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A series of ZrO2-SiO2 composite aerogels have been synthesized by adjusting the volume of tetraethoxysilane (TEOS) during supercritical fluid drying process. ZrO2 aerogels have been prepared via the sol-gel reaction using ZrOCl2ꞏ8H2O and the gel initiator malic acid as raw materials. Then the ZrO2-SiO2 composite aerogels have been obtained by supercritical fluid deposition (SCFD). The samples have been characterized applying XRD, FTIR, SEM, TEM, TGA and Nitrogen adsorption-desorption. The introduction of SiO2 can effectively restrain the growth of the nanoparticles and the transformation of crystalline phase, and reduce the linear shrinkage of the aerogels. It indicates the improvement of the thermostability of the ZrO2-SiO2 composite aerogels. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mo(CO) 6 is as nucleation site to grow MoS 2 film by supercritical fluid deposition. • MoS 2 domains size and coverage can be tuned. • Homogeneous and heterogeneous sulfuration reactions promote synthesis of MoS 2. • Mo obtained by decarbonylation of Mo(CO) 6 has a high reactivity by DFT analysis. The assistance of promoters, Molybdates or alkali metal salts can regulate the nucleation site of MoS 2 in chemical vapor deposition. However, the introduction of impurities inevitably reduces the MoS 2 quality. Here, we present the growth of monolayer MoS 2 by supercritical fluid deposition to pre-deposit Mo(CO) 6 precursors as nucleation sites, replacing difficult to clean conventional promoters. Domain-limited homogeneous and heterogeneous reactions occur at nucleation sites, and through optimization of sulfurization parameters, high-quality monolayer MoS 2 with about 20 μm domain size can be obtained by growing at 760 °C and 40 sccm argon for 20 min. Monolayer MoS 2 coverage ranged from 2.6 % to 39.1 % by regulating dissolution mass in range of 100–400 mg, utilizing the highly soluble Mo(CO) 6 in supercritical CO 2. Density functional theory calculations show that decarbonylated Mo(CO) 6 possesses higher sulfide reactivity. This study provides new insights into the impurity-free controlled site growth of two-dimensional materials. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we present a numerical study along with an exhaustive adsorption investigation in a binary dilute mixture model nearby the solvent’s critical point in a configuration relevant for soil remediation. By means of this model, mass and heat transfer efficiency were qualitatively and quantitatively discussed through this work. The convergence of the solution was evaluated on the values of the Nusselt and Sherwood numbers. The results reveal intense convection expanding into the cavity close to the critical point, thus enabling homogeneous adsorption of the solute. Moreover, the mass fraction perturbation isolines exhibit the existence, along the adsorbent plate, of a thin boundary layer which becomes thinner when approaching the critical point.

A small-volume hot-wall batch reactor with excess precursor loading was proposed for supercritical fluid deposition of Cu during the fabrication of sub-millimeter-scale, metal-coated terahertz (THz) wave devices. Conformal film formation was experimentally demonstrated, validating our method. Our method enables a much higher precursor concentration (at least 20 mol mâˆ'3) than the conventional method (below 2 mol mâˆ'3), facilitating conformal film formation on sub-millimeter structures. Kinetic analysis revealed that our proposed method was applicable for fabricating rectangular metal-coated THz waveguides; furthermore, it was promising for monolithically integrated THz wave devices. [ABSTRACT FROM AUTHOR]

Highly dispersed palladium nanoparticles (NPs) supported on UiO-66 as catalyst for CO2 methanation were prepared by supercritical fluid deposition (SFD). As a result, the most suitable Pd precursor salt and co-solvent are Na2PdCl4 and ethanol/DMF, respectively. The best SFD process condition to deposit the Pd precursor on UiO-66 is 40 °C, 10 MPa and 2 h. Under the above condition, 4% Pd/UiO-66 exhibits the highest activity with 53% of CO2 conversion and 95% of CH4 selectivity while the turnover frequency (TOF) value is 3669.4 h−1. The catalysts were characterized by XRD, BET, TEM, XPS, TGA, CO-DRIFTS and ICP-OES to investigate the structure–activity relationship. The 4% Pd/UiO-66 with the average size of 2.2 nm of Pd prepared in assistance of supercritical fluid behaved the similar activity as the 6%Pd/UiO-66 with average size of 9.7 nm of Pd prepared by sol–gel method. It is showed prospect of technique for reducing noble metal loading resulting from high dispersion effect. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ionic liquid solubility in CO 2 phase with co-solvent was predicted. • Peng-Robinson equation of state was chosen as the predictive model. • Application of critical temperature for the ionic liquid that was re-determined. • Predictive model with acceptable accuracy in several IL systems. Supercritical fluid deposition (SCFD) using supercritical carbon dioxide (CO 2) to impregnate substrates with ionic liquids (ILs) has attracted considerable attention for the preparation of porous-supported ILs. Because ILs are generally insoluble in pure CO 2 , it is essential to estimate the solubilities of ILs in supercritical CO 2 + co-solvent systems for developing the SCFD process. In this study, a methodology was developed to predict the solubility of ILs in supercritical CO 2 with co-solvents using the corresponding binary phase-equilibrium data. For the prediction, the binary interaction parameters for the Peng–Robinson equation of state (PR-EoS) were determined using the correlations to each phase-equilibrium system (i.e., IL + CO 2 , CO 2 + co-solvent, and IL + co-solvent). The predictive model using the PR-EoS, which included a re-determined critical temperature as a pure component parameter of ILs, could reproduce the effects of the temperature, pressure, and co-solvent concentration on the IL solubilities in the supercritical fluid phase without any fitting parameters for the ternary systems. The average absolute relative deviations based on the logarithmic scale for the predictions were <23 %, indicating that the methodology was acceptable for describing the IL solubilities in the supercritical CO 2 + co-solvent system. [ABSTRACT FROM AUTHOR]

