Solid Mixtures Research Articles

Study of nifedipine solubility in physical mixtures and solid dispersions

Introduction. Poor aqueous solubility significantly hinders the bioavailability of numerous orally administered drugs. Nifedipine, a widely-used cardiovascular agent, is categorized as practically insoluble according to pharmacopoeias, thus presenting a significant challenge in formulation development. This study investigates the potential of solid dispersion (SD) technology and physical mixtures to improve the dissolution profile of nifedipine.Aim. Development of a technological method for increasing the solubility of nifedipine by developing physical mixtures and SD with the aim of creating a dosage form with improved properties.Materials and methods. Nifedipine, methanol, nifedipine standard samples, potassium dihydrogen phosphate, sodium heptanesulfonate, phosphoric acid (85 %), purified water, and pvp K-30. Solubility studies were performed by HPLC using three objects: nifedipine, a physical mixture (PM), and SD of nifedipine with PVP K-30. The study assessed the effect of different ratios (nifedipine : PVP K-30) in the physical mixture and SD on nifedipine solubility. Fourier transform infrared spectroscopy (IR spectroscopy) and powder X-ray diffractometry were used to characterize the samples.Results and discussion. A notable increase in nifedipine solubility was observed in both PM3 (1 : 3 nifedipine : PVP K-30) and SD3 (1 : 3 nifedipine : PVP K-30). PM3 exhibited a solubility of 9.70 %, while SD3 demonstrated a remarkable enhancement to 32.07 % compared to the pure nifedipine (0.24 %). FTIR analysis did not reveal significant interactions between nifedipine and PVP K-30. PXRD results confirmed the transition of nifedipine from a crystalline to amorphous form within the hydrophilic PVP K-30 matrix, contributing to the observed solubility enhancement.Conclusion. The study highlights the effectiveness of SD technology in significantly improving nifedipine solubility and potential bioavailability. The 134-fold increase in solubility achieved with SD3 at a 1 : 3 ratio demonstrates the significant potential of this approach for enhancing the pharmacokinetic properties of poorly soluble drugs. This research opens up new avenues for developing innovative formulations with improved dissolution characteristics and potentially enhanced therapeutic efficacy.

Comparative evaluation of accuracy in near-infrared and Raman spectroscopic determinations of component concentration in packed solid mixtures under various packing densities

BackgroundPhysical characteristics of packed samples, such as packing density, influence subsequent near-infrared (NIR) and Raman spectral features. This potential decrease in accuracy is a concerning issue in practical applications, such as the analysis of pharmaceutical tablets using vibrational spectroscopy. Thus, we compared the accuracy tolerances of both methods under varying packing densities. For evaluation, diffuse reflectance NIR and two different Raman measurements with laser illumination diameters of 1 and 6 mm (referred to as the WAI-1 and WAI-6 schemes, respectively) were used to analyze paracetamol tablets with packing densities of 1.1, 1.17, 1.24, and 1.29 g/cm³. ResultsIn all three measurements, increased packing density resulted in an increase in band intensity and an upward-moving baseline due to the variation in void volume (equivalent to porosity) in the tablets. The Raman spectra acquired using the WAI-6 scheme were less sensitive to packing density variations by averaging out different photon propagations over a large area during spectral acquisition. The accuracies for determining paracetamol concentration using the WAI-6 scheme did not significantly deteriorate when the packing density difference was not large, such as between 1.17 and 1.24 g/cm³ (absolute difference of 0.07 g/cm³). The WAI-6 scheme enabled more robust compositional analysis of the tablets with different packing densities. SignificanceThe WAI-6 Raman scheme provides a more robust compositional analysis of tablets under variations in packing density, making it a preferable choice for practical applications. Using the WAI-6 scheme, an additional effective strategy to minimize accuracy deterioration is further beneficial.

