阅读说明：本技术 一种基于光致发光木聚糖碳量子点的微流控传感器对Cr(VI)的可视化检测的实现方法 (method for realizing visual detection of Cr (VI) by micro-fluidic sensor based on photoluminescence xylan carbon quantum dots ) 是由 王小英 韩光达 蔡济海 于 2019-08-31 设计创作，主要内容包括：本发明公开了一种基于光致发光木聚糖碳量子点的微流控传感器对Cr(VI)的可视化检测的实现方法。该方法包括：将木聚糖溶液升温,离心,透析,得到木聚糖碳量子点溶液；将丙烯酰胺、氧化纳米纤维素、过硫酸铵和N,N’-亚甲基双丙烯酰胺加入木聚糖量子点溶液中,滴加四甲基乙二胺,得到混合液,将混合液流延,得到荧光膜；将荧光膜及有机玻璃等组装成微流控芯片；将待测溶液泵入微流控芯片中,当荧光膜没有出现荧光猝灭,则不含有六价铬,当荧光膜出现荧光猝灭,则含有六价铬。该方法能够在紫外光下快速地、可视化地、高灵敏度地检测生活用水中的微量六价铬。该微流控芯片装置轻巧、便于携带,对六价铬的检测选择性好,检测范围较宽。(the invention discloses a method for realizing visual detection of Cr (VI) by a micro-fluidic sensor based on photoluminescence xylan carbon quantum dots. The method comprises the following steps: heating the xylan solution, centrifuging, and dialyzing to obtain a xylan carbon quantum dot solution; adding acrylamide, oxidized nano-cellulose, ammonium persulfate and N, N' -methylene bisacrylamide into a xylan quantum dot solution, dropwise adding tetramethylethylenediamine to obtain a mixed solution, and carrying out tape casting on the mixed solution to obtain a fluorescent film; assembling a fluorescent film, organic glass and the like into a microfluidic chip; and pumping the solution to be detected into the microfluidic chip, wherein when the fluorescence film does not have fluorescence quenching, the solution does not contain hexavalent chromium, and when the fluorescence film has fluorescence quenching, the solution contains hexavalent chromium. The method can rapidly, visually and sensitively detect the trace hexavalent chromium in the domestic water under the ultraviolet light. The micro-fluidic chip device is light and handy, is convenient to carry, and has good detection selectivity on hexavalent chromium and a wider detection range.)

1. a method for realizing visual detection of Cr (VI) by a micro-fluidic sensor based on photoluminescence xylan carbon quantum dots is characterized by comprising the following steps:

(1) Adding xylan into a NaOH/urea solution, and uniformly mixing to obtain a xylan solution; heating the xylan solution, carrying out hydrothermal reaction, centrifuging, taking supernate, and dialyzing to obtain xylan carbon quantum dot solution;

(2) adding acrylamide, oxidized nano-cellulose, ammonium persulfate and N, N' -methylene bisacrylamide into the xylan quantum dot solution obtained in the step (1), uniformly stirring, then dropwise adding tetramethylethylenediamine, uniformly mixing to obtain a mixed solution, then casting the mixed solution, and drying to obtain a fluorescent film;

(3) uniformly mixing polydimethylsiloxane and a curing agent to obtain a PDMS solution, pouring the PDMS solution into a mold, performing vacuum drying, removing bubbles to obtain a PDMS membrane layer with a groove, and assembling the fluorescent membrane, the PDMS membrane layer with the groove and organic glass in the step (2) into a micro-fluidic chip for detecting Cr (VI);

(4) Pumping a sample solution to be detected into the microfluidic chip for detecting Cr (VI) in the step (3), and observing the fluorescence quenching condition of the fluorescent film under the irradiation of an ultraviolet lamp; and when the fluorescence film does not have fluorescence quenching, the solution of the sample to be detected does not contain hexavalent chromium, and when the fluorescence film has fluorescence quenching, the solution of the sample to be detected contains hexavalent chromium.

