Gas Sensors Research Papers - Academia.edu (original) (raw)

Li and 11 B MAS-NMR Electrical and dielectric properties a b s t r a c t Nanocrystalline lithium magnesium borate (LiMgBO 3) powders were synthesized by a Pechini process. Thermal behavior of the polymeric intermediate of LiMgBO 3 sample was studied by TG-DTA. Structure and the local structural coordination of the as-prepared and calcined polymeric intermediate at 750 C of LiMgBO 3 sample were investigated by FT-IR and 7 Li & 11 B magic angle spinning-nuclear magnetic resonance (MAS-NMR) measurements respectively. XRD results confirm the formation of the pure nanocrystalline monoclinic phase of the LiMgBO 3 sample prepared at 750 C. The BET surface area of the calcined polymeric intermediate of LiMgBO 3 sample is found to be 60.48 m 2 g-1. The observed SEM mi-crographs of the LiMgBO 3 sample showed the formation of agglomerated sheet-like morphology particles and the existence of Mg and O elements in LiMgBO 3 are confirmed from the SEM-EDX spectral result. The band gap energy of LiMgBO 3 sample is evaluated and it was found to be 3.64 eV. From the analysis of the measured impedance data, at different frequencies and temperatures, the evaluated electrical conductivity of LiMgBO 3 sample was found to be 9.706 Â 10 À5 S cm À1 at 200 C. From the temperature dependence of conductivity (log sT vs. 1000/T) plot of the LiMgBO 3 sample, the evaluated activation energy (E a) for the migration of the charge carrier was found to be 0.62 eV. The measured impedance data and the LiMgBO 3 sample pellet dimensions were used for calculating AC conductivity (s ac), dielectric (ε 0 , ε 00 , tan d), electric modulus (M 0 and M 00) data and were analyzed to find out the electrical and dielectric properties of the LiMgBO 3 sample.

- by
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- Fuel Cells, Gas Sensors, Lithium-Ion Battery, Solid State Ionics

Pure and cobalt–ion-containing nickel ferrite samples Ni1–xCoxFe2O4 (x = 0, x = 0.01, x = 0.05 and x = 0.1)
were prepared by using the sol–gel auto-combustion method. To form the desired structure after the
auto-combustion process, the samples were annealed in air at 800 ◦C for 1 h, followed by slow cooling in
air (2.5 ◦C/min) or rapid cooling by quenching in water. The influences of cobalt ion addition and the cooling
rate on the electronic structure, morphology and electrical properties of Ni–Co ferrite were studied
using X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy
(XPS). The gas-sensing properties of pure and cobalt–ion-containing nickel ferrites were studied by using
acetone as a test gas. The gas-response of nickel ferrite samples was strongly influenced by the cooling
rate and cobalt addition. The effect was attributed to a change in the Ni3+ concentration and a restriction
of the transduction of the chemical signal into an output electrical signal. It was demonstrated that the
gas response of Ni1–xCoxFe2O4 tends to increase with decreasing cobalt ion content and with decreasing
concentration of the point defects such as cation vacancies and Ni3+ ions.

- by Andris Šutka
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- Nanomaterials, Nanotechnology, Sol-Gel Technology, Gas Sensors

An effective monitoring of the air quality in an urban environment requires the capability
to measure polluting gas concentrations in the low-ppb range, a limit so far virtually
neglected in most of the novel carbon nanotube (CNT)-based sensors, as they are usually
tested against pollutant concentrations in the ppm range. We present low-cost gas sensors
based on single-walled CNT (SWCNT) layers prepared on plastic substrates and operating
at room temperature, displaying a high sensitivity to [NH3]. Once combined with the low
noise, the high sensitivity allowed us to reach an ammonia detection limit of 13 ppb. This
matches the requirements for ammonia monitoring in the environment, disclosing the
possibility to access the ppt detection limit. Furthermore, a blend of SWCNT bundle layers
with indium-tin oxide (ITO) nanoparticles resulted in a threefold sensitivity increase with
respect to pristine CNT for concentrations above 200 ppb. Finally, the peculiar response of
the ITO-SWCNT blend to water vapor provides a way to tailor the sensor selectivity with
respect to the relevant interfering effects of humidity expected in outdoor environmental
monitoring.

The recent advent of conductive and biodegradable materials has opened enormous opportunities for biosensor applications and contributed to the elimination of major environmental and food wastes by decreasing the volume of electronic waste. Here, we aim to develop biosensors with electrically conductive and biodegradable composite materials and characterize their electrical, thermal, and biodegradable properties. A solvent casting and situ oxidative synthesis method were adopted to synthesize novel activated biochar (ABC) and polylactic acid (PLA) with AgNPs to prepare the conductive and biodegradable composite materials for biosensor applications. The obtained AgNP/ABC/PLA composite was electrically characterized via cyclic voltammetry (CV) and differential plus voltammetry (DPV), and results revealed that the peak current increased from 0.4 to 1.3 mA for CV and 0.6 to 0.9 mA for DPV. The developed ABC/PLA films were composted, and results showed that weight loss of ABC/PLA composite film effectively occurred over 10 weeks of biodegradation from ∼9% to ∼48.7%. The biosensor developed with AgNP/ABC/PLA composite revealed that the fabricated biosensor increased its sensing performance to detect ammonia (NH 3) over the range of 5-60 ppm. The results indicate that biosensor fabrication with AgNPs/ABC/PLA composite is promising, offering the potential to detect ammonia in food, agricultural, and environmental application.

