13C CPMAS NMR Research Articles

Evaluation of Ultrahigh-Temperature-Resistant Preformed Particle Gels for Conformance Control in North Sea Reservoirs

Summary Preformed particle gels (PPGs) are 3D, crosslinked, dried polymer particles that can swell to several hundred times on contact with formation water. PPGs have been used extensively to control water production problems in reservoirs with conformance problems. The current state-of-the-art PPGs are polyacrylamide-based hydrogel compositions which lack long-term thermal stability under high-temperature and -salinity conditions. There are many oil reservoirs across the globe exhibiting conditions of temperatures higher than 120°C with high salinity. A novel ultrahigh-temperature-resistant PPG composition (DMA-SSS PPG) was designed to fill up the technology gap between existing polyacrylamide-based PPG technology that degrades readily over 110°C temperatures. DMA-SSS PPG exhibited excellent thermal stability for greater than 18 months in North Sea formation and formation water environments at 130°C. DMA-SSS PPG described herein showed swelling capacities of up to 30 times in different salinity North Sea brines. DMA-SSS PPG’s physiochemical properties like swelling, swelling rate, and rheological behavior were studied as a function of temperature and salinity. DMA-SSS PPGs showed excellent elastic modulus (G’) of about 3200 Pa in formation water of 90% water content. Thermostability of DMA-SSS PPGs was assessed at 130 and 150°C in North Sea brines with different salinity conditions. DMA-SSS PPGs proved to be stable for more than 18 months without losing molecular integrity. Thermostability was further confirmed through different metrics such as cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (CPMAS 13C NMR), thermogravimetric analysis (TGA), and morphology. Laboratory coreflood experiments were performed to demonstrate the plugging efficiency of open fractures and effectiveness in reducing the permeability. DMA-SSS PPG comprehensive evaluation confirms its novelty for excellent hydrothermal stability, thus can be used to control water production problems for mature reservoirs exhibiting conditions of high salinity and high temperature.

N-(2-Arylethyl)-2-methylprop-2-enamides as Versatile Reagents for Synthesis of Molecularly Imprinted Polymers.

The paper describes the formation of six aromatic N-(2-arylethyl)-2-methylprop-2-enamides with various substituents in benzene ring, viz., 4-F, 4-Cl, 2,4-Cl2, 4-Br, 4-OMe, and 3,4-(OMe)2 from 2-arylethylamines and methacryloyl chloride in ethylene dichloride with high yields (46–94%). The structure of the compounds was confirmed by 1H NMR, 13C NMR, IR, and HR-MS. Those compounds were obtained to serve as functionalized templates for the fabrication of molecularly imprinted polymers followed by the hydrolysis of an amide linkage. In an exemplary experiment, the imprinted polymer was produced from N-(2-(4-bromophenyl)ethyl)-2-methylprop-2-enamide and divinylbenzene, acting as cross-linker. The hydrolysis of 2-(4-bromophenyl)ethyl residue proceeded and the characterization of material including SEM, EDS, 13C CP MAS NMR, and BET on various steps of preparation was carried out. The adsorption studies proved that there was a high affinity towards the target biomolecules tyramine and L-norepinephrine, with imprinting factors equal to 2.47 and 2.50, respectively, when compared to non-imprinted polymer synthesized from methacrylic acid and divinylbenzene only.

Low-cost Posidonia oceanica bio-adsorbent for efficient removal of antibiotic oxytetracycline from water.

The presence of antibiotics as micro-contaminants in the water and aqueous environments is a health concern to humans and the ecosystem. Therefore, their elimination by adsorption to available and cheap materials in water treatment plants is a research topic of high relevance. The present paper reports on the adsorption behavior of oxytetracycline on a bio-adsorbent prepared from Posidonia oceanica; an abundant Mediterranean biomass. Characterization of the pretreated Posidonia biomaterial was achieved using several analyses such as Boehm acid-base titration method, pHPZC determination, and analysis techniques (FTIR, 13C CP-MAS NMR, optical microscopy, and TGA). The pHPZC occurred around pH 2.11. Posidonia biomaterial showed a fast and high uptake rate throughout the adsorption process, which is a definite advantage for analytical applications such as water decontamination. The experimental kinetic data fitted very rightly the pseudo-second-order kinetic model and the equilibrium uptake can adopt the bi-Langmuir isotherm model for all studied pH values which assumes adsorptions at the two localized sites. Maximum adsorption capacities of 11.8mg∙g-1 and 4.4mg∙g-1 for the two adsorption sites are reached at pH 6. The oxytetracycline adsorption process onto Posidonia bio-adsorbent is spontaneous (ΔadsG0 < 0), exothermic (ΔadsH0 < 0), and entropically favorable (ΔadsS0 > 0). The effect of pH on adsorption behavior and the thermodynamic parameters of adsorption are consistent with a possible origin of adsorption of oxytetracycline by means of hydrogen bonding interactions between surface hydroxyl and phenolic groups of the biomaterial and oxytetracycline. The proposed green and environmentally friendly biomaterial offers potential benefits as a bio-adsorbent in the remediation of aquatic environments contaminated by various organic materials.

