Managing the Inner Workings of Collective Intelligence Approaches for Wicked Problems – An Assessment Model and Evaluation

Ill-defined and complex problems that affect multiple stakeholders with potentially conflicting perspectives are often referred to as wicked problems. The utilization of collective intelligence (CI) via web-based platforms is a promising approach for addressing such wicked problems. The management of these information systems would benefit from evidence-based decision support regarding facilitation and improvement efforts. However, to date, there is no suitable model to guide such efforts. Existing approaches address specific applications or cover certain assessment areas but do not provide a holistic perspective. Meanwhile, research offers substantial insights into best practices for addressing wicked problems and running CI applications. This paper develops an assessment model comprising five central success dimensions for information systems that address wicked problems. Their subdimensions and associated measurement metrics allow for evidence-driven facilitation and improvement of CI applications for wicked problems. Apart from the model’s capability to improve future runs and processes, it also offers the potential to provide immediate insights for facilitation efforts during runtime. The model was validated with a platform dealing with the assessment of risks presented by global climate change. This evaluation generated strong evidence for the model’s applicability and usefulness

A Simulation-Based Approach to Understanding the Wisdom of Crowds Phenomenon in Aggregating Expert Judgment

Research has shown that aggregation of independent expert judgments significantly improves the quality of forecasts as compared to individual expert forecasts. This “wisdom of crowds” (WOC) has sparked substantial interest. However, previous studies on strengths and weaknesses of aggregation algorithms have been restricted by limited empirical data and analytical complexity. Based on a comprehensive analysis of existing knowledge on WOC and aggregation algorithms, this paper describes the design and implementation of a static stochastic simulation model to emulate WOC scenarios with a wide range of parameters. The model has been thoroughly evaluated: the assumptions are validated against propositions derived from literature, and the model has a computational representation. The applicability of the model is demonstrated by investigating aggregation algorithm behavior on a detailed level, by assessing aggregation algorithm performance, and by exploring previously undiscovered suppositions on WOC. The simulation model helps expand the understanding of WOC, where previous research was restricted. Additionally, it gives directions for developing aggregation algorithms and contributes to a general understanding of the WOC phenomenon

Light triggered detection of aminophenyl phosphate with a quantum dot based enzyme electrode

An electrochemical sensor for p-aminophenyl phosphate (pAPP) is reported. It is based on the electrochemical conversion of 4-aminophenol (4AP) at a quantum dot (QD) modified electrode under illumination. Without illumination no electron transfer and thus no oxidation of 4AP can occur. pAPP as substrate is converted by the enzyme alkaline phosphatase (ALP) to generate 4AP as a product. The QDs are coupled via 1,4-benzenedithiol (BDT) linkage to the surface of a gold electrode and thus allow potential-controlled photocurrent generation. The photocurrent is modified by the enzyme reaction providing access to the substrate detection. In order to develop a photobioelectrochemical sensor the enzyme is immobilized on top of the photo-switchable layer of the QDs. Immobilization of ALP is required for the potential possibility of spatially resolved measurements. Geometries with immobilized ALP are compared versus having the ALP in solution. Data indicate that functional immobilization with layer-by-layer assembly is possible. Enzymatic activity of ALP and thus the photocurrent can be described by Michaelis- Menten kinetics. pAPP is detected as proof of principle investigation within the range of 25 μM - 1 mM

Plasmonic bimetallic two-dimensional supercrystals for H2 generation

Sunlight-driven H-2 generation is a central technology to tackle our impending carbon-based energy collapse. Colloidal photocatalysts consisting of plasmonic and catalytic nanoparticles are promising for H-2 production at solar irradiances, but their performance is hindered by absorption and multiscattering events. Here we present a two-dimensional bimetallic catalyst by incorporating platinum nanoparticles into a well-defined supercrystal of gold nanoparticles. The bimetallic supercrystal exhibited an H-2 generation rate of 139mmolg(cat)(-1)h(-1) via formic acid dehydrogenation under visible light illumination and solar irradiance. This configuration makes it possible to study the interaction between the two metallic materials and the influence of this in catalysis. We observe a correlation between the intensity of the electric field in the hotspots and the boosted catalytic activity of platinum nanoparticles, while identifying a minor role of heat and gold-to-platinum charge transfer in the enhancement. Our results demonstrate the benefits of two-dimensional configurations with optimized architecture for liquid-phase photocatalysis

Photoluminescence of Fully Inorganic Colloidal Gold Nanocluster and Their Manipulation Using Surface Charge Effects

