This review presents an exhaustive and in-depth description of inorganic nanoparticle biosynthesis from photosynthetic organisms, known mechanisms and bio-applications.

Several methodologies have been devised for the design of nanomaterials. The “Holy Grail” for materials scientists is the cost-effective, eco-friendly synthesis of nanomaterials with controlled sizes, shapes and compositions, as these features confer to the as-produced nanocrystals unique properties making them appropriate candidates for valuable bio-applications. The present review summarizes published data regarding the production of nanomaterials with special features via sustainable methodologies based on the utilization of natural bioresources. The richness of the latter, the diversity of the routes adopted and the tuned experimental parameters have led to the fabrication of nanomaterials belonging to different chemical families with appropriate compositions and displaying interesting sizes and shapes. It is expected that these outstanding findings will encourage researchers and attract newcomers to continue and extend the exploration of possibilities offered by nature and the design of innovative and safer methodologies towards the synthesis of unique nanomaterials, possessing desired features and exhibiting valuable properties that can be exploited in a profusion of fields.

Microalgae are microorganisms of choice in biotechnology thanks to their wide range of potential bio-applications, such as over-expression of pigments, bioremediation, biofuel production and toxicity studies. Recently, microalgae have been gaining attention from materials scientists worldwide owing to their versatility, and the ease and the variety of procedures through which the biosynthesis of valuable nanomaterials is implemented. This has resulted mainly in the production of nanoparticles made of noble metals, alloys, oxides and chalcogenides. Although still burgeoning, the biosynthesis of nanomaterials based on the exploitation of microalgal resources may thrive and witness dramatic developments in the near future.

International audiencePoly(oligoethylene glycol methacrylate), POEGMA, brushes were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) on gold-coated silicon wafers. Prior to ATRP, the substrates were grafted by brominated aryl initiators via the electrochemical reduction of a noncommercial parent diazonium salt of the formula BF4-, N-+(2)-C6H4-CH(CH3)Br. The diazonium-modified gold plates (Au-Br) served as macroinitiators for ATRP of OEGMA which resulted in hydrophilic surfaces (Au-POEGMA) that could be used for two distinct objectives: (i) resistance to fouling by Salmonella Typhimurium; (ii) specific recognition of the same bacteria provided that the POEGMA grafts are activated by anti-Salmonella. The Au-POEGMA plates were characterized by XPS, polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS) and contact angle measurements. Both Beer-Lambert equation and Tougaard's QUASES software indicated a POEGMA thickness that exceeds the critical similar to 10 nm value necessary for obtaining a hydrophilic polymer with effective resistance to cell adhesion. The Au-POEGMA slides were further activated by trichlorotriazine (TCT) in order to covalently bind anti-Salmonella antibodies (AS). The antibody-modified Au-POEGMA specimens were found to specifically attach Salmonella Typhimurium bacteria. This work is another example of the diazonium salt/ATRP process to provide biomedical polymer surfaces

The synthesis of nickel cobalt oxide materials and their electrocatalytic performance toward the oxygen reduction and evolution reactions are reported. Nickel cobalt oxides were synthesized in a sol‐gel process with different precursors, namely nitrate, sulfate, and chloride. Structural analyses show that the structures have mesoporous morphologies and indicate the formation of nickel cobalt oxide spinel structures with a size ranging from 35 to 65 nm. Furthermore, the physicochemical properties differ depending on the nature of the selected precursors, including the materials’ morphology and the chemical composition. Electrocatalytic investigations demonstrate that the catalytic activity toward the oxygen reduction reaction (ORR) could be modulated between two‐ and four‐electron pathways, depending on the precursors used. The Cl−NiCoO sample displays a selective two‐electron reduction of O2, with H2O2 production higher than 90 %. The sample prepared using sulfate displays the highest performance toward the oxygen evolution reaction (OER), with a low overpotential value (0.34 V) to drive a current density of 10 mA.cm−1. Overall, these results confirm that the chemical composition of the precursor used during the nanomaterials synthesis can be used to tune the electrocatalytic performances toward ORR and OER.

