Plasmonics最新文献

This work reports on the plasmonic properties of a Sn metasurface structure, in the wavelength region of 0.4–4(mu )m. On top of a glass substrate, the metasurface is formed by a central Sn nanobar surrounded with hexagonally oriented Sn nanobars. Multiple plasmonic resonances are observed, the plasmonic coupling effect at the Sn metasurface is revealed, and the corresponding electromagnetic field distributions are demonstrated. The results show that the electromagnetic field intensity near the surface of nanostructures can be enhanced by the near-field effect. The plasmonic resonance wavelength associated with the Sn nanobars can be tuned in the studied wavelength range, by adjusting the parameters of the metasurface. Based on this study, we suggest that the structure of the Sn metastructure proposed in this work be implemented in the design for plasmonic devices at 0.4–4(mu )m wavelengths.

A pulsed laser was used to make the Au@Ag@Au core-double shell nanoparticles in a DMF solution. The samples were characterized and inspected to confirm the structure investigated by XRD tests, and the average crystallite size was 51.988, 51.222, and 47.482 nm at laser energy 300, 500, and 700 mJ, respectively. Transmission electron microscopy (TEM) was employed to confirm the nanostructure of the particles. The particles were found to have a spherical form, with mean diameters of 15 nm, 9.5 nm, and 7.5 nm at laser energy of 300, 500, and 700 mJ, respectively. Showing the surface plasmon resonance peak for each gold and silver NPs, we observe a phenomenon a blue shift in absorption peak with increased laser energy, which signifies a reduction in the dimensions of the nanoparticles. The energy gap for samples was determined using Tauc’s relation, which were 1.52, 1.53, and 1.54 eV at laser energy 300, 500, and 700 mJ, respectively. The stability of the nanomaterials was assessed using zeta potential analysis, which measured the stability of every specimen in a DMF solution. The computed zeta potentials for the samples were − 19.6 mV, − 29.3 mV, and − 41.6 mV, at laser energy of 300, 500, and 700 mJ, respectively. After that, Au@Ag@Au core-double shells nanoparticles were tested as novel antimicrobial agents against Streptococcus mutans as well as Klebsiella pneumoniae. The results showed that the Au@Ag@Au core-double shells were great agents for killing both types of bacteria and inhibiting bacterial biofilm formation. The results collectively indicated that Au@Ag@Au NPs had the potential to serve as an alternate antibacterial agent.

Cancer continues to be a major global health challenge, where early detection is vital for enhancing patient survival rates. Conventional diagnostic techniques frequently face challenges related to sensitivity and specificity, which can result in delays in obtaining accurate diagnoses. To overcome these obstacles, the creation of highly sensitive and selective biosensors has emerged as a key focus of research. This paper presents the conceptualization and computational simulation of a terahertz surface plasmon resonance (SPR) sensor. The proposed sensor integrates graphene and gold metasurfaces with perovskite material, aimed at cancer detection applications. The sensor architecture is optimized to achieve optimal results. Numerical simulations are conducted to demonstrate the effects of varying graphene chemical potential and resonator dimensions on sensor performance metrics. The optimized configuration demonstrated a maximum sensitivity of 1000 GHzRIU⁻¹ and a figure of merit of 17.241 RIU⁻¹. Analysis of electric field distribution patterns depicts the frequency-dependent electromagnetic wave interactions within the sensor structure. The sensor design also exhibits consistent spectral characteristics, with an FWHM being 0.058 THz and quality factors ranging from 3.328 to 3.517. Furthermore, the proposed sensor demonstrates the promise for encoding applications. The proposed sensor shows considerable promise for early cancer detection applications, potentially contributing to improved diagnostic capabilities and patient outcomes in oncology.

In this work, we propose a THz metamaterial for biomedical applications. The full vectorial finite element method is used to design and analyze the reported biosensor. The proposed sensor is based on increasing the confinement of the electric and magnetic fields at the analyte layer at the resonance frequency. Hence, any slight variation of the optical properties of the analyte sample (typically the refractive index) can be detected. We demonstrate the potential of using the reported sensor for hemoglobin (Hb) concentration and early cancer detection. The geometrical parameters are studied to maximize the sensor sensitivity of the symmetric and asymmetric designs. An absorptivity of 0.98 is achieved at 1.1 THz, which depends on the analyte sample refractive index. High sensor sensitivity of 1.08 GHz/g/dL is obtained with high Q-factor of 13.2 and FWHM (full width at half maximum) of 140 GHz through hemoglobin (Hb) concentration change from 5 g/dL to 20 g/dL. Further, an average sensitivity of 556.325 GHz/RIU is realized for cancer early detection for basal cell, breast cell, Jurkat cell and Cervical cell. Therefore, the proposed design is a good candidate for biomedical applications.

