Diphenylalanine (FF) is a piezoelectric material that is widely known for its high piezoelectric constant, self-assembly characteristics, and ease of manufacture. Because of its biocompatible nature, it is useful for implantable applications. However, its use in real applications is challenging because it degrades too easily in the body due to its solubility in water (0.76 g/mL). Upon incorporation of hydrophobic and biocompatible porphyrins into the FF, the degradability of the piezoelectric FF and their piezoelectric nanogenerators (PENGs) is controlled. Porphyrin-incorporated FFs are also formed as piezoelectric nanostructures well aligned on the substrate through self-assembly, and their piezoelectric properties are comparable to those of FF. The FF-based PENG degrades in only 5 min, whereas the FF-porphyrin-based PENG produces a stable output for >15 min in phosphate-buffered saline. This strategy for realizing biodegradable functional materials and devices with tunable degradation rates in the body can be applied to many implantable electronics.

The wurtzite structured zinc oxide has been studied extensively because of its unique characteristics, such as transparency, semiconducting properties, and excellent piezoelectricity. However, the defects that are inevitably present in ZnO grown by the aqueous solution method generate excessive free electrons, which reduce the piezoelectric potential by the screening effect, thus reducing the piezoelectric output performance. Herein, direct current high‐performance piezoelectric nanogenerators (PENGs) based on Li‐doped ZnO nanosheets are demonstrated. Doping with the p‐type dopant Li reduces the number of free electrons in ZnO, minimizing the screening effect and improving the piezoelectric output performance. First, Li‐doped ZnO nanosheet is synthesized at various Li concentrations using the aqueous solution method. The doping effect on the morphology and crystal structure of the ZnO nanosheet is investigated via scanning electron microscopy and X‐ray diffraction. X‐ray photoelectron spectroscopy confirmed that the ZnO nanosheet is doped with lithium. The Li‐doped ZnO nanosheet‐based PENG produce an output power of 6.552 mW cm−2, that is, a 16‐fold enhancement in output power compared to that of the undoped ZnO nanosheet‐based PENGs.

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Surface modification of inorganic nanoparticles is critical for the quality and performance of pigments, cosmetics, and composite materials. We covered the titanium dioxide nanoparticles’ surface with 2-(acetoacetoxy) ethyl methacrylate, a polymerizable chelating agent. Through the in situ polymerization procedure, this molecule’s β-ketoester moiety quickly coordinated with the metal atoms on titanium dioxide nanoparticles, and its methacrylate group formed homogeneous coating layers. This coating layer significantly reduced the photocatalytic activity of titanium dioxide nanoparticles and prevented their aggregation. This nanoparticle dispersion showed low viscosity up to the solid content of 60% (w/w) in the liquid dispersant. As a result, it increased the UV screening performance and dispersion stability. Additionally, this coating layer widened the absorption spectrum of titanium dioxide and could change the color of nanoparticles from pale yellow to brown. It can also be helpful for cosmetic applications.