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We report the use of chemically-functionalized water soluble single-walled carbon nanotube (SWNT) graft copolymers for modulation of outgrowth of neuronal processes. The graft copolymers were prepared by the functionalization of SWNTs with poly-m-aminobenzene sulphonic acid and polyethylene glycol. When added to the culturing medium, these functionalized water soluble SWNTs were able to increase the length of various neuronal processes.

Single-walled carbon nanotubes (SWNTs) hold great promise for advanced applications in aerospace, electronics and medicine, yet these industries require materials with rigorous quality control. There are currently no accepted standards for quality assurance or quality control among the commercial suppliers of SWNTs. We briefly discuss the applicability of various techniques to measure SWNT purity and review, in detail, the advantages of near infrared (NIR) spectroscopy for the quantitative assessment of the bulk carbonaceous purity of SWNTs. We review the use of solution phase NIR spectroscopy for the analysis and characterization of a variety of carbon materials, emphasizing SWNTs produced by the electric arc (EA), laser oven (LO) and HiPco (HC) methods. We consider the applicability of Beer's law to carbon materials dispersed in dimethylformamide (DMF) and the effective extinction coefficients that are obtained from such dispersions. Analysis of the areal absorptivities of the second interband transition of semiconducting EA-produced SWNTs for a number of samples of differing purities has lead to an absolute molar extinction coefficient for the carbonaceous impurities in EA-produced SWNT samples. We conclude that NIR spectroscopy is the clear method of choice for the assessment of the bulk carbonaceous purity of EA-produced SWNTs, and we suggest that an absolute determination of the purity of SWNTs is within reach. Continued work in this area is expected to lead to a universal method for the assessment of the absolute bulk purity of SWNTs from all sources--such a development will be of great importance for nanotube science and for future customers for this product.

Organic field‐effect transistors (FETs) which employ two carefully selected active materials can function as n channel, p channel, or both n‐ and p‐channel devices. It is shown that under an appropriate set of bias conditions the channel current in FETs with α‐hexathienylene (α‐6T) and C60 active layers consist of electron and hole components that are injected from the source and drain contacts into the C60 and α‐6T layers, respectively.

Polymorphism-the phenomenon that a given compound forms more than one crystalline arrangement of the molecules in the solid state- plays a crucial role in understanding organic conductors, superconductors, and magnets. We have found that solutions of a new phenalenyl radical can give rise to two (nonpolymorphic) crystalline forms depending on whether the crystallization is allowed to proceed in the presence or absence of light. In both cases the crystals take the form of black shining blades and are indistinguishable by optical microscopy. We have fully characterized these crystalline forms, and we show that they differ by the presence or absence of a C-C sigma-bond between the unpaired electrons of the parent radical. These molecular forms crystallize from the same solvent to give rise to a sigma-dimerized insulator and a monomeric radical semiconductor as dictated by the presence or absence of light.

New synthetic methods for heterocyclic 1,3,2-dithiazolyl (DTA) radicals have been developed, and trends in the molecular spin distributions and electrochemical properties of a series of DTA radicals are reported. The crystal structures of [1,2,5]thiadiazolo[3,4-f][1,3,2]benzodithiazol-2-yl (TBDTA) and [1,3,2]pyrazinodithiazol-2-yl (PDTA) have been determined. The structure of TBDTA (at 293 and 95 K) contains two molecules in the asymmetric unit, each of which generates pi-stacked arrays, one consisting of antiparallel chains of centrosymmetrically associated dimers, the other comprising parallel chains of unassociated radicals. The structure of PDTA (at 293 and 95 K) is simpler, consisting of slipped stacks of pi-dimers. Variable-temperature magnetic susceptibility (chi(P)) measurements on TBDTA indicate essentially paramagnetic behavior for the unassociated radical pi-stacks over the range 5-400 K. By contrast PDTA is diamagnetic at all temperatures below 300 K, but between 300 and 350 K the value of chi(P) follows a sharp and well-defined hysteresis loop, with T(C) downward arrow = 297 K and T(C) upward arrow = 343 K. These features are symptomatic of a regime of bistability involving the observed low temperature pi-dimer structure and a putative high-temperature radical pi-stack. A mechanism for the interconversion of the two phases of PDTA and related structures is proposed in which hysteretic behavior arises from cooperative effects associated with the breaking and making of a lattice-wide network of intermolecular S- - -N' and/or S- - -S' interactions.

