Robust double-network polyvinyl alcohol-polypyrrole hydrogels as high-performance electrodes for flexible supercapacitors.

The growing demands of flexible and wearable electronic devices boost the rapid development of flexible supercapacitors (FSCs). Conductive hydrogels are considered to be one type of promising electrode materials for FSCs due to their good processability and electrochemical properties. However, the poor mechanical properties of conductive hydrogels hinder their practical applications. Building robust cross-linked network structures is a feasible way to enhance their mechanical properties. Herein, the double-network polyvinyl alcohol (PVA)-polypyrrole (PPy) conductive hydrogels are synthesized by the freeze-thaw and in-situ polymerization method. The double-network structure not only enhances mechanical properties of the hydrogels, but also promotes their electrolyte ion transport. The maximum elongation at break of the optimized PVA-PPy hydrogels can reach 156.4%, and the specific capacitance is 1718.7 mF cm-2 at 0.5 mA cm-2. Furthermore, the energy densities of the symmetrical PVA-PPy FSCs are 46.7 and 13.3 µWh cm-2 at power densities of 200.0 and 2000.0 µW cm-2. Such excellent electrochemical performances and mechanical properties make the synthesized PVA-PPy hydrogels a promising candidate for FSCs.

Weakened Triplet-Triplet Annihilation of Diiodo-BODIPY Moieties without Influence on Their Intrinsic Triplet Lifetimes in Diiodo-BODIPY-Functionalized Pillar[5]arenes.

The triplet-triplet annihilation (TTA) effect of sensitizers themselves can lead to the additional quenching of lifetimes of triplet states; therefore, how to weaken the TTA effect of sensitizers is an urgent issue to be resolved for their further applications. Besides, it remains a tremendous challenge for constructing supramolecular systems of photosensitizers based on photosensitizer-functionalized pillararenes because there have been very few investigations on them. Thus, 2,6-diiodo-1,3,5,7-tetramethyl-8-phenyl-4,4-difluoroboradiazaindacene (DIBDP) and ethoxy pillar[5]arene (EtP5) were utilized to synthesize a DIBDP-functionalized pillar[5]arene (EtP5-DIBDP), a cyano-containing DIBDP (G) used as a guest molecule was also prepared, and they were used to investigate the electron-transfer mechanism between EtP5 and DIBDP moieties and weaken the TTA effect of DIBDP moieties. The theoretical computational results of frontier molecular orbitals and isosurfaces of spin density preliminarily predicted that the cavities of the EtP5 moiety had influence on the fluorescence emission of DIBDP units but not on their triplet states in EtP5-DIBDP. The fluorescence emission intensities in a variety of solvents with different polarities and electrochemical studies revealed that there was electron transfer from EtP5 to the DIBDP units, and the electron-transfer process had influence on the fluorescence emission but not on the triplet states of DIBDP moieties in EtP5-DIBDP, which verified the results of density functional theory calculations. The triplet state lifetimes of EtP5-DIBDP were longer than those of DIBDP and G and the photooxidation abilities of EtP5-DIBDP were better than those of DIBDP and G at a high concentration (1.0 × 10-5 M) in various solvents; in contrast, the intrinsic triplet state lifetimes and singlet oxygen quantum yields (ΦΔ) of DIBDP, G, and EtP5-DIBDP were very similar. This was because the steric hindrance of EtP5 moieties could weaken the TTA effect of DIBDP moieties without influencing their intrinsic triplet state lifetimes in EtP5-DIBDP.

Introduction of an antifouling photoelectrode: an effective strategy for a high-performance photoelectrochemical cytosensor.

As nonspecific adsorption or biofouling has obvious side effects on the selectivity, it is a great challenge for cytosensors to detect target cells in practical biological samples. In this study, we first propose the design and synthesis of an antifouling photoelectrode. The antifouling photoelectrode not only has the desired photocurrent response, but also possesses an unexpected antifouling capability of resisting nonspecific adsorption of biomolecules. Herein, the PEDOT-HPG/SnS/ZnO-NT antifouling photoelectrode was formed and a robust photoelectrochemical cytosensor with enhanced sensitivity and selectivity has been demonstrated.

A distance-triggered signaling on-off mechanism by plasmonic Au nanoparticles: toward advanced photocathodic DNA bioanalysis.

An efficient signaling on-off mechanism was first proposed by integrating exciton-plasmon coupling and exciton energy transfer into cathodic PEC bioassays. This signaling on-off mechanism has endowed the cathodic PEC biosensor with powerful capability for ultrasensitive and specific detection of target DNA.