We studied the temperature dependence of the emission and absorption of PbS quantum dots deposited on glass by a supercritical CO2 fluid process. The results show that the emission is ruled by different transitions than the absorption, particularly at cryogenic temperatures. We found indications that these observations can be linked to the PbS concentration used to form the films in conjunction with the capability of the supercritical CO2 method to form dense homogeneous films. [ABSTRACT FROM AUTHOR]

We studied the temperature dependence of the emission and absorption of PbS quantum dots deposited on glass by a supercritical CO2 fluid process. The results show that the emission is ruled by different transitions than the absorption, particularly at cryogenic temperatures. We found indications that these observations can be linked to the PbS concentration used to form the films in conjunction with the capability of the supercritical CO2 method to form dense homogeneous films.

The adsorption of nickelocene (NiCp 2 ) and ruthenocene (RuCp 2 ) on MCM-48 and activated carbon in supercritical CO 2 is studied. Adsorption isotherms of NiCp 2 on MCM-48 at 70 °C and RuCp 2 on MCM-48 and Activated Carbon at 60 °C and pressures of 11, 14, 17 and 20 MPa have been determined and correlated with Langmuir, Modified Langmuir, Freundlich, Redlich-Peterson models and Brunauer-Emmett-Teller (BET) isotherm. Kinetics of adsorption of NiCp 2 on MCM-48 at 70 °C and 14 MPa have been experimentally determined and correlated with a pseudo-first order model with a constant rate k f = 0.274 h −1 . In the same way, kinetics of adsorption of RuCp 2 on MCM-48 and activated carbon at 60 °C and 11 MPa have been experimentally determined and correlated with a pseudo-first order model with a constant rate k f = 0.844 h −1 and k f = 0.278 h −1 respectively. [ABSTRACT FROM AUTHOR]

In recent years, single-atom catalysts (SAC) have emerged as a new frontier in the field of heterogeneous catalysis owing to their unique properties and minimized metal dosage. Herein, the Pd-ZIF-8 single-atom catalyst was successfully fabricated using ZIF-8 as support, and Pd(hfac) 2 as the precursor using the supercritical CO 2 deposition method. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM) images confirmed the formation of uniformly dispersed Pd atoms. Supercritical CO 2 has the advantage of zero-surface tension and high diffusibility, it can carry the molecules of Pd precursor into the micropores of ZIF-8. The dissolution and diffusion of precursor were observed by a visual view cell and the mechanism of the preparation was analyzed. Finally, semi-hydrogenation of phenylacetylene to styrene was performed to evaluate the catalytic activity of the prepared Pd-ZIF-8 catalyst. The conversion rate of 80.7% and selectivity of 92.2% were obtained at 70 °C and 4 h in the semi-hydrogenation of phenylacetylene. [Display omitted] • Pd-ZIF-8 SAC was prepared by supercritical CO 2 deposition for the first time. • A new path for preparing single-atom catalysts using pure ZIF-8 support was opened. • No high-temperature treatment, acids, or corrosive solvents were required during the process. • AC-HAADF-STEM directly confirmed the uniform dispersion of Pd atoms. • Phenylacetylene was hydrogenated with the conversion of 80.7% and the selectivity of styrene was 92.2%. [ABSTRACT FROM AUTHOR]

Cobalt depositions from supercritical carbon dioxide (scCO 2 ) were conducted on various surfaces including the native oxide surface of silicon wafers, tantalum nitride (TaN), carbon, and copper in a cold-wall reactor using bis(2,2,6,6-tetramethyl-3,5-heptanedionato) cobalt(II) as the precursor. Deposition onto TaN barrier layers at temperature above 300 °C yielded high purity cobalt films as determined by X-ray photoelectron spectroscopy with grain sizes of 200 nm or less. The volume resistivities, of about 200 nm thick films estimated from the surface resistivities, were about 2.5 times higher than that of the literature value of pure cobalt. Cobalt films could also be deposited on both carbon and copper surfaces with morphologies that varied depending on the amount of precursor loaded. Moreover, the cobalt film protected copper surface from oxidation in solution and also improved its resistance to oxidation in air as demonstrated respectively by cyclic voltammetry and X-ray photoelectron spectroscopy depth profiles. [ABSTRACT FROM AUTHOR]

