Thermally reduced mesoporous manganese MOF @reduced graphene oxide nanocomposite as bifunctional electrocatalyst for oxygen reduction and evolution.

Oxygen electrocatalysis plays a crucial role in harnessing energy from modern renewable energy technologies like fuel cells and metal-air batteries. But high cost and stability issues of noble metal catalysts call for research on tailoring novel metal-organic framework (MOF) based architectures which can bifunctionally catalyze O2 reduction and evolution reactions (ORR & OER). In this work, we report a novel manganese MOF @rGO nanocomposite synthesized using a facile self-templated solvothermal method. The nanocomposite is superior to commercial Pt/C catalyst both in material resource and effectiveness in application. A more positive cathodic peak (E pc = 0.78 V vs. RHE), onset (E onset = 1.09 V vs. RHE) and half wave potentials (E 1/2 = 0.98 V vs. RHE) for the ORR and notable potential to achieve the threshold current density (E @10 mA cm-2 = 1.84 V vs. RHE) for OER are features promising to reduce overpotentials during ORR and OER. Small Tafel slopes, methanol tolerance and acceptable short term stability augment the electrocatalytic properties of the as-prepared nanocomposite. Remarkable electrocatalytic features are attributed to the synergistic effect from the mesoporous 3D framework and transition metal-organic composition. Template directed growth, tunable porosities, novel architecture and excellent electrocatalytic performance of the manganese MOF @rGO nanocomposite make it an excellent candidate for energy applications.

Zeolitic imidazolate framework (ZIF)-derived porous carbon materials for supercapacitors: an overview.

The present analysis focuses on the synthetic methods used for the application of supercapacitors with various mysterious architectures derived from zeolitic imidazolate frameworks (ZIFs). ZIFs represent an emerging and unique class of metal-organic frameworks with structures similar to conventional aluminosilicate zeolites, consisting of imidazolate linkers and metal ions. Their intrinsic porous properties, robust functionalities, and excellent thermal and chemical stabilities have resulted in a wide range of potential applications for various ZIF materials. In this rapidly expanding area, energetic research activities have emerged in the past few years, ranging from synthesis approaches to attractive applications of ZIFs. In this analysis, the development of high-performance supercapacitor electrodes and recent strategies to produce them, including the synthesis of various heterostructures and nanostructures, are analyzed and summarized. This analysis goes via the ingenuity of modern science when it comes to these nanoarchitecture electrodes. Despite these significant achievements, it is still difficult to accurately monitor the morphologies of materials derived from metal-organic frameworks (MOFs) because the induction force during structural transformations at elevated temperatures is in high demand. It is also desirable to achieve the direct synthesis of highly functionalized nanosized materials derived from zeolitic imidazolate frameworks (ZIFs) and the growth of nanoporous structures based on ZIFs encoded in specific substrates for the construction of active materials with a high surface area suitable for electrochemical applications. The latest improvements in this field of supercapacitors with materials formed from ZIFs as electrodes using ZIFs as templates or precursors are discussed in this review. Also, the possibility of usable materials derived from ZIFs for both existing and emerging energy storage technologies is discussed.

Zinc oxide­selenium heterojunction composite: Synthesis, characterization and photo-induced antibacterial activity under visible light irradiation.

The designing of new antibacterial agents with high and long-lasting activities are urgently needed in order to cope with the fast-emerging bacterial resistance. Zinc oxide nanoparticles (ZnO) have shown a significant promise as broad-spectrum antibacterial agents, and are efficient material in compromising bacterial membrane stability that leads to an increased cell permeability to nano-products. However, further engineering is required to improve their biological activities and to minimize their toxicity to healthy cells. In an attempt to resolve this issue, two semiconductor materials, ZnO and selenium (Se), were fabricated into a unique structural composite by a newly developed facile green method, and the designed composite was applied as an antibacterial nanomedicine. The developed methodology involves the initial preparation of ZnO, followed by its fabrication with Se at different temperatures (70 °C to 95 °C). Our experimental data showed that well defined interpenetrated crystalline Se network on ZnO (ZnO-Se) can be obtained at 80 °C for 180 min. The as-prepared ZnO-Se showed promising results in inhibiting the challenged bacterial strains under light irradiation (visible light) as compared to free ZnO. The enhanced biocidal property of ZnO-Se could be ascribed to its improved light-harvesting ability for sustainable induction of reactive oxygen species (ROS) and an active contact killing mechanism. Thus, ZnO-Se composite with a novel architecture could be a promising material in the treatment of bacterial infections by a mutual antibacterial synergy from the incorporated elements. Interestingly, the ZnO-Se has the ability to scavenge the overproduction of hydroxyl radicals, thus protecting the healthy cells from oxidative damage.

One step fabrication of novel Ag-CdS@EP floating photocatalyst for efficient degradation of organic pollutants under visible light illumination.

