Surfactant effect on energy storage performance of hydrothermally synthesized Ni3V2O8

We report a study to improve the ternary oxide Ni3V2O8's electrochemical energy storage capabilities through correct surfactanization during hydrothermal synthesis. In this study, Ni3V2O8nanomaterials were synthesized in three different forms: one with a cationic surfactant (CTAB), one with an anionic surfactant (SLS), and one without any surfactant. FESEM study reveals that all the synthesized Ni3V2O8nanomaterials had a small stone-like morphology. The electrochemical study showed that anionic surfactant-assisted Ni3V2O8(NVSLS) had a maximum of 972 F g-1specific capacitance at 1 A g-1current density, whereas cationic surfactant-assisted Ni3V2O8(NVCTAB) had the lowest specific capacitance of 162 F g-1. The specific capacitance and the capacitance retention of the NVSLS(85% after 4000 cycles) based electrode was much better than that of the NVCTAB(76% after 4000 cycles) based electrode. The improved energy storage properties of the NVSLSelectrode are attributed to its high diffusion coefficient, high surface area, and enriched elemental nickel, as compared to the NVCTABelectrode. All these excellent electrochemical properties of NVSLSelectrode indicates their potential usage in asymmetric supercapacitor application.

Sculpting Windows onto AuAg Hollow Cubic Nanocrystals

Using surfactants in the galvanic replacement reaction (GRR) offers a versatile approach to modulating hollow metal nanocrystal (NC) morphology and composition. Among the various surfactants available, quaternary ammonium cationic surfactants are commonly utilised. However, understanding how they precisely influence morphological features, such as the size and void distribution, is still limited. In this study, we aim to uncover how adding different surfactants-CTAB, CTAC, CTApTS, and PVP-can fine-tune the morphological characteristics of AuAg hollow NCs synthesised via GRR at room temperature. Our findings reveal that the halide counterion in the surfactant significantly controls void formation within the hollow structure. When halogenated surfactants, such as CTAB or CTAC, are employed, multichambered opened nanoboxes are formed. In contrast, with non-halogenated CTApTS, single-walled closed nanoboxes with irregularly thick walls form. Furthermore, when PVP, a polymer surfactant, is utilised, changes in concentration lead to the production of well-defined single-walled closed nanoboxes. These observations highlight the role of surfactants in tailoring the morphology of hollow NCs synthesised through GRR.

On the O2 "Surfactant" Effect during Ag/SiO2 Magnetron Sputtering Deposition: The Point of View of In Situ and Real-Time Measurements

The use of gaseous species has been proposed in the literature to counteract the three-dimensional growth tendency of noble metals on dielectric substrates and favor an earlier percolation without compromising electrical properties. This "surfactant" effect is rationalized herein in the case of O₂ presence during magnetron sputtering deposition of Ag films on SiO₂. In situ and real-time techniques (X-ray photoemission, film resistivity, UV-visible optical spectroscopy) and ex situ characterizations (X-ray diffraction and transmission electron microscopy) were combined to scrutinize the impact of O₂ addition in the gas flow (%O₂), revealing three regimes of evolution of film resistivity, morphology, structure, and chemical composition. At low oxygen flow conditions (%O₂ < 4), the observed drastic decrease of the percolation threshold is assigned to a combination of (i) a change in nanoparticle density, wetting, and crystallographic texture and (ii) a delayed coalescence effect. The driving force is ascribed to the presence of specific adsorbed oxygen moieties, the nature of which starts evolving at intermediate oxygen flow conditions (10 ≤ %O₂ < 20). At high oxygen flow (20 ≤ %O₂ < 40), the found detrimental impact on film resistivity is assigned to an actual oxidation in the form of a Ag₂O-like poorly crystallized compound. For all %O₂, a composition gradient is observed across the film thickness, with a more metallic Ag at the substrate interface. A correlation between percolation and the nature of the detected O moieties is observed. In parallel to an oxygen spillover mechanism, this gradient can be explained by the competition between different surface processes occurring before percolation, namely, aggregation, metal oxidation, and substrate reactivity. Such findings pave the way to a rational use of O₂ as a modifier for Ag growth.