Green syntheses are more environmentally friendly alternatives to conventional synthesis techniques as they aim to reduce toxic elements and costs while benefiting from sustainable sources. There are two main categories of green synthesis: microbial, which uses bacteria and other microbes to produce nanoparticles either intracellularly or extracellularly, and phyto-synthesis, which uses plants to produce nanoparticles on a large scale. Green synthesis methods provide single step, non-toxic and cost effective production of nanoparticles for applications in medicine, environmental remediation, and more.

2.  Green syntheses are environmental friendly
alternatives to conventional synthesis techniques.
 They aim to reduce toxic elements used or
produced in conventional methods.
 Moreover, they benefit from sustainable sources
and can reduce production cost, in practical and
up-scalable manner.

3.  Clean and eco-friendly approach, as toxic
chemicals are not used.
 The active biological component itself act as
capping and reducing agent, therefore reduction
the overall cost of synthesis process.
 Can be used at large scale of nanoparticles.
 External experimental conditions like high energy
and high pressure are not required, leads to energy
saving process.

5.  two environmentally feasible syntheses
categorized
1. microbial synthesis
2. phyto-synthesis

6.  Microbial systems involving bacteria, fungi, yeasts
and viruses have been reported to produce a wide
variety of nanoparticles.
 These may have either intra-or extracellularly,
representing effective bio-factories for a
nanoparticle synthesis.

7. Intracellular:
Inside the cell, in cytoplasm or cytosol
Extracellular:
outside the cell on the surface or
between the cells inside a colony

8. Biological method:
Generalized flow
chart of various physio–
chemical approaches of
nanoparticles synthesis with
highlighting of biological
synthesis

9.  In order to increase the rate of synthesis as well as
to enhance the monodispersity of nanoparticles,
photo-biological methods are under exploration.
 Phytosynthesis is implemented with plants as
predominant sources.
 Thus is considered as an accessible alternative for
a large scale production of nanoparticles

10.  Protocol involving free from toxicity and capping
agents.
 Can generate silver and gold nanoparticles.
 Cost effective large scale production of metallic,
semiconductor and metal oxide nanoparticles.
 Provides single step biosynthesis.

11.  Green synthesized NPs play significant roles in
medicines, clinical applications and in vitro
diagnostic applications.
 NPs synthesized via green methods show excellent
antibacterial effects, antifungal effects and anti-
parasitic activity.
 Nano materials or their products are useful in
environmental remediation.
 Nano scale catalysts form
 chemical reactions more efficient and less wasteful

12.  Green nanomaterial have a wide scope in the
treatment of surface water, groundwater and
wastewater contaminated by toxic metal ions,
organic and inorganic solutes and
microorganisms.
 NPs are alternatives to pesticides in control and
management of plant disease and they also act as
effective fertilizers.

13.  Production of NPs using extracts from natural
substances is emerging as an important area in
nanotechnology.
 The use of natural resources for production of NPs
is sustainable, eco-friendly, inexpensive and free
of chemical contaminants for biological and
medical applications where purity of NPs is of
major concern.
 The waste products of plant extracts are non toxic
and easier to dispose off.
 Furthermore, NPs synthesized via green route are
more stable and effective in comparison with those
produced by physicochemical methods.