Preparation and characterization of vacuum deposited semiconducting nanocrystalline polymeric thin film sensors for detection of HCl

Detection and monitoring of hazardous species like HCl, by fast, simple, cost effective, highly specific and selective devices is the main issue for environmental scientists. The currently available detection methods are either indirect or time consuming and expensive. These sensors are operated at high temperatures and response time is very slow. The nanocomposite polymeric combinations have come out as efficient sensors for detection of hazardous gases. Nanocomposite copolymers of aniline and formaldehyde synthesized by chemical polymerization with metal complex of Fe-Al have been found to act as high selective and efficient sensors for HCl. Thin films of Fe-Al doped nanocomposite copolymer evaporated under high vacuum on various substrates like mica and glass have been found to exhibit high stability, sensitivity, selectivity and a fast response towards the presence of HCl vapors in the air. High stability, sensitivity, selectivity and specificity are obtained by optimization of doping (Fe-Al) in nanocomposite copolymer during synthesis. These sensors operate at room temperature. The preparation, optical, electrical, and structural characterization and behavioral acceptance test on the gas sensing properties of these sensors are reported here.     

A novel gas ionization sensor using Pd nanoparticle-capped ZnO

A novel gas ionization sensor using Pd nanoparticle-capped ZnO (Pd/ZnO) nanorods as the anode is proposed. The Pd/ZnO nanorod-based sensors, compared with the bare ZnO nanorod, show lower breakdown voltage for the detected gases with good sensitivity and selectivity. Moreover, the sensors exhibit stable performance after more than 200 tests for both inert and active gases. The simple, low-cost, Pd/ZnO nanorod-based field-ionization gas sensors presented in this study have potential applications in the field of gas sensor devices.     

香豆素类荧光传感器检测金属离子的研究进展

金属离子对自然环境和生物体的生长发育具有重要的影响,因此对环境中及生物体内的金属离子的识别和检测正日益受到人们广泛的关注。在不同的分析方法中,荧光分析法具有灵敏度高、选择性好和实时原位检测等优点,是实现环境中和生物体内金属离子识别和检测的良好工具。本文综述了近5年来香豆素类荧光传感器对一些重金属离子（Hg2+、Pb2+、Cd2+、Ni2+、Ag+）和一些具有重要生物学意义的过渡金属离子（Cu2+、Zn2+、Fe3+）的识别与检测及其应用进展情况,着重介绍了传感器分子的设计合成、识别机理、传感特性及其在环境分析和生物检测中的应用。随着金属离子检测要求的提高,未来香豆素类荧光传感器的设计将向着灵敏度更高、选择性更好、抗干扰性能更强的方向发展。此外,香豆素类传感器在生物检测中的应用研究有望得到进一步发展。     

MOF-801 polycrystalline membrane with sub-10 nm polymeric assembly layer for ion sieving and flow battery storage

Molecular sieving metal–organic framework (MOF) polycrystalline membranes have great potential for ion sieving and are desirable as efficient separators for devices of energy storage such as flow battery. Herein, we report a continuous MOF-801 polycrystalline membrane with an ultrathin polymeric assembly layer (less than 10 nm) for the vanadium flow battery (VFB). Owing to the precise sub-nanometer sieving pores and abundant H-bond networks in MOF-801 frameworks, the membrane exhibited better H/V selectivity (up to 194) and conductivity (about 0.028 S/cm) than commercial Nafion-117 membrane (H/V selectivity: ~9.5, conductivity: 0.017 S/cm). VFB results revealed that a cell with above MOF polycrystalline membrane showed high coulombic efficiency (CE: 96.1%) and excellent energy efficiency (EE: 83.2%) at 20 mA/cm², which was much comparable to Nafion membrane. This work demonstrates that MOF polycrystalline membrane is a promising candidate as ion sieving membrane for energy technique.     

