Facile Preparation of High-Quantum-Yield Gold Nanoclusters ...
Facile Preparation of High-Quantum-Yield Gold Nanoclusters: Application to Probing Mercuric Ions and Biothiols Heng-Chia Chang1, Ying-Feng Chang2, Nien-Chu Fan2 and Ja-an Annie Ho1,2* 1Department
of Chemistry, National Tsing Hua University, No. 101, Sec. 2, Kua`ng-Fu Road, Hsinchu, 30013 Taiwan 2BioAnalytical Chemistry and Nanobiomedicine Laboratory, Department of Biochemical Science and Technology, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 20617 Taiwan
*Corresponding author: Prof. Ja-an Annie Ho, e-mail: [email protected]
Supplementary Information Determination of Quantum Yield Fluorescence quantum yield is defined as the numbers of emitted photons per number of absorbed photons. Quantum yields can be characteristically measured by a relative comparison method.s1 Absorption and fluorescence spectra of concentration series of the test sample and a reference sample (with known quantum yield) were acquired before determination of quantum yield. To avoid inner filter effects, the optical density of tested solutions must be below 0.1 at the excitation wavelength. Rhodamine 6G dissolved in ethanol (Q=0.95) was used herein as reference sample. Fluorescent gold nanoclusters (MUA-AuNC607, 754, 814) dispersed in methanol were used. For each sample and concentration, the absorption (optical density) at 330 nm using Varian Cary 300, and the corresponding photoluminescence spectra using Varian Cary Eclipse were recorded. The intensity versus absorption gradients of each sample was linearly fitted. After correction with the refractive index of solvent, the quantum yield of the test sample could be determined with the formula below. The quantum yield of fluorescent gold nanoclusters was determined as ca. 13% in methanol. QY = QYref x ( I/Iref) x (Aref/A) x (η2 /ηref2) I = integrated luminescence intensity of AuNCs; A = absorption at 330 nm η = the refractive index of the solvent Through comparison with rhodamine 6G (QY = 95%, in EtOH), we determined the QY of the AuNCs (MUA- AuNCs607) to be ca. 13%, a great improvement, by at least 8 orders of magnitude, relative to that of bulk gold (QY = 10−8%) and approximately 1-2 orders of magnitude higher than the quantum S1
yield of Au NCs derived with other synthesis routes. Same comparison protocol was used to evaluate the QY of MUA-AuNCs754 and MUA-AuNCs814, they were determined to be 0.6% and 0.2%, respectively.
Table S1 Comparison of the present sensing probe with other AuNPs- and AuNC-based assays AuNPs/ Ligands on surface AuNCs of AuNPs/AuNCs
Detection method
Masking Agent
LOD (nM)
AuNPs AuNPs AuNPs AuNPs
single-strand DNA MPA MPA/HCys MPA/AMP/R6G
absorption absorption absorption FRET
no no PDCA no
100 100 25 50
AuNPs AuNPs AuNPs
peptide single-strand DNA single-strand DNA
no no no
26 1000 10
AuNPs AuNPs
single-strand DNA tween 20
absorption absorption Silver enhance -ment SPR absorption
PDCA NaCl
300 100
AuNPs
single-strand DNA/ OliGreen
FRET
no
25
AuNPs AuNPs
oligopeptides absorption quaternary absorption ammonium groupterminated thiols MUA Fluorescence
no no
10 30
PDCA
5
AuNCs AuNCs AuNCs
BSA BSA
Fluorescence Fluorescence
no no
0.5 80
AuNCs
Lysozyme type VI
Fluorescence
no
0.003
AuNCs
MUA
Fluorescence
PDCA
0.45
S2
Real Reference sample tested? no s2 no s3 no s4 Yes, s5 urine sample no s6 no s7 Yes, s8 lake water no Yes, drinking water Yes, pond water no Yes, drinking water Yes, pond water no Yes, river, tap and mineral water Yes, pond water Yes, lake water
s9 s10 s11 s12 s13 s14 s15 s16
s17 This study
Figure S1. Time evolution of the photoemission spectrum (excitation wavelength: 330 nm) for the reaction process of MUA–AuNCs607.
