Red-emissive carbon dots(R-CDs)have been widely studied because of their potential application in tis-sue imaging and optoelectronic devices.At present,most R-CDs are synthesized by using aromatic pre-cursors,but the synthesis of R-CDs from non-aromatic precursors is challenging,and the emission mechanism remains unclear.Herein,different R-CDs were rationally synthesized using citric acid(CA),a prototype non-aromatic precursor,with the assistance of ammonia.Their structural evolution and opti-cal mechanism were investigated.The addition of NH3·H2O played a key role in the synthesis of CA-based R-CDs,which shifted the emission wavelength of CA-based CDs from 423 to 667 nm.Mass spectrometry(MS)analysis indicated that the amino groups served as N dopants and promoted the formation of local-ized conjugated domains through an intermolecular amide ring,thereby inducing a significant emission redshift.The red-emissive mechanism of CDs was further confirmed by control experiments using other CA-like molecules(e.g.,aconitic acid,tartaric acid,aspartic acid,malic acid,and maleic acid)as precur-sors.MS,nuclear magnetic resonance characterization,and computational modeling revealed that the main carbon chain length of CA-like precursors tailored the cyclization mode,leading to hexatomic,pen-tatomic,unstable three/four-membered ring systems or cyclization failure.Among these systems,the hexatomic ring led to the largest emission redshift(244 nm,known for CA-based CDs).This work deter-mined the origin of red emission in CA-based CDs,which would guide research on the controlled synthe-sis of R-CDs from other non-aromatic precursors.

Xin Yang;Lin Ai;Jingkun Yu;Geoffrey I.N.Waterhouse;Laizhi Sui;Jie Ding;Baowei Zhang;Xue Yong;Siyu Lu

Green Catalysis Center,and College of Chemistry,Zhengzhou University,Zhengzhou 450000,China;School of Chemical Sciences,The University of Auckland,Auckland 1142,New Zealand;State Key Laboratory of Molecular Reaction Dynamics,Dalian Institute of Chemical Physics,Chinese Academy of Sciences,Dalian 116023,China;Department of Chemistry,University of Sheffield,Sheffield S3 7HF,UK

科学通报（英文版）

[1]Xin Yang;Lin Ai;Jingkun Yu;Geoffrey I.N.Waterhouse;Laizhi Sui;Jie Ding;Baowei Zhang;Xue Yong;Siyu Lu-.Photoluminescence mechanisms of red-emissive carbon dots derived from non-conjugated molecules)[J].科学通报（英文版）,2022(14):1450-1457

aconitic,hexatomic,tatomic

Photoluminescence,mechanisms,emissive,carbon,dots,derived,from,conjugated,molecules,Red,CDs,have,been,widely,studied,because,their,potential,application,tis,sue,imaging,optoelectronic,devices,At,present,most,are,synthesized,using,aromatic,but,synthesis,precursors,challenging,emission,remains,unclear,Herein,different,were,rationally,citric,acid,CA,prototype,assistance,ammonia,Their,structural,evolution,opti,investigated,addition,NH3,H2O,played,key,role,which,shifted,wavelength,Mass,spectrometry,analysis,indicated,that,amino,groups,served,dopants,promoted,formation,local,domains,through,intermolecular,amide,ring,thereby,inducing,significant,redshift,was,further,confirmed,experiments,other,like,tartaric,aspartic,malic,maleic,nuclear,magnetic,resonance,characterization,computational,modeling,revealed,chain,tailored,cyclization,leading,pen,unstable,three,four,membered,systems,failure,Among,these,largest,known,This,work,deter,mined,origin,would,guide,research,controlled

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