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Cacao pod husks (CHs), the most abundant by-product of cacao beans production, can potentially become a source of functional ingredients for the food, cosmetic, and pharmaceutical industries.

International audience; Petroporphyrins, geoporphyrins, or metalloporphyrins are the original petroleum biomarkers, identified by Alfred Treibs more than a century ago and the first molecular evidence for the biogenic origins of petroleum. Since discovery, analytical strategies have been developed to identify porphyrins in petroleum and its fractions. This review focuses on the advances enabled by ultrahigh resolving power Fourier transform ion cyclotron resonance mass spectrometry in tribute to Professor Alan G. Marshall.

Composite cellulose hydrogels result from physical or chemical crosslinking processes. Unique tridimensional architectures, arising from the hydrogel components’ interactions, make these materials ideal to design function-driven structures. We follow the development of cellulose nanofiber/silver nanoparticle (Ag NP) hydrogels in aqueous media. TEMPO-oxidized cellulose nanofibers (TOCNs), extracted from fique residual biomass, acted as both capping and reducing agents for the in-situ synthesis of Ag NPs. Temperature and COONa:AgNO3 molar ratios influence hydrogel formation. Increasing temperatures (60 oC) resulted in shorter reaction times (28 h) compared to the behavior at lower temperatures (25 oC), which required longer reaction times (192 h). High COONa:AgNO3 molar ratios (1:3) produced stiffer and darker TOCN/Ag NP hydrogels at the expense of large cubic Ag NP clusters formation (1 µm). Conversely, lower COONa:AgNO3 molar ratios (1:1) resulted in softer hydrogels with spherical Ag NPs exhibiting diameters between 15 and 80 nm. Ag NP formation and crosslinking processes strongly depend on unreacted aldehydes on the TOCN surfaces after the TEMPO oxidation reaction. IR spectra indicated that there is a bridging bidentate interaction between COO− groups and Ag+ ions. These carboxylate-metal complexes might weaken the hydrogen bond system by increasing the distance between cellulose molecules, decreasing the material’s crystallinity index, as observed in XRD analyses. TGA analyses demonstrated that Ag NPs significantly increased the TOCN/Ag NP hydrogels’ thermal stability compared to TOCN hydrogels. Rheological probing of the hydrogels elucidated the role of Ag NP distribution and loading on the elastic response to cyclical deformations, suggesting a myriad of uses for these materials, particularly in medicinal applications.

During TEMPO-mediated oxidation of cellulose, primary alcohols on the surface ideally undergo oxidation to carboxylic acids. However, it is well known that some of these hydroxyl groups partially oxidize to aldehydes. To increase the degree of oxidation (DO) of nanocellulose, these unreacted aldehydes can be fully oxidized to carboxylic acids employing various strategies. We performed post-oxidation reactions using NaClO2, on TEMPO-Oxidized Cellulose Nanofibers (TOCN) to investigate how this reaction influenced the physicochemical properties of nanocelulose before and after amidation with octadecylamine (ODA). We report on an increase in the content of carboxylate in TOCN (1.57 mmol/g of cellulose) up 40% after post-oxidation with NaClO2 (2.20 mmol/g of cellulose). These results indicate that with TEMPO-mediated oxidation, 1.57 mmol of hydroxymethyl groups per gram of cellulose were completely oxidized to –COOH, and after treatment with NaClO2, about 0.63 mmol of partially-oxidized alcohols (aldehyde groups) on TOCN were fully oxidized to COOH. Theoretical HLB values of 11.04 and 11.13 for TOCN and post-oxidized TOCN (TOCN-P) indicate that these materials behave as hydrophilic o/w surfactants or emulsifying agents with high affinity for polar phases. They also form highly stable dispersions in water due to an increased charge density as indicated by ζ-potential values of -56 mV for TOCN and -64 mV for TOCN-P. Low contact angles (CA) of 24o and 21o for TOCN and TOCN-P films confirm their hydrophilic nature. After amidation reactions with ODA, we observe a 73% and an 82% decrease in carboxylate content for TOCN and TOCN-P. These values can be related with the degree of coupling (DC) leading to amide formation on the nanocellulose surface, i.e., about 1.14 and 1.80 mmol of amide units were coupled per gram of cellulose on TOCN-ODA and TOCN-P-ODA. ζ-potential values decreased 34% and 52% after amidation, to -37 mV and -31 mV for TOCN-ODA and TOCN-P-ODA, indicating a low stability of these materials in water dispersions. Theoretical HLB values 125o) films illustrate the effect of octadecylamine alkyl chains on the hydrophobic properties of the nanocellulose’s surface. Thermal analysis indicates that amidation reactions can effectively shield in the nanocellulose’s surface from thermal degradation from by increasing the decomposition temperature from around 296 °C for “naked” TOCN to > 330 °C for the “protected” amidated nanocellulose.

Promising research over the past decades has shown that some types of pentacyclic triterpenes (PTs) are associated with the prevention of type 2 diabetes (T2D), especially those found in foods. The most abundant edible sources of PTs are those belonging to the ursane and oleanane scaffold. The principal finding is that Cecropia telenitida contains abundant oleanane and ursane PT types with similar oxygenation patterns to those found in food matrices. We studied the compositional profile of a rich PT fraction (DE16-R) and carried out a viability test over different cell lines. The biosynthetic pathway connected to the isolated PTs in C.telenitida offers a specific medicinal benefit related to the modulation of T2D. This current study suggests that this plant can assemble isobaric, positional isomers or epimeric PT. Ursane or oleanane scaffolds with the same oxygenation pattern are always shared by the PTs in C. telenitida, as demonstrated by its biosynthetic pathway. Local communities have long used this plant in traditional medicine, and humans have consumed ursane and oleanane PTs in fruits since ancient times, two key points we believe useful in considering the medicinal benefits of C. telenitida and explaining how a group of molecules sharing a closely related scaffold can express effectiveness.