S3
(A)
(B)
(C)
(D)
Figure S2. (A, B) Absorbance spectra of (A) MUA–AuNCs754 and (B) MUA–AuNCs814 (insets: photographs of MUA–AuNCs solution in room light). (C, D) Normalized fluorescence excitation (grey line) and emission (black line) spectra of (C) MUA–AuNCs754 and (D) MUA–AuNCs814 (insets: photographs of MUA–AuNCs solution under a hand-held UV lamp, with excitation at 365 nm).
S4
Figure S3. Fluorescence emission spectra of MUA–AuNCs607 before (black line) and after (grey line) adding excess NaBH4. The fluorescence was excited at 330 nm.
S5
(A)
(B)
Figure S4. HRTEM images of (A) MUA–AuNCs754 and (B) MUA–AuNCs814 (scale bar: 5 nm).
S6
(A)
(B)
Figure S5. XPS spectra (Au 4f) of (A) MUA–AuNCs754 and (B) MUA–AuNCs814.
References S1. Lin, A.-J.; Yang, T.-Y; Lee, C.-H; Huang, S.-H.; Sperling, R.A.; Zanella, M.; Li, J.-K.; Shen, J.-L.; Wang, H.-H.; Yeh, H.-I.; Parak, W.J.; Chang, W.H. Synthesis, Characterization, and Bioconjugation of Fluorescent Gold Nanoclusters Toward Biological Labeling Applications. ACS Nano. 2009, 3, 395–401. S2. Lee, J-S.; Han, M. S.; Mirkin, C. A. Colorimetric Detection of Mercuric Ion (Hg2+) in Aqueous Media Using DNA-functionalized Gold Nanoparticles. Angew. Chem. Int. Ed. 2007, 46, 40934096. S3. Huang, C-C.; Chang, H-T. Parameters for Selective Colorimetric Sensing of Mercury(II) in Aqueous Solutions Using Mercaptopropionic Acid-modified Gold Nanoparticles. Chem. Commun. 2007, 12, 1215-1217. S4. Darbha, G. K.; Singh, A. K.; Rai, U. S. Yu, E.; Yu, H.; Ray, R. C. Selective Detection of Mercury (II) Ion Using Nonlinear Optical Properties of Gold Nanoparticles. J. Am. Chem. Soc. 2008, 130, 8038-8043. S5. Yu, C-J.; Tseng, W-L. Colorimetric Detection of Mercury(II) in a High-Salinity Solution Using Gold Nanoparticles Capped with 3-Mercaptopropionate Acid and Adenosine Monophosphate. Langmuir 2008, 24, 12717-12722. S6. Slocik, J. M.; Zabinski, Jr, J. S.; Phillips, D. M.; Naik, R. R. Colorimetric Response of Peptidefunctionalized Gold Nanoparticles to Metal Ions. Small 2008, 4, 548-551. S7. Xue, X.; Wang, F.; Liu, X. One-Step, Room Temperature, Colorimetric Detection of Mercury (Hg2+) Using DNA/Nanoparticle Conjugates. J. Am. Chem. Soc. 2008, 130, 3244-3245. S8. Lee, J-S.; Mirkin, C. A. Chip-Based Scanometric Detection of Mercuric Ion Using DNAFunctionalized Gold Nanoparticles. Anal. Chem. 2008, 80, 6805-6808. S7
S9. Wang, L.; Li, T.; Du, Y.; Chen, C.; Li, B.; Zhou, M.; Dong, S. Au NPs-enhanced Surface Plasmon Resonance for Sensitive Detection of Mercury(II) Ions. Biosens. Bioelectron. 2010, 25, 26222626. S10. Lin, C-Y.; Yu, C-J.; Lin, Y-H.; Tseng, W-L. Colorimetric Sensing of Silver(I) and Mercury(II) Ions Based on an Assembly of Tween 20-Stabilized Gold Nanoparticles. Anal. Chem. 2010, 82, 68306837. S11. Liu, C-W.; Huang, C-C.; Chang, H-T. Control over Surface DNA Density on Gold Nanoparticles Allows Selective and Sensitive Detection of Mercury(II). Langmuir 2008, 24, 8346-8350. S12. Du, J.; Sun, Y.; Jiang, L.; Cao, X.; Qi, D.; Yin, S.; Ma, J.; Boey, F. Y. C.; Chen, X. Flexible Colorimetric Detection of Mercuric Ion by Simply Mixing Nanoparticles and Oligopeptides. Small 2011, 7, 