Mechanistic investigation of formation of highly-dispersed silver nanoparticles using sea buckthorn extract.

Nowadays, the greener pathways for the synthesis of nanostructures are being explored. The extracts of different parts of plantsvizleaves, stems, and roots have been investigated. However, these extracts have been prepared by simply boiling or microwaving, or sonicating the parts of plants with water. Therefore, to have deeper insight and to investigate the full potential of plant extracts, serial extraction of leaves of sea buckthorn (Hippophae rhamnoides L.) which is a medicinally important plant was attempted using the soxhlet apparatus. The as-obtained polyphenolic-rich extract was employed for the preparation of silver nanoparticles (Ag-NPs). Under optimized reaction conditionsviz60 °C temperature and 500µl of extract solution (5 mg ml-1) highly disperse spherical nanoparticles of the average size of 15.8 ± 4.8 nm were obtained. Further, the optical band gap of Ag-NPs prepared using optimized reaction conditions was found to be 2.6 eV using the Tauc equation. Additionally, to understand the reduction by the extract, kinetic studies were also carried out which suggest the predominant occurrence of pseudo-first-order reaction. Furthermore, the mechanism of formation of Ag-NPs using major components of extractvizgallic acid and catechin which were identified by HPLC were also investigated using DFT. The mechanistic investigation was performed for both the keto-enol and radical-mediated preparation of Ag-NPs. Such theoretical investigations will help in the efficient designing of greener and novel routes for the synthesis of Ag-NPs. Additionally, the prepared silver was also employed for the colorimetric detection of H2O2.

rGO-WO3 Heterostructure: Synthesis, Characterization and Utilization as an Efficient Adsorbent for the Removal of Fluoroquinolone Antibiotic Levofloxacin in an Aqueous Phase.

Herein, the heterostructure rGO-WO3 was hydrothermally synthesized and characterized by HRTEM (high-resolution transmission electron microscopy), FESEM (field emission scanning electron microscopy), XRD (X-ray diffraction), FT-IR (Fourier transform infrared spectroscopy), XPS (X-ray photoelectron microscopy), nitrogen physisorption isotherm, Raman, TGA (thermogravimetric analysis) and zeta potential techniques. The HRTEM and FESEM images of the synthesized nanostructure revealed the successful loading of WO3 nanorods on the surface of rGO nanosheets. The prepared heterostructure was utilized as an efficient adsorbent for the removal of a third-generation fluoroquinolone antibiotic, i.e., levofloxacin (LVX), from water. The adsorption equilibrium data were appropriately described by a Langmuir isotherm model. The prepared rGO-WO3 heterostructure exhibited a Langmuir adsorption capacity of 73.05 mg/g. The kinetics of LVX adsorption followed a pseudo-second-order kinetic model. The adsorption of LVX onto the rGO-WO3 heterostructure was spontaneous and exothermic in nature. Electrostatic interactions were found to have played a significant role in the adsorption of LVX onto the rGO-WO3 heterostructure. Thus, the prepared rGO-WO3 heterostructure is a highly promising material for the removal of emerging contaminants from aqueous solution.

The Epidemiologic Aspects of COVID-19 Outbreak: Spreading Beyond Expectations.

The coronavirus disease 2019 (COVID-19) outbreak started in late 2019 in Wuhan, Hubei Province of China, and quickly spread to the surrounding regions and neighboring countries. A novel coronavirus, the so-called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was found to be responsible for this outbreak potentially originating from pangolins. In China, the outbreak lasted for 1 month until it seemed to be controlled after affecting over 81,000 individuals and causing deaths in over 4200 patients. Subsequently, and after affecting over 118,000 individuals and causing over 4200 deaths, the condition was officially announced as a pandemic by the World Health Organization (WHO). In the meantime, the epidemic curve took a downtrend in China, the original epicenter of the pandemic, but started to rise in other countries with a steep slope. Among over 215 affected countries, the USA, European countries (Italy, Germany, Spain, France, the UK), Iran, and South Korea had the highest frequencies in the matters of infected patients and deaths. Importantly, different countries took different policies when encountered with an outbreak, especially in the matter of accuracy of the report and timing of the action. A part of the delays in reporting was expected, including the lag in the chain of reporting, the shortcomings of tests, missed patients, and inadequate testing facilities. However, there were also political and nontechnical reasons that caused the reporting to be inaccurate. Surveillance seems to be less of a reason for the observed in poor management, and it mostly originated from human decision-making failures and political issues. Besides, the culture of populations and their trust in their governments played an important role on how they reacted to the COVID-19 pandemic and acquired policies. Finally, the characteristics of the world today indicate the danger of probable upcoming outbreaks, and policymakers should utilize the existing opportunities, particularly the advancements in technology and media, to prevent or adequately manage them.

