Material thermal history markers, material marking method, and method for verifying the material thermal history

Abstract

The present invention relates to the use, as a marker of the thermal history of a material, of at least one coordination polymer of formula [[Lnx(ligand)y(H2O)z]∞ where: Ln is terbium and / or europium optionally doped with at least one of lanthanum, yttrium, gadolinium and lutetium; where x is 1 or 2, whether Ln represents terbium, europium or both; where (ligand)y represents 1 to 3 Ln ligands, the or each ligand consisting of a benzene ring independently substituted at least once by at least one of: -B(OH)2, -B(OH)3 -, -PO3 2-, -PO3H-, and –Cl and optionally also substituted at least once by -COO-; where y is 1 to 3; and where z is 0 to 10.

Description

Markers of the thermal history of a material, method of marking the material and method of verifying its thermal history

[0001] The present invention relates to markers of the thermal history of a material, a method of marking the material and a method of verifying the thermal history of the marked material.

[0002] Recent crises have accelerated awareness of the need for material traceability throughout their life cycle. Some materials are particularly sensitive to temperature and can lose their properties when subjected to excessive temperatures. It is therefore essential to be able to subsequently verify that they retain all of their properties and have not been thermally degraded. It is well known that certain medications or active ingredients can lose their effectiveness when subjected to excessive temperatures, but other materials may also be affected.

[0003] Of course, when temperature is an important parameter it is monitored but, most often, this monitoring is carried out globally (temperature of the storage shed, for example) and does not ensure that a particular product has not been exposed to excessive temperature.

[0004] Bulk doping, at very low doping rates, of the material or its packaging with a luminescent coordination polymer could constitute a solution to this problem.

[0005] A coordination polymer is a one-, two-, or three-dimensional compound in which ions of the transition elements (3d or 4f) are linked together by ligands. EW Berg; A. Alam, Studies on coordination polymers. Part I: Coordination polymers of 8,8'-dihydroxy-5,5'-biquinolyl. Anal. Chim. Acta 1962, 27, 454-459.

[0006] The present invention therefore firstly relates to the use, as a marker of the thermal history of a material, of at least one coordination polymer of formula [Ln x (ligand) y (H2O) z ] ∞in which:Ln is terbium and / or europium optionally doped with at least one of lanthanum, yttrium, gadolinium and lutetium;x is 1 or 2 whether Ln represents terbium, europium or a mixture of the two;(ligand)y represents 1 to 3 ligands of Ln, the or each ligand consisting of a benzene ring independently substituted at least once by at least one of: -B(OH)2, -B(OH)3 - , -PO3 2- , -PO3H - , –Cl and –COO - ;y is 1 to 3; andz is 0 to 10.

[0007] (ligand) can be chosen from: - OOC-C6H4-B(OH)2, the –COO substituents - and -B(OH)2 being preferably para to each other; - OOC-C6H4-B(OH)3 - , the substituents –COO - and -B(OH)3 - being preferably in para of one another; 2- O3P-C6H4-PO3H - , the substituents -PO3 2- and -PO3H - being preferably in para of one another; 2-O3P-C6H5 ; - HO3P-C6H5 ;( - OOC)2-C6Cl4, both substituents –COO - being preferably ortho to each other; and( - OOC)3-C6H3, two substituents –COO - preferably being ortho to the first substituent –COO - .

[0008] In particular, the coordination polymer may be at least one of:[Ln(OOC-C6H4-B(OH)3)(H2O)2.(OOC-C6H4-B(OH)2)] ∞ , Ln can be doped with yttrium, gadolinium and / or lutetium; [Ln(O3P-C6H5)(HO3P-C6H5)] ∞ Ln can be doped with lanthanum, gadolinium, yttrium and / or lutetium; [Ln2((OOC)2-C6Cl4)3(H2O)6] ∞ , Ln can be doped with yttrium and / or gadolinium; and[Ln((OOC)3-C6H3)(H2O)5.3,5H2O] ∞ , Ln can be doped with yttrium and / or lutetium.

[0009] The present invention also relates to a material containing at least one marker as defined above.

[0010] In one embodiment, the material may consist of a thermoplastic or thermosetting polymeric organic matrix, in which the marker(s) is(are) contained in an amount in particular of 1 to 20 mg per kg.

[0011] In another embodiment, the material may consist of a mineral matrix such as concrete, in which the marker(s) is(are) contained in an amount in particular of 1 to 20 mg per kg.

