bluuebunny/crossref_metadata_2025_split huggingface dataset:
PET Imaging of Tumor Uptake of a Biocompatible C60 Fullerene Drug Delivery Vector
Authors: Zaibaq Nicholas G. , Collins Michael J. , Pagel Mark D. , Wilson Lon J. 
Published: February 2020

Traditional chemotherapy is one of the standards in cancer treatment, but the delivery of drugs and biologics is hindered by various barriers throughout the cancer microenvironment. Recently, nanoparticles have been of great interest as drug vectors because they can be tailored for specific functions to increase the amount of administered drug in the tumor microenvironment. In particular, biocompatible C60 fullerene has potential as a drug delivery scaffold since it has been shown to penetrate very restrictive physiological membranes (e.g. blood-brain-barrier and nuclear membrane)1. Our long-term goal is to determine the biodistribution of a biocompatible C60 material, as well as other pharmacokinetic data in both small and large animal models in order to evaluate its potential as a clinical drug vector for anti-cancer drugs. In this work, we have synthesized a C60 derivative with a metal chelating agent covalently bound to the C60 cage. The chelating agent of this material can be easily radiolabeled with 64Cu2+ (β+ emitter; t1/2 = 12 h) and tracked in vivo using positron emission tomography (PET) imaging. Because of its extreme sensitivity and routine clinical use, PET is an ideal imaging technique for studying pharmacokinetic properties and tumor accumulation of a C60 fullerene delivery vector, for both preclinical and possible future clinical studies. The material has been synthesized following an optimized six-step synthesis and the stability of the 64Cu2+ ion in the chelate has been evaluated by challenge with biological media. Animal biodistribution data will be determined using PET imaging in tumor- and non-tumor-bearing murine models.
Acknowledgements:
We gratefully acknowledge The Welch Foundation (C-0627) for support of this work, as well as the Department of Chemistry and the Smalley-Curl Institute at Rice University and the Department of Cancer Systems Imaging at UT MD Anderson Cancer Center. Additionally, the work is supported by the National Science Foundation Graduate Research Fellowship Program under Grant No. 1450681 (N.G.Z.).
References:
(1) Raoof, M.; Mackeyev, Y.; Cheney, M. A.; Wilson, L. J.; Curley, S. A. Biomaterials
2012, 33 (10), 2952–2960.
(Invited) Molecular Requirement for Compounds Toward Facile Isolation of Adsorbent-Free Semiconducting Single-Walled Carbon Nanotubes Based on Supramolecular Chemistry
Authors: Toshimitsu Fumiyuki , Staykov Aleksandar , Nakashima Naotoshi 
Published: February 2020

The separation/purification of semiconducting single-walled carbon nanotubes (sem-SWNTs) with high quality is one of the most important issues in the science and technology of carbon nanotubes[1-5]. We have already reported that supramolecular coordination polymer and hydrogen bonding systems as well as use of flavin molecules are powerful methods for highly efficient adsorbent-free sem-SWNT separation.
Here, we describe a molecular requirement of flavins (Bitamin B2 analogs)/isoallozadines for facile isolation of adsorbent-free sem-SWNTs based on supramolecular chemistry. Together with experimental results and molecular mechanics and molecular dynamics simulations, we will report a computer simulation study on this separation.

References

[1] F. Toshimitsu, N. Nakashima, Nature Communications, 2014, 5, art no. 5041.
[2] F. Toshimitsu, N. Nakashima, Sci. Rep., 2015, 5, art. no.18066.
[3] F. Toshimitsu, N. Nakashima, Chem. Eur. J., 2015, 21, 3359-3366.
[4] K. Akazaki, F. Toshimitsu, H. Ozawa, T. Fujigaya, N. Nakashima, J. Am. Chem. Soc. 2012, 134, 12700-12707.
[5] H. Ozawa, X. Yi, T. Fujigaya, Y. Niidome, T. Asano and N. Nakashima, J. Am. Chem. Soc., 2011, 133, 14771–14777.
Influence of Carbon Nanotube Chirality on Sodium Cholate Adsorption in Aqueous Suspensions
Authors: Schoeppler Friedrich , Vollert Ivonne , Bergler Felix , Hertel Tobias 
Published: February 2020

