Ultrasensitive detection of aliphatic nitro-organics based on “turn-on” fluorescent sensor array

The broad class of explosives includes nitro aromatics as well as challenging aliphatic nitro-organics whose detection is important from counter-terrorism and national security perspectives. Here we report a turn-on fluorescent sensor array based on aggregation-induced emission (AIE) fluorophores as receptors. To achieve a good sensing system with fast response, good sensitivity and low detection limit, three receptors with abundant chemical diversities for target analytes were synthesized. The turn-on response of the individual receptor showed highly variable and cross-reactive analyte-dependent changes in fluorescence. The excellent ability to identify a variety of explosives, especially the challenging aliphatic nitro-organics (2,3-dimethyl-2,3-dinitrobutane (DMNB), 1,3,5-trinitro-1,3,5-triazinane (RDX), cyclotetramethylene tetranitramine (HMX) and entaerythritol tetranitrate (PETN)), was demonstrated in qualitative and quantitative analyses with 100% accuracy. The fluorescence signal amplification in the presence of explosives allows for application of these receptors in a sensor microarray suitable for high-throughput screening. These results suggested that the cross-reactive sensor array based on AIE fluorophores could find a wide range of applications for sensing various analytes or complex mixtures.     

Cross‐Reactive Sensor Arrays for the Detection of Peptides in Aqueous Solution by Fluorescence Spectroscopy

A simple but powerful method for the sensing of peptides in aqueous solution has been developed. The transition‐metal complexes [PdCl₂(en)], [{RhCl₂Cp*}₂], and [{RuCl₂(p‐cymene)}₂] were combined with six different fluorescent dyes to build a cross‐reactive sensor array. The fluorescence response of the individual sensor units was based on competitive complexation reactions between the peptide analytes and the fluorescent dyes. The collective response of the sensor array in a time‐resolved fashion was used as an input for multivariate analyses. A sensor array comprised of only six metal–dye combinations was able to differentiate ten different dipeptides in buffered aqueous solution at a concentration of 50 μM . Furthermore, the cross‐reactive sensor could be used to obtain information about the identity and the quantity of the pharmacologically interesting dipeptides carnosine and homocarnosine in a complex biological matrix, such as deproteinized human blood serum. The sensor array was also able to sense longer peptides, which was demonstrated by differentiating mixtures of the nonapeptide bradykinin and the decapeptide kallidin.     

Comparison Between Two Different Synthetic Routes of Pyrrolidinium Functional Polymeric Ionic Liquids

Summary: Two separate synthetic routes of preparation of new pyrrolidinium-based polymeric ionic liquids were compared. The first method utilized the modification of a commercial poly(diallyldimethylammonium) chloride via a direct anion exchange with several anions. The second route involved the anion exchange leading to several diallyldimethylammonium ionic liquid monomers having different anions and a subsequent polymerization. The latter method is particularly interesting for attaining tunable copolymers according to the desired properties of PILs. Both methods successfully resulted in ionic liquid polymers that are finding their way in a wide range of emerging applications.     

A Novel Thin‐Film Copper Array Based on an Organic/Inorganic Sensor Hybrid: Microfabrication,Potentiometric Characterization,and Flow‐Injection Analysis Application

A first step towards the microfabrication of a thin‐film array based on an organic/inorganic sensor hybrid has been realized. The inorganic microsensor part incorporates a sensor membrane based on a chalcogenide glass material (Cu‐Ag‐As‐Se) prepared by pulsed laser deposition technique (PLD) combined with an PVC organic membrane‐based organic microsensor part that includes an o‐xylyene bis(N,N‐diisobutyl‐dithiocarbamate) ionophore. Both types of materials have been electrochemically evaluated as sensing materials for copper(II) ions. The integrated hybrid sensor array based on these sensing materials provides a linear Nernstian response covering the range 1×10^?6–1×10^?1 mol L^?1 of copper(II) ion concentration with a fast, reliable and reproducible response. The merit offered by the new type of thin‐film hybrid array includes the high selectivity feature of the organic membrane‐based thin‐film microsensor part in addition to the high stability of the inorganic thin‐film microsensor part. Moreover, the thin‐film sensor hybrid has been successfully applied in flow‐injection analysis (FIA) for the determination of copper(II) ions using a miniaturized home‐made flow‐through cell. Realization of the organic/inorganic thin‐film sensor hybrid array facilitates the development of a promising sophisticated electronic tongue for recognition and classification of various liquid media.     

