Reversible Modulation of Plasmonic Coupling of Gold Nanoparticles Confined within Swellable Polymer Colloidal Spheres.

Dynamic optical modulation in response to stimuli provides exciting opportunities for designing novel sensing, actuating, and authentication devices. Here, we demonstrate that the reversible swelling and deswelling of crosslinked polymer colloidal spheres in response to pH and temperature changes can be utilized to drive the assembly and disassembly of the embedded gold nanoparticles (AuNPs), inducing their plasmonic coupling and decoupling and, correspondingly, color changes. The multi-responsive colloids are created by depositing a monolayer of AuNPs on the surface of resorcinol-formaldehyde (RF) nanospheres, then overcoating them with an additional RF layer, followed by a seeded growth process to enlarge the AuNPs and reduce their interparticle separation to induce significant plasmonic coupling. This configuration facilitates dynamic modulation of plasmonic coupling through the reversible swelling/deswelling of the polymer spheres in response to pH and temperature changes. The rapid and repeatable transitions between coupled and decoupled plasmonic states of AuNPs enable reversible color switching when the polymer spheres are in colloidal form or embedded in hydrogel substrates. Furthermore, leveraging the photothermal effect and stimuli-responsive plasmonic coupling of the embedded AuNPs enables the construction of hybrid hydrogel films featuring switchable anticounterfeiting patterns, showcasing the versatility and potential of this multi-stimuli-responsive plasmonic system.

Engineering Magnetic Nanoclusters for Highly Efficient Heating in Radio-Frequency Nanowarming.

Effective thawing of cryopreserved samples requires rapid and uniform heating. This is achievable through nanowarming, an approach that heats magnetic nanoparticles by using alternating magnetic fields. Here we demonstrate the synthesis and surface modification of magnetic nanoclusters for efficient nanowarming. Magnetite (Fe3O4) nanoclusters with an optimal diameter of 58 nm exhibit a high specific absorption rate of 1499 W/g Fe under an alternating magnetic field at 43 kA/m and 413 kHz, more than twice that of commercial iron oxide cores used in prior nanowarming studies. Surface modification with a permeable resorcinol-formaldehyde resin (RFR) polymer layer significantly enhances their colloidal stability in complex cryoprotective solutions, while maintaining their excellent heating capacity. The Fe3O4@RFR nanoparticles achieved a high average heating rate of 175 °C/min in cryopreserved samples at a concentration of 10 mg Fe/mL and were successfully applied in nanowarming porcine iliac arteries, highlighting their potential for enhancing the efficacy of cryopreservation.

Seeded Growth of Plasmonic Nanostructures in Deformable Polymer Confinement.

Plasmonic nanostructures exhibit optical properties highly related to their morphologies, enabling diverse applications in various areas such as biosensing, bioimaging, chemical detection, cancer therapy, and solar energy conversion. The expansive uses of these nanostructures necessitate robust and versatile synthesis methods suitable for large-scale production. Here, we introduce our recent efforts in developing a new strategy for controlling the seeded growth of plasmonic metal nanostructures, employing deformable polymer capsules to regulate the growth kinetics and the resulting particle morphology. Employing sol-gel-derived resorcinol-formaldehyde (RF) resin as a typical capsule material, we highlight its advanced features, including mechanical deformability and molecular permeability, that can be manipulated by tuning the capsule thickness and cross-linking degree. These features enable highly controllable confined seeded growth of plasmonic nanostructures. We reveal the significant role of the Ostwald ripening process of the seeds and the capsule structures in determining the morphological evolution of the plasmonic nanostructures. Moreover, we highlight some distinctive plasmonic nanostructures resulting from this unique synthesis strategy and their intriguing functionalities in various potential applications. Our discussion concludes with potential research directions to advance the development of the deformable polymer-confined seeded growth strategy into a general and robust synthesis platform for creating cutting-edge functional plasmonic nanostructures.

Colorimetric Pressure Sensing by Plasmonic Decoupling of Silver Nanoparticles Confined within Polymeric Nanoshells.