The comprehensive investigation of ternary PtIrCo-alloy nanoparticles supported on 3D carbon aerogel matrix toward Methanol Oxidation Reaction (MOR) and Oxygen Reduction Reaction (ORR) is focused on CO tolerance in MOR, methanol vs. oxygen selectivity in ORR, and the structural changes within the metal alloy nanoparticles caused by the heat treatment and the electrochemical conditioning. Amorphous tri-metallic Pt 59 Ir 34 Co 7 -nanoparticles with mean size of 1.47 ± 0.21 nm were formed within 3D CA matrix in supercritical CO 2 (scCO 2 ) from the Pt, Ir, and Co organometallic precursors. Depending on the heat-treatment temperature (600 °C or 900 °C), the amorphous organometallic phase of Pt, Ir and Co was transformed into a single-phase fcc PtIrCo-alloy nanoparticles with a mean particle size of 1.68 ± 0.33 nm and 2.68 ± 0.61 nm, respectively. The fcc lattice parameters of the PtIrCo-alloy (0.389 nm at 600 °C and 0.386 nm at 900 °C) were smaller than that of the Pt fcc lattice (0.392 nm) and the lattice parameters reduced proportionally to the heat-treatment temperatures. After 50 electrochemical cycles, PtIrCo/CA catalysts display improved MOR specific activity (∼2.5 X Pt/C), mass activity (∼3 X Pt/C) at 0.7 V vs. SHE, higher CO-tolerance, and better electrochemical stability than Pt/C, but less CO-tolerance and stability than PtRu/C. Regarding ORR, the PtIrCo/CA catalysts demonstrate enhanced ORR specific activity (∼5.5 X Pt/C) and mass activity (∼6.3 X Pt/C) at 0.7 V vs. SHE along with superior methanol-tolerance in comparison to Pt/C. The structural changes associated with PtIrCo/CA fcc -lattice parameter with respect to Pt-lattice have contributed to better MOR and ORR activities. Faster surface diffusion associated with weak adsorption of hydroxide species and higher selective adsorption of oxygen in comparison to methanol onto PtIrCo-alloy surface could have contributed to their better CO-tolerant MOR and methanol-resistant ORR activity compared to Pt-catalyst. [ABSTRACT FROM AUTHOR]

The functionalization of silicon oxide based substrates using silanes is generally performed through liquid phase methodologies. These processes involve a huge quantity of potentially toxic solvents and present some important disadvantages for the functionalization of microdevices or porous materials, for example the low diffusion. To overcome this drawback, solvent-free methodologies like molecular vapor deposition (MVD) or supercritical fluid deposition (SFD) have been developed. In this paper, the deposition process of 3,4-epoxybutyltrimethoxysilane (EBTMOS) on silicon oxide using supercritical carbon dioxide (scCO 2 ) as a solvent is studied for the first time. The oxirane ring of epoxy silanes readily reacts with amine group and is of particular interest for the grafting of amino-modified oligonucleotides or antibodies for diagnostic application. Then the ability of this specific EBTMOS layer to react with amine functions has been evaluated using the immobilization of amino-modified oligonucleotide probes. The presence of the probes is revealed by fluorescence using hybridization with a fluorescent target oligonucleotide. The performances of SFD of EBTMOS have been optimized and then compared with the dip coating and molecular vapor deposition methods, evidencing a better grafting efficiency and homogeneity, a lower reaction time in addition to the eco-friendly properties of the supercritical carbon dioxide. The epoxysilane layers have been characterized by surface enhanced ellipsometric contrast optical technique, atomic force microscopy, multiple internal reflection infrared spectroscopy and X-ray photoelectron spectroscopy. The shelf life of the 3,4-epoxybutyltrimethoxysilane coating layer has also been studied. Finally, two different strategies of NH 2 -oligonucleotide grafting on EBTMOS coating layer have been compared, i.e. reductive amination and nucleophilic substitution, S N 2. This EBTMOS based coating layer can be used for a wide range of applications such as the preparation of new supported and recoverable catalysts and new integrated silicon microdevices for healthcare purposes. [ABSTRACT FROM AUTHOR]

