Application Of Nanosensors Research Articles

High-Performance Nano-Sensing and Slow-Light Applications Based on Tunable Multiple Fano Resonances and EIT-Like Effects in Coupled Plasmonic Resonator System

A basic plasmonic system, consisting of a stub metal-insulator-metal (MIM) waveguide coupled with a ring resonator, is presented to realize Fano resonance and electromagnetically induced transparency-like (EIT-like) effect, which are numerically calculated by the finite element method (FEM). Meanwhile, the formation mechanism of Fano resonance is analyzed according to numerical simulations. Besides, the coupled mode theory (CMT) and the standing wave theory are used for explaining the Fano and EIT-like resonances phenomenon. Based on this system, an inner ring cavity is connected to the ring resonator by a slot and another ring cavity is later introduced under the stub resonator in order to constitute a new coupled plasmonic resonator system, providing quadruple Fano resonances and double EIT-like responses finally. In addition, the Fano and EIT-like resonances can be independently tuned by adjusting the structural parameters, which makes the design of highly integrated photonic circuits more flexible. The main contribution of this paper is that the proposed structure has a relatively good sensitivity of 1600 nm/RIU and an ultra-high FOM value of $1.2\times 10^{6}$ as a refractive index nanosensor. Moreover, it can serve as an all-optical switch with a high on/off extinction ratio of about 43 dB. Additionally, its maximum group delay time and group index are about 1.49 ps and 221, indicating that the proposed system has a pretty good slow light effect. Therefore, the proposed structures are believed to have significant applications in high-performance nanosensors, switches, slow light devices and nonlinear areas in highly integrated plasmonic devices.

Templating Gold Nanoparticles on Nanofibers Coated with a Block Copolymer Brush for Nanosensor Applications

Surface enhanced Raman spectroscopy (SERS)-based nanosensors that offer high spatial and temporal resolution as well as high sensitivity are promising for cell endoscopy studies. This requires fabr...

Fano Resonance in a MIM Waveguide with Two Triangle Stubs Coupled with a Split-Ring Nanocavity for Sensing Application.

Herein, a compact refractive index nanosensor comprising a metal- insulator- metal (MIM) waveguide with symmetric two triangle stubs coupled with a circular split-ring resonance cavity (CSRRC) is theoretically presented. An analysis of the propagation characteristics of the designed structure is discussed employing the finite element method (FEM). The calculation results revealed that a Fano resonance outline emerged, which results from an interaction between the continuous broadband state of the waveguide with two symmetric triangle stubs and the discrete narrowband state of the CSRRC. The influence of geometric parameters on sensing properties was studied in detail. The maximum sensitivity reached 1500 nm/RIU with a high figure of merit of 65.2. The presented structure has great applications for on-chip plasmonic nanosensors.

Electrochemically Exfoliated Graphene for Nanosensor Applications.

Water dispersible graphene layer are the excellent nano materials used for wide range of electronic applications. High quality graphene was synthesized by an eco-friendly, easy and cost effective electrochemical exfoliation method. In this work, graphite rod was used both as an anode and cathode for the production of graphene. Potassium sulphate (K₂SO₄) was used as an intercalating agent. Electrochemically exfoliated graphene (EEG) was coated on glassy carbon electrode (GCE) and evaluated towards the electrochemical oxidation of vanillin and L-phenylalanine. The fabricated electrode was able to detect vanillin and L-Phenylalanine as low as 0.2 μM with signal to noise ratio of 3. A significant increase in the current was observed for the graphene coated electrode for both vanillin and L-phenylalanine when compared to bare Glassy electrode. The finding clearly demonstrated the higher detection capability, selectivity and reproducibility of EEG.

Fano resonances based on plasmonic square resonator with high figure of merits and its application in glucose concentrations sensing

A compact plasmonic structure is proposed employing symmetrical metal–insulator-metal (MIM) waveguides coupled to the square resonator for nano-sensing applications, especially for water glucose sensing. Finite difference time domain method is chosen to derivate the output characteristics and magnetic-field distributions. Outcomes illustrate the Fano resonance in the output characteristics can be simply managed by varying the inner and outer lengths and the refractive index of the square cavity. Also, between Fano resonance wavelength and resonator length, a linear behavior exists. These features suggest that physical parameters provide flexibility to propose the structure. Our plasmonic device produces a sensitivity and figure of merit of about 6400 nm/RIU and 1 × 104, respectively. By utilizing the mathematical model for water refractive index, we aim to develop a sensor structure to detect the glucose concentration in water. This designed sensor may discover significant applications in future nanosensing domain.

