ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Green synthesis of a reduced graphene oxide–strontium oxide–poly(vinyl pyrrolidone) nanocomposite for enhanced photocatalytic dye degradation

Uma Koul, Ruchi Bharti, Renu Sharma, and Annu Pandey

Department of Chemistry, University Institute of Sciences, Chandigarh University, Mohali, India

E-mail: ruchi.uis@cumail.in

Received: 6 March 2026  Accepted: 22 May 2026

Abstract:

A facile green synthesis route was used to fabricate an rGO–SrO–PVP nanocomposite using Kalanchoe pinnata leaf extract as a dual reducing and stabilizing medium. Structural analyses confirmed the partial reduction of GO to rGO and the in situ formation of crystalline SrO nanoparticles (~ 50–100 nm) anchored on rGO sheets within a PVP-assisted matrix. The composite exhibited a mesoporous H3-type architecture with a moderate BET surface area of 17.05 m² g⁻¹. Although this value is lower than that of highly exfoliated rGO, the enhanced photocatalytic response is likely associated with accessible mesopores, reduced SrO agglomeration, and close rGO–SrO interfacial contact, which may facilitate charge migration and reduce recombination, as inferred from the improved kinetics and radical-trapping results. Under UV irradiation (365 nm), the rGO–SrO–PVP composite degraded approximately 95% of bromophenol blue (BPB) within 60–80 min, with an apparent pseudo-first-order/Langmuir–Hinshelwood rate constant of ~ 0.030 min⁻¹ exceeding pristine SrO (~ 0.010 min⁻¹) and rGO (~ 0.006 min⁻¹). Radical trapping experiments showed that hydroquinone and 2-propanol strongly suppressed BPB degradation to approximately 14% and 17%, respectively, indicating that ·O₂⁻ and ·OH are the principal reactive oxygen species, whereas AgNO₃ and EDTA showed lower inhibition and allowed approximately 80% and 76% degradation, respectively. Reusability testing demonstrated that the catalyst retained 84% BPB degradation after the fourth cycle, corresponding to 87.5% retention of the initial activity. The UV dependence is linked to the wide-band-gap nature of SrO; therefore, the present system is best described as a UV-assisted dye-degradation platform, while rGO integration provides a basis for future visible/solar-light optimization through doping or heterojunction engineering. Overall, this work presents a plant-assisted strategy for constructing rGO-supported alkaline-earth oxide photocatalysts for dye-contaminated wastewater treatment.

Graphical abstract

Keywords: Green synthesis; Reduced graphene oxide; Strontium oxide; Bromophenol blue; Photocatalytic degradation; Antioxidant assay

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-05107-7

Chemical Papers 80 (10) 11963–11979 (2026)