Optical and photocatalytic properties of sol-gel AuNPs@TiO2 ultrathin film

The optical and photocatalytic properties of ultrathin TiO2 layers were investigated in order to stress out the effect of nanoscale thickness on the film properties. The method relies on monitoring localized surface plasmon resonance (LSPR) through UV–visible spectroscopy and enhanced Raman spectroscopy (SERS). To achieve this, TiO2 thin films were prepared using the sol–gel method on high density gold nanoparticles arrays (AuNPs). TiO2 anatase phase was obtained by thermal annealing and confirmed by XRD, HRTEM, and SERS. Our results reveal that the thinnest TiO2 layers consist of compact TiO2NPs of small dimensions and lower porosity compared to the thicker TiO2NPs layers. Subsequently, these thin TiO2 layers functionalizing AuNPs were applied in plasmonic photocatalysis, specifically for the N-demethylation of methylene blue in the visible range. When comparing layers with the same thickness (a single deposition layer with layers prepared by stacking various thin layers), the stacked layers demonstrated enhanced photocatalytic activity. This novel, stable form of TiO2 has the potential to open numerous opportunities in the fields of photocatalysis and detection

Insights into Photopolymerization at the Nanoscale Using Surface Plasmon Resonance Imaging

Near-field photopolymerization (NFPP) driven by surface plasmon resonance has attracted increasing attention in nanofabrication. This interest comes from the nanometer-scale control of polymer thickness, due to the confinement of the evanescent wave within a highly restricted volume at the surface. In this study, a novel approach using a multi-spectral surface plasmon resonance instrument is presented that gives access to real-time images of polymer growth during NFPP with nanometer sensitivity. Using the plasmonic evanescent wave for both polymerization and real-time sensing, the influence of irradiance, concentration of dye, and initiator are investigated on the threshold energy and kinetics of NFPP. How oxygen inhibition in the near field strongly affects photopolymerization is highlighted, more than in the far field

Synthesis and Integration of Hybrid Metal Nanoparticles Covered with a Molecularly Imprinted Polymer Nanolayer by Photopolymerization

Interfacing recognition materials with transducers has consistently presented a challenge in the development of sensitive and specific chemical sensors. In this context, a method based on near-field photopolymerization is proposed to functionalize gold nanoparticles, which are prepared by a very simple process. This method allows in situ preparation of a molecularly imprinted polymer for sensing by surface-enhanced Raman scattering (SERS). In a few seconds, a functional nanoscale layer is deposited by photopolymerization on the nanoparticles. In this study, the dye Rhodamine 6G was chosen as a model target molecule to demonstrate the principle of the method. The detection limit is 500 pM. Due to the nanometric thickness, the response is fast, and the substrates are robust, allowing regeneration and reuse with the same performance level. Finally, this method of manufacturing has been shown to be compatible with integration processes, allowing the future development of sensors integrated in microfluidic circuits and on optical fibers

Plasmon‐Induced Photopolymerization of Molecularly Imprinted Polymers for Nanosensor Applications

Abstract A new simple, fast, and versatile method is developed to functionalize gold nanoparticles (AuNPs) via nanoscale layers of molecularly imprinted polymers (MIPs). The key step is based on near‐field radical photopolymerization of the MIP prepolymerization mixture. This enables the fabrication of AuNPs@MIPs hybrid nanoparticles, which are used as substrates for localized surface plasmon resonance and surface‐enhanced Raman spectroscopy (SERS) analysis with excellent sensitivity and specificity. To demonstrate the performance of AuNPs@MIPs, methylene blue‐specific MIPs are prepared. The sensitivity of SERS detection is in the range of 10 nm. Specificity is demonstrated by comparing the response to a non‐imprinted control polymer and by interference testing with two analogs (Rhodamine 6G and Rhodamine 110). This fabrication method allows to obtain robust and reusable sensor surfaces with high sensitivity and selectivity. The nanometric thickness of the MIP allows for shorter analysis times (10 min), thereby improving the performance of MIP‐based sensors and opening up new perspectives for the detection of molecules at very low concentrations

Exploiting thermoplasmonic effects for laser-assisted preparation of Au nanoparticles/InZnO thin film with visible range photodetection properties

International audienceWe propose a new method for preparing gold nanoparticles (Au NPs)/indium-zinc-oxide (IZO) nanocomposite thin films based on photothermal mechanisms with near-Infrared (NIR) laser-annealing, which allows integrating the nanomaterial on fragile substrates such as thin glass, plastic sheets, or 3D printed pieces. The Au NPs were first prepared by NIR laser dewetting of a thin Au layer. Then, the Au NPs were used to locally cure the semiconductor material and provide suitable electronic properties owing to their efficient thermoplasmonic effects under our NIR laser annealing conditions. Finally, the electronic properties of the Au NPs/IZO thin films were characterized in the dark and under light excitation. Good photoresponsivity at 410 nm (UV, > 100 A/W) was demonstrated, but interestingly, the presence of Au NPs significantly improved the detection ability to a longer wavelength range, such as to 515 nm (green, ~ 5 × 10-3 A/W), even extending to 630 nm (red, ~ 5 × 10-4 A/W), and 780 nm (NIR, ~ 10-4 A/W). In addition, with the critical evaluation of dynamic light detection and lifetime trace (> 22 days), the laser-annealed Au NPs/IZO photodetector (PD) demonstrated useful operating reliability and stability

