Electrochemiluminescence

Last updated

Electrochemiluminescence or electrogenerated chemiluminescence (ECL) is a kind of luminescence produced during electrochemical reactions in solutions. In electrogenerated chemiluminescence, electrochemically generated intermediates undergo a highly exergonic reaction to produce an electronically excited state that then emits light upon relaxation to a lower-level state. This wavelength of the emitted photon of light corresponds to the energy gap between these two states. [1] [2] ECL excitation can be caused by energetic electron transfer (redox) reactions of electrogenerated species. Such luminescence excitation is a form of chemiluminescence where one/all reactants are produced electrochemically on the electrodes. [3]

Contents

ECL is usually observed during application of potential (several volts) to electrodes of electrochemical cell that contains solution of luminescent species (polycyclic aromatic hydrocarbons, metal complexes, quantum dots or nanoparticles [4] ) in aprotic organic solvent (ECL composition). In organic solvents both oxidized and reduced forms of luminescent species can be produced at different electrodes simultaneously or at a single one by sweeping its potential between oxidation and reduction. The excitation energy is obtained from recombination of oxidized and reduced species.

In aqueous medium, which is mostly used for analytical applications, simultaneous oxidation and reduction of luminescent species is difficult to achieve due to electrochemical splitting of water itself so the ECL reaction with the coreactants is used. In the latter case luminescent species are oxidized at the electrode together with the coreactant which gives a strong reducing agent after some chemical transformations (the oxidative reduction mechanism).

Schematic representation of the "oxidative-reduction" heterogeneous ECL mechanisms for the couple Ru(bpy)3 /TPrA. The ECL generation is obtained only by TPrA oxidation and involving the homogeneous reaction of the radical cation (TPrAdeg ), as proposed by Bard. The luminophore in the excited state Ru * relaxes to the ground state and emits photon. Inset image of electrode surface during an ECL emission Heterogeneous ECL mechanism .tif
Schematic representation of the "oxidative-reduction" heterogeneous ECL mechanisms for the couple Ru(bpy)3 /TPrA. The ECL generation is obtained only by TPrA oxidation and involving the homogeneous reaction of the radical cation (TPrA° ), as proposed by Bard. The luminophore in the excited state Ru * relaxes to the ground state and emits photon. Inset image of electrode surface during an ECL emission

Applications

ECL proved to be very useful in analytical applications as a highly sensitive and selective method. [7] It combines analytical advantages of chemiluminescent analysis (absence of background optical signal) with ease of reaction control by applying electrode potential. As an analytical technique it presents outstanding advantages over other common analytical methods due to its versatility, simplified optical setup compared with photoluminescence (PL), and good temporal and spatial control compared with chemiluminescence (CL). Enhanced selectivity of ECL analysis is reached by variation of electrode potential thus controlling species that are oxidized/reduced at the electrode and take part in ECL reaction [8] (see electrochemical analysis).

It generally uses Ruthenium complexes, especially [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) which releases a photon at ~620 nm regenerating with TPrA (Tripropylamine) in liquid phase or liquid–solid interface. It can be used as monolayer immobilized on an electrode surface (made e.g. of nafion, or special thin films made by Langmuir–Blogett technique or self-assembly technique) or as a coreactant or more commonly as a tag and used in HPLC, Ru tagged antibody based immunoassays, Ru Tagged DNA probes for PCR etc., NADH or H2O2 generation based biosensors, oxalate and organic amine detection and many other applications and can be detected from picomolar sensitivity to dynamic range of more than six orders of magnitude. Photon detection is done with photomultiplier tubes (PMT) or silicon photodiode or gold coated fiber-optic sensors. The importance of ECL techniques detection for bio-related applications has been well established. [9] ECL is heavily used commercially for many clinical lab applications. [10] [11] [12]

See also

Related Research Articles

<span class="mw-page-title-main">Ruthenium</span> Chemical element with atomic number 44 (Ru)

Ruthenium is a chemical element; it has symbol Ru and atomic number 44. It is a rare transition metal belonging to the platinum group of the periodic table. Like the other metals of the platinum group, ruthenium is unreactive to most chemicals. Karl Ernst Claus, a Russian scientist of Baltic-German ancestry, discovered the element in 1844 at Kazan State University and named it in honor of Russia, using the Latin name Ruthenia. Ruthenium is usually found as a minor component of platinum ores; the annual production has risen from about 19 tonnes in 2009 to some 35.5 tonnes in 2017. Most ruthenium produced is used in wear-resistant electrical contacts and thick-film resistors. A minor application for ruthenium is in platinum alloys and as a chemistry catalyst. A new application of ruthenium is as the capping layer for extreme ultraviolet photomasks. Ruthenium is generally found in ores with the other platinum group metals in the Ural Mountains and in North and South America. Small but commercially important quantities are also found in pentlandite extracted from Sudbury, Ontario, and in pyroxenite deposits in South Africa.

