The 4f-Hybridization Strength in Ce m Mn In3m+2n Heavy-Fermion Compounds Studied by Angle-Resolved Photoemission Spectroscopy

We systemically investigate the nature of Ce 4f electrons in structurally layered heavy-fermion compounds Ce m M n In3m + 2n (with M = Co, Rh, Ir, and Pt, m = 1, 2, n = 0–2), at low temperature using on-resonance angle-resolved photoemission spectroscopy. Three heavy quasiparticle bands f 0, f 7 / 2 1 and f 5 / 2 1 , are observed in all compounds, whereas their intensities and energy locations vary greatly with materials. The strong f 0 states imply that the localized electron behavior dominates the Ce 4f states. The Ce 4f electrons are partially hybridized with the conduction electrons, making them have the dual nature of localization and itinerancy. Our quantitative comparison reveals that the f 5 / 2 1 –f 0 intensity ratio is more suitable to reflect the 4f-state hybridization strength.

Sensitivity-Enhanced SPR Sensor Based on Graphene and Subwavelength Silver Gratings

A novel surface plasmon resonance (SPR) sensor with graphene and subwavelength gratings is proposed to improve the sensing performance. A series of numerical analyses were performed to investigate the effect of structural parameters on the sensing performance, such as minimum reflectance at resonance (MRR), full width at half maximum (FWHM), and resonance angle. The results indicated that near-zero MRR (2.9 × 10−6) and narrow FWHM (about 3.5 deg) could be obtained by optimizing the geometrical parameters. Moreover, the influence of the number of graphene layers on sensitivity was also studied. The maximum sensitivity of the designed sensor could reach 192 deg/refractive index unit (RIU), which is a great enhancement compared to the silver-only SPR sensor. In addition, ethylene glycol solutions with different refractive indices were detected. The results showed that the sensitivity of the sensor could reach 220.67 deg/RIU, and the proposed sensor had excellent linearity between the resonance angle and refractive index, enabling extensive potential practical sensing applications.

Calculating Resonance Angle for Surface Plasmon Resonance Activation on Different Metals

Surface plasmon resonance (SPR) is the technique that has been used in many fields including biomedical science, optic, biosensing, photothermal plasmon and medicine. With the help of Kretschmann configuration, the setup allows to excite the electrons located around the metal which results in electron oscillation, also known as the plasmonic effect. However, SPR requires many factors in order to be activated. This paper approaches and analyzes two crucial features, the incident angle of incoming light and the effect of permittivity that different metals have in order to determine the sufficient value for the plasmon to exist. Different metals including gold, silver and iron are used with the dielectric air and water in order to figure out the most applicable metal with its resonance angle.

Integrated defect sensor for the inspection of fiber-reinforced plastics using air-coupled ultrasound

Air-coupled ultrasound (ACU) is a non-destructive testing (NDT) method with a rising significance in industrial use. Common cases where ACU is used are the testing of fiber-reinforced plastic or testing of weld joints between metal sheets. The advantage compared to contact ultrasound is the absence of a liquid, solid or gel-like couplant. The usage of a couplant is an obstacle for developers of automatic scanning systems for ultrasonic testing because it takes a huge effort to integrate a system that delivers a continuous flow of the couplant. In addition a further step of cleaning is often necessary. ACU needs specially adapted probes to compensate for the tremendous impedance difference between a solid and air. A standard method uses two ACU probes in a normal transmission mode. With slanted probes, it is possible to generate Lamb waves in plate-like materials. Because of the contact to the surrounding air, Lamb waves transmit ultrasound to the air on both sides of the plate continually. These so-called leaky Lamb waves can be used with only one accessible side, and by using a specific resonance angle, a higher signal-to-noise ratio (SNR) is achievable. In the past, the correct angle was determined using an iterative method, where the angle of incidence was changed manually while observing the amplitude level. With the stepper-motor-driven angle scanning system, introduced here, the determination of the resonance angle is possible automatically. The system allows changes of the incidence angle during the ultrasound scan too. This makes it possible to adapt the system to wall thickness changes and changes of the radii of the parts contour.

Optical Thickness Monitoring as a Strategic Element for the Development of SPR Sensing Applications

The importance of the monitoring of thickness and rate deposition is indispensable for the fabrication of thin film sensors, such as SPR sensors. The sensitivity of SPR responses varies with the thickness of the film, as well as the linear range. Thus, in the present work, we presented an experimental study of the plasmonic response of Cr/Au thin films deposited onto glass slides by evaporation, based on both a rotation and no-rotation system. The results show that the thickness of the gold film varies from 240 to 620 Å, depending on the glass slide position. The SPR response curves obtained experimentally were compared with simulated plasmonic responses and different parameters such as resonance angle, and the depth, slope and half-width of the SPR curve were analysed.

Polypyrrole-Chitosan-CaFe2O4 Layer Sensor for Detection of Anionic and Cationic Dye Using Surface Plasmon Resonance

A polypyrrole-chitosan-calcium ferrite nanocomposite was prepared using the electrodeposition method. The prepared layer was characterized by using Fourier transform infrared spectroscopy, the X-ray diffraction technique, and field emission electron microscopy. The thickness of the thin layers was in the range of 2.8 nm to 59.5 nm, and the refractive index of the composite layer was in the range of 1.66131+0.156i to 1.62734+0.167i. Detection and removal of cationic and anionic dyes, such as methylene blue and methylene orange, are subject of great interest for protecting environmental water. The layer composite was used to detect methylene orange and methylene blue using the surface plasmon resonance technique. Consequently, the polypyrrole-chitosan-calcium-ferrite composite layer interacted with the anionic and cationic dyes. The resonance angle shift for the detection of the cationic dye was larger than the resonance angle shift for the anionic dye. The sensor limit was achieved from a sensogram at about 0.01 ppm.

Spectroscopy Resonance Plasmon Efficient Tool for Cell Adsorption

It is important to analyze cell monolayer adherence for the development of biomedical devices of anti-thrombogenic vascular grafts. Endothelial cells must be firmly attached to the biomaterials when cells are seeded in order to create a natural lining. Polystyrene (PS) is presented as a reproducible implant model substrate for studying cell – material interactions. Polystyrene was deposited as a thin layer on a thiol functionalized gold electrode. Fibronectin (Fn), a protein promoting the cell monolayer adhesion was adsorbed on PS surface. The different steps of this multilayer assembly were characterized by Surface Plasmon Resonance (SPR) technique. A right shift of the SPR resonance angle θSPR was observed leading an increase from 65.5 deg in the case of gold electrode to 66.8 deg in the case where cell monolayer was cultured onto functionalized gold substrate. A shift in the SPR peak minimum intensity was detected in the SPR response of Au/Thiol/PS/Fn and Au/Thiol/PS/Fn/Cell multilayer assembly structures. This result is explained using Atomic Force Microscopy (AFM) images and according transverse profiles which indicate surface morphological modifications in term of thickness.