Low Recovery Time Research Articles

Change in the gas sensing mechanism and improved sensing response on ion-irradiated palladium-graphene oxide nanocomposite

In this study, we synthesized Pd-graphene oxide (Pd-GO) nanocomposite layers on SiO2/Si substrates using chemical method. Pd-GO layers were treated with swift heavy ion irradiation (100 MeV Ag ions, 1013 ions/cm2). The structural properties of the pristine as well as the ion irradiated samples were investigated using synchrotron grazing incidence x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) techniques. XRD shows peaks corresponding to Pd (FCC, space group-Fd-3m), GO and synthetic graphite. The relative graphite peak intensities increased after ion irradiation, indicating reduction of GO. The sensor responses of nanocomposite layers towards exposure of 35 ppm H2 at 100 °C, were measured for several cycles. Ion-irradiated Pd-GO samples show enhancement in the sensing response of H2 gas by about 24% and with lower recovery times (25%), as compared to pristine Pd-GO nanocomposite samples. The change in type of conductivity from p-type gas sensing layer in pristine nanocomposite to n-type conductivity, along with an increase in conductivity (about 500 times) in ion irradiated samples were observed. The change in type of conductivity on ion-irradiation is attributed to the reduction of GO layer and the changes in conductivity on hydrogen exposure is explained due to hydrogen spill-over effect in the two-component system. The improvement in sensitivity upon ion-irradiation was due to the increase in concentration of structural defects due to electronic energy loss, as studied by SRIM simulation. This study points towards using ion induced electronic energy loss as a new tool for varying the gas sensing properties of GO based sensors.

Treatment of Varicocele in Adults: Surgery versus Embolization: Experience of Mohammed V Military Instruction Hospital

Introduction: Varicocele is a varicose dilatation of the spermatic cord veins, particularly the pampiniform plexus. It is a frequent and benign affection, which may have a harmful effect on spermatogenesis. Aim: Through this work, we will try to compare the efficiency, complications and recurrence after treatment of varicocele in two patients groups: surgery and embolization. Material and Methods: This is a retrospective study that included all patients treated for idiopathic varicocele, symptomatic or associated with abnormalities of the semen analysis, by embolization, between 2016 and 2021, at the Moulay Ismail Military Instruction Hospital. Thirty patients were included. To compare, the last 30 patients treated by surgery (open or laparoscopic) were included in a second group. Patients in the embolization group were treated with coil embolization or sclerosant agent under local anesthesia. We compared the efficiency, complications and recurrence rate after treatment of varicocele in both groups. The statistical analysis was carried out by the epidemiology laboratory of the Faculty of Medicine and Pharmacy of Fes using the Chi test 2 and Anova test. Results: Surgery has a higher success rate than embolization. However, embolization offers many advantages in terms of surgical time (p = 0.001), duration of hospital stay (p = 0.001), lower recovery time, and less long-term complications. Recurrence was found in 4 patients in group 1 and in 2 patients in group 2. In both groups, there was an improvement in semen analysis, with pregnancy occurred in one couple in group 2, and four in group 1. Conclusion: These two treatment methods are effective in the treatment of idiopathic varicocele, but embolization is a faster, less invasive technique with low postoperative morbidity.

Use of Fantasy Points in Evaluating Professional Athlete Performance After Anterior Cruciate Ligament (ACL) Reconstruction.

