Photocatalytic properties of TiS2 nanodisc and [email protected]2 nanocomposite for methylene blue dye

Journal Pre-proof Photocatalytic properties of TiS2 nanodisc and Sb@TiS2 nanocomposite for methylene blue dye M. Parvaz, Numan Salah, Zishan H. Khan

PII:

S0030-4026(19)31708-5

DOI:

https://doi.org/10.1016/j.ijleo.2019.163810

Reference:

IJLEO 163810

To appear in:

Optik

Received Date:

4 September 2019

Accepted Date:

14 November 2019

Please cite this article as: Parvaz M, Salah N, Khan ZH, Photocatalytic properties of TiS2 nanodisc and Sb@TiS2 nanocomposite for methylene blue dye, Optik (2019), doi: https://doi.org/10.1016/j.ijleo.2019.163810

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Photocatalytic properties of TiS2 nanodisc and Sb@TiS2 nanocomposite for methylene blue dye

M. Parvaza, Numan Salahb & Zishan H. Khana*

a

Center of Nanotechnology, King Abdulaziz UniversityJeddah, Saudi Arabia.

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b

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Organic Electronics & Nanotechnology Research Laboratory, D/o Applied Sciences & Humanities, F/o Engineering & Technology, Jamia Millia Islamia (A Central University), New Delhi, India.110025.

*

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Corresponding [email protected]

Abstract:

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The present paper reports the remarkable photocatalytic properties of pure TiS2 nanodisc and Sb@TiS2 nanocomposite for methylene blue dye, generally found in large quantities in the waste-water released by textile industries. This waste water containing chemical dye is a serious

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threat to the environment for the developing nation like India. This is the first report on the use of TiS2 nanodisc and Sb@TiS2 nanocomposite for the removal of methylene blue dye. It is found that these materials remove almost 80% methylene blue dye, which is interesting and have a lot of potential for treating the waste-water of textile industries. XRD patterns confirmed the crystallinity, formation of pure TiS2 nanodisc and Sb@TiS2 nanocomposite. FESEM studies

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suggest the size of nanodisc is 500 nm to 5 μm. HRTEM images confirm the crystallinity and the diameter of these nanodisc are 30 nm to 60 nm.

Keywords: TiS2, XRD, HRTEM, Methylene blue, Photocatalytic degradation.

1. Introduction: After the discovery of graphene in 2004 and explanation of its outstanding chemical and physical properties, a lot of efforts have been devoted to other two dimensional (2D) materials [1-4]. As an important class of 2D material, transitional metal dichalcogenides (TMDCs) materials have drawn a lot of interest due to their interesting properties such as high mobility, nonsaturating magnetoresistance, tunable band gap and large Seebeck coefficient [5-7]. 2D-TMDCs have a variety of application in different fields such as superconductors [8], thermoelectric

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materials [9], and transistors [10] etc. During last few years, 2D-TMDCs materials have been synthesized and studied in bulk form [11, 12]. Recently improved scalable exfoliation methods

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have been used to synthesize the layered nanostructures of 2D-TMDCs materials [13-15]. These 2D-TMDCs materials are aspected to be the new materials for nanoelectronics, electrochemical

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energy storage/harvesting, photocatalysis, and sensing etc. [16-20].

Two dimensional transitional metal dichalcogenides (2D-TMDCs) materials are represented by

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common formula ZX2, (where Z is the transition metal and X is the chalcogens) and formed by stacking of X-Z-X layers are bonded by covalent bonds. 2D-TMDCs materials can be

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synthesized in different types of structures such as multilayer flakes, nanotubes, fullerene-like nanoparticles and graphene like flakes. A lot of synthesis methods such as chemical vapor deposition method, hydrothermal reaction method, chemical vapor transport (CVT) method, and

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physical ablation method have been used for the synthesis of 2D-TMDCs materials [21]. Out of the above methods, CVT is easy to used and cost effective with the possibility of mass scale production of these materials at low cost. Among 2D-TMDCs family, TiS2 layered material is an important material with the structure of S-Ti-S unit. In this material, titanium (Ti) and sulphur (S) are bonded covalently whereas

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adjacent S-Ti-S layers are bonded with weak Vander Waals forces. It has the energy band gap in the range of 0.05 eV-2.5 eV and behaves as semiconductor material. In present work, we have prepared TiS2 and Sb@TiS2 nanocomposite using CVT method and studied its optical and photocatalytic properties.

