Recovery Time Values Research Articles

Adsorption of thiotepa on B12N12, Mg12O12, and Si12C12 fullerene-like cages: A DFT study

We examined the adsorption of thiotepa (TTP) on the outer surface of B12N12, Mg12O12, and Si12C12 fullerene-like cages using density functional theory (DFT) calculations. The computations were carried out at the Perdew-Burke-Ernzerhof level with the D3 dispersion correction (PBE-D3) in a water solvent. The adsorption mechanism of TTP through N-head and S-head on the external surface of Si12C12 involves a covalent interaction (binding energy ∼ −1.31 eV) with the carrier surface. In contrast, the adsorption of the TTP molecule through N-head and S-head on the outer surfaces of B12N12 (binding energy ∼ −0.75 eV) and Mg12O12 (binding energy ∼ −0.62 eV) fullerene-like cages is driven by electrostatic interactions. Therefore, due to their low values of recovery time, both B12N12 and Mg12O12 fullerene-like cages can serve as carriers for TTP in the treatment of cancer. Thermodynamic parameters (Gibbs free energy and enthalpy energy) demonstrate that these interactions are exothermic and spontaneous. The results further reveal the significant disparity in the calculated HOMO and LUMO energies at the computational level. The formation of intricate bonds between the drug and the fullerene-like cages is attributed to the charge transfer dynamics that occur during their interactions. Through computational analysis and examination of the total density of state (TDOS) plots, it is evident that B12N12 and Si12C12 fullerene-like cages exhibit a high degree of sensitivity to the TTP drug. The adsorption process can increase the electrical conductivity of B12N12 and Si12C12, while having minimal effect on Mg12O12. This suggests that B12N12 could potentially serve as a suitable biosensor for detecting TTP.

Beryllium oxide (Be12O12) as a nanocarrier for cisplatin anticancer drug and some of its analogs: A DFT investigation

The potential of beryllium oxide (Be12O12) nanocarrier to adsorb Cisplatin (cisPtCl2) anticancer drug and some of its analogs (cisPtBr2 and cisPtI2) was comparatively investigated by means of DFT calculations. In the quest for a favorable adsorption process, the interactions within cisPtX2∙∙∙Be12O12 complexes were studied via various orientations. In terms of energy outcomes, significant interaction (Eint) and adsorption (Eads) energies were obtained with values elevated to –44.23 and –24.60 kcal/mol, respectively, for cisPtCl2∙∙∙Be12O12 complex within configuration A. In particular, the optimized cisPtCl2∙∙∙Be12O12 complexes showed more substantial values than other counterparts. From SAPT analysis, electrostatic forces dominated the instances of adsorption with Eelst up to the value of –71.92 kcal/mol for cisPtCl2∙∙∙Be12O12 complex within configuration A. FMOs illustrated the occurrence of the cisPtX2∙∙∙Be12O12 adsorption process through the redistribution of molecular orbitals of Be12O12 after the cisPtX2 adsorption. Further, changes in EHOMO, ELUMO, and the related parameters of Be12O12 were observed subsequent to the cisPtX2 adsorption. Following the adsorption of cisPtX2 over Be12O12, diminution in η and enhancement in S values of Be12O12 was observed. According to thermodynamic features, the nature of the adsorption process within all cisPtX2∙∙∙Be12O12 complexes was confirmed to be spontaneous and exothermic. Besides, QTAIM and NCI analyses exposed the occurrence and nature of the considered adsorption process. Significant recovery time values for all studied configurations were elucidated. The obtained data affirmed the promising application of the Be12O12 nanocarrier in drug delivery processes, particularly for anticancer drugs.

A new spinel compound, Ba0.25Sr0.25Fe2.5O4, developed for use in gas sensing applications

In this article, nanoscale materials of the spinel type Ba0.25Sr0.25Fe2.5O4 have been successfully prepared using the solvothermal method, with sodium acetate as a protective agent and polyvinylpyrrolidone (PVP) to control the size and shape of the particles. The structural, morphological, and gas sensing characteristics of the sample have been thoroughly examined. It has been confirmed that the compound Ba0.25Sr0.25Fe2.5O4 exhibits a crystallite size of 32 nm, a fully cubic structure, and significant porosity, as established by the Williamson–Hall method. The electrical properties have revealed the semiconductor-type (n) behavior of our compound. The results of the ethanol, acetone, and H2S detection tests highlighted a particularly pronounced sensitivity of Ba0.25Sr0.25Fe2.5O4.Gas detection tests were conducted on the prepared compound by varying the concentrations of ethanol, acetone, and H2S gases (500 ppb, 1 ppm, 5 ppm, 10 ppm, 20 ppm, 40 ppm, 80 ppm, 100 ppm). The compound Ba0.25Sr0.25Fe2.5O4 demonstrated very good reactivity towards the three gases, even at very low concentrations, with respective optimal operating temperatures of 200 °C, 200 °C and 120 °C. Furthermore, the response and recovery time values for these three gases were found to be very short.

