Molecular insights into sodium dodecyl sulphate mediated control of size for silver nanoparticles

• Published in: Journal of molecular liquids 2019-01, Vol.273, p.222-230
• Main Authors: Shah, V., Bharatiya, B., Mishra, M.K., Ray, D., Shah, D.O.
• Format: Article
• Language: English
• Subjects: Micellar stability; Monomers; Nucleation; Polydispersity; Wettability
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2018.10.042

A specific condition directing the formation of silver nanoparticles (AgNPs) with narrow size-distribution in aqueous sodium dodecyl sulphate (SDS) solutions, using trisodium citrate (TSC) is investigated. The peculiar control in distribution of size for AgNPs in presence of 35 mM (~1 wt%) aqueous SDS solution as stabilizing agent is evident. Water penetration through packed PTFE powder and dynamic surface tension measurements demonstrate formation of stable aggregates at the given condition and accordingly reduced numbers of free SDS monomers diffusing to the growing AgNP interface. The smaller size of AgNPs was also confirmed by TEM images, which illustrates mixed morphologies for the nanoparticles in an aggregated state. The NMR experiments reveal strong hydrophobic interactions between the alkyl chains of SDS molecules adsorbed on AgNPs. These results also indicate that TSC is molecularly distributed in bulk phase without binding to the SDS micellar aggregates. A plausible molecular mechanism is proposed based on diffusion of Ag+ ions to the growing AgNP surface along with SDS monomers and submicellar aggregates, subsequently forming bigger size AgNPs. The narrow distribution of size for AgNP in presence of 35 mM SDS is arguably driven by the capping of stable SDS micelles or monomers around growing nuclei and restricted number of SDS monomers and submicellar aggregates responsible for supply of Ag+ at the growing AgNP nuclei. [Display omitted] •AgNPs with narrow distribution of size are synthesized at 35 mM SDS concentration in presence of 3.5 mM TSC.•Least water penetration in packed PTFE powder is noticed for mixtures containing 35 mM SDS concentration.•NMR data reveal increase in hydrophobic interactions between the alkyl chains of SDS molecules during AgNP formation.•Large population of free monomers and submicellar aggregates presumably drives the Ag+ ions to the growing AgNP surface.•TEM images confirm the formation of anisotropic AgNP morphologies in presence of 35 mM SDS as stabilizer.