1407-1411. S13. Liu, D.; Qu, W.; Chen, W.; Zhang, W. ; Wang, Z.; Jiang, X. Highly Sensitive, Colorimetric Detection of Mercury(II) in Aqueous Media by Quaternary Ammonium Group-Capped Gold Nanoparticles at Room Temperature. Anal Chem. 2010, 82, 9606-9610. S14. Huang, C. C.; Yang, Z.; Lee, K. H.; Chang, H. T. Synthesis of Highly Fluorescent Gold Nanoparticles for Sensing Mercury(II). Angew. Chem. Int. Ed., 2007, 46, 6824-6828. S15. Xie, J.; Zheng, Y.; Ying, J. Y. Highly selective and ultrasensitive detection of Hg2+ Based on Fluorescence Quenching of Au Nanoclusters by Hg2+–Au+ Interactions. Chem. Commun. 2010, 46, 961-963. S16. Hu, D.; Sheng, Z.; Gong, P.; Zhang, P.; Cai, L. Highly Selective Fluorescent Sensors for Hg2+ Based on Bovine Serum Albumin-capped Gold Nanoclusters. Analyst 2010, 135, 1411-1416. S17. Lin, Y-H.; Tseng, W-L. Ultrasensitive Sensing of Hg2+ and CH3Hg+ Based on the Fluorescence Quenching of Lysozyme Type VI-Stabilized Gold Nanoclusters. Anal. Chem. 2010, 82, 9194-9200.
S8
of Chemistry, National Tsing Hua University, No. 101, Sec. 2, Kua`ng-Fu Road, Hsinchu, 30013 Taiwan 2BioAnalytical Chemistry and Nanobiomedicine Laboratory, Department of Biochemical Science and Technology, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 20617 Taiwan
*Corresponding author: Prof. Ja-an Annie Ho, e-mail: [email protected]
Supplementary Information Determination of Quantum Yield Fluorescence quantum yield is defined as the numbers of emitted photons per number of absorbed photons. Quantum yields can be characteristically measured by a relative comparison method.s1 Absorption and fluorescence spectra of concentration series of the test sample and a reference sample (with known quantum yield) were acquired before determination of quantum yield. To avoid inner filter effects, the optical density of tested solutions must be below 0.1 at the excitation wavelength. Rhodamine 6G dissolved in ethanol (Q=0.95) was used herein as reference sample. Fluorescent gold nanoclusters (MUA-AuNC607, 754, 814) dispersed in methanol were used. For each sample and concentration, the absorption (optical density) at 330 nm using Varian Cary 300, and the corresponding photoluminescence spectra using Varian Cary Eclipse were recorded. The intensity versus absorption gradients of each sample was linearly fitted. After correction with the refractive index of solvent, the quantum yield of the test sample could be determined with the formula below. The quantum yield of fluorescent gold nanoclusters was determined as ca. 13% in methanol. QY = QYref x ( I/Iref) x (Aref/A) x (η2 /ηref2) I = integrated luminescence intensity of AuNCs; A = absorption at 330 nm η = the refractive index of the solvent Through comparison with rhodamine 6G (QY = 95%, in EtOH), we determined the QY of the AuNCs (MUA- AuNCs607) to be ca. 13%, a great improvement, by at least 8 orders of magnitude, relative to that of bulk gold (QY = 10−8%) and approximately 1-2 orders of magnitude higher than the quantum S1
yield of Au NCs derived with other synthesis routes. Same comparison protocol was used to evaluate the QY of MUA-AuNCs754 and MUA-AuNCs814, they were determined to be 0.6% and 0.2%, respectively.
