Electrical, Optical, and Docking Properties of Conical Nanopores

Yao-Qun Li†*, Yu-Bin Zheng†, and Richard N. Zare‡*

^† Department of Chemistry, Xiamen University, Xiamen, 361005 China

^‡ Department of Chemistry, Stanford University, Stanford, California 94305-5080, United States

ACS Nano, Article ASAP

DOI: 10.1021/nn300356d

Publication Date (Web): February 3, 2012

Copyright © 2012 American Chemical Society

The diffusion-influenced translocation behavior of individual nanoparticles upon passage through a conical nanopore has been elucidated by using a pressure-reversal, resistive-pulse technique, as reported by Lan and White in this issue of ACS Nano. We outline here some recent progress in conical nanopore analysis, and we present some prospects for future developments. Compared to cylindrical nanopores, the geometric change brought about by tapered nanopores causes a dramatic difference in electrical and optical properties. Such conical nanopores may also be integrated into microfluidic chips to capture cells or nanoparticles, one per nanopore, and then to release them. These advances hold the promise of making conical nanopores useful as highly efficient actuators and sensors.

Massively Parallel Bacterial and Yeast Suspension Culture on a Chip

1. Mingzhe Gan¹, 
2. Yunfang Tang¹, 
3. Yiwei Shu²,
4. Hongkai Wu², 
5. Liwei Chen^1,*

Article first published online: 1 FEB 2012

DOI: 10.1002/smll.201102322

A new microfluidic chip integrated with 120 parallelmicrobial suspension culture units is demonstrated. Various bacterial strains and even yeast can be cultivated on the chip. With a high degree of integration and simple fabrication process, this chip could be a central component for future high-throughput microbial screening and selection systems

Manipulating Protein Conformations by Single-Molecule AFM-FRET Nanoscopy

Yufan He, Maolin Lu, Jin Cao, and H. Peter Lu*

Center for Photochemical Sciences, Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403, United States

ACS Nano, Article ASAP

DOI: 10.1021/nn2038669

Publication Date (Web): January 25, 2012

Copyright © 2012 American Chemical Society

Combining atomic force microscopy and fluorescence resonance energy transfer spectroscopy (AFM-FRET), we have developed a single-molecule AFM-FRET nanoscopy approach capable of effectively pinpointing and mechanically manipulating a targeted dye-labeled single protein in a large sampling area and simultaneously monitoring the conformational changes of the targeted protein by recording single-molecule FRET time trajectories. We have further demonstrated an application of using this nanoscopy on manipulation of single-molecule protein conformation and simultaneous single-molecule FRET measurement of a Cy3–Cy5-labeled kinase enzyme, HPPK (6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase). By analyzing time-resolved FRET trajectories and correlated AFM force pulling curves of the targeted single-molecule enzyme, we are able to observe the protein conformational changes of a specific coordination by AFM mechanic force pulling.

Microdroplet Patterning: Designer Hydrophilic Regions Regulate Droplet Shape for Controlled Surface Patterning and 3D Microgel Synthesi

1. Matthew J. Hancock^4,†, 
2. Fumiki Yanagawa^4,†, 
3. Yun-Ho Jang⁴, 
4. Jiankang He^4,5, 
5. Nezamoddin N. Kachouie⁴, 
6. Hirokazu Kaji^4,6, 
7. Ali Khademhosseini^1,2,3,4,*

Article first published online: 30 JAN 2012

DOI: 10.1002/smll.201290019

The cover image shows how the shape of micro- and nanodroplets can be controlled by patterning surfaces with special hydrophilic regions surrounded by hydrophobic boundaries. Shaped droplets may be used as a simple tool to controllably pattern planar surfaces with microparticles and cells. Under spiral droplets, a gradient deposition pattern is observed. Shaped droplets of prepolymer solution may also be crosslinked to synthesize microgels with tailored 3D geometry. Finite element simulations provide a design platform by linking the shape of the hydrophilic regions to that of the droplets, microgels, and particle deposition patterns.

Focusing on Energy and Optoelectronic Applications: A Journey for Graphene and Graphene Oxide at Large Scale

Xiangjian Wan, Yi Huang, and Yongsheng Chen*

Key Laboratory of Functional Polymer Materials and the Centre of Nanoscale Science and Technology, Institute of Polymer Chemistry, College of Chemistry, Nankai University, Tianjin, 300071, China

Acc. Chem. Res., Article ASAP

DOI: 10.1021/ar200229q

Publication Date (Web): January 26, 2012

Copyright © 2012 American Chemical Society

Carbon is the only element that has stable allotropes in the 0th through the 3rd dimension, all of which have many outstanding properties. Graphene is the basic building block of other important carbon allotropes. Studies of graphene became much more active after the Geim group isolated “free” and “perfect” graphene sheets and demonstrated the unprecedented electronic properties of graphene in 2004. So far, no other individual material combines so many important properties, including high mobility, Hall effect, transparency, mechanical strength, and thermal conductivity.

In this Account, we briefly review our studies of bulk scale graphene and graphene oxide (GO), including their synthesis and applications focused on energy and optoelectronics. Researchers use many methods to produce graphene materials: bottom-up and top-down methods and scalable methods such as chemical vapor deposition (CVD) and chemical exfoliation. Each fabrication method has both advantages and limitations. CVD could represent the most important production method for electronic applications. The chemical exfoliation method offers the advantages of easy scale up and easy solution processing but also produces graphene oxide (GO), which leads to defects and the introduction of heavy functional groups. However, most of these additional functional groups and defects can be removed by chemical reduction or thermal annealing. Because solution processing is required for many film and device applications, including transparent electrodes for touch screens, light-emitting devices (LED), field-effect transistors (FET), and photovoltaic devices (OPV), flexible electronics, and composite applications, the use of GO is important for the production of graphene.

Because graphene has an intrinsic zero band gap, this issue needs to be tackled for its FET applications. The studies for transparent electrode related applications have made great progress, but researchers need to improve sheet resistance while maintaining reasonable transparency. Proposals for solving these issues include doping or controlling the sheet size and defects, and theory indicates that graphene can match the overall performance of indium tin oxide (ITO). We have significantly improved the specific capacitance in graphene supercapacitor devices, though our results do not yet approach theoretical values. For composite applications, the key issue is to prevent the restacking of graphene sheets, which we achieved by adding blocking molecules.

The continued success of graphene studies will require further development in two areas: (1) the large scale and controlled synthesis of graphene, producing different structures and quantities that are needed for a variety of applications and (2) on table applications, such as transparent electrodes and energy storage devices. Overall, graphene has demonstrated performance that equals or surpasses that of other new carbon allotropes. These features, combined with its easier access and better processing ability, offer the potential basis for truly revolutionary applications and as a future fundamental technological material beyond the silicon age.