Probing the Initial Stages of Molecular Organization of Oligo(p-phenylenevinylene) Assemblies with Monolayer Protected Gold Nanoparticles

Rapid Semiconducting Supramolecular Mg(II)-Metallohydrogel: Exploring Its Potential in Nonvolatile Resistive Switching Applications and Antiseptic Wound Healing Properties

An effective strategy was employed for the rapid development of a supramolecular metallohydrogel of Mg(II) ion (i.e., Mg@PEHA) using pentaethylenehexamine (PEHA) as a low-molecular-weight gelator in aqueous medium under ambient conditions. The mechanical stability of the synthesized Mg@PEHA metallohydrogel was characterized by using rheological analysis, which showed its robustness across different angular frequencies and oscillator stress levels. The metallohydrogel exhibited excellent thixotropic behavior, which signifies that Mg@PEHA has a self-healing nature. Field emission scanning electron microscopy and transmission electron microscopy images were utilized to explore the rectangular pebble-like hierarchical network of the Mg@PEHA metallohydrogel. Elemental mapping through energy-dispersive X-ray spectroscopy analysis confirmed the presence of primary chemical constituents in the metallohydrogel. Fourier transform infrared spectroscopy spectroscopy provided insights into the possible formation strategy of the metallohydrogel. In this work, Schottky diode structures in a metal-semiconductor-metal geometry based on a magnesium(II) metallohydrogel (Mg@PEHA) were constructed, and the charge transport behavior was observed. Additionally, a resistive random access memory (RRAM) device was developed using Mg@PEHA, which displayed bipolar resistive switching behavior at room temperature. The researchers investigated the switching mechanism, which involved the formation or rupture of conduction filaments, to gain insights into the resistive switching process. The RRAM device demonstrated excellent performance with a high ON/OFF ratio of approximately 100 and remarkable endurance of over 5000 switching cycles. RRAM devices exhibit good endurance, meaning they can endure a large number of read and write cycles without significant degradation in performance. RRAM devices have shown promising reliability in terms of long-term performance and stability, making them suitable for critical applications that require reliable memory solutions. Significant inhibitory activity against the drug-resistant Klebsiella pneumonia strain and its biofilm formation ability was demonstrated by Mg@PEHA. The minimum inhibitory concentration value of the metallohydrogel was determined to be 3 mg/mL when it was dissolved in 1% DMSO. To study the antibiofilm activity, an MTT assay was performed, revealing that biofilm inhibition (60%) commenced at 1 mg/mL of Mg@PEHA when dissolved in 1% DMSO. Moreover, in the mouse excisional wound model, Mg@PEHA played a crucial role in preventing postoperative wound infections and promoting wound healing.

Two novel low molecular weight gelator-driven supramolecular metallogels efficient in antimicrobial activity applications

A remarkable ultrasonication technique was successfully employed to create two novel metallogels using citric acid as a low molecular weight gelator, in combination with cadmium(ii)-acetate and mercury(ii)-acetate dissolved in N,N-dimethyl formamide at room temperature and under ambient conditions. The mechanical properties of the resulting Cd(ii)- and Hg(ii)-metallogels were rigorously examined through rheological analyses, which revealed their robust mechanical stability under varying angular frequencies and shear strains. Detailed characterization of the chemical constituents within these metallogels was accomplished through EDX mapping experiments, while microstructural features were visualized using field emission scanning electron microscope (FESEM) images. Additionally, FT-IR spectroscopic analysis was employed to elucidate the metallogel formation mechanism. Significantly, the antimicrobial efficacy of these novel metallogels was assessed against a panel of bacteria, including Gram-positive strains such as Bacillus subtilis and Staphylococcus epidermidis, as well as Gram-negative species like Escherichia coli and Pseudomonas aeruginosa. The results demonstrated substantial antibacterial activity, highlighting the potential of Cd(ii) and Hg(ii)-based citric acid-mediated metallogels as effective agents against a broad spectrum of bacteria. In conclusion, this study provides a comprehensive exploration of the synthesis, characterization, and antimicrobial properties of Cd(ii) and Hg(ii)-based citric acid-mediated metallogels, shedding light on their promising applications in combating both Gram-positive and Gram-negative bacterial infections. These findings open up exciting prospects for the development of advanced materials with multifaceted industrial and biomedical uses.

