Optical Sensor Applications Research Articles

Fabrication of Flexible SWCNTs/Polyurethane Coatings for Efficient Electric and Thermal Management of Space Optical Remote Sensors

Given the requirement of high-efficiency thermal dissipation for large-aperture space optical remote sensors, a radiator based on single-walled carbon nanotubes (SWCNTs) filled with waterborne polyurethane (SWCNTs/WPU) coatings was proposed in this work. In situ polymerized SWCNTs/WPU coatings allowed for the uniform distribution of acid-purified SWCNTs in WPU matrix. Modified oxygen-containing groups on purified SWCNTs enhanced the interfacial compatibility of SWCNTs/WPU and enabled an improved tensile strength 9 (26.3 MPa) compared to raw-SWCNTs/WPU. A high electrical conductivity of 5.16 W/mK and thermal conductivity of 10.9 S/cm were achieved by adding 49.1 wt.% of SWCNTs. Only 2.85% and 4.2% of declined ratios for electric and thermal conductivities were presented after 1000 bending cycles, demonstrating excellent durability and flexibility. The designed radiator was composed of a heat pipe, SWCNTs/WPU coatings and an aluminum honeycomb core, allowing for −1.6~0.3 °C of temperature difference for the in-orbit temperature and thermal balance experimental temperature of the collector pipe. Moreover, the close temperature difference for the in-orbit and ground temperatures of the radiator indicated that the designed radiator with high heat dissipation met the mechanical environment requirements of a rocket launch. SWCNTs/WPU would be promising electric/thermal interface materials in the application of space optical remote sensors.

Light-Emitting Coordination Polymers: Stimuli-Responsive Gels, PMMA-Based Composite Films, and UV-Shielding.

Lanthanide-based light-emitting coordination polymers (CPs) and CP gels (CPGs) have significance for applications in optical systems, image processing/multiplexing, and optical sensors. In this study, we report two new luminescent CPs (EuL-CP (1) and TbL-CP (2)) and CPGs (EuL-gel (5) and TbL-gel (6)) using lanthanide(III) ions (Ln(III) = Eu(III) and Tb(III)) and 4-(4-carboxyphenyl)-2,2:6,2-terpyridine ligand (L) capable of forming stable thermoreversible gels. Probable structures of EuL-CP (1) and TbL-CP (2) and the formations of EuL-gel (5) and TbL-gel (6) are proposed based on adequate computational studies. The CPGs are stimuli-responsive and could be utilized as invisible security inks for encryption. Further, poly(methyl methacrylate) (PMMA) polymer doped with respective CPs (0.75 wt %) is found to be suitable for forming composite films with UV-shielding properties.

Advances in Selective Detection of Cadaverine by Electronic, Optical, and Work Function Sensors Based on Cu-Modified B12N12 and Al12N12 Nanocages: A Density Functional Theory (DFT) Study.

This work explores Cu-modified B12N12 and Al12N12 nanocages for cadaverine diamine (Cad) detection using advanced density functional theory (DFT) calculations. The study found that Cu modification altered the geometry of the nanocages, increased the dipole moment, reduced the energy gap, and enhanced the reactivity. While pristine B12N12 and Al12N12 were not sensitive to Cad, the modified Cu(b64)B12N12 and Cu(b66)Al12N12 nanocages showed significantly higher electronic sensitivity (Δgap = 39.8% and 35.6%, respectively), surpassing the literature data. However, molecular dynamics (MD) revealed that the Cu(b66)Al12N12 nanocage is not stable in the long term, since the nanocage changes configuration to Cu(b64)Al12N12, which is less sensitive and has an even longer recovery time for Cad sensing. Adsorption energy analysis (Eads) showed a strong interaction of Cad/nanocages, while charge analysis suggested that the nanocages act as Lewis acids, accepting electrons from Cad. UV-vis spectra confirmed that Cu(b64)B12N12 responds optically to the presence of Cad. Furthermore, Cu(b64)B12N12 showed greater sensitivity to Cad compared to NO, H2, H2S, CO, COCl2, N2O, N2 gases, or H2O, showing high selectivity to diamine against interfering gases or water, standing out as a promising material for environmental applications in electronic, optical or work function sensors for cadaverine detection, even in humid environments.

