The effects of the acidic treatment on the photovoltaic properties of the dye-sensitized solar cell (DSSC) were investigated. TiO
2
nanostructure was prepared by chemical bath deposition method and ...the surface was modified by various acidic treatments like hydrochloric acid (HCl), nitric acid (HNO
3
), sulphuric acid (H
2
SO
4
), and acetic acid (CH
3
COOH). The results exhibited a significant influence of acidic treatments on structural, morphological, optical, electrochemical, and photovoltaic properties. XRD analysis confirms the formation TiO
2
nanostructure electrodes. After acidic surface treatment photoconversion efficiency increases from 1.97% (for pristine electrode) to 3.23% (for acetic acid surface treatment). With respect to that electron lifetime increased from 0.34 to 0.54 ms and charge transfer resistance decreased from 25.76 Ω cm (pristine TiO
2
electrode) to 17.96 Ω cm.
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Semiconducting, large sheets of carbon as an active material in optoelectronic research are missing and reduced graphene oxide (rGO) can be a good candidate. However, chemical ...synthesis cannot produce large sheets of rGO (i.e. maximum: 20–30μm) as well as high quality rGO due to the restraints of fabrication method. Thus, a novel strategy for the synthesis of large sheets of semiconducting rGO is urgently required. Large area slightly oxidized graphene (SOG) is fabricated at the interface of silicon dioxide (SiO2) and silicon via Chemical Vapor Deposition (CVD) method, herein for the first time. Carbon atoms bond with oxygen functionalities (i.e. CO, COH) at the time of diffusion in SiO2 allowing for C/O ratios from 7 to 10 adjustable by the variation of SiO2 thickness, indicating the tunable oxidation. Moreover, electronic structure and morphology of SOG are similar to the chemically grown rGO. The fabrication mechanism of SOG is also investigated.
This study proposes a solvothermal method for synthesizing sulfate-functionalized hafnium-organic frameworks (Hf-BTC-SO4) for application in low-temperature NH3 gas sensors. Prior to the gas-sensing ...studies, solvothermal-processed Hf-BTC-SO4 is characterized using various techniques to obtain structural, elemental, morphological, and thermal stability information. Results of structural and thermal-stability analysis demonstrate that Hf-BTC-SO4 exhibits good crystallinity and high thermal stability with the functionalization of SO4 in the Hf-framework. Microstructural analysis reveals that nanoparticles aggregated to form compact clusters of Hf-BTC-SO4. In addition, Hf-BTC-SO4 has an ultra-high specific surface area of 1100 m2g−1 (with a pore size of 15 Å), suitable for gas detection owing to enhanced surface reactions. Gas-sensing studies confirm that the fabricated Hf-BTC-SO4 sensor exhibits selective detection of NH3 gas at a lower working temperature of 100 ºC. Notably, the Hf-BTC-SO4 sensor detected up to 1 ppm of NH3 (response = 1.41), with excellent response reversibility. The functionalized sulfate bonds and Hf-clusters within the framework form strong bonds with NH3, enhancing their interaction with the metal-organic frameworks. This study can motivate future research on the synthesis of functional organic frameworks for applications in low-temperature NH3 detection devices.
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•A novel sensing material based on Hf-BTC-SO4 was synthesized and characterized as a chemiresistive gas sensor.•As-synthesized Hf-BTC-SO4 features an ultra-high surface area of 1100 m2g−1.•Hf-BTC-SO4 sensor showed a selective detection of NH3 gas at a low temperature of 100 ºC.•Functionalized sulfate bonds and Hf-clusters enable NH3 molecules to adsorb by strong host-guest interactions to realize low-level NH3 detection.
The development of effective and efficient materials for the selective and sensitive detection of toxic gases and volatile organic compounds is crucial for protecting human health and the ...environment. In this respect, a well-known n-type semiconducting material, namely indium oxide (In2O3), has attracted significant attention because of its gas-sensing applications. The rapid advances in various synthesis techniques have enabled researchers to explore numerous novel nanostructures and their integration into smart gas-sensing devices. Despite sustainable development, the application of In2O3 in gas sensing is limited by its poor selectivity, high working temperature, and response deterioration under humid conditions. This review outlines various strategies, such as morphology and interface engineering, catalytic functionalization, shell structure and thickness, and doping, for improving the gas detection performance of In2O3-based chemiresistive gas sensors. The significant influence of the nanostructures with different morphologies on the gas-sensing performance of In2O3-based sensors is also demonstrated. Pristine In2O3 nanomaterials with zero-dimensional (0D) to three-dimensional (3D) morphologies are reviewed. Different composites of In2O3, including In2O3/metal oxides (p-type and n-type), In2O3/noble metal loading and encapsulation, In2O3/elemental doping, In2O3/conducting polymers, and In2O3/carbonaceous materials, were evaluated to improve their sensing performances. Finally, a future outlook on the further progress of the In2O3 gas sensors is suggested.