Recycling of Waste Poly(ethylene terephthalate) Bottles by Alkaline Hydrolysis and Recovery of Pure Nanospindle-Shaped Terephthalic Acid.

Poly(ethylene terephthalate) (PET) is a versatile engineering plastic which exhibits exceptional mechanical and thermal properties. Huge amounts of PET are consumed in various industries such as food packaging industry, textile industry, in the manufacturing of audio, video tapes and X-ray films and so on. But due to its substantial fraction by volume in water bodies and its high persistence to the atmospheric and biological agents, it could be considered as a hazard substance. Thereby chemical recycling of PET serves as a solution to solid waste problem as it transforms PET into its monomers via hydrolysis. Chemical recycling of post consumed waste PET bottles via alkaline hydrolysis is the main aim of this paper. Operating parameters such as reaction time and temperature were optimized for the conversion of PET into nanospindle-shaped terephthalic acid (TPA). Depolymerization of PET was carried out via alkaline hydrolysis by varying reaction time and temperature and maximum yield of 92% was obtained at 200 °C with reaction time of 25 minutes. The formed TPA nanospindles were further characterized in detail which exhibited high crystallinity, purity and fascinating thermal and surface properties.

Construction of multifunctional NH2-UiO-66 metal organic framework: sensing and photocatalytic degradation of ketorolac tromethamine and tetracycline in aqueous medium.

Existence of pharmaceutical residues in water has endangered environmental pollution worldwide, which makes it ineludible to develop prospective bifunctional materials which not only possess excellent fluorescence behaviour to monitor pharmaceuticals but also exhibit simultaneous photocatalytic removal efficiency. Strengthened by functionalized metal organic framework (MOF) materials, we present here an amine functionalized zirconium-based MOF NH2-UiO-66 which has been successfully synthesized using solvothermal approach. The as prepared MOF was subjected to numerous structural, morphological and compositional characterizations. Interestingly, featured by the excellent fluorescent intensity of MOF modulated by LMCT effect, NH2-UiO-66 was screened to detect pharmaceutical compounds with KTC and TC in aqueous solution. The prepared functionalized MOF showcased excellent sensing platform with magnificent response range (0‒3 µM), lower limit of detection (160 nM; KTC and 140 nM; TC), excellent selectivity and influential anti-interference capability. More importantly, the practical utility of the proposed sensor was further explored for the determination of pharmaceutical drugs in real water samples with suitable recoveries. Simultaneously, the synthesized MOF also exhibited high photocatalytic efficiency towards the removal of KTC and TC under solar light irradiation. The degradation efficiency for KTC and TC was found to be 68.3% and 71.8% within 60 and 280 min of solar light, respectively. Moreover, excellent recyclability was demonstrated by the current synthesized system over five cycles. Overall, this study presents a feasible route for the utilization of functionalized MOFs as potential dual functional materials towards the simultaneous detection and degradation of specific pharmaceuticals from aqueous medium.

Nanoscale designing of metal organic framework moieties as efficient tools for environmental decontamination.

Environmental pollutants, being a major and detrimental component of the ecological imbalance, need to be controlled. Serious health issues can get intensified due to contaminants present in the air, water, and soil. Accurate and rapid monitoring of environmental pollutants is imperative for the detoxification of the environment and hence living beings. Metal-organic frameworks (MOFs) are a class of porous and highly diverse adsorbent materials with tunable surface area and diverse functionality. Similarly, the conversion of MOFs into nanoscale regime leads to the formation of nanometal-organic frameworks (NMOFs) with increased selectivity, sensitivity, detection ability, and portability. The present review majorly focuses on a variety of synthetic methods including the ex situ and in situ synthesis of MOF nanocomposites and direct synthesis of NMOFs. Furthermore, a variety of applications such as nanoabsorbent, nanocatalysts, and nanosensors for different dyes, antibiotics, toxic ions, gases, pesticides, etc., are described along with illustrations. An initiative is depicted hereby using nanostructures of MOFs to decontaminate hazardous environmental toxicants.

Tungsten oxide nanostructures peculiarity and photocatalytic activity for the efficient elimination of the organic pollutant.

