Video 1: Chemical Approach
Now let us move on to the different chemical approaches which are being used.So again for the chemical approach there could be 2 things either you are using a bottomup approach or you are using a top-down approach, when we talk about top down approach we talkabout itching.So you have a bulk material, say for example so again the 2 options you have either topdown or bottom up.So whatever be the technique when we are going out top down we are talking about itching,itching in a sense you are taking a bulk material and using some kind of acid or some kind ofother chemical you are bringing on the size of it because of abrasive chemical actionand then we talk about the bottom up approach we mostly talk about self-assembly of particlesin the presence of capping agent and other agents do you know promote self-assembly.So let us just differentiated, now talking about the chemical methods which are beingemployed, they fall under so the chemical methods are falling underthese settings, so they have SOL gel synthesis, aerosol and gel will talk later about thedetail of these kind of synthesis your SOL gel synthesis, then we have micro emulsiontechnique, micro emulsion technique followed by hydrothermal synthesis.Then you have polyol synthesisfollowed by chemical vapour synthesis, then we have plasma enhancedchemical vapour deposition.So these are some of the broad classification of chemical synthesis of nanomaterials, SOLgel, micro emulsion, hydrothermal, polyol synthesis, chemical vapour synthesis and plasmaenhanced chemical vapour deposition.And if you look at these methods the last 2 like chemical vapour synthesis plus, minuschemical vapour deposition, even hydrothermal synthesis all these techniques requires reallyhigh energy.These are energy intensive just like your physical method where we talked about thesetechniques why do you need a significant amount of energy, here we are talk about high energyintensive processes.On the contrary when will look at these 2 techniques SOL gel or SOL gel synthesis, microemulsion technique.These in comparison with respect to a comparatively these are low energy intensive processes,once we talk in detail about this will highlight this fact why some of these techniques arelow energy requiring where is the other ones are high energy requiring.So now we have discussed as of now or enumerated as of now the physical and chemical synthesisroutes.Now from here will move on to the biological route, now when we talk about the biologicalroute why it is so critical that we understand the biological route, well if you look atnature the way nature functions let us take a simple example that plant world is the onlyplace or only kingdom which can picks a nitrogen from the environment.There is no other way you can fix nitrogen and there are these enzymes call nitrogenasewhich can trap the aerial nitrogen and convert it into some usable SOL, some usable formand that is why we are completely dependent on nitrogen fixing microbes which have a symbioticrelationship with legumes and other plants.So they are the one which enriches soil of nitrogen, otherwise there is no other wayyou can do it.Now even as Layman if you think of it plant does not have a chemical vapour depositiontechnique or laser pyrolysis or some hydrothermal synthesis or any of these sophisticated socalled sophisticated energy intensive tools to achieve this feet, what it does, it isdeveloped a genome effect and its synthesized some very unique enzymes which could assistin transforming and peak around with this bonds of you know getting the nitrogen gas.And transforming it attaching with some factor, so it assist in it and ensure that we getthe desired result, but this it does in a simple room temperature or maybe you knowI am at this point settings or delivering a talk at around 20 degree centigrade, thetemperature of the room outside will be like around 30, 35 degree centigrade.So within the physiological level of plant can do this.So in other words plant does these things without any extra requirements of energy interms of high energy requirements or in very sophisticated tools.So in other word nature is our best guide to understand what we call as bottom up approachof nanoparticle synthesis as well as nature can teach us how it does the top down approachbecause think of it when we talk about a top-down so what we are talking about the bulk materialout here.
