Low energy, nanosecond pulsed, bullet-like plasma plumes are generated with a concentric, tubular electrode-based device energized by unipolar ±6 kV, 140 ns pulses. The plasma plumes consist of ionization fronts propagating away from both electrodes at speeds of the order of 107 cm s−1, indicating photoionization may dominate the plasma formation and propagation process. The polarization of the transient electric field near the device nozzle exit affects the dynamics of the plasma plumes, resulting in differences in the plume length and propagation velocity. Although closely analogous to typical streamers, the plasma ‘bullets’ maintain unique characteristics in plasma initiation and formation.

To add to the understanding of the properties of functionalized carbon nanotubes in biological applications, we report a monotonic pH sensitivity of the intracellular fluorescence emission of single-walled carbon nanotube-fluorescein carbazide (SWCNT-FC) conjugates in human ovarian cancer cells. Light-stimulated intracellular hydrolysis of the amide linkage and localized intracellular pH changes are proposed as mechanisms. SWCNT-FC conjugates may serve as intracellular pH sensors.