The capture and fixation of CO 2 can effectively alleviate greenhouse effect. Propylene carbonate is a highly efficient solvent, which can be used as an excellent medium for lithium battery. It is of great significance to convert CO 2 into propylene carbonate. In this paper, ionic liquid BMImBr was immobilized into the pores of SBA-15 by supercritical deposition, and BMImBr@SBA-15 was obtained for catalytic conversion of CO 2. The catalytic properties of BMImBr and BMImBr@SBA-15 were investigated by batch method. Then the catalytic performance of supported catalyst BMImBr@SBA-15 was investigated by continuous method, which was carried out in a fixed-bed reactor. The continuous experiments controlled the CO 2 pressure change (0.5–2.0 MPa) when the inlet liquid flow rate was 0.02 mL/min and 0.04 mL/min. Under the conditions of 0.04 mL/min and 1.0 MPa, the yield was the highest (66.14 %). In this paper, through the calculation of the reaction rate constant, it can be concluded that the continuous method can avoid the repeated packing of the catalyst and obtain a higher yield in a short time. It has a broad prospect of industrialization. • BMImBr was immobilized on SBA-15 molecular sieve by supercritical deposition. • Catalyst activity of BMImBr@SBA-15 was investigated in batch and continuous modes. • The highest yield was 66.14 % in a continuous fixed bed reactor. • Si-OH cooperates with halogen anions to promote ring opening of epoxides. [ABSTRACT FROM AUTHOR]

Ru catalysts supported on activated carbon (AC) were prepared by supercritical fluid deposition (SFD) with ethanol added and their catalytic performance in butanone hydrogenation was investigated. The effects of ethanol amount on Ru particle size were systematically studied. As the amount of ethanol increased, Ru mean particle sizes always decreased firstly, then increased. And the minimum mean particle size of Ru was obtained at 10 ml ethanol. The catalysts with smaller Ru mean particle size presented higher catalytic activity. These results demonstrated that the role of ethanol may not be only co-solvent but also anti-solvent and extractant during the preparation of Ru/AC. [ABSTRACT FROM AUTHOR]

This work has focused on the synthesis of Cu nanostructured electrocatalysts for CO 2 electroreduction by supercritical fluid deposition (SFD) technique. Different synthesis strategies such as the suppression of cosolvent (methanol) and/or reducing agent (hydrogen) have been studied. Good copper deposition yields (around 85%) have been attained in the absence of hydrogen. This material (C-200Me) has been tested as catalyst in the electrochemical reduction of CO 2 in gas phase and the results obtained have been compared with those achieved with a catalyst synthesised using H 2 as reducing agent (C-200H 2 Me). CO and formic acid have been the main reduction products with both catalysts. CO 2 conversion rate has been almost six times higher with C-200H 2 Me, what may be probably attributed to a higher proportion of Cu0/Cu+ species in this catalyst. These results indicate the higher catalytic activity of Cu0 (than that of Cu 2 O) in the electrocatalytic reduction of CO 2 in gas phase. [Display omitted] • Supercritical fluid deposition of copper-based nanoparticles. • Deposition yields around 70% without hydrogen or methanol. • Cu0 nanoparticles more active than Cu 2 O in the electroreduction of CO 2 in gas phase. • CO and formic acid are the main CO 2 electroreduction products. • SFD allows controlling the copper species formed in the synthesised nanomaterial. [ABSTRACT FROM AUTHOR]

The kinetics of TiO2 thin-film deposition in a supercritical CO2/alcohol environment was studied using titanium di(isopropoxide)bis(tetramethylhexanedionate) [Ti(O-i-Pr)2(tmhd)2] as the precursor. The solvent effects of methanol, ethanol, and isopropanol on the supercritical fluid deposition (SCFD) of TiO2 were examined at deposition temperatures of 150–300°C. Methanol was the most effective of the three alcohols evaluated; it enhanced the TiO2-SCFD deposition rate 2–3-fold and decreased the activation energy from 49±4 to 28±3kJ/mol. Conformal deposition of TiO2 on a deep trench (aspect ratio of 30) was demonstrated at a growth rate of >2nm/min. [ABSTRACT FROM AUTHOR]

Abstract: Electrochemical capacitor electrodes were fabricated by depositing an ultra-thin layer of vanadium oxide on a high conducting, large specific surface area (SSA) materials (substrates) using a supercritical fluid adsorption–calcination method. The high SSA materials included binder free single walled carbon nanotube–activated carbon (SWCNT–AC) composites and the traditional electrode of activated carbon–carbon black–polymer binder (AC–CB–binder). The uptake of the organometallic precursor for the oxide (vanadium (III) acetylacetonate) on the substrates were investigated and related to their SSA. Precursor uptakes up to 54.7 wt% of the initial carbon substrate was achieved. Calcination conditions for converting the precursor to oxide and electrochemical properties of the electrodes were thoroughly investigated. The V2O5, which showed extremely high specific pseudo-capacitance (>1000 F g−1 at 100 mV s−1), greatly enhanced the overall electrode performances. Conversely, the V2O5 pseudo-capacitance was better utilized in the SWCNT–AC substrate, particularly at high working speeds, because of the significantly higher electrical conductivity. For example, the SWCNT–AC–V2O5 composite (weight ratio 40:60) had its volumetric capacitance doubled, comparing to the ∼50% increase in the AC–CB–binder sample at 100 mV s−1. [Copyright &y& Elsevier]

