29 research outputs found
Reversible Thermochromic Perovskite-Based Dynamic Optical Encryption and Holographic Inference
Perovskites have attracted extensive attention in the
field of
nanophotonics with a plethora of applications owing to their high
optical constants, tunable band gap, solution processability, and
large optical tunability. In this work, we demonstrate perovskite-based
dynamic photonic devices for applications of optical encryption and
holographic inference by femtosecond laser patterning all-inorganic
mixed halide perovskite CsPbIBr2 with thermochromic features.
During one cycle of moisture and evaporation treatment, the CsPbIBr2 perovskite pattern undergoes a reversible conversion between
a bright red (high-T) phase and a colorless transparent (low-T) phase,
accompanied by significant optical state changes, resulting in on/off
functionality switch. At a low-T state, the encoded fluorescent or
holographic information is hidden, and the function of optical inference
is invalid. Conversely, at a high-T state, the encrypted information
is reconstructed, and the ability of holographic inference is reactivated.
Moreover, the perovskite photonic devices exhibit outstanding operating
stability after 10 repeated conversion cycles without prominent performance
degradation. Such perovskite photonic devices not only provide a novel
approach to realize dynamic control of the desired optical functions
but also have huge applicable potential for diverse optical applications,
such as optical encryption, optical anticounterfeiting, and optical
artificial intelligence
Construction of Polyelectrolyte-Responsive Microgels, and Polyelectrolyte Concentration and Chain Length-Dependent Adsorption Kinetics
We report on the construction of a polyelectrolyte-responsive system
evolved from sterically stabilized protonated polyÂ(2-vinylpyridine)
(P2VPH<sup>+</sup>) microgels. Negatively charged sodium dodecylbenzenesulfonate
(SDBS) surfactants could be readily internalized into the cationic
microgels by means of electrostatic interactions, resulting in microgel
collapse and concomitant formation of surfactant micellar domains
(P2VPH<sup>+</sup>/SDBS)-contained electrostatic complexes. These
internal hydrophobic domains conferred the opportunity of fluorescent
dyes to be loaded. The obtained fluorescent microgel complexes could
be further disintegrated in the presence of anionic polyelectrolyte,
polyÂ(sodium 4-styrenesulfonate) (PNaStS). The stronger electrostatic
attraction between multivalent P2VPH<sup>+</sup> microgels and PNaStS
polyelectrolyte than single-charged surfactant led to triggered release
of the encapsulated pyrene dyes from the hydrophobic interiors into
microgel dispersion. The process was confirmed by laser light scattering
(LLS) and fluorescence measurements. Furthermore, the entire dynamic
process of PNaStS adsorption into P2VPH<sup>+</sup> microgel interior
was further studied by stopped-flow equipment as a function of polyelectrolyte
concentration and degree of polymerization. The whole adsorption process
could be well fitted with a double-exponential function, suggesting
a fast (Ï„<sub>1</sub>) and a slow (Ï„<sub>2</sub>) relaxation
time, respectively. The fast process (Ï„<sub>1</sub>) was correlated
well with the approaching of PNaStS with P2VPH<sup>+</sup> microgel
to form a nonequilibrium complex within the microgel shell, while
the slow process (Ï„<sub>2</sub>) was consistent with the formation
of equilibrium complexes in the microgel deeper inside. This simple
yet feasible design augurs well for the promising applications in
controlled release fields
Schizophrenic Core–Shell Microgels: Thermoregulated Core and Shell Swelling/Collapse by Combining UCST and LCST Phase Transitions
A variety
of slightly cross-linked polyÂ(2-vinylpyridine)–polyÂ(<i>N</i>-isopropylacrylamide) (P2VP–PNIPAM) core–shell
microgels with pH- and temperature-responsive characteristic were
prepared via seeded emulsion polymerization. Negatively charged sodium
