U.S. patent application number 16/614378 was filed with the patent office on 2021-01-28 for method for preparing ratiometric fluorescent probe for cymoxanil based on double-emission quantun dot-silver nanoparticle complex.
This patent application is currently assigned to Qingdao University. The applicant listed for this patent is QINGDAO UNIVERSITY. Invention is credited to Rijun GUI, Xiaowen JIANG, Hui JIN, Yujiao SUN.
Application Number | 20210025820 16/614378 |
Document ID | / |
Family ID | 1000005326336 |
Filed Date | 2021-01-28 |
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United States Patent
Application |
20210025820 |
Kind Code |
A1 |
GUI; Rijun ; et al. |
January 28, 2021 |
METHOD FOR PREPARING RATIOMETRIC FLUORESCENT PROBE FOR CYMOXANIL
BASED ON DOUBLE-EMISSION QUANTUN DOT-SILVER NANOPARTICLE
COMPLEX
Abstract
A method for preparing a ratiometric fluorescent probe for
cymoxanil based on a double-emission quantum dot-silver
nanoparticle complex, wherein, the double-emission carbon quantum
dots and the silver nanoparticles are prepared, and the inner
filter effect occurring between the double-emission carbon quantum
dots and the dispersed silver nanoparticles causes the blue
fluorescence quenching of the carbon quantum dots. However, the
specific binding of cymoxanil to silver nanoparticles causes the
silver nanoparticles to accumulate, and then the inner filter
effect occurring between the double-emission carbon quantum dots
and the dispersed silver nanoparticles causes the green
fluorescence quenching of carbon quantum dots. In this regard, the
linear relationship between the intensity ratio of two fluorescent
emission peaks of carbon quantum dots and the molar concentration
of cymoxanil is established, and the ratiometric fluorescent probe
for cymoxanil is constructed.
Inventors: |
GUI; Rijun; (Qingdao,
CN) ; JIANG; Xiaowen; (Qingdao, CN) ; JIN;
Hui; (Qingdao, CN) ; SUN; Yujiao; (Qingdao,
CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
QINGDAO UNIVERSITY |
Qingdao, Shandong |
|
CN |
|
|
Assignee: |
Qingdao University
Qingdao, Shandong
CN
|
Family ID: |
1000005326336 |
Appl. No.: |
16/614378 |
Filed: |
March 14, 2019 |
PCT Filed: |
March 14, 2019 |
PCT NO: |
PCT/CN2019/078075 |
371 Date: |
May 7, 2020 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C09K 11/65 20130101;
G01N 21/643 20130101; C09K 11/025 20130101; B82Y 40/00 20130101;
A01N 47/40 20130101; C09K 11/58 20130101 |
International
Class: |
G01N 21/64 20060101
G01N021/64; C09K 11/58 20060101 C09K011/58; C09K 11/65 20060101
C09K011/65; C09K 11/02 20060101 C09K011/02; A01N 47/40 20060101
A01N047/40 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 2, 2018 |
CN |
201811298081.2 |
Claims
1. A method for preparing a ratiometric fluorescent probe for
cymoxanil based on a double-emission carbon quantum dot-silver
nanoparticle complex, comprising the following steps: (1)
preparation of silver nanoparticles: preparing 100 mmol/L of silver
nitrate solution, 250 mmol/L of trisodium citrate solution and 5
mmol/L of sodium borohydride solution, adding the prepared silver
nitrate solution and trisodium citrate solution to 100 mL of
double-distilled water, under a magnetic stirring, adding 1 mL of
sodium borohydride solution, and then reacting under a stirring for
30 minutes to obtain a yellow solution; wherein the yellow solution
is centrifuged, washed by ethanol and vacuum dried at a low
temperature to obtain the silver nanoparticles, and the prepared
silver nanoparticles are stored in a dark place at 4.degree. C. for
use in subsequent experiments; (2) preparation of carbon quantum
dots: adding 54.5 mg of 3-aminophenol and 32.0 mg of oxalic acid to
50 mL of double-distilled water, stirring magnetically to mix well,
and then heating and reacting in a water bath to obtain a clear
homogeneous mixture; transferring the homogeneous mixture to a
high-pressure reactor and heating at 180.degree. C. for 12 hours;
wherein after an end of a reaction, a product solution is cooled to
room temperature and filtered by a 0.22 .mu.m filter membrane to
remove large particle impurities; a filtrate is subjected to a
rotary evaporation to remove water, washed by acetone and ethanol
alternately for two times, and then freeze-dried until the water is
completely removed, and a prepared carbon quantum dot powder is
stored at room temperature for further use; (3) formulating the
silver nanoparticles prepared in step (1) into a silver
nanoparticle aqueous solution for reacting at room temperature and
under slow magnetic stirring for 10 minutes to form a homogeneous
silver nanoparticle solution; (4) formulating the carbon quantum
