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Surface-to-volume ratio drives photoelelectron injection from nanoscale gold into electrolyte
摘要： Hot charge carriers from plasmonic nanomaterials currently receive increased attention due to their promising potential in important applications such as solar water splitting. While a number of important contributions were made on plasmonic charge carrier generation and their transfer into the metal’s surrounding in the last decades, the local origin of those carriers is still unclear. With our study employing a nanoscaled bicontinous network of nanoporous gold, we take a comprehensive look at both subtopics in one approach and give unprecedented insights into the physical mechanisms controlling the broadband optical absorption and the generation and injection of hot electrons into an adjacent electrolyte where they enhance electrocatalytic hydrogen evolution. This absorption behavior is very different from the well-known localized surface plasmon resonance effects observed in metallic nanoparticles. For small ligament sizes the plasmon decay in our network is strongly enhanced via surface collisions of electrons. These surface collisions are responsible for the energy transfer to the carriers, thus, the creation of hot electrons from a broad spectrum of photon energies. As we reduce the gold ligament sizes below 30 nm, we demonstrate an occurring transition from absorption that is purely exciting 5d-electrons from deep below the Fermi level to an absorption which significantly excites “free” 6sp-electrons to be emitted. We differentiate these processes via assessing the internal quantum efficiency of the gold network photoelectrode as a function of the feature size providing a size-dependent understanding of the hot electron generation and injection processes in nanoscale plasmonic systems. We demonstrate that the surface effect - compared to the volume effect – becomes dominant and leads to significantly improved efficiencies. The most important fact to recognize is that in the surface photoeffect presented here, absorption and electron transfer are both part of the same quantum mechanical event.
关键词： Hot electron,Photoemission,Water splitting,Hydrogen evolution,Carrier injection,Surface damping,Nanoporous Au
更新于2025-10-22 19:40:53
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Silicon-Based Embedded Trenches of Active Antennas for High-Responsivity Omnidirectional Photodetection at Telecommunication Wavelengths
摘要： Although the use of plasmonic nanostructures for photodetection below the band gap energy of the semiconductor has been intensively investigated recently, efficiencies of such hot electron-based devices have, unfortunately, remained low because of the inevitable energy loss of the hot electrons as they move and transfer in active antennas based on metallic nanostructures. In this work, we demonstrate the concept of high-refractive-index material-embedded trench-like (ETL) active antennas that could be used to achieve almost 100% absorbance within the ultrashallow region (approximately 10 nm) beneath the metal?semiconductor interface, which is a much smaller distance compared with the hot electrons’ mean free path in the noble metal layer. Taking advantage of these ETL-based active antennas, we obtained photoresponsivities under zero bias at wavelengths of 1310 and 1550 nm of 5854 and 693 nA mW?1, respectively—values higher than most those previously reported for active antenna-based silicon (Si) photodetectors that operate at optical telecommunication wavelengths. Furthermore, the ETL antenna strategy allowed us to preserve an omnidirectional and broadband photoresponse, with a superior degree of detection linearity of R2 = 0.98889 under the light of low power density (down to 11.1 μW cm?2). The photoresponses of the ETL antenna-based device varied by less than 10% upon changing the incident angle from normal incidence to 60°. Because these ETL-based devices provide high responsivity and omnidirectional detection over a broad bandwidth, they show promising potentials for use in hot electron-based optoelectronics for many applications (e.g., Si photonics, energy harvesting, photocatalysis, and sensing devices).
关键词： hot electron,embedded,plasmon,Schottky,high-refractive-index material
更新于2025-09-23 15:23:52
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Hot electron-induced electrochemiluminescence at cellulose derivatives-based composite electrodes
摘要： The possibility of using cellulose derivative films as (i) insulating material on metal electrodes or (ii) in composite electrode films on metal to produce hot electron-induced electrochemiluminescence (HECL) was studied. It was shown that the luminophores known to produce HECL at thin insulating film coated cathodes (e.g. Si/SiO2 and Al2O3 electrodes) produced HECL with the present novel electrodes. In the case of composite films consisting of cellulose material doped with conducting carbon particles, the optimal cellulose/carbon black ratios were investigated by measuring the time-resolved HECL (TR-HECL) of an aromatic Tb(III) chelate. In addition to Tb(III) chelate, other well-known labels, fluorescein and Ru(bpy)3 2+ chelate, were demonstrated to produce strong HECL at the present composite electrodes, which are more environmental friendly in disposable assay cartridges as the plastic-based composites we have studied previously. Thus, it is now possible on the present basis to manufacture biodegradable paper-based assay cartridges with HECL detection of labels at biodegradable electrodes. It was shown that the present composite films are stable over wide pH range, and also time-resolved detection of Ru(bpy)3 2+ chelate is possible although its luminescence lifetime if quite short. The calibration curves were measured for presently used aromatic Tb(III) chelate and for Ru(bpy)3 2+. The detection limit (s/n = 3) was 2 · 10?10 M for the Tb(III)-chelate and 4 · 10?9 M for Ru(bpy)3 2+ in time-resolved detection mode. The relative standard deviation for Tb(III)-L1 (n = 5) emission at 10?5 M concentration was 2%. Wide linear range and low detection limits suggests that cellulose based composite electrodes can be used in HECL bioaffinity assays which was finally demonstrated here by an immunometric immunoassay.
