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•Pd nanoparticle decorated SnO2 nanowires are fabricated.•Ppm scale hydrogen sensing properties are measured using Pd/SnO2 nanowires.•Sensing properties are optimized to manipulate ...the number of decorated Pd nanoparticles.•Enhanced sensing response of Pd/SnO2 nanowires are discussed using energy band diagram.
Pd nanoparticle-decorated SnO2 nanowires were synthesized to fabricate a highly selective and sensitive hydrogen gas sensor. The SnO2 nanowires were synthesized via a vapor–liquid–solid process, and Pd nanoparticles were decorated by a UV irradiation process using 1 mM PdCl2 solution to improve the hydrogen sensing properties of SnO2 nanowires. To generate Pd nanoparticles on the surface of SnO2 nanowires, 254 nm UV light was irradiated on SnO2 nanowires that were immersed in PdCl2 aqua solution, and the irradiation time was manipulated to control the number of Pd nanoparticles. The Pd nanoparticle-decorated SnO2 nanowires showed different hydrogen sensing responses followed by quantity of Pd nanoparticles, and the response of the optimum number of Pd nanoparticle-decorated SnO2 nanowires was 12.7 times that of bare-SnO2 nanowires when exposed 100 ppm of hydrogen gas. Furthermore, the selectivity of this nanowire-based sensor also improved as the Pd nanoparticles were decorated. The SnO2 nanowires exhibited similar sensing responses to several gases, but the hydrogen sensing response increased significantly after Pd nanoparticle decoration. In this case, the sensing response to hydrogen was 5 times higher than that of ethanol gas that showed the second-best response to the sensor. This improvement resulted from the catalytic effect of Pd nanoparticles and the formation of Schottky junctions between Pd nanoparticles and SnO2 nanowires. The mechanisms of the improved hydrogen sensing response of Pd nanoparticle-decorated SnO2 nanowires were discussed, and the optimum quantity of Pd nanoparticles required to obtain the best hydrogen sensing properties was discussed in this research.
Overall water splitting driven by a low voltage is crucial for practical H2 evolution, but it is challenging. Herein, anion‐modulation of 3D Ni–V‐based transition metal interstitial compound (TMIC) ...heterojunctions supported on nickel foam (Ni3N‐VN/NF and Ni2P‐VP2/NF) as coupled hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) catalysts for efficient overall water splitting is demonstrated. The heterointerface in Ni3N‐VN has a suitable H* absorption energy, being favorable for enhancing HER activity with onset overpotential (ηonset) of zero and Tafel slope of 37 mV dec−1 in 1 m KOH (close to that of Pt/C/NF). For the OER, the synergy of Ni2P‐VP2 with oxide species can give enhanced activity with ηonset of 220 mV and Tafel slope of 49 mV dec−1. The good activity is ascribed to heterointerface for activating the intermediates, good conductivity of TMICs for electron‐transfer, and porous structure facilitation of mass‐transport. Additionally, the minimal mutual influence of Ni3N‐VN/NF and Ni2P‐VP2/NF allows easy coupling for efficient overall water splitting with a low driving voltage (≥1.43 V), a voltage of 1.51 V at 10 mA cm−2, and remarkable durability for 100 h. It can be driven by a solar cell (1.5 V), indicating its potential to store intermittent energy.
An anion‐modulation strategy is presented to create 3D Ni–V interstitial compound heterojunctions (Ni3N–VN/nickel foam (NF) and Ni2P‐VP2/NF). The excellent hydrogen evolution reaction (HER) activity of Ni3N–VN/NF and oxygen evolution reaction (OER) activity of Ni2P–VP2/NF and minimal mutual influence make them easy to couple to achieve overall water splitting with a low driving voltage and remarkable stability.
