamine (primary amine).

[0097] In the solution prepared during substep (a1) of the process, the concentration of the precursor of A and, if present, the precursor of D is between 0.01 mol / L and 0.2 mol / L, in particular between 0.02 mol / L and 0.1 mol / L, in particular between 0.03 mol / L and 0.05 mol / L.

[0098] Advantageously, during sub-step (a1), the temperature of the solution T a1 Below 50°C, in particular below 40°C, in particular below 30°C. More particularly, the solution during sub-step (a1 ) is at ambient temperature. "Ambient temperature" is defined as a temperature of 20°C ± 5°C.

[0099] Sub-step (a1) of the method of the present invention is advantageously carried out under stirring. Different methods known to those skilled in the art can be used to stir the mixture used in sub-step (a1) of the method of the present invention. For example, a stirrer, a magnetic bar, an ultrasonic bath or a homogenizer can be used to stir the mixture.

[0100] Finally, substep (a1) of the process according to the invention can be combined with a flow of an inert gas, in particular a flow of argon, nitrogen or a mixture thereof.

[0101] Sub-step (a2) of the method of the present invention involves heating the mixture prepared in sub-step (a1) to a temperature higher than the initial temperature of the mixture (i.e., the temperature T as previously described). a1 )T a2 .

[0102] Advantageously, the temperature of the solution T a2 Below 300° C., in particular between 100° C. and 300° C., in particular between 150° C. and 280° C. More particularly, the temperature T a2 About 220° C. “A temperature of about 220° C.” is defined as a temperature of 220° C.±20° C.

[0103] Thus, once the solution has been prepared in sub-step (a1), the latter is brought from a temperature T a1 Raise to temperature T a2 This can be increased linearly or at least with an intermediate step. This can take place in a particularly advantageous manner in a linear manner, in particular with an increase of 5° C. to 80° C. per minute, in particular with an increase of 20° C. to 60° C. per minute, more particularly with an increase of 30° C. to 50° C. per minute.

[0104] Sub-step (a3) ​​of the process of the invention comprises introducing at least one precursor of B in liquid or solid form into a solution comprising at least one precursor of A and optionally a precursor of D, and maintaining the resulting mixture at a temperature T defined above. a2 During this step, the formation and growth of nanocrystals comprising semiconductor AB and optionally element D takes place.

[0105] Within the meaning of the present invention, the precursor of B used is selected from the group consisting of: precursors of antimony, precursors of arsenic, precursors of phosphorus, precursors of nitrogen and mixtures thereof. All precursors of antimony, arsenic, phosphorus and nitrogen known to the person skilled in the art, in particular in liquid or solid form, can be used in the present invention.

[0106] Advantageously, the precursor of B used in the present invention is of the formula B(F(R 11 )3)3, the compound of formula B (R 12 )3 or a compound of formula B(N(H)R 13 )3, wherein:

[0107] Each F is selected from the group consisting of silicon (Si), germanium (Ge), and tin (Sn);

[0108] Each R 11 , which are the same or different, are optionally substituted linear, branched or cyclic alkyl groups having 1 to 10 carbon atoms, especially 1 to 6 carbon atoms, in particular 1 to 3 carbon atoms;

[0109] Each R 12 , which are the same or different, are a hydrogen atom, a halogen such as chlorine (Cl), bromine (Br), iodine (I) or fluorine (F), or an optionally substituted linear, branched or cyclic alkyl group having 1 to 10 carbon atoms, especially 1 to 6 carbon atoms, in particular 1 to 3 carbon atoms; and

[0110] Each R 13 , which are the same or different, are a hydrogen atom, an optionally substituted straight-chain, branched or cyclic alkyl group having 1 to 10 carbon atoms, especially 1 to 6 carbon atoms, in particular 1 to 3 carbon atoms, or an optionally substituted straight-chain, branched or cyclic alkenyl group having 2 to 30 carbon atoms, especially 2 to 25 carbon atoms, in particular 2 to 20 carbon atoms.

[0111] In particular, the precursor of B, particularly preferably the precursor of phosphorus, has the general formula B(N(H)R 13 )3, where each R 13 , identical or different, are hydrogen atoms or alkyl or alkenyl groups as defined above. More particularly, the general formula of the precursor of B, particularly preferably the precursor of phosphorus, is B(N(H)R 13 )3, where each R 13 is an alkenyl group as defined above. A specific example of such a precursor of B, especially a phosphorus precursor, is of the formula P(N(H)C 18 H 35 )3 of trioleyl phosphine.

