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

Abstract

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

Flexible NO2gas sensor using multilayer graphene films by chemical vapor deposition

“…Although a high response to gas molecules was achieved in that report, the mass producing and integrating of graphene into a real device remained a challenge to be overcome. With that goal in mind, many researchers have developed high-performance NO 2 gas sensors using reduced graphene oxide sheets, obtained from high temperature annealing [9] or a chemical conversion with hydrazine [10] and ascorbic acid [11], for application as a low-cost, simple and practical sensor device. More recently, Joshi et al [12] reported a NO 2 gas sensor based on graphene films and ribbons grown on Ni-coated Si substrates using the microwave plasma enhanced chemical vapor deposition (MPECVD) method.…”

Human‐Like Sensing and Reflexes of Graphene‐Based Films

“…For rGO reduced by p‐phenylenediamine,113 the response to dimethyl methyl phosphonate (DMMP) of this sensor was enhanced to 4.7 times stronger than that of the sensor based on rGO, which also exhibited a better response repeatability. Besides, the rGO‐based gas sensor could also selectively detect corrosive vapors such as NO 2 and Cl 2 after reduced by ascorbic acid, whose limit of detection (LOD) was up to the range of 100 ppm to 500 ppb 114. Sulfonated rGO and ethylenediamine‐modified rGO (EDA–G) were also prepared and exhibited higher response of 4 to 16 times toward NO 2 than the pristine rGO 115.…”

Photo-reduction of Graphene Oxide during Photo-polymerization of Graphene Oxide/Epoxy-Novolac Nanocomposite Coatings

“…Therefore, in order to reconstruct the electrically desired Gr structure, reduction processes are necessary which is usually carried out by different strategies. Chemical and electrochemical reductions have been explored widely as the most effective routes of reduction [19][20][21][22][23]. By the way, photo-irradiation which involves UV irradiation of GO has also been demonstrated that can reduce GO [24] which is assisted in the presence of a photoinitiator and other catalysts [25][26][27][28][29][30] while photocatalyst-free reduction of GO to reduced GO (rGO) has been reported by Ding et al [31] In general, UV-irradiation methods offer advantages such as simplicity, cleanness and low cost.…”