活性炭负载的纳米金催化剂上葡萄糖氧化工艺

采用溶胶固定法制备了一系列的Au/C纳米催化剂,进行了透射电镜(TEM)表征,用于常压下以氧气为氧化剂碱性溶液中葡萄糖氧化制备葡萄糖酸钠,并对最佳的催化剂进行了反应条件影响考察。结果显示,使用溶胶固定法制备的质量分数为1%的Au/C催化效果最佳,纳米金颗粒直径小于2 nm且分布均匀,其较佳反应条件为50℃,pH 9.5,氧气流量40 mL/min,催化剂0.22 g,水溶液中质量分数为7.5%的葡萄糖,葡萄糖在1 h内,选择性及转化率均可同时达到100%,反应的转化频率(Turnover Frequency,TOF)高达1 560 h-1。上述研究表明溶胶固定法能制备一定纳米金颗粒大小的Au/C催化剂,且在该多相催化剂上反应时间短,活性高,选择性高。     

The production of oxygenated polycrystalline graphene by one-step ethanol-chemical vapor deposition

Large-area mono- and bilayer graphene films were synthesized on Cu foil (∼1 in.²) in about 1 min by a simple ethanol-chemical vapor deposition (CVD) technique. Raman spectroscopy and high resolution transmission electron microscopy revealed the synthesized graphene films to have polycrystalline structures with 2–5 nm individual crystallite size which is a function of temperature up to 1000 °C. X-ray photoelectron spectroscopy investigations showed about 3 at.% carboxylic (COOH) functional groups were formed during growth. The field-effect transistor devices fabricated using polycrystalline graphene as conducting channel (L_c = 10 μm; W_c = 50 μm) demonstrated a p-type semiconducting behavior with high drive current and Dirac point at ∼35 V. This simple one-step method of growing large area polycrystalline graphene films with semiconductor properties and easily functionalizable groups should assist in the realization of potential of polycrystalline graphene for nanoelectronics, sensors and energy storage devices.     

Lead-free double perovskite halide fluorescent oxygen sensor with high stability

Oxygen sensors, using organic-inorganic and all-inorganic lead halide perovskites, have demonstrated huge advantages in operating temperature, responding time, and reversing oxygen content detection. Nevertheless, the toxicity and instability issues hinder their wide application. In this work, for the first time, we report a sensitive fluorescence oxygen detector based on lead-free double perovskite Cs₂AgBiBr₆ thin film. The sensor has a remarkable performance in terms of fast response time of ≈56 s, recovery time of ≈91 s, and a relatively low limit of detection (LOD) of 150 ppm. More importantly, the unencapsulated sensor still exhibits an obvious response at low oxygen concentrations after two-week storage in ambient, and the device also exhibits good humidity, light, and thermal stability. Consequently, the lead-free double perovskite (Cs₂AgBiBr₆) will be promising environmentally friendly material in developing reversible, sensitive, high-efficiency, and stable perovskite oxygen sensors.     

Synthesis and anti-HIV activity of aryl-2-[(4-cyanophenyl)amino]-4-pyrimidinone hydrazones as potent non-nucleoside reverse transcriptase inhibitors

A series of novel diarylpyrimidines (DAPYs) with a ketone hydrazone substituent on the methylene linker between the pyrimidine nucleus and the aryl moiety at the C‐4 position were synthesized, and their antiviral activity against human immunodeficiency virus (HIV)‐1 in MT‐4 cells was evaluated. Most compounds of this class exhibited excellent activity against wild‐type HIV‐1, with EC₅₀ values in the range of 1.7–13.2 nM . Of these compounds, 2‐bromophenyl‐2‐[(4‐cyanophenyl)amino]‐4‐pyrimidinone hydrazone ( 9 k ) displayed the most potent anti‐HIV‐1 activity (EC₅₀=1.7±0.6 nM ), with excellent selectivity for infected over uninfected cells (SI=5762). In addition, the 4‐methyl phenyl analogue 9 d (EC₅₀=2.4±0.2 nM , SI=18461) showed broad spectrum HIV inhibitory activity, with EC₅₀ values of 2.4±0.2 nM against wild‐type HIV‐1, 5.3±0.4 μM against HIV‐1 double‐mutated strain RES056 (K103N+Y181C), and 5.5 μM against HIV‐2 ROD strain. Furthermore, structure–activity relationship (SAR) data and molecular modeling results for these compounds are also discussed.     

