Hydrogen peroxide (H2O2), as a reactive oxygen species, is widely generated in many biological systems. It has been considered as an important signaling molecule that mediates various physiological and biochemical processes in plants. Normal metabolism in plant cells results in H2O2 generation, from a variety of sources. Also, it is now clear that nitric oxide (NO) and calcium (Ca2+) function as signaling molecules in plants. Both H2O2 and NO are involved in plant development and abiotic responses. A wide range of evidences suggest that NO could be generated under similar stress conditions and with similar kinetics as H2O2. The interplay between H2O2 and NO has important functional implications to modulate transduction processes in plants. Moreover, close interaction also exists between H2O2 and Ca2+ in response to development and abiotic stresses in plants. Cellular responses to H2O2 and Ca2+ signaling systems are complex. There is quite a bit of interaction between H2O2 and Ca2+ signaling in responses to several stimuli. This review aims to introduce these evidences in our understanding of the crosstalk among H2O2, NO, and Ca2+ signaling which regulates plant growth and development, and other cellular and physiological responses to abiotic stresses.

The use of nanoparticles as a potential building block for photosensitizers has recently become a focus of interest in the field of photocatalysis and photodynamic therapy. Porphyrins and their derivatives are effective photosensitizers due to extended π-conjugated electronic structure, high molar absorption from visible to near-infrared spectrum, and high singlet oxygen quantum yields as well as chemical versatility. In this paper, we report a synthesis of self-assembled porphyrin nanoparticle photosensitizers using zinc meso-tetra(4-pyridyl)porphyrin (ZnTPyP) through a confined noncovalent self-assembly process. Scanning electron microscopy reveals formation of monodisperse cubic nanoparticles. UV-vis characterizations reveal that optical absorption of the nanoparticles exhibits a red shift due to noncovalent self-assembly of porphyrins, which not only effectively increase intensity of light absorption but also extend light absorption broadly covering visible light for enhanced photodynamic therapy. Electron spin-resonance spectroscopy (ESR) studies show the resultant porphyrin nanoparticles release a high yield of singlet oxygen. Nitric oxide (NO) coordinates to central metal Zn ions to form stabilized ZnTPyP@NO nanoparticles. We show that under light irradiation ZnTPyP@NO nanoparticles release highly reactive peroxynitrite molecules that exhibit enhanced antibacterial photodynamic therapy (APDT) activity. The ease of the synthesis of self-assembled porphyrin nanoparticles and light-triggered release of highly reactive moieties represent a completely different photosensitizer system for APDT application.

A nanoaggregated dispersed red 1‐grafted poly(N‐vinylcarbazole) (abbreviated PVDR) is self‐assembled via π–π stacking interactions of the carbazole groups in the polymer system after adding a solution of PVDR in N,N‐dimethylformamide to dichloromethane. Upon self‐assembly, the nanoaggregated PVDR film displays helical columnar stacks with large grain sizes, whereas a non‐aggregated PVDR film exhibits an amorphous morphology with smaller grain size. A write‐once read‐many‐times (WORM) memory device is shown whereby a pre‐assembled solution of PVDR is spin‐coated as the active layer and is sandwiched between an aluminum electrode and an indium‐tin‐oxide (ITO) electrode. This device shows very good memory performance, with an ON/OFF current ratio of more than 105 and a low misreading rate through the precise control of the ON and OFF states. The stability of the nanoaggregated PVDR device is much higher than that of the non‐nanoaggregated PVDR device. This difference in device stability under constant voltage stress can be mainly attributed to the difference in the film crystallinity and surface morphology. No degradation in current density was observed for the ON‐ and OFF‐states after more than one hundred million (108) continuous read cycles indicating that both states were insensitive to the read cycles. These results render the nanoaggregated PVDR polymer as promising components for high‐performance polymer memory devices.

A photocatalyst system is generally comprises a catalyst and cocatalyst to achieve light absorption, electron‐hole separation, and surface reaction. It is a challenge to develop a single photocatalyst having all functions so as to lower the efficiency loss. Herein, the active GaN4 site is integrated into a polymeric carbon nitride (CN) photocatalyst (GCN), which displays an excellent H2 production rate of 9904 μmol h−1 g−1. It is 162 and 3.3 times higher than that of CN with the absence (61 μmol h−1 g−1) and presence (2981 μmol h−1 g−1), respectively, of 1.0 wt % Pt. Under light irradiation the electron is injected and stored at the GaN4 site, where the LUMO locates. The HOMO distributes on the aromatic ring resulting in spatial charge separation. Transient photovoltage discloses the electron‐storage capability of GCN. The negative GaN4 promotes proton adsorption in the excited state. The positive adsorption energy drives H2 desorption from GaN4 after passing the electron to the proton. This work opens up opportunities for exploring a novel catalyst for H2 production.

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