Study On The New Methods For Curcumin,Chlorogenic Acid And Thiamine Determination By Spectrofluorimetry

Carbon quantum dots,also called carbon dots?CD_S?,are a novel type of carbon fluorescent nanomaterials.In recent years,duo to its simple and diverse preparation methods,low toxicity,environmental friendly,good water solubility,stability and unique optical properties,it has been widely applied in environmental detection,biosensor and medical sensing.Spectrofluorimetry is an economical and fast analysis method,because of its simple operation,high sensitivity,good selectivity and wide linear range;it is popular used in environmental analysis,drug detection,food safety and biologic imaging.This paper mainly through the fluorescent spectrometry to study the main properties of fluorescent carbon dots prepared by hydrotherma l method,and the fluorescence signal of curcumin and chlorogenic acid with carbon dots.Meanwhile,the interaction between Phen-Zn²⁺and thiamine was also analyzed by fluorescent spectrometry.Thus a new sensitive method for determination of curcumin,chlorogenic acid and thiamine was established,which applied to the determination of real samples with satisfactory results.The detailed results are summarized as follows:1.One-pot synthesis of fluorescent N,S co-doped carbon dots as switch-off sensing for sensitive determination of curcuminIn this approach,fluorescence nitrogen,sulfur co-doped carbon dots?N,S-CDs?were prepared using sodium citrate and thiourea through a simple and efficient one-step hydrothermal treatment.The morphology of synthesized N,S-CDs was characterized by transmission electron microscopy?TEM?,X-ray diffraction?XRD?,fourier transform infrared spectroscopy?FT-IR?,UV-vis absorption spectroscopy and energy dispers spectroscopy?EDS?,the results indicated that the obtained N,S-CDs showed excellent optical properties and own strong blue fluorescence at 440 nm upon excitation at 350nm with a high quantum yield of 26.9%,along with the fluorescence lifetime of ca.5.19ns.Additionally,there were the inner filter effect?IFE?between the as-prepared N,S-CDs and curcumin?CM?,which can effectively quench the fluorescence of N,S-CDs.Furthermore,the remarkable quenching of N,S-CDs positively proportional to the concentration of CM with a linear range of 0.15¹8.0?mol L^-11 and limit of detection as low as 0.04?mol L^-1,which proved as a sensitive switch-off fluorescent sensor for detection of CM,and the manner applied to the detection of CM in urine samples with satisfactory results.2.Synthesis of ultrabright N-doped carbon dots as fluorescent nanosensor for facile and fast determination of chlorogenic acid based on inner filter effectIn the work,a facile and sensitive fluorescence analysis platform for the determination of chlorogenic acid?CA?based on nitrogen-doped carbon dots?N-CDs?with inner filter effect?IFE?mechanism has been reported.In the sensor route,we synthesized the water-soluble N-CDs through one-step hydrothermal process with a high quantum yield and the obtained nanosensor showed excellent optical characteristics.More importantly,the as-fabricated fluorescence N-CDs displayed sensitive quenching response to CA and the present sensing platform was observed with the increasing concentration of CA based on IFE,displaying a good linear region over the range of 1.4¹35.0?mol L^-1 with a detection limit of 0.4?mol L^-1,which gives new insight and facile method on the detection of CA.Furtherfore,the strategy has successfully applied for the detection of CA in real samples.3.Construction of a novel turn-on-off fluorescence sensor used for selective detection of thiamine via its quenching effect on Phen-Zn²⁺complexIn this work,a simple and selective fluorescence sensor approach called“turn-on-off”for the determination of thiamine?TM?has developed.As we know,the o-phenanthroline?Phen?owned the inner fluorescence,when it reacted with zinc ions formed the Phen-Zn²⁺complex the fluorescence intensity was enhanced effectively,while upon addition of TM into that Phen-Zn²⁺solution,the intensity of the system would been gently quenched,which called the“turn-on-off”probe.Notably,the method possessed highly selective,sensitive determination for TM with a detection limit as low as 0.25?mol L^-1,and the recovery fluorescence intensity was proportional to the concentration of TM in the range of 0.84⁸0.0?mol L^-1.Besides,the proposed mechanism was also investigated through exploring the fourier transform infrared?FT-IR?,nuclear magnetic resonance?NMR?spectroscopy and the charge distribution.Furthermore,this method was successfully applied into practical samples for TM detection with satisfactory results.