Dynamics of magnetic inhomogeneity in La2CoMnO6 films probed by Raman spectroscopy.

We report the dynamic effects of magnetic inhomogeneity on the temperature evolution of the Raman modes in polycrystalline La2CoMnO6 (LCMO) films. The LCMO films were obtained via chemical solution deposition and annealed at different temperatures, 700, 800 and 900 °C. Temperature-dependent Raman spectroscopic studies uncover anomalous phonon energy behaviors, associated with strong spin-phonon couplings revealed even at ambient conditions. This effect, which is observed to occur well above ferromagnetic ordering temperature is ascribed to short-range Mn4+/Co2+ ferromagnetic clusters. Moreover, our study has shown that spin-phonon coupling strength is governed by competing antiferromagnetic (AFM) and ferromagnetic (FM) interactions. These results significantly enhance the understanding of the complex spin-phonon coupling mechanism to provide insights into magnetic inhomogeneity in systems with two or more magnetic sublattices. These findings suggest the presence of similar effects in other double perovskites within the RE2CoMnO6 (RE = rare earths) family, which exhibit analogous magnetic sublattice and order-disorder defects.

Raman laser intensity and sample clarification on biochemical monitoring over Zika-VLP upstream stages.

In the current biopharmaceutical scenario, constant bioprocess monitoring is crucial for the quality and integrity of final products. Thus, process analytical techniques, such as those based on Raman spectroscopy, have been used as multiparameter tracking methods in pharma bioprocesses, which can be combined with chemometric tools, like Partial Least Squares (PLS) and Artificial Neural Networks (ANN). In some cases, applying spectra pre-processing techniques before modeling can improve the accuracy of chemometric model fittings to observed values. One of the biological applications of these techniques could have as a target the virus-like particles (VLP), a vaccine production platform for viral diseases. A disease that has drawn attention in recent years is Zika, with large-scale production sometimes challenging without an appropriate monitoring approach. This work aimed to define global models for Zika VLP upstream production monitoring with Raman considering different laser intensities (200 mW and 495 mW), sample clarification (with or without cells), spectra pre-processing approaches, and PLS and ANN modeling techniques. Six experiments were performed in a benchtop bioreactor to collect the Raman spectral and biochemical datasets for modeling calibration. The best models generated presented a mean absolute error and mean relative error respectively of 3.46 × 105 cell/mL and 35 % for viable cell density (Xv); 4.1 % and 5 % for cell viability (CV); 0.245 g/L and 3 % for glucose (Glc); 0.006 g/L and 18 % for lactate (Lac); 0.115 g/L and 26 % for glutamine (Gln); 0.132 g/L and 18 % for glutamate (Glu); 0.0029 g/L and 3 % for ammonium (NH4+); and 0.0103 g/L and 2 % for potassium (K+). Sample without conditioning (with cells) improved the models' adequacy, except for Glutamine. ANN better predicted CV, Gln, Glu, and K+, while Xv, Glc, Lac, and NH4+ presented no statistical difference between the chemometric tools. For most of the assessed experimental parameters, there was no statistical need for spectra pre-filtering, for which the models based on the raw spectra were selected as the best ones. Laser intensity impacts quality model predictions in some parameters, Xv, Gln, and K+ had a better performance with 200 mW of intensity (for PLS, ANN, and ANN, respectively), for CV the 495 mW laser intensity was better (for PLS), and for the other biochemical variables, the use of 200 or 495 mW did not impact model fitting adequacy.

Diet composition and plastic ingestion in Poecilia reticulata from urban streams.

