Preparation Of Two Kinds Of Carbon Dots And Their Application In The Detection Of Heavy Metal Ions(Fe³⁺/Hg²⁺) And Veterinary Drug（Crystalline Violet） In Breeding Industry

Veterinary drug residues have always been a common concern worldwide,it is crucial to develop rapid and sensitive detection methods for the detection of heavy metals and veterinary drug residues in animal husbandry.Carbon dots（CDs）,as a new type of zero-dimensional nanomaterial,has been widely studied and applied in the field of fluorescence sensing because of its excellent optical properties,low cost,easy preparation and environmental protection.In this study,two kinds of doped fluorescent CDs（N-doped CDs and N,P-doped CDs）were synthesized separately by one-step hydrothermal method,and their morphological structures and optical properties were firstly investigated.Subsequently,the two kinds of CDs were applied to detect Fe³⁺/Hg²⁺and crystal violet（CV）in animal husbandry,respectively.The studies are as follows:Through a one-pot hydrothermal method,blue fluorescent Blood-CDs were synthesized using the mixture of chicken blood and trisodium citrate as raw material,then,the morphological structure and optical properties of Blood-CDs were investigated.Three N,P-doped carbon dots（A-CDs,N-CDs,and B-CDs）were prepared from a mixture of o-phenylenediamine and phosphate by adjusting the reaction environment to acidic,neutral,and basic with phosphoric acid and sodium hydroxide solutions,respectively.Subsequently,A preliminary comparison of their properties was made to explore the influence of acid-base reaction conditions on the synthetic products,and the optimal performance（A-CDs synthesized under acidic conditions）was selected for further exploration and development.The synthesized N-doped CDs（Blood-CDs）were developed as a fluorescent probe for the detection of Fe³⁺and Hg²⁺.The probe showed excellent selectivity and sensitivity towards Fe³⁺and Hg²⁺with a“on-off”fluorescence response.The probe exhibited a linear ranges for the determination of Fe³⁺（0-100μM）and Hg²⁺（0-120μM）with the detection limits of 0.23μM for Fe³⁺and 0.17μM for Hg²⁺,respectively.Moreover,it was found that F^-could recover the fluorescence quenching by Fe³⁺,and Al³⁺could recover the fluorescence quenching by Hg²⁺,showing an“off-on”fluorescence response.Therefore,Blood-CDs can be developed as an“on-off-on”dual-channel fluorescent probe for the detection and discrimination of Fe³⁺and Hg²⁺.The fluorescent probe was used for detecting Fe³⁺and Hg²⁺in swine feed and swine farm wastewater samples with good recovery result.The synthetic N,P-doped CDs（A-CDs）was developed as fluorescence probe to detect CV,which can complete CV detection in 0.5 min with a detection limit of 32 n M.Further exploration of A-CDs showed a gradual change from yellow fluorescence to red fluorescence with increasing CV detection concentration.Based on this phenomenon,an analytical method that enables on-site detection of CV was developed by using a portable UV lamp in combination with a smartphone application（APP）for analysis（LOD=0.167μM）.High recoveries（96.14%-106.06%）and low RSD（<1.48%）were also obtained for fish tissue and pond water samples analysis.In conclusion,the two CDs have great potential to be developed as fluorescent probes for the quantitative detection of Fe³⁺/Hg²⁺and CV in animal husbandry,respectively.