Determination of cysteine,homocysteine, cystine,and homocystine in biological fluids by HPLC using fluorosurfactant‐capped gold nanoparticles as postcolumn colorimetric reagents

We have demonstrated for the first time the suitability of fluorosurfactant‐capped spherical gold nanoparticles as HPLC postcolumn colorimetric reagents for the direct assay of cysteine, homocysteine, cystine, and homocystine. The success of this work was based on the use of an on‐line tris(2‐carboxyethyl)phosphine reduction column for cystine and homocystine. Several parameters affecting the separation efficiency and the postcolumn colorimetric detection were thoroughly investigated. Under the optimized conditions, cysteine, homocysteine, cystine, and homocystine in human urine and plasma samples were determined. Detection limits for cysteine, homocysteine, cystine, and homocystine ranged from 0.16–0.49 μM. The accuracy in terms of recoveries ranged between 94.0–102.1%. This proposed method was rapid, inexpensive, and simple.     

Ultra‐trace level determination of diquat and paraquat residues in surface and drinking water using ion‐pair liquid chromatography with tandem mass spectrometry: A comparison of direct injection and solid‐phase extraction methods

Direct injection and solid‐phase extraction methods for the determination of diquat and paraquat in surface and drinking water were developed using liquid chromatography with tandem mass spectrometry. The signal intensities of analytes based on six ion‐pairing reagents were compared with each other, and 12.5 mM nonafluoropentanoic acid was selected as the best suited amongst them. A clean‐up method was developed using Oasis hydrophilic–lipophilic balance; this was compared to the direct injection method, with respect to limits of detection, interference, precision, and accuracy. Limits of quantification of diquat and paraquat were 0.03 and 0.01 μg/L using the direct injection method, and 0.002 and 0.001 μg/L using the hydrophilic–lipophilic balance method. When the hydrophilic–lipophilic balance method was used to analyze target compounds in 114 surface water and 30 drinking water samples, paraquat and diquat were detected within a concentration range of 0.001–0.12 and 0.002–0.038 μg/L in surface water, respectively. When the direct injection method was used to analyze target compounds in the same samples, the detected concentrations of paraquat and diquat were within 25% in samples being >0.015 μg/L using the hydrophilic–lipophilic balance method. The liquid chromatography with tandem mass spectrometry method using direct injection can thus be used for routine monitoring of paraquat and diquat in surface and drinking water.     

Effects of substrate and transfer on CVD-grown graphene over sapphire-induced Cu films

We differentiated the effects of Cu films deposited on single crystalline a-,r-,and c-plane sapphire substrates upon graphene films synthesized with atmospheric pressure chemical vapor deposition(CVD).The data illustrate that the realization of high-crystalline Cu film is dependent not only on the crystallinity of underlying substrate,but also on the symmetric match of crystallographic geometry between metal film and substrate.We also systematically investigated the effects of PMMA removal on the Raman ID/IG and IG/I2D values of transferred graphene.The results reveal that different PMMA removal methods do not alter the ID/IG values;instead,the residue of PMMA increases the IG/I2D values and the thermal decomposition of PMMA leads to higher IG/I2D values than the removal of PMMA with acetone.The effects of PMMA removal on variations of the Raman spectra are also discussed.     

Ethylene (co-)polymerization by long-lifetime half-sandwich zirconium catalyst bearing a [SSO]-carborane ligand

Half-sandwich zirconium complex 3 containing tridentate carborane [S,S,O] ligand 2 [(HOC6H2R2-4,6)(CH2)SC(B10H10) C(Ph)2P=S, R=tBu] was synthesized by the reaction of CpZrCl3(Cp=η5-C5H5) with sodium salt of ligand 2. Zirconium complex 3 was characterized by elemental and NMR analyses. DFT calculations were also performed on complex 3 to analyze the stereochemistry. The results from DFT calculations indicate that structure S1, in which no sulfur atom bonds to the zirconium atom, exists at the lowest energy level. In the presence of methylaluminoxane(MAO), complex 3 exhibited good catalytic activities for ethylene polymerization and long life-time up to 10 h. Moreover, the complex 3/MAO system displayed excellent catalytic activities toword ethylene copolymerization with 1-hexene or polar olefins.     

