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Module 1: Synthesis of Nanomaterials

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Video 1: Biological Techniques
Welcome back we have been discussing about the basics of nanotechnology and in that context,we have talked about the different type of geometry of nanomaterials followed by thatwe have talked about the synthesis and the synthesis we have talked about the physicalsynthesis followed by the chemical synthesis.And now we will proceed towards the biological synthesis, as I told you in the initial outlinethat biological synthesis is one of the smartest synthesis in terms of conserving energy.And in terms of conducting the reaction at a very low temperature or a pressure or withinthe physiological regime.So that is lot more to learn about the biological synthesis of nanomaterials because that iswhere the feature lies a very sustainable route.So, if you recollect what we talked about the biological methods.So, basic idea is will be emulating nature by synthesis which is the green root and theraw materials are in friendly and these are eco-friendly things.And understanding the nano reactors or nano vessel where in a confined space that enzymesexecute addition and subtraction of bonds and leading to a self-assembly.And while we talk about the biological root these are mostly environmentally benign lowtoxic, cost effective and more efficient module.So, the 3 routes what has been followed as of now pretty much well documented or microorganismassisted biogenesis, bio template assisted biogenesis and plant extract assisted biogenesis.So, we will start our journey from where out here and all these techniques employ the biologicalsystems like bacteria, fungi, virus, yeast and actinomycetes and plant extracts.Let us resume from here, biological route ofnanomaterial synthesis and biological route of nanomaterial synthesis as we have alreadymention.The first one will be discussing is biogenic synthesis using microorganisms, biogenic synthesisusing microbes or microorganisms.So, the basic idea of biogenic synthesis using microbes is prokaryotic, bacteria like actinomycetes,fungi, algae, yeast, prokaryotic, bacteria, fungi, yeast, actinomycetes, there extensivelyused as bioreactors.So, these functions as the bioreactors if you consider these single cell organisms asbioreactor.And these bioreactors are use to synthesize the nanomaterials.And if you look at it the enormous scientific effort where may to develop the strategy ofproducing nanoparticles of silver, gold, palladium, titanium, cadmium mostly cadmium sulphide,microorganism grab the ion targets, the way they do it very straight forward.So, these microbes basically they grab the target ions from their environment and theyturned the metal ions into element metal through enzyme generated by cellular activities.The synthesis can be classified into intracellular and extracellular.So, for example they are pulling the ions, so this is the environment outside if thisis the microbes and this is the surrounding environment.They are pulling the raw material from the environment it could be x, y, z whatever andout here by enzymatic reaction at a very low temperature and pressure they are convertingthem into some of the intermediate whatever we are asking for.And then this is the time where we are intervening into this system to extract out these desiredproducts out of it.So, purification and different kind of routes and this is what is about the basic outlineof the process.And the synthesis could be classified into 2 level, this could happen either for examplefor addition route strategy it happens at this level also at the surface.So, in that situation what we are having is the microbe is say decorated with a seriesof enzyme on top.So, these what I am drawing now at the decorated enzymes sitting on top of the microbes.And these are helping in transforming some x, y, z whatever into some desired productby the enzyme activity to say XA, XB, XC or likewise depending on what is the desiredproduct we are asking about.But depending on where it is happening you have either these are extracellular or theseare intracellular.If it is happening outside like this we call this kind of synthesis as extracellular synthesisand if it is happening inside the cell here we call them intracellular synthesis.These are the 2 modes of synthesis following the microbes.The intracellular method involves transporting the metal into the microbial cell to formnanomaterial in the presence of enzyme as if it could see if the transport has to happen.So, which is slightly more energy intensive.The extracellular synthesis of nanomaterial involves cracking the metal ion on the surfaceas you could see on the surface of the cell and reducing the ion in the presence of enzyme.So, bacteria utilize number of anionic functional groups proteins and enzyme reducing sugarin bacterial biomass to reduce interacting metal ions.So, this is the basic, basic approach and this could be done by fungus where fungusmediated green chemist approach for synthesis of nanomaterial as several advantage in termsof bio-chem accumulation, economic viabilities, scaling up synthesis due to simple downstreamprocessing and biomass handling.That suppose you are using fungus most of these processes are fairly economical.And this is the part what we are talking about the downstream processing where you are isolatingthe desired product at a particular point and much of these downstream processing iswell within the economical limits of producing such nanomaterial.So, this is one of the basic methods in biological synthesis.