A Tunable Transparent Graphene Absorber with Multifrequency Resonance

AbstractThe demand for multinarrowband absorber has attracted increasing interest among researchers in recent years. However, integrating multifrequency absorption, tunability, and high optical transparency into an absorber remains a crucial challenge. In this study, a multiband, tunable, and transparent microwave meta‐absorber is theoretically proposed and experimentally demonstrated. This meta‐absorber is composed of resonant patterns made from graphene and indium tin oxide (ITO), placed on a substrate of lithium niobate (LN). By introducing P‐type doping to reduce the resistance of monolayer graphene to around 300 Ω, the impedance matching of the absorber is promoted, consequently manifesting ten absorption points within 40 GHz. The electric field distribution analysis and an equivalent circuit model are employed to elucidate the physical mechanisms of the multiband absorber. Additionally, the lithium niobate dielectric layer possesses a substantial dielectric constant and exhibits phase transition characteristics with temperature changes. When the temperature increases to 250 °C, a comprehensive tuning range of more than 5.49 GHz within 40 GHz range is realized. The maximum tuning range for a single frequency point is 1.33 GHz. With the broadening of the band, the meta‐absorber can provide multiple tunable ranges, making it more favorable for practical applications in optical modulator and sensor.

Electrostatic fence induced assembly of low-concentration colloidal nanospheres to form liquid photonic crystals

Liquid photonic crystals (LPCs) have great application potential in sensors, anti-counterfeiting materials and detection due to their sensitive dynamic responsiveness. Currently, the preparation of LPCs mainly relies on the supersaturation of colloidal nanospheres. However, the supersaturation method usually fails to obtain LPCs based on low-concentration colloidal nanospheres. In turn, the use of high-concentration colloidal nanospheres results in poor mobility of LPCs, which makes them inappropriate for subsequent utilization in responsive systems. In this study, self-assembly of LPCs with vibrant structural colors is achieved through the electrostatic fence effect by introducing an anionic carboxylate-containing polymer as an inducer into the system of low-concentration negatively charged colloidal nanospheres (≥1.25 wt%). It is shown that the anionic carboxylate groups on the inducer molecules and the appropriate molecular chain length are the decisive factors for the inducing effect. The obtained LPCs exhibit a typical non-close-packed structure with a face-centered cubic arrangement of nanospheres. The nearest inter-nanosphere surface distance is 12.10 nm, and the farthest one is as long as 40.30 nm. The LPCs possess good dynamic recovery performance and sensitive optical response characteristics, which are conducive to application in responsive optical sensors directly or after filling.

Design and tests of filtering actions for an AI-based RSOs detection and tracking algorithm

Space debris represent a huge threat for the actual and future space traffic. The continuous monitoring of the space environment around the Earth and the build-up, maintenance of Resident Space Objects (RSOs) catalogue are essential to enhance the space segment safety. In the last few years, trend towards Space Based Space Surveillance (SBSS) missions was relevant. In particular, the monitoring of space debris through on-board Star Trackers (STs) coupled with Artificial Intelligence (AI) based algorithms is being studied, modeling RSOs as clear streaks on a dark background. This work presents the advances in the development of an AI-based algorithm for streaks-like RSOs Detection & Tracking for on-board optical sensors applications like STs. The initial design of the RSOs monitoring algorithm (Mastrofini et al., 2022) is extended and tested for what concerns the tracking part with new filtering actions. The goal is the improvement of the tracking outputs quality and reliability when multiple RSOs passages occur, with different configurations. Tests both on real and simulated images from STs are shown and discussed.

