15 research outputs found
Facile One-Step Photochemical Fabrication and Characterization of an Ultrathin Gold-Decorated Single Glass Nanopipette
The
inner surface of a conical glass nanopipette was modified with
ultrathin gold film by a facile one-step photochemical approach, using
HAuCl<sub>4</sub> and ethanol as common reagents with the aid of UV
irradiation. The method is simple, straightforward, time-saving, and
environmentally friendly. The morphology and component of the as-prepared
ultrathin gold film was thoroughly characterized by transmission electron
microscopy (TEM), energy-dispersive X-ray (EDX) analysis, and X-ray
photoelectron spectroscopy (XPS). The mechanism of the gold film growth
was briefly discussed. Other small photochemical reagents with a hydroxy
group, e.g., ethylene glycol, methanol, and glucose, may also work
but with a different rate of reaction. The facile ultrathin gold decoration
of a single glass nanopipette renders the glass nanopipette-based
nanopore platform very easy for surface chemical modifications and
potential sensing applications. The success of the gold decoration
on the inner surface of the glass nanopore was further confirmed electrochemically
by surface modification of a small thiol molecule (cysteine), and
the pH (surface charge)-dependent ionic current rectification behaviors
through the nanopore were investigated. Due to its facile preparation,
the method and the Au-decorated glass nanopore would find promising
and extended applications in ultrasensitive detection and biosensing
Wet-Chemical Enzymatic Preparation and Characterization of Ultrathin Gold-Decorated Single Glass Nanopore
The conical glass nanopore was modified
through layer-by-layer
electrostatic deposition of a monolayer of glucose oxidase, and then
an ultrathin gold film was formed <i>in situ</i> through
enzyme-catalyzed reactions. The morphology and components of single
glass nanopore before and after ultrathin Au deposition were characterized
by transmission electron microscopy (TEM) and energy-dispersive X-ray
(EDX) analysis, respectively. In particular, the quenching of the
quantum dots fluorescence in the nanopore tip zone further illustrated
that the gold nanofilm was successfully deposited on the inner wall
of the single glass nanopore. The Au thin films make the glass nanopores
more biologically friendly and allow the nanopores facile functionalization
of the surface through the AuāS bonds. For instance, the ionic
current rectification (ICR) properties of the gold-decorated glass
nanopores could be switched readily at different pHs by introducing
different thiol molecules
High-Efficiency Plasmon-Enhanced and Graphene-Supported Semiconductor/Metal CoreāSatellite Hetero-Nanocrystal Photocatalysts for Visible-Light Dye Photodegradation and H<sub>2</sub> Production from Water
Solar-driven photocatalytic process
based on electronāhole
pair production in semiconductors is a long sought-after solution
to a green and renewable energy and has attracted a renaissance of
interest recently. The relatively low photocatalytic efficiency, however,
is a main obstacle to their practical applications. A promising attempt
to solve this problem is by combined use of metal nanoparticles, by
taking advantage of strong and localized plasmonic near-field to enhance
solar absorption and to increase the electronāhole pair generation
rate at the surface of semiconductor. Here, we report a semiconductor/metal
visible-light photocatalyst based on CdSe/CdS-Au (QD-Au) coreāsatellite
heteronanocrystals, and assemble them on graphene nanosheets for better
photocatalytic reaction. The as-synthesized photocatalyst exhibits
excellent plasmon-enhanced photocatalytic activities toward both photodegradation
of organic dye and visible-light H<sub>2</sub> generation from water.
