arXiv subjects

Priscila Vensaus

Publications and source records attributed to Priscila Vensaus.

6 recordsLinked to original sources

arXiv2026

Spin-Polarized Oxygen Evolution in Chiral-Molecule-Modified Plasmonic Photoanodes

Photoelectrochemical oxygen evolution is limited not only by multi-electron charge-transfer kinetics but also by the spin constraints associated with forming triplet O2. Here, we used a hybrid photoanode architecture to demonstrate spin-polarization of plasmonic hot holes through a chiral molecular layer. TiO2 photoanodes were modified with achiral Au nanoparticles to introduce visible-light plasmonic absorption, functionalized with cysteine as a chiral molecular interface, and coated with a NiFe-based oxygen-evolution catalyst. Wavelength-resolved photo-scanning electrochemical microscopy was used to directly detect locally evolved O2 under operando illumination while simultaneously monitoring the photoanode current. Chiral functionalization with homochiral L-cysteine enhanced both photocurrent and local O2 evolution relative to racemic DL-cysteine controls. The chirality-dependent enhancement was most pronounced under visible excitation overlapping the Au plasmon resonance, including a 130% photocurrent increase. These results provide evidence that chiral molecular layers, often used for chiral nanoparticle synthesis, can directly modulate plasmon-derived hot-carrier transfer through the chiral induced spin selectivity (CISS) effect. This work establishes a chiral plasmonic photoelectrochemical platform for coupling hot-carrier generation to spin-dependent water oxidation.

physics.chem-ph↗

arXiv2026

Metaphotonic Catalysis: Amorphous silicon metasurfaces encode photochemical activity

Solar-to-fuel conversion can benefit from photoelectrodes with engineered light-matter interactions, yet most nanostructured designs provide limited control over the spatial and spectral distribution of photochemical activity. Here, we present an all-dielectric amorphous-silicon metasurface photoelectrode that confines resonant light-matter interactions within a 220-nm-thick active layer. Tunable Mie-type and guided-mode resonances spectrally encode chemical reactivity and produce absorptance above 80% near the silicon band edge, compared with less than 30% for an unpatterned film of the same thickness. The metasurface simultaneously functions as the light absorber, carrier-transport layer, and catalytic interface without an added co-catalyst or engineered passivation layer. Operando photo-scanning electrochemical microscopy reveals wavelength- and structure-dependent redox activity and a tenfold enhancement in internal quantum efficiency near the silicon band edge relative to planar films. Power-dependent measurements support a photon-driven rather than nonlinear photothermal origin of the enhancement, while surface-sensitive ultrafast transient-reflectivity measurements probe the underlying carrier dynamics. Light-coupled scanning electrochemical cell microscopy further shows hydrogen-evolution enhancements of up to 21-fold under photocatalytic conditions and 15-fold under photoelectrochemical bias, corresponding to 11.2-fold and 7.7-fold enhancements after accounting for the estimated surface-area increase. The metasurfaces remain stable during more than 10 hours of immersion and prolonged laser illumination. These results establish amorphous silicon as a stable and versatile platform for resonantly programmed photocatalysis and solar-fuel generation.

physics.optics↗

arXiv2026

Revealing Wavelength- and Size-Dependent CO2 Reduction Selectivity via Operando Scanning Photo-Electrochemical Microscopy

