Sensing of biologically important cations such as Na(+), K(+), Ca(2+), Cu(2+), and Fe(3+) using magnetic nanoemulsions

• Published in: Langmuir 2013-04, Vol.29 (13), p.4252-4258
• Main Authors: Mahendran, V, Philip, John
• Format: Article
• Language: English
• Subjects: Calcium - chemistry; Cations - chemistry; Copper - chemistry; Emulsions - chemistry; Iron - chemistry; Magnetite Nanoparticles - chemistry; Sodium - chemistry
• ISSN: 1520-5827
• DOI: 10.1021/la400502b

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.