Sensor Probe Research Articles

High-speed mid-infrared laser absorption spectroscopy of CO_2 for shock-induced thermal non-equilibrium studies of planetary entry

A high-speed laser absorption technique is employed to resolve spectral transitions of CO_2 in the mid-infrared at MHz rates to infer non-equilibrium populations/temperatures of translation, rotation and vibration in shock-heated CO_2 - Ar mixtures. An interband cascade laser (DFB-ICL) resolves 4 transitions within the CO_2 asymmetric stretch fundamental bands (Delta v_3 = 1) near 4.19 upmu hbox {m}. The sensor probes a wide range of rotational energies as well as two vibrational states (00^00 and 01^10). The sensor is demonstrated on the UCLA high enthalpy shock tube, targeting temperatures between 1250 and 3100 K and sub-atmospheric pressures (up to 0.2 atm). The sensor is sensitive to multiple temperatures over a wide range of conditions relevant to Mars entry radiation. Vibrational relaxation times are resolved and compared to existing models of thermal non-equilibrium. Select conditions highlight the shortcomings of modeling CO_2 non-equilibrium with a single vibrational temperature.

Twisted fiber SPR sensor for copper ion detection

A novel fiber surface plasmon resonance (SPR) sensor for the detection of copper ions was reported in this paper. The twisted region was fabricated on the single-mode fiber by using the fiber hot melt torsion technology, and the light transmitted in the core was coupled to the cladding. The cladding was coated with nano gold film, and the cladding mode totally reflected at the interface between the cladding and the gold film, which excited the SPR effect. After optimizing the fabrication parameters of the twisted region, the twisted fiber with a pitch of 123 µm was selected to construct the SPR sensor probe, and its refractive index sensitivity is 2689.06 nm/RIU. Furthermore, the self-assembled chitosan / polyacrylic acid film was immobilized on the surface of the sensor layer by layer, and the concentration of copper ion was detected. The test results indicate that with the increase of Cu2+ concentration from 15.7 nM to 1.57 mM, the SPR resonance valley moves towards the long wavelength direction, the detection sensitivity is 3.46 nm/lgC, and the limit of detection (LOD) is 10.10 nM. The proposed fiber SPR sensor is simple to manufacture, which provides a new idea for heavy metal ion detection by fiber sensor.

Efficient Detection of 2,6-Dinitrophenol with Silver Nanoparticle-Decorated Chitosan/SrSnO3 Nanocomposites by Differential Pulse Voltammetry.

Herein, an ultra-sonication technique followed by a photoreduction technique was implemented to prepare silver nanoparticle-decorated Chitosan/SrSnO3 nanocomposites (Ag-decorated Chitosan/SrSnO3 NCs), and they were successively used as electron-sensing substrates coated on a glassy carbon electrode (GCE) for the development of a 2,6-dinitrophenol (2,6-DNP) efficient electrochemical sensor. The synthesized NCs were characterized in terms of morphology, surface composition, and optical properties using FESEM, TEM, HRTEM, BET, XRD, XPS, FTIR, and UV-vis analysis. Ag-decorated Chitosan/SrSnO3 NC/GCE fabricated with the conducting binder (PEDOT:PSS) was found to analyze 2,6-DNP in a wide detection range (LDR) of 1.5~13.5 µM by applying the differential pulse voltammetry (DPV) approach. The 2,6-DNP sensor parameters, such as sensitivity (54.032 µA µM-1 cm-2), limit of detection (LOD; 0.18 ± 0.01 µM), limit of quantification (LOQ; 0.545 µM) reproducibility, and response time, were found excellent and good results. Additionally, various environmental samples were analyzed and obtained reliable analytical results. Thus, it is the simplest way to develop a sensor probe with newly developed nanocomposite materials for analyzing the carcinogenic contaminants from the environmental effluents by electrochemical approach for the safety of environmental and healthcare fields in a broad scale.