Synthesis and Characterization of Copper Oxide Nanoparticles (CuO NPs) using Mangifera indica Leaf Extract

Metal oxide nanoparticles (NPs) receiving a significant consideration for their probable applications in nanodevices, optoelectronics, nanosensors, nanoelectronics, catalysis and information storage. The objective of the work was to be investigate the synthesis of CuO NPs and evaluation of its characterization of CuO NPs using leaf extract of <i>Mangifera indica</i>. <i>Mangifera indica</i> leaf extract was found suitable for the copper oxide nanoparticles synthesis through biological method ambient conditions. Spherical, polydispersity of CuO NPs of particle sizes ranging from 18 to 106 nm. The average size was 52.54 nm. The formation of color changes indicates that the synthesis of CuO NPs due to plasmon resonance with the active compounds present in the <i>Mangifera indica</i> leaf extract. CuO NPs further confirmed by FT-IR, UV–vis spectroscopy, XRD, EDX and SEM. The functional groups confirmed that the alcohol, phenol, aromatics and alkynes have a probable adherence capacity with copper oxide, which acting as a capping agent and responsible for the bioreduction process.<div><br></div>

Planar optical waveguide for refractive index determining with high sensitivity and dual-band characteristic for Nano-sensor application

In this paper, we develop an optical waveguide based on metal–insulator-metal as a refractive index sensor with dual-band feature and a high figure of merit (FOM) and sensitivity. In this model, we utilize a Z-shape slot based on two stubs model in both metal layers and this structure is placed over a dielectric layer of SiO2 as a substrate for planar application in the optical systems. In addition, the parametric studies are used to clarifying the elements influence on controlling the transmission and working frequency to achieve a dual-band characteristic at 1550 and 3100 nm which is suitable for optical fiber application. In fact, the compound stubs technique is suggested to modify the resonances of the waveguide for dual-band attributes based on the transmission line model. We simulate this waveguide using the Finite Integrated Technique (FIT) method. It is supposed that the waveguide is filled by various materials with the different refractive indexes in the range of 1 to 1.5. We obtain the FOM for these materials while the Fano response provides high FOM about the 3800 RIU−1 and the sensitivity is 1790 nm/RIU. Therefore, the compound stubs strategy help to improve the FOM factor in the optical waveguide.

Highly Luminescent Thermoresponsive Green Emitting Gold Nanoclusters for Intracellular Nanothermometry and Cellular Imaging: A Dual Function Optical Probe.

In view of many promising applications of gold nanoclusters (AuNCs), nanothermometry is an important field of research in biology and medicine. Here, we demonstrate the temperature dependent photophysical properties of highly luminescent green emitting 6-aza-2-thiothymine/l-arginine-stabilized Au nanosclusters (ATT/Arg Au NCs) by using steady state and time-resolved photoluminescence spectroscopy. Significantly, thermoresponsive properties of these highly photostable and biocompatible Au NCs are reversible, which endow the probe for further bioanalytical applications with great prospects. Additionally, protein-NC interaction mechanism has been elucidated in vitro and in vivo that dictates the complex behavior of the NCs with living organisms. These ultrasmall Au NCs are observed to accumulate in the cellular cytoplasm by translocating through the membrane as evidenced from the confocal laser scanning microscopy (CLSM). In vivo temperature sensing examined with human osteosarcoma cell line (MG-63 cell) by employing fluorescence lifetime imaging microscopy (FLIM) technique reveals the optimistic application of these lifetime-based nanosensors in biomedicine and biotechnology.

An Ultrasonic Fabrication Method for Epoxy Resin/SbSI Nanowire Composites, and their Application in Nanosensors and Nanogenerators.

