SYNTHESIS NANOMATERIALS TiO2 DOPED Cd, Se, S AND EVALUATE THE ABILITY PHOTOCATALYTIC DECOMPOSITION OF COLOR

COMPOUNDS

ABSTRACTNanomaterials TiO2 doped Cd, Se, S were synthesized by hydrothermal method from TiCl4,

Na2SO4, Cd (NO3)2 and Na2SeO3 solution. The hydrolysis solution is prepared at a temperature lower than 0°C in the optimal ratio, the hydrolysis process is carried out at 90°C for two hours, the precipitate is dried and heated at 300°C for two hours. Phase composition, particle size is determined by X-ray diffraction spectroscopy, scanning electron microscopy and transmitted electron microscopy. The composition of elements is determined by the energy dispersiive X-ray spectroscopy method. The results obtained TiO2 doped Cd, Se and S are single-phase anatase and about 5 nm in size. This product has the ability of photocatalyst in the visible area to decompose the color compound.

Key word : nanomaterials, TiO2 doped Cd, Se, S, photocatalyst.

1. INTRODUCTIONNanomaterials TiO2 is applied in the field of solar cells, photocatalysis, environmental

treatmeent, self-cleaning paint, electronic devices, sensors and in the field of microbicides [1,2]. With high photocatalytic activity, structural durability, non-toxic, easy and inexpensive modulation. Nanomaterials TiO2 is considered the most promising material to solve problems of environmental pollution and energy crisis [3,4].

However, because the blank band of TiO2 is quite large (3.25eV for anatase and 3.05eV for rutile), only ultraviolet light stimulates electrons from the valence band to the conduction band and causes photocatalyst phenomena. In order to use sunlight into TiO2's photocatalyst process, it is necessary to narrow its blank range. Researchers have modified TiO2 materials by various methods such as adding transition metal or nonmetal to reduce energy Eg of photocatalyst, expanding the ability to absorb electromagnetic radiation in the visible region [5,6].

In this work, focused on synthesis nanomaterials TiO2 and TiO2 doped Cd, Se, S and initially surveyed photocatalytic activity of the material used in the visible region. 2. EXPERIMENTAL2.1 Synthesis nanomaterials TiO2 and TiO2 doped Cd, Se, S

The solution (containing TiCl4, Cd(NO3)2, Na2SO4, Na2SeO3) was prepared according to the molar ratio predetermined in low temperature than 0°C, then gradually raised to 90oC for hydrolysis precipitated suspension for 2 hours. The suspension is centrifuged, filtered, washed with ethanol and distilled water, then dried in an oven at 900C vacuum during 1 hour. The solid after drying is ground by a mortar agate for about 15 minutes, then bring baked in a vacuum furnace at a temperature of 500 0C for 2 hours. The final product is crushed by a mortar agate powder for about 5 minutes.2.2 The sample survey methods

Phase and particle size of the product was determined by X-ray diffraction (XRD), on a X-ray Siemens D5005 used K∞ diffraction radiation of copper anode with wavelength = 0.154056 nm,

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recording spectrum at 25°C, scan angle 2: 10.000o – 70.000o with scan speed 0,030o/s. The average

crystal size is calculated according to Scherrer formula: Where : D is the average diameter of particles; is the width of the bar sells diffraction (in radians); K is the coefficient characterizing the shape factor (K = 0.89); is the Bragg angle.

Morphology and particle size was determined by scanning electron microscope (SEM), Hitachi S-4800 with magnifications from 20 to 8.8 million times and transmission electron microscopy (TEM), JEOL JEM - 1010 Electron Microscope .

The elemental composition of the material was analyzed by energy dispersive X-ray (EDX) on a JEOL 6490 - JEP2300.

The absorbance of the Methylene Blue solution was measured on V-670 JASCO at 664 nm wavelength optimization. Performance when photocatalysis incandescent lighting 40W/220V of the

sample is determined by the formula: Where: H% is the photocatalytic efficiency; Ao: optical absorbance of the Methylene Blue control solution; At: the absorbance of the Methylene Blue solution at the time of various kinds of TiO2.3. RESULTS AND DISCUSSION 3.1. Examined the effects of the percentage number of moles of substances in the hydrolysis solution to particle size

The survey on the impact of the percentage of the number of moles Na2SO4/TiCl4, to the particle size and crystal structure of TiO2 with a molar ratio range of Na2SO4/TiCl4 from 10% to 24%. From XRD measurement results, we get the value , β, and , calculate the average size of TiO2 particles and phase components. The results are presented in Figure 1 and Table 1.

