Ratiometric probing
of analytes presents a substantial advancement
in molecular recognition, offering self-calibrating signals that enhance
the measurement accuracy and reliability. We present a dual-emitting
probe based on (6,5) chirality-enriched single-walled carbon nanotubes
(SWCNTs) with oxygen defects for cholesterol (Chol) detection using
ratiometric fluorescence readouts. The interaction with Chol induced
significant intensity variations in the E
11 and E
11
* emission peaks of oxygen defect-induced SWCNTs,
giving rise to ratiometric fluorescence changes. The sensitivity of
these probes toward Chol in water and serum was 0.28 ± 0.01
and 0.72 ± 0.05 μM, respectively, which is comparable to
that of common gold standards for cholesterol detection used in clinical
samples. By utilizing ratiometric readouts, our approach enhanced
selectivity over numerous competing analytes, including amino acids,
sugars, cations, anions, proteins, steroid hormones, surfactants,
and phospholipids. Mechanistic investigations revealed that Chol detection
by defect-integrated SWCNTs was facilitated by Chol incorporation
within micelles formed by sodium cholate, the surfactant dispersant
used for the SWCNT suspension. Oxygen defects played a crucial role
by directly interacting with Chol. This strategy employing defect-integrated
dual-peak NIR-emitting SWCNTs as sensors for Chol in aqueous and serum
environments not only enables background-free detection of biologically
relevant analytes but also advances biosensing using SWCNTs through
tailored surface functionalization and advanced read-out concepts.