dots prepared in step (2) into a carbon quantum dot aqueous
solution, and adding the silver nanoparticle solution at room
temperature and under the slow magnetic stirring to form carbon
quantum dot solutions containing different concentrations of silver
nanoparticles, and then reacting under the magnetic stirring for 20
minutes to obtain a homogeneous solution; wherein fluorescent
emission spectra of carbon quantum dots corresponding to different
concentrations of silver nanoparticles are measured respectively,
and a linear relationship between an intensity ratio of two
fluorescent emission peaks of carbon quantum dots and the
concentration of silver nanoparticles is fitted; (5) adding
cymoxanil to the carbon quantum dot aqueous solution containing
silver nanoparticles prepared in step (4) for reacting under the
magnetic stirring for 20 minutes to form a homogeneous solution;
wherein fluorescent emission spectra of carbon quantum dots in the
homogeneous solution corresponding to different molar
concentrations of cymoxanil are measured, and a linear relationship
between the intensity ratio of two fluorescent emission peaks of
carbon quantum dots and the molar concentration of cymoxanil is
fitted, and the ratiometric fluorescent probe for cymoxanil is
constructed.
2. The method of claim 1, wherein, in step (1), a size of the
silver nanoparticles is 5-20 nm, an amount of the silver nitrate is
100-500 .mu.L, and an amount of the trisodium citrate is 100-500
.mu.L.
3. The method of claim 1, wherein, in step (2), a size of the
carbon quantum dots is 1-10 nm.
4. The method of claim 1, wherein, in step (3), a mass
concentration of the silver nanoparticles is 0.1-1.0 .mu.g/mL.
5. The method of claim 1, wherein, in step (4), a mass
concentration of the carbon quantum dot aqueous solution is 0.1-1.0
.mu.g/mL, a mass concentration of the silver nanoparticles is
0.01-0.2 .mu.g/mL, a mass concentration ratio of the carbon quantum
dots to the silver nanoparticles is 1:5-5:1.
6. The method of claim 1, wherein, in step (5), a mass
concentration ratio of the carbon quantum dot aqueous solution
containing the silver nanoparticles to the cymoxanil is 1:5-5:1, a
linear detection range of the molar concentration of cymoxanil is
0.01-1.0 .mu.mol/L, and a detection limit of the molar
concentration of cymoxanil is 0.01-0.5 .mu.mol/L.
Description
CROSS REFERENCE TO THE RELATED APPLICATIONS
[0001] This application is the national phase entry of
International Application No. PCT/CN2019/078075, filed on Mar. 14,
2019, which is based upon and claims priority to Chinese Patent
Application No. 201811298081.2, filed on Nov. 2, 2018, the entire
contents of which are incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure belongs to the technical field of
preparations of nanomaterials and fluorescent probes, and
particularly relates to a method for preparing a ratiometric
fluorescent probe for cymoxanil based on a double-emission quantum
dot-silver nanoparticle complex, and the probe prepared by the
method can be used for efficiently detecting cymoxanil.
BACKGROUND
[0003] Cymoxanil is a kind of a low-toxic fungicide having high
efficiency, and is widely used in the preservation and storage of
vegetables and fruits such as cucumber, grape, tomato, and lychee.
Cymoxanil is usually mixed with other pesticides to enhance the
efficacy of the pesticides. Vegetables and fruits are consumed
daily by humans and provide useful nutritions. Any pesticides that
stay in vegetables as a residual pesticide may be harmful to
humans. If the amount of residual pesticide in consumed products is
small, the pesticide may be processed and degraded by human body
resulting in no acute poisoning. However, long-term consumption of
unwashed agricultural products with residual pesticides in them,
may cause serious danger to human health. Cymoxanil is widely used
in fruits and vegetables, and the residue of cymoxanil can easily
be detected in the peel of fruits and vegetables. The residual
pesticides can be dispersed in water by volatilization, runoff, and
leaching. Cymoxanil is also highly toxic to aquatic organisms and
has long-term adverse effects on water environment. In the European
Union, the maximum residue level of cymoxanil is limited to 0.05
mg/kg. Excessive consumption of cymoxanil by human body will cause
diminishing of body's immunity, puts additional stress on liver,
may cause gastrointestinal diseases, and may even cause and trigger
cancer in severe cases. Excessive amount of cymoxanil consumption
may cause a series of safety issues. Therefore, a quantitative
detection of cymoxanil is an important matter.
