Owing to efficient catalytic character high electrolyte

Owing to efficient catalytic character, high electrolyte accessible area, easy fabrication and many other interesting properties, metal oxide nanoparticles are extensively used in a variety of electro-analytical processes [14]. Metal oxide nanoparticles immobilized over a conductive and large area support like graphene is shown to further enhance the performance [15], [16]. Electrochemical sensing using graphene based nanomaterials was first reported by Papakonstantinou [17] and later Dong et.al. [18] and Kim et al. [19]. demonstrated fast electron-transfer in graphene sheet. Consequent to the good electronic conductivity and efficient electrocatalytic property, different type graphene based biosensors are reported [20], [21], [22], [23], [24], [25], [26]. On the other hand, due to high chemical inertness and low toxicity, Zirconium oxide (ZrO2) is recognized as an environment friendly material [27]. Properties of ZrO2 like thermal stability, biocompatibility, cost effective production and electrochemical activity pave its way to superior electrode material in electrocatalysis [28], [29], [30], photocatalysis [31], [32], urea sensing [33], DMPO sensing [34], humidity sensing [35] and more importantly OPs detection [28], [29]. In the present article, we demonstrate ZrO2 immobilized graphene nanocomposite electrode for chloropyrifos detection. In amperometric detection of chloropyrifos using graphene supported ZrO2 electrode, our result indicate extended linear detection range many orders higher to the reported values in literature. Synthetic methodology of Reduced Graphene Oxide (RGO) supported ZrO2 nanocomposite and its biosensing mechanism for Chlorpyrifos detection is shown in Scheme 1. Pesticide detection methodology is based on the measurement of reduction in AChE activity by means of Faraday current. AChE breaks down the ATCl present in electrolyte and consequently releases two electrons in the process. So generated electronic current, is monitored as the electro-activity of ZrO2/RGO electrode. In the presence of Chlorpyrifos, activity of enzyme slows down because of irreversible binding that consequently results in decreased current.
Materials and methods
Result and discussion
Conclusion Nanostructured Reduced Graphene Oxide (RGO) supported ZrO2 nanocomposite (ZrO2/RGO) was synthesized via hydrothermal route and tested as an efficient electrode matrix for enzyme immobilization. AChE/ZrO2/RGO biosensor based on electrochemical principles exhibited cost efficiency and high sensitivity towards Chlorpyrifos detection. Our results demonstrate the Chlorpyrifos detection as low as 10M concentration with 28.27% enzyme inhibition. The enzyme inhibition was remarkably high (72.94%) for the samples containing 10M concentration of Chlorpyrifos. Biocompatibility tests of ZrO2/RGO matrix further demonstrate the application of biosensor in the conditions where living cells are involved. A quick literature survey as presented in Table 2, suggests that the AChE immobilized ZrO2/RGO matrix constitute a high performance Chlorpyrifos biosensor. Which is many orders of magnitude higher compared to other materials reported for pesticide detection. Literature reports mentioned in Table 2, support that the AChE/ZrO2/RGO biosensor is most sensitive and cost effective with fabrication and operational convenience reported till date.
Acknowledgements Authors are grateful to the University of Delhi, Delhi, India for providing financial assistance through R & D fund [RC/2014/6820], SERB-DST (SR/FT/CS-123/2010) and Sophisticated Analytical Instrument Facility (SAIF) – AIIMS, New Delhi, under the SAIF Program of DST for providing TEM facility. V. Sahu greatly acknowledges CSIR (Council of Scientific & Industrial Research) for providing SRF.
Introduction The chemical pesticide formulations employed to agricultural land very often contaminate aquatic habitat which in turn causes detrimental effects to the aquatic biota particularly to the economically important non-target organisms i.e. fishes [1].