Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Dual responsive magnetic Au@Ni nanostructures loaded reduced graphene oxide sheets for colorimetric detection and photocatalytic degradation of toxic phenolic compounds Gitashree Darabdhara a,b , Manash R. Das a,b, ⁎ a Advanced Materials Group, Materials Sciences and Technology Division, CSIR-North East Institute of Science and Technology, Jorhat, 785006, Assam, India b Academy of Scientific and Innovative Research, CSIR-NEIST Campus, India GRAPHICAL ABSTRACT ARTICLE INFO Keywords: Reduced graphene oxide Gold-nickel bimetallic nanoparticles Phenol Colorimetric detection Photocatalysis ABSTRACT We report the colorimetric detection and photocatalytic degradation of toxic phenolic compounds using Au@Ni loaded reduced graphene oxide (rGO) nanostructures. Core-shell nanoparticles of Au and Ni are successfully designed on rGO with size < 8 nm by a solvothermal route which demonstrate excellent enzyme mimic beha- viour towards the oxidation of 3,3ʹ,5,5ʹ tetramethylbenzidine (TMB), a peroxidase substrate and towards col- orimetric detection of phenols with detection limit as low as 1.68 μM, wide detection range of 1–300 μM and admirable selectivity. Additionally, the Au@Ni/rGO nanocomposite exhibits excellent photo responsive beha- viour towards degradation of phenol, 2-chlorophenol (2-CP) and 2-nitrophenol (2-NP) under natural sunlight irradiation with more than 87% degradation. The superiority of the bimetallic nanocomposite is established by comparing its activity to its monometallic counterparts. The sustainability of the nanocomposite is assessed through the reusability in the photocatalytic reaction upto six consecutive cycles without significant loss in https://doi.org/10.1016/j.jhazmat.2019.01.010 Received 1 July 2018; Received in revised form 2 January 2019; Accepted 6 January 2019 ⁎ Corresponding author at: Materials Sciences & Technology Division, CSIR–North East Institute of Science and Technology, Jorhat, 785006, Assam, India. E-mail addresses: mrdas@neist.res.in, mnshrdas@yahoo.com (M.R. Das). Journal of Hazardous Materials 368 (2019) 365–377 Available online 07 January 2019 0304-3894/ © 2019 Elsevier B.V. All rights reserved. T