PEDOT: Dye-Based, Flexible Organic Electrochemical Transistor for Highly Sensitive pH Monitoring

Organic electrochemical transistors (OECTs) are bioelectronic devices able to bridge electronic and biological domains with especially high amplification and configurational versatility and thus stand out as promising platforms for healthcare applications and portable sensing technologies. Here, we have optimized the synthesis of two pH-sensitive composites of PEDOT (poly­(3,4-ethylenedioxythiophene)) doped with pH dyes (BTB and MO, i.e., Bromothymol Blue and Methyl Orange, respectively), showing their ability to successfully convert the pH into an electrical signal. The PEDOT:BTB composite, which exhibited the best performance, was used as the gate electrode to develop an OECT sensor for pH monitoring that can reliably operate in a two-fold transduction mode with super-Nernstian sensitivity. When the OECT transconductance is employed as analytical signal, a sensitivity of 93 ± 8 mV pH unit^–1 is achieved by successive sampling in aqueous electrolytes. When the detection is carried out by dynamically changing the pH of the same medium, the offset gate voltage of the OECT shifts by (1.1 ± 0.3) × 10² mV pH unit^–1. As a further step, the optimized configuration was realized on a PET substrate, and the performance of the resulting flexible OECT was assessed in artificial sweat within a medically relevant pH range

Physical and Electrochemical Properties of PEDOT:PSS as a Tool for Controlling Cell Growth

Conducting polymers are promising materials for tissue engineering applications, since they can both provide a biocompatible scaffold for physical support of living cells, and transmit electrical and mechanical stimuli thanks to their electrical conductivity and reversible doping. In this work, thin films of one of the most promising materials for bioelectronics applications, poly­(3,4-ethylenedioxythiophene) poly­(styrenesulfonate) (PEDOT:PSS), are prepared using two different techniques, spin coating and electrochemical polymerization, and their oxidation state is subsequently changed electrochemically with the application of an external bias. The electrochemical properties of these different types of PEDOT:PSS are studied through cyclic voltammetry and spectrophotometry to assess the effectiveness of the oxidation process and its stability over time. Their surface physical properties and their dependence on the redox state of PEDOT:PSS are investigated using atomic force microscopy (AFM), water contact angle goniometry and sheet resistance measurements. Finally, human glioblastoma multiforme cells (T98G) and primary human dermal fibroblasts (hDF) are cultured on PEDOT:PSS films with different oxidation states, finding that the effect of the substrate on the cell growth rate is strongly cell-dependent: T98G growth is enhanced by the reduced samples, while hDF growth is more effective only on the oxidized substrates that show a strong chemical interaction with the cell culture medium

Synthesis Route to Supported Gold Nanoparticle Layered Double Hydroxides as Efficient Catalysts in the Electrooxidation of Methanol

This work describes a new one-step method for the preparation of AuNP/LDH nanocomposites via the polyol route. The novelty of this facile, simple synthesis is the absence of additional reactants such as reductive agents or stabilizer, which gives the possibility to obtain phase-pure systems free of undesiderable effect. The AuNP formation is confirmed by SEM, TEM, PXRD, and XAS; moreover, the electrochemical characterization is also reported. The electrocatalytic behavior of AuNP/LDH nanocomposites has been investigated with respect to the oxidation of methanol in basic media and compared with that of pristine NiAl-Ac. The 4-fold highest catalytic efficiency observed with AuNP/LDH nanocomposites suggests the presence of a synergic effect between Ni and AuNP sites. The combination of these experimental findings with the low-cost synthesis procedure paves the way for the exploitation of the presented nanocomposites materials as catalysts for methanol fuel cells

Role of Coating-Metallic Support Interaction in the Properties of Electrosynthesized Rh-Based Structured Catalysts

Rh-structured catalysts for the catalytic partial oxidation of CH₄ to syngas were prepared by electrosynthesis of Rh-containing hydrotalcite-type (HT) compounds on FeCrAlloy foams followed by calcination at 900 °C. During the calcination the simultaneous decomposition of the layered HT structure and formation of the protective FeCrAlloy outer shell in alumina occurred. Here, we studied the role of the coating-metallic support interaction in the properties of the catalysts after calcination, H₂ reduction, and catalytic tests, by a combination of electron (FEG-SEM/EDS) and synchrotron X-ray (XRF/XRPD and XRF/XANES) microscopic techniques. The characterization of crystalline phases in the metallic support and coating and distribution of Rh active species was carried out on several samples prepared by modifying the Rh content in the electrolytic solution (Rh/Mg/Al = 11.0/70.0/19.0, 5.0/70.0/25.0, 0/70.0/30.0 atomic ratio). A sample was also prepared with no aluminum in the electrolytic solution (Rh/Mg/Al = 13.6/86.4/0.0 atomic ratio) and calcined at 550 and 900 °C. The interaction between the elements of the metallic support and the catalytic coating increased the film adhesion during the thermal treatment and catalytic tests and modified the catalyst crystalline phases. A chemical reaction between Al coming from the foam and Mg in the coating occurred during calcination at high temperature leading to the formation of spinel phases in which rhodium is solved, together with some Rh₂O₃ and Rh⁰. The metallic support was oxidized forming the corundum scale and chromium oxides, moreover ι-Al₂O₃ was identified. For the Rh_11.0Mg_70.0Al_19.0 catalyst the inclusion of Rh in the spinel phase decreased its reducibility in the H₂ pretreatment. The reduction continued during catalytic tests by feeding diluted CH₄/O₂/He gas mixtures, evidenced by the catalyst activation. While under concentrated gas mixtures the deactivation occurred, probably by oxidation