Alessandra Paladini

Gold screen-printed electrodes (AuSPEs) are versatile and low-cost electrochemical sensors that typically require activation to remove organic residues from the printing process and increase their active surface area. This study demonstrates the feasibility of a high-throughput laser writing method for the rapid activation and regeneration of commercial AuSPEs. Using a 50 kHz femtosecond laser system at a fundamental wavelength of 1030 nm, distinct morphological changes based on laser fluence are identified. At low fluences (0.4-0.5 J/cm2) the treatment causes surface melting that closes 1–2 μm pores left by the screen-printing process. Conversely, higher fluences (0.7 - 0.9 J/cm2) lead to the formation of randomly oriented sub-100 nm structures, which significantly increase the electrode's active area. Electrochemical characterization reveals that these laser-treated electrodes at high fluence exhibit higher charge-transfer capacity, and double-layer capacitance, which lead to improved electrochemical features compared to untreated sensors. It has also been shown that the method is effective for regenerating electrodes previously loaded with large aptamers. The technique is therefore proposed as a precise, scalable, and intrinsically high-speed alternative for AuSPE activation.

In this study, we investigate the impact of formamidinium bromide (FABr) over-stoichiometry in the precursor solution on the optoelectronic properties and morphology of the resulting films of formamidinium lead bromide. Optical characterization, including steady-state absorption, photoluminescence (PL), and femtosecond transient absorption spectroscopy, reveals a systematic blueshift in emission energy with increasing FABr content, attributed to compositional variations induced by FABr excess. The excess of FABr also induces the reduction of defects associated with radiative recombination. Indeed, the stoichiometric film exhibits a PL band due to donor–acceptor pair (DAP) recombination as identified by the typical blueshift for increasing excitation intensity, whereas FABr-enriched samples show no evidence of DAP emission. Additionally, morphological characterization shows a reduction in grain size with increasing FABr excess, indicating a trade-off between improved electronic quality and enhanced structural disorder. The film synthesized with a 5% excess of FABr provides the optimal balance, yielding the highest power conversion efficiency (6.26%), average visible transmittance (61.6%), and light utilization efficiency (3.85%). These results demonstrate that fine-tuning the precursor stoichiometry represents a simple yet effective strategy to enhance the optoelectronic quality and performance of semitransparent perovskite solar cells.

When molecular fragmentation takes place in solution, solute–solvent interactions introduce additional pathways for radical recombination and secondary chemical transformations, adding complexity to the photodissociation dynamics in comparison to the dynamics observed in isolated systems. In this study, we investigate the ultrafast photodynamics of methyl p-tolyl sulfoxide (Metoso) in the 1–300 ps time range in dimethyl sulfoxide and ethanol solutions using ultrafast transient absorption spectroscopy. Density functional theory calculations have assisted in the interpretation of the experimental data. Upon UV irradiation, Metoso undergoes homolytic cleavage of one of the sulfur–carbon (S–CH₃) bonds, leading to the formation of methyl and para tolylsulfinyl radicals. We explore the competition between geminate recombination, diffusional separation, and alternative reaction pathways. Our results provide insights into the early-stage photochemistry of alkyl–aryl sulfoxides, highlighting the role of solvent interactions influencing radical lifetimes, recombination, and reaction dynamics. These findings contribute to a deeper understanding of sulfoxide photoreactivity, which is relevant to medicinal chemistry and organic synthesis.

Cuprous oxide (Cu2O) is a p-type semiconductor with promising applications as a photocathode material in photoelectrochemical cells for hydrogen production, owing to its visible-range bandgap and suitable band edge positions for water splitting. The incorporation of metallic Cu nanoparticles can further enhance light absorption and extend the absorption range of Cu2O toward the red and near-infrared due to the excitation of localized surface plasmon resonances within the metal nanoparticles (NPs). Starting from molecular-beam-epitaxy-grown metallic Cu NPs, post-growth thermal treatments under oxidizing and reducing conditions can be tuned to obtain either Cu@Cu2O core@shell NPs or Cu2O nanostructured films. The surface stoichiometry of the samples is investigated using x-ray photoelectron spectroscopy and Auger electron spectroscopy. Transmission electron microscopy, coupled with electron energy-loss spectroscopy, provides insights into the morphology and the local oxidation state of the NPs with nanometric resolution. Steady-state and time-resolved optical characterization of the samples confirms the presence of optical features related to localized surface plasmon resonances in the Cu cores and to exciton formation in the Cu2O shell.

