Zihui Meng

Detection of organophosphorus compounds using a molecularly imprinted photonic crystal.

A label free molecularly imprinted photonic crystal (MIPC) was developed to detect the degradation product of nerve agents. Mono-dispersed poly-methyl methacrylate colloidal particles with the diameter of 280 nm were used to fabricate a closely packed colloidal crystal array (CCA), and a methyl phosphonic acid (MPA) imprinted hydrogel was prepared within the CCA using 2-hydroxyethyl-methacrylate and N-isopropylacrylamide as monomers, ethyleneglycol dimethacrylate and N, N-methylenebisacrylamide as cross-linkers, a mixture of n-octanol and acetonitrile as porogen. The diffraction intensity of the MIPC decreased significantly upon the MPA adsorption with a limit of detection (LOD) of 10(-6) molL(-1). Furthermore, the diffraction intensity decreased and blue shifted with the increase of temperature, decreased and red shifted with the increase of ionic strength. At higher pH, the diffraction intensity increased without obvious diffraction shift. The MIPC provides an indirect path to detect nerve agents (Sarin, Soman, VX and R-VX) by monitoring the MPA released from the hydrolysis of nerve agents, with LODs of 3.5 × 10(-6) molL(-1), 2.5 × 10(-5) molL(-1), 7.5 × 10(-5) molL(-1) and 7.5 × 10(-5) molL(-1) for Sarin, Soman, VX and R-VX, respectively.

A 2-D photonic crystal hydrogel for selective sensing of glucose

A novel 2-D photonic crystal (PC) sensing material for the visual detection of glucose with high selectivity at a physiological ionic strength (150 mM) is developed. A monolayer polystyrene crystalline colloidal array (CCA) is embedded in a phenylboronic acid (PBA) functionalized hydrogel film to diffract light to sensitively report on the hydrogel surface area. This 2-D PC sensor is superior to the previously reported 3-D PC sensors due to its fast preparation and simple detection. The binding of glucose would increase the cross-linking of the hydrogel that could shrink the hydrogel to increase the Debye diffraction ring diameter. At a physiological ionic strength of 150 mM, the 2-D PC sensor exhibits significant sensitivity for glucose across the entire human physiological glucose range. Additionally, the 2-D PC sensor shows high selectivity for glucose rather than other sugars (fructose and galactose). The diffraction color change of the 2-D PC sensor can be observed. For validation, the prepared 2-D PC hydrogel sensor is applied for the sensing of glucose in the artificial tear fluid.

Detection of nitrobenzene compounds in surface water by ion mobility spectrometry coupled with molecularly imprinted polymers

Ion mobility spectrometry (IMS) was explored in the selective detection of nitrobenzene compounds in industrial waste water and surface water, and the selectivity was theoretically elucidated with the transformation energy in the product ion formation reaction. A linear detection range of 0.5-50 ppm and a limit of detection (LOD) of 0.1 ppm were found for 2,4,6-trinitrotoluene (TNT). With the IMS as the detection system of molecularly imprinted polymer (MIP) separation technique, the MIP-IMS system was proved to be excellent method to detect trace amount of nitrobenzene compounds in surface water, in which more than 87% of nitrobenzene compounds could be adsorbed on MIPs with 90-105% of recovery.

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.

Two-dimensional colloidal crystal heterostructures

We developed a simple method to fabricate colloidal crystal heterostructures (CCHs) with two or three stacked poly(methyl methacrylate) (PMMA) particle two-dimensional (2D) colloidal monolayer arrays of different particle spacings that independently diffract light. The 2D colloidal monolayer arrays of PMMA were prepared by using the air/water interface self-assembly method we recently developed. Two- and three-layer CCHs were fabricated by successive deposition of 2D PMMA colloidal monolayer arrays of different particle sizes. The structure and optical properties of 2D monolayer arrays and 2D CCHs were characterized with SEM, reflectance spectra, their Debye diffraction rings and their diffracted wavelengths. The layers maintain their spacing and ordering as they are transferred from the air/water interface onto the substrate. The 2D CCHs diffraction measurements suggest that the optical properties of the colloidal crystal heterostructures arise mainly from the independent diffraction of the individual 2D colloidal arrays. This enables selective combination of particular light wavelengths through diffraction of the 2D CCHs.

Synthesis of novel pleuromutilin derivatives. Part 1: Preliminary studies of antituberculosis activity

The worldwide threat from tuberculosis (TB) has resulted in great demand for new drugs, particularly those that can treat multidrug-resistant TB. We synthesized novel pleuromutilin derivatives with N-benzylamine side chain substituted at the C14 position and evaluated their activity in vitro against a virulent strain of Mycobacterium tuberculosis (H37Rv). The primary assay results showed that five compounds inhibited the H37Rv at 20μM, with a MIC of one of the analogues as low as 7.2μM.

