Plant-mediated biosynthesis of silver nanoparticles by leaf extracts of <Emphasis Type="Italic">Lasienthra africanum</Emphasis> and a study of the influence of kinetic parameters

Lasienthra africanum (LA) leaf extract was employed for nano-silver synthesis. The reducing effect of the plant extract was investigated at different times, pH, temperatures and concentrations. The effect of various kinetic parameters was studied using UV–vis spectroscopy. Blue-shifted surface plasmon bands indicating smaller sized nanoparticles were obtained at neutral pH (6.8–7.0), temperature of 65°C and concentration ratio of 1:10 (leaf extract: AgNO₃) with increasing reaction times under the reaction conditions. The kinetics of the reaction followed pseudo-first- and -second-order rate equations, and was thermodynamically favoured at higher time. Spherically shaped nanoparticles were obtained at different reaction conditions.     

Gold nanoparticles developed in sol–gel derived apatite—bioactive glass composites

The study is focussed on synthesis and characterisation of a new sol–gel derived composite system consisting of nanocrystalline apatite, bioactive glass and gold nanoparticles, which are of interest both for regenerative medicine and for specific medical applications of the releasable gold nanoparticles. Samples dried at 110°C and then heat treated for 30 min at 300 and 500°C were investigated by thermal analysis (DTA/TG), X-ray diffraction (XRD), UV–VIS–NIR, Fourier Transform Infrared (FTIR) spectroscopy, X-ray Photoelectron(XPS) spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Gold nanoparticles and nanocrystalline apatite are developed already after heat treatment at 300°C. XPS analysis clearly revealed the presence of both metallic and ionic gold species. The development of gold nanoparticles was evidenced by UV–VIS–NIR and TEM analysis, and their size increased from few nanometers to 25 nm by increasing the treatment temperature from 300 to 500°C. The bioactivity of the samples immersed in simulated body fluid was demonstrated by XRD and SEM results.     

Nanodispersions stabilized by β-cyclodextrin nanosponges: application for simultaneous enhancement of bioactivity and stability of sage essential oil

The aim of this work was to stabilize oil-in-water nanoemulsion containing sage (salvia officinalis) essential oil, for enhancing its physicochemical stability and enlarging its industrial applications. New β-cyclodextrin nanosponges were synthesized by polycondensation using naphthalene dicarboxylic acid as cross-linking agent, the latter system was characterized by FTIR spectroscopy, SEM, BET, and powder XRD. Nanoemulsions stabilized by free β-cyclodextrin or nanosponges were prepared, their physicochemical properties were determined (particles size, zeta potential, viscosity, turbidity, and essential oil content) and their stability was studied at different storage temperatures (4?°C, 20?°C, and 40?°C) during 3?months. Pharmaceutical application of prepared nanoemulsions was investigated in vitro by dissolution test study and in vivo by their antidiabetic activity evaluation in rats. Sage essential oil nanoemulsion stabilized by β-cyclodextrin-naphthalene dicarboxylic acid nanosponges presents very high stability and promising uses in pharmaceutical industry.     

Phytochemicals-mediated green synthesis of gold nanoparticles using Pterocarpus santalinus L. (Red Sanders) bark extract and their antimicrobial properties

In the present study, phytochemicals-mediated rapid, stable and eco-friendly synthesis of gold nanoparticles (GNPs) using Pterocarpus santalinus L. (Red Sanders) bark extract is reported. The powerful characteristics of different phytochemicals present in P. santalinus L. bark prompted us to determine their efficacy in the bio-reduction of gold chloride trihydrate to the corresponding GNPs. The biosynthesis of GNPs was investigated at the physiological condition (pH?=?7.4). The synthesized GNPs were characterized by UV–visible spectroscopy by measuring the peak in the range of 400–700?nm. The GNPs synthesized at physiological conditions revealed surface plasmon resonance (SPR) at 545?nm. The crystalline nature of GNPs was confirmed by using x-ray diffraction (XRD), and the functional groups adhered on the surface of the GNPs were analyzed by Fourier Transform Infrared spectroscopy (FTIR). Transmission Electron Microscopy (TEM) analysis showed spherical GNPs in the size range of 13–26?nm. The synthesized GNPs exhibited antibacterial activity against Gram-positive and Gram-negative bacterial strains.     