Phytoplanktonic species have photopigment reserves for their photosynthetic processes, which have several applications such as taxonomic fingerprintings and biomarkers. Pigments are analyzed using MALDI Mass Spectrometry (MS) assays. Ionization Potential (IP) is an important parameter considered.

Naphthenic acid (NA) fractions from heavy crude oils are typically analyzed in mass spectrometry via electrospray ionization (ESI). Here, we show that NA analysis is also possible by MALDI using a highly basic matrix (proton sponge). When compared with ESI, that allowed detection of six compound families, MALDI resulted in the observation of twenty-two compound families. Besides, MALDI analysis affords compositional-dependent information. Unlike ESI, where all NAs are detected as deprotonated molecules, in MALDI we observe both deprotonated molecules and radical anions. This indicates that ion formation in NA by MALDI can occur by either acid-base and electron-capture mechanisms, or both. Interestingly, the preferred ionization channel seems to be compound class dependent; for instance, the acid base mechanism (which allows detection of deprotonated NA species through a Bronsted-Lowry reaction) applies exclusively to NAs with high H/C ratios along the whole O/C range. On the other hand, for less saturated compounds both mechanisms apply, while the electron capture channel occurs exclusively in species with low H/C and high O/C ratios or high H/C and low O/C ratios (envelope of the van Krevelen plots). In summary, we demonstrate that MALDI(-) is an alternative method for the analysis of complex petrochemical samples offering additional advantages, when compared with ESI, such as increasing compositional space accessibility for polar samples, high throughput and exceptional tolerance to the presence of impurities and salts in the samples. Furthermore, exploration on semi-quantitative approaches in MALDI can provide additional advantages such as those offered by LC-ESI MS, currently used to quantify naphthenic acids.

We present a two-step method to prepare a hydrophobic cellulosic membrane involving a SiO2 sol-gel process, to increase surface roughness, followed by grafting of hexadecyltrimethoxysilane groups to chemically enhance the membrane’s water repellency. The modification processes induced morphological and chemical changes as observed by scanning electron microscopy and infrared spectroscopy, respectively. The hydrophobic membrane was used to separate immiscible oil/water mixtures with efficiencies over 99%. In addition, we tested the material for breaking an asphaltene–stabilized water in oil emulsion and registered separation efficiencies from 75% to 95%. The demulsification process depends on membrane surface hydrophobicity, emulsion viscosity and dispersed droplet size. The hydrophobic/oleophilic cellulose membrane was efficiently reused over 18 times to break a water/oil (50% water) emulsion. This facile solution for breaking low viscosity w/o emulsions and immiscible water/oil mixtures could be easily scalable and used to develop efficient separation methods driven solely by gravity.

Petroporphyrins are biomarkers derived from chlorophyll, bacteriochlorophyll and the heme group, commonly present in crude oils as vanadyl or nickel complexes. These compounds, which despite of the organic matter maturation process preserve the tetrapyrrolic core of their precursors, show low polydispersity, concentration and are commonly used in geochemistry to assess oil lithology, oxidation-reduction conditions, geothermal maturation, conversion of organic matter, and burial depth. The physicochemical characteristics of petroporphyrins make them excellent analytes for MALDI-MS. Electron transfer (ET) ionization in MALDI, using novel electron transfer matrices based on cyano-phenylenevinylenes (e.g. CNPV-CH3), allows direct observation of labile compounds such as polyaromatics and porphyrin-like compounds, chlorophylls and pigments, as has been previously demonstrated by our group. In this work, we analyze petroporphyrins from two South American heavy oils using CNPV-CH3 as ET MALDI matrix. Petroporphyrins were isolated by Soxhlet extraction, with acetonitrile, followed by fractionation using normal-phase column chromatography. UV–Vis measurements showed a strong absorption band at 408 nm assigned to porphyrin Soret band for some chromatographic fractions. The fractions enriched with petroporphyrins were subjected to ET MALDI analysis. We demonstrate the suitability of the CNPV-CH3 MALDI matrix for the efficient and selective desorption and ionization of vanadyl porphyrins, when compared with a commercial MALDI matrix (DCTB) and LDI conditions.

Worldwide only 8% of the biomass from harvested cacao fruits is used, as cacao beans, in chocolate-based products. Cacao mucilage exudate (CME), a nutrient-rich fluid, is usually lost during cacao beans fermentation. CME's composition and availability suggest a potential carbon source for cellulose production. CME and the Hestrin and Schramm medium were used, and compared, as growth media for bacterial cellulose (BC) production with Gluconacetobacter xylinus. CME can be used to produce BC. However, the high sugar content, low pH, and limited nitrogen sources in CME hinder G. xylinus growth affecting cellulose yields. BC production increased from 0.55 ± 0.16 g L−1 up to 13.13 ± 1.09 g L−1 after CME dilution and addition of a nitrogen source. BC production was scaled up from 30 mL to 15 L, using lab-scale experiments conditions, with no significant changes in yields and production rates, suggesting a robust process with industrial possibilities.