[0112] In the solution obtained during substep (a3) ​​of the above method, the concentration of the precursor of B is between 0.05 mol / L and 0.2 mol / L, in particular between 0.10 mol / L and 0.15 mol / L, in particular between 0.11 mol / L and 0.13 mol / L.

[0113] In the optional sub-step (a4) of the method according to the present invention, the nanocrystals obtained are purified from the reaction mixture, that is, the nanocrystals are separated from the reaction mixture. Those skilled in the art know the different techniques for using a precipitation step, a dilution step and / or a filtering step to carry out the above-mentioned purification. The techniques used in the prior art for purifying luminescent nanocrystals can be used in the context of the sub-step (a4) of the method of the present invention.

[0114] Within the meaning of the present invention, the precursor of C used during step (b) of the process is chosen from the group consisting of precursors of silver, precursors of copper, precursors of gold, precursors of mercury and mixtures thereof. All precursors of silver, copper, gold and mercury known to the person skilled in the art, in particular in liquid or solid form, can be used in the present invention.

[0115] Advantageously, the precursor of C is selected from the group consisting of: salts of C, halides of C, oxides of C and organometallic compounds of C. More particularly, "organometallic compounds of C" are more particularly defined as substituted C compounds, C carboxylates or C phosphonates.

[0116] "Substituted compounds of C" are defined within the meaning of the present invention as compounds of the formula (R 15 )C, wherein R 15 represents a hydrocarbon group having 1 to 20 carbon atoms, such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group.

[0117] Within the meaning of the present invention, a "carboxylate of C" is defined as a 16 COO)C, wherein R 16 represents a hydrocarbon group having 1 to 20 carbon atoms, such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group.

[0118] Within the meaning of the present invention, a "phosphonate of C" is defined as a 17 -P(OR 18 )(OR 19 )O]C compound, wherein

[0119] R 17 represents a hydrocarbon group having 1 to 20 carbon atoms, such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group;

[0120] R18 represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms (such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group), and

[0121] R 19 represents a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms (such as an alkyl group, an alkenyl group, an alkoxy group, an aryl group or an aryloxy group).

[0122] The alkyl, alkoxy, aryl and aryloxy groups are as defined for the precursors of A, and the alkenyl groups are as defined for the precursors of D.

[0123] Advantageously, the precursor of C used is C stearate.

[0124] Step (b) of the process according to the invention can be carried out by contacting the precursor of C with a solution comprising the nanocrystals obtained from substep (a3) ​​or with a solution in which the purified nanocrystals obtained after substep (a4) have been placed in suspension. Advantageously, the solution in which the purified nanocrystals have been placed in suspension comprises an organic solvent as defined above and optionally a primary amine as defined above.

[0125] As a reminder, the temperature T during step (b) must be b and period D b The temperature T used during step (b) is selected so that the nanocrystals, on average per nanocrystal, are doped with C atoms, in particular with the amount of C precursor and the amount of nanocrystals being varied. As mentioned above, the person skilled in the art can easily determine or predetermine the temperature T used during step (b). b and period D b , in particular determined or predetermined by techniques such as mass spectrometry and / or optical emission spectroscopy with high-frequency induced plasma, or based on the optical and physicochemical properties of the weakly doped nanocrystals that are the subject of the present invention.

[0126] At temperature T b The contact temperature T b Advantageously lower than the temperature T used during nanocrystal preparation a2 Typically, the temperature T b Between 100° C. and 200° C., in particular about 130° C. (ie 130° C.±20° C.). Thus, when the precursor of C comes into contact with the solution containing nanocrystals obtained at the end of substep (a3), the temperature of the solution is close to the temperature T a2 It is recommended to adjust the temperature of the solution to a temperature less than or equal to T before any contact. bAlternatively, if the precursor of C is contacted with a solution in which the purified nanocrystals have been placed back into suspension, the solution is treated to a temperature T before or after the contact. b is suitable.

[0127] The contact period D between the nanocrystal and the precursor of C b Typically it is less than 2 h, in particular comprised between 5 min and 50 min.

