Temperature-Triggered Self-Assembled Structural Transformation: From Pure Hydrogen-Bonding Quadrilateral Nanonetwork to Trihexagonal Structures.

Adequate control over the structures of molecular building blocks plays an important role in the fabrication of desired supramolecular nanostructures at interfaces. In this study, the formation of a pure hydrogen-bonding co-assembly supramolecular nanonetwork on a highly oriented pyrolytic graphite surface was demonstrated by means of a scanning tunneling microscope. The thermal annealing process was conducted to monitor the temperature-triggered structural transformation of the self-assembled nanonetwork. On the basis of the single-molecule-level resolution scanning tunneling microscopy images, together with the density functional theory calculations, the formation mechanisms of the formed nanoarrays were proposed. The results have great significance with regard to controlled construction of complex nanostructures on the surface.

Synthesis and optimization of ZnPc-loaded biocompatible nanoparticles for efficient photodynamic therapy.

Zinc(ii) phthalocyanine (ZnPc) is a promising photosensitizer for PDT but suffers from aggregation in a physiological aqueous environment. In this paper, a class of biocompatible polymeric nanoparticles (NPs) was prepared to encapsulate ZnPc molecules. Mostly because of the planar structure, ZnPc molecules were difficult to be encapsulated into the polymeric NPs unless further coated with a thick poly-l-lysine (PLL) layer. The PLL shell endowed the NPs with good biocompatibility, efficient cellular uptake, and potential bioconjugation. The degree of aggregation (DOA) of ZnPc molecules in PLL-NPs was thoroughly investigated based on self-defined relative DOA, and a loading capacity of 4 wt% was deduced as the turning point for aggravating aggregation. Similarly, the optimal loading capacity of ZnPc was determined to be 4% according to the 1O2 generation rate, demonstrating the feasibility of the DOA approach. Polymers with large rigid units (PVK and PFO) were also utilized to relieve the aggregation of ZnPc in NPs. Taking advantage of the optimized ZnPc-loaded NPs, high PDT efficacy was demonstrated in HepG2 cells and in tumor-bearing mice as well. Both high in vitro and in vivo PDT efficacy and biocompatibility are demonstrated. Aside from affording a class of efficient biocompatible nanophotosensitizers, this work is also instructive to design other types of ZnPc-based nanocarriers, in which aggregation should be well considered.

In situ STM investigation of two-dimensional chiral assemblies through Schiff-base condensation at a liquid/solid interface.

Nanoscaled two-dimensional (2D) chiral architectures are increasingly receiving scientific interest, because of their potential applications in many domains. In this paper, we present a new method for constructing 2D chiral architectures on surface. Based on in situ Schiff-base reaction of achiral dialdehyde with two types of achiral amines at the solid/liquid interface, two chiral species have been directly formed and confirmed by means of a scanning tunneling microscopy (STM) technique. This work introduces a novel strategy to construct 2D surface chirality, which might be applied in fabricating functional films and nanoelectronic devices.

[Spectral study of monoisothiocyanato-substituted 3:1 asymmetrical phthalocyanine zinc(II)].

Electronic absorption spectra of three monoisothiocyanato-substituted asymmetrical phthalocyanine zinc(II), 2-isothiocyanato-9,10,16,17,23,24-alkyloxyphthalocyanine zinc(II) [(RO)6 (NCS)PcZn(II)] (R = n-C4H9, n-C5H11, n-C10H21), were measured in five organic solvents. The effect and order of the substitute groups and solvents were studied by electronic absorption spectra. The changes of lamda(max) data are very small between monoamino- and monoisothiocyanato-substituted asymmetrical phthalocyanines. The order of lamda(max), data is listed here, CHCl3>CH2Cl2>toluene in non-coordination solvents; DMF>THF in O-coordination solvents. The fluorescence spectra of these complexes were measured in organic solvents at the same time. The effect and order of the substitute groups, solvents and concentrations were studied on the maximum wavelength of emission and fluorescence intensity. The lamda(em,max) data of fluorescence emission are among 690-700 nm. The order of lamda(em,max) data is listed here, DMF>THF in O-coordination solvents and almost the same in non-coordination solvents. The fluorescence intensity is very strong in DMF and THF. The order of fluorescence intensity is listed here, DMF>THF in O-coordination solvents; toluene> CH2Clz > CHCl3 in non-coordination solvents. They have special fluorescent effect and should be expected to become a photosensitizer of photodynamic therapy in future.