FLUORESCENT COMPOUND FOR DETECTION OF ISOCYANATE SUBSTANCES, PREPARATION METHOD AND USE THEREOF AS TEST-PAPER-TYPE DETECTION PROBE

Abstract

Disclosed is a fluorescent compound for the detection of isocyanate substances, a preparation method therefor and use thereof as a test-paper-type detection probe. The fluorescent compound is 2,4-di(((4′-(diphenylamino)-[1,1′-biphenyl]-4-yl)imino)methyl)phenol. The fluorescent compound is prepared by means of a one-step method. The fluorescent compound has simple and convenient preparation with high yield, and is capable of making a rapid and specific response to isocyanate substances. Moreover, the fluorescence intensity of the fluorescent compound will enhance with the increase of the isocyanate concentration. The fluorescent compound can be made into a portable test-paper-type probe for the detection of isocyanate substances in air, and can achieve the visual detection of volatile isocyanate gases. The probe has an aggregation-induced emission effect, and thus it has higher fluorescence quantum yield when using a test-paper-type probe for detection.

Claims

1. A fluorescent compound for detection of isocyanate substances, wherein the fluorescent compound has the chemical name of 2,4-di(((4′-(diphenylamino)-[1,1′-biphenyl]-4-yl)imino)methyl)phenol, a molecular formula of C.sub.56H.sub.42N.sub.4O, a molecular weight of 786.33, and has the structural formula of ##STR00004##

2. A method for preparing the fluorescent compound for the detection of isocyanate substances of claim 1, wherein the preparation has the following reaction formula: ##STR00005##

3. The method for preparing the fluorescent compound for the detection of isocyanate substances according to claim 2, comprising the following steps of: (1) dissolving N,N-diphenyl-[1,1′-biphenyl]-4,4′-diamine in acetonitrile with homogeneous ultrasonic agitation to obtain a solution 1; (2) dissolving 4-hydroxyisophthalaldehyde in acetonitrile with homogeneous ultrasonic agitation to obtain a solution 2; (3) dissolving potassium carbonate to water for ultrasonic agitation evenly to obtain an aqueous solution of potassium carbonate; and (4) mixing the solution 1 in step (1) with the solution 2 in step (2) evenly, and then being dropwise added into the aqueous solution of potassium carbonate in step (3), vacuumizing and charging with nitrogen, carrying out a heating reaction, then cooling to room temperature, separating and purifying to obtain the fluorescent compound for the detection of isocyanate substances.

4. The method for preparing the fluorescent compound for the detection of isocyanate substances according to claim 3, wherein a molar ratio of the N,N-diphenyl-[1,1′-biphenyl]-4,4′-diamine in step (1) to the 4-hydroxyisophthalaldehyde in step (2) is (2-5):1.

5. The method for preparing the fluorescent compound for the detection of isocyanate substances according to claim 3, wherein a molar ratio of the N,N-diphenyl-[1,1′-biphenyl]-4,4′-diamine in step (1) to the potassium carbonate in step (3) is 1:(1-10).

6. The method for preparing the fluorescent compound for the detection of isocyanate substances according to claim 3, wherein in the solution 1 of step (1), N,N-diphenyl-[1,1′-biphenyl]-4,4′-diamine has a concentration of 0.01 M-0.1 M; and in the solution 2 of step (2), 4-hydroxyisophthalaldehyde has a concentration of 0.01 M-0.1 M.

7. The method for preparing the fluorescent compound for the detection of isocyanate substances according to claim 3, wherein the aqueous solution of potassium carbonate in step (3) has a concentration of 1-6 mol/L.

8. The method for preparing the fluorescent compound for the detection of isocyanate substances according to claim 3, wherein the heating reaction in step (4) has a temperature of 25-120° C.; and the heating reaction lasts for 3 hours to 24 hours.

