Classical crystal growth models posit that crystallization outcomes are determined by nuclei that resemble mature crystal phases, but at a critical size where the volume free energy of nuclei begins to offset the unfavorable surface free energy arising from the interface with the growth medium. Crystallization under nanoscale confinement offers an opportunity to examine nucleation and phase transformations at length scales corresponding to the critical size, at which kinetics and thermodynamics of nucleation and growth intersect and dramatic departures in stability compared to bulk crystals can appear. This tutorial review focuses on recent investigations of the crystallization of organic compounds in nanoporous matrices that effectively provide millions of nanoscale reactors in a single sample, ranging from controlled porous glass (CPG) beads to nanoporous block-copolymer monoliths to anodic aluminum oxide (AAO) membranes. Confinement of crystal growth in this manner provides a snapshot of the earliest stages of crystal growth, with insights into nucleation, size-dependent polymorphism, and thermotropic behavior of nanoscale crystals. Moreover, these matrices can be used to screen for crystal polymorphs and assess their stability as nanocrystals. The well-aligned cylindrical nanoscale pores of polymer monoliths or AAO also allow determination of preferred orientation of embedded nanocrystals, affording insight into the competitive nature of nucleation, critical sizes, and phase transition mechanisms. Collectively, these investigations have increased our understanding of crystallization at length scales that are deterministic while suggesting strategies for controlling crystallization outcomes.

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The ability of natural peptides and proteins to influence the formation of inorganic crystalline materials has prompted the design of synthetic compounds for the regulation of crystal growth, including the freezing of water and growth of ice crystals. Despite their versatility and ease of structural modification, peptidomimetic oligomers have not yet been explored extensively as crystallization modulators. This report describes a library of synthetic N-substituted glycine peptoid oligomers that possess "dual-action" antifreeze activity as exemplified by ice crystal growth inhibition concomitant with melting temperature reduction. We investigated the structural features responsible for these phenomena and observed that peptoid antifreeze activities depend both on oligomer backbone structure and side chain chemical composition. These studies reveal the capability of peptoids to act as ice crystallization regulators, enabling the discovery of a unique and diverse family of synthetic oligomers with potential as antifreeze agents in food production and biomedicine.tailored additive | X-ray diffraction

To determine the pore structure characteristics of different coal ranks in Panguan syncline, both N 2 adsorption− desorption (LP-N 2 GA) and CO 2 adsorption (LP-CO 2 GA) were carried out with the goal of revealing the differentiation evolution of total pore volume (TPV), specific surface area (SSA), pore size distribution (PSD), and pore shape of 14 coal samples, and the influences of SSA to adsorption capability at different sizes (supermicroporous < 2 nm, micropore: 2−10 nm, transition pore: 10−100 nm) were further discussed. Density functional theory (DFT) is used for the determination of pore structure parameters to ensure its accuracy. Results show that the pore shape in the Panguan area is mostly the semi-open pores with poor connectivity (e.g., wedge-shaped, cylindrical, and slit-shaped pores with one closed side). Only a small amount of the pores is in open shapes (e.g., slit-shaped pores or cylindrical pores with two ends open). For most of the coal samples, the PSDs of pores tested by LP-N 2 GA appear to be multimodal, and the N 2 -TPV is mainly from the contribution of the transition pore (73.69−95.21%), followed by the micropore. The PSDs of supermicroporous (tested by LP-CO2GA) appear to be bimodal, with two peak values present at 0.52−0.61 nm and 0.82−0.87 nm, respectively, and a bigger pore volume distribution interval corresponds to a higher specific surface area. The N 2 -SSA (pore diameter ranges from 2 to 100 nm) mainly comes from the contribution of the pores 2−3 nm in diameter, and a bigger N 2 -TPV means a higher N 2 -SSA. The CO 2 -SSA (pore diameter ranges from 0.489 to 1.083 nm) which has a better positive linear correlation with Langmuir volume is related to CO 2 -TPV and the distribution frequency of pore volume at different pore sizes, and the contribution rate of CO 2 -SSA to the total SSA (CO 2 -SSA + N 2 -SSA) reaches 99%, indicating that supermicroporous has a significant effect on the coal adsorption capacity. With the increase of the vitrinite reflectance (R o,ran , 0.83 → 2.27%), the N 2 -SSA increase gradually, and its increase tendency presents to be a half-reversed "U" shape in the whole, while the CO 2 -SSA presents an extremely significant linear increase tendency. Accordingly, the Langmuir volume (2.61 → 21.26 m 3 /t) also displays a linear growth tendency with the increasing vitrinite reflectance. The results of this study will provide guidance to the CBM development in the Panguan area.

