Role of surfactants: One step facile synthesis of hetero structured Ag-Ni alloy by seed less approach

Surfactant assisted seedless synthesis of Ag-Ni alloy nanoparticles were carried out in an one step process by coreduction of mixed metal salts (AgNO3+ Ni(NO3)(2)) solutions using ascorbic acid as reducing agent. To explore the role of surfactant, two types of surfactants were studied; cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium dodecylbenzenesulphonate (SDBS). The surface plasmon resonance peak (SPR) of CTAB capped Ag- Ni and SDBS capped Ag-Ni located at 450 nm and 410 nm wavelengths, respectively. For SDBS, visual observations and time resolved spectra indicates that the reaction mixture containing different mixing orders of reactants (SDBS + Ag+ + Ni2+ + ascorbic acid and SDBS + Ni2+ + Ag+ + ascorbic acid) have different colours as well as different SPR band positions with time. Presence of SDBS delayed the nucleation processes. The Ag- Ni alloy with both surfactants shows that the a red shift to ca. 410 nm and 450 nm with respect to the SPR of AgNPs. The absence of SPR bands at ca. 375 nm and 500- 700 nm ruled out the possibility to the formation and/or deposition NiO + Ni(OH)(2) on the surface of Ag-Ni alloy. The average number of Ag-Ni atoms per nanoparticle, molar concentration of Ag-Ni and free energies (surface, volume and excess energy due to mixing) were calculated and discussed. The Ag-Ni alloy used as a catalyst to the photo-assisted degradation methyl orange and showed a higher photo catalytic activity. The synthetic method reported here suggests a very promising use of the suitable stabilizer for the preparation of an alloy nanoparticles having different optical properties, which is a subject of immense interest.