Synthesis of gold nanoparticles modified with ionic liquid based on the imidazolium cation

The synthesis and processing of nanoparticles consisting of metallic nanocrystal cores and organic monolayer shells promise interesting technological applications. Here, we report the synthesis of gold nanoparticles modified with ionic liquids based on the imidazolium cation. Aggregation-induced color changes of the gold nanoparticles in an aqueous solution were used as an optical sensor for anions via anion exchange of ionic liquid moiety. We also demonstrated the phase transfer of the gold nanoparticles from aqueous media to ionic liquid.     

Novel Boronlectins Based on Bispyridium Salt with a Flexible Linker: Discriminative Sensing of Lactose and Other Monosaccharides and Disaccharides in Aqueous Solution

N,N‐Di‐2‐picolylamine (DPA)‐derived diboronic acid receptors (NHBAs) with a flexible linker were designed and synthesized in this study, and two‐component sensing ensembles based on cationic NHBAs and an anionic fluorescent indicator 8‐hydroxypyrene‐1,3,6‐trisulfonic acid trisodium salt (HPTS) were successfully developed for both monosaccharides and disaccharides sensing. The dibranched ortho‐substituted receptor NHoBA exhibited unexpected selectivity towards lactose among five disaccharides used. The discrimination of five disaccharides and six monosaccharides was finally achieved by the integrated sensor array through linear discriminant analysis (LDA).     

Superflexible Multifunctional Polyvinylpolydimethylsiloxane‐Based Aerogels as Efficient Absorbents,Thermal Superinsulators,and Strain Sensors

Aerogels are porous materials but show poor mechanical properties and limited functionality, which significantly restrict their practical applications. Preparation of highly bendable and processable aerogels with multifunctionality remains a challenge. Herein we report unprecedented superflexible aerogels based on polyvinylpolydimethylsiloxane (PVPDMS) networks, PVPDMS/polyvinylpolymethylsiloxane (PVPMS) copolymer networks, and PVPDMS/PVPMS/graphene nanocomposites by a facile radical polymerization/hydrolytic polycondensation strategy and ambient pressure drying or freeze drying. The aerogels have a doubly cross‐linked organic–inorganic network structure consisting of flexible polydimethylsiloxanes and hydrocarbon chains with tunable cross‐linking density, tunable pore size and bulk density. They have a high hydrophobicity and superflexibility and combine selective absorption, efficient separation of oil and water, thermal superinsulation, and strain sensing.     

Metal‐Organic Frameworks (MOFs) as Functional Supramolecular Architectures for Anion Recognition and Sensing

Metal‐organic frameworks (MOFs) have experienced a tremendous growth during last few decades as porous crystalline molecular materials. The comprehensive effect of structural diversity, tunability and high surface area makes MOFs suitable for multifarious applications. MOFs can act as potential receptors toward different target components along with ionic species, small molecules, solvents, explosives etc. Anion recognition remains an important phenomena due to its involvement in many chemical and biological processes. Ligand designing, incorporation of appropriate functional groups and post‐synthetic modifications are key strategies in MOFs for selective recognition and scavenging of environmentally toxic and detrimental anions (i. e. cyanide, oxo‐anions etc.). The main focus of this personal account is on our research towards development and potential applications of MOFs with special emphasis on selective and sensitive anion sensing.     

