Porphyrin, as a planar macrocyclic molecule, extensively exists naturally in plants and animals and plays an important role in life activities. Normally, porphyrin exists in the form of nanostructures/aggregations through molecular self-assembly. Thus, it is of great interest for tuning nanostructures, understanding mechanisms, and exploring the diverse applications. In this issue, we present articles covering the synthesis and formation mechanisms of porphyrin nanostructures by self-assembly methods and their applications in solar-energy harvesting, water splitting, environmental pollutant reduction, and nanomedicine for tumor therapy. These articles present the recent developments and potential research directions of this field, and we hope they will interest and inspire readers to enter this growing field.

The design and engineering of the size and shapes of photoactive building blocks enable the fabrication of functional nanocrystals, especially for applications in light harvesting, photocatalytic synthesis, water splitting, and photodegradation. Synthesis of such nanocrystals has been demonstrated recently through noncovalent interactions such as π–π stacking and ligand coordination using optically active porphyrin as a functional building block. Depending on the kinetic conditions, the resulting nanocrystals exhibit well-defined one- to three-dimensional shapes such as spheres, nanowires, and nano-octahedra. These well-defined porphyrin nanocrystals show interesting size- and shape-dependent photocatalytic activity. This article reviews the synthesis and formation of porphyrin nanocrystals with controlled size and shape. Important photocatalytic processes such as photodegradation of organic pollutants, photocatalytic water splitting and hydrogen production, and photosynthesis of metallic fuel-cell catalysts are highlighted. Insights on size- and shape-dependent properties are discussed.

There has been widespread recent interest in self-assembly and synthesis of porphyrin and its derivatives-based ordered arrays aiming to emulate natural light-harvesting processes and energy storage. However, technologies that leverage the structural advantages of individual porphyrins have not been fully realized and have been limited by available synthesis methods. This article provides general perspectives on porphyrin and derivative chemistry, and discussions on surfactant-assisted cooperative self-assembly using amphiphilic surfactants and functional porphyrins and derivatives. The cooperative self-assembly amplifies the intrinsic advantages of individual porphyrins by engineering them into well-defined one-dimensional–three-dimensional (1D–3D) nanostructures. Surfactant-assisted self-assembly of amphiphilic surfactants and porphyrins has been utilized to form well-defined “micelle-like” nanostructures. Driven by intermolecular interactions, subsequent nucleation and growth confined within these nanostructures lead to the formation of 1D–3D ordered optically and electrically active nanomaterials with structure and function on multiple length scales.

Porphyrins and their associated derivatives have been widely used as photosensitizers for photodynamic therapy (PDT) of tumors. To overcome the limitations of porphyrin photosensitizers in PDT, the marriage of porphyrins and nanotechnology offers a new perspective to improve the efficacy and safety of porphyrin-based PDT. To date, various organic and inorganic nanoparticles have been developed for porphyrin delivery for high payload photosensitizers, protection from premature release of photosensitizers, and tumor-selective targeting. In this article, we summarize the strategies for porphyrin photosensitizer delivery, including encapsulation, covalent conjugation, self-assembly for PDT, and characterization methods of singlet oxygen (1O2) generation. We focus on the summarized strategies of improving cancer PDT efficacy by nanotechnology. Finally, the challenges and outlook for porphyrin-based nanocomposites-mediated PDT are discussed.

This article provides an overview of emerging directions in the materials science of biointegrated electronic and microfluidic systems, as defined by technologies that are capable of supporting long-term, intimate, physical interfaces to living organisms. Here, deterministic hard/soft composite structures, including those that leverage concepts in fractal mathematics, serve as the materials foundations for diverse devices of this type. Examples of “epidermal” or skin-like electronic systems for biophysical tracking of patient conditions that range from stroke to hydrocephalus illustrate the engineering maturity and operational sophistication that is now possible. Recent ideas in soft, skin-mounted, microfluidic lab-on-a-chip systems extend the capabilities of such platforms to include biochemical assessments of physiological status via capture, storage, manipulation, and in situ detection of biomarkers in microliter volumes of sweat, collected as it emerges from the surface of the skin. The article concludes with a description of mechanically guided assembly schemes that provide access to three-dimensional, open-mesh constructs, as a frontier area of materials development in this broader area of biointegrated systems.