Single-walled carbon nanohorn as new solid-phase extraction adsorbent for determination of 4-nitrophenol in water sample

Single-walled carbon nanohorn (SWCNH) was developed as new adsorbent for solid-phase extraction using 4-nitrophenol as representative. The unique exoteric structures and high surface area of SWCNH allow extracting a large amount of 4-nitrophenol over a short time. Highly sensitive determination of 4-nitrophenol was achieved by linear sweep voltammetry after only 120 s extraction. The calibration plot for 4-nitrophenol determination is linear in the range of 5.0 x 10(-8) M-1.0 x 10(-5) M under optimum conditions. The detection limit is 1.1 x 10(-8) M. The proposed method was successfully employed to determine 4-nitrophenol in lake water samples, and the recoveries of the spiked 4-nitrophenol were excellent (92-106%).

Progress in Ru (bpy)(3)(2+) Electrogenerated Chemiluminescence

Among various ECL systems, such as 9,10-diphenylanthracene, lucigenin, tris(2,2'-bipyridyl) ruthenium, peroxyoxalate, luminol, graphene, and nanocrystals, Ru(bpy)(3)(2+) ECL is one of the most widely studied ECL systems in recent years due to its broad applications in immunoassays, DNA probe assays, coreactants analysis, and aptasensors. In this review, the progress in Ru(bpy)(3)(2+) ECL has been summarized on the whole, and the future research trends have been proposed.

Nucleation in A/B/AB blends: Interplay between microphase assembly and macrophase separation

We study the interplay between microphase assembly and macrophase separation in A/B/AB ternary polymer blends by examining the free energy of localized fluctuation structures (micelles or droplets), with emphasis on the thermodynamic relationship between swollen micelles (microemulsion) and the macrophase-separated state, using self-consistent field theory and an extended capillary model. Upon introducing homopolymer B into a micelle-forming binary polymer blend A/AB, micelles can be swollen by B. A small amount of component B (below the A-rich binodal of macrophase coexistence) will not affect the stability of the swollen micelles. A large excess of homopolymer, B, will induce a microemulsion failure and lead to a macrophase separation.

A novel technique for NACE coupled with simultaneous electrochemiluminescence and electrochemical detection for fast analysis of tertiary amines

A simultaneous electrochemiluminescence (ECL) and electrochemical (EC) detection scheme for NACE was presented for fast analysis of tertiary amines. Both ECL and EC signals were generated at the same Pt electrode. Triethylamine (TEA), tripropylamine (TPrA), chlorpromazine, promethazine, and dioxopromethazine (DPZ) were selected to validate NACE-ECL/EC dual detection strategy. The linear ranges for TEA and TPrA were 0.01-500 and 0.01-10 mu M with the detection limits of 8.0 and 5.0 nM (S/N=3), respectively. The RSDs (n = 6) of the migration time and the ECL intensity for 1 mu M TEA and 0.5 mu M TPrA were 0.1 and 2.8%, and 0.2 and 1.8% with theoretical plate numbers of 180 000 and 700 000 per meter, respectively. These two analytes could be separated within 92 s and the Pt electrode did not need reactivation during the experiments.

Enantioseparation of Dioxopromethazine Hydrochloride in Urine with Liquid-Liquid Extraction by CE-ECL Detection

Capillary electrophoresis coupled with electrochemiluminescence detection was developed for the separation and determination of dioxopromethazine hydrochloride (DPZ) enantiomers. Performance parameters of the proposed method were evaluated. An improved separation of DPZ enantiomers could be achieved after adding boric acid to buffer. The enantiomers were completely separated with running buffer of 16.5 mM beta-CD in 25 mM tris-H3PO4-40 mM H3BO3 at pH 2.5. The proposed method was successfully applied to the separation and determination of DPZ enantiomers in human urine with a liquid-liquid extraction procedure.

Electrochemical Detection of Hydrazine Based on Electrospun Palladium Nanoparticle/Carbon Nanofibers

In this work, we developed an electrochemical method for the detection of hydrazine based oil palladium nanoparticle/carbon nanofibers (Pd/CNFs). Pd/CNFs were prepared by electrospinning technique and subsequent thermal treatments. The electrocatalytic behaviors of Pd/CNFs modified glassy carbon electrode (Pd/CNF-GCE) for hydrazine oxidation were evaluated by cyclic voltammetry (CV), an obvious and well-defined oxidation peak appeared at -0.32 V (vs. Ag/AgCl). The mechanism of the oxidation of hydrazine at Pd/CNF-GCE was also studied, which demonstrated an irreversible diffusion-controlled electrode process and a four-electron transfer involved in the overall reaction. Furthermore, the wide linear range, low detection limit, good reproducibility and excellent storage stability were obtained utilizing differential pulse voltammetry (DPV).

