Surface enhanced fluorescence spectroscopy

Robelek R, Stefani FD, Knoll W (2006) Oligonucleotide hybridization monitored by surface plasmon enhanced fluorescence spectroscopy with bio-conjugated core/shell quantum dots. Influence of luminescence blinking. Phys Status Solidi A-Appl Mater Sci 203 3468-3475... 

The extremely small cross sections for conventional Raman scattering, typically 10 111 to 10-25 cm2/molecule has in the past precluded the use of this technique for single-molecule detection and identification. Until recently, optical trace detection with single molecule sensitivity has been achieved mainly using laser-induced fluorescence [14], The fluorescence method provides ultrahigh sensitivity, but the amount of molecular information, particularly at room temperature, is very limited. Therefore, about 50 years after the discovery of the Raman effect, the novel phenomenon of dramatic Raman signal enhancement from molecules assembled on metallic nanostructures, known as surface-enhanced Raman spectroscopy or SERS, has led to ultrasensitive single-molecule detection. 

Alternatively, various analytical methods based on SPR phenomenon have been developed, including surface plasmon field-enhanced Raman scattering (SERS) [7], surface plasmon field-enhanced fluorescence spectroscopy (SPFS) [8-11], surface enhanced second harmonic generation (SHG) [12], surface enhanced infrared absorption (SEIRA) [13], surface plasmon field-enhanced diffraction spectroscopy (SPDS) [14-18], Most of these methods take advantage of the greatly enhanced electromagnetic field of surface plasmon waves, in order to excite a chromophoric molecule, e.g., a Raman molecule or a fluorescent dye. Therefore, a better sensitivity is expected. 

Surface Plasmon Field-Enhanced Fluorescence Spectroscopy... 

Chu L-Q, Forch R, Knoll W (2007) Surface-plasmon-enhanced fluorescence spectroscopy for DNA detection using fluorescently labeled PNA as DNA Indicator . Angew Chem Int Ed 46 4944-4947... 

Liebermann, T., and Knoll, W. (2000). Surface-plasmon field-enhanced fluorescence spectroscopy. Colloid and Surfaces A. Physicochemical and Engineering Aspects 171 115-130. 

Constantino, C. J. L., Aroca, R. F., Mendonca, C. R., Mello, S. V., Balogh, D. T., and Oliveira, O. N. (2001). Surface enhanced fluorescence and Raman imaging of Langmuir-Blodgett azopolymer films. Spectrochimica Acta, Part A Molecular and Biomolecular Spectroscopy 57A 281-289. 

Ekgasit, S., Thammacharoen, C., Yu, F., and Knoll, W. (2004). Evanescent Field in Surface Plasmon Resonance and Surface Plasmon Field-Enhanced Fluorescence Spectroscopies./Ina/. Chem. 76 2210-2219. 

Near-infrared surface-enhanced Raman spectroscopy Some of the major irritants in Raman measurements are sample fluorescence and photochemistry. However, with the help of Fourier transform (FT) Raman instruments, near-infrared (near-IR) Raman spectroscopy has become an excellent technique for eliminating sample fluorescence and photochemistry in Raman measurements. As demonstrated recently, the range of near-IR Raman techniques can be extended to include near-IR SERS. Near-IR SERS reduces the magnitude of the fluorescence problem because near-IR excitation eliminates most sources of luminescence. Potential applications of near-IR SERS are in environmental monitoring and ultrasensitive detection of highly luminescent molecules [11]. 

Abstract Optical detection continues to dominate detection methods in microfluidics due to its noninvasive nature, easy coupling, rapid response, and high sensitivity. In this review, we summarize two aspects of recent developments in optical detection methods on microfluidic chips. The first aspect is free-space (off-chip) detection on the microchip, in which the conventional absorption, fluorescence, chemiluminescence, surface plasmon resonance, and surface enhanced Raman spectroscopies are involved. The second aspect is the optofluidic (inside-chip) detection. Various miniaturized optical components integrated on the microfluidic chip, such as waveguide, microlens, laser, and detectors are outlined. 

Raman scattering spectroelectrochemical investigations can be carried out for polymers deposited at practically any electrode used in electrochemical investigations (platinum, ITO, glassy carbon and others). In addition, successful application of SERS (surface enhanced Raman spectroscopy) for polypyrrole [124] and polythiophene [117] allows for Raman spectroscopic studies of extremely thin layers of conjugated polymers. Raman spectra of conjugated polymers are sometimes obscured by strong fluorescence. This problem can be effectively resolved by the... 

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