Dithiolation of [60]fullerene with aliphatic primary thiols initiated by n-butylamine via aerobic oxidation reaction

A facile aerobic oxidation reaction of [60]fullerene with aliphatic primary thiols initiated by n-butylamine was studied. Interestingly, the reaction yielded liquid mixtures upon solvent evaporation, contrary to the typical formation of solid mixtures. The reaction products were purified using HPLC to isolate the fullerene dithiol epoxide compound (2), which was extensively characterized by 1H NMR, 13C NMR, HRMS, and UV–Vis spectra. Plausible reaction mechanisms leading to the formation of the observed products were proposed. Computational simulations and control experiment were conducted to elucidate the proposed reaction mechanisms. The electrochemical behavior of 1,2-O-4,15-(n-C5H11S)2C60 (2) was investigated, revealing its instability upon gradual reduction.

Real-time detection and discrimination of radioactive gas mixtures using nanoporous inorganic scintillators

The nuclear industry’s expansion to encompass carbon-free electricity generation from small modular reactors and nuclear fuel reprocessing necessitates enhanced detection and monitoring of pure beta-emitting radioactive elements such as 3H and 85Kr; this endeavour is crucial for nuclear safety authorities tasked with environmental monitoring. However, the short range of electrons emitted by these gases makes detection challenging. Current methods, such as ionization chambers and liquid scintillation, do not offer at the same time good sensitivity, real-time analysis and ease of implementation. We demonstrate an approach using a gas–solid mixture to overcome these limitations. We synthetized a transparent and scintillating nanoporous material, an aerogel of Y3Al5O12:Ce4+, and achieved real-time detection with an efficiency of 96% for 85Kr and 18% for 3H. The method reaches a sensitivity below 100 mBq per cm3 over 100 s measurement time. We are able to measure simultaneously as mixtures containing both 3H and 85Kr a capability not possible previously. Our results demonstrate a compact and robust detection system for inline measurement of strategic radioactive gases. This combination of concept and method enhances nuclear power plant management and contributes to environmental safeguarding. Beyond the detection issues, this concept opens a wide field of new methods for radionuclide metrology.

Copper-doped carbon dots nanozymes for multi-signal specific hydrogen sulfide assay and broad-spectrum antibacterial

The emergence of carbon dots-based nanozymes (CDNEs) has opened a broad horizon for multi-mode analysis and safety antibacterial application. However, the practical applications of CDNEs are currently hindered by unsatisfactory performance and complicated synthetic methodology. In this study, we developed a novel copper-doped CDNEs (Cu-CDNEs) with both excellent fluorescence property and peroxidase-like activity. The Cu-CDNEs can be synthesized easily by pyrolyzing a solid mixture of copper glutamate and ethylenediamine hydrochloride for 5 min. By investigating the inhibition of H2S on the peroxidase-like activity of Cu-CDNEs and the competitive interaction between H2S and 3,3′,5,5′-tetramethylbenzidine with reactive oxygen species, we established a dual-mode analysis system for colorimetric and fluorescent detection of H2S with the limit of detection of 20 nM and 25 nM, respectively. Furthermore, a convenient scanometric analysis mode also was developed and successfully applied for the accurate determination of H2S in actual water samples with recoveries of 96.8 %–107.7 %. Moreover, the designed Cu-CDNEs show good cytocompatibility from MTT results, and demonstrated broad-spectrum antibacterial capacity against Gram-positive/negative bacteria due to the surface positive charge and peroxidase-like activity. This study may provide valuable insights for rational design and broad applications in environmental and biomedical fields using functional nanozymes.