Zn(II)-Coordination Complex(s) from Chiral Bisamides of L-Phenylalanine: Nanoscale-Based Biological Applications and Metallogelation

Three 3-pyridyl-containing small organic bisamide molecules attached with innocent L-phenylalanine (PHE) side chain as building blocks and positional isomeric toluoyl terminals (PME, MME, and OME) have rationally been designed and synthesized for developing a new series of ZnII-coordination complexes. One of the unique molecular frameworks, having two hydrogen bond-equipped monodentate metal-coordinating sites and biologically potent chiral PHE moiety, was combined with ZnII halide salts under various conditions to produce the coordination complexes (CC1-CC7), thoroughly characterized by the single-crystal X-ray diffraction (SXRD) technique. Maintaining the similar component ratios of acquired CCs in 1:1 DMSO-water produced low-molecular weight metallogels (LMWGs) of PME/MME as envisaged from a rheology- and crystal engineering-based structural rationale. A structure-property correlation from the basis of PXRD of the bulk and xerogels and SXRD data of the isolated single crystals of reaction products clearly supports the crystal engineering-based design strategy based on which the metallogels are prepared. Hand-ground nanoscale ZnCl2-based coordination complex CC1 of PME was also studied for cytotoxicity (HEK-293 cell line) and anticancer activities (B16-F10 cell line) in the MTT assay.

A multistimulus-responsive self-healable supramolecular copper(ii)-metallogel derived from l-(+) tartaric acid: an efficient Schottky barrier diode

A low molecular weight gelator l-(+) tartaric acid- based self-healing supramolecular Cu(ii)-metallogel offers an electronic device of Schottky barrier diode at room temperature.

Pt Nanoparticles Supported on a Dynamic Boronate Ester-Based G-quadruplex Hydrogel as a Nanoreactor

Herein, we have reported a dynamic boronic ester mediated guanosine (G) based G-quadruplex hydrogel as an ideal template for in situ and 'green chemical' approach for the synthesis and stabilization of Pt NPs. ¹¹ B NMR and FT-IR spectra reveal the formation of dynamic boronate ester bonds. The TEM images of the G-quadruplex hydrogel reveal entangled three-dimensional (3D) crosslink nanofibrillar networks with average diameter of 20 nm. Similarly, AFM images of the hydrogel show dense nanofibrillar assembly with an average height of 6 nm. The in situ generated Pt NPs have been characterized using TEM and XPS techniques. The average size of the nanofiber supported Pt NPs is 1.5 nm. The Pt NPs embedded G-quadruplex hydrogel shows better mechanical stiffness than the native hydrogel as the storage modulus (G') increases to 2250 Pa from 317.08 Pa after the in situ generation of Pt NPs. Furthermore, G-quadruplex hydrogel supported Pt NPs have been used as a catalytic system for hydrogenation reaction of different aromatic nitro compounds in aqueous medium. The use of G-quadruplex molecular system as a template for the synthesis and stabilization of metal NPs would be an interesting area of research.

Use of a bis-1,2,3-triazole gelator for the preparation of supramolecular metallogels and stabilization of gold nanoparticles

In this work, a series of functional metallogels have been prepared using a bis-1,2,3-triazole gelator prepared using the isosteric substitution method.

Rheoreversible Metallogels Derived from Coordination Polymers

A series of mixed-ligand-based Cd^II /Co^II coordination polymers (CPs) that were derived from two bis(pyridyl)-bis(amide) ligands, 4,4'-oxybis(N-(pyridin-3-yl)benzamide) (LP) and 4,4'-oxybis(N-(pyridin-4-yl)benzamide) (LP1), and a variety of dicarboxylates isophthalates, terephthalates, 1,2-carboxytranscinamates, and 1,3- and 1,4-phenylene dicarboxylates were synthesized based on a rationale that they would occlude solvate guests inside their crystal lattice, thereby rendering these CPs suitable as metallogelators. The CPs were characterized by using single-crystal X-ray diffraction, elemental analysis, powder X-ray diffraction (PXRD), FTIR spectroscopy, and thermogravimetric analysis (TGA). Structural analyses revealed that the majority of the CPs were lattice-occluded molecular solids, which provided us with an opportunity to study their gelation behavior. We observed that, out of eight CPs that were tested, seven were able to produce metallogels. A thorough study of the rheological behavior of the metallogels was performed and CPG1, CPG2, CPG4, and CPG5 were found to exhibit rheoreversible behavior, which was further confirmed by rheological experiments. Interestingly, ligand LP was found to form an aqueous gel, which was exploited to produce silver nanoparticles.

Transforming a C 3-Symmetrical Liquid Crystal to a π-Gelator by Alkoxy Chain Variation

Rational understanding of the structural features involving different noncovalent interactions is necessary to design a liquid crystal (LC) or an organogelator. Herein, we report the effect of the number and positions of alkoxy chains on the self-assembly induced physical properties of a few π-conjugated molecules. For this purpose, we designed and synthesized three C ₃-symmetrical molecules based on oligo(p-phenylenevinylene), C ₃ OPV1-3. The self-assembly properties of these molecules are studied in the solid and solution states. All of the three molecules follow the isodesmic self-assembly pathway. Upon cooling from isotropic melt, C ₃ OPV1 having nine alkoxy chains (-OC₁₂H₂₅) formed a columnar phase with two-dimensional rectangular lattice and retained the LC phase even at room temperature. Interestingly, when one of the -OC₁₂H₂₅ groups from each of the end benzene rings is knocked out, the resultant molecule, C ₃ OPV2 lost the LC property, however, transformed as a gelator in toluene and n-decane. Surprisingly, when the -OC₁₂H₂₅ group from the middle position is removed, the resultant molecule C ₃ OPV3 failed to form either the LC or the gel phases.

