Lili Qiu

Visual detection of 2,4,6-trinitrotolune by molecularly imprinted colloidal array photonic crystal.

We developed a photonic crystal (PhC) sensor for the quantification of 2,4,6-trinitrotoluene (TNT) in solution. Monodisperse (210nm in diameter) molecularly imprinted colloidal particles (MICs) for TNT were prepared by the emulsion polymerization of methyl methacrylate and acrylamide in the presence of TNT as a template. The MICs were then self-assembled into close-packed opal PhC films. The adsorption capacity of the MICs for TNT was 64mg TNT/g. The diffraction from the PhC depended on the TNT concentration in a methanol/water (3/2, v/v) potassium dihydrogen phosphate buffer solution (pH=7.0, 30mM). The limit of detection (LOD) of the sensor was 1.03μg. The color of the molecularly imprinted colloidal array (MICA) changed from green to red with an 84nm diffraction red shift when the TNT concentration increased to 20mM. The sensor response time was 3min. The PhC sensor was selective for TNT compared to similar compounds such as 2,4,6-trinitrophenol, 2,4-dinitrotoluene, 2,6-dinitrotoluene, 2-nitromesitylene, 4-nitrotoluene, 2-nitrotoluene, 1,3-dinitrobenzene, methylbenzene, 4-nitrophenol, 2-nitroaniline, 3-aminophenol and 3-nitroaniline. The sensor showed high stability with little response change after three years storage. This sensor technology might be useful for the visual determination of TNT.

Colorimetric sensor arrays based on pattern recognition for the detection of nitroaromatic molecules

This research demonstrated that, in a colorimetric sensor array, 2,4,6-trinitrotoluene (TNT), 2,6-dinitrotoluene (2,6-DNT), 2,4-dinitrotoluene (2,4-DNT) and 4-nitrotoluene (4-MNT) were identifiable through a unique pattern in a qualitative and semi-quantitative manner. The adsorption capacity of the molecularly imprinted colloidal particles (MICs) for their corresponding templates was 0.27mmol TNT/g, 0.22mmol 2,6-DNT/g, 0.31mmol 2,4-DNT/g and 0.16mmol 4-MNT/g, respectively. Every optical sensor utilized in the arrays contained three-dimensional molecularly imprinted photonic crystal (MIPC) sensor with different imprinted templates. The intelligent materials can display different colors from green to red to 20mM corresponding nitroaromatics with varying diffraction red shifts of 84nm (TNT), 46nm (2,6-DNT), 54nm (2,4-DNT) and 35nm (4-MNT), respectively. With the assistance of principal component analysis (PCA) and rational design, the sensor array can illustrate the influence of the nitryl quantity and generate a separate response region of nitroaromatics for pattern recognition with 95.25% of variance explained in the measurements by the first three principal components (PCs). The statistical analysis endowed the cross-reactive array with better classification and identification ability and this novel detection platform provided a wider applied range among other harmful chemicals in a simple sensor array with customized functionality.

Solanesol extraction from tobacco leaves by Flash chromatography based on molecularly imprinted polymers

A novel solanesol extraction method based on molecularly imprinted polymer (MIP) as the Flash chromatography stationary phase was established and evaluated. Spherical MIP particles in a size range of 250-350 μm (d (0.5)=320 μm) for solanesol were synthesized by suspension polymerization, with imprinting factor of 3.9. The MIP particles (5.5 g) were packed in common Teflon column as the stationary phase while the sample solution and elution solvent were confirmed as methanol and methanol/acetic acid solution (80/20, v/v), loading at 4 ml/min and eluting 8 ml/min, respectively. Under the optimal chromatographic conditions, the adsorption capacity of the MIP-Flash column was determined as 107.3 μmol/g, and in each process, 370.8 mg purified solanesol (98.4%) could be obtained from the extract (20 mM, 40 ml) of tobacco leaves (14.7 g), and the yield of solanesol was 2.5% of the dry weight of tobacco leaves. The results reported here confirm the feasibility to extract highly purified active ingredients directly from natural products on a large scale by MIP-Flash chromatography.

