Nanoparticle Cluster with Efficient Visi

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C: Surfaces, Interfaces, Porous Materials, and Catalysis 2

One-Pot Approach for the Synthesis of Water-Soluble Anatase TiO Nanoparticle Cluster with Efficient Visible Light Photocatalytic Activity Jinfeng Lei, Meizhou Zhang, Shen Wang, Lei Deng, Defu Li, and Changdao Mu J. Phys. Chem. C, Just Accepted Manuscript • Publication Date (Web): 29 Oct 2018 Downloaded from http://pubs.acs.org on October 29, 2018

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The Journal of Physical Chemistry

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One-Pot Approach for the Synthesis of Water-Soluble Anatase TiO2

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Nanoparticle Cluster with Efficient Visible Light Photocatalytic Activity

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Jinfeng Lei,†,# Meizhou Zhang,†,‡,# Shen Wang,† Lei Deng,† Defu Li,*,† and Changdao Mu*,†

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†Department

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University, Chengdu 610065, China

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‡School

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Wuhan 430074, China

of Pharmaceutics and Bioengineering, School of Chemical Engineering, Sichuan

of Chemistry and Chemical Engineering, Huazhong University of Science and Technology,

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#These

authors contributed equally to this work and should be considered co-first authors

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ACS Paragon Plus Environment

The Journal of Physical Chemistry 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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ABSTRACT: Water contamination is one of the most serious problems today. Titanium dioxide (TiO2)

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has received increasing attention on water decontamination. It will be a great contribution to fabricate

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water-soluble anatase TiO2 nanoparticle with efficient visible light photocatalytic activity for water

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decontamination. Herein, we present a simple one-pot approach to synthesize water-soluble anatase

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TiO2 nanoparticle cluster with efficient visible light photocatalytic activity. PEG400 was used as

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stabilizer to improve the aqueous dissolubility while HCl was used to control the anatase phase of TiO2.

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In particular, titanium tetrachloride (TiCl4) and titanium butoxide were cooperatively served as

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precursors of titanium. The results indicated that the crystals of TiO2 were stacked together to form big

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crystal clusters cooperatively using TiCl4 and titanium butoxide as precursors of titanium. TiO2 crystal

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cluster presented good aqueous dissolubility and the anatase phase was successfully controlled. It is

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interesting that the UV-vis absorbance of aqueous solution of TiO2 crystal cluster was highly enhanced

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and expanded into visible region. The TiO2 crystal cluster possessed efficient photocatalytic activities

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both under UV and visible light irradiation. The water-soluble TiO2 clusters have application prospect

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in water decontamination.

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1. INTRODUCTION

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Environmental contamination is one of the most serious problems today. The large amounts of

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pollutants have been left in soil and water by reason of modern industrial activities.1 Organic pollutants

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like dyes, detergents and pesticides in the environment have caused serious health-risk issues.2,3

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Conventional treatments often cannot eliminate the majority of these pollutants.4 Moreover, many

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methods for the decontamination of dye wastewater are rather complicated, costly and

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time-consuming.5 In recent years, the photocatalytic oxidation technology has received increasing

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attention on degrading organic pollutants.

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Titanium dioxide (TiO2) has been used as a semiconductor photocatalyst for decades since

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Fujishima discovered the photocatalytic splitting of water on TiO2 electrodes.6-9 TiO2 is undoubtedly

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one of the most promising photocatalysts due to the advantages for instance the high chemical stability,

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environmental friendliness, easy availability and low cost.10-13 However, many traditional methods for

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the preparation of TiO2 nanoparticles (NPs) often lead to the insolubility of the products in aqueous

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solutions due to high temperature annealing or complex chemical processes.14 The application of TiO2

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NPs would be in consequence limited in aqueous environment. Nowadays, the water-soluble TiO2 is

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demanded by people, which is suitable for water decontamination. Moreover, the water-soluble TiO2

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can be easily separated from water by centrifugation. Recently, Wang and co-workers

