Liyun Ding

Synthesis and characterization of a novel nitric oxide fluorescent probe CdS-PMMA nanocomposite via in-situ bulk polymerization

A novel nitric oxide (NO) fluorescent probe CdS-poly(methyl methacrylate) (PMMA) nanocomposites with different molar ratios of CdS quantum dots (QDs) to PMMA are developed successfully via in-situ bulk polymerization method. The optical properties of CdS/PMMA nanocomposites are studied by UV-Vis absorption spectra and fluorescence (FL) spectra in detail. It is demonstrated that the optical properties from such nanocomposite solution are tuned and stabilized by simply varying the concentration of CdS in the final product. X-ray diffraction (XRD) patterns of CdS-PMMA nanocomposite with higher loading of CdS show broad pattern for cubic CdS, which has narrow particle size distribution with less than 5 nm in PMMA observed by transmission electron microscopy (TEM). The surface morphological characterization of the CdS-PMMA nanocomposite has been done through atomic force microscopy (AFM). The thermo-gravimetric analyses (TGA) and differential scanning calorimetry (DSC) confirm the enhanced thermal stability of CdS-PMMA nanocomposites than PMMA. NO can coordinate with Cd(2+) as a ligand for transition metal complexes, which will cause a quenching effect on the fluorescence of CdS QDs. Therefore, a significant quenching effect on the fluorescence of the CdS-PMMA nanocomposite is observed in the presence of NO. The fluorescence responses are concentration-dependent and can be well described by the typical Stern-Volmer equation, and a linear calibration I0/I=1.0021+0.1944[NO] (R(2)=0.96052) is obtained in the range from 1.4×10(-5) to 9.3×10(-3) mol/L NO with a detection limit of 1.0×10(-6) mol/L (S/N=3).

Immobilization of cholesterol oxidase on magnetic fluorescent core-shell-structured nanoparticles.

The magnetic fluorescent core-shell structured nanoparticles, Fe3O4@SiO2(F)@meso-SiO2 nanoparticles, were prepared. Cholesterol oxidase (COD) was immobilized on their surface to form Fe3O4@SiO2(F)@meso-SiO2@COD nanoparticles. Optimal immobilization was achieved with 2.5% (v/v) APTES, 2.0% (v/v) GA, 10mg COD (in 15 mg carrier) and solution pH of 7.0. Fe3O4@SiO2(F)@meso-SiO2@COD nanoparticles showed maximal catalytic activity at pH7.0 and 50°C. The thermal, storage and operational stabilities of COD were improved greatly after its immobilization. After the incubation at 50°C for 5h, the nanoparticles and free COD retained 80% and 46% of its initial activity, respectively. After kept at 4°C for 30 days, the nanoparticles and free COD maintained 86% and 65% of initial activity, respectively. The nanoparticles retained 71% of its initial activity after 7 consecutive operations. Since Fe3O4@SiO2(F)@meso-SiO2@COD nanoparticles contained tris(2,2-bipyridyl)dichloro-ruthenium(II) hexahydrate (Ru(bpy)3Cl2) and were optical sensitive to oxygen in solution, it might be used as the sensing material and has the application potential in multi parameter fiber optic biosensor based on enzyme catalysis and oxygen consumption.

Integration of conductive reduced graphene oxide into microstructured optical fibres for optoelectronics applications

Integration of conductive materials into optical fibres can largely expand functions of fibre devices including surface plasmon resonator/metamaterial, modulators/detectors, or biosensors. Some early attempts have been made to incorporate metals such as tin into fibres during the fibre drawing process. Due to the restricted range of materials that have compatible melting temperatures with that of silica glass, the methods to incorporate metals along the length of the fibres are very challenging. Moreover, metals are nontransparent with strong light absorption, which causes high fibre loss. This article demonstrates a novel but simple method for creating transparent conductive reduced graphene oxide film onto microstructured silica fibres for potential optoelectronic applications. The strongly confined evanescent field of the suspended core fibres with only 2 μW average power was creatively used to transform graphene oxide into reduced graphene oxide with negligible additional loss. Existence of reduced graphene oxide was confirmed by their characteristic Raman signals, shifting of their fluorescence peaks as well as largely decreased resistance of the bulk GO film after laser beam exposure.

Development of 2-Chlorophenol Sensor Based on a Fiber Optic Oxygen Transducer via Oxidation Reaction Catalyzed by Tetranitro Iron (II) Phthalocyanine

This paper develops a 2-chlorophenol sensor based on the improvement of a fiber optic oxygen transducer. The measurement of a sensor depends on the principle of stoichiometric relationship between dissolved oxygen and 2-chlorophenol in catalytic oxidation reaction. Specifically, oxygen was consumed fast in oxidation of 2-chlorophenol catalyzed by tetranitro iron (II) phthalocyanine (TNFe(II)Pc), and the concentration changes of dissolved oxygen could be measured by a fiber optic oxygen transducer. The phase-modulation technology was employed to record the signals of phase delay responding to the aerobic oxidation process catalyzed by TNFe(II)Pc. In addition, the sensing performance of this sensor could be demonstrated by a modified Stern-Volmer equation, φ = 0.12 + 3710[2 - CP] (R2 = 0.9949), where φ and [2-CP] represent the phase delay and concentration of 2-chlorophenol, respectively. The detection limit of this sensor is 8.0 × 10-7 M. In addition, this sensor shows the satisfactory results compared with that of HPLC method for detection of the samples from Changjiang river.

