Air Molecules Research Articles

High‐Performance Broadband Visible−Near Infrared Photodetector Enabled by Atomic Capping Layer

AbstractThis study employs an effective oxygen (O2) plasma treatment to fabricate multilayer molybdenum diselenide (MoSe2) photodetectors for visible and near‐infrared (NIR) detection. With the introduction of O2 plasma treatment, the atomic oxidized layer is generated to prevent direct interaction from O2 and water (H20) molecules in air, leading to an improved environmental stability. Meanwhile, bonded O atoms provide an electron‐rich atmosphere, which can effectively reduce the intrinsic Se vacancies and generate a strong built‐in electric field to suppress the recombination of photocarriers. As a result, the O2‐modified MoSe2 photodetector exhibits an excellent photoresponse, including a high responsivity of 889 mA W−1, a fast response time of 52 µs, and a high specific detectivity approaching 3.37 × 1014 Jones under 520 nm illumination with a light intensity of 2.02 mW cm−2 at 0.5 V. Moreover, the response spectra of MoSe2‐O2 photodetectors can be further extended to NIR region (λ = 980 nm), owing to perturbation of O atoms in the Se−Mo sublattice. Ultimately, a turbidity detection system based on the optimized photodetector is demonstrated, which illustrates an accurate turbidity measurement with the concentration ranging from 0 to 4000 NTU.

Crystal Structure, Magnetic Properties and Thermal Behavior of BaFe11.9In0.1O19 Ferrite

Herein, the crystal structure, surface morphology, and magnetic and thermal properties of the BaFe11.9In0.1O19‐substituted M‐type hexaferrite are investigated. This solid solution is fabricated using “two‐step” topotactic reactions. It is determined through the X‐ray diffraction method that the crystal structure of this solid solution under normal conditions has hexagonal symmetry with P63/mmc space group (No. 194) with the unit cell parameters a = 5.8992(1) Å and c = 23.2275(7) Å. It is determined by the scanning electron microscope (SEM) researches that the average size of the grains is = 6 μm. It is determined by the vibration magnetometry that the ferrimagnet–paramagnet phase transition happens at around T C = 420 °C. Using differential scanning calorimetry (DSC), it is found that air and water molecules leave the sample surface up to 420 °C and the resulting oxygen anions appearing as a result of a solvothermal reaction fill the oxygen vacancies in the crystal structure at high temperatures up to 800 °C. The thermal transitions repeated in the high temperatures are established. The oxidation behavior of this compound is determined from thermogravimetric analysis (TGA) in a wide temperature range.

Detection of marine aerosols using ocean colour sensors

Ocean colour sensors are equipped with atmospheric correction bands operating in the near infrared region of the spectrum. At these wavelengths, the ocean surface, because of high infrared absorption by water, acts as a dark background and the sensor detected radiance is due to solar radiation backscattered by the atmospheric air molecules and aerosols called Rayleigh and aerosol path radiances respectively. From the radiances in the atmospheric correction bands, after accounting for Rayleigh path radiance, it is possible to determine aerosol parameters like aerosol optical depth (AOD) and particle size distribution index. 
 
 While sensors like IRS P3 MOS-B, IRS P4 OCM, NOAA-AVHRR, etc detect AOD in the total atmospheric column, IRS P3 MOS-A sensor can detect AOD in two atmospheric layers by exploiting the differential absorption property of oxygen at four narrow band channels at the O2 A band around 760nm. The method of determination from ocean colour sensors and the results from IRS P3 MOS-B, IRS P4-OCM and IRS P3 MOS-A radiance data are presented and discussed.

