Liquid Deposition Method Research Articles

Improved hydrothermal durability of Cu-SSZ-13 NH3-SCR catalyst by surface Al modification: Affinity and passivation

To improve the hydrothermal durability of Cu-SSZ-13 selective catalytic reduction (SCR) catalyst, a thin Al2O3 modification layer was coated on the external surface of Cu-SSZ-13 by a chemical liquid deposition (CLD) method. The high-temperature SCR activity of the Al-modified Cu-SSZ-13 can be maintained upon 750–800 °C hydrothermal aging, and over-oxidation of NH3 is largely inhibited. Based on H2-TPR and EPR results, it is revealed that CuAl2O4-like species forms upon Al modification and converts further to CuAlO2-like species during aging, while the accumulation of CuO-like species is inhibited. The high affinity of Al-containing species (i.e., Al2O3 and CuAl2O4-like species) with Cu(OH)2 is suggested by DFT calculations, indicating that Cu(OH)2 detached from ion-exchange sites are captured by Al to form CuAlO2-like species instead of CuO-like species. The passivation of detached Cu species by coated Al leads to somewhat weakened low-temperature SCR activity, but successfully preserves the high-temperature SCR performance upon aging, which can be applied to high-temperature SCR scenarios.

Capsule-like zeolite catalyst fabricated by solvent-free strategy for para-Xylene formation from CO2 hydrogenation

An efficient Na-FeMn/HZSM-5@Silicalite-1 catalyst was rationally designed for direct conversion of CO2 to aromatics. The tailor-made HZSM-5@Silicalite-1 core-shell zeolite was prepared by a facile solvent-free method. The solvent-free synthesis of core-shell zeolite could not only address pollution issues by eliminating the large utilization of organic reagents, but also exhibit a better performance for separating para-Xylene (PX) from xylenes with the assistance of capsule-like zeolite oriented synthesis. For CO2 to aromatics reaction, Na-FeMn combining with capsule-like HZSM-5@Silicalite-1 catalyst could reach 81.1% PX/X (the C-mol ratio of PX to all xylenes) ratio, which was higher than those of conventional core-shell zeolites, such as HZSM-5@SiO2 and HZSM-5@Silicalite-1 core-shell zeolites which were obtained from traditional chemical liquid deposition and hydrothermal methods. The as-synthesized zeolite paves a new route for efficient conversion of CO2 molecules into valuable PX, and provides a facile method for regulating surface acid properties of zeolite.

Liquid deposition modification of nano-ZSM-5 zeolite and catalytic performance in aromatization of Hexene-1

The Olefin aromatization is an important method for the upgrade of catalytic cracking (FCC) gasoline and production of fuel oil with high octane number. The nano-ZSM-5 zeolite was synthesized via a seed-induced method, a series of modified nano-ZSM-5 zeolite samples with different Ga deposition amount were prepared by Ga liquid deposition method. The XRD, N2 physical adsorption, SEM, TEM, XPS, H2-TPR and Py-IR measurements were used to characterize the morphology, textural properties and acidity of the modified ZSM-5 zeolites. The catalytic performance of the Hexene-1 aromatization was evaluated on a fixed-bed microreactor. The effects of Ga modification on the physicochemical and catalytic performance of nano-ZSM-5 zeolites were investigated. The Ga species in the modified nano-ZSM-5 zeolites mainly exist as the form of Ga2O3 and GaO+, which provide strong Lewis acid sites. The aromatics selectivity over Ga modified nano-ZSM-5 zeolite in the Hexene-1 aromatization was significantly increased, which could be attributed to the improvement of the dehydrogenation activity. The selectivity for aromatics over the Ga4.2/NZ5 catalyst with suitable Ga deposition amount reached 55.4%.

