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A polyaniline/In2O3 nanofibre composite based layered surface acoustic wave (SAW) sensor has been developed and investigated for different gases. Chemical oxidative polymerization of aniline in the presence of finely divided In2O3 was employed to synthesize a polyaniline nanofibre/In2O3 nanoparticle composite. The nanocomposite was deposited onto a...
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... electron microscope (SEM) and transmission electron microscope (TEM) images of the nanocomposite are shown in Fig. 2 and Fig. 3 pattern is shown in Fig. 4, in which the sharp peaks are due to In 2 O 3 and the broader peaks at 2θ~26° are due to polyaniline [24]. The diffraction peaks from the nanocomposite sample are well matched to the sharp lines from the pure standard ...
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A double SAW resonator system was developed as a novel method for gas sensing applications. The proposed system was investigated for hydrogen sensing. Commercial Surface Acoustic Wave (SAW) resonators with resonance frequencies of 433.92 MHz and 433.42 MHz were employed in the double SAW resonator system configuration. The advantages of using this...
Citations
... These materials offer long response times, environmental stability, and high conductivity, making them ideal candidates for sensor applications. [83,84] Sensors based on conducting polymer nanocomposites are widely used for detecting various analyte vapours. For example, Shen et al. designed a PPy/rGO nanocomposite film gas sensor for ammonia gas using metal oxide semiconductor (MOS) and microelectromechanical (MEMS) techniques used in the deposition of the nanomaterials on the IDE surface. ...
Gas sensors are crucial in various industries like chemicals, food processing, pharmaceuticals, health monitoring through breath analysis, as well as in household and environmental monitoring to ensure human safety. Chemo‐resistive gas sensors based on metal oxides convert gas information into electrical signals by interacting with adsorption and desorption processes. For metal oxide semiconductor gas sensors, sensitivity and selectivity enhancements are achieved through doping, functionalization, composite formations, heterojunction creation, and morphological adjustments. The formation of heterojunctions notably boosts the efficacy of the sensing material, leveraging synergistic effects to reinforce adsorption rates, catalytic activity acceleration, and the depletion interface for electrons and holes. Over the past few decades, nanomaterials have played a critical role in gas sensing applications. They have enabled the detection of a wide array of harmful and polluting gases, as well as volatile organic compounds serving as disease biomarkers. Additionally, incorporating heterostructure nanomaterials into heterojunctions significantly impacts sensing performance and detection speed. This review discussed various types of gas sensing devices, categorizing them based on the sensing elements employed, each possessing its own set of unique advantages and disadvantages. Nevertheless, the review underscored the importance of several key parameters and factors that influence the performance of gas sensors. Additionally, recent advancements in the utilization of nanomaterial composites for gas sensor applications, particularly in the detection of gases such as ammonia, hydrogen sulphide, and sulphur dioxide vapours, were discussed. Furthermore, the review highlights recent research endeavours and fundamental parameters, including sensitivity, detection limits, selectivity, response times, and recovery times.
... Common materials such as conductive/non-conductive polymers and metal oxides have been chosen most often to recognise gas molecules [20,21]. But other materials have also been tested, including carbon-based nanostructures [22][23][24][25], composite materials [26,27], metals [28], metal-organic frameworks [29] and porous materials [30]. There are some reports in the literature on using a ferroelectric lead zirconium titanate (PZT) thin film as the sensing layer to improve the coupling coefficient of SAW devices [3,31,32]. ...
Thin film technology shows great promise in fabricating electronic devices such as gas sensors. Here, we report the fabrication of surface acoustic wave (SAW) sensors based on thin films of (1 − x) Ba(Ti0.8Zr0.2)O3−x(Ba0.7Ca0.3)TiO3 (BCTZ50, x = 50) and Polyethylenimine (PEI). The layers were deposited by two laser-based techniques, namely pulsed laser deposition (PLD) for the lead-free material and matrix assisted pulsed laser evaporation (MAPLE) for the sensitive polymer. In order to assay the impact of the thickness, the number of laser pulses was varied, leading to thicknesses between 50 and 350 nm. The influence of BCTZ film’s crystallographic features on the characteristics and performance of the SAW device was studied by employing substrates with different crystal structures, more precisely cubic Strontium Titanate (SrTiO3) and orthorhombic Gadolinium Scandium Oxide (GdScO3). The SAW sensors were further integrated into a testing system to evaluate the response of the BCTZ thin films with PEI, and then subjected to tests for N2, CO2 and O2 gases. The influence of the MAPLE’s deposited PEI layer on the overall performance was demonstrated. For the SAW sensors based on BCTZ/GdScO3 thin films with a PEI polymer, a maximum frequency shift of 39.5 kHz has been obtained for CO2; eight times higher compared to the sensor without the polymeric layer.
... The PCA analysis was performed to identify the presence of different VOCs. In [49], a ZnO/Y-X LiNbO 3 -based two-port resonator was used, and the dropcasted polyaniline/In 2 O 3 composite was used as the sensing layer. The lowest concentration of 60 ppm was successfully detected in the air. ...
