Measuring trace element fingerprinting for cereal bar authentication based on type and principal ingredient.

This paper introduces a method for determining the authenticity of commercial cereal bars based on trace element fingerprints. In this regard, 120 cereal bars were prepared using microwave-assisted acid digestion and the concentrations of Al, Ba, Bi, Cd, Co, Cr, Cu, Fe, Li, Mn, Mo, Ni, Pb, Rb, Se, Sn, Sr, V, and Zn were later measured by ICP-MS. Results confirmed the suitability of the analyzed samples for human consumption. Multielemental data underwent autoscaling preprocessing for then applying PCA, CART, and LDA to input data set. LDA model accomplished the highest classification modeling performance with a success rate of 92%, making it the suitable model for reliable cereal bar prediction. The proposed method demonstrates the potential of trace element fingerprints in distinguishing cereal bar samples according to their type (conventional and gluten-free) and principal ingredient (fruit, yogurt, chocolate), thereby contributing to global efforts for food authentication.

Enhancing Visible Light Photocatalytic Degradation of Bisphenol A Using BiOI/Bi2MoO6 Heterostructures.

With the growing population, access to clean water is one of the 21st-century world's challenges. For this reason, different strategies to reduce pollutants in water using renewable energy sources should be exploited. Photocatalysts with extended visible light harvesting are an interesting route to degrade harmful molecules utilized in plastics, as is the case of Bisphenol A (BPA). This work uses a microwave-assisted route for the synthesis of two photocatalysts (BiOI and Bi2MoO6). Then, BiOI/Bi2MoO6 heterostructures of varied ratios were produced using the same synthetic routes. The BiOI/Bi2MoO6 with a flower-like shape exhibited high photocatalytic activity for BPA degradation compared to the individual BiOI and Bi2MoO6. The high photocatalytic activity was attributed to the matching electronic band structures and the interfacial contact between BiOI and Bi2MoO6, which could enhance the separation of photo-generated charges. Electrochemical, optical, structural, and chemical characterization demonstrated that it forms a BiOI/Bi2MoO6 p-n heterojunction. The free radical scavenging studies showed that superoxide radicals (O2•-) and holes (h+) were the main reactive species, while hydroxyl radical (•OH) generation was negligible during the photocatalytic degradation of BPA. The results can potentiate the application of the microwave synthesis of photocatalytic materials.

Sequential SEM-EDS, PLM, and MRS Microanalysis of Individual Atmospheric Particles: A Useful Tool for Assigning Emission Sources.

In this work, the particulate matter (PM) from three different monitoring stations in the Monterrey Metropolitan Area in Mexico were investigated for their compositional, morphological, and optical properties. The main aim of the research was to decipher the different sources of the particles. The methodology involved the ex situ sequential analysis of individual particles by three analytical techniques: scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), polarized light microscopy (PLM), and micro-Raman spectroscopy (MRS). The microanalysis was performed on samples of total suspended particles. Different morphologies were observed for particles rich in the same element, including prismatic, spherical, spheroidal, and irregular morphologies. The sequential microanalysis by SEM-EDS/PLM/MRS revealed that Fe-rich particles with spherical and irregular morphologies were derived from anthopogenic sources, such as emissions from the metallurgical industry and the wear of automobile parts, respectively. In contrast, Fe-rich particles with prismatic morphologies were associated with natural sources. In relation to carbon (C), the methodology was able to distinguish between the C-rich particles that came from different anthopogenic sources-such as the burning of fossil fuels, biomass, or charcoal-and the metallurgical industry. The optical properties of the Si-rich particles depended, to a greater extent, on their chemical composition than on their morphology, which made it possible to quickly and accurately differentiate aluminosilicates from quartz. The methodology demonstrated in this study was useful for performing the speciation of the particles rich in different elements. This differentiation helped to assign their possible emission sources.

On the Effect of Ultralow Loading of Microwave-Assisted Bifunctionalized Graphene Oxide in Stereolithographic 3D-Printed Nanocomposites.