Fish are excellent bioindicators and can reveal the presence of plastic in the environment. Diagnosing the composition and abundance of polymers in the fish diet makes it possible to evaluate their point sources and possible trophic transfers. We aimed to use the gastrointestinal contents of Poecilia reticulata in subtropical urban streams to detect the occurrence, shape, color, size, and chemical composition of polymers. For this, the diet of 240 individuals was analyzed using the volumetric method, and the microplastics (MPs; < 5 mm) recorded were characterized using Raman spectroscopy. Individuals predominantly consumed organic detritus and aquatic macroinvertebrates, with higher proportions of Diptera. A total of 111 plastic particles (< 0.5 to 12 mm) were recorded, and a subset of 14.4% was subjected to a micro-Raman spectrometer (830 nm excitation). The occurrence of polyethylene terephthalate (PET) and polypropylene (PP) with phthalocyanine dye was recorded. Some fragments could not be identified by Raman, but they contained indigo blue dye. Poecilia reticulata had a predominantly detritivorous diet with a record of plastic consumption, reflecting environmental pollution. Our results demonstrate that individuals of P. reticulata have ingested MPs in urban streams. This reinforces the need for future studies on the relationship between the presence of MPs in fish and the level of pollution in streams, comparisons with species of different feeding habits, and the potentially harmful effects on the entire biota.

Novel Criteria to Provide a Locality/Normality Degree in Molecules and Their Relevance in Physical Chemistry.

In contrast to the traditional analysis of molecules using local mode behavior, where the degree of locality is given through a function in terms of Morse potential parameters, new criteria for locality/normality (LN) suitable for application to any molecular system are proposed. The approach is based on analysis of the connection between the algebraic normal and local mode representations. It is shown that both descriptions are equivalent as long as the polyad (total number of quanta) in the local representation is not conserved. The constraint of a local polyad conservation naturally provides a criterion for assigning an LN degree in quantitative form, without an analogue in configuration space. The correlation between the different parameters reveals the physical properties of molecules. A clear connection between the LN degree (based on the fundamentals) and spectroscopic properties is also presented, suggesting a promising approach for identifying mixtures of isotopologues.

Effect of Nanoscale Surface Roughness and Electron-Phonon Interaction on Vibrational Modes of Cadmium Telluride Using Resonant Raman Spectroscopy.

This study investigates the combined effects of nanoscale surface roughness and electron-phonon interaction on the vibrational modes of cadmium telluride (CdTe) using resonant Raman spectroscopy. Raman spectra simulations aided in identifying the active phonon modes and their dependence on roughness. Our results reveal that increasing surface roughness leads to an asymmetric line shape in the first-order longitudinal optical (1LO) phonon mode, attributed to an increase in the electron-phonon interaction. This asymmetry broadens the entire Raman spectrum. Conversely, the overtone (second-order longitudinal optical [2LO]) mode exhibits a symmetrical line shape that intensifies with roughness. Additionally, we identify and discuss the contributions of surface optical phonon mode and multiphonon modes to the Raman spectra, highlighting their dependence on roughness. This work offers a deeper understanding of how surface roughness and electron-phonon scattering influence the line shape of CdTe resonant Raman spectra, providing valuable insights into its vibrational properties.

Molecular Insight into the Response of Lactic Acid Bacteria to Bile Acids.

Bile acids (BAs) are the main endogenous modulators of the composition and metabolic activity of the intestinal microbiota. In the present work, the effect of conjugated (glycodeoxycholic, glycocholic, taurodeoxycholic, taurocholic acids) and free BAs [cholic acid (CA) and deoxycholic acid (DCA)] on the survival, biological molecules, and structural and surface properties of two potential probiotic lactic acid bacteria (LAB) was evaluated. For this, viability assays, Raman spectroscopy, scanning electron microscopy (SEM), and zeta potential (ZP) measurements were employed. Our results evidenced that free BAs were more toxic than conjugates, with CA being significantly more harmful than deoxycholic acid (DCA). RAMAN studies show that BAs modify the bands corresponding to proteins, lipids, carbohydrates, and DNA. SEM showed that BAs cause surface distortions with depressions and fold formation, as well as incomplete cell division. DCA was the one that least altered the ZP of bacteria when compared to CA and taurodeoxycholic acid, with gradual changes towards more positive values. In general, the magnitude of these effects was different according to the BA and its concentration, being more evident in the presence of CA, even at low concentrations, which would explain its greater inhibitory effect. This work provides solid evidence on the effects of BAs on LAB that will allow for the development of strategies by which to modulate the composition of the microbiota positively.