Without a templated mechanism, a new corner-like complex ([Fe(C25H32N8S)2]2+=[Fe]) and a new grid-like one ([Fe4(C23H28N8S)4]8+=[Fe4]) were obtained from the self-assembly of two structurally related bis(hydrazones) (C25H32N8S = 1; C23H28N8S = 2) with Fe(II) under identical reaction conditions, commonly employed for the efficient synthesis of grid-like complexes. The electrochemical and magnetic properties of these complexes were studied. Both complexes undergo a Fe(II)/Fe(I) reduction process in each of their metal centers, but only the grid-like complex exhibits easily oxidizable metal centers. In the solid state, both complexes are in the low spin state within a wide range of temperatures, but the corner also exhibits several types of high spin states coexisting at all times. From an exploratory viewpoint, our results are important to carry out the eventual synthesis of metal complexes with suitable properties for nanotechnological applications.

Asphaltenes are polydisperse, compositionally complex solubility fractions of crude oil, with a range of structural motifs that contain two primary structural classes: molecules with single aromatic cores (island) and bridged aromatic moieties (archipelago), each with varying degrees of alkyl substitution (e.g., varied-length alkyl units) and multi-heteroatom functionalities responsible for aggregate formation through weak and strong intermolecular associations. Understanding the link between asphaltene molecular composition and problematic behavior, such as deposit and emulsion formation, is vital to improve crude oils up- and downstream processes in petrochemical industries. Some reports suggest that asphaltene precipitation occurs primarily through self-association of polar functional groups and highlight direct correlations between aggregate size and emulsion stability. Here, we compare the molecular composition of whole and thin-layer chromatography (TLC)-fractioned PetroPhase 2017 asphaltenes charac...

As worldwide agricultural production rises, agro-industrial biomass becomes an abundant raw source for uses in energy and materials production. In Colombia fique plants (Furcraea spp.) are traditionally used to extract hard cellulosic fibers using mechanical decortication. Juice, pulp and tow, the by-products of this process, represent almost 95% of the fique leaf weight and are produced in large quantities. Data on these materials is scarce and greatly needed to guide and fuel fique agro-industrial development in Colombia. In this contribution we study the physicochemical properties of fique fibers and by-products (tow and pulp), before and after alkaline hydrogen peroxide treatment (AHP), using spectroscopic and microscopic techniques. Raw/clean fique tow is similar in structure and composition to fique fibers with average cellulose, hemicellulose and lignin contents of 52.3, 23.8 and 23.9%; in this by-product cellulose exists as a highly ordered structure with crystallinity index of 57%. Raw/clean fique pulp, composed of cellulose filaments from secondary cell walls and leaf epidermis, has average cellulose, hemicellulose and lignin contents of 30.5, 29.7 and 9.6%, with cellulose exhibiting an amorphous structure with a crystallinity index of 35%. The AHP treatment of these by-products effectively removed non-cellulosic compounds such as hemicellulose and lignin. After AHP lignin content in fique tow decreases to 2.8% while cellulose crystallinity increases up to 73%, Likewise, fique pulp shows a reduction in lignin to 2.1% and an increase in cellulose crystallinity up to 47%. IR spectroscopic analysis, after AHP, show a decrease of signals attributed to hemicellulose and lignin and FESEM images show a disruption of the lamellar structure in the macro fiber by the removal of hemicellulose, lignin and ground tissue, leaving cellulose fibrils exposed. As the first in-depth report on fique by-products characterization, our results indicate that pulp and tow are interesting lignocellulosic materials due to their significant content of crystalline and amorphous cellulose.

We report on a matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF) method to analyze naphthenic acids (NAs), from petrochemical samples, using 9-aminoacridine (9-AA) and a proton sponge 1,8-bis(dimethylamino) naphthalene (DMAN), as matrices. Singly charged deprotonated molecules of NAs, [M−H] − , dominated the negative ion MALDI mass spectra. The negative ions were pre-formed in solution through an acid/base Bronsted-Lowry reaction promoted by the highly basic matrices (9-AA and DMAN). The DMAN afforded cleaner spectra with absence of clusters, aggregates or matrix interferences at low m / z ; in addition, it provides molecular weight distributions similar to those observed with negative ion electrospray ionization (ESI). In contrast, MALDI spectra obtained with 9-AA exhibits matrix interferences at low mass, and bias towards aliphatic NAs. Finally, we observe the presence of monomeric species in the low mass region and non-covalent aggregates at higher masses in the negative mode MALDI spectra with both matrices, much like with negative mode ESI. We demonstrate that MALDI-TOF/MS is a viable tool for NAs analyses with added advantages such as high throughput and exceptional tolerance to the presence of impurities and salts in the samples, when compared with ESI.

Herein we report the synthesis and structural characterization of a new Ni-bis(hydrazone) complex with the chemical formula [Ni2(L)2(Cl)2](Cl)2·2H2O (L ​= ​2-(heptylthio)-4,6-bis(2-((E)-pyridin-2-ylmethylene)hydrazineyl)pyrimidine). Suitable crystals for X-ray diffraction showed the supramolecular interactions of this complex to exhibit a helical structure coordinating two Ni2+ metal ions bounded by two 2-(heptylthio)-4,6-bis(2-((E)-pyridin-2-ylmethylene)hydrazineyl)pyrimidine ligands. In addition, exploitation of the electrochemical properties by cyclic voltammetry, for this helicate, showed catalyzing ability for the reduction of H+ to H2.

