Study On New Methods For Optical Detection Of Ascorbic Acid Based On Carbon Nitride And Cobalt Oxyhydroxide Nanomaterials

Ascorbic acid（AA）,also known as vitamin C,is an essential trace element in many physiological and biochemical processes of the human body.It has strong antioxidant activity,which can reduce oxidative stress and reduce the risk of cancer and cardiovascular diseases.In addition,AA plays an important role in the formation and maintenance of collagen,and is also used to prevent and treat diseases such as cold,mental illness,infertility,cancer and AIDS.Studies have shown that AA plays a vital role in the synthesis of dopamine in human body,and the detection of AA in serum is one of the important ways to diagnose scurvy.Therefore,it is very important to establish a simple,sensitive,rapid and effective analytical method for the detection of AA in pharmaceutical,food and biological research fields.At present,the analytical methods commonly used in the detection of AA,including electrochemical methods,high performance liquid chromatography,fluorescence and colorimetric methods,have been widely applied.Among them,optical biosensing is the most simple,fast and sensitive.In recent years,with the continuous development of nanomaterials,nanomaterials exhibit unique optical properties,which greatly promote the application of optical biosensing in the fields of medical diagnosis,food and drug analysis,environmental monitoring,biological imaging and other fields.Based on the optical properties of carbon nitride and hydroxyl cobalt oxide nanomaterials and the activity of nano analog enzymes,three new optical sensing methods for the detection of ascorbic acid were constructed by optical sensing technology.The specific contents are as follows:1.Chemiluminescence system based on Luminol-H₂O₂-Co OOH nanomaterials for high sensitivity detection of H₂O₂ and AA.Co OOH can catalyze oxidation of Luminol-H₂O₂ system to produce chemiluminescence,showing good stability and catalytic activity.AA can effectively inhibit chemiluminescence.Based on this,a highly efficient and sensitive detection method for H₂O₂ and AA was constructed.Under the optimal conditions,the detection limits of H₂O₂ and AA were 4.53 nmol/L and 9.23 nmol/L respectively,and were successfully applied to the determination of AA in human serum samples.The method has the advantages of simple preparation,high sensitivity and selectivity,and is suitable for environmental,biological and medical fields.2.Based on the activity of CNNSs similar to peroxidase and the ability to catalyze oxidation of 3,3’,5,5’-four methylbiphenyl amine（TMB）-hydrogen peroxide（H₂O₂）,a simple and rapid colorimetric sensing method was used for the sensitive analysis of H₂O₂ and AA.In the presence of H₂O₂,CNNSs catalyzes H₂O₂ to oxidize TMB to produce blue ox TMB,while ultraviolet absorbance increases.Because AA has a certain reducibility.In the presence of AA,H2O2 oxidized TMB was inhibited,resulting in reduced ox TMB production and obvious color changes.Therefore,we constructed a quantitative analysis of H₂O₂ and AA through the change of absorbance value and visual method.Under the optimal conditions,the detection limits of H₂O₂ and AA were 1.02μmol/L and 39.51 nmol/L respectively.This method has been successfully applied to the visual detection of AA level in human serum.The sensor has the advantages of low cost,fast detection speed and good selectivity.3.Fluorescent sensors based on g-C₃N₄-Co OOH nanocomposite materials were developed and used for highly sensitive detection of ascorbic acid（AA）.g-C₃N₄ nanometers are a kind of nanomaterials with high fluorescence quantum yield.Co OOH is deposited on g-C₃N₄nanoscale by one step method,and fluorescence resonance energy transfer（FRET）occurs.The fluorescence of g-C₃N₄ is quenched.In the presence of AA,Co OOH is reduced to Co²⁺and FRET weakens,resulting in the fluorescence recovery of g-C₃N₄ nanosheets.Accordingly,a fluorescence sensing method for g-C₃N₄-Co OOH nanosheets composite was developed.Under the optimum conditions,the detection limit of AA in aqueous solution reaches 0.142μmol/L.g-C₃N₄-Co OOH nanomaterials have low toxicity and good biocompatibility.Therefore,the g-C₃N₄-Co OOH nanoscale sensor can be used for detection and imaging of intracellular AA.The sensor has the characteristics of high sensitivity,good selectivity and fast fluorescence response.It has potential application value in biology and clinical diagnosis.