Heteronanotrimers by Selective Photodeposition of Gold Nanodots on Janus-Type Cu S/CuInS Heteronanocrystals.

This study focuses on the development of environmentally friendly Au-CuS/CuInS heteronanotrimers. The chosen strategy relies on the laser photodeposition of a single gold nanodot (ND) onto Janus Cu S/CuInS heteronanocrystals (HNCs). This method offers precise control over the number, location, and size (5 to 8 nm) of the Au NDs by adjusting laser power for the career production, concentration of hole scavenger for charge equilibration in redox reactions, and gold precursor concentration, and exposure time for the final ND size.

Decay Dynamics of a Single Spherical Domain in Near-Critical Phase-Separated Conditions.

Domain decay is at the heart of the so-called evaporation-condensation Ostwald-ripening regime of phase ordering kinetics, where the growth of large domains occurs at the expense of smaller ones, which are expected to "evaporate." We experimentally investigate such decay dynamics at the level of a single spherical domain picked from one phase in coexistence and brought into the other phase by an optomechanical approach, in a near-critical phase-separated binary liquid mixture. We observe that the decay dynamics is generally not compatible with the theoretically expected surface-tension decay laws for conserved order parameters.

Numerical simulation of universal morphogenesis of fluid interface deformations driven by radiation pressure.

We report on numerical simulation of fluid interface deformations induced by either acoustic or optical radiation pressure. This is done by solving simultaneously the scalar wave propagation equation and the two-phase flow equations using the boundary element method. Using dimensional analysis, we show that interface deformation morphogenesis is universal, i.

Near-critical spreading of droplets.

We study the spreading of droplets in a near-critical phase-separated liquid mixture, using a combination of experiments, lubrication theory and finite-element numerical simulations. The classical Tanner's law describing the spreading of viscous droplets is robustly verified when the critical temperature is neared. Furthermore, the microscopic cut-off length scale emerging in this law is obtained as a single free parameter for each given temperature.

A versatile interferometric technique for probing the thermophysical properties of complex fluids.

Laser-induced thermocapillary deformation of liquid surfaces has emerged as a promising tool to precisely characterize the thermophysical properties of pure fluids. However, challenges arise for nanofluid (NF) and soft bio-fluid systems where the direct interaction of the laser generates an intriguing interplay between heating, momentum, and scattering forces which can even damage soft biofluids. Here, we report a versatile, pump-probe-based, rapid, and non-contact interferometric technique that resolves interface dynamics of complex fluids with the precision of ~1 nm in thick-film and 150 pm in thin-film regimes below the thermal limit without the use of lock-in or modulated beams.

Hole Scavenging and Electron-Hole Pair Photoproduction Rate: Two Mandatory Key Factors to Control Single-Tip Au-CdSe/CdS Nanoheterodimers.

Metal/semiconductor hetero-nanostructures are now considered as benchmark functional nanomaterials for many light-driven applications. Using laser-driven photodeposition to control growth of gold nanodots (NDs) onto CdSe/CdS dot-in-rods (DRs), we show that the addition of a dedicated hole scavenger (MeOH) is cornerstone to significantly reduce to less than 3.5% the multiple-site nucleation and 2.

Design of Metal@Titanium Oxide Nano-heterodimers by Laser-Driven Photodeposition: Growth Mechanism and Modeling.

In order to circumvent the usual nucleation of randomly distributed tiny metallic dots photodeposited on TiO nanoparticles (NPs) induced by conventional UV lamps, we propose to synthesize well-controlled nanoheterodimers (NHDs) using lasers focused inside microfluidic reactors to strongly photoactivate redox reactions of active ions flowing along with nanoparticles in water solution. Since the flux of photons issued from a focused laser may be orders of magnitude higher than that reachable with classical lamps, the production of electron-hole pairs is tremendously increased, ensuring a large availability of carriers for the deposition and favoring the growth of a single metallic dot as compared to secondary nucleation events. We show that the growth of single silver or gold nanodots can be controlled by varying the beam intensity, the concentration of the metallic salt, and the flow velocity inside the microreactor.

Convection flows driven by laser heating of a liquid layer.

When a fluid is heated by the absorption of a continuous laser wave, the fluid density decreases in the heated area. This induces a pressure gradient that generates internal motion of the fluid. Due to mass conservation, convection eddies emerge in the sample.

Fulminant isolated adenovirus hepatitis 5 months after haplo-identical HSCT for AML.

The principal limitation of allogeneic hematopoietic stem cell transplantation except relapse remains the transplant-related mortality (TRM). In addition to graft-versus-host disease (GvHD), infections contribute to TRM in many patients. We describe herein a case of an adult patient presenting 5 months after haplo-identical transplantation an isolated fulminant hepatitis due to adenovirus.

Enhancing optofluidic actuation of micro-objects by tagging with plasmonic nanoparticles.

