Dr Gary Wong (right) and Professor Rick Wong (left) find that the short metal-to-metal distance is a crucial parameter for the up conversion process in the study.


黃嘉良博士(右)與黃偉國教授(左)成功發現這段鉺金屬間的超短距離,是引發分子間的「上轉換」現象的關鍵。

Date: 12 Sep 2016 (Monday)

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HKBU and French scholars jointly publish research on energy conversion in "Nature Communications"

浸大與法國學者研能量轉換新現象     論文刊登於《自然-通訊》期刊

A team of Chemistry scholars from HKBU and their research collaborators in France jointly announced the outcome of their research project entitled “Room temperature molecular up conversion in solution”. The paper which demonstrates that the photon up conversion process in energy transfer can be achieved through a molecular level at room temperature was published in leading scientific journal Nature Communications (http://www.nature.com/ncomms/2016/160615/ncomms11978/full/ncomms11978.html).

The HKBU team comprises Associate Professor Dr Gary Wong; Vice President (Research and Development) and Chair Professor of Chemistry Professor Rick Wong; and PhD alumnus Dr Chan Chi-fai. Meanwhile, the French research team is led by Professor Loic J Charbonniere of L’Université de Strasbourg, France.

This study reveals that fluoride anions added to a D2O solution of a macrocyclic erbium complex (ErL) leads to the formation of a supramolecular [(ErL)2F]+ assembly which is able to convert low energy photons to high energy photons through a process known as “up conversion”. The structure has the fluoride anions sandwiched between two complexes and held by different chemical bonds.

Dr Gary Wong said, “Conventionally, luminescence processes often result in the emission of photons at a lower energy level than that of the incident beam, but up conversion process is far less common.”

Professor Rick Wong said, “This breakthrough revealed that there is a way to excite our supramolecule with a near-infrared light source and that it gives off green emission at a molecular level.” Near-infrared light is considered less phototoxic to the human skin and produces green emission that can be easily detected using microscopes in laboratories.

In the past few decades, the up conversion process has attracted great scholarly interest. However, it can only be observed at low temperatures or high complex concentration or by high power excitation. The erbium complex dimer in the study revealed that the short metal-to-metal distance is a crucial parameter for the up conversion process to occur without harsh experimental conditions mentioned above. However, such a short distance is attributed to various chemical bonds like erbium-to-fluoride bond, hydrogen bonds and aromatic interaction.

Dr Wong added that future developments on the structure and compositions of such complexes could lead to similar observations in non-deuterated water, hence marking the beginning of luminescence tagging in numerous bio-analytical applications.

浸會大學化學系的研究團隊與法國的研究小組,成功發現分子間的「上轉換」現象,並發表「分子於室溫溶液中的上轉換現象」的論文。該論文刊登於國際權威科學期刊《自然-通訊》(http://www.nature.com/ncomms/2016/160615/ncomms11978/full/ncomms11978.html)。

浸大的研究團隊由化學系副教授黃嘉良博士、副校長(研究及拓展)及化學系講座教授黃偉國教授、校友陳智輝博士等組成。法國的研究小組則由斯特拉斯堡大學Loic J Charbonniere教授帶領。

是次研究利用在氧化氘溶液中增加氟陰離子,從而令鉺複合物成為鉺超分子。這個超分子的結構由兩個鉺複合物通過不同的化學鍵將氟陰離子包在其中,它可以將低能量的光子轉化為高能量光子,即是一般稱為「上轉換」的現象。

黃嘉良博士說:「熒光分子的發光過程一般是通過光子從高能量轉化為低能量後所釋放的光能,但上轉換的過程則完全相反的,亦較為罕見。」

黃偉國教授說:「我們發現的超分子可以將能量較低的近紅外光轉化為能量較高的綠光,於分子層面來說算是一大突破!」近紅外光對人類皮膚較低光毒性,而所釋放的綠光亦只需使用實驗室顯微鏡便可觀察到。

在過去的數十年中,「上轉換」現象對科學界引起極大迴響,但這個現象只可以在極低溫或高強度激光的情況下才可觀察得到。而這個研究中的鉺複合物則不須於上述的嚴格情況下就可以觀察得到「上轉換」現象,因為當中的兩個鉺金屬之間被不同的化學鍵所吸引,例如鉺和氟的離子鍵,氫鍵和芳香環交互作用,而這段鉺金屬之間超短距離就是引發「上轉換」現象的關鍵。

黃博士補充說,研究人員更可以透過改良這種複合物的結構和成份,令日後不用於氘溶液中也可以觀察到「上轉換」現象,在生物分析的科技中,為熒光標記的應用展開新一頁。