Tuning the Fermi Level of Silver Nanoparticles by Thiocyanate Ions for Plasmonic Catalysis.

The Fermi level of plasmonic metals governs the generation and energetics of hot electrons, thereby determining their catalytic behavior. Herein, we introduce thiocyanate ions (SCN) as surface ligands to modulate the Fermi level of silver. Their strong and stable chemisorption enables efficient tuning of the electronic structure over a broad range.

Challenges and Prospects of Personalized Healthcare Based on Surface-Enhanced Raman Spectroscopy.

Personalized healthcare monitoring is a transformative tool for preventing potential risks and enhancing health status, particularly through molecular-level insights. Advances in nanotechnology, smart devices, and artificial intelligence (AI) have revolutionized personalized healthcare, especially in point-of-care testing (POCT), enabling early detection and timely intervention. Recently, surface-enhanced Raman spectroscopy (SERS) technology, particularly with flexible chips, has shown immense promise in this field due to its in situ, rapid, specific, and efficient detection capabilities.

Interwoven MXene Sediment Architecture Empowers High-Performance Flexible Microwave Devices.

Flexible microwave devices are critical in wearable electronic systems for wireless communication, where highly conductive materials are essential to ensure optimal electromagnetic performance. Titanium carbide (MXene), renowned for its excellent conductivity, lightweight, and easy fabrication, emerges as a promising alternative to conventional metal materials in wearable electronics. However, the technical limitation of MXene suspensions or sediments in fabricating high-performance microwave devices with low cost and scalable production present a huge challenge for their practical applications.

Unveiling the Cation Effects on Electrocatalytic CO Reduction via Operando Surface-enhanced Raman Spectroscopy.

The electrocatalytic carbon dioxide reduction reaction (CORR) can be significantly improved by the presence of alkali metal cations, yet the underlying mechanisms remain unclear. In this study, we developed clean Cu nanoparticles with tailored curvatures to modulate the local concentration of K cations and investigate their effects on CORR. The adjustment of particle curvature allows for direct control over cation concentrations within the electrochemical double layer, enabling broad-range modulation of cation concentration without concerns regarding solubility limitations or anionic interference.

High-specificity SERS sensing with magnet-powered hierarchically structured micromotors.

This work reports a hierarchically structured micromotor (HSM) surface-enhanced Raman scattering (SERS) platform comprising 3D tubular configurations with nanostructured outer walls. The HSMs can be powered by an external magnetic field in solution to enrich molecules with promoted adsorption efficiency. The nanostructured outer wall serves as containers to collect molecules and produce strong localized surface plasmon resonance to intensify Raman of the enriched molecules.

MXene-Based Micromotors: Active Molecular Enrichment and Selective Raman Enhancement.

This Letter introduces MXene-based rod-like micromotors, consisting of assembled FeO@TiC core-shell nanospheres, that leverage external magnetic fields for active molecular enrichment and selective surface-enhanced Raman scattering (SERS) sensing. These micromotors enhance SERS performance by concentrating target molecules directly onto MXene surfaces during movement, enabling rapid and precise detection. Our investigation reveals how these micromotors optimize SERS through effective molecular manipulation and explores the selective Raman enhancement facilitated by the MXene-based platforms, demonstrating their significant potential in analytical applications.

Wearable Hydrogel SERS Chip Utilizing Plasmonic Trimers for Uric Acid Analysis in Sweat.

Uric acid is typically measured through blood tests, which can be inconvenient and uncomfortable for patients. Herein, we propose a wearable surface-enhanced Raman scattering (SERS) chip, incorporating a hydrogel membrane with integrated plasmonic trimers, for noninvasive monitoring of uric acid in sweat. The plasmonic trimers feature sub 5 nm nanogaps, generating strong electromagnetic fields to boost the Raman signal of surrounding molecules.

Photoinduced Charge Transfer Empowers TaC and NbC MXenes with High SERS Performance.

This study introduces two-dimensional (2D) TaC and NbC MXenes as outstanding materials for surface-enhanced Raman scattering (SERS) sensing, marking a significant departure from traditional noble-metal substrates. These MXenes exhibit exceptional SERS capabilities, achieving enhancement factors around 10 and detection limits as low as 10 M for various analytes, including environmental pollutants and drugs. The core of their SERS functionality is attributed to the robust interfacial photoinduced charge-transfer interactions between the MXenes and the adsorbed molecules.