We report the use of chemically modified carbon nanotubes as a substrate for cultured neurons. The morphological features of neurons that directly reflect their potential capability in synaptic transmission are characterized. The chemical properties of carbon nanotubes are systematically varied by attaching different functional groups that confer known characteristics to the substrate. By manipulating the charge carried by functionalized carbon nanotubes we are able to control the outgrowth and branching pattern of neuronal processes.

We report a systematic evaluation of the use of refluxing nitric acid as a purification treatment for electric arc-produced single-walled carbon nanotubes (SWNTs), by using a combination of thermogravimetric analysis (TGA) and near-infrared (NIR) spectroscopy. Nitric acid is the standard reagent for purification of SWNTs and has traditionally constituted the first step in many different purification schemes. It has been suggested that nitric acid removes the transition metal catalyst that is used in the production of the SWNTs together with amorphous carbon. Under all conditions, we find that nitric acid destroys SWNTs to produce amorphous carbon while reducing the amount of transition metal catalyst remaining in the sample. Thus, nitric acid is suitable for removing the catalyst from SWNT samples, but only at the expense of a significant destruction of the SWNTs.

Electric arc produced single-walled carbon nanotube (SWNT) films have been purified by a selective oxidation process. The purification is monitored by Near-infrared (NIR) spectroscopy, which gives a quantitative estimate of relative purities. This technique also gives an estimate of the change in relative amounts of single-walled carbon nanotubes (SWNTs) and amorphous carbon impurities after each purification step, thereby providing accurate and selective control over the oxidation process. Oxidation was carried out by reaction in flowing oxygen at 265, 292 and 315°C for different time durations and the purity was evaluated after each oxidation step and compared to the starting as-prepared film. Relative purities, relative amounts of SWNTs and amorphous carbon impurities were monitored as a function of oxidation temperature and time. The maximum purity, which could be obtained by the present process, was three times that of the as-prepared SWNT film.

We discuss the use of far‐infrared spectroscopy in the characterization of doped and functionalized nanotube derivatives.

We repot observations of an enhancement of at least 3 orders of magnitude in the rate of photoinduced cross linking of C{sub 60} films under an ambient NO atmosphere. Under extended illumination (for as long as 48 h at 8 W/cm{sup 2}) the fullerene clusters disappear, and the film evolves toward an amorphous mixture of C, N, and O. Raman and XPS data show signatures of C-N bond formation. We propose a mechanism for the role of NO based on stabilization of the diradical intermediate formed in the primary photochemical step. The mechanism suggests a new generic pathway for photoinduced transformation of fullerene films. Related experiments with samples removed from NO and exposed to air also show a residual polymerization effect with decay time on the order of an hour. 11 refs., 3 figs.

N‐channel field effect transistors with excellent device characteristics have been fabricated by utilizing C60 as the active element. Measurements on C60 thin films in ultrahigh vacuum show on‐off ratios as high as 106 and field effect mobilities up to 0.08 cm2/V s.