Video 2: Summary of Nanomaterial Synthesis
The next one is in this line will be coming to template assisted which is bio-moleculesas template to design nanomaterials.Now when we talk about template assisted synthesis, so there are various bio-molecules like youknow you can use nucleic acids, they can use bi-lipid membranes, you can use differentviruses, you can use diatoms might what in wonder what its diatoms.These are algae, these are single cell algae and these are really one of the most populatedalgae in the algae family.And they have silicate cell membrane and those are really beautiful silicate cell membranes,if you just give a search in Google images then you go for diatoms silicate coveringyou will see amazing part on sentence.So, these diatoms could be used as a very interesting template for any kind of lithographicalapplications and some artifact.There are groups in the world we are trying to use those kind of pattern templates forbioelectronics application for developing transistors, developing electronic using themass electronic substrate coming back where we were.So, your nucleic acids, membranes, viruses and the diatoms these are used as templateto synthesize nanomaterial DNA is widely known as an excellent biomolecular template.That has the strong attraction with transition middle ions for any transition metal ion nanomaterialsynthesis DNA could be used as a template.And that shown that the DNA hydrogel could be made and crosslink before incorporatingtransition metal ions like gold to DNA macromolecules that eventually lead to the formation of goldnanomaterial.The process involve reduction of gold from it is 3 stabling the formation of gold atomand metal cluster that develop into gold nanomaterial on the chain of DNA.So, this is one way you can use DNA and DNA mediated synthesis or strategy to synthesizehighly stable wire like clusters or silver nanomaterial is also a very common new observedarea of research.So, one such area, so basically the whole idea is you are using a template in this casethe template is nucleic acid.Similarly, you can use diatom as a template, so on this template you are attracting yourmaterial which you are going to convert on this template to you know something like this.As I was showing in the previous example something like this, so these are template assistedsynthesis.And in the third in that series is the next one which is plant extract for nanomaterialsynthesis.So, the biosynthesis of nanomaterial using plant extract or plant biomass is one of thevery effective, rapid, clean and non-toxic and eco friendly method.This method has been utilized predominantly is to synthesize nanomaterials of double metals,metal oxide, bio metallic alloys.And they have been adequately demarcated various plant bio metabolites that could help in preparationof nanomaterial based on their valuable role as reducing agent and as capping agent.One of very common logic what is being followed in this kind of a plant extract-based nanomaterialsynthesis is you are utilizing the specific enzyme needed for forming some specific bondwhich otherwise in an inorganic setup could consume significant amount of energy and power.So, you are in a way where manipulating the milieu of the reaction by introducing an enzyme.And this is these are some of the very very very clean methods and these are economicaland they have a simple downstream processing and they are free frommuch hazards.Because you are not now dealing with living microbes, you are just using a plant extract.So, the core idea is very straightforward as I mention for making or breaking any kindof bonds the nature uses series of enzymes as a matter of fact our story of life is couldalso be called as story of enzymes.So here we are exploiting those gifts of nature to us was wonderful enzymes to make or breakbonds to synthesize the desired product or desired nanomaterial what we wish to obtain.So, let us summarize what all we have covered in this section as of now, to start off with.So, this is where we started on the module of nanotechnology.We talked about the classification of nanomaterial in terms of shape and geometry and the chemicalnature.There we talked nano cages, nano crystals, nano barrels, nano fibers, nano particles,nano tubes.Both hallow and solid.Nano wires, quantum dots and nano composites.Then in terms of synthesis of nanomaterials oh in terms of the chemical nature there couldbe either organic, inorganic or carbon based.And in terms of the synthesis you could have either top down approach or bottom up approach.And these are further classified based on the route we are following, there could bephysical, chemical or biological.Physical we have talked about all the techniques high energy ball milling, pulse vapor deposition,laser pyrolysis, plash spray pyrolysis, electro spraying, melt mixing and polymer compositedevelopment whereas in the chemical section we talked about SOL-gel synthesis.Micro-emulsion technique, hydrothermal synthesis, polyol synthesis using poly ethylene glycol,chemical vapor synthesis, plasma enhanced chemical vapor deposition.And now in the biological segment we talked about microorganism assisted biogenesis, bio-templateassisted biogenesis and plant extract assisted biogenesis.So, in this segment now you are left with the characterization of nanomaterials, sothis is in the module of nanotechnology.This is where we will be concluding once we talked about the characterization.So, we will close in here and in the next class we will talk about the characterizationof these different nanomaterials characterizing them based on their geometry, characterizingtheir chemical nature, characterizing their specific functional groups which are available.And that way we will be concluding this section and the way we are moving, so your first weekwe have devoted about the role agrochemicals in agriculture and the need of nanotechnologyin terms precision farming, in terms of reducing the usage of optimizing rather the right wordwill be optimizing the use of fertilizers and pesticides from there in the week 2 wemove into the nanotechnology.The basics of nanotechnology and there is a slight spillover of the second week intothe third week and after characterization.So, we talked about the classification nanomaterial, we talked about the synthesis and now willbe talking about the characterization after characterization we will move on to specificnanomaterials which have been tried out in the laboratory in the field for agriculturalapplication.So, let us catch up in the next class with the characterization of the nanomaterial beforewe proceeding to the application of nanomaterials in agriculture which includes plant, annualproduction, food packaging or post harvest technology and cleaning of water, thank you.