Unveiling the CO[formula omitted] adsorption capabilities of biphenylene network monolayers through DFT calculations

Nanomaterial synthesis and characterization advancements have led to the discovery of new carbon allotropes, such as the biphenylene network (BPN). BPN consists of four-, six-, and eight-membered rings of sp2-hybridized carbon atoms. Here, we employ density functional theory (DFT) calculations to investigate the CO2 adsorption capabilities in pristine and vacancy-endowed BPN monolayers. Our findings indicate that BPN lattices with a single-atom vacancy exhibit higher CO2 adsorption energies than pristine BPN. Unlike other 2D carbon allotropes, BPN does not exhibit precise CO2 sensing and selectivity by altering its band structure configuration. In pristine lattices, CO2 molecules are physisorbed in the eight-membered rings, while defective regions of vacancy-endowed lattices enable chemisorption of CO2. Regarding CO2 physisorption, the recovery time values are minimal, suggesting a rapid interaction between BPN and this molecule, with negligible relaxation time required to alter the electronic properties of BPN lattices.

Triquinoxalinylene and benzoquinone based covalent organic framework as robust material for mitigation of environmental pollutants-A theoretical approach

The physisorption of pollutant gases (NH3, HCN, H2S and PH3) on TQBQ-COF has been explored using DFT calculations. The strength and nature of interactions were determined through interaction energy, non-Covalent interactions- Reduced Density Gradient (NCI-RDG) plots, Frontier Molecular Orbital (FMO), Natural bond orbital (NBO), Electron Density Difference (EDD) and Quantum Theory of Atoms In Molecule (QTAIM) analysis. The optimized geometries and interaction energy calculations revealed that the analytes interacted with Oxygen and Nitrogen atoms of TQBQ-COF leading to adsorption energy ranging from −10.66 to −5.85 kcal/mol. The values of recovery time were in agreement to that of interaction energy and decreased with the increase in temperature. The NCI-RDG plots and QTAIM analysis revealed the presence of weak van der Waals forces in all complexes and partial covalent character in H2S@TQBQ-COF. Charge transfer study (employing NBO and EDD analysis) depicted the transfer of charge from surface to analytes. The study of HOMO-LUMO energy gap in FMO analysis depicted the high sensitivity of TQBQ-COF for H2S and NH3 compared to HCN and PH3 due to significant lowering of HOMO-LUMO energy gap upon the adsorption of H2S and NH3 on TQBQ-COF.

Pyrochlore cerium stannate (Ce2Sn2O7) for highly sensitive NO2 gas sensing at room temperature

Gas sensing at low temperatures remains a notable challenge at present. Owing to their strong catalytic activity, oxygen defects, and unique size, pyrochlore-based oxides have attracted considerable attention for preparing conductometric gas sensors that are effective at low temperatures. In this study, we prepared a pyrochlore-Ce2Sn2O7 structure using a facile hydrothermal method. The structure, morphology, and surface valance states of the prepared sample were analyzed. Additionally, we investigated the gas-sensing properties, such as the selectivity, response, response and recovery time, repeatability, stability, limit of detection, and influence of relative humidity on the sensing performance for NO2 gas molecules at room temperature (30 ± 2 ℃). The Ce2Sn2O7 exhibited outstanding selectivity for NO2 gas molecules compared with the interfering gas molecules such as N2O, CO, CO2, SO2, NH3,NO and H2S at room temperature (30 ± 2 ℃.). Moreover, the response and recovery time values were 4 s and 52.5 s, respectively, and an outstanding response of 125% was achieved toward 50 ppm NO2 gas molecules. The Ce2Sn2O7 sensor device exhibited excellent repeatability and stability over 90 days. The excellent gas-sensing performance was attributable to the high specific surface area, presence of oxygen vacancies, and surface-adsorbed oxygen molecules.