[0128] During step (b), the precursor of C can be used in solid form or in liquid form. In the latter case, it is advantageously used in a solution in an organic solvent as defined above, and optionally in the presence of a primary amine or a carboxylic acid as defined above. The organic solvent of the solution containing the precursor of C can be the same or different from the organic solvent of the solution containing the nanocrystals. In a specific embodiment, the organic solvent of the solution containing the precursor of C and the organic solvent of the solution containing the nanocrystals are the same. The solvent is especially octadecene. If present, the primary amine of the solution containing the precursor of C can be the same or different from the primary amine of the solution containing the nanocrystals. In a specific embodiment, the primary amine of the solution containing the precursor of C and the primary amine of the solution containing the nanocrystals are the same. The primary amine is especially oleylamine. In a more particular embodiment, in the solution containing the precursor of C, the volume of the organic solvent is equal to the volume of the primary amine.

[0129] The concentration of the precursor of C in the solution containing it is between 10 mmol / L and 100 mmol / L, in particular between 15 mmol / L and 50 mmol / L, in particular between 25 mmol / L and 35 mmol / L.

[0130] Thus, once contact is made, the concentration of the precursor of C in the resulting solution is between 0.2 mmol / L and 2.5 mmol / L, in particular between 0.5 mmol / L and 1.8 mmol / L, in particular between 0.75 mmol / L and 1.5 mmol / L. The "resulting solution" is defined as corresponding to a mixture between a solution containing nanocrystals and a solution containing a precursor of C, or a solution containing nanocrystals in which a precursor of C has been dissolved.

[0131] The weakly doped nanocrystals obtained from step (b) may be purified prior to step (c). In this case, all considerations for sub-step (a4) apply mutatis mutandis to this optional purification step.

[0132] Step (c) of the method according to the invention is a standard step in the field of core / shell nanocrystals. In fact, according to the chemical nature of the shell to be produced, a person skilled in the art will know how to select the most suitable precursor and obtain the operating conditions for the growth of such a shell.

[0133] Step (c) of the process according to the invention can be carried out by contacting one or more precursors of the shell with a solution containing the weakly doped nanocrystals obtained at the end of step (b) or a solution in which the weakly doped nanocrystals purified after step (b) are resuspended.

[0134] Alternatively, one or more precursors of the shell may be introduced into the mixture for preparing the core (i.e., for preparing the nanocrystal). In particular, one or more precursors of the shell may be present in a solution prepared during step (a1) as defined above. In this alternative, step (c) comprises raising the mixture obtained at the end of step (b) to a temperature above T b Temperature T c Typically, the temperature T c Below 300°C, in particular between 100°C and 300°C, in particular between 150°C and 280°C.

[0135] In a specific embodiment, the nanocrystal according to the present invention has a shell, the outer portion of which comprises the formula ZnS 1-x E x A semiconductor of , wherein E represents an element in the -II oxidation state and x is a decimal number such that 0 ≤ x < 1. Among the schemes that can be used to make such a shell, those described in the international application WO 2010 / 052221 [5] can be cited, including the parts related to the prior art and the parts related to the actual invention.

[0136] The invention relates to the use of nanocrystal assemblies according to the invention or which can be prepared by the method according to the invention in light-emitting diodes, photovoltaic cells, luminescence concentrators for solar cells and for the fluorescent labeling of chemical or biological molecules.

[0137] Further characteristics and advantages of the invention will become apparent to a person skilled in the art from the following examples, given by way of illustration and not limitation, with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0138] [ Figure 1 ] shows the UV-Vis and photoluminescence adsorption spectra of InP nanocrystals with statistically one dopant (Ag) per nanocrystal. Line width at median height: 70 nm.

[0139] [ Figure 2] shows the photoluminescence spectra of undoped InP nanocrystals ("core"), or InP nanocrystals doped with silver after 15 minutes of doping ("Ag-15"), or InP nanocrystals doped with silver after 30 minutes of doping ("Ag-30"), or InP nanocrystals doped with silver after 30 minutes of doping and then coated with ZnS shell ("AgCS"). Line width at median height: 72nm for AgCS.

[0140] [ Figure 3 ] shows the evolution of the photoluminescence spectrum (excitation wavelength: 400 nm) as a function of the dopant dosage (ratios Ag:In:Ag125=0.0125; Ag250=0.025; Ag500=0.05; Ag1000=0.1; Ag2000=0.2).

[0141] [ Figure 4 ] shows X-ray diffraction patterns of undoped InP nanocrystals ("no dopant"), or InP nanocrystals prepared with silver in a ratio of Ag:In=1:40 (i.e., 2.5%) ("Ag250"), or InP nanocrystals prepared with silver in a ratio of Ag:In=1:20 (i.e., 5%) ("Ag500").

