A method for predicting and regulating up-conversion nanomaterial mixed system luminescence lifetime

Abstract

The application relates to a method for predicting and regulating the up-conversion nanomaterial mixed system light-emitting life, and the specific method is as follows: first, synthesizing NaYF4-based up-conversion nanoparticles with different rare earth ion doping ratios, the two kinds of nanoparticles have different light-emitting lives; then, mixing the two kinds of up-conversion nanoparticles to obtain a life attenuation curve and a convolution fitting curve; combining the light-emitting intensity proportion of the two kinds of nanoparticles in the mixed system, the light-emitting life of the mixed system can be predicted, and the mixed system can also be designed according to a target light-emitting life. The method can continuously adjust the life, does not need a large amount of synthesis, and improves the optical code capacity in subsequent anti-counterfeiting, information encryption and the like.

Description

Technical Field

[0001] This invention relates to nanomaterials, and more specifically to a method for predicting the luminescence lifetime of a hybrid upconversion nanomaterial system. Background Technology

[0002] Luminescence lifetime is a crucial optical parameter for fluorescent materials, typically referring to the time it takes for the material's luminescence intensity to decay to 1 / e of its initial intensity after excitation ceases. Compared to fluorescent materials such as quantum dots and organic dyes, upconversion nanoparticles exhibit a longer luminescence lifetime, reaching hundreds of microseconds, and are less susceptible to interference from external factors such as excitation power. In recent years, the luminescence lifetime of upconversion nanoparticles has been used for optical coding. Combined with luminescence color and intensity, it can achieve multi-dimensional encryption, increasing the capacity of optical codes. However, to utilize luminescence lifetime for coding, it is necessary to adjust the luminescence lifetime of upconversion nanoparticles. Current methods cannot "design" the luminescence lifetime, cannot predict the adjusted lifetime, and the adjustment process is cumbersome, often involving large-scale material synthesis.

[0003] Currently, the main methods for controlling the upconversion luminescence lifetime are by altering the properties of nanoparticles, such as changing their size, the amount of lanthanide ion doping, and coating them with an inert layer. These methods can only estimate the trend of luminescence lifetime changes; for example, the luminescence lifetime increases when the nanoparticle size increases, the amount of activating ion doping decreases, or an inert layer (such as a NaYF4 shell) is applied, but the specific value of the luminescence lifetime cannot be predicted. Furthermore, in these methods, the luminescence lifetime corresponds one-to-one with the number of synthesized upconversion nanoparticles. To achieve high-capacity encoding in subsequent applications, a large number of upconversion nanoparticles must be synthesized, which is cumbersome and extremely labor-intensive. Summary of the Invention

[0004] The technical problem solved by this invention is that the regulation of the luminescence lifetime of upconversion nanoparticles is cumbersome and unpredictable. This invention proposes a method for predicting and regulating the luminescence lifetime of upconversion nanomaterials without the need for large-scale synthesis.

[0005] The technical solution adopted in this invention is a method for predicting and controlling the luminescence lifetime of a hybrid upconversion nanomaterial system. The luminescence lifetime is predicted and controlled by physically mixing upconversion nanomaterials, wherein the nanomaterials are rare earth ions (RE). 3+Two NaYF4-based upconversion nanoparticles, S and L, with different doping ratios, exhibit different luminescence lifetimes. Mixing the nanoparticles in a specific ratio can alter the luminescence lifetime. By calculating the proportion of luminescence intensity of different nanoparticles in the mixed system, the luminescence lifetime of the upconversion nanomaterial mixture can be predicted. Furthermore, based on the target luminescence lifetime, the mass concentrations of the two upconversion nanomaterials in the mixed system can be determined, thus enabling the regulation of the luminescence lifetime of the upconversion nanomaterial mixture. The specific steps are as follows: A. Preparation of rare earth ions RE 3+ S and L of two different doping ratios of NaYF4-based upconversion nanoparticles; B. Measure the emission spectra of the two types of nanoparticles at different mass concentrations of γ, and establish [a system / mechanism] at the characteristic emission wavelengths. The linear relationship between luminescence intensity I and mass concentration γ in the S and L systems; C. Determine the lifetime decay curves in the S and L systems respectively, and fit the convolutional curve f. S and f L , obtained actual measurement Optical lifetime; D. For a mixed system, based on the linear relationship between luminescence intensity and mass concentration, I = aγ + b, calculate the proportion of luminescence intensity of S and L in the mixed system as W. S and W L According to f=W S f S +W L f L Obtain convolution of hybrid systems Fitted curve f and predicted luminescence lifetime; E. The predicted luminescence lifetime of the hybrid system is compared with W L Fit the curve to obtain a standard curve; F. For the target luminescence lifetime, W is obtained using the standard curve described above. L Then, based on the linear relationship between luminescence intensity and mass concentration, the corresponding mass concentration γ is obtained.

