Current Nanoscience - Volume 17, Issue 4, 2021

Background: Currently, solution combustion synthesis (SCS) is considered a reproducible, flexible, and low-cost synthesis method for the preparation of nanomaterials. A new trend in the SCS method is the use of less polluting fuels, such as starch. The use of starch as fuel in SCS is very interesting for green chemistry, as it is renewable and has several advantages, including its abundance, low-cost, and non-toxicity. Objective: This paper provides a comprehensive review of the SCS method using starch as fuel. The main advantages of using starch as fuel will be illustrated with a wide variety of examples, highlighting its impact on the preparation of nanomaterials for energy and environmental applications. Conclusion: In a combustion reaction using starch as fuel, several positive effects are expected, such as non-violent propagation, combustion with the production of non-toxic gases (mainly CO2 and H2O), and development of pores during the release of gases. For example, several macroporous metal oxide foams were prepared using the SCS method, through an appropriate combination of urea and starch fuels. With this approach, it is possible to control the structure, lattice defects, crystallite size, specific surface area, porosity, and other characteristics of the synthetized nanomaterial. For example, by combining starch with other fuels, it is possible to control the concentration of lattice defects in metal oxides and modify the optical properties of these materials. These properties are of fundamental importance for the performance of these materials and their subsequent application in electrodes, electrocatalysts, and photocatalysts in the areas of energy and environment.

Nowadays, numerous researches have focused on the field of green nanotechnology worldwide and their various applications. The main reason is the environmental and biologically safe applications of nanoparticles. Until now, various nanoparticles have been fabricated and tested for different purposes, such as energy conversion, storage, and corrosion prevention. However, conventional nanoparticle production, like physical or chemical methods, caused undesirable adverse effects on humans and the environment. Various biological materials have numerous advantages, such as environmentally friendly, non-toxic, and abundant availability. Thanks to these advantages, green synthesis methods may have a wider field of use in the future compared to traditional methods. Furthermore, the use of green materials provides significant advantages such as less usage of energy, economic and natural resources. Recently, considerable efforts have been carried out to develop novel green nanoparticles using various biological sources and methods such as the hydrothermal method, microwave-assisted method, ultra-sonication assisted method and mechano-mixing methods. In this review, we discuss the main properties of green and recent nanoparticles synthesized by green and conventional methods for using in corrosion preventions and fuel cells. In the paper, the fundamental sources of green nanoparticles and the fabrication process are addressed. The main reasons for the corrosion and the prevention of corrosion are explained. Also, the current analysis methods used to characterize the morphological and chemical properties of the recently synthesized nanoparticles are explained.

Background: The different field of chemistry needs various greener pathways in our search toward attaining sustainability. True sustainability comes through circularity. Circular processes i.e., circular economy, circular chemistry, etc. are the only logical solutions for all challenges/ issues related to sustainability. Chemistry of matter changes with size. Nanoscale materials thus show magical properties and have a broad range of applications. Objective: Nanomaterials always fascinate researchers because of their unique and novel properties. Engineered nanomaterials hold great promise for catalysis, corrosion control, medicine, electronics, environmental remediation, and other fields. But when the nanomaterials or any new/novel materials are synthesized without considering environmental impacts at the beginning of the process, their long-term effects could undermine those advances. Sustainable nanomaterials have great capability to overcome the challenges associated with engineered nanomaterials. Presently, sustainable materials are needed to sustain life on earth. Size and shape controlled synthesis of nanomaterials is challenging to explore the various applications of nanomaterials. Conclusion: Application of nanomaterials in catalysis and protective coating of metals to prevent corrosion make it more sustainable. Present article briefly reviewed the fundamental aspects of nanomaterials, sustainable approaches of nanomaterials synthesis, and their sustainable applications i.e., catalysis and corrosion control.

Increasing energy crisis across the globe requires immediate solutions. Two-dimensional (2D) materials are of great significance because of their application in energy storage and conversion devices but the production process significantly impacts the environment thereby posing a severe problem in the field of pollution control. The green synthesis method provides an eminent way of reduction in pollutants. This article reviews the importance of green synthesis in the energy application sector. The focus of 2D materials like graphene, MoS2, VS2 in energy storage and conversion devices is emphasized based on supporting recent reports. The emerging Li-ion batteries are widely reviewed along with their promising alternatives like Zn, Na, Mg batteries and are featured in detail. The impact of green methods in the energy application field is outlined. Moreover, future outlook in the energy sector is envisioned by proposing an increase in 2D elemental materials research.

The concept of graphene in a carbon framework has given rise to enormous improvements to the specific properties of materials. Notably, the combination of graphene with polymeric, metallic and ceramic materials has significantly improved mechanical resistance, electrical and thermal conductivity, and thermal stability of the resulting composite material. In this review, we discuss comprehensive literature on graphene-based composite materials for biomedical and related energy storage applications with emphasis to the synthesis techniques and improved properties of the nanocomposite materials due to graphene addition.

A transforming society towards sustainable industrial practices and products chooses to implement “Green Nanomaterial”, with high energy efficiency, minimizing the damage to the environment and exploitation of non-renewable energy resources. A combined overview of recent developments in green nanostructured fuel cells with enhanced durability and activity is presented in this review along with the advancements of green nano materials in the area of corrosion inhibition. Fuel cells being the next generation ecofriendly energy source, the modification to the solid oxide, microbial and alkaline fuel cell through green nanomaterial are discussed with an emphasis on electrodes, electrolyte, electrode catalysts and membrane components. In addition, the role of green nanomaterial in the form of nano metal oxides, hydroxides, grains, dendrimers, gels, composites, functionalized graphene, halloysite nanotubes and ionic liquids in greening the phenomenon of corrosion inhibition, investigated by various researchers is briefly addressed. As no single engineered green nanomaterial is emerging as unparalleled and most viable, they are evaluated according to their economic impact, diverse properties, durability and stability. Eventually, these materials with improvement in biocompatibility, solubility, fabrication and handling techniques are predicted to change the environmental and occupational scenario, with some of them already have been found to impact upon the altering global energy needs.

