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A research on the effect of different buffers on the pH range of 6–10 on the thin oxide-covered surface of aluminum cathode has been conducted under the conditions corresponding with those generally used in bioaffinity assays or other determinations made by using aluminum probe based on time-resolved cathodic electrochemiluminoimmuno assay (tr-ECLIA or tr-CECLIA) detection. The experiments have been conducted on impedance and cathodic electrochemiluminescence (CECL) basis using a strong long lifetime having electroluminophore Tb(III)-1 chelate where the ligand 1 is 2,6-bis[N,N-bis(carboxymethyl)aminomethyl]-4-benzoylphenol and Ruthenium(II) tris(2,2′–bipyridine) (Ru(bpy)32+) as the CECL model luminophores. The results point out that the natural oxide layer at the electrode surface does not essentially change as to its thickness but as to its resistance, it can be concluded that the best buffer in these luminophore determinations based on CECL and Al probe use is borate buffer adjusted to pH around 7–8 where the surface of aluminum has its neutral character. In the bioaffinity assays the meaning of the buffer seems to be more difficult to realize due to the complex character of the surface with plenty of different coatings and special handling steps but still with the aforementioned borate buffer the results were noticed to be the most stabile. The tests also pointed out that the character of the pure aluminum surface and the oxide layer above it without any other coatings could be strongly affected by the surrounding solution composition and in that way to the durability of the aluminum probe already during the quite short exposure times. The reported results are useful especially in the field of CECL based on aluminum probe use but could also in a certain extent to be utilized in a large scale of analysis considering the use of aluminum probes.

The heterogeneous immunoassay of thyroid stimulating hormone (TSH) was detected by the time-resolved cathodic electrochemiluminescence immunoassay (tr-CECLIA) method using magnetic beads as a mobile support. The magnetic beads coated with sandwich type TSH immunoassay were captured with a magnet for washing and detection processes. The time-resolved cathodic electrochemiluminescence (tr-CECL) signal of Tb(III) chelate label was generated by cathodic pulse polarization in the aluminum working electrode and platinum counter electrode system. The detection method causes injection of high energy electrons into the aqueous solution near the aluminum electrode and creates rigid simultaneous oxidative and reductive conditions that excitate the Tb(III) chelate used as a label luminophore in the heterogeneous sandwich type immunoassay of TSH in the surface of the magnetic beads. The limit of detection of the method was about 50 mIU L−1. The precision of it was noticed to be good; the coefficient variation percentage was realized to be lower than 10 %. Unfortunately the limit of detection is not good enough for determination of analyte levels of very low concentrations for instance TSH in body fluids. The possible application areas of the method are in highly sophisticated micro or nano fluidic detection and sensor systems where the aspiration level of the analyte detection limit is not very high and the mobility and manageability and the large surface area of the magnetic beads can be utilized efficiently in separating, washing, moving, coating and detecting processes. In the case of tr-CECLIA the presented method makes possible to use multipurpose working electrodes instead of disposable ones.

Tris(2,2′-bipyridine)ruthenium(II) chelate exhibits strong electrogenerated chemiluminescence during cathodic high-voltage pulse-polarization of pointed Pt electrode in aqueous solutions. The present method is based on a field emission or other type of tunnel emission of hot electrons into an aqueous electrolyte solution. The method allows the detection of tris(2,2′-bipyridine)ruthenium(II) and its derivatives below nanomolar concentration levels and yields linear log-log calibration plots spanning several orders of magnitude of concentration.

Different micellar particles Mi(M + ) (Mi=Triton X-100, Triton N-101 R, Triton CF-10, Brij-35, M + =Na + , K + , Cs + ) have been prepared in different aqueous H 3 BO 3 /MOH background electrolytes. It has been observed that these particles can be used to disperse the highly hydrophobic spherical [60]fullerene ( 1 ) and ellipsoidal [70]fullerene ( 2 ). This dispersion is realised as either micelle-encapsulated monomers Mi(M + ) 1 m and Mi(M + ) 2 m or water-soluble micelle-bound aggregates Mi(M + ) 1 agg and Mi(M + ) 2 agg , where especially the hydration degree and polyoxyethylene (POE) thickness of the micellar particle seems to play a role of vital importance. Further, the encapsulation microenvironment of 1 m was found to depend strongly on the selected monovalent electrolyte cation, i.e ., the encapsulated 1 m is accommodated in the more hydrophobic microenvironment the higher the cationic solvation number is.

