All-Organic Vapor Sensor Using Inkjet-Printed Reduced Graphene Oxide

Films of graphene oxide and reduced graphene oxide are printed onto a flexible plastic surface (see picture), using inkjet techniques, which are used to detect chemically aggressive vapors such as NO₂ and Cl₂. Vapors in the 100 ppm–500 ppb concentration range can be detected in an air sample without the aid of a vapor concentrator.

http://onlinelibrary.wiley.com/doi/10.1002/anie.200905089/abstract


Angew. Chem. Int. Ed. 2010, 49, 2154 –2157

Dispersion of Alkyl-Chain-Functionalized Reduced Graphene Oxide Sheets in Nonpolar Solvents

Alkyl chains were grafted onto reduced graphene oxide sheets to allow their dispersion in toluene, a common and representative nonpolar solvent. The grafting occurred on a variety of oxygen-containing functionalities already present on reduced graphene oxide, such as hydroxyl and epoxide groups. The structure and the defect density of the sheets were not significantly altered during the synthesis. When dispersed in water−toluene mixtures, phase transfer from the aqueous to the organic phase was observed upon grafting. In addition, the dry powder obtained readily disperses in common organic solvents without the assistance of any sonication treatment.

http://pubs.acs.org/doi/abs/10.1021/la2051614

Langmuir. 2012, 28, 6691−6697

Graphene-Based Conducting Inks for Direct Inkjet Printing of Flexible Conductive Patterns and Their Applications in Electric Circuits and Chemical Sensors

A series of inkjet printing processes have been studied using graphene-based inks. Under optimized conditions, using water-soluble single-layered graphene oxide (GO) and few-layered graphene oxide (FGO), various high image quality patterns could be printed on diverse flexible substrates, including paper, poly(ethylene terephthalate) (PET) and polyimide (PI), with a simple and low-cost inkjet printing technique. The graphene-based patterns printed on plastic substrates demonstrated a high electrical conductivity after thermal reduction, and more importantly, they retained the same conductivity over severe bending cycles. Accordingly, flexible electric circuits and a hydrogen peroxide chemical sensor were fabricated and showed excellent performances, demonstrating the applications of this simple and practical inkjet printing technique using graphene inks. The results show that graphene materials—which can be easily produced on a large scale and possess outstanding electronic properties—have great potential for the convenient fabrication of flexible and low-cost graphene based electronic devices, by using a simple inkjet printing technique.

http://nanocenter.nankai.edu.cn/script/nanocenter/PDF/Nano%20Res_2011_LH.pdf

Nano Res. 2011, 4(7): 675–684

Structural evolution during the reduction of chemically derived graphene oxide

The excellent electrical, optical and mechanical properties of graphene have driven the search to find methods for its large-scale production, but established procedures (such as mechanical exfoliation or chemical vapour deposition) are not ideal for the manufacture of processable graphene sheets. An alternative method is the reduction of graphene oxide, a material that shares the same atomically thin structural framework as graphene, but bears oxygen-containing functional groups. Here we use molecular dynamics simulations to study the atomistic structure of progressively reduced graphene oxide. The chemical changes of oxygen-containing functional groups on the annealing of graphene oxide are elucidated and the simulations reveal the formation of highly stable carbonyl and ether groups that hinder its complete reduction to graphene. The calculations are supported by infrared and X-ray photoelectron spectroscopy measurements. Finally, more effective reduction treatments to improve the reduction of graphene oxide are proposed.


http://www.nature.com/nchem/journal/v2/n7/abs/nchem.686.html

Nature Chemistry, 2010,

2,

 

581–587.

High-quality single-layer graphene via reparative reduction of graphene oxide

Reduction of graphene oxide (GO) is a promising low-cost synthetic approach to bulk graphene, which offers an accessible route to transparent conducting films and flexible electronics. Unfortunately, the release of oxygen-containing functional groups inevitably leaves behind vacancies and topological defects on the reduced GO sheet, and its low electrical conductivity hinders the development of practical applications. Here, we present a strategy for real-time repair of the newborn vacancies with carbon radicals produced by thermal decomposition of a suitable precursor. The sheet conductivity of thus-obtained single-layer graphene was raised more than six-fold to 350–410 S/cm (whilst retaining >96% transparency). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy revealed that the conductivity enhancement can be attributed to the formation of additional sp2-C structures. This method provides a simple and efficient process for obtaining highly conductive transparent graphene films.


http://www.springerlink.com/content/k127017578016174/

Nano Res. 2011, 4(5): 434–439

Highly Heat and Oxidation-Resistant Materials Prepared Using Silicon- Containing Thermosetting Polymers

Highly heat and oxidation-resistant materials prepared using the silicon-containing thermosetting polymer, poly[(phenylsilylene)ethynylene-1,3-phenyleneethynylene] [-Si(Ph)(H)-C􀀁C-C6H4-C􀀁C-] are summarized. This polymer is light, moldable, soluble in solvent, and highly heat resistant. It is prepared by the dehydrogenative cross-coupling reaction of the Si-H bond of phenylsilane and the C-H bond of 1,3 diethynylbenzene in the presence of base catalysts. Applications of the polymer to particularly composite and ceramic materials are reviewed. Other polymers with molecules containing [Si(H)~C􀀁C] units are discussed. The chemistry and possible applications of the [Si(H)~C􀀁C] unit are also discussed.