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successfully prepared water-soluble anatase TiO2 NPs using ethylene glycol as a surfactant. Yan and

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co-workers

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anatase TiO2 NPs using polyethylene glycol 400 (PEG400) as a solvent and a stabilizer, with phases

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well controlled by introduction of HCl in the reaction system. In our previous work, a series of

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water-soluble TiO2 NPs have been successfully prepared by PEG-capping.16 In sum, the dissolubility of

14

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have

have reported a new and facile route for the controllable synthesis of water-soluble

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TiO2 NPs in aqueous solutions can be effectively promoted by PEG-capping. However, PEG molecular

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chains capped on the surface of TiO2 are detrimental to the transfer of photogenerated electrons and

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reactive oxygen species, resulting in passivation of the surface activity of TiO2 NPs. Thus,

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PEG-capping would reduce the photocatalytic activities of TiO2 NPs. In addition, pure TiO2 is active

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under UV irradiation that is a very small proportion (about 3–5%) of solar radiation 12. It is crucial to

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enhance the light harvesting of TiO2 in the visible region which accounts for more than 43% of the total

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solar energy.17 However, it is still a challenge to fabricate water-soluble TiO2 nanoparticle with

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efficient visible light photocatalytic activity.

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In this paper, we present an improved approach to synthesize water-soluble anatase TiO2

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nanoparticle cluster with efficient UV and visible light photocatalytic activity. PEG400 was used as

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stabilizer to improve the aqueous dissolubility while HCl was used to control the anatase phase of TiO2

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nanoparticle cluster. In particular, titanium tetrachloride (TiCl4) and titanium butoxide were

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cooperatively served as the precursors of titanium to prepare TiO2 nanoparticle cluster. The crystal

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structures and physicochemical properties of TiO2 NPs before and after adding TiCl4 were investigated.

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The photocatalytic activities of TiO2 NPs under UV and simulated sunlight irradiation were evaluated

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by monitoring the degradation of methyl orange (MO).

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2. MATERIALS AND METHODS

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2.1. Materials. Titanium butoxide (≥99.0%) and polyethylene glycol 400 (PEG400) were purchased

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from Aladdin Industrial Corporation (Shanghai, China). Hydrochloric acid (HCl, 36.0%～38.0%) was

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purchased from Kelong Chemical Reagent Company (Chengdu, China). Titanium tetrachloride (TiCl4)

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was purchased from Tianjin Zhiyuan Chemical Reagent Co., Ltd, China.

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2.2. Preparation of the Photocatalysts. TiO2 NPs were prepared according to our previous method 4


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with a slight modification.16 The 3 mL of titanium butoxide were mixed with 6 g of PEG400 under

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magnetic stirring at 65 oC to form a white titanium alkoxide complex. Then, 1 mL of HCl was added to

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the titanium alkoxide complex to get transparent slight yellow liquid. After that, a given volume of

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TiCl4 was added into the transparent slight yellow liquid. These mixtures were then transferred into a

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stainless poly (tetra fluoroethylene) (Teflon)-lined autoclave with 50 mL capacity. The autoclave was

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heated in a vacuum oven at 160 °C for 5 h, and then air-cooled to room temperature. The resulting

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reaction products were collected by high-speed centrifugation (10,000 rpm) and washed thoroughly

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with hot ethanol under stirring for 2-3 times. Then the products were dried in an oven at 50 °C for 24 h.

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The TiO2 NPs synthesized with addition of TiCl4 was named as TiO2-Ti. The products were exactly

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named as TiO2-Ti 0.5, TiO2-Ti 1.0, TiO2-Ti 1.5, TiO2-Ti 2.0, and TiO2-Ti 3.0 when the volume ratio of

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TiCl4 to titanium butoxide was 0.5:3, 1:3, 1.5:3, 2:3, and 3:3, respectively. The sample without addition

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of TiCl4 was prepared and named as original TiO2.