Cr2O3 nanoparticle-anchored SnO2 nanowires are synthesized to fabricate highly sensitive and selective ethanol gas sensor. SnO2 nanowires are synthesized by vapor-liquid-solid method as a gas ...detection material, and Cr2O3 nanoparticles are anchored to SnO2 nanowires to improve sensing properties. Anchoring Cr2O3 nanoparticles are synthesized to deep the SnO2 nanowire sample to chromium oxide colloid gel, and anneal this sample at 500°C, in a vacuum atmosphere. This hybrid structured sensor presents 4 times improved ethanol sensing response compared with as-synthesized SnO2 nanowires when exposed to 100ppm ethanol gas in 300°C. Furthermore, sensing selectivity of ethanol versus other volatile organic compound (VOC) gas is also drastically improved. Generally, nanostructured SnO2 is known as very sensitive material to chemical gas, but it is hard to apply to commercial gas sensor since its extremely low selectivity. However, using this hybrid structured sensor, highly sensitive and selective ethanol sensor can be fabricated. This improvement of ethanol sensing properties can be explained that variation of energy bandgap of homojunction between n-SnO2 and n-SnO2 and heterojunction between n-SnO2 and p-Cr2O3 of nanowires. Furthermore, catalytic properties of this hybrid structure nanowire make selectivity of sensor improved.
Introducing a groundbreaking solution, a room-temperature (RT, 25 °C) gas sensor addresses complexities in conventional sensors, promising enhanced performance. Synthesized through hydrothermal and ...thermal calcination processes, SnO2 hollow nanospheres (HNs) are integrated with In2O3 components to bolster sensing capabilities. The sensor detects triethylamine (TEA) gas upon UV light irradiation, owing to its unique surface properties and SnO2–SnO2 and SnO2–In2O3 homo- and heterojunctions. This results in unparalleled sensitivity to TEA gas (Ra/Rg = 34–100 ppm) and an exceptional limit of detection (3.98 ppt), attributed to photo-ionized O2− ions' heightened reactivity. The study proposes superior sensors backed by comprehensive analyses, demonstrating their performance improvements and underlying mechanisms. The optimized sensor design, based on In2O3-appended SnO2 HNs, presents exceptional selectivity, pattern recognition for low TEA gas concentrations, humidity resistance, and reliability under UV irradiation.
Many workflow applications are moved to clouds for elastic capacities. Elastic resource provisioning is one of the most important problems. Realistic factors are involved, including an interval-based ...charging model, data transfer time, VM loading time, software setup time, resource utilization, and the workflow deadline. A multirule-based heuristic is proposed for the problem under study which contains two components: a deadline division and task scheduling. Taking into account the gaps between tasks, the impact of different critical paths and the precedence constraints, the workflow deadline is properly divided into task deadlines based on the solution of a relaxed problem. The relaxed problem is modeled by integer programming and solved by CPLEX. All tasks are sorted in terms of the developed depth-based rule. For different realistic factors, three priority rules are developed to allocate tasks to appropriate available time slots, from which a weighted rule is constructed for task scheduling. The weights are calibrated by random instances. Experiments are conducted using a benchmark realistic workflow. Experimental results show that the proposal is effective and efficient for realistic workflows.
Toluene gas is hazardous but plays a vital role in several industries. Hence, the detection of toluene gas is important for human health and the environment. In this study, porous In2O3–ZnO ...nanofibers were prepared via a facile electrospinning method to fabricate a toluene gas sensor. Illumination by ultraviolet light (365 nm) was used to realize the room temperature (RT) operation of the fabricated sensor. The structural properties of the sensor were studied using various characterization techniques. The prepared nanofibers consisted of many sub-nanograins, particularly ZnO and In2O3, and contained numerous pores in-between the nanograins. Consequently, these nanofibers had a large surface area, increasing the probability of contact between the gas and sensor. The prepared sensors were functional at RT under UV illumination and showed excellent toluene-sensing properties. The porous In2O3-appended ZnO-nanofiber-based sensors showed more stable and sensitive response curves than those of the pure ZnO nanofiber–based sensor. Moreover, In2O3-appended ZnO nanofiber sensors could only faintly detect other gases, such as NO2, acetone, ethanol, H2S, and CO gases, indicating that the sensor exhibits highly selective toluene sensing.