- by Dr. Abdus Sobhan
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- Biosensors, Gas Sensors, Bionanotechnology
- by Hoa T Le and +1
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- Gas Sensors, ZnO (Zinc Oxide)

Air pollution is contamination of air with poisonous substance where the air is unfit to breathe and not only affect
humans but also all living things in the environment 90% of the people in the world breathe polluted air at present air pollution
is the thread to human life the entire pollution is affected by it. Some gases which causes air pollution are nitrogen oxide,carbon
monoxide, carbon dioxide and sulphur oxide. The combusion of fossils at power plant and industries are responsible for air
pollution. Sulphur dioxide which leads to heart disease and gases like carbon dioxide which leads to stopping of oxygen also
leads to death thus to make human aware of air the air they breathe and to know about their environmental situation the
proposed solution is used where an arduino which is attached to a gas sensor the gas sensor collects all the gases and transmits
to arduino this stores all the value in cloud as soon as the value reaches high the user will receive an alert in webpage about the
level of pollution in the particular area and also if the pollution level is to high an alert message will be displayed and the
pollution level for the future is being displayed to the user to aware of the current situation

- by IJRASET Publication
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- GPS Applications, Health Management, Internet of Things, Arduino

The present work reports the photocurrent response of the MOS sensor to the Hydrogen and ammonia gas moieties. The Au and Pd metals in contact form the gate of the MOS sensor. Depending on the laser excitation regions the photocurrent showed different sensitivity responses to gas exposition that is necessary condition for chemical image gas sensor. The chemical images for hydrogen and ammonia gases, obtained in this work, showed to have different pattern features, which permits the good classification task by using fractal dimension theory.

The project is to develop a robotic vehicle capable of detecting the presence of fire and extinguishing it automatically. It is a movable robot that consists of gas sensor for detecting the fire, gear motor and motor driver for the movement of the robot, relay driver for pump control and a Bluetooth module which are used for the detecting and extinguishing the fire. Usually, the robot moves at a steady speed. When the gas sensor detects the fire in the environment, the signal indicating the presence of fire will be sent to the Arduino through which the extinguishing is done. In the extinguishing process, whenever the detection of fire is positive the robot will stop at the place of fire occurred and starts the pump and sprinkle water through a sprinkler until the smoke is put off. The entire control is achieved using Arduino which is interfaced with the android mobile via Bluetooth module, so that the control of the robot can be made from an android mobile as well. Keywords: Arduino UNO R3, Gas Sensor, PC with Arduino Software, DC Motor and Driver Circuit, Single Channel Relay Driver Circuit, Pump and Sprinkler ________________________________________________________________________________________________________

Underground coal mining requires advance instrumentation for sustainable growth and safety of miners. Many parameters, such as emission of gases, strata conditions, temperature, air velocity, humidity, etc., need to be monitored simultaneously using suitable sensors. This paper presents applications of programmable logic controller (PLC) to key activities of underground automatic mining operations is the prefered option for increasing output, with safety in gassy underground mines by way of switching off power supply when concentration of flammable gases exceeds permissible limit and simultaneously raising alarm to help save miner's valuable lives and assets mines property. Beside, PLC can be used for monitoring strata conditions. Large scale implementation of PLC to automation in mining operations is able a grey area to be explored and there is a scope to design and develop instrumentation for mines for multiple output PLC system.

Amirkhan, F., Chow, D. M., Mahdiraji, G. A., Shee, Y. G, Zakariyah, S.S. and Adikan, F.R.M., " Acetylene Gas Sensing Using In-house Fabricated Solid-core Photonic Crystal Fiber with Large Air-holes", in 7th International Conference on Material for Advanced Technologies in Specialty Optical Fibers and Applications (ICMAT2013), MRS Singapore, 2013.

This paper reports on the high sensitivity of sub-spherical In 2 O 3-Pt nanoparticles (NPs) for detecting ppb levels of acetone, a biomarker for diabetes. The In 2 O 3-Pt NPs, in the form of monodisperse metal-oxide In 2 O 3 NPs with diameters of 6–8 nm, decorated with 2 wt% Pt metal NPs (2–3 nm) on the surface, were synthesized by a novel non-aqueous sol–gel route. NPs samples were investigated by X-ray powder diffraction (XRPD), using the advanced whole powder pattern modeling (WPPM) method, and high-resolution transmission electron microscopy (HR-TEM). The advantage of this preparative process is that it preserves metallic platinum NPs formed during the synthesis. The highly sensitive acetone sensor based on these NPs, showed a lower detection limit as low as 10 ppb or less, which is the lowest detection limit ever reported for any chemoresistive acetone sensors. This exceptional performance is likely due to the key role played by very small Pt metal NPs uniformly distributed in the In 2 O 3-Pt nanostructure. The developed sensor would be suitable for use as a highly sensitive, practical breath acetone checker for daily diet and diabetes management and diagnosis.