<span class="mw-page-title-main">Luminescence</span> Spontaneous emission of light by a substance

Luminescence is a spontaneous emission of radiation from an electronically or vibrationally excited species not in thermal equilibrium with its environment.  A luminescent object emits cold light in contrast to incandescence, where an object only emits light after heating. Generally, the emission of light is due to the movement of electrons between different energy levels within an atom after excitation by external factors. However, the exact mechanism of light emission in vibrationally excited species is unknown.

<span class="mw-page-title-main">Chemiluminescence</span> Emission of light as a result of a chemical reaction

Chemiluminescence is the emission of light (luminescence) as the result of a chemical reaction, i.e. a chemical reaction results in a flash or glow of light. A standard example of chemiluminescence in the laboratory setting is the luminol test. Here, blood is indicated by luminescence upon contact with iron in hemoglobin. When chemiluminescence takes place in living organisms, the phenomenon is called bioluminescence. A light stick emits light by chemiluminescence.

A biosensor is an analytical device, used for the detection of a chemical substance, that combines a biological component with a physicochemical detector. The sensitive biological element, e.g. tissue, microorganisms, organelles, cell receptors, enzymes, antibodies, nucleic acids, etc., is a biologically derived material or biomimetic component that interacts with, binds with, or recognizes the analyte under study. The biologically sensitive elements can also be created by biological engineering. The transducer or the detector element, which transforms one signal into another one, works in a physicochemical way: optical, piezoelectric, electrochemical, electrochemiluminescence etc., resulting from the interaction of the analyte with the biological element, to easily measure and quantify. The biosensor reader device connects with the associated electronics or signal processors that are primarily responsible for the display of the results in a user-friendly way. This sometimes accounts for the most expensive part of the sensor device, however it is possible to generate a user friendly display that includes transducer and sensitive element. The readers are usually custom-designed and manufactured to suit the different working principles of biosensors.

<span class="mw-page-title-main">Polypyridine complex</span>

Polypyridine complexes are coordination complexes containing polypyridine ligands, such as 2,2'-bipyridine, 1,10-phenanthroline, or 2,2';6'2"-terpyridine.

<span class="mw-page-title-main">Immunoassay</span> Biochemical test for a protein or other molecule using an antibody

An immunoassay (IA) is a biochemical test that measures the presence or concentration of a macromolecule or a small molecule in a solution through the use of an antibody (usually) or an antigen (sometimes). The molecule detected by the immunoassay is often referred to as an "analyte" and is in many cases a protein, although it may be other kinds of molecules, of different sizes and types, as long as the proper antibodies that have the required properties for the assay are developed. Analytes in biological liquids such as serum or urine are frequently measured using immunoassays for medical and research purposes.

Organopalladium chemistry is a branch of organometallic chemistry that deals with organic palladium compounds and their reactions. Palladium is often used as a catalyst in the reduction of alkenes and alkynes with hydrogen. This process involves the formation of a palladium-carbon covalent bond. Palladium is also prominent in carbon-carbon coupling reactions, as demonstrated in tandem reactions.

<span class="mw-page-title-main">Chronoamperometry</span> Analytical method in electrochemistry

In electrochemistry, chronoamperometry is an analytical technique in which the electric potential of the working electrode is stepped and the resulting current from faradaic processes occurring at the electrode is monitored as a function of time. The functional relationship between current response and time is measured after applying single or double potential step to the working electrode of the electrochemical system. Limited information about the identity of the electrolyzed species can be obtained from the ratio of the peak oxidation current versus the peak reduction current. However, as with all pulsed techniques, chronoamperometry generates high charging currents, which decay exponentially with time as any RC circuit. The Faradaic current - which is due to electron transfer events and is most often the current component of interest - decays as described in the Cottrell equation. In most electrochemical cells, this decay is much slower than the charging decay-cells with no supporting electrolyte are notable exceptions. Most commonly a three-electrode system is used. Since the current is integrated over relatively longer time intervals, chronoamperometry gives a better signal-to-noise ratio in comparison to other amperometric techniques.

