Seeding a conventional chemical oxidative polymerization of aniline with even very small amounts of biological, inorganic, or organic nanofibers (usually <1%) dramatically changes the morphology of the resulting doped electronic polymer polyaniline from nonfibrillar (particulate) to almost exclusively nanofibers. The nanoscale morphology of the original seed template is transcribed almost quantitatively to the bulk precipitate. These findings could have immediate impact in the design and development of high-surface area electronic materials.

Described herein is a flexible and lightweight chemiresistor made of a thin film composed of overlapped and reduced graphene oxide platelets (RGO film), which were printed onto flexible plastic surfaces by using inkjet techniques. The RGO films can reversibly and selectively detect chemically aggressive vapors such as NO 2 , Cl 2 , etc. Detection is achieved, without the aid of a vapor concentrator, at room temperature using an air sample containing vapor concentrations ranging from 100 ppm to 500 ppb. Inkjet printing of RGO platelets is achieved for the first time using aqueous surfactant-supported dispersions of RGO powder synthesized by the reduction of exfoliated graphite oxide (GO), by using ascorbic acid (vitamin C) as a mild and green reducing agent. The resulting film is has electrical conductivity properties (s % 15 S cm À1 ) and has fewer defects compared to RGO films obtained by using hydrazine reduction.Graphene has emerged as an environmentally stable electronic material with exceptional thermal, mechanical, and electrical properties because of its two-dimensional sp 2 -bonded structure. [1,2] Although individual graphene sheets have been synthesized on various surfaces using chemical vapor deposition, [2,3] an important chemical route to bulk quantities of RGO involves the conversion of graphite into GO using strong oxidants, and then subsequent reduction of the dispersed GO into RGO using strong reducing agents (e.g., hydrazine). [4,5] The large available surface area of graphene makes it an attractive candidate for use as a chemiresistor for chemical and biological detection. There are a few reports on vapor detection using graphene films on interdigitated arrays, [6][7][8][9] and one interesting report on singlemolecule detection. [9] In recent reports on reversible NO 2 vapor detection using graphene, either the response/recovery time of the signal is long, [7] or efforts to improve the recovery cycle by increasing the temperature was complicated by a smaller sensor response.[6] Herein we describe a rugged and flexible sensor using inkjet-printed films of RGO on poly-(ethylene terephthalate) (PET) to reversibly detect NO 2 and Cl 2 vapors within an air sample at the parts per billion level, and demonstrate the use of ascorbic acid as a mild and effective alternative to hydrazine to reduce GO into RGO.Ascorbic acid reduction of dispersed graphene oxide into RGO is carried out by first preparing GO from graphite using the method reported by Hummers and Offeman, [10] and then dispersing it in water containing 1 % polyethylene glycol. Ascorbic acid powder (3 g) is added to a 3 mg mL À1 aqueous GO dispersion and heated to 80 8C for 1 hour, at which point the color changes from yellow-brown to black, signaling the conversion into RGO platelets (Figure 1 a). This RGO powder is suction filtered and washed with water, and then

A convenient method to obtain patterns of films of single-walled carbon nanotubes (SWNT) bundles on flexible plastic is described. Using the Line Patterning method SWNT films of thickness ranging from approximately 300-1500 nm can be obtained from aqueous surfactant-supported dispersions of chemically purified SWNT bundles synthesized by the pulsed-laser ablation method. These films are strongly adherent and are competitive in performance with commercially available films of indium-tin-oxide (ITO) on plastics. For example, an approximately 1500 thick film of SWNT on poly(ethylene terephthalate) (PET) shows a surface resisitvity of approximately 80 Omega/sq, optical transparency >80%, and robust flexibility. Unlike ITO/PET, films of SWNT/PET can be folded and bent to a crease without cracking. The simple techniques involoved in obtaining these films (i.e., those without requiring lithography or ink-jet printing) could help facilitate the rapid fabrication of transparent, flexible electronic devices, heralding what promises to be a new approach towards the development of next-generation optoelectronic devices.

