Search

Transparent conductive oxides such as indium tin oxide (ITO) substrates are commonly employed as prime materials for optoelectronic applications. Enhancement in functions of such devices often compels stable and robust modification of the ITO substrate to improve its interfacial charge transfer characteristics. Thereby, in this work, naphthyl modifier multilayer films are fabricated on LTO substrate using conventional electrochemical reduction of 1-naphthyl diazonium salts (NAPH-D) via altering its concentration ranging from 2 mM to 12 mM with a step size of 2. Surface coverage was significantly tuned by varying NAPH-D concentration, keeping other parameters such as the number of scans and scan rate constant. For lower concentrations (2 mM), the molecular thickness ~6 nm was obtained, whereas higher concentrations (12 mM) produced around 15-18 nm thickness. Atomic force microscopy (AFM), cyclic voltammetry, and electrochemical impedance spectroscopy (EIS) in the presence of a ferrocene redox probe also supports the formation of well packed molecular film grown on the ITO surface. Further, the wettability property of the grafted naphthyl film was investigated at different surface coverages and correlated with charge transfer resistance ([R.sub.Ct]) obtained from EIS studies. Key words: electrochemical grafting, naphthyl diazonium salts, multilayer film, surface coverage, charge transfer resistance. Les oxydes conducteurs transparents tels que les substrats d'oxyde d'indium-etain (aussi appele ITO pour l'anglais indium-tin oxide) sont couramment utilises comme matieres premieres dans les dispositifs optoelectroniques. L'extension des fonctionnalites de ces dispositifs requiert souvent une modification stable et robuste du substrat d'ITO dans le but d'ameliorer ses caracteristiques de transfert de charge interfacial. Ainsi, dans le cadre des presents travaux, nous avons fabrique des films multicouches modifies par des groupes naphtyles sur un substrat d'lTO par reduction electrochimique classique de sels de 1-naphtyldiazonium (NAPH-D), en faisant passer leur concentration de 2 mM a 12 mM par increments de 2 mM. Nous avons regie avec une precision substantielle le recouvrement de la surface en faisant varier la concentration de NAPH-D, tout en maintenant constants d'autres parametres tels que le nombre de balayages et la vitesse de balayage. [Angstrom] la concentration la plus faible (2 mM), nous avons obtenu un film d'epaisseur moleculaire, soit environ 6 nm, tandis qu'a la concentration la plus elevee (12 mM), nous avons obtenu un film d'environ 15 a 18 nm d'epaisseur. La microscopie a force atomique (AFM), la voltamperometrie cyclique et la spectroscopic d'impedance electrochimique (SIE) en presence d'une sonde redox a base de ferrocene appuient egalement la formation bien compacte de films moleculaires et leur croissance a partir de la surface d'lTO. En outre, nous avons etudie la mouillabilite du film de naphtyle greffe a differents degres de recouvrement de la surface et nous l'avons mis en correlation avec la resistance au transfert de charge ([R.sub.tc]) obtenue a partir des analyses de SIE. [Traduit par la Redaction] Mots-cles: greffage electrochimique, sels de naphtyldiazonium, film multicouche, recouvrement de surface, resistance au transfert de charge., 1. Introduction Indium tin oxide (LTO) is an important n-type transparent conductive oxide (TCO) having wide applications in several optoelectronic devices such as organic light-emitting diodes, (1-3) photovoltaics, (4-6) solar [...]

Non-stoichiometric lead free polycrystalline Sr0.8Sn0.2Bi1.75Sm0.25Nb2O9 (SSBSN) ferroelectric ceramics were synthesized through conventional solid step route method by incorporating ball milling and microwave sintering method. X-ray diffraction along with the Rietveld refinement technique confirms the single-phase orthorhombic structure with A21 crystal symmetry. Additionally, the short-range ordering was confirmed by Raman spectroscopy. Doping induced crystallite size and strain were further calculated from the Williamson-Hall plot, which comes around 150 nm and 1.48 × 10–3 respectively. A plate like morphology with an average grain size of 0.41 μm was confirmed by scanning electron microscopy (SEM). A diffuse type ferroelectric to paraelectric phase transition was recorded at 395 °C, mostly arising due to structural heterogeneity at the inter-ferroelectric phase boundary. The temperature and frequency-dependent dielectric measurement of SSBSN ceramic reveal a Maxwell–Wagner relaxation, with prominent dielectric loss in a low frequency regime perhaps due to the generation of leakage current in the SSBSN system. Frequency dependent ac conductivity indicates the polaron assisted hopping mechanism in SSBSN, which further obeys Jonscher’s formulation. The intra and intergranular contributions to impedance in SSBSN ceramics were probed by the complex impedance spectroscopy (CIS) technique. A non-Debye type relaxation mechanism in SSBSN ceramics was indicated by the Cole–Cole plot, whereas the conduction mechanism and transport properties were briefly studied using modulus spectroscopy. [ABSTRACT FROM AUTHOR]

