Selective Sensor Research Articles

The Effective Sorting Technologies for Reducing Aflatoxins in Nuts and Dried Figs in Turkey

Background: RASFF notifications serve to determine the hazards responsible for food and feed. In case of determining risks to human health, the information provided to member countries via the rapid alarm system at the same time warned us to take the necessary measures. Objectives: In this research, the RASFF portal alerts over the last three years related to aflatoxins in hazelnut, fig, and peanut products were examined. The impact of image processing technologies on lowering the danger of aflatoxins in shelled hazelnuts and dried figs was also investigated, as well as Critical Control Points (CCPs) on aflatoxin hazard. Methods: The RASFF database was used in the RASFF Window portal and analyzed for aflatoxin alerts. ISO 22000:2018 was used for hazard and risk analysis for raw hazelnut, peanut, and fig products. Aflatoxin analyses were performed according to the AOAC 2000/991.31 method. Prior to and after hazelnut sorting methods, levels of aflatoxin were measured. Besides, aflatoxin contamination in peanuts harvesting in 2023 years from three local producers in Turkey was studied. Results: The number of RASFF notifications for hazelnuts, peanuts/groundnuts, dried figs, and their products for the period of 03/01/2020 to 01/06/2023 were 84, 283 and 173, respectively. As a result of HACCP implementation, especially for aflatoxin hazard management, optical-laser-manual sorting and aflatoxin detection using UV light stages are accepted as CCPs. When nuts were sorted using optical and laser systems were detected decreasing total aflatoxin levels. The mean value of Aflatoxin B1(AFB1) and total aflatoxins were reduced from 7.80±1.08 and 13.56±1.06 to 3.63±0.39 and 7.21±0.71, respectively. 79.16% of all sorted samples were found to comply with legal limits. Investigated peanut samples for aflatoxin B1 contents were found between 5.63 and 27.75 µg kg-1 in 19.5%. Conclusion: The alerts based on aflatoxin contamination above legal limits have been carried on for nuts and dried figs. The physical sorting methods using optical selection and high-resolution laser sensor systems aflatoxin-contaminated nuts from healthy nuts applied for in-shell Turkish nut sorting were able to assess the quality of the batch studied, and the systems were assigned significantly effective to reduce aflatoxin contents. Food business operators in Turkey, which is among the countries exporting agricultural and food products to the European Union (EU), have tended to prefer the most advanced technologies. Efficacies of reduction of aflatoxin by different physical and other (such as imaging, X-ray and acoustic, audio signals and hyperspectral images of moldy natural nuts etc.) methods will be developed in the near future.

A Review on Pyridine Based Colorimetric and Fluorometric Chemosensor for Detection of Hg2+ ion.

Pyridine, N-containing heterocyclic organic compound, displays strong coordination capabilities with various metal ions. It can be synthesized through various methods, such as Friedlander synthesis, heterocumulene synthesis, cross-coupling reactions, the Radziszewski reaction, Bonnemann cyclization, as well as cobalt-catalyzed synthesis. Experimental and spectroscopic analyses have demonstrated a strong binding affinity between pyridine and several heavy metal ions, including Pb2+, Hg2+, and Cd2+ ions. The escalating environmental pollution caused by the disposal of heavy metal ions in rivers, open air, and water reservoirs poses a significant threat to both ecosystem and human health. To address these environmental challenges, a cost-effective and easily synthesized chemosensor has been prepared for identifying toxic heavy metal ions in various samples. Pyridine's photophysical properties make it an effective sensor for detecting Hg2+ ions, displaying fluorescence quenching or enhancement in their presence. The coordination between pyridine and Hg2+ ions lead to shifts in the absorption spectra. The pyridine-based sensor has been evaluated for its sensitivity, selectivity, and detection limits under different experimental conditions. Pyridine's solubility and environmental stability make it applicable for real-time detection, making pyridine probes valuable tool for monitoring toxic Hg2+ ions in the environment. The results demonstrate that the pyridine-based chemosensor exhibits good selectivity and sensitivity for targeting Hg2+ ions, with detection limits within acceptable ranges. This review (from years 2011 to 2023) emphasizes the preparation of various substituted pyridine compounds as selective, sensitive, and specific sensors for real-time detection of Hg2+ ions.