Synthesis of multi-walled carbon nanotube/silver nanocomposite powders by chemical reduction in aqueous solution

Carbon nanotube (CNT)/silver nanocomposite powders with different volume fractions of CNTs 2.5, 5 and 10?vol.% were prepared by chemical reduction in solution. Multi-walled CNTs underwent surface modifications for functionalisations by acid treatments. The acid-treated CNTs were investigated by FT-IR and X-ray photoelectron spectroscopy. The spectroscopic investigations of the acid-functionalised CNTs detected that several kinds of functional groups attached with the graphene structure as well as produced short and de-caped CNTs. Acidic stannous chloride solution was used to sensitise the surface of the functionalised CNTs. Silver was deposited on the surface of sensitised CNTs with chemical reduction reaction of alkaline silver nitrate solution by formaldehyde at room temperature and pH?～?9. The morphology of the produced CNT/silver nanocomposite powder was investigated by high-resolution SEM and TEM. It was observed that the produced CNT/silver nanocomposite powders have decorated type of spherical silver particle size 2–5?nm deposited on the surface of CNTs as well as the CNTs were implanted in large spherical silver nanoparticles of particle size ～200?nm. The chemical analysis of the produced powder indicates that some oxygen content is included in the prepared powders which can be reduced by heat treatment at temperatures between 300°C and 400°C under hydrogen atmosphere.     

A glycerol–water-based nanofluid containing graphene oxide nanosheets

Nanofluids are simply the dispersion of nanometer-sized particles in different fluids. Graphene oxide nanosheets (GONs) were prepared by exfoliating the graphite oxide. The GONs were investigated using Fourier transform-infrared spectroscopy, Raman spectroscopy, XRD analysis, high-resolution emission electron microscopy, transmission electron microscopy, and UV–visible spectroscopy. GONs/glycerol–water-based nanofluid was prepared by the two-step method. The stability of the nanofluid was investigated with respect to time. Thermal and electrical conductivity of the prepared nanofluid was examined with different temperatures (25–45 °C) and weight fractions (0.02–0.1 wt%). The nanofluid is found to be stable for more than 5 months. The results showed an enhancement in thermal conductivity of about 4.5 % at 25 °C with a weight fraction of 0.02 %. The improvement was up to 11.7 % with a weight fraction of 0.1 wt% at 45 °C. The electrical conductivity was increased with increasing the weight fraction and temperature. The improvement in electrical conductivity was about 5890 % at 25 °C and 0.1 wt%.     

Photocatalytic degradation of ciprofloxacin pollutant and in-vitro cytotoxic activity of gold nanoparticles using seed extract of Abrus precatorius

Synthesis of nanoparticles from plant extract is a very simple reliable, rapid, affordable and un-hazardous technique. In the present exploration, gold nanoparticles (Au NPs) were rapidly synthesized using seed extract of Abrus precatorius. The prepared nanomaterials were systematically proved by FTIR, UV–Visible, Powder-XRD, SEM, EDAX and TEM analyses. The formation of Au NPs was primarily identified by the colour change from yellow to purple within 5 min and which showed a surface Plasmon peak around 535 nm. The dimension of the gold nanoparticles was found to be in the range of 10–20 nm. The particles were poly-dispersed with a triangular, spherical and hexagonal shape. The gold nanoparticles were used to degrade the antibiotic drug ciprofloxacin (CIP) with an efficiency of above 95%. Moreover, the bio-synthesized gold nanoparticles had been assessed for their in-vitro cytotoxic activity on human breast cancer cells (MCF-7) lines. The colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay was used to evaluate the Inhibitory Concentration (IC₅₀) value. The IC₅₀ value is 37?±?1.5 µg/mL. In future, this can be used for breast cancer therapy.

     

Synthesis and in vitro release study of ibuprofen-loaded gelatin graft copolymer nanoparticles

Objective: This work deals with the preparation, characterization and in vitro release study of IBU-loaded gel graft copolymer nanoparticles.