Production and SERS characterization of bacteriocin-like inhibitory substances by latilactobacillus sakei in whey permeate powder: exploring natural antibacterial potential.

Bacteriocins are antimicrobial compounds that have awakened interest across several industries due to their effectiveness. However, their large-scale production often becomes unfeasible on an industrial scale, primarily because of high process costs. Addressing this challenge, this work analyzes the potential of using low-cost whey permeate powder, without any supplementation, to produce bacteriocin-like inhibitory substances (BLIS) through the fermentation of Latilactobacillus sakei. For this purpose, different concentrations of whey permeate powder (55.15 gL-1, 41.3 gL-1 and 27.5 gL-1) were used. The ability of L. sakei to produce BLIS was evaluated, as well as the potential of crude cell-free supernatant to act as a preservative. Raman spectroscopy and surface-enhanced Raman scattering (SERS) provided detailed insights into the composition and changes occurring during fermentation. SERS, in particular, enhanced peak definition significantly, allowing for the identification of key components, such as lactose, proteins, and phenylalanine, which are crucial in understanding the fermentation process and BLIS characteristics. The results revealed that the concentration of 55.15 gL-1 of whey permeate powder, in flasks without agitation and a culture temperature of 32.5 °C, presented the highest biological activity of BLIS, reaching 99% of inhibition of Escherichia coli and Staphylococcus aureus with minimum inhibitory concentration of 36-45%, respectively. BLIS production began within 60 h of cultivation and was associated with class II bacteriocins. The results demonstrate a promising approach for producing BLIS in an economical and environmentally sustainable manner, with potential implications for various industries.

Differences in whole blood before and after hemodialysis session of subjects with chronic kidney disease measured by Raman spectroscopy.

This study aimed to identify differences in the composition of whole blood of patients with chronic kidney disease (CKD), before and after a hemodialysis session (HDS), and possible differences in blood composition between stages and between genders using Raman spectroscopy and principal component analysis (PCA). Whole blood samples were collected from 40 patients (20 women and 20 men), before and after a HDS. Raman spectra were obtained and the spectra were evaluated by PCA and partial least squares (PLS) regression. Mean spectra and difference spectrum between the groups were calculated: stages Before and After HDS, and gender Women and Men, which had their most intense peaks identified. Stage: mean spectra and difference spectrum indicated positive peaks that could be assigned to red blood cells, hemoglobin and deoxi-hemoglobin in the group Before HDS. There was no statistically significant difference by PCA. Gender: mean spectra and difference spectrum Before HDS indicated positive peaks that could be assigned to red blood cells, hemoglobin and deoxi-hemoglobin with greater intensity in the group Women, and negative peaks to white blood cells and serum, with greater intensity in the group Men. There was statistically significant difference by PCA, which also identified the peaks assigned to white blood cells, serum and porphyrin for Women and red blood cells and amino acids (tryptophan) for Men. PLS model was able to classify the spectra of the gender with 83.7% accuracy considering the classification per patient. The Raman technique highlighted gender differences in pacients with CKD.

Microplastic atmospheric pollution in an urban Southern Brazil region: What can spider webs tell us?