A supramolecular Cd(ii)-metallogel: an efficient semiconductive electronic device

A supramolecular Cd(ii)-metallogel with oxalic acid in DMF medium has been achieved, and the semi-conductive characteristics such as the Schottky barrier diode nature of the metallogel were explored.

High Order in a Self-Assembled Iridium(III) Complex Gelator Towards Nanostructured IrO2 Thin Films

The preparation and characterization of a new metallogelator based on the Ir^III discrete cyclometalated complex [(ppy)₂ Ir(bpy)](CH₃ CH₂ OCH₂ CO₂ ) are reported, where H(ppy) is 2-phenylpiridine and bpy is 2,2'-bipyridine, which is used as an ancillary ligand. The compound is able to self-assemble in water in a range of concentrations between 3 % and 6 % w/w, creating a luminescent ordered supramolecular gel. The gel and xerogel architectures were investigated through polarized optical microscopy (POM), SEM and TEM microscopies coupled with powder X-ray diffraction. The gel supramolecular organization is characterized by columnar tetragonal strands, already present at high dilution conditions, of cations surrounded by counteranions. These strands, in turn, are self-assembled in an oblique columnar cell upon gelification. The xerogel thin films obtained upon complete dehydration maintained the gel supramolecular order and can be used as a precursor for the preparation of nanostructured IrO₂ thin films.

Hierarchical self-assembly of photoluminescent CdS nanoparticles into a bile acid derived organogel: morphological and photophysical properties

A simple strategy for the preparation of a new bile acid derived organogel–CdS NP hybrid, and the study of its photophysical and morphological properties.

Enhancement of Energy Storage and Photoresponse Properties of Folic Acid-Polyaniline Hybrid Hydrogel by in Situ Growth of Ag Nanoparticles

Electrically conductive hydrogels are a fascinating class of materials that exhibit multifarious applications such as photoresponse, energy storage, etc., and the three-dimensional micro- and nanofibrillar structures of the gels are the key to those applications. Herein, we have synthesized a hybrid hydrogel based on folic acid (F) and polyaniline (PANI) in which F acts as a supramolecular cross-linker of PANI chains. The gels are mechanically robust and are characterized by field-emission scanning electron microscopy, transmission electron microscopy, and spectroscopic, rheological, and universal testing measurements. The hybrid xerogel exhibit a BET surface area 238 m² g-¹, conductivity of 0.04 S/cm, specific capacitance of 295 F/g at a current density of 1A/g, and photocurrent of ∼2 mA under white-light illumination. Silver nanoparticles (AgNPs) are in situ grown to elegantly improve the conductivity, energy storage, and photoresponse capability of the gels. The formation of AgNPs drastically improves the specific capacitances up to 646 F/g (at current density 1A/g), excellent rate capability (403 F/g at 20 A/g), and stable cycling performance with a retention ratio of 74% after 5000 cycles. The AgNPs embedded gel exhibits dramatic enhancement of photocurrent to 56 mA, and its time-dependent photoillumination corroborates faster rise and decay of current compared to those of folic acid-polyaniline hydrogel.

Strong and fast-recovery organic/inorganic hybrid AuNPs-supramolecular gels based on loofah-like 3D networks

Super strong and fast-recovery organic/inorganic hybrid gold nanoparticle (AuNPs)-supramolecular gels based on a three-dimensional loofah-like nanoscale network self-assembled by polyhedral oligomeric silsesquioxane (POSS) core supramolecular gelators are reported for the first time. Two series of POSS core organic/inorganic hybrid gelators, POSS-BOC-l-Homophenylalanine (POSS-Hpy) and POSS-Boc-Cys(Bzl)-OH (POSS-Cys), with two types of peripherals having different abilities for driving the self-assembly of AuNPs in gels were designed and synthesized, both of which self-assembled into three-dimensional loofah-like nanoscale gel networks producing hybrid physical gels with fast-recovery behaviors. The mechanical properties of the resultant hybrid gels were dramatically increased by as much as 100 times in the system of sulfur containing POSS-Cys gelators without destroying the fast-recovery behaviors, with the addition of AuNPs, which had direct interaction with AuNPs to give S-Au non-covalent driving force to lead AuNPs self-assemble onto the 3D loofah-like network nanofibres in the supramolecular hybrid gel system. However, in the POSS-Hpy gelator system without sulfur, no strong interaction with AuNPs existed and the POSS-Hpy nanocomposites showed no clear changes in morphology, thermal stability or rheological properties, confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), tube-inversion and rotational rheometer measurements. This indicated that the organic/inorganic hybrid gelator POSS-Cys could be applied to the formation of soft materials in which AuNPs were self-assembled and closely arranged into three-dimensional nanoscale networks. This hybrid material has great potential for applications in self-recovery, nano- and micron-scale electronic devices, because it has both a large mechanical strength and a fast-recovery capability.

