Gas Exposure Research Articles

Electronic Modulation of Semimetallic Electrode for 2D van der Waals Devices

The 2D semimetallic electrodes have been employed to show outstanding contact properties with 2D semiconducting transition‐metal dichalcogenides (TMDCs) channel, leading to large enhancement of 2D transistor and phototransistor performance. Herein, an innovative concept is established for a unique 2D semimetallic electrode‐2D TMDC channel (2D–2D) device configuration where the electronic structures of 2D semimetallic electrodes are systematically modulated to improve the contact properties with 2D monolayer molybdenum disulfide (MoS2) channel. The 2D semimetallic copper sulfide (CuS) electrodes are doped with iodine atoms by a direct exposure of iodine gas. The contact properties and charge‐transport behavior in the 2D–2D field‐effect transistors (FETs) are highly improved, which is attributed to the favorable energy band alignment and associated material properties between the iodine‐doped CuS (CuS–I) electrodes and 2D channel. The 2D–2D FETs show a high on current, high on/off ratio, and twofold improvement in mobility. Furthermore, 2D–2D phototransistors and flexible/transparent photodetectors are fabricated using the CuS–I/MoS2, which also performed outstanding photoresponsivity characteristics and mechanical durability under external bending strain conditions. These findings demonstrate a promising pathway that under the 2D–2D configuration, the electronic modulation by the iodine atoms may enable the development of future 2D electronic applications.

Highly Sensitive SF6 Decomposition Byproducts Sensing Platform Based on CuO/ZnO Heterojunction Nanofibers

Hydrogen sulfide (H2S) and sulfur dioxide (SO2) are two typical decomposition byproducts of sulfur hexafluoride (SF6), commonly used as an insulating medium in electrical equipment; for instance, in gas circuit breakers and gas insulated switchgears. In our work, fiber-like p-CuO/n-ZnO heterojunction gas sensing materials were successfully prepared via the electrospinning method to detect the SF6 decomposition byproducts, H2S and SO2 gases. The sensing results demonstrated that p-CuO/n-ZnO nanofiber sensors have good sensing performance with respect to H2S and SO2. It is noteworthy that this fiber-like p-CuO/n-ZnO heterojunction sensor exhibits higher and faster response–recovery time to H2S and SO2. The enhanced sensor performances can probably be attributed to the sulfuration–desulfuration reaction between H2S and the sensing materials. Moreover, the gas sensor exhibited a high response to the low exposure of H2S and SO2 gas (below 5 ppm). Towards the end of the paper, the gas sensing mechanism of the prepared p-CuO/n-ZnO heterojunction sensors to SO2 and H2S is discussed carefully. Calculations based on first principles were carried out for Cu/ZnO to construct adsorption models for the adsorption of SO2 and H2S gas molecules. Information on adsorption energy, density of states, energy gap values and charge density were calculated and compared to explain the gas-sensitive mechanism of ZnO on SO2 and H2S gases.

Environmental gas sensing studies using flower-like MoS2 hybrid structure

Molybdenum disulfide (MoS2) is one of the most potent transition metal dichalcogenide (TMDc) material for gas sensing applications due to its various advantageous properties. It exhibits modest electron mobilities, reduced dimensionality, and favorable mechanical properties. The deposition of metal nanoparticles on nanostructured MoS2 leads to the modification in their sensing properties. By keeping in view, present work reports the fabrication of stable MoS2 nanoflowers (MNF) and their hybrids (Au-MoS2 nanoflowers). The hydrothermal approach was used to synthesize MNF nanostructures and in order to form the hybrid Au-MoS2 nanoflower (AuMNF) Au nanoparticle were deposited over MNF by an inert gas evaporation method. X-ray Diffraction and micro–Raman spectroscopy were used to study MNF and AuMNF hybrid structures. XRD found MoS2 1 T-2H mixed-phase. The peak shift and broadening in E1g, J3, and E3g modes for AuMNF hybrids was observed compared to MNF. The flower-like morphology of the pristine and hybrid nanostructures was confirmed via the Scanning electron microscopy (SEM) technique and transmission electron microscopy (TEM). Furthermore, the fabricated samples MNF and AuMNF hybrids were investigated for environmental gas sensing. According to the results of the gas sensing tests, the AuMNF hybrid provides the best sensing response. The gas sensing measurements revealed that the best sensing response is found from the AuMNF hybrid. This hybrid shows a response of 21.2 % in the presence of CO, which is 5.5 times higher than the response of pure MoS2. These findings contribute to a better interpretation of how the resistance of MoS2 nanostructures reacts towards CO gas exposure. These findings contribute to a better interpretation of how the resistance of MoS2 nanostructures reacts towards CO gas exposure.

