Papers by Keyword: Sensitivity

Abstract: In this article, we propose a biosensor based on a hybrid photonic crystal, the studied system is a superlattice consisting of a periodic alternation of poly(methyl methacrylate) (PMMA) and silicon dioxide (SiO₂) layers. Our study demonstrates that breaking the periodicity of the superlattice enables the excitation of Bloch surface waves within the photonic bandgap. This feature, along with its experimental convenience, justifies our choice of this structure for designing a biosensor in the Kretschmann configuration. Furthermore, we also analyzed the effect of various parameters, such as the number of layer repetitions, the frequency of the light waves used, and the thickness of the defect layer, on the biosensor's performance, the optimal structure, MgF₂/(PMMA/SiO₂)₃/D, demonstrates excellent sensing performance, achieving an angular sensitivity of 74°/RIU and a high figure of merit (FOM) of 1495/RIU.

Abstract: In recent years, flexible strain sensors with high sensitivity and a wide sensing range have been developed for biosensors, wearable sensors, electronic skin, and soft robots. In this study, SR/CNT/SR composite-based sensors were fabricated using the sandwich manufacturing method. The sensors were then analyzed for electro-mechanical properties to test their performance. The flexible strain sensor showed a high sensitivity of 76.60 at 0-80% strain range. In addition, the sensor also showed a high linearity of 0.978 in one linear region. The sensor also constantly changes relative resistance at 10 cycles in the 0-40% range. While in the 45-80% strain range, the relative resistance value fluctuates. This is due to the large crack in the sensor when stretched. This sensor also has a fast response time of about 80 ms and a fast recovery of around 95 ms. This flexible strain sensor is also stable for durability testing at 500 loading and release cycles.

Abstract: The aim of this work is to evaluate the impact of maltose additive on the radiation sensitivity of the polymer gel dosimeter (PGD), made from a less toxic monomer, 2-hydroxyethylmethacrylate (HEMA). The sensitivity of the PGD recipe made from HEMA as monomer, N,N’- Methylene-Bis-Acrylamide (BIS) as cross linker, Gelatin as gel matrix and Tetrakis (Hydroxymethyl) phosphonium chloride (THPC) as antioxidant, was evaluated using UV-Visible Spectroscopy (UV-Vis.) when irradiated with x-ray, using clinical linear accelerator (LINAC), within the dose range of 0–30 Gy. The baseline correction was performed using three different approaches: using (i) deionized water (DI-H₂O), (ii) unirradiated sample in the reference compartment, and (iii) unirradiated sample in both the reference and the sample compartments. DI-H₂O or unirradiated sample was then used as a reference sample to scan the irradiated ones. The three approaches were compared and all of them confirmed that increasing the maltose concentration within the optimal range results in an improved sensitivity. However, they differed in the optimum concentration. The result revealed that using the third approach, maltose addition achieved an efficiency of 750.0% compared to the sample without the addition, while the first and the second approaches achieved efficiencies of 550.0% and 330.0% respectively. The reasons for these differences were discussed. These findings are important for enhancing radiation dosimetry using PGDs and we finally recommend the use of maltose additive in the HEMA-based PGD to improve radiation sensitivity, melting temperature and tissue equivalence for radiotherapy planning and dosimetry system.

Abstract: The explosive sensitivity of the supramolecular interaction between cations (Mⁿ⁺ = Li⁺, Na⁺, K⁺, Be²⁺, Ca²⁺ and Mg²⁺) with enol tautomers (c0 and c1) of 3-nitro-1,2,4-triazole-5-one (NTO) complexes has been investigated using Density Functional Theory (DFT). The effect of water as the solvent was included via the CPCM approach. At the gas phase, the presence of the metal cations, especially Be²⁺, significantly increased the bond dissociation energy (BDE) of C-NO₂ of the enol tautomers. However, in the presence of the solvent, the BDE was lower than in the gas phase, even in the supramolecular complex of Be²⁺ - c0 and Be²⁺ - c1.

Abstract: This study includes the preparation of the ferrite nanoparticles Cu_xCe_0.3-XNi_0.7Fe₂O₄ (where: x = 0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) using the sol-gel (auto combustion) method, and citric acid was used as a fuel for combustion. The results of the tests conducted by X-ray diffraction (XRD), emitting-field scanning electron microscopy (FE-SEM), energy-dispersive X-ray analyzer (EDX), and Vibration Sample Magnetic Device (VSM) showed that the compound has a face-centered cubic structure, and the lattice constant is increased with increasing Cu ion. On the other hand, the compound has apparent porosity and spherical particles, and there are no other elements other than those participating in the preparation of the compound, which means that it is of high purity. The prepared compound possesses excellent magnetic properties due to the narrowness of the magnetic hysteresis ring. The gas sensing system found that the compound has good sensitivity to H₂S gas.

Abstract: To improve the sensitivity of the steady combined forward and backward extrusion test proposed in previous work, an optimization job based on the finite element simulations was carried out. A raw material of 0.45% carbon steel was tested under different stain rates from 0.001s^-1 to 1s^-1 and different temperatures from 30°C to 400°C, and the material flow stresses were modelled by Hensel-Spittel equation. The deformation degree of the forward extrusion was set as 50%. The key parameters including the deformation degree of the backward extrusion, the ratio between the radius of the punch nose and the radius of the punch, the taper angle of the punch, the die angle, the sizing lands of the punch and the die were optimized. The sensitivity of the optimal design is improved about 20% compared with previous design when the friction factor is assumed as 0.03~0.15. The new group of calibration curves presents more scatter than the old group. The sensitivity improvement is also validated by the experimental works.

