How Fast Can Thiols Bind to the Gold Nanoparticle Surface?

Abstract

Kinetics of gold nanoparticle surface modification with thiols can take more than one hour for completion. 7-mercapto-4-methylcoumarin can be used to follow the process by fluorescence spectroscopy and serves as a convenient molecular probe to determine relative kinetics. SERS studies with aromatic thiols further support the slow surface modification kinetics observed by fluorescence spectroscopy. The formation of thiolate bonds is a relatively slow process; we recommend one to two hour wait for thiol binding to be essentially complete, while for disulfides, overnight incubation is suggested.

Insight on Mercapto-Coumarins: Synthesis and Reactivity

“…It is also indicated as a suitable matrix for the analysis of small molecular compounds [ 40 ]. The other described incorporation of this highly valuable scaffold is as a reporter molecule [ 41 ], reporters for thiol interactions at the nanoparticle surface [ 42 ], fluorescent probe [ 43 , 44 , 45 ], sugar acceptor [ 46 ], Raman reporter [ 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ], an excellent substrate for fluorescence spectroscopy [ 57 ], photodimerizable and healable reactant [ 58 ], fluorescent dye [ 59 , 60 ], and probe molecule on gold-coated silicon nanowires [ 61 ].…”

Biocatalytic Synthesis of Coumarin S-Glycosides: Towards Non-Cytotoxic Probes for Biomedical Imaging and Sensing

“…Moreover, its efficacy as a matrix for analyzing small molecular compounds is acknowledged [ 24 ]. The versatility of 7-MC is highlighted across diverse applications, as evidenced by its role as a reporter molecule [ 25 ], involvement in thiol interactions at the nanoparticle surface [ 26 ], serving as Raman reporter [ 27 , 28 , 29 ], proving to be an excellent substrate for fluorescence spectroscopy [ 30 ], demonstrating photodimerizable and healable properties [ 31 ], and functioning as fluorescent dye [ 32 , 33 ]. Additionally, it acts as a probe molecule on gold-coated silicon nanowires [ 34 ] and excels as a fluorophore [ 35 , 36 , 37 ], making it particularly valuable in biological and chemical sensing applications.…”

Inferring the Interfacial Reactivity of Gold Nanoparticles by Surface Plasmon Resonance Measurements

“…One of the most used is the Turkevich–Frens method where hot chloroauric acid (HAuCl 4 ) is reduced by sodium citrate, which also acts as a stabilizer. − Stabilization occurs electrostatically, which facilitates subsequent functionalization by ligand exchange, thanks to the weak bonding of citrates onto gold surfaces. − The high affinity of thiols for gold makes thiol derivatives among the most convenient/adapted molecules for such reactions. However, electrostatic repulsions between the nanoparticles may disappear after ligand exchange, which can destabilize the suspension leading to aggregation. ,− The choice of the ligand and the study of its replacement protocol and kinetics is therefore crucial.…”