[0142] [ Figure 5 ] shows a transmission electron microscopy image of weakly doped core / shell nanocrystals Ag:In(Zn)P / ZnS with an average of one dopant atom per nanocrystal. DETAILED DESCRIPTION

[0143] I. Materials and methods

[0144] I A Preliminary Note

[0145] All syntheses were performed in an inert atmosphere using argon.

[0146] For characterization, UV-visible absorption spectra were measured on a HP8420A spectrometer (spectral range at the following wavelengths: 190 nm to 820 nm, resolution 2 nm), and photoluminescence spectra were obtained with a HORIBA Fluorolog iHR320 spectrometer. For these spectral measurements, a colloidal solution of nanocrystals diluted in hexane was placed in a small quartz cuvette with a light path of 1 cm. The fluorescence quantum yield at ambient temperature was obtained by comparing the emission intensity (by spectral integration) of a dispersion of nanocrystals in hexane and a solution of Rhodamine 6G in ethanol, both solutions having the same optical density (<0.03) at the excitation wavelength (490 nm). X-ray diffraction patterns were obtained on an analytical instrument from Philips using a copper source at 40 kV and 40 mA. Transmission electron microscopy images were obtained with a FEI Polara microscope.

[0147] Except for zinc distearate (Riedel de All products except ) were purchased from Sigma-Aldrich and used as received: indium chloride (InCl3, purity 99.999%), zinc distearate (purity 90%), dodecanethiol (purity ≥98%), 1-octadecene (purity 90%), tris(dimethylamino)phosphine (PNMe2)3 (97%), oleylamine (OLA, ≥98%), NaOH, stearic acid, and AgNO3.

[0148] IB Preparation of phosphorus precursor (trioleyl phosphine, P(OLA)3)

[0149] To prepare a solution of P(OLA)3, tri(dimethylamino)phosphine (PNMe2)3 (1.3 mL, 7.2 mmol) was added to oleylamine (OLA, 7.1 mL, 21.6 mmol) and the mixture was stirred under primary vacuum (10 -2 -10 -1 mbar) and heated at 70° C. for 10 h with stirring. The obtained solution must be stored and used under an inert atmosphere (eg argon or nitrogen).

[0150] IC Preparation of Silver Stearate (AgSt):

[0151] 1 mL of NaOH aqueous solution (1 M) was added to 100 mL of stearic acid aqueous solution (0.15 M) and heated to 80° C. While stirring, 17 mL of AgNO3 aqueous solution (1 M) was added. The formed white precipitate was filtered and washed three times with 50 mL of distilled water, and then dried in an oven at 50° C.

[0152] ID Synthesis of Ag:In(Zn)P Phosphorus Nanocrystals (Ag500)

[0153] Indium chloride (InCl3, 0.3 mmol), zinc distearate (ZnSt2, 0.3 mmol), oleylamine (OLA, 1 mmol), 1-dodecanethiol (1-DDT, 0.3 mmol) and 1-octadecene (ODE, 25 mL, 8 mL) were mixed in a three-necked flask and purged under vacuum for 30 min.

[0154] The flask was then filled with argon, the reaction solution was heated to 220°C, and trioleylphosphine (P(OLA)3, 1.2 mmol) was quickly injected. After 3 min, the reaction solution was cooled.

[0155] Silver stearate (AgSt, 15 μmol) in a mixture of octadecene and oleylamine was added dropwise to the reaction solution containing In(Zn)P nanocrystals at 130° C. within 30 min.

[0156] IE Synthesis of Core / Shell Ag:In(Zn)P / ZnS Nanocrystals

[0157] After doping for 30 min, the reaction solution was heated to 220 °C again to allow the shell to grow for 1 h.

[0158] IF Other syntheses for comparison

[0159] Corresponds to Figure 3 and Figure 4 Synthesis of Ag250:

[0160] The procedure was the same as described for weakly doped Ag:In(Zn)P nanocrystals (Ag500), but using 7.5 μmol of silver stearate in the mixture of ODE and OLA (2 mL, 1:1 vol:vol).

[0161] Corresponds to Figure 3 Synthesis of Ag125 / Ag1000 / Ag2000:

[0162] The procedure was the same as described for weakly doped Ag:In(Zn)P nanocrystals (Ag500), but using 3.75 / 30 / 60 μmol silver stearate in a mixture of ODE and OLA (2 mL, 1:1 vol:vol).

