Brightening Gold Nanoparticles: New Sensing Approach Based on Plasmon Resonance Energy Transfer

Scattering recovered plasmonic resonance energy transfer (SR-PRET) was reported by blocking the plasmon resonance energy transfer (PRET) from gold nanoparticle (GNP) to the adsorbed molecules (RdBS). Due to the selective cleavage of the Si-O bond by F− ions, the quenching is switched off causing an increase in the brightness of the GNPs,detected using dark-field microscopy (DFM) were brightened. This method was successfully applied to the determination of fluoride ions in water. The SR-PRET provides a potential approach for a vitro/vivo sensing with high sensitivity and selectivity.


Figure S2
Characterization of gold nanoseeds and 60 nm GNPs by UV-Vis and SEM.

Figure S3
Dark-field images and scattering spectra of GNPs before and after modification of RdBS.

Figure S4
Detailed experimental configuration of a dark-field microscopy system.              Synthesis and characterization of 60 nm gold nanoparticles [1] Seed gold nanoparticles were prepared by the citrate-mediated reduction of HAuCl4. 50 mL of 0.01 wt% HAuCl4 was heated to reflux with vigorous stirring and then 5 mL sodium citrate (38.8 mM) was added quickly to the solution. The mixed solution was continued to heat for 15 min, stopped heating and kept stirring for an additional 15 min. The resulting solution of colloidal particles was filtered and characterized by an absorption maximum at 521 nm using an Ocean optical USB 2000+ UV-Vis spectrometer. These particles were then used as seed particles for the synthesis of 60 nm gold particles. To 25 mL of water, 1 mL of preformed seed gold particles and 100 μL of 0.2 M NH2OH·HCl was mixed. The mixture was stirred vigorously at room temperature and 3.0 mL of 0.1 wt% HAuCl4·3H2O was added drop-wise. Diameters were characterized by UV-Vis and SEM.      Glycol (3.0g, 48.5 mmol), DCC (1.03 g, 5 mmol) and DMAP (0.6 g, 5 mmol) were dissolved in 20 mL dry DCM, a solution of lipoic acid (1.0 g, 48.5 mmol) in 10 mL dry DCM was added dropwise at 0 ºC. Then the mixture was stirred at room temperature for 5 h before filtered. The filtrate was washed with brine, NaHCO3 and concentrated in vacuum. The residue was purified by silica gel column chromatography to obtain the pure product as a yellow oil 1 (2.1 g). 1  The synthetic procedure of 2 was the same as that of 1. 1 H NMR (400 MHz, CDCl3) δ 8.48 -8.39 (m, 1H), 7.80 -7.69 (m, 2H), 7.26 (dd, J = 6.9, 1.5 Hz, 1H), 7.11 (d, J = 9.5 Hz, 2H), 6.88 (dd, J = 9.5, 2.2 Hz, 2H), 6.82 (d, J = 2.1 Hz, 2H), 4.18 -4.10 (m, 2H), 3.63 (dd, J = 14.4, 7.1 Hz, 10H), 2.33 -2.18 (m, 4H), 1.33 (t, J = 7.1 Hz, 12H).
Diphenyldichlorosilane (2.28 mL, 1.1 mmol), Et3N (2.09 mL) was dissolved in50 mL dry DCM, then a solution of 1 (2.75 g, 1.1mmol) in 20 mL dry DCM was added dropwise at 0 ºC under the protection of argon. The solution was stirred at room temperature for 6 h, then refluxed for 36 h. The solvent was concentrated in vacuum and redissolved in 1:1 ether-hexane 10 mL. The solution was suction filtered and reconcentrated. The crude product 3 was used without further purification for the next step.
Compound 2 (0.5 g, 1.0 mmol) and Et3N (2 mL) were dissolved in 5 mL dry DCM, a solution of crude compound 3 (0.5 g) in 5 mL dry DCM was added dropwise at 0 ºC. The mixture was stirred at room temperature for 3 h, and then quenched with saturated NaHCO3. The solution was wash with H2O, brine. The residue was purified by silica gel column chromatography to obtain the pure product RdBS 0.3g. 1