Selective detection of BF3 in living cells and environmental water samples using Schiff-base fluorescent probe

A new pyrazole naphthalene-based Schiff base (3c) as a colorimetric and turn-on fluorescent sensor for rapid detection of BF3 was developed. Ligand 3c showed a significant fast response and superior selectivity for BF3 with significant color change by naked eye over other competitive species. Sensor probe 3c showed low detection limit (LOD) of 2.46 nM, which was far lower than the previous reports. Based on the Job’s plot, the binding association ratio of 3c with BF3 was found to be 1:1. The sensing mechanism of 3c with BF3 based on the intramolecular charge transfer (ICT) was confirmed by FTIR, 1H NMR titration, ESI mass spectra, and DFT calculation. Moreover, the sensing probe 3c was found to be reversible with the addition of triethylamine (NEt3), which revealed that 3c could behave as a good candidate for BF3 and NEt3 controlled “ON-OFF-ON” mode. Most importantly, probe 3c has been successfully applied to quantitatively detect BF3 species in various water samples, and using low-cost test paper strips as well as living cells.

Structural diversity and luminescent sensing of metal-organic frameworks with 2,6-Di(1H-imidazol-1-yl) naphthalene ligands

Reactions of ligands 2,6-Di(1H-imidazol-1-yl) Naphthalene (L) and corresponding metal salts under hydrothermal conditions gave rise to a new Metal-Organic Framework (MOF), namely Cd(L)(CNN)·3H2O (1). (H2CNN = 4-(4-Carboxy-2-Nitrobenzene)-3-Nitrobenzoic acid). The crystal structure was characterized by Powder X-ray diffraction (PXRD), thermogravimetric analyses (TGA), infrared spectra (IR), and elemental analyses (EA). 1 belongs to orthorhombic system, space group Pbcn, with a = 18.41(5) nm, b = 12.72(4) nm, c = 27.42(7) nm, V = 6421(3) nm3, Dc = 1.44 mg/m3, Z = 4, F (0 0 0) = 2792, GOF = 0.94, R1 = 0.06, wR2 = 0.15. This MOF has a three-dimensional (3D) penetration structure. Furthermore, the thermal stability and photoluminescence property of the MOF was investigated. Meanwhile, the thermal stability and luminescence properties of the crystal were tested. It was found that 1 is a highly efficient luminescent probe sensor for the identification and determination of Fe3+ cations, Cr2O72− and CrO42− anions, acetone organic small molecules, and antibiotics.

Continuous long-term glucose biosensor in agitation condition for bioconversion processes

The use of a glucose biosensor in the bioconversion processes is challenging due to a long period of intensive stirring that is required to mix the heterogenous substants together. In this work, a glucose biosensor was developed to be accurate and robust for an extended period of measuring time in agitated conditions. The sensor probe was fabricated by electro-polymerization of polyaniline (PANI) nanostructures on a gold wire before putting in gold nanoparticles (AuNPs) and carrageenan (carr) solution to make an PANI-carr-AuNPs layer. Then the probe was soaked in PQQ-Glucose dehydrogenase (GDH) solution before coating with polyurethane (PU) to prevent the enzymes from leaching away from the sensor. The sensor probe showed a sensitivity of 0.85 μA/mg/ml of glucose with R2 of 0.9973. The storage stability of the probe was up to 4 days with stable signal. In agitated condition of 150 rpm, steady signals from the sensor were continuously obtained for 72 h. In sugarcane bagasse hydrolysis with speed at 150 rpm for 72 h, the biosensor continuously displayed signals which were not significantly different in glucose concentration to the results from the HPLC method. This biosensor displayed promising applications in bioconversion processes.

