Lecture B1

Added: 2026-05-19

[00:00:01]Hello everyone in our lecture series we are discussing different uh topic in this direction. Today we are going to discuss the topic of electrochemical sensors using the uh nanomaterials. So there are different nanomaterial we are applying for the electrochemical sensor.

[00:00:20]how this nanom material are playing important role to effective uh determination of for the selective detection of various uh sensor various molecules.

[00:00:33]So if we're going to the discuss about the electrochemical sensors so why it is needed because our body has several biological important molecule and each this molecule playing a sign significant role in our metabolites activities.

[00:00:51]Suppose if any alteration either increase or decrease their concentration lead to uh health complication several health complication will occur.

[00:01:01]Therefore the selective information of this biomolelecule available in our body is very important for clinical point of view. Apart from there are different type of chemicals uh we have to investigate or we have to detect the accurate level. For example, if we take in the water sample, there are n type of pollutant molecules or small molecules has been appeared in our water molecules in our water ecosystems. For example, penal common it is highly carogenic chemical. So, we have to detect this pollutant chemical by simple and effective approach. Similarly, there are different adulteration of the food. uh recently there are adulteration has been growing rapidly.

[00:01:54]Uh so there are different type of adulteration additive has been mixed our food. So in order to monitor all kind of biological things or environmental or food related or foreign application there are different type of things we have to detect some kind of molecule.

[00:02:14]those molecule either will play important role in clinical applications or it may play important role in environmental toxic pollution or it may play a role in food food contamination or food toxin. So there are different type of molecule we have to detect by using a approach. So currently there are uh different method we are applying for the for the determinance of these several molecules here I will show for example this spectrophototry titrometry chromatography fluometry and electrochemical methods. So these are the method like spectrophotometric chromatographic flometry. These are the common method has been broadly utilize for the detection of various type of analyte molecule for the effective uh accurate determination of their concentration. But the major drawback of this conventional techniques it is time consuming process and record a large volume of sample and also before analyzing the sample we need a complicated pre-treatment process and also this expense these instruments are highly expensive and need a skilled person to operate uh this kind of instrument. However the main advantage of this instrument it is a highly sensitive instrument. So most of the analyte can at present can be detected by the this kind of material. Among the method the the past few years the electrochemical approach are wely used for the deduction of various analyte molecule in biological or environmental or food related toxins.

[00:04:08]There are any number of molecule we can approach the electrochemical technique.

[00:04:12]So when compared to this technique the electrochemical technique has a more advantage for example less time consuming for the detection because the electrochemical detection is very rapid and recur a very less than minute to detect this uh any analyte. So the further the instrument cost is very low cost. Further advantage it is a high selective and sensitive detection even in presence of mixed samples.

[00:04:43]So the main principle of the sensor is to accurately monitor the or accurate determination of analite molecule from mixer of compound. So this is the main sensor definitions. So in this direction this electrochemical sensor has high selectivity and sensitivity simple procedure to analyze the electrochemical technique. In some case we can directly uh there is no need of much complicated process for the sample preparation directly we can engate or directly we can add the our real samples. So for example even without any pre- treatment process directly add the blood for example best example is uh our commercially using glucometer. So without any predatement process simply we add into the we are adding one drop of blood over the uh the glucose strip and insert into the meter we will get a uh accurate glucose level.

[00:05:43]So similar way the electrochemical approach has a most advantage. Currently there are in number of devices are commercially available based on the this electrochemical technique. So the electrochemical technique has a high scope. So currently we can solve the many issue based on this electrochemical technique.

[00:06:05]So this is the electrochemical sensor.

[00:06:07]Here in this electrochemical sensor it is composed of different component. For example, transducer is based on the electrochemical uh parameter electrochemical input. Finally, the transducer releasing the measurable electrochemical signal in the form of based on current voltage or resistance. So another things receptor this is the analy the receptor tailoring of the receptor. Here trans over the trans we are modified or we are putting the some material or biological substrate which is called a receptor. So the receptor should be highly sensitive or specific to the particular analyte.

[00:06:50]So the tailoring of the modified electrode is a highly important. So there are different type of nanomaterial has been used for the various type of sensor. So the nanomaterial role main important for the effective determination of this particular analyte molecule. So the receptor here we can use for the some enzyme or DNA or optomer or protein.

[00:07:19]Similarly the receptor can be also used as a nanom material. There are variety of nanomaterial we are applying. So the the role of these two component in the sensor is transmit the signal without any amplification from selective component or forming the change reaction. So this is the definition for the electrochemical sensor. This is the schematic structure for the electrochemical sensors.