Electron-transfer ionization in matrix-assisted laser desorption/ionization (ET-MALDI) is widely used for the analysis of functional materials that are labile, unstable, and reactive in nature. However, conventional ET matrices (e.g., trans-2-[3-(4- tert-butylphenyl)-2-methyl-2-propenylidene] malononitrile (DCTB)) still lack in performance due to cluster formation, reactivity with analytes, and vacuum instability. In this contribution, we report the use of α-cyanophenylenevinylene derivatives as UV MALDI matrices for the analysis, by ET ionization, of nanoparticles, polymers, porphyrins, and fullerenes. The synthetic versatility of the phenylenevinylene (PV) core allowed us to modulate physicochemical properties, fundamental for efficient formation of primary ions in the gas phase under MALDI conditions, such as planarity, ionization potentials, molar absorptivity, and laser thresholds. For instance, introduction of -CN groups in vinyl positions of the PV core induced structural disruption in planarity in the new α-CNPV derivatives, shifting their maximum molar absorptivity to UV wavelengths and increasing their ionization energy values above 8.0 eV. UV MALDI-relevant photophysical properties in solution and solid state are reported (λ

Cement materials have good compression strength, but poor tensile resistence. Aiming to improve this property, natural fibers can be applied as reinforcement. However, natural fibers have low adhesion with cement, and surface treatments are needed. In this work, sisal fibers were submitted to a cationization process followed by the grafting of two kinds of nanoparticles, Fe2O3 and MnO2. It is a usual treatment to dye fibers to the fabrics. The fibers microstructural characteristics were evaluated, before and after treatment, by using FTIR, XRD, TGA, DSC, SEM, water absorption, and tensile strength tests. The effect of the nanoparticles on the sisal fiber-cement matrix adhesion was evaluated by single fiber pull-out tests. The results show the cationization process removes part of lignin, increasing the fiber crystallinity, while the grafting of nanoparticles reduces the fiber crystalline degree, which indicates that nanoparticles grafting in the lignin spaces. The nanoparticles grafting acts as a catalyst of cellulose formation during the thermal degradation changing the initial fiber degradation profile. All treatments have caused a reduction in the absorbed water amount, become the fibers more stable dimensionally. They have improved the fiber adhesion on the cementitious matrix, being the sisal fiber grafting with MnO2 the best result.

We report a ‘one-pot’ synthetic approach for TEMPO (2,2,6,6-tetramethyl-piperidin-1-oxyl) oxidized cellulose nanofibrils (TOCN) surface amidation by coupling up to 70% of superficial carboxylic units in TOCN with long alkyl chain primary amines (dodecylamine and octadecylamine) using TBTU [O-(1H-benzotriazol-1-yl)-N,N,N’,N’-tetramethyluronium tetrafluoroborate] uronium salt as coupling agent. Raw TOCNs were produced from commercial microcrystalline cellulose and have an elongated highly tangled morphology with nanometric diameters and lengths up to several micrometers with a crystallinity of 62%. TOCN´s degree of oxidation was 1.25 mmol –COOH groups/g cellulose. The TOCN-amidated products named TOCN-AMDC12 and TOCN-AMDC18 depending upon to the primary amine used for the synthesis (dodecylamine –C12– for the former and octadecylamine –C18– for the latter), were characterized using field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy with attenuated total reflectance and X-ray diffraction. After amidation the hydrated gel-like TOCNs become a cream-colored gel insoluble in water and soluble in toluene. IR data indicates formation of an amide bond after the reaction, and FESEM images suggest a slight increase in fibril width as a result of the long-chain amide derivatives grafted onto the TOCN’s surface. Thermal stability and hydrophobicity of the products were determined using thermogravimetrical analysis and contact angle (CA) measurements. The TOCN-amidated products showed improved thermal properties with maximum decomposition temperatures of 347 and 358 °C, for TOCN-AMDC12 and TOCN-AMDC18 respectively, when compared to the raw TOCN (Td 340 °C); and high hydrophobicity with CA of 61° and 67°, respectively. Finally, the proposed method for TOCN amidation has advantages over current amidation approaches in that it is performed in aqueous media, does not require heating and occurs rapidly (2 h).

Separation strategies coupled with HRMS analysis are vital to increase the scope of the instrumental technique. In this work, we use extrography and column chromatography as fractionation tools for increasing compositional space accessibility in the APPI-FT-ICR mass spectrometric analysis of heavy crude oils. Extrography fractionation was performed on a crude oil sample adsorbed on neutral alumina, using an elutropic series. The crude oil was adsorbed on neutral alumina, and then we applied Soxhlet extraction using acetonitrile, methanol, n-heptane, and toluene, to obtain fractions enriched in metal complexes, polar compounds, maltenes, and asphaltenes, respectively. Considering that polar compounds are responsible for complex operational problems such emulsion and deposit formation, we fractioned the polar extract using normal phase column chromatography to obtain six additional subfractions. All of the extracts were analyzed by APPI FT-ICR mass spectrometry. We detected eleven compound classes in fractions and sub-fractions which were undetectable when analyzing the entire crude oil sample. In terms of the number of molecular formulas, the whole crude oil sample exhibits ∼3700 while ∼11,800 compounds were detected in extrography fractions and column chromatographic sub-fractions. These results indicate that combination of extrography and column chromatography increase compositional space accessibility in around 70%. Specifically, fractionation processes allowed the detection of several compound classes such as NnSs, NnOo, OoSs, NnOoSs (with n = 1; s = 1, 2, 3; o = 1, 2, 3), and N4O1V1, which were undetectable in the analysis of the whole crude oil.

