جستجوی مقالات مرتبط با کلیدواژه « gas sensor » در نشریات گروه « شیمی »
تکرار جستجوی کلیدواژه «gas sensor» در نشریات گروه «علوم پایه»-
NO2 به عنوان یک گاز سمی در محیط زیست و صنعت، به وفور تولید می شود و نیاز به آشکار سازی دارد. در این پژوهش سنجش گاز NO2 با استفاده از نانوذرات ZnMn2O4 ساخته شده از طریق یک فرآیند ساده هم رسوبی مورد بررسی قرار گرفته است. ساختار و مورفولوژی سطح نمونه های تهیه شده به ترتیب توسط پراش اشعه ایکس و میکروسکوپ الکترونی روبشی مورد تجزیه و تحلیل قرار گرفته است. طیف پراش اشعه ایکس نشان می دهد که ساختار نمونه به خوبی و بدون ناخالصی شکل گرفته است. تصاویر میکروسکوپ الکترونی نشان می دهد که نانوذرات به صورت نانو صفحه های با ضخامت میانگین 30nm شکل گرفته اند. اندازه گیری های سنجش گاز با قرار دادن حسگر در معرض 5/0 درصد گاز NO_2 در دماهای بین °C150 تا °C375 انجام شد. اندازه گیری های انجام شده بر حسب دما، بیشینه پاسخ را در دمای 300 درجه، به 5/0 درصد گاز NO2 نشان داد. همچنین حسگرZnMn2O4 یک سیگنال الکتریکی تکرارپذیر و پایدار را نشان داد. از این رو، نانوذرات ZnMn2O4 دارای پتانسیل امیدوارکنندهای در زمینه حسگرهای گاز هستند.به عنوان یک گاز سمی در محیط زیست و صنعت، به وفور تولید میشود و نیاز به آشکار سازی دارد. د ر این پژوهش سنجش گاز NO2 با استفاده از نانوذرات ساخته شده از طریق یک فرآیند ساده سل- ژل مورد بررسی قرار گرفته است. ساختار و مورفولوژی سطح نمونه های تهیه شده به ترتیب توسط پراش اشعه ایکس و میکروسکوپ الکترون ی روبشی مورد تجزیه و تحلیل قرار گرفتهاست. طیف پراش اشعه ایکس نشان می دهد که ساختار نمونه به خوبی و بدون ناخالصی شکل گرفته است. تصاویر میکروسکوپ الکترونی نشان می دهد که نانوذرات به صورت نانو صفحه های با ضخامت میانگین 30nm شکل گرفته اند. اندازه گیریهای سنجش گاز با قرار دادن حسگر در معرض 0/5 درصد گازNO2 در دماهای بین °C150 تا °C375 انجام شد. اندازه گیریهای انجام شده بر حسب دما، بیشنه پاسخ را در دمای 300 درجه، به 0/5 درصد گاز NO2 نشان داد. همچنین حسگر ZnMn2O4 یک سیگنال الکتریکی تکرارپذیر و پایدار را نشان داد. از این رو، نانوذرات ZnMn2O4دارای پتانسیل امیدوارکنندهای در زمینه حسگرهای گاز هستند.
کلید واژگان: هم رسوبی, حسگر گاز, مورفولوژی, Znmn2o4}NO2 as a toxic gas in the environment and industry, is abundantly produced and needs to be detected. In this research, the measurement of NO2 gas using ZnMn2O4 nanoparticles made through a simple co-precipitation, process has been investigated. The structure and surface morphology of the prepared samples have been analyzed by X-ray diffraction and scanning electron microscopy, respectively. The X-ray diffraction spectrum shows that the structure of the sample is well formed without impurities. Electron microscope images show that the nanoparticles are formed as nanoplates with an average thickness of 30 nm. Gas sensing measurements were performed by exposing the sensor to %0.5 of NO2 gas at temperatures between 150 ℃ and 375 ℃. The measurements made in terms of temperature showed the maximum response at the temperature of 300 ℃, to %0.5 of NO2 gas. Also, the ZnMn2O4 sensor showed a repeatable and stable electrical signal. Therefore, ZnMn2O4 nanoparticles have a promising potential in the field of gas sensors.
