Chemical Sensor Applications Research Articles

Mxene-Ceria Nanocomposite for Health Monitoring Sensorssa

MXenes are an emerging class of 2D layered nanomaterials that provide large surface area, hydrophilicity, high ion transport properties, low diffusion barrier, biocompatibility, and ease of surface functionalization. Due to their unique features, MXenes have gained substantial attention in fields such as batteries and supercapacitors and their application in chemical and biological sensors is growing. Their composition and layered structure make MXenes particularly attractive for biosensing applications. This presentation is focused on the synthesis and characterization of MXene-CeO2 nanocomposite for glucose sensing. The developed MXene-nanoparticles hybrid was then used as a transducer surface and supporting material for the immobilization of enzymes in an electrochemical biosensor setup. The incorporation of MXene into the sensor design enhanced the efficiency of the developed biosensor in terms of facilitating charge transfer and maximizing cerium oxide and biomolecule loading. Opportunities for developing wearable sensors and systems with integrated biomolecule recognition will be highlighted.

Structural, Morphological and Raman Characteristics of Cs2SnCl6 Double-Perovskite Crystals

Sn-based perovskite Cs2SnX6 (X = Cl, Br, and I) are non‐toxic materials with a unique structure and wide energy bandgap (1.6-3.9 eV) caused by halide anions. We have successfully synthesized Cs2SnCl6 crystals and confirmed their underlying perovskite crystal structure. They show a cubic crystal structure, possessing a truncated octahedral morphology with an average crystalline grain size of around 0.5 µm. Experimental Micro-Raman scattering reveals three main peaks at ν (A1g) = 306 cm-1, ν(Eg) = 229 cm-1 and δ(F2g) = 164 cm-1. The Cs2SnCl6 crystals offer intriguing opportunities for their application in photonic, bioimaging, and chemical sensors.

Application of Chemical Sensors and Olfactometry Method in Ecological Audits of Degraded Areas.

Mineral excavation is a common process throughout the world. The open pits remaining after the closure of a mine require well-considered and meticulous reclamation activities aimed at restoring the environmental properties of a given area. The inspections carried out in Poland indicate numerous irregularities in implementing the reclamation process. The research in this study was conducted in six measurement series and includes both chemical and olfactometry determinations by devices: multisensor portable gas detector and field olfactometer. Statistical analysis of the results obtained show high concentrations in ambient air of both chemical compounds (NH3, VOCs, H2S, CH3SH) and odour, excluding the possibility of occurrence in the pit of only waste types contained in the administrative decision on reclamation. In addition to the unpleasant odour, the listed compounds can have dangerous effects on the health and life of living organisms. This paper presents a suitable method of control and detection of irregularities in the conducted processes. The main advantage is the relatively low cost of purchasing sensors and field olfactometers compared to other devices, and the possibility to test the polluted air in situ, without the risk of chemical processes occurring during transport of gas samples to the laboratory.

Numerical Analysis of Viscous Dissipation in Microchannel Sensor Based on Phononic Crystal.

Phononic crystals with phononic band gaps varying in different parameters represent a promising structure for sensing. Equipping microchannel sensors with phononic crystals has also become a great area of interest in research. For building a microchannels system compatible with conventional micro-electro-mechanical system (MEMS) technology, SU-8 is an optimal choice, because it has been used in both fields for a long time. However, its mechanical properties are greatly affected by temperature, as this affects the phononic bands of the phononic crystal. With this in mind, the viscous dissipation in microchannels of flowing liquid is required for application. To solve the problem of viscous dissipation, this article proposes a simulation model that considers the heat transfer between fluid and microchannel and analyzes the frequency domain properties of phononic crystals. The results show that when the channel length reaches 1 mm, the frequency shift caused by viscous dissipation will significantly affect detecting accuracy. Furthermore, the temperature gradient also introduces some weak passbands into the band gap. This article proves that viscous dissipation does influence the band gap of phononic crystal chemical sensors and highlights the necessity of temperature compensation in calibration. This work may promote the application of microchannel chemical sensors in the future.

