Video 1: X-Ray Photoelectron Spectroscopy
So, welcome back to the lecture series in nanotechnology in agriculture, so we havetalked about the characterization of the material in terms of characterizing the geometry, characterizingthe size and morphology by using transmission electron microscopy, scanning electron microscopyand atomic force microscopy.Study people to go through what is scanning tunneling microscopy of course I will be providingin the notes what is the detail of a scanning tunneling microscopy.But I just want that as an assignment for you to looking to it.So apart from it will be going through another physical technique which is understandingthe contact angle or understanding the hydrophilicity or hydrophobicity of nanoparticle.So, say for example you have one kind of nanoparticle which interacts with water better as comparedto the other one.How you can do it?How you can figure it out?What you can essentially do?you can do something called a contact angle measurement, so how do you it.So, this is where we were characterization of materials transmission electron microscopy,scanning electron microscope, atomic force microscopy and scanning tunneling microscopy.Now you are talking about physical properties of interaction in the polar and non-polarsolvents.So, say for example you have particular particle say make a film or you layer it something.These are the particle you are layering like that, so you performing a thin layer or amono layer of the particle.And now say for example you want to use this for different kind of fertilizer release orsome kind of insecticide release capsule or something.Now once you form a layer of it on a substrate you put a drop of water droplet.Now the possibilities of the drop of water will be either the drop of water will remainlike this on top it says for example this is a particle layer.So, either the drop of water will behave like this or it will be even much more somethinglike this or it will become like this or it will become like this or it will almost mixlike this.So, if you look at it with compare to the base start seeing what is the angle it ismaking, the angle is continuously changing almost and here it is almost mixing on thesubstrate.So now based on this angle you can calculate what will be it is hydrophilic nature andwhat will be its hydrophobic nature.So, this is done with an instrument called goniometerand this powerful technique is called contact angle measurements.And having while we are saying this there is another point which I wish to highlighthere you can change the hydrophilic or hydrophobic nature of a particle or of a material whileintroducing functional growth, say for example you want to make a material from say hydrophilicfrom hydrophobic, hydrophobic which is water heating, this is shown as water heating tohydrophilic which is water loving, what you have to do.You have to introduce in that material you are adding multiple OH groups, this OH groupswill eventually from hydrogen bonding and will let to a material which is hydrophilicin nature.So, hydrophobicity and hydrophilicity are the functions of the functional groups whichare attached to the material and which eventually decide how much it is going to interact withwater.Now after this we move on to the surface chemical properties which includes among the surfacechemical properties.We talked about the physical, the major surface chemical property is which is used in allsurface analysis is called XPS, so this is essentially x-ray, photo electron spectroscopy.So, the fundamental of x-ray photo electron spectroscopy is fairly simply say for examplewe talk about an atom.So, this is the nucleus where you have the proton and neutron and here you are havingthe electron cloud around it in a simplistic sense.These are the places where electrons are revolving around, now these electrons which are there.So, they have different orbital we know that s, p, d, f likewise, these are the differentorbitals where these electrons are happing around it.Now these electrons which are hopping around and different electron cloud have differentenergies.So, in order for an electron for example I supply some form of energy out here into it.And for this to eject out an electron for example and this electron form here is gettingejected out.It will eject out with a unique kinetic energy and that kinetic energy is essentially theenergy at which it is being part of that atom, so you have to give x that amount of energyyou know make it move out from it.So, say for example something is hold there with x amount of bond energy.So, you have to give that –x amount of energy to pull that out from that zone that is unique.This energy with which it is coming out from that particular atom is unique.So, you could develop a charge depending on element, so element say for example you havesilver, copper, aluminum, iron, sulfur and in thenext column you may have the kinetic energy of emitted electron of say for example somespecific shell we are talking about mostly the outermost shells, so we talk about theouter most shell.So, with what energy that electron is going to come out in electron gold, some some amount.Now say for example you give that much energy, so I have a surface like this, so I have ananoparticle like this which is lying there.And say for example these nanoparticles have equally that they have sulfur and they havesilver, and sulfur something like this.So, what will be saying on these particles you will have if I represent sulfur with orangethat the sulfur atoms sitting out there.And you will have the silver atom which I am representing in light blue, you will havethis silver ion sitting out there, tones of them sitting like this.Now if you put a beam of electron certain kinetic energy or a spectrum of it.So, the outermost electron from here will be coming out from the sulfur, this is weare representing sulfur and this one as silver.So, the electron will be coming out form each one of them at different electron hold whichis of course we are talking about the outer most and you can go to the other one alsomuch more core once.But at this point we are just ensuring the electrons are in the outermost shell, nowif you have a detector sitting out here which could measure that speed.Here you have a detector, then the detector will tell you what you are seeing whetherit is silver, sulfur or something else.So, this is essentially x-ray photoelectron spectroscopy this is the fundamental and Iwant based on this I want you people to see any literature available online on x-ray photoelectron spectroscopy.But the fundamental of x-ray photo electrons spectroscopy is this and it is one of themost powerful surface characterization technique by which you can do the power of the techniqueis you can do a very simple elemental analysis.You can give a surface analysis you can talk about some form of an advance imaging or atomicimaging of materials.And most importantly it has very very high resolution in terms of the amount some deltaamount on the surface one can detect.You can detect a very very trace amounts on a substrate or on a surface and (()) (13:39)won the Noble prize for developing this X-ray photo electron spectroscopy theories and theinstruments.So, this is one of the most widely used technique and I always will recommend you wherever youget chance try to explore this technique.
