An Experimental Investigation on the Stability of Gel-like Carbon dot Based Nanofluids

Highly photoluminescent gel-like carbon dots (G-CDs) have interesting applications in the fields of bio-sensing, thermofluids, and as photocatalysts to reduce water contaminants. G-CDs have been shown to be nontoxic and environmentally benign while exhibiting interesting characteristics as fluid additives. For additives like G-CDs to be effective, they need to stay suspended in the liquid medium. If they settle to the bottom, the positive benefits are lost, and the high-density lower region can experience adverse effects due to excessive particle loading. Many existing techniques are available to analyze suspension stability. However, most of these techniques are expensive and/or require specialized equipment. Moreover, these methods can be invasive and ultimately end up disturbing the suspension. Furthermore, these methods often focus on understanding the relation between colloidal stability and surface charge development through measuring the zeta potential, an indicator which is reported to be unsuitable while working with higher concentrations of nanomaterial in the colloidal suspension. To overcome the deficiencies of the traditional zetametry experiments, a novel, non-contact, non-invasive, quantitative, and economical experimental setup was deployed in this work to investigate the stability of G-CD nanofluids. The G-CD concentration is kept constant at 3wt%. Decane and small amount of water is used as dispersion media for the nanofluid in this study. Four different water concentrations of 1.5 wt%, 1 wt%, 0.75 wt% and 0.375 wt% are tested in this work. The results show the technique is both effective and inexpensive.