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Transition metal dichalcogenides (TMDCs) are often mechanically exfoliated on mica and examined under ambient conditions. It is known that above a certain relative humidity, a molecularly thin layer of water intercalates between the mica and the TMDC. Herein, the effect of molecularly thin liquid layers on the optical spectra of MoS2 and WS2 exfoliated on dry mica and exposed to the vapors of water, ethanol, and tetrahydrofuran (THF) is investigated. Photoluminescence and differential reflectance (ΔR/R) spectra on the TMDCs on dry mica show dominant trion emission due to n‐doping. Intercalation of water removes charge doping and results in purely neutral exciton emission, while an ethanol layer, which can be reversibly exchanged with water, does not completely suppress charge. Similarly, THF intercalates between TMDC and mica, as shown by atomic force microscopy, but it does not suppress the charging of mica. In MoS2 bi‐ and trilayers, an intercalated water layer leads to a near doubling of the intensity of the indirect band transition. The described charging/discharging of TMDCs by molecular thin liquid layers can provide important clues to better control the optical properties of TMDCs under environmental conditions. [ABSTRACT FROM AUTHOR]

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]

Aqueous multiphase systems have attracted a lot of interest recently espeically due to target applications in the biomedical field, cosmetics, and food. In turn, water‐in‐water Pickering emulsions are investigated frequently. In here, graphitic carbon nitride (g‐CN) stabilized water‐in‐water Pickering emulsions are fabricated via the dextran and poly(ethylene glycol)‐based aqueous two‐phase system. Five different derivatives of g‐CN as the Pickering stabilizer are described and the effect of g‐CN concentration on droplet sizes is investigated. Stable emulsions (up to 16 weeks) are obtained that can be broken on purpose via various approaches, including dilution, surfactant addition, and most notably light irradiation. The novel approach of water‐in‐water emulsion stabilization via g‐CN opens up considerable advances in aqueous multiphase systems and may also introduce photocatalytic properties. [ABSTRACT FROM AUTHOR]

Efficient delivery systems based on biopolymers offer new solutions to enhance food security by boosting crop yield and quality while decreasing agrochemical input and mitigating environmental impact. Herein, a novel Pickering emulsion fabrication method that utilizes antibody‐functionalized silk fibroin to enhance foliar adhesion upon application for efficient agrochemicals delivery is reported. Silk fibroin microparticles (SFMPs) stabilize both nonpolar and polar oil‐in‐water Pickering emulsions, revealing the cooperative function of both oil phase polarity and aqueous media pH in stabilization, where phytohormones addition influenced the stability and oil‐water contact angle. Phytohormone‐containing Pickering emulsions are functionalized with anti‐pectic polysaccharide (alpha‐1,5‐arabinan) antibody labeled SFMPs through adsorption, to enhance droplet adhesion to leaf cuticle surface. As a proof‐of‐concept, Pickering emulsion containing 0.1 mM jasmonic acid (JA) is applied to Arabidopsis thaliana via foliar spraying. Following washing, treatment with antibody‐functionalized Pickering emulsion increased trichome numbers on young leaves by 20% and 3%, when compared to nonencapsulated JA and nonfunctionalized emulsions, respectively. The functionalized Pickering emulsion stabilized by SFMPs exhibited no plant toxicity and biodegraded 50 wt.% in 7 days, catalyzed by Streptomyces griseus protease. Results highlight the potential of SFMP‐stabilized oleic acid‐in‐water Pickering emulsion as a sustainable and biodegradable solution to precisely deliver agrochemicals through foliar spray. [ABSTRACT FROM AUTHOR]

We report a novel stimuli-responsive fluorescent material platform that relies on an evocation of aggregation-induced emission (AIE) from tetraphenylethylene (TPE)-based surfactants localized at one hemisphere of biphasic micro-scale Janus emulsion droplets. Dynamic alterations in the available interfacial area were evoked through surfactant-induced dynamic changes of the internal droplet morphology that can be modulated as a function of the balance of interfacial tensions of the droplet constituent phases. Thus, by analogy with a Langmuir-Blodgett trough that enables selective concentration of surfactants at a liquid-gas interface, we demonstrate here a method for controllable modulation of the available interfacial area of surfactant-functionalized liquid-liquid interfaces. We show that a morphology-dependent alteration of the interfacial area can be used to evoke an optical signal, by selectively assembling synthesized TPE-based surfactants on the respective droplet interfaces. A trigger-induced increase in the concentration of TPE-based surfactants at the liquid-liquid interfaces results in an evocation of aggregation-induced emission (AIE), inducing an up to 3.9-fold increase in the measured emission intensity of the droplets., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)