Established chirality separation techniques for single-wall carbon nanotubes (SWNTs) in aqueous suspensions make use of chirality specific adsorption behavior of surfactants on these nano-carbon surfaces. Here, we investigate the adsorption of sodium cholate on SWNTs of different chirality with diameters ranging from 0.7 to 1 nm. Titration studies are performed at different temperatures by measuring photoluminescence emission energies of the diluted SWNT suspensions. The high sensitivity of the exciton to its environment allows to detect small changes in arrangement and concentration of surfactants on the SWNT surface, as recently shown for the (6,5) chirality by Bergler et al. [1]. Here we report on substrate-induced cooperative adsorption regimes for sodium cholate on five different SWNT chiralities. The critical micelle concentrations of the cholate-SWNT micelles exhibit a linear increase with SWNT diameter, while the thermodynamic stability of the cholate-SWNT micelles decreases. These diameter and temperature dependences may play a key role in the separation of SWNT chiralities by density gradient ultracentrifugation and aqueous two phase extraction and thus may help not only to understand the microscopic sorting mechanisms but also to improve empirical preparation protocols.
[1] Bergler et al., Langmuir 2016, 32, 9598-9603, DOI: 10.1021/acs.langmuir.6b02759
Confined Shear-Based Alignment of Carbon Nanotubes for Thin Film Transistors
Authors: Jinkins Katherine R , Chan Jason , Berson Arganthaël , Arnold Michael S 
Published: February 2020

Individual semiconducting single-walled carbon nanotubes (s-SWCNTs) exhibit the high charge-carrier mobility, current carrying capacity, and sensitivity needed for applications based on thin-film transistors (TFTs) such as flexible electronics, displays, and sensors. However, assembling s-SWCNTs into aligned arrays to exploit the exceptional electronic properties of this material has been a major roadblock toward the integration of s-SWCNTs into electronic devices. Here, we are able to use confined shear-based alignment to fabricate aligned arrays of s-SWCNTs across arbitrarily large substrates.
In this study, we demonstrate that large amounts of shear can be used to align s-SWCNTs from solution by forcing s-SWCNT ink at high volumetric flow rates through 20 - 100 µm tall channels on SiO2 substrates. We use Raman spectroscopy to quantify the ratio of the Raman G band (~1590 cm-1) to the Si peak (~520 cm-1) of our films. This ratio provides a measure of the amount of s-SWCNTs deposited. We study the deposition from three concentrations of ink (~70, 35, and 7 µg mL-1) while varying the volume of ink used at a set shear rate of 3.2*105 s-1. The G/Si ratio behavior is similar for each concentration. Initially, there is a steep increase in the G/Si ratio up to 100 µL of ink, after which, the G/Si ratio increases linearly with increasing volume of ink.
Polarized Raman spectroscopy is used to quantify the disorder in the film. We show that for the s-SWCNT ink concentrations used in this study, the concentration does not affect the degree of alignment in the aligned s-SWCNT films and that the shear rate is the main factor affecting the alignment. Assuming the s-SWCNTs are oriented within a Gaussian angular distribution, from polarized Raman spectroscopy, the angular width of distribution was measured to be σ = 30° for a shear rate of 3.2*105 s-1 regardless of ink concentration and volume. This degree of alignment makes this technique non-ideal for fabricating devices with small channel lengths for high-performance applications such as logic or radio-frequency devices. However, for long-channel devices, there must be some amount of disorder in the s-SWCNT films to allow for charge percolation. This means this shear alignment technique is ideal for fabricating films for long-channel devices such as TFTs. Here, we fabricate transistors from films of shear-aligned s-SWCNTs and study the effect of degree of alignment on the transistor performance.
Because of the simplicity of this technique, we are able to scale the deposition of aligned s-SWCNTs to arbitrarily large areas as long as the high shear rate is maintained. This makes the technique ideal for large-area scaling in industry applications. As a demonstration, we show the large-area, uniform alignment of s-SWCNTs via confined shear-based alignment across a 4” wafer.
Constraining Photoluminescent Defect States in Chirality-Sorted Covalently Doped Single-Walled Carbon Nanotubes
Authors: Saha Avishek , He Xiaowei , Ao Geyou , Zheng Ming , Tretiak Sergei , Htoon Han , Doorn Stephen K. 
Published: February 2020

