meso-Tetraphenylporphyrin (TPP) and its two substituted derivatives (meso-tetrakis(4-cyanophenyl)porphyrin [TPP(CN)₄] and meso-tetrakis(4-methoxyphenyl)porphyrin [TPP(OMe)₄]) were synthesized. Their nonlinear absorption and refraction properties were studied using the Z-scan technique in the picosecond (ps) and nanosecond (ns) regimes. The open aperture Z-scan results reveal that TPP and TPP(CN)₄ display an identical reverse saturable absorption (RSA) character in the ps and ns regimes. While TPP(OMe)₄ exhibits a transition from saturable absorption (SA) to RSA in the ps regime and a typical RSA character in the ns regime. The closed aperture Z-scan results show that TPP(CN)₄ and TPP(OMe)₄ have regular enhancement of the magnitude of nonlinear refraction as compared to their parent TPP in both the ps and ns regimes. In addition, the second-order molecular hyperpolarizabilities (γ) of these three porphyrins are calculated, and the γ values of TPP(CN)₄ and TPP(OMe)₄ are remarkable larger than that of TPP. The introduction of the electron-withdrawing group CN and the electron-donating group OMe into TPP has enhanced its nonlinear refraction and γ value, and tuned its nonlinear absorption (TPP(OMe)₄), which could be useful for porphyrin-related applications based on the desired NLO properties.

Nickel foam (NF) with a three-dimensional porous structure plays an important role in a wide variety of applications such as energy storage and conversion, catalysis, and sensor due to its high porosity, low density, and excellent conductivity. However, the main drawback of NF is that its ligaments are very smooth, and thus the surface area is relatively low. In this work, we propose a novel strategy, oxidization and reduction process, in situ to construct micron/nano pores on the ligaments of commercial NF to fabricate a typical hierarchical porous architecture. This process is simple and green, avoiding the use of sacrificial materials. Furthermore, MnO₂ is coated on the micron/nano-porous Ni foam (MPNF) to construct an oxygen evolution reaction (OER) electrode through pulse electrodeposition. The designed MPNF-MnO₂ electrode presents enhanced OER electrocatalysis activity with a low overpotential of 363.5 mV at the current density of 10 mA cm⁻² in an alkaline solution, which is 66.4 mV lower than that of the NF-MnO₂ electrode in the same operating conditions. Furthermore, the porous and wrinkled structures of the MPNF also improve the mechanical integrity of the electrode, resulting in super-long stability.

Self-powered photoelectrochemical (PEC) ultraviolet photodetectors (UVPDs) are promising for next-generation energy-saving and highly integrated optoelectronic systems. Constructing a heterojunction is an effective strategy to increase the photodetection performance of PEC UVPDs because it can promote the separation and transfer of photogenerated carriers. However, both crystal defects and lattice mismatch lead to deteriorated device performance. Here, we introduce a structural regulation strategy to prepare TiO₂ anatase-rutile heterophase homojunctions (A-R HHs) with oxygen vacancies (OVs) photoanodes through an in situ topological transformation of titanium metal–organic framework (Ti-MOF) by pyrolysis treatment. The cooperative interaction between A-R HHs and OVs suppresses carrier recombination and accelerates carrier transport, thereby significantly enhancing the photodetection performance of PEC UVPDs. The obtained device realizes a high on/off ratio of 10,752, a remarkable responsivity of 24.15 mA W⁻¹, an impressive detectivity of 3.28 × 10¹¹ Jones, and excellent cycling stability. More importantly, under 365 nm light illumination, a high-resolution image of “HUST” (the abbreviation of Harbin University of Science and Technology) was obtained perfectly, confirming the excellent optical imaging capability of the device. This research not only presents an advanced methodology for constructing TiO₂-based PEC UVPDs, but also provides strategic guidance for enhancing their performance and practical applications.