Chemical Sensors Research Articles

High-Active Surface of Centimeter-Scale β-In2S3 for Attomolar-Level Hg2+ Sensing.

Recognition layer materials play a crucial role in the functionality of chemical sensors. Although advancements in two-dimensional (2D) materials have promoted sensor development, the controlled fabrication of large-scale recognition layers with highly active sites remains crucial for enhancing sensor sensitivity, especially for trace detection applications. Herein, we propose a strategy for the controlled preparation of centimeter-scale non-layered ultrathin β-In2S3 materials with tailored high-active sites to design ultrasensitive Hg2+ sensors. Our results reveal that the highly active sites of non-layered β-In2S3 materials are pivotal for achieving superior sensing performance. Selective detection of Hg2+ at the 1 aM level is achieved via selective Hg-S bonding. Additionally, we evaluate that this sensor exhibits excellent performance in detecting Hg2+ in the tap water matrix. This work provides a proof-of-concept for utilizing non-layered 2D films in high-performance sensors and highlights their potential for diverse analyte sensing applications.

Revolutionizing sensing technologies: Crafting a green, ultra-sensitive bismuth optical sensor via fixation of 5-(2′,4′-dimethyl-phenylazo)-6-hydroxypyrimidine-2,4-dione on PVC membrane

An innovative and exceptionally responsive optical sensing device engineered to selectively identify Bi(III) ions in water-based solutions. The sensing component, 5-(2′,4′-dimethylphenylazo)-6-hydroxypyrimidine-2,4-dione (DMPAHPD), is incorporated into a plasticized polyvinyl chloride (PVC) membrane. The sensor demonstrates an exceptional selectivity for Bi(III) within a broad dynamic range spanning from 7.5 × 10−10 to 4.2 × 10−5 M at pH 2.25. Notably, it achieves lower quantification and detection limits of 7.25 × 10−10 and 2.15 × 10−10 M, respectively. The optode membrane’s response to Bi(III) proves to be entirely reversible, demonstrating remarkable selectivity for Bi(III) ions over a diverse range of other cations and anions. The sensor exhibits favorable performance characteristics, including good reversibility, a wide dynamic range, a prolonged lifespan, sustained response stability over the long term, and high reproducibility. This visual chemical sensor exhibits potential for real-world usage, offering consistent outcomes when assessing Bi(III) levels in matrices such as water, soil, plants, biological and synthetic mixtures. Importantly, the sensor’s performance is comparable to corresponding data achieved from inductively coupled plasma atomic emission spectroscopy (ICP-AES).

Functionalization of Si‐ and Al‐Based Materials with Phosphorus Dendrimers and their Properties

AbstractThe interactions of dendrimers having a phosphorus atom at each branching point, of type poly(phosphorhydrazone) (PPH), with different types of materials based on silicon and aluminum are reviewed. These dendrimers can be used for the functionalization of solid surfaces at the nanoscale, either by covalent immobilization, or by electrostatic interactions, especially for constructing perfectly controlled multi‐layers by layer‐by‐layer (LbL) deposit. The properties of such hybrid materials as chemical sensors, as very sensitive biological sensors, as well as substrates for the growing of cells are described. The PPH dendrimers can also be embedded inside materials. The resulting hybrid materials have been used for the capture of pollutants, in particular CO2 in air and chromate and methylene blue in waste water.

Design, Calibration and Morphological Characterization of a Flexible Sensor with Adjustable Chemical Sensitivity and Possible Applications to Sports Medicine.

Active life monitoring via chemosensitive sensors could hold promise for enhancing athlete monitoring, training optimization, and performance in athletes. The present work investigates a resistive flex sensor (RFS) in the guise of a chemical sensor. Its carbon 'texture' has shown to be sensitive to CO2, O2, and RH changes; moreover, different bending conditions can modulate its sensitivity and selectivity for these gases and vapors. A three-step feasibility study is presented including: design and fabrication of the electronic read-out and control; calibration of the sensors to CO2, O2 and RH; and a morphological study of the material when interacting with the gas and vapor molecules. The 0.1 mm-1 curvature performs best among the tested configurations. It shows a linear response curve for each gas, the ranges of concentrations are adequate, and the sensitivity is good for all gases. The curvature can be modulated during data acquisition to tailor the sensitivity and selectivity for a specific gas. In particular, good results have been obtained with a curvature of 0.1 mm-1. For O2 in the range of 20-70%, the sensor has a sensitivity of 0.7 mV/%. For CO2 in the range of 4-80%, the sensitivity is 3.7 mV/%, and for RH the sensitivity is 33 mV/%. Additionally, a working principle, based on observation via scanning electron microscopy, has been proposed to explain the chemical sensing potential of this sensor. Bending seems to enlarge the cracks present in the RFS coverage; this change accounts for the altered selectivity depending on the sensor's curvature. Further studies are needed to confirm result's reliability and the correctness of the interpretation.