Electrogenerated chemiluminescence (ECL) of lucigenin is induced at oxide-coated aluminum electrodes in aqueous solution by cathodic pulse polarization. This ECL can be enhanced by the presence of coreactants such as peroxodisulfalte. The present method is based on the injection of hot electrons into the aqueous electrolyte solution, which probably results in the generation of hydrated electrons as reducing mediators. The successive one-electron redox reactions result in the excited states of lucigenin or its fragmentation products. The method can detect lucigenin over several orders of magnitude of concentration with detection limit below nanomolar concentration level. In addition, the relatively long lifetime of the ECL of lucigenin makes time-resolved detection possible. This study suggests that the derivatives of lucigenin can be utilized as electrochemiluminescent labels in aqueous solution in bioaffinity assays at thin insulating film-coated cathodes. The cathodic ECL reaction mechanisms are discussed.

Rhodamine B (RhB) exhibits strong cathodic electrogenerated chemiluminescence (ECL) in aqueous solutions during high-amplitude pulse polarization at thin oxide film-coated aluminum electrodes. This method allows the detection of RhB below nanomolar concentration level and provides linear calibration plots spanning over several orders of magnitude of concentration. In addition, a relatively long ECL lifetime of RhB provides a basis for time-resolved detection. Thus, widely used RhB-based labels can also be suggested to be usable as electrochemiluminescent labels in fully aqueous solutions in bioaffinity assays such as in immunoassays and DNA-probing assays. Support was obtained for the chemiluminescence generation mechanism to be essentially the same as that of radiochemiluminescence in aqueous solution.

Time-resolved electrogenerated chemiluminescence of multidentate phenolic Eu(III) chelates were studied in aqueous solution. 2,6-bis[N,N-bis(carboxymethyl)-aminomethyl]-4-benzoylphenol forms a photoluminescent and electrochemiluminescent Eu(III) chelate, whereas 2,6-bis[N,N-bis(carboxymethyl)-aminomethyl]-4-methyl phenol-chelated Eu(III) turned out to be not luminescent at all. The importance of the redox properties of both the ground and the excited states of the ligands and the central ion is shown. The former chelate shows relatively weak ECL at an oxide-covered aluminum electrode but the ECL intensity can be strongly enhanced by the addition of peroxodisulfate ions. In the presence of 1 mM peroxodisulfate ions the ECL lifetime of this chelate is 0.94 ms, thus easily allowing time-resolved detection of the chelate. This chelate can be conjugated to antibodies by thioureido linkage and used as an electrochemiluminescent label in immunoassays as a marker which displays long-lived luminescence in the red end of the optical spectrum. The present ECL is mainly based on the ligand sensitized redox excitation of the chelate by analogous pathways to those known from the studies of aromatic Tb(III) chelates but the energy transfer from the emission centers of the aluminum oxide film can also have minor contribution to the excitation of the label.

Double insulating barrier tunnel emission electrodes were fabricated by adding a new pure aluminum layer upon oxidized aluminum electrodes by vacuum evaporation and thermally oxidizing the new aluminum layer in air at room temperature. Resulting Al/Al 2 O 3 /Al/Al 2 O 3 electrodes allow the use of various aluminum alloys in the electrode body necessary for hardness or shaping ability of the electrode while obtaining the luminescence properties of pure aluminum oxide. During electrical excitation of luminescent labels by cathodic hot electron injection into aqueous electrolyte solution, the background noise is mainly based on high-field-induced solid-state electroluminescence and F-center luminescence of the outer aluminum oxide film. The more defect states and/or impurity centers the outer oxide film contains, the higher is the background emission intensity. The present electrode fabrication method provides a considerable improvement in signal-to-noise ratio for time-resolved electrochemiluminescence (TR-ECL) measurements when the original native oxide film of the electrode body contains luminescence centers displaying long-lived luminescence. The excellent performance of the present electrodes is demonstrated by extremely low-level detection of Tb(III) chelates, luminol, Pt(II) coproporphyrin and Tb(III) labels in an immunometric immunoassay by time-resolved electrochemiluminescence.

