76th Annual Gaseous Electronics Conference
Volume 68, Number 9
Monday–Friday, October 9–13, 2023;
Michigan League, Ann Arbor, Michigan
Session HT3: Plasma Nanotechnology
1:30 PM–3:30 PM,
Tuesday, October 10, 2023
Room: Michigan League, Michigan
Chair: Satoshi Hamaguchi, Osaka University, Japan
Abstract: HT3.00007 : Plasma assisted synthesis of tunable luminescent carbon nanomaterials
3:00 PM–3:15 PM
Abstract
Presenter:
Sankhadeep Basu
(Michigan State University)
Authors:
Sankhadeep Basu
(Michigan State University)
Tanvi Nikhar
(Michigan State University)
Sergey V Baryshev
(Michigan State University)
Rebecca Anthony
(Michigan State University)
Luminescent semiconductor quantum dots (QDs) have attracted wide attention due to their multimodal abilities to absorb and emit light, perform photo- and electro-catalysis, and more. These materials can exhibit unique properties belonging to their nanoscale building blocks, as well as ensemble behavior at the micro- or macro-scales. However, typical semiconductor QDs contain toxic heavy metals which are not always environmentally friendly – hence, non-toxic and benign QDs like carbon nanomaterials are preferred for practical applications. In the present study luminescent carbon QDs are synthesized in a non-thermal plasma reactor using methane and argon as the reactant species. Radiofrequency power at 13.56 MHz was supplied through ring electrodes to a flow-through reactor tube held at 4.7 Torr. The QDs formed in the plasma were deposited onto arbitrary substrates via inertial impaction. The synthesized material was characterized using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Raman spectroscopy, and UV-Vis optical absorption. X-ray Diffraction revealed the presence of broad graphite peak around 2θ = 24º. The same was corroborated from the TEM micrographs which also showed the average QD diameter to be around 5 nm. Raman spectra exhibited sharp D and G peaks as expected from carbon nanostructures. The UV-Vis absorption spectrum showed a peak around 278 nm , which has been correlated with the ∏ -> ∏* transition of the carbon aromatic rings. On ultraviolet excitation of the carbon quantum dots suspended in toluene, the photoluminescence emission peak comes around 500 nm (green region of the visible spectrum) which can then be red shifted by changing the size of the crystalline core. On adding hydrogen to the gas mixture, we observed that the PL emission intensity increased remarkably, possibly due to passivation of the defect states on the surface with a simultaneous change in emission wavelength. Finally, we found the carbon QD samples to be hydrophobic with a water contact angle of 135º due to the surface C-H bonds, further illustrating their multifunctionality. These exciting properties signify the future prospects for plasma-produced carbon QDs in LEDs, circuits, coatings, and more.