[0006] Compared with existing technologies, this invention does not require multiple chemical reactions to alter the properties of nanoparticles and thus change the luminescence lifetime. Instead, lifetime regulation is achieved through simple physical mixing. Furthermore, this invention offers predictability and designability, overcoming the shortcomings of existing technologies. The features and advantages of this invention will be described in the subsequent detailed embodiments section. Attached Figure Description

[0007] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0008] In the attached diagram:

[0009] Figure 1 This is a transmission electron microscope image of the NaYF4:Yb,Tm (20:2mol%) nanoparticles in Example 1.

[0010] Figure 2 The image shows the X-ray diffraction pattern of the NaYF4:Yb,Tm (20:2mol%) nanoparticles in Example 1.

[0011] Figure 3 This is a transmission electron microscope image of the NaYF4:Yb,Tm (20:0.2 mol%) nanoparticles in Example 2.

[0012] Figure 4 The image shows the X-ray diffraction pattern of the NaYF4:Yb,Tm (20:0.2 mol%) nanoparticles in Example 2.

[0013] Figure 5 The emission spectra and lifetime decay curves of NaYF4:Yb,Tm (20:2 mol%) nanoparticles in Example 1 and NaYF4:Yb,Tm (20:0.2 mol%) nanoparticles in Example 2 are shown.

[0014] Figure 6 The graph shows the relationship between the luminescence intensity and mass concentration of NaYF4:Yb,Tm (20:2mol%) nanoparticles in Example 3.

[0015] Figure 7 The graph shows the relationship between the luminescence intensity and mass concentration of NaYF4:Yb,Tm (20:0.2mol%) nanoparticles in Example 4.

[0016] Figure 8 a represents the lifetime decay curves and convolution fitting curves of NaYF4:Yb,Tm(20:0.2mol%) and NaYF4:Yb,Tm(20:2mol%) nanoparticles in Example 5, and 8b represents the predicted convolution fitting curves of a series of mixed systems.

[0017] Figure 9 a is a comparison graph of predicted luminescence lifetime and measured luminescence lifetime in Example 5, and 9b is a standard curve of predicted luminescence lifetime and the proportion of luminescence intensity of NaYF4:Yb,Tm (20:0.2mol%) nanoparticles.

[0018] Figure 10 In Example 6, the fluorescence image, lifetime decoding infographic, and lifetime decoding grayscale image of the lifetime-encrypted building block under 980nm conditions are shown. Detailed Implementation

[0019] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0020] This invention provides a method for physically mixing nanoparticles to regulate the upconversion luminescence lifetime. Examples 1 and 2 prepared two types of NaYF4:Yb,Tm (20:2 mol%) nanoparticles and NaYF4:Yb,Tm (20:0.2 mol%) nanoparticles for regulating luminescence lifetime. Examples 3 and 4 illustrate the relationship between luminescence intensity and concentration of the NaYF4:Yb,Tm (20:2 mol%) and NaYF4:Yb,Tm (20:0.2 mol%) nanoparticles. Example 5 describes a method for predicting and regulating a specific lifetime using a mixed system through physical mixing. Example 6 describes the application of the nanoparticle mixing system for optical encoding.