Organic Carbon Speciation in Urban Anthrosols—The Legacy of Historical Waste Management

The impacts of waste management on various soils of agricultural and urban lands may last centuries or even millennia; however, generally, most studies tend to focus only on decadal or shorter timescales. This study investigates the characteristic properties of anthrosols in and around the urban settlement of St Andrews (Scotland), in the context of soil management and organic carbon content and speciation. Formed by the repeated application of fresh organic and pyrogenic wastes since the medieval period, these soils provide a 1000-year urban research context based on historical accounts of town waste management. We employed complementary methods of high-field solid-state 13C-CPMAS NMR, in situ magnetic susceptibility measurement, elemental micro-analysis and portable optically stimulated luminescence (OSL). A significant proportion of the soil organic carbon was present as refractory aromatic C structures, including aryl-C moieties. Portable OSL assessment revealed differences in the intensity and rate of sediment accumulation. The medieval urban areas had higher soil phosphorus concentrations, organic carbon content and magnetic susceptibility relative to the extra-urban site located outside of the medieval burgh. The study confirms that specific signatures, including carbon group functionalities, do reveal evidence of such induced long-lasting past anthropogenic soil modifications.

Selective capture of palladium(II) from highly acidic solution by proline-valinol amide functionalized silica nanoparticles

With the rapid development of the automobile industry and increasingly strict regulations on automobile exhaust emissions around the world, the production of waste purification catalysts for automobile exhaust will increase, leading to an increasing demand for palladium. Recycling waste three-way catalysts (TWCs) is an important way to obtain palladium resources. However, it is still a challenge to obtain highly selective adsorbents for palladium. Herein, we successfully fabricated two different kinds of Pd2+ selective composite adsorbents (PVA@MSNs and PVA@MONs) through covalent attachment of a proline-valinol amide (PVA) as the ligand on silica nanoparticles. The as-prepared adsorbents were characterized by TEM, SEM, elemental analysis, 29Si and 13C CP MAS NMR, N2-adsorption-desorption isotherm analysis, DLS, zeta-potential, p-XRD and FT-IR, revealing their high loading rate, and the mesoporous structure in the case of PVA@MSNs. In order to evaluate the ability of these two sorbents to selectively capture palladium(II), a series of sequential adsorption experiments were performed. The results showed that 56.35 mg and 67.74 mg of Pd2+ could be captured per gram by PVA@MSNs and PVA@MONs, respectively. Furthermore, they had a stronger selectivity towards Pd2+ than other cations (i.e. Co2+, Ni2+, Zn2+, Pb2+, Fe2+,) present in the simulated sample. Both sorbents were able to remain stable and show consistent performance in cyclic adsorption-desorption runs. Interestingly, the adsorbents realized for the first time the enrichment and recovery of palladium from organic solvents, offering a potential application in palladium catalyst-loaded industrial waste liquid processes.

Spick-and-span protocol for designing of silica-supported enantioselective organocatalyst for the asymmetric aldol reaction

In the present work, we report a ground-breaking strategy in the development of spick-and-span protocol for the synthesis of l-proline chiral scaffold tethered onto the silica matrix i.e., l-proline-(3°amine)-f-SiO2 via the reaction between l- proline methyl ester and N-methyl aminopropyl silica with absolutely no use of protecting/ deprotecting groups. The as-synthesized catalyst was well corroborated through various physicochemical techniques such as 13C CP MAS NMR, X-ray diffraction (XRD), HRTEM, N2 adsorption−desorption isotherms, elemental analysis and FT-IR spectral studies. Emphatically, l-proline-(3°amine)-f-SiO2 significantly promoted an asymmetric aldol reaction under ambient conditions with no use of redundant organic solvent, bestowing unprecedented activity with 100% conversion and (ee) > 99% enantioselectivity of S-isomer. Moreover, the as-synthesized catalyst was effortlessly recycled seven consecutive times with absolutely zero loss of activity as well.