Ionic Liquid Assisted Synthesis of Au–Pd Bimetallic Particles with Enhanced Electrocatalytic Activity

Morphology‐ and composition‐controlled synthesis of Au–Pd bimetallic particles was realized by a facile ionic liquid assisted route at room temperature. The morphologies of the synthesized particles, such as nanoflake‐constructed spheres with a core–shell structure, nanoparticle‐constructed spheres, and nanoparticle‐constructed dendrites, could be well controlled by the present route. The ionic liquid was found to play a key role in the formation of these interesting particles. Moreover, the composition (Au:Pd) of the particles could be modulated by means of the molar ratio of the metal precursors in the feeding solutions. The Au–Pd bimetallic particles exhibit high electrocatalytic activity toward oxidation of ethanol and formic acid. Furthermore, cyclic voltammetric studies on the as‐prepared Au–Pd bimetallic particles revealed good electroactivity for H₂O₂, which results in an effective amperometric H₂O₂ sensor.     

Superflexible Multifunctional Polyvinylpolydimethylsiloxane‐Based Aerogels as Efficient Absorbents,Thermal Superinsulators,and Strain Sensors

Aerogels are porous materials but show poor mechanical properties and limited functionality, which significantly restrict their practical applications. Preparation of highly bendable and processable aerogels with multifunctionality remains a challenge. Herein we report unprecedented superflexible aerogels based on polyvinylpolydimethylsiloxane (PVPDMS) networks, PVPDMS/polyvinylpolymethylsiloxane (PVPMS) copolymer networks, and PVPDMS/PVPMS/graphene nanocomposites by a facile radical polymerization/hydrolytic polycondensation strategy and ambient pressure drying or freeze drying. The aerogels have a doubly cross‐linked organic–inorganic network structure consisting of flexible polydimethylsiloxanes and hydrocarbon chains with tunable cross‐linking density, tunable pore size and bulk density. They have a high hydrophobicity and superflexibility and combine selective absorption, efficient separation of oil and water, thermal superinsulation, and strain sensing.     

Electrochemical polymerization of imidazolum‐ionic liquids bearing a pyrrole moiety

A series of imidazolium‐based ionic liquid monomers bearing a terminal pyrrole moiety were synthesized and electrochemically polymerized. It is found that the polymerizability of the synthesized ionic liquids is strongly dependent on the type of the counteranions. Although bromide monomer is not polymerizable, well‐defined polymeric films can be formed on various substrates in the cases of flour‐containing anions (BF₄^?, PF₆^?). The performed characterizations show that all resulting polypyrrole films are electroactive, and the imidazolium‐based ionic liquid moieties are correctly incorporated in polymer films during the electropolymerization process. This work not only provides a facile new method to immobilize ionic liquids on solid surface. Interestingly, without use of any template unique “knit” morphology and nanostructure, even hierarchical structures could also be produced by the electropolymerization of these new functionalized pyrrole monomers. We found that the properties of the pendant ionic liquid units on the surface of the formed polymer films preserved, and by simple anion exchange their surface energy and tension could be easily tuned without loss of the electrical, optical properties, and morphology of the polypyrrole films. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4151–4161, 2008     

Dicationic imidazolium ionic liquid modified silica as a novel reversed‐phase/anion‐exchange mixed‐mode stationary phase for high‐performance liquid chromatography

A dicationic imidazolium ionic liquid modified silica stationary phase was prepared and evaluated by reversed‐phase/anion‐exchange mixed‐mode chromatography. Model compounds (polycyclic aromatic hydrocarbons and anilines) were separated well on the column by reversed‐phase chromatography; inorganic anions (bromate, bromide, nitrate, iodide, and thiocyanate), and organic anions (p‐aminobenzoic acid, p‐anilinesulfonic acid, sodium benzoate, pathalic acid, and salicylic acid) were also separated individually by anion‐exchange chromatography. Based on the multiple sites of the stationary phase, the column could separate 14 solutes containing the above series of analytes in one run. The dicationic imidazolium ionic liquid modified silica can interact with hydrophobic analytes by the hydrophobic C₆ chain; it can enhance selectivity to aromatic compounds by imidazolium groups; and it also provided anion‐exchange and electrostatic interactions with ionic solutes. Compared with a monocationic ionic liquid functionalized stationary phase, the new stationary phase represented enhanced selectivity owing to more interaction sites.     

