Design Of Chemical Sensors Research Articles

A Diagnostic Case Study for Manufacturing Gas-Phase Chemical Sensors

In this work, we describe the design, manufacturing development, and refinement of a chemical detection platform designed to identify specific odorants in the natural gas industry. As the demand for reliable and sensitive volatile organic compound (VOC) detection systems is growing, our project aimed to construct multiple prototypes to enhance our detection capabilities and provide portable detection platforms. Throughout the development process across nominally identical and duplicated instruments, various failure modes were encountered, which provided insight into the design and manufacturing challenges present when designing such platforms. We conducted a post hoc root cause analysis for each failure mode, leading to a series of design modifications and solutions. This paper details these design and manufacturing challenges, the analytical methods used to diagnose and address them, and the resulting improvements in system performance. In the end, a debugging flow chart is presented to aid future researchers in solving the possible issues that could be encountered. Our findings show the complexities of bespoke chemical sensor design for unique applications and highlight the critical importance of iterative testing and problem-solving in the development of industrial detection technologies. Achieving consistency across devices is essential for optimizing device-to-device efficiency. The work presented is the first step towards ensuring uniform performance across a production run of chemically sensitive devices. In the future, a universal device calibration model will be implemented, eliminating the need to collect data from each individual device.

Synthesis, Characterization, and Application of TiO2 Nanorods for Hydrazine Sensing

This paper presents a comprehensive investigation into the synthesis, characterization, and application of titanium dioxide (TiO2) nanorods for the purpose of hydrazine chemical sensing. The nanorods were efficiently prepared through a low-temperature chemical synthesis process, and a detail characterization process was undertaken to assess their structural, morphological, compositional, and sensing properties. Employing sophisticated techniques such as field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM), the morphological characterizations unveiled a high-density growth of diminutive nanorods. Crystallographic examinations confirmed the exceptional crystallinity of the synthesized nanorods, showcasing a predominant anatase phase. These insights into the structural and morphological attributes contribute to a profound understanding of the nanorods’ potential in various applications. Notably, this study focuses on the utilization of TiO2 nanorods as electron mediating materials for the fabrication of a hydrazine chemical sensor. The fabricated sensor exhibited commendable sensitivity, registering a current response of 4.69 μA·μM−1·cm−2, coupled with a remarkably low detection limit of 174 μM. The outcomes of this investigation underscore the promising role of TiO2 nanorods as effective electron mediators in chemical sensor design. This work establishes a foundation for the development of sensors capable of detecting a spectrum of hazardous and toxic chemicals, with a specific emphasis on hydrazine.

Synthesis of new Tetrazole based-semiconducting polymers for optoelectronic application: Study of the effect of anthracene group on photophysical properties

This work aims to synthesize and characterize a new semiconducting anthracene-based polymer Poly-Tet-An-Is and its analogue anthracene-free Poly-Tet-Is. The two materials contain the Tetrazole group in the backbone and the Isosorbide group in the side chain. The polymers have been prepared through click chemistry polymerization. The effect of the anthracene group on photophysical and electrochemical proprieties, is investigated. Thermal characterization shows that the two polymers have a good thermal stability up to 330°C. The optical properties of these materials were explored by UV-vis absorption and photoluminescence spectroscopies. The UV-vis absorption spectrum reveals that the presence of anthracene group in the backbone limits the intramolecular interaction in dilute solution and the π-stacking in the thin film by its steric effect. The photoluminescence spectra reveals that the polymer Poly-Tet-Is has a blue emission in dilute solution and thin film. However, the Poly-Tet-An-Is emission shifted from blue to green, going from dilute solution to the thin film, respectively. Density Functional Density (DFT) has been used to evaluate the macromolecular geometry of both polymers and showed a remarkable variation in geometry depending on the incorporation of the anthracene group. An analysis by RDG was carried out on the optimized structures of the two organic materials in order to prove the intarmolecular interactions and its influence on their geometries.The interested photophysical properties of our new materials as well as the presence of the Tetrazole group in the main chain, could be applied in the design of chemical sensors and blue Organic light-emitting diode (OLED).