[0021] Example 1

[0022] Preparation of NaYF4:Yb,Tm (20:2 mol%) nanoparticles (S)

[0023] 3.2565 mL of yttrium acetate aqueous solution (Y(Ac)3, 0.2 mol / L), 0.835 mL of ytterbium acetate aqueous solution (Yb(Ac)3, 0.2 mol / L), and 0.835 mL of thulium acetate aqueous solution (Tm(Ac)3, 0.02 mol / L) were added to a 50 mL double-necked round-bottom flask, followed by 10 mL of oleic acid and 10 mL of 1-octadecene. The flask was placed in a silicone oil bath, and heating was started at 150 °C with stirring at 300 rpm for 90 minutes. The heating was then turned off, stirring was continued, and the mixture was cooled to room temperature to obtain the precursor solution.

[0024] The flask containing the precursor was fixed to a heating mantle and stirred steadily. 6.67 mmol of sodium oleate was then added to the flask, and the temperature was set to 100°C. Vacuum was applied for 1 hour after the temperature reached 100°C. After 1 hour, 2.649 mmol of ammonium fluoride was added, the temperature was raised to 160°C and maintained for 1 hour, followed by vacuuming. Nitrogen gas was introduced when no more bubbles appeared, and vacuuming was repeated until no more bubbles appeared in the flask (the entire process took approximately 15 minutes). Nitrogen gas was then introduced, and the reaction temperature was set to 320°C for 30 minutes. The heating was then turned off while stirring was maintained. After cooling to room temperature, anhydrous ethanol was added as a precipitant, and the mixture was centrifuged at 6000 rpm for 5 minutes. The precipitate was washed twice with cyclohexane and anhydrous ethanol to obtain NaYF4:Yb,Tm (20:2 mol%) nanoparticles, which were dispersed in 4 mL of cyclohexane. The NaYF4:Yb,Tm (20:2mol%) nanoparticles have a short luminescence lifetime, denoted as S.

[0025] Example 2

[0026] Preparation of NaYF4:Yb,Tm (20:0.2 mol%) nanoparticles (L)

[0027] Add 3.3315 mL of yttrium acetate aqueous solution (Y(Ac)3, 0.2 mol / L), 0.835 mL of ytterbium acetate aqueous solution (Yb(Ac)3, 0.2 mol / L), and 0.0835 mL of thulium acetate aqueous solution (Tm(Ac)3, 0.02 mol / L) to a 50 mL double-necked round-bottom flask, then add 10 mL of oleic acid and 10 mL of 1-octadecene. Place the flask in a silicone oil bath, set the temperature to 150 °C, and stir at 300 rpm for 90 minutes. Turn off the heat, continue stirring, and cool to room temperature to obtain the precursor solution.

[0028] The flask containing the precursor was fixed to a heating mantle and stirred steadily. 6.67 mmol of sodium oleate was then added to the flask, and the temperature was set to 100°C. Vacuum was applied for 1 hour after the temperature reached 100°C. After 1 hour, 2.649 mmol of ammonium fluoride was added, the temperature was raised to 160°C and maintained for 1 hour, followed by vacuuming. Nitrogen gas was introduced when no more bubbles appeared, and vacuuming was repeated until no more bubbles appeared in the flask (the entire process took approximately 15 minutes). Nitrogen gas was then introduced, and the reaction temperature was set to 320°C for 30 minutes. The heating was then turned off while stirring was maintained. After cooling to room temperature, anhydrous ethanol was added as a precipitant, and the mixture was centrifuged at 6000 rpm for 5 minutes. The precipitate was washed twice with cyclohexane and anhydrous ethanol to obtain NaYF4:Yb,Tm (20:0.2 mol%) nanoparticles, which were dispersed in 4 mL of cyclohexane. The NaYF4:Yb,Tm(20:0.2mol%) nanoparticles have a long luminescence lifetime, denoted by L.