Flexible Supercapacitors Based on CNT/MnO2-BP Composite Yarn Synthesized by In Situ Reduction

Solid-state flexible supercapacitors are considered significant prospective energy storage devices, and carbon nanotube (CNT) yarn is an ideal electrode material for constructing linear flexible supercapacitors because of its high electrical conductivity and flexibility. However, the relatively low specific capacitance and energy density of a supercapacitor made of pure CNT yarn limits its application. Here, we prepared a CNT/MnO2-BP composite yarn via a facile one-step liquid deposition method by the innovative introduction of few-layer black phosphorous (BP) nanosheets. The redox reaction between the BP and the potassium permanganate forms MnO2 and an electrolyte of phosphorus acids (HxPOy). The two-ply yarn supercapacitor composed of the CNT/MnO2-BP composite yarn shows excellent electrochemical properties with a volumetric capacitance of 441.79 F cm−3 at the scanning rate of 0.01 V s−1 and an energy density of 9.82 mWh cm−3 at a power density of 441.79 mW cm−3. Herein, this work provides a way to improve the electrochemical performance of CNT yarn-based supercapacitors that can act as flexible energy storage devices for wearable electronics.

DART-MS Spectral Similarity of Infrared Thermally Desorbed Solid Particulate and Solution Cast Propellant Samples.

Security and forensic applications employ test and reference materials to develop, calibrate, and validate analytical instrumentation such as mass spectrometry for the trace detection and chemical analysis of target analytes. An emerging class of target analytes includes homemade fuel oxidizer explosives based on pyrotechnics, propellants, and powder mixtures. Test materials for these compounds must appropriately and accurately embody the physical and chemical nature of the threat. Precision liquid deposition methods have long been employed for creation of trace level test materials. Mass spectral similarity and chemical signature differences between solid particulate and solution cast (i.e., liquid deposited) propellant samples were investigated by infrared thermal desorption direct analysis in real time mass spectrometry (IRTD-DART-MS). Differences in the mass spectra and ion distributions of solid and liquid deposited black powders and black powder substitutes were observed. These differences were attributed to chemical processes (e.g., degradation) and physical differences in the crystal formation, spatial distribution, morphology, and size. The production and deposition of test and reference materials remain critical to developing new technologies and detecting evolving threats.

Helical carbon nanofibers modified with Fe2O3 as a high performance anode material for lithium-ion batteries.

Helical carbon nanofibers (HCNFs) modified with Fe2O3 (Fe2O3/HCNFs) with a particle size of about 10-20 nm were first introduced for potential use as a novel anode material for lithium-ion batteries (LIBs). Fe2O3/HCNFs were successfully prepared via a chemical liquid deposition (CLPD) method in this study. HCNFs with a special three-dimensional helical structure improve the conductivity and also provide a strong supporting network space for stress and strain during the volume expansion of Fe2O3 nanoparticles. The Fe2O3/HCNF anode still retains its capacity of 816.3 mA h g-1 after 100 cycles at the current density of 200 mA g-1, which is significantly better than those of contrast samples (only 144.2 mA h g-1 for the bare Fe2O3, 241.2 mA h g-1 for HCNFs and 486.4 mA h g-1 for Fe2O3-HCNFs). These superior properties and facile preparation represent the potential of Fe2O3/HCNF anode materials for LIB application.

Preparation of Hollow SiO₂@BiOI Nanocomposites and Their Photocatalytic Performance in Ammonia Nitrogen Degradation.

Hollow SiO₂ microsphere-supported bismuth oxyiodide (BiOI) nanocomposites were prepared using Bi(NO₃)₃ · 5H₂O and KI as the precursors of BiOI at 80 °C in an aqueous solution by the liquid chemical deposition method. The BiOI nanosheets with the thicknesses of 25-40 nm and the widths of 1-2 μm were deposited on the hollow SiO₂ microsphere surfaces. There were interactions between the BiOI nanosheets and hollow SiO₂ microspheres, which enlarged the ban gap of the BiOI nanosheet as compared with the pure BiOI. The band gap energy increased with the increase in SiO₂/BiOI weight ratios. The hollow SiO₂@BiOI nanocomposites showed high photocatalytic activity in ammonia nitrogen degradation when the photocatalytic degradation reaction was performed in aqueous solution under visible light irradiation. The degradation extent of ammonia nitrogen was upto 81% when the ammonia nitrogen degradation reaction was photocatalyzed by the hollow SiO₂@BiOI(100:10) nanocomposite at an initial concentration of ammonia nitrogen of 10 mg L-1 and 25 °C for 4 h. The reaction kinetics of ammonia nitrogen degradation was well simulated by the first-order reaction model.