[0163] II. result

[0164] II.A. Optical properties

[0165] Figure 1 and Figure 2 Shown are the UV-Vis absorption and photoluminescence spectra of the samples obtained following the methods described in Sections IC and ID. Figure 1Absorption and photoluminescence spectra of Ag:In(Zn)P / ZnS core / shell nanocrystals weakly doped with an average of one atom of dopant per nanocrystal (excitation wavelength: 400 nm) are shown. The exciton peak in the 550 nm region is visible in the UV-visible absorption spectrum, and the photoluminescence spectrum shows a narrow emission line centered around 700 nm.

[0166] Figure 2 Shown are the evolution of the photoluminescence spectra (excitation wavelength: 400 nm) before doping (“core”), during contact of the dopant with the nanocrystal core (15:15 min, 30:30 min), and after growth of the ZnS shell (“AgCS”).

[0167] Figure 3 The evolution of the photoluminescence spectrum (excitation wavelength: 400 nm) as a function of the amount of dopant used (ratios Ag:In:Ag125=0.0125; Ag250=0.025; Ag500=0.05; Ag1000=0.1; Ag2000=0.2) is shown. For all samples, except (90 min) (referred to as "Ag500 90 min"), the contact time between the dopant and the In(Zn)P nanocrystals was 30 min. It can be seen that i) the photoluminescence intensity is maximum for the Ag:In ratio of 0.05 used (Ag500); ii) the extension of the contact time from 30 min to 90 min leads to a decrease in the photoluminescence intensity.

[0168] II.B. Physicochemical analysis by X-ray diffraction

[0169] Figure 4 The X-ray diffraction patterns of powders of control samples (ie, undoped samples) and samples prepared according to the methods described in ID and IF are provided in .

[0170] For nanocrystals doped statistically with 1 dopant per nanocrystal (Ag250, Ag500), the X-ray diffraction pattern corresponds to that of a control sample without dopant.

[0171] Figure 5 The transmission electron microscopy picture shown shows weakly doped Ag:In(Zn)P / ZnS core / shell nanocrystals with an average of one dopant atom per nanocrystal. The average size is 4.3±0.4 nm.

[0172] References

[0173] [1] Patent US 9,260,652 published on February 16, 2016.

[0174] [2] Thuy et al., 2013, Dalton Trans., vol. 42, pp. 12606-12610.

[0175] [3] Patent US 9,543,385 published on January 10, 2017.

[0176] [4] Sahu et al., Nano Lett., 2012, vol. 12, pp. 2587–2594.

[0177] [5] International application WO 2010 / 052221 published on May 14, 2010.

Claims

1. A group of nanocrystals comprising a semiconductor comprising A representing a metal or metalloid in a +III oxidation state and B representing an element in a -III oxidation state, the nanocrystals, on average per nanocrystal, being doped with one C atom selected from a transition metal in a +I or +II oxidation state.

2. The nanocrystal group according to claim 1, characterized in that A, which together with B forms the metal or metalloid in the +III oxidation state of the semiconductor included in the nanocrystal according to the present invention, is selected from gallium (Ga), indium (In), aluminum (Al) and mixtures thereof.

3. The nanocrystal group according to claim 1 or 2, characterized in that: The element B in -III oxidation state which together with A forms the semiconductor included in the nanocrystal according to the present invention is selected from antimony (Sb), arsenic (As), phosphorus (P), nitrogen (N) and mixtures thereof.

4. The nanocrystal group according to claim 1 or 2, characterized in that: Each nanocrystal, in addition to the semiconductor of formula AB and one C atom, comprises at least one further element D in the form of a metal or metalloid in the +II or +III oxidation state.

5. The nanocrystal group according to claim 1 or 2, characterized in that: The transition metal C in the +I or +II oxidation state doping the nanocrystals is selected from copper (Cu), silver (Ag), mercury (Hg), gold (Au) and mixtures thereof.

6. The nanocrystal group according to claim 1 or 2, characterized in that: The nanocrystals correspond to any one of the following formulas: Ag:InP, Au:InP, Cu:InP, Ag:In(Zn)P, Au:In(Zn)P, and Cu:In(Zn)P.

7. The nanocrystal group according to claim 1 or 2, characterized in that: The nanocrystal has a shell disposed on or covering all or part of the surface of the nanocrystal.