- by Robert C Pullar
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- Synthesis of nanoparticles, Biosensors, Diabetes, Nanobiotechnology
- by Jamal M. Rzaij
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- Semiconductors, Literature Review, Gas Sensors, Metal Oxides

Untuk menghindari terjadinya kebakaran pada rumah yang disebabkan oleh kebocoran gas, diperlukan sebuah sistem keamanan yang mudah dipakai. Seiring dengan berkembangnya jaman dan semakin luasnya penggunaan mikrokontroler periset menggembangkan sebuah simulasi perancangan sistem keamanan untuk me-monitoring keadaan didapur, khususnya di daerah yang rawan kebocoran gas dengan menggunakan sensor gas MQ2, modul sensor api, dan sensor suhu DS18B20 yang diindikatori dengan lampu LED dan LCD LM016L dengan menggunakan aplikasi Proteus 8. Dengan menggunakan komponen yang mudah didapatkan, simulasi ini dapat dibuat dengan mudah sebagai sistem alternatif untuk rumah tangga, hotel, atau perusahaan yang membutuhkan alat keamanan agar terhindar dari kecelakaan yang tidak diinginkan.

- by Alfian Gunadi
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- Arduino, Gas Sensors, Teknik Elektro, Simulasi

Safety plays a major role in today’s world and it is necessary that good safety systems are to be implemented in places of education and work. This work modifies the existing safety model installed in industries and this system also be used in homes and offices. The main objective of the work is designing
microcontroller based toxic gas detecting and alerting system. The hazardous gases like LPG and propane were sensed and displayed each and every second in the LCD display. If these gases exceed the normal level then an alarm is generated immediately and also an alert message (SMS) is sent to the
authorized person through the GSM. The advantage of this automated detection and alerting system over the manual method is that it offers quick response time and accurate detection of an emergency and in turn leading faster diffusion of the critical situation.

- by Shekhar Prajapati
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- Gas Sensors, Thin Films

Two-dimensional transition metal dichalcogenides have attracted much attention in the field of optoelectronics due to their tunable bandgaps, strong interaction with light and tremendous capability for developing diverse van der Waals... more

- by Dr. Hari Singh Nalwa, USA
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- Materials Science, Optoelectronics, Gas Sensors, Sensors
- by Dhivya Manian
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- Electrical Engineering, Sensors and Sensing, Renewable Energy, Sensor
- by ZAFER ŞEN
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- Gas Sensors, Electronic Nose, QCM, Principal component analysis (PCA)

Graphene, a single, one-atom-thick sheet of carbon atoms arranged in a honeycomb lattice and thetwo-dimensional building block for carbon materials, has attracted great interest for a wide range ofapplications. Due to its superior properties such as thermo-electric conduction, surface area and mechan-ical strength, graphene materials have inspired huge interest in sensing of various chemical species. Inthis timely review, we discuss the recent advancement in the field of graphene based gas sensors withemphasis on the use of modified graphene materials. Further, insights of theoretical and experimentalaspects associated with such systems are also discussed with significance on the sensitivity and selectivityof graphene towards various gas molecules. The first section introduces graphene, its synthesis methodsand its physico-chemical properties. The second part focuses on the theoretical approaches that discussthe structural improvisations of graphene for its effective use as gas sensing materials. The third sectiondiscusses the applications of pristine and modified graphene materials in gas sensing applications. Vari-ous graphene modification methods are discussed including using dopants and defects, decoration withmetal/metal oxide nanoparticles, and functionalization with polymers. Finally, a discussion on the futurechallenges and perspectives of this enticing field of graphene sensors for gas detection is provided.

- by Ahmed A Abdala
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- Graphene, Gas Sensors, Sensors, Graphene Oxide

Saat ini kebakaran dapat terjadi dimana saja, baik terjadi di gedung-gedung, perumahan, dan pusat-pusat perbelanjaan maupun juga dihutan. Ada bermacam-macam penyebab terjadinya kebakaran, yaitu korsletting listrik dan bisa juga berupa kelalaian-kelalaian kecil seperti meninggalkan kompor dengan keadaan masih menyala dan juga membuang putung rokok sembarangan. Dengan adanya sistem alarm kebakan diharapkan mampu untuk mendeteksi indikasi terjadinya kebakaran dan mengurangi terjadinya kebakaran baik dalam skala besar maupun skala kecil. Sistem alarm kebakaran ini tersusun atas perangkat keras (hardware) dan perangkat lunak (software). Perangkat kerasnya terdiri dari sensor gas MQ-2 dan sensor api Flame Sensor. Untuk sistem minimum mikrokontrollernya menggunakan Arduino Uno R3 sebagai pengendali input dan output, untuk rangkaian display output menggunakan virtual terminal dan rangkaian logic state untuk pernyataan bernilai satu (1) atau high dan nol (0) atau low. Apabila flame sensor dan MQ-2 mendeteksi adanya indikasi kebakaran maka logic state akan bernilai satu (1) atau high, buzzer dan lampu indikator sebagai output akan menyala untuk memberikan peringatan adanya indikasi kebakaran, dan apabila flame sensor dan MQ-2 tidak mendeteksi adanya indikasi kebakaran maka logic state akan bernilai nol (0) atau low, buzzer dan lampu indikator tidak akan menyala untuk memberikan peringatan adanya indikasi kebakaran.
At present fires can occur anywhere, both in buildings, housing, and shopping centers as well as forests. There are various causes of fires, namely electrical short circuiting and can also be in the form of minor negligence such as leaving the stove still on fire and also throwing cigarette nets at random. The presence of a fire alarm system is expected to be able to detect indications of fire and reduce the occurrence of fires both on a large scale and small scale. This fire alarm system is composed of hardware and software. The hardware consists of the MQ-2 gas sensor and the Flame Sensor fire sensor. For a minimum system the microcontroller uses Arduino Uno R3 as an input and output controller, for output display circuits using virtual terminals and a logic state circuit for statements worth one (1) or high and zero (0) or low. If the flame sensor and MQ-2 detect fire indications, the logic state will be worth one (1) or high, buzzer and indicator lights as output will light to give a warning of fire indication, and if the flame sensor and MQ-2 do not detect any indication fire, the logic state will be zero (0) or low, the buzzer and indicator lights will not light to give a warning of an indication of fire.

