Progress toward Applications of Carbon Nanotube Photoluminescence

In the fifteen years following the discovery of single-walled carbon nanotube (SWCNT) photoluminescence, investigators have made significant progress in their understanding of the phenomenon and toward the development of applications. The intrinsic potential of semiconducting carbon nanotubes – a family of bright, photostable near infrared (NIR) fluorophores (900–2100 nm) with tunable properties, has motivated their use as optical probes and sensors. In this perspective, we highlight the advances made in the synthesis, processing, modification, separation, and metrology of carbon nanotubes in the context of applications of their photoluminescence

DNA–Carbon Nanotube Complexation Affinity and Photoluminescence Modulation Are Independent

Short single-stranded DNA (ssDNA) has emerged as the natural polymer of choice for noncovalently functionalizing photoluminescent single-walled carbon nanotubes. In addition, specific empirically identified DNA sequences can be used to separate single species (chiralities) of nanotubes, with an exceptionally high purity. Currently, only limited general principles exist for designing DNA–nanotube hybrids amenable to separation processes, due in part to an incomplete understanding of the fundamental interactions between a DNA sequence and a specific nanotube structure, whereas even less is known in the design of nanotube-based sensors with determined optical properties. We therefore developed a combined experimental and analysis platform on the basis of time-resolved near-infrared fluorescence spectroscopy to extract the complete set of photoluminescence parameters that characterizes DNA–nanotube hybrids. Here, we systematically investigated the affinity of the d(GT)n oligonucleotide family for structurally defined carbon nanotubes by measuring photoluminescence response of the nanotube upon oligonucleotide displacement. We found, surprisingly, that the rate of displacement of the oligonucleotides is independent of the coverage on the nanotube, as inferred through the intrinsic optical properties of the hybrid. The kinetics of intensity modulation is essentially a single-exponential, and the time constants, which quantify the stability of DNA binding, span an order of magnitude. Surprisingly, these time constants do not depend on the intrinsic optical parameters within the hybrids, suggesting that the DNA–nanotube stability is not due to increased nanotube surface coverage by DNA. Further, a principal component analysis of the excitation and emission shifts along with intensity enhancement at equilibrium accurately identified the (8,6) nanotube as the partner chirality to (GT)6 ssDNA. When combined, the chirality-resolved equilibrium and kinetics data can guide the development of the DNA–nanotube pairs, with tunable stability and optical modulation. Additionally, this high-throughput optical platform could function as a primary screen for mapping the DNA-chirality recognition phase space

Single Nanotube Spectral Imaging To Determine Molar Concentrations of Isolated Carbon Nanotube Species

Electronic and biological applications of carbon nanotubes can be highly dependent on the species (chirality) of nanotube, purity, and concentration. Existing bulk methods, such as absorbance spectroscopy, can quantify sp2 carbon based on spectral bands, but nanotube length distribution, defects, and carbonaceous impurities can complicate quantification of individual particles. We present a general method to relate the optical density of a photoluminescent nanotube sample to the number of individual nanotubes. By acquiring 3-dimensional images of nanotubes embedded in a gel matrix with a reducing environment, we quantified all emissive nanotubes in a volume. Via spectral imaging, we assessed structural impurities and precisely determined molar concentrations of the (8,6) and (9,4) nanotube species. We developed an approach to obtain the molarity of any structurally enriched semiconducting single-walled carbon nanotube preparation on a per-nanotube basis

The legal framework for private sector development in a transitional economy : the case of Poland

The economies of Central and Eastern Europe are in the midst of a historic transition from central planning and state ownership to development of a market-driven private sector. This transition requires comprehensive changes in"rules of the game"- including the legal framework for economic activity. A market economy presupposes a set of property rights and a system of laws or customs that allow the exchange of those rights. The legal framework in a market economy has at least three basic functions: defining the universe of property rights; setting the rules for entry into and exit from productive activities; and setting the rules of market exchange. These legal tasks are accomplished by areas of law such as: company, foreign investment, bankruptcy, contract and competition law. Poland has a rich legal tradition dating from pre-socialist times, which was suppressed but not eliminated during its forty years of socialism. This tradition is being revised as the country moves toward a private market economy. The current legal framework in Poland closely follows other continental jurisdictions and has a clear and reasonable internal logic. Many of the laws are old, but most are flexible enough to permit a wide range of modern, market-oriented activity. Property law, however, remains a"jungle". The wide discretion and general lack of precedent create tremendous legal uncertainty that is sure to hamper private sector development.Environmental Economics&Policies,Banks&Banking Reform,Municipal Housing and Land,Legal Products,Land and Real Estate Development

The Legal Framework for Private Sector Development in a Transitional Economy: The Case of Poland

