Synthesis of α-MoO3 nano-flakes by dry oxidation of RF sputtered Mo thin films and their application in gas sensing
TL;DR: In this article, the synthesis of orthorhombic (α) MoO3 nano-flakes by dry oxidation of RF sputtered Mo thin film is presented, where the influence of Mo thickness variation, oxidation temperature and time on the crystallographic structure, surface morphology and roughness of MoO 3 thin films was studied using SEM, AFM, XRD and Raman spectroscopy.
Abstract: Synthesis of orthorhombic (α) MoO3 nano-flakes by dry oxidation of RF sputtered Mo thin film is presented. The influence of Mo thickness variation, oxidation temperature and time on the crystallographic structure, surface morphology and roughness of MoO3 thin films was studied using SEM, AFM, XRD and Raman spectroscopy. A structural study shows that MoO3 is polycrystalline in nature with an α phase. It was noticed that oxidation temperature plays an important role in the formation of nano-flakes. The synthesis technique proposed is simple and suitable for large scale productions. The synthesis parameters were optimized for the fabrication of sensors. Chrome gold-based IDE (interdigitated electrodes) structures were patterned for the electrical detection of organic vapors. Sensors were exposed to wide range 5–100 ppm of organic vapors like ethanol, acetone, IPA (isopropanol alcohol) and water vapors. α-MoO3 nano-flakes have demonstrated selective sensing to acetone in the range of 10–100 ppm at 150 °C. The morphology of such nanostructures has potential in applications such as sensor devices due to their high surface area and thermal stability.
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TL;DR: The properties and applications of molybdenum oxides are reviewed in depth, while an insightful outlook into future prospective applications for moly bdenum oxide is presented.
Abstract: The properties and applications of molybdenum oxides are reviewed in depth. Molybdenum is found in various oxide stoichiometries, which have been employed for different high-value research and commercial applications. The great chemical and physical characteristics of molybdenum oxides make them versatile and highly tunable for incorporation in optical, electronic, catalytic, bio, and energy systems. Variations in the oxidation states allow manipulation of the crystal structure, morphology, oxygen vacancies, and dopants, to control and engineer electronic states. Despite this overwhelming functionality and potential, a definitive resource on molybdenum oxide is still unavailable. The aim here is to provide such a resource, while presenting an insightful outlook into future prospective applications for molybdenum oxides.
465 citations
TL;DR: In this paper, a critical analysis of the present phase of knowledge concerning the exposure and effects of nanomaterials has been discussed in-depth, including the potential benefits and unknown dangers.
Abstract: Currently, nanotechnology is referred to be one of the attractive research sectors in several countries because of its vast potential and commercial impact. Nanotechnology includes the investigation, development, fabrication, and processing of structures and materials on a nanoscale in various fields of science, health care, agriculture, technology, and industries. As such, it has provided a steady restructuring of related technologies. However, the irregularities and uncertainties in dimensions and chemical compositions, makes the viability of such materials questionable. Concerns have been inclined about the transport, destiny, and transformation of nanomaterials discharged into the environment. A critical analysis of the present phase of knowledge concerning the exposure and effects of nanomaterials has been discussed in-depth. In this review, different nanomaterials along with their applications have also been reviewed, that include graphene-based nanomaterials, carbon nanotubes, and their composites, nanoclay composites, nanostructured thin films, metal-organic frameworks, conducting polymers and their composites, MXenes, chalcogenide nanocrystals, and quantum dots. Besides, a few of the groundbreaking applications of nanomaterials for different sectors like human health, processes, photochemical process, energy conversion and energy storage, separation and purification processes, optoelectronics, etc. are discussed in detail with their chemsitry. Moreover, the unique characteristics and applications of nanomaterials, they inherently introduce challenges for their applications and large-scale production. Acknowledgment of the potential benefits and unknown dangers of nanomaterials is critically is critically analyzed and discussed in the manuscript.
106 citations
TL;DR: In this paper, a solution combustion method was used to synthesize nanorod-like structure with a size of about 50nm dia and few microns long, which exhibited high specific capacitance with good cycle stability.
80 citations
TL;DR: This paper presents the performance of a highly selective ethanol sensor based on MoS2-functionalized porous silicon (PSi), and an enhancement in sensitivity and a selective response for ethanol were observed, with a minimum detection limit of 1 ppm.
Abstract: This paper presents the performance of a highly selective ethanol sensor based on MoS2-functionalized porous silicon (PSi) The uniqueness of the sensor includes its method of fabrication, wafer scalability, affinity for ethanol, and high sensitivity MoS2 nanoflakes (NFs) were synthesized by sulfurization of oxidized radio-frequency (RF)-sputtered Mo thin films The MoS2 NFs synthesis technique is superior in comparison to other methods, because it is chip-scalable and low in cost Interdigitated electrodes (IDEs) were used to record resistive measurements from MoS2/PSi sensors in the presence of volatile organic compound (VOC) and moisture at room temperature With the effect of MoS2 on PSi, an enhancement in sensitivity and a selective response for ethanol were observed, with a minimum detection limit of 1 ppm The ethanol sensitivity was found to increase by a factor of 5, in comparison to the single-layer counterpart levels This impressive response is explained on the basis of an analytical resistiv
56 citations
TL;DR: In this article, the photodegradative properties and role of dissolution products under different pH values of three MoO3 nanomaterials with different shapes and chemical properties (nanorods, nanowires, and nanoplates).