Oxide-covered aluminium electrodes were used to demonstrate that aromatic compounds, such as the simple derivatives of benzene, can be electrochemically excited at cathodically pulse-polarized conductor/insulator/electrolyte (C/I/E) tunnel junction electrodes (e.g. oxide-covered aluminium electrodes). The primary cathodic process at these electrodes was a tunnel emission of hot electrons into an aqueous electrolyte solution. Fluorescence (FL) and electrochemiluminescence (ECL) spectra were compared and the dependence of the electrochemiluminescence on the concentrations of benzene, toluene, phenol, p-cresol and aniline were measured and detailed mechanisms for the present electrochemiluminescence are proposed. Copyright © 2006 John Wiley & Sons, Ltd.

Strong electrogenerated chemiluminescence (ECL) of fluorescein is generated in aqueous solution during cathodic pulse polarization of oxide-covered aluminum electrodes. The present method is based on the injection of hot electrons into the aqueous electrolyte solution, which probably results in the generation of hydrated electrons as reducing mediators. The successive one-electron redox reactions result in fluorescein in its lowest excited singlet state, i.e., the emission spectrum is similar to the corresponding fluorescence emission spectrum. This ECL can be enhanced by added coreactants, e.g., by peroxodisulfate, peroxodiphosphate, hydrogen peroxide and azide ions. The method can detect fluorescein over several orders of magnitude of concentration with detection limit below nanomolar concentration level in the presence of azide ions. The results suggest that the derivatives of fluorescein, such as fluorescein isothiocyanate, can be used as electrochemiluminescent labels in aqueous solution in bioaffinity assays carried out on the surface of thin aluminum oxide film-coated aluminum electrodes. This cathodic ECL is mainly based on the one-electron oxidation of fluorescein by the cathodically produced oxidizing radicals followed by reduction of the formed semioxidized fluorescein by hot or hydrated electrons back to the original oxidation state which finally emits light.

Electrochemiluminescence (ECL) of aromatic Tb(III) chelates at thin insulating film-coated electrodes provides a means for extremely sensitive detection of Tb(III) chelates and also of biologically interesting compounds if these chelates are used as labels in bioaffinity assays. The suitability of silicon electrodes coated with thermally grown silicon dioxide film as disposable working electrodes in sensitive time-resolved ECL measurements is demonstrated, and a rapid electrochemiluminoimmunoassay (ECLIA) of human C-reactive protein (hCRP) is described. Tb(III) chelate labels can be detected almost down to picomolar level, and the calibration curve of these labels covers more than 6 orders of magnitude of chelate concentration. The calibration curve of the present immunometric hCRP assay was found to be linear over a wide range, approximately 4 orders of magnitude of hCRP concentration, the detection limit of the protein being 0.3 ng mL(-1) (mean background + 2SD) on CV values of about 10-30%, depending on the immunoassay incubation time. In the ECLIA measurements, different incubation times were tested from 15 min (giving above-mentioned performance) to as short as only 2 min, which still gave successful results with approximately 20,000 times better detection limit levels than traditional commercial assay methods. During the ECLIA process, also the Si electrode surface morphology was also investigated by atomic force microscope monitoring.

Hot electrons can be injected from conductor/insulator/electrolyte (C/I/E) junctions into an aqueous electrolyte solution by cathodic pulse-polarization of the electrode. Injected hot electrons induce electrogenerated chemiluminescence of various luminophores including coumarins in fully aqueous solutions. This is based on the tunnel emission of hot electrons into aqueous electrolyte solution, which can result in the generation of hydrated electrons as reducing mediators. These tunnel-emitted electrons allow also the production of highly oxidizing radicals from added precursors. This work shows that coumarin derivatives are suitable candidates as ECL labels for bioaffinity assays or other analytical applications in which detection is based on the ECL of pulse-polarized C/I/E tunnel-emission electrodes in fully aqueous solutions. The mechanisms of the ECL of coumarins are discussed and the analytical applicability of the ECL of three coumarin derivatives is studied.

