Reduced graphene oxide as an efficient support for CdS-MoS₂ heterostructures for enhanced photocatalytic H₂ evolution

Ben Ali, Monaam,Jo, Wan-Kuen,Elhouichet, Habib,Boukherroub, Rabah Elsevier 2017 International journal of hydrogen energy Vol.42 No.26

<P><B>Abstract</B></P> <P>Cadmium sulphide nanorods-reduced graphene oxide-molybdenum sulphide(CdS-rGO-MoS<SUB>2</SUB>) composites were successfully synthesized using hydrothermal process for enhancing the interfacial contact between CdS nanorods and MoS<SUB>2</SUB> layer. The good contact between CdS and MoS<SUB>2</SUB> is important for improving the photocatalytic hydrogen (H<SUB>2</SUB>) evolution. The morphological and structural studies showed the production of highly pure CdS phase with nanorod-like structure dispersed on rGO-MoS<SUB>2</SUB> layer. X-ray photoelectron spectroscopy (XPS) and Raman results confirmed the reduction of graphene oxide (GO) into reduced graphene oxide (rGO). The higher photocurrent density of CdS-rGO-MoS<SUB>2</SUB> composites compared to CdS/MoS<SUB>2</SUB> and the fluorescence quenching observed for this composite provided some evidence for an inhibition of electron-hole recombination, which leads to a longer life time of the photogenerated carriers. Fast electron transfer can occur from CdS nanorods by the bidimensionnel rGO area to MoS<SUB>2</SUB> layer due to the intimate interfacial contact. Composite CdS-rGO-MoS<SUB>2</SUB> with 20 wt% rGO was found to be the most effective photocatalyst for H<SUB>2</SUB> evolution (7.1 mmol h<SUP>−1</SUP>g<SUP>−1</SUP>). The good photocatalytic performance arose from the positive synergistic effect between CdS, rGO and MoS<SUB>2</SUB> elements.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CdS-rGO-MoS<SUB>2</SUB> composite was prepared by a hydrothermal technique. </LI> <LI> Reduced graphene oxide sheets led to a good adhesion between CdS and MoS<SUB>2</SUB>. </LI> <LI> Higher photocurrent density of CdS-rGO-MoS<SUB>2</SUB> composite is observed. </LI> <LI> The fluorescence of the nanocomposite was partially quenched. </LI> <LI> Good photocatalytic performance under visible light irradiation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Influence of adsorption parameters of basic red dye 46 by the rough and treated Algerian natural phosphates

Zahra Graba,Souaad Hamoudi,Djebar Bekka,Nacer Bezzi,Rabah Boukherroub 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.25 No.-

The paper reports on the adsorption behavior of basic red dye 46 from aqueous solution onto rough and treated Algerian natural phosphates. Adsorption tests were realized in static mode on natural rock phosphate and treated samples by sifting, chemical or thermal way. The adsorption process was evaluated as a function of various operating parameters such as contact time, pH of the medium, temperature, concentration, agitation speed and adsorbent mass. The adsorption ability depends mainly on the nature of mineralogical species as well as on the smoothness of the grains. It was found that the dye has more affinity for the carbonate-rich than for the phosphate-rich material. The amount of the dye adsorbed increases with the mass of adsorbent. The adsorption process was pH-dependent with a high adsorption capacity at pH 8. The chemical and thermal treatments performed on different phosphate samples have affected negatively their adsorption capacity of the dye used. The experimental isotherm data were analyzed using the Langmuir, Freundlich and Temkin models. The equilibrium data fit well the Langmuir isotherm. The calculations of the maximum amounts (qm) obtained from this model have shown that it is the fine fraction (T) which adsorbs the highest amount (28.5 mg g1), followed by the coarse fraction (C) (15.62 mg g1) and raw phosphate (RP) (14.7 mg g1). The best results were obtained for dye concentration of 15 mg g1, adsorbent mass of 3 g L1, agitation speed of 300 trs min1, and pH 8 at 20 8C. The experimental data were analyzed using three kinetic models: the pseudo first order, pseudo second order and intraparticle diffusion models. The linear regression, standard statistics of root mean squared error (RMSE) was carried out to support the best fit kinetic models. Based on the low RMSE values, the pseudo second order model is the one that best describes the adsorption of basic red dye 46 on phosphates. The results obtained in this study suggest that Algerian natural phosphates may be used as an efficient and low cost sorbent material for organic pollutants, and thus represent a promising alternative for eliminating dyes from industrial wastewaters.

