Weekly Featured Paper

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1 Reading and writing single-atom magnets

Authors: Fabian D. Natterer, Kai Yang, William Paul, Philip Willke, Taeyoung Choi,Thomas Greber1,5, Andreas J. Heinrich and Christopher P. Lutz. Choi, Taeyoung, William Paul, Steffen Rolf-Pissarczyk, Andrew J. Macdonald, Fabian D. Natterer, Kai Yang, Philip Willke, Christopher P. Lutz, and Andreas J. Heinrich. "Atomic-scale sensing of the magnetic dipolar field from single atoms." Nature Nanotechnology (2017).[1]

The single-atom bit represents the ultimate limit of the classical approach to high-density magnetic storage media. So far, the smallest individually addressable bistable magnetic bits have consisted of 3–12 atoms. Long magnetic relaxation times have been demonstrated for single lanthanide atoms in molecular magnets, for lanthanides diluted in bulk crystals, and recently for ensembles of holmium (Ho) atoms supported on magnesium oxide (MgO). These experiments suggest a path towards data storage at the atomic limit, but the way in which individual magnetic centres are accessed remains unclear. Here we demonstrate the reading and writing of the magnetism of individual Ho atoms on MgO, and show that they independently retain their magnetic information over many hours. We read the Ho states using tunnel magnetoresistance and write the states with current pulses using a scanning tunnelling microscope. The magnetic origin of the longlived states is confirmed by single-atom electron spin resonance on a nearby iron sensor atom, which also shows that Ho has a large out-of-plane moment of 10.1±0.1 Bohr magnetons on this surface. To demonstrate independent reading and writing, we built an atomic-scale structure with two Ho bits, to which we write the four possible states and which we read out both magnetoresistively and remotely by electron spin resonance. The high magnetic stability combined with electrical reading and writing shows that single-atom magnetic memory is indeed possible.

2 Silver nanoparticle-embedded polymersome nanocarriers for the treatment of antibiotic-resistant infections

Authors: Benjamin M. Geilich, Anne L. van de Ven, Gloria L. Singleton, Liuda J. Sepúlveda, Srinivas Sridhar, Thomas J. Webster.

Journal: Nanoscale, doi: 10.1039/C4NR05823B [2]

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The rapidly diminishing number of effective antibiotics that can be used to treat infectious diseases and associated complications in a physician’s arsenal is having a drastic impact on human health today. This study explored the development and optimization of a polymersome nanocarrier formed from a biodegradable diblock copolymer to overcome bacterial antibiotic resistance. Here, polymersomes were synthesized containing silver nanoparticles embedded in the hydrophobic compartment, and ampicillin in the hydrophilic compartment. Results showed for the first time that these silver nanoparticle-embedded polymersomes (AgPs) inhibited the growth of Escherichia coli transformed with a gene for ampicillin resistance (bla) in a dose-dependent fashion. Free ampicillin, AgPs without ampicillin, and ampicillin polymersomes without silver nanoparticles had no effect on bacterial growth. The relationship between the silver nanoparticles and ampicillin was determined to be synergistic and produced complete growth inhibition at a silver-to-ampicillin ratio of 1 : 0.64. In this manner, this study introduces a novel nanomaterial that can effectively treat problematic, antibiotic-resistant infections in an improved capacity which should be further examined for a wide range of medical applications.