Targeted Raman Imaging of Cells Using Graphene Oxide-Based Hybrids.

Graphene oxide (GO) is a reliable and multifunctional platform to perform cell imaging. In this work, a controllable Pt-seed-mediated method is used to prepare GO/gold nanoparticle (AuNP) hybrids, and after the covalent binding of folic acid (FA), GO/AuNP/FA hybrids are prepared. Selective labeling and Raman imaging of folate receptor (FR)-positive HeLa cells are realized using such GO-based hybrids. In this system, FA is the targeting agent, AuNPs work as surface-enhanced Raman scattering substrates, and GO takes the role of both supporting the AuNPs with FA and acting as a Raman probe. This research further extends the application of GO as a multifunctional platform in bioimaging and other biomedical processes.

Radiation pressure of active dispersive chiral slabs.

We report a mechanism to obtain optical pulling or pushing forces exerted on the active dispersive chiral media. Electromagnetic wave equations for the pure chiral media using constitutive relations containing dispersive Drude models are numerically solved by means of Auxiliary Differential Equation Finite Difference Time Domain (ADE-FDTD) method. This method allows us to access the time averaged Lorentz force densities exerted on the magnetoelectric coupling chiral slabs via the derivation of bound electric and magnetic charge densities, as well as bound electric and magnetic current densities. Due to the continuously coupled cross-polarized electromagnetic waves, we find that the pressure gradient force is engendered on the active chiral slabs under a plane wave incidence. By changing the material parameters of the slabs, the total radiation pressure exerted on a single slab can be directed either along the propagation direction or in the opposite direction. This finding provides a promising avenue for detecting the chirality of materials by optical forces.