Graphene Quantum Dots Derived from Carbon Fibers

Juan Peng†‡, Wei Gao§, Bipin Kumar Gupta†, Zheng Liu†, Rebeca Romero-Aburto†, Liehui Ge†, Li Song#, Lawrence B. Alemany§, Xiaobo Zhan†, Guanhui Gao†, Sajna Antony Vithayathil, Benny Abraham Kaipparettu, Angel A. Marti§, Takuya Hayashi+, Jun-Jie Zhu*‡, and Pulickel M. Ajayan*†§

^† Mechanical Engineering and Materials Science Department, Rice University, Houston, Texas 77005, United States

^‡ State Key Lab of Analytical Chemistry for Life Science, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, P. R. China

^§ Department of Chemistry, Rice University, Houston, Texas 77005, United States

 National Physical Laboratory (CSIR), Dr K S Krishnan Road, New Delhi 110012, India

 Department of Molecular Pathology, The University of Texas, MD. Anderson Cancer Center, Houston Texas 77054, United States

^# Research Center for Exotic Nanocarbons, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan

 Institute of Materials Science and Engineering, Ocean University of China, Qingdao, 266003, P.R. China

 Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, United States

 Department of Chemistry and Bioengineering, Rice University, Houston, Texas 77005, United States

⁺ Faculty of Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan

Nano Lett., Article ASAP

DOI: 10.1021/nl2038979

Publication Date (Web): January 4, 2012

Graphene quantum dots (GQDs), which are edge-bound nanometer-size graphene pieces, have fascinating optical and electronic properties. These have been synthesized either by nanolithography or from starting materials such as graphene oxide (GO) by the chemical breakdown of their extended planar structure, both of which are multistep tedious processes. Here, we report that during the acid treatment and chemical exfoliation of traditional pitch-based carbon fibers, that are both cheap and commercially available, the stacked graphitic submicrometer domains of the fibers are easily broken down, leading to the creation of GQDs with different size distribution in scalable amounts. The as-produced GQDs, in the size range of 1–4 nm, show two-dimensional morphology, most of which present zigzag edge structure, and are 1–3 atomic layers thick. The photoluminescence of the GQDs can be tailored through varying the size of the GQDs by changing process parameters. Due to the luminescence stability, nanosecond lifetime, biocompatibility, low toxicity, and high water solubility, these GQDs are demonstrated to be excellent probes for high contrast bioimaging and biosensing applications.

Crumpled Nanopaper from Graphene Oxide

Xiaofei Ma†‡, Michael R. Zachariah†‡, and Christopher D. Zangmeister*†

^† Material Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States

^‡ Department of Mechanical Engineering and Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States

Nano Lett., Article ASAP

DOI: 10.1021/nl203964z

Publication Date (Web): December 20, 2011

Graphene oxide (GO) in aqueous solution was aerosolized and rapidly dried to produce crumpled nanopaper-like sheets. Online size selection and aerosol mass analysis was used to determine the fractal dimension (D) of crumpled GO nanosheets as 2.54 ± 0.04. That is identical to macroscale materials, such as crumpled balls of paper and foil. Thermal reduction of crumpled GO nanosheets did not change D, even after loss of nearly 25% of the nanosheets mass. We demonstrate that D is able to be tuned by altering solvent conditions. A 10% acetone mixture increased D to 2.68 ± 0.02. Calculations of the confinement force show that crumpling of GO nanosheets is driven by the capillary force associated with rapid solvent loss.

Magnetic Helical Micromachines: Fabrication, Controlled Swimming, and Cargo Transport

1. Soichiro Tottori^1,2, 
2. Li Zhang^1,*, 
3. Famin Qiu¹,
4. Krzysztof K. Krawczyk³, 
5. Alfredo Franco-Obregón³, 
6. Bradley J. Nelson¹

Article first published online: 2 JAN 2012

A simple and general fabrication method for helical swimming micromachines by direct laser writing and e-beam evaporation is demonstrated. The magnetic helical devices exhibit varying magnetic shape anisotropy, yet always generate corkscrew motion using a rotating magnetic field. They also exhibit good swimming performance and are capable of pick-and-place micromanipulation in 3D. Cytotoxicity of the devices was investigated using mouse myoblasts.

