Samples F max (nm) Lifetime (ns) P max (nm) Lifetime (ms) ef The guest/host ratio and its influences on enantioselectivity were then investigated. The PL spectra were presented in Figure and Figure : when the host and the guest possess the same chirality (i.e., R@R or S@S), dramatically stronger RTP in the wavelength range of 600-720 nm emerges compared to samples of different chiralities (S@R or R@S), resulting in ef typically > 10. The ef value of a guest-host doping of 0.1% is found to be < 3 because of intense guest fluorescence extending to the red region and elevating the baseline. On the other hand, S@R (or R@S) also exhibits appreciable RTP intensity when doped at high concentrations (> 100 ppm), possibly from guest aggregates formation or contribution from the enantiomeric impurity limited by current instrument detections. The highest ef is obtained in a doping ratio range of 1 to 100 ppm (e.g., ef > 55 for the 10-ppm sample), which is consistent with the DE spectra (Figure ). Furthermore, the DE spectra present higher ef values (from 24.5 to 155.3 when guest/host ratio 1 ppm-100 ppm) than steady-state PL via eliminating short-lived luminescence interference (e.g., guest fluorescence and host phosphorescence), showcasing the prominent advantage from RTP chiral recognition. We found that the guest doping concentration of 1 ppm is sufficient for an highly enantioselective RTP enhancement of 24.5-32.0 folds, while many chiral recognition methods such as enantioselective fluorescence enhancement demands that the enantiomer analyte be at least in equal proportion or dozens of times in excess to the chiral selector With its high sensitivity, the guest-host RTP recognition method could be applied to ultratrace chiral analysis. Notably, samples with an identical chirality (S@S or R@R) present excitation-dependent PL emission (Figure Specially, in the 350-380 nm range, the P/F ratio decreases as the guest absorbance increases (Figure ). To test the chiral differentiation potential of the system, by using S-4FMNNI-doped R-4FBrBI (w/w 0.01%) as an example, the RTP spectroscopic changes with R-4FMNNI at varying enantiomeric composition were recorded, where S+0%R, S+1%R, S+5%R and S+10%R represent that the ee values, ([S]-[R])/([S]+[R]), of the partially racemic guest analyte 4FMNNI compounds are 100%, 98.02%, 90.48% and 81.82%, respectively (Figure and Figure ). As can be observed, the RTP intensity is enhanced with a higher R-guest proportion. Remarkably, there is a measurable RTP improvement (2-3 by tuning the excitation wavelength) between ee values of 100% and 98%, implying the successful distinguishability for an enantiomer (R-4FMNNI in this case) lower than 1% from the racemate with the current RTP chiral recognition method. i.e., the method can be used to resolve the enantiomeric composition and an enantiomer impurity with ee > 98%. Finally, the guest-host RTP chiral recognition method was extended to a different amino compound. Chiral amino alcohols have been extensively used in medicine, racemate resolution and asymmetric synthesis. Enantioselective recognition of amino alcohols has thus attracted significant research attention in recent years. Here we show that the same RTP chiral recognition method could be applied to a chiral amino alcohol, using 2-phenylglycinol (Pg) as an example. Following the same protocol, four chiral derivatives (Figure , R-PgMNNI and S-PgMNNI as guest molecules) and two racemate (Figure , Figure -S67) were synthesized and characterized. When doped at a concentration of 100 ppm, PL spectra (Figure and Figure and S28) reveal that the host-guest system with the same chirality (R@R and S@S) exhibits more pronounced RTP enhancement over S@R or R@S, where even the naked eye can readily discriminate the enantioselective luminescence under UV excitation, since S@R (or R@S) shows cyan emission while the other two are either orange or pink (photos in Figure ). The DE spectra (Figure ) also register an RTP enantioselective enhancement > 10 folds (IRR/ISR = 11.5 and ISS/IRS = 12.7) with a longer lifetime (Figure , 63.25 ms for S@S, 63.36 ms for R@R, Table ). The excitation dependent PL (Figure -28) and DE spectra (Figure ) are analogous to the amino fluorobenzyl compound, suggesting that a similar photophysical process may be involved for the chiral sensing scheme for both amino fluorobenzyl and amino alcohol compounds. In summary, we have successfully demonstrated a photoluminescence chiral recognition method by taking advantage of the more sensitive guest-host room-temperature phosphorescence (RTP). We show that by chemically modifying chiral amino compounds into phthalimide selector hosts and naphthalimide analyte guest, an RTP intensity difference of up to 196 folds can be obtained. In combination with fluorescence emission, the dramatic chirality-dependent RTP alters the emission color under UV light, making it easily recognized by the naked eye. To show its application potential, ultratrace analyses were also performed and the method was able to resolve enantiomeric impurity in a partial racemate with an ee value > 98%. Although the method is not yet general, it nevertheless gives one of the best performances in optical chiral recognition so far, and paves way for more generalized, energy-transferbased guest-host chiral recognition methodologies. The future reports will be focused on detailed mechanistic study for the amplified chirality-dependent RTP, as well as extension to other chemical modification methods for other chiral molecules.