Background: Tin oxide nanoparticles also show good photocatalytic efficiency due to wide bandgap and high recombination rates of photo-generated electron-hole pairs. Being non-toxic and chemically stable, the tin oxide nanoparticles are used as dynamic photo-catalyst for the degradation. Tin oxide nanocrystals suitable for charge storage devices are synthesized using the coprecipitation technique. Objectives: Synthesis of Tin oxide nanocrystals by using the co-precipitation method for photocatalytic activity under sunlight that can be used for photo-degradation. The method of synthesis and characterization are also discussed. Materials and Methods: The nanocrystals are prepared by co-precipitation method using stannic chloride and sodium carbonate. Sodium carbonate is added under constant stirring drop by drop for 90 minutes. The solution is settled for 4 hours. The precipitates are first washed using de-ionized water and then with ethyl alcohol. The dried powder of nanocrystals is then calcinated at 500°C for one hour in a muffle furnace. The structural, morphological, optical, and electrical characterization of these synthesized crystals is done using (XRD), (FESEM), (TEM), (UV-Visible), (FT-Raman), Zeta potential, and dielectric constant measurements. Results and Discussion: The sizes of synthesized nanocrystals vary from 25 nm to 100 nm and are found to be optically transparent. The dielectric constant of nanocrystals is measured in the frequency range of 100Hz-1MHz and it can be seen that it declines from ~2000 at a frequency of 100Hz to ~30 at 1MHz. However, this decline in dielectric constant with frequency can be explained well on the basis of strong space charge polarization and rotational direction polarization processes in nanostructures. In the high-frequency regions, these processes cannot follow the electrical field frequency variations that result in the rapid decrease of dielectric constant. Photocatalytic Activity: The photocatalytic activity of the particles under sunlight is also investigated, which shows that the crystals show degradation of the methylene blue dye under sunlight irradiation. Theoretical Investigations with DFT: The bandgap of the particles was also calculated from the UV-VIS spectra, which was found to be ~3.6 eV and this experimentally observed value of bandgap matches with that calculated theoretically from Density Functional Theory (DFT) using Local Density Approximation (LDA). Conclusion: The method of synthesis reported in the present paper is scalable and can be used for the commercial synthesis of SnO2 nano-crystals for electrodes and energy storage devices.

Nanocellulose has attracted much research interest owing to its biocompatibility, low density, environmental sustainability, flexibility, ease of surface modification, excellent mechanical properties and ultrahigh surface areas. Recently, lots of research efforts have focused on nanocellulose- based conductive hydrogels for different practical applications, including electronic devices, energy storage, sensors, composites, tissue engineering and other biomedical applications. A wide variety of conductive hydrogels have been developed from nanocellulose, which can be in the form of cellulose nanofibers (CNF), cellulose nanocrystals (CNC) or bacterial cellulose (BC). This review presents the recent progress in the development of nanocellulose-based conductive hydrogels, their advanced functions, including 3D printability, self-healing capacity and high mechanical performances, as well as applications of the conductive nanocellulose hydrogels.

Schiff bases and their complexes are versatile compounds, which have been synthesized from the condensation of carbonyl compounds with amino compounds and exhibit a broad range of applications in biological, medicinal, catalysis, and industrial purposes. Furthermore, Schiff basemetal complexes have been used as a precursors for the synthesis of different metal oxides, which include oxides of iron, cobalt, copper, nickel, manganese, vanadium, cadmium, zinc, mercury, etc. and ferrites such as Fe3O4, ZnFe2O4, and ZnCo2O4. These metal oxides have been utilized for several applications as a catalyst for several organic transformations and for biological activity. This review encompasses different methods of synthesis of metal oxides using Schiff base metal complexes precursor, their characterization, and various applications in detail.

Background: Due to the limitation of conventional cancer treatment using chemotherapy, the nanoparticle therapeutics have shown enhanced efficacy with alleviating side effects. Objective: The aim of this study was to prepare the superparamagnetic iron oxide nanoparticles (TC- SPION) for doxorubicin (DOX) loading and delivery. Methods: Here, we reported a simple green strategy to fabricate T-C-SPION using green tea extract and citric acid. Also, the anti-cancer drug, DOX, was used as a model drug to fabricate DOX-loaded nanoparticles. Results: The formed T-C-SPION nanoparticles were spherical with a diameter of 23.8 ± 0.8 nm, as confirmed by Transmission Electron Microscopy (TEM). Besides, Dynamic Light Scattering (DLS) revealed that the prepared nanoparticles were water-dispersible and stable while stored in water for 6 weeks. The CCK-8 assay showed T-C-SPION to have a good cytocompatibility using different iron concentrations (10 ∼ 120 ug/mL). Furthermore, T-C-SPION had a higher DOX encapsulation efficiency (Eencaps), around 43.2 ± 1.8 %, which resulted in a lagged release profile of DOX, compared to other types of iron oxide nanoparticles using green tea or citric acid alone. Next, cell viability assay indicated that T-C-SPION with a higher Eencaps showed superior and sustained cytotoxicity compared to the control group. Conclusion: The developed iron oxide nanoparticles synthesized by green tea extract and citric acid in this paper could be considered as a potential drug carrier for cancer therapy applications.