The World Health Organization categorizes air pollution as the presence of one or more contaminants in the atmosphere such as smoke, dust, and particulate matter like microplastics, which are considered a priority pollutant. However, only a few studies have been developed on atmospheric pollution, and knowledge about MPs in the atmosphere is still limited. Spider webs have been tested and used as a passive sampling approach to study anthropogenic pollution. Despite this, studies on microplastic contamination using spiderwebs as samplers are scarce. Thus, this study uses spider webs as passive indicators to investigate air quality regarding microplastic contamination in an urbanized area. Therefore, 30 sampling points were selected, and webs of Nephilingis cruentata were collected. The spider webs were dipped in KOH 10 %. After digestion, the solution was washed and sieved through a 90 µm geological sieve. The remaining material was transferred to a Petri dish with filter paper, quantified, and identified by type and color. The chemical composition of the polymers was determined using Raman spectroscopy. 3138 microplastics were identified (2973 filaments and 165 fragments). The most frequent colors were blue and black. Raman spectroscopy revealed five types of polymers: Isotactic Polypropylene, Polyethylene Terephthalate, Polyurethane, Polyamide, and Direct Polyethylene.

Evaluation of Ilex guayusa and Piper marginatum Extract Cytotoxicity on Human Dental Pulp Mesenchymal Stem Cells.

BACKGROUND: Amelogenesis imperfecta is a hereditary disorder affecting dental enamel. Among its phenotypes, hypocalcified AI is characterized by mineral deficiency, leading to tissue wear and, consequently, dental sensitivity. Excessive fluoride intake (through drinking water, fluoride supplements, toothpaste, or by ingesting products such as pesticides or insecticides) can lead to a condition known as dental fluorosis, which manifests as stains and teeth discoloration affecting their structure. Our recent studies have shown that extracts from Colombian native plants, Ilex guayusa and Piper marginatum, deposit mineral ions such as phosphate and orthophosphate into the dental enamel structure; however, it is unknown whether these extracts produce toxic effects on the dental pulp. OBJECTIVE: To assess cytotoxicity effects on human dental pulp stem cells (hDPSCs) exposed to extracts isolated from I. guayusa and P. marginatum and, hence, their safety for clinical use. METHODS: Raman spectroscopy, fluorescence microscopy, and flow cytometry techniques were employed. For Raman spectroscopy, hDPSCs were seeded onto nanobiochips designed to provide surface-enhanced Raman spectroscopy (SERS effect), which enhances their Raman signal by several orders of magnitude. After eight days in culture, I. guayusa and P. marginatum extracts at different concentrations (10, 50, and 100 ppm) were added. Raman measurements were performed at 0, 12, and 24 h following extract application. Fluorescence microscopy was conducted using an OLIMPUS fv1000 microscope, a live-dead assay was performed using a kit employing a BD FACS Canto TM II flow cytometer, and data analysis was determined using a FlowJo program. RESULTS: The Raman spectroscopy results showed spectra consistent with viable cells. These findings were corroborated using fluorescence microscopy and flow cytometry techniques, confirming high cellular viability. CONCLUSIONS: The analyzed extracts exhibited low cytotoxicity, suggesting that they could be safely applied on enamel for remineralization purposes. The use of nanobiochips for SERS effect improved the cell viability assessment.

Different modeling approaches for inline biochemical monitoring over the VLP-making upstream stages using Raman spectroscopy.

This work aimed to set inline Raman spectroscopy models to monitor biochemically (viable cell density, cell viability, glucose, lactate, glutamine, glutamate, and ammonium) all upstream stages of a virus-like particle-making process. Linear (Partial least squares, PLS; Principal components regression, PCR) and nonlinear (Artificial neural networks, ANN; supported vector machine, SVM) modeling approaches were assessed. The nonlinear models, ANN and SVM, were the more suitable models with the lowest absolute errors. The mean absolute error of the best models within the assessed parameter ranges for viable cell density (0.01-8.83 × 106 cells/mL), cell viability (1.3-100.0 %), glucose (5.22-10.93 g/L), lactate (18.6-152.7 mg/L), glutamine (158-1761 mg/L), glutamate (807.6-2159.7 mg/L), and ammonium (62.8-117.8 mg/L) were 1.55 ± 1.37 × 106 cells/mL (ANN), 5.01 ± 4.93 % (ANN), 0.27 ± 0.22 g/L (SVM), 4.7 ± 2.6 mg/L (SVM), 51 ± 49 mg/L (ANN), 57 ± 39 mg/L (SVM) and 2.0 ± 1.8 mg/L (ANN), respectively. The errors achieved, and best-fitted models were like those for the same bioprocess using offline data and others, which utilized inline spectra for mammalian cell lines as a host.

