Facile Synthesis and In Vitro Biological Screening of Pd@SiO₂ Core-Shell Nanoparticles

In this study, semiconductor core-shell Pd@SiO₂ nanoparticles (NPs) were prepared by Stober's method. The prepared final products were characterized by XRD, FT-IR, SEM, HR-TEM and EDX techniques. Cell viability of Pd@SiO₂ NPs against HeLa cell line was screened by MTT assay. The present study indicates that the core-shell Pd@SiO₂ NPs are extremely stable along with very high photodynamic efficiency under LED light illumination. The antibacterial activities of core- shell Pd@SiO₂ NPs were determined with Escherichia coli and Staphylococcus aureus by agar diffusion method. DNA binding affinity of the core-shell Pd@SiO₂ NPs towards CT-DNA was also investigated. The observed results showed that SiO₂ supported on the surface of Pd NPs not only prevented aggregation, but also proved the enhanced antimicrobial and DNA binding propensities than the free Pd NPs.

Simple Combustion Synthesis, Structural, Morphological, Optical and Catalytic Properties of ZnO Nanoparticles

In this present study, semiconductor zinc oxide (ZnO) nanoparticles were successfully prepared by microwave irradiation (ZnO-MIM) and conventional combustion (ZnO-CCM) method, respectively using Aloe vera plant extract as reducing agent. Crystal structure, purity and surface morphology of the samples were examined by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. UV-Visible diffuse reflectance (DRS) and photoluminescence (PL) spectral studies was used to analysis the optical property and band gap energy of the samples. The antibacterial activities of ZnO nanostructures (ZnO-MIM and ZnO-CCM) were tested against both gram positive (Bacillus subtilis, Staphylococcus aureus) and gram negative bacteria (Proteus mirabilis, Salmonella typhi) by modified disc diffusion method and observed enhanced activity against P. mirabilis and S. typhi. ZnO nanostructures (ZnO-MIM and ZnO-CCM) were used as the photo-catalysts for the degradation of methylene blue (MB) dye and observed enhanced efficiency of degradation of MB than that of their same bulk materials. Moreover, the synthesis method is easy with low cost and time consumable and also high yield purity products.

Enhanced Antibacterial Activity and Photo-Catalytic Properties of ZnO Nanoparticles: Pedalium Murex Plant Extract-Assisted Synthesis

Semiconductor ZnO samples with two different morphologies such as nanoparticles (ZnO-NPs) and nano-sheets (ZnO-NSs) was successfully prepared by microwave heating (MHM) and modified sol-gel (SGM) method, respectively using Pedalium Murex plant extract as the bio-reducing agent. Structural, purity and morphology of the samples was examined by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis. Optical property analysis and band gap calculation were carried out by UV-Visible diffuse reflectance (DRS) and photoluminescence (PL) spectroscopy techniques. Kubelka-Munk method was used to measure band band gap of the samples and it shows 3.42 eV and 3.23 eV for ZnO-NPs and ZnO-NSs, respectively. The antibacterial activities of ZnO-NPs and ZnO-NSs against both gram positive (Bacillus subtilis, Staphylococcus aureus) as well as gram negative bacteria (Proteus mirabilis, Salmonella typhi) were tested by modified disc diffusion method and showed important antibacterial activity against P. mirabilis and S. typhi. The photocatalytic activity of ZnO nano-catalysts (ZnO-NPs and ZnO-NSs) for the degradation of methylene blue (MB) dye was studied under solar lighting and the results showed that the samples ZnO-NPs with smaller particle size considerable degradation of MB than ZnO-NSs.

Okra (Abelmoschus esculentus) Plant Extract-Assisted Combustion Synthesis and Characterization Studies of Spinel ZnAl₂O₄ Nano-Catalysts

Spinel ZnAl2O4 nano-catalysts were synthesized by a simple, economical and eco-friendly microwave irradiation (MIM) and conventional heating methods (CHM), using metal nitrates and Okra (Abelmoschus esculentus) plant extract, which play a dual role of both oxidizing and reducing nature. Powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, energy dispersive X-ray (EDX) and selected area electron diffraction (SAED) pattern results were confirmed that the samples have a single-phase cubic spinel structure with high crystalline nature of ZnAl2O4. Surface morphology of the samples was revealed by high resolution scanning electron microscopy (HR-SEM) and high resolution transmission electron microscopy (HR-TEM) techniques and they are confirmed particle-like structure with grain size below 50 nm. The optical band gap (Eg) was measured using Kubelka-Munk model by UV-Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) and the Eg value is higher for MIM product than CHM, due to the smaller particle size of ZnAl2O4-MIM. The magnetic property of the samples was determined by vibrating sample magnetometer (VSM) and showed a superparamagnetic behavior. Spinel ZnAl2O4 nano-catalysts are magnetically recyclable and could be reused with no significant loss in catalytic activity. Both the samples were successfully tested as catalysts for the conversion of alcohols into respective carbonyl compounds using H2O2 (as oxidant) and acetonitrile (as a solvent) system. It was found that the ZnAl2O4-MIM nanocatalysts show best performance of conversion of alcohols into a carbonyl compounds than that of ZnAl2O4-CHM, due to the smaller particle size and higher surface area of ZnAl2O4-MIM samples.

