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Herein, we introduce a mechanistic study to design a hybrid junction in metallic‐semiconductor (M/SC) nanostructures. UV‐light‐induced hot electron generation in ZnO nanostructures is used to precisely tune the photoluminescence (PL) and photocatalytic (PC) properties in hybrid Au/ZnO nanomaterials. Both enhancement and quenching of the PL and PC functionalities are observed, depending on the properties of the Au nanoparticles (AuNPs) and the Au/ZnO molecular distance. Under UV irradiation free‐ligand AuNPs quench the luminescence of ZnONPs through direct charge transfer (CT) from ZnO to the AuNPs. In contrast, capped AuNPs enhance the ZnO emission through indirect CT from AuNPs to ZnONPs facilitated by the distance created by the CTAB ligand between both constituents of the hybrid systems. It is necessary to optimise the Au/ZnO molecular distance to achieve an enhancement of both the plasmonic photocatalysis reaction and photoelectric properties of M/SC nanostructures. This phenomena is mediated by the energy transfer (ET) from ZnONPs to AuNPs. The resulting PL enhancement is described by the plasmon‐induced resonance energy transfer effect (PIRET effect). [ABSTRACT FROM AUTHOR]

Abstract: This paper deals with the improvement of polymer microlenses at the extremity of an optical fiber. The process reported previously involves a spatially controlled light-induced polymerization within a drop of liquid photopolymerizable formulation deposited on the end of a cleaved fiber. The process is of highest interest for applications in optical connecting and optical fiber sensor since it is fast, highly flexible (curvature radii ranges from 0.2 to 200μm) and does not require expensive equipment. In particular, the spatial extend of the photopolymerization was demonstrated to be highly dependent on physico-chemical parameters of the formulation. The influence of parameters that govern the photopolymerization reaction and light propagation in the photopolymerizable medium such as irradiation time, light power, oxygen quenching and dye absorption, were studied in order to control the final properties of the polymer tip. The present study allowed selecting the synthesis parameters leading to well-controlled geometrical structures. From a fundamental point of view, this study appeared to be an interesting means to investigate the photostructuration of polymers at the micro- and nanoscales. [Copyright &y& Elsevier]

In this paper, a novel method is proposed for selective deposition of ZnO nanoparticles (NPs) and growth of ZnO Nanorods (NRs) on multi‐dimensional patterned polymer surfaces. The method involves microfabrication of functionalized 1D, 2D, and 3D polymer structures by two‐photon polymerization (TPP) followed by selective assembly of ZnO NPs acting as seeds before growing ZnO NRs by chemical bath deposition (CBD) technique at low temperature. The immobilization of the ZnO NPs seed layer is done by electrostatic interaction between the positively charged polymer surface functionalized by amine groups and the negatively charged ZnO NPs functionalized by citrate molecules. The influence of citrate molecules on the stability of the ZnO NPs dispersions and their immobilization on the polymer surface is demonstrated. Spatially controlled and selective growth of ZnO NRs is shown at low temperatures on multi‐dimensional structures up to 9 mm2 and having different shapes, including 1D polymer lines, 2D microplates, and 3D arrays of cones. The diameter of NRs and their orientation can be controlled through the size of ZnO NPs and the shape of the polymer structure respectively. [ABSTRACT FROM AUTHOR]

We report here a real-time study of interactions induced phase separation between β-lactoglobulin (BLG) and Acacia gum (AG) by analyzing the localized surface plasmon resonance of silver nanoparticles. We showed that the binding of BLG to AG is accompanied by refractive index changes, in relation with optical properties and structural changes of the complexes formed. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) films or layers are extensively used for various photonic and electronic applications since recent decades. Three‐dimensional (3D) nanostructures are the elegant fashion in micro‐optics, microfluidics, biomedicine, and imaging. In particular, 3D photoluminescent nanostructures play an important role in detection and sensing as well as emitting systems. In this work, 3D photoluminescent structures containing QDs with feature sizes down to 80 nm are fabricated via two‐photon polymerization‐based direct laser writing. The photoluminescent images and emission spectra show strong local emission of blue, green, and red light from the polymer micro and nanostructures. The influence of the QDs, laser power, and writing scan speed on the resolution of the as‐prepared structures is also investigated. It turns out that the presence of QDs increases the lateral resolution where the feature size of polymer lines can reach 75 nm in 3D. This promising result paves the way for the integration of single nano‐emitters with a fine control of their spatial positioning in some nanophotonic devices. High‐resolution 3D photoluminescent polymer structures containing QDs are fabricated via two‐photon polymerization‐based direct laser writing. The photoluminescence images and spectra show strong local emission of blue, green, and red light from the polymer micro and nanostructures. The presence of QDs increases the lateral resolution where the feature size of polymer lines can reach 75 nm in 3D. [ABSTRACT FROM AUTHOR]

