超分子在质量敏感压电化学传感器中的应用

以质量敏感为分析基础的压电化学传感器,其表面涂层往往决定其对分析物的选择性。超分子作为压电石英晶体涂层,应用主－客体分子识别的原理,显著提高压电化学传感器的选择性。该文详细论述了近十年有关超分子主体化合物在体波和表面波化学传感器的应用,并了涂膜技术及主－客体识别机理。     

Porphyrins-Functionalized Single-Walled Carbon Nanotubes Chemiresistive Sensor Arrays for VOCs

Single-walled carbon nanotubes (SWNTs) have been used extensively for sensor fabrication due to its high surface to volume ratio, nanosized structure and interesting electronic property. Lack of selectivity is a major limitation for SWNTs-based sensors. However, surface modification of SWNTs with a suitable molecular recognition system can enhance the sensitivity. On the other hand, porphyrins have been widely investigated as functional materials for chemical sensor fabrication due to their several unique and interesting physico-chemical properties. Structural differences between free-base and metal substituted porphyrins make them suitable for improving selectivity of sensors. However, their poor conductivity is an impediment in fabrication of prophyrin-based chemiresistor sensors. The present attempt is to resolve these issues by combining freebase- and metallo-porphyrins with SWNTs to fabricate SWNTs-porphyrin hybrid chemiresistor sensor arrays for monitoring volatile organic carbons (VOCs) in air. Differences in sensing performance were noticed for porphyrin with different functional group and with different central metal atom. The mechanistic study for acetone sensing was done using field-effect transistor (FET) measurements and revealed that the sensing mechanism of ruthenium octaethyl porphyrin hybrid device was governed by electrostatic gating effect, whereas iron tetraphenyl porphyrin hybrid device was governed by electrostatic gating and Schottky barrier modulation in combination. Further, the recorded electronic responses for all hybrid sensors were analyzed using a pattern-recognition analysis tool. The pattern-recognition analysis confirmed a definite pattern in response for different hybrid material and could efficiently differentiate analytes from one another. This discriminating capability of the hybrid nanosensor devices open up the possibilities for further development of highly dense nanosensor array with suitable porphyrin for E-nose application.     

Supramolecular Sensing of a Chemical Warfare Agents Simulant by Functionalized Carbon Nanoparticles

Real-time sensing of chemical warfare agents by optical sensors is today a crucial target to prevent terroristic attacks by chemical weapons. Here the synthesis, characterization and detection properties of a new sensor, based on covalently functionalized carbon nanoparticles, are reported. This nanosensor exploits noncovalent interactions, in particular hydrogen bonds, to detect DMMP, a simulant of nerve agents. The nanostructure of the sensor combined with the supramolecular sensing approach leads to high binding constant affinity, high selectivity and the possibility to reuse the sensor.     

Effect of Nanoparticle Size on Gas-sensing Properties of Tin Dioxide Sensors

Sn(OH)₄ was prepared by the conventional solution precipitate method, followed by supercritical CO₂ drying. The resultant Sn(OH)₄ was divided into three aliquots and calcined at 400, 600 and 800℃, respectively, thus SnO₂ nanoparticles with average crystallite sizes of 5, 10 and 25 nm were obtained. Furthermore, three SnO₂ thick film gas sensors(denoted as sensors S-400, S-600 and S-800) were fabricated from the above SnO₂ nanoparticles. The adhesion of sensing materials on the surface of alumina tube is good. Compared to the sensors S-600 and S-800, sensor S-400 showed a much higher sensitivity to 1000 μL/L ethanol. On the other hand, sensor S-800 showed a much lower intrinsic resistance and improved selectivity to ethanol than sensors S-400 and S-600. X-Ray diffraction(XRD), transmission electron microscopy(TEM) and selective area electron diffraction(SAED) measurements were used to characterize the SnO₂ nanoparticles calcined at different temperatures. The differences in the gas sensing performance of these sensors were analyzed on the basis of scanning electron microscopy(SEM).     

Design, construction and testing of a system for detection of toxic gases based on piezoelectric crystals

A system for static operation of toxic gas sensors based on piezoelectric crystals was constructed as a preliminary step in the development of this type of sensor. The sensing part of the setup consists of a twin oscillating circuit assembled from commercially available electronic parts mounted on a motherboard. The oscillating circuits can accommodate two piezoelectric crystals, of which one or both can be coated with different materials, or a single one, as required. The sensing assembly (crystals plus oscillating circuits) is placed in a customized test chamber that allows one to control and reproduce its internal environment. Once assembled and fine-tuned, the proposed setup was used to test a commercially available piezoelectric crystal for sensing formaldehyde in order to expand available information on this type of sensor.     

