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Broadening the scope of functionalities that can be covalently bound to single‐walled carbon nanotubes (SWCNTs) is crucial for enhancing the versatility of this promising nanomaterial class in applied settings. Here we report the covalent linkage of triphenylphosphine oxide [Ph3P(O)] to SWCNTs, a hitherto overlooked surface functionality. We detail the synthesis and structural characterization of a new family of phosphine oxide‐functionalized diaryliodonium salts that can facilitate direct Ph3P(O) transfer and afford novel SWCNTs with tunable Ph3P(O) content (SWCNT‐P). The molecularly‐distributed and robust nature of the covalent Ph3P(O) attachment in SWCNT‐P was supported by a combination of characterization methods including Raman, infrared, UV/Vis‐NIR and X‐ray photoelectron spectroscopies coupled with thermogravimetric analysis. Electron microscopy further revealed the effectiveness of the Ph3P(O) moiety for de‐bundling SWCNTs to yield SWCNT‐P with superior dispersibility and processability. Finally, electrochemical studies established that SWCNT‐P is sensitive to the presence of Li+, Na+ and K+ wherein the Gutmann‐Beckett Lewis acidity parameters of the ions were quantitatively transduced by Ph3P(O) to electrochemical responses. This work hence presents a synthetic, structural, spectroscopic and electrochemical foundation for a new phosphorus‐enriched responsive nanomaterial platform featuring the Ph3P(O) functionality. [ABSTRACT FROM AUTHOR]

Abstract: In this work two different Na x CoO2− y oxides (Na0.69CoO2− y and Na0.72CoO2− y ) were studied in terms of their crystal structure, sodium content, oxygen nonstoichiometry, transport properties (electrical conductivity and thermoelectric power) and electrochemical properties in Na/Na+/Na x CoO2− y cells. The materials were prepared by a solid-state method. XRD measurements with Rietveld analysis confirmed the presence of a single phase with P63/mmc symmetry. Oxygen nonstoichiometry, which was calculated on a basis of thermogravimetric reduction experiments was found to be small, not exceeding 0.04mol·mol−1. Electrical conductivity for both compounds shows metallic-type character, while values of thermoelectric power are high at room temperature, but decrease considerably for lower temperatures. Electrochemical studies performed for Na/Na+/Na x CoO2− y cells in 0.68≤ x ≤0.81 range indicated the presence of a step-like voltage curve with two characteristic voltage plateaus visible at potentials of 2.54V and 2.44V vs. metallic Na electrode. Crystal structure and deviation from the oxygen stoichiometry in the studied materials were related to the character of the discharge curve of Na/Na+/Na x CoO2− y cells and changes of transport properties of Na x CoO2− y oxides as a function of sodium content x and oxygen nonstoichiometry y. [Copyright &y& Elsevier]

In this paper we would like to show a new approach to an explanation of the nature of the discharge–charge curve of Na/Na+/NaxCoO2−y batteries, which can justify the existence of the step-like characteristics. This is still an open problem, which until now had no proper description in the literature. On the basis of comprehensive experimental studies of physicochemical properties of NaxCoO2−y cathode material (XRD, electrical conductivity, thermoelectric power, electronic specific heat) supported by calculations performed using the DFT method with accounting for chemical disorder, it has been shown that the observed step-like character of the discharge curve reflects the variation of the chemical potential of electrons (Fermi level) in the density of states of NaxCoO2−y, which is anomalously perturbed by the presence of the oxygen vacancy defects and sodium ordering. Our studies of structural, electronic and thermal properties of NaxCoO2−y cathode material as a function of concentration of electrochemically intercalated sodium document strong and step-like shift of the position of the Fermi level during introduction of electrons in this process. This effect is coherently supported by the shape of calculated density of states (DOS) of NaxCoO2−y having included oxygen defects and sodium ordering. [ABSTRACT FROM AUTHOR]

Sensors that can accurately assess oxygen (O 2 ) concentrations in real time are crucial for a wide range of applications spanning personal health monitoring, environmental protection, and industrial process development. Here a high-performance chemiresistive sensor that allows for the rapid detection of O 2 at room temperature under visible light illumination is described. Inspired by the operating principles of dye-sensitized solar cells, the chemiresistor is based on a single-walled carbon nanotube-titania hybrid (SWCNT-TiO 2 ) bearing a molecular Re-based photosensitizer [( P bpy)(CO) 3 ReBr] ( P bpy = 4,4'-[P(O)(OH) 2 ] 2 -2,2'-bipyridine). The resulting SWCNT-TiO 2 -Re composite undergoes photoinduced charge transfer that is sensitive to ppb levels of O 2 , thereby yielding a rapid and reversible chemiresistive response. Owing to its unique mode of operation and robust components, the sensor shows a high degree of selectivity for O 2 over a range of interferants, humidity tolerance, and multimonth benchtop stability. The approach presented herein demonstrates the translatability of concepts in light harvesting to the development of robust, rapid, and low-power sensing technologies., (© 2024 The Author(s). Advanced Science published by Wiley‐VCH GmbH.)

In this paper we would like to show a new approach to an explanation of the nature of the discharge-charge curve of Na/Na(+)/NaxCoO2-y batteries, which can justify the existence of the step-like characteristics. This is still an open problem, which until now had no proper description in the literature. On the basis of comprehensive experimental studies of physicochemical properties of NaxCoO2-y cathode material (XRD, electrical conductivity, thermoelectric power, electronic specific heat) supported by calculations performed using the DFT method with accounting for chemical disorder, it has been shown that the observed step-like character of the discharge curve reflects the variation of the chemical potential of electrons (Fermi level) in the density of states of NaxCoO2-y, which is anomalously perturbed by the presence of the oxygen vacancy defects and sodium ordering. Our studies of structural, electronic and thermal properties of NaxCoO2-y cathode material as a function of concentration of electrochemically intercalated sodium document strong and step-like shift of the position of the Fermi level during introduction of electrons in this process. This effect is coherently supported by the shape of calculated density of states (DOS) of NaxCoO2-y having included oxygen defects and sodium ordering.