In this study, we fabricated a hybrid plasmonic/semiconductor material by combining the chemical bath deposition of zinc oxide nanowires (ZnONWs) with the physical vapor deposition of aluminum nanostructures (AlNSs) under controlled temperature and atmosphere. The morphological and the optical properties of the ZnONWs/AlNSs hybrid material fabricated at different temperatures (250, 350, and 450 °C) and thicknesses (5, 7, and 9 nm) of Al layers were investigated. By adjusting the deposition and annealing parameters, it was possible to tune the size distribution of the AlNSs. The resonant coupling between the plasmonic AlNSs and ZnONWs leads to an enhanced photoluminescence response. The photocatalytic activity was studied through photodegradation under UV-light irradiation of methylene blue (MB) adsorbed at the surface of ZnO. The MB photodegradation experiment reveals that the ZnONWs covered with 7 nm aluminum film and annealed at 450 °C exhibit the highest degradation efficiency. The comparison between ZnONws and ZnONws/AlNSs shows a photoluminescence enhancement factor of 1.7 and an increase in the kinetics constant of photodegradation with a factor of 4. [ABSTRACT FROM AUTHOR]

Quantum dots optically excited in close proximity to a silver nanowire can launch surface plasmons. The challenge related to this promising hybrid system is to control the position of nanoemitters on the nanowire. We report on the use of a two-photon photopolymerization process to strategically position quantum dots on nanowires at controlled sites. A parametric study of the distance between the quantum dots and the nanowire extremity shows that precise control of the position of the launching sites enables command of light intensity at the wire end through surface plasmon propagation. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • First demonstration of efficient glycerol oxidation by laser activation of Gold Nanoparticles. • Glycerol oxidation is induced by thermoplasmonic effect of photoexcited GNPs. • More than 90% of Glycerol are converted after 2 h without any external source of heat. • The laser activation is 2.5 times more efficient than thermal activation at 60 °C. • Hot electron transfer between GNPs and TiO 2 contributes to the enhancement. Abstract In this work, we highlight the feasibility of new efficient catalytic processes by laser excitation, exemplified in the reaction of oxidation of glycerol over catalysts based on supported gold nanoparticles. We show that this catalytic oxidation reaction can efficiently proceed via laser excitation of surface plasmon resonance of gold nanoparticles, inducing local thermal heating effect. While the reaction did not occur in the absence of any external heat source, with this original approach, 88% of glycerol was converted after 2 h, leading to the formation of glyceric acid and tartronic acid as main products. The photonic activation led to 2.5 times more efficient conversion than an equivalent thermal activation by conventional heating source. Investigations of the laser power and the nature of support catalyst revealed a significant contribution of electron transfer from plasmonic nanoparticles to TiO 2 in the oxidation reaction. [ABSTRACT FROM AUTHOR]

A new methodology is developed to determine the shape distribution of gold nanoparticles (NPs) from optical spectroscopic measurements. Indeed, the morphology of Au colloids is deduced by fitting their absorption spectra with an effective medium theory which takes into account the nanoparticle shape distribution. The same procedure is applied to ellipsometric measurements recorded on photoresist films which contain Au NPs. Three spaces (L 2 , r 2 , P 2 ) are introduced to interpret the NPs shape distribution. In the P 2 space, the sphericity, the prolacity and the oblacity estimators are proposed to quantify the shape of NPs. The r 2 space enables the determination of the NP aspect ratio distribution. The distributions determined from optical spectroscopy were found to be in very good agreement with the shape distributions obtained by transmission electron microscopy. We found that fitting absorption or ellipsometric spectra with an adequate effective medium theory, provides a robust tool for measuring the shape and concentration of metallic NPs. [ABSTRACT FROM AUTHOR]

In this study, adsorption capacities of uremic toxins over Faujasite (HFAU) and Beta (HBEA) have been evaluated by varying the composition of solvent by using water, physiological, and sodium chloride solutions. HFAU was found to be more efficient in adsorption of these molecules. The adsorption results over HFAU were compared in various conditions to understand the adsorption mechanism. Thus, the adsorption mechanism was confirmed also by Fourier transform infrared and X-ray diffraction analysis, and it is found to be through the interaction of creatinine by hydrogen bonding on two types of sites on zeolites. Pseudo-second-order equation described well the adsorption kinetics data. Equilibrium isotherms were determined by Fowler-Guggenheim model. Finally, hydrophobic HFAU zeolite seems to be an efficient adsorbent; it is able to be easily regenerated under air, through retention of these initial adsorption properties. [ABSTRACT FROM AUTHOR]

This paper reports the complete ellipsometric characterization of gold nanoparticles (NPs) embedded in a photoresist films. The effective dielectric function of nanocomposite films as well as the shape distribution and the volume fraction of NPs are extracted from ellipsometric measurements by introducing an effective medium theory which takes into account the NP shape distribution and the intrinsic confinement effect. This theory remains valid as long as the nanoparticle interaction is negligible. We show that the magnitude of the confinement depends on the nanoparticle shape and the environment through chemical damping. This suggests that the NP shape distribution can be directly estimated by ellipsometry, while the determination of absolute radius distribution requires transmission electron microscopy measurements. The imaginary part of the effective dielectric function exhibits a strong asymmetric surface plasmon band, while a large variation of the real part occurs close to the resonance. The redshift and the broadening of the plasmon band as the gold volume fraction increases are correlated to the evolution of NP shape distribution. This evolution is attributed to a competition between the nucleation and the coalescence of NPs. This unambiguously demonstrates that ellipsometry combined with a shape-distributed effective medium theory is a powerful alternative tool to transmission electron microscopy for the NP shape analysis. [ABSTRACT FROM AUTHOR]