[0004] Anne-Claire et al. used three chromatographic methods to
detect cymoxanil (Pesticide residues in raspberries and lettuce:
Extrection and comparision of three chromatographic methods: HPLC,
HPTLC and GC, Anne-Claire Martel, Maurice Porthault, J. LIQ.,
CHROM. & REL. TECHNOL., 2000, 23, 3043-3058). Matt J. et al.
used a gas chromatographic method to detect cymoxanil (Development
of a Gas Chromatographic Method for Fungicide Cymoxanil Analysis in
Dried Hops, Matt J. Hengel, Takayuki Shibamoto, J. Agric. Food
Chem., 2001, 49, 570-573). Hulya Mercan et al. used stripping
voltammetry to detect the content of cymoxanil in pesticides
(Determination of Cymoxanil Fungicide in Commercial Formulation and
Natural Water by Square-wave Stripping Voltammetry, Hulya Mercan,
RecaiInam, Clean-Soil, Air, Water 2010, 38, 558-564). Among the
current methods for detecting cymoxanil, chromatography is mainly
used, such as high performance liquid chromatography (HPLC), high
performance liquid chromatography-mass spectrometry (HPLC-MS) and
gas chromatography (GC). Other methods include ultrasonic-assisted
extraction, microwave-assisted extraction, and Fourier Transform
infrared spectroscopy (FTIR). When chromatography is used, the
detection boundary is poor, and the spectral lines of many samples
may overlap and specific identification cannot be achieved. Other
methods also have some defects, such as requiring expensive
instruments, having high cost, pretreating complex samples, and
requiring difficult operation.
[0005] Fluorescence analysis is an instrumental method for
substance identification and content determination based on the
position and intensity of fluorescence lines of a specific
substance. The method has many advantages such as having high
sensitivity, high selectivity, and simple operation. In pesticide
detection, the fluorescence analysis has the advantages of having
high analytical sensitivity, good selectivity, and simple
operation. In current reports on detecting pesticide by
fluorescence, the interaction between fluorescent quantum dots and
pesticides causes change in the fluorescent intensity of quantum
dots, where the change in the fluorescent intensity is used to
detect the pesticide. This method relies on a single fluorescence
signal output mode. The method for detecting single fluorescence
signal is susceptible to the influence of background fluorescence,
reagent, system and environmental conditions, thereby resulting in
instability of the measurement results. Compared with the prior
art, the intensity ratio of the signal in the present process is
obtained by the dual signal ratio processing and can be
self-calibrated, thereby effectively eliminating the interference
of itself and background signals, and improving the accuracy and
reliability of the detection results. In this regard, the present
disclosure designs a method for preparing a novel ratiometric
fluorescent probe based on a double-emission quantum dot-silver
nanoparticle complex for efficiently detecting cymoxanil. So far,
detecting cymoxanil by using a ratiometric fluorescent probe or the
ratiometric fluorescent probe based on the double-emission quantum
dot-silver nanoparticle complex has not yet been reported in
domestic and foreign literatures and patents.
SUMMARY
[0006] The objective of the present disclosure is to overcome the
deficiencies of the prior art described above, and to provide a
method for preparing a ratiometric fluorescent probe for cymoxanil
based on a double-emission quantum dot-silver nanoparticle complex,
where the method is simple, low-cost and has high-sensitivity.