- by Hanif D
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- Gas Sensors, Fire Alarm Systems, Flame Sensor, Arduino Uno

The main idea of this paper is to implement automatic Liquefied Petroleum Gas (LPG) booking and security system for detecting leakage of gas by using gas sensor. In this system, the LPG leakage is detected through the sensor and information is sent to the customer by Short Message Service (SMS) and alerts the customer using a GSM module, while activating the alarm and exhaust fan. The additional advantage of the system is that it continuously monitors the level of the LPG present in the cylinder using weight sensor and automatically books the cylinder using a GSM module at dealer side along with VB software.

Chemical sensors for specific species with varying sensitivity levels are commercially available.
Common chemical sensors defer in terms of the sensing material and the nature of property change such as electrical
conductivity, optical characteristics and temperature. Some of the current sensor technologies include high temperature
oxide thin- film sensors, polymer based sensors, catalytic based sensors and surface acoustic wave (SAW) sensors are
described. In this the sensor array consists of Carbon Nano Tube (CNT) as sensing material and an interdigitated
electrode as a transducer is described. The gas sensors fabricated by using conducting polymers suchas polyaniline,
polypyrrole as the active layers have been reviewed. The macroscopic coaxial carbon cylinders consisting of aligned
CNT stacks have been used in CNT- polymer composite. The advantages and disadvantages of each sensor technology
are also highlighted. All these technologies have been used for the development of highly sensitive and responsive gas
sensors for the detection of flammable and hazardous gases. However, for improved sensitivity and selectivity for these
sensors, future trends and outlook for researchers are suggested in this review

- by Dr. Venkatesan T
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- Computational Modelling, Gas Sensors, SAW based sensors, Nanotechnology, CNT

Recently one dimensional (1-D) nanostructured metal-oxides have attracted much attention because of their potential applications in gas sensors. 1-D nanostructured metal-oxides provide high surface to volume ratio, while maintaining good chemical and thermal stabilities with minimal power consumption and low weight. In recent years, various processing routes have been developed for the synthesis of 1-D nanostructured metal-oxides such as hydrothermal, ultrasonic irradiation, electrospinning, anodization, sol-gel, molten-salt, carbothermal reduction, solid-state chemical reaction, thermal evaporation, vapor-phase transport, aerosol, RF sputtering, molecular beam epitaxy, chemical vapor deposition, gas-phase assisted nanocarving, UV lithography and dry plasma etching. A variety of sensor fabrication processing routes have also been developed.
Depending on the materials, morphology and fabrication process the performance of the sensor towards a specific gas shows a varying degree of success. This article reviews and evaluates the performance of 1-D nanostructured metal-oxide gas sensors based on ZnO, SnO2, TiO2, In2O3, WOx, AgVO3, CdO, MoO3, CuO, TeO2 and Fe2O3. Advantages and disadvantages of each sensor are summarized, along with the associated sensing mechanism. Finally, the article concludes with some future directions of research.

- by M. M. Arafat and +2
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- One dimensional nanostructures, Gas Sensors, Gas Sensing Mechanism, Nanostructured Toxic vapour/Gas sensors

The demand for portable gas sensors is increasing following the progress in the electronics industry; there is an equal need to increase the quality of gas sensors. Spinel ferrites have been used as electronic materials for more than 50 years and offer a suitable ceramic base for the gas sensor market. They are simple, low cost, and compared to other gas sensors have structural and compositional versatility. This review highlights the recent developments and shows the potential of the spinel ferrites on gas sensor technology. Sensing mechanisms for a range of gasses and humidity are explained for n-type, p-type, mixed and substituted spinel ferrite gas sensors. The change in conduction mechanism is discussed outlining electronic and chemical sensitization that both increase the conductivity. Some cation substitutions are shown to change the oxidation state, thereby increasing sensitivity, but noble metals are shown to chemically sensitize spinel ferrites. This review surveys synthesis methods for producing spinel ferrites and discusses future prospects for further improvements.

