Carbon Nanotube Based Chemical Sensors

Carbon nanotubes CNTs)have been receiving enormous attention in the last decade due to their extraordinary mechanical properties and unique elec- tronic properties.This combination has produced an unprecedented range of applications for CNTs:elec- tronic,logic and memory chips,chemical and biosen- sots,composites,lithium batteries,gas storage,filters and membranes,etc.This presentation will focus on carbon nanotube based sensors and discuss fabrication, testing and performance.

Ubiquitous Sensor Network for Chemical Sensors

Wireless sensor networks have been identified as one of the most important technologies for the 21 st century.Recent advances in micro sensor fabrication technology and wireless communication technology enable the practical deployment of large-scale,low-power,inexpensive sensor networks.Such an approach offers an advantage over traditional sensing methods in many ways:large-scale,dense deployment not only extends spatial coverage and achieves higher resolution,but also increases the system's fault-tolerance and robustness.Moreover,the ad-hoc nature of wireless sensor networks makes them even more attractive for military and other risk-associated applications,such as environmental observation and habitat monitoring.

Effect of Durian Peel Ash Added in Zinc Oxide/Reduced Graphene Oxide Composites Used as a Chemical Sensor for Hydrazine Detection

As the hydrazine is toxic, the methods to detect hydrazine at low concentrations are essential in scientific research. This preliminary study reported on how to increase the efficiency of ZnO/reduced graphene oxide (rGO) by adding durian peel ash (DPA) and using three-electrode method. The ZnO/rGO composites were prepared using chemical reaction of graphene oxide (GO) with zinc chloride. The rGO was prepared by the chemical reduction of GO using hydrazine. The properties of the samples were investigated using scanning electron microscopy, atomic force microscopy, X-ray diffraction, and Potentiostat/Galvanostat. The results showed that the optimal condition for the composite material was 70%DPA:30%ZnO/rGO with the sensitivity of 222.92 mA/mM·cm2 and the current density up to 116.50 ± 0.95 A/g. The relationship between the current and the hydrazine concentration was I (μA) = 48.69 + 21.91C (mM) with R2 of 0.9870. The minimum concentration of hydrazine solution that the modified electrode can measure was 0.125 mM. The DPA powder can then be used to enhance the hydrazine detection efficiency at low concentrations.

Recent developments in self-powered smart chemical sensors for wearable electronics

The next generation of electronics technology is purely going to be based on wearable sensing systems. Wearable electronic sensors that can operate in a continuous and sustainable manner without the need of an external power sources, are essential for portable and mobile electronic applications. In this review article, the recent progress and advantages of wearable self-powered smart chemical sensors systems for wearable electronics are presented. An overview of various modes of energy conversion and storage technologies for self-powered devices is provided. Self-powered chemical sensors (SPCS) systems with integrated energy units are then discussed, separated as solar cell-based SPCS, triboelectric nano-generators based SPCS, piezoelectric nano-generators based SPCS, energy storage device based SPCS, and thermal energy-based SPCS. Finally, the outlook on future prospects of wearable chemical sensors in self-powered sensing systems is addressed.

A Novel Electrochemical Oxygen Sensor for Determination of Ultra-low Oxygen Contents in Molten Metal

A novel electrochemical oxygen sensor has been developed by using Laβ-Al2O3 as solid electrolyte and Cr+Cr2O3 as reference electrode. The sensor not only can be used as normal oxygen sensor hot also as an ultra-low oxygen sensor. Especially, it is very sensitive to measure ultra-low oxygen in molten metal. For estimating the accuracy of Laβ-Al2O3 oxygen sensor, two series of oxygen activities in molten iron at different oxygen contents and different temperature were measured by both Laβ-Al2O3 oxygen sensor and ZrO2 oxygen sensor. The theoretical values of oxygen activities in molten iron (3.30%C, in mass fraction) at 1723K and 1745K were also evaluated for comparing the measuring results of two sensors. At last, the error of measurement for Laβ-Al2O3 oxygen sensor was discussed too.

Roles of Chemical Gas Sensors in the Filed of Safety

1 Introduction Gas sensors have been used in a range of applications where they play a crucial role in ensuring that we live safely and comfortablely.Gas safety products,such as gas detectors/alarms,especially those equipped with combustible gas,toxic gas,or oxygen sensors,are one of the most important applications for gas sensors.The purpose of gas detector/alarm units is

Chemical Investigation of the NO_x Detection Mechanisms by Semiconductor Metal Oxide Nanoparticles

This work reports an FTIR study of the NO_x adsorption/desorption cycles on tin oxide nanosized particles under the operating conditions of real sensors (150℃,in presence of O_2).The chemical reactions are monitored in situ and correlated with the variations of the SnO_2 electrical conductivity.On the basis of the FTIR spectra,two contributing mechanisms for the NO_x detection are suggested.The first one presents the formation of bridged nitrate groups bound to the SnO_2 surface via oxygen vacancies acting as electron donor sites.The second mechanism also involves surface oxygen vacancies in the coordination of NO_x,but this time the formation of NO_x anionic species is considered.Both mechanisms lead to the decrease of the electrical conductivity under NO_x adsorption.However,the bridged nitrate groups are not reversible under gas desorption and thus irreversibly contaminate the surface after the first NO_x adsorption.On the contrary,the nitrosyl anionic species are reversible and,from the second NO_x adsorption/desorption cycle,ensure the reproducibility of the sensor response.