Ruthenium(II) tris(2,2′-bipyridine) chelate shows chemiluminescence (CL) both during dissolution of metallic aluminium in alkaline conditions, and during dissolution of magnesium metal in acidic conditions. The presence of peroxodisulfate ions strongly enhances the CL. Magnesium system provides considerably better detectability of the present chelate giving linear calibration plot spanning over many orders of magnitude of concentration down to subnanomolar concentration levels. The possible primary species generated and luminescence mechanisms are shortly discussed.

Hot electrons can be injected from conductor/insulator/electrolyte (C/I/E) junctions into an aqueous electrolyte solution. Injected hot electrons induce electrogenerated chemiluminescence (ECL) of various luminophores in fully aqueous solutions. Such ECL gives the basis of electrochemiluminoimmunoassays and DNA-probe assays where different luminophores can be used as electrochemiluminescent labels. This work shows that SYBR® Green I is suitable as an ECL label in detection methods based on C/I/E tunnel-emission electrodes such as oxide-coated aluminium, magnesium and silicon electrodes.

For the first time, a blue and red photoluminescence of [60]fullerene in its aqueous sample solution is reported. The water solubility of [60]fullerene is achieved by its water-soluble bicapped complex with γ-cyclodextrin. Upon UV excitation at 320 nm, this complex produces intense blue and weak red photoluminescence at 440 and 710 nm which are assigned to the radiative 2 t 1g (LUMO+1)→4 h u (HOMO) and 5t 1u (LUMO)→4 h u (HOMO) transitions of [60]fullerene, respectively. Further, the contribution demonstrates that the blue photoluminescence can be used for a selective probing of [60]fullerene in its mixtures with higher fullerenes even at trace level.

A bicapped [60]fullerene–γ-cyclodextrin complex has been prepared in an aqueous boric acid–caesium borate buffer. It is shown that this water-soluble complex generates an anomalous [60]fullerene specific blue–green emission at the cathodically polarized aluminium/aluminium oxide interface but not at the zirconium/zirconium oxide and tantalum/tantalum oxide interfaces. A mechanistic pathway for the formation of this emission is proposed: the cathodic polarization of the aluminium/aluminium oxide interface injects a hot electron from the conduction band edge of the aluminium oxide to the higher acceptor levels 2t2g and/or 4ag of [60]fullerene. The relaxation of these acceptor levels to the 5t1u level (LUMO) of [60]fullerene initiates the intense emission peaking at around 445 nm. Further, use of this cathodic electroluminescence (EL) for the recognition of [60]fullerene from its mixtures with higher fullerenes is proposed.

A study has been conducted to explore the inter-lanthanide(III) energy interactions in self-assembled dimeric heterodinuclear 1 -Tb(III)–Ln(III)′- 1 chelates (Ln(III)′ = Dy(III), Nd(III), Y(III), Yb(III)) ( 1 = 2,6-bis[ N , N -bis(carboxymethyl)-aminomethyl]-4-benzoylphenol]) and their effects on the electrochemically initiated radiative 5 D 4 → 7 F j transitions of Tb(III) of these dinuclear chelates at a cathodically pulse-polarized oxide-covered aluminium electrode. From the selected heterodinuclear Tb(III)–Ln(III)′ edifices, (i) the Tb(III)–Dy(III) edifice initiates the exceptionally short-lived 5 D 4 → 7 F j transitions of Tb(III) with k i ≈ 9.0 ms −1 mainly due to the competitive inter-lanthanide(III) Tb(III)–Dy(III) 5 D 4 → 4 F 9/2 back energy transfer, (ii) likewise, the Tb(III)–Y(III) edifice initiates the 5 D 4 → 7 F j transitions of Tb(III) with k i ≈ 1.4 ms −1 caused by the absence of any Y(III)-specific energy level capable of acting as the acceptor level for the ligand-specific 3 ππ * and/or Tb(III)-specific 5 D 4 relaxations and, finally, (iii) the Tb(III)–Nd(III) and Tb(III)–Yb(III) edifices do not generate these radiative Tb(III) specific transitions; in the case of Ln(III)′ = Nd(III), this inhibition originates from the preferential ligand-specific 3 ππ * relaxation to the Nd(III)-specific acceptor levels while in the case of Ln(III)′ = Yb(III), this 3 ππ * relaxation seems to occur directly to the excited 2 F 5/2 state of Yb(III) by the ET intermediate.

