A fluorescence probe for regulating crystallinity of hydrotalcite colloidal sol based on pi-pi stacking and a preparation method thereof

Abstract

The application discloses a fluorescence probe for measuring crystallinity of hydrotalcite colloidal sol based on pi-pi stacking regulation and a preparation method thereof. The application adopts an imidazole anchoring naphthalene diamine (IANA) fluorophore with a planar naphthalene motif as the fluorescence probe. The imidazole group has strong binding capacity for transition divalent metal ions, and the transition metal enhances the ordered arrangement of the IANA after coordination with the imidazole, which is conducive to the face-to-face pi-pi stacking of the planar naphthalene motif and inhibits the absorption of ultraviolet light, thereby causing fluorescence quenching. However, the internal structure order and spatial atomic arrangement of different crystallinity materials are different, which will cause differences in the ordered arrangement of the IANA, affect the quenching degree of the probe, and then the crystallinity can be measured through the quenching degree. The application regulates the fluorescence to measure the crystallinity of the hydrotalcite colloidal sol through the pi-pi stacking, and opens up a new way for exploring a replacement scheme of X-ray diffraction.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent probe technology, and specifically relates to a fluorescent probe for measuring the crystallinity of hydrotalcite colloidal sol based on π-π stacking regulation and its preparation method. Background Technology

[0002] Colloidal sols of nanomaterials possess excellent electrical and / or optical properties and have been widely applied in sensing, catalysis, adsorption, energy, and medicine. Generally, their performance depends heavily on their intrinsic structure, such as crystallinity. Currently reported analytical techniques include X-ray diffraction (XRD), differential scanning calorimetry (DSC), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and terahertz spectroscopy. However, these techniques are often affected by overlap between crystalline and amorphous regions, as well as overlap in specific wavelength bands, leading to high analytical errors. Furthermore, these techniques are typically applicable to powder samples. It has been reported that the crystallinity of materials changes during the transition from liquid phase to solid powder. Simultaneously, for colloidal sol XRD detection, solvent absorption significantly affects accuracy. Therefore, exploring a simple and rapid method for determining the crystallinity of colloidal sols is essential. Summary of the Invention

[0003] The purpose of this invention is to provide a fluorescent probe for determining the crystallinity of hydrotalcite colloidal sol based on π-π stacking regulation and its preparation method.

[0004] The structural formula of the fluorescent probe for determining the crystallinity of hydrotalcite colloidal sol based on π-π stacking modulation is as follows:

[0005] .

[0006] The preparation method of the fluorescent probe for determining the crystallinity of hydrotalcite colloidal sol based on π-π stacking regulation is as follows: 2,3-diaminonaphthalene and imidazole-2-carboxaldehyde are dissolved in a methanol-ethanol mixed solvent with a volume ratio of 0.5-2, heated under reflux for 20-30 hours, cooled to room temperature, filtered, washed with methanol, and dried at 60-80℃ to obtain the fluorescent probe.

[0007] The method for determining the crystallinity of hydrotalcite colloidal sol is as follows:

[0008] (1) A blank solution was obtained by mixing the fluorescent probe solution for determining the crystallinity of hydrotalcite colloidal sol based on π-π stacking with water. A mixed solution was obtained by mixing the fluorescent probe solution for determining the crystallinity of hydrotalcite colloidal sol based on π-π stacking with water with hydrotalcite colloidal sol containing transition metals and different crystallinities and the same layer metal elements. The concentration of fluorescent probe in the blank solution and the mixed solution was the same, and the concentration of hydrotalcite in each mixed solution was the same. Fluorescence detection was performed on the blank solution and each mixed solution after the same reaction time. The excitation wavelength was 340-342 nm, and the detection wavelength was 450-470 nm. The difference in fluorescence intensity between the blank solution and the mixed solution was the fluorescence quenching value. A standard curve was plotted with crystallinity as the abscissa and fluorescence quenching value as the ordinate.

[0009] (2) The same liquid double hydroxides containing transition metals and the same fluorescent probe concentration and the same liquid double hydroxide concentration were prepared under the same preparation conditions. After the reaction time was the same, fluorescence detection was performed under the same conditions, and the fluorescence quenching value was calculated. Then the crystallinity was calculated according to the standard curve.