2. Experimental details: Polycrystalline TiS2 and Sb@TiS2 nanocomposite were synthesized by two step methods. In the first step, TiS2 was prepared with the help of CVT method. In this method, high purity of

titanium (Ti) and sulfur (S) metal powder were mixed properly using the pestle mortar for 30 minutes and were sealed in quartz ampoules with the help of vacuum sealing unit. The sealed ampoules were heated in a vacuum furnace at 500 0C for 12 h and the temperature was increased up to 800 0C and this temperature was maintained for 24 h [22, 23]. After completing the reaction process, the furnace was switched off and the ampoule were allowed to cool automatically at the room temperature. Finally, the powder containing TiS2 naodisc was obtained from the ampoule.In the second step, TiS2 and Sb (weight % of Sb = 0%, 30%, 50%) metal

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powder were mixed properly for 30 minutes with the help of pestle mortar and this mixed powder was filled in quartz ampoule using the vacuum sealing unit. After that the sealed

ampoule were heated in vacuum furnace at 650 0C for 12 h. After completing the reaction

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process, the furnace was switched off and were allowed to cool at room temperature. Finally, we obtained the Sb@TiS2 nanocomposite. The process used for the synthesis of TiS2 nanodisc and

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Sb@TiS2 nanocomposite using CVT method is shown in Fig.1

The as-prepared TiS2 nanodisc and Sb@TiS2 nanocomposite nanocomposite were characterized

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using different analytical techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-visible spectroscopy. The crystallinity of as-prepared materials were

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studied by Rigaku Ultima IV Diffractometer using Cu kα radiation (λ = 1.54056 Ao). The morphology of TiS2 and Sb@TiS2 nanocomposite were studied by NOVA NANOSEM 450 and high resolution transmission electron microscopy (model–G230S TWIN). UV-Vis

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spectrophotometer (Perkin Elmer, Lambda 365) and photoluminescence spectrometer (Perkin Elma Model-LS55) have been used to study the optical properties of as-synthesized materials. The photocatalytic degradation of methylene blue (MB) was carried out using visible lamp (Bluebird, 20W, and the light flux about 2000 lm).

3. Result and discussion:

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Fig.2. presents the XRD patterns of as-prepared pure TiS2 and Sb@TiS2 nanocomposite. The result of XRD diffraction patterns of as-prepared pure TiS2 and Sb@TiS2 nanocomposite show good agreement with the previous reported data [24, 25]. The diffraction peaks in the XRD pattern confirm the polycrystalline nature of as-prepared material. Various peaks of TiS2 are well indexed and are oriented at 15.404o (001), 31.252o (002), 34.054o (011), 44.015o (102), 47.742o (003), 53.640o (110), 56.166o (111), 57.544o (103), 65.310o (004), 72.117o (022). In case of Sb@TiS2 nanocomposite seven extra peaks of Sb are observed at 28.65o, 40.11o, 42.00o,

48.44.41o, 51.59o, 59.43o, and 68.53o corresponding to the planes of (012), (104), (110), (006), (202), (024), and (122) which is in agreement with the previous report [26]. X-ray diffraction crystallographic data of as-prepared material has been presented in Table 1 and Table 2. On the basis of these result, the hexagonal structure and polycrystalline nature of as-prepared material are confirmed.

The surface morphology of as-prepared pure TiS2 and Sb@TiS2 nanocomposite has been studied

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with the help of Field Emission Electron Microscopy (FESEM). Fig.3(a-b) presents the surface morphology of as-synthesized pure TiS2 sample. A high yield of nanodisc with size ranging

from 500 nm to 5 μm is observed. The FESEM images of Sb@TiS2 nanocomposite are shown in

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Fig.3(c-d). It is evident that a high yield of nanodisc is obtained. The size of these nanodisc is almost same to that of pure TiS2 nanodisc. The micro structural analysis of the as-prepared pure

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TiS2 nanodisc and Sb@TiS2 nanocomposite was explored with the help High Resolution Transmission Electron Microscopy (HRTEM). HRTEM images presented as Fig.4(a-d) and

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Fig.5(a-d) provide a deep understanding of the structure of as-prepared of pure TiS2 nanodisc and Sb@TiS2 nanocomposite. The diameter of pure TiS2 nanodisc ranges from 30 nm to 50 nm