Earth as a Proxy Exoplanet: Simulating DSCOVR/EPIC Observations Using the Earth Spectrum Simulator

Analyzing time-resolved disk-integrated spectral images of the Earth can provide a baseline for future exoplanet characterization. The Earth Polychromatic Imaging Camera (EPIC) onboard the Deep Space Climate Observatory (DSCOVR) provides ∼5000 full-disk sunlit Earth images each year in ten wavelengths from the ultraviolet to the near-infrared. A whole-disk radiative transfer model can improve our understanding of the temporal variation of Earth’s disk-integrated reflected radiance (“light curves”) at different wavelengths and create a pool of possible observations of Earth-like exoplanets. We use the two-stream-exact-single-scattering line-by-line radiative transfer model to build the Earth Spectrum Simulator (ESS) and reconstruct DSCOVR/EPIC spectral observations. Atmospheric effects, such as scattering by air molecules, clouds, aerosols, and gaseous absorption, are included. Surface contributions are treated using appropriate bidirectional reflectance distribution functions. We simulate ∼300 images in each channel for observations collected in 2016, with a spatial resolution of ∼2000 pixels over the visible disk. ESS provides a simultaneous fit to the observed light curves, with time-averaged reflectance differences typically less than 7% and root-mean-square errors less than 1%. The only exceptions are in the oxygen absorption channels, where reflectance biases can be as large as 19.55%; this is a consequence of simplified assumptions about clouds; especially their vertical placement. We also recover principal components of the spectrophotometric light curves and correlate them with atmospheric and surface features.

Effect of moisture content on bamboo’s mode I interlaminar fracture toughness: The competition between promoting and impeding crack growth

Most engineering materials are chosen based on their fracture toughness rather than their strength. However, water molecules in air would interact with these materials and affect their fracture toughness, especially for the biomass materials. Bamboo is an excellent engineering material, and the effect of water content on its fracture toughness was still unknown. Thus, in this study, the effect of water on bamboo’s fracture toughness was investigated, and the mechanism behind it was discussed. The results showed that the growth fracture toughness increased by 7.6 J/m2 per 1 % increase of environmental relative humidity. The effect of the water includes both promoting and impeding crack growth. The hydrated amorphous layer in cell wall impeded the propagation of cracks, while the water layer on cell wall promoted the propagation of cracks. The former effect was the stronger one in bamboo, and thus the fracture toughness increased. This competition mechanism stemmed from water was also found useful to explain the fracture properties of other kinds of materials, such as wood, stone, and clay. Therefore, a reasonable hypothesis to explain the mechanism of water content on fracture toughness of bamboo and even other materials was concluded in this study.

Atmospheric Pressure Electron Detection Method for MEMS Electron Microscope

The article presents the results of a new method for electron detection at atmospheric pressure (APED). This method is developed for a MEMS (Micro-Electro-Mechanical System) electron microscope to obtain images of a sample placed on a silicon nitride membrane in air. The electron beam is transmitted through the membrane and, under specific conditions, can reach the detector despite the presence of air molecules. The experiments were carried out on a miniature electron optical microcolumn model consisting of an octupole deflector, an anode with a Si₃N₄ membrane, and an electron collector. The anode, glass spacer, and electron collector formed a microchamber that was filled with air. Measurements were made using an electron beam from JEOL Scanning Electron Microscope (SEM). The first images obtained using the APED method and a quantitative description of the operation principle are presented.

Synthesis, structure and luminescent properties of Zn(II) metal–organic frameworks constructed by flexible and rigid ligands

The synthesis of new coordination polymers based on flexible ligands is a challenging task. The use of two types of ligands is a possible approach to obtain crystalline compounds. The combination of flexibility and rigidity can lead to unusual topologies and properties. We are managed to obtain two new metal–organic frameworks (MOFs) based on flexible 1,3-bis(2-methylimidazolyl)propane and rigid isophtalic (1,3-benzenedicarboxylic) acid: [Zn2(iph)2(bmip)2] (1) and [Zn4(iph)4(bmip)3]·2DMF·3.5H2O (2). Structure of both compounds were determined by single-crystal X-ray analysis. Compound 1 is 3-fold interpenetrating 3D framework with dmp topology. Compound 2 is 2-fold interconnecting 3D framework with rare topology, described as (4,6)-c net. Compound 2 contains guest DMF and water molecules. Interestingly, compound 2 easily loses guest molecules in air and undergoes to another crystalline compound 2a. The photoluminescence at room temperature of the compounds 1 and 2a were investigated in the solid state. Quantum yields (QY) of luminescence for 1 and 2a are 30.5% and 39.8%, respectively. The short decay times are allowed to attribute the emission to fluorescence characteristic for intraligand transitions.