Our aim in performing this study was to evaluate whether fantasy and wins above replacement (WAR) scores of athletes undergoing anterior cruciate ligament (ACL) reconstructive surgery in the National Football League (NFL), National Basketball Association (NBA), National Hockey League (NHL), and Major League Baseball (MLB) could be utilized in evaluating their performance post-surgery. We identified publicly accessible data on professional athletes from 1992 to 2015. Fantasy and WARscores were calculated for each player. A total of 83 professional players met the inclusion criteria for this cross-sectional study. Decreased fantasy scores ranged from 33% to 42% across the four leagues after the index operation. NHL players had the lowest return-to-play (RTP) rate at 11/17 (82%), and MLB players had the highest RTP rate at 14/15 (93%). RTP rates of NBA and NFL players were comparable at 22/26 (85%) and 22/25 (88%), respectively. NFL players had the lowest average career length after surgery at 26 months, while NBA players had the longest average career length at 64 months. MLB players on average required the longest time to return to the pre-surgical level of performance (21 months). NHL players had the shortest average recovery time (eight months), and NBA players had the longest average recovery time (13 months). Approximately, more than half of all the studied players exhibited a decline in fantasy or WAR scores. In addition, NFL players had the lowest average career length, and NBA players enjoyed the longest average career length after surgery. NHL players had the lowest recovery time, while NBA players had the longest recovery time.The strength of this study is the utilization of fantasy points and WAR scores as a single unifying measure of a player's performance, which acts as an objective measure after ACL reconstruction. The average performance of a professional athlete, as evaluated through their fantasy score output, tends to decrease after undergoing ACL reconstruction. There is an overall long-term performance decline after initial spikes in their performance after surgery. Additional largerstudies are needed to fully understand the effects of ACL reconstruction in professional athletes;however, the use of fantasy scores may be an objective tool in measuring the success rate of ACL reconstruction.

Copper decorated graphyne as a promising nanocarrier for cisplatin anti-cancer drug: A DFT study

Novel two-dimensional carbon allotrope namely pristine graphyne and Cu-doped graphyne have been proposed and their potentiality as nanocarriers for cisplatin anticancer drug is demonstrated theoretically. Based on binding energy calculation, it has been noted that pristine graphyne (-0.550 eV), as well as Cu-decorated graphyne (-0.750 eV), are suitable candidates for drug delivery, as the binding energy falls in the physisorption range. A charge transfer of 0.012 e from Cu-decorated graphyne is observed, which results in charge depletion in the Cu-doped graphyne system. The loss is mainly encountered by Cu (0.012 e) atom. Further, binding energy has been recalculated in the biological environment (acidic conditions) to infer drug release phenomena. A decrease in binding energy (-0.012 eV) and low recovery time reflects the successful release of cisplatin drug inside the body. Ab initio molecular dynamics simulation ensured that Cu-doped graphyne is stable at 300 K and can be used as nanocarrier for cisplatin drug. Interestingly, desorption temperature is slightly higher than body temperature and it comes closer to body temperature under acidic environment and this suggests cisplatin drug is certainly absorbed within the human body. Our theoretical predictions will inspire the experimentalist to design graphyne-based drug delivery systems.

First-principles study of electronic and optical properties of NH3-adsorbed Sc2CO2 monolayer and its application in gas sensors

Two-dimensional Sc2CO2 MXene materials have been considered highly potential for gas capture and gas sensor applications. In this study, the adsorption behaviors of small molecules such as NH3, SO3, O2, H2CO and C2H4 on Sc2CO2 monolayer were investigated using first-principles methods. Our results demonstrate the preferential adsorption of NH3 over other species with adsorption energies as high as −0.55 eV. And Sc2CO2 is transformed from an indirect bandgap semiconductor to a direct bandgap semiconductor after NH3 adsorption, and the appropriate band gap makes it potential for light absorption and photodetection. In addition, the carrier mobility of Sc2CO2 monolayer is significantly enhanced by adsorption, making it easy to detect changes in resistance. The room-temperature electron mobilities of NH3-adsorbed Sc2CO2 along armchair and zigzag directions are predicted to be as high as 16.75 × 103 and 13.19 × 103 cm2V−1S−1, while the room-temperature hole mobilities along armchair and zigzag directions are determined to be 10.77 × 103 and 11.09 × 103 cm2V−1S−1, respectively. According to the present results, Sc2CO2 monolayer is expected to be promising for the design and application of efficient NH3 gas sensor devices with high selectivity, high sensitivity and low recovery time through analytical methods based on optical and/or electronic responses.

