Search Results (28)

Gas sensors based on metal oxide semiconductors (MOS) have been widely used for the detection and monitoring of flammable and toxic gases. In this paper, p-type Cr₂O₃ and Ti-doped Cr₂O₃ (CTO) thin films were synthesized using an aerosol-assisted chemical vapor deposition (AACVD) method. Detailed analysis of the thin films deposited, including structural information, their elemental composition, oxidation state, and morphology, was investigated using XRD, Raman analysis, SEM, and XPS. All the gas sensors based on pristine Cr₂O₃ and CTO exhibited a reversible response and good sensitivity to isobutylene (C₄H₈) and ammonia (NH₃) gases. Doping Ti into the Cr₂O₃ lattice improves the response of the CTO-based sensors to C₄H₈ and NH₃. We describe a novel mechanism for the gas sensitivity of p-type metal oxides based on variations in the oxygen vacancy concentration. Full article

We report for the first time the successful synthesis of ZnO/WS₂ hybrid material using a combination of aerosol-assisted chemical vapor deposition (AA-CVD) and atmospheric pressure CVD techniques. The morphology and the composition of the grown films were investigated and the results confirm the co-existence of both materials. Moreover, gas-sensing results against 500 ppb of NO₂ revealed the influence of WS₂ material on the ZnO gas-sensing performance. The operating temperature shifted towards lower values, from 300 °C to 150 °C. Furthermore, at room temperature, the ZnO/WS₂ sensor was able to detect NO₂ at ppb level. Full article

In this work, efficient hydrogen gas sensors based on multilayered p-type bare MoS₂ and Pd-decorated MoS₂ were fabricated. MoS₂ was deposited onto alumina transducers using an airbrushing technique to be used as a sensing material. Aerosol-assisted chemical vapor deposition (AACVD) was used to decorate layered MoS₂ with Pd nanoparticles at 250 °C. The bare and Pd-decorated MoS₂ was characterized using field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), and Raman spectroscopy. The characterization results reveal the multilayered crystalline structure of MoS₂ with successful Pd decoration. The size of the Pd nanoparticles ranges from 15 nm to 23 nm. Gas sensing studies reveal that a maximum response of 55% is achieved for Pd-decorated MoS₂ operated at 150 °C to 100 ppm of H₂, which is clearly below the explosive limit (4%) in air. The higher sensitivity due to Pd nanoparticle decoration was owed to a spillover effect. This study reveals that the sensitivity of the sensors is highly dependent on the amount of Pd decoration. Moreover, sensor responses increase slightly when exposed to 50% relative humidity (RH at 25 °C). Full article

Ice accretion on transmission lines can cause operational difficulties and disastrous events. In this study, a micro/nano-structured epoxy resin/polydimethylsiloxane (EP/PDMS) film on glass, with water droplet contact angles (CA) observed as high as 160° and the water droplet sliding angle (SA) < 1° was fabricated by aerosol-assisted chemical vapor deposition (AACVD). The glaze icing performance of the superhydrophobic EP/PDMS films have been investigated by comparing the bare glass and room temperature vulcanized (RTV) silicon rubber-coated glass substrate representing the glass insulators and silicone rubber insulators, respectively. Compared with the bare glass and the RTV silicon rubber coating, the EP/PDMS superhydrophobic coating showed excellent performance in delaying glaze icing, especially in the early stages of icing. After 20 min of glaze icing with tilting angle of 90° at −5 and −10 °C, 38.9% and 85.7% of the RTV silicon rubber coating were covered, respectively, and less than 3% of the EP/PDMS coating was covered by ice when the blank glass sheet was completely covered. The EP/PDMS films also showed good mechanical robustness and long-term stability, which are important considerations in their widespread real-world adoption. Full article