Highlights: [•] SrRuO3 thin film formation was carried out using kinetics of RuO2 and SrO deposition. [•] High RuO2 deposition rate and easy SrO particle formation in the fluid induced Ru rich SrRuO3 film. [•] Stoichiometric SrRuO3 was deposited by controlling deposition temperature, O2 partial pressure and Sr to Ru precursor mol ratio. [•] Deposited SRO had good step coverage, which was 0.96 on trenches, having aspect ratio of 5. [ABSTRACT FROM AUTHOR]

Deposition of ibuprofen (IBU) into ordered mesoporous silica SBA-15 was carried out to prepare controlled release nanodrug using supercritical carbon dioxide (scCO2) as solvent at 17 MPa and 310.15 K. The maximum drug loading of IBU/SBA-15 was as high as 41.96%. The characterization of the obtained materials was performed using x-ray diffractometry (XRD), scanning electron microscopy (SEM), and nitrogen (N2) adsorption-desorption isotherms; the results indicate that most adsorbed drugs were inside the nanoscale channels. The in vitro study shows that the time of complete (100%) release significantly decreases as drug-loading decreases. The interesting aspect is that the samples with similar drug loading display different release rates, which may be due to differences in the drug quantity adsorbed inside the pores. In addition, the modified Noyes-Whitney equation was used to model the release kinetics for all the samples and a good agreement was obtained between the model representation and experimental data. In addition, the solubility of IBU in scCO2was tested through a high-pressure view cell at the temperature range of 298.15–320.15 K and pressure range of 7–17 MPa. The experimental solubility data were well correlated using Chrastil’s equation as well as Mendez-Santiago and Teja’s equation. [ABSTRACT FROM PUBLISHER]

Abstract: Pt and mixed Pt-ceria catalysts were deposited onto gas diffusion layers using supercritical fluid deposition (SFD) to fabricate thin layer electrodes for direct methanol fuel cells. Dimethyl (1,5-cyclooctadiene) platinum (II) (CODPtMe2) and tetrakis (2,2,6,6-tetramethyl 3,5-heptanedionato) cerium (IV) (Ce(tmhd)4) were used as precursors. Hydrogen-assisted Pt deposition was performed in compressed carbon dioxide at 60°C and 17.2MPa to yield high purity Pt on carbon-black based gas diffusion layers. During the preparation of the mixed Pt-ceria catalyst, hydrogen reduction of CODPtMe2 to yield Pt catalyzed the deposition of ceria from Ce(tmhd)4 enabling co-deposition at 150°C. The catalyst layers were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope-energy dispersive spectral (SEM-EDS) analyses. Their electrochemical performance toward methanol oxidation was examined in half cell mode using a three electrode assembly as well as in fuel cell mode. The thin layer electrodes formed via SFD exhibited higher performance in fuel cell operations compared to those prepared by the conventional brush-paint method. Furthermore, the Pt-ceria catalyst with an optimized composition exhibited greater methanol oxidation activity than pure platinum. [Copyright &y& Elsevier]

Abstract: We report the formation of yttria stabilized zirconia (YSZ) thin films by supercritical fluid deposition (SFD) in carbon dioxide at 20MPa and a stage temperature of 300°C via hydrolysis of zirconium(IV) hexafluoroacetylacetonate and yttrium(III) hexafluoroacetylacetonate. Post-deposition annealing of the films at 800°C yields crystalline films having the expected fluorite structure as evidenced by X-ray diffraction. Such films are suitable for the fabrication of electrolyte thin films for micro-solid oxide fuel cells (μ-SOFC). We show that a cyclic co-deposition process in which aliquots of precursor are introduced sequentially enables the depostion of YSZ thin films with uniform composition as evidenced by X-ray photoelectron spectroscopy. In each cycle, the mixed precursor solution in CO2 is introduced to the reactor and then purged following a short reaction interval. By contrast, simple batch SFD processes that employ hydrolysis of the mixed precursors introduced at the onset of the depositions lead to non-uniform distributions of the cations throughout the thickness of the films. The cyclic deposition approach extends supercritical fluid deposition to materials such as multi-cations oxides for which precise control of stoichiometry is required. [Copyright &y& Elsevier]

Abstract: The solubility of a titanium (Ti) complex, titanium diisopropoxide bis(dipivaloylmethanate) [Ti(Oi-Pr)2(dpm)2], in supercritical carbon dioxide (scCO2) fluid was measured under various fluid temperatures and pressures to clarify its effect on supercritical fluid deposition (SCFD) for titanium dioxide (TiO2) films, by means of the extraction method with 2-propanol as the extracting solvent and UV–vis spectroscopic analysis. The solubility which is expressed by molar ratio of Ti complex to CO2, μ, decreased with the fluid temperature, T f, from 40 to 60°C, while it increased rapidly with the fluid pressure, P f, from 6 to 10MPa and then increased gradually with P f from 10 to 20MPa. The behavior was analyzed by Chrastil''s equation model. The deposition rate of TiO2 films by SCFD was understood to be proportional to the difference in the mass concentration of Ti complex, S, between in the bulk transport medium and vicinity of the substrate surface. [Copyright &y& Elsevier]

