In-situ Raman spectroelectrochemical studies on thionine layer electrochemically grafted to the gold surface

Insight into Anionic Discrepancies in Bipolar Poly(Thionine) Organic Cathodes for Aqueous Zinc Ion Batteries

Electroactive organic electrode materials exhibit remarkable potential in aqueous zinc ion batteries (AZIBs) due to their abundant availability, customizable structures, sustainability, and high reversibility. However, the research on AZIBs has predominantly concentrated on unraveling the storage mechanism of zinc cations, often neglecting the significance of anions in this regard. Herein, bipolar poly(thionine) is synthesized by a simple and efficient polymerization reaction, and the kinetics of different anions are investigated using poly(thionine) as the cathode of AZIBs. Notably, poly(thionine) is a bipolar organic polymer electrode material and exhibits enhanced stability in aqueous solutions compared to thionine monomers. Kinetic analysis reveals that ClO4 - exhibits the fastest kinetics among SO4 2-, Cl-, and OTF-, demonstrating excellent rate performance (109 mAh g-1 @ 0.5 A g-1 and 92 mAh g-1 @ 20 A g-1). Mechanism studies reveal that the poly(thionine) cathode facilitates the co-storage of both anions and cations in Zn(ClO4)2. Furthermore, the lower electrostatic potential of ClO4 - influences the strength of hydrogen bonding with water molecules, thereby enhancing the overall kinetics in aqueous electrolytes. This work provides an effective strategy for synthesizing high-quality organic materials and offers new insights into the kinetic behavior of anions in AZIBs.

Surpassing the Redox Potential Limit of Organic Cathode Materials via Extended p-π Conjugation of Dioxin

The key to enabling high energy density of organic energy-storage systems is the development of high-voltage organic cathodes; however, the redox voltage (<4.0 V vs Li/Li⁺) of state-of-the-art organic electrode materials (OEMs) remains unsatisfactory. Herein, we propose a novel dibromotetraoxapentacene (DBTOP) redox center to surpass the redox potential limit of OEMs, achieving ultrahigh discharge plateaus of approximately 4.4 V (vs Li⁺/Li). As theoretically analyzed, electron delocalization between dioxin active centers and benzene rings as well as electron-withdrawing bromine atoms endows the molecule with a low occupied molecular orbital level by diluting the electron density of dioxin in the whole p-π conjugated skeleton, and the strong π-π interactions among the DBTOP molecules provide a faster electrochemical kinetic pathway. This tetraoxapentacene redox center makes the working voltage of OEMS closer to the high-voltage inorganic electrodes, and its chemical and structural tunability may stimulate the further development of high-voltage organic cathodes.

Poly(Thionine)-Modified Screen-Printed Electrodes for CA 19-9 Detection and Its Properties in Raman Spectroscopy

Polythionine (PTH) is an electroactive compound known for its excellent electron transfer capacity. It has stable and redox centers in its structure, and it can also be generated by electropolymerization of thionine (TH). Due to its properties, it has been used in a large number of applications, including the construction of electrochemical biosensors. In this work, PTH is explored for its ability to generate electrons, which allows it to act as an electrochemical probe in a biosensor that detects CA 19-9 on two different substrates, carbon and gold, using differential pulse voltammetry (DPV) as a reading technique in phosphate buffer (PhB). The analytical features of the resulting electrodes are given, showing linear ranges from 0.010 to 10 U/mL. The Raman spectra of PTH films on gold (substrates or nanostars) and carbon (substrates) are also presented and discussed as a potential use for SERS readings as complementary information to electrochemical data.

Spectroelectrochemistry, the future of visualizing electrode processes by hyphenating electrochemistry with spectroscopic techniques

Reviewing the future of electrochemistry combined with infrared, Raman, and nuclear magnetic resonance spectroscopy as well as mass spectrometry.

A label-free and ultrasensitive electrochemical aptasensor for lead(ii) using a N,P dual-doped carbon dot-chitosan composite as a signal-enhancing platform and thionine as a signaling molecule

Herein, a label-free and ultrasensitive electrochemical aptasensor for the determination of lead(ii) (Pb2+) was described. It was based on the application of a N,P dual-doped carbon dot-chitosan (N,P-CD-CS) composite as the signal molecule carrier and an aptamer (APT) as the specific binding probe for Pb2+ that were self-assembled on the surface of a gold electrode (GE). 6-Mercapto-1-hexanol (MCH) was used to block the nonspecific binding sites, and the electro-active molecule thionine (THi) was used as the signaling probe. The differential pulse voltammetry (DPV) response of THi at a rather low working potential of -0.17 V (vs. Ag/AgCl) was used to detect Pb2+. The electrochemical performances of the resulting modified electrode were investigated by cyclic voltammetry and electrochemical impedance spectroscopy. Under optimal experimental conditions, the modified electrode exhibited excellent DPV response depending on the concentration of Pb2+ in the 0.01 nM to 10 nM range. The limit of detection was 3.8 pM (at S/N = 3). The modified electrode displayed good reproducibility and excellent stability. It was successfully applied for the determination of Pb2+ in real water samples.