Keywords: Co-Precipitation, Gas Sensor, Morphology, Znmn2o4} -
Spray pyrolysis has been used to fabricate different mixed TiO2/NiO/In2O3 nanostructures. TiO2/NiO/In2O3 has been structurally and optically explored using X-ray diffraction, field emission scanning electron microscopy, and UV-Vis spectroscopy. The particles analysis using X-ray diffraction had a polycrystalline structure and all of the observed peaks can be assigned to the samples with nanostructure, while FESEM reveals that they are very small, spherical, and range in size from 14 to 100 nm. The UV-Vis observed the edge of absorbance at about 335-305 nm; the energy band gap was calculated to be 3.3-3.58 eV. The absorbance in this area is caused by the creation of TiO2/NiO/In2O3 nanoparticles. The synthesis of thin films was tested in gas sensor applications. The gas response of the tested samples to hydrogen sulfide gas at different operating temperatures was analysed. The thin film demonstrates that when the operating temperature got higher, sensitivity increased as well. With an increase in operational temperature, recovery and response times are slowed down.Keywords: TiO2, NiO, In2O3, Nanostructure, Gas Sensor, H2S Gas}
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Carbon monoxide is a tasteless and odorless gas produced by gas burning engines and the incomplete combustion of hydrocarbons. Carbon monoxide poisoning occurs due to the respiration of this gas. Lack of proper exhaust and ventilation of it causes poisoning and death. So inhalation of it reduces blood oxygenation and is dangerous. Therefore, timely and correct identification of this gas is important. Carbon monoxide is difficult to detect and can cause other common disorders. Graphene and its derivatives have been widely used for fabrication of gas sensors because they have two-dimensional atomic bonds that can interact by gas molecules. In this study, graphene oxide was used to detect carbon monoxide. In order to improve the response time, the sensitivity of the sensor and its selectivity were composite by silver and manganese nanoparticles. Graphene oxide was prepared by advanced Hummers method. Ultrasonic device was also used to prepare graphene oxide/silver and graphene oxide/manganese nanocomposite. The results show that the sensor prepared by graphene oxide/silver and graphene oxide/manganese nanocomposites are able to detect carbon monoxide at room temperature, with appropriate sensitivity and selectivity.Keywords: Carbon monoxide, Gas Sensor, graphene oxide, Nanocomposite}
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Phosphorene nanoribbon (PNR) is a two-dimensional crystalline substance possessing semiconductor property, which makes it a new promising gas sensor. The gas sensing performance significantly depends on the adsorption mechanism and the strength of bonding between gas molecules and phosphorene atoms. Adsorption of a gas molecule onto PNR can be investigated through different parameters, such as interatomic energy, distance between atoms, and changes in the band gap energy of PNR. In this research, first, the PNR relaxation is carried out for minimum energy of whole structure. Second, the folding and tubing of PNR are investigated for their stability and minimum energy specification. Next, we constructed a phosphorene nanotube (PNT) by connecting two folded PNR that we called it unconventional PNT (UPNT). We compared conventional cylindrical PNT (CPNT) with UPNT for their energies and electrical properties. In the final step, as gas nanosensor, the gas sensing behavior and specifications of CPNT and UPNT are investigated in the presence of several gases. Since a phosphorene nanotube generally has a stable structure, the presence of gas molecules causes deformation of crystalline of structure and change in its electronic properties. For evaluating the sensing properties of CPNT and UPNT, their I-V characteristics, density of states and energy band diagrams are calculated and compared in the absence and presence of gas molecules. The adsorption of CO, , , NH, and gas molecules onto UPNT and CPNT are done in detail. The results show that the sensitivity of UPNT gas sensor is higher than that of CPNT for detecting special gas molecules. We further investigated the amount of charge transfer utilizing the nonequilibrium Green’s function (NEGF) formalism which is applied on crystallized atomic configuration.Keywords: Density functional theory (DFT), Gas sensor, Nonequilibrium Green’s Function (NEGF), Phosphorene Nanoribbon (PNR), Phosphorene Nanotube (PNT)}