MoSe2-Layered Nanosheet Decorated SnO2 Hollow Nanofiber-Based Highly Sensitive and Selective Room Temperature H2S Gas Sensor.

In this work, we successfully demonstrated a MoSe2@SnO2 nanocomposite-based room temperature H2S gas sensor. A sensing mechanism was proposed based on experimental results and density functional theory calculations. The FESEM micrographs of the heterostructure formed by hydrothermally grown MoSe2-layered nanosheets and SnO2-hollow nanofiber result in a high surface area for H2S gas adsorption. On exposure to calcination, the electro-spun PVP/SnO2 nanofiber undergoes the Kirkendall phenomenon, resulting in 94.6 nm thick hollow nanofibers. The combination of TMD@SMO shows an abundance of charge transfer, resulting in an excellent response toward H2S gas. The MoSe2@SnO2 detects a low concentration of 500 ppb with a relative response of ∼19.9% at room temperature (RT). The simulation, using density functional theory (DFT), discloses that the adsorption energies ranged from -0.3645 to -0.5193 eV, indicating reduced bond lengths and significant H2S interactions. The sensor proves an excellent sensitivity toward H2S gas, ranging from 100 ppm to 500 ppb, with a LoD of ∼15 ppb at RT. As the sensor worked at RT with accuracy and reliability, consistent performance was observed upon exposure to various humidity levels, making it suitable for exhaled breath gas sensors. The sensor, as developed, also exhibited a good selectivity toward H2S gas in contrast to other gases as well as stability and longevity over time.

Maximum Energy Density for Evaluation of the Dynamic Accuracy of LVDT Sensors Applied in the Energy Industry

This paper presents a proposal in which the maximum energy density criterion is used to evaluate the dynamic accuracy of LVDT (Linear variable differential transformer) sensors for applications in the energy industry. The solutions proposed in the paper are based on a mathematical model of the LVDT sensor, represented by its frequency response. The mathematical foundations required for the synthesis of such a model and the formulae and algorithm necessary to determine the maximum energy density for the integral-square error criterion are presented. Numerical and simulation calculations are performed using MathCad 15 and MATLAB R2014a programs. The solutions presented in this paper can constitute a basis for the selection of LVDT sensors for applications in the energy industry, with a view to achieving accurate diagnostic measurements.

Formaldehyde Gas Response and Selectivity of ZnO-SnO2 Gas Sensors

Formaldehyde Gas Response and Selectivity of ZnO-SnO2 Gas Sensors

An ASIC-based system-in-package MEMS gas sensor with impedance spectroscopy readout and AI-enabled identification capabilities

The main advantages of micromachined metal oxide semiconductor (MOX) gas sensors, in particular their low cost, high sensitivity, miniaturization and low power consumption, are compromised by lack of selectivity and long-term sensor signal drifts, which often hinder their application in real-world sensing applications. To increase the sensor data dimensionality, temperature cycled operation (TCO) and impedance spectroscopy (IS) readout was proposed, enabling the acquisition of large datasets from a single sensor, as suitable to be exploited by machine learning techniques. Furthermore, recent studies have shown how the IS readout minimizes the issues represented by the sensor long-term signal drift.The aim of this work is the development of a smart system-in-package, integrating a state-of-the-art micromachined MOX gas sensor based on a wafer-level nanostructured sensing layer with a novel versatile sensor interface chip, capable of high performance IS readout. We propose a miniaturized sensing device, which is a small, lightweight low power consumption chemical sensing micro-system with fast and accurate classification capabilities, suitable to be deployed in long multi-node sensing cables or on unmanned aerial vehicles. A software suite comprising a sensor training wizard was also developed, enabling users with no technical background to train the sensing system.

