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Several strategies have been effectively tested in the past to improve the Laser Induced Breakdown Spectroscopy (LIBS) signal for the analysis of liquid samples, involving peculiar experimental configurations, such as Double Pulse LIBS (DP-LIBS). Recently, sample treatment has proven to be a viable and simple way to enhance the performances of LIBS towards the analysis of solutions. Among the various strategies, the most promising and versatile appears to be Thin Film Microextraction (TFME) using carbon-based adsorbents. Another sample pre-treatment procedure, Nanoparticle-Enhanced LIBS (NELIBS), has gained significant interest due to its relative simplicity and effectiveness. This methodology uses a deposition of silver nanoparticles (AgNPs) on the sample to greatly increase the emission of the LIBS plasma. In this work, we investigate for the first time the possibility of combining TFME and NELIBS. We developed TFME supports by depositing an aqueous graphene nano-sheets (aq-GRA) prepared by Pulsed Laser Ablation in Liquid (PLAL) on a glass substrate. The preparation of the supports was optimized with regards to the substrate nature, deposition method, sorbent volume and drying method. Then, the TFME supports were tested for the extraction of Chromium from aqueous solution at different extraction times and analyte concentration. Subsequently, the TFME supports were treated with a deposition of silver nanoparticles (AgNP) to test the feasibility of the NELIBS approach. We observed an enhancement in the emission lines of Cr when the AgNPs were applied, as well as a lower estimated LOD value when compared to plain graphene TFME supports.

Gallic acid (GA) is one of the most important and present natural phenolic compounds due to its well-known biological properties, and its detection and monitoring is of great importance. Silver nanoparticles (AgNPs) are one of the most studied metallic nanomaterials used in various fields, from biomedical applications to electrochemical sensing devices. In this work, we used the pulsed laser ablation technique in liquid for the one-step preparation of nanoparticles of silver from a pure silver plate base in N,N-dimethylformamide. Obtained nanomaterial was characterized using morphological and electrochemical methods and used for modification of screen-printed carbon electrodes (SPCE). Successful immobilization at the surface is confirmed using the surface profiling method. A newly obtained sensor was used for the detection of GA. After parameters optimization, a differential pulse voltammetric protocol was developed, using two approaches - concentration vs. current (GA determination) and peak area vs. current (estimation of the antioxidant capacity). For the first approach sensor linearity was found to be in the range from 0.50 µM to 10 µM, with the limit of detection (LOD) of 0.16 µM and limit of quantification (LOQ) of 0.50 µM. In the second system operating linear range was the same, while LOD and LOQ were 0.11 µM and 0.34 µM, respectively. Practical application of the method was tested using two approaches: direct measurement of gallic acid in biological fluids and estimation of the antioxidant capacity and food quality purpose.

Suspensions of poly(bisphenol A carbonate) (PBAC) nanoparticles of varying size and shape have been produced by ablation of a PBAC target in liquid media with the fourth harmonic of a Q-switched Nd:YAG laser (wavelength 266 nm, full width at half maximum 4 ns, repetition rate 10 Hz). The polymer target was placed at the bottom of a rotating glass vessel filled with around a 10 mm column of liquid. Laser ablation in water leads to spherical nanoparticles with diameters of several tens of nanometers for fluences close to 1 J/cm. Ablation at lower fluences, around 0.1 J/cm, results in the production of nanoparticles of smaller diameters and also of non-spherical nanoparticles. Additional irradiations at the fluence of 0.1 J/cm were performed in several liquid media with different properties, in terms of density, viscosity, thermal conductivity, boiling temperature, isothermal compressibility and polarity. The different size distributions observed were related to the thermal conductivity of the systems, while their viscosity seems to be responsible for the development of nanostructures with different morphologies.