Article pubs.acs.org/IC
Synthesis of Nanocrystalline TiOF2 Embedded in a Carbonaceous Matrix from TiF4 and D‑Fructose Claudio Evangelisti,† Mohammad Hayatifar,‡ Fabio Marchetti,‡,⊥ Marcello Marelli,† Guido Pampaloni,*,‡ and Fabio Piccinelli§ †
Istituto di Scienze e Tecnologie Molecolari (ISTM-CNR), Via G. Fantoli 16/15, I-20138 Milano, Italy Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via G. Moruzzi 13, I-56124 Pisa, Italy § Laboratorio di Chimica dello Stato Solido, Dipartimento di Biotecnologie, Università di Verona, Strada Le Grazie 15, I-37134 Verona, Italy ‡
S Supporting Information *
ABSTRACT: Nanostructured titanium oxide difluoride embedded in a matrix of amorphous carbon was synthesized by pyrolysis of D-fructose in the presence of titanium tetrafluoride (optimal Ti/fructose molar ratio = 5.5), both in the solid state at ca. 150 °C and in suspension of 1,2-dichloroethane at reflux temperature. The resulting solid materials were characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and elemental analysis. In every case, PXRD and TEM data indicated the presence of an unique crystalline phase (TiOF2) embedded in a light matrix (amorphous carbon). The average crystal size of the powder can be regulated by varying the reaction time.
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between TiF4 and SiO216 have been proposed for converting silica structures into replicas composed of other materials. In the course of our studies on the activation reactions of natural compounds by high-valent transition metal halides,17 we have found that nanostructured TiOF2 is easily obtained as incorporated in a carbonaceous matrix from D-fructose and commercially available TiF4. In the present paper, we report on the synthetic procedures and the solid-state characterization (including TEM and PXRD analyses) of the produced materials.
INTRODUCTION Titanium compounds have received considerable attention because many of them are nontoxic, converting in the environment into biocompatible titanium dioxide.1 The latter is found in nature mainly in the mineral rutile and, remarkably, has been accepted as a food additive (E171) according to the European Food Safety Authority (EFSA).2 The mixed oxide fluoride TiOF2 possesses valuable properties, justifying its application in catalysis and photocatalysis3 and as a component of UV-absorbing cosmetics, painting, or glasses, 4 batteries5 and electrochromic displays.6 More specifically, TiOF2 and other metal oxyfluorides have recently attracted great interest as electrode materials in Li-ion secondary battery systems.5,7,8 TiOF2 has been employed also in the preparation of other functional metal oxyfluoride materials, either as a component or as a metathesis reagent.9 Because of the emerging role of TiOF2 in different fields, several possible procedures for the preparation of this nonnaturally occurring material have been explored. Reddy and coworkers obtained TiOF2 by the reaction of powdery elemental titanium with a mixture of HF and HNO3.5 Large surface area or single crystals of TiOF2 have been obtained by fluorination of TiO2 with HF,10 of the pure polymorph anatase with HF5a or fluorine,8 of modified titanium dioxide with fluorocarbons in the gas phase,11 or by combination of TiCl2F2 with liquid Cl2O.12 Arrays of TiOF2 nanotubes have been prepared recently by the anodization of a Ti foil in an aqueous electrolyte containing the fluoride anion.13 Also aerosol spraying,3b solvothermal,14 and hydrothermal15 methods are effective for the preparation of single cubic crystals or nanotubes of TiOF2. High-temperature metathesis reactions © 2016 American Chemical Society
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EXPERIMENTAL SECTION
Caution! Titanium tetraf luoride (CAS 7783-63-3) and tantalum pentaf luoride (CAS 7783-71-3) are corrosive substances. Hydrogen f luoride (HF) (CAS 7664-39-3) is a toxic and corrosive substance. Special care must be taken when manipulating these substances. General Considerations. All manipulations were performed under atmosphere of prepurified nitrogen using standard Schlenk techniques. The reaction vessels were oven-dried at 150 °C prior to use, evacuated (10−2 mmHg), and then filled with nitrogen. TiF4 (98%) and TaF5 (98%) were purchased from Strem and stored under argon atmosphere as received. D-Fructose (≥99%) was purchased from Sigma-Aldrich and maintained in vacuo over P4O10 for 12 h before use. Solvents (Sigma-Aldrich) were distilled from appropriate drying agents under argon atmosphere before use. Carbon and hydrogen analyses were performed on Carlo Erba model 1106 instrument. Transmission electron microscopy (TEM) analyses of the powders were carried out with a ZEISS LIBRA 200FE HRTEM instrument, equipped with a field emission gun (FEG) source operating at 200 kV, in column second-generation omega filter. The samples were prepared Received: November 23, 2015 Published: January 29, 2016 1816
DOI: 10.1021/acs.inorgchem.5b02715 Inorg. Chem. 2016, 55, 1816−1820
Article
Inorganic Chemistry Table 1. Preparation of TiOF2 Samples: Reaction Conditions and Elemental Analysis
a
run
TiF4 (mg, mmol)
1 2 3
370, 2.99 439, 3.54 686, 5.54
D-fructose
(mg, mmol)
Ti/fructose molar ratio
yield (mg)
C (%)
H (%)
Ti (%)
1 3 5.5
564 340 640
25.62 (25.87)a 21.94 (22.18)b 9.95 (10.55)c
3.70 (4.27)a 2.98 (3.02)b