[0010] The solvent for the fluorescent probe solution is DMSO and / or ethanol.

[0011] The concentration of the fluorescent probe in the mixture is 10-20 μM, and the concentration of hydrotalcite is 8-15 μg / mL.

[0012] The reaction time is at least 1 hour.

[0013] This invention employs an imidazole-anchored naphthyl diamine (IANA) fluorophore with planar naphthyl inscriptions as a fluorescent probe. The imidazole group exhibits a strong binding affinity for transition divalent metal ions. Coordination between the transition metal and imidazole enhances the ordered arrangement of IANA, facilitating face-to-face π-π stacking of the planar naphthyl inscriptions and suppressing ultraviolet light absorption, thus causing fluorescence quenching. However, the internal structural order and spatial atomic arrangement differ among materials with varying crystallinity, leading to variations in the ordered arrangement of IANA and affecting the degree of probe quenching. This degree of quenching can then be used to determine crystallinity. This invention utilizes π-π stacking to regulate fluorescence for determining the crystallinity of hydrotalcite colloidal sols, opening a new avenue for exploring alternatives to X-ray diffraction. Attached Figure Description

[0014] Figure 1 Characterization of the fluorescent probe (IANA). (a) Synthesis steps of IANA, (b) ESI-MS spectrum of IANA, (c) IANA... 1H NMR spectrum, (d) FT-IR spectrum of IANA, (e) fluorescence excitation (black line), emission (dashed line) and UV-Vis absorption (gray line) spectrum of IANA (20 μM); inset shows photographs of IANA in visible light (left) and 365 nm UV light (right).

[0015] Figure 2 Characterization of CdAl-LDHs. XRD patterns (a), FT-IR spectra (b), TEM (c), and hydrodynamic diameter distributions (d) of CdAl-LDH-1, CdAl-LDH-2, CdAl-LDH-3, and CdAl-LDH-4.

[0016] Figure 3 Fluorescence emission spectra of IANA in the presence of different concentrations of CdAl-LDHs.

[0017] Figure 4 (a) Fluorescence emission spectra of IANA with and without the addition of CdAl-LDHs with different crystallinities, (b) Time-dependent relative fluorescence intensity of IANA with the addition of CdAl-LDHs with different crystallinities.

[0018] Figure 5 Time-dependent fluorescence emission spectra of IANA in the presence of CdAl-LDH-1 (a), CdAl-LDH-2 (b), CdAl-LDH-3 (c) and CdAl-LDH-4 (d), respectively.

[0019] Figure 6 Time-dependent fluorescence emission spectra of IANA in the presence of CdAl-LDH-X.

[0020] Figure 7 Fluorescence emission spectra (a) and UV-Vis absorption spectra (b) of IANA with and without (black line) CdAl-LDH-X (dashed line), (c) standard curves of fluorescence quenching degree and crystallinity, (d) XRD pattern of CdAl-LDH-X.

[0021] Figure 8 XRD patterns of ZnAl-LDH-52.7%, ZnAl-LDH-61.1%, ZnAl-LDH-69.3%, and ZnAl-LDH-79.9%.

[0022] Figure 9 Time-dependent fluorescence emission spectra of IANA in the presence of ZnAl-LDH-52.7% (a), ZnAl-LDH-61.1% (b), ZnAl-LDH-69.3% (c) and ZnAl-LDH-79.9% (d), respectively.

[0023] Figure 10 Standard curves for fluorescence quenching degree and ZnAl-LDHs crystallinity.

[0024] Figure 11 Fluorescence emission spectra of the supernatant after IANA reacts with CdAl-LDHs (dashed line) and ZnAl-LDHs (gray line).

[0025] Figure 12 Standard curves for fluorescence quenching degree and crystallinity of Cd2Al-LDHs.

[0026] Figure 13 Standard curves for fluorescence quenching degree and crystallinity of ZnCd2Al-LDHs.

[0027] Figure 14 XRD patterns of colloidal CdAl-LDHs.

