scCO2 Systems Research Articles

Thermodynamic study for the (butyl, hexyl and octyl) acetoacetate under high pressure CO2

Understanding the phase behavior of binary liquid mixtures containing butyl acetoacetate, hexyl acetoacetate, and octyl acetoacetate under high-pressure supercritical CO2 (sc-CO2) is essential for several applications. The solubility curves for these binary mixtures have been investigated at different temperature and pressure ranges, specifically between 313.2 K and 393.2 K and 2.39 MPa to 23.83 MPa. The three systems, namely butyl acetoacetate, hexyl acetoacetate, and octyl acetoacetate in high-pressure sc-CO2, exhibit critical mixture curves and a maximum in pressure–temperature (P, T) diagrams between the critical point of butyl acetoacetate/hexyl acetoacetate/octyl acetoacetate and carbon dioxide. These characteristics of the critical mixture plot fall under the category of type-I behavior.The Peng-Robinson equation, which utilizes van der Waals mixing rules and two interaction parameters, is employed to correlate experimental solubility curves and critical mixture curves of the aforementioned three systems. The root mean square deviation percentage (RMSD%) is calculated at each temperature (using temperature-dependent adjusted parameters) for the butyl acetoacetate + sc-CO2, hexyl acetoacetate + sc-CO2, and octyl acetoacetate + sc-CO2 systems, and it ranges from 3.11% to 5.92%, 2.09% to 3.97%, and 1.70% to 3.02%, respectively.

Experimental and computational phase behavior investigation for the CO2 + 1H, 1H-perfluorooctyl acrylate and CO2 + 1H, 1H-perfluorooctyl methacrylate systems at high pressure

The solubility information of fluoro-monomer (meth) acrylate in organic solvents is an important factor affecting their use in numerous engineering practices. This study investigated the phase equilibria of 1H, 1H-perfluorooctyl acrylate (PFOA) and 1H, 1H-perfluorooctyl methacrylate (PFOMA) in supercritical CO2 using optical fiber and contact lenses. The solubility curves investigations were conducted at different temperatures (313.2 to 393.2) K and pressures (3.31 to 16.84) MPa, and the mole fraction of (0.032 to 0.630).Results revealed that the PFOA + SC-CO2 and PFOMA + SC-CO2 systems exhibited a type-I behavior. The RMSD (%) for the PFOA + SC-CO2 [kij = 0.075, ηij = 0.0], and PFOMA + SC-CO2 [kij = 0.075, ηij = 0.0] models using two factors determined at 353.2 K evaluated with the alterable parameters at each T were 5.08 %, and 5.36 %, respectively. The correlation of the experimental response for the PFOA + SC-CO2 and PFOMA + SC-CO2 two component models were examined using Peng-Robinson (PR) equation of state (EOS) involving two parameters (kij, ηij) base on a fluid mixture rule. Additionally, the critical properties (pc, Tc and ω) and vapor pressure of PFOA and PFOMA were assessed using the Joback-Lyderson group impact.

Co-gasification of waste lignin and plastics in supercritical liquids: Comparison of water and carbon dioxide

Waste lignin and plastic can be converted into useful syngas by co-gasified in supercritical liquids. In this work, lignin with β-O-4 linkages and two kinds of common plastics, polyethylene and polypropylene, were simulated in the process of co-gasification. The processes in supercritical water (SCW) or supercritical carbon dioxide (SCCO2) environment at different temperatures and ratios of reactants were studied comparatively using ReaxFF molecular dynamics simulations. The composition of products has been analyzed, the co-gasification synergistic effect has been explored, and the reaction mechanisms were provided and compared. The addition of plastic increased the production of H2 in both the SCW and SCCO2 systems The effect of adding plastics on the initial pyrolysis of lignin in SCW was greater than that in SCCO2, resulting in the production of more H2 and CH4 and less CO in the SCW system.

Application of CO2 Supercritical Fluid to Optimize the Solubility of Oxaprozin: Development of Novel Machine Learning Predictive Models.

