A surfactant assisted facial hydrothermal process has been employed for the synthesis of rutile and wurtzite phase SnO
2
and ZnO nanoparticles, respectively, confirmed by X-ray diffraction studies. ...High resolution transmission electron microscopy studies revealed the formation of ∼15 and 20 nm of SnO
2
and ZnO nanoparticles, respectively, whereas, the structural analysis was done
via
Fourier transform infrared (FTIR) and Raman spectroscopy studies that suggested the minor doping of surfactant and surface adsorption of environmental oxygen. The gas sensing response of the prepared nanoparticles has been measured in ammonia environment and the sensing responses of the SnO
2
and ZnO nanoparticles are found to be 4.53 and 3.96%, respectively, at 46 ppm of ammonia. The mechanism of interaction of ammonia with metal oxide nanoparticles has been investigated through FTIR and Raman spectroscopic measurements performed in ammonia environment.
A surfactant assisted facial hydrothermal process has been employed for the synthesis of rutile and wurtzite phase SnO
2
and ZnO nanoparticles, respectively, confirmed by X-ray diffraction studies.
Ultra-violet photodetectors based on p-ZnO/n-Si
−
heterojunctions have been fabricated by radio-frequency magnetron sputtering technique. To develop heterojunction devices, thin films of pristine ZnO ...and Sb-doped (3 wt% and 5 wt%) ZnO are grown over the highly doped n-type silicon (Si) substrates. The so-grown thin films form isotype heterojunction between the n-type pristine ZnO and n-type Si substrate (n-ZnO/n-Si
−
) and p–n heterojunctions between p-type Sb-doped ZnO (Zn
0.97
Sb
0.03
O and Zn
0.95
Sb
0.05
O) and n-type Si substrates (p-Zn
1−
x
Sb
x
O/n-Si
−
). The structural analysis for the deposited films using Raman spectroscopy reveals the growth of high-quality ZnO thin films. In addition to the fundamental Raman modes of ZnO, some anomalous modes related to the multiphonon vibrations are also observed in the Raman spectra of the fabricated devices. The photoconduction behavior of the fabricated devices have been analyzed under UV-A (
λ
= 365 nm) and UV-C (
λ
= 254 nm) light at different illumination intensities from 0.152 to 1.0 mW/cm
2
. The average photoresponses of the n-ZnO/n-Si
−
, p-Zn
0.97
Sb
0.03
O/n-Si
−
, and p-Zn
0.95
Sb
0.05
O/n-Si
−
heterojunction devices in UV-C illumination are found to be 45.12, 52.23, and 58.31%, respectively, which are found to be lower than those recorded under UV-A light (~ 50.32, 72.53, and 82.62%, respectively) at an illumination intensity of 1 mW/cm
2
. The external quantum efficiency is an important parameter related to the device performance that is found to increase from 14.41 to 78.08% through 54.02%, with an increase in Sb-doping concentration from 0.0 to 5 wt% through 3 wt% in ZnO thin film. The response and recovery times of the fabricated devices are found to be lower than 1 s.
•Polypyrrole (PPy) nanoribbons and nanoparticles were grown by chemical method.•PPy nanoribbons and nanoparticles were tested for ammonia gas sensitivity.•Raman spectroscopic methods used for ammonia ...gas sensing for PPy samples to understand the gas sensing mechanism in polypyrrole.•Electrical and Raman sensing behavior is well correlated.
Nanostructured polypyrrole (PPy) has been synthesized in the presence of anionic azo dye {sodium 4-4-(dimethyl-amino)-phenyldiazo phenylsulfonate} (MO) and cationic surfactant {cetyltrimethyl ammonium bromide} (CTAB). The synthesis of the prepared PPy samples was confirmed by Fourier transform infrared spectroscopy and structural analysis was carried out using X-ray diffraction technique. Scanning electron microscopy and high resolution transmission electron microscopy investigations confirm the formation of nanostructured PPy. Both the samples have different shapes and dimensions. The sample prepared in the presence of MO has the higher doping level, bipolaron concentration and electrical conductivity (4Scm−1) as compared to the sample prepared in the presence of CTAB (1.69×10−4Scm−1). The prepared samples were tested for porosity through BET measurements. It has been found that the PPy nanowires (S1) have larger surface area (156,056.0cm2/g) as compared PPy nanoparticles (S2) (11,259.0cm2/g). Moreover, PPy nanowires have shown better gas sensitivity (∼6%) as compared to PPy nanoparticles (∼4%) and well corroborated with porosity, surface morphology, and the Raman investigations carried out under ammonia environment.