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2.3. Characterization of the Photocatalysts. FT-IR spectra of the samples were obtained from a

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Fourier transform infrared spectrometer (Nicolet is10, Thermo Scientific, MA, USA). The range of

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wavenumbers was from 4000 to 500 cm-1 with the resolution of 4 cm-1. The crystal structures of

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samples were identified by an 18 kW X-ray diffractometer (X'Pert Pro, Philips, Almelo, Netherlands)

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with a fixed CuKα radiation (λ=1.54 Å). The scanning range of the diffraction angle (2θ) was from 10°

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to 70° with a rate of 2° min-1. The surface composition and chemical states of each element in the

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samples were examined by X-ray photoelectron spectra (XPS) using an AXIS Ultra DLD instrument

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(Kratos, Manchester). The morphology and microstructure of the samples were characterized by

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transmission electron microscopy (TEM) (Zeiss Libra 200FE, Germany) and scanning electron

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microscopy (SEM) (JSM-7500F, JEOL, Japan). High resolution transmission electron microscopy

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(HRTEM) was performed on a carbon coated copper grid at an accelerating voltage of 200 kV. The

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morphology of TiO2 samples was also imaged by an atomic force microscope (AFM, SPM-9600, 5



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Shimadzu, Japan). The nanoparticles were dissolved in distilled water, and 1 drop of the dilute

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dispersion was placed on a freshly cleaved mica substrate and dried for 1 day at room temperature in a

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desiccator with silica gel. The samples were analyzed in air using tapping mode. The UV-vis

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absorbance spectra of TiO2 solutions were obtained using the UV-vis spectrophotometer at selected

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wavelengths from 200 to 800 nm.

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2.4. Photocatalytic Activity Evaluation of the Photocatalysts. The photocatalytic performances of

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the samples were evaluated by monitoring the degradation of methyl orange (MO, 20 mg L-1) dye. A

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1000 W Xe lamp (QIQIAN-V, Shanghai Qiqian Electronic Technology Co. Ltd., China) was employed

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as the source of simulated sunlight. A 300 W metal halide lamp (INTELLI-RAY 400, UV0338,

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Shenzhen Wisbay M&E Co., Ltd, China), for which the emission wavelength was from 315 nm to 400

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nm, was employed as the UV light source. During each photocatalytic degradation experiment, 80 mg

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of photocatalyst were added into a quartz photoreactor containing 80 mL of MO solution. The reaction

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solutions were stirred for 30 min in the dark to reach an adsorption-desorption equilibrium. After that,

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the above reaction solutions were irradiated with light to initiate the photocatalytic degradation reaction.

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At certain time, 3 mL of reaction solutions were taken out and centrifuged to remove the trace TiO2

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particles. Then they were tested using an Alpha-1860 UV-vis spectrophotometer (Shanghai

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Lab-Spectrum Instruments Co., Shanghai, China) at λ=500 nm to detect the changes of MO

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concentration. For comparison, blank experiment without catalyst was also carried out. The

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measurements were carried out for five times and the mean values were used.

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3. RESULTS AND DISCUSSION

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3.1. Preparation of the Photocatalysts. The photographs of TiO2 powder samples are presented in

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Figure 1A. All the TiO2 powder samples presented white color. Moreover, no color change was

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observed in the following five months, illustrating that the TiO2 powder samples are stable under 6


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ambient conditions. Figure 1B shows the photographs of aqueous solutions of TiO2 NPs with the

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concentration of 1 g L-1. The aqueous dissolubility of TiO2 NPs can be effectively promoted by

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PEG-capping. It was reported that the water solution of TiO2 NPs could keep stable for at least ten days

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using ethylene glycol as a surfactant15. It is worthy to note that the PEG400 capped TiO2 NPs could

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keep stable for more than one month without precipitation in water14. The molecular weight effects of

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PEG on the properties of PEG-capped TiO2 NPs were systematically studied in our previous work. We

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found that the dispersion of TiO2 NPs in water was getting better with the increase of molecular weight

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of PEG16. However, PEG-capping would reduce the photocatalytic activity of TiO2 NPs, which was

