Ultrasmall
noble metal nanoclusters (NCs; core size, <2 nm)
with a high surface atomic ratio and a tunable electronic structure
have attracted intensive interest; however, the controlled preparation
of stable metal NC assemblies is still a challenge. Here, star-like
diblock copolymer unimolecular micelles were used as a universal and
robust scaffold to synthesize ultrasmall metal NC assemblies with
a controlled size and amount of metal NCs (10–160). The size
of the NC assemblies can also be controlled by changing the length
of the P4VP block of the star-like polymers via atom transfer radical
polymerization. The thiolate ligands play an important role in the
control of the size of individual nanoclusters and largely enhance
the stability of the NC assemblies. The as-synthesized stable ultrasmall
metal NC assemblies will have broad application prospects in the fields
of catalysis, optics, and biomedicine.
Various
piezoelectric nanomaterials were utilized in ultrasound-mediated
atom transfer radical polymerization (ATRP), owing to their outstanding
piezoelectric effect. However, the relationship between the morphology
of those piezocatalysts and polymerization has not been clearly established.
Herein, we employed different piezoelectric zinc oxide (ZnO) nanomaterials
to achieve novel mechano-induced ATRP (mechano-ATRP). Based on the
synergistic effect of piezoelectric properties and specific surface
area, the catalytic activity of 1D ZnO nanorods (1D-ZnO NRs) with
increased aspect ratio outperformed that of 0D ZnO nanoparticles (0D-ZnO
NPs). Compared to the conventional ATRP system, this system exhibited
extraordinary activity toward the less activated monomer acrylonitrile
(67% conversion after 6 h), with a narrow molecular weight distribution
(polydispersity index ∼ 1.19). Furthermore, implications of
ZnO loading, copper salt amount, degree of polymerization, monomer,
and solvent were also studied for the highly efficient mechano-ATRP.
Although tremendous advancement regarding the highly stable metal halide perovskite nanocrystals (PNCs) has been achieved, previous studies were primarily focused on green light-emitting PNCs (i.e., bromine-based PNCs). The stability of chlorine-based PNCs with a violet or blue emission property was still lagging behind that of their bromine-based counterparts. Herein, a nondemanding and versatile strategy for in situ encapsulating allinorganic chlorine-based PNCs with multifold exceptionally high stabilities was presented. Wellordered mesoporous silica enabled the confined growth of PNCs in its pores followed by the porosity sealing by tetramethyl orthosilicate hydrolysis, thereby rendering full encapsulation of chlorine-based PNCs in dense silica that originated from high-temperature calcination. This judiciously designed structure imparted enclosed violet/blue emitting PNCs impart with outstanding long-term stability (>1.5 year) with high photoluminescence quantum yield (i.e., 30.4%) in pure water as the result of complete isolation of PNCs from detrimental stimuli, eventually leading to the application in the white light-emitting diode device.
A colloidal
nanocrystal cluster (CNC) is a hierarchical nanostructure
formed by clustering several nanocrystals into one nano-ensemble,
which may exhibit unique optical or catalytic properties different
from individual nanocrystals owing to the mutual interactions among
neighboring component nanocrystals. However, there is still no universal
synthetic route that could be applicable to diverse material compositions
with precisely controlled hierarchical structures (i.e., nanocrystal
number density, component nanocrystal size, and overall diameter of
the CNC) up to now. Herein, a general and novel synthetic strategy
was reported for crafting a wide range of inorganic CNCs (i.e., noble
metal, semiconductor, and metal oxide) via utilizing amphiphilic star-like
poly(4-vinylpyridine)-block-polystyrene diblock copolymers
as nanoreactors prepared by sequential atom transfer radical polymerization.
The hierarchical structure of rationally designed CNCs could be readily
tailored by varying the P4VP molecular weight of star-like nanoreactors
and the parameter optimization during the CNC preparation process,
which was inaccessible by conventional synthetic methods.
Highly ordered TiO2 nanotube arrays (TNTAs)
and their
heterostructure nanocomposites by structural engineering design were
utilized as heterogeneous photocatalysts for highly efficient broadband
photoinduced controlled radical polymerization (photoCRP), including
photoATRP and PET-RAFT. Highly efficient broadband UV–visible
light responsive photoCRP was achieved by combining the acceleration
effects of electron transfer derived from the distinctive highly ordered
nanotube structure of TNTAs and the localized surface plasmon resonance
(LSPR) effect combined with the formation of the Schottky barrier
via modification of Au nanoparticles. This polymerization system was
capable to polymerize acrylate and methacrylate monomers with high
conversion, “living” chain-ends, tightly regulated molecular
weights, and outstanding temporal control properties. The heterogeneous
nature of the photocatalysts enabled simple separation and effective
reusability in subsequent polymerizations. These results highlight
the modular design of highly efficient catalysts to optimize the controlled
radical polymerization process.
Herein, colloidal nanocrystal clusters (CNCs) formed from lignosulfonate (LS) and Ag nanoparticles (LS@ AgNPs) were prepared by in situ reduction, confined growth, and self-assembly methods. The LS micelles in solution served as a confined nano-reactor for the growth of AgNPs, and the phenolic hydroxyl groups in the structure provided complex sites as well as played a reducing role for the Ag ions. Following the addition of cetyltrimethyl ammonium bromide and anti-solvents, LS colloidal nanoparticles were achieved through self-assembly of LS micelles, and the AgNPs in the micelles entered the inner phase, forming the core@shell CNCs. However, the AgNPs in the CNCs were large in size (50 nm), few in number (<10 n/n), and unevenly distributed. The reason for this may be the low reduction ability of LS resulting in the loss of controlled growth of AgNPs in LS micelles. In contrast, the extra addition of a strong reducing agent significantly decreased the size of AgNPs and led to their more uniform distribution in the CNCs. Furthermore, LS@AgNPs CNCs showed good antibacterial activity, especially against Staphylococcus aureus (+). We expect these green, sustainable composite nanoparticles can be further applied in many other fields as well.
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