Designing Electronic Structures of Multiscale Helical Converters for Tailored Ultrabroad Electromagnetic Absorption

Atomic-scale doping strategies and structure design play pivotal roles in tailoring the electronic structure and physicochemical property of electromagnetic wave absorption (EMWA) materials. However, the relationship between configuration and electromagnetic (EM) loss mechanism has remained elusive. Herein, drawing inspiration from the DNA transcription process, we report the successful synthesis of novel in situ Mn/N co-doped helical carbon nanotubes with ultrabroad EMWA capability. Theoretical calculation and EM simulation confirm that the orbital coupling and spin polarization of the Mn-N4-C configuration, along with cross polarization generated by the helical structure, endow the helical converters with enhanced EM loss. As a result, HMC-8 demonstrates outstanding EMWA performance, achieving a minimum reflection loss of -63.13 dB at an ultralow thickness of 1.29 mm. Through precise tuning of the graphite domain size, HMC-7 achieves an effective absorption bandwidth (EAB) of 6.08 GHz at 2.02 mm thickness. Furthermore, constructing macroscale gradient metamaterials enables an ultrabroadband EAB of 12.16 GHz at a thickness of only 5.00 mm, with the maximum radar cross section reduction value reaching 36.4 dB m2. This innovative approach not only advances the understanding of metal-nonmetal co-doping but also realizes broadband EMWA, thus contributing to the development of EMWA mechanisms and applications.

Multi-response gelation based on the molecular assembly of Sudan I dye derivatives for phase selective gelators and chemosensors

Sudan I dye-based smart low molecular weight gelators with/without a perfluoroalkyl group have been successfully synthesized and characterized by rheological measurements, scanning electron microscopy (SEM), IR, and NMR spectroscopies. The gelation behaviors in response to temperature, pH changes, metal cations, and UV-vis light irradiation are investigated. Compounds 1 and 2 could selectively sense the Cu²⁺ cation in the presence of other metal cations. Moreover, compound 2 with a perfluoroalkyl group shows phase selective gelation ability. This work also provides a valuable reference for exploiting photosensitive materials as chemosensors.

Linear and Nonlinear Optical Properties of Azobenzene Derivatives Modified with an (Amino)naphthalene Moiety

The design of two-photon absorbing azobenzene (AB) derivatives has received much attention; however, the two-photon absorption (2PA) properties of bis-conjugated azobenzene systems are relatively less explored. Here, we present the synthesis of six azobenzene derivatives and three bis-azobenzenes substituted (or not) at para position(s) with one or two amino group(s). Their linear and nonlinear absorption properties are studied experimentally and theoretically. The switching behavior and thermal stability of the Z-isomer are studied for unsubstituted mono- (1a, 2a) and bis-azobenzene (3a) compounds, showing that when the length of the π system increases, the half-life of the Z-isomer decreases. Moreover, along with the increase of π-conjugation, the photochromic characteristics are impaired and the photostationary state (PSS) related to E-Z photoisomerization is composed of 89% of the Z-isomer for 2a and 26% of the Z-isomer for 3a. Importantly, the 2PA cross-section increases almost five-fold on extending the π-conjugation (2a vs 3a) and by about one order of magnitude when comparing two systems: the unsubstituted π-electron one (2a, 3a) with D-π-D (2c, 3c). This work clarifies the contribution of π-conjugation and substituent effects to the linear and nonlinear optical properties of mono- and bis-azobenzene compounds based on the experimental and theoretical approaches.