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detrimental to the transfer of photogenerated electrons and reactive oxygen species16. The

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photocatalytic activity of PEG-capped TiO2 NPs would decrease with the growth of PEG molecular

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chain. Considering the aqueous dissolubility and photocatalytic activity, PEG400 was used as stabilizer

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to improve the aqueous dissolubility of TiO2 nanoparticle cluster in this study. Figure 1B shows that all

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the samples have good dissolubility in water. Furthermore, we found that TiO2 NPs aqueous solutions

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can maintain stable for more than two months without obvious precipitation. The results indicate that

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PEG400 effectively promote the dissolubility of TiO2 NPs in aqueous solutions as expected.

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Figure 1. Photographs of (A) the TiO2 powder samples and (B) the aqueous solutions of TiO2 NPs.

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3.2. Structural Characterization of the Photocatalysts. FT-IR spectra of TiO2 NPs are presented in 7



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Figure 2A. It shows that all the TiO2 samples have almost the same absorption bands and no new peaks

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are observed with the addition of TiCl4. The absorption bands at about 3350, 2923, 1625 and 1080 cm-1

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can be seen in all TiO2 samples. These absorption bands are corresponding to the characteristic

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absorption bands of PEG400. The results indicate that PEG400 has been successfully capped on the

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surface of TiO2 NPs. The incorporation of TiCl4 cannot induce PEG400 to participate in any other

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chemical reaction. The typical XRD patterns of TiO2 NPs were measured and showed in Figure 2B. It

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shows that there is almost no difference among the crystallographic phases of all the six samples. The

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crystallographic phases of all the TiO2-Ti samples are consistent with original TiO2. They exhibit broad

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diffraction peaks at 2 theta 25.07, 37.57, 47.71, 53.94 and 62.38, corresponding to the anatase phase

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planes of (101), (004), (200), (105) and (204) according to JCPDS card no. 21-1272.18 The results

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indicate that the anatase phase of TiO2 NPs is successfully controlled by the introduction of HCl in the

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reaction system. The acid concentration has been successfully used to control the phase of TiO2 in

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previous works.14,19 TiO2 NPs naturally consist of ( TiO62- ) octahedra, which share edges and corners in

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different manners to form different crystal structures. The phase formation of TiO2 is governed by the

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rate of aggregation of octahedral complexes during condensation. The higher acid concentration

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promotes the slower aggregation and the formation of rutile. On the contrary, the lower acid

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concentration promotes the faster aggregation and therefore the formation of anatase.14,19 The lower

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HCl concentration was selected to ensure the formation of anatase TiO2 NPs in this study. Note that the

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diffraction peak of TiO2-Ti 3.0 is decreased, illustrating the reduction of crystallinity. The result

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indicates that excessive addition of TiCl4 will reduce the crystallinity of TiO2 NPs.

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Figure 2. (A) FT-IR spectra and (B) XRD patterns of TiO2 NPs: (a) TiO2, (b) TiO2-Ti 0.5, (c) TiO2-Ti

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1.0, (d) TiO2-Ti 1.5, (e) TiO2-Ti 2.0 and (f) TiO2-Ti 3.0. XPS spectra of (C1) Ti 2p and (C2) O 1s for

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TiO2 NPs.

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XPS measurements were carried out to investigate the chemical states of Ti and O in the samples.

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The XPS spectra of Ti 2p and O 1s for TiO2 NPs are showed in Figure 2C1 and C2. As shown in Figure

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2C1, two primary peaks at 464.6 eV and 458.8 eV are observed, which attribute to the characteristic Ti

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2p1/2 and Ti 2p3/2 peaks of Ti4+, respectively.17,20 The O 1s XPS spectra of TiO2 and TiO2-Ti 2.0 are

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showed in Figure 2C2. The peaks of O 1s at 530.1 eV and 532.3 eV are observed, which are ascribed to

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the lattice oxygen (Ti-O) in TiO2 and the surface hydroxyl group of TiO2 (Ti-OH), respectively.21-23 9



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The results confirm the successfully fabrication of TiO2. Moreover, the addition of TiCl4 has no

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influence on the chemical states of Ti and O in the as-prepared TiO2 NPs.

