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A Novel Physical Approach for Cationic-Thiolate Protected Fluorescent Gold Nanoparticles.

Ishida Y, Lee C, Yonezawa T - Sci Rep (2015)

Bottom Line: Knowledge on the synthesis of cationically charged fluorescent gold nanoparticles (Au NPs) is limited because the electrostatic repulsion between cationic ligands on the surface of NP hinders the formation of small Au NPs (usually less than ca. 2 nm) during nucleation in solvents.By controlling mercaptan concentration the size and photophysical characteristics of Au NPs were directly controlled, resulting in near IR fluorescence with a 0.9% of absolute quantum yield.Cationically charged fluorescent metal NPs are promising, especially in biological fields, and this work provides a novel methodology towards the synthesis of a new series of functional metal NPs.

View Article: PubMed Central - PubMed

Affiliation: Division of Material Science and Engineering, Faculty of Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan.

ABSTRACT
Knowledge on the synthesis of cationically charged fluorescent gold nanoparticles (Au NPs) is limited because the electrostatic repulsion between cationic ligands on the surface of NP hinders the formation of small Au NPs (usually less than ca. 2 nm) during nucleation in solvents. We herein propose a novel methodology for a synthesis of water-dispersible, cationic-thiolate protected fluorescent Au NPs by the sputtering of Au into liquid matrix containing thiolate ligands. By controlling mercaptan concentration the size and photophysical characteristics of Au NPs were directly controlled, resulting in near IR fluorescence with a 0.9% of absolute quantum yield. Cationically charged fluorescent metal NPs are promising, especially in biological fields, and this work provides a novel methodology towards the synthesis of a new series of functional metal NPs.

No MeSH data available.


Related in: MedlinePlus

Excitation (blue) and fluorescence (red) spectra of Au NPs prepared at 0.5 M TC in DG.Excitation spectrum was observed at 673 nm. Fluorescence spectrum was observed by the irradiation at 300 nm. For a comparison purpose, the extinction spectrum under the same condition is shown by a black line.
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f5: Excitation (blue) and fluorescence (red) spectra of Au NPs prepared at 0.5 M TC in DG.Excitation spectrum was observed at 673 nm. Fluorescence spectrum was observed by the irradiation at 300 nm. For a comparison purpose, the extinction spectrum under the same condition is shown by a black line.

Mentions: The absence of plasmon absorption and very small particle sizes led us to investigate the fluorescence property of Au NPs stabilized by TC. The excitation wavelength was set at 300 nm. Au NPs prepared at 0 and 0.01 M TC, which show plasmon absorption in Fig. 2, did not fluoresce. On the other hand, those prepared at 0.1 and 0.5 M TC showed fluorescence in the near IR region, as shown by the red line in Fig. 5 (only for the 0.5 M sample). The fluorescence spectra were almost the same for the 0.1 and 0.5 M samples, resulting from the similar average sizes of the Au NPs (2.1 and 2.0 nm for 0.1 and 0.5 M samples, respectively), within errors. The excitation spectrum of the 0.5 M sample was observed at the fluorescence maximum (673 nm) as shown in the blue line in Fig. 5. The excitation maximum was observed at 326 nm; therefore, the Stokes shift of our Au NPs can be calculated to be 347 nm (1.96 eV = 1.58 × 104 cm−1). The large Stokes shift of Au NPs has been reported in our previous matrix sputtering synthesis18, and the reason was assumed to be the stabilization of the d band and/or the destabilization of the sp–conduction band in the Au NPs that usually results in a blue shift in the absorption (excitation) spectrum.


A Novel Physical Approach for Cationic-Thiolate Protected Fluorescent Gold Nanoparticles.

Ishida Y, Lee C, Yonezawa T - Sci Rep (2015)

Excitation (blue) and fluorescence (red) spectra of Au NPs prepared at 0.5 M TC in DG.Excitation spectrum was observed at 673 nm. Fluorescence spectrum was observed by the irradiation at 300 nm. For a comparison purpose, the extinction spectrum under the same condition is shown by a black line.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4612736&req=5

f5: Excitation (blue) and fluorescence (red) spectra of Au NPs prepared at 0.5 M TC in DG.Excitation spectrum was observed at 673 nm. Fluorescence spectrum was observed by the irradiation at 300 nm. For a comparison purpose, the extinction spectrum under the same condition is shown by a black line.
Mentions: The absence of plasmon absorption and very small particle sizes led us to investigate the fluorescence property of Au NPs stabilized by TC. The excitation wavelength was set at 300 nm. Au NPs prepared at 0 and 0.01 M TC, which show plasmon absorption in Fig. 2, did not fluoresce. On the other hand, those prepared at 0.1 and 0.5 M TC showed fluorescence in the near IR region, as shown by the red line in Fig. 5 (only for the 0.5 M sample). The fluorescence spectra were almost the same for the 0.1 and 0.5 M samples, resulting from the similar average sizes of the Au NPs (2.1 and 2.0 nm for 0.1 and 0.5 M samples, respectively), within errors. The excitation spectrum of the 0.5 M sample was observed at the fluorescence maximum (673 nm) as shown in the blue line in Fig. 5. The excitation maximum was observed at 326 nm; therefore, the Stokes shift of our Au NPs can be calculated to be 347 nm (1.96 eV = 1.58 × 104 cm−1). The large Stokes shift of Au NPs has been reported in our previous matrix sputtering synthesis18, and the reason was assumed to be the stabilization of the d band and/or the destabilization of the sp–conduction band in the Au NPs that usually results in a blue shift in the absorption (excitation) spectrum.

Bottom Line: Knowledge on the synthesis of cationically charged fluorescent gold nanoparticles (Au NPs) is limited because the electrostatic repulsion between cationic ligands on the surface of NP hinders the formation of small Au NPs (usually less than ca. 2 nm) during nucleation in solvents.By controlling mercaptan concentration the size and photophysical characteristics of Au NPs were directly controlled, resulting in near IR fluorescence with a 0.9% of absolute quantum yield.Cationically charged fluorescent metal NPs are promising, especially in biological fields, and this work provides a novel methodology towards the synthesis of a new series of functional metal NPs.

View Article: PubMed Central - PubMed

Affiliation: Division of Material Science and Engineering, Faculty of Engineering, Hokkaido University, Kita 13, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628, Japan.

ABSTRACT
Knowledge on the synthesis of cationically charged fluorescent gold nanoparticles (Au NPs) is limited because the electrostatic repulsion between cationic ligands on the surface of NP hinders the formation of small Au NPs (usually less than ca. 2 nm) during nucleation in solvents. We herein propose a novel methodology for a synthesis of water-dispersible, cationic-thiolate protected fluorescent Au NPs by the sputtering of Au into liquid matrix containing thiolate ligands. By controlling mercaptan concentration the size and photophysical characteristics of Au NPs were directly controlled, resulting in near IR fluorescence with a 0.9% of absolute quantum yield. Cationically charged fluorescent metal NPs are promising, especially in biological fields, and this work provides a novel methodology towards the synthesis of a new series of functional metal NPs.

No MeSH data available.


Related in: MedlinePlus