- by Andris Šutka
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- Nanomaterials, Advanced Materials, Smart Materials, Ferrite

This thesis presents the development of a compact, 3D printed Photoacoustic Spec-troscopic (PAS) gas sensor with a double-resonator for multi-gas measurement of CO and CO2 in Near-Infrared range using two Distributed Feedback lasers and MEMS microphones. The resonance pro le of the sensor was characterized by developing a model in COMSOL and performing experiments. The Q-factors were shown to be 15 and 6 at the resonance frequencies of 10.25 kHz and 13.8 kHz respectively. The simultaneous gas measurement was demonstrated, albeit at a reduced sensitivity of =1,050 parts-per-million from the Allan-Werle variance analysis with 35 s averaging time using Erbium-Doped Ampli ers. The results were compared against an already available single-resonator sensor, which was also used to demonstrate the impact of high laser powers and flow rate stability on PAS signal. The discrepancy of the results with the model has shown the complexity of estimating Q-factors and the further work needed to improve the theoretical knowledge for their estimations.

- by Metin Ilke
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- Carbon Dioxide, Sensor, Spectroscopy, 3D printing

Ionic Liquids are salts that are liquid at (or just above) room temperature. They possess several advantageous properties (e.g. high intrinsic conductivity, wide electrochemical windows, low volatility, high thermal stability and good solvating ability), which make them ideal as non-volatile electrolytes in electrochemical sensors. This mini-review article describes the recent uses of ionic liquids in electrochemical sensing applications (covering the last 3 years) in the context of voltammetric sensing at solid/liquid, liquid/liquid interfaces and carbon paste electrodes, as well as their use in gas sensing, ion- selective electrodes, and for detecting biological molecules, explosives and chemical warfare agents. A comment on the future direction and challenges in this field is also presented.

- by Debbie Silvester
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- Electrochemistry, Electrochemical Sensors, Cyclic Voltammetry, Ionic Liquids

Undoped and different molar concentrations of Mg-doped ZnO thin films were deposited on glass substrates via. spray pyrolysis process. Doping concentration was varied from 0.002 to 0.01 M in steps of 0.002 M. Structural, morphological, optical, electrical and room temperature gas sensing characteristics of undoped and Mg-doped ZnO thin films were investigated using X-Ray Diffractometer (XRD), Field Emission Scanning Electron Microscope (FE-SEM), UVeVis Spectrophotometer and an electrometer respectively. Structural analysis revealed that all the films were polycrystalline in nature with hexagonal wurtzite crystal structure. Spherical shaped uniformly distributed grains were observed for all the films with slight change in size. The optical absorption edge shifted towards the lower wavelength with an increase in Mg-dopant concentration confirmed the blue-shift. Films with lower Mg-dopant concentration showed maximum response towards ammonia at room temperature with quick response and recovery times.

- by Parthasarathy Srinivasan and +1
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- Thin Films and Coatings, ZnO, Materials Science and Engineering, Gas Sensors
- by Gundars Mezinskis
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- Engineering, Materials Science, Nanomaterials, Sol-Gel Technology

The development of smart polymer materials is reviewed and illustrated. Important examples of these polymers include conducting polymers, ionic gels, stimulus-response be used polymers, liquid crystalline polymers and piezoelectric materials, which have desirable properties for use in wearable sensors. This review outlines the mode of action in these types of smart polymers systems for utilisation as wearable sensors. Categories of wearable sensors are considered as tattoo-like designs, patch-like, textile-based, and contact lens-based sensors. The advantages and disadvantages of each sensor types are considered together with information on the typical performance. The research gap linking smart polymer materials to wearable sensors with integrated power systems is highlighted. Smart polymer systems may be used as part of a holistic approach to improve wearable devices and accelerate the integration of wearable sensors and power systems, particularly in health care.

- by Christian Harito and +1
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- Sensors and Sensing, Wearable Computing, Biosensors, Sensor

Cadmium oxide (CdO) thin films were deposited on the glass substrate by the modified SILAR method, using cadmium acetate dihydrate and ammonium hydroxide aqueous solution as precursors. The structural, surface morphological, elemental composition and optical properties of the deposited films were investigated via X-Ray Diffraction (XRD), scanning electron microscopy, EDAX, optical absorption, photo luminescence and FT-IR spectroscopy. The XRD analysis reveals that the films were polycrystalline with cubic structure. Both crystallinity and grain size were found to increase with increasing solution concentration. The energy-dispersive spectroscopic analysis confirmed the presence of Cd and O elements. The films exhibited a maximum transmittance (50%-70%) in the infra-red region. Transmittance was found to increase with increasing precursor concentration and estimated band gap energy (Eg) was in the range of 2.17-2.21 eV.