Simple and rapid voltammetric determination of morphine at electrochemically pretreated glassy carbon electrodes

A simple and rapid method for morphine detection has been described based on electrochemical pretreatment of glassy carbon electrode (GCE) which was treated by anodic oxidation at 1.75 V, following potential cycling in the potential range from 0 V to 1.0 V vs. Ag vertical bar AgCl reference electrode. The sensitivity for morphine detection was improved greatly and the detection limit was 0.2 mu M. The reproducibility of the voltammetric measurements was usually less than 3% RSD for six replicate measurements. Moreover, this method could readily discriminate morphine from codeine. And an electrochemical detection of morphine in spiked urine sample was succeeded with satisfactory results.

Gold nanoparticle-based near-infrared fluorescent detection of biological thiols in human plasma

In this work, a new fluorescent method for sensitive detection of biological thiols in human plasma was developed using a near-infrared (NIR) fluorescent dye, FR 730. The sensing approach was based on the strong affinity of thiols to gold and highly efficient fluorescent quenching ability of gold nanoparticles (Au NPs). In the presence of thiols, the NIR fluorescence would enhance dramatically due to desorption of FR 730 from the surfaces of Au NPs, which allowed the analysis of thiol-containing amino acids in a very simple approach. The size of Au NPs was found to affect the fluorescent assay and the best response for cysteine detection was achieved when using Au NPs with the diameter of 24 nm, where a linear range of 2.5 x 10(-8) M to 4.0 x 10(-6) M and a detection limit of as low as 10 nM was obtained. This method also demonstrated a high selectivity to thiol-containing amino acids due to the strong affinity of thiols to gold.

Successful establishment of MEKC with electrochemiluminescence detection based on one functionalized ionic liquid

Herein, one water-soluble functionalized ionic liquid, 1-butyl-3-methylimidazolium dodecyl sulfate ([BMIm(+)][C12H25SO4-]), was designed and its superiorities either used as supporting electrolytes or as additives for successful establishment of MEKC with electrochemiluminescence (ECL) detection (MEKC-ECL) method were investigated. Compared with the common supporting electrolytes such as phosphate solution, 1-butyl-3-methylimidazolium dodecyl sulfate solution used as running buffers led to greatly enhanced ECL intensities and column efficiencies for negative targets, a little increase for neutral-charge ones while maintained nearly unchanged for positive ones due to the electrostatic forces between the large cation BMIm(+) and the solutes and the hydrophobic interactions resulting from the large anion C12H25SO4.

Surface modification of poly(dimethylsiloxane) microchips using a double-chained cationic surfactant for efficiently resolving fluorescent dye adsorption

This paper described a double-chained cationic surfactant, didodecyldimethylammonium bromide (DDAB). for dynamic surface modification of poly(dimethylsiloxane) (PDMS) microchips to reduce the fluorescent dyes adsorption onto the microchannel. When DDAB with a high concentration was present as the dynamic modification reagent in the running and sample buffer, it not only reversed the direction of electroosmotic flow, but also efficiently suppressed fluorescent dyes pyronine Y (PY) or rhodamine 8 (RB) adsorption onto the chip surface. In addition, vesicles formed by DDAB in the buffer with higher surface charge density and electrophoretic mobility could provide wider migration window and potential for the separation of compounds with similar hydrophobicity. Factors affecting modification, such as pH and concentrations of the buffer, DDAB concentration in the buffer were investigated. Compared with commonly used single-chained cetyltrimethylammonium bromide, DDAB provided a better modification performance.

Solid-state electrochemiluminescence sensor based on the Nafion/poly(sodium 4-styrene sulfonate) composite film

An effective electrochemiluminescence (ECL) sensor based on Nafion/poly(sodium 4-styrene sulfonate) (PSS) composite film-modified ITO electrode was developed. The Nafion/PSS/Ru composite film was characterized by atomic force microscopy, UV-vis absorbance spectroscopy and electrochemical experiments. The Nafion/PSS composite film could effectively immobilize tris(2,2'-bipyridyl)ruthenium(II) (Ru(bpy)(3)(2+)) via ion-exchange and electrostatic interaction. The ECL behavior of Ru(bpy)(3)(2+) immobilized in Nafion/PSS composite film was investigated using tripropylamine (TPA) as an analyte. The detection limit (S/N = 3) for TPA at the Nafion/PSS/Ru composite-modified electrode was estimated to be 3.0 nM, which is 3 orders of magnitude lower than that obtained at the Nafion/Ru modified electrode. The Nafion/PSS/Ru composite film-modified indium tin oxide (ITO) electrode also exhibited good ECL stability. In addition, this kind of immobilization approach was simple, effective, and timesaving.

