3 research outputs found
Facile Formation of Ordered Vertical Arrays by Droplet Evaporation of Au Nanorod Organic Solutions
Droplet
evaporation is a simple method to induce organization of Au nanorods
into ordered superstructures. In general, the self-assembly process
occurs by evaporation of aqueous suspensions under strictly controlled
experimental conditions. Here we present formation of large area ordered
vertical arrays by droplet evaporation of Au nanorod organic suspensions.
The uncontrolled (free air) evaporation of such suspensions yielded
to formation of ordered nanorod domains covering the entire area of
a 5 mm diameter droplet. Detailed investigation of the process revealed
that nanorods organized into highly ordered vertical domains at the
interface between solvent and air on a fast time scale (minutes).
The self-assembly process mainly depended on the initial concentration
of nanorod solution and required minimal control of other experimental
parameters. Nanorod arrays displayed distinct optical properties which
were analyzed by optical imaging and spectroscopy and compared to
results obtained from theoretical calculations. The potential use
of synthesized arrays as surface-enhanced Raman scattering probes
was demonstrated with the model molecule 4-aminobenzenthiol
Surface-Enhanced Raman Scattering of 4‑Aminobenzenethiol on Au Nanorod Ordered Arrays
A droplet
evaporation/stamping method was employed to fabricate
closely packed arrays of Au nanorods aligned parallel or perpendicular
to a support. The potential as SERS substrates was investigated using
model molecule 4-aminobenzenethiol (4-ABT), for which enhanced signals
where obtained compared to the signals of the bulk molecule. Enhancement
factors of the order of 10<sup>4</sup> and 10<sup>5</sup> were calculated
for parallel and perpendicular arrays, respectively. Quantitative
Raman detection of 4-ABT was obtained with detection limits in the
nM concentration range. Fabricated arrays displayed good stability
and uniformity, showing their potential as sensing platforms for plasmon-induced
optical molecular detection
Hot-Electron Injection in Au Nanorod–ZnO Nanowire Hybrid Device for Near-Infrared Photodetection
In this Letter, we present a new
class of near-infrared photodetectors
comprising Au nanorods–ZnO nanowire hybrid systems. Fabricated
hybrid FET devices showed a large photoresponse under radiation wavelengths
between 650 and 850 nm, accompanied by an “ultrafast”
transient with a time scale of 250 ms, more than 1 order of magnitude
faster than the ZnO response under radiation above band gap. The generated
photocurrent is ascribed to plasmonic-mediated generation of hot electrons
at the metal–semiconductor Schottky barrier. In the presented
architecture, Au-nanorod-localized surface plasmons were used as active
elements for generating and injecting hot electrons into the wide
band gap ZnO nanowire, functioning as a passive component for charge
collection. A detailed investigation of the hot electron generation
and injection processes is discussed to explain the improved and extended
performance of the hybrid device. The quantum efficiency measured
at 650 nm was calculated to be approximately 3%, more than 30 times
larger than values reported for equivalent metal/semiconductor planar
photodetectors. The presented work is extremely promising for further
development of novel miniaturized, tunable photodetectors and for
highly efficient plasmonic energy conversion devices