Plasmonics最新文献

Harnessing plasmonic interactions within iodide-modified frameworks offers an unconventional pathway for advancing next-generation optoelectronic and solar technologies. Here, we report the rational design of a molybdenum oxide iodide/iodine–poly(N-methylpyrrole) nanorod composite (Mo(VI)OI/I₂-PNMP), in which plasmon-active iodide species are intercalated within a conductive polymer matrix to establish synergistic light–matter coupling. The nanocomposite displays a distinctive rough-surfaced nanorod morphology (∼100 × 500 nm) with crystalline domains of ~11 nm, enabling strong interfacial charge delocalization. Optical analysis reveals a direct bandgap of 1.96 eV, optimally positioned for solar absorption, while the iodide component introduces localized surface plasmon resonances that enhance charge carrier excitation. Integration of Mo(VI)OI/I₂-PNMP with polypyrrole yields a hybrid thin-film device exhibiting efficient photovoltaic operation, with an open-circuit voltage of 0.45 V and photocurrent densities of 0.03 mA·cm⁻² (light) versus 0.005 mA·cm⁻² (dark). The device further demonstrates broadband photodetection, achieving photoresponsivity of 0.26 and 0.18 mA/W at photon energies of 3.6 and 2.3 eV, respectively, alongside detectivity up to 0.6 × 10⁸ Jones. These results establish iodide-driven plasmonic modulation as a powerful tool for tailoring optoelectronic responses in hybrid polymer–oxide systems. Beyond performance metrics, the scalable synthesis, low-cost processing, and multifunctionality of the Mo(VI)OI/I₂-PNMP/PPy architecture point toward transformative opportunities in integrated solar harvesting and advanced photodetection platforms.

This study focuses on the development of a specialized photodetector capable of operating across three spectral regions: ultraviolet (UV), visible, and near-infrared (NIR). The primary objective was to enhance the characteristics of the photodetector while extending its detection capabilities by addressing various challenges. To achieve this, n-type metal oxide cerium dioxide (CeO₂) thin films were deposited on porous silicon (100) substrate using pulsed laser deposition (PLD). The study systematically varied the pulse laser energies (600, 800, and 1000 mJ) to investigate their impact on the optical and structural properties of the resulting films. Porous silicon was produced through photoelectrochemical etching (PECE) for a duration of 25 min. Additionally, gold nanoparticles were synthesized via pulsed laser ablation in distilled water with a different laser energies (300–1000 mJ), laser energy of 300 mJ utilized as an outer layer above the ceria. The structural characteristics of the films were evaluated using X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). The results indicate that both the gold and ceria nanoparticles exhibit a cubic crystal structure, with optimum crystallinity observed in the films prepared at 1000 mJ. The optical properties of the photodetector were assessed through UV–Vis spectroscopy, Raman spectroscopy, and photoluminescence spectroscopy. CeO₂ NPs demonstrated their highest UV absorption at 345 nm in the film prepared at 1000 mJ, corresponding to a band gap of 3.17 eV. Photodetector properties measurements revealed a direct correlation between laser energy and both spectral responsivity and quantum efficiency, with notable increases observed as the laser energy escalated from 600 to 1000 mJ. The optimal spectral responsivity achieved was 0.30 in the near-infrared region, while the maximum quantum efficiency reached 51% within the same spectral range. These findings underscore the potential of the Au/CeO₂/PS photodetector for enhanced performance across multiple spectral regions.

In this study, surface-enhanced Raman spectroscopy (SERS) was used to analyze blood serum samples from patients having abnormal thyroid-stimulating hormone (TSH) levels, including hypothyroidism (hypo) and hyperthyroidism (hyper) disease patients, along with healthy individuals. The blood serum contains both low (LMWF) and high molecular weight fractions (HMWF), with HMWF potentially suppressing key disease biomarkers in LMWF. To resolve this problem, Amicon 100 kDa ultrafiltration centrifugation devices were used to separate whole blood serum into two portions: a filtrate containing LMWF and a residue representing HMWF. The filtrate portions from both patients having abnormal TSH levels and healthy ones were analyzed by surface-enhanced Raman spectroscopy (SERS). The silver nanoparticles, synthesized by the chemical reduction method, were used as a SERS substrate. The characteristic SERS peaks observed at 633, 677, 701, 763, 988, and 1075 cm⁻¹ are associated with LMWF and can be identified as potential SERS biomarkers for TSH-related disease. For advanced analysis, chemometric approaches, including principal component analysis (PCA) and partial least squares regression (PLSR), were employed to achieve both qualitative and quantitative differentiation among the distinct SERS spectral groups. The PCA analysis was found very helpful for the differentiation of the SERS spectral groups of healthy individuals and patients having abnormal TSH levels. The PLSR approach enabled the accurate quantification of TSH levels in unknown serum samples, with an RMSEC of 4.24, an RMSEP of 7.07, and an R² value of 0.94.

Surface-enhanced Raman spectroscopy (SERS) has become a cornerstone technique in nanoplasmonics, enabling ultrasensitive molecular detection through the excitation of localized surface plasmon resonances (LSPRs) in noble metal nanostructures. This review highlights the emerging role of microneedle and nanoneedle-based plasmonic platforms as efficient SERS substrates for applications in biomedical diagnostics, pharmaceutical monitoring, and environmental sensing. We explore the fundamental plasmonic mechanisms underlying electromagnetic field enhancement in needle-like architectures, along with recent progress in fabrication techniques, such as lithographic patterning, template-assisted growth, and chemical etching. Case studies involving cancer cell discrimination, antioxidant molecule detection, and drug level tracking are discussed, demonstrating the capabilities of these 3D plasmonic structures for label-free, in situ analysis. We also address critical challenges such as tip functionalization, penetration depth, and biocompatibility. Finally, future directions are proposed to optimize nanoneedle-based SERS systems for integration into wearable, flexible, and implantable sensing devices.