Azo-methoxy-calix[4]arene complexes with metal cations for chemical sensor applications: Characterization, QTAIM analyses and dispersion-corrected DFT- computations

In this work, the structures, quantum chemical descriptors, morphologic characterization of the azo-methoxy-calix[4]arene were investigated. The analyses and interpretation of the theoretical and the experimental IR spectroscopy results for the corresponding compounds was performed. The complexation of the azo-methoxy-calix[4]arene with Zn2+,Hg2+ , Cu2+ , Co2+, Ni2+ , Pb2+ and Cd2+metal cations has been calculated by the dispersion corrected density functional theory (DFT-D3). The values of the interaction energies show that the specific molecule is more selective to the Cu2+ cation. The study of the reactivity parameters confirms that the azo-methoxy-calix[4]arene molecule is more reactive and sensitive to the Cu2+ cation than that Co2+ and Cd2+. In addition, the investigation of the electrophilic and nucleophilic sites has been studied by the molecular electrostatic potential (MEP) analysis. The Hirshfeld surface (HS) analysis of the azo-methoxy-calix[4]arene-Cu2+ interaction have been used to understand the Cu⋯hydrogen-bond donors formed between the cation and the specific compound. The Quantum Theory of Atoms in Molecules (QTAIM) via Non covalent Interaction (NCI) analysis was carried out to demonstrate the nature, the type and the strength of the interaction formed between the Cu2+ cation and the two symmetrical ligands and the cavity. Finally, the chemical sensor properties based on the Si/SiO2/Si3N4/Azo-methoxy-calix[4]arene for detection of Cu2+ cation were studied. Sensing performances are determined with a linear range from 10-5.2 to 10-2.2 M. The Si/SiO2/Si3N4/azo-methoxy-calix[4]arene structure is a promoter to have a good performance sensor.

Polypyrrole derivatives for detection of toxic gases: A theoretical study

AbstractPolypyrrole (PPy) based compounds have been considered interesting materials for several technological applications, mainly due to their unique optoelectronic properties and high versatility of synthesis. In particular, the sensitivity of their electrical properties to external stimuli defines these polymers as promising candidates for chemical sensor applications. However, the demanding processes involved in the synthesis of 3‐4 substituted PPy derivatives hinders the development of optimized systems. In this report, electronic structure calculations were conducted for a set of branched PPy derivatives aiming to identify promising compounds for chemical sensors. The calculations were carried out in the framework of the density functional theory (DFT), by considering oligomeric systems. The influence of the side groups on the local reactivities and adsorption centers of the compounds were evaluated via condensed‐to‐atoms Fukui indexes and molecular electrostatic potentials. DFT‐based adsorption studies and fully atomistic reactive molecular dynamics (FARMD) simulations were conducted for selected systems considering toxic gases as analytes. The results point out PPy, PPy‐CCH and PPy‐CN as promising candidates for chemical sensor applications, presenting high potential for the detection of Cl2 and SO2. FARMD results indicate that the analysis of local reactivities and electrostatic potentials can be used to identify relevant adsorption centers and possible degradation processes.

Organic Electrochemical Transistors: Ultrahigh‐Gain Organic Electrochemical Transistor Chemosensors Based on Self‐Curled Nanomembranes (Adv. Mater. 29/2021)

Achieving synergy between electrochemistry and microelectronics is a hard-hitting task. In article number 2101518, Carlos C. Bof Bufon and co-workers employ rolling-origami nanotechnology to build up novel organic electrochemical transistors (OECTs) featuring outstanding performance. The findings also anticipate that rolling-origami OECTs are enormously appealing candidates to future applications in chemical and biological sensors (viz., for neurotransmitter detection).

Three-Dimensional (3D) Laser-Induced Graphene: Structure, Properties, and Application to Chemical Sensing.

Notwithstanding its relatively recent discovery, graphene has gone through many evolution steps and inspired a multitude of applications in many fields, from electronics to life science. The recent advancements in graphene production and patterning, and the inclusion of two-dimensional (2D) graphenic materials in three-dimensional (3D) superstructures, further extended the number of potential applications. In this Review, we focus on laser-induced graphene (LIG), an intriguing 3D porous graphenic material produced by direct laser scribing of carbonaceous precursors, and on its applications in chemical sensors and biosensors. LIG can be shaped in different 3D forms with a high surface-to-volume ratio, which is a valuable characteristic for sensors that typically rely on phenomena occurring at surfaces and interfaces. Herein, an overview of LIG, including synthesis from various precursors, structure, and characteristic properties, is first provided. The discussion focuses especially on transport and surface properties, and on how these can be controlled by tuning the laser processing. Progresses and trends in LIG-based chemical sensors are then reviewed, discussing the various transduction mechanisms and different LIG functionalization procedures for chemical sensing. A comparative evaluation of sensors performance is then provided. Finally, sensors for glucose detection are reviewed in more detail, since they represent the vast majority of LIG-based chemical sensors.

