Thermal management underpins essentially every energy technology, from solar harvesters and waste-heat recovery to industrial process heating and electronic cooling. Yet, thermal systems remain limited compared to their electrical and optical counterparts: they lack a direct equivalent of active control elements that enable on-demand pulse generation. As a result, in conventional thermal energy storage architectures, the amount of energy stored and the peak power at which it can be released are both fixed at design time by material properties and heat-exchanger geometry, locking each device to a single operating point in the energy–power plane. This rigidity is incompatible with applications that require short, high-power thermal bursts on demand. Here we show that a counter-flow heat oscillator admits an actively switchable effective thermal quality factor, Q, and that modulating Q on sub-dwell-time scales generates transient outlet power exceeding the steady input by more than an order of magnitude. We formalize the system as a dissipative resonant thermal cavity with Q controlled by the balance between advective and conductive transport and environmental losses, and we experimentally demonstrate, in a water-based dual-channel device, ∼5-fold transient power amplification through controlled flow detuning, in quantitative agreement with our thermofluidic model. Active Q-switching establishes a distinct mode of thermal power management, accessing ∼5× (demonstrated experimentally) to ∼40× (projected numerically) peak-power amplification on continuous input through a single architecture, a regime inaccessible to passive thermal storage and a missing analogue of the active pulse-generation tools long available in optics and electronics.

Optics that allow us to see clearly along one viewing direction while obscuring others' view of us are useful in numerous settings, including privacy-preserving window screens and one-way mirrors for psychological studies. Additionally, due to the rise of cameras that are able to see outside the visible spectrum, there is a need for optics that can also provide one-way visibility at these wavelengths. This is particularly challenging for thermal (i.e., infrared) imaging because most existing methods require precise control of scene illumination, which is difficult to achieve in the infrared. To address this challenge, we demonstrate broadband, passive one-way visibility by precisely tuning the position and optical parameters of a single optical scatterer. We show the benefits of our approach in both a simulated and an experimental testbed. With experimental data, we demonstrate a 5.22× and 5.23× improvement in the degree of asymmetry for midwave infrared (MWIR) and visible (VIS) wavelengths, respectively. Ultimately, our method introduces a robust, passive one-way visibility system at midwave infrared (MWIR), which can aid in numerous privacy preservation applications.

Oxygen vacancies on a metal oxide surface enhance its catalytic activity. Here we investigate the controlled introduction of oxygen vacancies on core-shell Al@TiO2 antenna-reactor nanoparticle photocatalysts. Thermal annealing in an H2-reducing atmosphere creates more oxygen vacancies in the surface TiO2 layer of Al@TiO2 nanoparticles compared to the same process under inert (He) or oxidative (O2) ambients. The photocatalytic reactivity enhancement was evaluated by investigating two reactions: hole-mediated methanol decomposition and electron-mediated hydrogen dissociation. The ability to modify plasmonic nanoparticle photocatalyst reactivity in this simple and controllable manner demonstrates the potential of this approach to tailor and enhance the performance of plasmonic antenna-reactor photocatalysts.

This work investigates electromagnetic energy transfer mechanisms in nanophotonic systems, focusing on ultrafast plasmonic photocatalysis and optimized photothermal cancer therapy enabled by predictive modeling techniques. Key findings demonstrate how photothermal effects can be quantified and enhanced through tailored designs and time-dependent excitation.

Identifying reactive sites and measuring their activities is crucial for enhancing the efficiency of every catalyst. Reactivity maps can guide the development of next-generation photocatalysts like 2D transition metal dichalcogenides, which suffer from low conversion rates. While their electrocatalytic sites are well-studied, their photocatalytic sites remain poorly understood. Using scanning photoelectrochemical microscopy, we spatially resolve the photoreactivity of MoS2 monolayers, a prototypical 2D transition metal dichalcogenide, for redox reactions, including H2 production from water. Aligned-unaligned excitation-detection measurements reveal that photogenerated holes and electrons exhibit distinct behaviors. Oxidation products localize at the excitation spot, indicating stationary holes, while photoreduction occurs up to at least 80 microns away, showing exceptional electron mobility. We also elucidate the photochemical reactivity according to the nature of the electronic excitation, showing that the internal quantum efficiency of strongly-bound A-excitons outperforms weakly-bound (free-carrier like) C-excitons across the flake. These findings offer novel guidance to rationally design 2D photocatalysts via engineering their optical and charge extraction abilities for efficient solar energy conversion.

