聲化學法合成螢光金奈米團簇之機制探討

近年來奈米螢光探針廣泛被應用在生醫診斷，而螢光探針中的螢光金奈米團簇具有生物相容性及光學特性等的優點，引起了學者們的研究興趣。螢光金奈米團簇合成方式很多，本研究團隊先前曾提出了一個螢光金奈米團簇創新簡易製備法，使用三氯化金(AuCl3)與甲苯(Toluene)合成藍色螢光金奈米團簇，並且使用超音波調控螢光金奈米團簇的螢光特性。目前仍然相關研究指出甲苯與三氯化金反應可以產生螢光金奈米團簇，所以本研究擬深入探討及驗證藍色螢光金奈米團簇的合成機制，以高解析電子能譜儀(HR-XPS)、核磁共振波譜儀(NMR)來鑑定此種螢光物質的組成成分及結構，並探討不同的超音波參數(時間、強度、自由基、熱效應)對於螢光金奈米團簇光學特性的影響。本研究的實驗結果證明了三氯化金與甲苯的合成藍色螢光金奈米團簇的步驟如下，(1)三氯化金介導甲苯金化反應形成氯化金(AuCl)，(2)氯化金經由歧化反應而產生Au0 和AuIII，(3)甲苯吸附於金奈米團簇表面進而穩定該結構並且發出藍色螢光。除此之外，本研究發現使用強度大的探針式超音波產生器可以使甲苯與三氯化金的螢光產生更大幅度的紅位移(453nm~510nm)，而且超音波的熱效應對於螢光特性調控是必須的條件。利用X射線光電子能譜(XPS) 分析金奈米團簇得到Au4f7/2為83.27eV可以證明其核心為金所組成，而核磁共振氫譜(1H-NMR)在6~8ppm的訊號可以證明金奈米團簇表面具有芳香族的分子。最後，利用兩性高分子披覆與溴化十六烷基三甲銨將有機相螢光金奈米團簇成功改質到水相，並且保有其原本的螢光特性，可以使這種合成方法簡單的有機相螢光金奈米團簇未來可以廣泛應用於廣泛應用在生醫標定、細胞追蹤、分子檢測等領域。

關鍵字

聲化學；奈米團簇；金；螢光

並列摘要

Researches on fluorescent semiconductor nanocrystals, also known as quantum dots, have shown tremendous advances over the past ten years in areas ranging from pure materials science to biological applications. However, most quantum dots are made of cadmium-based or lead-based materials, which contain toxic heavy metals and are therefore potentially harmful for environment. There are already some promising candidates for ‘greener’ quantum dots, such as semiconductors alternatives, metallic, carbon-based and silicon nanoparticles. The fluorescent properties and non-toxicity of Au nanoclusters make them to be one of powerful materials for biomedical probes. There are a lot of synthesis methods of fluorescent gold nanoclusters. Rescently, we proposed a novel method for fluorescent gold nanoclusters synthesis using gold (III) chloride (AuCl3) and toluene with ultrasound for fluorescence control. The purpose of this study would like to investigate the mechanism of fluorescent gold nanoclusters synthesis. Firstly, the fluorescent clusters composition and structure were identified with X-ray photoelectron spectrometer (XPS) and Nuclear magnetic resonance spectroscopy (NMR). Secondly, the relationship among the different ultrasound parameter (irradiation time, intensity, free radical, thermal effect), composition, structure and fluorescent properties of clusters were explored. Thirdly, the fluorescent gold nanoclusters were transferred into aqueous phase with amphiphilic polymer, and tested their photophysical properties. The results showed that (1) The forming of AuCl through the auration of toluene is mediated by AuCl3. (2) Au0 and AuIII are generated by the disproportionation of AuCl (3) The fluorescent gold nanoclusters are stabilized by aromatic compounds such as toluene with chemical adsorption. The red-shift value is varied with the ultrasound frequency and intensity such as the sonicator xl 4000 have lager photoluminescent red-shift (453nm to 510nm) than ultrasound cleaning baths (453nm to 492nm). The thermal effect of ultrasound is a necessary condition for gold nanoclusers synthesis and fluorescent control. The core structure of fluorescent nanoclusters is Au which is verified with X-ray photoelectron spectrometer (XPS) showing the Au signal of 4f 7/2 at 83.27eV. The aromatic groups attaching on the Au shell is evidenced by the Nuclear magnetic resonance spectroscopy (1H NMR) showing a broad signal at 6-8ppm. The organic phase of fluorescent gold nanoclusters can be transferred into water soluble phase easily through our polymer coating methods and could be conjugated with specific biological molecules for celluar and molecular labeling. The mechanism exploring here will be very useful on fluorescent nanoclusters synthesis and their fluorescence control, and the methods for greener probes will be developed more and more to improve our human helth in the future.

並列關鍵字

fluorescent ； gold ； nanoclusters ； sonochemistry

參考文獻

1. Cao, Y. C., Nanomaterials for biomedical applications. Nanomedicine 2008, 3 (4), 467-469.

2. Wang, F.; Tan, W. B.; Zhang, Y.; Fan, X. P.; Wang, M. Q., Luminescent nanomaterials for biological labelling. Nanotechnology 2006, 17 (1), R1-R13.

5. Chatterjee, D. K.; Gnanasammandhan, M. K.; Zhang, Y., Small Upconverting Fluorescent Nanoparticles for Biomedical Applications. Small 2010, 6 (24), 2781-2795.

6. Lin, C. A. J.; Lee, C. H.; Hsieh, J. T.; Wang, H. H.; Li, J. K.; Shen, J. L.; Chan, W. H.; Yeh, H. I.; Chang, W. H., Synthesis of Fluorescent Metallic Nanoclusters toward Biomedical Application: Recent Progress and Present Challenges. J. Med. Biol. Eng. 2009, 29 (6), 276-283.

7. Zhai, C. X.; Zhang, H.; Du, N.; Chen, B. D.; Huang, H.; Wu, Y. L.; Yang, D. R., One-Pot Synthesis of Biocompatible CdSe/CdS Quantum Dots and Their Applications as Fluorescent Biological Labels. Nanoscale Res. Lett. 2011, 6.

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聲化學法合成螢光金奈米團簇之機制探討

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