2D Gallium Sulfide-Based 1D Photonic Crystal Biosensor for Glucose Concentration Detection.

Unidimensional photonic crystal-based biosensors have gained much attention in the area of blood glucose measurement. In this paper, we propose two novel designs based on two-dimensional (2D) Van der Waals materials. The first 1D photonic crystal design consists of multilayers of 2D gallium sulfide and 2D muscovite mica [GaS/Mica]ND[GaS/Mica]N, and the second design consists of multilayers of 2D gallium sulfide [GaS/G]ND[GaS/G]N. We conducted a numerical analysis using the transfer matrix method to investigate the properties of photonic crystals, both with and without defect layers, in order to assess their suitability for biosensing applications. The biosensors' performances were investigated as a function of glucose concentration, revealing a high sensitivity of 832 nm/RIU, a notable figure-of-merit of 1.46 × 105 RIU-1, a Q-factor exceeding 105, and a minimum limit of detection of 3.4 × 10-7 RIU. Finally, we modified the [GaS/G]ND[GaS/G]Nstructure in order to enhance the sensitivity nearly 5-fold. The proposed biosensors offer the advantage of being label-free, making them promising platforms for the sensitive and reliable detection of blood glucose levels.

Optical and Structural Analysis of TiO2-SiO2 Nanocomposite Thin Films Fabricated via Pulsed Laser Deposition Technique.

TiO2-SiO2 nanocomposite thin films have gained the attention of the scientific community due to their unique physical and chemical properties. In this paper, we report on the fabrication and characterization of a TiO2-SiO2 nanocomposite disk-shaped target. The target was used for the deposition of TiO2-SiO2 nanocomposite thin films on fluorine-doped tin oxide/glass substrates using the pulsed laser deposition (PLD) technique. The thicknesses of the thin films were fixed to 100 nm, and the deposition temperature ranged from room temperature to 300 °C. As revealed by the microstructural and morphological characterizations revealed, the TiO2-SiO2 nanocomposite thin films are amorphous and display homogeneous distribution. The determined values of the indirect optical band gap range from 2.92 to 3.07 eV, while those of the direct optical band gap lie between 3.50 and 3.55 eV. Additionally, as the deposition temperature decreases, the light transmission increases in the visible and in the ultraviolet ranges, which is suitable for flexible perovskite solar cells. This research can uncover new insights into the fabrication of amorphous TiO2-SiO2-based nanostructured thin films using the PLD technique for perovskite solar cell technology.

Sequential Synthesis Methodology Yielding Well-Defined Porous 75%SrTiO3/25%NiFe2O4 Nanocomposite.

In this research, we reported on the formation of highly porous foam SrTiO3/NiFe2O4 (100-xSTO/xNFO) heterostructure by joint solid-state and sol-gel auto-combustion techniques. The colloidal assembly process is discussed based on the weight ratio x (x = 0, 25, 50, 75, and 100 wt %) of NiFe2O4 in the 100-xSTO/xNFO system. We proposed a mechanism describing the highly porous framework formation involving the self-assembly of SrTiO3 due to the gelation process of the nickel ferrite. We used a series of spectrophotometric techniques, including powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), N2 adsorption isotherms method, UV-visible diffuse reflectance spectra (UV-Vis DRS), vibrating sample magnetometer (VSM), and dielectric measurements, to investigate the structural, morphological, optical, magnetic, and dielectric properties of the synthesized samples. As revealed by FE-SEM analysis and textural characteristics, SrTiO3-NiFe2O4 nanocomposite self-assembled into a porous foam with an internally well-defined porous structure. HRTEM characterization certifies the distinctive crystalline phases obtained and reveals that SrTiO3 and NiFe2O4 nanoparticles were closely connected. The specific magnetization, coercivity, and permittivity values are higher in the 75STO/25NFO heterostructure and do not decrease proportionally to the amount of non-magnetic SrTiO3 present in the composition of samples.

Micro-Hall Sensors Based on Two-Dimensional Molybdenum Diselenide.

Sensors and electronic devices based on semiconductors in their two-dimensional forms have many advantages. In this paper, we studied micro-Hall sensors based on two-dimensional molybdenum diselenide for the first time. The micro-Hall sensor based on a Ti/MoSe2/Ti structure clearly showed a linear dependence of the Hall voltage as a function of the magnetic field, with a magnetic sensitivity of ∼16 V/AT. The magnetic sensitivity was higher in the Au/MoSe2/Au structure, with a maximum value of ∼120 V/AT at a bias current of 100 mA; the minimum detectable magnetic field was found to be 1.45 µT/Hz1/2 at the same current value, making our new micro-Hall sensor a very good candidate for magnetic sensing applications.

Thickness dependence on the optoelectronic properties of multilayered GaSe based photodetector.

Two-dimensional (2D) layered materials exhibit unique optoelectronic properties at atomic thicknesses. In this paper, we fabricated metal-semiconductor-metal based photodetectors using layered gallium selenide (GaSe) with different thicknesses. The electrical and optoelectronic properties of the photodetectors were studied, and these devices showed good electrical characteristics down to GaSe flake thicknesses of 30 nm. A photograting effect was observed in the absence of a gate voltage, thereby implying a relatively high photoresponsivity. Higher values of the photoresponsivity occurred for thicker layers of GaSe with a maximum value 0.57 AW(-1) and external quantum efficiency of of 132.8%, and decreased with decreasing GaSe flake thickness. The detectivity was 4.05 × 10(10) cm Hz(1/2) W(-1) at 532 nm laser wavelength, underscoring that GaSe is a promising p-type 2D material for photodetection applications in the visible spectrum.

Laser Power Dependent Optical Properties of Mono- and Few-Layer MoS2.

We report on the exponential decay of the red-shift of the photoluminescence A-exciton peak in monolayer molybdenum disulfide (MoS2) with the excitation laser power. The linear relationship found for the thermal variation of the same peak suggests that the laser power effect goes beyond the exciton dynamics associated to temperature variations. Laser exitation power effect on the broadening and red-shifting of the A(1g) and E(2g)1 phonon peaks observed by Raman spectroscopy reflect the damping of vibration due local thermal heating induced by the laser. Our results point out the laser excitation power dependence on the photoluminescence properties of monolayer MoS2.