Non-contact,radio frequency detection of ammonia with a printed polyaniline sensor

A novel system for the detection of ammonia was developed by monitoring the conductance of inkjet printed or screen printed polyaniline films with a radio frequency detector. The system has the advantage of non-contact detection of ammonia within sealed packages. Since the sensor is a passive printed film that is externally interrogated, it does not require an internal power source or associated circuitry, and therefore may be a low-cost device suitable for smart packaging applications. When printed on a suitable substrate, the sensor can be cycled several times using heat or a volatile acid to regenerate the polyaniline surface.     

Synthesis of a polymeric sensor containing an occluded pyrylium salt and its application in the colorimetric detection of trimethylamine vapors

A dense membrane (MS) based on vinyl polymers and containing a pyrylium salt [2,6‐diphenyl‐4(p‐methacryloyloxy)phenylpyryliumtetrafluoroborate] was prepared. The MS has hydrophilic and sensory properties that make it a good material for the selective colorimetric detection of trimethylamine (TMA) vapors, a biogenic amine of great importance in food safety. The polymeric sensor changes from yellow to an intense pink color with increasing concentrations of TMA. The material could be reused in the presence of HCl vapors for at least 10 times. The detection and quantification limits were determined by ultraviolet–visible absorption spectroscopy (4.42 and 13.40 ppm, respectively) and by the RGB parameters of digital color (3.37 and10.22 ppm, respectively). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46185.     

Gas sensor for ammonia detection based on poly(vinyl alcohol) and polyaniline electrospun

In this article, the results of the process and fabrication of ammonia gas sensors are obtained through the production of poly(vinyl alcohol) and polyaniline (PVA/PANI) nanofibers in different concentrations deposited on interdigitated electrodes (IDEs) The results showed good interaction between PVA and PANI, as well as the solvents involved, with good adhesion of the nanofibers in substrate, shown for morphological analysis by scanning electron microscopy (SEM). The good performance of the gas sensor was carried out by direct current measurements. It has been proven that the high surface density, dimensions, and quality of nanofibers are essential parameters for a good response of the ammonia gas sensor. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47288.     

Optimization of waste quail eggshells as biocomposites for polyaniline in ammonia gas detection

A simple, cost-effective, and novel chemical sensor for ammonia (NH₃) gas detection was developed from polyaniline (PANI)/quail eggshell (QES) composites. QES is a natural waste enriched in calcium carbonate. In this work, pure PANI was synthesized from chemical oxidation method and PANI/QES composites were prepared from physical mixing of QES with the synthesized PANI at different mass ratio. A series of complementary techniques including Fourier transform infrared and ultraviolet-visible spectrometers, scanning electron microscope with energy dispersive detection coupled with mapping, thermogravimetric analysis, and X-ray diffractometer were used to characterize the physicochemical and textural properties of the biocomposites. From the results, PANI/QES composite with a mass ratio of 1 exhibited the lowest NH₃ detection limit of 5.24 ppm with a linear correlation coefficient (R²) of close to unity (0.9932) between the signal and NH₃ gas concentration. As a whole, the PANI/QES biocomposites synthesized from this work exhibited excellent selectivity toward NH₃ gas even in the presence of other gas impurities, such as acetone, ethanol, and hexane. For the sensor reusability, the PANI/QES biocomposites can be reused in the application of NH₃ gas detection for at least 4 cycles.     

Three-terminal CNTs gas sensor for N2 detection

A novel three-terminal gas sensor was fulfilled by utilizing the vertically aligned carbon nanotubes (CNTs) mat. Carbon nanotubes were synthesized by thermal chemical vapor deposition (thermal CVD) at 700 °C under C₂H₂ gas flow rate of 30 sccm. Upon exposure to a with and without N₂ environment at the room temperature of 25 °C, the electrical resistance of as-made devices was found to increase and to return back, respectively. Compared to a low bias one, the sensitivity increased when applying a high source drain bias voltage. Furthermore, the device became more sensitive for N₂ detection by applying a negative gate voltage. It was concluded that the alteration of free holes concentration in the CNTs mat played the major mechanism for the N₂ gas detection.     

