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    Layer-by-layer assembly enabled by the anionic p-dopant CN6-CP•-K+: a route to achieve interfacial doping of organic semiconductors
    Highly efficient 2D (interfacial) doping of organic semiconductors, poly(3-hexylthiophene) (P3HT) and TIPS-pentacene, was achieved by a polyelectrolyte-supported layer-by-layer assembly of the dual-mode functional dopant CN6-CP•-K+, having an anionic group for its fixation onto oppositely charged surfaces/molecules as well as electron-deficient groups providing its p-doping ability. Polyelectrolyte-supported dopant layers were used to generate conductive channels at the bottom or at the top of semiconducting films. Unlike to the case of sequentially processed P3HT films doped by F4TCNQ (Moulé, J. Chem. Mater. 2015, 27, 5765; Koech, P. K. J. Mater. Chem. C 2013, 1, 1876; Schwartz, B. J. J. Phys. Chem. Lett. 2015, 6, 4786), the use of more polar CN6-CP•-K+ dopant and ultrathin polycation separation interlayer enables predominantly interfacial kind of doping placement with no or minimal intercalation of the dopant into the semiconductor bulk. The layered structure of the doped film was proved by transmission electron microscopy of the cross-section and it agrees well with other data obtained in this work. The interfacial doping enabled an impressive conductivity of 13 S/cm even for ultrathin P3HT films. We propose to explain the superior efficiency of the interfacial doping compared to the bulk doping in terms of unperturbed morphology of the semiconductor and high mobility of charge carriers, which are spatially separated from the dopant phase.
    Publicationtype: Journal Article
    Scopus© Citations 6  23
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    Conjugated Polymers as a New Class of Dual-Mode Matrices for MALDI Mass Spectrometry and Imaging
    Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) and MALDI MS imaging are ubiquitous analytical methods in medical, pharmaceutical, biological, and environmental research. Currently, there is a strong interest in the investigation of low molecular weight compounds (LMWCs), especially to trace and understand metabolic pathways, requiring the development of new matrix systems that have favorable optical properties and a high ionization efficiency and that are MALDI silent in the LMWC area. In this paper, five conjugated polymers, poly[N,N'-bis(2-octyldodecyl)-naphtalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'(2,2'-bithiophene) (PNDI(T2)), poly(3-dodecylthiophene-2,5-diyl) (P3DDT), poly[2,3-bis(3-octyloxyphenyl)quinoxaline-5,8-diyl]-alt-(thiophene-2,5-diyl) (PTQ1), poly[N,N'-bis(2-octyldodecyl)-isoindigo-5,5'-diyl]-alt-5,5'(2,2'-bithiophene) (PII(T2)), and poly(9,9-di-n-octylfluorenyl-2,7-diyl) (P9OFl) are investigated as matrices. The polymers have a strong optical absorption, are solution processable, and can be coated into thin films, allowing a vast reduction in the amount of matrix used. All investigated polymers function as matrices in both positive and negative mode MALDI, classifying them as rare dual-mode matrices, and show a very good analyte ionization ability in both modes. PNDI(T2), P3DDT, PTQ1, and PII(T2) are MALDI silent in the full measurement range (>m/z = 150k), except at high laser intensities. In MALDI MS experiments of single analytes and a complex biological sample, the performance of the polymers was found to be as good as two commonly used matrices (2,5-DHB for positive and 9AA for negative mode measurements). The detection limit of two standard analytes was determined as being below 164 pmol for reserpine and below 245 pmol for cholic acid. Additionally P3DDT was used successfully in first MALDI MS imaging experiments allowing the visualization of the tissue morphology of rat brain sections.
    Publicationtype: Journal Article
    Scopus© Citations 41  16