The release of antibiotics into the water environment can pose a serious threat to human and ecological health, so it is of great significance to effectively remove antibiotics from wastewater. In this work, porphyrinic zirconium metal−organic framework material, PCN-224, was first explored for the adsorption removal of antibiotics from water using tetracycline (TC) and ciprofloxacin (CIP) as examples. We prepared a series of PCN-224 with different particle sizes (150 nm, 300 nm, 500 nm, and 6 μm). Benefiting from the huge surface area (1616 m 2 g −1 ), the 300 nm-PCN-224 sample had the best adsorption properties for TC and CIP. Remarkably, it exhibits fast removal rates and high adsorption capacities of 354.81 and 207.16 mg g −1 for TC and CIP, respectively. The adsorption of TC and CIP in 300 nm-PCN-224 is consistent with the pseudo-second-order kinetic model and Langmuir isotherm model, which indicates that the adsorption can be regarded as homogeneous monolayer chemisorption, and the adsorption is exothermic, which has been confirmed by thermodynamic studies. Under visible-light irradiation, 300 nm-PCN-224 exhibited high photocatalytic activity for TC and CIP. The adsorption studies confirmed that the adsorption of adsorbates takes place via the formation of hydrogen bonding, π−π interactions, and electrostatic attraction. In addition, the adsorbent can be simply regenerated by photocatalysis under visible light, and the adsorption−desorption efficiency is still above 85% after repeated use five times. The work of MOFs to remove antibiotics from water shows that MOFs have great potential in this field and are worthy of further study.
Reliable quantification by surface enhanced Raman scattering (SERS) highly depends on the development of a reproducible substrate with excellent anti-interference capability. In this work, an intrinsic internal standard (IS) SERS substrate based on a diblock copolymer, polystyrene-block-poly-4-vinylpyridine (PS-b-P4VP), as a template was developed by a modified block copolymer lithography (BCL) technique of reserving the diblock copolymer template. This substrate generated a stable vibration peak at 1066 cm attributed to poly(4-vinylpyridine) (P4VP) which could be used as an intrinsic IS for precise SERS quantification. A series of characterization results showed that the diblock copolymer template endowed this substrate with homogeneous distribution of Au nanoparticles, excellent stability and reproducibility. A minor relative standard deviation (RSDs) of SERS responses at 1066 cm was measured and calculated to be 4.3% from ten different substrates in the same batch, which suggested good substrate-to-substrate reproducibility of this substrate. Finally, this intrinsic IS substrate was successfully applied for the rapid quantification of a trace banned dye, chrysoidine, in food samples with complicated matrices by SERS. It was proved that chrysoidine could be found and quantified to be 0.50 and 0.41 mg L in a positive dried bean curd stick and chilli powder sample respectively with good recoveries by this substrate coupled with SERS. The development of intrinsic IS substrates would benefit rapid and accurate quantification of trace targets in complex samples coupled with SERS analysis.
The safety of cosmetics attributing to the illegal addition of antibiotics for quick effect is a big concern nowadays. Nitrofurans, one of commonly added illegal antibiotics, are strictly banned in cosmetics in China. It is still a great challenge for the rapid and precise analysis of trace nitrofurans when facing various cosmetics with complicated matrices. Surface‐enhanced Raman spectroscopy (SERS) is emerging as a novel rapid on‐site analytical technique. In this work, an accurate SERS method was developed for the rapid analysis of trace nitrofurantoin in various cosmetics by use of nanoarrayed hydroxyl polystyrene (PS‐OH)‐based substrate. A series of characterizations indicated the successful synthesis of Au@PS‐OH substrate and the uniform distribution of gold nanoparticles on the substrate surface. The SERS substrate revealed good selectivity and reproducibility with an enhancement factor of 2.6×104. Finally, an analytical method for the determination of nitrofurantoin in cosmetics was established by SERS using Au@PS‐OH substrate coupling with efficient sample preparation process. It was satisfied that trace nitrofurantoin could be actually detected and quantified to be 1.77 and 7.74 mg/L in a mouthwash and rose‐mist sample, respectively, with good recoveries of 86.8‐106% and relative standard deviations of 0.9‐2.9%. The comparable analytical results for real samples were achieved by the traditional high‐performance liquid chromatography (HPLC) method, which validated the reliability of the proposed method. It is expected that this SERS method has great potential for the rapid and on‐site analysis of trace additives in cosmetics.
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