[0007] In order to achieve the aforementioned objective, according
to the present disclosure, a process of preparing a ratiometric
fluorescent probe for cymoxanil based on the double-emission carbon
quantum dot-silver nanoparticle complex includes the following
steps:
[0008] (1) Preparation of silver nanoparticles: preparing 100
mmol/L of silver nitrate solution, 250 mmol/L of trisodium citrate
solution and 5 mmol/L of sodium borohydride solution, adding the
prepared silver nitrate solution and trisodium citrate solution to
100 mL of double-distilled water, under magnetic stirring, adding 1
mL of sodium borohydride solution, and then reacting under stirring
for 30 minutes to obtain a yellow solution; wherein the yellow
solution is centrifuged, washed by ethanol and vacuum dried at the
low temperature to obtain the silver nanoparticles, and the
resulting silver nanoparticles are stored in a dark place at
4.degree. C. for use in subsequent experiments;
[0009] (2) Preparation of carbon quantum dots: adding 54.5 mg of
3-aminophenol and 32.0 mg of oxalic acid to 50 mL of
double-distilled water, stirring magnetically to mix well, and then
heating and reacting in a water bath to obtain a clear homogeneous
mixture. The homogeneous mixture is transferred to a high-pressure
reactor and heated at 180.degree. C. for 12 hours. After the end of
the reaction, the product solution is cooled to the room
temperature and filtered by a 0.22 .mu.m filter membrane to remove
large particle impurities. The filtrate is subjected to a rotary
evaporation to remove water, washed by acetone and ethanol
alternately for two times, and then freeze-dried until the water is
completely removed. The resulting carbon quantum dot powder is
stored at the room temperature for further use;
[0010] (3) Formulating the silver nanoparticles prepared in step
(1) into a silver nanoparticle aqueous solution for reacting at the
room temperature and under slow magnetic stirring for 10 minutes to
form a homogeneous silver nanoparticle solution;
[0011] (4) Formulating the carbon quantum dots prepared in step (2)
into a carbon quantum dot aqueous solution, and adding the silver
nanoparticle solution at the room temperature and under slow
magnetic stirring to obtain carbon quantum dot solutions having
different concentrations of silver nanoparticles, and then reacting
under magnetic stirring for 20 minutes to form a homogeneous
solution; wherein fluorescent emission spectra of carbon quantum
dots corresponding to different concentrations of silver
nanoparticles are measured respectively, and fitting a linear
relationship between the intensity ratio of two fluorescent
emission peaks of carbon quantum dots and the concentration of
silver nanoparticles;
[0012] (5) Adding cymoxanil to the carbon quantum dot aqueous
solution containing silver nanoparticles prepared in step (4), and
then reacting under magnetic stirring for 20 minutes to form a
homogeneous solution; wherein the fluorescent emission spectra of
carbon quantum dots in the homogeneous solution corresponding to
different molar concentrations of cymoxanil are measured, and the
linear relationship between the intensity ratio of two fluorescent
emission peaks of carbon quantum dots and the molar concentration
of cymoxanil is fitted, and the ratiometric fluorescent probe for
cymoxanil is constructed.
[0013] According to the present disclosure, in step (1), the size
of the silver nanoparticles is 5-20 nm, the amount of the silver
nitrate is 100-500 .mu.L, and the amount of the trisodium citrate
is 100-500 .mu.L; in step (2), the size of the carbon quantum dots
is 1-10 nm; in step (3), the mass concentration of the silver
nanoparticles is 0.1-1.0 .mu.g/mL; in step (4), the mass
concentration of the carbon quantum dot aqueous solution is 0.1-1.0
.mu.g/mL, the mass concentration of the silver nanoparticles is
0.01-0.2 .mu.g/mL, the mass concentration ratio of the carbon
quantum dots to the silver nanoparticles is 1:5-5:1; in step (5),
the mass concentration ratio of the carbon quantum dot aqueous
solution containing the silver nanoparticles to the cymoxanil is
1:5-5:1, the linear detection range of the molar concentration of
cymoxanil is 0.01-1.0 .mu.mol/L, and the detection limit of the
molar concentration of cymoxanil is 0.01-0.5 .mu.mol/L.
[0014] Compared with the prior art, in the present disclosure, the
inner filter effect occurs between the double-emission carbon
quantum dots and the dispersed silver nanoparticles, which causes
the blue fluorescence quenching of the carbon quantum dots.
However, the specific binding of the cymoxanil to the silver
nanoparticles causes the silver nanoparticles to accumulate, and
then the inner filter effect occurring between the double-emission
carbon quantum dots and the dispersed silver nanoparticles causes
the green fluorescence quenching of carbon quantum dots. In this
regard, the linear relationship between the intensity ratio of the
two fluorescent emission peaks of carbon quantum dots and the molar
concentration of cymoxanil is established, and the ratiometric
fluorescent probe for cymoxanil is constructed. The probe has
simple preparation process, low cost and high product sensitivity,
and can be developed into a novel ratiometric fluorescent probe for
cymoxanil, which is suitable for efficiently detecting cymoxanil in
pesticides.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic diagram showing preparation for
ratiometric fluorescent probe for cymoxanil based on
double-emission carbon quantum dot-silver nanoparticle complex and
detection principle of the ratiometric fluorescent probe for
cymoxanil according to the present disclosure;
[0016] FIG. 2 is a graph showing the response of a ratiometric
fluorescent probe for cymoxanil to intensities of two fluorescent
emission peaks of double-emission carbon quantum dots as the molar
concentration of cymoxanil increases according to the present
disclosure.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0017] The present disclosure will be further described below in
conjunction with the drawings and specific embodiments.
