A paper-based chip sensor for detecting total chromium in water using laser-induced breakdown spectroscopy

Abstract

The present invention discloses a paper-based chip sensor for detecting total chromium in water based on laser-induced breakdown spectroscopy technology, which relates to many fields such as spectroscopy, nanomaterials, and chemistry. Sodium borohydride is used as a reducing agent to in-situ synthesize gold, silver, and palladium trimetallic nanocomposite particles on a paper base. The nanoparticles have a high specific area and can efficiently adsorb chromium in water. By detecting other common metal ions and then using laser-induced breakdown spectroscopy technology for signal acquisition, it was found that it has strong specific adsorption properties for chromium. Moreover, it exhibits strong adsorption properties for the two common valence states of chromium, trivalent and hexavalent forms, so that rapid detection of total chromium in water can be achieved. The paper-based chip in the present invention is simple to modify, easy to synthesize and modify, and has low cost. It has certain use and application prospects in the field of excessive chromium in drinking water and environmental water bodies.

Description

Technical Field

[0001] The present invention relates to the technical field of paper-based chip sensors, and more particularly to a paper-based chip sensor for detecting total chromium in water using laser-induced breakdown spectroscopy. Background Art

[0002] Laser-induced breakdown spectroscopy (LIBS) is a rapidly developing element detection technology in recent years. Figure 1 LIBS (as shown in Figure 1) primarily uses a high-energy pulsed laser to ablate and penetrate a sample, generating a plasma containing information about the elemental composition and content. Rapid element detection is then achieved by collecting and analyzing the plasma. Compared to other technologies, LIBS has been widely used in various fields, including space exploration, deep-sea exploration, biomedicine, agriculture, food safety, and environmental testing, due to its advantages of requiring no pretreatment (solid, liquid, and gaseous states can be detected), rapid speed (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 materials such as water, soil, traditional Chinese medicine, plants, and food, with detection limits reaching sub-ppm levels. These advantages make LIBS technology an extremely attractive method for elemental detection. However, since harmful metals in the environment are generally trace elements, the LIBS detection limit is often at the sub-ppm level, making it difficult to directly detect trace heavy metal elements using LIBS. Therefore, efficient enrichment of heavy metal elements for detection has been proposed. Among them, nanomaterials, as a material with a porous structure and a large specific surface area, can efficiently and specifically adsorb heavy metal elements.

[0003] Paper-based microchips are microfluidic chips that use paper substrates (such as filter paper, chromatography test strips, and various cellulose membranes) as both a chip fabrication material and a biochemical analysis platform. They offer advantages such as rapid detection, ease of use, portability, and low cost. They are a research hotspot in various fields, including basic scientific research and biochemical testing, and have promoted the development of low-cost analytical technologies.

[0004] Existing solutions to technical problems: Currently, many detection methods (such as atomic absorption spectroscopy, atomic fluorescence spectroscopy, and inductively coupled plasma spectroscopy) are used for 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. In addition, there are differences in the results when different personnel perform the detection, which makes the detection time-consuming, labor-intensive, and costly, making it difficult to truly apply them to the actual in-situ detection of environmental heavy metals. In recent years, nanoions, as an environmentally friendly and multifunctional nanomaterial, have been widely used in medicine, sensing, and catalysis. Some biosensors based on noble metal nanoparticles have also been used in heavy metal detection. Their principle is mainly to use heavy metal ions to bind to certain specific substances to change the physical and chemical properties of noble metal nanoparticles (color development, fluorescence, catalytic activity, thermal effect, etc.). Finally, the changes in nanoparticle properties (such as absorbance, etc.) are measured by colorimetry, ultraviolet-visible spectroscopy, localized plasmon resonance, and fluorescence spectroscopy, thereby indirectly reflecting the heavy metal content in the analyte. Summary of the Invention

[0005] In view of this, the present invention provides a paper-based chip sensor for detecting total Cr in water using laser induced breakdown spectroscopy. The LIBS technology is combined with a nano paper-based chip to realize the detection of total heavy metal Cr in water.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] 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 chromium element (trivalent and hexavalent forms) in water. Finally, the spectral signal of the metal ion Cr is excited using LIBS technology, and a correlation model is established between the LIBS signal and the Cr concentration, thereby achieving highly sensitive detection of the total heavy metal Cr in water.

