An official website of the United States government
Abstract In situ monitoring of short‐lived transition states (TSs) is crucial for understanding electrochemical reaction mechanisms but remains challenging. Conventional electrochemical surface‐enhanced Raman spectroscopy (EC‐SERS) primarily provides vibrational information, with limitations in hotspot reproducibility and often overlooking electronic information associated with TSs. This study introduces a dual‐channel EC‐SERS strategy using nanolaminate nano‐optoelectrode (NLNOE) devices, integrating plasmon‐enhanced vibrational Raman scattering (PE‐VRS) and plasmon‐enhanced electronic Raman scattering (PE‐ERS) to concurrently probe TS dynamics within electrically connected plasmonic nanocavities. Using theAgCl(s) +e−⇌Ag(s) +Cl−(aq) redox system, this approach distinct PE‐VRS and PE‐ERS signatures of the (AgCl)*TS. Notably, a significant increase in PE‐ERS signals concurrent with (AgCl)*TS emergence, characterized by filled bonding and unoccupied antibonding orbitals with negligible energy gaps. This enhanced PE‐ERS signal correlates with increased (AgCl)*TS polarizability, leading to amplified PE‐VRS signals due to enhanced electron cloud distortion. By modulating Cl⁻ ion concentrations via electrolyte composition (1× PBS and 1× PBS‐equivalent KH₂PO₄) while maintaining constant total ion concentration, the competition between Ag/AgCl and Ag/AgH₂PO₄ redox reactions within Ag nanolayers is influenced. These results demonstrate the capability of dual‐channel EC‐SERS to distinguish interfacial redox reactions based on distinct electronic and vibrational signatures associated with covalent and ionic bond characteristics.
more »
« less
Voltage Modulation of Nanoplasmonic Metal Luminescence from Nano-Optoelectrodes in Electrolytes
Metallic nanostructures supporting surface plasmon modes can concentrate optical fields, and enhance luminescence processes from the metal surface at plasmonic hotspots. Such nanoplasmonic metal luminescence contributes to the spectral background in surface-enhanced Raman spectroscopy (SERS) measurements and is helpful in bioimaging, nano-thermometry, and chemical reaction monitoring applications. Despite increasing interest in nanoplasmonic metal luminescence, little attention has been paid to investigating its dependence on voltage modulation. Also, the hyphenated electrochemical surface-enhanced Raman spectroscopy (EC-SERS) technique typically ignores voltage-dependent spectral background information associated with nanoplasmonic metal luminescence due to limited mechanistic understanding and poor measurement reproducibility. Here, we report a combined experiment and theory study on dynamic voltage-modulated nanoplasmonic metal luminescence from hotspots at the electrode-electrolyte interface using multiresonant nanolaminate nano-optoelectrode arrays. Our EC-SERS measurements under 785 nm laser excitation demonstrate that short-wavenumber nanoplasmonic metal luminescence associated with plasmon-enhanced electronic Raman scattering (PE-ERS) exhibits a negative voltage modulation slope (up to ≈30 % V-1) in physiological ionic solutions. Furthermore, we have developed a phenomenological model to intuitively capture plasmonic, electronic, and ionic characteristics at the metal-electrolyte interface to understand the observed dependence of the PE-ERS voltage modulation slope on voltage polarization and ionic strength. The current work represents a critical step toward the general application of nanoplasmonic metal luminescence signals in optical voltage biosensing, hybrid optical-electrical signal transduction, and interfacial electrochemical monitoring.