Recent developments in carbon nanotube surface chemistry are leading to the emergence of unexpected new optical behaviors. Specifically, introduction of covalently-bound defect sites into the nanotube structure generates a new photoluminescent (PL) emitting state that is significantly red-shifted from the normal excitonic emitting state that results from optical excitation.1 These new states have been shown to significantly increase emission quantum yields and introduce new functionality including room-temperature single photon emission, near-IR photon upconversion, and multifunctionality generated by localization of excitons at these defect sites.2,3,4 The new optical behaviors present a broad range of unexplored photophysics yet to be fully understood. Of particular interest is the use of emerging functionalization chemistries to introduce sp3 defects that have highly tunable properties.
An important challenge arising from the functionalization chemistry is that seemingly similar and structurally simple functionalization can give rise to a broad diversity in observed PL spectral features.1,3,5 Low-temperature spectroscopy along with quantum chemistry calculations demonstrated that these multiple emissive defect states are likely due to the occurrence of multiple possible, chemically distinct, binding configurations on the nanotube surface.6 Following these results, we hypothesize that the diverse emissive states are also influenced by the interplay of nanotube chirality, structure of the dopant, and surface structures on the tube. In this regard, we aim to control the number of emissive states through control of these factors. We have studied a number of different chiral structures for aryldiazonium functionalization, ranging from so-called near-armchair to near-zigzag structures of varying diameter. We have demonstrated that zigzag carbon nanotubes tend to constrain photoluminescent defect states more efficiently than other chiralities. Density functional theory (DFT) calculations suggest that symmetry of the zigzag tube is the primary factor in creating a less diversified emission spectrum. Our findings on controlling the defect peak diversity could enhance the predictable functionality of these doped carbon nanotubes.

References:

Piao, et al. Chem., 5, 840 (2012).

Ma, et al. Nanotech., 10, 671 (2015).

Shiraki, et al., Rep., 6, 28393 (2016).

He, et al., Photonics,
11, 577 (2017).

Maeda, et al., Nanoscale,
8, 16916 (2016).

He, et. al., ACS Nano, DOI:1021/acsnano.7b03022, (2017).
(Invited) Nanotube Excitonic Emitter at the Subwavelength Scale
Authors: Rotkin Slava V. , Sofka Benjamin Joseph 
Published: February 2020

It is slightly embarrassing to accept the fact that after a decade of very intensive research on optics of single-wall carbon nanotubes (SWCNT) still there is no complete understanding of fundamental physics behind it. For example, our knowledge of excitonic effects in SWCNTs is limited, nailed at two extremes – sophisticated and often highly idealized numerical simulations of very small systems or rudimentary empirical models of more realistic systems, not even always yielding analytical results.
In this talk, one question arising in the physics of nanotube excitons is addressed: what is the shape of the excitation for a finite size SWCNT object? Since a whole SWCNT is sub-diffraction scale object, one may expect something similar to Hertz dipole, modified for a semiconductor material (as opposed to metal). To the best of our knowledge, such a solution was not known, thus a theory shedding light on the distribution of current of a nanotube excitonic emitter has been developed.
While in our earlier work we considered localization of a free excitonic wave (aka binding) on a single charged impurity[1], in this talk we assume localization effects due to SWCNT end reflections. Unlike many of earlier excitonic works we take this into account via a self-consistent response of the whole nanotube antenna. Unexpectedly, even for a charge neutral SWCNT system, plasmonic resonances were found to develop on top of the excitonic spectral response[2]. We demonstrate that these plasmonic features are robust and should be detectable in near-field experiments.
[1] BO. Tayo, SV. Rotkin, “Charge impurity as a localization center for singlet excitons in single-wall nanotubes”, Phys. Rev. B 86, 125431 (2012).
[2] B. Sofka, SV. Rotkin, “Nanotube exciton-antenna polaritons”, in preparation.
This research is supported by the NSF ECCS-1509786.
Fig. 1. Spectral current density distribution for an excitonic SWCNT emitter: 1d-current density is plotted vs. axial coordinate of a 50 nm long nanotube and vs. the frequency of excitation (in energy units).

Figure 1
The Dependence of Electrochemical Property on Carbon Cage in Tb2C90 Isomers
Authors: Nie Mengsi , Dong Wei , Lian Yongfu 
Published: February 2020

Soot containing Tb2C90 was synthesized in a modified Krätschmer-Huffman generator by vaporizing composite graphite rods (8 × 150 mm) filled a mixture of Tb4O7 (99.99%) and graphite powder (molar ratio of Tb: C = 1 : 15) under 400 mbar He atmosphere. The as-produced soot was collected and dispersed in 1, 2, 4-trichlorobenzene (TCB). After refluxing for 12 h, the resulting brown-yellow solution was distilled to remove TCB and immediately redissolved in toluene, and then subjected to HPLC for the isolation of Tb2C90 isomers. For endohedral fullerenes with two metal atoms, M2@C2n, there are two possible structures, i.e. dimetallofullerene, M2@C2n, and metal carbide fullerene, M2(μ-C2)@C2n-2. The UV-Vis-NIR absorption spectra of endohedral fullerenes are largely dependent on the fullerene cages and their electronic structures,1 since they are mostly due to the π−π* transitions of the fullerenes cages. Because the UV-Vis-NIR absorption spectra of Tb2C90（I）and Tb2C90（II）show much similar absorption features to those of Sm2@
C