The design of nanostructure colors is influenced by mechanisms such as quantum size effects, surface plasmon resonance, and structural coloration. These optical properties arise from the interaction between localized magnetic and electric dipole resonances, rendering them highly sensitive to changes in geometric parameters. However, conventional analytical methods are inefficient in optimizing geometric parameters to achieve target colors, particularly when faced with the challenges of large-scale and diverse structural color designs. To address this limitation, we propose a design framework based on a bidirectional deep neural network (DNN) consisting of both a forward network and an inverse design network. The forward network learns the relationship between geometry and color response through parameter scans, enabling precise color prediction for specific geometries. The inverse design network derives the corresponding geometry from target color coordinates (CIE1931 color space) and tackles the multi-solution challenges in inverse design by cross-validating with the forward network. Rigorous computational modeling demonstrates that this approach can generate over one million visible-spectrum nanostructure colors with a theoretically predicted color reproduction rate exceeding 98%. This research presents a highly efficient and accurate framework for the design of high-precision optical components, including those used in silicon-based color processing, optical displays, sensors, and photovoltaic systems.

A comprehensive investigation of both spectral characterizations and sensing performance of a Pd-Au core–shell dimer is conducted theoretically by the finite-difference time-domain (FDTD) numerical tool. The extinction spectrum of the two-particle model exhibits the excitation of three hybrid resonance modes, which introduces a reliable multi-site sensing platform for bio/chemical molecules. Altering either the core size (r_c) or the shell thickness (t) significantly impacts the overall optical properties, illustrating controlled optical tunability over a wide range of frequencies extending from the UV to the visible region. Increasing the shell thickness considerably improves sensing capability to changes in the dielectric properties of the host matrix. To maintain simultaneous and effective sensing standards at several spectral sites, a structural ratio of t ≤ (3/2)r_c should be maintained. Otherwise, the sensing performance of the high-energy site is degraded with any further increase in t. The optimal sensing performance is achieved for a core radius of r_c = 10 nm and a shell thickness of t = 15 nm, where both low- and high-energy plasmonic modes exhibit enhanced sensitivity factors. The structural tunability of the proposed bimetallic dimer provides detailed guidelines for designing plasmon-based nanosensors. Additionally, we conclude that our theoretical observations will have profound implications for the use of extinction cross-section spectra in characterizing bimetallic core–shell dimers.

In this paper, two novel tree-branch spoof surface plasmon polariton (SSPP) units are proposed by adding branches on both sides of the rectangular SSPP unit, and a wideband bandpass filter (BPF) and a dual-band BPF are successively designed based on the proposed SSPP structures. Compared with the rectangular SSPP unit, the proposed tree-branch SSPP unit can effectively excite multiple high-order modes of SSPPs in smaller longitudinal dimension. The designed filter only consists of four tree-branch SSPP units, which do not require the mode conversion transition structure, leading to a miniaturized design. More significantly, by changing the length ratio relationship between the upper and lower branches of the tree-branch SSPP unit, the adjustment of the frequency bandwidth of the high-order modes can be achieved. Therefore, the passband and stopband characteristics of the filter can be flexibly modulated, which is conducive to realize the suppression of unwanted spurious signals.

Early detection of cancer cells is vital for effective treatment and personalized healthcare. This study presents a dual-mode optical biosensor that integrates the Goos-Hänchen (GH) shift with surface plasmon resonance (SPR) for highly sensitive, label-free detection of cancer cells. The system utilizes a red diode laser, a beam splitter, a polarizer, a high-refractive-index prism, and a quadrant detector to measure lateral beam shifts with high precision. Lung (A549) and colon (LS180) cancer cells were cultured on gold-coated glass substrates, and their interaction with the evanescent field under total internal reflection induced measurable optical responses. Compared to normal lung and colon cells, cancer cells produced greater SPR angle shifts (~ 2.2° for A549, ~ 1.6° for LS180) and GH shifts (~ 6.5 μm for A549, ~ 5.8 μm for LS180). Refractive index sensitivities reached 220°/RIU (A549) and 160°/RIU (LS180), with detection limits as low as 2.73 × 10⁻⁵ RIU. The sensor exhibited stable performance with a detection threshold of ~ 5 × 10⁵ cells/cm², a FWHM of ~ 1.5°, and SNR of 20:1. Theoretical modeling and MATLAB-based numerical simulations elucidated coupling between SPR and GH modes, validating enhanced sensitivity over conventional SPR. These results highlight the sensor’s potential for rapid, non-invasive discrimination between cancerous and normal cells, offering a promising tool for clinical diagnostics.

Terahertz (THz) waves hold great promise for next-generation wireless communication systems due to their broadband bandwidth and capability for high-speed data transmission. Here, we propose a symmetric plasmonic waveguide that incorporates low-index dielectric layers sandwiched between the graphene sheet and GaAs microrods, enabling deep subwavelength THz field confinement. The mode properties are systematically optimized through finite element simulations. Our simulations reveal a normalized mode area as low as 10⁻⁴, propagation lengths exceeding 50 µm, and tunable modal characteristics can be achieved within the range of 2 to 4 THz. Furthermore, the proposed structure demonstrates robustness against fabrication misalignment, ensuring practical feasibility. Crosstalk analysis further demonstrates negligible mode coupling even at zero waveguide spacing, highlighting its potential for high-density photonic integration. These results pave the way for ultra-compact, low-loss THz devices, including modulators, waveguides, and sensors.