A U-bent fiberoptic absorbance biosensor array (ArFAB) for multiplexed analyte detection

Compact and dip-type U-bent fiber optic sensor (U-FOS) probes exhibit remarkably high evanescent wave absorbance (EWA) sensitivity and are highly suitable for label-free multiplexed detection of proteins, virii and bacteria by exploiting their intrinsic optical absorption property in the UV region. Here, we show the design and development of a novel EWA based eight-channel array fiber optic absorbance biosensor (ArFAB) using U-FOS probes for multi-analyte detection or multi-sample analysis in real-time. A proof-of-concept ArFAB is designed to consist of a UV LED (λmax = 285 nm) and a highly sensitive CMOS linear image sensor coupled to a sensor probe module through fan-out (1-to-8) and parallel (8 nos) fiber bundles respectively. The sensor probe module is designed to hold and efficiently couple the light to/from 8 U-FOS probes with the help of ceramic ferrules and mating sleeves. The CMOS line sensor, with 8 coupling fibers equidistantly placed along its length, distinctly quantifies the intensity response from each of the eight U-FOS probes. The ArFAB was systematically validated for reproducible optical intensity measurements and label-free multiplexed detection of proteins and bacteria was realized. Moreover, a novel sandwich immunoassay with plasmonic labels for immunoglobulin G (IgG) with picomolar analyte detection limits at 280 nm wavelength is demonstrated. With mass-producible U-FOS probes and a low-cost optoelectronic instrumentation that can be easily customized for LSPR or any other sensing phenomenon, the ArFAB is highly promising for cost-effective biomolecular interactions, and cell analyses and clinical diagnostic applications.

Miniaturized fiber optic ultrasound sensor with multiplexing for photoacoustic imaging

A miniaturized ultrasound sensor based on optical fiber is designed and realized for multichannel parallel ultrasound detection and photoacoustic imaging. The fiber optic sensor is composed of a polymer coating, a reflective mirror and a single-mode optical fiber, with only 125 µm in diameter. By integrating the coherent demodulation technology and multiplexing technology, which using a relatively cheap fixed wavelength laser, hundreds of sensors could work simultaneously. Meanwhile, highly sensitive ultrasound detection has been demonstrated with the noise equivalent pressure as low as 0.46 kPa and the sensor exhibits a nearly omnidirectional directivity. Furthermore, a photoacoustic imaging system based on three sensors working in parallel is demonstrated. High lateral resolutions of 165–217 µm and axial resolutions of 112–131 µm over a depth range of larger than 5 mm are obtained. A three-dimensional phantom imaging experiment is also demonstrated. Benefited from parallel detection, the imaging speed is three times faster than that of a single sensor. The miniaturized fiber optic ultrasound sensor probe provides a competitive alternative for mechanically scanning-free endoscopic imaging, which is beneficial from small size, omnidirectional directivity and parallel detection capability.

Lumi-HOF@Tb as Probes for Multiple Ratiometric Fluorescence and Chemiluminescence Sensing of α-Glucosidase.

The innovative assembly of luminescent hydrogen-bonded organic frameworks (HOFs) into multifunctional optical sensors is of great significance for developing advanced materials. Herein, we report a facile room-temperature synthesis strategy for the luminol HOF modified by Tb3+ (Lumi-HOF@Tb) and featuring sensitive chemiluminescence and fluorescence characteristics. Lumi-HOF@Tb is further pioneered as a dual-signal sensor for selective detection of α-glucosidase, a type of enzyme that plays a crucial role in the digestion of carbohydrates, and screening of its inhibitors. The sensor is constructed by combining the dual optical characteristics of luminol from the HOF and lanthanide ion assistance. From the hydrolysis of α-glucosidase and the 4-nitrophenyl-α-d-glucopyranoside (pNGP) substrate emerges the fluorescent luminol-p-nitrophenol (pNP) complex at 466 nm and changes the inner filter absorption to recover Tb3+ characteristic fluorescence at 546 nm; luminol also produces a chemiluminescence signal driven by H2O2 from additional glucose oxidase-catalyzed hydrolysis of α-d-glucose. Fluorescence and chemiluminescence assays for α-glucosidase activity have therefore been established and exhibit detection limits as low as 0.04 and 0.005 U L-1, respectively. This study not only presents the possibility of Ln3+-HOF-based sensors as intelligent optical materials by integration of fluorescence and chemiluminescence techniques but also demonstrates great potential for future applications in biosensing.

