Enhancing the Charge Carrier Separation and Transport via Nitrogen-Doped Graphene Quantum Dot-TiO₂ Nanoplate Hybrid Structure for an Efficient NO Gas Sensor

Abstract

Herein, we demonstrate the ultraviolet (UV) light activated high-performance room-temperature NO gas sensor based on nitrogen-doped graphene quantum dots (NGQDs)decorated TiO 2 hybrid structure. TiO 2 employed in the form of {001} facets exposed rectangular nanoplate morphology, which is highly reactive for the adsorption of active oxygen species. NGQD layers are grown on TiO 2 nanoplates by graphitization of precursors via hydrothermal treatment. The decoration of NGQDs on the TiO 2 surface dramatically enhanced the efficiency of gas and carriers exchange, charge carrier separation and transportation, and oxygen vacancies, which eventually improved the sensing performance. At room temperature, the TiO 2 @ NGQDs hybrid structure exhibited a response of 12.0% to 100 ppm NO, which is 4.8 times higher compared to that of pristine TiO 2 nanoplates. The response of TiO 2 @NGQDs hybrid structure is further upgraded by employing the ultraviolet light illumination and manipulating the operating temperature. Under the UV (λ = 365 nm) illumination at room temperature, the hybrid structure response escalated to ∼31.1% for 100 ppm NO. On the other hand, the tailoring of working temperature yielded a response of ∼223% at an optimum operating temperature of 250 °C. The NO gas-sensing mechanism of TiO 2 @NGQDs nanoplate's hybrid structure sensors under UV illumination and different working temperatures is discussed.

N-Doped Graphene Quantum Dots/Titanium Dioxide Nanocomposites: A Study of ROS-Forming Mechanisms, Cytotoxicity and Photodynamic Therapy

“…In the synthesized nanocomposites, N-GQDs with discrete electronic levels serve as a light absorber, generate electrons and enable donor–acceptor contact with TiO 2 , which facilitates direct contact with the TiO 2 surface. When p-type N-GQDs and n-type TiO 2 form a p-n heterojunction, free electrons in TiO 2 are transferred to N-GQDs and thus, create holes in the valence band (VB) of TiO 2 (Equation (3)) [ 66 ]. Upon NIR light irradiation, the N-GQDs absorb the light, leading to the excitation of electrons from the highest occupied molecular orbital (HOMO) to the lowest unoccupied molecular orbital (LUMO), as shown in Equation (4).…”

Room-Temperature Gas Sensors Under Photoactivation: From Metal Oxides to 2D Materials

“…Very recently, Murali and co-workers demonstrated a UV-activated high-performance RT NO gas sensor based on nitrogen-doped graphene quantum dots (NGQDs) decorated TiO 2 nanoplates with {001} facets exposed [76]. The response of the NGQDs/TiO 2 hybrids without UV activation was improved from 12.0% to 100 ppm NO the decoration of NGQDs on TiO 2 , which dramatically enhanced the generation of electron-hole pairs due to good light absorption ability of NGQDs.…”

65‐8: Transparent Electroluminescent QLEDs with High Brightness Double‐Side‐Emission Fabricated in Atmosphere

“…Quantum dots (QDs) are promising materials because of their fascinating optical properties such as size-tunable bandgap from UV to NIR, high luminescence efficiency, narrow emission bandwidth, and feasible synthetic process [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Recent advances and progress in internet of the things (IOT), information technology, augmented reality & virtual reality (AR & VR), and wearable devices attract much attention in developing transparent devices and displays in both academia and industry [19.20].…”