Investigation of aluminum nitride nanocarrier for drug delivery process of Favipiravir: A DFT study

The tendency of Al12N12 nanocarrier toward adsorbing Favipiravir (FPV), an anti-COVID-19 drug, was obviously unveiled within five configurations via O∙∙∙, N∙∙∙, and F∙∙∙Al interactions. The geometric and electronic properties of Al12N12 nanocarrier, FPV drug, and FPV∙∙∙Al12N12 complexes were thoroughly evaluated in gas and water phases. Among all the studied complexes, the most preferential negative interaction and adsorption energies were ascribed to configuration A with values of –51.11 and –38.82 kcal/mol, respectively. Symmetry-adapted perturbation theory (SAPT) analysis addressed the electrostatic force as the most dominant energetic component beyond the occurrence of the adsorption process within the studied complexes. Apparently, significant changes were noticed within the distributions of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the FPV and Al12N12 before and after the adsorption process. Noticeable increments in softness and decrement in hardness were also observed after the adsorption process, ensuring strong interactions within the studied complexes. The adsorption process was also studied in the water phase. The negative values of thermodynamic parameters ensured that the adsorption process had spontaneity and exothermic nature within almost all the studied complexes. Further favorability of the adsorption of FPV was noticed over the surface of Al12N12 nanocarrier compared to the B12N12 analog. For the FPV∙∙∙B12N12 complexes, unfavorable Gibbs free energy (ΔG) values along with neglected recovery time values revealed the bare tendency of the B12N12 nanocarrier toward adsorbing FPV drug. The findings of the presented study will serve as a springboard for further research into Al12N12 nanocarrier as well as the delivery of the FPV anti-COVID-19 drug.

Ultra-fast TiO2 nanopores broadband photodetector

TiO2 nanopores were fabricated on gold interdigitated silicon substrate by electrochemical anodization. The photoresponse of TiO2 nanopores under illumination was studied in a wide range of wavelengths from the near ultraviolet to infrared regions. The crystal structure and morphology of the samples was characterized by XRD and SEM. The electrical properties have been studied by making measurements of I–V curves with and without illumination. The manufactured device showed an ultrafast photoresponse with response and recovery time values reaching 10 ms/70 ms at 395 nm, 50 ms/230 ms at 560 nm and 7 ms/14 ms at 945 nm at bias voltage 1 V. The results suggest that the obtained TiO2 nanopores via anodized method are promising for broadband optoelectronic from ultraviolet to near-infrared range device applications.

Oxygen sensing performance improvement by the combination of narrowed electrospinning fibers and multi-cored phosphorescent photosensitizer: Strategy and performance comparison

Electrospinning fibers doped with phosphorescent Cu(I) complexes have been demonstrated as promising O2 sensing systems, but traditional oxygen sensing systems based on electrospinning fibers have low sensitivity (<10). In this work, three multi-cored phosphorescent Cu(I) probes were firstly synthesized and discussed via their single crystals and photophysical analysis. A long-lived lifetime of 7.9 μs with emission peaking at 441 nm and quantum yield of 0.45 was obtained. Time-dependent density functional theory (DFT) calculation was performed at RB3LYP/LANL2DZ level which revealed a metal-to-ligand-charge-transfer-based electronic transition in excited state, favoring oxygen sensing. Then narrowed electrospinning fibers (diameter<200 nm) were synthesized using a high-pressure pump. The Cu(I) probes were doped into these narrowed electrospinning fibers with three doping levels (5wt%, 10wt%, and 15wt%), so that sample specific surface area was increased to allow more collision chances with O2 molecules. A detailed comparison between normal fibers and narrowed fibers was performed. Our optimal sample showed sensitivity of 20.99 with a linear working equation of I0/I=0.656+0.198*[O2], R2=0.999. This value is by far the highest one among oxygen sensors based on phosphorescent Cu(I) complexes. The limit of detection was as low as 2.2% (O2%). Corresponding response and recovery time values were 7 and 20 seconds. It was found that using narrowed fibers as host was an effective way to improve oxygen sensing performance, showing higher sensitivity, linear calibration curve and faster response behavior.

