The spectral sensitization properties of indolenium squarylium cyanine dyes in silver bromide emulsion

Abstract

The spectral sensitization behaviour of a class of donor acceptor donor (D-A-D) molecules, bis(5-substitucnt-2,3,3,-trimethylindolenium-2-ylidcne) Squaraine (Sqel 8), has been inspected. In silver bromide tabular grain, all the dyes exhibited desensilization. The C-5 subslitucnt affects the desensitization efficiency to a large extent. Especially for the dye with the C-5 nitro group, an unexpectedly high desensitization efficiency is found. The dye aggregation properties in emulsion were determined. The high desensitization efficiency was attributed to an aggregation state, of which the dye-AgBr interaction is the most common. The sensitization mechanism was discussed and attributed to electron transfer.

Key Words:

• Spectral sensitization
• Squaraine
• Desensitization
• Dye
• Aggregation