Superbasic sites have been generated on the mesoporous silica materials for the first time, through a new strategy to prepare the MgO-modified SBA-15 in one-pot synthesis and then to disperse KNO3, possessing the good textural structure of the host and the high basic strength (H -) of 27.0. The in situ coated Mg species passivated the silanol groups on the surface of siliceous SBA-15 so that the mesostructure of SBA-15 could be reserved after the composite was loaded with KNO3 and activated at high temperature. Existence of the special protection layer of MgO on the surface of SBA-15 was also beneficial for decomposition of KNO3 to form superbasic sites on the mesoporous silica. The influence of coating amount of MgO on the protection of the textural properties of SBA-15 is examined and discussed in terms of consuming surface silanol groups. Dispersion and decomposition of KNO3 on the MgO layer is also explored. Other metal oxides such as CaO, ZnO, and Al2O3 are in situ coated on the surface of SBA-15 through one-pot synthesis and their function of protecting SBA-15 is evaluated for comparison with MgO.

Crystallization of glycine in the cylindrical nanopores of anodic aluminum oxide (AAO) revealed the formation of metastable β-glycine in pores having diameters less than 200 nm. Two-dimensional X-ray microdiffraction indicated that the [010] axis of the embedded β-glycine nanocrystals coincided with the pore direction, identical to behavior observed previously in the cylindrical nanopores of polymer monoliths. Whereas the β-glycine nanocrystals were stable indefinitely in ambient air and persisted upon heating, they transformed to the α polymorph upon standing at room temperature and 90% relative humidity (RH). The α-glycine nanocrystals were oriented with the [010] axis nearly perpendicular to the pore direction, reflecting a nearly 90° rotation of the glycine molecules during the transition. When the β-glycine nanocrystals were formed in the AAO cylinders in the presence of small amounts of racemic hydrophobic amino acid auxiliaries, which are known to bind selectively to the (010) and (010) faces on the fast-growing end of β-glycine enantiomorphs, the β → α phase transition at 90% RH was suppressed. In contrast, β-glycine nanocrystals grown in the presence of an enantiopure amino acid auxiliary, which binds to the fast-growing end of only one of the enantiomorphs, thus suppressing its formation and leaving the other enantiomorph unperturbed, transformed into the α polymorph under the same conditions. This observation confirms that binding of an amino acid to the {010} faces is stereoselective and that access of water to these faces is essential for the transition to the α polymorph.

The metastable β polymorph of glycine exhibits a single-crystal-to-single-crystal transformation (SCSCT) to either the α or γ phase with retention of the crystal habit of the parent β phase. X-ray diffraction and optical microscopy reveal that of 51 single crystals of the β parent phase, 24 form single domain crystals of α or γ with a single orientation matrix, confirming an SCSCT. The remaining 27 β parent crystals transform to crystals with a few domains of either α and/or γ, each domain arising from a single nucleation event. In three cases the β → α and β → γ transformations occurred within the same glycine single crystal. In all cases, regardless of the number of domains, the transformation occurred with retention of the original habit of the parent phase. Both β → α and β → γ transformations proceed in a non-topotactic manner, as evident from the random orientations of the daughter phases in the crystallographic reference frame of the parent β phase. The transformation rates, as measured by advancement of the growth front with polarized optical microscopy, vary from crystal to crystal as well as for different regions within the same crystal. Moreover, the transformation rate increases substantially with relative humidity, and at a relative humidity of 90% α-glycine was observed as the only product.

Two novel porous nitrosamine traps have been synthesized in order to eliminate carcinogens from the environment. A functional mesoporous material, CuO/SBA‐15, has been synthesized by using an in‐situ coating method, with the addition of a guest salt to the reaction system to modify the porous materials before the particles of SBA‐15 were incubated; the synthesis and modification processes were performed in a single step. The resulting mesoporous composites selectively adsorb N‐nitrosopyrrolidine (NPYR), a typical volatile nitrosamine, and are potential cigarette additives that can be used for the removal of nitrosamines from cigarette smoke, thereby protecting public health and the environment. In another reaction, silica gel is modified by being coated with magnesia and then corroded by NaOH solution.The magnesia is dispersed onto the silica by impregnating it with a magnesium acetate solution, followed by calcination. After corrosion of the calcined sample with caustic soda, only the silica particles that are completely covered by magnesia remain. This material exhibits a similar ability to SBA‐15 and zeolite NaY in its selective adsorption of NPYR.