Paper-based chip sensor for detecting total Cr in water body by using laser-induced breakdown spectroscopy

Abstract

The invention discloses a paper-based chip sensor for detecting total Cr in a water body based on a laser-induced breakdown spectroscopy technology, and relates to the fields of spectroscopy, nano materials, chemistry and the like. Sodium borohydride is used as a reducing agent to carry out in-situ synthesis on a paper base to synthesize gold-silver-palladium three-metal nano composite particles, and the nano particles have a relatively high specific area and can efficiently adsorb the chromium element in a water body. Through detection of other common metal ions and signal acquisition by using a laser-induced breakdown spectroscopy technology, it is found that the material has relatively strong specific adsorption performance on chromium. Moreover, the adsorbent has relatively strong adsorption performance on two common valence, trivalent and hexavalent forms of the chromium element, so that rapid detection of the total chromium element in the water body can be realized. The conventional common detection method can only detect a single valence state, but the method can realize the detection of two valence states, and the proportion of the two valence states basically does not influence the signal. By detecting chromium elements with different concentration gradients, a good linear model is established between a laser-induced breakdown spectroscopy signal and the chromium element concentration, and rapid and efficient detection is realized. The paper-based chip in the method is simple to modify, easy to synthesize and modify and relatively low in cost, and has certain use and application prospects in the field of standard exceeding of chromium in drinking water and environmental water.

Description

Technical Field

[0001] Laser induced breakdown spectroscopy, composite nanometal particles, paper-based chip sensors, total Cr detection. Background Art

[0002] Rapid and highly sensitive detection of heavy metals is crucial for environmental safety.

[0003] Laser-induced breakdown spectroscopy (LIBS) is a rapidly developing element detection technology in recent years. Figure 1 As shown in Figure 1, it mainly uses a beam of high-energy pulsed laser to ablate and break down the sample and generate plasma containing element composition and content information, and realizes rapid element detection by collecting and analyzing the plasma. Compared with other technologies, LIBS has been widely used in various fields, including space exploration, deep-sea exploration, biomedicine, agriculture, food safety and environmental testing, based on the advantages of no pretreatment (solid, liquid and gas can be detected), fast (μs level), portability and simultaneous analysis of all elements. In heavy metal detection, LIBS can detect heavy metals such as Pb, Cr, Cd, Hg, and Mn in water, soil, traditional Chinese medicine, plants, food and other materials, and the detection limit can reach sub-ppm level. Based on the above advantages, LIBS technology has become an extremely attractive means of element detection. However, since harmful metals in the environment are generally trace elements, the LIBS detection limit is often at the sub-ppm level, which makes it difficult for LIBS to directly detect trace heavy metal elements. Therefore, we propose to detect heavy metal elements through efficient enrichment. Among them, nanomaterials, as a material with a porous structure and a large specific surface area, can efficiently and specifically adsorb heavy metal elements.

[0004] Paper-based chips are microfluidic chips that use paper (such as filter paper, chromatography test paper, and various cellulose membranes) as chip manufacturing materials and biochemical analysis platforms. They have the advantages of fast detection speed, simple operation, portability, and low cost. They are often used as research hotspots in many fields such as basic scientific research and biochemical testing, and have promoted the development of low-cost analytical technology. Existing solutions to technical problems

[0005] At present, there are many detection methods (such as atomic absorption spectroscopy, atomic fluorescence spectroscopy and inductively coupled plasma spectroscopy) used in the rapid detection of heavy metal elements. Although the above methods can achieve high-sensitivity detection of heavy metal elements, they are often only used in laboratories and require professional operation. There are differences in the results of different personnel when detecting, which makes the detection time-consuming, labor-intensive and costly, and it is difficult to be truly applied to the actual in-situ detection of environmental heavy metals. In recent years, nanoions, as an environmentally friendly multifunctional nanomaterial, have been widely used in medicine, sensing and catalysis. Some biosensors based on precious metal nanoparticles have also been used in heavy metal detection. The principle is mainly to use heavy metal ions to bind to certain specific substances to change the physical and chemical properties of precious metal nanoparticles (color, fluorescence, catalytic activity, thermal effect, etc.). Finally, the changes in nanoparticle characteristics (such as absorbance, etc.) are measured by colorimetry, ultraviolet-visible spectroscopy, local plasma resonance and fluorescence spectroscopy, thereby indirectly reflecting the heavy metal content in the analyte. Technical problem to be solved by the present invention (purpose of the invention)