[00:07:42]So here what are the currently facing the electrochemic sensor because the electrochemical sensor we have to use some conducting substrate as a electrode which is called as a bar electrode. Here bar electro means without modifying any bio receipt layer or without modifying any material. So what will happen when applying a bar electrode for the detection of some biomolecule or some toxic chemical or some metal ion or some uh uh food related additive or adult trend what will happen? So bare electro commonly we are using gold electrode classic carbon electrode or platinum electrode. Usually the bar electrode the electro surface in most commonly it is a spherical structure. In some case we can use as flat surface also we can use as a working electrode. So the bare electrode what will happen if without modifying and without delaying the working electrode. If we use to detect the sensor component what will happen? It is occur a different uh issues like surface ping. For example, if you want to oxidize here some phenolic based compound for example dopamine or pispol what will happen when oxidizing the first reaction it can be clearly oxidized the bispinol too into the corresponding derivative compound whereas in the second oxidation the oxidized product completely cover over the electrode surface what will happen so the oxidized product completely cover the electro surface the electro surface will beame inactive or non-coneting property. So that uh working electrode surface is not available for the further electrochemical oxidation of some phenolic compound or some analyte molecule which is called a surface fing.

[00:09:33]So surface ping means when doing the electro oxidation reaction the oxidized product deposited over the electrode surface then the electro the highly conducting electrode substrate became a insulating characteristic. So what will happen if it is changed into the insulating characteristic when applying a either voltage or current or resistance or so we cannot pass through the electro surface the electro surface it will be inactive. So the electro cannot use for the further oxidation of any analyte.

[00:10:11]So this is the main uh drawback when use any conducting subset electrode without any modification which is called surface ping.

[00:10:22]Another main factor is here um sledges electron transfer. For example, some simple molecule the redux reaction oxidation reaction electron transfer reaction is a symbol. So we can easily oxidize the the formed by product also may dissolve or it may produce gas then does not affect the surface fing the electro reaction will be simple. So it can be perfectly work on the ber surface but in our case all the molecule we cannot expect as a simple molecule. Most of the molecule it may complicated compress molecule. So the electroo oxidation reaction it will involve two or three steps or complicated oxidation steps. So what will happen the reaction sled sledge is electro transfer it is not a simple oxidation reaction and also with there are different intermediate level. So if you use some macroolelecule not we cannot say macroolelecule some large molecule it has a different function what will happen the electron oxidation reaction will be complicated. So hence though those kind of uh mixed or complicated electro oxidation reaction the bode is not suitable because it cannot be uh delivered or it cannot be efficiently oxidized the particular analyte molecule when it has a mixed oxidation state. Further the bar electro gas less sensitive because the bar electrode has a normal surface area. So it can be interact with only the particular uh number of analyte molecule. So it can produce or it can be work only the high concentration. When we go to the low concentration what will happen? The uh measurable signal we cannot identify.

[00:12:17]So maybe very weak signal we cannot know down or we cannot check the things. So the parallel has a less sensitivity.

[00:12:29]Further the major drawback from this par electro it is a poor selectivity. So selectivity means here for example want we want to detect analyte only a. So in the real sample we cannot expect that analyte molecule has only a because the real sample has combination of different analyte molecules. So our aim to detect only the molecule A in the real sample.

[00:12:56]So but originally the real molecule sample has A and also the other analyte molecule like B C D E F. So we want to detect only the a from the mixer of the various analyte molecule. So what will happen when we use bare electrode it produce a poor selectivity. So it can be uh the oxidation or redux property of the a is severely affected in presence of other analyte molecule like bcd in the real samples. So when using bar electrode for the small reaction it may perfect perfectly work in the laboratory samples. So in the same electrode if we bring into the our real analysis with the real sample what will happen the bare electrode does not effective oxidize the our desired analite molecule in the real samples. Hence the bare electrode uh difficult to use for the all the electrochemical sensor for the detection of various molecules.

[00:13:57]Hence what will happen in order to solve this issue then they will they are using a modified electro surface.