Solar Energy Potentials of Some Selected Locations in Northeastern Nigeria

Sunlight is the primary source of clean and cheap energy but its intensity varies from one location to another depending on the latitude, altitude, atmospheric absorption and scattering by air molecules, dust particle and water vapour among others. The aim of this work is to determine the solar energy potentials of Gombe ( latitude 10° 16' 59.9988'' N and longitude of 11° 10' 0.0012'' E), Jalingo (latitude 8° 53' 34.2672'' N and Longitude 11° 22' 37.74'' E), Damaturu (Latitude 11° 44' 49.1856'' N and Longitude 11° 57' 58.2912'' E) and Bauchi (latitude 10° 18' 50.9724'' N and longitude 9° 50' 46.6152'' E) in northeastern Nigeria, the process involves obtaining the solar irradiation data for these four locations from a renewable energy simulation package ( photovoltaic geographical information system, PVGIS) for a period of 10 years, a daily, monthly and annual solar irradiation was obtained for each of these locations. A peak monthly values was obtained in the month of January for Gombe, Jalingo and Bauchi while the month of March has the peak value for Damaturu, an average daily solar irradiation of 5.8977kWh/m2/day, 5.9026 kWh/m2/day, 6.0337 kWh/m2/day and 5.9821kWh/m2/day and an annual values of 2154.44kWh/m2/yr, 2056.17 kWh/m2/yr, 2202.30kWh/m2/yr and 2150.60kWh/m2/yr for Gombe, Jalingo, Damaturu and Bauchi respectively. These locations have very similar atmospheric conditions and hence a closer range of solar energy potentials compared to places like Lagos, Onitsha and Sapele in Delta state with (4.42kWh/m2/day), (4.43kWh/m2/day, and 5.31 kWh/m2/day respectively. Damaturu has the highest solar irradiance among the four locations studied. Grid- connected PV system and thermal system (concentration thermal technology) can be built to support electricity generation and hot water production respectively for residential and industrial use. The utilization of Solar oven, cookers and coolers technology should be encourage by government and non-governmental organization, this will help stop global warning and desert encouragement and hence conserve other natural resources( such as forest) for other use ( furniture construction).

Instantaneous discharge characteristics and its methane ignition mechanism of coal mine rock damage.

The goaf is the main site of gas explosions in coal mines. A large number of accidents indicate that the occurrence of gas explosion in the goaf is related to the deformation and fracture of the goaf roof. An experimental system was constructed to study the instantaneous discharge characteristics and its ignition mechanism caused by rock damage. The research results reveal that different rocks produce avalanche-like dust clouds ejected outward during the fracture process, and the generation process takes an extremely short time. This dust cloud is not caused by rock fragments heated to incandescence because of friction. The electric sparks produced in the process of rock rupture and the appearance of instantaneous discharge are related not only to the quartz content of the rock, but also to the compressive strength of the rock. The piezoelectric effect of the rock becomes the key factor for the strength or the generation of an electric spark. The instantaneous discharge leaded to the collision of high-energy electrons released during the fracture process with air molecules, ionising, and breaking down the air. When the surrounding medium is gas air within the explosion limit, ionisation is formed and causes gas explosions.

