In situ synthesis of gold nanoparticles on novel nanocomposite lactose/alginate: Recyclable catalysis and colorimetric detection of Fe(III)

[Display omitted] •The novel hybrid nanocomposite AuNPs/Lac/Alg were first prepared.•Its structure was well characterized by various analysis techniques.•Recyclable catalytic activity was performed for degradation of four pollutants.•The dispersion solution of nanocomposite was used for detection of Fe3+ ions. This work presents a simply new method for in situ synthesis of gold nanoparticles (AuNPs) using the biodegradable polysaccharides. A novel composite of lactose/alginate (Lac/Alg) could be prepared easily through ionotropic gelation mechanism which can reduce in situ gold ions into AuNPs. Lactose plays a crucial role as a reducing reagent which are demonstrated by FTIR analysis. The crystalline structure of AuNPs with a mean size of 10 nm has been confirmed by analysis techniques. The nanocomposite powder possesses highly catalytic performance for degradation of contaminants including 4-nitrophenol, methyl orange, rhodamine 6 G and rhodamine B. The dispersion solution of AuNPs@Lac/Alg was used as an effective probe for highly selective detection of Fe3+ ions. The detection mechanism replies on the aggregation of nanocomposite in the presence of Fe3+ ions. LOD value was found to be 0.8 μM in a linear range of 2.0–80.0 μM.