C₆₀ in Water:  Nanocrystal Formation and Microbial Response

Abstract

Upon contact with water, under a variety of conditions, C60 spontaneously forms a stable aggregate with nanoscale dimensions (d = 25−500 nm), termed here “nano-C60”. The color, hydrophobicity, and reactivity of individual C60 are substantially altered in this aggregate form. Herein, we provide conclusive lines of evidence demonstrating that in solution these aggregates are crystalline in order and remain as underivatized C60 throughout the formation/stabilization process that can later be chemically reversed. Particle size can be affected by formation parameters such as rates and the pH of the water addition. Once formed, nano-C60 remains stable in solution at or below ionic strengths of 0.05 I for months. In addition to demonstrating aggregate formation and stability over a wide range of conditions, results suggest that prokaryotic exposure to nano-C60 at relatively low concentrations is inhibitory, indicated by lack of growth (≥0.4 ppm) and decreased aerobic respiration rates (4 ppm). This work demonstrates the fact that the environmental fate, distribution, and biological risk associated with this important class of engineered nanomaterials will require a model that addresses not only the properties of bulk C60 but also that of the aggregate form generated in aqueous media.

Theoretical Framework for Nanoparticle Reactivity as a Function of Aggregation State

“…For example, UV-vis spectroscopy measurements with peak broadening between 400 and 500 nm indicate aggregation of C 60 primary particles. 29 In Table 3, C 60 aggregates producing the largest amount of singlet oxygen are given a relative production of 100% (b) while those suspensions producing no detectable ROS are indicated as O (0%). It is clear from these data that conditions favoring very small aggregates and or aggregates of lower fractal dimension correspond to higher measured ROS production, including cases where small aggregates are produced using surfactants or encapsulation agents.…”

Polysulfone ultrafiltration membranes impregnated with silver nanoparticles show improved biofouling resistance and virus removal

“…Although fullerene molecules are hydrophobic and relatively insoluble, they can be dispersed in solution over long periods of stirring or sonication, thus being made bioavailable to bacteria in suspension (Former et al, 2005;Lyon et al, 2005a). An aqueous dispersion of C6o (nC6o) is essential for utilization of its antibacterial effects.…”

“…For example, fullerenes in Luria-Bertani broth will precipitate out of solution or be coated by proteins present in the media, thus becoming unavailable for interactions with bacteria (Former et al, 2005). Therefore, a minimal media was chosen for the following study.…”

Aqueous stability and mobility of C60 complexed by sodium dodecyl benzene sulfonate surfactant

“…Before the preparation of SDBS-complexed C 60 colloid, C 60 colloid was prepared employing the method of Fortner et al (2005) with modifications. 0.02 g C 60 was added to 400 mL THF and N 2 was sparged to remove oxygen.…”