7 research outputs found
Nanostructures de Pd anisotropes autoassemblées à grande surface comme nanocapteurs SERS efficaces
No full textIci, nous rapportons pour la première fois une voie de fabrication facile en une étape de nanoparticules de palladium non sphériques (NPs de Pd) par auto-assemblage de polymères. Des NP de Pd anisotropes se forment spontanément lors du revêtement par centrifugation d'une dispersion de précurseur de Pd-PMMA (polyméthacrylate de méthyle) sur une plaquette de silicium/ITO en raison d'une évaporation rapide des solvants volatils du PMMA. Précisément, le spin-coating conduit d'abord à un auto-assemblage du PMMA en micelles contenant du Pd2+, puis l'évaporation des solvants conduit à la formation d'un film de PMMA nano poreux, où les NP de Pd sont localisées à l'intérieur des trous. La conductivité du substrat joue un rôle majeur dans le mécanisme de synthèse puisqu'elle permet une réduction spontanée du précurseur de Pd en nanoparticules de Pd. La force d'interaction répulsive entre le couple (phase Pd hydrophile / phase PMMA hydrophobe) et le substrat permet de contrôler la taille et la morphologie finales des nanostructures produites. De plus, le nombre des NPs Pd peut également être modulé en ajustant les paramètres de synthèse tels que la concentration en précurseur et la solution de PMMA. Une grande configuration des NPs a été obtenu de précurseur de Pd. Ça conduit à un substrat à haute performance SERS malgré les faibles propriétés plasmoniques de Pd.Here, we report for the first time a facile one-step fabrication route of non-spherical palladium nanoparticles (Pd NPs) by polymer self-assembly. Anisotropic Pd NPs are spontaneously formed upon the spin coating of Pd precursor-PMMA (polymethyl methacrylate) dispersion on N-doped silicon wafer/ITO due to a rapid evaporation of the volatile solvents from PMMA. Precisely, the spin coating leads first to a self-assembly of PMMA into micelles containing Pd2+, and then the solvents’ evaporation leads to the formation of nano porous PMMA film, where Pd NPs are localized inside holes. The substrate conductivity plays a major role in the synthesis mechanism since it allows a spontaneous reduction of the Pd precursor into Pd nanoparticles. The repulsive interaction force between the couple (hydrophilic Pd phase /hydrophobic PMMA phase) and the substrate allows us to control the final size and morphology of the produced nanostructures. In addition, the number of Pd NPs can also be modulated by adjusting the synthesis parameters such as precursor concentration and PMMA solution. A high number of NPs with different morphologies separated by small gaps was obtained at high Pd precursor concentration and led to high SERS performance substrate despite the weak plasmonic properties of Pd
Assessment of an Tentative Novel Body of X-Ray tube in order to Decrease the Applicability Limitation in Medical Practice
Get PDFThe output of X-ray, especially in the field of required energy for diagnosing the disease is very low (in diagnosing lamps, it is less than 1%). In this kind of lamps the rest of the electrical energy is transformed to heat. This considerable amount of heat induces a myriad of too many limitations in choosing higher levels of radiation, particularly in specialized techniques. This process is the outcome of X-ray generating mechanism; thus, one of the proper solutions to reduce the limitations caused by generating high heat is enhancing the cooling rate in these lamps. In this project, the design and alloy of the framework, surface and the substance were altered in a manner whereby the cooling rate increases or heat accumulation in lamps decreases. This surface was designed in the shape of a two-part disc with wings whose substance is the same as the framework. The substance of the framework is made of an alloy of copper and chromium. The disc shape of the framework and its aerodynamic compatibility further expose its contacting surface to the air. This contacting surface can be expanded to 10 times more than the ordinary frameworks. The heat conductivity coefficient of this alloy is approximately 220 w/ mk, which in comparison with the heat conductivity coefficient of the ordinary lamps framework, being about 10, is 22 times more. The results of the tests reveal that the cooling rate of this framework is 10 times (or 1000%) more than the ordinary one. This process reduces the limitations of choosing radiation factors with the same proportio
Self-Assembled Pd Nanocomposites into a Monolayer for Enhanced Sensing Performance
