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The search for new synthesis methodologies based on the principles of green chemistry has led to various studies for the production of silver nanoparticles (AgNPs) using extracts from different parts of plants. Based on this, the present study aims to carry out green synthesis (biosynthesis), characterization, and antibacterial evaluation of reduced and stabilized silver nanoparticles (AgNPs) with aqueous extracts of Minthostachys acris in a simple, ecological, and environmentally safe manner. The extraction process of the organic components is performed using two methods: immersion and the agitation of the leaves of Minthostachys acris Schmidt Lebuhn (Muña) at 0.1% for different times (0.5, 1, 3, 6, and 10 min). Compounds such as hydroxycinnamic acid derivatives, quinic, caffeic, rosmarinic acids, and flavonols present in the Muña extract facilitate the formation of AgNPs; this compounds act as a coating and stabilizing agent. The bioactive components from natural resources facilitate the formation of AgNPs, partially or completely replacing the contaminating and toxic elements present in chemical reagents. The biosynthesis is carried out at room temperature for pH 7 and 8. The synthesized AgNPs are characterized by UV-visible spectroscopy to identify the surface plasmon resonance (SPR) band, which shows an absorption peak around 419 nm and 423 nm for pH 7 and p.H 8, respectively, and Fourier-transform infrared spectroscopy (FTIR) to identify the possible biomolecules responsible for bioreduction and stabilization, with a peak at 1634 cm−1. Dynamic light scattering (DLS) shows the hydrodynamic size of the colloidal nanoparticles between 11 and 200 nm, and scanning electron microscopy (SEM) reveals monodisperse AgNPs of different morphologies, mostly nanospheres, while Laser-Induced Breakdown Spectroscopy (LIBS) demonstrates the presence of Ag in the colloidal solution. The evaluation of the bactericidal activity of the AgNPs using the disk diffusion method against Escherichia coli (E. coli) and Staphylococus aureus (S.aureus) shows that the synthesized AgNPs have effective antibacterial activity against E. coli for the extracts obtained at 6 min for both the immersion and agitation methods, respectively. The significance of this work lies in the use of bioactive components from plants to obtain AgNPs in a simple, rapid, and economical way, with potential applications in biomedical fields. [ABSTRACT FROM AUTHOR]

The tones of iron oxide pigments range from yellow, red, brown and green to black. Iron oxide pigments are non‐toxic and have a nanometric particle size, which makes them ideal for use as pigments. The current study synthesised synthetic inorganic pigments based on iron oxides using the alkaline precipitation method. This approach to the synthesis of iron oxide pigments makes them less expensive for obtaining reproducible colours. Iron salts (iron (III) chloride, iron (III) nitrate, iron (II) sulphate [ferrous sulphate] and iron (III) sulphate) have been combined with alkaline solutions (sodium hydroxide, potassium hydroxide and ammonium hydroxide) to form coloured iron oxides, which are widely known as natural inorganic pigments. The 12 samples produced in four different colours (red, yellow, brown and black) were left in aqueous suspension and dispersed in commercial real white estate paint, to evaluate their behaviour as pigments. Structural characterisation (X‐ray diffractometry), composition (X‐ray fluorescence by dispersive energy), thermal analysis (i.e. thermogravimetric analysis and the differential thermal analysis) and spectroscopy (FTIR and photoacoustic), as well as colorimetry, were performed. The phases indexed by X‐ray diffractometry were goethite, haematite, magnetite and lepidocrocite. The inorganic pigments produced are compatible with natural inorganic pigments. They also showed dispersion compatibility in commercial white paint without changing the surface coating powder and are therefore an alternative to synthetic inorganic pigments. [ABSTRACT FROM AUTHOR]

In this study, raw smectite (Sm), from the Guarapuava–Parana–Brasil region, was saturated with copper ions (Cu-Sm) by ion exchange and the samples Sm and Cu-Sm were used in crystal violet (CV) adsorption and applied as an antimicrobial and antifungal hybrid pigment. Samples (Sm and Cu-Sm) were used to remove crystal violet (CV) dye from aqueous media, simulating wastewater. Samples after use as adsorbents were characterized and named smectite/adsorbed dye (Sm/Dye) and copper smectite/adsorbed dye (Cu-Sm/Dye); and they were applied as hybrid pigments with antimicrobial action. The Sm and Cu-Sm were characterized by X-ray diffractometry (XRD), energy dispersive X-ray fluorescence (EDXRF), vibrational spectroscopy (FTIR), Zeta potential (ζ), scanning electron microscopy (SEM), and colorimetry (CIE L*a*b*), enabling the identification of the presence of intercalated copper ions and on the smectite surface. The adsorption assays were carried out to evaluate the effects of initial dye concentration and contact time. Tests for application as a hybrid pigment showed good compatibility with commercial white paint being applied on plaster blocks and later photoaging and chemical stability tests were performed in acid and basic environments, both were discussed by colorimetry (CIE L*a*b*), thus being able to relate it to the color variation (∆E). The samples (Sm, Cu-Sm, Sm/Dye, and Cu-Sm/Dye) were dispersed in white paint at 10% and 20% (% w/w) to evaluate the ability to inhibit different microorganisms. The modification with copper ions promoted an increase in the adsorptive capacity relative to the raw smectite and provided antibacterial and antifungal action to the hybrid pigment against Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, and Candida albicans. The Cu-Sm and Cu-Sm/Dye samples showed excellent results against all studied microorganisms and reveal successful materials that can be used in environments that require microbiological protection. [ABSTRACT FROM AUTHOR]

