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| 1 | Neuronal photoactivation through secondharmonic near-infrared absorption by gold nanoparticles显示文摘Optical activation of neurons requires genetic manipulation or the use of chemical photoactivators with undesirable side effects.As a solution to these disadvantages,here,we demonstrate optically evoked neuronal activity in mouse cortical neurons in acute slices and in vivo by nonlinear excitation of gold nanoparticles.In addition,we use this approach to stimulate individual epitheliomuscular cells and evoke body contractions in Hydra vulgaris.To achieve this,we use a low-power pulsed near-infrared excitation at the double-wavelength of the plasmon resonance of gold nanoparticles,which enables optical sectioning and allows for high spatial precision and large penetration depth.The effect is explained by second-harmonic Mie scattering,demonstrating light absorption by a second-order nonlinear process,which enables photothermal stimulation of the cells.Our approach also minimizes photodamage,demonstrating a major advancement towards precise and harmless photoactivation for neuroscience and human therapeutics. | Wieteke D.A.M.de Boer Jan J.Hirtz Antonio Capretti Tom Gregorkiewicz Mercè Izquierdo-Serra Shuting Han Christophe Dupre Yuriy Shymkiv Rafael Yuste | 2018 | Light(Science & Applications)2018，7，1： | 1 |
| 2 | Surface brightens up Si quantum dots: direct bandgap-like size-tunable emission显示文摘Colloidal semiconductor quantum dots(QDs)constitute a perfect material for ink-jet printable large area displays,photovoltaics,light-emitting diode,bio-imaging luminescent markers and many other applications.For this purpose,efficient light emission/absorption and spectral tunability are necessary conditions.These are currently fulfilled by the direct bandgap materials.Si-QDs could offer the solution to major hurdles posed by these materials,namely,toxicity(e.g.,Cd-,Pb-or As-based QDs),scarcity(e.g.,QD with In,Se,Te)and/or instability.Here we show that by combining quantum confinement with dedicated surface engineering,the biggest drawback of Si—the indirect bandgap nature—can be overcome,and a‘direct bandgap’variety of Si-QDs is created.We demonstrate this transformation on chemically synthesized Si-QDs using state-of-the-art optical spectroscopy and theoretical modelling.The carbon surface termination gives rise to drastic modification in electron and hole wavefunctions and radiative transitions between the lowest excited states of electron and hole attain‘direct bandgap-like’(phonon-less)character.This results in efficient fast emission,tunable within the visible spectral range by QD size.These findings are fully justified within a tight-binding theoretical model.When the C surface termination is replaced by oxygen,the emission is converted into the well-known red luminescence,with microsecond decay and limited spectral tunability.In that way,the‘direct bandgap’Si-QDs convert into the‘traditional’indirect bandgap form,thoroughly investigated in the past. | Katerina Dohnalova Alexander N Poddubny Alexei A Prokofiev Wieteke DAM de Boer Chinnaswamy P Umesh Jos MJ Paulusse Han Zuilhof Tom Gregorkiewicz | 2013 | Light(Science & Applications)2013，2，1： | 0 |
| 3 | Carrier multiplication in germanium nanocrystals显示文摘Carrier multiplication is demonstrated in a solid-state dispersion of germanium nanocrystals in a silicon–dioxide matrix.This is performed by comparing ultrafast photo-induced absorption transients at different pump photon energies below and above the threshold energy for this process.The average germanium nanocrystal size is approximately 5–6 nm,as inferred from photoluminescence and Raman spectra.A carrier multiplication efficiency of approximately 190%is measured for photo-excitation at 2.8 times the optical bandgap of germanium nanocrystals,deduced from their photoluminescence spectra. | Saba Saeed Chris de Weerd Peter Stallinga Frank CM Spoor Arjan J Houtepen Laurens DA Siebbeles Tom Gregorkiewicz | 2015 | Light(Science & Applications)2015，4，1： | 0 |
| 4 | Thermally stimulated exciton emission in Si nanocrystals显示文摘Increasing temperature is known to quench the excitonic emission of bulk silicon,which is due to thermally induced dissociation of excitons.Here,we demonstrate that the effect of temperature on the excitonic emission is reversed for quantumconfined silicon nanocrystals.Using laser-induced heating of silicon nanocrystals embedded in SiO2,we achieved a more than threefold(4300%)increase in the radiative(photon)emission rate.We theoretically modeled the observed enhancement in terms of the thermally stimulated effect,taking into account the massive phonon production under intense illumination.These results elucidate one more important advantage of silicon nanostructures,illustrating that their optical properties can be influenced by temperature.They also provide an important insight into the mechanisms of energy conversion and dissipation in ensembles of silicon nanocrystals in solid matrices.In practice,the radiative rate enhancement under strong continuous wave optical pumping is relevant for the possible application of silicon nanocrystals for spectral conversion layers in concentrator photovoltaics. | Elinore MLD de Jong Huub Rutjes Jan Valenta M Tuan Trinh Alexander N Poddubny Irina N Yassievich Antonio Capretti Tom Gregorkiewicz | 2017 | Light(Science & Applications)2017，6，1： | 0 |
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