Bio-based matrix photocatalysts for photodegradation of antibiotics.

Antibiotics development during the last century permitted unprecedent medical advances. However, it is undeniable that there has been an abuse and misuse of antimicrobials in medicine and cosmetics, food production and food processing, in the last decades. The pay toll for human development and consumism is the emergence of extended antimicrobial resistance and omnipresent contamination of the biosphere. The One Health concept recognizes the interconnection of human, environmental and animal health, being impossible alter one without affecting the others. In this context, antibiotic decontamination from water-sources is of upmost importance, with new and more efficient strategies needed. In this framework, light-driven antibiotic degradation has gained interest in the last few years, strongly relying in semiconductor photocatalysts. To improve the semiconductor properties (i.e., efficiency, recovery, bandgap width, dispersibility, wavelength excitation, etc.), bio-based supporting material as photocatalysts matrices have been thoroughly studied, exploring synergetic effects as operating parameters that could improve the photodegradation of antibiotics. The present work describes some of the most relevant advances of the last 5 years on photodegradation of antibiotics and other antimicrobial molecules. It presents the conjugation of semiconductor photocatalysts to different organic scaffolds (biochar and biopolymers), then to describe hybrid systems based on g-C3N4 and finally addressing the emerging use of organic photocatalysts. These systems were developed for the degradation of several antibiotics and antimicrobials, and tested under different conditions, which are analyzed and thoroughly discussed along the work.

Optically Sensitive and Magnetically Identifiable Supraparticles as Indicators of Surface Abrasion.

Identifying and ensuring the integrity of products plays an important role in today's globalized world. Miniaturized information taggants in the packaging surface are therefore required to monitor the product itself instead of applying external labels. Ideally, multiple types of information are stored in such additives. In this work, micrometer-sized core-shell particles (supraparticles) were developed to provide material surfaces with both an identifier and a surface abrasion indication functionality. The core of the supraparticles contains iron oxide nanoparticles that allow identification of the surface with a spectral magnetic code resolved by magnetic particle spectroscopy. The fluorescent silica nanoparticles in the supraparticle shell can be abraded by mechanical stress and resolved by fluorescence spectroscopy. This provides information about the mechanical integrity of the system. The application as surfaces, that contain several types of information in one supraparticle, was demonstrated here by incorporating such bifunctional supraparticles as additives in a surface coating.

Modulation of laccase catalysed oxidations at the surface of magnetic nanoparticles.

We explored the coupling of laccases to magnetic nanoparticles (MNPs) with different surface chemical coating. Two laccase variants offering two opposite and precise orientations of the substrate oxidation site were immobilised onto core-shell MNPs presenting either aliphatic aldehyde, aromatic aldehyde or azide functional groups at the particles surface. Oxidation capabilities of the six-resulting laccase-MNP hybrids were compared on ABTS and coniferyl alcohol. Herein, we show that the original interfaces created differ substantially in their reactivities with an amplitude from 1 to > 4 folds depending on the nature of the substrate. Taking enzyme orientation into account in the design of surface modification represents a way to introduce selectivity in laccase catalysed reactions.

Magnetically recoverable catalysts based on mono- or bis-(NHC) complexes of palladium for the Suzuki-Miyaura reaction in aqueous media: two NHC-Pd linkages are better than one.

Pre-synthesized mono- and bis(NHC) palladium complexes have been grafted onto magnetic core/shell γ-Fe2O3/silica particles and tested as catalysts in model Suzuki-Miyaura coupling reactions. The bis(NHC) immobilized complex was found to be a robust catalyst that can operate under mild conditions in aqueous media, even for the activation of chloroarene, whereas the mono(NHC) counterpart rapidly deactivates. Moreover, it can be readily recovered by magnetic separation and reused many times, providing very high productivities, and with so low leaching of palladium that the crude products obtained contain ≤10 ppm Pd.

Epoxy-terminated self-assembled monolayers containing internal urea or amide groups.

