Lanthanide Luminescence Supramolecular Switch Based on Photoreactive Ammonium Molybdate

Specific smart sensing of electron-rich antibiotics or histidine improves the antenna effect, luminescence, and photodynamic sterilization capabilities of lanthanide polyoxometalates

Excessive discharge of antibiotics seriously threatens human health and is thus a global public health problem. This highlights the urgent need to develop intelligent sensing materials for specific antibiotics that are highly visual, fast, convenient, and inexpensive. Herein, two reverse α-octamolybdate polyoxometalates (POMs; Mo8) were used to chelate lanthanide ions to obtain lanthanide POMs (LnPOMs; LnMo16; Ln = Eu, Sm, Tb, Gd) with highly sensitive smart photoresponses to specific antibiotics (ofloxacin [OFN], norfloxacin [NOR], enrofloxacin [ENR], and oxytetracycline [OTC]) and histidine (His) with luminescence turn-on. Specific antibiotics and His, which has an electron-rich structure, can efficiently enhance the antenna effect, thereby greatly improving the luminescence of EuMo16. Surprisingly, OFN and NOR both enhanced the luminescence of Eu(III) ions and Mo8, whereas ENR and OTC only enhanced the luminescence of Eu(III) ions, showing a differentiated sensitization effect. More notably, the combination of POMs and Ln(III) ions enhanced the ability of LnPOMs to produce reactive oxygen species under light irradiation, and these LnPOMs showed significant sterilization effects on Escherichia coli and Staphylococcus aureus. To our knowledge, this is the first time electron-rich antibiotics or amino acids were used to enhance the luminescence of LnPOMs, achieving luminescence-enhanced photoresponse to specific antibiotics and amino acids.

Polyacrylamide/sodium alginate/sodium chloride photochromic hydrogel with high conductivity, anti-freezing property and fast response for information storage and electronic skin

Photochromic hydrogels have promising prospects in areas such as wearable device, information encryption technology, optoelectronic display technology, and electronic skin. However, there are strict requirements for the properties of photochromic hydrogels in practical engineering applications, especially in some extreme application environments. The preparation of photochromic hydrogels with high transparency, high toughness, fast response, colour reversibility, excellent electrical conductivity, and anti-freezing property remains a challenge. In this study, a novel photochromic hydrogel (PAAm/SA/NaCl-Mo7) was prepared by loading ammonium molybdate (Mo7) and sodium chloride (NaCl) into a dual-network hydrogel of polyacrylamide (PAAm) and sodium alginate (SA) using a simple one-pot method. PAAm/SA/NaCl-Mo7 hydrogel has excellent conductivity (175.9 S/cm), water retention capacity and anti-freezing properties, which can work normally at a low temperature of -28.4 °C. In addition, the prepared PAAm/SA/NaCl-Mo7 hydrogel exhibits fast response (<15 s), high transparency (>70 %), good toughness (maximum elongation up to 1500 %), good cyclic compression properties at high compressive strains (60 %), good biocompatibility (78.5 %), stable reversible discolouration and excellent sensing properties, which can be used for photoelectric display, information storage and motion monitoring. This work provides a new inspiration for the development of flexible electronic skin devices.

Multicharged cyclodextrin supramolecular assemblies

Multicharged cyclodextrin (CD) supramolecular assemblies, including those based on positively/negatively charged modified mono-6-deoxy-CDs, per-6-deoxy-CDs, and random 2,3,6-deoxy-CDs, as well as parent CDs binding positively/negatively charged guests, have been extensively applied in chemistry, materials science, medicine, biological science, catalysis, and other fields. In this review, we primarily focus on summarizing the recent advances in positively/negatively charged CDs and parent CDs encapsulating positively/negatively charged guests, especially the construction process of supramolecular assemblies and their applications. Compared with uncharged CDs, multicharged CDs display remarkably high antiviral and antibacterial activity as well as efficient protein fibrosis inhibition. Meanwhile, charged CDs can interact with oppositely charged dyes, drugs, polymers, and biomacromolecules to achieve effective encapsulation and aggregation. Consequently, multicharged CD supramolecular assemblies show great advantages in improving drug-delivery efficiency, the luminescence properties of materials, molecular recognition and imaging, and the toughness of supramolecular hydrogels, in addition to enabling the construction of multistimuli-responsive assemblies. These features are anticipated to not only promote the development of CD-based supramolecular chemistry but also contribute to the rapid exploitation of these assemblies in diverse interdisciplinary applications.