S.T. Navale

SnO2nanoparticles-modified polyaniline films as highly selective, sensitive, reproducible and stable ammonia sensors

AbstractNanocomposites of polyaniline (PANi) and tin oxide (SnO2) were prepared by adding SnO2 nanoparticles (NPs) in different weight ratios (0%–50%) into the PANi matrix. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were used to form the polyaniline-SnO2 nanocomposites (PANi-SnO2) — a polymer-composite. PANi films modified with SnO2NPs were prepared by the spin coating method. The gas sensing properties of PANi, SnO2 and PANi-SnO2 polymercomposite films were observed and it was found that:nThe response of PANi film to 100 ppm NH3 at room temperature was 30% (stability 58%).The response of SnO2 film to 100 ppm NO2 was 19% (stability 79%) at operating temperature 200°C, which is higher than the room temperature. However, SnO2 exhibited no response to NO2 and NH3 at room temperature.The properties of the polymer-composite as a gas sensor were studied for various reducing (CH3OH, C2H5OH, NH3, H2S) as well as oxidising (NO2 and Cl2) gases. We demonstrated that the PANi-SnO2 (50%) polymer-composite film offers high stability and reproducibility and is a superior sensor to toxic gases operating at room temperature. (Results showed that they are highly selective to NH3 along with maximum response − 72% to 100 ppm, fast-response time of 167 s and better stability − 86% at room temperature. The unique nanostructure of this polymer composite with its high surface area offers these advantages.

Camphor sulfonic acid doped PPy/α-Fe2O3 hybrid nanocomposites as NO2 sensors

PPy/α-Fe2O3 hybrid nanocomposites with different weight percentages (10–50%) of CSA were successfully prepared by using a solid state synthesis method. Thin films of prepared hybrid nanocomposites were deposited on glass substrates using a spin coating technique and have been characterized using various techniques such as XRD, FESEM and TEM. The gas sensing performance of 10–50% CSA doped PPy/α-Fe2O3 nanocomposite thin films were studied towards NO2, Cl2, NH3, H2S, CH3OH and C2H5OH gases. Among various compositions, 30% CSA doped thin films were found to be highly sensitive and selective towards NO2 gas at room temperature i.e. with a chemiresistive response of 64% at 100 ppm with a reasonably fast response time of 148 s. The sensor responses in relation to the CSA doping concentration and the gas concentration have been systematically studied. Additionally, other sensing properties such as reproducibility, cross-sensitivity, sensing linearity and stability were also studied and explored. The CSA doped PPy/α-Fe2O3 nanocomposites exhibited better response, stability and shorter recovery times as compared to PPy and PPy/α-Fe2O3 nanocomposites alone. Therefore, it is expected that such a material with excellent gas sensing properties at room temperature can be used for high performance selective NO2 sensors.

Facile method of preparation of PbS films for NO2 detection

A simple and inexpensive chemical bath deposition method was employed for the preparation of lead sulfide (PbS) thin films. Thin films of PbS were characterized using XRD, SEM, TEM, SAED, contact angle and two probe techniques. The gas sensing properties of PbS thin films (t = 0.443 μm) have been investigated for H2S, NH3, C2H5OH, CH3OH, Cl2 and NO2. PbS thin films have been found to be more highly sensitive and selective towards oxidizing NO2 gas than the other test gases. The PbS sensor exhibits a maximum response of 74% towards 100 ppm of NO2 gas with a response time of 20 s. PbS thin films are able to detect up to 5 ppm NO2 concentration at room temperature with excellent reproducibility and stability. The sensing mechanism of PbS thin films towards NO2 gas is also discussed. The interaction of NO2 gas with PbS film was also investigated using impedance spectroscopy.

Synthesis, structural, compositional, morphological and optoelectronic properties of tungsten oxide thin films

Low cost sol–gel drop cast method has been successfully employed for preparation of nanocrystalline tungsten oxide (WO3) thin films. The effect of processing temperature on the structure, morphology, electrical conductivity, thermoelectric power and band gap was studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field emission scanning electron microscope (FESEM), Transmission electron microscopy (TEM), Atomic force microscopy (AFM), two probe technique and UV-visible spectroscopy. XRD analysis showed that WO3 films are crystallized in the orthorhombic phase and present a random orientation. XPS confirms formation of WO3. FESEM analysis revealed that surface morphology of the tungsten oxide film consists nanocrystalline grains with uniform coverage of the substrate surface. TEM of WO3 film showed nanocrystals having diameter ranging from 60 to 80xa0nm. AFM analysis showed surface morphology of WO3 film is not smooth. The DC electrical conductivity showed the semiconducting nature with room temperature electrical conductivity increased from 7.264xa0×xa010−8 to 1.606xa0×xa010−7 (Ωxa0cm)−1 as processing temperature increased from 400 to 700xa0°C. Thermo electric power measurement confirms n-type conduction. The band gap energy of WO3 film decreased from 3.264 to 2.531xa0eV as processing temperature increased from 400 to 700xa0°C.

