SERS-Active MIL-100(Fe) Sensory Array for Ultrasensitive and Multiplex Detection of VOCs

The application of metal–organic frameworks (MOFs) as SERS-active platforms in multiplex volatile organic compounds (VOCs) detection is still unexplored. Herein, we demonstrate that MIL-100 (Fe) serves as an ideal SERS substrate for the detection of VOCs. The limit of detection (LOD) of MIL-100(Fe) for toluene sensing can reach 2.5 ppm, and can be even further decreased to 0.48 ppb level when “hot spots” in between Au nanoparticles are employed onto MIL-100 (Fe) substrate, resulting in an enhancement factor of 10¹⁰. Additionally, we show that MIL-100(Fe) substrate has a unique “sensor array” property allowing multiplex VOCs detection, with great modifiability and expandability by doping with foreign metal elements. Finally, the MIL-100(Fe) platform is utilized to simultaneously detect the different gaseous indicators of lung cancer with a ppm detection limit, demonstrating its high potential for early diagnosis of lung cancer in vivo.     

Polymer‐based fluoride‐selective chemosensor: Synthesis,sensing property,and its use for the design of molecular‐scale logic devices

A new styryl‐type monomer, 2‐(4‐vinylbenzyloxy)‐1 ‐naphthaldehyde thiosemicarbazone (VNT), was synthesized and then copolymerized with methyl methacrylate (MMA) by reversible addition fragmentation chain transfer polymerization affording a series of poly(MMA‐co‐VNT)s with different functional unit content, predetermined molecular weight, and narrow molecular‐weight distribution. The desired copolymers were structurally confirmed by various spectroscopic characterizations. Colorimetric and fluorescent titration spectra revealed that the copolymers are highly selective toward fluoride anions over other competitive species including Cl^?, Br^?, I^?, H₂PO₄^?, AcO^?, and HSO₄^?. On addition of F^?, a remarkable colorless‐to‐yellow color change is easily observed by naked eyes. The influence of the copolymer composition and molecular weight on its sensing capacity was then carefully investigated. The results showed that higher VNT‐incorporation amount within the copolymer chains leads to higher sensitivity toward F^? ions. Interestingly, the chromogenic process of the polymeric sensor can be switched back and forth by successively adding F^? and HSO₄^? anions into the dimethyl sulfoxide solution of the polymer, which may be represented by a complementary “IMPLICATION/INHIBIT” logic gate at molecular level using both the ions as the chemical inputs. Based on such a reversible and reproducible sensing system, we designed a molecular‐scale sequential information processing circuit displaying “writing–reading–erasing–reading” behavior and “multiwrite” function in the form of binary logic. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

A new “naked-eye” colorimetric and ratiometric fluorescent sensor for imaging Hg2+ in living cells

A new oligothiophene-based sensor 3 TH for monitoring Hg²⁺ has been designed and synthesized based on the intramolecular charge transfer (ICT) mechanism. The 3 TH shows the significant specificity toward Hg²⁺ through “naked-eye” colorimetric detection as well as via ratiometric fluorescence enhancement response with low detection limit of 62 nM. In addition, sensor 3 TH shows high selectivity and sensitivity for Hg²⁺ with fast response in a suitable pH range. Moreover, the 3 TH-based test strips was used to conveniently detect Hg²⁺ ions in water. Furthermore, considering its good ‘‘turn-on’’ fluorescent sensing behavior and low cell cytotoxicity, 3 TH was successfully applied to detect and image Hg²⁺ in real water samples and living cells, which shows great potentials for application in environmental and biological systems.     

Photochemical behaviour upon the inclusion for some volatile organic compounds in new fluorescent indolizine β-cyclodextrin sensors

The potentialities of three new fluorescent indolizine modified β-cyclodextrin have been investigated as molecular chemosensors. The pyridin-4-ylindolizine β-cyclodextrin derivatives were synthesised by an amidation between the fluorescent indolizine derivatives and 6-deoxy-6-amino-β-cyclodextrin. The multiconformational search by MM3 and AM1 method in gaseous state and in water respectively suggest the “open cavity” structure as the most probable. These compounds have been characterised spectroscopically by their emission spectra and their sensing ability towards 1-adamantanol, phenol and p-cresol. The fluorescent properties and sensitivity factor of the sensor containing an indolizine product with a perfluored aromatic fragment recommended it fairly as sensor for the detection of volatile organic compounds (VOCs), while the other two sensors, with an aliphatic fragment, can be utilised as biological markers. Finally, a significant bathochromic shift is observed for the sensor containing a t-butyl fragment, in such a way that this sensor may also lead to the detection of VOCs.     

