A method is used for preparing gold NRs with aspect ratios ranging from 1.5 to 10 which the surface plasmon absorption maxima are between 600 and 1300 nm. This has been adapted a previously published seed-mediated growth (Jana et al. Adv. Mater. 2001, 13, 1389). The disadvantages limitations of earlier (i.e., formation noncylindrical NRs, φ-shaped particles, large fraction spherical particles) have overcome by use hexadecyltrimethylammonium bromide (CTAB)-capped seed instead citrate-capped...

The surface structure of gold nanorods (NRs) capped with cationic surfactants in water was studied by FTIR, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). For nanorods, the FTIR results show formation new bands, which indicate binding surfactant headgroup to NR. These bands are stable at temperatures as high 350 °C. a mixture (used capping material), TGA shows weak weight loss peak 235 °C strong 298 assigned molecules monomer aggregated forms, respectively....

Gold nanorods have been found to change their shape after excitation with intense pulsed laser irradiation. The final irradiation products strongly depend on the energy of pulse as well its width. We performed a series measurements in which power was varied over range output an amplified femtosecond system producing pulses 100 fs duration and nanosecond optical parametric oscillator (OPO) having width 7 ns. transformations gold are followed by two techniques: (1) visible absorption...

Self-assembly of gold nanorods (NRs) with aspect ratio ∼4.6 (12 nm in diameter and 50−60 length) has been studied using transmission electron microscopy (TEM). Under appropriate conditions such as nanoparticle concentration, solvent evaporation, narrow size distribution, ionic strength, surfactant concentration the parent solution, assemble into one-, two-, three-dimensional structures. Some assemblies extend to superlattices NRs. The translation orientation symmetries self-assembled...

We studied the shape transformation (by use of TEM and optical absorption spectroscopy) gold nanorods in micellar solution by exposure to laser pulses different pulse width (100 fs 7 ns) energies (μJ mJ) at 800 nm, where longitudinal surface plasmon oscillation absorb. At moderate energies, femtosecond irradiation melts near spherical particles comparable volumes while nanosecond fragment them smaller near-spherical particles. high fragmentation is also observed for irradiation. A mechanism...

Surface-enhanced Raman scattering (SERS) of adsorbed molecules on gold nanorods (NRs) with dimensions 10 nm × 27 was studied silica surface low to high coverage NRs. The study carried out investigate both the dependence SERS intensity number NRs and spacing surface. such as 2-aminothiophenol (2-ATP) capping (hexadecyltrimethylammonium bromide) these surfaces using a near-IR laser excitation source (1064 nm). To produce covered NRs, two approaches were used. In first approach, monodispersed...

Gold nanorods prepared electrochemically and capped in micelles are examined using high-resolution transmission electron microscopy (TEM). It is found that they have an axial growth direction of [001] surfaces made {100} the unstable {110} facets. A detailed examination defect sites both these facets shows while defective regions stable show atom-height steps with no reconstruction, less higher energy missing-row reconstruction. The role stabilizing facet gold nanorod briefly discussed.

We studied the femtosecond dynamics of colloidal gold nanorods encapsulated in micelles after excitation with 400 nm pulses 100 fs duration. It is found that laser heating electron gas an average aspect ratio 3.8 leads to bleaching both transverse and longitudinal mode surface plasmon oscillation at 520 750 nm. The bleach recovers same time constant for oscillation, nanodots prepared by photothermal reshaping rods as well synthesized chemically citrate reduction (and known have twin...

The photoluminescence (PL) of CdSe quantum dots (QD) in aqueous media has been studied the presence gold nanoparticles (NP) with different shapes. steady state PL intensity QD (1.5-2 nm size) is quenched NP. Picosecond bleach recovery and nanosecond time-resolved luminescence measurements show a faster decrease lifetime emitting states quenchers. Surfactant-capped nanorods (NR) aspect ratio 3 surfactant-capped citrate-capped nanospheres (NS) 12 diameter were used as quenchers order to study...

The positioning and directed assembly of semiconductor nanowires (NWs) is considerable current interest for “bottom-up” approaches to the engineering intricate structures from nanoscale building blocks. We report a horizontal growth mode ZnO NWs on (112¯0) sapphire surface in which grow [11¯00]sap direction. This strictly depends size spacing Au nanodroplet catalysts competes with vertical NWs. An approach presented promotes growth, situ alignment, predictable strategy allows large scale...

