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•A benzothiazolinic spiropyran was synthesized with subsitutent at a unique position to bind metal ions.•The structure of the spiropyran derivative was established through x-ray ...crystallography.•The spiropyran derivative selectively detected highly toxic Hg2+ ions in aqueous solution.•The selectivity of the receptor was established using naked eye, digital imaging and spectroscopic techniques.•Computational studies established the stabilities of different stereoisomers of the receptor and their complex.
A substituted benzothiazolinic spiropyran was synthesized through a reaction between 2-hydroxy-3-methoxy-5-nitrobenzaldehyde and 2-ethyl-3-methylbenzodthiazol-3-ium-4-toluenesulfonate in the presence of piperidine. The spiropyran derivative was characterized using IR, NMR, mass and SCXRD analysis. Owing to the presence of a methoxy group ortho to the phenolic oxygen atom, the affinity of the synthesized spiropyran derivative towards toxic metal ions was investigated in CH3CN: water (1:1). A hypsochromic shift in the absorption and fluorescence spectra was observed in response to the presence of Hg2+ ions. The formation of complex was also observed through a visible change in color from dark yellow to colorless. UV–vis, fluorescence spectroscopy and digital image analysis were used to obtain good limit of detection value (5.5 μM, 78.5 nM and 0.62 μM, respectively) for the receptor towards Hg2+ ions. The 1H-NMR spectroscopy indicated the interaction of the phenolic oxygen atom and Hg2+ ions. The density functional theory was further used to investigate the stabilities of the different stereoisomers of the spiropyran derivative and their complex. The DFT studies also supported the interaction between the phenolic oxygen atom and the Hg2+ ions. TD-DFT studies were also performed to analyze the observed changes in the UV-Visible spectra upon addition of the Hg2+ ions, which indicates an increase in the HOMO-LUMO gap.
Morphology and structure play a crucial role in influencing the performance of gas sensors. Hollow structures, in particular, not only increase the specific surface area of the material but also ...enhance the collision frequency of gases within the shell, and have been studied in depth in the field of gas sensing. Taking SnOsub.2 as an illustrative example, a dual-shell structure SnOsub.2 (D-SnOsub.2) was prepared. D-SnOsub.2@Polyaniline (PANI) (DSPx, x represents D-SnOsub.2 molar content) composites were synthesized via the in situ oxidative polymerization method, and simultaneously deposited onto a polyethylene terephthalate (PET) substrate to fabricate an electrode-free, flexible sensor. The impact of the SnOsub.2 content on the sensing performance of the DSPx-based sensor for NHsub.3 detection at room temperature was discussed. The results showed that the response of a 20 mol% D-SnOsub.2@PANI (DSP20) sensor to 100 ppm NHsub.3 at room temperature is 37.92, which is 5.1 times higher than that of a pristine PANI sensor. Moreover, the DSP20 sensor demonstrated a rapid response and recovery rate at the concentration of 10 ppm NHsub.3, with response and recovery times of 182 s and 86 s.
The gas sensitivity of the W defect in WSsub.2 (Vsub.W/WSsub.2) to five toxic gases—HCHO, CHsub.4, CHsub.3HO, CHsub.3OH, and CHsub.3CHsub.3—has been examined in this article. These five gases were ...adsorbed on the Vsub.W/WSsub.2 surface, and the band, density of state (DOS), charge density difference (CDD), work function (W), current–voltage (I–V) characteristic, and sensitivity of adsorption systems were determined. Interestingly, for HCHO-Vsub.W/WSsub.2, the energy level contribution of HCHO is closer to the Fermi level, the charge transfer (B) is the largest (0.104 e), the increase in W is more obvious than other adsorption systems, the slope of the I–V characteristic changes more obviously, and the calculated sensitivity is the highest. To sum up, Vsub.W/WSsub.2 is more sensitive to HCHO. In conclusion, Vsub.W/WSsub.2 has a great deal of promise for producing HCHO chemical sensors due to its high sensitivity and selectivity for HCHO, which can aid in the precise and efficient detection of toxic gases.