44 citations
References
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TL;DR: In this article, the metal/metal-oxide interfaces involving a widely used oxide in organic electronics, MoO3, are examined and it is demonstrated that metal contacts tend to reduce the Mo6+ cation to lower oxidation states and, consequently, alter the oxide's valence electronic structure and work function when the oxide layer is very thin.
Abstract: When transition metal oxides are used in practical applications, such as organic electronics or heterogeneous catalysis, they often must be in contact with a metal. Metal contacts can affect an oxide's chemical and electronic properties within the first few nanometers of the contact, resulting in changes to an oxide's chemical reactivity, conductivity, and energy-level alignment properties. These effects can alter an oxide's ability to perform its intended function. Thus, the choice of contacting metal becomes an important design consideration when tailoring the properties of transition-metal oxide thin films or nanoparticles. Here, metal/metal-oxide interfaces involving a widely used oxide in organic electronics, MoO3, are examined. It is demonstrated that metal contacts tend to reduce the Mo6+ cation to lower oxidation states and, consequently, alter MoO3’s valence electronic structure and work function when the oxide layer is very thin (less than 10 nm). MoO3 becomes semimetallic and has a lower work function near metal contacts. The observed behavior is attributed to two causes: 1) charge transfer from the metal Fermi level into MoO3’s low-lying conduction band and 2) an oxidation-reduction reaction between the metal and MoO3 that results in oxidation of the metal and reduction of MoO3. These results illustrate how interfaces are important to an oxide's ability to provide energy-level alignment.
320 citations
TL;DR: Atomic force microscopy measurements show that the minimum resolvable thickness of these sheets of nanoscale thickness is 1.4 nm which is equivalent to the thickness of two double-layers within one unit cell of the alpha-MoO(3) crystal.
Abstract: The formation of MoO3 sheets of nanoscale thickness is described. They are made from several fundamental sheets of orthorhombic α-MoO3, which can be processed in large quantities via a low cost synthesis route that combines thermal evaporation and mechanical exfoliation. These fundamental sheets consist of double-layers of linked distorted MoO6 octahedra. Atomic force microscopy (AFM) measurements show that the minimum resolvable thickness of these sheets is 1.4 nm which is equivalent to the thickness of two double-layers within one unit cell of the α-MoO3 crystal.
243 citations
TL;DR: In this paper, a facile hydrothermal method using a molybdenum organic salt precursor was used to synthesize ultralong α-MoO3 nanobelts with an average length of 200-300 μm and uniform width of around 0.6-1.5 μm.
Abstract: Ultralong α-MoO3 nanobelts with an average length of 200–300 μm and uniform width of around 0.6–1.5 μm have been synthesized by a facile hydrothermal method using a molybdenum organic salt precursor. When evaluated for their lithium storage properties, the composite electrodes made from these nanobelts and bioderived polymer binders containing carboxy groups exhibit much better electrochemical performance than that composed of conventional poly(vinylidene fluoride) (PVDF) binder. Remarkably, the electrodes using sodium carboxymethyl cellulose (Na-CMC) binder can deliver the high specific capacity of over 730 mA h g–1 for over 200 cycles at a 0.2 C rate. Even cycled at high rates of 1–2 C, high capacities of around 430–650 mA h g–1 can be still retained. The positive effect of this type of binder on the electrode properties of α-MoO3 nanobelts is further evidenced by using another bioderived binder, the sodium alginate (Na-alginate). Stable capacity retention of around 800 mA h g–1 for over 150 cycles at 0...
237 citations
TL;DR: In this paper, the average diameter of agglomerated MoO3/TiO2 particles in aqueous solution is only 85−110 nm, which is about one-fifth to one-fourth of that of pure TiO2 suspension.
Abstract: By monolayer coverage of highly acidic semiconductors, such as MoO3 and WO3 on the surface of TiO2 nanoparticles (Degussa P25), the stability of colloidal suspensions in aqueous solution can be greatly improved. The average diameter of agglomerated MoO3/TiO2 and WO3/TiO2 particles in aqueous suspension is only 85−110 nm, respectively, which is about one-fifth to one-fourth of that of pure TiO2 suspension. The optically transparent photocatalytic films have been prepared with deposition of these colloidal suspensions. The colloidal particles in aqueous solution and the prepared transparent photocatalytic films were characterized with TEM, SEM, AFM, and other spectroscopic techniques. It has also been found that the photocatalytic activity of WO3/TiO2 film is 2.8−3 times that of pure TiO2 film in decomposing gas-phase 2-propanol, while MoO3/TiO2 film is less effective.
233 citations
TL;DR: The combination of stable doping and highly efficient charge extraction/injection allows the demonstration of simplified graphene-based OLED device stacks with efficiencies exceeding those of standard ITO reference devices.
Abstract: The interface structure of graphene with thermally evaporated metal oxide layers, in particular molybdenum trioxide (MoO3), is studied combining photoemission spectroscopy, sheet resistance measurements and organic light emitting diode (OLED) characterization. Thin (<5 nm) MoO3 layers give rise to an 1.9 eV large interface dipole and a downwards bending of the MoO3 conduction band towards the Fermi level of graphene, leading to a near ideal alignment of the transport levels. The surface charge transfer manifests itself also as strong and stable p-type doping of the graphene layers, with the Fermi level downshifted by 0.25 eV and sheet resistance values consistently below 50 Ω/sq for few-layer graphene films. The combination of stable doping and highly efficient charge extraction/injection allows the demonstration of simplified graphene-based OLED device stacks with efficiencies exceeding those of standard ITO reference devices.
223 citations