Exploration of a wide bandgap semiconducting supramolecular Mg(II)-metallohydrogel derived from an aliphatic amine: a robust resistive switching framework for brain-inspired computing

A rapid metallohydrogelation strategy has been developed of magnesium(II)-ion using trimethylamine as a low molecular weight gelator in water medium at room temperature. The mechanical property of the synthesized metallohydrogel material is established through the rheological analysis. The nano-rose like morphological patterns of Mg(II)-metallohydrogel are characterized through field emission scanning electron microscopic study. The energy dispersive X-ray elemental mapping analysis confirms the primary gel forming elements of Mg(II)-metallohydrogel. The possible metallohydrogel formation strategy has been analyzed through FT-IR spectroscopic study. In this work, magnesium(II) metallohydrogel (Mg@TMA) based metal-semiconductor-metal structures have been developed and charge transport behaviour is studied. Here, it is confirmed that the magnesium(II) metallohydrogel (Mg@TMA) based resistive random access memory (RRAM) device is showing bipolar resistive switching behaviour at room temperature. We have also explored the mechanism of resistive switching behaviour using the formation (rupture) of conductive filaments between the metal electrodes. This RRAM devices exhibit excellent switching endurance over 10,000 switching cycles with a large ON/OFF ratio (~ 100). The easy fabrication techniques, robust resistive switching behaviour and stability of the present system makes these structures preferred candidate for applications in non-volatile memory design, neuromorphic computing, flexible electronics and optoelectronics etc.

A thixotropic supramolecular metallogel with a 2D sheet morphology: iodine sequestration and column based dye separation

Sequestration of hazardous radioactive iodine and dye separation to reduce industrial waste through reutilization is pivotal for environmental safety. In this regard, herein, the synthesis of a new waterborne ultrasensitive supramolecular metallogel (Mg@DEOA) with a 2D sheet morphology is accomplished through direct mixing of a low molecular weight gelator diethanolamine and magnesium nitrate hexahydrate. This porous metallogel (180 m2 g-1) exhibits thixotropic properties and is injectable. The material was found to be an effective (587 mg g-1) host matrix for iodine sequestration from solution. Moreover, the Mg@DEOA xerogel was used to efficiently remove rhodamine B from a mixture of dyes with high separation factors through a xerogel packed column and as an adsorbent material for water-soluble dyes and CO. This column based application demonstrated by the metallogel could be useful for practical industrial dye-separation.

The crown ether size and stereochemistry affect the self-assembly, hydrogelation, and cellular interactions of crown ether/peptide conjugates

Crown ether ring size affects nanofiber morphology of hydrogels upon conjugation with D- and L-phenylalanine dipeptides. Random nanofibers showed enhanced cell adhesion and proliferation whereas twisted nanofibers displayed weak cell attachments.

Organogel-Derived Covalent-Noncovalent Hybrid Polymers as Alkali Metal-Ion Scavengers for Partial Deionization of Water

We show that crown ethers (CEs) 1-5 congeal both polar and nonpolar solvents via their self-assembly through weak noncovalent interactions (NCIs) such as CH···O and CH···π interactions. Diisopropylidene-mannitol (6) is a known gelator that self-assembles through stronger OH···O H bonding. These two gelators together also congeal nonpolar solvents via their individual self-assembly. Gelator 6 self-assembles swiftly to fibers, which act as templates and attract CE to their surface through H bonding and thereby facilitate their self-assembly through weak NCI. Polymerization of styrene gels made from CE and 6, followed by the washing off of the sacrificial gelator 6, yields robust porous polystyrene-crown ether hybrid matrices (PCH), having pore-exposed CEs. These PCHs not only were efficient in sequestering alkali metal ions from aqueous solutions but also can be recycled. This novel use of organogels for making solid sorbents for metal-ion scavenging might be of great interest.

Bimodal self-assembly of an amphiphilic gelator into a hydrogel-nanocatalyst and an organogel with different morphologies and photophysical properties

We design a flexible, amphiphilic LMWG consisting of donor and acceptor π-chromophores which self-assembles into a hydrogel and an organogel with different nano-morphologies. Different mechanisms of self-assembly evolve charge transfer (CT) emission in the hydrogel and LMWG-based emission in the organogel. Moreover, the hydrogel-nanostructure with surface exposed amide groups is explored for catalyzing Knoevenagel condensation reaction.

Acid–base-controlled and dibenzylammonium-assisted aggregation induced emission enhancement of poly(tetraphenylethene) with an impressive blue shift

The non-covalent interaction between dibenzylammonium chloride and DB24C8 groups in poly(tetraphenylethene)-based conjugated polymers not only leads to an AIEE feature but also a significant blue shift from 515 to 483 nm.

Protection of densely populated excited triplet state ensembles against deactivation by molecular oxygen

Different approaches towards protection of triplet excited states against deactivation by molecular oxygen are summarized and reviewed.

An additional fluorenylmethoxycarbonyl (Fmoc) moiety in di-Fmoc-functionalized L-lysine induces pH-controlled ambidextrous gelation with significant advantages

In recent years, several fluorenylmethoxycarbonyl (Fmoc)-functionalized amino acids and peptides have been used to construct hydrogels, which find a wide range of applications. Although several hydrogels have been prepared from mono Fmoc-functionalized amino acids, herein, we demonstrate the importance of an additional Fmoc-moiety in the hydrogelation of double Fmoc-functionalized L-lysine [Fmoc(Nα)-L-lysine(NεFmoc)-OH, (Fmoc-K(Fmoc))] as a low molecular weight gelator (LMWG). Unlike other Fmoc-functionalized amino acid gelators, Fmoc-K(Fmoc) exhibits pH-controlled ambidextrous gelation (hydrogelation at different pH values as well as organogelation), which is significant among the gelators. Distinct fibrous morphologies were observed for Fmoc-K(Fmoc) hydrogels formed at different pH values, which are different from organogels in which Fmoc-K(Fmoc) showed bundles of long fibers. In both hydrogels and organogels, the self-assembly of Fmoc-K(Fmoc) was driven by aromatic π-π stacking and hydrogen bonding interactions, as evidenced from spectroscopic analyses. Characterization of Fmoc-K(Fmoc) gels using several biophysical methods indicates that Fmoc-K(Fmoc) has several advantages and significant importance as a LMWG. The advantages of Fmoc-K(Fmoc) include pH-controlled ambidextrous gelation, pH stimulus response, high thermal stability (∼100 °C) even at low minimum hydrogelation concentration (0.1 wt%), thixotropic property, high kinetic and mechanical stability, dye removal properties, cell viability to the selected cell type, and as a drug carrier. While single Fmoc-functionalized L-lysine amino acids failed to exhibit gelation under similar experimental conditions, the pH-controlled ambidextrous gelation of Fmoc-K(Fmoc) demonstrates the benefit of a second Fmoc moiety in inducing gelation in a LMWG. We thus strongly believe that the current findings provide a lead to construct or design various new synthetic Fmoc-based LMW organic gelators for several potential applications.

pH sensitive smart gels of cetylpyridinium chloride in binary solvent mixtures: phase behaviour, structure and composition

Figure showing the effect of pH on CPC gel formation at 25 °C and fluorescence emission spectra of CPC solutions at pH ∼ 11.8.

Fluorescence responsive conjugated poly(tetraphenylethene) and its morphological transition from micelle to vesicle

A crown ether-functionalized poly(tetraphenylethene) (AP-TPE) is synthesized and the rotation of the TPE group is successfully restricted, leading to a stepwise enhanced fluorescence accompanied by a morphological transition from micellar to vesicular.