Polymerization of new aniline derivatives: synthesis, characterization and application as sensors.

This work is focused on modifying aniline monomers with various characteristics that allows one to study the effect of the substituent on the respective polymer. A series of new polyaniline (PANI) derivatives based on an ortho-substituted aniline derivative, 2-(1-methylbut-2-en-1-yl)aniline, were synthesized and characterized. The structures and composition of the polymers that we synthesized were confirmed by elemental analysis, proton nuclear magnetic resonance (1H NMR) spectroscopy, carbon nuclear magnetic resonance (13C NMR) spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), and ultraviolet-visible spectroscopy (UV). Characterization by FT-IR and UV-visible spectroscopy techniques indicated that the polymers exist in protonated emeraldine forms. Scanning electron microscope (SEM) results revealed that the surface morphology of the resulting polymers changed from a heterogeneous hierarchical to spherical structure upon changing the substituent in the aniline monomers. The polymers are soluble in common organic solvents, so they can be used to make films. The electrical properties of the polymers were studied and their high sensitivity to moisture and ammonia was demonstrated. The results of the studies showed the prospects of using thin polymer films in the design of chemical sensors. The impact of the substituent on the polymer characteristics is rationalized in terms of steric and electronic effects.

Flexible Chemical Sensors Using Signal Generation from Cyclodextrin-Analyte Interactions on Polymer Composites

We present the design of a chemical sensor and study the generation of electrical signals produced by the formation of a cyclodextrin inclusion complex. Flexible poly(dimethylsiloxane)/graphene hybrid composites were used as sensor substrates and sensing media, beta-cyclodextrin (beta-CD) molecules were incorporated using simple bio-coupling reactions. The feasibility of sensing molecules through the formation of beta-CD/analyte inclusion complexes was investigated systematically using direct electrical measurement. The acquisition and transduction of electrical signals generated by inclusion complex formation is a central focus of this study and extensive complementary experiments were carried out to characterize this phenomenon. Because it is useful for development of a sort of sensor system, electrical measurements were performed to measure the sensitivity of this system (10 nM). However, more study is required to determine the selectivity. This article will be a useful reference for the design of versatile chemical sensors utilizing a non-toxic sensing medium on flexible composite substrates.

Determination of Cr(III) ions based on plasmonic sensing and anodic stripping voltammetry with amplification of Ag nanoparticles

In this paper mercapto succinic acid (MSA) capped gold nanoparticles (AuNPs) upon indium tin oxide (ITO) glass strips (ITO/AuNPs/MSA) have been used as platform for detection of Cr(III) ions. Cr(III) ions can be immobilized on the surface of AuNPs through formation of complex with MSA, allowing the development of plasmonic and electrochemical methods in assays. The plasmonic sensing is based on the formation of complex between ITO/AuNPs/MSA-Cr(III) and BSA as the second complexant, resulting the red-shift of plasmonic AuNP peak due to the change of environmental refractive index. The concentration of Cr(III) ions could be detected in the linear range of 10 nM–1 mM. On the other hand, the electrochemical method is based on the formation of complex between ITO/AuNPs/MSA-Cr(III) and MSA capped silver nanoparticles (MSA/AgNPs), in which Ag can be detected by anodic stripping voltammetry. With the amplification of AgNPs, the sensitivity of the Cr(III) detection was further improved. The stripping current was found to be linearly proportional to the concentration of Cr(III) ions from 0.1 to 10 nM with detection limit of 0.05 nM. The proposed both methods have great potential in the design of chemical sensors for detection of metal ions in field analyses.

