Time to kick the butt of the most common litter item in the world: Ban cigarette filters.

Cigarette filters offer no public health benefits, are single-use plastics (cellulose acetate) and are routinely littered. Filters account for a significant proportion of plastic litter worldwide, requiring considerable public funds to remove, and are a source of microplastics. Used cigarette filters can leech toxic chemicals and pose an ecological risk to both terrestrial and aquatic ecosystems. Bottom-up measures, such as focusing on consumer behaviour, are ineffective and we need to impose top-down solutions (i.e., bans) if we are to reduce the prevalence of this number one litter item. Banning filters offers numerous ecological, socioeconomic, and public health benefits.

Functional Nano-Objects by Electrostatic Self-Assembly: Structure, Switching, and Photocatalysis.

The design of functional nano-objects by electrostatic self-assembly in solution signifies an emerging field with great potential. More specifically, the targeted combination of electrostatic interaction with other effects and interactions, such as the positioning of charges on stiff building blocks, the use of additional amphiphilic, π-π stacking building blocks, or polyelectrolytes with certain architectures, have recently promulgated electrostatic self-assembly to a principle for versatile defined structure formation. A large variety of architectures from spheres over rods and hollow spheres to networks in the size range of a few tenths to a few hundred nanometers can be formed. This review discusses the state-of-the-art of different approaches of nano-object formation by electrostatic self-assembly against the backdrop of corresponding solid materials and assemblies formed by other non-covalent interactions. In this regard, particularly promising is the facile formation of triggerable structures, i.e. size and shape switching through light, as well as the use of electrostatically assembled nano-objects for improved photocatalysis and the possible solar energy conversion in the future. Lately, this new field is eliciting an increasing amount of understanding; insights and limitations thereof are addressed in this article. Special emphasis is placed on the interconnection of molecular building block structures and the resulting nanoscale architecture via the key of thermodynamics.

Light-Responsive Shape: From Micrometer-Long Nanocylinders to Compact Particles in Electrostatic Self-Assembly.

A light-triggered shape change of supramolecular nanostructures is achieved through electrostatically self-assembly of linear polyelectrolytes and oppositely charged dyes in aqueous solution: Upon UV-irradiation, 1-µm-long, flexible cylinders with a cross-section of 10 nm convert into ellipsoids of 400 nm × 40 nm. The nano-object shape is encoded in the molecular dye structure.

Hydrogen-Bonded Polymer-Porphyrin Assemblies in Water: Supramolecular Structures for Light Energy Conversion.

In this study, a new type of functional, self-assembled nanostructure formed from porphyrins and polyamidoamine dendrimers based on hydrogen bonding in an aqueous solution is presented. As the aggregates formed are promising candidates for solar-energy conversion, their photocatalytic activity is tested using the model reaction of methyl viologen reduction. The self-assembled structures show significantly increased activity as compared to unassociated porphyrins. Details of interaction forces driving the supramolecular structure formation and regulating catalytic efficiency are fundamentally discussed.