Green synthesis of CuNb₂O₆ thin film using allium cepa as catalyst

ABSTRACT

The objective of this study was to synthesize and characterize a novel green synthesis of copper niobate (CuNb₂O₆) thin film using copper (II) sulfate pentahydrate (CuSO₄ · 5H₂O), an organometallic precursor of bis(cyclopentadienyl) niobium (IV) dichloride (C₁₀H₁₀Cl₂Nb), using Allium cepa as a catalyst. The synthesized thin film was characterized using the XRD, EDX, SEM FTIR, UVvis, and 4-point probe measurement. The XRD patterns of the thin film affirmed the formation of a pure monoclinic CuNb₂O₆ phase. Similarly, the SEM images illustrated the formation of the film and the different film microstructures. The EDX revealed that the thin film consisted of copper (Cu), niobium (Nb), and oxygen (O) elements. The thin film, however, possessed broad absorption in the Ultraviolet-Visible (UV–Vis) region with an absorption edge at 340 nm and an optical bandgap evaluated to be 3.18 eV. Also, the fabricated film’s transmittance ranged between 40% and 55%. A Raman shift of 690 cm⁻¹ was identified at the CuNb₂O₆ film. The results obtained from the FTIR analysis demonstrated characteristic IR bands at 608 cm⁻¹ and 940 cm⁻¹ which indicated the formation of the Cu-O and Nb-O-Nb bonds. With the rising temperature, an increase in conductivity and a decrease in resistivity were noticed from the plots. This indicated that the synthesized CuNb₂O₆ thin film exhibited good semiconducting qualities. The prepared CuNb₂O₆ thin film thus possesses improved electrical properties and can therefore be effectively utilized in photovoltaic solar cells.

KEYWORDS:

• Thin film
• copper niobate
• synthesize
• spin coating
• allium cepa

Highlights

• This study was on the fabrication of CuNb₂O₆ thin film from CuSO4·5H2O, C₁₀H₁₀Cl₂Nb, and waste Allium cepa peels extracts, via the sol-gel spin coating process.

• It investigated the deposited thin film relative to the annealing temperature effects from the deposition process.

• It also analyzed the films application processes which was as a result of the outcome from the characterization procedures.

Nomenclature

Table

Acknowledgments

The authors herewith dedicate acknowledgment to the National Research Foundation (NRF) South Africa, the Global Excellence Stature (GES), and the University Research Commission (URC) for being supportive financially.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Emeka Charles Nwanna

Emeka Charles Nwanna-PhD candidate, Department of Mechanical Engineering Science. University of Johannesburg, Johannesburg.

Patrick Ehi Imoisili

Patrick Ehi Imoisili- PhD, Research Fellow-Department of Mechanical Engineering Science. University of Johannesburg, South Africa.

Sarah Bitire

Sarah Bitire- Masters Student. Department of Mechanical Engineering Science. University of Johannesburg, South Africa.

Tien-Chien Jen

Tien-Chien Jen-Professor. Department of Mechanical Engineering Science. University of Johannesburg, South Africa.