A simple and highly selective chalcone fluorescent chemical sensor for the detection of tryptophane

In this study, 1-ferrocenyl-3-(2-hydroxyphenyl) allyl ketone (probe A) was synthesized using a solvent-free method in conjunction with solid-phase grinding and employed as a probe for the detection of tryptophan (Trp). The probe exhibits selective recognition of Trp as evidenced by UV–Vis and fluorescence spectra. In complex scenarios, the probe’s recognition of Trp remains unaffected by both the presence of interfering substances and the duration of exposure. A pH range of 8 to 12 is found to be optimal for the detection of Trp. Job’s curve analysis revealed that the binding ratio between the probe and Trp is 1:1. Based on the Benesi-Hildebrand equation, the binding constant for the interaction between probe A and Trp is calculated to be 1.5 × 107 M−1. The detection limit for Trp was determined to be 9.55 × 10−5 M. The sensing mechanism of the probe for Trp was elucidated through 1H NMR and FT-IR analyses.

Modulation of ZrO2-Ag2O-MoO3 nanocomposite into ultrasensitive hydrazine electrochemical sensor for environmental remediation

Herein, a facile single-step wet chemical approach was executed for the composition of semiconductor ternary metal oxides (TMO) i.e., ZrO2-Ag2O-MoO3 nanocomposite (NC)in an alkaline medium. For structural as well as morphological elucidation, the calcined nanocomposite was characterized through ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), powdered X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) and Brunauer-Emmett-Teller (BET) analysis. Later, the glassy carbon electrode (GCE) was modified into a highly responsive as well as selective hydrazine (HDZN) electrochemical probe (ZrO2-Ag2O-MoO3-NC/PEDOT:PSS/GCE) by the fabrication of thin layered ZrO2-Ag2O-MoO3NC onto GCE facilitated by 5 % PEDOT:PSS as conducting polymer binder. While examining the analytical parameters through novel current–potential (I-V) electrochemical approach, for the first time, the newly designed electrochemical probe, as selective hydrazine sensor, happened to own the low detection limit (LOD; 0.028 pM) with greater sensitivity (33.86 μAμM−1cm−2) and broad linear dynamic range (LDR; 0.1 M–1.0 nM) in addition to coefficient of correlation (r)/r2 square (r = 0.9941, r2 = 0.9882) and low limit of quantification (LOQ; 0.093 pM).Furthermore, reproducibility as well as prolonged stability of this newly proposed probe towards hydrazine were also assessed and found to be reliable in short response time. Hence, this work presents an inaugural report about the sensing of HDZN through the newly designed non reported ZrO2-Ag2O-MoO3-NC/PEDOT:PSS/GCE via an economical as well as novel electrochemical, current–potential (I-V),approach. Additionally, this proposed method is equally responsive towards both environmental and extracted real samples analysis on large scale.

Novel amino-functionalized MOF-based sensor for zinc ion detection in water and blood serum samples

Aquatic systems with low zinc levels can experience a significant decrease in carbon dioxide uptake and limited growth of phytoplankton species. In this study, we describe the use of a new fluorescent sensor based on NH2-MIL-53(Al), and modified with glutaraldehyde and sulfadoxine, for selectively detecting zinc ions in water and blood serum samples. Characterization of the synthesized material was performed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET) surface area analysis, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), confirming successful functionalization and preservation of the MOF structure. The sensor’s performance for Zn2+ detection was evaluated by spectrofluorometry, demonstrating a significant fluorescence enhancement upon Zn2+ binding due to the interaction between Zn2+ ions and the sulfonamide groups. With a detection limit as low as 3.14 × 10–2 ppm, the sensor demonstrates high selectivity for Zn2+ over other common metal ions. The sensor’s response is rapid, stable, and reproducible, making it suitable for practical applications. Real sample analysis was conducted in tap water and blood serum samples, with the results compared to those obtained using ICP-OES and a colorimetric test with 5-bromo-PAPS. The comparison confirmed the high accuracy and reliability of the fluorescent sensor in detecting Zn2+ ions in complex matrices. NH2-MIL-53(Al) modified with glutaraldehyde and sulfadoxine shows potential as a selective fluorescent sensor for Zn2+ detection, making it a valuable tool for monitoring the environment and biology.