Electrochemical Sensing of Chlorpyrifos,a Carcinogen Responsible for Breast Cancer,in Milk and Plasma of Lactating Mothers

In view of the increase in breast cancer cases at the global level, electrochemical sensing of the carcinogenic pesticide, chlorpyrifos (CPF) in breast milk is proposed. The determination is based on the nucleophilic substitution reaction of pralidoxime (PAM) with CPF. The proposed method offers a linear concentration range of 0.002 to 0.08 μmol/L. The limit of detection and limit of quantification was found to be 0.05×10⁻⁹ and 0.167×10⁻⁹M, respectively. The offered “unmodified edge plane pyrolytic graphite sensor” proved to be a better substrate than the earlier reported modified sensors. The limit of detection for the proposed method was found to be nearly fifty times lower than reported at modified electrodes. The interference study proved the adequate selectivity of the offered sensor. The sensor has good stability and reproducibility along with high sensitivity. The offered sensor is very useful for cancer hospitals, pesticide industries, and the study of environmental toxicity-related issues.     

Sensing A Paradigm Shift in the Field of Molecular Recognition: From Selective to Differential Receptors

Molecular recognition has evolved from a science designed to understand biological systems into a much more diverse area of research. While work continues to elucidate “nature's tricks” with respect to intermolecular interactions, much attention has turned to the perspective that molecular recognition, by design, can lead to new technologies. Applications ranging from molecular sensing to information storage and even working molecular machines have been envisioned. This review will highlight a few historical hallmarks of molecular recognition oriented at studying the basic science of intermolecular interactions, but then detail recent advances in molecular recognition aimed towards applications in the field of molecular sensing. Rational design can be used to create synthetic receptors with a good deal of predictability and selectivity, and many signal transduction mechanisms exist for converting these receptors into sensors. This is the first topic discussed. The concept of “differential” or “generalized” sensing is then presented, where one uses an array of sensors that do not necessarily conform to the “lock and key” principle. This approach to sensing is inspired by the mammalian senses of taste and smell, which we briefly describe. To mimic senses of taste and smell, one is naturally led to the use of combinatorial libraries, a direction of research that has seen continued growth over the past few years. We summarize the current state of the art in synthetic combinatorial receptors/sensors, and then predict a future direction that the field of molecular recognition will possibly take. The review is not meant for the specialist, but instead for a general audience. It does not present a highly detailed analysis of each individual topic: synthetic receptors, sensors, olfaction/gustation, and combinatorial receptors/sensors. Instead, this review shows how all these fields complement each other and fit together to create sensing devices. Our conclusion is that specific analyte sensing, differential sensing, and combinatorial chemistry can and will be combined to create sensor arrays, and give the subfield of molecular recognition that uses synthetic systems a bright future in this type of sensing scenario.     

Fluorescent Gold Clusters as Logic Gates for the Detection of Different Metal Ions

Metal cations can be selectively detected by restoring and quenching the fluorescent intensity of an “ON–OFF” gold nanocluster (Au NC ) sensor. The fluorescent intensity of Au NCs with metal cations can be restored by chelating with ethylenediaminetetraacetic acid except for Hg²⁺ ions. A highly selective detection of Hg²⁺ ion is also achieved under the coexistence of Fe³⁺ or Cr³⁺ ions. This assay was applied successfully for detecting Hg²⁺ in a water sample. The dynamic range of the system was 1 ppm to 25 ppb, and the limit of detection was 25 ppb.     