Video 2: Biological Approach
Now suppose this bulk material is under the influence of a microbe, this microbes if youcould increase the population of the microbes on it this can bring it down for small particlesover a period of time.So it is possible that it could reach out the particle or it may consume it but thenif we get this microbes which has consumed is particle and grind it together then bemuch more less intensive process and pull it out pull out those particles.So are these feasible could we think in that way or as you told you as we discussed justnow in the biological world the bottom up approach.So these are the principle or guideline in feature what provokes us to think that biologicalroute of nanomaterials synthesis is the future where we could emulate nature, emulating naturebecause why we wanted to emulate nature is basically a biosynthesis orwhich is a green synthesis.You are not using any caustic acid or any kind of caustic compound or any kind of harshenvironment to achieve this kind of synthesis, yet you achieve your goal.So what biology has to offer is what we have to learn is understandingthe nano reactors or nano vessels where in a confined space enzymes execute the additionand subtraction of bonds and thereby bringing about a self-assembly or even at times theseenzyme could catalyse executes the breaking of bulk.Thereby leading to small particles, so in other word what we are talking about in termsof biological route is we have to understand, so most of these provides environmental benignwhat is basically environmentally benign low toxic, cost effective and fairly efficientmodules of synthesis and the biological routes which are currently widely explode includesmicroorganism assisted biogenesis, microorganism assistedbiogenesis is one.The second thing is bio template assisted biogenesis and we will talk in detail aboutthis as well progressing in this area bio template assisted biogenesis, plant extractassisted biogenesis.So the logic is simple what is being followed out here is this employingbiological systems, employ biological systems like bacteria, fungi, viruses which is kindof tricky viruses, yeast, actinomycetes and plant extracts to bring about the biogenesisor synthesis of these kind of nanomaterial.Now one thing was realizing what you are essentially doing, the key idea is to is kind of if youlook at it more much of these research in the initial area of research out here areof you are trying to extract much of the enzymes from the system, which will help in the synthesisof the nanomaterials.Now one area which florist in last 30-40 years tremendous amount of research has taken placeis the area of by inorganic chemistry.So of you look at the work which has been carried out in by inorganic chemistry youwill realised there are people who have tried to module minimal unit of atoms needed tomimic the function of an enzyme.This tremendous amount of work which is gone in synthesizing such are you know say forexample modelling nitrogenase, modelling and these are just some examples I am giving modelling,water splitting, clusters which is mostly consist of manganese, cluster essentially.So these are the approach which has been there not under the banner of nanotechnology whichhas been there where people have say for example just to make understand.Say for example when we talk about an enzyme, so we talk about a huge protein moiety andwithin that protein moiety you have active site, say for example this blue is showingthe active site.And say for example this is an example of say nitrogenase we have talked about it.So this is the active site of nitrogenase.Now what people have been trying is this is the site where say nitrogen gas is comingout.Maybe some another site is binding and then there is a reaction which is happening andleading to transformation of the nitrogen and of course the enzyme is not getting usedup, but people have trying to do for a while, say for example they wanted to understandthis structure in atomic resolution and once they understand the structure in atomicalsolution what they try to do they wanted to synthesise this structure outside the system.Not by biological route, by sample inorganic route and if you could get it in inorganicroute then you can and if it is unstable inorganic approach stable route then you can actuallyproduce or you can transform nitrogen to your desired product in a controlled environment.So if one can achieve these desire product, then much of our synthesis of urea, ammonia,the high energy processes will kind of will be kept at bay if you understand this.So in other word what I wanted to highlight here is this, nanotechnology of course anotherbanner of nanotechnology these are not there, this is one of the key areas of by inorganicchemistry, but if you look at some of the development of by an organic chemistry andif you follow up with the people even in India as well as abroad where worked extensivelyin this area for last 20 to 30 years.You realise that they are nothing but figuring out low energy methods, modelling enzymesto create environmentally benign route to fix different kind of compounds which areneeded for agriculture, today we are kind of standing at that beautiful needs to realiseand appreciate the research which has undergone for last multiple decades in the area by inorganicchemistry.So I here I take the liberty it is say much of these by organic chemistry research ofmodelling the enzymes and synthesizing them is kind of laying the foundation stone ofmodern route of biological based systems for nanomaterial synthesis.That is kind of is where much of these biological routes are heading they are very very energy-efficientsystem the way in the for system 2 the manganese cluster which traps the water molecule andspirit of the water molecules to generate hydrogen and oxygen is just a magic.There is no system which could do it so very efficiently, not only that think of the waterchannels.If you could emulate water channel in terms of water purification, think of the way anitrogen fixing bacteria or microbes traps the nitrogen from the air or areal trapping.So these are some of the marvels of biology and that is why I mention the beginning theidea is to this word is critical for you to appreciate emulating nature.This is what lies answer to most of our tricky question which otherwise is not easy to answerby any means.Emulating nature the way nature does and we understand nature, the way does it then oneday probably much of these techniques will merge towards biological technique which inother word which will be much more precise is very precise route and these will be interms of the energy out here to compare it.So these will be energy low technique as well as small amount of raw materials to be needed.And will be much more eco-friendly, but these biological methods are just in there in fancywe are slowly very slowly realising that what all we can do using biological tool and thisis not a common genetic engineering and talk about slightly different that whole domainof bioinorganic chemistry and its application in nanomaterial synthesis.So this is broadly are the different methods under the heading of physical chemical andbiological methods of synthesis.Will go little bit after this in explaining very briefly about what is high energy ballmilling, what is pulse vapour deposition, what is laser pyrolysis, what is flash spraypyrolysis, what is electric spraying and melt mixing.Then in the chemical route will talk about the SOL gel method, micro emulsion technique,hydrothermal synthesis, polyol synthesis, chemical vapour synthesis, plasma enhancedchemical vapour deposition.And then in the biological routes we will talk about the microorganism assisted biogenesisbio template assisted biogenesis and plant extract assisted biogenesis.So closing here, in the next class will talk in detail about this techniques, thank you.
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