[0006] By synthesizing gold, silver and palladium trimetallic nanocomposite particles (AuAgPdNPs) on a paper-based chip, the paper-based chip modified with the nanocomposite particles can specifically enrich the total Cr element (trivalent and hexavalent forms) in the water body. Finally, the spectral signal of the metal ion Cr is excited by LIBS technology, and a correlation model is established between the LIBS signal and the Cr concentration, thereby realizing the high-sensitivity detection of the total heavy metal Cr in the water body ( Figure 2 as shown). Technical solution and specific implementation measures of the present invention

[0007] In this study, we used LIBS technology combined with nanopaper-based chips to detect the total heavy metal Cr in water.

[0008] Implementation plan: First, AuAgPdNPs are synthesized in situ on a paper substrate, and then a solution containing Cr ions is specifically adsorbed. The LIBS signal of the Cr element is collected using a LIBS instrument, and a quantitative relationship model is established between the LIBS signal of the Cr element and the concentration of Cr, thereby realizing the detection and analysis of total Cr in water. Technical Effects of the Invention

[0009] The present invention realizes efficient and rapid detection of total Cr in water bodies, and can be applied to rapid and efficient analysis of total Cr of heavy metals in water bodies. Experimental Section

[0010] The chemical reagents mainly involved in the experimental process of the scheme of the patent of this invention include: chloroauric acid (HAuCl4), silver nitrate (AgNO3), potassium tetrachloropalladate (K2PdCl4), sodium borohydride (NaBH4), Cr standard solution, and other conventional metal ion standard solutions. The experimental part includes: preparation of AuAgPdNPs modified paper-based chips, specificity experiments, adsorption detection of total Cr elements, LIBS signal acquisition and establishment of quantitative relationship model, actual sample detection and other performance tests. Preparation of AuAgPdNPs-modified paper-based chips

[0011] Preparation of AuAgPdNPs modified paper-based chips: Take 3mL of chloroauric acid solution (12mM), 3mL of silver nitrate solution (12mM), and 3mL of potassium tetrachloropalladate solution (12mM) respectively, mix them, place 50 filter papers (1cm*1cm) in them and shake for 10 minutes to allow the filter papers to completely adsorb the three metal ions until saturated. Then take out the filter papers and place them in 9mL of sodium borohydride solution (20mM) and continue to shake for 10 minutes to reduce the metal ions to the maximum extent into nanocomposite particles. Finally, wash the modified nanopaper base with deionized water twice and dry it at 37°C for use.

[0012] Specific detection: In order to verify and prove that the AuAgPdNPs-modified paper substrate has strong adsorption specificity for Cr, we compared the selective adsorption of AuAgPdNPs-modified paper substrates for a variety of common metal ions, where the concentration of each metal ion was set to 0.2 mg / L. After 15 minutes of shaking and adsorption, the paper substrate chip was removed and washed twice with deionized water. The LIBS signals of the characteristic peaks of the adsorbed metal ions corresponding to different paper substrates were collected, and then data processing and comparative analysis were performed.

[0013] Establishment of quantitative relationship model for Cr element detection: Prepare 4 mL of Cr solution with different concentration gradients (0.5, 1, 2, 5, 10, 50, 100, 200, 500, 1000 μg / L), then add a prepared AuAgPdNPs modified paper chip to each solution, shake for 15 minutes, take out the paper chip and wash it twice with deionized water, and finally detect the LIBS signal of Cr element on the paper chip. Establish a quantitative relationship model between Cr element concentration and its LIBS signal.

[0014] The quantitative relationship model for Cr element detection was established: pure water, tap water, pond water and river water were taken and the concentration of Cr in them was first detected by ICP-MS, and then spiked experiments were carried out on them (spike-added with 0.01 and 0.2 mg / L of Cr element, respectively), and the concentration values ​​and recovery rates were calculated.

