“…Recently, we have developed a new approach for the investigation of the efficiency of PSs on BLM based on measurements of boundary potentials at the membrane/water interface [17,18]. Using this approach, we have studied sulfonate-substituted aluminum phthalocyanine and 5,10,15,20tetrakis(p-sulfonatophenyl)porphyrin as photosensitizers [18][19][20] and have revealed several problems decreasing the efficiency of PSs, namely, the quenching of SO by phthalocyanines in the membrane [13,20] and weak binding of 5,10,15,20-tetrakis(p-sulfonatophenyl)porphyrin (TPPS4) to the BLM at low pH due to aggregation [19]. In this regard, porphyrins with positively charged peripheral groups seem to be the most promising molecules for PDT [21][22][23][24].…”