The pillar[5]arene-based spun thin films: preparation,characterization, development of optical and mass sensitive sensors for swelling dynamics and gas sensing abilities

Pillar[5]arene (P5)-based materials can be preferable one of the most sensing elements in chemical sensor applications due to their high cavity and their special chiral structure. While the P5-based macrocycle molecules have been utilized as thin-film materials, the reports of chemical sensor application by performing P5 as sensor molecules have been very limited in the available literature. In this report, quinoline P5 (P5-Q) molecules were used to produce thin films via spin coating technique. P5-Q spun films were characterized with Atomic Force Microscopy (AFM) and Ultraviolet–Visible (UV–Vis) spectrophotometer. The gas sensing abilities of these P5-Q spun films were investigated by Quartz Crystal Microbalance (QCM) and Surface Plasmon Resonance (SPR) techniques. In order to illuminate the gas sensing properties of P5-Q spun films, they were prepared as mass-sensitive and optical sensors. These sensors were utilized for its sensing abilities against organic vapours (acetone, methyl alcohol, and ethyl alcohol) by the mechanism of host–guest interaction. The current study also describes the diffusion coefficients of these organic vapors to illuminate the swelling dynamics of P5-Q spun films by performing Fick’s diffusion equation. The responses of P5-based optical (SPR) or mass sensitive (QCM) sensor in terms of the change in reflective intensity or the change in frequency and the values of diffusion coefficients showed that P5-Q molecules can be developed as potential chemical sensor element for acetone vapor compared to alcohol vapors.

     

A sulpha-drug sensitive sensor based on ion-pair complex modified PQC resonator

The construction and general performance characteristics of the piezoelectric sensors responsive to sulpha-drug are described here. The proposed sensing method is based on the use of the ion-pair complex of sulphadiazine-cetyltrioctylammonium. The complex, together with cholestyramine was embedded in PVC matrix. This sensor exhibited reasonable selectivity and a sensitive mass response to sulpha-drugs. The response range of the sensor was between 1.0x10(-7) and 1.0x10(-5) M with a detection limit of 8x10(-8) M at pH 8.63. The influencing factors were investigated in detail and optimized.     

Investigation of the origin of selectivity in cavitand-based supramolecular sensors

The sensing properties of functionalized cavitands have been studied by thin-film coating TMSR chemical sensors and by measuring their responses towards model analytes. We studied the relationship between the sensor performance, in terms of sensitivity and selectivity, and the molecular recognition properties of the cavitands. The Langmuir-like shape of the adsorption isotherm, obtained in the case of short-chain alcohols, demonstrated that selective binding can be achieved by the synergistic interactions of the cavity and the bridging PO(in) groups. In the absence of these substituents, the peripheral alkyl chains necessary for the formation of highly permeable thin films attenuate the cavity effect because of nonspecific dispersion interactions. This completely overrides the response originating from molecular recognition. The same effect is observed when the PO groups are oriented outward from the cavity. The use of multivariate chemometrics and the study of the correlations between sensors sensitivity and analyte properties provided further evidence of molecular recognition phenomena, whose intensity is enhanced by the permanent free volume created by the rigid cavity surrounding the PO(in) group.     

Synthesis and characterization of high-integrity solid-contact polymeric ion sensors

High-integrity solid-contact (SC) polymeric ion sensors have been produced by using spin casting and electropolymerization techniques in the preparation of the SC employing the conductive polymer, poly(3-octylthiophene) (POT). The physical and chemical integrity of the POT SCs have been evaluated using scanning electron microscopy (SEM), atomic force microscopy (AFM), secondary ion mass spectrometry (SIMS), and X-ray photoelectron spectroscopy (XPS). Furthermore, the electrochemical stability of SC polymeric ion sensors has been investigated using electrochemical impedance spectroscopy (EIS). The results of this study demonstrate that electropolymerization and spin casting methods also comprising annealing of the synthesized SC film are capable of producing SCs that are relatively free of imperfections such as pores and pinholes. This leads to electrochemically stable and robust polymeric ion sensors where the SC/sensor interface is resistant to the formation of a detrimental water layer that normally gives rise to spurious ion fluxes and a degradation in the sensitivity and selectivity of the SC polymeric ion sensor.     