Method: Gelatin (Gel) graft copolymer nanoparticles were prepared using styrene (Sty) and/or 2-hydroxyethyl methacrylate (HEMA) monomers in the presence of potassium persulfate and glutaraldehyde as an initiator and cross-linker, respectively. The prepared nanoparticles as sustained release drug carriers were investigated using the nonsteriodal anti-inflammatory model drug, ibuprofen (IBU).

Results: The prepared nanoparticles as sustained release drug carriers were investigated using the nonsteriodal anti-inflammatory model drug, IBU. The prepared Gel/HEMA and Gel/Sty nanoparticles exhibited particles size ranging from 15 to 17?nm and from 0.42 to 5?mm, respectively. The dissolution of IBU in phosphate buffer, pH 7.4, at 37°C from the prepared nanoparticles was evaluated using UV spectroscopy. In addition, the prepared nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), transmitting electron microscope (TEM) and zeta potential/particle size analyzer. In vitro dissolution study showed that the dissolution rates of the crosslinked nanoparticles were retarded relative to the uncrosslinked ones. Moreover, the released amount constantly decreases with increasing gluteraldehyde content in the gel nanoparticles.

Conclusion: Crosslinked gel-based graft copolymers exhibited slow IBU release within six hours. Furthermore, results from different characterization techniques such as TEM, particles size and zeta potential measurements confirmed the formation of pH-responsive gel-graft copolymer nanoparticles.     

Synthesis and antibacterial activity of stable bio-conjugated nanoparticles mediated by walnut (Juglans regia) green husk extract

Nanoparticles have gained significant attention in recent years due to their numerous applications in various aspects of human life. A variety of methods have been investigated for synthesis of nanoparticles among which, biogenic approaches are considered as both simple and eco-friendly. Here, a new single-step biological approach was employed for synthesis of silver chloride nanoparticles (AgCl-NPs) at room temperature, using walnut green husk extract. Macromolecules present in the plant extract, which might act as bio-reductants and/or stabilisers of nanoparticles were characterised by Fourier transform Infrared spectroscopy. X-ray diffraction pattern and transmission electron microscopy revealed that 1 mM of AgNO3 produced mostly spherical nanoparticles in a range of 4–30 nm in diameter with an average of 16 nm. Interestingly, the synthesised nanoparticles showed significant inhibitory effects against Escherichia coli and Staphylococcus aureus clinical isolates. Altogether, these data suggest a new encouraging application of a medicinal plant bound with synthesised AgCl nanoparticles.     

Characterization of TiO2 nanoparticles prepared using different surfactants by sol–gel method

Titania nanoparticles have been prepared using different surfactants such as, acetic acid (AA), oleic acid (OA), oley amine (OM), and a mixture of OA + OM at room temperature by sol–gel method. TiO₂ nanoparticles were collected by centrifugation of the precipitate obtained during gel formation. The collected samples were annealed at 550 and 950 °C to study the effect of annealing temperature on the structural and optical properties. The crystal structure and optical properties of titania nanoparticle is investigated by means of X-ray diffraction, Raman spectroscopy, UV–visible spectroscopy, and photoluminescence. After heat treatment at 950 °C, the mixed rutile and anatase phase of TiO₂ was revealed for the sample prepared with AA, whereas pure rutile phase was observed for the sample prepared in presence of OA, OM and the mixture of OA + OM. The energy band gap and transmittance of measured for titania nanoparticles was found to be systematically reduced with increase in annealing temperature for each surfactant. The ideality factor decreases with increase in annealing temperature for all surfactants could be related to the voltage dependence of the standard deviation of the distribution of barrier heights.     