Nano‐Graphene Oxide Based Multichannel Sensor Arrays towards Sensing of Protein Mixtures

Optical array‐based sensors are attractive candidates for the detection of various bio‐analytes due to their convenient fabrication and measurements. For array‐based sensors, multichannel arrays are more advantageous and used frequently in many electronic sensors. But most reported optically array based sensors are constructed on a single channel array. This difficulty is mainly instigated from the overlap in optical responses. In this report we have used nano‐graphene oxide (nGO) and suitable fluorophores as sensor elements to construct a multichannel sensor array for the detection of protein analytes. By using the optimized multichannel array we are able to detect different proteins and mixtures of proteins with 100 % classification accuracy at sub‐nanomolar concentration. This modified method expedites the sensing analysis as well as minimizes the use of both analyte and sensor elements in array‐based protein sensing. We have also used this system for the single channel array‐based sensing to compare the sensitivity and the efficacy of these two systems for other applications. This work demonstrated an intrinsic trade‐off associated with these two methods which may be necessary to balance for array‐based analyte detections.     

3,6‐Dinitropyrazolo[4,3‐c]pyrazole‐Based Multipurpose Energetic Materials through Versatile N‐Functionalization Strategies

A family of 3,6‐dinitropyrazolo[4,3‐c]pyrazole‐based energetic compounds was synthesized by using versatile N‐functionalization strategies. Subsequently, nine ionic derivatives of the N,N′‐(3,6‐dinitropyrazolo[4,3‐c]pyrazole‐1,4‐diyl)dinitramidate anion were prepared by acid‐base reactions and fully characterized by infrared, multinuclear NMR spectra, and elemental analysis. The structures of four of these compounds were further confirmed by single‐crystal X‐ray diffraction. Based on their different physical and detonation properties, these compounds exhibit promising potential as modern energetic materials and can be variously classified as green primary explosives, high‐performance secondary explosives, fuel‐rich propellants, and propellant oxidizers.     

含氰基基团的以C为中心的不对称阴离子离子液体的合成、表征及应用

首次通过不对称阴离子的钠盐/钾盐和不同的季胺化的咪唑,吡咯溴盐/氯盐进行离子交换,合成了一系列含氰基官能团的不对称阴离子功能化离子液体。通过红外、核磁共振、质谱和元素分析对离子液体的结构进行表征;通过TGA对离子液体的热稳定性进行测定,结果发现不对称功能化离子液体具有良好的热稳定性,其分解温度在219-319℃范围内。将功能化离子液体[Bmim][C(CN)2COCH3]作为弱配体应用于模型的Suzuki偶联反应,发现在反应中加入功能化离子液体[Bmim][C(CN)2COCH3]可以使反应收率提高10-15%。     

Generalized route to metal nanoparticles with liquid behavior

We report the generalized synthesis of metal nanoparticles with liquid-like behavior. We introduce a thiol-containing ionic liquid, N,N-dioctyl-N-(3-mercaptopropyl)-N-methylammonium bromide, which serves as a ligand for platinum, gold, palladium, and rhodium nanoparticles. A rapid reduction using THF-soluble metal salts in the presence of the thiol generates nanoparticles with tunable sizes and size distributions. The as-synthesized nanoparticles are a solid and decompose before melting. Upon exchange of the halide anion for an amphiphilic sulfonate anion, however, the nanoparticles exhibit liquid-like properties at room temperature. The liquids have high metal loadings; for example, the 2.7 nm platinum nanoparticle liquid is 36% platinum by mass.     

