Supramolecular gels are formed by the self-assembly of small molecules under the influence of various non-covalent interactions. As the interactions are individually weak and reversible, it is possible to perturb the gels easily, which in turn enables fine tuning of their properties. Synthetic supramolecular gels are kinetically trapped and usually do not show time variable changes in material properties after formation. However, such materials potentially become switchable when exposed to external stimuli like temperature, pH, light, enzyme, redox, and chemical analytes resulting in reconfiguration of gel matrix into a different type of network. Such transformations allow gel-to-gel transitions while the changes in the molecular aggregation result in alteration of physical and chemical properties of the gel with time. Here, we discuss various methods that have been used to achieve gel-to-gel transitions by modifying a pre-formed gel material through external perturbation. We also describe methods that allow time-dependent autonomous switching of gels into different networks enabling synthesis of next generation functional materials. Dynamic modification of gels allows construction of an array of supramolecular gels with various properties from a single material which eventually extend the limit of applications of the gels. In some cases, gel-to-gel transitions lead to materials that cannot be accessed directly. Finally, we point out the necessity and possibility of further exploration of the field.

/pdf/stimuli-responsive-dynamic-transformations-in-supramolecular-1kaeb90tu7.pdf

Stimuli responsive dynamic transformations in supramolecular gels

The removal of wastes through solar-induced technologies is gaining extensive momentum over the last few years. Photocatalytic (PC) removal of dyes and other waste products from the main stream and aquatic media is considering industrially feasible technologies. Photocatalytic degradation (PD) could economically convert complex molecules into smaller, non-toxic, and lower molecular weight species through photo-assisted redox reactions. Mechanistically, PD process is based on the production of highly reactive, photogenerated hydroxyl and superoxide anion radicals that attack dye molecules and completely mineralize it into more unaffected species, such as CO2 and H2O. This advance technology has advantages over other conventional methods in terms of simplicity, complete pollutants mineralization, no harmful byproducts, cost-effectiveness and reducing contaminants at parts per million (ppm) and parts per billion (ppb) level. The aim of this review is to provide a thorough overview of heterogeneous PD with the literature support. The first section of the review will address the basic principle and materials utilization. This will be followed by a brief section on the different mechanisms reported for PD over the years with suitable examples. Finally, an overview will be provided to various parameters, which influence the process and mechanism pathway. This review aims to not only educate the beginners in the field of PD but also target experienced researchers, who are involved in heterogeneous PD and predicting mechanistic studies.

Heterogeneous photodegradation of industrial dyes: An insight to different mechanisms and rate affecting parameters

The current study reports on polyphenols profile of pomegranate leaves (PL) Punica granatum grown in Egypt and exhibiting their role in development of an eco-friendly method of green synthesis of silver nanoparticles (AgNPs). PL aqueous alcohol extract was fractionated, the major phenolic compound was isolated from the polyphenols rich fraction (ethyl acetate fraction) and identified by conventional and spectroscopic methods of analysis as ellagic acid. Furthermore, the fraction was standardized and analysed using UPLC-PDA-UV and LC-MS-MS techniques revealing tentative identification of 23 polyphenolic compounds, quantifying ellagic acid as 43.14 ± 0.57 μg/mg of the fraction. AgNPs were successfully synthesized with the aid of polyphenols rich fraction. This is the first report revealing the systematic optimization of the green synthesis process using various independent variables. AgNPs were characterized by adopting UV-Vis spectroscopy, FTIR, XRD, and SEM, which revealed strong SPR band within average of λ max 425 nm and polygonal shaped nanoparticles of 26.22 nm size, respectively. The antimicrobial efficacies of AgNPs and polyphenols rich fraction were tested against Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus, and Sarcina lutea), Gram-negative bacteria (Salmonella paratyphi, Escherichia coli, and Pseudomonas aeruginosa) and fungi (Candida albicans). AgNPs showed a concentration-dependent activity against all the tested microorganisms.

/pdf/polyphenols-profile-of-pomegranate-leaves-and-their-role-in-1tnufj2go5.pdf

Polyphenols profile of pomegranate leaves and their role in green synthesis of silver nanoparticles.

Coupling solar-driven photothermal effect into photocatalysis for sustainable water treatment

Coupling solar-driven photothermal effect into photocatalysis for sustainable water treatment.

The current scenario of water resources shows the dominance of pollution caused by the draining of industrial effluents. The polluted waters have resulted in severe health and environmental hazards urging for a suitable alternative to resolve the implications. Various physical and chemical treatment steps currently in use for dye effluent treatment are more time consuming, cost-intensive, and less effective. Alternatively, nanoparticles due to their excellent surface properties and chemical reactivity have emerged as a better solution for dye removal and degradation. In this regard, the potential of silver nanoparticles in dye effluent treatment was greatly explored. Efforts were taken to unravel the kinetics and statistical optimization of the treatment conditions for the efficient removal of dyes. In addition, the role of silver nanocomposites has also experimented with colossal success. On the contrary, studies have also recognized the mechanisms of silver nanoparticle-mediated toxicity even at deficient concentrations and their deleterious biological effects when present in treated water. Hence, the fate of the silver nanoparticles released into the treated water and sludge, contaminating the soil, aquatic environment, and underground water is of significant concern. This review summarizes the current state of knowledge regarding the use of silver nanoparticles and silver-based nanocomposites in effluent treatment and comprehends the recent research on mitigation of silver nanoparticle-induced toxicity.

Silver nanoparticles in dye effluent treatment: A review on synthesis, treatment methods, mechanisms, photocatalytic degradation, toxic effects and mitigation of toxicity.

Antibiotics are natural or synthetic substances that inhibit the growth of infectious microorganisms and prevent from them, causing serious infections. Though the discovery of penicillin was claimed to be accidental, later on, systematic procedures for antibiotic discovery was introduced by Waksman through his streptomycin discovery. Adopting Waksman's platform, many researchers are exploring natural sources in search of antibiotics. On the other hand, the development of resistance to antibiotics is growing at a rate faster than the discovery of new antibiotics. While a number of semi synthetic and synthetic compounds with antimicrobial properties are emerging to combat the above problem, the microorganisms are in no way working inferior to resist the actions of such substances. In fact, the development of resistance by microorganisms to above said alternatives are observed at an even faster rate than the natural antimicrobial compounds obtained from microbes. The reason behind such a faster resistance development is due to the similar structural features of semi-synthetic and synthetic compounds to natural antibiotics from microbes. The treatment of infectious diseases becomes a big task and requires a greater concern nowadays to avoid increased rates of mortality. This is an alarming condition demanding for the discovery and development of new antimicrobial compounds that would end up as a better solution for the existing problem and avoid the development of resistance. This review presents the background of antibiotics discovery and resistance development and also provides an insight into the available strategies to combat the problem.

https://pharmascope.org/index.php/ijrps/article/download/1410/1484

Arul Jayanthi Antonisamy

Papers

Silver nanoparticles in dye effluent treatment: A review on synthesis, treatment methods, mechanisms, photocatalytic degradation, toxic effects and mitigation of toxicity.

Antibiotics resistance - a stumbling block to antibiotics research