Search for: All records

ABSTRACT Herein we report on the facile, one‐pot, scalable, room‐temperature (RT) synthesis of quantum‐confined, 1D lepidocrocite (1DL) titanate nanofilaments (NFs)—by reacting titanium oxysulfate with tetramethylammonium hydroxide, both cheap and ubiquitous precursors—for times that are significantly shorter than previously reported synthesis methods that required 80°C and, in some cases, days of reaction time. Samples are characterized by X‐ray diffraction, Raman and X‐ray photoelectron spectroscopies, small angle X‐ray scattering, SAXS, scanning and transmission electron microscopy, revealing no significant differences from the higher‐temperature synthesis methods, except in the fact that the lengths of the NFs varied. A parallelepiped model, one lepidocrocite layer thick, is used to fit the SAXS patterns of colloidal suspensions, CSs. The ribbons made from material reacted for 4 h are ≈33 nm long and 2.7 nm wide; after 12 h reaction time their lengths are >100 nm and their widths are ≈3.0 nm. This is the first diffraction‐based evidence that the ribbons actually lengthen with time. Powders made using this method can be dried and re‐dispersed in water. The resulting CS adsorbed more rhodamine 6G than any previous 1DL‐based CS tested. From Tauc plots, we obtain bandgap energies of ≈4.0 eV, which is only weakly dependent on reaction time. This work establishes a simple, one‐pot, RT, atmospheric‐pressure, inexpensive and highly scalable method to synthesize quantum‐confined titanate‐based nanomaterials optimized for photocatalytic, environmental, and optoelectronic applications among others. 

ABSTRACT This work presents a scalable, bottom‐up approach for doping quantum confined, 1D lepidocrocite (1DL) titanate nanofilaments (NFs) with transition metal (TM) cations Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, and Cu²⁺ to enhance their photo‐ and electrocatalytic properties. Here we react titanium oxysulfate with tetramethylammonium hydroxide at 80°C for 12 h at one atmosphere. By incorporating metal salts during synthesis, uniform doping within the 1DL backbone is achieved. The resulting TM‐doped 1DL NFs all exhibit lower bandgap energies, E_g, than the undoped samples (3.89 eV); some by as much as 0.8 eV for Mn²⁺ at 1 mol% doping, extending optical absorption into the visible region. X‐ray diffraction, scanning electron microscopy, UV–Vis spectroscopy, inductively coupled plasma analysis, and X‐ray photoelectron spectroscopy confirm the successful doping and structural integrity of our materials. The photocatalytic performance of the 1 mol% doped NFs is significantly enhanced, with a 95% degradation of rhodamine 6G dye under visible light in just 30 min, compared to only 65% degradation for the undoped 1DL NFs. In electrocatalysis, the Ni‐doped 1DL NFs show superior oxygen evolution reaction (OER) activity, with an overpotential of 319 mV at 10 mA cm⁻², which is lower than the 383 mV for undoped 1DL NFs. The Ni‐doped 1DL also has the lowest Tafel slope of 145 mV/dec at 1 mol% doping and 143 mV/dec at 5 mol%, compared to 204 mV/dec for the undoped 1DLs, indicating faster reaction kinetics. The Ni‐doped NFs also exhibit excellent stability, maintaining a constant potential at 10 mA cm⁻²for > 50 h. Adding methanol to all colloidal suspensions results in their gelation within seconds. These findings highlight the potential of TM doping as an effective strategy to optimize 1DL's electronic and photochemical catalytic properties. 

