The second near-infrared region of the electromagnetic spectrum (1,000 – 1,700 nanometers) offers significant advantages in medical science. Unlike shorter wavelengths, light in this range penetrates biological tissue more deeply and with less scattering. This transparency makes NIR-II ideal for medical imaging and therapies, including photoacoustic imaging. In this technique, light-induced heat generates ultrasonic waves that can either reveal detailed images or deliver targeted cancer treatments.
However, the effectiveness of such techniques relies on contrast agents capable of absorbing light in the NIR-II range while remaining stable under exposure. Most existing agents are optimized for the first near-IR range (700 – 1,000 nanometers), which limits their efficiency for deep tissue applications.