Highly Enhanced Electrochemiluminescence Luminophore Generated by Zeolitic Imidazole Framework-8-Linked Porphyrin and Its Application for Thrombin Detection

Novel and distinct enhancement in electrochemiluminescence (ECL) signals of advanced organic luminophores are of importance for expanding their applications in early diagnosis. This work reported the construction of an ultrasensitive label-free ECL aptasensor for thrombin (TB) detection by grafting zinc proto-porphyrin IX (ZnP) onto an aminated zeolitic imidazole framework-8 (defined as ZnP-NH-ZIF-8 for clarity) as the luminophore. The structure and optical properties of the resulting ZnP-NH-ZIF-8 were carefully characterized. For that, there appeared to be weak ECL radiation for ZnP in dichloromethane (DCM) containing tetra-n-butylammonium perchlorate (TBAP) because of the as-formed singlet-state oxygen via the "reduction-oxidation" route. More notably, the ECL signals display 153-times enhancement for ZnP-NH-ZIF-8, thanks to the excellent catalytic kinetics for the oxygen reduction reaction (ORR). By virtue of the specific interactions of the TB aptamer (TBA) with the TB protein and the highly efficient catalysis of the ZnP-NH-ZIF-8 for ORR, the as-prepared aptasensor showed a wider linear range (0.1 fM∼1 pM) and a lower detection limit (ca. 58.6 aM). This work provides some useful guidelines for synthesis of an advanced organic luminophore with largely boosted ECL signals in ultrasensitive analysis and clinical diagnosis.

Synthetic aspects of carbazole containing porphyrins and porphyrinoids

Porphyrins are tetrapyrrolic aromatic macrocycles and ubiquitous in nature. They are excellent dyes with strong absorption in the visible region (400–700 nm) and they exhibit decent fluorescence in the red region (620–900 nm). Carbazole is a nitrogen-containing electron rich aromatic heterocycle which can be linked to porphyrins and other chromophores. This review provides an overview of the different synthetic strategies that have been employed to prepare carbazole-substituted porphyrins and carbazole-fused porphyrinoids and similar systems. It also shows that how the substitution of carbazole occurs on the porphyrin core can alter its optical and electronic features. Introduction of carbazole moieties in the porphyrin ring resulted in fused porphyrinoids with changed aromaticity and significantly altered electronic features of the molecules.

Optical properties of β-brominated meso-tetraphenylporphyrins: Comparative experimental and computational studies

The UV-vis and fluorescence spectra of a series of [Formula: see text]-brominated derivatives of meso-tetraphenylporphyrin (H[Formula: see text]TPPBr[Formula: see text]; [Formula: see text] 0, 2, 4, 5, 6, 7, 8) were used to investigate the steroelectronic effects of bromine atoms on the optical properties of H[Formula: see text]TPP. The wavelength and intensity of the absorption and emission bands were found to be influenced by the bromine atoms. The degree of configuration interaction between the S[Formula: see text] and S[Formula: see text] excited states and fluorescence quantum yield and their dependence on the bromine atoms were also studied. Computational studies based on density functional theory and time-dependent density functional approach (DFT and TD-DFT) support and provide an explanation for the spectral changes associated with the bromination of H[Formula: see text]TPP. Furthermore, the solvent effect on the spectral properties of higher degrees of [Formula: see text]-bromination was attributed to the formation of relatively strong hydrogen bonds between their saddle-distorted porphyrin cores and the solvent molecules.