Relatively large gold nanoparticles (mean diameter of major axis 38.2 nm, mean aspect ratio 1.29) in aqueous solution were found to undergo shape transformations from ellipsoids spheres at ca. 940 °C, which is much lower than their melting point, 1060 °C. The transformation induced by a single pulse Nd:YAG laser (λ = 355 width 30 ps) was directly observed transmission electron microscope (TEM). Analysis the experimental data showed that threshold energy for photothermally on order 40 fJ...

The diffusivity of solvents in polymer solutions is crucial for thin film drying and influenced by the interactions between solvent. This study examines impact hydrogen bonding solvent on self-diffusion coefficient a poly(amic acid) (PAA) solution dimethylacetamide. A modified free-volume model (HBFV model) was developed, incorporating bonds. It assumes that some molecules form bonds with polymer, reducing their mobility free volume. Molecular dynamics simulations analyzed fraction...

The evolution of size distributions gold nanoparticles under pulsed laser irradiation (Nd:YAG, lambda = 355 nm, pulse width 30 ps) was carefully observed by transmission electron microscopy. Interestingly, the initial monomodal distribution turned into a bimodal one, with two peaks in number particles, one at 6 nm and other 16-24 nm. sizes for small particles depended very little on irradiated energy. This change is attributed to laser-induced reduction followed formation particles. In our...

The pulsed laser induced phase transition of gold nanoparticles in aqueous solution was observed via a transient absorption on nanosecond time scales and longer. Gold were excited with an intense picosecond pulse (355 nm, 30 ps), the subsequent changes monitored using two continuous wave wavelengths (488 635 nm). On scale, below 6.3 mJ cm(-2), no change observed; however, low fluence region between 17 produced bleach signal nm) attributed to melting nanoparticles, which decreased linearly...

A new cracking mode in silica colloidal films formed via quasi-one-dimensional directional drying is presented. Unlike typical parallel to the direction, unique periodic cracks perpendicular direction are when a suspension dries thin glass cell. The mechanism of formation discussed and mathematical model based on mass balance water, which describes experimental data well, proposed. Our reveals that rate water predominantly determines crack spacing it inversely related. Analogy inverse...

We describe a facile method to synthesize silicon nanoparticles through plasma-assisted decomposition of tetrabromide, novel precursor for gas phase synthesis. Raman spectroscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared analyses demonstrate that the obtained nanocrystals were covered with oxide layer. The can be easily dispersed in ethanol dispersion exhibited stable optical properties over half year, showing strong...

We demonstrate optical coherence tomography as an in-situ , quick and quantitative method for the measurement of particle concentrations in a drying colloidal suspension.

Molecular diffusion in polyimides and their precursors, such as poly(amic acid) (PAA) varnishes, must be quantitatively analyzed to understand reaction kinetics improve industrial production. Herein, the coefficients of dimethylacetamide (DMAc) PAA varnishes were measured using pulsed-field gradient nuclear magnetic resonance. The coefficient DMAc decreased with increasing concentration, dependency was stronger than expected, suggesting that diffusivity is influenced by strong interaction...

A simple and novel approach was developed to obtain water-dispersible silicon quantum dots (Si-QDs) of low toxicity that were able selectively label the endoplasmic reticulum (ER) in live cells. block copolymer (Pluronic F127) used coat surface Si-QDs. Si-QDs form aggregates with diameters 20–40 nm show an outstanding optical stability upon UV irradiation. Our F127-treated would be a powerful tool for long-term real-time observation ER

Aggregates of luminescent silicon quantum dots (Si-QDs) selectively label certain organelles, such as lysosomes, endoplasmic reticulum, cytosol and nuclei, depending upon the size aggregates their surface properties. We used Si-QDs in an aggregated form was controlled from ca. 30 to 270 nm diameter. In fixed human umbilical vein endothelial cells (HUVECs), allylamine-terminated labeled cell while Si-QDs, treated by amphiphilic block copolymer Pluronic® F127, uniformly cytosol. On other hand,...

A novel, controlled drug-release system was developed based on aggregation/dispersion of silicon quantum dots (Si-QDs) in response to a change the pH environment.

