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[Display omitted] • First time, femtosecond Bessel beam-induced novel, trimetallic, LIPSS have been fabricated. • We have achieved Ag-Au-Cu alloyed, ladder-like LIPSS with ∼540 nm periodicity. • Exotic topographical contrast found between fs Gaussian and Bessel beam structured surfaces. • The plasmonic nanostructures demonstrated outstanding excellence in SERS-based sensing. • Real-time explosive traces, Tetryl and PETN, have been detected with excellent reproducibility. Laser-induced periodic surface structures (LIPSS) have emerged as a potential branch of nanophotonics, offering unparalleled applications in numerous other research fields such as on-chip microelectronics, hydrogen evolution, solar-energy conversion, photodetectors, photocatalysis, and sensing. In this study, for the first time, we have created novel, Ag-Au-Cu alloyed trimetallic, ladder-like LIPSS nanostructures engaging an axicon-generated femtosecond Bessel beam. The LIPSS formation mechanism through modulation of ablation fluence profile, involving interference of photon-induced surface plasmon polariton with incident beam, has been meticulously divulged. The overlapping feature of Bessel beam profiles has been considered to improve the coupling of electromagnetic modes with the pre-patterned surfaces. The period (Λ) of the fabricated low spatial frequency LIPSS has been estimated to be 540 ± 12 nm. Also, as a comparative study, the distinct topographical features of nanostructures generated under a Gaussian beam with an identical fluence has also been presented. Additionally, these trimetallic plasmonic nanostructures have demonstrated outstanding excellence as active surface-enhanced Raman scattering substrates for sensing applications. Traces (200 nM) of real-time explosives such as Tetryl and pentaerythritol tetranitrate (PETN) have been detected, while achieving enhancement factors in the range of 105, making these viable for practical applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Simultaneous fabrication of GaAs nanoparticles (NPs) and nanostructures (NSs) in a single run experiment (i.e., using picosecond pulsed laser ablation in three different liquids such as distilled water, ethanol, and polyvinyl alcohol). • Non-linear optical properties are analysed and a clear two photon absorption is noticed for GaAs NPs in the colloidal form. • Multifunctional applications are verified for the GaAs NSs formed. • All the produced GaAs NSs have antireflective nature, hydrophobic nature (For GaAs NSs produced in DW, ethanol) and hydrophilic nature (For GaAs NSs produced in Polyvinyl alcohol). • These structures upon coating with a thin layer of gold acts as SERS substrates for detecting a pesticide (Thiram) and a dye molecule (Malachite Green) with excellent reproducibility and reusability. GaAs based nanomaterials have attracted significant attention owing to their applications in electronic, photonic, and sensing devices. In the present communication, we report on the simultaneous fabrication of GaAs nanoparticles (NPs) and nanostructures (NSs) in a single experiment achieved using picosecond pulsed laser ablation in liquids along with the demonstration of their versatile multifunctional applications. GaAs substrates are ablated in three different liquids of distilled water (DW), ethanol, and polyvinyl alcohol (PVA). The morphology and compositions of the synthesized NPs and NSs are analysed using various characterization techniques. Optical and nonlinear optical (NLO) studies are carried out for these NPs in the colloidal form which demonstrated the presence of two-photon absorption. Further, the ablated GaAs substrates exhibited quasi-periodic surface structures with wide angle anti-reflection property and hydrophobic nature. These NSs with a thin layer of gold acted as surface-enhanced Raman scattering (SERS) substrates for detecting trace level hazardous materials such as thiram (a pesticide molecule) and malachite green (a dye molecule). Furthermore, these NSs provided superior Raman enhancements with excellent reproducibility and reusability thereby evidencing their versatility. Collectively, this work reveals quite a few possible multifunctional applications of the laser ablation products of GaAs (NPs and NSs). [ABSTRACT FROM AUTHOR]

• Periodic/ripple‐like structures on Nickel fabricated using fs ablation in DW. • 3D-like (groove) features Ni substrates were obtained in acetone. • Ni periodic/3D-like structures were gold plated using thermal evaporation. • SERS studies performed on MG and NB using these structures. • Detection sensitives of 500 pM for MG and 5 nM for NB achieved. 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 platforms 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. [ABSTRACT FROM AUTHOR]