1

(21)-C90
and Sc2C2@
C

s(hept)C88,2-3 respectively, Tb2C90（I）isomer is estimated to be of Tb2@
C

1

(21)-C90
structure, and Tb2C90（II）isomer of Tb2C2@
C

s

(hept)-C88structure. Electrochemical characterization confirms that the redox properties of endohedral metallofullerenes are tremendously dependent on the structures of carbon cage.
References
[1] Chen N, Beavers C M, Mulet-Gas M et al. J. Am. Chem. Soc., 2012, 134(18): 7851-7860
[2] Chen CH, Abella L, Cerón MR et al. J. Am. Chem. Soc. 2016, 138(39): 13030-13037
[3] Zhang Y, Ghiassi KB, Deng Q et al. Angew. Chem., Int. Ed. 2014, 54(2): 495-499
(Invited) Isolation and Structural Characterization of Lu2C2n
Authors: Shen Wangqiang , Lu Xing , Li Fang-Fang 
Published: February 2020

Endohedral metallofullerenes (EMFs) with a composition of M2C2n may exist as di-EMFs, M2@C2n, or as carbide cluster metallofullerenes (CCMFs), M2C2@C2n-2. EMFs containing such metal atoms with a small ionic radius as scandium were found to prefer the CCMF form some of which had been incorrectly assigned as di-EMFs.[1] Lu-containing EMFs remain largely unexplored in spite that lutecium also takes small ionic radius so that . In this work, we report the single-crystal X-ray crystallographic results of a series of Lu-containing EMFs to show that all of them are di-EMFs, namely Lu2@C2n (2n=76-86). Theoretical results confirm the formation of direct Lu-Lu bonding between the two encapsulated metal atoms.[
2
]

References：
[1] X. Lu, T. Akasaka, S. Nagase, Acc. Chem. Res.
2013, 46, 1627-1635.
[2] W. Shen, L. Bao, Y. Wu, C. Pan, S. Zhao, H. Fang, Y. Xie, P. Jin, P. Peng, F.-F. Li, X. Lu, J. Am. Chem. Soc.
2017, 139, 9979−9984.
(Invited) Exciplex Formation and Decay in Porphyrin-Carbon Nanotube Ensembles
Authors: Imahori Hiroshi 
Published: February 2020

During the last few decades, considerable efforts have been made toward the construction of donor–acceptor (D–A) linked systems that efficiently yield photoinduced charge separation, a basic step in natural photosynthesis and solar energy conversion. Among the building units for such D–A systems, nanocarbons deserves a special attention because it reveals notable electronic conductivity, tenacious mechanical strength, and huge specific surface area. These singular properties place nanocarbon-based D–A systems in an attractive position as the next-generation material for energy-conversion devices. With this in mind, a variety of studies have been conducted to prepare covalently linked systems of electron-accepting nanocarbons with electron-donating units such as pyrenes, porphyrins and phthalocyanines. However, the D–A interface frequently undergoes a rapid relaxation of the exciplex with partially charge-separated (CS) character or the complete CS state to the ground state, failing to form a long-lived CS state that is essential for solar energy conversion. In-depth understanding of the relationship between the structure and photodynamics of the electron donor-nanocarbon electron acceptor linked systems is important for extracting the full potential of such D–A materials toward the future applications.
In this talk I will give an overviw of our recent achievements related to photodynamics of porphyrin- attached single-walled carbon nanotubes connected with oligophenylene bridges.
[1] T. Higashino, T. Yamada, M. Yamamoto, A. Furube, N. V. Tkachenko, T. Miura, Y. Kobori, R. Jono, K. Yamashita, and H. Imahori, Angew. Chem. Int. Ed., 55, 629-633 (2016).
[2] T. Umeyama, T. Hanaoka, J. Baek, T. Higashino, F. Abou-Chahine, N. V. Tkachenko, and H. Imahori, J. Phys. Chem. C, 120, 28337-28344 (2016).
[3] J. Baek, T. Umeyama, K. Stranius, H. Yamada, N. V. Tkachenko, and H. Imahori, J. Phys. Chem. C, 121, 13952-13961 (2016).
[4] J. Baek, T. Umeyama, S. Mizuno, N. V. Tkachenko, and H. Imahori, J. Phys. Chem. C, in press.
Bilayer Dielectrics for RRAM Devices
Authors: Misra Durgamadhab , Sultana Sabiha , Jain Barsha , Bhat Navakanta , Tapily Kandabara , Clark Robert D. , Consiglio Steven , Wajda Cory S. , Leusink Gert J. 
Published: February 2020

