With the rapid development of industry, water pollution has become one of the important problems that harm the ecological environment and human health. The extensive use and random discharge of dyes have caused serious damage to water resources. Hydrogel bead is a promising material for dye adsorption due to its advantages of rich functional groups and high specific surface area. Here, acrylic acid sodium salt (AAS) and 2-acrylamide-2-methylpropanesulfonic acid (AMPS) as monomers, N,N’-Methylene-bis-acrylamide (MBA) as crosslinking agent, sodium alginate (SA) as semi-interpenetrating network component, laponite as nano-clay additive, and single 2′,4′,5′,7′ −tetrabromofluorescein disodium salt (EY)/ Triethanolamine (TEOA)/ diphenyl iodonium hexafluorophosphate (DPI) as green light polymerization initiating system were combined to prepare composite hydrogel beads within 10 s under green LED irradiation. The composite hydrogels were characterized by infrared spectroscopy (FTIR), thermogravimetric analyzer (TG), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The addition of sodium alginate and laponite can improve the mechanical properties of hydrogel beads. In the adsorption study of malachite green, the influence of time, temperature, dye concentration, pH, ionic strength, and other factors on the adsorption effect were investigated. The adsorption process was consistent with the second-order kinetic process and Langmuir adsorption. At room temperature, the highest adsorption capacity of the hydrogel beads for malachite green reached 829.63 mg/g. The PAAS-SL hydrogel beads maintained a high adsorption effect in the pH range (3–10), and the capacity reached 575.0 mg /g at pH 3, which had a good ability to resist low pH. In the adsorption–desorption experiments, the removal rate of PAAS-SL hydrogel beads for MG is still more than 80 % after 5 cycles. Our research provides a promising strategy for the efficient and rapid preparation of hydrogel beads with excellent properties.
In this work, Ag nanoparticles (AgNPs) were embedded into a poly(N-isopropylacrylamide)-laponite (Ag/PNIP-LAP) hydrogel membrane for highly sensitive surface-enhancement Raman scattering (SERS) detection. In situ polymerization was initiated by UV light to encapsulate AgNPs in a PNIP-LAP hydrogel to prepare a highly active SERS membrane with a three-dimensional structure. Due to the surface plasmon resonance and high swelling/shrinkage ratio of the Ag/PNIP-LAP hydrogel SERS membrane, its network structure has a “sieving” effect, which makes it easier for hydrophilic small-molecule targets to enter the sterically confined hydrogel, and the AgNPs are close to each other to form a Raman “hot spot” through the shrinkage of the hydrogel, at the same time, the analyte is enriched in the confined space and close to the AgNPs to form a stronger SERS signal. The characterization of the SERS activity of the Ag/PNIP-LAP hydrogel showed that the prepared three-dimensional membrane had high detection sensitivity for urotropine, 2,5-dimethylpyrazine, pyrazinamide, and pyrazine; the detection limits (S/N = 3) were 17.4, 31.0, 53.1, and 1.11 μg/L, and the analytical time was 35 min. Due to the hydrophilicity of the Ag/PNIP-LAP hydrogel membrane, the small molecules can easily enter the SERS membrane, and the hydrophobic macromolecules are blocked outside the SERS membrane. The SERS method has good selectivity, stability, and reproducibility. The SERS method was applied to the detection of urotropine in dried bean curd sticks, 2,5-dimethylpyrazine in nuts and potato chips, and pyrazinamide in human plasma with recoveries of 81.8–116.8% and the relative standard deviation within 4.9–9.9%. The results matched well with that found by the corresponding chromatographic methods. The proposed method has the advantages of simple sample pretreatment, speediness, high sensitivity, and good selectivity to hydrophilic compounds and has potential application in the rapid on-site detection.
危险品化学品经营许可证（带存储）