In this paper, we present the fabrication of an expanded-perlite (EP)-based floating photocatalyst comprising CdS and Ag nanoparticles. In the Ag-CdS/EP nanocomposite, Ag-CdS was introduced as the photocatalytically active components and EP was employed as a low cost and sustainable support to reduce the problem of easy aggregation and improve the floating behavior of the designed catalyst. The Ag-CdS/EP photocatalyst was characterized via transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-vis diffuse spectroscopy (UV-vis DRS), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) and photoelectrochemical measurements. The XRD and HR-TEM results confirmed the formation of cubic crystalline silver nanoparticles anchored on the surface of EP-immobilized hexagonal cubic CdS. The significantly enhanced photocatalytic activities of the Ag-CdS/EP nanocomposite with varying Ag contents were investigated for the degradation of rhodamine B (RhB) and phenol under visible light irradiation, and it was found that the photocatalytic reaction proceeds via first order kinetics. Furthermore, the desirable cycling ability (5 runs) of the Ag-CdS/EP photocatalyst indicates its promising stability and reusability. The designed novel photocatalyst also conforms to the development of green chemistry since no organic solvents were required.

Tobramycin mediated silver nanospheres/graphene oxide composite for synergistic therapy of bacterial infection.

Graphene-based materials have attracted a significant attention in constructing hybrid systems for drug delivery with enhanced antimicrobial activities. In our work, we demonstrated the formation of silver nanoparticles (AgNPs) on graphene oxide (GO) using tobramycin (TOB), an aminoglycoside antibiotic, as reducing and decorating agent. The TOB decorated GO AgNPs (TOB-GO-Ag) composite was used as an antibacterial agent against multi-drug resistant Gram-negative E-coli (BL21 DE3). The reversal of surface potential from -30 mV (GO) to +20 mV confirms the successful reduction of GO by TOB. Atomic force microscopy (AFM) and high-resolution transmission electron microscopic (HRTEM) analyses confirmed the formation of uniformly distributed AgNPs on the reduced GO with an approximate particle size of 5 nm. The as-synthesized nanocomposite displayed significant antibacterial activity as compared to pure AgNPs and TOB. The positively charged TOB-GO-Ag interacts with the negatively charged E. coli membrane and inhibit bacterial growth by the antibacterial actions of the released silver, GO and tobramycin from the TOB-GO-Ag composite. The significant loss of bacterial membrane potential from -52 ±â€¯2 mV (control) to -2 ±â€¯1 mV (treated) indicates a severe cell wall damage caused by TOB-GO-Ag composite. Furthermore, fluorescence study also demonstrated a severe membrane disruption in bacterial cells treated with TOB-GO-Ag composite as compared to pure AgNPs and GO. In conclusion, the development of such hybrid systems would help in enhancing the efficacy of available drugs and eradicating the emerging bacterial resistance.

Synthesis of phytochemicals-stabilized gold nanoparticles and their biological activities against bacteria and Leishmania.

Nanoscale materials have shown promising results in the field of medicine as therapeutic agents and drugs delivery vehicles. In the current study, gold nanoparticles (AuNPs) were prepared by a green and facile method using the aqueous extract of Rhazya stricta decne as a source of reducing and stabilizing agents. The bio-fabricated AuNPs were characterized by UV-visible spectroscopy, X-ray diffraction (XRD), Transmission electron microscopy (TEM) and FTIR spectroscopy. Antimicrobial activities of the biosynthesized AuNPs were tested against Leishmania tropica (HTD7), E. coli and S. aureus. AuNPs were the most effective agents in inhibiting the growth of intra-THP-1 amastigotes at 100 µg/mL concentration (IC50 = 43 µg/mL) after 48-h incubation. In addition, the prepared AuNPs also displayed good activity against E. coli (MIC = 25.0 µg/mL) and Bacillus subtilis (50.0 µg/mL). Interestingly, biogenic AuNPs did not exhibit cytotoxic effect against the THP-1 cells after 24 h exposure. The findings of this study conclude that phytochemicals-stabilized AuNPs could be a safe and effective source of antimicrobial agents.

Punica granatum peel extracts: HPLC fractionation and LC MS analysis to quest compounds having activity against multidrug resistant bacteria.

BACKGROUND: Medicinal plants are rich source of traditional herbal medicine around the globe. Most of the plant's therapeutic properties are due to the presence of secondary bioactive compounds. METHODS: The present study analyzed the High Pressure Liquid Chromatography (HPLC) fractions of Puncia granatum (peel) extracts (aqueous, chloroform, ethanol and hexane) against multidrug resistant bacterial pathogens (Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus). All the fractions having antibacterial activity was processed for bioactive compounds identification using LC MS/MS analysis. RESULTS: Among total HPLC fractions (n = 30), 4 HPLC fractions of P. granatum (peel) showed potential activity against MDR pathogens. Fraction 1 (F1) and fraction 4 (F4) collected from aqueous extract showed maximum activity against P. aeruginosa. Fraction 2 (F2) of hexane showed antibacterial activity against three pathogens, while ethanol F4 exhibited antibacterial activity against A. baumannii. The active fractions were processed for LC MS/MS analysis to identify bioactive compounds. Valoneic acid dilactone (aqueous F1 and F4), Hexoside (ethanol F4) and Coumaric acid (hexane F2) were identified as bioactive compounds in HPLC fractions. CONCLUSION: Puncia granatum peel extracts HPLC fractions exhibited potential inhibitory activity against MDR bacterial human pathogens. Several bioactive compounds were identified from the HPLC fractions. Further characterization of these compounds may be helpful to conclude it as therapeutic lead molecules against MDR pathogens.