For environmental studies assessing uptake of orally ingested engineered nanoparticles (ENPs), a key step in ensuring accurate quantification ENPs is efficient separation the organism from that are either nonspecifically adsorbed to and/or suspended dispersion following exposure. Here, we measure 30 and 60 nm gold (AuNPs) by nematode, Caenorhabditis elegans, using sucrose density gradient centrifugation protocol remove noningested AuNPs. Both conventional inductively coupled plasma mass...

We report a bright fin light-emitting diode pixel that with increasing electrical current flux, can switch to laser.

Although optical lithography is suited for producing intricate architectures, its combination with "bottom-up" approaches becomes a very challenging issue. The challenge to electrically address the coordinates of millions nanoparticles (e.g., nanowires) on given surface. Here, we describe method that controls registries horizontally grown nanowires (NWs) and advances current state-of-the-art NW device assembly technology. In this architecture, NWs are where nanodevices will later be...

A study on the electron relaxation dynamics and thermal cooling of colloidal gold nanoparticles (see Figure) in air water finds that local energy exchange with surrounding medium occurs picosecond time scale, comparable electron–phonon relaxation, while a slow heat dissipation by ensures particles remain heated for hundreds picoseconds.

Growth habits and defects in epitaxial ZnO nanowires grown from Au catalyst on (00.1) GaN/sapphire substrate using the vapor-liquid-solid (VLS) technique were studied electron microscopy x-ray diffraction. The results revealed presence of both horizontal (crawling-like) vertical having similar orientation relationship to (00.1)ZnO‖(00.1)GaN, [11.0]ZnO‖[11.0]GaN. crawling-like growth precedes growth, coalescence overgrowth crawling produce a highly defective layer which separates nanorods....

We report a surface-directed vapor-liquid-solid process for planar growth of one-dimensional heterojunctions zinc oxide on single crystal gallium nitride (GaN) that enables their hierarchical assembly to light emitting diodes. An individual heterojunction is about 10 μm in length and 80 nm width formed by an n-type ZnO nanowire or nanowall p-type GaN surface using Au catalyst. Our results show nanocrystal at its nucleation site has six possible directions can be engineered controlled...

This study examines the role of microstructure and optical properties InGaN/GaN nanowire LED structures on Si(111) having different coverages. Cathodoluminescence (CL) measurements show that all samples exhibit broad emission around intended energy, 1.95 eV (635 nm). While absolute intensity is hard to compare for CL measurement, bandgap (∼3.4 eV) coming from GaN root more pronounced as coverage nanowires decreases, which has less coalescence formation. The width peak likely due variations...

ZnO nanowires (NWs) are grown on a bulk copper half-transmission electron microscopy grid by chemical vapor deposition in high temperature tube furnace. Photoluminescence (PL) revealed band gap emission at 380 nm and more intense visible around 520 due to defect states these NWs. High-resolution transmission shows that the NWs single crystalline with hexagonal structure. Auger spectroscopy (AES) energy dispersive X-ray reveal atoms present along length of NW. AES also found surface is oxygen...

Abstract In this paper, we summarize our results on the effect of changing size and shape semiconductor metallic nanocrystals. The change in (from 3.5 to 1.1 nm) spherical rod) CdSe nanocrystals is found affect both their optical nonradiative properties. gold quasi-spherical nanocrystals, dependence electron-phonon relaxation surrounding medium are presented. For nanorods, conclusions mechanism self-assembly Enhanced Raman scattering surfaces studied compared with that particle surfaces.

In metal-catalyzed horizontal growth of nanowires, our results show that the lattice match with substrate exists along width nanowire and not its length. This finding is in contrast what has been observed traditional planar nanowires could be used for fine tuning structure at nanoscale.

Recently, we showed large-scale fabrication of field-effect transistors from horizontal ZnO nanowires (NWs) on a-plane sapphire. Here, in examining the cross sections such nanodevices, use high-resolution transmission electron microscopy (HRTEM) and large-angle, convergent-beam diffraction (LACBED). We show how horizontally grown NWs influence their underlying sapphire surface substrate influences growth directionality NWs. As a NW grows sapphire, experiences compressive strain ≈7% its...