Enhancing the Sensing Performance of Zigzag Graphene Nanoribbon to Detect NO, NO, and NH Gases.

In this article, a zigzag graphene nanoribbon (ZGNR)-based sensor was built utilizing the Atomistic ToolKit Virtual NanoLab (ATK-VNL), and used to detect nitric oxide (NO), nitrogen dioxide (NO), and ammonia (NH). The successful adsorption of these gases on the surface of the ZGNR was investigated using adsorption energy (E), adsorption distance (D), charge transfer (∆Q), density of states (DOS), and band structure. Among the three gases, the ZGNR showed the highest adsorption energy for NO with -0.273 eV, the smallest adsorption distance with 2.88 Å, and the highest charge transfer with -0.104 e. Moreover, the DOS results reflected a significant increase of the density at the Fermi level due to the improvement of ZGNR conductivity as a result of gas adsorption. The surface of ZGNR was then modified with an epoxy group (-O-) once, then with a hydroxyl group (-OH), and finally with both (-O-) and (-OH) groups in order to improve the adsorption capacity of ZGNR. The adsorption parameters of ZGNR were improved significantly after the modification. The highest adsorption energy was found for the case of ZGNR-O-OH-NO with -0.953 eV, while the highest charge transfer was found for the case of ZGNR-OH-NO with -0.146 e. Consequently, ZGNR-OH and ZGNR-O-OH can be considered as promising gas sensors for NO and NO, respectively

DFT investigation of H2S adsorption on graphenenanosheets and nanoribbons: Comparative study

Graphenenanosheet (GNS), armchair graphenenanoribbon (AGNR), and zigzag graphenenanoribbon (ZGNR) systems were investigated by first principle calculations using the density functional theory (DFT). The DFT calculations explored the potential of utilization of these materials as gas sensors to detect hydrogen sulfide (H2S) gas. H2S gas adsorption was explored using: the adsorption energy (Eads), adsorption distance (D), charge transfer (ΔQ), density of states (DOS), and band structure of the generated systems before and after adsorption of H2S. The results showed that Eads of bare ZGNR was the highest of −0.171 eV as compared with GNS and AGNR. The surfaces of GNS, AGNR, and ZGNR have been modified with epoxy and then with a hydroxyl groups. The adsorption capacity of the three systems has been enhanced after the modifications with both the epoxy and hydroxyl groups. Based on the adsorption energy and charge transfer results, hydroxyl modified ZGNR system can be used effectively for detection applications of H2S since it exhibits the highest charge transfer and large adsorption energy.Open Access funding provided by the Qatar National Library

CO, CO2, and SO2 detection based on functionalized graphene nanoribbons: First principles study

In this study, density functional theory (DFT) has been used to build armchair graphene nanoribbon (AGNR) gas sensor and study its capacity to detect carbon monoxide (CO), carbon dioxide (CO2), and sulfur dioxide (SO2) gases. The adsorption of these gases on AGNR was confirmed based on the adsorption energy (Eads), adsorption distance (D), charge transfer (ΔQ), density of states (DOS), and band structure. In order to improve the adsorption capacity, three different modified AGNR systems have been built. AGNR was first functionalized with epoxy (-O-) group (AGNR-O), then with hydroxyl (-OH) group (AGNR-OH), and finally with (-O-) along with (-OH) groups (AGNR-O-OH). Before modification, the adsorption energies have been found to be −0.260, −0.145, and −0.196 eV due to the adsorption of CO, CO2, and SO2, respectively. After modification, the adsorption energy increased remarkably to −0.538 and −0.767 eV for the cases of AGNR-O-OH-CO2 and AGNR-O-OH-SO2, respectively. Indicating that functionalizing the surface of AGNR can improve significantly its performance for the field of gas sensing

First principle investigation of H2Se, H2Te and PH3 sensing based on graphene oxide

