Search Results (15)

While electromagnetic metamaterials completely revolutionized optics and radio frequency engineering, recent progress in the development of conceptually related electronic metamaterials was more slow. Similar to electromagnetic metamaterials, which engineer material response to the electromagnetic field of a photon, the purpose of electronic metamaterials is to affect electron propagation and its wave function by changing material response to its electric field. This makes electronic metamaterials an ideal tool for engineering light–matter interaction in semiconductors and superconductors. Here, we propose the use of Fermi’s quantum refraction, which was previously observed in the terahertz spectroscopy of Rydberg atoms and two-dimensional surface electronic states, as a novel tool in quantum electronic metamaterial design. In particular, we demonstrate several potential applications of this concept in two-dimensional metamaterial superconductors and “universal quantum dots” designed for operation in the terahertz frequency range. Full article

Electromagnetic waves (EMWs) have become an integral part of our daily lives, but they are causing a new form of environmental pollution, manifesting as electromagnetic interference (EMI) and radio frequency signal leakage. As a result, the demand for innovative, eco-friendly materials capable of blocking EMWs has escalated in the past decade, underscoring the significance of our research. In the realm of modern science, the creation of new materials must consider the starting materials, production costs, energy usage, and the potential for air, water, and soil pollution. Herein, we utilized biowaste materials generated during the distillation of fruit schnapps. The biowaste from apple and quince schnapps distillation was used as starting material, mixed with KOH, and carbonized at 850 °C, in a nitrogen atmosphere. The structure of samples was investigated using various techniques (infrared, Raman, energy-dispersive X-ray, X-ray photoelectron spectroscopies, thermogravimetric analysis, BET surface area analyzer). Encouragingly, these materials demonstrated the ability to block EMWs within a frequency range of 8 to 12 GHz. Shielding efficiency was measured using waveguide adapters connected to ports (1 and 2) of the vector network analyzer using radio-frequency coaxial cables. At a frequency of 10 GHz, carbonized biowaste blocks 78.5% of the incident electromagnetic wave. Full article

Surface-Enhanced Raman Spectroscopy (SERS) is a specialized spectroscopic technique based on the enhancement of the Raman scattering signals of molecules adsorbed or in close proximity to certain rough or nanostructured metal surfaces. It’s an extremely sensitive and powerful analytical tool for the investigation of biological molecules, revolutionizing the field of bioanalytical chemistry. The enhancement of Raman signal is due to various effects, the most important is thought to be the interaction between the electromagnetic wave associated with the laser used and the rough metal substrate (i.e., silver/copper/gold surfaces) on which the molecule is placed. When substrates are used, their characteristics are crucial for the reliability and sensitivity of experiments, as well as the ease of reproducibility of measurements. In the present work, we report on preliminary measurements to investigate the characteristics of two commercial SERS substrates, which have different nanostructures and patterns, properly designed to operate at an excitation wavelength of 785 nm. Aspirin C was used as a representative molecule to evaluate their application for SERS study of biological molecules, thanks to its characteristic fingerprint. Aspirin C is commercially available in the form of effervescent tablets, with acetylsalicylic acid and ascorbic acid as active principles with mainly analgesic and anti-inflammatory properties. The results are discussed also considering future applications for the detection of analytes of environmental interest. Full article

This review summarizes recent advances in leveraging localized surface plasmon resonance (LSPR) nanotechnology for sensitive cancer biomarker detection. LSPR arising from noble metal nanoparticles under light excitation enables the enhancement of various optical techniques, including surface-enhanced Raman spectroscopy (SERS), dark-field microscopy (DFM), photothermal imaging, and photoacoustic imaging. Nanoparticle engineering strategies are discussed to optimize LSPR for maximum signal amplification. SERS utilizes electromagnetic enhancement from plasmonic nanostructures to boost inherently weak Raman signals, enabling single-molecule sensitivity for detecting proteins, nucleic acids, and exosomes. DFM visualizes LSPR nanoparticles based on scattered light color, allowing for the ultrasensitive detection of cancer cells, microRNAs, and proteins. Photothermal imaging employs LSPR nanoparticles as contrast agents that convert light to heat, producing thermal images that highlight cancerous tissues. Photoacoustic imaging detects ultrasonic waves generated by LSPR nanoparticle photothermal expansion for deep-tissue imaging. The multiplexing capabilities of LSPR techniques and integration with microfluidics and point-of-care devices are reviewed. Remaining challenges, such as toxicity, standardization, and clinical sample analysis, are examined. Overall, LSPR nanotechnology shows tremendous potential for advancing cancer screening, diagnosis, and treatment monitoring through the integration of nanoparticle engineering, optical techniques, and microscale device platforms. Full article

