Nanoassembled Model Catalysts: Changing Efficiency and Selectivity Atom-by-Atom

2000 ◽  
Vol 648 ◽  
Author(s):  
U. Heiz ◽  
S. Abbet ◽  
H. Häkkinen ◽  
U. Landman
Keyword(s):  
High Selectivity ◽  
Bulk Material ◽  
Gold Cluster ◽  
Chemical Properties ◽  
Model Catalysts ◽  
Size Dependent ◽  
Phase Cluster ◽  
Physical And Chemical ◽  
Supported Pd ◽  
And Chemical Properties

AbstractCluster-assembled materials open fascinating new routes for tuning physical and chemical properties by changing cluster size and often these materials behave completely differently than their bulk analogues. By depositing gas phase cluster cations on various surfaces, cluster model catalysts are fabricated, which exhibit remarkable catalytic activity. While inert as bulk material, gold cluster catalysts oxidize carbon monoxide with Au8 to be the smallest active size. In contrast to the high selectivity of Pd(111) surfaces for the cyclotrimerization of acetylene, small supported Pdn clusters reveal a strongly size-dependent selectivity for the polymerization of acetylene and catalyze the cyclotrimerization as well as the hydrogenation of the formed intermediate C4H4.

Carbon Nanotube Composites

2019 ◽  
Vol 23 ◽  
pp. 75-81
Author(s):  
Ponnusamy Senthil Kumar ◽  
G. Janet Joshiba
Keyword(s):  
Carbon Nanotubes ◽  
Tensile Strength ◽  
Carbon Nanotube ◽  
Chemical Properties ◽  
Market Demand ◽  
Size Dependent ◽  
Nanotube Composites ◽  
Carbon Nanotube Composites ◽  
Physical And Chemical ◽  
And Chemical Properties

The discovery of carbon nanotubes is one of the remarkable achievement in the field of material science and it is a great advancement of Nanotechnology. A carbon nanotube is an expedient material used in several domains and paves way for the welfare of humans in many ways. Carbon nanotubes are nanosized tubes made from graphitic carbons and it is well known for its exclusive physical and chemical properties. The market demand for the nanotubes has increased progressively due to its size dependent, structure and mechanical properties. The carbon nanotubes possess high tensile strength and it is also found to be the durable fibre ever known. It is also found to possess exceptional electrical properties. The carbon nanotube composites have an excellent young’s modulus and higher tensile strength same as graphite carbon. This review plots the properties of carbon nanotubes and portrays the planning and properties of carbon nanotube composites. The wide application of carbon nanotube composites is also explained.

scholarly journals Detecting Fingerprints of Waterborne Bacteria on a Sensor

Chemosensors ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 33 ◽  
Author(s):  
Saylan ◽  
Erdem ◽  
Cihangir ◽  
Denizli
Keyword(s):  
Large Scale ◽  
High Selectivity ◽  
Chemical Properties ◽  
Surface Proteins ◽  
Polluted Water ◽  
Label Free ◽  
Recognition Element ◽  
Modification Method ◽  
Physical And Chemical ◽  
And Chemical Properties

Human fecal contamination is a crucial threat that results in difficulties in access to clean water. Enterococcus faecalis is a bacteria which is utilized as an indicator in polluted water. Nevertheless, existing strategies face several challenges, including low affinity and the need for labelling, which limit their access to large scale applications. Herein, a label-free fingerprint of the surface proteins of waterborne bacteria on a sensor was demonstrated for real-time bacteria detection from aqueous and water samples. The kinetic performance of the sensor was evaluated and shown to have a range of detection that spanned five orders of magnitude, having a low detection limit (3.4 × 104 cfu/mL) and a high correlation coefficient (R2 = 0.9957). The sensor also designated a high selectivity while other competitor bacteria were employed. The capability for multiple usage and long shelf-life are superior to other modalities. This is an impressive surface modification method that uses the target itself as a recognition element, ensuring a broad range of variability to replicate others with different structure, size and physical and chemical properties.