We report the sidewall functionalization of soluble HiPco single-walled carbon nanotubes (SWNTs) by addition of dichlorocarbene. The dichlorocarbene-functionalized SWNTs [(s-SWNT)CCl(2)] retain their solubility in organic solvents such as tetrahydrofuran and dichlorobenzene. The degree of dichlorocarbene functionalization was varied between 12% and 23% by using different amounts of the dichlorocarbene precursor. Because the addition of dichlorocarbene saturates the carbon atoms on the sidewall of the SWNTs and effectively replaces the delocalized partial double bonds with a cyclopropane functionality, the optical spectra of the SWNTs change dramatically. We estimate that the saturation of 25% of the pi-network electronic structure of the SWNTs is sufficient to remove all vestiges of the interband transitions in the infrared spectrum. The transitions at the Fermi level in the metallic SWNTs that appear in the far-infrared (FIR) region of the spectrum show a dramatic decrease of intensity on dichlorocarbene functionalization. The FIR region of the spectrum allows a clear differentiation between the covalent and the ionic chemistry of SWNTs. In contrast with covalent functionalization, we show that reaction of the SWNTs with bromine vapor leads to a strong increase in absorptions at the Fermi level that is observable in the FIR due to hole doping of the semiconducting SWNTs. Thermal treatment of the (s-SWNT)CCl(2) above 300 degrees C resulted in the breakage of C-Cl bonds, but did not restore the original electronic structure of the SWNTs.

The pseudo–one-dimensional (psuedo-1D) conjugated electronic structure of single-walled carbon nanotubes (SWNTs) allows them to exhibit semiconducting and metallic properties and to exhibit ballistic transport ( [1][1] ). We show that their unique electronic structure also offers the opportunity

We report a study of the organic compound $(TMTSF)_2 ClO_4$ in both a sample cooled very slowly through the anion ordering temperature (relaxed state) and a sample cooled more rapidly (intermediate state). For the relaxed state the entire sample is observed to be superconducting below about T_c ~ 1.2 K. The second moment of the internal field distribution was measured for the relaxed state yielding an in-plane penetration depth of ~ 12000 Angstroms. The intermediate state sample entered a mixed phase state, characterized by coexisting macroscopic sized regions of superconducting and spin density wave (SDW) regions, below T_c ~ 0.87 K. These data were analyzed using a back-to-back cutoff exponential function, allowing the extraction of the first three moments of the magnetic field distribution. Formation of a vortex lattice is observed below 0.87 K as evidenced by the diamagnetic shift for the two fields in which we took intermediate state data., Comment: 6 pages, 3 figures, to be submitted to Physica C

The fullerene C(60) can be converted into two different structures by high pressure and temperature. They are metastable and revert to pristine C(60) on reheating to 300 degrees C at ambient pressure. For synthesis temperatures between 300 degrees and 400 degrees C and pressures of 5 gigapascals, a nominal face-centered-cubic structure is produced with a lattice parameter a(o) = 13.6 angstroms. When treated at 500 degrees to 800 degrees C at the same pressure, C(60) transforms into a rhombohedral structure with hexagonal lattice parameters of a(o) = 9.22 angstroms and c(o) = 24.6 angstroms. The intermolecular distance is small enough that a chemical bond can form, in accord with the reduced solubility of the pressure-induced phases. Infrared, Raman, and nuclear magnetic resonance studies show a drastic reduction of icosahedral symmetry, as might occur if the C(60) molecules are linked.

In this Account we highlight the experimental evidence in favor of our view that carbon nanotubes should be considered as a new macromolecular form of carbon with unique properties and with great potential for practical applications. We show that carbon nanotubes may take on properties that are normally associated with molecular species, such as solubility in organic solvents, solution-based chemical transformations, chromatography, and spectroscopy. It is already clear that the nascent field of nanotube chemistry will rival that of the fullerenes.

The trifluoromethyl-substituted dithiadiazolyl and dithiazolyl radicals, F3CCNSSN (1) and F3CCSNSCCF3 (2) associate through pi*-pi* covalent and electrostatic S delta+...N delta- interactions in the solid state, but melt with a dramatic volume increase to generate paramagnetic liquids; these radicals exhibit thermal hysteresis, which arises through a meta-stable super-cooled liquid state, close to room temperature.

