Patterns of assembled colloidal particles can form on substrates due to solvent evaporation, and here we studied such phenomena in the drying of monodispersed colloidal hydrochar dispersions prepared ...by the hydrothermal carbonization of glucose and purified by dialysis. During the evaporation of water, line patterns or, in some cases, mud-like patterns formed. The line formation was investigated as a function of the pH of the dispersion, substrate shape, particle concentration, and concentration of sodium dodecylsulfate (SDS). The lines comprised dense assemblies of hydrochar particles. The line width increased with the successive evaporation of water. Sharper lines formed with the addition of SDS, which was ascribed to the effects of solubilization or moderated interactions. At greater particle concentrations, we also observed a continuous layer of colloidal particles between the lines. A mechanism for the line pattern formation derived from the literature on other colloids was proposed. Mud-like patterns formed on the substrate in concentrated samples without SDS addition and were put in the context of the formation of cracks in the drying of colloidal coatings. Hydrochars belong to carbon-rich colloids, which are of fundamental and technological importance. This research could be useful for in situ line printing within microfluidic devices, for example.
Amorphous order: Amorphous calcium carbonates (ACC) have an intrinsic structure relating to the crystalline polymorphs of calcite and vaterite. The proto‐crystalline structures of calcite and ...vaterite (pc‐ACC and pv‐ACC) are analyzed by NMR (see picture), IR, and EXAFS spectroscopy, which shows that the structuring of ACC relates to the underlying pH‐dependent equilibria.
The synthesis of carbonaceous materials with a high surface density of amino functions for CO2 sorption and sequestration is reported. The amino‐rich carbonaceous materials are characterized by ...elemental analysis, N2 sorption, scanning and transmission electron microscopy, zeta potential, TGA and FTIR measurements. A detailed discussion on the use of these materials in CO2 capture is provided. The materials show significant sorption capabilities for CO2 (4.3 mmol g−1at −20 °C and 1 bar). Furthermore, they show a high apparent selectivity for CO2 over N2 at both low and high temperatures.
Amino Royale: The synthesis of carbonaceous materials with a high surface density of amino functions for CO2 sorption and sequestration is reported. The biomass‐based materials show significant sorption capabilities for CO2 (4.3 mmol g−1at −20 °C and 1 bar).
It was hypothesized that activated carbons (ACs) prepared from hydrochar could be dispersed in solvents under certain conditions. The crude hydrochar formed by the hydrothermal carbonization (HTC) of ...glucose and was purified by dialysis. Dried dispersions of hydrochar were chemically activated with potassium bicarbonate (KHCO3) at temperatures of 750–800 °C in N2. The AC prepared from a freeze-dried dispersion of hydrochar could be dispersed in ethanol as 500 nm-sized colloids. It was noted that on regular drying of the hydrochar dispersions, macroscopically large, long, curved, and thin rods of hydrochar formed in the vials. The rods comprised colloidally-packed spherical particles. The rods may have formed from cracked and fractured colloidal coatings and detached from the wall of the vials. This conclusion was supported by analysing the structural features of the rods. The macroscopic shapes were retained on the chemical activation when the hydrochar precursor had been pyrolyzed in N2 before activation. The ACs had specific surface areas of up to 1800 m2/g, and CO2 uptake levels of up to 7.1 mmol/g at 0 °C and 101 kPa.
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Amorphous calcium carbonate (ACC) is known to play a prominent role in biomineralization. Different studies on the structure of biogenic ACCs have illustrated that they can have distinct short-range ...orders. However, the origin of so-called proto-structures in synthetic and additive-free ACCs is not well understood. In the current work, ACC has been synthesised in iso-propanolic media by direct precipitation from ionic precursors, and analysed utilising a range of different techniques. The data suggest that this additive-free type of ACC does not resemble clear proto-structural motifs relating to any crystalline polymorph. This can be explained by the undefined pH value in iso-propanolic media, and the virtually instantaneous precipitation. Altogether, this work suggests that aqueous systems and pathways involving pre-nucleation clusters are required for the generation of clear proto-structural features in ACC. Experiments on the ACC-to-crystalline transformation in solution with and without ethanol highlight that polymorph selection is under kinetic control, while the presence of ethanol can control dissolution re-crystallisation pathways.
Adsorbents with small pores are especially relevant for capturing carbon dioxide at large emission sources. Such sorbents could be used potentially to reduce the energy demands for separating carbon ...dioxide from flue gas as compared with today's technologies. Here, we review the literature for crystalline, inorganic, and potentially inexpensive adsorbents. A number of different adsorbents with narrow pore openings are compared.
A modular design for a novel heterogeneous synergistic catalytic system, which simultaneously activates the electrophile and nucleophile by the combined activation modes of a separate metal and ...non‐metal catalyst, for asymmetric cascade transformations on a solid surface is disclosed. This modular catalysis strategy generates carbocycles (up to 97.5:2.5 er) as well as spirocyclic oxindoles (97.5:2.5 to >99:0.5 er), containing all‐carbon quaternary centers, in a highly enantioselective fashion via a one‐pot dynamic relay process.