Low-temperature operating chemiresistive gas sensors are attractive for a variety of real-time gas monitoring applications, with benefits such as low power consumption, profitability, and ...miniaturization of devices. In this regard, we developed a low-temperature operating H2 gas sensor using solvothermal-processed novel amine-functionalized zinc-based metal-organic framework (Zn-BDC-NH2) as a detection material. The Zn-BDC-NH2 structure is consists of the Zn4O secondary building units and 2–aminoterephthalate acidic linker that form the 3D frame structure. Prior to sensing studies, various techniques were employed to confirm -NH2 functionalization and to characterize structure, surface morphology, thermal stability, surface area, and surface chemistry of synthesized Zn-BDC-NH2 materials. Benefitting from the simple synthesis process and larger surface area (880 m2g-1) with adequate porosity (~13 Å), Zn-BDC-NH2 has proven to be an excellent chemiresistive sensor for the effective sensing of low concentrations of H2 at 50 °C. Moreover, the sensor shown significant sensitivity to the detection of lower H2 concentrations of 1–10 ppm, a response value of 2.93–10 ppm H2, and complete recovery characteristics at 50 °C. We discussed the mechanisms for attaining the excellent H2 sensing. The utilized room temperature solvothermal approach opens up a perspective for synthesizing Zn-BDC-NH2 material with suitable functionalities and their use in low temperature H2 sensors.
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•A highly effective H2 gas sensor using a novel Zn-BDC-NH2 as the detection material was developed.•Solvothermal-processed Zn-BDC-NH2 features an ultra-high surface area of 880 m2g-1.•Zn-BDC-NH2 was an excellent sensor for the selective detection of low-concentration H2 at 50 °C.•Adding -NH2 groups to Zn-BDC MOFs increased the binding energy for H2 gas, ultimately improving H2 adsorption.
Present work proposes the insight towards synthesis of flower-like vanadium oxide hierarchical nanostructures (V2O5 HNs) through a simple and template-free hydrothermal method and their utilization ...as a potential xylene gas sensing materials. XRD and XPS analysis supports to the configuration of highly crystalline orthorhombic phase of V2O5. Surface morphologies of V2O5 were controlled through varying the reaction times during hydrothermal synthesis. SEM and TEM studies undoubtedly corroborates that the flower-like V2O5 HNs (3–5 μm in diameters) are composed of large number of nanosheet- and nanoneedle-type structures. BET and BJH analysis supports to the mesoporous character of V2O5 HNs with specific surface area of 19.5291 m2/g. Gas sensing studies on as-fabricated V2O5 HNs sensors were performed towards a various target gases, temperatures, and varying concentrations thoroughly and described. Gas sensing studies demonstrate that the flower-like V2O5 HNs sensors are selective and effective towards xylene @300 °C. Among various V2O5 HNs sensors, the sensor based on V2O5-3 exhibits maximum response of 3.03 to 500 ppm xylene together with good response repeatability and long term stability (towards 100 ppm, Ra/Rg = 2.20) @300 °C. Finally, the selective detection of xylene using as-grown flower-like V2O5 HNs can cover the road in the direction of the development of sensing systems for the acute detection and monitoring of toxic xylene.
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•Design of V2O5 HNs by a simple hydrothermal method followed by annealing treatment.•Flower-like V2O5 HNs are assembled of large number of nanosheet-/nanoneedle-shaped structures.•As-fabricated V2O5 HNs sensors are capable to sense as low as 1 ppm concentration of xylene @300 °C.•Xylene sensing performance of V2O5 HNs is attributed to their mesoporous structure and efficient surface areas.•Possible xylene sensing mechanism of flower-like V2O5 HNs sensor is proposed.
