10 research outputs found
Fabrication of Novel Magnetic Nanoparticles of Multifunctionality for Water Decontamination
Efficient
and powerful water purifiers are in increasing need because
we are facing a more and more serious problem of water pollution.
Here, we demonstrate the design of versatile magnetic nanoadsorbents
(M-QAC) that exhibit excellent disinfection and adsorption performances
at the same time. The M-QAC is constructed by a Fe<sub>3</sub>O<sub>4</sub> core surrounded by a polyethylenimine-derived corona. When
dispersed in water, the M-QAC particles are able to interact simultaneously
with multiple contaminants, including pathogens and heavy metallic
cations and anions, in minutes. Subsequently, the M-QACs along with
those contaminants can be easily removed and recollected by using
a magnet. Meanwhile, the mechanisms of disinfection are investigated
by using TEM and SEM, and the adsorption mechanisms are analyzed by
XPS. In a practical application, M-QACs are applied to polluted river
water 8000-fold greater in mass, producing clean water with the concentrations
of all major pollutants below the drinking water standard of China. The adsorption ability
of M-QAC could be regenerated for continuous use in a facile manner.
With more virtues, such as low-cost fabrication and easy scaling up,
the M-QAC have been shown to be a very promising multifunctional water
purifier with rational design and to have great potential for real
water purification applications
Interaction between Organic Compounds and Catalyst Steers the Oxidation Pathway and Mechanism in the Iron Oxide-Based Heterogeneous Fenton System
In the past decades, extensive efforts have been devoted
to the
mechanistic understanding of various heterogeneous Fenton reactions.
Nevertheless, controversy still remains on the oxidation mechanism/pathway
toward different organic compounds in the classical iron oxide-based
Fenton reaction, largely because the role of the interaction between
the organic compounds and the catalyst has been scarcely considered.
Here, we revisited the classic heterogeneous ferrihydrite (Fhy)/H2O2 system toward different organic compounds on
the basis of a series of degradation experiments, alcohol quenching
experiments, theoretical modeling, and intermediate analysis. The
Fhy/H2O2 system exhibited highly selective oxidation
toward the group of compounds that bear carboxyl groups, which tend
to complex with the surface Fe(III) sites of the Fhy catalyst.
Such interaction results in a nonradical inner sphere electron transfer
process, which seizes one electron from the target compound and features
negligible inhibition by the radical quencher. In contrast, for the
oxidation of organic compounds that could not complex with the catalyst,
the traditional HO· process makes the main contribution,
which proceeds via hydroxyl addition reaction and could be readily
suppressed by the radical quencher. This study implies that the interaction
between the organic compounds and the catalyst plays a decisive role
in the oxidation pathway and mechanism of the target compounds and
provides a holistic understanding on the iron oxide-based heterogeneous
Fenton system
Structure Evolution of Iron (Hydr)oxides under Nanoconfinement and Its Implication for Water Treatment
In the development of nanoenabled technologies for large-scale
water treatment, immobilizing nanosized functional materials into
the confined space of suitable substrates is one of the most effective
strategies. However, the intrinsic effects of nanoconfinement on the
decontamination performance of nanomaterials, particularly in terms
of structural modulation, are rarely unveiled. Herein, we investigate
the structure evolution and decontamination performance of iron (hydr)Âoxide
nanoparticles, a widely used material for water treatment, when confined
in track-etched (TE) membranes with channel sizes varying from 200
to 20 nm. Nanoconfinement drives phase transformation from ferrihydrite
to goethite, rather than to hematite occurring in bulk systems, and
the increase in the nanoconfinement degree from 200 to 20 nm leads
to a significant drop in the fraction of the goethite phase within
the aged products (from 41% to 0%). The nanoconfinement configuration
is believed to greatly slow down the phase transformation kinetics,
thereby preserving the specific adsorption of ferrihydrite toward
AsÂ(V) even after 20-day aging at 343 K. This study unravels the structure
evolution of confined iron hydroxide nanoparticles and provides new
insights into the temporospatial effects of nanoconfinement on improving
the water decontamination performance
Fluorous Cylindrical Micelles of Controlled Length by Crystallization-Driven Self-Assembly of Block Copolymers in Fluorinated Media
Fluorous solvents have recently found
broad applications in medical
treatments as well as catalytic transformations, yet the controlled
self-assembly of nanomaterials in fluorinated media has remained a
challenge. Herein, we report the synthesis of block copolymers containing
a crystalline polyferrocenylsilane metalloblock and a highly fluorinated
coil block and their controlled self-assembly in fluorinated media.
