Langmuir-Schaefer Film Investigation and Density Functional Theory Band Gap Calculations of Calix[n]arene-Para-Aminobenzoic Acid for Drug Nanosensor Application

Calix[n]arenes was utilized to detect PABA, the primary sunscreen component. This study investigates the interaction of calix[4]arene (C4), calix[6]arene (C6), and PABA using the Langmuir method and first-principle density functional theory (DFT). Using the Langmuir-Schaefer (LS) technique, an ultrathin film composed of calix[n]arenes and their complexes with PABA was deposited on various substrates. Based on the Langmuir study, the PABA molecule was bonded to the lower rims of both C4 and C6 with the host-guest ratio of 1:1. All of the LS films formed were then characterized by ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared spectroscopy (FTIR) and carbon, hydrogen, nitrogen, sulfur elemental analyzer (CHNS). The band gap reduction obtained in the DFT study denotes the charge transfer interaction with promising reactivity between the calix[n]arenes and PABA. The sensing of PABA by C4 and C6 is successful based on the formation of bonding between them due to the hosts' effective trapping capacity. The outcomes of this study could be applied to drug delivery systems for future pharmaceutical and medical applications.