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در این پژوهش نانوذرات نیم رسانای اکسیدقلع آلاییده با آهن با نسبت مولی آهن به قلع 0، 1، 2 و 3 درصد به روش مایکروویو سنتز شدند. ساختار بلوری، ریخت شناسی سطح، پیوندهای شیمیایی و ویژگی های نوری نمونه ها به وسیله پراش سنج پرتوایکس (XRD)، میکروسکوپ الکترونی روبشی اثر میدان (FESEM)، طیف سنج تبدیل فوریه فروسرخ (FTIR) و طیف سنجی (UV-vis) مطالعه شده است. آنالیز عنصرها به وسیله طیف سنجی پراکندگی انرژی پرتوایکس (EDAX) انجام شد. نتیجه های پراش پرتوایکس نشان داد که نمونه ها بس بلور بوده و دارای قله های ارجح مربوط به صفحات (110)، (101)، (200)، (211)، (220)، (002)، (310)، (112) و (301) فاز SnO 2 با ساختار چهارگوشه روتیل هستند. افزایش تراکم ناخالصی آهن از صفر به سه درصد، سبب کاهش اندازه متوسط نانوبلورک ها از 53 / 23 به nm 03 / 11، کاهش اندازه دانه ها از 37 به nm 28 و افزایش حجم سلول واحد از 61 / 70 به 40 / 71 و گاف نوری از 13 / 3 به eV 2 / 4 می شود. نتیجه های آنالیز FTIR پیوند SnO 2 را در نمونه ها تایید می کند. بررسی ویژگی های حس گری گاز اتانول به وسیله نمونه ها نشان داد که زمان پاسخ حس گرها در گستره 75 / 15 تا s 85 / 38 هست. حس گر ساخته شده با نانوذرات با تراکم یک درصد آهن شرایط بهینه حس گری را از خود نشان داد.
کلید واژگان: نانوذرات اکسیدقلع, ناخالصی آهن, مایکروویو, حس گری گازی, اتانول}Nano scale, Volume:7 Issue: 4, 2020, PP 33 -41In this study, iron-doped tin oxide semiconductor nanoparticles with an iron to tin mole ratio of 0, 1, 2 and 3% synthesized by microwave method. The crystal structure, surface morphology, chemical bonds, and optical properties of the samples were studied by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), infrared fourier transform spectroscopy (FTIR), and UV–Vis spectroscopy. Elements analysis was performed by EDAX. The X-ray diffraction results showed that the samples were polycrystalline, and have the preferred peaks of plates (110), (101), (200), (211), (220), (002), (310), (112), and (301) SnO2 phase with rutile rectangular structure. Increasing the iron impurity density from zero to three percent causes the reducing average size of nanocrystals from 23.53 to 11.03 nm, reducing grain size from 37 to 28 nm, and increasing unit cell volume from 70.61 to 71.40 and the optical band gap from 3.3 to 4.2 eV. The results of FTIR analysis confirm the SnO2 bond in the samples. Investigation of the sensing properties of ethanol gas by the samples showed that the response time of the sensors is in the range of 15.75 to 38.85 s. The sensor made with nanoparticles with a concentration of 1% iron exhibited optimum sensing conditions.
Keywords: Tin Oxide Nanoparticles, Iron Impurity, Microwave, Gas sensor, Ethanol} -
First-principle calculations have been investigated to study the adsorption of the molecules (SO2, CO, NH3, CO2, NO2, and NO) on the surface of mono boron (B) B-doped and dual B-doped graphene sheets to explore their potential applications as sensors. Our findings indicate that the adsorption of (CO and NH3) on B-doped graphene and (CO and SO2) on dual B-doped graphene are weak physisorption with adsorption energy between (0.128 to 0.810) eV. However, the adsorption of (CO2, NO2, SO2, and NO) on B-doped graphene and (CO2, NH3, NO and NO2) on dual B-doped graphene are strong chemisorption. The strong interaction of (CO2, NO2, SO2, and NO) on B-doped graphene and (CO2, NH3, NO and NO2) on dual B-doped graphene demonstrating that B-doped graphene and dual B-doped graphene could catalyse or activate, suggesting the possibility of B-doped graphene and dual B-doped graphene as a catalyst. Moreover, the energy gap of B-doped graphene and dual B-doped graphene is opened upon adsorption of (CO, CO2, NH3, NO, NO2 and SO2) in various ways. Our calculations demonstrate the feasibility of B-doped graphene may be a good sensor for (CO and NH3) and dual B-doped graphene could be a good sensor for (CO and SO2).Keywords: Adsorption, Boron-doped graphene, DFT, Electronic properties, Gas Sensor}