Development of a risk assessment method for the detailed consideration of the effects of liquid toxic substance leakage incidents on the human body: ethanol as a model substance.

To ensure safety in chemical plants handling a wide variety of liquid and gaseous hazardous substances, it is necessary to carry out highly accurate risk assessments and take appropriate measures. In this study, a risk assessment method was developed for the problem of the leakage of liquid hazardous substances. The risk assessment of toxic liquid leaks must consider the exposure of workers to the liquid and toxic gases produced by vaporization. The absorption and subsequent metabolism of hazardous substances in the body via multiple pathways after exposure to liquids and gases was calculated using a pharmacokinetic model. Estimation of exposure concentrations of toxic gases volatilized from leaked liquids was reproduced by computational fluid dynamics simulation. In this study, ethanol was selected as the hazardous substance and the risk of hazardous liquid leakage was assessed. The results of the analysis, which considered liquid and gas exposure under the conditions of the assumed scenario, showed that the maximum blood concentration of ethanol was 1640 µmol/L, which is sufficiently low compared to the concentration of 10,900 µmol/L at which acute toxic effects become apparent. These results suggest that work can be carried out safely under the conditions of the assumed scenario. The risk assessment methodology for liquid spills in this study confirms that risk assessment is possible under multiple scenarios, including individual differences, activity conditions, and the use of protective equipment.

High reactivity of mesoporous CeO2 to dissociate chemical warfare agent sarin

Spectroscopic surface characterization under exposure of sarin gas (also known as GB) as well as DFT modeling reveals the high reactivity of mesoporous ceria (CeO2) towards sarin degradation.

The effectiveness of potted plants in improving indoor air quality: A comparison between chamber and field studies

People spend up to 90% of their time inside buildings, making indoor air quality an extremely important factor affecting public health and building design. Due to the inherent ability to absorb/filter pollutants, plants present a promising method for improving indoor air quality. In recent decades, many studies have quantified plants’ effectiveness in removing indoor air pollutants using both chamber and field methods. This paper presents a review working covering these studies and discusses the differences between chamber and field studies, in terms of study methods and results. Through a meta-analysis of 41 chamber studies and 16 field studies, the effectiveness of 182 species in removing 25 pollutants has been estimated. From this work, a larger proportion of significant results were observed in chamber studies (88%), comparing to field studies (65%). Additionally, comparable studies revealed greater removal effectiveness of plants in chamber studies. These discrepancies could be attributed to many factors, such as the size and the airtightness of experimental setup, ventilation, gas exposure scheme, and environmental conditions. It is envisaged that these findings will help reduce the gap between chamber studies and field studies, and provide guidance for the future use of plants in buildings to improve indoor air quality.

Evaluation of Cytogenetic Alterations in Patients of Chronic Kidney Disease.