The electrochemical and spectroelectrochemical properties of N,N-diphenyl-1,4-phenylenediamine (PDA) were investigated in the absence and in the presence of 18-crown-6-ether (18C6) or dibenzo 24-crown-8-ether (DB24C8), in a solution of tetrabutylammonium hexafluorophosphate (TBAPF6) in acetonitrile and in the presence of trifluoroacetic acid (TFA) only for 18C6. In neutral acetonitrile, PDA undergoes two reversible oxidation processes, which lead first to the formation of the cation-radical considered as mixed valence (MV) compound, and then to the dicationic species. When 18C6 is added in the medium and depending on 18C6 concentration, cyclic voltammetry shows a marked shift to more cathodic potentials of the current waves of the second redox process only. This is attributed to a strong interaction between the PDA(+2) dication and two 18C6 molecules, leading to the formation of a supramolecular complex with an association constant value K(a) = 7.0 × 10(7) M(-2). The interaction of 18C6 with PDA(+2) dication has a direct effect on the PDA(+.) cation-radical corresponding to a decrease in the lifetime of the MV compound and of the intramolecular electron transfer rate when 18C6 is present. Indeed, it results in a large decrease in the intervalence charge transfer (IV-CT) between the two amine centers in the MV compound (k(th) = 1.35 × 10(10) s(-1) in 18C6-free neutral solution containing 5.0 × 10(-4) M PDA, and k(th) = 3.6 × 10(9) s(-1) in the same medium at [18C6]/[PDA] = 20/1). And the comproportionation constant K(co) falls from 6.0 × 10(6) in 18C6-free solution to 1.6 × 10(3) at [18C6]/[PDA] = 20/1. In acidified acetonitrile and when TFA concentration is increased, PDA still shows the two successive and reversible oxidation processes, but both are shifted to more anodic potentials. However, when 18C6 is added, the two oxidation waves shift to more cathodic potentials, indicating an interaction of all protonated PDA redox states with 18C6, resulting in the formation of supramolecular complexes. In the presence of TFA, the value of K(co) is decreased to 4.3 × 10(4), but it remains unchanged when 18C6 is added, indicating no change in the lifetime of the MV compound. In this medium, IV-CT in the MV compound is greater with 18C6 (k(th) = 2.3 × 10(10) s(-1) for [18C6]/[PDA] = 20/1) than without (k(th) = 1.4 × 10(9) s(-1)), which indicates a more important IV-CT rate when 18C6 is present. The results show for the first time that is it possible to control the IV-CT rate, through the lifetime and the potential range where the MV compound is the most important. This control is not obtained as usual by chemical modification of the structure of the starting molecule, but by varying either the acidity or the 18C6 concentration as external stimuli, which lead to reversible formation/dissociation of a supramolecular complex species. Moreover, we also studied the electrochemical properties of PDA in the presence of wider crown ether such as DB24C8. We showed that PDA undergoes the same electrochemical behavior with DB24C8 th...

The present work reports the immobilization of thin ionic layer onto glassy carbon and its use as a platform for the electrochemical growth of metallic nanoparticles. The ionic layer was electrochemically grafted during the reduction of the in situ generated diazonium bearing imidazolium, 1-nitrophenylethyl 3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Next, the metallic nanoparticles, platinum or palladium, were electrochemically grown onto the ionic layer modified electrodes. The physico-chemical properties of the generated modified electrodes were studied by surfaces analysis and electrochemical methods. Furthermore, the electron transfer properties of the modified electrodes were investigated at the local scale using scanning electrochemical microscope (SECM). The obtained results confirm the success of the ionic layer grafting as well as the formation of the metallic nanoparticles. The SECM investigations display change in the electron transfer properties of the modified electrodes depending on the used redox mediator. Finally, the as-prepared modified electrodes catalytic performances of towards the hydrogen evolution reaction (HER) were evaluated. Interestingly, the presence of the ionic layer displays an increase of the catalytic performances, for both investigated metallic nanoparticles. This behavior is probably due to the existence of synergistic effect between the grafted ionic layer and the metallic nanoparticles. Therefore, it is anticipated that the ionic layer immobilization had several features including the tuning of the electrode interface properties, acting as a platform and binder for the nanoparticles growth as well as the enhancement of the electrocatalytic performances.

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