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Titanium dioxide is an important metal oxide semiconductor (MOSs) used in many electronic applications, the most famous of which are gas sensor applications. This review discusses the techniques used for preparing the TiO2 thin films and the effect of the crystalline phases in which this compound forms, on the gas sensing properties. There are three phases to crystallize titanium dioxides, brookite, anatase, and rutile phase. Amongst these varied phases of crystal, the greatest steady main phase is rutile. The phase of anatase and brookite are usually more stable than the rutile phase as the surface energy of them is less than that of the rutile. Therefore, the applications of sensing by anatase TiO2 and rutile TiO2 were fully studied. TiO2 characterizations were established on surface reactions using oxidizing or reducing gases, which; therefore, influences the conductivity of the film. Titanium dioxide gas sensors have healthier steadiness and sensitivity at high temperature compared with that of the other metal oxides. Surveys on titanium dioxide thin film applied in gas sensor devices used in a varied range of applications such as sensor devices, dye-sensitized solar cells, and catalysis. The gas sensor is a function of the crystal structure, particle size, morphology, and the method of synthesis. In this work, characteristic of the titanium dioxide films investigated using various techniques, as reported by many researchers. The aim of this study was to review previous studies through which the best properties can obtained to manufacture TiO2 gas sensor thin films with high sensitivity.Keywords: TiO2, Metal oxide, Semiconductor, Thin films, Gas Sensor}
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نشریه شیمی کاربردی روز، پیاپی 54 (بهار 1399)، صص 273 -288نانو میله های MX%-CeO2 (M=Zr4+, V3+) به روش هیدروترمال ساخته شد. مورفولوژی سطح و خواص ساختاری آن ها با استفاده از میکروسکوپ الکترونی روبشی گسیل میدانی (FESEM)، طیف سنجی پراکندگی انرژی (EDS) و پراش اشعه ایکس (XRD) مورد بررسی قرار گرفت. این نانومیله ها برای ساخت حسگر مورد استفاده قرار گرفت و حساسیت آنها نسبت به ترکیبات آلی فرار شامل متانول، استون، اتانول و 2-پروپانول بررسی شد. نتایج نشان داد که آلایش با یون های +V3 و +Zr4 نقش مهمی در ساختار و اندازه نانو میله ها دارد. طبق نتایج مرتبط با حساسیت این نانو میله ها واکنش قوی تر و سریع تری را نسبت به گاز اتانول در مقایسه با CeO2 برهنه نشان دادند. حسگر گاز نانو میله های CeO2 نسبت به اتانول با غلظت 340ppm حدود 4/5 واحد حساسیت نشان می دهد. در حالی که آلاییدن نانومیله های CeO2 به یون های +V3 یا +Zr4 سبب افزایش حساسیت حسگر به ترتیب تا 10/32 و 5/66 واحد می شود. افزایش حساسیت بر اساس مدولاسیون پهنای کانال هدایت و ارتفاع سد پتانسیل بین فازی، تشریح شد. بر اساس نتایج بدست آمده، حسگرهای Zr20%-CeO2 و V1%-CeO2 نسبت به اتانول حساسیت و گزینش پذیری بیشتری را در مقایسه با سایر نمونه ها نشان داد.کلید واژگان: حسگر گازی, سد پتانسیل, آلاییدن, زیرکونیوم (IV), وانادیوم (III)}The MX%-CeO2 (M=Zr4+, V3+) nanorods were synthesized via hydrothermal method. The field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were used to investigate the surface morphology and know the structural properties of the nanorods. The nanorods were used to make sensors and their sensitivity be tested for volatile organic compounds including methanol, acetone, ethanol and 2-propanol. The results showed that Zr4+ and V3+ dopant ions play a vital role in the structure and the size of rods. According to the sensing results these nanorods exhibited stronger and faster response to ethanol gas than the bare CeO2. While the CeO2 nanorods showed the sensitivity of 4.5 units for 340ppm ethanol concentration, sensitivity of doped samples with V3+ and Zr4+ ions increased to 10.32 and 5.66 units, respectively. The sensitivity enhancement described by the larger modulation of the conduction channel width and interfacial potential barrier height. According to the results, Zr20%-CeO2 and V1%-CeO2 sensors were more sensitive and selective to ethanol, compared to the other samples.Keywords: Gas sensor, Potential barrier, Doping, Zirconium (IV), Vanadium (III)}
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The adsorption of a toxic gas, cyanogen chloride (CNCl) on pristine, Al– and Si–doped BN nanosheet investigated using density functional theory (DFT). The adsorption energies of the most stable complexes of CNCl on pristine, Al– and Si–doped BN nanosheet are –19.96, –95.02 and –176.90 kj/mol, respectively. We found that the CNCl gas has a chemisorption interaction over the Al– and Si–doped BN, with significant change in the structure shape of the CNCl molecule. The value of adsorption interaction energy of Si-boron nitride is very large than that of the Al-boron nitride toward the toxic gas. As a result the Si-boron nitride nanosheet is more reactive to dissociate the gas molecule into safely small fragments. The adsorption of the CNCl molecule can significantly decrease the HOMO–LUMO energy gap of the Al–doped BN by about 14.06%. It is suggested that the Al–doped BN can be considered as a potential nanostructure for sensing the toxic CNCl.