- by Karuna karan
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- Gas Sensors
- by Shekhar Prajapati
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- Thermal Spray Coating, Gas Sensors, Thin Films, Uv-Vis Spectroscopy

Vanadium pentoxide (V2O5) thin films were deposited on glass substrates using spray pyrolysis technique. Aqueous solution of ammonium vanadate with 0.1 M concentration was used to deposit V2O5 thin films at different substrate temperatures. The structural, morphological, electrical, optical and vapour sensing properties of the films were investigated. XRD patterns confirmed the polycrystalline nature of the films with orthorhombic structure. Crystallite size was increased with an increase in the substrate temperature. SEM images showed the formation of films with flower like morphology. From the optical absorbance spectra, the optical band gap was determined and varied between 3.34 to 3.24 eV. The charge carrier concentration was found to be increased with substrate temperature. Room temperature xylene sensing characteristics of the films were investigated. The influence of substrate temperature on the vapour sensing characteristics of V2O5 is reported.

- by Seema Lakhanpal Joshi
- •
- Nanoparticles, Gas Sensors, Ferrites

Surface Acoustic Waves (SAWs) are elastic waves travelling along the surface of solid piezoelectric materials
with amplitude that decays exponentially with depth. Using an Interdigital Transducer (IDT), these waves can be
demonstrated and reproduced in the laboratory in devices called SAW devices. Such devices find many applications as
delay lines, filters, resonators and sensors. The present paper provides a snapshot review and a description of the
function, operation and latest technical advancements seen in SAW sensors over the period from1997-2015. SAW
Sensors using different design and operating principles have been reported in this paper. Compared with other
currently available types of sensors, the SAW – based sensors have many advantages like: high sensitivity, quick
response time, easy predictability and good stability.

- by Dr. Venkatesan T
- •
- Computational Modelling, Literature Review, Gas Sensors, SAW based sensors

A volumetric system was used to assess carbon-based adsorbents for evaluation of the gas separation, equilibrium, and kinetics of oxygen (O 2), nitrogen (N 2), and carbon dioxide (CO 2) adsorption on granular activated carbon (GAC) and functionalized GAC at 298, 308, and 318 K under pressures up to 10 bar. The effects of ZnCl 2 , pH, arrangement of the pores, and heat-treatment temperature on the adsorptive capabilities of O 2 , N 2 , and CO 2 were evaluated. High-performance O 2 adsorption resulted with a fine sample (GAC-10-500) generated with a 0.1 wt % loading of ZnCl 2. The optimal sample structure and morphology were characterized by field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, and powder X-ray diffraction. On the basis of the adsorption−desorption results, the fine GAC provides a surface area of 719 m 2 /g. Moreover, it possessed an average pore diameter of 1.69 nm and a micropore volume of 0.27 m 3 /g. At 298 K, the adsorption capacity of the GAC-10-500 adsorbent improved by 19.75% for O 2 but was not significantly increased for N 2 and CO 2. Isotherm and kinetic adsorption models were applied to select the model best matching the studied O 2 , N 2 , and CO 2 gas uptake on GAC-10-500 adsorbent. At 298 K and 10 bar, the sip isotherm model with the highest potential adsorption difference sequence and gas adsorption difference compared with pure GAC adsorbent as O 2 > N 2 > CO 2 follows well for GAC-10-500. Eventually, the optimal sample is more effective for O 2 adsorption than other gases.

Kualitas udara dalam ruangan sangat krusial terhadap kesehatan manusia yang beraktivitas di dalamnya. Gas karbondioksida (CO₂) merupakan komponen gas yang paling banyak dalam ruangan dan meningkat secara signifikan seiring proses respirasi manusia. CO₂ dapat menyebabkan berbagai gangguan kesehatan jika konsentrasinya melampaui standar baku ASHRAE, yaitu 1000 ppm. Metode purifikasi udara ruangan dengan teknologi berbasis listrik kurang ekonomis, membutuhkan energi besar, dan tidak ramah lingkungan. Tanaman indoor seperti Aglaonema commutatum Schott dapat menjadi alternatif purifikasi udara dalam ruangan terutama dalam menyerap kandungan CO₂ berlebih. Penelitian ini dilakukan dengan mengaplikasikan tanaman Aglaonema commutatum Schott dalam sistem buatan yang merepresentasikan suatu ruangan. Tujuan penelitian ini adalah untuk membuat rancangan alat dalam mendeteksi pengurangan gas CO₂ di dalam ruangan dengan sensor MQ135 menggunakan tumbuhan Aglaonema commutatum Schott yang terukur dalam konsentrasi CO₂ dan laju reduksi CO₂ tiap detik. Sistem dilengkapi dengan pencahayaan lampu selama 12 jam untuk memfasilitasi proses fotosintesis sebagai mekanisme penyerapan CO₂ oleh tanaman. Monitoring terhadap penurunan atau kenaikan konsentrasi CO₂ dilakukan dengan sensor gas MQ135 yang terintegrasi dengan mikrokontroler Arduino UNO dan terhubung dengan Raspberry Pi yang memungkinkan monitor jarak jauh berbasis internet. Hasil percobaan menunjukkan bahwa terjadi penurunan kadar CO2 secara lebih signifikan dibanding kontrol dalam kurun waktu pengamatan 12 jam. Sistem secara efektif dapat mengurangi kadar CO₂ dengan laju 137,8 ppm/15 detik atau 9,14 ppm/detik apabila dibandingkan dengan kontrol yang hanya sebesar 77,47 ppm/15 detik atau 5,16 ppm/detik.