[0012] The invention also relates to a method for marking a material which is as defined above and of which it is desired to know, at a given moment in its life, whether it has undergone a temperature higher than a given temperature T, characterized by the fact that at least one marker is incorporated into this material, during its manufacture, which exhibits(s) a luminescence under UV characteristic of this temperature.

[0013] The invention also relates to a method for detecting whether a material as prepared above has undergone during its life a thermal event which has brought it above a given temperature T, characterized in that said material is irradiated at a UV excitation wavelength, the luminescence is measured over the entire visible spectrum from 400 to 800 nm to obtain a luminescence spectrum which is compared to standard luminescence spectra of the marker considered as a function of the temperature.

[0014] The following Examples illustrate the present invention without, however, limiting its scope.

[0015] Example 1: [Ln(OOC-C6H4-B(OH)3)(H2O)2.(OOC-C6H4-B(OH)2)] ∞

[0016] Lamontre shows projection views of the crystal structure of the title compound in which Ln = Tb. Synthesis

[0017] The title compounds were synthesized as described in the publications: A. Abdallah; S. Freslon; X. Fan; A. Rojo; C. Daiguebonne; Y. Suffren; K. Bernot; G. Calvez; T. Roisnel; O. Guillou, Lanthanide based coordination polymers with 1,4 carboxyphenylboronic ligand: multi emissive compounds for multi sensitive luminescent thermometric probes. Inorg. Chem. 2019, 58, 462-475; X. Fan; S. Freslon; C. Daiguebonne; L. Le Polles; G. Calvez; K. Bernot; O. Guillou, A family of lanthanide based coordination polymers with boronic acid as ligand. Inorg. Chem. 2015, 54, 5534-5546.

[0018] The synthesized compounds contain the lanthanides shown in Table 1 below:

[0019] TbEu1-1101-2011-30,90,1 Crystallographic data

[0020] Table 2 below presents the crystallographic data of compound 1-1.

[0021] Molecular formula TbO 11 C 14 H 17B2Molecular mass541.82 g.mol -1 Crystal systemOrthorhombicSpace groupPbca (no. 61)Lanyard parametersa = 8.5704 (1) Åb = 19.5441 (1) Åc = 21.4191 (3) ÅLanyard volume3587.71(7) Å 3 Z8Calculated density1.98 g.cm -3

[0022] Cambridge Crystallographic Data Center (CCDC) - 962513 X-ray diffraction

[0023] Lamontre shows the powder X-ray diffraction patterns of compounds 1-1, 1-2 and 1-3.

[0024] These diagrams demonstrate that compounds 1-1, 1-2, and 1-3 all have the same structure. In particular, the hetero-di-lanthanide compound (compound 1-3) is isostructural to the homonuclear compounds based on terbium (compound 1-1) and europium (compound 1-2). Thermogravimetric analysis

[0025] Thermogravimetric analysis (TGA) of compound 1-1 was carried out under a synthetic air atmosphere between room temperature and 950°C, with a heating ramp of 5°C / min. The curve obtained is shown in: the analysis shows an initial departure of 4 water molecules below 200°C, a plateau up to approximately 450°C, then a progressive decomposition of the ligand.

[0026] The X-ray diffraction pattern performed on the residual powder at the end of thermal analysis shows that the final compound obtained is TbBO3. The X-ray diffraction pattern of the compound TbBO3 was simulated from R. Velchuri et al. Materials Research Bulletin 46 (2011) 1219–1226.

[0027] Heat treatments – Luminescence properties

[0028] Compounds 1-1 and 1-3 were subjected to different heat treatments under the following conditions: heating to the set temperature at a rate of 5°C / min; temperature hold of 5 minutes; then natural return to room temperature.

[0029] The luminescence properties of the compounds were studied.

[0030] For this purpose, the emission spectra under UV irradiation (λ exc = 288 nm) of compounds 1-1 and 1-3 as a function of the heat treatment step temperature.

[0031] Lamontre shows the emission spectra of compound 1-1 after heat treatment as a function of the temperature of the heat treatment step.

[0032] Lamontre shows the emission spectra of compound 1-3 after heat treatment as a function of the temperature of the heat treatment step.

[0033] Figures 5 and 6 show that compounds that have undergone different heat treatment exhibit different luminescence properties that are easily identifiable.