Keywords: Gas Sensor, Cyanogen chloride, BN nanosheet, DFT} -
در این پژوهش، با استفاده از محاسبات مبتنی بر نظریه تابع چگالی، جذب مولکول های گاز H2S، 3NH، CO، و NO بر روی فسفرین مورد مطالعه قرار می گیرد. مکان های بهینه ی جذب هر یک از گازها توسط لایه ی دو بعدی بررسی می شوند. هرچه انتقال بار بیشتری بین مولکول و فسفرین اتفاق بیفتد، مقاومت لایه نیز تغییر بیشتری می کند و لذا با محاسبه ی تغییرات مقاومت می توان گازها را تشخیص داد و غلظت آنها را بدست آورد. نتایج نشان می دهند که فسفرین بیشترین حساسیت را به گازهای مبتنی بر اتم نیتروژن و بخصوص مولکول گاز NO دارد. به منظور بهبود عملکرد حسگر فسفرین، به مطالعه ی نقش کرنش در عملکرد حسگری آن پرداخته شد. مکان های بهینه ی جذب هر یک از گازها در کرنش های مختلف بدست آمد و تغییرات انرژی جذب گازها در اثر اعمال کرنش شناسایی شد. نتایج تاثیر اعمال کرنش نشان می دهند که اعمال کرنش به تک لایه، قابلیت تفکیک گازها را بهبود می بخشد. در نهایت می توان گفت که عملکرد حسگر گازی فسفرین بدون کرنش و همچنین تحت کرنش قابل قبول است و توانایی بالقوه ای در تفکیک گازها دارد.کلید واژگان: مواد دوبعدی, فسفرین, حسگر گازی, انتقال بار, کرنش}Nano scale, Volume:5 Issue: 4, 2019, PP 295 -303This work presents a comprehensive study on adsorption properties of H2S, NH3, CO, and NO on phosphorene, by employing first-principle calculations. The optimized atomic sites, directions and the associated adsorption mechanisms are carefully analyzed. Transfer of charge between the gas molecule and the layer modifies the layer’s resistance. Therefore, by evaluating the resistance variation, the concentration of gas molecules can be determined. The results indicate that nitrogen-based molecules especially NO, show the highest sensitivity among the studied gases. In addition, strain effects on sensor characteristics and adsorption behavior are investigated. The optimal locations for the absorption of the gases and the mechanism of absorption energy under various strain conditions are analyzed. The results indicate that sensitivity increases with strain and significantly improves the selectivity of the sensor. The results show that both strained and unstrained phosphorene are suitable candidates for sensitive gas sensing applications.Keywords: Two-dimensional, phosphorene, gas sensor, charge transfer, strain.}
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چکیده در این مقاله لایه های نازکIn2O3 ، SnO2 و ITO SnO2 10 In2O3 90 با استفاده از روش تبخیر حرارتی روی زیر لایه های شیشه انباشت شدند. ضخامت و آهنگ انباشت برای همه نمونه ها به ترتیب nm 220 و nm/s 1/0 انتخاب شد. خواص اپتیکی لایه ها در دمای بازپخت °C300 مورد بررسی قرار گرفت. در این مطالعه همه نمونه های بازپخت شده عبور بالایی در طیف نور مرئی از خود نشان دادند. بیش ترین عبور 91 را لایه بازپختی SnO2 نشان داد. ضرایب شکست نمونه های مختلف در طول موج 550 نانومتر در محدوده 88/1 تا 92/1 به دست آمد. هم چنین با افزودن ناخالصی SnO2 به In2O3 خواص فیزیکی این لایه ها مورد بررسی قرار گرفت. نتایج طیف پراش ایکس نشان می دهد لایه های In2O3 و ITO دارای ساختار بس بلورین بوده و در ساختار مکعبی متبلور می شوند. در نهایت به منظور مقایسه حساسیت لایه های SnO2، In2O3 و ITO نسبت به آشکارسازی بخار اتانول، به عنوان یکی از کاربرد مواد نیم رسانای شفاف پرداخته شده است. نتایج حساسیت بالای SnO2 در مقایسه با In2O3 و ITO را برای آشکارسازی بخار اتانول نشان می دهد.کلید واژگان: اکسید نیم رسانای شفاف, لایه های نانو ساختار, خواص اپتیکی, حسگر گاز}Nano scale, Volume:4 Issue: 4, 2018, PP 321 -330Abstract In this research, In2O3, SnO2 and 10 SnO2 90 In2O3 ITO thin films were deposited on glass substrates using thermal evaporation technique. The thickness and deposition rate for all the samples are 220 nm and 0.1 nm/s, respectively. The optical properties of the layers were investigated at annealing temperature of 300 ℃. In this study, all annealed samples indicate high transmittance in the visible wavelength region. The highest transmission for the annealed layers is 91 which is related to the SnO2. Refractive indexes