2,6-naphthalenedisulfonate (2,6-NDS) could be internalized into the
inner core, followed by formation of (P2VPH<sup>+</sup>/SO<sub>3</sub><sup>2–</sup>) supramolecular complex through the electrostatic
attractive interaction in acid condition. The thermoresponsive characteristic
feature of the (P2VPH<sup>+</sup>/SO<sub>3</sub><sup>2–</sup>)–PNIPAM core–shell microgels was investigated by laser
light scattering and UV–vis measurement, revealing an integration
of upper critical solution temperature (UCST) and lower critical solution
temperature (LCST) behaviors in the temperature range of 20–55
°C. The UCST performance arised from the compromised electrostatic
attractive interaction between P2VPH<sup>+</sup> and 2,6-NDS at elevated
temperatures, while the subsequent LCST transition is correlated to
the thermo-induced collapse of PNIPAM shells. The controlled release
of 2,6-NDS was monitored by static fluorescence spectra as a function
of temperature change. Moreover, stopped-flow equipped with a temperature-jump
accessory was then employed to assess the dynamic process, suggesting
a millisecond characteristic relaxation time of the 2,6-NDS diffusion
process. Interestingly, the characteristic relaxation time is independent
of the shell cross-link density, whereas it was significantly affected
by shell thickness. We believe that these dual thermoresponsive core–shell
microgels with thermotunable volume phase transition may augur promising
applications in the fields of polymer science and materials, particularly
for temperature-triggered release
Highly Selective Fluorogenic Multianalyte Biosensors Constructed via Enzyme-Catalyzed Coupling and Aggregation-Induced Emission
The development of a highly selective
and fast responsive fluorogenic
biosensor for diverse analytes ranging from bioactive small molecules
to specific antigens is highly desirable but remains a considerable
challenge. We herein propose a new approach by integrating substrate-selective
enzymatic reactions with fluorogens exhibiting aggregation-induced
emission feature. Tyrosine-functionalized tetraphenylethene, TPE-Tyr,
molecularly dissolves in aqueous media with negligible fluorescence
emission; upon addition of horseradish peroxidase (HRP) and H<sub>2</sub>O<sub>2</sub>, effective cross-linking occurs due to HRP-catalyzed
oxidative coupling of tyrosine moieties in TPE-Tyr. This leads to
fluorescence emission turn-on and fast detection of H<sub>2</sub>O<sub>2</sub> with high sensitivity and selectivity. As a validation of
the new strategy’s generality, we further configure it into
the biosensor design for glucose through cascade enzymatic reactions
and for pathologically relevant antigens (e.g., human carcinoembryonic
antigen) by combining with the ELISA kit
Photo- and Reduction-Responsive Polymersomes for Programmed Release of Small and Macromolecular Payloads
We
report on the preparation of photo- and reduction-responsive
diblock copolymers through reversible addition–fragmentation
chain transfer (RAFT) polymerization of a coumarin-based disulfide-containing
monomer (i.e., CSSMA) using a polyÂ(ethylene oxide) (PEO)-based macroRAFT
agent. The resulting amphiphilic PEO-<i>b</i>-PCSSMA copolymers
self-assembled into polymersomes with hydrophilic PEO shielding coronas
and hydrophobic bilayer membranes. Upon irradiating the polymersomes
with visible light (e.g., 430 nm), the coumarin moieties within the
bilayer membranes were cleaved with the generation of primary amine
groups, which spontaneously underwent inter/intrachain amidation reactions
with the ester moieties, thereby tracelessly cross-linking and permeating
the bilayer membranes. Notably, this process only gave rise to the
release of small molecule payloads (e.g., doxorubicin hydrochloride,
DOX) while large molecule encapsulants (e.g., Texas red-labeled dextran,
TR-dextran) were retained within the cross-linked polymersomes due
to the preservation of the integrity of the vesicular nanostructures.
