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.

Rice Labeling according to Grain Quality Features Using Laser-Induced Breakdown Spectroscopy.

Rice is an important source of nutrition and energy consumed around the world. Thus, quality inspection is crucial for protecting consumers and increasing the rice's value in the productive chain. Currently, methods for rice labeling depending on grain quality features are based on image and/or visual inspection. These methods have shown subjectivity and inefficiency for large-scale analyses. Laser-induced breakdown spectroscopy (LIBS) is an analytical technique showing attractive features due to how quick the analysis can be carried out and its capability of providing spectra that are true fingerprints of the sample's elemental composition. In this work, LIBS performance was evaluated for labeling rice according to grain quality features. The LIBS spectra of samples with their grain quality numerically described as Type 1, 2, and 3 were measured. Several spectral processing methods were evaluated when modeling a k-nearest neighbors (k-NN) classifier. Variable selection was also carried out by principal component analysis (PCA), and then the optimal k-value was selected. The best result was obtained by applying spectrum smoothing followed by normalization by using the first fifteen principal components (PCs) as input variables and k = 9. Under these conditions, the method showed excellent performance, achieving sample classification with 94% overall prediction accuracy. The sensitivities ranged from 90 to 100%, and specificities were in the range of 92-100%. The proposed method has remarkable characteristics, e.g., analytical speed and analysis guided by chemical responses; therefore, the method is not susceptible to subjectivity errors.

Mixed-Metal MOF-Derived Carbon Sponges for Oil Absorption.

AIMS: In this work, we propose the implementation of three carbon sponges, generated from the carbonization of melamine-formaldehyde sponges coated with different HKUST-type metal-organic frameworks (MOFs) in different thermal conditions. BACKGROUND: Nowadays, numerous investigations are focused on the development of new technologies for the rapid separation of water/oil mixtures. Several of these processes use hydrophobic materials of different nature for efficient oil capture. Despite these efforts, the water/oil separation still remains a great challenge. The main oil absorbers that are commercially available tend to be expensive and have complex synthesis; however, they usually have an acceptable cost/benefit ratio. Despite this, the passage of time has brought us new generations of materials, which seek to solve the problems in a more efficient way, as in the case of metal-organic frameworks (MOFs), which stand out for the great ease with which their morphological and surface aspects can be controlled. MOFs are extensively investigated in the fields of adsorption and catalysis; the MOF coated sponges do not meet the selectivity and stability standards to be applied in oil spills in water. However, this completely changes when subjected to the pyrolysis process, giving the material an increase in its surface area, hydrophobic and magnetic properties in addition to making the material suitable for its application. OBJECTIVE: Creation of a low-cost 3D template and the study of morphological properties of MOFs, for the formation of carbon-based materials by a fast, simple and low-cost method, promoting the use of new generations of materials to more effectively solve persistent environments. METHODS: The employed MOF precursors were trimesic acid (BTC), nickel and cobalt salts. The monometallic HKUST type MOFs were synthesized using a simple method of controlled precipitation, which starts from two precursor solutions. The first one consisted of a ligand solution, dissolving the BTC in deionized water. In the case of mixed-metal MOFs, they were synthesized using the same procedure described for monometallic MOFs, but in this case, a mixture of metal salts with a 1:1 molar ratio was performed. The methodology for the production of the sponges decorated with MOF was carried out in two steps. In the first stage, the sponges were subjected to a wash to remove dust and impurities, being rinsed with acetone in an ultrasonic bath for 30 min. The sponges were subsequently immersed in deionized water and subjected to an ultrasonic bath for 10 min. Finally, the sponges were dried at 60°C for 3 h. The second step was the addition of the HKUST-type MOFs to the sponges was carried out by means of the immersion method, preparing a dispersion of the corresponding MOFs in ethanol. RESULTS: It was revealed that the carbon sponges can selectively absorb oil in the water/oil mixture, possessing magnetic and enhanced hydrophobic and superhydrophobic properties. All the pyrolyzed carbon sponges, obtained at 500 and 700°C, were not the most optimal since they had absorption capacities of around 25 g/g and only supported up to 4 absorption cycles. On the other hand, the carbon sponges, obtained at 300°C, had absorption capacities greater than 40 g/g, in addition to being able to be reused up to 12 times without showing significant changes in their absorption capacity and having acceptable hydrophobic characteristics for the removal of oil dispersed in water. Among the three sponges obtained at 300°C, we highlight the sponges coated with BTC-Co, which have the highest absorption capacity (54 g/g) among all fabricated sponges. CONCLUSIONS: The sponges obtained in the present work are a promising alternative to the materials that are traditionally used since they have great advantages such as their simple production method, low-cost starting materials and good absorption capacities. This work sheds light on the production of carbon materials from 3D templates decorated with MOFs, through a one-step carbonization process and we demonstrate that these materials have characteristics that make them applicable in the removal of oil dispersed in water, giving us a practical, economic and friendly alternative to the environment.

