Greening the pathways: a comprehensive review of sustainable synthesis strategies for silica nanoparticles and their diverse applications.

Silica nanoparticles (SiNPs) have emerged as a multipurpose solution with wide-ranging applications in various industries such as medicine, agriculture, construction, cosmetics, and food production. In 1961, Stöber introduced a ground-breaking sol-gel method for synthesizing SiNPs, which carried a new era of exploration both in academia and industry, uncovering numerous possibilities for these simple yet multifaceted particles. Inspite of numerous reported literature with wide applicability, the synthesis of these nanoparticles with the desired size and functionalities poses considerable challenges. Over time, researchers have strived to optimize the synthetic route, particularly by developing greener approaches that minimize environmental impact. By reducing hazardous chemicals, energy consumption, and waste generation, these greener synthesis methods have become an important focus in the field. This review aims to provide a comprehensive analysis of the various synthetic approaches available for different types of SiNPs. Starting from the Stöber' method, we analyze other methods as well to synthesis different types of SiNPs including mesoporous, core-shell and functionalized nanoparticles. With increasing concerns with the chemical methods associated for environmental issues, we aim to assist readers in identifying suitable greener synthesis methods tailored to their specific requirements. By highlighting the advancements in reaction time optimization, waste reduction, and environmentally friendly precursors, we offer insights into the latest techniques that contribute to greener and more sustainable SiNPs synthesis. Additionally, we briefly discuss the diverse applications of SiNPs, demonstrating their relevance and potential impact in fields such as medicine, agriculture, and cosmetics. By emphasizing the greener synthesis methods and economical aspects, this review aims to inspire researchers and industry professionals to adopt environmentally conscious practices while harnessing the immense capabilities of SiNPs.

Humic acid-nanoceria composite as a sustainable adsorbent for simultaneous removal of uranium(VI), chromium(VI), and fluoride ions from aqueous solutions.

In this article, the multifunctional behavior of novel, efficient, and cost-effective humic acid-coated nanoceria (HA@CeO2 NPs) was utilized for the sorptive removal of U(VI), Cr(VI), and F- ions at different conditions. The production cost of HA@CeO2 was $19.28/kg and was well characterized by DLS, FESEM, HRTEM, FTIR, XRD, XPS, and TGA. Batch adsorption study for U(VI) (at pH ~ 8), Cr(VI) (at pH ~ 1), and F- (at pH ~ 2) revealed that the maximum percentage of sorption was > 80% for all the cases. From the contact time experiment, it was concluded that pseudo-second-order kinetics followed, and hence, the process should be a chemisorption. The adsorption study revealed that U(VI) and Cr(VI) followed the Freundlich isotherm, whereas F- followed the Langmuir isotherm. Maximum adsorption capacity for F- was 96 mg g-1. Experiments in real water suggest that adsorption is decreased in Kaljani River water (~ 12% for Cr(VI) and ~ 11% for F-) and Kochbihar Lake water (25.04% for Cr(VI) and 20.5% for F-) because of competing ion effect. Mechanism was well established by the kinetic study as well as XPS analysis. Because of high adsorption efficiency, HA@CeO2 NPs can be used for the removal of other harmful water contaminants to make healthy aquatic life as well as purified drinking water.

Adsorptive Elimination of a Cationic Dye and a Hg (II)-Containing Antiseptic from Simulated Wastewater Using a Metal Organic Framework.

Several types of pollutants have acute adverse effects on living bodies, and the effective removal of these pollutants remains a challenge. Safranin O (a biological dye) and merbromin (a topical mercury-containing antiseptic) are considered organic pollutants, and there are only a few reports on their removal. Synthesized and well-characterized (through PXRD, FTIR, FESEM, and EDS analysis) MOF-5 was used for the first time in the removal of safranin O and merbromin from simulated wastewater and real wastewater. In both cases, MOF-5 effectively removed contaminants. We found that in simulated wastewater, the highest efficiency of removal of safranin O was 53.27% (for 15 mg/L) at pH 10, and for merbromin, it was 41.49% (for 25 mg/L) at pH 6. In the case of real wastewater containing natural ions (Na+, K+, F-, Cl-, SO42-, PO43-, Mg2+, and Ca2+) and other molecules, the removal efficiencies of these two dyes decreased (34.00% and 26.28% for safranin O and merbromin, respectively) because of the presence of other ions and molecules. A plausible mechanism for the removal of these pollutants using MOF-5 was proposed.