Cu₃N has been grown on m-Al₂O₃ by aerosol-assisted chemical vapor deposition using 0.1 M CuCl₂ in CH₃CH₂OH under an excess of NH₃ at 600 °C, which led to the deposition of Cu that was subsequently converted into Cu₃N under NH₃: O₂ at 400 °C in a two-step process without exposure to the ambient. The reaction of CuCl₂ with an excess of NH₃ did not lead to the growth of Cu₃N, which is different to the case of halide vapor phase epitaxy of III-V semiconductors. The Cu₃N layers obtained in this way had an anti-ReO₃ cubic crystal structure with a lattice constant of 3.8 Å and were found to be persistently n-type, with a room temperature carrier density of n = 2 × 10¹⁶ cm⁻³ and mobility of µ_n = 32 cm²/Vs. The surface depletion, calculated in the effective mass approximation, was found to extend over ~0.15 µm by considering a surface barrier height of ϕ_B = 0.4 eV related to the formation of native Cu₂O. Full article

Arrays of aligned carbon nanotubes (CNTs) are anisotropic nanomaterials possessing a high length-to-diameter aspect ratio, channels passing through the array, and mechanical strength along with flexibility. The arrays are produced in one step using aerosol-assisted catalytic chemical vapor deposition (CCVD), where a mixture of carbon and metal sources is fed into the hot zone of the reactor. Metal nanoparticles catalyze the growth of CNTs and, during synthesis, are partially captured into the internal cavity of CNTs. In this work, we considered various stages of multi-walled CNT (MWCNT) growth on silicon substrates from a ferrocene–toluene mixture and estimated the amount of iron in the array. The study showed that although the mixture of precursors supplies evenly to the reactor, the iron content in the upper part of the array is lower and increases toward the substrate. The size of carbon-encapsulated iron-based nanoparticles is 20–30 nm, and, according to X-ray diffraction data, most of them are iron carbide Fe₃C. The reasons for the gradient distribution of iron nanoparticles in MWCNT arrays were considered, and the possibilities of controlling their distribution were evaluated. Full article

TiO₂ is a promising photocatalyst, but its large bandgap restricts its light absorption to the ultraviolet region. The addition of noble metals can reduce the bandgap and electron-hole recombination; therefore, we prepared TiO₂-Ag nanoparticle composite films by plasma-enhanced chemical vapor deposition (PECVD) using a mixture of aerosolized AgNO₃, which was used as a Ag nanoparticle precursor, and titanium tetraisopropoxide, which acted as the TiO₂ precursor. Notably, the use of PECVD enabled a low process temperature and eliminated the need for pre-preparing the Ag nanoparticles, thereby increasing the process efficiency. The structures and morphologies of the deposited films were characterized by ultraviolet (UV)—visible spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and energy-dispersive X-ray spectroscopy, and the effects of the AgNO₃ concentration on the photocatalytic activity of the deposited films were determined by assessing the degradation of methylene blue under UV light irradiation. The Ag ions were successfully reduced to metallic nanoparticles and were embedded in the TiO₂ film. The best photocatalytic activity was achieved for a 1 wt% Ag-loaded TiO₂ composite film, which was 1.75 times that of pristine TiO₂. Full article

Aerosol-assisted catalytic chemical vapor deposition (AACCVD) is a powerful one-step process to produce vertically aligned carbon nanotubes (VACNTs), characterized by the continuous supply of the catalyst precursor (metallocene). The behavior of catalyst species all along the synthesis is essential for the continuous growth of VACNTs. It is there investigated through detailed observations and elemental analyses at scales of VACNT carpets and of individual CNTs. Our approach is based on two complementary experiments: quenching of the sample cooling, and sequential injection of two distinct metallocenes. Metal-based nanoparticles nucleated in the gas-phase during the whole synthesis duration are shown to diffuse in between the growing VACNTs from the top of the CNT carpet towards the substrate. They are much smaller than the catalyst particles formed on the substrate in the initial steps of the process and evidences are given that they continuously feed these catalyst particles at the VACNT roots. Particularly, the electron energy-loss spectroscopy (EELS) analyses of metal-based segments found into a single CNT show that the second injected metal is very gradually incorporated in the particle initially formed from the metal firstly injected. The feeding of the catalyst particles by the nanoparticles continuously nucleated in the gas-phase is therefore an essential feature of the base-growth of CNTs by AACCVD. Full article