Detection of p-Nitrophenol Using Molecularly Imprinted Colloidal Array

Abstract p -Nitrophenol ( p -NP) molecularly imprinted colloidal microspheres were prepared by polymerization of functional monomers (acrylamide, AM) and template of p -NP in poly (methyl methacrylate, PMMA) pre-polymerization solution. Molecularly imprinted colloidal array (MICA) was prepared using the molecularly imprinted colloidal microspheres by self-assembly, and then fixed by an adhesive tape. The MICA on the adhesive tape was easy to handle and had strong stability. The MICA film combines both the high selectivity of molecular imprinting and facility to use of photonic crystal. This material senses p -NP in aqueous solution by shifting reflection wavelength. The adsorption of p -NP into molecularly imprinted colloidal microspheres would swell the microspheres, thus leading to a reflection peak red shift. The reflection peak redshifted nearly 60 nm when the concentration of p -NP increases from 0 mM to 30 mM, while non-imprinted molecularly imprinted colloidal array (NICA) red shifted about 40 nm. The color of MICA changed from red to blue-violet was observed. This method simplifies the preparation of photonic crystal material which is an efficient approach for developing high-performance chemical/biological sensors.

A covalently imprinted photonic crystal for glucose sensing

We demonstrate a glucose-sensing material based on the combination of photonic crystal templating and a molecular-imprinting technique. In the presence of the target molecule glucose, poly(N-isopropylacrylamide-co-2-hydroxyethyl methacrylate) hydrogel with pendent phenylboronic acid groups was synthesized in the void of a poly(methyl methacrylate) (PMMA) colloidal crystal. After removing the PMMA photonic crystal template and glucose molecules, a 3D-ordered porous covalently imprinted photonic crystal (CIPC) hydrogel was created. The unique 3D-ordered porous hydrogel revealed optical changes in response to glucose concentration. At pH = 11 and 37°C, the diffraction of CIPC redshifted from725 nmto 880nm in response to 20mmol L-1 glucose. Due to the covalently imprinted recognizer, boronic acid group, the selectivity of the CIPC towards glucose over D-ribose and L-rhamnose was improved significantly.

Analysis of L-Quebrachitol from the Waste Water of Rubber Latex Serum Using Hydrophilic Interaction Chromatography and Evaporative Light Scattering Detector Method

L-Quebrachitol (QCT) is a valuable active ingredient found in rubber latex serum. Due to its high polarity, quantitative analysis of QCT is difficult on traditional reverse phase liquid chromatography (RPLC). Hydrophilic interaction chromatography (HILIC) using a Shiseido PC HILIC column (250 × 4.6 mm) and an evaporative light-scattering detector (ELSD) was found to be convenient for the analysis of QCT. The mobile phase was acetonitrile–water (60:40, v/v), retention factor is 0.92. Outstanding detection linearity (5 × 10−5–4 g/L) and limit of detection (LOD, 8 × 10−6 g/L) was achieved. Using this method, 2.2% wt QCT was determined to be present in rubber latex waste water. The retention of QCT on PC HILIC, which was immobilized with phosphorylcholine, was also investigated theoretically, the interaction energy between QCT and phosphorylcholine group is −51.498 kJ/mol, and ΔH0 and ΔS0 for the retention of QCT on PC HILIC is −0.699 kJ/mol and 2.72 J/mol · K, respectively.

Characterization of Hydrazinium 3,5-Dinitroamine-1,2,4-triazole

The structure of hydrazinium 3,5-dinitroamine-1,2,4-triazole (HDNAT) was investigated with infrared (IR), mass spectrometry, 13C-NMR, scanning electron microscopy (SEM), and X-ray crystallography. The crystal density of HDNAT was determined as 1.91 g/cm3 using X-ray diffraction. The crystal belongs to a monoclinic system with the space group P2(1). The thermal decomposition process of HDNAT was investigated via thermogravimetry–differential thermal analysis (TG-DTA) at a heating rate of 10 K/min and differential scanning calorimetry (DSC) under nonisothermal conditions. The decomposition kinetic and thermodynamic parameters were obtained by the Kissinger and Ozawa method. HDNAT can be analyzed by using a C18 high-performance liquid chromatography (HPLC) column with water : acetonitrile : trifluoroacetic acid (97/3/0.1, v/v/v) as the mobile phase and a capacity factor of 1.33.