The generation and dynamics of plasmon-induced hot carriers in gold nanoparticles offer crucial insights into nonequilibrium states for energy applications, yet the underlying mechanisms remain experimentally elusive. Here, we leverage ultrafast X-ray absorption spectroscopy (XAS) to directly capture hot carrier dynamics with sub-50 fs temporal resolution, providing clear evidence of plasmon decay mechanisms. We observe the sequential processes of Landau damping (~25 fs) and hot carrier thermalization (~1.5 ps), identifying hot carrier formation as a significant decay pathway. Energy distribution measurements reveal carriers in non-Fermi-Dirac states persisting beyond 500 fs and observe electron populations exceeding single-photon excitation energy, indicating the role of an Auger heating mechanism alongside traditional impact excitation. These findings deepen the understanding of hot carrier behavior under localized surface plasmon resonance, offering valuable implications for applications in photocatalysis, photovoltaics, and phototherapy. This work establishes a methodological framework for studying hot carrier dynamics, opening avenues for optimizing energy transfer processes in nanoscale plasmonic systems.

The detection and identification of polycyclic aromatic hydrocarbons (PAHs) and their derivatives, polycyclic aromatic compounds (PACs), are essential for environmental and health monitoring, for assessing toxicological exposure and their associated health risks. PAHs/PACs are the most dangerous chemicals found in tobacco smoke, and cigarette use during pregnancy can convey these molecules to the developing fetus through the placenta. This exposure is associated with many negative health outcomes, from premature birth to sudden infant death syndrome and adverse neurodevelopmental disorders. This study demonstrates the use of surface-enhanced Raman and surface-enhanced infrared absorption spectroscopies for direct detection of PAHs/PACs in human placental tissue. We applied two spectroscopy-informed machine learning algorithms, Characteristic Peak Extraction (CaPE) and Characteristic Peak Similarity (CaPSim), to identify the specific PAHs and PACs present in the placenta of women who smoked tobacco cigarettes in pregnancy compared to spectra of the placenta from self-reported nonsmokers. CaPE and CaPSim analysis enabled a clear distinction between these two groups. Independent verification was accomplished by detecting PAH-DNA and PAC-DNA adducts in the smoking group by means of a 32P-postlabeling assay. These findings highlight the effectiveness of combining surface-enhanced spectroscopies with informed ML analysis for the streamlined detection of hazardous environmental compounds in human tissues, suggesting broader applications in clinical diagnostics and public health surveillance.

Surface-enhanced Raman spectroscopy (SERS) has evolved significantly over fifty years into a powerful analytical technique. This review aims to achieve five main goals. (1) Providing a comprehensive history of SERS's discovery, its experimental and theoretical foundations, its connections to advances in nanoscience and plasmonics, and highlighting collective contributions of key pioneers. (2) Classifying four pivotal phases from the view of innovative methodologies in the fifty-year progression: initial development (mid-1970s to mid-1980s), downturn (mid-1980s to mid-1990s), nano-driven transformation (mid-1990s to mid-2010s), and recent boom (mid-2010s onwards). (3) Illuminating the entire journey and framework of SERS and its family members such as tip-enhanced Raman spectroscopy (TERS) and shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) and highlighting the trajectory. (4) Emphasizing the importance of innovative methods to overcome developmental bottlenecks, thereby expanding the material, morphology, and molecule generalities to leverage SERS as a versatile technique for broad applications. (5) Extracting the invaluable spirit of groundbreaking discovery and perseverant innovations from the pioneers and trailblazers. These key inspirations include proactively embracing and leveraging emerging scientific technologies, fostering interdisciplinary cooperation to transform the impossible into reality, and persistently searching to break bottlenecks even during low-tide periods, as luck is what happens when preparation meets opportunity.

Aluminum, the most abundant metal in the earth's crust, is protected and stabilized by a native surface oxide layer. Once the oxide is breached, rapid oxidation can occur, igniting Al in particulate form. By slowly heating and cooling Al nanocrystals of well controlled size and shape, we observe a localized void formation under the surface oxide, occurring on specific crystalline facets. These voids form during the slow cooling phase following heating, even for temperatures below the threshold of oxidation, in a manner sensitive to Al nanocrystal size and morphology, surface facet, and the degree of oxide porosity. Because of these sensitivities, this void formation may provide new strategies for modifying Al nanocrystal growth and developing Al nanocrystal-based hybrid materials.