PCF Based Formalin Detection by Exploring the Optical Properties in THz Regime

Introduction: Ongoing amelioration of semiconductor nano-crystal in chemical sensing applications has led the Photonic Crystal Fiber (PCF) as the most appropriate candidate for chemical sensing. A PCF based sensor model has been proposed in this paper. Objective: The aim of this model is to detect formalin at a high level of sensitivity. Method: This sensor model has been designed and simulated in COMSOL MULTIPHYSICS to analyze the sensing performance based on the optical parameters such as relative sensitivity, confinement loss, and effective material loss. Formalin solution is placed into the core and then the simulation is performed in THz regime ranging from 1 to 2 THz to carry out the optical properties. Simulation data collected from COMSOL are used in Matlab to carry out the graphical representation of the optical parameters. Results: Simulation results demonstrate that the sensor model inherits high relative sensitivity of approximately 77.71 % at 1.8 THz. In addition to that, the proposed sensor exhibits zero confinement loss above 1.3 THz and very low effective material loss in the THz regime for the optimum model. Conclusion: All the optical parameters maintain standard and desirable values in the THz regime. Besides, the flexible fabrication of the proposed model is feasible using existing fabrication methods. Simulation results validate the high performance of this proposed model in formalin detection.

Hydrogel-Based Optical Ion Sensors: Principles and Challenges for Point-of-Care Testing and Environmental Monitoring.

Hydrogel is a unique family of biocompatible materials with growing applications in chemical and biological sensors. During the past few decades, various hydrogel-based optical ion sensors have been developed aiming at point-of-care testing and environmental monitoring. In this Perspective, we provide an overview of the research field including topics such as photonic crystals, DNAzyme cross-linked hydrogels, ionophore-based ion sensing hydrogels, and fluoroionophore-based optodes. As the different sensing principles are summarized, each strategy offers its advantages and limitations. In a nutshell, developing optical ion sensing hydrogels is still in the early stage with many opportunities lying ahead, especially with challenges in selectivity, assay time, detection limit, and usability.

Self-assembled photo-responsive black phosphorus-azobenzene composite Langmuir films with chemical gas sensor and photoelectric conversion applications

The reasonable design of various functionalized nanocomposites based on black phosphorus (BP) has sparked substantial attention from researchers. In this work, the bulk BP was successfully exfoliated into nanosheets (BPNS), the polyethyleneimine (PEI) was selected as the surface protective layer to modify the BPNS for strengthening its stability. We have designed and synthesized two kinds of BPNS-PEI Langmuir composite films containing azobenzene compounds (BPNS-PEI/N-Azo and BPNS-PEI/PAA-Azo) by Langmuir–Blodgett (LB) technology. The composite films were successfully assembled and analyzed the nanoscale structure and morphology using transmission electron microscopy (TEM), atomic force microscopy (AFM), scanning electron microscopy (SEM) and other different characterization methods. In addition, the BPNS-PEI/N-Azo composite films were proven to demonstrate the photoisomerization stability and the acid-alkali atmosphere gas responsiveness by ultraviolet-visible spectroscopy and Fourier transform infrared spectroscopy. Furthermore, the photoelectrochemistry performances of the acquired LB composite films were studied by transferring multilayer films on indium tin oxide (ITO) substrates. And the results demonstrated that the BPNS-PEI/N-Azo self-assembled LB film electrode showed higher photoelectric conversion efficiency. The self-assembled films based on BP, undertaking an appealing conception for gaining a wide range of nano-optical devices, gas sensors and optoelectronic devices.

Helical tube triggered two-stage emission behavior for tetraphenylethene-functionalised hemicyanine dye: Better dispersion stronger fluorescence

Aggregation-induced emission (AIE) luminogens have recently received great attention for their wide applications in chemical sensors and biological probes. However, it remains a formidable challenge to render them multi-stage emission in one system. Herein, the emission of a tetraphenylethene (TPE)-functionalised hemicyanine dye (TPEBe-I) is awoken using a poly(m-phenylene diethynylene)-based helical tube (Poly-1) in aqueous buffer solution, although TPEBe-I alone shows an aggregation-caused quenching (ACQ) phenomenon due to the heavy atom effect of iodide. Upon increasing Poly-1, the dyes first dock on Poly-1 surface to form an aggregation complex via electrostatic interaction, and then intercalate into the tubular cavities of Poly-1 with a confined space in the single-molecular form. As the increase of Poly-1, the restriction of intramolecular motions of dyes changes from partial to sufficient, leading to an unusual AIE phenomenon of better dispersion stronger fluorescence. At last, the fluorescence intensity is enhanced by 160-fold. As a result, a two-stage emission behavior in a single system is achieved.

