The influence of irradiation parameters,such as the irradiation time,temperature and the acrylate functionality of monomers on the infrared laser induced photopolymerization were investigated in this paper.A novel cat...The influence of irradiation parameters,such as the irradiation time,temperature and the acrylate functionality of monomers on the infrared laser induced photopolymerization were investigated in this paper.A novel cationic cyanine dye borate complex,1,3,3,1′,3′,3′ hexamethyl ll chloro 10,12 propylene tricarbocyanine triphenylbutylborate,was employed as the photoinitiator.It had maximum absorption wavelength λ max at 780 nm in 2 butanone with the maximum molar extinction coefficient ε max of 1 4×10 5 L·mol -1 ·cm -1 ,which matched well with the emitting wavelength,796 nm,of the adopted infrared laser diode.With poly(vinyl alcohol)(PVA)as oxygen barrier layer,photopolymerization system containing trihydroxymethylpropanetriacrylate(TMPTA),binder and photoinitiator was cured by 2 min of infrared laser irradiation.Modest improvement of the double bond conversion could be achieved by increasing the irradiation time or temperature.Furthermore,it was found that the monomer with diacrylate functionality had higher double bond conversion than that with triacrylate functionality under the same irradiation conditions.Double bond conversion of 52% could be achieved for diacrylate monomer phthalic diglycol diacrylate(PDDA)compared with 25% for triacrylate monomer TMPTA.展开更多
By using scanning tunneling microscope induced luminescence(STML)technique,we investigate systematically the bias-polarity dependent electroluminescence behavior of a single platinum phthalocyanine(PtPc)molecule and t...By using scanning tunneling microscope induced luminescence(STML)technique,we investigate systematically the bias-polarity dependent electroluminescence behavior of a single platinum phthalocyanine(PtPc)molecule and the electron excitation mechanisms behind.The molecule is found to emit light at both bias polarities but with different emission energies.At negative excitation bias,only the fluorescence at 637 nm is observed,which originates from the LUMOtHOMO transition of the neutral PtPc molecule and exhibits stepwise-like increase in emission intensities over three different excitation-voltage regions.Strong fluorescence in region(I)is excited by the carrier injection mechanism with holes injected into the HOMO state first;moderate fluorescence in region(II)is excited by the inelastic electron scattering mechanism;and weak fluorescence in region(III)is associated with an up-conversion process and excited by a combined carrier injection and inelastic electron scattering mechanism involving a spintriplet relay state.At positive excitation bias,more-than-one emission peaks are observed and the excitation and emission mechanisms become complicated.The sharp moleculespecific emission peak at〜911 nm is attributed to the anionic emission of PtPc-originated from the LUMO+1 tLUMO transition,whose excitation is dominated by a carrier injection mechanism with electrons first injected into the LUMO+1 or higher-lying empty orbitals.展开更多
Fe and Co porphyrins and phthalocyanines are excellent catalysts for the oxygen reduction reaction （ORR） and are promising alternatives to Pt in fuel cells. However, the stability of these molecular catalysts in aci...Fe and Co porphyrins and phthalocyanines are excellent catalysts for the oxygen reduction reaction （ORR） and are promising alternatives to Pt in fuel cells. However, the stability of these molecular catalysts in acidic media is poor. This study explores whether demetalation through proton ex- change causes these metal macrocyclic catalysts to be unstable in acidic media. We first present a theoretical scheme for investigating exchange reactions of metal ions in metal macrocyclic com- pounds with protons in acidic media. The equilibrium concentrations of metal ions in solution when various metalloporphyrins （MPs） and metallophthalocyanines （MPcs） are brought into contact with a strongly acidic solution （pH = 1） were then estimated using density functional theory calculations; these values were used to evaluate the stability of these metal macrocyclic compounds against demetalation in acidic media, The results show that Fe, Co, Ni, and Cu phthalocyanines and porphy- rins have considerable resistance to exchange with protons, whereas Cr, Mn, and Zn phthalocya- nines and porphyrins easily undergo demetalation through ion exchange with protons, This sug- gests that the degradation in the ORR activity of Fe and Co macrocyclic molecular catalysts and of carbon materials doped with Fe（Co） and nitrogen, which are believed to have metal-nitrogen coor- dination structures similar to those of macrocyclic molecules as ORR catalytic centers, is not the result of replacement of metal ions by protons. The calculation results show that electron-donating substituents could enhance the stability of Fe and Co phthalocyanines.展开更多