Synthesis and physicochemical properties of poly[2‐(2‐chloro‐1‐methylbut‐2‐en‐1‐yl)aniline] obtained with various dopants

AbstractHighly soluble polyaniline was synthesized from a newly designed aniline derivative, namely 2‐[2‐chloro‐1‐methylbut‐2‐en‐1‐yl]aniline. The corresponding polyanilines, PClPA‐HA, PClPA‐SA, PClPA‐NA and PClPA‐PA, were characterized by means of 1H NMR, 13C NMR, high resolution mass spectroscopy, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy and SEM images. The elemental analysis and electrical conductivity of the polymers are also presented. It is shown that the molecular weight of the polymers obtained depends on the method of synthesis. Spectroscopic studies confirmed the emeraldine form of the polyaniline derivatives. In the work, the dependence of the current passing through resistive structures based on thin poly[2‐(2‐chloro‐1‐methylbut‐2‐en‐1‐yl)aniline] films on the relative humidity of air was studied. The results of the studies showed the prospects of using thin polymer films in the design of chemical sensors. © 2020 Society of Chemical Industry

Design of chemical sensor based on dual core photonic crystal fiber

A chemical sensor based on dual core photonic crystal fiber (DC-PCF) is designed using COMSOL Multiphysics software based on finite element method. The two cores of the PCF are separated by an air hole and filled with different chemicals such as benzene, ethanol and water. The fundamental modes of the proposed DC-PCF are analyzed, and the maximum coupling length of the proposed sensor is 0.45 mm at 1.55 µm wavelength. Numerical simulation results show that the proposed DC-PCF sensor with a length of 0.5 cm provides a sensitivity of 9615 nm/RIU (refractive index unit).

Synthesis of a Novel Zn-Salphen Building Block and Its Acrylic Terpolymer Counterparts as Tunable Supramolecular Recognition Systems.

In this work, we present the synthesis of a novel Zn-Salphen complex containing an allyl group, which was used as building block in the further preparation of a new family of functional terpolymers. These polymers were obtained through radical co-polymerization with methyl metacrylate (MMA) and n-butyl acrylate (nBuA) in different ratios. The supramolecular recognition behavior of each polymer was evaluated via potentiometric measurements against selected anions in aqueous media. Interestingly, this proof of concept study shows that these systems were selective against only fluoride (F−) or both, fluoride and acetate (OAc−), by tailoring the relative content of Zn-Salphen monomer, thus making them a promising starting point for modular design of chemical sensors through straightforward synthetic approaches.

Surface Modifications for Photon-Upconversion-Based Energy-Transfer Nanoprobes.

An emerging class of inorganic optical reporters are near-infrared (NIR) excitable lanthanide-based upconversion nanoparticles (UCNPs) with multicolor emission and long luminescence lifetimes in the range of several hundred microseconds. For the design of chemical sensors and optical probes that reveal analyte-specific changes in their spectroscopic properties, these nanomaterials must be combined with sensitive indicator dyes that change their absorption and/or fluorescence properties selectively upon interaction with their target analyte, utilizing either resonance energy transfer (RET) processes or reabsorption-related inner filter effects. The rational development of UCNP-based nanoprobes for chemical sensing and imaging in a biological environment requires reliable methods for the surface functionalization of UCNPs, the analysis and quantification of surface groups, a high colloidal stability of UCNPs in aqueous media as well as the chemically stable attachment of the indicator molecules, and suitable instrumentation for the spectroscopic characterization of the energy-transfer systems and the derived nanosensors. These topics are highlighted in the following feature article, and examples of functionalized core-shell nanoprobes for the sensing of different biologically relevant analytes in aqueous environments will be presented. Special emphasis is placed on the intracellular sensing of pH.

Independent tunable multi-band absorbers based on molybdenum disulfide metasurfaces.

In this paper, we theoretically and numerically demonstrate a dual-band independently adjustable absorber comprising an array of stacked molybdenum disulfide (MoS2) coaxial nanodisks and a gold reflector that are separated by two dielectric insulating layers. The array plane functionality is explained by the dipole resonances with the MoS2 nanodisks. As a result, strong absorption is achieved at a wide range of incident angles under TE and TM polarizations. The structural parameters of the entire array and the carrier concentration in the MoS2 layers were varied to get the optimized absorption. The absorptance positioning can be adjusted by scaling the diameters of the MoS2 disks. We also proposed the array modification where nanodisks are replaced by a layer with nanoholes. The position of both absorptance peaks can be adjusted individually by changing the carrier concentration in the array. This structure can be useful for the design of chemical sensors, detectors or multi-band absorbers.