Potential of copper oxide thin film-based sensor probe for carbon dioxide gas monitoring

Potential of copper oxide thin film-based sensor probe for carbon dioxide gas monitoring

Ion recognition by 1,2,3‐triazole moieties synthesized via “click chemistry”

1,2,3‐Triazole‐based ligands obtained through copper(I)‐catalyzed azide‐alkyne cycloaddition (CuAAC) have been exploited in vast array of research domains owing to the stitching of simpler molecules through a needle of Cu(I) catalyst. The numerous reports on ion(s) detection capabilities of synthesized 1,4‐disubstituted 1,2,3‐triazole ligands using absorption and fluorescence spectroscopy are accessible. This review enlists substituted 1,2,3‐triazole‐based sensor probes, since 2010, synthesized selectively by CuAAC, having the ability to sense either a single ion or multiple ions under specific set of conditions along with their detection limits. The review also apprehends the different techniques and sensing mechanisms involved in the detection of ions by chemosensor probes.

Compact packaged silicon photonic Bragg grating sensor based on a ball lens interface

We demonstrate a ball-lens based optical interface for coupling between a single mode fiber and a silicon grating coupler from the back side of a photonic integrated circuit (PIC). This allows compact packaging solutions and keeps the PIC top side accessible, e.g. for interacting with the environment in case of sensing applications. Different configurations employing 300 μm diameter ball lenses made of both LASF-35 glass and sapphire were investigated. Without any modifications to the grating coupler, the peak coupling efficiency (for TE polarization and operating wavelength around 1550 nm) was experimentally found to be only between 1.4 dB and 2.2 dB lower when interfacing with a ball lens from the back side compared to coupling from the top side using a cleaved fiber. Furthermore, no noticeable change in the bandwidth was found. The potential of the ball lens interface was proven by realizing a compact (diameter less than 1.5 mm) optical temperature sensor probe based on a phased shifted silicon photonic Bragg grating structure on a PIC. The probe consisted of a single mode fiber which was terminated with a 1.25 mm ceramic ferrule onto which a ball lens holder and a PIC was glued. The holder was realized in fused silica glass with a femtosecond laser direct-write technology and served to accurately position the ball lens with respect to the fiber and PIC. The assembly allowed to cleanly read out the Bragg grating spectrum in reflection, using a single fiber interface and was compatible with commercial interrogator systems. A Bragg wavelength shift of 73 pm/°C was found in a tested temperature range between 15 °C and 60 °C.

Ag@MOF-199 metal organic framework for selective detection of nickel ions in aqueous media

Monitoring heavy metal ions (HMIs) in water is always a challenging and vital issue due to their hazardous effects on the environment and human health. Therefore, it is necessary to detect heavy metals in the water. Herein, we first-time report the use of silver nanoparticles (Ag NPs) incorporated copper benzene carboxylate (MOF-199) metal organic framework (Ag@MOF-199) for detection of heavy metal ions in water. A glassy carbon electrode-modified Ag@MOF-199 electrochemical sensor probe was fabricated and showed a selective and sensitive response towards nickel (Ni(II)) ions only by cyclic voltammetry. The Ag@MOF-199-based sensor did not offer any cyclic voltammetric sensing response towards cadmium (Cd(II)), lead (Pb(III)), chromium (Cr(III)), and ferric (Fe(III)) ions (1 μM/L) at pH values ranging from 3 to 10. The Ag@MOF-199 sensor displayed high sensitivity of 1.48 μA/nM on the exponential scale for Ni(II) ions at pH 7 and a lower detection limit of 6.06 nM/L with good reproducibility below US EPA suggested maximum contamination limit. The synthesized Ag@MOF-199 was characterized by spectroscopic (viz. UV–visible spectroscopy, Raman spectroscopy and mapping, energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy), surface area (viz. Brunauer–Emmett-Teller surface area analysis), electrochemical activity (viz. cyclic voltammetry, electrochemical impedance spectroscopy), morphological (viz. field emission scanning electron microscopy (FE-SEM)), structural (viz. X-ray diffraction (XRD)), and thermogravimetric analysis.

