Chiral superstructure of aragonite similar to Turritella terebra shell induced by CTAB's adsorption chirality.

A twisted dumbbell-like chiral superstructure can be easily assembled in aragonite under the co-action of CTAB and Mg2+, producing a microstructure that is very similar to that of Turritella terebra shell. Asymmetric adsorption of the CTAB head group on aragonite, namely "adsorption chirality", is the reason for the chiral assembly.

Preparation and Stability of Monodisperse Amorphous CaCO3 Microspheres of High Hardness and Sphericity.

Using amorphous CaCO3 (ACC) to biomimic the crustacean exoskeleton and optimize the physical and chemical properties of the polymeric phase of ACC holds great promise. Controlling the ACC morphology and stability is key in this process. For this article, monodisperse ACC microspheres, with a high sphericity of 0.973 ± 0.001 and a hardness of 0.6755 GPa, were prepared using the gas diffusion method in the presence of Mg2+. Their hardness is 3.58-16 times greater than that ever reported before for ACC microspheres. The stability of ACC is strongly affected by environmental conditions. The liquid phase and high temperature are not conducive to its stability, but ACC microspheres do have high stability under ambient conditions. After 100 days under such conditions, only a small amount of crystallization occurs, and their spherical shape survives intact. This article provides guidance for the preparation of ACC biomimetic composites, sheds light on the biological function of ACC in crustacean exoskeletons, and improves the theoretical understanding of the mechanism of biomineralization.

Robust All-Cellulose Nanofiber Composite from Stack-Up Bacterial Cellulose Hydrogels via Self-Aggregation Forces.

All-cellulose composites are usually prepared by removing impurities and using a surface-selective dissolution approach, which detract significantly from their environment-friendly properties. In this paper, we report an environment-friendly approach to fabricate all-cellulose nanofiber composites from stack-up bacterial cellulose (BC) hydrogels via self-aggregation forces of the hydrogen bond by water-based processing. Structural and mechanical properties of BC-laminated composites have been investigated. The results indicated that BC composites possess the structure of all nanofibers, a tensile strength of 116 MPa, and a storage modulus of 25 GPa. Additionally, the interfacial shear strength and tensile strength of piece-hot-press BC demonstrate the strong self-aggregation forces of BC nanofibers. Thus, BC-laminated composites will be attractive in structural material.

Low-temperature dependence on the THz spectrum of CL-20/TNT energetic cocrystal by molecular dynamics simulations.

Based on the unique advantages of terahertz (THz) spectrum on the detection of energetic cocrystals, the low-temperature dependent THz spectra of CL-20/TNT cocrystal were investigated by using molecular dynamics (MD) simulations from 5 to 296 K, as well as three different crystal faces, (001), (120), and (010). When the temperature decreases below 95 K, we have observed two new peaks for CL-20/TNT cocrystal, at 4.58 and 5.99 THz, respectively. Also, the THz peaks below 1.5 THz gradually disappear under cooling from 296 to 5 K, and they should originate from the lattice thermal vibrations. THz absorption peaks of CL-20/TNT cocrystal reveal frequency shifting, linearly dependent on temperature. Four of them are red shift and other two are blue shift of THz vibrational peaks of CL-20/TNT cocrystal with the temperature increase. The frequency shifts can be attributed to the effects of lattice thermal expansion on inter-/intramolecular vibrational modes as well as their coupling. From the temperature-dependent THz spectra of different crystal faces, we further confirm the response of different kinds of intermolecular interactions on the THz spectrum of CL-20/TNT cocrystal. Graphical abstractThe intermolecular interactions and peak positions of THz spectra of CL-20/TNT cocrystal in the range of 0-6 THz versus temperature.

A facile one-step method for preparation of Fe3O4/CS/INH nanoparticles as a targeted drug delivery for tuberculosis.

In this paper, Fe3O4/chitosan/isoniazid magnetic nanoparticles (Fe3O4/CS/INH-MNPs) were prepared as an environmental stimuli-responsive drug-delivery system by automated in situ click technology, in which Fe3O4 magnetic nanoparticles, chitosan and isoniazid were simultaneously in situ crystallized by one-step method. The Fe3O4 magnetic nanoparticles and tripolyphosphate act as stable crosslinkers to produce numerous intermolecular crosslinkages for the mobility of the chitosan chains. Characterization results indicated that the multifunctional drug delivery system with optimized size, excellent loading capacity, well magnetic properties, nontoxicity and pH triggered drug release property is expected to be applied in tuberculosis treatment with excellent magnetic sensitivity and sustained release.

Directly Insight Into the Inter- and Intramolecular Interactions of CL-20/TNT Energetic Cocrystal through the Theoretical Simulations of THz Spectroscopy.

Compared with cocrystal coformers, an explosive cocrystal has distinctive packing arrangements and complex intermolecular interactions. Identifying the spectral signatures of an explosive cocrystal and understanding the molecular low-frequency modes by means of the spectrum in the terahertz range are of great worth to the explicit mechanism of cocrystal formation. In this work, on the basis of the joint molecular dynamics (MD) simulations and solid-state density functional theory (DFT) calculations, we have investigated the terahertz (THz) absorption spectra of the CL-20/TNT cocrystal and its different directions as well as cocrystal coformers and determined the systematic and all-sided assignments of corresponding THz vibration modes. The THz spectral comparison of the cocrystal with different directions and the cocrystal coformers indicates that the CL-20/TNT cocrystal has five fresh low-frequency absorption features as unique and discernible peaks for identification, in which 0.25, 0.73, and 0.87 THz are attributed to intensive crystalline vibrations; 0.87 THz is also caused by C-H···O hydrogen-bonding bending vibrations; 1.60 and 1.85 THz features originate from C-H···O hydrogen-bond stretching vibrations. Additionally, the THz spectrum of the (001) direction of the CL-20/TNT cocrystal verifies that the molecular conformation of the CL-20 is the same as that in the ß-polymorph, other than the initial conformation of raw material ε-CL-20.

A molecular dynamics simulation of solvent effects on the crystal morphology of HMX.

The solvent has a large effect on the crystal morphology of the organic explosive compound octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX, C(4)H(8)N(8)O(8)). The attachment energy calculations predict a growth morphology in vacuum dominated by (020), (011), (102 ), (111 ) and (100) crystal forms. Molecular dynamics simulations are performed for these crystal faces of HMX in contact with acetone solvent. A corrected attachment energy model, accounting for the surface chemistry and the associated topography (step structure) of the habit crystal plane, is applied to predict the morphological importance of a crystal surface in solvent. From the solvent-effected attachment energy calculations it follows that the (100) face becomes morphologically more important compared with that in vacuum, while the (020) and (102 ) are not visible at all. This agrees well with the observed experimental HMX morphology grown from the acetone solution.