skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Polymorphic control in titanium dioxide particles
The hydrolysis–condensation reaction of TiO 2 was adapted to the phase inversion temperature (PIT)-nano-emulsion method as a low energy approach to gain control over the size and phase purity of the resulting metal oxide particles. Three different PIT-nano-emulsion syntheses were designed, each one intended to isolate high purity rutile, anatase, and brookite phase particles. Three different emulsion systems were prepared, with a pH of either strongly acidic (H 2 O : HNO 3 , pH ∼0.5), moderately acidic (H 2 O : isopropanol, pH ∼4.5), or alkaline (H 2 O : NaOH, pH ∼12). PIT-nano-emulsion syntheses of the amorphous TiO 2 particles were conducted under these conditions, resulting in average particle diameter distributions of ∼140 d nm (strongly acidic), ∼60 d nm (moderately acidic), and ∼460 d nm (alkaline). Different thermal treatments were performed on the amorphous particles obtained from the PIT-nano-emulsion syntheses. Raman spectroscopy and powder X-ray diffraction (PXRD) were employed to corroborate that the thermally treated particles under H 2 O : HNO 3 (at 850 °C), H 2 O : NaOH (at 400 °C), and H 2 O : isopropanol (at 200 °C) yielded highly-pure rutile, anatase, and brookite phases, respectively. Herein, an experimental approach based on the PIT-nano-emulsion method is demonstrated to synthesize phase-controlled TiO 2 particles with high purity employing fewer toxic compounds, reducing the quantity of starting materials, and with a minimum energy input, particularly for the almost elusive brookite phase.  more » « less
Award ID(s):
1827622
PAR ID:
10430514
Author(s) / Creator(s):
; ; ;
Date Published:
Journal Name:
Nanoscale Advances
Volume:
5
Issue:
2
ISSN:
2516-0230
Page Range / eLocation ID:
425 to 434
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; (, Physical Chemistry Chemical Physics)
    TiO 2 has been extensively studied in many fields including photocatalysis, electrochemistry, optics, etc. Understanding the mechanism of the anatase–rutile phase transition (ART) process is critical for the design of TiO 2 -based high-activity photocatalysts and tuning its properties for other applications. In this work, the ART process using individual anatase micro-particles with a large percentage of (001) facets was monitored and studied. Phase concentration evolution obtained via Raman microscopy was correlated with the morphological evolution observed in scanning electron microscope (SEM) images. The ART of anatase microcrystals is dominated by surface nucleation and growth, but the ART processes of individual anatase particles are distinctive and depend on the various rutile nucleation sites. Two types of transformation pathways are observed. In one type of ART pathway, the rutile phase nucleated at a corner of an anatase microcrystal and grew in one direction along the edge of the crystal firstly followed by propagation over the rest of the microcrystal in the orthogonal direction on the surface and to the bulk of the crystal. The kinetics of the ART follows the first-order model with two distinct rate constants. The fast reaction rate is from the surface nucleation and growth, and the slow rate is from the bulk nucleation and growth. In the other type of ART pathway, multiple rutile nucleation sites formed simultaneously on different edges and corners of the microcrystal. The rutile phase spread over the whole crystal from these nucleation sites with a small contribution of bulk nucleation. Our study on the ART of individual micro-sized crystals bridges the material gap between bulk crystals and nano-sized TiO 2 particles. The anatase/rutile co-existing particle will provide a perfect platform to study the synergistic effect between the anatase phase and the rutile phase in their catalytic performances. 
    more » « less
  2. ; ; ; ; ; ; ; (, Applied Physics Letters)
    In dusty plasma environments, spontaneous growth of nanoparticles from reactive gases has been extensively studied for over three decades, primarily focusing on hydrocarbons and silicate particles. Here, we introduce the growth of titanium dioxide, a wide bandgap semiconductor, as dusty plasma nanoparticles. The resultant particles exhibited a spherical morphology and reached a maximum monodisperse radius of 235 ± 20 nm after growing for 70 s. The particle grew linearly, and the growth displayed a cyclic behavior; that is, upon reaching their maximum radius, the largest particles fell out of the plasma, and the next growth cycle immediately followed. The particles were collected after being grown for different amounts of time and imaged using scanning electron microscopy. Further characterization was carried out using energy dispersive x-ray spectroscopy, x-ray diffraction, and Raman spectroscopy to elucidate the chemical composition and crystalline properties of the maximally sized particles. Initially, the as-grown particles exhibited an amorphous structure after 70 s. However, annealing treatments at temperatures of 400 and 800 °C induced crystallization, yielding anatase and rutile phases, respectively. Annealing at 600 °C resulted in a mixed phase of anatase and rutile. These findings open avenues for a rapid and controlled growth of titanium dioxide via dusty plasma. 