Recent progress in pillar[n]arene-based thin films on chemical sensor applications

Pillar[n]arene is one of the most favorited supramolecular materials that possess a special chiral structure. The major property of pillar-structured materials is their high cavity, and this structure is able to dominate the higher cavity values due to the big number of n (5,6,7) as hydroquinone units. Thanks to this significant property, pillar[n]arenes can be preferred to use in a wide application area. The chemical sensor application of pillar[n]arenes is one of the most applicable one, because they are more prominent than other macrocyclic skeletons (calixarene, crown ether, etc.) in the related area. Although the studies on chemical sensor application by using pillar[n]arenes as sensing elements have been performed so far, the thin film of these macrocyclic architectures, have been very limited in the available literature. Therefore, the recent developments of pillar[n]arene-based thin films and their chemical sensor applications are investigated and discussed in this review article.

Analysis of single and multi-wall carbon nanotubes (SWCNT/MWCNT) in the flow of Maxwell nanofluid with the impact of magnetic dipole

The study of non-Newtonian fluids flow over diverse geometries with significant physical implications has numerous applications in the manufacturing and engineering field. On the other hand, carbon nanotubes (CNT) have wide-ranging applications in nanotechnology, energy storage, industry, chemical sensors, conductive plastics, optics, and structural composite materials. Hence, the flow of Maxwell nanoliquid embedded with SWCNT/MWCNT over a stretching sheet with the consideration of thermal radiation and magnetic dipole is examined. The partial differential equations (PDEs) specifying the flow of liquid are transformed into ordinary differential equations (ODEs) with the assistance of suitable similarity transformations. The reduced ODEs are numerically solved by using Runge-Kutta Fehlberg 45 order (RFF 45) method with the aid of shooting scheme. Major result outcome unveils that, fluid velocity decreases with an upsurge of ferromagnetic interaction parameter thermal distribution enhances rapidly for heightening of Biot number and thermal radiation parameter. Rate of heat transfer growths with higher values of Biot number and thermal radiation parameter. Surface drag force enhances with heightens values of solid volume fraction but decreases for viscous dissipation parameter.

Gas Sensors Based on Copper Oxide Nanomaterials: A Review

Metal oxide semiconductors have found widespread applications in chemical sensors based on electrical transduction principles, in particular for the detection of a large variety of gaseous analytes, including environmental pollutants and hazardous gases. This review recapitulates the progress in copper oxide nanomaterial-based devices, while discussing decisive factors influencing gas sensing properties and performance. Literature reports on the highly sensitive detection of several target molecules, including volatile organic compounds, hydrogen sulfide, carbon monoxide, carbon dioxide, hydrogen and nitrogen oxide from parts-per-million down to parts-per-billion concentrations are compared. Physico-chemical mechanisms for sensing and transduction are summarized and prospects for future developments are outlined.

Bay-Substitution Effect of Perylene Diimides on Supramolecular Chirality and Optoelectronic Properties of Their Self-Assembled Nanostructures.

One-dimensional (1D) organic chiral supramolecules have received a great deal of attention for their promising applications in chiral recognition systems, chemical sensors, catalysts, and optoelectronics. Compared to modifications at the imide position of a perylene diimide (PDI), few studies have explored bay substitution of chiral PDIs and their self-assemblies into 1D nanomaterials. Herein, we describe the synthesis of three bay-substituted PDIs and explore the effects of bay substitution on supramolecular chirality by examining circular dichroism spectra and the optoelectronic performance of chiral PDI nanomaterials in phototransistors. Among the three fabricated self-assemblies, nanomaterials based on (R)-CN-CPDI-Ph exhibited the highest electron mobility of 0.17 cm2 V-1 s-1, a low threshold voltage of -1 V, and enhanced optoelectronic performance. For example, the photoresponsivity and external quantum efficiency of (R)-CN-CPDI-Ph assemblies were 4-fold higher than those of (R)-2Br-CPDI-Ph and (R)-2F-CPDI-Ph. All three nanomaterials exhibited fast switching speeds compared with previously reported N-substituted PDIs, suggesting that bay substitution can be an effective means of achieving rapid photoswitching. A comprehensive study using density functional theory calculations and crystal analyses revealed that the enhanced optoelectronic performance of (R)-CN-CPDI-Ph nanomaterials is related to the substitution of CN at the bay position of PDI. This minor change provides simultaneous improvements in electron injectability and structural order. Our findings demonstrate that bay substitution can significantly impact the self-assembly, supramolecular chirality, and optoelectronic properties of PDI nanomaterials.