Silica-gel films containing Au nanoparticles were fabricated by a photoreduction method, which functioned as medium for high-density optical recording. On irradiation of 532 nm laser light, corresponds to the surface plasmon resonance absorption particles, spectrum film showed blueshift. Using this property, hologram was recorded on film. Transmitting electron microscopy supported that change in due size reduction embedded particles caused irradiation. For recording hologram, threshold...

Flowerlike silicon particles are obtained by chemical etching of polycrystalline polyhedrons using a mixture hydrofluoric acid and nitric acid. The etched flowerlike show stable bright red photoluminescence under UV irradiation. formation pores with diameters 3, 5.5, 20 nm is revealed during etching. exhibit superhydrophobic behavior contact angle 158 degrees because the sharp tips their "petals". source shown to possess radial grain boundaries. Preferential along boundaries thought be key...

We observed the kinetics of formation colloidal films through directional drying with a pinned interface. The volume fraction particles accumulated at interface increased in two stages: it rapidly initial stage and then slowly increased. final filling factor dried decreased increasing flux. found threshold flux for below which uneven are formed This is well explained by competition between transport flow diffusion. also minimum thickness packed layer particles. due to was discussed.

Water evaporation rate decreases more severely when diffusion constant of dissolved polymer is small. Diffusion constants polymers were obtained in drying aqueous solutions by exploiting differential interference contrast an optical microscope.

We synthesized gold nanoparticles (mean diameter 8.3 nm, standard deviation 2.7 nm) from tetrachloroaurate complex (AuCl4-) solution by 308 nm laser irradiation without the use of any stabilizers. The combination photochemical particle growth with photothermal size reduction resulted in a narrow distribution. Photothermal controlled maximum which existed system, and their Using this technique, we were able to control distribution naoparticles. propose simple model for estimating formed...

Colloidal silica films, formed by the drop evaporation method, showed birefringent spherulite optical properties. They displayed a Maltese cross pattern under crossed polarizers, and interference colors, such as blue orange-red, polarizers with compensator. The difference in refractive index was estimated to be 9x10(-4) from colors. Scanning electron microscopy (SEM) results revealed anisotropic structures colloidal films. Particles radially ordered hexagonal arrays. method used this report,...

We investigated the origin of birefringence in colloidal films spherical silica particles. Although each particle is optically isotropic shape, formed by drop drying demonstrated birefringence. While periodic structures were observed films, no regular pattern was found blended and latex However, since both showed birefringence, film structure patterns not required to exhibit Instead, we propose that nanometer-scale anisotropy causes Due capillary flow from center edge a cast suspension,...

When cultured endothelial cells (ECs) are exposed to shear flow, initially cobblestone-like ECs spontaneously elongate and align along the flow direction, acquiring a similar architecture that of native endothelium in blood vessels. Though previous works have revealed how individual sense respond little is known about contribution cell–cell interaction this phenomenon. Here, we reveal response cell density-dependent, therefore possibly mediated by collective behavior (i.e. interaction). A...

We report on the formation of silicon nanowires via gas-phase reaction tetrachloride with zinc vapor at ca. 1000 °C. In this method, metal catalysts do not have to be prepared before synthesizing nanowires. The obtained form a "blanket" yellow color reactor wall. contrast common catalytic CVD rough surface were synthesized. fraction increased from 6% 40% when temperature was changed 920 1010 average diameter also 80 40 nm under same conditions. A growth direction analysis revealed that...

Abstract When a mixture of liquid crystal (LC) and photo reactive monomer is irradiated by UV light, polymerization occurs LC droplets form through phase separation, producing polymer dispersed LCs (PDLCs). Although size control reduced amounts in PDLC films are important applications, precise at low fraction has not yet been accomplished. In this study, the diagrams LC/initial LC/polymer during were used to droplet various fractions. Both relative position sample initial diagram shift...

We have investigated drying of water droplets stabilized by solid particles or surfactant molecules in a thin oil layer. The surfactant-stabilized isotropically shrink, whereas the spherical severely deform during because buckling particulate shells. However, shells hardly affects droplet drying. times for complete evaporation are almost same with initial diameter and time is independent type surface stabilizer (particles surfactant). kinetics well described mathematical models, which...