Described herein is a flexible and lightweight chemiresistor made of a thin film composed of overlapped and reduced graphene oxide platelets (RGO film), which were printed onto flexible plastic surfaces by using inkjet techniques. The RGO films can reversibly and selectively detect chemically aggressive vapors such as NO 2 , Cl 2 , etc. Detection is achieved, without the aid of a vapor concentrator, at room temperature using an air sample containing vapor concentrations ranging from 100 ppm to 500 ppb. Inkjet printing of RGO platelets is achieved for the first time using aqueous surfactant-supported dispersions of RGO powder synthesized by the reduction of exfoliated graphite oxide (GO), by using ascorbic acid (vitamin C) as a mild and green reducing agent. The resulting film is has electrical conductivity properties (s % 15 S cm À1 ) and has fewer defects compared to RGO films obtained by using hydrazine reduction.Graphene has emerged as an environmentally stable electronic material with exceptional thermal, mechanical, and electrical properties because of its two-dimensional sp 2 -bonded structure. [1,2] Although individual graphene sheets have been synthesized on various surfaces using chemical vapor deposition, [2,3] an important chemical route to bulk quantities of RGO involves the conversion of graphite into GO using strong oxidants, and then subsequent reduction of the dispersed GO into RGO using strong reducing agents (e.g., hydrazine). [4,5] The large available surface area of graphene makes it an attractive candidate for use as a chemiresistor for chemical and biological detection. There are a few reports on vapor detection using graphene films on interdigitated arrays, [6][7][8][9] and one interesting report on singlemolecule detection. [9] In recent reports on reversible NO 2 vapor detection using graphene, either the response/recovery time of the signal is long, [7] or efforts to improve the recovery cycle by increasing the temperature was complicated by a smaller sensor response.[6] Herein we describe a rugged and flexible sensor using inkjet-printed films of RGO on poly-(ethylene terephthalate) (PET) to reversibly detect NO 2 and Cl 2 vapors within an air sample at the parts per billion level, and demonstrate the use of ascorbic acid as a mild and effective alternative to hydrazine to reduce GO into RGO.Ascorbic acid reduction of dispersed graphene oxide into RGO is carried out by first preparing GO from graphite using the method reported by Hummers and Offeman, [10] and then dispersing it in water containing 1 % polyethylene glycol. Ascorbic acid powder (3 g) is added to a 3 mg mL À1 aqueous GO dispersion and heated to 80 8C for 1 hour, at which point the color changes from yellow-brown to black, signaling the conversion into RGO platelets (Figure 1 a). This RGO powder is suction filtered and washed with water, and then

No abstract

The morphology of doped polypyrrole.Cl powder changes dramatically from granular to nanofibrillar when a very small amount (1-4 mg) of V2O5 nanofibers are added to a chemical oxidative polymerization of pyrrole in aq 1.0 M HCl using (NH4)2S2O8 as the oxidant. Unlike the polyaniline system, a key synthetic requirement in the polypyrrole system is for the seed template to be "active", i.e., to be capable of independently oxidizing the pyrrole monomer. Thin, strongly adherent films can be obtained on inert surfaces such as glass, plastics, etc., directly from the polymerization mixture without any bulk product isolation steps, significantly simplifying the processing of these nanofibers.

No abstract

We report the far-infrared through visible photoinduced absorption (PA) spectra of polyaniline in the emeraldine-base and leucoemeraldine-base forms. The direct-absorption spectrum of emeraldine base (EB) has a broad absorption centered at 2 eV (the "exciton" band) and an absorption band at-3.6 eV (the m.-~* band gap). The PA spectra of EB for pumping into the "exciton" band and across the band gap are nearly identical, indicating the same types of charged defect states are created upon photoexcitation. The direct absorption spectrum of leucoemeraldine base (LB) shows only the~-m* band-gap absorption at-3.6 eV. For pumping into this absorption band, the PA spectrum of LB is very similar to that of EB, although important differences result from the lack of quinoid structures in this material. Based on our results, we propose a model for the photocreation of defect states in leucoemeraldine base and emeraldine base. The central roles of phenyl-ring rotations and of massive polarons are discussed.