碳纳米管基气体传感器研究进展

碳纳米管具有灵敏度高、响应快和工作温度低等优异的气敏特性,近年来碳纳米管基气体传感器的研究成为研究热点.概述了碳纳米管基气体传感器的种类、结构特点、气敏性能和未来的发展方向,着重介绍了纯的碳纳米管包括单壁碳纳米管、多壁碳纳米管和碳纳米管阵列的气敏特性,以及碳纳米管的修饰或碳纳米管与高分子材料、氧化物等复合对其气敏性能的影响.     

气敏新材料MXenes在呼出气体传感器中的应用

电子鼻结合人工智能对呼出气进行检测、分析和识别已成为非侵入性医疗检测领域的研究热点.然而,目前已报道的气体传感材料尚不能同时满足高灵敏度、高选择性和稳定的室温检测,阻碍了气体传感器在医疗健康领域的应用及发展,寻找合适的传感材料具有重要的意义和挑战.新型二维层状纳米材料MXenes具有种类多、比表面积大、导电性能强、表面...     

Potentiometric and theoretical studies of the carbonate sensors based on 3-bromo-4-hexyl-5-nitrotrifluoroacetophenone

Novel carbonate ionophore, trifluoroacetophenone derivative (TFA) substituted by two acceptor substituents in the phenyl ring (3-bromo-4-hexyl-5-nitrotrifluoroacetophenone), was synthesized. Solvent polymeric membrane sensors based on this ionophore exhibited heightened selectivity to carbonate ions in the presence of the most important interfering anions. A wide range of potentiometric properties were studied and compared with those of sensors based on mono-substituted ionophores. Special attention was paid to pH dependence of sensor responses and to elaboration of appropriate conditions for carbonate analysis. A segmented-sandwich membrane method was applied for determination of the stoichiometry of ionophore-carbonate complexes, which was determined to be 1:3, and apparent complex formation constants which were 14.4 and 13.6 for DOS- and NPOE-plasticized membranes, respectively. Theoretical studies on TFA derivatives by semi-empirical (AM1 and PM3) and ab initio(6-31+G*) methods were performed, considering different types of possible ionophore-ion interactions. The formation of hydrogen bonds between carbonate and hydrated TFA was proved to be much more favourable in terms of energy compared to tetrahedral nucleophilic adducts that earlier were postulated to being formed in the membrane phase. The final conclusion on the mechanism of carbonate sensing by TFA-based solvent polymeric membrane sensors was made on the basis of computational data and detailed analysis of the literature.     

Design of fluorescent materials for chemical sensing

There is an enormous demand for chemical sensors for many areas and disciplines. High sensitivity and ease of operation are two main issues for sensor development. Fluorescence techniques can easily fulfill these requirements and therefore fluorescent-based sensors appear as one of the most promising candidates for chemical sensing. However, the development of sensors is not trivial; material science, molecular recognition and device implementation are some of the aspects that play a role in the design of sensors. The development of fluorescent sensing materials is increasingly captivating the attention of the scientists because its implementation as a truly sensory system is straightforward. This critical review shows the use of polymers, sol-gels, mesoporous materials, surfactant aggregates, quantum dots, and glass or gold surfaces, combined with different chemical approaches for the development of fluorescent sensing materials. Representative examples have been selected and they are commented here.     

Graphdiyne:a Highly Sensitive Material for ppb-Level NO2 Gas Sensing at Room Temperature

Detection of a trace amount of NO2 at room temperature has very important applications in air quality monitoring,protection of human health and medical diagnose.However,the existing NO2 sensors often suffer from low sensitivity when the concentration at the ppb-level.Here,we report a new kind of materials based on graphdiyne(GDY)for highly sensitive detection of ppb-level(ppb:part per billion)NO2 at room temperature.After thermal treatment of the as-prepared GDY at 600℃under argon atmosphere for 2 h(the obtained sample denoted as GDY-600),the prepared sensor with GDY-600 displays excellent sensitivity with a response value of 6.2％towards 250 ppb NO2 at room temperature,which is better than most of reported sensing materials.In addition,the sensor exhibits significantly high selectivity to NO2 against typical interfering gases including CO,CO2,NH3,H2,H2S and toluene.Moreover,the sensor shows remarkable stability after repetitive measurements.The superior sensing performance of GDY-600 can be ascribed to the highly π-conjugated structure with special acetylenic bonds and abundant oxygen-containing functional groups,which are all beneficial for the gas adsorption and redox reaction on the surface.     

