Global demand for a more green and sustainable economy has impacted several industries, including the nanotechnology and materials field. ‘Green’ synthesis of materials has become a new area of research to produce materials and nanomaterials that are reliable, sustainable, and eco-friendly.
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The significance of this lies in the destructive consequence of using unsustainable processes to synthesize nanoparticles ubiquitous among laboratories. This article will provide an overview of the ‘green’ synthesis of nanoparticles and the benefits of this alternative compared to the conventional processes.
The two fundamental principles of synthesis include top-down and bottom-up techniques. In top-down approaches, nanoparticles and materials are prepared through a range of processes such as lithographic techniques. In contrast, within bottom-up approaches, the nanoparticles are grown from simpler molecules and consist of methods such as chemical vapor deposition.
Using biological materials to produce nanoparticles is a bottom-up approach that can be used as a sustainable alternative to conventional nanoparticle synthesis.
Challenges of Conventional Nanoparticle Synthesis
Nanoparticles have become a significant component of advancing industries from technology to medicine and the environment. However, the synthesis of nanoparticles can impact their ability to function effectively within real-world applications, and this can cause negative consequences.
These disadvantages include but are not limited to being unstable in hostile environments, bioaccumulation, toxicity, and the challenge of recycling, reusing, and regeneration.
These obstacles can be significant for nanoparticle applications. This is because research into their use in water purification systems can be more difficult as the stability of these nanoparticles is necessary due to the hostile environment of sewage and chemical waste.
Additionally, the toxicity of these nanoparticles would also be a concern, from use in medical therapeutics to use in degrading and oxidizing toxic pollutants and waste; these particles would need to be produced in a more sustainable method so as not to cause toxicity which can impact all lives.
With growing awareness in how unsustainable materials and processes have affected the Earth and the build-up of these materials that are not easily degradable, more sustainable approaches that produce less toxic waste are critical.
A New Era of Green Synthesis
Green synthesis of nanoparticles has gained admirable traction in nanotechnology research. This novel approach that utilizes processes such as regulation, control, clean-up, and remediation aims to increase the eco-friendly level of these essential particles.
By reducing harmful by-products produced through the process of conventional nanoparticle synthesis, there will be less toxic unsustainable products created. The use of natural resources such as organic systems will aid in achieving the goal of creating a greener and more sustainable economy; however, it will require industrial assistance with the adoption of these alternative approaches.
Metallic nanoparticles can be synthesized in a more sustainable and ‘green’ process through utilizing plant alternatives or biological materials such as bacteria, fungi, algae, and plant extracts. This greener approach can be a single step or ‘one pot’ process which requires a lower energy level than conventional processes. Another benefit is that this reduction method is more cost-efficient.
Using Biological Materials for Nanoparticle Synthesis
Biological materials such as bacteria can reduce metal ions. Prokaryotic bacteria and actinomycetes have been widely used to produce metal and metal oxide nanoparticles due to the ability to easily manipulate bacteria. Escherichia coli and Lactobacillus casei are examples of bacteria previously used to synthesize bio-reduced silver nanoparticles.
The use of fungi for a greener and more sustainable nanoparticle synthesis approach has also been effective, with this process producing monodispersed metal or metal oxide nanoparticles with well-defined morphologies. The presence of intracellular enzymes in this approach makes fungi an effective biological agent for nanoparticle production.
With these functional components such as enzymes, proteins, and reducing elements on their cell surfaces, this biological material can be seen as the most effective approach to synthesizing nanoparticles. Additionally, using competent fungi can be more efficient due to its ability to synthesize a more significant number of nanoparticles than bacteria.
The utilization of yeast, which are single-celled microorganisms in eukaryotic cells, can also be a suitable candidate for producing more green and sustainable nanoparticles. This can be supported through literature with reports of a silver-tolerant yeast strain and Saccharomyces cerevisiae broth producing silver and gold nanoparticles.
Plant extracts are also an intriguing route to a more sustainable production process towards nanoparticle synthesis with their potential to accumulate heavy metals. This technique retains benefits such as being low cost, simple and efficient.
Research into using plant leave extracts for metal or metal oxide nanoparticles is promising, due to carbohydrates, proteins, and coenzymes having the potential to reduce metal salt into nanoparticles. Plants including aloe vera, for example, have been used to achieve this and create silver and gold nanoparticles.
Future Outlooks for Green Synthesis
The significance of this research is paramount, with the need for hygienic and clean drinking water becoming a growing public health concern. Using metal and metal oxide semiconductor nanomaterials to oxidize toxic pollutants is a growing area of research due to the critical benefit of this real-world application. However, in creating these nanoparticles, the harmful by-products can minimize the benefit of these particles.
By focusing on a more sustainable approach, nanotechnology can advance past the limitations of conventional techniques, and this can aid in creating a more sustainable and safer future.
Continue reading: The Production of Green Hydrogen Using Nanoparticles.
References and Further Reading
Singh, J., Dutta, T., Kim, KH. et al. (2018) Green’ synthesis of metals and their oxide nanoparticles: applications for environmental remediation. J Nanobiotechnol 16, 84. Available at: https://doi.org/10.1186/s12951-018-0408-4