2. The method for visually detecting Cr (VI) by using the micro-fluidic sensor based on the photoluminescence xylan carbon quantum dots according to claim 1, wherein the preparation of the NaOH/urea solution in the step (1) comprises the steps of adding NaOH and urea into water, uniformly mixing to obtain the NaOH/urea solution, wherein the mass percentage concentration of NaOH in the NaOH/urea solution is 5wt% -9wt%, the mass percentage concentration of urea in the NaOH/urea solution is 8wt% -14wt%, and the mass-volume ratio of xylan to NaOH/urea solution is 0.5 ~ 1.5.5 g: 10 ~ 30 mL.

3. The method for visually detecting Cr (VI) by using the micro-fluidic sensor based on photoluminescence xylan carbon quantum dots as claimed in claim 1, wherein the temperature of the hydrothermal reaction in the step (1) is 180-240 ℃, and the time of the hydrothermal reaction is 12-24 h; in the step (1), a dialysis bag with the molecular weight cut-off of 500-1000 is used for dialysis, and the dialysis time is 3-7 d; the concentration of the xylan quantum dot solution in the step (1) is 0.1-0.5 mg/mL.

4. The method for visually detecting Cr (VI) by using the photoluminescent xylan carbon quantum dot based microfluidic sensor according to claim 1, wherein the mass-to-volume ratio of the acrylamide to the xylan quantum dot solution in the step (2) is 3 ~ 12g to 5 ~ 20mL, and the mass-to-volume ratio of the oxidized nanocellulose to the xylan quantum dot solution is 0.018 ~ 0.09.09 g to 5 ~ 20 mL.

5. The method for visually detecting Cr (VI) by using the photoluminescent xylan-carbon quantum dot-based microfluidic sensor according to claim 1, wherein the mass-to-volume ratio of the ammonium persulfate to the xylan quantum dot solution in the step (2) is 0.01 ~ 0.09.09 g to 5 ~ 20mL, and the mass-to-volume ratio of the N, N' -methylenebisacrylamide to the xylan quantum dot solution is 0.005 ~ 0.02.02 g to 5 ~ 20 mL.

6. The method for visually detecting Cr (VI) by using the photoluminescent xylan carbon quantum dot-based microfluidic sensor according to claim 1, wherein the volume ratio of the tetramethylethylenediamine to the xylan quantum dot solution in the step (2) is 15 ~ 30 μ L: 5 ~ 20mL, the drying temperature is 30-60 ℃, and the drying time is 10-30 min.

7. The method for visually detecting Cr (VI) by using the micro-fluidic sensor based on the photoluminescence xylan carbon quantum dots according to claim 1, wherein the curing agent in the step (3) is a silane coupling agent, the volume ratio of polydimethylsiloxane to the curing agent is 6:1 ~ 12:1, the vacuum drying temperature is 40-90 ℃, and the vacuum drying time is 3-12 h.

8. The method for visually detecting Cr (VI) by using the micro-fluidic sensor based on photoluminescence xylan carbon quantum dots according to claim 1, wherein the micro-fluidic chip for detecting Cr (VI) in the step (3) is composed of organic glass, a fluorescent film and a PDMS film layer; organic glass includes upper organic glass and lower floor's organic glass, supreme organic glass, PDMS rete, fluorescent screen and the upper organic glass range upon range of by lower floor are from down formed to the micro-fluidic chip.

9. The method for visually detecting Cr (VI) by using the photoluminescent xylan-carbon quantum dot based microfluidic sensor according to claim 8, wherein the PDMS film layer has a groove thereon, and the fluorescent film is laminated on the groove; the upper surface of the upper layer of organic glass is provided with a liquid inlet and a liquid outlet, the liquid inlet is communicated with the outside through a liquid inlet pipe, and the liquid outlet is communicated with the outside through a liquid outlet pipe; the liquid inlet is communicated with the groove of the PDMS film layer through a conduit, and a sample solution to be tested can enter the groove of the PDMS film layer through the liquid inlet to be contacted with the fluorescent film; the liquid outlet is communicated with the groove of the PDMS film layer through a conduit, and the sample solution to be detected can be discharged outside through the liquid outlet.