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with interlayer spacing of 0.571 nm (Fig.5(d)), whereas the diameter of Sb@TiS2 nanocomposite ranges from 30 nm to 60 nm with interlayer spacing of 0.572 nm (Fig.6(d)). These interlayer spacings agree with the XRD result (Table.1) and are in agreement with the previous reported

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results [27]. The circular spot of the rings in the SAED of pure TiS2 (inset of Fig 4(c)) and Sb@TiS2 nanocomposite (inset of Fig 5(c)) indicate the polycrystalline. UV–Visible absorption spectra of as-prepared samples were recored using the Perkin Elmer (Lambda 365) UV-visible spectrophotometer in the range of 225-700 nm at room temperature [24, 28]. Fig.6. presents the absorption spectra of pure TiS2 and Sb@TiS2 nanocomposite. On

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comparing with the absorption spectrum of pure TiS2 nanodic, the absorbance peak shifts to higher wavelength (red shift) on increasing the weight% of Sb in TiS2 nanodisc has been observed. Fig.7. presents the Tauc plot of hν Vs (αhν)2 for pure TiS2 and Sb@TiS2 nanocomposite. The band gap is calculated using the well-known Tauc relation formula (1) 𝐷 (ℎ𝜈 − 𝐸𝑔 ) = (αhν)𝑛 ----------- (1)

where D is a constant, hν is the photon energy, α is an absorption coefficient, Eg is the optical energy band gap, and n is an index can have values 1/3, 3, 1/2, 2 [23, 24]. In our case, the optical energy band gap of as-prepared pure TiS2 and Sb@TiS2 nanocomposite followed the direct transition rule and the equation (1) is expressed as equation (2) 𝐷 (ℎ𝜈 − 𝐸𝑔 ) = (αhν)2 --------- (2) The evaluated band gap values for pure TiS2 is 2.20 eV and for Sb@TiS2 nanocomposite (Sb = 30%, 50%) are 2.12 eV, and 2.03 eV respectively (Table.3). These values are in agreement with

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previous reported results [29, 30, 31-32]. The optical band gap decreases on increasing the weight% of Sb in TiS2 nanodisc (Fig.8). In case of Sb@TiS2 nanocomposite, this decrease in the

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value of optical band gap may be due to the creation of intermediate state between the valance band gap and conduction band gap in TiS2 sample.

The Photoluminescence spectroscopy (PL) is a powerful tool for studying the efficiency of

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charge carrier trapping & transfer, surface opto-electronic properties, and to understand the behavior of electron hole pairs in semiconductor materials [33]. The PL spectra of as-synthesized

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pure TiS2 nanodisc and Sb@TiS2 nanocomposites were performed using the excitation wavelength of 312 nm at room temperature. The PL spectra of the as-prepared materials are

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shown in Fig.9. The PL emission peak is observed at 420 nm in pure TiS2 nanodisc, which is in agreement with the previous reported results [24]. In case of Sb@TiS2 nanocomposite, the emission peak shifts to higher wavelength with low intensities on increasing the weight% of Sb

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in TiS2 nanodisc. These emission bands are attributed to near band emission due to free exciton recombination in TiS2 [34] and lower PL peak intensity indicates slower radiative recombination [35], which play an important role in improving the photocatalytic activity.

The photocatalytic activity of as-fabricated pure TiS2 and Sb@TiS2 nanocomposite were studied

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with different time intervals. For photocatalytic process, MB dye is an important pollutant released by textile industries is used. 0.2 gm of pure TiS2 is dispersed in 100 ml DI water with 0.5 ml MB dye. After that, this solution was stirred for different time intervals (0 – 85 minutes) under visible light. Absorbance spectra of MB dye using pure TiS2 nanodisc and Sb@TiS2 nanocomposite was recorded and presented in Fig.10. Fig.10 (a) shows that a small amount of MB dye is degraded using pure TiS2 nanodisc in 85 min. After 210 min visible light irradiation, a complete degradation is observed for pure TiS2 nanodisc and it is reproducible after 20 days

(Fig.10 (b)). In case of Sb@TiS2 nanocomposite (Fig.10(c, d)), the degradation of MB dyes is much faster than that of pure TiS2. This suggests that Sb@TiS2 nanocomposite shows superior photocatalytic properties for MB dye. Fig.11 presents the graph between C / C0 and time (t), where C0 is absorption of MB before light exposer and C is absorption of MB after exposer of light with different time intervals. The reaction kinetics can be observed by plotting linear curve for concentration ratio ln (C0 / C), against the exposer time and is presented as Fig.12. Fig.13 presents the degradation efficiency of pure TiS2 and Sb@TiS2 nanocomposite. In case of

