Electronic waste (E-waste) contain large environmental contaminants such as toxic heavy metals and hazardous chemicals. These contaminants would migrate into drinking water or food chains and pose a serious threat to environment and human health. Biodegradable green electronics has great potential to address the issue of E-waste. Here, we report on a novel biodegradable and flexible transparent electrode, integrating three-dimensionally (3D) interconnected conductive nanocomposites into edible starch-chitosan-based substrates. Starch and chitosan are extracted from abundant and inexpensive potato and crab shells, respectively. Nacre-inspired interface designs are introduced to construct a 3D interconnected single wall carbon nanotube (SCNT)-pristine graphene (PG)-conductive polymer network architecture. The inorganic one-dimensional SCNT and two-dimensional PG sheets are tightly cross-linked together at the junction interface by long organic conductive poly(3,4-ethylenedioxythiophene) (PEDOT) chains. The formation of a 3D continuous SCNT-PG-PEDOT conductive network leads to not only a low sheet resistance but also a superior flexibility. The flexible transparent electrode possesses an excellent optoelectronic performance: typically, a sheet resistance of 46 Ω/sq with a transmittance of 83.5% at a typical wavelength of 550 nm. The sheet resistance of the electrode slightly increased less than 3% even after hundreds of bending cycles. The lightweight flexible and biocompatible transparent electrode could conform to skin topography or any other arbitrary surface naturally. The edible starch-chitosan substrate-based transparent electrodes could be biodegraded in lysozyme solution rapidly at room temperature without producing any toxic residues. SCNT-PG-PEDOT can be recycled via a membrane process for further fabrication of conductive and reinforcement composites. This high-performance biodegradable transparent electrode is a promising material for next-generation wearable green optoelectronics, transient electronics, and edible electronics.

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A phase change material (PCM) essentially making up hexadecyl acrylate-grafted graphene (HDA-g-GN) was fabricated via a solvent-free Diels–Alder (DA) reaction. The novel material exhibits multiresponsive, enhanced thermal and electrical conductivities and valid thermal enthalpy. In addition, the optimum DA reaction conditions were explored. A variety of characterization techniques were used to study the thermal, crystalline, and structural properties of HDA-g-GN. The melting and crystallizing enthalpies of HDA-g-GN were as high as 57 and 55 J/g, respectively. Furthermore, the melting and freezing points of HDA-g-GN were 29.5 and 32.7 °C, respectively. The thermal conductivity of HDA-g-GN reached 3.957 W/(m K), which is well above that of HDA itself and the previously reported PCMs. HDA-g-GN exhibited an excellent electric conductivity of 219 S/m. Compared to HDA, the crystalline activation energy of HDA-g-GN decreased from 397 to 278 kJ/mol (Kissinger model) and 373 to 259 kJ/mol (Ozawa model). Moreover, HDA-g-GN exhibited excellent thermal stability, shape stability, and thermal reliability. More importantly, HDA-g-GN can be employed to realize high-performance light-to-thermal and electron-to-thermal energy conversion and storage, which provides wide application prospects in energy-saving buildings, battery thermal management system, bioimaging, biomedical devices, as well as real-time and time-resolved applications.

For the scalable fabrication of transparent electrodes and optoelectronic devices, excellent adhesion between the conductive films and the substrates is essential. In this work, a novel mussel-inspired polydopamine-functionalized graphene/silver nanowire hybrid nanomaterial for transparent electrodes was fabricated in a facile manner. Graphene oxide (GO) was functionalized and reduced by polydopamine while remaining stable in water without precipitation. It is shown that the polydopamine-functionalized GO (PFGO) film adhered to the substrate much more easily and more uniformly than the GO film. The PFGO film had a sheet resistance of ∼3.46 × 10(8) Ω/sq and a transparency of 78.2%, with excellent thermal and chemical stability; these characteristics are appropriate for antistatic coatings. Further reduced PFGO (RPFGO) as a conductive adhesion promoter and protective layer for the Ag nanowire (AgNW) significantly enhanced the adhesion force between AgNW networks and the substrate. The RPFGO-AgNW electrode was found to have a sheet resistance of 63 Ω/sq and a transparency of 70.5%. Moreover, the long-term stability of the RPFGO-AgNW electrode was greatly enhanced via the effective protection of the AgNW by RPFGO. These solution-processed antistatic coatings and electrodes have tremendous potential in the applications of optoelectronic devices as a result of their low production cost and facile processing.

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Poly(styrene-maleic anhydride) functionalized graphene (FG) and functionalized carbon nanotubes (FCNTs) were fabricated using in situ polymerization. The FG and FCNTs were used in the in situ ring-opening polymerization of e-caprolactam to form polyamide 6 (PA6)/FG/FCNTs composites. Both PA6 and the composite fibers were melt-spun in a piston spinning machine. The structure and properties of the composites and the fibers were characterized. The experimental results demonstrate that the mixture of graphene and carbon nanotubes exhibits good dispersion in a PA6 matrix. No obvious aggregation of graphene or CNTs was observed inside the composite fibers. The mechanical properties of PA6 are improved by inserting FG/FCNTs into the composite fibers, in particular, the tensile strength of composite fiber containing FG (0.2 wt%)/FCNTs (0.3 wt%) is 2.4 times that of pure PA6, and Young's modulus is 132 % higher than that of the control. The crystallinity of the composite fibers is also enhanced. With the improvement of the tensile strength and Young's modulus of PA6, its application will be expanded.

Piezoelectric organic films as flexible and wearable pressure sensors are ideal materials for manufacturing of electronic skin. Poly‐l‐lactic acid (PLLA)/graphene composite nanofibers are fabricated by electrospinning. The relative crystallinity of the PLLA/graphene electrospun composite nanofibers increases from 9% to 30%. The d14 value of sample K0.1 (d14 = 9.02 pC N−1) increases by 2048% compared with sample K0 (d14 = 0.42 pC N−1). Piezoelectric bioelectronic skin is fabricated using the PLLA/graphene electrospun nanofiber mat, polyester fabric, and poly(dimethylsiloxane) (PDMS). The maximum open‐circuit voltage (Voc) and short‐circuit current (Isc) of the wearable sensors are 184.6 V and 10.8 μA. The response generated by touching the bioelectronic skin can be converted to a digital signal. The piezoelectric bioelectronic skin is used to monitor the pulse of the human body. Based on the results, a pulse of 76 beats min−1 is calculated, which coincides with the normal human heart rate interval (60–100 beats min−1). The addition of graphene influences the fiber diameters, thermal stability, relative crystallinity, and the piezoelectric properties along the fiber axial direction (d14) of PLLA. This small, flexible sensor, which can achieve high sensitivity, can be used for physiological and health care monitoring phonetic recognition.