We report the synthesis of new coupling agents with internal amide or urea groups possessing an epoxy-terminal group and trimethoxysilyl-anchoring group. The structural characterizations of the corresponding self-assembled monolayers (SAMs) were performed by polarization modulation infrared reflection adsorption spectroscopy (PM-IRRAS). The molecular assembly is mainly based on the intermolecular hydrogen-bonding between adjacent amide or urea groups in the monolayers. Because of the steric hindrance of amide or urea groups, the distance between the alkyl chains is too large to establish van der Waals interactions, inducing their disorder. The reactivity of the epoxy-terminal groups was successfully investigated through reaction with a fluorescent probe. We show that SAMs containing internal urea or amide groups exhibited a higher density of accessible epoxide groups than the corresponding long-chain (C22) glycidyl-terminated SAM.

Immobilization of cryptophane derivatives onto SiO2/Au and Au substrates.

The synthesis of a cryptophane molecule bearing five methoxy substituents and an alkanethiol chain, 4, as well as its subsequent grafting onto a gold surface, is reported. Immobilization of cryptophane derivatives onto silica (SiO2/Au) surfaces was also performed by reacting a cryptophane molecule bearing one or six acid functions, 5 or 6, respectively, with an amino-terminated self-assembled monolayer (SAM). Polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) was used to characterize the two types of cryptophane monolayers. Surface coverage of cryptophane monolayers was estimated by comparing the PM-IRRAS intensity of cryptophane bands with that calculated from the optical constants of pentamethoxy-cryptophane for a compact monolayer. A very efficient grafting of 4 onto a gold surface was found, with a surface coverage close to 100%. On the other hand, the reaction of mono-acid, 5, or hexa-acid, 6, cryptophanes with amino-terminated SAM was less efficient, since the surface coverage did not exceed 15%. Finally, a good surface coverage (75%) was also obtained by using a cysteamine coupling agent to modify 5 before its grafting onto a gold surface.

Resolving the chemical nature of nanodesigned silica surface obtained via a bottom-up approach.

The covalent grafting on silica surfaces of a functional dendritic organosilane coupling agent inserted, in a long alkyl chain monolayer, is described. In this paper, we show that depending on experimental parameters, particularly the solvent, it is possible to obtain a nanodesigned surface via a bottom-up approach. Thus, we succeed in the formation of both homogeneous dense monolayer and a heterogeneous dense monolayer, the latter being characterized by a nanosized volcano-type pattern (4-6 nm of height, 100 nm of width, and around 3 volcanos/µm(2)) randomly distributed over the surface. The dendritic attribute of the grafted silylated coupling agent affords enough anchoring sites to immobilize covalently functional gold nanoparticles (GNPs), coated with amino PEG polymer to resolve the chemical nature of the surfaces and especially the volcano type nanopattern structures of the heterogeneous monolayer. Thus, the versatile surface chemistry developed herein is particularly challenging as the nanodesign is straightforward achieved in a bottom-up approach without any specific lithography device.

Functionalized hydrogen-bonding self-assembled monolayers grafted onto SiO2 substrates.

A novel urea coupling agent possessing a vinyl-terminal group and trimethoxysilyl anchoring group was synthesized and grafted onto SiO(2)/Au substrates. This ureido coupling agent exhibits a good capacity to directly yield homogeneous SAMs with a surface smoothing. Polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) was used to monitor these SAMs. Indeed, the different functional groups (alkyl chain, urea, and vinyl) of this coupling agent were clearly observed in the PM-IRRAS spectra. Chemical modifications of the terminal function for the covalent immobilization of biomolecules were monitored by PM-IRRAS for the first time. We have demonstrated the successful reactions of the conversion of the vinyl-terminated SAMs successively into SAM-COOH and SAM-NHS without any degradation of the monolayer. The reactivity of activated esters was successfully investigated in order to immobilize the protein A.

Enhanced catalyst recovery in an aqueous copper-free Sonogashira cross-coupling reaction.

