Phase transitions of adsorbed atoms and molecules on two-dimensional substrates are well explored, but similar transitions in the one-dimensional limit have been more difficult to study experimentally. Suspended carbon nanotubes can act as nanoscale resonators with remarkable electromechanical properties and the ability to detect adsorption at the level of single atoms. We used single-walled carbon nanotube resonators to study the phase behavior of adsorbed argon and krypton atoms as well as their coupling to the substrate electrons. By monitoring the resonance frequency in the presence of gases, we observed the formation of monolayers on the cylindrical surface, phase transitions within them, and simultaneous modification of the electrical conductance.

By slowing the rate of atomic addition to singly twinned seeds, we have grown silver nanobeams with lengths of 3-30 mum, widths ranging from 17 to 70 nm, and a width to thickness ratio of 1.4. The well-defined dimensions, smooth surface, and crystallinity of nanobeams make them promising candidates for studying the effects of size on electron transport. With a simple method that allows rapid characterization of single nanobeams, we find that even the thinnest nanobeams largely retain the low resistivity of bulk silver. Nanobeams can support remarkably high current densities of up to 2.6 x 10(8) A cm(-2) before the conduction path is broken by the formation of a nanogap.

Single‐atom nanozyme (SAzyme) with peroxidase‐like activity can alter cellular redox balance and shows promising potential for tumor therapy. However, the “cold” immune microenvironment and limited amount of hydrogen peroxide (H2O2) in solid tumors severely restrict its efficacy. Herein, a light‐controlled oxidative stress amplifier system is designed by co‐encapsulating Pd‐C SAzymes and camptothecin in agarose hydrogel, which exhibits enhanced synergistic antitumor activity by self‐producing H2O2 and transforming “cold” tumors. In this nanozyme hydrogel system, the Pd‐C SAzyme converts near‐infrared laser into heat, resulting in agarose degradation and consequent camptothecin release. The camptothecin increases H2O2 level in tumors by activating nicotinamide adenine dinucleotide phosphate oxidase, improving the catalytic performance of SAzymes with peroxidase‐like activity. Moreover, the combination of photothermal therapy, chemotherapy, and nanozyme‐based catalytic therapy further facilitates tumor immunogenic death and enhanced antitumor immunity. The results reveal the synergistic antitumor potential of the novel SAzyme/chemotherapeutics‐based hydrogel system.

We demonstrate charge pumping in semiconducting carbon nanotubes by a traveling potential wave. From the observation of pumping in the nanotube insulating state we deduce that transport occurs by packets of charge being carried along by the wave. By tuning the potential of a side gate, transport of either electron or hole packets can be realized. Prospects for the realization of nanotube based singleelectron pumps are discussed. DOI: 10.1103/PhysRevLett.95.256802 PACS numbers: 85.35.Kt, 72.50.+b, 73.23.Hk, 73.63.Kv The phenomenon of charge pumping has attracted considerable interest in the last two decades from both fundamental and applied points of view [1][2][3][4][5][6][7][8][9][10]. In pumping, a periodic in time and spatially inhomogeneous external perturbation yields a dc current. If a fixed number n of electrons is transferred during a cycle then the pumping current is quantized in units of ef, where e is the electron charge and f is the perturbation frequency. An important aspect of single-electron pumps is their potential to provide an accurate frequency-current conversion which could close the measurement triangle relating frequency, voltage, and current. Previously, a realization of quantized current I nef has been achieved in two different ways: first, using devices comprising charge islands and controlled by a number of phase-shifted ac signals [3,4,7]; and second, using one-dimensional (1D) channels within a GaAs heterojunction where a surface acoustic wave (SAW) produces traveling potential wells which convey packets of electrons along the channel [5]. In the SAW pumps, transport of charge resembles the pumping of water by an Archimedean screw. When this principle is combined with Coulomb blockade it results in the pumping of a fixed number of electrons n per cycle. For metrological applications, the delivered current should be in the range of 1 nA and at present only the SAW single-electron pumps satisfy this requirement. However, the accuracy of the SAW pumps must be improved significantly for them to find metrological applications.A quantum regime of pumping, in which quantum interference plays a key role, was first described by Thouless [1,2]. In the Thouless mechanism, a traveling periodic perturbation induces minigaps in the spectrum of an electronic system, and when the Fermi level lies in a minigap an integer number of electrons n are transferred during a cycle, resulting in a quantized current flowing without dissipation. From a fundamental physics standpoint, this mechanism represents a new macroscopic quantum phenomenon reminiscent of the quantum Hall effect and of superconductivity. Possible applications of charge pumping are not limited to metrology. For example, the ability of the pumps to control the position of single electrons could be used in various quantum information processing schemes [11,12].Recently it has been pointed out that carbon nanotubes have significant advantages over semiconductor and metallic systems in terms of single-electron pumping [8,9]. The typical Cou...