Detecting toxic gases is of great importance to protect our health and preserve the quality of life. In this work, graphene (G) and graphene oxide with three different modifications (G–O, G–OH, and G–O–OH) have been used to detect hydrogen selenide (H2Se), hydrogen telluride (H2Te), and phosphine (PH3) molecules based on Atomistic ToolKit Virtual NanoLab (ATK-VNL) package. The adsorption energy (Eads), adsorption distance (D), charge transfer (ΔQ), density of states (DOS), and band structure have been investigated to confirm the adsorption of H2Se, H2Te, and PH3 on the surface of G, G–O, G–OH, and G–O–OH systems. The results of G revealed highest Eads for the case of H2Te with −0.143 eV. After the functionalization of G surface, the adsorption parameters reflected an improvement due to the presence of the functional groups. Particularly, the highest adsorption energy was found between G–O system and H2Se gas with Eads of −0.319 eV. The smallest adsorption distance was found between G–OH system and H2Se gas. The highest charge transfer was found for the case of H2Se gas adsorbed on G–O–OH system. By thorough comparison of the adsorption energy, adsorption distance, and charge transfer between G, G–O, G–OH, and G–O–OH systems and the three gases, G–O–OH system can be considered as a potential sensor for H2Se gas.The publication of this article was funded by the Qatar National Library

Pt-doped armchair graphene nanoribbon as a promising gas sensor for CO and CO2: DFT study

In this work, four armchair graphene nanoribbon (AGNR) based sensor materials were built using Atomistic ToolKit Virtual NanoLab (ATK-VNL) and utilized to detect carbon monoxide (CO) and carbon dioxide (CO2) gases. First, the effect of passivating AGNR on the sensing performance toward CO and CO2 gases has been investigated, where AGNR was passivated with hydrogen (H-AGNR) and nitrogen (N-AGNR). The obtained results reflected no significant changes in the adsorption parameters of CO and CO2 molecules on H-AGNR and N-AGNR. Particularly, the adsorption energies between H-AGNR and N-AGNR systems and CO were found to be −0.446 and −0.436 eV, while for the case of CO2, the adsorption energies were found to be −0.426 and −0.432 eV, respectively. To enhance the sensing performance, both H-AGNR and N-AGNR systems were doped with platinum (Pt) forming another two systems: Pt–H-AGNR, and Pt–N-AGNR. After doping, the results revealed a significant increase in the adsorption energy to almost 9 times than the non-doped systems for the cases of CO on Pt–N-AGNR as well as CO2 on both Pt–H-AGNR and Pt–N-AGNR. Moreover, an increase of almost 13 times was observed in the adsorption energy for the case of CO on Pt–H-AGNR. Besides to the adsorption energy (Eads), the adsorption distance ((D), charge transfer (ΔQ), the density of states (DOS), as well as the band structure have been examined to confirm the adsorption of CO and CO2 on the four systems.The publication of this article was funded by the Qatar National Library

Adsorption and gas sensing properties of CuFe2O4 nanoparticles

Spinel ferrite nanoparticles in the form CuFe2O4 were tested for gas sensing applications. Nanoparticles pressed in a disk form were used to construct conductometric gas sensors. The disk was placed between two electrical electrodes wherein the top electrode had a grid structure. The produced sensors were tested against H2S and H2 gases and they were found to be selective and sensitive to H2S concentration as low as 25 ppm. The composition of the nanoparticles was confirmed by X-ray diffraction and energy dispersive X-ray spectroscopy measurements. The crystal structure was verified by both X-ray diffraction and transmission electron microscope. The observations obtained from the experiments demonstrated the high potential of using CuFe2O4 nanoparticles for H2S sensing applications.This work was supported by the Khalifa University under the Grant Number RIFP-14312 and the Qatar University under the Grant Number QUCG-CAS-2018\2019-1.Scopu

DNA sequencing via Z-shaped graphene nano ribbon field effect transistor decorated with nanoparticles using first-principle transport simulations