Synthesis, crystal structure and exploration of N,N'-(ethane-1,2-diyl)bis(4-acetylbenzenesulfonamide) (EDBABS) fabricated glassy carbon electrode as highly sensitive barium (Ba2+) sensor: An electrochemical approach

Environmental pollution spurred by dint of noxious chemicals and heavy metals has popped up as a pressing threat for present day community. In this study, we synthesized the N,N'-(ethane 1,2-diyl)bis(4-acetylbenzene-1-sulfonamide) (EDBABS) and N,N'-(cyclohexane-1,2-diyl)bis(4-acetylbenzenesulfonamide) (CDBABS) as bidentate chelating agents with the intention to detect the heavy metal cations in water systems. Conventional spectroscopic techniques such as UV-Vis spectroscopy, Fourier transform-infra red (FT-IR) spectroscopy, 1H-NMR and 13C-NMR in addition to single crystal X-ray diffraction studies were performed to expound structural characterization data of these newly synthesized non-reported bidentate chelating agents. After Characterization, a novel electrochemical current – potential (I-V) approach based on their modified GCEs was applied to detect the toxic cations in water systems. For this purpose, Keithley electrometer was employed as a constant voltage source. On the trail of fabricating an efficient as well as selective electrochemical sensor, for the detection of heavy metal cations in phosphate buffer system of pH = 7.0, EDBABS and CDBABS coupled with nafion as adhesive conducting binder were coated separately onto the Glassy Carbon Electrodes (GCEs). it was delineated that newly designed EDBABS/Nafion/GCE induced a high current response for Ba2+ cations in the presence of other interfering heavy metal cations (Y3+, Sn2+, Sb3+, Mn2+, Hg2+, Cr3+, As3+ and Ag+) than CDBABS/Nafion/GCE and found to be selective and sensitive towards Ba2+ cations, predominantly contributing towards environmental pollution. In order to optimize this newly designed EDBABS/Nafion/GCE as selective electrochemical Ba2+ cationic sensor, different analytical parameters such as sensitivity, limit of detection (LOD) at S/N of 3, limit of quantification (LOQ), and linear dynamic range (LDR) turned out to be satisfactory towards Ba2+ cations. The calibration curve emerged to be linear with a broad concentration range of Ba2+ cations from 0.1 nM to 0.01M and sensitivity was estimated as 3.481 × 10−3µAµM−1cm−2 in addition to (r2) as 0.9834, limit of detection (LOD) as 0.027nM (at S/N=3) and limit of quantification (LOQ) as 0.091nM. Within the realm of extensive environmental protection and public health care field, this work inducts a reliable and effective way for the fabrication of sensitive as well as selective cationic electrochemical sensors based on chelating agents which can be launched as an advanced approach for quick probing of heavy metal cations in water systems, reliably and effectively.

A Multimode fluorescent sensor for sequential detection of Cu2+ and cysteine as well as pH sensor with real sample Applications: Extensive experimental and DFT studies

Highly responsive and optically selective (E)-1-((4-phenoxyphenyl) diazenyl)naphthalen-2-ol) sensor PDN with aggregation induced emission enhancement (AIEE) properties has been developed for the sequential detection of Cu2+ and L- Cysteine through fluorescence On-Off-On strategy. The selectivity of sensor depends on the presence of a diazo functional group and its appropriate cavity location in sensor molecule. Azo dye-based (E)-1-((4-phenoxyphenyl) diazenyl)naphthalen-2-ol) sensor PDN has been synthesized by utilizing a simple diazotization synthetic methodology that showed extraordinary AIEE behavior with bathochromic shift owing to the formation of J-aggregates. The morphology and size of aggregates were analyzed by SEM and DLS analysis, respectively. The calculated LOD of sensor PDN for Cu2+, and L-cysteine is 0.113 nM, and 84 nM, respectively. Fluorescence, UV–visible, 1H and 13C NMR titration were carried out to understand the interaction of sensor with Cu2+. The sensor was practically utilized in the sequential sensing of Cu2+ and Cys in real samples. Interestingly, sensor PDN was successfully employed for the sensing of a strong acid and base as well as the detection of Cu2+ ions in the solid state. Moreover, these experimental results were supported through DFT calculations.