Design of guanidinium ionic liquid based microwave‐assisted extraction for the efficient extraction of Praeruptorin A from Radix peucedani

A series of novel tetramethylguanidinium ionic liquids and hexaalkylguanidinium ionic liquids have been synthesized based on 1,1,3,3‐tetramethylguanidine. The structures of the ionic liquids were confirmed by ¹H NMR spectroscopy and mass spectrometry. A green guanidinium ionic liquid based microwave‐assisted extraction method has been developed with these guanidinium ionic liquids for the effective extraction of Praeruptorin A from Radix peucedani. After extraction, reversed‐phase high‐performance liquid chromatography with UV detection was employed for the analysis of Praeruptorin A. Several significant operating parameters were systematically optimized by single‐factor and L₉ (3⁴) orthogonal array experiments. The amount of Praeruptorin A extracted by [1,1,3,3‐tetramethylguanidine]CH₂CH(OH)COOH is the highest, reaching 11.05 ± 0.13 mg/g. Guanidinium ionic liquid based microwave‐assisted extraction presents unique advantages in Praeruptorin A extraction compared with guanidinium ionic liquid based maceration extraction, guanidinium ionic liquid based heat reflux extraction and guanidinium ionic liquid based ultrasound‐assisted extraction. The precision, stability, and repeatability of the process were investigated. The mechanisms of guanidinium ionic liquid based microwave‐assisted extraction were researched by scanning electron microscopy and IR spectroscopy. All the results show that guanidinium ionic liquid based microwave‐assisted extraction has a huge potential in the extraction of bioactive compounds from complex samples.     

Tunable protic ionic liquids as solvent-catalysts for improved synthesis of multiply substituted 1,2,4-triazoles from oxadiazoles and organoamines

More than green alternatives to traditional volatile molecular organic solvents, protic ionic liquids as dual solvent-catalysts have been successfully used to promote reactions of organoamines with oxadiazoles to afford sterically hindered 1,2,4-triazoles. Among the tested protic ionic liquids, pyridinium trifluoroacetate and acetate showed the highest efficiency for the reactions of arylamines and alkylamines, respectively, indicating that tunable catalysis could be readily effected with protic ionic liquid solvent-catalysts by simply tuning their cation and anion counterparts. A general and efficient approach has been developed for synthesis of multiply substituted 1,2,4-triazoles based on the tunable protic ionic liquid solvent-catalyst systems.     

Ionic aggregation in random copolymers containing phosphonium ionic liquid monomers

Copolymers of n‐butyl acrylate and phosphonium ionic liquid monomers possessing various alkyl substituents and counterions were synthesized through a combination of conventional free radical copolymerization and anion exchange. Differential scanning calorimetry and dynamic mechanical analysis provided the thermal and mechanical properties of these phosphonium cation‐containing random copolymers. Factors including alkyl chain length of phosphonium substituents, counterion type, as well as ionic concentration significantly influenced the association of phosphonium cations. Phosphonium ionomers with trialkyl substituents on phosphonium cations did not display the characteristic small‐angle X‐ray scattering peak, suggesting the absence of ionic clusters. However, low q peaks in wide‐angle X‐ray diffraction was indicative of significant concentration fluctuations wherein the ionic monomeric units associated. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Ionic Liquid‐Based Routes to Conversion or Reuse of Recycled Ammonium Perchlorate

New, potentially green, and efficient synthetic routes for the remediation and/or re‐use of perchlorate‐based energetic materials have been developed. Four simple organic imidazolium‐ and phosphonium‐based perchlorate salts/ionic liquids have been synthesized by simple, inexpensive, and nonhazardous methods, using ammonium perchlorate as the perchlorate source. By appropriate choice of the cation, perchlorate can be incorporated into an ionic liquid which serves as its own electrolyte for the electrochemical reduction of the perchlorate anion, allowing for the regeneration of the chloride‐based parent ionic liquid. The electrochemical degradation of the hazardous perchlorate ion and its conversion to harmless chloride during electrolysis was studied using IR and ³⁵Cl NMR spectroscopies.