The formation energy, [Delta]H[sub f], of fullerite intercalation compounds A[sub n]C[sub 60] with A = Na, K, Rb, and Cs and n = 6 is measured using differential scanning calorimetry. The alkali metals, K, Rb, and Cs react with C[sub 60] powders readily and directly form the bcc A[sub 6]C[sub 60]. [Delta]H[sub f] values are found to be [minus]28, [minus]39, [minus]40, and [minus]47 kcal/mol per alkali metal for Na, K, Rb, and Cs, respectively. The activation energy of diffusion of the alkali metals Rb and Cs in the corresponding A[sub 6]C[sub 60] compound is evaluated to be approximately 30 kcal/mol. 25 refs., 4 figs., 1 tab.

A WIDE variety of alkali-metal fullerides (AxC60) have been prepared, with stoichiometries varying between 1⩽=x⩽=11 (refs 1,2). Most of the compounds with x = 3 are superconductors with unusually high transition temperatures (Tc) which increase with the size of the face-centred cubic unit cell3. The increase in Tc on lattice expansion is attributed to a decrease in the conduction band width, and therefore one ultimately expects a saturation or downturn of Tc followed by a metal–insulator transition. We have sought to explore this regime by expanding the A3C60 structure through intercalation of neutral molecules capable of solvating the A+ ions. Here we report that the reaction of ammonia with Na2CsC60 (Tc = 10.5K; lattice constant α = 14.132 A) produces the compound (NH3)4Na2CsC60, which has an expanded unit cell (a = 14.473 A) and an increased Tc of 29.6 K. The structure contains the Na(NH3)+4 cation on the octahedral site.

We have demonstrated the covalent functionalization of carbon nanotubes and graphene with a variety of chemistries including the use of nitrophenyl groups, Diels-Alder reactions and organometallic derivatization. The chemical formation of covalent carbon-carbon bonds involving the basal plane carbon atoms modifies the electronic properties of graphene; the transformation of the carbon centers from sp2 to sp3 introduces a barrier to electron flow by saturating the carbon atoms and opening a band gap which potentially allows the generation of insulating and semiconducting regions in graphene wafers. In this talk I will discuss our recent results on the electronic and magnetic properties of chemically modified graphene, the observation of ferromagnetism, and the application of organometallic chemistry to facilitate the interconnection of single-walled carbon nanotubes.

The development of low cost and environmentally friendly energy conversion andstorage systems is currently of the utmost priority. Here we discuss the impact of chemical design of carbon nanomaterials on their performance as active materials for supercapacitor and catalyst support for fuel cell applications. Chemical modification of single-walled carbon nanotubes (SWNTs) and graphene, is a powerful means to improve the charge capacitance of the materials. By introducing oxygen-containing groups the gravimetric capacity of SWNTs and graphene can be doubled. Furthermore, the combination of 1D SWNTs and 2D graphene affords hybrid structures with enhanced synergistic electrochemical performance. We also demonstrate the advantages of functionalized SWNTs for the fabrication of SWNT thin film catalyst support layers in polymer electrolyte membrane fuel cells (PEMFCs). Introducing an optimum level of carboxylic groups in the SWNTs allows the fabrication of SWNT-based PEMFC with efficient Pt catalyst utilization. This offers an attractive route to the manufacture of highly efficient fuel cells that meet some of the US DOE 2017 technical targets.

We report an improved chromatographic purification of soluble single-walled carbon nanotubes (s-SWNTs) using gel permeation chromatography. Three fractions are separated by gel permeation chromatography, and the first fraction contains 74% of the s-SWNTs as detected by atomic force microscopy and UV and near-infrared spectroscopy.

