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Ceramics International 41 (201 em a in ence d fo ine 2 rods m n u ique photocatalytic activity in photodegrading rhodamine B in water under the UV light illumination. & 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved. certain crystal growing procedures that cannot be ascribed to 2 in the various fields of photocatalysis [6–8], dye-sensitized which demand both a high reaction temperature and a high was achieved under a low temperature of 80 1C, demanding no high pressure vessels. The hollow microspheres exhibited significant ability to assist photodegradation of rhodamine B in water under the illumination of UV light. http://dx.doi.org/10.1016/j.ceramint.2015.06.060 0272-8842/& 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved. nCorresponding author.
E-mail address: firstname.lastname@example.org (J.-M. Wu).the classical Ostwald ripening theory . On the basis of the
OA mechanism, Colfen et al. deduced a non-classical particlemediated crystallization pathway which resulted in the formation of mesoscopically structured crystals, that is, mesocrystals [3,4]. Mesocrystals are colloidal crystals built up from individual nanocrystals that align in a common crystallographic structure to form porous quasi-single crystals, which not only inherit advantages of single crystals, but also possess a specific surface area larger than that of single crystals [3–5].
Considerable attention has been paid to TiO nanomaterials pressure atmosphere. Topotactic conversions of NH4TiOF3 precursors [18,24,25] are capable of producing TiO2 mesocrystals under a relatively low temperature and in an open atmosphere; however, the synthesis procedure is surfactantdependent, or involves the releases of dangerous gas. It is highly desirable to explore a simple yet effective approach to synthesize TiO2 mesocrystals. Herein, we report our finding that pure rutile mesocrystals, which further assemble into hollow microspheres, can be obtained via a facile one-pot and template-/surfactant-free route. The well-crystallized rutileKeywords: D. TiO2; Rutile mesocrystals; Hollow microspheres; Photocatalysis 1. Introduction
The oriented attachment (OA) mechanism, in which secondary mono-crystalline particles are achieved through attachments of primary particles in an irreversible and highly oriented fashion, has been well developed  to explain solar cells [9–11], Li-ion batteries [12–14], and so forth. Up to now, TiO2 mesocrystals with various morphologies have been synthesized, including nanorods , nanoflowers , hollow nanobricks , dumbbell-shaped mesocrystals,  and sheets . TiO2 mesocrystals are mainly fabricated by hydrothermal [19,20] and solvothermal reactions [21–23],Hollow TiO2 microspheres ass
Low-temperature one-pot synthesis
Lu-Lu Lai, J
State Key Laboratory of Silicon Materials and School of Materials Sci
Received 9 May 2015; received in revise
Hollow TiO2 microspheres assembled with rutile mesocrystal nano (C2O4)2, H2O2 and HNO3 at a low temperature of 80 1C. The hollow diameter of 200 nm and length of 500 nm. The morphology evolutio through a hydrolysis–dissolution–precipitation procedure. The unINTERNATIONAL 5) 12317–12322 bled with rutile mesocrystals: nd the photocatalytic performance -Ming Wun and Engineering, Zhejiang University, Hangzhou 310027, PR China rm 3 June 2015; accepted 13 June 2015 0 June 2015 were precipitated directly from a mixed aqueous solution of K2TiO icrospheres consisted of rutile mesocrystal nanorods with an average pon the reaction duration suggests that the microstructure is formed nanostructure of the hollow microspheres showed remarkable www.elsevier.com/locate/ceramint 2. Experimental section 2.1. Synthesis
In a beaker, 100 mM K2TiO2(C2O4)2 and 0.87 mM HNO3 were added to 50 mL 10 wt% H2O2 aqueous solution. The beaker was sealed and placed in an oven maintained at 80 1C for 72 h. After the reaction, the precipitates were collected by centrifugation, followed by washing in sequence with deionized water and ethanol for three times, and then dried in air at 80 1C overnight. 2.2. Characterization
The powder morphology was examined by a field-emission scanning electron microscopy (FESEM, Hitachi, S-4800) and a transmission electron microscopy (TEM, JEOL, JEM-2010). The Xray diffraction (XRD) tests were performed using a Rigaku D/max3B diffractometer with a CuKα radiation, operated at 40 kV, 36 mA (λ=0.15406 nm). The low-temperature nitrogen sorption measurement was conducted at 77 K using a Nova 3000e (Quantachrome
Instruments, USA) with a Quantachrome V11.0 software. The
Brunauer–Emmett–Teller (BET) approach using adsorption data and
Fig. 1. XRD pattern of rutile mesocrystal hollow microspheres.
Fig. 2. FESEM image of the hollow microsphere (a) and the flower-like rutile mesocrystal nanorods assembling the microspheres (b). The inset in (a) shows the low magnification FESEM image.
Fig. 4. The N2 adsorption–desorption isotherm of the rutile mesocrystal hollow microspheres. The inset shows the corresponding pore size distribution curve.
L.-L. Lai, J.-M. Wu / Ceramics International 41 (2015) 12317–1232212318ig. 3. TEM (a) and HRTEM (b) images of rutile mesocrystal nanorods assembling the hollow microspheres. The inset in (b) shows the corresponding FFT pattern. the relative pressure below 0.3 was utilized to determine the surface area. The pore size distribution and pore volume were calculated by the Barrett–Joyner–Halenda (BJH) method using the adsorption curve. The sample was degassed at 60 1C for 25 h to remove physisorbed gases prior to the measurement. 2.3. Photocatalytic activity test
The photocatalytic activity of powders was evaluated by degradation of rhodamine B in water with an initial concentration of 0.01 mM. For each run, 25 mg powders were dispersed
L.-L. Lai, J.-M. Wu / Ceramics International 41 (2015) 12317–12322 12319Fig. 5. FESEM morphologies of the powders derived using different reaction time of (a, b) 12 h, (c, d) 24 h, (e, f) 36 h, (g, h) 48 h, and (i, j) 60 h. covered with nanorods were obtained (Fig. 5g and i).