SiRNA and shRNA screens advance key understanding of host factors required for HIV-1 replication

A recent RNAi screen used a genome-wide shRNA library to search for cellular factors required for HIV-1 replication. This work complements three other siRNA-based screening studies and potentially opens the door to the discovery of factors that are important for HIV-1 replication in physiological host cells such as T lymphocytes. shRNA screens can be further improved, and they could promise to unravel new pathways and new facets of virus-cell interactions. © 2009 Kok et al; licensee BioMed Central Ltd.published_or_final_versio

Excitonic quantum confinement modified optical conductivity of monolayer and few-layered MoS2

2016-2017 > Academic research: refereed > Publication in refereed journal201804_a bcmaVersion of RecordPublishe

Optically-Triggered Nanoscale Memory Effect in a Hybrid Plasmonic-Phase Changing Nanostructure

Nanoscale devices, such as all-optical modulators and electro-optical transducers, can be implemented in heterostructures that integrate plasmonic nanostructures with functional active materials. Here we demonstrate all-optical control of a nanoscale memory effect in such a heterostructure by coupling the localized surface plasmon resonance (LSPR) of gold nanodisk arrays to a phase-changing material (PCM), vanadium dioxide (VO<inf>2</inf>). By latching the VO<inf>2</inf> in a distinct correlated metallic state during the insulator-to-metal transition (IMT), while concurrently exciting the hybrid nanostructure with one or more ultraviolet optical pulses, the entire phase space of this correlated state can be accessed optically to modulate the plasmon response. We find that the LSPR modulation depends strongly but linearly on the initial latched state, suggesting that the memory effect encoded in the plasmon resonance wavelength is linked to the strongly correlated electron states of the VO<inf>2</inf>. The continuous, linear variation of the electronic and optical properties of these model heterostructures opens the way to multiple design strategies for hybrid devices with novel optoelectronic functionalities, which can be controlled by an applied electric or optical field, strain, injected charge, or temperature.Department of Applied Physic

Hybrid plasmonic gap modes in metal film-coupled dimers and their physical origins revealed by polarization resolved dark field spectroscopy

2015-2016 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Maximizing surface-enhanced Raman scattering sensitivity of surfactant-free Ag-Fe₃O₄ nanocomposites through optimization of silver nanoparticle density and magnetic self-assembly

Author name used in this publication: Zhi Yong Bao2013-2014 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Ablation of nanoparticles and efficient harmonic generation using a 1-kHz laser

Author name used in this publication: D. Y. Lei2013-2014 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Temporal broadening of attosecond photoelectron wavepackets from solid surfaces

The response of solids to electromagnetic fields is of crucial importance in many areas of science and technology. Many fundamental questions remain to be answered about the dynamics of the photoexcited electrons that underpin this response, which can evolve on timescales of tens to hundreds of attoseconds. How, for example, is the photoexcited electron affected by the periodic potential as it travels in the solid, and how do the other electrons respond in these strongly correlated systems? Furthermore, control of electronic motion in solids with attosecond precision would pave the way for the development of ultrafast optoelectronics. Attosecond electron dynamics can be traced using streaking, a technique in which a strong near-infrared laser field accelerates an attosecond electron wavepacket photoemitted by an extreme ultraviolet light pulse, imprinting timing information onto it. We present attosecond streaking measurements on the wide-bandgap semiconductor tungsten trioxide, and on gold, a metal used in many nanoplasmonic devices. Information about electronic motion in the solid is encoded on the temporal properties of the photoemitted electron wavepackets, which are consistent with a spread of electron transport times to the surface following photoexcitation

Antenna-assisted picosecond control of nanoscale phase transition in vanadium dioxide

Nanoscale devices in which the interaction with light can be configured using external control signals hold great interest for next-generation optoelectronic circuits. Materials exhibiting a structural or electronic phase transition offer a large modulation contrast with multi-level optical switching and memory functionalities. In addition, plasmonic nanoantennas can provide an efficient enhancement mechanism for both the optically induced excitation and the readout of materials strategically positioned in their local environment. Here, we demonstrate picosecond all-optical switching of the local phase transition in plasmonic antenna-vanadium dioxide (VO2) hybrids, exploiting strong resonant field enhancement and selective optical pumping in plasmonic hotspots. Polarization- and wavelength-dependent pump-probe spectroscopy of multifrequency crossed antenna arrays shows that nanoscale optical switching in plasmonic hotspots does not affect neighboring antennas placed within 100 nm of the excited antennas. The antenna-assisted pumping mechanism is confirmed by numerical model calculations of the resonant, antenna-mediated local heating on a picosecond time scale. The hybrid, nanoscale excitation mechanism results in 20 times reduced switching energies and 5 times faster recovery times than a VO2 film without antennas, enabling fully reversible switching at over two million cycles per second and at local switching energies in the picojoule range. The hybrid solution of antennas and VO2 provides a conceptual framework to merge the field localization and phase-transition response, enabling precise, nanoscale optical memory functionalities