In this manuscript, a new fabrication technology for epoxy resin/antimony sulpho-iodide (SbSI) nanowire composites is presented. SbSI nanowires, with lateral dimensions of 10 nm to 100 nm and lengths up to several micrometres, have been synthesised using ultrasound irradiation. The prepared SbSI nanowires have been bound with epoxy resin in a mass ratio of 1:4, and then ultrasound irradiation has been used again for homogenization of the mixture. The fabricated epoxy resin/SbSI nanowire composites, due to the piezoelectric properties of SbSI (electromechanical coefficient k33 = 0.9, and piezoelectric coefficient dV = 0.9 × 10−9 C/N) may be used as an active layer in nanosensors and nanogenerators. The preliminary investigations of epoxy resin/SbSI nanowire composites for sound excitation (frequency f = 175 Hz; L = 90 dB), vibrations (f = 24 Hz; A = 1 mm; F = 0.73 N), and shock wave (p = 6 bar), allowed for the determination of the composite’s open circuit voltage: 0.0153 VRMS, 0.166 VRMS, and 4.51 Vp-p, respectively. Maximum power output densities of 0.45 nW/cm3 and 860 nW/cm3 have been achieved for excitation by sound and vibration, respectively, for a 0.6 mm thick layer of composite.

Recent Developments in Nanosensors for Imaging Applications in Biological Systems.

Sensors are key tools for monitoring the dynamic changes of biomolecules and biofunctions that encode valuable information that helps us understand underlying biological processes of fundamental importance. Because of their distinctive size-dependent physicochemical properties, materials with nanometer scales have recently emerged as promising candidates for biological sensing applications by offering unique insights into real-time changes of key physiological parameters. This review focuses on recent advances in imaging-based nanosensor developments and applications categorized by their signal transduction mechanisms, namely, fluorescence, plasmonics, MRI, and photoacoustics. We further discuss the synergy created by multimodal nanosensors in which sensor components work based on two or more signal transduction mechanisms.

Three-dimensional FDTD analysis of a nanostructured plasmonic sensor in the near-infrared range

Finding new ways to access the nanoscale and high-Q-factor plasmonics resonance remains a major challenge in the field of plasmonic metasurfaces. In the present paper, we aim to report a nanoscale gold metasurface containing structure to realize high-quality plasmon-induced transparency (PIT) responses. The properties of the proposed model are numerically investigated with different physical parameters by the three-dimensional finite difference time domain (3D-FDTD) method. For this purpose, the effects of the geometrical parameters, metasurface materials, dielectric constant, and incident angle in the visible to near-infrared regions are studied. To obtain of dynamical tunability of the proposed model, graphene metasurfaces are then utilized. Numerical results show that the proposed devices are able to operate as high-quality PIT sensors with a maximum figure-of-merit of 1090, and sensitivity of 700 nm/refractive index unit for slight change of Δn=0.15, in the refractive index of the dielectric layer, which originates from its ultra-narrow transparency window and strong coupling between dark–bright modes. Moreover, the structure has a nanoscale footprint of 40 nm×60 nm×31 nm. We believe that the proposed sensor can be used as a promising platform for future nanosensing applications, such as nanostructure plasmonic sensors.

Pyridyl DPP based soluble nanoaggregates for ratiometric/fluorescent detection of Cu2+/Hg2+ in water

A new diketopyrrolopyrrole amphiphile, namely 2-(2-(2-methoxyethoxy)-ethyl)- 3,6-di(pyridin-2-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (PyDPP), is designed and synthesized as a novel ratiometric/fluorescent chemosensor for Cu2+/Hg2+. PyDPP forms soluble loose nanoaggregates by molecular self-assembly in water and maintains intrinsic bright fluorescence and color. The UV–vis absorption spectra data show that PyDPP nanoaggregates exhibits high sensitivity and selectivity toward Cu2+/Hg2+ among other metal cations in PBS (pH 7.4) solution. The reaction mechanism involved in PyDPP-Cu/Hg was investigated by MS, XPS and DFT calculation. The limit of detection of the present nanosensor for Cu2+ is calculated to be 87 nM. This research provides another view in the design and application of FONs nanosensor for heavy metal ions detection.

