title: Sensing of biologically important cations such as Na(+), K(+), Ca(2+), Cu(2+), and Fe(3+) using magnetic nanoemulsions.
abstract: We report a simple approach to the ultrasensitive detection of biologically important metal ions using a magnetic nanoemulsion. The nanoemulsion used in our study was an oil-in-water emulsion droplet of average size ∼190 nm containing ferrimagnetic iron oxide nanoparticles of average size ∼10 nm. In a static magnetic field, the emulsion droplets self-assemble into a nanoarray with distinct interdroplet spacing. In the presence of cations in the solution, the nanofluid array shows a large blue shift in the diffracted Bragg peak and a visually perceivable color change due to changes in the electrical double layer upon the diffusion of cations. The colloidal force-distance measurements in the presence of cations show large variations at the onset of repulsion in the presence of cations. The sensor shows good selectivity to Na(+), K(+), Ca(2+), Cu(2+), and Fe(3+) ions and offers a rapid response compared to conventional techniques. This approach can be useful for the recognition of biologically important cations.
authors.affiliation: SMARTS, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, TamilNadu, India.
authors.forename: V
authors.initials: V
authors.lastname: Mahendran
authors.forename: John
authors.initials: J
authors.lastname: Philip
mesh_terms: D002118:Calcium / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D003300:Copper / Q000737:chemistry*; D004655:Emulsions / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry*
chemical_list: D002412:Cations; D004655:Emulsions; D058185:Magnetite Nanoparticles; D003300:Copper; D012964:Sodium; D007501:Iron; D002118:Calcium