Pure blue light emitting quantum dots made from indium, phosphorous and sulphur precursors. Credit: Pradyut Roy at IISER, Pune

Chemists have synthesised a unique type of core-shell quantum dot capable of emitting pure blue light in a solid state and solution1. Each dot has a core of indium phosphide surrounded by a thin shell of zinc sulphide.

The quantum dots do not contain toxic metals and could be used for imaging live cells and making solid-state display devices, says a team at the Indian Institute of Science Education and Research in Pune.

Most existing quantum dots contain toxic metals such as cadmium and lead, which limits their use in electronic and medical devices. The scientists produced the safer core-shell quantum dots using a combination of indium, phosphorous and sulphur precursors, leading to uniform growth of the dots.

The team, led by Pramod P. Pillai, found that each shell around a dot has three monolayers. The dots emitted pure blue light in organic solution and in water. They did not degrade after being exposed to ultraviolet light for 10 hours.

Almost 95% of specific human cells survived exposure to a high concentration of the quantum dots, demonstrating their biocompatibility. The dots emitted blue light even inside the biological cells.

The researchers say the emission from the new quantum dots did not interfere with the emission from commercially available imaging agents. This indicates that the dots could be used for multicolour bioimaging studies, they add.