In Situ Nanoscale Investigation of Catalytic Reactions in the Liquid Phase Using Zirconia-Protected Tip-Enhanced Raman Spectroscopy Probes

Abstract

Tip-enhanced Raman spectroscopy (TERS) is a promising technique that enables nondestructive and label-free topographical and chemical imaging at the nanoscale. However, its scope for in situ characterization of catalytic reactions in the liquid phase has remained limited due to the lack of durable and chemically inert plasmonically active TERS probes. Herein, we present novel zirconia-protected TERS probes with 3 orders of magnitude increase in lifetime under ambient conditions compared to unprotected silver-coated probes, together with high stability in liquid media. Employing the plasmon-assisted oxidation of p-aminothiophenol as a model reaction, we demonstrate that the highly robust, durable, and chemically inert zirconia-protected TERS probes can be successfully used for nanoscale spatially resolved characterization of a photocatalytic reaction within an aqueous environment. The reported improved lifetime and stability of probes in a liquid environment extend the potential scope of TERS as a nanoanalytical tool not only to heterogeneous catalysis but also to a range of scientific disciplines in which dynamic solid–liquid interfaces play a defining role.

Reactivity mapping of nanoscale defect chemistry under electrochemical reaction conditions

“…Using TERS in air, Ren and co-workers have resolved the energetic differences in the step edge and terrace reactivity of Pd islands on Au(111) with adsorbed organic probing molecules reaching a chemical spatial resolution of impressive 3 nm 17 . Kumar et al 18 recently managed to study the dimerization reaction of p -aminothiophenol attached to rough Ag surfaces in contact with a water droplet and the Van Duyne group mapped the spatially heterogeneous surface potential distribution on ITO grains with 40 nm resolution using EC-TERS 19 . The challenge is now to combine the key abilities of these striking works—chemical site-specificity on the nanoscale, 2D in situ reactivity imaging starting from and ending at the plain catalyst surface, and electrochemical (potential) control of reversible catalyst (de)activation—into one single experimental approach.…”

Deciphering the Structure and Chemical Composition of Drug Nanocarriers: From Bulk Approaches to Individual Nanoparticle Characterization

“…Although AFM has the advantage to allow operating within fluid cells, it is difficult to achieve a good fixation of NCs on their support during investigations in liquid state and cantilever oscillations are prone to be dampened by water. [ 196 ] Thanks to technical advances, nanoscale resolutions have been demonstrated in liquid s‐SNOM and PTIR in liquid s‐SNOM and PTIR for catalase nanocrystals and biomimetic peptoid nanosheets, [ 197 ] organic monolayers [ 198,199 ] and bilayers, [ 200 ] single‐wall carbon nanotubes, [ 201 ] functionalized gold triangles, [ 202 ] chemical reactions at the solid‐liquid interface, [ 203,204 ] living cells, [ 205 ] thin poly(methyl methacrylate) films [ 206 ] and amyloid peptide fibrils. [ 207 ] Further perspectives are intended to extend the IR spectral range to enlarge the NC detection possibilities in biological media but more investigations are needed to improve the relatively weak spatial resolution of this promising approach.…”

Shining light on the solid–liquid interface:in situ/operandomonitoring of surface catalysis

“…Weckhuysen and co-workers recently developed a novel atomic force microscopy (AFM)-TERS probe wherein the multilayer metal tip coating was protected by an ultrathin layer of zirconia. 54 This design overcomes TERS limitations such as a short tip lifetime, chemical inertness, and instability in a liquid environment. The zirconia coated (AFM)-TERS probe was used to map the photocatalytic oxidation of a p-aminothiophenol (pATP) self-assembled monolayer to p,p′-dimercaptoazobenzene (DMAB) across a heterogeneous metal surface in water.…”