[0029] Example 3

[0030] Take a 1mL glass bottle, place it in a 70℃ forced-air drying oven and heat for 30 minutes. Then remove it, cool it to room temperature, and weigh it, recording the mass as m1. Take 0.1mL of the S nanoparticles from Example 1 into the above glass bottle, place it in a 70℃ forced-air drying oven and heat for 4 hours. Then remove it, cool it to room temperature, and weigh it, recording the mass as m2. Calculate the mass concentration γ of the S nanoparticle solution from Example 1 based on m1 and m2. S .

[0031] A series of S nanoparticle solutions with different mass concentrations were prepared, specifically, the mass concentration of γ... S The concentrations were 0.1, 0.2, 0.3, 0.4, and 0.5 mg / mL, and their emission spectra were measured under 980 nm near-infrared light excitation, as shown in the attached figure. Figure 6 a. Luminous intensity (I S ) and mass concentration (γ) S The relationship between them is linear, as shown in the attached figure. Figure 6 Equation 1 in b, I S =7.69×10 6 γ S +8881.75.

[0032] Example 4

[0033] Take a 1mL glass bottle, place it in a 70℃ forced-air drying oven and heat for 30 minutes. Then remove it, cool it to room temperature, and weigh it, recording the mass as m1. Take 0.1mL of the L nanoparticles from Example 2 into the above glass bottle, place it in a 70℃ forced-air drying oven and heat for 4 hours. Then remove it, cool it to room temperature, and weigh it, recording the mass as m2. Calculate the mass concentration γ of the L nanoparticle solution from Example 2 based on m1 and m2. L .

[0034] A series of L nanoparticle solutions with different mass concentrations were prepared, specifically, the mass concentration γ... L The concentrations were 0.1, 0.2, 0.3, 0.4, and 0.5 mg / mL, and their emission spectra were measured under 980 nm near-infrared light excitation, as shown in the attached figure. Figure 7 a. Luminous intensity (I L ) and mass concentration (γ) L The relationship between them is linear, as shown in the attached figure. Figure 7 Equation 2 in b, I L =9×10 6 γ L +87766.85.

[0035] Example 5

[0036] The lifetime decay curves of the S and L systems at the characteristic emission wavelength of 475 nm under 980 nm laser excitation were measured respectively (see attached). Figure 8 a) Obtain the convolution fitting curve f by fitting it. S and f L The measured luminescence lifetimes were 255 μs and 630 μs. A mixed system of nanoparticles S and L was designed, in which the luminescence intensity of L nanoparticles accounted for W. L =I L / (I S +I L The luminescence intensity ratio of S nanoparticles is W. S =I S / (I S +I L ) = 1 - W L By changing W L Nine hybrid systems were designed, among which W L =0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, through equation 3: f = W S f S +W L f L The convolution fitting curve of the hybrid system was calculated (as shown in the attached figure). Figure 8 b) The predicted luminescence lifetimes of the hybrid system were obtained as 319, 376, 426, 469, 507, 539, 568, 591, and 611 μs.

[0037] Based on equations 1 and 2, for W L For mixed systems with concentrations of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9, the mass concentrations of L and S nanoparticles in each system were calculated. (The text then abruptly shifts to a different topic: "using W...") L For example, γ = 0.1 L =0.04 mg / mL, γ S =0.54 mg / mL, denoted as γ L / γ S =0.04 / 0.54. Similarly, W L In the mixed system with concentrations of 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9, the mass concentrations γ of L and S nanoparticles are... L / γ S=0.09 / 0.48, 0.14 / 0.42, 0.20 / 0.36, 0.25 / 0.30, 0.30 / 0.24, 0.35 / 0.18, 0.40 / 0.12, 0.45 / 0.06. The above-mentioned hybrid systems were prepared separately, and excited with a 980nm laser. The lifetime decay curves of the hybrid systems at 475nm were measured. Convolutional fitting curves were obtained by fitting these curves, and the measured emission lifetimes were 312, 372, 426, 473, 502, 540, 562, 583, and 611 μs, respectively. Compared with the predicted emission lifetimes obtained through Equation 3, the error is within 3% (see attached). Figure 9 a). The predicted luminescence lifetime of the hybrid system and W L By fitting the equation, we obtain equation 4: luminescence lifetime = (1 + 3.96 * W) L ) / (0.004+0.0039*W L (See attached) Figure 9 b, with a correlation of 0.9997.