Density functional theory (DFT) computation of pristine and metal-doped MC59 (M = Au, Hf, Hg, Ir) fullerenes as nitrosourea drug delivery systems

In recent times, C60 fullerene and its derivatives have drawn increasing attention in nanomedicine due to their bioavailability and low toxicity. Herein, we investigated the interactions of nitrosourea (NU) drug with pristine and metal-doped MC59 (M = Au, Hf, Hg, Ir) at the M06–2X/gen/LanL2DZ/def2-SVP level of theory. The structural, adsorption energy, charge transfer, electronic, QTAIM, and NCI analyses were investigated based on the density functional theory (DFT). In contrast to physisorption of NU drug on the pristine C60 surface, the metal-doped NU@MC59 complexes have stronger interactions and are chemically adsorbed on the metal-doped fullerene surfaces, with NU@HfC59 having the strongest interaction. Similarly, metal-doping altered global hardness and energy gap values such that reactivity and sensitivity increased for NU@HfC59, NU@HgC59, and NU@IrC59. Meanwhile, the reactivity and sensitivity decreased for NU@AuC59. Among all the complexes, NU@HfC59 exhibited the highest electrical conductivity and sensitivity due to its least HOMO-LUMO energy gap value. The QTAIM and NCI analyses indicated that the complexes are formed predominantly via non-covalent interactions. The results suggest that metal doping enhanced the sensitivity and conductivity of pristine C60. With moderate adsorption energy and low recovery time, especially for HfC59 and IrC59 fullerenes, this indicates that the metal-doped fullerenes are promising nitrosourea drug delivery candidates in nanomedicine.

Shape selective comprehensive gas sensing study of different morphological manganese-cobalt oxide based nanocomposite as potential room temperature hydrogen gas sensor

The design of morphology-based spinel structures has appeared as an effective approach for improving the performance of the sensor in hydrogen gas sensing to facilitate hydrogen economy. In this study, we report a detailed shape selective analysis of four different morphological spinel structures supported on reduced graphene oxide (rGO) as an efficient hydrogen sensor. Our study revealed that the response of manganese-cobalt oxides are strongly depended on the morphology of the system (flower, rod, flakes and sphere) which can be explained by combined effects of surface area, defects generated on the surface and crystallinity. The n-type responses of all native oxides and the composite modified with rGO indicated the formation of n-n heterojunction at their interface. The bare flower-like structure showed higher responses (S% = 6.3) with low response time (17 s) and recovery time (18 s) at higher temperature (160 °C). In comparison, the improved sensing behavior of the composite with highest response (12.77%) and lowest response-recovery time (9 s and 13 s, respectively) at room temperature can be attributed to the higher electrical conductivity of rGO with fast charge carrier mobility. Also, this novel gas sensor demonstrated superior sensitivity, higher stability, and better selectivity against various gaseous mixtures.

Comparative DFT study on the H2 adsorption and the sensing properties of BN-, BP-, AlN-, and AlP-decorated graphene nanoflakes

In this research, the application of BN, BP, AlN, and AlP edge-doped graphene nanoflakes as sensor for sensing of H 2 molecule was studied by DFT approach. The M06-2X/6-311G++(d,p) level of theory have been used in the calculations. The results showed that the adsorption of H 2 molecule on the BN, BP, and AlN was very weak (−0.97, −0.16, and −1.14 kcal.mol −1 , respectively). By considering the acceptable adsorption of H 2 molecule on the AlP-doped graphene with −5.03 kcal.mol −1 , further calculations were performed on this sheet. Upon adsorption of H 2 molecule, the HOMO–LUMO gap ( E g ) of the AlP-doped graphene nanoflake decreased slightly from 2.01 to 1.92 eV. Therefore, the electrical conductivity of AlP-doped graphene sheet increased. Moreover, Δ H ad = −3.38 kcal.mol −1 and Δ G ad = −1.38 kcal.mol −1 show that the adsorption of H 2 molecule on the AlP-doped graphene is an exothermic and spontaneous phenomenon at room temperature. The NCI-RDG analyses verifies the presence of vdW interactions between H 2 molecule and the AlP-doped graphene. Finally, according to the very low recovery time as 4.65 ns, AlP-doped graphene might be utilized as an effective and fast sensor for H 2 molecule at room temperature. • The effect of BN, BP, AlN, and AlP edge doping of graphene on the H 2 sensing is studied. • Adsorption of H 2 molecule on the AlP-edge doped graphene occurs thermodynamically effective. • NCI-RDG analysis shows that the H 2 adsorption on the AlP-edge doped graphene occurs via vdW interactions. • AlP-edge doped graphene can be considered as an ultrafast H 2 sensor with 4.65 ns recovery time.