8. The nanocrystal group according to claim 1 or 2, characterized in that: The nanocrystal according to the present invention has a core and a shell, wherein the core comprises a semiconductor material corresponding to any one of the following formulas or is composed of a semiconductor material corresponding to any one of the following formulas Composition: Ag:InP, Au:InP, Cu:InP, Ag:In(Zn)P, Au:In(Zn)P and Cu:In(Zn)P, the shell comprises a ZnS having the formula containing E and x 1-x E x Semiconductor materials, or composed of the formula ZnS containing E and x 1-x E x wherein E represents an element in a -II oxidation state, and x is a decimal number such that 0≤x<1.

9. A method for preparing a group of nanocrystals as defined in any one of claims 1 to 8, the method comprising the steps of: a) preparing nanocrystals comprising a semiconductor comprising A representing a metal or metalloid in a +III oxidation state and B representing an element in a -III oxidation state and optionally D representing a metal or metalloid in a +II or +III oxidation state; b) mixing the nanocrystals prepared in step (a) with a precursor of C at a temperature T b Next contact for a period of time D b , making it possible to obtain nanocrystals comprising a semiconductor and optionally D representing a metal or metalloid in the +II oxidation state, C being chosen from said transition metal in the +I or +II oxidation state, said semiconductor comprising A representing a metal or metalloid in the +III oxidation state and B representing an element in the -III oxidation state, said nanocrystals being doped, on average per nanocrystal, with one C atom chosen from said transition metal in the +I or +II oxidation state; c) optionally coating all or part of the surface of the nanocrystal comprising a semiconductor obtained in step (b) with a shell, the semiconductor comprising A representing a metal or metalloid in a +III oxidation state and B representing an element in a -III oxidation state, the nanocrystals being doped, on average per nanocrystal, with one C atom, the exterior of the shell comprising or consisting of an oxide or semiconductor material.

10. The method according to claim 9, characterized in that The step (a) of the method according to the present invention comprises the following sub-steps: a1) At temperature T a1 preparing a solution comprising at least one precursor of A and optionally at least one precursor of D; a2) heating the mixture obtained in sub-step (a1) from a temperature T a1 Raised above temperature T a1 Temperature T a2 ; a3) obtaining and maintaining the temperature T in sub-step (a2) a2 introducing at least one precursor of B into the mixture; and a4) optionally purifying nanocrystals comprising a semiconductor comprising A representing a metal or metalloid in the +III oxidation state and B representing an element in the -III oxidation state and optionally D representing a metal or metalloid in the +II or +III oxidation state.

11. The method according to claim 10, characterized in that The precursor of A is selected from the group consisting of a salt of A, a halide of A, an oxide of A and an organometallic compound of A.

12. The method according to claim 10 or 11, characterized in that: The precursor of D is selected from the group consisting of: a salt of D, a halide of D, an oxide of D and an organometallic compound of D.

13. The method according to claim 10 or 11, characterized in that: The solution prepared in the sub-step (a1) includes a solvent and a component selected from the group consisting of a stabilizer for the surface of the nanocrystals, a primary amine, and a mixture thereof.

14. The method according to claim 10 or 11, characterized in that: The temperature T a2 Below 300℃.

15. The method according to claim 10 or 11, characterized in that: The precursor of B is of formula B(F(R 11 )3)3, the compound of formula B (R 12 )3 or a compound of formula B(N(H)R 13 )3, wherein: Each F is selected from the group consisting of silicon (Si), germanium (Ge), and tin (Sn); Each R 11 The same or different, are optionally substituted linear, branched or cyclic alkyl groups of 1 to 10 carbon atoms; Each R 12 are the same or different and are hydrogen, halogen, or an optionally substituted linear, branched or cyclic alkyl group of 1 to 10 carbon atoms; and Each R 13 The same or different is a hydrogen atom, an optionally substituted straight chain, branched chain or cyclic alkyl group of 1 to 10 carbon atoms, or an optionally substituted straight chain, branched chain or cyclic alkenyl group of 2 to 30 carbon atoms.

16. The method according to claim 10 or 11, characterized in that The precursor of C is selected from the group consisting of C salts, C halides, C oxides and C organometallic compounds.

17. The method according to any one of claims 9 to 11, characterized in that The temperature T b Between 100°C and 200°C.

18. Use of a group of nanocrystals as defined in any one of claims 1 to 8 or which can be prepared according to the method as defined in any one of claims 9 to 17 in light-emitting diodes, photovoltaic cells, luminescent concentrators for solar cells and for fluorescent labeling of chemical molecules or biological molecules.

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