Technological advances made in constructing high-resolution instrumentation have enabled fabrication of sophisticated counterfeit products. As a result, the need to develop novel anti-counterfeiting materials and systems is greatly increasing. Accordingly, various functional materials that display distinct chemical, physical as well as optical and electrical properties have been investigated for preventing and detecting counterfeiting. In this feature article, we describe recent strategies that have been devised for anti-counterfeiting purposes that focus on colorimetric and fluorometric approaches that are employed in the determination of the authenticity of banknotes, documents, medicine, etc. In addition, methods of incorporating organic electronics on banknotes as active authentication tools as well as molecular imaging techniques based on mass spectrometry are briefly described.

Owing to the color (blue-to-red) and fluorescence (non-to-fluorescent) changes that take place in response to environmental perturbations, conjugated polydiacetylenes (PDAs) have been actively employed as sensory materials for the detection of biologically-, environmentally- and chemically-important target molecules. Until recently, the majority of PDA sensors have been prepared in the form of aqueous suspensions or Langmuir-type thin films on solid substrates. In order to overcome the limitations associated with conventional solution/film sensors, conceptually new formats, such as immobilized PDAs in and on solid substrates, microarrayed PDA sensors, microfluidic PDA sensors, as well as PDA-embedded electrospun fiber sensors and resonance energy transfer (RET)-based PDA sensors, have been developed recently. In this tutorial review, the recent conceptual and technological achievements made in the area of conjugated PDA chemosensors are described.

While a large variety of conjugated polymers exist, polydiacetylenes (PDAs) remain a major research area among scientists due to their interesting optical, spectral, electronic, and structural properties. Heavily reviewed in regards to their stimuli responsive properties, much is known about the assortment of sensing and detection capabilities of PDAs. In this article, we look more upon the structural diversities of polydiacetylenes that have been achieved in recent years, particularly from a hierarchical perspective of 1, 2, and 3-dimensional configurations. In addition, we examine how these different dimensional arrangements of PDAs have heralded clear applications in several key areas. Successful integration of these stimuli-responsive “smart” materials into various geometries has required researchers to have a comprehensive understanding of both the fabrication and synthesis processes, as well as the signalling mechanism for the optical, fluorogenic or spectral transitions. The on-going discovery of new PDA formulations continues to provide interesting structural manifestations such as liposomes, tubes, fibres, organic/inorganic incorporated hybrids and composite structures. By highlighting some of the recent conceptual and technological developments, we hope to provide a measure of the current pace in new PDA derivative development as core components in efficient sensor, imaging and display systems.