Application of an artificial neural network (ANN) and piezoelectric chemical sensor array for identification of volatile organic compounds

A piezoelectric chemical sensor array was developed using four quartz crystals. Gas chromatographic stationary phases were used as sensing materials and the array was connected to an artificial neural network (ANN). The application of the ANN method proved to be particularly advantageous if the measured property (mass, concentration, etc.) should not be connected exactly to the signal of the transducers of the piezoelectric sensor. The optimum structure of neural network was determined by a trial and error method. Different structures were tried with several neurons in the hidden layer and the total error was calculated. The optimum values of primary weight factors, learning rate (η=0.15), momentum term (μ=0.9), and the sigmoid parameter (β=1) were determined. Finally, three hidden neurons and 900 training cycles were applied. After the teaching process the network was used for identification of taught analytes (acetone, benzene, chloroform, pentane). Mixtures of organic compounds were also analysed and the ANN method proved to be a reliable way of differentiating the sensing materials and identifying the volatile compounds.     

Application of an artificial neural network (ANN) and piezoelectric chemical sensor array for identification of volatile organic compounds

A piezoelectric chemical sensor array was developed using four quartz crystals. Gas chromatographic stationary phases were used as sensing materials and the array was connected to an artificial neural network (ANN). The application of the ANN method proved to be particularly advantageous if the measured property (mass, concentration, etc.) should not be connected exactly to the signal of the transducers of the piezoelectric sensor. The optimum structure of neural network was determined by a trial and error method. Different structures were tried with several neurons in the hidden layer and the total error was calculated. The optimum values of primary weight factors, learning rate (η=0.15), momentum term (μ=0.9), and the sigmoid parameter (β=1) were determined. Finally, three hidden neurons and 900 training cycles were applied. After the teaching process the network was used for identification of taught analytes (acetone, benzene, chloroform, pentane). Mixtures of organic compounds were also analysed and the ANN method proved to be a reliable way of differentiating the sensing materials and identifying the volatile compounds.     

Optical sensing based on analyte recognition by enzymes,carriers and molecular interactions

Despite the tremendous variety of methods suitable for sensing applications, we face the fact that chemical sensors displaying sensitivity, selectivity and reversibility are still scarce and are mostly confined to low-molecular-weight species. Obviously, it is not the lack of optical (or other) transduction methods that limit the performance of present day sensor desingns, but rather the insufficient selectivity of the recognition process, particularly in the field of sensors for organic and bioorganic species. The use of enzymes, ion carriers and natural or synthetic receptor/carriers which can under go specific interactions with the species to be recognized (such as through hydrogen bonding or charge-transfer interaction) can result in specific recognition and, consequently, sensing. Examples for optical sensing schemes for clinically or biologically important species including enzyme substrates, metabolites, drugs, alkali and ammonium ions and other will be given. In enzyme-based sensors various options exist: depending on which species is immobilized, assays for substrates (such as glucose, ethanol, lactate or creatine), enzymes (such as esterases) or inhibitors (such as organophosphates) can be designed. In addition, the intrinsic optical properties of certain enzymes, coenzymes or metabolites can be utilized for sensing purposes, a fact that presents an interesting alternative to enzyme sensors with chemical transducers.Notwithstanding the selectivity of biocatalytic sensors, their stability and sensitivity is moderate. Bioorganic synthetic molecules which can recognize and reversibly bind other species offer an attractive alternative, particularly in terms of stability. However, quite a different situation is found in such cases because receptors, in contrast to enzymes, do not “digest” their substrates. Hence, while the steady-state response in enzyme-based sensors is a result of kinetic equilibration, substrate binding in non-metabolizing receptors results in thermodynamic equilibration. However, most existing receptors (except antibodies) lack the unique specificity of enzymes. On the other side, new bioorganic molecules and stable receptor/carriers along with polymer materials of proper permeation selectivity can help to overcome current limitations of protein-based systems. Neutral ion carriers, which may be considered as ion receptors, are a useful example of sometimes highly specific recognition/carrier molecules with excellent stability. Unfortunately, no receptor /carrier molecules of similar specificity do exist yet for most other organic and clinical parameters of interest. There is an obvious need for new and stable molecules suitable for specific recognition of low-molecular weight organic species.We will report on the use of such new receptor/carrier molecules, the respective sensor materials, and how the process of recognition can be coupled to optical transduction. Such receptors/carriers also allow other kinds of discriminations: if, for instance, it is enantio-selective (i.e. preferably binds one species out of a pair of optical isomers), a fairly specific recognition of enantiomers of biogenic amines (such as some drugs and biogenic amines) will become possible. Specific examples will also be given of new types of sensors based on recognition by charge-transfer interaction, through-space interaction and hydrogen bonding, with fair specificity for thiamine, penicilline, nitrate, salicylate and cholic acids. Finally, current problems and the significant challenges for sensors research in the 1990s will be discussed.     