Employing a plasmonic decoupling mechanism, we report the design of a colorimetric pressure sensor that can respond to applied pressure with instant color changes. The sensor consists of a thin film of stacked uniform resorcinol-formaldehyde nanoshells with their inner surfaces functionalized with silver nanoparticles. Upon compression, the flexible polymer nanoshells expand laterally, inducing plasmonic decoupling between neighboring silver nanoparticles and a subsequent blue-shift. The initial color of the sensor is determined by the extent of plasmonic coupling, which can be controlled by tuning the interparticle distance through a seeded growth process. The sensing range can be conveniently customized by controlling the polymer shell thickness or incorporating hybrid nanoshells into various polymer matrices. The new colorimetric pressure sensors are easy to fabricate and highly versatile, allow for convenient tuning of the sensing range, and feature significant color shifts, holding great promise for a wide range of practical applications.

Colocalization of protein and microRNA markers reveals unique extracellular vesicle subpopulations for early cancer detection.

Extracellular vesicles (EVs) play important roles in cell-cell communication but are highly heterogeneous, and each vesicle has dimensions smaller than 200 nm with very limited amounts of cargos encapsulated. The technique of NanOstirBar (NOB)-EnabLed Single Particle Analysis (NOBEL-SPA) reported in the present work permits rapid inspection of single EV with high confidence by confocal fluorescence microscopy, thus enables colocalization assessment for selected protein and microRNA (miRNA) markers in the EVs produced by various cell lines, or present in clinical sera samples. EV subpopulations marked by the colocalization of unique protein and miRNA combinations were discovered to be able to detect early-stage (stage I or II) breast cancer (BC). NOBEL-SPA can be adapted to analyze other types of cargo molecules or other small submicron biological particles. Study of the sorting of specific cargos to heterogeneous vesicles under different physiological conditions can help discover distinct vesicle subpopulations valuable in clinical examination and therapeutics development and gain better understanding of their biogenesis.

Magnetic assembly of plasmonic chiral superstructures with dynamic chiroptical responses.

Plasmonic nanostructures exhibiting dynamically tunable chiroptical responses hold great promise for broad applications such as sensing, catalysis, and enantioselective analysis. Despite the successful fabrication of chiral structures through diverse templates, creating dynamic chiroptical materials with fast and reversible responses to external stimuli is still challenging. This work showcases reversible magnetic assembly and active tuning of plasmonic chiral superstructures by introducing a chiral magnetic field from a cubic permanent magnet. Manipulating the strength and direction of the magnetic field controls both the chiral arrangement and plasmonic coupling of the nanoparticle assembly, enabling fast and reversible tunability in not only the handedness of the superstructures but also the spectral characteristics of their chiroptical properties. The dynamic tunability further enables the fabrication of color-changing optical devices based on the optical rotatory dispersion effect, showcasing their potential for application in anti-counterfeiting and stress sensors.

Visible-Light-Responsive Photoreversible Multi-Color Switching for Rewritable Light-Printing and Information Display.

Photoreversible color switching systems (PCSSs) exhibiting multi-color responses to visible light are favored for sustainable societal development over those relying on ultraviolet light due to safer operation and better penetration depth. Here, a PCSS capable of multi-color switching responsive to visible light based on highly photoreductive rutile-phase Sn-doped TiO2-x nanoparticles is reported. The Sn-doping significantly red-shifts the absorption band of the nanoparticles to the visible region, improving charge separation and transfer efficiencies and introducing Ti3+ species and oxygen vacancies as internal sacrificial electron donors for scavenging photogenerated holes. The resulting Sn-doped TiO2-x nanoparticles feature exceptional photoreduction ability and activity, thereby enabling photoreversible color switching of various redox dyes operational under visible light illumination. Furthermore, multi-color switching can be achieved via the color overlay effect by combining different redox dyes in one system, opening the door to many advanced applications, as demonstrated in their successful uses for developing visible-light-driven rewritable multi-color light-printing systems and visual information displays.

Dual-Responsive Fe3O4@Polyaniline Chiral Superstructures for Information Encryption.

