Nanopipette‐based electrochemical SERS platforms: Using electrodeposition to produce versatile and adaptable plasmonic substrates

Abstract

A method for fabricating localized EC‐SERS probes based on nanopipettes and electrodeposition is described. Gold particles of fractal geometry with excellent SERS performance are produced, reliably and at low cost. By adapting the electrodeposition procedure, nanostructures of different sizes can be obtained, allowing the SERS platform to be tailored to many experimental configurations. In particular, by producing unique SERS platforms of dimensions comparable to the laser spot, quantitative comparison with electrochemical current is possible. By analyzing hundreds of samples, we thoroughly characterize the resulting geometry of the structures and their ability to enhance Raman signal, providing guidelines for the fabrication of optimized platforms. Control over the probes' surface potential also allows convenient modulation of surface‐analyte affinity and enable chemically unstable materials, such as Cu, to be reliably used. These are demonstrated by showing that Cu particles exposed to air can be easily re‐reduced, with no detriment in SERS performance.

Preface to the special issue dedicated to Professor Richard P. Van Duyne (1945–2019)

“…Versatile electrochemical SERS platforms with tailored nanostructure and chemical features can be conveniently constructed on nanopipettes by adapting the method to meet different experimental requirements. [ 7 ]…”

“…Versatile electrochemical SERS platforms with tailored nanostructure and chemical features can be conveniently constructed on nanopipettes by adapting the method to meet different experimental requirements. [7] Chikkaraddy, Baumberg, et al study the dynamics of single bonds through SERS from single SERS-marker molecules containing a distinctive single alkyl bond. Assembly of the nanogaps and positioning of single molecules inside the EM hot spot are precisely controlled using DNA origami constructs.…”

Surface potential modulation as a tool for mitigating challenges in SERS-based microneedle sensors

“…Moreover, if continuous monitoring is required, binding of the analyte must be reversible, and the association and dissociation of the analyte and receptor should have rate constants that allow rapid equilibration but still sufficient affinity to detect the analyte at relevant concentrations. Alternatively, complex degradation strategies can be designed, which require extra preparation steps, and might be difficult to implement in some situations 32 – 34 .…”

“…In another approach, surface potential can be used to manipulate adsorption and desorption of analytes on SERS sensors 32 , 35 – 37 . In this paper, we explore this methodology, applying electrical potential to selectively localize analytes in the interfacial region of plasmonic microneedles, where they can be detected.…”

Gold-Etched Silver Nanowire Endoscopy: Toward a Widely Accessible Platform for Surface-Enhanced Raman Scattering-Based Analysis in Living Cells

“…Despite this being the most commonly used approach, it suffers from significant limitations such as poor spatiotemporal control and irreversible cellular uptake of the NPs. As a consequence of these shortcomings, interest has risen toward the development of 1D “nano-endoscopes”, which can be physically inserted into live cells to target local spots. − The pioneer works performed in this context rely on conical-shaped silver nanopipettes or glass pipettes coated with noble metal NPs. − Although diameters as small as 100 nm have been reported at the tip, the large apex angle and rigid structure confer significant damage to the cell health once the tip is inserted, altering the outcomes of the investigations performed . Recently, carbon nanotubes decorated with gold NPs have been elegantly designed. , Although outstanding, this approach requires elaborate fabrication protocols for obtaining an ideal NP decoration for high SERS enhancements while retaining a suitable probe diameter for a non-invasive insertion in cells .…”