PHOTOLUMINESCENT GOLD QUANTUM CLUSTERS: A PROMISING CLASS OF NOVEL IMAGING TOOLS
BALÁZS SÖPTEI1*, IMOLA CSILLA SZIGYÁRTÓ1, LÍVIA NASZÁLYI NAGY1, PÉTER BARANYAI1, FERENC HUDECZ2, GÁBOR MEZŐ2, ILDIKÓ SZABÓ2, ATTILA BÓTA1 1 RESEARCH CENTRE FOR NATURAL SCIENCES, HUNGARIAN ACADEMY OF SCIENCES 2 INSTITUTE OF CHEMISTRY, EÖTVÖS LORÁND UNIVERSITY *e-mail: soptei.balazs@ttk.mta.hu
About gold quantum clusters Gold quantum clusters (GQCs) are particles with an organized structure at the sub-nanometer level. The behavior of GQCs is rather different from that of bulk gold and classical gold nanoparticles (GNPs), which is a consequence of unusual lattice characteristics and the dominance of aurophilicity.
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emission (nm)
Figure 1/1. Photo of GOQC suspension under UV lamp (lexcitation = 365nm); inset shows emission spectrum of the product
Gold Red Quantum Clusters (GRQCs) Protein and peptide based synthesis lemission is tunable in the range of 610-650nm P L In ten s ity (a. u .)
P L In ten s ity (a. u .)
Gold Orange Quantum Clusters (GOQCs) Amino acid based synthesis lemission = 585nm
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emission (nm)
Figure 2/1. Photo of GRQC suspension under UV lamp (lexcitation = 365nm); inset shows emission spectrum of the product
Optical properties One of the unique characteristics of gold quantum clusters is their high photostability under UV excitation. Another one is their emission lifetime, which is in the microsecond scale, and has been attributed to the energy I transfer between Au species. t1 (ms)
a1
t2 (ms)
a2
GOQCs
1.2
0.6
5.5
0.4
GRQCs
0.9
0.3
2.7
0.7
Table 1. Emission lifetime values (t) and preexponential constants (a) of gold quantum clusters in phosphate buffered saline
Due to their structure, GQCs show different plasmonic behavior compared to GNPs. A b s o rb an ce
Figure 3/1. UV-Visible spectra of GNPs (purple), GRQCs (red), and GOQCs (orange)
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Figure 1/2. Transmission electron micrograph of GOQCs
Figure 2/2. Transmission electron micrograph of GRQCs
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900
Methods We prepare photoluminescent gold clusters in aqueous phase using biomolecule (protein, peptide, amino acid) reagents. Biomolecules play an important role in the reduction and complex formation of gold species, and also protect the clusters from aggregation, forming hybrid conjugates. The products have a hydrophilic character, which provides an opportunity for application in aqueous media and biological systems. Acknowledgement This work was supported by the Hungarian Scientific Research Fund (OTKA, Hungary) and the National Innovation Office (NIH, Hungary) under grant agreement CNK-81056. We would like to thank Teréz Kiss and Eszter Drotár for the transmission electron microscopy measurements.