Raman Spectroscopy on Free-Base Meso-tetra(4-pyridyl) Porphyrin under Conditions of Low Temperature and High Hydrostatic Pressure.

We present a Raman spectroscopy study of the vibrational properties of free-base meso-tetra(4-pyridyl) porphyrin polycrystals under various temperature and hydrostatic pressure conditions. The combination of experimental results and Density Functional Theory (DFT) calculations allows us to assign most of the observed Raman bands. The modifications in the Raman spectra when excited with 488 nm and 532 nm laser lights indicate that a resonance effect in the Qy band is taking place. The pressure-dependent results show that the resonance conditions change with increasing pressure, probably due to the shift of the electronic transitions. The temperature-dependent results show that the relative intensities of the Raman modes change at low temperatures, while no frequency shifts are observed. The experimental and theoretical analysis presented here suggest that these molecules are well represented by the C2v point symmetry group.

Raman spectra soft modeling of the biodiesel oxidation through evolving factor analysis & multivariate curve resolution.

The oxidative stability of biodiesel is defined by its relative resistance to the action of oxygen at room temperature. Its determination is an essential reference to the quality of biofuel and a significant parameter to be determined. This parameter concerns the quality of the biodiesel to be supplied to the consumer, and its determination is fundamental to maintaining the engine's proper functioning. Raman spectroscopy allows the rapid obtaining of structural information regarding biodiesel quality and, when aided by multivariate analysis methods, allows a quantitative determination of specific properties. This work uses Raman spectroscopy, Multivariate Curve Resolution with Alternative Least Squares (MCR-ALS) method, and Evolving Factor Analysis (EFA) to study biodiesel's oxidation kinetics. Also, the vibrational modes C = C, CH2, and CH3 were identified as the main structural groups involved in this process, corroborating previous studies. The MCR-ALS & EFA combination allowed modeling of the degradation kinetics following an A â†’ B â†’ C mechanism, where A corresponds to the biodiesel (starting material), B is related to the hydroperoxide mixture, and C is the final product. The results also suggested that this process follows a first-order reaction, with kinetic constant values of k1 = 0.0056 min-1 and k2 = 0.0031 min-1.

Honey induces changes in the molecular structure and microstructure of gluten in wheat-rye sourdoughs.

Chemical oxidizers and redox enzymes have traditionally been used to enhance the quality of baked goods. However, consumers now seek natural and clean-label ingredients, avoiding those with chemical-sounding names. Honey, a natural source of glucose oxidase (GOX), represents a promising alternative to purified enzymes for baking purposes. This study aimed to evaluate the effect of honey on the molecular structure and microstructure of gluten proteins in sourdough fermented by different lactic acid bacteria (LAB) strains. Four wheat-rye (1:1) sourdoughs were prepared, each supplemented with honey and inoculated with a different LAB strain. Additionally, two uninoculated doughs, one with honey (honey dough) and the other without (control dough), were prepared under identical conditions. Electronic paramagnetic resonance spectroscopy revealed the presence of hydrogen peroxide in honey solutions, indicating its role as an active source of GOX. Raman spectroscopy showed that honey addition altered the molecular structure of gluten by increasing the proportion of random coils at the expense of α-helix structures. This change is likely attributed to the competition between honey sugars and gluten proteins for water molecules in this system. Moreover, honey led to a decrease in the free sulfhydryl content of gluten compared to the control dough, suggesting an increase in disulfide crosslinking points. These enhanced protein-protein interactions were observed in scanning electron microscopy micrographs as a coarse gluten network composed of interconnected strands and fibrils. All LAB strains exhibited optimal acidification (pH < 4.3) in honey-supplemented sourdoughs, promoting the hydrolysis of gluten proteins into smaller fragments. Overall, honey-supplemented sourdoughs showed a gradual increase in the ß-sheet content while decreasing the proportion of random coils over time. This trend suggests that the polypeptide fragments interacted through interchain hydrogen bonds, leading to a more ordered structure, which likely contributes to providing dough with good baking aptitude.