Co-torrefaction and synergistic effect of spent coffee grounds and tea waste for sustainable waste remediation and renewable energy

This study states the enhancement of higher heating value (HHV) by blending spent coffee grounds (SCG) and tea waste (TW) during torrefaction. Torrefied biomass mixture is a carbon-neutral solid biofuel that can be used to replace coal. The synergistic effect ratio (SER) exhibits the synergistic interplay between SCG and TW, consequently elevating HHV and carbon content. Results show that the highest SER occurs at TWS25 (from blending 75 % TW and 25 % SCG is 3.26). Ca contained in TW has the catalytic effect of pyrolyzing the lipid of SCG into higher carbon content in a torrefied solid biofuel mixture, thereby increasing its HHV. The lipid and carbon contents contribute TWS25's HHV by 4.71 % and 95.29 %, respectively. This also illustrated the importance of the carbonization degree during torrefaction to the calorific value of solid biofuel mixture. The XRD, water activity, ATR, contact angle, and mildew observation results indicate that TWS25 has good thermal stability and storage properties. The ignition temperature and combustion reactivity of TWS25 are 325 °C and 3.059 wt%∙min−1∙°C−1, respectively. Overall, the torrefied solid biofuel mixture from blending TW and SCG is a potential biofuel alternative to coal to achieve carbon neutrality, circular bioeconomy, waste remediation, and low carbon initiative.

Modeling and optimizing gas solid distribution in fluidized beds

In fluidized bed reactors, uniform distribution of gas and solids is critical to achieve the desired hydrodynamic and kinetic performance. For FCC units, Technip Energies uses a proprietary distributor design to terminate both reactor risers and spent catalyst lift lines to distribute the exiting gas-solid stream into a fluidized bed.In Technip Energies' Resid FCC unit, air and spent catalyst are distributed from an upward flowing stream into a catalyst bed for coke combustion on catalyst. Proper distribution is key to achieve a uniform coke burn and an even temperature profile throughout the bed. In PropyleneMax™ Catalytic Cracking (PMcc™) technology, the reactor riser also terminates in a fluidized bed, requiring proper distribution of the hydrocarbon vapor and solid mixture into the reactor bed, which is key to providing adequate contact for further cracking to valuable products. This paper discusses Technip Energies' gas-solid distribution technology and the recent work performed to develop an improved distributor for use as a riser termination device in both the PMcc reactor and the RFCC regenerator to achieve improved performance. The use of CFD modeling to screen and evaluate the initial concepts and optimize the final selected concept are presented here. The performance matrices used to quantify the benefits of the optimized distributor design with respect to the existing one in the reactor application are highlighted, showing the benefits of improved gas solid distribution on hydrodynamic and kinetic performance. The paper presents a systematic approach to develop a novel industrial device using physics-based computational tools.

Pelatihan Pembuatan Beton bagi Siswa SMK N 3 Semarang

<div align="justify"><p><em>Concrete is a solid mixture that hardens, consisting of components such as cement, sand, gravel, and water that are mixed. Civil engineering construction is related to concrete, including the construction of roads, buildings, dams, houses, and irrigation channels. Considering the importance of knowledge related to concrete, students of SMK N 3 Semarang who are majoring in construction engineering and housing need to be well informed. Many vocational high school students are still unaware of the proper process of making concrete that meets the desired quality standards. Students of SMKN 3 Semarang, who are expected to be able to work immediately after completing their studies, need to be equipped with knowledge about the concrete-making process. The purpose of this activity is to improve the knowledge of SMKN 3 Semarang students regarding the quality of concrete materials, the making of K-225 quality concrete, and the value of the concrete slump test. The PkM team from Universitas Semarang conducted training on making concrete for SMK N 3 Semarang students using discussion methods and laboratory practice. As a result of this training, the majority of students understand the process of making concrete in terms of material quality, K-225 concrete mix design, and slump test testing.</em></p></div>

Hierarchically porous Fe-N-C microspheres via pyrolyzing hypercrosslinked polypyrrole synthesized by Fe3+-catalysis for efficient oxygen reduction in Zn-air battery