Silsesquioxane-based porous polymer derived from organic chromophore with AIE characteristics for selective detection of 2,4-dinitrophenol and Ru3+

A novel silsesquioxane-based polymers (PCS-DPB) was prepared by the Friedel-Crafts reaction of octavinylsilsesquioxane (OVS) with AIE-active 4-[1-cyano-2-[4-(diphenylamino)phenyl]ethenyl]-α-[[4-(diphenylamino)phenyl]methylene]benzeneea-cetonitrile (CN-DPB). FTIR, solid state 29Si MAS and 13C CP MAS NMR spectroscopy analyses are performed to confirm its chemical structure and the presence of silsesquioxane units in the cross-linked network. XRD and TEM results prove its amorphous feature of the PCS-DPB material. TGA shows a high thermal stability of PCS-DPB with 5% mass loss temperature about 438 °C due to the highly cross-linking density and the presence of the inorganic silsesquioxane cage. The CN-DPB unit endows PCS-DPB with an excellent luminescence and a large red shift of 120 nm, which makes it to act as a probe to detect 2,4-dinitrophenol (DNP) and Ru3+ with high selectivity and sensitivity.

Synthesis of a novel freestanding conjugated triazine-based microporous membrane through superacid-catalyzed polymerization for superior CO2 separation

This study aims at developing a novel freestanding conjugated triazine-based membrane (ETM-1) with permanent porosity via a low-temperature superacid-promoted polymerization reaction. In this venue, we used the bifunctional 4-ethynylbenzonitrile (4-EBN) monomer featuring ethynyl (CCH) and nitrile (CN) functionalities. At the same time, trifluoromethanesulfonic acid (CF3SO3H) served as both the catalyst and solvent. The cross-linked Polymer's physicochemical properties were systematically examined using TGA, BET, solid-state 13C CP-MAS NMR, ATR-FT-IR, and XPS spectroscopy techniques. With conjugated s-triazine (as a result of cyclotrimerization of nitrile) and CCH (as a result of cationic polymerization of ethynyl), the microporous ETM-1 membrane displayed a superior CO2 uptake capacity of up to 3.87 mmol g−1 (170.3 mg g−1) and enhanced ideal CO2/N2 and CO2/CH4 permselectivity values of 47 ± 2 and 21 ± 1 at 298 K and 1 bar, respectively. The notable selectivity of ETM-1 towards CO2 can be stated in terms of the molecular sieving (i.e., kinetic selection) characteristic of the microporous membrane, its electron-rich π-conjugated skeleton, and enhanced basicity, suitable for interacting with CO2via dipole-quadrupole and acid-base interactions. Moreover, ETM-1 exhibited the isosteric heat of CO2 adsorption ranging from 28.1 to 34.3 kJ mol−1, implying strong physisorption of CO2 upon the high-affinity adsorption sites of the membrane.

Controlled hydrophobic modification of cellulose nanocrystals for tunable Pickering emulsions

This work gives a comprehensive view of the surface acylation of cellulose nanocrystals (CNCs), as a tool to monitor Pickering emulsions. It investigates the impact of the grafted chain length and surface degree of substitution (DSsurf), on the type (direct or inverse) of such emulsions. CNC samples were prepared by grafting 10 different linear acyl groups containing 2 to 18 carbons, with reaction times from 30 min to 5 h to vary the DSsurf. The grafting was evaluated by FT-IR and 13C CP-MAS NMR spectroscopies. Whatever the DSSurf, CNCs grafted with linear acyl chains of 2 to 6 carbons led to the exclusive formation of direct oil-in-water (O/W) emulsions with hexadecane. Distinctively, both O/W and water-in-oil (W/O) emulsions could be obtained when the linear chain contained 8 carbons or more, at low and high DSSurf, respectively. By adjusting the length of the grafted chain, DSSurf and particles concentration, we were able to monitor the type of emulsion formed, droplet size and surface coverage at the oil/water interface.

