Polyaniline (PANI) has been projected as an efficient electrochemical actuator due to its ease of synthesis, lightweight, biocompatibility, low cost, and possible low operating potential and high stress generation. However, challenges such as low inherent ionic and electronic conductivity of the polymer lead to small accumulation of ions and high ionic diffusion path length inside the polymer remain. In the present study, a highly conjugated, planar, conducting polaronic form of PANI with a nanofiber morphology is synthesized using in situ electrochemical polymerization on a reduced graphene oxide (rGO) electrode. The polymerization is carried out in the Schaefer mode at the air–water interface under controlled surface pressure in a Langmuir trough. Electrochemical, UV–visible, XPS, and Raman spectroscopic studies confirm the formation of the planar polaronic PANI form. Polymerization without surface pressure leads to the bipolaronic form of PANI. The two forms are subsequently used to understand their contributions toward electrochemical actuation in a bilayer configuration. The conducting polaronic PANI/EGO (exfoliated graphene oxide) exhibits a remarkably larger total angular displacement of 220° in aqueous 1 M NaClO4 during a potential scan in the range ±0.9 V than the bipolaronic counterpart which exhibits a total angular displacement of 125°. Current imaging in the scanning electrochemical microscopy mode confirms a high volumetric expansion in the case of the polaronic form as compared to its bipolaronic counterpart. Raman spectroscopy reveals the oxidation to the emeraldine form in the polaronic PANI and to the pernigraniline form in the bipolaronic form during actuation. Electrochemical impedance spectroscopy study evidences the existence of a small charge transfer resistance with high bulk capacitance for the polaronic structure.
Transition-metal dichalcogenides based on different chalcogen atoms give origins to many new phenomena due to symmetry breaking and exhibit better physicochemical characteristics than pristine dichalcogenides. In this work, the formation of a perfectly tiled uniform monolayer of MoSSe using the Langmuir− Blodgett (LB) technique under ambient conditions is demonstrated. The aligned monolayer of the 1T phase depicts a film thickness of 1.2−2.4 nm corresponding to a single to a bilayer of MoSSe. The LB-prepared substrates are subsequently used for Raman sensing of R6G. The presence of MoSSe quenches the fluorescence of the R6G. Regarding surface-enhanced Raman spectroscopy sensitivity, 1T MoSSe could sense R6G up to picomolar concentrations with an enhancement factor of ∼6 × 10 6 . This is 3 to 4 orders higher than the corresponding sulfide or the selenide analogues (1T MoS 2 and 1T MoSe 2 ). This increased sensitivity of 1T MoSSe is attributed to a large number of active sites with intrinsic dipole moment and high electronic conductivity, which leads to strong substrate-analyte vibronic coupling. Absorption and Raman spectroscopy confirms the static coupling between the substrates and R6G molecules. First principle density functional theory calculations reveal high density of states near the Fermi level in the case of distorted 1T MoSSe as compared to the pristine sulfide or selenide with less energy difference between the highest occupied molecular orbital of R6G and the Fermi level of 1T MoSSe. This might result in a facile charge transfer during the photoinduced charge transfer-driven chemical mechanism leading to a strong coupling of the metal−analyte complex, thus resulting in significant Raman enhancement.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.