Abstract: Most of the recent reduced graphene oxide (rGO) based sensors shows gas sensitivity above 50^o to 150°C. The present investigation deals with the gas sensing at 50°C temperature. In the present research work, thick film sensors of rGO were developed on glass substrate by using standard screen-printing technique. The silver paste of rGO was used to make electrodes for contact on thick films for the electrical and gas sensing system. The electrical properties of rGO thick films such as resistivity, activation energy and temperature coefficient were studied. The resistivity of rGO thick films was found to be 84.84 Ω/m. The morphological, elemental and structural properties of rGO thick films were analyzed by SEM, EDS and XRD techniques respectively. The crystallite size of rGO thick films was found as 28.42 nm by using Scherer’s formula. The rGO thick films were prepared and exposed to Ethanol, NH₃, NO₂ and LPG gases to determine sensitivity and selectivity. The sensitivity of NO₂ has been found to be maximum among other exposed gases. The maximum sensitivity of NO₂ gas was 92.55 % at 50 °C found with fast response (~ 11 sec) and recovery (~ 19 sec) time.

Abstract: In this research, SnO₂ nanostructure thin films were fabricated by spray pyrolysis method, using concentration of tin (Sn) salt solution deposited on a glass substrate at temperature of 450 °C. The tin solution was prepared by solves 2.2563gm of SnCl₂.2H₂O (molecular weight 219.4954 g/mole) in 100 ml of ethanol, then add 60 drops of pure hydrochloric acid ( HCl) using drop by drop technique. Different concentrations of antimony oxide (1%, 2%, 3%, 4%) hve been used to depose the thin films. The structure has been examined by X-ray diffraction technique, which shown that all films are polycrystalline with tetragonal rutile crystalline structure with preferential orientation in the (200) direction and, grain size decreases with increasing doping concentration. Optical measurements shown that the films are transparently in the visible region, with an average transmittance more then 80% and, sharp absorption edge nearly at 350 nm, the nature of the optical transition were direct allowed with band gap varies between (2.97 - 3.75 eV) which is directly proportional to doping concentration. The results also show that the doping has led to improved the response time of the sensing. Two kinds of gases NO₂ and NH₃ have been used to test the sensing performance, at different operating temperatures (R.T, 100, 200, 250, 300 and 350) oC , and bias voltage (3 Volt). For NO₂ gas the highest sensitivity was 77%, the shortest response time 2.9 s and the recovery time 19 s, while for NH₃ gas sensitivity was 11.5%, the response time 4.1 s and the shortest recovery time 20s,

Abstract: The objective of this research is to advance the affectability of Surface Plasmon Resonance (SPR) biosensor utilizing core-shell Fe₃O₄@Ag nanoparticles (Fe₃O₄@Ag NPs) with a variation of Ag concentration (20, 40, 60, 80, 100) mM. Fe₃O₄@Ag NPs were synthesized by the aqueous solution method. The characterization by utilizing X-ray Diffractometer (XRD) depicts that the crystal structure of Fe₃O4 compares to the cubic inverse spinel structure and based on Transmission Electron Microscopy (TEM) estimation, the particle size average of Fe₃O₄@Ag NPs is 14.45 nm. The magnetic properties of Fe₃O₄@Ag NPs were evaluated by Vibrating Sample Magnetometer (VSM), the result appears that the more concentration of Ag increases, the more remanent magnetization (Mr), saturation magnetization (Ms), and coercitivity field (Hc) diminishes. In this research, a Fe₃O₄@Ag NPs, a spherical nanoparticle consisting of a spherical Fe₃O₄ core covered by an Ag shell, was used as an active material to enhance the signal detection of SPR, with a wavelength of 632.8 nm in the Kretschmann configuration. The system consists of a four-layer material, i.e., prism/Au film/ Fe₃O₄@Ag NPs. The results show that the SPR angle shifted to the larger angle of incident light by using Fe₃O₄@Ag NPs. However, the effect of Ag concentration appears that the more concentration of Ag extends, the lower angle of SPR shifts. The addition of a core-shell in the conventional SPR-based biosensor leads to the enhancement of the SPR biosensor sensitivity if the fractional volume of the core-shell is large.

Abstract: Functionalized-multi wall carbon nanotubes (F-MWCNTs) and functionalized-single wall carbon nanotubes (F-SWCNTs) were well enhanced using NiO Nanoparticles. The sensor device consisted of a film of sensitive material (F-MWCNTs/ Nickel oxide nanoparticles) and (F-SWCNTs/ Nickel oxide nanoparticles) deposited by drop casting on n-type porous silicon substrate. The two sensors perform high sensitivity to NO₂ gas at particular temperatures. The analysis indicated that the (F-MWCNTs/NiONPs) have a better performance than (F-SWCNTs/NiONPs). The F-SWCNTs/NiONPs gas sensor shows high sensitivity (18.2 %) at RT with response time 16 sec, while F-MWCNTs/NiONPs gas sensor show better sensitivity (45 %) at RT with response time 26 sec. The device shows a very reproducible sensor performance, with high repeatability, complete recovery and adequate response. A demonstration of the improvement in sensing of NO₂ gas using NiO-functionalized nanotubes is provided.