A comparative study of tea waste derived humic-like substances with lignite-derived humic substances on chemical composition, spectroscopic properties and biological activity.

Emerging demand for humic substances escalated the short supply of coal-related resources from which humic substances are extracted in large quantities for various applications. Production of humic-like substances from lignocellulosic waste materials similar in structural and functional properties to humic substances has gained interest recently. Tea waste is a by-product from tea manufacturing factories enriched in lignocellulose is used to extract two types of humic fractions. One fraction has purified humic-like acid (HLA), and the other has unpurified humic and fulvic acids called as humic-like substances (HLS). Elemental composition, spectroscopic (13C CPMAS NMR and FTIR) properties, and biological activity of tea waste derived humic-like substances (TWDHLS) were compared with commercially available humic acid (CHA) extracted from lignite. Elemental analysis and FTIR characterization showed slight differences between HLA and HLS, while NMR results revealed that both have similar carbon distribution and are abundant in cellulosic polysaccharides and lignin derivatives. The presence of more stable compounds in TWDHLS contribute to its recalcitrant nature. NMR spectra of CHA significantly varied with TWDHLS and were rich in aliphatic compounds. The biological activity of TWDHLS and CHA was studied at five different concentrations (0, 20, 40, 80, and 160mg L-1). The results show that soil application TWDHLS at 80mg L-1 concentration showed better results on the growth of tea nursery plants similar to CHA, contrasting to the variation in their structural properties. Our findings revealed that TWDHLS could be used not only as a potential plant biostimulant but also as a better substitute for humic substances.

Metal/metal oxide-decorated covalent organic frameworks as electrocatalysts for electrocarboxylation and water splitting

A o-tolidine based triazine (TTP) covalent organic framework was prepared, and successful formation of the porous polymer network was confirmed by solid state 13C and 15N CP-MAS NMR spectra, XRD, and other morphological techniques. The synthesized TTP was decorated with transition metal/metal oxide nanoparticles (Cu, Ni, and Cu–Ni). The presence of CuO and NiO nanoparticles on the TTP matrix were confirmed by Raman spectroscopy and the PXRD analysis and different morphologies with modest changes in particle size and porosity were confirmed by FE-SEM and HR-TEM studies. As evidenced by onset potential and current density, the Cu-TTP sample exhibited excellent electrocatalytic activity for the electrochemical carboxylation of propylene oxide in the presence of CO2 and HER, whereas the Ni-TTP sample displayed excellent OER activity. The presence of pyridinic, pyrrolic, and quaternary nitrogen was attributed to the excellent catalytic activity of Cu-TTP for electrocarboxylation and HER activity, whereas secondary amine bonds and a combination of mechanisms were responsible for the increased OER activity of Ni-TTP the sample, as evidenced by XPS.

Highly active and scalable SO3H functionalized carbon catalyst synthesized from bagasse for transformation of bio-based platform chemicals into fuel precursors and its in-depth characterization studies

Scalable synthesis of SO3H functionalized carbon from sugar industry waste (bagasse) and detailed structural characterization and activity were reported. The incorporation of SO3H functionality groups on the carbon surface and the growth of the aromatic carbon framework was supported by FT-IR and 13C CP-MAS NMR analysis. The hydrothermally synthesized carbon exhibited total acidity of 5 mmol/g and uniform distribution of sulphur on the surface of carbon. The synthesized catalyst was found to be efficient for the acetalization, alkylation and alcoholysis reactions and exhibits excellent stability during the reactions. Various bio-derived carbonyl compounds were demonstrated by the solvent-free acetalization of bio-derived glycerol gives 50–100% conversion and 52–98% selectivity towards solketal derivatives at room temperature. The synthesized catalyst's reactivity was better than the commercially used Brønsted/Lewis acids. Furthermore, the SO3H functionalized carbon was also used for alcoholysis followed by ring-opening of furfuryl alcohol, giving 67–98% selectivity towards alkyl levulinates with complete conversion of furfuryl alcohol. The mechanistic pathway suggests that the alcoholysis reaction goes through three different intermediates (2-alkoxymethylfuran, 4,5,5-trialkoxypentan-2-one, and 5-hydroxy-4,5-dialkoxypentan-2-one) to produce the alkyl levulinates. Additionally, the catalyst was tested for solvent-free condensation of 2-methylfuran with various carbonyl compounds to selectively produce an excellent yield of fuel precursors (for C12-C15 hydrocarbons) at 60 °C. The catalyst was reused up to four cycles with 14% loss in the conversion of furfural for acetalization of glycerol, and negligible losses in the alkylation of 2-methylfuran were observed.