VS4 -Decorated Carbon Nanotubes for Lithium Storage with Pseudocapacitance Contribution.

The application of metal oxides and sulfides for lithium-ion batteries (LIBs) is hindered by the limited Li+ diffusion kinetics and inevitable structural damage. Pseudocapacitance for electrochemical lithium storage provides an effective and competitive solution for developing electrode materials with large capacity, high rate capability, and stability. Herein, a composite composed of VS4 nanoplates tightly bound to carbon nanotubes (VS4 /CNTs) is developed to demonstrate pseudocapacitance-assisted lithium storage. The texture of the assembled VS4 nanoplates supplies efficient electrolyte/ion diffusion, as well as exposed surface for pseudocapacitive behavior. The effective coupling between VS4 and CNTs ensures fast electron transfer and high stability. The VS4 /CNTs anode exhibits high capacity of 1144 mAh g-1 at 0.1 A g-1 , superior cycling stability (capacity retention of 100 % at 1 A g-1 after 400 cycles), and good rate capability. The pseudocapacitive behavior plays an important role in determining the excellent electrochemical properties, contributing to the increased charge rate and reaching as high as 42 % of the total charge at a scan rate of 1 mV s-1 . This study demonstrates the potential application of metal sulfides with pseudocapacitive contribution in LIBs.

Biocompatible off-stoichiometric copper indium sulfide quantum dots with tunable near-infrared emission via aqueous based synthesis.

The present study reports an aqueous synthesis approach towards off-stoichiometric copper indium sulfide quantum dots with emissions in the near-infrared spectral range. The photoluminescence properties of the dots, and in particular the appearance of dual emission at high Cu deficiency, were studied with temperature-dependent steady-state and transient photoluminescence spectroscopy.

Target-induced formation of multiple DNAzymes in solid-state nanochannels: Toward innovative photoelectrochemical probing of telomerase activity.

Solid-state nanochannels have great potentials in the vibrant field of photoelectrochemical (PEC) bioanalysis. This work herein demonstrates the innovative use of DNA-decorated nanoporous anodic alumina (NAA) nanochannels for sensitive PEC bioanalysis of telomerase (TE) activity. Specifically, telomerase primer sequences (TS) were initially immobilized within the NAA nanochannels and then extended by TE in the presence of deoxyribonucleoside triphosphates (dNTPs). The as formed single-strand DNA was then directed to hybrid with many partially matched single-strand assisting DNA (aDNA), leading to the formation of multiple DNAzymes by the unmatched parts and the subsequent DNAzyme-stimulated biocatalytic precipitation (BCP) within the nanochannels. Because the inhibited signals of the photoelectrode could be correlated with TE-enabled TS extension, an innovative nanochannels PEC bioanalysis could be realized for probing TE activity. This work features the ingenious use of DNA-associated nanochannels for PEC bioanalysis of TE activity. Given the versatile functions of DNA molecules, the extension of this strategy easily allows for addressing numerous other targets of interest. Also, we envision this work could inspire more interest for the further development of nanochannels PEC bioanalysis.

A nanocomposite consisting of MnO2 nanoflowers and the conducting polymer PEDOT for highly sensitive amperometric detection of paracetamol.

An electrochemical sensor for paracetamol is described that consists of a glassy carbon electrode (GCE) that was modified with the conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) doped with MnO2 nanoflowers. The hydrothermally synthesized MnO2 nanoflowers possess a large surface area and can be doped into PEDOT through electrochemical deposition to form a conducting polymer nanocomposite. The nanoflowers are shown to be uniformly distributed within the nanocomposite as revealed by elemental mapping analysis. The nanocomposite displays excellent catalytic activity toward the electrochemical oxidation of paracetamol. The modified GCE, best operated at a working potential of around 0.37 V (vs. SCE) has a linear response in 0.06 to 435 µM paracetamol concentration range and a very low limit of detection (31 nM at a signal-to-noise ratio of 3). The sensor exhibits excellent reproducibility and stability, and satisfying accuracy for paracetamol detection in pharmaceutical samples. Graphical abstract A highly sensitive electrochemical sensor capable of detecting paracetamol with a limit of detection down to 31 nM was developed based on MnO2 nanoflowers doped conducting polymer PEDOT.

Separating photoanode from recognition events: toward a general strategy for a self-powered photoelectrochemical immunoassay with both high sensitivity and anti-interference capabilities.

A general, efficient strategy for a self-powered PEC immunoassay with an evident photocurrent response was proposed by separating the photoanode from recognition events. The immunoassay demonstrates the exciting features of both high sensitivity and anti-interference capabilities.