The H<sub>2</sub> evolution rate achieves a maximum of 3113 Ī¼mol
h<sup>ā1</sup> g<sup>ā1</sup> for the heteronanocrystal-graphene
composites, which is about 155% enhancement compared to nonplasmonic
QD-G sample and 340% enhancement compared to control QD-Au-G sample,
and the apparent quantum efficiency (QE) reaches to 25.4% at wavelength
of 450 nm
Significantly Enhancing Supercapacitive Performance of Nitrogen-doped Graphene Nanosheet Electrodes by Phosphoric Acid Activation
In this work, we present a new method
to synthesize the phosphorus,
nitrogen contained graphene nanosheets, which uses dicyandiamide to
prevent the aggregation of graphene oxide and act as the nitrogen
precursor, and phosphoric acid (H<sub>3</sub>PO<sub>4</sub>) as the
activation reagent. We have found that through the H<sub>3</sub>PO<sub>4</sub> activation, the samples exhibit the remarkably enhanced supercapacitive
performance, and depending on the amount of H<sub>3</sub>PO<sub>4</sub> introduced, the specific capacitance of the samples is gradually
increased from 7.6 to 244.6 F g<sup>ā1</sup>. Meanwhile, the
samples also exhibit the good rate capability and excellent stability
(up to 10ā000 cycles). Through the transmission electron microscopy,
high-resolution transmission electron microscopy, X-ray diffraction,
X-ray photoelectron spectroscopy and BrunauerāEmmettāTeller
analyses, H<sub>3</sub>PO<sub>4</sub> treatment induced large pore
volume and phosphorus related function groups in the product are assumed
to response for the enhancement
Controllable Shrinking of Glass Capillary Nanopores Down to sub-10 nm by Wet-Chemical Silanization for Signal-Enhanced DNA Translocation
Diameter is a major
concern for nanopore based sensing. However,
directly pulling glass capillary nanopore with diameter down to sub-10
nm is very difficult. So, post treatment is sometimes necessary. Herein,
we demonstrate a facile and effective wet-chemical method to shrink
the diameter of glass capillary nanopore from several tens of nanometers
to sub-10 nm by disodium silicate hydrolysis. Its benefits for DNA
translocation are investigated. The shrinking of glass capillary nanopore
not only slows down DNA translocation, but also enhances DNA translocation
signal and signal-to-noise ratio significantly (102.9 for 6.4 nm glass
nanopore, superior than 15 for a 3 nm silicon nitride nanopore). It
also affects DNA translocation behaviors, making the approach and
glass capillary nanopore platform promising for DNA translocation
studies
Smart Plasmonic Glucose Nanosensors as Generic Theranostic Agents for Targeting-Free Cancer Cell Screening and Killing
Fast
and accurate identification of cancer cells from healthy normal
cells in a simple, generic way is very crucial for early cancer detection
and treatment. Although functional nanoparticles, like fluorescent
quantum dots and plasmonic Au nanoparticles (NPs), have been successfully
applied for cancer cell imaging and photothermal therapy, they suffer
from the main drawback of needing time-consuming targeting preparation
for specific cancer cell detection and selective ablation. The lack
of a generic and effective method therefore limits their potential
high-throughput cancer cell preliminary screening and theranostic
applications. We report herein a generic in vitro method for fast, <i>targeting-free</i> (avoiding time-consuming preparations of
targeting moiety for specific cancer cells) visual screening and selective
killing of cancer cells from normal cells, by using glucose-responsive/-sensitive
glucose oxidase-modified Ag/Au nanoshells (Ag/Au-GOx NSs) as a smart
plasmonic theranostic agent. The method is generic to some extent
since it is based on the distinct localized surface plasmon resonance
(LSPR) responses (and colors) of the smart nanoprobe with cancer cells
(typically have a higher glucose uptake level) and normal cells
Free-Standing Monolayered Metallic Nanoparticle Networks as Building Blocks for Plasmonic Nanoelectronic Junctions
The effective coupling of optical
surface plasmons (SPs) and electron transport in a plasmonic-electronic
device is one of the fundamental issues in nanoelectronics and the
emerging field of plasmonics, and offer promise in providing a solution
to next generation nanocircuits in which all coupling is in the near
field. Attempts toward this end, however, are limited because of the
integration challenge to compatible nanodevices. To date, direct electrical
detection of SP-electron coupling from metallic nanostructures alone
are not reported, and thus it remains a great experimental challenge.
