Chemical Sensors Research Articles

A One‐Pot Synthesized Chemodosimetric Chemosensor for Highly Sensitive Cyanide Ion Detection in Aqueous Media and from Tobacco Smoke

AbstractA sustainable future world consistently attributes to the development of eco‐friendly methods and materials for detection and elimination of toxic substances from the environment. While addressing the issues, pyrazole carbonitrile derived Schiff base PYR−TZ has been designed and employed for colorimetric and turn on fluorometric cyanide ion sensing. PYR−TZ demonstrated high cyanide ion (CN−) sensitivity with a 1 : 1 binding stoichiometry in aqueous solution. By preventing intramolecular charge transfer, the PYR−TZ sensor demonstrated excellent selectivity towards CN, which caused a color transition from colorless to yellow and impressive “turn‐on” fluorescence emission. The detection thresholds for CN− are 6.5 nm for absorbance spectra and 0.396 nm emission spectra, respectively. Under typical ecological and physiological settings (pH 1–12), the PYR−TZ sensor can function as an effective chemical sensor for detecting the CN− ions. Additionally, the sensor can find CN in tobacco commercial products like cigarettes and cigars. PYR−TZ is a great cyanide sensor probe that has a number of benefits, which includes simple synthesis, distinct color and emission change, a high degree of selectivity, lesser limit of detection, reversibility, and good anti‐interference ability to analyze solution and tobacco commercial things, together with fluorescence imaging. The theoretical optimized structure and electronic transitions were confirmed by DFT and TDDFT studies. On the basis of theoretical and experimental calculations (DFT), the mechanism of the metal ion complex is postulated.

Highly sensitive and reversible MXene-based micro quartz tuning fork gas sensors with tunable selectivity

Due to their distinctive morphology, significant surface-to-volume ratio, and metal-like electrical conductivity, MXenes have emerged as highly promising gas-sensing materials. Traditional MXene-based gas sensors predominantly rely on the electrical conductivity of MXenes for signal transduction. However, it is crucial to explore alternative signal transduction mechanisms to fully unlock the potential of MXenes in gas sensing applications. In this study, we have successfully showcased the development of a mass-transduction-based MXene gas sensor, utilizing MXenes as the adaptable receptor and MQTF as the transducer. The interaction between the gas analyte and MXenes induces a change in mass, resulting in a resonant frequency shift of the MQTF. This signal transduction mechanism eliminates the dependency on the electrical conductivity of MXenes, offering a broader range of possibilities for chemical modification of MXenes without concerns about compromising their conductivity. By engineering Ti3C2Tx surfaces, we have demonstrated high sensitivity and selectivity tuning of MXene-MQTF gas sensors for detecting CO, SO2, and NH3. This antisymmetric mass-transduction-based (low-cost, stable, sensitive, and practical tuning fork-based) MXene gas sensor demonstrated exceptional sensing performance, customizable selectivity, and high cost-effectiveness. This study paves the way for designing high-performance MXene-based chemical sensors and expands the scope of potential applications in air quality monitoring, wearable devices, the Internet of Things (IoT), and robotics.

Moisture–resistant and ppb–level trace chemical warfare agent optical gas sensor based on ZIF–67 3D photonic crystals with structural engineering

The rapid and trace detection of sulfur mustard (SM), a classical hazardous chemical warfare agents (CWAs) causing irreversible health damages and fatal, is an urgently serious issue for security safeguard but remains challenges especially in real-time changing atmospheric humidity. Herein, a zeolite imidazolate framework–67 (ZIF–67) three–dimensional (3D) photonic crystal optical sensor has been designed and proposed to detect trace SM simulants 2–chloroethyl ethyl sulfide (CEES). Compared to traditional semiconductors, the optical sensor can work at room temperature and shows significant moisture resistance. At real-time relative humidity (RH) of 35%, the sensor exhibits excellent selectivity among seven interfering gases due to the co-interactions of metal sites Co atoms of ZIF–67 via Co···Cl and Co···S with CEES (C4H9ClS), the ultralow detection limit (16.5 ppb), ultrafast response (0.5 s) for CEES can benefit from the ordered structure of ZIF-67 3D photonic crystal and its complete photonic bandgap. Most importantly, at higher RH 50%–95%, the sensor shows excellent moisture resistance and still keeps excellent selectivity, ultralow detection limit (19.1 ppb), ultrafast response (0.5 s), long–term stability and reusability for CEES even at RH 95%, warranting its utility as a moisture–resistant trace chemical warfare agent optical sensor.