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Sb@TiS2 nanocomposite, Sb@TiS2 nanocomposite with 50% of Sb showed the better degradation efficiency. The degradation efficiency of as-fabricated materials was calculated with the help of following equation:

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ƞ = (1 − 𝐶⁄𝐶 ) 𝑋 100 -------- (3) 0

Where C0 is absorption of MB before light exposer and C is absorption of MB after exposer of

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light with different time intervals [36, 37]. The degradation efficiency are found to be 45.59% for pure TiS2 and 74.35%, 78.60% for Sb@TiS2 (Sb = 30%, 50%) nanocomposite respectively. The

given by the following equation 𝐶⁄ = 𝑒 −𝑘𝑡 ------------- (4) 𝐶0

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photocatalytic activity of as-prepared material follows the pseudo first-order kinetics, which is

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Where k is the rate constant of pseudo first-order reaction [38].The rate constant of pseudo firstorder reaction for pure TiS2 is found 0.0043 min-1 and for Sb@TiS2 nanocomposite are found 0.0242 min-1, and 0.0543 min-1 (with Sb 30% and 50%) respectively. The rate constant of pure TiS2 and Sb@TiS2 nanocomposite is shown in Table.3. Thus, the highest degradation rate constant is observed for Sb@TiS2 (with 50% Sb) nanocomposite.

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The phocatalytic mechanism of as-prepared Sb@TiS2 nanocomposite is shown in Fig.14 and has been explained with the help of following reaction. On exposing visible light to Sb@TiS2 nanocomposite, electrons and hole are generated due to narrowing band gap. The photogenerated holes may oxidizing the water to the hydroxyl radicals, whereas photogenerated electrons react with the adsorbed oxygen as electron acceptor in the formation of superoxide radicals anions, hydrogen peroxide and hydroxyl radicals. These reactions have been represented by the equation

(5-12). Due to these reaction, the recombination of the electrons and holes pairs decreases, resulting in the degradation of MB dye to the stable product. − + 𝑇𝑖 𝑆2 /𝑆𝑏 + ℎ𝜈 → 𝑇𝑖 𝑆2 /𝑆𝑏 (𝑒𝐶𝐵 + ℎ𝑉𝐵 )

---------- (5)

+ ℎ𝑉𝐵 + 𝐻2 𝑂 → −𝑂𝐻 + 𝐻 +

---------- (6)

+ ℎ𝑉𝐵 + 𝑂𝐻 − → .𝑂𝐻

---------- (7)

− 𝑒𝐶𝐵 + 𝑂2→ .𝑂2−

---------- (8)

2

+ + ℎ𝑉𝐵 → 𝐻𝑂2−

---------- (9)

2𝐻𝑂2− → 𝑂2 + 𝐻2 𝑂2

---------- (10)

𝐻2 𝑂2 + .𝑂2− → .𝑂𝐻 +.𝑂𝐻 + 𝑂2

---------- (11)

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𝐷𝑦𝑒 + .𝑂𝐻 + 𝑂2 → 𝐶𝑂2 + 𝐻2 𝑂 + 𝑜𝑡ℎ𝑒𝑟 𝑝𝑟𝑜𝑑𝑢𝑐𝑡 ------- (12)

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.𝑂 −

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4. Conclusion:

The structural studies confirm the formation as well as Sb doping inTiS2 nanodisc. It is reveal

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that these nanodisc are uniform and well shaped. HRTEM image confirm the crystallinity of these nanodisc. The diameter of these nanodisc is 30 nm to 60 nm. The band gap of pure TiS2 nanodisc is found to be 2.20 eV, which decreases on the increases the weight% of Sb. The PL

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emission peak of pure TiS2 is observed at 420 nm, which increases to higher wavelength with low intensities on increasing the weight% of Sb in TiS2 nanodisc. On the basis of photocatalysis

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studies, the degradation efficiency for MB dye of pureTiS2 nanodisc is 45.59% which increases

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with the increase the weight% of Sb.

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Table caption:

Table 1: X-ray diffraction peaks of pure TiS2 and Sb@TiS2 nanocomposite.

Table 1:

2θ

d-spacing

(deg.)

