Chlorine Gas Sensor Research Articles

Tailoring the performance of phthalocyanine-based sensor: Side chain substitution and nanofabrication

Room temperature Cl2 sensing properties of chemiresistive gas sensor based on Zinc Phthalocyanine (ZnPc) were improved by functionalizing ZnPc molecule with peripheral substitution of alkoxy side chains. The chemiresistive sensors of substituted ZnPc (ZnPcOC8) were made using spin-coated films and solution-processed nanostructures. These sensors were highly selective and sensitive towards Cl2 as compared to NH3, NO and NO2. The chlorine response kinetics of ZnPc and substituted ZnPcOC8-based sensors were investigated for Cl2 concentration range 5–1500 ppb. The ZnPcOC8-based sensors exhibit a limit of 5 ppb Cl2 with faster sensing kinetics as compared to ZnPc-based sensor. Among the three sensors, the solution-processed nanostructured-based sensor exhibits the best performance. The gas sensing mechanism of sensors has been investigated by XPS, suggesting that Zn+2 were the preferred sites for Cl2 interaction. These investigations suggest that alkoxy substitution on phthalocyanine molecules leads to development of cost effective and highly sensitive chlorine gas sensors.

Chlorine Gas Sensor with Surface Temperature Control.

The work describes the design, manufacturing, and user interface of a thin-film gas transducer platform that is able to provide real-time detection of toxic vapor. This proof-of-concept system has applications in the field of real-time detection of hazardous gaseous agents that are harmful to the person exposed to the environment. The small-size gas sensor allows for integration with an unmanned aerial vehicle, thus combining high-level mobility with the ability for the real-time detection of hazardous/toxic chemicals or use as a standalone system in industries that deal with harmful gaseous substances. The sensor was designed based on the ability of thin-film metal oxide sensors to detect chlorine gas in real time. Specifically, a concentration of 10 ppm of Cl2 was tested.

ZnO–SnO2 nano-heterostructures with high-energy facets for high selective and sensitive chlorine gas sensor

The n-ZnO/n-SnO2 nano-heterostructures surrounded by high-energy facets have been designed and synthesized via a simple two-stage route and used as functional materials of chlorine gas sensor. The composition, morphology and structure of ZnO–SnO2 nano-heterostructures are characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). It is found that both the SnO2 octahedra nanoparticles and the ZnO–SnO2 nano-heterostructures are surrounded by high-energy (221) facets. The sensor with the ZnO–SnO2 nano-heterostructure nanoparticles presents a much higher response (230.52) to Cl2 (upgrade to 50 times) than that of the sensor with the pure SnO2 nanoparticles. Moreover, a new and reasonable method is used to calculate the detection limit of two sensors. The sensor with 10% ZnO–SnO2 sample (ZnO: SnO2 = 10%, mol%) reveals lower detection limit (0.06 ppm) than that of pure SnO2 sample (1.10 ppm). The superior Cl2 sensing performance is closely related to the effects of the high-energy facets and the formation of energy barrier between ZnO and SnO2.

High sensitivity and ultra-low detection limit of chlorine gas sensor based on In2O3 nanosheets by a simple template method

Chlorine (Cl2) gas sensors with outstanding gas response and ultra-low detection limit by an easy and economical fabrication are increasingly in demand in practical application. In this work, In2O3 nanosheets with excellent gas sensing properties for Cl2 have been successfully synthesized using melamine-formaldehyde (MF) sponge as the template via a simple soak-drying-calcination approach. The gas response (Rgas/Rair) of In2O3 nanosheets sensor is up to 2353.4 toward 3 ppm Cl2 at 200 °C, which is about 158 times compared with In2O3 particles (14.9). The selectivity to Cl2 reaches up to 254.3 against other interferential gases. Additionally, the sensor based on In2O3 nanosheets displays extremely low detection limit of 0.037 ppb. Such excellent gas sensing performance is primarily ascribed to the unique sheet structure and abundant oxygen vacancies which are formed during the removal of MF sponge template. Therefore, the In2O3 nanosheets sensor shows great potential in Cl2 detection.

