We will highlight the main achievements made recently in the preparation and application of 3D graphene porous materials in lithium-ion batteries, super-capacitors, solar cells, catalysis, thermal management, environment pollution enrichment and separation, chemical sensors, etc.

Exposure to mercury ions, even at very low levels, is known to cause a wide variety of diseases in the brain, kidney, and central nervous system, which is an increasing serious problem for human beings and the environment. Accordingly, great efforts have been devoted to the development of colorimetric sensors, which can selectively and conveniently detect Hg²⁺. In this feature article, to present the readers a better understanding of the specific methods and their mechanisms, we will highlight colorimetric sensors according to their receptors into several categories, including organic dye-based sensors, complex based sensors, polymer based sensors, and nanoparticles based sensors, which are mentioned in the literature and our own work during the recent years.

Heavy metal contamination has posed a great threat to human survival and social development. For this, a series of nanoenzyme-based colorimetric sensors, e.g., metal nanoparticles, metal oxides, metal sulfides, graphene-based nanomaterials, G-quadruplex and so on, were developed for the rapid and efficient detection of toxic heavy metal ions, whose detection limit for heavy metal ions could be as low as the nmol L⁻¹ level. The recognition mechanism was based on the catalysis and signal amplification of nanozymes, a new type of nanomaterial possessing specific catalytic activity towards certain chemical reactions such as the oxidation of colorless TMB to blue oxTMB. In this work, we are trying to present readers with a better understanding of this important colorimetric sensing material by illustrating its application in the detection of heavy metal ions using metal nanoparticles, metal oxides, metal sulfides, graphene-based nanomaterials, G-quadruplex, etc. respectively.