International audienceFully inorganic, colloidal gold nanoclusters (NCs) constitute a new class of nanomaterials that are clearly distinguishable from their commonly studied metal–organic ligand-capped counterparts. As their synthesis by chemical methods is challenging, details about their optical properties remain widely unknown. In this work, laser fragmentation in liquids is performed to produce fully inorganic and size-controlled colloidal gold NCs with monomodal particle size distributions and an fcc-like structure. Results reveal that these NCs exhibit highly pronounced photoluminescence with quantum yields of 2%. The emission behavior of small (2–2.5 nm) and ultrasmall (<1 nm) NCs is significantly different and dominated by either core- or surface-based emission states. It is further verified that emission intensities are a function of the surface charge density, which is easily controllable by the pH of the surrounding medium. This experimentally observed correlation between surface charge and photoluminescence emission intensity is confirmed by density functional theoretical simulations, demonstrating that fully inorganic NCs provide an appropriate material to bridge the gap between experimental and computational studies of NCs. The presented study deepens the understanding of electronic structures in fully inorganic colloidal gold NCs and how to systematically tune their optical properties via surface charge density and particle size

Functional Gold Nanoparticles for Biomedical Applications

Abstract Subjects of the present dissertation are the synthesis, the functionalization and the characterization of colloidal gold nanoparticles. The employed nanoparticles consist of an inorganic Au core of approximately 5 nm diameter, which is stabilized by hydrophobic surface molecules. To transfer the nanoparticles to aqueous environments (an indispensable necessity for biomedical applications) they are coated with an amphiphilic polymer, which generates water solubility and moreover gives the ability for further functionalization. The physico-chemical properties of such nanoparticles are verified within different purposes: First, several fundamental intrinsic surface properties are quantified, including the establishment of pH titration as characterization tool. It is found that the carboxylic groups, responsible for the colloidal stabilization, partly have different properties (like their pKa) compared to free standing carboxylic acids. These findings are crucial for the colloidal stabilization of nanoparticles as well as for their further functionalization. Secondly, two species of fluorescently labeled nanoparticles, which differed in first order only in the net surface charge, are employed to study charge dependent interaction of nanoparticles with biological systems, including proteins as well as living cells. The main finding is, that a so called protein corona forms around nanoparticles, what has far-reaching impacts on cell internalization abilities. Moreover it is found that positively charged nanoparticles show a higher cell association as well as a higher toxicity. Thirdly, nanoparticles are modified towards sensing applications by surface functionalization with ion sensitive dyes. Positively charged nanoparticles are modified with a Cl- sensitive dye and negatively charged nanoparticles are modified with a Zn2+ sensitive dye. The goals of the dissertation can be synoptically depicted as: 1) Extension of the existing techniques for nanoparticle functionalization, particularly regarding new types of functional polymers. 2) A fundamental and comprehensive characterization of nanoparticles ranging from the verification of intrinsic, physico-chemical properties to biomedical applications

On the Use of pH Titration to Quantitatively Characterize Colloidal Nanoparticles

International audienceFunctional nanoparticles (NPs) for bioapplications have been achieved, thanks to synthesis providing high quality nanocrystals, efficient procedures for transfer in water, and further conjugation of (bio)active molecules. However, these nanomaterials are still subjected to batch-to-batch variability and investigations of their physicochemical properties and chemical reactivity are still in their infancy. This may be due to lack of a routine, cost-effective, and readily available quantitative method for characterizing functional NPs. In this work, we show that pH titrations can be a powerful tool for investigating the surface properties of charged NPs and quantifying their surface functionalities. We demonstrate how this method can be useful in characterizing the colloidal and chemical stability, composition, and purity of the nanomaterial. The method also shows potential for the optimization of conjugation conditions

Polymer-Coated Nanoparticles Interacting with Proteins and Cells: Focusing on the Sign of the Net Charge

To study charge-dependent interactions of nanoparticles (NPs) with biological media and NP uptake by cells, colloidal gold nanoparticles were modified with amphiphilic polymers to obtain NPs with identical physical properties except for the sign of the charge (negative/positive). This strategy enabled us to solely assess the influence of charge on the interactions of the NPs with proteins and cells, without interference by other effects such as different size and colloidal stability. Our study shows that the number of adsorbed human serum albumin molecules per NP was not influenced by their surface charge. Positively charged NPs were incorporated by cells to a larger extent than negatively charged ones, both in serum-free and serum-containing media. Consequently, with and without protein corona (i.e., in serum-free medium) present, NP internalization depends on the sign of charge. The uptake rate of NPs by cells was higher for positively than for negatively charged NPs. Furthermore, cytotoxicity assays revealed a higher cytotoxicity for positively charged NPs, associated with their enhanced uptake.status: publishe