Fe-N-C catalysts have developed into the most promising substitute for Pt-based precious metal catalysts toward cathodic oxygen reduction reaction (ORR) of fuel cells and Zn-air batteries. Hypercrosslinked polypyrrole microspheres coordinated with Fe (HCP-Py-Fe) were first prepared by condensation of pyrrole (Py) and dimethoxymethane (FDA) in the presence of FeCl3 as both catalyst and Fe source, and then thermally activated with KOH during pyrolysis followed by acid leaching and heat-treatment, thus constructing hierarchically porous Fe-N-C microspheres (denoted as PPy/FDA-Fey-HT2-x). The morphology and structural properties of the final synthesized PPy/FDA-Fey-HT2-x could be tailored to a certain extent by controlling the adding quantities of KOH (x) in the initial solid mixture before pyrolysis and FeCl3 (y) during condensation of Py and FDA. As a result, the PPy/FDA-Fe0.4-HT2–0.25 demonstrated the highest half-wave potential of 0.87 V vs. RHE, with a desired 4-electron transfer for ORR in alkaline medium, which is attributed to the hierarchically micro/mesoporous structure, high surface area and extremely low content of magnetic iron species. Remarkable methanol resistance and durability with only a loss of ∼4 mV in half-wave potential after 10000 potential cycles were obtained as well. The aqueous Zn-air battery (ZAB) fabricated with the PPy/FDA-Fe0.4-HT2–0.25 as cathode catalyst delivered a comparable discharge performance to that of the Pt/C-based ZAB but far superior cycling stability. This facile route is promising for large-scale production of Fe-N-C materials as cathodic electrocatalyst applied in practical energy conversion devices.

Measurement and theoretical analysis of effective thermal conductivity of lanthanum pentanickel powder beds for hydrogen storage in different particle sizes and bed porosities

Particle diameter and bed porosity change due to the expansion and contraction of metal hydride particles during hydrogen absorption and desorption, which leads to variations in the effective thermal conductivity of metal hydride beds. Therefore, the effective thermal conductivity of the metal hydride beds under different bed porosities and particle diameters must be measured for the design of metal hydride-based hydrogen storage tanks. In this study, the effective thermal conductivities of four kinds of lanthanum pentanickel (LaNi5) powder beds with different bed porosities and particle diameters were measured in various gas atmospheres with gas pressure varying from 0.1 to 4.0 MPa. The volume mean diameters of the four kinds of LaNi5 powders equal 335.2, 196.4, 147.7, and 23.7 μm, respectively. Subsequently, the effects of bed porosity and particle diameter on the effective thermal conductivities were analyzed through the modified Zehner–Schlünder–Damköhler model considering the Smoluchowski effect. Experimental results show that particle diameter and bed porosity influence markedly the effective thermal conductivity of lanthanum pentanickel (LaNi5) powder beds. However, the findings of theoretical analysis based on the modified Zehner–Schlünder–Damköhler model reveal the considerably weaker effect of particle diameter on the effective thermal conductivity under identical bed porosity compared with the measurement results. Such a finding was observed because the variation in particle diameter inevitably changed bed porosity during the effective thermal conductivity measurement, which also affected the effective thermal conductivity of the beds. In addition, decreasing bed porosity and increasing particle diameter can remarkably improve the heat transport via the gas–solid mixture pathway, which improved the effective thermal conductivity of the beds and thus explained the experimental results.

Forging inner-disk Al-rich chondrules by interactions of CAI-like melt and ambient gas