Écriture laser de materiaux fonctionnels inorganiques preparés par voie sol-gel

International audienceLes matériaux semi-conducteurs ont des propriétés optoélectroniques intéressantes pour de nombreuses applications microélectroniques. Leur introduction sous forme de films minces sur des substrats fragiles, tels que du verre fin, des feuilles de plastique souple ou des pièces imprimées en 3D, permet de créer de nouveaux matériaux intelligents en introduisant des capteurs ou des photodétecteurs. Dans cet article, nous illustrons l’intérêt de nouvelles approches basées sur des technologies laser et une chimie sol-gel pour intégrer des matériaux fonctionnels inorganiques semi-conducteurs ou diélectriques, dans des procédés rapides, agiles, avec des résolutions spatiales aux échelles micro et nanométriques

Laser Direct Writing of Crystallized TiO2 by Photothermal Effect Induced by Gold Nanoparticles

International audienceAbstractNear‐infrared (NIR) laser annealing is successfully used to crystallize TiO2 thin films from a sol–gel solution deposited on gold nanoparticle arrays (AuNPs). The AuNPs are used as nano‐heaters allowing a local temperature increase up to 500 °C in the film. The temperature reached under the laser is deduced from the presence of the anatase phase in the samples obtained by laser exposure, showing that crystallized TiO2 can be obtained by the photothermal effect. Different analytical techniques supported this study, such as grazing X‐ray diffraction (GIXRD), UV–vis, and Raman spectroscopy. The temperature increase is confirmed by a numerical model that emphasizes the role of NPs coupling in the photothermal effect. Direct laser patterning by NIR laser and in combination with Deep‐UV photolithography (DUV) are demonstrated. This fabrication method opens new perspectives in applications such as photonics, photocatalysis, or biosensing

Plasmonic Au Nanoparticle Arrays for Monitoring Photopolymerization at the Nanoscale

International audienceThe localized surface plasmon resonance (LSPR) of Au nanoparticles (NPs) was used to monitor photopolymerization at the nanoscale, by in situ monitoring the optical response of AuNPs during the light-induced polymerization process. To show the interest of this approach, two configurations were used which correspond to a resonant and a non-resonant excitation regime between the photopolymer and the AuNPs used as nanoprobes. We show that not only this method enables the progress monitoring of the photopolymerization reaction at the nanometric scale but also can highlight the near-field coupling effect responsible for the acceleration of the photoinduced reaction. This methodology appears very interesting to study the photoinduced nanofabrication processes of metal/polymer hybrid nanoparticles and more globally as a methodology to study the photopolymerization reactions at the nanometric scale

Reversible Optical Data Storage via Two-Photon Micropatterning of o-Carboranes-Embedded Switchable Materials

Two-photon polymerization (2PP) constitutes a powerful light-triggered 3D stereolithography, allowing the fabrication of micro- or nanostructures with spatially encoded functionalities. In the present report, we take advantage of this programmable property in order to develop a photoresist authorizing the direct 2PP-lithography of luminescent switchable μ-structures. In this single step processing method, we highlight the pivotal role of a quadrupolar o-caborane initiator comprising a 9, 10-disubstituted anthracene core capable of chemically entrap oxygen-inhibiting species during the free radical two-photon initiation step. Such an O2 sequestration approach not only enhances the two-photon initiation performance of the polymerization, but also generates a non-luminescent endoperoxide by-product embedded in the polymerized macrostructure. Interestingly, simple heating of the final materials promotes endoperoxide thermolysis, resulting in the recovery of the luminescent o-carborane dye. This original luminescence turn OFF/ON property exhibits excellent fatigue resistance through a large number of alternated thermal and light stimuli cycles. The potential of this direct laser writing strategy for reversible data storage applications is finally demonstrated by the two-photon patterning of a series of matricially organized μ-structures used as rewritable binary optical memories which can be easily encoded on demand.This work was financially supported by MICINN (PID2019-106832RB-I00 and the Severo Ochoa Program for Centers of Excellence for the FUNFUTURE CEX2019-000917-S project) and by Generalitat de Catalunya (2021-SGR00442).With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe

Reversible Optical Data Storage via Two-Photon Micropatterning of o‑Carboranes-Embedded Switchable Materials

Two-photon polymerization (2PP) constitutes a powerful light-triggered 3D stereolithography, allowing the fabrication of micro- or nanostructures with spatially encoded functionalities. In the present report, we take advantage of this programmable property in order to develop a photoresist authorizing the direct 2PP-lithography of luminescent switchable μ-structures. In this single step processing method, we highlight the pivotal role of a quadrupolar o-caborane initiator comprising a 9, 10-disubstituted anthracene core capable of chemically entrap oxygen-inhibiting species during the free radical two-photon initiation step. Such an O2 sequestration approach not only enhances the two-photon initiation performance of the polymerization, but also generates a non-luminescent endoperoxide by-product embedded in the polymerized macrostructure. Interestingly, simple heating of the final materials promotes endoperoxide thermolysis, resulting in the recovery of the luminescent o-carborane dye. This original luminescence turn OFF/ON property exhibits excellent fatigue resistance through a large number of alternated thermal and light stimuli cycles. The potential of this direct laser writing strategy for reversible data storage applications is finally demonstrated by the two-photon patterning of a series of matricially organized μ-structures used as rewritable binary optical memories which can be easily encoded on demand.Ministerio de Ciencia, Innovación y Universidades(España)Severo Ochoa Program for Centers of ExcellenceGeneralitat de CatalunyaDepto. de Química en Ciencias FarmacéuticasFac. de FarmaciaTRUEpu