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Singapore scientists discover new synthetic strategy to control ultra-small luminescent nanocrystals

02 Mar 2010

Dr Lim Chin Seong of the ASTAR Data Storage Institute; Assoc Prof Hong Minghui who is under a joint appointment with the NUS Department of Electrical & Computer Engineering and ASTAR Data Storage Institute; Dr Liu Xiaogang from the NUS Department of Chemistry; Dr Chen Hongyu from NTU; Dr Zhang Chun of NUS Department of Chemistry and Physics; Dr Wang Feng of NUS Department of Chemistry; Mrs Wang Juan of the NUS Department of Chemistry; Dr Xu Jun from NTU and Dr Lu Yunhao of NUS Department of Physics.
Singapore scientists from NUS, the Agency for Science, Technology and Research (A*STAR), NTU and King Abdullah University of Science and Technology (KAUST) have discovered a new synthetic strategy for controlling the properties of ultra-small luminescent nanocrystals. Their findings have been published in the prestigious Nature journal on 25 February 2010.

Over the past decade, upconversion nanocrystals have attracted significant research interest for their ability to convert lower-energy near-infrared light into a visible emission. Upconversion nanocrystals are used in a wide variety of imaging devices for the biomedicine and life science fields.

"The discovery is fundamentally important for a better understanding of crystal growth process. In addition, it provides a convenient method for controlled preparation of ultra-small luminescent nanocrystals that could find applications ranging from biological labelling and volumetric 3D graphic displays," said Dr Liu Xiaogang of the NUS Department of Chemistry.

NUS researchers Dr Liu Xiaogang, Dr Zhang Chun, Dr Wang Feng, Dr Lu Yunhao and Ms Wang Juan worked with Assoc Prof Hong Minghui (under an NUS Department of Electrical & Computer Engineering and A*STAR Data Storage Institute joint appointment) and Dr Lim Chin Seong from A*STAR Data Storage Institute to carry out this study. The team's research is sponsored by A*STAR and supported by NUS, the Singapore-MIT Alliance and the Ministry of Education.

The team of scientists made it possible to simultaneously control the size, structure and colour emission of nanocrystals and at the same time, drastically reducing the required reaction time (from several days to less than two hours) and reaction temperature from 300 to 230 degrees Celsius. The dramatically shortened reaction time and lowered reaction temperature would potentially lead to substantial cost and energy savings in the expensive process of manufacturing nanocrystals.

In addition, the new technique pioneered by the team makes it possible to do away with the need to use hazardous metals or solvents, making it a more environmentally friendly method in comparison with existing methods.

On the applications of the research, Dr Liu shared that the development of upconversion nanocrystals capable of converting near-infrared light into visible range provides an opportunity for the utilisation of these nanomaterials in photodynamic therapy. These nanocrystals could be excited by near-infrared radiation which can penetrate deep inside biological tissues. Photodynamic therapy is used in treatment of a wide variety of cancers as well as age-related macular degeneration.