    more » « less
  3. ; ; ; ; (, Physical Chemistry Chemical Physics)
    We report how the binary HNO 3 (H 2 O) interaction is modified upon complexation with a nearby Cs + ion. Isomer-selective IR photodissociation spectra of the D 2 -tagged, ternary Cs + (HNO 3 )H 2 O cation confirms that two structural isomers are generated in the cryogenic ion source. In one of these, both HNO 3 and H 2 O are directly coordinated to the ion, while in the other, the water molecule is attached to the OH group of the acid, which in turn binds to Cs + with its –NO 2 group. The acidic OH stretching fundamental in the latter isomer displays a ∼300 cm −1 red-shift relative to that in the neutral H-bonded van der Waals complex, HNO 3 (H 2 O). This behavior is analyzed with the aid of electronic structure calculations and discussed in the context of the increased effective acidity of HNO 3 in the presence of the cation. 
    more » « less
  4. ; ; ; ; ; ; (, ACS Applied Bio Materials)
    Coordination of clinically employed bisphosphonate, risedronate (RISE), to bioactive metals, Ca2+, Mg2+, and Zn2+, allowed the formation of bisphosphonate-based coordination complexes (BPCCs). Three RISE-based BPCCs, RISE-Ca, RISEMg, and RISE-Zn, were produced, and their structures were elucidated by single crystal X-ray difraction. Interestingly, the addition of an auxiliary ligand, etidronic acid (HEDP), resulted in the recrystallized protonated form of the ligand, H-RISE. The pH-dependent structural stability of the RISE-based BPCCs was measured by means of dissolution profles under neutral and acidic simulated physiological conditions (PBS and FaSSGF, respectively). In comparison to RISE (Actonel), the complexes showed a lower equilibrium solubility (∼70−85% in 18−24 h) in PBS, while a higher equilibrium solubility (∼100% in 3 h) in acidic media. The results point to the capacity to release this BP in a pH-dependent manner from the RISE-based BPCCs. Subsequently, the particle size of RISE-Ca was reduced, from 300 μm to ∼350 d.nm, employing the phase inversion temperature (PIT)-nanoemulsion method, resulting in nano-Ca@RISE. Aggregation measurements of nano-Ca@RISE in 1% fetal bovine serum (FBS):H2O was monitored after 24, 48, and 72 h to study the particle size longevity in physiological media, showing that the suspended material has the potential to maintain its particle size over time. Furthermore, binding assays were performed to determine the potential binding of nano-Ca@RISE to the bone, where results show higher binding (~1.7×) for the material to hydroxyapatite (HA, 30%) when compared to RISE (17%) in 1 d. The cytotoxicity efects of nano-Ca@RISE were compared to those of RISE against the human breast cancer MDA-MB-231 and normal osteoblast-like hFOB 1.19 cell lines by dose−response curves and relative cell viability assays in an in vitro setting. The results demonstrate that nano-Ca@RISE signifcantly decreases the viability of MDA-MB-231 with high specifcity, at concentrations ∼2−3× lower than the ones reported employing other third-generation BPs. This is supported by the fact that when normal osteoblast cells (hFOB 1.19), which are part of the tissue microenvironment at metastatic sites, were treated with nano-Ca@RISE no signifcant decrease in viability was observed. This study expands on the therapeutic potential of RISE beyond its antiresorptive activity through the design of BPCCs, specifcally nano-Ca@RISE, that bind to the bone and degrade in a pH-dependent manner under acidic conditions 
    more » « less
  5. ; ; ; ; ; (, Metallomics)
    null (Ed.)
    After exposure to micron-sized TiO 2 particles, anatase and/or rutile, Rhodococcus ruber GIN-1 accumulates an increased concentration (2.2 ± 0.2 mg kg −1 ) of mobilized Ti into its biomass with concomitant decreases in cellular biometals Fe, Zn, and possibly Mn, while levels of Cu and Al are unaffected. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email