UV-Vis spectrophotometric determination of isoprene in atmosphere based on Diels–Alder reaction

Isoprene is the most abundant biogenic volatile organic compound in the atmosphere. Till now, chromatography is the main detection method for isoprene, dependent on sophisticated instruments and complex operations. An UV-Vis spectrophotometric method based on the Diels–Alder (D-A) reaction was developed to detect isoprene in the atmosphere. The fast D-A reaction between the probe 4-phenyl−1,2,4-triazolin−3,5-dione (PTAD) and isoprene may cause absorbance decrease, which enable it to detect isoprene in solution at 118 nmol·L−1 level. Further, isoprene in air at the level of ppbv was detected using this method. Compared with chromatography this method has the advantages of low cost, fast and less dependence on instrument.</p

Lanthanide-Doped Luminescent Nanoparticles with Dual-Mode Color Modulation Enable Cross-Correlation Anticounterfeiting

Lanthanide-doped upconversion nanoparticles (Ln-UCNPs) hold great potential in anticounterfeiting applications owing to their salient optical properties. However, a single-mode anticounterfeiting strategy based on common Ln-UCNPs typically confronts challenges in terms of imitation based on alternatives with a similar luminescence feature. Multilevel anticounterfeiting strategies on the basis of the multicolor beaconing luminescence generated upon dual- or multimode excitation are promising for addressing such a challenge and those based on the intrinsic mutual authentication of the dynamic signals generated via distinct manipulating manners are expected to present a higher security level. Herein, we demonstrate that low-concentration Yb/Er/Tm-codoped UCNPs with optimized formulation enable modulation of luminous color by manipulating the power of a continuous-wave 980-nm laser or the pulse parameter of the pulsed laser. The crucial role of acting as the red-emission-associated transient energy trapping center that Tm3+ species plays can be attenuated by Yb3+-mediated laser-power-dependent sensitization processes. The key intermediate states associated with red and green emission states are populated and deplete via different processes with distinct rates, which enables dependence of the emission feature on the pulse parameters of the laser. The unique feature of this type of Ln-UCNPs in terms of dual-mode luminous color modulation and its potential are preliminarily verified in our proof-of-concept cross-correlation experiment, which provides a feasible modality for high-level anticounterfeiting applications in specific scenarios such as high-value marketable securities and bond certificates