Non-volatile resistive random-access memory (RRAM) devices are currently being investigated as a low power, high density and high-speed alternative DRAM (1). A transition metal oxide dielectric layer is typically used as an insulating layer in a metal-insulator-metal (MIM) structure. To reduce the large variability of switching parameters and high operation current in these RRAM devices, bilayer dielectric structures are being explored.
In this work we have used several different bilayer structures using different dielectrics. In each device the bottom electrode (BE) was 10nm Ti/50nmTiN followed by 1nm Al2O3. The second dielectric layer or the switching layer was a 7-nm HfO2 (R3), HfZrO2 (R4 with Hf:Zr%=50%) or HfAlO2 (R1 with Hf:Al%= 3%) followed by the top electrode (TE) constituting of 8nm Ti/6nm ALD TiN+50nm PVD TiN. In some cases, the top electrode was varied to 2nm ALD TiN/8nm Ti/6nm ALD TiN+50nm PVD TiN (R5) by adding a 2nm ALD TiN layer prior to 8nm Ti. Some devices with HfZrO2 (R2) were subjected to a post deposition anneal (PDA) at 700oC for 60 s. In all cases, to enhance the switching characteristics on the top electrode 8 nm Ti was used as the cap layer material except in the case of R5 where 2nm of ALD TiN was deposited prior to 8 nm of Ti. The use of thin dielectric layer of 1nm Al2O3 was to suppress the sneak-path problem (3) in the low resistance state (RON).
Comparing the variation of switching layer, it was observed that the device with 1nm Al2O3/7nm HfAlO2 (R1) provided the superior average Roff/Ron values and both set and reset power compared to HfO2 (R3), and HfZrO2 (R4) devices. When the HfZrO2 (R4) devices were compared with the identical device with PDA (R2) Ron increased and Roff decreased for the PDA device, reducing the Roff/Ron value. Variation of cap layer to TiN instead of Ti also showed similar Roff/Ronbehavior.

D. Ielmini, Semicond. Sci. Technol. Vol. 31, 063002, 2016.

Xiaorong Chen and Jie Feng, Appl. Phys. A, vol. 120, 67 2015

U. Chand, K-C. Huang, C-Y. Huang, and T-Y. Tseng, IEEE Trans. on Electron Devices, vol. 62(11), 3665, 2015
Voltage Pulse Induced Resistance Change Response of Reram with HfO2 Dielectric layer
Authors: Azuma Atsushi , Yoshida Hayato , Nakajima Ryo , Shimizu Tomohiro , Ito Takeshi , Shingubara Shoso 
Published: February 2020

ReRAM is one of promising nonvolatile memories with excellent properties such as low power, high switching speed, and scalability against downsizing. Recently, ReRAM has been attracted attention as artificial neuron devices such as synapse which changes resistance according to input voltage or current signals.
Recently we observed multiple resistance states in the RESET process of Ti/HfOx/Pt ReRAM devices. Then we found that the resistance of the reset state changed according to input of voltage pulses. In this study, we focused resistance change response of the SET as well as RESET processes of the Ti/HfO2/Pt ReRAM device. The size of the cross-point device area was 1×1 μm2. The HfOx layer was deposited by reactive sputtering using Ar and O2 mixture gases.
Fig.1 shows the typical bipolar resistance switching characteristic. Compliance current was SET to 500 μA. We applied voltage pulse train of constant voltage with 1 μsec pulse width and 2 μsec interval. Fig.2 shows resistance changes of the device during 200 pulses at various voltages. There was an initial abrupt increase of resistance followed by gradual increase. Pulse numbers before initiating abrupt increase of resistance was smaller as the absolute voltage value was larger. Fig.2 shows voltage dependence of the r5000 (resistance after 5000 voltage pulses were applied), and r5000 was continuously changed with applied negative voltage.
On the other hand, resistance change behaviors in the set process is completely different as shown in Fg.4. Resistance was high around 106 W when the applied voltage was lower than 1.1 V, ad it changed to low around 103 W when the applied voltage was higher than 1.5 V . In the voltage pulse ranges between 1.2 and 1.4 V, the resistance state indicated only two values of high and low. There were binary resistance states existed. From these experimental results, it maybe suggested that voltage pulse response of the RESET process is suitable for application to artificial synapse.