title: A simple strategy to improve the interfacial activity of true Janus gold nanoparticles: a shorter hydrophilic capping ligand.
abstract: Janus gold nanoparticles (JPs) of ∼4 nm-diameter half functionalized with 1-hexanethiol as a hydrophobic capping ligand exhibit significantly higher interfacial activity, reproducibility and rheological response when the other half is functionalized with 1,2-mercaptopropanediol (JPs-MPD) than with 2-(2-mercaptoethoxy)ethanol (JPs-MEE), both acting as hydrophilic capping ligands. The interfacial pressure measured by pendant drop tensiometry reaches 50 mN m(-1) and 35 mN m(-1) for the JPs-MPD at the water/air and water/decane interface, respectively. At the same area per particle, the JPs-MEE reveal significantly lower interfacial pressure: 15 mN m(-1) and 5 mN m(-1) at the water/air and water/decane interface, respectively. Interfacial dilatational rheology measurements also show an elastic shell behaviour at higher compression states for JPs-MPD while the JPs-MEE present near-zero elasticity. The enhanced interfacial activity of JPs-MPD is explained in terms of chemical and hydration differences between the MPD and MEE ligands, where MPD has a shorter hydrocarbon chain and twice as many hydroxyl terminal groups as MEE.
authors.affiliation: Biocolloid and Fluid Physics Group, Applied Physics Department, Faculty of Sciences, University of Granada, Granada, Spain. rhidalgo@ugr.es.
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: Fernandez-Rodriguez
authors.affiliation: Department of Chemistry and Biochemistry, University of California, 1156 High Street, Santa Cruz, CA 95064, USA.
authors.forename: Limei
authors.initials: L
authors.lastname: Chen
authors.affiliation: Department of Chemistry and Biochemistry, University of California, 1156 High Street, Santa Cruz, CA 95064, USA.
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Deming
authors.affiliation: Biocolloid and Fluid Physics Group, Applied Physics Department, Faculty of Sciences, University of Granada, Granada, Spain. rhidalgo@ugr.es.
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: Rodriguez-Valverde
authors.affiliation: Department of Chemistry and Biochemistry, University of California, 1156 High Street, Santa Cruz, CA 95064, USA.
authors.forename: Shaowei
authors.initials: S
authors.lastname: Chen
authors.affiliation: Biocolloid and Fluid Physics Group, Applied Physics Department, Faculty of Sciences, University of Granada, Granada, Spain. rhidalgo@ugr.es.
authors.forename: Miguel Angel
authors.initials: MA
authors.lastname: Cabrerizo-Vilchez
authors.affiliation: Biocolloid and Fluid Physics Group, Applied Physics Department, Faculty of Sciences, University of Granada, Granada, Spain. rhidalgo@ugr.es.
authors.forename: Roque
authors.initials: R
authors.lastname: Hidalgo-Alvarez