Using the crystallization-driven self-assembly approach, cylindrical
micelles have been prepared with controlled lengths and narrow length
polydispersities by self-seeding. Finally, by partial functionalization
of these block copolymers with fluorescent dye molecules, we show
that well-defined, functional nanomaterials can be obtained in the
fluorous phase
Polyferrocenylsilane Crystals in Nanoconfinement: Fragmentation, Dissolution, and Regrowth of Cylindrical Block Copolymer Micelles with a Crystalline Core
Two samples of rod-like micelles in decane were prepared
by seeded
growth from a sample of a polyÂ(isoprene-<i>b</i>-ferrocenyldimethylsilane)
diblock copolymer (PI<sub>1000</sub>âPFS<sub>50</sub>, where
the subscripts indicate the degree of polymerization). These micelles
were uniform in length with a mass/length of 1.9 molecules/nm. The
longer micelles (L-1250) had a number-average length <i>L</i><sub>n</sub> = 1243 nm, whereas the shorter micelles (L-250) had <i>L</i><sub>n</sub> = 256 nm. We used transmission electron microscopy
(TEM) to examine the behavior of these micelles when dilute solutions
of L-1250 or L-250 or their mixtures were heated at temperatures ranging
from 40 to 75 °C and then cooled to room temperature. At 55 °C,
the L-1250 sample underwent kinetically controlled fragmentation to
give a broad distribution of micelle lengths. At this temperature,
fragmentation was much less prominent in the L-250 sample. At higher
temperatures, micelles with narrow distributions of lengths were obtained
in each case (<i>L</i><sub>w</sub>/<i>L</i><sub>n</sub> â 1.01). This process operates under thermodynamic
control, and <i>L</i><sub>n</sub> values increased strongly
with an increase in temperature. These results indicate that the micelles
fragment, and polymer molecules dissolve, as the samples were heated.
The fraction of surviving fragments decreased significantly at elevated
temperatures, presumably reflecting a distribution of crystallinity
in the cores of the micelle precursor. When the solutions were cooled,
the surviving fragments served as seeds for the epitaxial growth of
the micelles as the polymer solubility decreased. The most striking
result of these experiments was the finding that fragments formed
from the L-1250 micelles had a distribution of dissolution temperatures
shifted by about 5 °C to higher temperature than the shorter
L-250 micelles
Highly Efficient Water Decontamination by Using Sub-10 nm FeOOH Confined within Millimeter-Sized Mesoporous Polystyrene Beads
Millimeter-sized
polymer-based FeOOH nanoparticles (NPs) provide
a promising option to overcome the bottlenecks of direct use of NPs
in scaled-up water purification, and decreasing the NP size below
10 nm is expected to improve the decontamination efficiency of the
polymeric nanocomposites due to the size and surface effect. However,
it is still challenging to control the dwelled FeOOH NP sizes to sub-10
nm, mainly due to the wide pore size distribution of the currently
available polymeric hosts. Herein, we synthesized mesoporous polystyrene
beads (MesoPS) via flash freezing to assemble FeOOH NPs. The embedded
NPs feature with α-crystal form, tunable size ranging from 7.3
to 2.0 nm and narrow size distribution. Adsorption of AsÂ(III/V) by
the resultant nanocomposites was greatly enhanced over the α-FeOOH
NPs of 18 Ă 60 nm, with the iron mass normalized capacity of
AsÂ(V) increasing to 10.3 to 14.8 fold over the bulky NPs. Higher density
of the surface hydroxyl groups of the embedded NPs as well as their
stronger affinity toward AsÂ(V) was proved to contribute to such favorable
effect. Additionally, the as-obtained nanocomposites could be efficiently
regenerated for cyclic runs. We believe this study will shed new light
on how to fabricate highly efficient nanocomposites for water decontamination
Evolving Role of Ca<sup>2+</sup> on the Long-Term Phosphate Adsorption-Regeneration Performance of Nanoconfined Hydrated Lanthanum Oxides: Short-Term Enhancement and Long-Term Inhibition
Phosphorus (P) advanced treatment
by adsorption reduces the risk
of eutrophication in natural waters and reservoirs. The impact of
ubiquitous Ca2+ on long-term P removal is critical in assessing
the regeneration efficiency of one adsorbent, which is a vital indicator
for cost-effectiveness. Given the critical role of lanthanum (La)-based
composite materials in P removal, in this study, we unravel the long-term
evolving role of Ca2+ on phosphate removal by nanosized
hydrated lanthanum oxides (HLO) confined in cross-linked polystyrene
beads (HLO@201) over 20 adsorption-regeneration cycles and fixed-bed
column runs, with a combination of macroscopic adsorption experiments,
microscopic structural investigation, and theoretical calculations.