The WO3 nanostructures were synthesized by a simple hydrothermal route in the presence of C14TAB and gemini-based twin-tail surfactant. The impact of using these special shape and size directing agents for the synthesis of nanostructures was observed in the form of different shapes and sizes. The WO3 web of chains type nanostructure was obtained using C14TAB in comparison to the cube-shaped nanoparticles through twin-tail surfactant. On contrary, the twin-tail surfactant provides sustainable and controlled growth of cube shape nanoparticles of size ~ 15 nm nearly half of the size ~ 35 nm obtained using conventional surfactant C14TAB, respectively. For the detailed structural features, the Williamson-Hall analysis method was implemented to find out the crystalline size and lattice strain of the prepared nanostructures. Owing to the strong quantum confinement effect, the WO3 cube-shaped nanoparticles with an optical band gap of 2.69 eV of the prepared nanoparticles showed excellent photocatalytic efficacy toward organic pollutant (fast green FCF) compared to the web of chain nanostructures with an optical band gap of 2.66 eV. The ability of the prepared systems to decompose the organic pollutant (fast green FCF) in water was tested under visible light irradiations. The percentage degradation was found to be 94% and 86% for WO3 cube-shaped nanoparticles and WO3 web of chains, respectively. The simplicity of the fabrication method and the high photocatalytic performance of the systems can be promising in environmental applications to treat water pollution.

Water-pluronic-ionic liquid based microemulsions: Preparation, characterization and application as micro-reactor for enhanced catalytic activity of Cytochrome-c.

Microemulsions (µEs), comprising water as polar component, pluronic (normal, L35 and reverse, 10R5) as surfactant and a hydrophobic ionic liquid (HIL) as non-polar component have been prepared and characterized. Owing to higher surface activity, pluronics have promoted the formation of µEs without the use of co-surfactant. Thus prepared µEs have been utilized as nano-reactors for the oxidation of guaiacol in the presence of Cytochrome-c (Cyt-c) at 15, 20, and 25 °C. A 3.2- and 1.3-fold increase in the rate of formation of product of enzymatic catalysis in direct µE (HIL-in-water) with reverse pluronic (10R5) is observed at 15 and 20 °C as compared to that in buffer. However, negligible enzymatic activity is observed in the direct µE formed by normal pluronic (L35). The catalytic activity of Cyt-c decreases in reverse µEs (water-in-HIL) as compared to direct µEs irrespective of the nature of pluronic used. The contrasting nature of nano-interfaces formed by pluronics in µEs and the extent of hydration of these nano-interfaces controlled by temperature exerts varying influence on the catalytic activity of Cyt-c. It is expected that the present work would result in providing a versatile platform for the creation of new IL and pluronic-based µEs for bio-catalytic applications, which have never been reported.

Development of nanostructured lipid carriers as a promising tool for methotrexate delivery: physicochemical and in vitro evaluation.

The aim of the present study is to fabricate the stable nanostructured lipid carriers (NLCs) using biocompatible excipients for the encapsulation of Methotrexate (MTX), a chemotherapeutic agent for breast cancer treatment. MTX has restricted clinical applications owing to its low solubility, non-specific targeting and adverse side effects. Glyceryl Monostearate (GMS) and Miglyol 812 (MI1) were chosen as solid and liquid lipids, respectively, for the fabrication of NLCs, and the influence of variation of solid and liquid composition was investigated. The prepared NLCs exhibited long-term stability and spherical shape morphology as characterized by electron microscopy. The internal structure of fabricated NLCs was arranged into cubic crystalline as confirmed by small-angle X-ray scattering (SAXS) analysis. MTX's encapsulation efficiency of ∼85 ± 0.9%. and sustained in vitro release of MTX ∼ 52% ± 3.0 in 24 h was achieved. Classical molecular dynamics (MD) simulations were performed to study the structural stability of the MTX encapsulated NLCs. Hemolysis carried out on the NLCs showcased the biosafety of the formulation under the tolerance limit (<10%). Further, the MTT assay demonstrates that MTX-loaded NLCs exhibited toxicity against HeLa and MCF-7 cell lines as compared to blank NLCs. The finding demonstrates NLCs as promising vehicles for MTX delivery to address cancer.Communicated by Ramaswamy H. Sarma.

A luminescent Zn-MOF for the detection of explosives and development of fingerprints.

