Novel Nanocrystals With Advanced Optical Properties Developed For Use As Luminescent Biomarkers

Upconversion emission materials are ideal for bioimaging due to its effectiveness as contrast agents for the detection of cancer cells, more so when the background emission of non-cancerous tissues can be minimised. These materials could be used as biomarkers for luminescent labeling of cancerous cells. Opaque tissues can be turned into glassy, transparent substances by using these biomarkers which rely on near-infrared excitation. The Singapore research team led by Associate Professor Xiaogang Liu and its co-researchers from Saudi Arabia and China succeeded in developing an efficient upconversion process in nanoparticles, ensuring a broad tunability of light emission that could be used in imaging applications. They found a chemical structure that can exhibit efficient upconversion properties through a special arrangement of energy levels. Their synthesis of lanthanide-doped core-shell nanocrystals which resulted in advanced optical properties that can control light, proved to be a novel approach.

For sensing applications, separating optical signals from the background can be tricky when the signal and noise occur at the same wavelength. This problem can be solved with upconversion -- a nonlinear optical process -- where two low-energy photons of an incident beam can be converted into a single photon of higher energy, which can then be easily distinguished from the background.

The ability to convert light using these nanomaterials for heating also offers promising applications in photodynamic therapy and drug delivery.

The work of Assoc Prof Liu and team was reported in Nature Materials on 23 October 2011. His team comprises research fellow Dr Feng Wang and graduate students Renren Deng and Juan Wang from the National University of Singapore's (NUS) Department of Chemistry. They worked alongside researchers from King Abdullah University of Science and Technology and Fujian Institute of Research on the Structure of Matter. Assoc Prof Liu and Dr Feng Wang are also scientists at the Institute of Materials Research and Engineering (IMRE), a research institute of Singapore's Agency for Science, Technology and Research (A*STAR).

The published research work was funded by Singapore's A*STAR and Ministry of Education.