Highly Efficient Near-Infrared Photothermal Conversion of a Single Carbon Nanocoil Indicated by Cell Ejection

Carbon nanocoil (CNC), which has excellent properties of near-infrared (NIR) absorption and photoelectrical response, is considered as a potential NIR sensing and bioengineering material. In this work, a high-speed living cell ejection is realized in a yeast cell solution based on the photothermal conversion induced by a NIR laser irradiation on the surface of a CNC. The cell ejection reveals a thermal convection of solution induced by the laser irradiated CNC and can be used to evaluate the photothermal conversion ability of CNC. The dynamic behavior of the thermal convection behind cell ejection is studied experimentally and analytically. It is found that the initial solution flow velocity of the dynamic process reaches more than 10³ μm/s. Approximately, 60% of the laser energy illuminated on the CNC is converted into thermal energy. The unique helical morphology of CNC enables its high NIR photothermal conversion efficiency. The average convective heat transfer coefficient on the contact area between CNC and surrounding water is deduced to be as high as 7.0 × 10⁵ W/(m²·K). These results indicate that CNC has promising potential applications on microfluidics, laser-operated flow cytometers, bioparticle ejection, and micro-/nano-laser-operated heat generators and exchangers.