Optical modeling of laterally-corrugated ridge-waveguide gratings

The paper presents some model improvements for the optical simulation of laterally-corrugated ridge-waveguide distributed feedback lasers. Simulation results are discussed and design principles for achieving single-longitudinal-mode operation are outlined. The effects of the laterally-corrugated ridge geometry both on the coupling coefficient and on the Bragg wavelength of different transverse modes are presented. The improved modeling has been used to design 980 nm distributed feedback lasers with laterally-corrugated ridge-waveguide third-order gratings. The lasers fabricated using nanoimprint lithography exhibited single-mode operation with 50 dB side-mode suppression ratio.     

Hydrogenation of sp-bonded carbon surfaces using methane plasma

Highly ordered pyrolytic graphite was exposed to radio-frequency methane plasma to produce a hydrogen-terminated carbon surface. The effects of treatment parameters, namely exposure time, applied power and methane pressure, upon the treated surfaces’ chemical and morphological properties were systematically investigated. Scanning tunnelling microscopy measurements showed growth features on the plasma treated surface, the coverage of which was shown to increase with plasma exposure time or applied plasma power and decrease with gas pressure. Analyses of post-treated surface structures (via static secondary ion mass spectrometry with the aid of principle component analysis) showed an increase in surface hydrogen with plasma exposure time, applied plasma power and decreasing gas pressure. The results of these analyses were further supported by elastic recoil detection analysis measurements, which showed similar trends for the experimental parameters on the resultant surface hydrogen content.     

Nanotechnology knowledge diffusion: measuring the impact of the research networking and a strategy for improvement

Radiolabelling of industrially manufactured nanoparticles is useful for nanoparticle dosimetry in biodistribution or cellular uptake studies for hazard and risk assessment. Ideally for such purposes, any chemical processing post production should be avoided as it may change the physico-chemical characteristics of the industrially manufactured species. In many cases, proton irradiation of nanoparticles allows radiolabelling by transmutation of a tiny fraction of their constituent atoms into radionuclides. However, not all types of nanoparticles offer nuclear reactions leading to radionuclides with adequate radiotracer properties. We describe here a process whereby in such cases nanoparticles can be labelled with ⁷Be, which exhibits a physical half-life of 53.29 days and emits γ-rays of 478 keV energy, and is suitable for most radiotracer studies. ⁷Be is produced via the proton-induced nuclear reaction ⁷Li(p,n)⁷Be in a fine-grained lithium compound with which the nanoparticles are mixed. The high recoil energy of ⁷Be atoms gives them a range that allows the ⁷Be-recoils to be transferred from the lithium compound into the nanoparticles by recoil implantation. The nanoparticles can be recovered from the mixture by dissolving the lithium compound and subsequent filtration or centrifugation. The method has been applied to radiolabel industrially manufactured SiO₂ nanoparticles. The process can be controlled in such a way that no alterations of the ⁷Be-labelled nanoparticles are detectable by dynamic light scattering, X-ray diffraction and electron microscopy. Moreover, cyclotrons with maximum proton energies of 17–18 MeV that are available in most medical research centres could be used for this purpose.     

Systems membranes--combining the supramolecular and dynamic covalent polymers for gas-selective dynameric membranes

The adequate selection of components makes possible the generation of double dynameric membranes, allowing the fine constitutional modulation of the gas transport performances.     

Formation of nonclassical carbonyls of Au3+ in zeolite NaY: characterization by infrared spectroscopy

Adsorption of CO on gold supported in zeolite NaY at 85 K led to the formation of (i) various carbonyls and isocarbonyls typical of the zeolite and (ii) carbonyls formed at cationic gold sites (observed in the 2186-2171 cm(-1) region). Analysis of the behavior of the bands allows their assignment to carbonyls of Au(3+) ions. At temperatures higher than 220 K, CO adsorption led to the formation of a new type of Au(3+)-CO species (2207 cm(-1)). Once formed, these complexes could be transformed into the dicarbonyls Au(3+)(CO)(2) when the sample was cooled to 85 K in the presence of CO. The results are explained by migration of Au(3+) ions to more accessible positions within the zeolite at increasing temperatures. When a CO molecule is already adsorbed, it stabilizes the Au(3+) ion in the new position, and a second CO molecule can be coordinated, thus forming a geminal species. These results are the first evidence of Au(3+)(CO)(2) complexes.     

Constitutional self-selection of [2 x 2] homonuclear grids from a dynamic mixture of copper(I) and silver(I) metal complexes

This paper describes the controlled self-selection and quantitative parallel amplification of the homonuclear grid architectures derived from the same ligand 1 of different conformational geometries and Cu+ and Ag+ metal ions of different coordination behavior and ionic size.     

Trends in worldwide nanotechnology patent applications: 1991 to 2008

Nanotechnology patent applications published during 1991–2008 have been examined using the “title–abstract” keyword search on esp@cenet “worldwide” database. The longitudinal evolution of the number of patent applications, their topics, and their respective patent families have been evaluated for 15 national patent offices covering 98% of the total global activity. The patent offices of the United States (USA), People’s Republic of China (PRC), Japan, and South Korea have published the largest number of nanotechnology patent applications, and experienced significant but different growth rates after 2000. In most repositories, the largest numbers of nanotechnology patent applications originated from their own countries/regions, indicating a significant “home advantage.” The top applicant institutions are from different sectors in different countries (e.g., from industry in the US and Canada patent offices, and from academe or government agencies at the PRC office). As compared to 2000, the year before the establishment of the US National Nanotechnology Initiative (NNI), numerous new invention topics appeared in 2008, in all 15 patent repositories. This is more pronounced in the USA and PRC. Patent families have increased among the 15 patent offices, particularly after 2005. Overlapping patent applications increased from none in 1991 to about 4% in 2000 and to about 27% in 2008. The largest share of equivalent nanotechnology patent applications (1,258) between two repositories was identified between the US and Japan patent offices.     

Longitudinal Nanotechnology Development (1991--2002): National Science Foundation Funding and its Impact on Patents

Nanotechnology holds the promise to revolutionize a wide range of products, processes and applications. It is recognized by over sixty countries as critical for their development at the beginning of the 21st century. A significant public investment of over $1 billion annually is devoted to nanotechnology research in the United States. This paper provides an analysis of the National Science Foundation (NSF) funding of nanoscale science and engineering (NSE) and its relationship to the innovation as reflected in the United States Patent and Trade Office (USPTO) patent data. Using a combination of bibliometric analysis and visualization tools, we have identified several general trends, the key players, and the evolution of technology topics in the NSF funding and commercial patenting activities. This study documents the rapid growth of innovation in the field of nanotechnology and its correlation to funding. Statistical analysis shows that the NSF-funded researchers and their patents have higher impact factors than other private and publicly funded reference groups. This suggests the importance of fundamental research on nanotechnology development. The number of cites per NSF-funded inventor is about 10 as compared to 2 for all inventors of NSE-related patents recorded at USPTO, and the corresponding Authority Score is 20 as compared to 1.8.