The mechanism of gas-melt interactions and the compositions of precursors are key to understanding the formation of chondrules. To shed light on the two enigmas, we studied the petrography, chemistry, and oxygen isotopes of six Al-rich chondrules (ARCs, five glassy and one plagioclase-bearing) in unequilibrated ordinary chondrites (OCs, petrologic subtype: 3.05). The plagioclase-bearing ARC was also investigated with Al-Mg chronology. Elemental zonation and inter-element correlations in glassy mesostasis of two ARCs indicate the condensation of gaseous Mg, SiO, Fe, and Na onto chondrule melt. The plagioclase-bearing ARC appears to display internal mass-independent oxygen isotope fractionation with δ18O increasing following the order of mineral crystallization, suggesting partial oxygen isotope exchange with ambient gas during crystallization. Oxygen isotopes of the six ARCs are distributed along a mixing line of slope = 0.99 ± 0.05, which intersects with calcium-aluminum-rich inclusions (CAIs), consistent with a small portion of OC type IA chondrules, but deviates from other OC ferromagnesium chondrules (FMCs) towards higher δ17O, suggesting that OC ARCs and some IA chondrules were established by interactions between CAI-like melts and 16O-poor ambient gas, rather than simply remelting solid mixtures of CAI and FMC materials.All six ARCs have unfractionated refractory lithophile element patterns with bulk concentrations ranging from ∼7 × CI to ∼15 × CI, indicating ∼ 30–100 % of CAI-like materials in their precursors. Their bulk compositions are linearly evolved toward the Mg: SiO ∼ 3:2 to 2:1 (in atomic) apex, consistent with adding gaseous Mg and SiO to the chondrule bulk via gas–melt interactions. The back-calculated compositions of the recycled CAI-like materials closely overlap with pyroxene-anorthite-rich CAIs, suggesting that extensive interactions between the melt of pyroxene-anorthite-rich CAI-like materials and ambient gas could make OC ARCs. The Al-Mg age of the plagioclase-bearing ARC is ∼2.2 Ma after CAIs, similar to typical OC FMCs, suggesting that the refractory component arrived at the OC reservoirs in the late stage of the chondrule heating events.

Elucidating Synergetic Effects of Anaerobic Co-Digestion of Slaughterhouse Waste with Livestock Manures

This study quantitatively analyzed the synergistic effects of co-digestion of slaughterhouse waste (SHW) with cattle manure (CM) and pig manure (PM) on methane production by applying statistical methods. The biochemical methane potential of volatile solid concentration-based mixtures showed that the biodegradability (BD) of the co-substrates was improved as the mixing proportion of the highly biodegradable SHW increased. Furthermore, mathematical analysis using the modified Gompertz model showed that an increase in the SHW mixture ratio shortened the lag phase at the initial period by more than 58%. The synergy index (SI) analysis revealed that co-digestion of CM and SHW mixed at an equal ratio of 1:1 in sample S4 resulted in a higher SI of 1.18 compared to 1.10 for PM and SHW in sample S5. An overlay plot based on BD and SI identified the optimal mixture ratio as 26.9:31.0:42.1 (CM/PM/SHW), where both BD and SI reached their maximum values. The study successfully demonstrated that co-digestion of SHW with livestock manure enhances BD through a synergistic effect.

Computational workflow to monitor the electroosmosis of nanofluidic flow in the vicinity of a bounding surface

This investigation studies the flow of a boundary layer with electroosmotic forces on a nanofluid with gyrotactic microorganisms along the vertical Riga plate. This sort of fluid movement necessitates specific mathematical techniques and numerical simulations. In addition, the boundary-layer flow is induced by the mass and heat transfer, Joule heating, and viscous dissipation. A mathematical model is simulated by non-linear partial differential equations (PDEs). The combination of PDEs is turned into a set of non-linear ordinary differential equations using proper transformations. Some analysis tools are used to investigate the morphological characteristics of the problem while applying suitable boundary conditions. The influence of parameters on the derived solutions is numerically and visually explained through sets of figures. It is elucidated that the concentration of the microorganisms reduces due to an increase in Lewis number which leads to a decrease in the motile microorganism’s density profile. It is seen that the temperature distribution is improved when the chemical reaction and Casson parameter increase. In addition, we find that the application of electro-osmotic forces applied to the surfaces helps to dewater and separate microorganisms from incompressible solid and liquid mixtures.

Partitioning photochemically formed CO2 into clathrate hydrate under interstellar conditions.