Here, we present the first observation of magneto-transport properties of graphene foam (GF) composed of a few layers in a wide temperature range of 2–300 K. Large room-temperature linear positive ...magnetoresistance (PMR ≈ 171% at B ≈ 9 T) has been detected. The largest PMR (∼213%) has been achieved at 2 K under a magnetic field of 9 T, which can be tuned by the addition of poly(methyl methacrylate) to the porous structure of the foam. This remarkable magnetoresistance may be the result of quadratic magnetoresistance. The excellent magneto-transport properties of GF open a way toward three-dimensional graphene-based magnetoelectronic devices.
Present article demonstrates the facial synthesis of nickel oxide (NiO) films via an easy and cost-effective successive ionic layer adsorption and reaction (SILAR) method onto glass substrate using ...nickel (II) chloride as precursor and their gas sensing activity towards different target gases. Structural elucidation and elemental composition analysis measurements were conducted using X-ray diffraction, Raman and energy dispersive X-ray techniques, respectively. Platelet-type morphology was confirmed from the plane-view images recorded on field-emission scanning electron and transmission electron microscopes at different magnifications. Chemo-resistive performance of NiO films was carried out towards hazardous and explosive gases such as ammonia, methanol, ethanol, liquefied petroleum gas (LPG) and nitrogen dioxide as a function of working temperature and gas concentration. Amongst diverse gases, NiO sensor film exhibits better response of 72% to 5000 ppm LPG at lower operating temperature (180 °C). Effect of LPG concentration on gas response of the NiO film was systematically investigated and explored. Also, the synergistic interaction between LPG molecules and NiO nanoplates was studied and explored using potential barrier model.
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•Nickel oxide films are directly grown onto a glass substrate via SILAR method.•Films are polycrystalline and are made up of upright standing nanoplates.•Chemoresistive performances toward ammonia, methanol, ethanol, liquefied petroleum gas and nitrogen dioxide gases are tested and reported.•Good response of 72% to 5000 ppm LPG at 180 °C operating temperature is evidenced.•Interaction between gas molecules and nickel oxide is proposed through potential barrier model.
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•Fabrication of amorphous carbon (a-C) thin film on insulating substrate silicon dioxide (SiO2) via Chemical Vapor Deposition (CVD).•Detection of anisotropic magnetoresistance (AMR) ...in a-C thin films, which is useful for magnetic field position sensor.•Explanation of AMR phenomenon in a-C thin films via Brysksin – Klein (B-K) model.
Herein, for the first time, anisotropic magnetotransport phenomenon in amorphous carbon (a-C) thin films has been examined on the basis of Brysksin – Klein (B-K) model. The sign of magnetoresistance turns negative at (θ, ϕ)=(0°, 90°) to positive at (θ, ϕ)=(90°, 90°) where θ and ϕ are the angle between applied magnetic field and normal to the plane and the angle between applied magnetic field and current, respectively. The sign of magnetoresistance of a-C thin films varies continuously at θ=0–360° and ϕ=0–90°, suggesting good potential for the position sensing of large magnetic field.
Random copolymer gels of N‐isopropylacrylamide (NIPAM) and N‐ethylacrylamide (NEAM) are synthesized using different monomer compositions in 1:1 methanol–water mixtures. The samples are characterized ...by scanning electron microscopy, atomic force microscopy (AFM), and rheological studies. It is observed that with the variation of the monomer compositions in the reaction mixture, the thermoresponsive, morphological, AFM, and rheological properties varied significantly. Porosity and roughness of the gels gradually increase with the gradual increase in NIPAM loading in the gels, lower critical solution temperature, mechanical strength (Young's modulus, storage modulus) significantly decreases with the increase in poly(N‐isopropylacrylamide) loading in the gels. All results can be explained on the basis of the differences in thermoresponsive character of homo‐ and copolymer gels of NIPAM and NEAM in water, their composition in the reaction mixtures, and their different kind of interactions with solvents.
Copolymer gels of versatile morphological, mechanical, thermoresponsive properties form by free radical polymerizations of different compositions of N‐isopropylacrylamide and N‐ethylacrylamide in 1:1 methanol–water (v/v) mixtures. Porosities and roughnesses of the gels gradually increase with the increase in N‐isopropylacrylamide loading in the system. At the same time, Young's modulus and lower critical solution temperature gradually decrease with the increase in the same.
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