In this paper, we succeed in preparing a new suspended-film-type nanoelectronic
junction, in which free-standing 2D fractal nanoparticle networks
act as plasmonically active nanocomponents. Direct electrical detection
of optical collective SPs was evidenced by photocurrent response of
the junction upon illumination. Room-temperature <i>I</i>ā<i>V</i> characteristics, differing from nonlinear
to Ohmic behaviors, are found to be sensitive to the nanometer-scale
morphology changes of the nanomembranes. The finding and approach
may enable the development of advanced plasmonic nanocircuits and
new nanoelectronics, nanophotonics, and (solar) energy applications
Synthesis of Monodisperse Plasmonic Au CoreāPt Shell Concave Nanocubes with Superior Catalytic and Electrocatalytic Activity
This
work describes a facile and effective method for synthesis
of concave Au@Pt nanocubes via a galvanic replacement process using
preformed Au@Ag truncated nanocubes as templates. We found that the
as-prepared concave Au@Pt nanocubes exhibit a unique plasmonic optical
property and catalytic activity higher than that of a commercial Pt
black catalyst in the catalytic reduction of <i>p</i>-nitrophenol
into <i>p</i>-aminophenol by NaBH<sub>4</sub>, and more
importantly, the as-prepared concave Au@Pt nanocubes exhibit significantly
higher electrocatalytic activity and greater durability for the ethanol
oxidation reaction in alkaline media than commercial Pt black. The
as-synthesized plasmonic Au coreāPt shell nanocubes, because
of their well-defined concave coreāshell nanostructure and
high level of electrocatalytic performance, may find promising potential
applications in various fields, such as ethanol fuel cells
Graphene Oxide-Supported Ag Nanoplates as LSPR Tunable and Reproducible Substrates for SERS Applications with Optimized Sensitivity
Nanoparticles and nanohybrids with
well-defined structures, along with tunable localized surface plasmon
resonance (LSPR) properties and optimized sensitivity, are crucial
and highly desired for surface-enhanced Raman spectroscopy (SERS)
applications. In this article, we report on a very promising and flexible
SERS platforms with a tunable LSPR response and sensitivity based
on Ag nanoplates and graphene oxide (GO). The SERS detection sensitivity
can be easily optimized and significantly improved by fine-tuning
the LSPR band of the Ag nanoplate/GO substrates (to enhance the SERS
response) during sample preparation. We applied the as-prepared SERS
platform for sensitive SERS detection of 4-mercaptobenzoic acid and
4-aminothiophenol and found that the SERS signal varied markedly (by ā¼10ā15-fold)
with the fine-tuning of the LSPR band. The SERS enhancement factor
of the Ag nanoplate/GO complexes was more than 10<sup>4</sup> times
larger than that obtained using spherical Ag nanoparticles. The as-prepared
Ag nanoplate/GO platforms, because of their excellent stability and
tunable LSPR properties, will find promising practical SERS applications
In Situ Nanoplasmonic Probing of Enzymatic Activity of Monolayer-Confined Glucose Oxidase on Colloidal Nanoparticles
In
situ probing proteināparticle interactions and activities
of proteins on colloidal nanoparticle (NP) surfaces is a long-standing
key challenge in understanding the nanobio interfaces and virtually
important for a variety of biological and biomedical applications.
The interactions of NPs with proteins, for instance, are known to
form NP bioconjugates or protein coronas; protein surface immobilization
and molecular layer-by-layer deposition techniques are widely used,
but a clear understanding of the confinement effect on protein activity
by molecular coating, at the monolayer level, remains poorly understood.
We explore here a novel approach, using colloidal plasmonic nanocomplexes
coated with glucose oxidase (GOx) as self-sensing nanoprobes for in
situ optical probing of surface-confined enzymatic activity, which
is at least 1ā2 orders of magnitude more sensitive than standard
colorimetric assays for detecting GOx activity. We found that enzymatic
activity of monolayer-confined GOx on colloidal NPs was significantly
enhanced as compared with free GOx (also proved by conformational
changes from circular dichroism studies), with a low apparent MichaelisāMenten
constant <i>K</i><sub>m</sub> of ā¼0.115 mM and high
turnover <i>k</i><sub>cat</sub>/<i>K</i><sub>m</sub> of ā¼8394 M<sup>ā1</sup>Ā·s<sup>ā1</sup>; compared with the āanchored-typeā suspending GOx,
the outmost polyelectrolyte monolayer-protected āsandwiched-typeā
GOx exhibits significantly improved enzymatic activities toward higher
temperatures and wider pH range. This finding is of fundamental important
and instructive for safe use of such nanomaterials for bioapplications