Fresh water scarcity is a pressing global issue exacerbated by climate change and growing populations. Current desalination technologies face limitations: reverse osmosis requires grid electrical power and specialized membranes, thermal desalination is inefficient and membrane systems are prone to fouling. Here we introduce Solar Thermal Resonant Energy Exchange Desalination (STREED)-a robust, membrane-free and efficient solar thermal desalination approach. STREED couples the basic mechanisms of humidification-dehumidification distillation to Resonant Energy Transfer, a dynamic energy recovery scheme described in the language of oscillators. Resonant Energy Transfer achieves optimized and controllable thermal gradients for passive evaporation and condensation. Dynamic tuning of system flow rates in response to varying solar intensities substantially increases efficiency, extending fresh water production over 24 hours per day. We predict week-long fresh water productivity increases of 77% with an average gained output ratio near similar to 1.9 at seawater salinity, depending on available solar irradiation. STREED adapts to fluctuating solar inputs, offering a scalable solution for decentralized, off-grid water treatment crucial for remote communities facing water scarcity.

Plasmonic nanostructures enable efficient light-to-chemical energy conversion by concentrating optical energy into nanoscale volumes. A key mechanism in this process is chemical interface damping (CID), where surface plasmons are damped by adsorbed molecules, enabling the transfer of charge to adsorbed molecules. Here, we investigate the relationship between CID and adsorbate-induced changes in dc electrical resistivity for four molecular adsorbates on gold surfaces. Our results reveal two distinct CID regimes. On one hand, CID takes place via direct resonant electronic transitions to the lowest unoccupied molecular orbital. This mechanism is dependent on plasmon energy. In the second regime, plasmon damping takes place through inelastic electron scattering at the metal-molecule interface. This regime shows a weaker dependency on plasmon energy. This mechanism also leads to adsorbate-induced changes in dc resistivity. These findings provide previously unidentified insights into the microscopic origins of plasmon damping and offer a unified framework for understanding metal-adsorbate energy transfer.

Catalyst stability is critical for determining the scientific and industrial value of important catalytic processes. In industry, catalysts invariably undergo deactivation, requiring frequent regeneration or replacement. Traditional methods for enhancing stability typically involve modifying the catalyst composition or structure and optimizing the reaction conditions. Plasmonic photocatalysis is emerging as a promising technology for efficient, environmentally friendly catalysis, frequently demonstrating improved performance due to nonequilibrium, "hot" carriers generated by plasmon decay. Here we demonstrate how hot carriers in plasmonic photocatalysis enhance the catalyst stability. Using copper-based antenna-reactor photocatalysts in three representative reactions (nitrous oxide decomposition, carbon monoxide oxidation, and steam methane reforming), we observe how hot carriers facilitate desorption of poisoning species, maintaining catalyst stability. Furthermore, plasmonic photocatalysis improves the structural stability by preventing catalyst sintering, which is a common phenomenon in thermocatalysis. Our findings highlight hot carrier generation as an effective strategy for stabilizing copper-based antenna-reactor photocatalysts, paving the way for extended catalyst lifetimes.

Surface-enhanced Raman spectroscopy (SERS) gained much attention following initial claims and subsequent verifications of single-molecule sensitivity. SERS substrates based on plasmonic nanoparticles in close proximity create "hot spots" when illuminated, which, in the single-molecule limit, follow log-normal statistics for molecular occupancy. Here, we rigorously examine the transition from the single-molecule limit to the limit of hot spot saturation, a regime that follows Gaussian statistics, by varying a 1:1 bianalyte concentration over 3 orders of magnitude. The bianalyte model is extended here to follow this transition, and the electromagnetic "hot spots" of both Au nanoparticle and Au nanoshells-based SERS substrates are described theoretically. This combined experimental-theoretical study provides a rigorous foundation for quantifying trace analyte detection over a wider and highly practical concentration range.

Catalysis stands as an indispensable cornerstone of modern society, underpinning the production of over 80% of manufactured goods and driving over 90% of industrial chemical processes. As the demand for more efficient and sustainable processes grows, better catalysts are needed. Understanding the working principles of catalysts is key, and over the last 50 years, surface-enhanced Raman Spectroscopy (SERS) has become essential. Discovered in 1974, SERS has evolved into a mature and powerful analytical tool, transforming the way in which we detect molecules across disciplines. In catalysis, SERS has enabled insights into dynamic surface phenomena, facilitating the monitoring of the catalyst structure, adsorbate interactions, and reaction kinetics at very high spatial and temporal resolutions. This review explores the achievements as well as the future potential of SERS in the field of catalysis and energy conversion, thereby highlighting its role in advancing these critical areas of research.

Steam methane reforming (SMR) is the major industrial process for hydrogen production. It currently relies on high-temperature operating conditions and is associated with high carbon intensity. Photocatalytic SMR could provide greener and potentially more efficient H2 production. Here we demonstrate a plasmonic photocatalytic approach based on a Cu-Rh antenna-reactor photocatalyst for highly reactive, selective and stable SMR due to plasmon-mediated hot carrier contributions. We observe that the photocatalyst is intrinsically stable in photocatalysis but deactivates under thermocatalysis; however, the thermally deactivated catalyst can be regenerated by resonant illumination. The regeneration mechanism is studied in detail and found to be caused by plasmon-induced associative desorption of oxygen and carbon species. Catalysts used for steam methane reforming frequently suffer from deactivation by coking and oxidation. Here an active Cu-Rh plasmonic antenna-reactor photocatalyst is selective and stable under illumination but deactivates under purely thermal conditions. The thermally deactivated catalyst can then be regenerated under illumination.