Recent advances in Metal-Organic Framework derived nanocomposites in gas and chemical sensors: a review

Recent advances in Metal-Organic Framework derived nanocomposites in gas and chemical sensors: a review

Evidence of transient potentials in ion-selective electrodes based on thin-layer ion-exchange membranes

Polymeric membranes with ion-exchange properties have found numerous applications in water treatment, dialysis, energy storage, chemical sensors, and bio-interfaces, among others. Notably, it is common to operate under non-equilibrium conditions while pursuing specific features (e.g., current generation) through an electron-to-ion mechanism. To maximize the final performance, it is crucial to understand the role of each interface within the system, which becomes complex when the device is tailored with several materials and films. This is the case for ion sensors based on thin membranes in backside contact with a redox active conducting polymer. Herein, we investigate such a system operating under a charge transfer mechanism, which features electroneutrality maintenance as the main driving force upon application of a linear sweep potential. This potential is modeled as being unequally distributed among the various system interfaces. Our results demonstrate and quantify the existence of a transient membrane potential at the membrane-electrolyte interface, owing to the implementation of a strategical measurement point on the buried membrane side and connected to a built-in electrometer for the exclusive acquisition of the potential difference at such an interface. The transient membrane potential was found to be <1 % of the total applied potential, meaning that the ion-transfer process at the electrolyte-membrane interface is less energetically costly that the electron transfer and doping processes occurring at the conducting polymer side. This small contribution can be potentiated by increasing the ion-exchange capacity of the membrane, which indirectly enlarges the system current and serves as a strategy for increasing the efficiency of the device.

Molten salt-modified Ti3C2Tx MXene with tunable oxygen-functionalized surfaces for effective detection of NO2 at room temperature

The abundant tunable functional groups and room-temperature sensing properties of MXenes have garnered increasing interest in the field of gas sensing. However, the majority of research has exclusively focused on the combined impact of external substances with MXenes functional groups, with limited exploration into the modulation of MXenes’ intrinsic functional groups. In this work, we successfully produced molten salt-modified Ti3C2Tx MXene (M-Ti3C2Tx) with tunable oxygen-functionalized surfaces using the molten salt immersion method and employed it as a chemical resistive gas sensor to detect NO2 at room temperature (RT). Using diverse analytical techniques, we propose the O−addition effect on the surface titanium atoms and the O−substitution effect on the edge carbon atoms, refining the existence form of –O functional groups as well as realizing the effective regulation of the intrinsic functional groups. With a high response (∼25.87%−100 ppm NO2, whose response value is five times higher than that of pristine Ti3C2Tx), relatively rapid response speed (∼99 s−25 ppm NO2), high sensitivity (∼0.29 ppm−1), low detection limits (theoretical LoD is 3.3 ppm), good selectivity and long-term stability (maintain stable within 28 days) at RT, the sensor based on M-Ti3C2Tx demonstrates excellent NO2 sensing performance. To understand the sensing mechanism, density functional theory (DFT) calculations were conducted to explore adsorption behaviors. Theoretical analysis validates that M-Ti3C2Tx has a stronger adsorption capacity for NO2 (Ead = −1.149 eV) owing to the formation of covalent bond between the –O functional group and the nitrogen atom of NO2. The application of the molten salt can effectively modulate the intrinsic functional groups of MXenes, expanding the scope of MXenes surface modification engineering and creating new opportunities for enhancing the gas sensing capabilities of MXenes.

Recent Progress in Flexible Surface Acoustic Wave Sensing Technologies.