Manganese Oxide Applications in Sulfonamides Electrochemical, Thermal and Optical Sensors: A Short Review

AbstractIn recent years, the development of highly sensitive and selective electrochemical sensors has been a pivotal area of research, driven by the growing demand for environmental monitoring and industrial process control. Among various materials investigated for sensor applications, manganese oxide (MnO2) nanoparticles have garnered significant attention due to their excellent electrochemical properties, environmental friendliness, and natural abundance. Critical analyses of the synthesis of MnO2 using different techniques such as hydrothermal method, chemical precipitation, and sol–gel process which allows for the fine-tuning of particle size and morphology while enhancing the electrochemical sensing capabilities have been reviewed. The review also provides a comprehensive overview of the recent advancement evaluation of manganese oxide-based electrodes for detecting sulfonamides and other analytes in water across diverse matrices. This paper sets the stage for a comprehensive exploration of the synthesis methods and application areas of MnO2 nanoparticles in electrochemical sensors, highlighting their role in advancing sensor technology and their impact on various sectors. Graphical Abstract

In Situ Label‐Free Monitoring of Riboflavin Concentration in Shewanella via a Fiber‐Optic Biosensor Modified by Ti3C2‐MXene@ SGNps Composites

AbstractRiboflavin is a common marker of microbial corrosion and can act as an electron shuttle in the solvated state to enhance electron transfer efficiency. In this paper, an in‐situ label‐free fiber‐optic biosensor modified by Ti3C2‐MXene@Square Gold nanoparticles (SGNps) composites and riboflavin kinase is developed, which behaved with high sensitivity for measuring riboflavin. The sensing interface of the sensor is constructed by stepwise assembly of SGNps and riboflavin kinase using Ti3C2‐MXene nanosheets as the supporting substrate. Riboflavin kinase catalyzed the phosphorylation of riboflavin to form flavin mononucleotides in the presence of adenine nucleoside triphosphate and Mg2+. Experimental results showed that the sensitivity of riboflavin measurement is 5.61 nm µm−1 and the limit of detection (LOD) is 115 nmol L−1 (nm) in the concentration range of 0–2.656 µm. In situ label‐free monitoring of riboflavin in Shewanella, the sensitivity of the sensor in bacterial fragmentation fluid is 53.90 nm/OD within the optical density (OD) of 0–0.175, and the LOD is OD = 0.017. The above results verified the feasibility of the sensor for in situ monitoring of riboflavin in microbial corrosive environments, with ultra‐low detection limit and good selectivity, which undoubtedly provided great research value for the application of optical fiber sensors in microbial corrosion monitoring.

Open-loop optimization method based on the GRU and dual-grating demodulation principle for a PZT based optical voltage sensor

Distributed online monitoring of grid voltage is crucial for ensuring power quality, providing a foundational data layer for effective grid management. Piezoelectric grating optical voltage sensing presents a cost-effective solution with high bandwidth and long-distance transmission capabilities. This paper introduces an open-loop optimization approach that leverages the gate recurrent unit (GRU) and dual-grating demodulation principles to enhance the real-time response accuracy and extend the measurement range of piezoelectric-based optical voltage sensors. Experiments conducted within a 2.8 kV sensing range analyze the voltage response and spectral characteristics. After applying corrections, the sensor achieves a linearity of 99.93%, with a maximum deviation of 2.07% and a maximum hysteresis of 3.33%. This method significantly enhances real-time response accuracy and optimizes the utilization of the sensor’s nonlinear measurement range, advancing the application of optical voltage sensors in power grids.

Exploring solvatochromism: a comprehensive analysis of research data of the solvent -solute interactions of 4-nitro-2-cyano-azo benzene-meta toluidine

This study investigates the solvatochromic behavior of a new D1 disperse dye, focusing on the 4-nitro-2-cyano-azo-Benzene-metaToluidine type. Using UV-visible spectroscopy, we analyze the dye’s performance in single solvents and binary mixtures. Our analysis includes the evaluation of solvent polarity parameters and dye structure parameters, with emphasis on the longest wavelength intramolecular charge transfer absorption band. We identify nonlinear and linear patterns in the electronic transition energies plots with respect to solvent composition. Statistical analysis considers correlation coefficients, root mean squared error, mean absolute percentage error, and other parameters, providing insights into data accuracy and precision. This experimental and statistical study explores the absorption spectrum, wavelength characteristics, absorption energy, and polarity of a novel azo dye across various solvent and solute environments. These findings contribute to a comprehensive understanding of the dye’s photophysical and photochemical properties, potentially enabling applications in optical sensors and advanced materials.Graphical abstract

