Synthesis and Characterization of Double Core-shell Au@Ag@Au Nanoparticles by Pulsed Laser Ablation in Liquid and Analysis of Their Antibacterial Properties

Our research involved the synthesis of a double core-shell structure using gold and silver NPs. The core material used was gold. The initial shell had a silver coating, while the subsequent shell was encased in gold. The wavelength of the laser was 1046 nm and was employed, along with 250 pulses at a frequency of 1 Hz, delivering an energy of 500 mJ into 5 ml of deionized water; the focal length of the lens was 12 cm. A comparison was made between the double core-shell construction consisting of individual silver (Ag) and gold (Au) nanoparticles and the single core-shell structure. Various tests were conducted on the samples, including XRD, TEM, UV-visible, FTIR, and zeta potential, to analyze their characteristics. Additionally, the energy gap was determined for each sample. Next, the study examined the impact of particles with a double core-shell and single particles on S. aureus and E. coli bacteria. The findings revealed that a double coating exhibited exceptional effectiveness in eliminating bacterial cells when compared to single particles and a single core-shell. This was demonstrated through the implementation of a zone of inhibition and antibiofilm activity. They were able to verify the existence of the two metal substances (Au and Ag) in each and every sample by using X-ray diffraction (XRD). TEM images clearly depict the formation of the core-shell system. Also presented were TEM images of colloidal particles made of gold and silver, which were smaller than 10 nm in size. The formation of certain nanoparticles resulted in a shift in the peak wavelength, confirming the occurrence of a superficial overlap. The energy transition was calculated using the Tauc relation, with specific values for the different nanoparticles involved. Based on the zeta potential, it is observed that the stability of Ag NPs is greater than that of Au NPs. Additionally, the core double-shell structure formed is found to be less stable compared to the individual Au NPs and Ag NPs. During the ICP-MS analysis, it was observed that the amount of the double shells reduced in comparison to both the individual shell and the individual gold and silver particles. The particles were linked to each other to produce the shells. The current study suggested the potential role of Au@Ag@Au NPs for antibacterial applications in the future.