Elaboration of Pd-supported catalysts for catalytic combustion is, nowadays, considered as an imperative task to reduce the emissions of methane. This study provides new insight into the method of deposition, chemical state of Pd and oxygen storage capability of transition metal ions and their effects on the catalytic reactivity of supported catalysts for the combustion of methane. The catalyst with nominal composition La(Co_0.8Ni_0.1Fe_0.1)_0.85Pd_0.15O₃ was supported on SiO₂-modified/γ-alumina using two synthetic procedures: (i) aerosol assisted chemical vapor deposition (U-AACVD) and (ii) wet impregnation (Imp). A comparative analysis shows that a higher catalytic activity is established for supported catalyst obtained by wet impregnation, where the PdO-like phase is well dispersed and the transition metal ions display a high oxygen storage capability. The reaction pathway over both catalysts proceeds most probably through Mars–van Krevelen mechanism. The supported catalysts are thermally stable when they are aged at 505 °C for 120 h in air containing 1.2 vol.% water vapor. Furthermore, the experimentally obtained data on La(Co_0.8Ni_0.1Fe_0.1)_0.85Pd_0.15O₃—based catalyst, supported on monolithic substrate VDM^®Aluchrom Y Hf are simulated by using a two-dimensional heterogeneous model for monolithic reactor in order to predict the performance of an industrial catalytic reactor for abatement of methane emissions. Full article

Low-temperature atmospheric pressure (AP) plasma technologies have recently proven to offer a range of interesting opportunities for the preparation of a variety of nanocomposite (NC) coatings with different chemical compositions, structures, and morphologies. Since the late 2000s, numerous strategies have been implemented for the deposition of this intriguing class of coatings by using both direct and remote AP plasma sources. Interestingly, considerable progress has been made in the development of aerosol-assisted deposition processes in which the use of either precursor solutions or nanoparticle dispersions in aerosol form allows greatly widening the range of constituents that can be combined in the plasma-deposited NC films. This review summarizes the research published on this topic so far and, specifically, aims to present a concise survey of the developed plasma processes, with particular focus on their optimization as well as on the structural and functional properties of the NC coatings to which they provide access. Current challenges and opportunities are also briefly discussed to give an outlook on possible future research directions. Full article

This research endeavor aimed to synthesize the lead (II) diphenyldiselenophosphinate complex and its use to obtain lead selenide nanostructured depositions and further the impedance spectroscopic analysis of these obtained PbSe nanostructures, to determine their roles in the electronics industry. The aerosol-assisted chemical vapor deposition technique was used to provide lead selenide deposition by decomposition of the complex at different temperatures using the glass substrates. The obtained films were revealed to be a pure cubic phase PbSe, as confirmed by X-ray diffraction analysis. SEM and TEM micrographs demonstrated three-dimensionally grown interlocked or aggregated nanocubes of the obtained PbSe. Characteristic dielectric measurements and the impedance spectroscopy analysis at room temperature were executed to evaluate PbSe properties over the frequency range of 100 Hz–5 MHz. The dielectric constant and dielectric loss gave similar trends, along with altering frequency, which was well explained by the Koops theory and Maxwell–Wagner theory. The effective short-range translational carrier hopping gave rise to an overdue remarkable increase in ac conductivity (?_ac) on the frequency increase. Fitting of a complex impedance plot was carried out with an equivalent circuit model (R_g C_g) (R_gb Q_gb C_gb), which proved that grains, as well as grain boundaries, are responsible for the relaxation processes. The asymmetric depressed semicircle with the center lower to the impedance real axis provided a clear explanation of non-Debye dielectric behavior. Full article