In recent years, there has been a rise in chronic kidney disease (CKD), and it has been estimated that by 2040, CKD will be the fifth most common cause of death globally. In addition to diabetes, hypertension, obesity, hyperlipidemia, and nonalcoholic fatty liver disease commonly associated with CKD, exposure to various toxins as a result of pollution or industrial disasters is also discussed as a cause for multi-organ pathology including kidneys. Although few cytogenetic studies were undertaken to assess the genetic damage in survivors of the disaster, no studies are available on the cytogenetic damage of toxic-gas exposed population having CKD. Therefore, the present multi-group cross-sectional study was undertaken to assess the independent role of CKD as well as toxic gas exposure on cytogenetics. The cytogenetic alterations were evaluated through chromosomal aberration analysis and micronuclei assay. The study included 608 study participants divided into four groups on the basis of history of exposure to the leaked gas and presence or absence of CKD. The results of the study showed no statistically significant difference in cytogenetic damage between gas-exposed and non-exposed patients of CKD, whereas significantly higher cytogenetic damage was observed among gas-exposed participants having CKD compared to gas-exposed participants free from CKD, suggesting that cytogenetic changes could be due to CKD itself. Thus, to conclude, the cytogenetic alterations observed in the study can be partly attributed to the disease itself.

Euthanasia of Neonatal Rats and Mice using Carbon Monoxide.

Minimization of potential pain and distress of rodents undergoing euthanasia is a touchstone of veterinary clinical medicine. Evaluation of this issue in postweanling rodents has supported revisions to the AVMA (American Veterinary Medical Association) Guidelines on Euthanasia in 2020. However, relatively little information is available on humane aspects of anesthesia and euthanasia in neonatal mice and rats. These neonates are not reliably euthanized by exposure to commonly used inhalant anesthetic agents due to their physiologic adaptations to hypercapnic environments. Therefore, options such as prolonged inhalant anesthetic gas exposure, decapitation, or use of injectable anesthetics are recommended for neonates. All of these recommended methods have operational implications, ranging from reported job dissatisfaction by animal care staff to rigorous reporting requirements associated with the use of controlled substances. This lack of a euthanasia method that does not entail operational issues hampers the ability of veterinary professionals to provide appropriate guidance to scientists working with neonates. This study was designed to assess the effectiveness of carbon monoxide (CO) as an alternative euthanasia agent for mouse and rat pups on postnatal days (PND) 0 to 12. The study demonstrates that CO may be a potential alternative for preweanling mice and rats at PND6 or older but is not appropriate for neonates at PND5 or younger.

Chlorine gas exposure and evolutive patterns of reactive airways dysfunction syndrome: a systematic review

Resumo Introdução: o cloro é o gás irritante a que as pessoas estão comumente expostas no cotidiano. Um dos seus efeitos tóxicos é a síndrome da disfunção reativa das vias aéreas (SDRA). Objetivo: resumir as principais evidências dos padrões evolutivos da SDRA. Métodos: Revisão sistemática da literatura de artigos publicados entre setembro de 1985 e julho de 2021 no repositório da Universidade de São Paulo (USP) e nas bases BVS/LILACS, PubMed/Medline e SciELO. Foram utilizados os descritores “cloro” e “asma ocupacional” associados à “síndrome da disfunção reativa das vias aéreas” ou “asma induzida por irritantes”. Dois revisores independentes selecionaram e avaliaram a qualidade dos estudos, com apoio do checklist do Instituto Joanna Briggs. Resultados: selecionaram-se 22 estudos: 11 séries de casos, oito relatos de caso e três estudos transversais. Os estudos selecionados abrangeram 1.335 participantes de 11 países, e apenas 170 tiveram diagnóstico de SDRA com evolução documentada. Destes, 115 (65%) foram devido à exposição ocupacional. Os padrões evolutivos mais frequentes foram persistência prolongada dos sintomas, alterações espirométricas e/ou hiper-responsividade brônquica, principalmente no ambiente ocupacional. Observou-se falta de padronização no relato de informações adequadas. Conclusões: a cronicidade foi o padrão evolutivo da SDRA mais frequente. Houve falta de informação apropriada que impediu uma análise adequada dos resultados.

