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Malicka, Joanna; Gryczyński, Ignacy; Fang, Jiyu; Kuśba, Józef; Lakowicz, Joseph R.

doi:10.1023/a:1021370111590

Cited by 69 publications

(57 citation statements)

References 17 publications

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“…The spectra are blue shifted at larger angles (62°) and red shifted at smaller angles (56°) compared to the central angle of 59°. This shift is not due to different local environments of 2-AP but rather to the intrinsic wavelength dispersion of SPCE.In earlier studies of fluorophores near metallic particles, 23,24 we found decreases in lifetimes as compared to fluorophores distant from the particles. Hence, we examined the lifetime for 2-AP (Figure 8).…”

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confidence: 50%

Ultraviolet Surface Plasmon-Coupled Emission Using Thin Aluminum Films

et al. 2004

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Surface plasmon-coupled emission (SPCE) is the directional radiation of light into a substrate due to excited fluorophores above a thin metal film. To date, SPCE has only been observed with visible wavelengths using silver or gold films. We now show that SPCE can be observed in the ultraviolet region of the spectrum using thin (20 nm) aluminum films. We observed directional emission in a quartz substrate from the DNA base analogue 2-aminopurine (2-AP). The SPCE radiation occurs within a narrow angle at 59° from the normal to the hemicylindrical prism. The excitation conditions precluded the creation of surface plasmons by the incident light. The directional emission at 59° is almost completely p-polarized, consistent with its origin from surface plasmons due to coupling of excited 2-AP with the aluminum. The emission spectra and lifetimes of the SPCE are those characteristic of 2-AP. Different emission wavelengths radiate at slightly different angles on the prism providing intrinsic spectral resolution from the aluminum film. These results indicate that SPCE can be used with numerous UV-absorbing fluorophores, suggesting biochemical applications with simultaneous surface plasmon resonance and SPCE binding assays.Surface plasmon resonance (SPR) is widely used for detection of bioaffinity reactions on surfaces. [1][2][3] Surface plasmons are oscillating electrical charges on a metallic surface. When a thin metal film is illuminated through a glass prism, and the angle of incidence is appropriate, the surface plasmons in resonance with the incident light occur at the metal-air or water interface. This results in strong absorption, which is measured as a decrease of reflectivity. The SPR angle is sensitive to the refractive index of the sample above the metal, distal from the glass prism. The origin of this sensitivity is the evanescent field from the plasmons, which penetrates approximately λ/3 into the sample.In several recent reports we described a related phenomenon, surface plasmon-coupled emission (SPCE). 4,5 We found that excited fluorophores near a thin metal surface can couple with the surface plasmons, resulting in directional radiation into the glass substrate. The spectral properties of the radiation were found to be essentially identical to those of the fluorophore, except for a highly p-polarized emission, too large to be due to optical photoselection. The angular dependence of the radiation, as well as the p-polarization, are consistent with radiating surface plasmons, the reverse process of surface plasmon absorption.Our previous studies of SPCE used thin silver 5-7 or gold 8 surfaces. This choice of metals restricts the selection of fluorophores to those absorbing and emitting at visible or longer wavelengths. However, many widely used fluorophores absorb or emit at ultraviolet wavelengths. We now report that SPCE at UV wavelengths can be observed using thin *To whom correspondence should be addressed: lakowicz@cfs.umbi.umd.edu. NIH Public Access MATERIALS AND METHODS Sample PreparationQuar...

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Ultraviolet Surface Plasmon-Coupled Emission Using Thin Aluminum Films

et al. 2004

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“…Silver nanostructures, used in recent studies for metal-enhanced fluorescence, 13,14,[17][18][19][20][21][22][23][24][25][26]29,34 show blinking that is dependent on both the type of structure studied and irradiance of the illumination source. We typically observed that silver fractal-like structures could readily be made luminescent with irradiances of 30 W/cm 2 or more, as compared to silver island films, which required at least a 3-5-fold increase, >100 W/cm 2 .…”

Section: Discussionmentioning

confidence: 99%

“…The favorable effects produced by close proximity fluorophores to metallic nanostructures includes increased quantum yields and reduced lifetimes, 13,14,17,18 increased fluorophore photostability, 13,14,19,20 enhanced multiphoton excitation, 21,22 and modified rates of energy transfer. [23][24][25] These interactions have been described as due to changes in the photonic mode density, PMD, around the fluorophore,26 and are considered to be through-space as compared to SERS, which is widely thought to be a contact interaction.27 , 28 Such effects are not normally observed in bulk media, where the photonic mode density is not that different from a vacuum, but can be changed by close proximity silver nanostructures. 26 We have recently referred to this phenomenon as radiative decay engineering (RDE), 13, 14 , 26 because we were primarily interested in changes in the radiative decay rate, which results in more detectable photons from fluorophores, but occasionally we use the term "metal-enhanced fluorescence" which additionally accounts for another favorable metal-induced effect, namely increased rates of excitation.…”

Section: Introductionmentioning

confidence: 99%

Luminescent Blinking from Silver Nanostructures.

Geddes¹,

Parfenov²,

Gryczyński³

et al. 2003

ChemInform

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Silver nanostructures deposited on glass showed luminescent blinking when excited at a high 442 nm irradiance. The irradiance required to photoactivate the silver, was dependent on the nature of the silver nanostructures. Silver fractal-like structures were found to be highly emissive, requiring only ≈30 W/cm 2 for photoactivation as compared to silver island films and spin-coated silver colloids, which required a significantly higher irradiance, > 100 W/cm 2 , to observe similar luminescent emission. In contrast to our recent findings for gold colloids, foci with different color blinking were also observed, with an increase in luminescence intensity as a function of time. We place these findings in context with recent work from our laboratory which employs these silver nanostructures for applications in metal-enhanced fluorescence, a relatively new phenomenon in fluorescence, whereby metallic particles, colloids, and fractal-like structures can modify the intrinsic radiative decay rate of close proximity fluorescent species. These effects are a consequence of localized changes in photonic mode density around the fluorophores, and we can now report are typically observed at significantly lower illumination intensities as compared to those required to photoactivate silver. Subsequently, our findings strongly suggest that the enhanced fluorescence emission of fluorophores positioned in close proximity to metallic silver structures is not due to either intrinsic silver blinking, or indeed the silver luminescence pumping the fluorophore. Further, the intrinsic luminescence properties of silver reported here, suggest a new class of luminescence probes and labels.

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“…Under appropriate conditions proximity of fluorophores to metallic silver particles can result in increased quantum yields, increased photostability, and decreased lifetimes. Such changes are favorable for the use of fluorescence in DNA analysis [15,16] and immunoassays [17].…”

Section: Introductionmentioning

confidence: 99%