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NEWS


MATERIALS SCIENCE Transforming synthesis MARIA BURKE


Australian researchers have used liquid metals to create two-dimensional materials no thicker than a few atoms. The breakthrough could transform chemical synthesis, and eventually be applied to enhance data storage and make faster electronics. Two-dimensional oxides


have a variety of applications in electronics and other areas. However, many oxides are not easy to synthesise as 2D materials because of the challenges in peeling off thin sheets from bulk crystals. Kourosh Kalantar-zadeh


and Torben Daeneke from RMIT University’s School of Engineering in Melbourne exploited liquid


BIOCHEMISTRY Gut bacteria aid immunity MARIA BURKE


Laboratory mice given the gut bacteria of wild mice can survive flu virus infection and fight colorectal cancer much better. The wild mice’s immunological advantages may partly explain why disease experiments in lab mice often turn out very differently in humans or other animals.


Mammals depend on their microbiota:


the collection of microorganisms they host in and on their bodies. Lab mice are carefully bred, fed and raised in tightly controlled conditions so that each mouse has predictable traits and genetics. While a great advantage in biology research, it means that a controlled environment – and not the survival pressures of the outside world – has shaped the microbiotas of lab mice. To see if this might explain why lab


mice are limited in how well they model mammalian diseases, the team trapped more than 800 wild mice from eight locations to find suitable candidates for gut microbiota donation. Then they compared the gut microbiomes – collective gut microbiota genomes – of the wild mice and a common strain of laboratory mice called C57BL/6. Next, they introduced the microbiota of wild mice to pregnant, germ-free C57BL/6


mice. (Germ-free mice are raised in a sterile environment and don’t have microbiomes of their own.) For a control group comparison, the researchers also introduced microbiota from ordinary C57BL/6 mice into a separate group of pregnant, germ-free mice. Four generations later, the mice still carried either the wild microbiomes or the control lab microbiomes. When exposed to a high dose of influenza virus, 92% of the lab mice with wild microbiomes survived, compared with only 17% of lab mice and control group mice (Cell, doi: http:// dx.doi.org/10.1016/j. cell.2017.09.016). In other experiments, the lab mice without wild microbiomes had a greater number of tumours and more severe disease when induced with colorectal cancer. In both models, the beneficial effects


of the wild microbiota were associated with reduced inflammation. ‘We think that by restoring the natural


‘microbial identity’ of laboratory mice, we will improve the modelling of complex diseases of free-living mammals, which includes humans,’ says senior author Barbara Rehermann of the National Institute of Health’s Institute of Diabetes and Digestive and Kidney Diseases in Bethesda, Maryland, US. Natural microbiota could help researchers discover protective


mechanisms relevant in the natural world.


metals at room temperature to synthesise 2D oxides of gallium, hafnium, gadolinium and aluminium. They used non-toxic eutectic gallium-based alloys as the reaction solvent. The 2D sheets appeared on the surface after Hf, Gd, or Al was dissolved into the bulk alloy and were isolated either on substrates or in suspension, as extremely thin sub-nanometer layers of HfO2 Al2


, O3 , and Gd2 O3 (Science, doi:


10.1126/science.aao4249). ‘We found an extraordinary,


yet very simple method to create atomically thin flakes of materials that don’t naturally exist as layered structures,’ says Daeneke. ‘This oxide layer can then be exfoliated by simply touching the liquid metal with a smooth surface,’ he explains.


‘Larger quantities of these atomically thin layers can be produced by injecting air into the liquid metal, in a process similar to frothing milk when making a cappuccino.’ The process is cheap and


simple, he added: ‘I could give these instructions to my mum, and she would be able to do this at home.’


The 2D oxide that surfaces


is the oxide with the lowest energy, suggesting that it should be possible to make other 2D oxides using the same process, as well as create other previously inaccessible 2D materials. The discovery should have


profound implications, says Kalantar-zadeh. ‘We predict the developed technology applies to approximately one-third


of the periodic table. Many of these atomically thin oxides are semiconducting or dielectric materials. Semiconducting and dielectric components are the foundation of today’s electronic and optical devices. Working with atomically thin components is expected to lead to better, more energy efficient electronics. This technological capability has never been accessible before.’ The breakthrough could also be applied to catalysis as metal oxides are common catalysts. ‘This method takes [synthesis]


to the next level of producing metal oxides,’ comments Melik Demirel of Penn State University. ‘Beyond synthesis, the key discovery will be when these materials demonstrate novel properties.’


09 | 2017


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