10. The method for visually detecting Cr (VI) by using the micro-fluidic sensor based on the photoluminescence xylan carbon quantum dots according to claim 8, wherein the upper organic glass is colorless transparent glass, ultraviolet light can be projected onto the fluorescent film through the upper organic glass, and the color change of the fluorescent film can be visually observed through the upper organic glass.

Technical Field

The invention relates to the field of heavy metal ion detection, in particular to a method for realizing visual detection of Cr (VI) by a micro-fluidic sensor based on photoluminescence xylan carbon quantum dots.

Background

In recent years, due to the rapid development of urbanization and industrialization, the random discharge of waste gas, waste residue and waste water from industrial production process causes more and more serious heavy metal pollution, and heavy metal ions have obvious biotoxicity and accumulation effect on human bodies, thereby seriously threatening the health of human bodies. Among these heavy metal ions, cr (vi) is very toxic, low concentrations of hexavalent chromium can lead to renal failure and rhinitis, and high concentrations of hexavalent chromium can lead to cancer. The concentration of chromium in drinking water is strictly controlled, but it is difficult to identify it by sensory means. Therefore, there is a significant need for a simple, visual, sensitive and cost-effective method for on-site detection of cr (vi) for rapid detection of cr (vi) in domestic water (e.g., open water and drinking water).

The current method for detecting Cr (VI) in water is far from meeting the requirement. Several conventional techniques have been used to detect cr (vi) in domestic water, such as gas chromatography, high performance liquid chromatography, Atomic Absorption Spectroscopy (AAS), ultraviolet-visible absorption spectroscopy (UV-vis), X-ray fluorescence, and the like. These conventional detection methods generally require expensive, large instruments and the detection process is extremely time consuming. Moreover, their conventional utilization is still hampered by multi-step operations and complex detection equipment. Furthermore, the requirement that a professional or trained worker perform the above tests may be a major obstacle to effectively practicing the method. New fluorescence-based methods have been developed that are more convenient and cost-effective than AAS and UV-vis. The fluorescence method is more advantageous for detecting Cr (VI), on one hand, it has the advantages of high sensitivity and good selectivity for detecting Cr (VI), and on the other hand, it can carry out on-site visual detection. Therefore, there is a need to create a fast, accurate, potentially portable, easy to use, visual and inexpensive optical method.

Compared to conventional organic dyes, semiconductor QDs and noble metal nanoparticles, carbon quantum dots CQDs have many advantages, including low toxicity, excellent biocompatibility, good photobleaching resistance, stable luminescence and ease of modulation. Thus, CQDs have been customized as fluorescent probes to selectively detect a number of analytes capable of quenching the fluorescence of CQDs. The fluorescence quenching mechanism is based on light-induced electron transfer from the excited CQD to the analyte (usually an electron acceptor), and this "on-off" sensing scheme can be applied to selectively detect multiple target analytes. However, these studies generally report new synthetic pathways for appropriately functionalized CQDs and demonstrate their use as soluble fluorescent probes for turn-off selective sensing co-dispersed with target analytes. These studies are based on liquid fluorescence sensing, in contrast, solid fluorescence sensing has the advantages of being convenient to transport and easy to carry. Although solid-state fluorescence sensors are more practical from an application point of view, the use of CQDs as fluorescence sensing probes immobilized on a surface is relatively scarce. Therefore, there is a need to develop a CQD-based fluorescent solid-state sensing platform for cr (vi) detection.

disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a method for realizing the visual detection of Cr (VI) by a micro-fluidic sensor based on photoluminescence xylan carbon quantum dots.

the purpose of the invention is realized by at least one of the following technical solutions.

Aiming at the defects of the prior art, the invention provides a method for realizing the visual detection of Cr (VI) by a micro-fluidic sensor based on photoluminescence xylan carbon quantum dots; the method uses a sensor for detecting Cr (VI) in domestic water, and specifically xylan carbon quantum dots attached to a film on a microfluidic device can be used in an optical solid sensor for Cr (VI) identification. The preparation method adopts xylan in biomass as a raw material, and prepares xylan carbon quantum dots through hydrothermal carbonization; then, mixing acrylamide as a film forming matrix, oxidized nano-cellulose as a film performance reinforcing agent, ammonium persulfate as an initiator, N, N' -methylene-bisacrylamide as a cross-linking agent and tetramethylethylenediamine as an accelerator with the xylan carbon quantum dot solution to prepare the fluorescent film. The micro-fluidic chip for detecting Cr (VI) assembled by the fluorescent film can realize visual detection of Cr (VI) in the domestic water. The Cr (VI) is hexavalent chromium ions.