A luminescent 3D metal-organic framework [Zn(NDA)(AMP)] = PUC1 (where, NDA = naphthalene-2,6-dicarboxylic acid and AMP = 4-aminomethyl pyridine) was synthesized under solvothermal conditions. The synthesized 3D framework was fully characterized with the help of different analytical techniques such as SCXRD, FTIR, TGA, PXRD, SEM, BET, etc. PUC1 exhibited a strong emission peak at 371 nm when excited at 290 nm and the resulting emission was efficiently quenched in the presence of various organic explosive substances like pentaerythritol tetranitrate (PETN), 2,4,6-trinitrophenyl-N-methylnitramine (Tetryl), trinitrotoluene (TNT), 1,3,5-trinitroperhydro-1,3,5-triazine (RDX), and 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane (HMX). PUC1 revealed highly sensitive and selective detection of PETN and Tetryl with high quenching constant values of 0.1 × 106 and 0.12 × 105 M-1 and low detection limits of 0.315 and 0.404 µM respectively. The strong luminescent properties of PUC1 lead to its successful application in the development of latent fingermarks on different non-porous surfaces using the powder dusting method. The accuracy and applicability of the synthesized material were determined by developing fingerprints by using secretions from eccrine and apocrine glands on a glass slide and various other surfaces, followed by dusting the surfaces. The results so obtained were found to be very accurate and promising.

Highly photoluminescent and pH sensitive nitrogen doped carbon dots (NCDs) as a fluorescent sensor for the efficient detection of Cr (VI) ions in aqueous media.

Fluorescent carbon dots (CDs) are contemporary class of fluorescent materials that has emerged recently and have gathered increasing attention due to its excellent properties as compared to traditional semiconductor quantum dots. CDs have lucrative benefits of less toxicity, biocompatibility, eco friendliness, tunable fluorescence, high chemical and photostability, effortless synthesis routes and uncomplicated surface modifications and functionalization. In the present work, nitrogen-doped carbon dots (NCDs) were prepared by a facile hydrothermal process using l-ascorbic acid and ethylene diamine as precursors. The as-prepared NCDs were hydrophilic in nature and could remain stable for several weeks. NCDs displayed bright blue fluorescence under UV light irradiation and also exhibited an extensive range of emission spectra in the visible region to infra-red region based upon the excitation wavelength. NCDs possessed quasi-spherical morphology and high density growth. NCDs were further utilized as nanoprobes for the pH sensing and proficient sensitive and selective detection of chromium (VI) ions present in aqueous phase. Under augmented modifications and conditions, the photoluminescence intensity of NCDs against various micromolar concentration of chromium (VI) ions presented a linear relationship, as per Stern-Volmer equation. The calibration curve was found to be linear in the range of 0-4 µM and from the slope of the linear curve, the limit of detection (LOD) was calculated to be 2.598 nM. The Stern-Volmer calibration curve was also plotted against different temperatures, verifying static quenching mechanism. Therefore, the as synthesized NCDs can be successfully demonstrated for the efficient pH sensing and the detection of Cr (VI) ions.

Bi2WO6/C-Dots/TiO2: A Novel Z-Scheme Photocatalyst for the Degradation of Fluoroquinolone Levofloxacin from Aqueous Medium.

Photocatalytic materials and semiconductors of appropriate structural and morphological architectures as well as energy band gaps are materials needed for mitigating current environmental problems, as these materials have the ability to exploit the full spectrum of solar light in several applications. Thus, constructing a Z-scheme heterojunction is an ideal approach to overcoming the limitations of a single component or traditional heterogeneous catalysts for the competent removal of organic chemicals present in wastewater, to mention just one of the areas of application. A Z-scheme catalyst possesses many attributes, including enhanced light-harvesting capacity, strong redox ability and different oxidation and reduction positions. In the present work, a novel ternary Z-scheme photocatalyst, i.e., Bi2WO6/C-dots/TiO2, has been prepared by a facile chemical wet technique. The prepared solar light-driven Z-scheme composite was characterized by many analytical and spectroscopic practices, including powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), N2 adsorption-desorption isotherm, Fourier-transform infrared spectroscopy (FT-IR), photoluminescence (PL) and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the Bi2WO6/C-dots/TiO2 composite was evaluated by studying the degradation of fluoroquinolone drug, levofloxacin under solar light irradiation. Almost complete (99%) decomposition of the levofloxacin drug was observed in 90 min of sunlight irradiation. The effect of catalyst loading, initial substrate concentration and pH of the reaction was also optimized. The photocatalytic activity of the prepared catalyst was also compared with that of bare Bi2WO6, TiO2 and TiO2/C-dots under optimized conditions. Scavenger radical trap studies and terephthalic acid (TPA) fluorescence technique were done to understand the role of the photo-induced active radical ions that witnessed the decomposition of levofloxacin. Based on these studies, the plausible degradation trail of levofloxacin was proposed and was further supported by LC-MS analysis.

pH-Sensing Strips Based on Biologically Synthesized Ly-MgO Nanoparticles.

