Conjugate of biotin-modified dimer and phthalocyanine dye

A conjugate of a compound represented by the following formula (1) or a salt thereof and a phthalocyanine dye:

• wherein:
• X1a, X1b, X2a and X2b each independently represent O or NH,
• Y1 and Y2 each independently represent C or S,
• Z1 and Z2 each independently represent O, S or NH,
• V1 and V2 each independently represent S or S+—O−,
• n1 and n2 each independently represent an integer of 0 or 1,
• L1 and L2 each independently represent a divalent linking group,
• L3 represents a group comprising a functional group capable of binding to a phthalocyanine dye at the terminus, and
• L4 represents a trivalent linking group.