Table S1 Comparison of the present sensing probe with other AuNPs- and AuNC-based assays AuNPs/ Ligands on surface AuNCs of AuNPs/AuNCs
Detection method
Masking Agent
LOD (nM)
AuNPs AuNPs AuNPs AuNPs
single-strand DNA MPA MPA/HCys MPA/AMP/R6G
absorption absorption absorption FRET
no no PDCA no
100 100 25 50
AuNPs AuNPs AuNPs
peptide single-strand DNA single-strand DNA
no no no
26 1000 10
AuNPs AuNPs
single-strand DNA tween 20
absorption absorption Silver enhance -ment SPR absorption
PDCA NaCl
300 100
AuNPs
single-strand DNA/ OliGreen
FRET
no
25
AuNPs AuNPs
oligopeptides absorption quaternary absorption ammonium groupterminated thiols MUA Fluorescence
no no
10 30
PDCA
5
AuNCs AuNCs AuNCs
BSA BSA
Fluorescence Fluorescence
no no
0.5 80
AuNCs
Lysozyme type VI
Fluorescence
no
0.003
AuNCs
MUA
Fluorescence
PDCA
0.45
S2
Real Reference sample tested? no s2 no s3 no s4 Yes, s5 urine sample no s6 no s7 Yes, s8 lake water no Yes, drinking water Yes, pond water no Yes, drinking water Yes, pond water no Yes, river, tap and mineral water Yes, pond water Yes, lake water
s9 s10 s11 s12 s13 s14 s15 s16
s17 This study
Figure S1. Time evolution of the photoemission spectrum (excitation wavelength: 330 nm) for the reaction process of MUA–AuNCs607.
S3
(A)
(B)
(C)
(D)
Figure S2. (A, B) Absorbance spectra of (A) MUA–AuNCs754 and (B) MUA–AuNCs814 (insets: photographs of MUA–AuNCs solution in room light). (C, D) Normalized fluorescence excitation (grey line) and emission (black line) spectra of (C) MUA–AuNCs754 and (D) MUA–AuNCs814 (insets: photographs of MUA–AuNCs solution under a hand-held UV lamp, with excitation at 365 nm).
S4
Figure S3. Fluorescence emission spectra of MUA–AuNCs607 before (black line) and after (grey line) adding excess NaBH4. The fluorescence was excited at 330 nm.
S5
(A)
(B)
Figure S4. HRTEM images of (A) MUA–AuNCs754 and (B) MUA–AuNCs814 (scale bar: 5 nm).
S6
(A)
(B)
Figure S5. XPS spectra (Au 4f) of (A) MUA–AuNCs754 and (B) MUA–AuNCs814.