2-D Be2C as Multitime Reversible Environmental Oxygen- and Nitrogen-Containing Gases Sensor Material Under First Principle Investigations

A combined density functional theory and nonequilibrium Green’s function (DFT-NEGF) approach has been conducted to examine the potential of monolayer Be2C nanosheet as a promising sensor for various environmentally toxic/nontoxic nitrogen- and oxygen-containing multigases (NCGs and OCGs). A total of eight gases comprising four OCGs (O2, CO, CO2, and H2O) and four NCGs (NO, NO2, N2O, and NH3) are investigated on the surface of monolayer Be2C to identify its gas sensing potential. The nontoxic O2, CO2, and H2O are also included in the study considering their obvious presence in the environment. Our investigation suggests that at room temperature, larger adsorption energy of NO, NH3, and O2 gas molecules on the surface of Be2C reflects a more significant recovery time as 1016, 105, and 1012 s, respectively. The positive higher adsorption energy of NO2 gas molecules as 0.91 eV adsorbed on the Be2C nanosheet at room temperature results in a very short recovery time of 10−29 s. The adsorption energy of the NO2 gas molecule is positive, making it unsuitable for gas sensors. In all cases, notable variation is observed in electronic and adsorption properties, charge transfer, recovery time, work function, and transport characteristics of OCGs and NCGs on Be2C surface. OCGs and NCGs show electron acceptor nature during interaction with Be2C nanosheet. The electronic transport of Be2C sheet shows its highly selective and sensitive nature toward OCGs and NCGs. Overall, monolayer Be2C reveals as an excellent multitime reversible multigas sensor material for four gases, viz. CO, CO2, H2O, and N2O with their significantly low recovery time, whereas it appears to be one-time disposable sensor material for O2, NO, and NH3 gases with higher adsorption energy and relatively long recovery time.

Hybrid breast augmentation: our surgical approach and formula for preoperative assessment of fat graft volume.

Autogenous fat grafting (AFG) is a well-known procedure utilized in addition to breast augmentation (BA) to improve breast appearance. Plastic surgeons usually estimate the ideal AFG volume relying on their personal experience based on similar previous cases: inaccurate predictions could result in incorrect evaluation of donor sites and even needless fat transfer. The purpose of this paper is to describe and prove the validity of our surgical technique and provide a simple and easy-to-use mathematical formula to assess the adequate proportion, between the volume of the implants and of the AFG, in order to obtain a natural shape and a proper volume in BA. One hundred and twenty-two patients (244 breasts) were subjected to primary/secondary hybrid BA (HBA). A formula was utilized to assess the volume of fat graft. Data about their age, body mass index (BMI), incision and implants were collected. Follow-up for analysis was fixed at less than 15 days, 1, 3, 6 and 12 months for analysis. Preoperative photographs were compared with postoperative at 12 months. Pre and postoperative Breast-Q© were administered to every patient. A statistical analysis was performed comparing Breast-Q© preoperative means with postoperative ones through t-student test. We globally defined the patients as follows: "very dissatisfied" if total score 0-25; "somewhat dissatisfied", score 26-50; "somewhat satisfied", score 51-75; "very satisfied", score 76-100. All patients received Ergonomix-style Motiva Smooth/SilkSurface with low/high projection (range, 120-225 mL, mean 170 mL) and an average AFG volume of 600 mL (range, 480-720 mL). Breast-Q© analysis showed a statistically significant difference between preoperative and postoperative modules; 122 (100%) patients were "very satisfied". Thirteen cases of complications presented in 12 patients (10.65%): 5 hypertrophic scarring (4.09%), 3 wound dehiscence (2.46%), 3 hematomas (2.46%), 1 seroma (0.82%), 1 fat necrosis (0.82%). Our surgical technique proves low complication rate and short recovery times. Our mathematical formula to calculate the AFG seems to be both predictive and a precise guide for surgical decision-making in planning the treatment of patients candidated for HBA. In fact, the analysis of Breast-Q© questionnaires shows a high grade of satisfaction among patients. Further investigations should be performed in order to study a wider population and different type of implants.