Abstract An innovative process to multifunctional vitrimer nanocomposites with a percolative MXene minor phase is reported, marking a significant advancement in creating stimuli‐repairable, reinforced, sustainable, and conductive nanocomposites at diminished loadings. This achievement arises from a Voronoi‐inspired biphasic morphological design via a straight‐forward three‐step process involving ambient‐condition precipitation polymerization of micron‐sized prepolymer powders, aqueous powder‐coating with 2D MXene (Ti₃C₂T_z), and melt‐pressing of MXene‐coated powders into crosslinked films. Due to the formation of MXene‐rich boundaries between thiourethane vitrimer domains in a pervasive low‐volume fraction conductive network, a low percolation threshold (≈0.19 vol.%) and conductive polymeric nanocomposites (≈350 S m⁻¹) are achieved. The embedded MXene skeleton mechanically bolsters the vitrimer at intermediate loadings, enhancing the modulus and toughness by 300% and 50%, respectively, without mechanical detriment compared to the neat vitrimer. The vitrimer's dynamic‐covalent bonds and MXene's photo‐thermal conversion properties enable repair in minutes through short‐term thermal treatments for full macroscopic mechanical restoration or in seconds under 785 nm light for rapid localized surface repair. This versatile fabrication method to nanocoated pre‐vitrimer powders and morphologically complex nanocomposites is compatible with classic composite manufacturing, and when coupled with the material's exceptional properties, holds immense potential for revolutionizing advanced composites and inspiring next‐generation smart materials. 

Abstract When a few drops of acid (hydrochloric, acrylic, propionic, acetic, or formic) are added to a colloid comprised of 1D lepidocrocite titanate nanofilaments (1DLs)–2 × 2 TiO₆octahedra in cross‐section–a hydrogel forms, in many cases, within seconds. The 1DL synthesis process requires the reaction between titanium diboride with tetramethylammonium (TMA⁺), hydroxide. Using quantitative nuclear magnetic resonance (qNMR), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), the mass percent of TMA⁺after synthesis is determined to be ≈ 13.1 ± 0.1%. The TMA⁺is completely removed from the gels after 2 water soak cycles, resulting in the first completely inorganic, TiO₂‐based hydrogels. Ion exchanging the TMA⁺with hydronium results in gels with relatively strong hydrogen bonds. The hydrogels' compression strengths increased linearly with 1DL colloid concentration. At a 1DL concentration of 45 g L⁻¹, the compressive strength, at 80% deformation when acrylic acid is used, is ≈325 kPa. The strengths are ≈ 50% greater after the TMA⁺is removed. The removal of all residual organic components in the hydrogels, including TMA⁺, is confirmed by qNMR, Fourier‐transformed infrared spectroscopy (FTIR), and TGA/DSC. The 1DL phase is retained after gelation, TMA⁺removal, and 80% compression. 

Abstract Nanostructured titania, TiO₂, holds significant importance in various scientific fields and technologies for their distinctive properties and multipurpose characteristics. In this article, the facile, economical, and scalable synthesis of 1D lepidocrocite, 1DL, titania nanostructures derived from a water‐soluble Ti precursor, titanium oxysulfate (with oxidation of Ti⁺⁴) at temperature <100 °C under atmospheric pressure is discussed. Titanium oxysulfate with tetramethyl ammonium hydroxide, TMAH, is simply reacted to yield individual lepidocrocite titania‐based chain‐forming nanofilaments, NFs, 6 × 6 Ųin minimal cross‐section and aspect ratios of ≈20 1DLs. If only ethanol is used for washing, the 1DL self‐assemble into ≈10 µm, porous mesostructured particles, PMPs. If water is used, quasi‐2D sheets form instead. Characterization of the resulting powders showed them to be quite similar to those derived from TiB₂, and other water‐insoluble Ti precursors. The 1DL bandgap energies are ≈4 eV, due to quantum confinement. They adsorbed rhodamine 6G. The latter also sensitized the 1DLs and allowed for dye degradation using only visible light. Used as electrodes in supercapacitors, the 1DLs can be cycled over 1.6 V and result in high power densities (300 W kg⁻¹). Stronger birefringence started to appear in samples with concentrations >15 gL⁻¹indicating the formation of a liquid crystal phase. This new synthesis protocol enables the cheaper scalable production of 1DLs with significant implications across various fields. 

Vertically aligned lepidocrocite TiO₂ hosts promote uniform lithium nucleation and growth though high surface area and intrinsic Li⁺ affinity, enabling homogeneous Li deposition and suppressing dendrite growth in anode-free Li metal batteries.