A synergistic approach to enhance sensitivity and selectivity of room temperature operable ammonia gas sensor with humidity assistance using RGO/WO3nanocomposite.

In this study, the fabrication of an ultrahigh selective NH3gas sensor based on RGO/WO3nanocomposite has been proposed. The hydrothermal method was employed to synthesize the RGO/WO3nanocomposite. The formation of RGO/WO3nanocomposite and the elemental composition, structure and morphology of the as-synthesized materials were confirmed through an array of analytical techniques, including XRD, Raman, FT-IR, XPS and TEM. For gas sensing applications, pure RGO and RGO/WO3have effectively spin-coated onto the interdigitated electrodes (IDE's) based on fluorine doped tin oxide (FTO) respectively, and their sensitivity towards NH3was tested. Gas sensing characteristics of prepared materials were analyzed at room temperature (25 °C) under different relative humidity (RH) levels. The developed RGO/WO3sensor was subjected to different NH3concentrations, demonstrating a high sensing response of 89% towards 500 ppm NH3under 11%-97%-11% RH conditions. Notably, the sensor exhibited rapid response and recovery times with an average response time of 92 s and recovery time of 26 s when exposed to 500 ppm NH3under the specified RH conditions. To gauge the material selectivity, the prepared nanocomposite was exposed to a range of volatile organic compounds and the results showcased the sensor's remarkable selectivity and sensitivity specifically toward NH3vapor. This superior performance can be attributed to the abundant active sites and the excellent electron transport properties inherent to the RGO component. Importantly, the RGO/WO3sensor displayed high reproducibility and consistent responses, with minimal degradation (1.98% degradation) over 30 d at 11%-97%-11% RH. Furthermore, we examined the sensor's response with varying levels of relative humidity to assess its potential for real-world applications. The sensor exhibited extremely low power consumption, outperforming a commercially available metal oxide sensor while operating at ambient temperature. The robust performance of RGO/WO3coupled with low power requirements and ambient temperature operation, positions it as a promising candidate for next-generation gas sensing technologies.

An investigation into the hybrid architecture of Mn-Co nanoferrites incorporated into a polyaniline matrix for photoresponse studies.

In this study, an enhanced photoresponse was observed in the Mn-Co Nanoferrites (MCFs)-Polyaniline (PANI) nanohybrid architecture due to the formation of interface between PANI and MCFs, which provided a conduction pathway for the movement of charge carriers, and these interfaces were observed in a high-resolution transmission electron micrograph (HR-TEM). X-ray photoelectron spectroscopy (XPS) suggests that the carbon (C 1s) of the MCF-PANI nanohybrid shows peaks at 287.80 eV for CO, 286.17 eV for C-O, 285.24 eV for C-N, 284.50 eV for the sp3 hybridized carbon (C-C/C-H) and 283.84 eV for the sp2 hybridized carbon (CC). Current-voltage (I-V) curves reveal an ohmic nature of the MCF-PANI nanohybrid photodetector device. The photoresponse measurements were analyzed using the trap depth concept, demonstrating that the conductive polymer increases the photoconduction mechanism efficiency of MCFs. The constructed photodetector device exhibits a high photoresponsivity of 22.69 A W-1, a remarkable detectivity of 1.36 × 1012 cm Hz1/2 W-1 and a fast rise/decay time of 0.7/0.8 s. The excellent performance of the as-fabricated photodetector device could be explained by the intimate interaction between MCFs and PANI at their interface.

Tailored mesoporous γ-WO3 nanoplates: unraveling their potential for highly sensitive NH3 detection and efficient photocatalysis.

Herein, the monoclinic phase of tungsten oxide (γ-WO3) was successfully obtained after annealing hydrothermally synthesised WO3 powder at 500 °C. As per the result obtained from the N2 adsorption-desorption isotherm, the material has been identified as mesoporous with a specific surface area of 3.71 m2 g-1 from BET (Brunauer-Emmett-Teller) analysis. Moreover, the average pore size (49.52 nm) and volume (0.050 cm3 g-1) were also determined by the BJH (Barrett-Joyner-Halenda) method. FE-SEM (field emission scanning electron microscopy) and HR-TEM (high resolution transmission electron microscopy) have confirmed the formation of nanoplates with an average diameter of approximately 274 nm. Raman spectroscopy has shown peaks at the lower wavenumber region (270 cm-1 and 326 cm-1) and the higher wavenumber region (713 cm-1 and 806 cm-1) for O-W-O bending modes and stretching modes, respectively. The combined effect of relative humidity (RH-11%-RH-95%-RH-11%) and NH3 (150 ppm, 300 ppm, 450 ppm, 600 ppm, 700 ppm, and 800 ppm) was investigated in this reported work. The synthesised γ-WO3 has shown highly responsive behaviour for humidity of 96.5% (RH-11%-95%) and NH3 sensing (under humidity) of 97.4% (RH-11%-95% with 800 ppm NH3). The response and recovery time were calculated as 15 s and 52 s, and 16 s and 54 s for humidity, and NH3 under humidity, respectively. The experimental findings demonstrated that the resistance of the sensor depends on the concentration of NH3 and humidity. Moreover, γ-WO3 has been investigated as a promising catalyst for the dye degradation of methylene blue (MB) with a degradation efficiency of 72.82% and methyl orange (MO) with a degradation efficiency of 53.84% under visible light exposure. This dye degradation occurred within 160 min in the presence of a catalyst under visible light irradiation.