[0034] It is recognized that spectroscopic measurements depend on the equipment used. To avoid this pitfall, it is possible to use compounds containing two different lanthanide ions simultaneously. The luminescence of these two ions does not vary identically during dehydration or crystalline phase changes. Measuring the ratio of the intensities of the characteristic peaks of one and the other thus makes it possible to do without the equipment.

[0035] The intensity ratio of the major peak attributable to europium (615 nm) and the major peak attributable to terbium (545 nm) was calculated for compound 1-3 at each of the heat treatment step temperatures.

[0036] Lamontre shows these peak ratios as a function of bearing temperature.

[0037] The colorimetric coordinates of the thermally treated samples are shown, which were calculated based on the emission spectra. They allow the unambiguous identification of the thermal treatment undergone by the sample.

[0038] Example 2: [Ln(O3P-C6H5)(HO3P-C6H5)] ∞

[0039] La shows a projection view of the crystal structure of the title compound in which Ln = La. Synthesis

[0040] An aqueous solution of phenylphosphonic acid sodium salt (1 mmol in 10 mL of water) is added to an aqueous solution of lanthanide chloride (0.5 mmol in 10 mL). After 24 hours, the precipitate is filtered, rinsed with water and air dried (yield is approximately 90%).

[0041] The synthesized compounds contain the lanthanides shown in Table 3 below:

[0042] TbEu2-1102-201 Crystallographic data

[0043] Table 4 below shows the crystallographic data of the compound [La(O3P-C6H5)(HO3P-C6H5)] ∞ .

[0044] Molecular formula LaP2C 12 H 11 O6Molecular mass452.07 g.mol -1 Crystalline systemtriclinicSpace groupP-1 (n°2)Mesh parametersa = 8.410 (3) Åb = 15.696 (7) Åc = 5.636 (1) Åα = 90.24 (3) °β = 108.99 (1) °γ = 85.59 (4) °Mesh volume701.3 (4) Å 3 Z2Calculated density2.141 g.cm -3

[0045] CCDC: 1190447

[0046] Ren-Chain Wanget al.Chemistry of Materials1992,4, 864-971 X-ray diffraction

[0047] Lamontre shows the powder X-ray diffraction patterns of compounds 2-1 and 2-2.

[0048] These diagrams demonstrate that compounds 2-1 and 2-2 have the same structure. Thermogravmetric analysis

[0049] Thermogravimetric analysis (TGA) of compound 2-1 was carried out under synthetic air atmosphere between room temperature and 950°C, with a heating ramp of 5°C / min. The curve obtained is shown in: the analysis shows a first progressive and moderate mass loss (5%) below 350°C followed by an abrupt decomposition of the ligand around 400°C. The microcrystalline powder recovered at the end of the analysis corresponds to the compound TbPO4, as can be seen on the X-ray diffraction pattern of, the pattern of the compound EuPO4 being simulated from the reference DF Mullica et al. / Inorganica Chimica Acta 109 (1985) 105-110.

[0050] Heat treatments – Luminescence properties

[0051] Compounds 2-1 and 2-2 were subjected to different heat treatments under the following conditions: heating to the set temperature at a rate of 5°C / min; temperature hold of 2 hours; then natural return to room temperature.

[0052] The luminescence properties of the compounds were studied.

[0053] For this purpose, the emission spectra under UV irradiation (λ exc = 272 nm) of compounds 2-1 and 2-2 as a function of the heat treatment step temperature.

[0054] Lamontre shows the emission spectra of compound 2-1 after heat treatment as a function of the temperature of the heat treatment step.

[0055] Lamontre shows the emission spectra of compound 2-2 after heat treatment as a function of the temperature of the heat treatment step.

[0056] Figures 13 and 14 show that compounds that have undergone different heat treatment exhibit different luminescence properties that are easily identifiable.

[0057] Example 3: [Ln2((OOC)2-C6Cl4)3(H2O)6] ∞

[0058] Lamontre shows a perspective view of the crystal structure of the title compound in which Ln = Y. Synthesis

[0059] An aqueous solution of tetrachlorophthalic acid sodium salt (0.75 mmol in 10 mL of water) is added to an aqueous solution of lanthanide chloride (0.5 mmol in 10 mL) heated to 80°C. After 24 hours at reflux, the precipitate is filtered, rinsed with water and air dried (the yield is approximately 90%).