Embodiment 1
[0018] This embodiment relates to preparation of a ratiometric
fluorescent probe for cymoxanil based on the double-emission carbon
quantum dot-silver nanoparticle complex and detection for the
ratiometric fluorescent signal of cymoxanil. The preparation
process and the principle of the ratiometric fluorescent probe are
shown in FIG. 1, and the specific process steps are as follows.
[0019] Preparation of silver nanoparticles: 100 mmol/L of silver
nitrate solution, 250 mmol/L of trisodium citrate solution and 5
mmol/L of sodium borohydride solution are prepared, the resulting
silver nitrate solution and trisodium citrate solution are added to
100 mL of double-distilled water, under magnetic stirring, 1 mL of
sodium borohydride solution is added, and then a reaction is
performed under stirring for 30 minutes to obtain a yellow
solution. The yellow solution is centrifuged, washed by ethanol and
vacuum dried at the low temperature to obtain the silver
nanoparticles, and the prepared silver nanoparticles are stored in
a dark place at 4.degree. C. for use in subsequent experiments.
[0020] Preparation of carbon quantum dots: 54.5 mg of 3-aminophenol
and 32.0 mg of oxalic acid are added to 50 mL of double-distilled
water, and stirred magnetically to mix well, and then heating and
reaction are carried out in the water bath to obtain the clear
homogeneous mixture. The homogeneous mixture is transferred to the
high-pressure reactor and heated at 180.degree. C. for 12 hours.
After the end of the reaction, the product solution is cooled to
the room temperature and filtered by a 0.22 .mu.m filter membrane
to remove large particle impurities. The filtrate is subjected to
rotary evaporation to remove water, washed by acetone and ethanol
alternately for two times, and then freeze-dried until the water is
completely removed. The resulting carbon quantum dot powder is
stored at the room temperature for further use.
[0021] The resulting silver nanoparticles with the average size of
5 nm are formulated into a silver nanoparticle aqueous solution for
reacting at the room temperature and under slow magnetic stirring
for 10 minutes to form the homogeneous silver nanoparticle
solution. The resulting carbon quantum dots with the average size
of 2 nm are formulated into the carbon quantum dot aqueous
solution, and the silver nanoparticle solution is added at the room
temperature and under the slow magnetic stirring to obtain the
carbon quantum dot solutions having the different concentrations of
silver nanoparticles, and then the homogeneous solution is obtained
after reacting under magnetic stirring for 20 minutes. Fluorescent
emission spectra of carbon quantum dots corresponding to different
concentrations of silver nanoparticles are measured respectively,
and the linear relationship between the intensity ratio of two
fluorescent emission peaks of carbon quantum dots and the
concentration of silver nanoparticles is fitted, wherein the mass
concentrations of silver nanoparticles and carbon quantum dots are
0.1-0.5 .mu.g/mL and 0.01-0.1 .mu.g/mL, respectively.
[0022] Cymoxanil is added to the resulting carbon quantum dot
aqueous solution containing silver nanoparticles for reacting under
magnetic stirring for 20 minutes to form the homogeneous solution.
Fluorescent emission spectra of carbon quantum dots in the
homogeneous solution corresponding to different molar
concentrations of cymoxanil are measured, and linear relationship
between the intensity ratio of two fluorescent emission peaks of
carbon quantum dots and the molar concentration of cymoxanil is
fitted, and the ratiometric fluorescent probe for cymoxanil is
constructed. Fluorescent emission spectra of carbon quantum dots
corresponding to different molar concentrations of cymoxanil are
measured, and linear relationship between the intensity ratios
I.sub.425/I.sub.525 of two fluorescent emission peaks and the
concentration C.sub.CYM of cymoxanil is fitted (see FIG. 2), that
is I.sub.425/I.sub.525=0.7180+1.7922C.sub.CYM (R.sup.2=0.9920),
wherein the concentration range of cymoxanil is 0.05-0.50
.mu.mol/L, and the detection limit of cymoxanil is 0.02
.mu.mol/L.