Liquefied petroleum gas sensing performance of solochemically synthesized ZnO nanorods: Role of precursors and fractal analysis

Nanorods of ZnO were grown successfully using a template free solochemical route using zinc chloride, zinc nitrate and zinc acetate precursors at 70 °C. The structural and morphological analysis of synthesized all ZnO samples were tested by X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscopy (TEM) techniques. Whole pattern fitting of XRD patterns shows less strain in unit cell is observed in case of ZnO sample synthesized from zinc chloride precursor. Variations in aspect ratios of ZnO nanorods synthesized using different precursors were observed from TEM results. The ZnO nanorods composed thin films were fabricated via spin coating technique and its liquefied petroleum gas (LPG) sensing performance was investigated. The surface topographical studies and fractal analysis of these films were examined by atomic force microscopy (AFM). These results reveals that thin film composed ZnO nanorods prepared using zinc chloride precursor possess average roughness ~133 nm and fractal dimension ~ 2.42, which is higher than other films. This film exhibits maximum gas response ~502 towards 50 ppm LPG, along with low response and recovery time, repeatability, great selectivity as compared with thin films synthesized from other precursors. The reason of enhancement of gas response for ZnO thin film synthesized using precursor zinc chloride as compared to zinc acetate and zinc nitrate is explained on the basis of aspect ratio and fractal roughness. The LPG sensing mechanism towards ZnO nanorod is also discussed. • ZnO nanorods are prepared by a simple and low-cost solochemical method. • Excellent LPG performance of spin- coated films using ZnO nanorods explored. • Effect of precursors on LPG sensing and fractal analysis evaluated. • The sensor exhibits a fast response (~6–7 s) and a quick recovery (~6–7 s). • Role of precursors during gas sensing performance assessed on the basis of fractal analysis.

Density Functional Theory Study of Cu-Modified B12N12 Nanocage as a Chemical Sensor for Carbon Monoxide Gas.

The development of efficient B12N12-based toxic gas sensors has received considerable attention from the scientific community. Thus, in this regard, quantum chemical calculations were performed using density functional theory (DFT) at the B97D/6-31G(d,p) level for all of the studied systems. Modification of copper on B12N12 results in five optimized structures, named CuB11N12 and B12N11Cu (doped structures), Cu@b66 and Cu@b64 (decorated structures), and Cu@B12N12 (encapsulated structure). The results indicate that the CO gas weakly physisorbed on the B12N12 nanocage. It was found that the gas adsorption performance of B12N12 is improved due to the introduction of the Cu atom, but the interaction between CO and B12N11Cu, Cu@B12N12, Cu@b64, and Cu@b66 nanocages is strong, limiting the applications as a sensor. Particularly, the CuB11N12 system shows moderate adsorption (Eads = -0.6 eV) and a high electronic sensitivity (ΔEgap = 81.6%) toward CO gas, compared to other modified systems. Furthermore, based on the sensor performance analysis, it was found that CuB11N12 presented low recovery time (14 ms) and high selectivity for CO detection, making it a promising fast response sensor. Finally, our results demonstrated the capability of CuB11N12 as a superior sensor material for applications involving the selective detection of CO gas.

Fast and accurate measurement of the polarization-dependent detection efficiency of superconducting nanowire single photon detectors.

Superconducting nanowire single photon detectors (SNSPDs) have been extensively investigated due to their superior characteristics, including high system detection efficiency, low dark count rate and short recovery time. The polarization sensitivity introduced by the meandering-type superconductor nanowires is an intrinsic property of SNSPD, which is normally measured by sweeping hundreds of points on the Poincaré sphere to overcome the unknown birefringent problem of the SNSPD's delivery fiber. In this paper, we propose an alternative method to characterize the optical absorptance of SNSPDs, without sweeping hundreds of points on the Poincaré sphere. It is shown theoretically that measurements on the system detection efficiencies (SDEs) subject to cases of four specific photon polarization states are sufficient to reveal the two eigen-absorptances of the SNSPD. We validate the proposed method by comparing the measured detection spectra with the spectra attained from sweeping points on the Poincaré sphere and the simulated absorption spectra.