This study investigates the impacts of structure and composition on the optical and electronic properties of a series of pyridinium-based bismuth iodide complexes. Organic substrates with various functional groups, such as 4-aminopyridine (4-Ampy), 4-methylpyridine (4-Mepy), 4-dimethylaminopyridine (4-Dmapy), and 4-pyridinecarbonitrile (4-CNpy) with different electron-donating and electron-withdrawing groups at the para position of the pyridine ring were employed. Crystallographic analysis reveals various bismuth iodide structures, including 1D chains and discrete 0D motifs. The optical band gap of these materials, identified via diffuse reflectance spectroscopy (DRS) and verified with density functional theory (DFT) calculations, is influenced by the crystal packing and stabilising interactions. Through a comprehensive analysis, including Hirshfeld surface (HS) and void assessment, the study underscores the influence of noncovalent intermolecular interactions on crystal packing. Spectroscopic evaluations provide insights into electronic interactions, elucidating the role of electron donor and acceptor substituents within the lattice. Thermogravimetric differential thermal analysis (TG–DTA) indicates structural stability up to 250 °C. Linear sweep voltammetry (LSV) reveals significant conductivity in the range of 10–20 mS per pixel at 298.15 K. X-ray absorption spectroscopy (XAS) at the Bi L3 edge indicates a similar oxidation state and electronic environment across all samples, underscoring the role of bismuth centres surrounded by iodides. [ABSTRACT FROM AUTHOR]

Hume‐Rothery rules along with Vegard's law form the basis of systematic doping variation resulting into similar changes in unit cell parameters and volume. Many recent reports have highlighted positive–negative departure from Vegard's law in binary semiconducting systems and a few oxide alloys as well. The current work targets investigations on the missing response of bismuth molybdate on low tungsten doping onto molybdenum sites (Bi2Mo1−xWxO6). Bismuth molybdate and bismuth tungstate have been widely reported for lattice oxygen migration‐driven photocatalytic response and pressure‐sensitive Raman scattering. Octahedral tilting in low‐tungsten‐doped Bi2Mo0.94W0.06O6 carries an interesting lattice oxygen folding toward a–c plane. As a result, unit cell polarity increases drastically and becomes a source for intense Raman scattering phase that is normally observable at pressures around 8.3 GPa. An interesting departure from Vegard's law behavior at around 5–6% tungsten doping confirms nearly identical unit cell structure rather than mix unit cell‐based alloy formation. [ABSTRACT FROM AUTHOR]

First layer Aurivillius Bismuth Molybdate Tungstate ceramic [Bi2Mo1−xWxO6 (BMoW); x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.08 and 0.10] compositions are prepared using deep penetrating microwave sintering in air. All samples show known perovskite phase formation just after 5 h calcinations at 575 °C. X-ray diffraction and transmission electron microscopy based energy dispersive spectroscopy are used to confirm the phase-purity and gross elemental concentration change besides particle size. Nearly doubleε′-values are obtained for investigated BMoW materials compared to earlier reported values. Silver percolation through electrodes in bismuth oxide deficient surfaces of BMoW ceramic powders induces radio wave absorption in the frequency range 2 to 4 MHz. Characteristic third phase transition (γ→γ″′) of Bi2MoO6 material dissolves gradually on increasing tungsten concentration. The introduction of tungsten in BMo matrix increases the dipolar strength of MoO6 octahedrons bending against infrared absorption as evidenced from FTIR analysis. Additionally appearing FTIR peaks provide a strong indication of CO and CO2 contamination on exposed powder surfaces useful for photocatalytic applications. [ABSTRACT FROM AUTHOR]