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.

Characterization of Chemically Activated Pyrolytic Carbon Black Derived from Waste Tires as a Candidate for Nanomaterial Precursor.

Pyrolysis is a feasible solution for environmental problems related to the inadequate disposal of waste tires, as it leads to the recovery of pyrolytic products such as carbon black, liquid fuels and gases. The characteristics of pyrolytic carbon black can be enhanced through chemical activation in order to produce the required properties for its application. In the search to make the waste tire pyrolysis process profitable, new applications of the pyrolytic solid products have been explored, such as for the fabrication of energy-storage devices and precursor in the synthesis of nanomaterials. In this study, waste tires powder was chemically activated using acid (H2SO4) and/or alkali (KOH) to recover pyrolytic carbon black with different characteristics. H2SO4 removed surface impurities more thoroughly, improving the carbon black's surface area, while KOH increased its oxygen content, which improved the carbon black's stability in water suspension. Pyrolytic carbon black was fully characterized by elemental analysis, inductively coupled plasma-optical emission spectrometry (ICP-OES), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), N2 adsorption/desorption, scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS), dynamic light scattering (DLS), and ζ potential measurement. In addition, the pyrolytic carbon black was used to explore its feasibility as a precursor for the synthesis of carbon dots; synthesized carbon dots were analyzed preliminarily by SEM and with a fluorescence microplate reader, revealing differences in their morphology and fluorescence intensity. The results presented in this study demonstrate the effect of the activating agent on pyrolytic carbon black from waste tires and provide evidence of the feasibility of using waste tires for the synthesis of nanomaterials such as carbon dots.

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.

A Comparison of Different Methods of MWCNTs Metalation in a Single Step Using Three Different Silver-containing Compounds.

BACKGROUND: Synthesis and applications of Ag-coated carbon nanotubes are currently under intensive research, resulting in a series of recent patents. Silver nanoparticles are normally obtained from silver nitrate. However, there are also other silver-containing compounds that can facilitate the production of silver nanoparticles, such as silver(I) acetate and silver(II) oxide. Being combined with carbon nanotubes, silver nanoparticles can transfer to them some of their useful properties, such as conductivity and antibacterial properties, and contribute to improving their dispersion in solvents. OBJECTIVE: To apply three different silver-containing precursors of Ag nanoparticles for the decoration of carbon nanotubes and study the morphology of formed composites by several methods. METHOD: Three different silver compounds were used as Ag source to carry out the functionalization and decoration of carbon nanotubes under ultrasonic treatment of the reaction system, containing, commercial carbon nanotubes, organic peroxides as oxidants or hydrazine as a reductant, and a surfactant. Resulting samples were analyzed by XRD and XPS spectroscopy, as well as TEM and SEM microscopy to study the morphology of formed nanocomposites. RESULTS: Silver nanoparticles can be produced without the presence of a reducing agent. Applying hydrazine, as a reducing agent, it is possible to obtain functionalized carbon nanotubes doped with silver nanoparticles, in which their sizes are smaller (1-5 nm) compared to those obtained without using hydrazine. CONCLUSION: Silver nanoparticles having a size range between 2-60 nm can be produced without the presence of a reducing agent. The use of a reducing agent, such as hydrazine, affects the size of silver nanoparticles.

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.