RESUMO
Nanorobotic motion on solid substrates is greatly hindered by strong nanofriction, and powerful nanomotorsâthe core components for nanorobotic motionâare still lacking. Optical actuation addresses power and motion control issues simultaneously, while conventional technologies with small thrust usually apply to fluid environments. Here, we demonstrate micronewton-thrust nanomotors that enable the autonomous nanorobots working like conventional robots with precise motion control on dry surfaces by a photothermal-shock technique. We build a pulsed laser-based actuation and trapping platform, termed photothermal-shock tweezers, for general motion control of metallic nanomaterials and assembled nanorobots with nanoscale precision. The thrust-to-weight ratios up to 107 enable nanomotors output forces to interact with external micro/nano-objects. Leveraging machine vision and deep learning technologies, we assemble the nanomotors into autonomous nanorobots with complex structures, and demonstrate multi-degree-of-freedom motion and sophisticated functions. Our photothermal shock-actuation concept fundamentally addresses the nanotribology challenges and expands the nanorobotic horizon from fluids to dry solid surfaces.
RESUMO
Tailoring excitonic photoluminescence (PL) in molybdenum disulfide (MoS2) is critical for its various applications. Although significant efforts have been devoted to enhancing the PL intensity of monolayer MoS2, simultaneous tailoring of emission from both A excitons and B excitons remains largely unexplored. Here, we demonstrate that both A-excitonic and B-excitonic PL of chemical vapor deposition (CVD)-grown monolayer MoS2 can be tuned by electrostatic doping in air. Our results indicate that the B-excitonic PL changed in the opposite direction compared to A-excitonic PL when a gate voltage (V g) was applied, both in S-rich and Mo-rich monolayer MoS2. Through the combination of gas adsorption and electrostatic doping, a 12-fold enhancement of the PL intensity for A excitons in Mo-rich monolayer MoS2 was achieved at V g = -40 V, and a 26-fold enhancement for the ratio of B/A excitonic PL was observed at V g = +40 V. Our results demonstrate not only the control of the conversion between A0 and A-, but also the modulation of intravalley and intervalley conversion between A excitons and B excitons. With electrostatic electron doping, the population of B excitons can be promoted due to the enhanced intravalley and intervalley transition process through electron-phonon coupling. The electrostatic control of excitonic PL has potential applications in exciton physics and valleytronics involving the B excitons.
RESUMO
Premna microphylla Turcz. is a commonly used traditional Chinese medicine totreatdysentery and appendicitis. Present study is focused to explore antioxidants and other compounds in the Premna microphylla Turcz. stem. Assessment of chemical composition was done with high sensitivity UPLC-LTQ-Orbitrap-MS and for Separation Thermo Hypersil Gold (100 mm × 2.1 mm, 1.9 µm) was used while electrospray ionization (ESI) was used for the mass spectrometry. 18 compounds were identified including Vitexin (1), Schaftoside (2), Vicenin-2 (3), Apigenin-6, 8-di-C-arabinoside (4), Apigenin-7-O-ß-d-glucoside (5), Carnosic acid (6), Apigenin-8-C-ß-d-xylopyranoside (7), Prostratin (8), Aurantio-obtusin-ß-d-glucoside (9), Royleanone (10), 5-hydroxy-7,3',4'-Trimethoxy flavonols (11), 6-Hydroxy-5,6-dehydrosugiol (12), 14-deoxycoleon (13), Arucadiol (14), Obtusinone-B (15), Trehalose (16), Citric acid (17) and Betaine (18). Among these, 6 compounds including (6), (8), (9), (16), (17) and (18) were identified first time within this genus and plant. Study highlights the importance of Premna microphylla Turcz. stem extract for strong therapeutic potential against oxidation-related diseases.
