Synthesis Of Novel Fluorescent Carbon Dots And Their Application In Detection Of Ag(?),Glutathione,Isoniazid And Uric Acid

The carbon dots are a new type of nanomaterial with a size of less than 10 nm.In recent years,more and more researchers have studied carbon dots because of their advantages of biocompatibility,cell optical properties,water solubility,stability,low toxicity,simple preparation,and low cost.Up to now,carbon dots have been used in pH measurement,cation measurement,anion and molecular measurement.This paper proposes the synthesis of three new carbon dots and their application in the detection of silver ions in tap water,glutathione in blood,isoniazid in drugs and uric acid in body fluids.1.Powder carbonization to synthesize novel carbon dots derived from uric acid for the detection of Ag?I?and glutathioneSilver atoms lose an electron to form silver ions?Ag⁺?.Silver ions have the function of sterilization and disinfection,which are widely used in the fields of water purification,daily necessities and medicine.Silver ions have bioaccumulative in the environment and in the human body.The concentration of silver ions exceeds a certain value,which is not conducive to the environmental sustainability and people's health.Therefore,the detection of the content of silver ions is very necessary.In addition,glutathione?GSH?is formed by the condensation of glutamic acid,glycine and cysteine.Glutathione plays a regulatory role in the immune system and has an antioxidant effect.Glutathione can be found in all animal and plant cells.In animals and plants,abnormal levels of glutathione can reflect some adverse symptoms.Therefore,the detection of glutathione content in organisms is very meaningful.This section described a new step of uric acid powder pyrolysis synthesis of new carbon dots?UCDs?.The carbon dots had a maximum excitation wavelength at 350 nm and an emission wavelength at 402nm.Its fluorescence quantum yield was 52.06%.After the silver ions were added to the carbon dots,the fluorescence of the system was quenched.The fluorescence intensity of the carbon dots had a linear relationship with Ag⁺concentrations(0.1².0mmol L^-1),and the detection limit was 39 nmol L^-1.After adding glutathione,the fluorescence of the UCDS-Ag⁺system could be restored.The degree of fluorescence quenching of the carbon dots had a good linear relationship with the concentration of isoniazid(4mmol L^-19mmol L^-1),and the detection limit was 66 nmol L^-1.Based on these phenomena,we proposed a novel fluorescence method for the detection of Ag⁺and glutathione.In addition,the method was applied to the detection of Ag⁺in mineral water and the detection of glutathione in serum.The recoveries of spiked samples were 98.7%¹05.5%and 97.4%¹02.5%,respectively.The results were satisfactory.2.Pyrolysis synthesis of excitation-independent emission carbon dots and its application to isoniazid detectionIsoniazid?4-picolinyl hydrazide,remi?belongs to the hydrazide of isonicotinic acid.Isoniazid can treat tuberculosis because it kills or inhibits tuberculosis.Although isoniazid has the efficacy of treating tuberculosis,it has certain side effects in terms of its therapeutic safety.Therefore,the detection of isoniazid content is very necessary.This section presented a new type of fluorescent carbon dots?FCDs?that were processed by a one-step solid pyrolysis folic acid method.The carbon dots were uniform in size distribution and had the characteristic of exciting independent emission.The fluorescence quantum yield of this carbon dots was 39.09%.Without modification of the other functional groups,the carbon dots were directly applied to the detection of isoniazid content by the fluorescence quenching strategy.The reaction mechanism was a synergistic effect of the internal filtration effect and the static quenching effect.The isoniazid concentration was in the range of 4.0¹40mmol L^-1,and the fluorescence of the carbon dots was gradually quenched.Therefore,a method for detecting isoniazid by carbon dots had been proposed.The method was applied to the detection of isoniazid in isoniazid tablets.The average spike recoveries were 98.12%¹02.67%,and the results were satisfactory.3.Determination of uric acid by fluorescence quenching method based on carbon dotsUric acid?7,9-dihydro-2,6,8?3H?trione-1H-indole?is the ultimate metabolite of hydrazine.The uric acid content value below or above a certain range is detrimental to human health.Therefore,we urgently need to find a sensitive and fast sensor to detect the content of uric acid.In this section,the high performance fluorescent carbon dots were synthesized with maleic acid,tris and benzoic acid as raw materials by one-step hydrothermal method.The obtained carbon dots were evenly distributed in size and emitted strong blue fluorescence,which the maximum excitation and emission wavelength were located at 250 nm and 415 nm,respectively.Under the conditions of the optimized experiment,the fluorescence quenching degree of the carbon dots showed a good linear relationship with the uric acid concentration(5mmol L^-170mmol L^-1),and the detection limit was 2.20mmol L^-1.The reaction principle of carbon dots and uric acid was the synergistic effect of fluorescence internal filtration effect and static quenching.The fluorescence internal filter effect sensing system was constructed by using uric acid as the absorbable material and carbon dots as the luminophore.Hence,a fluorescent sensing platform for the determination of uric acid was founded and confirmed in human fluids.The method was applied to the detection of uric acid in serum samples and urine samples.The recoveries were 91.10%¹03.9%and96.77%¹03.44%,respectively,and the results were satisfactory.