Search

The 2D self-assemblies and structural transitions of pentacene on a Cd(0001) surface have been investigated with low temperature scanning tunneling microscopy (STM). With increasing coverage, pentacene molecules show a structural evolution from the initial disordered gas-like phase through the porous network phase to the herringbone phase, and finally to the brickwall phase at the full monolayer. In particular, orientational frustration and cooperative rotation of pentacene molecules take place in the herringbone phase. Furthermore, successive STM scanning leads to structural interconversions between the porous network phase, herringbone phase, and brickwall phase, indicating the metastability of the 2D assembled structures of pentacene on Cd(0001). These structural transitions and interconversion can be attributed to the interplay between the repulsive electrostatic forces resulting from the charge transfer from the substrate to pentacene and the attractive effects originating from dipole-dipole interactions and intermolecular van der Waals forces.

Chiral resolution is of fundamental importance to conglomerate or racemate crystallization. Here we demonstrate that the spontaneous chiral resolution of pentahelicene racemates occurred in the monolayer domains. When deposited on a Cd(0001) surface, pentahelicene molecules crystallize into a commensurate (6 × 6) R 0° structure built mainly from homochiral trimers. Spontaneous chirality separation takes place in the form of opposite mirror domains, where 2D enantiomorphism is not expressed by the oblique adlattice, but by the supramolecular chirality of the pentahelicene trimers. Furthermore, annealing the sample or extreme close-packing lead to the presence of lattice handedness through the formation of a porous network structure or an edge-on phase. These results provide valuable insight for 2D conglomerate crystallization and stereochemical recognition.

The interfacial structures of C 60 molecules adsorbed on solid surfaces are essential for a wide range of scientific and technological processes in carbon-based nanodevices. Here, we report structural transitions of the C 60 monolayer on the Bi(111) surface studied via low-temperature scanning tunneling microscopy (STM). With an increase in temperature, the structure of the C 60 monolayer transforms from local-order structures to a (√93 × √93) R20° superstructure, and then to a (11 × 11) R0° superstructure. Moreover, the individual C 60 molecules in different superstructures have different orientations. C 60 molecules adopt the 6 : 6 C-C bond and 5 : 6 C-C bond facing-up, mixed orientations, and hexagon facing-up in the local-order structure, (√93 × √93) R20°, and (11 × 11) R0° superstructure, respectively. These results shed important light on the growth mechanism of C 60 molecules on solid surfaces., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Dietary salt is a vital ingredient associated with sensory performance in processed foods, while reduced salt intake linked to public health is highly desired by consumers and food manufacturers. In this paper, quillaja saponin (QS) based hollow salt particles (∼10 μm) were fabricated by simple spray drying, and utilized as solid carriers to enhance sensory aromas with reduced sodium intake. QS-coated nanodroplets were firstly prepared as a reservoir for flavor oils (lemon and garlic oil), and then served as frameworks to construct hollow salt particles via general spray drying. Headspace gas chromatography-mass spectrometry (DHS-GC-MS) and panel sensory analysis conclude that the hollow salt particles loaded with flavor oils enhance typical aroma attributes and saltiness perception in comparison with their mixture control. The QS-based hollow salt particles could be developed into novel vehicles for improving flavor performance with reduced sodium intake, and furthermore used for delivery of hydrophobic bioactives in food systems.

[(CuimZnL-2H)(CuimZnL-H)](ClO4)3, the first imidazolate-bridged Cu(II)-Zn(II) complex of a unique single macrocyclic ligand with two flexible hydroxyethyl pendants, L (L = 3,6,9,16,19,22-hexaaza-6,19-bis(2-hydroxyethyl)tricyclo[22.2.2.2(11,14)]triaconta-1,11,13,24,27,29-hexaene) has been obtained, in which the macrocyclic ligand with two hydroxyethyl arms possesses a markedly different conformation compared to its dicopper analogue.