Synthesis,characterization and catalytic activity of Au supported on functionalized SBA-15 for low temperature CO oxidation

SBA-15 functionalization with 3-mercaptopropyltrimethoxysilane was used to prepare a supported gold catalyst for the low temperature CO oxidation reaction. Catalytic runs were performed at atmospheric pressure and T = 40–150 °C and the influence of different thermal treatments of the sample prior to reaction was studied. The modifications induced by the pre-treatments in the physico-chemical properties of both the carrier and the disperse phase were investigated by chemical analysis, CHS elemental analysis, N₂ adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), solid state cross-polarization magic-angle-spinning nuclear magnetic resonance spectroscopy (CPMAS NMR) of ²⁹Si and ¹³C and Fourier transform infrared spectroscopy (FTIR). The pre-treatment conditions were found to strongly affect both the gold particle size and the nature of the Au surface species. An appreciable catalytic activity was found on samples treated at 600 °C in H₂/He atmosphere, provided that the functionalizing agent had been completely removed by a previous high-temperature calcination.     

Gold nanoparticles by Terminalia bellirica aqueous extract – a rapid green method

Synthesis of metal nanoparticles (NPs) using plant extracts as reducing agents is of great interest due to its ease and environmental friendly process. Reports show biogenic green synthesis reaction times in forming gold metal nanoparticles (Au NPs) varying from minutes to several hours. In this article, an instantaneous (less than 10?s) method for the green synthesis of gold NPs using aqueous extract of Terminalia bellirica as a reducing and stabilising agent has been reported. Formation of Au NPs was instantaneous and confirmed by UV-Vis spectroscopy where surface plasmon resonance band centred at 530?nm. Formation of anisotropic Au NPs was evidenced from transmission electron microscope studies. High levels of polyphenols in T. bellirica were responsible for the rapid reduction and stabilisation. The Au NPs did not display toxicity when tested by the brine shrimp (Artemia salina) assay.     

Biogenic Syntheses of Gold Nanoparticles Using Plant Extracts

A biogenic approach for the synthesis of gold nanoparticles (GNPs) by reducing chloroauric acid (HAuCl₄) with three different plant extracts (from Angelica, Hypericum, and Hamamelis) is described. The content of reducing compounds (polyphenols) in each plant extract was determined by photometric dosing. The formation of GNPs was tracked by ultraviolet-visible spectroscopy and their characterization was performed using transmission electron microscopy (TEM) and atomic force microscopy (AFM) imaging and FTIR spectra. GNPs, with diameters ranging from about 4 nm to 8 nm, were obtained at room temperature and pH value about 8. They present various shapes from spherical, to ovals, heart or polyhedral forms. Generally, the GNPs colloidal dispersions are rather stable in time, and the self assembly of GNPs is sparsely observed. However, at lower concentration of the plant extract the tendency to self aggregation of the GNPs increased. The plant extracts contain reducing agents, compounds with stabilizing effect on the GNPs, but also components which mediate their self assembly. The GNPs obtained by these biogenic syntheses have potential biological and medical applications, taking into account at least two characteristics, their size and aqueous stability.     

Acalypha indica–mediated green synthesis of ZnO nanostructures under differential thermal treatment: Effect on textile coating,hydrophobicity, UV resistance,and antibacterial activity

In this study, ZnO nanoparticles were green-synthesized from Acalypha indica leaf extract using zinc acetate as a precursor. The prepared ZnO nanoparticles were calcined at three different temperatures, namely 100, 300, and 600?°C. The structure/morphology of the green-synthesized ZnO nanoparticles was ascertained through X-ray diffraction, particle size analysis, scanning electron microscopy, transmission electron microscopy, and surface area analysis techniques. It was observed from the physico-chemical and biological characterization studies that ZnO nanoparticles calcined at high temperature (600?°C) exhibit high surface area (230?m²?g^?1) and small particle size (20?nm) with good antibacterial activity against Escherichia coli (22.89?±?0.06?mm) and Staphylococcus aureus (24.62?±?0.08?mm). In addition, cotton fabrics coated with these nanoparticles showed higher UV-protection (87.8?UPF), hydrophobicity (155°), and maximum zone of bacterial inhibition against E. coli and S. aureus (25.13?±?0.05 mm and 30.17?±?0.03?mm) than those coated with particles calcined at 100?°C and 300?°C. High temperature calcination has a vital role in the crystallization of the particles towards nanoscale with increased resistivity to UV exposure, washing treatments, and microbial infection in fabrics. Thus, the cost-effective ZnO nanoparticles obtained through green synthesis method proves their potential applications in the field of biomedical, textile, and cosmetic applications.     