Video 2: X-ray Diffraction and Fourier Transform-Infrared Spectroscopy
The next in the line is after X-ray photo electrons spectroscopy you have XRD whereyou are detecting the crystal or amorphous properties of materials whetherthey are repeated units are not said for example if you go back nano crystals, we talk aboutnano belts.We talk about nano cages we talk about.So, what will be the crystal structure how that crystalline crystallinity will work outwhether they will be repetitive units to make crystals or it will be much more like amorphouswhere there very little repeatability in the structure.So, these kind of whether these particles are crystalline or they are amorphous.In order to understand that your best bet is x-ray diffraction, these stands for diffraction.So, this is where you are using x-ray for determining the stereo chemical propertiesor in space how these atoms are arranged.This is the technique what you are using.The next in the line will be FTIR Fourier transforms infrared spectroscopy.So, this technique gives you a knowledge, so I am not getting into the depth of thetechnique which I will again leave for you to explore this technique gives you an idea.Say for example what are the different kind of functional groups which are present onyour sample, types of functional groups, say for example you are increasing the hydrophilicityof the particle alright.So, what are the kind of functional groups which are present and all these details thatyou can obtain using Fourier transform infrared spectroscopy, this is the power of the technique.So, we have to summarize what all you can do from this includes you’re the surfacechemical techniques you have XPS, you have XRD, you have FTIR, prior to that you cando the physical properties, you can figure out in terms of their interaction with water.You can figure out the hydrophilicity and hydrophobicity of the surface using contactangle measurements and using the instrument called goniometer, apart from it in orderto figure out the geometry size and morphology.You have transmission electron microscopy, have a scanning electron microscopy.You have a scanning tunneling microscopy and you have atomic force microscopy.So, to summarize this part what we covered here is classification nanomaterial in termsof shape and geometry chemical nature in terms of chemical nature the organic nature, inorganicnature and carbon-based nature.Then we talked about the synthesis where we talked about physical, chemical and biologicaland followed by that we talked about the characterization of nanomaterial in terms of figuring out theshape and geometry using different form of electron microscopy.And AFM and STM which includes SEM and TEM then we talked about all the chemical waysof understanding the atomic architecture using XPS, XRD and FTIR.And then we talked about water heating and water loving properties in terms of contactangle.So that kind of covers our basic understanding of nanotechnology which will be need it tounderstand this course in greater details of how basically all the synthesis processesare taking place.And how these syntheses could be done and what are the basic absolutely fundamentalrequirements for you to documentary your work in terms of how you classify your material,how you synthesize your material and how you characterize your material.And then of course introducing it to the its agricultural relevance.So, based on this frame work we will start our journey of different kind of nanomaterialswhich are currently under intense exploration for their application in increasing agriculturalproductivity water purification and myriad of other applications, thank you.
Log in to save your progress and obtain a certificate in Alison’s free Understanding Nanotechnology in Agriculture online course
Sign up to save your progress and obtain a certificate in Alison’s free Understanding Nanotechnology in Agriculture online course
Please enter you email address and we will mail you a link to reset your password.