Inkjet Printing High-Resolution, Large-Area Graphene Patterns by Coffee-Ring Lithography

1. Lei Zhang^1,2, 
2. Hongtao Liu^1,2, 
3. Yan Zhao^1,2,
4. Xiangnan Sun^1,2, 
5. Yugeng Wen^1,2, 
6. Yunlong Guo¹, 
7. Xike Gao³, 
8. Chong-an Di¹, 
9. Gui Yu¹,
10. Yunqi Liu^1,*

Article first published online: 21 DEC 2011

Taking advantage of the “coffee-ring” effect, graphene electrodes with channel lengths as low as 1−2 micrometers are patterned by inkjet printing. Organic thin film transistors and complementary inverters are also fabricated using these graphene electrodes and show excellent performance.

Hydrogen-Bubble-Propelled Zinc-Based Microrockets in Strongly Acidic Media

Wei Gao, Aysegul Uygun, and Joseph Wang*

Department of Nanoengineering, University of California, San Diego, La Jolla, California 92093, United States

J. Am. Chem. Soc., Article ASAP

DOI: 10.1021/ja210874s

Publication Date (Web): December 20, 2011

Copyright © 2011 American Chemical Society

Tubular polyaniline (PANI)/Zn microrockets are described that display effective autonomous motion in extreme acidic environments, without any additional chemical fuel. These acid-driven hydrogen-bubble-propelled microrockets have been electrosynthesized using the conical polycarbonate template. The effective propulsion in acidic media reflects the continuous thrust of hydrogen bubbles generated by the spontaneous redox reaction occurring at the inner Zn surface. The propulsion characteristics of PANI/Zn microrockets in different acids and in human serum are described. The observed speed–pH dependence holds promise for sensitive pH measurements in extreme acidic environments. The new microrockets display an ultrafast propulsion (as high as 100 body lengths/s) along with attractive capabilities including guided movement and directed cargo transport. Such acid-driven microtubular rockets offer considerable potential for diverse biomedical and industrial applications.

Transparent and Conducting Graphene–RNA-Based Nanocomposites

1. Faranak Sharifi², 
2. Reg Bauld², 
3. M. Shafiq Ahmed², 
4. Giovanni Fanchini^1,*

Article first published online: 27 DEC 2011

Ribonucleic acid (RNA) is proposed as a nonionic surfactant for the efficient exfoliation of graphite in thin flakes of few-layer graphene and the subsequent preparation of transparent and conducting thin films. Parameters such as the type of RNA used and the size of starting graphite flakes are demonstrated to be essential for obtaining RNA–graphene thin films of good quality. A model explaining the exfoliation of graphene by RNA in water is suggested. A number of post- and predeposition treatments (including thermal annealing, functionalization of the films, and the preoxidation of graphite) are critical to improve the performance of graphene–RNA nanocomposites as transparent conductors. The study establishes an ideal link between RNA and graphene, the fundamental building blocks for nanobiology and carbon-based nanotechnology.

Imbricate Scales as a Design Construct for Microsystem Technologies

1. Seok Kim¹, 
2. Yewang Su², 
3. Agustin Mihi³,
4. Seungwoo Lee⁴, 
5. Zhuangjian Liu⁵, 
6. Tanmay K. Bhandakkar¹, 
7. Jian Wu⁶, 
8. Joseph B. Geddes III³, 
9. Harley T. Johnson¹, 
10. Yongwei Zhang⁵, 
11. Jung-Ki Park⁴, 
12. Paul V. Braun³,
13. Yonggang Huang², 
14. John A. Rogers^7,*

Article first published online: 19 DEC 2011

Spatially overlapping plates in tiled configurations represent designs that are observed widely in nature (e.g., fish and snake scales) and man-made systems (e.g., shingled roofs) alike. This imbricate architecture offers fault-tolerant, multifunctional capabilities, in layouts that can provide mechanical flexibility even with full, 100% areal coverages of rigid plates. Here, the realization of such designs in microsystems technologies is presented, using a manufacturing approach that exploits strategies for deterministic materials assembly based on advanced forms of transfer printing. The architectures include heterogeneous combinations of silicon, photonic, and plasmonic scales, in imbricate layouts, anchored at their centers or edges to underlying substrates, ranging from elastomer sheets to silicon wafers. Analytical and computational mechanics modeling reveal distributions of stress and strain induced by deformation, and provide some useful design rules and scaling laws.