文摘The influence of irradiation parameters,such as the irradiation time,temperature and the acrylate functionality of monomers on the infrared laser induced photopolymerization were investigated in this paper.A novel cationic cyanine dye borate complex,1,3,3,1′,3′,3′ hexamethyl ll chloro 10,12 propylene tricarbocyanine triphenylbutylborate,was employed as the photoinitiator.It had maximum absorption wavelength λ max at 780 nm in 2 butanone with the maximum molar extinction coefficient ε max of 1 4×10 5 L·mol -1 ·cm -1 ,which matched well with the emitting wavelength,796 nm,of the adopted infrared laser diode.With poly(vinyl alcohol)(PVA)as oxygen barrier layer,photopolymerization system containing trihydroxymethylpropanetriacrylate(TMPTA),binder and photoinitiator was cured by 2 min of infrared laser irradiation.Modest improvement of the double bond conversion could be achieved by increasing the irradiation time or temperature.Furthermore,it was found that the monomer with diacrylate functionality had higher double bond conversion than that with triacrylate functionality under the same irradiation conditions.Double bond conversion of 52% could be achieved for diacrylate monomer phthalic diglycol diacrylate(PDDA)compared with 25% for triacrylate monomer TMPTA.
基金This work is supported by the National Key R&D Program of China(No.2016YFA0200600 and No.2017YFA0303500)the National Natural Science Foundation of China,the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36000000)Anhui Initiative in Quantum Information Technologies.
文摘By using scanning tunneling microscope induced luminescence(STML)technique,we investigate systematically the bias-polarity dependent electroluminescence behavior of a single platinum phthalocyanine(PtPc)molecule and the electron excitation mechanisms behind.The molecule is found to emit light at both bias polarities but with different emission energies.At negative excitation bias,only the fluorescence at 637 nm is observed,which originates from the LUMOtHOMO transition of the neutral PtPc molecule and exhibits stepwise-like increase in emission intensities over three different excitation-voltage regions.Strong fluorescence in region(I)is excited by the carrier injection mechanism with holes injected into the HOMO state first;moderate fluorescence in region(II)is excited by the inelastic electron scattering mechanism;and weak fluorescence in region(III)is associated with an up-conversion process and excited by a combined carrier injection and inelastic electron scattering mechanism involving a spintriplet relay state.At positive excitation bias,more-than-one emission peaks are observed and the excitation and emission mechanisms become complicated.The sharp moleculespecific emission peak at〜911 nm is attributed to the anionic emission of PtPc-originated from the LUMO+1 tLUMO transition,whose excitation is dominated by a carrier injection mechanism with electrons first injected into the LUMO+1 or higher-lying empty orbitals.
基金supported by the National Basic Research Program of China(973 program,2012CB215500 and 2012CB932800)~~
文摘Fe and Co porphyrins and phthalocyanines are excellent catalysts for the oxygen reduction reaction （ORR） and are promising alternatives to Pt in fuel cells. However, the stability of these molecular catalysts in acidic media is poor. This study explores whether demetalation through proton ex- change causes these metal macrocyclic catalysts to be unstable in acidic media. We first present a theoretical scheme for investigating exchange reactions of metal ions in metal macrocyclic com- pounds with protons in acidic media. The equilibrium concentrations of metal ions in solution when various metalloporphyrins （MPs） and metallophthalocyanines （MPcs） are brought into contact with a strongly acidic solution （pH = 1） were then estimated using density functional theory calculations; these values were used to evaluate the stability of these metal macrocyclic compounds against demetalation in acidic media, The results show that Fe, Co, Ni, and Cu phthalocyanines and porphy- rins have considerable resistance to exchange with protons, whereas Cr, Mn, and Zn phthalocya- nines and porphyrins easily undergo demetalation through ion exchange with protons, This sug- gests that the degradation in the ORR activity of Fe and Co macrocyclic molecular catalysts and of carbon materials doped with Fe（Co） and nitrogen, which are believed to have metal-nitrogen coor- dination structures similar to those of macrocyclic molecules as ORR catalytic centers, is not the result of replacement of metal ions by protons. The calculation results show that electron-donating substituents could enhance the stability of Fe and Co phthalocyanines.