of different samples n at a wavelength of 550 nm are in the range of 1.88-1.92. Also, the effect of adding SnO2 as impurity to In2O3 on physical properties of these films were investigated. X-ray diffraction results show that In2O3 and In2O3 doped with tin layer have a polycrystalline structure and are crystallized in the cubic structure. Finally, the influence of nanoparticles of SnO2, In2O3 and ITO for sensing ethanol vapor as an application of transparent semiconductor oxides is discussed. The results show a high sensitivity of SnO2 films compared to the In2O3 and ITO films for detecting ethanol vapor.Keywords: Transparent semiconductor oxide, Nanostructured films, Optical properties, Gas sensor}
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A new nitrobenzene vapor chemiresistor sensor was introduced based on a nanocomposite of graphene/imprinted polymer nanoparticles/poly (methyl methacrylate). The nano-sized molecularly imprinted polymers (nano-MIP) holding the cavities compatible with nitrobenzene molecules were synthesized utilizing methacrylic acid and vinyl benzene as the functional monomers and Divinylbenzene as the cross-linker. The copolymerization reaction was fulfilled in acetonitrile via precipitation method. The nano-MIP particles were mixed with graphene to produce a chemiresistor gas sensor. The addition of poly(methyl methacrylate) in the nanocomposite resulted in better physical durability, enhanced selectivity and higher resistance against humidity effect. The response of MIP based sensor was considerably higher than that of the NIP based gas sensor. The response of the gas sensor was reversible and a relative standard error equal to 3.1% was calculated for 4 relations in the determinations. The sensor showed linear response in the concentration range of 0.1055.0 ppm. The detection limit was calculated to be 0.04 parts per million (S/N).Keywords: Graphene, Nanocomposite, Imprinted polymer nanoparticles, Chemiresistor, Nitrobenzene, Gas sensor}
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Nowadays, the semiconductor nanowires (NWs) typically used in hydrogen gas sensors. Gallium nitride (GaN) with a wide band gap of 3.4 eV, is one of the best semiconductors for this function. NWs surface roughness have important role in gas sensors performance. In this research, GaN NWs have been synthesized on Si substrate by plasma-assisted vapor phase deposition at different deposition time, without using any catalyst. The precursors were gallium (Ga) metal and nitrogen (N) plasma. The GaN NWs were characterized by X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy )FE-SEM(, photoluminescence (PL) and Raman Spectroscopy. The results indicate the serrated morphology for hexagonal structure of GaN NWs. The band gap energy of GaN NWs was obtained about 3.41 eV. The Raman results show two Raman active optical phonons at 563 cm-1 and 720 cm-1 due to E2(high) and A1(LO), respectively and indicates a good crystallinity of the NWs with the presence of defects in the crystal lattice.Keywords: Gallium nitride, Nanowires, Gas Sensor}
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Indium (1at %) doped ZnO and ZnO nanoparticles have been synthesized via sol gel method. The structural characters of the synthesized nanoparticles have been studied by X-ray diffraction pattern (XRD), scanning electron microscopy (SEM) and energy-dispersiveX-ray spectroscopy (EDX). From synthesized nanopowders a tablet was prepared by using the isostatic pressing and then sintered at 600°C. Then, the gas-sensing properties of ZnO and IZO powder tablets were evaluated with respect to the acetone gas at different temperatures and concentrations. XRD pattern and SEM images showed the prepared samples were crystallized in the wurtzite structure with the average particle size of 32 and 27 nm. The gas sensing measurement results showed that the indium dopant ions improved the gas sensitivity of ZnO for high acetone concentrations effectively. Therefore, it is suggested that the IZO tablet can act as reliable and low cast gas sensor for acetone detection. Sintering temperature strongly increased the grain size and density of samples. EDX analysis confirmed the presence of indium in zinc oxide structure.Keywords: Acetone, Gas Sensor, Indium ions, Zinc oxide}