Integrated aerobic exercise with LDE-docetaxel treatment: a novel approach to combat prostate cancer progression.

The variability in response to conventional prostate cancer (PC) therapies, coupled with the emergent issue of drug resistance, underscores the critical need for innovative treatment strategies. Aerobic physical exercise reduced incidence of several cancers, but the mechanism underlying these effects associated the nanoemulsion not fully understood. The application of a lipid nanoemulsion (LDE) delivery system for docetaxel (DTX), showing marked enhancement in therapeutic efficacy when combined with aerobic physical exercise. This novel intervention potentiates the antitumor activity of LDE-delivered DTX by augmenting nanoparticle internalization and inducing cell cycle arrest. Our findings reveal that this synergistic treatment not only significantly reduces prostate weight and mitigates adenocarcinoma proliferation but also attenuates anti-apoptotic BCL-2 protein expression. Concurrently, it elevates pro-apoptotic proteins and diminishes inflammatory markers. Metabolic profiling of the combined therapy group disclosed additional benefits, such as reduced lipid and plasma glucose levels. Collectively, our data illuminate the profound impact of integrating LDE-mediated DTX delivery with structured physical exercise, which together spearhead a dual-front assault on PC. This multimodal approach heralds a new paradigm in PC management, accentuating the promise of combined pharmacological and non-pharmacological interventions to elevate tumor suppressor protein activity and refine patient outcomes.

Ripening process in exocarps of scarlet eggplant (Solanum aethiopicum) and banana (Musa spp.) investigated by Raman spectroscopy.

In this work, we used Raman spectroscopy to identify compounds present at different maturation stages of the exocarp of scarlet eggplant and two banana cultivars, 'prata' and 'nanica'. Raman spectral analyses of both fruits showed bands attributed to phenolic acids, flavonoids, carotenoids, and fatty acids. During the scarlet eggplant's maturation process, Raman spectral profile changes are mainly observed in the carotenoid content rather than flavonoids. Furthermore, it is suggested that naringenin chalcone together with ß-carotene determines the orange-red color of the ripe stage. Variations in chemical composition among the maturation stages of bananas were observed predominantly in 'prata' when compared to 'nanica'. In contrast to scarlet eggplant changes in the spectral profile were more evident in the content of the flavonoid/phenolic acids. The in situ analysis was demonstrated to be useful as a guide in selecting bioactive compounds on demand from low-cost horticultural waste.

Interaction of L-phenylalanine with carbonyl groups in mixed lipid membranes.

The interaction of L-Phe with the membrane components, i.e., lipids and proteins, has been discussed in the current literature due to the interest to understand the effect of single amino acids in relation to the formation of amyloid aggregates. In the present work, it is shown that L-Phe interacts with 9:1 DMPC (1,2-dimyristoyl-sn-glycero-3 phosphocholine)/DPPC (1,2-dipalmitoyl-sn-glycero-3 phosphocholine) mixtures but not in the 1:9 one. An important observation is that the interaction disappears when DPPC is replaced by diether PC (2-di-O-hexadecyl-sn-glycero-3-phosphocholine) a lipid lacking carbonyl groups (CO). This denotes that CO groups may interact specifically with L-Phe in accordance with the appearance of a new peak observed by Infrared spectroscopy (FTIR-ATR). The interaction of L-Phe affects the compressibility pattern of the 9:1 DMPC/DPPC mixture which is congruent with the changes observed by Raman spectra. The specific interaction of L-Phe with CO, propagates to phosphate and choline groups in this particular mixture as analyzed by FTIR-ATR spectroscopy and is absent when DMPC is dopped with diether PC.