Cathodic pulse polarisation of oxide-covered aluminum electrodes in Tl(I) solutions induce strong Tl(I)-specific electrogenerated luminescence (EL). It is mainly regarded as electrochemiluminescence, induced by one-electron oxidation of cathodically produced thallium atoms in the close vicinity of the electrode surface, but solid state electroluminescence is also produced, especially, with thicker oxide films. Depending on the EL system applied, the oxidant in response of the excitation event is either a cathodically produced hydroxyl or sulfate radical, or an F + -centre of the thin oxide film, and the source of short-lived thallium atom colloids is a reduction of Tl(I) ions by tunnel-emitted hot electrons and/or cathodically generated hydrated electrons. The present method allows the detection of Tl(I) ions below nanomolar concentration level and provides linear log-log calibration graphs spanning several orders of magnitude of concentration of Tl(I).

The near-infrared electrogenerated chemiluminescence (IR ECL) of Yb(III) chelates at a pulse-polarized oxide-covered aluminium cathode is described for the first time. The observed 2 F 5/2 → 2 F 7/2 radiative transition of Yb(III) is the lowest-energy ECL in aqueous solution reported to date. Also, a proposed explanation for the excitation and emission processes of this near-IR ECL of Yb(III) chelates has been given. The phenomenon offers many new application possibilities for analytical purposes, for example, a new point of view for wavelength discrimination.

Oxide-covered aluminium electrodes as well as other tunnel emission electrodes allow various label molecules having very different redox and optical properties to be excited cathodically. Low detection limits are obtained and the linear calibration concentration range of the labels spans 5 or 6 orders of magnitude. The lowest detection limits are obtained with Tb(III) chelates which can be detected down to picomolar levels in aqueous solution using time-resolved measurement techniques. Luminophores, such as, 9-fluorenylmethyl chloroformate, derivatives of fluorescein and its analogues, aromatic lanthanide(III) chelates, various coumarins and porphyrins can be used as labels emitting in different spectral regions. The extraordinary analytical power of the tunnel emission electrodes lies in the possibility of simultaneously exciting several different labels emitting either in the UV, visible or NIR range and luminescence lifetimes varying from the ns to the ms range. Therefore, wavelength or time discrimination or their combination can be exploited in separation of the electrochemiluminescence signals from different labels.

Dissolution of X-ray irradiated sodium chloride or additively coloured potassium chloride induces generation of hydrated electrons which produce thallium(I)-specific chemiluminescence in the presence of thallium(I) ions. Such a luminescence is also called extrinsic lyoluminescence (ELL) of X-ray irradiation coloured sodium chloride, or additively coloured potassium chloride. The present ELL is considered chemiluminescence induced by dissolution-produced strong reducing and oxidising agents, i.e. hydrated electrons, surface-bound and only partially hydrated hole centres, and hydroxyl or sulphate radicals (in the case of additively coloured potassium chloride dissolved in solution containing peroxodisulphate ions). Dichlorothallate(I) (Tl(I)Cl − 2 ) was the main emitter in the ELL processes at about 430 nm. The reduction-initiated excitation pathway of TlCl − 2 involves a colloidal thallium atom surrounded by chloride anions (Tl(O):2Cl − ) while in the less important oxidation-initiated excitation pathway the precursor of excited Tl(I)Cl − 2 is transiently existing Tl(II)Cl − 2 produced by dissolution-uncovered hole centres (or sulphate radicals). Both of the lyoluminescence procedures allow Tl(I) to be detected below nanomolar concentrations, yielding linear log–log calibration plots spanning several orders of magnitude of concentration.

