Fluorescence of Nanosized Composite of Mesoporous Molecular Sieve and Europium (Ⅲ) Complex

Rare earth complexes Eu(Phen)_2(TTA)(Bipy)(NO_3)_3 and Eu(L)_x(TTA)_(4-x)(NO_3)_3 (L=Phen or Bipy; x=4, 3, 2, 1, 0) solutions (1×10^(-3) mol·L^(-1)) were prepared in EtOH. The luminescent experimental results show that the synergy effect of Phen and TTA exists in Eu^(3+) complexes. But when the ligands of Bipy and TTA coexist in europium complex, the synergy effect does not exist. If a solution of a europium complex has a specific electron configuration of excited state, the solution of the complex has an intensity of fluorescence and a quantum yield. 2.5×10^(-5) mol·L^(-1) Eu(Phen)_2(TTA)_2(NO_3)_3 solution (λ_(ex)=347.0 nm) possesses a maximal quantum yield (0.25) and the strongest fluorescent intensity. The nanosized mesoporous molecular sieves possess spherical cage structure that is fit for preparation of composite materials with encapsulation method. The research results of XRD and IR show that the guest molecule is encapsulated into the channels of the host. The thermostability of the guest molecule in the channels of the host (CH_3)_3Si-MCM-41 is enhanced. The fluorescent intensity and the half-life of nanosized composites of (CH_3)_3Si-MCM-41 and Eu^(3+) complexes are stronger and longer than those of encapsulation products of MCM-41 and Eu^(3+) complexes. Supramolecular encapsulation products emit characteristic radiation of Eu^(3+) ion, vesting in the transitions of (()~5D_0→()~7F_J) (J=0, 1, 2, 3, 4), respectively; each excitation peak of fluorescent spectra of the composites is assigned to an excited electron configuration of Eu^(3+) ion. The host with lipophilic channels is more favourable to fluorescence of the rare earth complex than hydrophilic mesoporous molecular sieve; The fluorescent intensity of (CH_3)_3Si-MCM-41-Eu(Phen)(TTA)_3(NO_3)_3 can match with that of Eu(Phen)(TTA)_3(NO_3)_3 powder sample. These results could be assumed to result from strong radiation absorption of the guest complex molecule (blue shift of maximum excitation wavelength), greatly reducing of silanol group vibration relaxation of the host (CH_3)_3Si-MCM-41, energy transfer from host to guest, and presence of discrete luminescent center associated with nanosized material structures. The selectivity of host to guest and the interaction between the host and the guest influence greatly the luminescent properties of supramolecular system.

Structural characteristics and the label-free detection of poly(3,4-ethylenedioxythiophene/cucurbit[7]uril)pseudorotaxane at single molecule level

A multi-technique approach to prove the preparation of poly(3,4-ethylenedioxythiophene/cucurbit[7]uril)pseudorotaxanes(PEDOT∙CB7-PPs)is reported.Molecular docking simulation and matrix-assisted laser desorption/ionization mass spectrometry(MALDI MS)validate the complexation ability of the CB7 molecule towards 3,4-ethylenedioxythiophene(EDOT),which leads to the EDOT∙CB7 inclusion complex.Oxidative polymerization of EDOT∙CB7 enabled the synthesis of PEDOT∙CB7-PPs.The water-soluble part of PEDOT∙CB7-PPs was selected,freeze-dried,and chemically characterized.Furthermore,dynamic light scattering(DLS)has been used to study the particle size and z-potential(ZP-ζ)of PEDOT∙CB7-PPs.The ZP-ζvalue(35 mV)evidenced that the PEDOT∙CB7-PPs formed stable water dispersion.By combining the emerging nanopore resistive pulse sensing technique(Np-RPS)and computational modeling,we identified strong interactions of PEDOT∙CB7-PPs with the aerolysin(Ael)nanopore.PEDOT∙CB7-PPs behave as positive charged species,and thus trans negative bias promotes its interactions with the Ael nanopore.The computational modeling results are fully consistent with the Np-RPS detection,which also reveals strong interactions between PEDOT∙CB7-PPs and the Ael nanopore.With this study,we hope to provide new insights and a better understanding of the interactions between supramolecular complexes based on CB7 and biological entities,which is instrumental for future applications in the field of nanobiotechnology.