Science art (collection)

A beautiful collection of art based on science 

A single-atom transistor

• Martin Fuechsle,
• Jill A. Miwa,
• Suddhasatta Mahapatra,
• Hoon Ryu,
• Sunhee Lee,
• Oliver Warschkow,
• Lloyd C. L. Hollenberg,
• Gerhard Klimeck
• & Michelle Y. Simmons

• Affiliations
• Contributions
• Corresponding author

Nature Nanotechnology

 

(2012)

 

doi:10.1038/nnano.2012.21

The ability to control matter at the atomic scale and build devices with atomic precision is central to nanotechnology. The scanning tunnelling microscope¹can manipulate individual atoms² and molecules on surfaces, but the manipulation of silicon to make atomic-scale logic circuits has been hampered by the covalent nature of its bonds. Resist-based strategies have allowed the formation of atomic-scale structures on silicon surfaces³, but the fabrication of working devices—such as transistors with extremely short gate lengths⁴, spin-based quantum computers^{5, 6, 7, 8} and solitary dopant optoelectronic devices⁹—requires the ability to position individual atoms in a silicon crystal with atomic precision. Here, we use a combination of scanning tunnelling microscopy and hydrogen-resist lithography to demonstrate a single-atom transistor in which an individual phosphorus dopant atom has been deterministically placed within an epitaxial silicon device architecture with a spatial accuracy of one lattice site. The transistor operates at liquid helium temperatures, and millikelvin electron transport measurements confirm the presence of discrete quantum levels in the energy spectrum of the phosphorus atom. We find a charging energy that is close to the bulk value, previously only observed by optical spectroscopy¹⁰.

Multiphoton Lithography of Nanocrystalline Platinum and Palladium for Site-Specific Catalysis in 3D Microenvironments

Lauren D. Zarzar†, B. S. Swartzentruber‡, Jason C. Harper§, Darren R. Dunphy§, C. Jeffrey Brinker§, Joanna Aizenberg*†#, and Bryan Kaehr*§

^† Department of Chemistry and Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States

Integration of catalytic nanostructured platinum and palladium within 3D microscale structures or fluidic environments is important for systems ranging from micropumps to microfluidic chemical reactors and energy converters. We report a straightforward procedure to fabricate microscale patterns of nanocrystalline platinum and palladium using multiphoton lithography. These materials display excellent catalytic, electrical, and electrochemical properties, and we demonstrate high-resolution integration of catalysts within 3D defined microenvironments to generate directed autonomous particle and fluid transport.

Ligand-Directed Acyl Imidazole Chemistry for Labeling of Membrane-Bound Proteins on Live Cells

Sho-hei Fujishima†, Ryosuke Yasui†, Takayuki Miki†, Akio Ojida*‡, and Itaru Hamachi*†

^† Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan

^‡ Graduate School of Pharmaceutical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/ja2108855

Publication Date (Web): February 21, 2012

Copyright © 2012 American Chemical Society

Chemistry-based protein labeling in living cells is undoubtedly useful for understanding natural protein functions and for biological/pharmaceutical applications. Here, we report a novel approach for endogenous membrane-bound protein labeling for both in vitro and live cell conditions. A moderately reactive alkyloxyacyl imidazole (AI) assisted by ligand-binding affinity (ligand-directed AI (LDAI)) chemistry allowed us to selectively modify natural proteins, such as dihydrofolate reductase (DHFR) and folate receptor (FR), neither of which could be efficiently labeled using the recently developed ligand-directed tosylate approach. It was clear that LDAI selectively labeled a single Lys(K32) in DHFR, proximal to the ligand-binding pocket. We also demonstrate that the fluorescein-labeled (endogenous, by LDAI) FR works as a fluorescent biosensor on the live KB cell surface, which allowed us to carry out unprecedented in situ kinetic analysis of ligand binding to FR.

Inverse-Phosphocholine Lipids: A Remix of a Common Phospholipid

Emily K. Perttu, Aditya G. Kohli, and Francis C. Szoka, Jr.*

Department of Bioengineering and Therapeutic Sciences, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, California 94143-0912, United States

The UC Berkeley-UCSF Graduate Program in Bioengineering, University of California Berkeley, Berkeley, CA 94720-1762, United States