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The high crystallinity ZnO nanoparticles with an average particle diameter 30 nm have been successfully synthesized with a surfactant-mediated method. The cationic surfactant (cetyltrimethylammonium bromide, CTAB) and the hydrous metal chlorides (ZnCl2⋅2H2O) appear to be the good candidates for obtaining a high yield of nanoparticles. The structural and morphological characterizations were carried out by X-ray powder diffraction, scanning electron microscope and transmission electron microscopy, respectively. The resulting powders are highly crystalline and largely monodisperse ZnO nanoparticles. When used as a sensing material in gas sensor, it exhibits the high-performance gas sensing performances including high gas response, good selectivity, fast response/recovery time, good repeatability as well as stability towards low-ppm-level (10 to 100 ppm) n-butanol gas. At the optimal operating temperature (260 ºC), its gas response toward 100 ppm butanol is 174.8. The response and recovery time are 18 and 11 seconds, respectively. Theses findings not only provide a novel approach to fabricate ZnO nanoparticles via a surfactant-mediated method, but also explore a promising gas sensor towards n-butanol.Keywords: Gas response, Gas Sensor, n-butanol, Surfactant-mediated, ZnO nanoparticles}
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In this work, hierarchical WO3 core-shell microspheres were synthesized via a facile template-free precipitation method. Gas sensing properties of the synthesized powder to acetone and some other volatile organic compounds were comparatively investigated with commercial WO3 nanoparticles. The synthesized and commercial powders were characterized by X-ray diffraction, scanning electron microscopy, particle size distribution analysis, BrunauerEmmettTeller and Barrette-Joyner-Halenda techniques. Gas sensors were fabricated by deposition of powders between/on interdigitated electrodes via sedimentation approach. The results show that both sensors are sufficiently sensitive to detect 1.8 ppm of acetone; diabetes diagnosis threshold in human exhaled breath. Indeed, the hierarchical based one is highly sensitive and more selective to acetone.Keywords: Acetone, Core, shell microspheres, diabetes, Gas sensor, Nanoparticles, WO3}
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Thin films of SnO2 nanowires were successfully prepared by using chemical vapor deposition (CVD) process on quartz substrates. Afterwards, a thin layer of palladium (Pd) as a catalyst was coated on top of nanowires. For the deposition of Pd, a simple and low cost technique of spray pyrolysis was employed, which caused an intensive enhancement on the sensing response of fabricated sensors. Prepared sensor devices were exposed to liquid petroleum gas (LPG) and vapor of ethanol (C2H5OH). Results indicate that SnO2 nanowires sensors coated with Pd as a catalyst show decreasing in response time (~40s) to 1000ppm of LPG at a relatively low operating temperature (200oC). SnO2 /Pd nanowire devices show gas sensing response time and recovery time as short as 50s and 10s respectively with a high sensitivity value of ~120 for C2H5OH, that is remarkable in comparison with other reports.Keywords: Chemical vapor deposition, Gas sensor, Nanowires, Response time, Spray pyrolysis}
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