Methane has been successfully encapsulated within cages of C
60
fullerene, which is an appropriate model system to study confinement effects. Its chemistry and physics are also relevant for ...theoretical model descriptions. Here we provide insights into intermolecular interactions and predicted spectroscopic responses of the CH
4
@C
60
complex and compared them with results from other methods and with data from the literature. Local energy decomposition analysis (LED) within the domain-based local pair natural orbital coupled cluster singles, doubles, and perturbative triples (DLPNO-CCSD(T)) framework was used, and an efficient protocol for studies of endohedral complexes of fullerenes is proposed. This approach allowed us to assess energies in relation to electronic and geometric preparation, electrostatics, exchange, and London dispersion for the CH
4
@C
60
endohedral complex. The calculated stabilization energy of CH
4
inside the C
60
fullerene was −13.5 kcal mol
−1
and its magnitude was significantly larger than the latent heat of evaporation of CH
4
. Evaluation of vibrational frequencies and polarizabilities of the CH
4
@C
60
complex revealed that the infrared (IR) and Raman bands of the endohedral CH
4
were essentially "silent" due to the dielectric screening effect of C
60
, which acted as a molecular Faraday cage. Absorption spectra in the UV-vis domain and ionization potentials of C
60
and CH
4
@C
60
were predicted. They were almost identical. The calculated
1
H/
13
C NMR shifts and spin-spin coupling constants were in very good agreement with experimental data. In addition, reference DLPNO-CCSD(T) interaction energies for complexes with noble gases (Ng@C
60
; Ng = He, Ne, Ar, Kr) were calculated. The values were compared with those derived from supramolecular MP2/SCS-MP2 calculations and estimates with London-type formulas by Pyykkö and coworkers
Phys. Chem. Chem. Phys.
, 2010,
12
, 6187-6203, and with values derived from DFT-based symmetry-adapted perturbation theory (DFT-SAPT) by Hesselmann & Korona
Phys. Chem. Chem. Phys.
, 2011,
13
, 732-743. Selected points at the potential energy surface of the endohedral He
2
@C
60
trimer were considered. In contrast to previous theoretical attempts with the DFT/MP2/SCS-MP2/DFT-SAPT methods, our calculations at the DLPNO-CCSD(T) level of theory predicted the He
2
@C
60
trimer to be thermodynamically stable, which is in agreement with experimental observations.
High-level electronic structure calculations provide quantitative insights into noncovalent interactions in endohedral complexes of fullerene C
60
(X@C
60
; X = He, He
2
, Ne, Ar, Kr, CH
4
).
Hydrothermal carbonization converts organics in aqueous suspension to a mixture of liquid components and carbon-rich solids (hydrochars), which in turn can be processed into activated carbons. We ...investigated whether milk could be used as a medium for hydrothermal carbonization, and found that hydrochars prepared from milk, with or without an added fibrous biomass, contained more carbon (particularly aliphatic carbon), less oxygen, and more mineral components than those prepared from fibrous biomass in water. Activated carbons produced from hydrochars generated in milk had lower specific surface areas and CO
capacities than those from hydrochars formed in water; however, these differences disappeared upon normalizing to the combustible mass of the solid. Thus, in the context of N
and CO
uptake on activated carbons, the primary effect of using milk rather than water to form the hydrochar precursor was to contribute inorganic mass that adsorbed little CO
. Nevertheless, some of the activated carbons generated from hydrochars formed in milk had specific CO
uptake capacities in the normal range for activated carbons prepared by activation in CO
(here, up to 1.6 mmol g
CO
at 15 kPa and 0 °C). Thus, hydrothermal carbonization could be used to convert waste milk to hydrochars and activated carbons.
•Wet pyrolysis of glucose was performed with catalytic amounts of FeSO4.•Thin blue and carbon rich films formed on macroscopic pieces of hydrochar.•Macroscopic pieces consisted also of aggregates of ...hydrochar particles.•EELS and XPS analysis showed that thin films were more carbonized than the regular hydrochar.
We hypothesized that the morphology of the hydrochar from hydrothermal carbonization of glucose would be affected by Fe2+; and indeed, with such ions, large pieces of hydrochar formed that comprised aggregated spherical particles and blue and thin films. Thin carbonized films formed at the bottom of the autoclave liners or on TeflonTM tape used as a template. Free-standing films could be prepared by stretching the TeflonTM tape after the synthesis. The carbonized films that formed at the bottom of the autoclave adhered to spherical hydrochar particles. The blueness was ascribed to thin-film interference under white-light irradiation and related to the film thickness, which was about 200 nm. Analysis of transmission electron microscopy (TEM) images showed that the films consisted of a layered amorphous carbon. The amorphous and thin films were more carbonized than the amorphous carbon of the TEM grid, as derived via electron energy loss spectroscopy (EELS). Additional analysis of one of the thin films by X-ray photoelectron spectral analysis showed a higher carbon fraction than for bulk hydrochar, supporting the EELS analysis. We believe that the synthesis of thin films of hydrochar can open up new colloidal processing pathways, which could be useful in the preparation of carbon-based materials and alike.
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