Synthesis and characterization of NiO nanoparticles and their PMMA nanocomposites obtained by in situ bulk polymerization

A nickel oxide (NiO) precursor was prepared using Pechini method. The NiO nanoparticles were prepared by calcination of NiO precursor at temperatures ranging from 300 to 700 °C. The resulting NiO nanoparticles were characterized by X-ray photoelectron spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy. To hamper NiO nanoparticles aggregation, the NiO nanoparticles surface was treated using (3-mercaptopropyl)-trimethoxysilane as a coupling agent. Next, nanocomposites of poly(methyl methacrylate) and modified NiO nanoparticles were successfully prepared by in situ bulk polymerization with 2,2′-azobis(isobutylonitrile) as initiator. The obtained nanocomposites were characterized by XRD and thermogravimetric analysis. L. A. García-Cerda is on sabbatical leave at UT-Dallas, USA.     

Gold—sulphide versus sulphide centres on (100) AgIBr surfaces: characterization and mechanism

Abstract

Cubic AgIBr emulsions sensitized by sulphur-plus-gold with gold added at 40°C either before or after sulphur sensitization at 70°C were prepared and studied. Gold ions incorporate into the silver-sulphide centres and decrease the diffuse reflectance spectroscopy (DRS) response. The emulsions with gold added before the heat cycle through 70°C showed a dependence on the amount of gold for a speed increase at 0.01 s and their reciprocity failure property, whereas the emulsion with gold added at 40°C after the heat cycle did not. Gold present at the elevated sensitization temperature enhanced long-wavelength sensitivity in a wider wavelength region than gold added after the heat cycle. The different sensitometric behaviour between gold added before or after the heat cycle could be explained by the enhanced thiosulphate conversion effect of gold at 70°C. The electron trapping energy level of the sensitization centre is speculated to be slightly higher for sulphur-plus-gold than sulphur sensitization. Opposite trends were observed in DRS and long-wavelength sensitivity when the gold level increased. Whether the electronic effect of gold during exposure on top of its latensification effect in sulphur-plus-gold sensitization could be observed seems to be dependent on the sulphur level. A mechanism is proposed.     

Nanoalloying and phase transformations during thermal treatment of physical mixtures of Pd and Cu nanoparticles

Nanoscale alloying and phase transformations in physical mixtures of Pd and Cu ultrafine nanoparticles are investigated in real time with in situ synchrotron-based x-ray diffraction complemented by ex situ high-resolution transmission electron microscopy. The combination of metal–support interaction and reactive/non-reactive environment was found to determine the thermal evolution and ultimate structure of this binary system. At 300 °C, the nanoparticles supported on silica and carbon black intermix to form a chemically ordered CsCl-type (B2) alloy phase. The B2 phase transforms into a disordered fcc alloy at higher temperature (> 450 °C). The alloy nanoparticles supported on silica and carbon black are homogeneous in volume, but evidence was found of Pd surface enrichment. In sharp contrast, when supported on alumina, the two metals segregated at 300 °C to produce almost pure fcc Cu and Pd phases. Upon further annealing of the mixture on alumina above 600 °C, the two metals interdiffused, forming two distinct disordered alloys of compositions 30% and 90% Pd. The annealing atmosphere also plays a major role in the structural evolution of these bimetallic nanoparticles. The nanoparticles annealed in forming gas are larger than the nanoparticles annealing in helium due to reduction of the surface oxides that promotes coalescence and sintering.     

In Vitro Stability of Poly(D,L-lactide) and Poly(D,L-lactide)/Poloxamer Nanoparticles in Gastrointestinal Fluids

