A novel strategy for highly sensitive detection and discrimination of explosives is developed based on the metal–organic polyhedra (MOP)-decorated plasmonic substrate. It is found that the careful selection of the geometric and electronic characteristics of the assembly units (organic ligands and unsaturated metals sites) embedded within the MOP cage allows for the integration of multiple weak molecular interactions in a controllable fashion and thus the MOP cage can serve as an excellent receptor for selective uptake and binding of explosives. By further grafting of the MOP cage onto a plasmonic substrate with good surface-enhanced Raman scattering enhancement factor, the resulting sensor shows a good sensing capability to various groups of ultratrace explosives, especially the challenging aliphatic nitro-organics.

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.

Based on the combination of the unique features of both polyionic liquids and spherical colloidal crystals, a new class of inverse opaline spheres with a series of distinct properties was fabricated. It was found that such photonic spheres could not only be used as stimuli-responsive photonic microgels, but also serve as multifunctional microspheres that mimic the main characteristics of conventional molecules, including intrinsic optical properties, specific molecular recognition, reactivity and derivatization, and anisotropy.

Based on the simple counterion exchange of ionic liquids, a rapid, facile, and efficient strategy to create a cross-reactive sensor array with a dynamic tunable feature was developed, and exemplified by the construction of a sensor array for the identification and classification of nitroaromatics and explosives mimics. To achieve a good sensing system with fast response, good sensitivity, and low detection limit, the synthesized ionic liquid receptors were tethered onto a silica matrix with a macro-mesoporous hierarchical structure. Through the facile anion exchange approach, abundant ionic-liquid-based individual receptors with diversiform properties, such as different micro-environments, diverse molecular interactions, and distinctive physico-chemical properties, were easily and quickly synthesized to generate a distinct fingerprint of explosives for pattern recognition. The reversible anion exchange ability further endowed the sensor array with a dynamic tunable feature as well as good controllability and practicality for real-world application. With the assistance of statistical analysis, such as principal component analysis (PCA) and linear discrimination analysis (LDA), an optimized-size array with a good resolution was rationally established from a large number of IL-based receptors. The performed experiments suggested that the ionic-liquid-based sensing protocol is a general and powerful strategy for creating a cross-reactive sensor array that could find a wide range of applications for sensing various analytes or complex mixtures.

Taking theophylline and (1R,2S)-(−)-ephedrine as template molecules, two imprinted photonic-hydrogel films are prepared by a combination of colloidal-crystal and molecular-imprinting techniques. This paper shows a new approach for rapid and handy stimulant detection with high sensitivity and specificity. One film is proposed for analogous molecule assay, another one for chiral recognition. The key point of this approach is that the imprinted photonic polymer (IPP) consists of a three-dimensional (3D), highly-ordered and interconnected macroporous array with a thin hydrogel wall, where nanocavities complementary to analytes in shape and binding sites are distributed. This special, bicontinuous, hierarchical structure enables this polymer to report quickly, easily, sensitively and directly a molecular recognition event without any transducers and treatments for analytes (label-free). The inherent affinity of the nanocavities, deriving from molecular imprinting, makes these sensors highly specific to analytes, even if in a competitive environment. Their sensitive and specific responses to stimulants in buffer are determined by Bragg diffractive shifts due to the lattice change of their 3D ordered macroporous arrays resulting from their preferential rebinding to the target molecules. The measurements show that the prepared hydrogel films exhibit high sensitivity in such a 0.1 fM concentration of analytes and specificity even in a competitive urinous buffer. The reported method provides a rapid and handy approach for stimulant assay and drug analysis in athletic sports.

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

A series of novel “jellyfish-like” graft copolymers with chitooligosaccharide (COS) as shorter backbone and poly(ε-caprolactone) as longer branches were synthesized using ring-opening polymerization of ε-caprolactone via a protection-polymerization-deprotection procedure with trimethylsilylchitooligosaccharide as intermediate and triethylaluminum as catalyst precursor. The obtained chitooligosaccharide-graft-poly(ε-caprolactone) polymers possess amphiphilic structure with hydrophilic COS backbone and hydrophobic polycaprolactone branches. Because of this unique “jellyfish-like” structure, these graft copolymers could self-assemble to form various morphologies of aggregates in a mixture solution of water and tetrahydrofuran. The transmission electron microscopy studies revealed that the formed aggregates exhibited necklace-like, flower-like onion vesicle, and tubular morphologies. It is found that the hydrogen-bonding formed by the hydroxyl and amino groups remained on the COS backbone played an important role during the aggregation of these graft copolymers, and their morphologies were changed with the varying length of poly (ε-caprolactone) branches, the concentration of the graft copolymer, and the self-assembly process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4889–4904, 2008

Based on the combination of colloidal-crystal templating and a molecular imprinting technique, a sensor platform for efficient detection of atrazine in aqueous solution has been developed. The sensor is characterized by a 3D-ordered interconnected macroporous structure in which numerous nanocavities derived from atrazine imprinting are distributed in the thin wall of the formed inverse polymer opal. Owing to the special hierarchical porous structure, the molecularly imprinted polymer opals (or molecularly imprinted photonic polymer; MIPP) allow rapid and ultrasensitive detection of the target analyte. The interconnected macropores are favorable for the rapid transport of atrazine in polymer films, whereas the inherent high affinity of nanocavites distributed in thin polymer walls allows MIPP to recognize atrazine with high specificity. More importantly, the atrazine recognition events of the created nanocavities can be directly transferred (label-free) into a readable optical signal through a change in Bragg diffraction of the ordered macropores array of MIPP and thereby induce color changes that can be detected by the naked eye. With this novel sensory system, direct, ultrasensitive (as low as 10⁻⁸ ng mL⁻¹), rapid (less than 30 s) and selective detection of atrazine with a broad concentration range varying from 10⁻¹⁶ M to 10⁻⁶ M in aqueous media is achieved without the use of label techniques and expensive instruments.

Novel functionalized poly(p-phenylene ethynylene)s (PPEs) bearing facially amphiphilic cholic and deoxycholic acid units are synthesized by a Pd-catalyzed Sonogashira cross-coupling reaction. Some interesting properties, particularly their optical and self-assembly characteristics, are unraveled. The PPEs that carry bile acid substituents exhibit remarkable solvatochromism in a wide range of solvent systems, and judicious choice of the solvents can adjust the size and morphology of the formed nanoscale supramolecular aggregates. The incorporation of these naturally occurring building blocks can also impart biocompatibility to the conjugated system and stimulate the growth of living cells.