No full textInternational audienceTo date, the advanced synthetic approaches for palladium nanoparticle-based catalysts involve multistep, toxic, and high-cost fabrication routes with low catalytic and sensing performance. In this work, we introduce a new one-shot approach to produce highly sensitive Pd nanocomposites using a large-area polymer self-assembly strategy. This synthesis method allowed us to control the Pd nanoparticle shape and to tailor their plasmonic band positions in a wide light spectral range from ~350 to ~800 nm. We thus determined the critical synthesis conditions that give rise to a ringlike morphology in a reproducible manner. No need for a reducing agent and preliminary functionalization of the surface supporting the nanoparticles upon synthesis. To the best of our knowledge, few works have demonstrated the good performance of PdNPs in sensing. Here, we have demonstrated a robust SERS response for 4-mercaptopyridine with an enhancement factor of 4.2 × 105. We were able to exceed this high value, which matches the current maximum found in the literature, by decreasing the gap distances between Pd nanorings due to the high density of hotspots and the exacerbation of the coupling effect between PdNPs. These tailored products provide new insights for the use of Pd nanomaterials in photocatalysis applications, according to the well-established catalytic performance of Pd materials obtained in this work
Facile Synthesis of Palladium Nanorods: Self-Assembly into Thin 2D Layers for SERS Sensing
No full textThis study presents a simple, high-throughput synthesis approach for fabricating palladium (Pd) nanomaterials with anisotropic shapes, specifically Pd nanorods, via a self-assembly process. This method avoids the use of reducing agents, surface functionalization, and stabilizing agents. Palladium–poly(methyl methacrylate) (Pd-PMMA) nanocomposites were successfully synthesized using a vapor-induced phase separation (VIPS) method. The formation of Pd nanorods was controlled by tuning key parameters, such as the Pd precursor concentration, choice of solvents, and spin coating speed. Notably, the resulting nanorods exhibited high reproducibility and ultrasensitivity as a surface-enhanced Raman scattering (SERS) platform, achieving an enhancement factor of approximately 1.8 × 105, despite the relatively weak plasmonic properties of Pd. This work represents a novel, facile strategy for Pd nanorod synthesis, offering new potential for the design of Pd-based nanosensors for chemical sensing applications
Self-Assembled Ag Nanocomposites into Ultra-Sensitive and Reproducible Large-Area SERS-Active Opaque Substrates
No full textThis 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
Anisotropic Ag@Au architectures through real-time surface-based strategy of synthesis: Large-area enhanced nanosensors
No full textInternational audienceHere, we report an innovative facile polymer-templated synthesis of Ag/Au bimetallic nanoparticles (BNPs) on large surface for sensing. By controlling the reaction kinetics, the bimetallic nanoparticles have been successfully prepared with a variety of structures: heterostructures, eccentric core-shells, and physical mixtures of two metals. The amount and initial shape of the Au seeds determined the final architectures of bimetallic nanostructures. The underlying synthesis mechanism of BNPs was regulated by a seed-mediated growth (SMG) on the surface. The newly formed Ag atoms were directed to selectively nucleate and then epitaxially grow on specific facets of cubic/hexagonal Au seeds. Comprehensive results demonstrating an optical response of two metallic/poly (methyl methacrylate) (M+/PMMA) layers on opaque surfaces by micro-extinction measurements were obtained. Sensors based on anisotropic bimetallic substrates were ideal for sensitive 4,4′ -bipyridine (4,4’-BP) detection. The polymer surface-induced accumulation of high electric fields on nanoscale sensing volumes of anisotropic core/shell BNPs allowed more analyte molecules to access their high-index facets. This sample possessed a high surface-enhanced Raman scattering (SERS) sensitivity despite only being validated on very small densities of surfaces; thanks to the synergistic effects between the two coupled metals. The present findings suggest that a surfactant-free synthesis can be used as a powerful mean of defining growth strategies based on silicon substrate platforms
Large-area self-assembly of anisotropic Palladium nanostructures for SERS applications
No full textHere, we report for the first time a facile one-step fabrication route of anisotropic palladium nanoparticles (Pd NPs) with high SERS performance by polymer self-assembly