A Study of High-Frequency Noise for Microplastics Classification Using Raman Spectroscopy and Machine Learning.

Given the growing urge for plastic management and regulation in the world, recent studies have investigated the problem of plastic material identification for correct classification and disposal. Recent works have shown the potential of machine learning techniques for successful microplastics classification using Raman signals. Classification techniques from the machine learning area allow the identification of the type of microplastic from optical signals based on Raman spectroscopy. In this paper, we investigate the impact of high-frequency noise on the performance of related classification tasks. It is well-known that classification based on Raman is highly dependent on peak visibility, but it is also known that signal smoothing is a common step in the pre-processing of the measured signals. This raises a potential trade-off between high-frequency noise and peak preservation that depends on user-defined parameters. The results obtained in this work suggest that a linear discriminant analysis model cannot generalize properly in the presence of noisy signals, whereas an error-correcting output codes model is better suited to account for inherent noise. Moreover, principal components analysis (PCA) can become a must-do step for robust classification models, given its simplicity and natural smoothing capabilities. Our study on the high-frequency noise, the possible trade-off between pre-processing the high-frequency noise and the peak visibility, and the use of PCA as a noise reduction technique in addition to its dimensionality reduction functionality are the fundamental aspects of this work.

Influence of Defects and Charges on the Colloidal Stabilization of Graphene in Water.

Mastering graphene preparation is an essential step to its integration into practical applications. For large-scale purposes, full graphite exfoliation appears as a suitable route for graphene production. However, it requires overpowering attractive van der Waals forces demanding large energy input, with the risk of introducing defects in the material. This difficulty can be overcome by using graphite intercalation compounds (GICs) as starting material. The greater inter-sheet separation in GICs (compared with graphite) allows the gentler exfoliation of soluble graphenide (reduced graphene) flakes. A solvent exchange strategy, accompanied by the oxidation of graphenide to graphene, can be implemented to produce stable aqueous graphene dispersions (Eau de graphene, EdG), which can be readily incorporated into many processes or materials. In this work, we prove that electrostatic forces are responsible for the stability of fully exfoliated graphene in water, and explore the influence of the oxidation and solvent exchange procedures on the quality and stability of EdG. We show that the amount of defects in graphene is limited if graphenide oxidation is carried out before exposing the material to water, and that gas removal of water before the incorporation of pre-oxidized graphene is advantageous for the long-term stability of EdG.

Study of the degradation in an ultisol of alginate-chitosan complex and its stability and applicability as a soil conditioner.

The present work describes the process of degradation of a polyelectrolytic complex (PEC) based on sodium alginate (ALG) and chitosan (CHI), buried for different time intervals, in a clayey soil (ultisol) collected from the municipality of Campos dos Goytacazes, in the northern region of the state of Rio de Janeiro, Brazil. The influence of PEC on soil moisture was also investigated. The results showed that soil moisture increased with the presence of PEC after 7 days of testing, and remained high until the end of the study. FTIR and Raman spectra showed that the breaking of the glycosidic bond (C-O-C) was responsible for the PEC degradation. Thermogravimetry results revealed that alginate was possibly degraded faster than chitosan. Microscopic analysis of the PEC revealed a fragile and fragmented surface of the samples that were buried, in comparison with those not buried. The microbiological assays of the soil confirmed the biodegradation of the polysaccharides. Chemical analysis of soil indicated that PEC did not significantly influence soil fertility. Therefore, we conclude that the PEC (ALG: CHI), formed only by electrostatic interaction, buried in clayey soil, even being biodegraded, can be a promising soil conditioner for agricultural applications.