We report experimentally and theoretically on the significant exaltation of optical forces on microparticles when they are partially coated by metallic nanodots and shined with laser light within the surface plasmon resonance. Optical forces on both pure silica particles and silica-gold raspberries are characterized using an optical chromatography setup to measure the variations of the Stokes drag versus laser beam power. Results are compared to the Mie theory prediction for both pure dielectric particles and core-shell ones with a shell described as a continuous dielectric-metal composite of dielectric constant determined from the Maxwell-Garnett approach.

Break-up dynamics of fluctuating liquid threads.

The thinning dynamics of a liquid neck before break-up, as may happen when a drop detaches from a faucet or a capillary, follows different rules and dynamic scaling laws depending on the importance of inertia, viscous stresses, or capillary forces. If now the thinning neck reaches dimensions comparable to the thermally excited interfacial fluctuations, as for nanojet break-up or the fragmentation of thermally annealed nanowires, these fluctuations should play a dominant role according to recent theory and observations. Using near-critical interfaces, we here fully characterize the universal dynamics of this thermal fluctuation-dominated regime and demonstrate that the cross-over from the classical two-fluid pinch-off scenario of a liquid thread to the fluctuation-dominated regime occurs at a well-defined neck radius proportional to the thermal length scale.

Thermocapillary migration in small-scale temperature gradients: application to optofluidic drop dispensing.

We experimentally investigate the thermocapillary migration induced by local laser heating of the advancing front of a growing droplet confined in a microfluidic channel. When heating implies an effective increase in interfacial tension, the laser behaves as a "soft door" whose stiffness can be tuned via the optical parameters (beam power and waist). The light-driven thermocapillary velocity of a growing droplet, which opposes the basic flow, is characterized for different types of fluid injection, either pressure or flow rate driven, and various channel aspect ratios.

Liquid optical fibers with a multistable core actuated by light radiation pressure.

We report on spatiotemporal behavior of self-adapted dielectric liquid columns generated and sustained by light radiation pressure. We show that single- or multivalued liquid column diameter depends on the excitation light beam. When the beam diameter is sufficiently small, we observe a well-defined stationary column diameter.

Stretching and squeezing of sessile dielectric drops by the optical radiation pressure.

We study numerically the deformation of sessile dielectric drops immersed in a second fluid when submitted to the optical radiation pressure of a continuous Gaussian laser wave. Both drop stretching and drop squeezing are investigated at steady state where capillary effects balance the optical radiation pressure. A boundary integral method is implemented to solve the axisymmetric Stokes flow in the two fluids.

Universal behavior of photochemical deposition in liquid solutions driven by a one-photon transition.

Even if photochemical deposition of nearly all types of materials has been used for decades to pattern almost any kind of substrate for various applications (catalysis, chemical sensing, magnetic data storage, optoelectronics, spin-dependent electron transport, and solar cells), a rationalized description is still missing. This paper aims at fulfilling this lack by presenting a unified approach of the photodeposit growth initiated by a one-photon photochemical reaction. We experimentally investigate the robustness of growth scalings predicted for photochemical deposition driven by a continuous laser wave.

An optical toolbox for total control of droplet microfluidics.

The use of microfluidic drops as microreactors hinges on the active control of certain fundamental operations such as droplet formation, transport, division and fusion. Recent work has demonstrated that local heating from a focused laser can apply a thermocapillary force on a liquid interface sufficient to block the advance of a droplet in a microchannel (C. N.

Liquid transport due to light scattering.

Using experiments and theory, we show that light scattering by inhomogeneities in the index of refraction of a fluid can drive a large-scale flow. The experiment uses a near-critical, phase-separated liquid, which experiences large fluctuations in its index of refraction. A laser beam traversing the liquid produces a interface deformation on the scale of the experimental setup and can cause a liquid jet to form.

Thermocapillary valve for droplet production and sorting.

Droplets are natural candidates for use as microfluidic reactors, if active control of their formation and transport can be achieved. We show here that localized heating from a laser can block the motion of a water-oil interface, acting as a microfluidic valve for two-phase flows. A theoretical model is developed to explain the forces acting on a drop due to thermocapillary flow, predicting a scaling law that favors miniaturization.

Light-induced deformation and instability of a liquid interface. II. Dynamics.

We study the dynamics of the deformation of a soft liquid-liquid interface by the optical radiation pressure of a focused cw Gaussian laser beam. We measured the temporal evolution of both the hump height and the hump curvature by direct observation and by detecting the focusing effect of the hump acting as a lens. Extending the results of Yoshitake [J.

Growth of monodisperse mesoscopic metal-oxide colloids under constant monomer supply.

In closed systems, control over the size of monodisperse metal-oxide colloids is generally limited to submicrometric dimensions. To overcome this difficulty, we explore the formation and growth of silica particles under constant monomer supply. The monomer source is externally driven by the progressive addition into the system of one of the precursors.