VNU-HN-SI EMENS D5005 - Mau Ti0, 616

2 1 -1 2 7 6 (*) - Ru tile , s y n - TiO2 - Y: 5 6 .3 6 % - d x b y : 1 .00 0 - WL : 1 .54 05 61 )

File : Th o m-DHSP-T i0 ,61 6 .raw - Ty p e : 2 Th /Th loc k e d - Start: 1 0.0 0 0 ° - En d : 7 0 .0 0 0 ° - Ste p: 0 .0 3 0 ° - S tep time : 1.0 s - Te mp .: 2 5 .0 °C (Ro om) - Ano d e : Cu - Cre a tio n : 03 /2 6 /14 13 :1 9 :59 - Ob s . Ma x : 27 .4 4 7 ° - d (Ob s . Ma x ): 3 .2 4 7 - Max In t.: 35 5 .8 7 0 Cp s - Ne t He ig h t: 3 3 7.8 9 0 Cp s - FWHM: 0.4 6 7 °

Lin (

Cps)

0

1 0 0

2 0 0

3 0 0

4 0 0

5 0 0

2-Thet a - Scale

1 0 20 30 40 5 0 6 0 70

d=3

.24

7

d=2

.48

49

d=2

.29

95

d=2

.18

54

d=2

.05

66

d=1

.68

55

d=1

.62

34

d=1

.47

75

d=1

.45

16

d=1

.35

99

VNU-HN-SI EMENS D5005 - Mau Ti0, 6Cd20Se8S20

2 1 -1 2 7 2 (*) - An a tas e , s y n - TiO2 - Y: 3 6 .6 5 % - d x b y : 1 .0 00 - WL : 1 .5 4 0 5 61 )

File : Th o m-DHSP-Ti0 ,6 Cd 20 Se 8 S2 0 .raw - Ty p e : 2 Th /Th lo c k e d - Sta rt: 1 0 .0 0 0 ° - En d : 7 0 .0 00 ° - Ste p : 0 .03 0 ° - Ste p time : 1 .0 s - Te mp .: 2 5 .0 °C (Roo m) - An o d e : Cu - Cre a tio n : 01 /20 /1 4 0 9 :5 6 :1 8 - Ob s . Ma x : 25 .2 9 7 ° - d (Ob s . Ma x ): 3 .5 1 8 - Max In t.: 2 7 5.8 8 3 Cp s - Ne t He ig h t: 2 5 3 .6 5 6 Cp s - FWHM: 0 .8 1 5 °

Lin (

Cps)

0

1 0 0

2 0 0

3 0 0

4 0 0

2-Thet a - Scale

1 0 2 0 3 0 4 0 5 0 6 0 7 0

d=

3.5

23

d=

2.3

72

6

d=

1.8

94

0

d=

1.6

98

4 d

=1

.66

72

d=

1.4

80

5

d=

1.3

60

6

Figure 1. (a): XRD spectrum of TiO2; (B): XRD spectrum of TiO2 doped Cd, S, Se.

Table 1: Phase and an average particle size (D) depends on the percentage of the number of moles Na2SO4/TiCl4.

% ratio of moles Na2SO4/TiCl4

Phaseβ

(radian)2 (độ)

D(nm)

0 Rutile 0.008151 27.447 17.3210 Anatase 0.008727 25.311 16.10

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15 Anatase 0.010280 25.309 13.6717 Anatase 0.010699 25.294 13.1318 Anatase 0.011065 25.307 12.7019 Anatase 0.012462 25.289 11.2820 Anatase 0.014224 25.297 9.8821 Anatase 0.012758 25.295 11.0122 Anatase 0.012549 25.315 11.2023 Anatase 0.012078 25.307 11.6324 Anatase 0.010734 25.299 13.09

For Na2SeO3 and Cd(NO3)2 was conducted similar surveys in the molar ratio range of Na2SeO3/TiCl4 from 5% to 20%; Cd(NO3)2/TiCl4 from 15% to 30%. Results determine the particle size are shown on Table 2.Table 2: Dependence of average particle size (D) to component of hydrolysis solution

% ratio of moles Na2SeO3/TiCl4

D(nm)

% ratio of moles Cd(NO3)2/TiCl4

D(nm)

5 12.46 15 12.686 12.14 18 11.847 11.50 19 10.788 9.88 20 9.889 11.18 21 10.5710 11.69 22 10.5811 12.25 23 10.8715 12.70 25 11.0020 15.45 30 11.40

The XRD measurement results showed that nanomaterials TiO2 is single rutile phase and TiO2 doped Cd, Se, S is anatase single phase. The spectral peaks of TiO2 doped Cd, Se, S is light movement toward small 2 corner and the expansion of spectral peaks on the XRD schema of TiO2 doped Cd, Se, S can be predicted is the influence of impurities to grain size and the oxygen vacancies in the crystal caused.3.2. Investigate the influence of calcination temperature and time to form particle size