Hole concentration modulated gas sensor for selective detection of 2-methoxy ethanol

The inhaling rate of toxic gases in daily life is increasing alarmingly; in turn, human health is in question. To resolve this dilemma, the possible remedy is the early detection and adequate regulation of VOCs in the atmosphere via sensors. Therefore, the investigation focused on developing a gas sensor for sensing several VOCs and flourished with a highly selective C₃H₈O₂ gas sensor at room temperature. In-depth structural, elemental, and morphological analysis followed by the sensing test affirmed the enhanced C₃H₈O₂ detection performance of Ag–NiO over pure NiO. The nanosized sphere formation was confirmed via XRD and TEM characterizations alongside the effect of sintered temperature on the shape and crystallite size. Moreover, the XPS examined the combined effect of sintering temperature and doping on the synthesized nanostructures and optimized the exact temperature as 500 °C because of the improved hole concentration. The Ag–NiO(500 °C) exhibited appealing sensing characteristics, specifically, a high response of 6491.57 for 100 ppm C₃H₈O₂ at room temperature. The sensor displayed a quick response and recovery (10 s,10 s) C₃H₈O₂ alongside long-term repeatability and stability; it showed practical implementation in real-time scenarios.     

混合气体保护焊薄板焊接工艺的开发

描述了利用熔化极混合气体保护焊技术焊接薄板的工艺开发方法,并以具体实例数据为依据作了有关展开介绍及分析。对于熔化极混合气体保护焊技术在金属加工中的推广应用有一定的参考价值。     

One-pot synthesis of zinc oxide - polyaniline nanocomposite for fabrication of efficient room temperature ammonia gas sensor

Development of efficient room temperature ammonia (NH₃) gas sensor from one pot synthesized zinc oxide (ZnO) – polyaniline (PANI) nanocomposite is reported in the present article. Prior to gas sensing study, the material is characterized to understand the structural, morphological, compositional, optical and thermal properties. Structural and morphological studies indicate good incorporation of ZnO particles in PANI matrix. The gas sensing efficiency of ZnO-PANI nanocomposite is examined at room temperature for ethanol (C₂H₅OH), methanol (CH₃OH) and NH₃ gas. The results confirm that ZnO-PANI nanocomposite to be highly selective for NH₃ with fast response time and better stability. The response and recovery times are observed to be significantly dependent on NH₃ concentration and the lowest detectivity limit of the sensor for NH₃ is found 10 ppm. ZnO-PANI nanocomposite shows better gas sensing efficiency as compared to the sensors developed from single phase PANI film.     

Deodorization performance of charcoal particles loaded with orthophosphoric acid against ammonia and trimethylamine

A deodorant was prepared by drying charcoal particles after dipping in aqueous H₃PO₄ solutions. The deodorization performances of the samples against NH₃ and (CH₃)₃N odor gases were examined by a detection test tube method and compared with those of a conventional coconut shell-derived active carbon loaded with H₃PO₄ in the same manner. The charcoal particles with H₃PO₄ exhibited higher performances than those of the other against both the odor gases. Ammonia gas was caught on the sample surface through reaction with the loaded H₃PO₄ to form NH₄H₂PO₄ and further (NH₄)₂HPO₄ but the deodorization mechanism for (CH₃)₃N could not be decided. The high performances of the charcoal particles loaded with H₃PO₄ were due to its characteristic porous structure consisting of large pores, i.e., such pores were suited for loading a large amount of H₃PO₄ and were not apt to be blocked by the loaded H₃PO₄. Also large pores were not blocked by expansion of H₃PO₄ on the pore surface through the deodorization reactions. The active carbon being composed of a large number of micropores did not exhibit these advantages.     