In this contribution, we use high-resolution mass spectrometry to unveil the molecular composition of occluded compounds inside Colombian asphaltenes macrostructures. We use Soxhlet extraction, with n-heptane, coupled with asphaltene maceration to obtain four fractions enriched with chemical compounds occluded inside asphaltene networks. We focused our efforts on the fraction enriched with compounds interacting with asphaltenes via strong intermolecular forces, and used normal phase column chromatography to fractionate it and atmospheric pressure photoionization coupled to Fourier transform ion cyclotron resonance mass spectrometry to obtain a detailed molecular description. Our results indicate that the occluded compounds obtained in the last stage of the washing process are by themselves a complex mixture, consisting mostly of saturated compounds including molecular formulas corresponding to biomarkers, alkyl aromatics with high heteroatom content (up to four heteroatoms), vanadyl porphyrins, and highly...

Formation of water/oil emulsions is a frequent and challenging problem to deal with during crude oil extraction and processing. Crude oil must have water contents (BSW however, alternative surface-active compounds such as biosurfactants are nowadays the topic of active research. In this contribution, we report the use of aqueous suspensions of cellulose nanoparticles, both nanocrystals (CNC) and nanofibrils (CNF), to inhibit the formation of w/o emulsions. HLB values of 13.0 for CNF and 10.7 for CNC indicate that these materials are hydrophilic o/w emulsifying agents, and as such can also act as destabilizers for w/o emulsions. We observe, by recovered water and Near-Infrared (NIR) scattering measurements, that CNC and CNF can effectively function as inhibitors of synthetic w/o and natural w/crude oil emulsions. Aqueous suspensions of CNC and CNF decrease the amount of emulsified water, inhibiting the formation of w/o emulsions up to 75% in some cases.

With heavy crude oil refining on the rise, upgrading strategies are fundamental to yield high-value products. Hydroconversion and thermal cracking are well-established and widely used upgrading processes for heavy oils’ distillation cuts and residues. Recognizing molecular changes in these fractions after upgrading, particularly of asphaltenic compounds, is fundamental to understand and optimize the processes. In this work, we follow compositional changes in the asphaltene fraction of a Colombian heavy crude, after hydroconversion and thermal cracking, using high-resolution mass spectrometry. The liquid products from the upgrading processes were fractionated into maltenes and residual asphaltenes, with yields between 33% and 38% in maltenes from the original asphaltene feedstock. Contoured plots of double bond equivalents versus carbon number and van Krevelen diagrams show maltenic fractions exhibiting lower aromaticity, smaller molecular size, fewer heteroatomic species, and higher content of alkyl side ...

We report on the use of fique natural fibers as solid matrices for the deposition of zinc oxide (ZnO). Fique fibers, native to Colombia, are composed of cellulose (63–70 %) and have a heterogeneous surface morphology with high oxygen density that facilitates metal oxide nanoparticle growth and stabilization. Fique fiber–ZnO biocomposites were synthesized by a co-precipitation method using ZnSO4 as precursor, NaOH for hydroxide formation and thermal/ultrasound energy to promote Zn(OH)2/Zn(OH) 4 2− decomposition and ZnO formation. The biocomposite was characterized using X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy with attenuated total reflectance, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The synthesis of ZnO nanoparticles has been widely reported on inorganic substrates and soft natural fibers; however studies on how experimental parameters affect ZnO features on heterogeneous phase reactions are scarce, as well as the use of hard complex cellulosic fibers as solid supports for its growth. We observed that [OH−]/[Zn2+] ratios, heating or sonication time wield a strong influence on the amount, shape, size and distribution of ZnO crystals on the fique fibers; hence confirming the potential of hard natural fibers as surface active materials for novel biocomposites synthesis. We believe these materials, where the hard fiber robustness and the transition metal oxide catalytic properties are synergistically combined, could be promising functional alternatives that will favor a widespread nanoparticle usage for environmental applications such as wastewater treatment processes.

Asphaltene adsorption properties on mineral surfaces are fundamental to understanding wettability changes in rocks and fluid behavior in reservoirs. In this contribution we report an analytical approach to investigate the molecular features responsible for asphaltene–silica interactions. We used high performance thin layer chromatography silica plates and an elutropic series of solvents to fractionate asphaltenes according to their particular affinity with the mobile and stationary phases. We observed three characteristic asphaltene fractions (with Rfs of 0, 0.69, and 0.90), which were in turn desorbed and analyzed by atmospheric pressure photoionization FT-ICR mass spectrometry (APPI-FT-ICR-MS). In general, polar noneluted compounds highly retained by the silica surface with Rf = 0 exhibit molecular compositions with N1, NnOo and Oo (o = 1, 2, 3 and n = 1, 2) classes and the lowest H/C ratios compared to the other subfractions. Polar CH2Cl2:MeOH-eluted compounds, with Rf = 0.69, have predominantly HC, N...

Phenylenevinylene oligomers (PVs) have outstanding photophysical characteristics for applications in the growing field of organic electronics. Yet, PVs are also versatile molecules, the optical and physicochemical properties of which can be tuned by manipulation of their structure. We report the synthesis, photophysical, and MS characterization of eight PV derivatives with potential value as electron transfer (ET) matrices for UV-MALDI. UV-vis analysis show the presence of strong characteristic absorption bands in the UV region and molar absorptivities at 355 nm similar or higher than those of traditional proton (CHCA) and ET (DCTB) MALDI matrices. Most of the PVs exhibit non-radiative quantum yields (φ) above 0.5, indicating favorable thermal decay. Ionization potential values (IP) for PVs, calculated by the Electron Propagator Theory (EPT), range from 6.88 to 7.96 eV, making these oligomers good candidates as matrices for ET ionization. LDI analysis of PVs shows only the presence of radical cations (M+.) in positive ion mode and absence of clusters, adducts, or protonated species; in addition, M+. threshold energies for PVs are lower than for DCTB. We also tested the performance of four selected PVs as ET MALDI matrices for analytes ranging from porphyrins and phthalocyanines to polyaromatic compounds. Two of the four PVs show S/N enhancement of 1961% to 304% in comparison to LDI, and laser energy thresholds from 0.17 μJ to 0.47 μJ compared to 0.58 μJ for DCTB. The use of PV matrices also results in lower LODs (low fmol range) whereas LDI LODs range from pmol to nmol.

