21 research outputs found
Non-Resonant Large Format Surface Enhanced Raman Scattering Substrates for Selective Detection and Quantification of Xylene Isomers
Non-Resonant Large Format Surface Enhanced Raman Scattering
Substrates for Selective Detection and Quantification of Xylene Isomer
Investigating Unexpected Magnetism of Mesoporous Silica-Supported Pd and PdO Nanoparticles
The synthesis and magnetic behavior
of matrix-supported Pd and
PdO nanoparticles (NPs) are described. Mesoporous silica with hexagonal
columnal packing is selected as a template, and the impregnation method
with thermal annealing is used to obtain supported Pd and PdO NPs.
The heating rate and the annealing conditions determine the particle
size and the phase of the NPs, with a fast heating rate of 30 °C/min
producing the largest supported Pd NPs. Unusual magnetic behaviors
are observed. (1) Contrary to the general belief that smaller Pd NPs
or cluster size particles have higher magnetization, matrix-supported
Pd NPs in this study maintain the highest magnetization with room
temperature ferromagnetism when the size is the largest. (2) Twin
boundaries along with stacking faults are more pronounced in these
large Pd NPs and are believed to be the reason for this high magnetization.
Similarly, supported PdO NPs were prepared under air conditions with
different heating rates. Their phase is tetragonal (P4<sub>2</sub>/mmc) with cell parameters of <i>a</i> = 3.050 Ă
and <i>c</i> = 5.344 Ă
, which are slightly larger than in the
bulk phase (<i>a</i> = 3.03 Ă
, <i>c</i> =
5.33 Ă
). Faster heating rate of 30 °C/min also produces
larger particles and larger magnetic hysteresis loop, although magnetization
is smaller and few twin boundaries are observed compared to the supported
metallic Pd NPs
Selective Magnetic Evolution of Mn<sub><i>x</i></sub>Fe<sub>1â<i>x</i></sub>O Nanoplates
Ironâmanganese
oxide (Mn<sub><i>x</i></sub>Fe<sub>1â<i>x</i></sub>O) nanoplates were prepared by the
thermal decomposition method. Irregular development of crystalline
phases was observed with the increase of annealing temperature. Magnetic
properties are in accordance with their respective crystalline phases,
and the selective magnetic evolution from their rich magnetism of
Mn<sub><i>x</i></sub>Fe<sub>1â<i>x</i></sub>O and MnFe<sub>2</sub>O<sub>4</sub> is achieved by controlling the
annealing conditions. Rock-salt structure of Mn<sub><i>x</i></sub>Fe<sub>1â<i>x</i></sub>O (space group <i>Fm</i>3Ì
<i>m</i>) is observed in as-synthesized
nanoplates, while MnFe<sub>2</sub>O<sub>4</sub> and Mn<sub><i>x</i></sub>Fe<sub>1â<i>x</i></sub>O with significant
magnetic interactions between them are observed at 380 °C. In
nanoplates annealed at 450 °C, soft ferrites of Mn<sub>0.48</sub>Fe<sub>2.52</sub>O<sub>4</sub> with Mn<sub><i>x</i></sub>Fe<sub>1â<i>x</i></sub>O are observed. It is assumed
that the differential and early development of crystalline phase of
Mn<sub><i>x</i></sub>Fe<sub>1â<i>x</i></sub>O and the inhomogeneous cation mixing between Mn and Fe cause this
rather extraordinary magnetic development. In particular, the prone
nature of divalent metal oxides to cation vacancy and the prolonged
annealing time of 15 h which enables ordering are also thought to
contribute to these irregularities
Compositing Polyetherimide with Polyfluorene Wrapped Carbon Nanotubes for Enhanced Interfacial Interaction and Conductivity
A novel approach to chemically functionalize
multiwalled carbon nanotubes (MWCNTs) for making superior polyetherimide
(PEI) nanocomposites with polyfluorene polymer is presented. In this
approach, MWCNTs are non-covalently functionalized with polyÂ(9,9-dioctyfluorenyl-2,7-diyl)
(PFO) through ÏâÏ stacking as confirmed by UV-vis,
fluorescence, and Raman spectra. Atomic force microscopy as well as
scanning and transmission electron microscopy shows the PFO coated
MWCNTs, which provides excellent dispersion of the latter in both
solvent and PEI matrix. The strong interaction of PFO with PEI chains,
as evidenced from fluorescence spectra, supports the good adhesion
of dispersed MWCNTs to PEI leading to stronger interfacial interactions.
As a result, the addition of as little as 0.25 wt % of modified MWCNTs
to PEI matrix can strongly improve the mechanical properties of the
composite (increase of 46% in storage modulus). Increasing the amount
of MWCNTs to 2.0 wt % (0.5 wt % PFO loading) affords a great increase
of 119% in storage modulus. Furthermore, a sharp decrease of 12 orders
of magnitude in volume resistivity of PEI composite is obtained with
only 0.5 wt % of PFO modified MWCNT
Histidineâdialkoxyanthracene dyad for selective and sensitive detection of mercury ions
<p>Histidine-dialkoxyanthracene (HDA) was synthesised as a turn off type fluorescent sensor for fast and sensitive detection of mercury ions (Hg<sup>2+</sup>) in aqueous media. The two histidine moieties act as âclawsâ to selectively complex Hg<sup>2+</sup>. The binding ratio of HDA to Hg<sup>2+</sup> was 1:1 (metal-to-ligand ratio). The association constant for Hg<sup>2+</sup> towards the receptor HDA obtained from BenesiâHildebrand plot was found to be 3.22Â ĂÂ 10<sup>4</sup>Â M<sup>â1</sup> with detection limit as low as 4.7Â nM (0.94Â ÎŒg/L).</p
Surface Modification of Multiwalled Carbon Nanotubes with Cationic Conjugated Polyelectrolytes: Fundamental Interactions and Intercalation into Conductive Poly(methyl methacrylate) Composites
This
research investigates the modification and dispersion and
of pristine multiwalled carbon nanotubes (MWCNTs) through a simple
solution mixing technique based on noncovalent interactions between
polyÂ(phenylene ethynylene)-based conjugated polyelectrolytes functionalized
with cationic imidazolium solubilizing groups (PIM-2 and PIM-4) and
MWCNTs. Spectroscopic studies demonstrated the ability of PIMs to
strongly interact with and efficiently disperse MWCNTs in different
solvents, mainly due to Ï interactions between the PIMs and
the MWCNTs. Transmission electron microscopy and atomic force microscopy
revealed the coating of the polyelectrolytes on the walls of the nanotubes.
