Konjugierte Polyelektrolyte: Synthese, Photophysik und Anwendungen

Efficient imidazolium-biomolecule interaction-assisted amplified quenching for ultrasensitive detection of heparin

Detection of Heparin (HP) under physiological conditions is difficult due to the presence of biological obstructions including proteins and lipids. Thus, it is highly challenging to selectively detect HP and to increase its sensitivity in complex systems. Here, we report the detection of HP at nanomolar levels via efficient imidazolium-HP interaction-assisted fluorescence quenching amplification. The self-assembled pyrenyl aggregates are devised as a conduit for efficient exciton transport, which induces amplified fluorescence quenching for HP detection. This amplified quenching is enhanced by introducing an imidazolium receptor designed to have high affinity to HP via electrostatic and/or additional interactions with C2 protons, resulting in a very high Stern-Volmer quenching constant of approximately 1.17 ☓ 10 8 M -1 .

Saccharide-Functionalized Poly(Zn-salphen)-alt-(m- and p-phenyleneethynylene)s as Dynamic Helical Metallopolymers

The study of metallopolymers with controllable helical sense remains in its infancy. We report arabinose-functionalized (Zn-salphen)-based conjugated polymers that display mirror-image circular dichroism spectra for L- and D-sugar sidechains respectively, signifying ordered (helical) coiling of the polymer backbone with opposite screw-sense preferences. The observation of different spectroscopic behavior and Cotton effects for a variety of solvents (in a reversible manner) and temperatures, ascribed to changes in the extent of intrachain (Zn⋅⋅⋅O(salphen) and π-stacking) interactions between Zn-salphen moieties, thus indicate the flexible, responsive and dynamic nature of the folded helical conformation in these systems. An application study signifying that activity can be governed by the structure and helical sense of the polymer is described.

Redox-Active Heteroatom-Functionalized Polyacetylenes

The discovery of metallic conductivity in polyacetylene [-HC=CH-]_n upon doping represents a landmark achievement. However, the insolubility of polyacetylene and a dearth of methods for its chemical modification have limited its widespread use. Here, we employ a ring-opening metathesis polymerization (ROMP) protocol to prepare functionalized polyacetylenes (fPAs) bearing: (1) electron-deficient boryl (-BR₂ ) and phosphoryl (-P(O)R₂ ) side chains; (2) electron-donating amino (-NR₂ ) groups, and (3) ring-fused 1,2,3-triazolium units via strain-promoted Click chemistry. These functional groups render most of the fPAs soluble and can lead to intense light absorption across the visible to near-IR region. Also, the presence of redox-active boryl and amino groups leads to opposing near-IR optical responses upon (electro)chemical reduction or oxidation. Some of the resulting fPAs show greatly enhanced air stability when compared to known polyacetylenes. Lastly, these fPAs can be cross-linked to yield network materials with the full retention of optical properties.

A Conjugated Polymer Containing Arylazopyrazole Units in the Side Chains for Field-Effect Transistors Optically Tunable by Near Infra-Red Light

Optically tunable field-effect transistors (FETs) with near infra-red (NIR) light show promising applications in various areas. Now, arylazopyrazole groups are incorporated in the side chains of a semiconducting donor-acceptor (D-A) polymer. The cis-trans interconversion of the arylazopyrazole can be controlled by 980 nm and 808 nm NIR light irradiation, by utilizing NaYF₄ :Yb,Tm upconversion nanoparticles and the photothermal effect of conjugated D-A polymers, respectively. This reversible transformation affects the interchain packing of the polymer thin film, which in turn reversibly tunes the semiconducting properties of the FETs by the successive 980 nm and 808 nm light irradiation. The resultant FETs display fast response to NIR light, good resistance to photofatigue, and stability in storage for up to 120 days. These unique features will be useful in future memory and bioelectronic wearable devices.

Immobilized Poly(aryleneethynylene) pH Strips Discriminate Different Brands of Cola

Fluorescent, water-soluble poly(p-aryleneethynylene)s (PAE) were immobilized on commercially available nylon membranes by using a slot plotter, creating fluorescent, barcode-like sensor strips. Digital imaging by using a standard digital camera, before and after immersion of the strips in buffers of different pH, displays a unique color for each pH value. Statistical evaluation, multivariate analysis of variance (MANOVA) and principal component analysis (PCA), of the acquired data revealed that the immobilized PAEs are superior to the identical fluorophores when dissolved. The pH sensor array discriminates 20 different brands of commercial-cola soft drinks through differences in pH and colorant-PAE interactions.