Bio-functionalized magnetic nanoparticles for cost-effective adsorption of U(vi): experimental and theoretical investigation.

U(vi) removal using cost-effective (production cost: $14.03 per kg), biocompatible, and superparamagnetic Cinnamomum tamala (CT) leaf extract-coated magnetite nanoparticles (CT@MNPs or CT@Fe3O4 nanoparticles) from water resources was studied. From pH-dependent experiments, the maximum adsorption efficiency was found to be at pH 8. Isotherm and kinetic studies were performed and found to follow Langmuir isotherm and pseudo-second order kinetics, respectively. The maximum adsorption capacity of CT@MNPs was calculated to be 45.5 mg of U(vi) per g of nanoparticles (NPs). Recyclability studies suggest that over 94% sorption was retained even after four consecutive cycles. The sorption mechanism was explained by the point of the zero-charge experiment and the XPS measurement. Additionally, calculations using density functional theory (DFT) were carried out to support the experimental findings.

A facile cost-effective electrolyte-assisted approach and comparative study towards the Greener synthesis of silica nanoparticles.

Nowadays, silica nanoparticles are gaining tremendous importance because of their wide applications across different domains such as drug delivery, chromatography, biosensors, and chemosensors. The synthesis of silica nanoparticles generally requires a high percentage composition of organic solvent in an alkali medium. The eco-friendly synthesis of silica nanoparticles in bulk amounts can help save the environment and is cost-effective. Herein, efforts have been made to minimize the concentration of organic solvents used during synthesis via the addition of a low concentration of electrolytes, e.g., NaCl. The effects of electrolytes and solvent concentrations on nucleation kinetics, particle growth, and particle size were investigated. Ethanol was used as a solvent in various concentrations, ranging from 60% to 30%, and to optimize and validate the reaction conditions, isopropanol and methanol were also utilized as solvents. The concentration of aqua-soluble silica was determined using the molybdate assay to establish reaction kinetics, and this approach was also utilized to quantify the relative concentration changes in particles throughout the synthesis. The prime feature of the synthesis is the reduction in organic solvent usage by up to 50% using 68 mM NaCl. The surface zeta potential was reduced after the addition of an electrolyte, which made the condensation process faster and helped reaching the critical aggregation concentration in a shorter time. The effect of temperature was also monitored, and we obtained homogeneous and uniform nanoparticles by increasing the temperature. We found that it is possible to tune the size of the nanoparticles by changing the concentration of electrolytes and the temperature of the reaction using an eco-friendly approach. The overall cost of the synthesis can also be reduced by ∼35% by adding electrolytes.

Adsorption and Desorption Study of Reusable Magnetic Iron Oxide Nanoparticles Modified with Justicia adhatoda Leaf Extract for the Removal of Textile Dye and Antibiotic.

The release of tetracycline hydrochloride (TCH) and methylene blue (MB) dye into the aquatic system uncontrollably caused major environmental and health problems; hence, their prevention required serious attention. Adsorption process is now being researched in order to increase adsorption efficiency and reprocess to alleviate environmental issues. The use of magnetic nanoparticle as an adsorbent for wastewater treatment has a lot of prospective. A magnetic iron oxide nanoparticle surface modified by Vasaka (Justicia adhatoda) leaf extract (JA-MIONs) is used to give a fast removal approach for MB dye and TCH antibiotics. Dynamic light scattering, UV-Vis and band gap measurement, powder X-ray diffraction, Fourier-transform infrared spectroscopy, and transmission electron microscopy were operated to analyse the formation and size of these magnetic nanoparticles. The impacts of different factors such as contact time (30-150 min), adsorbate concentration (10-50 mg/L), pH (4-10), and adsorbent dose (2-10 mg) were explored. Adsorption kinetics and isotherms show that it follows the pseudo-first-order kinetic and the Freundlich isotherm, with maximum adsorption capacities of 76.92 mg/g for MB and 200 mg/g for TCH at 298 K. The reusability of the JA-MIONs eventually exhibited a decline in the adsorption percentage of MB and TCH after five and four times respectively. After the desorption-adsorption cycles, this adsorbent continued to exhibit significant adsorption capacity. This investigation furnished the significant reference data for the synthesis of JA-MIONs as a novel and auspicious adsorbent for the industrial clean-up of toxic dyes and heavily used antibiotics from water.