Experimental Study on the Heat Transfer in the Al Powder

2009 ◽  
Vol 83-86 ◽  
pp. 953-958
Author(s):  
Ching Yen Ho ◽  
Yu Hsiang Tsai ◽  
Mao Yu Wen
Keyword(s):  
Heat Transfer ◽  
Thermal Conduction ◽  
Room Temperature ◽  
Bulk Material ◽  
Chemical Properties ◽  
Bulk Materials ◽  
Processing Technologies ◽  
Insulating Material ◽  
Physical And Chemical ◽  
And Chemical Properties

Nanometer-sized particles possess characteristic physical and chemical properties different from those of bulk materials due to an increase in surface-to-volume ratios as well as of confinement of electrons, excitons, and photons into small volumes. Therefore it is worthwhile to discuss the thermal behaviours of powders constituted by nanometer-sized particles. The heat transfer in the powder composed of nanoparticles is experimentally investigated in this paper. The understanding for thermal properties of the powder is advantageous to the advancement of the processing technologies such as laser cladding, laser sintering, powder metallurgy and its other applications. The powder is wrapped up in the slender tube made of insulating material. One end of the slender tube filled with powder is maintained at temperature 0°C and the other end is kept at room temperature. The temperature histories at two different locations in the slender tube are recorded using thermal couples. The results show that the thermal diffusivity in the powder composed of nanoparticles is larger than that in bulk material. The pressure on the Al powders enhances the rate of heat transport due to the increase of contact area for thermal conduction.

Shape transformation of self-assembled Au nanoparticles by the systematic control of deposition amount on sapphire (0001)

RSC Advances ◽  
2015 ◽  
Vol 5 (81) ◽  
pp. 66212-66220 ◽  
Author(s):  
Puran Pandey ◽  
Mao Sui ◽  
Ming-Yu Li ◽  
Quanzhen Zhang ◽  
Eun-Soo Kim ◽  
...  
Keyword(s):  
Au Nanoparticles ◽  
Chemical Properties ◽  
Shape Transformation ◽  
Au Nps ◽  
Size Dependent ◽  
Deposition Amount ◽  
Significant Research ◽  
Physical And Chemical ◽  
Systematic Control ◽  
And Chemical Properties

The shape and size dependent optical, physical and chemical properties of isotropic and anisotropic gold nanoparticles (Au NPs) have attracted significant research interest for their application in various optoelectronic devices.

scholarly journals Materials for Micro- and Nanofluidics

MRS Bulletin ◽  
2006 ◽  
Vol 31 (2) ◽  
pp. 87-94 ◽  
Author(s):  
Paul J.A. Kenis ◽  
Abraham D. Stroock
Keyword(s):  
Material Properties ◽  
Bulk Material ◽  
Chemical Properties ◽  
Operating Conditions ◽  
Biological Studies ◽  
Wide Range ◽  
Properties Of Materials ◽  
The Many ◽  
Physical And Chemical ◽  
And Chemical Properties

AbstractOver the last two decades, our ability to create networks of fluidic channels of submillimeter or even sub-micrometer diameters has led to a wide range of microchemical applications. Whereas early efforts were directed toward the development of microanalysis systems, in more recent times the development of microreactors and tools for biotechnology and basic biological studies has emerged. This issue of MRS Bulletin highlights the many different ways in which material properties are crucial in the fabrication, assembly, and operation of micro- and nanofluidic systems. Choice-of-material considerations range from an assessment of whether a desired channel design can be microfabricated in a certain material to whether the material is compatible with the operating conditions (i.e., pressure, temperature) and the chemical composition (solvent, solutes) of the fluid used. Moreover, in certain cases, specific surface or bulk material properties can be used to the benefit of the application of the device. In the development of today's wide range of integrated micro- and nanofluidic applications, a common challenge emerges: meeting the often contradictory set of constraints imposed on the physical and chemical properties of materials by the envisioned applications. This issue reviews these challenges and their solutions and provides an outlook on how the ingenious use of existing and new materials can spur the development of ever more sophisticated micro- and nanofluidic systems.