9. The method for preparing the fluorescent compound for the detection of isocyanate substances according to claim 3, wherein the separating and purifying in step (4) comprise the following steps of: extracting with dichloromethane and deionized water; collecting an organic phase and drying by anhydrous sodium sulfate; distilling under reduced pressure to remove solvents, and subjecting to column chromatography on silica gel.

10. Use of the fluorescent compound for the detection of isocyanate substances of claim 1 as a test-paper-type detection probe in analysis and detection of isocyanate substances.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Description of the Drawings

[0035] FIG. 1 is a schematic diagram showing that a fluorescent compound for the detection of isocyanate substances provided by the present invention transforms between Enol form and Keto form structures;

[0036] FIG. 2 is a schematic diagram showing the response mechanism that the fluorescent compound for the detection of isocyanate substances provided by the present invention makes a response to isocyanate;

[0037] FIG. 3 is a Hydrogen Nuclear Magnetic Resonance (.sup.1H NMR) of 2,4-di(((4′-(diphenylamino)-[1,1′-biphenyl]-4-yl)imino)methyl)phenol prepared in Example 1.

[0038] FIG. 4 is fluorescence spectra of the fluorescent compound for the detection of isocyanate substances provided by the present invention as a fluorescent probe before and after making a response to isocyanate.

[0039] FIG. 5 is absorption spectra of the fluorescent compound for the detection of isocyanate substances provided by the present invention as a fluorescent probe before and after making a response to isocyanate.

[0040] FIG. 6 is fluorescence spectra of a reaction product BTPAP-iso in Example 4 in a mixed solution of dichloromethane/methanol in varying proportions.

[0041] FIG. 7 is a diagram showing fluorescence intensity changes of BTPAP-iso in Example 4 at 425 nm in a mixed solution of dichloromethane/methanol in varying proportions.

[0042] FIG. 8 is fluorescence spectra of the fluorescent compound BTPAP for the detection of isocyanate substances prepared in Example 4 in response to different concentrations of isocyanate.

[0043] FIG. 9 is a diagram showing fluorescence intensity of the fluorescent compound BTPAP for the detection of isocyanate substances prepared in Example 4 in response to different concentrations of isocyanate.

DETAILED DESCRIPTION

Embodiments of the Invention

[0044] Detailed embodiments of the present invention will be further described in detail in combination with the accompanying drawings and examples, but embodiments of the present invention are not limited thereto. It needs to be pointed that any process not specified particularly in detail below should be achieved or understood by reference to the prior art by a person skilled in the art. Any reagent or instrument not marked with a manufacturer should be regarded as a conventional product available in the market.

[0045] The chemical equation for preparing the fluorescent compound for the detection of isocyanate substances in examples is as follows:

##STR00003##

Example 1

[0046] A method for preparing a fluorescent compound for the detection of isocyanate substances, including the following steps of:

[0047] (1) 672 mg N,N-diphenyl-[1,1′-biphenyl]-4,4′-diamine was dissolved in 20 mL acetonitrile with homogenous ultrasonic agitation to obtain a solution 1;

[0048] (2) 150 mg 4-hydroxyisophthalaldehyde was dissolved in 10 mL acetonitrile with homogenous ultrasonic agitation to obtain a solution 2;

[0049] (3) meanwhile, 138 mg potassium carbonate was dissolved to deionized water with homogenous ultrasonic agitation evenly to obtain a 1 mol/L aqueous solution of potassium carbonate; and

[0050] (4) the solution 1 in step (1) and the solution 2 in step (2) were mixed evenly, and then dropwise added into 1 mol/L aqueous solution of potassium carbonate prepared in step (3), vacuumized and nitrogen was charged, a heating reaction was carried out for 3 hours, where the reaction temperature was controlled at 25° C.; then the reaction was stopped, after cooling to room temperature, then the obtained product was separated and purified to obtain 565.9 mg orange-yellow powder, 2,4-di(((4′-(diphenylamino)-[1,1′-biphenyl]-4-yl)imino)methyl)phenol, namely, the fluorescent compound (BTPAP) for the detection of isocyanate substances with a yield of 72%;