In this work, the major methods for implementing flexible sensing technology-flexible surface acoustic wave (SAW) sensors-are summarized; the working principles and device characteristics of the flexible SAW sensors are introduced; and the latest achievements of the flexible SAW sensors in the selection of the substrate materials, the development of the piezoelectric thin films, and the structural design of the interdigital transducers are discussed. This paper focuses on analyzing the research status of physical flexible SAW sensors such as temperature, humidity, and ultraviolet radiation, including the sensing mechanism, bending strain performance, device performance parameters, advantages and disadvantages, etc. It also looks forward to the development of future chemical flexible SAW sensors for gases, the optimization of the direction of the overall device design, and systematic research on acoustic sensing theory under strain. This will enable the manufacturing of multifunctional and diverse sensors that better meet human needs.

Recent Development on Copper-Sensor and its Biological Applications: A Review.

Metal ion recognition is one of the most prospective research topics in the field of chemical sensors due to its wide range of clinical, biological and environmental applications. In this context, hydrazones are well known compounds that exhibit metal sensing and several biological properties due to the presence of N=CH- bond. Some of the biological properties includes anti-cancer, anti-tumor, anti-oxidant, anti-microbial activities. Hydrazones are also used as a ligand to detect metal ion as well as to generate metal complexes that exhibit medicinal properties. Thus, in recent years, many attempts were made to develop novel ligands with enhanced metal sensing and medicinal properties. In this review, some of the recent development on the hydrazones and their copper complexes are covered from the last few years from 2015-2023. These includes significance of copper ions, synthesis, biological properties, mechanism and metal sensing properties of some of the copper complexes were discussed.

Powders to Thin Films: Advances in Conjugated Microporous Polymer Chemical Sensors.

Chemical sensing of harmful species released either from natural or anthropogenic activities is critical to ensuring human safety and health. Over the last decade, conjugated microporous polymers (CMPs) have been proven to be potential sensor materials with the possibility of realizing sensing devices for practical applications. CMPs found to be unique among other porous materials such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) due to their high chemical/thermal stability, high surface area, microporosity, efficient host-guest interactions with the analyte, efficient exciton migration along the π-conjugated chains, and tailorable structure to target specific analytes. Several CMP-based optical, electrochemical, colorimetric, and ratiometric sensors with excellent selectivity and sensing performancewere reported. This review comprehensively discusses the advances in CMP chemical sensors (powders and thin films) in the detection of nitroaromatic explosives, chemical warfare agents, anions, metal ions, biomolecules, iodine, and volatile organic compounds (VOCs), with simultaneous delineation of design strategy principles guiding the selectivity and sensitivity of CMP. Preceding this, various photophysical mechanisms responsible for chemical sensing are discussed in detail for convenience. Finally, future challenges to be addressed in the field of CMP chemical sensors are discussed.

Lung cancer detection in perioperative patients' exhaled breath with nanomechanical sensor array

IntroductionBreath analysis using a chemical sensor array combined with machine learning algorithms may be applicable for detecting and screening lung cancer. In this study, we examined whether perioperative breath analysis can predict the presence of lung cancer using a Membrane-type Surface stress Sensor (MSS) array and machine learning. MethodsPatients who underwent lung cancer surgery at an academic medical center, Japan, between November 2018 and November 2019 were included. Exhaled breaths were collected just before surgery and about one month after surgery, and analyzed using an MSS array. The array had 12 channels with various receptor materials and provided 12 waveforms from a single exhaled breath sample. Boxplots of the perioperative changes in the expiratory waveforms of each channel were generated and Mann-Whitney U test were performed. An optimal lung cancer prediction model was created and validated using machine learning. ResultsSixty-six patients were enrolled of whom 57 were included in the analysis. Through the comprehensive analysis of the entire dataset, a prototype model for predicting lung cancer was created from the combination of array five channels. The optimal accuracy, sensitivity, specificity, positive predictive value, and negative predictive value were 0.809, 0.830, 0.807, 0.806, and 0.812, respectively. ConclusionBreath analysis with MSS and machine learning with careful control of both samples and measurement conditions provided a lung cancer prediction model, demonstrating its capacity for non-invasive screening of lung cancer.