Gold nanoparticles were synthesized on the surface of natural fique fibers extracted from the leaves of Furcraea spp., a plant native to the Andean mountains in Colombia. Fique fibers have a low density, are biodegradable, flexible, highly resistant to wear and exhibit excellent thermal degradation making them promising materials for the textile and packing industries as well as fillers for fiber-reinforced composites. Fique fiber surface was rendered positive using a cationizing agent 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHTAC) under strong alkaline conditions. Cationic fique fibers were impregnated with an anionic gold complex that was further reduced to generate gold nanoparticles onto the fibers surface. The influence of CHTAC reaction times and NaOH:CHTAC molar ratios were examined. It was found that increasing the NaOH:CHTAC molar ratio had a negligible effect on nanoparticle size, while the surface coverage density was positively influenced. We hypothesize that the number of positive charges on the fiber surface is the key factor behind this observation. UV–Vis diffuse reflectance spectroscopy; mechanical tests and field emission scanning electron microscopy were used to characterize the modified fibers and the resulting nanoparticles. The proposed method opens a new path for the development of functional natural renewable substrates.

The synthesis and characterization of the copper(II) complexes of a series of tetradentate, pentadentate and hexadentate aminopyridine ligands that contain ethylenediamine and/or propylenediamine groups are described. The ligands include: 1,12-bis(2-pyridyl)-2,5,8,11-tetraazadodecane, TRIEN-pyr; 1,13-bis(2-pyridyl)-2,5,9,12-tetraazatridecane, DIEN-PN-pyr; 1,14-bis(2-pyridyl)-2,6,9,13-tetraazatetradecane, DIPN-EN-pyr; 1,15-bis(2-pyridyl)-2,6,l0,14-tetraazapentadecane, TRIPN-pyr; 1,9-bis(2-pyridyl)-2,5,8-triazanonane, DIEN-pyr; 1,11-bis(2-pyridyl)-2,6,10-triazaundecanenane, DIPN-pyr; 1,6-bis(2-pyridyl)-2,5-diazahexane, EN-pyr; and 1,7-bis(2-pyridyl)-2,6-diazaheptane, PN-pyr. The following methods were used to determine the binding geometries of the copper(II) complexes in the solid, solution, and gas phases: magnetic susceptibility measurements, absorption spectroscopy, EPR spectroscopy, electrochemistry, and electrospray ionization mass spectrometry. An X-ray structure was determined for the DIPN-pyr complex. The solid state structures were all found to be monomeric Cu(II) complexes with the coordination number set by the denticity of the ligand while the solution structures of all of the complexes except those with TRIPN-pyr and DIPN-pyr were found to be square pyramidal or elongated octahedral. The TRIPN-pyr and DIPN-pyr complexes showed considerable trigonal bipyramidal distortions. The gas phase data showed that the substitution of 6-membered for 5-membered chelate rings helped the ligand span more coordination sites. The TRIEN-pyr complex was 4- or 5-coordinate compared to the 5- or 6-coordination seen with the other three hexadentate ligands, and the DIPN-pyr complex was weakly 5-coordinate as compared to the 4-coordinate DIEN-pyr complex. The preferred structures of the ligands were consistent with their electrochemical behavior which showed the stability of the Cu(II) complex decreased in the order: DIPN-EN-pyr, TRIEN-pyr, DIEN-PN-pyr > DIEN-pyr > DIPN-pyr > TRIPN-pyr > PN-pyr > EN-pyr.

The gas-phase reactions of ammonia with M(EN-(py)2)2+, M(en)(phen)2+, and M(phen)22+, where M is Mn(II), Fe(II), Co(II), Ni(II), Cu(II), or Zn(II), EN-(py)2 is 1,6-bis(2-pyridyl)-2,5-triazahexane, en is ethylenediamine, and phen is 1,10-phenanthroline, have been studied in a quadrupole ion trap mass spectrometer. The trends in reactivity as a function of the metal are noticeably different for each complex despite the similarity of the ligand donor groups. These results indicate that coordination geometry and electronic structure have a significant impact on the gas-phase reactivity of four-coordinate metal complex ions. Specifically, for M(EN-(py)2)2+ the equilibrium constants for the reactions with ammonia follow the trend Mn ≈ Fe ≈ Co > Zn ≫ Cu > Ni. The trend for the equilibrium constants of the M(en)(phen)2+ complexes is Mn ≈ Co ≫ Ni > Cu > Zn, and for the M(phen)22+ complexes, the trend is Ni > Mn ≈ Fe > Co > Cu > Zn. The most notable changes in reaction equilibrium constants occur for the Ni and Zn ...

