Strongly optical absorptive nanofluids and rheology in bonded fullerene C60 via poly(vinyl pyrrolidone) molecules in water

This study was performed to illustrate how a model grafting between C₆₀ and poly (vinyl pyrrolidone) PVP of small flocculates results in maximum optical absorption and rheology in a nanofluid in correlation to microstructure while C₆₀-content was varied in an ideal optical host of 40.0 g/L PVP in water. Broad absorption band observed in the 250–450 nm region in the π → π* C(sp²) electron transition in PVP-grafted C₆₀ of small assemblies indicate a cross-linking between the PVP and C₆₀ molecules in a complex structure. Above a threshold value of 11.2 μM C₆₀, a deviation from a linear Beer-Lambert law could arise from a solubilization capacity limit of PVP to solubilize C₆₀ molecules in a charge transfer (CT) C₆₀:PVP complex. A nearly 4 times enhancement in the shear viscosity (η) of PVP solution by raising the C₆₀-content by a factor ～15 explicitly divulges that insertion of C₆₀ helps in expanding the anchoring between two moieties in a C₆₀:PVP CT complex. As the imposition of shear force breaks the soft C₆₀:PVP complex into small nanostructures, the η-value relaxes slowly to the base value on increasing the shear rate from 10 to 100 s^?1. Synthesis of C₆₀:PVP nanofluid exhibiting such characteristics are useful for drug delivery, lubrication, antibacterial activity, and many biological applications.