more »
« less
- Award ID(s):
- 2139317
- PAR ID:
- 10475696
- Publisher / Repository:
- ACS
- Date Published:
- Journal Name:
- ACS Nano
- Volume:
- 17
- Issue:
- 9
- ISSN:
- 1936-0851
- Page Range / eLocation ID:
- 8634 to 8645
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Plasmonic metal nanostructures are essential for plasmon‐mediated chemical reactions (PMCRs) and surface‐enhanced Raman spectroscopy (SERS). The nanostructures are commonly made from the coinage metals gold and silver. Copper (Cu) is less used mainly due to the difficulties in fabricating stable nanostructures. However, Cu is an attractive option with its strong plasmonic properties, high catalytic activities, and relatively cheap price. Herein, we fabricated tunable, reliable, and efficient Cu nanoelectrodes (CuNEs). Using time‐resolved electrochemical SERS, we have comprehensively studied the reversible chemical transformations between aromatic amine and nitro groups modified on the CuNE surface. Their PMCRs are well‐controlled by changing the surface roughness, the oxidation states of Cu, and the applied electrode potential. We thus demonstrate that the Cu nanostructures enable better investigations in the interplays between PMCR, electrochemistry, and Cu catalysis.more » « less
-
Electrochemical nitrogen reduction reaction (NRR) for ammonia synthesis might offer an alternative means to the capital- and carbon-intensive thermochemical process (Haber-Bosch) in a clean, sustainable, and decentralized way if the process is coupled to renewable electricity sources. One of the challenges in electrochemical ammonia synthesis is finding catalysts with a suitable activity for breaking N2 triple bonds at or near ambient conditions. Improving the design of electrocatalysts, electrolytes, and electrochemical cells is required to overcome the selectivity and activity barrier in electrochemical NRR. In-situ and operando surface-enhanced Raman spectroscopy (SERS) is a well-suited technique to probe electrochemical reactions at the solid-liquid (electrode/electrolyte) interface. Operando SERS allows for the detection of intermediate species even in low abundance and is used to provide insights into NRR mechanisms using hybrid plasmonic nanostructures (e.g., Au-Pd) by combining spectroscopy and electrochemistry. A potentiostat is used to apply potential on a SERS active substrate that is then monitored by changes in a spectrum. The spectroelectrochemical cell is developed to operando probe the trace of NH3 and possible intermediate species produced at the electrode/electrolyte interface. This work would aid in understanding the reaction mechanism and ultimately designing more efficient catalysts for electrochemical energy conversion systems. This material is based upon work supported by the National Science Foundation under grant no. 1904351.more » « less
-
Abstract Two‐dimensional transition metal dichalcogenides (TMDs)/graphene van der Waals (vdW) heterostructures integrate the superior light–solid interaction in TMDs and charge mobility in graphene, and therefore are promising for surface‐enhanced Raman spectroscopy (SERS). Herein, a novel TMD (MoS2and WS2) nanodome/graphene vdW heterostructure SERS substrate, on which an extraordinary SERS sensitivity is achieved, is reported. Using fluorescent Rhodamine 6G (R6G) as probe molecules, the SERS sensitivity is in the range of 10−11to 10−12mon the TMD nanodomes/graphene vdW heterostructure substrates using 532 nm Raman excitation, which is comparable to the best sensitivity reported so far using plasmonic metal nanostructures/graphene SERS substrates, and is more than three orders of magnitude higher than that on single‐layer TMD and graphene substrates. Density functional theory simulation reveals enhanced electric dipole moments and dipole–dipole interaction at the TMD/graphene vdW interface, yielding an effective means to facilitate an external electrostatic perturbation on the graphene surface and charge transfer. This not only promotes chemical enhancement on SERS, but also enables electromagnetic enhancement of SERS through the excitation of localized surface plasmonic resonance on the TMD nanodomes. This TMD nanodome/graphene vdW heterostructure is therefore promising for commercial applications in high‐performance optoelectronics and sensing.more » « less
-
Abstract Multicellular systems, such as microbial biofilms and cancerous tumors, feature complex biological activities coordinated by cellular interactions mediated via different signaling and regulatory pathways, which are intrinsically heterogeneous, dynamic, and adaptive. However, due to their invasiveness or their inability to interface with native cellular networks, standard bioanalysis methods do not allow in situ spatiotemporal biochemical monitoring of multicellular systems to capture holistic spatiotemporal pictures of systems‐level biology. Here, a high‐throughput reverse nanoimprint lithography approach is reported to create biomimetic transparent nanoplasmonic microporous mesh (BTNMM) devices with ultrathin flexible microporous structures for spatiotemporal multimodal surface‐enhanced Raman spectroscopy (SERS) measurements at the bio‐interface. It is demonstrated that BTNMMs, supporting uniform and ultrasensitive SERS hotspots, can simultaneously enable spatiotemporal multimodal SERS measurements for targeted pH sensing and non‐targeted molecular detection to resolve the diffusion dynamics for pH, adenine, and Rhodamine 6G molecules in agarose gel. Moreover, it is demonstrated that BTNMMs can act as multifunctional bio‐interfaced SERS sensors to conduct in situ spatiotemporal pH mapping and molecular profiling ofEscherichia colibiofilms. It is envisioned that the ultrasensitive multimodal SERS capability, transport permeability, and biomechanical compatibility of the BTNMMs can open exciting avenues for bio‐interfaced multifunctional sensing applications both in vitro and in vivo.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acsnano.3c01491