http://www.benthamscience.com/open/tomsj/articles/V005/152TOMSJ.pdf

The Open Materials Science Journal, 2011, 5, 152-161

Solvent effects on the charge storage ability in polypyrrole

Solvent e€ect on the charge storage ability of the polypyrrole have been studied in two di€erent ways: analyzing
both the ion-solvent and polymer-solvent interactions and by a multiple regression procedure. The first way was not sucient to explain all the results obtained. By the multiple regression, influence of the four di€erent variables of the solvents simultaneously has been obtained. Solvents having high dipole moments and low polarizability and having a high capacity to donate electrons are the best solvents among those investigated in this paper to obtain high charge storage abilities.


http://www.upct.es/~equimica/laboratorio/ArticulosenPDF/Electrochim.%20Acta/1999%20Electrochim.%20Acta%2044pg2053.pdf

Electrochimica Acta 44 (1999) 2053±2059

Challenges in the development of advanced Li-ion batteries: a review

http://pubs.rsc.org/en/content/articlepdf/2011/ee/c1ee01598b

Li-ion battery technology has become very important in recent years as these batteries show great promise as power sources that can lead us to the electric vehicle (EV) revolution. The development of new materials for Li-ion batteries is the focus of research in prominent groups in the field of materials science throughout the world. Li-ion batteries can be considered to be the most impressive success story of modern electrochemistry in the last two decades. They power most of today's portable devices, and seem to overcome the psychological barriers against the use of such high energy density devices on a larger scale for more demanding applications, such as EV. Since this field is advancing rapidly and attracting an increasing number of researchers, it is important to provide current and timely updates of this constantly changing technology. In this review, we describe the key aspects of Li-ion batteries: the basic science behind their operation, the most relevant components, anodes, cathodes, electrolyte solutions, as well as important future directions for R&D of advanced Li-ion batteries for demanding use, such as EV and load-leveling applications.

Studying the Characteristics of Polypyrrole and its Composites

Polypyrrole and its composites were prepared chemically using FeCl3 as an oxidant in aqueous and non-aqueous media. The effect of various solutions such as water, ethylacetate, acetonitrile, methylacetate, methanol, ethylmethylketone and surface active agents, poly (ethylene glycol) and poly (vinyl acetate) on the properties of product were studied. The electrically conducting polymer and its composites have been characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopy. The results indicate that the morphology, conductivity and structure of products are dependent on the type of solution and additive.

World Journal of Chemistry. 2007, 2 (2), 67-74.

http://idosi.org/wjc/2(2)07/3.pdf

Polymers with Tailored Electronic Structure for High Capacity Lithium Battery Electrodes

A conductive polymer is developed for solving the long-standing volume change issue in lithium battery electrodes. A combination of synthesis, spectroscopy and simulation techniques tailors the electronic structure of the polymer to enable in situ lithium doping. Composite anodes based on this polymer and commercial Si particles exhibit 2100 mAh g⁻¹ in Si after 650 cycles without any conductive additive.


Adv. Mater. 2011, 23, 4679–4683

http://onlinelibrary.wiley.com/doi/10.1002/adma.201102421/pdf

Selection of Conductive Additives in Li-Ion Battery Cathodes

The lithium-ion cell has been successively improved with adoption of new cathode electrochemistries, from LiCoO₂ to higher-capacity LiNi_1−xCo_xO₂ to lower cost LiNi_1−xCo_xO₂. The addition of conductive additives to cathode materials has been demonstrated to improve each type. Four systems have emerged as important cathodes in recent studies: (i) the spinel LiMn₂O₄, (ii) LiFePO₄, (iii) the “Gen 2” material, Li(Ni_0.8Co_0.15Al_0.05)O₂, and (iv) the Li(Ni_1/3Co_1/3Mn_1/3)O₂system. The architectures of model composite cathodes weregenerated using our prior approach in simulating packing of polydisperse arrangements; conductivity was then simulated for several realizations of each case. A key finding was that the conductive coatings significantly improve overall conductivity. Percolation was achieved for the volume fraction of active material (30%) in studied cases, which was larger than the percolation threshold (29%) for a 3D spherical particulate system. Neither surface nor bulk modifications of active-material particle conductivities seem desirable targets for improvement of laminate conductivity at present. As part of future work, trade-offs between conductivity and capacity will be considered. 



J. Electrochem. Soc. 154, A978 (2007)

http://dx.doi.org/10.1149/1.2767839

Electrical energy storage for transportation—approaching the limits of, and going beyond, lithium-ion batteries

Electrical energy storage for transportation—approaching the limits of, and going beyond, lithium-ion batteries

The escalating and unpredictable cost of oil, the concentration of major oil resources in the hands of a few politically sensitive nations, and the long-term impact of CO2 emissions on global climate constitute a major challenge for the 21st century. They also constitute a major incentive to harness alternative sources of energy and means of vehicle propulsion. Today’s lithium-ion batteries, although suitable for small-scale devices, do not yet have sufficient energy or life for use in vehicles that would match the performance of internal combustion vehicles. Energy densities 2 and 5 times greater are required to meet the performance goals of a future generation of plug-in hybrid-electric vehicles (PHEVs) with a 40–80 mile all-electric range, and all-electric vehicles (EVs) with a 300–400 mile range, respectively. Major advances have been made in lithium-battery technology over the past two decades by the discovery of new materials and designs through intuitive approaches, experimental and predictive reasoning, and meticulous control of surface structures and chemical reactions. Further improvements in energy density of factors of two to three may yet be achievable for current day lithium-ion systems; factors of five or more may be possible for lithium–oxygen systems, ultimately leading to our ability to confine extremely high potential energy in a small volume without compromising safety, but only if daunting technological barriers can be overcome.