Organic solvents are routinely used as a dispersing medium in liquid phase exfoliation (LPE) approaches in which layered crystals are exposed to ultrasonication to form nanosheets. In such approaches, it is presumed that ultrasonication only acts upon the layered crystals, and has no bearings whatsoever on the organic solvents. However, we show that ultrasonication does affect the organic solvents - it transforms the organic molecules into photoluminescent carbon quantum dots (CQDs)! Although, in retrospect, this insight is intuitive, it has remained unacknowledged in the design of experiments that involve ultrasonication of organic solvents. For example, the optical properties of dispersions obtained by LPE methods have always been attributed to the nanosheets derived from layered crystals. We show that the optical properties of such dispersions also carry a signature from the concomitantly formed CQDs. We also present insights on how the organic solvents transform into CQDs and an in-depth analysis of the morphological, chemical, optical, and photoluminescent properties of the CQDs. Thus, through this poster we hope to add to the existing body of knowledge about LPEs and draw attention to the fact that there is more than what meets the eye when it comes to inferring the optical properties of nanomaterial dispersions produced by these methods.

Transformation of organic solvents into photoluminiscent carbon quantum dots during liquid phase exfoliation assisted by ultrasonication: An unexpected discovery

ACS Spring Meeting 2021

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