Over the last two decades, oxide nanostructures have been continuously evaluated and used in many technological applications. The advancement of the controlled synthesis approach to design desired morphology is a fundamental key to the discipline of material science and nanotechnology. These nanostructures can be prepared via different physical and chemical methods; however, a green and ecofriendly synthesis approach is a promising way to produce these nanostructures with desired properties with less risk of hazardous chemicals. In this regard, ZnO and TiO2 nanostructures are prominent candidates for various applications. Moreover, they are more efficient, non-toxic, and cost-effective. This review mainly focuses on the recent state-of-the-art advancements in the green synthesis approach for ZnO and TiO2 nanostructures and their applications. The first section summarizes the green synthesis approach to synthesize ZnO and TiO2 nanostructures via different routes such as solvothermal, hydrothermal, co-precipitation, and sol-gel using biological systems that are based on the principles of green chemistry. The second section demonstrates the application of ZnO and TiO2 nanostructures. The review also discusses the problems and future perspectives of green synthesis methods and the related issues posed and overlooked by the scientific community on the green approach to nanostructure oxides.

Nanomaterials based on metal oxides are extensively studied for several applications due to their versatility. Improvements in their performances can be obtained due to specific structural modifications. One possible modification is by doping the crystal structure, which can affect the materials structure and properties, especially in nanosized particles. Electronic features are among the properties that can be modified through the doping process, consequently morphological and optical parameters can also be controlled by this process. In this sense, this review presents some modifications to tin dioxide (SnO2), one the most studied materials, mainly through the doping process and their impact on several properties. The article starts by describing the SnO2 structural features and the computational models used to explain the role of the doping process on these features. Based on those models, some applications of doped SnO2, such as photocatalytic degradation of pollutants, CO2 reduction, and desulfurization of fossil fuels are presented and discussed. Additionally, the review describes many biological applications related to antimicrobial activity for doped SnO2 and its nanostructures. Although most of the examples presented in this article are based on the doped SnO2, it also presents examples related to SnO2 composites with other nanomaterials forming heterojunctions. The metal oxides SnO2, doped-SnO2 and their nanostructures are promising materials, with results reported in many fields presented in this review, such as theoretical and computational chemistry, environmental remediation, nanoparticle morphology control, fossil fuels improvement, and biomedical applications. Although widely explored, there are still fields for innovation and advances with tin dioxide nanostructures, for example, in transparent conducting oxides, in forensics as materials for latent fingerprints visualization, and sensors in medicine for detection of exhaled volatile organic compounds. Therefore, this article aims to be a reference regarding correlating the doping processes and the properties presented by the SnO2 nanostructures.

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Agricultural use and management systems in tropical soils of the Brazilian Cerrado may directly influence its chemical properties, in the conventional cultivation systems with pastures or grains, as well as in areas with a crop-livestock-forest integration system. Thus, the objective was to evaluate the chemical attributes of the soil under different use and management systems. The research was carried out at Boa Vereda Farm, in the state of Goiás, Brazil. The experimental design was completely randomized with a 5 x 3 factorial arrangement divided into five production systems: (1) among the rows of Eucalyptus (CLFI), (2) within the rows of Eucalyptus (CLFI), (3) in conventional agricultural monoculture, (4) pasture, and (5) -natural Cerrado (control treatment). Samples were collected in three soil depths (0-0.5; 0.5-0.1 and 0.1-0.2 m), with four replicates each. Among the chemical properties of the soil studied, the organic matter, calcium, magnesium and potassium contents, base saturation, and cation exchange capacity, are higher in the soil with natural Cerrado. The area of agricultural monoculture showed the highest levels of phosphorus and copper, but has the lower levels of organic matter in the soil. The chemical properties of the soil were similar in the CLFI system, regardless of the evaluation point (within or among rows). The chemical properties of the soil evaluated were similar between the pasture cultivated in CLFI and the conventional system. Therefore, the land use and management system do not directly influence the chemical properties of the soils evaluated.

Manganese (Mn) is important to increase forage crop yields. However, there is little information regarding the adequate Mn-fertilizer rates for Brachiaria humidicula species. The objective of this research was to evaluate the effect of manganese on growth, nutrition and yield of Brachiaria humidicula. The study was carried out in a green house in a randomized block design with five rates of manganese (0, 15, 30, 60 and 120 mg dm -3 ) and four replicates. Were evaluated plant height, leaf area, relative chlorophyll index, dry matter production, manganese accumulation and content, besides absorption efficiencies and transport and use of manganese (Mn). Brachiaria humidicula showed high tolerance to this nutrient, because the application of only 120 mg dm -3 to the soil was phytotoxic, showing symptoms such as brown spots and leaf tip curling. Manganese applied at a dose of 120 mg dm -3 reduced aerial part biomass yield by 25% and promoted lower efficiency of use of this nutrient by the forage by 49%. However, even with the initial content of manganese in the soil considered sufficient to meet nutritional demands to achieving high yields, the application of 60 mg dm -3 of manganese to the soil is recommended.