Real-Time Sniffing Mass Spectrometry Aided by Venturi Self-Pumping Applicable to Gaseous and Solid Surface Analysis

Based on the Venturi self-pumping effect, real-time sniffing with mass spectrometry (R-sniffing MS) is developed as a tool for direct and real-time mass spectrometric analysis of both gaseous and solid samples. It is capable of dual-mode operation in either gaseous or solid phase, with the corresponding techniques termed as Rg-sniffing MS and Rs-sniffing MS, respectively. In its gaseous mode, Rg-sniffing MS is capable of analyzing a gaseous mixture with response time (0.8–2.1 s rise time and 7.3–9.6 s fall time), spatial resolution (<80 μm), three-dimensional diffusion imaging, and aroma distribution imaging of red pepper. In its solid mode, an appropriate solvent droplet desorbs the sample from a solid surface, followed by the aspiration of the mixture using the Venturi self-pumping effect into the mass spectrometer, wherein it is ionized by a standard ion source. Compared with the desorption electrospray ionization (DESI) technique, Rs-sniffing MS demonstrated considerably improved limit of detection (LOD) values for arginine (0.07 μg/cm2 Rs-sniffing vs 1.47 μg/cm2 DESI), thymopentin (0.10 μg/cm2vs 2.67 μg/cm2), and bacitracin (0.16 μg/cm2vs 2.28 μg/cm2). Rs-sniffing is applicable for the detection of C60(OCH3)6Cl–, an intermediate in the methoxylation reaction involving C60Cl6 (solid) and methanol (liquid). The convenient and highly sensitive R-sniffing MS has a characteristic separation of desorption from the ionization process, in which the matrix atmosphere of desorption can be interfaced by a pipe channel and self-pumped by the Venturi effect with consequent integration using a standard ion source. The R-sniffing MS operates in a voltage-, heat-, and vibration-free environment, wherein the analyte is ionized by a standard ion source. Consequently, a wide range of samples can be analyzed simultaneously by the R-sniffing MS technique, regardless of their physical state

Nitrogen-Embedded Quintuple [7]Helicene: A Helicene–Azacorannulene Hybrid with Strong Near-Infrared Fluorescence

Herein, a nitrogen-embedded quintuple [7]­helicene (N-Q7H) with an azapentabenzocorannulene core, which can be considered to be a helicene/azacorannulene hybrid π-system, was synthesized from azapentabenzocorannulene in a three-step process. N-Q7H is the first example of a multiple helicene with an azabuckybowl core. Single-crystal X-ray diffractometry unambiguously confirmed the structure of the propeller-shaped hybrid π-system. Owing to nitrogen-atom doping in the multiple helicenes and effective hybridization between the helicene and azacorannulene, N-Q7H exhibits considerably redshifted absorption and emission (yellow-to-green color change and green-to-near-infrared fluorescence change) relative to the azapentabenzocorannulene core. The broad absorption from the ultraviolet–visible to the NIR region is ascribable to the allowed transition between the highest occupied molecular orbital and the lowest unoccupied molecular orbital after symmetry breaking, as revealed by density functional theory calculations. Compared to previous propeller-shaped multiple helicenes with corannulene or hexabenzocoronene (etc.) as cores, N-Q7H demonstrates a significantly higher NIR fluorescence quantum efficiency of 28%. Additionally, the chiral-resolution and redox properties of N-Q7H were investigated. The excellent photophysical and inherent chiral properties of N-Q7H suggest that azapentabenzocorannulene can be used as an outstanding nitrogen-embedded core to construct novel multiple helicenes with wide application potential, including as NIR fluorescent bio-probes