Supramolecular nanoarchitectonics with TPPS porphyrin as a fluorescent probe for detection of aminoglycoside antibiotics and their photocatalytic applications for the degradation of rhodamine B dye

The meso-tetra(4-sulfonatophenyl)porphyrin (TPPS) porphyrin was successfully synthesized and applied as a selective turn-off sensor for detecting neomycin and gentamicin antibiotics in aqueous media. The sensing ability of TPPS porphyrin was studied by naked-eye detection as well as UV-vis absorption and fluorescence spec-troscopy. The emission intensity of TPPS porphyrin was observed to be decreased dramatically upon addition of neomycin and gentamicin antibiotics. The quantum yield of TPPS porphyrin (56%) which decreases to 2% and 9% upon addition of neomycin and gentamycin, respectively. The quenching efficiency of neomycin and gentamicin towards the TPPS porphyrin was 99.13% and 96% respectively. The detection limit was calculated to be 7.5 x 108 M and 1.1 x 107 M for gentamicin and neomycin respectively, indicating both the antibiotics exhibited efficient quenching abilities. Moreover, the self-assembly of TPPS porphyrin with gentamicin antibiotic have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and FTIR spectros-copy. Interestingly, TPPS porphyrin with 0-10 equiv. of gentamicin, produces nanorod-like structures. The key driving force for the formation of self-assembled nanostructure of TPPS porphyrin with gentamicin is H-bonding between sulfonate group of TPPS and -NH2 and -OH group of gentamicin. The-self-assembled nanostructure exhibited band gap energy in the range of 2.7 to 3 eV. Therefore, these nanostructures were used as a photo -catalyst for degradation of RhB dye. Interestingly, nanostructure obtained from 1:2 equiv. of TPPS: gentamicin showed excellent photocatalytic performance, degraded almost 100% of RhB dye in aqueous media within 240 min. with simulated visible light irradiation with rate constant of 2 x 10-2 min-1. A possible mechanism for the photodegradation of RhB using nanorod like structure is also discussed.