[0015] Principle exploration: The nano-paper substrate can efficiently and specifically adsorb the Cr element. The principle may be: 1. The paper substrate modified with AuAgPdNPs is a tri-metal nanocomposite material. The nanomaterial itself has a porous structure and a large specific surface area, which can effectively adsorb heavy metal ions; 2. There may be a stronger binding ability between AuAgPd and the Cr element; 3. The nanomaterial increases the density of the number of particles in the plasma phase during the ablation process, which can further improve the LIBS signal of the element Cr to be measured and improve the sensitivity. Are there any other related patent inventions?

[0016] (1) Keywords: paper-based chip, total Cr detection, LIBS technology Search results: 0 Literature materials similar to the present invention (including journals, books or papers)

[0017] Keywords: test paper, nanoparticles, LIBS, metal ions detection The relevant search results are as follows: Detection of heavy metal ions using laser induced breakdownspectroscopy combined with filter paper modified with PtAg bimetallic nanoparticles. Journal of hazardous materials .2023,443,130188. This article introduces a highly sensitive and rapid detection technology for multiple heavy metal elements based on LIBS technology combined with silver-platinum nanoparticle modified filter paper, which realizes the efficient detection of three common heavy metal elements Hg, Cr and Pb in water bodies, with a detection limit of 8 μg / L. The difference from this document is that the three-alloy nanoparticles used in this patent can realize the enrichment detection of the total Cr (trivalent and hexavalent) of the heavy metal element, while the former can only adsorb trivalent Cr and has poor adsorption of hexavalent Cr, so it is impossible to realize the analysis and detection of total Cr in water bodies.

[0018] Rapid Determination of Cr3+ and Mn2+ in Water Using Laser-InducedBreakdown Spectroscopy Combined with Filter Paper Modified with GoldNanoclusters. Biosensors, 2024, 14(6), 267. This article introduces a LIBS-based paper-based gold nanocluster-modified Cr 3+ and Mn 2+ Simultaneous detection of Cr 3+ The detection limit is 7.5 μg / L. This document only has a certain detection performance for trivalent Cr and cannot realize the analysis and detection of total Cr in water.

[0019] The three-metal modified nanopaper substrate proposed in this patent can detect total Cr in water with a detection limit of 0.29 μg / L, and the sensitivity is improved by about 27 times. Conclusion

[0020] Specificity: From Figure 3 It can be seen that the AuAgPdNPs paper-based chip shows strong adsorption specificity for both trivalent Cr and hexavalent Cr, the signal for mercury is weaker than that for Cr, and it has basically no adsorption capacity for other metal elements. Based on this phenomenon, we proposed that the trimetallic AuAgPdNPs paper-based chip can realize the adsorption detection of total Cr in water.

[0021] Sensitivity analysis: From Figure 4 It can be seen that after the AuAgPdNPs paper-based chip adsorbed Cr elements of different concentrations (0-1000μg / L), the LIBS spectrum showed a trend of gradually increasing signals at 425.43nm with the increase of Cr concentration. Figure 5 It can also be seen that the LIBS signal intensity is positively correlated with Cr in a certain concentration range. In order to establish a better linear correlation and the best detection limit, we used the LIBS signal intensity at low concentrations (0-50μg / L, y=265.7+201.6x, Figure 5 ) and high concentration range (50-1000μg / L, y=9277.6+10.9x, Figure 6 ) respectively established corresponding quantitative relationship models to achieve more accurate quantitative detection. The detection limit of total Cr in water was calculated to be 0.29 μg / L for the low concentration range. In order to eliminate the influence of the ratio of Cr in two valence states (trivalent and hexavalent) on the detection and analysis of total Cr in the whole water, we prepared solutions of total Cr in two valence states with different ratios and ensured a total concentration of 200 μg / L. After enrichment of AuAgPdNPs paper-based chips, LIBS device was used to collect data and analyze the data. Figure 7 The results show that the change in the ratio of Cr in the two valence states has little effect on the overall LIBS signal. Therefore, based on this result, it is further proved that the AuAgPdNPs modified paper-based chip can realize the analysis and detection of total Cr in water.