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Figure 3. SEM images of (a) TiO2 and (b) TiO2-Ti 2.0.

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SEM was used to study the surface morphology of TiO2 NPs. SEM images of TiO2 and TiO2-Ti

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2.0 are showed in Figure 3a and b. It shows that TiO2 NPs gather together to form large smooth

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granules. As seen from the insets in Figure 3a and b, TiO2 and TiO2-Ti 2.0 present spherical shapes.

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Then TEM and HRTEM analyses were performed to gain further microstructure information of TiO2

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NPs. TEM images of TiO2 and TiO2-Ti 2.0 are showed in Figure 4a and d. As seen in Figure 4a,

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original TiO2 samples are made up of single crystal nucleus. However, TEM of TiO2-Ti 2.0 (Figure 4d)

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reveals that several crystals of TiO2 are stacked together to form a big crystal nucleus cluster. Figure 4b

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and e present HRTEM images of TiO2 and TiO2-Ti 2.0. Only one crystallographic plane in a crystal

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can be observed for original TiO2 samples, but several crystallographic planes can be seen in a crystal

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for TiO2-Ti 2.0. The results verify that big crystal nucleus cluster is formed with the addition of TiCl4.

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It may be due to that TiCl4 reacts with titanium alkoxide complex to form new crystal nucleus. The 10


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corresponding selected area electron diffraction SAED patterns are presented in Figure 4c and f.

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Indexing of the primary rings are consistent with the existence of anatase phase ((101), (004), (200),

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(105) and (204) crystal planes), which is in agreement with the XRD result in Figure 2B. These results

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also indicate that TiCl4 cannot influence the crystal types of TiO2 NPs.

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Figure 4. TEM images, HRTEM images and SAED patterns of (a-c) TiO2 and (d-f) TiO2-Ti 2.0.

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Furthermore, AFM was used to study the morphology of TiO2 NPs. Figure 5a and b present AFM

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images of TiO2 and TiO2-Ti 2.0. From SEM images, it cannot be concluded that whether the surface

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morphology of TiO2 NPs has been changed after adding TiCl4 due to the existence of Au nanoparticles.

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But AFM images clearly illustrate that the morphology of TiO2 NPs has been influenced by TiCl4. As

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shown in Figure 5a, original TiO2 NPs present the morphology of single nanoparticles. Whereas from 11



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Figure 5b it can be seen that many bigger crystal nucleus clusters are observed for TiO2-Ti 2.0. The

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results are in accordance with TEM images. It is confirmed that the additive TiCl4 facilitates the

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formation of a bigger crystal nucleus cluster. Furthermore, the formation of bigger crystal nucleus

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cluster consequently increases particle sizes of TiO2 NPs. The corresponding height images of TiO2

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and TiO2-Ti 2.0 (Figure 5a1 and b1) clearly show that particle sizes of TiO2 NPs are increased in view

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of the addition of TiCl4.

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Figure 5. AFM images and the corresponding height images of (a) TiO2 and (b) TiO2-Ti 2.0.

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Based on the above results, a possible formation mechanism of TiO2 nanoparticle cluster is

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proposed, as illustrated in Figure 6. As we have studied, TiO2 NPs obtained from titanium butoxide and

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PEG400 have excellent dissolubility in water. However, TiO2 NPs obtained from TiCl4 and PEG400

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cannot be dissolved in water. So we speculate that PEG400 cannot be capped on the surface of TiO2

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NPs when using TiCl4 as the precursor of titanium. It can be supposed that TiCl4 reacts with titanium

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alkoxide complex to synthesize anatase TiO2 NPs when using TiCl4 and titanium butoxide as the

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precursors of titanium. Then these TiO2 NPs with and without being capped by PEG400 are stacked

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together to form a bigger crystal nucleus cluster.