Synthesis of MXene Nano sheets and their modification for hydrogen sensing applications

In 2011 MXenewas discovered and due to their 2-D structure with excellent metallic like conductivity and chemical active surface properties these are useful for gas sensing application. There are several routes, viz. acidic etching and chemical vapor deposition (CVD), which have been use to fabricated 2D MXene. Generally, 2-D MXenenanosheet is fabricated by selective etching thelayersfrom the MAX phases with toxic fluorine-based acids. In the present work, MXenenanosheets were prepared in a two-steps,in which, firstly MAX phase (Ti3AlC2) percussor was synthesized thenin next stepMXene(Ti3C2) nanosheets was synthesized by selective etching of Al layer using hydrofluoric (HF) acid, for long hours of stirring. The hydrogen sensing behaviour was detected by monitoring the change in resistance withthe time after hydrogen gas exposure using computer control indigenously developed hydrogen gas storage and sensing setup. In results we found that the fabricated sensor shows the response of ∼1.24 towards hydrogen gasat room temperature. The structural order and surface characteristic properties of fabricated MXene samples have also been examined by XRD, Raman and SEM techniques.

Effect of MWNT concentration on hydrogen gas sensing property of MWNT-ployaniline composite

In this present work, we have synthesized conducting MWNT/PANI nanocomposite using in-situ oxidative polymerization at low temperatures. The MWNT content has been varied in the PANI matrix within the range of 2 wt%, 5 wt%, 7.5 wt%, and 10 wt% and characterized the physicochemical properties using XRD, SEM, TEM, and I–V plots. The MWNT loading effect on the gas sensing properties of MWNT-PANI composite for hydrogen (H2) was analyzed by preparing chemiresistor type gas sensors. The XRD, SEM, TEM, and electrical measurements clearly show that the properties like crystallite, conductivity, stability, and morphology of composite material have been affected and improved after MWNT addition to the PANI matrix. The sensor performance at different temperatures was tested by monitoring the variation in resistance of the chemiresistor after hydrogen gas exposure. We found that the more sensitivity and fast response of Hydrogen gas (500 ppm) for 10% MWNT/PANI is 2.1 with response time 150 s. It has been observed that the sensing behavior of MWNT/PANI thin film suitable sensor for the detection of Hydrogen gas at low temperatures.

Polyethyleneimine-Starch Functionalization of Single-Walled Carbon Nanotubes for Carbon Dioxide Sensing at Room Temperature.

There is an ever-growing interest in the detection of carbon dioxide (CO2) due to health risks associated with CO2 emissions. Hence, there is a need for low-power and low-cost CO2 sensors for efficient monitoring and sensing of CO2 analyte molecules in the environment. This study reports on the synthesis of single-walled carbon nanotubes (SWCNTs) that are functionalized using polyethyleneimine and starch (PEI-starch) in order to fabricate a PEI-starch functionalized SWCNT sensor for reversible CO2 detection under ambient room conditions (T = 25 °C; RH = 53%). Field-emission scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy are used to analyze the physiochemical properties of the as-synthesized gas sensor. Due to the large specific surface area of SWCNTs and the efficient CO2 capturing capabilities of the amine-rich PEI layer, the sensor possesses a high CO2 adsorption capacity. When exposed to varying CO2 concentrations between 50 and 500 ppm, the sensor response exhibits a linear relationship with an increase in analyte concentration, allowing it to operate reliably throughout a broad range of CO2 concentrations. The sensing mechanism of the PEI-starch-functionalized SWCNT sensor is based on the reversible acid-base equilibrium chemical reactions between amino groups of PEI and adsorbed CO2 molecules, which produce carbamates and bicarbonates. Due to the presence of hygroscopic starch that attracts more water molecules to the surface of SWCNTs, the adsorption capacity of CO2 gas molecules is enhanced. After multiple cycles of analyte exposure, the sensor recovers to its initial resistance level via a UV-assisted recovery approach. In addition, the sensor exhibits great stability and reliability in multiple analyte gas exposures as well as excellent selectivity to carbon dioxide over other interfering gases such as carbon monoxide, oxygen, and ammonia, thereby showing the potential to monitor CO2 levels in various infrastructure.

