Fabrication of nanocages on nickel using femtosecond laser ablation and trace level detection of malachite green and Nile blue dyes using surface enhanced Raman spectroscopic technique

Over the last decade several research groups have accomplished the fabrication of 2D periodic and 3D nanocage like structures on different materials using diverse lithographic approaches. Herein, we present the detailed studies on the fabrication of femtosecond (fs) laser-induced periodic/ripple-like surface structures on nickel (Ni) substrate in distilled water whereas 3D-like (nanocages) features on Ni substrates in acetone by tailoring the laser processing parameters (pulse energy). The morphological studies of simultaneously obtained Ni nanoparticles (NPs)/nanostructures (NSs) in distilled water/acetone were meticulously studied using transmission electron microscope (TEM) and field emission scanning electron microscope (FESEM). The fabricated Ni periodic/3D-like structures were gold (Au) plated using thermal evaporation technique and subsequently utilized as surface enhanced Raman scattering (SERS) active sensors for detecting the traces of various analyte molecules such as malachite green (MG) and Nile blue (NB). The grooved Ni-Au substrates allowed us to detect extremely low concentrations of MG (500 pM) and NB (5 nM) and, significantly, utilizing a simple, portable Raman spectrometer. Moreover, the substrates have demonstrated superior reproducibility as well as multi-utility nature with a relative standard deviation (RSD) of < 17%. Additionally, Au-coated Ni grooved SERS substrates have demonstrated superior sensitivity and reproducibility in comparison to commercially available Ag-based SERS sensors (SERSitive, Poland). The proposed method of fabricating ripple and nanocages of Ni SERS plat forms are highly viable to overcome the cost and one-time usage of substrates for on-site detection of several analyte molecules using a portable/hand-held Raman spectrometer.