Aluminum nanocrystals created by catalyst-driven colloidal synthesis support excellent plasmonic properties, due to their high level of elemental purity, monocrystallinity, and controlled size and shape. Reduction in the rate of nanocrystal growth enables the synthesis of highly anisotropic Al nanowires, nanobars, and singly twinned "nanomoustaches". Electron energy loss spectroscopy was used to study the plasmonic properties of these nanocrystals, spanning the broad energy range needed to map their plasmonic modes. The coupling between these nanocrystals and other plasmonic metal nanostructures, specifically Ag nanocubes and Au films of controlled nanoscale thickness, was investigated. Al nanocrystals show excellent long-term stability under atmospheric conditions, providing a practical alternative to coinage metal-based nanowires in assembled nanoscale devices.

The recent rise of plasmonic materials for solar-to-chemical energy conversion places a focus on the mechanisms associated with charge and energy flow at the metal–molecule interface. Understanding the connection between these effects and their roles in the plasmonic excitations of adsorbed molecules has been challenging. In this Review, we strive to provide a general framework—based on the concept of electron scattering—that encompasses the most important effects at the plasmonic metal–molecule interface. First we use the model of adsorbate-induced surface resistivity to understand the chemical specificity of the electron scattering process. We then analyse two of the most prominent effects in plasmonics through the lens of the electron scattering model: chemical interface damping and the chemical model of surface-enhanced Raman scattering. We show how most metal–adsorbate charge- or energy-transfer interactions can be mapped into two major classes—electron scattering through molecular resonances and direct non-resonant electron scattering. Plasmonic excitations can enhance the interaction between a metal and molecules adsorbed onto its surface. This Review summarizes the different effects involved in this process and places them into a framework based on electron scattering.

Correlating data from optical, structural, and theoretical methods allows the properties of highly faceted Cd2SnO4 (CTO) inverted spinel plasmonic semiconductor nanocrystals (PSNCs) to be fully evaluated. The use of Sn(II) in the colloidal reaction for CTO results in reproducible octahedral PSNCs with an aspect ratio of 1.30. Correlating extinction spectra with magnetic circular dichroism yields a carrier density (n = 5.19 x 10(19 )cm(-3)) and carrier effective mass (m* = 0.022m(e)) respectively. Cd-113 and Sn-119 solid-state NMR experiments show clear evidence of metallic-like carriers in CTO NCs based upon the observation of Knight shifts. These data suggest that carrier formation in CTO arises from Sn antisite occupation of octahedral Cd sites (Sn-Cd)(.) From a broader perspective, the results point to wide-bandgap spinels as being an important but understudied class of plasmonic PSNCs.

Next-generation wearable and optoelectronic technologies requires highly adaptable light manipulation capabilities for applications in sensors, displays, and optical switches on flexible substrates. Here, a cost-effective approach is presented for realizing a Tamm Plasmon (TP) resonant device on a flexible platform by combining nanoimprint lithography with layer-by-layer assembly. The TP device incorporates a stretchable, 1D bragg (BRG) stack coupled with a gold (Au) and aluminum (Al) metasurface, whose dimensions are designed to enable tunability in the visible and near-infrared (NIR) regions of the spectrum. The device exhibits substantial reflected intensities (approximate to 75%) and a well-defined, narrow TP minimum of approximately 30 nm. Both TP and Fano resonances can be clearly observed by incorporating symmetry-broken metasurface features with the BRG stack. The integrated system is subjected to both uniaxial (up to 37% strain) and biaxial (up to 25% strain) stretching, demonstrating dynamic chromatic responses in both the visible and near-infrared regimes with sensitivities of approximate to 6.2 nm/%. This work clearly demonstrates a cost-effective route for the fabrication of multi-plasmon resonant devices with tunable colors on a flexible platform. This study introduces a cost-effective method for constructing Tamm Plasmon (TP) resonant devices on flexible substrates, crucial for advancing flexible and wearable technology platforms. Combining nanoimprint lithography with layer-by-layer assembly integrates a stretchable Bragg stack with gold and aluminum metasurfaces, facilitating tunable structural colors and optical resonances from visible to near-infrared ranges. Additionally, this stretchable device exhibits long-term stability, reversibility, and high spectral sensitivity to mechanical strains. image