关键词： Bioaffinity assays,Cellulose derivatives,Lanthanide electrochemiluminescence,Immunoassays,Electrochemiluminescence,Hot electron electrochemistry
更新于2025-09-23 15:23:52
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Direct Imaging of Surface Plasmon-Driven Hot Electron Flux on the Au Nanoprism/TiO <sub/>2</sub>
摘要： Direct measurement of hot electron flux from a plasmonic Schottky nanodiode is important for obtaining fundamental insights explaining the mechanism for electronic excitation on a surface. Here, we report the measurement of photo-induced hot electrons on a triangular Au nanoprism on TiO2 under incident light with photoconductive atomic force microscopy (pc-AFM), which is direct proof of the intrinsic relation between hot electrons and localized surface plasmon resonance. We find that the local photocurrent measured on the boundary of the Au nanoprism is higher than that inside the Au nanoprism, indicating that field confinement at the boundary of the Au nanoprism acts as a hot spot, leading to the enhancement of hot electron flow at the boundary. Under incident illumination with a wavelength near the absorption peak (645 nm) of a single Au nanoprism, localized surface plasmon resonance resulted in the generation of a higher photo-induced hot electron flow for the Au nanoprism/TiO2, compared with that at a wavelength of 532 nm. We show that the application of a reverse bias results in a higher photocurrent for the Au nanoprism/TiO2, which is associated with a lowering of the Schottky barrier height caused by the image force. These nanoscale measurements of hot electron flux with pc-AFM indicate efficient photon energy transfer mediated by surface plasmons in hot electron-based energy conversion.
关键词： hot electron,Photoconductive atomic force microscopy,localized surface plasmon resonance,Schottky diode,field confinement,Au nanoprism
更新于2025-09-23 15:23:52
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Broadband light harvesting for highly efficient hot-electron application based on conformal metallic nanorod arrays
摘要： The utilization of nonradiative decay of surface plasmons (SPs) in the form of hot electrons in metallic nanostructures has a great potential for applications in photovoltaics, photocatalysis, photodetection, and surface imaging. Unfortunately, the metallic nanostructures usually support only narrowband plasmon resonances; moreover, the hot-electron thermalization loss during the transport to Schottky interface and the confined momentum space for hot-electron injection into semiconductor together result in an inefficient internal quantum process. In this study, we propose and experimentally demonstrate a broadband super absorber based on the metallic nanorod arrays (NRs). Optically, the average absorption across the entire visible band is up to 0.8, which is over 16-fold enhancement of the planar reference. Electrically, the hot electrons are controlled to be preferentially generated near Schottky interface within the mean free path, relieving the severe hot-electron thermalization loss. Moreover, the three-dimensional Schottky junction provides much increased hot-electron momentum space for injection at the vertical surface. These optical and electrical benefits lead to over 30-fold enhancement in the IPCE (incident photon-to-electron conversion efficiency) relative to the reference. The IPCE can be up to 10.9% at Eph = 3.1 eV, which is close to the limit of the thick-film single-barrier hot-electron devices. The conformal NRs system provides a promising strategy to simultaneously improve the hot-electron generation, transport and collection efficiencies and could be an outstanding candidate for efficient hot-electron optoelectronic and photocatalysis systems.
关键词： hot electron,surface plasmons,nanorod arrays,broadband absorber
更新于2025-09-23 15:21:21
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Effect of Hot Electron Stress on AlGaN/GaN HEMTs of Hydrogen Poisoning
摘要： We have investigated the effect of hot electron stress on the electrical properties of AlGaN/GaN high electron mobility transistors (HEMTs) of hydrogen poisoning. The AlGaN/GaN HEMTs were biased at the semi-on state, and they suffered from the hot electron stress. The devices of hydrogen poisoning were degraded, while there is almost no degradation for the fresh ones. The hot electron stress leads to the significantly positive shift of threshold voltage and the notable decrease of drain-to-source current for the AlGaN/GaN HEMTs of hydrogen poisoning. For the AlGaN/GaN HEMTs of hydrogen poisoning, the trap density increases by about one order of magnitude after the hot electron stress experiment. The physical mechanism can be attributed to electrically active traps due to the dehydrogenation of passivated point defects at AlGaN surface, AlGaN barrier layer, and heterostructure interface. The results of this study may be useful in the design and application of AlGaN/GaN HEMTs.
