Enhanced photocatalytic activity in ZnO nanoparticles developed using novel Lepidagathis ananthapuramensis leaf extract

Abstract

Focussing on the green synthesis of ZnO NPs using a novel Lepidagathis ananthapuramensis (LA) leaf template and its photocatalytic activity.

Green Synthesis of TiO2 Using Impatiens rothii Hook.f. Leaf Extract for Efficient Removal of Methylene Blue Dye

“…The positively charged holes in the valence band react with water molecules or hydroxyl anions, resulting in hydrogen cation ions (H + ) and hydroxyl radicals (OH • ). Hydroxyl radicals, which are powerful oxidants, can react with organic pollutants and degrade them to environmentally harmless products . Generally, the following steps take place in photocatalysis of organic pollutants (1) absorption of photon energy and excitation of electron to the conduction band, (2) reduction, (3) oxidation, and (4) pollutant degradation as given in eqs –. ,− IL − Ti O 2 + hv → IL − Ti O 2 ( normalh VB + + normale CB − ) e CB − + O 2 → O 2 • − false) O 2 • − + H + → HO 2 • 2 HO 2 • → H 2 O 2 + O 2 2 HO 2 • → H 2 O 2 + O 2 • − → OH • + O 2 + OH − …”

“…Hydroxyl radicals, which are powerful oxidants, can react with organic pollutants and degrade them to environmentally harmless products. 18 Generally, the following steps take place in photocatalysis of organic pollutants (1) absorption of photon energy and excitation of electron to the conduction band, (2) reduction, (3) oxidation, and (4) pollutant degradation as given in eqs 6−13. (13) 3.9.…”

“…There are four basic steps in the photocatalysis of pollutants: (1) absorption of light having an energy greater than the band gap of semiconductor material to form electron–hole pairs (excitons), (2) separation of excitons, (3) migration of electrons and holes to the surface of the semiconductor, and (4) the charged electrons and holes participating in the redox processes (electrons are utilized in reduction, and holes are utilized in oxidation process). − In recent decades, transition metal oxides such as ZrO 2 , CuO, WO 3 , ZnO, and TiO 2 are the well-known photocatalysts that generate the redox reactions at their surfaces when stimulated by the UV–visible light irradiation appropriate to their band gap energy. ,, Among them, TiO 2 is the most effective in photocatalytic splitting of water and photodegradation of organic pollutants and has good antibacterial activity …”

Photocatalytic degradation of organic dyes using transition metal based mixed metal oxide nanocomposite under different illumination

“…The relatively high band gap in the synthesized CZ5 nanocomposite material is probable to avoid the recombination of photo generated free electron and holes, which are liable for the creation of reactive free radicals such as OH • and O2 •− . They are responsible for the degradation of organic dyes into carbon dioxide and water [13][14][15] . The nanocomposite of CZ5 with spherical morphology was found to have high band gap values and hence its higher activity can be accounted.…”