We demonstrate the continued growth of single-walled carbon nanotubes (SWNTs) from ordered arrays of open-ended SWNTs in a way analogous to epitaxy. Nanometer-sized metal catalysts were docked to the SWNT open ends and subsequently activated to restart growth. SWNTs thus grown inherit the diameters and chirality from the seeded SWNTs, as indicated by the closely matched frequencies of Raman radial breathing modes before and after the growth.
Atomically-thin materials such as single-walled carbon nanotubes and graphene are prone to chemical attack because all of the constituent atoms are exposed. Here we describe progress from our lab in the synthetic creation of a tube-in-a-tube (Tube^2) semiconductor and their first applications in the electrical detection of small molecules and implications on biological sensing. A Tube^2 is equivalent to a pristine single-walled carbon nanotube (SWCNT) nested within a chemically tailored, impermeable, and atomically-thick functional shell. Compared with SWCNTs and graphene, electrical sensors created using Tube^2 can be readily tailored with robust covalent chemistries to enable chemical selectivity while maintaining exceptional SWCNT-like sensitivity.
Previous work identified TK6 and WTK1 as human lymphoblast cell lines from one donor that have different capacities to catalyze recombination and that vary significantly in their response to ionizing radiation. WTK1 cells are more resistant to the toxic effects of X-rays yet more sensitive to induced mutation. We demonstrate here that although both cell lines contain equal levels of p53 mRNA, baseline protein levels are 4 times higher in WTK1. Irradiation leads to higher levels of p53 protein in both lines but to a greater extent in TK6. TK6 contains a wild-type p53 sequence, while WTK1 has a homozygous mutation in codon 237 of exon 7. We also observed a significant difference in the kinetics but not the overall degree of apoptosis induced by X-rays in these cells; apoptotic death is delayed for 3 days in WTK1. We hypothesize that this p53 mutation is responsible for the difference in apoptosis as well as for the differences in mutability and mutational spectra reported previously.
By using metal nitrates, rare earth oxides as raw materials and citric acid as complexing agent, Y3Al5O12: Eu3+ red phosphors were prepared by a citrate-gel method. The purified crystalline phase of Y3Al5O12 was obtained at 1000 degrees C, which is 450 degrees C lower than that of ordinary solid state reaction. The result of XRD indicates that the samples are indexed to cubic symmetry, and the cell parameter a of Y3-xEuxAl5O12 (0.025 F-7(1) transition. Compared with the sample synthesized by solid state reaction, the phosphor obtained by citric-gel method shows lower emission intensity, but it has relatively higher red/orange ratio and better color purity.
We demonstrate the separation of chirality-enriched single-walled carbon nanotubes (SWCNTs) by degree of surface functionalization using high-performance CE. Controlled amounts of negatively charged and positively charged functional groups were attached to the sidewall of chirality-enriched SWCNTs through covalent functionalization using 4-carboxybenzenediazonium tetrafluoroborate or 4-diazo-N,N-diethylaniline tetrafluoroborate, respectively. Surfactant- and pH-dependent studies confirmed that under conditions that minimized ionic screening effects, separation of these functionalized SWCNTs was strongly dependent on the surface charge density introduced through covalent surface chemistry. For both heterogeneous mixtures and single-chirality-enriched samples, covalently functionalized SWCNTs showed substantially increased peak width in electropherogram spectra compared to nonfunctionalized SWCNTs, which can be attributed to a distribution of surface charges along the functionalized nanotubes. Successful separation of functionalized single-chirality SWCNTs by functional density was confirmed with UV-Vis-NIR absorption and Raman scattering spectroscopies of fraction collected samples. These results suggest a high degree of structural heterogeneity in covalently functionalized SWCNTs, even for chirality-enriched samples, and show the feasibility of applying CE for high-performance separation of nanomaterials based on differences in surface functional density.
Atomic defect color centers in solid-state systems hold immense potential to advance various quantum technologies. However, the fabrication of high-quality, densely packed defects presents a significant challenge. Herein we introduce a DNA-programmable photochemical approach for creating organic color-center quantum defects on semiconducting single-walled carbon nanotubes (SWCNTs). Key to this precision defect chemistry is the strategic substitution of thymine with halogenated uracil in DNA strands that are orderly wrapped around the nanotube. Photochemical activation of the reactive uracil initiates the formation of sp3 defects along the nanotube as deep exciton traps, with a pronounced photoluminescence shift from the nanotube band gap emission (by 191 meV for (6,5)-SWCNTs). Furthermore, by altering the DNA spacers, we achieve systematic control over the defect placements along the nanotube. This method, bridging advanced molecular chemistry with quantum materials science, marks a crucial step in crafting quantum defects for critical applications in quantum information science, imaging, and sensing.