Multinuclear solid-state NMR: Unveiling the local structure of defective MOF MIL-120

Metal-organic frameworks (MOFs) are emerging materials with many current and potential applications due to their unique properties. One critical feature is that the physical and chemical properties of MOFs are tunable. One of the methods for tuning MOF properties is to introduce defects by design for desired applications. Characterization of MOF defects is important, but very challenging due to the local nature and short-range ordering. In this work, we have introduced the ordered vacancies (the defects) in the form of the coordinatively unsaturated sites (CUSs) into the framework of MOF MIL-120(Al). The creation of ordered vacancies is achieved by replacing one quarter of the BTEC (1,2,4,5-benzenetetracarboxylate) with BDC (benzene-1,4-dicarboxylate) linkers. Both parent and defective MOFs were characterized by multinuclear solid-state NMR spectroscopy. 1H MAS NMR is used to characterize the hydrogen bonding in these MOFs, whereas 13C CP MAS NMR confirms unambiguously that the BDC is incorporated into the framework. One-dimensional 27Al MAS NMR provides direct evidence of the coordinatively unsaturated Al sites (the defects). Furthermore, 27Al 3QMAS experiments at 21.1 ​T allow direct identification of one penta-coordinated and three chemically inequivalent octahedral Al sites in the defective MIL-120(Al). Two of the above-mentioned octahedral Al sites are in the domain which appears defect-free. The third octahedral Al site is near the defective site. This work clearly demonstrates the power of solid-state NMR spectroscopy for characterization of defective MOFs.

Silica Bonded Bis(Hydrogensulphato)Benzene as a New, Sustainable Catalytic Material for an Efficient and Aqueous Based Synthesis of 5-Oxo-4H-Pyrano[3,2-c]Quinolone Scaffolds

Catalytic use of benzene-1,3-disulfonic acid at an ordinary condition gets restricted due to its high hygroscopic and moisture sensitive nature. In the present study, a new catalytic material silica bonded bis(hydrogensulphato)benzene (SiO2-BHSB) was synthesized through a sequence of reactions, where the active catalytic part benzene-1,3-disulfonic acid was grafted on the surface of micro-sized silica by the chemical bonding. Structural features, purity, thermal stability, and acid strength of the synthesized SiO2-BHSB material were confirmed by the adequate analytical techniques such as FT-IR, solid-state CP-MAS 13C-NMR, CP-MAS 29Si-NMR, EDX, DTG, TGA, and volumetric studies. The synthesized material SiO2-BHSB was observed as an efficient and sustainable reaction promoter for a tandem reaction between 4-hydroxy-1-methyl-2(1H)-quinolone, malononitrile, and structurally diverse aldehydes to offer pyrano[3,2-c]quinolone scaffolds. An environmentally benign catalytic protocol in aqueous based solvent and at ordinary energy conditions was developed, wherein a tiny amount (3 mol%) of SiO2-BHSB was observed sufficient to catalyze the synthesis pyrano[3,2-c]quinolone scaffolds. Structures of the synthesized pyrano[3,2-c]quinolone derivatives were established from their physical and spectrometric data. Catalyst recovery and reuse study revealed that SiO2-BHSB sustains its catalytic activity even after five runs of its reuse. Use of aqueous-based solvent, environmentally compatible reaction conditions, ease of catalyst recovery and reuse are the additional salient features of the present protocol.

Poly(vinylbenzyl Pyridinium Salts) as Novel Sorbents for Hazardous Metals Ions Removal.