[00:14:08]What will happen which is called modified surface. The electro has been modified with some component. For example the electro can be modified with some biomolelecules like it in a enzyme or protein. We can modify anything. Similarly we can modify with some nanomaterial like carbon nanot tubes some conducting substrate like carbon nanot and conducting polymers either polyanolenol polyurol and then noble metal nanop particle like gold nanop particles platinum nanoparticle silver nanop particle then transition metal based oxide like copper oxide nickel nickel oxide there any number of metal oxide and the sulfide and then phosphate compound. So metal oxide metal phosphate. So there are different nanom material we can modify but we have to choose the nanom material very carefully for the uh for the uh selective detection of our particular analyte because all the nanomaterial cannot work for the all the sensor. So each nanom material has a specific characteristic specific property. So what will happen when modifying with the nanomaterial. So the nanom material playing a very play a important role to improve the high sensitivity good selectivity no fing of it fast electron transfer because the nanomaterial has high surface area. areas here good electrical conductivity and electrocatalytic property because the nanom material has some uh redux sender or redux active area to effective oxidation to effective determination of some particular analyte. So in this lecture series we will see the different kind of nanom material how we can prepare and uh can be modified over the electro surface or we can call as a transitive surface as a sensing platform for the detection of or electro oxidation of various compound. So this electrochemical oxidation or the electrochemical sensor is a major role or playing a important uh analytical approach for the effective detection of various analyte. So here the modified electrode is a key component for determining the or to confirm the effective working nature of any sensor. For example, this uh modified electrode, how it will happen? Because the molecule electrode if it has a large surface area, what will happen? Analite molecule has been absorbed over the modified electro surface area high amount when compared to bare electro. Whereas bar electro for if we assume the barro has absorb only 10 analle whereas the modle electro very high surface area compared to bar. So here it can be absorbed maybe here 10 means here it may be 50 molecules. So what will happen the reaction will be n further what will happen here when applying either voltage or current the molecule will be oxidized. So the corresponding electron efficiently transfer from the surface to electrode. So we can get a clear signal even at a very low concentration. This is the beauty of nanomaterial uh when used as a sensing platform over the transducer surface.

[00:17:47]When analyte molecule interact with the nanomaterial modified surface it can be oxidized. The oxidized electron effectively without any struggle or without any effect it can be completely transferred through the transducer surface and we can detect a clear signal even at a very low concentration. Whereas here what will happen uh even if it is high concentration when applying either voltage or current the molecule has been involved redux reaction that the electron has been transferred to from the surface to the uh through the transducer. What will happen if any surface falling happen because of the spare electrode does not highly active.

[00:18:29]So what will happen if any surface falling happen the electron cannot be transferred effectively through the trans surface. So we cannot get here any proper response or we may get a some weak response. Hence the bar electrode is not suitable for the effective selective detection of the any analite molecule. Hence there are we can found there are any number of application or any number of report has been used some nanom material as a sensing platform or modifier for the detection of various analyte molecule.

[00:19:06]So in this lecture series we will check the uh how what are the monomaterial we can apply for the chemical sensor. For example, the nanomaterial we can classify zero dimensional, one dimensional and threedimensional nanomaterial. There are different nanomaterial like carbon based nanomaterial. If you take a faline, graphine and carbon nanotives similarly that there are different type of 2D maxine and metal based compound. So further the different type of trans metal and uh transmetal oxide because this nanom material not only useful for the electrochemical sensor applications and also it can be applied for the various application like biomedical battery therronistic photoolic cell photoc catalysis drug delivery opto electronic because of the unique property of the nanomedical because material provide a special chemical and physical property.

[00:20:10]This property uh will be useful for the enhance the uh performance of the any device.

[00:20:19]So here we will see the especially we are focusing in the uh inorganic based material preparation how it will be influenced or will affect the sensing performance. Further here main things the nanomaterial preparation for example if we take some nanomaterial for example here copper oxide means that synthesis process of copper oxide is uh highly dependent or highly sensitive based on the parameter. Uh so the when changing the parameter like synthesis condition the property of the non material also we can tune. So the synthesis condition also major playing role for the effective detection of the any analyte. So and then this synthesis condition also when changing the condition changing the precursor or changing the some solvent nature or changing the some surfactant property of the or the surface marbology of the property are also significantly altered.

[00:21:22]So the marbology of the product also major role to get the uh high sensitivity of the detections. So here the so in this uh direction we are going to see the first two things transition metal cargoid or we can simply called transition metal sulfide. So this is the MX2. This is the congenital formula MX2 or MX. Here M refer to the transcendent metal atoms.

[00:21:56]In the name of group from 4 to 7 it has a different for example iron, copper, nickel, malibu, titanium, copper, tension. There are different type of transmal we can apply in this formula.

[00:22:09]Similarly X refer to the sulfide selenide and for example here instead of M if you choose a copper X if I choose sulfide which is called a copper sulfide. So the copper sulfate may be formed CU S or CU S2 also this is general formula. So mixed base also may be form for example C copper is 1.5 S is.5 like that mixed composition also may possible to form. So compared to this metal oxide this metal sulfide or metal selenide or metal telenide which is called a metal calogenase. Chalco has a uh attractive property has a special advantage compared to the uh metal oxide conventional metal oxide. So why this? Because this uh this metal carboate it has a special characteristic like good catalytic property, good conductivity and it can be uh highly stable for the uh long-term application.