A novel fluorescence probe 9-(4-(1,2-diamine)benzene-N1-phenyl)acridine for nitric oxide determination

A novel fluorescent probe 9-(4-(1,2-diamine)benzene-N1-phenyl)acridine (DABPA) was synthesized for the detection of nitric oxide (NO) and characterized by IR, 1H-NMR and EI-MS spectroscopy. Based on a photoelectron transfer mechanism, the fluorescence intensities of DABPA were investigated with the different concentrations of NO. Under the optimal experimental conditions, the fluorescence intensity of DABPA had a good linear relationship (R2=0.9977) with NO concentration in the range from 1×10−7 to 1.5×10−6 mol/L with a detection limit of 1×10−8 mol/L. The cytotoxicity induced by DABPA was evaluated by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5diphenyl tetrazolium bromide) assay for biological application. Furthermore, the probe DABPA had also been successfully applied to real-time image NO produced in PC12 cells in the presence of L-arginine.

A Fiber Optic Sensor for 2-cholrophenol Analysis based on Oxygen Sensing System

A fiber optic 2-cholrophenol (2-CP) sensor was developed based on the fluorescence quenching of molecular oxygen on the oxygen-sensitive membrane and O2 consumption during catalytic oxidation reaction of 2-CP. The 2-CP concentration can be determined by utilizing a lock-in amplifier to measure the change in the fluorescence lifetime of an oxygen-sensitive membrane, in which the tris (2,2′-bipyridyl) ruthenium(II) chloride complexes (Ru(II)(byp)3Cl2) were immobilized in cellulose acetate (CA) via simple hybridized approach. The experimental results show the good linear relationship between the phase delay of sensitive membrane and 2-CP concentration in its detection range of 1×10−7 to 1×10−5 mol/L and 1×10−5 to 1×10−4 mol/L. The detection limit of the sensor is 7×10−8 mol/L (S/N=3) and the response time is 5 min. Our experimental measurements confirmed good response characteristics of the as-prepared fiber optic 2-CP sensor, as well as its capability to detect the 2-CP concentration in practical water samples.

Enhancing heterogeneous catalytic activity of iron (II) phthalocyanine by ethanol and its application in 2,4-dichlorophenol detection

A chemical system for facile and accurate detection of 2,4-dichlorophenol (DCP) via iron (II) phthalocyanine (Fe(II)Pc) catalyzed chromogenic reaction is reported for the first time. In this system, DCP could be oxidized by dioxygen with the catalysis of Fe(II)Pc and then coupled with 4-aminoantipyrine (4-AAP) to generate pink antipyrilquinoneimine dye. Control experiments showed that the addition of ethanol could obviously enhance the catalytic activity of heterogeneous Fe(II)Pc catalysts because of the partial dissolution of Fe(II)Pc nanocubes, which was confirmed by the SEM analysis. On the basis of the detection results of DCP in the range from 2×10−5 to 9×10−4 mol/L, we obtained a regression equation (A = 0.187 5 + 0.01 209C (R2=0.995 6)) with the detection limit (3σ) of 3.26×10−6 mol/L, which could be successfully used in detecting the real samples.

Development of a sensitive fiber optic sensor monitoring NO based on vicinal diaminobenzoacridine fluorophore

A new fiber optic sensor has been developed for determination of NO using a fluorescent vicinal diaminobenzoacridine (VDABA) probe. The sensitive membrane was prepared from cellulose acetate (CA) embedded with VDABA, which caused a fluorescence recovery based on a photoelectron transfer (PET) mechanism. Modulation of optical phase shift of the sensor is observed with different NO concentrations. Under optimum conditions, a linear calibration (r2=0.9902) was obtained in the range of 1.0×10-8 to 1.0×10-5 mol/L NO concentration with a detection limit of 1.0×10-9 mol/L (S/N=3). This sensor was successfully applied to the determination of NO in the rabbit serum.

A “Turn-On” Fluorescence Copper Biosensor Based on DNA Cleavage-Dependent Graphene Oxide-dsDNA-CdTe Quantum Dots Complex

A novel “turn-on” fluorescent copper biosensor is developed successfully based on the graphene oxide (GO)-dsDNA-CdTe quantum dots (QDs) complex via chemical crosslink method. The optical and structure properties of GO-dsDNA-CdTe QDs complex are studied by fluorescence (FL) spectra and transmission electron microscopy (TEM) in detail. It is demonstrated that the fluorescence quenching of CdTe QDs is a process of fluorescence resonance energy transfer (FRET) due to the essential surface and quenching properties of two-dimensional GO. Copper ions induce the catalytic reaction of DNA chain and irreversibly break at the cleavage site, which will cause the G-quadruplex formation, moreover further result in the CdTe QDs separated from GO and restored its fluorescence. Therefore, a significant recovery effect on the fluorescence of the GO-dsDNA-CdTe QDs complex is observed in the presence of copper ions. The fluorescence responses are concentration-dependent and can be well described by a linear equation. Compared with other metal ions, the sensor performs good selectivity for copper ions.

Detection of nitrite based on fluorescent carbon dots by the hydrothermal method with folic acid

A fluorescent carbon dots probe for the detection of aqueous nitrite was fabricated by a one-pot hydrothermal method, and the transmission electron microscope, X-ray diffractometer, UV–Vis absorption spectrometer and fluorescence spectrophotometer were used to study the property of carbon dots. The fluorescent property of carbon dots influenced by the concentration of aqueous nitrite was studied. The interaction between the electron-donating functional groups and the electron-accepting nitrous acid could account for the quenching effect on carbon dots by adding aqueous nitrite. The products of the hydrolysis of aqueous nitrite performed a stronger quenching effect at lower pH. The relationship between the relative fluorescence intensity of carbon dots and the concentration of nitrite was described by the Stern–Volmer equation (I0/I − 1 = 0.046[Q]) with a fine linearity (R2 = 0.99). The carbon dots-based probe provides a convenient method for the detection of nitrite concentration.