Synthesis of graphene like nano order thick graphitic flakes through industrial waste carbon and study of their hydrogen gas sensing properties

Research progress in the field of synthesis of graphene-like nanosheets has been expeditiously growing in the recent years because of their incredible properties in various fields offered by these two-dimensional nanostructures. Nano order thick graphitic flakes, one of the forms of graphene, can be used for many applications such as conductive inks, supercapacitors, nanofluids, gas sensing, etc. Synthesis of graphene flakes definitely the way to reach bulk quantity production. Preparation of stack layer graphene-like nanosheets from industrial waste carbon flake is important for scalable production at a low cost and societal uses. Our novel work surmised the fabrication of Nano order thick graphitic flakes from industrial waste using the modified hummer's method. The basic morphological characteristics have been examined by X Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Gas sensor was prepared by depositing a thin film on a figure-type interdicted electrode epoxy substrate. The sensing behavior was detected by monitoring the change in resistance after hydrogen gas exposure using a computer control indigenously developed hydrogen gas sensing unit.

Properties and modification of native oxides of InP(100)

Properties of oxidized InP surfaces, which are known to cause less electrical and optical losses than other III–V oxides, are relevant to develop the passivation of current and future applications of III–V crystals (e.g. lasers, detectors). We report that a proper low-temperature (LT) (<400 °C) gas exposure with NH3 or O2 enables beneficial modifications of InP native oxides, of which formation is difficult to avoid in devices. Effects of the gas exposure depend on the doping of InP. NH3 exposure without a plasma source at 250 °C or lower temperature increases photoluminescence (PL) intensity of native-oxide covered n-InP crystals, which interestingly provide a stronger PL signal than n-InP with the HCl-cleaned surface. In contrast, O2 exposure around 300 °C increases PL signal of native-oxide covered p-type InP. Core-level photoelectron spectra reveal that N atoms are incorporated into the native oxide system of InPO4/InP during LT NH3 exposures. Scanning tunneling microscopy shows a band bending and a tendency to crystallization at native-oxide covered InP surfaces. Photoelectron spectra, which are analyzed with recent calculations, show larger variation in the bonding environment for the host In atoms and for incorporated N atoms, as compared to the P bonding sites in the InPO4 native oxide.

Feasibility Study of Recrosslinkable Preformed Particle Gels for Natural Gas Injection Profile Control

SummaryRecrosslinkable preformed particle gel (RPPG), a preformed particle gel (PPG) of which particles can bond together to form a strong bulk gel system after being placed inside the target formation, has been successfully applied to control conformance problems for waterflooding projects. However, no research has been conducted about whether RPPG is feasible in improving gasflooding performance in mature reservoirs. The study presents a systematic evaluation of acrylamide (AM) and 2-acrylamide-2-methylpropane sulfonate acid (AMPS)-based RPPG including phase stability under different gel-gas kinetics and plugging performance to natural gas and water. Different experimental apparatuses were designed to quantify and visualize the RPPG phase stability under static and dynamic gel-gas interactions. The RPPG phase stability was evaluated under a different range of injection pressure, gas exposure time, and swelling ratio (SR). Also, the RPPG stability was compared to the in-situ gel system hydrolyzed polyacrylamide crosslinked with chromium acetate [HPAM/Cr(III)], which has been applied in oil fields to control gas injection conformance. The RPPG plugging efficiency was evaluated using open fractured cores with different apertures. The results showed that the RPPG was stable under both static and dynamic gel-natural gas interactions and was stable when being exposed to an acidic environment with an insignificant total percentage weight loss (&amp;lt;3%). Additionally, the strength of the RPPG was further improved with the longevity of the gas exposure. Furthermore, different from the in-situ gel system HPAM/Cr(III), which exhibited a high degree of dehydration under natural gas and exhibited substantial syneresis under acidic conditions, the microstructure of the RPPG remained stable after the dynamic gas exposure. The results of the coreflooding experiments demonstrated that the RPPG had excellent plugging efficiency, which was closely related to the SR and the fracture aperture. This is the first study where a polymer gel system has been systematically assessed through varied testing methodologies using natural gas as opposed to other studies where nitrogen (N2) was used to simulate natural gas behavior. The robustness of the RPPG system makes it a viable candidate for improving the gasflooding processes in mature reservoirs dominated by conformance problems such as void space conduits (VSCs), fractures, and high-permeability channels.

