International Journal of Environmental & Agriculture Research (IJOEAR) ISSN:[2454-1850] [Vol-3, Issue-4, April- 2017] Page | 61 SERS of insecticides and fungicides assisted by Au and Ag nanostructures produced by laser techniques P.A. Atanasov 1 , N.N. Nedyalkov 2 , Ru. Nikov 3 , N. Fukata 4 , W. Jevasuwan 5 , T. Subramani 6 , D. Hirsch 7 , B. Rauschenbach 8 1,2,3 Institute of Electronics, Bulgarian Academy of Sciences, Tzarigradsko chaussee 72, Sofia 1784, Bulgaria 4,5,6 International Center for Materials for NanoArchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044, Japan 7,8 Leibniz Institute of Surface Modification (IOM), Permoserstrasse 15, D-04318 Leipzig, Germany Abstract— This study deals with the use of laser techniques for preparation of advanced Au and Ag nanostructures on SiO 2 (001) substrates to be applied to high-resolution analyses, namely, surface enhanced Raman spectroscopy (SERS) analyses. The optical and morphological properties of the nanostructures are compared with those of the PLD thin films. The activity is tested of the structures fabricated as substrates for SERS covered by small quantities (usually applied in agricultural medicine) of the Aktara 25 BG (thiamethoxam) insecticide and the Dithane DG (mancozeb) fungicide. To the best of our knowledge, Raman spectra of Aktara 25 BG are presented for the first time. The study has a direct bearing on the human health and food quality by way of assisting the detection of small amounts or residue of harmful pollutants. Keywords— laser deposition and annealing, Ag and Au nanostructures, SERS, insecticide Aktara 25 BG, fungicide Dithane DG. I. INTRODUCTION The properties of noble metallic nanostructures (NSs) have been the subject of considerable fundamental and technological interest. Metal nanoparticles (NPs) play an important role in scientific investigation and nanotechnology. As a result of the progress in nanotechnologies during the last two decades, nanosystems find nowadays application in many areas, such as chemistry, optics, biology, agriculture, medicine, microelectronics, etc. [1]. The excitation spectrum of noble metallic sub-wavelength structures is determined by its surface plasmon resonance. The energy of the plasmon resonance depends strongly on the shape and composition of the nanostructures. The tunability of the plasmon resonances of noble metallic NPs can be exploited to position the optical resonances at specific wavelength regions of interest and has led to a wide range of applications. The strong local electro-magnetic field enhancement accompanying the surface plasmon resonances has also been used to manipulate light-matter interactions, so that noble metallic sub- wavelength structures have been widely applied in surface enhanced Raman spectroscopy (SERS) [2,3]. The enhancement of the Raman signal may reach a factor of 10 8 -10 12  the method is thus capable of detecting even a single molecule [2]. The increase of the Raman signal is a result of a local electromagnetic field enhancement in the vicinity of a structured surface due to the excitation of local and surface plasmons. In addition to their fundamental importance, plasmonic nanostructures are receiving a great deal of attention for their potential applications in areas such as sub-wavelength waveguides, optical nanoantennas, photovoltaic technology for efficient light coupling into solar cells, metamaterials, chemical and biological sensing, and biomedical applications [4-7]. Among the physical techniques, laser-based syntheses of nanomaterials have constituted a continuously growing field of research. In particular, pulsed laser ablation of solid targets in different environments, e.g. vacuum, background gas or liquid, has become an attractive method for the generation of NPs and deposition of NPs-assembled materials [8]. Among the successfully applied techniques one can mention the ns-laser deposition of thin metal films and the post-deposition structuring [9-13]. The nanostructuring of thin metal films by excimer laser pulses has been introduced as a technique for production of nanoparticles on different substrates [12,14]. The fragmentation of the metal surface into nanosized droplets during the melting is due to the poor wetting between the substrate and the liquid phase [15]. Moreover, femtosecond laser nanostructuring of silicon-based SERS substrates has also been reported [14,16]. Au and Ag NSs produced by laser methods have been used successfully in SERS analyses. Thus, an enhancement has been observed of the R6G Raman spectrum on Au nanocolumns formed by off-axis pulsed laser deposition (PLD). Concentrations of R6G as low as 1 nМ [3] have been measured and a maximum enhancement higher than 10 5 has been achieved.