Unravelling the interaction between boron nitride nanosheets and organic pesticides through density functional theory studies

In recent years, the concerns over the contamination of water resources due to pesticides and their residues have risen. To address this issue, the present study investigates the adsorption of some commonly used pesticides (acetamiprid, clothianidin, imidacloprid, thiacloprid and tri-allate) on monolayer boron nitride nanosheets (BNNs) from wastewater based on the first-principle density functional theory. A standard B3LYP model and 6-311G basis set were used to obtain the electrostatic potential maps, the density of states plot and HOMO-LUMO energy distributions. The feasibility of adsorption was confirmed from the adsorption energy calculations. The recovery time values were evaluated to examine the recovery of BNNs sheets after the adsorption. The electrostatic potential maps examined the local electron density distribution over the pesticides before and after adsorption. Quantum mechanical descriptors were evaluated to understand the chemical activity of the species involved in the process. The HOMO-LUMO distribution and DOS plots indicated that HOMOs of pesticides play an important role in the interactions. The quantum descriptors indicated weak interactions between pesticides and BNNs. The RDG and NCI plots confirmed the dominance of Van der Waals forces during adsorption interactions and showed that the forces operate to a greater extent during adsorption of imidacloprid.

Understanding the mechanism of thioguanine's binding to Ag6 and bimetallic (Ag3–Au3 and Ag3–Cu3) clusters

Using Ag6, Ag3Au3 and Ag3Cu3 clusters, density functional theory (DFT) methods were used to elucidate the interaction behavior of thione-containing thioguanine drug (TGN) on silver. The CAM-B3LYP functional with LANL2DZ basis set was used to study the different features and bonding qualities of resultant metal complexes. The drug molecule tends to anchor on the cluster with binding energies ranging from −16 to −23 kcal/mol. Due to the recovery time values and change in energy gap, the metal clusters can be turned into an electrical signal for detecting TGN. TGN-metal cluster interactions are reversible events, and a drug release mechanism has been postulated. As a result of a modest change in pH in tumor cells, the drug is able to detach from metal surfaces. Non-covalent interactions studies show that TGN's NH2 group is more important for hydrogen bonding, and the heterocyclic N and S atoms may play a role in weak interactions.

Vacancy defects in monolayer boron carbon nitride for enhanced adsorption of paraben compounds from aqueous stream: A quantum chemical study

Paraben compounds have gained attention as emerging pollutants are a preservative in cosmetic and personal care products. In this work, the adsorption of paraben compounds (methylparaben, propylparaben and butylparaben) was studied on the monolayered boron carbon nitride (BCN) surface with B, C and N vacancies using first-principle density functional theory calculations. The electrostatic potential function on paraben compounds and BCN surface was calculated to understand the local electron density. Build-up of negative electrostatic potential was observed in the BCN surfaces with vacancy defects. The localization of electrons was studied using the electron localization function. The covalent nature of the bond was observed between the atoms of BCN surfaces. From the optimized geometries, it was clear that the paraben compounds were closest to the surface of the BCN surface with a B defect. The HOMO-LUMO distributions and the bandgap data were used to determine the quantum mechanical descriptors through Koopmans' approach. The adsorption energy of the paraben compounds with BCN surfaces was in the range of -0.50 to -0.20 eV, confirming the feasibility of the interactions. The recovery time values also supported the weak nature of interactions. The weak Van der Waals interactions during the adsorption of paraben compounds on the BCN surfaces (with and without vacancy) through the reduced density gradient plots and non-covalent interaction isosurface analysis. This study concluded that N vacancy enhanced the adsorption interactions between the BCN surface and paraben compounds.

Comparison of the Stability of 2H Nanosurfaces by the Adsorption of Small Molecules : A DFT Study

Density functional theory (DFT) calculations were carried out to understand the structural stability of 2D nanosheets of gold and silver in hexagonal phase of 2H by the adsorption of small molecules. In this work, we have obtained the bonding and adsorption properties of such small molecules as H2O, H2O2, and C2H5OH on 2H phase of gold and silver nanosurfaces, through DFT method using Quantum Expresso (QE) code. The high absorption energy values of (-2.45 eV, -2,46 eV, -2, 41 eV) for H2O, H2O2, and C2H5OH molecules on 2H-Au surfaces, respectively obtained than that of 2H-silver surfaces that the interaction between small molecules and both 2H nanosurfaces corresponds to physisorption. However, during the adsorption, the gold surface in the 2H phase (2H-Au) seems to preserve its atomic structure, while 2H-Ag surface changes from 2H to the fcc structure. Based on the analysis of electronic and physicochemical properties, the composite systems of 2H-gold/2H-silver-small molecules exhibit semiconductor behaviour. While 2H-Ag surfaces have short recovery time values for hydrogen peroxide (H2O2), this time is quite long for 2H-Au surfaces. Because of the long recovery time, Au-2H reported surfaces can be a candidate for possible applications of viral capture. Thus, the reported results are significant, and they would stimulate the experimental and further studies.