Certified Registered Nurse Anesthetists’ occupational exposure to inhalational anesthetic agents: a survey of anesthetic gas safety

BackgroundAnesthetic gases have been known to cause damage when inhaled over long periods of time. Modern safety measures have been put in place to reduce the risk to anesthesia providers, however there is continued lack of information on providers experiencing short term effects (lethargy, fatigue, headache, slowed cognitive ability, nausea, and mucosal irritation) thereby leading to long-term sequalae (sister chromatid exchanges, micronuclei, chromosomal aberrations, and comet assays).MethodA thirteen item, multiple choice survey was sent to 3,000 anesthesia providers, of which 463 completed the survey. A Chi-square test of independence was used to determine the association between gas exposure and participant self-reported symptoms. A Spearman’s Correlation test was also utilized to interpret this data since both frequency of smelling gas and frequency of symptoms were ordinal variables for which Spearman’s rho correlation was the appropriate measure of association.ResultsThe major findings were that as the frequency of smelling anesthetic gas increased, so too did the frequency of self-reported headaches and fatigue. Spearman’s rho = .148 and .092. P value = .002 and .049, respectively.ConclusionThere have been many efforts to decrease the risk of exposure of anesthesia providers to anesthetic gases. While there is a decrease in reported exposures, indications of possible long-term effects remain a concern in anesthesia providers. Potential implications of exposure could lead to chromosomal aberrations, sister chromatid exchanges, comet assays, spontaneous abortions, and genotoxic effects.

Comparison between modulations of contact and channel potential in nitrogen dioxide gas response of ambipolar carbon nanotube field-effect transistors

Carbon nanotubes (CNTs) are promising materials for gas sensing because of their large specific area and high sensitivity to charge differentiation. In CNT-based field-effect transistors (FETs) for gas sensing, both CNT potential modulation in the channels and Schottky barrier height modulation at the CNT/metal electrode contact influence the current properties. However, researchers have not used Schottky barrier height modulation for gas detection. To investigate and compare the effects of Schottky barrier height modulation and CNT channel potential modulation on NO2 gas exposure, we fabricated ambipolar CNT FETs by the dielectrophoretic assembly. We exposed CNT FET gas sensors to N2 gas containing 100-ppb NO2 and observed two different responses in the electric properties: a steady current shift in the positive direction in the hole-conduction region because of the channel potential modulation, and an abrupt decrease in transconductance in the electron-conduction region because of the Schottky barrier modulation. The CNT channels and CNT/metal contact both contributed to the sensor response, and the modulation rate of the Schottky barrier was higher than that of the CNT potential shift in the channel.

Evaluation of bioactive compounds from robust consortium microalgae species under actual flue gas exposure

The application of phototrophic microalgae for biological CO2 fixation has been regarded as a sustainable means to curb emissions, treat wastewater, and provide essential and valuable bioactive compounds that can serve multitudes industries, e.g., aquaculture, nutraceutical, and biofuel. This article highlights the utilization of microalgae consortium to enhance carbon fixation ability. Marine microalgae species were isolated and identified from their native condition of seawater discharge canals at the TNB Janamanjung Sdn. Bhd.’s coal-fired power station. The experimental runs were performed with exposure of actual flue gas as a CO2 source from a live operating coal-fired power plant. The bioassays of protein and amino acids were conducted to the consortium to explore potential bio-products. The proximate analysis illustrated that the consortium content of protein (45%), lipid (21%), and carbohydrate (17%) is comparable and more balanced from other types of mono species. Also, the essential amino acid content of 42% is encouragingly good and exceeds some other species and other sources. Premises and observations from various microalgae research works are collated and presented in a manner sufficient to highlight the essential roles of this tiny creature to become our mentor in providing some solutions to our worldly problems.