An efficient copper(II) salamo-based complex fluorescence chemosensor for detecting sulfide ions: Structure exploration and practical application

A novel salamo-based fluorescent chemical sensor l-Cu2+ was designed and prepared via the reaction of H2L and Cu(OAc)2·H2O. The whole research has found that Cu(II) atom in the complex crystal are located in the N2O2 cavity of H2L, forming a four-coordination system. Hirshfeld surface analysis confirmed the presence of hydrogen bonding and π···π stacking interactions. As a probe molecule, l-Cu2+can selectively and sensitively detect S2- without interference from other ions, and can be effectively used within the biological pH range. In addition, DFT theoretical calculations and molecular electrostatic potential analysis (ESP) were used to investigate the electron cloud density and positive and negative electrostatic potentials inside the probe, as well as the mechanism for identifying sulfur ions. Finally, the probe l-Cu2+has shown good practical application effects and can recognize S2− in three different water samples. It can also be used as a qualitative detection strip. l-Cu2+complex possesses excellent application prospect in bacteriostasis.

The Art of Fluorescence Imaging with Chemical Sensors: The Next Decade 2012–2022

Imaging methods by the means of optical sensors are applied in diverse scientific areas such as medical research and diagnostics, aerodynamics, environmental analysis, or marine research. After a general introduction to the field, this review is focused on works published between 2012 and 2022. The covered topics include planar sensors (optrodes), nanoprobes, and sensitive coatings. Advanced sensor materials combined with imaging technologies enable the visualization of parameters which exhibit no intrinsic color or fluorescence, such as oxygen, pH, CO2, H2O2, Ca2+, or temperature. The progress on the development of multiple sensors and methods for referenced signal read out is also highlighted, as is the recent progress in device design and application formats using model systems in the lab or methods for measurements’ in the field.

Low traces of acetone detection with WO3-based chemical sensors

This work presents the ability of WO3-based sensors to detect low traces of acetone, specifically within the range of 0.25–5 ppm, specific to the in-field atmosphere. The WO3 powder was synthesised through the hydrothermal method. Morpho-structural investigations showed a monoclinic structure and a good crystallization of the WO3 powder, containing well-grown and faceted grains along low-index crystallographic planes. The paste obtained by mixing the powder with propanediol was screen-printed as a thick layer onto commercial alumina substrates, obtaining the chemical sensors. A dynamic computer-controlled Gas Mixing System was utilized to ensure controlled airflow with variable relative humidity and acetone concentrations. The sensor response was explained based on physico-chemical equations, taking into consideration pre-adsorbed species of oxygen and water, both of which are relevant constituents of atmospheric conditions. The results highlight the applicative potential of WO3, having a good signal-to-noise ratio in relative humidity conditions up to 90% and a pronounced sensitive selectivity to acetone.

Research Progress in Detection of Explosives by Chemical Colorimetric Method

This article reviews the current application status and research progress of colorimetric detection methods based on chemical colorimetry in the detection of explosives.It mainly introduced colorimetric sensors, colorimetric sensor arrays, and chemical colorimetric sensors based on novel material substrates. The application prospect of chemical colorimetric method in the field of explosives detection was prospected.

Highly sensitive fluorescence turn-OFF and reversible chemical sensor for Hg2+ ion based on pyrene appended 2-thiohydantoin

