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Honey, renowned for its nutritional and therapeutic properties, has recently come under scrutiny due to its contamination by microplastics, in multiple ways. Bees’ exposure to plastic pollution impacts the whole hive’s ecosystem, and plastic tends to accumulate in hive products. Plastic packaging as polyethylene terephthalate (PET) is used to store honey in small flexible packages, which also increases the risk of microplastic migration. This study aims to establish three practical detection methods for PET microplastics and nanoplastics in honey, using readily available laboratory equipment without the need for chemical digestion or costly pretreatment protocols, in a laboratory-based simulation. The first method utilizes Raman micro-spectroscopy, offering high-resolution identification of PET microplastics on cellulose acetate filters with Raman mapping, eliminating the need for organic solvents or dyes. The second method employs optical microscopic observation under fluorescence with the aid of 4-dimethylamino-4′-nitrostilbene dye and ultraviolet radiation to enhance microplastic visibility, making it suitable for laboratories with standard optical microscopes. To isolate MPs from the solid honey particles, a density separator has been introduced using pentane. Lastly, the third method employs the use of electrospray ionization mass spectrometry for the detection of nanoplastics (<200 nm) in honey samples, through the examination of the different extraction phases of density separation. All the aforementioned methods contribute to efficient microplastic detection in honey, ensuring its quality and safe consumption. Full article

Multi-state n-electron valence state second order perturbation theory (MS-NEVPT2) was utilized to reveal the photorelaxation pathways of 4-(N,N-dimethylamino)-4′-nitrostilbene (DANS) upon S₁ excitation. Within the interwoven networks of five S₁/S₀ and three T₂/T₁ conical intersections (CIs), and three S₁/T₂, one S₁/T₁ and one S₀/T₁ intersystem crossings (ISCs), those competing nonadiabatic decay pathways play different roles in trans-to-cis and cis-to-trans processes, respectively. After being excited to the Franck–Condon (FC) region of the S₁ state, trans-S₁-FC firstly encounters an ultrafast conversion to quinoid form. Subsequently, the relaxation mainly proceeds along the triplet pathway, trans-S₁-FC → ISC-S₁/T₂-trans → CI-T₂/T₁-trans → ISC-S₀/T₁-twist → trans- or cis-S₀. The singlet relaxation pathway mediated by CI-S₁/S₀-twist-c is hindered by the prominent energy barrier on S₁ surface and by the reason that CI-S₁/S₀-trans and CI-S₁/S₀-twist-t are both not energetically accessible upon S₁ excitation. On the other hand, the cis-S₁-FC lies at the top of steeply decreasing potential energy surfaces (PESs) towards the CI-S₁/S₀-twist-c and CI-S₁/S₀-DHP regions; therefore, the initial twisting directions of DN and DAP moieties determine the branching ratio between α_C=C twisting (cis-S₁-FC → CI-S₁/S₀-twist-c → trans- or cis-S₀) and DHP formation relaxation pathways (cis-S₁-FC → CI-S₁/S₀-DHP → DHP-S₀) on the S₁ surface. Moreover, the DHP formation could also take place via the triplet relaxation pathway, cis-S₁-FC → ISC-S₁/T₁-cis → DHP-T₁ → DHP-S₀, however, which may be hindered by insufficient spin-orbit coupling (SOC) strength. The other triplet pathways for cis-S₁-FC mediated by ISC-S₁/T₂-cis are negligible due to the energy or geometry incompatibility of possible consecutive stepwise S₁ → T₂ → T₁ or S₁ → T₂ → S₁ processes. The present study reveals photoisomerization dynamic pathways via conical intersection and intersystem crossing networks and provides nice physical insight into experimental investigation of DANS. Full article