[0060] The synthesized compounds contain the lanthanides shown in Table 5 below:

[0061] TbEu3-1203-2023-31,60,4 Crystallographic data

[0062] Table 6 below shows the crystallographic data of the compound [Y2((OOC)2-C6Cl4)3(H2O)6] ∞ .

[0063] Molecular formula Y2Cl 12 O 18 C 24 H 12 Molecular mass1179.49 g.mol -1 Crystal systemmonoclinicSpace groupP21 / c (no. 14)Lattice parametersa = 6.2155 (2) Åb = 19.6652 (7) Åc = 30.3720 (9) Åβ = 94.63 (0) °Lattice volume3700.22 (37) Å 3 Z4Calculated density2.11715 g.cm -3 X-ray diffraction

[0064] Lamontre shows the powder X-ray diffraction patterns of compounds 3-1, 3-2 and 3-3.

[0065] These diagrams demonstrate that compounds 3-1, 3-2 and 3-3 have the same structure as the compound [Y2((OOC)2-C6Cl4)3(H2O)6] ∞ . Thermogravimetric analysis

[0066] Thermogravimetric analysis (TGA) of compound 3-2 was carried out under a synthetic air atmosphere between room temperature and 950°C, with a heating ramp of 5°C / min. The curve obtained is shown in the: the analysis shows an initial mass loss corresponding to the departure of the coordination water molecules below 200°C followed by a plateau up to 400°C and then an abrupt decomposition of the ligand. The microcrystalline powder recovered at the end of the analysis corresponds to the compound EuClO, as can be seen on the X-ray diffraction pattern of the, the pattern of the compound EuClO being simulated from the reference H. Bärnighausen et al. / Zeitschrift fur anorganische und allgemeine Chemie 338 (1965) 250-265.

[0067] Heat treatments – Luminescence properties

[0068] Compounds 3-2 and 3-3 were subjected to different heat treatments under the following conditions: heating to the set temperature at a rate of 5°C / min; temperature hold of 5 minutes; then natural return to room temperature.

[0069] The luminescence properties of the compounds were studied.

[0070] For this purpose, the emission spectra under UV irradiation (λ exc = 300 nm) of compounds 3-2 and 3-3 as a function of the heat treatment step temperature.

[0071] Lamontre shows the emission spectra of compound 3-2 after heat treatment as a function of the temperature of the heat treatment step.

[0072] Lamontre shows the emission spectra of compound 3-3 after heat treatment as a function of the temperature of the heat treatment step.

[0073] Figures 19 and 20 show that compounds that have undergone different heat treatment exhibit different luminescence properties that are easily identifiable.

[0074] The intensity ratio of the major peak attributable to europium (615 nm) and the major peak attributable to terbium (545 nm) was calculated for compound 3-3 at each of the heat treatment step temperatures.

[0075] Lamontre shows these peak ratios as a function of bearing temperature.

[0076] The colorimetric coordinates of the thermally treated samples are shown, which were calculated based on the emission spectra. They allow the unambiguous identification of the thermal treatment undergone by the sample.

[0077] Example 4:[Ln(OOC)3-C6H3)(H2O)5.3.5H2O] ∞

[0078] Lamontre shows a projection view of the crystal structure of the title compound in which Ln = Er. Synthesis

[0079] An aqueous solution of 1,3,5-benzenetricarboxylic acid sodium salt (0.5 mmol in 10 mL of water) is added to an aqueous solution of lanthanide chloride (0.5 mmol in 10 mL). After 10 minutes, the precipitate is filtered, rinsed with water and air-dried (yield is approximately 90%).

[0080] The synthesized compound contains the lanthanides shown in Table 7 below:

[0081] YEu4-10,80,2 Crystallographic data

[0082] Table 8 below presents the crystallographic data of the compound [Er(OOC)3-C6H3)(H2O)5.3,5H2O] ∞ .

[0083] Molecular formula ErC9H 17 O 14.5 Molecular mass 527.5 g.mol -1 Crystal systemMonoclinicSpace groupC2 / c(n°15)Lattice parametersa = 14.7496 (15) Åb = 16.9874 (15) Åc = 14.4591 (14) Åβ = 118.754 (9) °Lattice volume3173.96 (100) Å 3 Z8Calculated density2.208 g.cm-3

[0084] CCDC: 101659

[0085] C.Daiguebonne et al. Inorganica Chimica Acta1999, 284, 139-145 X-ray diffraction

[0086] Lamontre shows the powder X-ray diffraction patterns of compound 4-1.

