[en] Highlights: • Aqueous phase exfoliation of defect free graphene sheets employing nicotine based non-cytotoxic surface active ionic liquid (SAIL). • In-situ preparation of nanocomposite (NC) of Ag/AgBr janus nanoparticles (JNPs) and graphene sheets (Ag/AgBr@G) under sunlight. • Photo-degradation of an antibiotic, ciprofloxacin and organic dye, Rhodamine-B, respectively employing Ag/AgBr@G NC. • Enhanced photocatalytic activity of Ag/AgBr@G NC as compared to Ag/AgBr JNPs has been observed due to good electron-hole separation in prepared NC. Aqueous phase exfoliation of defect free graphene sheets is achieved employing nicotine based non-cytotoxic surface active ionic liquid (SAIL). The SAIL stabilizing the graphene acts as template, reducing agent and precursor of Br⁻ ions for in-situ preparation of of Ag/AgBr janus nanoparticles (JNPs) decorating graphene sheets under sunlight within 5 min of exposure, for the first time. Thus, prepared Ag/AgBr@Graphene nanocomposite (NC) shows 2.4–3.0 fold enhancement in photocatalytic activity towards degradation of an antibiotic, ciprofloxacin and Rhodamine-B dye, respectively in water under sunlight/visible light as compared to Ag/AgBr JNPs and other reported photocatalysts. Greater adsorption of contaminated molecules at Ag/AgBr@Graphene NC along with good elctron-hole separation lead to enhanced photocatalytic activity as compared to Ag/AgBr JNPs