Safer nanoparticles for inks and pigments

Nanoparticles are tiny particles measuring between 1 and 100 nanometres (by comparison, human hair is 80 000 nanometres wide). As a bridge between bulk materials and atomic molecules, nanoparticles have unique properties and countless applications ranging from medicinal to electronic.

Along with exciting possibilities, however, comes the risk associated with highly-reactive particles that are small enough to pass through cell membranes. The ink and pigment industry, for example, uses potentially toxic nanoparticles including titanium dioxide (TiO2), zinc oxide (ZnO), silver (Ag) and nanostructures called “quantum dots”.

The EU-funded NANOMICEX (Mitigation of risk and control of exposure in nanotechnology based inks and pigments) initiative assessed the risks of producing and handling nano-based inks and pigments, and developed safer alternatives. Their studies revealed that ZnO, Ag and nanocomposite quantum dots are potentially hazardous to workers.

To reduce their toxicity, researchers modified the nanoparticles’ surfaces. They did this by attaching a protein called bovine serum albumin onto silica-coated ZnO, and by coating quantum dots with glucose.

None of their attempted modifications to Ag worked, however, and they established that its toxicity stemmed from its very small size (just a few nanometres). NANOMICEX concluded that Ag nanoparticles should be made larger to reduce their toxicity to cells.

Another important consideration for NANOMICEX was whether workers are exposed to airborne nanoparticles in pigment and ink factories. Researchers found that workers handling powdered materials were at risk from breathing in the nanoparticles; however respirators, filters and protective clothing provided good protection.

NANOMICEX conducted four case studies to test whether these nanoparticle modifications and safety protocols could be implemented on an industrial scale. They found that their ZnO and quantum dot modifications were safe, cost-effective and did not affect the nanoparticles’ important properties. These nanomaterials are therefore suitable for industrial-scale manufacture of pigments and inks.

NANOMICEX’s safety measures will improve European competitiveness in the ink and pigment industry, while improving the health of workers exposed to nanoparticles.