Studies designed to investigate the environmental or biological interactions of nanoscale materials frequently rely on the use of ultrasound (sonication) to prepare test suspensions. However, the inconsistent application of ultrasonic treatment across laboratories, and the lack of process standardization can lead to significant variability in suspension characteristics. At present, there is widespread recognition that sonication must be applied judiciously and reported in a consistent manner that is quantifiable and reproducible; current reporting practices generally lack these attributes. The objectives of the present work were to: (i) Survey potential sonication effects that can alter the physicochemical or biological properties of dispersed nanomaterials (within the context of toxicity testing) and discuss methods to mitigate these effects, (ii) propose a method for standardizing the measurement of sonication power, and (iii) offer a set of reporting guidelines to facilitate the reproducibility of studies involving engineered nanoparticle suspensions obtained via sonication.

Suspensions of natural graphite particles were prepared in an aqueous medium using carboxymethyl cellulose (CMC) and emulsified styrene-butadiene copolymer latex as part of an environmentally friendly fabrication process for graphite anodes (negative electrodes) intended for application in Li-ion batteries. Suspensions were characterized by adsorption isotherms, electroacoustic measurements, rheology and sedimentation tests, at two different degrees of carboxymethyl substitution (DS) on CMC. A lower DS value (0.7) resulted in greater uptake of CMC on graphite compared with a higher DS value (1.28). This was attributed to attractive hydrophobic interactions associated with the lower carboxymethyl substitution. The greater adsorption for <mml:math display="inline"><mml:mrow><mml:mi>DS</mml:mi><mml:mo>=</mml:mo><mml:mn>0.7</mml:mn></mml:mrow></mml:math>DS=0.7 correlates with lower relative viscosity in concentrated graphite suspensions, a higher adhesion strength with a copper substrate, and a greater retention of discharge capacity after cycling. The effect of DS is attributed to differences in the aqueous dispersion properties and stability of graphite suspensions. Based on these results, we fabricated high-capacity graphite negative electrodes characterized by gravimetric and volumetric energy densities of greater than <mml:math display="inline"><mml:mrow><mml:mn>340</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mA</mml:mi><mml:mi mathvariant="normal">h</mml:mi><mml:mo>∕</mml:mo><mml:mi mathvariant="normal">g</mml:mi></mml:mrow></mml:math>340mAh∕g and <mml:math display="inline"><mml:mrow><mml:mn>560</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mi>mA</mml:mi><mml:mi mathvariant="normal">h</mml:mi><mml:mo>∕</mml:mo><mml:msup><mml:mi>cm</mml:mi><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>560mAh∕cm3 , respectively. This formulation also led to improved adhesion strength, giving the as-fabricated cell an attractive cycle life greater than 90% of initial discharge capacity after <mml:math display="inline"><mml:mrow><mml:mn>200</mml:mn><mml:mspace width="0.3em"></mml:mspace><mml:mtext>cycles</mml:mtext></mml:mrow></mml:math>200cycles .