Jie Jiang

Industrial-scale organic electrosynthesis predominantly employs galvanostatic (constant-current) electrolysis, yet electrochemistry−mass spectrometry (EC−MS) methods for mechanistic studies have been developed almost exclusively under potentiostatic (constant-potential) conditions. Here, we report a robust constant-current electrochemical microreactor-mass spectrometry (CCEM-MS) platform that bridges this methodological gap, enabling real-time mechanistic investigation under galvanostatic conditions directly relevant to industrial practice. We demonstrate its utility across three mechanistically distinct C−N bond-forming electrosynthetic reactions, unambiguously detecting and structurally assigning key reactive intermediates: (i) pyridine radical cations and aryl pyridinium ions from the anodic coupling of electron-rich arenes with pyridine; (ii) carbon-centered neutral radicals and carbocations from non-Kolbe electrolysis; and (iii) nitrogen-centered radical cations from cross-coupling reactions that furnish triarylamine derivatives. These experimentally validated mechanistic insights directly informed the predictive design and experimental realization of two new electrosynthetic methodologies: (a) anodic generation of previously unreported heterocyclic pyridinium ions and (b) oxidative assembly of acridine-based triarylamines.

Optical elements for polarization control, including polarizers and waveplates, are crucial for quantum optics, sub‐diffraction imaging, and biomedical sensing. Polarization state modulators based on metasurface enable miniaturized, ultrathin, and highly integrated optical components; however, their geometry‐encoded functionality limits multifunctional integration. Here, a single‐port Fabry‐Pérot cavity resonance system is designed based on atomically thin MoS ₂ supported on a ZnO/SiO ₂ /Si substrate, which enables significant reflective phase modulation arising from phase singularities. Both theoretical and experimental results demonstrate that monolayer MoS ₂ supported on a ZnO(30 nm)/SiO ₂ (300 nm)/Si substrate can convert 45° linearly polarized incident light into 0° linearly polarized reflected light, circularly polarized reflected light, and a highly linearly polarized reflected state with a polarization orientation of 135°, depending on the incident angle and operating wavelength. Through appropriate control of structural parameters, including film thickness and incident angle, this resonant system can realize three polarization functionalities, acting as a linear polarizer, a quarter‐wave plate, and a half‐waveplate. The operating wavelength range, degree of linear polarization, and degree of circular polarization are systematically analyzed. This MoS ₂ ‐based resonant system features a simple structure and versatile polarization modulation capabilities, providing guidance for the design and fabrication of planar integrated optical components.

Microdroplets are highly efficient microreactors, yet conventional mass spectrometry typically evaluates their reactivity as an ensemble average, obscuring the independent catalytic roles of positively and negatively charged microdroplets. In this study, we developed a microdroplet separation mass spectrometry method. By separating mixed-charge microdroplet plumes prior to MS sampling, this approach enables the independent, online analysis of positively and negatively charged microdroplets. The performance was validated by combining experiments and simulations. Application of this methodology to perfluorooctanoic acid (PFOA) degradation revealed that negatively charged microdroplets exhibit a higher degradation efficiency than positive counterparts. Mechanistic investigations, supported by radical trapping and density functional theory, reveal that negative interfacial charge effectively stabilizes the transition state, facilitating a hydroxyl radical (•OH)-driven degradation pathway. This polarity-dependent enhancement proved universal across varying reaction conditions and other perfluorinated compounds with diverse chain lengths and terminal functional groups. Moreover, we rationally modulated the microenvironment via negative voltage application and Fenton’s reagent supplementation, boosting the PFOA degradation from approximately 38% to 83%. These findings demonstrate that the developed separation-MS method is a reliable tool for resolving mixed-charge microdroplet behaviors and provides insights for reasonably elucidating and optimizing charge-regulated microdroplet interfacial chemistry.

Secondary organic aerosols (SOAs) are key components of aerosols, but their formation pathways remain incompletely elucidated. This study reveals a new pathway for SOA formation in water microdroplets by employing both experimental and theoretical methods. It is found that inert CO₂ can react rapidly with atmospheric organic acids in water microdroplets, producing low-volatility compounds that contribute to SOA formation. Radical quenching experiments and direct observation of carbocations indicate that the carbocations generated from organic acids are the key active intermediates. Such carbocations are proposed to subsequently react with the counterion HCO₃^-, derived from CO₂, to yield the observed products. Density functional theory calculations confirm that the carbocation mechanism is most favorable, with a reaction energy barrier of 5.24 kcal/mol. Further studies find that various organic acids can undergo similar reactions, and the reaction efficiency is positively correlated with the number and radius of halogen atoms but negatively correlated with carbon chain length. Overall, this study unveils a novel pathway for SOA formation involving ubiquitous CO₂ and organic acids, offering mechanistic insights into the chemistry of atmospheric CO₂ and SOAs.

The single-electron oxidation reaction is a critical initial step in organic synthesis. Currently, the influence of halide ions on single-electron oxidation in water microdroplets remains unclear. In this study, different halide ions were observed to have the opposite influence on single-electron oxidation reactions. Specifically, F^- and Cl^- inhibited single-electron oxidation, while Br^- and I^- promoted this reaction. These influences had a distinct dependence on the concentration. The microdroplet size distribution, quantity of microdroplets, and generation of radicals were systematically investigated to probe the mechanism. The inhibitory effects of F^- and Cl^- were mainly attributed to charge neutralization, while the promotional effects of Br^- and I^- were mainly due to the generation of radicals. Overall, this study reveals the dual nature of halide ions in the unique environment of microdroplets, enhancing our understanding of ion-specific effects in microdroplet chemistry.

The direct mass spectrometric analysis of complex biological samples is often hindered by matrix interference and the need for extensive sample preparation. In this study, an online electroextraction method based on nano-electrospray mass spectrometry (OEE-nESI-MS) was proposed for the high-sensitivity and rapid analysis of urine samples. Compared with other methods, OEE-nESI-MS requires only 5 μL of sample and 35 μL of extraction solvent to achieve the migration and simultaneous ionization of the target from the sample solution to the extraction solvent in the nano tip, and online extraction and simultaneous analysis can be achieved within 8 min, while maintaining comparable sensitivity to other detection methods. The OEE-nESI-MS showed good linearity (R² > 0.995) in the range of 1-600 ng mL^-1 for the five catecholamines (CAs) in urine, with detection limits as low as 0.39-0.89 ng mL^-1 with recoveries of 91.9-104.9% (RSD ≤ 8.9%). Exploration of the OEE-nESI mechanism emphasized the electric field applied as a key factor facilitating online electroextraction. The OEE-nESI-MS was successfully applied to the analysis of five CAs in real urine samples. This advancement provides a very simplified solution for the online rapid, highly sensitive, and quantitative determination of complex samples.