Terahertz spectrum splitting by a graphene-covered array of rectangular grooves.

We propose a bidirectional terahertz (THz) spectrum splitter using a practically simple metamaterial structure consisting of rectangular grooves covered by graphene. Thanks to the graphene optoelectronic tunability and by adjusting the grooves width, this structure provides nearly 2π phase shift. At the same time, the reflection efficiency is acceptable throughout the phase shifts. We design each of the meta-atoms using a circuit model, and then we synthesize the final supercell based on the generalized Snell's law so that the structure reflects different frequency waves to totally different directions. The full-wave simulations demonstrate the beam splitting with a remarkable efficiency of around 80%.

An elliptical nanoantenna array plasmonic metasurface for efficient solar energy harvesting.

Plasmonic metasurfaces with subwavelength nanoantenna arrays have attracted much attention for their ability to control and manage optical properties. Solar absorbers are potential candidates for effectively converting photons into heat and electricity. This study introduces a novel ultrathin metasurface solar absorber employing elliptical-shaped nanoantenna arrays. We theoretically and numerically demonstrate a near-perfect broadband absorber with over 90% absorption efficiency in a wide range of wavelengths of 300-2500 nm, using finite element (FEM) and finite-difference time-domain (FDTD) methods. The proposed nanostructure configuration enhances light absorption by exciting localized surface plasmon resonances (LSPRs) between elliptical-shaped nanoantenna gaps at many wavelengths, maintaining stability at wide incident angles and insensitivity to light polarization. Compared to other state-of-the-art absorbers with a thickness of less than 300 nm, the designed nanostructure with 260 nm thickness achieves over 90% optical absorption across a broad range of wavelengths of 300-1116 nm in air (or vacuum) environments and performs effectively under water conditions for solar energy harvesting in a range of wavelengths of 300-1436 nm, and therefore can serve as a solar evaporator. Combining refractory plasmonic titanium nitride (TiN) and semiconductor gallium nitride (GaN) nanostructures holds great potential for efficient optoelectronic and photocatalytic applications, especially in harsh and high-temperature environments like thermophotovoltaic systems. The TiN-based metasurface absorber, with its ultrathin nanostructure and suitable spectral absorption in ultraviolet-visible-infrared spectra, offers scalability and cost-effectiveness. The findings in this work will deepen our understanding of LSPRs and pave a novel path for efficient solar energy conversion.

PC12 differentiation to neuron cells activated by a low-level laser at 660†nm on UV pre-treated CR-39 scaffolds with parallel microchannels.

The lack of regeneration of injured neurons in the central and peripheral neural system leads to the failure of damaged tissue repair in patients. While there is no definitive cure for most neurodegenerative diseases, new therapeutic methods that cause the proliferation and differentiation of neurons are of interest. Challenges such as the inability of neuronal cells to proliferate after injury, the lack of a stimulus for initial stimulation, and the presence of the microenvironment around CNS neurons contain several inhibitory factors that prevent neuron regeneration, thus, creating a structure similar to the extracellular matrix helps the cell proliferation in current treatment. A rapid method of neuron-like cell differentiation of PC12 cells is introduced here based on a novel synthetic scaffold. Initially, poly allyldiglycol carbonate (CR-39) substrate is textured under a high dose of ArF UV excimer laser (1000 shot, 300 mJ/pulse equivalent to 300 J/cm2 at 193 nm) to create superficial periodic parallel microchannels with the micrometer spacing and sub-micron width. Ultraviolet treated CR-39 (UT CR-39) provides a suitable scaffold to speed up the transformation/differentiation of PC12 cells. The latter is pheochromocytoma of the rat adrenal medulla as an embryonic origin from the neural crest usually exposed to the nerve growth factor (NGF). In fact, PC12 cells are seeded on the microchannels and simultaneously are stimulated by coherent red photons at 660 nm within the therapeutic window. The UT CR-39 scaffold undergoes extra improvement of ∼ 30% after 12 minutes of laser activation regarding the photo-biomodulation (PBM) mechanism. The cell activation due to the coherent photons also gives rise to enhanced proliferation/differentiation. Here, PC12 cells are efficiently differentiated into neurons according to immunocytochemistry (ICC) and Western Blot verification tests based on MAP2 and synapsin-1 protein expression. In general, UT CR-39 acts as a superior bed to elevate the population of neuron-like cells up to threefold against those of untreated (control)ones. We conclude that the surface cross-linking due to UV exposure and subsequent induced hydrophilicity notably contribute to the neuron-like cell differentiation of PC12 without adding NGF.

Signal enhancement in spark-assisted laser-induced breakdown spectroscopy for discrimination of glioblastoma and oligodendroglioma lesions.

Here, the discrimination of two types of lethal brain cancers, i.e., glioblastoma multiforme (GBM) and oligodendroglioma (OG) are investigated under the laser-induced breakdown spectroscopy (LIBS) and the electrical spark-assisted laser-induced breakdown spectroscopy (SA-LIBS) in order to discriminate the human brain glioma lesions against the infiltrated tissues. It is shown there are notable differences between the plasma emissions over the brain gliomas against those of infiltrated tissues. In fact, a notable enhancement appears in the characteristic emissions in favor of SA-LIBS against those of conventional LIB spectra. Moreover, the plasma properties such as temperature, electron density, and degree of ionization are probed through the data processing of the plasma emissions. The corresponding parameters, taken from SA-LIBS data, attest to be lucidly larger than those of LIBS up to one order of magnitude. In addition, the ionic species such as Mg II characteristic line at 279 nm and caII emission at 393 nm are notably enhanced in favor of SA-LIBS. In general, the experimental evidence verifies that SA-LIBS is beneficial in the discrimination and grading of GBM/OG neoplasia against healthy (infiltrate) tissues in the early stages.

Spectroscopic properties of various blood antigens/antibodies.

Since the traditional method generates biological waste, there is a significant demand for an easy, quick technique of blood type identification without contamination. In fact, individuals can be divided into four main blood groups whose antigens are available in red blood cell (RBC) membranes and the antibodies in the plasma. Here, UV-vis and photoluminescence (PL) spectroscopic methods are systematically used to find the spectra of blood typing antigens (A, B and AB) and antibodies i.e. A-Anti, B-Anti, AB-Anti and D reagent. The PL spectra of RBCs in different blood groups as well as the corresponding antibodies are successfully resolved for the purpose of blood typing. The unique photophysical characteristics of these biomolecules including signal intensity and peak emission wavelength in PL spectra are lucidly anticipated to accurately discriminate ABO groups. PL spectra of RBC in positive blood typing indicate larger signal and shorter emission peak wavelength corresponding to negative ones. Furthermore, the monoclonal antibody PL emissions emphasize that Anti-A benefits higher intensity and shorter peak wavelength (blue shift) than B-Anti. In the following, lucid blue shifts are obtained in terms of antibody concentrations accompanying the elevation of fluorescence signal, most likely due to the aggregation induced emission (AIE) phenomenon, quite the opposite of the aggregation-caused quenching (ACQ) that is widely observed from conventional chromophore. Those are envisaged as unique properties of each antibody to utilize in the spectral blood typing.