Solvent-induced modulation of the chemical sensing performance of gold nanoparticle film chemiresistors

The analyte sensitivity of a chemical sensor is commonly tuned by the type of chemical recognition element. Here, it is shown that the solvent also plays a critical role in the sensing performance of thiol-capped gold nanoparticle film chemiresistors. Both the resistance change and speed of response of the chemiresistor can be optimised by adjusting the composition of methanol and water used for detection of the pesticide permethrin. It is shown that the resistance change is governed by the partitioning of the analyte between the thiol coating of the gold nanoparticles and the solvent. The partition coefficient, log P, has a strong influence on the response magnitude and is directly correlated to the response time. By varying the solvent, the log P of extremely high partitioning analytes such as permethrin in water can be lowered, and a much larger resistance change can be obtained in a shorter time period (5 min). A theoretical model is developed that correlates the experimental findings to changes in analyte partition coefficient with solvent type and composition. The results have significant implications for the design of chemical sensors and solvent conditions that can offer an enhanced signal within a practical timeframe.

Enhanced room temperature gas sensing of aligned Mn3O4 nanorod assemblies functionalized by aluminum anodic membranes

The study includes a conductometric chemical sensor design using aligned Mn3O4 nanorods. Nanostructuring is an emerging field of prominence due to its capacity to introduce unprecedented properties in materials with potential applications. A hydrothermally prepared in situ Mn3O4 sample appears with an urchin rod-like morphology, which changes to a spherical shape upon annealing. An aluminum anodic membrane/template (AAO) is used for the growth of the nanorods and also as a medium to support the sensor. The aligned Mn3O4 nanorods are formed in the pores of the AAO by vacuum infiltration approach, which is later on annealed. The gold electrical contacts are deposited on the top or bottom ends of the Mn3O4-embedded AAO to ensure conductometric sensing along the length of the Mn3O4 nanorods. In comparison to the Mn3O4 film-based sensor, the Mn3O4 nanorods in the AAO template have enhanced sensitivity for detecting ethanol and acetone vapor at room temperature. The novel property observed is a result of the large surface area and number of oxygen vacancies of the uniformly aligned and parallel assemblies of the nanorods. The sensor exhibits the lowest response time at 4 s for ethanol and 2 s for acetone at room temperature with a concentration of 50 ppm. The response time is 7 and 5 s, respectively, for 25 ppm. The maximum sensitivities of the sensor at room temperature for ethanol and acetone gases are 67% and 68%, respectively, for 50 ppm concentration. The growth mechanism of the aligned nanorods formed in the AAO template is well established through FESEM analysis. The XPS and HRTEM study give additional evidence for the presence of oxidation states and structure of the prepared nanostructures, respectively.

A model for the electric conduction in metal/poly-TiO2/metal structure

Intensely studied memristive devices have M′/MO/M″ structures, wherein MO is a nanometer-sized metal oxide crystallite sandwiched between the M′ and M″ metal electrodes. The most widely used oxide for this purpose is TiO2 and the electrodes are of noble metals such as platinum, silver, and gold. The memristive features of the device is believed to originate from the motion of the ionized oxygen vacancies within the oxide crystal. The operation of the device is further complicated by the motion of the mobile cations originating from the metal electrodes. The complexity of the device performance increases further when the noble metal electrodes form Schottky barriers at their junctions with TiO2, as the conduction takes place through these energy barriers. In a recent publication, the authors have shown that, owing to the ohmicity of the Ti/TiO2 junctions, electronic observations on the devices with Ti/TiO2/Ti structure can be easier to model. The presented model clarified that in a Ti/poly-TiO2/Ti structure, the ionic motion and the electronic conduction take place on the TiO2 grain surfaces and grain boundaries rather than the grain interiors. Here, we show that the suggested model has important implications for chemical sensor design and fabrication.

