Core–Shell Particles for Simultaneous 3D Imaging and Optical Tweezing in Dense Colloidal Materials

Core?shell particles for simultaneous 3d imaging and optical tweezing in dense colloidal materials were studied. In the first stage, a core particle is coated by a relatively low concentration of hydrolyzed 3-trimethoxysilyl propyl methacrylate (hTPM) under basic condition to form evenly sized lobes on the surface of the core particle. In the second stage, the TPM nucleates on the surface of the raspberry particle and rapidly coalesces, resulting in raspberry particles with the interstitial spaces between the lobes filled with unpolymerized TPM oil. The different stages of the synthesis can be directly observed using brightfield microscopy. The two-step mechanism and core?shell morphology is furthermore demonstrated using selective fluorescent labeling of the particle at the various stages of the synthesis. By dragging a core?shell particle through a dense colloidal crystal, the unique capability of our new colloidal system for performing quantitative 3D confocal imaging while simultaneously optically trapping was demonstrated.