Surface electric field enhanced biosensor based on symmetrical U-tapered HCF structure for gastric carcinoma biomarker trace detection

In this article, a novel U-tapered hollow-core fiber (HCF) surface plasmon resonance (SPR) biosensor coated with PtS2 for early-stage gastric carcinoma (GC) diagnosis was demonstrated. The article proposed the first investigation to detect Interleukin-10 (IL10) and Interleukin-1β (IL1β) which were associated with the risk of developing gastric carcinoma, using optical fiber SPR technology. Herein, the sensitivity of sensor was effectively improved through a combination of tapered and U-shaped structures. Additionally, to further enhance the detection capability, two-dimensional material PtS2 was utilized to increase the surface electric field intensity of the sensor. Simultaneously, optimization of structural parameters such as taper ratio, bending diameters, and Au film thickness was conducted. Ultimately, the designed sensor achieved a remarkable sensitivity of 13210 nm/RIU within the refractive index (RI) range of 1.33–1.37. The sensor demonstrated exceptional performance, achieving sensitivities of 3.64 nm/(ng/ml) and 7.46 nm/(ng/ml) for the detection of IL10 and IL1β biomarkers, respectively, along with limit of detection (LOD) of 2.74 pg/ml and 1.33 pg/ml, and successfully detecting the presence of these biomarkers in the serum of gastric cancer patients. Overall, the proposed sensor exhibits significant potential in early gastric cancer detection and advances the application of optical fiber SPR sensors in trace biodetection.

Investigating Cellulose Nanocrystal and Polyvinyl Alcohol Composite Film in Moisture Sensing Application

This study focused on utilizing cellulose nanocrystal (CNC)–polyvinyl alcohol (PVA) composite in optical sensor applications to detect high humidity conditions and determine water concentration in ethanol. We focused on the composite’s effectiveness in moisture absorption to demonstrate visual color change. We demonstrated that the different molecular weights of PVA significantly affect CNC’s chiral nematic structure and moisture absorption capability. PVA with molecular weight 88 k–97 k exhibited the disintegration of its chiral nematic structure at 30 wt%, whereas low molecular weight PVA (n~1750) showed no structural disintegration even at 100 wt% concentration when analyzed through UV-Vis spectroscopy. Further, the thermal crosslinking of the CNC-PVA composite showed no significant loss of moisture sensitivity for all molecular weights of the PVA. We observed that the addition of PVA to the sulfated CNC obtained from sulfuric acid hydrolysis did not facilitate moisture absorption significantly. A CNC-PVA sensor was developed which can detect high humidity with 2 h. of exposure time. 2,2,6,6-tetramethylpiperidin-1-piperidinyloxy oxidized CNC (TEMPO-CNC) having carboxylic functionality was also used to prepare the CNC-PVA composite films for comparing the effect of functional groups on moisture sensitivity. Finally, we demonstrated a facile method for utilizing the composite as an optical sensor to detect water concentration in ethanol efficiently; thus, it can be used in polar organic solvent dehydration applications.

Experimental study on practical application of optical fiber sensor (OFS) for high-temperature system

This study explores the application of Raman scattering-based optical fiber sensors (OFSs) in extreme environments, specifically focusing on a loop heater vessel with temperatures ranging from 200 °C to 680 °C. This condition generally covers the advanced reactor designs, such as Sodium-cooled Fast Reactor and High Temperature Reactor. Various optical fiber combinations were employed for temperature measurements, taking into consideration the operating temperature of the target equipment. Two types of OFSs, gold-coated and polyimide-coated, were utilized. Protective tubes made of stainless steel (STS) and carbon were introduced to ensure reliable temperature data collection in high-temperature settings. Results indicate that the STS tube with a gold-coated OFS exhibited the highest consistency and agreement with thermocouple measurements, making it suitable for extreme environments. The study emphasizes the applicability of this system in high-temperature environments, such as liquid metal reactors, high-temperature thermal energy storage system, and hydrogen production system, for environmental monitoring.

