Gel-nanocomposites are rapidly emerging functional advanced materials having widespread applications in materials and biological sciences. Herein, we review syntheses, properties, and applications of ...various gel-nanocomposites assembled from different metal-based nanoparticles or nanocarbons fullerene, carbon nanotubes (CNTs), and graphenes with tailor-made supramolecular (small molecular) or polymeric physical organogels and hydrogels. Dynamic supramolecular self-assembly of gelators prove to be excellent hosts for the incorporation of these dimensionally different nanomaterials. Thus, gel-nanocomposites doped with preformed/in situ synthesized nanoparticles show magnetic or near-infrared-responsive, catalytic or antibacterial properties. Fullerene-based gel-nanocomposites show applications in organic solar cells. Gel-nanocomposites based on CNTs and graphenes and their functionalized (covalent/noncovalent) analogues find interesting properties including electrical conductivity, viscoelasticity, thermal robustness, magnetic, phase-selective, redox and near-infrared radiation sensitive properties. We present appropriate rationale to explain most of these phenomena at the molecular level, which provide useful perspectives for future designs and new spin-offs. Finally, a possible outlook is projected for the design and syntheses of next generation multifunctional gel-nanocomposites, which could be achieved by increasing the complexity of the system upon adding selective nanomaterials with desired properties in a multicomponent mixture following a de novo design in order to take advantage of their individual properties.
Selective detection of nitro-aromatic compounds (NACs) at nanomolar concentration is achieved for the first time in multiple media including water, micelles or in organogels as well as using test ...strips. Mechanism of interaction of NACs with highly fluorescent p-phenylenevinylene-based molecules has been described as the electron transfer phenomenon from the electron-rich chromophoric probe to the electron deficient NACs. The selectivity in sensing is guided by the pK a of the probes as well as the NACs under consideration. TNP-induced selective gel-to-sol transition in THF medium is also observed through the reorganization of molecular self-assembly and the portable test trips are made successfully for rapid on-site detection purpose.
Organogels made of pyridine-end oligo-p-phenylenevinylenes with tartaric acid exhibit remarkable J-aggregation induced red-shifts (Δλ = 55 nm) and notable chirality transcription. Induction of ...liquid-crystalline behavior is also tuned in the supramolecular assembly.
Environment-friendly management of fruit flies involving pheromones is useful in reducing the undesirable pest populations responsible for decreasing the yield and the crop quality. A nanogel has ...been prepared from a pheromone, methyl eugenol (ME) using a low-molecular mass gelator. This was very stable at open ambient conditions and slowed down the evaporation of pheromone significantly. This enabled its easy handling and transportation without refrigeration, and reduction in the frequency of pheromone recharging in the orchard. Notably the involvement of the nano-gelled pheromone brought about an effective management of Bactrocera dorsalis, a prevalent harmful pest for a number of fruits including guava. Thus a simple, practical and low cost green chemical approach is developed that has a significant potential for crop protection, long lasting residual activity, excellent efficacy and favorable safety profiles. This makes the present invention well-suited for pest management in a variety of crops.
Oligo(p-phenylenevinylene) based bis-pyridinium derivatives show 'ratiometric' detection of heparin in water. For the first time, we present a dose-dependent, multi-color emission switching in the ...presence of heparin. The reversible self-assembly of probes with heparin as the stimulus is also exploited for the screening of heparinase I enzyme.
The synthesis, hydrogelation, and aggregation‐induced emission switching of the phenylenedivinylene bis‐N‐octyl pyridinium salt is described. Hydrogelation occurs as a consequence of π‐stacking, van ...der Waals, and electrostatic interactions that lead to a high gel melting temperature and significant mechanical properties at a very low weight percentage of the gelator. A morphology transition from fiber‐to‐coil‐to‐tube was observed depending on the concentration of the gelator. Variation in the added salt type, salt concentrations, or temperature profoundly influenced the order of aggregation of the gelator molecules in aqueous solution. Formation of a novel chromophore assembly in this way leads to an aggregation‐induced switch of the emission colors. The emission color switches from sky blue to white to orange depending upon the extent of aggregation through mere addition of external inorganic salts. Remarkably, the salt effect on the assembly of such cationic phenylenedivinylenes in water follow the behavior predicted from the well‐known Hofmeister effects. Mechanistic insights for these aggregation processes were obtained through the counterion exchange studies. The aggregation‐induced emission switching that leads to a room‐temperature white‐light emission from a single chromophore in a single solvent (water) is highly promising for optoelectronic applications.
Worth its salt: The π hydrogelation of a phenylenedivinylene bis‐pyridinium salt is described. Variations in the amount of salts or temperature resulted in an aggregation‐induced switch of emission colors (see figure). Thus, room‐temperature white‐light emission is generated from a single chromophore in a single solvent. The effect of different anions and cations on the aggregation follows the Hofmeister series.
Low-molecular-mass organogelators (LMOGs) based on photochromic molecules aggregate in selected solvents to form gels through various spatio-temporal interactions. The factors that control the mode ...of aggregation of the chromophoric core in the LMOGs during gelation, gelation-induced changes in fluorescence, the formation of stacked superstructures of extended π-conjugated systems, and so forth are discussed with selected examples. Possible ways of generating various light-harvesting assemblies are proposed, and some unresolved questions, future challenges, and their possible solutions on this topic are presented.
In molecular biology, understanding the functional and structural aspects of DNA requires sequence-specific DNA binding probes. Especially, sequence-specific fluorescence probes offer the advantage ...of real-time monitoring of the conformational and structural reorganization of DNA in living cells. Herein, we designed a new class of D2A (one-donor-two-acceptor) near-infrared (NIR) fluorescence switch-on probe named quinone cyanine-dithiazole ( QCY-DT: ) based on the distinctive internal charge transfer (ICT) process for minor groove recognition of AT-rich DNA. Interestingly, QCY-DT: exhibited strong NIR-fluorescence enhancement in the presence of AT-rich DNA compared to GC-rich and single-stranded DNAs. We show sequence-specific minor groove recognition of QCY-DT: for DNA containing 5'-AATT-3' sequence over other variable (A/T)4 sequences and local nucleobase variation study around the 5'-X(AATT)Y-3' recognition sequence revealed that X = A and Y = T are the most preferable nucleobases. The live cell imaging studies confirmed mammalian cell permeability, low-toxicity and selective staining capacity of nuclear DNA without requiring RNase treatment. Further, Plasmodium falciparum with an AT-rich genome showed specific uptake with a reasonably low IC50 value (<4 µM). The ease of synthesis, large Stokes shift, sequence-specific DNA minor groove recognition with switch-on NIR-fluorescence, photostability and parasite staining with low IC50 make QCY-DT: a potential and commercially viable DNA probe.
Surfactants containing more than one head group are known to exhibit a wide range of interesting properties as they undergo aggregation in water. The correlation between the molecular structure of ...these surfactants and their properties (for example, critical micellar concentration, aggregation number, morphology, counterion dissociation, fractional charge, etc.) can provide useful information to define the structure−activity relationship. The influence of the number of head groups on the surfactant aggregation is further evident from interesting interfacial behavior, seen in biological applications. This Perspective highlights recent trends in surfactant aggregation effects and focuses on emerging challenges in the field.
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