Near-field Electrical Detection of Optical Plasmons and Single Plasmon Sources

Photonic circuits can be much faster than their electronic counterparts, but they are difficult to miniaturize below the optical wavelength scale. Nanoscale photonic circuits based on surface plasmon polaritons (SPs) are a promising solution to this problem because they can localize light below the diffraction limit. However, there is a general tradeoff between the localization of an SP and the efficiency with which it can be detected with conventional far-field optics. Here we describe a new all-electrical SP detection technique based on the near-field coupling between guided plasmons and a nanowire field-effect transistor. We use the technique to electrically detect the plasmon emission from an individual colloidal quantum dot coupled to an SP waveguide. Our detectors are both nanoscale and highly efficient (0.1 electrons/plasmon), and a plasmonic gating effect can be used to amplify the signal even higher (up to 50 electrons/plasmon). These results enable new on-chip optical sensing applications and are a key step towards "dark" optoplasmonic nanocircuits in which SPs can be generated, manipulated, and detected without involving far-field radiation.Comment: manuscript followed by supplementary informatio

Ion Mobility-Derived Collision Cross-Sections Add Extra Capability in Distinguishing Isomers and Compounds with Similar Retention Times: The Case of Aphidicolanes

The hyphenation of ion mobility spectrometry with high-resolution mass spectrometry has been widely used in the characterization of various metabolites. Nevertheless, such a powerful tool remains largely unexplored in natural products research, possibly mainly due to the lack of available compounds. To evaluate the ability of collision cross-sections (CCSs) in characterizing compounds, especially isomeric natural products, here we measured and compared the traveling-wave IMS-derived nitrogen CCS values for 75 marine-derived aphidicolanes. We established a CCS database for these compounds which contained 227 CCS values of different adducts. When comparing the CCS differences, 36 of 57 pairs (over 60%) of chromatographically neighboring compounds showed a ΔCCS over 2%. What is more, 64 of 104 isomeric pairs (over 60%) of aphidicolanes can be distinguished by their CCS values, and 13 of 18 pairs (over 70%) of chromatographically indistinguishable isomers can be differentiated from the mobility dimension. Our results strongly supported CCS as an important parameter with good orthogonality and complementarity with retention time. CCS is expected to play an important role in distinguishing complex and diverse marine natural products