A novel fluorometric chemical sensor (PY-2TH) based on 2-thiohydantoin (2TH) in conjugation with pyrene (PY) was designed by facile one-pot Knoevenagel condensation reaction and explored for the sensitive and selective detection of Hg2+ ion in solution and solid state methods. Different analytical techniques like NMR and LC-MS concomitantly confirmed the structure of PY-2TH. Absorption and emission studies demonstrate positive solvatochromic effects indicating intramolecular charge transfer in polar solvents. PY-2TH exhibits unprecedented selectivity for detecting Hg2+ ions in tetrahydrofuran (THF) through turn-OFF fluorescence with 90% decrease in the emission intensity with a limit of detection (LOD) of ∼4.4 ppb. The mechanistic investigation through NMR and optical studies confirm the formation of a 2:1 complex between PY-2TH and Hg2+. Thin films of PY-2TH exhibits the J-aggregate formation in the solid state leading to a shift in the emission towards the near-infrared region. Further, we have demonstrated the applicability of PY-2TH for detection of Hg2+ ions and fluorescence imaging in live Zebrafish larvae and the toxicological effects are explored. Cytotoxic evaluation on Zebrafish larval cells revealed that PY-2TH is found to be non-toxic. Detailed analysis demonstrate the potential of PY-2TH for ultra-sensitive Hg2+ ion detection and removal in aqueous environments, highlighting its applicability for identification of metal contamination in live organisms and environmental toxicity.

A Review on Carbon Nanotubes Family of Nanomaterials and Their Health Field.

The use of carbon nanotubes (CNTs), which are nanometric materials, in pathogen detection, protection of environments, food safety, and in the diagnosis and treatment of diseases, as efficient drug delivery systems, is relevant for the improvement and advancement of pharmacological profiles of many molecules employed in therapeutics and in tissue bioengineering. It has contributed to the advancement of science due to the development of new tools and devices in the field of medicine. CNTs have versatile mechanical, physical, and chemical properties, in addition to their great potential for association with other materials to contribute to applications in different fields of medicine. As, for example, photothermal therapy, due to the ability to convert infrared light into heat, in tissue engineering, due to the mechanical resistance, flexibility, elasticity, and low density, in addition to many other possible applications, and as biomarkers, where the electronic and optics properties enable the transduction of their signals. This review aims to describe the state of the art and the perspectives and challenges of applying CNTs in the medical field. A systematic search was carried out in the indexes Medline, Lilacs, SciELO, and Web of Science using the descriptors "carbon nanotubes", "tissue regeneration", "electrical interface (biosensors and chemical sensors)", "photosensitizers", "photothermal", "drug delivery", "biocompatibility" and "nanotechnology", and "Prodrug design" and appropriately grouped. The literature reviewed showed great applicability, but more studies are needed regarding the biocompatibility of CNTs. The data obtained point to the need for standardized studies on the applications and interactions of these nanostructures with biological systems.

Atomic ordered doping leads to enhanced sensitivity of phosgene gas detection in graphene nanoribbon: a quantum DFT approach

We explore a novel sensor for detection of phosgene gas by graphene derivatives such as pristine and doped graphene nanoribbons via first principles calculations. The interaction of phosgene molecule with various edge and center doped configurations of boron, phosphorus and boron-phosphorus co-doped armchair graphene nanoribbon (AGNR) and zigzag graphene nanoribbon (ZGNR) is investigated through density functional theory (DFT). P-doped systems showcase chemisorption, displaying enhanced sensitivity to phosgene detection as reflected by a more negative adsorption energy values, accompanied by a prominent charge transfer due to the doping. Regardless of nanoribbon geometry, the binding energies of P-doped systems exhibit notable uniformity within the range of −8.01 eV to −8.49 eV, however the adsorption energies in ZGNR are significantly lower than those observed in AGNR. Due to much higher(lower) electron-donating (accepting) capacity of phosphorous(boron) atoms in comparison to ‘C’ atom, substitutional doping with ‘P’ or ‘B’ atoms in AGNR has signifiant impact on the structural, electronic and adsorption properties of the nanoribbons. We observe that phosphorus doped configurations (edge/center) effectively interact with phosgene molecule with higher adsorption that corresponds to the chemisorption phenomenon. The strongest adsorption energy (−8.83 eV) is obtained for P doped configurations, followed by that for B+P co-doped AGNR (−4.23 eV). These results suggest significantly stronger adsorption of phosgene gas on P doped AGNR than on any other systems reported so far. Band structure analysis estimates that by phosphorus doping, changes in the band gap is significant and it also shows prominent changes in the band structures. Isosurface electronic charge density plots identify that the transfer of charge takes place from graphene system to phosgene molecule. Thus, significant variation in adsorption and electronic properties of P doped AGNR reveal that these geometries immensely promote the detection of phosgene gas, and may be considered as promising chemical sensor for phosgene removal.