Handedness Inversion of Chiral 3-Aminophenol Formaldehyde Resin Nanotubes Mediated by Metal Coordination

Precise adjustment of microstructure and handedness of chiral nanomaterials is important to regulate their properties and performance. Herein, helical 3-aminophenol formaldehyde resin (APF) nanotubes and corresponding carbonaceous nanotubes with controllable handedness and optical activity were obtained via an external metal ion-mediated supramolecular co-templating method in an enantiomerically pure template system, in which an appropriate amount of Mn²⁺ (Co²⁺ or Ni²⁺ ) with moderate coordination abilities can reverse the spatial arrangement of the phenylglycine-based amphiphilic template molecules through metal coordination. Different stacking modes of coordination complexes in disparate metal ion systems lead to diverse helical senses (diameter and pitch) of the obtained helical APF. In addition, this coordination mode of metal intervention can be applied to other amine-based helical polymer synthesis systems, which paves the way for the design of high-quality chiral nanomaterials with satisfactory physical parameters and properties.

Novel liquid crystalline organogelators based on terephthalic acid and terephthalaldehyde derivatives: properties and promotion through the formation of halogen bonding

Terephthalic acid-based aromatic amides A1 and A2 and a terephthalaldehyde Schiff-base SB are synthesized, allowing stable gelation with numerous types of organic solvents.

Photoresponsive Zn2+-specific metallohydrogels coassembled from imidazole containing phenylalanine and arylazopyrazole derivatives

Stimuli-responsive supramolecular gels and metallogels have been widely explored in the past decade, but the fabrication of metallogels with reversible photoresponsive properties remains largely unexplored.

Room temperature diazotization and coupling reaction using a DES-ethanol system: a green approach towards the synthesis of monoazo pigments

An environmentally benign, one-pot diazotization and coupling reaction using ChCl:tartaric acid DES at room temperature is described. The bulky tartrate ion renders stability to the diazonium salt at room temperature, also evidenced by ¹H NMR. The isolated diazonium salt is stable and active even after 192 h at room temperature.

A Natural Glycyrrhizic Acid-Tailored Light-Responsive Gelator

The construction of stimuli-responsive materials by using naturally occurring molecules as building blocks has received increasing attention owing to their bioavailability, biocompatibility, and biodegradability. Herein, a symmetrical azobenzene-functionalized natural glycyrrhizic acid (trans-GAG) was synthesized and could form stable supramolecular gels in DMSO/H₂ O and MeOH/H₂ O. Owing to trans-cis isomerization, this gel exhibited typical light-responsive behavior that led to a reversible gel-sol transition accompanied by a variation in morphology and rheology. Additionally, this trans-GAG gel displayed a distinct injectable self-healing property and outstanding biocompatibility. This work provides a simple yet rational strategy to fabricate stimuli-responsive materials from naturally occurring, eco-friendly molecules.

Tunable multicolor emissions in a monocomponent gel system by varying the solvent, temperature and fluoride anion

The facile tuning of the fluorescent properties of organogels is highly desirable for optical switches, light-emitting diodes, chemosensors and bioprobes. The design of organic molecules with multiple emission colors but only one molecular platform remains challenging. Herein, a new cholesterol-based organogelator N1 containing D-A pairs (salicylaldehyde and naphthalimide units) was designed. We successfully obtained multiple solvent-tuned emission colors in both the solution and gel states using a unimolecular platform. Moreover, the effects of the solvent on the gel morphology, rheology and anion-responsive properties were studied. Finally, we showed that the gel in benzene displayed reversible thermochromic properties with changes in emission color from yellow-green to red. Several experiments suggested that a short-distance and ordered array of the D-A pairs facilitated the efficient intermolecular electron transfer of the fluorophores.

Robust, universal biomarker assay to detect senescent cells in biological specimens

Cellular senescence contributes to organismal development, aging, and diverse pathologies, yet available assays to detect senescent cells remain unsatisfactory. Here, we designed and synthesized a lipophilic, biotin-linked Sudan Black B (SBB) analogue suitable for sensitive and specific, antibody-enhanced detection of lipofuscin-containing senescent cells in any biological material. This new hybrid histo-/immunochemical method is easy to perform, reliable, and universally applicable to assess senescence in biomedicine, from cancer research to gerontology.

Emission enhanced two-component gels for the detection of organic amine vapors

A two-component gelator with enhanced emission could be used to quantitatively detect and discriminate between aliphatic and aromatic organic amine vapors.