[0051] The product was characterized by H-NMR below: .sup.1H NMR (600 MHz, DMSO-d6) δ 9.91 (s, 1H), 8.79 (s, 1H), 8.47 (s, 1H), 7.93 (dd, J=17.1, 9.0 Hz, 2H), 7.65 (dd, J=8.2, 3.2 Hz, 4H), 7.40 (dd, J=15.6, 8.3 Hz, 8H), 7.27-7.23 (m, 10H), 7.13-7.08 (m, 6H), 7.07-6.98 (m, 9H). Particularly, “a” having a chemical shift at 9.91 ppm belonged to a hydroxyl proton characteristic peak; “b” and “c” at 8.79 ppm and 8.47 ppm respectively belonged to proton characteristic peaks on a Schiff base structure; proton peaks at 7.93 ppm and 7.65 ppm mainly belonged to characteristic peaks of a benzene ring structure connected with triphenylamine; “g” at 7.3-6.9 ppm mainly belonged to a proton characteristic peak on three aromatic rings of triphenylamine. By the analysis of NMR, it can be determined that the synthesized product was a target product. The HNMR thereof was shown in FIG. 3.

Example 2

[0052] A method for preparing a fluorescent compound for the detection of isocyanate substances, including the following steps of:

[0053] (1) 1008 mg N,N-diphenyl-[1,1′-biphenyl]-4,4′-diamine was dissolved in 50 mL acetonitrile with homogenous ultrasonic agitation evenly to obtain a solution 1;

[0054] (2) 150 mg 4-hydroxyisophthalaldehyde was dissolved in 50 mL acetonitrile with homogenous ultrasonic agitation evenly to obtain a solution 2;

[0055] (3) 690 mg potassium carbonate was dissolved in deionized water with homogenous ultrasonic agitation evenly to obtain a 3 mol/L aqueous solution of potassium carbonate; and

[0056] (4) the solution 1 in step (1) and the solution 2 in step (2) were mixed evenly, and then dropwise added into 3 mol/L aqueous solution of potassium carbonate prepared in step (3), vacuumized and nitrogen was charged, a heating reaction was carried out for 12 hours, where the reaction temperature was controlled at 70° C.; then the reaction was stopped, after cooling to room temperature, then the obtained product was separated and purified to obtain 644.5 mg orange-yellow powder, 2,4-di(((4′-(diphenylamino)-[1,1′-biphenyl]-4-yl)imino)methyl)phenol, namely, the fluorescent compound (BTPAP) for the detection of isocyanate substances with a yield of 82%.

[0057] The characterization of the fluorescent probe compound BTPAP obtained in this example was the same as the characterization result in Example 1, referring to FIG. 3.

Example 3

[0058] A method for preparing a fluorescent compound for the detection of isocyanate substances, including the following steps of:

[0059] (1) 1680 mg N,N-diphenyl-[1,1′-biphenyl]-4′-diamine was dissolved in 500 mL acetonitrile with homogenous ultrasonic agitation evenly to obtain a solution 1;

[0060] (2) 150 mg 4-hydroxyisophthalaldehyde was dissolved in 100 mL acetonitrile for with homogenous ultrasonic agitation evenly to obtain a solution 2;

[0061] (3) 1380 mg potassium carbonate was dissolved in deionized water with homogenous ultrasonic agitation evenly to obtain a 6 mol/L aqueous solution of potassium carbonate; and

[0062] (4) the solution 1 in step (1) and the solution 2 in step (2) were mixed evenly, and then dropwise added into 6 mol/L aqueous solution of potassium carbonate prepared in step (3), vacuumized and nitrogen was charged, a heating reaction was carried out for 24 hours, where the reaction temperature was controlled at 120° C.; then the reaction was stopped, after cooling to room temperature, then the obtained product was separated and purified to obtain 707.4 mg orange-yellow powder, 2,4-di(((4′-(diphenylamino)-[1,1′-biphenyl]-4-yl)imino)methyl)phenol, namely, the fluorescent compound (BTPAP) for the detection of isocyanate substances with a yield of 90%.

