High-performance Detection Of Paes Plasticizer Based On Functionalized MOFs@Ag Surface-enhanced Raman Scattering

Phthalate esters（PAEs）are the most common type of plasticizer,reaching 80%of the total added amount of all plasticizers.PAEs are only combined with plastic polymers through physical action.Under the influence of external temperature and p H,they are easy to migrate from the plastic to the surrounding environment.PAEs have an effect similar to estrogen.After long-term exposure,affect the synthesis and metabolism of hormones in the body,and damage human health.Surface enhanced Raman scattering（SERS）has become a reliable and sensitive nondestructive detection technology due to its simple technical operation and short time-consuming.The key to this technology is the excellent performance of the substrate,which helps to generate increased Raman signal for sensitive detection.In this paper,by combining porous metal organic frameworks（MOFs）with Ag,as SERS substrates to realize the rapid identification and highly sensitive determination of PAEs in plastics.The main contents of this paper are as follows:（1）A new method for detecting di-（2-ethylhexyl）phthalate（DEHP）based on Zr-UIO-66@Ag NPs using Raman enhanced spectroscopy was established,and the mechanism of Raman enhancement was explored.First,with Zr⁴⁺as the metal active center and terephthalic acid as the overseas ligand,the octahedral Zr-UIO-66 was synthesized by hydrothermal method,and the surface was loaded with silver nanoparticles to prepare the Zr-UIO-66@Ag NPs substrate for the detection of DEHP in plastics.Studies have shown that the strengthening effect of the Zr-UIO-66@Ag NPs composite substrate was significantly stronger than that of Ag NPs or Zr-UIO-66 alone.Zr-UIO-66 has a large specific surface area and strong absorption capacity.Dispersing Ag NPs on the surface of Zr-UIO-66 can not only reduce the agglomeration of Ag NPs,but also bind Zr-UIO-66 adsorption function.When the mixing concentration of Zr-UIO-66 and Ag NPs was 1:2,Ag NPs were uniformly distributed on the surface of Zr-UIO-66.At this time,the particle size of Ag NPs was about 46 nm,and the gap between particles was about 26.nm,the local surface plasmon resonance"hot spots"were the most abundant.In the Raman test of DEHP,it shows a wide detection concentration range of 10^-4～10^-11 mol/L,and the detection limit was as low as 3×10^-12 mol/L.At the same time,it was successfully applied to the identification and determination of DEHP in actual plastics.The sample recovery rate was 81.9-110.1%,and satisfactory test results were obtained.（2）Preparation and characterization of Co-ZIF-67 and Ag nanowires（Co-ZIF-67@Ag NWs）composites as SERS substrates to establish a Raman enhanced spectroscopy quantitative analysis method for dibutyl phthalate（DBP）.Firstly,the Ag nanowires were synthesized by hydrothermal reaction.By adjusting the mixing ratio of Ag MWs and Co-ZIF-67,Co-ZIF-67 with porous structure was grown on Ag NWs to prepare functionalized Co-ZIF-67@Ag NWs composite substrate.The characterization results showed that the Ag NWs surface in the composite substrate was rough and had obvious sharp points.And maintaining the zero-valent valence state was conducive to the generation of strong electromagnetic fields.Although Co-ZIF-67 was damaged during the growth process,it still had a high adsorption performance.The Raman test of DBP with Co-ZIF-67@Ag NWs as the substrate shows that Co-ZIF-67@Ag NWs had a high linear correlation（R~2=0.9964）,good repeatability（RSD=6.18%）and strong stability（RSD=5.32%）.Finally,in the test of actual plastics,it was found that the plastics contain a certain amount of DBP,but the content is far less than the national and international standards.（3）The Co-ZIF-67@Ag NWs substrate was used to quantitatively analyze a variety of PAEs.Seven PAEs such as dimethyl phthalate（DMP）,dinonyl phthalate（DNP）,didecyl phthalate（DNDP）,diisobecyl phthalate（DIHP）,diphenyl phthalate（DPHP）,DEHP and DBP were tested as the research objects,and the similarities and differences of PAEs in Raman spectra were analyzed.The results show that the Raman spectra of the seven PAEs all contain the same peaks,which were because the PAEs have ortho-phenyl groups and ester groups in the structure.The characteristic peaks of were produced by the vibration of these two structures,but there were still differences between different PAEs.Such as,different carbon chain lengths（DMP and DNP）,isomers（DNDP and DIDP）,and types of substituents（DPHP and DEHP）will cause differences in the characteristic peak position,peak intensity and peak width.Therefore,the established Co-ZIF-67@Ag NWS Raman enhancement method can quickly identify different types of PAEs.