[0028] Figure 15 Crystallinity values ​​were calculated using fluorescence (black) and XRD (gray) methods. Detailed Implementation

[0029] Example 1

[0030] Synthesis steps of a fluorescent probe (naphthalene diamine derivative fluorescent probe IANA) for determining the crystallinity of hydrotalcite colloidal sol based on π-π stacking regulation: 2,3-diaminonaphthalene (0.15 g, 0.95 mmol) and imidazole-2-carboxaldehyde (0.10 g, 1.1 mmol) were dissolved in a mixed methanol-ethanol solvent (20 mL, v / v = 1:1). The mixture was heated to reflux and stirred for 24 hours. Then, the solution was cooled to room temperature, filtered, washed with methanol, and dried under vacuum at 60 °C for 12 hours to remove residual solvent, yielding product IANA (yellow solid) in 52% yield. IANA was dissolved in DMSO to prepare a 1 mM fluorescent probe solution for later use.

[0031] The structural formula of the fluorescent probe prepared above is as follows:

[0032] .

[0033] Example 2

[0034] Synthesis steps of CdAl-LDHs with different crystallinities:

[0035] Solution A was prepared by dissolving 0.39 g Al(NO3)3·9H2O in 100 mL of deionized water, and salt solution B was prepared by dissolving 0.82 g Cd(NO3)2·4H2O in 60 mL of deionized water. The pH of solution A was adjusted to 10.3 using saturated Ca(OH)2 solution. Under vigorous stirring, the saturated Ca(OH)2 solution and solution B were simultaneously and slowly added dropwise to the reaction system to maintain a constant pH. The reaction was completed within 40 minutes, and the white precipitate was aged at 120°C for 10 h to obtain hydrotalcite, denoted as CdAl-LDH-4. The obtained hydrotalcite was divided into two equal volumes, denoted as Sample 1 and Sample 2, and centrifuged at 10,000 rpm and washed with ethanol. Sample 1 was dried in an oven at 60°C and weighed; the weight of sample 2 hydrotalcite was the same as that of sample 1. Using the weight of sample 1 as a control, the undried sample 2 was ultrasonically dispersed with water to obtain a colloidal sol with a concentration of 1 mg / mL for later use.

[0036] The reaction time was adjusted to 5 min, pH 10.0, and no aging was allowed, while all other conditions remained the same, resulting in hydrotalcite denoted as CdAl-LDH-1. The post-treatment method was the same, yielding a colloidal sol of 1 mg / mL.

[0037] The reaction time was adjusted to 10 min, pH 10.3, and no aging was performed, while all other conditions remained the same, resulting in hydrotalcite denoted as CdAl-LDH-2. The post-treatment method was the same, yielding a colloidal sol of 1 mg / mL.

[0038] The reaction time was adjusted to 40 min, pH 10.3, and no aging was performed, while all other conditions remained the same, resulting in hydrotalcite denoted as CdAl-LDH-3. The post-treatment method was the same, yielding a colloidal sol of 1 mg / mL.

[0039] The reaction time was adjusted to 10 min, pH 10.3, aging temperature 120°C, and aging time 10 h, with all other conditions remaining the same, to obtain hydrotalcite, denoted as CdAl-LDH-X. The post-treatment method was the same, yielding a colloidal sol of 1 mg / mL.

[0040] Application Example 1

[0041] Investigation of the fluorescence response of IANA to different concentrations of CdAl-LDHs-1:

[0042] 0, 5, 10, 15, 20, 35, and 50 μL of CdAl-LDHs-1 colloidal sol were added to water to make a total volume of 980 μL. After thorough mixing, 20 μL of the IANA solution from Example 1 was added, and the mixture was reacted with continuous shaking at 950 rpm for 1 hour at room temperature before testing. The test scan range was 360 nm-600 nm, with a slit width of 5 nm and a voltage of 600 V. Figure 3 As shown, at an excitation wavelength of 340 nm, the fluorescence peak at 462 nm gradually quenched to almost disappear with the increase of LDH content, proving that the fluorescence quenching degree of the IANA probe is related to the LDH concentration and increases with the increase of concentration.