A Fuel Cell Sensing Platform for Selective Detection of Acetone in Hyperglycemic Patients

In this work, a three-electrode fuel cell sensor is integrated with a miniaturized potentiostat (LMP91000) and a microcontroller (nRF51822) for selective detection of acetone. Elevated level of acetone in breath or sweat is an indication of systemic ketosis, hyperglycemia or type-I diabetes [1]. Rise of ketone concentrations leads to an increase in acid levels in the blood, called ‘Ketoacidosis’. Ketoacidosis is a serious hyperglycemic condition in patients with type-I diabetes. Among the conventional sensing methods (e.g. breathalyzer for lung ketone analysis, chemical strips, laboratory blood test and urine test), continuous monitoring is a challenge [2]. Also, though real time detection of acetone from different biofluids is promising, interference from other biomarkers remains an issue [3]. To address the above in non-invasive detection, we have developed a statistical model and algorithm which enable separation of signals and eliminate interference from other associated biomarkers. In the developed sensing platform, our fabricated sensor comprises an electrolyte membrane, nafion and monel mesh, as electrodes. Catalytic oxidation of acetone occurs on the working electrode in presence of moisture while oxygen is reduced on the counter electrode. Applying a constant potential across the working and reference electrodes, current is measured between the working and counter electrodes. With the change of concentrations of acetone, the current varies linearly. From this study, it is observed that the sensor is capable to detect as low as 1 ppm of acetone with the sensitivity of 60 nA ppm-1 cm-2. The developed platform has been based on the pre-calibrated data to interpret precise measurement of acetone. Reference: Matzeu, G.; Florea, L.; Diamond, D. 2015. Advances in wearable chemical sensor design for monitoring biological fluids, Sensors and Actuators B, 211:403–418.Tricoli, A.; Nasiri, N.; De, S. 2017. Wearable and Miniaturized Sensor Technologies for Personalized and Preventive Medicine, Advanced Functional Materials, 27(15): 1-19.Jalal, A. H.; Umasankar, Y.; Gonzalez, P. J.; Alfonso, A.; Bhansali, S. 2017. Multimodal technique to eliminate humidity interference for specific detection of ethanol, Biosensors and Bioelectronics, 87(15): 522–530.

Layer-by-Layer Approach for Design of Chemical Sensors and Biosensors

The review highlights the application of Layer-by-Layer (LbL) structures for the design of chemical sensors. The first part of this review focuses on atomic and molecular layer deposition from vapor phase. In the second and third parts of the review we emphasize the formation of multilayers from solutions. LbL films and LbL prepared capsules are considered as elements of sensing systems. It is shown that LbL nanostructures can significantly increase sensitivity and selectivity of sensors and biosensors. Different materials for the multilayers’ formation, deposition techniques, and mechanisms for enhancement of the sensing properties are discussed. Keywords: Atomic and molecular layer deposition, biosensors, layer-by-layer, multilayers, sensors.

Field effect transistor with integrated microfluidic channel as pH sensor

This paper presents an original design of chemical sensors with an integrated microfluidic channel. Targeted applications are pH-meters devices. The integration of the microfluidic channel allows decreasing the volume required for each measurement. The sensing part of the device consists of a field effect transistor (FET) with a suspended gate directly performed above the fluidic channel. Chemicals under test are driven through the sensing area between the electrical channel of the FET and the suspended gate. By this way products that flow in the microfluidic channel directly module the concentration of charges inside the transistor’s gap and thus induce changes in the transfer characteristic. This paper describes the fabrication process and the technological choices for materials. Electrical tests, performed in air and in liquid, have shown a good behavior of the transistor, linked to a good mechanical sustain of the fluidic channel. The system is able to detect transition between air and liquid media. Moreover, it has shown a high sensitivity (about 300 mV/pH) to pH measurements.