A Complete Electroenzymatic Choline Microprobe Based on Nanostructured Platinum Microelectrodes and an IrOx On‐probe Reference Electrode

A microelectrode array microprobe with a choline sensing site and an on‐probe reference electrode was constructed by depositing permselective polymer films and choline oxidase (ChOx) on one microelectrode, and iridium oxide (IrOx) on another, both of which were coated previously with a nanostructured Pt deposit. Scanning electron microscopy (SEM) of the nanostructured Pt layer revealed a unique pillar‐like, “nanograss” structure. Polyphenylenediamine (PPD) and Nafion were coated sequentially on the working (i. e. sensing) electrode surface to serve as the permselective polymer films. The microsensor exhibited high sensitivity to choline (123±13 μA mM^?1 cm^?2), low detection limit (3.2±0.8 μM), and fast response time (3–5 s). The choline sensor also was tested at physiological concentrations of electroactive interfering species common to brain extracellular fluid (i. e. ascorbic acid, dopamine, DOPA, and DOPAC) and showed excellent selectivity. Selectivity likely was aided by the relatively low potential of 0.35 V vs. IrOx that was made possible by the enhanced H₂O₂ electrooxidation activity of the underlying nanostructured Pt‐coated working electrode. Thus, Pt “nanograss” appears to be an excellent electrode surface modification for creation of high performance electroenzymatic biosensors.     

Fiber-optic fluorescence sensor for dissolved oxygen detection based on fluorinated xerogel immobilized with ruthenium (II) complex

A fiber-optic sensor based on fluorescence quenching was designed for dissolved oxygen (DO) detection. The fluorinated xerogel-based sensing film of the present sensor was prepared from 3, 3, 3-trifluoropropyltrimethoxysilane (TFP–TriMOS). Oxygen-sensitive fluorophores of tris (2, 2′- bipyridine) ruthenium (II) (Ru(bpy)₃²⁺) were immobilized in the sensing film and the emission fluorescence was quenched by dissolved oxygen. In the sensor fabrication, a two-fiber probe was employed to obtain the best fluorescence collection efficiency and the sensing film was attached to the probe end. Scanning electron microscope (SEM), UV–Vis absorption spectroscopy (UV–Vis) and fourier transform infrared spectroscopy (FTIR) measurements have been used to characterize the sensing film. The sensor sensitivity is quantified by I _deoxy/I _oxy, where I _deoxy and I _oxy represented the detected fluorescence intensities in fully deoxygenated and fully oxygenated environments, respectively. Compared with tetramethoxysilane (TMOS) and methyltriethoxysilane (MTMS)-derived sensing films, TFP–TriMOS-based sensor exhibited excellent performances in dissolved oxygen detection with short response time of 4 s, low limit of detection (LOD) of 0.04 ppm (R.S.D. = 2.5%), linear Stern–Volmer calibration plot from 0 to 40 ppm and long-term stability during the past 10 months. The reasons for the preferable performances of TFP–TriMOS-based sensing film were discussed.     

Zirconia-based amperometric sensor using ZnO sensing-electrode for selective detection of propene

The sensing characteristics to propene (C₃H₆) were examined at 600 °C under wet condition for the amperometric sensor using a yttria-stabilized zirconia (YSZ) tube and ZnO (+8.5 wt%Pt) sensing-electrode (SE). In order to improve the sensitivity to C₃H₆, the “pulsed-potential method” was adopted here. It was found that the current response varied almost linearly with C₃H₆ concentration in the range of 0–200 ppm when SE was polarized at +1.0 V (vs. Pt/air reference electrode) for a period of 0.3 s. By using the present “pulsed-potential method”, the sensitivity to 100 ppm C₃H₆ was increased about 1000 times, compared with the normal “constant-potential method”. The excellent selectivity to C₃H₆ was also obtained for the present sensor without influence of other hydrocarbons, NO_x, CO, H₂, etc.     

A highly selective diarylethene chemosensor for dual channel recognition of CN− and Zn2+ and its application

A novel diarylethene chemosensor comprising 3-aminobenzofuran-2-carboxamide Schiff base (1O) was synthesized and the photophysical and sensing behaviors of 1O were further investigated. Importantly, the introduction of electron-withdrawing group to 1O made the sensor an efficient tool for detection of toxic cyanide even in the presence of other plausible interfering anions including fluoride and acetate. In particular, addition of CN^? to 1O visibly changes the color from colorless to orange-red, which can be observed by the naked eye. Apart from this, it also exhibited an outstanding fluorometric sensing toward Zn²⁺ with high selectivity and sensitivity. Moreover, the remarkable spectral responses of the devised sensor prompted us to fabricate molecular logic circuit. Furthermore, the sensor was successfully applied to the detection of CN^? on test strips and silica coated microslides, and the methods were very simple to operate without resorting to any spectroscopic instrumentation. In addition, the 1O can also effectively detect CN^? and Zn²⁺ in actual water samples.     