[0008] Technical solutions and specific implementation measures:

[0009] LIBS technology is used in combination with nanopaper-based chips to detect the total heavy metal Cr in water.

[0010] Implementation plan: First, AuAgPdNPs are synthesized in situ on a paper substrate. Then, a solution containing Cr ions is specifically adsorbed, and the LIBS signal of the Cr element is collected using a LIBS instrument. 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.

[0011] It can be seen from the above technical solution that compared with the existing technology, the present invention discloses a paper-based chip sensor that uses laser-induced breakdown spectroscopy to detect total Cr in water, which realizes efficient and rapid detection of total Cr in water and is suitable for rapid and efficient analysis of total heavy metal Cr in water. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of the structure of the laser induced breakdown spectroscopy instrument provided by the present invention;

[0013] Figure 2 Schematic diagram of the production process of the AuAgPdNPs-modified paper-based chip provided by the present invention;

[0014] Figure 3 Schematic diagram of the adsorption results of some common metal ions by the AuAgPdNPs paper-based chip provided by the present invention;

[0015] Figure 4 This is the LIBS spectrum of the AuAgPdNPs paper-based chip provided by the present invention for the adsorption detection of total Cr in water;

[0016] Figure 5 Schematic diagram of the quantitative model establishment for the AuAgPdNPs paper-based chip provided by the present invention for detecting total Cr in water in the low concentration range (0-50 μg / L);

[0017] Figure 6 Schematic diagram of the quantitative model establishment for the detection of total Cr in water in the high concentration range (50-1000 μg / L) using the AuAgPdNPs paper-based chip provided by the present invention;

[0018] Figure 7 Schematic diagram of the effect of different concentration ratios of trivalent Cr and hexavalent Cr on the detection of total Cr in water by the AuAgPdNPs paper-based chip provided by the present invention;

[0019] In the figure, 1-1 is a signal delay generator; 1-2 is a laser; 1-3 is a plasma; 1-4 is a 3D detection platform; 1-5 is a nano-paper-based chip adsorbed with Cr; 1-6 is an optical fiber; 1-7 is a spectrometer; 1-8 is a focusing lens; 1-9 is a mirror;

[0020] 2-1 is a reaction container (centrifuge tube); 2-2 is gold, silver and palladium metal ions; 2-3 is a paper-based chip; 2-4 is a nanopaper-based chip modified with AuAgPdNPs tri-metal nanoparticles; 2-5 is the Cr element; 2-6 is a nanopaper-based chip adsorbed with Cr ions; 2-7 is a LIBS laser. DETAILED DESCRIPTION

[0021] The embodiment of the present invention discloses a paper-based chip sensor for detecting total Cr in water using laser-induced breakdown spectroscopy. The manufacturing process is as follows: Figure 2 As shown in the figure, the main chemical reagents involved in the experimental process 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 testing and other performance tests.

[0022] 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 paper pieces (1cm*1cm) in them and shake for 10 minutes to allow the filter paper to completely adsorb the three metal ions until saturated. Then remove the filter paper and place it in 9mL of sodium borohydride solution (20mM) and continue shaking for 10 minutes to allow the metal ions to be reduced to nanocomposite particles to the greatest extent. Finally, wash the modified nanopaper base twice with deionized water and dry it at 37°C for use.

[0023] Specificity Detection: To verify and demonstrate the strong adsorption specificity of AuAgPdNPs-modified paper for chromium, we compared the selective adsorption of various common metal ions onto the AuAgPdNPs-modified paper substrate, with each metal ion concentration set at 0.2 mg / L. After 15 minutes of agitation and adsorption, the paper chip was removed and rinsed twice with deionized water. LIBS signals were collected for the characteristic peaks of the adsorbed metal ions corresponding to the different paper substrates, and then data processing and comparative analysis were performed.

