Precise evaluation of adsorption behavior of cationic porphyrin on monolayer of perovskite-type niobia nanosheet by absorption spectroscopy

To evaluate adsorption behavior of organic dyes on nanosheet surface precisely and reproducibly, we are proposing simple method based on absorption spectroscopy. Typical cationic dye, 5,10,15,20-tetrakis (1-methyl-pyridinium-4-yl) porphyrin (TMPyP), and anionic nanosheet, perovskite-type niobia nanosheet (NNS), were selected as a guest molecule and a host nanosheet, respectively. The lambda(max) of TMPyP was redshifted by an adsorption on the nanosheets. When the relationship between the loading level of TMPyP and absorbance, the clear inflection point was observed at approximately 71% of the amount of TMPyP added to the cation exchange capacity of NNS. A highly linear plots was observed in the absorbance region around this point, indicating that our experimental method can be used to evaluate the adsorption behavior in detail even at very small absorbance in the order of 0.001. The evaluation of the adsorption behavior of dyes on nanosheet monolayers based on absorption spectroscopy is expected to be a universal method to discuss the behavior of dye molecules on solid surfaces in detail.

Automated summary

This study proposes a simple method based on absorption spectroscopy to evaluate the adsorption behavior of organic dyes on nanosheet surfaces. The research found a clear inflection point in absorbance around 71% of the dye's adsorption capacity, with highly linear plots in this region.