Nanoscale & Nanoscale Advances Blog

Scientists from Tsinghua University in China have found a way to synthesis water soluble nanocrystals with sizes smaller than 10nm using a formamide solvent-system.

So far, many groups have been successful in synthesising hydrophobic nanocrystals, but their inability to disperse in water has hindered their applications in electronics, catalysis and biomedicine. Hydrophobic nanocrystals can be made hydrophilic by using ligands to modify the surface, although these post-synthesis treatments are usually time-consuming and not environmentally friendly.  Wang and co-workers have solved these problems with their direct synthesis of water-soluble nanocrystals, which does not use toxic solvents and has no need for post-modifications.

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Formamide: an efficient solvent to synthesize water-soluble, sub-10-nanometer nanocrystals
Xun Wang, Biao Xu and Zhi Cheng Zhang
DOI: 10.1039/C3NR00643C

Gaoquan Shi and co-workers have made composite films comprising graphene oxide sheets and silk fibroin in a layered structure, which mimic natural nacre. They demonstrate a facile solution-casting method for incorporating the fibroin into graphene oxide.

The impressive mechanical properties of their material, surpassing those of natural nacre in some ways, make it potentially useful as a high-strength structural material. The biocompatibility of the material components also makes the composite promising for biological applications, such as tissue engineering.

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Strong composite films with layered structures prepared by casting silk fibroin–graphene oxide hydrogels
Liang Huang, Chun Li, Wenjing Yuan and Gaoquan Shi
DOI: 10.1039/C3NR00196B

Camouflaging nanoparticles so that they are not attacked by the immune system is a major challenge in developing long-circulating, effective drug-delivery vehicles. Attaching CD47, a transmembrane protein that serves as a universal molecular ‘marker-of-self’, to the surface of nanoparticles is one way to enable active immune evasion. However, functionalising the particle surface evenly and with uniformly oriented protein is very difficult.

Liangfang Zhang et al. show that their membrane translocation approach is very effective for functionalizing nanoparticles with molecules of CD47 in their recent Nanoscale Communication. They were able to coat nanoparticles with immunomodulatory proteins at an equivalent density to those on red blood cells, and in the correct orientation.

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‘Marker-of-self’ functionalization of nanoscale particles through a top-down cellular membrane coating approach
Che-Ming J. Hu, Ronnie H. Fang, Brian T. Luk, Kevin N. H. Chen, Cody Carpenter, Weiwei Gao, Kang Zhang and Liangfang Zhang
DOI: 10.1039/C3NR00015J

Lixia Yuan, Yunhui Huang and co-workers report a simple one-pot method to synthesize a nanocluster composite assembled by interconnected ultrafine  SnO2@C nanospheres in their recent Nanoscale paper. They found that with a mixture of sodium carboxyl methyl cellulose and styrene butadiene rubber as a binder, the SnO2@C nanocluster anode exhibits superior cycling stability and rate capability.

Electrode materials are crucial for the overall performance of lithium ion batteries. Graphite is a traditionally used anode material, and tin dioxide is one promising alternative with a higher theoretical lithium storage capacity. However, the practical use of tin dioxide is limited by its rapid capacity fading, low initial coulombic efficiency and poor rate performance. Scientists from China have recently come up with a clever solution to these problems by skilfully combining SnO2@C nanoclusters with a suitable binder.

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A SnO2@carbon nanocluster anode material with superior cyclability and rate capability for lithium-ion batteries
Min He, Lixia Yuan, Xianluo Hu, Wuxing Zhang, Jie Shu and Yunhui Huang
DOI: 10.1039/C3NR34133J

Scientists from Italy, the UK, Belgium and France provide insights into the efficiency of pyrene sulfonic sodium salts for the preparation of graphene in their recent Nanoscale paper, and clarify the role of different molecular properties on graphene exfoliation.

They compared pyrene derivatives with increasing number of sulfonic groups for their efficiency as exfoliating agents in the preparation of graphene. They combined different experimental and modelling techniques to find a correlation between the graphene-pyrene dye interaction, the molecular structure and the amount of graphene flakes solubilised. They found that a large dipole and molecular asymmetry are important for adsorption of the dye molecule on graphene. The dipole allows the molecule to “slide” into the solvent layer between the graphene surface and the aromatic core of the dye, and displace the water molecules.

The efficiency of pyrene derivatives in exfoliating graphene is well known, but the details of their interactions with graphene have been somewhat unclear so far. An understanding of these interactions is important for developing the processability of graphene, which holds great potential for technological applications in numerous fields.

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Nanoscale insight into the exfoliation mechanism of graphene with organic dyes: effect of charge, dipole and molecular structure
Andrea Schlierf, Huafeng Yang, Elias Gebremedhn, Emanuele Treossi, Luca Ortolani, Liping Chen, Andrea Minoia, Vittorio Morandi, Paolo Samorì, Cinzia Casiraghi, David Beljonne and Vincenzo Palermo
DOI: 10.1039/C3NR00258F

In their recent Nanoscale Communication, Borsali et al. varied the composition of the annealing co-solvent in order to control the orientation of nanocylinders in sugar-based block copolymer thin films. Their method, which achieves nanopatterning in three dimensions, could have important applications in next-generation nanoelectronics.

The group have developed a novel class of natural-synthetic “hybrid” block copolymer, where one of the blocks consists of poly- or oligosaccharides. The rod-like structures formed by the saccharide blocks further sterically increase the incompatibility of the hydrophobicity-hydrophilicity imbalance of the saccharide and synthetic polymer blocks.  The authors used H₂O -THF mixtures as the annealing solvent system, since the saccharide component of the polymer is soluble in H₂O, but not in THF, and vice versa for the other block polymer component. By changing the composition of the H₂O-THF mixture, the orientation of the cylinder domain in the block copolymer thin film on a silicon substrate was successfully controlled from horizontal to perpendicular.

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Control of 10 nm scale cylinder orientation in self-organized sugar-based block copolymer thin films
Issei Otsuka, Salomé Tallegas, Yoko Sakai, Cyrille Rochas, Sami Halila, Sébastien Fort, Ahmad Bsiesy, Thierry Baron and Redouane Borsali
DOI: 10.1039/C3NR00332A

Wenping Lv and Ren’an Wu from the Dalian Institute of Chemical Physics have investigated the aggregation of two graphene nanosheets in water and the role of the interfacial water monolayer in the aggregation mechanism.

They found that the interfacial water monolayers hinder the aggregation of graphene nanosheets, attributed to the many  structurally ordered H-bonds of the water monolayer. Their findings advance understanding of the hydrophobic assembly of nanomaterials, such as proteins in aqueous solution.

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The interfacial-organized monolayer water film (MWF) induced “two-step” aggregation of nanographene: both in stacking and sliding assembly pathways
Wenping Lv and Ren’an Wu
DOI: 10.1039/C3NR33447C