INTERCALATING solid C60 with dopant atoms yields materials with a remarkable range of properties1. Alkali metal atoms, for example, readily form charge-transfer compounds2,3, AxC60 (where A is an alkali metal), which can be metallic, superconducting or insulating depending on the dopant concentration4–9. In all cases, the superconducting phase has a face-centred cubic (f.c.c.) structure and stoichiometry A3C60, which suggests a common mechanism for superconductivity dependent, at least in part, on the external coordination number of the C60 molecules. More recently, it has been shown10 that the alkaline earth metal calcium can also be intercalated with fulleride to form a superconducting phase, again with a f.c.c.-derived structure, near a Ca:C60 ratio of 5:1. Here we report the intercalation of fulleride with barium, in which a pure body-centred cubic phase with a lattice constant of 11.171 A is realized near a stoichiometry of Ba6C60. This phase is also superconducting (with a transition temperature of 7 K), suggesting that the mechanism of superconductivity is related to an intrinsic property of the C60 molecules, rather than the external coordination number.

Measurements of the superconducting ${\mathit{T}}_{\mathit{c}}$ and Raman spectra in isotopically modified ${\mathrm{Rb}}_{3}$${\mathrm{C}}_{60}$ are reported. A decrease in ${\mathit{T}}_{\mathit{c}}$ of 0.65\ifmmode\pm\else\textpm\fi{}0.10 K in samples with (75\ifmmode\pm\else\textpm\fi{}5)% substitution of $^{13}\mathrm{C}$ for $^{12}\mathrm{C}$ yields an exponent of \ensuremath{\alpha}=0.37\ifmmode\pm\else\textpm\fi{}0.05. This interpreted as evidence for phonon-mediated pairing.

FCC C{sub 60} crystals exposed to pure O{sub 2} are converted to carbon-oxygen adducts at {approximately}200{degrees}C. The carbon-oxygen species decompose into CO and CO{sub 2} gases at a higher temperature, {approximately}400{degrees}C. The total heats of oxidation of C{sub 60} are determined by calorimetry to be {approximately}53 kcal/mol. The activation energy for the oxidation is 58.2 kcal/mol. The C{sub 60} powders in inert gases such as N{sub 2} and Ar sublime at {approximately}600{degrees}C. A method is derived to determine the heats of sublimation from thermogravimetric analysis. The heat of sublimation of C{sub 60} powders in pure N{sub 2} or Ar is found to be {approx_gt}39 kcal/mol. 16 refs., 4 figs., 1 tab.

In pure oxygen at moderate temperatures of 200 °C, an fcc C60 transforms into amorphous carbon‐oxygen compounds and the icosahedral C60 molecular structure is destroyed. The maximum oxygen uptake of pure C60, O/C60, is 12. Isothermal TGA transformation curves are sigmoid‐shaped with the kinetic exponent n∼5/2 which conforms with a two‐dimensional nucleation and growth mode. The heat of formation for the carbon‐oxygen compounds is 90 kcal/mol O, and the formation energy for the reaction: 60C (graphite)→C60 molecule is estimated to be ∼600 kcal/mol.

Thermal sublimation of pure C60 and C70 has been used for depositing well‐characterized fullerene films on a variety of substrates. Film purity is determined by infrared absorption spectra and the extent of crystallinity of the face‐centered cubic structure by x rays. Thickness‐dependent optical and electrical measurements reveal uniform films over the thickness range 200–1000 A. We obtain optical absorption coefficients having values between those of Si and Ge and a relative permittivity having a value close to that of amorphous SiO2.

SUPERCONDUCTING K3C60 (ref. 1) has been shown2 to have an intercalated face-centred cubic (f.c.c.) structure, and other A3C60 compounds (where A is K, Rb or mixtures of K, Rb and/or Cs) form an isostructural series with superconducting transition temperatures up to 31.3 K (ref. 3). Recently we reported413C NMR studies of KxC60 for x

Photoemission spectra of vacuum deposited layers of C(60), before and after exposure to K vapor, show that the K donates its conduction electron into the band derived from the lowest unoccupied molecular orbital. A compound with composition of K(3)C(60), corresponding to the maximum conductivity, has been prepared. In it the potassium atoms presumably occupy both the octahedral and the two tetrahedral interstitial sites of the face-centered-cubic (fcc) C(60) structure.