Optimization of the polyaniline solid contact in potentiometric sensors for detection of paralytic shellfish toxins in mussels

The present study optimized the properties of the electropolymerized polyaniline (PANI) solid inner contact for a potentiometric chemical sensor by varying the thickness of the polymer layer. A potentiometric sensor for detecting one of the paralytic shellfish toxins, decarbamoyl saxitoxin (dcSTX), in mussel extracts was selected as a case study. The plasticized PVC membrane composition, developed in previous work for the detection of this toxin, was used. The structure and electrical properties of PANI layers of different thicknesses were studied using scanning electron microscopy and electrochemical impedance spectroscopy. The effect of PANI solid contact thickness on the characteristics of the potentiometric sensor, including sensitivity, detection limit, and selectivity to dcSTX in buffer solutions and mussel extracts, was evaluated. The formation of a water layer at the inner solid contact and PVC membrane interface was investigated using electrochemical impedance spectroscopy and a water test. PANI layer thickness 1.1 µm was found to be optimal for solid inner contact for potentiometric sensor with PVC membrane providing highest sensitivity and selectivity.

Recent advances in photonic crystal fiber based chemical and industrial sensors: a review

Recent advances in photonic crystal fiber based chemical and industrial sensors: a review

Single mode optical fiber sensor based on surface plasmon resonance for the detection of the Lactic acid for the chemical sensor

Single mode optical fiber sensor based on surface plasmon resonance for the detection of the Lactic acid for the chemical sensor

Analysis of Exhaled Human Breaths using Graphene Gas Sensor Based on the Male Gender

Breath analysis is an intriguing method that has the potential to significantly improve non-implantable physical health management via the use of flexible sensors to monitor breathing behaviours. In comparison to other analytical techniques for detecting breath elements, non-invasive breathing diagnostics based on chemical sensors can provide numerous benefits, including nanotechnology, power efficiency, simplicity of structure, and cost-effectiveness, contributing to the flexibility of experimental studies. This paper presents the graphene-based human breath sensor. Graphene was prepared in a paste form by mixing the graphene powder with two types of the binder. Two binders were prepared to compare their performance to human breath. The graphene paste was deposited using screen-printing on different substrates, Kapton film, and glass. The sensing film was thermally annealed at 200°C for 30 minutes and characterized using SEM and FTIR. All graphene gas sensor samples responded well to collected male human breath samples: Bumiputera (Sarawak), Malay, Chinese, and Indian. The best graphene gas sensor for males was OG-T(G) and OG-T(K) with sensitivity, S=1.10415 and S=1.01629. Based on the comparison results of male human breath, the fastest response time and recovery time were 0.52s and 13s, respectively.

Nanomedicines with Versatile GSH-Responsive Linkers for Cancer Theranostics.

Glutathione (GSH)-responsive nanomedicines have generated significant interest in biochemistry, oncology, and material sciences due to their diverse applications, including chemical and biological sensors, diagnostics, and drug delivery systems. The effectiveness of these smart GSH-responsive nanomedicines depends critically on the choice of GSH-responsive linkers. Despite their crucial role, comprehensive reviews of GSH-responsive linkers are scarce, revealing a gap in the current literature. This review addresses this gap by systematically summarizing various GSH-responsive linkers and exploring their potential applications in cancer treatment. We provide an overview of the mechanisms of action of these linkers and their bioapplications, evaluating their advantages and limitations. The insights presented aim to guide the development of advanced GSH-responsive agents for cancer diagnosis and therapy.

Dirac Electrons with Molecular Relaxation Time at Electrochemical Interface between Graphene and Water.