The experience available sample the influence of calcination temperature and calcination time is prepared from solution of TiCl4 0.6 M; Na2SO4 0.12 M; Na2SeO3 0.048 M and Cd(NO3)2 0.12 M. The results are shown on the table 3.Table 3: Dependence average particle size to the calcination temperature and time.

calcination temperature

(oC) D (nm)

calcination time at 300oC

(giờ)D (nm)

250 6.89 1 7.08300 5.96 1.5 6.89

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350 6.93 2 5.96450 8.08 2.5 6.63500 9.88 3 7.19

600 20.86

From experimental results, the calcination temperature and calcination time are selected : sample is baked at 300oC for 2 hours has given the smallest average size.3.3 Surveying the effect of temperature and concentrations of TiCl4 to a particle size

In the hydrolysis process, temperature and concentration of TiCl4 in hydrolysis solution affect the hydrolysis rate and the number of seed crystals to form. So will affect the size of the crystal. Results in Tables 4, 5 and Figure 2 show that the optimal hydrolysis temperature chosen is 90oC with concentration 0.7 M of TiCl4.Table 4: Phase and an average size of TiO2 doped Cd, Se, S depends on the hydrolysis temperature.

hydrolysis temperature (oC)

Phase 2 (độ) D

(nm)70 Anatase 25,270 11,26

80 Anatase 25,247 8,49

90 Anatase 25,394 5,96100 Anatase 25,311 9,01

Table 5: Phase and average size of TiO2 doped Cd, Se, S depends on the concentration of TiCl4 in solution.

CM TiCl4 Phase 2 (độ)D

(nm)0.4 Anatase 25.390 6.530.45 Anatase 25.630 6.520.5 Anatase 25.270 6.20.55 Anatase 25.240 6.010.6 Anatase 25.394 5.960.65 Anatase 25.240 5.390.7 Anatase 25.630 4.570.75 Anatase 25.417 5.380.8 Anatase 25.210 5.770.85 Anatase 25.269 6.240.9 Anatase 25.240 7.121 Anatase 25.333 8.1

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VNU-HN-SIEMENS D5005 - Mau TiCl4-0,7M-Cd20Se8S20 - 300 - 2h

21 -1 2 72 (*) - An ata s e , s y n - TiO2 - Y: 1 4 .02 % - d x by : 1 .0 00 - WL : 1 .5 4 05 61 )

File : Th om-DHSP-TiCl4 -0,7 M-Cd2 0 Se8 S20 -30 0 -2 h.ra w - Ty p e : 2Th /Th lo c k e d - Sta rt: 1 0.0 0 0 ° - En d: 7 0 .0 00 ° - Step : 0 .0 30 ° - Ste p time : 1 .0 s - Te mp.: 2 5 .0 °C (Ro om) - An o d e: Cu - Cre a tio n: 0 6 /0 2/1 4 11 :3 1:5 7 - Ob s . Max : 2 5 .63 0 ° - d (Obs . Ma x ): 3 .4 7 3 - Max In t.: 86 .4 0 7 Cp s - Ne t Heig h t: 4 7.6 07 Cp s - FWHM: 1 .7 63 °

Lin (

Cps)

0

1 0

2 0

3 0

4 0

5 0

6 0

7 0

8 0

9 0

1 0 0

11 0

1 2 0

2-Thet a - Scale

11 2 0 3 0 4 0 5 0 6 0 7 0

d=

3.4

95

d=

1.8

99

2

Figure 2: XRD spectrum of the samples obtained from the hydrolysis solution of TiCl4 0.7 M.

3.4 Survey morphology and composition of elements in TiO2 doped Cd,Se, STo confirm the results obtained from XRD, the surface of TiO2 and TiO2 doped Cd, Se, S by scanning electron microscope (SEM) in Figure 3 and electronic transmission microscope (TEM) in Figure 4:

(a) ( b )

Figure 3: (a) SEM images of TiO2; (b) SEM images of TiO2 doped Cd, Se, S.

Figure 4: TEM images of TiO2 doped Cd, Se, S.

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The results showed that the nanocrystalline particles formed quite evenly, with good crystallization, average size in accordance with the results calculated from X-ray diffraction spectra.

The composition of the elements in the samples is determined in two different regions by X-ray energy dispersion (EDX).

Figure 5: EDX spectra of TiO2 doped Cd, Se, S in two different areas of the sampleTable 6. Composition of elements in TiO2 doped Cd, Se, S.

% atomic elements

Ti O Cd S Se

Area 1 32.09 54.28 0.06 3.61 9.96Area 2 34.63 53.21 0.06 3.57 8.54

Average 33.36 53.75 0.06 3.59 9.25

The results in Figure 5 and Table 6 show that the TiO2 doped Cd, Se, S contains the desired chemical composition and the particles TiO2 doped Cd, Se, S are pure, free from other impurities. The content of elements in the regions are quite uniform.3.5 Photocatalyst performance of TiO2 and TiO2 doped Cd, Se, S.

