Network service chaining, originally conceived in the network function virtualization (NFV) framework for software defined networks (SDN), is becoming an attractive solution for enabling service ...differentiation enforcement to microflows generated by data centers, 5G fronthaul and Internet of Things (IoT) cloud/fog nodes, and traversing a metro-core network. However, the current IP/MPLS-over optical multi-layer network is practically unable to provide such service chain enforcement. First, MPLS granularity prevents microflows from being conveyed in dedicated paths. Second, service configuration for a huge number of selected flows with different requirements is prone to scalability concerns, even considering the deployment of a SDN network. In this paper, effective service chaining enforcement along traffic engineered (TE) paths is proposed using segment routing and extended traffic steering mechanisms for mapping micro-flows. The proposed control architecture is based on an extended SDN controller encompassing a stateful path computation element (PCE) handling microflow computation and placement supporting service chains, whereas segment routing allows automatic service enforcement without the need for continuous configuration of the service node. The proposed solution is experimentally evaluated in segment routing over an elastic optical network (EON) network testbed with a deep packet inspection service supporting dynamic and automatic flow enforcement using Border Gateway Protocol with Flow Specification (BGP Flowspec) and OpenFlow protocols as alternative traffic steering enablers. Scalability of flow computation, placement, and steering are also evaluated showing the effectiveness of the proposed solution.
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•Coupling nanoparticles with ECL provides unprecedented sensitivity.•Over 80% of the articles in this field has been published in the last 5 years.•The best nanomaterials for ECL ...signal amplification are here discussed.•The understanding of the mechanisms of ECL is fundamental for higher sensitivities.
The coupling of nanomaterials, and nanoparticles in particular, with one of the most powerful transduction techniques, electrochemiluminescence (ECL), i.e., chemiluminescence triggered by electrochemical reactions at electrodes, has recently provided sensing tools with unprecedented sensitivity limits. This review aims to give an overview of the state of the art in the field over the last 5 years, i.e., a time span covering over 80% of the scientific production in this context. The results herein discussed would demonstrate that the use of nanoparticles in the ECL technique represents one of the most interesting research lines for the development of ultrasensitive analytical tools, offering an insight to recognize and select the best nanomaterials for ECL signal amplification, with particular emphasis in biosensing.
An electrogenerated chemiluminescence (ECL) system by in situ coreactant production, where Ru(bpy)3 2+ emission is generated at a boron-doped diamond (BDD) electrode, is presented. The system takes ...advantage of the unique properties of BDD to promote oxidation of carbonate (CO3 2–) into peroxydicarbonate (C2O6 2–), which further reacts with water to form hydrogen peroxide (H2O2), which acts as a coreactant for Ru(bpy)3 2+ ECL. Investigation of the mechanism reveals that ECL emission is triggered by the reduction of H2O2 to hydroxyl radicals (OH•), which later react with the reduced Ru(bpy)3 + molecules to form excited states, followed by light emission. The ECL signal was found to increase with the concentration of CO3 2–; therefore, with the concentration of electrogenerated H2O2, although at the same time, higher concentrations of H2O2 can quench the ECL emission, resulting in a decrease in intensity. The carbonate concentration, pH, and oxidation parameters, such as potential and time, were optimized to find the best emission conditions.
Electrochemiluminescence (ECL) microscopy is an emerging technique with a wide range of imaging applications and unique properties in terms of high spatial resolution, surface confinement and ...favourable signal-to-noise ratio. Despite its successful analytical applications, tuning the depth of field (
i.e.
, thickness of the ECL-emitting layer) is a crucial issue. Indeed, the control of the thickness of this ECL region, which can be considered as an "evanescent" reaction layer, limits the development of cell microscopy as well as bioassays. Here we report an original strategy based on chemical lens effects to tune the ECL-emitting layer in the model Ru(bpy)
3
2+
/tri-
n
-propylamine (TPrA) system. It consists of microbeads decorated with Ru(bpy)
3
2+
labels, classically used in bioassays, and TPrA as the sacrificial coreactant. In particular we exploit the buffer capacity of the solution to modify the rate of the reactions involved in the ECL generation. For the first time, a precise control of the ECL light distribution is demonstrated by mapping the luminescence reactivity at the level of single micrometric bead. The resulting ECL image is the luminescent signature of the concentration profiles of diffusing TPrA radicals, which define the ECL layer. Therefore, our findings provide insights into the ECL mechanism and open new avenues for ECL microscopy and bioassays. Indeed, the reported approach based on a chemical lens controls the spatial extension of the "evanescent" ECL-emitting layer and is conceptually similar to evanescent wave microscopy. Thus, it should allow the exploration and imaging of different heights in substrates or in cells.