Functionalized photonic crystal for the sensing of Sarin agents

The indiscriminate use of nerve agents by terrorist groups has attracted attention of the scientific communities toward the development of novel sensor technique for these deadly chemicals. A photonic crystal (PhC) hydrogel immobilized with butyrylcholinesterase (BuChE) was firstly prepared for the sensing of Sarin agents. Periodic polystyrene colloidal (240nm) array was embedded inside an acrylamide hydrogel, and then BuChE was immobilized inside the hydrogel matrix via condensation with 3-(diethoxyphosphoryloxy)-1,2,3-benzotriazin-4(3h)-one (DEPBT). It indicated that a total of 3.7 units of BuChE were immobilized onto the PhC hydrogel. The functionalized hydrogel recognized the Sarin agent and then shrunk, thus the diffraction of PhC hydrogel blue shifted significantly, and a limit of detection (LOD) of 10(-15)molL(-1) was achieved.

Preparation of free-standing two-dimensional colloidal crystal arrays

A simple method was developed to prepare ultra-thin, large-area, free-standing two-dimensional (2D) polymethylmethacrylate (PMMA) colloidal crystal array monolayers by assembling PMMA colloids suspended in toluene on water surface. Diffraction of the free-standing films could be adjusted through the particle size or operation time.

Simultaneous selective extraction of nitramine explosives using molecularly imprinted polymer hollow spheres from post blast samples

Molecularly imprinted polymer hollow spheres (MIHSs) were produced by using hexanitrohexaazaisowurtzitane (HNIW or CL-20) as a template, silica nanospheres as a sacrificial matrix, acrylamide as a functional monomer, ethylene glycol dimethacrylate as a cross-linker and acetonitrile as a porogen at 4 °C under UV irradiation. This sorbent was applied to the selective solid-phase extraction (SPE) of several explosives simultaneously by using a newly-developed SPE procedure. For the first time, 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) and CL-20 were selectively extracted and determined simultaneously from simulated post-blast samples prepared from motor oil and vacuum pump oil. The matrix effects were successfully eliminated and accurate quantization was achieved. When the loading amounts of HMX, RDX, TNT and CL-20 were, respectively, below 10, 2, 5 and 20 nmol for 100 mg of MIHS, these explosives were almost retrieved completely (above 98%). For the MIHSs and non-imprinted polymer hollow spheres (NIHSs), in acetonitrile and methanol, the imprinting factors (IFs) of CL-20 and tetraacetyldibenzylhexaazaisowurtzitane (TADB, a structural analogue of CL-20) changed dramatically, from 7.75 to 1.57 and 0.88 to 2.39, respectively. It highlighted the significant effect of solvents on imprinted sites.

Self-assembly of a nano hydrogel colloidal array for the sensing of humidity

Traditional artificial opals are assembled from silica or polystylene colloidals which have poor swellability and a lower response to stimuli. A novel three-dimensional photonic crystal array sensor which has a high stability and desired structural colour was fabricated from the self assembly of nano hydrogel colloids. The nano hydrogel colloids were prepared by co-polymerisation of N-isopropylacrylamide, functional monomer acrylic acid and N-tert-butylacrylamide. The relative humidity from 20% to 100% could be detected rapidly via the reflection spectrum of the nano hydrogel colloidal array with a maximum amount of red shift of 24 nm. The response kinetics for humidity of the nano hydrogel colloidal array were investigated, and correspondingly, a rational response mechanism of the compactness of the close-packed structure caused by the swelling of the nano hydrogel colloidal array was discussed. The nano hydrogel colloidal array sensor presented good reversibility and can be reused for at least five rounds.

Acetylcholinesterase-functionalized two-dimensional photonic crystals for the detection of organophosphates

Due to the indiscriminate usage of organophosphates in military and agriculture, there is an increasing demand to develop sensors for monitoring organophosphorus nerve agents and pesticides. Herein, a sensitive two-dimensional photonic crystal (2D-PC) biosensor as a part of a portable device for the detection of Dipterex is presented. The 2D-PC array was self-organized on the water–air interface using 600 nm polystyrene (PS) colloidal particles, and it was further embedded into a polyacrylamide-acrylic acid (PAM-AA) hydrogel. After condensation between the amine groups of acetylcholinesterase (AChE) and the carboxyl groups of the hydrogel, a novel sensing platform of 2D-PC hydrogel with AChE as the recognition agent was constructed. The lattice spacing of AChE-functionalized 2D-PC was inversely proportional to the logarithm of the Dipterex concentration from 10−14 mol L−1 to 10−4 mol L−1 with estimated limit of detection (LOD) of 7.7 × 10−15 mol L−1. Simultaneously, the structural color of AChE-functionalized 2D-PC varied from yellow to blue. The biosensor achieved “naked-eye” detection due to which the use of AChE-functionalized 2D-PC is a promising technique for onsite and fast screening of organophosphates.