[00:23:17]Hence this copper or this metal called compound has been effectly utilized for the various application like for example fel currently the fel most commonly in the commercial pessel we are using the wellknown standard catalyst like platinum or iridium paste or rutinium paste or nickel cobalt so the standard catalyst has a certain limitation even it provide high output are high performance. However, the cost of the standard catalyst limit the application for the broad range of usage. Hence, there are alternative ultra catalyst they are finding uh continuously to replace the conventional catalyst.

[00:24:03]Similarly, this metal uh metal chalogenates broadly used for the fuel cell application because of the unique property. Similarly this metal called jalogenise can be applied even water splitting applications also because of the high catalytic active sides in this metal charcoalogenesides for example water splitting means it can be the catalyst high performance catalyst. So then only it can be effectively split the water into hydrogen and oxygen.

[00:24:38]Similarly, this compound can also utilize for the lithium and battery and then energy storage application for example super capacitor because the material has a high surface area and also good redux property and it can act as a both sudo and capacitive characteristics based on the material choosing the trans metal as well as marbology of the product. We can use as a energy storage application and also solar cell application because solar cell it can be effectly absorb energy from the our solar then it convert into a energy. This is a simple concept of the solar cell device. So this the transition metal based amount also can be used as a solar cell application because why this material particularly interested or will give or has given a good performance in various electrochemical related application like solar cell fuel cell electrochemical water splitting electrochemical energy storage and energy conversion application. Because of this metal cargo has a very attractive property in various uh application because the uh the synthesis uh conditions also we can perform through our simple synthesis method does not require any sophisticated or any high higher end model to fabricate this uh metal sulfide as for example if If you want to prepare only copper sulfate mean just if I use some copper fusion like copper nitrate or copper chloride or copper sulfate mix with in solution a particular solution the for example if you want to prepare sulfide we can use a sulfide source there are different type of sulfur source was available for the making of metal sulfide compound for example the main sulaur is a thuria it is a very cheap and cost effective sulfur source and also we can use other sulfur source like thio acetamide. is one of the major sulfur source for this preparation of this metal uh metal sulfide compound and then we can also use uh thora and cio acetamide even pure sulfur powder also we can utilize for the metal uh uh metal sulfide. So these are the common fig we are using for the preparation of metal. Similarly selenide powder we can directly used here also telerate powder.

[00:27:25]Similar way we can use a sulfate powder.

[00:27:27]So for example here I am taking a copper chloride as a copper pas sulfide powder sulfide gas. When mixing into the solution when applying some particular temperature or pressure or particular treatment what will happen both will react with copper and sulfur to form a copper sulfate. So here uh the copper sulfate has a particular characteristic.

[00:27:53]So when changing the uh ratio of copper and sulfur what will happen? We will get a different composition of the copper sulfur. So based on this composition formation we can easily tune the conductivity nature of the compound.

[00:28:13]So these are the main advantage for this uh metalulfate preparation. Similar way we can uh tune the different metal sulfate. For example, see here this is the general formula of CU S Y. So here synthetic name isolate copper sulfate in material form which is called CUTS carosite. So this is the different composition of this copper sulfate.

[00:28:40]CUS4, CUS S3, CUS S4, SS this is a such comp classification. So the low carbonate monocenic and exagonal cubic and then electra these are the different compositional crystal structure of this copper. So what will happen when changing the reaction or experiment condition we will tune the what kind of copper sulfate we are going to achieve.

[00:29:09]So the when changing this composition what will happen when sulfur low and copper which means the material has a good conductivity. So in order to reduce the cond means if we decrease the copper content if increase the sulfur what will happen automatically the conductivity moderately reduce and the sulfur content will be high.

[00:29:32]So here the based on the composition changing we can easily tune the uh conductive property of the this particular material because some catalytic or energy storage and conversion application we need a mixed property because only conductivity is not only confirm the property will the material will give you a good performance. So the any material it has a combination of mixed property like it it should be a moderate conductivity it should be a surface area it should be active side it should be a good catalytic property it should be a uh hydro hydroicity like that there are different parameter involving to provide a good performance for the various electrocy application. So the for example in the following uh lecture series we will see the how we can prepare the simple copper sulfate uh by simple approach and it can be utilized for the effective effective utilization of this as per copper sulfane material for the ultra catalyst application as and also electrochemical sensor application in the following lecture series. So thank you.