Abstract:
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 spectroscopy. 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 percent) which decreases to 2 percent and 9 percent upon addition of neomycin and gentamycin, respectively. The quenching efficiency of neomycin and gentamicin towards the TPPS porphyrin was 99.13 percent and 96 percent respectively. The detection limit was calculated to be 7.5 x 10 sup(8) M and 1.1 x 10 sup(7) 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 spectroscopy. 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 -NH sub(2) 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 photocatalyst for degradation of RhB dye. Interestingly, nanostructure obtained from 1:2 equiv. of TPPS: gentamicin showed excellent photocatalytic performance, degraded almost 100 percent of RhB dye in aqueous media within 240 min. with simulated visible light irradiation with rate constant of 2 x 10 sup(-2) min sup(-1). A possible mechanism for the photodegradation of RhB using nanorod like structure is also discussed.