The Role of Mn(2+)-Doping on Structural, Morphological, Optical, Magnetic and Catalytic Properties of Spinel ZnFe2O4 Nanoparticles

Spinel Mn(x)Zn(1-x)Fe2O4 (0.0 ≤ x ≤ 1.0) nanoparticles (NPs) were successfully synthesized by a facile one-pot microwave combustion method using urea as the fuel. The formation of single phase cubic spinel structure was confirmed by powder X-ray diffraction (XRD), Rietveld analysis and Fourier transform infrared (FT-IR) spectroscopy and the calculated average crystallite size is in the range of 37.57 nm to 25.43 nm. The high resolution scanning electron microscopy (HR-SEM) and high resolution transmission electron microscopy (HR-TEM) results indicated that the as-prepared spinel Mn(x)Zn(1-x)Fe2O4 NPs showed high crystallinity and uniform size distribution with particles-like morphologies. The energy dispersive X-ray (EDX) analysis was confirmed the elemental composition and purity of the samples. The estimated band gap energy from UV-Visible diffuse reflectance spectroscopy (UV-Vis. DRS) is about 1.88 eV to 2.35 eV. The broad visible emission band is observed in the entire photoluminescence (PL) spectroscopy for all compositions. The variation of magnetization (M(s)) value of the samples was studied by vibrating sample magnetometer (VSM) and the lower compositions (x = 0.0, 0.2 and 0.4) show a superparamagnetism and the higher composition (x = 0.6, 0.8 and 1.0) show a ferromagnetic behavior with hysteresis and that the M(s) values increased with increasing Mn2+ content to reach a maximum value of 60.99 emu/g for MnFe2O4. All composition of spinel Mn(x)Zn(1-x)Fe2O4 NPs were successfully tested as catalyst for the oxidation of benzyl alcohol into benzaldehyde, which has resulted 83.29 and 96.51% conversion efficiency of ZnFe2O4 and Mn0.6Zn0.4Fe2O4 respectively.

Eave Screening and Push-Pull Tactics to Reduce House Entry by Vectors of Malaria

Long-lasting insecticidal nets and indoor residual spraying have contributed to a decline in malaria over the last decade, but progress is threatened by the development of physiological and behavioral resistance of mosquitoes against insecticides. Acknowledging the need for alternative vector control tools, we quantified the effects of eave screening in combination with a push-pull system based on the simultaneous use of a repellent (push) and attractant-baited traps (pull). Field experiments in western Kenya showed that eave screening, whether used in combination with an attractant-baited trap or not, was highly effective in reducing house entry by malaria mosquitoes. The magnitude of the effect varied for different mosquito species and between two experiments, but the reduction in house entry was always considerable (between 61% and 99%). The use of outdoor, attractant-baited traps alone did not have a significant impact on mosquito house entry but the high number of mosquitoes trapped outdoors indicates that attractant-baited traps could be used for removal trapping, which would enhance outdoor as well as indoor protection against mosquito bites. As eave screening was effective by itself, addition of a repellent was of limited value. Nevertheless, repellents may play a role in reducing outdoor malaria transmission in the peridomestic area.

Aloe vera Plant Extracted Green Synthesis, Structural and Opto-Magnetic Characterizations of Spinel Co(x)Zn₁₋xAl₂O₄Nano-Catalysts

Spinel Co(x)Zn₁₋xAl₂O₄ (0 ≤ x ≤ 1) nano-catalysts were synthesized by a simple Aloe vera plant extracted green synthesis route. Powder XRD patterns and Rietveld analysis confirmed the formation of single phase, cubic spinel gahnite structure without other impurities. The lattice parameter increased from 8.089 to 8.125 A with increasing CO²⁺ content. The average crystallite sizes were estimated using Scherrer's method, and it was found to be in the range of 15.72 nm to 26.53 nm. FT-IR spectra showed vibrational stretching frequencies corresponding to the spinel structure. HR-SEM and HR-TEM images showed the features of well particle shaped crystals with nano-sized grains. The elemental compositions of Co, Zn, Al and O were quantitatively obtained from EDX analysis. The band gap energy estimated using Kubelka-Munk method by UV-Visible DRS method, and the values are decreased with increasing the Co²⁺ content (4.12 eV to 3.67 eV), due to the formation of sub bands in between the energy gap. PL spectra showed emission bands in UV as well as in the visible regions for ZnAl₂O₄ and Co-doped ZnAl₂O4, due to the defect centers acting as the trap levels. VSM measurements revealed that pure ZnAl₂O₄ has diamagnetic, while Co doped ZnAl₂O₄ samples (x = 0.2 to 0.8) have superparamagnetism, whereas the sample CoAl₂O₄ has ferromagnetic in nature. Catalytic oxidation of benzyl alcohol to benzaldehyde was found that the sample Co₀.₆Zn₀.₄Al₂O₄ showed 93.25% conversion with 99.56% selectivity, whereas for pure ZnAl₂O₄, the conversion was only 86.31% with 92.85% selectivity.

