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. 2025 Jul 1;15(1):21179.
doi: 10.1038/s41598-025-03229-8.

Bioinspired Conyza bonariensis-mediated ZnO/rGO NCs for effective degradation of toxic compounds under visible-light irradiation

Rohit S Madankar  1 , Pavan Bhilkar  1 , Mohammad Raish  2 , Ajay Potbhare  3   4 , Małgorzata Norek  5 , Subhash Somkuwar  6 , Ankita Daddemal-Chaudhary  7 , Aniruddha Mondal  8 , Ratiram Chaudhary  9
Affiliations

Bioinspired Conyza bonariensis-mediated ZnO/rGO NCs for effective degradation of toxic compounds under visible-light irradiation

Rohit S Madankar et al. Sci Rep. .

Abstract

This study reports a green, cost-effective synthesis of ZnO/rGO nanocomposites (NCs) using Conyza bonariensis leaf extract as a novel bio-reducing agent. The nanocomposites were prepared via a simple hydrothermal method. Extensive characterization techniques including XRD, FT-IR, EDS, UV-DRS, XPS, BET, SEM, TEM, and AFM were employed to evaluate the crystallite size, phase structure, chemical composition, surface morphology, porosity, and particle size of the synthesized material. XRD analysis confirmed the formation of a hexagonal wurtzite ZnO phase with an average crystallite size of approximately 17.22 nm, calculated using the Debye-Scherrer equation. SEM revealed a distinctive "tuberose flower"-like morphology of ZnO particles distributed on the reduced graphene oxide (rGO) sheets, with flower diameters ranging from 1 to 2 μm and petal widths of 40-70 nm. Further, TEM supported the uniform distribution of ZnO tubular petals on graphene nanosheets. BET analysis demonstrated the mesoporous nature of NCs. Remarkably, the bioinspired ZnO/rGO NCs exhibited excellent photocatalytic activity under visible-light irradiation, effectively degrading industrial dyes such as Congo red (CR), Methylene blue (MB), and Thymol blue (TB). The enhanced photocatalytic performance is attributed to the nanocomposites' unique scaffold-like architecture, increased light absorption, and efficient charge separation.

Keywords: Bioinspired ZnO/rGO NCs; Environmental mitigation; Mesoporous material; Nature-inspired synthesis; Photocatalytic performance; Toxic dyes.

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Conflict of interest statement

Declarations. Competing interests: The authors declare no competing interests.

Figures

Fig. 1
Fig. 1
Conyza bonariensis-mediated phytosynthesis of ZnO-rGO NCs.
Fig. 2
Fig. 2
Mechanism of formation of the ZnO-rGO NCs using Conyza bonariensis leaf extract.
Fig. 3
Fig. 3
a XRD, b FT-IR spectra, c Raman and d EDX of ZnO-rGO NCs.
Fig. 4
Fig. 4
a UV-DRS spectra, and b bandgap (by K-M plot) of ZnO-rGO NCs.
Fig. 5
Fig. 5
XPS spectrum a survey, b Zn-2p, c O1s, and d C1s of ZnO-rGO NCs.
Fig. 6
Fig. 6
a–d SEM image of ZnO-rGO NCs.
Fig. 7
Fig. 7
a–d TEM image, e SAED, and f particle size histogram of ZnO-rGO NCs.
Fig. 8
Fig. 8
a Nitrogen adsorption-desorption isotherm, and b AFM micrograph of ZnO–rGO NCs.
Fig. 9
Fig. 9
Absorbance spectra of dyes a CR, c MB and e TB, and optimization of dyes b CR, d MB, (f TB using ZnO-rGO NCs in visible-light irradiation.
Fig. 10
Fig. 10
Effects (optimization) of ZnO-rGO NCs loading (a, c and e) on photodegradation, and (b, d and f) reaction kinetics for CR, MB and TB.
Fig. 11
Fig. 11
a, c and e Comparison of degradation efficiency of ZnO-rGO NCs, and (b, d and f) reaction kinetics for CR, MB and TB dyes.
Fig. 12
Fig. 12
Decolouration photographs of a CR, b MB, and c TB in 90 min of degradation.
Fig. 13
Fig. 13
Possible photocatalytic mechanism of the dye degradation by ZnO-rGO NCs.
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