4,218 publications from this institution
Rings of bundled single-walled carbon nanotubes with perfectly toroidal geometries (see figure), are fabricated in high yields by a floating chemical vapor deposition process involving the thermal decomposition of acetylene. The nanotube rings can be grown with varying densities on a wide variety of substrates at relatively low temperatures, which is a significant advantage for nanoelectronics applications.
Abstract Unconstrained measurement of physiological signals including electrocardiograph, respiration, and temperature by sensors through incorporation into commonly used objects has sparked a notable revolution in healthcare monitoring. However, unconstrained precision epidermal pulse wave monitoring is rarely reported. Although the current flexible skin‐mounted sensors can capture pulse waves, they lack the capability to perceive tiny pulse pressure in an unconstrained manner. Herein, utilizing thin‐film materials and multilevel microstructure design, an ultrathin and flexible sensor (UFS) with the features of high flexibility, shape‐adaptability, and ultra‐broad‐range high pressure sensitivity is proposed for unconstrained precision pulse wave sensing. Given these compelling features, the UFS is mounted to the surfaces of commonly used objects and successfully detects the fingertip pulse wave even under an ultra‐broad‐range finger‐touching force. Key cardiovascular parameters are also extracted from the acquired fingertip pulse wave accurately. Furthermore, a proof‐of‐concept healthcare system, by combining the UFS and flexible devices (for example, flexible phones or E‐newspapers) is demonstrated, offering a great advancement in developing an all‐in‐one system for IoT‐based bio‐health monitoring at all times and places.
Electron dynamics in gold nanoparticles with an average diameter between 9 and 48 nm have been studied by femtosecond transient absorption spectroscopy. Following the plasmon bleach recovery after low power excitation indicates that a non-Fermi electron distribution thermalizes by electron–electron relaxation on a time scale of 500 fs to a Fermi distribution. This effect is only observed at low excitation power and when the electron distribution is perturbed by mixing with the intraband transitions within the conduction band (i.e., when the excitation wavelength is 630 or 800 nm). However, exciting the interband transitions at 400 nm does not allow following the early electron thermalization process. Electron thermalization with the lattice of the nanoparticle by electron–phonon interactions occurs within 1.7 ps under these conditions, independent of the excitation wavelength. In agreement with the experiments, simulations of the optical response arising from thermalized and nonthermalized electron distributions show that a non-Fermi electron distribution leads to a less intense bleach of the plasmon absorption. Furthermore, the difference between the response from the two electron distributions is greater for small temperature changes of the electron gas (low excitation powers). No size dependence of the electron thermalization dynamics is observed for gold nanoparticles with diameters between 9 and 48 nm. High-resolution transmission electron microscopy (HRTEM) reveals that these gold nanoparticles possess defect structures. The effect of this on the electron–phonon relaxation processes is discussed. 18 nm gold–silver alloy nanoparticles with a gold mole fraction of 0.8 are compared to 15 nm gold nanoparticles. While mixing silver leads to a blue-shift of the plasmon absorption in the ground-state absorption spectrum, no difference is observed in the femtosecond dynamics of the system.
The packing in self-assembled nanocrystal superlattices is determined to a large extent by the geometry of the nanocrystals, as is demonstrated here by the preparation and analysis of wellordered arrays of predominantly tetrahedral silver nanocrystals. The Figure shows the model proposed to explain the monolayer self-assembly of tetrahedral silver nanocrystals passivated by bundled thiolate molecules.
A [6 + 1] annulation reaction via cascade 1,6-hydride transfer/cyclization is reported to construct a polycyclic 3,4-fused azepinoindole skeleton. The newly designed 4-amino-indole-3-carbaldehyde is applied as a novel six-atom synthon, interacting with arylamines and malononitrile to achieve the [6 + 1] annulation. Notably, the reaction proceeds smoothly under redox-neutral and metal-free conditions, providing a wide range of azepinoindoles in up to 94% yields, with water as the only byproduct. Besides, the advantage of high step- and atom-economy further highlights the practicality of this methodology.