- by Marcelino P Perdana and +1
- •
- Bioengineering, Air Quality, Indoor Air Quality, Carbon Dioxide

This paper describes a comparative modelling study of Surface Acoustic Wave (SAW) devices. The Surface Acoustic Waves (SAWs) are generated and received by the interdigital transducer (IDT) on a piezoelectric substrate. SAW device design parameters like piezoelectric substrate, structure of IDT, number of finger pairs, device frequency and etc., are optimized and its frequency responses achieved by using three models, namely, Impulse response Model, Crossed-field
Equivalent Circuit Model and Coupling-of-Modes Model. The modelling of ST-X Quartz based SAW Delay line with 40 finger pairs operating at a centre frequency of 300 MHz has been undertaken and its modelled frequency response studied via three models. Employing a custom made MATLAB® algorithm, the device is modelled by varying its design parameters. The modelled results are analyzed and compared for attaining better performances for potential applications in a SAW sensor.

- by Dr. Venkatesan T
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- Gas Sensors, SAW based sensors, SAW (Surface acoustic waves)

Here we report on the mask-less deposition of Au–SnO 2 nanocomposites with a silicon-on-insulator (SOI) complementary metal oxide semiconductor (CMOS) micro electro mechanical system (MEMS) platform through the use of dip pen nanolithography (DPN) to create a low-cost ethanol sensor. MEMS technology is used in order to achieve low power consumption, by the employment of a membrane structure formed using deep reactive ion etching technique. The device consists of an embedded tungsten micro-heater with gold interdigitated electrodes on top of the SOI membrane. The tungsten micro-heater is used to raise the membrane temperature up to its operating temperature and the electrodes are used to measure the resistance of the nanocomposite sensing layer. The CMOS MEMS devices have high electro-thermal efficiency, with 8.2 °C temperature increase per mW power of consumption. The sensing material (Au– SnO 2 nanocomposite) was synthesised starting from SnO nanoplates, then Au nanoparticles were attached chemically to the surface of SnO nanoplates, finally the mixture was heated at 700 °C in an oven in air for 4 h. This composite material was sonicated for 2 h in terpineol to make a viscous homogeneous slurry and then 'written' directly across the electrode area using the DPN technique without any mask. The devices were characterised by exposure to ethanol vapour in humid air in the concentration range of 100–1000 ppm. The sensitivity varied from 1.2 to 0.27 ppm −1 for 100–1000 ppm of ethanol at 10% relative humid air. Selectivity measurements showed that the sensors were selective towards ethanol when they were exposed to acetone and toluene. S Online supplementary data available from stacks.iop.org/NANO/27/125502/mmedia

- by Andrea De Luca and +2
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- Nanomaterials, Gas Sensors, MEMS design: Sensors and Actuators, CMOS Technology

Pure SnO 2 , ZnO nanoparticles, and a SnO 2 /ZnO core/shell nanocomposite (NC) were prepared via a sol–gel technique. The structure and morphology of the obtained materials were characterized by X-ray diffraction (XRD), micro-Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM). The results showed that highly crystalline materials were formed, and the resulting composites exhibited core/shell structure with a size of 30 nm, whereas the fabricated films exhibited porous morphology. The gas sensing performance of the SnO 2 , ZnO nanoparticles, and the SnO 2 /ZnO NC films was investigated for different volatile organic compound (VOC) vapors in the temperature range from 150 to 350 1C. The gas sensing results confirmed that the SnO 2 /ZnO NC film shows a high selectivity, sensitivity, good stability, and fast response time towards isopropanol at the optimum operating temperature of 300 1C.

Providing a constant and perpetual energy source is a key design challenge for implantable medical devices. Harvesting energy from the human body and the surrounding is one of the possible solutions. Delivering energy from outside the body through different wireless media is another feasible solution. In this paper, we review different state-of-the-art methods that process " in-body " energy harvesting as well as " out-of-body" wireless power delivery. Details of the energy sources, transmission media, energy harvesting, coupling techniques and the required energy transducers will also be discussed. The merits and disadvantages of each approach will be presented. Different types of mechanisms have very different characteristics on their output voltage, amount of harvested power and power transfer efficiency. Therefore different types of power conditioning circuits are required. Issues of designing the building blocks for the power conditioning circuits for different energy harvesting or coupling mechanisms will be compared.

Ti/Pt as heating element for gas sensor applications was fabricated on silicon (Si) wafer substrate. The fabricated device was subjected to heat treatment at different prescribed time periods for thermal stability. The energy dispersion spectroscopy (EDS) results of the device indicated that there were no Ti traces on the Pt surface after heat treatment at 450 1C for 3 and 4 h in an argon (Ar) atmosphere. A maximum temperature coefficient of resistance (TCR) with a value of 2.88 Â 10 À 3 K À 1 was obtained for the device with 3 h heat treatment.