Shape-controlled SnO and their improved properties in the field of gas sensor, photocatalysis, and lithium-ion battery

In this paper, over 20 kinds of tin monoxide (SnO) morphologies are prepared by using a facile solvothermal process. Among all these obtained SnO materials, the shapes with unique morphologies such as bowl-, pompon-, sheet-, hollow frame-like structures exhibit excellent NO2 gas sensing, photocatalytic degradation, and lithium-ion batteries properties due to their large specific surface area and more active sites compared with other shapes. For the NO2 gas sensors properties, these SnO with unique morphologies exhibit excellent sensing performance, including low detection limits (≤ 100 ppb, even reaching 5 ppb), short response and recovery time (< 100 s). Finally, the as-prepared SnO are used as the efficient photocatalysts and lithium-ion battery anode material. These performances have been improved significantly compared with other shaped SnO proposed by other reports. All these advantages indicate the huge application potential of SnO in the field of photocatalysis, gas sensitivity, and lithium-ion battery performance.

(Invited) Breakdown Improvement and Reverse Recovery Characterization in Vertical GaN PN Diodes

Wide bandgap semiconductor devices based on gallium nitride (GaN) and silicon carbide (SiC) are attractive semiconductor technologies for future generation power electronics.Lateral GaN HEMTs have dominated the low voltage arena, while SiC MOSFETs have been the preferred technology for higher voltage applications. Devices based on GaN are regarded as having a strong potential for next generation power electronics owing to their high electron mobility, high thermal conductivity, high critical electric field and very low reverse recovery time. The theoretical high voltage capability of GaN is superior to both SiC and silicon (Si), which has resulted in significant government investment for the development of vertical GaN architectures, with a particular emphasis on thicker epitaxial layers, as well as more reliable substrates. The relative improvement in the development of native GaN substrates over the recent years has encouraged production of homo-epitaxial GaN-on-GaN vertical devices with low defect densities and reduced capacitances. Some major advantages of vertical GaN devices include their design robustness, due to avalanche breakdown capability, as well as their ability to attain higher blocking voltages through appropriate edge termination. One of the major challenges in designing junction terminations in GaN vertical devices is the limitation in selective area ptype doping. Selective area p-type doping in GaN is typically performed via Mg implantation, which is known to have a low activation efficiency as well as limited range of implant energy and dosage. Addressing these limitations requires innovative design of termination structures. Iterative refinement between TCAD modeling and fabrication can facilitate design optimization to improve breakdown potential. Circuit simulation can be used to project the performance of the device in various applications and benchmark its performance against other conventional materials.This paper proposes a vertical GaN diode with a blocking capability of 1.3 kV, acquired through a simple technique of edge termination. The initial device design consists of a very highly doped (2 × 1020 cm−3) p++ capping layer on top of the pGaN layer to facilitate the formation of a low resistance ohmic contact with the anode metal. Four samples differing in p-type doping levels are studied under reverse bias using Sentaurus TCAD (Synopsys). The simulations are used to examine the regions of the device that are highly susceptible to field crowding, leading to design considerations for improved breakdown performance. It is shown both through simulations and empirically, that elimination of the highly doped p++ capping layer allows the lower doped p-type layer to serve as a Junction Termination Extension (JTE). The proposed simplified technique of edge termination is produced by the regulation of charge in the lower doped pGaN layer, and does not require selective area p-type doping, thereby substantially improving the manufacturability. The empirically validated diode characteristics are then exported to a circuit simulator and compared to a similarly-rated commercially available Si ultra-fast diode using a double pulse test (DPT). Comparison of the switching characteristics of both the diodes reveals that the proposed GaN diode shows significantly higher efficiency during reverse recovery.Fig. 1 shows the shows the initial device design under consideration. A TCAD model of this device was then implemented in Sentaurus TCAD (Synopsys). The simulated device structure is shown in Fig. 2. Fig. 2(a) illustrates a magnified view of the drift and pGaN layer, above the substrate, while the mesh structure of the entire device is shown Fig. 2(b). Fig. 3 illustrates simulated and experimental static characteristics of the devices, both in terms of forward conduction, and reverse breakdown. As can be seen in Fig. 3, the model accurately predicts the static characteristics of the device. However, wafers two and three (W2 and W3) have significantly lower pGaN doping than wafer one and wafer four. This would suggest a greater breakdown voltage for wafer 2 and wafer 3. However, as seen in Fig. 3, this was not the case.Further analysis via TCAD reveals that the p++ capping layer is the reason for the premature breakdown of W2 and W3. Fig. 4 shows electric field distribution plots for W3 before and after selective removal of the p++ capping layer. Prior to removal, the electric field is unable to uniformly spread across the junction, as seen in Fig. 4(a). On the contrary, after removal of the p++ capping layer, a more uniform electric field distribution is obtained.These simulated results were validated experimentally as seen in Fig. 5. The p++ capping layer was etched away everywhere except underneath the anode. From Fig. 5, the breakdown potential of the device improves by approximately 50%. Figure 1