Scanning electron microscopy (SEM) studies confirm the homogeneous
dispersion of PIM-modified MWCNTs in the polyÂ(methyl methacrylate)
(PMMA) matrix. The addition of 1 wt % PIM-modified MWCNTs to the matrix
has led to a significant decrease in DC resistivity of the composite
(13 orders of magnitude). The increase in electrical conductivity
and the improvement in the thermal and mechanical properties of the
membranes containing the PIM-modified MWCNTs is ascribed to the formation
of MWCNT networks and cross-linking sites that provided channels for
the electrons to move in throughout the matrix and reinforced the
interface between MWCNTs and PMMA
Colorimetric Peroxidase Mimetic Assay for Uranyl Detection in Sea Water
Uranyl (UO<sub>2</sub><sup>2+</sup>) is a form of uranium in aqueous
solution that represents the greatest risk to human health because
of its bioavailability. Different sensing techniques have been used
with very sensitive detection limits especially the recently reported
uranyl-specific DNAzymes systems. However, to the best of our knowledge,
few efficient detection methods have been reported for uranyl sensing
in seawater. Herein, gold nanoclusters (AuNCs) are employed in an
efficient spectroscopic method to detect uranyl ion (UO<sub>2</sub><sup>2+</sup>) with a detection limit of 1.86 ÎŒM. In the absence
of UO<sub>2</sub><sup>2+</sup>, the BSA-stabilized AuNCs (BSA-AuNCs)
showed an intrinsic peroxidase-like activity. In the presence of UO<sub>2</sub><sup>2+</sup>, this activity can be efficiently restrained.
The preliminary quenching mechanism and selectivity of UO<sub>2</sub><sup>2+</sup> was also investigated and compared with other ions.
This design strategy could be useful in understanding the binding
affinity of protein-stabilized AuNCs to UO<sub>2</sub><sup>2+</sup> and consequently prompt the recycling of UO<sub>2</sub><sup>2+</sup> from seawater
âLight-onâ Sensing of Antioxidants Using Gold Nanoclusters
Depletion
of intracellular antioxidants is linked to major cytotoxic
events and cellular disorders, such as oxidative stress and multiple
sclerosis. In addition to medical diagnosis, determining the concentration
of antioxidants in foodstuffs, food preservatives, and cosmetics has
proved to be very vital. Gold nanoclusters (Au-NCs) have a core size
below 2 nm and contain several metal atoms. They have interesting
photophysical properties, are readily functionalized, and are safe
to use in various biomedical applications. Herein, a simple and quantitative
spectroscopic method based on Au-NCs is developed to detect and image
antioxidants such as ascorbic acid. The sensing mechanism is based
on the fact that antioxidants can protect the fluorescence of Au-NCs
against quenching by highly reactive oxygen species. Our method shows
great accuracy when employed to detect the total antioxidant capacity
in commercial fruit juice. Moreover, confocal fluorescence microscopy
images of HeLa cells show that this approach can be successfully used
to image antioxidant levels in living cells. Finally, the potential
application of this âlight-onâ detection method in multiple
logic gate fabrication was discussed using the fluorescence intensity
of Au-NCs as output
Photoresponsive Bridged Silsesquioxane Nanoparticles with Tunable Morphology for Light-Triggered Plasmid DNA Delivery
Bridged silsesquioxane nanocomposites
with tunable morphologies
incorporating <i>o</i>-nitrophenyleneâammonium bridges
are described. The systematic screening of the solâgel parameters
allowed the material to reach the nanoscale with controlled dense
and hollow structures of 100â200 nm. The hybrid composition
of silsesquioxanes with 50% organic content homogeneously distributed
in the nanomaterials endowed them with photoresponsive properties.
Light irradiation was performed to reverse the surface charge of nanoparticles
from +46 to â39 mV via a photoreaction of the organic fragments
within the particles, as confirmed by spectroscopic monitorings. Furthermore,
such nanoparticles were applied for the first time for the on-demand
delivery of plasmid DNA in HeLa cancer cells via light actuation
Photoresponsive Bridged Silsesquioxane Nanoparticles with Tunable Morphology for Light-Triggered Plasmid DNA Delivery
Bridged silsesquioxane nanocomposites
with tunable morphologies
incorporating <i>o</i>-nitrophenyleneâammonium bridges
are described. The systematic screening of the solâgel parameters
allowed the material to reach the nanoscale with controlled dense
and hollow structures of 100â200 nm. The hybrid composition
of silsesquioxanes with 50% organic content homogeneously distributed
in the nanomaterials endowed them with photoresponsive properties.
Light irradiation was performed to reverse the surface charge of nanoparticles
from +46 to â39 mV via a photoreaction of the organic fragments
within the particles, as confirmed by spectroscopic monitorings. Furthermore,
such nanoparticles were applied for the first time for the on-demand
delivery of plasmid DNA in HeLa cancer cells via light actuation