Chemical bath deposition of h-MoO3 on optical fibre as room-temperature ammonia gas sensor

This study successfully developed a semiconductor metal oxide-based ammonia gas sensor that was powered by an Ultraviolet–Visible-near-IR optical light source. However, optical fibre gas sensors using single metal oxide nanomaterial are limited. To address this situation, a h-MoO₃ nanorod was grown on a tapered region of optical fibre glass using a simple chemical bath deposition to form a unique sensing element. An additional annealing treatment was then performed to modify the oxidation state of h-MoO₃. The property changes of the samples were characterised using different techniques, such as FESEM, TEM, XRD, XPS, TGA and UV–Vis. Overall, the annealing treatment improved the sensitivity performance, response and recovery time of the sensor towards NH₃. h-MoO₃ that was annealed at 150 °C in air showed stable room temperature absorbance responses of 0.05, 0.18, 0.22, 0.28 and 0.35, a fast response time of 210 s towards 500 ppm of NH₃ and strong stability and repeatability. The optical NH₃ gas-sensing behaviour was significantly correlated with the non-stoichiometric Mo⁵⁺ content. The chemisorbed oxygen species and physiosorbed NH₃ altered the refractive index and its absorption coefficient on the nanorod, which manipulated the optical signal and acts as a sensing mechanism. These results verify that a chemical bath deposition growth of the h-MoO₃ nanorod exhibits a promising optical sensing characteristic, which paves a path for emerging gas-sensing technology.     

Hydrogen storage in trimethylamine hydrate: Thermodynamic stability and hydrogen storage capacity of hydrogen+trimethylamine mixed semi-clathrate hydrate

The thermodynamic stability and hydrogen occupancy for the hydrogen+trimethylamine mixed semi-clathrate hydrate system were investigated by means of phase equilibrium (pressure–temperature) measurements and Raman spectroscopic analyses. The hydrogen molecule gradually advanced to occupy the empty small cage of trimethylamine hydrate in proportion to pressure increase. Almost all small cages were filled up with the hydrogen molecules at about 80 MPa. Isothermal Raman spectroscopic analysis showed that the absorption-rate of hydrogen to the pre-treated trimethylamine hydrate was comparable to those of tetrahydrofuran hydrate. Only one hydrogen molecule was enclosed with one small cage at the equilibrium state in pre-treated trimethylamine hydrate.     

LaNiTiO3-SE-based stabilized zirconium oxide mixed potentiometric SO2 gas sensor

In this paper, a mixed potential gas sensor based on YSZ solid electrolyte and LaNiTiO₃ sensing electrode was produced. The perovskite-type oxide LaNiTiO₃ was synthesized by the sol-gel method as a sensitive electrode, which was intended to detect the low-level concentration of SO₂ in the environment. After the aging process and continuous testing, it was found that the LaNiTiO₃-SE sensor had the best response value of ?27.5 mV to 5 ppm SO₂ at 510 °C, at this temperature, as low as 50 ppb SO2 still had a response of -1mV. Meanwhile, when the sensor was tested at 510 °C, it was found that the response value of the sensor showed a piecewise linear relationship with the logarithm of SO₂ concentration, with a sensitivity of -4 mV/decade for 0.05–1 ppm SO₂ and -40mV/decade for 1–100 ppm SO₂. In addition, the sensor also showed good selectivity, and the response to interference gases could be ignored such as NO₂, CO, CH₄, NH₃, H₂, ethanol, and formaldehyde. At the same time, the sensor also shows good repeatability and stability, being still relatively stable after two weeks of continuous operation at high-temperature.     

Development of MgO:TiO2 thin films for gas sensor applications

In this study, structural, morphological and optical properties, and gas sensor performance of magnesium oxide (MgO) doped titanium dioxide (TiO₂) thin films were investigated in detail. Gas sensor metallic patterns were fabricated on Si substrate using traditional photolithographic technique. MgO doped TiO₂ thin films were deposited on formed Pt electrode surface by confocal sputtering (co-sputtering) system as the active layer. Thin film characterizations were realized by using secondary ion mass spectroscopy (SIMS), atomic force microscope (AFM) and UV–Vis Spectrometer (UV–Vis). Gas sensing measurements were performed by gas sensing test system against methane gas at working temperature of 300?°C. To evaluate deposition and thermal annealing effects on the sensing performance, sensors were tested under gas. The sensitivity and response/recovery time of gas sensors were measured in 1000?ppm. MgO doped TiO₂ based sensor at substrate temperature of 100?°C has high sensitivity and short response/recovery time.     

