Abstract
Permethrin, 3-Phenoxybenzyl (1 RS)-cis,trans-3-(2,2-dichlorovinyl)- 2,2-dimethylcyclopropanecarboxylate, has a wide range of applications like insecticide, insect repellent and prevents mosquito-borne diseases, such as dengue fever and malaria in tropical areas. In this work, we develop a prominent monitoring method for the detection of permethrin pesticide using surface-enhanced Raman scattering (SERS) optical fibre substrates. The novel SERS-active optical fibre substrates were grown and deposited silver (Ag) nano-dendrites on the end of multi-mode fibre core by laser-assisted photochemical method. The characteristic of the Ag-nanostructures could be controlled by the experimental conditions, namely, laser illumination time. Ag nanoparticles optical fibre substrates and Ag nano-dendrites optical fibre substrates were prepared with laser illumination time of 3 min and 8 min, respectively. The achieved SERS-activity optical fibre substrates were tested with Rhodamine 6G aqueous solutions. We demonstrate that the SERS activity coupled with Ag nano-dendrites optical fibre substrate has higher Raman enhancement factor due to the creation of many of hot-spots for amplifying Raman signals. Besides, the stability and reproducibility of the Ag nano-dendrites optical fibre substrate were also evaluated with stored time of 1000 hours and relative standard deviation of less than 3%. The Ag nano-dendrite optical fibre substrate was selected for detection of permethrin pesticide in the concentration range of 0.1 ppm–20 ppm with limit of quantification (LOQ) of 0.1 ppm and calculated limit of detection (LOD) of 0.0035 ppm, proving its great potential for direct, rapid detection and monitoring of permethrin.
Highlights
Pesticides are exploited in agricultural production intended for increasing the yield, as well as improving the quality of crops
The components of the silver nanostructure surface-enhanced Raman scattering (SERS) optical fibre substrate were analysed by investigating the Energy dispersive X-ray spectroscopy (EDX) spectrum measured in the marked region of the inset as displayed in Fig. 2(b), in which the sharp peaks as O, Ge www.nature.com/scientificreports and Si corresponding to the components of typical optical fibre with Ge doped into SiO2 substrate and the sharp peak Ag definitively demonstrated Ag nanostructures growth after assisted-laser
The evolution of the growth of silver nanostructures can be clearly observed with different exposure time as demonstrated by SERS spectra shown in Fig. 3(with curves A, B, C) and the scanning electron microscope (SEM) images depicted in Fig. 3(A1, B1, C1 correspond to these curves)
Summary
Pesticides are exploited in agricultural production intended for increasing the yield, as well as improving the quality of crops. The SERS substrates with many hot-spots and uniform distribution of nanostructures on the surface will have a large Raman enhancement and high repetition of measurement. The dendritic Ag nanostructure has been of interest and usually fabricated by electrochemical deposition method to increase high density hot-spots for enhanced SERS activity[22,23]. We propose a novel SERS-active on optical fibre substrates with synthesized silver nano-dendrites structure by a facile and low-cost laser-assisted photochemical method. It is found that the Raman enhancement factor of the Ag nano-dendrites SERS optical fibre substrate was increased. The proposed Ag nano-dendrite optical fibre substrates were applied in detection of permethrin pesticide in the concentration range of 0.1 ppm–20 ppm with LOQ and LOD of 0.1 ppm and 0.0035 ppm, respectively. The goal of this study was to investigate the feasibility of this proposed SERS optical fibre substrate and prove its great potential for chemical and environmental compact optical fibre sensors
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