The invention provides a method for realizing visual detection of Cr (VI) in domestic water by a micro-fluidic chip based on photoluminescence xylan carbon quantum dots. The micro-fluidic chip is pushed by a pump, a sample solution to be detected is input into the micro-fluidic chip device, under the irradiation of an ultraviolet lamp, whether the liquid contains hexavalent chromium is judged according to the fluorescence quenching of the fluorescent film, and the concentration of the hexavalent chromium is judged according to the brightness of the fluorescence quenching of the fluorescent film.

The invention provides a method for realizing visual detection of Cr (VI) by a micro-fluidic sensor based on photoluminescence xylan carbon quantum dots, which comprises the following steps:

(1) Adding xylan into a NaOH/urea solution, and uniformly mixing to obtain a xylan solution; heating the xylan solution, carrying out hydrothermal reaction, centrifuging, taking supernate, and dialyzing to obtain xylan carbon quantum dot solution;

(2) Adding acrylamide, oxidized nano-cellulose, ammonium persulfate and N, N' -methylene bisacrylamide into the xylan quantum dot solution obtained in the step (1), uniformly stirring, then dropwise adding tetramethylethylenediamine, uniformly mixing to obtain a mixed solution, then casting the mixed solution, and drying to obtain a fluorescent film;

(3) Uniformly mixing polydimethylsiloxane (PDMS prepolymer) and a curing agent to obtain a PDMS solution, pouring the PDMS solution into a mold, performing vacuum drying, removing bubbles to obtain a PDMS film layer with a groove, and assembling the fluorescent film, the PDMS film layer with the groove and organic glass in the step (2) into a micro-fluidic chip for detecting Cr (VI);

(4) Pumping a sample solution to be detected into the microfluidic chip for detecting Cr (VI) in the step (3), and observing the fluorescence quenching condition of the fluorescent film under the irradiation of an ultraviolet lamp; and when the fluorescence film does not have fluorescence quenching, the solution of the sample to be detected does not contain hexavalent chromium, and when the fluorescence film has fluorescence quenching, the solution of the sample to be detected contains hexavalent chromium.

Preferably, the stirring in step (1) is magnetic stirring.

Further, the preparation of the NaOH/urea solution in the step (1) comprises the steps of adding NaOH and urea into water, and uniformly mixing to obtain the NaOH/urea solution, wherein the mass percentage concentration of NaOH in the NaOH/urea solution is 5wt% -9wt%, the mass percentage concentration of urea in the NaOH/urea solution is 8wt% -14wt%, and the mass volume ratio of xylan to the NaOH/urea solution is 0.5 ~ 1.5.5 g: 10 ~ 30 mL.

Further, the temperature of the hydrothermal reaction in the step (1) is 180-; in the step (1), a dialysis bag with the molecular weight cut-off of 500-1000 is used for dialysis, and the dialysis time is 3-7 d; the concentration of the xylan quantum dot solution in the step (1) is 0.1-0.5 mg/mL.

Preferably, the centrifugation rate in the step (1) is 10000-14000rpm, and the centrifugation time is 1-10 min.

Further, the mass-to-volume ratio of the acrylamide to the xylan quantum dot solution in the step (2) is 3 ~ 12 g: 5 ~ 20mL, and the mass-to-volume ratio of the oxidized nano-cellulose to the xylan quantum dot solution is 0.018 ~ 0.09.09 g: 5 ~ 20 mL.

Further, the mass-to-volume ratio of the ammonium persulfate to the xylan quantum dot solution in the step (2) is 0.01 ~ 0.09.09 g to 5 ~ 20mL, the mass-to-volume ratio of the N, N' -methylenebisacrylamide to the xylan quantum dot solution is 0.005 ~ 0.02.02 g to 5 ~ 20mL, and the volume ratio of the tetramethylethylenediamine to the xylan quantum dot solution in the step (2) is 15 ~ 30 muL to 5 ~ 20 mL.