Surface-assisted laser desorption–ionization mass spectrometry on titanium dioxide (TiO₂) nanotube layers

Piret, Gaë,lle,Kim, Doohun,Drobecq, Hervé,Coffinier, Yannick,Melnyk, Oleg,Schmuki, Patrik,Boukherroub, Rabah The Royal Society of Chemistry 2012 The Analyst Vol.137 No.13

<P>The paper reports on the use of a titanium oxide (TiO<SUB>2</SUB>) nanotube layer as a sensitive substrate for surface-assisted laser desorption–ionization mass spectrometry (SALDI-MS) of peptides and small molecules. The nanotube layers were prepared by electrochemical anodization of titanium foil. The optimized TiO<SUB>2</SUB> nanotubes morphology coupled to a controlled surface chemistry allowed desorption–ionization (D/I) of a peptide mixture (Mix1) with a detection limit of 10 femtomoles for the neurotensin peptide. The performance of the TiO<SUB>2</SUB> nanotubes for the D/I of small molecules was also tested for the detection of sutent, a small tyrosine kinase inhibitor, and verapamil. A detection limit of 50 fmol was obtained for these molecules, as compared to 500 fmol using classical matrix-assisted laser desorption–ionization mass spectrometry (MALDI-MS). Both amorphous and anatase TiO<SUB>2</SUB> layers displayed a comparable performance for D/I of analyte molecules. In a control experiment, we have performed D/I of analyte molecules on a flat TiO<SUB>2</SUB> layer. The absence of signal emphasizes the role of the nanostructured substrate in the D/I process.</P> <P>Graphic Abstract</P><P>The paper reports the use of a titanium oxide (TiO<SUB>2</SUB>) nanotube layer as a sensitive substrate for surface-assisted laser desorption–ionization mass spectrometry (SALDI-MS) of peptides and small molecules. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2an35207a'> </P>

Short-term exposure to gold nanoparticle suspension impairs swimming behavior in a widespread calanoid copepod

Michalec, Franç,ois-Gaë,l,Holzner, Markus,Barras, Alexandre,Lacoste, Anne-Sophie,Brunet, Loï,c,Lee, Jae-Seong,Slomianny, Christian,Boukherroub, Rabah,Souissi, Sami Elsevier 2017 Environmental pollution Vol.228 No.-

<P><B>Abstract</B></P> <P>Calanoid copepods play an important role in the functioning of marine and brackish ecosystems. Information is scarce on the behavioral toxicity of engineered nanoparticles to these abundant planktonic organisms. We assessed the effects of short-term exposure to nonfunctionalized gold nanoparticles on the swimming behavior of the widespread estuarine copepod <I>Eurytemora affinis</I>. By means of three-dimensional particle tracking velocimetry, we reconstructed the trajectories of males, ovigerous and non-ovigerous females. We quantified changes in their swimming activity and in the kinematics and geometrical properties of their motion, three important descriptors of the motility patterns of zooplankters. In females, exposure to gold nanoparticles in suspension (11.4 <I>μ</I>g L<SUP>−1</SUP>) for 30 min caused depressed activity and lower velocity and acceleration, whereas the same exposure caused minimal effects in males. This response differs clearly from the hyperactive behavior that is commonly observed in zooplankters exposed to pollutants, and from the generally lower sensitivity of female copepods to toxicants. Accumulation of gold nanoparticles on the external appendages was not observed, precluding mechanical effects. Only very few nanoparticles appeared sporadically in the inner part of the gut in some samples, either as aggregates or as isolated nanoparticles, which does not suggest systemic toxicity resulting from pronounced ingestion. Hence, the precise mechanisms underlying the behavioral toxicity observed here remain to be elucidated. These results demonstrate that gold nanoparticles can induce marked behavioral alterations at very low concentration and short exposure duration. They illustrate the applicability of swimming behavior as a suitable and sensitive endpoint for investigating the toxicity of nanomaterials present in estuarine and marine environments. Changes in swimming behavior may impair the ability of planktonic copepods to interact with their environment and with other organisms, with possible impacts on population dynamics and community structure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We studied the motion of copepods exposed to non-functionalized gold nanoparticles. </LI> <LI> Exposure depressed swimming activity and velocity in females but not in males. </LI> <LI> This response differs from the hyperactivity commonly observed with pollutants. </LI> <LI> We observed accumulation neither in the digestive track nor on the appendages. </LI> <LI> Nanomaterials can induce marked behavioral toxicity at very low concentrations. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>