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Multi-functionality plays a decisive role in tuning and improving fundamental properties of active molecules, and grafting polymerization/conjugation development imparts properties of active molecules to the backbones. Recently, metal-polyphenol coordination networks have attracted a great deal of attention. A variety of transition metal ions can freely combine with catechol/keto-enol containing polyphenols to form metal-polyphenol networks. Herein, the recently studied conjugated polyphenols were summarized and compared to dopamine-conjugated polymers with evaluation of their properties and gelation behaviors. The biomimetic understanding of bioinspired adhesion, metal ion coordination of hydroxyl groups, and their rearrangement within aglycone could expand the ability for the development of biomimetic, eco-friendly, and biocompatible polymers.

Aluminum nitride (AlN) has an ultra-wide bandgap energy of 6.2 eV and is resistant to chemical etching owing to its high chemical stability, making it intractable in the device fabrication process. We developed a facile method of electrochemical (EC) etching of a high-quality AlN epitaxial layer, where both spatial selectivity and a controllable etch rate were achieved. Underneath porous metal electrodes, the lateral etch rate increased with the increasing external anodic bias, from 400 nm/min at 5 V to 700 nm/min at 15 V. Nonporous metal electrodes protected the AlN from etching in hot H3PO4, enabling the spatial selectivity. The high EC etch rate is attributed to the enhanced hole-assisted oxidation at the interface between the AlN and the etchant. The etch pit formed by EC etching exhibited an inverse hexagonal pyramid structure with {1 0 –1 −1} face. As an alternative to dry etching, our method can be applied to the low-damage patterning of AlN with a controllable etch rate.