Over the last years, extensive motivation has emerged towards the application of supercritical carbon dioxide (SCCO2) for particle engineering. SCCO2 has great potential for application as a green and eco-friendly technique to reach small crystalline particles with narrow particle size distribution. In this paper, an artificial intelligence (AI) method has been used as an efficient and versatile tool to predict and consequently optimize the solubility of oxaprozin in SCCO2 systems. Three learning methods, including multi-layer perceptron (MLP), Kriging or Gaussian process regression (GPR), and k-nearest neighbors (KNN) are selected to make models on the tiny dataset. The dataset includes 32 data points with two input parameters (temperature and pressure) and one output (solubility). The optimized models were tested with standard metrics. MLP, GPR, and KNN have error rates of 2.079 × 10−8, 2.173 × 10−9, and 1.372 × 10−8, respectively, using MSE metrics. Additionally, in terms of R-squared, they have scores of 0.868, 0.997, and 0.999, respectively. The optimal inputs are the same as the maximum possible values and are paired with a solubility of 1.26 × 10−3 as an output.

The adsorption behavior and phase transfer catalytic fixation of a special dye SCF-AOL2 on cotton in supercritical carbon dioxide

Supercritical carbon dioxide (SC-CO2) dyeing technique is a powerful alternative method to conventional ones. In this work, the uptake behavior and the build-up performance of a special dye SCF-AOL2 involving a potential reactive group of β-ethylsulfone sulfate on cotton in SC-CO2 was investigated. Particularly, a phase transfer catalytic method, involving series of reactions and a supposed mechanism in a supercritical fixation system was introduced for the special dye fixation by employing a phase transfer catalyst. The results show that the uptake behaviors of the special dye were significantly improved with temperature, pressure and duration in both pure and cosolvent involved SC-CO2 systems. Moreover, the fixation efficiency and the color fastness of the uptake dye on the substrate were notably improved by employing the catalytic fixation method. Furthermore, the dye uptake and catalytic fixation behaviors were also verified with color measurement, dye fixation efficiency, FT-IR analysis and color fastness evaluation.

Experimental and computational investigation of two-component mixtures for the alkyl (ethyl, propyl and butyl) oleate in supercritical carbon dioxide

The main aim of the current study is to understand of solubility curve in solvents at supercritical conditions and including thermodynamics modeling, as well as van der Waals-type models. A thermodynamic approach was commissioned to predict the solubility of a model alkyl oleate monomers in supercritical carbon dioxide (Sc-CO2). Furthermore, the experimental data of phase equilibrium were employed here which are based on measuring the solubility of alkyl oleate monomers in CO2 at supercritical conditions, and the experiments were performed using common synthetic-type method. The thermodynamic equilibrium properties for the two-component mixture of ethyl oleate, propyl oleate and butyl oleate in Sc-CO2 were reported. Bubble (dew)-point data determinations were performed through the synthetic method from various temperatures T= (313.2 to 393.2) K and pressures p = (3.07 to 31.71) MPa. The obtained results indicated that the phase equilibria of Sc-CO2 were found to increase monotonically with the augmented of system temperatures and mole fraction of (ethyl oleate, propyl oleate and butyl oleate) in binary (solute + solvent) mixtures. The solubility curve of ethyl oleate, propyl oleate, and butyl oleate in the ethyl oleate + Sc-CO2, propyl oleate + Sc-CO2, and butyl oleate + Sc-CO2 models rises as the temperature raises at a persistent pressure. The ethyl oleate + Sc-CO2, propyl oleate + Sc-CO2, and butyl oleate + Sc-CO2 models show type-I phase behavior. Moreover, laboratory investigated results of these systems were adequately compared with the P-R EOS. RMSD for the ethyl oleate + Sc-CO2 [κij = 0.060, ηij=-0.030], propyl oleate + Sc-CO2 [κij = 0.062, ηij=-0.030], and butyl oleate + Sc-CO2 [κij = 0.061, ηij=-0.030] models using 2 factors determined at 353.2 K were 4.06 %, 7.43 %, and 5.06 % correspondingly. Also, RMSD of ethyl oleate + Sc-CO2, propyl oleate + Sc-CO2, and butyl oleate + Sc-CO2 systems predicted by adjusted factors at each temperature was 8.46 %, 9.43 %, and 6.29 %, respectively.