分子印迹在化学传感器及阵列领域的研究进展

分子印迹聚合物因其具有高选择性、预定识别性、制备简单、价格低廉等优点,成为当前研究的热点之一。本文对分子印迹聚合物在化学传感器及传感器阵列领域的应用进展进行了综述。作为选择性化学传感器,重点探讨了分子印迹聚合物在电化学传感器、光化学传感器和质量敏感型传感器中的应用。相对于分子印迹传感器,基于分子印迹聚合物交叉敏感性原理的分子印迹聚合物传感器阵列的应用较少,仅对有限例子的光化学传感器阵列进行了探讨。受益于印迹机理的深入理解,分子印迹化学传感器及其阵列将在食品分析、药物控制、环境监测等领域表现出较好的应用前景。     

A novel approach for evaluation of polymeric interface materials for chemical sensors using alternate indirect methods

The heart of a chemical sensor based on bulk or surface acoustic wave devices is a polymer‐coated piezoelectric substrate that selectively sorbs and concentrates the target analyte vapors. The development of such sensors often necessitates the screening and evaluation of suitable polymeric interface materials meeting the specified sensitivity and selectivity toward the analytes of interest. The magnitude and dynamics of sorption–desorption of the vapors in the polymer and the extent of polymer–vapor interactions largely determine the performance of a sensor. The standard protocol used for the purpose is rather tedious, involving the generation and calibration of individual analyte vapors, with stringent control on temperature, humidity, and test parameters. This article outlines four different alternative techniques based on mass uptake of the analyte vapors, on its partitioning in polymers, or both, which in combination can determine the characteristics of an interface material used for coating a piezoelectric substrate in acoustic wave‐based chemical sensors. These methods were applied to poly(ethylene maleate), a representative interface material. The analytes ranged from volatile organic chemicals to sarin—a chemical warfare agent—and its simulant, dimethyl methylphosphonate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3428–3432, 2004     

Microwave-assisted synthesis of highly water-soluble graphene towards electrical DNA sensor

Graphene sheets have the potential for practical applications in electrochemical devices, but their development has been impeded by critical problems with aggregation of graphene sheets. Here, we demonstrated a facile and bottom-up approach for fabrication of DNA sensor device using water-soluble sulfonated reduced graphene oxide (SRGO) sheets via microwave-assisted sulfonation (MAS), showing enhanced sensitivity, reliability, and low detection limit. Key to achieving these performances is the fabrication of the SRGOs, where the MAS method enabled SRGOs to be highly dispersed in water (10 mg mL(-1)) due to the acidic sulfonated groups generated within 3 min of the functionalization reaction. The water-soluble SRGO-DNA (SRGOD) hybrids prepared by electrostatic interactions between a flat single layer of graphene sheets and DNAs are suitable for fabrication of electrical DNA sensor devices because of the unique electrical characteristics of SRGODs. The high sensing performance of SRGOD sensors was demonstrated with detection of DNA hybridization using complementary DNAs, single base mismatched DNAs, and noncomplementary DNAs, with results showing higher sensitivity and lower detection limit than those of reduced graphene oxide-based DNA sensors. Simple and easy fabrication of DNA sensor devices using SRGODs is expected to provide an effective way for electrical detection of DNA hybridization using miniature sensors without the labor-intensive labeling of the sensor and complex measurement equipment.     

Novel potentiometric sensors for the selective determination of domperidone

The fabrication and electrochemical response characteristics of two novel potentiometric sensors for the selective determination of domperidone (DOM) are described. The two fabricated sensors incorporate DOM–PTA (phosphotungstic acid) ion pair as the electroactive material. The sensors include a PVC membrane sensor and a carbon paste sensor. The sensors showed a linear, stable, and near Nernstian slope of 56.5 and 57.8 mV/decade for PVC membrane and carbon paste sensors, respectively over a relatively wide range of DOM concentration (1.0 × 10^?1–1.0 × 10^?5 and 1.0 × 10^?1–3.55 × 10^?6 M). The response time of DOM–PTA membrane sensor was less than 25 s and that in the case of carbon paste sensor was less than 20 s. A useful pH range of 4–6 was obtained for both types of sensors. A detection limit of 7.36 × 10^?5 M was obtained for PVC membrane sensor and 1.0 × 10^?6 M was obtained for carbon paste sensor. The proposed sensors showed very good selectivity to DOM in the presence of a large number of other interfering ions. The analytical application of the developed sensors in the determination of the drug in pharmaceutical formulations such as tablets was investigated. The results obtained are in good agreement with the values obtained by the standard method. The sensors were also applied for the determination of DOM in real samples such as urine by the standard addition method.     

