**1. Introduction**

Titanium dioxide (TiO2 ) exists in three different crystal structures that are anatase, rutile, and brookite, where rutile is known as the most stable form [1]. The band gap energy of anatase, rutile, and brookite are 3.2, 3.0, 3.2 eV, respectively [1–5]. It means that they can only be activated with UV light irradiation having a wavelength (λ) of 387 nm or lower. Many studies in the area show the use of UV radiation as a photon source for both photocatalytic inactivation of microorganisms [6–11] and dye degradation [12–30].

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

The titania has been employed as a photocatalyst in several photocatalytic reactions due to its high photoactivity, low cost, low toxicity and good chemical and thermal stability [1–3]. However, its large energy band gap inhibits it from being active under UV light [31–35]. The solar spectrum consists of only 4–5% UV light and around 40% visible light [31]. Therefore, the efficiency of TiO<sup>2</sup> as a photocatalyst under sunlight irradiation is limited.

The viscous sol was heated at about 60°C to evaporate organic solvents to yield dry gel [72]. The

been done including the use of acetic acid [83], micellar medium [75], spin coating technique

drying at 150°C followed with calcination of the product at 500°C [68]. Some modifications in the impregnation method such as the use of capping agent [74] and combustion method [63,

The modification starts with silver nanoparticles preparation in polyvinylpyrrolidone (PVP)

with PVP. The mixture is refluxed for 3 h at 110°C to give a yellow-orange color solution. The solvent was evaporated at 55°C, and the obtained Ag nanoparticles were dispersed into ethanol and thoroughly washed with hexane and ethanol. The Ag nanoparticles are redis-

mixture is sonicated for 3 h and is dried at 60°C to remove the solvent followed temperature

glycine as fuel in the muffle furnace at 150°C for 2 h [63, 64]. The remaining solid from the

In the precipitation method, titanium tetra-isopropoxide and silver nitrate were used as

prepared by controlled addition of TTIP to absolute ethanol with constant stirring to get a clear solution. A sufficient amount of surfactant solutions (1% CTAB +1% SDS) was added to the solution with constant stirring. The aqueous solution of silver nitrate was added to the solution. A solution of aqueous ammonia was added dropwise to the last solution under stirring with the special arrangement at room temperature until the solution pH reaches 8. After complete precipitation, the solid was washed with Millipore deionized water and acetone several times to remove excess of surfactant. The precipitate was kept under microwave irradiation for 20 min. The dried powder was ground and calcined at 300°C for 3 h in a temperature-controlled muffle furnace [68]. Following calcination, the

The combustion method is carried out by heating a mixture of AgNO3

a source of titanium and silver, respectively. Ag-doped TiO2



http://dx.doi.org/10.5772/intechopen.75918

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<sup>3</sup> − Ag + O2 (35 0° C)4 TiO2 − AgNP + 6 H2 O (2)

Silver Nanoparticle Incorporated Titanium Oxide for Bacterial Inactivation and Dye Degradation




in water for 24 h. The solvent is later removed by

solution is added to methanol and is mixed

powder is added to the solution. This

, titanyl nitrate and

nanocrystalline powder was

dry gel is calcined at about 350°C to produce TiO2

mixed with the suspension of TiO2

as a capping agent. For this purpose, the AgNO3

persed into the ethanol under sonication, and TiO2

4Ti (OH)

[82], with the purpose to improve TiO2

In the preparation of TiO2

**2.2. Impregnation method**

The synthesis of TiO2

64] are also possible.

rise to 90°C [74].

**2.3. Precipitation**

TiO2

combustion is supposed to be TiO2


AgNO3

Modification of TiO<sup>2</sup> to improve the photocatalytic efficiency of TiO<sup>2</sup> under sunlight visible irradiation is necessary. The modification by non-metal [36–51] and metal [52–83] doping on TiO2 has been attempted. The metal doping agents introduced for TiO2 are transition metals (Fe, Cu, Cr, Co, and Ni) [52–56] and noble metals (Ag, Au, Pd, and Pt) [57–83]. Among the noble metals, silver has received considerable interest due to its additional potential as an antibacterial agent [84]. The importance of medical applications of metallic silver [85, 86] and antibacterial activity of TiO2 [6–11] attracts researchers to think of manufacturing silver-doped titania. There are ongoing works related with the use of Ag for possible medical devices [79], dental implants [78, 79], food packagings [80], air conditioning filters, and so on [79]. Some works focus on bacterial inactivation [34, 63] and dye waste treatment under visible light irradiation [66, 67, 81–83]. Hence, the preparation and characterization of the TiO2 -based photocatalyst and its activity are presented.

#### **2. Preparation of TiO2 -AgNP**