The chemically prepared pristine and graphene-doped polyaniline (PANI) samples are utilized for the fabrication of room temperature methanol sensors. For the fabrication of PANI/graphene-based ...sensing devices, four samples of PANI/graphene composites were prepared with four different concentrations of graphene (2, 4, 6 and 8 wt%). The surface morphology of the prepared composites was analyzed under field emission scanning electron microscopy (FE-SEM), which revealed the agglomerated structures of PANI/graphene composites. X-Ray diffraction studies carried out on these samples revealed the semi-crystalline nature of the samples, whereas, Raman studies confirmed the growth of PANI with the presence of all fundamental bands of PANI in the pristine as well as in its doped state. The prepared PANI/graphene composites devices were tested for alcohol detection at two different concentrations (50 and 100 ppm) of methanol. The change in electric current with the change in environment has been recorded as a sensing parameter and is employed to determine other sensor parameters such as percentage response, response time and recovery time. The sensing response of the prepared samples is found to increase with graphene doping concentration as well as methanol ppm level. The PANI/graphene composite with 8 wt% doping of graphene has shown the highest response (~ 61.5% at 100 ppm) and the lowest response time (55 s). The mechanism of gas sensing has also been discussed in details with the possible theoretical analogy with the adsorption and desorption of gas molecules in accordance with Langmuir kinetic theory.
Polyaniline–vanadium pentoxide-based organic/inorganic hybrid sensors were fabricated and employed for methanol detection at room temperature (~ 28 °C). The four different loading concentrations (5, ...10, 20, 30% by weights) of vanadium pentoxide (V
2
O
5
) were incorporated in the polyaniline matrix to improve the sensing properties of the polymeric materials. The synthesized materials were examined for crystalline structures, chemical bonding, and surface properties using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and Field emission scanning electron microscopy (FE-SEM) techniques. The XRD studies revealed the semi-crystalline nature of the polyaniline composites with V
2
O
5
nanoparticles. The fabricated devices were analyzed in different chemical environments of carbon dioxide, hexane, chloroform, acetone, ethanol, and methanol. The selectivity values of polyaniline composite with 30% (by weight) loading of V
2
O
5
towards these chemicals were found to be ~ 2.96, 3.51, 5.25, 8.14, 34.23 and 46.91%. The highest sensing response and selectivity of the fabricated sensors were observed toward methanol vapors as compared to other chemical vapors. The sensing responses of the fabricated sensors with loading concentrations of 00, 05, 10, 20 and 30% by weights of V
2
O
5
were found to be ~ 18.27, 21.36, 25.04, 31.79, and 36.41%, respectively, in the methanol environment (at 60 ppm).
Graphical abstract
The electrochemical behavior of the prepared solid state supercapacitors based on the composites of polyaniline (PANI) with multiwalled carbon nanotubes (MWCNTs) have been reported in this study. The ...PANI/MWCNTs composites are prepared by simple chemical oxidation polymerization method with different doping concentrations (2, 4, 6 and 8 wt%) of MWCNTs. X-ray diffraction studies performed on the pristine and composite samples reveal the semi-crystalline nature of PANI, with three well visualized reflections at 2θ values of 16, 22 and 25
o
, corresponding to the hkl planes (011), (020) and (200) respectively, of PANI. The absence of crystalline peaks of MWCNTs in the composites reveal the complete wrapping of PANI chains over the MWCNTs. Field emission scanning electron microscopy studies reveal the agglomerated structural form of the prepared samples. Raman spectroscopic studies confirm the growth of PANI and its composites with MWCNTs, consisting of all the characteristic bands of PANI. The electrochemical activity of the prepared supercapacitor is recorded through cyclic voltammetry. The prepared supercapacitor with 8 wt% doping concentration of MWCNTs, has significantly high values of 446.89 F/g, 248.29 Wh/kg and 16,865.12 W/kg for the specific capacitance, energy density and power density, respectively. The high values of these parameters for the supercapacitor with 8 wt% doping concentration of MWCNTs can be attributed to the high electrical conductivity, low internal resistance and inherent porous nature of MWCNTs. The PANI-MWCNTs composites have more stability with capacitance retention of 83.97% for PANI/MWCNTs composite (8 wt%), whereas, pristine PANI exhibits only 64.12% of the original capacitance after 10,000 cycles and the stability increases with the increase in doping concentration of MWCNTs.
