The experimental cell shown in Figure and Figure was fit onto the stage of an inverted microscope (IX50, Olympus) and filled with the external aqueous electrolyte solution (0.1 M NaCl and 10 mM PB, pH 7 for liposome studies and 0.1 M NaCl, 10 mM PB (pH 7), 0.1% SDS, and 0.1 % Triton X-100 for PS studies). The SDS and Triton X-100 surfactants were needed to prevent the PS particles from irreversibly adsorbing onto the nanopipette surface. The nanopipette was filled with the same electrolyte as the external electrolyte solution. The internal Ag/AgCl electrode and fiber optic cable (405-532nm Single Mode Patch Cable, Thorlabs) was inserted into the back of the nanopipette using a SMA Opto-pipette holder attached to a SMA dovetail fiber holder (HEKA Elektronik). The optical fiber was positioned ~ 1 mm from the end of the nanopipettes tip. The pipette holder was attached to a micromanupliator (MP-225, Sutter Instruments) and positioned over the microscope objective (LCPlanFl 40x/0.60 na, Olympus). A fiber coupled laser source (Agiltron) was used to deliver the 488 nm excitation light at 2 mW power through the fiber optic. A 500 nm high-pass emission filter was used in the inverted microscope to block light below 500 nm, including the 488 nm excitation light, from reaching the detector. The entire experimental setup was placed inside of a large grounded Faraday cage.