[0038] Equations 1, 2, 3, and 4 provide a method for predicting the luminescence lifetime of hybrid systems and designing and synthesizing hybrid systems with specific luminescence lifetimes. When predicting the luminescence lifetime of a hybrid system, the lifetime decay curves of the pure-phase systems S and L are first measured, and a convolutional fitting curve is obtained. Based on γ... S and γ L The proportion of luminous intensity W in the mixture system is calculated using equations 1 and 2. S and W L Substituting this into Equation 3 yields the convolution fitting curve, thus obtaining the predicted luminescence lifetime of the hybrid system. When controlling the design of a specific luminescence lifetime, the predicted luminescence lifetime of the hybrid system can be obtained first using the method described above, and then compared with W... L Equation 4 was obtained through fitting. For the target luminescence lifetime, the proportion of luminescence intensity contributed by L nanoparticles, W, can be calculated using Equation 4. L Based on Equations 1 and 2, the mass concentration γ of the two components in the mixed system can be calculated. L and γ S This allows for the formulation of a nanoparticle hybrid system with the target luminescence lifetime.

[0039] Example 6

[0040] Preparing life-encoded building blocks

[0041] Weigh approximately 0.1 g of commercial UV-curable adhesive (density approximately 1.5014 g / mL). Disperse upconversion nanoparticles S and L, totaling 2.668 mg, in 0.6 mL of chloroform. Then mix with the UV-curable adhesive, and add 0.09 g of polyvinylpyrrolidone (PVP, Mw ~ 29000). Sonicate for 10 minutes to thoroughly mix. Subsequently, drop the mixture onto building blocks and irradiate with 365 nm ultraviolet light for 1.5 hours to fully cure the mixture, obtaining building blocks with encrypted information.

[0042] Keeping the mass of the photocurable adhesive and PVP and the volume of chloroform constant, the masses of S nanoparticles and L nanoparticles were varied to prepare building blocks containing different nanoparticle mass concentrations, and the linear relationship between the luminescence intensity and the nanoparticle mass concentration in the building blocks was determined.

[0043] Referring to Example 5, a series of building blocks with different luminescence lifetimes were obtained. Under 980nm laser irradiation, the building blocks emitted the same color and had similar luminescence intensity, but the luminescence lifetimes at 475nm were different. By assigning different gray levels to the luminescence lifetimes measured in 10b, musical note patterns appeared, thus achieving information encryption.

[0044] Example 7

[0045] In Examples 1-5, S and L were replaced with NaYF4:Yb,Er (20:2mol%) and NaYF4:Yb,Er (20:0.2mol%), respectively. The characteristic emission wavelength was changed from 475nm to 542nm. Other conditions remained unchanged. The emission lifetime of the mixed system was predicted by fitting Equation 3. The mixed system was configured, and the error between the measured emission lifetime and the predicted emission lifetime was <3%.

[0046] Example 8

[0047] In Examples 1-5, S and L were replaced with NaYF4:Yb,Ho (20:2 mol%) and NaYF4:Yb,Ho (20:0.2 mol%), respectively. The characteristic emission wavelength was changed from 475 nm to 660 nm. Other conditions remained unchanged. The emission lifetime of the mixed system was predicted by fitting Equation 3. The mixed system was configured, and the error between the measured emission lifetime and the predicted emission lifetime was <3%.