Current trends in carbon-based quantum dots development from solid wastes and their applications.

Urbanization and a massive population boom have immensely increased the solid wastes (SWs) generation and are expected to reach 3.40 billion tons by 2050. In many developed and emerging nations, SWs are prevalent in both major and small cities. As a result, in the current context, the reusability of SWs through various applications has taken on added importance. Carbon-based quantum dots (Cb-QDs) and their many variants are synthesized from SWs in a straightforward and practical method. Cb-QDs are a new type of semiconductor that has attracted the interest of researchers due to their wide range of applications, which include everything from energy storage, chemical sensing, to drug delivery. This review is primarily focused on the conversion of SWs into useful materials, which is an essential aspect of waste management for pollution reduction. In this context, the goal of the current review is to investigate the sustainable synthesis routes of carbon quantum dots (CQDs), graphene quantum dots (GQDs), and graphene oxide quantum dots (GOQDs) from various types SWs. The applications of CQDs, GQDs, and GOQDs in the different areas are also been discussed. Finally, the challenges in implementing the existing synthesis methods and future research directions are highlighted.

Is degradation of dyes even possible without using photocatalysts? - a detailed comparative study.

Herein, catalyst-free, eco-friendly, photo-triggered, self-degradation of malachite green (MG) and crystal violet (CV) dyes in comparison to photocatalytic degradation were investigated. To the best of our knowledge, this is the first systematic study to demonstrate the reactive oxygen species (ROS), electron (e-) and hole (h+) generation ability of dyes to initiate self-degradation in the presence of direct solar energy (a free source of UV radiation) and UV light (254 and 365 nm). Various experimental conditions, e.g., different dye concentrations, pH, vessel-materials (borosilicate glass and quartz) were optimized to achieve the optimum degradation outcomes. The degradation kinetics of dyes suggested the applicability of second-order-kinetics to all kinds of applied light sources. Investigation of the thermodynamic approach reveals that the self-degradation procedure was endothermic, with activation energies of 46.89 and 52.96 kJ mol-1, respectively, for MG and CV. The self-degradation mechanism was further corroborated by the quantum calculations, while the formation of final degraded products for dye-degradations was established on the basis of mass spectroscopy and total organic carbon (TOC) analysis. The computed emission energies for MG and CV advocate that the excitation energy occurs due to the sole-attribution electron excitation from the Highest Occupied Molecular Orbital (HOMO) to the Lowest Unoccupied Molecular Orbital (LUMO). The close energy difference between the hydroxyl anions and the dyes also facilitates the creation of the hydroxyl radical. In a similar manner, the excited electrons from the aforementioned dyes may readily be transferred to triplet molecular oxygen, which makes it possible to generate super oxide. The radical generated in the process facilitates the self-degradation of the dyes.

Corticosteroids: A boon or bane for COVID-19 patients?