Sesamum indicum Plant Extracted Microwave Combustion Synthesis and Opto-Magnetic Properties of Spinel MnxCo₁₋xAl₂O₄Nano-Catalysts

Spine Mn(x)Co₁₋xAl₂O₄ (x = 0, 0.3 and 0.5) nanoparticles were synthesized using Sesamum indicum (S. indicum) plant extracted microwave-assisted combustion method. S. indicum plant extract simplifies the process, provides an alternative process for a simple, economical and environment friendly synthesis. The absence of surfactant/catalysts has led to a simple, cheap and fast method of synthesis of spinel nanoparticles. The as-synthesized spinel nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, high resolution scanning electron microscopy (HR-SEM), high resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), Brunauer Emmett Teller (BET) surface area analysis, UV-Visible diffuse reflectance spectroscopy (DRS), Photoluminescence (PL) spectroscopy, and vibrating sample magnetometer. The formation of spinel nanoparticles was confirmed by HR-SEM and HR-TEM and their possible formation mechanisms were also proposed. Powder XRD, FT-IR, SAED and EDX results confirmed the formation of pure and single cubic phase CoAl₂O₄ with well-defined crystalline. The optical property was determined by DRS and PL spectra. VSM measurements revealed that pure and Mn-doped CoAl₂O₄ samples have weak ferromagnetic behavior and the magnetization values increases with increasing the concentration of Mn²⁺ ions in the CoAl₂O₄ lattice. The sample Mn₀.₅Co₀.₅Al₂O₄ possessed higher surface area and smaller crystallite size than other samples, which led to enhance the performance toward the selective oxidation of benzyl alcohol into benzaldehyde.

Phenyl 2,3,4-tri-O-benzyl-1-thio-α-d-mannopyran-oside monohydrate

In the title compound, C₃₃H₃₄O₅S·H₂O, the mannopyran­oside ring adopts a chair conformation with the 2-α-thio­phenyl group occupying an axial position. One of the pendant benzyl groups is disordered over two sets of sites in a 0.5:0.5 ratio. In the crystal, the water mol­ecule makes two O—H⋯O hydrogen bonds to an adjacent sugar mol­ecule with the O atoms of the primary alcohol and ether groups acting as acceptors. At the same time, the OH group of the sugar makes a hydrogen bond to a water mol­ecule.

Fullerene sugar balls

Fullerene hexakis-adducts bearing 12 peripheral carbohydrate moieties have been prepared by grafting sugar derivatives onto the fullerene core through the copper mediated Huisgen 1,3-dipolar cycloaddition of azides and alkynes.

Stereoselective glycal fluorophosphorylation: synthesis of ADP-2-fluoroheptose, an inhibitor of the LPS biosynthesis

Heptosides are found in important bacterial glycolipids such as lipopolysaccharide (LPS), the biosynthesis of which is targeted for the development of novel antibacterial agents. This work describes the synthesis of a fluorinated analogue of ADP-L-glycero-beta-D-manno-heptopyranose, the donor substrate of the heptosyl transferase WaaC, which catalyzes the incorporation of this carbohydrate into LPS. Synthetically, the key step for the preparation of ADP-2F-heptose is the simultaneous and stereoselective installation of both the fluorine atom at C-2 and the phosphoryl group at C-1 through a selectfluor-mediated (selectfluor=1-chloromethyl-4-fluorodiazoniabicyclo[2.2.2]octane bis(triflate)) electrophilic addition/nucleophilic substitution involving a heptosylglycal. Therefore, we detail in this article 1) the stereoselective preparation of the key intermediates heptosylglycals, 2) the development of a new fluorophosphorylation procedure allowing an excellent beta-gluco stereoselectivity with "all-equatorial" glycals, 3) the synthesis of the target ADP-2F-heptose, and 4) some comments on the contacts observed between the fluorine atom of the final molecule and the protein in the crystallographic structure of heptosyltransferase WaaC.

Synthesis of 2'-C-methyl-beta-D-ribofuranosylimidazo [4,5-d]-pyridazine derivatives (2-aza-3-deazapurine nucleoside analogues)

In order to evaluate their antiviral properties, two imidazo[4,5-d]pyridazine 2'-C-methyl-beta-D-ribofuranonucleoside derivatives have been synthesized.

Synthesis of 5-aza-7-deazaguanine nucleoside derivatives as potential anti-flavivirus agents

Coupling suitable sugars (D- or L-ribofuranose, 2' or 3-deoxysugar, branched sugars) with 2-aminoimidazo[1,2-a]-s-triazin-4-one was carried out using the different reaction conditions: 1) condensation in the presence of sodium hydride; or 2) condensation using Vorbrüggen's methods. The 5-aza- 7-deazaguanine nucleoside analogues obtained were evaluated in cell culture experiments for the inhibition of the replication of a number of RNA viruses, including BVDV, YFV, and WNV.