(A0)

Sb@TiS2 (Sb = 30%)

Sb@TiS2 (Sb = 50%)

nanocomposite

nanocomposite

2θ (deg.)

2θ (deg.)

d-spacing

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Pure TiS2

(A0)

(001)

15.500

5.7144

15.490

2

(002)

31.290

2.8575

3

(011)

34.110

2.6274

34.120

4

(102)

44.030

2.0558

44.060

5

(003)

47.800

1.9021

6

(110)

53.660

1.7074

7

(111)

56.290

8

(103)

9

(004)

10

(022)

5.7181

15.480

5.72

2.6267

34.110

2.6274

2.0544

43.050

2.0549

1.7038

53.630

1.7083

1.6337

56.290

1.6337

56.290

1.6337

57.510

1.6019

57.540

1.6011

57.540

1.6011

65.250

1.4294

65.240

1.4296

65.240

1.4296

72.000

1.3111

72.000

1.3111

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53.780

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1

d-spacing (A0)

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(hkl)

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S.N.

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71.850

1.3134

Table 2: X-ray diffraction crystallographic data of pure TiS2 and Sb@TiS2 nanocomposite.

Table 2: Pure TiS2

Sb@TiS2 (Sb = 30%) Sb@TiS2 (Sb = 50%) nanocomposite

nanocomposite

Lattice parameter

a = b = 3.37

a = b = 3.37

a = b = 3.35

(a=b, c) (𝐀𝟎 )

c = 5.71

c = 5.71

c = 5.72

56.15

56.15

55.59

𝟑

ro

of

Cell volume (V) 𝐀𝟎

Table 3:

Band gap

Degradation Degradation rate

(eV)

(%) at 85

re

S.N. Material used

-p

Table 3: optical data of pure TiS2 and Sb@TiS2 nanocomposite.

constant (k) / min

min

Sb@TiS2 (Sb = 30%)

45.59

0.0043

2.12

74.35

0.0242

2.03

78.60

0.0543

lP

2.

2.20

Pure TiS2

ur na

1.

nanocomposite

3.

Sb@TiS2 (Sb = 50%)

Jo

nanocomposite

Figure caption: Fig.1. schematic diagram of as-synthesized pure TiS2 and Sb@TiS2 nanocomposite . Fig.2. XRD- spectra of as-synthesized pure TiS2 and Sb@TiS2 nanocomposite. (a) pure TiS2, (b) 30% Sb@TiS2, (c) 50% Sb@TiS2. Fig.3. SEM- micrograph of as-synthesized pure TiS2 and Sb@TiS2 nanocomposite. (a-b) pure

ro

Fig.4(a-d). HRTEM images of as-synthesized pure TiS2 nanodisc.

of

TiS2, (c-d) Sb@TiS2 (Sb = 50%) nanocomposite.

Fig.5(a-d). HRTEM images of as-synthesized Sb@TiS2 (Sb = 50%) nanocomposite.

-p

Fig.6. UV-visible spectra of as-synthesized pure TiS2 and Sb@TiS2 nanocomposite. (a) pure TiS2, (b) 30% Sb@TiS2, (c) 50% Sb@TiS2.

lP

(b) 30% Sb@TiS2, (c) 50% Sb@TiS2.

re

Fig.7. (αhν)2 Vs hν plot of as-synthesized pure TiS2 and Sb@TiS2 nanocomposite. (a) pure TiS2,

Fig.8. variation of optical band gap (Eg) as function of different weight% of Sb in TiS2 (Sb = 0%, 30%, 50%) nanocomposite.

ur na

Fig.9. PL spectra of as-synthesized pure TiS2 and Sb@TiS2 nanocomposite. (a) pure TiS2, (b) 30% Sb@TiS2, (c) 50% Sb@TiS2.

Fig.10. Time-dependent UV-visible spectra of MB dye in presence of pure TiS2 and Sb@TiS2 nanocomposite. (a) pure TiS2, (b) after 20 days of pure TiS2 (c) 30% Sb@TiS2, (d) 50%

Jo

Sb@TiS2.

Fig.11. Relative intensity (C / C0) of absorption vs time in pure TiS2 and Sb@TiS2 nanocomposite. (a) pure TiS2, (b) 30% Sb@TiS2, (c) 50% Sb@TiS2. Where C0 is the initial intensity and C is the intensity at time (t). Fig.12. Kinetic plot of ln (C0 / C) as function of time for the degradation of MB in pure TiS2 and Sb@TiS2 nanocomposite. (a) pure TiS2, (b) 30% Sb@TiS2, (c) 50% Sb@TiS2.