The present study described three synthesis routes using different natural polysaccharides as low-cost non-toxic fuels and complexing agents for obtaining MgO. Cassava starch, Aloe vera leaves (mainly acemannan) gel, and citric pectin powder were mixed with magnesium nitrate salt and calcined at 750 °C for 2 h. The samples were named according to the polysaccharide: cassava starch (MgO-St), citrus pectin (MgO-CP), and Aloe vera (MgO-Av). X-ray diffraction identified the formation of a monophasic periclase structure (FCC type) for the three samples. The N2 adsorption/desorption isotherms (B.E.T. method) showed an important difference in textural properties, with a higher pore volume (Vmax = 89.76 cc/g) and higher surface area (SA = 43.93 m2/g) obtained for MgO-St, followed by MgO-CP (Vmax = 11.01 cc/g; SA = 7.01 m2/g) and MgO-Av (Vmax = 6.44 cc/g; SA = 6.63 m2/g). These data were consistent with the porous appearance observed in SEM images. Porous solids are interesting as adsorbents for removing metallic and molecular ions from wastewater. The removal of copper ions from water was evaluated, and the experimental data at equilibrium were adjusted according to the Freundlich, Langmuir, and Temkin isotherms. According to the Langmuir model, the maximum adsorption capacity (qmax) was 6331.117, 5831.244, and 6726.623 mg·g−1 for the adsorbents MgO-St, MgO-Av, and MgO-CP, respectively. The results of the adsorption isotherms indicated that the synthesized magnesium oxides could be used to decrease the amount of Cu2+ ions in wastewater. [ABSTRACT FROM AUTHOR]

The synthesis of structured MgO is reported using feedstock starch (route I), citrus pectin (route II), and Aloe vera (route III) leaf, which are suitable for use as green fuels due to their abundance, low cost, and non-toxicity. The oxides formed showed high porosity and were evaluated as antimicrobial agents. The samples were characterized by energy-dispersive X-ray fluorescence (EDXRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The crystalline periclase monophase of the MgO was identified for all samples. The SEM analyses show that the sample morphology depends on the organic fuel used during the synthesis. The antibacterial activity of the MgO-St (starch), MgO-CP (citrus pectin), and MgO-Av (Aloe vera) oxides was evaluated against pathogens Staphylococcus aureus (ATCC 6538P) and Escherichia coli (ATCC 8739). Antifungal activity was also studied against Candida albicans (ATCC 64548). The studies were carried out using the qualitative agar disk diffusion method and quantitative minimum inhibitory concentration (MIC) tests. The MIC of each sample showed the same inhibitory concentration of 400 µg. mL−1 for the studied microorganisms. The formation of inhibition zones and the MIC values in the antimicrobial analysis indicate the effective antimicrobial activity of the samples against the test microorganisms. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) can adsorb ionic dyes to generate hybrid pigments. Porous zinc oxide was prepared by combining gelled citrus pectin (80 °C) with zinc nitrate, followed by calcination (600 °C). The product had a high surface area (25 m2 g−1), pore volume (0.049 cc g−1), and pore radius (17 Å), indicative of a macroporous structure. ZnO comprised the wurtzite phase, as characterized by X-ray diffraction. Owing to its textural properties, ZnO effectively removed textile dyes, such as carcinogenic Congo red, from aqueous media. The adsorption of Congo red on the porous ZnO was monitored using UV–vis spectroscopy at aqueous dye concentrations ranging from 100 to 250 mg L−1. Porous ZnO with the adsorbed dye was applied as a hybrid pigment and dispersed in white real estate paint. The resulting colors were evaluated by colorimetry measurements, according to the CIE L*a*b* method. [ABSTRACT FROM AUTHOR]

The annual growth of the world population increasingly provokes the search for highly productive agriculture, with an effective and economical application of fertilizers capable of supplying the necessary nutrients to the plants. In this context, the development of technologies to control these fertilizers in the environment is relevant. This study presents a potential slow-release fertilizer created from the intercalation of urea in the expanded vermiculite (EV) and encapsulated in a sphere constituted of alginate/collagen. The intercalation tests were performed by the mechanochemical process between EV and urea, and the intercalated materials were characterized by XRD, TGA/DSC, and FTIR. The results showed that urea was intercalated at all studied ratios, but the sample containing 20% of urea (EVU20%) did not present peaks from the starting reagents. Thus, the sample EVU20% was chosen for the encapsulation process and release test. Urea concentration released was determined by colorimetric analysis, and the test revealed that the spheres produced with EVU20% encapsulated into an alginate/collagen matrix were able to release the urea up to 210 hours. Therefore, this system has the potential to be a new fertilizer of slow-release to be applied in agriculture, promoting the gradual release of urea for plant development. [ABSTRACT FROM AUTHOR]

Layered double hydroxide (LDH) containing different metal constituents (Zn, Co, and Ni) was intercalated with different organic anions and has been used as fillers in low‐density polyethylene (LDPE), and its thermal and flammability behavior was evaluated. The best thermal stability (∆T0.5 = 21 °C) was obtained with the LDPE‐Ni/Al‐dodecyl sulfate (4 wt %) nanocomposite. Addition of hydrophobic LDHs systematically decreases the enthalpy of melting and crystallization compared to the neat polymer. In LDPE‐Co/Al‐dodecyl sulfate (2 wt %) nanocomposite, the melting and crystallization enthalpies declined by about 45 J/g, indicating a good interaction of the filler with the polymer matrix. A reduction of 20% of the flammability for the LDPE‐Ni/Al‐stearate (4 wt %) nanocomposite was obtained. On the other hand, Zn–Co LDH as filler in LDPE nanocomposite did not affect effectively the same property. In an innovative study, results indicate that different metal constituents and interlayer anion of LDH as filler can change thermal and flammability properties of the polymer nanocomposite. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48737. [ABSTRACT FROM AUTHOR]