Clathrate hydrates (CHs), host-guest compounds of water forming hydrogen-bonded cages around guest molecules, are now known to exist under interstellar conditions. Experimental evidence demonstrated that prolonged thermal treatment of a solid mixture of water and CO2/CH4 produces CHs at 10-30 K under simulated interstellar conditions. However, in the current study, we show that CO2 produced photochemically by vacuum ultraviolet irradiation of H2O-CO mixtures at 10 K and ∼10-10 mbar, gets partitioned into its CH phase and a matrix phase embedded in amorphous ice. The process occurring under simulated interstellar conditions was studied at different temperatures and H2O-CO compositions. The formation of CO2 CH and other photoproducts was confirmed using reflection absorption infrared spectroscopy. The UV-induced photodesorption event of CO2 may provide the mobility required for the formation of CHs, while photoproducts like methanol can stabilize such CH structures. Our study suggests that new species originating during such energetic processing in ice matrices may form CH, potentially altering the chemical composition of astrophysical environments.

Chemical specificity in polyzwitterion-polyelectrolyte coacervates: polycations vs polyanions

Aqueous solutions containing polyzwitterions and polyelectrolytes were studied to probe the effects of chemical specificity on the complexation among different types of chains and resulting liquid–liquid phase separation (coacervation). Two kinds of blends were studied. A polyzwitterion, poly(sulfobetaine methacrylate) (PSBMA), was blended with either (1) a polycation, poly(diallydimethylammonium chloride) (PDADMAC), or (2) a polyanion, sodium poly(styrene sulphonate) (NaPSS). Coacervation was observed in both blends after equilibration, while the freshly prepared blend solutions exhibited distinct behavior dependent on the mixing protocols. Mixing solutions of the polyzwitterions and the polycations led to coacervation almost instantaneously. In contrast, the blends containing the same polyzwitterions and the polyanions exhibited no such coacervation by following the same mixing protocol. However, blends prepared after dissolving a solid mixture containing the same polyzwitterions and the polyanions in water exhibited coacervation. Based on the small-angle X-ray scattering (SAXS), cryo-electron microscopy, and rheology measurements, complexation and coacervation in the polyzwitterion-polyelectrolyte blends is rationalized in terms of the entropy change associated with reorganization of solvent (water), which appears to be larger in the polyzwitterion-polycation case in comparison with the polyzwitterion-polyanion blends. These results highlight the importance of chemical specificity and mixing protocols leading to metastable structures in designing a new class of materials based on macromolecular complexation of polyzwitterions.

Regioselective Synthesis of Hamilton-Receptor-Fullerene Oligo-Adducts for the Supramolecular Binding of Cyanuric Derivatives.

A new concept for the regioselective synthesis of Hamilton-receptor and cyanurate-functionalized oligo adducts of the fullerene C60 was developed. Based on an in-situ deprotection and click-post-functionalization approach with novel azido precursors, the corresponding fullerene hexakis-adducts with octahedral addition patterns and up to twelve Hamilton-receptor/cyanurate moieties surrounding the fullerene sphere were synthesized. The versatility of this approach was further demonstrated by the synthesis of Hamilton-receptor/cyanurate functionalized fullerene mono-adducts, which are not accessible by direct cyclopropanation. Several fullerene target compounds were purified by simple washing procedures of the solid crude reaction mixture without the need for chromatography. The resulting fullerene mono- and hexakis-adducts were fully characterized and their supramolecular properties were investigated by NMR-spectroscopy and isothermal titration calorimetry (ITC).