Formation of [Ru(bpy)(3)](2+)-containing microstructures induced by electrostatic assembly and their application in solid-state detection of electrochemiluminescence

Tris(2,2'-bipyridine)ruthenium(II) ((Ru(bpy)(3)](2+)) is one of the most extensively studied and used electrochemiluminescent (ECL) compounds owing to its superior properties, which include high sensitivity and stability under moderate conditions in aqueous solution. In this paper we present a simple method for the preparation of [Ru(bpy)(3)](2+)-containing microstructures based on electrostatic assembly The formation of such micro-structures occurs in a single process by direct mixing of aqueous solutions of [Ru(bpy)(3)]Cl-2 and K-3[Fe(CN)(6)] at room temperature. The electrostatic interactions between [Ru(bpy)(3)]Cl-2 cations and [Fe(CN)(6)](3-) anions cause them to assemble into the resulting microstructures. Both the molar ratio and concentration of reactants were found to have strong influences on the formation of these microstructures. Most importantly, the resulting [Ru(bpy)(3)](2+)- containing microstructures exhibit excellent ECL behavior and, therefore, hold great promise for solid-state ECL detection in capillary electrophoresis (CE) or CE microchips.

SYNTHESIS AND CHARACTERIZATION OF A CROSSLINKING POLYETHYLENIMINE AS SMART GENE CARRIER AND EFFECTS OF PEGYLATION DEGREE

A smart biodegradable cationic polymer (CBA-PEI) based on the disulfide bond-containing cross-linker cystamine bisacrylamide (CBA) and low molecular weight branched polyethylenimine (1800-Da, PEI1800) was successfully synthesized by Michael addition reaction in our recent study. Furthermore, a series of copolymers (CBA-PEI-PEG) with different PEGylation degree were obtained by the mPEG-SPA (5000-Da) reacting with CBA-PEI at various weight ratios directly. The molecular structures of the resulting polymers CBA-PEI and CBA-PEI-PEG were evaluated by nuclear magnetic resonance spectroscopy (H-1-NMR) and capillary viscosity measurements, all of which had successfully verified formation of the copolymers. The polymer/DNA complexes based on CBA-PEI and CBA-PEI-PEG were measured by dynamic light scattering and gel retardation assay. The results showed that the particle size and zeta potential of complexes were reduced with increasing amount of PEG grafting, even no particle formation. The particle size of CBA-PEI/DNA complexes was in range of 103.1 to 129.1 nm, and the zeta potential was in range of 14.2 to 24.3 mV above the 2:1 weight ratio. In the same measure condition, the particle size of CBA-PEI-PEG complexes was reduced to a range of 32.2 to 55 nm, and the zeta potential was in range of 9.3 to 13.8 mV at the 2:1 weight ratio.

Luminescent supramolecular microstructures containing Ru(bpy)(3)(2+): Solution-based self-assembly preparation and solid-state electrochemiluminescence detection application

In this correspondence, we report on the first preparation of novel, robust Ru(bpy)(3)(2+)-containing supramolecular microstructures via a solution-based self-assembly strategy, carried out by directly mixing H2PtCl6 and Ru(bpy)(3)Cl-2 aqueous solutions at room temperature. It reveals that both the molar ratio and concentration of reactants have a heavy influence on the morphologies of such microstructures. The electrochemical behavior of the Ru(bpy)(3)(2+) components contained in the solid film of the microstructures formed on the electrode surface is also studied and found to exhibit a diffusion-controlled voltammetric feature. Most importantly, such microstructures exhibit excellent electrochemiluminescence (ECL) behaviors and therefore hold great promise as new luminescent materials for solid-state ECL detection in capillary electrophoresis (CE) or CE microchip.

Electrochemiluminescence sensor based on partial sulfonation of polystyrene with carbon nanotubes

Herein, homogenously partial sulfonation of polystyrene (PSP) was performed. An effective electrochemiluminescence (ECL) sensor based on PSP with carbon nanotube (CNTs) composite film was developed. Cyclic voltammetry and electrochemical impendence spectroscopy were applied to characterize this composite film. The PSP was used as an immobilization matrix to entrap the ECL reagent Ru(bpy)(3)(2+) due to the electrostatic interactions between sulfonic acid groups and Ru(bpy)(3)(2+) cations. The introduction of CNTs into PSP acted not only as a conducting pathway to accelerate the electron transfer but also as a proper matrix to immobilize Ru(bpy)(3)(2+) on the electrode by hydrophobic interaction. Furthermore, the results indicated the ECL intensity produced at this composite film was over 3-fold compared with that of the pure PSP film due to the electrocatalytic activity of the CNTs. Such a sensor was verified by the sensitive determinations of 2-(dibutylamino)ethanol and tripropylamine.