Nanohybrid Comprising Gold Nanoparticles – MoS2 Nanosheets for Electrochemical Sensing of Folic Acid in Serum Samples

AbstractFolic acid (FA) deficiency is associated with several clinical conditions such as megaloblastic anemia, neuropsychiatric, and pregnancy‐related syndromes, this makes FA an important metabolite to be monitored. We have fabricated an electrochemical biosensor based on gold nanoparticles decorated molybdenum disulfide nanosheets (AuNPs−MoS2NSs) nanocomposite as a transducer matrix for specific and rapid electrochemical detection of FA. Differential pulse voltammetry (DPV) studies displayed a rapid analytical response of the fabricated AuNPs−MoS2NSs/GCE sensor probe towards FA in a wide concentration range of 0.001–100 μM with a very low detection limit of 0.72±0.03 nM. The selectivity of the fabricated sensor probe has been examined in the presence of interferents such as dopamine, uric acid, ascorbic acid, glucose, and urea. The clinical potential of the fabricated biosensor was established by monitoring FA in human serum samples. The developed AuNPs−MoS2NSs/GCE sensor probe showed high reproducibility and stability, indicating its promise for FA detection in clinical settings.

Analysis and Development of IoT-based Aqua Fish Monitoring System

Water quality is critical in fish farming activities, where criteria must be measured to ensure water quality. Unwanted amounts of water quality factors will affect aquatic life. It has been discovered that some breeders fail to maintain their ponds, causing water quality to worsen and affecting fish hibernation and mortality. Manual pond water quality testing was ineffective and time-consuming, causing the water quality to suffer. This study created a fishpond IoT system to monitor a pond's water quality, temperature, pH level, and ammonia toxicity. A real-time data analytics platform was created to collect data from the water temperature, pH level, and toxicity of ammonia sensors embedded into the IoT system. The NodeMCU ESP32 controller was used to process the data collected from all sensors, and real-time data may be viewed via mobile devices using the Blynk application. Three sensors are embedded to the system which are an ammonia gas sensor, an analog pH sensor, and a temperature probe sensor. As a result, a mobile fishpond monitoring system has been successfully created. The study reveals that the ammonia level is low at 0.021 ppm, the average temperature is 27.02°C, and the pH level is almost neutral at 6.85. It has been determined that the ammonia level is safe for fish hibernation. Temperature and pH had little effect on ammonia levels, while temperature and pH have a high association. This research is essential because it assists fish breeders in improving pond water quality, which supports aquatic life production and health. Keywords—water quality monitoring, ammonia, Internet of Things, ESP32, pH, temperature

IoT-Based Agricultural Compost Monitoring System: Prototype Development and Sensor Technology Evaluation

Smart agriculture refers to the application of advanced technologies in the field of agriculture, such as the Internet of Things, big data, edge/cloud computing, among others. These technologies facilitate the monitoring, tracking, recording, visualization, automation, and analysis of various agricultural operations. One critical process in this domain is composting, an organic waste disposal method that enriches soil with nutrients and encourages sustainable farming practices. However, it requires constant monitoring to ensure high-quality compost production at an optimal rate, without the development of harmful toxins. In this context, we propose a novel IoT-based agricultural compost monitoring system. The system is composed of an IoT sensor probe, edge/cloud platforms, and integrated solutions for networking, monitoring, logging, reporting, and visualization. This paper provides a comprehensive physical implementation of the probe, including detailed prototype components, testing of pertinent sensor technologies, and analysis of experiments conducted on a compost site using several probe variants. The main contributions of this paper are twofold: (1) the development of a novel IoT system prototype for efficient compost monitoring, and (2) the identification of the optimal sensor technology for measuring compost temperature. Our findings indicate that infrared sensing technology delivers the fastest and most accurate readings.