[0024] A quantitative relationship model for chromium detection was established: 4 mL of chromium solutions with varying concentration gradients (0.5, 1, 2, 5, 10, 50, 100, 200, 500, and 1000 μg / L) were prepared. A pre-prepared AuAgPdNPs-modified paper chip was added to each solution. After shaking for 15 minutes, the paper chip was removed and rinsed twice with deionized water. Finally, the LIBS signal of chromium on the paper chip was measured. A quantitative relationship model between chromium concentration and its LIBS signal was established.

[0025] A quantitative relationship model for Cr element detection was established: purified water, tap water, pond water, and river water were taken and the Cr concentration in them was first detected by ICP-MS. Then, spiked experiments were performed on them (with spiked Cr concentrations of 0.01 and 0.2 mg / L, respectively), and the concentration values and recoveries were calculated.

[0026] Principle exploration: The nanopaper substrate can efficiently and specifically adsorb the Cr element. The possible principles are: 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 enhance the LIBS signal of the element Cr to be measured and improve the sensitivity.

[0027] 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, it is proposed that the trimetallic AuAgPdNPs paper-based chip can realize the adsorption detection of total Cr in water.

[0028] Sensitivity analysis: From Figure 4 It can be seen that after the AuAgPdNPs paper-based chip adsorbed Cr elements of different concentrations (0-1000 μg / L), the LIBS spectrum showed a trend of gradually increasing signals at 425.43 nm with the increase of Cr concentration, and Figure 5 It can also be seen that the LIBS signal intensity and Cr show a positive correlation within a certain concentration range. In order to establish a good linear correlation and the best detection limit, at low concentrations (0-50μg / L, y=265.7+201.6x, Figure 5 ) and high concentration range (50-1000 μg / L, y=9277.6+10.9x, Figure 6 ) were used to establish corresponding quantitative relationship models to achieve more accurate quantitative detection. The detection limit of total Cr in water was calculated to be 0.29μg / L for the low concentration range. In order to eliminate the influence of the ratio of Cr in the two valence states (trivalent and hexavalent) on the detection and analysis of total Cr in the water, solutions of total Cr in the two valence states with different ratios were prepared to ensure a total concentration of 200μg / L. After enrichment of AuAgPdNPs paper-based chips, data were collected and analyzed using a LIBS device. 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.

[0029] Implementation case analysis: In order to verify the practicality of this method, actual samples (pure water, tap water, pond water and river water) spiked with water samples were analyzed and tested. Table 1 shows the test results of the actual sample spiked and the calculation results of the recovery rate. The recovery rate can be maintained between 90% and 110%.

[0030] Table 1

[0031]

[0032] Key Points: This example utilizes a trimetallic composite nanomaterial for the first time, demonstrating efficient adsorption of chromium in both valence states. This ultimately enables highly sensitive detection of total chromium in water, with a sensitivity of 0.29 μg / L. Actual samples were also tested, demonstrating potential practical applications in aquatic environmental pollution.

Claims

1. A paper-based chip sensor for detecting total chromium in water using laser-induced breakdown spectroscopy, characterized in that: Preparation of paper-based microarrays, including: Take 3mL of 12mM chloroauric acid solution, 3mL of 12mM silver nitrate solution and 3mL of 12mM potassium tetrachloropalladate solution respectively, mix them, place filter paper in them and shake for 10 minutes to allow the filter paper to completely adsorb the three metal ions until saturated. Then take out the filter paper and place it in 9mL of 20mM sodium borohydride solution and continue to shake for 10 minutes to reduce the metal ions to the maximum extent to form nanocomposite particles. Finally, the modified nanopaper base is washed with deionized water and dried to obtain the AuAgPdNPs modified paper-based chip.

2. The paper-based chip sensor for detecting total chromium in water using laser-induced breakdown spectroscopy according to claim 1, characterized in that: The AuAgPdNPs-modified paper-based chip can specifically enrich the total Cr element in water, which includes trivalent and hexavalent forms.

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