14 Dec 2017, The Royal Society of Chemistry Advances
A. Liu, L. Yang, M. Verwegen, D. Reardonb and J. J. L. M. Cornelissen
Plant viruses have been widely used as templates for the synthesis of organic–inorganic hybrids. However,the fine-tuning of hybrid nanoparticle structures, especially the control of inorganic particle size as well as where the silication occurs (i.e. outside and/or inside of the capsid), by simply tuning the pH remains a challenge. By taking advantage of the templating effect of Cowpea Chlorotic Mottle Virus (CCMV) protein cages, we show that the silication at the exterior or interior surface of protein capsids, as well as the resulting structures of silica/virus hybrid nanoparticles can be fine-tuned by pH. At pH 4.0, only small silica particles (diameter of 2.5 nm) were formed inside the protein cages; at pH 6.0, silication mainly takes place inside of the protein cages, leading to monodisperse silica nanoparticles with diameters of 14 nm; and at pH 7.5, silica deposition takes place both at the interior and exterior surfaces of protein cages in aqueous conditions. Under these reaction conditions, multiple component hybrid virus/nanoparticulate systems, such as CCMVAu/silica and Au/silica nanoparticles were prepared step-by-step.Upon removal of the CCMV template by thermal degradation a single gold nanoparticle can be encapsulated in a hollow silica shell emulating the structure of a baby's rattle with an unattached solid particle within a hollow particle. The Au/silica core-hollow shell nanoparticles can then be further used as a stable catalyst. It is anticipated that these synthetic methods provide a versatile methodology to prepare core–shell nanomaterials with well-designed structure and functionality.
Xinchang Wang, Pixian Peng, Wei Xuan, Yu Wang, Yongbin Zhuang, Zhongqun Tian and Xiaoyu Cao *
Narcissistic chiral self-sorting prevailed in the assembly of molecular face-rotating polyhedra from a C3h building block 5,5,10,10,15,15-hexabutyl-truxene-2,7,12-tricarbaldehyde and racemic mixtures of 1,2-diamines. Out of 124 possible stereoisomers, a pair of racemic polyhedra dominated, wherein (1R,2R)-diamines were segregated in AAAA polyhedra and (1S,2S)-diamines in CCCC polyhedra. This chiral self-sorting process is regulated by facial non-covalent interactions in the polyhedra. In contrast, D3h facial building blocks 1,3,5-tris-(4-formyl-phenyl)triazine and racemic mixtures of 1,2-diamines assembled into polyhedra without facial interactions, and their assembly process did not undergo apparent chiral self-sorting.
Chiral cage compounds are mainly constructed from chiral precursors or based on the symmetry breaking during coordination-driven self-assembly. Herein, we present a strategy to construct chiral organic cages by restricting the P or M rotational configuration of tetraphenylethylene (TPE) faces through dynamic covalent chemistry. The combination of graph theory, experimental characterizations and theoretical calculations suggests emergent chirality of cages is originated from complex arrangements of TPE faces with different orientational and rotational configurations. Accompanied by the generation of chirality, strong fluorescence also emerged during cage formation, even in dilute solutions with various solvents. In addition, the circularly polarized luminescence of the cages is realized as a synergy of their dual chiral and fluorescence properties. Chirality and fluorescence of cages are remarkably stable, because intramolecular flipping of phenyl rings in TPE faces is restricted, as indicated by calculations. This study provides insight into construct chiral cages by the rational design through graph theory, and might facilitate further design of cages and other supramolecular assemblies from aggregation-induced emission active building blocks.
To facilitate the design and construction of complex functional materials, the field of molecular assembly can learn from the well-established field of catalysis including its branches such as electrocatalysis and photo-electrocatalysis. In this study, we establish a “photo-electro-catassembly” strategy to repeatedly fabricate two-dimensional molecular assemblies on electrode surface by learning from the concept of photo-electrocatalysis. With the rational design of the linear diacetylene building blocks, Au electrode surface itself and the thiol-functionalized electrode both can assist the formation of two-dimensional assemblies and their subsequent covalent stabilization through the polymerization of diacetylene groups. Nevertheless, when using the Au electrode surface as a direct template, the polymerized product would be hardly removed from the electrode due to the strong synergistical interactions through multivalent Au-S bonds. By contrast, when using the thiol-functionalized electrode as an indirect template, the diacetylene building block forms a well-ordered second layer over the thiol monolayer due to the solvent-phobic and solvent-philic effects. After photo-polymerization, the polymerized product can still be removed from the electrode along the electro-induced removal of the thiol monolayer. Driven by electricity and photoirradiation, the thiol-functionalized electrode assists the combined process of assembly and photo-polymerization as a “photo-electrocatassembler”, and it works repeatedly to produce covalently stabilized two-dimensional assemblies.
We report the post-synthesis interconversion of two enantiomeric organic cages through turning inside out. By scrutinizing the thermodynamics and kinetics, we are able to control the racemization rate by various reaction conditions and reveal that the turning-inside-out interconversion is realized through a partial disassembly pathway. The kinetics investigation also provides insight into the dynamic essence of imine chemistry using different solvents and catalysts.
21 May 2017, Computer Animation and Virtual Worlds
Shihui Guo, Meili Wang, Gabriel Notman, Jian Chang, Jianjun Zhang, and Minghong Liao
This paper simulates the behaviour of collective transport where a group of ants transports an object in a cooperative fashion. Different from humans, the task coordination of collective transport, with ants, is not achieved by direct communication between group individuals, but through indirect information transmission via mechanical movements of the object. This paper proposes a stochastic probability model to model the decision‐making procedure of group individuals and trains a neural network via reinforcement learning to represent the force policy. Our method is scalable to different numbers of individuals and is adaptable to users' input, including transport trajectory, object shape, external intervention, etc. Our method can reproduce the characteristic strategies of ants, such as realign and reposition. The simulations show that with the strategy of reposition, the ants can avoid deadlock scenarios during the task of collective transport.