5 research outputs found
Media 1: Parallel Raman microspectroscopy using programmable multipoint illumination
Originally published in Optics Letters on 15 April 2012 (ol-37-8-1289
Media 2: Parallel Raman microspectroscopy using programmable multipoint illumination
Originally published in Optics Letters on 15 April 2012 (ol-37-8-1289
EBL-Based Fabrication and Different Modeling Approaches for Nanoporous Gold Nanodisks
We report electron
beam lithography (EBL) based fabrication and
different modeling techniques for disk-shaped nanoporous gold nanoparticles
(NPG disk). The EBL technique can provide large area 2D patterns of
regularly or randomly distributed nanodisks with narrow size distribution
and flexible interdisk (center to center) distance. Such flexibility
is essential to obtain quasi-single NPG disk response, which typically
peaks in the near-infrared (NIR) spectrum beyond 1 ÎĽm, from
ensemble measurements by common UV/vis/NIR spectrometers instead of
a specialized NIR spectroscopic microscope. NPG disks of 200 to 500
nm diameter and 50 nm thickness have been fabricated and characterized.
To model the NPG disk and calculate its plasmonic properties, two
different modeling approaches have been developed. A model based on
the Bruggeman effective medium theory (B-EMT model) requires little
information about the nanoporous structure. In contrast, the nanoporous
model (NP model) retains the essential nanoporous structural features
of NPG disk. To evaluate the performance of these models, simulated
extinction spectra have been compared to the experimental data. Both
the B-EMT and NP models perform well to estimate the far-field plasmon
resonance peak position. However, to obtain the accurate information
about the plasmon peak width/plasmon lifetime and near-field plasmonic
hot-spots formation within the nanopores, the NP model is essential
since the B-EMT model lacks the nanoporous network
Nanoporous Gold Disks Functionalized with Stabilized G‑Quadruplex Moieties for Sensing Small Molecules
We
report label-free small molecule sensing on nanoporous gold disks
functionalized with stabilized Guanine-quadruplex (G4) moieties using
surface-enhanced Raman spectroscopy (SERS). By utilizing the unique
G4 topological structure, target molecules can be selectively captured
onto nanoporous gold (NPG) disk surfaces via π–π
stacking and electrostatic attractions. Together with high-density
plasmonic “hot spots” of NPG disks, the captured molecules
produce a remarkable SERS signal. Our strategy represents the first
example of the detection of foreign molecules conjugated to nondouble
helical DNA nanostructures using SERS while providing a new technique
for studying the formation and evolution of G4 moieties. The molecular
specificity of G4 is known to be controlled by its unit sequence.
Without losing generality, we have selected dÂ(GGT)<sub>7</sub>GG sequence
for the sensing of malachite green (MG), a known carcinogen frequently
abused illegally in aquaculture. The newly developed technique achieved
a lowest detectable concentration at an impressive 50 pM, two orders
of magnitude lower than the European Union (EU) regulatory requirement,
with high specificity against potential interferents. To demonstrate
the translational potential of this technology, we achieved a lowest
detectable concentration of 5.0 nM, meeting the EU regulatory requirement,
using a portable probe based detection system
Gold Nanoshell-Decorated Silicone Surfaces for the Near-Infrared (NIR) Photothermal Destruction of the Pathogenic Bacterium E. faecalis
Catheter-related infections (CRIs)
are associated with the formation of pathogenic biofilms on the surfaces
of silicone catheters, which are ubiquitous in medicine. These biofilms
provide protection against antimicrobial agents and facilitate the
development of bacterial resistance to antibiotics. The application
of photothermal agents on catheter surfaces is an innovative approach
to overcoming biofilm-generated CRIs. Gold nanoshells (AuNSs) represent
a promising photothermal tool, because they can be used to generate
heat upon exposure to near-infrared (NIR) radiation, are biologically
inert at physiological temperatures, and can be engineered for the
photothermal ablation of cells and tissue. In this study, AuNSs functionalized
with carboxylate-terminated organosulfur ligands were attached to
model catheter surfaces and tested for their effectiveness at killing
adhered Enterococcus faecalis (E. faecalis) bacteria. The morphology of the AuNSs
was characterized by scanning electron microscopy (SEM) and transmission
electron microscopy (TEM), while the elemental composition was characterized
by energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron
spectroscopy (XPS). Furthermore, optical and photothermal properties
were acquired by ultraviolet–visible (UV-vis) spectroscopy
and thermographic imaging with an infrared camera, respectively. Bacterial
survival studies on AuNS-modified surfaces irradiated with and without
NIR light were evaluated using a colony-formation assay. These studies
demonstrated that AuNS-modified surfaces, when illuminated with NIR
light, can effectively kill E. faecalis on silicone surfaces