Suitability of chlorobenzene-based single-electron transistor as HCN, AsH3, and COCl2 sensor.

A density functional theory (DFT)-based first principle approach has been employed to investigate the suitability of chlorobenzene-based single-electron transistor (SET) for the detection of few toxic gases such as hydrogen cyanide, arsine, and phosgene. The adsorption aspect of toxic gas molecules on the chlorobenzene with different orientations has been analyzed. The attributes such as charge density, molecular energy spectrum, density of states, and Mulliken population have been computed to scrutinize the effect of gas molecules on the surface of chlorobenzene. The sensing mechanism of adsorbate (toxic gases) with the adsorbent (chlorobenzene) has been authenticated in a single-electron transistor (SET) environment through total energy vs. gate voltage plot and charge stability diagram. The recovery time of the chlorobenzene-based SET gas sensor on the adsorption of HCN, AsH3, and COCl2 has been computed as 1.93ns, 0.45ns, and 36.31ns, respectively. Based on these findings, it is interesting to see that the COCl2 gas molecule shows strong physical adsorption with the most significant adsorption distance (3.629Å) with chlorobenzene, while AsH3-adsorbed chlorobenzene SET displays a low recovery time in comparison with other considered gases. The present analysis confirms a significantly better range of detection and improved recovery time using chlorobenzene-based single-electron transistor.

FexZn1-xOy as room temperature dual sensor for formaldehyde and ammonia gas detection

The present research centres on synthesizing Zinc Oxide (ZnO) nanostructures with exceptional surface modification via Iron (Fe) doping (2–8%) using the sol-gel route. The as-synthesized samples were analyzed to scrutinize the structural, morphological, optical and gas sensing attributes of ZnO and Iron doped ZnO (Fe-ZnO). The investigation discloses appreciable sensing performance for different volatile organic compounds(VOCs), exclusively for Ammonia (NH3) and Formaldehyde (HCHO) gases. The X-ray diffraction pattern revealed a well hexagonal wurtzite structure and slight (1 0 1) preferred orientation growth. The crystallite size was increased from 13.43 nm to 14.93 nm by increasing the doping level of Fe in ZnO. Moreover, gas sensor studies of ZnO and Fe doped ZnO nanomaterials synthesized at various doping amounts were tested at room temperatures and at different NH3 and HCHO gas concentrations. The sensor response for the 8% Fe doped ZnO sample was observed as 305 and 83, whereas response and recovery time were (1.71 s, 2.06 s) and (1.6 s, 1.23 s) for NH3 and HCHO, respectively, at room temperature. For 100 ppm NH3 and HCHO concentration, ZnO, Fe-ZnO (2%), Fe-ZnO (4%), Fe-ZnO (6%), Fe-ZnO (8%) gas sensors displayed gas responses of 8688.03, 1426, 2426.92, 5893.76, 27173.22 and 60.25, 268.22, 369.70, 2560.92, 34105.16 respectively. Hence, 8% Fe-doped ZnO sensor displayed appreciable response and low response and recovery time than sensors based on pure and Fe doped NiO with dopant concentration 2–6%.

