Chahinez Dab

The higher cost of Ag and Au and their resonance frequency shift limitation opened the way to find an alternative solution by developing new nanohybrid antenna based on silicon and silicon dioxide coated with metallic nanoparticles. The latter has been recently solicited as a promising configuration for more large-scale plasmonic utilisation. This work reports a multitude of fascinating new phenomenon on LSPR on silicon antenna wires coated with core-shell nanospheres and the studying of the nanoplasmonics amplifiers to control optical and electromagnetic properties of materials. The LSPR modes and their interaction with the silicon nanowires are studied using numerical methods. The suggested configuration offers resonance covering the UV-visible and NIR regions, making them an adaptable addition to the nanoplasmonics toolbox.

The α- and β-polymorphs of Cd[Pt(CN)₄] are densely packed 3-D coordination polymers with quantum yields of 0.85 and 0.79. They react with donor solvent vapours to give emissive 2-D CdL₂[Pt(CN)₄] (L = DMSO, DMF, pyridine) cyanometallate sheets.

Controlling contagious diseases necessitates using diagnostic techniques that can detect infection in the early stages. Although different diagnostic tools exist, there are still challenges related to accuracy, rapidity, cost-effectiveness, and ease of use. Surface-enhanced Raman spectroscopy (SERS) is a rapid, simple, less expensive, and accurate method. We continue our previous work published on SERS detection of the SARS-CoV-2 receptor-binding domain (RBD) in water. In this work, we replace water with saliva to detect SARS-CoV-2 proteins at very low concentrations and during a very short time. We prepared a very low concentration of 10⁻⁹ M SARS-CoV-2 spike protein (S) and SARS-CoV-2 receptor-binding domain (RBD) in saliva to mimic a real case scenario. Then, we drop them on a SERS substrate. Using modified SERS measurements on the control and the sample containing the biomolecules, confirmed the sensitivity of the target identification. This technique provides different diagnostic solutions that are fast, simple, non-destructive and ultrasensitive. Simulation of the real-world of silicon wire covered with silver and gold, were performed using an effective and accurate tool, COMSOL Multiphysics software, for the enhancement properties study.

Vanadium is an abundant and cheap metal but near-infrared luminescent vanadium complexes are extremely rare with largely unexplored photophysics and photochemistry. We delineate the photodynamics of VCl ₃ (ddpd) to infer novel design strategies.

We report on surface plasmon polaritons (SPPs) observed by functionalized‐tip/surface enhanced Raman scattering. In particular, a short‐range SPPs was detected on a rough gold film with high spatial resolution. The SPPs are launched by large noble metal nanostructures. SPPs interferences patterns with a beating period of around 400 nm are observed. Manipulation of the optical enhancement has been carried out by tuning the tip‐sample distance. An increase of Raman scattering due to the highly directional surface plasmon coupled emission is observed. A finite element simulation has been carried out in order to simulate the SPPs patterns and also the influence of the emission angle and the tip to sample distance on far field intensity. These simulations in particular confirm that the SPPs mode is resulting from the interference between the wave vector of the incident and scattered light and the wave vector of the scattered SPPs. The contribution of surface plasmon coupled emission in increasing the sensitivity of Raman intensity with a tip‐enhanced Raman scattering configuration is observed.

The thickness of multifunctional oxide films directly affects the localized enhancement of the electromagnetic field and hence is a key factor for realizing novel photonic or optoelectronic devices. To this end, we theoretically exploit the principle of tip‐enhanced Raman spectroscopy on the surface of multifunctional oxide films (bismuth ferrite and barium titanate) on a gold substrate. An electromagnetic field enhancement of up to 10⁴ in close proximity of the tip apex was obtained. The good agreement between simulation and experiment of spatial resolution of the tip supports the validity of our model. By investigation of surface plasmon polaritons that propagates at the interface between the multifunctional film and the gold substrate, we demonstrated a thickness dependent propagation length and amplitude. This study indicates a critical thickness of the films above which neither a considerable near‐field nor a tip‐mediated excitation are observed. This confirms the validity, promise, and power of tip‐enhanced Raman spectroscopy technique for the analysis of various electro‐optic materials.

Tunable plasmonic noble metal nanoparticles are indispensable for chemical sensors and optical near field enhancement applications. Laser wavelengths within the absorption spectrum of the nanoparticle and Localized Surface Plasmon Resonances (LSPR) in the visible and near infrared range are the key points to be met for the successful utilization in the field of aforementioned high sensitivity sensors. This way, Surface Enhanced Raman Spectroscopy (SERS) has been pushed to the sensitivity level of single molecule. The tunability, i.e. the modulation of the surface plasmon resonance wavelength as a function of the ambient refractive index is one of the important criteria to be understood clearly. Among various noble metals, gold and silver nanoparticles have the strongest surface enhancement factors for the Raman signal and their tunability for many practical applications has been experimentally demonstrated. We present a comprehensive numerical investigation by means of a finite element analysis on Ag/Au core–shell nanospheres including agglomerated and non-agglomerated dimers. Tunability as a function of shell thickness, total nanosphere radius and fraction of overlap between the dimer is discussed. Our studies show that tunability is considerably affected by the nanosphere radius rather than the shell thickness. These findings may be helpful in the synthesis of nanoplasmonic structures, especially related to an optimized use of gold as the shell material for the targeted application.

Optical near-field mapping of plasmonic nanostructures prepared by nanosphere lithography Optical near-field mapping of plasmonic nanostructures prepared by nanosphere lithography

We report on photochemical and photophysical properties produced by Surface Plasmon Resonance (SPR) on metallic nanograins by means of high resolution Functionalized Tip-Enhanced Raman Spectroscopy (F-TERS).