电化学传感器检测植物生长调节剂的研究进展

近年来,植物生长调节剂(PGRs)的检测方法备受研究者广泛关注。由于电化学传感器具有较高的灵敏度和选择性、响应时间短、成本低、方便携带等优点,在现场快速检测中受到研究者的青睐。从电化学传感器检测PGRs的4个方面进行了总结:1)直接电化学行为传感,主要是通过不同的修饰材料对电极进行增敏,从而实现对具有电化学活性的PGRs进行直接检测;2)电化学生物传感,主要通过酶和抗原抗体对PGRs进行特异性识别;3)光电化学传感,主要是利用具有光催化性能的材料实现对电化学活性较差的PGRs进行光电转化检测;4)分子印迹电化学传感,通过构建能够特异性识别PGRs的聚合物薄膜从而进行专属检测。同时对电化学传感器现状进行了阐述以及对未来发展趋势进行展望。     

Microbial sensors: Fundamentals and application for process control

Microbial sensors consist of microorganisms in intimate contact with transducer devices converting the biochemical reaction to a quantifiable electrical response signal. The aim of this combination is the sensitive determination of a large spectrum of substances in various fields, especially in fermentation processes and pollution control. Microbial sensors for more than 50 different parameters have been described in the literature. In this paper, the following main aspects are discussed: microbial and physical basis of microbial sensors, immobilization of microbes, principle of measurement, approaches for enhancing the selectivity and sensitivity of microbial sensors, applications in bioreactor and environmental control of microbial sensors.     

Development of Polypyrrole Modified Screen-Printed Carbon Electrode Based Sensors for Determination of L-Tyrosine in Pharmaceutical Products

Good health, of vital importance in order to carry out our daily routine, consists of both physical and mental health. Tyrosine (Tyr) deficiency as well as its excess are issues that can affect mental health and can generate disorders such as depression, anxiety, or stress. Tyr is the amino acid (AA) responsible for maintaining good mental health, and for this reason, the present research presents the development of new electrochemical sensors modified with polypyrrole (PPy) doped with different doping agents such as potassium hexacyanoferrate (II) (FeCN), sodium nitroprusside (NP), and sodium dodecyl sulfate (SDS) for a selective and sensitive detection of Tyr. The development of the sensors was carried out by chronoamperometry (CA) and the electrochemical characterization was carried out by cyclic voltammetry (CV). The detection limits (LOD) obtained with each modified sensor were 8.2 × 10⁻⁸ M in the case of PPy /FeCN-SPCE, 4.3 × 10⁻⁷ M in the case of PPy/NP-SPCE, and of 3.51 × 10⁻⁷ M in the case of PPy/SDS-SPCE, thus demonstrating a good sensitivity of these sensors detecting L-Tyr. The validation of sensors was carried out through quantification of L-Tyr from three pharmaceutical products by the standard addition method with recoveries in the range 99.92–103.97%. Thus, the sensors present adequate selectivity and can be used in the pharmaceutical and medical fields.     