Abstract: The kinetics of ruthenium thin film deposition via the hydrogen assisted reduction of bis(2,2,6,6-tetramethyl-3,5-heptanedionato)(1,5-cyclooctadiene)ruthenium(II) [Ru(tmhd)2cod] in supercritical carbon dioxide was studied. Deposition temperature was varied from 240°C to 280°C and the apparent activation energy was determined to be 45.3kJ/mol. Deposition rates up to 30nm/min were attained. The growth rate dependence on precursor concentration between 0 and 0.2wt.% in CO2 was studied at 260°C using excess hydrogen. The results indicated first order deposition kinetics with respect to precursor at concentrations lower than 0.06wt.% and zero order dependence at concentrations above 0.06wt.%. The ability to access regimes of zero order growth kinetics is advantageous for conformal depositions in high aspect ratio features. Growth rate was second order with respect to hydrogen at concentrations less than 0.26 wt.% and zero order at higher concentrations. The reaction byproducts, cyclooctadiene and cyclooctene, both had negative first order effects on growth rate while cyclooctane had a small negative impact on film growth rate. The effect of reaction pressure on the growth rate was studied at a constant reaction temperature of 260°C and pressures between 159bar and 200bar and found to have no significant effect on the growth rate. [Copyright &y& Elsevier]

Copper nanoparticles and nanorods were prepared in the one-dimensional channels of SBA-15 supported by a modified supercritical fluid deposition (SCFD) method. In this approach, cheap and widely available copper nitrate, which is insoluble in supercritical CO2 (scCO2), was used as the copper source and ethanol as the co-solvent, thus avoiding the employment of expensive and less available scCO2-soluble precursors. The deposition was carried out at the pressure of 21-25 MPa and temperature of 50°C, followed by calcinations at 500°C and H2 reduction at 500°C. The results showed that highly dispersed Cu nanoparticles or nanorods were obtained controllably just by varying the deposition time, as characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). On the other hand, when Cu(acac)2 was used as the precursor and without any co-solvent, only nanoparticles were formed in the channels of SBA-15 no matter how long the deposition time. [ABSTRACT FROM AUTHOR]

A fivefold increase in adhesion energy is observed for poly(acrylic acid) (PAA) modified Cu/TaN interfaces in which the thin copper fl/ins are deposited by the hydrogen assisted reduction of bis(2,2, 7-trimethyloctane-3,5-dionato) copper in supercrirical carbon dioxide. The PAA adhesion layer is sacrificial at the reaction conditions used, and X-ray photoelectron spectroscopy has shown that the Cu/TaN interface is free of contamination following deposition. The resulting average intemfacial adhesion energy is just above 5 J/m2, which meets adhesion requirements for integration in Cu interconnects. The adhesion measurements are performed with a custom built four-point bend fracture mechanics testing system. Comparison of the copper film thickness to the measured adhesion energy indicated that there is no effect on the adhesion energy as the film thickness changes. [ABSTRACT FROM AUTHOR]

Abstract: We studied supercritical carbon dioxide fluid deposition of titanium oxide (TiO2) in trench features on Si substrates using a flow-type deposition apparatus from titanium diisopropoxide bis(dipivaloylmethanate), aiming at fabricating conformal films at a relatively low temperature. We investigated the deposition rate and step coverage under a fluid temperature from 40 to 60°C, a pressure from 8.0 to 10.0MPa, and a substrate temperature from 80 to 120°C. They were dependent on the fluid density, indicating that the solubility difference between the bulk fluid and the neighborhood of the substrate surface plays a decisive role for the deposition. An excellent conformal filling of the trench features was achieved from the fluid of 60°C under 8MPa on the substrate kept at 80–100°C. The XPS spectra of the deposited film suggested partial formation of TiO2, and the XRD spectra showed the existence of some crystalline TiO2 (anatase). [Copyright &y& Elsevier]

Supported single-atom catalytic materials (SACMs) have aroused extensive interest due to their remarkable properties. Herein, a novel method was proffered to prepare Co-NC SACMs using custom-designed N-doped carbon (NC) as support, CoCl 2 as the precursor in supercritical CO 2 with appropriate co-solvent. It was found that when ethanol was used as co-solvent, nanoparticles were obtained while only Co single-atom was obtained when N, N-Dimethylformamide (DMF) was used as co-solvent. Both the theoretical loading and the deposition time influenced the Co loading a lot, and the maximum Co loading was as high as 1.71 wt%. Strong acid, strong alkali, corrosive solvent, and high-temperature treatment were avoided in the whole process. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (AC-HAADF-STEM), X-ray photoelectron spectroscopy (XPS), Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), and Energy Dispersive X-ray spectroscopy (EDX) were conducted to confirm the existence and uniform distribution of Co atoms over the N-doped carbon materials. The conversion rate of 90.0% and selectivity of 86.0% were obtained for the solvent-free selective oxidation of benzyl alcohol to benzaldehyde at 70 °C and 1 h using the Co-NC SACMs. [Display omitted] • Co-NC single-atom catalysts were synthesized by supercritical CO 2 deposition. • No high-temperature treatments, strong acids, or corrosive solvents were required. • AC-HAADF-STEM showed a uniform dispersion of Co atoms on the NC support. • Co-NC with 1.71 wt% Co selectively oxidized benzyl alcohol to benzaldehyde at 70 °C [ABSTRACT FROM AUTHOR]

