| Pharmaceutical analysis is a subject of research and development of total quality control,focusing on the quality control of drugs and their preparations.Conventional approaches used in pharmaceutical analysis are instrumental analysis besides chemical and physical analysis,such as biological mass spectrometry,chromatography and infrared analysis and so on.Pharmaceutical spectral analysis has been wide sued owing to the advantages of high sensitivity,high selectivity,easy-obtained synthesis approach and simple instrument operation,et al.Among so many optical probes in pharmaceutical analysis,carbon dots(CDs),including carbon nanodots(CNDs),carbon quantum dots(CQDs)and graphene quantum dots(GODs),as a new kind of excellent optical probes in pharmaceutical analysis,including in vivo drug metabolism and long-time bio-imaging because of their excellent biocompatibility,long-time anti-photobleaching and other optical properties.However,most of these CDs show low photoluminescence(PL)quantum yields(QY),short wavelength emission and limited applications,which limits the applications in pharmaceutical analysis.Hence,at this moment,the research focusing on enhancing the PL QY of CDs,synthesizing long wavelength emission CDs and broadening the applications of CDs besides PL applications in promoting applying CDs in pharmaceutical analysis.There are amounts of approaches to achieve the aim of high PL QY,long wavelength emission and functionalization,such as screening the raw materials for synthesis,heteroatom doping,and so on.In this work,unique approaches were used to gain these aims.PL QY of CDs was enhanced through modifying them after the synthesis process.Long wavelength emissive CDs were obtained through careful separation.Functionalization also achieved through changing the synthesis methods and raising the synthesis temperature.And finally these CDs with outstanding properties were used for pharmaceutical analysis and drug loading.The detail research contents as followings:(1)One-pot hydrothermal synthesis of CQDs with aggregation induced emission enhancement(AIIEE)property for detection of tetrahydrofuran(THF)in the drug residuesAt first,by screening the raw materials,tannic acid(TA),which have abundant phenolic hydroxyl groups,was selected as the single carbon source.CQDs with relative PL QY of 7.16% was obtained through one-pot hydrothermal synthesis route.High resolution transmission electronic microscope(HRTEM),dynamic light scattering(DLS)were used to confirm that the CQDs were well dispersed spherical nanoparticles.Fourier transform infrared(FTIR)spectroscopy,X-ray photoelectron spectroscopy(XPS)analysis and Raman spectrum were used to prove the existence of abundant hydroxyl groups on the surface of this CQDs.The as-prepared CQDs showed excitation-dependentemission feature with the PL emission centered at 455 nm when excited at 350 nm.While the PL property of the CQDs was investigated,we found that the PL intensity has a simple relationship with the permittivity(?)of the solvents.The PL QY reached 42.65% when dissolved in THF/water mixture with the ratio of 4:1.Further experiments confirmed the reason for enhancement of CQDs was aggregation caused hindered rotation vibration of the surface functional groups.Then,the non-radiation decay decreased and the process of radiation decay increased.Following experiments found that other approaches who can limit the rotation vibration of the surface functional groups of CQDs can also enhance the PL efficiency.Nowadays,there are kin of rare studies about AIEE feature of CQDs,while it is the first time to report using CQDs with AIEE feature to detect organic solvents in drug residues.(2)Ultra-high PL QY CQDs with emission wavelength ranging from blue to near infrared(NIR)obtained through one-pot hydrothermal synthesis and careful separation.PL mechanism was investigated and the CQDs with NIR emission.CQDs with relative PL QY of 97.64% were obtained through one-pot hydrothermal synthesis using perylene-3,4,9,10-tetracarboxylic dianhydride and trimethylamine as the raw materials.Because of the wide excitation and emission peaks,careful separation through a silica gel column followed and a series CQDs with the emission wavelength ranging from blue to NIR were obtained.Instruments like HRTEM,XPS,Raman were used to analysis the size distributions and functional groups of the CQDs acquired from silica gel column.When the size distributions were controlled to be same,the PL emission wavelength were same too.But with the change of functional groups,the PL emission wavelength still shifted slightly.When these CQDs had similar ratio of sp2/sp3,in another word,had same core-shell structures,the PL emission wavelength had an obvious red shift.This conclusion was confirmed through density functional theory(DFT)calculation.Further investigation through measuring the AC impedance spectrum,the CQDs were identified as a kind of semiconductor.The PL mechanism of the CQDs was electron transition by calculating the radiative transition rate constant,but not exciton transition.Since long-wavelength emission does little harm for organisms and has good penetrating,the separated long-wavelength emissive CQDs have potential applications in real time analysis and bioimaging in organisms in vivo.(3)One-pot thermolysis synthesis of zigzag-edged Cu(I)-doped CQDs for catalyzing the reaction of azide–alkyne cycloadditionsThese Cu(I)-doped CQDs [Cu(I)-CQDs] were one-pot synthesized by carrying out a thermolysis of Na2[Cu(EDTA)] and ascorbic acid(AA)at 250 °C.It is easy to obtain zigzag edged CQDs since the temperature was very high using thermolysis synthesis route.These formation of zigzag structures could enhance the activation energies of CQDs,which preferentially stabilized the Cu(I).Besides,the as-prepared CQDs can emit PL under appropriate excitation wavelength owing to the split and recombination of electron and hole pairs,and the excitation and emission wavelength were 430 nm and 515 nm.Since the energy needed for excitation was lower than UV light,electrons split from the holes and did not come back to the hole when excited under UV irradiation.The hole was positively charged and can strongly compete with Cu(I),leading to the release of Cu(I).In the catalysis system,Cu(I)-doped CQDs were added as the catalyzer,using UV light as switch,and then the released Cu(I)can catalyze the reaction of azide–alkyne cycloadditions,one reaction of “click chemistry”.The reaction efficiency was 78%.Usually,the combination of nanoparticles and drug molecules was necessary in drug loading and release process,while CQDs play the role as the catalyzer when combination which leading to the decrease of biotoxicity.(4)Coupling aptamer and high PL QY CQDs by “click chemistry” for cell membrane imaging.Modify alkynyl groups to the CQDs in the second part and then couple azide modified aptamer to the surface of the CQDs using the Cu(I)-CQDs as the catalyzer.After the separation process,this composite material was then used for cell membrane imaging.This part solved the modification problem and extended the applications of CQDs.Coupling the non-PL aptamer and non-targeted CQDs can obtain both advantages of the two materials,which could lay foundation for the application of carbon dots in the field of bioimaging analysis.In summary,CQDs have great potential applications in drug residues detection,in vivo detection and catalyzed coupling drug loading.In this paper,based on the aggregation caused PL change property of CQDs,simple,fast and accurate detection of THF in drug residues could be realized.Ultra-high PL QY CQDs with emission wavelength ranging from blue to near infrared(NIR)were obtained through one-pot hydrothermal synthesis and careful separation using perylene-3,4,9,10-tetracarboxylic dianhydride and trimethylamine as the raw materials.PL mechanism was further clarified through investigating the full wavelength emissive CQDs.One-pot thermolysis synthesis of zigzag-edged Cu(I)-doped CQDs for catalyzing the reaction of azide–alkyne cycloadditions broadened the applications of CQDs.Combining the CQDs in the second and third part realized the applications of CQDs in in the field of bioimaging analysis.According to the studies in this paper,more approaches for pharmaceutical analysis and drug loading can be explored based on the bio-friendly CQDs.It is significant to realize a simple and sensitive pharmaceutical analysis and detection and high efficient drug loading. |
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