A novel ethylene linkage-based covalent organic framework for turn-on fluorescence sensing for Al3+ with excellent selectivity and sensitivity

Covalent organic Framework (COFs) has become a new platform for functional research and material design. A novel covalent organic framework (CN-COF) was first synthesized with p-xylylene dicyanide and 2-hydroxy-1,3,5-benzenetrialdehyde through the Knoevenagel condensation reaction. CN-COF is a porous crystal material with strong thermal and chemical stability. CN-COF exhibits a selective “turn-on” fluorescence response to Al3+ in ethanol with blue-shifted emission spectra over the other tested metal ions. The color changes from pink to earth yellow, and the fluorescence effect is clearly visible. The fluorescence intensity of CN-COF was linearly related to the concentration of Al3+, and the detection limit was 1.815 μM. Importantly, CN-COF exhibits a satisfactory recovery for detecting Al3+ in drinking water and fish samples. CN-COF also showed the intuitive semi-quantitative detection ability for Al3+ via the color change with the naked eyes. The special pore structure is conducive to allow Al3+ enter to coordinate with O and N atoms on the wall of CN-COF scaffold. The revisable fluorescence change upon the selective addition of Al3+ and XRD, EDTA, XPS and DFT results demonstrated the complex process. The inhibition of the photoinduced electron transition from O atoms to Al3+ induced the fluorescence enhancement. This study not only presents a synthesis idea for a new structural organic framework, but also offers a highly selective and sensitive fluorescence chemical sensor for the identification and detection of Al3+.

Deposition of Polymers on Titanium Nitride Electrodes

The application of titanium nitride (TiN) as an electrode for electrochemical deposition or characterization requires the removal of an insulating layer from its surface. This process was studied and optimized, and the conditions for the complete removal of this layer through treatment with oxalic acid were formulated. The obtained TiN surfaces were used for the deposition of various conducting and non-conducting polymers. Two different approaches were applied: (i) in situ electrochemical synthesis of the main classes of conducting polymers, including polyaniline, polypyrrole, polythiophene, and selected derivatives thereof, and (ii) electrostatically driven layer-by-layer (LbL) deposition of multilayers of oppositely charged polyelectrolytes. The deposited polymers were characterized by electrochemical methods. The electrochemical properties of the deposited conducting polymers and their deposition on the TiN surface were comparable to those of the metallic electrodes. The films produced via LbL deposition exhibited a pronounced influence of the charge of the last deposited polymer on the redox reaction of ferri/ferrocyanide, validating the charge alteration with each successive polymer layer deposition. The studied deposition technologies can be used for the modification of TiN surfaces required in applications of this material in chemical sensors and other devices.

Continuous and precise recognition of N2H4 and Cu2+ has been achieved using chalcone derivatives as a D-A-D΄-type fluorescent chemical sensor

A fluorescent probe, FZ, based on the ESIPT and ICT mechanisms was designed. It transformed from a ratio probe to a fluorescence turn-on probe using the properties of the ICT mechanism, enhancing the sensitivity for detecting N2H4. The calculated detection limit was 3.39 × 10-8 M. The existence of intramolecular hydrogen bonds between O–H and C = O was confirmed through single crystal structure analysis. Additionally, taking advantage of the structural features of FZN generated from the reaction of FZ with N2H4, it was developed into a new quenching-type Cu2+ fluorescent probe with a detection limit of 1.47 × 10-8 M, achieving high sensitivity and selectivity for Cu2+ detection. Furthermore, it was adapted into a fluorescence TLC testing plate for detecting trace amounts of Cu2+ in the environment, demonstrating its potential applicability in Cu2+ detection.