Several drugs and antibodies have been repurposed to treat COVID-19. Since the outcome of the drugs and antibodies clinical studies have been mostly inconclusive or with lesser effects, therefore the need for alternative treatments has become unavoidable. However, corticosteroids, which have a history of therapeutic efficacy against coronaviruses (SARS and MERS), might emerge into one of the pandemic's heroic characters. Corticosteroids serve an immunomodulatory function in the post-viral hyper-inflammatory condition (the cytokine storm, or release syndrome), suppressing the excessive immunological response and preventing multi-organ failure and death. Therefore, corticosteroids have been used to treat COVID-19 patients for more than last two years. According to recent clinical trials and the results of observational studies, corticosteroids can be administered to patients with severe and critical COVID-19 symptoms with a favorable risk-benefit ratio. Corticosteroids like Hydrocortisone, dexamethasone, Prednisolone and Methylprednisolone has been reported to be effective against SARS-CoV-2 virus in comparison to that of non-steroid drugs, by using non-genomic and genomic effects to prevent and reduce inflammation in tissues and the circulation. Clinical trials also show that inhaled budesonide (a synthetic corticosteroid) increases time to recovery and has the potential to reduce hospitalizations or fatalities in persons with COVID-19. There is also a brief overview of the industrial preparation of common glucocorticoids.

Review on some metal oxide nanoparticles as effective adsorbent in wastewater treatment.

Water contamination has turned into one of the most serious issues in the world. Nanomaterials are proficient to carry away heavy metals, organic and inorganic dyes, pesticides, and small molecules from polluted water. In this regard, nanoparticles have gained much attention due to their extraordinary properties compared to bulk materials. Metal oxide nanoparticles and nanocomposites have several advantages such as elevated surface area, low concentration, easily separable after treatment and so on. Among many feasible techniques, the adsorption process is one of the most useful techniques for removing heavy ions and dyes from wastewater and has gained much attention from researchers. Several studies on metal oxide nanoparticles and their use in wastewater treatment have been published in the literature. This chapter gives an outline about five metal oxide based nanomaterials and nanocomposites as well as their applications in water pollution removal where the efficiency, limits and favourable circumstances are compared and explored. This article surely helps to gather information about some metal oxide nanoparticles and nanocomposites in wastewater treatment by the adsorption technique. In this review article, we primarily focused on five metal oxide nanoparticles and some of their recent applications published in the last two years.

Design, synthesis and docking study of Vortioxetine derivatives as a SARS-CoV-2 main protease inhibitor.

PURPOSE: Vortioxetine an anti-depressant FDA-drug recently reported showing better in vitro efficacy against SARS-CoV-2. METHODS: In this study, we have synthesized ten new derivatives having alkenes, alkynes, benzyl, aryl, and mixed carbamate at the N-terminal of vortioxetine. Then the binding energy and interactions with the crucial amino acid residues in the binding pocket of main protease (Mpro) of SARS-CoV-2, of reported and ten newly synthesized vortioxetine derivatives (total thirty-one) in comparison with remdesivir are analyzed and presented in this paper. RESULTS: Based on the docking scores predicted by ADV and AD, most vortioxetine derivatives showed better binding efficiency towards Mpro of SARS-CoV-2 in comparison with remdesivir (an EUA approved drug against SARS-CoV-2 Mpro) and vortioxetine. CONCLUSION: This study shows that some vortioxetine derivatives can be developed into promising drugs for COVID-19 treatment.

Anticancer, Antibacterial, Antioxidant, and DNA-Binding Study of Metal-Phenalenyl Complexes.

Phenalenyl (PLY)-based metal complexes are a new addition to the metal complex family. Various applications of metal-based phenalenyl complexes (metal-PLY) have been reported, such as catalyst, quantum spin simulators, spin electronic devices, and molecular conductors, but the biological significance of metal-PLY (metal = Co(II), Mn(III), Ni(II), Fe(III), and Al(III)) systems has yet to be explored. In this study, the anticancer properties of such complexes were investigated in ovarian cancer cells (SKOV3 and HEY A8), and the cytotoxicity was comparable to that of other platinum-based drugs. Antibacterial activity of the metal-PLY complexes against both gram-negative (E. coli) and gram-positive (S. aureus) bacteria was studied using a disk diffusion test and minimum inhibitory concentration (MIC) methods. All five metal-PLY complexes showed significant antibacterial activity against both bacterial strains. The antioxidant properties of metal-PLY complexes were evaluated following the 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging method and were acceptable. The DNA-binding properties of these metal-PLY complexes were investigated using absorption spectroscopy, fluorescence spectroscopy, viscosity measurements, and thermal denaturation methods. Experimental evidence revealed that the complexes bind to DNA through intercalation, and the molecular docking study supported this conclusion.