Ru-Catalyzed Repetitive Batch Borylative Coupling of Olefins in Ionic Liquids or Ionic Liquids/scCO2 Systems

The first, recyclable protocol for the selective synthesis of (E)-alkenyl boronates via borylative coupling of olefins with vinylboronic acid pinacol ester in monophasic (cat@IL) or biphasic (cat@IL/scCO2) systems is reported in this article. The efficient immobilization of [Ru(CO)Cl(H)(PCy3)2] (1 mol%) in [EMPyr][NTf2] and [BMIm][OTf] with the subsequent extraction of products with n-heptane permitted multiple reuses of the catalyst without a significant decrease in its activity and stability (up to 7 runs). Utilization of scCO2 as an extractant enabled a significant reduction in the amount of catalyst leaching during the separation process, compared to extraction with n-heptane. Such efficient catalyst immobilization allowed an intensification of the processes in terms of its productivity, which was indicated by high cumulative TON values (up to 956) in contrast to the traditional approach of applying volatile organic solvents (TON = ~50–100). The reaction was versatile to styrenes with electron-donating and withdrawing substituents and vinylcyclohexane, generating unsaturated organoboron compounds, of which synthetic utility was shown by the direct transformation of extracted products in iododeborylation and Suzuki coupling processes. All synthesized compounds were characterized using 1H, 13C NMR and GC-MS, while leaching of the catalyst was detected with ICP-MS.

Supercritical Carbon Dioxide Based Skin Preservation: Solving the Soak Liquor Effluent Crisis of the Leather Industry

Salt-based preservation of hides/skins contributes to about 50% total dissolved solids (TDS) in tannery wastewaters. In this study, raw skins have been preserved by exposing them to a continuous flow of supercritical carbon dioxide (SCCO2) in a pressurized reactor. The process was carried out in reactors of two different capacities to ensure scalability. The skins thus dried could be stored at room temperature for a period of 30 days. The SCCO2–dried skins were less conducive for microbial growth than wet-salted skins. The soak liquor of SCCO2–dehydrated skin showed a 90% reduction in chloride content and significantly lower BOD and COD levels than soak liquor from wet-salted skins. The leathers produced from SCCO2-preserved skins and wet-salted skin had no significant quality differences. As SCCO2 systems have been reported as alternatives to all other unit operations, establishing SCCO2–based preservation will complete the circle of total leather manufacture with SCCO2.

Prediction of minimum miscibility pressure of pure CO2, carbon dioxide gas mixtures and polymer-supercritical CO2 in oil using modified quadrupole Cubic Plus Association Equation of State (mqCPA EoS)

In this work, the modified quadrupole Cubic Plus Association Equation of State (mqCPA EoS) is used to predict the minimum miscibility pressure (MMP) of pure carbon dioxide, carbon dioxide gas mixtures and polymer-supercritical carbon dioxide (scCO2) systems with the different oils. Carbon dioxide is accounted as a quadruple molecule and by applying Ahmadi and Johns's algorithm, which is a multiple mixing cell (MMC) method, minimum miscibility pressures (MMP) for some scCO2-oil systems are predicted. Moreover, a specific parameterization work was performed so that the new binary interaction parameters, kij, were optimized for the hydrocarbon-CO2 pairs using mqCPA with the quadropolar term. For comparison of the present equation of state (EoS) with the common EoSs, the predictive Peng-Robinson 78 (PPR78) and Soave-Redlich-Kwong (SRK) are applied along with the binary interaction parameter correlations of the Pedesen and Xu et al. kij (Industrial & Engineering Chemistry Research, 54 (2015) 2816–2824). The obtained MMP values by mqCPA EoS are compared to the experiments and those obtained using the PPR78 and SRK EoSs. It is shown that the calculated results by mqCPA EoS demonstrate a good agreement with the experimental values, especially for injected of pure CO2 and leads to the better results in comparison with PPR78 and SRK EoSs. To predict MMP of the polymer-scCO2 systems, three types of poly(lactic acid) (PLA), three types of poly(1-O-(vinyloxy) ethyl-2,3,4,6-tetra-O-acetyl-β-d-glucopyranoside) (P(AcGlcVE)) and seven types of poly(vinyl acetate-alt-dibutyl maleate) (PVAc-alt-PDBM) are used. To our best knowledge, this is the first effort to predict the MMP of these polymer-scCO2-oil systems.