[0043] Application Example 2

[0044] Fluorescence response kinetics of the interaction between IANA and CdAl-LDHs with different crystallinities:

[0045] A blank solution was prepared by mixing 20 μL of IANA solution with 980 μL of water. 15 μL each of the following colloidal sols were added to 965 μL of water, mixed thoroughly, and then 20 μL of IANA solution was added to obtain a mixed solution. The mixture was reacted at 950 rpm in an oscillator at room temperature, and fluorescence kinetics were measured. The excitation wavelength was set to 340 nm, the test scan range to 360 nm–600 nm, the slit width to 5 nm, and the voltage to 600 V. Figure 4 As shown in figure a, the addition of CdAl-LDHs to IANA, despite significant fluorescence quenching, did not cause any visible changes in the IANA emission spectrum. Furthermore, the quenching efficiency was directly proportional to the crystallinity of the CdAl-LDHs. Figure 4 As shown in b, the fluorescence intensity of IANA decreased rapidly after the addition of CdAl-LDHs. After 60 min of reaction, the fluorescence quenching degree of IANA reached >39%. These results indicate that the interaction between CdAl-LDHs and IANA may affect the fluorescence behavior of IANA. The fluorescence response kinetics of IANA to four CdAl-LDHs are as follows: Figure 5 As shown, with the increase of crystallinity of CdAl-LDHs, the internal structure becomes more ordered and the spatial atomic arrangement becomes more regular, resulting in a more ordered arrangement of IANA after Cd-imidazolium coordination, a stronger face-to-face π-π stacking degree, and the degree of fluorescence quenching varies with different crystallinity.

[0046] Based on the fluorescence kinetics spectrum obtained above, the fluorescence intensity values ​​at 462 nm were extracted for the blank solution and each mixed solution (after 60 min of reaction). The difference in fluorescence intensity between the blank solution and the mixed solution was the fluorescence quenching value. A standard curve was obtained by plotting crystallinity on the x-axis and the fluorescence quenching value on the y-axis: y = 0.595x + 21.135, R0. 2 =0.994, as Figure 7 As shown in c.

[0047] Application Example 3

[0048] The CdAl-LDHs-X colloidal sol was prepared under the same conditions as in Application Example 2 to obtain the test mixture, and fluorescence detection was performed. Figure 6 As shown, the fluorescence intensity of the IANA solution gradually decreased after the addition of CdAl-LDH-X. Calculations showed that the fluorescence quenching degree was approximately 44.6% after 60 minutes of reaction. Figure 7 a). After adding CdAl-LDH-X, the UV-Vis absorption spectrum of IANA also showed a significant decrease ( Figure 7 b). The fluorescence quenching value was calculated using the same method, and then the crystallinity was calculated to be 39.5% based on the standard curve. To verify the measurement accuracy, the XRD pattern of CdAl-LDH-X was analyzed ( Figure 7 d) The crystallinity of CdAl-LDH-X was calculated to be 38.9%, which is close to the result of the fluorescence method described above, with a relative error of 1.5%, indicating that the crystal detection method of the present invention has high accuracy.

[0049] Application Example 4

[0050] ZnAl-LDHs with different crystallinities were formulated into colloidal sols at a concentration of 1 mg / mL. For example... Figure 8 As shown, the crystallinity calculated by XRD was 52.7%, 61.1%, 69.3%, and 79.9%, respectively. 30 μL of ZnAl-LDHs colloidal sol with different crystallinities was added to 950 μL of water, mixed thoroughly, and then 20 μL of IANA solution was added. The mixture was reacted at room temperature in a shaker at 950 rpm, and fluorescence kinetics were measured. The test scan range was 360 nm–600 nm, the slit width was 5 nm, and the voltage was 600 V. Similar to CdAl-LDHs, the fluorescence intensity of IANA decreased rapidly after the addition of ZnAl-LDHs. Figure 9 ).at the same time, Figure 10 The reaction showed a good linear relationship between the fluorescence quenching degree of IANA and the crystallinity of ZnAl-LDHs after 60 min (y = 0.611x + 0.450, R0). 2 =0.998). The fluorescence quenching degree of ZnAl-LDHs was lower than that of CdAl-LDHs, indicating that there may be different quenching efficiencies. Figure 11 As shown, 15 μL of ZnAl-LDHs and CdAl-LDHs were added to 965 μL of water, respectively. After mixing thoroughly, 20 μL of IANA solution was added and the reaction was carried out for 60 min. The fluorescence intensity of the supernatant showed a significant difference, indicating that CdAl-LDHs has a stronger binding ability to IANA compared with ZnAl-LDHs.

