New approach to green synthesis of metallic nanoparticles

Indian researchers have shared an eco-friendly method of making metal nanoparticles in their latest paper available as pre-proof in the journal Environmental nanotechnology, monitoring and management.

Study: Carbon pellets as a sustainable alternative to plant extracts for the green synthesis of noble metal nanoparticles. Image Credit: Kateryna Kon/

Importance of metallic nanoparticles

In simple terms, metallic nanoparticles could be defined as nanoscale derivatives of pure metals such as gold, thallium and silver, or their compounds. Metal nanoparticles (MNPs) have a metal core formed from synthetic metal or metal oxide that is usually surrounded by an organic or inorganic substance or metal oxide shell.

The production of noble metal nanoparticles has become an exciting process of scientific study. Due to their outstanding toxicological and photonic characteristics, silver and gold nanoparticles have received great attention, paving the way for extraordinary applicability in the fields of electromagnetics, semiconductors, photonics , biomedical, biosensing, catalysis and medicine.

Preparation methods

Metal nanoparticles are often produced by reducing assorted metal salt solutions with reduction-enhancing substances such as sodium borohydride and citrate under harsh experimental parameters. Additionally, encapsulation entities are required, organic ligands containing amines or thiols and other surfactants being used to create these nanoparticles.

Previously, phytomediated reduction processes using plant extracts have been used in the manufacture of metallic nanoparticles to meet the green standard in reactions by avoiding hazardous chemicals.

Despite significant progress in the manufacture and use of NPMs around the world, there is still a significant lack of information on the consequences related to the toxicity of these on health and the environment.

Why are carbon points (CD) important?

Carbon dots (CDs), a recent addition to the family of nano-carbons distinguished by the functional group bonded to the carbon nucleus, possess exceptional biochemical and optoelectronic properties such as tunable fluorescence, high water dispersion , low cytotoxicity and excellent stability.

C-dots are a new type of small-carbon luminous nanocomposites with particle sizes below 10 nm. Due to these characteristics, they have emerged as attractive candidates in sensing, catalyst supports, bioimaging, illumination, biomedical applications, and other fields.

Future research will focus on creating various target-specific morphologies, dimensions, and carbon points. Synthetic pathways to DCs, like any other nanomaterial, are loosely categorized into top-down and bottom-up processes.

Greener methods of carbon dot synthesis

Much attention has been devoted to implementing green solutions for manufacturing CDs from affordable environmental assets in a greener and more environmentally friendly way.

Plant sources such as peppermint, coriander, banana peel, lemon, and others have been used as an alternative to synthetic backgrounds in the manufacture of carbon nanodots.

CDs have also been recently discovered for their reducing nature. Despite the fact that DCs have been discovered as a tool to sustainably reduce the production of noble metal nanoparticles via environmental initiatives, this topic is still in its infancy.

In the present study, carbon points generated from the foliage of organic herbs, Plectranthus amboinicus (PA-CD) and Leucas lavandulifolia (LA-CD), showed an excellent state of reduction.

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By using carbon dots as a reducing agent, a green technique for the creation of silver and gold nanoparticles is proposed. DCs are micro-spherical nanoparticles less than 5 nm in diameter that emit blue glowing light when exposed to UV light.

Heating, pH, and stimulating wavelength all have an effect on the luminescence of these DCs.

These carbon particles could act as both reducing and stabilizing agents in the creation of noble metal nanoparticles. Compared to previous publications on the reduction ability of DCs in the production of noble metal nanoparticles, the current technique was simpler and less time-consuming, as DCs produced metal nanoparticles without the need for auxiliary chemicals.

Under typical circumstances, AgNPs with sizes ranging from 10 to 16 nm were produced within minutes.

With the inclusion of starch residues, mild heat treatment of the Au(III) solution resulted in the reduction to elemental gold particles of size 50-60 nm.

FT-IR spectrum measurements indicated the importance of surface functional groups in the reduction and stabilization processes during the creation of metallic nanoparticles.

In addition to achieving sustainable and environmentally friendly noble metal synthesis, in the reduction technique, CDs have proven to be a superior method to comparable harvests, especially in terms of dimension, SPR peak location , response time and durability. generated nanoparticles.


Varsha Raveendran, P. and Renuka, N., (2022) Carbon Dots as a Sustainable Alternative to Plant Extracts for Green Noble Metal Nanoparticle Synthesis. Environmental Nanotechnology, Monitoring & Management, p.100676.

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