A Rigorous Exploration of the Plexcitonic Phenomena: Hybridized Light-Matter States using Gold Nanoparticles and J-aggregates

147 p.This work is focused on investigating the interplay between plasmon-exciton interactions within strongly coupled plexcitonic systems. Here, gold nanoparticles were used as the plasmonic component and molecular chains known as J-aggregates formed the excitonic component. To begin with, different spectroscopic techniques were used to characterize the photophysical properties of the excitonic systems including estimation of the exciton delocalization length in J-aggregates. This analysis was applied to various organic dyes that show the formation of J-aggregates upon increase of ionic strength and pH respectively. Later, we used carefully chosen interparticle interactions to establish the formation of two different plexcitonic systems using both the dyes. This demonstrates our control over the designs principles to reliably establish strongly coupled systems using different plasmonic and excitonic components. Subsequently, thorough characterizations were conducted to analyze the photophysical properties and evaluate the strength of coupling between the plasmonic and excitonic components. The results of this study draw the first steps into the application of strongly coupled plexcitonic systems for sensing and photocathalytic applications

Metal–Polymer Heterojunction in Colloidal-Phase Plasmonic Catalysis

[EN] Plasmonic catalysis in the colloidal phase requires robust surface ligands that prevent particles from aggregation in adverse chemical environments and allow carrier flow from reagents to nanoparticles. This work describes the use of a water-soluble conjugated polymer comprising a thiophene moiety as a surface ligand for gold nanoparticles to create a hybrid system that, under the action of visible light, drives the conversion of the biorelevant NAD+ to its highly energetic reduced form NADH. A combination of advanced microscopy techniques and numerical simulations revealed that the robust metal-polymer heterojunction, rich in sulfonate functional groups, directs the interaction of electron-donor molecules with the plasmonic photocatalyst. The tight binding of polymer to the gold surface precludes the need for conventional transition-metal surface cocatalysts, which were previously shown to be essential for photocatalytic NAD+ reduction but are known to hinder the optical properties of plasmonic nanocrystals. Moreover, computational studies indicated that the coating polymer fosters a closer interaction between the sacrificial electron-donor triethanolamine and the nanoparticles, thus enhancing the reactivity.This work was supported by grant PID2019-111772RB-I00 funded by MCIN/AEI/10.13039/501100011033 and grant IT 1254-19 funded by Basque Government. The authors acknowl- edge the financial support of the European Commission (EUSMI, Grant 731019). S.B. is grateful to the European Research Council (ERC-CoG-2019 815128). The authors acknowledge the contributions by Dr. Adrian Pedrazo Tardajos related to sample support and electron microscopy experiments

Unveiling the Synergy of Coupled Gold Nanoparticles and J-Aggregates in Plexcitonic Systems for Enhanced Photochemical Applications

Plexcitonic systems based on metal nanostructures and molecular J-aggregates offer an excellent opportunity to explore the intriguing interplay between plasmonic excitations and excitons, offering unique insights into light–matter interactions at the nanoscale. Their potential applications in photocatalysis have prompted a growing interest in both their synthesis and the analysis of their properties. However, in order to construct a high-performing system, it is essential to ensure chemical and spectral compatibility between both components. We present the results of a study into a hybrid system, achieved through the coupling of gold nanobipyramids with organic molecules, and demonstrate the strengthened photochemical properties of such a system in comparison with purely J-aggregates. Our analysis includes the absorbance and photoluminescence characterization of the system, revealing the remarkable plexcitonic interaction and pronounced coupling effect. The absorbance spectroscopy of the hybrid systems enabled the investigation of the coupling strength (g). Additionally, the photoluminescence response of the J-aggregates and coupled systems reveals the impact of the coupling regime. Utilizing fluorescence lifetime imaging microscopy, we established how the photoluminescence lifetime components of the J-aggregates are affected within the plexcitonic system. Finally, to assess the photodegradation of J-aggregates and plexcitonic systems, we conducted a comparative analysis. Our findings reveal that plasmon-enhanced interactions lead to improved photostability in hybrid systems