Fig.13. MB dye degradation efficiency graph as function of time in pure TiS2 and Sb@TiS2 nanocomposite. (a) pure TiS2, (b) 30% Sb@TiS2, (c) 50% Sb@TiS2. Fig.14. Photocatalysis mechanism in Sb@TiS2 nanocomposite under visible light.

Filled ampoule with mixture of Ti and S

1:2

+

ro

Mixing of TiS2 and Sb powder

re

furnace

-p

S

Mixing of Ti and S powder

Vacuum sealing unit

of

Ti

Jo

ur na

Vacuum sealing unit

Sealed ampoule

Sealed ampoule

furnace

Fig.1. schematic diagram of as-synthesized pure TiS2 and Sb@TiS2 nanocomposite.

Sb@TiS2 nanocomposite

Filled ampoule

lP

f

20

30

40

of

Sb(122)

30% Sb@TiS2

ro 50

60

Pure TiS2

(022)

(004)

-p (110) (111) (103)

(003)

(102)

re

10

50% Sb@TiS2

Sb(122)

Sb(024)

Sb(202)

Sb(104) Sb(110)

Sb(006) Sb(202)

Sb(104) Sb(110)

Sb(012) Sb(012)

(a)

(011)

1000 800 600 400 200 0 0

(b)

(002)

1000 800 600 400 200 0

(c)

(001)

Intensity (a.u.)

1000 800 600 400 200 0

70

80

90

lP

2 Theta (degree) Fig.2. XRD- spectra of as-synthesized pure TiS2 and Sb@TiS2 nanocomposite. (a) pure

Jo

ur na

TiS2, (b) 30% Sb@TiS2, (c) 50% Sb@TiS2.

(a)

(c)

(d)

-p

ro

of

(b)

re

Fig.3. SEM- micrograph of as-synthesized pure TiS2 and Sb@TiS2 nanocomposite. (a-b)

Jo

ur na

lP

pure TiS2, (c-d) Sb@TiS2 (Sb = 50%) nanocomposite.

of ro -p re lP

Jo

ur na

Fig.4(a-d). HRTEM images of as-synthesized pure TiS2 nanodisc.

of ro -p re

Jo

ur na

lP

Fig.5(a-d). HRTEM images of as-synthesized 50% Sb@TiS2 nanocomposite

1.0 (a) Pure TiS2

0.9

(b) 30% Sb@TiS2 (c) 50% Sb@TiS2

0.7 0.6

of

(b)

0.5

(c) (a)

0.3 0.2

300

400

500

Wavelength (nm)

re

.

600

ro

0.4

700

-p

Absorbance (a.u.)

0.8

Fig.6.UV-visible spectra of as-synthesized pure TiS2 and Sb@TiS2 nanocomposite. (a) pure

Jo

ur na

lP

TiS2, (b) 30% Sb@TiS2, (c) 50% Sb@TiS2.

4.50E+008

1.00E+009

30% Sb@TiS2

Pure TiS2 9.00E+008

4.00E+008

8.00E+008

(a)

3.50E+008

(b)

(h)

(h)

7.00E+008 3.00E+008

2.50E+008

6.00E+008 5.00E+008

2.00E+008

4.00E+008

Eg= 2.20 (eV) 1.50E+008

Eg=2.12 (eV)

3.00E+008 1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

1.4

h (eV)

1.8

2.0

2.2

2.4

2.6

2.8

3.0

ro

h (eV)

50% Sb@TiS2

(c)

-p

6.00E+008

4.00E+008

re

(h)

1.6

of

1.4

Eg= 2.03 (eV)

1.6

1.8

2.0

ur na

lP

2.00E+008 1.4

2.2

2.4

2.6

2.8

3.0

h (eV)

Fig.7. (αhν)2 Vs hν plot of as-synthesized pure TiS2 and Sb@TiS2 nanocomposite. (a) pure

Jo

TiS2, (b) 30% Sb@TiS2, (c) 50% Sb@TiS2.

2.22 2.20

2.16 2.14 2.12

of

Band gap (eV)

2.18

2.10

ro

2.08 2.06

2.02 0

10

20

30

40

50

lP

re

% of Sb

-p

2.04

Fig.8. variation of optical band gap (Eg) as function of different weight% of Sb in TiS2 (Sb

Jo

ur na

= 0%, 30%, 50%) nanocomposite.