Halogen bonding and chalcogen bonding mediated sensing

Sigma–hole interactions, in particular halogen bonding (XB) and chalcogen bonding (ChB), have become indispensable tools in supramolecular chemistry, with wide-ranging applications in crystal engineering, catalysis and materials chemistry as well as anion recognition, transport and sensing. The latter has very rapidly developed in recent years and is becoming a mature research area in its own right. This can be attributed to the numerous advantages sigma–hole interactions imbue in sensor design, in particular high degrees of selectivity, sensitivity and the capability for sensing in aqueous media. Herein, we provide the first detailed overview of all developments in the field of XB and ChB mediated sensing, in particular the detection of anions but also neutral (gaseous) Lewis bases. This includes a wide range of optical colorimetric and luminescent sensors as well as an array of electrochemical sensors, most notably redox-active host systems. In addition, we discuss a range of other sensor designs, including capacitive sensors and chemiresistors, and provide a detailed overview and outlook for future fundamental developments in the field. Importantly the sensing concepts and methodologies described herein for the XB and ChB mediated sensing of anions, are generically applicable for the development of supramolecular receptors and sensors in general, including those for cations and neutral molecules employing a wide array of non-covalent interactions. As such we believe this review to be a useful guide to both the supramolecular and general chemistry community with interests in the fields of host–guest recognition and small molecule sensing. Moreover, we also highlight the need for a broader integration of supramolecular chemistry, analytical chemistry, synthetic chemistry and materials science in the development of the next generation of potent sensors.

Sigma–hole mediated detection of anions is rapidly emerging as a new paradigm in supramolecular sensor chemistry. Herein, we provide an overview of this field including halogen bonding and chalcogen bonding optical, electrochemical and other sensors.     

Transistor-Based Work-Function Measurement of Metal–Organic Frameworks for Ultra-Low-Power,Rationally Designed Chemical Sensors

A classic challenge in chemical sensing is selectivity. Metal–organic frameworks (MOFs) are an exciting class of materials because they can be tuned for selective chemical adsorption. Adsorption events trigger work-function shifts, which can be detected with a chemical-sensitive field-effect transistor (power ≈microwatts). In this work, several case studies were used towards generalizing the sensing mechanism, ultimately towards our metal-centric hypothesis. HKUST-1 was used as a proof-of-principle humidity sensor. The response is thickness independent, meaning the response is surface localized. ZIF-8 is demonstrated to be an NO₂-sensing material, and the response is dominated by adsorption at metal sites. Finally, MFM-300(In) shows how standard hard–soft acid–base theory can be used to qualitatively predict sensor responses. This paper sets the groundwork for using the tunability of metal–organic frameworks for chemical sensing with distributed, scalable devices.     

Dosimetric gelator probes and their application as sensors

Supramolecular gels formed by the self-assembly of organic molecules are useful in many areas from materials to medicine. Of the different applications, exploitation of gels for the visual detection of analytes is a fairly recent trend in gel chemistry. Most of the gel-based sensors rely on non-covalent interactions between the gelator molecules and the added chemical analytes and therefore, often suffer from less selectivity and long response time. In this context, dosimetric gelator probes are superior to other gel-based sensors with high selectivity and fast response time. Unlike non-covalent binding sites, dosimetric gelators typically contain a reaction centre and undergo a specific chemical reaction selective to an analyte resulting in either formation or rupturing of covalent bonds. In this review, we provide an up-to-date report of various reaction-based gel systems applied for the sensing of analytes. We elaborately discuss the concept, design principles, self-assembly properties, and reaction mechanisms of such gelators. We also highlight the limitations, challenges, and the necessity of further exploration of dosimetric gels in this domain.