First-principles study of CO adsorption on zigzag ZnO nanoribbons towards nanosensor application

The efficient detection of toxic gases and development of compact, low dimensional sensors is the center of research activities in the past two decades. In this direction, here we gauged the potential of monatomic thick zigzag ZnO (zZnO) nanoribbons towards the sensing of most abundant toxic gas i.e. CO. The adsorption of CO molecules on zZnO nanoribbons (zZnONR) has been studied in different possible ways. It is revealed that electronic and transport properties of zZnONR are affected by the interaction of CO molecules. Moreover, it is noticed that CO molecules always bond with the nanoribbons edges through the C-side and adsorption takes place via formation of a stable chemical bond. The transport properties reveal a peculiar behavior that the current magnitude is significantly higher when CO adsorption happens at O-edge. Furthermore, the maximum current is obtained when CO is adsorbed at both the edges of ribbon. Our findings show that selective configurations of CO adsorption are helpful for the designing of nano sensors with considerably lower recovery time.

Enhanced Gas Sensing Performance of Nano‐Structured Ta2O5‐SnO2 Composite for Low Concentration CO Detection

AbstractIn the present work, the superior performance of nanostructured Ta2O5‐SnO2 nanocomposite homo‐junction was demonstrated for the detection of CO gas at low concentration (5‐10 ppm) and low operating temperature (50 °C). The gas sensing performance of this material is comparable to the state of the art materials reported to date in the literature. In addition, the material exhibits high selectivity to CO gas over other interfering gases such as CO2, H2, CH4, NO2, and SO2 etc. The sensing performance of the composite was significantly higher than its individual oxides. The composite is robust and shows good reproducibility and chemical stability with low response and recovery time. The strategy employed herein to create homo‐junction nanocomposites of semiconducting metal oxides significantly improved the sensitivity and selectivity to CO gas closer to room temperature and thus could pave the way for the development of efficient homo‐junction nanocomposites for gas sensing applications.

Amorphous molybdenum trioxide thin films for gas sensing applications

Uniform and smooth substoichiometric Molybdenum trioxide (MoO3−x) films have been achieved via thermal evaporation technique. MoO3 thin films were deposited onto glass and fluorine doped tin oxide (FTO) coated glass slides. The field-emission scanning electron microscopy micrographs reveal the amorphous behavior for films deposited either on glass or FTO substrates. The two thicknesses 500 and 650 nm of MoO3−x films which are deposited on glass and FTO coated glass slides were electrically examined as sensors towards NO,CO2 and HCl gases. The sensing process have been explained based on the electrical dipole layer formation consisting of the two unlike charged ion- layers and causing an energy band bending at the surface region of the film as a result of the gas adsorption. MoO3−x films on glass substrate is a perfect sensor towards oxidizing CO2 and NO gasses. The sensors are very sensitive towards low gas flow rate (20 standard cubic centimeters per minute (sccm)) and manifest the highest sensitivity values at relatively low temperatures compared with the other MOS with short response and recovery times (4 min for CO2 and 2 min for NO). The recorded sensitivity of MoO3−x sensor towards CO2 and NO gases at temperature 200 0 C shows that these samples are more sensitive towards CO2 gas, so this sensor is selective to CO2 gas more than NO. These results confirm that MoO3−x film deposited on glass of 500 nm thick can solve a large section of detecting CO2 gas problems such as selectivity, sensitivity to low gas concentrations, short response, recovery time, reversibility and low working temperature. Finally, the MoO3−x films (with thickness of 500 nm) deposited on FTO substrate was examined as gaseous HCl sensor at room temperature. It manifests a very high sensitivity towards gaseous HCl but cannot be applied for detecting it due to irreversibility and no stability of their properties after HCl vapor adsorption.