The objective of this paper is to better describe the structure of the hydrothermal carbon (HTC) process and put it in relationship with the more classical pyrolytic carbons. Indeed, despite the low ...energetic impact and the number of applications described so far for HTC, very little is known about the structure, reaction mechanism, and the way these materials relate to coals. Are HTC and calcination processes equivalent? Are the structures of the processed materials related to each other in any way? Which is the extent of polyaromatic hydrocarbons (PAH) inside HTC? In this work, the effect of hydrothermal treatment and pyrolysis are compared on glucose, a good model carbohydrate; a detailed single-quantum double-quantum (SQ-DQ) solid state (13)C NMR study of the HTC and calcined HTC is used to interpret the spectral region corresponding to the signal of furanic and arene groups. These data are compared to the spectroscopic signatures of calcined glucose, starch, and xylose. A semiquantitative analysis of the (13)C NMR spectra provides an estimation of the furanic-to-arene ratio which varies from 1:1 to 4:1 according to the processing conditions and carbohydrate employed. In addition, we formulate some hypothesis, validated by DFT (density functional theory) modeling associated with (13)C NMR chemical shifts calculations, about the possible furan-rich structural intermediates that occur in the coalification process leading to condensed polyaromatic structures. In combination with a broad parallel study on the HTC processing conditions effect on glucose, cellulose, and raw biomass (Falco, C.; Baccile, N.; Titirici, M.-M. Green Chem., 2011, DOI: 10.1039/C1GC15742F), we propose a broad reaction scheme and in which we show that, through HTC, it is possible to tune the furan-to-arene ratio composing the aromatic core of the produced HTC carbons, which is not possible if calcination is used alone, in the temperature range below 350 °C.
Despite the structural, load‐bearing role of cellulose in the plant kingdom, countless efforts have been devoted to degrading this recalcitrant polysaccharide, particularly in the context of biofuels ...and renewable nanomaterials. Herein, we show how the exposure of plant‐based fibers to HCl vapor results in rapid degradation with simultaneous crystallization. Because of the unchanged sample texture and the lack of mass transfer out of the substrate in the gas/solid system, the changes in the crystallinity could be reliably monitored. Furthermore, we describe the preparation of cellulose nanocrystals in high yields and with minimal water consumption. The study serves as a starting point for the solid‐state tuning of the supramolecular properties of morphologically heterogeneous biological materials.
Vapor over the cracks: The adsorption of hydrogen chloride vapor on water‐covered cellulose microfibrils results in rapid degradation and increased crystallinity without a change in fiber morphology. This process constitutes an example of supramolecular tuning of native biological materials directly in the solid state.
The term biosurfactants refers to a complex mixture of metabolites with surface-active properties produced by specific microorganisms. However, nowadays trends moves towards isolation, screening and ...purifying single biocompatible, biodegradable biosurfactants with high commercialisation potential. Current legislation limiting petrochemicals combined with environmentally concerned consumers did not only stimulate research and development but it also promoted large-scale production of this class of molecules. However, recent data recorded on single congeners question the actual pertinence of using the word ‘biosurfactant’ associated to these molecules. By evaluating the accepted characteristics of surfactants and comparing them to the actual self-assembly and bulk properties in water of molecules traditionally called ‘biosurfactants’, this opinion article aims at showing that the term ‘biosurfactant’ can be somewhat reductive when applied to specific individual compounds produced by fermentation. The use of a more generic term, like bioamphiphile could probably be more pertinent and appropriate for consideration in the future.
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The demand for microbially produced surface‐active compounds for use in industrial processes and products is increasing. As such there has been a comparable increase in the number of publications ...relating to the characterisation of novel surface‐active compounds; novel producers of already characterised surface‐active compounds and production processes for the generation of these compounds. We devised this review as a guide to both researchers and the peer review process to improve the stringency of future studies and publications within this field of science.
Summary
The demand for microbially produced surface‐active compounds for use in industrial processes and products is increasing. As such, there has been a comparable increase in the number of publications relating to the characterization of novel surface‐active compounds: novel producers of already characterized surface‐active compounds and production processes for the generation of these compounds. Leading researchers in the field have identified that many of these studies utilize techniques are not precise and accurate enough, so some published conclusions might not be justified. Such studies lacking robust experimental evidence generated by validated techniques and standard operating procedures are detrimental to the field of microbially produced surface‐active compound research. In this publication, we have critically reviewed a wide range of techniques utilized in the characterization of surface‐active compounds from microbial sources: identification of surface‐active compound producing microorganisms and functional testing of resultant surface‐active compounds. We have also reviewed the experimental evidence required for process development to take these compounds out of the laboratory and into industrial application. We devised this review as a guide to both researchers and the peer‐reviewed process to improve the stringency of future studies and publications within this field of science.
We present a simple and green one‐step pathway towards nitrogen‐doped carbon nanostructures with controlled mesoporosity through hydrothermal treatment of glucose in the presence of model proteins. ...Performing the reaction with different amounts of egg white ovalbumin protein (OvA), carbonaceous nanoparticles or continuous nanosponges with high specific surface areas can be efficiently produced. The nitrogen content of the structures is rather high (up to 8 wt %) and can be kept constant up to 950 °C, while oxygen elimination and graphitization of the carbon material occurs. We demonstrate here that sustainable natural resources can be efficiently used in the synthesis of pure high‐potential nanomaterials.
Hydrothermal treatment: We present a simple and green one‐step pathway towards nitrogen‐doped carbon nanostructures with controlled mesoporosity through hydrothermal treatment of glucose in the presence of model proteins.
The adsorption properties of various organo-modified mesoporous silicas towards a methoxy-modified chlorophenol in water have been studied. Phenyl, propyl, hexyl and hexadecyl groups were selected to ...study the possible interactions that the pollutant could preferentially develop with the surface sites. The best performing sample appears to be the hexyl-modified porous silica and one of the least performing the un-modified mesoporous silica. The physical state of the adsorbed chlorophenol in these two confined environments as well as the pollutant/surface interactions were characterized by a combination of solid-state NMR techniques. The
1H and
13C NMR responses show a high mobility of the molecules in both the modified and un-modified silica, suggesting the absence of strong interactions between the pollutant and the surface, despite the large difference in the chemical nature of the silica surface sites.
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