PPy/α-Fe2O3 hybrid nanocomposites: effect of CSA doping on structural, morphological, optical and electrical transport properties

Hybrid nanocomposites of camphor sulfonic acid (CSA) doped organic polypyrrole and inorganic alpha-ferric oxide (PPy/α-Fe2O3) have been successfully prepared using different weight percentages of CSA (10–50xa0%) dispersed in PPy/α-Fe2O3 hybrid nanocomposite by solid state synthesis method. These hybrid nanocomposites are characterized by using various techniques such as X-ray diffraction (XRD), fourier transform infra red (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–visible spectroscopy and two probe techniques respectively. The XRD spectra revealed that the addition of CSA has no effect on crystallinity of PPy/α-Fe2O3 hybrid nanocomposite. The FTIR results show that, the characteristic peaks of PPy/α-Fe2O3 hybrid nanocomposite shift to higher wave number after addition of CSA in the PPy/α-Fe2O3 nanocomposites indicates some chemical interactions and better conjugation between CSA and PPy/α-Fe2O3 hybrid nanocomposites. SEM studies revealed that strong effect on morphology of PPy/α-Fe2O3 nanocomposite. The AFM analysis show uniform nano porous granular morphology. UV–visible spectroscopy studies have provided insight into the electronic interaction between the PPy, α-Fe2O3 and CSA. DC electrical conductivity showed a steeply increase in electrical conductivity of PPy/α-Fe2O3 nanocomposites with increase in amount of CSA from 10 to 50xa0%.

NH3 sensor based on CSA doped PANi-SnO2 nanohybrid

The PANi-SnO2 hybrid nanocomposite based thin films doped with 10–50 wt % CSA were deposited on the glass substrates using the spin coating technique. The sensor response in relation to the CSA doping concentration and the gas concentration has been systematically studied. A significant sensitivity (91%) towards 100 ppm NH3 operating at room temperature is observed for the 30 wt % CSA doped PANi-SnO2 nanohybrid. The sensing mechanism of CSA doped PANi-SnO2 materials to NH3 was presumed to be the effect of p–n heterojunctions.

Investigation of structural, morphological and electrical properties of nanocomposite based on SnO2 nanoparticles filled polypyrrole matrix

A facile solid-state approach was used to prepare polypyrrole-tin oxide (PPy–SnO2) (0–50xa0wt%) hybrid nanocomposites (NCs). The structure and morphology of the hybrid NCs were characterized using X-ray photoelectron spectroscopy, X-ray diffraction (XRD), Fourier transform infrared (FTIR), ultraviolet–visible (UV–Vis), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) measurement techniques. Two point-probe method was used to study electrical transport properties of PPy–SnO2 hybrid NCs. The structures of SnO2 as well as PPy–SnO2 hybrid NCs (0–50%) were confirmed from the XRD patterns. The FESEM surface images of the hybrid NCs reveal uniform distribution of the SnO2 nanoparticles (NPs) in the PPy matrix. The characteristic FTIR peaks of PPy and UV–Vis absorption wavelength shift to a higher wavenumber and wavelength sides in PPy–SnO2 hybrid NCs, which are attributed to interaction of SnO2 NPs with PPy molecular chains. The negatively charged O2− surface of SnO2-NPs transfers electrons to polypyrrole which is in its highly reduced form. A strong localization of charge carriers in the reduced polypyrrole makes PPy–SnO2 hybrid NCs highly resistive.

Development of Fe2O3sensor for NO2detection

Fe 2 O 3 nanosensors fabricated on glass substrate using sol gel spin coating technique. The relative sensitivity of the Fe 2 O 3 nanoparticles-based NO 2 sensor was evaluated by electrical resistance measurements. Our reproducible experimental results show that Fe 2 O 3 nanoparticles have a great potential for nitrogen dioxide sensing applications at 200°C.

Development of Fe[sub 2]O[sub 3] sensor for NO[sub 2] detection

Fe 2 O 3 nanosensors fabricated on glass substrate using sol gel spin coating technique. The relative sensitivity of the Fe 2 O 3 nanoparticles-based NO 2 sensor was evaluated by electrical resistance measurements. Our reproducible experimental results show that Fe 2 O 3 nanoparticles have a great potential for nitrogen dioxide sensing applications at 200°C.

Development of Fe2O3 sensor for NO2 detection

Fe 2 O 3 nanosensors fabricated on glass substrate using sol gel spin coating technique. The relative sensitivity of the Fe 2 O 3 nanoparticles-based NO 2 sensor was evaluated by electrical resistance measurements. Our reproducible experimental results show that Fe 2 O 3 nanoparticles have a great potential for nitrogen dioxide sensing applications at 200°C.