Synthesis of Platinum Nanoparticles by Pulsed Laser Ablation with an Excimer KrF Laser in Deep Eutectic Solvents

This work reports for the first time the fabrication of metallic nanoparticles from platinum material (Pt-NPs) implying pulsed laser ablation in choline chloride-ethylene glycol deep eutectic solvent (DES) as well as in their mixtures with ethanol in a 1:3 ratio as liquid media. KrF excimer laser (lambda = 248 nm) has been used as an irradiation source. The Pt target is placed in a Teflon pad on the bottom of a beaker and immersed in the corresponding liquid. The created Pt-NPs by pulsed laser ablation are dispersed in the surrounding medium, forming a colloid with it, and are characterized by the detailed methods described. A synergistic effect is achieved by combining the nontoxicity of the liquid and the biocompatibility of the Pt-NPs for the fabrication of very small, nonaggregated NPs, applicable, also, in the medical field. The peculiarities of the liquid do not allow the production parameters to be varied in wide ranges. The investigation of the Pt-NPs' optical characteristics by UV/vis spectroscopy showed the existence of three bands. The origins of two of the bands are presumably due to interband transition and plasmonic absorption, respectively. The origin of the third band needs further in-depth investigation. The morphological properties were studied through high-resolution scanning transmission electron microscopy (HR-STEM). The minimum value of the mean size of 2.2 nm is achieved at 7 Hz RR and 40 min ablation time when the pure mixture of choline chloride-ethylene glycol, denoted as ILEG, is used. In support, the obtained Pt-NPs were analyzed by direct analysis in real time mass spectrometry (DART-MS) to demonstrate their existence in the colloidal solution. The face-centered cubic (FCC) phase for the Pt-NPs with the predominant orientation of the (220) crystalline plane was determined by X-ray diffraction (XRD). FTIR and Raman spectroscopy measurements did not show the existence of additional bonds between pure ILEG and Pt-NPs. One application of the synthesized NPs was illustrated by the increased sensitivity of detecting methylene blue through the surface-enhanced Raman spectroscopy (SERS) method.