Novel efficient complexing resins—poly(vinylbenzyl pyridinium salts) fabricated through poly(vinylbenzyl halogene-co-divinylbenzene) quaternization of N-decyloxy-1-(pyridin-3-yl)ethaneimine and N-decyloxy-1-(pyridin-4-yl)ethaneimine—were tested as adsorbents of Pb(II), Cd(II), Cu(II), Zn(II), and Ni(II) from aqueous solutions. The structure of these materials was established by 13C CP-MAS NMR, X-ray photoelectron spectroscopy, elemental analysis, and Fourier transform infrared spectroscopy, as well as thermogravimetric and differential thermal analyses. The textural properties were determined using scanning electron microscopy and low-temperature N2 sorption. Based on the conducted sorption studies, it was shown that the uptake behavior of the metal ions towards novel resins depended on the type of functionalities, contact time, pH, metal concentrations, and the resin dosage. The Langmuir model was investigated to be the best one for fitting isothermal adsorption equilibrium data, and the corresponding adsorption capacities were predicted to be 296.4, 201.8, 83.8, 38.1, and 39.3 mg/g for Pb(II), Zn(II), Cd(II), Cu(II), and Ni(II), respectively. These results confirmed that owing to the presence of the functional pyridinium groups, the resins demonstrated proficient metal ion removal capacities. Furthermore, VBBr-D4EI could be successfully used for the selective uptake of Pb(II) from wastewater. It was also shown that the novel resins can be regenerated without significant loss of their sorption capacity.

Decreased soil aggregation and reduced soil organic carbon activity in conventional vegetable fields converted from paddy fields

AbstractSoil structure and organic carbon are key factors that reflect soil quality in sustainable agricultural production. Many studies have concentrated on soil aeration under intensive anthropogenic agricultural practices, but the relationship between soil aggregate stability and soil organic carbon (SOC) functional groups is poorly understood, particularly in degraded greenhouse vegetable fields converted from paddy fields. To solve this problem, soil samples were collected from local vegetable fields and adjacent paddy fields. Conventional open‐air vegetable fields and greenhouse vegetable fields, both with a 6–8‐year cultivation history following conversion from paddy fields, were considered. SOC functional groups were characterised by 13C cross‐polarisation magic‐angle‐spinning nuclear magnetic resonance (13C CPMAS NMR). The results showed that the mean weight diameter (MWD) values of water‐stable soil aggregates in the open‐air vegetable fields and greenhouse vegetable fields decreased by 64.6% and 66.7%, respectively, compared with those in the paddy fields. Similar results were obtained for the soil aggregate distribution, and soil aggregates in the greenhouse vegetable fields and open‐air vegetable fields were mainly in the 0.25–2 mm size classes. Among all SOC functional groups, O‐alkyl C exhibited the greatest decrease after the conversion of paddy fields to vegetable fields, no matter whether greenhouse vegetable fields or open‐air vegetable fields. The degradation of soil structure decreased the physical protection of SOC functional groups by soil aggregates, and therefore, decreased the total SOC content and labile C functional group fractions in bulk soil. At the soil aggregate scale, the decrease of O‐alkyl C mainly occurred in microaggregates (0.053–0.25 mm), while aromatic C decreased significantly in macroaggregates (&gt;0.25 mm) in the greenhouse vegetable fields converted from paddy fields. Correlation analysis showed that O‐alkyl C was significantly positively related to MWD and the proportion of large soil macroaggregate (&gt;2 mm). This result suggested that soil aggregates become fragile in long‐term vegetable cultivation after conversion from paddy fields, and a large loss of O‐alkyl C might be the main reason for this phenomenon.Highlights Soil aggregation was significantly decreased in conventional vegetable fields converted from paddy fields. SOC accumulation was closely positively related to soil macroaggregate formation. O‐alkyl C mainly decreased in microaggregates, with the opposite observed for aromatic C, in soil of greenhouse vegetable fields. The large loss of O‐alkyl C may explain the degradation of soil aggregates.

Ferrocene-Based Porous Organic Polymer (FPOP): Synthesis, Characterization and an Electrochemical Study

Ferrocene-based porous organic polymers (FPOPs) were prepared from phenol-formaldehyde polymer (Bakelite) and phenol as starting materials; and two possible mechanisms for polymerization were discussed. Solid-state 13C CP-MAS NMR, FTIR, powder XRD, elemental analysis and ICP (Fe, Na, B) were performed to characterize the prepared materials. The two synthetic approaches produced polymers with different pore sizes: the FPOP synthesized through Bakelite presented a higher surface area (52 m2 g−1) when compared to the one obtained by the bottom-up polymerization from phenol (only 5 m2 g−1). Thermogravimetric analysis confirmed the thermal stability of the material, which decomposed at 350 °C. Furthermore, cyclic voltammetry (CV) of the new FPOP on modified electrodes, in ACN and 0.1 M TBAP as an electrolyte, showed fully reversible electron transfer, which is similar to that observed for the ferrocene probe dissolved in the same electrolyte. As a proof-of-concept for an electrochromic device, this novel material was also tested, with a color change detected between yellow/brownish coloration (reduced form) and green/blue coloration (oxidized form). The new hybrid FPOP seems very promising for material science, energy storage and electrochromic applications, as well as for plastic degradation.

