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Home > News > The challenge of creating visible and nontoxic nanomaterials for sensing

November 2nd, 2007

The challenge of creating visible and nontoxic nanomaterials for sensing

Nanotechnologies opened a new door towards the development of novel techniques and devices for probing biological systems such as biomolecules and single cells. The most reliable bioprobes today rely on fluorescent or radioactive labeling. Phosphorescent emitters are preferable for use in sensing or biological labeling schemes because the emission occurs over a very long timescale (for nanoscientists, 'very long timescale' is a relative term; here we are talking about 1 microsecond). Especially semiconductor nanocrystals (quantum dots) possess several properties that make them very attractive for fluorescent tagging: broad excitation spectrum, narrow emission spectrum, precise tunability of their emission peak, longer fluorescence lifetime than organic fluorophores and negligible photobleaching. Scientists have discovered that these nanocrystals can enable researchers to study cell processes at the level of a single molecule and may significantly improve the diagnosis and treatment of diseases such as cancers. However, the band gap of most emissive semiconductors, with the exception of cadmium-containing materials, is either too high or too low to easily make visible emitting quantum dots. Unfortunately, cadmium is quite toxic and therefore not really suitable for medical applications. In a step towards circumventing the issues with cadmium toxicity, researchers have make progress in demonstrating visible phosphorescence from doped nanocrystal systems. A recent example is the synthesis of a nanoscopic material composed of the non-toxic elements zinc, selenium, sulfur and manganese which displays efficient visible emission.


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