© 2020 The Author(s). Published by IOP Publishing Ltd on behalf of the Institute of Physics and Deutsche Physikalische Gesellschaft. DNA detection has revolutionized medical and biological research fields. It provides a wealth of medical information for each individual, which can be used in a personalized medicinal procedure in the future. Genome sequence helps to enhance our perception of inheritance, disease, and individuality. This work aims to improve DNA sequencing accuracy and the overall current signal using a novel nano pore based sensor that is developed to detect and identify the DNA bases. Herein, a novel z-shaped field effect transistor with a nano pore for the aim of DNA detection is studied, where a gate terminal is added below the center of the z-shaped graphene nano ribbon. First-principle transport calculations are used to identify the DNA bases and electronic signature. An efficient density functional theory approach combined with non-equilibrium Green's function formalism (DFT + NEGF) are utilized to detect the transmission spectrum and current for DNA nucleo bases: Adenine, Thymine, Guanine, and Cytosine. Using transmission current, a distinctive electronic signature is generated for each DNA base to detect each DNA sequence. Various orientations and lateral position for each DNA base are considered. Moreover, the effect of decorating the developed DNA sensor with gold and silver nanoparticles on the sensor's electrical current and transmission spectra is studied and analyzed. The results suggest that the z-shaped sensor could achieve DNA sequencing with high accuracy. The practical implementation of this work represents the capability to anticipate and cure diseases from the genetic makeup perspective.The authors would like to acknowledge the financial support by United Arab Emirates University (Zayed Center for Health Sciences) with Fund number 31R128

Nanostructured Metal Oxide-Based Acetone Gas Sensors: A Review.

Acetone is a well-known volatile organic compound that is widely used in different industrial and domestic areas. However, it can have dangerous effects on human life and health. Thus, the realization of sensitive and selective sensors for recognition of acetone is highly important. Among different gas sensors, resistive gas sensors based on nanostructured metal oxide with high surface area, have been widely reported for successful detection of acetone gas, owing to their high sensitivity, fast dynamics, high stability, and low price. Herein, we discuss different aspects of metal oxide-based acetone gas sensors in pristine, composite, doped, and noble metal functionalized forms. Gas sensing mechanisms are also discussed. This review is an informative document for those who are working in the field of gas sensors

Fabrication of H2S gas sensors using ZnxCu1-xFe2O4 nanoparticles

Spinel ferrite nanoparticles can be easily retrieved and utilized for multiple cycles due to their magnetic properties. In this work, nanoparticles of a ZnxCu1-xFe2O4 composition were synthesized by employing a sol–gel auto-combustion technique. The morphology, composition, and crystal structure were examined using scanning electron microscopy, infrared spectroscopy, and X-ray diffraction. The produced nanoparticles are in the range of 30–70 nm and manifest spinel cubic structure. The nanoparticles were tested for their sensitivity to H2 and H2S gases, and the Cu-based spinel ferrite nanoparticles were found the most sensitive and selective to H2S gas. Their enhanced response to H2S gas was attributed to the production of metallic CuFeS2 that manifest higher electrical conductivity as compared with CuFe2O4. The fabricated sensors are functional at low temperatures, and consequently, they need low operational power. They are also simple to fabricate with appropriate cost

Production of flexible nanocomposite membranes for x-ray detectors

Flexible membranes of poly(vinyl alcohol) (PVA) polymer and CuO nanoparticles for x-ray detection applications are reported in this work. PVA represents a polymer matrix for nanoparticles, and its flexibility and electrical conductivity are enhanced by addition of glycerol (GL) plasticizer. Nanoparticles of an average size of 6.3∓2.4nm are produced by a solvothermal method and added to the PVA + GL solution with different concentrations. The flexible membranes are fabricated by solution casting on glass substrates. The effect of blending of PVA + GL with nanoparticles on different characteristics of the membranes including the flexibility as well as the melting, glass transition, and degradation temperatures are tested by differential scanning calorimetry, thermal gravimetric analysis, as well as both Raman and Fourier-transform infrared spectroscopy. Electrical impedance tests reveal that both dc resistance and activation energy decrease with increasing temperature as well as nanoparticle concentration. The produced membranes reveal electrical response to x-ray due to the presence of CuO nanoparticles, and this response rises with x-ray generator voltage. The results presented in this study specify that the produced membranes are easy to produce with low cost, thus, they represent potential candidates for practical applications including x-ray detection