ZnO nanowires were prepared by oxidized ZnS nanowires. The sensing performance of these ZnO nanowires for NO2 gas was enhanced by decorating Au nanoparticles on their surface. The scanning electron ...microscopy results revealed that diameter and length of the ZnO nanowires showed 150–200 nm and up to a few hundreds of μm, respectively. The diameters of Au nanoparticles which were decorated on the ZnO nanowires were 5–20 nm and they were distributed evenly on the surface of the nanowires. The transmission electron microscopy results revealed that the ZnO nanowires obtained after 2 h of the oxidation treatment process were composed of lots of nanograins with a diameter of 50–100 nm, which rendered the surface of the nanowires rough and full of void spaces. The hierarchical structure of the nanowires increased their surface-to-volume ratio and contributed to the adsorption of gas on their surface, improving their sensing performance. In this study, the NO2 gas sensing mechanism of the Au nanoparticle-decorated ZnO nanowires sensors were investigated under UV illumination at room temperature.
Co3O4 nanoparticle-attached SnO2 nanowires are synthesized to fabricate highly sensitive acetone gas sensor by vapor-liquid-solid (VLS), sol-gel, and thermal annealing processes. To analyze enhanced ...acetone gas sensing responses, Co3O4 nanoparticles are attached SnO2 nanowires, and several samples are synthesized followed by the cycles of Co3O4 nanoparticle attachment process. The sensing response of Co3O4 nanoparticle-attached SnO2 nanowires, which are one time performed Co3O4 nanoparticle attachment process, is improved by 7 times compared with as-synthesized SnO2 nanowires when exposed to 50 ppm acetone gas. In particular, when exposed to 0.5 ppm acetone gas, as-synthesized SnO2 nanowires present an extremely low response — close to negligible. However, when Co3O4 nanoparticles are attached, the response is improved drastically. Furthermore, the sensing selectivity toward acetone gas is improved compared with its counterpart. This improved sensing property is derived from the increasing variation in the surface depletion area located in the p-n heterojunction.
In XaaS clouds, resources as services (e.g., infrastructure, platform and software as a service) are sold to applications such as scientific and big data analysis workflows. Candidate services with ...various configurations (CPU type, memory size, number of machines and so on) for the same task may have different execution time and cost. Further, some services are priced rented by intervals that be shared among tasks of the same workflow to save service rental cost. Establishing a task-mode (service) mapping (to get a balance between time and cost) and tabling tasks on rented service instances are crucial for minimizing the client-oriented cost to rent services for the whole workflow. In this paper, a multiple complete critical-path based heuristic (CPIS) is developed for the task-mode mapping problem. A list based heuristic (LHCM) concerning the task processing cost and task-slot matching is developed for tabling tasks on service instances based on the result of task-mode mapping. Then, the effectiveness of the proposed CPIS is compared with that of the previously proposed CPIL, the existing state-of-the-art heuristics including PCP, SC-PCP ( an extension to PCP), DET, and CPLEX. The effectiveness of the proposed LHCM is evaluated with its use with different task-mode mapping algorithms. Experimental results show that the proposed heuristics can reduce 24 percent of the service renting cost than the compared algorithms on the test benchmarks at most for non-shareable services. In addition, half of the service renting cost could be saved when LHCM is applied to consolidate tasks on rented service instances.
A flower-like ZnO was successfully synthesized via a simple chemical precipitation method at room temperature (RT) in distilled water, without the use of any catalysts or substrates. The sample’s ...structure was analyzed using various techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (FETEM), and X-ray photoelectron spectroscopy (XPS), which confirmed its hexagonal structure. UV–visible optical absorption measurements also revealed the presence of UV absorption at 365 nm. A reasonable growth mechanism for the formation of flower-like ZnO was proposed based on these analyses. The response of the sample to low concentrations of NO2 (1 ppm) was evaluated at different calcination temperatures, and the results showed that the best response was achieved when the sample was calcined at 600 °C. The flower-like ZnO sample labeled as 6ZnO showed the highest response of 54.18 when exposed to 1 ppm of NO2 gas at RT. Additionally, 6ZnO exhibited good response and recovery properties of 11 s and 93 s, respectively, at low concentrations of NO2 at 1 ppm. The gas sensing mechanism and the mechanism of the enhanced gas response of the flower-like ZnO are discussed.
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