<span class="mw-page-title-main">2,2′-Bipyridine</span> Chemical compound

2,2′-Bipyridine (bipy or bpy, pronounced ) is an organic compound with the formula C10H8N2. This colorless solid is an important isomer of the bipyridine family. It is a bidentate chelating ligand, forming complexes with many transition metals. Ruthenium and platinum complexes of bipy exhibit intense luminescence, which may have practical applications.

<span class="mw-page-title-main">Tris(bipyridine)ruthenium(II) chloride</span> Chemical compound

Tris(bipyridine)ruthenium(II) chloride is the chloride salt coordination complex with the formula [Ru(bpy)3]Cl2. This polypyridine complex is a red crystalline salt obtained as the hexahydrate, although all of the properties of interest are in the cation [Ru(bpy)3]2+, which has received much attention because of its distinctive optical properties. The chlorides can be replaced with other anions, such as PF6−.

<span class="mw-page-title-main">Horseradish peroxidase</span> Chemical compound and enzyme

The enzyme horseradish peroxidase (HRP), found in the roots of horseradish, is used extensively in biochemistry applications. It is a metalloenzyme with many isoforms, of which the most studied type is C. It catalyzes the oxidation of various organic substrates by hydrogen peroxide.

In electrochemistry, the working electrode is the electrode in an electrochemical system on which the reaction of interest is occurring. The working electrode is often used in conjunction with an auxiliary electrode, and a reference electrode in a three-electrode system. Depending on whether the reaction on the electrode is a reduction or an oxidation, the working electrode is called cathodic or anodic, respectively. Common working electrodes can consist of materials ranging from inert metals such as gold or platinum, to inert carbon such as glassy carbon, boron-doped diamond or pyrolytic carbon, and mercury drop and film electrodes. Chemically modified electrodes are employed for the analysis of both organic and inorganic samples.

<span class="mw-page-title-main">Electrocatalyst</span> Catalyst participating in electrochemical reactions

An electrocatalyst is a catalyst that participates in electrochemical reactions. Electrocatalysts are a specific form of catalysts that function at electrode surfaces or, most commonly, may be the electrode surface itself. An electrocatalyst can be heterogeneous such as a platinized electrode. Homogeneous electrocatalysts, which are soluble, assist in transferring electrons between the electrode and reactants, and/or facilitate an intermediate chemical transformation described by an overall half reaction. Major challenges in electrocatalysts focus on fuel cells.

<span class="mw-page-title-main">Dichlorotris(triphenylphosphine)ruthenium(II)</span> Chemical compound

Dichlorotris(triphenylphosphine)ruthenium(II) is a coordination complex of ruthenium. It is a chocolate brown solid that is soluble in organic solvents such as benzene. The compound is used as a precursor to other complexes including those used in homogeneous catalysis.

Water oxidation is one of the half reactions of water splitting:

<span class="mw-page-title-main">Lesley Yellowlees</span> British chemist

Lesley Jane Yellowlees is a British inorganic chemist conducting research in Spectroelectrochemistry, Electron transfer reactions and Electron paramagnetic resonance (EPR) Spectroscopy. Yellowlees was also elected as the president of the Royal Society of Chemistry 2012–14 and was the first woman to hold that role.

<span class="mw-page-title-main">Photoredox catalysis</span>

Photoredox catalysis is a branch of photochemistry that uses single-electron transfer. Photoredox catalysts are generally drawn from three classes of materials: transition-metal complexes, organic dyes, and semiconductors. While organic photoredox catalysts were dominant throughout the 1990s and early 2000s, soluble transition-metal complexes are more commonly used today.

Photo-Induced Cross-Linking of Unmodified Proteins (PICUP) is a protein cross-linking method by visible light irradiation of a photocatalyst in the presence of an electron acceptor and the protein of interest. Irradiation results in a highly reactive protein radical that forms a covalent bond between the amino acid side chains of the proteins to be linked. Cross-linking methods developed prior to PICUP, including the use of physical, oxidative, and chemical cross-linkers, often require more time and result in protein byproducts. In addition, the cross-linked protein yield is very low due to the multifunctionality of the cross-linking reagents.

The Stahl oxidation is a copper-catalyzed aerobic oxidation of primary and secondary alcohols to aldehydes and ketones. Known for its high selectivity and mild reaction conditions, the Stahl oxidation offers several advantages over classical alcohol oxidations.