Enhancing higher-energy spectral resolution for electron particle simulations in air

In the presence of an electric field, electrons would theoretically accelerate asymptotically to relativistic energies. However, regular collisions with air molecules limit the increase in electron energy. The stochastic nature of collisions leaves a theoretical probability that an electron elude inelastic collisions thereby accumulating an atypically high energy. Such an electron, under specific criteria, could be called a “thermal” or “cold runaway”. Depending on the electric field, the runaway probability might be too low to be computationally observed without resorting to Monte Carlo importance sampling. This article provides a method for fixing the spectral energy resolution of electrons through the combined methodology of Russian roulette and probabilistic splitting in order to render the study of runaway mechanism amenable to electron swarm simulations in various plasma physics applications. Program summaryProgram title: particle-energy-compaction.pyCPC Library link to program files:https://doi.org/10.17632/k2y2r73t69.1Developer's repository link:https://osf.io/c6wyhLicensing provisions: CC By 4.0Programming language: Python 3Nature of problem: Currently, electron thermal runaway simulations in electric discharges cannot properly resolve the electron energy-spectrum tail. Most codes apply a super-particle restriction algorithm without efficiently or systematically allocating more space for scarcer electrons located at higher-energies. This results in a poor estimation of the thermal runaway rates at electric fields below the critical runaway threshold.Solution method: We provide a methodology based on the Monte-Carlo variance reduction techniques of Russian roulette and splitting, to allocate particles in different energy domains according to a given target super-particle energy density function. The algorithm converts an input set of super-particle energies and weights into another set that matches the desired spectral resolution. To avoid a sudden surge of super-particles in a low-populated spectral region, the algorithm takes also as input a minimum super-particle weight threshold relative to the physical number of particles in the simulation.Additional comments including restrictions and unusual features: A good knowledge of the problem is required in order to design the target spectrum function. An inappropriate selection of the target spectrum can result in a decrease of spectral resolution or also a severe deterioration of the swarm properties due to large stochastic fluctuations. It is recommended that the users first devise the target spectrum based on the physical spectrum obtained from their simulations, and start designing from there.

Heat Transfer Enhancement of Ionic Wind Assisted Slot Jet Reattachment Nozzle: A Numerical Study

Abstract Impinging jet nozzles are omnipresent in industrial applications. Innovative impinging jet nozzles, such as radial jet reattachment (RJR) and slot jet reattachment (SJR) nozzles, have been proven to be highly efficient tools to enhance heat and mass transfer, compared to traditional in-line jet and slot-jet nozzles. However, the heat and mass transfer in the region immediately underneath these reattachment nozzles are relatively inefficient. The ionic wind is a promising technique for heat transfer enhancement. The ionic flow is induced when free ions are accelerated by an electric field, and exchange momentum with neutral air molecules. In this numerical study, the performance of the SJR nozzle is improved by the application of an electric field, specifically, ionic wind, which is generated in the region directly between the nozzle and the exposed impingement surface. The two-dimensional numerical model is based on the flow field generated by an ionic wind-assisted SJR nozzle. The simulation results show a significant secondary flow induced under the nozzle, due to ionic wind. A significant enhancement of local and average heat transfer coefficients is achieved. The heat transfer increases with the applied potential and nozzle exit velocity. However, the SJR flow pattern is altered when the air exit velocity is below a certain threshold. The simulation results provide an in-depth understanding of the heat transfer characteristics under various operating conditions and pave the way for developing this novel impinging nozzle design.

Five Surprising Facts About Molecules of Water and Air

This article presents answers to five questions about molecules of water and air. In Chapter 1 of Volume 1 of The Feynman Lectures on Physics, Richard Feynman suggests that: “If in some cataclysm all scientific knowledge were to be destroyed, and only one sentence passed on to the next generation of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis … that all things are made of atoms ….”

Detection of Airborne Nanoparticles through Enhanced Light Scattering Images.