We present the design, fabrication, and experimental test of a THz all-dielectric phase shifter plate. The design consists of two wave plate zones coupled in a perpendicular orientation with respect to each other. A large surface area device is realized by an additive manufacturing technique using Acrylonitrile Butadiene Styrene (ABS). Its characteristics are analytically evaluated and experimentally measured in the THz band using time domain spectroscopy and imaging routines. The proposed design enables the creation of quasi-ideal phase retardation in between the two planes with good uniformity on a large surface area. We also achieve the flexibility to select the plane of symmetry around the chosen central axes of choice with a sensitive control over the electromagnetic field polarization direction without inducing any temporal shifts in between the wave front components of the traversed beam. Due to its inherent simplicity and robustness, the phase shifter can be easily scaled at higher frequencies and potentially used in several advanced applications, including free-electron laser (FEL) systems where an accurate polarization control of high intensity beams is required. Full article

Surfaces of semiconducting materials excited by femtosecond laser pulses emit electromagnetic waves in the terahertz (THz) frequency range, which by definition is the 0.1–10 THz region. The nature of terahertz radiation pulses is, in the majority of cases, explained by the appearance of ultrafast photocurrents. THz pulse duration is comparable with the photocarrier momentum relaxation time, thus such hot-carrier effects as the velocity overshoot, ballistic carrier motion, and optical carrier alignment must be taken into consideration when explaining experimental observations of terahertz emission. Novel commercially available tools such as optical parametric amplifiers that are capable of generating femtosecond optical pulses within a wide spectral range allow performing new unique experiments. By exciting semiconductor surfaces with various photon energies, it is possible to look into the ultrafast processes taking place at different electron energy levels of the investigated materials. The experimental technique known as the THz excitation spectroscopy (TES) can be used as a contactless method to study the band structure and investigate the ultrafast processes of various technologically important materials. A recent decade of investigations with the THz excitation spectroscopy method is reviewed in this article. TES experiments performed on the common bulk A3B5 compounds such as the wide-gap GaAs, and narrow-gap InAs and InSb, as well as Ge, Te, GaSe and other bulk semiconductors are reviewed. Finally, the results obtained by this non-contact technique on low-dimensional materials such as ultrathin mono-elemental Bi films, InAs, InGaAs, and GaAs nanowires are also presented. Full article

The paper presents the application of the acousto-optic tunable filter (AOTF) in surface plasmon resonance (SPR) spectroscopy to measure the optical thickness of thin dielectric coatings. The technique presented uses combined angular and spectral interrogation modes to obtain the reflection coefficient under the condition of SPR. Surface electromagnetic waves were excited in the Kretschmann geometry, with the AOTF serving as a monochromator and polarizer of light from a white broadband radiation source. The experiments highlighted the high sensitivity of the method and the lower amount of noise in the resonance curves compared with the laser light source. This optical technique can be implemented for nondestructive testing in the production of thin films in not only the visible, but also the infrared and terahertz ranges. Full article

An acicular microtextured sheet was developed as a heat radiation device from the high-temperature source to the cooling medium in the infrared (IR) spectrum. The copper surface was modified by acicular micro-texturing to place a semi-regular micro-/nano-cone structure onto it. FT-IR (Fourier transformation IR) spectroscopy was utilized to measure the transmittance diagram in near-IR to far-IR wavelengths. The wavelength (λ) of 6.7 μm, where the highest absorbance valley was detected in the diagram, was equivalent to the doubled size of the micro-cone average height, with H_ave = 3.3 μm; λ ~ 2 × H_ave. The electromagnetic waves in the far-IR wavelength were emitted by acicular micro-textured metallic sheets. The heat radiation transfer experiment was performed to describe this low-temperature heat radiation behavior. No temperature rise was detected on the black-colored polycarbonate (BC-PC) plate away from the bare copper sheet without textures, located on the high-temperature source. The temperature increased by 4 K on the BC-PC plate using the acicular textured copper sheet device. The emitter temperature also decreased significantly by 50 K or 50% of the heat source temperature. Full article