Selective Extraction and In Situ Reduction of Precious Metal Salts from Model Waste To Generate Hybrid Gels with Embedded Electrocatalytic Nanoparticles

A hydrogel based on 1,3:2,4-dibenzylidenesorbitol (DBS), modified with acyl hydrazides which extracts gold/silver salts from model waste is reported, with preferential uptake of precious heavy metals over other common metals. Reduction of gold/silver salts occurs spontaneously in the gel to yield metal nanoparticles located on the gel nanofibers. High nanoparticle loadings can be achieved, endowing the gel with electrochemical activity. These hybrid gels exhibit higher conductances than gels doped with carbon nanotubes, and can be used to modify electrode surfaces, enhancing electrocatalysis. We reason this simple, industrially and environmentally relevant approach to conducting materials is of considerable significance.

Improved mechanical and electronic properties of co-assembled folic acid gel with aniline and polyaniline

Co-assembled folic acid (F) gel with aniline (ANI) (ANI:F = 1:2, w/w) is produced at 2% (w/v) concentration in water/DMSO (1:1, v/v) mixture. The gel is rigid and on polymerization of the gel pieces in aqueous ammonium persulfate solution co-assembled folic acid - polyaniline (F-PANI) gel is formed. Both the co-assembled F-ANI and F-PANI gels have fibrillar network morphology, the fiber diameter and its degree of branching increase significantly from those of F gel. WAXS pattern indicates co-assembled structure with the F fiber at the core and ANI/PANI at its outer surface and the co-assembly is occurring in both F-ANI and F-PANI systems through noncovalent interaction of H-bonding and π stacking processes between the components. FTIR and UV-vis spectra characterize the doped PANI formation and the MALDI mass spectrometry indicates the degree of polymerization of polyaniline in the range 24-653. The rheological experiments support the signature of gel formation in the co-assembled state and the storage (G') and loss (G″) modulii increase in the order F gel< F-ANI gel < F-PANI gel, showing the highest increase in G' ≈ 1100% for the F-PANI gel. The stress at break, elasticity, and stiffness also increase in the same order. The dc-conductivity of F-ANI and F-PANI xerogels is 2 and 7 orders higher than that of F xerogel. Besides, the current (I)-voltage (V) curves indicate that the F-xerogel is insulator, but F-ANI xerogel is semiconductor showing both electronic memory and rectification; on the other hand, the F-PANI xerogel exhibits a negative differential resistance (NDR) property with a NDR ratio of 3.0.

Metal induced gelation from pyridine cored poly(aryl ether) dendrons with in situ synthesis and stabilization of hybrid hydrogel composites

Metal induced gel formation from pyridine cored poly(aryl ether) dendrons has been achieved. In addition, the gel is successfully utilized for in situ synthesis and stabilization of silver nanoparticles (AgNPs), which form an unprecedented, well-organized arrangement on the nanofibers.

Size-selective 2D ordering of gold nanoparticles using surface topography of self-assembled diamide template

Size-selective organization of ~2 nm dodecanethiol stabilized gold nanoparticles (AuNPs) into periodic 1D arrays by using the surface topographical features of a soft template is described. The template consists of micrometer length nanotapes organized into nanosheets with periodic valleys running along their length and is generated by the hierarchical self-assembly of a diamide molecule (BHPB) in cyclohexane. The AuNP ordering achieved simply by mixing the preformed template with the readily available ~2 nm dodecanethiol stabilized AuNPs is comparable to those obtained using programmable DNA and functional block copolymers. The observed periodicity of the AuNP arrays provided valuable structural clues about the organization of nanotapes into nanosheets. Self-assembling BHPB molecules in the presence of AuNPs by heating and cooling the two components led to a comparatively disordered organization because the template structure was changed under these conditions. Moreover, the template could not order larger AuNPs (~5 nm) into a similar 1D array, owing to the steric restriction imposed by the dimension of the valleys on the template. Interestingly, this geometric constraint led to AuNP size sorting when a polydisperse sample (2.5 ± 0.9 nm) was used for organization, with AuNPs attached to the template edges being larger (≥2.2 ± 0.9 nm) than those associated to the inner valleys (1.6 ± 0.8 nm). This is a unique example of size-sorting induced by the surface topographical features of a soft template.