The photocatalyst performance of TiO2 and TiO2 doped Cd, Se and S are evaluated through processing decomposition of Methylene Blue in visitable light, which is shown in Figure 6.

0 30 60 90 120 150 1800

102030405060708090

TiO2 pha tạp

TiO2

R

(H%)

(Phút)

Figure 6: The dependence of the photocatalyst performance of the TiO2 and TiO2 doped Cd, Se, S over time.

The results showed that the ability of photocatalytic of TiO2 doped Cd, Se and S is higher than TiO2 in visible region. This shows that the energy of empty space TiO2 doped Cd, Se and S is reduced to the equivalent of radiant energy in the visible region.

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EDX area 1 EDX area 2

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00

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nts O

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STiTi

TiLsum

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SeSeLsum

Cd

CdCd

CdCd

CdCd

Cd

0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00

keV

002

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nts

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Se

SeLsum

CdCd

CdCd

CdCd

CdCd

4. CONCLUSSION The influence of some factors on crystal structure and average size of particles TiO2 doped Cd,

Se and S, which is synthesized by hydrolysis method, have been studied. Nanomaterials TiO2 doped Cd, Se, S were obtained as single-phase anatase and the average particles size is about 5 nm.

Initial research on photocatalyst application of nanomaterials TiO2 doped Cd, Se, S in visible light area based on Methylene Blue decomposition reaction. The efficiency of methylene blue decomposition process of TiO2 doped Cd, Se, S is much higher than that of TiO2.

REFERENCES1. Yu Long Xie, 2013, Enhanced photovoltaic performance of hybrid solar cell using highly oriented CdS/CdSe modified TiO2 nanorods, Electrochimica Acta, Vol. 105, pp. 137-141.2. Zhu J., Yang D., Geng J., Chen D., Jiang Z., 2008, Synthesis and characterization of bamboo-like CdS/TiO2 nanotubes composites with enhanced visible-light photocatalytic activity, Journal of Nanoparticle Research, Vol. 10, pp. 729-736.3. OliviaNiitsoo, Shaibal K. Sarkar, ChristophePejoux, Sven Rühle, David Cahen, Gary Hodes, 2006, Chemical bath deposited CdS/CdSe-sensitized porous TiO2 solar cells, Journal of Photochemistry and Photobiology, A: Chemistry, Vol.191, pp 306-313.4. Zhengguo Zhang, Chengwu Shi, JunjunChen, Guannan Xiao, LongLi, 2017, Combination of short-length TiO2 nanorod arrays and compact PbS quantum-dot thin films for efficient solid-state quantum-dot-sensitized solar cells, Applied Surface Science, Vol. 4310, pp 8-13.5. Guidong Yang, Zheng Jiang, Huahong Shi, Tiancun Xiao and Zifeng Yan, 2010, Preparation of highly visible-light active N-doped TiO2 photocatalyst, Joural of Materials Chemistry, DOI: 10.1039/c0jm00376j.6. Yan Wang, Yungeng Zhang, Peichen Li, 2017, Pt/N Co-doped Titanium Dioxide Visible-Light-Active Photocatalyst: Preparation and Characterization, IOP Conf. Series : Earth and Evironmental Science, DOI: 10.1088/1755-1315/81/1/012022.

TỔNG HỢP VẬT LIỆU NANO TiO2 PHA TẠP Cd, Se, S VÀ ĐÁNH GIÁ KHẢ NĂNG QUANG XÚC TÁC PHÂN HỦY HỢP CHẤT MÀU

Vật liệu nano TiO2 pha tạp Cd, Se, S được tổng hợp bằng phương pháp thủy nhiệt từ dung dịch chứa TiCl4, Na2SO4, Cd(NO3)2 và Na2SeO3. Dung dịch thủy phân được chuẩn bị ở nhiệt độ thấp hơn 0oC theo tỉ lệ tối ưu, quá trình thủy phân được thực hiện ở 90oC trong hai giờ, Phần kết tủa được sấy và nung ở 300oC trong hai giờ. Thành phần pha, kích thước hạt được xác định bằng các phương pháp phổ nhiễu xạ tia X, chụp ảnh kính hiển vi điện tử quét và kính hiển vi điện tử truyền qua. Thành phần các nguyên tố được xác định bằng phương pháp phổ tán sắc năng lượng tia X. Kết quả thu được vật liệu nano TiO2 doped Cd, Se và S là đơn pha anatase có kích thước khoảng 5 nm. Sản phẩm này có khả năng quang xúc tác trong vùng khả kiến phân hủy hợp chất màu.

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