Surface functionalization of graphene oxide (GO) is one of the best ways to achieve homogeneous dispersions of GO within polymeric matrices and composites. Nonetheless, studies regarding how the level of GO functionalization affects the macroscopic properties of three-dimensional (3D) printed nanocomposites are still few. Furthermore, the bifunctionalization of GO with the NH2/NH3+ groups to obtain improved thermomechanical macroscopic properties at ultralow loads has not been reported. In this paper, fast and straightforward surface bifunctionalization of GO with a controlled ratio of NH2/NH3+ groups at low, medium, and high functionalization levels (AGOL, AGOM, and AGOH) in a one-step microwave-assisted synthesis is reported for the first time. The functionalization mechanism was disclosed, wherein three graft densities (Gφ) were obtained. A plateau of maximum functionalization (Gφ = 4.9 µmol/m2 = 2.9 molecules/nm2) was reached, suggesting that full coverage of the GO surface is achievable. Also, an increase in the exfoliation of functionalized layers was obtained, ranging from d002 = 8.6 Å up to d002 = 15.8 Å. X-ray photoelectron spectroscopy (XPS) reveals the successful functionalization of GO, as well as an atomic relationship NH2/NH3+ of about 50/50% in all functionalized samples. Stereolithographic (SLA) 3D-printed nanocomposites (AGOL/R, AGOM/R, and AGOH/R) were obtained using ultralow loads (0.01 wt %) of each bifunctionalized material. This ultralow amount was sufficient to enhance thermal stability (up to 4 °C) and a significant increase in the glass transition temperature (93 °C ≤ Tg ≤ 120 °C). Interestingly, we found that low and medium grafting density promotes a ductile material (ε > 5%); meanwhile, a high graft density produces brittle materials. Also, we observe that the toughness can be tuned as a function of the graft density (AGOH: 24 MPa, AGOM: 342 MPa, AGOL: 562 MPa) at ultralow loadings. The 3D-printed nanocomposites using GO with low graft density (AGOL) increase their tensile strain by 90% in comparison with the control sample (without filler). Finally, the underlying mechanisms were discussed to explain the findings.

The Role of α, γ, and Metastable Polymorphs on Electrospun Polyamide 6/Functionalized Graphene Oxide.

The present paper describes the addition of nitroxide-functionalized graphene oxide (GOFT) into polyamide 6 (PA6) micro- and nanofibers, which are obtained through electrospinning. Scanning electron microscopy micrographs demonstrate the presence of fibers. Tensile testing presents an unexpected and non-obvious behavior, in which the Young's modulus, tensile strength, and elongation simultaneously and remarkably increase compared to the pristine polymer nanofibers. GOFT induces the hydrogen bonding between the NH group from PA6 with the functional groups, thus promoting higher crystallinity of the polymer matrix. Nonetheless, deconvoluted curves by differential scanning calorimetry reveal the presence of two quasi-steady polymorphs (ß and Î´ phases) contributing to 46% of the total crystallinity. This evidence suggests that their presence and high ratios are responsible for the unexpected and simultaneous enhancement of tensile properties.

Environmental Levels, Sources, and Cancer Risk Assessment of PAHs Associated with PM2.5 and TSP in Monterrey Metropolitan Area.

In this work, the content of polycyclic aromatic hydrocarbons (PAHs) in total suspended particles and particulate matter with an aerodynamic diameter ≤ 2.5 µm (PM2.5) was analyzed using gas chromatography-mass spectrometry. In addition, a sequential chemical analysis of C-rich particles was performed through the parallel coupling of micro-Raman spectroscopy and scanning electron microscopy with X-ray scattering detection. Samples were collected at four sites in the Monterrey metropolitan area, Mexico. A total of 13 PAHs were quantified; indeno(1,2,3-cd)pyrene, chrysene, and benzo(a)anthracene were the most abundant. The total PAH concentrations at the four sampling sites ranged from 1.34 to 8.76 µg/m3. The diagnostic relation of the PAHs indicates that these compounds were emitted by the burning of gasoline and diesel and by the burning of charcoal and biomass. The sequential analysis correlated the morphology and the elemental/molecular composition of the C-rich particles, associated with the PAHs, with their possible emission sources. The estimated lifetime excess cancer risk for inhalation was higher than that established by the World Health Organization, which clearly makes this a potential health risk for the population.

Seasonal variation and chemical composition of particulate matter: A study by XPS, ICP-AES and sequential microanalysis using Raman with SEM/EDS.

During the winter period (January-March 2016), the total suspended particles (TSP) and particulate matter smaller than 2.5µm (PM2.5) were characterized by the application of various analytical techniques in four zones of the Metropolitan Area of Monterrey in Mexico. To evaluate the seasonal variation of some elements in the particulate matter, the results of this study were compared with those obtained during the summer season (July-September 2015). The speciation of the C1s signal by X-ray photoelectron spectroscopy revealed the contribution of aromatic and aliphatic hydrocarbons as the main components in both seasons. Conversely, carboxylic groups associated with biogenic emissions were detected only in winter. The percentages of SO42- ions were lower in winter, possibly caused by the decrease in the solar radiation, and relative humidity recorded. The results of the ICP analysis revealed that Fe, Zn and Cu were the most abundant metals in both TSP and PM2.5 in the two seasons. There were significant seasonal variations for concentrations of As, Ni and Zn in the urban area and for Fe, As, Cd, Ni and Zn in the industrial zone. This was attributed to the greater burning of fuels as well as to an increase in vehicular traffic, the effect of thermal inversion and changes in some meteorological parameters. The results of the sequential microanalysis by Raman spectroscopy and SEM/EDS allowed observation of deposits of carbonaceous material on the particles and to perform the speciation of particles rich in Fe and Pb, which helped infer their possible emission sources.