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Photothermally Assisted Thinning of Silicon Nitride Membranes for Ultrathin Asymmetric Nanopores
摘要： Sculpting solid-state materials at the nanoscale is an important step in manufacturing of numerous types of sensor devices, in particular solid-state nanopore sensors. Here we present mechanistic insight into laser-induced thinning of low-stress silicon nitride (SiNx) membranes and films. In a recent study, we observed that focusing a visible wavelength laser beam on a SiNx membrane results in efficient localized heating, and used this effect to control temperature at a solid-state nanopore sensor. A side-effect of the observed heating was that the pores expand/degrade under prolonged high-power illumination, prompting us to study the mechanism of this etching process. We find that SiNx can be etched under exposure to light of ~107 W/cm2 average intensity, with etch rates that are influenced by the supporting electrolyte. Combining this controlled etching with dielectric breakdown, an electrokinetic process for making pores, nanopores of arbitrary dimensions as small as 1-2 nm in diameter and thickness can easily be fabricated. Evidence gathered from biomolecule-pore interactions suggests that the pore geometries obtained using this method are more funnel-like, rather than hourglass-shaped. Refined control over pore dimensions can expand the range of applications of solid-state nanopores, for example, biopolymer sequencing and detection of specific biomarkers.
关键词： photothermal heating,single-molecule,dielectric breakdown,Nanopores,nanofabrication
更新于2025-09-23 15:21:21
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Plasmonic Nanostructures for Photothermal Heating and Near-Field Enhancements: A Comparative Survey of Nineteen Metals
摘要： Localized surface plasmon resonances (LSPRs) optically excited in metallic nanoparticles (NPs) produce beneficial thermal and non-thermal effects. Non-thermal effects, such as enhancing and localizing fields on subwavelength scales and photo-generating hot carriers, have been extensively exploited, while interest in highly localized photothermal heating is reviving. Both effects may work together synergistically, such as increasing the efficiency of a photocatalytic process, or they may work against each other, such as accelerating desorption of analytes in surface enhanced spectroscopy. To compare how these effects depend on the composition and size of the NP, we report a quantitative survey of thermal and non-thermal properties in the visible-solar (1.7–4.1 eV) and UV (3.1-6.2 eV) ranges for nineteen metals, including conventional plasmonic materials (gold, silver, copper), an alkaline earth metal (magnesium), post-transition metals (aluminum, gallium, indium), and a wide variety of transition metals. Figures of merit that reflect the resistive losses and electric field enhancement factor of the NPs were used in this comparative analysis.
关键词： Photothermal heating,Nanoparticles,Near-field enhancements,Plasmonics,Metals
更新于2025-09-23 15:19:57
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Cellulose paper support with dual-layered nanoa??microstructures for enhanced plasmonic photothermal heating and solar vapor generation
摘要： Plasmonic nanoparticles, such as gold nanoparticles (AuNPs), have been actively applied in solar vapor generation for seawater desalination and water purification, owing to their photothermal heating performances. Such nanoparticles have been frequently anchored within porous supporting materials to ensure easy handling and water absorption. However, there has been limited progress in improving the transport efficiency of light to nanoparticles within porous supports to achieve more effective photothermal heating. Here, we show an enhanced light absorption of AuNPs by supporting on a cellulose paper with tailored porous structures for efficient photothermal heating. The paper consists of AuNP-anchored cellulose nanofibers and cellulose pulp as the top and bottom layers, respectively, which provides dual-layered porous nano-microstructures in the perpendicular direction. Then, the bottom layer with pulp-derived microstructures reflects the transmitted light back to AuNPs within the top layer, which improves their light absorptivity. Thus, under 1 sun illumination, the dual-layered paper demonstrates superior performance in photothermal heating (increases from 28 °C to 46 °C) and solar vapor generation (1.72 kg m?2 h?1) compared with the single-layered AuNP-anchored cellulose nanofiber paper even at the same AuNP content. Furthermore, the water evaporation rate per AuNP content of the dual-layered paper is more than 2 times higher than those of the state-of-the-art AuNP-anchored porous materials under the same light irradiation. This strategy enables the efficient use of precious plasmonic nanoparticles for further development of solar vapor generation.