However, cross-linked polymersomes undergo further structural disintegration
upon incubation with glutathione (GSH) due to the scission of disulfide
linkages, resulting in the release of macromolecular payloads. Thus, dual-stimuli
responsive polymersomes with tracelessly cross-linkable characteristics
enable sequential release of payloads with spatiotemporal precision,
which could be of promising applications in synergistic loading and
programmed release of therapeutics
Rationally Engineering Phototherapy Modules of Eosin-Conjugated Responsive Polymeric Nanocarriers via Intracellular Endocytic pH Gradients
Spatiotemporal
switching of respective phototherapy modes at the
cellular level with minimum side effects and high therapeutic efficacy
is a major challenge for cancer phototherapy. Herein we demonstrate
how to address this issue by employing photosensitizer-conjugated
pH-responsive block copolymers in combination with intracellular endocytic
pH gradients. At neutral pH corresponding to extracellular and cytosol
milieu, the copolymers self-assemble into micelles with prominently
quenched fluorescence emission and low <sup>1</sup>O<sub>2</sub> generation
capability, favoring a highly efficient photothermal module. Under
mildly acidic pH associated with endolysosomes, protonation-triggered
micelle-to-unimer transition results in recovered emission and enhanced
photodynamic <sup>1</sup>O<sub>2</sub> efficiency, which synergistically
actuates release of encapsulated drugs, endosomal escape, and photochemical
internalization processes
Near-Infrared Light-Activated Photochemical Internalization of Reduction-Responsive Polyprodrug Vesicles for Synergistic Photodynamic Therapy and Chemotherapy
The
use of intracellular reductive microenvironment to control
the release of therapeutic payloads has emerged as a popular approach
to design and fabricate intelligent nanocarriers. However, these reduction-responsive
nanocarriers are generally trapped within endolysosomes after internalization
and are subjected to unwanted disintegration, remarkably compromising
the therapeutic performance. Herein, amphiphilic polyprodrugs of polyÂ(<i>N</i>,<i>N</i>-dimethylacrylamide-<i>co</i>-EoS)-<i>b</i>-PCPTM were synthesized via sequential reversible
addition–fragmentation chain transfer (RAFT) polymerization,
where EoS and CPTM are Eosin Y- and camptothecin (CPT)-based monomers,
respectively. An oil-in-water (O/W) emulsion method was applied to
self-assemble the amphiphilic polyprodrugs into hybrid vesicles in
the presence of hydrophobic oleic acid (OA)-stabilized upconversion
nanoparticles (UCNPs, NaYF<sub>4</sub>:Yb/Er), rendering it possible
to activate the EoS photosensitizer under a near-infrared (NIR) laser
irradiation with the generation of singlet oxygen (<sup>1</sup>O<sub>2</sub>) through the energy transfer between UCNPs and EoS moieties.
Notably, the <i>in situ</i> generated singlet oxygen (<sup>1</sup>O<sub>2</sub>) can not only exert its photodynamic therapy
(PDT) effect but also disrupt the membranes of endolysosomes and thus
facilitate the endosomal escape of internalized nanocarriers (i.e.,
photochemical internalization (PCI)). Cell experiments revealed that
the hybrid vesicles could be facilely taken up by endocytosis. Although
the internalized hybrid vesicles were initially trapped within endolysosomes,
a remarkable endosomal escape into the cytoplasm was observed under
980 nm laser irradiation as a result of the PCI effect of <sup>1</sup>O<sub>2</sub>. The escaped hybrid vesicles subsequently underwent
GSH-triggered CPT release in the cytosol, thereby activating the chemotherapy
process. The integration of PDT module into the design of reduction-responsive
nanocarriers provides a feasible approach to enhance the therapeutic
performance
Efficient Synthesis of Single Gold Nanoparticle Hybrid Amphiphilic Triblock Copolymers and Their Controlled Self-Assembly
We report on a robust approach to the size-selective
and template-free
synthesis of asymmetrically functionalized ultrasmall (<4 nm) gold
nanoparticles (AuNPs) stably anchored with a single amphiphilic triblock
copolymer chain per NP. Directed NP self-assembly in aqueous solution
can be facilely accomplished to afford organic/inorganic hybrid micelles,
vesicles, rods, and large compound micelles by taking advantage of
the rich microphase separation behavior of the as-synthesized AuNP
hybrid amphiphilic triblock copolymers, PEO–AuNP–PS,
which act as the polymer–metal–polymer analogue of conventional
amphiphilic triblock copolymers. Factors affecting the size-selective
fabrication and self-assembly characteristics and the time-dependent
morphological evolution of NP assemblies were thoroughly explored
Nitric Oxide (NO) Endows Arylamine-Containing Block Copolymers with Unique Photoresponsive and Switchable LCST Properties
The
fabrication of materials that are responsive to endogenous
gasotransmitter molecules (i.e., nitric oxide, hydrogen sulfide, and
carbon monoxide) has emerged as an area of increasing research interest.