Influence of isochronal heat treatment on spray-deposited mixed phase tin based thin films for ammonia gas sensor applications

The current work applied the spray pyrolysis (SP) approach to coat mixed-phase SnS thin films at 3500C, and then air annealed at 400,450,5000C for use in sensor and solar cells applications. A variety of methods were employed to evaluate the structural, morphological, compositional, optical, and electrical characteristics of synthesized mixed-phase films. Films annealed at 5000C are reported to have bigger crystal sizes, and all deposited SnS films exhibit the orthorhombic phase in addition to tetragonal phase of SnO2, with other visible secondary phases like SnS2,Sn2S3. Fourier transform infrared spectroscopy and Raman analyses verified the molecular structure and vibrational mode of SnS films. The Scanning electron microscopy tests reveal a consistent, size-varying two-dimensional flake like grain structure, while the optical studies show a variation in optical direct band-gap from 1.79-2.75eV. The Hall-effect shows that films subsequently annealed at 4000C have improved electrical properties. An efficient metal oxide semiconductor gas sensor was developed by applying mixed-SnS film on the conducting side of an indium tin oxide coated glass plate. To examine the sensor selectivity at room temperature, a variety of test gases, such as NO2, H2S, C2H5OH, NH3, were purged at different concentrations. The optimum working temperature and concentration for NH3 selective gas have been determined to be 3500C and 5ppm. The sensor sensitivity is found to be maximum at operating temperature of 2000C towards NH3 gas. An inexpensive, fabricated MOS-gas sensor based on mixed-phase SnS can be easily mass produced and may find potential applications in industrial and environmental monitoring.

A rapid colorimetric sensor for the detection of mercury in environmental samples employing 2 aminobenzohydrazide schiff base functionalized silver nanoparticles

Mercury (Hg2+) is an extremely toxic and dangerous element for living organisms. Herein, a simple and selective sensor based on the Schiff base of 2-aminobenzohydrazide with triazole thiazole substituted vanillin (EAHT) functionalized silver nanoparticles (EAHT-AgNPs) is proposed for the detection of Hg2+ in environmental water samples. The chemical reduction method was employed to synthesize EAHT-AgNPs using sodium borohydride as the reducing agent. The synthesized nanoparticles were initially confirmed by UV-visible and FTIR spectroscopy, followed by analysis with a zeta sizer to determine their average size, surface charge and polydispersity index. The atomic force microscopy (AFM) and scanning electron microscopy (SEM) were employed to determine the size and morphology of EAHT-AgNPs. Additionally, the functionalized particles exhibited stability at varying pH values, salinity concentrations and elevated temperature. The addition of Hg2+ altered the yellow color of EAHT-AgNPs to colorless, confirming the complex formation. The analytical response constructed as a decrease in absorbance versus concentration showed linearity (R2 = 0. 991) from 0.1 to 100 µM with a limit of detection of 0.04 µM (40 nM) and limit of quantification of 0.085 µM (85 nM). The sensor was successfully applied for the detection of Hg2+ ions in tap water. In conclusion, Schiff base of 2-aminobenzohydrozide with triazole thiazole substituted vanillin silver nanoparticle-based chemosensor is highly sensitive and selective for the detection of Hg2+ in water samples. The proposed sensor has been applied for mercury detection tap water, future research should explore its applications in more complex samples like industrial wastewater and marine environments. Further, studies may focus on the integrating of the approach into the portable devices such as smartphone for on-site detection of mercury.

Facile fabrication of foldable electrospun nanofiber electrodes for electrodes for electronic biosensing

This study presents a rapid, sensitive and selective sensor based on electrospun nanofibers on laser-patterned electrodes, in which the laser micromachining process can directly fabricate the graphene electrode device for the electronical detection of glucose molecule. The layer of graphene film was formed on the glass substrate by a screen printing technique, and then the graphene electrodes can be fabricated by the ultraviolet (UV) nanosecond laser process with the wavelength of 355 nm. Based on the controlled the laser fluence and pulses, the electrode gap of 60 μm within the device can be fabricated. The polyvinyl alcohol (PVA) and glucose oxidase (GOD) composite nanofiber with weight percentage of 8% can be used by the electrospun process with used Glutaraldehyde(GA) steam for cross linking process. After that, it is blended with the conductivity of poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS), and the foldable nanofiber structures was made by electrospun process on the graphene electrode device. Finally, the electrical detection of graphene electrode device with the nanofibers at different concentrations of glucose can be measured, resulting in the linear variation is detecting the glucose concentration ranging form 0.01 to 3.12 mM. This work indicated that the low concentration and highly sensitive can be used for electronic biosensors

Porous PDMS-ZnO Wearable Gas Sensor for Acetone Biomarker Detection and Breath Analysis.

