Advances in the use of carbonaceous materials for the electrochemical determination of persistent organic pollutants. A review.

Persistent organic pollutants (POPs) are key pollutants due to their persistence, refractory biodegradation, high toxicity and bioaccumulation in the food chain. This review (with 93 refs.) covers the progress made in the past decades in the application of carbonaceous materials for electrochemical detection of POPs as listed in the Stockholm Convention. Following an introduction into the field, typical carbonaceous materials for use in electrodes are discussed, with subsection on carbon nanotubes, graphene, reduced graphene oxide, graphitic carbon nitride and carbon dots. This is followed by a section on application of carbonaceous materials in electrochemical detection, with subsections on the use of carbon nanotubes, of (doped-) graphene, of reduced graphene oxide, of graphitic carbon nitride, and of carbon dots. The review concludes with conclusions and future perspectives. The detection mechanisms of POPs are also discussed. Graphical abstract Advanced carbonaceous materials for the electrochemical determination of persistent organic pollutants.

An image reconstruction method for transmission computed tomography with the constraint of the linear attenuation coefficients.

For the reconstructed image of transmission computed tomography, the linear attenuation coefficients of the diagnosed object may improve the image quality by adding additional constraint besides the projection data. In the present work, an image reconstruction method with the constraint of the linear attenuation coefficients is developed and two models including a classical numerical Shepp-Logan model and a Monte Carlo model are used to show the corresponding benefits. The results indicate that the number of the projection angles is potentially decreased to 1/3 of itself while the quality of the reconstructed image is not deteriorated.

Health Effects of Particulate Uranium Exposure.

Uranium contamination has become a nonnegligible global health problem. Inhalation of particulate uranium is one of the predominant routes of occupational and environmental exposure. Uranium particle is a complex two-phase flow of matter that is both particulate and flowable. This particular physicochemical property may alter its biological activity. Epidemiological studies from occupationally exposed populations in the uranium industry have concluded that there is a possible association between lung cancer risk and uranium exposure, while the evidence for the risk of other tumors is not sufficient. The toxicological effects of particulate uranium exposure to animals have been shown in laboratory tests to focus on respiratory and central nervous system damage. Fibrosis and tumors can occur in the lung tissue of the respiratory tract. Uranium particles can also induce a concentration-dependent increase in cytotoxicity, targeting mitochondria. The understanding of the health risks and potential toxicological mechanisms of particulate uranium contamination is still at a preliminary stage. The diversity of particle parameters has limited the in-depth exploration. This review summarizes the current evidence on the toxicology of particulate uranium and highlights the knowledge gaps and research prospects.

Uranium inhibits mammalian mitochondrial cytochrome c oxidase and ATP synthase.

As an emerging pollutant, uranium poses serious concerns to ecological and human health. The kidney has been established as a major deposition site and the most sensitive target organ for uranium poisoning, and the underlying toxicological mechanisms have been associated with oxidative stress and mitochondrial respiration. However, the identities of key molecular targets in uranium-induced toxicity remain elusive. In this study, we comprehensively evaluated the in vitro effects of uranium on ten critical enzymes in the mitochondrial respiration pathway and discovered that respiratory chain complex IV (cytochrome c oxidase) and complex V (ATP synthase) were strongly inhibited. The inhibitory effects were validated with mitochondria from human renal proximal tubule cells-the most affected renal site in uranium poisoning. The IC50 values (around 1 mg/L) are physiologically relevant, as they are comparable to known kidney accumulation levels in uranium poisoning. In addition, these inhibitory effects could explain the well-documented uranium-induced reactive oxygen species generation and mitochondrial alterations. In conclusion, cytochrome c oxidase and ATP synthase are possibly key molecular targets underlying the toxic effects of uranium.

Graphene quantum dot electrochemiluminescence increase by bio-generated H2O2 and its application in direct biosensing.

In this study, a novel signal-increase electrochemiluminescence (ECL) biosensor has been developed for the detection of glucose based on graphene quantum dot/glucose oxidase (GQD/GOx) on Ti foil. The proposed GQD with excellent ECL ability is synthesized through a green one-step strategy by the electrochemical reduction of graphene oxide quantum dot. Upon the addition of glucose, GOx can catalytically oxidize glucose and the direct electron transfer between the redox centre of GOx and the modified electrode also has been realized, which results in the bio-generated H2O2 for ECL signal increase in GQD and realizes the direct ECL detection of glucose. The signal-increase ECL biosensor enables glucose detection with high sensitivity reaching 5 × 10-6 mol l-1 in a wide linear range from 5 × 10-6 to 1.5 × 10-3 mol l-1. Additionally, the fabrication process of such GQD-based ECL biosensor is also suitable to other biologically produced H2O2 system, suggesting the possible applications in the sensitive detection of other biologically important targets (e.g. small molecules, protein, DNA and so on).

Graphene oxide amplified electrochemiluminescence of graphitic carbon nitride and its application in ultrasensitive sensing for Cu(2+).