Energy transfer between aluminium oxide F-center and lanthanide cations at an oxide-covered aluminium electrode during the cathodic pulse-polarization of the electrode is investigated by means of Stern-Volmer luminescence quenching kinetics. Terbium III -specific extrinsic luminescence is observed while some other lanthanides are observed to quench the F-center luminescence. Different quenching efficiencies of the lanthanides are discussed to be dependent on the different energy acceptor characteristics of the tri- or divalent lanthanides.

Luminol shows strong chemiluminescence with an emission maximum at ∼430 nm in the presence of sulfate radicals. Sulfate radicals were produced by the dissolution of UV-irradiated potassium peroxodisulfate powder in aqueous luminol solutions. The UV irradiation at 6.7 eV produces a solid solution of sulfate radical in potassium peroxodisulfate by rupturing −O−O− bonds, as in solution, but now the solid solution is stable in a time scale of years in dryness. In the present system, luminol chemiluminescence is produced via several parallel pathways having a common triggering step, one-electron oxidation of luminol monoanion by sulfate or hydroxyl radical. Present chemiluminescence allows sensitive luminol detection from picomolar to micromolar level with a linear response over 5 orders of magnitude, after which luminescence is too strong for single-photon counting. The high sensitivity of luminol detection allows us to propose extrinsic lyoluminescence of potassium peroxodisulfate as a new and simple method ...

1-Aminonaphthalene-4-sulfonate (ANS)-specific extrinsic lyoluminescence (LL) of X-ray irradiated sodium chloride is observed at 425 nm when the irradiated salt is dissolved in an aqueous solution of ANS. The paper discusses, in detail, the mechanism of the ANS-specific LL and its analytical applicability. Also, the intrinsic LL of X-ray irradiated sodium chloride is studied. Hydrated electron as well as hole scavenger experiments support the proposal that in the case of the intrinsic LL of X-ray irradiated sodium chloride, trapped electrons (mainly F-center electrons) are released and hydrated whereas trapped holes (V-centers) remain surface-bound and are only partially hydrated before recombination occurs. These hydrated electrons and dissolving solid surface-bound hole centers, which are probably only partially hydrated, are able to act as reducing and oxidizing agents, respectively, in the luminophore oxidation-initiated reductive excitation pathway of ANS. Solution additives (halides and pseudohalides) show that in the chemiluminescence processes in question, oxidizing agents will follow the Marcus theory of electron transfer reactions. The LL method described allows the determination of ANS in the concentration range ≈10 −11 − 10 −7 M. This suggests that aminonaphthalene derivatives can be used as label molecules in high sensitivity lyoluminobioaffinity assays.

Hot electron injection into aqueous electrolyte solutions from metal/insulator/metal/electrolyte and metal/insulator/electrolyte tunnel junctions is considered and the possibility of an electrochemical generation of hydrated electrons is discussed. The hot electron-induced UV electrochemiluminescence of (9-fluorenyl)methanol was used to demonstrate the presence of highly energetic transient species in aqueous solution at several metal/insulator/electrolyte hot electron tunnel emitters. These transient species cannot be produced electrochemically in fully aqueous solutions at any active metal electrodes. A detailed mechanism for the present electrochemiluminescence is suggested.

Electrogenerated luminescence of lanthanides is reviewed with emphasis on the electrochemiluminescence (ECL) of lanthanide chelates. Main application area of lanthanide chelates in this field is their use as electrochemiluminescent labels in bioaffinity assays such as in immunoassays or DNA probe assays. With lanthanide chelates as labels, hot electron-induced ECL at thin insulating film-coated cathodes outperforms ECL based on traditional electrochemistry at active metal electrodes. ECL excitation of lanthanide(III) chelates occurs normally by ligand-sensitized mechanisms wherein the ligand is first excited by redox reactions followed by energy transfer from ligand to the central ion, which finally emits by f–f transitions. Luminescent lanthanide ions can be excited at oxide-coated metal electrodes when these ions act as luminescence centers in the oxide film and/or at the oxide/electrolyte interface or as solvated in the close vicinity of the electrode surface. These ions typically show high field-induced solid-state electroluminescence when embedded inside of the oxide films and ECL at the surface of the electrode or in solution close to the electrode surface. These lanthanide-doped oxide films can be fabricated either by anodization of certain lanthanide-doped valve metals or from pure valve metals by anodization in lanthanide ion-containing anodization bath preferably with AC voltages. Some lanthanide ions can be electrically excited also in strongly acidic sulfuric acid solutions at platinum electrodes with mechanisms not known with certainty.