A new method is proposed in this paper to detect airborne nanoparticles, detecting the light scattering caused by both the particle and the surrounding molecules, which can surpass the limitations of conventional laser optical methods while maintaining simplicity and cost-effectiveness. This method is derived from a mathematical analysis that describes the particle light scattering phenomenon more exactly by including the influence of light scattered from surrounding gas molecules. The analysis shows that it is often too much of a simplification to consider only light scattering from the detected nanoparticle, because light scattering from the surrounding gas molecules, whether visible or invisible to the sensor, is important for nanoparticle detection. An image detection approach utilizing the light scattering from surrounding air molecules is described for the detection of airborne nanoparticles. Tests using monodisperse nanoparticles confirm that airborne particles of around 50 nm in size can even be detected using a low-cost testing device. This shows further that even when using a simple image processing code, captured particle light scattering images can be converted digitally into instantaneous particle counts or concentrations. The factors limiting conventional pulse detection are further discussed. This new method utilizes a simple static light scattering (SLS) approach to enable the development of new devices with better detection capabilities, paving the way for the further development of nanoparticle detection technology.

Detection of Environmentally Toxic Molecules Using Carbon Nanotubes: A First-Principles Theoretical Study

The adsorption process of environmentally harmful (CO2), toxic (CO, NO and NO2) and common (O2 and N2) molecules in air on boron and nitrogen-doped carbon nanotubes (CNTs) and its effects on quantum transport are studied using the first-principles density-functional calculations combined with the quantum transport method. It is found that CO, NO, NO2 and O2 molecules can strongly bind on the B-doped (10,0) CNTs while only NO and NO2 molecules are strongly adsorbed on the N-doped (10,0) CNTs in air. Quantum transport properties of (10,0) CNTs regarding the adsorption of the molecules are quantitatively investigated, and it is found that the adsorption of the molecules changes sizably the quantum conductance of the CNTs, which depends on the types of the adsorbed molecules. The origin associated with the wide variation of the quantum conductance induced by the molecular adsorption is revealed, and the possibility to selectively detect toxic CO, NO, and NO2 molecules in air is discussed.

Performance enhancement of solution-processed InZnO thin-film transistors by Al doping and surface passivation

Solution-processed oxide semiconductors have been considered as a potential alternative to vacuum-based ones in printable electronics. However, despite spin-coated InZnO (IZO) thin-film transistors (TFTs) have shown a relatively high mobility, the lack of carrier suppressor and the high sensitivity to oxygen and water molecules in ambient air make them potentially suffer issues of poor stability. In this work, Al is used as the third cation doping element to study the effects on the electrical, optoelectronic, and physical properties of IZO TFTs. A hydrophobic self-assembled monolayer called octadecyltrimethoxysilane is introduced as the surface passivation layer, aiming to reduce the effects from air and understand the importance of top surface conditions in solution-processed, ultra-thin oxide TFTs. Owing to the reduced trap states within the film and at the top surface enabled by the doping and passivation, the optimized TFTs show an increased current on/off ratio, a reduced drain current hysteresis, and a significantly enhanced bias stress stability, compared with the untreated ones. By combining with high-capacitance AlO x , TFTs with a low operating voltage of 1.5 V, a current on/off ratio of > 10 4 and a mobility of 4.6 cm2/(V·s) are demonstrated, suggesting the promising features for future low-cost, low-power electronics.

Unraveling Heat Transport and Dissipation in Suspended MoSe2 from Bulk to Monolayer (Adv. Mater. 10/2022)

Thin Films When thinning down silicon films toward nanometer thickness, their thermal conductivity decreases dramatically. In article number 2108352, Klaas-Jan Tielrooij and co-workers report a combined experimental–theoretical study that shows that this is not the case for the layered semiconductor MoSe2. For the thinnest MoSe2 films, the decreasing thermal conductivity is compensated by low-energy, long-mean-free-path heat-carrying modes. These thin films furthermore exhibit efficient heat dissipation to air molecules.