Study on the photoluminescence performance and thermal sensitivity of (Y,Gd)2O3:Tb3+,Dy3+,Tm3+ phosphors

Using ammonia as a precipitation agent, (Y,Gd)2O3:Tb3+x,Dy3+y,Tm3+z phosphors were synthesized by the co-precipitation method. In order to improve the luminescence performance of the luminescent center Tb3+, Tb3+-Dy3+ co-doping and Tb3+-Dy3+-Tm3+ tri-doping were successively carried out, and the optimal component formulations were determined by the controlled variable method (x = 0.03, y = 0.005, z = 0.001). XRD results showed that the sample has a cubic phase Y2O3 structure with good crystalline properties. SEM results revealed that the samples have a unique micro morphology of small ball aggregation. The effects of doping concentration of Dy3+ and Tm3+ on the luminescence properties of Tb3+ were systematically investigated. The energy transfer mechanism among the three ions of Tb3+-Dy3+-Tm3+ was demonstrated by photoluminescence spectroscopy, and the main interaction modes between ions were elucidated. In addition, the matrix lattice environment can change the thermal stability properties of phosphors. In this paper, the temperature characteristics of Y2O3:Tb3+,Dy3+,Tm3+ phosphors are expected to be changed by microtuning the Y2O3 matrix lattice with the introduction of Gd3+. The fluorescence intensity ratio (FIR) and thermal sensitivity indicated that Gd3+ has good temperature sensitivity, and its introduction can effectively improve the temperature sensing performance of the phosphors, which has a wide range of applications in optical temperature measurement sensors.

Reliability Assessment of Fiber Optic Shape Sensing

Fiber optic shape sensing is a promising technology capable of enriching the field of Structural Health Monitoring (SHM), with many potential applications that expand the uses of distributed optical fiber sensors. The operational principle is based on the simultaneous strain acquisition from several optical fiber cores deployed in a single sensing cable (or multicore fiber). The parallel strain traces of these cores can be combined to extract curvature and torsion distributions along the sensing cable, that can be used for the three-dimensional reconstruction of the underlying shape. This study evaluates the reliability of fiber optic shape sensing for damage detection through the use of a model-assisted probability of detection framework specifically developed to simulate a carbon fiber-reinforced polymers specimen under quasi-static loading monitored by distributed optical fiber sensors based on Rayleigh backscattering. Specifically, we compare the performance of a traditional distributed optical fiber strain sensor with the one of a hypothetical distributed shape sensing cable (or multicore fiber). To perform this comparison, we redefine the damage index definition, which is usually based on the measured strain values, to make it compatible with shape sensing, where it can be defined in terms of curvature and torsion. With these preliminary results, we aim to evaluate whether shape sensing technology can be employed for damage detection to detect damage-related deformation, whether we can obtain better results compared to traditional optical fiber sensor applications, and discuss how damage metrics need to be modified. In future activities, these aspects will be further investigated taking into account other case studies and shape sensing configurations.

Tuning the Optical Anisotropy in Gradient Porous Germanium on Si Substrate

AbstractPorous semiconductors have garnered significant attention owing to their distinctive physical and chemical properties. In this study, optical anisotropy is presented in porous germanium (PGe) on a Si (001) substrate. Both n‐ and p‐type PGe, achieved through bipolar electrochemical etching, exhibit optical anisotropy along the Ge <001> direction, as determined by spectroscopic ellipsometry. Birefringence and depolarization factors are controllable by adjusting the etching parameters and doping concentration of the epitaxial Ge layer. The gradient porosity and pore distribution in PGe can be well captured by the optical models. The findings of optical anisotropy in PGe‐on‐Si hold promise for applications in optical elements or sensors for gas or biomolecules.

Research on the application of interferometric optical fiber sensors in high-pressure gas pipelines

The advantages of fiber optic sensors based on fiber optic interferometers with explosion-proof safety in gas pipeline monitoring has gradually emerged. A monitoring system for natural gas pipelines was designed and implemented using a Michelson interferometer as the core structure of the fiber optic sensor and processed the collected data using phase carrier generation demodulation algorithms. Addressing practical issues such as phase wrapping and arm length difference losses, an improved phase carrier demodulation algorithm based on tangent transformation and arctangent-differential self-cross-multiplication was proposed. Field experiments were conducted in gas valve chambers, to analyze the characteristics of leak signals in the pipeline. This study lays the foundation for the application of fiber optic interferometer sensors in gas pipeline monitoring, promising enhanced safety and efficiency.