Facile growth of aluminum oxide thin film by chemical liquid deposition and its application in devices

Abstract Uniform and continuous Al2O3 thin films were prepared by the chemical liquid deposition (CLD) method. The breakdown field strength of the amorphous CLD-Al2O3 film is 1.74 MV/cm, making it could be used as a candidate dielectric film for electronic devices. It was further proposed to use the CLD-Al2O3 film as an electron blocking layer in a triboelectric nanogenerator (TENG) for output performances enhancement. Output voltages and currents of about 200 V and 9 µA were obtained, respectively, which were 2.6 times and 3 times, respectively, higher than TENG device without an Al2O3. A colloidal condensation-based procedure controlled by adjusting the pH value of the solution was proposed to be the mechanism of CLD, which was confirmed by the Tyndall effect observed in the growth liquid. The results indicated that the CLD could serve as a low-cost, room temperature, nontoxic and facile new method for the growth of functional thin films for semiconductor device applications.

Visible-light-driven AgBr–TiO2-Palygorskite photocatalyst with excellent photocatalytic activity for tetracycline hydrochloride

Tetracycline hydrochloride (TC) wastewater has complex components, high concentration of organic matter and certain biological toxicity. Photocatalytic degradation is of great application prospect due to its green, thorough and efficient removal of TC. In this study, heterojunction photocatalyst supported on Palygorskite (Pal) AgBr–TiO2-Pal with visible light response was successfully prepared via sol-gel and liquid deposition method successfully. Taking TC as the target pollutant, the photocatalytic performance of AgBr–TiO2-Pal photocatalys excited by visible light was studied. The spreading/grafting of AgBr–TiO2 on the surface of Pal was improved by a series of structural characterization and composition analysis. The results also demonstrated that the specific surface area of AgBr–TiO2-Pal was about 48.06 m2⋅g−1 with uniform mesoporous slit. The AgBr–TiO2-Pal catalyst was very effective for the degradation of TC, and it still retained its high stability and reusability after five cycles. The results showed that under the best reaction conditions (initial concentration of tetracycline 10 mg⋅L−1, catalyst dosage 0.5 g⋅L−1, pH value 9), with the excitation of visible light, the maximum removal ratio of TC was 90%, and the mineralization ratio was 67%. The removal efficiency and degradation rate of TC by AgBr–TiO2-Pal catalyst were 2.17 and 4.75 times as much as those of TiO2 respectively. The outstanding photocatalytic performance of heterogeneous AgBr–TiO2-Pal catalyst was obtained by fully participate in the reaction by photoinduced charge. This study could be expected to be used in photocatalytic degradation of antibiotic pollutants in wastewater treatment.

Effects of silylation on Ga/HZSM-5 for improved propane dehydroaromatization

Dehydroaromatization of propane to high value-added aromatics, especially benzene, toluene and xylene (BTX), has attracted widespread attention. Many works have been done to improve the catalytic performance of gallium loaded HZSM-5 catalysts. However, there were few reports focused on reducing the cracked by-products, such as methane and ethylene, derived from propane cracking reaction on external Brønsted acidic sites of zeolite. Herein, chemical liquid deposition (CLD) method was adopted to passivate the external strong Brønsted acid of Ga/HZSM-5, aiming to increase the most value-added BTX production by suppressing the undesired propane cracking reaction. The content of deposited SiO2 on the external surface of zeolite was tunable by varying the amount of liquid deposition reagent and duration time of CLD process. The results showed that an appropriate content of SiO2 on external surface of catalyst was beneficial to disable the external strong Brønsted acid sites. Due to depressing the undesired propane cracking reaction, BTX selectivity of 55% with propane conversion of 49% was achieved on Ga/Z5-4Si catalyst, higher than those of Ga/HZSM-5. Otherwise, prolonging the duration time of CLD process narrowed the micropore mouth size of zeolite, which could enhance the shape selective effect of Ga/ZSM-5 to increase the proportion of para-xylene in total xylene products.