Abstract: Four liquid chemical reagents (ethanol, 2-propanol, hydrogen peroxide, and formic acid) were evaluated as reducing agents for supercritical fluid deposition of Cu (Cu-SCFD) using bis(2,2,6,6-tetramethyl-3,5-heptanedionato)copper as a precursor onto a Ru-coated Si substrate for ultra large scale integration metallization. Deposition was carried out using a batch-type reactor and heating the substrate from 40 °C to 250 °C at a rate of 4.5 °C/min. 2-propanol and hydrogen peroxide yielded Cu grains, but not a continuous Cu film. Only formic acid yielded a high-purity continuous film. Solvent effect of two chemical reagents (ethanol and 2-propanol) on Cu-SCFD with H2 as a reducing agent was also investigated by using in situ method, in which optical reflectivity of growing surface at wavelength of 770 nm was used. Ethanol addition enhanced the deposition reaction without degrading both the surface morphology and high purity of the deposited Cu film. [Copyright &y& Elsevier]

Abstract: Fluid flow patterns and temperature profiles within cold wall, high pressure supercritical fluid (SCF) reactors were investigated by simulation and experiment at conditions relevant to the deposition of copper and other metals for applications in microelectronics. Steep thermal gradients between the heated platen, the bulk fluid, and the reactor walls produce large density gradients in the supercritical fluid. Rayleigh numbers are in excess of 1×1010 and the flow is highly turbulent. Natural convection and buoyancy forces dominate the flow within the reactor in both the batch (closed domain) and continuous flow (open domain) configurations. The situation is unlike that in low pressure chemical vapor deposition reactors in which thermal gradients do not give rise to significant density gradients, flow is laminar, and forced convection dominates natural convection. Temperature distributions and flow patterns within cylindrical cold wall reactors containing supercritical carbon dioxide were simulated by computational fluid dynamics (CFD) and conjugate heat transfer calculations. Good agreement with experiment was achieved. The implications of the results for reactor design are discussed. [Copyright &y& Elsevier]

• [Emim][Tf 2 N]-SILMs were prepared by supercritical fluid deposition method. • SILMs has high gas separation performance with CO 2 permeance of 22.6 GPU and CO 2 /N 2 selectivity of 27.1. • [Emim] [Tf 2 N] first filled top layer of γ-Al 2 O 3 to obtain a thin membrane with higher CO 2 permeability. • SILM could resist transmembrane pressure difference of at least 150 kPa. ga1 Supported ionic liquid membrane (SILM) using low surface tension ionic liquid [Emim] [Tf 2 N] and γ-Al 2 O 3 is prepared with the supercritical fluid deposition (SCFD) method, and supercritical carbon dioxide (scCO 2) shuttles and diffuses into the interior of the support to render the deposition of ionic liquid (IL) in its nano-micro pores. In this study, the influence of preparation parameters includes deposition pressure (9–18MPa), deposition time (0–24 h), ethanol amount (0–18.75 vol%) and IL amount (1.0–5 mg/g) were investigated. Besides, the performance of SILMs were evaluated by analyzing IL load, N 2 and CO 2 permeability, and ideal CO 2 /N 2 selectivity. Under the optimum condition, the [Emim] [Tf 2 N]-SILMs exhibited separation performance with CO 2 permeance of 22.6 GPU and CO 2 /N 2 selectivity of 27.1. Furthermore, [Emim] [Tf 2 N]-SILM maintains proper pressure resistance and long-term stability, which is more suitable for CO 2 separation, capture and storage in large-scale applications. [ABSTRACT FROM AUTHOR]