Selective sensing of CrVI and FeIII ions in aqueous solution by an exceptionally stable TbIII-organic framework with an AIE-active ligand

We herein report a new lanthanide metal-organic framework (MOF) that exhibits excellent chemical stability, especially in the aqueous solution over a wide pH range from 1 to 14. In contrast to many reported lanthanide MOFs, this Tb-based MOF emits cyan fluorescence inherited from the integrated AIE-active ligand, rather than Ln³⁺ ions. More remarkably, its fluorescence signal features a highly selective and sensitive “turn-off” response toward CrO₄²⁻, Cr₂O₇²⁻ and Fe³⁺ ions, highlighted with the low detection limits down to 68.18, 69.85 and 138.8 ppm, respectively. Thus, the exceptional structural stability and sensing performance render this material able to be a superior luminescent sensor for heavy metal ions in wastewater.     

Molecular weight distributions in radiation-induced polymerization. VII. γ-ray-induced polymerization of “wet” styrene in the solid state

In the present paper kinetic and molecular weight distribution results are reported for the γ-ray-initiated polymerization of styrene in the solid state. “In-source” polymerization over the temperature range ?35°C to ?55°C and post-polymerization at ?35°C have been investigated for “wet” styrene samples (water concentration ≈ 10^?3 mole/l.). An interesting feature of the solid-state polymerization of styrene is the bimodal nature of the molecular weight distribution. On a qualitative basis the results resemble those obtained previously for the polymerization of rigorously dried (“dry”) styrene. However, there are noticeable differences on a quantitative basis resulting from the considerable difference in the water content between wet and dry samples. On the basis of these studies, the kinetic and molecular weight distribution data have been interpreted as being indicative of polymerization occurring simultaneously via free-radical and cationic mechanisms.     

Electro-active silver oxide nanocubes for label free direct sensing of bisphenol A to assure water quality

This research, for the first time, demonstrates a direct electrochemical detection of bisphenol A (BPA) using silver oxide (Ag₂O) nanocubes (NCs) modified platinum electrode. The Ag₂O NCs, size ranging from 60 to 100 nm utilized in this research as a smart electro-active sensing platform were pure and synthesized using a cost-effective, affordable, and facile chemical route. The Ag₂O NCs modified electrochemical sensor exhibited a low limit of detection (LOD) as 20 nmol dm^?3, high sensitivity as 95 μA (μmol dm^?3)^?1 cm^?2, and linear dynamic range (LDR) varies from 80 nmol dm^?3- 4.8 μmol dm^?3. This sensor also showed good selectivity, reproducibility, and reusability for BPA detection. The practical application of developed sensor was also tested using real water samples. The outcomes of this research suggested that Ag₂O NCs based sensor can be useful for effective and efficient electrochemical BPA sensing in both real and lab samples.     

Molecularly Imprinted Photonic Polymers as Sensing Elements for the Creation of Cross‐Reactive Sensor Arrays

By combining molecular imprinting and colloidal crystal templating, molecularly imprinted inverse‐opal photonic polymers (MIPPs) acting as sensing elements have been exploited to create sensor arrays for the first time. With this new strategy, abundant sensing elements with differential sensing abilities were easily accessible. Because of the unique hierarchical porous structure integrated in each sensing element, high sensitivity and selectivity, fast response and self‐reporting (label‐free) detection could be simultaneously achieved. All these fascinating features indicate that MIPPs are ideal sensing elements for creating sensor arrays. By integrating the individual sensing elements on a substrate, the formed array chip delivers better portability and high‐throughput capability. As a demonstration, six kinds of contaminants were selected as analytes. The detection and discrimination of these analytes and even their mixtures in a wide range of concentrations, particularly trace amounts of analyte against a high background of other components, could be achieved, indicating the powerful capability of MIPPs‐based sensor array for sensing. These results suggest that the described strategy opens a new route for sensor array creation and should find important applications in a wide range of areas.     