A photoacoustic sensor system (PAS) intended for carbon dioxide (COsub.2) blood gas detection is presented. The development focuses on a photoacoustic (PA) sensor based on the so-called two-chamber ...principle, i.e., comprising a measuring cell and a detection chamber. The aim is the reliable continuous monitoring of transcutaneous COsub.2 values, which is very important, for example, in intensive care unit patient monitoring. An infrared light-emitting diode (LED) with an emission peak wavelength at 4.3 µm was used as a light source. A micro-electro-mechanical system (MEMS) microphone and the target gas COsub.2 are inside a hermetically sealed detection chamber for selective target gas detection. Based on conducted simulations and measurement results in a laboratory setup, a miniaturized PA COsub.2 sensor with an absorption path length of 2.0 mm and a diameter of 3.0 mm was developed for the investigation of cross-sensitivities, detection limit, and signal stability and was compared to a commercial infrared COsub.2 sensor with a similar measurement range. The achieved detection limit of the presented PA COsub.2 sensor during laboratory tests is 1 vol. % COsub.2. Compared to the commercial sensor, our PA sensor showed less influences of humidity and oxygen on the detected signal and a faster response and recovery time. Finally, the developed sensor system was fixed to the skin of a test person, and an arterialization time of 181 min could be determined.
Gas sensors play a pivotal role in environmental monitoring, with NOsub.2 sensors standing out due to their exceptional selectivity and sensitivity. Yet, a prevalent challenge remains: the prolonged ...recovery time of many sensors, often spanning hundreds of seconds, compromises efficiency and undermines the precision of continuous detection. This paper introduces an efficient NOsub.2 sensor using TeOsub.2 nanowires, offering significantly reduced recovery times. The TeOsub.2 nanowires, prepared through a straightforward thermal oxidation process, exhibit a unique yet smooth surface. The structural characterizations confirm the formation of pure-phase TeOsub.2 after the anneal oxidation. TeOsub.2 nanowires are extremely sensitive to NOsub.2 gas, and the maximum response (defined as the ratio of resistance in the air to that under the target gas) to NOsub.2 (10 ppm) is 1.559. In addition, TeOsub.2 nanowire-based sensors can return to the initial state in about 6–7 s at 100 °C. The high sensitivity can be attributed to the length–diameter rate, which adsorbs more NOsub.2 to facilitate the electron transfer. The fast recovery is due to the smooth surface without pores on TeOsub.2 nanowires, which may release NOsub.2 quickly after stopping the gas supply. The present approach for sensing TeOsub.2 nanowires can be extended to other sensor systems as an efficient, accurate, and low-priced tactic to enhance sensor performance.
MXenes are a new family of two-dimensional (2D) nanomaterials. They are inorganic compounds of metal carbides/nitrides/carbonitrides. Titanium carbide MXene (Tisub.3Csub.2-MXene) was the first 2D ...nanomaterial reported in the MXene family in 2011. Owing to the good physical properties of Tisub.3Csub.2-MXenes (e.g., conductivity, hydrophilicity, film-forming ability, elasticity) various applications in wearable sensors, energy harvesters, supercapacitors, electronic devices, etc., have been demonstrated. This paper presents the development of a piezoresistive Tisub.3Csub.2-MXene sensor followed by experimental investigations of its dynamic response behavior when subjected to structural impacts. For the experimental investigations, an inclined ball impact test setup is constructed. Stainless steel balls of different masses and radii are used to apply repeatable impacts on a vertical cantilever plate. The Tisub.3Csub.2-MXene sensor is attached to this cantilever plate along with a commercial piezoceramic sensor, and their responses for the structural impacts are compared. It is observed from the experiments that the average response times of the Tisub.3Csub.2-MXene sensor and piezoceramic sensor are 1.28±0.24 μs and 31.19±24.61 μs, respectively. The fast response time of the Tisub.3Csub.2-MXene sensor makes it a promising candidate for monitoring structural impacts.