We report the synthesis of a superparamagnetic nanoparticle MNP (γ-Fe(2)O(3)/polymer) supported dendritic catalyst based on a bulky electron-rich phosphine Pd(II) complex. The high reactivity of this catalyst is described in a copper-free Sonogashira C-C cross-coupling reaction in water, and the significant role of surfactant additives is highlighted in the recovery study.

Dendron-functionalized core-shell superparamagnetic nanoparticles: magnetically recoverable and reusable catalysts for suzuki C--C cross-coupling reactions.

A metallodendron functionalized with dicyclohexyldiphosphino palladium complex was synthesized. The metallodendron was grafted onto core-shell superparamagnetic nanoparticles (gamma-Fe(2)O(3)/polymer, 200-500 nm) to give optimal catalytic reactivity in cross-coupling reactions. The grafted nanoparticles were used as recoverable and reusable catalysts for Suzuki C--C cross-coupling reactions. They showed remarkable reactivity towards iodo- and bromoarenes under mild conditions, and unprecedented reactivity towards chloroarenes. On completion of the catalytic reaction, the catalysts were readily recovered by using a simple magnet to attract the superparamagnetic grafted nanoparticles. Catalysts were recovered more than 25 times with almost no discernable loss of reactivity.

Efficient and recyclable dendritic Buchwald-type catalyst for the Suzuki reaction.

A Buchwald-type ligand attached to a star-shape molecule was synthesized in high yield, and its catalytic properties for the Suzuki reactions are shown to be excellent (down to 50 ppm with a simple chloroarene) including recovery/re-use of this hexa ligand.

Efficient dendritic diphosphino Pd(II) catalysts for the Suzuki reaction of chloroarenes.

reaction: see text]. The monomeric diphosphino Pd(II) complex 1 and the first three generations of dendritic analogues G1, G2, and G3 are efficient catalysts for the Suzuki coupling reaction of halogenoarenes, including chloroarenes with phenylboronic acid. The recovery and reuse of the dendritic catalysts G1, G2, and G3 are discussed.

Copper-free monomeric and dendritic palladium catalysts for the Sonogashira reaction: substituent effects, synthetic applications, and the recovery and re-use of the catalysts.

A series of bis(tert-butylphosphine)- and bis(cyclohexylphosphine)-functionalized Pd(II) monomers and polyamino (DAB) dendritic catalysts were synthesized and investigated for Sonogashira carbon-carbon coupling reactions in a copper-free procedure. The influence of phosphine substituents (tBu versus Cy) on the reaction kinetics was investigated by a GPC technique to monitor the reactions. The dendritic catalysts containing the cyclohexylphosphine ligands could be recovered and reused without loss of efficiency until the fifth cycle. The dendritic Pd(II) catalysts show a negative dendritic effect, that is, the catalyst efficiency decreases as the dendrimer generation increases.

Copper-free, recoverable dendritic Pd catalysts for the Sonogashira reaction.

Three generations of bidentate phosphinated Pd(II) dendrimers are efficient catalysts in the absence of copper co-catalyst for the Sonogashira reaction and are, with two cyclohexyl substituents on the phosphorus atoms, recovered by precipitation and re-used.

A very efficient, copper-free palladium catalyst for the Sonogashira reaction with aryl halides.

The new complex [Pd[t-Bu2PCH2N(CH2Ph)CH2P t-Bu2](OAc)2] is a very efficient catalyst for the Sonogashira cross-coupling reaction of aryl halides with acetylenes at room temperature, without co-catalyst.

Rational Design of Low Molecular Mass Organogelators: Toward a Library of Functional N-Acyl-1,ω-Amino Acid Derivatives.

N-Acyl amino acids RCONH(CH2 )n COOR1 represent a new family of organogelators that can be obtained in a combinatorial approach from libraries of activated acids and amino acids. The amounts required for gel formation in solvents such as DMF are less than 1 mg mL-1 and the gels formed are very stable. n=5, 7, 10, 12; R=aromatic or aliphatic group; R1 =H or alkali metal (Na).