Bio-modified magnetic nanoparticles with Terminalia arjuna bark extract for the removal of methylene blue and lead (II) from simulated wastewater.

This study reports a greener, cheaper and convenient approach to synthesize Terminalia arjuna bark extract coated magnetite nanoparticles (TA@MNPs) using the co-precipitation method and efficient removal of methylene blue (MB) and lead ions [Pb(II)] from simulated wastewater. The synthesized nanoparticles (NPs) were characterized by various techniques such as DLS, XRD, FTIR, HRTEM, AGM, and TGA. From TGA analysis, TA@MNPs was found to be stable even after 500 °C. Using the batch method, maximum removal was achieved at pH 9.0 for MB and pH 3.0 for Pb(II) solutions, respectively. Adsorption study showed that TA@MNPs followed pseudo-second-order kinetics by both adsorbates while isotherm modeling towards adsorption of Pb(II) and MB exhibited Langmuir and Freundlich isotherm respectively. The maximum adsorption capacity for Pb(II) on TA@MNPs was 210.5 mg g-1. The thermodynamic study proved the spontaneity of the physisorption process. Regeneration studies were also performed using five different eluents for the two adsorbents. Overall, TA@MNPs effectively removed pollutants from wastewater and thus could be potentially useful in providing clean water in a cheaper way.

Advances in mercury(II)-salt-mediated cyclization reactions of unsaturated bonds.

The synthesis of complex cyclic compounds is extremely challenging for organic chemists. Many transition-metal-salt-mediated cyclizations are reported in literature. Hg(II) salts have been successfully employed in cyclizations to form complex heterocyclic and carbocyclic structures that are impossible to synthesize with other transition metal salts. In this review, we have summarized cyclization reactions that are performed with Hg(II) salts. These salts are also successfully applied in stoichiometric or catalytic amounts to form complex cyclic structures and natural products.

A Mini-Review on the Effectiveness of Peptoids as Therapeutic Interventions against Neurodegenerative Diseases.

Neurodegenerative diseases have emerged as one of the major age-associated diseases in recent years. Hence, the urge to understand the mechanism and to find targeted therapeutics becomes inevitable. Peptide-based compounds have emerged as one of the important tools for their therapy. However, due to a lack of tolerability, specificity, and proteolytic degradation, they have lost their applicability in the broader sense. Thus, the search for suitable alternatives or peptidomimetics becomes an important criterion for neurotherapeutics. One of the versatile peptidomimetics is N-substituted glycines or peptoids, which retain many properties of peptides but successfully evade the drawbacks of peptides. Peptoids are manifested with greater cellular permeability, less immunogenicity, and their ability to be administered intra-nasally. These properties enhance their potential as neurotherapeutics with respect to their peptide counterparts. Recently, peptoids have been explored for neurotherapeutic applications as aggregation inhibitors, cell signaling pathways modulators, and agents for inhibiting inflammation via multiple mechanisms. Peptoids, due to their versatility and low production cost, are becoming popular among peptidomimetics as potential neurotherapeutic agents. In this review, the diverse applications of peptoids with respect to neurodegenerative disease have been explored.

Repurposed Antiviral Drugs for the Treatment of COVID-19: Syntheses, Mechanism of Infection and Clinical Trials.

COVID-19 is a public health emergency of international concern. Although considerable knowledge has been acquired with time about the viral mechanism of infection and mode of replication, yet no specific drugs or vaccines have been discovered against SARS-CoV-2 to date. There are few small molecule antiviral drugs like Remdesivir and Favipiravir, which have shown promising results in different advanced stages of clinical trials. Chloroquinine, Hydroxychloroquine, and Lopinavir- Ritonavir combination, although initially were hypothesized to be effective against SARSCoV- 2, are now discontinued from the solidarity clinical trials. This review provides a brief description of their chemical syntheses along with their mode of action, and clinical trial results available on Google and in different peer-reviewed journals till 24th October 2020.

