Sustainable preparation of gold nanoparticles via green chemistry approach for biogenic applications

Novel premises of ‘Green Nanotechnology’ have tremendous impacts towards industrial scale revolution. The furtive extracted from natural precursors have driven to the generation of biogenic resources for the fabrication of cutting-edge nanomaterials in simple and cost-effective process. This inspection is an intension of the coupling hypothesis of Nanotechnology via ‘Green-Chemistry’ avenue. So, as to diminish the negative effects of technological applications in the health of human beings and the environment, society is focused towards a greener future. Nanoscience assures a promising future by its improvement in green chemistry to develop the 'Greenary Nanoscience and Nanotechnology'. The improvement and execution of chemical assisted processes in order to reduce the usage of harmful substances, the ‘Green Chemistry’ approach is one and only remarkable authentication, which attributed to long range surface area and higher pore volume of gold-nanoparticles. As of now, the efficient biogenic mechanism dramatically reduces the utilization and hazardous reagents have been employed to low-price natural and waste products to yield value-added nanomaterials with extensive relevance, suggesting an economical and green solution to environmental issues. In depth investigation of this critical review illustrates, novel biogenic screening platform was also conducted against antimicrobial strains and degradation of gold-nanoparticles products well explored-from selection precursors evolved from natural extracts, as well as eventually disintegration into bio-degradable yet potentially recyclable byproducts.     

Enantioselective solvent-free Robinson annulation reactions

The enantioselective cyclization of the prochiral cyclic substrates1 to7 and26, can be carried out in theneat using S-proline as catalyst. The substrates18 to22 and27 could not be cyclized with S-proline but could be cyclized with a mixture of S-phenylalanine and d-camphorsulphonic acid. The enantioselective cyclization of prochiral acyclic triones45 and47 and also the racemic tricarbonyl compounds54 to57 could also be carried out in theneat using S-proline as catalyst. The optically active enediones obtained in the above cyclizations could also be obtained directly from 1,3-diones or 2-hydroxymethylene cycloalkanones in a one-pot reaction with methyl vinyl ketone (MVK) and S-proline in the absence of solvents.¹³C NMR studies of the one-pot synthesis ofS-11 andS-14 reveal that the annulations involve initial formation of an acid-base complex followed by a Michael reaction and then an enantioselective cyclization. Such enantioselective cyclizations probably occur on the surface of S-proline crystals.     

Large force fluctuations in a flowing granular medium

We study fluctuations in the force at the boundary of a 2D granular flow. The forces are mainly impulsive at all flow rates. The probability distribution of impulses decays exponentially at large impulses, as do the forces in a static granular medium. At small impulses, the distribution evolves continuously with flow rate with no indication of the transition from collisional flow to intermittently jamming flows. However, the distribution of the time interval between collisions tends to a power law, P(tau) - tau(-3/2), showing a clear dynamical signature of the approach to jamming.     

Electroactive, Internal Anthraquinonoid Dendritic Cores(1)

The modification of the extended 1 --> 3 anthraquinonoid monomer 1 by substitution of the central aliphatic moiety with a more rigid, aromatic moiety has allowed the syntheses of the new branched building block 6 possessing multiple, internal redox sites. This monomer was used to generate the first tier, dendritic macromolecules 8 and 9, which incorporate different internal redox centers within the infrastructure as well as the traditional peripheral multifunctionality. Using cyclic voltammetry experiments, the electrochemical response and electronic interactions between the two electroactive sites (the anthraquinonoid and nitroaromatic moieties) of these dendritic constructs were explored.     

Holographic moiré in real time

The body of knowledge necessary to observe holographic-moiré patterns in real time is introduced. The basic factors influencing fringe visibility in holographic moiré are analyzed and expressions to evaluate fringe visibility for any given displacement and deformation are given. The application of the introduced theory in the case of real-time observation is discussed. It is shown that the maximum benefits of this technique are achieved by combining it with closed-circuit TV. Several examples of application are given.     

Resonantly enhanced off-specular X-ray scattering from polymer/polymer interfaces<Superscript>⋆</Superscript>

We have used measurements of the absolute intensity of diffuse X-ray scattering to extract the interfacial tension of a buried polymer/polymer interface. Diffuse scattering was excited by an X-ray standing wave whose phase was adjusted to have a high intensity at the polymer/polymer interface and simultaneously a node at the polymer/air interface. This method permits the capillary-wave-induced roughness of the interface, and hence the interfacial tension, to be measured independently of the polymer/polymer interdiffusion.     

Real-time evolution of the distribution of nanoparticles in an ultrathin-polymer-film-based waveguide

We report a novel application of an ultrathin-polymer-film-based, resonance-enhanced x-ray waveguide as a real-time nanoprobe for elucidating dilute, yet disordered, gold nanoparticles embedded in the polymer matrix. This nanoprobe promises a sensitivity enhancement of several orders of magnitude, hence revealing in real time the lateral nanoparticle distribution with subnanometer spatial resolution. We observed that the motion of the nanoparticles is strongly anisotropic, with in-plane coalescence taking place more rapidly than out-of-plane diffusion, which can ultimately facilitate the formation of two-dimensional structures.     

Fluidized granular medium as an instance of the fluctuation theorem

We study the statistics of the power flux into a collection of inelastic beads maintained in a fluidized steady state by external mechanical driving. The power shows large fluctuations, including frequent large negative fluctuations, about its average value. The relative probabilities of positive and negative fluctuations in the power flux are in close accord with the fluctuation theorem of Gallavotti and Cohen, even at time scales shorter than those required by the theorem. We also compare an effective temperature that emerges from this analysis to the kinetic granular temperature.     

Microstructure and dynamics near an attractive colloidal glass transition

The microstructure and dynamics of a colloidal system interacting via short-ranged interparticle potential is studied by ultra-small-angle x-ray scattering and x-ray photon correlation spectroscopy. A colloidal gas-liquid type transition is induced when the short-ranged attractive interactions attain sufficient magnitude. The development of liquidlike structure is preceded by a systematic transition in the particle dynamics from diffusive to constrained motion and then completely frozen behavior. This demonstrates the existence of a jamming transition induced by strong short-ranged attractive interactions even at low packing fractions.     

A sagittally focusing double‐multilayer monochromator for ultrafast X‐ray imaging applications

The development of a sagittally focusing double‐multilayer monochromator is reported, which produces a spatially extended wide‐bandpass X‐ray beam from an intense synchrotron bending‐magnet source at the Advanced Photon Source, for ultrafast X‐ray radiography and tomography applications. This monochromator consists of two W/B₄C multilayers with a 25 Å period coated on Si single‐crystal substrates. The second multilayer is mounted on a sagittally focusing bender, which can dynamically change the bending radius of the multilayer in order to condense and focus the beam to various points along the beamline. With this new apparatus, it becomes possible to adjust the X‐ray beam size to best match the area detector size and the object size to facilitate more efficient data collection using ultrafast X‐ray radiography and tomography.