Multi-layer hollow-core PMMA grating tube waveguides for THz sensing applications

Multi-layer hollow-core PMMA tube waveguides with varying grating structures were theoretically and experimentally investigated for the terahertz (THz) chemical material sensor applications. Compared with single-layer tube, the multi-layer cases can produce a delayed response in the time domain with an improved extinction ratio. A double tube combination consisted of a thick double-groove chirped grating tube and a thin single-groove chirped grating one can realize an improved detection sensitivity. With different extinction ratio of the measured THz spectra, ethanol and vinegar can be distinguished with a sensitivity of about 18 dB/mL. The proposed multi-layer hollow-core grating waveguide can be further applied for the THz gas sensing applications.

Polythiophene derivatives as chemical sensors: a DFT study on the influence of side groups.

Conjugated polymers have been considered promising candidates for applications in chemical sensors, mainly due to their high versatility of synthesis, low cost, light weight, and suitable optoelectronic properties. In this context, polythiophene (PT) derivatives have been successfully employed. However, at the same time that the versatility of the synthesis allows the production of varied derivatives, the complexity of interactions with analytes hinders an efficient design of compounds with improved sensing properties. In the present report, electronic structure calculations were employed to identify promising PT derivatives for chemical sensor applications. Structural, optoelectronic, and reactivity properties of a set of branched PT derivatives were evaluated. Adsorption studies considering different gaseous compounds were conducted for selected systems. The results suggest that an appropriate choice of the side groups can lead to derivatives with improved sensorial properties. In particular, PT-CN derivative was identified as the most promising compound for high sensitive chemical sensors towards SO2 and NH3 analytes.

Phosphorescent MoS2 quantum dots as a temperature sensor and security ink.

Currently, few phosphorescent materials (PMs) possess a long phosphorescence lasting time and have potential for application in chemical sensors. Herein, we disclose that the incorporation of few-layer molybdenum disulfide quantum dots (FL-MoS2 QDs) into poly(vinyl alcohol) (PVA) matrices leads to the emission of bright green phosphorescence with a long lasting time of 3.0 s and a phosphorescence quantum yield of 20%. This enhanced phosphorescence originates from the formation of O–H⋯S hydrogen bonding networks between the rich sulfur sites of the FL-MoS2 QDs and the hydroxyl groups of the PVA molecules, which not only rigidifies the vibration modes of the FL-MoS2 QDs but also provides an oxygen barrier. Further investigations reveal that the FL-MoS2 QD/PVA composites exhibit a longer phosphorescence lasting time than N,S-doped carbon dots, few layer tungsten disulfide quantum dots, Rhodamine 6G, and Rhodamine B in PVA matrices. Since heat efficiently induced the removal of water moisture from PVA matrices, the FL-MoS2 QD/PVA composites could be implemented for phosphorescence turn-on and naked-eye detection of temperature variations ranging from 30 to 70 °C. By contrast, the carbon dot/PVA composites were incapable of sensing environmental temperature due to their weak hydrogen bonding with the hydroxyl groups of PVA matrices. Additionally, this study reveals the potential of the FL-MoS2 QD/PVA composites as an advanced security ink for anti-counterfeiting and encryption applications. The given results could open a new direction for potential application of two-dimensional quantum dots in phosphorescence-based sensors and security inks.

Luminescent and thermal properties of novel orange\u2013red emitting MgNb2O6:Sm3+ phosphors for displays, photo catalytic and sensor applications

Novel Sm3+ doped columbite-type orthorhombic structured MgNb2O6 (MNO) orange-red emitting phosphors were prepared by solution combustion method using ODH as a fuel. The powder phase purity, particle morphology, size, elemental composition, luminescence properties, photocatalytic behaviors and electrochemical studies of prepared samples were studied in detail. Photoluminescence emission spectra of MNO:Sm3+ nanophosphors show all the characteristic emissions of Sm3+ cations corresponds to the transitions 4G5/2 → 6Hj/2(j=5,7,9,11) when excited at 463 nm energy. Among these the strongest emission peak was at 608 nm which corresponds to 4G5/2 → 6H7/2 transition of Sm3+ cations in the host lattice. The luminescence quenching was confirmed by the dipole–dipole interaction among Sm3+ ions. As a result of J-O analysis the branching ratio (~ 58% > 50%) show that the phosphor was highly suitable for color display devices. Photocatalytic activity of MNO:Sm3+ (5 mol%) under UV light shows 99% degradation of AR-88 dye. Electrochemical Impedance Spectroscopy (EIS) confirms the reversibility of the redox reaction, which helps in sensing the presence of paracetamol and alcohol. Thus, MNO:Sm3+ phosphors have great potential applications in display, catalytic, photonic, chemical and thermal sensor applications.