Fabrication Of Controlled Structure Of Gold Nanoparticles And Their Hybrid Materials With Polymer For Sensing Applications

The highly porous noble metal hybrid materials show unique properties,make it applicable to the versatile class of applications in sensors,electrocatalysis,SERS,and water splitting.To achieve high applicability from these noble metal hybrid materials,it is necessary to integrate the different aspects of particles i.e.highly porous nature,the high surface,the active sites available for reaction.However to the best of our knowledge,it was hard enough to get a cost effective,highly responsive and multifunctional hybrid materials by utilizing easiest ways.AuNPs due to their extra ordinary optical,electrical,thermal and chemical properties has gained a lot of attention.Further,to utilize these NPs with smart polymers can give more functional and advantageous hybrid materials that can cause a new way to sensing and catalytic advancement.As our preliminary studies,we have paid attention to the AuNPs and polymer composite.Humidity sensor has received considerable attention in recent years because of its significance and wide applications in agriculture,industries,goods stores,and medical fields.However,the conventional humidity sensors usually possessed the complexed sensing mechanism,low sensitivity,and required a time-consuming,labor-intensive process.The exploring an ideal sensing material to amplify the sensitivity of humidity sensor is still a big challenge.Herein,we developed a simple,low-cost and scalable fabrication strategy to construct a highly sensitive humidity sensor based on polymer/gold nanoparticles(AuNPs)hybrid materials.The hybrid polymer/AuNPs aerogel was prepared by a simple freeze-drying method.By taking the advantage of the conductivity of AuNPs and high surface area of the highly porous structure,the hybrid poly-N-isopropyl acrylamide(PNIPAm)/AuNPs aerogel showed high sensitivity to water molecules.Interestingly,the hybrid PNIPAm/AuNPs aerogel-based humidity sensor can be used to detect human breath in different states such as normal breath,fast breath,and a deep breath,or by different individuals such as a person in illness,smoking and normal,which is promising in practical flexible wearable devices for human health monitoring.In addition,the humidity sensor can be used in whistle tune recognition.Next,hybrid aerogels have been exposed in various fields such as catalysis,energy storage,heat generation,and electrochemical systems.However,it is still difficult to utilize the optical properties of gold nanoparticles(AuNPs)with graphene in the form of hydrogels and aerogels.The challenge to explore the ideal materials for maximal exploitation of the Au NP optical and thermal properties is still expected of future advancement.Herein,we developed a simple,low cost and time effective approach to obtain Au NP heat generation,hydrogel formation and graphene oxide(GO)reduction simultaneously.Red light irradiation on AuNPs,GO and N-isopropyl acrylamide(IPAM)induced heat generation from the Au NP.This heat generation causes the increase in temperature which further catalyzes hydrogel formation and goes reduction.Further other freeze drying hydrogel can convert to hybrid aerogel and cause humidity sensing and electrochemical cyclic voltammetry(CV)application.The simulation has explained the interaction mechanism of the synthesized aerogel material.How to prepare precisely tunable gold nanoparticles in monometallic,bimetallic and trimetallic structures with precisely controlled structure morphology and repeatability is still challenging.Furthermore,less attention has paid toward the self-assembly of high index facet(HIF)structured bimetallic and trimetallic nanoparticles to achieve large areas two dimensional(2-D)monolayer film.Finally,the synthesis of different shapes of gold nanoparticles has been studied extensively.Further,to achieve high index facet core-shell multimetallic nanoparticles(Au@Pt@Pd)we have successfully used gold nanorods(AuNRs).In this aspect,second metal like Pd has played an important role to get a precise and well defined concave and convex(Concave-X)shaped uniform nanostructures.The concentration of Pd and Pt,temperature and shape of nanorods has played an important role in the synthesis of Concave-X nanostructures.Further,the formation of large area 2-D monolayer film has been achieved successfully for such a HIF structure that is useful for the catalysis.Coating of film on the spherical surface of glass electrode has shown extra ordinary stability against temperature,solvent effects,and basic and acidic media.This Au@Pt@Pd coated glass electrode has used in the electrochemical catalysis of methanol oxidation with stability to about 5000 cycles.