Strong electrogenerated chemiluminescence (ECL) of fluorescein is generated during cathodic pulse polarization of oxide-covered aluminum electrodes and the resulting decay of emission is so sluggish that time-resolved detection of fluorescein is feasible. The present ECL in aqueous solution is based on the tunnel emission of hot electrons into the aqueous electrolyte solution, which probably results in the generation of hydrated electrons and hydroxyl radicals acting as redox mediators. The successive one-electron redox steps with the primary radicals result in fluorescein in its lowest excited singlet state. The method allows the detection of fluorescein (or its derivatives containing usable linking groups to biomolecules) over several orders of magnitude of concentration with detection limits well below nanomolar concentration level. The detection limits can still be lowered, e.g., by addition of azide or bromide ions as coreactants. The results suggest that the derivatives of fluorescein, such as fluorescein isothiocyanate (FITC), can be detected by time-resolved measurements and thus be efficiently used as electrochemiluminescent labels in bioaffinity assays.

A pulse-polarization of an oxide-covered aluminium cathode in an aerated aqueous buffer containing micelle-incorporated [60]fullerene and [70]fullerene generates fullerene specific emissions at λ 440 nm and λ 425 nm which respond to the fullerene concentrations down to around 10 -7 M.

TbIII chelates containing aromatic moieties show sonoluminescence in aqueous solutions during the sonolysis of water. The observed 5D4→7FJ transitions of TbIII are due to the excitation of ligand, followed by an intramolecular energy transfer from the ligand to the central ion, which finally emits. No sonoluminescence of hydrated or EDTA-chelated TbIII ion could be observed. Ligand excitation can be based either on an energy transfer from the intrinsic emission centres of the sonolysis of water to the aromatic ligand, or on redox reactions between the ligand and hydroxyl radicals and hydrogen atoms produced by the sonolysis of water. Experimental results give greater support to the latter, chemiluminescent, excitation pathway.

An instrumentally simple on-column time-resolved luminescence capillary electrophoresis (CE) detector for determining and characterizing migrated europium(III) chelates on the basis of their long-lived 5D0→7F-multiplet transitions has been constructed. In addition to the background fluorescence arising from the cell walls, this time-resolved luminescence method of measurement also allows an efficient discrimination of the analyte emission against the short-lived background fluorescence caused by possible fluorescent impurities in the electrophoresis buffer; this should provide a feasible means of constructing a CE detector for the trace analysis of europium(III) chelates and also of samples of biological interest labelled with europium(III) chelates. If supplied additionally with a device for determining the excited-state lifetimes of separated europium(III) chelates, this time-resolved luminescence detector should make possible the peak identification of migrated europium(III) chelates.

Some of the luminescent aromatic Tb(III) chelates can be excited at oxide-covered magnesium and n-ZnO:Al/MgO composite electrodes by cathodic pulse polarization in aqueous solution. This is based on the cathodic injection of hot electrons into the aqueous electrolyte solution and successive redox reactions in one-electron steps resulting in the excited states of the chelates. Due to the relatively long luminescence lifetime of multidentate Tb(III) chelates, these chelates can be very sensitively detected by time-resolved electrochemiluminescence (TR-ECL) measurements using the present working electrodes. Thus, metal or highly doped semiconductor electrodes coated by a thin MgO film lend themselves as nontransparent or in some cases, even optically transparent working electrodes for generation of free radicals and cathodic ECL in aqueous solution. The results suggest that also other even more efficient optically transparent composite tunnel emission electrodes than the present n-ZnO:Al/MgO electrodes could be constructed by coating n-ZnO:Al glass electrodes with other wide band gap insulating oxides.