Nanoscale heterojunctions of rGO-MoS₂ composites for nitrogen dioxide sensing at room temperature

Abstract

Chemiresistive sensors, employing binary and ternary hybrids of reduced graphene oxide (rGO), are developed to detect nitrogen dioxide (NO 2 ) gas at parts per billion level (ppb) at room temperature. The sensors based on hierarchical structures of molybdenum disulphide (MoS 2 ) sheets decorated rGO and further integration of it with silver nanoparticles (Ag NPs) exhibit improved sensing responses with lower detection limits than the unary counterpart (rGO). An increase of nearly 500% in sensing response is observed in the ternary hybrid device over rGO alone at a concentration of 1 ppm and a 1145% increase in response is observed at 104 ppm. The ternary hybrid device outperforms the binary and the unary counterparts in terms of sensitivity to NO 2 over a wide concentration range from 1 ppm to 104 ppm. Additionally, the ternary hybrid device is highly selective to NO 2 amongst other atmospheric pollutants like ammonia, sulphur dioxide and carbon monoxide. An experimental detection limit of 50 ppb is further achieved with this device which is lesser than the 53 ppb permissible limit declared by Environmental Protection Agency (EPA). A synergistic effect was achieved with the binary and the ternary hybrids with the electronic modulations at the nanoscale interfaces at the nanoheterojunctions playing a key role in selective and enhanced adsorption of NO 2 at room temperature.

Role of the electrode-edge in optically sensitive three-dimensional carbon foam-MoS2based high-performance micro-supercapacitors

“…30 The formation of a 3D porous CF-MoS 2 nanostructure is due to the hydrothermal reaction conditions and the precursor materials (sodium molybdate and sodium thiocyanate) used in the synthesis. 37 The reaction mechanisms are described in previous references: 37,38 A transmission electron microscopy (TEM) image further conrms the presence of entangled nanosheets of CF-MoS 2 , as shown in Fig. 1(c).…”

“…30 The formation of a 3D porous CF–MoS 2 nanostructure is due to the hydrothermal reaction conditions and the precursor materials (sodium molybdate and sodium thiocyanate) used in the synthesis. 37 The reaction mechanisms are described in previous references: 37,38 sodium molybdate releases MoO 4 − and sodium ions, and sodium thiocyanate releases sulphur ions acting as sources for the formation of 3D MoS 2 . The MoO 4 − ions, owing to a layered structure, react with sulphur ions to form MoS 2 ; meanwhile, the intercalation of sodium ions prevents the stacking of MoS 2 nanostructures, leading to self-assembled MoS 2 nanostructures on the 3D framework of CF.…”

“…41 For CF–MoS 2 beyond these carbon-related bands, there are also two Raman characteristics bands at 379 cm −1 and 405 cm −1 corresponding to in-plane E 1 2g and out-of-plane A 1g modes of MoS 2 respectively. 37 The E 1 2g mode is attributed to the opposite vibration of S atoms with Mo atoms, whereas the other mode is related to the vibration of only S atoms in opposite directions. The frequency difference of two bands at around ∼26 cm −1 indicates the presence of a few layers of MoS 2 .…”

A highly efficient rGO grafted MoS2 nanocomposite for dye adsorption and electrochemical detection of hydroquinone in wastewater

“…13,14 Although MoS 2 is a p-type semiconductor, restacking it with GO overcomes the gaps and improves the electronic properties of both nanomaterials. 15 rGO-MoS 2 nanocomposites have been utilized for antimicrobial activity, 16 detection of nitrogen dioxide, 17 energy conservation, antibiotics determination 18 and supercapacitor applications. 19 In the present work, hydrothermally synthesized rGO-MoS 2 nanocomposite has been used for the detection of Hq and for dye adsorption to treat contaminated water.…”

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