Controlling product selectivity in plasmonic catalysis, particularly in CO2 reduction (CO2R), remains a central unsolved challenge with direct implications for light-driven fuel and chemical synthesis. Here, we deploy quantitative operando scanning photoelectrochemical microscopy (photo-SECM) to provide a direct demonstration that tuning photon energy switches CO2R selectivity through an electronically driven pathway. On plasmonic Au/p-GaN photocathodes, interband excitation (460-560 nm) drives selective CO production while intraband excitation (640-800 nm) favors H2 evolution. By maintaining constant absorbed power across wavelengths and confirming linear power dependence, we isolate the role of hot-carrier energy from photonic and photothermal contributions. Density functional theory calculations reveal that higher-energy interband excitation progressively increases the overlap between hot-electron-accessible states and the CO-producing intermediate, selectively promoting CO over formate, in excellent agreement with experiment. We further show that selectivity is geometrically gated by hot-carrier transport: sub-100 nm nanostructures sustain CO2R activity, while ~300 nm nanodisks suffer transport losses that suppress it, consistent with ab initio hot-carrier transport calculations. Together, these results establish photon energy, carrier transport, and nanostructure geometry as coupled design parameters for plasmonic CO2R selectivity, resolve a longstanding debate on the origin of plasmon-driven selectivity effects, and position photo-SECM as a broadly applicable operando platform for photo(electro)catalysis.

physics.chem-ph↗

arXiv2025

Towards Environmentally Responsive Hypersound Materials

The engineering of acoustic phonons in the gigahertz (GHz) range holds significant potential for technological breakthroughs in areas such as data processing, sensing and quantum communication. Novel approaches for nanophononic resonators responsive to external stimuli provide additional control and functionality for these devices. Mesoporous thin films (MTFs) for example, featuring nanoscale ordered pores, support GHz-range acoustic resonances. These materials are sensitive to environmental changes, such as liquid and vapor infiltration, modifying their effective optical and elastic properties. Here, a SiO$_{2}$ MTF-based open-cavity nanoacoustic resonator is presented, in which the MTF forms the topmost layer and is exposed to the environment. Using a transient reflectivity setup, acoustic responses under varying humidity conditions are investigated. A pronounced shift in acoustic resonance frequency with changes in relative humidity is observed for the first time, demonstrating a simple way to tune hypersound confinement. In addition, resonators with varying pore sizes and thicknesses are compared, revealing that resonance frequencies are primarily influenced by material properties and film thickness, rather than pore size. The proposed open-cavity resonator design provides a versatile platform for future studies on the mechanical response of MTFs to liquid and vapor infiltration, opening the gate to environment-responsive hypersound devices.

cond-mat.mes-hall↗

arXiv2025

Large area monocrystalline and surfactant-free copper microflake synthesis

Copper is one of the most extensively studied materials for energy conversion and catalytic systems, with a wide range of other applications from nanophotonics to biotechnology. However, existing synthesis methods are limited with many undesirable by-products and poorly defined morphologies. Here, we report a surfactant-free on-substrate wet synthesis approach that yields monocrystalline metallic Cu microflakes with (111) crystalline exposed surface. By systematically studying the growth mechanism, we achieve unprecedented sizes of more than 130 μm, which is two orders of magnitude larger than reported in most previous studies, along with higher aspect ratios of over 400. Furthermore, we show distinctly higher stability against oxidation provided by the halide adlayer. Overall, our facile synthesis approach delivers an exciting venue for the emerging fields of catalysis and nanophotonics.

physics.chem-ph↗

arXiv2023

Design of Cost-Effective Nanoacoustic Devices based on Mesoporous Thin Films

Gigahertz acoustic resonators have the potential to advance data processing and quantum communication. However, they are expensive and lack responsiveness to external stimuli, limiting their use in sensing applications. In contrast, low-cost nanoscale mesoporous materials, known for their high surface-to-volume ratio, have shown promise in various applications. We recently demonstrated that mesoporous silicon dioxide (SiO2) and titanium dioxide (TiO2) thin layers can support coherent acoustic modes in the 5 to 100 GHz range. In this study, we propose a new method for designing tunable acoustic resonators using mesoporous thin films on acoustic distributed Bragg reflectors. By infiltrating the pores with different chemicals, the material's properties could be altered and achieve tunability in the acoustic resonances. We present four device designs and use simulations to predict resonators with Q-factors up to 1000. We also observe that the resonant frequency and intensity show a linear response to relative humidity, with a tunability of up to 60 %. Our platform offers a unique opportunity to design cost-effective nanoacoustic sensing and reconfigurable optoacoustic nanodevices.

cond-mat.mes-hall↗