Investigation of the adsorption behavior of two anticancer drugs on the pristine and BN-doped graphdiyne nanosheet: A DFT-D3 perception

Hydroxyurea (HU) and 5-Fluorouracil (FU) are well-known drugs that are widely used in the treatment of cancers. Interaction of the HU and FU molecules on the pristine graphdiyne (GDY) and BN-doped graphdiyne (BNGDY) nanosheet was evaluated by density functional theory (DFT) method in gas and solution phases. Various adsorption sites of GDY/BNGDY have been examined for different HU/FU drug orientations. The results indicate that the 18-membered ring area and top of the acetylenic linkage are the most suitable sites, unlike the hexagonal ring. The S1, S6, S8, and S10 structures are the most stable configurations for GDY/HU, GDY/FU, BNGDY/HU, and BNGDY/FU with the highest Eads about −0.598, −0.417, −1.289, and −0.603 eV in the gas phase and −0.960, −0.592, −1.599 and −1.485 eV in solution phase, respectively. For GDY + HU/FU, the highest Eads is due to interaction of hydrogen atom of drug with GDY; while, in BNGDY+HU/FU, the oxygen atom of drug interacts effectively with the boron atom of the sheet. Likewise, in GDY complexes, charge transfer occurs from sheet to drug, but it is inverse in BNGDY complexes. The band gap values of the GDY and BNGDY are 0.470 and 0.486 eV, respectively, that drug adsorption decreases them in the range of 2.34 to 22.43%. Adsorption behavior of the structures is further discussed and interpreted using quantum molecular descriptors, band structure, and PDOS diagrams. Recovery time values show that in the field of targeted drug delivery and nanomedicine, GDY and BNGDY are more suitable as carrier for the HU and FU drugs, respectively.

Calf and non-calf hemodynamic recovery in patients with arterial claudication: Implication for exercise training

BackgroundPrevious studies in patients with arterial claudication have focused on calf hemodynamic recovery. We hypothesized that the duration of hemodynamic recovery with TcpO2 at calf and non-calf levels would be shorter than 10 min. We analyzed the factors that influence the recovery time. MethodsWe monitored limb changes minus chest changes from rest (DROP) of transcutaneous oximetry on buttocks, thighs and calves, during and following a treadmill test (3.2 km/h; 10% grade). We calculated the time required to reach 50% (50%RT) and 10% (90%RT) of minimal DROP value (DROPm) from walking cessation. Regression analyses were used to determine the factors associated to 50%RT and 90%RT. ResultsOf the 132 patients studied, 18.2% reported isolated non-calf pain by history. Of the 792 recovery time values, only 3 (0.4%) and 23 (2.9%) were in excess of 10 min for 50%RT and for 90%RT, respectively. A weak correlation was found between each of the 792 DROPm and 50%RT (r = −0.270, p < 0.001) as well as for 90%RT (r = −0.311 p < 0.001). Lowest DROPm and BMI (but not age, sex, the use of beta-blockers, the duration of the walking period) were associated to both 50%RT and 90%RT. ConclusionAlthough recovery duration correlates significantly with the severity of ischemia of the same location, a wide discrepancy exists and the longest recovery time does not always correlate to the localization of the most severe ischemia. Non-calf ischemia should be measured when one aims at objectifying the biological effects of exercise or the effects of treatments on recovery from exercise.

Development of a Ternary AlMgZnO-Based Conductometric Sensor for Carbon Oxides Sensing

In this article is reported a simple and low-cost conductometric sensor based on a ternary AlMgZnO thick film for the detection of carbon oxides (CO and CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ). The optimized ternary AlMgZnO sensing material containing 5at(%) of Al and 1at(%) of Mg (sample code 5Al1MgZnO), was synthesized by a simple sol–gel method and extensively characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis-Nir diffuse reflectance spectroscopy (UV-Vis-NIR-DRS), and photoluminescence (PL). The developed AlMgZnO sensor showed good characteristics in terms of sensitivity and lower limit of detection, short response, and recovery time values for detecting simultaneously CO and CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , which could be of practical application in the biomedical field.