[0087] These diagrams demonstrate that compound 4-1 has the same crystal structure as the reference compound. Thermogravimetric analysis

[0088] Thermogravimetric analysis (TGA) of compound 4-1 was carried out under a synthetic air atmosphere between room temperature and 950°C, with a heating ramp of 5°C / min. The curve obtained is shown in: the analysis shows an initial mass loss corresponding to the departure of the coordination water molecules below 200°C followed by a plateau up to 400°C and then an abrupt decomposition of the ligand. The microcrystalline powder recovered at the end of the analysis corresponds to the compound [Y 1.6 I04 O3], as can be seen from the X-ray diffraction pattern of the, the pattern of the compound being Y2O3simulated from the reference Baldinozzi, G., Berar, J.-F., Calvarin, G., Mater.Sci.Forum(1998),278-281, 680.

[0089] Heat treatments – Luminescence properties

[0090] Compound 4-1 was subjected to various heat treatments under the following conditions: heating to the set temperature at a rate of 5°C / min; temperature hold of 5 minutes; then natural return to room temperature.

[0091] The luminescence properties of the compound were studied.

[0092] For this purpose, the emission spectra under UV irradiation (λ exc = 312 nm) of compound 4-1 as a function of the heat treatment step temperature.

[0093] Lamontre shows the emission spectra of compound 3-2 after heat treatment as a function of the temperature of the heat treatment step.

[0094] Lamontre shows that compounds that have undergone different heat treatment exhibit different luminescence properties that are easily identifiable.

[0095] Example 5: Marking of a polyvinylidene fluoride (PVDF) part with the compound (1-3)[Tb 0,9 I 0,1 (OOC-C6H4-B(OH)3)(H2O)2.(OOC-C6H4-B(OH)2)] ∞ Sample preparation.

[0096] Compound 1-3 prepared as described in Example 1 is dispersed in a mixture of PVDF (150 mg) and DMF (2 mL) at room temperature. The suspension is then placed in an oven (80°C) for evaporation. A colorless film is finally obtained (sample 5-1).

[0097] Heat treatments and luminescence properties.

[0098] Sample 5-1 was subjected to various heat treatments under the following conditions: heating to the set temperature at a rate of 5°C / min; temperature hold of 5 minutes; then natural return to room temperature.

[0099] The luminescence properties of this sample were studied.

[0100] For this purpose, the emission spectra under UV irradiation (λ exc = 288 nm) of sample 5-1 as a function of the heat treatment step temperature.

[0101] Shows the emission spectra of sample 5-1 after heat treatment as a function of the heat treatment step temperature.

[0102] Based on these emission spectra, the colorimetric coordinates were calculated. They are shown in the.

[0103] Figures 28 and 29 show that PVDF samples doped with compound 1-3 and having undergone different heat treatment exhibit different luminescence properties that are easily identifiable.

[0104] Example 6: Marking of a polyvinylidene fluoride (PVDF) part with the compound (3-3)[Tb 1,6 I 0,4 (OOC)2-C6Cl4)3(H2O)6] ∞ Sample preparation.

[0105] Compound 3-3 prepared as described in Example 3 is dispersed in a mixture of PVDF (150 mg) and DMF (2 mL) at room temperature. The suspension is then placed in an oven (80°C) for evaporation. A colorless film is finally obtained (sample 6-1).

[0106] Heat treatments and luminescence properties.

[0107] Sample 6-1 was subjected to various heat treatments under the following conditions: heating to the set temperature at a rate of 5°C / min; temperature hold of 5 minutes; then natural return to room temperature.

[0108] The luminescence properties of this sample were studied.

[0109] For this purpose, the emission spectra under UV irradiation (λ exc = 300 nm) of sample 6-1 as a function of the heat treatment step temperature.

[0110] Lamontre shows the emission spectra of sample 6-1 after heat treatment as a function of the heat treatment step temperature.

[0111] Based on these emission spectra, the colorimetric coordinates were calculated. They are shown in the.

[0112] Figures 30 and 31 show that PVDF samples doped with compound 3-3 and having undergone different heat treatment exhibit different luminescence properties that are easily identifiable.

