Green Synthesis Offer Eco-Friendly Alternative to Toxic Nanoparticles
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A collaboration with Department of Chemical Engineering and Technology, Jazan University of Saudi Arabia and School of Chemical Engineering, Yeungnam University of South Korea, researchers at the Faculty of Science (FOS) have been investigating the feasibility of utilising biological nanoparticles in seeking novel solutions in engineering, material science and electronics.

Zinc Oxide nanoparticles have been popular in industries, medicine and agriculture due to their non-toxicity, antimicrobial activity and low cost. Previously, a number of biosynthesised Zinc Oxide nanoparticles by plants such as Lantana (Lantana Aculeata), Hibiscus (Rosa sinensis), Avarampoo (Cassia auriculata), Indian borage (Plectranthus amboinicus) and Lemon eucalyptus (Corymbia citriodora) have already been studied.

The research team which includes Professor Mohammad Mansoob Khan, Nurin Hayatus Saadah, Mohammad Ahtisham Khan, Mohammad Hilni Harunsani and Ai Ling Tan observed the potential of Red Button Ginger (Costus woodsonii) leaf extract in producing narrow band gap Zinc Oxide nanoparticles. With Zinc Nitrate as a precursor, the leaf extracts were used instead of toxic chemicals.

Following the preparation of unboiled and boiled leaf extracts where calcination resulted in a light-yellow powder, x-ray diffraction patterns of the samples showed that as-synthesised Zinc Oxide nanoparticles contained a hexagonal wurtzite structure, which was similar and well-matched with Zinc-Oxide crystals.

In addition, the samples were analysed by UV-vis diffuse reflectance spectroscopy, fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and transmission electron microscopy.

Inorganic nanoparticles such as semiconducting metal oxides Zinc Oxide, Titanium Dioxide, Tin Oxide and Cerium Oxide have many advantages as they provide a wide range of material properties with versatility in their function and they exhibit unique optical properties. However the physical and chemical synthesis which include solvothermal synthesis, sol-gel techniques and laser ablation can be toxic, are hazardous to health and not environmentally friendly.

Biological or green synthesis has led to many interesting and eco-friendly approaches to the development of biologically synthesised nanoparticles from environmentally benign materials which range from macro to micro-organisms. These include plants, bacteria and algae. Extracts containing various known biomolecules and metabolities of a diverse range of plant species, obtained from the leaves, stems, flowers, seed, roots and bulbs have proven to act as a potential source for the synthesis of nanoparticles.

Green synthesis using plants and microbes produce nanomaterials that are non-toxic with safe reagents as the main reactions involved are reduction and oxidation. The process is very economical because it can be used as a substitute to the large-scale production of nanoparticles. In addition, green nanotechnology can help advance the development of clean technologies, minimise possible adverse health effects and reduce environmental risks.

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