ABSTRACT
Epoxies, their derivatives, and composites, due to superior specific strength, are preferred for many potential applications in the field of automobiles, aircraft, bonding of structures, protective coatings, water filtration, etc. As structural members in automobiles and aircraft, the epoxy-based components are exposed to various static/dynamic mechanical loading conditions during their service life. The interfacial interactions, between the matrix and reinforcement, greatly affect the final properties of the composites. The present study demonstrates that the solvent used for the preparation of the composite can also contribute toward interfacial interactions. Present research systematically finds out a suitable solvent (acetone) and reinforcement type [multi-walled carbon nanotube (CNT)] for epoxy [bisphenol-A (BPA)] nanocomposites. Dynamic and static strengths of the as-prepared epoxy-CNT nanocomposites were carefully investigated. Well dispersed CNTs in acetone were mixed with an ester of BPA under constant magnetic stirring conditions. Samples of tablet shape were prepared for testing static and dynamic performance of the composite using a nano-indentation technique. Considerable enhancement by 55 and 22% in the static elastic modulus and hardness of BPA-CNT composites, respectively, was observed (compared with that of pristine BPA). The storage modulus and tan-delta of the nanocomposites were also improved by 14 and 46%, respectively. Improved static and dynamic performance, reported in this work, significantly enhances the scope of utilization of BPA-CNT-based nanocomposites under severe static and dynamic loading conditions simultaneously. Static and dynamical analysis of CNT-reinforced epoxy provides more realistic understanding of the mechanical performance of the nanocomposite. Density functional theory (using QuantumATK software) simulations were performed to investigate and identify the alterations in the atomic morphology of CNTs during interfacial interaction with the acetone molecule and epoxy matrix. The calculations predicted that CNTs with mild defects as compared to pristine CNTs were better suited for synthesis of the nanocomposite and also assisted in a homogeneous distribution of CNTs in BPA without aggregation (with acetone as the solvent). Furthermore, structural changes in CNTs after treatment with BPA and the curing agent and the role of defects are studied in detail.
ABSTRACT
The increasing level of pesticides and herbicides in food and water sources is a growing threat to human health and the environment. The development of portable, sensitive, specific, simple, and cost-effective sensors is hence in high demand to avoid exposure or consumption of these chemicals through efficient monitoring of their levels in food as well as water samples. The use of nanomaterials (NMs) for the construction of an immunosensing system was demonstrated to be an efficient and effective option to realize selective sensing against pesticides/herbicides. The potential of such applications has hence been demonstrated for a variety of NMs including graphene, carbon nanotubes (CNTs), metal nanoparticles, and nano-polymers either in pristine or composite forms based on diverse sensing principles (e.g., electrochemical, optical, and quartz crystal microbalance (QCM)). This article evaluates the development, applicability, and performances of NM-based immunosensors for the measurement of pesticides and herbicides in water, food, and soil samples. The performance of all the surveyed sensors has been evaluated on the basis of key parameters, e.g., detection limit (DL), sensing range, and response time.
Subject(s)
Biosensing Techniques , Herbicides , Nanostructures , Nanotubes, Carbon , Pesticides , Humans , Immunoassay , Pesticides/analysisABSTRACT
Gold nanoparticles (GNPs) have generated keen interest among researchers in recent years due to their excellent physicochemical properties. In general, GNPs are biocompatible, amenable to desired functionalization, non-corroding, and exhibit size and shape dependent optical and electronic properties. These excellent properties of GNPs exhibit their tremendous potential for use in diverse biomedical applications. Herein, we have evaluated the recent advancements of GNPs to highlight their exceptional potential in the biomedical field. Special focus has been given to emerging biomedical applications including bio-imaging, site specific drug/gene delivery, nano-sensing, diagnostics, photon induced therapeutics, and theranostics. We have also elaborated on the basics, presented a historical preview, and discussed the synthesis strategies, functionalization methods, stabilization techniques, and key properties of GNPs. Lastly, we have concluded this article with key findings and unaddressed challenges. Overall, this review is a complete package to understand the importance and achievements of GNPs in the biomedical field.
ABSTRACT
Graphene, two-dimensional (2D) sheet of carbon structure, in its purest form has shown potential for application in the fields of electronics, semiconductor, sensing, energy, displays, biomedical engineering, etc. Graphene oxide (GO) is easier to synthesise than the pristine graphene, scores comparable in terms of mechanical strength, but lags in electrical and thermal conductivity. GO plays an important role in nano-composites for use in loading conditions requiring superior mechanical strength. GO is a suitable candidate as reinforcement due to its better solubility in the epoxy polymer, resulting in improved properties. The present work reports the reinforcement of graphene oxide in epoxy matrix to enhance visco-elastic properties of the E-GO nano-composite. GO was prepared by wet chemical oxidation method from graphite flakes that were used as precursor. The E-GO nano-composite samples were prepared by solution mixing method, without the use of any external stimulus to exclusively understand the effect of GO reinforcement. Dynamic mechanical characterisation of the fabricated E-GO nano-composites for the visco-elastic properties was carried out using nano-indentation technique. Storage modulus and loss modulus of the nano-composites were tested over the frequency range of 20-200 Hz. Tan-delta or loss function was calculated to characterise energy storage capacity of the nano-composite samples under the loading. Tandelta showed 12% improvement at 1 wt% of GO reinforcement in the nano-composite. Hardness of the nano-composites improved upto 10% with GO reinforcement. Epoxy-based aircraft repair applications require epoxy to deliver superior elastic properties and the present report verifies the improvement in elastic behaviour of epoxy with the addition of GO.