Transition metal complexes of 2,2'-bipyridine are coordination complexes containing one or more 2,2'-bipyridine ligands. Complexes have been described for all of the transition metals. Although few have any practical value, these complexes have been influential. 2,2'-Bipyridine is classified as a diimine ligand. Unlike the structures of pyridine complexes, the two rings in bipy are coplanar, which facilitates electron delocalization. As a consequence of this delocalization, bipy complexes often exhibit distinctive optical and redox properties.

References

  1. ↑ Forster RJ, Bertoncello P, Keyes TE (2009). "Electrogenerated Chemiluminescence". Annual Review of Analytical Chemistry. 2: 359–85. Bibcode:2009ARAC....2..359F. doi:10.1146/annurev-anchem-060908-155305. PMID   20636067.
  2. ↑ Valenti G, Fiorani A, Li H, Sojic N, Paolucci F (2016). "Essential Role of Electrode Materials in Electrochemiluminescence Applications". ChemElectroChem. 3 (12): 1990–1997. doi:10.1002/celc.201600602. hdl: 11585/591485 .
  3. ↑ Electrogenerated Chemiluminescence, Edited by Allen J. Bard, Marcel Dekker, Inc., 2004
  4. ↑ Valenti G, Rampazzo R, Bonacchi S, Petrizza L, Marcaccio M, Montalti M, Prodi L, Paolucci F (2016). "Variable Doping Induces Mechanism Swapping in Electrogenerated Chemiluminescence of Ru(bpy)32+ Core−Shell Silica Nanoparticles". J. Am. Chem. Soc. 138 (49): 15935–15942. Bibcode:2016JAChS.13815935V. doi:10.1021/jacs.6b08239. hdl: 11585/583548 . PMID   27960352.
  5. ↑ Miao W, Choi J, Bard A (2002). "Electrogenerated Chemiluminescence 69: The Tris(2,2′-bipyridine)ruthenium(II), (Ru(bpy)32+)/ Tri-n-propylamine (TPrA) System RevisitedsA New Route Involving TPrA•+ Cation Radicals". J. Am. Chem. Soc. 124 (48): 14478–14485. doi:10.1021/ja027532v. PMID   12452725.
  6. ↑ Valenti G, Zangheri M, Sansaloni S, Mirasoli M, Penicaud A, Roda A, Paolucci F (2015). "Transparent Carbon Nanotube Network for Efficient Electrochemiluminescence Devices". Chemistry: A European Journal. 21 (36): 12640–12645. doi:10.1002/chem.201501342. PMID   26150130.
  7. ↑ Zanut, A.; Fiorani, A.; Canola, S.; Saito, T.; Ziebart, N.; Rapino, S.; Rebeccani, S.; Barbon, A.; Irie, T.; Josel, H.; Negri, F.; Marcaccio, M.; Windfuhr, M.; Imai, K.; Valenti, G.; Paolucci, F. (2020). "Insights into the mechanism of coreactant electrochemiluminescence facilitating enhanced bioanalytical performance". Nat. Commun. 11 (1): 2668. Bibcode:2020NatCo..11.2668Z. doi: 10.1038/s41467-020-16476-2 . PMC   7260178 . PMID   32472057.
  8. ↑ Fähnrich, K.A.; Pravda, M.; Guilbault, G. G. (May 2001). "Recent applications of electrogenerated chemiluminescence in chemical analysis" (PDF). Talanta. 54 (4): 531–559. doi:10.1016/S0039-9140(01)00312-5. PMID   18968276.[ permanent dead link ]
  9. ↑ Miao, Wujian (2008). "Electrogenerated Chemiluminescence and Its Biorelated Applications". Chemical Reviews. 108 (7): 2506–2553. doi:10.1021/cr068083a. PMID   18505298.
  10. ↑ Lee, Won-Yong (1997). "Tris (2,2′-bipyridyl)ruthenium(II) electrogenerated chemiluminescence in analytical science". Microchimica Acta. 127 (1–2): 19–39. doi:10.1007/BF01243160.
  11. ↑ Wei, Hui; Wang, Erkang (2008-05-01). "Solid-state electrochemiluminescence of tris(2,2′-bipyridyl) ruthenium". TrAC Trends in Analytical Chemistry. 27 (5): 447–459. doi:10.1016/j.trac.2008.02.009.
  12. ↑ Wei, Hui; Wang, Erkang (2011-03-01). "Electrochemiluminescence of tris(2,2′-bipyridyl)ruthenium and its applications in bioanalysis: a review". Luminescence. 26 (2): 77–85. doi:10.1002/bio.1279. ISSN   1522-7243. PMID   21400654.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.