The excessive concentration of heavy-metal mercury ions (Hgsup.2+) in the environment seriously affects the ecological environment and even threatens human health. Therefore, it is necessary to ...develop rapid and low-cost determination methods to achieve trace detection of Hgsup.2+. In this paper, an Electrochemiluminescence (ECL) sensing platform using a functionalized rare-earth material (cerium oxide, CeOsub.2) as the luminescent unit and an aptamer as a capture unit was designed and constructed. Using the specific asymmetric matching between Hgsup.2+ and thymine (T) base pairs in the deoxyribonucleic acid (DNA) single strand, the “T−Hg−T” structure was formed to change the ECL signal, leading to a direct and sensitive response to Hgsup.2+. The results show a good linear relationship between the concentration and the response signal within the range of 10 pM–100 µM for Hgsup.2+, with a detection limit as low as 0.35 pM. In addition, the ECL probe exhibits a stable ECL performance and excellent specificity for identifying target Hgsup.2+. It was then successfully used for spiked recovery tests of actual samples in the environment. The analytical method solves the problem of poor Hgsup.2+ recognition specificity, provides a new idea for the efficient and low-cost detection of heavy-metal pollutant Hgsup.2+ in the environment, and broadens the prospects for the development and application of rare-earth materials.
Real-time sensing of hydrogen sulfide (Hsub.2S) at room temperature is important to ensure the safety of humans and the environment. Four kinds of different nanocomposites, such as MXene ...Tisub.3Csub.2Tsub.x, Tisub.3AlCsub.2, WSsub.2, and MoSesub.2/NiCosub.2Osub.4, were synthesized using the hydrothermal method in this paper. Initially, the intrinsic properties of the synthesized nanocomposites were studied using different techniques. P-type butane and Hsub.2S-sensing behaviors of nanocomposites were performed and analyzed deeply. Four sensor sheets were fabricated using a spin-coating method. The gas sensor was distinctly part of the chemiresistor class. The MXene Tisub.3Csub.2Tsub.x/NiCosub.2Osub.4-based gas sensor detected the highest response (16) toward 10 ppm Hsub.2S at room temperature. In comparison, the sensor detected the highest response (9.8) toward 4000 ppm butane at 90 °C compared with the other three fabricated sensors (Tisub.3AlCsub.2, WSsub.2, and MoSesub.2/NiCosub.2Osub.4). The MXene Tisub.3Csub.2Tsub.x/NiCosub.2Osub.4 sensor showed excellent responses, minimum limits of detection (0.1 ppm Hsub.2S and 5 ppm butane), long-term stability, and good reproducibility compared with the other fabricated sensors. The highest sensing properties toward Hsub.2S and butane were accredited to p–p heterojunctions, higher BET surface areas, increased oxygen species, etc. These simply synthesized nanocomposites and fabricated sensors present a novel method for tracing Hsub.2S and butane at the lowest concentration to prevent different gas-exposure-related diseases.
In the present work, three kinds of nanosized SnOsub.2 samples were successfully synthesized via a hydrothermal method with subsequent calcination at temperatures of 500 °C, 600 °C, and 700 °C. The ...morphology and structure of the as-prepared samples were characterized using X-ray diffraction, transmission electron microscopy, selected area electron diffraction, Brunauer–Emmett–Teller analysis, and X-ray photoelectron spectroscopy. The results clearly indicated that the SnOsub.2 sample calcined at 600 °C had a higher amount of chemisorbed oxygen than the SnOsub.2 samples calcined at 500 °C and 700 °C. Gas sensing investigations revealed that the cataluminescence (CTL) sensors based on the three SnOsub.2 samples all exhibited high selectivity toward Hsub.2S, but the sensor based on SnOsub.2−600 °C exhibited the highest response under the same conditions. At an operating temperature of 210 °C, the SnOsub.2−600 °C sensor showed a good linear response to Hsub.2S in the concentration range of 20–420 ppm, with a detection limit of 8 ppm. The response and recovery times were 3.5 s/1.5 s for Hsub.2S gas within the linear range. The study on the sensing mechanism indicated that Hsub.2S was oxidized into excited states of SOsub.2 by chemisorbed oxygen on the SnOsub.2 surface, which was mainly responsible for CTL emission. The chemisorbed oxygen played an important role in the oxidation of Hsub.2S, and, as such, the reason for the SnOsub.2−600 °C sensor showing the highest response could be ascribed to the highest amount of chemisorbed oxygen on its surface. The proposed SnOsub.2-based gas sensor has great potential for the rapid monitoring of Hsub.2S.
![Room Temperature NH[sub.3] ...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1424-8220/small "Room Temperature NH[sub.3] Selective Gas Sensors Based on Double-Shell Hierarchical SnO[sub.2]@polyaniline Composites")