The time dynamics of charge accumulation at the electrochemical interface between graphene and water is important for supercapacitors, batteries, and chemical and biological sensors. By using impedance spectroscopy, we have found that measured capacitance (Cm) at this interface with the gate voltage Vgate ≈ 0.1 V follows approximate laws Cm~T1.2 and Cm~T0.11 (T is Vgate period) in frequency ranges (1000-50,000) Hz and (0.02-300) Hz, respectively. In the first range, this dependence demonstrates that the interfacial capacitance (Cint) is only partially charged during the charging period. The observed weaker frequency dependence of the measured capacitance (Cm) at frequencies below 300 Hz is primarily determined by the molecular relaxation of the double-layer capacitance (Cdl) and by the graphene quantum capacitance (Cq), and it also implies that Cint is mostly charged. We have also found a voltage dependence of Cm below 10 Hz, which is likely related to the voltage dependence of Cq. The observation of this effect only at low frequencies indicates that Cq relaxation time is much longer than is typical for electron processes, probably due to Dirac cone reconstruction from graphene electrons with increased effective mass as a result of their quasichemical bonding with interfacial molecular charges.

Designing new sulfate ionophores for potentiometric membrane sensors: Selectivity assessment and practical application

Developing potentiometric chemical sensors for sulfate determination is a rather challenging task due to a considerable hydrophilicity of this anion and its poor affinity to lipophilic plasticized polymeric membranes – one of the most popular sensor membrane materials nowadays. Not too many research works were devoted to this problem in the last years. Here we report on the successful development of several novel sulfate ionophores based on the synthetic modification of the commercially available sulfate ionophore I. The newly developed sensors outperform commercial analogue in terms of elelctrochemical sensitivity and selectivity. We have highlighted certain problems with numerical selectivity assessment in case when primary and interfering ions have different charges. The counterintuitive results yielded by conventional selectivity quantification methods implies the relevance of using alternative approach – visualizing sensor response curves towards primary ion in the presence of interfering ions. Novel sulfate sensors were applied for direct potentiometric measurements of sulfate content in river water samples demonstrating real applicability of the developed sensor membranes.

Toward Integrated Multifunctional Laser-Induced Graphene-Based Skin-Like Flexible Sensor Systems.

The burgeoning demands for health care and human-machine interfaces call for the next generation of multifunctional integrated sensor systems with facile fabrication processes and reliable performances. Laser-induced graphene (LIG) with highly tunable physical and chemical characteristics plays vital roles in developing versatile skin-like flexible or stretchable sensor systems. This Progress Report presents an in-depth overview of the latest advances in LIG-based techniques in the applications of flexible sensors. First, the merits of the LIG technique are highlighted especially as the building blocks for flexible sensors, followed by the description of various fabrication methods of LIG and its variants. Then, the focus is moved to diverse LIG-based flexible sensors, including physical sensors, chemical sensors, and electrophysiological sensors. Mechanisms and advantages of LIG in these scenarios are described in detail. Furthermore, various representative paradigms of integrated LIG-based sensor systems are presented to show the capabilities of LIG technique for multipurpose applications. The signal cross-talk issues are discussed with possible strategies. The LIG technology with versatile functionalities coupled with other fabrication strategies will enable high-performance integrated sensor systems for next-generation skin electronics.

Novel Schiff base decorated cyclotriphosphazene chemosensors for Fe and Cu ions detection

In this study, new 2-aminobenzothiazole derivative Schiff base decorated cyclotriphosphazene compounds (SBCTP 1 and 2), which are likely to have chemical sensor properties, were designed and synthesized successfully. The compounds were structurally characterized by mass analysis and NMR (1H, 13C and 31P) spectroscopies. Photophysical and chemosensory properties of SBCTP 1 and 2 against some analytes were examined by UV–vis and Fluorescence spectrophotometry. While a significant increase was observed in the UV–vis absorption signals observed at 350 nm with the addition of Fe3+ and Fe2+ ions and a new absorption band was observed at 290 nm with the addition of Cu2+. In addition, according to Job's plot obtained from UV–vis absorption titrations, the complex stoichiometries of SBCTP 1 and 2 with selective analytes were determined as 1:1 (L/M) and 1:2 (L/M), respectively. The selective interaction of donor atoms on SBCTP 1 and 2 with Cu2+, Fe2+ and Fe3+ ions give these compounds chemosensory properties. This study showed that the synthesized Schiff base decorated cyclotriphosphazene compounds (SBCTP 1 and 2) could be new chemosensors with high selective and immediate sensitivity for the detection of iron and copper ions.

