Fluorescence Characteristics Of Rhodamine Dyes In Solution Under Different Temperature And Pressure Conditions

Various optical or spectroscopic diagnostic techniques have been developed to observe the mechanical and thermal parameters of material in real-time under high temperature and high pressure conditions caused by shock compression.These techniques have the advantages of high detection sensitivity,non-contact measurement,and real-time synchronous control,etc.The fluorescence spectra of some fluorescent dyes are related to temperature and pressure,and the emission lifetime is very short.Therefor such material can be used as probe of the temperature and pressure parameters,so as to simultaneously observe the temperature and pressure parameters and their time developed behaviors under shock conditions.Rhodamine dyes are ideal probe molecules that meet these requirements.Two typical rhodamine dyes rhodamine B(RhB)and rhodamine 6G(R6G)were used in this work.The steady-state and nanosecond time-resolved fluorescence dynamics of the rhodamine dyes were observed in solution environment under different temperature and pressure conditions.The coupling mechanism of temperature and pressure were analyzed from the spectral characteristics.This work provides a more comprehensive basis for the use of rhodamine as temperature and pressure probes in the material under impact compression.Firstly,the sample concentration was determined to be 1× 10-4 mol / L based on F(?)rster fluorescence resonance energy transfer theory.The absorption and fluorescence spectra of R6 G dissolved in different solvents were collected to resolve the solvent effects.The relationship between the spectroscopic parameters such as the peak position and lifetime and the solvent polarizability were analyzed.It was found that the peak positions of the absorption and fluorescence spectra of R6 G are linearly dependent on the solvent polarizabilities,and is not immediately related with solvent polarity.The absorption and fluorescence peak positions were mainly determined by the polarization of solvent.Then,the temperature effects on the fluorescence spectra were analyzed.The fluorescence loses intensity and blue shifts with the rising temperature and the blue shifts are linearly related with temperature.For R6 G,the fluorescence lifetimes is insensitive with the rising temperature.But for RhB,the fluorescence lifetime reduce monotonically with the rising temperature,and the lifetime varieties are much obviously than R6 G.This is because the RhB molecular structure of the diethylamine in the high temperature of the rotation caused by intense excitation of the rapid quenching of electrons,and thus shorter life expectancy more significant.The pressure effects on the fluorescence spectra were then analyzed.The fluorescence peak positions in the ethanol and benzyl alcohol red shift with the rising pressure.However,in ethylene glycol solvent,the fluorescence peak of R6 G and RhB red shift before phase transition(~0.8 Gpa),and then blue shift at higher pressure.This result suggests that the phase of solvent have significant effects on the emission properties of rhodamine dyes.The lifetime of RhB in glycol and benzyl alcohol remain almost constant,while in ethanol it increase significantly with the rising pressure.This is due to the differences in solvent viscosities.Finally,the temperature and pressure coupling effects on rhodamine fluorescence spectra were observed and analyzed.The observed fluorescence parameters under different temperature and pressure conditions were simulated based on previous data and a linearly coupling mode.In this mode,the corporate effects of temperature and pressure are assumed to be the linear combination of the temperature and pressure effects alone.This provides quite import information for exploring the coupling mechanism of temperature and pressure on fluorescence spectra of rhodamine probes.