The main research fields are briefly described as follow:
(1) Potential-resolved Electrochemiluminescence
(2) Electrochemiluminescence on Nanoparticle self-assembled Electrodes
(3) Liquid Phase Chemiluminescence Induced by Gold Nanoparticles
(4)
Exploration of New chemiluminescence systems
(5)
Enhancement and Inhibition effects of Chemiluminescence

1. Potential-resolved Electrochemiluminescence


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 12th 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

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2. Electrochemiluminescence on Nanoparticle self-assembled Electrodes


    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

 


S
cheme 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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3. Liquid Phase Chemiluminescence Induced by Gold Nanoparticles


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

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4. Exploration of New chemiluminescence systems


    It is well known that lots of present chemiluminescent reactions have low quantum yields and are difficult to have practical analytical applications, although there are many system for chemiluminescence. Therefore, there is a great significance for analysts to explore new chemiluminescent system. We found Ce(IV) + Tween20 and Ce(IV) + rhodamine 6G + phenolic compounds systems, proposed their reaction mechanisms, and established a high sensitivity CL detection method for many phenolic compounds and flavonic compounds.

    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)

    It is believed that this work will have a bright future for the practical analytical applicaiton in drug analysis, food safety determination, and monitoring of environment. The first paper was published on "Analyst". The record from Royal Society of Chemistry demonstrated that the click number of this paper was top 3 in May, 2001.

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5. Enhancement and Inhibition effects of Chemiluminescence


    The linear relationship between the concentration of analyte and the corresponding CL/ECL strength can be used as a quantitative analytical tool. However, the proper systems for CL/ECL are limited, which greatly limited the application of CL/ECL analysis method. In this case, the enhancement and inhibition effects for different compounds to the same or few CL/ECL system play an important role in the analytical determination. Unfortunately, the rules in CL enhancement and inhibition effects are still not clear.
    Therefore, we had a systematic study about the influence of a series of phenolic and aniline compounds, and amino acids on many CL systems, such as luminol-K3[Fe(CN)6], luminol-H2O2-Co(II), luminol-DMSO-OH-, luminol-H2O2-IO4-, lucigenin-H2O2-Co(II), Ce(IV)-Tween 20, etc, and ECL systems, such as luminol,
Ru(bpy)32+/C2O42-, Ru(bpy)32+/TPA, etc, in different conditions. Based on these experimental results, we found the rules of  enhancement and inhibition effects are greatly dependent on the molecular structure, concentration, and the pH of solution. What's more, the mechanisms of these phenomenon were also proposed. And then, the corresponding flow-injection with CL detection method and the HPLC-CL method of these compounds were established. Furthermore, we discovered a new CL system, i.e., Ce (IV) + Tween 20, proposed the reaction mechanism, and established the high sensitivity CL analysis to many phenolic and flavonic compounds.

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