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Figure 6. Possible schematic of the formation mechanism of TiO2 NPs.

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3.3. Optical Properties of the Photocatalysts. UV-vis absorbance spectra of the TiO2 aqueous

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solutions are showed in Figure 7. It shows that the UV-vis absorbance of TiO2-Ti aqueous solutions is

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highly enhanced. TiO2-Ti 2.0 solution shows the strongest absorption intensity. Furthermore, the 13



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absorption of TiO2-Ti solutions expands into visible region. In addition, Figure 7 shows that the

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absorption intensity of TiO2 NPs aqueous solutions increases with the increasing dosage of TiCl4. The

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results can be attributed to that the bigger TiO2 crystal nucleus clusters cause stronger light scattering in

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solutions, which enhances light absorption ability of TiO2 NPs aqueous solutions. However, TiO2-Ti

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3.0 solution presents lower absorption intensity than TiO2-Ti 2.0 solution. The result maybe result from

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that the crystallinity of TiO2-Ti 3.0 has been reduced with excess addition of TiCl4. It has been reported

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in previous works that the optical properties of a photocatalyst and its catalytic performance are closely

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related.4,24 The absorption in the visible light region implies that the prepared samples can be activated

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by visible light and more photogenerated electrons and holes can be created to participate in the

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photocatalytic oxidation reactions.17 Therefore, it can be predicted that the photocatalytic activities of

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TiO2-Ti nanoparticle cluster may be better than that of original TiO2 NPs.

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Figure 7. UV-vis absorbance spectra of the TiO2 aqueous solutions.

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3.4. Photocatalytic Activity of the Photocatalysts. The photocatalytic activities of TiO2 NPs were

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evaluated by monitoring the degradation of MO. Figure 8A presents the photocatalytic degradation of

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MO in the presence of TiO2 NPs under UV light irradiation versus irradiation time. For comparison, the

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photodegradation of MO without photocatalyst (blank) has been investigated. As observed in Figure 14


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8A, it can be seen that no significant degradation of MO was observed in the absence of any

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photocatalyst. Note that MO molecules were degraded completely in 15 s when TiO2-Ti 2.0 was used

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as photocatalyst. For original TiO2, TiO2-Ti 0.5, TiO2-Ti 1.0, TiO2-Ti 1.5 and TiO2-Ti 3.0, 15.8%,

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61.4%, 87.1%, 91.8% and 78.5% of MO were degraded in 15 s, respectively. About 33.8% of MO

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molecules were degraded in 30 s when original TiO2 was used as the photocatalyst, but MO molecules

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were degraded completely when TiO2-Ti NPs were used as photocatalysts. It would spend around 7

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min for original TiO2 to degrade MO molecules completely by continuing experiment, indicating that

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the photocatalytic activity of TiO2 NPs under UV light irradiation can be enhanced for about 28 times

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after adding TiCl4 (TiO2-Ti 2.0). The water-soluble PEG400-capped anatase TiO2 NPs have been

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prepared using tetra-n-butyl titanate as the only precursor of titanium in previous work14. We found that

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the photocatalytic activity of TiO2-Ti 2.0 under UV light irradiation was 30-40 times that of the

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reported sample14. All these results verify that the photocatalytic activities of TiO2 NPs under UV light

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irradiation have been enhanced after adding TiCl4 and TiO2-Ti 2.0 presents the best photocatalytic

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activity.

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The photocatalytic activities of TiO2 NPs under simulated sunlight irradiation were also evaluated

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by monitoring the degradation of MO. Figure 8B shows the photocatalytic degradation of MO in the

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presence of TiO2 NPs under simulated sunlight irradiation versus irradiation time. It also can be seen

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from Figure 8B that no significant degradation of MO was observed in the absence of any photocatalyst.