Gold nanorods (AuNRs) were synthesized and optimized with the aim of obtaining strongly hydrophilic nanomaterials, suitable as a drug delivery system (DDS) for copper-based drugs. After careful purification, AuNRs were characterized by ultraviolet–visible–near-infrared spectroscopy (UV–Vis–NIR), showing two typical localized surface plasmon resonance (LSPR) bands in the range 550–750 nm. Fourier Transform Infrared (FT-IR) and high-resolution X-ray photoelectron (HR-XPS) spectroscopies verified the surface functionalization. Transmission electron microscopy (TEM) showed AuNRs with regular shape and size, with an aspect ratio (AR) of 2.6. Dynamic Light Scattering (DLS) measurements confirmed the size and the stability in water for up to 3 months. The AuNRs were conjugated with copper(I) drugs, i.e., [Cu(PTA)₄]BF₄ (PTA = 1,3,5-triaza-7-phosphadamantane). The drug loading procedures and efficiency were optimized, and the best loading was η (%) = 50 ± 7%. The non-covalent interactions of the Cu(I) complex with the AuNRs were studied by means of UV–Vis–NIR, ζ-potential, HR-TEM, FT-IR, synchrotron radiation-induced X-ray photoelectron (SR-XPS), and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy measurements. The MTT assay performed on Vero E6 cells showed that AuNRs and AuNR-Cu(I) conjugates had no significant effect on cell viability, being biocompatible, causing a reduction in cell viability only after prolonged exposure.

When molecular fragmentation takes place in solution, solute–solvent interactions introduce additional pathways for radical recombination and secondary chemical transformations, adding complexity to the photodissociation dynamics in comparison to the dynamics observed in isolated systems. In this study, we investigate the ultrafast photodynamics of methyl p-tolyl sulfoxide (Metoso) in the 1-300 picosecond time range in dimethyl sulfoxide and ethanol solutions using ultrafast Transient Absorption Spectroscopy. Density functional theory calculations have assisted in the interpretation of the experimental data. Upon UV irradiation, Metoso undergoes homolytic cleavage of one of the sulfur–carbon (S–CH3) bonds, leading to the formation of methyl and para tolylsulfinyl radicals. We explore the competition between geminate recombination, diffusional separation, and alternative reaction pathways. Our results provide insights into the early-stage photochemistry of alkyl-aryl sulfoxides, highlighting the role of solvent interactions influencing radical lifetimes, recombination, and reaction dynamics. These findings contribute to a deeper understanding of sulfoxide photoreactivity, which is relevant to medicinal chemistry and organic synthesis.

The assembly of plasmonic nanoparticles into superstructures represents a promising strategy toward the development of tunable optical materials. So far, however, the ultrafast dynamics of charge carriers in dense plasmonic superstructures is underexplored. Here, superparticles are used as a model system to study the optical behavior of gold nanoparticles under precise structural control. Gold nanoparticles are assembled into face‐centered cubic crystals through slow emulsion densification, decreasing the distance between nearest neighbors via ligand exchange. Ultrafast transient absorption microscopy is used to investigate the influence of the inter‐nanoparticle distance on the ultrafast photodynamics of carriers at the single superparticle level. The measurements show that reducing the distance between neighboring nanoparticles induces a blueshift of the plasmonic resonance and slows the electron‐phonon scattering process. The blueshift is attributed to a long‐range cross‐talk between nanoparticles within the crystalline superlattice, while electromagnetic simulations suggest that the dynamics slowdown is due to enhanced near‐field coupling between nearest neighbors, increasing the local population of hot carriers and delaying thermalization. This combination of experiments and numerical modeling demonstrates the sensitivity of the collective response of dense plasmonic superstructures to the inter‐nanoparticle distance, paving the way to tailorable plasmonic superstructures for applications in nanophotonics, sensing, and energy conversion.

Understanding charge separation dynamics in organic semiconductor blends is crucial for optimizing the performance of organic photovoltaic solar cells. In this study, the optoelectronic properties and charge separation dynamics of a PCE10:FOIC blend, by combining steady‐state and time‐resolved spectroscopies with high‐level DFT calculations. Femtosecond transient absorption spectroscopy revealed a significant reduction of the exciton‐exciton annihilation recombination rate in the acceptor when incorporated into the blend, compared to its pristine form. This reduction is attributed to a decrease in exciton density within the acceptor, driven by an efficient hole‐separation process that is characterized by following the temporal evolution of the transient signals associated with the excited states of the donor when the acceptor is selectively excited within the blend. The analysis of these dynamics enabled the estimation of the hole separation time constant from the acceptor to the donor, yielding a time constant of (1.3 ± 0.3) ps. Additionally, this study allowed the quantification of exciton diffusion and revealed a charge separation efficiency of ≈60%, providing valuable insights for the design of next‐generation organic photovoltaic materials with enhanced charge separation and improved device efficiency.

The understanding of charge transfer processes in mixed‐dimensional quasi‐2D perovskites is crucial for their application in high‐performance photovoltaic devices. In this work, the link between charge transport dynamics and morphology is investigated in a thin film of quasi‐2D perovskites (PEA ₂ MA _n−1 Pb _n I _3n+1 ), grown with a distinct dimensionality gradient, where the n = 1 phase is concentrated near the substrate and phases with higher dimensionality progressively increase in concentration toward the surface. By selectively exciting the n = 4 phase, efficient hole transfer to the n = 2 and n = 3 phases occurring within a few tens of picoseconds after excitation is observed. In contrast, the n = 1 phase acts as a hole‐blocking layer, limiting the overall charge transport efficiency. These results emphasize the critical importance of minimizing or eliminating the n = 1 layer to enhance charge carrier separation and transport, offering valuable insights into the optimization of quasi‐2D perovskite‐based solar cells.