Further, the drying temperature in the step (2) is 30-60 ℃, and the drying time is 10-30 min.

further, the curing agent in the step (3) is a silane coupling agent, the volume ratio of the polydimethylsiloxane to the curing agent is 6:1 ~ 12: 12, the vacuum drying temperature is 40-90 ℃, and the vacuum drying time is 3-12 h.

Preferably, the microfluidic chip in step (3) can be designed by using CorelDraw software.

Preferably, the microfluidic chip in the step (3) has a size of 25 × 40 × 10 mm ³.

Further, the microfluidic chip for detecting Cr (VI) in the step (3) is composed of organic glass, a fluorescent film and a PDMS film layer; organic glass includes upper organic glass and lower floor's organic glass, supreme organic glass, PDMS rete, fluorescent screen and the upper organic glass range upon range of by lower floor are from down formed to the micro-fluidic chip.

further, the PDMS film layer is provided with a groove, and the fluorescent film is laminated on the groove; the upper surface of the upper layer of organic glass is provided with a liquid inlet and a liquid outlet, the liquid inlet is communicated with the outside through a liquid inlet pipe, and the liquid outlet is communicated with the outside through a liquid outlet pipe; the liquid inlet is communicated with the groove of the PDMS film layer through a conduit, and a sample solution to be tested can enter the groove of the PDMS film layer through the liquid inlet to be contacted with the fluorescent film; the liquid outlet is communicated with the groove of the PDMS film layer through a conduit, and the sample solution to be detected can be discharged outside through the liquid outlet.

Furthermore, the upper organic glass is colorless transparent glass, ultraviolet rays can be projected onto the fluorescent film through the upper organic glass, and the color change of the fluorescent film can be observed through the upper organic glass visually.

preferably, the microfluidic chip for detecting cr (vi) in step (3) is composed of organic glass, a fluorescent film and a PDMS film; the organic glass comprises an upper layer of organic glass and a lower layer of organic glass, and the microfluidic chip is formed by laminating the lower layer of organic glass, a PDMS film layer, a fluorescent film and the upper layer of organic glass from bottom to top; the PDMS film layer is arranged between the upper glass plate and the lower glass plate and is provided with a non-penetrating Y-shaped groove, and the fluorescent film is placed in the Y-shaped groove of the PDMS film layer; four corners of the upper layer of glass plate and the lower layer of glass plate are respectively provided with 1 small round hole, and the small round holes are used for fixing screws and nuts.

In the step (4), the concentration of the hexavalent chromium can be judged according to the brightness of fluorescence quenching of the fluorescent film.

The method for realizing the visual detection of Cr (VI) by the micro-fluidic sensor based on the photoluminescence xylan carbon quantum dots can detect a sample solution with the heavy metal ion concentration of 60-480 mu mol/L.

according to the method for realizing the visual detection of Cr (VI) by the micro-fluidic sensor based on the photoluminescence xylan carbon quantum dots, the assembled micro-fluidic sensor device for detecting Cr (VI) can rapidly, visually and highly sensitively detect trace hexavalent chromium in domestic water on site under ultraviolet light.

the invention provides a method for realizing visual detection of Cr (VI) by a micro-fluidic sensor based on photoluminescence xylan carbon quantum dots, which can be applied to the field of heavy metal detection of domestic water and the field of hexavalent cadmium pollution detection of environmental water resources.

The invention provides a method for realizing visual detection of Cr (VI) by a micro-fluidic sensor based on photoluminescence xylan carbon quantum dots, which specifically comprises the following steps:

(1) Dissolving xylan in NaOH/urea solution, stirring and mixing uniformly by magnetic force, transferring the mixed solution into a reaction kettle, and then placing the reaction kettle in a muffle furnace for hydrothermal reaction. Centrifuging and dialyzing the reacted mixed solution to obtain the xylan carbon quantum dots.