In response to the growing demand for global health monitoring, we report a nonintrusive health detection method using a compact, conformal wearable ultraviolet (UV)-assisted gas-sensing system based on an intrinsically flexible porous polydimethylsiloxane (PDMS)-zinc oxide (ZnO) composite layer (PPZL) for the breath acetone (BrAce) detection and breath event analysis. The enhanced acetone response is attributed to the synergistic effect of UV irradiation and the high surface area of the porous structure, which also improves the mechanical robustness. The UV-assisted wearable sensor reliably detects acetone concentrations ranging from 1 to 100 ppm at room temperature under 4.05 mW/cm2 UV intensity, even under mechanical strains such as a bending radius of 5 mm and 60% tensile strain. It accurately analyzes different breathing patterns (12-20 breaths per minute) and BrAce concentrations, maintaining a stable performance over 20 days with less than 5% signal degradation. The sensor exhibits response and recovery times of average 110-150 and 130-180 s, respectively, and maintains a consistent 3 ppm BrAce response under varying humidity levels up to 70% relative humidity, ensuring accurate detection of BrAce concentrations during real-world breath tests. Additionally, the sensor targets only specific gases, and the sensor's selectivity is not a key concern. This flexible acetone gas sensor offers a portable solution for health management and a fabrication method for designing flexible metal oxide materials.

Flexible and highly selective NO2 gas sensor based on direct-ink-writing of eco-friendly graphene oxide for smart wearable application

Nitrogen dioxide (NO2) is a major cause of respiratory disorders in outdoor and indoor environments. Real-time NO2 monitoring using nonintrusive wearable devices can save lives and provide valuable health data. This study reports a room-temperature, wearable, and flexible smart NO2 gas sensor fabricated via cost-effective printing technology on a polyimide substrate. The sensor uses alkali lignin with edge-oxidised graphene oxide (EGO-AL) ink, demonstrating a sensitivity of 1.70% ppm⁻1 and a detection limit of 12.70 ppb, with excellent selectivity towards NO2. The high sensing properties are attributed to labile oxygen functional groups from GO and alkali lignin, offering abundant interacting sites for NO2 adsorption and electron transfer. The sensor fully recovers to the baseline after heat treatment at 150 °C, indicating its reusability. Integration into lab coats showcased its wearable application, utilising a flexible printed circuit board to wirelessly alert the wearer via cell phone to harmful NO2 levels (>3 ppm) in the environment. This smart sensing application underscores the potential for practical, real-time air quality monitoring, personal safety enhancement, and health management.

Theoretical Perspective on the Sensing Mechanism of a Pyrazinium‐Based Fluorescent Probe Towards 2,4,6‐Trinitrophenol

ABSTRACTRapid detection of chemical explosives plays a critical role in national security and public safety. An in‐depth study of the sensing mechanism is particularly urgent for the development of highly efficient, sensitive, and selective chemical sensors for the precise detection of chemical explosives. Density functional theory (DFT) and time‐dependent DFT approaches were used in this work to examine the sensing mechanism of a novel fluorescent probe 1‐benzyl‐3,5‐di (thiophen‐2‐yl)pyrazin‐1‐ium bromide (BTPyz) for the detection of 2,4,6‐trinitrophenol (TNP). A comprehensive theoretical exploration was carried out, and a different interaction mode between the probe and TNP from that in the original experiment was proposed. The π–π stacking was established to be the recognition interaction between BTPyz and TNP anion, and the active site was determined from the three potential sizes according to the Gibbs free energy analysis results. The rationality of the reaction mode and the π–π stacking product between the BTPyz and TNP (BTN) was further confirmed by the fluorescence properties (absorption and emission spectra). According to the findings of frontier molecular orbitals (FMOs), photoinduced electron transfer (PET) is the intrinsic mechanism through which TNP quenches the probe's fluorescence.

