Measuring binding kinetics of aromatic thiolated molecules with nanoparticles via surface-enhanced Raman spectroscopy

Abstract

Colloidal plasmonic nanomaterials, consisting of metals such as gold and silver, are excellent candidates for advanced optical probes and devices, but precise control over surface chemistry is essential for realizing their full potential. Coupling thiolated (R-SH) molecules to nanoprobe surfaces is a convenient and established route to tailor surface properties. The ability to dynamically probe and monitor the surface chemistry of nanoparticles in solution is essential for rapidly manufacturing spectroscopically tunable nanoparticles. In this study, we report the development of surface-enhanced Raman spectroscopy (SERS) as a method to monitor the kinetics of gold-thiolate bond formation on colloidal gold nanoparticles. A theoretical model combining SERS enhancement with the Beer-Lambert law is proposed to explain ensemble scattering and absorption effects in colloids during chemisorption. In order to maximize biological relevance and signal reproducibility, experiments used to validate the model focused on maintaining nanoparticle stability after the addition of water-soluble aromatic thiolated molecules. Our results indicate that ligand exchange on gold nanoparticles follow a first-order Langmuir adsorption model with rate constants on the order of 0.01 min 1. This study demonstrates an experimental spectroscopic method and theoretical model for monitoring binding kinetics that may prove useful for designing novel probes.

Toward the Development of Ultrasensitive Detectors for Environmental Applications: A Kinetic Study of Cr(III) Monitoring in Water Using EDTA and SERS Techniques

“…Fitting the data versus time reveals a Langmuir-type curve. 29 , 50 Indeed, it is likely that when a complex collides with the NPs, a direct adsorption on the surface could occur or it will return to the aqueous phase, indicating a first-order chemical kinetics.…”

“…The SERS peak growth that follows a time-dependent Langmuir kinetics is described by the following equation 29 , 50 where θ represents the surface coverage at time t , θ sat represents the saturation coverage which is dependent on the association or dissociation constants of the adsorption reaction, and k obs is the adsorption rate constant.…”

“…For example, DeVetter et al reported the development of a SERS-based method to figure out the kinetics of gold–thiolate bond formation on colloidal gold NPs. 29 Although the detection of Cr(III) using EDTA and SERS techniques on AgNPs has been reported, no kinetic studies on metal detection using the SERS technique are found in the literature to the best of our knowledge. In this work, we investigate the kinetic studies of Cr(III) detection in solution on colloidal AgNPs with the objective of finding the optimal conditions necessary for a successful preparation of optical nanoprobes and enhance the detection signal using SERS technique.…”

How Fast Can Thiols Bind to the Gold Nanoparticle Surface?

“…The process is well understood when it involves the formation of self‐assembled monolayers (SAM) on atomically flat gold surfaces, but to a lesser extent in the case of AuNP where polydispersity and irregularities on the surface and curvature variations make the binding process more complex and the conclusions more difficult to generalize . Surface enhanced Raman spectroscopy (SERS) has proven a useful tool to study structural effects and kinetics of thiol‐AuNP interactions , although relatively large particle sizes (e.g. 50–200 nm) and aromatic thiols tend to be preferred to suit SERS optimal experimental conditions .…”

Nature Inspired Plasmonic Structures: Influence of Structural Characteristics on Sensing Capability

“…Raman spectroscopy is a powerful vibrational spectroscopy technique that has many advantages. It is an analytical technique with high specificity for the identification of various chemical compounds [1][2][3]. In addition, it is a non-invasive approach that allows measurements to be performed without any sample preparation, and the measurement time is generally very short.…”