The synthesis and characterization of the nickel(II) complexes of a series of pentadentate and hexadentate aminopyridine ligands that contain ethylenediamine and/or propylenediamine groups are described. The ligands include: 1,12-bis(2-pyridyl)-2,5,8,11-tetraazadodecane, TRIEN-pyr; 1,13-bis(2-pyridyl)-2,5,9,12-tetraazatridecane, DIEN-PN-pyr; 1,14-bis(2-pyridyl)-2,6,9,13-tetraazatetradecane, DIPN-EN-pyr; 1,15-bis(2-pyridyl)-2,6,10,14-tetraazapentadecane, TRIPN-pyr; 1,9-bis(2-pyridyl)-2,5,8-triazanonane, DIEN-pyr; and 1,11-bis(2-pyridyl)-2,6,10-triazaundecane, DIPN-pyr. The following methods were used to determine the binding geometries of the nickel(II) complexes in the solid, solution, and gas phases: magnetic susceptibility measurements, absorption spectroscopy, EPR spectroscopy, electrochemistry, and electrospray ionization mass spectrometry. All of the ligands form 6-coordinate compounds in the solid, liquid, and gas states, with the exception of the TRIEN-pyr, DIEN-PN-pyr(partially), DIPN-pyr, and DIEN-pyr ligands which form 5-coordinate species in the gas state. All of the complexes could be oxidized to Ni(III) species electrochemically, although the Ni(III) complexes of TRIPN-pyr and DIPN-pyr were much less stable than the other four ligands. EPR spectra of the frozen solutions showed the low spin d7 Ni(III) complexes of TRIEN-pyr and DIPN-EN-pyr to be similar to those that have been found for poly-aza macrocyclic compounds.

Gas-phase ion–molecule reactions of metal complex ions with acetonitrile in a quadrupole ion trap mass spectrometer are shown to have some potential for determining the number and types of functional groups bound to a metal. Metal complexes with varying coordination spheres show significant differences in their gas-phase reactivity with acetonitrile. The relative product ion intensities observed in the mass spectrum after a given reaction time provide the appropriate data to distinguish complexes with different coordination spheres. Experimental parameters suspected to have an effect on the reproducibility of these intensities are examined in order to understand better which factors need to be most closely controlled to maximize precision. Ni(II) and Cu(II) complex ions of the pentadentate ligands 1,9-bis(2-imidazolyl)-2,5,8-triazanonane (DIEN-(imi)2) and 1,9-bis(2-tetrahydrofuranyl)-2,5,8-triazanonane (DIEN-(THF)2) are reacted in the gas-phase at different temperatures, pressures of acetonitrile, and pressures of buffer gas (helium) in a modified quadrupole ion trap mass spectrometer. The effects of such experimental variations on the product ion intensities are measured and analyzed. Under conditions where the precision is maximized, the temperature and acetonitrile pressure seem to have the biggest impact on the reproducibility of the resulting product ion intensity with the acetonitrile level being slightly more important. The reproducibility of ion intensities for the reactions of the Ni(II) complexes are the lowest due to their higher reactivity, while the measurements for the Cu(II) complexes have a higher degree of precision. In general, with careful control of the temperature and reagent gas pressure, ion–molecule (I–M) reactions seem to be a promising method for providing a rapid and sensitive analysis of the functional groups bound to a metal in a given complex.

Biodegradable polymers are currently viable alternatives to traditional synthetic polymers. For instance, polyhydroxybutyrate (PHB) is intracellularly produced and accumulated by Bacillus species, among others. This study reports several wild-type Bacillus strains with the ability to accumulate PHB using raw glycerol from biodiesel production as the sole carbon source. Out of 15 strains from different sources, B. megaterium B2 was selected as the most promising strain for further statistical optimization of the medium composition. Plackett-Burman and central composite designs were used to establish key variables and optimal culture conditions for PHB production using both 250-mL shake flasks and a 7.5-L bioreactor. Temperature and concentrations of glycerol and Na2HPO4 are the experimental variables with the most significant influence on PHB production by B2. After 14 hours of fermentation in shake flasks with optimized medium, B2 produced 0.43 g/L of PHB with a 34% accumulation in the cells. In contrast, under the same conditions, a maximum PHB concentration of 1.20 g/L in the bioreactor was reached at 11 hours. These values correspond to a 48% and 314% increase in PHB production compared to the initial culture conditions. These results suggest the potential of B2 as a PHB producer using raw glycerol, which is an inexpensive, abundant and readily available carbon source.

Secondary volatile metabolites were isolated by simultaneous distillation-solvent extraction (SDE) and supercritical (CO2) extraction (SFE) from flowers, leaves and stems of Spilanthes americana (Mutis) Hieron (Compositae). The extracts were analyzed by capillary gas chromatography using flame ionization, nitrogen-phosphorus (NPD) or mass spectrometric detection. Compounds were identified according to their Kovats indexes, mass spectra (EI, 70 eV), or by comparison with standard substances. The method of extraction (SDE, SFE) and the source of the plant material (flowers, stems, leaves) affected the composition of the extracts. SFE extracts from stems were rich (>40%) in sesquiterpenes (α- and s-bisabolenes, caryophyllene and cadinenes), while those from leaves and flowers were abundant in nitrogenated (43 and 27%) and oxygenated (36 and 23%) compounds. N-(isobutyl)-2E,6Z,8E-decatrienamide, N-(2-methylbutyl)-2E,6Z,8E-decatrienamide, decatrienamide, N-(isobutyl)-6Z,83-decadienamide and N-(2-phenelethyl)2-E,6Z,-8E-decatrienamide are examples of the nitrogenated compounds found. SDE extracts from stems, leaves, and flowers of S. americana contained sesquiterpene levels of 32, 28 and 20%, and a generally higher proportion of oxygenated compounds (28, 52 and 32%) and monoterpenes (27, 10 and 42%) than their SFE counterparts. Only trace-level contents of nitrogenated compounds were found using NPD in SDE extracts. Some heavy hydrocarbons (Cn>20) originated from flower pigments and waxes were isolated by SFE but not by SDE. SFE was both selective and highly efficient in the isolation of sesquiterpenes, heavy hydrocarbons and nitrogenated compounds (amides).