(2) under the condition of stirring, adding acrylamide, oxidized nano-cellulose, ammonium persulfate and N, N' -methylene bisacrylamide into the xylan quantum dot solution, after the solution is uniformly stirred, dropwise adding a certain amount of tetramethyl ethylenediamine, then coating the mixed solution into a Y-shaped groove by using a tape casting method, and reacting in an oven for a period of time to obtain the fluorescent film.

(3) After the microfluidic chip was delineated using CorelDraw software, the "Y" shape was engraved by intaglio on a laser engraving machine on a plexiglass plate of 70 x 70 mm ² to obtain a "Y" shaped groove mold, which was used as a fluorescent film.

(4) Engraving a mold of a Y-shaped microfluidic chip on organic glass by a laser engraving machine in a positive engraving way, then uniformly mixing PDMS prepolymer (polydimethylsiloxane) and curing agent (silane coupling agent) according to a certain volume ratio, pouring the mixed solution into the mold, removing bubbles through vacuum drying, and peeling off to obtain the PDMS membrane with the groove after curing and molding. And assembling the PDMS film and organic glass into a microfluidic chip for detecting Cr (VI).

(5) The solution to be detected is input into the microfluidic chip device by the driving of the pump, under the irradiation of an ultraviolet lamp, whether the liquid contains hexavalent chromium is judged according to the fluorescence quenching of the fluorescent film, and the concentration of the hexavalent chromium is judged according to the brightness of the fluorescence quenching of the fluorescent film.

Further, in the step (1), the hydrothermal reaction temperature and time are respectively 180 ~ 240 ℃ and 12 ~ 24 h.

further, in the step (1), the rotation speed and time of the centrifugal cleaning are 10000 ~ 14000rpm and 1 ~ 10min respectively.

further, in the step (1), the cut-off molecular weight of the dialysis bag is 500 ~ 1000, and the dialysis time is 3 ~ 7 d.

Further, in the step (2), the concentration of the xylan quantum dots is 0.1 ~ 0.5.5 mg/ml, and the volume of the xylan quantum dot solution is 5 ~ 20 ml.

further, in the step (2), the oven temperature and the reaction time are respectively 30 ~ 60 ℃ and 10 ~ 30 min.

Further, in the step (3), the intaglio power is 5 ~ 8%;

Further, in the step (3), the intaglio speed is 25 ~ 75 mm/s.

further, in the step (4), the etching power is 5 ~ 8%;

Further, in the step (4), the etching speed is 25 ~ 75 mm/s;

Further, in the step (4), the volume ratio is 6:1 ~ 12: 1;

Further, in the step (4), the temperature and the time of the vacuum drying oven are respectively 40 ~ 90 ℃ and 3 ~ 12 h.

further, in the step (4), the size of the microfluidic chip is 25 × 40 × 10 mm ³.

The micro-fluidic chip for detecting Cr (VI) based on photoluminescence xylan carbon quantum dots, which is prepared by the preparation method, can rapidly, visually and highly sensitively detect trace hexavalent chromium in domestic water in situ under the irradiation of ultraviolet light.

The method utilizes xylan as a carbon source to prepare the carbon quantum dots, and the carbon dots can selectively identify hexavalent chromium; the oxidized nano-cellulose and acrylamide are used for forming a film to load xylan carbon quantum dots, so that the problem that the liquid optical sensing is inconvenient to realize and apply is solved; by utilizing the micro-fluidic chip for detecting Cr (VI), the problems of large sample requirement, complex detection process, difficult carrying and incapability of on-site visual detection are solved.

the method for realizing the visual detection of Cr (VI) by the micro-fluidic sensor based on the photoluminescence xylan carbon quantum dots has the potential of automation, rapidity and portability, and the micro-fluidic system or chip Laboratory (LOC) technology can overcome the defects of complex sample pretreatment and special laboratory requirement. The integration of microfluidic platforms into a homemade miniature optical analyzer is a promising method for rapid, economical, continuous and accurate in-situ assays. Xylan carbon quantum dots attached to membranes on microfluidic devices can be used in optical solid sensors to identify cr (vi). Compared with direct fluorescence detection, the fluorescence detection of the microfluidic chip has the advantages of less sample quantity requirement, convenience in carrying, continuity in detection, simplicity in storage, convenience in visual observation and the like.

the invention develops a micro-fluidic sensor of photoluminescence xylan carbon quantum dots, and realizes effective detection of Cr (VI).