Facile synthesis of water-soluble Fe3O4 and Fe3O4@PVA nanoparticles for dual-contrast T1- and T2-weighted magnetic resonance imaging.

Superparamagnetic iron oxide nanoparticles (SPIONs) are widely used as a robust negative contrast agent on conventional MRI. The development of new types of high-performance nanoparticulate MR contrast agents with either positive (T1) or dual-contrast (both positive and negative, T1 + T2) ability is of great importance. Here we report a facile synthesis of Fe3O4 and Fe3O4@PVA nanoparticles for dual-contrast T1- and T2-weighted MRI. The produced iron oxide nanoparticles were of high crystallinity and size uniformity with an average diameter of 7.25 & 8.64 nm and can be individually dispersed in the physiological buffer with high stability. The functional compositions and formation of PVA-magnetite composite were confirmed by FTIR analysis. VSM studies have shown that magnetite and PVA-magnetite composite nanoparticles exhibit superparamagnetic behavior at room temperature with saturation magnetization value of 54.82 emu/g, 39.62 emu/g respectively. It's due to the presence of nonmagnetic PVA molecule on magnetite and decrease in the size of the magnetite. The XPS and Mössbauer spectra reveals presence of pure Fe3O4 nanoparticles. In-vitro relaxivity and contrast enhancement analysis show that, among both tested nanoparticles, Fe3O4@PVA nanoparticles possess optimal molar relaxivities and contrast enhancement values, which can shorten the spin-lattice and spin-spin relaxation times, simultaneously.

Earth-abundant and environmentally benign Ni-Zn iron oxide intercalated in a polyaniline based nanohybrid as an ultrafast photodetector.

Nickel-zinc iron oxide (NZF) was introduced into a polyaniline (PANI) matrix by an in situ chemical oxidation polymerization approach. The surface composition and chemical states were investigated by X-ray photoelectron spectroscopy (XPS), which revealed an Fe 2p spectrum with the two peak positions of Fe 2p3/2 and Fe 2p1/2 at 711.00 and 724.48 eV, respectively. Deconvolution of the Fe 2p3/2 peak revealed two components with binding energies of 713.98 and 718.16 eV, corresponding to the presence of Fe cations in the octahedral and tetrahedral sites. Additionally, the Rietveld refinement of NZF showed a cubic system with the Fd3m space group. High-resolution transmission electron microscopy (HRTEM) analysis showed that the NZF material strongly interacts with polyaniline, while the selected area electron diffraction (SAED) pattern perfectly matched with the XRD data. Lognormal distribution was used to determine the particle size, which was found to be in the range of 1-100 nm. A flexible photodetector device utilizing the NZF-PANI nanohybrid was fabricated on an environmentally friendly, biodegradable cellulose paper substrate and the device exhibited excellent performance, i.e., a responsivity of 0.069 A W-1 and detectivity of 7.258 × 1010 Jones at a very low voltage of 0.1 V. The non-stretched device showed a responsivity of 24.980 A W-1 at 5 V, whereas at 2 cm-1 bending curvature, the device showed a responsivity of 20.175 A W-1, which was much higher than the responsivity of a commercial photodetector (<0.5 A W-1).

Study of pressure induced phase transformation in CTAB capped CdS nanoparticles.

Effect of high pressure on as prepared 20mM CTAB capped CdS nanoparticles (size ~4nm) has been analyzed in this paper. Raman scattering has been used to observe the phase transition pressure. X-ray diffraction pattern is used for structural characterization. Raman scattering predicts the phase transition occur from mixed cubical phase to rock salt phase above 6.6 GPa. One of the representative XRD pattern at 9.7 GPa confirms the existence of rock salt phase above 6.6 GPa.