Atomic layer deposition of conductive and semiconductive oxides

Conductive and semiconductive oxides constitute a class of materials of which the electrical conductivity and optical transparency can be modulated through material design (e.g., doping and alloying) and external influences (e.g., gating in a transistor or gas exposure in a gas sensor). These (semi)conductive oxides, often categorized as amorphous oxide semiconductors or transparent conductive oxides, have, therefore, been commonplace in, for example, solar cells and displays, as well as in an increasing variety of other applications including memory, logic, photonics, and sensing. Among the various deposition techniques, the use of atomic layer deposition (ALD) has been gaining in popularity in recent years. Specifically since the early 2000s, many ALD processes for doped and compound conductive metal oxides have been developed. The interest in such oxides prepared by ALD can most likely be attributed to the distinct merits of ALD, such as low-temperature processing, excellent uniformity and conformality, and accurate control over the doping level and composition. Moreover, as device dimensions shrink the need for high-quality, ultrathin materials becomes ever more important. These merits of ALD stem directly from the self-limiting nature of the surface chemistry that drives the ALD growth. On the other hand, the strong role that surface chemistry has in the growth mechanism brings in many intricacies, and detailed understanding of these aspects has been vital for the development of high-quality doped and compound oxides by ALD. Examples of growth effects that can occur during ALD of compound oxides include growth delays, clustering of dopants, and interruption of grain growth by doping. Such effects often need to be accounted for or mitigated, while on the other hand, there are also clear cases where such growth effects can be leveraged to achieve enhanced or new functionality. In this review paper, an overview of the library of ALD processes that has emerged is presented. Available precursor chemistries, dopants as well as achieved film properties—most notably the carrier densities and (field-effect) mobilities of the films—are presented. A selection of important ALD effects that can occur during the deposition of doped and compound conductive oxides is showcased, and their effect on the optical and electrical properties are highlighted. Mitigation and improvement strategies for negative growth effects are presented. This is done through case studies that clearly illustrate these effects, drawing both from literature and from our own recent work.

Influence of heat treatment on H2S gas sensing features of NiO thin films deposited via thermal evaporation technique

In this study, NiO thin films are prepared on Ni foil using thermal evaporation method and the effect of deposition conditions on structural, morphological and H2S gas sensing properties of NiO thin films is investigated. Structural analysis of the NiO films are conducted by means of X-ray diffraction (XRD), and the films are found to have the FCC phase with preferred (111) and (200) Bragg reflections. Based on XRD and scanning electron microscopy results, it is shown that the crystallite size and the size of homogeneous nanoclusters on the surface of the films increase after increasing oxidation temperature. Also, the EDS patterns of NiO films demonstrate a rise in the intensity of O peak upon increasing the oxidation temperature due to the enhancement of oxygen in the NiO films. The Raman spectrum of NiO thin films several bands correspond to Ni–O vibrations. The obtained gas sensing results demonstrate the sensing response to 20 ppm of hydrogen sulfide at 700 °C. Upon increasing the amount of hydrogen sulfide gas to more than 20 ppm, the fabricated sensors show no significant change in their response, indicating that no additional active sites were exist to interplay with hydrogen sulfide molecules for the higher concentration of hydrogen sulfide. The response of the sensors, recorded 10 s after H2S gas exposure, depended on the deposition temperature. The current study shows that NiO thin films-based sensors prepared by a simple thermal evaporation method are potentially useful for the detection of H2S gas.