Modeling of Pressure Dependence of Interfacial Tension Behaviors of Supercritical CO2 + Crude Oil Systems Using a Basic Parachor Expression

Parachor based expressions (basic and mechanistic) are often used to model the experimentally observed pressure dependence of interfacial tension (IFT) behaviors of complex supercritical carbon dioxide (sc-CO2) and crude oil mixtures at elevated temperatures. However, such modeling requires various input data (e.g. compositions and densities of the equilibrium liquid and vapor phases, and molecular weights and diffusion coefficients for various components present in the system). In the absence of measured data, often phase behavior packages are used for obtaining these input data for performing calculations. Very few researchers have used experimentally measured input data for performing parachor based modeling of the experimental IFT behaviors of sc-CO2 and crude oil systems that are of particular interest to CO2 injection in porous media based enhanced oil recovery (EOR) operations.This study presents the results of parachor based modeling performed to predict pressure dependence of IFT behaviors of a complex sc-CO2 and crude oil system for which experimentally measured data is available in public domain. Though parachor model based on calculated IFT behaviors shows significant deviation from the measured behaviors in high IFT region, difference between the calculated and the experimental behaviors appears to vanish in low IFT region. These observations suggest that basic parachor expression based calculated IFT behaviors in low IFT region follow the experimental IFT behaviors more closely.An analysis of published studies (basic and mechanistic parachor expressions based on modeling of pressure dependence of IFT behaviors of both standard and complex sc-CO2 and crude oil systems) and the results of this study reinforce the need of better description of gas-oil interactions for robust modeling of pressure dependence of IFT behavior of these complex systems.

Modified quadrupole Cubic Plus Association Equation of State (mqCPA EoS) for thermodynamic modeling of polymer-supercritical CO2 systems

In this work, a modified quadrupole Cubic Plus Association Equation of State (mqCPA EoS) is used to model the cloud point pressure of polymers-supercritical carbon dioxide (scCO2) systems. The residual Helmholtz free energy is expressed as sum of SRK and Quadrupole terms. We used the experimental data of the cloud point pressure for the different copolymer-scCO2 systems to investigate the capability of the present model through liquid-liquid equilibrium calculations. Using mqCPA EoS, the cloud point pressures of the polymer-scCO2 systems for the three types of poly(lactic acid) (PLA), the three types of poly(1-O-(vinyloxy) ethyl-2,3,4,6-tetra-O-acetyl-β-d-glucopyranoside) (P(AcGlcVE) and seven types of poly(vinyl acetate-alt-dibutyl maleate) (PVAc-alt-PDBM) were calculated. These copolymers have different molecular structures, end groups and molar masses. Moreover, we applied both PC-SAFT and PCP-SAFT equations of state for the same polymer-scCO2 systems and their results were compared to those obtained by mqCPA EoS that showed in overall the both PCP-SAFT and mqCPA EoSs give better results with very good accuracy.

Adsorption equilibria of rhodium acetylacetonate with MCM-41, MSU-H, and HMS silica substrates in supercritical carbon dioxide for preparing catalytic mesoporous materials

Adsorption isotherms of rhodium(III) acetylacetonate (Rh(acac)3) in supercritical carbon dioxide (scCO2) with methanol co-solvent for three types of mesoporous silica (MCM-41, MSU-H, and HMS) at 313–353K and at 15.0MPa were measured using a fixed bed method. The measured adsorption equilibria varied among the adsorbent substrates and depended on the specific surface area and pore structure of the adsorbents. The amount of adsorbed Rh(acac)3 increased with increasing temperature owing to strong effects of the CO2 density. Fitting parameters determined from correlation of the data with the Dubinin-Astakhov (DA) equation demonstrated that the interaction of the precursor for the adsorbents, CO2 density and pore structure of adsorbents were dominant factors in the adsorption equilibria of metal precursors in scCO2. The impregnation of Rh on the silica supports by a batch method in scCO2 could be characterized by the DA equation for which Eprec showed correlation with impregnated Rh particle size and W0,prec showed correlation with Rh loading amount. The DA equation is useful for characterizing adsorption equilibria in mesoporous materials with scCO2 systems and allows estimation of conditions required for impregnating metals into mesoporous silica substrates.

Study of self-association of gradient copolymers in supercritical CO2 thanks to synchrotron and in-house small-angle X-rays scattering measurements

Specific comblike gradient copolymers made of metal-complexing CO2-phobic units and fluorinated CO2-philic units were designed to study their self-association when solubilised in supercritical CO2 (scCO2). This paper shows that in-house SAXS measurements on scCO2 systems are now possible thanks to both high-energy X-rays and specific high-pressure cell designed with beryllium windows. The copolymer system poly(1,1,2,2-tetrahydroperfluorodecylacrylate-co-4-(diphenylphosphino)styrene), poly(FDA-co-DPPS) was compared to homopolymer with thiol endgroup poly(FDA)-SH and more classical molecule, C8F17C2H4-SH (RfSH). The results show that the presence of the CO2-phobic part of the copolymer does not necessarily tend to favour self-association probably due to the polymer conformation. However, this CO2-phobicity favours inter-object correlation leading to aggregation.