High sensitivity and selectivity chlorine gas sensors based on 3D open porous SnO2 synthesized by solid-state method

Abstract A simple solid-state reaction method was employed to synthesize the three-dimensional open porous SnO2 (3D OP-SnO2) by grinding the mixture of tin tetrachloride pentahydrate, sodium hydroxide and sodium chloride. Sodium chloride worked as a template to build the 3D open porous structure. The morphological feature was three-dimensional open porous with diameters about 300–500 nm and the edge of the 3D open porous were composed of numerous SnO2 nanoparticles with grain size around 5.8 nm. The chlorine (Cl2) gas sensing properties of 3D OP-SnO2 and bulk SnO2 (B–SnO2) sensors were systematically investigated. Gas response of the 3D OP-SnO2 sensor was 792.85 to 5 ppm Cl2 at 160 °C, which was 61 times higher than that of B–SnO2. Such outstanding gas sensing performance was mainly ascribed to the small grain size, which resulted in the change of conductivity mechanism and the decreased mobility of electrons. Thereby, the resistance of OP-SnO2 increased dramatically. Moreover, the unique structure and abundant oxygen vacancies also contributed to the excellent gas sensing performance, because they can elevate the specific surface area and provide sufficient Cl2 adsorption sites.

A tetracene-based single-electron transistor as a chlorine sensor

An organic molecular single-electron transistor (SET) based on a tetracene quantum dot has been modeled and employed for sensing of chlorine gas, within the framework of density functional theory. The sensing behavior of the SET is estimated through a charge-stability diagram and total energy as a function of gate potential (TE vs. Vg) for varying distances of chlorine from the SET quantum dot, which could be used as an electronic fingerprint for detection. The better sensing ability, high power efficiency and large operational temperature range of tetracene SET, in comparison to conventional sensors, makes it a very powerful candidate for a chlorine gas sensor.

Highly Sensitive NiO Nanoparticle based Chlorine Gas Sensor

We have synthesized a chemiresistive sensor for chlorine (Cl2) gas in the range of 2–200 ppm based on nickel oxide (NiO) nanoparticles obtained by wet chemical synthesis. The nanoparticles were characterized by x-ray diffraction (XRD) analysis, field-emission scanning electron microscopy (FE-SEM), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, ultraviolet–visible (UV–Vis) spectroscopy, and photoluminescence (PL) spectroscopy. XRD spectra of the sensing layer revealed the cubic phase of NiO nanoparticles. The NiO nanoparticle size was calculated to be ∼ 21 nm using a Williamson-Hall plot. The bandgap of the NiO nanoparticles was found to be 3.13 eV using Tauc plots of the absorbance curve. Fast response time (12 s) and optimum recovery time (∼ 27 s) were observed for 10 ppm Cl2 gas at moderate temperature of 200°C. These results demonstrate the potential application of NiO nanoparticles for fabrication of highly sensitive and selective sensors for Cl2 gas.

Ag modified bismuth ferrite nanospheres as a chlorine gas sensor

Pure phase bismuth ferrite (BiFeO3, BFO) nanospheres were synthesized via a sol–gel method, and Ag was loaded on the surface of BFO by photodeposition. The effects of the Ag-modification on the morphologies and microstructural characteristics were investigated using transmission electron microscopy (TEM) and X-ray powder diffraction (XRD) analyses. Only BFO peaks but no Ag peaks were observed for all samples in the XRD patterns, which is related to the small size and low loading of Ag. The gas-sensing tests show that the response of 4 mg AgNO3 modified BiFeO3 (ABFO4) was 72.62 to 10 ppm Cl2 at 240 °C, which was 2.5 times higher than that of the pristine BFO. Such outstanding gas sensing performances are attributed to the fact that the presence of Ag not only increases the density of holes and the amount of gas adsorption sites but also has a catalytic effect.

Controllable preparation of copper phthalocyanine single crystal nano column and its chlorine gas sensing properties

The unsubstituted copper phthalocyanine (CuPc) single crystal nano columns were fabricated for the first time as chlorine (Cl2) gas sensors in this paper. The nano columns of CuPc have been prepared on different substrates via template-free physical vapor deposition (PVD) approach. The growth mechanism of CuPc nano column on quartz was explored and the same condition used on other substrates including glass, sapphire (C-plane<0001>, M-plane<101¯0>, R-plane<11¯02>), Si and SiO2/Si came to a same conclusion, which confirmed that the aligned growth of CuPc nano column is not substrate-dependent. And then the CuPc nano column with special morphology was integrated as in-situ sensor device which exhibits high sensitivity and selectivity towards Cl2 at room temperature with a minimum detection limit as low as 0.08 ppm. The response of sensor was found to increase linearly (26∼659%) with the increase for Cl2 within concentration range (0.08∼4.0ppm). These results clearly demonstrate the great potential of the nano column growth and device integration approach for sensor device.

Influence of a Morphology Sensitive Layer of Resistive Gas Sensors on Chlorine Sensing

In presented work the influence of microstructure and shape factor of zinc oxide active layer on sensing parameters of resistive chlorine gas sensor is described. Three sensors were made using different methods of sensitive layer fabrication: screen printing and chemical bath deposition, with and without presence of electric field. Obtained results show that choice of fabrication method has a significant influence on electrical and sensing properties of designed sensors. Performed SEM measurements indicate that by using CBD method a q-1D ZnO structures were synthesized. THS studies have shown that the smaller zinc oxide structures have the higher conductivity and better chlorine sensitivity.