Investigation of the transmission properties of a plasmonic MIM waveguide coupled with two ring resonators

Transmission characteristics of a plasmonic MIM waveguide coupled with two ring resonators are investigated both numerically and analytically. It is shown that due to the field-driven interactions between the two ring resonators, the second-order resonant mode of the directly-coupled ring resonator is split into two resonances, and as a result, a clear transmission dip emerges on the transmission spectrum. Simulations also show that the splitting is not only sensitive to the geometry parameters, but also sensitive to the refractive index of the dielectrics filled in the ring resonators. The group index can be varied from positive to negative, and thus indicates the properties of normal and abnormal dispersion related to the slow- and fast-light feature. The proposed structure is not only helpful to the application of nanoscale plasmonic filters and nano sensors with its sensitivity up to 685 nm/RIU in the area of highly integrated optical circuits, but also paves a new way towards the realization of controlling the light speed.

Implanted Nanosensors in Marine Organisms for Physiological Biologging: Design, Feasibility, and Species Variability.

In recent decades, biologists have sought to tag animals with various sensors to study aspects of their behavior otherwise inaccessible from controlled laboratory experiments. Despite this, chemical information, both environmental and physiological, remains challenging to collect despite its tremendous potential to elucidate a wide range of animal behaviors. In this work, we explore the design, feasibility, and data collection constraints of implantable, near-infrared fluorescent nanosensors based on DNA-wrapped single-wall carbon nanotubes (SWNT) embedded within a biocompatible poly(ethylene glycol) diacrylate (PEGDA) hydrogel. These sensors are enabled by Corona Phase Molecular Recognition (CoPhMoRe) to provide selective chemical detection for marine organism biologging. Riboflavin, a key nutrient in oxidative phosphorylation, is utilized as a model analyte in in vitro and ex vivo tissue measurements. Nine species of bony fish, sharks, eels, and turtles were utilized on site at Oceanogràfic in Valencia, Spain to investigate sensor design parameters, including implantation depth, sensor imaging and detection limits, fluence, and stability, as well as acute and long-term biocompatibility. Hydrogels were implanted subcutaneously and imaged using a customized, field-portable Raspberry Pi camera system. Hydrogels could be detected up to depths of 7 mm in the skin and muscle tissue of deceased teleost fish ( Sparus aurata and Stenotomus chrysops) and a deceased catshark ( Galeus melastomus). The effects of tissue heterogeneity on hydrogel delivery and fluorescence visibility were explored, with darker tissues masking hydrogel fluorescence. Hydrogels were implanted into a living eastern river cooter ( Pseudemys concinna), a European eel ( Anguilla anguilla), and a second species of catshark ( Scyliorhinus stellaris). The animals displayed no observable changes in movement and feeding patterns. Imaging by high-resolution ultrasound indicated no changes in tissue structure in the eel and catshark. In the turtle, some tissue reaction was detected upon dissection and histopathology. Analysis of movement patterns in sarasa comet goldfish ( Carassius auratus) indicated that the hydrogel implants did not affect swimming patterns. Taken together, these results indicate that this implantable form factor is a promising technique for biologging using aquatic vertebrates with further development. Future work will tune the sensor detection range to the physiological range of riboflavin, develop strategies to normalize sensor signal to account for the optical heterogeneity of animal tissues, and design a flexible, wearable device incorporating optoelectronic components that will enable sensor measurements in moving animals. This work advances the application of nanosensors to organisms beyond the commonly used rodent and zebrafish models and is an important step toward the physiological biologging of aquatic organisms.

Prediction of strong piezoelectricity in 3R-MoS2 multilayer structures

We present the first calculation of piezoelectric constants of 3R-MoS2 which is one of three known polytypes of MoS2. We demonstrate that the 3R-MoS2 structure with 5 layers has the highest reported piezoelectric constant of all MoS2 multilayer structures. The maximum piezoelectric constant is approximately 13% above the monolayer value. Also 3R-MoS2 structures with 4 and 6 layers have a larger piezoelectric coefficient compared to monolayer MoS2. Results are obtained using the molecular dynamics computational package LAMMPS subject to room temperature simulations. Our results indicate strong potential for multilayer 3R-MoS2 structures in nanosensor and nanogenerator applications.