Comparison of relative permeability–saturation–capillary pressure models for simulation of reservoir CO2 injection

Constitutive relations between relative permeability (kr), fluid saturation (S), and capillary pressure (Pc) determine to a large extent the distribution of brine and supercritical CO2 (scCO2) during subsurface injection operations. Published numerical multiphase simulations for brine–scCO2 systems so far have primarily used four kr−S−Pc models. For the S−Pc relations, either the Brooks–Corey (BC) or Van Genuchten (VG) equations are used. The kr−S relations are based on Mualem, Burdine, or Corey equations without the consideration of experimental data. Recently, two additional models have been proposed where the kr−S relations are obtained by fitting to experimental data using either an endpoint power law or a modified Corey approach. The six models were tested using data from four well-characterized sandstones (Berea, Paaratte, Tuscaloosa, Mt. Simon) for two radial injection test cases. The results show a large variation in plume extent and saturation distribution for each of the sandstones, depending on the used model. The VG–Mualem model predicts plumes that are considerably larger than for the other models due to the overestimation of the gas relative permeability. The predicted plume sizes are the smallest for the VG–Corey model due to the underestimation of the aqueous phase relative permeability. Of the four models that do not use fits to experimental relative permeability data, the hybrid model with Mualem aqueous phase and Corey gas phase relative permeabilities provide the best fits to the experimental data and produce results close to the model with fits to the capillary pressure and relative permeability data. The model with the endpoint power law resulted in very low, uniform gas saturations outside the dry-out zone for the Tuscaloosa sandstone, as the result of a rapidly declining aqueous phase relative permeability. This observed behavior illustrates the need to obtain reliable relative permeability relations for a potential reservoir, beyond permeability and porosity data.

Partitioning of organics between ionic liquids and supercritical CO2: Limiting K-factors in [bmim][N(CN)2]–scCO2 system and generalized correlation with cation- and anion-specific LSERs

Infinite dilution partition coefficients (K-factors) of a selection of organic solutes in biphasic 1-n-butyl-3-methylimidazolium dicyanamide ([bmim][dca])–supercritical carbon dioxide (scCO2) system were obtained from retention measurements by open tubular capillary column supercritical fluid chromatography (SFC) with [bmim][dca] serving as the stationary liquid and scCO2 as the carrier fluid. Therefore, the SFC-based route to solute K-factors in ionic liquid (IL)–scCO2 systems is feasible even with low viscosity ILs such as [bmim][dca].The experimental K-factors in [bmim][dca]–scCO2 system were used to test an earlier generalized correlation of solute K-factors in IL–scCO2 systems. Further, another version of the generalized correlation was introduced and tested. In the linear solvation energy (LSER) part of the former correlation the IL has been treated as a single species whereas, in the new version, the IL cation- and anion-specific LSER part has been employed. The introduction of the ion-specific LSERs resulted in some performance improvement of the correlation.

Electrochemical fixation of CO2 to organohalides in room-temperature ionic liquids under supercritical CO2

The electrochemical properties of novel reaction media, ionic liquid (IL)/supercritical CO2 (scCO2) systems, were evaluated and the electrochemical carboxylation of various organohalides in these systems was demonstrated. Voltammetric studies revealed that the CO2 solubility in an IL such as N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium bis(trifluoromethanesulfonyl) imide ([DEME][TFSI]) increased in the presence of scCO2. The IL/scCO2 systems were found to be effective for the electrochemical carboxylation of various organohalides.

