Several laser dyes were evaluated as quantum counters for obtaining corrected fluorescence spectra in the near infrared regions. Preliminary results indicate that hexamethylindotricarbocyanine (HITC) and LDS-798 (Exciton Chemical Co., Overlook, OH) both have quantum yields that are independent of wavelength and can extend the limits of spectral correction to 800 and 700 nm, respectively. A binary quantum counter containing a mixture of Rhodamine B (RhB) and HITC was also evaluated. The quantum yields of HITC and LDS-798 were estimated to be 0.28 and 0.14, respectively, compared to a value of 0.95 attributed to RhB. Examples of corrected spectra obtained using LDS-798 and HITC are compared with absorbance spectra and other accepted standards. Preliminary stability tests are discussed and further studies suggested.
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