The invention discloses a visual detection method of a micro-fluidic sensor for Cr (VI) based on photoluminescence xylan carbon quantum dots. Dissolving xylan in NaOH/urea solution, performing hydrothermal carbonization to obtain xylan carbon quantum dot solution, and removing insoluble substances and salt through centrifugal dialysis; the mixed solution containing the xylan carbon quantum dots, the acrylamide and the oxidized nanocellulose is subjected to thermal crosslinking to form a fluorescent film, and then the fluorescent film is placed into a designed microfluidic device to form a sensor (microfluidic chip) for detecting Cr (VI). The sensor prepared by the invention can rapidly, visually and highly sensitively detect trace hexavalent chromium in domestic water on site under ultraviolet light. The sensor is an optical solid sensor, the device is light, simple and convenient to carry, the detection selectivity to hexavalent chromium is good, and the detection range is wide (60-480 mu mol/L). On the other hand, the fluorescent film is light and convenient, and can effectively realize solid fluorescence sensing.

compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the invention provides a method for realizing the visual detection of Cr (VI) by a micro-fluidic sensor based on photoluminescence xylan carbon quantum dots, the adopted carbon quantum dots take xylan as a carbon source, the source is wide, the cost is low, and the micro-fluidic sensor is safe and nontoxic and has stable performance;

(2) In the method for realizing the visual detection of Cr (VI) by the micro-fluidic sensor based on the photoluminescence xylan carbon quantum dots, oxidized nanocellulose is used as a reinforcing agent of a fluorescent film, and the xylan carbon quantum dots can be well fixed because hydroxyl and carboxyl of the oxidized nanocellulose can generate hydrogen bond action with the xylan carbon quantum dots, and the oxidized nanocellulose and the xylan carbon quantum dots are assembled into an optical solid sensor together with a micro-fluidic chip of a micro-fluidic device (for detecting Cr (VI)); the sensor can selectively detect hexavalent chromium in the domestic water, and has high sensitivity;

(3) the method for realizing the visual detection of Cr (VI) by the micro-fluidic sensor based on the photoluminescence xylan carbon quantum dots has the advantages of simple process, wide raw material source and low energy consumption, and the used micro-fluidic chip is beneficial to large-scale industrial production;

(4) the invention provides a method for realizing visual detection of Cr (VI) by a micro-fluidic sensor based on photoluminescence xylan carbon quantum dots, which has a wide detection range of 60 ~ 480 mu mol/L, and the used micro-fluidic chip (the micro-fluidic sensor for detecting Cr (VI)) has the performances of rapidness, accuracy, potential portability, easy use, visualization, low price, long storage duration and the like, and can be applied to detection of hexavalent chromium in domestic water and environmental water resources.

Drawings

FIG. 1 is a schematic view of a microfluidic chip in an example;

wherein, 1-screw hole; 2-liquid inlet pipe; 3-a groove; 4-upper organic glass.

FIG. 2 is the fluorescence spectra obtained in example 2 with different concentrations of hexavalent chromium added to xylan-containing quantum dots.

FIG. 3 is a graph showing the quenching degree of hexavalent chromium with respect to the phosphor film obtained in example 2.

fig. 4 is a bar graph of fluorescence intensity of different ions on xylan quantum dots obtained in example 2.

FIG. 5 is a graph of fluorescence intensity of xylan quantum dots at different excitation wavelengths obtained in example 2.

FIG. 6 is a schematic diagram showing the fluorescence change of the fluorescent film after injecting the different solutions obtained in example 2 into the microfluidic chip.

Detailed Description

The following examples are presented to further illustrate the practice of the invention, but the practice and protection of the invention is not limited thereto. It is noted that the processes described below, if not specifically described in detail, are all realizable or understandable by those skilled in the art with reference to the prior art. The reagents or apparatus used are not indicated to the manufacturer, and are considered to be conventional products available by commercial purchase.