Structural, optical and photocatalytic applications of biosynthesized NiO nanocrystals

ABSTRACT

NiO is one of the most important candidates for semiconductors metal oxide nanocrystals by the arrangement of photocatalytic application. However, the photocatalytic performance of biosynthesized nanocrystals using Aspalathus linearis (Burm.f.) R. Dahlgren has not been investigated yet. In this contribution, we synthesize α-Ni(OH)₂ using an A. linearis. A heat treatment of the α-Ni(OH)₂ is carried out at 300–400°C for 2 h at normal air yields. Furthermore, we have characterized the structural, optical and photocatalytic activity of the samples. The optical results indicate that biosynthesized nanocrystals exhibit UV–visible light absorption and a narrow range distribution of intense green light (518.95 nm) emission, which decreases significantly as annealing temperature increases. The bandgap energies of the sample annealed at 300–400°C shift to lower photon energy, compared to bulk NiO (∼ 4 eV). Moreover, the photocatalytic experimental results reveal that NiO nanocrystals enable color switching of methylene blue.

GRAPHICAL ABSTRACT

KEYWORDS:

• NiO nanocrystals
• Aspalathus linearis
• photocatalytic application
• methylene blue

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

A. Diallo completed his B.Sc in 2005 at Cheikh Anta Diop University, Senegal, followed by his M.Sc. in Physics and Chemistry at the same University in 2006. In 2016, he completed his Ph.D. in Condensed Mater Physics, also at Cheikh Anta Diop University. In 2017, he completed his PhD in Physics at the University of South Africa. He is currently a Lecturer at the Department of Physics and Chemistry, Faculty of Sciences and Technologies of Formation and Education, University Cheikh Anta Diop, Senegal.

K. Kaviyarasu is an expert in materials sciences and engineering from iThemba Labs.

S. Ndiaye is an expert in X-rays diffraction & Raman spectroscopy from Cheikh Anta Diop.

B. M. Mothudi is an expert in nanophosphors and photoluminescence from the University of South Africa.

A. Ishaq is an expert in ion beam modification & analysis of nanomaterials from the National Center for Physics, Quaid-i-Azam University, Islamabad-44000, Pakistan.

V. Rajendran is an expert in materials sciences and director of the centre for Nano Science & Technology, K.S. Rangasamy College of Technology, Tiruchengode, Tamil Nadu, India.

M. Maaza holds the UNESCO-UNISA Africa Chair in nanosciences and nanotechnology. He is an expert in materials at the nanoscale. He is a fellow of the Royal Society of Chemistry, London, African Academy of Sciences, Islamic Academy of Sciences, and the New York Academy of Sciences.

ORCID

A. Diallo http://orcid.org/0000-0002-4032-0477

V. Rajendran http://orcid.org/0000-0001-9471-5311

Additional information

Funding

This research program was generously supported by the National Research Foundation of South Africa (NRF), iThemba LABS-National Research Foundation, the UNESCO-UNISA Africa Chair in Nanosciences-Nanotechnology, College of Graduate Studies, University of South Africa, the Centre for Science and Technology of the Non-Aligned and Other Developing Countries (NAM S&T Centre), New Delhi [NAM-05/74/2015], the Centre for Nano Science and Nanotechnology, K.S. Rangasamy College of Technology, Tiruchengode 63721, Tamil Nadu, India, the Abdus Salam ICTP via the Nanoscience African network (NANOAFNET) as well as the African Laser Center.