Incorporating stimuli-responsive mechanisms into chiral assemblies of nanostructures offers numerous opportunities to create optical materials capable of dynamically modulating their chiroptical properties. In this study, we demonstrate the formation of chiral superstructures by assembling Fe3O4@polyaniline hybrid nanorods by using a gradient magnetic field. The resulting superstructures exhibit a dual response to changes in both the magnetic field and solution pH, enabling dynamic regulation of the position, intensity, and sign of its circular dichroism peaks. Such responsiveness allows for convenient control over the optical rotatory dispersion properties of the assemblies, which are further integrated into the design of a chiroptical switch that can display various colors and patterns when illuminated with light of different wavelengths and polarization states. Finally, an optical information encryption system is constructed through the controlled assembly of the hybrid nanorods to showcase the potential opportunities for practical applications brought by the resulting responsive chiral superstructures.

A magnetic assembly approach to chiral superstructures.

Colloidal assembly into chiral superstructures is usually accomplished with templating or lithographic patterning methods that are only applicable to materials with specific compositions and morphologies over narrow size ranges. Here, chiral superstructures can be rapidly formed by magnetically assembling materials of any chemical compositions at all scales, from molecules to nano- and microstructures. We show that a quadrupole field chirality is generated by permanent magnets caused by consistent field rotation in space. Applying the chiral field to magnetic nanoparticles produces long-range chiral superstructures controlled by field strength at the samples and orientation of the magnets. Transferring the chirality to any achiral molecules is enabled by incorporating guest molecules such as metals, polymers, oxides, semiconductors, dyes, and fluorophores into the magnetic nanostructures.

Colocalization of Protein and microRNA Markers Reveals Unique Extracellular Vesicle Sub-Populations for Early Cancer Detection.

Extracellular vesicles (EVs) play important roles in cell-cell communication but they are highly heterogeneous, and each vesicle has dimensions smaller than 200 nm thus encapsulates very limited amounts of cargos. We report the technique of NanOstirBar (NOB)-EnabLed Single Particle Analysis (NOBEL-SPA) that utilizes NOBs, which are superparamagnetic nanorods easily handled by a magnet or a rotating magnetic field, to act as isolated "islands" for EV immobilization and cargo confinement. NOBEL-SPA permits rapid inspection of single EV with high confidence by confocal fluorescence microscopy, and can assess the colocalization of selected protein/microRNA (miRNA) pairs in the EVs produced by various cell lines or present in clinical sera samples. Specific EV sub-populations marked by the colocalization of unique protein and miRNA combinations have been revealed by the present work, which can differentiate the EVs by their cells or origin, as well as to detect early-stage breast cancer (BC). We believe NOBEL-SPA can be expanded to analyze the co-localization of other types of cargo molecules, and will be a powerful tool to study EV cargo loading and functions under different physiological conditions, and help discover distinct EV subgroups valuable in clinical examination and therapeutics development.

Acoustic emission characteristics and fracture mechanism of cemented tailings backfill under uniaxial compression: experimental and numerical study.

Cemented tailings backfill (CTB) is the most cost-effective and environmentally friendly method to recycle tailings for filling mining. It is of great significance to study the fracture mechanism of CTB for safe mining. In this study, three cylindrical CTB samples with a cement-tailings ratio of 1:4 and a mass fraction of 72% were prepared. An acoustic emission (AE) test under uniaxial compression (UC) with WAW-300 microcomputer electro-hydraulic servo universal testing machine and DS2 series full information AE signal analyzer was carried out to discuss the AE characteristics of CTB, such as hits, energy, peak frequency, and AF-RA. Combined with particle flow and moment tensor theory, a meso AE model of CTB was constructed to reveal the fracture mechanism of CTB. The results show that (1) the AE law of CTB under UC has periodic characteristics, which can be divided into the rising stage, stable stage, booming stage, and active stage. (2) The peak frequency of the AE signal is mainly focused on three frequency bands. The ultra-high frequency AE signal may be the precursor information for CTB failure. (3) The low frequency band AE signals represent shear crack, while the medium and high frequency band AE signals represent tension crack. The shear crack initially decreases and then increases, and the tension crack is the opposite. (4) The fracture types of the AE source are divided into tension crack, mixed crack, and shear crack. The tension crack is dominant, while a larger magnitude AE source is frequently shear crack. The results can provide a basis for the stability monitoring and fracture prediction of CTB.