In this study, zinc oxide (ZnO)/polypyrrole (PPy) composites with flower- and rod-like structures were successfully fabricated by in situ polymerization and the hydrothermal method and used as microwave absorption (MWA) materials. The surface morphologies, crystal structures, and electromagnetic features of the as-prepared samples were measured by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and vector network analyzer (VNA). The results show that the conductive polymer PPy was successfully decorated on the surface of ZnO substrates. The MWA ability of flower- and rod-like ZnO/PPy composites is significantly enhanced after introduction of PPy. Rod-like ZnO/PPy composites exhibited superior MWA properties than those of flower-like ZnO/PPy. The former achieved a minimum reflection loss (RL_min) of −59.7 dB at 15.8 GHz with a thickness of 2.7 mm, and the effective absorption bandwidth (EAB, RL < −10 dB) covered 6.4 GHz. PPy addition and stacked structure of rod-like ZnO/PPy composites can effectively improve the dielectric properties, form multiple reflections of incident electromagnetic waves, and generate an interfacial polarization effect, resulting in improved MWA properties of composite materials. Full article

The purpose of this study is to prepare a resistive lossy material using conducting polymers for electromagnetic wave absorbers. This paper presents a conductive paste largely composed of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) with a polyurethane binder. The various secondary compounds are added in small amounts to an aqueous blended solution in order to enhance the electrical and mechanical properties of the conductive thin film. The synthesized conductive paste is characterized through electrical, chemical, and morphological analyses. The electrical conductivity of the thin film is measured using a four-point probe and surface profiler. The chemical and morphological changes are studied in various experiments using a Raman microscope, X-ray photoelectron spectroscopy, a scanning electron microscope, and an atomic force microscope. In order to verify the applicability of the synthesized conductive paste, which is composed of 70 wt% PEDOT:PSS, 30 wt% polyurethane, and secondary additives (DMAE 0.4 wt%, A-187 0.5 wt%, DMSO 7 wt%, Dynol 604 0.1 wt%, PUR 40 2.5 wt%), the Salisbury screen absorber is fabricated and evaluated in the X-band. According to the results, the absorber resonates at 9.7 GHz, the reflection loss is −38.6 dB, and the 90% absorption bandwidth is 3.4 GHz (8.2 to 11.6 GHz). Through this experiment, the applicability of the PEDOT:PSS-based conductive paste is sufficiently verified and it is found that excellent radar-absorbing performance can be realized. Full article

We present a facile approach for the determination of the electromagnetic field enhancement of nanostructured TiN electrodes. As model system, TiN with partially collapsed nanotube structure obtained from nitridation of TiO₂ nanotube arrays was used. Using surface-enhanced Raman scattering (SERS) spectroscopy, the electromagnetic field enhancement factors (EFs) of the substrate across the optical region were determined. The non-surface binding SERS reporter group azidobenzene was chosen, for which contributions from the chemical enhancement effect can be minimized. Derived EFs correlated with the electronic absorption profile and reached 3.9 at 786 nm excitation. Near-field enhancement and far-field absorption simulated with rigorous coupled wave analysis showed good agreement with the experimental observations. The major optical activity of TiN was concluded to originate from collective localized plasmonic modes at ca. 700 nm arising from the specific nanostructure. Full article

Nano coatings for anti-corrosion and electromagnetic wave absorbing can simultaneously implement the functions of assimilating electromagnetic waves and reducing the corrosion of materials caused by corrosive environments, such as seawater. In this work, a composite material for both electromagnetic wave absorption and anti-corrosion was prepared by an in-situ chemical oxidation and surface coating method using carbonyl iron powder (CIP), graphene oxide (GO) and aniline (AN). The synthesized composite material was characterized by scanning electron microscopy (SEM), infrared spectroscopy (FT-IR) and XRD. The carbonyl iron powder-graphene oxide-polyaniline (CIP-GO-PANI) composite material was used as the functional filler, and the epoxy resin was the matrix body for preparing the anticorrosive wave-absorbing coating. The results show that CIP had strong wave-absorbing properties, and the anti-corrosion property was greatly enhanced after being coated by GO-PANI. Full article