A High-Sensitivity SPR Sensor Based on MMF-Tapered HCF-MMF Fiber Structure for Refractive Index Sensing

In this article, a high-sensitivity surface plasmon resonance (SPR) sensor based on multimode fiber (MMF)-tapered hollow core fiber (THCF)-MMF structure is fabricated and proposed for refractive index (RI) sensing. As the measurement RI increases, the SPR peak right shifts, a multimode interference (MMI) spectrum will also appear in the visible wavelength in front of the SPR peak, and the MMI resonance wavelength left shifts with the RI increases. The RI changes can be detected by monitoring the resonance wavelength difference between the MMI wavelength and the SPR peak, which is a new method used to measure the RI. The RI sensing performance for the proposed sensor probes with different taper ratios and different HCF core diameters is explored. The experimental results show that the sensitivity could be significantly improved at large RI for the MMF-THCF-MMF probe with a large taper ratio. For the probe with an HCF core diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$30 ~\mu \text{m}$ </tex-math></inline-formula> and a taper ratio of 3.3, a high RI sensitivity of 7592.25 nm/RIU is obtained at the RI of 1.40. The proposed SPR sensor is easily fabricated and has a simple structure, which has potential applications in biochemical sensing fields.

Research and application of deformation measurement method of hydraulic turbine head cover

Aiming at the deformation of hydraulic turbine head cover during operation, a non-contact eddy current sensor is proposed. In this method, the turbine pit wall is taken as the static reference point, a fixed support is erected on it, and the eddy current probe is fixed at the other end of the support. Measure the gap change between the eddy current sensor probe and the head cover to calculate the absolute deformation of the head cover. The effectiveness of the proposed method is verified by taking the lifting amount test of hydraulic turbine head cover in a power plant as an example. The results show that this method has the characteristics of simple test equipment, strong adaptability and high accuracy, and can be applied to the field test of hydraulic turbine head cover deformation.

Magnetic field measurements on the mini-ICAL detector using Hall probes

The magnetised 51 kton Iron Calorimeter (ICAL) detector proposed to be built at INO is designed with a focus on detecting 1–20 GeV muons. The magnetic field will enable the measurement of the momentum of the μ - and μ + generated from the charge current interactions of atmospheric νμ and ν̅μ separately within iron in the detector, thus permitting the determination of the neutrino mass ordering/hierarchy, among other important goals of ICAL. Hence it is important to determine the magnetic field as accurately as possible. The mini-ICAL detector is an 85-ton prototype of ICAL, which is operational at Madurai in South India. We describe here the first measurement of the magnetic field in mini-ICAL using Hall sensors. A set-up was developed to calibrate the Hall probe sensors using an electromagnet. The readout system has been designed using an Arduino Nano board for selection of channels of Hall probes mounted on the PCB and the output voltage was measured. The magnetic field has been measured in the small gaps (provided for the purpose) between iron plates in the top layer of mini-ICAL as well as in the air just outside the detector. A precision of better than 3% was obtained, with a sensitivity down to about 3 mT when measuring the small fringe fields outside the detector.

Detailed investigation of spectral properties of SMS fiber segment and its sensing performance under varying multimode fiber lengths

Here, a comprehensive analysis of the impact of the multimode fiber (MMF) lengths on different sensitivities of single mode-multi mode-single mode (SMS) fiber segment sensor probe under different external perturbations such as temperature, strain and refractive index has been propounded and studied thoroughly. In addition, different phenomenal characteristics of the SMS segment namely fast Fourier transform, fringe visibility, the free spectral range of the observed transmission spectrum and most importantly the self-imaging phenomena have been investigated meticulously. These aforementioned characteristics are also verified theoretically. The experimental results show that the sensitivities increase with an increase of the MMF length and are restricted to 12 cm length due to the superimposing and less resolution of the probing dips beyond this. Experimental results illustrate that our proposed sensing probe is capable to achieve superior sensitivities better than 93 pm/°C, −2.56 pm/ με and −38.55 nm/RIU for temperature, strain and refractive index, respectively for the 12 cm length of the MMF. The higher sensitivities and resolutions assure potential employment and promising solution of the proposed sensor in various sensing applications.