Synthesis of MWCNT/PPY nanocomposite using oxidation polymerization method and its employment in sensing such as CO2 and humidity

This paper includes the synthesis of a composite of multiwall carbon nanotube (MWCNT) and conducting polymer polypyrrol (PPY) and its characterizations along with the applications direct liquid injection chemical vapour deposition (DLICVD) and oxidation polymerization method have been used for the synthesis of MWCNT and MWCNT/PPY nanocomposite respectively. MWCNT/PPY's thin film was prepared using the technique of spin coating and characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), particle size analyzer and X-ray diffractometer (XRD). Raman spectroscopy has been used to observe the vibrational and rotational spectra of MWCNT and MWCNT/PPY nanocomposite. The optical bandgap and minimum crystallite size have been calculated and found to be 3.2 eV and 8.1 nm respectively. The synthesized MWCNT/PPY has been used for CO2 and humidity sensing at room temperature (300 K). The sensor response of thin-film towards CO2 was found to be 7.2 at 1000 ppm and minimum response and recovery time at 250 ppm were found to be 30 s and 37 s respectively. The sensitivity of thin-film towards humidity was found to be 41.33 kΩ/%RH. The theoretical calculation was also performed in support of experimental data.

Annealing temperature dependent structural and electrical properties of (Mn,Ni,Co)3O4 thin films

Here, we demonstrated that polycrystalline (Mn,Ni,Co)3O4 films with a high negative temperature coefficient of resistance (NTCR) behavior can be achieved at low annealing temperatures (≤400 °C) via a liquid flow deposition method. The processing conditions applied to obtain the high-quality films were investigated with focus on the flow rate of the oxidizing agent (H2O2) and annealing temperature (Ta). The introduction of an appropriate amount of H2O2 solution into the deposition system led to the partial oxidation of Me2+ ions (Me = Mn, Ni and Co) to Me3+ which subsequently adsorbed to the films, with only little effect on the film surface quality. The pre-existing Mn3+ ions enabled the possibility of reducing the final annealing temperature to 300 °C for the film crystallization with a pure cubic spinel phase. We also studied the dependence of the electrical properties on the Ta in the range of 285–400 °C. It was found that the films were highly conductive and showed a typical NTCR characteristic at annealing temperatures of 300 °C and above. Notably, at Ta ≥ 350 °C, the films exhibited an absolute temperature coefficient of resistance (TCR) exceeding 2.43% K−1 together with a moderate resistivity (ρ) of <3 kΩ cm, indicating their excellent potential for application in infrared detectors. In addition, the films showed good electrical stability with time, as their aging coefficient (ΔR/Ro) varied in a range of 5.9–6.4% after 500 h of aging in air at 150 °C. To the best of our knowledge, there have been no reports on cubic spinel Mn3O4-based thin films at temperatures below 400 °C.

Crystallographically Controlled Synthesis of SnSe Nanowires: Potential in Resistive Memory Devices

AbstractHere the controlled growth of SnSe nanowires by a liquid injection chemical vapor deposition (CVD) method employing a distorted octahedral [SnCl4{nBuSe(CH2)3SenBu}] single‐source diselenoether precursor is reported. CVD with this single‐source precursor allows morphological and compositional control of the SnSex nanostructures formed, including the transformation of SnSe2 nanoflakes into SnSe nanowires and again to SnSe nanoflakes with increasing growth temperature. Significantly, highly crystalline SnSe nanowires with an orthorhombic Pnma 62 crystal structure can be controllably synthesized in two growth directions, either &lt;011&gt; or &lt;100&gt;. The ability to tune the growth direction of SnSe will have important implications for devices constructed using these nanocrystals. The SnSe nanowires with a &lt;011&gt; growth direction display a reversible polarity‐dependent memory switching ability, not previously reported for nanoscale SnSe. A resistive switching on/off ratio of 103 without the use of a current compliance limit is seen, illustrating the potential use of SnSe nanowires for low‐power nonvolatile memory applications.