References S1. Lin, A.-J.; Yang, T.-Y; Lee, C.-H; Huang, S.-H.; Sperling, R.A.; Zanella, M.; Li, J.-K.; Shen, J.-L.; Wang, H.-H.; Yeh, H.-I.; Parak, W.J.; Chang, W.H. Synthesis, Characterization, and Bioconjugation of Fluorescent Gold Nanoclusters Toward Biological Labeling Applications. ACS Nano. 2009, 3, 395–401. S2. Lee, J-S.; Han, M. S.; Mirkin, C. A. Colorimetric Detection of Mercuric Ion (Hg2+) in Aqueous Media Using DNA-functionalized Gold Nanoparticles. Angew. Chem. Int. Ed. 2007, 46, 40934096. S3. Huang, C-C.; Chang, H-T. Parameters for Selective Colorimetric Sensing of Mercury(II) in Aqueous Solutions Using Mercaptopropionic Acid-modified Gold Nanoparticles. Chem. Commun. 2007, 12, 1215-1217. S4. Darbha, G. K.; Singh, A. K.; Rai, U. S. Yu, E.; Yu, H.; Ray, R. C. Selective Detection of Mercury (II) Ion Using Nonlinear Optical Properties of Gold Nanoparticles. J. Am. Chem. Soc. 2008, 130, 8038-8043. S5. Yu, C-J.; Tseng, W-L. Colorimetric Detection of Mercury(II) in a High-Salinity Solution Using Gold Nanoparticles Capped with 3-Mercaptopropionate Acid and Adenosine Monophosphate. Langmuir 2008, 24, 12717-12722. S6. Slocik, J. M.; Zabinski, Jr, J. S.; Phillips, D. M.; Naik, R. R. Colorimetric Response of Peptidefunctionalized Gold Nanoparticles to Metal Ions. Small 2008, 4, 548-551. S7. Xue, X.; Wang, F.; Liu, X. One-Step, Room Temperature, Colorimetric Detection of Mercury (Hg2+) Using DNA/Nanoparticle Conjugates. J. Am. Chem. Soc. 2008, 130, 3244-3245. S8. Lee, J-S.; Mirkin, C. A. Chip-Based Scanometric Detection of Mercuric Ion Using DNAFunctionalized Gold Nanoparticles. Anal. Chem. 2008, 80, 6805-6808. S7
S9. Wang, L.; Li, T.; Du, Y.; Chen, C.; Li, B.; Zhou, M.; Dong, S. Au NPs-enhanced Surface Plasmon Resonance for Sensitive Detection of Mercury(II) Ions. Biosens. Bioelectron. 2010, 25, 26222626. S10. Lin, C-Y.; Yu, C-J.; Lin, Y-H.; Tseng, W-L. Colorimetric Sensing of Silver(I) and Mercury(II) Ions Based on an Assembly of Tween 20-Stabilized Gold Nanoparticles. Anal. Chem. 2010, 82, 68306837. S11. Liu, C-W.; Huang, C-C.; Chang, H-T. Control over Surface DNA Density on Gold Nanoparticles Allows Selective and Sensitive Detection of Mercury(II). Langmuir 2008, 24, 8346-8350. S12. Du, J.; Sun, Y.; Jiang, L.; Cao, X.; Qi, D.; Yin, S.; Ma, J.; Boey, F. Y. C.; Chen, X. Flexible Colorimetric Detection of Mercuric Ion by Simply Mixing Nanoparticles and Oligopeptides. Small 2011, 7, 1407-1411. S13. Liu, D.; Qu, W.; Chen, W.; Zhang, W. ; Wang, Z.; Jiang, X. Highly Sensitive, Colorimetric Detection of Mercury(II) in Aqueous Media by Quaternary Ammonium Group-Capped Gold Nanoparticles at Room Temperature. Anal Chem. 2010, 82, 9606-9610. S14. Huang, C. C.; Yang, Z.; Lee, K. H.; Chang, H. T. Synthesis of Highly Fluorescent Gold Nanoparticles for Sensing Mercury(II). Angew. Chem. Int. Ed., 2007, 46, 6824-6828. S15. Xie, J.; Zheng, Y.; Ying, J. Y. Highly selective and ultrasensitive detection of Hg2+ Based on Fluorescence Quenching of Au Nanoclusters by Hg2+–Au+ Interactions. Chem. Commun. 2010, 46, 961-963. S16. Hu, D.; Sheng, Z.; Gong, P.; Zhang, P.; Cai, L. Highly Selective Fluorescent Sensors for Hg2+ Based on Bovine Serum Albumin-capped Gold Nanoclusters. Analyst 2010, 135, 1411-1416. S17. Lin, Y-H.; Tseng, W-L. Ultrasensitive Sensing of Hg2+ and CH3Hg+ Based on the Fluorescence Quenching of Lysozyme Type VI-Stabilized Gold Nanoclusters. Anal. Chem. 2010, 82, 9194-9200.
S8