[0113] Example 7: Marking of a part in Polymethyl methacrylate acrylic by the compound (3-3)[Tb 1,6 I 0,4 (OOC)2-C6Cl4)3(H2O)6] ∞ Sample preparation.

[0114] Compound 3-3 prepared as described in Example 3 is dispersed in a mixture of PMMA (40 mg) and chloroform (CCl3) (2 mL) at room temperature. The suspension is then left in the air for evaporation. A colorless film is finally obtained (sample 7-1).

[0115] Heat treatments and luminescence properties.

[0116] Sample 7-1 was subjected to various heat treatments under the following conditions: heating to the set temperature at a rate of 5°C / min; temperature hold of 5 minutes; then natural return to room temperature.

[0117] The luminescence properties of this sample were studied.

[0118] For this purpose, the emission spectra under UV irradiation (λ exc = 300 nm) of sample 7-1 as a function of the heat treatment step temperature.

[0119] Shows the emission spectra of sample 7-1 after heat treatment as a function of the heat treatment step temperature.

[0120] Based on these emission spectra, the colorimetric coordinates were calculated. They are shown in the.

[0121] Figures 32 and 33 show that PMMA samples doped with compound 3-3 and having undergone different heat treatment exhibit different luminescence properties that are easily identifiable.

Claims

– Use, as a marker of the thermal history of a material, of at least one coordination polymer of formula [Ln x (ligand) y (H2O) z ] ∞ in which:Ln is terbium and / or europium optionally doped with at least one of lanthanum, yttrium, gadolinium and lutetium;x is 1 or 2 whether Ln represents terbium, europium or a mixture of the two;(ligand)y represents 1 to 3 ligands of Ln, the or each ligand consisting of a benzene ring independently substituted at least once by at least one of: -B(OH)2, -B(OH)3 - , -PO3 2- , -PO3H - , –Cl and –COO - ;y is 1 to 3; andz is 0 to 10. – Use according to claim 1, characterized in that (ligand) is chosen from: - OOC-C6H4-B(OH)2, the –COO substituents - and -B(OH)2 being preferably para to each other; - OOC-C6H4-B(OH)3 -, the substituents –COO - and -B(OH)3 - being preferably in para of one another; 2- O3P-C6H4-PO3H - , the substituents -PO3 2- and -PO3H - being preferably in para of one another; 2- O3P-C6H5 ; - HO3P-C6H5 ;( - OOC)2-C6Cl4, both substituents –COO - being preferably ortho to each other; and( - OOC)3-C6H3, two substituents –COO - preferably being ortho to the first substituent –COO - . - Use according to one of claims 1 and 2, characterized by the coordination polymer being at least one of [Ln(OOC-C6H4-B(OH)3)(H2O)2.(OOC-C6H4-B(OH)2)] ∞ , Ln can be doped with yttrium, gadolinium and / or lutetium; [Ln(O3P-C6H5)(HO3P-C6H5)] ∞ , Ln can be doped with lanthanum, gadolinium, yttrium and / or lutetium;[Ln2((OOC)2-C6Cl4)3(H2O)6] ∞, Ln can be doped with yttrium and / or gadolinium; and[Ln((OOC)3-C6H3)(H2O)5.3,5H2O] ∞ , Ln can be doped with yttrium and / or lutetium. – Material containing at least one marker as defined in one of claims 1 to 3. – Material according to claim 4, characterized in that it consists of a thermoplastic or thermosetting polymeric organic matrix, in which the marker(s) is(are) contained in an amount in particular of 1 to 20 mg per kg. – Material according to claim 5, characterized in that it consists of a mineral matrix such as concrete, in which the marker(s) is or are contained in an amount in particular of 1 to 20 mg per kg. – Method for marking a material which is as defined in one of claims 4 to 6 and of which it is desired to know, at a given moment in its life, whether it has undergone a temperature higher than a given temperature T, characterized by the fact that at least one marker is incorporated into this material, during its manufacture, which exhibits(s) a luminescence under UV characteristic of this temperature. – Method for detecting whether a material as prepared in claim 7 has undergone during its life a thermal event which has brought it above a given temperature T, characterized in that said material is irradiated at a UV excitation wavelength, the luminescence is measured over the entire visible spectrum from 400 to 800 nm to obtain a luminescence spectrum which is compared to standard luminescence spectra of the marker considered as a function of temperature.

Images