Essential oils from fruit peel and leaves of colombian lemon ( Citrus volkameriana ), mandarin ( C. reticulata ) and orange ( C. sinensis ) were obtained by steam distillation and/or cold pressing. The extracts were analysed by high-resolution gas chromatography using either a flame ionization detector or a mass selective detector (electron impact ionization, 70 eV). The oil constituents were identified according to their mass spectra and Kova´ts retention indices determined on both polar and non-polar stationary phase capillary columns. The concentration of volatile secondary metabolites was maximum when the citrus fruits were at an intermediate maturation stage characterized by a greenish yellow coloration (45–75% green). While citrus peel oils contained from 94.01 to 98.66% of monoterpenes (C 10 H 16 ), limonene as a major component and from 0.82 to 5.84% of oxygenated compounds, the extracts from citrus leaves contained only 65.26, 31.23 and 79.43% of monoterpenes (C 10 H 16 ) in lemon, mandarin and orange, respectively. Oxygenated compounds in these oils represented 33.08, 68.47 and 16.38%, respectively.

Volatile secondary metabolites from different parts (flowers, leaves, stems, and roots) of Colombian rue (Ruta graveolens) were obtained by combined steam distillation-solvent extraction. The various oils were analyzed by means of GC using FID, NPD, or MSD. The chemical composition of the oils extracted from the aerial parts differed drastically from those extracted from the roots. 3-Pyrrolidinol, 1,4-dimethylpiperazine, and various 1,3-benzodioxole derivatives were detected in the Colombian rue oil for the first time.

The dependence of the limonene content of lemon (Citrus volkameriana) peel oil on the degree of ripeness of the fruit has been studied by using steam distillation and cold pressing to extract the oils from lemon fruit peel at different stages of maturation (green, greenish-yellow, and yellow-orange peel coloration). Samples of essential oils were analyzed by high resolution GC and GC-MS, using tetradecane as internal standard for quantitation. Forty components were detected; thirty eight were positively identified by comparison of their mass spectra (El, 70 eV) and Kovats retention indexes (determined using a non-logarithmic scale on capillary columns coated with both polar (DB-Wax) and non-polar (DB-1) stationary phases) with those of standards and with data reported in the literature. The limonene concentration reached a maximum level of 79.4% when the fruit was in the intermediate maturation stage characterized by greenish-yellow coloration.

Five-coordinate metal complex ions of the type [ML](2+) [where M = Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II) and L= 1,9-bis(2-pyridyl)-2,5,8-triazanonane (DIEN-(pyr)(2)) and 1,9-bis(2-imidazolyl)-2,5,8-triazanonane (DIEN-(imi)(2)] have been reacted with acetonitrile in the gas phase using a modified quadrupole ion trap mass spectrometer. The kinetics and thermodynamics of these reactions show that the reactivity of these complexes is affected by metal electronic structure and falls into three groups: Mn(II) and Ni(II) complexes are the most reactive, Fe(II) and Co(II) complexes exhibit intermediate reactivity, and Cu(II) and Zn(II) complexes are the least reactive. To help explain the experimental trends in reactivity, theoretical calculations have been used. Due to the relatively large size of the metal complexes involved, we have utilized a two-layered ONIOM method to perform geometry optimizations and single point energy calculations for the [ML](2+) and [ML + CH(3)CN](2+) systems. The calculations show that the reactant five-coordinate complexes ([ML](2+)) exhibit structures that are slightly distorted trigonal bipyramidal geometries, while the six-coordinate complexes ([ML + CH(3)CN](2+)) have geometries that are close to octahedral. The Delta G values obtained from the ONIOM calculations roughly agree with the experimental data, but the calculations fail to completely explain the trends for the different metal complexes. The failure to consider all possible isomers as well as adequately represent pi-d interactions for the metal complexes is the likely cause of this discrepancy. Using the angular overlap model (AOM) to obtain molecular orbital stabilization energies (MOSE) also fails to reproduce the experimental trends when only sigma interactions are considered but succeeds in explaining the trends when pi interactions are taken into account. These results indicate that the pi-donor character of the CH(3)CN plays a subtle, yet important, role in controlling the reactivity of these five-coordinate complexes. Also, the AOM calculations are consistent with the experimental data when the [ML](2+) complexes have high-spin trigonal bipyramidal configurations. Generally, these results suggest that ion-molecule reactions can be very sensitive to metal complex coordination geometry and thus may have some promise for providing gas-phase coordination structure.

We report on the in situ synthesis of nanostructured MnO2 onto natural fique fibers. The fiber surface was rendered positive by exposure to alkaline conditions, and permanganate anions (MnO4−) were embedded onto the resultant alkali cellulose via coulombic interactions. An ultrasound-assisted procedure was used to reduce MnO4− and yield MnO2 nanoparticles (NPs). UV-Vis diffuse reflectance was used to assess the influence of the precursor concentration, loading and reduction times on the synthesis of the nanostructured MnO2. FESEM provided direct evidence that MnO2 NPs and aggregates could be formed on the fiber's surface. The catalytic activity of the new bionanocomposite was tested for the removal of indigo carmine dye in water samples. The MnO2–fique fiber bionanocomposite was able to remove up to 98% of the colour present in the contaminated water samples in less than 5 minutes. Mass spectrometry was used to determine the degradation route of the dye. Additionally, we found that the bionanocomposite can be reused with no effect on the dye degradation efficiency. The reported procedure provides a new route for the development of biodegradable and easy to synthesize composite materials capable of efficiently degrading pollutants found in industrial effluents.