Advances in synthesis and application of near-infrared absorbing squaraine dyes

Due to the specially rigid, planar and zwitterionic structures, squaraine dyes have strong absorption (ε ≥ 105 L mol−1 cm−1) in the visible to near-infrared region. Therefore, squaraine dyes have been extensively investigated from both fundamental and technological viewpoints. To present the readers a better understanding of the important dyes, in this article, we will highlight the recent synthetic developments of squaraine derivatives as a class of functional near infrared absorbing optic materials and their application in the areas of anti-aggregation, sensor, solar cell, nonlinear optics and self-assembly functional materials based on our own work during the recent years.