Nanocomposites, multiphase solid materials with at least one nanoscaled component, have been attracting ever‐increasing attention because of their unique properties. Graphene is an ideal filler for high‐performance multifunctional nanocomposites in light of its superior mechanical, electrical, thermal, and optical properties. However, the 2D nature of graphene usually gives rise to highly anisotropic features, which brings new opportunities to tailor nanocomposites by making full use of its excellent in‐plane properties. Here, recent progress on graphene/polymer nanocomposites is summarized with emphasis on strengthening/toughening, electrical conduction, thermal transportation, and photothermal energy conversion. The influence of the graphene configuration, including layer number, defects, and lateral size, on its intrinsic properties and the properties of graphene/polymer nanocomposites is systematically analyzed. Meanwhile, the role of the interfacial interaction between graphene and polymer in affecting the properties of nanocomposites is also explored. The correlation between the graphene distribution in the matrix and the properties of the nanocomposite is discussed in detail. The key challenges and possible solutions are also addressed. This review may provide a constructive guidance for preparing high‐performance graphene/polymer nanocomposite in the future.

The reduced graphene oxide (rGO) sponges exhibit exciting electromagnetic absorption (MA) performance in high-frequency range. However, it is still a great challenge to realize desirable MA property at low frequency (2-4 GHz) due to the great difficulty in balancing the good interfacial impedance matching and strong dielectric loss. Herein, the MA metamaterials based on rGO sponge with different unit shapes are reported. The relationship between the unit shape and MA performance is explored by experiment and simulation. The results show that frustum pyramid metamaterial exhibits ultrabroad band MA; the qualified absorption (the reflection loss lower than −10 dB) of electromagnetic wave can be achieved at 2.4-40 GHz. The average absorption intensity is −22.9 dB in the band of 2-40 GHz. Moreover, the bandwidth for strong absorption with an absorption rate of 99% (−20 dB) is up to 32 GHz. It is significant that the reflection loss has ignorant change even though the incident angle is increased from 5° to 40°. These are contributed to the excellent impedance matching and strong dielectric loss. These lightweight frustum pyramid metamaterials are very promising in the application for broadband electromagnetic protection.

A portable litmus‐type chemosensor is developed for the effective detection of environmentally hazardous volatile organic compounds (VOCs) using polydiacetylene (PDA) and graphene stacked within a composite film. The graphene is exploited as a transparent and efficient supporter for the highly ordered PDA monolayer. This colorimetric sensor exhibits a sensitive response to low concentrations of VOCs (∼0.01%), including tetrahydrofuran (THF), chloroform (CHCl3), methanol (CH3OH), and dimethylformamide (DMF). The color change that is caused by relatively high concentrations of VOCs can be perceived by the naked eye, and it is noteworthy that a logarithmic relationship is observed between the chromatic response and the VOC concentration in the range of ∼0.01%–10%. The structural conformation changes of the PDA molecules, caused by interactions with VOCs, are directly observed by scanning tunneling microscopy (STM), which reveals the intrinsic mechanism of the chromatic variety at the molecular level.

Developing microwave absorption materials with broadband and lightweight characters is of great significance. However, it is still a great challenge for carbonized biomass without loading magnetic particles to cover the broad microwave frequency. Herein, it is proposed to carbonize freeze‐dried waxberry to make full use of its natural hierarchical gradient structure to target the ultrabroad band microwave absorption. The carbonized freeze‐dried waxberry shows radial‐gradient and hierarchical structure. The different components of hierarchical waxberry demonstrate gradient dielectric properties: the outer component shows anisotropic dielectric constants with smaller value, while the inner core shows higher dielectric constants. This gradient dielectric property is beneficial to the impedance matching and strong polarization. As a result, the bandwidth of carbonized waxberry exhibits an ultrabroad band microwave absorption, ranging from 1 to 40 GHz with the reflection loss value below −8 dB. Meanwhile, the bandwidth can cover from 8 to 40 GHz when the reflection loss is below −15 dB. The ultrabroad microwave absorption is attributed to the hierarchical radial‐gradient structure of carbonized waxberry, which provides good impedance matching with air media. This achievement paves the way for the exploitation of natural hierarchical biomass as a superlight and broadband high‐performance microwave absorption material.