Measurements of the elastic and anelastic properties of sandstone flooded with supercritical CO2

ABSTRACTThe aim of this study was to investigate the effects of supercritical CO2 (scCO2) injection on the elastic and anelastic properties of sandstone at seismic and ultrasonic frequencies. We present the results of the low‐frequency and ultrasonic experiments conducted on water‐saturated sandstone (Donnybrook, Western Australia) flooded with scCO2. The sandstone was cut in the direction perpendicular to a formation bedding plane and tested in a Hoek triaxial pressure cell. During the experiments with scCO2, the low‐frequency and ultrasonic systems and the pump dispensing scCO2 were held at a temperature of 42°C. The elastic parameters obtained for the sandstone with scCO2 at seismic (0.1 Hz–100 Hz) and ultrasonic (∼0.5 MHz) frequencies are very close to those for the dry rock. The extensional attenuation was also measured at seismic frequencies for the dry, water‐saturated, and scCO2‐injected sandstones. The applicability of Gassmann's fluid substitution theory to obtained results was also tested during the experiments.

Modelling of the inactivation kinetics of Escherichia coli, Saccharomyces cerevisiae and pectin methylesterase in orange juice treated with ultrasonic-assisted supercritical carbon dioxide

The combined effect of supercritical carbon dioxide (SC-CO2) and high power ultrasound (HPU) on the inactivation kinetics of Escherichia coli, Saccharomyces cerevisiae and pectin-methyl esterase (PME) in orange juice was studied in order to select models that can predict their inactivation behaviour based on process parameters. Experiments were performed at different temperatures (31–41°C, 225bar) and pressures (100–350bar, 36°C). The inactivation rate of E. coli, S. cerevisiae and PME increased with pressure and temperature during SC-CO2+HPU treatments. The SC-CO2+HPU inactivation kinetics of E. coli, S. cerevisiae and PME were represented by models that included temperature, pressure and treatment time as variables, based on the Biphasic, the Peleg Type B, and the fractional models, respectively. The HPU-assisted SC-CO2 batch system permits the use of mild process conditions and treatment times that can be even shorter than those of continuous SC-CO2 systems.

Generalized linear solvation energy model applied to solute partition coefficients in ionic liquid–supercritical carbon dioxide systems

Biphasic solvent systems composed of an ionic liquid (IL) and supercritical carbon dioxide (scCO2) have become frequented in synthesis, extractions and electrochemistry. In the design of related applications, information on interphase partitioning of the target organics is essential, and the infinite-dilution partition coefficients of the organic solutes in IL–scCO2 systems can conveniently be obtained by supercritical fluid chromatography. The data base of experimental partition coefficients obtained previously in this laboratory has been employed to test a generalized predictive model for the solute partition coefficients. The model is an amended version of that described before by Hiraga et al. (J. Supercrit. Fluids, in press). Because of difficulty of the problem to be modeled, the model involves several different concepts – linear solvation energy relationships, density-dependent solvent power of scCO2, regular solution theory, and the Flory–Huggins theory of athermal solutions. The model shows a moderate success in correlating the infinite-dilution solute partition coefficients (K-factors) in individual IL–scCO2 systems at varying temperature and pressure. However, larger K-factor data sets involving multiple IL–scCO2 systems appear to be beyond reach of the model, especially when the ILs involved pertain to different cation classes.

RETRACTED ARTICLE: Controlling the properties of silver nanoparticles deposited on surfaces using supercritical carbon dioxide for surface-enhanced Raman spectroscopy

Silver nanoparticles (AgNPs) have been deposited on silicon and glass surfaces via a supercritical carbon dioxide (sc-CO2) synthesis route for application in surface-enhanced Raman spectroscopy (SERS). Arrhenius plots revealed that nucleation and growth processes in this system depend on both temperature and surface chemistry. Results also demonstrated that temperature and surface chemistry could be varied to control nanoparticle properties, such as the mean nanoparticle size, density, and surface coverage, providing two useful variables for manipulating the properties of AgNPs deposited on surfaces in this system. These data also provide scientific insight into the underlying mechanisms governing heterogeneous AgNP deposition on a substrate in a sc-CO2 system in addition to engineering insight into the variables that can be used to manipulate AgNP characteristics. The mean particle size could be tuned over the range 20–200 nm, the interparticle distance could be tuned over the range 70 nm–1 μm, and the surface coverage could be tuned over the range 0.035–0.58. Products were analyzed by scanning electron microscopy with image analysis, transmission electron microscopy, X-ray diffraction, and SERS. The silver nanoparticle-coated substrates were successfully applied in SERS, detecting the model analyte Rhodamine 6G at a concentration of 1 μM, a three orders of magnitude improvement over SERS surfaces previously fabricated in sc-CO2 systems. Such surfaces can find use in trace concentration analyte detection in biomedical, chemical, and environmental applications.