Novel high performance Fano resonance sensor with circular split ring resonance

This study conducts an in-depth discussion on the Fano resonance phenomenon and its application in optical sensors. A circular split ring was proposed. By designing a metal-insulator-metal (MIM) waveguide structure with specific geometric parameters, we successfully excited the Fano resonance, which produced a unique asymmetric Fano through the coupling of discrete and continuous states. Resonance transmission spectroscopy. The sensitivity of Fano resonance is extremely sensitive to changes in structural parameters. This characteristic provides a theoretical basis for the development of highly sensitive optical sensors. The simulation results show that by optimizing the structural parameters, high sensitivity Fano resonance characteristics can be obtained, further enhancing the performance of the optical sensor. The calculated sensitivity is as high as 1250 nm/RIU, and the figure of merit (FOM) reaches 54, indicating that the designed MIM waveguide structure has excellent sensing capabilities. This study not only demonstrates the potential of Fano resonance in improving sensor sensitivity, but also provides valuable guidance for the design and development of future optical sensors.

Dissecting PM sensor capabilities: A combined experimental and theoretical study on particle sizing and physicochemical properties

Recent advancements in particulate matter (PM) optical measurement technology have enhanced the characterization of particle size distributions (PSDs) across various temporal and spatial scales, offering a more detailed analysis than traditional PM mass concentration monitoring. This study employs field experiments, laboratory tests, and model simulations to evaluate the influence of physicochemical characteristics of particulate matter (PM) on the performance of a compact, multi-channel PM sizing sensor. The sensor is integrated within a mini air station (MAS) designed to detect particles across 52 channels. The field experiments highlighted the sensor's ability to track hygroscopicity parameter κ-values across particle sizes, noting an increasing trend with particle size. The sensor's capability in identifying the size and mass concentration of different PM types, including ammonium nitrate, sodium chloride, smoke, incense, and silica dust particles, was assessed through laboratory tests. Laboratory comparisons with the Aerodynamic Particle Sizer (APS) showed high consistency (R2 > 0.96) for various PM sources, supported by Kolmogorov-Smirnov tests confirming the sensor's capability to match APSsize distributions. Model simulations further elucidated the influence of particle refractive index and size distributions on sensor performance, leading to optimized calibrant selection and application-specific recommendations. These comprehensive evaluations underscore the critical interplay between the chemical composition and physical properties of PM, significantly advancing the application and reliability of optical PM sensors in environmental monitoring.

Optical sensor reveals the hidden influence of cell dissociation on adhesion measurements

Cell adhesion experiments are important in tissue engineering and for testing new biologically active surfaces, prostheses, and medical devices. Additionally, the initial state of adhesion (referred to as nascent adhesion) plays a key role and is currently being intensively researched. A critical step in handling all adherent cell types is their dissociation from their substrates for further processing. Various cell dissociation methods and reagents are used in most tissue culture laboratories (here, cell dissociation from the culture surface, cell harvesting, and cell detachment are used interchangeably). Typically, the dissociated cells are re-adhered for specific measurements or applications. However, the impact of the choice of dissociation method on cell adhesion in subsequent measurements, especially when comparing the adhesivity of various surfaces, is not well clarified. In this study, we demonstrate that the application of a label-free optical sensor can precisely quantify the effect of cell dissociation methods on cell adhesivity, both at the single-cell and population levels. The optical measurements allow for high-resolution monitoring of cellular adhesion without interfering with the physiological state of the cells. We found that the choice of reagent significantly alters cell adhesion on various surfaces. Our results clearly demonstrate that biological conclusions about cellular adhesion when comparing various surfaces are highly dependent on the employed dissociation method. Neglecting the choice of cellular dissociation can lead to misleading conclusions when evaluating cell adhesion data from various sources and comparing the adhesivity of two different surfaces (i.e., determining which surface is more or less adhesive).