Magnetic Field-Modulated Plasmonic Scattering of Hybrid Nanorods for FFT-Weighted OCT Imaging in NIR-II.

We report a method for fast Fourier transform (FFT)-weighted optical coherence tomography (OCT) in the second biological tissue transparency window by actively modulating the plasmonic scattering of Fe3O4@Au hybrid nanorods using magnetic fields. Instead of tracking the nanoparticles' lateral displacement in conventional magnetomotive OCT imaging, we monitor the nanorod rotation and optical signal changes under an alternating magnetic field in real time. The coherent rotation of the nanorods with the field produces periodic OCT signals, and the FFT is then used to convert the periodic OCT signals in the time domain to a single peak in the frequency domain. This allows automatic screening of nanorod signals from the random biological noises and reconstruction of FFT-weighted images using a computer program based on a time-sequence image set. Compared with conventional magnetomotive OCT, the FFT-weighted imaging technique creates enhanced OCT images with dB-scale contrast over an order of magnitude higher than the original images.

Fast Fourier Transform-weighted Photoacoustic Imaging by In Vivo Magnetic Alignment of Hybrid Nanorods.

Photoacoustic (PA) imaging uses photon-phonon conversion for high-resolution tomography of biological tissues and functions. Exogenous contrast agents are often added to improve the image quality, but the interference from endogenous molecules diminishes the imaging sensitivity and specificity. We report a background-free PA imaging technique based on the active modulation of PA signals via magnetic alignment of Fe3O4@Au hybrid nanorods. Switching the field direction creates enhanced and deactivated PA imaging modalities, enabling a simple pixel subtraction to effectively minimize background noises. Under an alternating magnetic field, the nanorods exhibit PA signals of coherently periodic changes that can be converted into a sharp peak in a frequency domain via the fast Fourier transform. Automatic pixel-wise screening of nanorod signals performed using a computational algorithm across a time-sequence set of PA images regenerates a background-free PA image with significantly improved contrast, specificity, and fidelity.

Rapid High-Contrast Photoreversible Coloration of Surface-Functionalized N-Doped TiO2 Nanocrystals for Rewritable Light-Printing.

Pristine titanium dioxide (TiO2 ) changes color from white to black when it is reduced from TiIV to TiIII by photoexcited electrons. However, the black coloration requires substantial light energy to create, and it vanishes instantaneously upon exposure to air. This work reports the synthesis of surface-functionalized N-doped TiO2 nanocrystals that rapidly change color (i.e., within seconds) from whitish to black under low-power irradiation with excellent color stability in atmospheric conditions. The N-doping plays a critical role in promoting the surface-adsorption of polyol groups to stabilize the TiIII species and accelerate the coloration process. A rewritable paper fabricated using these nanocrystals exhibits excellent writing and erasing reversibility in response to UV irradiation and oxygen exposure. The low-cost, rapid response, excellent reversibility, and good color stability are vital advantages of N-doped TiO2 nanocrystals for color-switching applications.

Giant Hepatic Hemangioma Regressed Significantly Without Surgical Management: A Case Report and Literature Review.

Hepatic hemangioma (HH) is a congenital vascular anomaly comprising networks of abnormal blood and/or lymphatic vessels with endothelial cell proliferation. Their pathophysiology is not fully understood, and no specific drug is available to treat them. Conservative management, which limits observation, is preferred for most patients. A HH larger than 4 cm is considered a giant HH that may be treated using surgery ranging from embolization to hepatic resection or liver transplantation. Here, we describe a case with multiple and giant HHs that regressed significantly after treatment with azithromycin (AZM). A systematic literature review of HH and the effects of AZM on angiogenesis was then conducted.

Deposition of Atomically Thin Pt Shells on Amorphous Palladium Phosphide Cores for Enhancing the Electrocatalytic Durability.