30

pure TiS2

(a)

400

450

500

550

(b)

600

30% Sb@TiS2

20 0 350 40 30

400

450

500

550

(c)

600

50% Sb@TiS2

20

400

450

500

-p

10 0 350

of

10

ro

Normalized PL Intensity (a.u.)

500 400 300 200 100 0 350 40

550

600

re

Wavelength (nm)

lP

Fig.9. PL spectra of as-synthesized pure TiS2 and Sb@TiS2 nanocomposite. (a) pure TiS2,

Jo

ur na

(b) 30% Sb@TiS2, (c) 50% Sb@TiS2.

2.0

Absorbance (a.u.)

1.6

2.0

0 min 5 min 15 min 25 min 35 min 45 min 55 min 65 min 75 min 85 min

Pure TiS2 (a)

1.4 1.2 1.0 0.8

1.6

0.6 0.4

(b)

1.4 1.2 1.0 0.8 0.6

0.2 500

600

700

800

0.0 400

900

500

800

1.2 1.0 0.8 0.6 0.4

1.6 1.4

ro

1.4

1.8

50% Sb@TiS2

900

0 min 5 min 15 min 25 min 35 min 45 min 55 min 65 min 75 min 85 min

(d)

-p

(c)

2.0

Absorbance (a.u.)

0 min 5 min 15 min 25 min 35 min 45 min 55 min 65 min 75 min 85 min

30% Sb@TiS2

1.2 1.0 0.8 0.6

re

Absorbance (a.u.)

700

Wavelength (nm)

2.0

1.6

600

of

Wavelength (nm)

1.8

0 min 5 min 15 min 25 min 35 min 45 min 55 min 65 min 75 min 85 min 95 min 115 min 125 min 145 min 155 min 165 min 175 min 195 min 210 min

0.4

0.2 0.0 400

After 20 days, absorbance spectra of MB

1.8 dye using pure TiS2

Absorbance (a.u.)

1.8

0.4

0.2

0.2

500

600

700

800

900

lP

0.0 400

ur na

Wavelength (nm)

0.0 400

500

600

700

800

900

Wavelength (nm)

Fig.10. Time-dependent UV-visible spectra of MB dye in presence of pure TiS2 and Sb@TiS2 nanocomposite. (a) pure TiS2, (b) after 20 days of pure TiS2 (c) 30% Sb@TiS2, (d)

Jo

50% Sb@TiS2.

1.0

(a) Pure TiS2

(a)

0.9

(b) 30% Sb@TiS2

0.8

(c) 50% Sb@TiS2

0.7

(b)

0.5 0.4

of

C / C0

0.6

(c)

0.3

ro

0.2 0.1

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

re

Time (minutes)

-p

0.0 0

Fig.11. Relative intensity (C / C0) of absorption vs time in pure TiS2 and Sb@TiS2

lP

nanocomposite. (a) pure TiS2, (b) 30% Sb@TiS2, (c) 50% Sb@TiS2. Where C0 is the initial

Jo

ur na

intensity and C is the intensity at time (t).

1.6

(c) 1.4

(a) Pure TiS2 (b) 30% Sb@TiS2

1.0

(b)

0.8

(c) 50% Sb@TiS2

0.6

of

ln (C0 / C)

1.2

(a) 0.2

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

re

Time (minutes)

-p

0.0 0

ro

0.4

Fig.12. Kinetic plot of ln (C0 / C) as function of time for the degradation of MB in pure TiS2

Jo

ur na

lP

and Sb@TiS2 nanocomposite. (a) pure TiS2, (b) 30% Sb@TiS2, (c) 50% Sb@TiS2.

90

(c)

70 60

(b)

50

30

(a) 10 0 0

(a) Pure TiS2

ro

20

of

40

(b) 30% Sb@TiS2 (c) 50% Sb@TiS2

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

re

Time (minutes)

-p

Degradation efficiency (%)

80

Fig.13. MB dye degradation efficiency graph as function of time in pure TiS2 and Sb@TiS2

Jo

ur na

lP

nanocomposite. (a) pure TiS2, (b) 30% Sb@TiS2, (c) 50% Sb@TiS2.

of ro -p re

Jo

ur na

lP

Fig.14. Photocatalysis mechanism in Sb@TiS2 nanocomposite under visible light.