Herein, a low-temperature sublimation-based vapor deposition (SVD) method is developed to synthesize hexagonal crystal plates of cyanuric acid-melamine (CAM) with outstanding crystallinity. Through meticulous design of the reaction apparatus and careful selection of source materials, substrate-confined SVD in a tube furnace is explored to grow single crystals of CAM in hexagonal shapes. Additionally, the orientation preference of the (202) facet is revealed, corresponding to the 2D arrangement of the H-bonded network, of single-crystalline plates on surfaces using selected area electron diffraction and X-ray diffraction techniques. By employing atomic force microscopy and scanning electron microscopy for topography characterization, a mechanism of three-stage step-growth crystallization is proposed, including nucleation, in-plane expansion, and out-of-plane growth. Furthermore, it is found that the interactions among melamine molecules in CAM synthesized via SVD are more intense compared to those in CAM synthesized via water-based methods, as evidenced by infrared and photoluminescent spectra studies. Subsequent nanoindentation tests on the (202) facet of CAM single-crystalline plates reveals a reduced modulus and hardness of 12.8 and 0.82 GPa, respectively. This methodology addresses the longstanding challenge of synthesizing hexagonal CAM single crystals and provides valuable insights for the fabrication of functional organic crystalline materials. A substrate-confined sublimation-based vapor deposition method is developed to obtain the hexagonal single crystals of the famous supramolecular crystals of cynuric acid-melamine. A mechanism of three-stage step-growth crystallization is proposed including nucleation, in-plane expansion, and out-of-plane growth. This methodology addresses the longstanding challenge of synthesizing hexagonal CAM single crystals and provides insights for the fabrication of functional organic crystalline materials. image

ZSM-48 zeolites with exterior Al-rich (Z-48-Sx) are synthesized by the recrystallization method. The crystal structure of Z-48-Sx with the Al-rich outer layer is verified by analyzing the crystallization process of Z-48-Sx and the EDS of the ultrathin section. The diffusion properties of Z-48-S3 and Z-48-C are investigated by the zerolength column (ZLC) method, and the synthesized ZSM-48 zeolite with an Al-rich external layer effectively improves the diffusion ability. The effective diffusion constants of Z-48-S3 are 53 %-102 % higher than those of the conventional ZSM-48 (Z-48-C). Meanwhile, the values of turnover frequency (TOF) of Z-48-S3 are increased by 14 %-63 % at similar n-dodecane conversions compared with Z-48-C, which is closely related to the diffusion characteristics. In addition, the depth of hydroisomerization (Iiso) of Z-48-S3 is decreased by 65.3 %, and the isomerization selectivity is increased by 52.5 % at 340 degrees C compared with that of Z-48-C. Hence, the ZSM-48 molecular sieves synthesized by the recrystallization hydrothermal method are beneficial for controlling the depth of hydroisomerization of the catalyst and reducing the occurrence of the cracking reaction. Meanwhile, the isomer distribution does not change significantly compared with that of the conventional ZSM-48, and the 5methylundecane is still the main isomerization product.

In this work, competition between different supramolecular interactions is investigated based on a fibrous crystal composed of hydrogen-bonded cyanuric acid (CA) and amidinothiourea (ADT). Melamine (M) is found to prevail over ADT and bond to CA due to its stronger triple H-bonding affiliation, forming hollow microtubes assembled by oriented CAM crystalline arrays, as guided by the directionality of peripheral hydrogen bonds. Furthermore, competitive interaction between hydrogen bonding and ionic/covalent bonding is demonstrated by mixing Ag+ ions with the CA-ADT fibers, where sulfur atoms are abstracted from ADT molecules to produce Ag2S ligaments. The in situ-formed Ag2S serves as a binding glue to generate CA-ADT/Ag2S composites with significantly enhanced mechanical strength compared to the pristine CA-ADT fiber pellet. [GRAPHICS] .