Meissner-effect and microwave-absorption measurements on bulk samples show that ${\mathrm{Rb}}_{\mathit{x}}$${\mathrm{C}}_{60}$ is superconducting with a maximum transition temperature of 28 K. This is a 10-K (60%) increase over the K-doped material. Only ${\mathrm{Ba}}_{0.6}$${\mathrm{K}}_{0.4}$${\mathrm{BiO}}_{3}$ and the cuprate superconductors have higher transition temperatures.

BULK C60 (fullerite) is a solid composed of extremely hard pseudospherical molecules bonded by weak van der Waals interactions. We expect that pressurization will probe this diversity as the intermolecular distance is reduced. Here we present experimental measurements of the room-temperature pressure–volume equation of state of C60 fullerite to pressures of 20 GPa. The face-centred cubic phase remains stable under hydrostatic compression to this pressure, with an atmospheric-pressure isothermal bulk modulus of K0 = 18.1 ± 1.8 GPa and dK0/dP = 5.7 ± 0.6, characteristic of isotropic van der Waals intermolecular bonding. X-ray diffraction intensity changes are consistent with the compressibility of the C60 molecule being significantly lower than that of the bulk fullerite solid. Under non-hydrostatic compression, a transition to a crystallographic structure of lower symmetry is observed at 16±1 GPa.

THE recent syntheses1,2 of macroscopic quantities of C60 have suggested possible applications in host–guest and organic chemistry, tribology, electrochemistry and semiconductor tech-nology. Here we report the preparation of alkali-metal-doped films of C60 and C70 which have electrical conductivities at room temperature that are comparable to those attained by n-type doped polyacetylene. The highest conductivities observed in the doped films are: 4Scm−1 (Cs/C60), 100 (Rb/C60), 500 (K/C60), 20 (Na/C60), 10 (Li/C60), 2 (K/C70). The doping process is reversed on exposure of the films to the atmosphere. At high doping levels, the films become more resistive. We attribute the conductivity induced in these films to the formation of energy bands from the π orbitals of C60 or C70, which become partially filled with carriers on doping. The smaller alkali metal ions should be able to fit into the interstices in the lattice without disrupting the network of contacts between the carbon spheroids. In the case of C60, this would allow the development of an isotropic band structure, and we therefore propose that these materials may constitute the first three-dimensional 'organic' conductors.

The 7π radical CF3[graphic omitted]CF3+˙1, which is the first isolated example of a R[graphic omitted]R+˙ cation, is prepared by the reaction of S8(AsF6)2, S4(AsF6)2, AsF5 and CF3CCCF3 in SO2; the X-ray crystal structure consists of planes containing both monomeric radical cations and anions, the solid exhibiting Curie–Weiss paramagnetism between 25 and 200 K (µ= 1.68 µB).

The authors report solid-state {sup 13}C NMR measurements on powder samples of C{sub 60} and of a mixture of C{sub 60} and C{sub 70}. The NMR results show that, at 296 K, C{sub 60} molecules rotate rapidly and isotropically in the solid state, while C{sub 70} molecules rotate somewhat more anisotropically. These results are consistent with the proposed spherical geometry of C{sub 60} and prolate spheroidal geometry of C{sub 70}. The rotational correlation time of C{sub 60} molecules in the solid state becomes greater than 50 {mu}s at about 100 K.

Carbon nanotubes are strong, flexible, conduct electrical current, and can be functionalized with different molecules, properties that may be useful in basic and applied neuroscience research. We report the first application of carbon nanotube technology to neuroscience research. Methods were developed for growing embryonic rat-brain neurons on multiwalled carbon nanotubes. On unmodified nanotubes, neurons extend only one or two neurites, which exhibit very few branches. In contrast, neurons grown on nanotubes coated with the bioactive molecule 4-hydroxynonenal elaborate multiple neurites, which exhibit extensive branching. These findings establish the feasability of using nanotubes as substrates for nerve cell growth and as probes of neuronal function at the nanometer scale.

