**2. Materials and methods**

#### **2.1 Materials**

Textile dyes namely Tartrazine (TAZ), Reactive Yellow-17 (RY-17) and Reactive Black (RB-5) were procured from Bagmul Sons, India and was used without any further purification.

The anatase form of TiO2 (P-25 Degussa) with particle size 30 nm and surface area 50 m<sup>2</sup> g<sup>−</sup><sup>1</sup> was used as such. The precursors for titania, Ag, Au and Pt were titanium isopropoxide (Lancaster >99% pure), Silver nitrate (Merck >99% pure), Chloroauric acid (Merck >99% pure) and tetraammineplatinum (II) chloride (Merck >99% pure) were used as received.

All other chemicals namely NaCl, C2H5OH, Na2CO3, H2O2, K2S2O8, NH4OH, H2SO4, isopropanol and acetic acid were obtained from Merck (purity >98%) and were used as received. The water employed for the studies was doubly distilled.

## **2.2 Synthesis of photocatalysts**

The catalytic materials used in the present study were synthesised as described below:

## *2.2.1 Synthesis of TiO2*

Sol gel process was adopted for the synthesis of TiO2. Titanium isopropoxide, isopropanol, water and acetic acid were used as starting materials. Solution A contained 17 mL titanium isopropoxide and 40 mL of isopropanol and Solution B contained 60 mL of isopropanol, 15 mL acetic acid and 5 mL water. Solutions A and B were mixed and stirred for 2 h. The formed TiO2 sol was aged to get the gel of TiO2. The obtained gel was dried, ground with mortar and pestle and finally calcined at 500°C for 3 h [8].
