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This article reports a novel way to synthesize carbon nanotubes and Cu/ZnO nanoparticles using metal hyperaccumulator plants. Metal hyperaccumulator plants are traditionally used for phytoremediation to clean soil polluted by toxic metals. However, the transfer of toxic metals in plant shoots and leaves is an environmental issue because animals and other living organisms feeding on plants will transfer the metals to the ecosystem. Therefore, we suggest that hyperaccumulator plants could be used to synthesize nanoparticles. Here, Brassica juncea L., a Cu-hyperaccumulator plant, was collected around a copper mine and used as a raw chemical to produce carbon nanotubes and Cu/ZnO nanoparticles. The chlorophyll in shoots of B. juncea plants was ethanol extracted to yield chlorophyllin. Cu and Zn were extracted by HNO 3 to form Cu/Zn(NO 3 ) 2 . The chlorophyllin reacted with Cu/ Zn(NO 3 ) 2 to form Cu/Zn chlorophyllin. Cu/ZnO nanoparticles were synthesized by direct precipitation of Cu/Zn chlorophyllin with NaOH and ethanol. The vascular bundles in B. juncea plants, which have been purified and carbonized by HNO 3 , were rapidly heated to about 400°C and then they were cooled to room temperature to obtain carbon nanotubes. Results indicate that the outer diameter of carbon nanotubes was around 80 nm. Cu/ZnO nanoparticles have a Cu 0.05 Zn 0.95 O composition, and had a diameter of about 97 nm. Our study not only inspires the search for a new strategy on the synthesis of nanostructure from renewable natural products, but also breaks through the traditional and limited ideas about the reuse of metals by hyperaccumulator plants.

Hyperaccumulators contain tubular cellulose and heavy metals, which can be used as the sources of carbon and metals to synthesize nanomaterials. In this paper, carbon nanotubes (CNTs), Cu(0.05)Zn(0.95)O nanoparticles, and CNTs/Cu(0.05)Zn(0.95)O nanocomposites were synthesized using Brassica juncea L. plants, and the ultraviolet (UV)-light-driven photocatalytic degradations of bisphenol A (BPA) using them as photocatalysts were studied. It was found that the outer diameter of CNTs was around 50 nm and there were a few defects in the crystal lattice. The synthesized Cu(0.05)Zn(0.95)O nanocomposites had a diameter of around 40 nm. Cu(0.05)Zn(0.95)O nanocomposites have grown on the surface of the CNTs and the outer diameter of them was around 100 nm. The synthesized hybrid carbon nanotubes using B. juncea could enhance the efficiency of photocatalytic degradation on BPA. The complete equilibration time of adsorption/desorption of BPA onto the surface of CNTs, Cu(0.05)Zn(0.95)O nanoparticles, and CNTs/Cu(0.05)Zn(0.95)O nanocomposites was within 30, 20, and 30 min, and approximately 14.9, 8.7, and 17.4 % BPA was adsorbed by them, respectively. The combination of UV light irradiation (90 min) with CNTs, Cu(0.05)Zn(0.95)O nanoparticles, and CNTs/Cu(0.05)Zn(0.95)O nanocomposites could lead to 48.3, 75.7, and 92.6 % decomposition yields of BPA, respectively. These findings constitute a new insight for synthesizing nanocatalyst by reusing hyperaccumulators.

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