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The degradation ratio of MO was very fast in first one hour and then decreased quickly when TiO2-Ti

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NPs were used as photocatalysts. TiO2-Ti 2.0 presented the best photocatalytic activity and 87.4% of

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MO molecules could be decomposed in 1 h. For original TiO2, TiO2-Ti 0.5, TiO2-Ti 1.0, TiO2-Ti 1.5

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and TiO2-Ti 3.0, 2.6%, 12.0%, 39.9%, 84.1% and 65.3% of MO were degraded in 1 h, respectively.

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The visible photocatalytic activity of TiO2-Ti 2.0 was increased by 33 times compared to original TiO2.

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The results demonstrate that the photocatalytic activities of TiO2 NPs under simulated sunlight 15



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irradiation have been highly enhanced by adding TiCl4. The bismuth oxychloride photocatalyst has

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been prepared with the assistance of PEG for visible photocatalytic activity. The results showed that

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PEG-assisted bismuth oxychloride exhibited higher visible photocatalytic performance25. However, we

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found that the visible photocatalytic activity of TiO2-Ti 2.0 was about 4.5 times that of PEG-assisted

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bismuth oxychloride. It indicates that the as-prepared TiO2 crystal nucleus clusters exhibit the great

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potential in visible light photocatalysis. In sum, the TiO2 crystal nucleus clusters possess efficient

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photocatalytic activities both under UV and visible light irradiation.

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Figure 8. Photocatalytic degradation of MO in the presence of TiO2 NPs under UV light irradiation (A)

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and simulated sunlight irradiation (B) versus irradiation time.

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Jaiswal et al. reported that the recombination of photogenerated charges, visible light absorption

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capability, and the surface area of photocatalyst were the three main factors controlling the

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photocatalytic activity.26 It suggests that the photocatalytic activities of as-prepared TiO2-Ti are mainly

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controlled by light absorption capability. With the addition of TiCl4, bigger crystal nucleus clusters

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were formed, which can cause stronger light scattering and in consequence enhance light absorption

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ability of TiO2 NPs. Furthermore, the absorption spectra of TiO2-Ti expand into visible region after 16


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adding TiCl4. Hence, more photogenerated electrons and holes can be created to take part in the

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photocatalytic reactions process due to the increased light absorption. So addition of TiCl4 can enhance

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the photocatalytic activities of TiO2 NPs under UV and visible light irradiation. The TiO2-Ti 2.0

312

possesses the best photocatalytic activity due to the strongest light absorption ability.

313 314

4. CONCLUSIONS

315

The anatase TiO2 nanoparticles with high photocatalytic activities and good aqueous dissolubility have

316

been prepared by a simple solvothermal method. PEG400 was used as stabilizer to improve the

317

aqueous dissolubility while HCl was used to control the anatase phase of TiO2. In particular, titanium

318

tetrachloride (TiCl4) and titanium butoxide were cooperatively served as the precursors of titanium.

319

The results show that TiCl4 cannot influence the crystal structures of TiO2 and has no influence on the

320

chemical states of Ti and O. With the addition of TiCl4, bigger crystal nucleus clusters will be formed,

321

which can cause stronger light scattering and in consequence enhance light absorption ability of TiO2.

322

Moreover, the absorption spectra of TiO2 aqueous solutions expand into visible region after adding

323

TiCl4. Hence, more photogenerated electrons and holes can be created to take part in the photocatalytic

324

reactions process. As a result, the TiO2 crystal nucleus cluster possesses enhanced photocatalytic

325

activities both under UV light and visible irradiation.

326 327

AUTHOR INFORMATION

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Corresponding Authors

329

*(D.L.) Phone: +086-028-85405221; e-mail: [email protected].

330

*(C.M.) Phone: +086-028-85405221; e-mail: [email protected].

331

ORCID

332

Defu Li: 0000-0001-6466-4947 17



333

Notes

334

The authors declare no competing financial interest.

Page 18 of 21

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ACKNOWLEDGMENTS

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This work was financially supported by the Key Research and Development Project of Sichuan

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Province (SCST18ZDYF1426), Project of Youth Science and Technology Innovation Research Team

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of Sichuan Province (2017TD0010).

340 341

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Nanoparticle Cluster with Efficient Visi

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