Mesures en haute resolution de la chaleur massique pour des champs magnetiques allant jusqu'a ST. Observation d'un saut ΔC a la transition supraconductrice. L'application du champ elargit la transition mais la decroit legerement. Les valeurs du champ critique sont superieures a celles obtenues par mesure de magnetoconductivite

Naked metallic and semiconducting single-walled carbon nanotubes (SWNTs) were dissolved in organic solutions by derivatization with thionychloride and octadecylamine. Both ionic (charge transfer) and covalent solution-phase chemistry with concomitant modulation of the SWNT band structure were demonstrated. Solution-phase near-infrared spectroscopy was used to study the effects of chemical modifications on the band gaps of the SWNTs. Reaction of soluble SWNTs with dichlorocarbene led to functionalization of the nanotube walls.

A silicon micromechanical magnetometer was constructed and successfully used in 60-tesla pulsed magnetic fields of less than 100-millisecond duration. The device is small, inexpensive to fabricate, and easy to use. It features a fast mechanical response (up to 50,000 hertz) and extremely high sensitivity yet is relatively robust against electrical and mechanical noise. Quantum oscillations in the magnetization of a 1-microgram sample of an organic superconductor, κ-[bis(ethylenedithio)tetrathiafulvalene] 2 Cu(NCS) 2 , have been observed with this device.

Covalent derivatization of the acidic functional groups in oxidized graphite with octadecylamine renders graphite soluble in common organic solvents. Atomic force microscopic characterization of the soluble species supports the idea that the solutions consist of single and few layer graphene sheets, and we report the first solution properties of graphite.

The electronic structure of the two organic, layered metals κ-ET2Cu(SCN)2 and K-ET 2Cu[N(CN)2]Br has been studied using a combination of soft X-ray emission (SXE) and soft X-ray absorption (SXA) spectroscopy. These techniques are powerful probes of the site and angular-momentum resolved partial density of states (PDOS) for both occupied and unoccupied states. Therefore these spectroscopies are particularly suited for an analysis of the density of states of multi-atomic, complex materials as the ET-based organic conductors, allowing site-specific electronic structure to be measured. Furthermore, for certain materials, the electronic structure of specific layers can be measured. We present a preliminary picture of the electronic structure of κ-ET 2Cu(SCN)2 and κ-ET 2Cu[N(CN)2]Br as measured by SXE and SXA performed at the C-Is and N- Is core levels.

not Available.

The zebrafish provides an important model for vertebrate inner ear development. The otic placode becomes visible at approximately 16 hours (at 28.5 degrees C) and forms a vesicle with a lumen by cavitation at approximately 18 hours. Two otoliths appear in the lumen by 19.5 hours, and at about 24 hours the first sensory hair cells are seen, grouped in two small patches, one beneath each otolith, corresponding to future maculae. Staining with fluorescent phalloidin reveals 10-20 hair cells in each macula by 42 hours; between 3 days and 7 days the numbers grow to approximately 80 per macula. Neurons of the statoacoustic ganglion are first visible by staining with HNK-1 antibody at about 24 hours. Serial sections and time-lapse films show that the neuronal precursors originate by delamination from the ventral face of the otocyst; the peak period of delamination is from 22 hours to 30 hours. The system of semicircular canals forms between 42 hours and 72 hours by outgrowth of protrusions from the walls of the otocyst to form pillars of tissue spanning the lumen. Three further clusters of hair cells also become visible in this period, forming the three cristae. Thus, by the end of the first week, all key components of the ear are present. Subsequent growth produces thousands more hair cells; additional neurons probably derive from proliferation of neuronal precursors within the ganglion. Although the timetable is species-specific, the principles of inner ear development in the zebrafish seem to be the same as in other vertebrates.