Adapalene as a chemical sensor for sensitive determination of manganese

ABSTRACT The work describes the use of 6-[3-(1-adamantyl)-4-methoxyphenyl]-2- naphthoic acid, or Adapalene (ADP) as a fluorescence tagging reagent, in a straightforward and very specific spectrofluorometric approach for the trace measurement of manganese (VII) in water. The process is based on the redox interaction of ADP with manganese (VII) in an acidic solution, which forms the complex [Mn (II)-ADP] and causes fluorescence at λex max/λem max = 323/400 nm. High-intensity fluorescence at 400 nm was seen in the fluorescence spectra of the formed complex ion association, Mn (II)-ADP, at pH 4. 1.55 µg mL−1 was the quantification limit, and 0.51 µg mL−1 was the detection limit and the correlation coefficient (R2) was 0.9863. 1.2173 L mol−1 was determined to be the Stern-Volmer. Spectrofluorometric technique is used to validate the approach in environmental water samples, yielding reasonable recovery percentages (89–93%). The current approach is advised to be used for reliable and accurate assessment of manganese (VII) in all wastewater and seawater samples, without the need for complex instrumentation and lengthy procedures.

Light-Modulated Humidity Sensing in Spiropyran Functionalized MoS2 Transistors.

The optically tuneable nature of hybrid organic/inorganic heterostructures tailored by interfacing photochromic molecules with 2D semiconductors (2DSs) can be exploited to endow multi-responsiveness to the exceptional physical properties of 2DSs. In this study, a spiropyran-molybdenum disulfide (MoS2) light-switchable bi-functional field-effect transistor is realized. The spiropyran-merocyanine reversible photo-isomerization has been employed to remotely control both the electron transport and wettability of the hybrid structure. This manipulation is instrumental for tuning the sensitivity in humidity sensing. The hybrid organic/inorganic heterostructure is subjected to humidity testing, demonstrating its ability to accurately monitor relative humidity (RH) across a range of 10%-75%. The electrical output shows good sensitivity of 1.0% · (%) RH-1. The light-controlled modulation of the sensitivity in chemical sensors can significantly improve their selectivity, versatility, and overall performance in chemical sensing.

A Microrobotic Design for the Spontaneous Tracing of Isochemical Contours in the Environment

Microrobotic platforms hold significant potential to advance a variety of fields, from medicine to environmental sensing. Herein, minimally functional robotic entities modeled on readily achievable state‐of‐the‐art features in a modern lab or cleanroom are computationally simulated. Inspired by Dou and Bishop (Phys Rev Res. 2019;1(3):1–5), it is shown that the simple combination of unidirectional steering connected to a single environmental (chemical) sensor along with constant propulsion gives rise to highly complex functions of significant utility. Such systems can trace the contours orthogonal to arbitrary chemical gradients in the environment. Also, pairs of such robots that are additionally capable of emitting the same chemical signal are shown to exhibit coupled relative motion. When the pair has unidirectional steering in opposite directions within the 2D plane (i.e., counter‐rotating), they move in parallel trajectories to each other. Alternatively, when steering is in the same direction (corotation), the two move in the same epicyclical trajectory. In this way, the chirality of the unidirectional steering produces two distinct emergent phenomena. The behavior is understood as a ratchet mechanism that exploits the differential in the radii of curvature corresponding to different spatial locations. Applications to environmental detection, remediation, and monitoring are discussed.

A rare extra-long flexible salamo-based bisoxime as highly efficient and selective probe for fluorescent identification of CO32− ion and mechanism exploration

A novel extra-long carbon-chain salamo-like fluorescent chemical probe DNS (named as 2,2′-[1,10-(decanedioxy)bis(nitromethyldyne)]dinaphthol) containing ten methylene groups was synthesized based on the 2-hydroxy-1-naphthylaldehyde unit. Research has shown that the fluorescent probe DNS can achieve efficient and selective recognition of CO32− anions, with a detection limit LOD=1.59 × 10−8 M. The binding constant Ka = 3.7 × 104 M−1 and quantification limit is as low as LOQ=4.31 × 10−8 M, respectively. The possible identification mechanism of the fluorescent chemosensor DNS was analyzed and studied through fluorescence titration and nuclear magnetic titration. The results showed that the fluorescence chemical sensor DNS is deprotonated by CO32− anions, enhancing its fluorescence and producing a ICT effect.