Specific microbiome signatures under the canopy of Mediterranean shrubs

Shrub encroachment (SE) is a phenomenon in which grasses and herbaceous vegetation are replaced by woody shrubs. Many previous studies have highlighted the effects of SE on soil respiration rates and nutrient storage, but little is known about impacts on soil microbiota. While previous work considered shrubs to be non-species specific or as a single intervening species, we selected an Ampelodemsos mauritanicus grassland and six coexisting shrubs (i.e. Pistacia lentiscus L., Juniperus phoenicea L., Myrtus communis L., Rosmarinus officinalis L., Olea europaea L., and Euphorbia dendroides L.) to investigate the effects of their encroachment on soil microbiota. We used high-throughput sequencing, coupled with soil chemical analyses and litter using 13C CPMAS NMR spectroscopy. Results showed a strong influence of shrub species on bacterial and fungal community diversity, species richness and overall community composition in the soil. Litter chemistry was dominated by O-alkyl-C, with the highest content in Ampelodesmos and E. dendroides, but richer of aromatic C in P. lentiscus and R. officinalis. Bacterial diversity was highest under J. phoenicea and E. dendroides, while lowest under R. officinalis and grassland. Conversely, fungal diversity was highest under O. europaea and E. dendroides, while lowest under M. communis and grassland. Moreover, soil C and N contents were highest under O. europaea, P. lentiscus and M. communis compared to the other shrub species. In addition, grassland and R. officinalis had the highest Fe content. Structural equation model (SEM) analysis ascertained that the shifts of bacterial and fungal community composition and diversity were closely related with the changes of litter and soil chemical properties. Our results suggest that the individual effect of each shrub on the grassland matrix depends mainly on the chemical properties of the shrub litter, which alters the chemical profile of the soil and, in cascade, shapes the associated microbiota.

Insight into the measurements for determining the ageing degree of ancient silk

Evaluating the degradation degree of aged silk is a challenge but worthwhile to determine the structure change and stability of silk. To date, the characterizations of silk degradation are widely studied, however, it still remains a lack of systematic research on measuring and quantifying the degradation degree of silk with effective ageing indicators. In this research, ancient silk samples from two different ages and regions were investigated by means of X-ray diffraction, X-ray photoelectron spectroscopy, EPR spectroscopy and 13C CPMAS NMR in an attempt to provide numerical indicators for assessing their ageing degree. As a result, the crystallinity, oxidation and carbonization degree, variation of amino acid content and content of random coil were proved to be the valuable indexes for interpreting the distinct deterioration and fragility level of aged silk. This work may shed light on studying the ageing status and stability of historical silk and further providing evidence for the conservation and preservation of silk cultural relics.

Chemical and Molecular Composition of the Chrysalis Reveals Common Chitin-Rich Structural Framework for Monarchs and Swallowtails

The metamorphosis of a caterpillar into a butterfly is an awe-inspiring example of how extraordinary functions are made possible through specific chemistry in nature’s complex systems. The chrysalis exoskeleton is revealed and shed as a caterpillar transitions to butterfly form. We employed solid-state NMR to evaluate the chemical composition and types of biomolecules in the chrysalides from which Monarch and Swallowtail butterflies emerged. The chrysalis composition was remarkably similar between Monarch and Swallowtail. Chitin is the major polysaccharide component, present together with proteins and catechols or catechol-type linkages in each chrysalis. The high chitin content is comparable to the highest chitin-containing insect exoskeletons. Proteomics analyses indicated the presence of chitinases that could be involved in synthesis and remodeling of the chrysalis as well as cuticular proteins which play a role in the structural integrity of the chrysalis. The nearly identical 13C CPMAS NMR spectra of each chrysalis and similar structural proteins supports the presence of underlying design principles integrating chitin and protein partners to elaborate the chrysalis.