Adsorption of CO gas molecules on zigzag BN/AlN nanoribbons for nano sensor applications

First-principle calculations have been performed to study the sensing of CO gas in various considered configurations. The adsorption of CO on zigzag BN nanoribbon (ZBNNR) and zigzag AlN nanoribbon (ZAlNNR) was modelled in five different possibilities. The effect of CO adsorption is to reduce the band gap in both types (BN/AlN) of the nanoribbons. Interestingly, a finite magnetic moment (0.96 μB for ZBNNR and 0.69 μB for ZAlNNR) has been obtained which depends upon the adsorption configuration of CO. Half-metallicity was also observed upon selective CO adsorption on ZAlNNR irrespective of the ribbon width. Present findings suggest that CO gas molecules could be detected through adsorption on BN/AlN nanoribbons via changes in electronic and/or magnetic properties.

Enhancing Optical Readout from Diamond AFM Tips for Quantum Nanosensing

Color centers in diamond are promising candidates for quantum nanosensing applications. The efficient collection of the optical signal is the key to achieving high sensitivity and resolution, but it is limited by the collection optics. Embedding the color centers in diamond microstructures can help to enhance the collection efficiency, but often require challenging fabrication and integration. Here we investigate the photoluminescence (PL) of silicon-vacancy (SiV) centers in commercially available atomic force microscope (AFM) diamond pyramid (DP) tips. We find that the DP geometry efficiently channels PL emitted at the DP apex towards the base, where we experimentally demonstrate an enhanced PL collection of up to 8 times higher compared to other directions. Our experimental observations are in good agreement with numerical simulations using a finite-difference time-domain (FDTD) method. Our results indicate that AFM tips could be an economical, efficient and straightforward way of implementing color-center-based nanosensing as they provide enhanced sensitivity and easy integration with existing AFM platforms.

Independently Tunable Fano Resonances Based on the Coupled Hetero-Cavities in a Plasmonic MIM System.

In this paper, based on coupled hetero-cavities, multiple Fano resonances are produced and tuned in a plasmonic metal-insulator-metal (MIM) system. The structure comprises a rectangular cavity, a side-coupled waveguide, and an upper-coupled circular cavity with a metal-strip core, used to modulate Fano resonances. Three Fano resonances can be realized, which originate from interference of the cavity modes between the rectangular cavity and the metal-strip-core circular cavity. Due to the different cavity-cavity coupling mechanisms, the three Fano resonances can be divided into two groups, and each group of Fano resonances can be well tuned independently by changing the different cavity parameters, which can allow great flexibility to control multiple Fano resonances in practice. Furthermore, through carefully adjusting the direction angle of the metal-strip core in the circular cavity, the position and lineshape of the Fano resonances can be easily tuned. Notably, reversal asymmetry takes place for one of the Fano resonances. The influence of the direction angle on the figure of merit (FOM) value is also investigated. A maximum FOM of 3436 is obtained. The proposed structure has high transmission, sharp Fano lineshape, and high sensitivity to change in the background refractive index. This research provides effective guidance to tune multiple Fano resonances, which has important applications in nanosensors, filters, modulators, and other related plasmonic devices.

Optical absorption properties and nanosensing application based on metallic rectangle nanoparticles array

This work studies field distribution and nanosensing based on a metallic rectangle nanoparticles arrays structure. The structure consists of a metallic rectangle nanoparticles layer, a dielectric layer and a metallic layer. A finite-difference time-domain approach is adopted to investigate the optical properties. Simulation results show that the localised surface plasmon resonance of the metallic rectangle nanoparticles give rise to absorption peaks in the spectra. Also, the absorption spectrum can be controlled by varying the geometrical parameters of the structure. It is also found that the reflection spectra dependence on the surrounding refractive index. The proposed structure can be used as an excellent plasmonic nanosensor. The simulation results show that the proposed plasmonic structure can serve as an optical absorber in the range of 700–1800 nm, which will have potential application in optical switching, optical modulator and nanosensors.

Sensing analysis based on tunable Fano resonance in terahertz graphene-layered metamaterials

We theoretically investigate the sensing characteristics based on tunable Fano resonance in terahertz graphene-layered metamaterials. A Fano phenomenon comes from destructive interference in a narrow frequency range, and it can lead to a high figure of merit of ∼9786. A simple model for sensitivity is presented, and the sensitivity can reach up to 7885 nm/RIU. Besides, the Fano peak becomes more and more unobvious as symmetry breaking slowly recovers. We use an appropriate theoretical theory to explain the generation of Fano phenomena. Our proposed structure and investigation may pave the way for fundamental research of nanosensor applications and designs in highly integrated optical circuits.