• Cu-based nanoparticles deposited on different carbon supports have been synthesized. • Supercritical fluid deposition obtains homogeneous Cu nanoparticles distribution. • CO, formic acid and methane have been the main reaction products obtained. • Higher CO 2 conversion rate has been obtained with Cu/CNT catalyst. • CO is promoted with Cu/CNT and Cu/CB and formic acid with Cu/rGO. Climate change caused by carbon dioxide anthropogenic emissions has turned into one of the most important environmental concerns of our society. Among the different actions proposed for mitigation of CO 2 emissions, electrocatalytic reduction appears as a very promising technology for recycling CO 2 to synthetic fuels and other valuable products. One of the most important challenges of this technology is the development of catalysts that allow obtaining high efficiencies in the reduction of the CO 2 molecule. This work is focused in the development of Cu based nanostructured catalysts deposited on carbon supports. Supercritical fluid deposition (SFD) technique has been used for the copper deposition on three different carbon supports: carbon black (CB), carbon nanotubes (CNT) and reduced graphene oxide (rGO). SFD is an environmentally friendly technology that has demonstrated good results in the synthesis of nanomaterials. Results obtained in this work show that SFD technique allows a homogeneous deposition of copper nanoparticles on the different carbon supports used with deposition yields close to 90%. The average size of copper nanoparticles formed is between 13 and 19 nm. The activity of these catalysts (Cu/CB, Cu/CNT and Cu/rGO) in the electrocatalytic reduction of carbon dioxide has been carried out in gas phase in a PEM type electrochemical cell. Results show a higher CO 2 conversion rate (around 40%) when using Cu/CNT catalyst. In every case, CO, formic acid and methane are the main reaction products obtained from the CO 2 reduction. Nevertheless, Cu/CNT and Cu/CB catalysts promote the formation of CO, whereas formic acid is the main reaction product with Cu/rGO. This could be attributed to the presence of oxygenated groups observed in the rGO based catalyst. These results point out that the interaction between the copper nanoparticles and the carbon support plays an important role in the CO 2 electrocatalytic reduction process. [ABSTRACT FROM AUTHOR]

Climate change has turned into one of the most important concerns for scientist in the last years due to the huge increase of CO 2 concentration in the atmosphere in the last century. Electrocatalytic reduction seems to be a very promising technology to help to reduce industrial CO 2 emissions. The development of catalysts capable of activating the CO 2 molecule is the main challenge of this technology. In this work a copper supported on carbon nanotubes (Cu/CNT) catalyst has been synthesized using supercritical fluid deposition (SFD) and assembled into a polymer electrolyte membrane (PEM) type cell to carry out the electrochemical reduction of CO 2. The influence of current density, temperature and CO 2 flowrate has been analysed and results have been compared with those previously obtained with Pt/CNT and Pb/CNT catalysts synthesized by SFD. The CO 2 reduction rate and the products distribution attained with the three catalysts have been analysed. CO has been the main reaction product attained with the Cu/CNT catalyst developed in this work, followed by small amounts of formic acid and methane. This can be considered the main difference observed in relation with Pt or Pb based catalysts that promote the production of formic acid as main reaction product. CO 2 conversion rate increases with temperature and CO 2 flowrate and is much higher than that attained when using Pt or Pb based catalysts in the same experimental conditions (up to 27 times higher depending on the experimental conditions). • Supercritical fluid deposition obtains homogeneous Cu nanoparticles distribution. • CO has been the main product obtained from the CO 2 reduction with Cu/CNT catalyst. • CO 2 conversion rate increases with temperature and CO 2 flowrate. • CO 2 conversion rate is up to 27 times higher with Cu/CNT than with Pt/CNT or Pb/CNT. [ABSTRACT FROM AUTHOR]

• scCO2 flows of a semicircular tube reactor with two inlets were investigated by CFD. • The flow proceeded obliquely downward just after introduction into the reactor. • Vortical flows perpendicular to the main flow could be observed near the hot ceiling. • The velocity of the vortical flows increased with decreasing pressure. • Velocity distribution in the axial direction clearly depended on the outlet size. Computational fluid dynamic (CFD) simulations of supercritical carbon dioxide (scCO 2) were performed in a semicircular tubular reactor to clarify the flow behavior of CO 2. The reactor used had a heated ceiling wall, two inlets, and one outlet. When the ceiling temperature was higher than that of the circumferential wall, the CO 2 flow proceeded obliquely downward just after introduction into the reactor with the CO 2 at the inlets set to the same temperature as the circumferential wall temperature. Moreover, vortical CO 2 flows perpendicular to the main flow could be observed in the vicinity of the heated ceiling wall even at points far from the inlets. The values of the temperatures and the velocities of the vortical flows in the vicinity of the heated ceiling wall depended on pressure that ranged from (15 to 30) MPa. Furthermore, the shapes of the velocity distribution were clearly changed by changing the outlet size. [ABSTRACT FROM AUTHOR]

Metallic photonic crystals (MPCs) exhibit wavelength-selective thermal emission enhancements and are promising thermal optical devices for various applications. Here, we report a scalable fabrication strategy for MPCs suitable for high-temperature applications. Well-defined double-layer titanium dioxide (TiO 2 ) woodpile structures are fabricated using a layer-by-layer soft-imprint method with TiO 2 nanoparticle ink dispersions, and the structures are subsequently coated with high purity, conformal gold films via reactive deposition from supercritical carbon dioxide. The resulting gold-coated woodpile structures are effective MPCs and exhibit emissivity enhancements at a selective wavelength. Gold coatings deposited using a cold-wall reactor are found to be smoother and result in a greater thermal emission enhancement compared to those deposited using a hot-wall reactor.