The ability of luminescent species in the near-field to both induce and couple to surface plasmons has been known for many years, with highly directional emission from films (Surface Plasmon Coupled ...Luminescence, SPCL) facilitating the development of sensitive near-field assay sensing platforms, to name but just one application. Because of the near-field nature of the effect, only luminescent species (fluorescence, chemiluminescence and phosphorescence) within a few hundred nanometers from the surface play a role in coupling, which in terms of biosensing, provides for limited penetration into optically dense media, such as in whole blood. Another attractive feature is the highly polarized and angular dependent emission which allows both fixed angle and wavelength dependent emission angles to be realized at high polarization ratios. In this paper, a generic procedure based on theoretical Fresnel calculations, which outlines the step-by-step selection of an appropriate metal for SPCL applications is presented. It is also shown that 11 different metals have differing properties in different spectral regions and offer either fixed angle or wavelength-dependent angular shifts in emission. In addition, it is shown that both chemiluminescence and phosphorescence can also be observed in a highly directional manner similar to coupled fluorescence.
This review article summarises the relevant theory and work to date for halide sensing (halide ions or organic halides) using fluorescence quenching methods. Such measurements can have several ...advantages over other techniques, eg, ion selective electrodes, in that halide concentrations can be determined in very small sample volumes, no pre-treatment of samples is generally required and measurements can be non-invasive, very quick or even continuous. However, fluorescence quenching is not a particularly selective process and other halides, pseudohalides, heavy atoms or even dissolved molecular oxygen can perturb measurements. Fortunately, interference can be readily corrected provided that the fluorophore response to the interference is known. Another advantage of halide sensing using fluorescence quenching is that halide concentrations can be determined using either intrinsic or extrinsic fluorescence probes. It is likely that future halide concentrations may be determined with lifetime based, multiple dye halide sensors (fibre optic or implant) where sensors may be constructed with dyes immobilized on the surface of an inert support or fibre for greater halide sensitivity. (Abstract quotes from original text)
Metal-enhanced fluorescence (MEF) has become an increasingly important technology in recent years, with thorough research addressing the fundamentals of MEF. In many studies, spectral distortion is ...observed in the enhanced spectra as compared to free-space fluorescence emission profiles. Despite this observation, very little experimentation has hitherto been undertaken to investigate the mechanistic underpinnings of spectral distortion in MEF. Herein, we investigate MEF spectral distortion using Rose Bengal and fluorescein on silver nanoparticle substrates, subsequently isolating the coupled fluorescence spectrum for a deeper understanding of the spectral modifications. Clear experimental evidence for bathochromic distortion is reported. Remarkably, we also report hypsochromic distortion in one of the first experimental observations of plasmonic coupling to high-energy excited states. Additionally, the coupled fluorescence spectra from other published literature have also been both extracted and examined, and the subsequent spectral distortions are reported here. The previously asserted theory of radiative decay rate modification for spectral distortion is discussed in the context of both plasmonic properties as well as fluorophore photophysical characteristics including lifetime and quantum yield. The dual enhancement mechanism of MEF is also explored in the context of spectral distortion. The results and discussion reported herein subsequently provide one of the first comprehensive examinations of spectral distortion in MEF to date.
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•Zinc nanoparticulate films yield spectral distortion in Metal-Enhanced Fluorescence.•Both red edge and blue edge distortions are observed from Rose Bengal emission.•Favored ...enhancement of slow (red) and fast (blue) transitions causes distortion.
Metal-enhanced fluorescence (MEF) is a promising technology with impact in diagnostics, electronics, and sensing. Despite investigation into MEF fundamentals, some properties remain unresearched, notably spectral distortion. To date, publications have described its underpinnings, yet comprehensive analysis is needed, as presented recently for silver films. Herein we expand this description using zinc substrates (ZnNPs). Significant red-edge and blue-edge distortions are reported using Rose Bengal. Radiative decay rate modification is identified as key in amplifying fast/slow electronic transitions by the enhanced emission mechanism. Furthermore, we identify distortion in published studies, bolstering our thinking that spectral distortion is an intrinsic property of MEF.