Silver-Based Nanomaterials as Therapeutic Agents Against Coronaviruses: A Review.

Since the identification of the first human coronavirus in the 1960s, a total of six coronaviruses that are known to affect humans have been identified: 229E, OC43, severe acute respiratory syndrome coronavirus (SARS-CoV), NL63, HKU1, and Middle East respiratory syndrome coronavirus (MERS-CoV). Presently, the human world is affected by a novel version of the coronavirus family known as SARS-CoV-2, which has an extremely high contagion rate. Although the infection fatality rate (IFR) of this rapidly spreading virus is not high (ranging from 0.00% to 1.54% across 51 different locations), the increasing number of infections and deaths has created a worldwide pandemic situation. To provide therapy to severely infected patients, instant therapeutic support is urgently needed and the repurposing of already approved drugs is presently in progress. In this regard, the development of nanoparticles as effective transporters for therapeutic drugs or as alternative medicines is highly encouraged and currently needed. The size range of the viruses is within 60-140 nm, which is slightly larger than the diameters of nanoparticles, making nanomaterials efficacious tools with antiviral properties. Silver-based nanomaterials (AgNMs) demonstrate antimicrobial and disinfectant effects mostly by generating reactive oxygen species (ROS) and are presently considered as a versatile tool for the treatment of COVID-19 patients. Other metal-based nanoparticles have been primarily reported as delivery agents or surface modifying agents, vaccine adjuvant against coronavirus. The present review summarizes and discusses the possible effectiveness of various surface-modified AgNMs against animal coronaviruses and presents a concept for AgNM-based therapeutic treatment of SARS-CoV-2 in the near future.

Design, synthesis and biological evaluation of vortioxetine derivatives as new COX-1/2 inhibitors in human monocytes.

In order to identify a suitable alternative to non-steroidal anti-inflammatory drugs (NSAIDs) we aimed to develop derivatives of vortioxetine, a multimodal anti-depressive drug that has been shownpreviously to be endowed withanti-inflammatory activity in human monocytes/macrophages. Vortioxetine (1) was synthesized in good yield and different alkyl and aryl derivatives were prepared based on their structural diversity and easy availability. The compounds were tested on human monocytes isolated from healthy donors for theireffect on superoxide anion production and cytokine gene expression, and for COX-1/2 gene expression and activity modulation. Moreover, a docking study was performed to predict the interactions between the synthesized compounds and COX-1 and COX-2. Correlating experimental biological data to the molecular modelling studies, it emerged that among the novel compounds, 6 was endowed of antioxidant and anti-COX-1 activity, vortioxetine and 3 were good antioxidants and mild anti-COX-1/2 inhibitors, while 7 was a good anti-COX-1/2 inhibitor and 11 was more specific versus COX-2.

Green Synthesis, Characterization and Application of Natural Product Coated Magnetite Nanoparticles for Wastewater Treatment.

Adsorption of organic pollutants, toxic metal ions, and removal of harmful bacteria can give us clean and pure drinkable water from wastewater resources. Respective magnetite nanoparticles (MNPs) were synthesized using a cheaper and greener way in an open-air environment with the use of crude latex of Jatropha curcas (JC) and leaf extract of Cinnamomum tamala (CT). Characterization of MNPs had been performed by dynamic light scattering (DLS), Ultraviolet-visible (UV-vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, powdered X-ray diffraction (XRD), and field emission scanning electron microscope (FE-SEM). The size ranges of the synthesized MNPs were observed in between 20-42 nm for JC-Fe3O4 and within 26-35 nm for CT-Fe3O4 by FE-SEM images. The effect of synthesized magnetic nanoparticles in wastewater treatment (bacterial portion), dye adsorption, toxic metal removal as well as antibacterial, antioxidant, and cytotoxic activities were studied. This purification will lead to an increase in the resources of pure drinking water in the future.

Author Correction: Computationally designed antibody-drug conjugates self-assembled via affinity ligands.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.