New properties arise as the size of a crystal reaches the Bohr radius of excitons. This phenomenon, known as quantum confinement, has enabled powerful synthetic strategies to control the optical and electronic properties of a material through size engineering. In this talk, we will discuss a fundamentally new approach that allows systematic tailoring of nanostructure excitons through covalently bonded surface functional groups that are themselves non-emitting. Specifically, we show that by varying the surface functional groups, a semiconducting carbon nanotube can be chemically converted to create a large series of distinct near-infrared quantum emitters that are molecularly specific, systematically tunable, and significantly brighter than the parent semiconductor. In contrast with quantum confinement, where size matters, this new property-tailoring capability arises from the creation of fluorescent quantum defects that can be chemically controlled at the molecular level. This new family of quantum emitters opens up exciting new opportunities for potential applications ranging from bioimaging and sensing to quantum information processing.
A monitoring network for biodiversity change is essential for wildlife conservation. In recent years, many soundscape monitoring projects have been carried out to investigate the diversity of vocalizing animals. However, the acoustic-based biodiversity assessment remains challenging due to the lack of sufficient recognition database and the inability to disentangle mixed sound sources. Since 2014, an Asian Soundscape monitoring project has been initiated in Taiwan. So far, there are 15 recording sites in Taiwan and three sites in Southeast Asia, with more than 20,000 hours of recordings archived in the Asian Soundscape. In this study, we employed the visualization of long-duration recordings, blind source separation, and clustering techniques, to investigate the spatio-temporal variations of forest biodiversity in the Triangle Mountain, Lienhuachih, and T aipingshan. On the basis of blind source separation, biological sounds, with prominent diurnal occurrence pattern, can be separated from the environmental sounds without any recognition database. Thus, clusters of biological sounds can be effectively identified and employed to measure the daily change in bioacoustic diversity. Our results show that the bioacoustic diversity was higher in the evergreen broad-leaved forest. However, the seasonal variation in bioacoustic diversity was most evident in the high elevation coniferous forest. This study demonstrates that a suitable integration of machine learning and ecoacoustics can facilitate the evaluation of biodiversity changes. In addition to biological activities, we can also measure the environmental variability from soundscape information. In the future, the Asian Soundscape will not only serve as an open database for soundscape recordings, but also will provide tools for analyzing the interactions between biodiversity, environment, and human activities.
Botanicals are complex mixtures of natural organic compounds. This complexity causes a great challenge in the determination of herbal ingredients. Natural components have to be separated from each other in order to be identified and determined as individual entities forming a composite phytochemical "fingerprint" characteristic of a single plant species. The fingerprint of botanically authenticated raw material serves as a primary reference against which unknown material can be characterized. High performance thin layer chromatography (HPTLC) is an important quality control tool for the evaluation of botanical materials. This technique is both efficient and cost effective for the analysis of botanicals. Several examples are illustrated for the application of HPTLC in fingerprint analysis and quality control of botanicals like chamomile, buchu, bees propolis, licorice and passiflora for flavonoids; hoodia, dioscorea and cyanotis vaga for steroidal compounds; and adulteration of curcumin by synthetic dyes.
A rapid method is developed for the analysis of cannabinoids in extracts of cannabis samples using supercritical fluid chromatography (SFC) coupled to UV and electrospray ionization-mass spectroscopic (ESI-MS) detection. Eleven cannabinoids, viz. CBL, CBD, Δ8-THC, THCV, Δ9-THC, CBC, CBN, CBG, THCA-A, CBDA and CBGA, were well separated in an 8 min run. The developed SFC method was validated according to ICH guidelines and used to quantitate these cannabinoids in 29 different Cannabis sativa plant samples. The quantitation results were verified by comparison with a standard UPLC method. The described method offers an alternative means for identification and quantification of cannabinoids in Cannabis plants and products. In addition, conditions for decarboxylation of the acid forms of the major cannabinoids were examined at 80 °C, 95 °C, 110 °C, 130 °C and 145 °C with different time intervals in order to select the most appropriate condition for complete decarboxylation.
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