关键词： gold nanoparticles,Plasmonic nanoparticles,cellulose paper,nano-microstructures,photothermal heating,solar vapor generation
更新于2025-09-23 15:19:57
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From normal diffusion to superdiffusion: Photothermal heating of plasmonic core-shell microgels
摘要： The motion of core-shell colloids during laser heating is studied using angle-dependent pump-probe dynamic light scattering. The cores consist of a single spherical gold nanoparticle whose localized surface plasmon resonance has a strong spectral overlap with the wavelength of the pump laser. They are homogeneously encapsulated in thick hydrogel shells composed of either chemically cross-linked poly-N-isopropylacrylamide or poly[2-(2-methoxyethoxy)ethyl methacrylate], both of which exhibit a temperature-dependent volume phase transition. Thus, upon heating beyond the transition temperature, the hydrogel shells shrink. Intensity-time autocorrelation functions are recorded while illuminating the samples with the pump laser and hence heating the gold cores. With increasing laser intensity, the dynamics changes from normal Brownian motion to superdiffusion. Nevertheless, in the high-q limit, the relaxation times can be extracted and used to estimate the temperature increase, which can reach almost 10 K. This causes a significant deswelling of the hydrogel shells, which is also measured.
关键词： temperature-dependent volume phase transition,photothermal heating,dynamic light scattering,superdiffusion,plasmonic core-shell microgels
更新于2025-09-16 10:30:52
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Taking the Heat Off of Plasmonic Chemistry
摘要： Plasmon-excitation-mediated chemistry, which is a rapidly growing field, is founded on a simple principle: the excitation of the localized surface plasmon resonance (LSPR) of metal nanoparticles triggers chemical reactions on the surfaces of the nanoparticles. Early examples of plasmon-excitation-driven nanoparticle synthesis and hot-electron-driven chemical reactions induced by ultrashort pulse excitation of metal nanoparticles can be thought of as precursors to the findings of direct photocatalysis by plasmonic nanoparticles, which is the focus of this Viewpoint. The field in its current state was, in large part, invigorated by a 2011 paper, which showed that the excitation of the LSPR of Ag nanoparticles by continuous-wave (CW), visible-frequency light triggered the dissociation of adsorbed O2. The O· atoms thus produced were utilized for industrially relevant oxidation reactions such as those of propylene and ethylene, which would have otherwise required high-temperature and -pressure conditions to proceed at appreciable rates. In the absence of visible-light excitation, the bond dissociation and oxidation reactions proceeded at appreciably low rates, which indicated that plasmonic excitation enhanced the rates of these chemical reactions. The phenomenon is, therefore, termed as plasmonic catalysis or plasmonic photocatalysis.
关键词： Plasmonic catalysis,Plasmonic photocatalysis,Chemical reactions,Hot electrons,Photothermal heating
更新于2025-09-16 10:30:52
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Effects of Mid‐Infrared Graphene Plasmons on Photothermal Heating
摘要： We theoretically investigate the plasmonic heating of graphene-based systems under the mid-infrared laser irradiation, where periodic arrays of graphene plasmonic resonators are placed on dielectric thin films. Optical resonances are sensitive to structural parameters and the number of graphene layers. Under mid-infrared laser irradiation, the steady-state temperature gradients are calculated. We find that graphene plasmons significantly enhance the confinement of electromagnetic fields in the system and lead to a large temperature rise compared to the case without graphene. The correlations between temperature change and the optical power, laser spot, and thermal conductivity of dielectric layer in these systems are discussed. Our numerical results are in accordance with experiments.
关键词： plasmonics,metamaterials,photothermal heating,graphene
更新于2025-09-12 10:27:22