The economies of Central and Eastern Europe are in the midst of an historic transition from central planning and state ownership to market driven private sector development. This transition requires comprehensive changes in the rules of the game – i.e. the legal framework for economic activity. Markets presuppose a set of property rights and a system of laws or customs that enable the exchange of those rights. The legal framework in a market economy has at a minimum three basic functions: to define the universe of property rights in the system, to set the rules for the entry and exit of actors into and out of productive activities, and to set the rules of market exchange. Each of these three functions typically involves numerous areas of law. Property rights are defined in practice in most market economies by a wide array of laws regulating the ownership and use of real, personal, and intangible property, as well as shares in going concerns. Company, foreign investment, and bankruptcy laws are among the subset of laws that govern the entry and exit of actors into and out of productive activities. General rules of market exchange govern contract and competition law, while more detailed laws and regulations may govern more specific rules of market exchange in particular sectors. This paper analyzes the evolving legal framework for private sector development in Poland using this general classification. Poland has a rich legal tradition dating from pre-socialist times. This tradition, suppressed but not eliminated during its forty years of socialism, is being revised as the country moves toward a private market economy. The current legal framework in Poland closely follows other continental jurisdictions, particularly the French system, and has a clear and reasonable internal logic. While many of the laws are old, most are flexible enough to permit a wide range of modern market oriented activity. The 1964 Civil Code, modelled closely after the French Napoleonic Code, lays out underlying property and contract rights. Although adopted under the socialist regime, the Civil Code was drafted by law professors and, after being recently purged of socialist rhetoric, the Code is suitable for a market economy. Recent legislation, including the 1990 Antimonopoly Law and the recently adopted Securities and Foreign Investment Laws, appears to be quite well designed for private sector development. Moreover, Parliament (the Sejm ) recently adopted a new personal income tax, and a new value-added tax law is being considered and probably will be adopted in 1992. The most problematic area is property law, which is still, in the words of one Polish legal practitioner, a jungle. Although the legal structure is generally satisfactory in most areas, practice remains uncertain in all areas. The generality of the laws leaves wide discretion for administrators and courts, and a body of cases and practice to further define the rules of the game has not yet developed. Although the courts are generally honest and are used by the population, they have little experience in economic matters. Judges are not well paid, and the best lawyers have a strong incentive to go into private practice. The wide discretion and general lack of experience and competence of judges create legal uncertainty that could hamper private sector development. The answer is not a change in the law, however, but a building of precedent and competence through training and dissemination of information

Lipid-Modified Aminoglycoside Derivatives for In Vivo siRNA Delivery

Rationally designed siRNA delivery materials that are enabled by lipid-modified aminoglycosides are demonstrated. Leading materials identified are able to self-assemble with siRNA into well-defined nanoparticles and induce efficient gene knockdown both in vitro and in vivo. Histology studies and liver function tests reveal that no apparent toxicity is caused by these nanoparticles at doses over two orders of magnitude.Damon Runyon Cancer Research Foundation (DFS-#2050-10)Alnylam Pharmaceuticals (Firm)National Institutes of Health (U.S.) (grant EB000244)National Institutes of Health (U.S.) (grant 1-RO1-CA132091-03

Perturbative Matching of the staggered four-fermion operators for e'/e

Using staggered fermions, we calculate the perturbative corrections to the bilinear and four-fermion operators that are used in the numerical study of weak matrix elements for $\epsilon'/\epsilon$. We present results for one-loop matching coefficients between continuum operators, calculated in the Naive Dimensional Regularization (NDR) scheme, and gauge invariant staggered fermion operators. These results, combined with existing results for penguin diagrams, provide the complete one-loop renormalization of the staggered four-fermion operators.Comment: 36 pages. will appear in physical review

Hyperspectral Microscopy of Near-Infrared Fluorescence Enables 17-Chirality Carbon Nanotube Imaging

The intrinsic near-infrared photoluminescence (fluorescence) of single-walled carbon nanotubes exhibits unique photostability, narrow bandwidth, penetration through biological media, environmental sensitivity, and both chromatic variety and range. Biomedical applications exploiting this large family of fluorophores will require the spectral and spatial resolution of individual (n,m) nanotube species € fluorescence and its modulation within live cells and tissues, which is not possible with current microscopy methods. We present a wide-field hyperspectral approach to spatially delineate and spectroscopically measure single nanotube fluorescence in living systems. This approach resolved up to 17 distinct (n,m) species (chiralities) with single nanotube spatial resolution in live mammalian cells, murine tissues ex vivo, and zebrafish endothelium in vivo. We anticipate that this approach will facilitate multiplexed nanotube imaging in biomedical applications while enabling deep-tissue optical penetration, and single-molecule resolution in vivo

One Spin Trace Formalism for BK B_K

It has been known for some time that there are two methods to calculate $B_K$ with staggered fermions: one is the two spin trace formalism and the other is the one spin trace formalism. Until now, the two spin trace formalism has been exclusively used for weak matrix element calculations with staggered fermions. Here, the one spin trace formalism to calculate $B_K$ with staggered fermions is explained. It is shown that the one spin trace operators require additional chiral partner operators in order to keep the continuum chiral behavior. The renormalization of the one spin trace operators is described and compared with the two spin trace formalism.Comment: 47 pages, latex, 4 figures are available on reques