Fluorescent Carbon Dots with Red Emission: A Selective Sensor for Fe(III) Ion Detection

We present a procedure for the synthesis and purification of p-phenylenediamine-based carbon dots that can be used for the recognition of Fe(III) ions. Carbon dots have an approximately spherical shape with an average size of 10 nm and are composed of a carbonaceous core surrounded by functional groups attached to it, both of which are responsible for their dual fluorescence properties. The emission bands have a different behavior, with a blue band dependent and a red emission independent of the excitation wavelength, respectively. Red emission is appropriate for the detection of ions and other molecules in biological environments because this high wavelength prevents the occurrence of processes such as resonance energy transfer and internal filter effects. In particular, the presence of Fe(III) ions produces an important quenching phenomenon that can be applied to the fabrication of a sensor. The platform is very sensitive, with a detection limit of 0.85 µM, which is within the lowest values reported for this ion, and a high selectivity that is believed to be due to the formation of a specific complex in the ground state through specific interactions of Fe (III) ions with pyridinic and amino groups on the surface of the nanomaterials.

Preparation of ultra-sensitive and selective hydrogen peroxide-based colorimetric sensor using highly exfoliated g-C3N4 nanosheets with peroxidase-like activity.

Ahighly sensitive, portable, rapid, and accurate colorimetricsensing method is presented.It isbased upon exfoliated g-C3N4 nanosheets (E-g-C3N4 NSs), having peroxidase nanozyme-like properties. The as-prepared catalyst (E-g-C3N4 NSs) tends to oxidize the colorless tetramethyl-benzidine (TMB) into oxidized-TMB in the presence of hydrogen peroxide (H2O2) generating adark blue color and corresponding ultraviolet visible-spectral changes following aMichaelis-Menten kinetic. The prepared colorimetric sensor exhibited response within the range 0.001-0.450μM having R2 value of 0.999 and adetective limit (LOD) of 0.15 ± 0.04nM. Furthermore, the sensor also displayed outstanding selectivity, ample stability (10weeks), and excellent practicability in real sample applications. All these outstanding properties were highly attributed to the large surface area with exposed actives sites, high surface energy, and large conductive structure of E-g-C3N4 NSs. For comparison of thecatalytic study, we have also explored the sensing mechanism of B-g-C3N4, using thesame optimized experimental conditions. Resultantly, we concluded that the proposed sensor (E-g-C3N4 NSs) will gain considerable attention for on-site environmental and health monitoring in future endeavor.

β-Cyclodextrin/Zn-Fe layered double hydroxides/graphitic carbon nitride nanomaterials based potentiometric sensor for paroxetine determination in environmental water samples.

Developing targeted and sensitive analytical techniques for drug monitoring in different specimens are of utmost importance. Herein, a first attempt was made for the determination of paroxetine (Prx+) in environmental water samples using a novel, sensitive, selective, stable, accurate and eco-friendly potentiometric sensor based on Zn-Fe layered double hydroxides/graphitic carbon nitride (Zn-Fe LDH/g-C3N4) nanomaterials with β-cyclodextrin (β-CD) as the sensing ionophore and dibutyl phthalate (DBP) as the plasticizer. The prepared nanomaterial was characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The surface properties of the proposed sensor were characterized by electrochemical impedance spectroscopy (EIS). The sensor exhibited an excellent Nernstian slope of 59.3 ± 0.7 mV decade-1 covering a wide linear working range of 1.0 × 10-6 to 1.0 × 10-2 mol L-1, low detection limit of 3.0 × 10-7 mol L-1, low quantification limit of 9.9 × 10-7 mol L-1, long life time, sufficient selectivity, high chemical and thermal stability within a wide pH range of 2.0-9.0. This analytical method was successfully implemented for Prx+ determination in a pure form, pharmaceutical formulation and different water samples.