[0022] Implementation case analysis: In order to verify the practicality of this method, we analyzed and tested water samples spiked with actual samples (pure water, tap water, pond water and river water). Table 1 shows the test results of actual sample spikes and the calculation results of the recovery rate. The recovery rate can be maintained between 90% and 110%. Key points of the present invention

[0023] This invention patent utilizes tri-metal composite nanomaterials for the first time, showing efficient adsorption performance for two valence forms of Cr, and ultimately achieves highly sensitive detection of total Cr in water, with a sensitivity of 0.29 μg / L. Actual samples have also been tested, and it has potential practical application value in water environmental pollution. Figures and Schedules

[0024] In order to make the purpose and technical solution of the present invention clearer, the experimental details and results of the present invention will be further described in detail below in conjunction with the accompanying drawings: Figure 1 :Laser Induced Breakdown Spectroscopy Instrumentation 1: Signal delay generator 2: Laser 3: Plasma generated 4: 3D detection platform 5: Nanopaper-based chip adsorbed with Cr 6: Fiber Optic 7: Spectrometer 8: Focusing mirror 9: Mirror Figure 2 : Fabrication process of AuAgPdNPs modified paper-based chip 1: Reaction vessel (centrifuge tube) 2: Gold, silver, palladium metal ions 3: Paper-based chip 4: AuAgPdNPs tri-metal nanoparticles modified nanopaper substrate 5: Cr 6: Nanopaper substrate adsorbed with Cr ions 7: LIBS laser Figure 3: Adsorption results of some common metal ions on AuAgPdNPs paper-based chips Figure 4 : LIBS spectra of AuAgPdNPs paper-based chip for total Cr adsorption detection in water Figure 5 :Establishment of a quantitative model for the detection of total Cr in water in the low concentration range (0-50μg / L) using AuAgPdNPs paper-based chip Figure 6 :A quantitative model for the detection of total Cr in water in the high concentration range (50-1000μg / L) based on AuAgPdNPs paper-based chip Figure 7 :Effects of different concentration ratios of trivalent Cr and hexavalent Cr on the detection of total Cr in water using AuAgPdNPs paper-based chip Table 1: Cr actual sample detection Table 1 Actual water sample Sample No. ICP-MS test results Spiked concentration (mg / L) Detection value (mg / L) Recovery rate Purified water 1 0.023 (μg / L) 0 \ \ 2 0.01 0.01051 104.87% 4 0.2 0.19976 99.87% Tap water 5 0.218 (μg / L) 0 \ \ 6 0.01 0.00981 95.92% 8 0.2 0.21008 104.93% Pond water 9 0.096 (μg / L) 0 \ \ 10 0.01 0.00950 94.04% 12 0.2 0.20616 103.03% River water 13 0.102 (μg / L) 0 \ \ 14 0.01 0.01037 102.68 16 0.2 0.18944 94.67%

Claims

1. A paper-based chip method based on nanocomposite particles modified with gold, silver and palladium metals, characterized in that: By in situ synthesizing gold, silver and palladium tri-metallic nanocomposite particles on a paper substrate, the nanomaterial has a large specific surface area and can highly specifically adsorb chromium in water. The paper substrate, as a relatively uniform substrate, can ensure the uniformity of adsorption and the stability of the signal.

2. The method for realizing the paper-based chip of gold, silver and palladium tri-metal modified nanocomposite particles according to claim 1, characterized in that: Including but not limited to the three types of metal elements, gold, silver and palladium, for in-situ modification of paper-based chips, such as other elements such as platinum, copper, zinc and other elements for modification.

3. The method for realizing the paper-based chip of gold, silver and palladium tri-metal modified nanocomposite particles according to claim 1, characterized in that: Including but not limited to paper as the substrate, other materials of the substrate can also be used to modify the nanoparticles in situ.

4. The method for realizing the paper-based chip of gold, silver and palladium tri-metal modified nanocomposite particles according to claim 1, characterized in that: The signal output method is not limited to the laser induced breakdown spectroscopy technique, and other technical means may also be used for signal acquisition.

5. The method for realizing the paper-based chip of gold, silver and palladium tri-metal modified nanocomposite particles according to claim 1, characterized in that: It includes but is not limited to the detection of chromium in water samples, and can also be used to detect other liquid samples.

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