Directed Self-Assembly of Poly(3,3‴-dialkylquarterthiophene) Polymer Thin Film: Effect of Annealing Temperature

Self-assembly of π-conjugated polymers in desired manner plays a vital role in structure, orientations, crystalline packing, and also in electrical charge transport properties. Despite this, there is lack of thorough study about the direct formation of smooth, oriented, crystalline, and aligned films using self-assembly property of π-conjugated polymers. In this study, we have discussed the crystallization behavior and an easy method to study face-on orientation, crystallization, and alignment in organic films, giving as an example poly­(3,3‴-dialkylquarterthiophene) (PQT-12). The effect of annealing temperature (80 and 120 °C) is also studied for this polymer film as the ordering of the polymer backbone and side chains highly depends on temperature. We have directed the self-assembly of PQT-12 using facile “floating film transfer method (FTM)” for obtaining crystalline, oriented, smooth, and aligned polymer films directly without further processing. Unpolarized, polarized UV–vis spectra and selected area electron diffraction (SAED) pattern are used to investigate the ordering/crystallinity, orientation, and alignment (optical anisotropy) of PQT-12 polymer films. Further, an easy electrochemical method is explored to study the crystalline and amorphous phases in the polymer films. Atomic force microscopy (AFM) topography is carried out to study the surface morphology, which shows formation of very smooth films with roughness below 1 nm. Raman spectra show the increase in intensity of signal-to-noise ratio (SNR) (1457 cm^–1) and decrease in ratio of SNR intensity (1457 cm^–1/1393 cm^–1) as a function of annealing temperature. Finally, this study helps in improving the charge transport properties of films and is characterized into two modes, perpendicular and along the films surface with the effect of annealing temperature on PQT-12 films

Enhanced Electrocatalytic Oxygen Reduction Performance of Differently Optimized S,N Heteroatom Dual-Doped Carbon-Encapsulated Iron Carbide–Carbon (Fe₃C@C-SN) Nanostructures

In this study, we present a pyrolytically derived iron-based nonprecious metal catalyst (NPMC), Fe3C embedded in heteroatom (S,N)-codoped carbon matrix, and explored it as a potential NPMC for oxygen reduction in alkaline media. The as-prepared catalysts are well characterized for their structure, crystallite size, morphology, different bonding states of the dopants, and defect levels in the carbon matrix. The optimization is performed for ideal reaction temperature and dopant amounts in Fe3C@C nanostructures. From the electrochemical study, it is found that among the different variants, the sample prepared at a temperature of 800 °C with 20 wt % dopant, i.e., Fe3C@C-SN/25-800, shows a more positive onset potential (Eonset) of 0.844 V (vs reversible hydrogen electrode (RHE)) and a low half-wave potential (E1/2) value of 0.670 V. It also shows good long-term oxygen reduction reaction (ORR) stability and methanol tolerance in a 0.1 M KOH aqueous electrolyte. The measurement of intrinsic parameters, double-layer capacitance (Cdl), and charge transfer resistance (RCT) values validate the current–voltage profile of the samples. The major active sites are identified as Fe–Nx and Nx–C in the nanostructures. Fe3C@C-SN/25-800 also exhibits considerable oxygen evolution reaction (OER) activity among its variants and requires a potential difference (ΔE = E1/2(ORR) – EJ=10 mA cm–2 (OER)) of 0.980 V for overall oxygen electrochemistry. The best electrocatalytic activity can be attributed to the combination of several factors, namely, chosen reaction temperature, dopant concentration, better graphitization, and the presence of a high amount of heteroatoms suitably aligned in the carbon matrix (pyridinic-N, thiophenic-S, etc.) that synergistically enhance the overall performance

Homogenous Dispersion of MoS₂ Nanosheets in Polyindole Matrix at Air–Water Interface Assisted by Langmuir Technique

Two-dimensional (2D) inorganic layered materials when embedded in organic polymer matrix exhibit exotic properties that are grabbing contemporary attention for various applications. Here, nanosheet morphology of molybdenum disufide (MoS₂) synthesized via one-pot facile hydrothermal reaction are exfoliated in benign aqueous medium in the presence of indole to obtain a stable dispersion. These exfoliated nanosheets then act as host to template the controlled polymerization of indole. The preassembled MoS₂-polyindole (MoS₂–PIn) nanostructures are reorganized at the air–water interface using the Langmuir method to facilitate maximum interfacial interaction between nanosheet and polymer. This report emphasizes large area, homogeneous dispersion of uniform-sized MoS₂ nanosheets (40–60 nm diameter) in the PIn matrix and the formation of stable and uniform film via the Langmuir–Schaefer (LS) method. These self-assembled, MoS₂ decorated PIn LS films are characterized using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The fabricated LS films in sandwiched structure Al/MoS₂–PIn/ITO as the Schottky diode portrayed remarkable enhancements in charge transport properties. Our study illustrates the potential of the MoS₂–PIn LS film in electronic applications and opens a new dimension for uniform dispersion of 2D materials in other polymers via the Langmuir method for device fabrication and enhancement of electrical properties

Donor−π–Acceptor-Type Configured, Dimethylamino-Based Organic Push–Pull Chromophores for Effective Reduction of Mild Steel Corrosion Loss in 1 M HCl

In this work, donor−π–acceptor-type four crystalline compounds have been tested for the first time to restrict the corrosion of mild steel in 1 M HCl. The details of the compounds are: C1, 4-<i>N</i>,<i>N</i>-dimethylamino-β-nitrostyrene; C2, 2-(4-(dimethylamino) benzylidene)­malononitrile; C3, ethyl 2-cyano-3-(4-(dimethylamino) phenyl)­acrylate; and C4, methyl 2-cyano-3-(4-(dimethylamino)­phenyl)­acrylate. The corrosion inhibition potentials of the compounds have been primarily investigated by electrochemical techniques, such as linear polarization resistance, Tafel polarization curves, and electrochemical impedance spectroscopy. The secondary investigation is performed by scanning electron microscopy, fluorescence surface imaging, spectroscopic techniques (UV–visible and Fourier transform infrared spectroscopy), and X-ray diffraction patterns. The results disclosed that 50 mg L^–1 of the compounds (1–4) in 1 M HCl provided the maximum inhibition efficiency as 93% (1), 88% (2), 82% (3), and 86% (4). The function of the compounds as corrosion inhibitors is explained with equilibrium corrosion potential, adsorption isotherms, and the frontier molecular orbital energies of the compounds (<i>E</i>_HOMO and <i>E</i>_LUMO) estimated by cyclic voltammetry curves and UV–visible spectra