WITHDRAWN: Hydrogen molecule detection based on Ti-embedded single vacancy defective stanene monolayer as an appropriate sensing material: A DFT study

Abstract Density functional theory calculations were carried out to investigate the interaction between hydrogen molecule and pristine/Ti-embedded defective stanene nanosheets. Ti embedding in stanene provides a satisfied surface for hydrogen molecule adsorption and sensing as can be evidenced by the enhanced adsorption energy on the Ti-embedded stanene system. The van der Waals (vdW) interactions were included to obtain the stable geometrical structures of stanene monolayers with adsorbed hydrogen molecules. Both pure and Ti-embedded stanene nanosensors exhibited semiconducting behavior as confirmed by the electronic band structure diagrams. Besides, the Ti doping provides a band gap opening for stanene at the Fermi level. The charge density difference and total electron density plots also revealed the accumulation of electron density on the adsorbed hydrogen molecule. Furthermore, there are electron depletion between the hydrogen molecule and stanene nanosheet, indicating the weak physical interaction between them. The work function was slightly reduced after doping of Ti atom, as well as the binding of hydrogen molecules on the Ti-embedded stanene sensors. The calculated recovery time values showed the unique reusability of the stanene based hydrogen molecule sensors. These insights would be quite relevant to the rational design of novel Ti-embedded stanene based sensors for hydrogen molecule detection.

Novel methodology for assessing total recovery time in response to unexpected perturbations while walking.

Walking stability is achieved by adjusting the medio-lateral and anterior-posterior dimensions of the base of support (step length and step width, respectively) to contain an extrapolated center of mass. We aimed to calculate total recovery time after different types of perturbations during walking, and use it to compare young and older adults following different types of perturbations. Walking trials were performed in 12 young (age 26.92 ± 3.40 years) and 12 older (age 66.83 ± 1.60 years) adults. Perturbations were introduced at different phases of the gait cycle, on both legs and in anterior-posterior or medio-lateral directions, in random order. A novel algorithm was developed to determine total recovery time values for regaining stable step length and step width parameters following the different perturbations, and compared between the two participant groups under low and high cognitive load conditions, using principal component analysis (PCA). We analyzed 829 perturbations each for step length and step width. The algorithm successfully estimated total recovery time in 91.07% of the runs. PCA and statistical comparisons showed significant differences in step length and step width recovery times between anterior-posterior and medio-lateral perturbations, but no age-related differences. Initial analyses demonstrated the feasibility of comparisons based on total recovery time calculated using our algorithm.

Hydrothermally grown α-MnO2 interlocked mesoporous micro-cubes of several nanocrystals as selective and sensitive nitrogen dioxide chemoresistive gas sensors

The interesting and multifunctional properties of alpha-manganese dioxide (α-MnO2) are considered to be highly sensitive and selective to nitrogen dioxide (NO2) chemresistive gas sensors. The α-MnO2 mesoporous interlocked micro-cubes composed of several interconnected nanocrystals synthesized by a facile and low-cost hydrothermal method on soda-lime glass substrate are envisaged as selective and sensitive NO2 gas sensors. Phase-purity and surface area with pore-size distribution are initially screened. The three-dimensional α-MnO2 mesoporous-cube-based gas sensors tested for NO2 gas from room-temperature (27 °C) to 250 °C have demonstrated 33% response for 100 ppm NO2 levels at 150 °C. The response and recovery time values of the α-MnO2 sensor are found to be 26 s and recovery 91 s, respectively, with high selectivity, good sensitivity, and considerable chemical and environmental stabilities, confirming the gas sensor applications potentiality of α-MnO2 morphology which is a combination of interlocked mesoporous micro-cubes and well-connected nanocrystals.

Zinc oxide hierarchical nanostructures as potential NO2 sensors

A superficial thermal evaporation method has been employed for the fabrication of hierarchical zinc oxide (ZnO) nanostructured films, composed of nanorods (NR's) and bunch of nanowires (BNW's), on glass substrate and the diverse atmospheric annealing effect on their structural, morphological, compositional, and gas sensing properties has been systematically studied and reported. Structural investigation corroborates the formation of crystalline hexagonal wurtzite ZnO. The arrays of vertically aligned nanorods and bunch of nanowires of ZnO were observed on the substrate surface. As-prepared ZnO NR's and BNW's are utilized as a sensing material for detection of toxic nitrogen dioxide (NO2). The ZnO sensors exhibit high response to NO2 along with rapid response and recovery time values @200°C. In addition, ZnO sensors respond to a very small exposure of NO2 gas i.e. 1ppm. Furthermore, the developed sensors attain excellent stability and reproducibility in response. Finally, the interaction of NO2 gas molecules with hierarchical nanostructured ZnO sensors has successfully been studied and discussed by employing an electrochemical impedance spectroscopy measurement.