As an excellent electrocatalyst, platinum (Pt) is often deposited as a thin layer on a nanoscale substrate to achieve high utilization efficiency. However, the practical application of the as-designed catalysts has been substantially restricted by the poor durability arising from the leaching of cores. Herein, by employing amorphous palladium phosphide (a-Pd-P) as substrates, we develop a class of leaching-free, ultrastable core-shell Pt catalysts with well-controlled shell thicknesses and surface structures for fuel cell electrocatalysis. When a submonolayer of Pt is deposited on the 6 nm nanocubes, the resulting Pd@a-Pd-P@PtSML core-shell catalyst can deliver a mass activity as high as 4.08 A/mgPt and 1.37 A/mgPd+Pt toward the oxygen reduction reaction at 0.9 V vs the reversible hydrogen electrode and undergoes 50 000 potential cycles with only ∼9% activity loss and negligible structural deformation. As elucidated by the DFT calculations, the superior durability of the catalysts originates from the high corrosion resistance of the disordered a-Pd-P substrates and the strong interfacial Pt-P interactions between the Pt shell and amorphous Pd-P layer.

Polarization-Modulated Multidirectional Photothermal Actuators.

Photothermal actuators have attracted increasing attention due to their ability to convert light energy into mechanical deformation and locomotion. This work reports a freestanding, multidirectional photothermal robot that can walk along a predesigned pathway by modulating laser polarization and on-off switching. Magnetic-plasmonic hybrid Fe3 O4 /Ag nanorods are synthesized using an unconventional templating approach. The coupled magnetic and plasmonic anisotropy allows control of the rod orientation, plasmonic excitation, and photothermal conversion by simply applying a magnetic field. Once the rods are fixed with desirable orientations in a bimorph actuator by magnetic-field-assisted lithography, the bending of the actuator can be controlled by switching the laser polarization. A bipedal robot is created by coupling the rod orientation with the alternating actuation of its two legs. Irradiating the robot by a laser with alternating or fixed polarization synergistically results in basic movement (backward and forward) and turning (including left-, right-, and U-turn), respectively. A complex walk along predesigned pathways can be potentially programmed by combining the movement and turning modes of the robots. This strategy provides an alternative driving mechanism for preparing functional soft robots, thus breaking through the limitations in the existing systems in terms of light sources and actuation manners.

Janus Evaporators with Self-Recovering Hydrophobicity for Salt-Rejecting Interfacial Solar Desalination.

The recent advancements in interfacial evaporation of salty water using renewable solar energy provide one of the promising pathways to solve worldwide water scarcity. Pursuing a stable evaporation rate of water has been the central focus of this field, as it is directly related to the throughput, while salt deposition on the evaporator becomes a critical issue. Although Janus-structured evaporators with an upper hydrophobic layer and a bottom hydrophilic layer have been demonstrated as an effective way to suppress the salt precipitation, the hydrophobic upper layer, achieved usually by some special organic groups, suffers from a photochemical oxidation when exposed to oxidative chemicals in water and high-energy light, resulting in a deteriorated surface hydrophobicity. Here, we report our design of an efficient salt-rejecting Janus evaporator by taking advantage of the self-recovering surface hydrophobicity of poly(dimethylsiloxane) (PDMS) against photochemical damages, which ensures a long-term surface hydrophobicity. With its upper layer partially covered with PDMS, the Janus evaporator demonstrates an excellent salt rejection capability and exhibits a stable evaporation rate of 1.38 kg·m-2·h-1 under 1 sun illumination for 400 min of continuous operation, or 90 d of intermittent work. By combining the advantages of high structural integration, long-term salt-rejection, and efficient evaporation, our Janus evaporator holds great promise for the stable production of clean water from seawater.

Dual Roles of Polymeric Capping Ligands in the Surface-Protected Etching of Colloidal Silica.

In this work, we reveal the dual roles of polymeric capping ligands in the hollowing of silica nanospheres during their surface-protected etching. We first show that polymeric capping ligands, if they have a stronger interaction with the surface Si-OH groups than water, can reduce the condensation of the silica network, allowing the diffusion of OH- ions through the shell to dissolve the inner silica. Also, the polymeric ligands can passivate the surface silica, making it less likely to be dissolved by OH- ions. The combination of these two roles ensures highly selective etching of the interior of the colloidal silica spheres, making the surface-protected etching a robust process for the synthesis of hollow silica nanoshells. Our insight into the specific roles of the ligands is expected to elucidate the impact of polymeric ligands on the colloidal chemistry of silica, particularly in its condensation and etching behaviors, and offer new opportunities in the design of silica and other oxide-based nanostructures.