Cross determination of exciton coherence length in J-aggregates

The coherence length of the Frenkel excitons (Ncoh) is one of the most critical parameters governing many key features of supramolecular J-aggregates. Determining experimentally the value of Ncoh is a nontrivial task since it is sensitive to the technique/method applied, causing discrepancies in the literature data even for the same chemical compound and aggregation conditions. By using a combination of different experimental techniques including UV–vis–NIR, fluorescence emission, time-resolved photoluminescence, and transient absorption spectroscopies, we determined Ncoh values for J-aggregates of a cyanine dye. We found that the absorption spectroscopy alone - a widely used technique- fails in determining right value for Ncoh. The correct approach is based on the modification of photoluminescence lifetime and nonlinear response upon aggregation and careful analysis of the Stokes shift and electron–phonon coupling strength. This approach revealed that Ncoh of JC-1 J-aggregates ranges from 3 to 6.Y.R. acknowledges the support from the Basque Government (grants no. PIBA_2021_1_0026 and IT1526-22). Y.R. also acknowledges support from the Office of Naval Research Global (Award No. N62909-22-1-2031). The authors acknowledge support from MCIN/AEI/10.13039/501100011033 (Grant PID2019-111772RB-I00). V.K. has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie Grant Agreement No. 101025664 (QESPEM).Peer reviewe

Metal-polymer heterojunction in colloidal-phase plasmonic catalysis

[Image: see text] Plasmonic catalysis in the colloidal phase requires robust surface ligands that prevent particles from aggregation in adverse chemical environments and allow carrier flow from reagents to nanoparticles. This work describes the use of a water-soluble conjugated polymer comprising a thiophene moiety as a surface ligand for gold nanoparticles to create a hybrid system that, under the action of visible light, drives the conversion of the biorelevant NAD(+) to its highly energetic reduced form NADH. A combination of advanced microscopy techniques and numerical simulations revealed that the robust metal–polymer heterojunction, rich in sulfonate functional groups, directs the interaction of electron-donor molecules with the plasmonic photocatalyst. The tight binding of polymer to the gold surface precludes the need for conventional transition-metal surface cocatalysts, which were previously shown to be essential for photocatalytic NAD(+) reduction but are known to hinder the optical properties of plasmonic nanocrystals. Moreover, computational studies indicated that the coating polymer fosters a closer interaction between the sacrificial electron-donor triethanolamine and the nanoparticles, thus enhancing the reactivity

Metal–Polymer Heterojunction in Colloidal-Phase Plasmonic Catalysis

Plasmonic catalysis in the colloidal phase requires robust surface ligands that prevent particles from aggregation in adverse chemical environments and allow carrier flow from reagents to nanoparticles. This work describes the use of a water-soluble conjugated polymer comprising a thiophene moiety as a surface ligand for gold nanoparticles to create a hybrid system that, under the action of visible light, drives the conversion of the biorelevant NAD+ to its highly energetic reduced form NADH. A combination of advanced microscopy techniques and numerical simulations revealed that the robust metal–polymer heterojunction, rich in sulfonate functional groups, directs the interaction of electron-donor molecules with the plasmonic photocatalyst. The tight binding of polymer to the gold surface precludes the need for conventional transition-metal surface cocatalysts, which were previously shown to be essential for photocatalytic NAD+ reduction but are known to hinder the optical properties of plasmonic nanocrystals. Moreover, computational studies indicated that the coating polymer fosters a closer interaction between the sacrificial electron-donor triethanolamine and the nanoparticles, thus enhancing the reactivity

Metal–Polymer Heterojunction in Colloidal-Phase Plasmonic Catalysis

Plasmonic catalysis in the colloidal phase requires robust surface ligands that prevent particles from aggregation in adverse chemical environments and allow carrier flow from reagents to nanoparticles. This work describes the use of a water-soluble conjugated polymer comprising a thiophene moiety as a surface ligand for gold nanoparticles to create a hybrid system that, under the action of visible light, drives the conversion of the biorelevant NAD+ to its highly energetic reduced form NADH. A combination of advanced microscopy techniques and numerical simulations revealed that the robust metal–polymer heterojunction, rich in sulfonate functional groups, directs the interaction of electron-donor molecules with the plasmonic photocatalyst. The tight binding of polymer to the gold surface precludes the need for conventional transition-metal surface cocatalysts, which were previously shown to be essential for photocatalytic NAD+ reduction but are known to hinder the optical properties of plasmonic nanocrystals. Moreover, computational studies indicated that the coating polymer fosters a closer interaction between the sacrificial electron-donor triethanolamine and the nanoparticles, thus enhancing the reactivity