A new phenothiazine-based fluorescence sensor for imaging Hg2+ in living cells

A new phenothiazine-based sensor PHE-Ad for monitoring Hg²⁺ has been designed and synthesized based on the intramolecular charge transfer (ICT) mechanism. The probes were characterized by FTIR, ¹H NMR, and HRMS, and their optical properties were detected by UV and FL. It's showed the probes detection of Hg²⁺ compared to other metal ions (Mg²⁺, Cu²⁺, Hg²⁺, Ag⁺, Co²⁺, Cr³⁺, Al³⁺, Ni²⁺, Zn²⁺, Ca²⁺, Fe³⁺, Fe²⁺, K⁺, Na⁺, and Cd²⁺) based on the test results. Besides, the detection limits were determined to be 2.12 × 10⁻⁸ M through the standard curve plot. In addition, sensor PHE-Ad shows high selectivity and sensitivity for Hg²⁺ with a fast response in a suitable pH range. Furthermore, taking into account its good “turn-on” fluorescent sensing behavior and low cell cytotoxicity, PHE-Ad was successfully applied to detect and image Hg²⁺ in real water samples and living cells, which shows great potentials for application in environmental and biological systems.     

A Biphasic Mercury‐Ion Sensor: Exploiting Microfluidics to Make Simple Anilines Competitive Ligands

Combining the molecular wire effect with a biphasic sensing approach (analyte in water, sensor‐dye in 2‐methyltetrahydrofuran) and a microfluidic flow setup leads to the construction of a mercury‐sensitive module. We so instantaneously detect Hg²⁺ ions in water at a 500 μM concentration. The sensor, conjugated non‐water soluble polymer 1 (XFPF), merely supports dibutylaniline substituents as binding units. Yet, selective and sensitive detection of Hg²⁺‐ions is achieved in water. The enhancement in sensory response, when comparing the reference compound 2 to that of 1 in a biphasic system in a microfluidic chip is >10³. By manipulation of the structure of 1 , further powerful sensor systems should be easily achieved.     

基于低温等离子体辅助催化发光的乙烯传感器

将等离子体的高活化性能与催化发光的传感特性相结合,以成本低、合成简单的碱土金属纳米MgO为传感材料,构建了基于低温等离子体辅助的催化发光传感器,用于乙烯的快速检测.由于等离子体具有高活化性能,本方法的检测温度远低于传统的催化发光检测法的常用温度(300~500℃),无需加热装置,在室温下实现了对乙烯快速、灵敏的检测.室温(25℃)下,对乙烯的检出限为37 ng/mL (30 ppm),线性范围为112~4997 ng/mL (90~3998 ppm, R=0.97669),传感器具有良好的选择性和重现性.此传感器制备简单、稳定性高、低能耗、成本低,与传统的气体检测方法相比具有良好的实用性和普适性,为开发性能优异的新型催化发光传感器提供了策略.     

A new nano-composite electrode as a copper (II) selective potentiometric sensor

A macrocyclic ligand “7,10,13-triaza-1-thia-4,16-dioxa-20,24-dimethyl-2,3;17,18-dibenzo-cyclooctadecane-6,14-dione” as an efficient ionophore was used into a new Cu²⁺ nano-composite potentiometric carbon paste sensor containing multi-walled carbon nanotubes (MWCNTs), nanosilica particles, and room temperature ionic liquid (1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMP]Tf₂N). This potentiometric sensor responds to copper ions in a wide linear dynamic range of 4.50 × 10^?8 to 1.00 × 10^?2 mol L^?1 with Nernstian slope of 29.64 ± 0.10 mV per decade. The detection limit of 2.34 × 10^?8 mol L^?1 was obtained at the pH range 3.5–6.0. It has a fast response with response time of about 10 s, and can be used for at least 16 weeks without any considerable divergence in the potentials. The suggested sensor thus allows sensitive, selective, simple, low cost, and stable electrochemical sensing of Cu²⁺ ions in the presence of a large number of alkali, alkaline earth, transition and heavy metal ions. This sensor was successfully applied in the determination of copper ions in water and waste water samples.     

Selective CO Detection Using YSZ-based Sensor with a Combination of CuCrFeO4 and CoCrFeO4 Electrodes

A solid-state potentiometric sensor using yttria-stabilized zirconia (YSZ) as a solid electrolyte and oxide electrodes has been developed for selective CO detection. At 450^oC, the YSZ-based sensor using CuCrFeO₄ sensing-electrode (SE) was found to have similar gas sensing characteristic with the sensor using CoCrFeO₄-SE, except toward CO. When both SEs was paired on a YSZ tube, the responses to various gases except for CO could be cancelled out for the resulting combined-SEs sensor. Thus, this sensor could generate a sensitive and selective response to CO at 450^oC even under humid conditions.