Preparation and Characteristics Study of Porous Silicon for Vacuum Sensor Application

Vacuum is a technique that can be employed to measure pressures less than atmosphere (101325 mbar), the vacuum is too important in numerous fields of life. In the present research, the sensor of vacuum has been produced using a porous layer of silicon (Psi). N-type of silicon wafer (Si) has been used for formulating Psi samples utilizing photo-electrochemical etching (PECE) technique. The experimental work was carried out under different etching times (30, 60, and 90 min) while fixing the other parameters, including (24%) Hydrofluoric (HF) acid and (20 mA/cm2) current density. The pore width and depth and porosity % were confirmed using Scanning Electron Microscope (SEM) and Atomic Force Microscope (AFM) tests. The tests shown a sponge-like structure of Psi and the surface roughness increased along with etching time. X-ray diffraction (XRD) verified the formation of porous silicon, the crystal size reduced, and photoluminescence (PL) elucidated that the emission peaks centered at approximately (600-625 nm) corresponding to energy bandgap (1.72-1.94 eV). The electrical properties were investigated by the electrical resistance of porous silicon with vacuum. The results evinced that the porosity, pore depth, surface roughness and the intensity of Psi increased significantly as the etching time increased, and the vacuum value was sensed by varying the electrical resistance value of the Psi after removing the air molecules from the pores, thus the resistance gradually decreased after exceeding the vacuum value 10-3 mbar.

Plasma‐water‐based nitrogen fixation: Status, mechanisms, and opportunities

AbstractNitrogen‐based crop fertilizers are the most important industrial chemicals supporting the global food supply. Plasma‐water‐based nitrogen fixation (PWBNF) provides a clean, sustainable, and flexible alternative, which is amenable for decentralized, small‐to‐medium‐scale production systems. This process is based on the targeted activation of N2 or air molecules by plasmas. Plasma can interact with water molecules, water droplets, and water layers through the plasma physical and chemical mechanisms. This review summarizes the current state of the art of PWBNF and provides insights into the effective mechanisms for the synthesis of NH3, NO2− and NO3− in highly reactive plasma environments. The opportunities and challenges for this plasma‐enabled approach are identified to guide the development of sustainable nitrogen fixation technology.

Performance of THz Communications Over Cascaded RISs: A Practical Solution to the Over-Determined Formulation

As a last resort for radio frequency communication, Terahertz bands (0.1-10 THz) are targeted thanks to their ability to provide ultra-wide bandwidth satisfying varieties of emerging applications. However, the waves propagating at THz frequencies suffer from high losses due to absorption in air molecules which forces their use into short-range links. We propose a multi-hop system to extend the range of THz links with the aid of multiple passive reconfigurable intelligent surfaces (RIS). In contrast with existing literature, we address the challenge of the over-determined system of equations arising from optimizing the phases of cascaded RISs taking into account the practical case of highly directional antennas and spatially correlated channels in THz bands. We propose an efficient method to jointly optimize the phases induced by the RISs in order to maximize the power at the receiver side.

Design and analysis of Microcontroller based air scrubber using ANSYS CFD

The important part for human survival is air the and growing pollution in the environment is a major concern for mankind therefore there is a need for a device is that can remove the gaseous components in the air molecules. With the use of thermoplastic elements, gas-liquid absorption can occur. The concept of scrubber for the absorption of gases was introduced in late 1980 and with the growth of modern techniques, the gas liquids absorption and phase change is been studied for a very long time. A packed column is process equipment, and it is widely used in industries that produce toxic elements. Bed scrubber washing technique for removal of gaseous contaminants to a large extent bus stop with the use of a microcontroller for monitoring the emissions the basic idea of installing this machine in the end or environment for residential and commercial use is a need of the hour. The work relates to the design and performance of the back scrubber and the study of the practical approach results by using it in an indoor environment. The use of IoT in this process is enhancing its quality and we are adding a step towards optimizing the air pollution standards. As the government has taken a lot of efforts for halting the growth of air contaminants by implementing some loss on engine combustion so the work is innovation in the field of air pollution and control.