This research aims to synthesize the Bis(di-isobutyldithiophosphinato) nickel (II) complex [Ni(iBu₂PS₂)] to be employed as a substrate for the deposition of nickel sulfide nanostructures, and to investigate its dielectric and impedance characteristics for applications in the electronic industry. Various analytical tools including elemental analysis, mass spectrometry, IR, and TGA were also used to further confirm the successful synthesis of the precursor. NiS nanostructures were grown on the glass substrates by employing an aerosol assisted chemical vapor deposition (AACVD) technique via successful decomposition of the synthesized complex under variable temperature conditions. XRD, SEM, TEM, and EDX methods were well applied to examine resultant nanostructures. Dielectric studies of NiS were carried out at room temperature within the 100 Hz to 5 MHz frequency range. Maxwell-Wagner model gave a complete explanation of the variation of dielectric properties along with frequency. The reason behind high dielectric constant values at low frequency was further endorsed by Koops phenomenological model. The efficient translational hopping and futile reorientation vibration caused the overdue exceptional drift of ac conductivity (?_ac) along with the rise in frequency. Two relaxation processes caused by grains and grain boundaries were identified from the fitting of a complex impedance plot with an equivalent circuit model (R_g C_g) (R_gb Q_gb C_gb). Asymmetry and depression in the semicircle having center present lower than the impedance real axis gave solid justification of dielectric behavior that is non-Debye in nature. Full article

Despite the high potential impact of aqueous battery systems, fundamental characteristics such as cost, safety, and stability make them less feasible for large-scale energy storage systems. One of the main barriers encountered in the commercialization of aqueous batteries is the development of large-scale electrodes with high reversibility, high rate capability, and extended cycle stability at low operational and maintenance costs. To overcome some of these issues, the current research work is focused on a new class of material based on phenethylammonium bismuth iodide on fluorine doped SnO₂-precoated glass substrate via aerosol-assisted chemical vapor deposition, a technology that is industrially competitive. The anode materials were electrochemically investigated in Zn²⁺ aqueous electrolytes as a proof of concept, which presented a specific capacity of 220 mAh g^?1 at 0.4 A g^?1 with excellent stability after 50 scans and capacity retention of almost 100%. Full article

Thin films of metallic rhodium (Rh) are developed on two different supports, nickel foam (NF) and titanium foil (Ti), and evaluated for electrochemical hydrogen evolution reaction (HER). The electrodes are prepared by aerosol-assisted chemical vapor deposition technique using a Rh diethyldithiocarabamte precursor for three distinct time periods of 40, 80, and 120 min at 500 °C. The film consists of phase pure metallic Rh with hierarchical flower-like morphology. The structural features of such nanostructures can be modulated by adjusting the growth time. The HER catalytic performance data for the optimized films (i.e., with the deposition time of 80 min) suggest that the Rh deposited on Ti foil (Rh/Ti) catalyze the reaction substantially faster than Rh deposited on Ni foam (Rh/NF). To produce current density of 100 mA cm^?2, the Rh/NF needed over potential of 263 mV, while the Rh/Ti electrode required only 175 mV. In spite of lower electrical conductivity, caused by the bare Ti foil, the Rh/Ti electrode exhibits superior HER performance. The Tafel slopes of Rh/NF and Rh/Ti electrodes are determined to be 52 and 42 mV dec^?1, while the turnover frequencies are estimated to be 1.1 and 37.3 s^?1 at over potential of 260 mV. Full article

Plasma Enhanced–Chemical Vapor Deposition (PE-CVD) of polyethylene oxide-like (PEO)-like coatings represent a successful strategy to address cell-behavior on biomaterials. Indeed, one of the main drawbacks of organic and hydrophilic films, like PEO-like ones, often consists in their poor adhesion to the substrate, especially in biological fluids where the biomaterial is required to operate. In this paper, low pressure (LP) and aerosol-assisted atmospheric pressure (aerosol-assisted AP) PE-CVD of PEO-like coatings is compared. The stability of the two different classes of coatings was investigated, both in water and in the cell culture media, during cell culture experiments. The obtained results show that, when deposited at atmospheric pressure (AP), the adhesion of the PEO-like coatings to the substrate has to be granted by an intermediate gradient layer. This interlayer can match the properties of the substrate with that of the topmost coatings, and, in turn, can dramatically improve the coating’s stability in complex biological fluids, like the cell culture medium. An accurate modulation of the experimental conditions, both at LP and AP, allowed control of the film chemical structure and surface properties, to permanently promote or discourage the cellular adhesion on the surfaces of biomaterials. Full article