A highly sensitive chlorine gas sensor and enhanced thermal DC electrical conductivity from polypyrrole/silicon carbide nanocomposites

We report the synthesis of polypyrrole (PPy) and polypyrrole/silicon carbide nanocomposites (PPy/SiC) and PPy/SiC/dodecylbenzenesulfonic acid (DBSA) byin situchemical polymerization and their application as sensors for the detection of highly toxic chlorine gas.

Surface Plasmon Resonance-Based Fiber Optic Chlorine Gas Sensor Utilizing Indium-Oxide-Doped Tin Oxide Film

Fabrication and characterization of a surface plasmon resonance (SPR)-based fiber optic chlorine gas sensor are carried out. The fiber optic probe is fabricated by depositing a thin layer of indium-oxide-doped tin oxide over a silver-coated unclad core of the fiber. The SPR spectra of the chlorine gas for its different concentrations are obtained. It is observed that the resonance wavelength increases as the concentration of the chlorine gas increases and appears to saturate for higher concentrations of the gas. The sensitivity of the sensor depends on the thickness and the doping concentration of the indium-oxide-doped tin oxide film. The optimum thickness and the atomic weight percent doping concentration of the film are found to be 12 nm and 6 at. wt.%, respectively. To compare the performance, experiments are also carried out on probes coated with indium oxide and tin oxide layers over silver coated unclad core of the fiber. The performance of both the probes is found to be inferior to the one coated with indium-oxide-doped tin oxide layer. Further, the indium oxide doped tin oxide layer based probe is highly sensitive to chlorine gas for low concentrations. The sensor has low response time and is reversible. The proposed probe has advantages of online monitoring and remote sensing.

Fabrication and Characterization of a SPR Based Fiber Optic Sensor for the Detection of Chlorine Gas Using Silver and Zinc Oxide

A fiber optic chlorine gas sensor working on surface plasmon resonance (SPR) technique fabricated using coatings of silver and zinc oxide films over unclad core of the optical fiber is reported. The sensor probe is characterized using wavelength interrogation and recording SPR spectra for different concentrations of chlorine gas around the probe. A red shift is observed in the resonance wavelength on increasing the concentration of the chlorine gas. The thickness of the zinc oxide film is optimized to achieve the maximum sensitivity of the sensor. In addition to wavelength interrogation, the sensor can also work on intensity modulation. The selectivity of the sensor towards chlorine gas is verified by carrying out measurements for different gases. The sensor has various advantages such as better sensitivity, good selectivity, reusability, fast response, low cost, capability of online monitoring and remote sensing.

Room-temperature chlorine gas sensor based on CdSnO3 synthesized by hydrothermal process

The perovskite-structure CdSnO3 was obtained by calcinating CdSnO3·3H2O precursor at 550 °C, which was synthesized by hydrothermal process at 170 °C for 16 h. The phase and microstructure of the obtained CdSnO3 powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The CdSnO3 powders exhibit uniformly cubic structure with side length of about 100 nm. The effects of working temperature and concentration of detected gas on the gas response were studied. The selectivity of chlorine gas against other gases and response-recovery time of the sensor were also investigated. The results reveal that the CdSnO3 gas sensor has enhanced sensing properties to 1–10 ppm chlorine gas at room temperature; the value of gas response can reach 1338.9 to 5 ppm chlorine gas. Moreover, the sensor shows good selectivity and quick response behavior (23 s) to chlorine gas, indicating its application in detecting chlorine gas at room temperature in the future.

Application of anion-conducting lanthanum oxychloride for potentiometric chlorine gas sensors

The prototype potentiometric chlorine gas sensor was constructed using Na3Zr2Si2PO12 (Nasicon) as a solid electrolyte, two-phase (1–y)LaOCl–yNaCl as a sensing electrode, and 0.85Na2Ti3O7-0.15Na2Ti6O13 as a reference electrode. Nasicon, 0.85Na2Ti3O7–0.15Na2Ti6O13 two-phase system and LaOCl powders were prepared by solid‐state reaction method. Two-phase materials (1–y)LaOCl–yNaCl of different compositions were obtained by doping LaOCl with Na2CO3. The best preparation conditions were determined based on differential thermal analysis and thermogravimetry (DTA and TG). All the samples were studied by X-ray diffraction (XRD) analysis. Electrical conductivity of (1–y)LaOCl–yNaCl was measured using electrical impedance spectroscopy (EIS). The source voltage (SV) of the fabricated cell was measured as a function of temperature (400–600°C), Cl2 partial pressure in the range 1–9Pa and time. Constructed sensor shows the most effective performance at 500°C and in Cl2 pressure range of 3–9Pa.