Abstract

Poty(D,L-lactide) (PLA) nanoparticles of various surface and bulk properties were prepared by a nanoprecipitation procedure and evaluated for their physical and chemical in vitro stability in simulated gastrointestinal fluids of 37°C. The influence of polymer characteristics and poloxamer 188 (POL 188) adsorption was studied. Physical stability was followed by visual appearance, particle size, and zeta potential measurements. Molecular weight changes were analyzed by gel permeation chromatography (GPC). Due to a sharp decrease in their negative zeta potential, poloxamer-free nanoparticles flocculated in simulated gastric fluid, irrespective of the polymer properties. Their physical stability in protein-free intestinal fluids increased with an increase in carboxy end group concentration of the PLA and thus, with an increase in their negative zetapotential. Protein effects at pH 7.5 were rather complex indicating a stabilizing effect of negatively charged proteins and a destabilizing effect of positively charged proteins. Poloxamer 188 adsorption sterically stabilized the nanoparticles against flocculation in gastric fluid, irrespective of the PLA characteristics. Physical stability of the PLA/POL 188 nanoparticles in intestinal fluids was affected by the PLA characteristics. Poloxamer 188 increased the physical stability of nanoparticles composed of hydrophobic PLA, irrespective of the proteins present. A gradual particle size increase could, however, be observed for PLA/POL nanoparticles composed of PLA with a high content of carboxy end groups, especially in combination with positively charged proteins. This effect is most likely due to a decrease in PLA/POL interactions resulting from the ionization of the carboxy end groups located on the nanoparticle surface and leading to conformational changes and/or a distinct desorption of POL 188. The chemical stability of PLA and PLA/POL nanoparticles depended on the glass transition temperature (T_gH) of the hydrated polymer matrix. Enzymatic effects could not be detected. Nanoparticles with T_gH > 37°C were chemically stable in both gastric and intestinal fluids at 37°C over a time period of more than 48 hr.     

Characterization of an antioxidant surfactant-free topical formulation containing Castanea sativa leaf extract

Context: Inclusion of antioxidants in topical formulations can contribute to minimize oxidative stress in the skin, which has been associated with photoaging, several dermatosis and cancer.

Objective: A Castanea sativa leaf extract with established antioxidant activity was incorporated into a semisolid surfactant-free formulation. The objective of this study was to perform a comprehensive characterization of this formulation.

Materials and methods: Physical, microbiological and functional stability were evaluated during 6?months storage at 20?°C and 40?°C. Microstructure elucidation (cryo-SEM), in vitro release and in vivo moisturizing effect (Corneometer® CM 825) were also assessed.

Results and discussion: Minor changes were observed in the textural and rheological properties of the formulation when stored at 20?°C for 6?months and the antioxidant activity of the plant extract remained constant throughout the storage period. Microbiological quality was confirmed at the end of the study. Under accelerated conditions, higher modifications of the evaluated parameters were observed. Cryo-SEM analysis revealed the presence of oil droplets dispersed into a gelified external phase. The release rate of the antioxidant compounds (610?±?70?µgh^?0.5) followed Higuchi model. A significant in vivo moisturizing effect was demonstrated, that lasted at least 4?h after product’s application.

Conclusion: The physical, functional and microbiological stability of the antioxidant formulation was established. Specific storage conditions should be recommended considering the influence of temperature on the stability. A skin hydration effect and good skin tolerance were also found which suggests that this preparation can be useful in the prevention or treatment of oxidative stress-mediated dysfunctions.     

Silver, gold and bimetallic nanoparticles production using single-cell protein (Spirulina platensis) Geitler

Interaction of single-cell protein of Spirulina platensis with aqueous AgNO₃ and HAuCl₄ was investigated for the synthesis of Ag, Au and Au core—Ag shell nanoparticles. Biological reduction and extracellular synthesis of nanoparticles were achieved in 120 h at 37 °C at pH 5.6. The nanometallic dispersions were characterized by surface plasmon absorbance measuring at 424 and 530 nm for Ag and Au nanoparticles, respectively. For bimetallic nanoparticles, absorption peak was observed at 509, 486 and 464 nm at 75:25, 50:50 and 25:75 (Au:Ag) mol concentrations, respectively. High-resolution transmission electron microscopy showed formation of nanoparticles in the range of 7–16 (silver), 6–10 (gold) and 17–25 nm (bimetallic 50:50 ratio). XRD analysis of the silver and gold nanoparticles confirmed the formation of metallic silver and gold. Fourier transform infrared spectroscopic measurements revealed the fact that the protein is the possible biomolecule responsible for the reduction and capping of the biosynthesized nanoparticles.