The adsorption of amantadine antiparkinsonian drug on the B24N24 and Al24N24 nanoclusters: An investigation using the density functional theory

By employing the density functional theory (DFT), the present investigation studied the adsorption of an anti-Parkinson drug called Amantadine (AM) onto the nanoclusters of B24N24 and Al24N24. Through their –NH2 group, the molecules of Amantadine interacted with the B or Al head of the AlN(BN) nanoclusters, and it was found that the change in the free Gibbs energy was –32.3 (−27.2) kcal/mol. The increased dosage of Amantadine led to weaker AM/cluster interactions, which is attributable to the steric effect. The molecule of Amantadine was subjected to electrostatic adsorption onto the nanoclusters of AlN and charge transfer adsorption onto the nanoclusters of BN. The Amantadine adsorption led to a dramatic decrease from 4.47 eV to 3.63 eV in the work function of the AlN nanoclusters. As a result, the electron field emission improved. Thus, one may use AlN nanoclusters as an Φ-type chemical sensor for the detection of Amantadine molecules. The AM adsorption onto the BN nanoclusters resulted in noticeable HOMO destabilization and decreased HOMO-LUMO energy gap from 6.84 eV to 5.67 eV. Consequently, a great increase was observed in the electrical conductivity of the BN nanoclusters. As a result, one may use BN nanoclusters as a suitable candidate for manufacturing electronic sensors with the capability of detecting Amantadine.

Critical review on toxic contaminants in surface water ecosystem: sources, monitoring, and its impact on human health.

Surface water pollution is a critical and urgent global issue that demands immediate attention. Surface water plays a crucial role in supporting and sustaining life on the earth, but unfortunately, till now, we have less understanding of its spatial and temporal dynamics of discharge and storage variations at a global level. The contamination of surface water arises from various sources, classified into point and non-point sources. Point sources are specific, identifiable origins of pollution that release pollutants directly into water bodies through pipes or channels, allowing for easier identification and management, e.g., industrial discharges, sewage treatment plants, and landfills. However, non-point sources originate from widespread activities across expansive areas and present challenges due to its diffuse nature and multiple pathways of contamination, e.g., agricultural runoff, urban storm water runoff, and atmospheric deposition. Excessive accumulation of heavy metals, persistent organic pollutants, pesticides, chlorination by-products, pharmaceutical products in surface water through different pathways threatens food quality and safety. As a result, there is an urgent need for developing and designing new tools for identifying and quantifying various environmental contaminants. In this context, chemical and biological sensors emerge as fascinating devices well-suited for various environmental applications. Numerous chemical and biological sensors, encompassing electrochemical, magnetic, microfluidic, and biosensors, have recently been invented by hydrological scientists for the detection of water pollutants. Furthermore, surface water contaminants are monitored through different sensors, proving their harmful effects on human health.

Current Trends and Challenges in Explosives Detection using Nanotechnology

Objective: This article highlights the applications of nanotechnology in the detection of explosives. Evidence acquisition: The increasing rise in terrorist acts throughout the globe has brought attention to the significance of locating hidden bombs and motivated new propelled breakthroughs to ensure public safety. Recognizing explosives and closely related-threatening combinations has already risen to the top of the priority list for contemporary national security and counterterrorism applications. Sensors based on nanotechnology have a fair probability of fulfilling all the criteria needed to be a practical solution for explosive trace detection. Results: Nanowire/nanotube, nanomechanical devices, and electronic noses are three nanosensor technologies that have the most potential to develop into commercially viable technology platforms for the detection of trace explosives. Certain functionalized nanoparticles can exhibit different behaviors as a result of unique interactions with nitroaromatics. Semiconducting singlewalled carbon nanotubes (SWCNT) have been used as wearable chemical sensors. Conclusion: In this paper, the potential of nanosensors has been exposed that can be used to build a sensor system with high selectivity and sensitivity and appropriate platforms for signal transduction for the detection of explosives.