“…Zinc phthalocyanines (Zn Pcs), an important category of porphyrin dyes, exhibit unique optical, magnetic, and electronic properties that make them good candidates for a broad range of applications. − Such a wide applicability originates from some intrinsic properties, especially a strong and intense absorption in the red region (600–800 nm) resulting from a largely extended π-conjugated ring, high and long-lived fluorescence, high thermal and chemical stability, and long exciton lifetime. Nevertheless, Zn Pcs show a tendency to aggregate in aqueous media due to hydrophobic interactions, which are largely affected by their substitution pattern, leading to optical properties that are largely structure-dependent. − The aggregation strongly affects the photophysical and photochemical properties of Zn Pcs, resulting in broadening, shift, and loss of peak height intensity of the Q-band (>500 nm) in the absorption spectrum (also featuring a higher energy, Soret band), quenching in fluorescence intensity, loss of catalytic activity, and shortening of their triplet state lifetime. − …”