Sulfur- and Nitrogen-Containing Porous Donor–Acceptor Polymers as Real-Time Optical and Chemical Sensors

Abstract

Real-Time Optical and Chemical Sensors. ChemRxiv. Preprint.Fully aromatic, organic polymers have the advantage of being composed from light, abundant elements, and are hailed as candidates in electronic and optical devices "beyond silicon", yet, applications that make use of their π-conjugated backbone and optical bandgap are lacking outside of heterogeneous catalysis. Herein, we use a series of sulfur-and nitrogen-containing porous polymers (SNPs) as real-time optical and electronic sensors reversibly triggered and re-set by acid and ammonia vapors. Our SNPs incorporate donor-acceptor and donor-donor motifs in extended networks and enable us to study the changes in bulk conductivity, optical bandgap, and fluorescence life-times as a function of π-electron de-/localization in the pristine and protonated states. Interestingly, we find that protonated donor-acceptor polymers show a decrease of the optical bandgap by 0.42 eV to 0.76 eV and longer fluorescence life-times. In contrast, protonation of a donor-donor polymer does not affect its bandgap; however, it leads to an increase of electrical conductivity by up to 25-fold and shorter fluorescence life-times. The design strategies highlighted in this study open new avenues towards useful chemical switches and sensors based on modular purely organic materials. File list (4) download file view on ChemRxiv 20190929_Manuscript_CLEAN.docx (1.67 MiB) download file view on ChemRxiv 20190929_SI_CLEAN.docx (16.08 MiB) download file view on ChemRxiv 20190929_Manuscript_CLEAN.pdf (1.23 MiB) download file view on ChemRxiv Video 1-YAR SNP-NDT1.mp4 (3.71 MiB)

Multifunctional Visible‐Light Powered Micromotors Based on Semiconducting Sulfur‐ and Nitrogen‐Containing Donor–Acceptor Polymer

“…This phenomenon can be explained by the narrowing of the polymer bandgap due to molecular backbone protonation, caused by the addition of hydrochloric acid. [ 49a ] In addition, the Stern–Volmer linear relationship, plotted for the different acid concentrations, proves, that HCl interacts with SNP‐MMs and quenches the fluorescence of the excited state of the light‐sensitive material (Figure S18, Supporting Information). [ 51 ]…”

“…Previous reports have shown that fully organic SNPs and triazine‐based COF material built from D–A dyads act as rapid and reversible acid‐base chemosensors in the solid state. [ 49 ] Herein we demonstrate the pH response of SNP‐MMs in aqueous media. Upon addition of hydrochloric acid solution at concentrations from 0.1 to 15 wt%, the SNP‐MMs suspension shows an immediate color change (from yellow to red), which can be observed by naked‐eye ( Figure a).…”

Rational Fabrication of Crystalline Smart Materials for Rapid Detection and Efficient Removal of Ozone

“…[38][39][40] Moreover,o ur observation agreed well with literature results that the protonation of the imines decreased the optical band gaps in the visible part of the spectrum, thus causing the color change (Figure 3a). [41] Moreover,w e observed that the excess ozone can further react with imine groups after the initial optical color change process (i.e., partial protonation) ( Figure S18). FT-IR spectra ( Figure S19) showed that the C=NH + at the position of 1644 cm À1 was retained, while the characteristic peaks assigned to -NO 2 and -COOH groups gradually appeared.…”

“…Moreover, ozone decomposition can be accelerated by initiators such as OH − which can be generated by the protonation of imine groups with water molecules [38–40] . Usually, alteration of the chemical environment of functional groups (e.g., imine) will affect the optical band gaps of materials in the visible part of the spectrum, thus causing the color change [35, 41] . Therefore, imine can be an ideal responsive group for ozone‐related applications.…”

“…[38][39][40] Usually,alteration of the chemical environment of functional groups (e.g., imine) will affect the optical band gaps of materials in the visible part of the spectrum, thus causing the color change. [35,41] Therefore,imine can be an ideal responsive group for ozone-related applications.T ot he best of our knowledge,u sing imine-based materials for ozone sensing and removal application has not been reported yet. Astraightforward strategy to design ozone responsive materials is to use imines as the linkage of COFs (Scheme 1), [42][43][44] whose ordered structures and high porosity can benefit their performance.Inthis contribution, we for the first time expanded the application scope of COFs to ozonerelated applications:the selected COFs not only can serve as smart ozone sensors with rapid, visible optical responses but also can be applied for ozone removal with both high capacity and efficiency.…”