Embodiment 2
[0023] The specific process steps for preparing the silver
nanoparticles and the carbon quantum dots in this embodiment are
the same as those in embodiment 1, wherein the amounts of the added
silver nitrate and trisodium citrate in volume are increased
compared with embodiment 1. The resulting silver nanoparticles with
the average size of 10 nm are formulated into the silver
nanoparticle aqueous solution for reacting at the room temperature
and under slow magnetic stirring for 10 minutes to form the
homogeneous silver nanoparticle solution. The resulting carbon
quantum dots with the average size of 5 nm are formulated into the
carbon quantum dot aqueous solution, and the silver nanoparticle
solution is added at the room temperature and under the slow
magnetic stirring to obtain the carbon quantum dot solutions having
the different concentrations of silver nanoparticles, and then the
homogeneous solution is obtained after reacting under magnetic
stirring for 20 minutes. Fluorescent emission spectra of carbon
quantum dots corresponding to different concentrations of silver
nanoparticles are measured respectively, and linear relationship
between the intensity ratio of two fluorescent emission peaks of
carbon quantum dots and the concentration of silver nanoparticles
is fitted, wherein the mass concentrations of silver nanoparticles
and carbon quantum dots are 0.2-0.8 .mu.g/mL and 0.02-0.2 .mu.g/mL,
respectively. Cymoxanil is added to the resulting carbon quantum
dot aqueous solution containing silver nanoparticles for reacting
under magnetic stirring for 20 minutes to form the homogeneous
solution. Fluorescent emission spectra of carbon quantum dots in
the homogeneous solution corresponding to different molar
concentrations of cymoxanil are measured, and linear relationship
between the intensity ratio of two fluorescent emission peaks of
carbon quantum dots and the molar concentration of cymoxanil is
fitted, and the ratiometric fluorescent probe for cymoxanil is
constructed. Fluorescent emission spectra of carbon quantum dots
corresponding to different molar concentrations of cymoxanil are
measured, and linear relationship between the intensity ratio
I.sub.425/I.sub.525 of two fluorescent emission peaks and the
concentration C.sub.CYM of cymoxanil is fitted, wherein the
concentration range of cymoxanil is 0.02-0.50 .mu.mol/L, and the
detection limit of cymoxanil is 0.01 .mu.mol/L.
Embodiment 3
[0024] The specific process steps for preparing the silver
nanoparticles and the carbon quantum dots in this embodiment are
the same as those in embodiment 1, wherein the amounts of the added
silver nitrate and trisodium citrate in volume are increased
compared with embodiment 1. The resulting silver nanoparticles with
the average size of 15 nm are formulated into the silver
nanoparticle aqueous solution for reacting at the room temperature
and under the slow magnetic stirring for 10 minutes to form the
homogeneous silver nanoparticle solution. The resulting carbon
quantum dots with the average size of 8 nm are formulated into the
carbon quantum dot aqueous solution, and the silver nanoparticle
solution is added at the room temperature and under the slow
magnetic stirring to obtain the carbon quantum dot solutions having
the different concentrations of silver nanoparticles, and then the
homogeneous solution is obtained after reacting under magnetic
stirring for 20 minutes. The fluorescent emission spectra of carbon
quantum dots corresponding to different concentrations of silver
nanoparticles are measured respectively, and linear relationship
between the intensity ratio of two fluorescent emission peaks of
carbon quantum dots and the concentration of silver nanoparticles
is fitted, wherein the mass concentrations of silver nanoparticles
and carbon quantum dots are 0.5-1.0 .mu.g/mL and 0.05-0.2 .mu.g/mL,
respectively. Cymoxanil is added to the resulting carbon quantum
dot aqueous solution containing silver nanoparticles for reacting
under magnetic stirring for 20 minutes to form the homogeneous
solution. Fluorescent emission spectra of carbon quantum dots in
the homogeneous solution corresponding to different molar
concentrations of cymoxanil are measured, and linear relationship
between the intensity ratio of two fluorescent emission peaks of
carbon quantum dots and the molar concentration of cymoxanil is
fitted, and the ratiometric fluorescent probe for cymoxanil is
constructed. Fluorescent emission spectra of carbon quantum dots
corresponding to different molar concentrations of cymoxanil are
measured, and linear relationship between the intensity ratio
I.sub.425/I.sub.525 of two fluorescent emission peaks and the
concentrations C.sub.CYM of cymoxanil is fitted, wherein the
concentration range of cymoxanil is 0.05-1.0 .mu.mol/L, and the
detection limit of cymoxanil is 0.05 .mu.mol/L.
* * * * *