In the case of nitric oxide (NO), <i>o</i>-phenyleneÂdiamine
derivatives have traditionally been employed due to their ability
to react with NO in the presence of oxygen (O<sub>2</sub>) with the
formation of benzotriazole residues. Herein, we report the synthesis
of a novel NO-responsive polymer containing aromatic primary amine
groups derived from <i>p</i>-phenyleneÂdiamine groups
(i.e., isomers of <i>o</i>-phenyleneÂdiamine). A new
NO-responsive monomer, <i>N</i>-(4-aminoÂphenyl)Âmethacrylamide
(<i>p</i>-NAPMA), was first synthesized via the amidation
of one of the primary amine groups in the <i>p</i>-phenyleneÂdiamine
with methacrylic anhydride. Notably, the <i>p</i>-NAPMA
monomer can efficiently react with NO in aqueous solution in the presence
of O<sub>2</sub> with the generation of phenylÂdiazonium groups
rather than benzotriazole moieties. While the resultant phenylÂdiazonium
residues were relatively stable in aqueous solution, they were highly
sensitive to UV irradiation (i.e., λ<sub>max</sub> = 365 nm)
which gave the formation of phenol derivatives. After incorporation
into a thermoresponsive block copolymer using reversible addition–fragmentation
chain transfer (RAFT) polymerization, the resulting diblock copolymer,
polyÂ(ethylene glycol)-<i>b</i>-(<i>N</i>-isopropylÂacrylamide-<i>co</i>-<i>p</i>-NAPMA) (PEG-<i>b</i>-PÂ(NIPAM-<i>co</i>-<i>p</i>-NAPMA)), was rendered with unique
NO- and UV-responsive characteristics. Specifically, the NO-triggered
transformation of <i>p</i>-NAPMA moieties into phenylÂdiazonium
residues dramatically elevated the lower critical solution temperature
(LCST) of the block copolymer due to increased water solubility of
phenylÂdiazonium residues at neutral pH (i.e., pH 7.4). Further,
subsequent UV irradiation significantly decreased the LCST due to
the formation of relatively hydrophobic phenol derivatives from the
hydrophilic phenylÂdiazonium intermediate. These results demonstrate,
for the first time, that NO-responsive polymers can be synthesized
without the necessity of incorporating <i>o</i>-phenyleneÂdiamine
groups and that a further solubility switch can be stimulated by irradiation
with ultraviolet light
Application of Heterocyclic Polymers in the Ratiometric Spectrophotometric Determination of Fluoride
Herein
we report the use of heterocyclic functional polymers in
the ratiometric spectrophotometric determination of fluoride (F<sup>–</sup>). Polymers incorporating benzoÂ[d]Â[1,2,3]Âtriazole moieties
linked to the polymer backbone via urea links are demonstrated to
have utility for the ratiometric detection of the F<sup>–</sup> ion, with a detection limit in the order of ∼2 μM.
The hydrogen-bonding recognition between the benzoÂ[d]Â[1,2,3]Âtriazole
moiety and F<sup>–</sup> ion was investigated using UV–vis
spectrophotometry and NMR analysis. The importance of the urea linkage
was elucidated by investigating a second benzoÂ[d]Â[1,2,3]Âtriazole functional
monomer wherein the heterocyclic group is attached to the polymerizable
group via a carbamate linkage. The replacement of the urea link with
a carbamate group led to significantly reduced F<sup>–</sup> sensitivity. Moreover, by examining an analogous benzoÂ[d]Âimidazole
monomer it was demonstrated that having a nitrogen atom in the 2-position
of the heterocycle was important for maximizing the sensitivity of
the assay. Taken together, these results demonstrated that the urea-substituted
benzoÂ[d]Â[1,2,3]Âtriazole motif greatly enhances F<sup>–</sup> ion detection. Importantly, the F<sup>–</sup> ion sensing
capability of the monomer is retained after incorporating into a diblock
copolymer using reversible addition–fragmentation chain transfer
(RAFT) polymerization