[0048] Example 9

[0049] In Examples 1-5, S and L were replaced with NaYF4:Yb,Nd (20:2 mol%) and NaYF4:Yb,Nd (20:0.2 mol%), the excitation wavelength was changed from 980 nm to 808 nm, and the characteristic emission wavelength was changed from 475 nm to 980 nm. Other conditions remained unchanged. The luminescence lifetime of the mixed system was predicted by fitting Equation 3. The mixed system was configured, and the error between the measured luminescence lifetime and the predicted luminescence lifetime was <3%.

Claims

1. A method for predicting the luminescence lifetime of a hybrid upconversion nanomaterial system, characterized in that... Two upconversion nanomaterials with different luminescence lifetimes are mixed, and the luminescence lifetime of the mixed system is predicted by the ratio of the luminescence intensity of the two nanomaterials. The specific steps include: Preparation of rare earth ion RE 3+ Two different doping ratios of NaYF4-based upconversion nanoparticles, S and L, were used, in which rare earth ions RE... 3+ For Tm 3+ Nd 3+ Er 3+ Or Ho 3+ ; The emission spectra of two types of nanoparticles at different mass concentrations γ were measured. At the characteristic emission wavelength, the linear relationship between the emission intensity I and the mass concentration γ in the S and L systems was established as I = aγ + b, where a and b are constants. The lifetime decay curves in the S and L systems were measured separately, and the convolution fitting curve f was obtained. S and f L The measured luminescence lifetime was obtained. For a mixed system, based on the linear relationship between luminescence intensity and mass concentration, I = aγ + b, the proportion of luminescence intensity of S and L in the mixed system was calculated as W. S and W L According to f=W S f S +W L f L The convolution fitting curve f of the hybrid system is obtained, and the predicted luminescence lifetime is obtained.

2. The method for predicting the luminescence lifetime of an upconversion nanomaterial hybrid system according to claim 1, characterized in that... Rare earth ions RE 3+ For Tm 3+ .

3. A method for regulating the luminescence lifetime of a hybrid upconversion nanomaterial system, characterized in that... Two upconversion nanomaterials with different luminescence lifetimes are mixed. The luminescence intensity ratio of the two nanomaterials is calculated based on the target luminescence lifetime of the mixed system. The mass concentration of each of the two upconversion nanomaterials in the mixed system is determined, and the upconversion nanomaterial mixed system with the target luminescence lifetime is obtained. The specific steps include: Preparation of rare earth ion RE 3+ Two different doping ratios of NaYF4-based upconversion nanoparticles, S and L, were used, in which rare earth ions RE... 3+ For Tm 3+ Nd 3+ Er 3+ Or Ho 3+ ; The emission spectra of two types of nanoparticles at different mass concentrations γ were measured. At the characteristic emission wavelength, the linear relationship between the emission intensity I and the mass concentration γ in the S and L systems was established as I = aγ + b, where a and b are constants. The lifetime decay curves in the S and L systems were measured separately, and the convolution fitting curve f was obtained. S and f L The measured luminescence lifetime was obtained; for a mixed system, based on the linear relationship between luminescence intensity and mass concentration, the proportion of luminescence intensity of S and L in the mixed system was calculated as W. S and W L According to f=W S f S +W L f L The convolution fitting curve f of the hybrid system is obtained, and the predicted luminescence lifetime is obtained. The predicted luminescence lifetime of the hybrid system is compared with the proportion of luminescence intensity W of L in the hybrid system. L Fit the curve to obtain a standard curve; For the target luminescence lifetime, the proportion of luminescence intensity W of L in the hybrid system is obtained by calculation using a standard curve. L Then, based on the linear relationship between luminescence intensity and mass concentration, the mass concentrations γ of S and L in the mixed system are obtained.

4. The method for regulating the luminescence lifetime of an upconversion nanomaterial hybrid system according to claim 3, characterized in that, The predicted luminescence lifetime of the hybrid system and W L The standard curve obtained by fitting is: luminescence lifetime = (1 + c × W) L ) / (d+e×W L ), where c, d, and e are constants.

5. The method for regulating the luminescence lifetime of an upconversion nanomaterial hybrid system according to claim 4, characterized in that... Rare earth ions RE 3+ For Tm 3+ .

Images