Microwave synthesized strontium bismuth niobate Sr 1-x Sn x Bi 1.95 La 0.05 Nb 2 O 9 (SSBLN) materials are investigated for non-Debye conduction and photocatalytic response. Lone electron pair repulsions between doping tin (Sn2+) and layer bismuth (Bi3+) generate optimal lattice strain. Lattice oxygen, that is critical in photocatalytic applications, is observed to fold along a-c plane on introducing tin. SSBLN compositions possess higher porosity with reduced dimensions. Porosity derived capacitive boundaries promote polaronic hopping in SSBLN materials over diffused ionic conduction. The visible spectrum photocatalytic response is better after doping tin in SSBLN compositions. Mesoporous network and electron-hole pair generation play crucial role in augmented photocatalytic behaviour of SSBLN materials. Image 1 • Asymmetric charge density of tin (in +2 form) induces maximum lattice strain in a-b plane. • Tin doping increases porosity as arranges more grains in limited volume. • Polaronic hopping developed due to tin doping converts SSBLN composition into a kinetically slow. • Tin-doped SSBLN shows improved photocatalytic behaviour due to microwave induced porosity and electron-hole pair generation. [ABSTRACT FROM AUTHOR]

In recent years, metal oxide‐based, inexpensive, stable electrodes are being explored as a potent source of high performance, sustainable supercapacitors. Here, the employment of industrial waste red mud as a pseudocapacitive electrode material is reported. Mechanical milling is used to produce uniform red mud nanoparticles, which are rich in hematite (Fe2O3), and lower amounts of other metal oxides. A comprehensive supercapacitive study of the electrode is presented as a function of ball‐milling time up to 15 h. Ten‐hour ball‐milled samples exhibit the highest pseudocapacitive behavior with a specific capacitance value of ≈317 F g−1, at a scan rate of 10 mV s−1 in 6 m aqueous potassium hydroxide electrolyte solution. The modified electrode shows an extraordinary retention of ≈97% after 5000 cycles. A detailed quantitative electrochemical analysis is carried out to understand the charge storage mechanism at the electrode–electrolyte interface. The formation of uniform nanoparticles and increased electrode stability are correlated with the high performance. This work presents two significant benefits for the environment; in energy storage, it shows the production of a stable and efficient supercapacitor electrode, and in waste management with new applications for the treatment of red mud. Herein an industrial waste red mud is successfully utilized as a pseudocapacitive electrode material. A ball‐milling technique is employed to produce hematite (Fe2O3)‐rich uniform, spherical, red mud nanoparticles. The nanoparticle‐modified electrode exhibits a promising charge storage ability with an extraordinary retention of ≈97% of initial capacitance even after 5000 cycles at a higher current of 6 A g−1. [ABSTRACT FROM AUTHOR]

This study investigates the impacts of structure and composition on the optical and electronic properties of a series of pyridinium-based bismuth iodide complexes. Organic substrates with various functional groups, such as 4-aminopyridine (4-Ampy), 4-methylpyridine (4-Mepy), 4-dimethylaminopyridine (4-Dmapy), and 4-pyridinecarbonitrile (4-CNpy) with different electron-donating and electron-withdrawing groups at the para position of the pyridine ring were employed. Crystallographic analysis reveals various bismuth iodide structures, including 1D chains and discrete 0D motifs. The optical band gap of these materials, identified via diffuse reflectance spectroscopy (DRS) and verified with density functional theory (DFT) calculations, is influenced by the crystal packing and stabilising interactions. Through a comprehensive analysis, including Hirshfeld surface (HS) and void assessment, the study underscores the influence of noncovalent intermolecular interactions on crystal packing. Spectroscopic evaluations provide insights into electronic interactions, elucidating the role of electron donor and acceptor substituents within the lattice. Thermogravimetric differential thermal analysis (TG-DTA) indicates structural stability up to 250 °C. Linear sweep voltammetry (LSV) reveals significant conductivity in the range of 10-20 mS per pixel at 298.15 K. X-ray absorption spectroscopy (XAS) at the Bi L 3 edge indicates a similar oxidation state and electronic environment across all samples, underscoring the role of bismuth centres surrounded by iodides.