[0063] The characterization of the fluorescent probe compound (BTPAP) obtained in this example was the same as the characterization result in Example 1, referring to FIG. 3.

Example 4

[0064] Test on Spectroscopic Performance.

[0065] (1) Measurement of Fluorescence Spectra and Absorption Spectra of a Fluorescent Compound BTPAP Before and after Making a Response to Isocyanate:

[0066] 1.6 mg fluorescent compound 2,4-di(((4′-(diphenylamino)-[1,1′-biphenyl]-4-yl)imino)methyl)phenol was dissolved to 2 mL DCM and prepared into a stock solution of the fluorescent compound having a concentration of 1 mM. During test, the fluorescent compound kept a concentration of 5 μM, and total volume of the test system was kept 3 mL (containing dichloromethane having a volume percent of 10%); isocyanate compounds included multiple kinds of compounds containing an isocyanate group; in this example, chloroethyl isocyanate was used as a model analyte; an isocyanate solution was dropwise added to a probe BTPAP solution at 25° C., shaken for 5 minutes to test the response performance of BTPAP to isocyanate; and test results were shown in FIGS. 4 and 5. It can be seen from FIGS. 4 and 5 that after making a response to isocyanate, emission wavelength and absorption spectrum showed a certain degree of blue shift; this was because the ESIPT effect disappeared after isocyanate reacted with aromatic hydroxy, resulting in the failure of the transformation between Enol form and Keto form; and meanwhile, the electronic effect also changed, resulting in the blue shift and enhancement of fluorescence emission.

[0067] (2) Test on the Aggregation-Induced Emission Feature of BTPAP-Iso:

[0068] When the fluorescent compound BTPAP was subjected to a chemical reaction with isocyanate, the phenolic hydroxyl group in molecules was transformed to carbamate, thus generating a new substance (BTPAP-iso). Test on the aggregation-induced emission feature of BTPAP-iso was performed below.

[0069] A mixed solution of dichloromethane and methanol in different volume fractions was prepared, of which the volume percent of methanol was respectively 0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, and 99%; during test, BTPAP-iso had a concentration of 5 μM; the test temperature was room temperature; 360 nm was adopted as excitation wavelength; and the measured spectra were shown in FIG. 6; and the fluorescence intensity at 425 nm with the change of volume fraction of methanol was shown in FIG. 7. It can be seen from FIG. 7 that in a test solution system having a relatively small volume fraction of methanol (<50%), the solution had weak fluorescence; when the volume fraction of methanol increased gradually, fluorescence intensity enhanced gradually, especially when the volume fraction of methanol increased to 99%, fluorescence intensity increased to the maximum. This is because the probe molecule had better solubility in dichloromethane, and its molecule can rotate and vibrate in the solution freely; and electron can dissipate the excited energy via intramolecular movements when the excited-state electrons return to the ground state, making fluorescence weak; while with the increase of the volume fraction of a poor solvent, such as methanol, it makes the space for intramolecular free rotation and vibration in the test solution system smaller and smaller, and even makes molecules agglomerated together due to the decrease of solubility, thus opening the radiative pathway that the excited-state electrons transit to the ground state, thus capable of releasing fluorescence, which reflects the characteristic of aggregation-induced emission phenomenon fully. Moreover, it can be further seen from FIG. 7 that a quantification curve of the fluorescence intensity at 425 nm versus the increase of the volume fraction of methanol also indicates the presence of the above phenomenon.