The ductility possessed by alpha-Ag2S renders it a promising candidate for various forthcoming stretchable electronic devices. There is a significant need for a facile approach for producing alpha-Ag2S thin film with a dense surface. This study has opted for the spin coating technique to prepare alpha-Ag2S thin films from the colloidal solution. This method starts by mixing AgNO3 and amidino thiourea solution and is easy, straightforward and much less timeconsuming compared to self-assembling procedure. The thickness of the film can be well-controlled by coating multiple layers on various substrates. The observed resistive switching behavior in the obtained dense alpha-Ag2S thin film, along with the integrity of the film in the bending test, suggests its potential utility in electronic applications. It is hoped that our work can offer an innovative mean for crafting flexible alpha-Ag2S thin film applicable in future devices.

A series of Fe substituted ZSM-48 nanocrystal aggregates were synthesized by the dynamic hydrothermal method. Through incorporation of Fe into ZSM-48 framework, the acidity of ZSM-48 zeolites has been modified. The hydroisomerization performances of n-dodecane were investigated on Pt supported ZSM-48 and Fe incorporated ZSM-48 zeolites. Fe incorporated ZSM-48 catalysts show higher n-C12 hydroisomerization selectivity compared with parent sample due to weaker acid strength of Si–OH–Fe than Si–OH–Al. High temperature favor the generation of the multi-branched isomers (mainly dimethyl isomers) following the “Key-Lock” mode. Meanwhile, 5-methylundecane is the main product in the monomethyl isomers (MOB) and 2,6-dimethyldecane is the main product in the multi-branched isomers (MUB), which suggests the excellent shape selectivity of ZSM-48 and the “Key-Lock” mode is preferred on ZSM-48 catalysts regardless Fe substituted or not. The relationship between the mono-methyl isomers and the butene-TPD results has been correlated and investigated. Four desorption peaks corresponding to butene weakly adsorbed over Si–OH, Fe–OH or Lewis acid sites, the “Key-Lock” mode adsorbed butene, the “Pore-Mouth” mode adsorbed butene and the strongly adsorbed butene respectively, can be distinguished. ZLC results indicate that Fe modified ZSM-48 can effectively increase n-hexane diffusion rate and reduce the activation energy of diffusion of n-hexane, which is benefit for the hydroisomerization performance. SMOB/SMUB can be altered by Fe modification, however, the distribution of the mono-methyl isomers can hardly be affected.

We report a new supramolecular structure of cyanuric acid–melamine–zinc (CA–M–Zn) demonstrating unique molecular rotation induced negative thermal expansion along the c axis, accompanied by a significant decrease of β angle (−3.8%).

Chemical reactions in homogenous systems are generally associated with positive-order kinetics; that is, the reaction rate increases with the increased concentration of reactants. In this work, we report a coordination reaction of Cu2+ ions, cyanuric acid (CA), and pyridine in aqueous solution which shows negative-order kinetics with respect to the concentration of pyridine. As the pyridine concentration increases, the complexation of CA with pyridine overwhelms its dissociation in water, resulting in the redistribution of CA; that is, CA is sealed in the pyridine phase by forming an unreactive hydrogen bonded complex. As a result, the number of accessible anionic CA for crystallization in water decreases, and thus the crystallization slows down and almost terminates. Further, the crystallization yields two types of crystals with similar structures but disparate colors (red and blue), and the origin is investigated by the ligand field analysis.

The growth of flexible semiconductor thin films and membranes is highly desirable for the fabrication of next-generation wearable devices. In this work, we have developed a one-step, surface tension-driven method for facile and scalable growth of silver sulfide (Ag2S) membranes with a nanomesh structure. The nanomesh membrane can in principle reach infinite size but only limited by the reactor size, while the thickness is self-limited to ca. 50 nm. In particular, the membrane can be continuously regenerated at the water surface after being transferred for mechanical and electronic tests. The free-standing membrane demonstrates exceptional flexibility and strength, resulting from the nanomesh structure and the intrinsic plasticity of the Ag2S ligaments, as revealed by robust manipulation, nanoindentation tests and a pseudo-in situ tensile test under scanning electron microscope. Bendable electronic resistance-switching devices are fabricated based on the nanomesh membrane.