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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 35: Poster Session II

CPP 35.24: Poster

Wednesday, March 29, 2023, 11:00–13:00, P1

Accelerating self-assembly of colloidal particles at air-water interface by laser induced heating of upconverting particle — •Lokesh Chinnakanna Muruga, Gokul Nalupurackal, Sresta Roy, Snigdhadev Chakraborty, Jayesh Goswami, and Basudev Roy — Indian Institute of Technology Madras, Chennai, India - 600036

Particles can be assembled at the air-water interface due to optically induced local heating. This induces convection currents in the water which brings particles to the surface. We improve the technique by employing an upconverting particle (UCP), which, when illuminated with 975 nm light, not only emits visible emission but also generates heat owing to the poor efficiency of the upconversion process. This induces strong convection currents which makes particles dispersed in the suspension assemble at the interface and immediately under the UCP. We show assembly of polystyrene particles of 1 µm diameter and diamonds of 500 nm diameter bearing Nitrogen-Vacancy (NV) centers around the UCP. We also show, for the first time, that the microdiamonds are assembled within about 30 nm at the bottom of the UCP by utilizing non-radiative energy transfer that reduces the lifetime of the 550 nm emission from about 90 µs to about 50 µs.