[0051] Application Example 5

[0052] Using the same preparation and detection conditions as in Application Example 2, Cd₂Al-LDHs (Cd / Al = 2 / 1) and ZnCd₂Al-LDHs with different crystallinities were prepared. The crystallinity calculated by XRD was fitted to the fluorescence quenching degree of IANA after 60 min of reaction. The results showed a good linear relationship between the fluorescence quenching degree of IANA and the crystallinity of Cd₂Al-LDHs and ZnCd₂Al-LDHs. The fitted standard curves were y = 0.485x + 18.178, R₀ = 0.485x + 18.178. 2 =0.996; y=0.615x+16.634, R 2 =0.997; for example Figure 12 and Figure 13 As shown.

[0053] Application Example 6

[0054] Application of fluorescence technology in detecting the crystallinity of layered materials in practical synthesis and testing:

[0055] Based on Example 2, five CdAl-LDHs with different crystallinities were synthesized by changing the reaction pH and temperature. Figure 14 A series of tests were conducted. The fluorescence quenching degree of CdAl-LDHs with different crystallinities was obtained through fluorescence quenching kinetics. Based on the linear relationship (Application Example 2), the crystallinities of the five CdAl-LDHs were calculated to be 36.0%, 44.2%, 51.8%, 61.4%, and 70.0%, respectively. XRD technology calculated the corresponding crystallinities to be 34.9%, 43.0%, 50.9%, 60.3%, and 68.7%, respectively. Figure 15 The crystallinity obtained by different methods is very close.

Claims

1. A method for determining the crystallinity of hydrotalcite colloidal sol, characterized in that, The specific steps of the method are as follows: (1) A blank solution was obtained by mixing the fluorescent probe solution for determining the crystallinity of hydrotalcite colloidal sol based on π-π stacking with water. A mixed solution was obtained by mixing the fluorescent probe solution for determining the crystallinity of hydrotalcite colloidal sol based on π-π stacking with water with hydrotalcite colloidal sol containing transition metals and having different crystallinities and the same layer metal elements. The concentration of fluorescent probe in the blank solution and the mixed solution was the same, and the concentration of hydrotalcite in each mixed solution was the same. Fluorescence detection was performed on the blank solution and each mixed solution after the same reaction time. The excitation wavelength was 340-342 nm, and the detection wavelength was 450-470 nm. The difference in fluorescence intensity between the blank solution and the mixed solution was the fluorescence quenching value. A standard curve was plotted with crystallinity as the abscissa and fluorescence quenching value as the ordinate. (2) The same liquid double hydroxides containing transition metals and the same fluorescent probe concentration and the same liquid double hydroxide concentration were prepared under the same preparation conditions. After the reaction time was the same, fluorescence detection was performed under the same conditions, and the fluorescence quenching value was calculated. Then the crystallinity was calculated according to the standard curve. The structural formula of the fluorescent probe for determining the crystallinity of hydrotalcite colloidal sol based on π-π stacking modulation is as follows: 。 2. The method according to claim 1, characterized in that, The preparation method of the fluorescent probe for determining the crystallinity of hydrotalcite colloidal sol based on π-π stacking regulation is as follows: 2,3-diaminonaphthalene and imidazole-2-carboxaldehyde are dissolved in a methanol-ethanol mixed solvent with a volume ratio of 0.5-2, heated under reflux for 20-30 hours, cooled to room temperature, filtered, washed with methanol, and dried at 60-80℃ to obtain the fluorescent probe.

3. The method according to claim 1, characterized in that, The solvent for the fluorescent probe solution is DMSO and / or ethanol.

4. The method according to claim 1, characterized in that, The concentration of the fluorescent probe in the mixture is 10-20 μM, and the concentration of hydrotalcite is 8-15 μg / mL.

5. The method according to claim 1, characterized in that, The reaction time is at least 1 hour.

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