Ethnomedicinal Cichorium intybus Seed Extracts: An Impending Preparation against Multidrug Resistant Bacterial Pathogens.

BACKGROUND: The present study was undertaken to analyze the phytochemical content and biological activity of Cichorium intybus seeds traditionally used in Charsadda, Pakistan against multidrug resistant (MDR) bacterial pathogens. OBJECTIVES: This study explored the qualitative and quantitative antibacterial potential of C. intybus. Further qualitative analysis of phytochemical content was performed. METHODS: Cichorium intybus seed extracts were prepared in aqueous, chloroform, ethanol, and hexane separately. RESULTS: All the extracts of C. intybus seeds were screened for antibacterial activity and phytochemical content. Cichorium intybus seed extract showed considerable activity against MDR pathogenic bacteria. In the well diffusion method, aqueous extracts showed a higher zone of inhibition against Pseudomonas aeruginosa (16 mm ± 0.7 mm) and Acinetobacter baumannii (13 mm ± 0.5 mm), whereas chloroform, ethanol, and hexane extracts showed activity against P. aeruginosa (11 mm ± 0.3 mm, 12 mm ± 0.5 mm, and 11 mm ± 0 mm, respectively) as compared to Imipenem, a broad spectrum antibiotic. Minimum inhibitory concentration and minimum bactericidal concentration values for aqueous and ethanol extracts indicate that they were more effective against MDR bacteria. Phytochemical analysis revealed that aqueous and ethanol extracts were rich in alkaloids, carbohydrates, gallotannins, and triterpenoids, whereas chloroform and hexane extracts were more concentrated with phenolics, pseudotannins, saponins, and tannins. Cichorium intybus seed extract demonstrated potential activity against MDR human pathogenic bacteria. CONCLUSIONS: The undertaken study has for the first time reported the effects of C. intybus seed extracts against MDR bacterial pathogens. Findings of the current study will be helpful for further elucidation of bioactive molecules for therapeutic use against MDR bacterial pathogens.

Alkanna tinctoria leaves extracts: a prospective remedy against multidrug resistant human pathogenic bacteria.

BACKGROUND: Plants are rich source of chemical compounds that are used to accomplish biological activity. Indigenously crude extracts of plants are widely used as herbal medicine for the treatment of infections by people of different ethnic groups. The present investigation was carried out to evaluate the biological potential of Alkanna tinctoria leaves extract from district Charsadda, Pakistan against multidrug resistant human pathogenic bacteria including Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus. METHODS: Anti-multi-drug resistant bacterial activity of aqueous, chloroform, ethanol and hexane extracts of Alkanna tinctoria leaves were evaluated by well diffusion method. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of different extracts were determined. Moreover qualitative phytochemicals screening of the studied extracts was performed. RESULTS: All four selected bacteria including A. baumannii, E. coli, P. aeruginosa and S. aureus were categorized as multi-drug resistant (MDR) as they were found to be resistant to 13, 10, 19 and 22 antibiotics belonging to different groups respectively. All the four extract showed potential activity against S. aureus as compare to positive control antibiotic (Imipenem). Similarly among the four extracts of Alkanna tinctoria leaves, aqueous extract showed best activity against A. baumannii (10±03 mm), P. aeruginosa (12±0.5 mm), and S. aureus (14±0.5 mm) as compare to Imipenem. The MICs and MBCs results also showed quantitative concentration of plant extracts to inhibit or kill MDR bacteria. When phytochemicals analysis was performed it was observed that aqueous and ethanol extracts showed phytochemicals with large number as well as volume, especially Alkaloides, Flavonoides and Charbohydrates. CONCLUSION: The undertaken study demonstrated that all the four extracts of Alkanna tinctoria leaves exhibited considerable antibacterial activity against MDR isolates. Finding from the current study will be helpful for further elucidation of lead molecules from Alkanna tinctoria leaves for future therapeutic use against MDR pathogens.

Antibacterial activity of some medicinal plants against selected human pathogenic bacteria.

Medicinal plants are traditionally used for the treatment of human infections. The present study was undertaken to investigate Bergenia ciliata, Jasminum officinale, and Santalum album for their potential activity against human bacterial pathogens. B. ciliata, J. officinale, and S. album extracts were prepared in cold and hot water. The activity of plant extracts and selected antibiotics was evaluated against five bacterial pathogens including Staphylococcus aureus, Bacillus subtilis, Proteus vulgaris, Pseudomonas aeruginosa, and Escherichia coli using agar well diffusion method. Among the three medicinal plants, B. ciliata extracts displayed potential activity against bacterial pathogens. Cold water extract of Bergenia ciliate showed the highest activity against B. subtilis, which is comparable with a zone of inhibition exhibited by ceftriaxone and erythromycin. J. officinale and S. album extracts demonstrated variable antibacterial activity. Further studies are needed to explore the novel antibacterial bioactive molecules.