Chirality-Selective Functionalization of Semiconducting Carbon Nanotubes with a Reactivity-Switchable Molecule

Chirality-selective functionalization of semiconducting single-walled carbon nanotubes (SWCNTs) has been a difficult synthetic goal for more than a decade. Here we describe an on-demand covalent chemistry to address this intriguing challenge. Our approach involves the synthesis and isolation of a chemically inert diazoether isomer that can be switched to its reactive form <i>in situ</i> by modulation of the thermodynamic barrier to isomerization with pH and visible light that resonates with the optical frequency of the nanotube. We found that it is possible to completely inhibit the reaction in the absence of light, as determined by the limit of sensitive defect photoluminescence (less than 0.01% of the carbon atoms are bonded to a functional group). This optically driven diazoether chemistry makes it possible to selectively functionalize a specific SWCNT chirality within a mixture. Even for two chiralities that are nearly identical in diameter and electronic structure, (6,5)- and (7,3)-SWCNTs, we are able to activate the diazoether compound to functionalize the less reactive (7,3)-SWCNTs, driving the chemical reaction to near exclusion of the (6,5)-SWCNTs. This work opens opportunities to chemically tailor SWCNTs at the single chirality level for nanotube sorting, on-chip passivation, and nanoscale lithography

Box plots showing the distributions of CRA_max, CRV_min, and CRV_max expressed as percentages of the ocular circulatory cycle relative to CRA_min.

<p>The time point of CRA_min was set as the reference (i.e., time zero). CRA_max, maximum diameter of the central retinal artery; CRA_min, minimum diameter of the central retinal artery; CRV_max, maximum diameter of the central retinal vein; CRV_min, minimum diameter of the central retinal vein.</p

Schematic diagram illustrating the central retinal artery and vein pulse curves during one ocular circulatory cycle.

<p>The amplitude is presented in order to facilitate the understanding of the pulsation cycle, although the amplitude is not based on the actual measurement of the diameters of the artery and vein.</p

Chemical Control and Spectral Fingerprints of Electronic Coupling in Carbon Nanostructures

The optical and electronic properties of atomically thin materials such as single-walled carbon nanotubes and graphene are sensitively influenced by substrates, the degree of aggregation, and the chemical environment. However, it has been experimentally challenging to determine the origin and quantify these effects. Here we use time-dependent density-functional-theory calculations to simulate these properties for well-defined molecular systems. We investigate a series of core–shell structures containing C₆₀ enclosed in progressively larger carbon shells and their perhydrogenated or perfluorinated derivatives. Our calculations reveal strong electronic coupling effects that depend sensitively on the interparticle distance and on the surface chemistry. In many of these systems we predict considerable orbital mixing and charge transfer between the C₆₀ core and the enclosing shell. We predict that chemical functionalization of the shell can modulate the electronic coupling to the point where the core and shell are completely decoupled into two electronically independent chemical systems. Additionally, we predict that the C₆₀ core will oscillate within the confining shell, at a frequency directly related to the strength of the electronic coupling. This low-frequency motion should be experimentally detectable in the IR region

Measurement of the clock-hour location and extent of the retinoschisis.

<p>The superior clock hour was 12 o'clock; the others were assigned in a clockwise manner in the right eye and counterclockwise in the left.</p

Interobserver intraclass correlation coefficients (ICCs) for measurements of the timing of the minimum and maximum diameter of the vessels.

<p>CRA_max, maximum diameter of the central retinal artery; CRV_max, maximum diameter of the central retinal vein; CRA_min, minimum diameter of the central retinal artery.</p

Comparison of clinical factors between glaucomatous eyes with retinoschisis and those without.

<p>IOP - intraocular pressure, MD - mean deviation, F/U – follow-up.</p><p>Values are shown in mean ± SD.</p><p>Statistically significant values are shown in bold.</p><p>* Comparisons were performed using independent samples t-test for continuous variables and chi-squire test for categorical variables.</p>†<p>IOP at the time of retinoschisis detection for eyes with retinoschisis development.</p>‡<p>Average of the IOPs obtained during the observation period.</p>§<p>Standard deviation of the IOPs obtained during the observation period.</p

Relationship of Spontaneous Retinal Vein Pulsation with Ocular Circulatory Cycle

<div><p>Purpose</p><p>To determine the timing of spontaneous venous pulsation (SVP) relative to the ocular circulatory cycle by using the movie tool of confocal scanning laser ophthalmoloscope.</p><p>Methods</p><p>A video recording of the fundus was obtained using a confocal scanning laser ophthalmoscope (Spectralis HRA, Heidelberg Engineering, Heidelberg, Germany) at 8 frames/s in 47 eyes (15 glaucoma patients and 32 glaucoma suspects) with visible pulsation of both the central retinal artery (CRA) and vein (CRV). The timing of the maximum and minimum diameters of the CRA (CRA_max and CRA_min, respectively) and CRV (CRV_max and CRV_min, respectively) was identified during four pulse cycles. The interval between CRV_min and CRA_min, and between CRV_max and CRA_max was expressed as the number of frames and as a percentage of the ocular circulatory cycle.</p><p>Results</p><p>The ocular circulatory cycle (from one CRA_max to the next) lasted 7.7±1.0 frames (958.8±127.2 ms, mean±SD), with a mean pulse rate of 62.6 beats/min. The diameter of the CRA was increased for 2.4±0.5 frames (301.9±58.8 ms) and decreased for 5.3±0.9 frames (656.9±113.5 ms). CRV_max occurred 1.0±0.2 frames after CRA_max (equivalent to 13.0% of the ocular circulatory cycle), while CRV_min occurred 1.1±0.4 frames after CRA_min (equivalent to 14.6% of the ocular circulatory cycle).</p><p>Conclusions</p><p>During SVP, the diameter of the CRV began to decrease at early diastole, and the reduction persisted until early systole. This finding supports that CRV collapse occurs during ocular diastole.</p></div

Demographics of the subjects.

<p>IOP, intraocular pressure</p

Retinal layers (A) and circular extent (B) involved in retinoschisis.

<p>(A) Involvement of only the RNFL was most frequent (13 retinoschisis). The RNFL was involved together with other layers in 12 retinoschisis. RNFL = retinal nerve fiber layer, GCL = ganglion cell layer, IPL = inner plexiform layer, INL = inner nuclear layer, OPL = outer plexiform layer, ONL = outer nuclear layer, ELM = external limiting membrane, IS-OS = junction between the photoreceptor inner and outer segments.</p