... The sensor can detect the ammonia from 5 ppm to 100 ppm [17]. Sadek et.al [18] have developed a polyaniline/In 2 O 3 nanofiber sensor for H 2 , CO and NO 2 . Polyaniline is used for various gas detection such as methanol [19], hydrogen [20], ammonia [21], carbon dioxide [22] etc. Polyaniline titanium dioxide nanocomposite sensor is able to sense 23 ppm of ammonia gas [23]. ...
Polymer metal oxide nanocomposite (PMON) material is synthesized by the chemical oxidative polymerization. The synthesized nanocomposite is characterized by the Field Emission Scanning Electron Microscope (FESEM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). The FESEM images of the PANI (polyaniline) shows the formation of nanofibers of length 200 nm and diameter 50 nm. The FESEM micrograph composite shows that polyaniline is encapsulating the TiO2-Al3+ nanomaterials. The average size of the encapsulation is found to be 300 nm in diameter. The well defined peaks in the XRD spectra confirm the crystalline structure of TiO2-Al3+. Our sensor is able to detect up to 5 ppm concentration of ammonia gas. The sensor is stable up to 100 days and works at room temperature. The slight shift of base line is seen. The sensor is recovered automatically without flushing nitrogen gas. The sensor has the sensitivity of 1.0913 ppm-1
... It was observed clearly from the SEM image that PDI-CFF, in presence of Fe 3+ ion, formed nanofibers connected with each other in a dense network containing different pore size randomly distributed throughout the structures. 44,45 From the ImageJ measurement, it was observed that the pore size of the SEM images was about 220 nm. It can be shown from DLS data that the size ranges from 650 to 990 nm ( Figure S5c). ...
A dipeptide appended perylenediimide (PDI-CFF) fluorescent molecule was designed, synthesized and characterized. Though the molecule does not dissolve in any individual solvent, it dissolves well in an organic/water mixed solvent system such as tetrahydrofuran (THF)/water. This new fluorescent molecule was self-assembled in a THF/water mixture to form both nanofibrous network structures and a nano ring structure. It has shown nanofibril morphology by the interactions with ferric ions (PDI-CFF/Fe3+ system) with diminishing fluorescent property. Interestingly, L-ascorbic acid (LAA) interacts with the PDI-CFF/Fe3+ system, showing turn-on fluorescence. Another interesting feature is that the minimum detection limits for Fe3+ ions and LAA are at the sub-micromolar level of 6.2 × 10-8 M and 3 × 10-8 M, respectively. Moreover, the fluorescent (10 μM) signals can be monitored by the naked eye under hand-held UV lamp irradiation at 365 nm, and this is very convenient for the real application. In this study, the molecule offers the opportunity for processing these sequential fluorescence responses in order to fabricate a combinatorial molecular logic gate that includes NOT, AND and OR simple logic gates using chemical stimuli (ferric ions and LAA) as inputs and fluorescence emission at 536 nm as output. The detailed mechanism of interactions of Fe3+ with PDI-CFF and LAA with the PDI-CFF/Fe3+ system is vividly studied by using FT-IR analysis and fluorescence. Moreover, this new molecule was reusable for several times without significant loss of its activity. The construction of logic gates using biologically important molecules/ions holds future promise for the design and development of new bio-logic gates.
... The morphology structure, such as surface analysis, porosity, crystallinity, etc. may affect the sensing behaviour [24]. The morphology structureincluding the shape and size of Ti 3 AlC 2 MAX phase powder and the Ti 3 C 2 MXene nano-sheet was studied by SEM, which are predicted in Fig. 5 (a-1 &a-2)and Fig. 6 (b-1 -b-3) respectively. ...
In 2011 MXenewas discovered and due to their 2-D structure with excellent metallic like conductivity and chemical active surface properties these are useful for gas sensing application. There are several routes, viz. acidic etching and chemical vapor deposition (CVD), which have been use to fabricated 2D MXene. Generally, 2-D MXenenanosheet is fabricated by selective etching thelayersfrom the MAX phases with toxic fluorine-based acids. In the present work, MXenenanosheets were prepared in a two-steps,in which, firstly MAX phase (Ti 3 AlC 2) percussor was synthesized thenin next stepMXene(Ti 3 C 2) nanosheets was synthesized by selective etching of Al layer using hydrofluoric (HF) acid, for long hours of stirring. The hydrogen sensing behaviour was detected by monitoring the change in resistance withthe time after hydrogen gas exposure using computer control indigenously developed hydrogen gas storage and sensing setup. In results we found that the fabricated sensor shows the response of~1.24 towards hydrogen gasat room temperature. The structural order and surface characteristic properties of fabricated MXene samples have also been examined by XRD, Raman and SEM techniques.
... Indeed, in 1979, Wohltjen and Dessy [84,85] first demonstrated the application and possibility of chemical/gas sensors based on SAW devices. Since then, by depositing different sensitive layers, SAW device-based gas sensors have been developed for detection of H 2 [86], H 2 S [87,88], NO 2 [89,90], CO 2 [89], CH 4 [91], SO 2 [92], NH 3 [93], O 3 [94], O 2 [95], CO [96], volatile organic compounds (VOCs) [97][98][99], explosives [100,101], etc. In 2022, Singh et al. [102] reported a SAW-based particulate matter (PM2.5) ...