MODIFICATION OF LANTHANUM OXYCHLORIDE SOLID ELECTROLYTE FOR CONVENTIONAL POTENTIOMETRIC CHLORINE GAS SENSOR

La 1-x Mg x OCl 1-x (x = 0.025, 0.05 and 0.1) and La 0.9 Ca 0.1 OCl 0.9 samples were prepared by a solid state reaction method. The best preparation conditions were determined by means of the differential thermal analysis and thermogravimetry (DTA&TG). The samples were studied by X-ray diffraction (XRD) analysis. Electrical conductivity of La 0.9 Mg 0.1 OCl 0.1 was measured using electrical impedance spectroscopy (EIS). The prototype chlorine gas sensor was constructed from La 0.9 Mg 0.1 OCl 0.1 solid electrolyte. The source voltage (SV) of the constructed device was measured as a function of temperature (500–800°C), Cl 2 gradient partial pressure and time. Similar measurements of SV was carried out in atmosphere of synthetic air in argon.

A new optochemical chlorine gas sensor based on the application of amphiphilic co-networks as matrices

A sensor for chlorine gas detection, consisting of an amphiphilic polymer co-network with an immobilised oxidation indicator, o-tolidine, is described. Data describing gas sensing properties and long-term stability will be presented. This study focuses on APCN thin films as a matrix for indicator immobilisation. Thin films of poly(2-hydroxyethyl acrylate)-l-polydimethylsiloxane PHEA-l-PDMS were prepared as immobilisation matrices for o-tolidine. We present a simple, non-expensive, but highly sensitive optical sensor for chlorine gas detection. The thin film response is reproducible and irreversible. With our kinetic-optical method rapid response times were achieved. The determination of chlorine is performed on the basis of the oxidation of o-tolidine as the chromogenic reagent to a coloured product which can be monitored at 650 nm. The results reveal a fast response to chlorine gas down to concentrations of 0.01 ppm.

Fast response chlorine gas sensor based on mesoporous SnO 2

Mesoporous SnO 2 is obtained through a simple hydrothermal process by using tin chloride as a raw material, urea as a pore-forming agent and pH regulator. X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) nitrogen adsorption–desorption measurements are employed to characterize the obtained mesoporous structures. The results show that the as synthesized material after calcination can be well indexed to tetragonal phase SnO 2 with a mesoporous structure. The sensing properties of the sensor based on mesoporous SnO 2 are investigated. The results reveal that the response to dilute Cl 2 gas of the materials is very high and fast. The short recovery time mainly attributes to the bigger pore size of mesoporous SnO 2. Finally, the reaction mechanism is proposed.

A simple microfluidic chlorine gas sensor based on gas–liquid chemiluminescence of luminol-chlorine system

In this work, a microfluidic chlorine gas sensor based on gas–liquid interface absorption and chemiluminescence detection was described. The liquid chemiluminescence reagent-alkaline luminol solution can be stably sandwiched between two convex halves of a microchannel by surface tension. When chlorine gas was introduced into the micro device, it was dissolved into the interfacial luminol solution and transferred to ClO −, and simultaneously luminol was excited and chemiluminescence emitted. The emitted chemiluminescence light was perpendicularly detected by a photomultiplier tube on a certain detection region. The remarkable advantage of the detection system is that both adsorption and detection were carried out at the gas–liquid interface , which avoids the appearance of bubbles. The whole analytical cycle including filling CL reagent, sample injection, CL detection and emptying the device was as short as 30 s. The linear concentration range of chlorine gas detection with direct introduction of sample method is from 0.5 to 478 ppm. The detection limit of this method is 0.2 ppm for standard chlorine gas and the relative standard deviation of five determinations of 3.19 ppm spiked chlorine sample was 5.2%.

Micro-patterning of biodegradable polymer using electrical field induced polystyrene micro mold

A micro chlorine gas sensor with an inner-circulation diffuser pump is newly developed. The sensor based on electro-chemical principle, only has the size of one-tenth in comparison with the conventional one. The sensor consists of an air–liquid separation membrane, a PZT-driven diffuser pump and micro electrodes which were manufactured by micro machining. The inner-circulation is generated by driving the diffuser pump with trapped air working as a buffer, in order to preserve the condition of internal reagent. The properties of the sensor were evaluated by circulation rate of the pump, pressure-proof of the membrane, and responsibility to chlorine gas.