Antibacterial and solar-driven photocatalytic activities of Co_xSn_1−xO_2−δ nanoparticles for wastewater treatment

Abstract

Transition metal doped nanoparticles have potential for photodegradation, antibacterial activity, and water splitting. Co-doped SnO₂ nanoparticles (Co_xSn_1−xO_2−δ: x = 0–7%) with an average diameter of ≈ 32 nm are successfully synthesized using the coprecipitation method. The structural properties are investigated using an X-ray diffractometer (XRD) that shows tetragonal structure of the nanoparticles. Microstrain and average crystallite size of the nanoparticles are investigated using different XRD models. It is observed that 7% Co-doping reduces the optical bandgap down to 17% (3.04 eV). The nanoparticles show 75% photodegradation of methylene blue dye under sunlight exposure, and enhance antibacterial activity against both gram-positive and gram-negative bacteria. These results may provide pathways to utilize Co_xSn_1−xO_2−δ nanoparticles as efficient photocatalysts, antibacterial agents for industrial wastewater treatment, and water-splitting applications as well.

Appendix

The Young’s modulus of a tetragonal structure can be determined using following expression [33].

$$\frac{1}{{E_{hkl} }} = \frac{{s_{11} \left( {h^{2} + k^{2} } \right) + l^{2} \left( {2s_{13} + s_{44} } \right)}}{{\left( {h^{2} + k^{2} + l^{2} } \right)}} + \frac{{l^{4} \left( {s_{33} - 2s_{13} - s_{44} } \right) + h^{2} k^{2} \left( {2s_{12} + s_{66} } \right)}}{{\left( {h^{2} + k^{2} + l^{2} } \right)^{2} }},$$

(14)

where S₁₁, S ₁₂, S₁₃, S_33, S ₄₄, S₆₆ are the elastic compliances of the tetragonal structure of Co_xSn_1−xO_2−δ nanoparticles (s_ij in TPa⁻¹) that are calculated from the constants of elastic stiffness c₁₁, c₁₂, c₁₃, c₃₃, c₄₄, c₆₆ (c_ij in GPa) using following relations

$$s_{11} = \frac{{c_{33} }}{2c} + \frac{1}{{2\left( {c_{11} - c_{12} } \right)}},$$

(15)

$$s_{12} = \frac{{c_{33} }}{2c} - \frac{1}{{2\left( {c_{11} - c_{12} } \right)}},$$

(16)

$$s_{13} = - \frac{{c_{13} }}{c},$$

(17)

$$s_{33} = \frac{{\left( {c_{11} + c_{12} } \right)}}{c},$$

(18)

$$s_{44} = \frac{1}{{c_{44} }},$$

(19)

$$s_{66} = \frac{1}{{c_{66} }},$$

(20)

$$c \, = \left( {c_{11} + c_{12} } \right)c_{33} {-} \, 2c_{13}^{2} .$$

(21)

Considering the values of elastic stiffness constants the values of elastic compliances S₁₁, S ₁₂, S₁₃, S_33, S₄₄, S₆₆ are taken as 7.426, − 4.408, 1.0438, 2.946, 9.7, 4.8216, respectively [33, 34].