Detection of Phenylalanine by Iridium Nanoclusters Using Time-Dependent Density Functional Theory Calculations

Metal nanoclusters have several applications in biological processes, medicine, cancer therapy, catalysis, etc. Iridium (Ir) nanoclusters exhibit excellent detection behavior compared to their bulk material. This work includes a deep insight into the interaction of Ir nanoclusters of four atoms (Ir₄) with amino acids and the analysis of Ir-amino acid (Ir-AAc) complexes. UV-visible spectroscopy of the Ir₄ nanocluster, amino acids, and their complexes was discussed as a way to detect amino acids with the help of the Ir₄ nanocluster. In UV-visible analysis, the UV-visible peak of phenylalanine (Phe) appeared at 204 nm with an excitation energy of 6.02 eV with a 0.0516 oscillator strength. Meanwhile, only in the Ir₄ nanocluster-phenylalanine (Ir-Phe) complex, the UV-visible peak was observed at 661 nm with an excitation energy of 1.87 eV and oscillator strength of 0.0051. This peak was observed due to the transition from HOMO-1 to LUMO+3. In the other complexes, no UV-visible peaks are observed. Thus, the results predict that the Ir₄ nanocluster can be used in the detection of Phe via UV-visible spectra.