The past few decades have witnessed the ultra-fast development of wireless telecommunication systems, such as mobile communication, global positioning, and data transmission systems. In these applications, radio frequency (RF) acoustic devices, such as bulk acoustic waves (BAW) and surface acoustic waves (SAW) devices, play an important role. As the integration technology of BAW and SAW devices is becoming more mature day by day, their application in the physical and biochemical sensing and actuating fields has also gradually expanded. This has led to a profusion of associated literature, and this article particularly aims to help young professionals and students obtain a comprehensive overview of such acoustic technologies. In this perspective, we report and discuss the key basic principles of SAW and BAW devices and their typical geometries and electrical characterization methodology. Regarding BAW devices, we give particular attention to film bulk acoustic resonators (FBARs), due to their advantages in terms of high frequency operation and integrability. Examples illustrating their application as RF filters, physical sensors and actuators, and biochemical sensors are presented. We then discuss recent promising studies that pave the way for the exploitation of these elastic wave devices for new applications that fit into current challenges, especially in quantum acoustics (single-electron probe/control and coherent coupling between magnons and phonons) or in other fields.
... Sadek and co-workers prepared the composite structure from PANI and In 2 O 3 using in situ chemical polymerization method for sensing hydrogen, carbon monoxide, and NO 2 [231]. However, the CPNC structure comprised of PANI and WO 3 was used for efficient detection of NH 3 , H 2 , trimethylamine gas due to the adsorptive and catalytic nature of WO 3 [232]. ...
Advances in conducting polymer-based nanocomposites (CPNCs) as sensing materials offer unique prospects to apprehend previously inaccessible sensing properties and applications. In this review article, the synthesis and properties of CPNCs are highlighted as pioneer transducers for designing advanced sensing devices. Synthetic strategies of CPNC are also discussed in the brief and classified into ex-situ and in-situ categories employing (1) chemical; (2) electrochemical; (3) photochemical; and (4) hybrid approach. The composite structure of conducting polymers (CPs), with inorganic and organic compounds, has enhanced surface adsorption, responsiveness, catalytic, and/or electron transport behavior for sensing applications. Thus, CPNCs are explored to sense atmospheric gases, humidity, explosives, water pollutants, and food adulterants. The literature reveals that sensor technology has been effectively improved in terms of sensitivity and selectivity due to progress in CPNCs. However, there are still several technical challenges that need to be solved for CPNCs based sensor technology. Herein, the key issues regarding the use of CPNC based materials in the development of state-of-the-art sensors are discussed. Furthermore, a perspective on the next-generation sensor technology concerning materials has been demonstrated with exclusive examples of conducting polymers based nano composite.
... For this purpose, the development of gas sensitive materials has shown a new trend from single materials to composite materials, including single metal inorganic semiconductors to compound inorganic semiconductors, organic semiconductors, conductive polymers, and nanocomposite materials [8]. As a new material, the conductive polymer is sensitive to specific gases at room temperature, which has attracted extensive attention [9][10][11]. ...
The development of rapid response gas sensors for the detection of the ammonia gas in the air at room temperature remains many challenges, limited by the unsatisfactory sensing characteristic. In this work, H2SO4-doped polyaniline (H2SO4/PANI) was synthesized by chemical oxidation polymerization, and the effects of different working environments, mainly temperature and humidity, on the gas sensitive properties of PANI were systematically studied. X-ray diffraction, SEM–EDS, FT-IR, and Raman detection techniques were used to study the changes in phase and morphology structure of doped PANI materials. The sensing H2SO4/PANI was found to be highly selective toward ammonia gas. The performance was stable and highly repeatable when exposed to the different concentrations of ammonia several times. The excellent ammonia sensing capability of the doped PANI sensor even in a humid environment and when operated at room temperature made it a suitable candidate for environmental monitoring. It resulted that the response recovery process, selectivity, repeatability, and stability of PANI materials were analyzed, which laid a foundation for further study of the gas sensitive mechanism of PANI matrix composites.
... 32 Most novel techniques involve in situ polymerization (chemical or electrochemical) of polyaniline on the transducer (yielding high surface area nanofibers) 4,39,40 or nanoparticles seeded into the polymer matrix. 3,29,[31][32][33][34] Table I lists the typical processing of polyaniline-based environmental gas sensors. Dopant choice can influence the overall sensor response to target analytes. ...
Polyaniline is a conducting polymer in which both redox and protonating/ deprotonating conduction mechanisms are activated in the presence of gaseous compounds, making it a gas sensor. Resistive chemosensors based on PANI, in particular, have been well studied for their gas sensing properties and are considered important sensing materials for a wide range of applications as they operate at room temperature. There is, however, a novel class of polyaniline hybrids with cellulose acetate that may be suitable for detecting biomarkers emitted from the skin and in measuring the pH of breath condensate for diseases and thus, worth studying them further.