Plasmonic engineering of singlet oxygen generation Zhang, Yongxia; Aslan, Kadir; Previte, Michael J.R ...
Proceedings of the National Academy of Sciences - PNAS,
02/2008, Letnik:
105, Številka:
6
Journal Article
Recenzirano
Odprti dostop
In this article, we report metal-enhanced singlet oxygen generation (ME¹O₂). We demonstrate a direct relationship between the singlet oxygen yield of a common photosensitizer (Rose Bengal) and the ...theoretical electric field enhancement or enhanced absorption of the photosensitizer in proximity to metallic nanoparticles. Using a series of photosensitizers, sandwiched between silver island films (SiFs), we report that the extent of singlet oxygen enhancement is inversely proportional to the free space singlet oxygen quantum yield. By modifying plasmon coupling parameters, such as nanoparticle size and shape, fluorophore/particle distance, and the excitation wavelength of the coupling photosensitizer, we can readily tune singlet oxygen yields for applications in singlet oxygen-based clinical therapy.
Gold colloids are well known to display strong plasmon absorption bands due to electron oscillations induced by the incident light. When the colloids are in proximity, the plasmon absorption bands ...are often perturbed. This has enabled us recently to successfully develop a glucose sensing platform based on the disassociation of dextran-coated gold colloids, cross-linked with Con A, by glucose. However, a much more useful and simpler property of gold colloids, which has been ill explored with regard to sensing, is their ability to efficiently scatter excitation light. We have found that our nanogold sensing aggregates are indeed efficient light scatters around the nanogold plasmon absorption band. By measuring the ratio of scattered light intensities at two different arbitrary wavelengths, 560 and 680 nm, glucose concentrations can be readily determined from a few millimolar up to ∼60 mM, using a simple white light LED and detection system. Further, by measuring the ratio of the scattered intensities, this sensing approach is independent of the total sensing aggregate concentration and the excitation and detection instrumentation fluctuations or drifts. This simplistic and low-cost approach to glucose sensing, coupled with the sensing aggreagates' ability to scatter red light, suggests the potential use of these aggregates for use in physiological transdermal glucose monitoring, either for implantable skin sensors or glucose sensing tattoos (discussed later).
Clostridium difficile is the primary cause of antibiotic associated diarrhea in humans and is a significant cause of morbidity and mortality. Thus the rapid and accurate identification of this ...pathogen in clinical samples, such as feces, is a key step in reducing the devastating impact of this disease. The bacterium produces two toxins, A and B, which are thought to be responsible for the majority of the pathology associated with the disease, although the relative contribution of each is currently a subject of debate. For this reason we have developed a rapid detection assay based on microwave-accelerated metal-enhanced fluorescence which is capable of detecting the presence of 10 bacteria in unprocessed human feces within 40 seconds. These promising results suggest that this prototype biosensor has the potential to be developed into a rapid, point of care, real time diagnostic assay for C. difficile.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We describe the process of generating a fluorophore-induced plasmonic current (FIPC) from copper nanoparticle films. Previous work and the literature have shown that excited near-field fluorophores ...are able to plasmonically couple with metal nanoparticle films (MNFs), inducing surface plasmons in the films. These induced surface plasmons are then in turn able to generate a directly measurable electrical current across the film. These generated currents have been quantified and detected in noble metal films, such as those made from Ag and Au, but due to the cost of such films, there has been a push to use lower cost materials for FIPC. Previous work has detailed the use of gold, silver, and aluminum films for these purposes, and in this paper, we will subsequently examine the ability of thermally deposited copper films to generate FIPC when in close proximity to excited near-field fluorophores. We report the effects of copper film thickness, the effects of light polarization and solution conductance, and the effects of metal-enhanced fluorescence (MEF) emission on the generation of plasmonic current.
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