A new liquid-crystalline ion gel exhibits unprecedented properties: conductivity up to 8 mS cm(-1) , thermal stability to 300 °C, and electrochemical window to 6.1 V, as well as adjustable transport anisotropy (up to 3.5×) and elastic modulus (0.03-3 GPa). The combination of ionic liquid and magnetically oriented rigid-rod polyanion provides widely tunable properties for use in diverse electrochemical devices.

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A facile and efficient strategy for the syntheses of novel hyperbranched poly(ether amide)s (HPEA) from multihydroxyl primary amines and (meth)acryloyl chloride has been developed. The chemical structures of the HPEAs were confirmed by IR and NMR spectra. Analyses of SEC (size exclusion chromatography) and viscosity characterizations revealed the highly branched structures of the polymers obtained. The resultant hyperbranched polymers contain abundant hydroxyl groups. The thermoresponsive property was obtained from in situ surface modification of abundant OH end groups with N-isopropylacrylamide (NIPAAm). The study on temperature-dependent characteristics has revealed that NIPAAm-g-HPEA exhibits an adjustable lower critical solution temperature (LCST) of about 34−42 °C depending on the grafting degree. More interestingly, the work provided an interesting phenomenon where the HPEA backbones exhibited strong blue photoluminescence.

A flexible graphene field-effect transistor (Gr-FET) biosensor for ultrasensitive and specific detection of miRNA without labeling and functionalization is reported. The flexible biosensor presents robust performance even after multiple cycles of bending to a cylinder with an 8 mm radius. A DNA probe is designed with partial segment complementary to target miRNA, and immobilized on the graphene surface though π−π stacking interaction. After capture of target miRNA, a Dirac point shift in Gr-FET is induced, which shows a linear relationship with the target miRNA concentration on a semi-log scale. The Gr-FET-based biosensor finishes miRNA detection in 20 min, and is able to achieve a miRNA detection limit as low as 10 fM without any functionalization and labeling. The interaction processes of DNA-graphene and DNA-miRNA are confirmed through surface-enhanced Raman scattering technology. The proposed biosensor will have prospective applications in wearable electronics for health monitoring and disease diagnosis.

The ubiquitous biomacromolecule DNA has an axial rigidity persistence length of ~50 nm, driven by its elegant double helical structure. While double and multiple helix structures appear widely in nature, only rarely are these found in synthetic non-chiral macromolecules. Here we report a double helical conformation in the densely charged aromatic polyamide poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) or PBDT. This double helix macromolecule represents one of the most rigid simple molecular structures known, exhibiting an extremely high axial persistence length (~1 micrometer). We present X-ray diffraction, NMR spectroscopy, and molecular dynamics (MD) simulations that reveal and confirm the double helical conformation. The discovery of this extreme rigidity in combination with high charge density gives insight into the self-assembly of molecular ionic composites with high mechanical modulus (~ 1 GPa) yet with liquid-like ion motions inside, and provides fodder for formation of other 1D-reinforced composites.

Combining molecular alignment with selective ion transport can increase the freedom to design ion-conducting polymeric materials and thus enhance applications such as battery electrolytes, fuel cells, and water purification. Here we employ pulsed-field-gradient (PFG) NMR diffusometry, 2H NMR spectroscopy, polarized optical microscopy, and small-angle X-ray scattering to determine relations between counterion transport, dynamic coupling of water, and molecular alignment in aqueous solutions of a rigid rod sulfonated-aramid polyelectrolyte: poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) (PBDT). 23Na PFG NMR on PBDT solutions and simple sodium salt solutions shows significantly slower Na+ counterion diffusion in PBDT, providing agreement between counterion condensation theory and quantitative transport information. Strikingly, from 2H NMR spectroscopy we observe that the orientational order parameter of partially aligned solvent D2O molecules increases linearly with polymer weight percentage over a large concentration range (1.4 to 20 wt %), while the polymer chains possess essentially a large and fixed order parameter S matrix = 0.76 as observed using both SAXS and 2H NMR on labeled polymers. Finally, we apply a two-state model of water dynamics and a physical lattice model to quantitatively relate D2O spectral splittings and nematic rod–rod distance. These studies promise to open new pathways to understand a range of anisotropic polymer systems including aligned polymer electrolyte membranes, wood composites, aligned hydrogels, liquid crystals, and stretched elastomers.

The recent outbreak of coronavirus disease 2019 (COVID-19) is highly infectious, which threatens human health and has received increasing attention. So far, there is no specific drug or vaccine for COVID-19. Therefore, it is urgent to establish a rapid and sensitive early diagnosis platform, which is of great significance for physical separation of infected persons after rapid diagnosis. Here, we propose a colorimetric/SERS/fluorescence triple-mode biosensor based on AuNPs for the fast selective detection of viral RNA in 40 minutes. AuNPs with average size of 17 nm were synthesized, and colorimetric, surface enhanced Raman scattering (SERS), and fluorescence signals of sensors are simultaneously detected based on their basic aggregation property and affinity energy to different bio-molecules. The sensor achieves a limit detection of femtomole level in all triple modes, which is 160 fM in absorbance mode, 259 fM in fluorescence mode, and 395 fM in SERS mode. The triple-mode signals of the sensor are verified with each other to make the experimental results more accurate, and the capacity to recognize single-base mismatch in each working mode minimizes the false negative/positive reading of SARS-CoV-2. The proposed sensing platform provides a new way for the fast, sensitive, and selective detection of COVID-19 and other diseases.

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