Hydrogen peroxide sensor based on modified vitreous carbon with multiwall carbon nanotubes and composites of Pt nanoparticles-dopamine

Sensors using nanostructured materials have been under development in the last decade due to their selectivity for the detection and quantification of different compounds. The physical and chemical characteristics of carbon nanotubes provide significant advantages when used as electrodes for electronic devices, fuel cells and electrochemical sensors. This paper presents preliminary results on the modification of vitreous carbon electrodes with Multiwall Carbon Nanotubes (MWCNTs) and composites of Pt nanoparticles-dopamine (DA) as electro-catalytic materials for the hydrogen peroxide (H₂O₂) reaction. Chemical pre-treatment and consequent functionalization of MWCNTs with carboxylic groups was necessary to increase the distribution of the composites. In addition, the presence of DA was important to protect the active sites and eliminate the pasivation of the surface after the electro-oxidation of H₂O₂ takes place. The proposed H₂O₂ sensor exhibited a linear response in the 0-5 mM range, with detection and quantification limits of 0.3441 mM and 1.1472 mM, respectively.     

Antibody-Based Submicron Biosensor for Benzo[A]Pyrene DNA Adduct

Abstract

Fiberoptic-based sensors have been developed for monitoring human exposure and health effects associated with polycyclic aromatic compounds such as benzo[a]pyrene. These sensors take advantage of the physical properties of optical fibers including their relatively small size, remote sensing capabilities, and their inertness to electrical interferences. the recent development of submicron-sized optical fibers provides an opportunity to further reduce the size of fiberoptic-based sensors for application in submicron environments. This paper describes the development of an antibody based submicron fiber biosensor. the antibody-based biosensor is more selective and sensitive than a nonantibody sensor and has an absolute detection limit of ≈ 300 zeptomoles (10^?21 moles) for benzo pyrene tetrol, a product of the benzo[a]pyrene DNA adduct. This submicron-size biosensor could provide a useful tool for measurements of toxic chemicals and related metabolites in sub cellularsize environments.     

Humidity Sensor Based on PEO/PEDOT:PSS Blends for Breath Monitoring

The discrimination of humidity in exhaled breath is of utmost importance to turn breath analysis into an efficient noninvasive tool for early diagnosis or treatment monitoring of several diseases. Herein, by assembling different ratios of the conductive poly(3,4-ethylenedioxythiophene): polystyrene sulfonate with the polymer matrix polyethylene oxide (PEO), humidity chemiresistor-based sensors are designed and investigated. The testing results display a broad relative humidity detection range (6–92%), repeatability, reproducibility, and good reversibility. Meanwhile, the sensors possess good reliability for distinct temperatures and in the presence of typical volatile organic compounds found in human exhaled air. The hygroscopic idiosyncrasy of PEO is attributed to be the main responsible for the high sensibility toward humidity. In a proof-of-principle for detection of respiration humidity, the outcome shows the ability of the chemiresistors to detect the humidity variation in a real case of breath exposure up to 2 s intervals. The 30 d trial of stability readings shows a standard deviation of only 2.6%. These sensing devices appear as a new array component able to distinguish moisture from biomarkers of diagnosed diseases in breath analysis.     

Polyacrylonitrile‐carbon Nanotube‐polyacrylonitrile: A Versatile Robust Platform for Flexible Multifunctional Electronic Devices in Medical Applications

Flexible multifunctional electronic devices are of high interest for a wide range of applications including thermal therapy and respiratory devices in medical treatment, safety equipment, and structural health monitoring systems. This paper reports a scalable and efficient strategy of manufacturing a polyacrylonitrile‐carbon nanotube‐polyacrylonitrile (PAN‐CNT‐PAN) robust flexible platform for multifunctional electronic devices including flexible heaters, temperature sensors, and flexible thermal flow sensors. The key advantages of this platform include low cost, porosity, mechanical robustness, and electrical stability under mechanical bending, enabling the development of fast‐response flexible heaters with a response time of ≈1.5 s and relaxation time of ≈1.7 s. The temperature‐sensing functionality is also investigated with a range of temperature coefficient of resistances from ?650 to ?900 ppm K^?1. A flexible hot‐film sensing concept is successfully demonstrated using PAN‐CNT‐PAN with a high sensitivity of 340 mV (m s^?1)^?1. The sensitivity enhancement of 50% W^?1 is also observed with increasing supply power. The low cost, porosity, versatile, and robust properties of the proposed platform will enable the development of multifunctional electronic devices for numerous applications such as flexible thermal management, temperature stabilization in industrial processing, temperature sensing, and flexible/wearable devices for human healthcare applications.