Femtosecond excited state dynamics of liquid deposited magnesium phthalocyanine thin films

Phthalocyanines (Pcs) are one of the most widely studied organic semiconductor materials, and many film fabrication methods have been developed and used in the Pcs film fabrication. Here, we introduced a low-cost liquid deposition method to prepare magnesium phthalocyanine (MgPc) film and characterized it using AFM, XRD, UV–vis absorption spectroscopy and femtosecond transient absorption spectroscopy. We found that the Q band of MgPc red-shifted in the solid-state film and the aggregation in the solid film state has a little influence on the decay of singlet excited state, but have a more significant impact on the non-radiative relaxation of the triplet state.

Effect of different chemical liquid deposition methods on the microstructure and properties of polyimide-polyvinylpolymethylsiloxane composite aerogels

In this study, the polyimide-polyvinylpolymethylsiloxane composite aerogel (PPCA) was synthesized by two different methods, stepwise chemical liquid deposition (SCLD) and direct chemical liquid deposition (DCLD). It is found that polyimide (PI) chains can only be introduced into the backbone of amine-modified polyvinylpolymethylsiloxane (PVPMS) by SCLD method. The introduced PI can further crosslink with PVPMS to form a PI-PVPMS cross-linked network structure, which makes the skeleton dense and endows the sample with high mechanical strength. For DCLD method, PI chains can only be coated on the surface of the sample rather than the whole skeleton, which leads to a loose internal structure. Furthermore, samples prepared by SCLD method possess higher initial thermal decomposition temperature compared with that by DCLD method.

Effect of surface properties of ZnO rods on the formation of anatase-phase TiO2 tubes prepared by liquid deposition method

The effects of the surface properties of ZnO rods on the formation of anatase-phase TiO2 tubes prepared by liquid deposition method is reported. A template made of ZnO rods was prepared on FTO-coated glass by chemical bath deposition and this was then treated under different experimental conditions in an aqueous solution of ammonium hexafluorotitanate and boric acid to investigate the role of the neutral and polar (zinc/oxygen terminated) surfaces of ZnO rods on the formation of TiO2. A calcination step at 550 °C in air was applied to convert the developed Ti-based complexes on the ZnO rods into anatase-phase TiO2 nanostructures. It was observed that a 10-min deposition process led to the development of a mixture of end-capped, open-ended and perforated TiO2 tubes with dimensions resembling those of the ZnO template. Further chemical modification of the surfaces of ZnO rod templates led to the development of anatase-phase TiO2 tubes with open-ends. The surfaces of ZnO rods act as reaction sites for the synthesis of Ti-based complexes. The production of these complexes on the ZnO surface takes place on the neutral side facets of the ZnO rods, while etching of the ZnO rods occurs preferentially along the c-axis (i.e. on the Zn-(O) terminated faces. Consequently, the deposition of TiO2 is considered to happen in two stages: an early and a late stage. The early stage is characterised by the development of Ti-based complexes (Ti hydroxide monomers) on the ZnO surfaces, while the late stage is characterised by polymerisation of these monomers into Ti hydroxide polymers. At the early stage, the deposition process starts on lateral surfaces constituting a foundation for more Ti hydroxide development. Upon calcination at 550 °C in air, these tubular amorphous structures are converted into end-capped anatase-phase TiO2 tubes.

Synthesis and photocatalytic properties of three dimensional laminated structure anatase TiO2/nano-Fe0 with exposed (001) facets.

