Developing new flexible and electroactive materials is a significant challenge to producing safe, reliable, and environmentally friendly energy storage devices. This study introduces a promising electrolyte system that fulfills these requirements. First, polypyrrole (PPy) nanotubes are electropolymerized in graphite‐thread electrodes using methyl orange (MO) templates in an acidic medium. The modification increases the conductivity and does not compromise the flexibility of the electrodes. Next, flexible supercapacitors are built using hydrogel prepared from poly(vinyl alcohol) (PVA)/sodium alginate (SA) obtained by freeze–thawing and swollen with ionic solutions as an electrolyte. The material exhibits a homogenous and porous hydrogel matrix allowing a high conductivity of 3.6 mS cm−1 as‐prepared while displaying great versatility, changing its electrochemical and mechanical properties depending on the swollen electrolyte. Therefore, it allows its combination with modified graphite‐thread electrodes into a quasi‐solid electrochemical energy storage device, achieving a specific capacitance (Cs) value of 66 F g−1 at 0.5 A g−1. Finally, the flexible device exhibits specific energy and power values of 19.9 W kg−1 and 3.0 Wh kg−1, relying on the liquid phase in the hydrogel matrix produced from biodegradable polymers. This study shows an environment friendly, flexible, and tunable quasi‐solid electrolyte, depending on a simple swell experiment to shape its properties according to its application.

In this study, polypyrrole nanotubes (PPy-NT) and gold nanoparticles (AuNPs) were electrochemically synthesized to form a hybrid material and used as an electroactive layer for the attachment of proteins for the construction of a high-performance biosensor. Besides the enhancement of intrinsic conductivity of the PPy-NT, the AuNPs act as an anchor group for the formation of self-assembly monolayers (SAMs) from the gold–sulfur covalent interaction between gold and Mercaptopropionic acid (MPA). This material was used to evaluate the viability and performance of the platform developed for biosensing, and three different biological approaches were tested: first, the Avidin-HRP/Biotin couple and characterizations were made by using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), wherein we detected Biotin in a linear range of 100–900 fmol L−1. The studies continued with folate group biomolecules, using the folate receptor α (FR-α) as a bioreceptor. Tests with anti-FR antibody detection were performed, and the results obtained indicate a linear range of detection from 0.001 to 6.70 pmol L−1. The same FR-α receptor was used for Folic Acid detection, and the results showed a limit of detection of 0.030 nmol L−1 and a limit of quantification of 90 pmol L−1. The results indicate that the proposed biosensor is sensitive and capable of operating in a range of clinical interests.

Herein, we report the design and synthesis of a layered redox‐active, antiferromagnetic metal organic semiconductor crystals with the chemical formula [Cu(H2O)2V(µ‐O)(PPA)2] (where PPA is phenylphosphonate). The crystal structure of [Cu(H2O)2V(µ‐O)(PPA)2] shows that the metal phosphonate layers are separated by phenyl groups of the phenyl phosphonate linker. Tauc plotting of diffuse reflectance spectra indicates that [Cu(H2O)2V(µ‐O)(PPA)2] has an indirect band gap of 2.19 eV. Photoluminescence (PL) spectra indicate a complex landscape of energy states with PL peaks at 1.8 and 2.2 eV. [Cu(H2O)2V(µ‐O)(PPA)2] has estimated hybrid ionic and electronic conductivity values between 0.13 and 0.6 S m−1. Temperature‐dependent magnetization measurements show that [Cu(H2O)2V(µ‐O)(PPA)2] exhibits short range antiferromagnetic order between Cu(II) and V(IV) ions. [Cu(H2O)2V(µ‐O)(PPA)2] is also photoluminescent with photoluminescence quantum yield of 0.02%. [Cu(H2O)2V(µ‐O)(PPA)2] shows high electrochemical, and thermal stability.