Plasmonic trimers designed as SERS-active chemical traps for subtyping of lung tumors.

Plasmonic materials can generate strong electromagnetic fields to boost the Raman scattering of surrounding molecules, known as surface-enhanced Raman scattering. However, these electromagnetic fields are heterogeneous, with only molecules located at the 'hotspots', which account for ≈ 1% of the surface area, experiencing efficient enhancement. Herein, we propose patterned plasmonic trimers, consisting of a pair of plasmonic dimers at the bilateral sides and a trap particle positioned in between, to address this challenge.

Charge-transfer-driven ultrasensitive SERS sensing in a two-dimensional titanium carbonitride MXene.

Two-dimensional (2D) MXenes stand out as promising platforms for surface-enhanced Raman scattering (SERS) sensing owing to their metallic feature, various compositions, high surface area, compatibility with functionalization, and ease of fabrication. In this work, we report a high-performance 2D titanium carbonitride (TiCN) MXene SERS substrate. We reveal that the abundant electronic density of states near the Fermi level of TiCN MXene boosts the efficiency of photo-induced charge transfer at the interface of TiCN/molecule, resulting in significant Raman enhancement.

Probing Oxidation Mechanisms in Plasmonic Catalysis: Unraveling the Role of Reactive Oxygen Species.

Plasmon-induced oxidation has conventionally been attributed to the transfer of plasmonic hot holes. However, this theoretical framework encounters challenges in elucidating the latest experimental findings, such as enhanced catalytic efficiency under uncoupled irradiation conditions and superior oxidizability of silver nanoparticles. Herein, we employ liquid surface-enhanced Raman spectroscopy (SERS) as a real-time and tool to explore the oxidation mechanisms in plasmonic catalysis, taking the decarboxylation of -mercaptobenzoic acid (PMBA) as a case study.

Alloy Engineering Allows On-Demand Design of Ultrasensitive Monolayer Semiconductor SERS Substrates.

The chemical mechanism (CM) of surface-enhanced Raman scattering (SERS) has been recognized as a decent approach to mildly amplify Raman scattering. However, the insufficient charge transfer (CT) between the SERS substrate and molecules always results in unsatisfying Raman enhancement, exerting a substantial restriction for CM-based SERS. In principle, CT is dominated by the coupling between the energy levels of a semiconductor-molecule system and the laser wavelength, whereas precise tuning of the energy levels is intrinsically difficult.

Flexible plasmonic nanocavities: a universal platform for the identification of molecular orientations.

The molecular orientation provides fundamental images to understand molecular behaviors in chemistry. Herein, we propose and demonstrate sandwich plasmonic nanocavities as a surface-selection ruler to illustrate the molecular orientations by surface-enhanced Raman spectroscopy (SERS). The field vector in the plasmonic nanocavity presents a transverse spinning feature under specific excitations, allowing the facile modulation of the field polarizations to selectively amplify the Raman modes of the target molecules.

VSe O @Pd Sensor for Operando Self-Monitoring of Palladium-Catalyzed Reactions.

Operando monitoring of catalytic reaction kinetics plays a key role in investigating the reaction pathways and revealing the reaction mechanisms. Surface-enhanced Raman scattering (SERS) has been demonstrated as an innovative tool in tracking molecular dynamics in heterogeneous reactions. However, the SERS performance of most catalytic metals is inadequate.

Monolayer Iron Oxychloride with a Resonant Band Structure for Ultrasensitive Molecular Sensing.

Two-dimensional layered materials (2DLMs) are expected to be next-generation commercial sensors for surface-enhanced Raman scattering (SERS) sensing owing to their unique structural features and physicochemical properties. The low sensitivity and poor universality of 2DLMs are the dominant barriers toward their practical applications. Herein, we report that monolayer iron oxychloride (FeOCl) with a naturally suitable band structure is a promising candidate for ultrasensitive SERS sensing.

Flexible two-dimensional MXene-based antennas.