Here for the first time, we present a novel electrochemiluminescence (ECL) sensor based on graphitic carbon nitride/graphene oxide (g-C3N4/GO) hybrid for the ultrasensitive detection of Cu(2+), which is a common pollutant in environmental system. The g-C3N4/GO shows stable ECL signal in the presence of the self-produced coreactant from oxygen reduction, and the ECL signal could be effectively quenched by Cu(2+), the possible ECL detection mechanism has been proposed in detail. GO can not only significantly enhance the cathodic ECL signal of g-C3N4 (∼3.8 times), but also serve as immobilization platform for g-C3N4. After optimization of experimental conditions, the proposed protocol can offer an ultrasensitive, highly selective and recyclable method for the detection of Cu(2+) with a low detection limit of 1.0 × 10(-11) M and a wide linear range from 1.0 × 10(-11) to 1.0 × 10(-7) M. Moreover, the practicability of the ECL sensor in real wastewater samples is also tested, showing that the proposed ECL sensor could be a promising alternative method for the emergency and routine monitoring of Cu(2+) in real sample.

Design and efficient synthesis of a pillar[5]arene-based [1]rotaxane.

A pillar[5]arene-based [1]rotaxane was simply prepared in a high yield of 73%. Its stucture was confirmed by (1)H NMR, 2D NMR spectra, mass spectra and theoretical calculation.

A responsive supramolecular polymer formed by orthogonal metal-coordination and cryptand-based host-guest interaction.

Herein, a cation responsive linear supramolecular polymer was constructed in an orthogonal fashion by unifying the themes of coordination-driven self-assembly and cryptand-based host-guest interaction.

Pseudorotaxanes from self-assembly of two crown ether-based cryptands and a 1,2-bis(pyridinium) ethane derivative.

Pseudorotaxanes from self-assembly of two crown ether-based cryptand wheels and a 1,2-bis(pyridinium) ethane derivative axle were prepared.

Four constitutional isomers of BMpillar[5]arene: synthesis, crystal structures and complexation with n-octyltrimethyl ammonium hexafluorophosphate.

Four constitutional isomers of BMpillar[5]arene were prepared from 1-butoxy-4-methoxybenzene and they showed different binding abilities with n-octyltrimethyl ammonium hexafluorophosphate.

DIBPillar[n]arenes (n = 5, 6): syntheses, X-ray crystal structures, and complexation with n-octyltriethyl ammonium hexafluorophosphate.

DIBPillar[n]arenes (n = 5, 6) were synthesized. They showed different host-guest properties with n-octyltriethyl ammonium hexafluorophosphate G due to their different cavity sizes. DIBpillar[5]arene showed no complexation with G, while DIBpillar[6]arene formed a 1:1 complex with G with an association constant of 334 (±24) M(-1) in chloroform. In this letter, the first pillar[6]arene crystal structure and the first investigation of the host-guest chemistry of pillar[6]arenes are reported.

Syntheses of copillar[5]arenes by co-oligomerization of different monomers.

Three copillar[5]arenes, pillar[5]arenes containing different repeating units, were successfully prepared by co-oligomerization of different monomers. It was demonstrated that the yields of pillararenes could be improved by using hydroquinone diethers with appropriate aliphatic chain lengths. Pseudorotaxane-type threaded structures were obtained in the solid state by the inclusion of an n-hexane molecule into the cavity of either a homopillar[5]arene, a pillar[5]arene containing only one repeating unit, or a copillar[5]arene.

Fabrication of DNA functionalized carbon nanotubes/Cu(2+) complex by one-step electrodeposition and its sensitive determination of nitrite.

In this paper, DNA functionalized single-wall carbon nanotubes/Cu(2+) (DNA-CNTs/Cu(2+)) complex was one-step electrodeposited onto the glassy carbon electrode (GCE), which fabricated a DNA-CNTs/Cu(2+)/GCE sensor to detect nitrite. Cyclic voltammogram of DNA-CNTs/Cu(2+)/GCE showed a pair of well-defined redox peaks for Cu(2+)/Cu(+). Compared with DNA-CNTs/GCE and DNA-Cu(2+)/GCE, the prepared DNA-CNTs/Cu(2+)/GCE exhibited more excellent electrochemical properties. Thus, the prepared DNA-CNTs/Cu(2+)/GCE was proposed as nitrite sensor. The effects of Cu(2+), CNTs and DNA concentration in the mixture together with electrodeposition time and determination conditions such as applied potential, pH value on the current response of DNA-CNTs/Cu(2+)/GCE toward nitrite were optimized to obtain the maximal sensitivity. In addition, electrochemical experiments revealed that the modified electrode showed high electrocatalytic activity to the reduction of nitrite ion (NO(2)(-)). The linear range for the detection of NO(2)(-) was 3x10(-8) to 2.6x10(-3)M, and the response was very fast (less than 3s). A low detection limit of 3x10(-8)M (S/N=3) for NO(2)(-) was achieved.