The sensitivity of a gold-silver bilayer system for gas detection was investigated using angle-fixed reflectance measurements and numerical calculations based on the transfer-matrix method. Two configurations of bilayer systems were analyzed: gold on silver and silver on gold. According to calculations, the best sensitivity values were achieved with a total thickness of approximately 55 nm for the gold on silver system and approximately 65 nm for the silver on gold system. These calculations were supported by experimental results in a Kretschmann configuration for ethanol gas sensing. The bilayer systems showed a huge advantage compared to the widely used single gold thin film; however, special attention should be paid to the silver on gold configuration, as corrosion plays an important role in decreasing sensitivity.

In the present study, a simple and low-cost spectrophotometric method was reported for the quantification of selenium. The method was based on the surface manipulation of citrate-capped silver nanoparticles by selenium in ammonia-ammonium nitrate buffer solution (pH = 9). Citric acid on the surface of nanoparticles could reduce selenium ions to Se⁰ atoms which can react with the silver atoms to form Ag₂Se surrounding silver particles. This process resulted in the deformation and aggregation of nanoparticles which can be detected by a decrease in response intensity. The effect of important experimental parameters such as pH, buffer type and concentration, volume of silver nanoparticle solution, and incubation time on analytical response were investigated and optimized. Under the optimal conditions, the calibration graph was linear in a concentration range of 0.05 to 0.8 µmol L⁻¹ with a detection limit of 0.024 µmol L ⁻¹. The method was successfully used for the selenium analysis in Selen plus ACE capsule, selenium sulfide shampoo, and walnuts with satisfactory results.

This research explores the design, analysis, and optimisation of a biosensor utilising a one-dimensional superconductor-dielectric photonic crystal structure (1D-SD-PC). To the best of our knowledge, a superconductor-dielectric 1D-PC distributed Bragg structure (DBS) is used for the first time in the design and analysis of a biosensor. Materials that are superconductor and dielectric are used to construct the bilayer stack. Air is used as a dielectric material, and YaBa₂Cu₃O₇ is used as a superconductor layer. As the middle cavity layer of the SD structure, a bio-sample layer containing the sample being tested is added. The structural characteristics are optimally adjusted to maximise sensor efficiency. According to the observed results, the suggested structure has the highest RI sensitivity, measuring 65 nm/RIU and having 90.6% reflection with a Q factor of 8571. The suggested sensing device is appropriate for use in medical bio-sensing applications.

In this research, within the visible frequency band region, the scattering phenomenon of plane electromagnetic waves from two-piece nano-spheres, consisting of metal-dielectric (spherical metal-dielectric Janus nanoparticles), will be investigated theoretically. Mie’s theory, which addresses wave scattering from spherical structures, and the point-matching method for solving field equations, are the two main mathematical tools utilized in this work. Simulations have been conducted for objects with several dual combinations of metal-dielectric materials, such as Gold metal paired with dielectrics like Alumina, PVC, Teflon, and Rexolite. This investigation also extends to objects incorporating Silver metal. The diagrams depicting the variations of the scattering cross-section versus wave frequency have been presented. It will be demonstrated that, at certain frequencies, the diagrams of the scattering cross-section exhibit peaks. These peaks indicate the state in which the densities of surface plasmon dipoles at the metal-dielectric boundary have the most significant and optimal response to the presence of an electromagnetic wave. Since the maxima in the scattering cross-section diagram occur at specific frequencies within the visible region, they can be attributed as a reason for the dominant color observed in colloidal solutions containing spherical metal-dielectric Janus nanoparticles.

Creatinine level is a crucial indicator in the clinical assessment and diagnosis of renal diseases, and achieving simple and accurate detection of urinary creatinine levels in resource-limited point-of-care settings is of great significance in the timely prevention and diagnosis of kidney diseases. As a popular zero-dimensional material, gold nanoparticles (AuNPs) exhibit intriguing optical properties and thus have become a promising material for many sensing detection applications. Here, we proposed a simple, efficient, and sensitive quantitative detection of creatinine by studying the relative absorbance (ΔA) of AuNPs in absence and presence of creatinine. The method relies on the aggregation of AuNPs via ligand-exchanged of citrate ions and creatinine on the surface of AuNPs to achieve colorimetric detection. With this assay, the limit of detection for creatinine was as low as 0.16 mM, and the dynamic detection range was 0.5 to 20 mM under optimized conditions. In our experiments, the specificity of the proposed method was investigated and successfully applied to detect creatinine in urine sample. It reveals that the proposed colorimetric protocol has demonstrated a high sensitivity and selectivity for creatinine, and has a potential practicability in clinical diagnostics.

Au nanoparticles are known for substantially modifying their properties depending on the particle size. In the field of radiotherapy, the interaction of low-energy X-rays with high-Z plasmonic nanomaterials endow them with the ability to sensitize radiotherapy. In this study, Au nanofilms and nanoparticles were deposited on a B₂O₃ glass substrate using an electron beam evaporation technique and bombarded with X-ray at 150 kVp at 1 mA. Thermoluminescent (TL) measurement responses were measured using thermoluminescence dosimetry (TLD). The assembled structure with tunable properties leads to versatile applications in drug delivery and cancer treatment which is beneficial in the health treatment industry.