关键词： Hydrogen Poisoning,Hot Electron Stress,GaN HEMT
更新于2025-09-23 15:21:21
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Planar hot-electron photodetector utilizing high refractive index MoS<sub>2</sub> in fabry-p??rot perfect absorber
摘要： Hot electron photodetection (HEPD) excited by surface plasmon can circumvent bandgap limitations, opening pathways for additional energy harvesting. However, the costly and time-consuming lithography and electron beam lithography-free hot electron photodetector based on the Fabry-Pérot resonance has long been a barrier for large-area and mass production of HEPD. In this paper, we proposed a planar and electron beam lithography-free hot electron photodetector based on the Fabry-Pérot resonance composed of Au/MoS2/Au cavity. The hot electron photodetector has a nanoscale thickness, high spectral tenability, and multicolour photoresponse in the near-infrared region due to the increased round-trip phase shift by using high refractive index MoS2. We predict that the photoresponsivity can achieve up to 23.6 mA/W when double cavities are integrated with the Fabry-Pérot cavity. The proposed hot electron photodetector that has a nanoscale thickness and planar stacking is a perfect candidate for large-area and mass production of HEPD.
关键词： Hot electron,photodetection,Molybdenum disulphide,Fabry-Pérot resonance,perfect absorption
更新于2025-09-23 15:21:01
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Unified theory of plasmon-induced resonance energy transfer and hot electron injection processes for enhanced photocurrent efficiency
摘要： Plasmons in metal nanoparticles (MNPs) promise to enhance solar energy conversion in semiconductors. Two essential mechanisms of enhancement in the near-field regime are hot electron injection (HEI) and plasmon-induced resonance energy transfer (PIRET). Individual studies of both mechanisms indicate that the PIRET efficiency is limited by the short lifetime of the plasmon, whereas the hot electrons result from the plasmon decay. The development of a unified theory of the coupled HEI and PIRET processes is fundamentally interesting and necessary for making reliable predictions but is complicated by the multiple interactions between various components that participate in the enhancement process. In this paper, we use the model-Hamiltonian approach to develop a combined theoretical framework including both PIRET and HEI. The coupled dynamics as well as the time evolution of hot electron energy distribution are studied. The theory further predicts an interference-induced asymmetry in the spectral dependence of PIRET, which can be used to distinguish it from HEI. As the relative contributions of PIRET and HEI strongly depend on the size of the MNPs, this presents itself as a simple route to control the strength of their contributions. The results presented here can further guide future applications of plasmonic solar energy harvesting.
关键词： plasmon,metal nanoparticles,hot electron injection,solar energy conversion,plasmon-induced resonance energy transfer
更新于2025-09-23 15:21:01
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Stepwise Two-Photon-Induced Electron Transfer from Higher Excited States of Noncovalently Bound Porphyrin-CdS/ZnS Core/Shell Nanocrystals
摘要： There has been an increasing amount of interest in stepwise two-photon absorption (2PA)-induced photochemical reactions because of their extremely lower power thresholds compared to that of the simultaneous process and drastic reaction enhancements in some cases. However, stepwise 2PA-induced photochemical reactions were reported only in single chromophores and covalently bound bi-chromophores and there are few reports on these reactions in noncovalently bound systems because of weak electronic interactions among chromophores. This study demonstrated the stepwise 2PA-induced electron transfer from higher excited states in noncovalently bound protoporphyrin IX·CdS/ZnS core/shell nanocrystals (NCs). The electron transfer from higher excited states of porphyrin to CdS NCs successfully overcomes the activation barrier associated with the wide bandgap ZnS shell, indicating that a high reduction potential can be obtained with the stepwise 2PA process. The concept presented in this study can be applied to various noncovalently bound multi-chromophore systems to explore nonlinear photoresponses.
关键词： Nonlinear,Anti-Kasha type,colloidal nanocrystals,hybrid nanomaterial,hot electron transfer
更新于2025-09-23 15:21:01
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Strong Lighta??matter Interaction in Au Plasmonic Nanoantennas Coupled with Prussian Blue Catalyst on BiVO4 for Photoelectrochemical Water Splitting
摘要： We establish a facial and large scale compatible fabrication route affording a high performance heterogeneous plasmonic-based photoelectrode for water oxidation that incorporates a CoFe-Prussian blue analog (PBA) structure as the water oxidation catalytic center. For this purpose, an angled deposition of gold (Au) was used to selectively coat the tips of the bismuth vanadate (BiVO4) nanostructures, yielding Au capped BiVO4 (Au-BiVO4). The formation of multiple size/dimension Au capping islands provides strong light-matter interaction at nanoscale dimensions. These plasmonic particles not only enhance light absorption in the bulk BiVO4 (through the excitation of Fabry-Perot (FP) modes) but also contribute to photocurrent generation via the injection of sub-bandgap hot electrons. To substantiate the activity of the photoanodes, the interfacial electron dynamics is significantly improved using a PBA water oxidation catalyst (WOC) resulting in Au-BiVO4/PBA assembly. At 1.23 V vs RHE, the photocurrent value for a bare BiVO4 photoanode was obtained as 190 μA cm?2, while it was boosted to 295 μA cm?2, and 1,800 μA cm?2 for Au-BiVO4, and Au-BiVO4/PBA, respectively. Our results suggest that this simple and facial synthetic approach paves the way for plasmonic-based solar water splitting, in which a variety of common metals and semiconductors can be employed in conjunction with catalyst designs.
关键词： photoelectrochemical water splitting,Prussian blue,plasmonics,hot electron,cyanide chemistry
更新于2025-09-23 15:19:57