[0070] (3) Response Test of a BTPAP Fluorescent Probe to Different Concentrations of Isocyanate:

[0071] Different concentrations of isocyanate test sample solutions (concentrations were respectively 0 μM, 1 μM 2 μM, 3 μM, 5 μM, 8 μM, 10 μM, 15 μM, 20 μM, 30 μM, and 40 μM) were prepared. During test procedure, the probe concentration was kept 5 μM, and the volume fraction of DCM and methanol was 1/99; the test temperature was room temperature; the response time was 5 min; 360 nm served as excitation wavelength to measure the fluorescence spectra (fluorescence intensity at 425 nm) of the fluorescent probe in response to different concentrations of isocyanate; and the test results were shown in FIG. 8. Moreover, the fluorescence intensity curves to different concentrations of isocyanate were shown in FIG. 9. It can be seen from FIG. 8 that the fluorescent compound prepared by the present invention had a good response effect to different concentrations of isocyanate; and with the increase of the isocyanate concentration, the fluorescence intensity also enhanced gradually. It can be seen from FIG. 9 that the fluorescence enhancement amplitude slowed down when the isocyanate concentration was up to 20 μM, indicating that the reaction system became saturated. Thus, the probe prepared by the present invention is suitable for detecting different concentrations of isocyanate, and has a wider scope of application concentration.

Example 5

[0072] Response Test of a Test-Paper-Type Fluorescent Probe Containing BTPAP to Different Concentrations of Isocyanate:

[0073] 1 mM fluorescent probe BTPAP stock solution was prepared, and evenly dropped onto a Whatman filter paper, then air dried naturally at room temperature, and prepared into a test-paper-type probe (appeared apparent yellow), afterwards, a test paper was suspended in an isocyanate atmosphere having a concentration of 5 μM, standing for 5 minutes, the change of apparent color can be seen under visible light; and in the presence of isocyanate substances, the test paper changed to white from apparent yellow, and the color change can be visible by naked eyes. Moreover, the test paper was respectively placed in different concentrations (0 μM-5 μM) of isocyanate atmosphere, after standing for 5 minutes, a variation diagram of fluorescence under the irradiation of a 15 W 365 nm portable UV lamp can be observed directly; it can be seen that the fluorescence intensity of the probe enhanced and fluorescence color gradually changed to bright blue from dark orange with the increase of isocyanate concentration under the excitation at 365 nm. On the other hand, the probe molecule itself has better aggregation-induced emission effect, and has very strong fluorescence intensity due to high fluorescence quantum yield in solid aggregation state. The above results indicate that the test-paper-type probe prepared by the probe molecule can make a response to isocyanate, and has visible changes observable by naked eyes. Moreover, the test-paper-type probe has simple preparation process, easy operation, and is easy to carry, store and use.

[0074] In the present invention, the fluorescent probe molecule 2,4-di(((4′-(diphenylamino)-[1,1′-biphenyl]-4-yl)imino)methyl)phenol (BTPAP) can be used to detect isocyanate; and the probe molecule (the fluorescent compound used for the detection of isocyanate substances) has AIE feature itself, and has changed and enhanced fluorescence with the increase of the isocyanate concentration in a test solution, larger range of fluorescence variation, and has high distinguishable degree of color. Furthermore, the present invention can be prepared into a test-paper-type probe, suitable for the detection of volatile isocyanate substances existing in air; and the color change of the test-paper-type probe can be visible by naked eyes under visible light in the presence of isocyanate; and under a 365 nm UV lamp, the fluorescence intensity of the test-paper-type probe makes blue shift and enhancement with the increase of isocyanate gas concentration. The above results indicate that the fluorescent probe prepared by the present invention can be used for the detection of isocyanate substances in a solution and of gaseous isocyanate substances, and specifically can be used to monitor isocyanate, such a hazardous substance in atmospheric air, water resources, working space of a factory and industrial wastewater.

[0075] The above examples are only preferred embodiments of the present invention, and only used for explaining the present invention, but not limiting the present invention. Moreover, any alteration, replacement, modification and the like made by a person skilled in the art within the spirit of the present invention shall fall within the protection scope of the present invention.