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/ja210989h

Publication Date (Web): February 27, 2012

Copyright © 2012 American Chemical Society

Zwitterionic inverse-phosphocholine (iPC) lipids contain headgroups with an inverted charge orientation relative to phosphocholine (PC) lipids. The iPC lipid headgroup has a quaternary amine adjacent to the bilayer interface and a phosphate that extends into the aqueous phase. Neutral iPC lipids with ethylated phosphate groups (CPe) and anionic iPC lipids nonethylated phosphate groups (CP) were synthesized. The surface potential of CPe liposomes remains negative across a broad pH range and in the presence of up to 10 mM Ca²⁺. CP liposomes aggregate in the presence of Ca²⁺, but at a slower rate than other anionic lipids. Hydrolysis of CP lipids by alkaline phosphatases generates a cationic lipid. CPe liposomes release encapsulated anionic carboxyfluorescein (CF) 20 times faster than PC liposomes and release uncharged glucose twice as fast as PC liposomes. As such, iPC lipids afford a unique opportunity to investigate the biophysical and bioactivity-related ramifications of a charge inversion at the bilayer surface.

Direct Transfer Patterning of Electrically Small Antennas onto Three-Dimensionally Contoured Substrates

1. Carl Pfeiffer¹, 
2. Xin Xu², 
3. Stephen R. Forrest^3,*, 
4. Anthony Grbic^1,*

Article first published online: 31 JAN 2012

DOI: 10.1002/adma.201104290

A direct transfer patterningprocess is presented that allows metallic patterns to be stamped onto a contoured substrate. This process was used to make some of the most efficient electrically small antennas to date, while maintaining bandwidths approaching the physical limit.

Controlled Synthesis of 3D Multi-Compartmental Particles with Centrifuge-Based Microdroplet Formation from a Multi-Barrelled Capillary

1. Kazuki Maeda¹, 
2. Hiroaki Onoe^1,2,
3. Masahiro Takinoue^1,†, 
4. Shoji Takeuchi^1,2,*

Article first published online: 6 FEB 2012

Controlled synthesis of micro multi-compartmental particles using a centrifuge droplet shooting device (CDSD) is reported. Sodium alginate solutions introduced in a multi-barreled capillary form droplets at the capillary orifice under ultrahigh gravity and gelify in a CaCl₂ solution. The size, shape, and compartmentalization of the particles are controlled. Co-encapsulation of Jurkat cells and magnetic colloids into Janus particles is demonstrated. The Janus particles present sensitive reaction toward magnetic fields, while the viability of the encapsulated cells is 91%.

Broadband light management using low-Q whispering gallery modes in spherical nanoshells

• Yan Yao,
• Jie Yao,
• Vijay Kris Narasimhan,
• Zhichao Ruan,
• Chong Xie,
• Shanhui Fan
• & Yi Cui

• Affiliations
• Contributions
• Corresponding author

Nature Communications

 

3,

 

Article number:

 

664

 

doi:10.1038/ncomms1664

Received

 

28 July 2011 

Accepted

 

03 January 2012 

Published

 

07 February 2012

Light trapping across a wide band of frequencies is important for applications such as solar cells and photodetectors. Here, we demonstrate a new approach to light management by forming whispering-gallery resonant modes inside a spherical nanoshell structure. The geometry of the structure gives rise to a low quality-factor, facilitating the coupling of light into the resonant modes and substantial enhancement of the light path in the active material, thus dramatically improving absorption. Using nanocrystalline silicon (nc-Si) as a model system, we observe broadband absorption enhancement across a large range of incident angles. The absorption of a single layer of 50-nm-thick spherical nanoshells is equivalent to a 1-μm-thick planar nc-Si film. This light-trapping structure could enable the manufacturing of high-throughput ultra-thin film absorbers in a variety of material systems that demand shorter deposition time, less material usage and transferability to flexible substrates.

Polydiacetylene paper-based colorimetric sensor array for vapor phase detection and identification of volatile organic compounds

J. Mater. Chem., 2012, Advance Article

Detection and identification of VOCs in their vapor phase is essential for safety and quality assessment. In this work, a novel platform of a paper-based polydiacetylene (PDA) colorimetric sensor array is prepared from eight diacetylene monomers, six of which are amphiphilic and the other two are bolaamphiphilic. To fabricate the sensors, monomers are coated onto a filter paper surface using the drop-casting technique and converted to PDAs by UV irradiation. The PDA sensors show solvent induced irreversible color transition upon exposure to VOC vapors. When combined into a sensing array, the color change pattern as measured by RGB values and statistically analyzed by principal component analysis (PCA) is capable of distinguishing 18 distinct VOCs in the vapor phase. The PCA score and loading plots also allow the reduction of the sensing elements in the array from eight to three PDAs that are capable of classifying 18 VOCs. Utilizing an array containing only two PDAs, various types of automotive fuels including gasoline, gasohol and diesel are successfully classified.