to distinguish propanol isomers such as Lucas test, silver mirror reaction, nuclear magnetic resonance, and Fourier transformed infrared spectrophotometer are usually complex and costly. [11][12][13][14][15] More importantly, these methods can only qualitatively distinguish two isomer solutions, but not quantitatively give out the proportions of propanol isomers components. Owing to their extremely similar physical and chemical properties, the efficient methods to distinguish propanol isomers remain scarce, let alone the quantitatively detection of n-propanol in isopropanol solvent. [16][17][18] Fluorescence-based sensors exhibit promising potential in biology, pharmacology, and environmental fields due to their low-cost, excellent selectivity and sensitivity, quick detection, and low detection limits. [19][20][21][22][23][24][25][26][27][28][29][30][31] Unfortunately, there are currently no fluorescent probes reported to detect propanol solvents, especially for the distinction of propanol isomers. Considering the difference of electron-withdrawing abilities between isopropanol and n-propanol isomers, one of the promising solutions is to design a fluorescent probe that is sensitive to them due to the change of excited state characteristic.Recently, Ma and Yang reported a series of hybridized local and charge-transfer (HLCT) materials. [32][33][34][35][36][37][38][39][40][41][42][43] These novel HLCT emitters simultaneously exhibited the locally-excited (LE) state character and the charge-transfer (CT) state character, guaranteeing both high photoluminescence quantum yields (PLQYs) and stimuli-responsive functionalization. Among them, the non-equivalent hybridization emitter is easy to de-hybridize by external stimulation because of the unbalanced LE and CT components, and thus to exhibit sensing properties with changes in color and emission intensity. [44][45][46][47] It means that the highly efficient fluorescent probe can be expected to achieve through the excited state regulation. [48] What is more, the fluorescence decay of HLCT emitter associates with fast nanosecond process, guaranteeing a high sensitivity and a shortened response time.In this work, we reported a novel fluorescence probe of 4-(acridin-9-yl)-N,N-diphenylaniline (TPA-9AC) to detect propanol isomers with high sensitivity. Theoretical calculations combined with photophysical experiments show that TPA-9AC exhibits non-equivalent hybridization features and high PLQYs.Isopropanol has been widely applied in various fields as an important chemical solvent, which is produced by direct hydration of propylene accompanied with the byproduct of n-propanol. Herein, an ultra-sensitive fluorescent probe of TPA-9AC, based on a non-equivalent hybridized local and charge-transfer (HLCT) material, is designed and synthesized to quantitatively detect the percentage of n-propanol in propanol isomers. Owing to the stronger electron acceptor ability of n-propanol, the excited state of probe transfers from highly emissive HLCT state to non-emissive charge-transfer s...