Extraction of coal-tar pitch using NMP/ILs mixed solvents

Coal-tar pitch(CP)is a promising carbon raw material for producing needle coke,carbon fiber etc.During processing,the H/C ratio,ash content,and quinoline insoluble(QI)in the CP are the key factors that influence the material preparation.In this study,NMP was selected to extract CP first;then[BMIM]Cl/NMP mixed solvent was used;and finally a series of ionic liquids(ILs)mixtures with NMP were developed for the extraction of CP to obtain the refined pitch.The extracts were analyzed via elemental analysis,TGA,FT-IR,and 13C-NMR.Results indicate that different NMP/IL mass ratios or different kinds of ILs have impact on the extraction yield.The relationship of the hydrogen to carbon(H/C)ratio changed with different solvents and QI extracts were obtained.Results showed that the H/C ratios changed little between NMP extracts and could be adjusted by changing the NMP/ILs mass ratio or using different ILs.The extracts are suitable for preparation mesophase pitch because of no ash content,low QI,and appropriate H/C ratios.As a result,NMP can be used to refine pitch.In addition,[BMIM]Cl is good mixed with NMP for CP extraction,because it can obtain a relatively high yield under the same extraction conditions.     

Effect of Various Intercalators on the Fenton‐Type Oxidative Cleavage of Double‐Stranded DNA

The intensity of the linear dichroism (LD) in the absorption region of DNA (about 260 nm) decreased with time in the presence of [Fe(EDTA)]²⁺ (EDTA=ethylenediaminetetraacetic acid), H₂O₂, and ascorbate. The decrease in the LD signal indicated either an increase in flexibility, a shortening of the DNA stem, or both, owing to oxidative cleavage, and was best described by the difference between the two single‐exponential‐decay curves, thereby suggesting the involvement of two sequential first‐order reactions. The fast reaction was assigned to cleavage of one of two DNA strands, which increased the flexibility of the DNA. The slow reaction corresponded to cleavage at or near the first cleavage site, thereby shortening the DNA stem. The presence of an intercalator, including ethidium, propidium, 9‐aminoacridine, and proflavine, inhibited the first step of the cleavage reaction. One of the possible reasons for the observed inhibition might be a change in the DNA conformation near the intercalation site. Intercalation caused an unwinding and elongation of the DNA and resulted in changes in the location of the H atoms of the sugar moiety, which is known to be the main site at which hydroxyl radicals react.     

Photo‐ and pH‐Tunable Multicolor Fluorescent Nanoparticle‐Based Spiropyran‐ and BODIPY‐Conjugated Polymer with Graphene Oxide

We report a stimuli‐responsive fluorescent nanomaterial, based on graphene oxide coupled with a polymer conjugated with photochromic spiropyran (SP) dye and hydrophobic boron dipyrromethane (BODIPY) dye, for application in triggered target multicolor bioimaging. Graphene oxide (GO) was reduced by catechol‐conjugated polymers under mildly alkaline conditions, which enabled to formation of functionalized multicolor graphene nanoparticles that can be induced by irradiation with UV light and by changing the pH from acidic to neutral. Investigation of these nanoparticles by using AFM, fluorescence emission, and in vitro cell and in vivo imaging revealed that they show different tunable colors in bioimaging applications and, more specifically, in cancer‐cell detection. The stability, biocompatibility, and quenching efficacy of this nanocomposite open a different perspective for cell imaging in different independent colors, sequentially and simultaneously.     

Efficient Diketopyrrolopyrrole‐Based Small‐Molecule Bulk‐Heterojunction Solar Cells with Different Electron‐Donating End‐Groups

A series of small molecules that contained identical π‐spacers (ethyne), a central diketopyrrolopyrrole (DPP) unit, and different aromatic electron‐donating end‐groups were synthesized and used in organic solar cells (OSCs) to study the effect of electron‐donating groups on the device performance. The three compounds, DPP‐A‐Ph , DPP‐A‐Na , and DPP‐A‐An , possessed intense absorption bands that covered a wide range, from 350 to 750 nm, and relatively low HOMO energy levels, from ?5.50 to ?5.55 eV. DPP‐A‐An , which contained anthracene end‐groups, demonstrated a stronger absorbance and a higher hole mobility than DPP‐A‐Ph , which contained phenyl groups, and DPP‐A‐Na , which contained naphthalene units. The power‐conversion efficiencies (PCEs) of OSCs based on organic:PC₇₁BM blends (1:1, w/w) with a processed DIO additive were 3.93 % for DPP‐A‐An , 3.02 % for DPP‐Na , and 2.26 % for DPP‐A‐Ph . These findings suggest that a DPP core that is functionalized with electron‐donating capping groups constitutes a promising new class of solution‐processable small molecules for OSC applications.