Objective and task description
The objective is to study the evaporation of liquid droplet on slippery liquid infused porous surface (slippery surface) and apply it for surface enhanced Raman scattering (SERS).To detect extremely dilute analyte in a droplet, a common method is to dry the droplet and detect and concentrated analyte. However, the so-called coffee ring effect1 causes inhomogeneous deposition of analyte which undermines the detection performance. Recently developed slippery surface2 which holds lubricant oil in solid matrix can efficiently suppress coffee ring effect, and is promising for highly sensitive and highly uniform detection.
For even higher sensitivity, we add plasmonic nanoparticles such as gold nanoparticles in to the droplet to induce SERS (approach 1 in the figure)3, 4: when gold nanoparticles aggregate after drying, “hot spots” between particles are created which increases Raman signal of the analyte by several orders of magnitude. Therefore, SERS on slippery surface could achieve ultrahigh sensitivity, which we aim to realize in this project.
As another approach (approach 2 in the figure), we may also directly fabricate a slippery gold nanostructured surface, and evaporate the droplet on it. The lubricant on the slippery surface is subsequently dried. Analyte will sit in the gold nanostructures, giving SERS effect.
In this project, you will characterize the suppression of coffee ring effect on slippery surface, and characterize the aggregation of gold nanoparticles. Then using dye molecules with changing concentrations, you will characterize the enhancement of Raman signal. Approach 1 will be tested first, and if it does not work, approach 2 will be carried out.
Some of the skills and trainings which the student will obtain in this project, besides obtaining knowledge of coffee ring effect, slippery surface, Raman, SERS, and getting hands-on-experience in performing experiments, are:
- Operating Raman instrument, and perform SERS measurement
- Fabricating slippery surface substrate.
- Working with optical microscope.
- Dr Jun Gao, Meander 160, tel. 1239
2. Wong T-S, Kang SH, Tang SKY, Smythe EJ, Hatton BD, Grinthal A, Aizenberg J Nature 2011, 477, 443.
4. Yang S, Dai X, Stogin BB, Wong T-S Proceedings of the National Academy of Sciences 2016, 113, 268.