The role of Ca2+ gradually evolves from positive (5â70%
higher than Ca2+-free group) to negative (18â41%
lower than the Ca2+-free group) with ongoing cyclic runs
of HLO@201, which is distinctive from the bulky HLO. The presence
of Ca2+ enhances P uptake by HLO@201 possibly through LaâPâCaâP
multiple complexation and CaâP precipitation (i.e., hydroxyapatite,
HAP) inside the polymeric host, which creates an antagonistic effect
with HLO over time. The formed CaâP precipitates may accumulate
and encapsulate on the surface of HLO nanoparticles, which induce
the formation of irreversible LaPO4·xH2O under nanoconfinement that deplete the active adsorptive
sites. A two-step (acid wash + NaOH) regeneration method can partially
recover the P removal performance of HLO@201. We envision that this
study could be a cautionary tale for advanced treatment of P by adsorption,
to inspire re-evaluation on the long-term performance of adsorption
processes
Effective Drug Carrier Based on Polyethylenimine-Functionalized Bacterial Cellulose with Controllable Release Properties
The
development of low-cost biological materials with controlled
drug release profile is of great importance but challenging in pharmaceutical
industry. Recently, bacterial cellulose nanofibers have provoked intensive
research interests in tissue engineering and the pharmaceutical science
due to their stability, availability, sustainability, and low toxicity.
Here we describe the development of a PEI (polyethylenimine)-grafted
bacterial cellulose (BC) as an efficient drug delivery system. The
PEI-BC aerogels were characterized by scanning electron microscopy,
Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy,
thermogravimetric analysis, and zeta potential measurements. The optimum
sample exhibited enhanced mechanical strength, remarkable adsorption
capacity toward aspirin, BSA, and gentamicin, prolonged and pH-dependent
drug release, and low cytotoxicity. Our work has presented a rational
structure design from biomass for controllable drug carrier
Uniform, High Aspect Ratio Fiber-like Micelles and Block Co-micelles with a Crystalline ÏâConjugated Polythiophene Core by Self-Seeding
Monodisperse fiber-like micelles
with a crystalline Ï-conjugated
polyÂthiophene core with lengths up to ca. 700 nm were successfully
prepared from the diblock coÂpolymer polyÂ(3-hexylÂthiophene)-<i>block</i>-polyÂstyrene using a one-dimensional self-seeding
technique. Addition of a polyÂthiophene block coÂpolymer
with a different corona-forming block to the resulting nanofibers
led to the formation of segmented B-A-B triblock co-micelles by crystallization-driven
seeded growth. The key to these advances appears to be the formation
of a relatively defect-free crystalline micelle core under the self-seeding
conditions
A High-Sensitivity Lanthanide Nanoparticle Reporter for Mass Cytometry: Tests on Microgels as a Proxy for Cells
This paper addresses the question
of whether one can use lanthanide
nanoparticles (e.g., NaHoF<sub>4</sub>) to detect surface biomarkers
expressed at low levels by mass cytometry. To avoid many of the complications
of experiments on live or fixed cells, we carried out proof-of-concept
experiments using aqueous microgels with a diameter on the order of
700 nm as a proxy for cells. These microgels were used to test whether
nanoparticle (NP) reagents would allow the detection of as few as
100 proteins per âcellâ in cell-by-cell assays. Streptavidin
(SAv), which served as the model biomarker, was attached to the microgel
in two different ways. Covalent coupling to surface carboxyls of the
microgel led to large numbers (>10<sup>4</sup>) of proteins per
microgel,
whereas biotinylation of the microgel followed by exposure to SAv
led to much smaller numbers of SAv per microgel. Using mass cytometry,
we compared two biotin-containing reagents, which recognized and bound
to the SAvs on the microgel. One was a metal chelating polymer (MCP),
a biotin end-capped polyaspartamide containing 50 Tb<sup>3+</sup> ions
per probe. The other was a biotinylated NaHoF<sub>4</sub> NP containing
15â000 Ho atoms per probe. Nonspecific binding was determined
with bovine serum albumin (BSA) conjugated microgels. The MCP was
effective at detecting and quantifying SAvs on the microgel with covalently
bound SAv (20â000 SAvs per microgel) but was unable to give
a meaningful signal above that of the BSA-coated microgel for the
samples with low levels of SAv. Here the NP reagent gave a signal
2 orders of magnitude stronger than that of the MCP and allowed detection
of NPs ranging from 100 to 500 per microgel. Sensitivity was limited
by the level of nonspecific adsorption. This proof of concept experiment
demonstrates the enhanced sensitivity possible with NP reagents in
cell-by-cell assays by mass cytometry