Dynamical interactions of the magnetic field in a binary mixture of interacting thermoelastic solids

A more focused scientific approach in the context of a mixture of thermoelastic solids would entail investigating the basic ideas guiding the behavior of the complex materials, including constitutive model development, multi-scale modeling at various length scales, and design optimization for thermoelastic solids with their precise properties. The present work is set up to study the effect of the magnetic field as an external effect on the mixture of two interacting thermoelastic solids. The fundamental mathematical equations were shown and solved by the analytical harmonic wave solution to give the solution of the descriptive functions of the discussed problem. The displacements and stresses for the mixture of the two interreacted thermoelastic solids with the mutual temperature were clarified in the 2-D and 3-D. The results are analyzed and discussed. The obtained solution for the functions is finite everywhere. The solutions for the quantities of practical interest are represented graphically with different choices of the wave number of the harmonic wave as the magnetic field with time. In addition to the numerous physical factors in the governing field equations as depicted in the figures, boundary conditions also play a role in the current damping phenomenon.

Chemistry Informed Machine Learning-Based Heat Capacity Prediction of Solid Mixed Oxides.

Knowing heat capacity is crucial for modeling temperature changes with the absorption and release of heat and for calculating the thermal energy storage capacity of oxide mixtures with energy applications. The current prediction methods (ab initio simulations, computational thermodynamics, and the Neumann-Kopp rule) are computationally expensive, not fully generalizable, or inaccurate. Machine learning has the potential of being fast, accurate, and generalizable, but it has been scarcely used to predict mixture properties, particularly for mixed oxides. Here, we demonstrate a method for the generalizable prediction of heat capacity of solid oxide pseudobinary mixtures using heat capacity data obtained from computational thermodynamics and descriptors from ab initio databases. Models trained through this workflow achieved an error (mean absolute error of 0.43 J mol-1 K-1) lower than the uncertainty in differential scanning calorimetry measurements, and the workflow can be extended to predict other properties derived from the Gibbs free energy and for higher-order oxide mixtures.

Exploring High‐Pressure Polymorphism in Carbonic Acid through Direct Synthesis from Carbon Dioxide Clathrate Hydrate

AbstractCarbon dioxide (CO2) is widespread in astrochemically relevant environments, often coexisting with water (H2O) ices and thus triggering a great interest regarding the possible formation of their adducts under various thermodynamic conditions. Amongst them, solid carbonic acid (H2CO3) remains elusive, yet being widely studied. Synthetic routes followed for its production have always been characterised by drastic irradiation on solid ice mixtures or complex procedures on fluid samples (such as laser heating at moderate to high pressures). Here we report about a simpler yet effective synthetic route to obtain two diverse carbonic acid crystal structures from the fast, cold compression of pristine clathrate hydrate samples. The two distinct polymorphs we obtained, differing in the water content, have been deeply characterised via spectroscopic and structural techniques to assess their composition and their astonishing pressure stability, checked up to half a megabar, also highlighting the complex correlations between them so to compile a detailed phase diagram of this system. These results may have a profound impact on the prediction and modelisation of the complex chemistry which characterises many icy bodies of our Solar System.

Exploring High-Pressure Polymorphism in Carbonic Acid through Direct Synthesis from Carbon Dioxide Clathrate Hydrate.

Carbon dioxide (CO2) is widespread in astrochemically relevant environments, often coexisting with water (H2O) ices and thus triggering a great interest regarding the possible formation of their adducts under various thermodynamic conditions. Amongst them, solid carbonic acid (H2CO3) remains elusive, yet being widely studied. Synthetic routes followed for its production have always been characterised by drastic irradiation on solid ice mixtures or complex procedures on fluid samples (such as laser heating at moderate to high pressures). Here we report about a simpler yet effective synthetic route to obtain two diverse carbonic acid crystal structures from the fast, cold compression of pristine clathrate hydrate samples. The two distinct polymorphs we obtained, differing in the water content, have been deeply characterised via spectroscopic and structural techniques to assess their composition and their astonishing pressure stability, checked up to half a megabar, also highlighting the complex correlations between them so to compile a detailed phase diagram of this system. These results may have a profound impact on the prediction and modelisation of the complex chemistry which characterises many icy bodies of our Solar System.