A versatile mechanism based on a chemical lens to control the electrochemiluminescence (ECL) spatial distribution is presented. Changing the buffer capacity modifies the rate of ECL reactions, and therefore the thickness of the ECL-active layer.
A novel co-reactant-free electrogenerated chemiluminescence (ECL) system is developed where Ru(bpy)32+ emission is obtained on boron-doped diamond (BDD) electrodes. The method exploits the unique ...ability of BDD to operate at very high oxidation potential in aqueous solutions and to promote the conversion of inert SO42- into the reactive co-reactant S2O82-. This novel procedure is rather straightforward, not requiring any particular electrode geometry, and since the co-reactant is only generated in situ, the interference with biological samples is minimized. The underlying mechanism is similar to that of the Ru(bpy)32+/S2O82- system; however, the intensity of the emitted signal increases linearly with SO42- up to ∼0.6 M, with possible implications for analytical uses of the proposed procedure.
The combination of highly sensitive techniques such as electrochemiluminescence (ECL) with nanotechnology sparked new analytical applications, in particular for immunoassay‐based detection systems. ...In this context, nanomaterials, particularly dye‐doped silica nanoparticles (DDSNPs) are of high interest, since they can offer several advantages in terms of sensitivity and performance. In this work we synthesized two sets of monodispersed and biotinylated Ru(bpy)32+‐doped silica nanoparticles, named bio‐Triton@RuNP and bio‐Igepal@RuNP, obtained following the reverse microemulsion method using two different types of nonionic surfactants. Controlling the synthetic procedures, we were able to obtain nanoparticles (NPs) offering highly intense signal, using tri‐n‐propylamine (TPrA) as coreactant, with bio‐Triton@RuNps being more efficient than bio‐Igepal@RuNP.
Using silica nanoparticles, a 8.5‐fold higher ECL intensity was achieved with respect to a system mimicking a commercial immuno‐sensing system, benefiting from the deep knowledge acquired by combining ECL with nanostructures.
Electrochemiluminescence (ECL) is a powerful transduction technique with a leading role in the biosensing field due to its high sensitivity and low background signal. Although the intrinsic ...analytical strength of ECL depends critically on the overall efficiency of the mechanisms of its generation, studies aimed at enhancing the ECL signal have mostly focused on the investigation of materials, either luminophores or coreactants, while fundamental mechanistic studies are relatively scarce. Here, we discover an unexpected but highly efficient mechanistic path for ECL generation close to the electrode surface (signal enhancement, 128%) using an innovative combination of ECL imaging techniques and electrochemical mapping of radical generation. Our findings, which are also supported by quantum chemical calculations and spin trapping methods, led to the identification of a family of alternative branched amine coreactants, which raises the analytical strength of ECL well beyond that of present state-of-the-art immunoassays, thus creating potential ECL applications in ultrasensitive bioanalysis.
The phenomenon of electrochemiluminescence (ECL) is luminescence triggered by electrochemical reactions at electrodes. Heterogeneous electron transfers are deeply dependent on electrode materials, ...therefore, besides the usual parameters, the right choice of the electrode is a crucial point to address properly in order to maximize the emission efficiency. Many different electrodes have been studied, from metallic platinum or gold through transparent indium‐doped tin oxide to carbon‐based electrodes, and others, such as paper‐based and boron‐doped diamond. This review summarizes results of ECL at different electrode surfaces, disclosing the relative advantages and disadvantages, with a particular attention to the reference Ru(bpy)32+/TPrA coreactant system. In other words, we offer an insight to recognize and select the optimal electrode material for the ECL systems of interest with particular emphasis on the biosensing applications.
Do the right thing: The role of different electrode materials in electrochemiluminescence is critically reviewed, compared, and advantages and disavantages evaluated. The purpose is to offer guidelines for users to choose the best electrode material for the electrochemiluminescence systems of interest.
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