- by Azlan Abdul Aziz
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- Sensors and Sensing, Thin Films and Coatings, Gas Sensors

Iron oxide nano-particles are synthesized from aqueous iron (III) nitrate solution through citric acid and ethy-lene glycol assisted modified Pechini route. Synthesized particles are calcined at 400 and 600 C in air to achieve better crystallization. The phase formation behaviors of the dried and calcined powders are studied by analyzing the respective X-ray diffraction patterns. The particles calcined at 600 C are identified as pure hematite phase. However, maghemite is found as impurity with the desired hematite phase in dried particles and their counterpart calcined at 400 C. The chemi-resistive hydrogen sensing characteristics of the sensing elements prepared from the dried and calcined powders are investigated by varying the operating temperature of the sensor (275–350 C) and concentration of hydrogen gas (250–1660 ppm). The study reveals that the synthesized iron oxide particles are promising for the detection of hydrogen gas.

Ni 1−x Co x Fe 2 O 4 nanoparticles with x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 (named NC0, NC10, NC20, NC30, NC40, and NC50, respectively) were synthesized by wet chemical co-precipitation method. The prepared nanoparti-cles were crystallized in the cubic spinel structure of space group Fd3m with a narrow size distribution from 13 to 24 nm. The saturation magnetization was strongly influenced with Co 2+ concentrations. The cation distribution, the spin canting, and the presence of Fe 2+ ions along with Fe 3+ ions were responsible for the variation in saturation magnetization. Cation distribution estimated from saturation magnetization suggested the mixed spinel structure of Ni 1−x Co x Fe 2 O 4 system. The calculated g values from electron spin resonance spectra were consistent with the variation of saturation magnetization. UV–vis diffuse spectra indicated that Ni 1−x Co x Fe 2 O 4 samples were indirect band gap materials and band gap decreased with increasing Co 2+ concentration. Dielectric constant and dielectric loss showed frequency-dependent dispersion along with enhancement dielectric constant with increasing Co 2+ concentration. The complex impedance analysis confirmed that the conduction process predominantly takes place through grain boundaries.

- by Seema Lakhanpal Joshi
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- Materials Science, Nanomaterials, Ferrite, Gas Sensors

Ammonia sensing characteristics of undoped and cobalt (Co)-doped nanostructured ZnO thin films were investigated. Polycrystalline nature with hexagonal wurtzite structure and high crystalline quality with dominant (002) plane orientation of Co-doped ZnO film were confirmed by the X-ray diffractogram. Scanning electron micrographs of the undoped film demonstrated the uniform deposition of sphere-shaped grains. But, smaller particles with no clear grain boundaries were observed for Co-doped ZnO thin film. Band gap values were found to be 3.26 eV and 3.22 eV for undoped and Co-doped ZnO thin films. Ammonia sensing characteristics of Co-doped ZnO film at room temperature were investigated in the concentration range of 15 to 1000 ppm. Variation in the sensing performances of Co-doped and pure ZnO thin films has been analyzed and compared.

- by Ganesh Kumar Mani
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- Thin Films and Coatings, Gas Sensors, Nanowires based gas sensors, Zinc Oxide

In the present paper, a study on bismuth sodium titanate thin film based liquefied petroleum gas sensing was carried out. The thin film of synthesized material has been prepared by using sol-gel spin coating technique and was characterized by various techniques such as XRD, TGA, SEM, TEM, EDS, UV-Spectroscopy, Raman and FTIR. XRD analysis confirms the formation of bismuth sodium titanate (BNT) with a minimum crystallite size of 9 nm. SEM images show the microporous surface structure of the film. Optical characterization of the film was carried out by UV-vis spectrophotometer; Fourier transforms infrared spectroscopy and Raman spectroscopy. Thermal analysis graph of BNT precursor via Thermal Gravimetric process was studied. LPG sensing of bismuth sodium titanate was done at room temperature below LEL. Maximum sensitivity was found as 2.158 at 3 vol% and minimum response time of 22 s and recovery time 26 s for 0.25 vol% of LPG.

- by Ashok Ranjan
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- Materials Science, Gas Sensors
- by Murat Ates
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- Biomedical Engineering, Sensors and Sensing, Biosensors, Conducting Polymers

The possibility of using novel architectures based on carbon nanotubes (CNTs) for a realistic monitoring of
the air quality in an urban environment requires the capability to monitor concentrations of polluting gases
in the low-ppb range. This limit has been so far virtually neglected, as most of the testing of new ammonia
gas sensor devices based on CNTs is carried out above the ppm limit. In this paper, we present single-wall
carbon nanotube (SWCNT) chemiresistor gas sensors operating at room temperature, displaying an
enhanced sensitivity to NH3. Ammonia concentrations in air as low as 20 ppb have been measured, and
a detection limit of 3 ppb is demonstrated, which is in the full range of the average NH3 concentration
in an urban environment and well below the sensitivities so far reported for pristine, non-functionalized
SWCNTs operating at room temperature. In addition to careful preparation of the SWCNT layers,
through sonication and dielectrophoresis that improved the quality of the CNT bundle layers, the lowppb
limit is also attained by revealing and properly tracking a fast dynamics channel in the desorption
process of the polluting gas molecules.

- by Federica Rigoni
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- Carbon Nanotubes, Environmental Monitoring, Air pollution, Dielectrophoresis