Here, we report the fabrication of the p-n hetero-junction devices of p-Zn
1-x
Sb
x
O/n-Si
−
grown by utilizing the radio-frequency sputtering technique. The fabricated devices were analyzed for ...morphological and structural modifications under atomic force microscopy (AFM) and X-Ray diffraction (XRD) techniques. The AFM studies reveal the growth of agglomerated nanoparticles like structures distributed throughout the surfaces of the deposited films, whereas, XRD studies reveal the significant change in crystallite size, lattice parameters, stress and strain with the incorporation of antimony (Sb) in ZnO matrix. The conduction behavior of charge carriers has been systematically analyzed in the fabricated hetero-junction devices. Current–Voltage (I–V) characteristics reveal a trap free space charge limiting current conduction in the fabricated devices. The room temperature mobility of charge carriers for the pristine ZnO, Zn
0.97
Sb
0.03
O and Zn
0.95
Sb
0.05
O thin film devices are found to be 8.06 × 10
–2
, 19.0 × 10
–2
and 40.69 × 10
–2
cm
2
/Vs, respectively.
Pristine and zinc-doped nickel oxide isotype heterojunction devices have been fabricated on p-type silicon substrates using the sol–gel spin coating deposition technique. The structural, composition, ...defect state, and phase analyses have been done by utilizing X-ray diffraction and Raman spectroscopy techniques. Field emission scanning electron microscopy (FESEM) has been utilized to analyze the morphology of the deposited films, whereas the elemental composition has been studied through EDS spectra. The non-linear current–voltage (I–V) characteristics of the fabricated isotype heterojunction devices reveal the diodic behavior of the devices. A combination of mathematical and physical approaches based on the modified Shockley equation and Lambert
W
function has been applied to analyze the performances of the devices. The ultraviolet (UV) photodetection behavior of the fabricated devices was studied under the illumination of UV light of wavelengths 365 and 254 nm under zero bias conditions. It is found that pristine NiO is inactive towards both wavelengths; however, incorporating Zn
2+
in NiO leads to a significantly large photoresponse of ~ 473%, 1111%, and 1725% for 5, 10, and 15% of Zn
2+
molar concentrations, respectively. External quantum efficiency (EQE), responsivity, linear dynamic range (LDR), and detectivity have also been found to improve with Zn
2+
concentration. The photoconduction mechanism of the fabricated devices has been discussed in detail.
•We fabricated a room temperature functioning, highly sensitive and flexible ammonia (NH3) gas sensor based on polyaniline (PANI).•NH3 gas-sensing properties of the sensor are examined at room ...temperature in the range 5–1000ppm.•The observed response is linear for the range 5–1000ppm, indicating PANI film based sensors are high potential candidates for NH3 gas detection.•The bending of the sensor has no significant effect on its sensing performance, indicating good mechanical reliability.
Here we present, a useful ammonia (NH3) gas sensor based on polyaniline (PANI) film as an active sensing layer. The PANI films were successfully deposited on a polyethylene terephthalate (PET) flexible substrate by a simple in-situ polymerization technique. Ammonia (NH3) gas-sensing properties of the films prepared at optimum conditions were examined at room temperature in the range of 5–1000ppm. The room temperature functioning of the sensor is critical, which facilitates low-power operation and also enhances the life time of a sensor. The observed variation in resistance of PANI film corresponding to 1000ppm and 200ppm of NH3 exposure, is approximately 520 and 110 times of that observed for ∼5ppm of NH3. Furthermore, good reproducibility and long-term stability were also observed over a concentration range from 5 to 1000ppm. Moreover the sensor is mechanically robust and can be bent sharply without damage, demonstrating excellent mechanical stability and exhibiting no lack in performance even after several bending cycles. These results indicate that the PANI films on flexible substrates are promising for portable on-site detection.
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