Special issue for the 2nd International Congress on Advanced Materials

It may be somewhat unexpected to find a special issue of Chemical Monthly dealing with materials science, because the journal is of course especially well known among scientists focusing on synthetic chemistry. However, as the borders between different natural sciences diminish, this is even more so for dividing lines within a specialization such as chemistry. The main challenges in synthetic chemistry are dominated by two driving forces: one is to design novel functional molecules or to find practicable synthetic strategies, especially targeting diagnostics and treatment of diseases; the other is to design novel, high-performance materials to ensure cost-effective and sustainable technological development. The strong interest in the field of developing and designing novel materials leads to a correspondingly large number of conferences on materials science each year. This special issue of Chemical Monthly collects papers presented at the 2nd International Congress on Advanced Materials (AM2013; http://am2013.ujs.edu.cn) held at Jiangsu University, Zhejiang, PR China, from May 16th to 19th, 2013. It brought together almost 600 scientists from China and abroad. The organizing committee of this relatively new conference series consists of an international group of scientists strongly rooted in China, Europe, North America, and Africa and is supported by the International Union of Advanced Materials (http://www.iuam.org) and the Chinese Advanced Materials Society (http://www.thecams. org). The conference was held for the second time in 2013, having been organized before in Jinan in 2011. Chemical Monthly has agreed to be one of the journals to publish selected topics presented at ICAM 2013 to an international audience. After peer review, the 34 papers collected in this issue remained. They cover a very broad range of topics with slight emphasis on analytical applications, be it materials analysis or the use of materials science for improving analytical apparatus. Here, special attention is paid to the design of chemical sensors. This is in a way natural, because sensors aim at providing goodvalue analysis, albeit for exactly defined analytical tasks. Generally, the papers clearly represent the shift of materials science from dealing with somewhat ‘‘classical, inorganic’’ solid-state discussions towards both organic structures and the very dynamically developing field of nanotechnology. Both of course allow for tailoring material functionalities on the way to so-called smart materials. In line with this discussion on functionality is the increasing interest in materials synthesis inspired directly by nature, i.e., biomimetic approaches. It has been a great pleasure and honor for me to act as a guest editor for this issue of Chemical Monthly. I hope that all readers find these papers as enjoyable and useful as the participants at the conference. In addition, I also want to thank the editorial board of Chemical Monthly for their constant support in bringing this issue together. I would be especially pleased if it would motivate some readers to attend the 3rd International Congress on Advanced Materials, which is planned for 2015 and will be announced in due time.

Carbon nanotubes and graphene in analytical sciences

Nanosized carbon materials are offering great opportunities in various areas of nanotechnology. Carbon nanotubes and graphene, due to their unique mechanical, electronic, chemical, optical and electrochemical properties, represent the most interesting building blocks in various applications where analytical chemistry is of special importance. The possibility of conjugating carbon nanomaterials with biomolecules has received particular attention with respect to the design of chemical sensors and biosensors. This review describes the trends in this field as reported in the last 6 years in (bio)analytical chemistry in general, and in biosensing in particular.

Electrochemical impedance detection of Hg2+, Ni2+ and Eu3+ ions by a new azo-calix[4]arene membrane

Due to their recognition properties and efficiency for the detection of toxic metals, calixarenes have already found applications in the design of chemical sensors based on using an electrochemical transduction. In this study, a new chromogenic azo-calix[4]arene derivative was deposited on gold electrode by spin coating to develop a new electrochemical sensor. Adhesion and morphological properties of the membrane have been firstly developed using contact angle measurements and scanning electronic microscopy (SEM) respectively. Electrochemical impedance spectroscopy (EIS) is used to study the response of the calixarenes membrane in contact with aqueous solutions of various metallic cations. The impedance behavior of the structures has been modeled by an equivalent circuit using the Z-View software. This technique has shown a selective response of this membrane towards Hg2+, Ni2+ and Eu3+. The differences in selectivity are found to be represented by variations in the resistance of the membrane (Rm) and in the charge transfer resistance (Rct) of the interface. Variation of CPE1 and CPE2 have been also investigated which were correlated to the porosity of the film and the exchange of the charge between the substrate and the electrolyte respectively.