用于防毒面具的氨吸收剂的研究

佩戴含有氨吸收剂的防毒面具是在氨气大量泄露的情况下,工作人员在处理事故过程中保护自身的最简便的、最有效的方法。本文介绍了可用于现有防毒面具的氨吸收剂的制备方法及其性能测试方法。详细讨论了制备过程中各因素对氨吸收剂性能的影响,得出了满足防毒要求的氨吸收剂的制备工艺条件。     

Development of a disposable sensor for electrocatalytic detection of guanine and ss-DNA using a modified sol-gel screen-printed carbon electrode

The electrocatalytic oxidation of guanine and DNA is demonstrated on a sol-gel coated carbon screen printed electrode modified with {MeReO(edt)}₂ using cyclic and differential pulse voltammetric techniques. An oxidation peak at 370 mV was found, but no corresponding reduction peaks could be detected in the negative scan, which indicates that the oxidation of guanine is completely irreversible process. The oxidation peak potentials are shifted to more negative values with increasing pH. The utility of applying the sensor for determination of guanine and ss-DNA were investigated. The linear ranges were 0.19-10.8 and 0.45-7.8 μg ml⁻¹ for guanine and DNA, respectively. Detection limits of 0.1 and 0.32 μg ml⁻¹ were obtained for guanine and ss-DNA, respectively.     

合成氨原料气超高效除油净化器

将凝聚式过滤机理应用于合成氨工业领域,采用不锈钢丝毡折叠滤芯与微米级超细玻璃纤维复合滤芯两级过滤,研制了除油效率高达００１μｍ、残余含油量仅为０１ｍｇ／ｍ３的氮氢工艺气专用超高效除油过滤器。着重从其原理、结构、技术性能及经济效益分析等方面进行了讨论。     

含氨尾气的氨吸附研究

在模拟含氨尾气组成的条件下,研究了复合吸附剂对氨的吸附。结果表明,常压下复合吸附剂的纯氨吸附量达到0.25 g/g;以氮气作为载气时,对氨吸附量影响很小;水蒸气的存在对复合吸附剂的氨吸附量影响较大;在较低温度、较高氨分压时,复合吸附剂对氨具有较好的吸附效果。复合吸附剂的吸附稳定性好、吸附量高,吸附法是一种很有前景的处理含氨尾气的方法。     

Zinc(II)porphyrin-poly(lactic acid) nanoporous fiber membrane for ammonia gas detection

A functional zinc(II)porphyrin-poly(lactic acid) nanoporous fiber membrane (Zn(II)TPP-PLA NFM) for ammonia (NH₃) gas detection was developed via the one-step electrospinning method. With the porous structure, Zn(II)TPP-PLA NFM overcomes the limited gas absorption and diffusion of the sensing materials and thus is beneficial to NH₃ gas detection. FE-SEM and FT-IR were employed to characterize the morphology and structure of the Zn(II)TPP-PLA NFM. NH₃ gas sensing properties of the Zn(II)TPP-PLA NFM were studied by UV–visible spectroscopic techniques. Results showed the Zn(II)TPP-PLA NFM with the volume ratio of dichloromethane/tetrahydrofuran (DCM/THF) 4/1 has a relatively higher porosity of 38 % and the Zn(II)TPP-PLA NFM with 2.0 mg mL^?1 Zn(II)TPP content exhibits an excellent response/recovery performance toward sub-ppm levels of NH₃ gas. The detection limit was found to be 0.264 ppm toward NH₃ at room temperature. In addition, the performance of this sensor was highly stable after five cycles of tracing NH₃ gas and recovery.     

Effects of trimethylamine and ammonia on cBN content in the samples prepared by hydrothermal method

The previous results have proved that the phase-selective synthesis route is an effective method for preparing cubic boron nitride (cBN) from hydrothermal solutions. However, the experimental parameters are still required to be optimized in order to synthesize pure cBN at high yield. Here we report the results of investigating the effects of adding trimethylamine (N(CH₃)₃) and ammonia (NH₃·H₂O) (denoted as secondary nitrogen source) into the reacting solutions. It was found that the content of cBN could be increased by adding appropriate amount of N(CH₃)₃ and decreased with excess amount of it. On the contrary, hexagonal boron nitride (hBN) was always promoted by adding NH₃·H₂O into the reacting solutions. The samples were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectrum (FTIR) and high resolution transmission electron microscopy (HRTEM). The experimental results were briefly discussed based on a reported model.