Three dimensional laminated structure anatase TiO2/nano-Fe0 with exposed (001) facets used as photocatalysts were synthesized by a two-step solvothermal route and a liquid phase reduction deposition method. The resulting samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy and selected-area electron diffraction. Characterization and experimental results indicated that the three dimensional laminated structure of anatase TiO2 was assembled by two dimensional TiO2-sheets with a thickness of approximately 30 nm. The three dimensional laminated structure anatase TiO2/nano-Fe0 photocatalysts with improved visible-light responsive capability, high charge-hole mobility, and low electron–hole recombination exhibited higher photocatalytic performance in the photocatalytic degradation of methylene blue. The composite of nano-Fe0 and TiO2 could effectively promote the generation of hydroxyl radicals (˙OH) with a synergistic effect and Photo-Fenton theory. This study provided new insights into the fabrication and practical application of high-performance photocatalysts in degrading organic pollutants.

Synthesis and characterization of Fe, Co, and Ni colloids in 2-mercaptoethanol

Metal colloids in 2-mercaptoethanol using nanoparticles (NPs) of iron (Fe), cobalt (Co), and nickel (Ni) were prepared by chemical liquid deposition method. Transmission electron microscopy, electron diffraction, UV-VIS spectroscopy, and scanning electron microscopy with electron dispersive X-ray spectroscopy characterized the resulting colloidal dispersions. The NPs exhibited sizes with ranges from 9.8 nm for Fe, 3.7 nm for Co, and 7.2 nm for Ni. The electron diffraction shows the presence of the metals in its elemental state Fe (0), Co (0), and Ni (0) and also some compounds FeO (OH), CoCo2S4, and NiNi2S4.

Promotion of the Ni/γ-Al2O3 catalyst for the hydrogenation of naphthalene by silica coating

The γ-Al2O3 was coated with silica through the chemical liquid deposition method with tetraethyl orthosilicate as a deposition agent. The effects of the silica coating on the reduction behaviors of nickel species, acidity and hydrogenation activities of the Ni/γ-Al2O3 catalysts were studied. The results show that the silica coating has a great promotion on the reduction behaviors of nickel species as the catalyst was activated under air atmosphere but little influence under H2. The acidity of the catalyst was improved by the silica coating. Therefore, the activities of Ni/γ-Al2O3 catalysts for the hydrogenation of naphthalene are promoted by the silica coating, but the promotion effects on the catalysts activated under air and H2 atmosphere are difference. The promotion on the catalyst activated under air is due to the enhancement of its reduction degree and acidity, but only acidity for the catalyst activated under H2. As a result, the activity is improved about 230% for the catalyst activated under air but only about 110% for the catalyst activated under H2.

The optical properties of Ce-doped SnS quantum dots with fast nanosecond lifetime

The doping of luminescent semiconductor nanoparticles has been a hotspot of research, especially rare earth element doped Nano-fluorescent material as a result of their distinct electronic structures. Herein, the investigation of the Ce3+ doping content effect on the UV–vis absorption, electronic structures, luminescence decay, and photoluminescence of SnS is one of crucial orientations of this. In this work, a reproducible gas and liquid chemical deposition method is used to synthesize the SnS and SnS:Ce3+ quantum dots. It has been detected that by doping Ce3+, the photoluminescence peak SnS can be enhanced clearly and the direct bandgap energy of SnS:Ce3+ quantum dots has gradually decreased, which indicates doping Ce3+ can effectively control the optical properties of SnS. The lifetime values of SnS:Ce3+ quantum dots has significantly shorten in comparison to the pure SnS and due to the overlapped energy levels of Ce3+ and Sn2+, the luminescence of SnS quantum dots will improve. By using the first principles of density functional theory (DFT), we calculated the total density of states (TDOS), the band structure and the partial densities of states (PDOS) of SnS and SnS:Ce3+ structures. The aforesaid experimental results have been attested by the calculating results exactly.