비만아 부모의 돌봄 경험: q 방법론

Carbon Nanomaterials for Biological Imaging and Nanomedicinal Therapy

Graphene-based nanomaterials for drug delivery and tissue engineering.

Creating functional electrical circuits using individual or ensemble molecules, often termed as “molecular-scale electronics”, not only meets the increasing technical demands of the miniaturization of traditional Si-based electronic devices, but also provides an ideal window of exploring the intrinsic properties of materials at the molecular level. This Review covers the major advances with the most general applicability and emphasizes new insights into the development of efficient platform methodologies for building reliable molecular electronic devices with desired functionalities through the combination of programmed bottom-up self-assembly and sophisticated top-down device fabrication. First, we summarize a number of different approaches of forming molecular-scale junctions and discuss various experimental techniques for examining these nanoscale circuits in details. We then give a full introduction of characterization techniques and theoretical simulations for molecular electronics. Third, we highlig...

Molecular-Scale Electronics: From Concept to Function

The ultimate in electronic device miniaturization would be the creation of circuit elements consisting of an individual molecule. A single-molecule transistor exploiting the electrostatic modulation of a molecule's orbital energy is a theoretical possibility. Now Hyunwook Song and colleagues report the successful realization of such a device, a proof of concept that should enhance the practical prospects for molecularly engineered electronics. A longstanding aim in molecular-scale electronics is to create a true transistor analogue in which charge transport through a molecule is directly controlled by external modulation of the molecular orbitals. The observation of such a solid-state molecular device is now reported. The data demonstrate that true molecular transistors can be created, and clear the way for molecularly engineered electronic devices. The control of charge transport in an active electronic device depends intimately on the modulation of the internal charge density by an external node1. For example, a field-effect transistor relies on the gated electrostatic modulation of the channel charge produced by changing the relative position of the conduction and valence bands with respect to the electrodes. In molecular-scale devices2,3,4,5,6,7,8,9,10, a longstanding challenge has been to create a true three-terminal device that operates in this manner (that is, by modifying orbital energy). Here we report the observation of such a solid-state molecular device, in which transport current is directly modulated by an external gate voltage. Resonance-enhanced coupling to the nearest molecular orbital is revealed by electron tunnelling spectroscopy, demonstrating direct molecular orbital gating in an electronic device. Our findings demonstrate that true molecular transistors can be created, and so enhance the prospects for molecularly engineered electronic devices.

/pdf/observation-of-molecular-orbital-gating-2yblbwhjsy.pdf

Observation of molecular orbital gating.

As an emerging applied material, graphene has shown tremendous application potential in many fields, including biomedicine. However, the biological behavior of these nanosheets, especially their interactions with cells, is not well understood. Here, we report our findings about the cell surface adhesion, subcellular locations, and size-dependent uptake mechanisms of protein-coated graphene oxide nanosheets (PCGO). Small nanosheets enter cells mainly through clathrin-mediated endocytosis, and the increase of graphene size enhances phagocytotic uptake of the nanosheets. These findings will facilitate biomedical and toxicologic studies of graphenes and provide fundamental understanding of interactions at the interface of two-dimensional nanostructures and biological systems.

Size-dependent cell uptake of protein-coated graphene oxide nanosheets

We have used an electromigration technique to fabricate C60-based single-molecule transistors We detail the process statistics and the protocols used to infer the successful formation of a single-molecule transistor At low temperatures each transistor acts as a single-electron device in the Coulomb blockade regime Resonances in the differential conductance indicate vibrational excitations consistent with a known mode of C60 In several devices we observe conductance features characteristic of the Kondo effect, a coherent many-body state comprising an unpaired spin on the molecule coupled by exchange to the conduction electrons of the leads The inferred Kondo temperature typically exceeds 50 K, and signatures of the vibrational modes persist into the Kondo regime

The Kondo effect in C60 single-molecule transistors

In single-molecule transistors, we observe inelastic cotunneling features that correspond energetically to vibrational excitations of the molecule, as determined by Raman and infrared spectroscopy. This is a form of inelastic electron tunneling spectroscopy of single molecules, with the transistor geometry allowing in situ tuning of the electronic states via a gate electrode. The vibrational features shift and change shape as the electronic levels are tuned near resonance, indicating significant modification of the vibrational states. When the molecule contains an unpaired electron, we also observe vibrational satellite features around the Kondo resonance.

/pdf/inelastic-electron-tunneling-via-molecular-vibrations-in-23hclsul62.pdf

Inelastic electron tunneling via molecular vibrations in single-molecule transistors.

We report Kondo resonances in the conduction of single-molecule transistors based on transition metal coordination complexes. We find Kondo temperatures in excess of 50 K, comparable to those in purely metallic systems. The observed gate dependence of the Kondo temperature is inconsistent with observations in semiconductor quantum dots and a simple single-dot-level model. We discuss possible explanations of this effect, in light of electronic structure calculations.

/pdf/kondo-resonances-and-anomalous-gate-dependence-in-the-587xtgki1h.pdf

Kondo Resonances and Anomalous Gate Dependence in the Electrical Conductivity of Single-Molecule Transistors

Single-molecule transistors (SMTs) incorporating individual small molecules are unique tools for examining the fundamental physics and chemistry of electronic transport in molecular systems at the single nanometer scale. We describe the fabrication and characterization of such devices, and the synthesis and surface attachment chemistry of novel transition metal complexes that have been incorporated into such SMTs. We present gate-modulated inelastic electron tunneling vibrational spectroscopy of single molecules, strong Kondo physics (TK ∼ 75 K) as evidence of excellent molecule/electrode electronic coupling, and a demonstration that covalent attachment chemistry can produce SMTs that survive repeated thermal cycling to room temperature. We conclude with a look ahead at the prospects for these nanoscale systems.

/pdf/single-molecule-transistors-electron-transfer-in-the-solid-3hzov05yz0.pdf

Lam H. Yu

Papers

Size-dependent cell uptake of protein-coated graphene oxide nanosheets

The Kondo effect in C60 single-molecule transistors

Inelastic electron tunneling via molecular vibrations in single-molecule transistors.

Kondo Resonances and Anomalous Gate Dependence in the Electrical Conductivity of Single-Molecule Transistors

Single-molecule transistors: Electron transfer in the solid state