Preparation,Low-Powered Upconversion Performance And Application Based On Xanthene Spiro Derivatives With "Turn-on" Luminescence

In this paper,11 kinds of xanthene-based spiro-ring probes(containing rhodamine spiro-derivatives and luciferin spiro-derivatives were synthesized and characterized by Mass spectra and NMR spectra.Under the excitation of visible light,these probes do not emit fluorescence,however,the bright yellow emission were observed only when addition some specific ions into the probe solution,indicating that these probe molecules possess high selectivity.Interestingly,such excellent“turn-on”signal was observed not only in the Stokes fluorescence,but also in the anti-Stokes fluorescence including one-photon hot-band absorption upconversion(OPA-UC)and triplet-triplet annihilation upconversion(TTA-UC)channels.Meanwhile,the sensitivity of these probes was also investigated.The details are as follows:1.Preparation and detection performance of rodamine derivative(Rh-1):Rhodamine B hydrazine was designed as a novel dual-channel ion probe detecting nitrite among anions and mercury ion among cations,which shows fluorescence and OPA-UC fluorescence enhancement responding.This probe in UC channel has ten times wider ions detection range than in fluorescence channel,while the probe in fluorescence channel has a higher sensitivity than it in UC channel.These results demonstrated that different detection ranges and sensitivities could be qualitatively and quantitatively detected.And different level detection ranges and sensitivities can be simultaneously realized by one fluorescent probe through two luminescent channels.One fluorescent probe can own both wide detection range and high sensitivity simultaneously.Therefore,a flexible detection strategy achieving the win-win situation in one probe has been demonstrated to meet the ion detection's demand in real environmental analysis,that is,Stokes fluorescence detection channel can be used when accurate detection results were needed while UC channel was applied when wide detection range of ions were required.2.Preparation and detection performance of rodamine derivatives(Rh-2?Rh-4):Three rhodamine-anthracene derivatives(named as Rh-2?Rh-4)were synthesized by inserting different lengths of diamine alkyl between rhodamine and anthracene groups.By different excitation modes(i.e.,excited anthracene ring,excited rhodamine and excited rhodamine thermal vibration level),the effect of the length of the intramolecular flexible carbon chain on the performance of ion detection was studied.The results showed that Rh-2 showed better selectivity to Hg²⁺,while Rh-3 and Rh-4 showed better selectivity to Fe³⁺.Since Rh-2 probe containing shorter flexible chain,which shows easily binding the soft Hg²⁺,while Rh-3?Rh-4 probes containing longer flexible chain,which is easy to bind the hard Fe³⁺.The results have shown that the selectivity of probe can be tuned by the insertion of different lengths of alkyl groups.3.Preparation and detection performance of luciferin derivatives(Luc-1?Luc-7):Luciferin derivatives(Luc-1?Luc-7)were prepared where Luc-1?Luc-5 containing nitrogen(N)atom,while Lu-6?Lu-7 containing sulfur(S)atom.Thus,the influence of nitrogen and sulfur atoms on the detection performance of the probes was studied.The results showed that the selectivity of the probes can be converted from Cu²⁺to Hg²⁺when the probes containging nitrogen to those containing sulfur.Multi-channel upconversion(UC)probing Hg²⁺based on a new luciferin-based probe Luc-7 was investigated in detailed.This probe with“opening state”was found to exhibit not only one-photon absorption upconversion(OPA-UC)character but also the triplet sensitization and the later can induce annihilator to emit triplet-triplet annihilation upconversion(TTA-UC).By means of the OPA-UC and TTA-UC detection channels,the detection range and the probing limit can achieve at?10^-3 M and 1.45×10^-9 M,respectively.The importance in this study may provide a new idea for investigators who are interested in much higher concentration ion detection or much lower microscale probing via the upconversion approaches.