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Materials capable of dynamically and reversibly altering their emission are relevant for numerous optical applications. Here, the anisotropic morphology‐directed light emission from fluorescent Janus emulsion droplets, an intrinsically chemo‐responsive material platform, is investigated. Informed by experimental observations of morphology‐dependent optical confinement of internally emitted light within the higher refractive index phases, ray‐tracing is used to predict and fine‐tune the droplets' optical properties and their ability to concentrate light. Theoretical prediction and closely matching experimental results show that the collection of incident light and the confinement of emitted light in the internal droplet phase due to total internal reflection both contribute to the droplets' anisotropic light emission profile. A novel ratiometric dual‐angle fluorescence detection approach that exploits the gravitational alignment of the droplets is implemented to quantify the morphology‐dependent large‐scale chemically‐induced modulation of the anisotropic emission of droplet layers. Relevant emulsion design parameters are systematically examined to enhance the signal‐to‐noise ratio, and a second emitter is co‐compartmentalized inside the droplets to amplify the anisotropic light confinement via an absorption–emission cascade. Preferential excitation of dyes in proximity to the internal droplet interface enhances the collected light intensity, demonstrating that dye‐loaded Janus emulsion droplets function as stimuli‐responsive, tunable, fluorescent optical elements. [ABSTRACT FROM AUTHOR]

Responsive materials capable of autonomously regulating and adapting to molecular recognition‐induced chemical events hold great promise in the design of artificial chemo‐intelligent life‐like soft material platforms. In this context, the design of a synthetically minimal artificial emulsion platform that, regulated by interfacial supramolecular recognition events, is capable to autonomously and reversibly adapt to its chemical environment is reported. The systems exhibit programmed up‐ and down‐regulating capabilities that are realized via selective assembly of synthesized crown ether surfactants onto one hemisphere of anisotropic biphasic emulsion droplets. Dynamic and reversible interfacial host–guest complexation of, for example, metal and ammonium ions or amino acids transduce into interface‐triggered morphological reconfigurations of the complex emulsion droplets, which mediate their ability to selectively present, hide, or expand liquid–liquid interfaces. The separate responsive modalities are then used to showcase the utility of such adaptive soft material platforms for a self‐regulated uptake and release of metal ions or phase‐transfer catalysts, a biomimetic recognition of biomolecules including amino acids, carbohydrates, and antibodies, and for triggered surface‐encoded payload release applications. [ABSTRACT FROM AUTHOR]

The catalytic activity of metal nanoparticles (NPs) supported on porous supports can be controlled by various factors, such as NPs size, shape, or dispersivity, as well as their interaction with the support or the properties of the support material itself. However, these intrinsic properties are not solely responsible for the catalytic behavior of the overall reaction system, as the local environment and surface coverage of the catalyst with reactants, products, intermediates and other invloved species often play a crucial role in catalytic processes as well. Their contribution can be particularly critical in liquid‐phase reactions with gaseous reactants that often suffer from low solubiltiy. One example is D‐glucose oxidation with molecular oxygen over gold nanoparticles supported on porous carbons. The possibility to promote oxygen delivery in such aqueous phase oxidation reactions via the immobilization of heterogenous catalysts onto the interface of perfluorocarbon emulsion droplets is reported here. Gold‐on‐carbon catalyst particles can stabilize perfluorocarbon droplets in the aqueous phase and the local concentration of the oxidant in the surroundings of the gold nanoparticles accelerates the rate‐limiting step of the reaction. Consequently, the reaction rate of a system with the optimal volume fraction of fluorocarbon is higher than a reference emulsion system without fluorocarbon, and the effect is observed even without additional oxygen supply. [ABSTRACT FROM AUTHOR]

The adsorption, desorption, co-adsorption, and exchange behavior of phosphonic acid, carboxylic acid, and catechol derivatives on the surface of titanium oxide (anatase) nanoparticles are investigated. Thermogravimetric analysis provides a facile and fast-track quantitative determination of the wet-chemical monolayer adsorption constants and grafting densities of ten adsorbates, all under neutral pH conditions. This characterization protocol allows straightforward quantification of the relevant thermodynamic data of ligand adsorption and a comparison of ligand adsorption strengths. The reported procedure is proposed as a universal tool and it should be applicable to many other colloidal metal oxide materials. Moreover, the determined values for the adsorption constants and the monolayer grafting densities provide a toolbox for the assessment of the adsorbates' behavior in desorption, exchange, and co-adsorption equilibria. This versatile evaluation procedure will help to identify optimal monolayer-surface combinations and to evaluate critical parameters, such as monolayer robustness, ligand exchange rates, or targeted mixed assembly of functionalities. [ABSTRACT FROM AUTHOR]

A new prototype of reversible self‐assembly between functionalized gold and titanium dioxide nanoparticles (NPs) utilizing hydrogen bonding interactions was developed and established. The gold nanoparticles were functionalized with a Hamilton‐receptor functionality bearing a thiol moiety as anchoring group. The titanium dioxide nanoparticles were modified with cyanurate derivatives which contained phosphonic acids as anchoring groups. The host–guest type interaction between two functionalized nanoparticles yielded a highly integrated nanoparticle system in chloroform. Moreover, by presenting a competing ligand in an exchange reaction, the product of self‐assembly can be segregated into the individual soluble components of functionalized nanoparticles. The self‐assembly and the exchange reaction were followed and monitored in detail by UV/Vis spectroscopy. The structure of the self‐assembly product was investigated using scanning electron microscopy (SEM) and small‐angle X‐ray scattering (SAXS). [ABSTRACT FROM AUTHOR]