The development of silver (Ag) thin films and the fabrication of Ag nanosquare arrays with the use of an anodic aluminum oxide (AAO) template and leaf extracts were successfully carried out using the DC sputtering and spin coating deposition methods. Ag thin films and Ag nanosquare arrays are developed to monitor cancer prognosis due to the correlation between serum albumin levels and prognostic factors, as well as the binding of serum albumin to the surface of these electrodes. Nanosquare structures were fabricated using AAO templates with varying diameters and a gap distance between adjacent unit cells of 100 nm. The nanosquare array with a diameter of 250 nm and irradiated with electromagnetic waves with a wavelength of around 800 nm possessed the greatest electric field distribution compared to the other variations of diameters and wavelengths. The results of the absorption measurement and simulation showed a greater shift in absorption peak wavelength when carried out using the Ag nanosquare array. The absorption peak wavelengths of the Ag nanosquare array in normal blood and blood with cancer lymphocytes were 700–774 nm and 800–850 nm, respectively. The electrochemical test showed that the sensitivity values of the Ag thin-film electrode deposited using DC sputtering, the Ag thin-film electrode deposited using spin coating, and the Ag nanosquare array in detecting PBS+BSA concentration in the cyclic voltammetry (CV) experiment were 1.308 µA mM⁻¹cm⁻², 0.022 µA mM⁻¹cm⁻², and 39.917 µA mM⁻¹cm⁻², respectively. Meanwhile, the sensitivity values of the Ag thin film and the Ag nanosquare array in detecting the PBS+BSA concentration in the electrochemical impedance spectroscopy (EIS) measurement were 6593.76 Ohm·cm²/mM and 69,000 Ohm·cm²/mM, respectively. Thus, our analysis of the optical and electrochemical characteristics of Ag thin films and Ag nanosquare arrays showed that both can be used as an alternative biomedical technology to monitor the prognosis of blood cancer based on the concentration of serum albumin in blood. Full article

The response of materials to impinging electromagnetic waves is mainly determined by their dielectric (complex permittivity) and magnetic (complex permeability). In particular, radar absorbing materials are characterized by high complex permittivity (and eventually large values of magnetic permeability), Indeed, energy dissipation by dielectric relaxation and carrier conduction are principally responsible for diminishing microwave radiation reflection and transmission in non-magnetic materials. Therefore, the scientific and technological community has been investigating lightweight composites with high dielectric permittivity in order to improve the microwave absorption (i.e., radar cross-section reduction) in structural materials for the aerospace industry. Multiwalled carbon nanotubes films and their composites with different kind of polymeric resins are regarded as promising materials for radar absorbing applications because of their high permittivity. Nanocomposites based on commercial multi-wall carbon nano-tube (MWCNT) fillers dispersed in an epoxy resin matrix were fabricated. The morphology of the filler was analyzed by Field emission scanning electron microscopy (FESEM) and Raman spectroscopy, while the complex permittivity and the radiation reflection coefficient of the composites was measured in the radio frequency range. The reflection coefficient of a single-layer structure backed by a metallic plate was simulated based on the measured permittivity. Simulation achievements were compared to the measured reflection coefficient. Besides, the influence of morphological MWCNT parameters (i.e., aspect ratio and specific surface area) on the reflection coefficient was evaluated. Results verify that relatively low weight percent of MWCNTs are suitable for microwave absorption applications when incorporated into polymer matrixes (i.e., epoxy resin). Full article

A facile and environmentally friendly method is proposed to prepare reduced graphene oxide–nickel (RGO–Ni) nanocomposites using γ-ray irradiation. Graphene oxide (GO) and Ni²⁺ are reduced by the electrons which originated from the gamma radiolysis of H₂O. The structure and morphology of the obtained RGO–Ni nanocomposites were analyzed using X-ray diffraction (XRD) and Raman spectroscopy. The results show that Ni nanoparticles were dispersed uniformly on the surface of the RGO nanosheets. As expected, the combination of RGO nanosheets and Ni nanoparticles improved the electromagnetic wave absorption because of the better impedance matching. RGO–Ni nanocomposites exhibited efficient electromagnetic wave absorption performance. The minimum reflection loss (RL) of RGO–Ni reached −24.8 dB, and the highest effective absorption bandwidth was up to 6.9 GHz (RL < −10 dB) with a layer thickness of 9 mm. Full article