Metal oxide semiconductors hold great promise for applications in energy conversion and storage, environmental remediation, and other areas. However, critical factors such as the high rate of charge–carrier recombination and limited light absorption have restricted more practical and viable applications. In this context, plasmonic nanostructures of noble metals in combination with semiconductors offer a promising future for the next generation of energy needs. In this work we investigate the coupling between Plasmonic gold nanostructures and catalyst supports such as TiO 2 , ZnO and Al 2 O 3 in order to study the photocatalytic degradation of Bisphenol A (BPA) under visible irradiation (laser source and LED). The experimental investigations have shown extremely fast and complete photodegradation of organic pollutants in water. The influence of laser power and photocatalyst band gap on the catalytic activity was investigated as well. Au/TiO 2 catalyst showed the fastest degradation of BPA due to efficient electron transfer from excited noble metal gold nanoparticles to the semiconductor. [ABSTRACT FROM AUTHOR]

This work describes a novel, one-shot strategy to fabricate ultrasensitive SERS sensors based on silver/poly(methyl methacrylate) (PMMA) nanocomposites. Upon spin coating of a dispersion of PMMA and silver precursor on N-doped silicon substrate, closely separated silver nanoparticles were self-assembled into uniform nanospheres. As a result, a thin hydrophobic PMMA layer embedded with Ag nanoparticles (AgNPs) was obtained on the whole silicon substrate. Consequently, a large-scale, reproducible SERS platform was produced through a rapid, simple, low-cost, and high-throughput technology. In addition, reproducible SERS features and high SERS enhancement factors were determined (SEF ~1015). This finding matches the highest SEF reported in literature to date (1014) for silver aggregates. The potential and novelty of this synthesis is that no reducing agent or copolymer was used, nor was any preliminary functionalization of the surface carried out. In addition, the AgNPs were fabricated directly on the substrate's surface; consequently, there was no need for polymer etching. Then, the synthetic method was successfully applied to prepare opaque SERS platforms. Opaque surfaces are needed in photonic devices because of the absence of secondary back reflection, which makes optical analysis and applications easier. [ABSTRACT FROM AUTHOR]

One of the key issues for SERS-based trace applications is engineering structurally uniform substrates with ultrasensitivity, stability, and good reproducibility. A label-free, cost-effective, and reproducible fabrication strategy of ultrasensitive SERS sensors was reported in this work. Herein, we present recent progress in self-assembly-based synthesis to elaborate precisely shaped and abundant gold nanoparticles in a large area. We demonstrated that shape control is driven by the selective adsorption of a cation (Na+, K+, and H+) on a single facet of gold nanocrystal seeds during the growth process. We studied SERS features as a function of morphology. Importantly, we found a correlation between the shape and experimental SERS enhancement factors. We observed a detection threshold of 10−20 M of bipyridine ethylene (BPE), which matches the lowest value determined in literature for BPE until now. Such novel sensing finding could be very promising for diseases and pathogen detection and opens up an avenue toward predicting which other morphologies could offer improved sensitivity. [ABSTRACT FROM AUTHOR]

Pointed carbon nanotips have been deposited on polymer microlensed optical fibers and used as highly resolving scattering nanoprobes. Optical characterizations supported by simulations demonstrate an efficient spatial filtering where the light scattered by the carbon tip is selectively coupled into the fiber core. As an application, a channel surface waveguide was characterized in collection mode. A special attention was given to the polarization response, and the s-polarized field is found to be slightly favored due to the detection direction. The proposed hybrid probe's robustness, the symmetric detection and design flexibility it offers, makes it an attractive tool for nano-optics. [ABSTRACT FROM AUTHOR]

Here, we demonstrate for the first time a strategy to self-assemble ZnO nanoparticles (NP) on a large area by a facile one-step process. First, rough and random ZnO nanocrystals (NC), were produced by free-stabilizing aqueous synthesis. Therefore, a post thermal treatment at various temperatures ranging from 80 to 800 °C was necessary to obtain size-tunable and photoluminescent crystalline NP. The fabricated NP had both efficient UV photoluminescence and photocatalytic activity by photo-degradation of Methylene Blue (MB) dye. The annealed NP showed an absorption blue shift in the UV region with decreasing size. This shift was attributed to high quantum confinement effect since ZnO NP diameter reached values lower than the Bohr radius of ZnO (~2.7 nm). The photocatalytic activity displayed dependency on the particle's size, number, and crystallinity. Subsequently, the NP were self-assembled inside poly(methyl methacrylate) (PMMA) nanoholes. Subsequently, large area substrate of homogenous properties ZnO NP was obtained. Moreover, the synthesis facility, photoemission and photocatalytic properties of ZnO NP could be a new insight into the realization of high performance and low cost UV laser devices. [ABSTRACT FROM AUTHOR]