Narrow Band Gap Conjugated Polyelectrolytes

Two essential structural elements define a class of materials called conjugated polyelectrolytes (CPEs). The first is a polymer framework with an electronically delocalized, π-conjugated structure. This component allows one to adjust desirable optical and electronic properties, for example the range of wavelengths absorbed, emission quantum yields, electron affinity, and ionization potential. The second defining feature is the presence of ionic functionalities, which are usually linked via tethers that can modulate the distance of the charged groups relative to the backbone. These ionic groups render CPEs distinct relative to their neutral conjugated polymer counterparts. Solubility in polar solvents, including aqueous media, is an immediately obvious difference. This feature has enabled the development of optically amplified biosensor protocols and the fabrication of multilayer organic semiconductor devices through deposition techniques using solvents with orthogonal properties. Important but less obvious potential advantages must also be considered. For example, CPE layers have been used to introduce interfacial dipoles and thus modify the effective work function of adjacent electrodes. One can thereby modulate the barriers for charge injection into semiconductor layers and improve the device efficiencies of organic light-emitting diodes and solar cells. With a hydrophobic backbone and hydrophilic ionic sites, CPEs can also be used as dispersants for insoluble materials. Narrow band gap CPEs (NBGCPEs) have been studied only recently. They contain backbones that comprise electron-rich and electron-poor fragments, a combination that leads to intramolecular charge transfer excited states and enables facile oxidation and reduction. One particularly interesting combination is NBGCPEs with anionic sulfonate side groups, for which spontaneous self-doping in aqueous media is observed. That no such doping is observed with cationic NBGCPEs indicates that the interplay between electrostatic forces and the redox chemistry of the organic semiconducting chain is essential for stabilizing the polaronic states and increasing the conductivity of the bulk. Capitalizing upon the properties of NBGCPEs has resulted in a range of new applications. When doped, they can be introduced as interlayers in organic and perovskite solar cells. Single-walled carbon nanotubes can be n- or p-doped with NBGCPEs, depending on whether the same backbone contains attached cationic or anionic side groups, respectively. The resulting dispersions can be used to fabricate flexible thermoelectric devices in which the n- and p-semiconductor legs are nearly identical in terms of chemical composition. Electrostatic interactions with negatively charged cell walls, in combination with the long-wavelength absorption and high photothermal efficiencies, have been used to create effective agents for photothermal killing of bacteria. Additionally, recent results have shown that cationic NBGCPEs can effectively n-dope graphene and that this doping is temperature-dependent. The preferential charge carriers can therefore be chosen to be electrons or holes depending on the applied temperature.

Bright quantum-dot-sized single-chain conjugated polyelectrolyte nanoparticles: synthesis, characterization and application for specific extracellular labeling and imaging

We report a simple method to fabricate quantum-dot-sized nanoparticles (NPs) from poly[9,9-bis((6-N,N,N-trimethylammonium)hexyl)fluorene-alt-co-2,1,3-benzo-xadiazole dibromide] (PFBD). The transmission electron microscope results reveal that the obtained NPs have a mean diameter of ≈4 nm, which is composed of a single PFBD chain. The NPs show bright fluorescence with an emission maximum at ≈636 nm and a quantum yield of ≈26% in water. The fluorescence properties of the NPs are characterized by steady fluorescence microscopy, fluorescence dynamic study and single nanoparticle microscopy, which show superior brightness over commercial quantum dots QD655. The NPs are further conjugated with streptavidin to yield PFBD-SA NPs, which serve as a specific extracellular labeling and imaging probe with high specificity and good photostability.

Electronic properties of conjugated polyelectrolyte/single-walled carbon nanotube composites

Two narrow-bandgap conjugated polyelectrolytes (CPEs) of identical backbone structure but different pendant charges are used to disperse single-walled carbon nanotubes (SWNTs) in MeOH. Films of the resulting CPE:SWNT composites have electrical conductivity dependent on the SWNT loading, which can be increased with acid vapor treatment. The anionic CPE gives higher electrical conductivity for the composite immediately after deposition, whereas a more-significant increase is observed for the cationic counterpart after acid treatment.

Facile doping of anionic narrow-band-gap conjugated polyelectrolytes during dialysis

PCPDTBTSO3 K, an anionic, narrow-band-gap conjugated polyelectrolyte, was found to be doped after dialysis. The proposed doping mechanism involves protonation of the polymer backbone, followed by electron transfer from a neutral chain, to generate radical cations, which are stabilized by the pendant sulfonate anions. Formation of polarons is supported by spectroscopy and electrical-conductivity measurements.

Synthesis of amphiphilic polythiophene for cell imaging and monitoring the cellular distribution of a cisplatin anticancer drug

A new amphiphilic conjugated polythiophene derivative (PT-Boc) is synthesized via Suzuki coupling reaction. The amphiphilic characteristic makes it form nanoaggregates in water, in which hydrophobic moieties come together to form the inner core. The polymer shows good photostability and no toxicity to human lung epithelial (A549) cells even at a high concentration (100 μg mL(-1) ). It therefore meets the crucial requirement for cellular imaging and other biological applications. The anticancer drug cisplatin is used as a model, and is linked to polythiophene to obtain a conjugate 'PT-Pt' by coordinated interactions between cisplatin and the amine groups of the polythiophene side chain. The PT-Pt can be used for monitoring the cellular distribution of cisplatin by fluorescence microscopy. The amphiphilic polythiophene provides a platform for fluorescent imaging of drugs and biological molecules in living cells.

An anion-conjugated polyelectrolyte designed for the selective and sensitive detection of silver(I)

A novel conjugated polyelectrolyte P1, having a meta-substituted monopyridyl in the backbone, is designed and synthesized for Ag(+) detection in aqueous solution. As a chemosensor, P1 shows high sensitivity, low detection limit, and excellent selectivity for Ag(+) over other metal ions. The sensing mechanism is based on the specific interaction between Ag(+) and the pyridyl group of P1. The aggregated state of the polymer in water can amplify its quenching efficiency.