Electrochemiluminescence cell assembly

    Under cyclic voltammetric conditions, several electrochemiluminescece (ECL) channels can be resolved at different potentials for conventional ECL systems, which is referred to as potential-resolved electrochemiluminescence (PRECL). However, ECL initiated by electropulse signals cannot resolve these channels. The PRECL behaviors of typical chemiluminescence systems, such as luminol, lucigenin and tris(2,2’-bipyridyl) ruthenium, on various electrodes (including Pt, Au, Cu, glass carbon, paraffin-impregnated graphite, and Ti rod electrodes) have been systematically investigated. It reveals that the ECL of luminol, lucigenin and tris(2,2’-bipyridyl) ruthenium exhibit multi-channel emission, which depends on the electrode material, the applied potential and the surface state of the electrodes. Furthermore, the mechanisms of each channel have also discussed. 

The potential-resolved electrochemiluminescence has opened a new ground for the research of electrochemiluminescence. It is not only of great importance for probing into the mechanism of ECL and exploiting new ECL systems, but also of great potential for developing highly sensitive and selective ECL analytical methods.  

The papers about the research mentioned above have published on Anal. Chem., J. Electroanal. Chem., and so on.

Reviewers commented: “Future interesting development of this work, in analytical science, would consist in possible multi-channel light emissions.” Related work had orally reported on the 12^th International Symposium on Bioluminescence and Chemiluminescence.

H. Cui, G.Z. Zou, X.Q. Lin
” Electrochemiluminescence of luminol in alkaline solution at a paraffin-impregnated graphite electrode ”
Anal. Chem. 2003, 75(3), 324-331.

Compare PRECL curve with CV curve of luminol on paraffin-impregnated graphite electrode

    Previous work has revealed that the behavior of luminol ECL is strongly affected by a number of factors, including the applied potential, electrode material, and surface state of the electrode. These results indicate that it is expected that ECL-based detection can be improved through optimization of the composition and surface structure of the electrode. Nanoparticle self-assembled electrodes have received considerable attention in electrochemistry and electroanalytical chemistry. Various metal, metal oxide and nonmetal oxide nanoparticles or clusters have assembled on different electrodes, including Au, Pt, Ag, C and so on. These self-assembled electrodes exhibit fascinating surface-absorption, molecule-identifying, electrocatalytic properties and high reactivity. However, the study concerning ECL on nanoparticle self-assembled electrodes has not been reported until now.

CCD image of luminol ECL on a gold nanoparticle self-assembled electrode

Scheme of preparation of gold electrode modified with gold nanoparticles

H. Cui, Y. Xu, Z.F. Zhang
” Multi-channel electrochemiluminescence of luminol in neutral and alkaline aqueous solutions on a gold nanoparticles self-assembled electrode ”
Anal. Chem., 2004, 76(14): 4002-4010

Recently, our group has assembled gold nanoparticles on various conventional electrodes, and explored the ECL behaviors of luminol and lucigenin on these gold nanoparticle self-assembled electrodes. It was found that the light intensity was greatly enhanced; new emission channels appeared; stability and reproducibility were largely improved, which did not exist on conventional electrodes. These results show that the sensitivity of luminol and lucigenin detection system can be largely improved on gold nanoparticle self-assembled electrodes.

This work is not only of great importance for enriching our knowledge on the unique properties of microscaled substances, but also of great potential for practical application of nanotechnology in analytical chemistry.

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Beautiful CL in liquid phase

    The special optical properties of nanoparticles contain a plenty of information of their energy level structure and surface states, and therefore, it attracts more and more researchers. At present, the research about the optical properties of nanoparticles mainly includes the surface plasmon resonance absorption (SPR), surface enhanced raman spectroscopy (SERS), and the photo-generated luminescence, etc.

    Chemiluminescence is the light emission phenomenon go with the chemical reaction. It played an important role in the research field of thermodynamics, kinetics, and light emission property of physical and chemical process. Since Albrecht observed the CL phenomenon of luminol in alkaline solution, several liquid-phase CL system were widely studied and developed, including luminol and its derivatives, acridinium ester, bis(2,4,6-trichlorphenyl)oxalate (TCPO), acidic potassium permanganate (KMnO₄), ruthenium(II) polypyridine (Ru(bpy)₃²⁺), and Ce(IV), etc. However, the study of liquid-phase chemiluminescence often focused on the molecular and atomic level, or simple congeries, such as micelles and microemulsions. In recent years, the study of CL and ECL behaviour of semiconductor nanoparticles attracted many groups' eyes.

    Recently, we found gold that nanoparticles could induce the liquid-phase CL reaction, playing important roles as both the reduction reagent and the catalyst. For example, the gold colloid could have a reaction in KIO₄-NaOH/Na₂CO₃ system and generate a strong chemiluminescence. According to our present analysis, the three CL peaks of its CL spectroscopy are corresponded to emission of singlet oxygen (490-500nm), CO₂ bi-molecules (430-450nm) and Au(I) intermediate, respectively (See detailed information on J. Phys. Chem. B. 2005, 109, 3099). In the other work, we found the catalysis effect of gold nanoparticles to luminol chemiluminescent reaction, and its good potential for analytical application. It is believed that this work expanded the CL object from molecule, ion systems to metal nanoparticles.

Luminol-H₂O₂ CL spectroscopy of different particles radius

    The flowing chart for HPLC-CL analysis of Ce(IV) + Tween20 system.

(see left)

    The chromatography curve of a practical sample of HPLC-CL detection of Ce(IV) +Tween20 system. (see right)