Electrogenerated chemiluminescence sensor for the determination of metoclopramide using ordered mesoporous carbon for immobilizing tris(2,2'-bipyridyl)ruthenium

A novel electrogenerated chemiluminescence(ECL)sensor for the determination of metoclopramide was developed by employing ruthenium complex as an ECL signal producer and an ordered mesoporous carbon(OMC)material as modified material.The ECL sensor was fabricated by adsorption ruthenium complex into a mixture of OMC and Nafion,which showed good electrochemical and ECL behaviors.It was found that the ECL intensity of the sensor fabricated was greatly enhanced in the presence of metoclopramide.Based on this finding,a highly sensitive and reproducible ECL method was developed for the determination of metoclopramide.The result showed that the ECL intensity was linear with the concentration of metoclopramide in the range from 1.0×10-10 to 5.0×10-7M and the detection limit was 3×10-11M.The ECL sensor exhibited a long-term stability and a fine reproducibility with relative standard deviation of 1.0 % for 1.0×10-10M metoclopramide in 18 continuous determinations.The developed method has been applied to the determination of metoclopramide in tablet samples with satisfactory results.

A Review on Surface Stress-Based Miniaturized Piezoresistive SU-8 Polymeric Cantilever Sensors

In the last decade, microelectromechanical systems(MEMS) SU-8 polymeric cantilevers with piezoresistive readout combined with the advances in molecular recognition techniques have found versatile applications,especially in the field of chemical and biological sensing.Compared to conventional solid-state semiconductor-based piezoresistive cantilever sensors, SU-8 polymeric cantilevers have advantages in terms of better sensitivity along with reduced material and fabrication cost. In recent times,numerous researchers have investigated their potential as a sensing platform due to high performance-to-cost ratio of SU-8 polymer-based cantilever sensors. In this article, we critically review the design, fabrication, and performance aspects of surface stress-based piezoresistive SU-8 polymeric cantilever sensors. The evolution of surface stress-based piezoresistive cantilever sensors from solid-state semiconductor materials to polymers, especially SU-8 polymer, is discussed in detail. Theoretical principles of surface stress generation and their application in cantilever sensing technology are also devised. Variants of SU-8 polymeric cantilevers with different composition of materials in cantilever stacks are explained. Furthermore, the interdependence of the material selection, geometrical design parameters, and fabrication process of piezoresistive SU-8 polymeric cantilever sensors and their cumulative impact on the sensor response are also explained in detail.In addition to the design-, fabrication-, and performancerelated factors, this article also describes various challenges in engineering SU-8 polymeric cantilevers as a universal sensing platform such as temperature and moisture vulnerability. This review article would serve as a guideline for researchers to understand specifics and functionality of surface stress-based piezoresistive SU-8 cantilever sensors.

The recent progress of laser-induced graphene based device applications

Laser writing is a fast and efficient technology that can produce graphene with a high surface area,whereas laser-induced graphene(LIG)has been widely used in both physics and chemical device application.It is necessary to update this important progress because it may provide a clue to consider the current challenges and possible future directions.In this review,the basic principles of LIG fabrication are first briefly described for a detailed understanding of the lasing process.Sub-sequently,we summarize the physical device applications of LIGs and describe their advantages,including flexible electronics and energy harvesting.Then,chemical device applications are categorized into chemical sensors,supercapacitors,batteries,and electrocatalysis,and a detailed interpretation is provided.Finally,we present our vision of future developments and challenges in this exciting research field.

Advances and challenges of cellulose functional materials in sensors

As the most abundant natural polymer material on the earth,cellulose is a promising sustainable sensing material due to its high mechanical strength,excellent biocompatibility,good degrada-tion,and regeneration ability.Considering the inherent advantages of cellulose and the success of modern sensors,applying cellulose to sensors has always been the subject of considerable investigation,and significant progress has been made in recent decades.Herein,we reviewed the research progress of cellulose functional materials(CFMs)in recent years.According to the different sources of cellulose,the classification and preparation methods for the design and func-tionalization of cellulose were summarized with the emphasis on the relationship between their structure and properties.Besides,the applications of advanced sensors based on CFMs in recent years were also discussed.Finally,the potential challenges and prospects of the development of sensor based on CFMs were outlined.