With the growing development of the Internet of things, wearable electronic devices have been extensively applied in civilian and military fields. As an essential component of data transmission in wearable electronics, a flexible antenna is one of the key aspects of research. Conventional metal antennas suffer from a large skin depth, and cannot satisfy the requirements of wearable electronics such as light weight, flexibility, and thinness.

Two-dimensional MBenes with ordered metal vacancies for surface-enhanced Raman scattering.

As an emerging class of two-dimensional (2D) materials, MBenes show enormous potential for optoelectronic applications. However, their use in molecular sensing as surface-enhanced Raman scattering (SERS)-active material is unknown. Herein, for the first time, we develop a brand-new high-performance MBene SERS platform.

High-specificity molecular sensing on an individual whispering-gallery-mode cavity: coupling-enhanced Raman scattering by photoinduced charge transfer and cavity effects.

Optical whispering-gallery-mode (WGM) cavities have gained considerable interest because of their unique properties of enhanced light-matter interactions. Conventional WGM sensing is based on the mechanisms of mode shift, mode broadening, or mode splitting, which requires a small mode volume and an ultrahigh -factor. Besides, WGM sensing suffers from a lack of specificity in identifying substances, and additional chemical functionalization or incorporation of plasmonic materials is required for achieving good specificity.

Investigation of the Plasmon-Activated C-C Coupling Reactions by Liquid-State SERS Measurement.

The implementation of plasmonic materials in heterogeneous catalysis was limited due to the lack of experimental access in managing the plasmonic hot carriers. Herein, we propose a liquid-state surface-enhanced Raman scattering (SERS) technique to manipulate and visualize heterogeneous photocatalysis with transparent plasmonic chips. The liquid-state measurement conquers the difficulties that arise from the plasmon-induced thermal effects, and thus the plasmon based strategies can be extended to investigate a wider range of catalytic reactions.

Flexible Two-Dimensional Vanadium Carbide MXene-Based Membranes with Ultra-Rapid Molecular Enrichment for Surface-Enhanced Raman Scattering.

Two-dimensional (2D) MXene materials have attracted broad interest in surface-enhanced Raman scattering (SERS) applications by virtue of their abundant surface terminations and excellent photoelectric properties. Herein, we propose to design highly sensitive MXene-based SERS membranes by integrating a 2D downsizing strategy with molecular enrichment approaches. Two types of 2D vanadium carbide (VC and VC) MXenes are demonstrated for ultrasensitive SERS sensing, and corresponding SERS mechanisms including the effect of 2D vanadium carbide thickness on their electron density states and interfacial photoinduced charge transfer resonance were discussed.

Electromagnetic Mechanisms or Chemical Mechanisms? Role of Interfacial Charge Transfer in the Plasmonic Metal/Semiconductor Heterojunction.

The plasmonic metal/semiconductor heterojunction provides a unique paradigm for manipulating light to improve the efficiency of plasmonic materials. Previous studies suggest that the improvement originates from the enhanced carrier exchanges between the plasmonic component of the heterojunction and molecules. This viewpoint, known as the chemical mechanism, is reasonable but insufficient, because the construction of the heterojunction will lead to a charge redistribution in the plasmonic component and cause changes in its physical characteristics.

Verification and Analysis of Single-Molecule SERS Events via Polarization-Selective Raman Measurement.

We propose polarization-selective Raman measurement as a decent method for single-molecule surface-enhanced Raman scattering (SMSERS) verification. This approach features rapid acquisition of SMSERS events and appeals liberal requirements for analyte concentration. It is demonstrated as an efficient tool in sorting out dozens of SMSERS events from a large-scale plasmonic dimer array.

Manipulating Hot-Electron Injection in Metal Oxide Heterojunction Array for Ultrasensitive Surface-Enhanced Raman Scattering.

Efficient photoinduced charge transfer (PICT) resonance is crucial to the surface-enhanced Raman scattering (SERS) performance of metal oxide substrates. Herein, we venture into the hot-electron injection strategy to achieve unprecedented enhanced PICT efficiency between substrates and molecules. A heterojunction array composed of plasmonic MoO and semiconducting WO is designed to prove the concept.