MgO nanoparticles (NPs) are widely used in diverse areas ranging from catalysis to sensing. Besides this, there is a lack of information regarding their toxicity on fauna and flora. The venture of this work is to evaluate the toxicity behavior and pH-sensing performance of l-lysine-modified MgO (Ly-MgO) NPs synthesized by the green approach using the clove (Syzygium aromaticum) bud extract. The detailed investigations revealed that concentration plays an important role toward in vitro toxicity of Ly-MgO NPs. The Ly-MgO NPs showed 105% biocompatibility toward Vigna radiata (green gram) seeds at 100 ppm concentration. Zero inhibition on microbial growth was observed toward two bacterial strains. Further, pH-sensing strips based on these Ly-MgO nanostructures were developed to test pH-sensing performance at pH values ranging from 2.0 to 13.0. The repeatability as well as recyclability of the prepared pH strips was also analyzed. Nanobased pH paper strips based on Ly-MgO NPs provide a simple, reliable, nontoxic, and affordable method for pH measurements.

Effect of lipid chain length on nanostructured lipid carriers: Comprehensive structural evaluation by scattering techniques.

The objective of the present investigation was to evaluate nano-dispersed systems of differently chained lipids (solid phases) using various scattering techniques. Nanostructured lipid carriers (NLCs) were fabricated by employing the microemulsification methodology in which dialkyldimethyl ammonium bromide (DxDAB) of different alkyl chain length (x = 12, 14, 16, 18) and oleic acid were used as the solid lipid and liquid lipid, respectively. For the first time, the effect of DxDAB as a function of the chain length of the double alkyl chain on the structural characteristics of NLCs was investigated. Dynamic light scattering (DLS) and static light scattering (SLS) results showed that a small but systematic size increase occurs with increase in the chain length 'x' of the DxDAB from 12 to 16, yet D18DAB based NLCs exhibited the smallest size irrespective of its higher hydrophobicity. Small angle neutron scattering (SANS) analysis revealed the structural make up of NLCs having spherical nanoparticles and triaxial ellipsoidal core-shell micelles in the system. In-vitro cytotoxicity evaluation indicated that toxicity is simply concentration-dependent phenomena and NLCs with less than 5 mg/mL are preferred for better in-vivo tolerance.

Rapid Solar-Light Driven Superior Photocatalytic Degradation of Methylene Blue Using MoS2-ZnO Heterostructure Nanorods Photocatalyst.

Herein, MoS2-ZnO heterostructure nanorods were hydrothermally synthesized and characterized in detail using several compositional, optical, and morphological techniques. The comprehensive characterizations show that the synthesized MoS2/ZnO heterostructure nanorods were composed of wurtzite hexagonal phase of ZnO and rhombohedral phase of MoS2. The synthesized MoS2/ZnO heterostructure nanorods were used as a potent photocatalyst for the decomposition of methylene blue (MB) dye under natural sunlight. The prepared MoS2/ZnO heterostructure nanorods exhibited ~97% removal of MB in the reaction time of 20 min with the catalyst amount of 0.15 g/L. The kinetic study revealed that the photocatalytic removal of MB was found to be in accordance with pseudo first-order reaction kinetics with an obtained rate constant of 0.16262 min-1. The tremendous photocatalytic performance of MoS2-ZnO heterostructure nanorods could be accredited to an effective charge transportation and inhibition in the recombination of photo-excited charge carriers at an interfacial heterojunction. The contribution of active species towards the decomposition of MB using MoS2-ZnO heterostructure nanorods was confirmed from scavenger study and terephthalic acid fluorescence technique.

Highly effective Fe-doped TiO2 nanoparticles photocatalysts for visible-light driven photocatalytic degradation of toxic organic compounds.

This paper reports the synthesis of various molar concentrations of iron (Fe)-doped TiO2 nanoparticles and their efficient use as potential photocatalysts for photocatalytic degradation of toxic and harmful chemical, paranitrophenol. The nanoparticles were synthesized by a novel and facile ultrasonic assisted hydrothermal method and characterized in detail by various analytical techniques in terms of their morphological, structural, compositional, thermal, optical, pore size distribution, etc properties. The photocatalytic activities of the as-prepared Fe-doped TiO2 nanoparticles were examined under visible light illumination using para-nitrophenol as target pollutant. By detailed experimental findings revealed that the Fe dopant content crucially determines the catalytic activity of TiO2 nanoparticles. The maximum degradation rate of para-nitrophenol observed was 92% in 5 h when the Fe(3+) molar concentration was 0.05 mol%, without addition of any oxidizing reagents. The prepared nanoparticles demonstrated excellent photocatalytic response because of their small size, excellent crystalline structure, increase in threshold wavelength response and maximum separation of photogenerated charge carriers. Further, the determination of reaction intermediates has also been carried out and plausible mechanism of photocatalytic degradation of para-nitrophenol has been proposed.