Synthesis and Gas Sensing of TiO_2 Ultrafine Powders by Precipitating

We investigated the gas sensing characteristics of rutile and anatase TiO_2 nano-particle sensors for chemical warfare agents.TiO_2 nano-powders with rutile and anatase structure were fabricated by controlling pH value without heat treatment respectively.The mean particle size of TiO_2 powders were below 10 nm.As-prepared TiO_2 powders have several advantages of nano particle size and high surface area and could be a prominent candidate for nano-sensors.TiO_2 sensors were examined with DMMP for chemical warfare agents detection.

Micro/Nanofiber Optical Sensors

As a low-dimensional optical fiber with diameter close to or below the wavelength of light,optical micro/nanofiber(MNF)offers a number of favorable properties for optical sensing,which have been exploited in a variety of sensing applications,including physical,chemical,and biological sensors.In this paper we review the principles and applications of silica,glass,and polymer optical micro/nanofibers for physical and chemical sensing.

Electrochemically driven dynamic plasmonics

Dynamic plasmonics with the real-time active control capability of plasmonic resonances attracts much interest in the communities of physics,chemistry,and material science.Among versatile reconfigurable strategies for dynamic plasmonics,electrochemically driven strategies have garnered most of the attention.We summarize three primary strategies to enable electrochemically dynamic plasmonics,including structural transformation,carrier-density modulation,and electrochemically active surrounding-media manipulation.The reconfigurable microstructures,optical properties,and underlying physical mechanisms are discussed in detail.We also summarize the most promising applications of dynamic plasmonics,including smart windows,structural color displays,and chemical sensors.We suggest more research efforts toward the widespread applications of dynamic plasmonics.

Self-assembled core-shell structured organic nanofibers fabricated by single-nozzle electrospinning for highly sensitive ammonia sensors

Electrospinning is a unique method to prepare 1-dimentional nanofiber for largescalemanufacturing. Here in, we demonstrated chemical sensors based on thesemiconducting nanofibers with core-shell structure by simple single-nozzleelectrospinning with the spontaneous phase separation. The core-shell structurenanofiber has large active sites which make it highly sensitive to chemical analytes.The thickness of the sensing shell can be tuned by controlling the mass ratio ofcore and shell components. As a demonstration, the nanofiber-based sensorexhibits high sensitivity to low-concentration ammonia (ppb level), as well as stabilityand reversibility. This unique fast single-nozzle electrospinning techniqueused to fabricate semiconducting nanofibers with core-shell structure provides afacile and designable process for the integration of multifunctional organic semiconductinglayer into the organic electronic system.

Polyaniline Nanofiber Composites with Amines:Novel Materials for Phosgene Detection

Several orders of magnitude of change in resistance are observed upon chemical doping and dedoping of the conducting polymer polyaniline.This large conductivity range can be utilized to make sensitive chemical sensors.Polyaniline,in its nanofiber form,has even greater sensing capabilities due to the small fiber diameters,high surface area,and porous nanofiber network that enhances gas diffusion into the fibers.Polyaniline nanofibers have been synthesized using a rapid mixing method and dispersed in water allowing them to be easily modified with water soluble agents,making new composite materials.Polyaniline nanofiber composite materials can be used to enhance detection of analytes that unmodified polyaniline would not otherwise be able to detect.The detection mechanism involves the reaction of an additive with the analyte to generate a strong acid that is easily detected by polyaniline,resulting in orders of magnitude changes in resistance.The reaction of the additive alone with the analyte produces no electrical response,however.In this paper,an array of amine-polyaniline nanofiber composite materials is investigated for the detection of phosgene gas.The influence of environmental conditions such as humidity and temperature are examined and a detection mechanism is presented.

基于受体修饰的双层有机场效应晶体管化学传感器用于高灵敏检测锂离子电池电解液泄漏

易燃易爆的锂离子电池电解液泄漏是电池故障的早期症状之一,甚至会导致电池自燃或电动汽车爆炸.因此,有必要找到一种快速简单的方法来监测电解液泄漏.现有的传感器难以有效且快速地检测微量电解液泄漏.我们首次提出了一种将有机场效应晶体管(OFET)的灵敏度和联二脲受体的选择性相结合,以检测电池电解液泄漏的策略.复合后的传感器与没有受体的原始传感器相比,灵敏度显著提高,传感器对碳酸二乙酯的检测限低至1.4 ppm.并且可以在几秒钟内有效地检测到微量的泄漏, 200 n L电解液泄漏能够导致3%的响应.受体复合后的OFET传感器的优异性能使其成为锂离子电池安全监测的良好候选者,并为传感技术的发展提供了一个有前途的平台.