scholarly journals Microcavity phonon polaritons from the weak to the ultrastrong phonon–photon coupling regime

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
María Barra-Burillo ◽  
Unai Muniain ◽  
Sara Catalano ◽  
Marta Autore ◽  
Fèlix Casanova ◽  
...  
Keyword(s):  
Strong Coupling ◽  
Coupling Strength ◽  
Hexagonal Boron Nitride ◽  
Bulk Material ◽  
Chemical Properties ◽  
Thin Layers ◽  
Phonon Polaritons ◽  
Physical And Chemical ◽  
Photon Coupling ◽  
And Chemical Properties

AbstractStrong coupling between molecular vibrations and microcavity modes has been demonstrated to modify physical and chemical properties of the molecular material. Here, we study the less explored coupling between lattice vibrations (phonons) and microcavity modes. Embedding thin layers of hexagonal boron nitride (hBN) into classical microcavities, we demonstrate the evolution from weak to ultrastrong phonon-photon coupling when the hBN thickness is increased from a few nanometers to a fully filled cavity. Remarkably, strong coupling is achieved for hBN layers as thin as 10 nm. Further, the ultrastrong coupling in fully filled cavities yields a polariton dispersion matching that of phonon polaritons in bulk hBN, highlighting that the maximum light-matter coupling in microcavities is limited to the coupling strength between photons and the bulk material. Tunable cavity phonon polaritons could become a versatile platform for studying how the coupling strength between photons and phonons may modify the properties of polar crystals.

Statistical criteria of stellar population types

1966 ◽  
Vol 24 ◽  
pp. 101-110
Author(s):  
W. Iwanowska
Keyword(s):  
Stellar Population ◽  
Chemical Properties ◽  
Spectrophotometric Study ◽  
Physical And Chemical Properties ◽  
Population Type ◽  
The Galaxy ◽  
Distribution Parameters ◽  
Physical And Chemical ◽  
Statistical Criteria ◽  
And Chemical Properties

In connection with the spectrophotometric study of population-type characteristics of various kinds of stars, a statistical analysis of kinematical and distribution parameters of the same stars is performed at the Toruń Observatory. This has a twofold purpose: first, to provide a practical guide in selecting stars for observing programmes, second, to contribute to the understanding of relations existing between the physical and chemical properties of stars and their kinematics and distribution in the Galaxy.

Tailoring microstructures of materials through biomimetics

1993 ◽  
Vol 51 ◽  
pp. 500-501
Author(s):  
Mehmet Sarikaya ◽  
Ilhan A. Aksay
Keyword(s):  
Chemical Properties ◽  
Design And Synthesis ◽  
Structure Sensitive ◽  
Macro Scale ◽  
Methods Of Synthesis ◽  
Successive Level ◽  
Engineering Materials ◽  
Physical And Chemical ◽  
And Chemical Properties ◽  
Synthesis Of Materials

Biomimetics involves investigation of structure, function, and methods of synthesis of biological composite materials. The goal is to apply this information to the design and synthesis of materials for engineering applications.Properties of engineering materials are structure sensitive through the whole spectrum of dimensions from nanometer to macro scale. The goal in designing and processing of technological materials, therefore, is to control microstructural evolution at each of these dimensions so as to achieve predictable physical and chemical properties. Control at each successive level of dimension, however, is a major challenge as is the retention of integrity between successive levels. Engineering materials are rarely fabricated to achieve more than a few of the desired properties and the synthesis techniques usually involve high temperature or low pressure conditions that are energy inefficient and environmentally damaging.In contrast to human-made materials, organisms synthesize composites whose intricate structures are more controlled at each scale and hierarchical order.

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