Controllable Synthesis and Crystallization of Nanoporous TiO₂ Deep-Submicrospheres and Nanospheres via an Organic Acid-Mediated Sol−Gel Process

Abstract

Although considerable progress has been achieved in the preparation of uniform hydrous TiO 2 spheres (HTS) through the sol−gel process, there is plenty of room left in tailoring the size and morphology of HTS on the deep-submicron scale or even nanoscale since the diameters of the so far reported HTS are mostly on the (sub)micron scale (0.3−1.2 μm).Here, we develop a novel titanium tetraisopropoxide (TTIP)−organic acid (OA)−acetonitrile (ACN)−methanol (MeOH)−H 2 O system, which facilitates the control of nanoporous HTS to the range of 50−300 nm. The synthetic parameters including OA, (co-)solvent, concentration of precursor, and reaction temperature are comprehensively optimized, aiming at reproducible preparation and precise size control. Among the various OAs, n-valeric acid presents the best capability in controlling the spherical morphology and size uniformity. The synthesized amorphous HTS containing numerous micropores and mesopores show excellent hydrothermal stability and offer suitable self-template for the subsequent synthesis of mesoporous anatase TiO 2 spheres (MAT) with a large surface area of 99.1 m 2 /g. The obtained TiO 2 deepsubmicrospheres and nanospheres with tunable sizes show great potential in various research fields.

Unveiling the Formation Mechanism and Phase Purity Control of Nanostructured Li4Ti5O12 via a Hydrothermal Process

“…Different from the crystallized TiO 2 , amorphous TiO 2 undergoes a distinct crystal transformation pathway to Li 4 Ti 5 O 12 . AHTS are derived from a classic sol–gel process through the rapid hydrolysis of Ti­( i -OPr) 4 at room temperature. , Each spherical AHTS consists of numerous nanosized TiO 2 hydrates that are amorphous and contain adsorbed water and organic residuals with a total weight ratio of 12.8%, according to our TGA analysis. , No detectable diffraction peaks can be resolved in their XRD pattern. Upon the hydrothermal process and the reaction with LiOH, the diffraction patterns of the as-hydrothermal sample, as shown in Figure c, are well matched with those of the lithium titanate oxide hydrate (Li 2– x H x Ti 2 O 4 (OH) 2 ) phase (ICDD #47–0123) .…”

“…20 AHTS are derived from a classic sol−gel process through the rapid hydrolysis of Ti(i-OPr) 4 at room temperature. 21,22 Each spherical AHTS consists of numerous nanosized TiO 2 hydrates that are amorphous and contain adsorbed water and organic residuals with a total weight ratio of 12.8%, according to our TGA analysis. 23,24 No detectable diffraction peaks can be resolved in their XRD pattern.…”

Phase-Selective Synthesis of Anatase and Rutile TiO2 Nanocrystals and Their Impacts on Grapevine Leaves: Accumulation of Mineral Nutrients and Triggering the Plant Defense

“…Nanostructured TiO 2 can be prepared by several chemical and physical routes [ 15 , 16 ]. For the chemical fabrication of TiO 2 nanoparticles (NPs), the most frequently applied syntheses are the sol-gel and hydro- or solvothermal methods [ 17 , 18 ]. The sol-gel method is favored because it can be carried out without difficulties, and the composition of the metal oxide is well-controlled.…”

Sn‐Ti Submicrospheres with Tunable Particle Size for Cyclohexanone Baeyer‐Villiger Oxidation

“…In the process of submicrosphere particle preparation, if no new nuclei are formed during the nuclear growth stage, the particle size of microsphere would decrease with the increase of nuclear centers number. [19] Thus, the submicrosphere particle size prepared by sol-gel method often depends on the number of nuclear centers formed in the solvent, [20] which is decided by the hydrolysis rate of the precursor. The faster hydrolysis rate of the precursor, more nuclear centers can be formed in the solvent.…”